Cardiac chloride and pH regulation in health and disease

健康和疾病中的心氯和 pH 调节

• 批准号: 10586799
• 负责人: Xiao-Dong Zhang
• 金额: $ 39.95万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10586799
• 关键词: Ablation; Acids; Action Potentials; Affect; Anions; Arrhythmia; Bicarbonates; Biochemical; Buffers; Cardiac; Cardiac Myocytes; Cardiovascular Diseases; Cations; Cell physiology; Cells; Cessation of life; Chlorides; Conscious; Coronary heart disease; Coupled; Data; Disease; EKG QRS Complex; Electrocardiogram; Electrophysiology (science); Family; Frequencies; Generations; Goals; Health; Heart; Heart Atrium; Heart Diseases; Homeostasis; Human; Human Cloning; Image; Impairment; Ischemia; Knockout Mice; Link; Malignant Neoplasms; Mechanics; Mediating; Microscopy; Molecular; Motivation; Mus; Muscle Cells; Myocardial Infarction; Myocardial Ischemia; Myocardium; Pacemakers; Pathologic; Physiological; Play; Protein Isoforms; Reagent; Regulation; Reperfusion Injury; Reperfusion Therapy; Reporting; Role; Signal Transduction; Sinus Bradycardia; Skeletal Muscle; System; Techniques; Telemetry; Testing; Therapeutic; Transcript; United States; Ventricular; antiporter; base; cardioprotection; confocal imaging; design; dynamic system; experimental study; genetic approach; heart function; in vivo; insight; interdisciplinary approach; member; mortality; mouse model; multimodality; new therapeutic target; novel; second harmonic; solute; symporter; Ablation; Acids; Action Potentials; Affect; Anions; Arrhythmia; Bicarbonates; Biochemical; Buffers; Cardiac; Cardiac Myocytes; Cardiovascular Diseases; Cations; Cell physiology; Cells; Cessation of life; Chlorides; Conscious; Coronary heart disease; Coupled; Data; Disease; EKG QRS Complex; Electrocardiogram; Electrophysiology (science); Family; Frequencies; Generations; Goals; Health; Heart; Heart Atrium; Heart Diseases; Homeostasis; Human; Human Cloning; Image; Impairment; Ischemia; Knockout Mice; Link; Malignant Neoplasms; Mechanics; Mediating; Microscopy; Molecular; Motivation; Mus; Muscle Cells; Myocardial Infarction; Myocardial Ischemia; Myocardium; Pacemakers; Pathologic; Physiological; Play; Protein Isoforms; Reagent; Regulation; Reperfusion Injury; Reperfusion Therapy; Reporting; Role; Signal Transduction; Sinus Bradycardia; Skeletal Muscle; System; Techniques; Telemetry; Testing; Therapeutic; Transcript; United States; Ventricular; antiporter; base; cardioprotection; confocal imaging; design; dynamic system; experimental study; genetic approach; heart function; in vivo; insight; interdisciplinary approach; member; mortality; mouse model; multimodality; new therapeutic target; novel; second harmonic; solute; symporter

Heart disease is the leading cause of mortality in the United States and causes more deaths than all cancers combined. Coronary heart disease (or ischemic heart disease, IHD), the most common type of heart disease, is accompanied by a major decline of local pH in myocardium. However, the mechanisms of pH regulation and the homeostasis of H+ neutralizing buffers, such as HCO3- and Cl- in cardiomyocytes remain incompletely understood, making it difficult to design therapeutic strategies targeting pH regulation. Recently, we have identified and cloned different isoforms of a solute carrier, Slc26a6, from cardiac myocytes. Slc26a6 is the predominant Cl-/HCO3- exchanger in the heart. We demonstrated that Slc26a6 mediates electrogenic Cl-/HCO3- exchange activities in both atrial and ventricular myocytes. Our findings raise the possibility that Slc26a6 may represent the predominant Cl-/HCO3- regulatory mechanism in the heart. We have obtained exciting data to support the critical roles of Slc26a6 in cardiac excitability and contractility. We documented that null deletion of Slc26a6 in mice results in shortened action potentials (APs), sinus bradycardia, fragmented QRS complexes and impaired cardiac function compared to wild type littermates. We have identified and characterized two isoforms of human SLC26A6 in human heart, which are also electrogenic, akin to mouse cardiac Slc26a6. In addition, we recently identified and reported a dynamic beat-to-beat intracellular pH (pHi) regulation system, termed “pHi transients”, which dovetails with the prevailing three known dynamic systems, namely electrical, Ca2+, and mechanical systems. However, critical questions remain unanswered. How do Slc26a6 activities affect not only pHi, but also cardiac AP and contractility? The goal of study is to determine the mechanistic links between the Slc26a6 activities and cardiac AP and contractility. Contributions of Slc26a6-mediated Cl-/HCO3- towards the pHi transients will also be tested. Taken together, we hypothesize that the activities of Slc26a6 on pHi will directly contribute towards intracellular Na+ homeostasis, through Na+/HCO3- cotransporter (NBCe) and Na+/H+ exchanger (NHE), and subsequently regulate intracellular Ca2+ concentration through sarcolemmal Na+- Ca2+ exchanger (NCX). Therefore, ablation of Slc26a6 will result in a reduction in intracellular Na+ and Ca2+ through the actions of NHE/NBCe and NCX, respectively. We further hypothesize that Slc26a6 plays important roles in the dynamic pHi regulation in the heart regulating cardiac pacemaking activities and contractility. We will test our hypothesis using multidisciplinary approaches including functional electrophysiological recordings, imaging, biochemical, molecular and genetic approaches as well as ex vivo and in vivo functional studies. Wild type and cardiac-specific Slc26a6 knockout mouse model as well as human cardiomyocytes will be tested. Three specific aims are: 1. To determine the regulatory mechanisms of Slc26a6 on cardiac pHi and function. We will test how Slc26a6 regulates dynamic cardiac pHi, Na+ and Ca2+ homeostasis, hence, excitability and contractility. The relationship between pHi and cardiac function will be directly tested to gain mechanistic insights into the functional roles of Slc26a6 in the heart. We will use novel techniques including multimodal second harmonic generation (SHG) microscopy and our recently established dynamic pH recording techniques. 2. To determine the mechanistic roles of Slc26a6 in cardiac ischemia/reperfusion (I/R). We will test the contributions of Slc26a6 to cardiac function in the I/R mouse model. Mechanistic roles of Slc26a6 in cardiac I/R injury will be tested using ex vivo confocal imaging of pHi, intracellular Na+ and Ca2+ concentrations. I/R injury will be employed in control and Slc26a6-/- mice. 3. To determine the functional roles and regulatory mechanisms of Slc26a6 in cardiac pacemaking activities. We will test the mechanistic roles of Slc26a6 in the regulation of AP firing frequency, pacemaker currents, Ca2+ signaling, and pHi in SAN cells. Additionally, ECG telemetry will be used to test the roles of Slc26a6 in conscious control and SAN-specific Slc26a6-/- mice. Our studies will unravel a missing molecular link between pHi regulation and Na+, and Ca2+ homeostasis in the heart. The anticipated results will provide novel insights into the roles of Slc26a6 in cardiac pHi regulation, cardiac excitability, and function under physiological and pathological conditions. At the translational level, Slc26a6 may represent a novel therapeutic target for cardioprotection in cardiac ischemia and arrhythmia.

心脏病是美国死亡率的主要原因，并造成与所有机会相比，死亡更多 合并。冠心病（或缺血性心脏病，IHD）是心脏病最常见的类型，是 伴随着心肌的局部pH值大幅下降。但是，pH调节的机制和 H+中和缓冲液的稳态，例如HCO3-和CL-心肌细胞中的稳态不完全 理解，使设计针对pH调节的理论策略变得困难。最近，我们有 可溶性载体SLC26A6的不同同工型从心肌细胞鉴定并克隆了不同的同工型。 Slc26a6是 心脏中主要的Cl-/hco3-交换器。我们证明SLC26A6介导了电源Cl-/hco3- 心房和心室肌细胞中的交换活动。我们的发现提出了SLC26A6可能的可能性 代表心脏中主要的Cl-/HCO3-调节机制。我们已经获得了令人兴奋的数据 支持SLC26A6在心脏兴奋性和收缩性中的关键作用。我们记录了无效的删除 小鼠中的SLC26A6导致缩短动作电位（AP），鼻窦心动过缓，碎片QRS络合物 与野生型同窝仔相比，心脏功能受损。我们已经确定并表征了两个 人心脏中人类SLC26A6的同工型也具有电源，类似于小鼠心脏SLC26A6。在 此外，我们最近确定并报道了动态的Beat-beat细胞内pH（PHI）调节系统，即 称为“ phi瞬变”，它与盛行的三个已知动态系统（即电气）相吻合 CA2+和机械系统。但是，关键问题仍未得到答复。 SLC26A6活动如何影响 不仅是PHI，而且心脏AP和收缩性吗？研究的目的是确定机械链接 在SLC26A6活动与心AP和收缩力之间。 SLC26A6介导的Cl-/HCO3-的贡献 朝向PHI瞬变也将进行测试。综上所述，我们假设SLC26A6的活动 PHI将直接通过Na+/Hco3-共转运蛋白（NBCE）和 Na+/H+交换器（NHE），随后通过肌膜Na+ - 调节细胞内Ca2+浓度 CA2+交换器（NCX）。因此，SLC26A6的消融将导致细胞内Na+和Ca2+的减少 分别通过NHE/NBCE和NCX的动作。我们进一步假设SLC26A6起重要 在调节心脏起搏活动和收缩力的心脏中的动态PHI调节中的作用。我们将 使用多学科方法来检验我们的假设，包括功能电生理记录， 成像，生化，分子和遗传方法以及体内和体内功能研究。荒野 将测试类型和心脏特异性SLC26A6敲除小鼠模型以及人类心肌细胞。三 具体目的是：1。确定SLC26A6在心脏PHI和功能上的调节机制。我们将 测试SLC26A6如何调节动态心脏PHI，Na+和Ca2+稳态，因此，兴奋性和收缩性。 PHI与心脏功能之间的关系将直接测试，以获取机械洞察力 SLC26A6在心脏中的功能作用。我们将使用包括多模式第二谐波在内的新技术 生成（SHG）显微镜和我们最近建立的动态pH记录技术。 2。确定 SLC26A6在心脏缺血/再灌注（I/R）中的机械作用。我们将测试SLC26A6的贡献 在I/R鼠标模型中进行心脏功能。 SLC26A6在心脏I/R损伤中的机械作用将使用 PHI，细胞内Na+和Ca2+浓度的离体共聚焦成像。 I/R伤害将在控制中受到 和SLC26A6 - / - 小鼠。 3。确定SLC26A6在心脏中的功能作用和调节机制 起搏活动。我们将测试SLC26A6在AP发射频率调节中的机械作用， SAN细胞中的起搏器电流，Ca2+信号传导和PHI。此外，ECG遥测将用于测试 SLC26A6在有意识控制和SAN特异性SLC26A6 - / - 小鼠中的作用。我们的研究将揭示失踪的 PHI调节与Na+之间的分子联系，心脏中的Ca2+稳态。预期的结果将 提供有关SLC26A6在心脏PHI调节，心脏兴奋性和功能下的作用的新见解 身体和病理状况。在翻译层面，SLC26A6可能代表一种新的疗法 心脏缺血和心律不齐的心脏保护的靶标。