The autoimmune encephalitis-related cytokine TSLP in the brain primes neuroinflammation by activating the JAK2-NLRP3 axis

Abstract

SummaryNLRP3 inflammasome hyperactivation contributes to neuroinflammation in autoimmune disorders, but the underlying regulatory mechanism remains to be elucidated. We demonstrate that compared with wild-type (WT) mice, mice lacking thymic stromal lymphopoietin (TSLP) receptor (TSLPR) (Tslpr−/− mice) exhibit a significantly decreased experimental autoimmune encephalomyelitis (EAE) score, reduced CD4+ T cell infiltration, and restored myelin basic protein (MBP) expression in the brain after EAE induction by myelin oligodendrocyte glycoprotein35–55 (MOG35–55). TSLPR signals through Janus kinase (JAK)2, but not JAK1 or JAK3, to induce NLRP3 expression, and Tslpr−/− mice with EAE show decreased JAK2 phosphorylation and NLRP3 expression in the brain. JAK2 inhibition by ruxolitinib mimicked loss of TSLPR function in vivo and further decreased TSLP expression in the EAE mouse brain. The NLRP3 inhibitor MCC950 decreased CD4+ T cell infiltration, restored MBP expression, and decreased IL-1β and TSLP levels, verifying the pro-inflammatory role of NLRP3. In vitro experiments using BV-2 murine microglia revealed that TSLP directly induced NLRP3 expression, phosphorylation of JAK2 but not JAK1orJAK3, and IL-1β release, which were markedly inhibited by ruxolitinib. Furthermore, EAE induction led to an increase in the Th17 cell number, a decrease in the regulatory T (Treg) cell number in the blood, and an increase in the expression of the cytokine IL-17A in the WT mouse brain, which was drastically reversed in Tslpr−/− mice. In addition, ruxolitinib suppressed the increase in IL-17A expression in the EAE mouse brain. These findings identify TSLP as a prospective target for treating JAK2-NLRP3 axis-associated autoimmune inflammatory disorders.