Rac1信号调控香烟诱导气道上皮细胞－间充质细胞转化的分子机制

Chronic airway inflammatory diseases including chronic obstructive pulmonary diseases(COPD), asthma, idiopathic pulmonary fibrosis has a different reason and degree of epithelial cell damage. Damage-induced epithelial-to－mesenchymal transformation (EMT) is recognized as a key cause of airway remodeling and fibrosis.Cigarette smoking is an important risk factor for the respiratory system diseases. Our previous research has shown cigarette smoking can lead to Rac1 and Rac2 activation in lung tissue, but Rac1 inhibitor could significantly reduce increase in neutrophils and macrophages, oxidative stress and proinflammatory factors, and suggested the important regulatory effect of Rac1 signal pathway on the lung inflammation caused by smoking. And we found that the mice exposed to cigarette can cause lung epithelial cells to EMT. Cigarette smoking extract can induced lung epithelial cells to EMT in vitro, which can be inhibited by Rac1 specific inhibitors. In the studies, we presume Rac1 as a potential signal pathway in lung epithelial cells to EMT. We will apply the Rac1 knockout mice, Rac specificity inhibitor and molecular pharmacological methods, to explore regulatory mechanism of the Rac1 signal pathway on smoking-induced EMT in the lung, epithelial cell proliferation and secretion and apoptosis. We suggest that Rac may be a potential target for therapeutic intervention of epithelial-mesenchymal cells transformation.

慢性气道炎症性疾病包括COPD、哮喘、特发性肺纤维化等都有不同原因和程度的上皮细胞损伤，损伤引起的上皮-间充质细胞转化(EMT)被认为是导致气道重塑和纤维化的关键。吸烟是呼吸系统疾病的重要诱导因素。之前的研究我们已经证明LPS或吸烟激活肺组织中Rac1抑制剂能显著减少吸烟所导致的中性粒细胞和巨噬细胞的肺组织内的浸润、氧化损伤和炎症介质的产生，揭示了Rac1在吸烟所致的肺部炎症中的重要地位。同时我们发现香烟暴露小鼠可导致肺上皮细胞EMT和香烟提取物诱导人肺上皮细胞引起EMT，这些变化可被Rac特异性抑制剂所减轻。为了进一步深入研究，我们将以Rac1作为影响EMT的潜在信号，采用Rac1基因敲除的小鼠、siRNA干扰、Rac1特异性抑制剂等工具和分子药理学方法，探索Rac1信号在吸烟引起的气道EMT，上皮细胞增殖、分泌和凋亡的调节机制，为COPD治疗建立新的药物靶点。

慢性气道炎症性疾病包括COPD、哮喘、特发性肺纤维化等都有不同原因和程度的上皮细胞损伤，损伤引起的上皮-间充质细胞转化(EMT)被认为是导致气道重塑和纤维化的关键。吸烟是呼吸系统疾病的重要诱导因素。之前的研究我们已经证明Rac1抑制剂能显著减少LPS所导致的中性粒细胞和巨噬细胞在肺组织内的浸润、氧化损伤和炎症介质的产生，揭示了Rac1在肺部炎症中的重要地位。本研究表明，1）香烟烟雾提取物(CSE)诱导肺上皮细胞Rac1的激活，增加TGF-β1表达。阻断TGF-β1通路能抑制CSE诱导的EMT相关因子的变化。Rac1特异性抑制剂NSC或Rac1基因敲除减少CSE诱导的TGF-β1释放，改善CSE诱导的EMT。在香烟暴露的小鼠EMT模型中，NSC也能减少TGF-β1释放和EMT标志物的表达。此外，在体外肺上皮细胞上抑制Rac1的表达和活性可以缓解CSE诱导的Smad2和AKT激活，Smad2，PI3K和AKT抑制剂能逆转CSE诱导的EMT因子表达的变化。因此，CSE通过上调TGF-β1的表达、Rac1及其下游Smad2和AKT通路的激活来促使上皮细胞向间质细胞的转型；2）CSE能诱导支气管上皮细胞炎症因子IL-6和IL-8的表达和释放，通过抑制Rac1的表达或活性能逆转CSE诱导的IL-6和IL-8的表达。在香烟暴露的小鼠急性肺炎模型中，Rac1特异性抑制剂也能减少IL-6和IL-8的释放和改善肺部炎症。这个过程的调节主要通过Erk1/2 MAPK和STAT3信号通路起作用。上述两个模型的研究结果表明Rac1在香烟烟雾暴露诱导的炎症和EMT中是一个重要的信号分子，Rac1可能是治疗COPD小气道纤维化的潜在靶点。