Summary: Even low doses of alcohol can trigger transcriptomic and epigenomic changes in brain regions linked to addiction.
Source: University of Illinois
New rodent research finds that even modest amounts of alcohol can rapidly change gene expression and chromatin structure in brain circuitry critical to addiction.
Researchers at the University of Illinois Chicago report that the same neural pathways associated with alcohol’s pleasurable effects—euphoria and anxiolysis (reduction of anxiety while remaining awake)—also appear to prime the brain for future alcohol use disorder (AUD). These findings point to molecular mechanisms by which seemingly low-risk drinking could increase vulnerability to addictive behaviors.
“When the brain experiences relaxation and the mild buzz of drinking, it may simultaneously be undergoing changes that make it more susceptible to AUD,” said senior author Subhash Pandey, Joseph A. Flaherty endowed professor of psychiatry and director of the Center for Alcohol Research in Epigenetics at UIC College of Medicine. The study, Pandey notes, does not claim that a single drink causes addiction in humans, but it does illuminate biological processes that could help explain why some people are more prone to developing AUD.
Pandey emphasized that dependent behaviors may emerge not only from prolonged heavy drinking but also from rapid epigenetic alterations in the brain. This study demonstrates that such changes can begin after low-dose alcohol exposure.
Published in Molecular Psychiatry, the paper reports experiments comparing control rats with animals exposed to low concentrations of alcohol. Researchers observed behavior in an elevated plus maze—measuring time spent in enclosed versus open arms as an index of anxiety—then analyzed amygdala tissue with RNA sequencing and chromatin accessibility assays to map transcriptomic and epigenomic changes.
One gene stood out: hypoxia inducible factor 3 alpha subunit (Hif3a). Alcohol exposure increased Hif3a expression in the amygdala even at low doses and was associated with reduced anxiety-like behavior in the maze. Notably, these effects were observed in both male and female rats, indicating no clear sex difference in this model.
To validate Hif3a’s role, the team used targeted knockdown of the gene in the central amygdala. Blocking Hif3a raised anxiety in control animals, a pattern similar to withdrawal after chronic alcohol exposure, and prevented alcohol’s immediate anti-anxiety effects. These manipulations support a causal role for Hif3a in mediating alcohol-induced anxiolysis.
Mechanistically, the study found that chromatin around Hif3a was in a more open, permissive state after acute alcohol exposure. Open chromatin is more accessible for transcription, and the researchers observed increased activating histone acetylation marks and reduced DNA methylation at Hif3a regulatory regions—epigenetic signatures consistent with increased gene transcription.
The authors caution that the study does not define a “safe” alcohol dose for rodents or people; rather, it demonstrates that low doses can prime epigenetic pathways linked to AUD. Pandey advises that social or episodic drinking should not be assumed risk-free, especially given alcohol use disorder’s complexity and treatment challenges.
“Understanding these early molecular events in the brain may lead to improved strategies for preventing and treating AUD, and potentially to new pharmaceutical targets,” Pandey said.
Co-authors of the study, titled “Unraveling the epigenomic and transcriptomic interplay during alcohol-induced anxiolysis,” include Harish Krishnan, Huaibo Zhang, Ying Chen, John Peyton Bohnsack, Annie Shieh, Handojo Kusumo, Jenny Drnevich, Chunyu Liu, Dennis Grayson and Mark Maienschein-Cline.
Funding: This research was supported by grants from the National Institute on Alcohol Abuse and Alcoholism (P50AA-022538, U01AA-019971, U24AA-024605, R01AA-010005) and the U.S. Department of Veterans Affairs (I01BX004517, IK6BX006020).
About this neuroscience and addiction research news
Author: Jacqueline Carey
Source: University of Illinois
Contact: Jacqueline Carey – University of Illinois
Image: The image is in the public domain
Original Research: Open access. “Unraveling the epigenomic and transcriptomic interplay during alcohol-induced anxiolysis” by Harish Krishnan et al., Molecular Psychiatry.
Abstract
Unraveling the epigenomic and transcriptomic interplay during alcohol-induced anxiolysis
Positive effects of alcohol—such as anxiolysis and euphoria—are major drivers in the initiation and maintenance of alcohol use disorder (AUD). Yet the molecular cascade that links chromatin reorganization to transcriptomic changes after acute ethanol exposure has remained unclear.
Using ATAC-seq (Assay for Transposase-Accessible Chromatin sequencing) alongside RNA-seq, the study examined epigenomic and transcriptomic alterations in the amygdala that correspond with ethanol-induced anxiolysis in an animal model. ATAC-seq revealed a generally more open chromatin landscape after acute ethanol exposure, aligned with changes in gene expression in the amygdala.
The investigators identified Hif3a as a candidate gene showing increased chromatin accessibility, elevated activating histone acetylation marks, and reduced DNA methylation—epigenetic features linked to higher transcriptional activity. Hif3a mRNA increased after acute ethanol exposure but decreased during withdrawal following chronic exposure.
Targeted knockdown of Hif3a in the central nucleus of the amygdala blunted ethanol-induced increases in Hif3a mRNA and blocked anxiolysis in rats. These findings support a model in which chromatin accessibility and transcriptional responses in the amygdala underlie alcohol’s acute anxiolytic effects and may prime chromatin for pathways that contribute to AUD.