Ah Receptor and Endothelin-Dependent Hypertension

描述（由申请人提供）：心血管疾病发生在1 / 4的成年人中，是美国死亡的主要原因，内皮素-1 （ET- 1）是许多此类疾病发病机制中涉及的一个因素。ET-1的生物合成受基因转录调控，而缺氧是最有效的刺激之一。我们认为芳基烃受体（AhR）是一种配体激活的转录因子，影响ET-1表达的氧调控，并调节ET-1依赖性心血管疾病的发病机制。当AhR基因被删除时，正常环境下的小鼠表现出组织前蛋白ET-1 mRNA和血浆ET-1升高，并发生心肌肥大。然而，当AhR缺失小鼠暴露于轻度缺氧（~ 1500 m）时，ET-1进一步被诱导，心脏肥厚的进展加快，小鼠发生高血压。此外，与野生型小鼠相比，AhR缺失小鼠在轻度缺氧下表现出血管紧张素（Ang） II和活性氧的增加。这些数据表明，AhR影响基础和缺氧诱导的ET-1表达，ET-1和Ang II都可能介导轻度缺氧下的组织病理。因此，我们将验证AhR抑制基础和缺氧诱导的ET-1转录的假设，因此AhR的缺失增加了对缺氧诱导的ET-1表达的敏感性，导致肾素-血管紧张素系统（RAS）的激活，高血压和通过诱导活性氧（ROS）导致器官损伤。在目的1中，我们将确定缺氧诱导的ET-1、RAS激活和ROS产生对AhR缺失小鼠组织病理的贡献。在正常缺氧和轻度缺氧条件下对AhR缺失小鼠进行研究，比较RAS基因表达和酶活性；血管、心脏和肾脏损伤；和活性氧的产生。Ang II和ET-1的贡献将使用ACE抑制剂/ETA受体拮抗剂组合来研究，而ROS的贡献将使用超氧化物来研究。模拟歧化酶，tempol。在目标2中，我们将通过使用Cre/Lox技术研究仅在内皮细胞中删除AhR的小鼠，来描述内皮细胞中AhR对缺氧诱导、et -1介导的RAS激活、高血压和器官损伤的贡献。在aim 3中，我们将利用在ET-1启动子控制下表达荧光素酶的转基因小鼠，并在原代小鼠内皮细胞中进行ET-1启动子分析，建立AhR抑制ET-1转录的机制。我们的研究结果将为抑制缺氧诱导的ET-1提供新的调控途径，并可用于开发ET-1依赖性心血管疾病的新疗法。

DESCRIPTION (provided by applicant): Cardiovascular disease occurs in 1 in 4 adults and is the leading cause of death in the U.S. Endothelin-1 (ET- 1) is one factor that has been implicated in the pathogenesis of many of these diseases. ET-1 biosynthesis is regulated by gene transcription and hypoxia is one of the most potent stimuli. We propose that the aryl hydrocarbon receptor (AhR), a ligand activated transcription factor, influences oxygen-regulation of ET-1 expression and modulates the pathogenesis of ET-1-dependent cardiovascular diseases. When the AhR is genetically deleted, null mice under normoxic conditions exhibit elevated tissue preproET-1 mRNA and plasma ET-1, and develop cardiac hypertrophy. However, when AhR null mice are exposed to mild hypoxia (~1,500 m), ET-1 is induced further, the progression of cardiac hypertrophy is accelerated, and the mice become hypertensive. Additionally, AhR null mice exhibit increased angiotensin (Ang) II and reactive oxygen species under mild hypoxia, compare to wildtype mice. These data suggest that AhR influences basal and hypoxia-induced ET-1 expression and that both ET-1 and Ang II may mediate tissue pathologies under mild hypoxia. Thus, we will test the hypothesis that AhR suppresses basal and hypoxia-induced ET-1 transcription so that loss of AhR increases the sensitivity to hypoxia-induced ET-1 expression, leading to activation of the renin-angiotensin system (RAS), hypertension and organ damage via induction of reactive oxygen species (ROS). In aim 1, we will establish the contribution of hypoxia-induced ET-1, RAS activation, and ROS production to tissue pathologies in AhR null mice. Studies in AhR null mice maintained under normoxia or mild hypoxia will compare RAS gene expression and enzyme activity; vascular, cardiac, and renal injury; and ROS production. The contribution of Ang II and ET-1 will be investigated using an ACE inhibitor/ETA receptor antagonist combination, while the contribution of ROS will be investigated using the superoxide. dismutase mimetic, tempol. In aim 2, we will delineate the contribution of the AhR in endothelial cells to hypoxia-induced, ET-1-mediated RAS activation, hypertension, and organ damage by studying mice where AhR is deleted only in endothelial cells using Cre/Lox technology. In aim 3, we will establish the mechanism by which AhR suppresses ET-1 transcription using transgenic mice that express luciferase under ET-1 promoter control and by conducting ET-1 promoter analysis in primary murine endothelial cells. Our results will define a novel regulatory pathway for suppression of hypoxia-induced ET- 1, which could be used to develop new therapies for ET-1-dependent cardiovascular diseases.