NLRP6 function in inflammatory monocytes reduces susceptibility to colitis in mice

Abstract

NLRP6 is a member of the Nod-like receptor (NLR) family, whose members are involved in the recognition of microbes and/or tissue injury. NLRP6 was previously shown to regulate IL-18 secretion and is important for protecting mice against chemically-induced colitis and colitis-associated colon cancer. However, the cellular mechanisms by which NLRP6 reduces susceptibility to colonic inflammation remain unclear. Here, we determined that NLRP6 expression is specifically upregulated in Ly6Chi inflammatory monocytes that infiltrate into the colon during dextran sulfate sodium (DSS)-induced inflammation. Adoptive transfer of WT Ly6Chi inflammatory monocytes into Nlrp6−/− mice was sufficient to protect them from mortality, significantly reducing intestinal permeability and damage. NLRP6-deficient inflammatory monocytes were specifically defective in TNFα production, which was important for reducing DSS-induced mortality and dependent on autocrine IL-18 signaling by inflammatory monocytes. Our data reveal a previously unappreciated role for NLRP6 in inflammatory monocytes, which are recruited during colitis to promote barrier function and limit bacteria-driven inflammation. This study also highlights the importance of early cytokine responses, particularly NLRP6-dependent and IL-18-dependent TNFα production, in preventing chronic dysregulated inflammation that occurs in patients with inflammatory bowel disease.