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 虽然对缝隙连接的研究经常引用它们对正常的电激活的基本重要性 心脏方面，对于减缓电激活所需的缝隙连接重塑的程度，几乎没有达成一致意见。 我们之前的工作有以下开创性的观察结果。首先，心脏的水合程度可以 调整间隙结去耦合是否会与可测量的传导减慢和 心律失常风险增加。其次，心脏内邻近缝隙连接斑块的微区丰富。 钠通道亚型NaV1.5，名义上长150 nm，宽10-20 nm。通过使用超级- 分辨率显微镜、电子显微镜、光学测绘和尖端计算模拟，我们 提供的证据表明，周围神经丛是一个强有力的候选结构作为心电。第三，我们 证明用于进行体外全心研究的缓冲液可以调节会宽度和 心脏传导与缝隙连接的关系。简而言之，改变细胞外钠和 钾可以补偿50%的缝隙连接蛋白43的丢失，从而使传导看起来正常。这些发现 与各个小组分析传导速度之间的关系是完全一致的 和缝隙连接，以至于有可能通过后自组织文献分析来确定一组 将发现传导减慢仅次于Cx43的损失，仅仅是因为所使用的缓冲器。这项工作不仅重要 以了解电子通信的其他模式，但它指出了一个更发人深省的问题： 体外和体外生物学的基础工具(缓冲器)可以简单地产生依赖于研究者的结果 基于离子缓冲剂组合物。在本应用程序中，我们将测试三个新目标。1.我们将测试Unique 缝隙连接和触觉耦合的计算预测表明，传导储备 假设是连续的“索状”传播所独有的，触觉耦合可以自我衰减。 当细胞间宽度非常窄时的传导。2.我们将演示如何改变纤维间和 会分离单独改变心脏传导。这些发现将与以下模型进行比较 触觉耦合，以进一步支持这样的假设，即触觉耦合是 肌细胞间的电耦合。3.我们提供的证据表明，改变灌流液离子浓度可以 在酸中毒时达到与基于缝隙连接的治疗相同程度的抢救传导。在这个最终目标中，我们将 确定灌流液成分如何在无血流缺血和完全性期间调节电耦合 冠状动脉结扎术。此外，我们还将测试灌流液的成分是否能减轻GAP的影响 缺血时的连接疗法。