Oxidant Stress in the Brain and Hypertension

描述（由申请人提供）：神经系统对血压和其他心血管参数的控制有强大的影响。大多数心血管疾病，特别是高血压，涉及自主神经系统的致病性功能障碍。中枢神经系统（CNS）中的血管紧张素II （angll）信号已被认为是高血压患者神经心血管功能障碍的罪魁祸首，但其潜在的分子底物和生理回路仍有待阐明。早在十年前，就有开创性的研究发现活性氧（reactive oxygen species， ROS）在血液循环中胆固醇升高引起的高血压中起着关键作用。从那时起，大多数关于高血压和ROS的研究都集中在血管系统或肾脏上。在上一个周期的资助使我们发现中枢神经系统中的氧化还原信号在Ang - 1介导的神经心血管调节和疾病中至关重要。在此基础上，并实施新开发的遗传工具来解剖氧化分子在中枢神经系统中的功能作用，我们将解决全体性angll依赖性高血压是由大脑关键心血管核中特定NADPH氧化酶（Nox）衍生的ROS过量产生引起的总体假设。利用脑定点病毒传递系统，我们将引入时空控制的基因修饰，以选择性、局部和有效地调节小鼠大脑中特定神经回路的氧化还原状态。结合复杂的自由基生物学和有意识小鼠的综合心血管生理学，我们将通过解决三个假设来剖析中枢神经-心血管控制的氧化机制。1)脑关键心血管核中ROS的过量生成促进了系统性Ang依赖型高血压和相关的自主神经功能障碍。异常中枢氧化还原信号和angll依赖性神经心血管失调机制之间的因果关系将被研究，重点是生理回路的功能映射和涉及的自由基种类。2)大脑特定心血管核中的AT1a受体在全身angll水平升高引起的ROS过量产生和中枢神经-心血管功能障碍中起关键作用。两种用于测试脑AT1a受体作用的小鼠模型：一种在中枢神经系统中选择性表达外源性AT1a受体，另一种具有固定的AT1a受体基因以靶向cre介导的缺失，将用于解剖氧化还原信号通过中枢AT1a受体在全身性高血压中的作用。3)关键心血管核内的特定Nox酶在全身性angll诱导的高血压及相关神经体液后遗症中发挥着重要而独特的作用。研究人员将利用病毒递送特异性靶向nox的RNAi，研究Nox1、Nox2和Nox3在关键中枢神经系统回路中的表达模式、调控和神经心血管功能。这项研究对中枢神经系统导向抗氧化剂在高血压和其他神经心血管疾病患者中的新治疗应用具有重要意义。

DESCRIPTION (provided by applicant): The nervous system exerts a powerful influence on control of blood pressure and other cardiovascular parameters. Most cardiovascular diseases, notably hypertension, involve pathogenic dysfunction of the autonomic nervous system. Angiotensin II (Ang ll) signaling in the central nervous system (CNS) has emerged as a primary culprit in driving neuro-cardiovascular dysfunction in hypertension, however the underlying molecular substrates and physiological circuits remain to be elucidated. Pioneering work a decade ago established that reactive oxygen species (ROS) play a pivotal role in hypertension caused by elevated circulating Ang ll. Since then, most investigations of Ang ll hypertension and ROS have focused on the vasculature or kidney. Funding during the previous cycle led to our discovery that redox signaling in CNS is critical in Ang ll-mediated neuro-cardiovascular regulation and disease. Building on this and implementing newly developed genetic tools for dissecting the functional role of oxidant molecules in the CNS, we will address the overall hypothesis that systemic Ang ll-dependent hypertension is caused by excessive production of specific NADPH oxidase (Nox)-derived ROS in key cardiovascular nuclei of the brain. Using a brain site-directed viral delivery system, we will introduce spatiotemporally controlled gene modifications for selective, localized and efficient modulation of the redox status of specific neural circuits in mouse brain. Coupled with sophisticated free radical biology and integrative cardiovascular physiology in conscious mice, we will dissect oxidant mechanisms of central neuro-cardiovascular control by addressing three hypotheses. 1) Systemic Ang ll-dependent hypertension and associated autonomic dysfunction are fueled by excessive generation of ROS in key cardiovascular nuclei of the brain. Causal links between abnormal central redox signaling and mechanisms underlying Ang ll-dependent neuro-cardiovascular deregulation will be investigated, with a focus on functionally mapping the physiological circuits and free radical species involved. 2) AT1a receptors in specific cardiovascular nuclei of the brain play a key role in excessive ROS production and central neuro-cardiovascular dysfunction caused by elevated systemic Ang ll levels. Two mouse models engineered for testing the role of brain AT1a receptors: one with expression of exogenous AT1a receptors selectively in CNS, and another with a floxed AT1a receptor gene for targeted Cre-mediated deletion will be used to dissect the role of redox signaling through central AT1a receptors in systemic Ang ll hypertension. 3) Specific Nox enzymes in key cardiovascular nuclei each play important and distinct roles in systemic Ang ll-induced hypertension and related neurohumoral sequelae. Expression patterns, regulation and neuro- cardiovascular function of Nox1, Nox2 and Nox3 in key CNS circuits will be investigated using viral delivery of specific Nox-targeted RNAi. This research has important implications for novel therapeutic use of CNS-directed antioxidants in humans with hypertension and other neuro-cardiovascular diseases.