Inhibitory effect of nitric oxide on the induction of cytochrome P450 3A4 mRNA by 1,25-dihydroxyvitamin D₃in 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.

Roles of nitric oxide in inflammatory downregulation of human cytochromes P450

“…CYP3A4 expression was suppressed at the RNA level in cells exposed to the NO donor, which is consistent with previous work in Caco-2 cells, a human colon carcinoma cell line, in which NO donors inhibited the induction of CYP3A4 mRNA by 1,25-dihydroxyvitamin D3 [25,26]. The mechanism of the effect in Caco-2 cells apparently involves the induction of c-myc, which represses CYP3A4 transcription [26].…”

“…NO donors can down-regulate CYP mRNAs and proteins in colon carcinoma [25,26] and hepatocarcinoma [27] cell lines, and it was reported that in HT-29 cells, NOS2 inhibitors or antisense oligonucleotides could block the down-regulation of CYP3A4 protein by ceramide [28], a putative mediator of the effects of pro-inflammatory cytokines on CYP expression [29]. We are aware of one published study on the regulation of CYP expression by physiological or pharmacological NO in primary human hepatocytes, which is the optimal system to study regulation of the human drug-metabolizing CYPs.…”

Contribution of Hepatocyte Nuclear Factor-4 to Down-Regulation of CYP2D6 Gene Expression by Nitric Oxide

“…Carlson and Billings (1996) also demonstrated that the suppression of CYP1A2 and CYP2B1/2 by cytokines is largely prevented by NOS inhibitors and that exogenous NO down-regulates these P450s. We reported that 1,25-dihydroxyvitamin D 3 -induced CYP3A4 gene expression in human colon carcinoma Caco-2 cells is inhibited by NO donors (Hara et al, 2000). These results suggested that NO plays an important role in the regulation of P450, but the mechanism of this effect is unknown.…”

C-JUN N-TERMINAL KINASE MODULATES 1,25-DIHYDROXYVITAMIN D3-INDUCED CYTOCHROME P450 3A4 GENE EXPRESSION

“…The nuclear receptor, pregnane X receptor, is known to contribute to the CYP3A4 gene induction by these drugs Lehmann et al, 1998;Goodwin et al, 1999). It has recently been demonstrated that 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) is a potent inducer of the CYP3A4 gene in the human colon carcinoma cell line Caco-2, which has been extensively used as an experimental model of small intestinal cells (Schmiedlin-Ren et al, 1997;Hara et al, 2000).…”

“…The nuclear receptor, pregnane X receptor, is known to contribute to the CYP3A4 gene induction by these drugs Lehmann et al, 1998;Goodwin et al, 1999). It has recently been demonstrated that 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) is a potent inducer of the CYP3A4 gene in the human colon carcinoma cell line Caco-2, which has been extensively used as an experimental model of small intestinal cells (Schmiedlin-Ren et al, 1997;Hara et al, 2000).1,25(OH) 2 D 3 , the most active metabolite of vitamin D, functions to regulate cellular proliferation and differentiation and calcium homeostasis in the intestine, bone, and kidney (Christakos et al, 1996). Most of these physiological activations are mediated by the vitamin D receptor (VDR), which belongs to the nuclear hormone receptor superfamily.…”