Endogenous cardiotonic hormones in kidney disease and hypertension

描述(由申请人提供)：最近的发现证明，Na，K-ATPase除了作为离子泵的众所周知的作用外，还是内源性强心类固醇(CTS)激素的重要激素受体。CTSS与Na，K-ATPase上高度保守的CTS受体相互作用，调节肾脏的盐处理、血压和肾脏、心脏和血管系统的组织重塑。强心性类固醇的循环水平在多种高血压疾病中升高，并与血压直接相关。慢性高血压会导致肾脏重塑和肾功能衰竭。这项建议解决了该领域的两个关键空白：1)只有少数在体内介导这些作用的强心类固醇(CTS)激素已被结构鉴定；2)强心类固醇组织储存的作用完全未知，尽管它们占哺乳动物总CTS含量的99%。具体目的1是从肾脏中分离纯化一种新的哺乳动物强心激素，并对其结构进行鉴定。假设是新的强心激素存在于哺乳动物中，并具有不同的化学结构，这是它们在肾脏、心脏和血管系统中不同作用的基础。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，并将与位于麦迪逊的国家磁共振设施合作，使用高场强低温核磁共振对其结构进行表征。具体目的2是研究强心激素的组织储存在血压急性调节中的生理作用。其他研究表明，压力或运动会导致血浆中CTS浓度的大幅、急剧变化。这表明，CTS可以作为一种快速调节的激素，对变化的需求做出反应。值得注意的是，运动应激源在血浆CTS中的增加是慢性高血压患者稳定升高的数百倍，而且它与血压的急性变化直接相关。这一增加太快太大，不能用肾上腺中CTS的含量来解释，这表明必须存在更多的储存和释放场所。目标2的假设是，强心类固醇的组织储存有助于血压调节，以应对急性应激源。该方法将测量在体育锻炼或诱发肌肉收缩期间的血压和强心类固醇的血浆浓度，在野生型和基因靶向的小鼠中，由于其受体在Na，K-ATPase上的亲和力或表达改变而导致组织存储耗尽。总体而言，该项目将提供一种来自肾脏的新的哺乳动物激素的确定结构，并更全面地了解CTS激素的组织储存在急性血压调节中的作用。这一贡献将产生重要影响，因为它将引导人们以新的方式思考强心激素及其受体在肾脏疾病和血压调节中的作用，并使未来能够研究它们作为高血压治疗靶点的潜力。

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.