Neurosteroids (allopregnanolone) and alcohol use disorder: From mechanisms to potential pharmacotherapy

Alcohol Use Disorder (AUD) is a multifaceted relapsing disorder that is commonly comorbid with psychiatric disorders, including anxiety. Alcohol exposure produces a plethora of effects on neurobiology. Currently, therapeutic strategies are limited, and only a few treatments - disulfiram, acamprosate, and naltrexone - are available. Given the complexity of this disorder, there is a great need for the identification of novel targets to develop new pharmacotherapy. The GABAergic system, the primary inhibitory system in the brain, is one of the well-known targets for alcohol and is responsible for the anxiolytic effects of alcohol. Interestingly, GABAergic neurotransmission is fine-tuned by neuroactive steroids that exert a regulatory role on several endocrine systems involved in neuropsychiatric disorders including AUD. Mounting evidence indicates that alcohol alters the biosynthesis of neurosteroids, whereas acute alcohol increases and chronic alcohol decreases allopregnanolone levels. Our recent work highlighted that chronic alcohol-induced changes in neurosteroid levels are mediated by epigenetic modifications, e.g., DNA methylation, affecting key enzymes involved in neurosteroid biosynthesis. These changes were associated with changes in GABA_A receptor subunit expression, suggesting an imbalance between excitatory and inhibitory signaling in AUD. This review will recapitulate the role of neurosteroids in the regulation of the neuroendocrine system, highlight their role in the observed allostatic load in AUD, and develop a framework from mechanisms to potential pharmacotherapy.