Alcohol alters hepatic microtubule and membrane dynamics

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DESCRIPTION (provided by applicant): More than 20,000 people each year die of alcoholic liver disease, the seventh largest cause of death in Americans. Because the liver is the major site of ethanol metabolism, it is the most susceptible organ to alcohol-induced injury. In the early stages of the disease, a fatty liver develops which leads to hepatocyte necrosis, liver fibrosis, and ultimately to cirrhosis. Although the disease progression is well described clinically, the molecular basis for alcohol-induced liver injury is not understood. Our long-term goal is to understand the mechanisms that lead to alcohol-induced hepatotoxicity. Our recent studies have been performed in cultured WIF-B cells. These hepatic cells are highly differentiated and maintain liver-specific activities in culture, including the ability to efficiently metabolize ethanol. Thus, these cells are an excellent model to examine alcohol-induced hepatotoxicity and allow us to perform mechanistic studies that cannot be done in animals. Recently, we found that microtubules are more stable and acetylated 2-3-fold more in ethanol-treated cells than in control. We confirmed these results in hepatocytes from ethanol-fed rats indicating the findings have physiologic importance. We further determined that increased microtubule acetylation in WIF-B cells is dependent on ethanol metabolism. This proposal focuses on two major questions emerging from these recent results. First, what is the mechanism that leads:; to microtubule hyperacetylation and increased stability in ethanol-treated cells and are other hepatic proteins hyperacetylated via similar mechanisms? Secondly, we will test whether microtubule hyperacetylation ;contributes to alcohol-induced defects observed in protein trafficking. Our considerable expertise in the culture and use of WIF-B cells and our expertise in polarized hepatocyte protein trafficking situate us perfectly to perform these exploratory, mechanistic experiments. These novel research areas will open the door to novel approaches and hypotheses that we will apply to our future studies of hepatotoxicity.