Divergent Roles for Macrophage C-Type Lectin Receptors, Dectin-1 and Mannose Receptors, in Inflammatory Bowel Diseases

Colonic macrophages are considered as major effectors of inflammatory bowel diseases (IBD), and the control of gut inflammation through C-type lectin receptors is an emerging concept. We show that during colitis the loss of Dectin-1 prevents intestinal inflammation, while the lack of MR exacerbates it. A marked increase in Dectin-1 expression in DSS-exposed MR-deficient mice, support the critical contribution of Dectin-1 in the development of colitis. Dectin-1 is crucial for Ly6ChighCCR2high monocyte population enrichment in the blood and their recruitment to inflamed colon as precursors of M1 inflammatory macrophages. Dectin-1 also promotes inflammasome-dependent IL-1β secretion through the leukotriene B4 production. Interestingly, the colonic inflammation is associated with a concomitant overexpression of Dectin-1/CCL2/LTA4H and a down-regulation of MR on macrophages from IBD patients. Thus, MR and Dectin-1 on macrophage are important mucosal inflammatory regulators during IBD. Finally, this study offers breakthroughs on the mechanism may contribute to the pathogenesis of IBD in humans.