Sahi Jasminder, Shord Stacy S, Lindley Celeste, Ferguson Stephen, LeCluyse Edward L
Department of Pharmacokinetics Pharmacodynamics and Metabolism, Pfizer Global Research and Development, Ann Arbor, MI 48105, USA.
J Biochem Mol Toxicol. 2009 Jan-Feb;23(1):43-58. doi: 10.1002/jbt.20264.
Cytochrome P450 2C9 (CYP2C9) expression is regulated by multiple nuclear receptors including the constitutive androstane receptor (CAR) and pregnane X receptor (PXR). We compared coregulation of CYP2C9 with CYP2B6 and CYP3A4, prototypical target genes for human CAR and PXR using human hepatocyte cultures treated for three days with the PXR activators clotrimazole, rifampin, and ritonavir; the CAR/PXR activator phenobarbital (PB); and the CAR-selective agonists CITCO, (6-(4-chlorophenyl)imidazo[2,1-beta][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime) and phenytoin. Clotrimazole, rifampin, ritonavir, phenytoin, and phenobarbital induced CYP2C9 consistent with previous findings for CYP3A4. We observed EC(50) values of 519 microM (phenobarbital), 11 microM (phenytoin), and 0.75 microM (rifampin), similar to those for CYP3A4 induction. Avasimibe, a potent PXR activator, produced nearly identical concentration-dependent CYP2C9 and CYP3A4 activity profiles and EC(50) values. In 17 donors, rifampin increased mean basal CYP2C9 activity from 59 +/- 43 to 143 +/- 68 pmol/mg protein/min; fold induction ranged from 1.4- to 6.4-fold. Enzyme activity and mRNA measurements after rifampin, CITCO and PB treatment demonstrated potency and efficacy consistent with CYP2C9 regulation being analogous to CYP3A4 rather than CYP2B6. We demonstrate that hepatic CYP2C9 is differentially regulated by agonists of CAR and PXR, and despite sharing common regulatory mechanisms with CYP3A4 and CYP2B6; this enzyme exhibits an induction profile more closely aligned with that of CYP3A4.
细胞色素P450 2C9（CYP2C9）的表达受多种核受体调控，包括组成型雄烷受体（CAR）和孕烷X受体（PXR）。我们比较了CYP2C9与CYP2B6和CYP3A4（人CAR和PXR的典型靶基因）的共调节情况，使用人肝细胞培养物，用PXR激活剂克霉唑、利福平、利托那韦处理三天；CAR/PXR激活剂苯巴比妥（PB）；以及CAR选择性激动剂CITCO（6-(4-氯苯基)咪唑[2,1-β][1,3]噻唑-5-甲醛-O-(3,4-二氯苄基)肟）和苯妥英。克霉唑、利福平、利托那韦、苯妥英和苯巴比妥诱导CYP2C9，与先前关于CYP3A4的研究结果一致。我们观察到EC(50)值分别为519 microM（苯巴比妥）、11 microM（苯妥英）和0.75 microM（利福平），与CYP3A4诱导的EC(50)值相似。强效PXR激活剂阿伐司他产生几乎相同的浓度依赖性CYP2C9和CYP3A4活性谱及EC(50)值。在17名供体中，利福平使平均基础CYP2C9活性从59±43增加到143±68 pmol/mg蛋白/分钟；诱导倍数范围为1.4至6.4倍。利福平、CITCO和PB处理后的酶活性和mRNA测量结果表明，其效力和效果与CYP2C9的调节类似于CYP3A4而非CYP2B6一致。我们证明肝脏CYP2C9受CAR和PXR激动剂的差异调节，尽管与CYP3A4和CYP2B6共享共同的调节机制；但该酶的诱导谱与CYP3A4更为接近。
