Inflammation, PXR Modification and Drug Disposition

描述（由申请人提供）：我的实验室的长期目标是提高我们对控制药物处置和药物代谢的基本调节机制的理解。有一个明确的认识，药物不良反应（adr）的频率增加患者的潜在全身性炎症。在这些个体中，不同的药物反应不一定与遗传多态性有关，而是由于编码重要药物代谢酶（DMEs）和药物转运蛋白的关键基因的表达迅速和急剧减少。在肝脏中，孕激素受体（PXR）是主要的异种“传感器”。PXR的配体依赖性激活增加了大量外源药物和处方药的整体摄取、代谢、运输和最终消除。基于强有力的初步数据，我们假设在接受利福平治疗的患者中发生的免疫抑制作用是通过PXR蛋白的翻译后修饰发生的。我们提供的证据表明，TNFalpha促进配体pxr的多聚酰化，以反馈抑制NF-kappa b靶基因。目的1将使用一种新颖的、创新的基于质谱的方法，依次在体外、培养细胞和肝细胞中定义配体激活的PXR SUMOylation的特定位点。Aim 2将通过生化方法验证炎症反应的选择性抑制机制是由于sumo修饰的PXR阻止核受体辅抑制因子/ nf - κ B复合物的清除。了解PXR如何从肝脏DMEs的正调节因子转化为肝脏组织炎症的转录抑制因子的生化细节和分子机制，将为理解药物介导的肝脏炎症反应抑制提供新的分子范式。关于PXR SUMOylation生物学的新分子见解将为开发解决adr的新药理学策略提供新的机会，并最终有助于识别用于治疗炎症性肝病的小分子。

DESCRIPTION (provided by applicant): The long-term objectives of my laboratory are to improve our understanding of the basic regulatory mechanisms that govern drug disposition and drug metabolism. There is a clear recognition that the frequency of adverse drug reactions (ADRs) is increased in patients affected with an underlying systemic inflammation. In these individuals, variable drug responses are not necessarily related to genetic polymorphisms but are due to the rapid and dramatic reduction in the expression of key genes that encode important drug metabolizing enzymes (DMEs) and drug transporter proteins. In liver, the pregnane x receptor (PXR) is the master- xenobiotic 'sensor'. Ligand-dependent activation of PXR increases the overall uptake, metabolism, transport and eventual elimination of a myriad of xenobiotics and prescription drugs. Based upon strong preliminary data, we hypothesize that the immunosuppressive effects that occur in patients following Rifampicin therapy occurs via the post-translational modification of the PXR protein. We provide evidence that TNFalpha promotes poly-sumoylation of liganded-PXR to feedback repress NF-kappa B-target genes. Aim 1 will define the specific sites of ligand-activated PXR SUMOylation sequentially in vitro, in cultured cells, and then in hepatocytes using a novel and innovative mass spectrometry-based approach. Aim 2 will test the hypothesis that the mechanism of selective repression of the inflammatory response is due to SUMO-modified PXR preventing clearance of nuclear receptor corepressor/NF-kappa B complexes using biochemical methods. Understanding the biochemical details and molecular mechanisms of how PXR is converted from a positive regulator of hepatic DMEs into a transcriptional suppressor of inflammation in liver tissue will provide a new molecular paradigm for understanding drug-mediated repression of the hepatic inflammatory response. New molecular insights regarding the biology of PXR SUMOylation will provide new opportunities to develop novel pharmacological strategies for addressing ADRs, and will eventually help to identify small molecules that will be used to treat inflammatory liver diseases. PUBLIC HEALTH RELEVANCE: The information gathered from the successful completion of this research proposal represents the key first step in developing novel pharmaceutical strategies that could be used to prevent ADRs in patients on combination therapy that are experiencing acute or systemic inflammation. This information will help to predict and prevent ADRs in patients experiencing acute or systemic inflammation.