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. Although the progression of alcoholic liver disease 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 the polarized, hepatic WIF-B cells, an emerging model system for the study of alcohol-induced liver injury. We found that microtubules are more stable and hyperacetylated in alcohol-treated WIF-B cells. We also found that increased microtubule acetylation and stability is dependent on ethanol metabolism and is likely responsible for alcohol-induced defects in endocytosis and secretion. These results have been confirmed in livers from ethanol-fed rats and in ethanol-treated liver slices indicating the physiologic importance of our WIF- B observations. In this proposal we explore an interesting paradox surrounding TNF-1 and IL-6-mediated signaling. The levels of each of these cytokines are increased in alcoholic human patients and in ethanol-fed animals where they exert proinflammatory responses. However, both of these ligands are also known to promote hepatoprotective activities and are required for liver regeneration. Why are the hepatoprotective and hepatomitogenic effects of TNF-1 and IL-6 selectively lost in alcohol-treated hepatocytes despite their high circulating levels? This proposal focuses on two major questions to explain this paradox. First, does increased microtubule acetylation and stability alter IL-6 and TNF-1-mediated signaling by impairing receptor trafficking (Aim 1)? Secondly, does increased microtubule acetylation and stability alter IL-6 and TNF-1-mediated signaling by impairing the nuclear translocation of the associated transcription factors (Aim 2)? Our studies will be initiated in WIF-B cells and confirmed in precision-cut liver slices, a more physiologically relevant model system. Our considerable expertise in WIF-B cell biology and in polarized hepatic protein trafficking well- situates us to perform these mechanistic experiments. These novel research areas will hopefully lead to our further understanding of alcohol-induced hepatotoxicity.
Approximately 75% of all Americans consume alcohol and 100,000 deaths per year are attributed to alcohol consumption. Of those deaths, greater than 20,000 are caused by cirrhosis of the liver, the seventh largest cause of death in Americans. Clearly, alcoholic liver disease is a major biomedical health concern in the United States.
|Groebner, Jennifer L; Fernandez, David J; Tuma, Dean J et al. (2014) Alcohol-induced defects in hepatic transcytosis may be explained by impaired dynein function. Mol Cell Biochem 397:223-33|
|Shepard, Blythe D; Tuma, Dean J; Tuma, Pamela L (2012) Lysine acetylation induced by chronic ethanol consumption impairs dynamin-mediated clathrin-coated vesicle release. Hepatology 55:1260-70|
|Shepard, Blythe D; Tuma, Dean J; Tuma, Pamela L (2010) Chronic ethanol consumption induces global hepatic protein hyperacetylation. Alcohol Clin Exp Res 34:280-91|