: The overall hypothesis of the proposed studies is that the gastrointestinal tract contributes to host defense through stereotypic functional responses that are orchestrated by the profile of cytokines present. Crohn's disease and most murine models of colitis are linked to exaggerated production of Th1 cytokines. In contrast, the host defense to enteric nematode infection is dependent primarily on the type 2 cytokines, IL-4 and IL- 13. Of the type 2 cytokines, IL-4 is most important for the establishment of the Th2 profile and for the down regulation of Th1 pathway, yet there are few studies of IL-4, or other type 2 cytokines, in vivo. In addition, IL-13 shares many biological activities with IL-4 by acting at a common receptor chain. The central premise of this proposal is that colitis-induced changes in the smooth muscle and epithelial cell function will be improved by administration of exogenous IL-4 or IL-l3, or by up-regulation of their endogenous production via nematode infection. We propose that the mechanism by which cytokines alter gut function involves receptor-mediated activation of Stat6 signaling pathways, mast cells and mast cell mediators, and enteric nerves. There are 3 specific aims. 1.) Determine that the profile of cytokines present in the gut controls epithelial cell and smooth muscle function in colitis and nematode infection; 2.) Determine the role of altered Th2 cytokines in colitis-induced alterations in epithelial cell and smooth muscle function; 3.) Determine the mechanisms of altered epithelial cell and smooth muscle function in mice with and without colitis and treated with IL-4, IL-13, or nematode infection. Based on our preliminary data, we expect that type 2 cytokines have significant region-specific actions on the small and large bowel, and that restoration of the balance of type 1/type 2 profiles will be of therapeutic benefit to the impaired secretomotor function in IBD.
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