Receptor-interacting protein kinase 1 regulates microglial polarization via the Csf3-JAK2/STAT3 axis in...

In numerous demyelinating diseases, brain tissue exhibits excessive inflammatory responses that promote the activation of immune cells, thereby exacerbating cellular damage and amplifying inflammatory cascades. Emerging evidence highlights receptor-interacting protein kinase 1 (RIPK1) is a pivotal regulator of neuroinflammation, and its dysregulation contributes to the pathogenesis of various central nervous system (CNS) disorders. While our previous work established that RIPK1 kinase inhibition promotes remyelination in acute demyelinating models, however, the precise mechanisms of RIPK1 in microglial activation remain unclear. Here, to investigate RIPK1's role in microglial polarization, we employed lipopolysaccharide (LPS)-stimulated BV2 cells and the lysolecithin (LPC)-induced demyelination mouse model. By combining RIPK1^D138N kinase-dead knock-in mice and the pharmacological inhibitor Nec-1s，we performed experiments in both in vitro and in vivo models. We demonstrated that RIPK1 inhibition significantly attenuates M1 microglial polarization and pro-inflammatory cytokine production. Mechanistically, we identified that RIPK1 orchestrates the expression of colony-stimulating factor 3 (Csf3), which subsequently activates the JAK2/STAT3 signaling pathway. Pharmacological inhibition of RIPK1 decreased Csf3 expression, leading to reduced phosphorylation of JAK2/STAT3 and subsequent suppression of M1 polarization. Our findings reveal a novel RIPK1-Csf3-JAK2/STAT3 signaling axis governing microglial polarization and highlight its potential as a therapeutic target for demyelinating diseases.