Endocrinology, Vol 126, 2868-2875, Copyright © 1990 by Endocrine Society

ARTICLES

Expression of 25-hydroxyvitamin D3-24-hydroxylase activity in Caco-2 cells. An in vitro model of intestinal vitamin D catabolism

M Tomon, HS Tenenhouse and G Jones
Medical Research Council Genetics Group, McGill University-Montreal Children's Hospital, Quebec, Canada.

The C-24 oxidation pathway plays a major role in the degradation of vitamin D metabolites in kidney and other target tissues. The aim of the present study was to establish an intestinal cell culture system to study the mechanisms regulating the vitamin D catabolic pathway. 25- Hydroxyvitamin D3-24-hydroxylase (24-hydroxylase), the first enzyme in the catabolic sequence, was examined in Caco-2 cells, a human colon adenocarcinoma cell line which exhibits differentiated functions of absorbing intestinal epithelial cells. While untreated Caco-2 cells did not exhibit 24-hydroxylase activity, significant catabolic activity was induced by prior treatment of cell monolayers with 1,25- dihydroxyvitamin D3(1,25-(OH)2D3). Induced 24-hydroxylase D3 (25OHD3) and 1,25-(OH)2D3 was detected 6 h after treatment of cells with 10(-8)M 1,25-(OH)2D3, peaked at 16 h, and decreased thereafter. Treatment of cells with 10(-7) M 1,25-(OH)2D3 elicited a maximal 24-hydroxylase response. Comparable time courses of induction by 1,25-(OH)2D3 and 1,25- (OH)2D3-dose response curves were observed in cultured human skin fibroblasts and Caco-2 cells. 25OHD3 was not as good an inducer of the vitamin D catabolic pathway in Caco-2 cells as 1,25-(OH)2D3. Induction of 24-hydroxylase activity by 1,25-(OH)2D3 was inhibited by pretreatment of Caco-2 cells with either actinomycin D, alpha-amanitin, or cycloheximide suggesting that mRNA and protein synthesis are required for induction. The present study demonstrates that 1,25- (OH)2D3-treated Caco-2 cells express the vitamin D catabolic pathway and, therefore, constitute a useful in vitro model to study the mechanism of induction by 1,25-(OH)2D3.

This article has been cited by other articles:

				R. J. Wood, L. Tchack, G. Angelo, R. E. Pratt, and L. A. Sonna DNA microarray analysis of vitamin D-induced gene expression in a human colon carcinoma cell line Physiol Genomics, April 13, 2004; 17(2): 122 - 129. [Abstract] [Full Text] [PDF]

				R. Vieth Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety Am. J. Clinical Nutrition, May 1, 1999; 69(5): 842 - 856. [Abstract] [Full Text] [PDF]

				G. JONES, S. A. STRUGNELL, and H. F. DeLUCA Current Understanding of the Molecular Actions of Vitamin D Physiol Rev, October 1, 1998; 78(4): 1193 - 1231. [Abstract] [Full Text] [PDF]

				F. J. Dilworth, G. R. Williams, A.-M. Kissmeyer, J. L. Nielsen, E. Binderup, M. J. Calverley, H. L. J. Makin, and G. Jones The Vitamin D Analog, KH1060, Is Rapidly Degraded Both in Vivo and in Vitro via Several Pathways: Principal Metabolites Generated Retain Significant Biological Activity Endocrinology, December 1, 1997; 138(12): 5485 - 5496. [Abstract] [Full Text] [PDF]