Search

Background: Mucin 5AC, oligomeric mucus/gel-forming (MUC5AC) expression is significantly increased in allergic and inflammatory airway diseases. Interleukin (IL) 36 gamma is predominantly expressed in airway epithelial cells and plays an important role in innate and adaptive immune responses. IL-36 gamma is induced by many inflammatory mediators, including cytokines and bacterial and viral infections. However, the association between IL-36 gamma and mucin secretion in human airway epithelial cells has not yet been fully investigated. Objective: The objective of this study was to determine whether IL-36 gamma might play a role in the regulation of mucin secretion in airway epithelial cells. We investigated the effect and brief signaling pathway of IL-36 gamma on MUC5AC expression in human airway epithelial cells. Methods: Enzyme immunoassay, immunoblot analysis, immunofluorescence staining, reverse transcriptase–polymerase chain reaction (PCR), and real-time PCR were performed in mucin-producing human airway epithelial NCI-H292 cells and in human nasal epithelial cells after pretreatment with IL-36 gamma, several specific inhibitors, or small interfering RNAs (siRNA). Results: IL-36 gamma induced MUC5AC expression and activated the phosphorylation of extracellular signal regulated kinase (ERK) 1 and 2, p38, and nuclear factor-kappa-light-chain-enhancer of activated B cells (NF–kappa B). IL-36 receptor antagonist significantly attenuated these effects. The specific inhibitor and siRNA of ERK1, ERK2, p38, and NF–kappa B significantly attenuated IL-36 gamma induced MUC5AC expression. Conclusion: These results indicated that IL-36 gamma induced MUC5AC expression via the IL-36 receptor–mediated ERK1/2 and p38/NF–kappa B pathway in human airway epithelial cells.

BackgroundMUC5AC, a major secreted mucin, is increased in chronic inflammatory airway disease. Spleen tyrosine kinase (SYK) is a mediator, which acts as an important regulator of intracellular signal transduction in the inflammatory response. SYK was originally identified in hematopoietic cells, and its expression in some nonhematopoietic cells, including respiratory epithelial cells, was recently demonstrated. However, the effects of SYK on mucin secretion in human airway epithelial cells have not been studied. The objective of this study was to investigate the effect and brief signaling pathways of SYK on MUC5AC expression in human airway epithelial cells.MethodsIn mucin-producing human NCI-H292 cells and primary cultures of human nasal epithelial cells, the effects and signaling pathways of SYK on MUC5AC expression were investigated by reverse transcriptase–polymerase chain reaction, real-time polymerase chain reaction, enzyme immunoassay, and immunoblot analysis with several specific inhibitors and small interfering RNA (siRNA).ResultsSYK induced MUC5AC expression. SYK activated significant phosphorylation of extracellular signal-related kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) signaling pathways. SYK-induced MUC5AC expression was significantly attenuated by pretreatment with U0126 (ERK1/2 MAPK inhibitor) and SB203580 (p38 MAPK inhibitor). In addition, the knockdown of ERK2 and p38 MAPK by ERK2 and p38 MAPK siRNA significantly blocked SYK-induced MUC5AC expression.ConclusionThese results indicated that SYK increased MUC5AC expression via ERK2 and p38 MAPK signaling pathways in human airway epithelial cells.

Background Asian sand dust (ASD) is a natural phenomenon and originates from the deserts of China and is known to contain various chemical and biomolecular components that enhance airway inflammation. The overproduction of airway mucins is an important pathologic finding in inflammatory airway diseases. However, the mechanism of ASD on mucin production of airway epithelial cells has not been elucidated. Objective To investigate the effect and signaling pathway of ASD on mucin expressions in human airway epithelial cells. Methods In the NCI-H292 cells and the primary cultures of human nasal epithelial cells, the effect and signaling pathway of ASD on MUC8 and MUC5B expressions were investigated using reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassay, and immunoblot analysis with several specific inhibitors and small interfering RNA (siRNA). Results ASD increased MUC8 and MUC5B expressions and activated the phosphorylations of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). U0126 (ERK1/2 MAPK inhibitor) and SB203580 (p38 MAPK inhibitor) inhibited ASD-induced MUC8 and MUC5B expressions. In addition, knockdowns of ERK2 and p38 MAPK by siRNA blocked ASD-induced MUC8 and MUC5B mRNA expressions. Toll-like receptor 4 (TLR4) mRNA expression was increased after treatment with ASD. Knockdown of TLR4 by siRNA blocked ASD-induced MUC8 and MUC5B mRNA expressions. Furthermore, the phosphorylations of ERK1/2 and p38 MAPK were blocked by knockdown of TLR4. Conclusions These results show that ASD induces MUC8 and MUC5B expressions via TLR4-dependent ERK2 and p38 MAPK signaling pathway in human airway epithelial cells.

Background Glutaredoxins (GRX)-1 is glutathione-dependent oxidoreductase. However, the role of these enzymes remains unknown in airway inflammatory diseases. Therefore, we aimed to establish the expression pattern of GRX-1 in the nasal polyps (NPs) and to assess the regulatory mechanisms associated with GRX-1 expression in interleukin (IL)-1beta-treated airway epithelial cells. Methods The expression of GRX-1 in NPs and normal nasal mucosa were analyzed by reverse-transcription polymerase chain reaction and immunohistochemical staining. IL-1beta–induced reactive oxygen species (ROS) formation and GRX-1 expression in the airway epithelial cells was determined by flow cytometry and immunoassay. Results The expression level of GRX-1 in NPs was significantly higher than in the normal nasal mucosa (p < 0.05). GRX-1 was highly expressed in the surface epithelial cells and the submucosal glandular cells in the NPs. IL-1beta increased the intracellular ROS formation and GRX-1 expression in airway epithelial cells. The inhibition of IL-1beta–induced ROS production by N-acetyl-cystein, an ROS scavenger, reduced GRX-1 expression. Diphenyleneiodonium and apocynin, NADPH oxidase inhibitors, did not abolish IL-1beta–induced ROS ormation and GRX-1 expression, whereas budesonide attenuated it. Conclusion High GRX-1 expression in NPs might be a primary de ense against chronic in lammatory oxidative stress in nasal mucosa. IL-1beta–induced up-regulation o GRX-1 in airway epithelial cells is probably mediated by ROS. Glucocorticoids can regulate IL-1beta–induced ROS ormation and GRX-1 expression.