Physiology of ClC-K2/b Cl- channel in the collecting duct

集合管中 ClC-K2/b Cl-通道的生理学

• 批准号: 10207617
• 负责人: Oleh Pochynyuk
• 金额: $ 35.1万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10207617
• 关键词: Acute; Address; Aldosterone; American; Angiotensin II; Angiotensin II Receptor; Angiotensin II Signaling Pathway; Bicarbonates; Blood Pressure; Cells; Chloride Channels; Chronic; Clinical; Clinical Research; Coupling; Cues; Diet; Distal; Duct (organ) structure; Electrolytes; Electrophysiology (science); Endocrine; Excretory function; Exhibits; Functional disorder; Human; Hypertension; Hypovolemia; Hypovolemics; Infusion procedures; Intake; Intercalated Cell; Intercalated Duct; Kidney; Mediating; Mosaicism; Movement; Mus; Pathology; Physiological; Physiology; Pilot Projects; Potassium; Probability; Process; Receptor, Angiotensin, Type 1; Regulation; Renal tubule structure; Renin-Angiotensin System; Renin-Angiotensin-Aldosterone System; Role; Scheme; Shapes; Sodium Chloride; Stimulus; Structure; Time; Transgenic Mice; Variant; basolateral membrane; blood pressure regulation; clinically relevant; collecting tubule structure; dietary; dietary salt; driving force; epithelial Na+ channel; fighting; hyperkalemia; insight; novel; operation; patch clamp; response; salt intake; salt sensitive; tool; trafficking; urinary; wasting

Abundant basic and clinical evidence identify a critical role of the augmented epithelial Na+ channel (ENaC) mediated reabsorption in the collecting duct (CD) principal cells in the pathology of salt-sensitive and Angiotensin II (Ang II)-dependent hypertension. On the contrary, aldosterone-mediated increases in ENaC activity during hyperkalemia are necessary to stimulate potassium secretion with no sign of volume retention. Here, we propose that the unique mosaic structure of the CD, consisting of electrically uncoupled principal and intercalated cells, is instrumental for separate control of Na+, K+ and Cl- fluxes to determine its transport profile from volume retention (Na+ and Cl- reabsorption) to Na+/K+ exchange (coupling Na+ reabsorption to K+ secretion). We further generated strong preliminary evidence supporting essential role of ClC-K2/b channel mediated Cl- flux in intercalated cells in this process. Using freshly isolated murine CDs, we found that ClC-K2/b activity and expression is inversely related to dietary Cl- but not K+ intake. Moreover, Ang II exhibits multicomponent stimulatory effects on ClC-K2/b activity, trafficking and channel abundance in the CD intercalated cells implicating its important role in ClC-K2/b activation during low Cl- diet and volume depletion. Consistently, mice lacking Angiotensin type 1 receptors (AT1R) are hypovolemic and have reduced renal ClC-K2/b expression. Overall, we hypothesize that ClC-K2/b function in intercalated cells is primarily regulated by dietary Cl- intake likely in an Ang II-dependent manner. This discretional anionic ClC-K2/b-mediated Cl- influx reduces the ENaC- generated driving force for K+ secretion enabling to tune CD transport profile from Na+/K+ exchange during hyperkalemia (only aldosterone is elevated) to NaCl reabsorption during hypovolemia (both aldosterone and Ang II are increased). Concomitant over-stimulation of ENaC and ClC-K2/b shifts the CD operation to NaCl reabsorptive mode, thereby contributing to the pathology of Ang II-induced hypertension. To address this central hypothesis, we developed 3 specific aims: SA1: Examine regulation of ClC-K2/b activity and expression in the CD by dietary cues. Establish the contribution and supremacy of Ang II and aldosterone in this process. SA2: Define the mechanism of action and delineate the cellular signaling pathway of Ang II regulation of ClC- K2/b activity in the CD. SA3: Establish pathophysiological ramifications of augmented ClC-K2/b activity in the CD in the pathology of Ang II-dependent hypertension using transgenic mice with targeted channel deletion. In summary, this proposal seeks to greatly expand our understanding how electrolyte transport in principal and intercalated cells integrate for proper CD response to dietary and endocrine inputs. Moreover, it also provides physiologically relevant means to target ClC-K2/b-dependent Cl- reabsorption in the CD as a tool to fight salt-sensitive and Ang II-dependent hypertension in clinical setting.

大量的基本和临床证据确定了增强上皮Na+通道（ENAC）的关键作用 盐敏感和血管紧张素病理学中的收集管（CD）主要细胞中介导的重吸收 II（ANG II）依赖性高血压。相反，醛固酮介导的ENAC活性的增加 高钾血症对于刺激钾的分泌是必要的，没有体积保留的迹象。在这里，我们建议 CD的独特镶嵌结构，由电气未偶联的主和插入的细胞组成， 有助于单独控制Na+，K+和Cl-Fluxes，以确定其体积的传输曲线 保留（Na+和Cl-可吸收）到Na+/K+交换（耦合Na+重吸收到K+分泌）。我们进一步 产生了强大的初步证据，支持CLC-K2/B通道介导的Clux在 在此过程中插入的细胞。使用新鲜隔离的鼠CD，我们发现CLC-K2/B活性和 表达与饮食中的CL-相反，但与K+摄入无关。此外，ANG II展示了多组分 刺激对CD插入细胞中CLC-K2/B活性，运输和通道丰度的影响 暗示其在低Cl饮食和体积消耗期间在CLC-K2/B激活中的重要作用。一贯，小鼠 缺乏血管紧张素1型受体（AT1R）的血容量低，肾脏CLC-K2/B表达降低。 总体而言，我们假设插入细胞中的CLC-K2/B功能主要受饮食中的调节 可能以ANG II依赖性方式。这种独立的阴离子CLC-K2/B介导的Cl-涌入可减少ENAC- 为K+分泌产生的驱动力，可在Na+/K+交换中调整CD传输曲线 在低血容量期间，高钾血症（仅醛固酮升高）至NaCl重吸收（醛固酮和ANG II增加）。 ENAC和CLC-K2/B的过度刺激将CD操作转移到NaCl 重吸收模式，从而有助于ANG II诱导的高血压的病理。解决这个中央 假设，我们开发了3个具体目标： SA1：通过饮食提示检查CD中CLC-K2/B活性和表达的调节。建立 在此过程中，ANG II和醛固酮的贡献和至高无上。 SA2：定义作用机理，并描述ANG II调控Clc-的细胞信号传导途径 CD中的K2/B活性。 SA3：在病理学中，CD中增强CLC-K2/B活性的病理生理分析 使用具有靶向通道缺失的转基因小鼠的ANG II依赖性高血压。 总而言之，该提议旨在极大地扩展我们的理解力如何在本金中运输 插入的细胞集成了对饮食和内分泌输入的适当反应。而且，也是如此 提供与生理相关的手段，以靶向CD中的CLC-K2/B依赖性CL-作为一种工具 在临床环境中对抗盐敏感和ANG II依赖性高血压。