Loss of Dok-1 and Dok-2 in mice causes severe experimental colitis accompanied by reduced expression of IL-17A and IL-22.

Appropriate immune responses and mucosal barrier functions are required for the maintenance of intestinal homeostasis. Defects in this defense system may lead to inflammatory disorders such as inflammatory bowel disease. Downstream of tyrosine kinases 1 (Dok-1) and its closest homolog, Dok-2, are preferentially expressed in immune cells, and play essential roles in the negative regulation of multiple signaling pathways in both innate and adaptive immunity. However, the function of these proteins in intestinal homeostasis remained unclear. Here we show that Dok-1/-2 double knockout (DKO) mice were highly susceptible to dextran sodium sulfate (DSS)-induced colitis compared with Dok-1 or Dok-2 single KO and wild type (WT) mice. Furthermore, DSS-treated Dok-1/-2 DKO mice exhibited increased colonic tissue damage accompanied by reduced proliferation of the epithelial cells relative to WT controls, suggesting that Dok-1/-2 DKO mice have defects in the repair of intestinal epithelial lesions. In addition, the levels of the Th17 cytokines IL-17A and IL-22, which have protective roles in DSS-induced colitis, were reduced in DSS-treated Dok-1/-2 DKO mice compared with WT mice. Taken together, our results demonstrate that Dok-1 and Dok-2 negatively regulate intestinal inflammation, apparently through the induction of IL-17A and IL-22 expression.