Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201, USA.
Pharm Res. 2011 Aug;28(8):2034-44. doi: 10.1007/s11095-011-0429-2. Epub 2011 Apr 13.
To investigate the roles of the constitutive androstane receptor (CAR) in cyclophosphamide (CPA)- and ifosfamide (IFO)-mediated induction of hepatic drug-metabolizing enzymes (DME).
Induction of DMEs was evaluated using real-time RT-PCR and Western blotting analysis in human primary hepatocyte (HPH) cultures. Activation of CAR, pregnane X receptor (PXR), and aryl hydrocarbon receptor by CPA and IFO was assessed in cell-based reporter assays in HepG2 cells and/or nuclear translocation assays in HPHs.
CYP2B6 reporter activity was significantly enhanced by CPA and IFO in HepG2 cells co-transfected with CYP2B6 reporter plasmid and a chemical-responsive human CAR variant (CAR1 + A) construct. Real-time RT-PCR and Western blotting analysis in HPHs showed that both CPA and IFO induced the expressions of CYP2B6 and CYP3A4. Notably, treatment of HPHs with CPA but not IFO resulted in significant nuclear accumulation of CAR, which represents the initial step of CAR activation. Further studies in HPHs demonstrated that selective inhibition of PXR by sulforaphane preferentially repressed IFO- over CPA-mediated induction of CYP2B6.
These results provide novel insights into the differential roles of CAR in the regulation of CPA- and IFO-induced DME expression and potential drug-drug interactions.
研究组成型雄烷受体（CAR）在环磷酰胺（CPA）和异环磷酰胺（IFO）介导的肝药物代谢酶（DME）诱导中的作用。
采用实时 RT-PCR 和 Western blot 分析检测人原代肝细胞（HPH）培养物中 DME 的诱导。在 HepG2 细胞中的基于细胞的报告基因测定和/或 HPH 中的核易位测定中评估 CPA 和 IFO 对 CAR、孕烷 X 受体（PXR）和芳烃受体的激活。
CPA 和 IFO 在共转染 CYP2B6 报告质粒和化学反应性人 CAR 变体（CAR1 + A）构建体的 HepG2 细胞中显著增强 CYP2B6 报告基因活性。在 HPH 中的实时 RT-PCR 和 Western blot 分析表明，CPA 和 IFO 均诱导 CYP2B6 和 CYP3A4 的表达。值得注意的是，CPA 而非 IFO 处理 HPH 导致 CAR 的显著核积累，这代表 CAR 激活的初始步骤。在 HPH 中的进一步研究表明，通过萝卜硫素选择性抑制 PXR 优先抑制 IFO 介导的 CYP2B6 诱导，而不是 CPA 介导的诱导。
这些结果为 CAR 在调节 CPA 和 IFO 诱导的 DME 表达和潜在药物相互作用中的差异作用提供了新的见解。
