FACTORS DETERMINING HYPERREPSONSIVENESS FOR INTACT AIRWAYS

决定完整气道高反应性的因素

• 批准号: 8049611
• 负责人: KENNETH R LUTCHEN
• 金额: $ 48.97万
• 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/8049611
• 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）的哮喘表型中起什么作用？大量研究证实，孤立ASM的长度振荡可以调节和减轻其对激动剂的净反应。在分子水平上出现了两个相关的假设来解释孤立的肌动蛋白发现，即对拉伸的正常反应是由肌动蛋白-肌球蛋白交叉桥和/或肌动蛋白细胞骨架流化的失衡引起的。然而，从孤立的ASM研究到完整气道的实际AHR的分子水平假设之间存在差距，因为它在三维上收缩。许多重要的相互作用发生在完整气道的细胞外基质（ECM）内，可以影响ASM的收缩性，从而导致气道原位收缩。我们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。在这里，ASM处于其自然的几何状态，嵌入气道壁的ECM中，气道暴露于生理相关的跨壁压力（Ptm）波动。该系统允许在任何生理Ptm波动和/或诱导收缩期间，在完整气道的整个长度上同步实时测量管腔直径和壁厚。这些测量使我们能够计算完整气道系统的宏观力学性能的广泛集合。我们还可以应用生化和组织学方法来检查ASM细胞和ECM纤维的微观特性。综上所述，这些初步数据表明，在完整气道中，Ptm的变化可能会引起交叉桥脱离和/或肌动蛋白解聚的细胞机制（可能与细胞骨架流化有关），但不一定会导致气道扩张。基于此，我们提出验证以下假设：假设：在完整气道系统中，生理呼吸时的跨壁压力变化不足以减弱反应性，因为气道壁ECM的力学特性阻止了ASM交叉桥循环和肌动蛋白聚合的有效破坏。推论：在体内，哮喘的AHR不能简单地解释为不能适当地拉伸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：确定动态Ptm变化对完整气道的细胞内和细胞外影响。目的3：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力变化的完整气道的反应性。该提案将解决与孤立的ASM收缩相关的机制是否以及如何在动态和复杂的完整气道系统中相关的关键问题，因此，与调节气道反应相关。我们的建议是理解气道高反应性相关机制的重要一步。