ILC2介导嗜酸祖细胞原位分化在柴油车尾气颗粒诱发的嗜酸细胞性支气管炎发病中的作用

Eosinophilic bronchitis (EB) is one of the most common causes of chronic cough in China. Its prevalence is much higher than that in Europe and US. The majority of EB are not atopic, which indicates that the Th2 pathway might not play a key role in airway eosinophilic inflammation in EB. However, the mechanism of EB remains unclear. Diesel exhaust particles (DEPs) is the most important source of urban atmospheric PM2.5 and could induce cough，and non-allergic eosinophilic inflammation in murine models as well. Since eosinophil progenitors (EoP) can differentiate into mature eosinophil through in-situ differentiation in the airway. We hypothesize that type 2 innate lymphoid cell (ILC2)-induced in-situ differentiation of EoP play a role in the pathogenesis of EB. Firstly, in different phenotypic patients with EB, the level of in-situ differentiation of EoP in airway would be investigated, as well as its relationship with the ILC2 level. Besides, using a co-culture system of ILC2 and epithelium cells, combining with the DEPs exposure experiment in mice, how DEPs inducing airway eosinophilic inflammation through ILC2 -induced in-situ differentiation of EoP will be explored in series vivo and vitro studies. Finally, a mixed cohort study, based on the established clinical database, will be performed to evaluate the effect of DEPS exposure on EB relapse and in-situ differentiation of EoP through a cox proportional hazards model.All above will be useful to explain the pathogenesis of EB and reveal the effects of DEPs on chronic airway diseases.

嗜酸粒细胞性支气管炎(EB)为我国慢性咳嗽最常见的病因之一，患病率明显高于欧美。EB大多缺乏变应征，气道嗜酸细胞增高并非主要由Th2通路所致，但病因未明。柴油车尾气颗粒（DEPs）是我国城市大气PM2.5重要来源，可引起咳嗽及实验动物非变应性嗜酸细胞气道炎症。由于嗜酸祖细胞（EoP）原位分化可导致局部嗜酸细胞炎症，我们推测：DEPs可以损伤上皮激活ILC2引起EOP原位分化，导致局部非变应性嗜酸细胞性炎症的产生。本项目将观察不同表型EB患者EoP原位分化水平及其与ILC2的关系；构建支气管上皮细胞与ILC2共培养体系，结合柴油车尾气暴露小鼠实验，从细胞及动物实验水平上探讨DEPs通过激活ILC2介导的EoP原位分化的作用及途径。在前期建立的临床患者数据库基础上，采用混合队列评估DEPs暴露水平对EB患者EoP原位分化及症状复发的影响。最终阐明EB的发病机制并揭示DEPs的健康效应。

嗜酸粒细胞性支气管炎（NAEB）为我国慢性咳嗽最常见的病因之一，患病率明显高于欧美。NAEB大多缺乏变应征，气道嗜酸粒细胞增高并非主要由Th2通路所致，但病因未明。柴油机尾气颗粒（DEPs）是我国城市大气PM2.5重要来源，可引起咳嗽及实验动物非变应性嗜酸细胞气道炎症。由于嗜酸祖细胞（EoP）原位分化可导致局部嗜酸细胞炎症，我们认为DEPs可以损伤上皮激活ILC2引起EoP原位分化，介导局部非变应性嗜酸细胞性炎症产生。本项目纳入NAEB患者，通过流式细胞学对总体及不同临床表型NAEB患者外周血及诱导痰ILC2、EoP、Th2细胞水平进行检测，同时评估随访后变化。通过构建柴油机颗粒暴露体系，以小鼠为范式，明确最佳暴露浓度及时程，探讨ILC2在该暴露模型中的作用。结果发现：1）气道内的ILC2、EoP水平显著增高，外周血未见异常。2）局部ILC2水平与气道嗜酸粒细胞、CD4+CRTH2+T细胞、FeNO水平均成中等程度相关，局部EoP水平与气道嗜酸粒细胞性水平成中等程度相关，3）一月吸入激素治疗后虽然哮喘患者症状有改善，但是气道ILC2、EoP水平仍维持较高水平。4）发现高浓度暴露4周组为最佳暴露时程，BALB/C小鼠的气道反应性在4周时最高，炎症评分均较阴性对照组增高，产生Th2/Th17混合型气道炎症，伴有气道阻力增加。相对于传统的CD4+T细胞，ILC2、IL-17+ILCs活化程度更高。5）敲除CD4+T细胞后，ILC2可以独立介导DEP引起的Th2/Th17混合型气道炎症及高反应性。本项目研究结果首次发现了NAEB患者气道炎症的其他可能通路，证实了气道EoP原位分化和ILC2固有免疫反应两条炎症通路均参与了NAEB患者中嗜酸细胞炎症反应。同时成功构建柴油机尾气暴露模型，该模型可模拟NAEB患者临床特点，证实ILC2在介导柴油机尾气直接暴露诱导的小鼠气道炎症中起着重要的作用，为临床NAEB乃至空气污染诱导的呼吸道疾病的发病机制提供了强有力的理论依据。