Depletion of HSP60 in Microglia Leads to Synaptic Dysfunction and Depression-Like Behaviors Through Enhanced Synaptic Pruning in Male Mice.

AIMS: Microglia, as resident macrophages in the brain, play an important role in depression. Heat shock protein 60 (HSP60), as a chaperone protein, plays a role in cell stress. However, the role of microglial HSP60 in depression remains unclear. METHODS: CX3CR1-CreER was used to generate microglial-specific HSP60 knockout (HSP60 cKO) mice. Behavioral tests, western blotting, Golgi staining, biochemical assays, and proteomics were employed to assess depression-like symptoms, microglial activation, and synaptic changes. RESULTS: HSP60 cKO male mice exhibited depressive-like behaviors, without anxiety-like behavior, including increased immobility in the forced swimming and tail suspension tests, reduced sucrose preference, and elevated corticosterone (CORT) levels, indicating HPA axis activation. Microglial activation was confirmed by the increased expression levels of CD68 and CD86, the elevated transcription of the cybb gene, and reduced branch complexity. Enhanced phagocytosis of excitatory synapses, reduced dendritic spine density, and decreased glutamate levels were observed, with downregulation of synaptic proteins (AMPAR2, Synapsin-1, PSD95), indicating dysregulated synaptic pruning. Moreover, GO analysis showed 20 significant differentially expressed proteins (DEPs) from proteomics are associated with the presynaptic endosome, which plays a crucial role in maintaining synaptic function. Treatment with PLX3397, a CSF1R inhibitor, alleviated depressive-like behaviors and restored synaptic density in HSP60 cKO male mice. CONCLUSIONS: HSP60 deletion in microglia leads to overactivation of microglia, impaired synaptic function, and depression-like behaviors, highlighting the importance of microglial homeostasis in mood regulation and the potential therapeutic role of microglial modulation.