Institute of Biology, Biomedical Center, University of Iceland, Landspitali, Eiriksgata 5, Reykjavik, Iceland.
Am J Respir Cell Mol Biol. 2010 Jan;42(1):62-8. doi: 10.1165/rcmb.2008-0357OC. Epub 2009 Apr 16.
Tight junctions (TJs) play a key role in maintaining bronchial epithelial integrity, including apical-basolateral polarity and paracellular trafficking. Patients with chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) often suffer from chronic infections by the opportunistic Gram-negative bacterium Pseudomonas aeruginosa, which produces multiple virulence factors, including rhamnolipids. The macrolide antibiotic azithromycin (azm) has been shown to improve lung function in patients with CF without reducing the bacterial count within the lung. However, the mechanism of this effect is still debated. It has previously been shown that azm increased transepithelial electrical resistance (TER) in a bronchial epithelial cell line. In this study we used an air-liquid interface model of human airway epithelia and measured TER, changes in TJ expression and architecture after exposure to live P. aeruginosa PAO1, and PAO1-Deltarhl which is a PAO1 mutant lacking rhlA and rhlB, which encode key enzymes for rhamnolipid production. In addition, the cells were challenged with bacterial culture medium conditioned by these strains, purified rhamnolipids, or synthetic 3O-C(12)-HSL. Virulence factors secreted by P. aeruginosa reduced TER and caused TJ rearrangement in the bronchial epithelium, exposing the epithelium to further bacterial infiltration. Pretreatment of the bronchial epithelium with azm attenuated this effect and facilitated epithelial recovery. These data suggest that azm protects the bronchial epithelium during P. aeruginosa infection independent of antimicrobial activity, and could explain in part the beneficial results seen in clinical trials of patients with CF.
紧密连接 (TJs) 在维持支气管上皮完整性方面发挥着关键作用，包括顶-底极性和细胞旁转运。慢性阻塞性肺疾病 (COPD) 和囊性纤维化 (CF) 患者常遭受机会性革兰氏阴性菌铜绿假单胞菌的慢性感染，该菌产生多种毒力因子，包括鼠李糖脂。大环内酯类抗生素阿奇霉素 (azm) 已被证明可改善 CF 患者的肺功能，而不会减少肺部的细菌计数。然而，这种作用的机制仍存在争议。先前已经表明，azm 增加了支气管上皮细胞系的跨上皮电阻 (TER)。在这项研究中，我们使用了人气道上皮的气液界面模型，并在暴露于活铜绿假单胞菌 PAO1 和缺乏 rhlA 和 rhlB 的 PAO1 突变体 PAO1-Deltarhl 后测量了 TER、TJ 表达和结构的变化，rhlA 和 rhlB 编码鼠李糖脂产生的关键酶。此外，用这些菌株的细菌培养液、纯化的鼠李糖脂或合成的 3O-C(12)-HSL 对细胞进行了挑战。铜绿假单胞菌分泌的毒力因子降低了 TER 并导致支气管上皮 TJ 重排，使上皮细胞更容易受到进一步的细菌渗透。用 azm 预处理支气管上皮可减弱这种作用并促进上皮恢复。这些数据表明，azm 在铜绿假单胞菌感染期间保护支气管上皮，独立于抗菌活性，这可以部分解释 CF 患者临床试验中观察到的有益结果。
