ABSTRACT
Chronic alcohol misuse is a major risk factor for alcohol-associated liver disease, a serious health
condition that represents approximately 50% of deaths in the U.S. related to chronic liver disease.
Known pathophysiological processes associated with alcohol-induced liver injury (ALI) include oxidative
stress, alteration of cell signaling, and inflammation; however, little is known about the effects of alcohol
on the hepatic epigenome, an emerging area with significant implications in the pathogenesis and
progression of ALI. Specifically, changes in histone acetylation, which includes the alcohol-induced
H3K9Ac chromatin mark, have been observed in several studies utilizing various cell culture and animal
models of acute and chronic alcohol exposure. A key feature of alcohol-induced histone acetylation
changes is that ethanol-derived metabolites can be incorporated directly into the hepatic
epigenome (i.e., acetate to Acetyl-CoA used for histone acetylation), which could have a significant
impact on transcriptional processes and subsequent pathophysiological outcomes related to chronic
alcohol use. Interestingly, ACSS2, a nucleocytosolic enzyme that catalyzes the conversion of acetate
to Acetyl-CoA, has recently been shown to play a role in regulation of lipid metabolism genes where
deletion of Acss2 protects against high fat diet-induced hepatic steatosis. However, in the context of
alcohol-induced hepatic steatosis and associated histone acetylation changes, the role of ACSS2 is
essentially unknown. We propose a novel metabolic tracing approach using stable isotope (non-
radioactive)-labeled ethanol and high-resolution mass spectrometry to accurately quantify the
contribution of ethanol-derived Acetyl-CoA and ACSS2 to hepatic histone acetylation at site-specific
levels in a chronic plus binge alcohol exposure model. We hypothesize that ethanol metabolism as
well as ACSS2 activity will enhance alcohol-induced hepatic histone acetylation and that enrichment of
these histone acetylation sites occurs at gene/gene promoter regions associated with markers and/or
pathways relevant to alcohol-induced liver injury phenotype. To test this hypothesis, we will 1) quantify
the hepatocyte-specific contribution of Acetyl-CoA derived from ethanol metabolism and ACSS2 activity
to histone acetylation in a mouse model of chronic ethanol exposure and 2) determine the impact of
site-specific histone acetylation increases induced by ethanol metabolism and ACSS2 activity on ALI
phenotype. The results from this project could reveal a novel link between alcohol-induced changes in
hepatic histone acetylation and liver injury phenotype, ultimately providing a foundation to guide future
mechanistic studies related to the specific role of ACSS2 in the progression of severe liver injury
brought about by excessive alcohol misuse.
