Project 4 - Smita Ghare, PhD

Alcoholic liver disease (ALD) carries a high morbidity and mortality, and has no FDA approved therapy. Sustained hepatic inflammation is an important factor in progression of alcoholic liver disease and elevated hepatic and circulating levels of CCL2 and CXCL2 chemokines are seen in both early and later stages of liver disease. However, the molecular mechanisms involved in alcohol-induced upregulation of these chemokines are not completely elucidated. Emerging evidence indicates that alcohol affects epigenetic regulatory mechanisms and thus significantly contributes to the development of hepatic pathology. Post-translational modifications (PTMs) specifically, acetylation is important for gene transcription and is maintained by Histone deacetylases (HDACs) and histone acetyltransferases (HATs). In this regard, we have shown that binge alcohol exposure alters expression of hepatic HDAC and also affect global hepatic histone H3 acetylation. The role of Class I HDACs has been also described in inflammation with a particular pro-inflammatory role for HDAC3. In the context of chemokine expression, our preliminary data, examining the effects of chronic ethanol on CCL2 upregulation showed that in correlation with increased promoter histone acetylation, there was an increase in the binding of critical transcription factor NFB-p65 to the CCL2 promoter. Further, the data show that a dietary HDAC inhibitor (tributyrin - prodrug of butyrate) attenuates alcohol-induced CCL2 and CXCL2 expression, neutrophil infiltration and prevents hepatic inflammation and injury. Based on these findings, we hypothesize that chronic alcohol-induced alterations in hepatic HDACs drive pathogenic posttranslational modifications of histones and non-histone proteins specifically transcription factor NFB, upregulating CCL2 and CXCL2 chemokines expression contributing to liver inflammation and injury. The major goal of this proposal is to conduct studies that determine the molecular mechanisms underlying chronic alcohol-induced chemokine upregulation and the development of ALD. Moreover, the proposal examines the potential of nutrition-based interventions targeted at HDAC inhibition in mitigating alcohol-induced chemokine expression and liver inflammation/injury. The specific aims of the proposal are: 1) Examine the role of alcohol-induced promoter histone modifications in regulating pro-inflammatory CCL2 and CXCL2 chemokine expression in ALD; 2) Determine the role of HDAC mediated regulation of NFB transactivation function and chemokine expression in ALD; and 3) Evaluate the therapeutic potential of tributyrin in attenuating CCL2 and CXCL2 chemokine expression and development of ALD. We expect that the results of our study will provide critical molecular insights and facilitate the development of therapeutic interventions for ALD.