Effect of ciprofloxacin on lethal and sublethal challenge with endotoxin and on early cytokine responses in a murine in vivo model

The influence of ciprofloxacin on immune responses has been suggested by results of in vitro and in vivo studies. This effect was studied using a murine model that measured mortality and early cytokine responses after challenge with endotoxin. C57/BL6 mice weighing between 18 and 21 g were given a single intraperitoneal dose of lipopolysaccharide (LPS), ranging from 200 to 1000 microg. Mice were pre-treated with an intraperitoneal injection of 5% dextrose in sterile water containing 0.0-6.0 mg of ciprofloxacin 1 h before LPS challenge. Cytokine responses were assessed by measuring concentrations in serum separated from blood obtained by cardiac puncture of anaesthetized mice at 0, 1, 3, 6 and 24 h following LPS administration. Mice were observed for 72 h following administration of LPS and serum cytokines were measured using ELISA. More than 4.5 mg of ciprofloxacin (675-900 mg/m(2) or 225-300 mg/kg) given 1 h before LPS challenge consistently protected mice from a lethal dose of LPS (14/14 versus 0/7, P < 0.00001). Ciprofloxacin significantly attenuated the production of tumour necrosis factor-alpha and interleukin-12 response after LPS challenge. In addition, ciprofloxacin significantly increased serum interleukin-10 concentrations but had little or no effect on interleukin-6 or interleukin-1beta serum concentrations. Similar effects were evident with sublethal doses of LPS and were most pronounced at the lowest dose of LPS studied. These observations indicate that ciprofloxacin can prevent endotoxin-mediated death and alter early host cytokine responses. This effect may influence the course of infection in a manner that is independent of the drug's antimicrobial activity.