Regulation of K+ balance by distal nephron TRPV4 channel

远端肾单位 TRPV4 通道对 K 平衡的调节

基本信息

批准号：
10203950
负责人：
Oleh Pochynyuk
金额：
$ 34.65万
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：
2018
资助国家：
美国
起止时间：
2018-09-18 至 2023-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10203950
关键词：
Acid-Base Equilibrium Address Animal Model Animals Arrhythmia Cardiovascular system Cells Chronic Kidney Failure Clinical Development Diet Dietary Potassium Distal Duct (organ) structure Electrolytes Electrophysiology (science)Epithelial Cells Equilibrium Excretory function Fruit Functional disorder Genetic H(+)-K(+)-Exchanging ATPase Homeostasis Human Hyperaldosteronism Hypokalemia Image Ingestion Intake Kidney Life Maintenance Measurement Mediating Microscopy Molecular Monitor Mus Muscle Nephrons Neurons Osmolar Concentration Pathology Permeability Pharmacology Physiological Physiology Potassium Process Publishing Regimen Regulation Renal function Rodent Role Scheme Signal Transduction Site Testing Tissues Tubular formation Urine Vanilloid Variant Water base cardiovascular health dietary manipulation extracellular genetic manipulation hyperkalemia knockout animal large-conductance calcium-activated potassium channels novel strategies patch clamp receptor recruit response urinary

项目摘要

SUMMARY Tight regulation of K+ balance is fundamental for normal physiology. Disturbed K+ homeostasis is associated with a wide spectrum of cardiovascular- and kidney-related pathologies. The distal nephron (DN), including the connecting tubule (CNT) and the collecting duct (CD), is the major site of controlled potassium transport in the kidney, which is essential to match urinary K+ excretion to varying dietary K+ intake. In this proposal, we posit that the mechanosensitive Ca2+-permeable TRPV4 channel abundantly expressed in the DN is a critical determinant of renal potassium handling capable of stimulating flow-dependent K+ secretion via maxi-K (BK) channel and inhibiting H+-K+ ATPase-dependent K+ reabsorption. We generated abundant supportive evidence that the TRPV4 activity in the DN is regulated by dietary potassium intake with its dysfunction causing significant distortions of systemic K+ balance. TRPV4 -/- mice have a markedly reduced BK channel activity in the DN and develop hyperkalemia when dietary potassium intake is high. On the contrary, TRPV4 deletion augments H+-K+ ATPase activity and protects against hypokalemia when dietary potassium intake is low. Overall, we hypothesize that TRPV4 serves as a physiologically relevant kaliuretic factor during adaptations to dietary potassium regimen by stimulating BK-mediated K+ secretion and inhibiting H+-K+ ATPase-dependent K+ reabsorption. To address this central hypothesis, we developed three specific aims: SA1: Examine molecular and signaling determinants of TRPV4 regulation in the DN by dietary K+ intake. SA2: Establish the importance of TRPV4 function for BK-mediated K+ secretion in the DN and define pathophysiological ramifications of its disruption on systemic K+ balance. SA3: Explore the mechanism and relevance of regulation of K+ reabsorption in the DN by TRPV4. To bring this project to fruition, we recruit strong collaborative expertise and implement a comprehensive experimental arsenal which involves monitoring TRPV4 and BK channels activity with patch clamp electrophysiology, intracellular Ca2+ and H+-K+ ATPase-mediated pH measurements, confocal immunofluorescent microscopy in native DN cells of rodents and humans, balance studies upon manipulation of dietary K+ intake in conventional and genetically manipulated animals. Overall, we expect to directly demonstrate the physiological relevance of mechanosensitive TRPV4 channel in the DN at the systemic level and will define pathophysiological ramifications of TRPV4 dysfunction on systemic K+ homeostasis. Furthermore, this will urge development of novel strategies based on targeting TRPV4 to manage life-threatening states of hyper- and hypokalemia in clinical setting.

概括 K+平衡的严格调节对于正常生理学是基础。不安的K+稳态是相关的具有广泛的心血管和肾脏相关病理。远端肾单位（DN），包括连接小管（CNT）和收集管（CD）是受控钾转运的主要部位肾脏，这对于将尿液K+排泄与不同的饮食K+摄入量相匹配至关重要。在此提案中，我们认为在DN中大量表达的机械敏感Ca2+可渗透的TRPV4通道是关键肾脏钾处理的决定因素，能够通过Maxi-K（BK）刺激流动依赖的K+分泌通道和抑制H+ -K+ ATPase依赖性K+重吸收。我们产生了丰富的支持证据 DN中的TRPV4活性受膳食钾摄入量调节，其功能障碍会引起明显系统性K+平衡的扭曲。 TRPV4 - / - 小鼠在DN中的BK通道活性明显降低，并且当饮食中钾摄入量很高时，会发展高钾血症。相反，TRPV4删除增加H+-K+ 当饮食中的钾摄入量低时，ATPase活性并预防低钾血症。总体而言，我们假设该TRPV4在适应饮食钾方案期间是生理上相关的kaliuretic因子通过刺激BK介导的K+分泌并抑制H+ -K+ ATPase依赖性K+重吸收。为了解决这一中心假设，我们开发了三个具体目标：SA1：检查分子和通过饮食K+摄入量，TRPV4调控的信号传导决定因素。 SA2：建立 TRPV4功能对DN中BK介导的K+分泌的重要性并定义了病理生理学其在系统性K+平衡上的破坏的影响。 SA3：探索的机制和相关性通过TRPV4对DN中K+重吸收的调节。为了实现这个项目，我们招募了强大的协作专业知识并实施全面的实验武器库，其中涉及监视TRPV4 用斑块夹电生理学，细胞内Ca2+和H+ -K+ ATPase介导的pH值和BK通道活性测量，啮齿动物和人类天然DN细胞中的共聚焦免疫荧光显微镜，平衡关于在常规和遗传操纵动物中操纵饮食K+摄入量的研究。总体而言，我们期望直接证明DN在DN中机械敏感的TRPV4通道的生理相关性系统水平并将定义TRPv4功能障碍的系统性K+功能障碍的病理生理后果稳态。此外，这将促使基于针对TRPV4的新型策略的制定来管理在临床环境中危及生命的高血肿状态。