Transcriptional dysregulation of cholesterol synthesis underlies hyposensitivity to γ-aminobutyric acid in the ventral tegmental area during acute alcohol withdrawal.

BACKGROUND: The ventral tegmental area (VTA) is a dopaminergic brain area critical in the development and maintenance of addiction. During withdrawal from chronic ethanol exposure, the response of VTA neurons to GABA is reduced through an epigenetically regulated mechanism. A whole genome transcriptomic approach was utilized to investigate the underlying molecular mechanism of GABA hyposensitivity in VTA during withdrawal after chronic ethanol exposure.

METHODS: We performed RNA sequencing (RNA-Seq) of the VTA of Sprague-Dawley male rats withdrawn for 24 hours from chronic ethanol diet as well as the VTA from control Lieber-DeCarli diet-fed rats. RNA-Seq data was analyzed using weighted gene co-expression network analysis (WGCNA) to identify modules that contained co-expressed genes. Validation was performed with qPCR, GC-MS and electrophysiological assays.

RESULTS: Pathway and network analysis of WGCNA module 1 revealed a significant downregulation of genes associated with the cholesterol synthesis pathway. Consistent with this association, VTA cholesterol levels were significantly decreased during withdrawal. Chromatin immunoprecipitation (ChIP) indicated a decrease in levels of H3K27ac at the transcriptional control regions of these genes. Electrophysiological studies in VTA slices demonstrated that GABA hyposensitivity during withdrawal that was normalized by addition of exogenous cholesterol. In addition, inhibition of cholesterol synthesis produced GABA hyposensitivity, which was reversed by adding exogenous cholesterol to VTA slices.

CONCLUSIONS: These results suggest that decreased expression of cholesterol synthesis genes might regulate GABA hyposensitivity of VTA neurons during alcohol withdrawal. Increasing cholesterol levels in the brain may be a novel avenue for therapeutic intervention to reverse detrimental effects of chronic alcohol exposure.