A new hepatic encephalopathy model to monitor the change of neural amino acids and astrocytes with behaviour disorder.

BACKGROUND/AIMS: To elucidate the pathogenesis of hepatic encephalopathy (HE), we developed a new HE model with behaviour disorder. METHODS: Male Wistar rats were divided into four treatment groups: a HE model: acetaminophen (APAP)+3-methylcholanthrene (3-MC) group (APAP+MC group); control group: acetaminophen group; 3-methylcholanthrene group; and a no-treatment group. We monitored the changes of neural amino acids in the synaptic cleft and astrocytes in the brain during behaviour disorder. RESULTS: In the APAP+MC group, alanine amino transferase, blood ammonia and glucose increased from 3 h and total bilirubin increased at 6 h. Prothrombin time was prolonged from 3 h in the APAP+MC group. The APAP+MC group exhibited centrilobular necrosis in the liver after 8 h. In the APAP+MC group, rats jumped vertically and this vertical activity increased significantly from 4 to 7 h. During the behaviour disorder, we found that glutamate and aspartate increased in the synaptic cleft from 4 h after treatment with APAP+3-MC, glutamate increased 23.9-fold at 7 h and aspartate increased 16.1-fold at 4 h, whereas glutamine did not change. At that time, we observed morphological changes of the astrocytes by immunostaining for the glial fibrillary acidic protein. CONCLUSIONS: Our new HE model demonstrated that increased excitatory neural amino acids and morphological change in astrocytes were involved in the behaviour disorder that occurs with HE.

Hydrogen peroxide induced chemokine production in the glia-rich cultured cerebellar granule cells under acidosis.

We have documented the time-dependent production of chemotactic cytokine, i.e., IL-8, in the extracellular fluid of astrocyte-rich cultured rat cerebellar granule cells under acidified conditions. In this paper, the mechanism of this production was evaluated based on the production of hydrogen peroxide (H2O2). Significant and time-dependent increases of cytosolic H2O2 were detected under acidosis in astrocyte-rich cultured cell. Upon exposure to 10 microM H2O2, significant levels of IL-8 appeared in the extracellular fluid of astrocyte-rich cells, although an initial transient increase of IL-8 was also seen in the intracellular space. Concurrently, after H2O2 exposure cell injury and a delayed increase of cytosolic Ca2+ levels were detected in astrocyte-rich cells. However, in the absence of extracellular Ca2+, the cell injury and the increase of IL-8 production were significantly attenuated. A synergistic effect of cyclosporine A (an inhibitor of the Ca2+/calmodulin-regulated protein phosphatase) and trifluoperazine (an inhibitor of phospholipase A2) on the suppression of H2O2-induced IL-8 production was clearly evident. These results suggest that extracellular acidosis induced Ca2+-dependent H2O2 production, which in turn stimulated IL-8 expression. which is regulated by the cytosolic Ca2+ cascade. Thus, the production of IL-8 from glia cells may have a role in regulating in the process of cell injury.