Suppressor of cytokine signaling-1 ameliorates dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD) is a chronic disorder of the gastrointestinal tract. Although the etiology and pathogenesis of IBD remain unknown, pro-inflammatory cytokines including IFN-γ play an important role in the development of IBD. Suppressor of cytokine signaling-1 (SOCS-1) is a crucial inhibitor of cytokine signaling, particularly of IFN-γ. In this study, we investigated the role of SOCS-1 in the development of murine dextran sulfate sodium (DSS)-induced colitis, a model of colitis resembling human IBD. SOCS-1 heterozygous (SOCS-1^+/-) and wild-type (WT) mice were given 3% DSS dissolved in drinking water for 5 days. Activation and expression of signal transducers and activators of transcription (STAT) in colonic tissues were assessed by western blot analysis. The expression of CD4, IFN-γ, IL-4, IL-17 and Forkhead box P3 (Foxp3) in colonic lamina propria lymphocytes was analyzed by flow cytometry and cytokine concentrations in serum were measured. DSS-treated SOCS^-1+/- mice developed more severe colitis than DSS-treated WT mice. Enhanced activation of STAT1, a higher ratio of CD4⁺ IFN-γ⁺T cells and a lower frequency of Foxp3⁺ regulatory T (Treg) cells, were observed in the colon of DSS-treated SOCS-1^+/- mice compared with DSS-treated WT mice. DSS-treated SOCS-1^+/- mice showed higher levels of IFN-γ in sera than did DSS-treated WT mice. Furthermore, T cell-specific SOCS-1-conditional knockout mice developed more severe colitis than control mice after DSS administration. Our findings suggest that SOCS-1, particularly in T cells, prevents the development of DSS-induced colitis in mice by inhibiting IFN-γ/STAT1 signaling and by subsequently regulating Treg cell development.