CELLULAR MECHANISMS FOR ANGIOTENSIN RESPONSES IN BRAIN

中枢性肾素-血管紧张素系统(RAS)参与血管紧张素转换酶的调控 动脉压。神经元上存在血管紧张素(Ang)II受体， 星形胶质细胞和血管分子，并可能在这一调节中合作。 在本供资期间，我们表明：1)具体区域 星形胶质细胞不同地含有高亲和力的Ang II受体和 高亲和力内化部位；2)这些受体是不同的 偶联磷脂酶C与前列环素的释放；3)血管紧张素Ⅱ 差异性调控血管紧张素原基因的表达 (Aogen)在区域特异性星形胶质细胞中，可能受核调控 血管紧张素Ⅱ受体对内化的血管紧张素Ⅱ受体的反应 分离的星形胶质细胞对磷脂酶C不敏感 高血压(MREN-2)大鼠27只。在目前的应用中，这些研究 将被扩展以确定胶质RAS在病理生物学中的作用 使用这个高血压大鼠模型，在这个模型中，中枢 RAS基因过度表达。建立了(MREN-2)27转基因(TG)大鼠 通过将小鼠下颌下肾素基因插入大鼠基因组。 转基因和血管紧张素转换酶II水平升高存在于转基因大鼠脑内 与血压正常的对照组相比。而延髓中的血管紧张素Ⅱ受体 与对照组相比，TG组大鼠的下丘脑和 II诱导的下丘脑加压素释放在 与我们观察到的磷脂酶C活性降低一致 培养的星形胶质细胞。我们假设TH肾素的过度表达 转基因TG大鼠脑内血管紧张素Ⅱ及其上调水平的研究 星形胶质细胞产生Aogen的过程。我们进一步假设AT1 从TG大鼠脑分离的星形胶质细胞上的受体是脱敏的， 导致纤溶酶原激活物抑制物-1(PAI-1)分泌减少 1)和从原肾素产生活性肾素的增加。这将导致 血管紧张素原和活性肾素过度产生，血管紧张素转换酶水平升高 II，交感神经流出增加和血压升高。在……里面 在本申请中，我们建议演示Ang II水平是 TG大鼠脑内培养星形胶质细胞因过度刺激而升高 肾素的表达。我们将确定AT1受体是否 因血管紧张素Ⅱ水平升高而脱敏，导致 PAI-1的生产。此外，我们还将确定Aogen mRNA是否 TG大鼠血管紧张素转换酶II水平升高对其表达无调节作用 星形胶质细胞及其是否通过激活核血管紧张素II而发生 受体。最后，我们将演示血浆的脱敏作用 膜AT1受体与TG大鼠星形胶质细胞Aogen的过度表达 通过降低内源性血管紧张素Ⅱ水平或阻断血管紧张素转换酶1来预防 感受器。这些研究将扩大我们对 中枢RAS在血压调节中的作用并提供对 内源性水平不同的高血压病患者的病理 血管紧张素Ⅱ的水平升高。

The central renin-angiotensin system (RAS) participates in the control of arterial pressure. Angiotensin (Ang) II receptors are present on neurons, astrocytes and vascular elements and likely cooperate in this regulation. During the current funding period, we showed that 1) region-specific astrocytes differentially contain high affinity Ang II receptors and a high affinity internalization site; 2) these receptors are differentially coupled to phospholipase C and the release of prostacyclin; 3) Ang II differentially regulates expression of the mRNA for angiotensinogen (Aogen) in region-specific astrocytes, which may be regulated by a nuclear Ang II receptor that responds to the internalized Ang II receptors coupled to phospholipase C are desensitized in astrocytes isolated from hypertensive (mRen-2)27 rats. In the current application, these studies will be expanded to identify the role of the glial RAS in the pathobiology of hypertension, using this hypertensive rat model in which the central RAS is overexpressed. The (mRen-2) 27 transgenic (TG) rat was developed by insertion of the mouse submandibular renin gene into the rat genome. The transgene and elevated levels of Ang II are present in TG rat brain as compared to normotensive controls. While Ang II receptors in the medulla and hypothalamus are similar in the TG rat as compared to controls, Ang II-induced vasopressin release from the hypothalamus is attenuated in agreement with the reduced phospholipase C activity that we observe in cultured astrocytes. We hypothesize that overexpression of th renin transgene in TG rat brain elevates the levels of Ang II and upregulates the production of Aogen by astrocytes. We further hypothesize that AT1 receptors on astrocytes isolated from TG rat brain are desensitized, resulting in reduced secretion of plasminogen activator inhibitor-1 (PAI- 1) and elevated production of active renin from prorenin. This results in overproduction of Aogen and active renin, producing elevated levels of Ang II, increased sympathetic outflow and an increase in blood pressure. In this application, we propose to demonstrate that Ang II levels are elevated in cultured astrocytes isolated from TG rat brain due to over- expression of renin. We will determine whether AT1 receptors are desensitized by the elevated levels of Ang II, leading to decreased production of PAI-1. Furthermore, we will determine whether Aogen mRNA expression is un-regulated by the elevated levels of Ang II in TG rat astrocytes and whether this occurs through activation of a nuclear Ang II receptor. Finally, we will demonstrate that desensitization of the plasma membrane AT1 receptor and overexpression of Aogen in TG rat astrocytes can be prevented by reducing endogenous Ang II levels or by blocking AT1 receptors. These studies will extend our understanding of the role of the central RAS in blood pressure regulation and provide insight into the pathology of forms of essential human hypertension where endogenous levels of Ang II are elevated.