Watabe Masahiko, Isogai Yumiko, Numazawa Satoshi, Yoshida Takemi
Department of Biochemical Toxicology, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
Life Sci. 2003 Nov 21;74(1):99-108. doi: 10.1016/j.lfs.2003.07.006.
Cytochrome P450 (CYP) 3A4, which is abundant in human liver and small intestine and participates in the metabolism of various drugs and xenochemicals, is known to be induced by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in the colon carcinoma cell line Caco-2 cells. Nitric oxide (NO) is able to inhibit CYP3A4 expression and catalytic activity. In this study, we investigated the mechanism of suppression by NO of 1,25(OH)2D3-induced CYP3A4 expression in Caco-2 cells. Caco-2 cells were exposed for 36 h to 400 nM 1,25(OH)2D3, and the induction of CYP3A4 mRNA expression was detected by real-time PCR. Because c-Myc regulates the expression of several genes, we examined its effect on the CYP3A4 expression induced by 1,25(OH)2D3. The expression of c-myc mRNA was increased in the early stage but decreased 36 h after the treatment of Caco-2 cells with 1,25(OH)2D3. The NO donor NOR-4 suppressed CYP3A4 expression induced by 1,25(OH)2D3 in Caco-2 cells in contrast, it significantly induced c-myc gene expression. Treatment of Caco-2 cells with the c-myc antisense oligonucleotide reversed the inhibitory effect of NOR-4 on CYP3A4 expression induced by 1,25(OH)2D3. These results suggest that the suppression of 1,25(OH)2D3-induced CYP3A4 expression by NO is due to c-myc expression.
细胞色素P450（CYP）3A4在人类肝脏和小肠中含量丰富，参与多种药物和外源性化学物质的代谢，已知在结肠癌细胞系Caco-2细胞中可被1,25-二羟基维生素D3（1,25(OH)2D3）诱导。一氧化氮（NO）能够抑制CYP3A4的表达和催化活性。在本研究中，我们探究了NO对Caco-2细胞中1,25(OH)2D3诱导的CYP3A4表达的抑制机制。将Caco-2细胞暴露于400 nM的1,25(OH)2D3中36小时，通过实时PCR检测CYP3A4 mRNA表达的诱导情况。由于c-Myc调节多个基因的表达，我们研究了其对1,25(OH)2D3诱导的CYP3A4表达的影响。在用1,25(OH)2D3处理Caco-2细胞后，c-myc mRNA的表达在早期增加，但在36小时后下降。相反，NO供体NOR-4抑制了Caco-2细胞中1,25(OH)2D3诱导的CYP3A4表达，它显著诱导了c-myc基因的表达。用c-myc反义寡核苷酸处理Caco-2细胞可逆转NOR-4对1,25(OH)2D3诱导的CYP3A4表达的抑制作用。这些结果表明，NO对1,25(OH)2D3诱导的CYP3A4表达的抑制是由于c-myc的表达。
