大气细颗粒物通过Shp2/MAPK炎性信号通路诱导气道高反应性的作用和机制

PM2.5 is regarded as a risk factor for respiratory diseases and induces respiratory diseases, such as asthma. Airway hyper-reactivity (AHR) is the characteristics of airway obstructive diseases. Many studies showed that environmental risk factors trigger inflammation leading to AHR, but knowledge about the underlying molecular mechanisms on how PM2.5 leads to the development of AHR is limited. The applicant found that contractile G-protein coupled receptor up-regulation is the basis of AHR and the Shp2/MAPK signaling pathway is involved in receptor up-regulation. Therefore, we hypothesized that PM2.5 exposure causes AHR by up-regulating airway contractile receptors via the Shp2/MAPK pathway which is activated by airway inflammation. On the basis of previous studies, the effects of PM2.5 exposure on receptors expression, inflammatory cytokines expression and Shp2/MAPK pathway activation level will be evaluated by using organ culture and cell models in vitro and intratracheal instillation model in vivo. Furthermore, the role of Shp2/MAPK signaling pathway in PM2.5-induced up-regulation of contractile receptors and inflammatory cytokines will be examined by pathway inhibitors and RNA interference technique. The completion of the project may reveal the underlying molecular mechanism of PM2.5-induced contractile receptor up-regulation in AHR. It may provide novel target in intracellular inflammatory signal pathways for treatment of PM2.5-associated AHR respiratory diseases.

PM2.5是呼吸系统疾病危险因素，易诱发哮喘等疾病。气道高反应性是其重要特征。目前认为环境刺激因素引起的气道高反应性与炎症相关，但PM2.5如何通过炎症诱导气道高反应性国内外尚无报道。我们初步发现气道平滑肌收缩性G蛋白偶联受体上调是PM2.5诱导气道高反应性的基础，Shp2/MAPK炎性通路在受体上调中起关键作用。我们假设PM2.5通过诱发气道炎症，激活炎性通路，上调收缩性受体，诱导气道高反应性。本研究拟用离体器官培养模型、大鼠气管滴注模型和人支气管平滑肌细胞作为研究对象，检测PM2.5对受体介导收缩功能和表达的影响，检测炎性因子及炎性通路活化水平；用信号通路抑制剂和基因转染技术抑制胞内信号通路表达反向观察Shp2/MAPK通路与PM2.5诱导气道炎症和受体上调的关系。揭示PM2.5诱导气道高反应性、调控受体表达变化的机制，在细胞炎性信号通路水平寻找防治PM2.5诱发气道高反应性的新靶点。

大气细颗粒物与呼吸系统疾病的发生发展密切相关，炎症和气道高反应性是哮喘等呼吸系统疾病的重要特征，但PM2.5如何引起上述变化，其具体分子机制目前仍不清楚。在本项目中，我们发现：①用不同溶剂提取PM2.5水溶性、脂溶性及全颗粒组分，分别处理离体支气管环和细胞，PM2.5脂溶性组分能增强离体支气管平滑肌毒蕈碱受体、内皮素A和内皮素B受体介导的收缩，但对5-羟色胺诱导的支气管收缩反应无明显作用。PM2.5全颗粒和脂溶性组分均能抑制肺泡上皮细胞和支气管平滑肌细胞增殖，且其作用且呈时间和浓度依赖性。②分别通过气道滴注和PM2.5滴鼻建立大/小鼠气道高反应性模型。PM2.5能引起动物肺部炎症和氧化应激，造成呼吸频率等肺功能指标异常，引起ERK1/2 MAPK和p38 MAPK信号通路的活化，上调气道平滑肌毒蕈碱受体诱导气道高反应性。PM2.5通过炎性反应，促使肺泡上皮细胞增生、胶原纤维和弹性纤维表达增加，参与气道重塑。PM2.5处理大鼠离体动脉环，增强了血栓素受体介导的收缩反应，增强p-ERK1/2、p-JNK和p-p38蛋白的表达，激活MAPK信号通路，进而引起受体上调，诱发血管高反应。PM2.5处理细胞，MAPK通路抑制剂及地塞米松可拮抗PM2.5对支气管平滑肌细胞增殖的抑制作用，增强对肺泡上皮细胞增殖的抑制作用，作用呈时间和浓度依赖性；且可抑制PM2.5诱导的炎症介质释放。③炎症和氧化应激是PM2.5诱发或加重呼吸系统疾病的主要作用机制。抗氧化剂可有效缓解PM2.5造成的大鼠肺功能损伤，改善肺部炎症、增强抗氧化酶活性，改善PM2.5所致大鼠肺组织病理损伤，减少炎性浸润，减轻肺组织胶原纤维和弹性纤维增生。本研究的完成将揭示PM2.5相关呼吸系统疾病的机理，为其预防和治疗提供新思路。