Cellular Regulation of Angiotensin Converting Enzyme 2

描述(申请人提供)：几十年的研究已经确定肾素-血管紧张素系统是血压、体内平衡和细胞增殖的主要调节因素。肾素-血管紧张素系统的作用是通过血管紧张素II(Ang II)和血管紧张素-(1-7)[Ang-(1-7)](血管扩张剂和生长抑制物)的相反作用介导的。血管紧张素转换酶2(ACE2)是血管紧张素转换酶(ACE)的同系物，优先由Ang II生成Ang-(1-7)。高血压大鼠肾脏中ACE2表达减少，提示其参与了Ang-(1-7)与Ang-(1-7)的平衡。虽然ACE2最初定位于心脏、肾脏和睾丸等外周器官，但我们在新生和成年SD大鼠以及培养的神经元和星形胶质细胞的不同脑区发现了ACE2的mRNA和蛋白。此外，我们还证明了血管紧张素转换酶II处理培养的神经元和星形胶质细胞后，血管紧张素转换酶2的mRNA和蛋白显著减少。在令人兴奋的新结果中，我们发现抑制ACE2减少了对心率的压力感受性反射控制，这表明ACE2的调节和Ang II/Ang-(1-7)比例的变化在中枢控制血压中起着关键作用。我们认为ACE2是脑内AngⅡ/Ang-(1-7)浓度平衡的主要调节因子。在具体目标1中，我们将确定Ang II是否调节表达多肽浓度改变的转基因大鼠脑内ACE2mRNA和蛋白，以及这些大鼠的压力感受性反射对心率的控制是否改变或ACE2活性受到抑制。特异性目标2的研究将集中在培养的星形胶质细胞分泌ACE2，以评估其底物特异性，并确定培养的星形胶质细胞和神经元以及完整脑片分泌ACE2的分子机制。最后，在特定的目标3中，我们将确定ACE2在星形胶质细胞和神经元中的转录调节因子。相关性：ACE2优先将Ang II转化为Ang-(1-7)，这是一种在中枢控制血压中具有相反作用的多肽。ACE2的调节可能是维持大脑中肾素-血管紧张素系统正常功能的关键。

DESCRIPTION (provided by applicant): Decades of research have established the renin-angiotensin system as a major regulator of blood pressure, homeostasis, and cell proliferation. Renin-angiotensin system effects are mediated by the opposing actions of the peptides angiotensin II (Ang II), a potent vasoconstrictor and mitogen, and angiotensin-(1-7) [Ang-(1- 7)], a vasodilator and growth inhibitor. Angiotensin-converting enzyme 2 (ACE2) recently was identified as a homologue of ACE that preferentially forms Ang-(1-7) from Ang II. Reduced ACE2 expression in the kidney of hypertensive rats suggests its contribution to the balance of Ang II to Ang-(1-7). Although ACE2 was initially localized in peripheral organs such as heart, kidney and testis, we identified ACE2 mRNA and protein in distinct brain regions from both neonatal and adult Sprague-Dawley rats as well as cultured neurons and astrocytes. Further, we demonstrated that treatment of cultured neurons and astrocytes with Ang II caused a marked reduction in ACE2 mRNA and protein. In exciting new results, we showed that inhibition of ACE2 reduced baroreflex control of heart rate, suggesting that the regulation of ACE2 and alterations in the ratio of Ang II to Ang-(1-7) is critical in central control of blood pressure. We propose that ACE2 serves as a major regulator of the balance of Ang ll/Ang-(1-7) concentration in the brain. In Specific Aim 1, we will ascertain whether Ang II regulates ACE2 mRNA and protein in the brain of transgenic rats expressing altered peptide concentrations and whether baroreflex control of heart rate is altered in these rats or following inhibition of ACE2 activity. Studies in Specific Aim 2 will focus on ACE2 secreted from cultured astrocytes, to assess its substrate specificity and determine the molecular mechanism of ACE2 secretion from cultured astrocytes and neurons and from intact brain slices. Finally, in Specific Aim 3, we will identify the transcriptional regulators of ACE2 in astrocytes and neurons. Relevance: ACE2 preferentially converts Ang II to Ang-(1-7), peptides which have opposing actions in the central control of blood pressure. The regulation of ACE2 may be critical to maintaining the normal function of the renin-angiotensin system in the brain.