Effects of CCL20/CCR6 Modulators in a T Cell Adoptive Transfer Model of Colitis

Background/Objectives: IBDs are chronic relapsing inflammatory intestinal disorders whose precise etiology is still only poorly defined: critical for their pathogenesis is the CCL20/CCR6 axis, whose modulation by small molecules may represent an innovative therapeutic approach. The aim of the present work is to test the potential efficacy of two molecules, MR120, a small selective CCR6 antagonist, active in TNBS- and chronic DSS-induced murine models of intestinal inflammation, and its derivative MR452, a well-tolerated agent endowed with improved anti-chemotactic in vitro properties, in the adoptive transfer colitis model. To the best of our knowledge, this is the first attempt of using adoptive transfer colitis to test modulators of the CCL20/CCR6 axis. Methods and Results: The induction of colitis in immunocompromised mice receiving CD4⁺CD25⁻ T cells i.p. resulted in a moderate inflammation and was met with limited protective responses following daily subcutaneous administration of MR120 or MR452 for 8 weeks. Both compounds significantly reduced colonic myeloperoxidase activity, MR452 also lowered CCL20 levels in the gut, but they failed to prevent the increase in disease activity index, colon wall thickening, and macroscopic inflammation score. Conclusions: Our findings suggest that the pharmacological targeting of the CCL20/CCR6 axis in the adoptive transfer model has only a modest effect in ameliorating the IBD-like phenotype driven by the altered balance between Treg and Th17. The CCL20/CCR6 inhibitors MR120 and MR452 appear more clearly involved in the control of Th1 and Th2 adaptive immune responses, as it results from the beneficial effects displayed by MR120 against subacute TNBS- and chronic DSS-induced colitis.