Cardiac chloride and pH regulation in health and disease

健康和疾病中的心氯和 pH 调节

基本信息

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
项目类别：
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

项目摘要

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.

心脏病是美国的首要死因，导致的死亡人数比所有癌症还要多冠心病（或缺血性心脏病，IHD）是最常见的心脏病类型。伴随着心肌局部 pH 值的大幅下降，然而 pH 调节机制和 H+ 中和缓冲液（例如心肌细胞中的 HCO3- 和 Cl-）的稳态仍不完全理解，使得设计针对 pH 调节的治疗策略变得困难。从心肌细胞中鉴定并克隆了溶质载体 Slc26a6 的不同亚型。我们证明 Slc26a6 介导生电 Cl-/HCO3-。我们的研究结果提出了 Slc26a6 可能存在于心房和心室肌细胞中的交换活动。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。我们记录了 Slc26a6 在心脏兴奋性和收缩性中的关键作用。小鼠中的 Slc26a6 导致动作电位 (AP) 缩短、窦性心动过缓、QRS 波群碎片与野生型同窝小鼠相比，我们已经鉴定并表征了两种小鼠的心脏功能受损。人类心脏中的人类 SLC26A6 亚型，也具有产电性，类似于小鼠心脏 Slc26a6。此外，我们最近发现并报告了一种动态逐搏细胞内 pH (pHi) 调节系统，称为“pHi 瞬变”，它与流行的三种已知动态系统相吻合，即电、 Ca2+ 和机械系统然而，Slc26a6 活性如何影响的关键问题仍未得到解答。不仅是 pHi，还有心脏 AP 和收缩力？研究的目标是确定其中的机制联系 Slc26a6 活性与心脏 AP 和收缩力之间的关系。 pHi 瞬态也将一起进行测试，我们研究了 Slc26a6 的活性。 pHi 将通过 Na+/HCO3- 协同转运蛋白 (NBCe) 直接促进细胞内 Na+ 稳态 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 的消除将导致细胞内 Na+ 和 Ca2+ 的减少。分别通过 NHE/NBCe 和 NCX 的作用，我们进一步认为 Slc26a6 发挥着重要作用。动态 pHi 调节在心脏调节心脏起搏活动和收缩力中的作用。使用多学科方法检验我们的假设，包括功能性电生理记录，成像、生化、分子和遗传学方法以及离体和体内功能研究。类型和心脏特异性 Slc26a6 敲除小鼠模型以及人类心肌细胞将进行测试。具体目标是： 1. 确定Slc26a6对心脏pHi和功能的调节机制。测试 Slc26a6 如何调节动态心脏 pHi、Na+ 和 Ca2+ 稳态，从而调节兴奋性和收缩性。将直接测试 pHi 和心脏功能之间的关系，以深入了解 pHi 和心脏功能之间的关系。 Slc26a6 在心脏中的功能作用我们将使用包括多模态二次谐波在内的新技术。一代（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) 中的机制作用我们将测试 Slc26a6 的贡献。将使用以下方法测试 Slc26a6 在心脏 I/R 损伤中的机制作用。 pHi、细胞内 Na+ 和 Ca2+ 浓度的离体共聚焦成像将用于对照。 3. 确定Slc26a6在心脏中的功能作用和调节机制。我们将测试 Slc26a6 在调节 AP 放电频率中的机制作用，此外，ECG 遥测将用于测试 SAN 细胞中的起搏器电流、Ca2+ 信号传导和 pHi。 Slc26a6 在意识控制和 SAN 特异性 Slc26a6-/- 小鼠中的作用我们的研究将解开一个缺失的谜团。 pHi 调节与心脏中 Na+ 和 Ca2+ 稳态之间的分子联系预期的结果将。为 Slc26a6 在心脏 pHi 调节、心脏兴奋性和功能中的作用提供新的见解在翻译水平上，Slc26a6 可能代表一种新的治疗方法。心脏缺血和心律失常的心脏保护目标。