The role of Enterococcus faecalis in alcoholic liver disease

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Alcohol abuse and alcohol-related diseases are a major cause of morbidity and mortality among Veterans. Chronic alcoholism is associated with changes in the intestinal microbiota, increased intestinal permeability, and elevated systemic levels of bacterial products. How chronic alcohol use results in intestinal dysbiosis and whether specific bacterial species mediate alcoholic liver disease is not known. Results from our laboratory indicate that Enterococcus faecalis (E faecalis) is sufficient to cause mild steatotic liver disease and to exacerbate alcoholic liver disease in mice. Most importantly, we observed significantly greater numbers of E faecalis in fecal samples from alcohol-dependent patients with or without liver disease than healthy controls. Our preliminary data further shows that alcohol-mediated suppression of the antimicrobial protein regenerating islet derived-3 (REG3G) allows E faecalis colonization of intestinal mucosal surfaces and translocation to the liver. E faecalis induces liver inflammation via binding to pathogen recognition receptors on Kupffer cells. A subsequent increase in expression and secretion of the inflammatory cytokine interleukin (IL)-1β contributes to the development of ethanol-induced liver disease. This is supported by our findings that chimeric mice lacking toll-like receptor (TLR)-2 on bone-marrow derived cells have reduced E faecalis-exacerbated alcoholic liver disease. The focus of this application is to characterize the role of E faecalis in preclinical models of alcoholic liver disease and Veterans with alcohol abuse. We hypothesize that E faecalis is an important etiological factor in the modulation of hepatic inflammation and the development of alcoholic liver disease. Our experimental approach is to use mouse models of chronic alcohol feeding to investigate the role of alcohol-induced suppression of intestinal REG3G. Lower intestinal REG3G facilitates overgrowth of E faecalis on mucosal surfaces in the intestine and translocation to the liver (Aim 1). We will investigate the molecular mechanism of how translocation of E faecalis contributes to hepatic inflammation and hepatocyte death during alcoholic liver disease (Aim 2). Using a precision-microbiome approach, we will test the hypothesis that targeted manipulation of alcohol-associated dysbiosis can ameliorate alcoholic liver disease (Aim 3). We believe these studies will provide novel insights into the contribution of the microbiota to alcoholic liver disease. Innovative and novel strategies will be developed to prevent or ameliorate alcoholic liver disease in Veterans.