To examine the in vivo effects of macrolide antibiotics on mucus hypersecretion, we induced hypertrophic and metaplastic changes of goblet cells in rat nasal epithelium by intranasal instillation of ovalbumin (OVA) in OVA-sensitized rats and by intranasal LPS instillation. Oral administration of clarithromycin (CAM) (5–10 mg/kg) significantly inhibited OVA- and LPS-induced mucus production and neutrophil infiltration, whereas josamycin and ampicillin showed no effect. In vitro effects of macrolide antibiotics on airway epithelial cells were examined using NCI-H292 cells and human nasal epithelial cells cultured in air–liquid interface. Mucus secretion was evaluated by ELISA using anti-mucin monoclonal antibodies (anti-MUC5AC and HCS18). CAM and erythromycin significantly inhibited spontaneous and tumor necrosis factor–α (20 ng/ml)–induced mucus secretion from NCI-H292 cells at 10−6 to 10−7 M and from human nasal epithelial cells at 10−4 to 10−5 M. MUC5AC messenger RNA expression was also significantly inhibited. These results indicate that the 14-member macrolide antibiotics, CAM and erythromycin, exert direct inhibitory effects on mucus secretion from airway epithelial cells and that they may be useful for the treatment of mucus hypersecretion caused by allergic inflammation and LPS stimulation.

Epithelial cells at mucosal surfaces are integral components of innate and adaptive immunity. IL-25 is reportedly produced by epithelial cells and likely plays vital roles in regulating type-2 immune responses. However, little is known regarding the mechanisms that control production and extracellular releases of IL-25. We hypothesized that proteases from the multiple allergens may induce IL-25 production in airway epithelial cells. In this study, we found that IL-25 is constitutively produced and detectable in cytoplasm of resting normal human bronchial epithelial (NHBE) cells. When exposed to airborne allergens such as house dust mite (HDM), stored IL-25 was released rapidly to the extracellular space. IL-25 release was not accompanied by cell death, suggesting involvement of active secretory mechanism(s). HDM also enhanced IL-25 mRNA transcription, which was dependent on their protease activities. Furthermore, activation of NHBE cells with authentic proteases, such as trypsin and papain, or with a peptide agonist for protease-activated receptor 2 was sufficient to enhance IL-25 mRNA transcription and protein. Protease-driven increase in mRNA transcription and allergen-driven extracellular release of IL-25 protein was also observed in primary nasal epithelial cells from healthy individuals. These findings suggest that IL-25 production by airway epithelial cells is regulated by the transcription and protein release levels and that allergen proteases likely play pivotal roles in both biological processes.

The effect of biochemical components on the viscoelasticity of nasal mucus from 24 patients with chronic sinusitis (CS) was investigated by multiple stepwise regression analysis. The dynamic viscosity ( η′ ) and the elastic modulus (G ′ ) of nasal mucus were determined with an oscillating sphere magnetic rheometer at oscillatory frequencies of 1 and 10 Hz. The η′ and G ′ values of mucus determined at 1 Hz were 1.6 ± 1.5 Pa/s and 31.8 ± 31.0 Pa, respectively, and these values were much higher than optimal viscoelasticity for mucociliary transport. The concentrations of fucose, N-acetyl neuraminic acid, albumin, IgG, secretory-IgA, and lysozyme were measured in the same mucus samples. The multiple regression analysis showed that the concentration of fucose, a marker of mucous glycoproteins, was the most important determinant of η′ and G ′. The analysis also revealed that the level of IgG was the next important determinant. The coefficients of multiple determination for fucose and IgG were 0.732 and 0.733 when the response variables were η′ and G ′, respectively. The results indicate that locally produced mucous glycoproteins may largely contribute to the high viscoelasticity of nasal mucus in CS.

The natural anticoagulant-activated protein C may inhibit inflammation and fibrosis in the lung. Platelet-derived growth factor is involved in the pathogenesis of lung fibrosis. This study assessed the effect of activated protein C on platelet-derived growth factor expression in human cell lines and in an in vivo model of lung fibrosis. Activated protein C significantly inhibited the secretion and expression of platelet-derived growth factor in human lung cell lines, primary bronchial epithelial cells, and macrophages. In vitro studies also showed that the endothelial activated protein C receptor is expressed by lung epithelial cells and macrophages, and that this receptor and the proteolytic activity of activated protein are implicated in the inhibition of platelet-derived growth factor expression. In the in vivo model of lung fibrosis, intratracheal administration of activated protein C decreased the expression of platelet-derived growth factor and suppressed the development of lung fibrosis. Concomitant intratracheal administration of activated protein C and anti-endothelial activated protein C receptor or anti-platelet-derived growth factor suppressed the inhibitory activity of activated protein C in vivo. In brief, this study describes a novel biological function of activated protein C that may further explain its inhibitory activity on lung inflammation and fibrosis.

Background: Predominant eosinophil infiltration and tissue remodeling are common characteristics of chronic airway inflammation such as nasal polyposis and bronchial asthma. This study was designed to elucidate the role of eosinophils in tissue remodeling of chronic airway inflammation; eosinophil–epithelial interactions were examined by the coculture of airway epithelial cell line NCI-H292 with the eosinophilic cell line EoL-1 or with human blood eosinophils. Methods: The coculture-induced production of MUC5AC mucin, platelet-derived growth factor AB (PDGF-AB), vascular endothelial growth factor (VEGF), transforming growth factor (TGF) beta1, and interleukin-8 (IL-8) were evaluated by enzyme-linked immunosorbent assay and reverse transcription–polymerase chain reaction. Results: Eosinophil–epithelial interactions significantly stimulated the secretion of MUC5AC, PDGF-AB, VEGF, TGF-beta1, and IL-8 in culture supernatants. The epidermal growth factor receptor tyrosine kinase inhibitor AG1478 inhibited the coculture-induced secretion of MUC5AC, PDGF-AB, VEGF, and IL-8. Neutralizing antibodies directed against TGF-alpha or amphiregulin and pan-metalloproteinase inhibitor GM6001 inhibited the coculture-induced secretion of MUC5AC and amphiregulin from the cocultured NCI-H292 cells. Coculture of NCI-H292 cells with peripheral blood eosinophils also significantly stimulated MUC5AC production. Conclusion: The results of this study indicate that eosinophil–epithelial cell interactions are important in the pathogenesis of tissue remodeling of eosinophil-predominant airway inflammation such as occurs in nasal polyposis and bronchial asthma.