A Novel Role of Spred2 in the Colonic Epithelial Cell Homeostasis and Inflammation

Rapid and adequate mucosal healing is important for a remission of ulcerative colitis (UC) patients. Here, we examined whether Spred2, a member of the Sprouty-related EVH1-domain-containing proteins that inhibit the Ras/Raf/ERK pathway, plays a role in colonic mucosal homeostasis and inflammation by using Spred2 knockout (KO) mice. We first detected increased epithelial cell proliferation and cadherin 1 expression in the colon of naïve Spred2 KO mice compared to wild-type mice. Interestingly, Spred2 KO mice were resistant to dextran sulfate sodium (DSS)-induced acute colitis as indicated by lower levels of body weight loss and disease activity index. Histologically, epithelial cell injury and inflammation were milder in the colonic mucosa of Spred2 KO mice on day 3 and almost undetectable by day 8. Experiments with bone chimeric mice indicated that Spred2-deficiency in non-hematopoietic cells was responsible for the reduced sensitivity to DSS. Finally, Spred2 KO mice developed significantly fewer tumors in response to azoxymethane plus DSS. Taken together, our results demonstrate, for the first time, that Spred2 plays an important role in the regulation of colonic epithelial cell proliferation and inflammation by potentially down-regulating the activation of ERK. Thus, Spred2 may be a new therapeutic target for the treatment of UC.