Microglial CHOP expression contributes to the consequences of ethanol withdrawal

Repeated cycles of ethanol intoxication and withdrawal induce profound changes in gene expression that contribute to physiological and behavioral consequences. Since neuroinflammation is an important mediator of these changes, we investigated the impact of repeated cycles of chronic intermittent ethanol vapor exposure and withdrawal on gene translation in striatal microglia. We performed deep sequencing of the microglia “translatome” in male and female RiboTag mice, yielding a snapshot of RNA translation during ethanol intoxication and after 8 hours of withdrawal. Chronic intermittent ethanol (CIE) produced robust changes in the translatome, with increases in genes and pathways associated with cytokine signaling, neuroinflammation, and microglial activation. After 8 hours of ethanol withdrawal, we saw evidence of increased cellular stress, including additional inflammatory pathways, damaged and misfolded protein responses, and pro-apoptotic pathways. Using unbiased network analysis, we identified gene modules that were differentially expressed in withdrawing animals. Several pathways and numerous genes involved in managing damaged or misfolded proteins were over-represented in one such module after withdrawal, including heat shock proteins (HSPs) and the transcription factor Ddit3 (CHOP), an important regulator of the endoplasmic reticulum (ER) unfolded protein response (UPR). We tested the impact of a Cx3cr1-specific CHOP knockout on CIE related behaviors. Following withdrawal from chronic intermittent ethanol, these mice had reduced thermoregulatory disturbances, anxiety-like behavior, and voluntary ethanol consumption compared to wild-type littermates. We conclude that blocking CHOP and promoting mitigation of damaged or misfolded proteins in microglia may be important targets for reducing the impacts of ethanol withdrawal.