Novel in vivo regulatory mechanisms of human CYP3A4

摘要。 细胞色素P450（CYP）3A 4是人类肝脏中最丰富的CYP酶，其代谢约60% 已知的药物。CYP 3A 4介导的药物代谢在感染、糖尿病、癌症 心血管疾病、肝脏疾病和许多其他疾病。疾病中药物代谢的破坏 与炎症标志物的诱导和炎症抑制酶表达的减少有关。因此在 大多数患者的药物暴露于炎症介质被激活的微环境中。 这增加了这些患者发生药物相互作用和药物不良反应的风险。客观 这一探索性建议的一个重要方面是进行全基因组作图和生物信息学分析， 参与体内下调人CYP 3A 4酶的调节剂。CYP 3A 4基因表达是 由基础转录因子以及核受体（NR）调节。体外研究表明 CYP 3A 4的表达也受microRNA（miRNAs）的调控。因此，CYP 3A 4酶的下调 可能是转录因子的转录和转录后修饰的累积效应， NR和/或miRNA。我们的中心假设是，CYP 3A 4表达的下调是由以下因素控制的： 转录因子/NR相关的表观遗传修饰在靶染色质以及通过改变 与CYP 3A 4 mRNA结合的miRNA。本建议的第一个目标将审查的假设，向下- CYP 3A 4基因的调节受转录因子/NR相关的表观遗传修饰控制， 靶向染色质。第二个目标是确定miRNA在下调CYP 3A 4酶中的作用， vivo. CYP 3A 4表达可被多种诱导NR的化学物质激活，包括CYP 3A 4 X 受体（PXR）。另一方面，CYP 3A 4可被炎症介质下调，包括 细胞因子和与疾病相关的细菌内毒素、脂多糖（LPS）。以识别 参与改变CYP 3A 4酶的关键调节剂，我们的策略是利用以下联合方法： PXR配体（例如PCN）诱导CYP 3A 4和LPS下调CYP 3A 4。拟议的研究 使用基于基因组的方法可以解开新的调节元件， 人CYP 3A 4酶在体内。然后，可以将这些调节剂作为目标，以防止 由于CYP 3A 4介导的药物代谢的变化。最终，这可能会导致 提高个体患者用药安全性的新策略。

ABSTRACT. Cytochrome P450 (CYP) 3A4 is the most abundant CYP enzyme in the human liver, and it metabolizes ~60% of known drugs. CYP3A4-mediated drug metabolism is impaired in patients with infections, diabetes, cancer, cardiovascular diseases, liver disorders and many other diseases. Disruptions in drug metabolism in diseases are associated with induction of inflammatory markers and reductions in expression of CYP enzymes. Thus, in most patients, medications are exposed to a micro-environment where inflammatory mediators are activated. This increases the risks of drug-drug interactions and adverse drug reactions in these patients. The objective of this exploratory proposal is to perform genome-wide mapping and bioinformatics analysis to identify key regulators involved in down-regulation of human CYP3A4 enzymes in vivo. CYP3A4 gene expression is regulated by basal transcription factors as well as nuclear receptors (NRs). In vitro studies have shown that CYP3A4 expression is also regulated by microRNAs (miRNAs). Thus, down-regulation of CYP3A4 enzymes may be a cumulative effect of transcriptional and post-transcriptional modifications by transcription factors, NRs and/or miRNAs. Our central hypothesis is that down-regulation of CYP3A4 expression is controlled by transcription factor/NR-associated epigenetic modifications at the target chromatin as well as by changes in miRNA binding to CYP3A4 mRNA. The first aim of this proposal will examine the hypothesis that down- regulation of CYP3A4 gene is controlled by transcription factor/NR-associated epigenetic modifications at the target chromatin. The second aim will determine the role of miRNAs in down-regulation of CYP3A4 enzymes in vivo. CYP3A4 expression can be activated by diverse chemicals which induce NRs, including pregnane X receptor (PXR). On the other hand, CYP3A4 can be down-regulated by inflammatory mediators including cytokines and the bacterial endotoxin, lipopolysaccharide (LPS) which are associated with diseases. To identify the key regulators involved in alteration of CYP3A4 enzymes, our strategy is to utilize a combined approach of CYP3A4 induction by PXR ligand (e.g. PCN) and CYP3A4 down-regulation by LPS. The proposed studies using genome-based approaches can unravel novel regulatory elements which contribute to down-regulation of human CYP3A4 enzymes in vivo. These regulators can then be targeted to prevent undesirable effects of drugs due to changes in CYP3A4-mediated drug metabolism. Ultimately, this can lead to the development of new strategies to improve the safety of medications in individual patients.