CELLULAR MECHANISMS FOR ANGIOTENSIN RESPONSES IN BRAIN

中枢肾素-血管紧张素系统（RAS）参与了对 动脉压 血管紧张素II受体存在于神经元上， 星形胶质细胞和血管成分，并可能在这种调节中合作。 在当前的资助期间，我们表明：1）区域特定 星形胶质细胞差异性地含有高亲和力的血管紧张素II受体， 高亲和力内化位点; 2）这些受体是差异性的 偶联磷脂酶C和前列环素的释放; 3）Ang II 差异调节血管紧张素原mRNA的表达 （Aogen）在区域特异性星形胶质细胞中，可能受核内 与内化的血管紧张素II受体偶联的血管紧张素II受体 对磷脂酶C的敏感性降低， 高血压（mRen-2）大鼠27只。 在本申请中，这些研究 将扩大到确定神经胶质RAS在病理学中的作用， 使用高血压大鼠模型， RAS过度表达。 建立了（mRen-2）27转基因（TG）大鼠 通过将小鼠下颌下的肾素基因插入到大鼠基因组中。 转基因和升高的Ang II水平存在于TG大鼠脑中， 与血压正常的对照组相比。 而髓质中的血管紧张素II受体 与对照组相比，TG大鼠的下丘脑和下丘脑中的Ang II-诱导的下丘脑加压素释放减弱， 这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 我们推测，高表达的Threnin 转基因TG大鼠脑内Ang II水平升高， 星形胶质细胞产生Aogen。 我们进一步假设AT 1 从TG大鼠脑分离的星形胶质细胞上的受体被脱敏， 导致纤溶酶原激活物抑制剂-1（派-1）分泌减少， 1)以及从原肾素产生活性肾素的增加。 这导致 Aogen和活性肾素的过量产生，产生升高的Ang水平 第二，交感神经流出增加，血压升高。 在 在本申请中，我们建议证明Ang II水平是 在从TG大鼠脑中分离的培养星形胶质细胞中升高， renin的表达。 我们将确定AT 1受体是否 通过升高的Ang II水平脱敏，导致降低 生产派-1。 此外，我们将确定Aogen mRNA是否 TG大鼠血管紧张素II水平升高不影响其表达 星形胶质细胞，以及这是否通过激活核血管紧张素II 受体的 最后，我们将证明等离子体的脱敏 TG大鼠星形胶质细胞膜AT 1受体和Aogen的过度表达， 通过降低内源性Ang II水平或通过阻断AT 1 受体。 这些研究将扩展我们对 中心RAS在血压调节中的作用，并提供了对 内源性高血压的病理学 血管紧张素II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.