Abstract
BackgroundMucus hypersecretion and goblet cell upregulation are common features of chronic rhinosinusitis with nasal polyps (CRSwNP). Although epidermal growth factor (EGF) has been reported to stimulate the expression of MUC5AC, the major macro-molecular constituent of airway mucus, the precise mechanisms underlying the regulation of MUC5AC expression are still not fully understood. The aim of this study therefore was to investigate the role of EGF in regulation of mucin MUC5AC expression and define the involvement of transmembrane protein 16A (TMEM16A) in mediating the EGF-induced mucus overexpression.MethodsHuman nasal epithelial cells (HNECs) derived from tissue of patients with CRSwNP and control subjects were established as air–liquid interface (ALI) cultures. Differentiated cultures were treated with different concentrations of EGF for 4–24 h, and assessed for the expression of TMEM16A and MUC5AC by real-time RT-PCR, Western blotting, ELISA and immunofluorescence. Cultures pretreated for 30 min with T16Ainh-A01 (a specific TMEM16A inhibitor) or LY294002 (a phosphoinositide 3-kinase (PI3K) inhibitor) were also assessed similarly following EGF treatment.ResultsEGF treatment (10–100 ng/ml for 4–24 h) significantly increased the expression of both TMEM16A and MUC5AC mRNA and protein, as well as the percentage of TMEM16A-positive cells, MUC5AC-positive cells and cells coexpressing TMEM16A and MUC5AC in HNECs compared to control non-EGF-treated HNECs. Pretreatment of the HNECs with T16Ainh-A01 and LY294002 attenuated these EGF-induced effects.ConclusionsThis study demonstrated that EGF upregulates the expression of MUC5AC in HNECs from CRSwNP patients. Furthermore, the EGF-mediated regulation of MUC5AC expression is likely to involve a PI3K-TMEM16A signalling pathway in CRSwNP.
Highlights
Mucus hypersecretion and goblet cell upregulation are common features of chronic rhinosinusitis with nasal polyps (CRSwNP)
Effect of epidermal growth factor (EGF) on transmembrane protein 16A (TMEM16A) expression in Human nasal epithelial cells (HNECs) Figure 1 shows the effect of different concentrations of EGF (10, 50, 100 ng/ml) on TMEM16A expression in HNECs
We compared the response to 50 ng/ml EGF stimulation between control culture and CRSwNP-derived culture, and found that EGF induced an increase of TMEM16A mRNA and protein in both
Summary
Mucus hypersecretion and goblet cell upregulation are common features of chronic rhinosinusitis with nasal polyps (CRSwNP). Epidermal growth factor (EGF) has been reported to stimulate the expression of MUC5AC, the major macro-molecular constituent of airway mucus, the precise mechanisms underlying the regulation of MUC5AC expression are still not fully understood. MUC5AC is the major macro-molecular constituent of airway mucus, and because it is expressed in goblet cells, regulation of MUC5AC synthesis and secretion is critical for the maintenance of goblet cell upregulation. A positive correlation between EGFR expression and goblet cell hyperplasia has been shown in CRSwNP patients [2] and EGF treatment has been reported to stimulate MUC5AC expression in airway epithelial cells [5]. Our study demonstrated that T16Ainh-A01, a TMEM16A inhibitor, down-regulated IL-13-induced expression of both TMEM16A and MUC5AC, indicating a potentially important role of TMEM16A in mucin secretion in CRSwNP [6]
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