Role of c-Myc in nitric oxide-mediated suppression of cytochrome P450 3A4.
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.
Watabe
Masahiko
M
Department of Biochemical Toxicology, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
Isogai
Yumiko
Y
Numazawa
Satoshi
S
Yoshida
Takemi
T
D000818:Animals; D001483:Base Sequence; D018938:Caco-2 Cells; D002117:Calcitriol / Q000494:pharmacology; D002417:Cattle; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D009569:Nitric Oxide / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D065607:Cytochrome P-450 Enzyme Inhibitors; D017931:DNA Primers; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D009569:Nitric Oxide; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D002117:Calcitriol