Oxidant Stress in the Brain and Hypertension

描述(申请人提供)：原发性高血压(HTN)是一个主要的健康问题，困扰着30%的人口，并容易患上影响大脑、心脏和肾脏的严重疾病。有令人信服的证据表明，原发性HTN以神经体液功能障碍为特征，中枢神经系统(CNS)中不适当的血管紧张素II(AngII)信号是主要罪魁祸首。穹隆下器(SFO)是一种缺乏血脑屏障的前脑结构，被认为是通向中枢循环因子的关键“门户”，与血管紧张素Ⅱ依赖型HTN密切相关。在这项资助的前几个周期中，我们已经证明了血管紧张素Ⅱ(1型受体，AT1R)在SFO中诱导的活性氧(ROS)信号介导了“慢升压性”血管紧张素ⅡHTN，这是一种慢性小鼠模型，概括了基本HTN的关键特征。然而，我们对血管紧张素Ⅱ在SFO中诱导的ROS如何转化为对控制血压的神经通路的强大影响的了解仍然不完整。最近，内质网(ER)应激已成为许多心血管和代谢性疾病的主要氧化还原相关机制；然而，它在HTN中的作用尚不清楚。目前，血管紧张素Ⅱ与多种心血管细胞类型的内质网应激直接相关，中枢神经系统的内质网应激通过参与脑血管紧张素Ⅱ依赖的HTN的分子机制导致神经功能的长期变化。在过去的一年里，我们已经获得了令人兴奋的初步数据，表明在培养的神经元和活体的SFO中，Angii、ROS和内质网应激之间存在联系，同时有证据表明，中枢神经系统中的内质网应激的化学操作对血压有显著影响。基于这些发现，我们建议检验这样一个假设，即SFO中的内质网应激在Angii、ROS和CNS变化之间提供了重要的联系，这些变化导致了Angii慢加压小鼠模型中的HTN。目的1利用分子、免疫细胞化学和超微结构分析，验证血管紧张素转换酶在体内诱导血管紧张素Ⅱ受体依赖性内质网应激的假说。目的2验证内质网应激和氧化应激在慢升压血管紧张素Ⅱ介导的SFO效应中起关键作用的假说。这将通过病毒传递ROS清除剂、遗传内质网应激抑制剂和氧化荧光探针在SFO中原位测量ROS来实现。目的3将利用SFO靶向的ER容量的遗传操作和综合心血管生理学来验证SFO中的ER应激是慢升压性Angii HTN和相关神经体液后遗症的原因因素的假说。该项目的一个显著优势是在中枢神经心血管调节和HTN(Davisson，Mark)、内质网应激生物学(Kaufman，QI)、氧化还原生物学(Davisson，Kaufman)和CNS CV回路神经解剖学(Pickel，Piells)方面拥有互补专业知识的研究人员的参与。该项目解决了HTN研究中一个非常新颖的主题，有可能从根本上促进对连接CNS和HTN的基本机制的理解，这可能为新的治疗方法提供线索。该项目还有可能在HTN研究方面开辟新的道路。

DESCRIPTION (provided by applicant): Essential hypertension (HTN) is a major health problem, afflicting 30% of the population and predisposing to serious diseases affecting the brain, heart and kidneys. There is compelling evidence that essential HTN is characterized by neurohumoral dysfunction, and inappropriate angiotensin II (AngII) signaling in the central nervous system (CNS) is a primary culprit. The subfornical organ (SFO), a forebrain structure that lacks a blood-brain-barrier and is considered a key "gateway" to the CNS for circulating factors, is strongly implicated in AngII-dependent HTN. In previous cycles of this grant, we have shown that AngII (type 1 receptor, AT1R)- induced reactive oxygen species (ROS) signaling in the SFO mediates "slow-pressor" AngII HTN, a chronic mouse model that recapitulates key features of essential HTN. However, our understanding of how AngII- induced ROS formation in the SFO translates into powerful effects on neural pathways controlling blood pressure is still incomplete. Recently, endoplasmic reticulum (ER) stress has emerged as a major redox- associated mechanism in a number of cardiovascular and metabolic diseases; its role in HTN, however, is not known. AngII is now directly linked to ER stress in several cardiovascular cell types, and ER stress in the CNS leads to long-term changes in neural function through molecular mechanisms known to be involved in brain AngII-dependent HTN. During the past year, we have obtained exciting preliminary data showing links between AngII, ROS and ER stress in cultured neurons and in the SFO in vivo, along with evidence that chemical manipulation of ER stress in the CNS has significant effects on blood pressure. Based on these findings, we propose to test the overall hypothesis that ER stress in the SFO provides an important link between AngII, ROS and CNS alterations that lead to HTN in the AngII slow-pressor mouse model. Aim 1 will utilize molecular, immunocytochemical and ultrastructural analyses to test the hypothesis that AngII induces AT1R- dependent ER stress in the SFO in vivo. Aim 2 will test the hypothesis that the coupling of ER stress and oxidant stress is critical in slow-pressor AngII-mediated effects in the SFO. This will be accomplished through a combination of viral delivery of ROS scavengers, a genetic ER stress inhibitor and oxidative fluoroprobes for ROS measurements in the SFO in situ. Aim 3 will utilize SFO-targeted genetic manipulations of ER capacity combined with integrative cardiovascular physiology to test the hypothesis that ER stress in the SFO is a causal factor in slow-pressor AngII HTN and related neurohumoral sequelae. A notable strength of the project is the involvement of investigators with complementary expertise in central neural cardiovascular regulation and HTN (Davisson, Mark), ER stress biology (Kaufman, Qi), redox biology (Davisson, Kaufman) and neuroanatomy of CNS CV circuits (Pickel, Pierce). This project, which addresses a highly novel topic in HTN research, has the potential to fundamentally advance understanding of basic mechanisms linking the CNS with HTN, which could provide clues into novel treatments. The project also has the potential to forge new trails in HTN research.