Microglial-specific transcriptome changes following chronic alcohol consumption

Microglia are fundamentally important immune cells within the central nervous system (CNS) that respond to environmental challenges to maintain normal physiological processes. Alterations in steady-state cellular function and over-activation of microglia can facilitate the initiation and progression of neuropathological conditions such as Alzheimer’s disease, Multiple Sclerosis, and Major Depressive Disorder. Alcohol consumption disrupts signaling pathways including both innate and adaptive immune responses that are necessary for CNS homeostasis. Unbiased RNA-Seq profiling was used to identify gene expression changes in isolated microglia in response to recurring bouts of voluntary alcohol drinking behavior. Gene coexpression analysis identified a coordinately regulated group of genes, unique to microglia, that collectively are associated with alcohol consumption. Several genes in this group were involved in toll-like receptor signaling and production of the inflammatory cytokine interferon-gamma. Coordinate expression of these genes is not ascertained from an admixture of CNS cell-types, underscoring the importance of examining isolated cellular populations to reveal systematic gene expression changes arising from mature microglia. We identified a distinctive microglial gene expression signature for neuroimmune responses related to alcohol consumption that provides valuable insight into microglia-specific changes underlying the development of substance abuse, as well as related CNS disorders. We examined mRNA from both total homogenate (mixture of all cell types) and microglia from the cortex of control mice and mice that have undergone chronic voluntary ethanol consumption