Crosstalk between epigenetic and inflammatory signalling pathways in alcohol dependence

Sandra Helinski

Johnstone AL1,2, Barbier E3, Khomtchouk BB1,2, Rienas CA1,2, Tapocik JD4, Meinhardt MW5, VanBooven DJ6, Sommer WH5, Heilig M3,4, Wahlestedt C1,2

1Center for Therapeutic Innovation and the 2Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL; 3Department of Clinical and Experimental Medicine, Division of Cell Biology, Faculty of Health Sciences, Linköping University, Linköping, Sweden; 4Laboratory of Clinical and Translational Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD; 5Department of Psychopharmacology, Central Institute of Mental Heath, Mannheim, Germany; 6John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami FL

Epigenetic mechanisms coordinate gene expression changes in response to environmental cues. There are hundreds of enzymes that oversee epigenetic modifications. While a few of these have recently been shown to mediate behaviors associated with substance abuse, the vast majority have not been explored in alcohol dependence. We hypothesize that alcohol exposure influences long-term gene expression and behavioral abnormalities through changes in epigenetic enzyme activity. To investigate this, we used Nanostring nCounter analysis to profile the expression of over 120 epigenetic enzymes in the nucleus accumbens of alcohol dependent rats compared to controls. Dysregulation of four enzymes was confirmed by quantitative real-time PCR (qRT-PCR). One of these enzymes was also dysregulated in the prefrontal cortex of alcohol dependent rats as well as human alcoholics. This enzyme, KDM6B, is a histone demethylase that activates gene transcription by removing repressive tri-methyl groups from histone H3, lysine 27 (H3K27me3). Western blot analysis showed that KDM6B protein was increased in the nucleus accumbens of alcohol dependent rats. Consistent with the known demethylase activity of KDM6B, H3K27me3 was significantly decreased. KDM6B is a well-known mediator of inflammatory responses through direct promotion of NF-κB transcription and modulation of NF-κB target gene expression. We found that NF-κB is significantly activated in the nucleus accumbens of alcohol dependent rats. Further, preliminary analysis of ChIP-seq (chromatin immunoprecipitation followed by DNA-sequencing) data identified H3K27me3-mediated disruption of inflammatory signaling pathways in response to alcohol exposure. These findings implicate a novel signaling pathway that involves epigenetic-mediated regulation of inflammatory gene transcription in alcohol dependence. Ongoing experiments aim to determine whether KDM6B functionally alters inflammatory responses and contributes to alcohol-seeking behaviors. These studies may elucidate how an epigenetic mechanism translates alcohol exposure into long-term inflammatory changes that underlie chronic alcohol abuse.