RACK1调控支气管上皮细胞损伤-修复过程在哮喘气道重塑中的作用机制及大环内酯类药物的干预作用

Bronchial epithelial cells that secrete transforming growth factor beta 1, through the TGF-β1/Smad signaling pathways involved in the formation of the airway remodeling of asthma. Scaffold protein RACK1 has already been confirmed as downstream target genes of TGF-β. Through interactions between proteins, RACK1 plays a feedback regulation role in the formation of fibrosis in cells. Regulation of RACK1 function of the bronchial epithelial cells is to implement the new strategy of refractory asthma treatment. Azithromycin often used in the treatment of children severe persistent asthma. In previous study, we have found that low doses of azithromycin could inhibit the bronchial epithelial cell apoptosis via down-regulating TGF-β1 to play a vital role in treating the airway remodeling of asthma. However, RACK1 protein level was significantly increased with azithromycin treatment as compared to asthma without treatment. Therefore, this project is designed to reveal the molecular mechanism of RACK1 in regulating the TGF-β1 mediated bronchial epithelial cell apoptosis and epithelial to mesenchymal transition (EMT), and eventually to clarify the regulation function and its mechanism of RACK1 on airway remodeling in asthma.

支气管上皮细胞能够分泌转化生长因子-β1，通过TGF-β1/Smad信号通路参与哮喘气道重塑过程。支架分子RACK1作为已确证的TGF-β下游的靶基因，通过蛋白之间的相互作用，在细胞纤维化的形成中具有反馈调节作用，调节支气管上皮细胞RACK1功能是实现难治性哮喘治疗的新策略。阿奇霉素是临床常用于治疗儿童中-重度持续性哮喘的药物，申请者前期发现小剂量阿奇霉素具有下调TGF-β1发挥治疗哮喘气道重塑时支气管上皮细胞凋亡的作用，但此时RACK1蛋白却显著上调。因此，本项目以RACK1对TGF-β1的反馈调控机制为切入点，从整体、细胞和分子水平研究、阐明RACK1对支气管上皮细胞损伤-修复过程的调控作用及其机制，预期研究结果将揭示RACK1对TGF-β1介导的支气管上皮细胞凋亡及上皮-间质转化的调节作用规律及分子机制，为研发靶向支气管上皮细胞凋亡及上皮-间质转化的理想治疗药物提供新的靶标。

本项目采用TGF-β1刺激体外培养的人支气管上皮细胞株(BEAS-2B)建立支气管上皮细胞凋亡及上皮-间质转化的细胞模型；同时采用大鼠、小鼠分别以OVA致敏、激发建立动物模型，系统评价在哮喘支气管上皮细胞损伤-修复过程中RACK1表达的特点，分析RACK1调控支气管上皮细胞损伤-修复过程在哮喘气道重塑中的作用机制及大环内酯类药物的干预作用，结果发现，TGF-β1刺激BEAS-2B细胞出现支气管上皮细胞凋亡和上皮-间质转化以及OVA诱导动物发生哮喘时，肺组织、支气管上皮细胞的RACK1蛋白表达均显著性升高；siRACK1转染细胞后，不仅可以抑制TGF-β1诱导的支气管上皮细胞凋亡，而且对上皮-间质转化也具有明显的抑制作用；进一步分析调控机制发现，RACK1主要通过调控p-ERK1/2间接激活Smad3信号通路，调节支气管上皮-间质转化；而通过上调并激活JNK调节Smad3转录以及P53表达，分别参与哮喘气道重塑时支气管上皮细胞凋亡及上皮-间质转化的形成；随后从细胞水平和整体动物水平，全面评价了阿奇霉素对哮喘气道重塑时支气管上皮细胞凋亡及上皮-间质转化的治疗作用，并深入揭示了作用的分子机制为：下调TGF-β1/RACK1。. 因此，该项目揭示了RACK1在哮喘气道重塑相关的支气管上皮细胞损伤-修复过程中的核心地位以及调控机制，从而为确立RACK1调控TGF-β1介导的支气管上皮细胞凋亡及上皮-间质转化作为阿奇霉素治疗哮喘气道重塑的新靶点奠定了一定的理论基础。. 该项目的部分研究成果已发表于SCI期刊Life Sci, 2017 Feb 1; 170: 1-8和Int Immunopharmacol, 2018 Mar 19; 58: 87-93。