title: Inhibitory effect of nitric oxide on the induction of cytochrome P450 3A4 mRNA by 1,25-dihydroxyvitamin D3 in Caco-2 cells.
abstract: Cytochrome P450 (CYP)-dependent drug metabolism decreases in vivo and in cultured hepatocytes under various immunostimulatory conditions. Nitric oxide (NO) released during inflammation is presumed to be involved in this phenomenon. CYP3A4, which is abundant in the liver and small intestine and participates in the metabolism of various drugs, is known to be induced by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in the colon carcinoma cell line Caco-2. In this study we examined whether NO affected CYP3A4 gene expression induced by 1,25(OH)2D3 in Caco-2 cells. Induction of CYP3A4 mRNA by 1,25(OH)2D3 was suppressed in a dose-dependent manner by treatment with the NO donors NOR-4 (15-500 microM) or S-nitroso-N-acetylpenicillamine (30 microM-1 mM), which spontaneously release NO. These results indicated that NO has an inhibitory effect on the induction of CYP3A4 mRNA by 1,25(OH)2D3 in Caco-2 cells. Treatment with the guanylate cyclase inhibitor ODQ failed to prevent the inhibition of induction of CYP3A4 mRNA by 1,25(OH)2D3. 8-Bromo cGMP had no effect on 1,25(OH)2D3-induced CYP3A4 gene expression. Therefore, the suppression of CYP3A4 mRNA by NO might be mediated through a guanylate cyclase-independent pathway.
authors.affiliation: Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, Japan. harah@gifu-pu.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Hara
authors.forename: N
authors.initials: N
authors.lastname: Mitani
authors.forename: T
authors.initials: T
authors.lastname: Adachi
mesh_terms: D018938:Caco-2 Cells / Q000201:enzymology*; D002117:Calcitriol / Q000494:pharmacology*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004355:Drug Stability; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006801:Humans; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009569:Nitric Oxide / Q000494:pharmacology*; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis*
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D011810:Quinoxalines; D012333:RNA, Messenger; D009569:Nitric Oxide; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D006162:Guanylate Cyclase; D002117:Calcitriol