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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. Vitamin D deficiency is in fact common in patients with IBD. The aim of the study was to determine whether vitamin D could affect IL-13 and IL-6 levels, and regulate the activity of tight-junction proteins. Claudin-1, -2, -4, and -7 in the inflamed and non-inflamed colonic mucosa of UC patients., Material and Methods: Biopsies from inflamed and non-inflamed tract of colon and rectum from the same active UC patients were cultured with1,25(OH)2D3. IL-13, IL-6 and the tight-junction proteins level were determined., Results: Claudin-1 and claudin-2 proteins were up-regulated in active UC. The treatment with 1,25(OH)2D3 decreases the claudin-1 and claudin-2 protein levels in both inflamed and non-inflamed tract. Claudin-4 and claudin-7 proteins were down-regulated and their levels increase after incubation with the 1,25(OH)2D3. When the biopsies were incubated with 1,25(OH)2D3, a decrease in IL-13 and IL-6 levels was registered., Conclusions: Our results, indicating the inhibition of cytokine levels and the regulation of claudin-2, claudin-4, and claudin-7 by 1,25(OH)2D3, suggest that vitamin D may represent a potential therapeutic agent for the treatment of active UC.

Background: In the group of inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn's disease (CD) are considered to be more frequent in Western countries and in areas with a high socioeconomic development but relatively infrequent in southern Europe. Sporadic reports have indicated a lower incidence and a milder course of the disease in Mediterranean countries. Although conclusive data on this point are still lacking, recent reports suggest an increase in both incidence and prevalence rates., Methods: The incidence of UC and CD during the period January 1978 to December 1992 and their prevalence on 31 December 1992 were estimated in the 15-year-old population of the metropolitan area of Florence. Clinical, demographic, and follow-up information was collected for all identified IBD patients., Results: A total of 796 residents (345 females and 454 males) were newly diagnosed as having IBD during the study period. Of these 593 had UC and 203 CD. The age-standardized incidence rates, calculated for each of five 3-year consecutive periods, rose from 3.8 (in 1978-80) to 9.6 per 100,000 person-years (in 1990-92) for UC and from 1.9 (in 1978-80) to 3.4 (in 1990-92) for CD. Both trends were statistically significant. The prevalence estimated on 31 December 1992 was 121.0 and 40.0 per 100,000 inhabitants for UC and CD, respectively., Conclusions: Our results confirm that IBD incidence rates and prevalence in this area of central Italy are currently comparable with those reported in northern Europe. These data are necessary for planning adequate health care services for IBD patients.