Identification of novel pregnane X receptor (PXR) agonists by In silico and biological activity analyses and reversal of cigarette smoke-induced PXR downregulation.
Identification of novel pregnane X receptor (PXR) agonists by In silico and biological activity analyses and reversal of cigarette smoke-induced PXR downregulation.
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DOI：
10.1016/j.bbrc.2021.02.145
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发表时间：
2021-05-28
影响因子：
3.1
通讯作者：
Nyunoya T
中科院分区：
文献类型：
--
作者：
Reddy RT;Nyunoya T
香烟烟雾(CS)含有许多毒素，这些毒素几乎共同损害身体的每个器官，吸烟是许多慢性病的关键危险因素。除了毒性作用外，CS还可以改变药物和类固醇结合的孕烷X受体(PXR)的表达，当激活时，PXR上调细胞色素P450(CYP)酶、谷胱甘肽转移酶(GSTs)和多药耐药蛋白1(MDR1)的表达，MDR1是一种适应性代谢阵列，介导CS组分毒素的清除。我们试图寻找新的PXR激动剂，在抑制PXR活性的条件下恢复PXR活性，以及它们结合和激活PXR的机制。与其他核受体相比，PXR具有独特的更大、疏水和高度灵活的配体结合结构域(LBD)，使其能够与结构不同的分子相互作用。我们测试了某些钙通道阻滞剂(CCB)作为潜在PXR配体的药理亚集，通过分子对接方法进行分析，并确定了PXR LBD中可能的活性部位，以及相关的键和键能。我们详细分析了非洛地平的结合和激动剂活性，因为它显示了所测试的CCB中结合能最低的。我们发现非洛地平是一种有效的PXR激动剂，而结合能较高的CCB则效力较弱(氨氯地平)或几乎无效(马尼地平)，并且它诱导了已知的PXR激动剂靶点--HepG2细胞中CYP3A4的表达。非洛地平还可诱导HepG2肝细胞PXR基因的表达，并能降低CS提取物诱导的PXR表达水平，提示其调节PXR的表达。这些结果阐明了配体诱导PXR激活的机制，并确认非洛地平是一种新的PXR激动剂。
Cigarette smoke (CS) contains many toxins that collectively harm nearly every organ in the body, and smoking is a key risk factor for many chronic diseases. Aside from its toxic actions, CS may alter expression of the drug- and steroid-binding pregnane X receptor (PXR), which when activated upregulates expression of cytochrome P450 (CYP) enzymes, glutathione transferases (GSTs), and multidrug resistance protein 1 (MDR1), an adaptive metabolic array that mediates clearance of CS component toxins. We sought to identify new PXR agonists that may be useful for restoring PXR activity in conditions wherein it is suppressed, and their mechanisms of PXR binding and activation. PXR has a uniquely larger, hydrophobic, and highly flexible ligand-binding domain (LBD) vs. other nuclear receptors, enabling it to interact with structurally diverse molecules. We tested certain calcium channel blockers (CCBs) as a pharmacological subset of potential PXR ligands, analyzing by molecular docking methods, and identified a putative active site in the PXR LBD, along with the relevant bonds and bonding energies. We analyzed felodipine binding and agonist activity in detail, as it showed the lowest binding energy among CCBs tested. We found felodipine was a potent PXR agonist as measured by luciferase reporter assay, whereas CCBs with higher binding energies were less potent (amlodipine) or nearly inactive (manidipine), and it induced CYP3A4 expression in HepG2 cells, a known target of PXR agonism. Felodipine also both induced PXR mRNA in HepG2 hepatocytes and reduced CS extract-induced diminution of PXR levels, indicating it modulates PXR expression. The results illuminate mechanisms of ligand-induced PXR activation and identify felodipine as a novel PXR agonist.
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