Immunoproteasome subunit PSMB8 regulates microglia-mediated neuroinflammation upon manganese exposure by PERK signaling

Excessive manganese (Mn) exposure gives rise to various neurological disorders, including motor dysfunction and cognitive impairment. Microglia-mediated neuroinflammation plays an essential role in the pathogenesis of Mn neurotoxicity. However, the underlying mechanisms have not been fully clarified. Immunoproteasome is a specialized proteasome. Recent studies have shown that immunoproteasome, especially catalytic subunit PSMB8, is highly associated with various neurological diseases. Whether PSMB8 is involved in Mn-neurotoxicity is still unknown. In this study, in vivo and in vitro models were established, and our data showed that Mn exposure upregulated the expression and activity of PSMB8. Selective inhibition of PSMB8 mitigated neuroinflammation with reduced microglial activation and fewer TNF-α, iNOS, and CCL12 production in Mn-treated mice and BV2 cells. Learning and memory tests and Golgi staining further confirmed that inhibition of PSMB8 alleviated Mn-induced recognition memory impairments and synapse deficits. Besides, we found that blocking of PERK signaling inhibited Mn-induced elevation of PSMB8. And inhibition of PSMB8 reduced the phosphorylation of NF-κB p65. Together, our data demonstrated that PSMB8 played an essential role in microglia-mediated neuroinflammation upon Mn exposure, and the underlying mechanisms may be via PERK/NF-κB pathways. These results provide a novel target for the prevention and treatment of Mn-neurotoxicity.