Calcium and Sodium Transport in Hypertension

描述（由申请人提供）：盐潴留和随之而来的血浆容量扩张不可避免地导致血压（BP）升高，在慢性状态（高血压）下，血压（BP）升高是通过外周血管总阻力（TPR）增加来维持的。令人惊讶的是，盐潴留增加TPR和BP的“信号通路”尚未得到解决。我们的目标是通过小鼠模型阐明盐潴留与高血压之间的特定分子机制，因为盐依赖性高血压在人类和啮齿动物中是相似的。我们将使用药理学工具和基因工程小鼠来验证以下假设：i)内源性瓦阿因（EO）， ii)用（瓦阿因敏感的，S） a2催化亚基抑制动脉Na+泵的活性，以及iii)通过动脉Na- ca交换器-1 （NCX1）增加Ca2+进入是信号通路的关键步骤。具体目标涉及三个子假设：1)转基因g蛋白偶联受体激酶-4 [GRK4？（A486V）]是由EO、a2 Na+泵和NCX1介导的。膳食盐对非转基因GRK4？和盐敏感的GRK4？(A486V)老鼠。Digibind（结合瓦巴因的抗体）、PST-2238（瓦巴因拮抗剂）和SEA0400 （NCX1阻滞剂）以及a2 Na+泵的敲除或NCX1表达的降低对盐依赖性血压升高的影响(？BP)将被确定。2)降低a2 Na+泵表达会增加盐敏感性，并且盐依赖性？BP由作用于a2 Na+泵的EO和NCX1介导。在WT （a2S/S）小鼠和具有1个零突变a2等位基因（a2S/-）的小鼠中，测定膳食盐对血浆EO和BP的影响。Digibind、PST-2238、SEA0400和NCX1表达降低对盐依赖性？英国石油公司。3)平滑肌（sm）特异性NCX1.3过表达引起的盐敏感性与对瓦巴因的过敏相关，并因a2 Na+泵丰度降低而增强。在WT小鼠和smNCX1.3过表达小鼠（NCX1.3smTg/Tg）中测定膳食盐对血浆EO和BP的影响；Digibind和PST-2238的作用，以及sm-a2泵表达的下调，将在盐依赖性？英国石油公司。我们将在WT、NCX1.3smTg/Tg和sm特异性NCX1敲除小鼠中比较输注乌巴因和血管紧张素II对BP的影响。结果将阐明盐与高血压之间的一些关键机制，为人类研究提供路线图，并将确定新的治疗靶点。

DESCRIPTION (provided by applicant): Salt retention and consequent plasma volume expansion inevitably cause elevation of blood pressure (BP) which, in the chronic state (hypertension), is sustained by increased total peripheral vascular resistance (TPR). Surprisingly, the "signaling pathway" by which salt retention increases TPR and BP is unresolved. Our goal is to elucidate the specific molecular mechanisms that link salt retention to hypertension using mouse models because salt-dependent hypertension is similar in humans and rodents. We will employ pharmacological tools and genetically-engineered mice to test the hypothesis that: i) Endogenous ouabain (EO), ii) Inhibited activity of arterial Na+ pumps with a (ouabain-sensitive, S) a2 catalytic subunit, and iii) Increased Ca2+ entry via arterial Na-Ca exchanger-1 (NCX1) are key steps in the signaling pathway. The Specific Aims address three sub-hypotheses: 1) That salt-dependent hypertension in mice with transgenic G-protein coupled receptor kinase-4 [GRK4?(A486V)] is mediated by EO, a2 Na+ pumps, and NCX1. The effects of dietary salt on plasma EO and BP will be measured in non-transgenic GRK4? and salt-sensitive GRK4?(A486V) mice. The effects of Digibind (antibodies that bind ouabain), PST-2238 (ouabain antagonist) and SEA0400 (NCX1 blocker), and of knock-down of a2 Na+ pump or reduced NCX1 expression, on the salt-dependent rise in BP (?BP) will be determined. 2) That reduced a2 Na+ pump expression increases salt-sensitivity, and that salt-dependent ?BP is mediated by EO acting on a2 Na+ pumps, and by NCX1. The effects of dietary salt on plasma EO and BP will be measured in WT (a2S/S) mice and mice with one null mutant a2 allele (a2S/-). The effects of Digibind, PST-2238, SEA0400 and reduced NCX1 expression will be tested on the salt-dependent ?BP. 3) That salt sensitivity due to smooth muscle (sm)-specific NCX1.3 overexpression correlates with hypersensitivity to ouabain and is augmented by reduced a2 Na+ pump abundance. The effects of dietary salt on plasma EO and BP will be measured in WT mice and mice that overexpress smNCX1.3 (NCX1.3smTg/Tg); the effects of Digibind and PST-2238, and of knock-down of sm-a2 pump expression, will be tested on salt-dependent ?BP. The effects of ouabain and angiotensin II infusion on BP will be compared in WT, NCX1.3smTg/Tg, and sm-specific NCX1 knockout mice. The results will elucidate some key mechanisms that link salt to hypertension, will provide a roadmap for human studies, and will pinpoint new therapeutic targets. PUBLIC HEALTH RELEVANCE: The goal of this project is to determine the specific mechanisms by which ingestion of excess salt raises blood pressure. We will study proposed steps in the pathway that links salt to hypertension by using genetically-modified mice in which these steps are augmented or suppressed. The results will elucidate key mechanisms that participate in this salt-hypertension pathway in humans as well as in rodents, will provide a roadmap for human studies, and will identify new targets for drug therapy.