Resistin-like molecule β regulates intestinal mucous secretion and curtails TNBS-induced colitis in mice

Background: Resistin and resistin-like molecule (RELM)beta comprise a novel class of cysteine-rich proteins secreted into the circulation implicated in hepatic insulin resistance and inflammation. RELM beta is specifically produced by intestinal goblet cells but regulation of its expression and much of its local function are not elucidated. RELM beta has been suggested to regulate colonic inflammation susceptibility, which is dependent on the mucosal barrier integrity. Methods: In this work we explored the physiopathological role of RELM beta in the colon. Among agents tested, carbachol and gastrin were strong inhibitors of RELM beta mRNA accumulation. We examined the effect of recombinant RELM beta on mucin secretion by human mucus-secreting HT29-Cl.16E cells in culture and by mouse colonic goblet cells in vivo. Results: RELM beta upregulated MUC2 and MI/MUC5AC gene expression in HT29-Cl.16E cells. RELM beta enhanced MI/MUC5AC secretion by human colonic HT29-Cl.16E cells and MUC2 secretion by murine intestinal goblet cells. RELM beta exerted its action exclusively on the apical side of HT29-Cl.16E cells, in agreement with its luminal mucosecretagogue effect in mice. Its action required calcium, protein kinase C, tyrosine kinases, and extracellular-regulated protein kinase activities and was synergized by carbachol. An intracolonic RELM beta challenge was performed in the trinitrobenzene sulfonic acid (TNBS)-murine model of colitis and macroscopic and histological scores were monitored. The macroscopic and histopathological severity of TNBS-induced colitis was significantly attenuated by RELM beta pretreatment. Conclusions: A direct participation in maintaining the mucosal defense barrier can be ascribed to RELM beta in line with a regulatory role in intestinal inflammation.