Cytosolic flagellin receptor NLRC4 protects mice against mucosal and systemic challenges

Bacterial flagellin is a dominant innate immune activator of the intestine. Therefore, we examined the role of the intracellular flagellin receptor, NLRC4, in protecting the gut and/or driving inflammation. In accord with NLRC4 acting via transcription-independent pathways, loss of NLRC4 did not reduce the rapid robust changes in intestinal gene expression induced by flagellin administration. Loss of NLRC4 did not alter basal intestinal homeostasis nor predispose mice to development of colitis upon administration of an anti-IL-10R monoclonal antibody. However, in response to epithelial injury induced by dextran sulfate sodium (DSS), loss of NLRC4 resulted in more severe disease indicating a role for NLRC4 in protecting the gut. Moreover, loss of NLRC4 resulted in increased mortality in response to flagellate, but not aflagellate Salmonella infection. Thus, despite not being involved in rapid intestinal gene remodeling upon detection of flagellin, NLRC4-mediated inflammasome activation protects mice from mucosal and systemic challenges Flagellin (FliC) from WT Salmonella enterica serovar Typhimurium (SL3201, fljB–) was purified through sequential cation and anion-exchange chromatography and purity was verified as previously described 4. WT, T5KO, N4KO and T5/N4-DKO mice (n=6) were given either 0.2 mL PBS or flagellin (10μg/mouse in 0.2 mL PBS) intraperitoneally. After 1h, mice were euthanized and colon was taken and stored in RNAlater (Invitrogen) for 1 day. Total mRNA was isolated from colonic tissues using TRIzol (Invitrogen) and purified using the RNeasy® Plus Mini kit (Qiagen) according to the manufacturer’s instructions