Novel in vivo regulatory mechanisms of human CYP3A4

描述（由申请人提供）：细胞色素P450 (CYP) 3A4是人类肝脏中最丰富的CYP酶，它代谢约60%的已知药物。cyp3a4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患者中受损。疾病中药物代谢的中断与炎症标志物的诱导和CYP酶表达的减少有关。因此，在大多数患者中，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。本探索性提案的目的是进行全基因组定位和生物信息学分析，以确定体内参与下调人类CYP3A4酶的关键调节因子。CYP3A4基因的表达受基础转录因子和核受体的调控。体外研究表明，CYP3A4的表达也受microRNAs （miRNAs）的调控。因此，CYP3A4酶的下调可能是转录因子、rna和/或miRNAs转录和转录后修饰的累积效应。我们的中心假设是CYP3A4表达的下调是由靶染色质上的转录因子/ nr相关表观遗传修饰以及miRNA与CYP3A4 mRNA结合的变化控制的。本提案的第一个目的将检验CYP3A4基因的下调是由转录因子/ nr相关的表观遗传修饰在靶染色质上控制的假设。第二个目的是确定mirna在体内CYP3A4酶下调中的作用。CYP3A4的表达可被多种化学物质激活，包括妊娠X受体（PXR）。另一方面，CYP3A4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）。为了确定参与CYP3A4酶改变的关键调节因子，我们的策略是利用PXR配体（例如PCN）诱导CYP3A4和LPS下调CYP3A4的联合方法。使用基因组方法的拟议研究可以揭示有助于体内下调人类CYP3A4酶的新调控元件。然后可以靶向这些调节因子，以防止由于cyp3a4介导的药物代谢变化而导致的药物不良影响。最终，这可能会导致新策略的发展，以提高个别患者的药物安全性。

DESCRIPTION (provided by applicant): 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.