Abstract
Abstract: :
Purpose: The purpose of this study was to assess the cytotoxic effects of the fluoroquinolone, ofloxacin, and the aminoglycoside, netilmicin, on stromal human keratocytes in vitro. Methods: Cultured human keratocytes were exposed to various concentrations of ofloxacin or netilmicin (0.16–5.0 mg/ml). Both cell viability (MTT assay) and cell morphology (phase–contrast microscopy) were assessed after 1, 4, 12 and 24 hours of incubation. Measurement of annexin V binding performed in association with the dye exclusion test using propidium iodide (PI) was also performed by FACS analysis. Results: Both drugs induced dose and time dependent morphologic changes in keratocytes, however, the effect of netilmicin was less pronounced. A statistically significant difference between the two compounds was observed after 24 hours exposure with concentrations above 0.6 mg/ml. Both drugs induced a dose dependent inhibition of cell viability after 24 hours of exposure but the effect of ofloxacin was more powerful than that of netilmicin (ANOVA, p=0.0003). After 4 hours of exposure, the basal expression of the apoptotic marker, annexin V, was significantly reduced by ofloxacin 5 ng/ml, while captation of the necrotic marker, PI, was increased. Netilmicin induced similar but less pronounced changes. Conclusions: Relative effects of aminoglycosides and fluoroquinolones on stromal keratocytes appear to be different: netilmicin was shown to be significantly less toxic than ofloxacin. This finding is particularly relevant in deciding the optimal antibiotic to be applied in clinical situations in which the epithelium is absent or compromised, as after photorefractive keratectomy.
Keywords: antibiotics/antifungals/antiparasitics • cornea: stroma and keratocytes • refractive surgery: PRK