title: Increased vitamin D receptor level enhances 1,25-dihydroxyvitamin D3-mediated gene expression and calcium transport in Caco-2 cells.
abstract: Altered vitamin D receptor (VDR) level has been proposed to explain differences in intestinal responsiveness to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We tested whether the enterocyte VDR level influences 1,25(OH)2D3-mediated gene expression and transepithelial calcium (Ca) transport in the human intestinal cell line Caco-2. Cells were stably transfected with a human metallothionein (hMT) IIA promoter-human VDR (hVDR) complementary DNA (cDNA) transgene that overexpressed hVDR in response to heavy metals. In MTVDR clones, induction of 25-hyroxyvitamin D3-24-hydroxylase (24-OHase) messenger RNA (mRNA) expression by 1,25(OH)2D3 (10(-9) M, 4 h) was correlated to metal-induced changes in nuclear VDR level (r2 = 0.99). In MTVDR clones, basal VDR level was 2-fold greater and 1,25(OH)2D3-mediated Ca transport (10(-7) M, 24 h) was 43% higher than in parental Caco-2 cells. Treatment of MTVDR clones with Cd (1 microM, 28 h) increased VDR level by 68%, significantly enhanced 1,25(OH)2D3-mediated Ca transport by 24%, and increased accumulation of calbindin D9K mRNA by 76% relative to 1,25(OH)2D3 alone. These observations support the hypothesis that the enterocyte VDR level is an important modulator of intestinal responsiveness to 1,25(OH)2D3.
authors.affiliation: United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, USA.
authors.forename: A
authors.initials: A
authors.lastname: Shao
authors.forename: R J
authors.initials: RJ
authors.lastname: Wood
authors.forename: J C
authors.initials: JC
authors.lastname: Fleet
mesh_terms: D018938:Caco-2 Cells; D002104:Cadmium / Q000494:pharmacology; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D005813:Genes, Synthetic; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D008668:Metallothionein / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D018167:Receptors, Calcitriol / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis / Q000235:genetics; D013268:Stimulation, Chemical; D014162:Transfection; D019076:Transgenes; D015032:Zinc / Q000494:pharmacology
chemical_list: D064026:Calbindins; D018076:DNA, Complementary; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D011993:Recombinant Fusion Proteins; D064030:S100 Calcium Binding Protein G; C576506:S100G protein, human; D002104:Cadmium; D008668:Metallothionein; D002117:Calcitriol; D015032:Zinc; D002118:Calcium