Alcohol, a leading cause of morbidity and mortality in the world, affects many organs, most notably liver and central nervous system. An important biochemical consequence of alcohol abuse is a significant decrease in S-adenosyl methionine (SAM) level and a corresponding increase in S-adenosyl homocysteine (SAH) level. Our hypothesis is that alcohol-induced alteration in hepatic SAM and SAH levels plays a key role in modifying liver epigenome leading to altered gene expression that causes hepatic dysfunction, liver toxicity and ultimately hepatocarcinogeneis. The long term objective of this study is to advance our understanding of the role of epigenetic regulation of specific genes in mediating alcohol-mediated liver dysfunction. Altered SAM level also affects cellular redox state that influences histone modification and ultimately gene expression. The present study will test the hypothesis using mouse promoter microarray and ChlP-on-Chip analysis as well as Dnmt1 (the major DNA methyltransferase) hypomorphic mice with reduced level of Dnmt1 .
The specific aims are (1) identify alcohol-induced post-translational modifications of histone H4 that occur in vivo in the livers of alcohol-fed mice by acid-urea gel electrophoresis, in-gel digestion, MALDI-TOF MS and LC/MS-MS analysis, (2) determine alterations in the DNA methylation machinery by western blot analysis and changes in the liver epigenome that occur in mice exposed to alcohol by identifying genes with altered DNA methylation status and histone post-translational modification profile using differential methylation hybridization and ChlP-on-chip analysis respectively and (3) investigate pathological changes that occur in the livers of Dnmt1 hypermorphic mice after chronic alcohol exposure and determine whether the methylation profile of genome in the livers of these mice is distinct from that of the wild type mice subjected to chronic alcohol exposure. It is anticipated that this study will identify critical epigenetic alterations that occur in alcohol-induced liver diseases. Because epigenetic changes can be reversed with relative ease by pharmacological intervention with small molecule inhibitors of DNA methyltransferase and/or histone deacetylases some of these agents could be used effectively as potential theapeutic agents in alcohol-induced liver injury. This proposal also fits well with the mission of the National Institute of Alcohol Abuse and Alcoholism on """"""""alcohol metabolism and epigenetic effects on tissue injury"""""""". ? ? ?
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