Drocourt L, Pascussi J M, Assenat E, Fabre J M, Maurel P, Vilarem M J
Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Montpellier, France.
Drug Metab Dispos. 2001 Oct;29(10):1325-31.
The expression of three cytochromes P450 (CYP3A4, CYP2C9, and CYP2B6) was investigated in primary human hepatocyte cultures following treatment with four calcium channel modulators (CCM) of the dihydropyridine family, three antagonists (nifedipine, nicardipine, and isradipine), and one agonist (BK8644). Induction of CYP3A4 was studied by Northern blot, Western blot, and enzymatic activity. Induction began between 1 and 10 microM CCM and was dependent on the presence of dexamethasone (100 nM) in the medium. CYP3A4 mRNA accumulation started only after 16 h of treatment because pregnane X receptor (hPXR) synthesis was needed. Cotransfection experiments showed that the proximal and the distal PXR response elements of the CYP3A4 promoter and hPXR (HepG2 cells) or dexamethasone-induced hPXR (primary hepatocytes) were necessary to obtain full induction. Furthermore, glutathione S-transferase pull-down assays demonstrated that the CCM tested can act as hPXR ligands. In addition, cotransfection experiments in CV1 cells showed that these compounds failed to reverse CAR (constitutively activated receptor) inactivation by androstenol. Finally, 10 microM CCM induced both CYP2C9 and CYP2B6, strengthening the evidence that hPXR is involved in the regulation of these genes. All together, these results widen the field of hPXR activators to a new class of ligand, namely the CCM of the dihydropyridine family.
在用二氢吡啶类的四种钙通道调节剂（CCM）、三种拮抗剂（硝苯地平、尼卡地平和平尼地平）以及一种激动剂（BK8644）处理原代人肝细胞培养物后，研究了三种细胞色素P450（CYP3A4、CYP2C9和CYP2B6）的表达。通过Northern印迹、Western印迹和酶活性研究了CYP3A4的诱导情况。诱导在1至10微摩尔CCM之间开始，并且依赖于培养基中地塞米松（100纳摩尔）的存在。CYP3A4 mRNA积累仅在处理16小时后开始，因为需要孕烷X受体（hPXR）的合成。共转染实验表明，CYP3A4启动子的近端和远端PXR反应元件以及hPXR（HepG2细胞）或地塞米松诱导的hPXR（原代肝细胞）对于获得完全诱导是必要的。此外，谷胱甘肽S -转移酶下拉实验证明所测试的CCM可以作为hPXR配体。另外，CV1细胞中的共转染实验表明这些化合物不能逆转雄烯醇对组成型激活受体（CAR）的失活。最后，10微摩尔CCM诱导了CYP2C9和CYP2B6两者，强化了hPXR参与这些基因调控的证据。总之，这些结果将hPXR激活剂的领域扩展到一类新的配体，即二氢吡啶类的CCM。
