Mitochondrial Redox Systems in Neurogenic Hypertension

描述（由申请人提供）：脑血管紧张素II （AngII）信号的失调与心血管疾病的发病机制有关，包括心力衰竭和高血压。血液中AngII水平升高可通过作用于血脑屏障缺陷的脑区，即心室周围器官（CVOs），导致神经源性高血压的发生。CVOs的激活可以改变包括交感神经兴奋在内的中枢心血管输出。为了更好地了解AngII在神经源性高血压发展中的核心作用，并确定新的治疗靶点，有必要研究大脑中AngII的神经元内信号传导机制。之前，我们和其他人发现了活性氧（ROS），特别是超氧自由基（O2）。-)，由NADPH氧化酶产生，作为中枢神经元受AngII刺激的重要信号中间体。然而，额外的氧气来源。——包括线粒体，这是O2的主要位置。在大多数细胞中，这种现象尚未得到研究。此外，NADPH氧化酶和线粒体来源的O2之间的潜在联系。-在AngII神经元内信号传导中的作用仍有待阐明。在此，我们提出了一系列分子、生化和综合心血管生理实验来验证我们的假设，即血管敏感神经元中线粒体定位的NADPH氧化酶有助于线粒体O2的增加。-，反过来通过作用于已知的控制神经元放电和交感神经兴奋的氧化还原敏感蛋白介导血管依赖性高血压。我们将在三个具体目标中检验这一假设。在Specific Aim 1中，我们将研究NADPH氧化酶在产生线粒体定位O2中的作用。在受血管刺激的神经元中。这个目标建立在我们的初步数据上，显示AngII增加线粒体O2。-在培养的神经元中，NADPH氧化酶催化亚基（Nox4）存在于神经元的线粒体中。在具体目标2中，我们将研究线粒体产生O2的机制。-调节AngII诱导的神经元活化。我们的新初步数据表明，线粒体O2的清除能力增加，这一目标得到了支持。通过腺病毒介导的锰超氧化物歧化酶（MnSOD）的过表达。-清除酶特异性靶向线粒体，减弱AngII诱导的神经元钾电流抑制。最后，在Specific Aim 3中，我们将通过研究线粒体产生的O2的作用来扩展我们之前的观察，即大脑中MnSOD过表达抑制急性中枢血管诱导的压力反应。-在脑内介导慢性交感神经兴奋和血管依赖性神经源性高血压小鼠模型高血压的发展。这些研究将为AngII的神经元内信号传导机制提供新的信息，并可能确定线粒体定位的O2。作为血管依赖性神经心血管疾病（如高血压）的重要治疗靶点。

DESCRIPTION (provided by applicant): Dysregulation of brain angiotensin II (AngII) signaling is implicated in the pathogenesis of cardiovascular diseases, including heart failure and hypertension. Increased circulating levels of AngII can lead to the development of neurogenic hypertension by acting on blood-brain-barrier deficient brain regions, known as circumventricular organs (CVOs). Activation of the CVOs can alter central cardiovascular outputs including sympatho-excitation. To better understand the central actions of AngII in the development of neurogenic hypertension and to identify novel therapeutic targets of the disease, it is essential to investigate the intra- neuronal signaling mechanisms of AngII in the brain. Previously, we and others identified reactive oxygen species (ROS), particularly superoxide radicals (O2.-), generated by NADPH oxidase as important signaling intermediates in central neurons stimulated with AngII. However, additional sources of O2.-- including mitochondria, which are the primary sites for O2.- generation in most cells, have yet to be investigated. In addition, a potential link between NADPH oxidase and mitochondria-derived O2.- in the intra-neuronal signaling of AngII remains to be elucidated. Herein, we propose a series of molecular, biochemical, and integrative cardiovascular physiological experiments to test our hypothesis that a mitochondria-localized NADPH oxidase in AngII-sensitive neurons contributes to an increase in mitochondrial O2.-, which in turn mediates AngII-dependent hypertension by acting on redox-sensitive proteins known to control neuronal firing and sympatho-excitation. We will test this hypothesis in three Specific Aims. In Specific Aim 1, we will investigate the role of NADPH oxidase in producing mitochondria-localized O2.- in AngII-stimulated neurons. This aim builds upon our preliminary data showing that AngII increases mitochondrial O2.- in cultured neurons and that a NADPH oxidase catalytic subunit (Nox4) is present in mitochondria of neurons. In Specific Aim 2, we will examine the mechanisms by which mitochondrial-produced O2.- regulates AngII- induced neuronal activation. This aim is supported by our new preliminary data indicating that increased scavenging of mitochondrial O2.- via adenoviral-mediated overexpression of manganese superoxide dismutase (MnSOD), the O2.- scavenging enzyme specifically targeted to mitochondria, attenuates AngII- induced inhibition of neuronal potassium current. Finally, in Specific Aim 3, we will expand our previous observation that MnSOD overexpression in the brain inhibits the acute central AngII-induced pressor response by investigating the role of mitochondrial-produced O2.- in the brain in mediating the chronic sympatho-excitation and the development of hypertension in a mouse model of AngII-dependent neurogenic hypertension. These studies will provide new information on the intra-neuronal signaling mechanisms of AngII, and may identify mitochondrial-localized O2.- in neurons as important therapeutic targets in AngII-dependent neuro-cardiovascular diseases, such as hypertension. PUBLIC HEALTH RELEVANCE: Hypertension and heart failure and are two cardiovascular diseases associated with abnormal stimulation in the brain. Free radicals and oxidants produced in brain cells called neurons have been shown to be involved in these cardiovascular diseases. By investigating and identifying the specific neuronal cell location where these oxidants are generated this project will advance opportunities to develop new therapeutics that may need to be targeted to specific cellular locations for the improved treatment of hypertension.