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: 10018019
• 负责人: Oleh Pochynyuk
• 金额: $ 35.03万
• 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/10018019
• 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 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.

大量的基础和临床证据证实了增强上皮 Na+ 通道 (ENaC) 的关键作用 盐敏感和血管紧张素病理学中集​​合管（CD）主细胞介导的重吸收 II (Ang II) 依赖性高血压。相反，醛固酮介导的 ENaC 活性增加 高钾血症是刺激钾分泌所必需的，且没有容量潴留的迹象。在此，我们建议 CD独特的镶嵌结构，由电不耦合的主细胞和插层细胞组成， 有助于单独控制 Na+、K+ 和 Cl- 通量，从而根据体积确定其传输曲线 潴留（Na+ 和 Cl- 重吸收）到 Na+/K+ 交换（Na+ 重吸收与 K+ 分泌耦合）。我们进一步 产生了强有力的初步证据支持 ClC-K2/b 通道介导的 Cl-通量在 在此过程中插入细胞。使用新鲜分离的鼠 CD，我们发现 ClC-K2/b 活性和 表达与膳食 Cl- 摄入量呈负相关，但与 K+ 摄入量无关。此外，Ang II 表现出多组分 对 CD 嵌入细胞中 ClC-K2/b 活性、运输和通道丰度的刺激作用 暗示其在低 Cl-饮食和容量消耗期间 ClC-K2/b 激活中的重要作用。一致地，老鼠 缺乏 1 型血管紧张素受体 (AT1R) 的患者血容量不足，并且肾脏 ClC-K2/b 表达减少。 总体而言，我们假设闰细胞中的 ClC-K2/b 功能主要受膳食 Cl- 摄入量的调节 可能以 Ang II 依赖性方式。这种任意的阴离子 ClC-K2/b 介导的 Cl- 流入减少了 ENaC- 产生 K+ 分泌的驱动力，能够在过程中通过 Na+/K+ 交换调节 CD 运输曲线 高钾血症（仅醛固酮升高）导致低血容量期间 NaCl 重吸收（醛固酮和血管紧张素均升高） II 增加）。 ENaC 和 ClC-K2/b 的同时过度刺激将 CD 操作转移到 NaCl 重吸收模式，从而导致血管紧张素II诱导的高血压的病理学。为了解决这个中央 假设，我们制定了 3 个具体目标： SA1：检查饮食因素对 CD 中 ClC-K2/b 活性和表达的调节。建立 Ang II 和醛固酮在此过程中的贡献和优势。 SA2：定义作用机制并描绘 Ang II 调节 ClC- 的细胞信号通路 CD 中的 K2/b 活性。 SA3：在病理学中建立 CD 中增强的 ClC-K2/b 活性的病理生理学后果 使用具有靶向通道缺失的转基因小鼠来治疗血管紧张素II依赖性高血压。 总之，该提案旨在极大地扩展我们对电解质传输原理的理解 和嵌入细胞整合，以实现 CD 对饮食和内分泌输入的适当反应。此外，它还 提供了生理相关的方法来靶向 CD 中 ClC-K2/b 依赖性 Cl-重吸收，作为一种工具 在临床环境中对抗盐敏感性和血管紧张素II依赖性高血压。