Human PXR-mediated induction of intestinal CYP3A4 attenuates 1α,25-dihydroxyvitamin D3 function in human colon adenocarcinoma LS180 cells

Abstract

Oxidative catabolism of 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] is mediated by either CYP24A1 or CYP3A4. In this paper, we tested whether induction of CYP3A4 in the LS180 intestinal cell model enhances clearance of 1α,25(OH)2D3 and blunts its hormonal effect on expression of the apical membrane calcium transport protein, TRPV6. Treatment with the hPXR agonist rifampin significantly increased CYP3A4 mRNA content and catalytic activity, but had no effect on CYP24A1 or TRPV6 mRNA content. Pre-treating cells with rifampin for 48 hrs, prior to a 24 hr 1α,25(OH)2D3 treatment phase, was associated with a subsequent 48% increase in the elimination of 1α,25(OH)2D3 and a 35% reduction of peak TRPV6 mRNA. Introduction of the CYP3A4 inhibitor, 6′,7′-dihydroxybergamottin, an active inhibitor in grapefruit juice, reversed the effects of rifampin on 1α,25(OH)2D3 clearance and TRPV6 expression. Over-expression of hPXR in LS180 cells greatly enhanced the CYP3A4 responsiveness to rifampin pretreatment, and elicited a greater relative suppression of TRPV6 expression and an increase in 1α,25(OH)2D3 disappearance rate, compared to vector expressed cells, following hormone administration. Together, these results suggest that induction of CYP3A4 in the intestinal epithelium by hPXR agonists can result in a greater metabolic clearance of 1α,25(OH)2D3 and reduced effects of the hormone on the intestinal calcium absorption, which may contribute to an increased risk of drug-induced osteomalacia/osteoporosis in patients receiving chronic therapy with potent hPXR agonists. Moreover, ingestion of grapefruit juice in the at-risk patients could potentially prevent this adverse drug effect.

Pregnane xenobiotic receptor in cancer pathogenesis and therapeutic response

“…Although this report supports anti-proliferative role for PXR, the overall trend supports proliferative, metastatic and antiapoptotic role for PXR in sporadic colon cancer. More recent literature is supportive of these findings as human PXR agonists increase metabolic clearance of 1a, 25-OH Vitamin D3 thereby attenuating any protective effects of this hormone in LS180 cells [46]. Similarly, the PXR promoter is significantly silenced by methylation in normal colon cells as opposed to tumor cells [47].…”

Interplay between vitamin D and the drug metabolizing enzyme CYP3A4

“…However, it has been demonstrated that 1α,25(OH) 2 D 3 can also enhance the transcription of CYP3A4 by a VDR-mediated pathway. Treatment of Caco-2 cells [7–9], LS180 cells [10, 11], HepG2 cells [12], and human hepatocytes [13] with 1α,25(OH) 2 D 3 results in increased CYP3A4 mRNA levels and accumulation of the encoded, functional enzyme. In addition, treatment of rats with 1α,25(OH) 2 D 3 increases intestinal CYP3A23 (a homolog of CYP3A4 ) expression and CYP3A metabolic activity [14, 15].…”

Functional Comparison of Human Colonic Carcinoma Cell Lines and Primary Small Intestinal Epithelial Cells for Investigations of Intestinal Drug Permeability and First-Pass Metabolism

“…Although LS180 cells exhibit basal and inducible CYP3A4 activity (Zheng et al, 2012), they are thought not to form tight junctions in culture. In contrast, T84 cells are known to form tight junctions (Dharmsathaphorn et al, 1984); however, expression of CYP3A4 by T84 cells is controversial (Juuti-Uusitalo et al, 2006;Bourgine et al, 2012), and its inducibility has not been reported.…”