ABSTRACTFusobacterium nucleatumis one of the most common anaerobic bacteria in periodontitis and is responsible for several extraoral infections, including respiratory tract diseases. In this study, we examined whetherF. nucleatuminduces mucin secretion in airway epithelial cells. We also examined the effects of macrolides onF. nucleatum-induced mucus production compared with the effects of other antibiotics that exert anti-anaerobic activities. The production of MUC5AC, the major core protein of mucin secreted from the airway surface epithelium, in bronchial epithelial cells after stimulation with culture supernatants (Sup) ofF. nucleatumwas analyzed by performing enzyme-linked immunosorbent assay and quantitative RT-PCR. The cell-signaling pathway ofF. nucleatumSup stimulation was also analyzed by Western blotting. For inhibition studies, cells were treated with azithromycin, clarithromycin, clindamycin (CLDM), and metronidazole (MTZ). TheF. nucleatumSup induced NCI-H292 cells to express MUC5AC at both the protein level and the mRNA level in both a time- and dose-dependent manner. Macrolides inhibitedF. nucleatumSup-induced MUC5AC production, while CLDM and MTZ were less effective.F. nucleatumSup induced the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), and this induction was suppressed by macrolides.F. nucleatumSup-induced MUC5AC production was blocked by the ERK pathway inhibitor U0126.F. nucleatumis likely to contribute to excessive mucin production, which suggests that periodontitis may correlate with the pathogenesis of chronic respiratory tract infection. Macrolides seem to reduce this mucin production and might represent an additional means of therapeutic intervention forF. nucleatumrespiratory tract infections other than CLDM and MTZ.
Exposure to mold proteases stimulates mucin production in airway epithelial cells through Ras/Raf1/ERK signal pathway
