Role of the Extracellular Space as a Modulator of the Cardiac Gap Junction - Conduction Velocity Relationship

细胞外空间作为心脏间隙连接调节器的作用 - 传导速度关系

• 批准号: 9240166
• 负责人: Steven Poelzing
• 金额: $ 53.31万
• 依托单位: VIRGINIA POLYTECHNIC INST AND ST UNIV
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-01 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9240166
• 关键词: Acidosis; Affect; Agreement; Albumins; Arrhythmia; Attenuated; Biology; Buffers; Cardiac; Charge; Colloids; Communication; Computer Simulation; Connexin 43; Connexins; Coronary; Coronary artery; Coupling; Data; Dextrans; Disease; Disease model; Edema; Electron Microscopy; Evaluation; Extracellular Space; Foundations; Funding; Gap Junctions; Generations; Genetic; Glucose; Heart; Heart Diseases; Hydration status; Impairment; In Vitro; Intercalated disc; Ions; Ischemia; Ligation; Literature; Mannitol; Measurable; Measurement; Mediating; Membrane Potentials; Metabolic stress; Microscopy; Missense Mutation; Modeling; Molecular Weight; Mus; Muscle Cells; Myocardial Ischemia; Optics; Osmolite; Pharmacology; Phenotype; Post-Translational Protein Processing; Potassium; Predisposition; Preparation; Protein Family; Protein Isoforms; Protons; Publishing; Reporting; Research Personnel; Resolution; Risk; Role; Secondary to; Seminal; Sodium; Sodium Channel; Stress; Structure; Testing; Tissues; Transgenic Organisms; Ventricular; Width; Work; attenuation; base; crystalloid; driving force; expectation; extracellular; indium arsenide; interstitial; mathematical model; mouse model; oculodentodigital dysplasia; papillary muscle; predictive modeling; response; sobriety; targeted agent; theories; tool

Project Abstract While studies of gap junctions often cite their fundamental importance to normal electrical activation of the heart, there is little agreement on the degree of gap junction remodeling required to slow electrical activation. Our prior work has made the following seminal observations. First, the degree of cardiac hydration can modulate whether gap junction uncoupling will be associated with measurable conduction slowing and increased arrhythmia risk. Second, the microdomain adjacent to gap junction plaques is rich in the cardiac sodium channel isoform Nav1.5, is nominally 150 nm long and 10-20 nm wide. Through the use of super- resolution microscopy, electron microscopy, optical mapping, and cutting edge computations simulations, we provided evidence that the perinexus is a strong candidate structure as the cardiac ephapse. Third, we demonstrate that the buffer used to perform ex vivo whole-heart studies can modulate both perinexal width and the relationship between cardiac conduction and gap junctions. In short, altering extracellular sodium and potassium can compensate for a 50% loss of connexin43 such that conduction appears normal. These findings are entirely consistent with the various groups that have analyzed the relationship between conduction velocity and gap junctions, so much so that it is possible by post-hoc literature analysis to determine whether a group will find conduction slowing secondary to loss of Cx43 simply by the buffer used. This work is not just important for understanding alternative modes of electrical communication, but it points out an even more sobering issue: the foundational tool of ex vivo and in vitro biology (buffers) may yield investigator dependent results simply based on ionic buffer composition. In this application we will test three new aims. 1. We will test unique computational predictions of gap junctional and ephaptic coupling to demonstrate that the conduction reserve hypothesis is unique to continuous “cable-like” propagation, and ephaptic coupling can self-attenuate conduction when intercellular widths are very narrow. 2. We will demonstrate how changing interfibrillar and perinexal separation separately alters cardiac conduction. These findings will be compared to models of ephaptic coupling in order to further support the hypothesis that ephaptic coupling is an alternative form of electrical coupling between myocytes. 3. We provide evidence that altering perfusate ion concentration can rescue conduction to the same degree as gap junction based therapy during acidosis. In this final aim, we will determine how perfusate composition modulates electrical coupling during no-flow ischemia and complete coronary artery ligation. Also, we will test whether perfusate composition can agonize the effects of gap junction therapy during ischemia.

项目摘要 尽管间隙连接的研究通常会引用其对正常电激活的基本重要性 心脏，几乎没有一致性的间隙连接重塑的程度来减慢电动激活。 我们先前的工作已经进行了以下第二个观察。首先，心脏水合的程度可以 调节间隙连接解偶联是否会与可测量的传导放慢和 心律不齐的风险增加。其次，与间隙连接斑相邻的微区域富含心脏 钠通道同工型NAV1.5，名义上为150 nm，宽10-20 nm。通过使用超级 分辨率显微镜，电子显微镜，光学映射和尖端计算模拟，我们 提供的证据表明，对心脏的衰减是一种强大的候选结构。第三，我们 证明用于执行体内全心研究的缓冲液可以调节周期宽度和 心脏传导与间隙连接之间的关系。简而言之，改变细胞外钠和 钾可以补偿50％的连接蛋白43损失，从而使传导看起来正常。这些发现 与分析传导速度之间关系的各个组完全一致 和间隙连接，以至于事后文献分析可以确定一个小组是否可以通过 只需通过使用的缓冲液，将发现传导减慢了CX43的损失。这项工作不仅很重要 为了了解电通通信的替代方式，但它指出了一个更加清醒的问题： 离体和体外生物学（缓冲液）的基础工具可以简单地产生研究者的依赖性结果 基于离子缓冲液组成。在此应用程序中，我们将测试三个新目标。 1。我们将测试独特 差距连接和绝经耦合的计算预测，以证明传导储备 假设是连续的“电缆状”传播所独有的，并且边缘耦合可以自我侵入 当细胞间宽度非常狭窄时传导。 2。我们将演示互动之间的变化和 周期分离分别改变心脏传导。这些发现将与 字符耦合以进一步支持以下假设： 肌细胞之间的电耦合。 3。我们提供了改变灌注液离子浓度的证据 在酸中毒过程中，挽救与基于间隙连接的治疗的程度相同。在这个最终目标中，我们将 确定灌注液组成如何调节无流量缺血期间的电耦合并完成 冠状动脉结扎。另外，我们将测试灌注液组成是否可以使差距的影响感到痛苦 缺血期间的交界疗法。