epidermal-growth-factor and Airway-Obstruction

Topics: Adrenal Cortex Hormones; Adrenergic alpha-2 Receptor Agonists; Adult; Aged; Aged, 80 and over; Airway Obstruction; Airway Remodeling; Asthma; Chronic Disease; Elasticity; Epidermal Growth Factor; Female; Follow-Up Studies; Humans; Leukotriene Antagonists; Lung; Male; Middle Aged; Muscarinic Antagonists; Prospective Studies; Pulmonary Emphysema; Radiography

The airway epithelial barrier provides defenses against inhaled antigens and pathogens, and alterations of epithelial barrier function have been proposed to play a significant role in the pathogenesis of chronic airway diseases. Although the epidermal growth factor receptor (EGFR) plays roles in various physiological and pathological processes on the airway epithelium, the role of EGFR on barrier function in the airway remains largely unknown. In the present study, we assessed the effects of EGFR activation on paracellular permeability in airway epithelial cells (AECs). EGFR activation induced by the addition of EGF increased transepithelial electrical resistance (TER) in AECs. An EGFR-blocking antibody eradicated the development of TER, paracellular influx of dextran, and spatial organization of tight junction. Moreover, the effects of EGFR activation on paracellular permeability were eradicated by knockdown of occludin. To identify the EGFR signaling pathway that regulates permeability barrier development, we investigated the effects of several MAP kinase inhibitors on permeability barrier function. Pretreatment with a JNK-specific inhibitor, but not an ERK- or p38-specific inhibitor, attenuated the development of TER induced by EGFR activation. Rac1 is one of the upstream activators for JNK in EGFR signaling. Rac1 knockdown attenuated the phosphorylation of JNK activation and EGFR-mediated TER development. These results suggest that EGFR positively regulates permeability barrier development through the Rac1/JNK-dependent pathway.

Topics: Airway Obstruction; Cell Membrane Permeability; Epidermal Growth Factor; Epithelial Cells; ErbB Receptors; Humans; Lung; MAP Kinase Kinase 4; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; rac1 GTP-Binding Protein; Tight Junctions

Matrix metalloprotease (MMP)-9 is present in abundance in various chronic airway disorders and is involved in lung remodeling. MMP may cleave membrane-bound precursor proteins and release epidermal growth factor-like ligands that subsequently bind to epidermal growth factor receptor (EGFR). We hypothesized that MMP-9 may stimulate the airway epithelium to produce fibrogenic mediators through activation of membrane-bound receptors.. Human airway epithelial cells were grown on air-liquid interface culture inserts. MMP-9 was employed to stimulate the cells. Conditioned medium following MMP-9 stimulation was co-incubated with human lung fibroblasts.. MMP-9 stimulated human airway epithelial cells to produce transforming growth factor (TGF)-β(1) at both the mRNA and protein level. Using a microarray, increased phosphorylation of EGFR tyrosine kinase (TK) was identified and further confirmed by immunoprecipitation and Western blot analysis. A significant increase in EGF and TGF-α release was observed after MMP-9 had been added for 30min. Protease inhibitor, EGFR monoclonal antibody and EGFR-TK inhibitor blocked this action and subsequent TGF-β(1) production. Neutralizing antibodies against EGF and TGF-α substantially inhibited TGF-β(1) production following MMP-9 stimulation. MMP-9-induced TGF-β(1) production occurred through MAP kinase p44/42 phosphorylation. Selective p44/42 kinase inhibitor UO126 successfully inhibited TGF-β(1) production. Conditioned medium from epithelial cells treated with MMP-9 significantly induced Smad3 phosphorylation and subsequent fibroblast proliferation after 24h culture.. These data indicate that MMP-9 induces TGF-β(1) production in the airway epithelium through the cleavage of EGF and EGF-like ligands and activating EGFR, suggesting potential targets of therapeutic intervention in airway fibrotic disorders.

Topics: Airway Obstruction; Blotting, Western; Cell Proliferation; Epidermal Growth Factor; ErbB Receptors; Fibroblasts; Humans; Matrix Metalloproteinase 9; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinases; Phosphorylation; Receptor Protein-Tyrosine Kinases; Respiratory Mucosa; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Smad3 Protein; Transforming Growth Factor alpha; Transforming Growth Factor beta1