Vitamin D regulates the tight-junction protein expression in active ulcerative colitis.

Objective: Epithelial barrier function is primarily regulated by the tight-junction proteins. Ulcerative colitis (UC) is characterized by Th2 immune response with inflammation and epithelial barrier dysfunction, including an elevation of claudin-2 protein function. Recent studies support an important role of vitamin D in the pathogenesis as well as potential therapy of IBD.