Brain-targeted ACE2 over-expression on angiotensin-II-mediated hypertension

描述(申请人提供)：肾素-血管紧张素系统(RAS)是健康和疾病中心血管(CV)和肾功能的主要调节因子。中枢血管紧张素转换酶控制区RAS组分的活性和表达增加，以及高血压伴中枢损害或应用血管紧张素Ⅱ(Ang-II)拮抗剂的降压作用减弱，在几种遗传和实验模型中支持了脑RAS功能亢进可能参与高血压发病机制的观点。到目前为止，普遍的假设是Ang-II是这个系统的主要参与者。血管紧张素转换酶2(ACE2)是RAS的一个新成员，已在与心血管功能相关的器官和组织(如心脏、肾脏、血管)中被发现，并似乎是缓冲Ang-II过量的反向调节途径的一部分。我们最近在参与血压中枢调节的脑区发现了ACE2蛋白，并表明它受RAS的其他成分的调节。此外，我们最近观察到，ACE2在穹隆下器(SFO)的过度表达显著降低了小鼠对中枢应用Ang-II的升压反应，并减少了细胞内的氧化应激。这些观察结果增加了ACE2在Ang-(1-7)等生物活性多肽产生中的作用，为面对正常和病理生理状态下大脑的进一步探索提供了理论基础。在这一建议中，我们假设中枢ACE2在高血压过程中起主要的代偿作用；ACE2的过度表达将促进Ang-(1-7)的形成和Ang-II的降解，从而加强代偿机制，预防高血压和相关的氧化应激。利用我们在生理基因组学(一门研究基因操作的生理后果的科学)方面的专业知识，结合清醒小鼠心血管功能的最新记录和分析，我们建议调查慢性ACE2过度表达对神经源性高血压发展的影响。利用一种新的基因工程小鼠模型，通过脑靶向ACE2的过度表达，我们将：1)建立脑靶向ACE2过度表达在神经源性高血压中的功能后果。2)明确SFO和RVLM在ACE2介导的Syn-ACE2转基因小鼠降压中的作用及其激活的分子后果。3)研究ACE2过表达对Ang-II和Ang-(1-7)受体信号通路的影响。我们相信，这个独特的模型将使我们能够确定体内中枢ACE2在神经源性高血压中的生理作用。ACE2在血压调节中发挥有益作用的证据可能会导致新疗法的开发，以及更好地利用现有疗法治疗高血压和其他心血管疾病。公共卫生相关性：在心血管疾病中，全球高血压患病率估计可能高达10亿人，每年约有710万人死于高血压。使用转基因小鼠，这项应用将描述一种新的酶，ACE2，防止高血压发展的能力。如果得到证实，ACE2可能成为治疗高血压和其他心血管疾病的新靶点。

DESCRIPTION (provided by applicant): The renin-angiotensin system (RAS) is a major regulator of cardiovascular (CV) and renal function in health and disease. Elevated activity and expression of RAS components in central CV control regions and attenuation of the Hypertension with central lesions or administration of angiotensin-II (Ang-II) antagonists have supported the notion that a hyper-functioning brain RAS may be involved in the pathogenesis of Hypertension in several genetic and experimental models. Until now, the common assumption was that Ang-II served as the main actor of this system. A new member of the RAS, ACE2 (angiotensin converting enzyme type 2) has been identified in organs and tissues related to CV function (e.g. heart, kidney, vessels) and appears to be part of a counter-regulatory pathway buffering the excess of Ang-II. We recently identified the ACE2 protein in brain regions involved in the central regulation of blood pressure (BP) and showed that it is regulated by other components of the RAS. In addition, we recently observed that ACE2 over-expression in the subfornical organ (SFO) dramatically reduces the pressor response to central administration of Ang-II in mice and reduces oxidative stress in cells. These observations added to the role of ACE2 in the generation of biologically active peptides like Ang-(1-7), supply a rationale for further explorations in the brain in the face of normal and pathophysiological states. In this proposal, we hypothesize that central ACE2 plays a major compensatory role during Hypertension; ACE2 over-expression will promote Ang-(1-7) formation and Ang-II degradation, resulting in the reinforcement of compensatory mechanisms and preventing Hypertension and the associated oxidative stress. Taking advantage of our expertise in physiological genomics, a science that studies the physiological consequences of gene manipulation, combined to state of the art recording and analysis of CV function in conscious mice, we propose to investigate the consequences of chronic ACE2 over-expression on the development of neurogenic Hypertension. Using a new genetically-engineered mouse model, with brain-targeted ACE2 over- expression, we will: 1) Establish the functional consequences of brain-targeted ACE2 over-expression in neurogenic hypertension. 2) Identify the role of the SFO and RVLM in the ACE2-mediated reduction of Hypertension in Syn- ACE2 transgenic mice and the molecular consequences of their activation. 3) Determine the effects of ACE2 over-expression on Ang-II and Ang-(1-7) receptors signaling pathways. We believe that this unique model will allow us to determine the physiological role of central ACE2 in- vivo in neurogenic Hypertension. Evidence of a beneficial role of ACE2 in BP regulation could lead to the development of new therapeutics as well as a better utilization of existing therapeutics for the treatment of Hypertension and other CV diseases. PUBLIC HEALTH RELEVANCE: Among cardiovascular diseases, worldwide prevalence estimates for Hypertension may be as much as 1 billion individuals, and approximately 7.1 million deaths per year may be attributable to Hypertension. Using transgenic mice, this application will describe the ability of a new enzyme, ACE2, to prevent the development of Hypertension. If confirmed, ACE2 could become a new target for the treatment of Hypertension and other cardiovascular diseases.