Function And Mechanism Of Mindin-CD18 Axis In Inflammatory Bowel Disease

Background and aims Inflammatory bowel disease(IBD)is a chronic intestinal disorder.Its pathogenesis is not fully understood.It is generally believed that IBD results from a combination of genetic,immune,microbial and environmental factors.Mindin interacts with integrins and pathogens to initiate the innate immune response.Integrin CD18 is the β subunit of lymphocyte function-associated antigen 1(LFA-1),which is essential for host defense.Previous studies have shown that CD 18 is a membrane receptor for Mindin.Their binding promotes phagocytosis by macrophages.However,the biological role of Mindin and CD18 in the regulation of IBD remains not been fully elucidated.This study aimed to investigate the impact and immunomodulatory mechanisms of Mindin/CD18 knockdown in mice colitis.Methods RNAscope in situ hybridization was used to localize Mindin in mice colon;ImmGen database and flow cytometry were used to analyze Mindin expression in immune cells;ELISA was used to detect serum Mindin levels in IBD patients and healthy controls;DSS-induced acute colitis mice were examined for Mindin expression in serum and intestinal mucosa;WT,Mindin-/-,CD 18-/-and DKO mice colitis models were constructed,and body weight and colon length were recorded;intestinal tissues were obtained for H&E,TUNEL,immunohistochemistry and PAS staining;the number and subpopulation ratio of immune cells in the lamina propria of the colon of mice with colitis were analyzed by flow cytometry;the expression of intestinal cytokines in mice with chronic colitis was detected by qPCR;the levels of STAT1,STAT3 and YAP phosphorylation in the intestine of mice with chronic colitis were detected by Western blot.Results(1)RNAscope ISH showed that Mindin was located primarily in lamina propria and highly expressed in ILC3.(2)Serum Mindin were decreased in CD and UC patients compared with healthy controls,while the difference was not significant.(3)Expression of Mindin in serum was decreased at early time and gradually increased with the progression of inflammation in mice with acute colitis;the mRNA expression of Mindin in colon tissue increased on day 7 of modeling.(4)After knockdown of Mindin and CD 18,mice with acute colitis showed more significant weight loss,more severe intestinal pathological damage increased apoptosis,decreased epithelial barrier integrity,increased macrophages and their inflammatory subsets in the lamina propria of the colon and decreased DC,CD4+T and B cells.(5)After Mindin and CD18 knockdown,the number of DC and their subsets and B cells in the lamina propria of the colon of mice with chronic colitis was reduced;the proportion of CD4+T cells was decreased;IL-1β,IL-6,IL-17 mRNA expression in intestinal tissues was increased;STAT3 phosphorylation levels in colon tissues of CD18-/-and DKO mice were decreased;YAP phosphorylation in colon tissues of DKO mice levels were reduced.Conclusions(1)Mindin/CD18 promote intestinal injury repair and maintain mucosal barrier integrity in vivo.(2)Mindin significantly reduces inflammatory macrophage differentiation;alone or together,they mediate DC activation and effectively initiate T cells in vivo.(3)Mindin/CD18 attenuate DSS-induced intestinal inflammation in mice,possibly through activation of STAT3 and YAP.