Transgenic Models of Ah Receptor Action

描述(申请人提供)：芳烃受体(AHR)是一种配体激活的转录因子，介导多环芳烃(PAHs)、卤代二恶英(“二恶英”)、-二苯并呋喃、-联苯(PCB)和-二苯醚的生物效应。由于它在大量环境污染物的急性毒性、致畸和致癌中起着核心作用，有关AHR信号的机制信息被监管机构用来确定这些污染物的可接受暴露水平。这一建议的主要假设是，至少存在三种不同的AHR信号通路，它们对人类种群和一般脊椎动物物种具有毒理学意义。我们认为，这三种途径可以通过它们对靶细胞群体内转录谱的独特影响来区分，这些途径可以根据它们对AHR部分激活的依赖、它们的细胞环境以及它们通过被称为AHREs的增强子元件对基因表达的影响来进一步定义。这项提案的目标是确定反映激动剂暴露及其诱导的毒性反应的生物标记物。我们将通过在新型重组小鼠模型的肝细胞和内皮细胞中鉴定低亲和力和高亲和力的AHRE来实现这一点。为此，我们提出了以下具体目标：具体目标1：在ES细胞中使用基因打靶来产生来自配体响应版本的AhR的重组等位基因。具体目标2：证明AHR细胞表达和浓度的重要性。具体目标3：利用基因组学方法对高亲和力和低亲和力Are电池进行分类。具体目的4：提供环境AHR激动剂可以刺激内源性AHR途径的证据。我们认为，这项工作的结果将提供新的模型，将揭示二恶英对人类的毒性机制，表征毒性的DNA特征，并测试一个新的假设，即发育毒性来自对内源性AHR途径的干扰。总体而言，这些研究将为对人类进行更准确和更有信息量的风险评估奠定基础。 公共卫生相关性：该项目旨在了解AHR介导的转录激活机制，该机制导致二恶英暴露的适应性、毒性和发育后果，并寻找预测这些不同结果的生物标志物。这些实验将允许对AHR介导的二恶英毒性进行更相关的评估，并产生预测二恶英暴露的相关终点的生物标记物。

DESCRIPTION (provided by applicant): The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the biological effects of polycyclic aromatic hydrocarbons (PAHs), halogenated-dioxins ("dioxins"), - dibenzofurans, -biphenyls (PCBs), and -diphenylethers. Because of its central role in acute toxicity, teratogenesis and carcinogenesis of a large number of environmental contaminants, mechanistic information about AHR signaling is used by regulatory agencies to establish acceptable exposure levels for these pollutants. The overarching hypothesis of this proposal is that at least three distinct AHR signaling pathways exist that are of toxicological significance to human populations and vertebrate species in general. We propose that these three pathways can be distinguished by their unique impacts on transcriptional profiles within target cell populations and that these pathways can be further defined based upon their dependence on fractional activation of the AHR, by their cellular context, and their influence on gene expression through enhancer elements known as AHREs. The goal of this proposal is to identify biomarkers that reflect exposure to agonists and their induced toxic responses. We will accomplish this through the identification of low and high affinity AHREs in the hepatocyte and endothelial cell compartments of novel recombinant mouse models. To these ends, we propose the following specific aims: Specific Aim 1: Use gene targeting in ES cells to generate recombinant alleles derived from a ligand responsive version of Ahr. Specific Aim 2: Demonstrate the importance of the cellular expression and concentration of AHR. Specific Aim 3: Classify the high and low affinity AHRE batteries using genomic approaches. Specific Aim 4: Provide evidence that environmental AHR agonists can stimulate the endogenous AHR pathway. We propose that the results of this effort will provide new models that will inform the mechanism of dioxin toxicity in humans, characterize DNA signatures of toxicity, and test a novel hypothesis that developmental toxicity arises from interference with the endogenous AHR pathway. Collectively these studies will set the stage for more accurate and informative risk assessment in man. PUBLIC HEALTH RELEVANCE: This project aims to understand the mechanisms of AHR-mediated transcriptional activation which leads to the adaptive, toxic, and developmental consequences of dioxin exposure and to search for biomarkers that are predictive of these disparate outcomes. These experiments will allow more relevant assessments of AHR-mediated dioxin toxicity as well as generate biomarkers predictive for relevant endpoints of dioxin exposure.