Vascular Mechanisms in Pregnancy-Induced Hypertension

描述(申请人提供)：先兆子痫是妊娠的主要并发症，以高血压(HTN)和蛋白尿为特征；然而，其潜在的机制尚不清楚。妊娠晚期大鼠子宫灌注压(RUPP)的降低与HTN、血管收缩增加和松弛减少有关。在寻找RUPP与HTN之间联系的机制中，我们发现晚期妊娠大鼠血浆肿瘤坏死因子水平的升高与血管松弛减少、血管收缩和血压(BP)增加有关。此外，RUPP与血浆中可溶性FMS样酪氨酸激酶-1(sFlt-1)水平的升高有关，怀孕大鼠sFlt-1的慢性升高会导致血压升高。然而，涉及的中央血管靶点尚不清楚。内皮素-1(ET-1)是一种主要的血管收缩因子，与某些形式的HTN相关，包括HTN-Preg。ET-1激活血管平滑肌中的内皮素A受体(ETAR)引起血管收缩，而内皮中的ETBR则引起血管扩张物质的释放。尽管ETAR在血管收缩和HTN中的作用已被广泛研究，但血管ETBR的作用，特别是在妊娠期间，还不太清楚。我们的数据表明，与未成年大鼠相比，Norm-Preg组大鼠肠系膜微血管中ET-1诱导的血管收缩作用减弱，而RUPP大鼠的血管收缩作用增强。此外，ETBR激动剂IRL-1620和Sarafotoxc(S6c)对Norm-Preg大鼠的微血管扩张作用比未成年大鼠和RUPP大鼠更大，表明ETBR介导的松弛通路在Norm-Preg期间上调，在HTN-Preg中减少。这项建议的总体目标是检验ETBR是孕期微血管功能和血压的重要调节器这一中心假设。在Norm-Preg过程中，内皮ETBR上调导致微血管松弛增强，血管收缩和血压降低。ETBR表达/活性降低在血管内皮细胞功能障碍和血管收缩中的作用 HTN-Preg；因此，增加ETBR的活性可以促进HTN-Preg的血管扩张和降压。研究将在处女、Norm-Preg、RUPP、肿瘤坏死因子β和sFlt-1输注怀孕的SD大鼠和ETBR缺陷小鼠上进行。除了测量血压外，还将对加压的肠系膜和子宫微血管进行体外功能研究和体外分子和机制研究。具体目的是测试：1)在Norm-Preg期间，上调血管ETBR是否会导致血管松弛增强，血管收缩减弱，血压下降。2)ETBR表达/活性降低在HTN-Preg引起的内皮功能障碍和血管收缩增强中起一定作用。3)增强ETBR活性是HTN-Preg促进血管扩张和降压的中心靶点。这些研究将有助于明确ETBR在Norm-Preg期间增强血管松弛和降低血压中的作用，有助于更好地了解血管ETBR在HTN-Preg发病机制中的变化，并强调增加ETBR的活性在治疗先兆子痫中的潜在用途。

DESCRIPTION (provided by applicant): Preeclampsia is a major complication of pregnancy characterized by hypertension (HTN) and proteinuria; however, the underlying mechanisms are unclear. Reduction in uterine perfusion pressure (RUPP) in late pregnant rats is associated with HTN, increased vasoconstriction and reduced relaxation. In search for the mechanisms linking RUPP to HTN, we have found that elevation of plasma levels of tumor necrosis factor-¿ (TNF¿) in late-Preg rats is associated with decreased vascular relaxation, and increased vasoconstriction and blood pressure (BP). Also, RUPP is associated with increased plasma levels of soluble fms-like tyrosine kinase-1 (sFlt-1), and chronic elevation of sFlt-1 in pregnant rats causes increases in BP. However, the central vascular targets involved are unclear. Endothelin-1 (ET-1) is a major vasoconstrictor associated with some forms of HTN including HTN-Preg. ET-1 activates endothelin A receptor (ETAR) in vascular smooth muscle to induce vasoconstriction, and ETBR in the endothelium to induce the release of vasodilator substances. Although the role of ETAR in vasoconstriction and HTN has been studied extensively, the role of vascular ETBR, particularly during pregnancy, is less clear. Our data suggest that ET-1 induced vasoconstriction is reduced in mesenteric microvessels of Norm-Preg compared to virgin rats and enhanced in RUPP rats. Also, the ETBR agonists IRL-1620 and sarafotoxin c (S6c) cause greater dilation in microvessels of Norm-Preg than virgin and RUPP rats, suggesting that ETBR-mediated relaxation pathways are upregulated during Norm-Preg and reduced in HTN-Preg. The overall objective of this proposal is to test the central hypothesis that ETBR is an important regulator of microvascular function and BP during pregnancy. During Norm-Preg, upregulation of endothelial ETBR leads to enhanced microvascular relaxation, and reduced vasoconstriction and BP. Decreased expression/activity of ETBR play a role in the endothelial cell dysfunction and vasoconstriction in HTN-Preg; and consequently, increasing the activity of ETBR should promote vasodilation and decrease BP in HTN-Preg. Studies will be performed on virgin, Norm-Preg, RUPP, TNF¿- and sFlt-1 infused pregnant Sprague-Dawley rats and ETBR-deficient mice. In addition to measuring BP, ex vivo functional studies and in vitro molecular and mechanistic studies will be performed on pressurized mesenteric and uterine microvessels. The specific aims are to test whether: 1) During Norm-Preg, upregulation of vascular ETBR leads to enhanced vascular relaxation, blunting of vasoconstriction, and reduction in BP. 2) Decreased expression/activity of ETBR play a role in the endothelial dysfunction and enhanced vasoconstriction associated with HTN-Preg. 3) Enhancing ETBR activity is a central target to promote vasodilation and reduce BP in HTN-Preg. These studies should help define the role of ETBR in enhancing vascular relaxation and reducing BP during Norm-Preg, provide a better understanding of the changes in the vascular ETBR in the pathogenesis of HTN-Preg, and highlight the potential usefulness of increasing the activity of ETBR in the management of preeclampsia.