Ethanol-induced liver cirrhosis is a major cause of death worldwide. The exact mechanism by which ethanol (ETOH) induces liver fibrosis is unknown but several hypothesis have been proposed: a) Products derived from either ETOH metabolism or injured cells activate Kupffer cells to produce cytokines that induce fat-storing cell (FSC) proliferation and excess collagen production. b) Inflammatory cells driven to the liver by chemoattactants produce cytokines that induce fibrogenesis. c) Products derived from ETOH metabolism or injured cells are fibrogenic and directly induce collagen gene expression. The various mechanisms may occur simultaneously,l however, their relative contribution to fibrogenesis is unknown. Lack of appropriate models to study alcohol-induced liver cirrhosis has hampered understanding of basic mechanisms by which ETOH induces liver fibrosis. Baboon and rat models are costly and unavailable for routine studies. We developed a co-culture, system that contains two of the important cells involved in alcoholic fibrosis, hepatocytes and FSCs. While the former transform ETOH to acetaldehyde (ACAL), the latter respond to ACAL by increasing transcription of type I collagen gene. Therefore, this model of liver fibrosis could be useful in exploring the mechanisms by which ETOH and other hepatotoxins induce hepatocyte damage and liver fibrosis. The model is simple, reproducible and can be analyzed in the absence or presence of inflammatory components.
Our specific aims are to determine: a) the relative contribution of hepatocytes and FSC to collagen production after ETOH or ACAL administration and, b) to determine at the molecular level, possible mechanisms by which ETOH and/or ACAL induce the expression of type I collagen mRNA. We shall determine whether the effects are mediated 'via' the production of TGF-beta or other cytokines. We shall establish whether specific sequences in the promoter of type I collagen are required for collagen gene expression after ETOH or ACAL administration, and we shall attempt to study whether specific nuclear proteins are required for transcriptional activation of type I collagen gene. Our long-term goals are to understand the mechanisms of induction of liver fibrosis, and to develop drugs with antifibrogenic activity capable of preventing or reverting fibrosis.
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