Regulation of renal Na handling in the collecting duct by local purinergic tone

局部嘌呤能调节肾集合管中钠的处理

• 批准号: 8277403
• 负责人: James D Stockand
• 金额: $ 30.66万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8277403
• 关键词: Address; Affect; Aldosterone; Americas; Animals; Blood Pressure; Cells; Complement; Connexins; Cues; Diet; Distal; Diuresis; Down-Regulation; Duct (organ) structure; Electrophysiology (science); Employee Strikes; Engineering; Environment; Equilibrium; Event; Excretory function; Feedback; Financial compensation; Healthcare; Hereditary Disease; Homeostasis; Human; Hypertension; Hypotension; Immunofluorescence Immunologic; Immunohistochemistry; Kidney; Knock-out; Link; Locales; Location; Measurement; Measures; Mediating; Mineralocorticoids; Molecular; Molecular Genetics; Molecular Mechanisms of Action; Mono-S; Mus; Mutagenesis; Natriuresis; Nephrons; P2Y2 receptor; Physiological; Plasma; Play; Quality of life; Regimen; Regulation; Relative (related person); Renin; Renin-Angiotensin-Aldosterone System; Role; Signal Pathway; Signal Transduction; Sodium; Sodium Chloride; Source; Stimulus; System; Test Result; Testing; Tissues; Urine; Water; autocrine; blood pressure regulation; epithelial Na+ channel; feeding; gain of function; paracrine; pressure; public health relevance; reconstitution; response; salt sensitive; tissue fixing; urinary

DESCRIPTION (provided by applicant): The activity of the epithelial Na+ channel (ENaC) in principal cells of the aldosterone-sensitive distal nephron is central to renal salt and water handling, and thus, regulation of blood pressure. Indeed, gain and loss of ENaC function causes marked increases and decreases in blood pressure. Negative-feedback regulation of ENaC by the renin-angiotensin-aldosterone system (RAAS) is well described where changes in blood pressure ultimately affect ENaC activity in the kidney. Emerging evidence suggests that ENaC is also under feedback control by signaling intrinsic to the kidney mediated by local factors. However, compared to extrinsic regulation by RAAS, less is known about intrinsic control. Purinergic signaling factors are leading candidates as autocrine/paracrine factors important to distal nephron Na+ transport. Our overarching idea is that distal nephron salt and water handling is influenced by intrinsic systems to lessen distal compensation of proximal events enabling excretion to appropriately match systemic conditions. Loss of such intrinsic regulation is expected to cause or exacerbate improper renal Na+ retention and thus, hypertension. It is striking that mice engineered to lack purinergic P2Y2 receptors or connexin 30 hemi-channels, which likely are responsible, in part, for ATP release in the distal nephron, have hypertension associated with facilitated renal Na+ retention. In consideration of our strong preliminary results, we test our central hypothesis that physiological down- regulation of ENaC activity in response to local ATP signaling in the distal nephron through luminal P2Y2 receptors tempers Na+ reabsorption by addressing four specific aims: 1) determine whether physiological concentrations of ATP affect ENaC activity in the mammalian distal nephron and determine the cellular signaling pathway and mechanism of action; 2) determine the consequence of dysfunctional regulation of ENaC by compromised paracrine/autocrine ATP signaling; 3) define the role of connexin 30 in ATP regulation of ENaC; and 4) quantify the relation between systemic salt-loading and regulation of ENaC activity in the distal nephron by purinergic tone. We investigate purinergic regulation of ENaC using a comprehensive strategy combining direct measurements of channel activity with electrophysiology with a molecular genetics approach that unequivocally establishes the role of the P2Y2 receptor and probes Cx30 as a conduit for autocrine ATP release. Physiologically relevant tissue (freshly isolated murine collecting duct) containing native ENaC in its normal cellular environment is used. Moreover, the scope of this proposal is comprehensive probing regulation of ENaC by purinergic tone and ATP release via Cx30 in the collecting duct from the animal to molecular mechanism of action. PUBLIC HEALTH RELEVANCE: Hypertension is prevalent in America and continues to rise making it one of the major obstacles for better quality of life and health care in the U.S. A. Appropriate salt handling by the kidneys is critical to proper control of blood pressure. The current proposal investigates the cellular and molecular mechanisms underlying renal salt handling particularly at the distal nephron, the location where systemic salt and water balance is fine-tuned in humans.

描述（由申请人提供）：醛固酮敏感的远端肾单位主细胞中上皮Na+通道（ENaC）的活性对于肾脏盐和水的处理以及因此的血压调节至关重要。事实上，ENaC 功能的增强和丧失会导致血压显着升高和降低。肾素-血管紧张素-醛固酮系统 (RAAS) 对 ENaC 的负反馈调节已得到充分描述，其中血压的变化最终影响肾脏中的 ENaC 活性。新出现的证据表明，ENaC 也受到局部因素介导的肾脏固有信号的反馈控制。然而，与 RAAS 的外在调节相比，人们对内在控制知之甚少。嘌呤能信号因子是对远端肾单位 Na+ 转运很重要的自分泌/旁分泌因子的主要候选因子。我们的总体想法是，远端肾单位盐和水的处理受到内在系统的影响，以减少近端事件的远端补偿，使排泄能够适当地匹配全身条件。失去这种内在调节预计会导致或加剧肾钠潴留不当，从而导致高血压。令人惊讶的是，经过基因工程改造的小鼠缺乏嘌呤能 P2Y2 受体或连接蛋白 30 半通道（这些受体可能部分负责远端肾单位 ATP 的释放），但其患有与促进肾 Na+ 潴留相关的高血压。考虑到我们强有力的初步结果，我们测试了我们的中心假设，即通过管腔 P2Y2 受体响应远端肾单位局部 ATP 信号传导而对 ENaC 活性进行生理下调，通过解决四个具体目标来调节 Na+ 重吸收：1）确定 ATP 的生理浓度是否影响哺乳动物远端肾单位中的 ENaC 活性，并确定细胞信号传导途径和作用机制； 2) 通过旁分泌/自分泌 ATP 信号传导受损来确定 ENaC 调节功能失调的后果； 3) 定义连接蛋白30在ENaC的ATP调节中的作用； 4) 量化全身盐负荷与嘌呤能调节远端肾单位 ENaC 活性之间的关系。我们使用一种综合策略来研究 ENaC 的嘌呤能调节，该策略将通道活性的直接测量与电生理学和分子遗传学方法相结合，明确地确定了 P2Y2 受体的作用并探针 Cx30 作为自分泌 ATP 释放的管道。使用在正常细胞环境中含有天然 ENaC 的生理相关组织（新鲜分离的鼠集合管）。此外，该提案的范围是全面探讨动物集合管中嘌呤能音调和 ATP 释放对 ENaC 的调节，以及分子作用机制。 公共卫生相关性：高血压在美国很普遍，并且持续上升，使其成为美国提高生活质量和医疗保健的主要障碍之一。 A. 肾脏适当处理盐对于正确控制血压至关重要。目前的提案研究了肾脏盐处理的细胞和分子机制，特别是在远端肾单位，这是人体体内盐和水平衡进行微调的位置。