Abstract 165: Chronic Ethanol Consumption Impacts Post-Myocardial Infarction Cardiac Function and Modulates Gene Expression in Cardiac Cell Types through Alteration of Histone 3 Lysine 79 Methylation

Abstract

The beliefs surrounding the cardiac effects of chronic ethanol (EtOH) consumption in humans are known to be dictated by the frequency of ingestion. Studies have established that moderate consumption (i.e. 1-2 drinks/day) imparts a cardiac benefit to patients by reducing the frequency of adverse cardiovascular events (ACE). EtOH consumption beyond moderate levels (i.e. >2 drinks per day) is associated with a significant increase in ACEs. Despite this knowledge, little is known regarding the functional impact of chronic EtOH consumption on post-myocardial infarct repair or the cellular mechanisms involved in this process. Therefore, we investigated the post-AMI functional consequences of chronic ethanol consumption in mice. Mice received chronic ethanol via the Lieber-DeCarli paradigm and each group of mice received either: 0%, 1% (moderate) or 5% (high) ethanol v/v in an isocaloric fashion for 8 weeks. After 8 weeks, mice then underwent a 60 minute ischemic/reperfusion injury and the subsequent assessment of their cardiac function at 1, 2 and 4 weeks after AMI. As early as two weeks post-AMI, mice fed the 1% EtOH displayed significant improvements in ejection fraction, systolic ventricular volumes and infarct size as compared to control mice. Conversely, mice that consumed the 5% EtOH diet displayed diminished ejection fraction and increased systolic chamber volume and infarct size. To investigate the mechanistic basis behind these changes, isolated murine cardiac fibroblasts (CFBs) were exposed to EtOH using a “chronic” 5 day treatment paradigm in which media ± EtOH was replaced daily. CFB lysates were then harvested and several epigenetic histone marks were assessed via western blotting. Specifically, methylation of histone 3 lysine 79 (H3K79) was significantly increased at the moderate dose (0.1% v/v) and severely diminished at the high dose (0.5% v/v). H3K79 is exclusively methylated by the methyl-transferase Dot1, suggesting that chronic ethanol may have biphasic dose effects on the regulation of genes influenced by H3K79 methylation. This data represents the first indication that chronic EtOH may affect cells of the post-ischemic heart by influencing their gene expression profiles through manipulation of their epigenetic fingerprint.