Mechanistic insights into epigenetic modulation of ethanol consumption

Abstract

There is growing evidence that small-molecule inhibitors of epigenetic modulators, such as histone deacetylases (HDAC) and DNA methyltransferases (DNMT), can reduce voluntary ethanol consumption in animal models, but molecular and cellular processes underlying this behavioral effect are poorly understood. We used C57BL/6J male mice to investigate the effects of two FDA-approved drugs, decitabine (a DNMT inhibitor) and SAHA (an HDAC inhibitor), on ethanol consumption using two tests: binge-like drinking in the dark (DID) and chronic intermittent every other day (EOD) drinking. Decitabine but not SAHA reduced ethanol consumption in both tests. We further investigated decitabine's effects on the brain's reward pathway by gene expression profiling in the ventral tegmental area (VTA), using RNA sequencing and electrophysiological recordings from VTA dopaminergic neurons. Decitabine-induced decreases in EOD drinking were associated with global changes in gene expression, implicating regulation of cerebral blood flow, extracellular matrix organization, and neuroimmune functions in decitabine actions. In addition, an in vivo administration of decitabine shortened ethanol-induced excitation of VTA dopaminergic neurons in vitro, suggesting that decitabine reduces ethanol drinking via changes in the reward pathway. Taken together, our data suggest a contribution of both neuronal and non-neuronal mechanisms in the VTA in the regulation of ethanol consumption. Decitabine and other epigenetic compounds have been approved for cancer treatment, and understanding their mechanisms of actions in the brain may assist in repurposing these drugs and developing novel therapies for central disorders, including drug addiction.

Keywords: Alcohol; Behavior; Drug repurposing; Epigenetics; Neuronal activity; Transcriptome.

Fig. 1

Effects of SAHA (A) and decitabine (B) on ethanol intake in a limited-access DID procedure. Asterisks indicate a main effect of Treatment (*** = p < 0.001).

Fig. 2

Effects of SAHA and decitabine on ethanol intake (A) and preference (B) in a chronic intermittent EOD procedure. Drugs were administered 1 h before ethanol consumption on days 4, 6, 10, and 12, while vehicle was administered before day 8. Asterisks indicate statistically significant differences between the Decitabine and Vehicle groups (Bonferroni post hoc test, * = p < 0.05; ** = p < 0.01).

Fig. 3

Effects of in vivo pretreatment with decitabine on firing rates of DA neurons in vitro. There was no group difference in basal firing rate (A). The Decitabine group showed a faster desensitization of ethanol-induced excitation: all data summarized at 20-sec intervals (B), and critical time points representing the peak of ethanol effect in the Decitabine group (1 min), the peak of ethanol effect in the Vehicle group (5 min), and returning to baseline for both groups (9 min) (C). Asterisks indicate statistically significant differences between the Decitabine and Vehicle groups (Bonferroni post hoc test, ** = p < 0.01).