RT Journal Article
SR Electronic
T1 Transcriptional Control of Intestinal Cytochrome P-4503A by 1α,25-Dihydroxy Vitamin D<sub>3</sub>
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1399
OP 1406
DO 10.1124/mol.60.6.1399
VO 60
IS 6
A1 Kenneth E. Thummel
A1 Cynthia Brimer
A1 Kazuto Yasuda
A1 Jaideep Thottassery
A1 Tauri Senn
A1 Yvonne Lin
A1 Hitoshi Ishizuka
A1 Evan Kharasch
A1 John Schuetz
A1 Erin Schuetz
YR 2001
UL http://molpharm.aspetjournals.org/content/60/6/1399.abstract
AB It was previously shown that CYP3A4 is induced in the human intestinal Caco-2 cell model by treatment with 1α,25-dihydroxy vitamin D3 (1,25-D3). We demonstrate the vitamin D analog, 19-nor-1α,25-dihydroxy vitamin D2, is also an effective inducer of CYP3A4 in Caco-2 cells, but with half the potency of 1,25-D3. We report that treatment of LS180 cells, a human intestinal cell line, with 1 to 10 nM 1,25-D3 dose dependently increased CYP3A4 protein and CYP3A4 mRNA expression.CYP3A4- and CYP3A23-promoter-Luciferase reporter constructs transiently transfected into LS180 cells were transcriptionally activated in a dose-dependent manner by 1,25-D3, whereas mutation of the nuclear hormone receptor binding motif (ER6) in the CYP3A4 promoter abrogated 1,25-D3 activation of CYP3A4. Although theCYP3A4 ER6 promoter element has been shown to bind the pregnane X receptor (PXR), this receptor does not mediate 1,25-D3 induction of CYP3A4 because a) PXR is not expressed in Caco-2 cells; b) PXR mRNA expression is not induced by 1,25-D3 treatment of LS180 cells; and c) the ligand binding domain of human PXR was not activated by 1,25-D3. 1,25-D3 uses the vitamin D receptor to induce CYP3A4 because a) the vitamin D receptor (VDR)-retinoid X receptor (RXR) heterodimer binds specifically to the CYP3A4 ER6; b) selective mutation of the CYP3A4 ER6 disrupted the binding of VDR-RXR; and c) reporter constructs containing only three copies of the CYP3A4 ER6 linked to a TK-CAT reporter were activated by 1,25-D3 only in cells cotransfected with a human VDR expression plasmid. These data support the hypothesis that 1,25-D3 and VDR induce expression of intestinal CYP3A by binding of the activated VDR-RXR heterodimer to theCYP3A PXR response element and promoting gene transcription.