Alcohol-Induced Alterations in Sperm Noncoding RNAs Persist After One Month Cessation and Correlate with Indicators of Epididymal Mitochondrial Dysfunction II
Background Chronic preconception paternal alcohol use modifies the sperm epigenome, inducing fetoplacental growth defects in the offspring of exposed males. A crucial outstanding question in the field of paternal epigenetic inheritance concerns the resilience of the male reproductive tract and the germline's capacity to recover and correct sperm-inherited epigenetic errors after stressor withdrawal. Objectives  We set out to determine if measures of the sperm-inherited epigenetic program revert to match the control treatment one month after withdrawing daily alcohol treatments. Materials and Methods  Using a voluntary access model, we exposed C57Bl6/J males to 10% alcohol for ten weeks, withdrew alcohol treatment for four weeks, and used RNA sequencing to examine gene expression patterns in the caput section of the epididymis. We then compared the abundance of sperm small RNA species between treatments.   Results  In the caput section of the epididymis, chronic alcohol exposures induced changes in the transcriptional control of genetic pathways related to mitochondrial function, oxidative phosphorylation, the generalized stress response (EIF2 signaling), and Sirtuin signaling. Subsequent analysis identified region-specific, alcohol-induced changes in mitochondrial DNA copy number across the epididymis, which correlated with increases in the mitochondrial DNA content of alcohol-exposed sperm. Notably, in the corpus section of the epididymis, increases in mitochondrial DNA copy number persisted one month after alcohol cessation. Analysis of sperm noncoding RNAs between Control and Alcohol-Exposed males one month after alcohol withdrawal revealed a ~100-fold increase in mir-196a, a microRNA induced as part of the Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2)-driven cellular antioxidant response.  Discussion and Conclusion Our data reveal that alcohol-induced epididymal mitochondrial dysfunction and differences in sperm noncoding RNA content persist after alcohol withdrawal. Further, differences in mir-196a and sperm mitochondrial DNA copy number may serve as viable biomarkers of adverse alterations in the sperm- inherited epigenetic program. Overall design: RNA seq on EtOH treated and EtOH ceased isolated caput portions of the epididymis