title: Vitamin D regulates the tight-junction protein expression in active ulcerative colitis.
abstract: 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.
  
  
  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.
authors.affiliation: a Department of Biomedical, Experimental and Clinical Sciences , "Mario Serio" University of Florence , Florence , Italy ;
authors.forename: Maria
authors.initials: M
authors.lastname: Stio
authors.affiliation: b Gastroenterology Unit , Azienda Ospedaliero-Universitaria Careggi , Florence , Italy.
authors.forename: Luigina
authors.initials: L
authors.lastname: Retico
authors.affiliation: b Gastroenterology Unit , Azienda Ospedaliero-Universitaria Careggi , Florence , Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Annese
authors.affiliation: b Gastroenterology Unit , Azienda Ospedaliero-Universitaria Careggi , Florence , Italy.
authors.forename: Andrea Giovanni
authors.initials: AG
authors.lastname: Bonanomi
mesh_terms: D000328:Adult; D001706:Biopsy; D002478:Cells, Cultured; D062446:Claudin-2 / Q000378:metabolism*; D062506:Claudin-4 / Q000378:metabolism*; D057167:Claudins / Q000378:metabolism*; D003093:Colitis, Ulcerative / Q000473:pathology*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D018793:Interleukin-13 / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D007413:Intestinal Mucosa / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015854:Up-Regulation; D014807:Vitamin D / Q000097:blood*
chemical_list: C473255:CLDN7 protein, human; D062446:Claudin-2; D062506:Claudin-4; D057167:Claudins; C508600:IL6 protein, human; D018793:Interleukin-13; D015850:Interleukin-6; D014807:Vitamin D
keywords: Tight-junctions proteins; ulcerative colitis; vitamin D