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Abstract The activation of the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome triggers pyroptosis proinflammatory cell death in experimental autoimmune encephalomyelitis (EAE). However, the underlying mechanisms of the inflammatory processes of microglia in EAE remain unclear. Our previous studies suggested that interleukin-1 receptor-associated kinase (IRAK)-M down-regulates the toll-like receptor 4/interleukin-1 receptor signaling pathway. Here, we used IRAK-M knockout (IRAK-M−/−) mice and their microglia to dissect the role of IRAK-M in EAE. We found that deletion of IRAK-M increased the incidence rate and exacerbated the clinical symptoms in EAE mice. We then found that IRAK-M deficiency promoted the activation of microglia, activated NLRP3 inflammasomes, and enhanced GSDMD-mediated pyroptosis in the microglia of EAE. In contrast, over-expression of IRAK-M exerted inhibitory effects on neuroinflammation, NLRP3 activation, and pyroptosis. Moreover, IRAK-M deficiency enhanced the phosphorylation of IRAK1, while IRAK-M over-expression downregulated the level of phosphorylated IRAK1. Finally, we found upregulated binding of IRAK1 and TNF receptor-associated factor 6 (TRAF6) in IRAK-M−/− EAE mice compared to WT mice, which was blocked in AAVIRAK-M EAE mice. Our study reveals a complex signaling network of IRAK-M, which negatively regulates microglial NLRP3 inflammasomes and pyroptosis by inhibiting IRAK1 phosphorylation during EAE. These findings suggest a potential target for the novel therapeutic approaches of multiple sclerosis (MS)/EAE and NLRP3-related inflammatory diseases.

Abstract Pathologic findings showed that neutrophils played an important role in the pathogenesis of NMO. This study aims to investigate the CSF levels of neutrophil‐related chemokines in NMO. CXCL1, CXCL5, and CXCL7 were measured in 95 patients with NMO, 15 patients with MS, 18 patients with GFAP astrocytopathy, and 16 controls. The CSF level of CXCL1, CXCL5, and CXCL7 was significantly elevated in the NMO group but not correlated with the patient clinical severity. Besides, the CSF CXCL1, CXCL5, and CXCL7 could act as biomarkers to distinguish NMO from MS with good reliability, especially the CXCL7.