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：
8540426
负责人：
Oleh Pochynyuk
金额：
$ 31.9万
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 2017-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8540426
关键词：
Address Affect Agonist Aldosterone American Angiotensins Animals Attenuated Blood Circulation Blood Pressure Bradykinin Cells Cleaved cell Complement Coupling Data Development Diet 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 epithelial Na+ channel mortality novel paracrine patch clamp receptor response salt intake salt sensitive 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，醛固酮会影响远端肾单位的ENAC活性以调节钠平衡，从而调节血压。这项提议挑战了我们目前对ENAC活动如何通过鉴定与醛固酮独立的这种调节方法来应对饮食盐摄入量变化的看法。具体而言，我们已经开发了证据表明，刺激性ANG II和抑制性心动激肽（BK）级联反应是适当适应ENAC活性以适应饮食钠的变化所必需的。我们的初步工作强烈支持了我们的中心假设，即ANG II直接刺激了哺乳动物醛固酮敏感的远端肾单位（ASDN）中的ENAC介导的Na+ - 重吸收，并且该调节对醛固酮对eNAC的作用无多余。此外，我们假设在钠限制过程中ANG II级联反应的激活通过限制了BK信号在ENAC上的抑制作用，从而进一步增强了ENAC活性。相比之下，BK信号传导对于抑制盐升高期间的ENAC活性是必要的，其功能障碍在缺乏B2受体的小鼠中，由于ENAC活性升高而导致过度Na+保存。重要的是，删除的B2受体的小鼠会产生盐敏感的高血压。为了检验这一假设，我们解决了3个具体目的：1）确定通过全身性盐摄入对醛固酮独立调节ENAC的生理重要性。定义ANG II调节ENAC在此过程中的作用。 2）定义作用机理，并描绘哺乳动物ASDN中ENAC活性的ANG II调节的细胞信号传导途径。 3）确定ANG II和BK信号之间的功能耦合如何响应全身盐的变化来控制ENAC活性，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）斑块夹的测量在开放式开放的鼠远端肾小管中的ENAC活性，并通过Western印迹/RPPA和2 ）在小鼠中使用分子遗传工具评估肾脏Na+排泄的平衡研究，以定义肾脏对醛固酮非依赖性ENAC和钠处理的生理作用。从药理学的角度来看，这项工作的重要性将促使B2激动剂的发展作为矫正远端肾脏钠处理的工具，以控制血压。