GPR35 Promote Inflammation Bowel Disease By Inhibiting IFN? Signal Pathway

Inflammatory bowel disease(IBD)is a group of inflammatory disorders with a global morbidity of 3-5 billion patients each year.IBD may cause abdominal pain,blood in the stool,weight loss and extreme fatigue.Some patients with severe symptoms have to undergo surgery to repair or remove the damaged bowel,and sustained inflammation can increase the risk of colon cancer.Therefore,it is urgent to study the pathogenesis of IBD and find the new therapeutic targets.G protein coupled receptor 35(GPR35)is a member of the G protein coupled receptor family.It is suggested that GPR35 may be involved in a range of physiological processes and pathological conditions including asthma,cardiovascular disease,diabetes etc,and is a promising therapeutic target.GPR35 is highly expressed in human gastrointestinal organs.and multiple genome-wide association studies(GWAS)have found that GPR35 polymorphism is closely related to the development of IBD,but the relation between GPR35 and IBD has not been studied.We constructed two mutant vectors of GPR35 to analysis the activity of mutated GPR35(GPR35T108M and GPR35S294R).By using the ?-arrestin recruitment experiment assay,CRE luciferase reporter system and calcium flow assay,we found that the activity of two mutated GPR35 against the ligand Zaprinast is significantly improved.It is proved that the activation of GPR35 in human body is related to the development of IBD.By using Gpr35 knockout mice,we found that Gpr35 deficiency mouse showed less body weight lose,lower DAI score,colon histology score,inflammatory factor level and less immune cell infiltration than wild-type mice in DSS induced IBD model.AOM-DSS model also demonstrated that the colon tumor size,number and histology scores of Gpr35 knockout mouse were much lower than wild-type mouse.All of the results demonstrated that Gpr35 promote the development of IBD and colon cancer.The RNAseq results of the Gpr35 knockout mice showed that interferon ?(IFN?)expression and related signaling pathways,which play a inhibition role in IBD,were significantly up-regulated in Gpr35 knockout mouse.Subsequent cell experiments and animal models demonstrated that GPR35 can inhibit the expression of IFN? in the intestinal tract by inhibiting the phosphorylation level of TBK1.Our study demonstrated that GPR35 could inhibit the expression of interferon beta and the activity of downstream signaling pathways by regulating the phosphorylation level of TBK1 in the intestine,which in turn promote the development of IBD.Taken together,GPR35 can be used as a therapeutic target for the treatment of IBD.