Targeting actin dynamics to inhibit airway hypperresponsiveness and inflammation

描述(由申请者提供)：炎症细胞重新聚集到肺部和呼吸道高反应性是哮喘的关键组成部分。变应原诱导的肺部炎症反应是关键的呼吸道驻留细胞和释放局部介质的炎症细胞相互作用的结果。呼吸道平滑肌(ASM)通过表型变化参与肺的炎症反应，包括合成炎症介质以及收缩能力的增加。虽然抗炎药和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药物，但非常需要新的治疗靶点来改变哮喘的发展和治疗。因此，可以预测可以抑制过敏性炎症反应和支气管收缩的分子靶点是非常可取的。肌动蛋白动力学被公认为许多细胞类型的运动和迁移的主要机制，包括炎性细胞。因此，针对涉及肌动蛋白动力学的步骤可能构成一种抑制炎症细胞向肺部招募和迁移的机制。收缩刺激还会导致肌动蛋白(ASM)细胞中肌动蛋白的聚合，为了产生活性张力，除了交叉桥循环外，肌动蛋白聚合必须发生。该提案中提出的令人兴奋和新颖的数据也暗示了肌动蛋白动力学在ASM组织对炎症刺激的直接反应中的作用。ASM中调节肌动蛋白聚合的分子机制类似于所描述的细胞迁移机制；因此，靶向调节平滑肌和炎症细胞中肌动蛋白动力学共同的分子中介可能提供一种有效的抑制呼吸道反应性和炎症的手段。由于p21激活的蛋白激酶(PAK)参与了F-肌动蛋白动力学的调节，它们可能为抑制炎症和ASM收缩提供一个分子靶点。提出了Pak在细胞骨架信号通路中作用的新的分子机制，该信号通路既介导ASM细胞的收缩反应，又介导ASM细胞的炎症反应。初步数据支持，在体外和体内哮喘小鼠模型中，Pak在调节ASM的过敏性炎症反应方面发挥了重要作用。小分子PAK抑制剂目前正在开发中，用于癌症化疗，因此在可预见的未来可能会进入临床。认为PAK可能是哮喘治疗的理想靶点，因为它们可能直接参与ASM的反应性以及肺和呼吸道的炎症反应的调节，将在3个特定的目的下进行，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)靶向肌动蛋白调节通路是否抑制哮喘小鼠的气道反应性、炎症和重塑；3)急性抑制PAK活性是否可以防止小鼠哮喘模型的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.