In vitro accumulation of enfloxacin in phagocytes and effect of enrofloxacin on the phagocytic function

Abstract

Accumulation of enrofloxacin (ENR) was compared in resting DH82 macrophages and cerebral endothelia cells (CVE) (negative control) incubated with ENR (4 []g/ml) for certain hours. Both supernatant and cells were collected and subjected to analysis of ENR and its active metabolite, ciprofloxacin (CIP). CIP was not evident in any study. The ratio of intracellular to extracellular concentration (C/E) of ENR at steady-state (6 hrs) of 1.188 was greater than that at other times and greater than that in CVE at any time. The effect of lipopolysaccharides on phagocytosis was studied in DH82 canine macrophages, MH-S mouse macrophage and circulating canine phagocytes (predominantly neutrophils). LPS appeared to have no effect on phagocytic activity of DH82 nor circulating canine phagocytes. The addition of canine serum to the culture media negatively influenced phagocytosis in non-LPS stimulated DH82 cells; temperature positively influenced LPS-exposed DH82 cells. LPS did not appear to stimulate phagocytosis of inert particles as determined by flow cytometry in DH82 or in circulating phagocytes, but did in MH-S cells compared to non-stimulated cells in each cell type. ENR (1[]g/ml or 4 []g/ml) had no effect on phagocytosis of MH-S macrophages exposed to: drug for one hour before LPS exposure (Group 1); both drug and LPS simultaneously for 72 hours (Group 2); drug for 1 hour after exposure to LPS for 72 hours (Group 3). The percentage of cells with 1 or more phagocytized particles in each group was, respectively, for Group 1: 42.19% for ENR at 1 []g/ml, 35.87% for at 4 []g/ml, compared to 40.62% in control cells (no drug); Group 2: 44.88% at 1 []g/ml, 54.99% at 4 []g/ml, and 48.6% for control cells; and for Group 3: 49.11% at 1 []g/ml, 47.89% at 4 []g/ml, and 54.62% for control cells (Group 3). These data indicate that under these test conditions, inactivated DH82 cells poorly accumulate ENR; LPS has minimal effect on the phagocytic activity of DH82 cells or circulating phagocytes; and at clinically relevant concentrations, ENR does not affect phagocytosis of LPS-stimulated MH-S cells. Further studies are indicated to fully evaluate the potential effect of ENR on phagocytic function.