SPI1 triggers the formation of neutrophil extracellular traps in multiple sclerosis through CXCL4

Multiple sclerosis (MS) is a common demyelinating disease of the central nervous system, accompanied by chronic inflammation and neurodegeneration. Neutrophils and the formation of neutrophil extracellular traps (NETs) play a significant role in central nervous system diseases. Spi-1 proto-oncogene (SPI1) is a crucial regulator for the development and maturation of myeloid cells. However, the role of SPI1 in MS remains unclear. In this study, an MS model was established in mice through the induction of experimental autoimmune encephalomyelitis (EAE). Hematoxylin-eosin staining, Luxol fast blue staining, western blot, SYTOX Green, and immunofluorescence (IF) staining were performed to study the effects of SPI1 after MS. In vitro experiments involved the use of western blot, IF staining, and ELISA to assess the effects of SPI1 on neutrophils and NETs. To confirm the interaction between SPI1 and CXCL4, chromatin immunoprecipitation and dual-luciferase reporter assays were conducted. Neutrophils in the spinal cord of mice were activated upon EAE induction. We revealed that SPI1 expression was elevated in neutrophils from both EAE mice and those stimulated with phorbol myristate acetate (PMA). Inhibition of SPI1 delayed neutrophil activation, reduces the release of proinflammatory cytokines, chemokines, and NETs, and promoted the maturation of oligodendrocyte precursor cells and myelin formation, thereby alleviating MS in mice. Further analysis demonstrated that SPI1 positively regulated CXCL4 transcription. Knockdown of CXCL4 partially reversed the effects of SPI1 overexpression on PMA-induced neutrophils. These results indicated that SPI1 serves as a crucial regulator of NETS in MS by regulating the CXCL4 promoter. The inhibition of SPI1 emerges as a potential therapeutic target for MS treatment.