ClC-K2 in the collecting duct intercalated cells contributes to blood pressure regulation during variations in dietary Cl-intake

Abstract

Hypertension is the major clinically relevant problem affecting millions of people in the US. The renal collecting duct is known to play a critical role in setting salt-sensitivity of blood pressure. Originally, the majority of clinical and basic effort has been devoted to defining the detrimental roles of elevated dietary Na + in pathophysiology of hypertension. However, emerging evidence indicates that the dietary Cl - is as important for blood pressure control. The collecting duct has two independent types of cells: principal and intercalated having different functions and physiological roles. Principal cells regulate Na + reabsorption, whereas intercalated cells are responsible for transport of Cl - . ClC-K2 is a Cl - permeable channel abundantly expressed on the basolateral membrane of several distal nephron segments from the thick ascending limb to the collecting duct. Loss-of-function mutations in ClC-Kb (human orthologue of ClC-K2) cause Bartter’s syndrome type 3, which is associated with urinary salt wasting and hypotension. While the function of ClC-Kb in the thick ascending limb and distal convoluted tubule are thought to be responsible for the salt-wasting phenotype in patients with Bartter’s syndrome, the role of the channel in the collecting duct intercalated cells is not known. To address this critical gap, we compared the blood pressure phenotype and systemic Cl - balance in newly created mice with deletion of ClC-K2 in the renal nephron (RN-KO) and selectively in intercalated cells (IC-KO) using cre-loxP strategy. Since the commonly used Na + deficient diet only partially reduces chloride content and does not lead to appreciable reduction in blood pressure in rodents, we used the diet lacking both Na + and Cl - . As anticipated, RN-KO ClC-K2 mice had lower blood pressure on both regular and NaCl deficient diets when compared to the respective genetic controls (WT). In addition, the mutants exhibited larger urinary volume and Cl - wasting in response to dietary Cl - restriction. Importantly, IC-KO ClC-K2 mice had comparable blood pressure on regular diet, but became more hypotonic when compared to WT in response to dietary NaCl deficiency. Moreover, patch clamp studies in freshly isolated collecting ducts from WT mice revealed that ClC-K2 activity is proportionally increased to the amount of Cl - reduction in a diet suggesting that ClC-K2 is instrumental in augmenting Cl - reabsorption during Cl - deficiency.In conclusion, our results demonstrate, for the first time, the significance of ClC-K2 function in the collecting duct intercalated cells in setting salt sensitivity of blood pressure. This research was supported by NIH-NIDDK DK117865, DK119170, AHA EIA35260097 (to O. Pochynyuk) and AHA-19CDA34660148 (to V. N. Tomilin). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.