Vascular Angiotensin Type-2 Receptor in Normal and Hypertensive Pregnancy

描述(由申请人提供)：在妊娠期高血压(HTN-Preg)和先兆子痫期间观察到肾素-血管紧张素系统的上调和对血管紧张素II(AngII)的血管收缩反应增加。尽管肾素-血管紧张素系统在正常妊娠期间上调(Norm-Preg)，但常可观察到血压降低和血管对Angii的钝性收缩，其中涉及的血管机制尚不清楚。血管紧张素Ⅱ激活血管紧张素1型受体(AT1R)诱导血管收缩，激活血管紧张素2型受体(AT2R)诱导血管扩张物质释放，促进血管松弛。这一建议的目的是验证AT2R介导的信号是怀孕期间血管功能和血压的重要调节因素的假设。在Norm-Preg期间，血管AT2R的上调导致血管松弛增强，血管收缩减弱，血压降低。AT2R介导的信号表达/活性降低在HTN-Preg相关的内皮细胞功能障碍和血管收缩中起作用，因此，AT2R系统的活性增加促进了HTN-Preg的血管扩张和血压下降。研究将在处女、Norm-Preg Spraogue-Dawley大鼠和妊娠晚期降低子宫灌流压力(RUPP)产生的HTN-Preg大鼠模型上进行。体外和分子研究将在分离的肾动脉和肠系膜动脉以及加压的微血管上进行。目的1确定Norm-Preg过程中血压降低和血管扩张增加是否反映了血管AT2R和受体后血管松弛通路的上调。血管对血管紧张素Ⅱ和苯肾上腺素的收缩/松弛将在AT2R激动剂和AT1R拮抗剂的存在和不存在的情况下进行测量。血管AT2R将通过RT-PCR、Western印迹分析和放射性标记的AT受体结合研究进行定量，并使用免疫组织化学进行定位。测定血管一氧化氮合酶和环氧合酶的表达，AT2R诱导的缓激肽释放，亚硝酸盐/硝酸盐和前列腺素I2的产生，以及膜电位。目的2确定AT2R介导的信号通路表达/活性降低是否在HTN-Preg相关的内皮细胞功能障碍和血管收缩增强中起作用。实验将测试在Norm-Preg大鼠中长期注入AT2R拮抗剂阻断AT2R是否会导致血管松弛减少，血管收缩和血压增加。我们还将测试AT2R介导的信号和血管松弛通路在HTN-Preg的RUPP大鼠模型中是否下调。此外，我们还将测试增强AT2R系统的活性是否会促进HTN-Preg的血管扩张和降低血压。这些研究应该有助于更好地确定血管AT2R在Norm-Preg期间增强血管松弛和降低血压方面的作用。这一结果也将有助于更好地了解血管AT2R系统在HTN-Preg和子痫前期发病机制中的变化。 公共卫生相关性：尽管血管紧张素1型受体(AT1R)在血管收缩中的作用已被很好地描述，但血管紧张素2型受体(AT2R)在血管松弛中的作用尚不清楚，尤其是在妊娠期间。这项拨款提案的目的是验证AT2R介导的信号是正常妊娠期间血管功能和血压的重要调节因素的假设。AT2R介导的信号通路的表达/活性降低在妊娠高血压综合征相关的内皮细胞功能障碍和血管收缩中起作用，因此，AT2R系统的活性增加促进了妊娠高血压综合征和先兆子痫患者的血管扩张和血压下降。

DESCRIPTION (provided by applicant): Upregulation of the renin-angiotensin system and increased vasoconstrictive response to angiotensin II (AngII) are observed during hypertension in pregnancy (HTN-Preg) and preeclampsia. Although the renin- angiotensin system is upregulated during normal pregnancy (Norm-Preg), reduction in blood pressure (BP) and blunted vascular contraction to AngII are often observed, and the vascular mechanisms involved are unclear. AngII activates angiotensin type 1 receptor (AT1R) to induce vasoconstriction, and angiotensin type 2 receptor (AT2R) to induce the release of vasodilator substances and promote vascular relaxation. The objective of this proposal is to test the hypothesis that AT2R-mediated signaling is an important regulator of vascular function and BP during pregnancy. During Norm-Preg, upregulation of vascular AT2R leads to enhanced vascular relaxation, blunting of vasoconstriction, and reduction in BP. Decreased expression/activity of AT2R-mediated signaling plays a role in the endothelial cell dysfunction and vasoconstriction associated with HTN-Preg, and consequently, increasing the activity of the AT2R system promotes vasodilation and decreases BP in HTN-Preg. Studies will be performed on virgin, Norm-Preg Sprague-Dawley rats and a rat model of HTN-Preg produced by reduction in uterine perfusion pressure (RUPP) during late pregnancy. Ex vivo and molecular studies will be performed on isolated renal and mesenteric arteries and pressurized microvessels. Aim 1 will determine whether the decreased BP and increased vasodilation during Norm-Preg reflects upregulation of vascular AT2R and postreceptor vascular relaxation pathways. Vascular contraction/relaxation to AngII and phenylephrine will be measured in the absence and presence of AT2R agonists and AT1R antagonists. Vascular AT2R will be quantified using RT-PCR, western blot analysis, and radiolabeled AT receptor binding studies, and localized using immunohistochemistry. Expression of vascular NOS and COX, and the AT2R-induced bradykinin release, nitrite/nitrate and PGI2 production, and membrane potential will be measured. Aim 2 will determine whether decreased expression/activity of AT2R-mediated signaling plays a role in the endothelial cell dysfunction and enhanced vasoconstriction associated with HTN-Preg. Experiments will test whether AT2R blockade by chronically infusing AT2R antagonist in Norm-Preg rats results in decreased vascular relaxation, and increased vasoconstriction and BP. We will also test whether AT2R-mediated signaling and vascular relaxation pathways are downregulated in RUPP rat model of HTN-Preg. Also, we will test whether enhancing the activity of the AT2R system promotes vasodilation and reduces BP in HTN-Preg. These studies should help to define better the role of vascular AT2R in enhancing vascular relaxation and reducing BP during Norm-Preg. The results will also provide a better understanding of the changes in the vascular AT2R system in the pathogenesis of HTN-Preg and preeclampsia. PUBLIC HEALTH RELEVANCE: Although the role of angiotensin Type 1 receptor (AT1R) in vascular contraction is well-characterized, the role of angiotensin Type 2 receptor (AT2R) in vascular relaxation, particularly during pregnancy, is less clear. The objective of this grant proposal is to test the hypothesis that AT2R-mediated signaling is an important regulator of vascular function and BP during normal pregnancy. Decreased expression/activity of AT2R- mediated signaling pathways plays a role in the endothelial cell dysfunction and vasoconstriction associated with hypertension in pregnancy, and consequently, increasing the activity of the AT2R system promotes vasodilation and decreases BP in hypertension in pregnancy and preeclampsia.