A role for epigenetic mechanisms in the regulation of prodynorphin expression by alcohol

Background and Aim: Alcohol alters several neurotransmitter systems within the brain and accumulated evidences indicate the endogenous opioid system as an important target of its action. We studied, in vitro and in vivo the molecular alterations occurring in the prodynorphin gene following different exposures to alcohol. Methods: Human neuroblastoma SH-SY5Y cells were exposed to low, clearly not intoxicating, and high etha- 208 European Opioid Conference 2011, Kraków, Poland nol concentrations at different time points. Sprague Dawley rats received alcohol intragastrically trying to mimic human drinking that establishes tolerance and dependence conditions. Real-time RT-PCR was used to assess the abundance of mRNAs of interest. DNA methylation was analyzed by Methylation Specific-Real Time PCR and bisulfite-Pyrosequencing. Specific histone modifications at gene promoters were evaluated by Chromatin ImmunoPrecipitation. Results: In the cellular model we demonstrated a temporal relationship between selective chromatin modifications induced by ethanol or acetaldehyde, and changes in prodynorphin gene expression were demonstrated. In the amygdala complex of alcoholtreated rats differential changes in prodynorphin gene expression changes were observed depending on the time of exposure; consistently, we propose potential epigenetic mechanisms responsible for these alterations, at least upong short ethanol exposure. Conclusion: Our findings indicate a linkage between gene expression alterations and epigenetic modulation in prodynorphin promoter, thus adding novel information on how the opioid system can be affected by alcohol in several ways. Studies are ongoing to evaluate the chromatin remodelling in the neuroplasticity occurring in the progression of alcohol abuse. It will be also of value to study the ability of epigenetic modulators in reverting dynorphin genetic/epigenetic alterations and alcohol abuse-related behaviours. Moreover, opioid drugs already available in alcoholism treatment could also have possible epigenetic modulating properties.