Targeting actin dynamics to inhibit airway hypperresponsiveness and inflammation

描述（由申请人提供）：炎症细胞募集到肺部和气道高反应性是哮喘的关键组成部分。过敏原诱导的肺部炎症反应是由关键气道驻留细胞和释放局部介质的炎症细胞相互作用引起的。气道平滑肌（ASM）通过表型变化参与肺的炎症反应，所述表型变化包括合成炎症介质以及收缩性增加。尽管抗炎药和β-肾上腺素能支气管扩张剂仍然是慢性和急性支气管收缩发作的主要治疗方法，但仍然非常需要能够改变哮喘发展和治疗的新治疗靶点。出于这个原因，可能被预测为抑制过敏性炎症反应以及支气管收缩的分子靶点是高度期望的。肌动蛋白动力学被公认为许多细胞类型（包括炎性细胞）运动和迁移的主要机制。因此，参与肌动蛋白动力学的靶向步骤可能构成抑制炎症细胞募集和迁移到肺中的机制。收缩刺激也导致聚合的肌动蛋白池（ASM）细胞，和肌动蛋白聚合必须发生除了crossbridge循环的主动张力的产生。该提案中提出的令人兴奋的新数据也暗示了ASM组织对炎症刺激的直接反应中的肌动蛋白动力学。调节ASM中肌动蛋白聚合的分子机制与描述的细胞迁移的分子机制类似;因此，靶向调节平滑肌和炎症细胞中肌动蛋白动力学的常见分子中介体可能提供抑制气道反应性和炎症的有效手段。由于p21活化蛋白激酶（PAK）参与调节F-肌动蛋白动力学，它们可能为抑制炎症和ASM收缩性提供分子靶点。提出了一种新的分子机制，Pak在细胞骨架信号通路中的作用，介导了ASM细胞的收缩和炎症反应。初步数据支持Pak在体外调节ASM的过敏性炎症反应和在小鼠哮喘模型中的重要作用。目前正在开发用于癌症化疗的小分子PAK抑制剂，因此在可预见的将来可能会在临床上使用。PAKs可能作为哮喘治疗的理想靶点，因为它们可能直接参与调节ASM的反应性以及肺和气道的炎症反应，这一假设将在3个特定目的中进行，以确定：1）Pak调节ASM对收缩和炎症刺激的反应的分子机制; 2）靶向肌动蛋白调节途径是否抑制哮喘小鼠模型中的气道反应性、炎症和重塑; 3）PAK活性的急性抑制是否可以预防哮喘小鼠模型中气道炎症和气道重塑的发展。

DESCRIPTION (provided by applicant): Inflammatory cell recruitment into the lungs and airway hyperresponsiveness are key components of asthma. The allergen-induced inflammatory response in the lungs results from the interaction of key airway resident cells and inflammatory cells that release local mediators. Airway smooth muscle (ASM) participates in the inflammatory response of the lungs by phenotypic changes that include synthesizing inflammatory mediators as well as an increase in contractility. Although anti-inflammatory agents and beta-adrenergic bronchodilators remain the primary treatment for chronic and acute episodes of bronchoconstriction, there is a great need for newer therapeutic targets that can modify the development and treatment of asthma. For that reason, molecular targets that might be predicted to suppress allergic inflammatory responses as well as bronchoconstriction are highly desirable. Actin dynamics is well established as the primary mechanism for motility and migration for many cell types, including inflammatory cells. Thus, targeting steps involved in actin dynamics might constitute a mechanism for suppressing the recruitment and migration of inflammatory cells into the lungs. Contractile stimulation also causes the polymerization of a pool of actin in (ASM) cells, and actin polymerization must occur in addition to crossbridge cycling for the generation of active tension. Exciting and novel data presented in the proposal also implicates actin dynamics in the direct responses of ASM tissues to inflammatory stimuli. The molecular mechanisms that regulate actin polymerization in ASM are analogous to those described for cell migration; therefore targeting molecular intermediaries common to the regulation of actin dynamics in smooth muscle and inflammatory cells might provide an effective means of suppressing airway responsiveness and inflammation. As p21-activated protein kinases (PAK) are involved in regulation of F-actin dynamics, they may provide a molecular target for the inhibition of both inflammation and ASM contractility. A novel molecular mechanism for the role of Pak in cytoskeletal signaling pathways that mediate both the contractile and inflammatory responses of ASM cells is proposed. Preliminary data support an important role for Pak in modulating the allergic inflammatory responses of ASM in vitro and in a murine model of asthma in vivo. Small molecular PAK inhibitors are currently under development for cancer chemotherapy and may thus become clinically available in the foreseeable future. The hypothesis that PAKs may serve as an ideal target for asthma therapy because they may be directly involved in the regulation of ASM responsiveness as well the inflammatory responses of the lungs and airways will be pursued in 3 Specific Aims to determine: 1) the molecular mechanisms by which Pak regulates the responses of ASM to contractile and inflammatory stimuli; 2) whether targeting an actin regulatory pathway inhibits airway responsiveness, inflammation and remodeling in a murine model of asthma; 3) whether the acute inhibition of PAK activity can prevent the development of airway inflammation and airway remodeling in a murine asthma model.