Sphk1 mediates neuroinflammation and neuronal injury via TRAF2/NF-κB pathways in activated microglia in cerebral ischemia reperfusion

Abstract

Sphingosine kinase 1 (Sphk1), a key enzyme responsible for phosphorylating sphingosine into sphingosine1-phosphate (S1P), plays an important role in mediating post-stroke neuroinflammation. However, the pathway and mechanism of the Sphk1-mediated inflammatory response remains unknown. In this study, we found that suppression of Sphk1 decreased IL17 production and relieved neuronal damage induced by microglia in cerebral ischemia reperfusion (IR) or in an in vitro oxygen-glucose deprivation reperfusion (OGDR) system. Inhibition of Sphk1 with an inhibitor or siRNA decreased tumor necrosis factor receptor-associated factor 2 (TRAF2) and nuclear factor-kappa B (NF-κB) sequentially in microglia in response to IR or OGDR. Moreover, we also found that after suppression of TRAF2 or NF-κB by siRNA in microglia, reductions in the downstream molecules NF-κB and IL-17 and in neuronal apoptosis were observed in response to OGDR. Taken together, we hypothesize that Sphk1, TRAF2 and NF-κB form an axis that leads to increased IL-17 and neuronal apoptosis. This axis may be a potential therapeutic target to control neuroinflammation in brain IR.