Cell-Autonomous Regulation of Astrocyte Activation by the Circadian Clock Protein BMAL1

Circadian clock dysfunction is a common symptom of aging and neurodegenerative diseases, though its impact on brain health is poorly understood. Astrocyte activation occurs in response to diverse insults and plays a critical role in brain health and disease. We report that the core circadian clock protein BMAL1 regulates astrogliosis in a synergistic manner via a cell-autonomous mechanism and a lesser non-cell-autonomous signal from neurons. Astrocyte-specific Bmal1 deletion induces astrocyte activation and inflammatory gene expression in vitro and in vivo, mediated in part by suppression of glutathione-S-transferase signaling. Functionally, loss of Bmal1 in astrocytes promotes neuronal death in vitro. Our results demonstrate that the core clock protein BMAL1 regulates astrocyte activation and function in vivo, elucidating a mechanism by which the circadian clock could influence many aspects of brain function and neurological disease. [Display omitted] •Circadian disruption promotes astrocyte activation•Astrocyte-specific deletion of the circadian clock gene BMAL1 induces activation•BMAL1 regulates astrocyte activation by altering glutathione-S-transferase signaling•Loss of astrocyte BMAL1 enhances neuronal cell death in a co-culture system Lananna et al. show that the circadian clock protein BMAL1 regulates astrocyte activation via a cell-autonomous mechanism involving diminished glutathione-S-transferase signaling. This finding elucidates a function of the core circadian clock in astrocytes and reveals BMAL1 as a modulator of astrogliosis.