Diabetes and cirrhosis.
Post-Doctoral, Biomedical sciences, Université de Montréal
Direction:
- Dr Christopher Rose
2019 - 2021
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Mariana Macedo de Oliveira, Alexis Monnet-Aimard, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Hepatic encephalopathy (HE) is a debilitating neurological complication of chronic liver disease (CLD). Hyperammonemia plays an important role in HE's pathogenesis, acting synergistically with systemic oxidative stress. During CLD, muscle plays a compensatory role in detoxifying ammonia, and therefore muscle loss leads to an increase in the risk of developing HE. With most animal studies involving males, sex's impact on the development of CLD and associated complications such as HE and muscle loss remains unknown. Therefore, we aimed to identify the impact of sex on CLD, HE, and muscle mass loss in a rodent model of CLD. Liver injury markers, hyperammonemia, oxidative stress, muscle mass, and ammonia clearance were measured in female and male bile-duct ligated (BDL) rats. In addition, covert HE was assessed in females while ammonia-precipitated severe HE was assessed in female and male BDL rats, and male BDL rats treated with allopurinol (100 mg/kg), an antioxidant (xanthine oxidase inhibitor). Female BDL developed CLD and HE (impaired motor coordination and night activity) compared to respective SHAM. Hyperammonemia and muscle ammonia clearance were similar between female and male BDL. However, only female BDL rats did not develop muscle loss, brain edema, and short-term memory impairment (vs. female SHAM) and systemic oxidative stress and decreased albumin levels (vs. male BDL). Furthermore, both female BDL and allopurinol-treated male BDL rats were protected against ammonia-induced overt HE. In conclusion, female and male BDL rats develop distinct features of CLD and HE, with systemic oxidative stress playing a pivotal role in the susceptibility to ammonia-precipitated overt HE.
Impact of sex on muscle mass loss and hepatic encephalopathy in rats with chronic liver disease.
Mariana M. Oliveira, Alexis Monnet-Aimard, Cristina Bosoi, Mélanie Tremblay, Christopher Rose.
Background: In chronic liver disease (CLD) loss of muscle mass (sarcopenia) is highly prevalent which leads to an increased risk of hepatic encephalopathy (HE). Muscle plays a compensatory role during CLD in clearing ammonia since it expresses glutamine synthetase (GS). Therefore, diminished muscle mass in CLD leads to a further reduced capacity to clear ammonia. Male rats with CLD due to bile-duct ligation (BDL) have been shown to result in a loss of muscle in association with hyperammonemia and HE. However, these complications have not been explored in female CLD rats. Purpose: Our aim was to identify whether female sex impacts muscle mass loss, blood ammonia levels and HE in ratswith CLD. Method: Five weeks after either BDL (n=8) or Sham (n=8) surgery in male and female rats, we assessed markers of liver injury (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP)) and function (albumin and bilirubin). Neurophenotyping was achieved using the open field test and the elevated plus maze test for anxiety, the rota-rod test for motor coordination, the novel object recognition for short-term memory and the nighttime activity test. In addition, brain edema was assessed using the gravimetric technique. Body parameters (weight, composition (MRI)) and muscle (gastrocnemius weight and circumference and grip strength) were also evaluated. In addition, muscle GS activity, ammonia clearance as well as glutamine generation (femoral venous-arterial difference)were evaluated in female vs. male BDL rats. Result(s): Female and male BDL rats had similar levels of impaired liver markers (ALP, AST, bilirubin and albumin (p<0.001)) and both developed HE (impaired motor-coordination and night activity (p<0.05)) when compared to respective Shams. However, female BDL rats did not develop brain edema and did not have loss of short-term memory. Male BDL rats experienced loss of lean mass as well as reduced muscle circumference, weight and strength (p<0.01) compared to Sham rats, while similar differences between female BDL vs. Sham rats were not found. Male and female BDL rats had comparable blood ammonia levels as well as similar muscle ammonia clearance and glutamine production. However, GS activity was lower in female vs. male BDL rats (p<0.01). Conclusion(s): Our results demonstrate that following BDL surgery, female rats develop similar degrees of CLD compared to male rats. As in male BDL rats, female rats also develop HE but female BDL rats acquire unique features (not observed in males) such as lack of brain edema and intact short-term memory. Contrary to males, female BDL rats did not develop sarcopenia compared to respective controls. However, preserved muscle mass in female BDL did not result in increased muscle ammonia clearance and glutamine production. Therefore, the similar degrees of hyperammonemia in males vs. females may be due to an upregulation in GS found in the muscle of male BDL rats. Thus, the female-induced protection against brain edema and short-term memory in BDL rats likely involves additional factors besides ammonia.
Rafael Ochoa‐Sanchez, Mariana M. Oliveira, Mélanie Tremblay, Grégory Petrazzo, Asha Pant, Cristina R. Bosoi, Mylene Perreault, William Querbes, Caroline B. Kurtz, Christopher F. Rose.
Marc-André Clément, Cristina R. Bosoi, Mariana M. Oliveira, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Hepatic encephalopathy (HE) is a debilitating neurological complication of cirrhosis. By definition, HE is considered a reversible disorder, and therefore HE should resolve following liver transplantation (LT). However, persisting neurological complications are observed in as many as 47% of LT recipients. LT is an invasive surgical procedure accompanied with various perioperative factors such as blood loss and hypotension which could influence outcomes post-LT. We hypothesize that minimal HE (MHE) renders the brain frail and susceptible to hypotension-induced neuronal cell death. Six-week bile duct-ligated (BDL) rats with MHE and respective SHAM-controls were used. Several degrees of hypotension (mean arterial pressure of 30, 60 and 90mmHg) were induced via blood withdrawal from the femoral artery and maintained for 120 minutes. Brains were collected for neuronal cell count and apoptotic analysis. In a separate group, BDL rats were treated for MHE with the ammonia-lowering strategy ornithine phenylacetate (OP; MNK-6105), administered orally (1g/kg) for 3 weeks before induction of hypotension. Hypotension 30 and 60mmHg (not 90mmHg) significantly decreased neuronal marker expression (NeuN) and cresyl violet staining in the frontal cortex compared to respective hypotensive SHAM-operated controls as well as non-hypotensive BDL rats. Neuronal degeneration was associated with an increase in cleaved caspase-3, suggesting the mechanism of cell death was apoptotic. OP treatment attenuated hyperammonemia, improved anxiety and activity, and protected the brain against hypotension-induced neuronal cell death. Our findings demonstrate that rats with chronic liver disease and MHE are more susceptible to hypotension-induced neuronal cell degeneration. This highlights MHE at the time of LT is a risk factor for poor neurological outcome post-transplant and that treating for MHE pre-LT might reduce this risk.
Diabetes is associated to the development of hepatic encephalopathy in cirrhotic patients.
Cristina R. Bosoi, Corina Cerlat, Mimosa Nguyen, Mélanie Tremblay, Catherine Vincent, Christopher F. Rose, Chantal Bémeur.
Background: Non-alcoholic fatty liver disease (NAFLD) is associated with type II diabetes (T2D) and has become the main cause of cirrhosis. Both NAFLD and T2D are associated with cognitive and neurological impairments. T2D has been established as a risk factor for first-time development of overt hepatic encephalopathy (HE) in cirrhotic patients. The onset of HE in diabetic patients with cirrhosis develops earlier compared to cirrhosis patients without T2D. However it remains unclear whether NAFLD-induced cirrhosis increases the risk for HE. The present study aims to address the association between NAFLD, T2D and HE. Methods: Our retrospective study includes 102 cirrhotic patients on the liver transplant list at the Liver Unit of the Montreal University Hospital Center. Patients were classified by etiology of cirrhosis; 1) NAFLD and 2) non-NAFLD. Demographic data, blood biochemistry, clinical information on T2D-related comorbidities and cirrhosis complications (including number and severity of HE episodes) were collected. These factors were statistically associated with HE episodes. Results: Our cohort comprised 20 (19%) NAFLD and 82 (79%) non-NAFLD patients presenting similar MELD and Child-Pugh scores. The prevalence of T2D was higher in NAFLD vs non-NAFLD cirrhotics (15 (75%) vs 24 (29%) respectively) and was associated to co-morbidities such as cardiac disease, dyslipidemia, hypertension and obesity. Among non-NAFLD cirrhotics, 47 (57%) patients had a history of HE whereas 8 (40%) were found in the NAFLD cirrhotics (p>0.05). Since T2D is already known as a risk factor for HE, we subdivided both NAFLD and non-NAFLD groups into non-T2D and T2D subgroups. HE was significantly more prevalent in patients with T2D: in the NAFLD group, 5 (25%) T2D patients had developed an episode of HE compared to 3 (15%) patients without T2D (p<0.05); in the non-NAFLD group, 16 (67%) patients had T2D and HE compared to 31 (53%) HE patients without T2D (p<0.001). Fasting glycemia levels analysis in the 4 sub-groups of patients revealed increased levels in patients with history of HE and T2D, regardless of NAFLD etiology; in the NAFLD group 8.60 ± 0.84 mmol/l in patients with HE and T2D vs 6.00 ± 1.35 mmol/l in patients with HE without T2D (p<0.01); in the non-NAFLD group: 9.23 ± 0.93 mmol/l in patients with HE and T2D vs 5.82 ± 0.27 mmol/l in patients with HE without T2D (p<0.001). Conclusion: Our results sustain the association between T2D and HE and suggest high glucose might play a pathological role in the development of cognitive decline. NAFLD is not a risk factor for the development of HE. These interesting results provide new insights in the role of T2D in the development of HE and further studies are required to understand the underlying mechanisms. Furthermore, identifying patients who are at higher risk of developing HE is imperative to initiate early treatment strategies to protect neurological decline in patients with cirrhosis.
Diabetes is associated to the development of hepatic encephalopathy in cirrhotic patients.
Corina Cerlat, Cristina R. Bosoi, Mimosa Nguyen, Mélanie Tremblay, Catherine Vincent, Christopher F. Rose, Chantal Bémeur.
Background: Non-alcoholic fatty liver disease (NAFLD) is associated with type II diabetes (T2D) and has become the main cause of cirrhosis. Both NAFLD and T2D are associated with cognitive and neurological impairments. T2D has been established as a risk factor for first-time development of overt hepatic encephalopathy (HE) in cirrhotic patients. The onset of HE in diabetic patients with cirrhosis develops earlier compared to cirrhosis patients without T2D. However it remains unclear whether NAFLD-induced cirrhosis increases the risk for HE. The present study aims to address the association between NAFLD, T2D and HE. Methods: Our retrospective study includes 102 cirrhotic patients on the liver transplant list at the Liver Unit of the Montreal University Hospital Center. Patients were classified by etiology of cirrhosis; 1) NAFLD and 2) non-NAFLD. Demographic data, blood biochemistry, clinical information on T2D-related comorbidities and cirrhosis complications (including number and severity of HE episodes) were collected. These factors were statistically associated with HE episodes. Results: Our cohort comprised 20 (19%) NAFLD and 82 (79%) non-NAFLD patients presenting similar MELD and Child-Pugh scores. The prevalence of T2D was higher in NAFLD vs non-NAFLD cirrhotics (15 (75%) vs 24 (29%) respectively) and was associated to co-morbidities such as cardiac disease, dyslipidemia, hypertension and obesity. Among non-NAFLD cirrhotics, 47 (57%) patients had a history of HE whereas 8 (40%) were found in the NAFLD cirrhotics (p>0.05). Since T2D is already known as a risk factor for HE, we subdivided both NAFLD and non-NAFLD groups into non-T2D and T2D subgroups. HE was significantly more prevalent in patients with T2D: in the NAFLD group, 5 (25%) T2D patients had developed an episode of HE compared to 3 (15%) patients without T2D (p<0.05); in the non-NAFLD group, 16 (67%) patients had T2D and HE compared to 31 (53%) HE patients without T2D (p<0.001). Fasting glycemia levels analysis in the 4 sub-groups of patients revealed increased levels in patients with history of HE and T2D, regardless of NAFLD etiology; in the NAFLD group 8.60 ± 0.84 mmol/l in patients with HE and T2D vs 6.00 ± 1.35 mmol/l in patients with HE without T2D (p<0.01); in the non-NAFLD group: 9.23 ± 0.93 mmol/l in patients with HE and T2D vs 5.82 ± 0.27 mmol/l in patients with HE without T2D (p<0.001). Conclusion: Our results sustain the association between T2D and HE and suggest high glucose might play a pathological role in the development of cognitive decline. NAFLD is not a risk factor for the development of HE. These interesting results provide new insights in the role of T2D in the development of HE and further studies are required to understand the underlying mechanisms. Furthermore, identifying patients who are at higher risk of developing HE is imperative to initiate early treatment strategies to protect neurological decline in patients with cirrhosis.
Valentina Agostoni, G. Giacalone, Cristina R. Bosoi, Christopher F. Rose, Jean-Christophe Leroux.
Introduction: Liposome-supported peritoneal dialysis (LSPD) has recently emerged as a versatile biodetoxification platform for improving the peritoneal extraction of small ionizable molecules via the intraperitoneal instillation of transmembrane pH-gradient liposomes.1 In a proof-of-concept study, these scavenging vesicles efficiently trapped weak bases/acids (e.g. ammonia), and were subsequently withdrawn together with their toxic cargo at the end of the dialysis session.1 We investigated here the translational potential of LSPD for treating hyperammonemia-associated hepatic encephalopathy, a life-threatening condition arising from impaired liver functions. The initial steps towards the clinical development of this technology consisted in optimizing the manufacturing process, assessing efficacy and safety in appropriate animal models, investigating interferences with drugs commonly administered to liver impaired patients, and establishing the extraction fingerprint of LSPD fluids. Methods: LSPD fluids were prepared by an osmotic-shock based method, sequentially mixing liposome aqueous suspensions with a hypertonic citrate solution (acidic) and an isotonic xylitol-based solution (alkaline).2 Efficacy experiments were performed in a rat model of secondary biliary cirrhosis induced by bile duct ligation.2 After 4 consecutive 4-h dialysis sessions with LSPD or a control fluid, brain edema was measured by densitometry, and plasma and dialysate ammonia concentrations determined by enzymatic assay. The immunogenicity of LSPD fluids was assessed in a porcine model of complement activation-related pseudoallergy (CARPA).2 For the interaction study, nine drugs commonly taken by liver impaired patients (e.g. antibiotics, β-blockers, diuretics) were tested for their influence on the in vitro ammonia scavenging activity of LSPD fluids. The metabolites’ fingerprints of LSPD or conventional PD, prior and after dialysis in healthy rats, were established by mass spectrometry. Results: LSPD fluids were prepared via an innovative, osmotic shock-based method overcoming sterilization and long-term stability issues.2 The liposomal suspensions outperformed conventional PD fluids in lowering plasmatic ammonia levels, and attenuating brain edema in cirrhotic rats and did not trigger any hypersensitive reaction in pigs, a gold standard model of CARPA.2 In general, the in vitro ammonia uptake of LSPD fluids was barely affected by the presence of the selected drugs in the incubation medium. Only the β-blocker propranolol considerably lowered the liposome scavenging capability. Metabolomics studies revealed a similar extraction profile between conventional PD and LSPD, confirming that important endogenous metabolites other than ammonia were not preferentially removed by LSPD. Conclusion: LSPD appeared as a promising strategy for ammonia detoxification, a first valuable alternative to extracorporeal dialysis, when the latter is not available or too risky. Acknowledgements. This work was supported by Versantis AG, the Swiss National Science Foundation (31003A_124882), Swiss Commission for Technology and Innovation (17525.1 PFLS-LS), and the OPO Foundation. The authors thank Seroscience Ltd (Budapest, Hungary) for their involvement in the safety studies.
José I. Fortea, Alexander Zipprich, Carolina Fernandez-Mena, Marta Puerto, Cristina R. Bosoi, Jorge Almagro, Marcus Hollenbach, Juan Bañares, Belén Rodríguez-Sánchez, Emilia Cercenado, Marc-André Clément, Christopher F. Rose, Rafael Bañares, Javier Vaquero, Cristina Ripoll.
Recent studies suggest that heparins reduce liver fibrosis and the risk of decompensation of liver disease. Here, we evaluated the effects of enoxaparin in several experimental models of advanced cirrhosis. Cirrhosis was induced in male Sprague-Dawley (SD) rats by: i. Oral gavage with carbon tetrachloride (CCl4ORAL ), ii. Bile duct ligation (BDL), and iii. CCl4 inhalation (CCl4INH ). Rats received saline or enoxaparin s.c. (40 IU/Kg/d or 180 IU/Kg/d) following various protocols. Blood biochemical parameters, liver fibrosis, endothelium- and fibrosis-related genes, portal pressure, splenomegaly, bacterial translocation, systemic inflammation, and survival were evaluated. Endothelial dysfunction was assessed by in-situ bivascular liver perfusions. Enoxaparin did not ameliorate liver function, liver fibrosis, pro-fibrogenic gene expression, portal hypertension, splenomegaly, ascites development and infection, serum IL-6 levels or survival in rats with CCl4ORAL or BDL-induced cirrhosis. Contrarily, enoxaparin worsened portal pressure in BDL rats and decreased survival in CCl4ORAL rats. In CCl4INH rats, enoxaparin had no effects on hepatic endothelial dysfunction, except for correcting the hepatic arterial dysfunction when enoxaparin was started with the CCl4 exposure. In these rats, however, enoxaparin increased liver fibrosis and the absolute values of portal venous and sinusoidal resistance. Our results do not support a role of enoxaparin for improving liver fibrosis, portal hypertension or endothelial dysfunction in active disease at advanced stages of cirrhosis. These disease-related factors and the possibility of a limited therapeutic window should be considered in future studies evaluating the use of anticoagulants in cirrhosis. This article is protected by copyright. All rights reserved.
The bile duct ligated rat: A relevant model to study muscle mass loss in cirrhosis.
Cristina R. Bosoi, Mariana M. Oliveira, Rafael Ochoa-Sanchez, Mélanie Tremblay, Gabriella A. Ten Have, Nicolaas E. Deutz, Christopher F. Rose, Chantal Bémeur.
Muscle mass loss and hepatic encephalopathy (complex neuropsychiatric disorder) are serious complications of chronic liver disease (cirrhosis) which impact negatively on clinical outcome and quality of life and increase mortality. Liver disease leads to hyperammonemia and ammonia toxicity is believed to play a major role in the pathogenesis of hepatic encephalopathy. However, the effects of ammonia are not brain-specific and therefore may also affect other organs and tissues including muscle. The precise pathophysiological mechanisms underlying muscle wasting in chronic liver disease remains to be elucidated. In the present study, we characterized body composition as well as muscle protein synthesis in cirrhotic rats with hepatic encephalopathy using the 6-week bile duct ligation (BDL) model which recapitulates the main features of cirrhosis. Compared to sham-operated control animals, BDL rats display significant decreased gain in body weight, altered body composition, decreased gastrocnemius muscle mass and circumference as well as altered muscle morphology. Muscle protein synthesis was also significantly reduced in BDL rats compared to control animals. These findings demonstrate that the 6-week BDL experimental rat is a relevant model to study liver disease-induced muscle mass loss.
Marc-André Clément, Cristina R. Bosoi, Mariana Oliveira, Mélanie Tremblay, Gabriella A. Ten Have, Nicolaas E. Deutz, Christopher F. Rose.
Background and Aims: Chronic liver disease (CLD) induces numerous complications including muscle mass loss and hepatic encephalopathy (HE) which negatively impact clinical outcomes. Hyperammonemia is considered the central component in the pathogenesis of HE, however recent studies have suggested ammonia to be toxic to other organs/tissues aside the brain, such as the muscle. The aim of this study was to investigate the effect of lowering ammonia on muscle mass in cirrhotic rats treated with an oral formulation of ornithine phenylacetate (OP; OCR-002). Methods: Six-week bile-duct ligated (BDL) and sham rats were used. OP was administered orally by gavage (1g/kg) daily for 5 weeks starting 1 week after surgery. Locomotor activity (day/night) was assessed in infrared beam cages for 24 h. Body weight, fat and lean mass (EchoMRI) were measured. Stable isotope tracers were injected (ip) in order to assess fractional protein synthesis rate (FSR). Blood ammonia and cerebral edema was also evaluaeted. Results: BDL rats demonstrated a 4-fold increase in blood ammonia vs sham-operated controls. This increase was reduced by 40% in OP-treated BDL rats. BDL rats gained less body weight compared to sham-operated controls (body weight of 360.2g ± 13.6 vs 476.8g ± 10.38 p<0.001) which was accompanied with a lower gain of lean mass and a lower muscle FSR. OP-treated BDL rats showed a significant increase in body weight (p<0.001 vs BDL) with a significant higher lean mass (303.1g ± 10.7 in BDL+OP vs 264.4g ± 10.5 in BDL p<0.01). Fat mass remained unchanged between the treated and untreated BDL groups. OP treatment normalized brain water content in BDL rats. In contrast, OP-treatment reduced muscle FSR in SHAM animals, but not in BDL rats. Locomotor activity in BDL rats was reduced compared with sham-operated controls but no significant change was found between BDL+OP and SHAM+OP. Conclusions: This is the first study demonstrating the efficient ammonia-lowering effect of an oral formulation of OP. Long-term treatment with OP is a safe, effective, non-antibiotic alternative demonstrating a significant ammonia-lowering effect, as well as a protective effect on the development of brain edema and muscle mass loss in rats with CLD. Whether the beneficial effect of OP on muscle mass loss is a result of lowering blood ammonia or direct result of OP on muscle metabolism remains to be established.
Rafael Ochoa-Sanchez, Mélanie Tremblay, Mariana Oliveira, Cristina Bosoi, Marc-André Clément, Christopher F. Rose.
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, a major complication of chronic liver disease (CLD, cirrhosis). With an increasing prevalence of obesity-induced cirrhosis and evidence on obesity affecting neurological function, we hypothesize that obesity increases the risk, severity and accelerates the progression of HE in non-alcoholic fatty liver disease (NAFLD)-related cirrhosis. AIM: To develop and characterize an animal model of cirrhosis and obesity to investigate the synergistic effect of obesity and CLD on the development of neurological impairment and HE. M&M: Animal model of CLD and obesity: The 6-week bile-duct ligation (BDL) rat is a surgical model in which obstruction of the bile duct leads to cirrhosis and HE. We induced obesity with a high-fat diet (HFD). Previously, HFD was given after BDL, but it was not well accepted, and the body weight did not increased. Now we are pre-feeding the rats with HFD to see if that is a better model. Thus, rats will be fed HFD for 3 weeks (pre-BDL) and 6 weeks post-BDL. Food consumption, weight gain, as well as lean vs fat mass will be monitored. Preliminary results: 3-week HFD increases body weight (12.1%) and fat (30.5 vs 44.1g) mass compared to rats fed normal diet. Food consumption was decreased (HFD 12g/day vs normal diet 27g/day), while the calorie intake was not affected. Discussion: obesity-induced cirrhosis in patients may result in more complex neurological manifestations, suggesting these patients might be more susceptible to neuronal loss and poor neurological performance. Thus, this animal model of CLD and obesity will give important clues about psychiatric diseases including, HE and how they might be treated. Funded: CIHR
Cristina R. Bosoi, Mariana Oliveira, Marc-André Clément, Mélanie Tremblay, Gabriella A. Ten Have, Nicolaas E. Deutz, Christopher F. *Rose.
Background and Aims: Chronic liver disease (CLD) induces numerous complications including muscle mass loss and hepatic encephalopathy (HE) which negatively impact the clinical outcome. Furthermore, muscle mass wasting and HE have been shown to lead to poor prognosis following liver transplantation. Hyperammonemia is considered the central component in the pathogenesis of HE, however recent studies have suggested ammonia to be toxic to other organs besides the brain, such as the muscle. The aim of this study was to investigate the effect of ammonia on muscle mass in rats treated with an oral formulation of ornithine phenylacetate (OP; OCR-002). Methods: Six-week bile-duct ligated (BDL) and sham rats were used. OP was administered orally by gavage (1g/kg) daily for 5 weeks starting 1 week after surgery. Locomotor activity (day/night) was assessed in infrared beam cages for 24 h. Body weight, fat and lean mass (EchoMRI) were measured, followed by i.p. injection of a stable isotopes tracers cocktail in order to asses fractional synthesis of protein (FSR). Samples for blood ammonia, cerebral edema and muscle FSR were collected. Results: BDL rats demonstrated a 4-fold increase in blood ammonia vs sham-operated controls. This increase was reduced by 40% in OP-treated BDL rats. BDL rats gained less body weight compared to sham-operated controls (body weight of 360.2g ± 13.6 vs 476.8g ± 10.38 p<0.001) which was accompanied with a lower gain of lean mass and a lower muscle FSR. OP-treated BDL rats showed a significant increase in body weight (429.6g ± 117.9 p<0.001 vs BDL) with a significant higher lean mass (303.1g ± 10.7 in BDL+OP vs 264.4g ± 10.5 in BDL p<0.01). Fat mass remained unchanged between the treated and untreated BDL groups. OP treatment normalized brain water content in BDL rats. In contrast, OP-treatment reduced muscle FSR in SHAM animals, but not in BDL rats. Locomotor activity in BDL rats was reduced compared with sham-operated controls but no significant change was found between BDL+OP and SHAM+OP. Conclusions: This is the first study demonstrating the efficient ammonia-lowering effect of an oral formulation of OP. Long-term treatment with OP is a safe, non-antibiotic alternative demonstrating a significant ammonia-lowering effect, as well as a protective effect on the development of brain edema and muscle mass loss in rats with CLD. Whether the effect of OP on muscle mass loss attenuation is a result of lowering blood ammonia or directly improves muscle metabolism remains to be established.
Marc-André Clément, Cristina Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following liver transplantation (LT). However, persisting neurological complications remain a common problem affecting as many as 47% of LT recipients. LT is a major surgical procedure accompanied by intraoperative stress, including blood loss and hypotension. Aim : We hypothesize, in the setting of minimal HE (MHE), the compromised brain becomes susceptible to hypotensive insults, resulting in cell injury and death. Methods: Six-week bile-duct ligated (BDL) rats with MHE and respective controls (SHAM) were used. Blood is withdrawn from the femoral artery (inducing hypovolemia) until a mean arterial pressure of 30, 60 and 90 mmHg (hypotension) and maintained for 120 minutes. Cerebral blood flow (BCF) was assessed by injecting fluorescent microspheres through the brachial artery. Upon sacrifice, brains were extracted for apoptotic analysis (western blot) and neuronal cell count (immunohistochemistry). In a separate group, BDL rats were treated for MHE with ornithine phenylacetate (OP; OCR-002), administered orally (1g/kg) for 3 weeks. Results: Both BDL rats and SHAM-operated controls without hypotension did not display any cell injury or neuronal loss. However, BDL rats following hypotension (30 and 60mmHg) demonstrated a significant decrease in neuronal cell count in the frontal cortex (using NeuN+DAPI and Cresyl Violet) compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cleaved caspase-3, suggesting apoptotic cell death. CBF decreased in BDL rats compared to SHAM and correlated with degree of hypotension insult. BDL rats treated with OP resulted in a decrease in blood ammonia and improvement in behaviour and did not lead to neuronal cell death following hypotension. Discussion: These findings strongly suggest that cirrhotic patients with MHE are more susceptible to hypotension-induced neuronal cell loss. Moreover, these results suggest a patient with HE (even MHE), with a “frail brain”, will fare worse during liver transplantation and consequently result in poor neurological outcome. Combination of MHE and hypotension may account for the persisting neurological complications observed in a number of cirrhotic patients following LT. Therefore, MHE, should not to be ignored and merits to be treated in order to reduce the risk of neurological complications occurring post-LT.
Estudio del efecto de la enoxaparina sobre la cirrosis e hipertensión portal experimental.
Jose Ignacio Fortea, Alexander Zipprich, Carolina Mena Fernandez, Christopher F. Rose, Juan Bañares, Marta Puerto, Cristina R. Bosoi, Jorge Almagro, Marcus Hollenbach, Marc-André Clément, Javier Vaquero, Rafael Bañares, Cristina Ripoll.
INTRODUCCIÓN Y OBJETIVOS: Recientes estudios clínicos y experimentales sugieren que la administración de anticoagulantes podría reducir la fibrosis hepática y prevenir el desarrollo de complicaciones de la cirrosis hepática. Nuestro OBJETIVO fue evaluar los efectos de la enoxaparina sobre la fibrosis y la hemodinámica hepática en varios modelos experimentales de cirrosis. MÉTODOS: Utilizamos tres protocolos de cirrosis experimental en ratas Sprague- Dawley macho: 1) CCl4 oral; 2) CCl4 inhalado; 3) Ligadura del colédoco (LC). Los grupos (n=8-15/grupo) recibieron tratamiento diario con suero salino o con diferentes protocolos de enoxaparina sc: a) 40 U/Kg de peso corporal desde la 8a semana de administración de CCl4, b) 180 U/Kg desde la 1a u 8a semana de CCl4, y c) 180 U/Kg desde la 2a semana tras la LC. Se realizaron las siguientes mediciones: 1) presión portal (vena ileocólica), 2) fibrosis hepática (tinción de rojo Sirio y expresión de los genes Col1a1, Acta2 y Timp1 en hígado), 3) infección de líquido ascítico (cultivo en tioglicolato), 4) respuesta inflamatoria sistémica (niveles circulantes de IL-6), y 5) disfunción endotelial (estudios de perfusión hepática ex-vivo en ratas con cirrosis inducida por inhalación de CCl4). RESULTADOS: En comparación con los grupos control, las ratas con cirrosis inducida por la administración orogástrica de CCl4 mostraron una tendencia a una menor supervivencia y menor ganancia de peso corporal, las cuales fueron agravadas por el tratamiento con enoxaparina a dosis de 180 UI/kg (p<0,01). La administración de CCl4 oral también resultó en la alteración de diversos parámetros analíticos (elevación de INR, AST, ALT, bilirrubina y disminución de albúmina, glucosa y plaquetas), la cual no fue prevenida por el tratamiento con enoxaparina. La administración de enoxaparina no atenuó el aumento de presión portal en las ratas con cirrosis inducida por la administración oral de CCl4 o por la LC respecto a sus correspondientes controles (p<0,001). El desarrollo de fibrosis, la infección del líquido ascítico y los niveles circulantes de IL-6 tampoco fueron influidos por la enoxaparina en ninguno de los modelos. No se observaron efectos de la enoxaparina sobre la reactividad vascular hepática salvo en aquellas ratas que recibieron enoxaparina a dosis de 180 UI/Kg desde el inicio de la administración de CCl4, las cuales presentaron valores más elevados de resistencia venosa hepática con la exposición a dosis crecientes de acetilcolina y de S-nitroso acetilpenicilamina (SNAP, ambos p<0,05), y un incremento de la resistencia sinusoidal tras la adición de SNAP (p<0,05). CONCLUSIONES: La administración crónica de enoxaparina no mejoró la fibrosis hepática, la hipertensión portal o la disfunción endotelial en diversos modelos experimentales de cirrosis hepática avanzada en rata.
Cristina R. Bosoi, Mariana Oliveira, Marc-André Clément, Mélanie Tremblay, Gabrie Ten Have, Nicholaas Deutz, Christopher F. Rose.
Background: Chronic liver disease (CLD) induces numerous complications including muscle mass loss and hepatic encephalopathy (HE) which negatively impact the clinical outcome. Furthermore, muscle mass wasting and HE have been shown to lead to poor prognosis following liver transplantation. Hyperammonemia is considered the central component in the pathogenesis of HE, however recent studies have suggested ammonia to be toxic to other organs besides the brain, such as the muscle. Aims: The aim of this study was to investigate the effect of ammonia on muscle mass in rats treated with an oral formulation of ornithine phenylacetate (OP; OCR-002). Methods: Bile-duct ligated (BDL) rats were divided into 4 experimental groups; 1) Sham; 2) BDL; 3) Sham + OP; 4) BDL + OP. OP was administered orally by gavage (1g/kg) daily for 5 weeks starting 1 week after surgery. Two days before sacrifice, locomotor activity (day/night) was assessed in infrared beam cages for 24 h. The day of the sacrifice, body weight, fat and lean mass (EchoMRI) were measured, followed by i.p. injection of a stable isotopes tracers cocktail (Phe/Gly) in order to asses fractional synthesis of protein (FSR). At sacrifice, samples were collected to measure blood ammonia (commercial kit), cerebral edema (specific gravity method) and muscle FSR. Results : At 6-weeks, BDL rats demonstrated a 4-fold increase in blood ammonia vs Sham-operated controls. This increase was reduced by 40% in OP-treated BDL rats. Body weight decreased in BDL rats compared to sham-operated controls (360.2g±13.6 vs 476.8g±10.4; p<0.001) and significantly increased following OP-treatment (429.6g±117.9; p<0.001 vs BDL). This was due to a higher gain of lean mass in OP-treated BDL rats compared to BDL rats (303.1g±10.7 in BDL+OP vs 264.4g±10.5 in BDL, p<0.01). This was accompanied by increased muscle FSR in OP-treated BDL rats. Fat mass remained unchanged between treated and untreated BDL groups. OP treatment also normalized brain water content in BDL rats. Locomotor activity in BDL rats was reduced compared with sham-operated controls but no significant change was found between BDL+OP and SHAM+OP. Conclusions: This is the first study demonstrating the efficient ammonia-lowering effect of an oral formulation of OP. Moreover, OP long-term treatment is a safe, non-antibiotic alternative with protective effects on the development of cirrhosis complications such as HE and muscle mass loss in rats with CLD. Whether the effect of OP on muscle mass loss attenuation is a result of lowering blood ammonia or directly improves muscle metabolism remains to be established.
Liposome-supported peritoneal dialysis for the treatment of hepatic encephalopathy.
Valentina Agostoni, Soo Hyeon Lee, Vincent Forster, Meriam Kabbaj, Cristina Bosoi, Mélanie Tremblay, Matthias Zadory, Christopher F. Rose, Jean-Christophe Leroux.
Hyperammonemia can lead to cerebral dysfunction, encephalopathy, coma, and death if not treated adequately. The poor prognosis associated with this condition reflects the unmet medical need for effective ammonia-lowering treatments. Here, the translational potential of liposome-supported peritoneal dialysis (LSPD), a recently-developed detoxification strategy for the removal of small ionizable molecules like ammonia, is described. Dialysis fluids supplemented with micrometer-sized, transmembrane pH-gradient liposomes are prepared via an innovative, osmotic shock-based method overcoming sterilization and long-term stability issues. LSPD is able to sequester ammonia in healthy rats in relation to the injected dose, buffering capacity of the liposomal core, and membrane composition. In a rat model of cirrhosis, LSPD outperforms conventional peritoneal dialysis in lowering plasmatic ammonia levels and attenuating brain edema. LSPD does not trigger any hypersensitive reaction in pigs, a side effect commonly observed upon the injection of colloids in this animal model and in humans. These findings support the development of LSPD for the treatment of hyperammonemia-induced encephalopathy.
Leucine et exercices : bénéfique lors d'encéphalopathie expérimentale.
Corine Fontaine, Marc-André Clément, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose, Chantal Bémeur.
Introduction : L’encéphalopathie hépatique (EH) est une complication neuropsychiatrique sérieuse de la maladie hépatique chronique (cirrhose). La pathogénèse de l’EH serait attribuable, entre autres à l’ammoniac. L’accumulation de cette neurotoxine jouerait un rôle clé. De plus, la malnutrition est associée à un risque élevé de développer une perte sévère de masse musculaire et à l’EH; ces complications augmentent le risque de mortalité. La déficience en leucine, a été démontrée lors de cirrhose. La leucine sert de substrat énergétique et de précurseur pour d’autres acides aminés en plus de stimuler la synthèse protéique. De plus, l’expression de mammalian target of rapamycin (mTOR) et sa cible p70S6 kinase, deux protéines impliquées dans de nombreuses réactions en lien avec la survie cellulaire, serait altérée dans le muscle lors de maladie hépatique chronique. Une masse musculaire optimale lors d’EH contribuerait à réduire l’ammoniac via l’enzyme glutamine synthase (GS). L’hypothèse de recherche est que l’optimisation de la masse musculaire permet de prévenir/atténuer les épisodes d’EH. Matériel et méthode: Un modèle deligature des voies biliaires (BDL) chez le rat qui récapitule les caractéristiques de la cirrhose et de l’EH est utilisé. Cinq groupes sont évalués: 1) Contrôle avec simulation de la chirurgie (Sham); 2) BDL; 3) BDL+ Leucine; 4) BDL + Exercices; 5) BDL + Leucine + Exercices. Six semaines post-chirurgie, l’EH est vérifiée par des tests comportementaux et phénotypage neurologique. La masse musculaire est évaluée par imagerie par résonance magnétique. Les rats sont ensuite sacrifiés et les muscles sont prélevés. L’expression protéique de mTOR et de p70S6 kinase est mesurée par immunobuvardage. Résultats: Chez le groupe BDL, on remarque une baisse de la masse musculaire et de la synthèse protéique comparativement au groupe Sham. La supplémentation en leucine et l’exercice favorise une augmentation de la masse musculaire chez les rats BDL. La voie de signalisation via mTOR semble moins exprimée dans le muscle du groupe BDL versus Sham. Conclusion: Dans le but d’optimiser le statut nutritionnel et d’améliorer la qualité de vie des patients cirrhotiques atteints d’EH, des recherches plus approfondies devront être effectuées.
Cristina R. Bosoi, Mariana Oliveira, Marc-André Clément, Mélanie Tremblay, Gabrie Ten Have, Nicolaas E. P. Deutz, Christopher F. Rose.
Background: Chronic liver disease (cirrhosis; CLD) is characterized by numerous metabolic disturbances which lead to complications that impact the clinical outcome. Among these, loss of muscle, characterized by a deterioration of muscle quantity and quality, leads to a decrease in functional capacity, adversely affecting survival, quality of life and outcome following liver transplantation. Hyperammonemia is central in the development of hepatic encephalopathy, a major complication of cirrhosis. However, it is speculated the toxic effect of ammonia extends beyond the brain, possibly affecting muscle. Therefore, we hypothesized that lowering blood ammonia will attenuate muscle mass loss in cirrhotic rats. Ornithine phenylacetate (OP; OCR-002) was used to lower blood ammonia. Methods: We induced CLD in rats following 6-week bile-duct ligation (BDL). Four experimental groups were tested; 1) Sham; 2) BDL; 3) Sham + OP; 4) BDL + OP. One week following BDL, rats were orally administered (gavage) OP (1g/kg) daily for 5 weeks. Body weight, fat and lean mass (EchoMRI), blood ammonia, cerebral edema (specific gravity method), fractional synthesis of protein (FSR) in muscle (with D2O) and locomotor activity (day/night) were measured. Results: At the end of the 6-weeks experiment, BDL rats demonstrated a 4-fold increase in blood ammonia vs Sham-operated controls. This increase was reduced by 40% in OP-treated BDL rats. BDL rats gained less body weight compared to sham-operated controls (body weight of 360.2g 13.6 vs 476.8g 10.38; p<0.001) which was accompanied with a lower gain of lean mass and a lower muscle FSR. OP-treated BDL rats showed a significant increase in body weight (429.6g 117.9; p<0.001 vs BDL) with a significant higher lean mass (303.1g 10.7 in BDL+OP vs 264.4g 10.5 in BDL, p<0.01). Fat mass remained unchanged between the treated and untreated BDL groups. OP treatment normalized brain water content in BDL rats. In contrast, OP-treatment reduced muscle FSR in SHAM animals, but not in BDL rats. Locomotor activity in BDL rats was reduced compared with sham-operated controls but no significant change was found between BDL+OP and SHAM+OP. Conclusion: This is the first study demonstrating the efficient ammonia-lowering effect of an oral formulation of OP. Long-term treatment with OP is a safe, non-antibiotic alternative demonstrating a significant ammonia-lowering effect, as well as a protective effect on the development of brain edema and muscle mass loss in rats with CLD. Whether the effect of OP on muscle mass loss attenuation is a result of lowering blood ammonia or directly improves muscle metabolism remains to be established.
Minimal hepatic encephalopathy leads to hypotension-induced neuronal cell loss in BDL rats.
Marc-André Clément, Cristina Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. The only curative treatment to date remains liver transplantation (LT). Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following LT. However, persisting neurological complications remain a common problem affecting as many as 47% of LT recipients. LT is a major surgical procedure accompanied by intraoperative stress and confounding factors, including blood loss and hypotension. We hypothesize, in the setting of minimal HE (MHE), the compromised brain becomes susceptible to hypotensive insults, resulting in cell injury and death. Methods: Six-week bile-duct ligated (BDL) rats with MHE and respective controls (SHAM) were used. Blood is withdrawn from the femoral artery (inducing hypovolemia) until an mean arterial pressure of 30 and 60 mmHg (hypotension) and maintained for 120 minutes. Cerebral blood flow (BCF) was assessed by injecting fluorescent microspheres (1x106 microspheres/ml) through the brachial artery. Upon sacrifice, brains were extracted for apoptotic analysis (western blot) and neuronal cell count (immunohistochemistry). In a separate group, BDL rats were treated for MHE with ornithine phenylacetate (OP; OCR-002) (1g/kg) for 3 weeks. Results: Both BDL rats and SHAM-operated controls without hypotension did not display any cell injury or neuronal loss. However, BDL rats following hypotension (30 and 60mmHg) demonstrated a significant decrease in neuronal cell count in the frontal cortex (using NeuN+DAPI and Cresyl Violet) compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cellular stress protein, hsp32, hsp70 and caspase-3, suggesting apoptotic cell death. CBF decreased in BDL rats compared to SHAM and correlated with degree of hypotension insult. BDL rats treated with OP did not lead to neuronal cell death following hypotension. Discussion: These findings strongly suggest that cirrhotic patients with MHE are more susceptible to hypotension-induced neuronal cell loss. Moreover, these results suggest a patient with HE (even MHE), with a “frail brain”, will fare worse during liver transplantation and consequently result in poor neurological outcome. Combination of MHE and hypotension may account for the persisting neurological complications observed in a number of cirrhotic patients following LT. Therefore, MHE, i) should not to be ignored and ii) deserves to be treated in order to reduce the risk of neurological complications occurring post-LT.
Jose Ignacio Fortea, Alexander Zipprich, Carolina-Mena Fernandez, Christopher F. Rose, Juan Bañares, Marta Puerto, Cristina R. Bosoi, Jorge Almagro, Marcus Hollenbach, Marc-André Clément, Javier Vaquero, Rafael Bañares, Cristina Ripoll.
Recent clinical and experimental studies suggest that the administration of low molecular weight heparin may reduce the risk of decompensation of liver disease and liver fibrosis. Our aim was to evaluate the effects of enoxaparin on liver fibrosis and hemodynamics in several experimental models of cirrhosis. Methods: Cirrhosis was induced in male SD rats using 3 protocols: 1) Oral gavage with carbon tetrachloride (CCl4) twice a week for 12 weeks, 2) Inhalation of CCl4 twice a week for 12 weeks, and 3) Bile duct ligation (BDL) surgery. Rats (n= 8-15/group) underwent daily sc treatment with saline or diverse protocols of enoxaparin: 40 U/kg bw from 8th week of CCl4, 180 U/kg bw from 1st week or 8th week of CCl4, and 180 U/kg from 2nd week of BDL. Control groups of rats gavaged with water or sham-operated rats followed the same protocols. Portal pressure was measured in the ileocolic vein, liver fibrosis was assessed in Sirius Red and Masson’s Trichrome stained liver sections. Ascitic fluid was evaluated for bacterial growth in thioglycolate medium. Ex-vivo liver perfusion experiments were performed for assessing endothelium-dependent and -independent reactivity. Results: Compared with controls, rats with oral CCl4 gavage tended to show decreased survival and body weight gain, both of which were further worsened by enoxaparin 180 U/kg bw (p< 0.01). Rats with CCL4-induced cirrhosis showed altered laboratory parameters (increased INR, AST, ALT, bilirubin / decreased albumin, total proteins, glucose and platelets) regardless of enoxaparin treatment. In all experimental models, cirrhotic rats receiving saline and those receiving enoxaparin showed similar increases in the area of liver fibrosis compared with controls (p< 0.001). Rats with cirrhosis induced by oral CCl4 gavage and by BDL surgery developed increases of portal pressure and spleen-to-bw ratios compared with control rats (p< 0.001), regardless of enoxaparin treatment. Among rats with ascites, a similar proportion presented positive bacterial cultures (CCl4+saline 2 of 7 vs. CCl4+enoxaparin 4 of 8, NS; BDL+saline 1 of 6 vs. BDL+enoxaparin 2 of 7, NS). Potential effects of enoxaparin on hepatic vascular reactivity were only observed in rats receiving enoxaparin 180 U/kg bw from the beginning of CCl4 administration, and consisted of increased portal venous resistance after addition of acetylcholine or S-nitroso acetyl-penicillamine (SNAP, both p< 0.05) and increased sinusoidal resistance after addition of SNAP (p< 0.05). Conclusion: Our experimental data do not support a role of long-term treatment with enoxaparin for improving liver fibrosis, portal hypertension or endothelialdysfunction in cirrhosis.
Liposome-Supported Peritoneal Dialysis in the Treatment of Severe Hyperammonemia.
Valentina Agostoni, Vincent Forster, Cristina Bosoi, Mélanie Tremblay, Christopher Rose, Jean-Christophe Leroux.
Purpose: Hyperammonemia (HA) is a clinical condition characterized by toxic increases in systemic ammonia levels predominantly resulting from inherited or acquired impairments in hepatic detoxification (e.g. cirrhosis). If not treated, HA can lead to irreversible brain damages and death in severe cases. The poor prognosis associated to this condition reflects the still unmet clinical need for a safe, fast, and efficient ammonia-removal therapy. Hemodialysis, the current standard of care for treating severe HA, suffers indeed some major drawbacks as it is technically difficult to implement, not readily available in hospitals and highly risky for some patients (e.g., newborns and patients suffering from hemodynamic instability). Peritoneal dialysis (PD) may represent a valuable therapeutic alternative as it is a less invasive procedure since it uses the peritoneum as a semipermeable filter and the peritoneal cavity as a dialysis chamber. However, its clinical application is limited by its lower clearance capacity compared with hemodialysis. To address this problem, we report herein a novel dialysis fluid based on transmembrane pH-gradient liposomes (acidic core) that efficiently scavenge the excess of ammonia from the body. The ammonia-removal efficacy of this system was assessed in a rat model of cirrhosis induced by bile duct ligation. The cirrhotic rats develop hyperammonemia, and consequently brain edema. Methods: Liposome-supplemented peritoneal dialysis (LSPD) fluids (350 mOsm/L, pH 6.5), were prepared by sequentially mixing sterile liposomes aqueous suspensions, obtained by film hydration method, with a hypertonic acidic citrate buffer (pH 2) and an isotonic xylitol-based basic solution (pH 12.4). The first step allowed the encapsulation of an acidic medium in the vesicles core by means of an osmotic shock; the second established the transmembrane pH-gradient. Dose-response studies were first performed in healthy Sprague-Dawley rats by injecting LSPD fluids (60 mL/kg) with increasing liposome concentrations (4, 8 and 16 mM) in the peritoneal space, and evaluating their ammonia extraction efficiency over 4 h of dialysis. Efficacy studies were then performed in a rat model of secondary biliary cirrhosis induced by bile duct ligation. Control normal rats (SHAM) underwent a sham operation. Five weeks after the surgery, two different groups of cirrhotic rats (LSPD and PD) received 4 consecutive PDs performed every other day with LSPD or a conventional glucose-based PD solution (injected dose = 50 mL/kg). One group (positive control) did not receive any treatment. At the end of the study, the brain edema was assessed by measuring the brain water content in the frontal cortex by densitometry method. The ammonia concentration in dialysate and plasma samples was determined by enzymatic method using a commercial kit. Results: LSPD was shown to efficiently scavenge ammonia in the peritoneal space of healthy rats in a dose-dependent manner. The extracted ammonia levels progressively increased over time reaching a concentration of 0.48 ± 0.05 mM, 1.25 ± 0.2 mM and 1.72 ± 0.24 mM in fluids supplemented with liposomes 4, 8 and 16 mM, respectively. In light of these results, the LSPD fluid 8 mM, which exhibited a good ammonia uptake, was tested in a cirrhotic rat model. Compared to the control PD solution, the liposomal formulation showed an enhanced ammonia extraction capability. At the end of each dialysis session, the ammonia concentrations in the liposome-supplemented dialysate exceeded those obtained with the control solution by 7-fold. Importantly, this improved ammonia clearance led to a significant attenuation of the brain edema. Indeed after four consecutive LSPDs, the brain water content of cirrhotic rats was significantly decreased and reverted to normal levels. On the contrary, no significant reduction was observed with the control solution. Plasma ammonia levels were also found to significantly decrease after treatment with LSPD fluid but not with the control PD solution. Conclusion: These findings demonstrate that LSPD is a promising strategy to improve the clearance capacity of PD towards ammonia, and pave the way for a less invasive, safe and efficient approach for treating severe HA. Financial support from the Swiss Commission for Technology and Innovation (17525.1 PFLS-LS) is acknowledged.
Marc-André Clément, Cristina R. Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Introduction L’encéphalopathie hépatique (EH) est une complication neuropsychiatrique causée par les maladies du foie. Ce syndrome est considéré comme un désordre métabolique réversible, qui devrait être réglé par la transplantation hépatique (TH), cependant les complications neurologiques persistent chez près de 47% des patients. La TH est une procédure accompagnée de stress intra-opératoires dont l’hypovolémie et l’hypotension. Nous supposons que le cerveau fragilisé devient plus susceptible à une hypotension, résultant en un stress ainsi que la mort cellulaire. Méthodologies Une hypotension par hypovolémie de l’artère fémorale est effectuée pour atteindre une pression artérielle de 30mmHg durant 2 heures chez des rats de 6 semaines avec ligation de la voie biliaire (BDL) et leurs contrôles respectifs (SHAM). Les cerveaux sont prélevés pour immunobuvardage et immunohistochimie. Résultats Les rats BDL avec hypotension ont démontré une diminution du compte neuronal dans le cortex préfrontal en utilisant NeuN+DAPI et le Crésyl violet, comparativement aux contrôles SHAM hypotendus. De plus, la protéine de stress cellulaire HSP32 est augmentée chez les groupes BDL hypotendus, tout comme la caspase-3 clivée, suggérant une mort cellulaire par apoptose. Les groupes contrôles sans hypotension ne démontrent aucune perte neuronale avec les marqueurs précédents. Discussion Ces résultats démontrent que les patients atteints d’EH sont plus susceptibles à une insulte hypotensive induisant une mort neuronale, et peuvent expliquer pourquoi certains patients ayant reçu une TH expérimentent des complications neurologiques.
Marc-André Clément, Cristina R. Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. The only curative treatment to date remains liver transplantation (LT). Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following LT. However, even following the implantation of a new liver, persisting neurological complications remain a common problem affecting as many as 47% (8 47%) of liver transplant recipients. LT is a major surgical procedure accompanied by intraoperative stress and confounding factors, including blood loss (hypovolumia) and hypotension. We hypothesize, in the setting of MHE, that the compromised brain becomes predisposed to what would normally be an innocuous hypotensive insult, resulting in cell injury and death. Methods: Six-week bile-duct ligated (BDL) rats with MHE and respective controls will be used. Blood is withdrawn from the femoral artery (inducing hypovolemia) until an arterial pressure of 30 mmHg (hypotension) and maintained for 150 minutes. Upon sacrifice, brains are perfused and extracted for apoptotic analysis (western blot) and neuronal cell count (immunohistochemistry). Results: Both BDL rats and SHAM-operated controls without hypotension do not display any neuronal loss. However, BDL rats following hypotension demonstrated a significant decrease in neuronal cell count in the frontal cortex using NeuN+DAPI and Cresyl Violet compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cellular stress protein, hsp32, hsp70 and caspase-3, suggesting apoptotic cell death. Discussion: These findings suggest that patients with MHE are more susceptible to hypotension-induced neuronal cell loss. Moreover, these results suggest a patient with HE (even MHE), with a “frail brain”, will fare worse during LT and consequently result in poor neurological outcome. The combination of MHE and hypotension may justify for the persisting neurological complications observed in a number of cirrhotic patients following LT. This implies the impact of MHE on outcome is undervalued. MHE should not to be ignored and patients with MHE merit to be treated pre-LT.
Marc-André Clément, Cristina R. Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. The only curative treatment to date remains liver transplantation (LT). Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following LT. However, even following the implantation of a new liver, persisting neurological complications remain a common problem affecting as many as 47% (8 47%) of liver transplant recipients. LT is a major surgical procedure accompanied by intraoperative stress and confounding factors, including blood loss (hypovolumia) and hypotension. We hypothesize, in the setting of MHE, that the compromised brain becomes predisposed to what would normally be an innocuous hypotensive insult, resulting in cell injury and death. Methods: Using 6-week bile-duct ligated rats and respective controls, blood is withdrawn from the femoral artery (inducing hypovolemia) until an arterial pressure of 30 mmHg (hypotension) and maintained for 150 minutes. Upon sacrifice, brains are perfused and extracted for western blotting and immunohistochemistry. Results: Both BDL rats and SHAM-operated controls without hypotension do not display any neuronal loss. However, BDL rats following hypotension demonstrated a significant decrease in neuronal cell count in the frontal cortex using NeuN+DAPI and Cresyl Violet compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cellular stress protein, hsp32 and caspase-3, suggesting apoptotic cell death. Discussion: These findings suggest that patients with HE are more susceptible to hypotension-induced neuronal cell loss and this may explain why transplanted patients are experiencing persisting neurological complications. Aside from cirrhotic patients having a stroke, these results also suggest a patient with HE (even MHE) with a “frail brain”, fare worse during transplantation leading to poor neurological outcome. This implies MHE should not be ignored and therefore treated pre-LT.
Muscle mass optimization prevents experimental hepatic encephalopathy.
Sara Ghezzal, Marc-André Clément, Cristina R. Bosoi, Roxanne Beauchamp, Mélanie Tremblay, Christopher F. Rose, Chantal Bémeur.
Background: Malnutrition is an important prognostic factor potentially influencing clinical outcome of patients suffering from chronic liver disease (cirrhosis; CLD). Malnutrition exacerbates severe muscle loss and hepatic encephalopathy (HE) in cirrhotic patients. New management strategies focussing on improving nutritional status and attenuating CLD-related complications are an unmet clinical need. Aims: We hypothesize supplementation with branched-chain amino acid leucine (LEU) and exercise training (EX) could possibly attenuate muscle mass loss and prevent HE (characterized by brain edema as well as cognitive and psychomotor impairments) in CLD. Methods: CLD was induced in rats following 6-week bile-duct ligation (BDL). Five experimental groups were tested; 1) BDL; 2) BDL + LEU; 3) BDL + EX; 4) BDL + LEU + EX; 5) Sham-operated rats. One week following BDL, rats were submitted to 15 min EX (10 cm/s) every other day and BDL rats receiving LEU, were gavaged daily (1.35 mg/kg) for five weeks. Body weight, muscle (gastrocnemius) mass, metabolic state (calculation of energy expenditure independent of food intake and fecal mass), cerebral edema (specific gravity method) and cognitive/psychomotor function (open-field test; anxiety-like behavior assessment and novel object recognition test; memory testing) were measured in all groups. Results: BDL rats gained less body weight compared to sham-operated rats (125.0±24.9 g vs 226.0±38.5 g; P<0.05). LEU-treated BDL rats display an improvement in brain edema (78.50±0.03% vs 80.27±0.14%; P<0.05), muscle mass (5.48±0.90 g/kg vs 4.83±0.11 g/kg; P<0.05) and circumference (15.6±0.8 cm/kg vs 13.1±0.7 cm/kg ; P<0.05) and metabolic activity (27.48±1.15 vs 32.99±2.35; P<0.05), which was further ameliorated with EX, compared to BDL animals. In addition, BDL rats receiving LEU and EX exhibited less anxiety-like behavior (4.9±1.2 s vs 2.2±0.9 s passed in the center; P<0.01) as well as better novel object recognition memory (69.6±15.2% vs 25.4±9.6%; P<0.01), in comparison with BDL rats. Conclusions: Our results demonstrate that supplemental LEU along with EX reduces body weight and muscle mass loss, improves metabolic activity, attenuates brain edema and improve cognitive and psychomotor function. These findings suggest that strategies aiming at improving nutritional status will attenuate muscle mass loss, reduce the risk of developing HE and therefore improve quality of life and decrease mortality in CLD. LEU supplementation and EX could rapidly be translated into clinical practice. Funding Agency: CIHR.
Marc-André Clément, Cristina R. Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Introduction L’encéphalopathie hépatique (EH) est une complication neuropsychiatrique causée par les maladies du foie. Ce syndrome est considéré comme un désordre métabolique réversible, qui devrait être réglé par la transplantation hépatique (TH), cependant les complications neurologiques persistent chez près de 47% des patients. La TH est une procédure accompagnée de stress intra-opératoires dont l’hypovolémie et l’hypotension. Nous supposons que le cerveau fragilisé devient plus susceptible à une hypotension, résultant en un stress ainsi que la mort cellulaire. Méthodologies Une hypotension par hypovolémie de l’artère fémorale est effectuée pour atteindre une pression artérielle de 30 mmHg durant 2 heures chez des rats de 6 semaines avec ligation de la voie biliaire (BDL) et leurs contrôles respectifs (SHAM). Les cerveaux sont prélevés pour immunobuvardage et immunohistochimie. Résultats Les rats BDL avec hypotension ont démontré une diminution du compte neuronal dans le cortex préfrontal en utilisant NeuN+DAPI et le Crésyl violet, comparativement aux contrôles SHAM hypotendus. De plus, la protéine de stress cellulaire HSP32 était augmentée chez les groupes BDL hypotendus, tout comme la caspase-3 clivée, suggérant une mort cellulaire par apoptose. Les groupes contrôles SHAM et BDL sans hypotension ne démontrent aucune perte neuronale avec les marqueurs précédents.
Jimmy Huynh, Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Brain edema is a serious complication associated with hepatic encephalopathy (HE) due to chronic liver disease (CLD). An increase in blood brain barrier (BBB) ion permeability can occur across an intact BBB through alterations in transport mechanisms. NH4+ has very similar ionic properties to K+ and can be transported through K+ channels and cotransporters, implying that hyperammonemia could result in BBB hyperpermeability. An increase in BBB permeability via transport Na+-K+-2Cl- (NKCC1) has shown to promote brain edema and astrocyte swelling under pathophysiological conditions such as ischemia. Aim: To study the BBB integrity (vasogenic vs cytotoxic) and the role of NKCC1 in the pathogenesis of brain edema in cirrhotic rats. Methods: Two distinct animal models of HE are used in the present study; 1) biliary cirrhosis model (6 weeks bile duct ligation (BDL)). 2) portacaval shunt model (4 weeks portacaval anastomosis (PCA)). Both models develop hyperammonemia however brain edema is only observed in BDL. BBB breakdown was assessed by measuring brain extravasation of Evans blue and sodium fluorescein (injected i.v). Expression of BBB tight junction proteins (occludin, claudin-5, ZO-1 and ZO-2) were assessed by Western blot. Bumetanide was administered (i.p) for 10 days in BDL and SHAM animals. Brain water content was measured in the frontal cortex using the specific gravimetric method. Levels of brain NKCC1 mRNA were evaluated by RT-PCR in cerebral microvessels. Results: Extravasation of Evans blue and sodium fluorescein was not detected and no significant change in all tight junction protein was observed in both BDL and PCA models. Brain water content was reduced in bumetanide-treated BDL rats compared to control (77.66±0.15% vs 78.12±0.21%). In brain microvessels, NKCC mRNA increased in BDL rats compared to BDL SHAM (0.78±0.09 vs. 1.92±0.42) whereas no change was found in PCA compared to PCA SHAM (1.72±0.52 vs. 1.53±0.23). Conclusions: BDL rats did not demonstrate a change in BBB integrity or expression of tight junction proteins concluding brain edema in BDL is not of vasogenic origin. Furthermore, since brain edema was only observed in BDL rats (vs PCA), this implies additional factors aside ammonia, are involved in the pathogenesis of brain edema. Moreover, an increase of NKCC1 mRNA and an attenuation of brain edema following bumetanide treatment were demonstrated in BDL rats suggesting NKCC1 plays a role in the development of brain edema in CLD. These results demonstrate the potential therapeutic use of bumetanide for the treatment of HE.
Optimizing muscle mass: therapeutic target to prevent experimental hepatic encephalopathy.
Chantal *Bémeur, Sara Ghezzal, Marc-André Clément, Cristina R. Bosoi, Roxanne Beauchamp, Mélanie Tremblay, Christopher F. Rose, Chantal Bémeur.
Background: Malnutrition is an important prognostic factor potentially influencing clinical outcome of patients suffering from chronic liver disease (cirrhosis; CLD). Malnutrition, considered a consequence of metabolic disturbances (hypermetabolism), exacerbates severe muscle loss and hepatic encephalopathy (HE) (complex neuropsychiatric disorder) in cirrhotic patients. New management strategies focussing on improving nutritional status and attenuating CLD-related complications are an unmet clinical need. We hypothesize supplementation with branched-chain amino acid leucine (LEU) and exercise training (EX) could possibly attenuate muscle mass loss and prevent HE (characterized by brain edema as well as cognitive and psychomotor impairments) in CLD. Methods: CLD was induced in rats following 6-week bile-duct ligation (BDL). Five experimental groups were tested; 1) BDL; 2) BDL + LEU; 3) BDL + EX; 4) BDL + LEU + EX; 5) Sham-operated rats. One week following BDL, rats were gavaged with LEU (1.35 mg/kg) daily and submitted to 15 min EX (10 cm/s) every other day for 5 weeks. Body weight, muscle (gastrocnemius) mass, metabolic state (calculation of energy expenditure independent of food intake and fecal mass), cerebral edema (specific gravity method) and cognitive/psychomotor function (open-field test; anxiety-like behavior assessment and novel object recognition test; memory testing) were measured. Results: BDL rats gained less body weight compared to sham-operated rats (125.0g ± 24.9 vs 226.0g ± 38.5; p<0.05). LEU-treated BDL rats display an improvement in brain edema (78.50% ± 0.03 vs 80.27% ± 0.14; p<0.05), muscle mass (5.48g/kg ± 0.90 vs 4.83g/kg ± 0.11; p<0.05) and circumference (15.6cm/kg ± 0.8 vs 13.1cm/kg ± 0.7; p<0.05) and metabolic activity (27.48 ± 1.15 vs 32.99 ± 2.35; p<0.05), which was further ameliorated with EX, compared to BDL animals. In addition, BDL rats receiving LEU and EX exhibited less anxiety-like behavior (4.9s ± 1.2 vs 2.2s ± 0.9 passed in the center; p<0.01) as well as better novel object recognition memory (69.6 ± 15.2% vs 25.4 ± 9.6%; p<0.01), in comparison with BDL rats. Conclusion: Our results demonstrate that supplemental LEU along with EX recovers body weight loss, increases muscle mass, improves metabolic activity, attenuates brain edema and improves cognitive and psychomotor function. These findings suggest that strategies aiming at improving nutritional status will attenuate muscle mass loss and reduce the risk of developing HE. This in turn will improve quality of life, decrease mortality and enhance outcome post-liver transplantation. LEU supplementation and EX could rapidly be translated into clinical practice.
Cristina R. Bosoi, Marc-André Clément, Mélanie Tremblay, Christopher F. Rose.
Background: Ammonia plays a major role in the pathogenesis of hepatic encephalopathy (HE) and therefore ammonia-lowering treatments remain a primary therapeutic strategy. Glutamine deamidation by the mitochondrial enzyme glutaminase (GLS) is believed to a major source of ammonia production in cirrhotic patients and increased intestinal GLS activity has been shown to be linked to minimal HE and to an increased risk of developing overt HE. CB-839 is a potent, selective and orally bioavailable GLS inhibitor (Gross et al., Mol Cancer Ther 13:890) that is currently in Phase 1 clinical trials for the treatment of cancer (clinicaltrials.gov). Aim: To evaluate the effect of CB-839, a GLS inhibitor, in preventing the onset of hyperammonemia following an oral glutamine challenge (OGC) in rats with portacaval anastomosis (PCA). Methods: Four week PCA rats received a single dose of CB-839 (gavage, 200 mg/kg diluted in 5ml/kg of vehicle). Control PCA rats received equivalent volumes of vehicle. Four hours after CB-839 or vehicle administration, PCA rats received an oral glutamine challenge (gavage, 100 mg/kg). Repeated aortic blood samples were obtained at baseline, 0.5h, 1h, 1.5h, 2.5h, 2.5h, 3h and 4h following OGC. Glutamine and ammonia were measured using commercial available kits. Results: Baseline ammonia levels were similar in both PCA groups. Following OGC, blood ammonia increased in vehicle-treated PCA rats with a peak at 2h (2.3-fold increase vs baseline, p<0.05). In CB-839 treated-PCA rats, ammonia levels did not change compared to the baseline value and were significantly decreased compared to non-treated PCA rats (p<0.05). At 4h, ammonia levels returned to baseline values in both groups. Baseline glutamine levels were not significantly different between treated and non-treated PCA rats. Following OGC, no significant difference between glutamine levels was observed in non-treated PCA rats compared to baseline values. However, in PCA rats treated with CB-839 glutamine levels significantly increased compared to non-treated PCA controls attaining a peak at 2.5 h (1.59 ± 0.40 mM vs 0.60 ± 0.15 mM, p<0.05). At 4h, glutamine levels remained significantly increased. Conclusions: CB-839 treatment inhibited glutamine induced hyperammonemia in PCA rats. These preliminary results strongly suggest CB-839 is an effective agent to attenuate GLS-induced ammonia production. Further studies are warranted to evaluate CB-839 as a novel agent for the treatment of HE.
Marc-André Clément, Cristina Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.
Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. The only curative treatment to date remains liver transplantation (LT). Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following LT. However, even following the implantation of a new liver, persisting neurological complications remain a common problem affecting as many as 47% (8 47%) of liver transplant recipients. LT is a major surgical procedure accompanied by intraoperative stress and confounding factors, including blood loss (hypovolumia) and hypotension. We hypothesize, in the setting of MHE, that the compromised brain becomes predisposed to what would normally be an innocuous hypotensive insult, resulting in cell injury and death. Methods: Using 6-week bile-duct ligated rats and respective controls, blood is withdrawn from the femoral artery (inducing hypovolemia) until an arterial pressure of 30 mmHg (hypotension) and maintained for 150 minutes. Upon sacrifice, brains are perfused and extracted for western blotting and immunohistochemistry. Results: Both BDL rats and SHAM-operated controls without hypotension do not display any neuronal loss. However, BDL rats following hypotension demonstrated a significant decrease in neuronal cell count in the frontal cortex using NeuN+DAPI and Cresyl Violet compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cellular stress protein, hsp32, hsp70 and caspase-3, suggesting apoptotic cell death. Discussion: These findings suggest that patients with HE are more susceptible to hypotension-induced neuronal cell loss and this may explain why transplanted patients are experiencing persisting neurological complications. Aside from cirrhotic patients having a stroke, these results also suggest a patient with HE (even MHE) with a “frail brain”, fare worse during transplantation leading to poor neurological outcome. This implies MHE should not be ignored and therefore treated pre-LT.
Chantal *Bémeur, Sara Ghezzal, Marc-André Clément, Cristina R. Bosoi, Roxanne Beauchamp, Mélanie Tremblay, Christopher F. Rose, Chantal Bémeur.
Background: Malnutrition is an important prognostic factor potentially influencing clinical outcome of patients suffering from chronic liver disease (cirrhosis; CLD). Malnutrition, considered a consequence of metabolic disturbances (hypermetabolism), exacerbates severe muscle loss and hepatic encephalopathy (complex neuropsychiatric disorder) in cirrhotic patients. New management strategies focussing on improving nutritional status and attenuating CLD-related complications are an unmet clinical need. We hypothesize supplementation with branched-chain amino acid leucine (LEU) and exercise training (EX) could possibly attenuate muscle mass loss and prevent hepatic encephalopathy (characterized by brain edema as well as cognitive and psychomotor impairments) in CLD. Methods: CLD was induced in rats following 6-week bile-duct ligation (BDL). Five experimental groups were tested; 1) BDL; 2) BDL + LEU; 3) BDL + EX; 4) BDL + LEU + EX; 5) Sham-operated rats. One week following BDL, rats were submitted to 15 min EX (10 cm/s) every other day and BDL rats receiving LEU, were gavaged daily (1.35 mg/kg) for 5 weeks. Body weight, muscle (gastrocnemius) mass, metabolic state (calculation of energy expenditure independent of food intake and fecal mass), cerebral edema (specific gravity method) and cognitive/psychomotor function (open-field test; anxiety-like behavior assessment and novel object recognition test; memory testing) were measured in all groups. Results: BDL rats gained less body weight and muscle mass compared to sham-operated rats. LEU-treated BDL rats display an improvement in brain edema, muscle mass and circumference and metabolic activity, which was further ameliorated with EX. In addition, BDL rats receiving LEU and EX exhibited less anxiety-like behavior as well as better novel object recognition memory. Conclusion: Our results demonstrate that supplemental LEU along with EX reduces body weight and muscle mass loss, improves metabolic activity, attenuates brain edema and improve cognitive and psychomotor function. These findings suggest that strategies aiming at improving nutritional status will attenuate muscle mass loss, reduce the risk of developing hepatic encephalopathy and therefore improve quality of life and decrease mortality in CLD. LEU supplementation and EX could rapidly be translated into clinical practice.
Jimmy Huynh, Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Brain edema is a serious complication associated with hepatic encephalopathy (HE) due to chronic liver disease. An increase in BBB ion permeability (increase uptake of ions and accompanied by water fluxes towards the brain) can occur across an intact BBB through alterations in transport mechanisms. Endothelial cells that comprise the BBB secrete up to 40% of brain interstitial fluid as they transport Na+, K+ and 2 Cl- across the BBB. NH4+ has very similar ionic properties to K+ (similar ionic radius and diffusion coefficient) and can be transported through K+ channels and cotransporters, implying that hyperammonemia could result in BBB hyperpermeability. An increase in BBB permeability via transport Na+-K+-2Cl- (NKCC1) has shown to promote brain edema and astrocyte swelling under pathophysiological conditions such as ischemia. Aim: To study the BBB integrity (vasogenic vs cytotoxic) and the role of NKCC1 in the pathogenesis of brain edema in cirrhotic rats. Methods: Two distinct animal models of chronic liver failure and HE are used in the present study; 1) biliary cirrhosis model (6 weeks bile duct ligation (BDL)). 2) portacaval shunt model (4 weeks portacaval anastomosis (PCA)). Both models develop hyperammonemia however brain edema is only observed in BDL. BBB breakdown was assessed by measuring brain extravasation of Evans blue and sodium fluorescein (injected i.v). Expression of BBB tight junction proteins (occludin, claudin-5, ZO-1 and ZO-2) were assessed by Western blot. Bumetanide was administered (i.p) for 10 days in BDL and BDL SHAM. Brain water content was measured in the frontal cortex using the specific gravimetric method. Levels of brain NKCC1 mRNA were evaluated by RT-PCR in cerebral microvessels. Results: Extravasation of Evans blue and sodium fluorescein was not detected and there was no significant change in all tight junction protein levels measured in both BDL and PCA models. Brain water content was reduced in bumetanide-treated BDL rats compared to control (77.66±0.15% vs 78.12±0.21%). In brain microvessels, NKCC mRNA increased in BDL rats compared to BDL SHAM (0.78±0.09 vs. 1.92±0.42) whereas no change was found in PCA compared to PCA SHAM (1.72±0.52 vs. 1.53±0.23). Conclusions: BDL rats did not demonstrate a change in BBB integrity or in expression of BBB tight junction proteins. This suggests brain edema in BDL is not of vasogenic origin. Furthermore, since brain edema was only observed in BDL rats (vs PCA), this implies additional factors aside ammonia, are involved in the pathogenesis of brain edema. Moreover, an increase of NKCC1 mRNA and an attenuation of brain edema following bumetanide treatment were demonstrated in BDL rats suggesting NKCC1 plays a role in the development of brain edema in chronic liver disease. Furthermore, these results demonstrate the potential therapeutic use of bumetanide for the treatment of HE.
Systemic oxidative stress induction leads to brain edema in hyperammonemic portacaval-shunted rats.
Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Hepatic encephalopathy is a neuropsychiatric disorder; a major complication of liver disease. Impairment in liver function leads to a reduced capacity to clear ammonia (via urea cycle) and subsequently hyperammonemia arises. The consequent neurotoxic levels of ammonia are considered to play a major role in the pathogenesis of hepatic encephalopathy. However, a correlation between ammonia and severity of neurological impairment is poor. Oxidative stress is another factor believed to play a role in the pathogenesis of this syndrome as it has demonstrated to exacerbate the neuropsychological effects of hyperammonemia. In the setting of liver disease, oxidative stress represents a systemic phenomenon induced by several mechanisms: decreased antioxidant synthesis, increased systemic release of oxidant enzymes, generation of reactive oxygen species and impaired neutrophil function. Furthermore, it has been demonstrated that high ammonia concentrations can induce oxidative stress. However, significantly lower degrees of hyperammonemia (<500 µM) are observed in patients with end-stage liver disease (cirrhosis), concentrations which do not induce cerebral nor systemic oxidative stress. Therefore defining ammonia and oxidative stress as independent factors. Data from both animal and human studies strongly suggest there is a synergistic effect between systemic oxidative stress and ammonia in the pathogenesis of hepatic encephalopathy and that induction of cerebral oxidative stress may be associated with severe neurological symptoms.
Glutathione depletion leads to brain edema in portacaval-shunted rats.
Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Aims: The pathogenesis of hepatic encephalopathy (HE) is multifactorial. Even though ammonia is the central component in the pathogenesis of HE, oxidative stress is believed to play a role in exacerbating the neuropsychological effects of ammonia in patients with liver disease. With new, highly sensitive imaging techniques, brain edema is observed in HE patients. We previously demonstrated that portacaval shunted hyperammonemic rats do not develop oxidative stress or brain edema. In order to define a synergistic effect between hyperammonemia and systemic oxidative stress, the present study investigates the role of oxidative stress in the pathogenesis of brain edema in PCA rats following glutathione depletion by diethyl maleate (DEM). Methods: In the first set of experiments, we evaluated the effect of DEM in PCA and SHAM-operated control rats by injecting DEM at a dose of 0.4 and 1 mg/kg/day intraperitoneally for 10 days starting at day 18 after surgery. Rats were sacrificed at day 28 and oxidative stress was evaluated by arterial malon-dialdehyde (MDA, commercial kit). In the second set of experiments, 1 mg/kg/day DEM was used to induce oxidative stress. Ammonia (commercial kit) as well as other different oxidative stress markers: reactive oxygen species (DCFDA fluorescence technique), and 4-hydroxy-2-nonenal (HNE, Western blot) were assessed in arterial plasma and frontal cortex tissue. Brain water content was measured in the frontal cortex using a specific gravimetric technique. Results: DEM at 1 mg/kg/day (not 0.4 mg/kg/day) induced a significant increase in MDA levels in PCA rats. No increase in MDA was detected following either dose of DEM in SHAM-operated controls. Ammonia levels in both DEM-treated and non-treated PCA rats were significantly increased vs respective sham-operated controls (p<0.001) and remained unchanged between non-treated and DEM-treated PCA groups (p>0.05). An increase in brain water content was observed in DEM-treated PCA rats vs non-treated PCA rats (PCA+DEM: 78.45 ± 0.13% vs PCA: 77.38 ± 0.11, p< 0.001). Although no significant changes in reactive oxygen species were observed, there was an increase in plasma levels of HNE in DEM-treated PCA rats compared to non-treated PCA rats. No significant changes in any oxidative stress markers were observed in the frontal cortex. Conclusions: DEM treatment in PCA rats induced systemic oxidative stress but not central oxidative stress. This, imposed on hyperammonemia, was accompanied by the onset of brain edema in rats with PCA. Oxidative stress and brain edema were not detected in SHAM-operated rats, which were not hyperammonemic. Our findings suggest a synergistic effect between hyperammonemia and systemic oxidative stress is implicated in the pathogenesis of brain edema in hepatic encephalopathy.
Sara Ghezzal, Marc-André Clément, Cristina R. Bosoi, Roxanne Beauchamp, Mélanie Tremblay, Christopher F. Rose, Chantal Bémeur.
Aims: The pathogenesis of hepatic encephalopathy (HE) is multifactorial. Even though ammonia is the central component in the pathogenesis of HE, oxidative stress is believed to play a role in exacerbating the neuropsychological effects of ammonia in patients with liver disease. With new, highly sensitive imaging techniques, brain edema is observed in HE patients. We previously demonstrated that portacaval shunted hyperammonemic rats do not develop oxidative stress or brain edema. In order to define a synergistic effect between hyperammonemia and systemic oxidative stress, the present study investigates the role of oxidative stress in the pathogenesis of brain edema in PCA rats following glutathione depletion by diethyl maleate (DEM). Methods: In the first set of experiments, we evaluated the effect of DEM in PCA and SHAM-operated control rats by injecting DEM at a dose of 0.4 and 1 mg/kg/day intraperitoneally for 10 days starting at day 18 after surgery. Rats were sacrificed at day 28 and oxidative stress was evaluated by arterial malon-dialdehyde (MDA, commercial kit). In the second set of experiments, 1 mg/kg/day DEM was used to induce oxidative stress. Ammonia (commercial kit) as well as other different oxidative stress markers: reactive oxygen species (DCFDA fluorescence technique), and 4-hydroxy-2-nonenal (HNE, Western blot) were assessed in arterial plasma and frontal cortex tissue. Brain water content was measured in the frontal cortex using a specific gravimetric technique. Results: DEM at 1 mg/kg/day (not 0.4 mg/kg/day) induced a significant increase in MDA levels in PCA rats. No increase in MDA was detected following either dose of DEM in SHAM-operated controls. Ammonia levels in both DEM-treated and non-treated PCA rats were significantly increased vs respective sham-operated controls (p<0.001) and remained unchanged between non-treated and DEM-treated PCA groups (p>0.05). An increase in brain water content was observed in DEM-treated PCA rats vs non-treated PCA rats (PCA+DEM: 78.45 ± 0.13% vs PCA: 77.38 ± 0.11, p< 0.001). Although no significant changes in reactive oxygen species were observed, there was an increase in plasma levels of HNE in DEM-treated PCA rats compared to non-treated PCA rats. No significant changes in any oxidative stress markers were observed in the frontal cortex. Conclusions: DEM treatment in PCA rats induced systemic oxidative stress but not central oxidative stress. This, imposed on hyperammonemia, was accompanied by the onset of brain edema in rats with PCA. Oxidative stress and brain edema were not detected in SHAM-operated rats, which were not hyperammonemic. Our findings suggest a synergistic effect between hyperammonemia and systemic oxidative stress is implicated in the pathogenesis of brain edema in hepatic encephalopathy.
Chantal Bémeur, Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Malnutrition is an important prognostic factor potentially influencing clinical outcome of patients suffering from chronic liver disease (CLD). Malnutrition, considered a consequence of metabolic disturbances (hypermetabolism), exacerbates sarcopenia (severe muscle loss) and hepatic encephalopathy (complex neuropsychiatric disorder) in cirrhotic patients. New management strategies focussing on improving nutritional status and attenuating CLD-related complications are an unmet clinical need. We hypothesize supplementation with branched-chain amino acid isoleucine (ILE) and exercise could possibly attenuate muscle mass loss and prevent brain edema, a common entity of hepatic encephalopathy, in CLD. Methods: CLD was induced in rats following 6-week bile-duct ligation (BDL). Five experimental groups were tested; 1) BDL; 2) BDL + ILE; 3) BDL + EX; 4) BDL + ILE + EX; 5) Sham-operated rats. Two weeks following BDL, rats were submitted to 15 min exercise (10 cm/s) every other day and BDL rats receiving ILE, were gavaged daily (1.5 mg/kg) for 4 weeks. Body weight, muscle (gastrocnemius) mass, metabolic state (calculation of energy expenditure independent of food intake and fecal mass) and cerebral edema (specific gravity method) were measured in all groups. Results: BDL rats gained less body weight (33.7 6.3 g vs 204.5 26.0 g; p < 0.01) and muscle mass (weight/body weight ratio) (0.0047 0.0002 vs 0.0051 0.0002; p < 0.05) compared to sham-operated rats, respectively. ILE-treated BDL rats submitted to exercise demonstrated an increase in weight gain and an increase in muscle mass (weight/body weight ratio) (0.0056 0.0003 vs 0.0047 0.0003; p < 0.05) and an attenuation in hypermetabolic status, compared to BDL rats respectively. ILE+exercsie also attenuated brain water content in BDL rats. Conclusion: Our results demonstrate that supplemental ILE along with exercise reduces body weight and muscle mass loss, improves metabolic activity and attenuates brain edema. These findings suggest that strategies aiming at improving nutritional status and preventing muscle mass loss will attenuate the onset of sarcopenia and hepatic encephalopathy, and therefore improve outcome in CLD. EX and ILE supplementation could rapidly be translated into clinical practice.
Inhibiting lactate synthesis: a new therapeutic target for the treatment of hepatic encephalopathy.
Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Chronic liver disease leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE). Neurotoxic effects of ammonia are known to induce numerous metabolic alterations such as increased brain glutamine and lactate. However, their roles in the development of brain edema are not defined. Aims: Having previously demonstrated an increase in both glutamine and lactate in six-week bile-duct ligated rats (BDL) in association with HE, our aim in the present study was to define the role of lactate in the pathogenesis of brain edema by inhibiting brain lactate production. Methods: BDL rats were treated with dichloroacetate (DCA, 25 mg/kg intraperitoneally, for 7 days starting at week 5 after bile-duct ligation). DCA, a pyruvate dehydrogenase kinase inhibitor leads to pyruvate dehydrogenase stimulation, therefore favoring the oxidation of pyruvate and consequently leading to a decrease in lactate production. Rats were sacrificed at week 6 after bile-duct ligation. In all experimental groups, brain edema was assessed using the specific gravimetric technique, lactate was measured following its oxidation by lactate oxidase to pyruvate and hydrogen peroxide which reacts with AmplexRed (10-acetyl-3,7-dihidroxyphenoxazine) generating measurable resorufin (fluorescent product) and glutamine was quantified using high performance liquid chromatography. Results: Six weeks following BDL, rats develop brain edema, as well as increased brain lactate and glutamine compared to SHAM-operated controls. DCA treatment normalized brain lactate in BDL rats (76.17±3.31 µM/100 µg protein vs BDL: 254.60±10.12 µM/100 µg protein, p<0.001; non-significant vs SHAM: 111.70±7.08 µM/100 µg protein). DCA-treated BDL rats demonstrated a significant reduction of brain water content reaching values similar to those seen in SHAM-operated rats (77.49±0.07% vs BDL: 78.46±0.28%; p<0.05; non-significant vs SHAM: 77.35±0.17%). Glutamine levels were increased in BDL vs sham operated rats and remained high in DCA-treated BDL rats (569.20±80.44 µM vs BDL: 796.60±71.50 µM; p<0.001; both increased vs SHAM: 442.80±33.79 µM; p<0.01). Conclusions: Inhibition of lactate synthesis led to an attenuation in brain edema and brain lactate levels while brain glutamine levels remained elevated. Our findings suggest increased brain lactate, not glutamine, is an important factor in the pathogenesis of brain edema. DCA has previously demonstrated a long-term safety profile in patients with congenital lactic acidosis and beneficial effects with no adverse reactions in other diseases such as cancer and chronic obstructive pulmonary disease. Therefore, inhibition of lactate synthesis can rapidly provide a promising therapeutic approach for the management of patients with end-stage liver disease.
Induction of systemic oxidative stress leads to brain oedema in portacaval shunted rats.
Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
The pathogenesis of hepatic encephalopathy (HE) is multifactorial and often associated with the development of brain oedema. In addition to ammonia playing a central role, systemic oxidative stress is believed to aggravate the neuropsychological effects of ammonia in patients with chronic liver disease (CLD). The aim of this study was to (i) induce systemic oxidative stress in hyperammonaemic portacaval anastomosed (PCA) rats by inhibiting the antioxidant glutathione using Dimethyl maleate (DEM) and (ii) investigate whether a synergistic relationship between ammonia and oxidative stress contributes to the pathogenesis of brain oedema in CLD.Four-week PCA and sham-operated rats received DEM (0.4-4 mg/kg/day) for the last 10 days before sacrifice when oxidative stress markers [reactive oxygen species (ROS) and malondialdehyde (MDA)] were assessed in blood and frontal cortex. Brain water content was measured using a specific gravimetric technique.Dimethyl maleate induced an increase in ROS and MDA in the blood, but not in the brain, of the PCA rats, compared with non-treated PCA rats. This was accompanied with an increase in brain water content (PCA+DEM: 78.45 ± 0.13% vs. PCA: 77.38 ± 0.11 P < 0.001). Higher doses of DEM induced systemic oxidative stress in sham-operated controls, but brain oedema did not develop.Dimethyl maleate provoked systemic, not central, oxidative stress in PCA rats, resulting in the development of brain oedema. Independently, hyperammonaemia and systemic oxidative stress do not precipitate brain oedema; therefore, our findings sustain that a synergistic effect between hyperammonaemia and systemic oxidative stress is responsible for the development of brain oedema in HE.
Elevated cerebral lactate: Implications in the pathogenesis of hepatic encephalopathy.
Cristina R. Bosoi, Christopher F. Rose.
Hepatic encephalopathy (HE), a complex neuropsychiatric syndrome, is a frequent complication of liver failure/disease. Increased concentrations of lactate are commonly observed in HE patients, in the systemic circulation, but also in the brain. Traditionally, increased cerebral lactate is considered a marker of energy failure/impairment however alterations in lactate homeostasis may also lead to a rise in brain lactate and result in neuronal dysfunction. The latter may involve the development of brain edema. This review will target the significance of increased cerebral lactate in the pathogenesis of HE.
Cristina R. Bosoi, Claudia Zwingmann, Helen Marin, Christian Parent-Robitaille, Jimmy Huynh, Mélanie Tremblay, Christopher F. Rose.
The pathogenesis of brain edema in patients with chronic liver disease (CLD) and minimal hepatic encephalopathy (HE) remains undefined. This study evaluated the role of brain lactate, glutamine and organic osmolytes, including myo-inositol and taurine, in the development of brain edema in a rat model of cirrhosis.Six-week bile-duct ligated (BDL) rats were injected with (13)C-glucose and de novo synthesis of lactate, and glutamine in the brain was quantified using (13)C nuclear magnetic resonance spectroscopy (NMR). Total brain lactate, glutamine, and osmolytes were measured using (1)H NMR or high performance liquid chromatography. To further define the interplay between lactate, glutamine and brain edema, BDL rats were treated with AST-120 (engineered activated carbon microspheres) and dichloroacetate (DCA: lactate synthesis inhibitor).Significant increases in de novo synthesis of lactate (1.6-fold, p<0.001) and glutamine (2.2-fold, p<0.01) were demonstrated in the brains of BDL rats vs. SHAM-operated controls. Moreover, a decrease in cerebral myo-inositol (p<0.001), with no change in taurine, was found in the presence of brain edema in BDL rats vs. controls. BDL rats treated with either AST-120 or DCA showed attenuation in brain edema and brain lactate. These two treatments did not lead to similar reductions in brain glutamine.Increased brain lactate, and not glutamine, is a primary player in the pathogenesis of brain edema in CLD. In addition, alterations in the osmoregulatory response may also be contributing factors. Our results suggest that inhibiting lactate synthesis is a new potential target for the treatment of HE.
Cristina R. *Bosoi, Chantal Bémeur, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Introduction: La malnutrition est un important facteur de pronostique qui peut affecter le résultat clinique des patients souffrant d’une maladie hépatique chronique (MHC). Étant une cause du hypermétabolisme, la malnutrition aggrave l’encéphalopathie hépatique et la sarcopénie chez les patients cirrhotiques. Des nouvelles stratégies de traitement visant l’amélioration de l’état nutritionnel et l’atténuation des complications de la MHC sont un besoin clinique à satisfaire. Notre hypothèse était que la supplémentation avec l’acide aminé ramifié isoleucine (ILE) et l’exercice physique (EX) peuvent atténuer la perte de masse musculaire et prévenir l’œdème cérébral dans la MHC. Méthodes : MHC a été induite chez des rats suite à une ligature de la voie biliaire (LVB). 5 groupes expérimentaux ont été étudiés : 1) LVB; 2) LVB + ILE; 3) LVB + EX; 4) LVB + ILE + EX; 5) SHAM opérés. Deux semaines après la LVB, les rats LVB + EX ont subi des sessions d’exercice de 15 min (10 cm/s) à chaque 2 jours et les rats ILE ont été gavés à chaque jour (1.5 mg/kg ILE) pendant 4 semaines. Le poids, la masse musculaire (muscle gastrocnémien), l’état métabolique (la dépense énergétique indépendante de la quantité de nourriture et masse fécale) et l’œdème cérébral (gravimétrie spécifique) ont été mesurés. Résultats : LVB + EX + ILE ont démontré un gain du poids corporel significatif (LVB + ILE + EX: 112.3 g vs LVB: 33.7 g; p < 0.05), une augmentation de la masse musculaire (poids muscle/poids corporel) (LVB + ILE + EX: 0.0056 vs LVB: 0.0047; p < 0.05) et une atténuation de l’état hypermétabolique. Le contenu en eau cérébrale a diminué chez les rats LVB+ ILE + EX comparé aux rats LVB. Conclusion: Nos résultats démontrent que l’EX et l’ILE améliorent le poids corporel, la masse musculaire, le métabolisme et atténuent l’œdème cérébral. Cela suggère que des stratégies visant l’optimisation de la masse musculaire et l’amélioration de l’état nutritionnel pourraient diminuer les complications chez des patients cirrhotiques.
Chantal Bémeur, Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Malnutrition is an important prognostic factor which can influence clinical outcome of patients suffering from chronic liver disease (CLD). Believed to cause hypermetabolism, malnutrition exacerbates hepatic encephalopathy and sarcopenia in cirrhotic patients. New management strategies focussing on improving nutritional status and attenuating CLD complications are an unmet clinical need. We hypothesize supplementation with branched-chain amino acid isoleucine (ILE) and exercise (EX) could possibly attenuate muscle mass loss and prevent brain edema in CLD. Methods: CLD was induced in rats following 6-week bile-duct ligation (BDL). Five experimental groups were tested; 1) BDL; 2) BDL + ILE; 3) BDL + EX; 4) BDL + ILE + EX; 5) Sham-operated rats. Two weeks post BDL, BDL + EX rats were submitted to 15 min exercise (10 cm/s) every other day and BDL rats receiving ILE, were gavaged daily (1.5 mg/kg) for 4 weeks. Body weight, muscle (gastrocnemius) mass, metabolic state (calculation of energy expenditure independent of food intake and fecal mass) and cerebral edema (specific gravity method) were measured in all groups. Results: BDL + EX + ILE demonstrated a significant gain in body weight (BDL + ILE + EX: 112.3 g vs BDL: 33.7 g; p < 0.05), an increase in muscle mass (weight/body weight ratio) (BDL + ILE + EX: 0.0056 vs BDL: 0.0047; p < 0.05) and attenuated hypermetabolic status. Brain water content was decreased in BDL + ILE + EX rats compared to BDL animals. Conclusion: Our results demonstrate that EX and supplemental ILE improve body weight, muscle mass, metabolic activity and attenuate cerebral edema. These findings suggest that strategies aiming at muscle mass optimization and improving nutritional status attenuate complications and therefore improve outcome in patients with CLD. EX and ILE supplementation could rapidly be translated into clinical practice.
Attenuation of oxidative stress protects the brain in rats with “acute-on-chronic” liver failure.
Cristina R. Bosoi, Chantal Bémeur, Bich Nguyen, Mélanie Tremblay, Christopher F. Rose.
Background: Acute-on-chronic liver failure (ACLF) is defined as an acute decompensation of chronic liver disease. Brain edema is frequently observed in hepatic encephalopathy associated with both acute and chronic liver disease. While in acute liver failure, toxic levels of ammonia induce cerebral oxidative stress and brain edema, in chronic liver disease, systemic (not central) oxidative stress and hyperammonemia synergistically cause brain edema. This study investigated the role of both systemic and central oxidative stress and ammonia in relation to brain edema in a rat model of ACLF. Methods: ACLF was induced in male Sprague-Dawley rats by portacaval shunt (PCA), followed 4 weeks later by hepatic artery ligation (HAL). Acute liver failure (ALF) induced by concomitant PCA and HAL, PCA (4 weeks) and SHAM-operated rats were used as controls. ACLF rats were divided into 2 groups that were sacrificed at: 1) coma stage of hepatic encephalopathy (defined as loss of corneal reflex) (ACLF-C) and 2) in parallel with ALF-induced coma (ACLF-P) rats. Brain edema (specific gravimetric technique), ammonia levels (commercial kit) and oxidative stress markers (plasmatic and cerebral reactive oxygen species, fluorescence spectroscopy) were evaluated along with hepatic function (routine biochemistry, haematoxylin-phloxine-saffron histopathology). Results: Coma was delayed by 8h in ACLF compared to ALF rats (p< 0.01). Liver biochemistry markers did not differ between ACLF-C, ACLF-P and ALF rats; liver histopathology showed mild necrosis in ACLF-P, moderate in ALF and severe in ACLF-C. Brain water content was significantly attenuated in both ACLF-C and ACLF-P vs. ALF rats (p< 0.01). Arterial ammonia concentration followed a similar pattern: they were attenuated in ACLF-C: 0.35±0.07 mM and ACLF-P: 0.49±0.14 mM vs. ALF: 1.34±0.09 mM (p< 0.001), but remained high compared to SHAM: 0.06±0.01 mM (p< 0.001). Systemic oxidative stress was present in both ACLF and ALF rats, while cerebral oxidative stress was present only in ALF rats. Conclusion: Brain edema, ammonia levels and oxidative stress are reduced in ACLF rats compared to ALF rats. These findings suggest that during chronic liver failure, compensatory mechanisms that prevent the apparition of brain edema and attenuate oxidative stress during an acute deterioration are developed.
Attenuation of oxidative stress protects the brain in rats with “acute-on-chronic” liver failure.
Cristina R. Bosoi, Chantal Bémeur, Bich Nguyen, Mélanie Tremblay, Christopher F. Rose.
Background: Acute-on-chronic liver failure (ACLF) is defined as an acute decompensation of chronic liver disease. Brain edema is frequently observed in hepatic encephalopathy associated with both acute and chronic liver disease. While in acute liver failure, toxic levels of ammonia induce cerebral oxidative stress and brain edema, in chronic liver disease, systemic (not central) oxidative stress and hyperammonemia synergistically cause brain edema. This study investigated the role of both systemic and central oxidative stress and ammonia in relation to brain edema in a rat model of ACLF. Methods: ACLF was induced in male Sprague-Dawley rats by portacaval shunt (PCA), followed 4 weeks later by hepatic artery ligation (HAL). Acute liver failure (ALF) induced by concomitant PCA and HAL, PCA (4 weeks) and SHAM-operated rats were used as controls. ACLF rats were divided into 2 groups that were sacrificed at: 1) coma stage of hepatic encephalopathy (defined as loss of corneal reflex) (ACLF-C) and 2) in parallel with ALF-induced coma (ACLF-P) rats. Brain edema (specific gravimetric technique), ammonia levels (commercial kit) and oxidative stress markers (plasmatic and cerebral reactive oxygen species, fluorescence spectroscopy) were evaluated along with hepatic function (routine biochemistry, haematoxylin-phloxine-saffron histopathology). Results: Coma was delayed by 8h in ACLF compared to ALF rats (p< 0.01). Liver biochemistry markers did not differ between ACLF-C, ACLF-P and ALF rats; liver histopathology showed mild necrosis in ACLF-P, moderate in ALF and severe in ACLF-C. Brain water content was significantly attenuated in both ACLF-C and ACLF-P vs. ALF rats (p< 0.01). Arterial ammonia concentration followed a similar pattern: they were attenuated in ACLF-C: 0.35±0.07 mM and ACLF-P: 0.49±0.14 mM vs. ALF: 1.34±0.09 mM (p< 0.001), but remained high compared to SHAM: 0.06±0.01 mM (p< 0.001). Systemic oxidative stress was present in both ACLF and ALF rats, while cerebral oxidative stress was present only in ALF rats. Conclusion: Brain edema, ammonia levels and oxidative stress are reduced in ACLF rats compared to ALF rats. These findings suggest that during chronic liver failure, compensatory mechanisms that prevent the apparition of brain edema and attenuate oxidative stress during an acute deterioration are developed.
Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Liver failure/disease leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy. There is increasing evidence that oxidative stress exacerbates the neuropsychological effects of hyperammonemia in patients with liver disease, possibly by inducing brain edema. The latter represents a common entity in cirrhotic patients with hepatic encephalopathy. Since rats following 4-week portacaval anastomosis (PCA) become hyperammonemic but do not develop oxidative stress or brain edema, we aimed to investigate the impact of oxidative stress on the development of brain edema in this rat model. Methods: Oxidative stress was induced following glutathione (GSH) depletion by diethyl maleate (DEM). PCA and SHAM-operated rats received DEM (1 mg/kg/day intraperitoneally) for 10 days starting at day 18 after surgery. Rats were sacrificed at day 28 and oxidative stress markers, such as glutathione (GSH), malon-dialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE) were assessed in arterial plasma and brain (frontal cortex) tissue. Plasma ammonia and liver function markers (AST, ALT, bilirubin) were also evaluated. Brain water content was measured using a specific gravimetric technique. Results: DEM induced a significant decrease in plasmatic GSH, which lead to an increase in arterial MDA (2.5 fold) and HNE (1.4 fold) levels in PCA rats compared to non-treated PCA rats. An increase in brain water content was observed in DEM-treated PCA rats vs non-treated PCA rats (PCA+DEM: 78.45 ± 0.13% vs PCA: 77.38 ± 0.11%, p< 0.001). In the brain, oxidative stress markers measured in the frontal cortex did not differ between the two groups. DEM treatment did not affect the degree of hyperammonemia or lead to an alteration in liver function in comparison to non-treated PCA rats. Conclusions: DEM induced systemic, not central, oxidative stress in PCA rats. This, imposed on hyperammonemia, resulted in an increase in brain water content. Since oxidative stress and brain edema were not detected in non-treated hyperammonemic PCA rats, together our findings suggest that a synergistic effect between hyperammonemia and systemic oxidative stress is implicated in the pathogenesis of brain edema in hepatic encephalopathy.
Cristina R. Bosoi, Chantal Bémeur, Bich Nguyen, Mélanie Tremblay, Christopher F. Rose.
Aims: Acute-on-chronic liver failure (ACLF), an acute deterioration of liver function during compensated chronic liver disease, is associated with the development of hepatic encephalopathy (HE). Brain edema is frequently observed in patients with HE induced by either acute liver failure (ALF) or chronic liver disease. We recently demonstrated in a rat model of cirrhosis that hyperammonemia and systemic oxidative stress synergistically lead to brain edema. Therefore, the aim of this study was to develop a rat model of ACLF by inducing an acute liver insult, superimposed onto a chronic hyperammonemia background, and to investigate the role of oxidative stress and ammonia in relation to brain edema. Methods: ACLF was induced in male Sprague-Dawley rats by portacaval shunt (PCA), followed 4 weeks later by hepatic artery ligation (HAL). Liver devascularisation by concomitant PCA and HAL was used to induce ALF. SHAM and PCA (chronic hyperammonemic) rats, sacrificed 4 weeks after surgery, were included as controls. Liver status (routine biochemistry and histopathology), blood ammonia and brain edema (specific gravimetric technique) were assessed. Oxidative stress was evaluated by plasmatic and cerebral levels of reactive oxygen species (DCFDA fluorescence), glutathione (DTNB method), and activities of xanthine oxidase and catalase (Amplex Red method). Results : Coma developed in ALF rats 8h after HAL; it was significantly delayed in ACLF rats, where it occurred after 16h. Liver necrosis markers AST and ALT did not differ between pair-killed ACLF and ALF rats; however, liver histopathology showed more severe necrosis in ACLF than in ALF rats. Brain water content increased in ALF rats and was significantly attenuated in ACLF rats: 80.04±0.13% p<0.01vs ALF (81.39±0.15%), n.s. vs SHAM. The increase in arterial ammonia, as seen in ALF rats, was prevented in ACLF rats: 0.35±0.07 mM, p<0.001vs ALF (1.34±0.09 mM), p<0.01 vs SHAM. Oxidative stress was present in the blood of both ACLF and ALF rats, while signs of oxidative stress in the brain were present only in the ALF rats. Conclusions: The alterations observed in ALF are attenuated in ACLF. In spite of a more severe hepatic necrosis in the ACLF rats, the onset of coma was delayed, and brain edema, ammonia levels and oxidative stress were reduced in comparison to the ALF rats. In conclusion, severe HE is alleviated by compensatory mechanisms comprising oxidative stress, which are developed during chronic hyperammonemia prior to an acute liver deterioration. A better understanding of these mechanisms may help define the pathogenesis of ACLF.
Oxidative stress: a systemic factor implicated in the pathogenesis of hepatic encephalopathy.
Cristina R. Bosoi, Christopher F. Rose.
Although ammonia is considered the main factor involved in the pathogenesis of hepatic encephalopathy (HE), it correlates well with the severity of HE in acute liver failure, but not in chronic liver disease. Oxidative stress is another factor believed to play a role in the pathogenesis of this syndrome; it represents an imbalance between the production and neutralization of reactive oxygen species, which leads to cellular dysfunction. In the setting of liver disease, oxidative stress represents a systemic phenomenon induced by several mechanisms: decreased antioxidant synthesis, increased systemic release of oxidant enzymes, generation of reactive oxygen species, and impaired neutrophil function. High ammonia concentrations induce cerebral oxidative stress, thus contributing to severe hepatic encephalopathy, as observed in acute liver failure. In chronic liver disease, significantly lower degrees of hyperammonemia (<500 μM) do not induce cerebral nor systemic oxidative stress. Data from both animal and human studies sustain that there is a synergistic effect between systemic oxidative stress, and ammonia that is implicated in the pathogenesis of hepatic encephalopathy.
Brain edema in acute liver failure and chronic liver disease: Similarities and differences.
Cristina R. Bosoi, Christopher F. Rose.
Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome that typically develops as a result of acute liver failure or chronic liver disease. Brain edema is a common feature associated with HE. In acute liver failure, brain edema contributes to an increase in intracranial pressure, which can fatally lead to brain stem herniation. In chronic liver disease, intracranial hypertension is rarely observed, even though brain edema may be present. This discrepancy in the development of intracranial hypertension in acute liver failure versus chronic liver disease suggests that brain edema plays a different role in relation to the onset of HE. Furthermore, the pathophysiological mechanisms involved in the development of brain edema in acute liver failure and chronic liver disease are dissimilar. This review explores the types of brain edema, the cells, and pathogenic factors involved in its development, while emphasizing the differences in acute liver failure versus chronic liver disease. The implications of brain edema developing as a neuropathological consequence of HE, or as a cause of HE, are also discussed.
Le méthylglyoxal et l'encéphalopathie hépatique.
Vi T. Tran, Laurent Bilodeau, Cristina R. Bosoi, Mélanie Tremblay, Mireille Bélanger, Christopher F. Rose.
Introduction : L’encéphalopathie hépatique (EH) est un syndrome neuropsychiatrique métabolique qui survient comme complication majeure de la cirrhose hépatique. Les causes de l’EH sont multifactorielles, mais les mécanismes précis ont encore besoin d’être élucidés. Le méthylglyoxal (MG) est un sous-produit toxique de la glycolyse et un agent puissant de glycation des molécules cellulaires, et est associé à des maladies affectant le cerveau comme l’encéphalopathie diabétique et la maladie d’Alzheimer. Dans cette étude, nous explorons l’implication du MG dans la physiopathologie de l’EH. Méthodes : La cirrhose a été induite suite à une ligature de voie biliaire (BDL) pendant 6 semaines et une dérivation portosystémique (PCA) a été effectuée pour 4 semaines. Chez ces modèles animaux de l’EH, nous avons dosé des marqueurs du MG, le D-lactate et les produits de glycation avancée (AGEs), par fluorescence et Western Blot, respectivement. L’expression protéique des enzymes glyoxalase 1 (Glo1) et glyoxalase 2 (Glo2) a été effectuée par Western Blot alors que l’activité de Glo1 a été évaluée par cinétique enzymatique en spectrophotométrie UV. Résultats : Aucune différence significative du D-lactate et des AGEs, deux marqueurs du métabolisme du MG, a été détectée dans les modèles animaux de l’EH. De plus, aucune altération de l’expression protéique de Glo1 et Glo2 ainsi que l’activité de Glo1 a été observée dans le système glyoxalase, détoxifiant le MG, dans l’EH. Conclusion : Cette étude, pour la première fois, caractérise la relation entre MG et l’EH et suggère aucune implication de celui-ci dans l’EH. Financement: Bourse d’étude V Tran : COPSE de l’Université de Montréal. L. Bilodeau : American Gastroenterological Association. C. Bosoi : FRQS
Cristina R. Bosoi, Chantal Bémeur, Bich Nguyen, Mélanie Tremblay, Christopher F. Rose.
Introduction: Les patients avec une insuffisance hépatique chronique souffrent fréquemment de décompensations aigues de la fonction hépatique (DAH). L’œdème cérébral est une complication de l’insuffisance hépatique aigue ainsi que de celle chronique. Le stress oxydatif et l’ammoniaque contribuent à l’induction de l’œdème cérébral lors d’une insuffisance hépatique chronique. Le but de cette étude est d’investiguer le rôle du stress oxydatif et de l’hyperammoniémie en relation avec l’œdème cérébral dans un modèle de DHA chez le rat. Méthodes: DHA a été induite chez des rats suite à une anastomose portocave (APC) suivie par la ligature de l’artère hépatique (LAH), 4 semaines plus tard. L’insuffisance hépatique aigue (IHA) a été induite par une APC et une HAL effectuées simultanément. Des rats contrôles SHAM et APC ont été sacrifiés 4 semaines après la chirurgie. L’œdème cérébral (gravimétrie spécifique), les espèces réactives d’oxygène et le glutathion (spectrophotométrie) ont été mesurés dans le plasma et dans le cerveau. Résultats: Le début du coma a été significativement retardé chez les rats DHA comparé aux rats IHA. L’examen histopathologique du foie a démontré une nécrose plus sévère chez les rats DHA que chez les rats IHA. Pourtant l’œdème cérébral et l’augmentation de l’ammoniaque ont été prévenus chez ces rats : eau cérébrale 80.04±0.13 % (p<0.01 vs IHA) et ammoniaque plasmatique 0.35±0.07 mM (p<0.001 vs IHA). Chez les rats DHA, le stress oxydatif a été seulement détecté systémiquement tandis que chez les rats IHA, il était présent tant au niveau systémique que cérébral. Conclusions: Les altérations observées dans l’insuffisance hépatique aigue sont améliorées lors d’une DHA survenant sur une hyperammoniémie chronique: l’œdème cérébral, l’ammoniaque et le stress oxydatif sont réduits et le coma est retardé. Cela suggère que des mécanismes compensatoires développés durant une hyperammoniémie chronique préviennent les manifestations sévères d’une insulte hépatique aigue
Le méthylglyoxal et l'encéphalopathie hépatique.
Vi T. Tran, Laurent Bilodeau, Cristina R. Bosoi, Mélanie Tremblay, Mireille Bélanger, Christopher F. Rose.
Introduction : L’encéphalopathie hépatique (EH) est un syndrome neuropsychiatrique métabolique qui survient comme complication majeure de la cirrhose hépatique. Les causes de l’EH sont multifactorielles, mais les mécanismes précis ont encore besoin d’être élucidés. Le méthylglyoxal (MG) est un sous-produit toxique de la glycolyse et un agent puissant de glycation des molécules cellulaires, et est associé à des maladies affectant le cerveau comme l’encéphalopathie diabétique et la maladie d’Alzheimer. Dans cette étude, nous explorons l’implication du MG dans la physiopathologie de l’EH. Méthodes : La cirrhose a été induite suite à une ligature de voie biliaire (BDL) pendant 6 semaines et une dérivation portosystémique (PCA) a été effectuée pour 4 semaines. Chez ces modèles animaux de l’EH, nous avons dosé des marqueurs du MG, le D-lactate et les produits de glycation avancée (AGEs), par fluorescence et Western Blot, respectivement. L’expression protéique des enzymes glyoxalase 1 (Glo1) et glyoxalase 2 (Glo2) a été effectuée par Western Blot alors que l’activité de Glo1 a été évaluée par cinétique enzymatique en spectrophotométrie UV. Résultats : Aucune différence significative du D-lactate et des AGEs, deux marqueurs du métabolisme du MG, a été détectée dans les modèles animaux de l’EH. De plus, aucune altération de l’expression protéique de Glo1 et Glo2 ainsi que l’activité de Glo1 a été observée dans le système glyoxalase, détoxifiant le MG, dans l’EH. Conclusion : Cette étude, pour la première fois, caractérise la relation entre MG et l’EH et suggère aucune implication de celui-ci dans l’EH. Financement: Bourse d’étude V Tran : COPSE de l’Université de Montréal. L. Bilodeau : American Gastroenterological Association. C. Bosoi : FRQS
Role of cerebral lactate in the pathogenesis of brain edema in cirrhotic rats.
Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE). Neurotoxic effects of ammonia induce numerous metabolic alterations, such as increased cerebral lactate and glutamine. In brain edema associated with acute liver failure, glutamine plays a controversial and lactate a well-defined role. Brain edema is also present in chronic liver failure; however, roles of lactate and glutamine are less understood. We previously demonstrated an increase in de novo synthesis of lactate in bile-duct ligated rats (BDL). To define the role of lactate in the pathogenesis of brain edema, this study investigates its relationship with ammonia and the effects of inhibiting lactate production. Methods: BDL rats were treated either with AST-120 (spherical carbon adsorbent, 1 g/kg/day for 6 weeks, by gavage) or with dichloroacetate (DCA, 25 mg/kg for 7 days starting at week 5 after intervention, intraperitoneally). AST-120 acts as an ammonia sink in the gut. DCA is a pyruvate dehydrogenase kinase inhibitor that leads to pyruvate dehydrogenase stimulation and to a shift of pyruvate metabolism from glycolysis to oxidation and, consequently, to a decrease in lactate production. Brain lactate (Amplex red fluorescence) and glutamine (HPLC), as well as edema (specific gravimetric technique) were measured in brain tissue of non-treated and treated BDL rats. Results: Brain lactate and glutamine increased and brain edema developed in BDL rats vs SHAM-operated controls. AST-120 treatment partially decreased lactate levels: AST-120-treated BDL: 155.1±12.8 µM (p<0.05 vs SHAM, p<0.001 vs BDL) compared to BDL: 254.6±10.1 µM (p<0.001 vs SHAM) and SHAM: 111.7±7.1 µM; while glutamine levels did not change: AST-120-treated BDL: 1024.2.±65.2 µM (p<0.001 vs SHAM, ns vs BDL) compared to BDL: 796.6±71.5 µM (p<0.001 vs SHAM) and SHAM: 442.8±33.8 µM. Following DCA treatment, in treated BDL rats brain lactate normalized (76.2±3.3 µM, ns vs SHAM, p<0.001 vs BDL) and glutamine levels remained unchanged (569.2±80.4 µM, p<0.05 vs SHAM, ns vs BDL). Both AST-120 and DCA treatments led to a significant reduction of brain water content, reaching similar values to those seen in SHAM-operated rats. Conclusions: Ammonia-lowering therapy prevented the apparition of brain edema by partially decreasing brain lactate, thus suggesting that ammonia is not the only factor that contributes to an increase in brain lactate. Inhibition of lactate production attenuated brain edema, while cerebral glutamine remained high. Our findings reveal that increased brain lactate, and not glutamine, contributes to the pathogenesis of brain edema in minimal HE.
Cristina R. Bosoi, Chantal Bémeur, Bich Nguyen, Mélanie Tremblay, Christopher F. Rose.
Background: Acute-on-chronic liver failure (ACLF) represents an acute decompensation of chronic liver disease. Brain edema is frequently observed in hepatic encephalopathy associated with both acute and chronic liver disease. Since systemic oxidative stress and ammonia are believed to act synergistically in inducing brain edema in chronic liver failure, the objective of this study was to develop a rat model of hepatic encephalopathy following ACLF, and to investigate the role of oxidative stress and ammonia in relation to brain edema. Methods: ACLF was induced in male Sprague-Dawley rats by portacaval shunt (PCA), followed 4 weeks later by hepatic artery ligation (HAL). Liver devascularisation by concomitant PCA and HAL was used to induce acute liver failure (ALF). Body temperature and blood glucose were monitored and maintained throughout the progression to coma. Control SHAM and PCA rats, sacrificed 4 weeks after surgery, were also included. Routine biochemistry and liver histopathology were used to assess liver status. Brain edema (specific gravimetric technique), reactive oxygen species and glutathione levels (spectrophotometry) were measured in plasma and brain tissue of all groups. Results: The onset of coma was significantly delayed in ACLF compared to ALF rats by approximately 8h. Liver necrosis markers AST and ALT did not differ between ACLF and ALF rats; however, liver histopathology showed more severe necrosis in ACLF than in ALF rats. Brain water content was significantly attenuated in acute-on-chronic rats: ACLF: 80.04±0.13 % (ns vs SHAM; p<0.01 vs ALF); SHAM: 80.12±0.09 %; ALF: 81.39±0.15 % (p<0.01 vs SHAM). Increase in arterial ammonia concentration was prevented in ACLF rats: ACLF: 0.35±0.07 mM (p<0.001 vs SHAM; p<0.001 vs ALF); SHAM: 0.06±0.01 mM; ALF: 1.34±0.09 mM (p<0.001 vs SHAM). Evidence of oxidative stress (increased reactive oxygen species and decreased glutathione levels) was systemically present in both ACLF and ALF rats, while signs of oxidative stress in the brain were present only in ALF rats. Conclusions: Our animal model of acute liver insult, superimposed on chronic hyperammonemia, reproduces the alterations observed in acute liver failure; however, the latter were attenuated. In spite of a more severe liver necrosis in ACLF rats, the onset of coma was delayed, and brain edema, ammonia levels and oxidative stress were reduced when compared to ALF rats. These findings therefore suggest that during chronic liver failure, compensatory mechanisms are developed, which in turn prevent the apparition of brain edema and attenuate oxidative stress during acute deterioration.
Increased cerebral lactate contributes to brain edema in cirrhotic rats.
Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Aims: Neurotoxic effects of ammonia have been shown to induce numerous metabolic alterations such as increased brain glutamine and lactate. In brain edema associated with acute liver failure, glutamine plays a controversial role and a few studies demonstrated lactate is also involved. Brain edema is also present in patients with chronic liver failure; in this situation roles of lactate and glutamine are less understood. We previously demonstrated an increase in lactate de novo synthesis in bile-duct ligated rats (BDL), a known model of chronic liver failure/minimal hepatic encephalopathy. To define the role of lactate in the pathogenesis of brain edema, the present study investigates the effects of inhibiting lactate production. Methods: BDL rats were treated with dichloroacetate (DCA, 25 mg/kg for 7 days starting at week 5 after intervention, intraperitoneally), a pyruvate dehydrogenase kinase inhibitor that leads to pyruvate dehydrogenase stimulation, therefore to a shift of pyruvate from glycolysis to oxidation and consequently to a decrease in lactate production. Brain edema (specific gravimetric technique) and glutamine (HPLC) were measured in brain tissue of BDL rats vs sham operated controls. Results: 6 weeks following BDL, rats develop brain edema and increased brain lactate compared to SHAM-operated controls. DCA treatment normalized brain lactate in BDL rats. DCA-treated BDL rats demonstrated a significant reduction of brain water content reaching values similar to those seen in SHAM-operated rats. Glutamine levels were increased in BDL vs sham operated rats and remained high in DCA-treated BDL rats (569.20±80.44 µM vs BDL: 796.60±71.50 µM, and vs SHAM: 442.80±33.79 µM). Conclusions: Inhibition of lactate production attenuated brain edema while cerebral glutamine levels remained high. Our findings suggest increased brain lactate, not glutamine, is associated with brain edema. Impaired lactate metabolism contributes to the pathogenesis of brain edema in minimal hepatic encephalopathy.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Introduction: L’insuffisance hépatique mène à l’hyperammonémie, le facteur principal de l’encéphalopathie hépatique (EH). Toutefois, le stress oxydatif peut avoir un rôle important dans l’exacerbation des effets neuropsychologiques de l’hyperammonémie chez les patients atteints de maladies hépatiques, dont l’œdème cérébral. Les rats cirrhotiques développent l’hyperammonémie et l’œdème cérébral, mais aussi une augmentation des espèces réactives d’oxygène (ROS) plasmatiques suite à une augmentation de l’activité de la xanthine oxydase. Afin de mieux comprendre la relation entre l’ammoniaque et le stress oxydatif dans la pathogenèse de l’œdème cérébral, dans cette étude nous avons investigué l’effet de l’allopurinol, un inhibiteur de la xanthine oxydase, chez des rats cirrhotiques. Méthodes: La cirrhose a été induite suite à une ligature de voie biliaire (BDL) pendant 6 semaines. Des rats BDL et contrôles SHAM-opérés ont reçu l’allopurinol (100 mg/kg/jour pour les derniers 10 jours). Des groupes contrôles BDL et SHAM-opérés ont reçu de la saline. L’ammoniaque et les ROS ont été mesurés dans le plasma (artériel) par, respectivement, un kit commercial et une technique de fluorescence. Le contenu en eau du cerveau a été mesuré dans le cortex frontal par une technique spécifique gravimétrique. Résultats: Chez les rats BDL traités avec allopurinol, nous avons observé une diminution significative des ROS et de l’ammoniaque systémique vs les rats BDL non-traités, aux valeurs similaires de celles des rats SHAM. Le contenu en eau du cerveau a été normalisé suite au traitement avec allopurinol. Conclusion: Le traitement avec allopurinol diminue les ROS et l’ammoniaque plasmatique et atténue l’œdème cérébral. Cela a démontré que le stress oxydatif joue un rôle dans le métabolisme de l’ammoniaque et dans la pathogenèse de l’œdème cérébral. Nos résultats suggèrent qu’un traitement antioxydant dirigé vers l’inhibition de la production des ROS pourrait être bénéfique dans le traitement de l’EH.
Cristina R. *Bosoi, Chantal Bémeur, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Aims: Acute-on-chronic liver failure (ACLF) represents an acute decompensation of liver cirrhosis. End-to-side portacaval anastomosis (PCA) followed by hepatic artery ligation (HAL) performed after 4 weeks represents a model of liver decompensation. In this model, the onset of coma is delayed compared to acute liver failure induced by hepatic devascularisation. As oxidative stress plays a role in brain edema in chronic liver failure, the objective of this study was to investigate the role of oxidative stress in the pathogenesis of brain edema in ACLF. Methods: Male Sprague-Dawley rats were subjected to PCA followed by hepatic artery ligation (HAL) either concomitantly (HAL-0) or 4 weeks (HAL-4W) following shunt surgery or to a SHAM intervention. Body temperature and blood glucose were monitored and maintained throughout the experiments. Brain edema (specific gravimetric technique) and glutathione levels (spectrophotometry) were measured in brain tissue of all groups. Results: Brain water content was significantly attenuated in “acute-on-chronic” rats (SHAM: 80.12±0.09 %; HAL-0: 81.39±0.15 % (p<0.01 vs SHAM); HAL-4W: 80.04±0.13 % (ns vs SHAM; p<0.01 vs HAL-0)). Arterial ammonia concentration followed a similar pattern (control: 0.060±0.007 mM; HAL-0: 1.340±0.090 mM (p<0.001 vs SHAM); HAL-4W: 0.350±0.070 mM (p<0.001 vs SHAM; p<0.001 vs HAL-0)). Glutathione levels did not change in HAL-4W compared to SHAM and were significantly decreased in the brains of HAL-0 rats (by 36% vs SHAM, p<0.05 and by 25% vs HAL-4W). These effects were not due to an improvement in liver function, as liver necrosis markers AST and ALT did not differ between HAL-4W and HAL-0 rats. Conclusions: Brain edema, ammonia levels and oxidative stress are reduced in ACLF rats compared to acute liver failure rats. These findings suggest that during chronic liver failure compensatory mechanisms are developed that prevent the apparition of brain edema and attenuate oxidative stress during an acute deterioration.
Christian Parent-Robitaille, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Introduction: L'encéphalopathie hépatique (EH), une complication grave de la maladie du foie, se manifeste par un syndrome métabolique neuropsychiatrique complexe mais ayant toujours été considérée comme réversible. La transplantation hépatique (TH) est le seul traitement efficace pour traiter les patients de maladie hépatique, par contre les complications neurologiques survenant suite à une TH restent un problème persistant. Avec l’EH pré-TH, l'hypotension et une hypoxie cérébrale pendant la période péri-opératoire peuvent affecter les fonctions neurologiques. Ces observations nous ont conduits à l'hypothèse suivante: un patient cirrhotique atteint d’EH est plus à risque de subir des dommages cérébraux suite à une insulte d’hypotension/hypoxie. Méthodes: Pour vérifier cette hypothèse, nous évaluons l’effet d’une hypotension/hypoxie cérébrale chez un rat avec ligature de la voie biliaire (BDL) de 6 semaines (modèle établi de la maladie chronique du foie et de l’EH). Les animaux ont été sacrifiés et leurs cerveaux ont été évalués pour une perte/altération cellulaire par marquage neuronal (au violet de crésyl et par immunohistochimie avec NeuN) ainsi que pour détecter des protéines pro- et anti-apoptotiques (par western blot). Résultats: Jusqu’à maintenant, nous avons démontré qu’une hypotension/hypoxie cérébrale de 90 minutes ne cause pas de perte neuronale ni une augmentation de marqueurs apoptotiques dans le cerveau de rats encéphalopatiques comparativement aux cerveaux de rats normaux. Conclusions: Nous sommes présentement en train d’évaluer les cerveaux de rats ayant subi une hypotension/hypoxie de 30 minutes. À cause de la fragilité d’un cerveau encéphalopatique, nous croyons qu’une hypotension/hypoxie moindre pourrait donner lieu à une plus grande perte/altération cellulaire que dans un cerveau normal. Nous allons par la suite utiliser d’autres techniques telles que le marquage avec fluorojade, un marqueur d’apoptose et TUNEL une méthode pour détecter fragmentation de l'ADN
Le rôle du stress oxydatif dans la pathogenèse de l’œdème cérébral dans l’encéphalopathie hépatique.
Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
L'encéphalopathie hépatique (EH), un syndrome métabolique neuropsychiatrique, est une complication majeure de la maladie hépatique. L’hyperammonémie est le facteur central dans l’EH. L’œdème cérébral est une importante caractéristique pathophysiologique de l’EH. Nous avons investigué le rôle du stress oxydatif dans deux modèles de maladie du foie/EH chez le rat; 1) dérivation portosystémique (PCA), et 2) ligature de la voie biliaire (BDL). L’ammoniaque et les espèces réactives d’oxygène (ROS) ont été mesurés dans le plasma (artériel) et au niveau cérébral. Le contenu cérébral en eau a été mesuré dans le cortex frontal. L’hyperammonémie s’est développée dans les deux groupes, PCA et BDL (p<0.001 vs contrôles). En conséquence, l’ammoniaque cérébrale était aussi élevée, sans différence significative entre les PCA et BDL. Seuls les rats BDL montraient une augmentation des ROS plasmatiques. Nous n’avons pas observé d’augmentation des ROS cérébraux chez les PCA et BDL. Le contenu en eau du cerveau était augmenté seulement chez les rats BDL (p<0.05 vs contrôles) ; il a été normalisé suite à un traitement avec un antioxydant (allopurinol). L’induction du stress oxydatif chez les rats PCA à l’aide du diméthyle maléate (inhibiteur de glutathion) a provoqué l’augmentation de l’eau cérébrale (p<0.05 vs contrôles). En conclusion, le stress oxydatif systémique est impliqué dans l’œdème cérébral et son effet synergique avec l’ammoniaque contribue à la progression de l’EH.
Implication de la glutaminase dans l'insuffisance hépatique chronique.
Ada Rivera, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
L’encéphalopathie hépatique (EH), un syndrome métabolique neuropsychiatrique, est une complication majeure de la maladie hépatique. L'EH est caractérisée par des troubles cognitifs, psychiatriques et moteurs allant jusqu'au coma hépatique et la mort. Les causes de l'EH sont multifactorielles et encore assez peu connues. L’ammoniaque, neurotoxique, est considérée comme le facteur principal. Celle-ci est produite par la dégradation des protéines au niveau intestinal. Elle est détoxiquée par le cycle d'urée dans le foie, une voie métabolique qui permet d’éliminer de l’organisme les excès d’azote d’origine endogène ou exogène. Au cours de l’insuffisance hépatique chronique, le cycle d’urée est déficient et en conséquence une concentration anormalement élevée d’ammoniaque circule dans le sang (hyperammoniémie) et atteint le cerveau. L’ammoniaque peut aussi être produite par désamination de la glutamine en glutamate et en ammoniaque par la glutaminase, une enzyme exprimée dans les hépatocytes périportaux. La glutaminase est également exprimée dans les cellules épithéliales des tubules rénaux, où l'ammoniaque produit est excrétée sous forme d'ions ammonium, un mécanisme important de la fonction rénale de la régulation acide-base. On la retrouve aussi dans le cerveau où elle joue un rôle essentiel dans la production du neurotransmetteur glutamate. L’hypothèse du projet est que la glutaminase joue un rôle fondamental dans le développement de l’hyperammoniémie dans l’insuffisance hépatique chronique. Ce projet a comme objectif principal de mesurer l’activité enzymatique (par dosage enzymatique) et l’expression (par immunobuvardage) de la glutaminase dans le rein, le foie et le cerveau lors d’insuffisance hépatique chronique induite chez le rat. Les résultats de ce travail nous permettront de comprendre le rôle de la glutaminase dans l’hyperammoniémie observée chez les patients atteints d’insuffisance hépatique chronique.
Systemic oxidative stress induction leads to brain edema in hyperammonemic portacaval-shunted rats.
Cristina Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Aims: Although ammonia is the central component in the pathogenesis of hepatic encephalopathy, it is believed oxidative stress (OS) plays a role in the pathogenesis of brain edema during liver disease. We previously demonstrated that portacaval shunted hyperammonemic rats do not develop OS or brain edema (Bosoi et al., FRBM, 2012). To define whether a synergistic effect exists between hyperammonemia and OS in the development of brain edema, the present study investigates the role of OS in the pathogenesis of brain edema in PCA rats following glutathione depletion by diethyl maleate (DEM). Methods: We evaluated the effect of DEM (1 mg/kg/day intraperitoneally for 10 days starting day 18 after surgery) in PCA and SHAM-operated rats. Rats were sacrificed at day 28 and OS was evaluated by measuring arterial and cerebral malon-dialdehyde (MDA, commercial kit), reactive oxygen species (ROS, DCFDA fluorescence), and 4-hydroxy-2-nonenal (HNE, Western blot). Ammonia levels (commercial kit) were also assessed. Frontal cortex brain water was measured using a specific gravimetric technique. Results: DEM induced a significant increase in plasma MDA, ROS and HNE levels in PCA rats. No increase was detected in DEM-treated SHAM-operated controls. No changes in cerebral OS markers were observed in any group. Ammonia levels increased in non-treated and DEM-treated PCA vs SHAM-operated rats (p<0.001) and remained unchanged between non-treated and DEM-treated PCA groups. Brain water content increased in DEM-treated PCA rats vs non-treated PCA rats (PCA+DEM: 78.45±0.13% vs PCA: 77.38±0.11%, p< 0.001). Conclusions: DEM treatment in PCA rats induced systemic, not central OS. This, superimposed on hyperammonemia, led to the development of brain edema. Similar DEM doses did not result in increased OS and brain edema in SHAM-operated rats, suggesting PCA rats are more susceptible to OS. Our findings support a synergistic effect between hyperammonemia and systemic OS in the pathogenesis of brain edema in hepatic encephalopathy.
Glutathione depletion leads to brain edema in portacaval-shunted rats.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Aims: The pathogenesis of hepatic encephalopathy (HE) is multifactorial. Even though ammonia is the central component in the pathogenesis of HE, oxidative stress is believed to play a role in exacerbating the neuropsychological effects of ammonia in patients with liver disease. With new, highly sensitive imaging techniques, brain edema is observed in HE patients. We previously demonstrated that portacaval shunted hyperammonemic rats do not develop oxidative stress or brain edema. In order to define a synergistic effect between hyperammonemia and systemic oxidative stress, the present study investigates the role of oxidative stress in the pathogenesis of brain edema in PCA rats following glutathione depletion by diethyl maleate (DEM). Methods: In the first set of experiments, we evaluated the effect of DEM in PCA and SHAM-operated control rats by injecting DEM at a dose of 0.4 and 1 mg/kg/day intraperitoneally for 10 days starting at day 18 after surgery. Rats were sacrificed at day 28 and oxidative stress was evaluated by arterial malon-dialdehyde (MDA, commercial kit). In the second set of experiments, 1 mg/kg/day DEM was used to induce oxidative stress. Ammonia (commercial kit) as well as other different oxidative stress markers: reactive oxygen species (DCFDA fluorescence technique), and 4-hydroxy-2-nonenal (HNE, Western blot) were assessed in arterial plasma and frontal cortex tissue. Brain water content was measured in the frontal cortex using a specific gravimetric technique. Results: DEM at 1 mg/kg/day (not 0.4 mg/kg/day) induced a significant increase in MDA levels in PCA rats. No increase in MDA was detected following either dose of DEM in SHAM-operated controls. Ammonia levels in both DEM-treated and non-treated PCA rats were significantly increased vs respective sham-operated controls (p<0.001) and remained unchanged between non-treated and DEM-treated PCA groups (p>0.05). An increase in brain water content was observed in DEM-treated PCA rats vs non-treated PCA rats (PCA+DEM: 78.45 ± 0.13% vs PCA: 77.38 ± 0.11, p< 0.001). Although no significant changes in reactive oxygen species were observed, there was an increase in plasma levels of HNE in DEM-treated PCA rats compared to non-treated PCA rats. No significant changes in any oxidative stress markers were observed in the frontal cortex. Conclusions: DEM treatment in PCA rats induced systemic oxidative stress but not central oxidative stress. This, imposed on hyperammonemia, was accompanied by the onset of brain edema in rats with PCA. Oxidative stress and brain edema were not detected in SHAM-operated rats, which were not hyperammonemic. Our findings suggest a synergistic effect between hyperammonemia and systemic oxidative stress is implicated in the pathogenesis of brain edema in hepatic encephalopathy.
Xanthine oxidase inhibition attenuates brain edema in in rats with liver failure.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Aims: Liver disease leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE). There is increasing evidence that systemic oxidative stress may exacerbate the neuropsychological effects of hyperammonemia in patients with liver disease. With new, highly sensitive imaging techniques, brain edema is commonly being observed in patients with cirrhosis and HE. Bile duct ligated rats, six-week after intervention, present with brain edema, hyperammonemia and also an increase in plasma reactive oxygen species (ROS) along with an increase in xanthine oxidase activity. In order to better understand the relationship between oxidative stress and ammonia and their role in the pathogenesis of brain edema, we evaluated the effect of xanthine oxidase inhibition in rats with cirrhosis. Methods: Cirrhosis was induced in rats by bile duct ligation (BDL) for 6 weeks. BDL and SHAM-operated rats received 100 mg/kg/day of allopurinol (xanthine oxidase inhibitor) during the last 10 days before sacrifice. As control groups, separate BDL and SHAM-operated rats received equivalent volume of saline. AST and ALT were measured at the end of the treatment period to assess liver function. Ammonia and ROS were assessed in arterial plasma using a commercially available kit and a DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique. Results: Arterial ROS and ammonia levels were significantly increased in BDL vs SHAM-operated rats (p<0.001). BDL rats treated with allopurinol demonstrated a significant decrease in systemic ROS as well as ammonia levels vs non-treated BDL rats (1.70 ± 0.53RFU vs 4.97 ± 1.38RFU, p<0.05, 37.9 ± 13.8µM vs 101.1 ± 10.1µM, p<0.001, respectively), reaching values similar to those seen in SHAM-operated rats. Brain water content increased in BDL vs SHAM-operated rats and normalised in allopurinol treated BDL rats (77.20 ± 0.08% vs BDL: 78.46 ± 0.28%, p<0.05). Liver function markers, AST and ALT, increased in BDL rats compared to their respective SHAM-operated controls (p<0.001) and were not attenuated following allopurinol treatment. Conclusions: Allopurinol treatment decreased systemic ROS and attenuated brain edema as well as arterial ammonia levels. The effect of allopurinol demonstrates oxidative stress plays a role in ammonia metabolism and in the pathogenesis of brain edema. Our results suggest antioxidant treatment directed towards inhibiting ROS production could be beneficial in lowering ammonia and treating HE. Additional studies are warranted to evaluate the implication of oxidative stress in ammonia metabolism.
Cristina R. Bosoi, Xiaoling Yang, Jimmy Huynh, Christian Parent-Robitaille, Wenlei Jiang, Mélanie Tremblay, Christopher F. Rose.
Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE); however, a correlation between blood ammonia levels and HE severity remains controversial. It is believed oxidative stress plays a role in modulating the effects of hyperammonemia. This study aimed to determine the relationship between chronic hyperammonemia, oxidative stress, and brain edema (BE) in two rat models of HE: portacaval anastomosis (PCA) and bile-duct ligation (BDL). Ammonia and reactive oxygen species (ROS) levels, BE, oxidant and antioxidant enzyme activities, as well as lipid peroxidation were assessed both systemically and centrally in these two different animal models. Then, the effects of allopurinol (xanthine oxidase inhibitor, 100mg/kg for 10days) on ROS and BE and the temporal resolution of ammonia, ROS, and BE were evaluated only in BDL rats. Similar arterial and cerebrospinal fluid ammonia levels were found in PCA and BDL rats, both significantly higher compared to their respective sham-operated controls (p<0.05). BE was detected in BDL rats (p<0.05) but not in PCA rats. Evidence of oxidative stress was found systemically but not centrally in BDL rats: increased levels of ROS, increased activity of xanthine oxidase (oxidant enzyme), enhanced oxidative modifications on lipids, as well as decreased antioxidant defense. In PCA rats, a preserved oxidant/antioxidant balance was demonstrated. Treatment with allopurinol in BDL rats attenuated both ROS and BE, suggesting systemic oxidative stress is implicated in the pathogenesis of BE. Analysis of ROS and ammonia temporal resolution in the plasma of BDL rats suggests systemic oxidative stress might be an important "first hit", which, followed by increases in ammonia, leads to BE in chronic liver failure. In conclusion, chronic hyperammonemia and oxidative stress in combination lead to the onset of BE in rats with chronic liver failure.
Cristina R. Bosoi, Christian Parent-Robitaille, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Aims: Brain edema is a common occurrence in patients with hepatic encephalopathy (HE) due to chronic liver disease however the underlying pathophysiological mechanisms are weakly described. Hyperammonemia is considered the central component, but levels of plasma ammonia and severity of HE poorly correlate. Oxidative stress and impaired lactate metabolism are pathogenetic factors believed to be involved. This study investigates the temporal resolution of increases in ammonia, oxidative stress and lactate in relation to the development of brain edema in bile-duct ligated rats (BDL), a widely used rat model of chronic liver disease and HE. Methods: Cirrhosis was induced in rats through ligation of the bile duct. Ammonia and reactive oxygen species (ROS) were assessed in arterial plasma using a commercially available kit and a DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique and lactate by Amplex Red fluorescence. Measurements were performed in BDL rats vs sham operated controls at 2, 4 and 6 weeks after surgical intervention in plasma and cerebrospinal fluid or brain tissue. Results: See table. Conclusions: Following 2 weeks of BDL, an increase in plasma ROS is observed with no increase in the other factors. Following 4 weeks of BDL, in addition to an increase in systemic ROS, an increase in plasma and brain ammonia and brain (not plasma) lactate is demonstrated however no evidence of brain edema. Brain edema appears at 6 weeks, along with an increase in all 3 factors. The further significant increase in brain lactate and ammonia at 6 weeks compared to 4 weeks, superimposed on systemic oxidative stress, may be responsible the of development of brain edema in BDL rats. Our results support the multifactorial pathogenesis of brain edema in HE and suggests systemic oxidative stress might be an important “first hit”, followed by increases in ammonia and lactate, in the pathogenesis of brain edema in chronic liver failure. SHAMⱡBDL 2 weeksBDL 4 weeksBDL 6 weeks PLASMA AMMONIA(μM)37.24±12.5433.24±16.7371.32±12.03*118.50±10.78* ROS(RFU)0.08±0.032.94±0.39***2.05±0.59***3.68±0.86*** LACTATE(mM)1.40±0.191.22±0.181.21±0.131.75±0.35 CEREBROSPINAL FLUID AMMONIA(μM)36.12±13.2335.94±9.6389.38±13.07*128.4±36.66*** ROS(RFU)26.11±9.9423.95±12.2613.61±1.6325.97±8.21 BRAIN TISSUE LACTATE(μM/ 100 g proteins)88.51±5.2698.06±7.78190.26±26.14*254.60±10.12*** BRAIN EDEMA (%)78.05±0.1477.73 ±0.0777.69±0.0779.03±0.31* ⱡ mean value of SHAM-operated rats 2, 4 and 6 weeks *p<0.05 vs SHAM ***p<0.01 vs SHAM $p<0.05 vs BDL 4 weeks
Allopurinol attenuates systemic oxidative stress and hyperammonemia in bile-duct ligated rats.
Cristina R. Bosoi, Christian Parent-Robitaille, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Background: Liver disease leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE). There is increasing evidence systemic oxidative stress may exacerbate the neuropsychological effects of hyperammonemia in patients with liver disease. With new highly sensitive imaging techniques, brain edema is frequently being observed in patients cirrhosis and HE. Six-week cirrhotic rats develop brain edema, hyperammonemia and also an increase in plasma reactive oxygen species (ROS) along with an increase in xanthine oxidase activity. In order to better understand the relationship between oxidative stress and ammonia and their role in the pathogenesis of brain edema, we evaluated the effect of allopurinol, a xanthine oxidase inhibitor, in rats with cirrhosis. Methods: Secondary biliary cirrhosis was induced in rats by bile duct ligation (BDL) for 6 weeks. BDL and SHAM-operated rats received 100 mg/kg/day of allopurinol for 10 days. A group of BDL and SHAM-operated rats received saline. AST and ALT were measured at the end of the treatment period to assess liver function. Ammonia and ROS were assessed in arterial plasma using a commercially available kit and a DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique. Results: Arterial ROS and ammonia levels were significantly increased in BDL vs SHAM-operated rats (p<0.001). BDL rats treated with allopurinol demonstrated a significant decrease in systemic ROS as well as ammonia levels vs non-treated BDL rats (1.70 ± 0.53RFU vs 4.97 ± 1.38RFU, p<0.05, 37.9 ± 13.8µM vs 101.1 ± 10.1µM, p<0.001, respectively), reaching values similar to those seen in SHAM-operated rats. Brain water content increased in BDL vs SHAM-operated rats and normalised in allopurinol treated BDL rats (77.20 ± 0.08% vs BDL: 78.46 ± 0.28%, p<0.05). Liver function markers, AST and ALT, increased in BDL rats compared to their respective SHAM-operated controls (p<0.001) and were not attenuated following allopurinol treatment. Conclusions: Allopurinol treatment decreased systemic ROS and attenuated brain edema as well as arterial ammonia levels. The effect of allopurinol demonstrates oxidative stress plays a role in ammonia metabolism and in the pathogenesis of brain edema. Our results suggest antioxidant treatment directed towards inhibiting ROS production could be beneficial in lowering ammonia and treating HE. Additional studies are warranted to evaluate the implication of oxidative stress in ammonia metabolism.
Jimmy Huynh, Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Brain edema is a serious complication associated with hepatic encephalopathy (HE) due to chronic liver failure (CLF) and its pathogenesis remains undefined. NKCC1, a Na-K-Cl cotransporter, located on the blood-brain barrier (BBB) has been demonstrated to be implicated in the pathogenesis of brain edema in experimental models of ischemia. Therefore, our aim was to 1) investigate the relationship of hyperammonemia, 2) study the integrity of the BBB and 3) determine the role of NKCC1, in association with brain edema in rats with CLF. Methods: Two distinct animal models of CLF and HE were used; i) biliary cirrhosis model (6 weeks bile duct ligation (BDL)) ii) portacaval shunt model (4 weeks portacaval anastomosis (PCA)). Brain water content was measured using the specific gravimetric method. BBB breakdown was assessed by measuring brain extravasation of injected BBB permeability tracers (Evans blue and sodium fluorescein). Expression of BBB tight junction proteins (occludin, claudin-5, ZO-1 and ZO-2) were assessed by immunoblot. Levels of brain NKCC1 mRNA were evaluated by RT-PCR in isolated cerebral microvessels. Rats were treated with bumetanide (an NKCC inhibitor; administered (i.p) for 10 days). Results: Similar degree of hyperammonemia was measured in both BDL and PCA rats however brain edema was only found in BDL rats. In brains of both BDL and PCA rats, extravasation of Evans blue and sodium fluorescein was not detected and no significant change in the levels of all tight junction proteins was found. Brain water content was reduced in bumetanide-treated BDL vs BDL-non treated (77.35±0.18% vs 78.89±0.25%). A 2.4 fold increase in NKCC1 mRNA was detected in BDL vs BDL-sham rats whereas no change was found in PCA vs PCA-sham rats. Conclusions: Chronic hyperammonemia independently does not lead to an increase in brain water. Brain edema, present in BDL rats, is not associated with a change in either BBB integrity or expression of BBB tight junction proteins and is therefore not of vasogenic origin. Furthermore, an increase in NKCC1 mRNA and attenuation of brain edema following bumetanide treatment, suggests NKCC1, independent of hyperammonemia, plays a role in the development of brain edema in CLF.
Claudia Zwingmann, Jimmy Huynh, Cristina R. Bosoi, Christian Parent-Robitaille, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Aims: Brain edema represents a constant finding in patients with hepatic encephalopathy (HE) due to chronic liver failure; however its pathogenetic mechanisms are poorly described. Hyperammonemia is considered the central component in the pathogenesis of HE, but ammonia levels are not correlated with severity of HE. Other factors such as oxidative stress and impaired lactate metabolism are believed to be involved. Temporal resolution of these factors involved in the progression of the disease and brain edema might elucidate the relationship between these pathogenetic factors. The present study investigates temporal resolution of ammonia, oxidative stress and lactate in relation to the development of brain edema in bile-duct ligated rats (BDL), a widely used rat model of chronic liver failure and HE. Methods: Ammonia (commercial kit), reactive oxygen species (ROS) (DCFDA fluorescence), lactate (Amplex Red fluorescence) and brain edema (specific gravimetric technique) were measured in BDL rats vs sham operated controls at 2, 4 and 6 weeks after surgical intervention in plasma and cerebrospinal fluid or brain tissue. Results: See table.Conclusions: Following 2 weeks of BDL, an increase in plasma oxidative stress is observed with no appearance of hyperammonemia, hyperlactataemia, increased brain lactate and ammonia or brain edema. Following 4 weeks of BDL, in addition to an increase in systemic oxidative stress, an increase in plasma and brain ammonia and brain (not plasma) lactate is demonstrated but still no evidence of brain edema. Brain edema appears at 6 weeks, along with an increase in all 3 pathogenetic factors. The further increase in brain lactate and ammonia compared to 4 weeks, superimposed on systemic oxidative stress, may be responsible the development of brain edema in BDL rats. Our results support the multifactorial pathogenesis of brain edema in HE and suggests systemic oxidative stress might be an important “first hit”, followed by increases in ammonia and lactate, in the pathogenesis of brain edema in chronic liver failure.
Christian Parent-Robitaille, Cristina R. Bosoi, Claudia Zwingmann, Jimmy Huynh, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Aims: Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE). Neurotoxic effects of ammonia induce numerous metabolic alterations such as increased brain lactate (Lac) and glutamine (Gln) levels. Brain edema is present in patients with chronic liver failure however the pathophysiological mechanisms are not clearly understood. The present study investigates the role of brain ammonia, Lac and Gln in pathogenesis of brain edema in 2 different rat models of chronic liver failure/HE; 1) portacaval anastomosis (PCA), and 2) bile-duct ligation (BDL). Methods: Ammonia (commercial kit), brain edema (specific gravimetric technique) Lac (Amplex Red fluorescence) and Gln (1H nuclear magnetic spectroscopy) were measured in brain tissue of PCA and BDL rats vs sham operated controls. De novo synthesis of Lac and Gln was assessed in brain tissue by 13C nuclear magnetic resonance spectroscopy, after injecting PCA and BDL rats along with their respective sham operated controls with [U-13C] glucose (500 mg/kg, i.p) 30 minutes before sacrifice. Lac, Gln and brain edema were also investigated in BDL rats at 2, 4 and 6 weeks after surgery and after reducing ammonia levels with AST-120 (spherical carbon adsorbent), at 1g/kg/day for 6 weeks. Results: Hyperammonemia developed in both PCA (177.3±8.9μM vs sham: 52.1±11.3μM; p<0.0001) and BDL (155.0±8.9μM vs sham: 41.0±11.2μM; p<0.0001); with no significant difference between the groups. An increase in brain water content was observed in rats with BDL (81.88±0.12% vs sham: 81.13±0.15%, p<0.05), as well as total Lac levels; whereas no significant change in brain water and total Lac was found in PCA. Gln levels significantly increased in PCA rats and BDL rats vs respective sham-operated controls. A significant increase in de novo synthesis of 13C Lac and 13C Gln from 13C glucose was found in BDL rats, whereas in PCA rats only de novo synthesis of 13C Gln increased. In addition, total Lac levels were increased in BDL rats before the apparition of brain edema. Following AST-120 treatment, Lac levels and brain edema significantly decreased, while Gln levels remained unchanged. Conclusions: BDL and PCA rats both presented with similar levels of hyperammonemia and Gln, as well as increased de novo synthesis of Gln from glucose. However only BDL rats demonstrated an increase in brain water and Lac as well as increased de novo synthesis of Lac from glucose. Our findings suggest increased brain Lac, not increased brain Gln, is associated with brain edema. We conclude that impaired Lac metabolism may contribute to the pathogenesis of brain edema in HE.
Jimmy Huynh, Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Aims: Brain edema is a serious complication associated with hepatic encephalopathy (HE) due to chronic liver failure. It is unclear whether brain edema is of vasogenic (blood brain barrier (BBB) breakdown) or of cytotoxic (disturbance of neurocellular metabolism) origin. It has been demonstrated that the Na-K-Cl cotransporter (NKCC) located on the luminal side of the BBB is implicated in the pathogenesis of brain edema in different animal models of ischemia. Furthermore, following the administration of bumetanide, an inhibitor of NKCC, brain edema is attenuated. Therefore, our aim was to study the BBB integrity and the role of NKCC in the pathogenesis of brain edema in cirrhotic rats. Methods: Two distinct animal models of chronic liver failure and HE are used in the present study; 1) biliary cirrhosis model (6 weeks bile duct ligation (BDL)). 2) portacaval shunt model (4 weeks portacaval anastomosis (PCA)). Both models develop hyperammonemia however brain edema is only observed in BDL. BBB breakdown was assessed by measuring brain extravasation of BBB permeability tracers. Evans blue and sodium fluorescein were injected (i.v), brains were perfused and extravasation was determined by spectophotometry. Expression of BBB tight junction proteins (occludin, claudin-5, ZO-1 and ZO-2) were assessed by immunoblot. Bumetanide was administered (i.p) for 10 days in BDL and BDL SHAM. Brain water content was measured in the frontal cortex using the specific gravimetric method. Levels of brain NKCC mRNA were evaluated by RT-PCR in microvessels isolated using centrifugation methods. Results: Extravasation of Evans blue and sodium fluorescein was not detected and there was no significant change in all tight junction protein levels measured in both BDL and PCA (negative control) models. Brain water content was reduced in bumetanide-treated BDL rats compared to control (77.66±0.15% vs 78.12±0.21%). In brain microvessels, NKCC mRNA increased in BDL rats compared to BDL SHAM (0.78±0.09 vs. 1.92±0.42) whereas no change was found in PCA compared to PCA SHAM (1.72±0.52 vs. 1.53±0.23). Conclusions: BDL rats did not demonstrate a change in BBB integrity or a change in expression of BBB tight junction proteins. This suggests brain edema in BDL is not of vasogenic origin. Moreover, an increase of NKCC mRNA and an attenuation of brain edema following bumetanide treatment were demonstrated in BDL rats suggesting NKCC plays a role in the development of brain edema in chronic liver failure.
Cristina R. Bosoi, Christian Parent-Robitaille, Keith Anderson, Mélanie Tremblay, Christopher F. Rose.
The pathogenesis of hepatic encephalopathy is multifactorial, involving gut-derived toxins such as ammonia, which has been demonstrated to induce oxidative stress. Therefore, a primary hepatic encephalopathy treatment target is reducing ammonia production in the gastrointestinal tract. AST-120, an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600 m(2) /g, acts as a sink for neurotoxins and hepatotoxins present in the gut. We evaluated the capacity of AST-120 to adsorb ammonia in vitro and to lower blood ammonia, oxidative stress and brain edema in cirrhotic rats. Cirrhosis was induced in rats by bile duct ligation for 6 weeks. AST-120 was administered by gavage preventively for 6 weeks (0.1, 1, and 4 g/kg/day). In addition, AST-120 was evaluated as a short-term treatment for 2 weeks and 3 days (1 g/kg/day) and as a sink to adsorb intravenously infused ammonium acetate. In vitro, AST-120 efficiently adsorbed ammonia. Ammonia levels significantly decreased in a dose-dependent manner for all AST-120-treated bile duct-ligated rats (nontreated: 177.3 ± 30.8 μM; AST-120, 0.1 g/kg/day: 121.9 ± 13.8 μM; AST-120, 1 g/kg/day: 80.9 ± 30.0 μM; AST-120, 4 g/kg/day: 48.8 ± 19.6 μM) and significantly correlated with doses of AST-120 (r = -0.6603). Brain water content and locomotor activity normalized after AST-120 treatments, whereas arterial reactive oxygen species levels remained unchanged. Furthermore, AST-120 significantly attenuated a rise in arterial ammonia after ammonium acetate administration (intravenously). Conclusion:AST-120 treatment decreased arterial ammonia levels, normalized brain water content and locomotor activity but did not demonstrate an effect on systemic oxidative stress. Also, AST-120 acts as an ammonia sink, efficiently removing blood-derived ammonia. Additional studies are warranted to evaluate the effects of AST-120 on hepatic encephalopathy in patients with advanced liver disease. (HEPATOLOGY 2011;).
Cristina R. Bosoi, Claudia Zwingmann, Jimmy Huynh, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Introduction: L’insuffisance hépatique mène à l’hyperammonémie, la composante centrale dans la pathogénèse de l’encéphalopathie hépatique (EH). Les niveaux neurotoxiques d’ammoniaque induisent des nombreuses altérations métaboliques telles que l’augmentation du lactate et glutamine au niveau cérébral. Des nouvelles techniques d’imagerie ont démontré que l’œdème cérébral est présent chez les patients avec insuffisance hépatique chronique, mais les mécanismes pathophysiologiques ne sont pas bien connus. Dans cette étude, nous avons investigué l’implication de la synthèse de novo du lactate et glutamine dans la pathogénèse de l’œdème cérébral en utilisant 2 modèles différents d’insuffisance hépatique chronique/EH chez le rat: 1) la dérivation portosystémique (PCA); et 2) la ligature de voie biliaire (BDL). Méthodes: Des rats PCA et BDL, ainsi que contrôles SHAM-opérés ont été injectés avec [U-13C] glucose (500 mg/kg, i.p) et sacrifiés après 30 minutes. Les niveaux totaux, ainsi que la synthèse de novo de glutamine et du lactate ont été mesurés dans le tissu cérébral par spectroscopie de résonance magnétique nucléaire 1H et 13C. L’ammoniaque a été mesurée dans le plasma artériel et le liquide céphalorachidien par un kit commercial. Le contenu en eau du cerveau a été mesuré dans le cortex frontal par une technique spécifique gravimétrique. Résultats: L’hyperammonémie s’est développée dans les deux groupes; PCA: 177.3 ± 8.9 μM vs SHAM: 52.1 ± 11.3 μM; p<0.001 et BDL: 155.0 ± 8.9 μM vs SHAM: 41.0 ± 11.2 μM; p<0.001, sans différence significative entre les 2 groupes. Des résultats similaires ont été observés dans le liquide céphalorachidien; PCA: 179.5 ± 10.3 μM vs SHAM: 34.9 ± 6.3 μM; p<0.001 et BDL: 142.6 ± 28.3 μM vs SHAM: 27.9 ± 4.9 μM; p<0.001. Le contenu en eau du cerveau a augmenté dans les rats BDL (BDL: 81.88 ± 0.12% vs SHAM: 81.13 ± 0.15%, p<0.05), par contre dans les rats PCA il n’y avait pas une différence significative comparativement au rats SHAM-opérés. Les niveaux de glutamine étaient augmentés 3 fois chez les rats PCA vs SHAM et 2 fois chez les rats BDL vs SHAM. Une augmentation significative de la synthèse de novo du 13C lactate et 13C glutamine provenant du 13C glucose administré a été observée chez les BDL (1.6 fois, respectivement 2 fois vs SHAM), tandis que chez les rats PCA seulement une augmentation de la synthèse de novo de 13C glutamine a été observée. Conclusions: Les rats PCA et BDL présentent des taux similaires d’ammoniaque plasmatique et cérébral et une augmentation de la synthèse de novo de glutamine cérébrale provenant du glucose, mais seulement les rats BDL présentent l’œdème cérébral ainsi qu’une augmentation de la synthèse de novo du lactate cérébral provenant du glucose. Nos résultats suggèrent que le lactate est un important facteur dans la pathogénèse de l’œdème cérébral dans l’insuffisance hépatique chronique. Projet subventionné par: Instituts de recherche en santé du Canada
Jimmy Huynh, Cristina Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Objectif : L’œdème cérébral est un symptôme sévère de l’encéphalopathie hépatique (EH) lors d’une insuffisance hépatique chronique. La cause de l’œdème cérébral est ambigüe parce qu’elle peut être de type vasogénique, la rupture des jonctions serrées de la barrière hémato-encéphalique (BHE), ou de type cytotoxique, la perturbation du métabolisme neurocellulaire. Plusieurs recherches démontrent que le cotransporteur Na-K-Cl 1 (NKCC1) serait impliqué dans la pathogénèse de l’œdème cérébral dans différents modèles animaux d’ischémie cérébrale et qu’un traitement avec de la bumetanide, un inhibiteur de NKCC1, atténue l’augmentation d’eau dans le cerveau. Ainsi, notre objectif était d’étudier l’intégrité de la BHE et le rôle de NKCC1 dans la pathogénèse de l’œdème cérébral chez des rats cirrhotiques. Méthodes : Deux modèles animaux d’insuffisance hépatique chronique sont utilisés dans cette étude. Le premier modèle (cirrhose biliaire de 6 semaines (BDL)), est une ligature de la voie biliaire. Alors, la bile synthétisée par les hépatocytes s’accumule dans le foie et provoque la cirrhose du foie. Ce modèle présente une hyperammonémie et du stress oxydatif plasmatique ainsi que l’œdème cérébral. Le deuxième modèle (dérivation portocave de 4 semaines (PCA)), est une anastomose de la veine porte à la veine cave inférieure. Ainsi, le sang provenant du système digestif n’est pas filtré par le foie, ce qui provoque une hyperammonémie mais elle n'est pas accompagnée par une induction de stress oxydatif et d’œdème cérébral alors ce sera un contrôle négatif. Pour déterminer la perméabilité générale de la barrière hémato-encéphalique, l’extravasation de l’Evans blue, un colorant qui se lie aux protéines (dont l’albumine sérique), et du fluorophore, fluorescéine de sodium, a été évaluée par spectrophotométrie et l’expression des protéines des jonctions serrées (occludin, claudin-5, ZO-1, ZO-2) a été mesurée par immunobuvardage dans les deux modèles. La bumetanide a été administrée i.p pendant 10 jours chez les BDL et BDL SHAM. La quantité d’eau dans le cortex cérébral a été mesurée par gravimétrie. L’expression d’ARNm de NKCC1 a été mesurée dans les microvaisseaux sanguins isolés à partir de cerveaux des deux modèles à l’aide d’un protocole de centrifugation. Résultats : L’extravasation des colorants n’a pas été détectée et l’expression des protéines de jonctions serrées est demeurée inchangée dans les deux modèles. L’œdème cérébral a été atténué lorsque la bumetanide a été administrée chez les BDL comparé aux contrôles (77.66±0.15% vs 78.12±0.21%). Dans les microvaisseaux sanguins cérébraux, le niveau d’ARNm de NKCC1 était augmenté chez les BDL comparé aux BDL SHAM (1.92±0.42 vs. 0.78±0.09) tandis qu’il restait inchangé chez les PCA comparé aux PCA SHAM (1.72±0.52 vs. 1.53±0.23). Conclusion : L’extravasation est absente et l’expression des protéines de jonctions serrées est inchangée donc l’œdème cérébral n’est pas de type vasogénique. L’augmentation d’ARNm de NKCC1 et l’atténuation de l’œdème cérébral par la bumetanide suggèrent que l’œdème cérébral est de type cytotoxique chez les rats avec une insuffisance hépatique chronique.
Cristina R. Bosoi, Claudia Zwingmann, Jimmy Huynh, Helen Marin, Mélanie Tremblay, Christopher F. Rose.
Background: Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy. Neurotoxic effects of ammonia have been shown to induce numerous metabolic alterations such as increased brain lactate and glutamine levels. Newly developed imaging techniques have demonstrated brain edema is present in patients with chronic liver failure however the pathophysiological mechanisms are not clearly understood. The present study investigates the role of de novo synthesis of brain lactate and glutamine in pathogenesis of brain edema in 2 different rat models of chronic liver failure/hepatic encephalopathy; 1) portacaval anastomosis (PCA), and 2) bile-duct ligation (BDL). Methods: PCA and BDL rats along with their respective sham-operated controls were injected with [1-13C] glucose (500 mg/kg, i.p) and sacrificed 30 minutes later. Glutamine and lactate were assessed in brain tissue by 1H and 13C nuclear magnetic resonance spectroscopy. Ammonia levels were measured in arterial plasma and cerebrospinal fluid using a commercially available kit. Brain water content was measured in frontal cortex using a specific gravimetric technique. Results: Hyperammonemia developed in both PCA (177.3 ± 8.9μM vs sham: 52.1 ± 11.3μM; p< 0.0001) and BDL (155.0 ± 8.9μM vs sham: 41.0 ± 11.2μM; p< 0.0001); with no significant difference between the groups (p> 0.05). Similar results were found in cerebrospinal fluid (PCA: 179.5 ± 10.3μM vs sham: 34.9 ± 6.3μM; p< 0.0001 and BDL: 142.6 ± 28.3μM vs sham: 27.9 ± 4.9μM; p< 0.0001); with no significant difference between the groups (p> 0.05). An increase in brain water content was observed in rats with BDL (81.88 ± 0.12% vs sham: 81.13 ± 0.15%, p< 0.05) whereas no significant change in brain water content was found in PCA vs their respective sham-operated controls. Glutamine levels significantly increased 3 fold in PCA rats and 2 fold in BDL rats vs respective sham-operated controls. A significant increase in de novo synthesis of 13C lactate and 13C glutamine from 13C glucose was found in BDL rats (1.6 fold and 2 fold respectively vs sham), whereas in PCA rats only de novo synthesis of 13C glutamine increased. Conclusion: BDL and PCA rats both presented with similar levels of hyperammonemia and increased brain ammonia, increased de novo synthesis of glutamine from glucose however only BDL rats demonstrated an increase in brain water as well as an increase in de novo synthesis of lactate from glucose. Our findings suggest lactate is an important pathogenic factor implicated in the pathogenesis of brain edema in chronic liver failure.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Ammonia is central in the pathogenesis of hepatic encephalopathy (HE) and clinical sequelae are exacerbated by systemic inflammation. Sequestration of ammonia in the gut represents a primary treatment target for HE. AST-120 (spherical carbon adsorbent), an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600m2/g works as a sink for neuro- and hepato–toxins present in the gut. In this study, we evaluated the capacity of AST-120 to lower arterial ammonia, brain edema and systemic inflammatory markers in cirrhotic rats. Methods: Cirrhosis was induced in rats by bile duct ligation (BDL). BDL and SHAM-operated rats received AST-120 dispersed in methylcellulose by gavage at a dose of 0.1, 1 or 4g/kg/day for 6 weeks. Ammonia and the pro-inflammatory cytokine TNF-α were measured in arterial plasma using a commercially available kit and ELISA technique respectively. Brain water content was measured in the frontal cortex, cerebellum and brain stem using the specific gravimetric technique. Results: Arterial ammonia increased in non-treated BDL vs SHAM-operated controls (166.9±21.1uM vs 70.5±14.4uM, p<0.01). All doses of AST-120 decreased ammonia in BDL to similar levels found in respective SHAM-operated controls; 0.1g/kg/day (117.2±12.6uM vs 100.4±7.3uM, p>0.05); 1g/kg/day (78.9±22.3uM vs 78.1±8.9uM, p>0.05) and 4g/kg/day (48.8±19.6uM vs 49.9±14.7uM, p>0.05). Ammonia levels significantly correlated with doses of AST-120 (r=-0.66, p<0.0001). Brain water content increased in frontal cortex, cerebellum and brain stem in BDL vs SHAM-operated and was normalized in all AST-120 treatment groups compared to respective controls. Circulating levels of TNF-α were significantly increased in BDL vs SHAM-operated rats (p<0.05). AST-120 treatment did not attenuate TNF-α levels compared to respective SHAM-operated controls. Conclusion: AST-120 treatment dose-dependently decreased arterial ammonia levels, which resulted in normalization of multi-foci brain edema. This response was not correlated with differences in levels of circulating TNF-α. AST-120 treatment is a safe, non-antibiotic alternative demonstrating a significant ammonia-lowering effects, as well as a protective effect on the development of brain edema in rats with chronic liver disease. AST-120 represents a useful tool to elucidate further the relationship between circulating ammonia and gut-derived or systemic inflammatory components of liver disease.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
AIMS: The pathogenesis of hepatic encephalopathy (HE) is multifactorial involving gut-derived toxins such as ammonia. Liver disease leads to hyperammonemia and neurotoxic levels of ammonia which have been demonstrated to induce oxidative stress. Therefore a primary treatment target for HE is to decrease ammonia production in the gastrointestinal tract. AST-120 (spherical carbon adsorbent), an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600m2/g acts as a sink for neuro- and hepato-toxins present in the gut. In this study, we evaluated the protective effect of AST-120 in lowering arterial ammonia and oxidative stress and in attenuating brain edema in rats with cirrhosis. METHODS: Secondary biliary cirrhosis was induced in rats by bile-duct ligation (BDL) for 6 weeks. BDL and SHAM-operated rats received AST120 (dispersed in methylcellulose (MC)) by gavage at a dose of 0.1, 1 or 4g/kg/day for 6 weeks. Control BDL and SHAM-operated groups received MC only. AST and ALT were measured to assess liver function. Ammonia and reactive oxygen species (ROS) were measured in arterial plasma using a commercially available kit and DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique. RESULTS: AST-120 was well-tolerated with no deaths in either of the treatment groups. Brain water content increased in BDL vs SHAM-operated rats (79.2±0.2% vs 78.7±0.1%, p<0.05). All AST-120 treatments, 0.1, 1 and 4g/kg/day, normalised brain water content in BDL rats. Arterial ammonia levels increased in the BDL control group vs SHAM-operated controls (169.9±21.1uM vs 70.5±14.4uM, p<0.05) and decreased significantly to SHAM levels in 0.1g/kg/day (117.2±12.6uM, p<0.05), 1g/kg/day (78.9±22.3uM, p<0.05) and 4g/kg/day (48.7±19.5uM, p<0.05) AST-120 treated BDL rats. Circulating levels of ROS were significantly increased in BDL vs SHAM-operated rats (11 fold, p<0.001). AST-120 treatments did not attenuate arterial levels of ROS compared to respective SHAM-operated controls. Liver functions enzymes, AST and ALT, were increased in all BDL rats compared to their respective SHAM-operated controls (p<0.001) but were not attenuated following AST120 treatments. CONCLUSIONS: AST-120 treatment normalized brain water content and decreased arterial ammonia levels but did not demonstrate an effect on systemic ROS. Long-term treatment with AST-120 is a safe, non-antibiotic alternative with significant ammonia-lowering effect as well as a protective effect on the development of brain edema in rats with chronic liver failure. Additional studies are warranted to evaluate the effects of AST-120 on HE in patients with advanced liver disease.
Portacaval anastomosis-induced hyperammonemia does not lead to oxidative stress.
Xiaoling Yang, Cristina R. Bosoi, Wenlei Jiang, Mélanie Tremblay, Christopher F. Rose.
Ammonia is neurotoxic and believed to play a major role in the pathogenesis of hepatic encephalopathy (HE). It has been demonstrated, in vitro and in vivo, that acute and high ammonia treatment induces oxidative stress. Reactive oxygen species (ROS) are highly reactive and can lead to oxidization of proteins resulting in protein damage. The present study was aimed to assess oxidative status of proteins in plasma and brain (frontal cortex) of rats with 4-week portacaval anastomosis (PCA). Markers of oxidative stress, 4-hydroxy-2-nonenal (HNE) and carbonylation were evaluated by immunoblotting in plasma and frontal cortex. Western blot analysis did not demonstrate a significant difference in either HNE-linked or carbonyl derivatives on proteins between PCA and sham-operated control rats in both plasma and frontal cortex. The present study suggests PCA-induced hyperammonemia does not lead to systemic or central oxidative stress.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Introduction: La pathogénèse de l'encéphalopathie hépatique (EH) est multifactorielle et implique des toxines provenant des intestins, telle que l'ammoniaque. L'insuffisance hépatique mène à l'hyperammonémie et aux niveaux neurotoxiques d’ammoniaque qui peuvent induire le stress oxydatif. Ainsi, la première cible du traitement de l'EH est la diminution de la production intestinale d'ammoniaque. AST-120 (adsorbant sphérique de charbon), un adsorbant oral de microsphères activées par ingénierie ayant une surface de plus de 1600m2/g, adsorbe les neuro- et hépato-toxines présentes dans les intestins. Dans cette étude, nous avons évalué l'effet protecteur d'AST-120 sur l'œdème cérébral et sa capacité à diminuer l'ammoniaque artérielle et le stress oxydatif chez les rats cirrhotiques. Méthodes: La cirrhose a été induite par la ligature de la voie biliaire (BDL) pour 6 semaines. Les rats BDL et SHAM ont reçu durant 6 semaines une dose d'AST-120 de 0.1 et 1mg/kg/jour dispersé dans la méthylcellulose (MC) par gavage. Des rats contrôles BDL et SHAM ont reçu seulement le véhicule. L'AST et ALT ont été mesurés à la fin du traitement pour évaluer la fonction du foie. L'ammoniaque et les espèces réactives d'oxygène (ROS) ont été mesurées dans le plasma artériel par un kit commercial et une technique de fluorescence. Le contenu en eau du cerveau a été mesuré dans le cortex frontal par une technique spécifique gravimétrique. Résultats: Le traitement avec AST-120 a été bien toléré. Les marqueurs de la fonction hépatique, AST et ALT, étaient augmentés dans tous les groupes de rats BDL vs SHAM (p<0.001). Le contenu en eau du cerveau a augmenté dans les rats BDL (BDL: 81.8±0.1% vs SHAM: 81.3±0.2%, p<0.05). Les deux dosages d'AST-120 de 0.1 et 1mg/kg/jour ont normalisé le contenu en eau du cerveau dans les rats BDL. L'ammoniaque artérielle était augmentée chez les rats BDL (175.5± 48.1uM vs SHAM: 105.3±27.3uM, p<0.05) et diminuée significativement dans les BDL 0.1mg/kg/jour (118.0±6.4uM, p<0.05) et BDL 1mg/kg/jour (75.4±31.4uM, p<0.05). Les niveaux de ROS étaient augmentés chez les rats BDL vs SHAM (augmentation de 11 fois vs SHAM). AST-120 n'a pas diminué les niveaux plasmatiques de ROS comparativement aux SHAM. Conclusions: Le traitement avec AST-120 normalise le contenu en eau du cerveau et diminue les niveaux artériels d'ammoniaque, mais n'a pas d'effet sur les ROS systémiques. AST-120 administré à long terme a été prouvé une alternative sûre de traitement non-antibiotique pour l'EH, en démontrant un effet significatif sur la diminution de l'ammoniaque, en même temps qu'un effet protecteur sur l'œdème cérébral chez les rats avec ligature de voie biliaire. Projet subventionné par: Instituts de recherche en santé du Canada et Ocera Therapeutics Inc. (CA, USA)
Xiaoling Yang, Cristina R. Bosoi, Mélanie Tremblay, Christopher F. Rose.
Introduction: L'ammoniaque joue un rôle majeur dans la pathogénèse de l'encéphalopathie hépatique. Le stress oxydatif est toutefois également proposé d'être impliqué. Des études récentes sont à l'origine de notre projet : 1) la concentration neurotoxique d'ammoniaque induisant le stress oxydatif a été démontrée in vitro et 2) le stress oxydant systémique exacerbe les effets neuropsychologiques de l'hyperammonémie observée chez les patients atteints d’une maladie hépatique. Notre étude vise à mesurer le stress oxydant systémique et central en association avec l'œdème cérébral chez les rats atteints de cirrhose. Méthodes: Les rats ont été sacrifiés six semaines après la ligature de la voie biliaire (bile-duct ligation, BDL), induisant une cirrhose. Le plasma artériel et le liquide céphalo-rachidien (LCR) ont été prélevés afin de mesurer l'ammoniaque (kit commercial), les espèces réactives de l'oxygène (ROS, technique de fluorescence DCFDA), l'oxyde nitrique (NO, méthode de Griess) et la peroxydation lipidique (malondialdéhyde, MDA, kit commercial). Le cortex frontal a été disséqué pour mesurer l'activité de la catalase (antioxydant, technique de fluorescence avec l'Amplex Red) et les dérivés de S-nitrosylation du résidu cystéine (immunobuvardage). Le volume en eau du cerveau a été déterminé en utilisant la technique gravimétrique spécifique. Résultats: Le volume en eau du cerveau a augmenté dans les rats avec BDL vs sham-contrôles (81.91 ± 0.19% vs 81.23 ± 0.20%, p <0.05). Les rats avec BDL ont développé, vs les sham-contrôles, une augmentation plasmatique de concentration d'ammoniaque (91.8 µM ± 18.4 vs 41.2 µM ± 13.2, p<0.05), de NO (2.9 fois plus élevé), de ROS (4.9 fois plus élevé), de MDA (41.9 µM ± 7.4 vs 9.9 µM ± 0.6, p<0.005) et de dérivés de S-nitrosylation du résidu cystéine, ainsi qu'une diminution de l'activité de la catalase (1.3 U/ml ± 0.5 vs 3.2 U/ml ± 1.4, p<0.05). Dans le système nerveux central, les rats avec BDL (vs sham-contrôles) ont développé une augmentation de l'ammoniaque dans le LCR (123.5 µM ± 21.7 vs 23.3 µM ± 6.1, p<0.05) mais n'ont pas développé une augmentation de ROS et de NO dans le LCR ou une augmentation de MDA et de dérivés de S-nitrosylation du résidu cystéine dans le cerveau. En outre, l'activité de la catalase dans le cerveau est restée inchangée dans les rats avec BDL. Conclusions: Six semaines après la ligature de la voie biliaire, les rats ont développé un œdème cérébral. L'augmentation de l'ammoniaque artérielle a été accompagnée d'une élévation du NO, des ROS, de la peroxydation lipidique et de la S-nitrosylation, ainsi qu'une diminution de l'activité de la catalase. Toutefois, une hausse du niveau d'ammoniaque dans le LCR conduit à des résultatss inverses dans le cerveau, où aucune augmentation des marqueurs du stress oxydatif n'a été trouvée. Nos résultatss suggèrent que 1) l'ammoniaque n'induit pas le stress oxydatif dans le cerveau, 2) le stress oxydatif systémique est liée à une diminution de l'activité de la catalase et 3) l'œdème cérébral chez les rats avec BDL est associé à un stress oxydatif systémique, et non central.
Christopher F. *Rose, Cristina Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: The pathogenesis of hepatic encephalopathy (HE) is multifactorial involving gut-derived toxins such as ammonia. Liver disease leads to hyperammonemia and neurotoxic levels of ammonia which have been demonstrated to induce oxidative stress. Therefore a primary treatment target for HE is to decrease ammonia production in the gastrointestinal tract. AST-120 (spherical carbon adsorbent), an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600m2/g works as a sink for neuro- and hepato–toxins present in the gut. In this study, we evaluated the protective effect of AST-120 in attenuating brain edema and the capacity of AST-120 to lower arterial ammonia and oxidative stress in rats with cirrhosis. Methods: Secondary biliary cirrhosis was induced in rats by bile duct ligation (BDL) for 6 weeks. BDL and SHAM-operated rats received AST-120 by gavage in methylcellulose (MC) at a dose of 0.1 or 1g/kg/day for 6 weeks. Control BDL and SHAM-operated groups received MC only. AST and ALT were measured at the end of the treatment period to assess liver function. Ammonia and reactive oxygen species (ROS) were measured in arterial plasma using a commercially available kit and DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique. Results: AST-120 was well-tolerated with no deaths in either of the treatment groups. Brain water content increased in BDL vs SHAM-operated rats (81.8 ± 0.1% vs 81.3 ± 0.2%, p<0.05). Both 0.1 and 1g/kg/day AST-120 treatments normalised brain water content in BDL rats. Arterial ammonia increased in the BDL control group vs SHAM-operated controls (175.5 ± 48.1uM vs 105.3 ± 27.3uM, p<0.05) and decreased significantly in BDL 0.1g/kg/day (118.0 ± 6.4uM, p<0.05) and BDL 1g/kg/day (75.4 ± 31.4uM, p<0.05). Circulating levels of ROS were significantly increased in BDL vs SHAM-operated rats (11 fold, p<0.001). AST-120 treatment did not attenuate arterial levels of ROS compared to respective SHAM-operated controls. Liver functions enzymes, AST and ALT, were increased in all BDL rats compared to their respective SHAM-operated controls (p<0.001). Conclusions: AST-120 treatment normalized brain water content and decreased arterial ammonia levels but did not demonstrate an effect on systemic ROS. Long-term treatment with AST-120 is a safe, non-antibiotic alternative demonstrating a significant ammonia-lowering effect, as well as a protective effect on the development of brain edema in rats with chronic liver failure. Additional studies are warranted to evaluate the effects of AST-120 on HE in patients with advanced liver disease.
Xiaoling Yang, Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Ammonia plays a major role in the pathogenesis of hepatic encephalopathy however oxidative stress is also believed to be involved. Two lines of evidence lead us to the following aim of our study: 1) neurotoxic levels of ammonia have demonstrated to induce oxidative stress in vitro and 2) systemic oxidative stress is believed to exacerbate the neuropsychological effects of hyperammonemia observed in patients with liver disease. Our aim was to measure oxidative stress markers systemically and centrally, in association with brain edema in rats with cirrhosis. Methods: Rats were sacrificed 6 weeks following bile-ligated induced cirrhosis. Arterial plasma and cerebrospinal fluid (CSF) were collected to measure ammonia (commercially available kit), reactive oxygen species (ROS) (DCFDA-fluorescent technique), nitric oxide (NO) (Griess method) and lipid peroxidation (malondialdehyde, MDA) (commercially available kit). Frontal cortex was dissected to measure antioxidant catalase activity (Amplex Red fluorescent technique), S-nitrosylation of cystein thiols (immunoblotting) and brain water content was determined using the specific gravimetric technique. Results: Brain water content increased in BDL rats vs SHAM-operated controls (81.91 ± 0.19% vs 81.23 ± 0.20%, p<0.05). BDL rats vs SHAM-operated controls developed an increase in plasma arterial levels of ammonia (91.8 ± 18.4uM vs 41.2 ± 13.2uM, p<0.05), ROS (4.9 fold increase), NO (2.9 fold increase), MDA (41.9 ± 7.4uM vs 9.9 ± 0.6uM, p<0.005), S-nitrosylated proteins and a decrease in catalase activity (1.3 ± 0.5U/ml vs 3.2 ± 1.4U/ml, p<0.05). Centrally, BDL rats vs SHAM-operated controls developed an increase in CSF ammonia (123.5 ± 21.7uM vs 23.3 ± 6.1uM, p<0.05) but did not develop an increase in CSF ROS and NO or in brain MDA and S-nitrosylation detection. Furthermore, catalase activity in the brain was unchanged in BDL vs SHAM-operated controls. Conclusions: Six weeks following BDL, rats developed brain edema. An increase in arterial ammonia was accompanied with an increase in lipid peroxidation, NO, ROS and S-nitrosylation with a decrease in catalase activity. However, a similar increase in ammonia levels in CSF lead to contrary results where no increase in oxidative stress markers was found in brain. Our findings suggest 1) ammonia does not induce oxidative stress in the brain, 2) systemic oxidative stress is related to a decrease in catalase activity and 3) brain edema in BDL rats is associated with systemic, and not central, oxidative stress.
Cristina Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. *Rose.
Background: The pathogenesis of hepatic encephalopathy (HE) is multifactorial involving gut-derived toxins such as ammonia. Liver disease leads to hyperammonemia and neurotoxic levels of ammonia which have been demonstrated to induce oxidative stress. Therefore a primary treatment target for HE is to decrease ammonia production in the gastrointestinal tract. AST-120 (spherical carbon adsorbent), an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600m2/g works as a sink for neuro- and hepato-toxins present in the gut. In this study, we evaluated the protective effect of AST-120 in attenuating brain edema and the capacity of AST-120 to lower arterial ammonia and oxidative stress in rats with cirrhosis. Methods: Secondary biliary cirrhosis was induced in rats by bile duct ligation (BDL) for 6 weeks. BDL and SHAM-operated rats received AST-120 by gavage in methylcellulose (MC) at a dose of 0.1 or 1g/kg/day for 6 weeks. Control BDL and SHAM-operated groups received MC only. AST and ALT were measured at the end of the treatment period to assess liver function. Ammonia and reactive oxygen species (ROS) were measured in arterial plasma using a commercially available kit and DCFDA-fluorescent technique respectively. Brain water content was measured in the frontal cortex using the specific gravimetric technique. Results: AST-120 was well-tolerated with no deaths in either of the treatment groups. Brain water content increased in BDL vs SHAM-operated rats (81.8 ± 0.1% vs 81.3 ± 0.2%, p<0.05). Both 0.1 and 1g/kg/day AST-120 treatments normalised brain water content in BDL rats. Arterial ammonia increased in the BDL control group vs SHAM-operated controls (175.5 ± 48.1uM vs 105.3 ± 27.3uM, p<0.05) and decreased significantly in BDL 0.1g/kg/day (118.0 ± 6.4uM, p<0.05) and BDL 1g/kg/day (75.4 ± 31.4uM, p<0.05). Circulating levels of ROS were significantly increased in BDL vs SHAM-operated rats (11 fold, p<0.001). AST-120 treatment did not attenuate arterial levels of ROS compared to respective SHAM-operated controls. Liver functions enzymes, AST and ALT, were increased in all BDL rats compared to their respective SHAM-operated controls (p<0.001). Conclusions: AST-120 treatment normalized brain water content and decreased arterial ammonia levels but did not demonstrate an effect on systemic ROS. Long-term treatment with AST-120 is a safe, non-antibiotic alternative demonstrating a significant ammonia-lowering effect, as well as a protective effect on the development of brain edema in rats with chronic liver failure. Additional studies are warranted to evaluate the effects of AST-120 on HE in patients with advanced liver disease.
Xiaoling Yang, Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Ammonia plays a major role in the pathogenesis of hepatic encephalopathy however oxidative stress is also believed to be involved. Two lines of evidence lead us to the following aim of our study: 1) neurotoxic levels of ammonia have demonstrated to induce oxidative stress in vitro and 2) systemic oxidative stress is believed to exacerbate the neuropsychological effects of hyperammonemia observed in patients with liver disease. Our aim was to measure oxidative stress markers systemically and centrally, in association with brain edema in rats with cirrhosis. Methods: Rats were sacrificed 6 weeks following bile-ligated induced cirrhosis. Arterial plasma and cerebrospinal fluid (CSF) were collected to measure ammonia (commercially available kit), reactive oxygen species (ROS) (DCFDA-fluorescent technique), nitric oxide (NO) (Griess method) and lipid peroxidation (malondialdehyde, MDA) (commercially available kit). Frontal cortex was dissected to measure antioxidant catalase activity (Amplex Red fluorescent technique), S-nitrosylation of cystein thiols (immunoblotting) and brain water content was determined using the specific gravimetric technique. Results: Brain water content increased in BDL rats vs SHAM-operated controls (81.91 ± 0.19% vs 81.23 ± 0.20%, p<0.05). BDL rats vs SHAM-operated controls developed an increase in plasma arterial levels of ammonia (91.8 ± 18.4uM vs 41.2 ± 13.2uM, p<0.05), ROS (4.9 fold increase), NO (2.9 fold increase), MDA (41.9 ± 7.4uM vs 9.9 ± 0.6uM, p<0.005), S-nitrosylated proteins and a decrease in catalase activity (1.3 ± 0.5U/ml vs 3.2 ± 1.4U/ml, p<0.05). Centrally, BDL rats vs SHAM-operated controls developed an increase in CSF ammonia (123.5 ± 21.7uM vs 23.3 ± 6.1uM, p<0.05) but did not develop an increase in CSF ROS and NO or in brain MDA and S-nitrosylation detection. Furthermore, catalase activity in the brain was unchanged in BDL vs SHAM-operated controls. Conclusions: Six weeks following BDL, rats developed brain edema. An increase in arterial ammonia was accompanied with an increase in lipid peroxidation, NO, ROS and S-nitrosylation with a decrease in catalase activity. However, a similar increase in ammonia levels in CSF lead to contrary results where no increase in oxidative stress markers was found in brain. Our findings suggest 1) ammonia does not induce oxidative stress in the brain, 2) systemic oxidative stress is related to a decrease in catalase activity and 3) brain edema in BDL rats is associated with systemic, and not central, oxidative stress.
Cristina R. Bosoi, Xiaoling Yang, Wenlei Jiang, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Liver failure/disease leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy. However, it is believed systemic oxidative/nitrosative stress may exacerbate the neuropsychological effects of hyperammonemia observed in patients with liver disease. The present study aims to investigate the role of oxidative/nitrosative stress in 2 rat models of liver disease/hepatic encephalopathy; 1) portacaval anastomosis (PCA), and 2) bile-duct ligation (BDL). Methods: Rats were sacrificed 4 weeks following PCA and 6 weeks following BDL. Arterial plasma and cerebrospinal fluid (CSF) were collected to measure ammonia, reactive oxygen species (ROS), hydrogen peroxide (H2O2) and nitric oxide (NO). S-nitrosylation of cystein thiols was measured in the frontal cortex and plasma proteins by immunoblotting. Brain water content was measured in the frontal cortex using a specific gravimetric technique. Results: Hyperammonemia developed in both PCA (PCA: 181.0 ± 8.5uM vs sham: 60.5 ± 7.0uM; p< 0.0001) and BDL (BDL: 101.1 ± 11.0uM vs sham: 41.7 ± 9.2uM; p< 0.05) rats with PCA rats being significantly higher compared to BDL rats (p< 0.001). Consequently, ammonia increased in CSF in both PCA (PCA: 159.5 ± 15.8uM vs sham: 32.5 ± 3.7uM; p< 0.0001) and BDL (BDL: 123.5 ± 21.7uM vs sham: 23.3 ± 6.1uM; p< 0.05), but no significant change was observed between PCA and BDL. Only rats with BDL demonstrated an increase in plasma levels of ROS (5.8-fold increase vs sham; p< 0.001), H2O2 (3.2-fold increase vs sham; p< 0.05) and NO (2.9-fold increase vs sham; p< 0.05). This was accompanied by an increase in S-nitrosylation of plasma proteins. An increase in brain water content was observed in rats with BDL (BDL: 81.91 ± 0.19% vs sham: 81.23 ± 0.20, p< 0.05) whereas no significant change in brain water content was found in PCA vs sham-operated control rats. Conclusion: Hyperammonemia together with systemic oxidative stress are associated with brain edema in rats with BDL which is not demonstrated in PCA rats where only hyperammonemia is observed. Our findings suggest systemic oxidative stress is implicated in the pathogenesis of brain edema and its synergistic effect with ammonia may lead to progression of hepatic encephalopathy.
Cristina R. Bosoi, Wenlei Jiang, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Introduction: L'insuffisance/maladie hépatique mène à l'hyperammonémie, le facteur central dans la pathogénèse de l'encéphalopathie hépatique. Toutefois, le stress oxydatif/nitrosatif peut avoir un rôle important dans l'exacerbation des effets neuropsychologiques de l'hyperammonémie chez les patients atteints de maladies hépatiques. Cette étude a comme objectif l'investigation du rôle du stress oxydatif/nitrosatif dans deux modèles de maladie du foie/encéphalopathie hépatique chez le rat; 1) dérivation portosystémique (PCA), et 2) ligature de la voie biliaire (BDL). Méthodes: Les rats ont été sacrifiés 4 semaines après la PCA ou 6 semaines après la BDL. L'ammoniaque, les espèces réactives d'oxygène (ROS), le H2O2 et l'oxyde nitrique (NO) ont été mesurés dans le plasma (artériel) et l'ammoniaque, les ROS et le NO dans le liquide céphalorachidien (CSF), respectivement par un kit commercial, une technique de fluorescence et la réaction Griess. Le contenu en eau du cerveau a été mesuré dans le cortex frontal par une technique spécifique gravimétrique. Résultats: L'hyperammonémie s'est développée dans les deux groupes, PCA (PCA: 173.7 ± 13.6 uM vs sham: 77.8 ± 11.2 uM; p<0.001) et BDL (BDL: 114.1 ± 19.2 uM vs sham: 33.2 ± 4.7 uM; p<0.05) et les valeurs pour les rats PCA sont significativement plus élevées que celles des BDL (p<0.05). En conséquence, l'ammoniaque est élevée dans le CSF chez les rats PCA (PCA: 146.6 ± 26.0 uM vs sham: 31.5 ± 6.9 uM; p<0.001) et BDL (BDL: 128.4 ± 36.7 uM vs sham: 23.3 ± 6.1 uM; p<0.05). On n'observe pas de différences significatives entre les PCA et BDL. Seulement les rats BDL montrent une augmentation des niveaux plasmatiques de ROS (augmentation de 5.8 fois vs sham; p<0.001) et H2O2 (augmentation de 3.2 fois vs sham; p<0.05). On n'observe pas de différences significatives entre les valeurs des ROS dans le CSF chez les PCA et BDL, comparativement aux groupes contrôles. De plus, on observe une augmentation du contenu en eau du cerveau seulement dans les rats BDL (BDL: 81.52 ± 0.15% vs sham: 80.43 ± 0.21%, p<0.05). Aucun changement significatif dans les niveaux plasmatiques des ROS, H2O2 ou du contenu en eau cérébrale dans les PCA vs les contrôles sham-opérés n'a été trouvé. Conclusion: Le stress oxydatif superposé à l'hyperammonémie entraîne une augmentation du contenu cérébral en eau dans les rats BDL qui n'est pas observée chez les rats PCA, où seulement l'hyperammonémie est présente. Nos résultatss suggèrent que le stress oxydatif systémique est impliqué dans la pathogénèse de l’œdème cérébrale et que son effet synergique avec l'ammoniaque peut mener à la progression de l'encéphalopathie hépatique.
Cristina R. Bosoi, Xiaoling Yang, Wenlei Jiang, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Liver failure/disease leads to hyperammonemia which is central in the pathogenesis of hepatic encephalopathy. However, it is believed systemic oxidative/nitrosative stress may play an important role in exacerbating the neuropsychological effects of hyperammonemia observed in patients with liver disease. The present study aims to investigate the role of oxidative/nitrosative stress in 2 rat models of liver disease/hepatic encephalopathy; 1) portacaval anastomosis (PCA), and 2) bile-duct ligation (BDL). Methods: Rats were sacrificed 4 weeks following PCA and 6 weeks following BDL. Arterial plasma and cerebrospinal fluid (CSF) were collected to measure ammonia, reactive oxygen species (ROS), hydrogen peroxide (H2O2) (only measured in plasma) and nitric oxide (NO) using a commercially available kit, the DCFDA and Amplex Red fluorescent techniques and the Griess reaction respectively. S-nitrosylation of cystein thiols was measured in the frontal cortex and plasma proteins by immunoblotting. Brain water content was measured in the frontal cortex using a specific gravimetric technique. Results: Hyperammonemia developed in both PCA (PCA: 181.0 ± 8.5uM vs sham: 60.5 ± 7.0uM; p<0.0001) and BDL (BDL: 101.1 ± 11.0uM vs sham: 41.7 ± 9.2uM; p<0.05) rats with PCA rats being significantly higher compared to BDL rats (p<0.001). Consequently, ammonia increased in CSF in both PCA (PCA: 159.5 ± 15.8uM vs sham: 32.5 ± 3.7uM; p<0.0001) and BDL (BDL: 123.5 ± 21.7uM vs sham: 23.3 ± 6.1uM; p<0.05), but no significant change was observed between PCA and BDL. Only rats with BDL demonstrated an increase in plasma levels of ROS (5.8-fold increase vs sham; p<0.001), H2O2 (3.2-fold increase vs sham; p<0.05) and NO (2.9-fold increase vs sham; p<0.05). This was accompanied by an increase in S-nitrosylation of plasma proteins. No significant changes in CSF ROS and NO, nor in S-nitrosylation of frontal cortex proteins were found in BDL or PCA compared to their respective control groups. In addition, an increase in brain water content was observed in rats with BDL (BDL: 81.91 ± 0.19% vs sham: 81.23 ± 0.20, p<0.05). No significant change in brain water content was found in PCA rats vs sham-operated controls. Conclusion: Systemic oxidative stress together with hyperammonemia results in an increase in brain water in rats with BDL which is not demonstrated in PCA rats where only hyperammonemia is observed. Our findings suggest systemic oxidative stress is implicated in the pathogenesis of brain edema and its synergistic effect with ammonia may lead to progression of hepatic encephalopathy.
Identifying the direct effects of ammonia on the brain.
Cristina R. Bosoi, Christopher F. Rose.
Elevated concentrations of ammonia in the brain as a result of hyperammonemia leads to cerebral dysfunction involving a spectrum of neuropsychiatric and neurological symptoms (impaired memory, shortened attention span, sleep-wake inversions, brain edema, intracranial hypertension, seizures, ataxia and coma). Many studies have demonstrated ammonia as a major player involved in the neuropathophysiology associated with liver failure and inherited urea cycle enzyme disorders. Ammonia in solution is composed of a gas (NH(3)) and an ionic (NH(4) (+)) component which are both capable of crossing plasma membranes through diffusion, channels and transport mechanisms and as a result have a direct effect on pH. Furthermore, NH(4) (+) has similar properties as K(+) and, therefore, competes with K(+) on K(+) transporters and channels resulting in a direct effect on membrane potential. Ammonia is also a product as well as a substrate for many different biochemical reactions and consequently, an increase in brain ammonia accompanies disturbances in cerebral metabolism. These direct effects of elevated ammonia concentrations on the brain will lead to a cascade of secondary effects and encephalopathy.
Cristina R. Bosoi, Christian Parent-Robitaille, Mélanie Tremblay, Christopher F. Rose.
Background: Liver failure/disease leads to hyperammonemia which is central in the pathogenesis of hepatic encephalopathy. However, it is believed systemic oxidative/nitrosative stress may play an important role in exacerbating the neuropsychological effects of hyperammonemia observed in patients with liver disease. The present study aims to investigate the role of oxidative/nitrosative stress in 2 rat models of liver disease/hepatic encephalopathy; 1) portacaval anastomosis (PCA), and 2) bile-duct ligation (BDL). Methods: Rats were sacrificed 4 weeks following PCA or 6 weeks following BDL. Ammonia, reactive oxygen species (ROS), H2O2 and nitric oxide (NO) were measured in plasma (arterial) and ammonia, ROS and NO were measured in cerebrospinal fluid (CSF) using respectively a commercially available kit, a fluorescent technique and the Griess reaction. Brain water was measured in the frontal cortex using a specific gravimetric technique. Results: Hyperammonemia developed in both PCA (PCA: 173.7 ± 13.6 uM vs sham: 77.8 ± 11.2 uM; p<0.001) and BDL (BDL: 114.1 ± 19.2 uM vs sham: 33.2 ± 4.7 uM; p<0.05) rats with PCA rats being significantly higher compared to BDL rats (p<0.05). Consequently, ammonia increased in CSF in both PCA (PCA: 146.6 ± 26.0 uM vs sham: 31.5 ± 6.9 uM; p<0.001) and BDL (BDL: 128.4 ± 36.7 uM vs sham: 23.3 ± 6.1 uM; p<0.05). No significant change was observed between PCA and BDL. Only rats with BDL demonstrated an increase in plasma levels of ROS (5.8-fold increase vs sham; p<0.001) and H2O2 (3.2-fold increase vs sham; p<0.05). No significant change in CSF ROS was found in BDL or PCA compared to their respective control groups. In addition, an increase in brain water content was only observed in rats with BDL (BDL: 81.52 ± 0.15% vs sham: 80.43 ± 0.21%, p<0.05). No significant change in plasma ROS, H2O2 or brain water was found in PCA rats vs sham-operated controls. Conclusion: Oxidative stress in addition to hyperammonemia results in an increase in brain water in rats with BDL which is not in PCA rats where only hyperammonemia is observed. Our findings suggest systemic oxidative stress is implicated in the pathogenesis of brain edema and its synergistic effect with ammonia may lead to progression of hepatic encephalopathy.
Hyperammonemia does not induce oxidative/nitrosative stress in rats with portacaval anastomosis.
Cristina Bosoi, Mélanie Tremblay, Christopher F. Rose.
Background: Ammonia is central in the pathogenesis of hepatic encephalopathy however it is believed systemic oxidative/nitrosative stress may play an important role in exacerbating the neuropsychological effects of hyperammonemia observed in patients with cirrhosis. Furthermore, it has recently been demonstrated in vitro that pathophysiological concentrations of ammonia induce oxidative/nitrosative stress in brain (cultured astrocytes), however this remains to be evaluated in vivo. The present study aims to investigate the role of oxidative/nitrosative stress in a well characterized hyperammonemic rat model of portacaval anastomosis (PCA). Methods: Rats were sacrificed 4 weeks following PCA or SHAM-operation. Ammonia, nitrate/nitrite, reactive oxygen species and total glutathione were measured in both plasma (arterial) and cerebrospinal fluid. Activities of antioxidant enzymes (catalase, superoxide dismutase and glutathione reductase/peroxidase) were measured in both plasma (arterial) and frontal cortex of the brain. Results: Ammonia concentrations were increased in both plasma (PCA: 173.7 ± 13.58uM vs SHAM: 77.8 ± 11.2uM; p<0.001) and cerebrospinal fluid (PCA: 146.6 ± 26.0uM vs SHAM: 31.5 ± 6.9uM; p<0.001) in PCA rats compared to SHAM operated controls. Furthermore, PCA rats showed a significant increase in catalase (PCA: 3.27 ± 0.03U/ml vs SHAM: 3.10 ± 0.05U/ml; p<0.05) and superoxide dismutase (PCA: 97.30 ± 0.47 vs SHAM: 95.57 ± 0.45 % inhibition; p<0.05) activities, but no significant differences were found in frontal cortex between the two groups. In addition, no significant changes in reactive oxygen species, nitrate/nitrite and total glutathione levels, nor in glutathione reductase and peroxidase activities were found in both plasma and brain tissue of PCA and SHAM rats. Conclusion: Rats with PCA develop hyperammonemia which leads to toxic levels of ammonia in the brain. This in turn does not induce oxidative/nitrosative stress systemically or centrally. Maintenance of systemic antioxidant activity in rats with PCA preserves a balanced redox status and prevents progression of encephalopathy.
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