Significance of Epac signaling in renal Na+ handling and hypertension

Epac 信号在肾钠处理和高血压中的意义

• 批准号: 10864073
• 负责人: XIAODONG CHENG
• 金额: $ 15万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10864073
• 关键词: Address; Adverse effects; Animal Model; Antihypertensive Agents; Automobile Driving; Binding; Biological Availability; Biology; Blood Pressure; Body Water; Clinical; Collaborations; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Development; Diet; Diuretics; Duct (organ) structure; Electrolytes; Electrophysiology (science); Epithelium; Equilibrium; Excretory function; Exhibits; G-Protein-Coupled Receptors; Genes; Genetic Models; Homeostasis; Hormones; Human; Hypertension; Hypotension; Hypovolemia; Hypovolemics; Imaging Device; Impairment; Individual; Intake; Kidney; Laboratories; Link; Mediating; Mitochondria; Molecular; Molecular Target; Mus; Natriuresis; Nephrons; Ontology; Oxidative Stress; Pathology; Pathway interactions; Pattern; Pharmacology; Physiological; Physiology; Play; Preparation; Process; Production; Protein Isoforms; Proteins; Publishing; Reactive Oxygen Species; Regulation; Renal function; Renal tubule structure; Rodent; Rodent Model; Role; Scheme; Signal Transduction; Sodium; Sodium Chloride; System; Testing; Toxic effect; Tubular formation; Variant; Water; absorption; blood pressure control; blood pressure elevation; blood pressure reduction; clinically significant; dietary; dietary salt; drug discovery; epithelial Na+ channel; fighting; hyperkalemia; hypertension treatment; hypertensive; improved; in vivo; inhibitor; membrane activity; mouse model; novel; pharmacologic; response; salt balance; salt intake; saluretic; small molecule; sodium-hydrogen exchanger 3; synergism; therapeutic target; therapeutically effective; tool; transcriptome sequencing; urinary

PROJECT SUMMARY Kidneys play a central role in regulation of water-salt balance with excessive renal Na+ conservation being tightly associated with hypertension. The existing diuretics inhibit Na+ reabsorption in individual renal tubule segments, which often involves a compensatory response in other segments to limit their efficiency. Thus, targeting Na+ transporting systems in multiple segments simultaneously might represent a more effective way to fight hypertension. Our groups generated abundant multicomponent evidence that exchange protein directly activated by cAMP (Epac) isoforms 1 and 2 are critical regulators of renal Na+ handling in the proximal tubule (PT) and the collecting duct (CD). Epac1 and Epac2 deletion compromises renal Na+ conservation in mice, leading to reduced blood pressure during dietary Na+ restriction. This is associated with decreased activity and expression of the sodium hydrogen exchanger-3 (NHE-3) in PT and epithelial Na+ channel (ENaC) in CD. Furthermore, RNAseq Gene Ontology enrichment analysis revealed an improvement of mitochondria function and reduction in the reactive oxygen species (ROS) production in PT and CD upon Epac deletion. Interestingly, renal Epac expression is drastically increased during hypertension arguing for deleterious ramifications of Epac over-activation in driving Na+ retention and the development of elevated blood pressure. To this end, we have developed novel pharmacological tools to selectively inhibit Epac isoform(s), and observed natriuretic actions of these small molecules while exhibiting low toxicity and potent bioavailability profiles. Overall, we hypothesize that Epac1 and Epac2 isoforms are physiologically relevant regulators of sodium reabsorption in both PT and CD in response to hypovolemia. On the contrary, over-activation of Epac cascade contributes significantly to the development of renal sodium retention and hypertension, in part by increasing ROS production and oxidative stress. We propose that pharmacological inhibition of Epac signaling could be a novel, potent, and safe strategy to counteract hypertension and improve renal function. We plan to test this with 3 specific aims: SA1. Determine salt-sensitivity associated with Epac-induced changes on tubular transport in mice lacking Epac isoforms to establish roles of renal and extra-renal components of Epac signaling. SA2. Examine the molecular targets and signaling mechanisms of Epac-dependent regulation of Na+ transport in the PT and CD. SA3. To test the hypothesis that Epac1 and 2 are effective therapeutic targets of hypertension using optimized Epac specific inhibitors. In summary, we develop this proposal by merging highly complementary and synergistic expertise in renal physiology/epithelial transport and Epac signaling/drug discovery from neighboring laboratories of Dr. Pochynyuk and Dr. Cheng within the Department of Integrative Biology and Pharmacology, UTHSC at Houston. We anticipate to uncover previously unrecognized physiologically relevant means of Epac signaling in the kidney and to establish the pharmacological potential of Epac blockade in treatment of hypertension.

项目概要 肾脏在调节水盐平衡中发挥着核心作用，过度的肾脏Na+保存受到严格控制 与高血压有关。现有的利尿剂抑制个别肾小管段的Na+重吸收， 这通常涉及其他部门的补偿性反应，以限制其效率。因此，针对 Na+ 同时多个部分的运输系统可能是一种更有效的战斗方式 高血压。我们的小组产生了丰富的直接交换蛋白质的多组分证据 由 cAMP (Epac) 激活的亚型 1 和 2 是近曲小管肾 Na+ 处理的关键调节因子 (PT) 和集合管 (CD)。 Epac1 和 Epac2 缺失会损害小鼠肾 Na+ 保存， 限制饮食 Na+ 导致血压降低。这与活动减少有关 PT 中钠氢交换器 3 (NHE-3) 和 CD 中上皮 Na+ 通道 (ENaC) 的表达。 此外，RNAseq Gene Ontology 富集分析揭示了线粒体功能的改善 Epac 缺失后 PT 和 CD 中活性氧 (ROS) 产生减少。有趣的是， 高血压期间肾 Epac 表达急剧增加，争论 Epac 的有害后果 过度激活导致 Na+ 潴留和血压升高。为此，我们有 开发了新的药理学工具来选择性抑制 Epac 亚型，并观察到利尿钠排泄作用 这些小分子同时表现出低毒性和有效的生物利用度。总的来说，我们假设 Epac1 和 Epac2 亚型是 PT 和 PT 中钠重吸收的生理相关调节因子 CD 对低血容量的反应。相反，Epac 级联的过度激活显着促进 肾钠潴留和高血压的发展，部分是通过增加ROS的产生和氧化 压力。我们认为 Epac 信号传导的药理学抑制可能是一种新颖、有效且安全的策略 对抗高血压和改善肾功能。我们计划通过 3 个具体目标进行测试： SA1。确定与 Epac 诱导的小鼠肾小管运输变化相关的盐敏感性 缺乏 Epac 亚型来确定 Epac 信号传导的肾脏和肾外成分的作用。 SA2。 检查 Epac 依赖性 Na+ 运输调节的分子靶点和信号传导机制 在 PT 和 CD 中。 SA3。检验 Epac1 和 2 是有效治疗靶点的假设 使用优化的 Epac 特异性抑制剂治疗高血压。 总之，我们通过合并肾脏领域高度互补和协同的专业知识来制定这一提案 来自 Dr. 邻近实验室的生理学/上皮运输和 Epac 信号/药物发现 Pochynyuk 和 Cheng 博士就职于休斯敦 UTHSC 综合生物学和药理学系。 我们期望揭示肾脏中 Epac 信号传导的先前未被识别的生理相关手段 并确定 Epac 阻断治疗高血压的药理学潜力。