Role of airway epithelial Beta2-adrenergic receptors

气道上皮β2-肾上腺素能受体的作用

• 批准号: 6686968
• 负责人: Phillip H Factor
• 金额: $ 36.79万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-18 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6686968
• 关键词: allergens; beta adrenergic receptor; biological models; bronchus; catecholamines; cell membrane; chemosensitizing agent; gene deletion mutation; immunocytochemistry; inflammation; laboratory mouse; lung disorder; model design /development; nitric oxide; phosphorylation; polymerase chain reaction; prostaglandin E; protein structure function; receptor expression; respiratory airway pressure; respiratory epithelium; respiratory function; transfection

DESCRIPTION (provided by applicant): It is well established that activation of beta2-adrenergic receptors ((beta2AR) on airway smooth muscle (ASM) cells decreases bronchomotor tone. Less well appreciated is that bronchial epithelial cells have a higher density of (beta2ARs than do ASM and that in vitro studies of primary and immortalized airway epithelial cells have identified cAMP sensitive mechanisms capable of causing ASM relaxation. Conversely, ex vivo studies using epithelium intact and denuded tracheal tubes suggest that the epithelium impedes beta-agonist mediated ASM relaxation by serving as diffusion barrier that limits access of beta-agonists to ASM (2ARs. Thus, the results of cell-based in vitro experiments regarding epithelial (2ARs have not translated into physiologically relevant mechanisms in animal models nor are there data to suggest that epithelial beta2ARs participate in the regulation of bronchomotor tone in humans with asthma. This lack of consensus about epithelial beta2ARs has resulted in a paradigm of asthma that assumes, by default, that beta-agonists affect bronchodilation solely via activation of beta2ARs on ASM. We find it striking that the location and mechanism of action of a key therapeutic modality for asthma, inhaled beta-agonists, are uncertain. The absence of a defined role for epithelial beta2ARs, stems from the inability of prior in vivo studies to separate the physiologic effects of epithelial (beta2ARs from the direct bronchodilating effects of ASM beta2ARs. We believe that resolution of the role of epithelial beta2ARs could improve our understanding of reactive airway disease and better define how beta-agonists interacts with the airway to reduce airway reactivity. We have conducted preliminary experiments in which we observed that overexpression of a human beta2ARs cDNA in the airway epithelium of normal mice confers substantial protection from methacholine-induced bronchospasm. We also noted that the absence or inhibition of epithelial beta2ARs significantly increases airway reactivity in mice. These observations have caused us to hypothesize that: Bronchial epithelial beta2ARs participate in the regulation of airway reactivity. The lack of consensus regarding bronchial epithelial (2ARs and our ongoing studies of alveolar beta2ARs have led us to several questions regarding airway epithelial beta2ARs: 1) Do airway epithelial (2ARs regulate airway reactivity in normal mice? 2) Does agonist-induced receptor desensitization of epithelial beta2ARs affect airway reactivity? and 3) Does bronchopulmonary inflammation affect epithelial beta2ARs function? To address our hypothesis and questions we have structured 3 inter-related scientific aims that merge molecular tools with in vivo models to help repair the long-standing gap in knowledge regarding the role of epithelial beta2ARs. These studies will tell us how beta2ARs interact with catecholamines, if they affect airway reactivity, and whether they are affected by bronchopulmonary inflammation. We believe that confirmation of an important role for epithelial beta2ARs could justify the development of epithelial cell specific, gene-based, therapies that positively modulate epithelial beta-receptor function to produce sustained protection from bronchospastic challenges. Such therapies could significantly improve the health of patients with asthma.

描述(由申请人提供)：众所周知，激活气道平滑肌(ASM)细胞上的β2-肾上腺素能受体(Beta2AR)会降低支气管运动张力。较少被认识到的是，与ASM相比，支气管上皮细胞具有更高的(β2受体)密度，而且对原代和永生化的呼吸道上皮细胞的体外研究已经确定了能够引起ASM松弛的cAMP敏感机制。相反，使用完整的上皮和裸露的气管的体外研究表明，上皮通过作为扩散屏障来阻碍β-激动剂介导的ASM松弛，从而限制β-激动剂对ASM的访问(2ARs)。因此，关于上皮细胞(2ARs)的体外实验结果没有在动物模型中转化为生理学相关的机制，也没有数据表明上皮β2ARs参与哮喘人类支气管运动张力的调节。由于对上皮性β2受体缺乏共识，导致了一种哮喘的范例，默认假设β-激动剂仅通过激活ASM上的β2受体来影响支气管扩张。我们发现，哮喘的一种关键治疗方式-吸入β-激动剂-的位置和作用机制尚不确定，这一点令人震惊。 上皮β2受体缺乏明确的作用，源于先前的活体研究无法将上皮(β2受体)的生理效应与ASMβ2受体的直接支气管扩张效应分开。我们认为，解决上皮β2受体的作用可以提高我们对反应性呼吸道疾病的理解，并更好地定义β-激动剂如何与呼吸道相互作用来降低呼吸道反应性。我们已经进行了初步的实验，我们观察到，在正常小鼠的呼吸道上皮细胞中过表达人β2ARs基因可以有效地保护小鼠免受乙酰甲胆碱诱导的支气管痉挛。我们还注意到，上皮β2受体的缺失或抑制显著增加了小鼠的呼吸道反应性。这些观察结果使我们假设：支气管上皮β2受体参与了呼吸道反应性的调节。 对于支气管上皮(2ARs)和我们正在进行的对肺泡β2ARs的研究缺乏共识，这导致了我们对呼吸道上皮β2ARs的几个问题：1)气道上皮(2ARs)是否调节正常小鼠的气道反应性？2)激动剂诱导的上皮β2ARs受体脱敏是否影响呼吸道反应性？3)支气管炎是否影响上皮β2受体功能？ 为了解决我们的假设和问题，我们构建了3个相互关联的科学目标，将分子工具与体内模型相结合，以帮助修复关于上皮Beta2ARs作用的长期知识缺口。这些研究将告诉我们，β2受体如何与儿茶酚胺相互作用，它们是否影响呼吸道反应性，以及它们是否受到支气管炎的影响。 我们认为，确认上皮β受体的重要作用可以证明开发上皮细胞特异性的、基于基因的治疗方法是合理的，这些治疗方法积极地调节上皮β受体的功能，以产生针对支气管痉挛挑战的持续保护。这种疗法可以显著改善哮喘患者的健康。