IL-33 Attenuates Sepsis by Inhibiting IL-17 Receptor Signaling through Upregulation of SOCS3.

BACKGROUND/AIMS Sepsis is a systemic inflammatory response during infection. There are limited therapeutic options for sepsis patients. Interleukin (IL)-33 has been reported recently with a beneficial effect in mouse sepsis. METHODS In this study, we initiated a clinical study to measure serum levels of pro-inflammatory cytokines including IL-33 in sepsis patients. Next, we employed cecal ligation and puncture (CLP) to study the role of IL-33 during sepsis. To further dissect the molecular mechanism, we used in vivo knockout models and in vitro knockdown murine embryonic fibroblasts (MEFs) to investigate the cross-talk between IL-33 and IL-17 signaling, and to identify the potential downstream mediators. RESULTS IL-33 and IL-17 were upregulated in both clinical and experimental sepsis. In CLP, IL-33 (-/-) mice showed higher mortality rate, and IL-33 treatment improved the survival rate. Elevated proinflammatory cytokines in sepsis were related to IL-17 from γδT cells. IL-33 treatment suppressed production of these cytokines by targeting IL-17 signaling both in vivo and in vitro. Finally, IL-33 was shown to inhibit the IL-17 pathway via activating suppressor of cytokine signaling (SOCS)-3. CONCLUSION Collectively, the results suggest that IL-33 plays a negative regulatory role in sepsis progression by inhibiting IL-17 pathway through activating SOCS3. This finding would inspire a new therapeutic strategy for treating sepsis.