内质网应激介导IL-17致支气管扩张慢性炎症反应的作用研究

Bronchiectasis is a chronic respiratory disease where there is permanent enlargement of bronchi in the lung. It is characterized by polymorphonuclear cells (PMN)-dominated inflammation and epthelial cell death in the airway. The underlying cause of bronchiectasis is not completely revealed, and at present there is no disease-modifying treatment available for bronchiectasis. Our preliminary data have demonstrated that IL-17A level was significantly increased in bronchoalveolar lavage fluid (BALF) from bronchiectasis patients, Endoplasmic reticulum (ER) stress marker BIP and unfolded protein response (UPR) signaling pathway were found to be activated in samples from bronchiectasis patients, and those protein expression were also elevated in airway epithelial cells upon IL-17 treatment. Based on those data we propose that after binding with TLR4 Pseudomonas aeruginosa induces cytokines (eg. IL-1β, IL-6 and TGF-β etc.) secretion from epithelila cells and macrophages to promote Th17 differentiation and IL-17 secretion; Secreted IL-17 activates ER stress and its downstream signaling pathways by binding with IL-17 receptor in airway epithelial cells, 1) to promote the release of inflammatory mediators from airway epithelial cells, recruitment and activation of PMN; 2) to induce epithelial cell death, resulting in airway remodeling, lung tissue damage and pulmonary function decline. In order to test these hypotheses, the clinical samples, in vitro and in vivo models will be applied to identify the possible mechanism by which IL-17 and ER stress signaling pathways is involved in regulating the release of inflammatory mediators, PMN infiltration in the pathological process of bronchiectasis, providing evidence that therapeutic intervention to modulate the IL-17 and ER stress signaling may be an effective strategy to promote the resolution of inflammation in bronchiectasis.

支气管扩张是常见的慢性呼吸系统疾病，上皮细胞死亡及肺部过度中性粒细胞(PMN)引起的气管炎症是其病理表征。引起支气管扩张的机制目前未明，致使缺乏有效的干预措施。项目前期研究发现：支气管扩张患者肺泡灌洗液中IL-17水平增加，肺组织中内质网应激标记物升高，且IL-17能够诱导气道上皮细胞发生内质网应激。我们推测：铜绿假单胞菌通过TLR4诱导细胞产生细胞因子促进Th17细胞分化及IL-17分泌；IL-17与气道上皮细胞表面IL-17受体结合，激活内质网应激及下游信号通路，一方面促进炎症介质的释放，募集和活化PMN，另一方面诱导上皮细胞发生死亡，导致气道壁结构破坏和肺组织损伤，最终引起肺功能受损。本研究将运用临床样本，体外及体内模型阐明IL-17和内质网应激信号通路参与调节炎症介质释放、PMN浸润和上皮细胞死亡在支气管扩张炎症进程中的作用，以期为临床开辟新的治疗策略提供理论指导和帮助。

病原微生物感染是支气管扩张症（BE）最主要的潜在诱因，因此研究宿主针对病原体抗感染的免疫分子机制，解析这些免疫信号通路参与调节炎症介质释放与细胞死亡的具体过程，对BE发病机制探索及临床治疗研究具有重要意义。我们发现胞外环核苷二磷酸（eCDNs）可通过网格蛋白依赖的内吞途径被DNA识别受体cGAS所识别，并通过STING激活宿主固有免疫应答，该研究为进一步理解细菌来源CDNs对支气管扩张发生的作用及机制提研究提供了新思路；通过小鼠脓毒症模型，发现了中性粒细胞胞外陷阱（NETs）源性的HMGB1可通过RAGE-Dynamin通路，引起溶酶体cathepsin B 释放，进而诱导焦亡小体形成与Caspase-1活化，最终诱导细胞焦亡，该研究揭示了NETs在介导PMN–Mϕ交互作用及炎症进展中的重要性；此外，我们采用采用CRISPR/Cas9胚胎基因编辑技术，建立了免疫系统中缺乏成熟的T、B和NK细胞的Rag1-/-Rag2-/-Il2rg-/-大鼠（SD-RG大鼠），该种新型免疫缺陷大鼠可应用于免疫学、肿瘤学等研究，并利于CDX及PDX等模型的构建。本课题的研究拓展了炎症反应领域前沿知识，为支气管扩张症、肺癌等肺部良恶性疾病的致病机理提供了新理论依据及研究工具。