The clinical outcome from any liver disease depends on the degree of hepatic failure that results from hepatocyte injury and subsequent cell death. We have postulated that during toxic liver injury, this cell death is due not only to the direct damage induced by the hepatotoxin, but also to other factors produced as part of the injury/repair process. In support of this hypothesis, we have shown that the cytokine tumor necrosis factor-alpha (TNF-alpha) contributes significantly to the liver damage after toxic injury. By examining the molecular events during the injury response, we have recently obtained evidence that the hepatocyte's commitment to undergo cell death after toxic injury is regulated by activation of the transcription factors Myc, AP-1 and NF-kappaB. The goal of the current studies is to elucidate the mechanisms by which these transcriptional regulators modulate hepatic cellular injury and resultant death by necrosis and apoptosis. The ultimate objective of these investigations is to advance the understanding of liver cell injury and death in order to guide the development of therapies to prevent liver failure.
The specific aims of this proposal are: (1) To determine whether TNF- alpha induces hepatocyte cell death through the upregulation of c-myc expression. These studies will investigate the ability of TNF-alpha combined with toxic injury to selectively activate Myc, as well as the role of Myc in the induction of cell death from TNF-alpha. The mechanism by which increased Myc causes cell death through the generation of a lethal oxidative stress and cellular glutathione depletion will also be determined. (2) to investigate whether AP-1 transcriptional activation during toxic hepatocyte injury is a common signal in the cellular commitment to death from necrosis or apoptosis. The activation of AP-1 through the effects of toxic hepathocyte injury on Jun nuclear kinase, and the contribution of AP- 1 to cell death that occurs through either necrosis of apoptosis will be examined. (3) To determine of inhibition of NF-kappaB transcriptional activation during toxic liver injury promotes hepatocyte cell death. The ability of toxic injury to block the normal cellular activation of NF-kappaB, and the role of this event in sensitizing hepatocytes to TNF-alpha cytotoxicity will be investigated.
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