The effect of cyclophosphamide with and without dexamethasone on cytochrome P450 3A4 and 2B6 in human hepatocytes
The effect of cyclophosphamide with and without dexamethasone on cytochrome P450 3A4 and 2B6 in human hepatocytes
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DOI：
10.1124/dmd.30.7.814
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发表时间：
2002-07-01
影响因子：
3.9
通讯作者：
LeCluyse, EL
中科院分区：
文献类型：
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作者：
Lindley, C;Hamilton, G;LeCluyse, EL
本研究的目的是研究环磷酰胺(CPA)加和不加地塞米松(DEX；10um)在代表标准剂量和大剂量CPA治疗(25~750um)的浓度下对培养的人肝细胞中细胞色素P3A4和细胞色素P42B6表达的量效关系。CPA诱导的细胞色素P3A4和细胞色素P42B6活性和免疫活性蛋白的浓度依赖性增加，分别在250和125微米时达到峰值，之后下降。CPA单独及与地塞米松合用对CYP2B6的诱导作用强于对CYP3A4的诱导作用。为进一步研究CPA对细胞色素P3A4的诱导作用，我们在10份肝细胞标本中检测了CPA(250微米)和地塞米松(10微米)的单独和联合作用。CPA和地塞米松联合使用比单独使用产生更高的6β-羟睾酮生成率。然而，在基线活性相对较高的人肝细胞培养中，这种影响小于相加作用，而在基线活性相对较低的人肝细胞培养中，这种作用是相加或协同的。CPA和CPA加地塞米松的诱导指数与CYP3A4基础活性高度相关(r(2)=0.75和r(2)=0.85)。为探讨CPA诱导细胞色素P450 3A4活性升高的可能机制，采用瞬时转染法研究了CPA单独及与地塞米松合用对孕烷X受体(PXR)的激活作用。CPA对PXR的激活呈剂量依赖性增加，在所研究的最高CPA浓度(500um)时达到最大。与单独使用CPA相比，在CPA中加入地塞米松后，PXR的激活略有增加。这些结果表明，CPA单独或联合地塞米松以浓度依赖的方式诱导细胞色素P3A4和细胞色素B的表达，这可能部分是通过激活PXR来实现的。这些效应对CPA治疗的疗效和毒性的影响值得进一步研究。
The purpose of this study was to characterize the concentration-response effects of cyclophosphamide (CPA) with and without dexamethasone (DEX; 10 muM) on the expression of CYP3A4 and CYP2B6 in cultured human hepatocytes at concentrations representative of standard- and high-dose CPA therapy (25 to 750 muM). CPA produced concentration-dependent increases in CYP3A4 and CYP2B6 activity and immunoreactive protein that peaked at 250 and 125 muM, respectively, and declined thereafter. The inductive effect of CPA alone and in combination with DEX was greater in magnitude for CYP2B6 compared with CYP3A4. To further examine the inductive effect of CPA on CYP3A4, CPA (250 muM) and DEX (10 muM) alone and in combination were examined in 10 hepatocyte preparations. The combination of CPA and DEX yielded higher rates of 6beta-hydroxytestosterone formation than either agent alone. However, the effect was less than additive in human hepatocyte cultures with relatively high baseline CYP3A4 activity and additive or synergistic in human hepatocyte cultures with relatively low baseline CYP3A4 activity. Induction index was highly correlated with CYP3A4 baseline activity for both CPA (r(2) = 0.75) and CPA plus DEX (r(2) = 0.85). To investigate the potential mechanism for CPA-induced increases in CYP3A4 activity, the ability of CPA alone and in combination with DEX to activate pregnane X receptor (PXR) was explored using transient transfection assays. CPA produced a dose-dependent increase in PXR activation that was maximal at the highest CPA concentration studied (500 muM). The addition of DEX to CPA resulted in a minor increase in PXR activation compared with CPA alone. These results indicate that CPA alone and in combination with DEX differentially induces the expression of CYP3A4 and 2B in a concentration-dependent manner, which may be mediated partially through activation of PXR. The impact of these effects on the efficacy and toxicity of CPA therapy warrants further investigation.