Leveraging single-cell transcriptomic data to identify AUD-associated differences in communication pathways between cell types allowed us to integrate the transcriptomic and epigenetic alterations in each cell type into predictions of upstream signaling events. Signaling from microglial cells to astrocytes that involves proinflammatory molecules IL-1β, TNF, and oncostatin M is higher in individuals with AUD, concordant with the hypothesis that activated microglia induce neurotoxic reactive astrocytes.54 These three molecules have been shown to work synergistically in astrocytes and other cells to induce pro-inflammatory and neurotoxic molecules such as nitric oxide79 and prostaglandin E(2).56 Although reactive astrocytes can induce death of neurons and oligodendrocytes, we did not observe a significant difference between individuals with and without AUD in relative proportions of neuronal cell types or oligodendrocytes. We found increased signaling via TFGB1-ITGB8 from both microglia and astrocytes to oligodendrocytes. TGF-β1 signaling is known to increase after injury, and studies have shown that ethanol exposure induces TGF-β1 signaling in rats.80,81 Previous work showed that TGF-β1 expression increases in astrocytes and microglia in animal models of cerebral ischemia,82 and another study has shown that TGF-β1 signaling plays a role in myelination in oligodendrocytes.83
