外泌体介导抗菌肽LL-37调控支气管上皮细胞-成纤维细胞对话促进COPD气道重塑的机制研究

气道重塑是COPD气流受限的主要原因，外泌体参与支气管上皮细胞-成纤维细胞对话促进COPD气道重塑发生，但机制不明。课题组前期研究发现：①COPD患者支气管上皮细胞TLR4及抗菌肽LL-37高表达，LL-37与小气道壁厚度及胶原沉积正相关；②CSE刺激支气管上皮细胞外泌体LL-37高表达，LL-37通过ERK通路促进成纤维细胞胶原合成。基于此，提出如下假说：TLR4调控支气管上皮细胞LL-37被包裹进入外泌体，LL-37经由外泌体途径被转运至成纤维细胞，与甲酰肽样受体结合激活ERK通路，促进成纤维细胞增殖、向肌成纤维细胞分化及胶原合成，促进COPD气道重塑。本课题拟采用细胞共培养、基因敲除小鼠等多种实验方法，从临床标本、细胞及动物等不同层面，探索LL-37经由外泌体途径调控支气管上皮细胞-成纤维细胞对话促进COPD气道重塑的分子机制，尝试以新的理论探讨COPD发病机理，为其防治提供科学依据

Airway remodeling is the most important causing of the airflow limitation of Chronic Obstructive Pulmonary Disease. Exosome plays a pivotal role in modulation of crosstalk between bronchial epithelial cells and lung fibroblasts which further promotes the airway remodeling in Chronic Obstructive Pulmonary Disease, but the molecular mechanism still remains unclear. Our previous study confirmed that the expression of TLR4 and antimicrobial peptide LL-37 was significantly elevated in bronchial epithelial cells of COPD patients and the level of LL-37 was positively correlated with small airway wall thickness and collagen deposition. Cigarette smoke extract-induced epithelial secretion of LL-37 in exosome could up-regulate collagen expression of lung fibroblasts via activation of ERK signaling pathway. Based on the literature review and our previous study, we hypothesize that activation of TLR4 enhances exosomal shuttle of LL-37 in bronchial epithelial cells, LL-37 could be incorporated into exosome and transmitted to lung fibroblasts and then promote the proliferation and myofibroblast differentiation and the deposition of collagen in lung fibroblasts via activation of FPRL1-mediated ERK signaling pathway. To test this hypothesis, we will investigate the role and mechanism of exosome-transmitted LL-37 in regulation of crosstalk between bronchial epithelial cells and lung fibroblasts through the method of in vitro cell co-culture and knockout mice. This will further help us understand the pathogenesis of COPD, and will shed new lights on prevention and treatment of COPD.