Optimizing Beta-Adrenoceptor Signaling Bias in Asthma

描述（由申请人提供）：β -2肾上腺素能受体（ß2AR）激动剂，通常被称为ß-激动剂，近半个世纪以来一直是哮喘治疗的基石。然而，尽管ß-激动剂具有实用性，但它们在哮喘治疗中存在问题，包括功能性速反应、哮喘控制恶化和死亡率问题。无法理解为什么存在这些问题，也未能显著改善ß2AR药理学，这反映在20多年来NIH项目宣布需要更安全、更有效的哮喘治疗替代品。我们最近发表和未发表的研究为ß-激动剂存在问题的原因提供了令人信服的见解，同时为其临床应用提供了解决方案。我们的数据强烈表明，ß2AR激动剂在过敏性肺部炎症和相关气道高反应性（AHR）的发展中起着纵容作用，内源性（肾上腺素）和外源性ß-激动剂激发了促进哮喘表型的致病机制。新的数据表明，在气道细胞中，ß2ARs转导了2种性质不同的信号通路：由ß-arrestin2介导的促炎信号，以及由Gs蛋白介导的抗炎和支气管保护信号。我们提出通过确立这些ß2AR信号通路在调节哮喘表型中的细胞特异性作用来解决哮喘“ß2AR悖论”的研究，并从当前和新生成的ß2AR配体或调节剂中识别出那些具有偏倚信号特性的配体或调节剂，这些配体或调节剂具有通过抑制因子拮抗致病性ß2AR信号的最佳能力，同时促进有益的G蛋白信号传导。我们将使用许多系统，包括细胞、组织和体内模型，来验证中心假设，即通过气道上皮中ß-arrestin2的ß2AR信号传导对过敏原诱导的哮喘表型至关重要，并且在激活Gs蛋白信号传导的同时拮抗ß-arrestin2信号传导的偏配体或调节剂在治疗哮喘方面更有效。Aim 1将采用细胞特异性ß2AR基因消融或表达的遗传策略，以确定在气道上皮细胞和平滑肌细胞中ß2AR激动作用介导过敏性肺炎症、粘蛋白产生和AHR的需要和充充性。Aim 2将采用类似的遗传方法来确定ß 2ar介导的PKA-和抑制蛋白依赖信号在体内调节哮喘表型中的作用，以及分子生物学方法来表征PKA-和抑制蛋白依赖对人和小鼠气道上皮细胞中粘蛋白产生和炎症因子的调节。Aim 3将利用药理学和遗传学方法，确定已批准的和新的ß2AR配体的偏导信号特性，最终确定PKA和骤停蛋白信号在调节哮喘表型中的作用。总的来说，这些研究将通过确定过敏性肺部炎症的基本致病信号机制，并通过表征用于管理哮喘患者的最佳ß2AR配体，显著推进哮喘生物学和哮喘药理学领域。

DESCRIPTION (provided by applicant): Agonists of the beta-2-adrenoceptor (ß2AR), commonly referred to as ß-agonists, have been a cornerstone of asthma treatment for nearly half a century. Despite their utility, however, ß-agonists used in asthma management have problems, including functional tachyphylaxis, deterioration of asthma control, and mortality concerns. The inability to understand why such problems exist and the failure to significantly improve ß2AR pharmacology is reflected by over 2 decades of NIH Program announcements declaring the need for safer, more efficacious alternatives to asthma treatment. Our recent published and unpublished studies provide compelling insight into why ß-agonists are problematic while offering a solution to their clinical application. Our data strongly suggest that ß2AR agonism plays a permissive role in the development of allergic lung inflammation and associated airway hyperresponsiveness (AHR), and that endogenous (epinephrine) as well as exogenous ß-agonists invoke pathogenic mechanisms promoting the asthma phenotype. New data suggest that ß2ARs transduce 2 qualitatively distinct signaling pathways in airway cells: pro-inflammatory signaling mediated by ß-arrestin2, and anti-inflammatory and bronchoprotective signaling mediated by Gs proteins. We propose studies to solve the asthma "ß2AR paradox" by establishing the cell-specific role of these ß2AR signaling pathways in regulating the asthma phenotype, and identifying from among current and newly generated ß2AR ligands or modulators those with biased signaling properties that are optimal in their ability to antagonize pathogenic ß2AR signaling via arrestins, yet promote beneficial G protein signaling. We will employ many systems, including cell, tissue, and in vivo models, to test the central hypothesis that ß2AR signaling via ß-arrestin2 in airway epithelia is critical to the allergen-induced asthma phenotype, and biased ß2AR ligands or modulators that antagonize ß-arrestin2 signaling while enabling Gs protein signaling are more efficacious in the treatment of asthma. Aim 1 will employ genetic strategies enabling cell-specific ß2AR gene ablation or expression to establish the requirement and sufficiency of ß2AR agonism in airway epithelial and smooth muscle cells in mediating allergic lung inflammation, mucin production, and AHR. Aim 2 will employ similar genetic approaches to establish the roles of ß2AR-mediated PKA- and arrestin-dependent signaling in regulating the asthma phenotype in vivo, as well as molecular biology approaches to characterize PKA- and arrestin-dependent regulation of mucin production and inflammatory agents in both human and murine airway epithelial cells. Aim 3 will utilize pharmacological and genetic approaches, and determine the biased signaling properties of approved and new ß2AR ligands to conclusively establish the roles for PKA and arrestin signaling in regulating the asthma phenotype. Collectively, these studies will significantly advance the fields of asthma biology and asthma pharmacology by identifying a fundamental pathogenic signaling mechanism involved in allergic lung inflammation, and by characterizing the optimal ß2AR ligands used to manage asthmatics.