Elucidation of epidermal growth factor receptor pathway in cigarette smoke medium-mediated expression of mucin genes and release of IL-8 in human airway epithelial cells

Abstract

Introduction: Chronic obstructive pulmonary disease (COPD), an inflammatory disease characterised by chronic irreversible airflow limitation, is predicted to be the third leading cause of death worldwide by 2030. The most important risk factor of COPD is cigarette smoking. Chronic exposure of airways to cigarette smoke has been found to promote excessive mucus production and amplify inflammatory response leading to impaired mucociliary function and ultimately airway obstruction. We hypothesise that epidermal growth factor receptor (EGFR) pathway plays a crucial role in the regulation of airway goblet cell hyperplasia, mucus hypersecretion, and inflammation. Methods: NCI-H292 cells were cultured in RPMI1640 (Gibco) supplemented with 10% foetal bovine serum. After starvation, cells were exposed to various concentrations of cigarette smoke medium (CSM) of 1 to 4% for 24 hours, or pretreated without or with AG1478 (0.1-10 µM) for 30 minutes before 4% CSM exposure for 24 hours. After treatment, cell lysates and cell culture supernatants were collected for gene expression studies, western blot analysis, and measurement of pre-inflammatory marker IL-8, respectively. Results: CSM caused a concentration-dependent elevation of MUC5AC and MUC5B mRNA, and IL-8 release in NCI-H292 cells, but no significant induction of MUC2 mRNA was observed. AG1478 alone had no effect on mucins mRNA level and IL-8 release but inhibited CSM-induced elevation of MUC5AC and MUC5B mRNA and IL-8 release. Phosphorylation of EGFR was confirmed to be crucial in the cigarette smoke induction of mucins mRNA and IL-8 release. Conclusion: EGFR activation by phosphorylation is crucial in CSM-induced mucus hypersecretion and airway inflammation. AG1478 may be a possible pharmacological intervention for the symptomatic treatment of mucus hypersecretion and the underlying chronic inflammation.