Lipopolysaccharide induces ICAM-1 expression via a c-Src/NADPH oxidase/ROS-dependent NF-κB pathway in human pulmonary alveolar epithelial cells.

Abstract

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-κB (Bay11-7082) and transfection with siRNAs of c-Src, EGFR, PDGFR, Akt, p47(phox), 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, p47(phox), 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 established that LPS induced p42/p44 MAPK activation via a c-Src/NADPH oxidase/ROS/EGFR, PDGFR/PI3K/Akt-dependent pathway in these cells. Finally, we observed that LPS significantly enhanced NF-κB and IκBα phosphorylation, NF-κB translocation, and NF-κB promoter activity, which were inhibited by PP1, Edaravone, apocynin, diphenyleneiodonium chloride, AG1478, AG1296, LY294002, or U0126. These results demonstrated that LPS induces p42/p44 MAPK activation mediated through the TLR4/MyD88/TRAF6/c-Src/NADPH oxidase/ROS/EGFR, PDGFR/PI3K/Akt pathway, which in turn initiates the activation of NF-κB and ultimately induces ICAM-1 expression in HPAEpiCs.

• Authors: Rou-Ling Cho, Chien-Chung Yang, I-Ta Lee, Chih-Chung Lin, Pei-Ling Chi, Li-Der Hsiao, Chuen-Mao Yang
• Journal: American journal of physiology. Lung cellular and molecular physiology (Am J Physiol Lung Cell Mol Physiol) Vol. 310 Issue 7 Pg. L639-57 (04 01 2016) ISSN: 1522-1504 [Electronic] United States
• PMID: 26747779 (Publication Type: Journal Article)
• Copyright: Copyright © 2016 the American Physiological Society.

Chemical References

• Lipopolysaccharides
• RELA protein, human
• Transcription Factor RelA
• Intercellular Adhesion Molecule-1
• NADPH Oxidases
• EGFR protein, human
• ErbB Receptors
• Receptors, Platelet-Derived Growth Factor
• CSK Tyrosine-Protein Kinase
• src-Family Kinases
• CSK protein, human
• Proto-Oncogene Proteins c-akt

Topics

• Alveolar Epithelial Cells (immunology, metabolism)
• CSK Tyrosine-Protein Kinase
• Cells, Cultured
• ErbB Receptors (metabolism)
• Humans
• Intercellular Adhesion Molecule-1 (genetics, metabolism)
• Lipopolysaccharides (immunology, pharmacology)
• Lung (immunology, pathology)
• NADPH Oxidases (metabolism)
• Phosphatidylinositol 3-Kinases
• Proto-Oncogene Proteins c-akt (metabolism)
• Receptors, Platelet-Derived Growth Factor (metabolism)
• Signal Transduction
• Transcription Factor RelA (metabolism)
• Transcriptional Activation (immunology)
• src-Family Kinases (physiology)