Roles and Regulation of Kupffer Cell Programmed Cell Death in Alcoholic Liver Disease Pathogenesis

Cleveland Clinic Lerner Com-Cwru, Cleveland OH

Investigators

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Abstract

Project Summary/Abstract: Excessive ethanol consumption affects 18 million Americans and is the fourth leading cause of preventable death in the United States. An important consequence of chronic alcohol abuse that continues to be a major public health burden is alcoholic liver disease (ALD), which consists of a spectrum of disorders that includes hepatic steatosis, alcoholic hepatitis, fibrosis, cirrhosis, and potentially hepatocellular carcinoma. Few new therapies exist to address the liver injury and inflammation in ALD, and the prognosis for patients remains poor. Cell death of hepatocytes has been recognized to play an important part in the development of ALD. Apoptosis is a key driver in fibrosis, but inhibition of apoptosis is not sufficient to prevent ethanol-induced hepatocyte injury or expression of pro-inflammatory cytokines in mouse models. Recent research has pointed towards a role for necroptosis, a more pro-inflammatory mode of cell death, in ethanol-induced liver injury. Previous work in our lab has been published showing increased RIP3 expression in livers from patients with ALD and that RIP3 necroptosis in mice drives ethanol-induced increases in ALT, AST, and hepatic inflammation. While much progress has been made into the molecular mechanisms, not as much is known about the cellular basis of these pathways in alcohol-induced liver injury, yet progression of ALD involves complex interactions of non-parenchymal and parenchymal cells. This work in this proposal focuses on Kupffer cells, the liver-resident macrophages that are sensitized to gut- derived endotoxin during chronic ethanol exposure and are a major source of reactive oxygen species and inflammatory mediator production leading to liver damage. The overall goal of this proposal is to understand the roles and regulation of programmed cell death in Kupffer cells in alcohol-induced liver injury through two specific aims using in vivo and cell culture models. Specific Aim 1 will determine the role of RIP3 expression and necroptosis in myeloid cells versus hepatocytes in liver injury under chronic ethanol feeding. Specific Aim 2 will identify mechanisms of differential sensitivity of Kupffer cells to programmed cell death in ALD. These studies will provide useful insight into roles of and mechanisms affecting programmed cell death in Kupffer cells that lead to the progression of ALD.