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We previously demonstrated that the quinolone moxifloxacin prevents Candida albicans pneumonitis and epithelial nuclear factor kappaB (NF-kappaB) nuclear translocation in immunosuppressed mice.To explore the anti-inflammatory effects of moxifloxacin directly on a lung epithelial cell line.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-kappaB 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.Stimulation with the cytokines interleukin-1beta(IL-1beta)/interferon-gamma (IFN-gamma) increased NO up to 3.3-fold and moxifloxacin inhibited this up to 68% (P0.05). Similarly, the increase in iNOS levels was inhibited in cells pre-treated with moxifloxacin by up to 62%. IL-1beta 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-kappaB, as measured by electrophoretic mobility shift assay, was inhibited up to 72% by moxifloxacin. Western-blot analysis revealed that IL-1beta enhanced NF-kappaB p65 and p50 proteins by 1.7- and 3.6-fold, respectively, whereas moxifloxacin inhibited the proteins by up to 60%.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.

We previously showed that moxifloxacin (MXF) exerts protective anti-inflammatory effects in immunosuppressed mice infected withCandida albicansby inhibiting interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α) production in the lung. Immunohistochemistry demonstrated inhibition of nuclear factor (NF)-κB translocation in lung epithelium and macrophages in MXF-treated mice. In the present study we investigated the effects of MXF on the production of proinflammatory cytokines (i.e., IL-8, TNF-α, and IL-1β) by activated human peripheral blood monocytes and THP-1 cells and analyzed the effects of the drug on the major signal transduction pathways associated with inflammation: NF-κB and the mitogen-activated protein kinases ERK and c-Jun N-terminal kinase (JNK). The levels of IL-8, TNF-α, and IL-1β secretion rose 20- and 6.7-fold in lipopolysaccharide (LPS)-activated monocytes and THP-1 cells, respectively. MXF (5 to 20 μg/ml) significantly inhibited cytokine production by 14 to 80% and 15 to 73% in monocytes and THP-1 cells, respectively. In THP-1 cells, the level of NF-κB nuclear translocation increased fourfold following stimulation with LPS-phorbol myristate acetate (PMA), and this was inhibited (38%) by 10 μg of MXF per ml. We then assayed the degradation of inhibitor (I)-κB by Western blotting. LPS-PMA induced degradation of I-κB by 73%, while addition of MXF (5 μg/ml) inhibited I-κB degradation by 49%. Activation of ERK1/2 and the 46-kDa p-JNK protein was enhanced by LPS and LPS-PMA and was significantly inhibited by MXF (54 and 42%, respectively, with MXF at 10 μg/ml). We conclude that MXF suppresses the secretion of proinflammatory cytokines in human monocytes and THP-1 cells and that it exerts its anti-inflammatory effects in THP-1 cells by inhibiting NF-κB, ERK, and JNK activation. Its anti-inflammatory properties should be further assessed in clinical settings.