Microglial NLRP3 inflammasome activates neurotoxic astrocytes in depression-like mice.

The function and regulation of different heterogeneous reactive states of astrocytes in depression remain unclear. Here, we demonstrate that neurotoxic reactive (A1-like) astrocytes are strongly induced, prior to behavioral impairments and dendritic atrophy, in depression-like mice. More interestingly, global or microglia-specific knockout of Nod-like receptor protein 3 (Nlrp3) markedly mitigates A1-like astrocyte induction, whereas astrocyte-specific Nlrp3 depletion is ineffective. Microglial Nlrp3 ablation also alleviates the neuronal dysfunction induced by A1-like astrocytes both in vitro and in vivo. We further show that in microglia the NF-κB pathway activates the NLRP3 inflammasome which in turn activates caspase-1 to induce the secretion of A1 inductors, leading to the production of A1-like astrocytes. Altogether, this study reveals the function of microglial NLRP3 inflammasome in the induction of neurotoxic astrocytes via activating neuroinflammatory caspase-1 pathway in response to chronic stress and suggests a potential therapeutic strategy for depression.