Background: Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, a major complication of chronic liver disease (CLD). Defined as a metabolic disorder, HE is understood to be reversible following liver transplantation (LT). However, up to 47% of LT patients have been documented to have persisting neurological complications. Retrospective studies have revealed that patients with a history of overt HE are associated with a poor neurological outcome post-LT. However, the impact of HE episodes on neuro¬logical in¬tegrity is unknown. We hypothesize that episodes of HE will accelerate and/or exasperate neurological deterioration. Purpose: Our goal was to characterize an animal model of episodic HE and to evaluate the impact of cumulative episodes induced by hyperammonemia on neurological status and brain injury in cirrhotic rats. Method: For animal model of CLD and HE, 5-week bile-duct ligation (BDL) rats, and Sham-operated controls were used. Rats, both Sham and BDL, were divided in two groups, episodic and non-episodic. Injection (ip) of ammonium acetate was used to induce episodes of overt HE (pre-coma; loss of righting reflex) every 4 days starting at 3-weeks post-BDL surgery (total 4 episodes). Saline was injected as vehicle for non-episodic group. Three days following the last episode of HE, neurological status was assessed. Upon sacrifice, plasma ammonia was measured, and brains were collected for western blot analysis; Neuronal nuclei (NeuN), caspase-3 (apoptotic marker) and GFAP (astrocyte marker) were measured to evaluate neurological integrity. Results: BDL rats (vs Sham) following ammonia insult developed overt HE (loss of righting reflex). Long-term memory (LTM) was impaired in both non-episodic and episodic BDL groups vs respective controls. However, LTM impairment was further aggravated in episodic BDL rats. Both GFAP and cleaved caspase-3 protein expression were significantly increased, whereas NeuN was significantly decreased in hippocampus of episodic BDL rats vs non-episodic BDL rats. Blood ammonia levels were found to be higher in episodic vs non-episodic BDL rats. Conclusion: HE episodes exasperate neurological impairments in BDL rats. LTM impairment was associated with an increase in the apoptotic marker (caspase-3) and a decrease in neuronal marker (NeuN) in the hippocampus, suggesting neuronal injury/loss. Elevated levels of GFAP in the hippocampus insinuates gliosis as a consequence of neuronal loss. These results suggest that multiple episodes of HE may cause permanent cell damage and therefore will less likely be reversible following LT justifying persisting neurological complications post-LT.
