Novel role of the vitamin D receptor in maintaining the integrity of the intestinal mucosal barrier.
Emerging evidence supports a pathological link between vitamin D deficiency and the risk of inflammatory bowel disease (IBD). To explore the mechanism we used the dextran sulfate sodium (DSS)-induced colitis model to investigate the role of the vitamin D receptor (VDR) in mucosal barrier homeostasis. While VDR(+/+) mice were mostly resistant to 2.5% DSS, VDR(-/-) mice developed severe diarrhea, rectal bleeding, and marked body weight loss, leading to death in 2 wk. Histological examination revealed extensive ulceration and impaired wound healing in the colonic epithelium of DSS-treated VDR(-/-) mice. Severe ulceration in VDR(-/-) mice was preceded by a greater loss of intestinal transepithelial electric resistance (TER) compared with VDR(+/+) mice. Confocal and electron microscopy (EM) revealed severe disruption in epithelial junctions in VDR(-/-) mice after 3-day DSS treatment. Therefore, VDR(-/-) mice were much more susceptible to DSS-induced mucosal injury than VDR(+/+) mice. In cell cultures, 1,25-dihydroxy-vitamin D(3) [1,25(OH)(2)D(3)] markedly enhanced tight junctions formed by Caco-2 monolayers by increasing junction protein expression and TER and preserved the structural integrity of tight junctions in the presence of DSS. VDR knockdown with small interfering (si)RNA reduced the junction proteins and TER in Caco-2 monolayers. 1,25(OH)(2)D(3) can also stimulate epithelial cell migration in vitro. These observations suggest that VDR plays a critical role in mucosal barrier homeostasis by preserving the integrity of junction complexes and the healing capacity of the colonic epithelium. Therefore, vitamin D deficiency may compromise the mucosal barrier, leading to increased susceptibility to mucosal damage and increased risk of IBD.
Kong
Juan
J
Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
Zhang
Zhongyi
Z
Musch
Mark W
MW
Ning
Gang
G
Sun
Jun
J
Hart
John
J
Bissonnette
Marc
M
Li
Yan Chun
YC
D000818:Animals; D018938:Caco-2 Cells; D002117:Calcitriol / Q000494:pharmacology; D002465:Cell Movement; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology / Q000648:ultrastructure; D016264:Dextran Sulfate; D004195:Disease Models, Animal; D017097:Electric Impedance; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010539:Permeability; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012720:Severity of Illness Index; D019108:Tight Junctions / Q000378:metabolism; D013997:Time Factors; D014456:Ulcer / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism*; D014945:Wound Healing
D008565:Membrane Proteins; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol; D014807:Vitamin D; D016264:Dextran Sulfate; D002117:Calcitriol