Essential role of Kir4.1/Kir5.1 channels in renal salt handling and blood pressure control

血压对盐摄入量的敏感性增强存在于近一半的美国人中， 高血压，包括约75%的非洲裔美国人高血压患者。基底外侧向内 整流K+（Kir）通道，特别是Kir4.1和Kir4.1/Kir5.1（由Kcnj 10和Kcnj 16基因编码），发挥着重要作用。 在调节醛固酮敏感性远端肾单位的水和电解质转运中起主导作用。肾 Kir4.1/Kir5.1异源四聚体是远端和集合管主细胞处的初级基底外侧通道， 在调节血浆K+水平和Na+重吸收中起重要作用。这个频道的故障 由遗传或药物相关因素引起的低钾血症，高钾血症和 人类高血压病。另一方面，精确的药理学或遗传调节 Kir4.1或Kir5.1亚基可能为调节体内电解质平衡提供一种新的有用工具， 为治疗和预防盐敏感性高血压和肾损伤开辟了新的途径。的 Dahl盐敏感（SS）大鼠是一种自然发生的盐敏感性高血压模型， 进行性人类疾病的各个方面提供了对盐敏感性机制的关键见解。我们 已经建立了两种大鼠模型，其中Kir4.1或Kir5.1在SS大鼠中被敲除（SSKcnj 10-/-和SSKcnj 16-/-）。 /-大鼠），使我们能够评估Kir4.1和Kir4.1/Kir5.1通道在K+控制中的作用 体内平衡和盐敏感性高血压的发展。鉴于Kir4.1/Kir5.1的报告关联 对于各种心肾疾病，重要的是要了解Kir4.1/Kir5.1可以 影响电解质稳态，其他通道和转运蛋白的活性，以及血压控制。 盐诱发的高血压。本建议的具体目标是：1）确定动态相互作用 肾脏Kir4.1/Kir5.1、ENaC通道与RAAS的关系及其与对照组的关系 体内电解质平衡。高盐和高钾条件下RAAS激素的变化 补充剂，DCT和CCD小管的单个细胞中的基底外侧膜电位，ENaC通道活性， 将检测钠/钾稳态和盐皮质激素（醛固酮）受体抑制剂的作用 SSKcnj 10-/-和SSKcnj 16-/-大鼠。2)为了确定Kir4.1/Kir5.1的药理学抑制是否有利于盐- 诱发性高血压我们的初步实验显示，去甲替林，一种FDA批准的第二代- 一代三环抗抑郁药，显着降低Kir4.1/Kir5.1介导的K+选择性电导， 调节CCD细胞中的ENaC活性。此外，我们将使用对Kir4.1通道特异性的新型化合物，如 VU 992，在WT和SSKcnj 16-/-大鼠中描述Kir通道作为药物靶点的重要作用， 体内Na+/K+稳态。我们假设基底外侧Kir通道活性的直接调节 在盐性高血压的发展中起保护作用，并将导致更多的发现。 有效治疗高血压。

Enhanced sensitivity of blood pressure to salt intake is present in nearly half of Americans affected by hypertension, including approximately 75% of African American hypertensive patients. Basolateral inwardly rectifying K+ (Kir) channels, specifically Kir4.1 and Kir4.1/Kir5.1 (encoded by Kcnj10 and Kcnj16 genes), play a dominant role in modulating water and electrolyte transport in the aldosterone-sensitive distal nephron. Renal Kir4.1/Kir5.1 heterotetramer is a primary basolateral channel at the distal and collecting ducts principal cells and plays an essential role in the regulation of plasma K+ level and Na+ reabsorption. The malfunction of this channel caused by genetic or medication-related factors can be directly involved in hypokalemic, hyperkalemic and hypertensive pathologies in humans. From the other side, precise pharmacological or genetic modulation of Kir4.1or Kir5.1 subunits may provide a new useful tool to the control of electrolyte balance in the body and will open new ways to treat and prevent the development of salt-sensitive hypertension and kidney damage. The Dahl Salt-Sensitive (SS) rat, a naturally occurring model of salt-sensitive hypertension, recapitulates many aspects of progressive human disease providing key insights into mechanisms underlying salt-sensitivity. We have created two rat models in which Kir4.1or Kir5.1 have been knocked out in the SS rat (SSKcnj10-/- and SSKcnj16- /- rats, respectively), enabling us to assess the role of both Kir4.1and Kir4.1/Kir5.1 channels in the control of K+ homeostasis and the development of salt-sensitive hypertension. Given the reported associations of Kir4.1/Kir5.1 with a variety of cardiorenal diseases, it is important to understand the mechanisms by which Kir4.1/Kir5.1 can influence electrolyte homeostasis, the activity of other channels and transporters, and blood pressure control in the setting of salt-induced hypertension. The Specific Aims of this proposal are 1) To define the dynamic interplay between Kir4.1/Kir5.1, ENaC channels and RAAS in the kidney and relation of these mechanisms to the control of electrolyte balance in the body. Changes in RAAS hormones under high salt and dietary potassium supplements, basolateral membrane potential in individual cells of DCT and CCD tubules, ENaC channel activity, sodium/potassium homeostasis and effect of the inhibitor mineralocorticoid (aldosterone) receptor will be tested on SSKcnj10-/- and SSKcnj16-/- rats. 2) To determine if pharmacological inhibition of Kir4.1/Kir5.1 is beneficial for salt- induced hypertension. Our preliminary experiments revealed that nortriptyline, an FDA-approved second- generation tricyclic antidepressant, significantly decreases Kir4.1/Kir5.1 -mediated K+-selective conductance and modulate ENaC activity in CCD cells. Additionally, we will use novel compounds specific for Kir4.1 channel, like VU992, in WT and SSKcnj16-/- rats to delineate the critical role of Kir channels as a pharmacological target for Na+/K+ homeostasis in the body. We hypothesize that direct modulation of basolateral Kir channels activity will play a protective role in the development of salt-induced hypertension and will lead to the discovery of more effective treatments for high blood pressure.