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Objectives: The purpose of this study was to develop an animal model for the study of mucus overproduction and to assess the effect of a 14-membered macrolide antibiotic and a glucocorticoid on lipopolysaccharide (LPS)-induced mucus production. Methods: Tracheas from donor rats were homografted to recipient rats for 4 weeks, and the usefulness of this tracheal homograft model in the study of mucus production was examined. Results: Oral administration of clarithromycin (CAM) to recipient rats for 4 weeks significantly reduced LPS-induced mucus production in the homografted trachea. Dexamethasone administered for 4 weeks also significantly reduced the mucus volume in LPS-treated homografted trachea compared with that in the control rats. The implanted trachea containing control medium was not histologically different from normal trachea. When the medium instilled into the implanted trachea contained 1 µg/ml LPS, the volume and spinability of mucus produced in the tracheal lumen were significantly increased compared to those in the trachea instilled with control medium. Goblet cell metaplasia was also observed in the implanted trachea containing LPS. Conclusions: The present study shows that LPS-administered homografted trachea is a good animal model of chronic hypersecretory diseases of the upper and lower airways. CAM and dexamethasone could be treatment choices in such hypersecretory diseases.

Objectives: Eosinophilic chronic rhinosinusitis (ECRS) is considered a refractory and intractable disease with thick mucus production, long-term nasal congestion, loss of sense of smell and intermittent acute exacerbations secondary to bacterial infections. In this study, we investigated which growth factor is deeply involved in the mucin overproduction in ECRS. Method: We employed fluorescence immunohistochemical analysis to evaluate whether or not TGF-α expression was upregulated in the nasal tissue of ECRS patients. We also examined MUC5AC transcription using a luciferase reporter plasmid in HM3-MUC5AC cells and A549 cells in order to assess the role of TGF-α in human epithelial cells. Results: TGF-α immunoreactivity was found markedly increased in the submucosal tissue in the ECRS patient compared with that of a normal patient and with noneosinophilic CRS. TGF-α synergized with TNF-α to upregulate MUC5AC expression in human epithelial cells through the ERK signaling pathway. Conclusion: Our results demonstrated that TGF-α was highly expressed in the upper airway tract in ECRS patients and is deeply involved in mucus hypersecretion.

Background/Aims: Long-term macrolide therapy is an effective treatment for chronic sinusitis and diffuse panbronchiolitis. However, long-term use of macrolides may promote the growth of drug-resistant bacteria; therefore, development of macrolides with no antibacterial action is desirable. A new erythromycin (EM) derivative, (8R,9S)- 8,9-dihydro-6,9-epoxy-8,9-anhydropseudoerythromycin A (EM900), does not possess antibacterial action. Methods: To determine whether EM900 induced a clinically relevant anti-inflammatory response and repressed mucin gene expression in cells derived from human airway epithelia, we assessed the effects of EM900 on IL-1β-induced inflammatory cytokines in A549 cells and MUC5AC gene expression in HM3-MUC5AC cells. We also investigated the effects of EM900 on IL-1β-induced NF-ĸB activation. We performed reporter gene assays and quantitative PCR in A549 and HM3-MUC5AC cells. Results: Both EM and EM900 suppressed IL-1β-induced IL-8 expression in A549 cells. EM900 also suppressed IL-1β-induced IL-1β and TNF-α expression in A549 cells. EM900 inhibited IL-1β-induced MUC5AC expression in HM3-MUC5AC cells. Both EM and EM900 suppressed IL-1β-induced NF-ĸB activation in A549 cells. Conclusion: This study demonstrated that EM900 suppressed the induction of inflammatory cytokines and MUC5AC gene expression in cells derived from human airway epithelia, and our findings indicate that these effects may be mediated by the suppression of NF-ĸB activation.

Pranlukast is a selective cysteinyl leukotriene1 (cysLT1) receptor antagonist, and is now widely used in the treatment of asthma. The anti-asthmatic effect of pranlukast may be rendered not only by antileukotriene activity, but also by other pharmacological activity. This study was designed to investigate whether pranlukast had inhibitory effects on nuclear factor-ĸB (NF-ĸB) activation and mucin gene expression in cultured human epithelial cells. Luciferase assay was mainly used for analysis. Cultured epithelial cells were transfected with NF-ĸB luciferase vector, MUC2 or MUC5AC luciferase vectors. Lipopolysaccharide (LPS) significantly increased NF-ĸB activation in NCI-H292 cells, which was inhibited by the pretreatment by pranlukast in a dose-dependent manner. Either LTD4 or pranlukast alone did not increase NF-ĸB activation in NCI-H292 cells. Pranlukast also inhibited NF-ĸB activation induced by phorbol 12-myristate 13-acetate (PMA). Pranlukast also significantly inhibited LPS-induced MUC2 mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR) analysis in NCI-H292 cells. Pranlukast also inhibited LPS-induced MUC2 gene expression in HM3-MUC2 cells. However, pranlukast did not inhibit MUC5AC gene transcription activity induced by lipoteichoic acid (LTA) in NCI-H292 cells. These results suggest that pranlukast may inhibit NF-ĸB activation and MUC2 gene transcription through pathways distinct from cysLT1 receptor antagonism in cultured human epithelial cells.

Background: Interleukin-31 (IL-31) is a newly discovered T helper lymphocyte-derived cytokine that plays an important role in allergic inflammation. However, the effects of IL-31 on mucus production in nasal allergic inflammation are completely unknown. Objective: To investigate the effects of IL-31 on mucin gene expression (MUC5AC) in patients with allergic rhinitis and in human airway epithelial cells. Methods: Expression levels of IL-31 and IL-31 receptor A (IL-31RA) were evaluated in the inferior turbinate of patients with allergic rhinitis and non-allergic rhinitis with immunohistochemistry. IL-31-induced MUC5AC gene expression was measured with a MUC5AC luciferase reporter assay in human epithelial HM3-MUC5AC cells and quantified by quantitative real-time polymerase chain reaction in human airway epithelial A549 cells. Results: IL-31RA was primarily localized in submucosal glands and upregulated in allergic rhinitis. IL-31 was detected in submucosal tissue and increased in allergic inflammation. MUC5AC gene expression was induced by IL-31 stimulation both in HM3-MUC5AC and A549 cells. Additionally, IL-31 cooperated with Th2 cytokines on MUC5AC gene expression in HM3-MUC5AC cells. Conclusion: IL-31 and IL-31RA are upregulated in patients with allergic rhinitis, and induce MUC5AC gene expression in human airway epithelial cells. These findings suggest that IL-31 plays an important role in mucus overproduction in nasal allergic inflammation.

Pranlukast is a selective cysteinyl leukotriene(1 )(cysLT(1)) receptor antagonist, and is now widely used in the treatment of asthma. The anti-asthmatic effect of pranlukast may be rendered not only by antileukotriene activity, but also by other pharmacological activity. This study was designed to investigate whether pranlukast had inhibitory effects on nuclear factor-kappaB (NF-kappaB) activation and mucin gene expression in cultured human epithelial cells. Luciferase assay was mainly used for analysis. Cultured epithelial cells were transfected with NF-kappaB luciferase vector, MUC2 or MUC5AC luciferase vectors. Lipopolysaccharide (LPS) significantly increased NF-kappaB activation in NCI-H292 cells, which was inhibited by the pretreatment by pranlukast in a dose-dependent manner. Either LTD(4) or pranlukast alone did not increase NF-kappaB activation in NCI-H292 cells. Pranlukast also inhibited NF-kappaB activation induced by phorbol 12-myristate 13-acetate (PMA). Pranlukast also significantly inhibited LPS-induced MUC2 mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR) analysis in NCI-H292 cells. Pranlukast also inhibited LPS-induced MUC2 gene expression in HM3-MUC2 cells. However, pranlukast did not inhibit MUC5AC gene transcription activity induced by lipoteichoic acid (LTA) in NCI-H292 cells. These results suggest that pranlukast may inhibit NF-kappaB activation and MUC2 gene transcription through pathways distinct from cysLT(1) receptor antagonism in cultured human epithelial cells.

Macrolide antibiotics are believed to inhibit mucus secretion but the mechanism of action is unclear. This study was designed to investigate an effect of roxithromycin on MUC2 gene expression in cultured intestinal epithelial cells (HM3-MUC2 cells). A reporter gene assay was used for analysis. Roxithromycin suppressed MUC2 gene transcriptional activity in a dose-dependent manner in HM3-MUC2 cells. Phorbol 12-myristate 13-acetate (PMA), lipoteichoic acid (LTA), lipopolysaccharide (LPS) and leukotriene D4 (LTD4) significantly increased MUC2 luciferase activities in the following order: PMA > LTA > LTD4 > LPS. Roxithromycin also decreased MUC2 gene transcriptional activity induced by PMA in a dose-dependent manner. NF-ĸB activation, but not AP-1 activation, was significantly suppressed by roxithromycin in HM3-MUC2 cells. A suppression of NF-ĸB activation was also observed in NCI-H292 cells. These results suggest that roxithromycin suppresses MUC2 gene expression in epithelial cells and that this suppression is probably via inhibition of NF-ĸB activation.