Département de Médecine, Centre de Recherche, Centre Hospitalier de l'Université de Montréal-Hôtel-Dieu, 3840 St. Urbain, Montréal, PQ, Canada.
Am J Physiol Lung Cell Mol Physiol. 2010 Mar;298(3):L417-26. doi: 10.1152/ajplung.00170.2009. Epub 2009 Dec 11.
Pseudomonas aeruginosa is a gram-negative bacterium that causes chronic infection in cystic fibrosis patients. We reported recently that P. aeruginosa modulates epithelial Na(+) channel (ENaC) expression in experimental chronic pneumonia models. For this reason, we tested whether LPS from P. aeruginosa alters ENaC expression and activity in alveolar epithelial cells. We found that LPS induces a approximately 60% decrease of ENaC apical current without significant changes in intracellular ENaC or surface protein expression. Because a growing body of evidence reports a key role for extracellular nucleotides in regulation of ion channels, we evaluated the possibility that modulation of ENaC activity by LPS involves extracellular ATP signaling. We found that alveolar epithelial cells release ATP upon LPS stimulation and that pretreatment with suramin, a P2Y(2) purinergic receptor antagonist, inhibited the effect of LPS on ENaC. Furthermore, ET-18-OCH3, a PLC inhibitor, and Go-6976, a PKC inhibitor, were able to partially prevent ENaC inhibition by LPS, suggesting that the actions of LPS on ENaC current were mediated, in part, by the PKC and PLC pathways. Together, these findings demonstrate an important role of extracellular ATP signaling in the response of epithelial cells to LPS.
铜绿假单胞菌是一种革兰氏阴性细菌，可导致囊性纤维化患者的慢性感染。我们最近报道，铜绿假单胞菌在实验性慢性肺炎模型中调节上皮钠离子通道（ENaC）的表达。基于此，我们测试了铜绿假单胞菌的 LPS 是否会改变肺泡上皮细胞中 ENaC 的表达和活性。我们发现 LPS 诱导 ENaC 顶端电流约减少 60%，而细胞内 ENaC 或表面蛋白表达无明显变化。由于越来越多的证据表明细胞外核苷酸在调节离子通道方面发挥着关键作用，我们评估了 LPS 对 ENaC 活性的调节是否涉及细胞外 ATP 信号转导。我们发现 LPS 刺激肺泡上皮细胞释放 ATP，而 P2Y（2）嘌呤能受体拮抗剂苏拉明预处理可抑制 LPS 对 ENaC 的作用。此外，PLC 抑制剂 ET-18-OCH3 和 PKC 抑制剂 Go-6976 可部分阻止 LPS 对 ENaC 的抑制，表明 LPS 对 ENaC 电流的作用部分通过 PKC 和 PLC 途径介导。综上所述，这些发现表明细胞外 ATP 信号在细胞对 LPS 的反应中起着重要作用。
