FACTORS DETERMINING HYPERREPSONSIVENESS FOR INTACT AIRWAYS

决定完整气道高反应性的因素

• 批准号: 7889840
• 负责人: KENNETH R LUTCHEN
• 金额: $ 46.62万
• 依托单位: BOSTON UNIVERSITY (CHARLES RIVER CAMPUS)
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7889840
• 关键词: Actins; Address; Affect; Agonist; Asthma; Attenuated; Biochemical; Biology; Biophysics; Breathing; Bronchodilator Agents; Caliber; Cell Culture Techniques; Cell physiology; Characteristics; Complex; Contracts; Data; Digestion; Dimensions; Dose; Ensure; Equilibrium; Extracellular Matrix; F-Actin; Fiber; Frequencies; Future; G Actin; Imaging Techniques; In Situ; Inflammation; Intervention; Length; Link; Lung; MYLK gene; Measurement; Measures; Mechanics; Microscopic; Molecular; Molecular Target; Muscle Contraction; Myosin ATPase; Phenotype; Physiological; Physiology; Play; Process; Property; Research Design; Role; Smooth Muscle; Smooth Muscle Myocytes; Stretching; Structure; Symptoms; System; Testing; Thick; Time; Translating; Ultrasonography; Variant; Work; airway hyperresponsiveness; asthmatic airway; asthmatic patient; base; constriction; extracellular; in vivo; muscle stress; neglect; novel; polymerization; pressure; prevent; public health relevance; respiratory smooth muscle; response; therapy design

DESCRIPTION (provided by applicant): What role does the airway smooth muscle (ASM) play in producing the asthmatic phenotype of airway hyperresponsiveness (AHR)? A plethora of studies confirm that length oscillations of isolated ASM can modulate and mitigate its net response to an agonist. Two related hypotheses at the molecular level have emerged to explain isolated ASM findings, namely that the normal responses to stretch arise from perturbed equilibrium of actin-myosin crossbridges and/or cytoskeletal fluidization of the ASM cell. However, a gap exists in bridging molecular level hypotheses from isolated ASM studies to actual AHR for an intact airway as it constricts in three-dimensions. Many important interactions occur within an intact airway's extracellular matrix (ECM) that can impact ASM contractility and hence airway constriction in situ. We have developed a unique ultrasound imaging-based system to dynamically probe intact airways. Here, the ASM is in its natural geometric state embedded within the airway wall's ECM, and the airway is exposed to physiologically relevant transmural pressure (Ptm) fluctuations. This system allows for concurrent real-time measurements of luminal diameter and wall thickness over the full length of an intact airway during any physiological Ptm fluctuations and/or induced constriction. These measurements allow us to calculate an extensive set of macroscopic mechanical properties of the intact airway system. We can also apply biochemical and histological approaches to examine the microscopic properties of the ASM cells and ECM fibers. Jointly, these preliminary data suggest in intact airways, Ptm variations may invoke cellular mechanisms of crossbridge detachment and/or actin de-polymerization (perhaps associated with cytoskeletal fluidization) but without necessarily resulting in airway dilation. Based on this, we propose to test the following hypothesis: HYPOTHESIS: In the intact airway system, transmural pressure variations during physiological breathing are insufficient to attenuate responsiveness because the mechanical properties of the airway wall's ECM prevent the effective disruption of ASM crossbridge cycling and actin polymerization. Corollary: In vivo, AHR in asthma cannot be explained simply as the inability to properly strain the ASM. Aim 1: To determine the contribution of dynamic Ptm variations to the responsiveness of intact airways. Aim 2: To determine the intra- and extracellular consequences of dynamic Ptm variations on intact airways. Aim 3: To determine how airway wall structural constituents and ASM cellular processes impact the responsiveness of intact airways exposed to dynamic transmural pressure variations. This proposal will address the crucial questions of if and how mechanisms associated with ASM contraction in isolation are relevant in a dynamic and complex intact airway system and, hence, relevant in modulating airway responsiveness. Our proposal represents an essential step to understand mechanisms relevant to airway hyperresponsiveness. PUBLIC HEALTH RELEVANCE: Asthma treatments are designed to target the smooth muscle, or inflammation, or airway wall remodeling, or some combination thereof; what works "best" for some subjects may be minimally effective in another. Our results will have a significant impact on interpreting previous and future studies based on isolated ASM strips and ASM cell cultures. Finally, we also expect that our results will eventually become useful in the treatment of asthmatic patients because we will provide a link between cellular processes and airway function, and hence symptoms.

描述（由申请人提供）：气道平滑肌（ASM）在产生气道高反应性（AHR）哮喘表型中起什么作用？大量的研究证实，分离的ASM的长度振荡可以调节和减轻其对激动剂的净反应。两个相关的假设在分子水平上已经出现，以解释孤立的ASM的研究结果，即拉伸的正常反应产生的肌动蛋白-肌球蛋白crossbridge和/或细胞骨架流化的ASM细胞的扰动平衡。然而，存在一个差距，在桥接分子水平的假设，从孤立的ASM研究，以实际的AHR为一个完整的气道，因为它在三维压缩。许多重要的相互作用发生在一个完整的气道的细胞外基质（ECM），可以影响ASM的收缩性，因此气道收缩原位。我们已经开发了一种独特的基于超声成像的系统来动态探测完整的气道。这里，ASM处于其嵌入气道壁的ECM内的自然几何状态，并且气道暴露于生理相关的跨壁压（Ptm）波动。该系统允许在任何生理Ptm波动和/或诱导的收缩期间在完整气道的全长上同时实时测量管腔直径和壁厚度。这些测量使我们能够计算一组广泛的宏观力学性能的完整的气道系统。我们还可以应用生物化学和组织学方法来检查ASM细胞和ECM纤维的微观特性。联合，这些初步数据表明，在完整的气道，Ptm的变化可能会引起细胞的过桥分离和/或肌动蛋白解聚机制（可能与细胞骨架流化），但不一定导致气道扩张。基于此，我们建议测试以下假设：假设：在完整的气道系统中，在生理呼吸过程中的跨壁压力变化是不足以减弱响应，因为气道壁的ECM的机械性能防止有效破坏ASM的跨桥循环和肌动蛋白聚合。推论：在体内，哮喘中的AHR不能简单地解释为不能适当地拉紧ASM。目的1：确定动态Ptm变化对完整气道反应性的贡献。目的2：确定完整气道内和细胞外动态Ptm变化的后果。目标三：确定气道壁结构成分和ASM细胞过程如何影响暴露于动态跨壁压变化的完整气道的反应性。这项建议将解决的关键问题，如果和如何与ASM收缩隔离的机制是相关的动态和复杂的完整的气道系统，因此，相关的调节气道反应性。我们的建议是了解气道高反应性相关机制的重要一步。 公共卫生相关性：哮喘治疗旨在靶向平滑肌，或炎症，或气道壁重塑，或它们的某种组合;对某些受试者“最好”的治疗可能对另一些受试者效果最低。我们的研究结果将对解释以前和将来基于分离的ASM条和ASM细胞培养物的研究产生重大影响。最后，我们还希望我们的结果最终能用于哮喘患者的治疗，因为我们将提供细胞过程和气道功能之间的联系，因此症状。