Aldosterone-independent regulation of ENaC by systemic salt

全身盐对 ENaC 的不依赖醛固酮的调节

基本信息

批准号：
8908002
负责人：
Oleh Pochynyuk
金额：
$ 33.06万
依托单位：
UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-09-05 至 2016-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8908002
关键词：
Address Affect Agonist Aldosterone American Angiotensins Animals Attenuated Blood Circulation Blood Pressure Bradykinin Cells Cleaved cell Complement Coupling Data Development Dietary Sodium Distal Duct (organ) structure Electrophysiology (science)Enzyme Inhibition Equilibrium Excretory function Functional disorder Genetic Human Hypertension Immunohistochemistry Intake Kidney Kininogenase Kinins Measurement Mediating Molecular Genetics Morbidity - disease rate Mus Nephrons Peptides Peptidyl-Dipeptidase A Physiological Population Positioning Attribute Potassium Process Publishing Regulation Renin-Angiotensin-Aldosterone System Role Scheme Signal Pathway Signal Transduction Sodium Sodium Chloride System Testing Urine Variant Western Blotting Work blood pressure regulation dietary salt epithelial Na+ channel mortality novel paracrine patch clamp receptor response salt intake salt sensitive hypertension tool urinary wasting

项目摘要

DESCRIPTION (provided by applicant): It is well known that aldosterone affects ENaC activity in the distal nephron to regulate sodium balance and, consequently blood pressure. This proposal challenges our current view on how ENaC activity responds to variations in dietary salt intake by identifying aldosterone-independent means of this regulation. Specifically, we have developed evidence that coordinated coupling between stimulatory Ang II and inhibitory Bradykinin (BK) cascades is necessary for proper adaptation of ENaC activity to variations in dietary sodium. Our preliminary work strongly supports our central hypothesis that Ang II directly stimulates ENaC-mediated Na+- reabsorption in the mammalian aldosterone-sensitive distal nephron (ASDN) and this regulation is non- redundant to aldosterone actions on ENaC. In addition, we hypothesize that the activation of Ang II cascade during sodium restriction further augments ENaC activity by limiting inhibitory actions of BK signaling on ENaC. In contrast, BK signaling is necessary to suppress ENaC activity during elevated salt intake with its dysfunction in mice lacking B2 receptors causing excessive Na+ conservation as a result of elevated ENaC activity. Importantly, mice with deleted B2 receptors develop salt-sensitive hypertension. To test this hypothesis we address 3 specific aims: 1) Establish the physiological importance of aldosterone-independent regulation of ENaC by systemic salt intake. Define the role of Ang II regulation of ENaC in this process. 2) Define the mechanism of action and delineate the cellular signaling pathway of Ang II regulation of ENaC activity in mammalian ASDN. 3) Determine how functional coupling between Ang II and BK signaling cascades controls ENaC activity in response to changes in systemic salt and establish the patho-physiological consequences of disrupting this regulation in B2 -/- mice. Our experimental approach ranges from electrophysiology in native distal nephron cells to whole animal balance studies and will combine 1) patch clamp measurements of ENaC activity in the split-open murine distal nephrons with ENaC expression levels probed by western blotting/RPPA and immunohistochemistry, and 2) balance studies to assess renal Na+ excretion with molecular genetic tools in mice to define a physiological role of aldosterone-independent regulation of ENaC and sodium handling by the kidney. From a pharmacological standpoint, the importance of this work will urge the development of B2 agonists as tools for correction of sodium handling in the distal nephron to control blood pressure.

描述（由申请人提供）：众所周知，醛固酮影响远端肾单位中的 ENaC 活性，以调节钠平衡，从而调节血压。该提案通过确定与醛固酮无关的调节方式，挑战了我们目前关于 ENaC 活性如何响应膳食盐摄入量变化的观点。具体来说，我们已经证明，刺激性血管紧张素II和抑制性缓激肽（BK）级联之间的协调耦合对于 ENaC 活性适当适应膳食钠的变化是必要的。我们的初步工作有力地支持了我们的中心假设，即Ang II直接刺激哺乳动物醛固酮敏感远端肾单位（ASDN）中ENaC介导的Na+重吸收，并且这种调节对于ENaC上的醛固酮作用是非冗余的。此外，我们假设钠限制期间 Ang II 级联的激活通过限制 BK 信号对 ENaC 的抑制作用进一步增强 ENaC 活性。相比之下，BK 信号传导对于在盐摄入量增加期间抑制 ENaC 活性是必要的，而在缺乏 B2 受体的小鼠中，BK 信号传导功能障碍会导致 ENaC 活性升高而导致过度的 Na+ 保守。重要的是，B2 受体缺失的小鼠会出现盐敏感性高血压。为了检验这一假设，我们提出了 3 个具体目标：1) 确定全身盐摄入对 ENaC 的独立醛固酮调节的生理重要性。定义 Ang II 调节 ENaC 在此过程中的作用。 2) 明确哺乳动物 ASDN 中 Ang II 调节 ENaC 活性的作用机制并描绘细胞信号通路。 3) 确定 Ang II 和 BK 信号级联之间的功能耦合如何控制 ENaC 活性以响应全身盐的变化，并确定破坏 B2 -/- 小鼠中这种调节的病理生理后果。我们的实验方法范围从天然远端肾单位细胞的电生理学到整个动物平衡研究，并将结合 1) 膜片钳测量劈开的小鼠远端肾单位中的 ENaC 活性与通过蛋白质印迹/RPPA 和免疫组织化学探测的 ENaC 表达水平，以及 2 ) 平衡研究，利用分子遗传学工具评估小鼠肾 Na+ 排泄，以确定 ENaC 的醛固酮独立调节和肾脏钠处理的生理作用。从药理学的角度来看，这项工作的重要性将推动 B2 激动剂的发展，作为纠正远端肾单位钠处理以控制血压的工具。