In this study, we examined the effects of fluoroqinolones, namely ciprofloxacin (CIP) and ofloxacin (OFX) on nitric oxide (NO) production in an in vitro lipopolysaccharide(LPS)-activated macrophage model. Thioglycollate-elicited;ed peritoneal cells from BALB/c mice were exposed to varying concentrations of CIP and OFX for 1 or 4 days before LPS stimulation. NO response was measured by nitrite accumulation. On the first day of antibiotic exposure, nitrite production after LPS stimulation (1 mu g/ml) decreased by 49.3% (p0.05) and by 29.7% (p0.05) in the presence of 1 mM, 100 mu M and 10 mu M CIP and OFX, respectively. The inhibitory effects did not change significantly after 4 days' of exposure. The results indicate that, in this in vitro murine macrophage model, fluoroquinolones inhibit nitrite production in a dose-dependent manner and may have similar immunomodulatory effects in vivo
