transforming-growth-factor-alpha and Carcinoma--Mucoepidermoid

Mucous hypersecretion is an important feature of obstructive airway diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. Multiple stimuli induce mucin production via activation of an epidermal growth factor receptor (EGFR) cascade, but the mechanisms that exaggerate mucin production in obstructive airway diseases remain unknown. In this study, we show that binding of CCL20, a G protein-coupled receptor (GPCR) ligand that is upregulated in the airways of subjects with obstructive airway diseases, to its unique GPCR CCR6 induces MUC5AC mucin production in human airway epithelial (NCI-H292) cells via metalloprotease TNF-α-converting enzyme (TACE)-dependent EGFR activation. We also show that EGFR activation by its potent ligand TGF-α induces reactivation of EGFR via binding of endogenously produced CCL20 to its receptor CCR6 in NCI-H292 cells but not in normal human bronchial epithelial (NHBE) cells, exaggerating mucin production in the NCI-H292 cells. In NCI-H292 cells, TGF-α stimulation induced two phases of EGFR phosphorylation (EGFR-P). The second EGFR-P was TACE-dependent and was responsible for most of the total mucin induced by TGF-α. Binding of endogenously produced CCL20 to CCR6 increased the second EGFR-P and subsequent mucin production induced by TGF-α. In NHBE cells, TGF-α-induced EGFR activation did not lead to significant CCL20 production or to EGFR rephosphorylation, and less mucin was produced. We conclude that NCI-H292 cells but not NHBE cells produce CCL20 in response to EGFR activation, which leads to a second phase of EGFR-P and subsequent exaggerated mucin production. These findings have potentially important therapeutic implications in obstructive airway diseases.

Topics: Carcinoma, Mucoepidermoid; Cell Communication; Cell Line, Tumor; Chemokine CCL20; ErbB Receptors; Feedback, Physiological; Humans; Ligands; Lung Neoplasms; Mucin 5AC; Phosphorylation; Protein Binding; Receptors, CCR6; Respiratory Mucosa; Transforming Growth Factor alpha

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death in the U.S. Because cigarette smoking is so importantly implicated in the pathogenesis of COPD and because mucus hypersecretion plays such an important role in COPD, understanding of the mechanisms of smoking-induced mucus hypersecretion could lead to new therapies for COPD. Cigarette smoke causes mucin overproduction via EGF receptor (EGFR) in airway epithelial cells, but the cellular mechanism remains unknown. Airway epithelial cells contain EGFR proligands on their surfaces, which can be cleaved by metalloprotease and subsequently bind to EGFR resulting in mucin production. We hypothesize that TNF-alpha-converting enzyme (TACE) is activated by cigarette smoke, resulting in increased shedding of EGFR proligand, leading to EGFR phosphorylation and mucin induction in human airway epithelial (NCI-H292) cells. Here we show that cigarette smoke increases MUC5AC production in NCI-H292 cells, an effect that is prevented by an EGFR-neutralizing antibody and by specific knockdown of transforming growth factor-alpha (TGF-alpha) using small interfering RNA (siRNA) for TGF-alpha, implicating TGF-alpha-dependent EGFR activation in the responses. Cigarette smoke increases TGF-alpha shedding, EGFR phosphorylation, and mucin production, which are prevented by metalloprotease inhibitors (GM-6001 and TNF-alpha protease inhibitor-1) and by specific knockdown of TACE with TACE siRNA, implicating TACE in smoking-induced responses. Furthermore, pretreatment with antioxidants prevents smoking-induced TGF-alpha shedding and mucin production, suggesting that reactive oxygen species is involved in TACE activation. These results implicate TACE in smoking-induced mucin overproduction via the TACE-proligand-EGFR signal pathway in NCI-H292 cells.

Topics: ADAM Proteins; ADAM17 Protein; Carcinoma, Mucoepidermoid; Cell Line, Tumor; ErbB Receptors; Gene Expression; Humans; Ligands; Lung Neoplasms; Metalloendopeptidases; Mucin 5AC; Mucins; Phosphorylation; Protein Precursors; Pulmonary Disease, Chronic Obstructive; Reactive Oxygen Species; Respiratory Mucosa; Smoking; Transforming Growth Factor alpha; Tumor Necrosis Factor-alpha; Up-Regulation