Endogenous cardiotonic hormones in kidney disease and hypertension

描述（由申请人提供）：最近的发现已经确定，Na，K-ATP酶除了其作为离子泵的众所周知的作用之外，还作为内源性强心类固醇（CTS）激素的重要激素受体。CTS与Na，K-ATP酶上高度保守的CTS受体相互作用，以调节肾盐处理、血压以及肾、心脏和脉管系统中的组织重塑。强心类固醇的循环水平在广泛的高血压疾病中升高，并与血压直接相关。慢性血压升高会导致肾脏重塑和肾衰竭。该提议解决了该领域中的两个关键空白：1）仅少数在体内介导这些作用的强心类固醇（CTS）激素已在结构上被鉴定;以及2）强心类固醇的组织储存的作用完全未知，尽管它们占哺乳动物中总CTS含量的> 99%。具体目的1是纯化和结构表征一种新的哺乳动物强心激素从肾脏获得。这些假说认为，哺乳动物中存在新型强心激素，它们具有独特的化学结构，这是它们在肾脏、心脏和血管系统中发挥不同作用的基础。该化合物将使用一种创新的、基于酶受体亲和力的方法进行纯化，其结构将与麦迪逊的国家磁共振设施合作，使用高场强低温NMR进行表征。具体目标2是研究强心激素组织库在血压急性调节中的生理作用。其他研究表明，压力或运动会使血浆中的CTS浓度产生巨大的急性变化。这表明，CTS可以作为一种快速调节的激素来响应改变的需求。值得注意的是，血浆CTS的运动应激源增加是慢性高血压中发现的稳定升高的数百倍，并且它与血压的急性变化直接相关。这种增加是太快，太大，不能占的内容，肾上腺中的CTS，并建议，必须存在额外的存储和释放网站。目的2的假设是强心类固醇的组织储存有助于对急性应激源的血压调节。该方法将是测量血压和强心类固醇的血浆浓度在体育锻炼或诱发的肌肉收缩，在野生型和基因靶向小鼠具有耗尽的组织存储由于改变的亲和力或其受体在Na，K-ATP酶的表达。总的来说，该项目将提供一种新的哺乳动物肾脏激素的确定结构，以及对CTS激素组织储存在急性血压调节中的作用的更完整的理解。这一贡献将产生重要影响，因为它将导致对强心激素及其受体在肾脏疾病和血压调节中的新思维方式，并使未来研究其作为高血压治疗靶点的潜力成为可能。

DESCRIPTION (provided by applicant): Recent discoveries have established that the Na,K-ATPase, in addition to its well known role as an ion pump, serves as an important hormone receptor for endogenous cardiotonic steroid (CTS) hormones. CTSs interact with the highly conserved CTS receptor on the Na,K-ATPase to regulate renal salt handling, blood pressure, and tissue remodeling in the kidney, heart and vasculature. Circulating levels of cardiotonic steroids are elevated in a wide range of hypertensive disorders and correlate directly with blood pressure. Chronically elevated blood pressure leads to kidney remodeling and renal failure. This proposal addresses two critical gaps in the field: 1) only a few of the cardiotonic steroid (CTS) hormones which mediate these actions in vivo have been structurally identified; and 2) the role of the tissue stores of cardiotonic steroids is completely unknown, although they comprise > 99% of the total CTS content in mammals. Specific Aim 1 is to purify and structurally characterize a novel mammalian cardiotonic hormone obtained from kidney. The hypotheses is that novel cardiotonic hormones are present in mammals and have distinct chemical structures which underlie their diverse actions in the kidney, heart and vasculature. This compound will be purified using an innovative, enzyme receptor affinity-based method, and its structure will be characterized using high field-strength cryo-NMR, in collaboration with the National Magnetic Resonance Facility at Madison. Specific Aim 2 is to investigate the physiological role of the tissue stores of cardiotonic hormone in the acute regulation of blood pressure. Other studies have shown that stress or exercise produces large, acute changes in the plasma concentration of CTSs. This demonstrates that CTSs can behave as a rapidly regulated hormone in response to altered demand. Notably, the exercise stressor increase in plasma CTS is hundreds fold greater than the steady elevation found in chronic hypertension and it correlates directly with acute changes in blood pressure. This increase is too rapid and large to be accounted for by the content of CTS in adrenals, and suggests that additional storage and release sites must exist. The hypothesis for Aim 2 is that the tissue stores of cardiotonic steroids contribute to blood pressure regulation in response to acute stressors. The approach will be to measure blood pressure and plasma concentrations of cardiotonic steroids during physical exercise or evoked muscle contraction, in wild-type and gene targeted mice having depleted tissue stores due to altered affinity or expression of its receptor on Na,K-ATPase. Overall, this project will provide the definitive structure of one novel mammalian hormone from kidney, and a more complete understanding of the role of the tissue stores of CTS hormones in acute blood pressure regulation. This contribution will have an important impact because it will lead to new ways of thinking about the cardiotonic hormones and their receptors in kidney disease and blood pressure regulation, and enable future studies of their potential as therapeutic targets for hypertension.