细菌感染引起大鼠气道上皮细胞损伤及其机制探讨

Study on the rat airway epithelial cell injury induced by bacterial infection and its pathogenesis

目的 探讨肺炎克雷伯杆菌感染导致气道 ,尤其是小气道上皮细胞的损伤及其发生机制。方法 应用多次经鼻腔注入肺炎克雷伯杆菌液的呼吸道感染方法诱发大鼠气道炎症、慢性阻塞性肺疾病动物模型 ,采用扫描电镜、透射电镜及光镜动态观察大鼠气道的损伤改变 ,用免疫组织化学(SABC法 )和原位杂交法检测小气道上皮细胞肌动蛋白、肿瘤坏死因子 (TNF) α、fos及Jun蛋白及其mRNA表达的变化 ,用放射免疫分析法检测肺组织中TNF α含量。结果 肺炎克雷伯杆菌感染组第1周 ,气管上皮细胞纤毛粘连、倒伏 ,部分脱落 ,小气道上皮细胞间紧密连接破坏 ,间隙增宽 ;第 2周细胞内微丝排列呈束状。第 2、4周 ,各级支气管上皮细胞损伤加重 ,慢性炎症明显 ,细支气管管壁增厚 ,管腔狭窄 ,形成肺气肿。与对照组相比 ,TNF αmRNA表达在第 2、4周显著增高 (P <0 .0 1) ,第 4周时 ,其蛋白表达水平显著增高 (P <0 .0 1) ,小气道上皮细胞fos蛋白及其mRNA水平从第 1周起显著增高(P <0 .0 1)。肺组织中TNF α含量第 1周起显著增高 (P <0 .0 1) ,并持续至第 8周。结论 肺炎克雷伯杆菌吸入可诱发大鼠气道炎症和肺气肿 ,早期气道上皮细胞损伤表现为纤毛粘连、倒伏、脱落 ,细胞间隙增宽 ,有利于细菌侵袭 ,其原因可能与细胞内微丝排列改变有?

Objective To explore the rat airway, especially small airway epithelium injury induced by Klebsiella pneumoniae infection and its pathogenesis. Methods A rat airway inflammation and COPD model was induced by repeated intranasal infection with Klebsiella pneumoniae. The injury changes were dynamically observed under SEM, TEM and LM. Actin, TNF α, Fos, Jun protein and their mRNA expression levels in small airway epithelium were analyzed by immunohistochemistry and in situ hybridization. The changes of lung TNF α content were examined by radioimmunoassay. Results 1 week after Klebsiella pneumoniae infection the epithelial cilia cohered, fell down, partially fell off and the tight intercellular connection destroyed. 2 and 4 weeks after the infection, the injury of bronchus epithelia worsened with pronounced chronic inflammation in all bronchi. The bronchioles walls became thickened, lumen narrowed and emphysema was noted. Compared with control group, TNF α mRNA expression was higher ( P <0.01) in the 2nd and 4th week while TNF α protein was higher at 4 weeks ( P <0.01). From 1st week after the infection, Fos protein and mRNA expression began to elevate ( P <0.01). TNF α content of lung began to increase ( P <0.01) and kept at a higher level until the 8th week. Conclusions Repeated intranasal injection of a certain amount of Klebsiella pneumoniae can induce airway inflammation and emphysema. The main features of early airway epithelia injury are damage of cilia and intercellular junctions, the cause of which may be associated with changes in microfilament arrangement of epithelia. High expression of TNF α protein in the airway epithelia and lung parallels with epithelium injury. Fos and Jun proteins may also play important roles in up regulating the TNF α protein.