Effects of Ethanol TNF Induced Cytotoxicity

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DESCRIPTION (provided by applicant): Alcoholic liver disease (ALD) constitutes a spectrum of disorders in liver structure and function. The alterations in ALD are broadly categorized into alcohol induced steatosis, steatohepatitis and cirrhosis. Tumor necrosis factor (TNF) has been shown to play a critical role in the progression of ALD, partly through it ability to bring about the injury and death of hepatocytes. In the preceding period of support we have uncovered that hepatocytes exposed to ethanol display an increased sensitivity to TNF induced cytotoxicity and that this is driven by an enhanced susceptibility of the mitochondria to injury, which in turn is exploited by alterations in signaling pathways elicited by TNF in ethanol exposed cells. In the present application we intend to both narrow and broaden the scope of our studies. Firstly, we propose that modifications to hepatocyte lipogenesis contribute to the increased vulnerability to TNF induced damage that characterizes the mitochondria of ethanol exposed cells. Specifically, increased expression of acyl CoA binding protein (ACBP) and the peripheral benzodiazepine receptor (PBR) in ethanol exposed cells, proteins involved in lipid and cholesterol metabolism, establish an enhanced susceptibility of the mitochondria to TNF induced damage. Also, derangements of the PI3-kinase/Akt pathway brought about by ethanol exposure results in phosphorylation of the voltage dependent anion carrier (VDAC), with detrimental consequences for mitochondrial function and resistance to injury. The preliminary data also reveal that the alterations imposed on mitochondria by ethanol exposure may mitigate the beneficial effects of adiponectin against TNF induced cytotoxicity, potentially by impeding adiponectin induced activation of the AMPK pathway. The working hypothesis for this proposal is that the derangement of lipogenesis triggered by ethanol exposure causes alterations in mitochondrial function, particularly through an increased expression of acyl CoA binding protein, the peripheral benzodiazepine receptor, phosphorylation of the voltage dependent anion carrier (VDAC) and endoplasmic reticulum stress, all of which render the mitochondria and cell more sensitive to TNF induced injury. Moreover these effects of ethanol can be ameliorated by activation of AMPK.