Quinolone antibiotics such as ciprofloxacin modify immune and inflammatory responses in some cells. We have shown previously that ciprofloxacin decreases the accumulation of interleukin (IL)-6 protein from a human endothelial cell line, whilst IL-8 protein production was increased. It is not known whether this occurs through effects on transcription and mRNA expression. We therefore investigated the effect of ciprofloxacin on mRNA for IL-6 and IL-8, and on three transcription factors known to be involved in the regulation of these cytokines. We investigated the effect of ciprofloxacin on tumour necrosis factor α- and IL-1β-mediated activation of the transcription factors nuclear factor κB (NFκB), activator protein-1 (AP-1) and nuclear factor IL-6 (NF-IL-6) using an electrophoretic mobility shift assay, and the effect on expression of mRNA for IL-6 and IL-8 by reverse transcriptase–PCR in the EAhy926 endothelial cell line. Ciprofloxacin decreased IL-6 mRNA (P < 0.05) and increased IL-8 mRNA (P < 0.05) expression. Ciprofloxacin did not modulate activation of NFκB or AP-1. However, NF-IL-6 binding was decreased in the presence of 100 µg/ml ciprofloxacin (P < 0.05). The study shows that ciprofloxacin-mediated decreased IL-6 release by a human endothelial cell line is reflected by decreased mRNA expression and decreased NF-IL-6 but not NFkB or AP-1 activation. Increased IL-8 mRNA in response to ciprofloxacin was not reflected by altered transcription factor activation and may represent increased mRNA stability.

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