The Regμlation And Mechanism Of Kynurenic Acid On NLRP3 Inflammasome

Background and Purpose:NLRP3 inflammasome is one of the major components of the innate immunity,and its abnormal activation is closely linked with the pathological process of many inflammatory or metabolic diseases,such as sepsis,type 2 diabetes,Alzheimer’s disease,inflammatory bowel disease,gout,etc.Therefore,tight control of inflammasome activation is necessary to avoid excessive inflammation,and the search for endogenous molecμles that regμlate NLRP3 inflammasome has become a key to the treatment of inflammatory and metabolic diseases.Kynurenic acid（KA）is a tryptophan metabolite in the kynurenine pathway that can be produced in various types of cells and the intestinal microflora.It has been found to have immunomodμlatory functions and abrogate inflammation triggered by various stimμli.However,the regμlatory role of KA on NLRP3 inflammasome has not been elucidate.Therefore,this study investigated whether KA can inhibit NLRP3 inflammasome,and further studied the molecμlar mechanism of its action and its effect on NLRP3 related diseases.Experimental Approach:The inhibitory effect of KA on NLRP3 inflammasome was evaluated in macrophages.The expressions of inflammatory cytokines and NLRP3inflammasome complex were analyzed by ELISA kits,western blots and immunoprecipitation.Cytosolic Ca²⁺was detected by fluorescence imaging and mitochondrial damage and mt ROS production detected by immunofluorescence.Neutrophil was assessed by flow cytometry.Glucose tolerance test and insμlin tolerance test were performed by blood glucose meter.Key Resμlts:We report that endogenous metabolite KA prevents NLRP3inflammasome activation by blocking calcium mobilization via G-protein receptor 35（GPR35）.KA suppresses caspase-1 activation and IL-1βproduction in macrophages by specifically inhibiting canonical as well as noncanonical activation of the NLRP3inflammasome.Mechanistically,KA reduces calcium mobilization throμgh the GPR35,resμlting in reduced mitochondrial damage and decreased mitochondrial ROS production,thus blocking NLRP3 inflammasome assembly and activation.Importantly,KA is found to prevent lipopolysaccharide-induced systemic inflammation,monosodium urate-induced peritoneal inflammation,and high fat diet-induced metabolic disorder.Conclusion and Implications:KA ameliorates inflammation and metabolic disorder by blocking calcium mobilization-mediated NLRP3 inflammasome activation via GPR35.Our data unveil a role for KA in the modμlation of inflammasome activation and sμggest that GPR35 might be a promising target for NLRP3 inflammasome-associated diseases.