Wnt/beta-catenin 信号在协调肺泡上皮细胞与巨噬细胞宿主防御机制中的作用

Increasing incidences of morbidity and mortality of lung diseases including the pulmonary tuberculosis and lung cancer have been reported worldwide in recent years, Alveoli of lungs are the solo sites for gas-exchanges and the terminals of the airway in lung，they are thus attacked by the exogenous microorganisms and particle materials of air, as well as the last defense line for the exogenous invasions. Therefore, the immunological homeostasis in alveoli plays a key role in normal lung function. We recently found that the Wnt/?-catenin signaling exerted different immunoregulatory functions between the alveolar epithelial cells (AEC) and alveolar macrophages (AM) in response to mycobacterial infection, which implies that it may be able to coordinate these two types of alveolar cells in response to an infection and play a regulatory role in the maintenance of immunological homeostasis in alveoli. The overall goal of present proposal is aimed to interrogate the underlying mechanisms of AECs and AMs in response to pathogenic microbial infection, and the immunoregulatory roles of Wnt/beta-catenin signaling in inflammatory responses, phagocytosis of bacteria and the modes of cell death between the AECs and AMs upon an exogenous pathogenic stimulation，using an novel air-liquid interface (ALI) AEC model, an ALI AEC/AM co-culture model and a murine model. The acomplishment of studies will provide novel insights into the underlying mechanisms of pulmonary infectious diseases.

肺泡作为呼吸道的终端是实现气体交换的唯一场所，无时不受到空气中微生物和异物的侵袭，是肺脏抵抗外来物的最后防线，所以，肺泡及其细胞的动态平衡是维护肺脏正常功能的关键。我们最近研究发现，Wnt/beta-catenin信号在肺泡上皮细胞（AEC）和巨噬细胞(AM)抗结核分枝杆菌BCG感染过程中发挥不尽相同的免疫调节作用，提示该信号可能在肺泡内协调肺泡上皮细胞和巨噬细胞抗感染过程中发挥作用，以维持肺泡细胞的免疫动态平衡。本项目旨在建立新型肺泡上皮细胞体外气液相培养模型的基础上，利用巨噬细胞-上皮细胞共培养技术和小鼠模型，研究肺泡内AEC和AM抗病原微生物感染的免疫学反应性，以及Wnt/?-catenin信号在协调肺泡内AEC和AM抵抗外源病原微生物感染过程中调节细胞的炎症反应性、吞噬细菌能力和细胞死亡方式的作用机制。该项目的实施对于阐明肺脏传染病的免疫致病机理有重要的理论意义。

肺泡微环境主要由肺泡上皮细胞和定居在肺泡内的巨噬细胞组成，而两者之间通过信号网络调控相互作用以维持应激状态下肺泡微环境的稳态。除在胚胎发育和组织损伤修复中发挥重要作用外，Wnt/beta-catenin信号在免疫调控中的作用也越来越受到重视，而阐明它如何调控巨噬细胞免疫反应以维护肺泡微环境稳态的作用与机制是揭示该信号在维持肺脏稳态和肺脏疾病发生的关键。因此本项目通过建立肺泡上皮细胞、巨噬细胞共培养模型，探讨肺脏上皮细胞Wnt/beta-catenin信号调控巨噬细胞抗结核分枝杆菌感染免疫反应，以及其对巨噬细胞极化的作用机制。结果发现牛、羊气道上皮细胞对Toll样受体信号介导的抗结核分枝杆菌感染具有细胞和病原种属特异性，以及肺泡上皮细胞Wnt/β-catenin信号对肺脏纤维细胞间质化特征的调控作用机制。上皮细胞可以通过Wnt/β-catenin信号抑制剂GSK3β和mTOR信号共同调控PI3K/MAPK介导的巨噬细胞抗结核分枝杆菌感染的炎性反应。而且在白介素(IL)-17或IL-21存在炎性环境下，Wnt/β-catenin能够通过JAK/STAT信号负反馈调控巨噬细胞的极化。重要的是，研究发现经典的Wnt/β-catenin信号和 Wnt非经典信号在调控肺脏上皮细胞抗结核肺脏杆菌感染的免疫反应中发挥相反的作用，提示经典和非经典Wnt信号的平衡在维持肺泡微环境免疫稳态中可能发挥重要作用。同时非经典Wnt配体Wnt5a具有调控肺脏上皮细胞抗结核杆菌感染炎性反应和增强肺癌细胞耐顺铂的作用。 这些发现对进一步探讨Wnt 信号在协调肺泡上皮细胞和巨噬细胞抵抗外源病原微生物感染和肺癌病理发生的作用机制，以及阐明肺脏疾病病理发生机理有重要的理论意义。