Background/aimsAcute liver failure (ALF) due to ischemic or toxic liver injury is a clinical condition that results from massive loss of hepatocytes and may lead to hepatic encephalopathy (HE), a serious neuropsychiatric complication. Although increased expression of tumor necrosis factor-alpha (TNF-α) in liver, plasma and brain has been observed, conflicting results exist concerning its roles in drug-induced liver injury and on the progression of HE. The present study aimed to investigate the therapeutic value of etanercept, a TNF-α neutralizing molecule, on the progression of liver injury and HE in mice with ALF resulting from azoxymethane (AOM) hepatotoxicity.Methods/Principal FindingsMice were administered saline or etanercept (10 mg/kg; i.p.) 30 minutes prior to, or up to 6 h after AOM. Etanercept-treated ALF mice were sacrificed in parallel with vehicle-treated comatose ALF mice and controls. AOM induced severe hepatic necrosis, leading to HE, and etanercept administered prior or up to 3 h after AOM significantly delayed the onset of coma stages of HE. Etanercept pretreatment attenuated AOM-induced liver injury, as assessed by histological examination, plasma ammonia and transaminase levels, and by hepatic glutathione content. Peripheral inflammation was significantly reduced by etanercept as shown by decreased plasma IL-6 (4.1-fold; p<0.001) and CD40L levels (3.7-fold; p<0.001) compared to saline-treated ALF mice. Etanercept also decreased IL-6 levels in brain (1.2-fold; p<0.05), attenuated microglial activation (assessed by OX-42 immunoreactivity), and increased brain glutathione concentrations.ConclusionsThese results indicate that systemic sequestration of TNF-α attenuates both peripheral and cerebral inflammation leading to delayed progression of liver disease and HE in mice with ALF due to toxic liver injury. These results suggest that etanercept may provide a novel therapeutic approach for the management of ALF patients awaiting liver transplantation.

In vitro and in vivo studies have suggested that reduced astrocytic uptake of neuronally released glutamate, alterations in expression of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP-4) contribute to brain edema in acute liver failure (ALF). However, there is no evidence to date to suggest that these alterations occur in patients with ALF. We analyzed the mRNA expression of excitatory amino acid transporters (EAAT-1, EAAT-2), GFAP, and AQP-4 in the cerebral cortex obtained at autopsy from eight patients with ALF and from seven patients with no evidence of hepatic or neurological disorders by real-time PCR, and protein expression was assessed using immunoblotting and immunohistochemistry. We demonstrated a significant decrease in GFAP mRNA and protein levels in ALF patients compared to controls. While the loss of EAAT-2 protein in ALF samples was post-translational in nature, EAAT-1 protein remained within normal limits. Immunohistochemistry confirmed that, in all cases, the losses of EAAT-2 and GFAP were uniquely astrocytic in their localization. AQP-4 mRNA expression was significantly increased and its immunohistochemistry demonstrated increased AQP-4 immunoreactivity in the glial end-feet process surrounding the microvessels. These findings provide evidence of selective alterations in the expression of genes coding for key astrocytic proteins implicated in central nervous system (CNS) excitability and brain edema in human ALF. Keywords: acute liver failure, aquaporin-4, astrocyte protein, brain edema, EAAT-1, EAAT-2, GFAP.

Wernicke's encephalopathy is a cerebral disorder caused by thiamine (vitamin B 1 ) deficiency (TD). Neuropathologic consequences of TD include region-selective neuronal cell loss and blood-brain barrier (BBB) breakdown. Early increased expression of the endothelial isoform of nitric oxide synthase (eNOS) occurs selectively in vulnerable brain regions in TD. We hypothesize that region-selective eNOS induction in TD leads to altered expression of tight junction proteins and BBB breakdown. In order to address this issue, TD was induced in C57BL/6 wild-type (WT) and eNOS )/) mice by feeding a thiamine-deficient diet and treatment with the thiamine antagonist pyrithiamine. Pair-fed control mice were fed the same diet with additional thiamine. In medial thalamus of TD-WT mice (vulnerable area), increased heme oxygenase-1 and S-nitrosocysteine immunostaining was observed in vessel walls, compared to pair-fed control-WT mice. Concomitant increases in IgG extravasation, decreases in expression of the tight junction proteins occludin, zona occludens-1 and zona occludens-2, and up-regulation of matrix metalloproteinase-9 in endothelial cells were observed in the medial thalamus of TD-WT mice. eNOS gene deletion restored these BBB alterations, suggesting that eNOS-derived nitric oxide is a major factor leading to cerebrovascular alterations in TD. However, eNOS gene deletion only partially attenuated TD-related neuronal cell loss, suggesting the presence of mechanisms additional to BBB disruption in the pathogenesis of these changes.Keywords: blood-brain barrier, endothelial nitric oxide synthase, neuronal cell death, thiamine deficiency, Wernicke's encephalopathy.

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