Vascular Angiotensin Type-2 Receptor in Normal and Hypertensive Pregnancy

描述（由申请人提供）：在妊娠高血压（HTN-Preg）和子痫前期，观察到肾素-血管紧张素系统的上调和血管紧张素II （AngII）的血管收缩反应增加。虽然肾素-血管紧张素系统在正常妊娠（Norm-Preg）期间上调，但经常观察到血压（BP）降低和血管收缩至AngII的钝化，其中涉及的血管机制尚不清楚。AngII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）诱导血管舒张物质释放，促进血管舒张。本研究的目的是验证at2r介导的信号是妊娠期血管功能和血压的重要调节因子的假设。在正常妊娠期间，血管AT2R的上调导致血管舒张增强，血管收缩减弱，血压降低。AT2R介导的信号表达/活性的降低在HTN-Preg相关的内皮细胞功能障碍和血管收缩中起作用，因此，增加AT2R系统的活性可促进HTN-Preg的血管舒张并降低血压。研究将在未怀孕、正常妊娠的Sprague-Dawley大鼠和妊娠后期子宫灌注压（RUPP）降低产生的HTN-Preg大鼠模型上进行。离体和分子研究将在孤立的肾脏和肠系膜动脉和加压微血管上进行。目的1将确定Norm-Preg期间血压下降和血管舒张增加是否反映了血管AT2R和受体后血管舒张通路的上调。在没有和存在AT2R激动剂和AT1R拮抗剂的情况下，测量血管对AngII和苯肾上腺素的收缩/松弛。血管AT2R将通过RT-PCR、western blot分析和放射标记AT受体结合研究进行定量，并使用免疫组织化学进行定位。测量血管NOS和COX的表达，以及at2r诱导的缓激肽释放、亚硝酸盐/硝酸盐和PGI2的产生以及膜电位。目的2将确定at2r介导的信号表达/活性降低是否在内皮细胞功能障碍和HTN-Preg相关的血管收缩增强中起作用。实验将检验在正常妊娠大鼠长期输注AT2R拮抗剂阻断AT2R是否导致血管舒张降低，血管收缩和血压升高。我们还将检测at2r介导的信号通路和血管舒张通路是否在RUPP大鼠HTN-Preg模型中下调。此外，我们将测试增强AT2R系统的活性是否能促进HTN-Preg的血管舒张并降低血压。这些研究将有助于更好地定义血管AT2R在正常妊娠期间增强血管舒张和降低血压中的作用。该结果也将更好地理解血管AT2R系统在HTN-Preg和先兆子痫发病机制中的变化。

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.