Regulation of Drug Transport Proteins and Drug Metabolizing Enzymes by Nuclear Receptors

背景-细胞内化学分子的浓度决定了它们的活性和毒性。这不仅适用于药物，也适用于维生素和激素等内源性分子。膜转运蛋白是决定作用于细胞内靶点的可用浓度的通道。细胞内酶调节许多分子的新陈代谢，以使它们解毒和/或使它们更适合消除。被称为核受体的蛋白质严格控制着这些转运蛋白和代谢酶的数量。这项研究计划的总体目标是加深我们对决定药物转运体和代谢酶活性的过程的理解。这将帮助我们了解身体处理药物、维生素和其他荷尔蒙的方式。 目标-拟议的研究计划的目的是：1)研究一种名为促红细胞生成素的激素在调节代谢酶下调中的作用，2)确定肠道细菌及其产生的代谢物对转运体和代谢酶的作用，以及3)确定核受体活性对细胞内代谢途径的影响。 科学方法-我们实验室之前的研究确定了一种在肾脏中制造的激素，称为促红细胞生成素(EPO)，它显著降低了一种基本代谢酶(CYP3A)的表达和活性。为了阐明这种作用的机制，我们将分离肝脏细胞，并用EPO以及各种EPO信号抑制剂来处理它们，以确定这种作用的机制。 为了评估肠道产生的细菌代谢产物对核受体介导的转运蛋白和代谢酶表达的影响，我们将使用无菌小鼠和抗生素来改变肠道细菌含量。然后我们将使用代谢组分析，这使我们能够识别和测量代谢物形成的差异。我们将使用这项技术来确定这些治疗在肠道、肝脏和肾脏等靶器官中引起的变化。 虽然在药物反应方面，核受体对酶和转运蛋白的调节作用得到了很好的评价，但这些过程的内源性生物学作用尚不清楚。我们将使用已建立的两种重要核受体(如PXR和CAR)的核受体基因敲除小鼠模型进行基因组和代谢分析，以确定受这些关键蛋白调控的新途径。 预期意义-本研究项目的发现将在分子水平上阐明与膜运输蛋白和代谢酶基因表达调控相关的机制。最终，这些研究将帮助我们了解身体如何处理和处理外源性和内源性化合物。

Background - The intracellular concentration of chemical molecules determines their activity and toxicity. This applies not only to drugs but also to endogenous molecules such as vitamins and hormones. Membrane transport proteins act as a gateway to determine the concentration available to act on intracellular targets. Intracellular enzymes mediate the metabolism of numerous molecules to detoxify them and/or render them more suitable for elimination. Proteins called nuclear receptors tightly regulate the amount of these transporters and metabolic enzymes. The overall goal of this research program is to further our understanding of the processes that determine the activity of drug transporters and metabolic enzymes. This will help us understand the way the body handles drugs, vitamins and other hormones. Objectives - The objectives of the proposed research program are to: 1) Investigate the role of a hormone called erythropoietin in mediating the downregulation of metabolic enzymes, 2) To determine the role of intestinal bacteria and the metabolites they produce on transporters and metabolic enzymes, and 3) To determine the impact of nuclear receptor activity on intracellular metabolic pathways. Scientific Approach - Previous studies in our lab determined a hormone made in the kidney called erythropoietin (EPO), significantly decreases expression and activity of an essential metabolic enzyme (CYP3A). To elucidate the mechanism for this effect, we will isolate cells of the liver and treat them with EPO as well as various inhibitors of EPO signalling to determine the mechanism accounting for this effect. To evaluate the impact of intestinally produced bacterial metabolites on nuclear receptor mediated expression of transporters and metabolic enzymes, we will use germ free mice and antibiotics to alter the intestinal bacterial content. We will then use metabolomic analysis, which allows us to identify and measure the differences in metabolite formation. We will use this technology to determine the changes these treatments induce in target organs such as the intestine, liver and kidney. Although the contribution of nuclear receptors to regulation of enzymes and transporters is well appreciated in terms of response to drugs, the endogenous biological role of these processes is unknown. We will use established nuclear receptor knockout mouse models of two of important nuclear receptors (e.g. Pxr and Car) to perform genomic and metabolomic analysis in order to identify novel pathways regulated by these essential proteins. Expected Significance -The findings from this program of research will elucidate the mechanisms associated with modulation in gene expression of membrane transport proteins and metabolic enzymes at the molecular level. Ultimately these investigations will help us understand how the body handles and processes exogenous and endogenous compounds.