Hara H, Mitani N, Adachi T
Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, Japan.
Free Radic Res. 2000 Sep;33(3):279-85. doi: 10.1080/10715760000301441.
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.
在多种免疫刺激条件下，细胞色素P450（CYP）依赖的药物代谢在体内和培养的肝细胞中均会降低。炎症期间释放的一氧化氮（NO）被认为与这一现象有关。CYP3A4在肝脏和小肠中含量丰富，参与多种药物的代谢，已知在结肠癌细胞系Caco-2中可被1,25-二羟基维生素D3（1,25(OH)2D3）诱导。在本研究中，我们检测了NO是否影响Caco-2细胞中1,25(OH)2D3诱导的CYP3A4基因表达。用可自发释放NO的NO供体NOR-4（15 - 500 microM）或S-亚硝基-N-乙酰青霉胺（30 microM - 1 mM）处理，以剂量依赖方式抑制了1,25(OH)2D3对CYP3A4 mRNA的诱导。这些结果表明，NO对Caco-2细胞中1,25(OH)2D3诱导的CYP3A4 mRNA具有抑制作用。用鸟苷酸环化酶抑制剂ODQ处理未能阻止1,25(OH)2D3对CYP3A4 mRNA诱导的抑制。8-溴环鸟苷酸对1,25(OH)2D3诱导的CYP3A4基因表达无影响。因此，NO对CYP3A4 mRNA的抑制可能是通过不依赖鸟苷酸环化酶的途径介导的。
