Moxifloxacin inhibits cytokine-induced MAP kinase and NF-κB activation as well as nitric oxide synthesis in a human respiratory epithelial cell line

Background: We previously demonstrated that the quinolone moxifloxacin prevents Candida albicans pneumonitis and epithelial nuclear factor κB (NF-κB) nuclear translocation in immunosuppressed mice. Objectives: To explore the anti-inflammatory effects of moxifloxacin directly on a lung epithelial cell line. Methods: We studied the effect of clinically relevant concentrations of moxifloxacin (2.5-10 mg/L) on cytokine-induced activation of nitric oxide (NO) secretion, inducible NO synthase (iNOS) expression and the activation of signal transduction pathways of inflammation, NF-κB and the mitogen-activated protein kinases [extracellular signal-regulated kinases (ERK1/2) and C-Jun N-terminal kinase (JNK)], in the A549 lung epithelial cell line. Results: Stimulation with the cytokines interleukin-1β(IL-1β)/interferon-γ (IFN-γ) increased NO up to 3.3-fold and moxifloxacin inhibited this up to 68% (P < 0.05). Similarly, the increase in iNOS levels was inhibited in cells pre-treated with moxifloxacin by up to 62%. IL-1β stimulated a rapid increase in the activities of early intracellular signalling molecules, ERK1/2 and JNK. Moxifloxacin inhibited ERK1/2 by up to 100% and p-JNK activation by 100%. NF-κB, as measured by electrophoretic mobility shift assay, was inhibited up to 72% by moxifloxacin. Western-blot analysis revealed that IL-1β enhanced NF-κB p65 and p50 proteins by 1.7- and 3.6-fold, respectively, whereas moxifloxacin inhibited the proteins by up to 60%. Conclusions: Moxifloxacin inhibits intracellular signalling, iNOS expression and NO secretion in a lung epithelial cell line. Future studies may uncover a primary site of quinolone immunomodulation, either upstream or at the cell membrane. Eventually, this quinolone might become an important therapy for inflammatory lung diseases.