CYP3A induction by liver X receptor ligands in primary cultured rat and mouse hepatocytes is mediated by the pregnane X receptor
CYP3A induction by liver X receptor ligands in primary cultured rat and mouse hepatocytes is mediated by the pregnane X receptor
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DOI：
10.1124/dmd.32.1.66
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发表时间：
2004-01-01
影响因子：
3.9
通讯作者：
Kocarek, TA
中科院分区：
文献类型：
--
作者：
Shenoy, SD;Spencer, TA;Kocarek, TA
在原代培养的啮齿类动物肝细胞中评价了氧固醇和肝X受体（LXR）的药物配体对细胞色素P450表达的影响。用25-羟基胆固醇或24（S），25-环氧胆固醇（10（-5）至5 × 10（-5）M）处理大鼠肝细胞培养物，导致CYP 3A mRNA和免疫反应性蛋白水平呈浓度依赖性升高，但不增加CYP 1A 1、CYP 2B或CYP 4A基因产物的量。24（S），25-环氧胆固醇对CYP 3A含量的影响远大于25-羟基胆固醇，这与这些甾醇结合和激活LXR的相对能力一致。为了理解这些观察结果的机制基础，使用从LXR α/β-或双烷X受体（PXR）-缺失小鼠制备的原代培养肝细胞进行实验。用24（S），25-环氧胆固醇处理后，野生型和LXR缺失小鼠肝细胞中的CYP 3A mRNA水平均升高。相比之下，24（S），25-环氧胆固醇和两种另外的有效LXR配体22（R）-羟基胆固醇和N-羟基胆固醇中的任一种都不具有LXR活性。（2，2，2-三氟乙基）N-[4-[2，2，2-三氟-1-羟基-1-甲基-IH-吡唑-1-基]-2-氧代-1H-吡唑（三氟甲基）乙基]苯基]-苯磺酰胺（T0901317），改变了从PXR缺失小鼠制备的肝细胞中的CYP 3A mRNA水平，尽管这些药物诱导了野生型培养物中的CYP 3A mRNA含量。作为LXR配体也激活大鼠肝细胞中PXR的证据，用显性阴性PXR共转染原代培养物在用任何测试试剂处理后消除了报告基因诱导。这些结果表明，选择的LXR配体能够激活PXR，可能作为一种防御措施，以防止这些潜在的毒性内源性分子的积累。
The effects of oxysterol and drug ligands of the liver X receptor (LXR) on cytochrome P450 expression were evaluated in primary cultured rodent hepatocytes. Treatment of rat hepatocyte cultures with either 25-hydroxycholesterol or 24(S),25-epoxycholesterol (10(-5) to 5 x 10(-5) M) produced concentration-dependent elevations in CYP3A mRNA and immunoreactive protein levels but did not increase the amounts of CYP1A1, CYP2B, or CYP4A gene products. The effects of 24(S),25-epoxycholesterol on CYP3A content were much greater than were those of 25-hydroxycholesterol, consistent with the relative abilities of these sterols to bind and activate LXR. To understand the mechanistic basis of these observations, experiments were performed using primary cultured hepatocytes prepared from LXRalpha/beta- or pregnane X receptor (PXR)-null mice. CYP3A mRNA levels were increased after treatment with 24( S), 25-epoxycholesterol in both wild-type and LXR-null mouse hepatocytes. In contrast, neither 24(S),25-epoxycholesterol nor either of two additional potent LXR ligands, 22(R)-hydroxycholesterol and N-(2,2,2-trifluoroethyl)N-[4-[2,2,2-trifluoro-1-hydroxy-1(trifluoromethyl)ethyl]phenyl]-benzenesulfonamide (T0901317), altered CYP3A mRNA levels in hepatocytes prepared from PXR-null mice, although these agents induced CYP3A mRNA content in wild-type cultures. As evidence that the LXR ligands also activated PXR in rat hepatocytes, cotransfection of primary cultures with a dominant negative PXR abolished reporter gene induction after treatment with any of the test agents. These results indicate that selected LXR ligands are capable of activating PXR, probably as a defensive measure to prevent the accumulation of these potentially toxic endogenous molecules.