Increased Vitamin D Receptor Level Enhances 1,25‐Dihydroxyvitamin D3‐Mediated Gene Expression and Calcium Transport in Caco‐2 Cells

• Published in: Journal of bone and mineral research 2001-04, Vol.16 (4), p.615-624
• Main Authors: Shao, A., Wood, R. J., Fleet, J. C.
• Format: Article
• Language: English
• Subjects: 1,25‐dihydroxyvitamin D3; 24‐hydroxylase; Biological and medical sciences; Caco-2 Cells; Cadmium - pharmacology; calbindin D9k; Calbindins; Calcitriol - pharmacology; Calcium - metabolism; calcium transport; DNA, Complementary - genetics; enterocyte; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Genes, Synthetic; Humans; Intestine. Mesentery; Ion Transport - drug effects; Metallothionein - genetics; Promoter Regions, Genetic - drug effects; Receptors, Calcitriol - genetics; Receptors, Calcitriol - physiology; Recombinant Fusion Proteins - physiology; RNA, Messenger - biosynthesis; S100 Calcium Binding Protein G - biosynthesis; S100 Calcium Binding Protein G - genetics; Stimulation, Chemical; Transfection; Transgenes; Vertebrates: digestive system; vitamin D receptor; Zinc - pharmacology
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.2001.16.4.615

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 μM, 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.