Lipopolysaccharide induces ICAM-1 expression via a c-Src/NADPH oxidase/ROS-dependent NF-{kappa}B pathway in human pulmonary alveolar epithelial cells

Upregulation of intercellular adhesion molecule-1 (ICAM-1) is frequently implicated in lung inflammation. Lipopolysaccharide (LPS) has been shown to play a key role in inflammation via adhesion molecule induction and then causes lung injury. However, the mechanisms underlying LPS-induced ICAM-1 expression in human pulmonary alveolar epithelial cells (HPAEpiCs) remain unclear. We showed that LPS induced ICAM-1 expression in HPAEpiCs, revealed by Western blotting, RT-PCR, real-time PCR, and promoter assay. Pretreatment with the inhibitor of c-Src (protein phosphatase-1, PP1), reactive oxygen species (ROS) (Edaravone), NADPH oxidase (apocynin and diphenyleneiodonium chloride), EGFR (AG1478), PDGFR (AG1296), phosphatidylinositol-3-kinase (PI3K) (LY294002), MEK1/2 (U0126), or NF-B (Bay11-7082) and transfection with siRNAs of c-Src, EGFR, PDGFR, Akt, p47phox, Nox2, Nox4, p42, and p65 markedly reduced LPS-induced ICAM-1 expression and monocyte adherence to HPAEpiCs challenged with LPS. In addition, we established that LPS stimulated phosphorylation of c-Src, EGFR, PDGFR, Akt, or p65, which was inhibited by pretreatment with their respective inhibitors. LPS induced Toll-like receptor 4 (TLR4), MyD88, TNF receptor-associated factor 6 (TRAF6), c-Src, p47phox, and Rac1 complex formation 2, which was attenuated by transfection with c-Src or TRAF6 siRNA. Furthermore, LPS markedly enhanced NADPH oxidase activation and intracellular ROS generation, which were inhibited by PP1. We establishe...
Source: AJP: Lung Cellular and Molecular Physiology - Category: Respiratory Medicine Authors: Tags: ARTICLES Source Type: research