Atamanchuk Anna, Pyrshev Kyrylo, Kordysh Mariya, Zaika Oleg, Pochynyuk Oleh
Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
FASEB J. 2025 May 31;39(10):e70598. doi: 10.1096/fj.202500588RR.
Maintaining systemic Cl homeostasis plays a critical yet underappreciated role in setting the baseline and salt sensitivity of blood pressure. ClC-K2 Cl-permeable channel is localized on the basolateral membrane of the distal nephron segments. Impaired NaCl reabsorption in the thick ascending limb and distal convoluted tubule has been proposed as the underlying cause of polyuria and hypotension in patients with the Bartter's syndrome type 3 due to loss-of-function of the channel. However, the relevance of ClC-K2 in the collecting duct intercalated cells (ICs) for renal function and Cl homeostasis remains obscure. Here, we compared the systemic manifestations and examined signaling components in ClC-K2 Pax8 (lacking ClC-K2 in renal nephron) and ClC-K2 B1 ATPase (lacking ClC-K2 in ICs) mice. ClC-K2 Pax8 mice exhibited hypotension, reduced glomerular filtration rate, urinary NaCl wasting, and metabolic alkalosis with hypokalemia, thereby recapitulating the phenotype of Bartter's syndrome. While ClC-K2 deletion in ICs did not affect urinary volume and baseline blood pressure, ClC-K2 B1 ATPase mice developed moderate hypotension in response to dietary Cl deficiency. Decreased expression and impaired apical translocation of pendrin (Slc26A4) were causative for the augmented urinary Cl excretion. Furthermore, ClC-K2 deletion in ICs interfered with the development of Angiotensin II-dependent hypertension. The reduced pendrin function, along with a compensatory upregulation of the epithelial Na channel, caused hypokalemic metabolic alkalosis in ClC-K2 B1 ATPase mice. In summary, we show that ClC-K2 activity in ICs of the collecting duct plays physiologically relevant roles in the regulation of systemic Cl balance and acid-base homeostasis.
维持全身氯离子(Cl)稳态在设定血压的基线和盐敏感性方面起着关键但未得到充分重视的作用。ClC-K2氯离子通透通道定位于远端肾单位节段的基底外侧膜上。由于该通道功能丧失,厚壁升支和远曲小管中氯化钠重吸收受损被认为是3型巴特综合征患者多尿和低血压的潜在原因。然而,ClC-K2在集合管闰细胞(ICs)中对肾功能和Cl稳态的相关性仍不清楚。在此,我们比较了ClC-K2 Pax8(肾单位中缺乏ClC-K2)和ClC-K2 B1 ATPase(ICs中缺乏ClC-K2)小鼠的全身表现,并检测了信号传导成分。ClC-K2 Pax8小鼠表现出低血压、肾小球滤过率降低、尿NaCl流失以及伴有低钾血症的代谢性碱中毒,从而重现了巴特综合征的表型。虽然ICs中ClC-K2的缺失不影响尿量和基线血压,但ClC-K2 B1 ATPase小鼠在饮食Cl缺乏时会出现中度低血压。pendrin(Slc26A4)表达降低和顶端易位受损是尿Cl排泄增加的原因。此外,ICs中ClC-K2的缺失干扰了血管紧张素II依赖性高血压的发展。pendrin功能降低,以及上皮钠通道的代偿性上调,导致ClC-K2 B1 ATPase小鼠出现低钾性代谢性碱中毒。总之,我们表明集合管ICs中的ClC-K2活性在调节全身Cl平衡和酸碱稳态中发挥着生理相关作用。