Inhibition of MUC5AC gene expression by anethole in human airway epithelial cell via TAK1-MAPK-AP-1 and TAK1-IκB-NF-κB pathways

Abstract

Mucin overproduction is a hallmark of chronic rhinosinusitis. Natural compounds with mucin-suppressive property are attractive and effective as mucin regulatory agents in airway diseases such as chronic rhinosinusitis. The aim of this study was to investigate whether anethole suppresses interleukin (IL)-1β induced MUC5AC gene expression in human airway epithelial cells and whether this activity of anethole is related to TAK1-MAPK-AP-1 and TAK1-IκB-NF-κB signaling pathways. NCI-H292 cells were pretreated with 50 μM of anethole for 1 h, then 10 ng/mL of IL-1β was added for 24 h. MUC5AC mRNA expression was then measured by real-time PCR. The phosphorylation levels of proteins were assayed by western blot. The nuclear components of NF-κB and AP-1 were assayed using luciferase activity. And the nuclear translocation of NF-κB and AP-1 from cytosol was observed by the confocal laser scanning microscopy. Cell survival remained above 90% in the presence of anethole at a concentration of 50 μM. IL-1β induced MUC5AC mRNA expression was significantly decreased by 50 μM anethole, to the level of the untreated control group, as opposed to an increase to 3.2 ± 0.5-fold for IL-1β alone, and this suppression of MUC5AC expression was dose-dependent. This decrease in MUC5AC expression by anethole was mediated via the MAPK pathway, such as phospho-p38 and phospho-ERK. And the suppression of MUC5AC by anethole was also mediated via the TAK1-MAPK-AP-1 and TAK1-IκB-NF-κB signaling pathways. In suppressing IL-1β-induced MUC5AC gene expression by anethole, NF-κB or AP-1 was important transcription factor. These results suggest that anethole suppresses IL-1β-induced MUC5AC gene expression in human airway epithelial cells via the TAK1-MAPK-AP-1 and TAK1-IκB-NF-κB signaling pathways, and may be considered an anti-hypersecretory agent.