Toxicity of Dexamethasone on Neurosensory Retinal Cells

Abstract

Abstract: : Purpose:To evaluate the in vitro toxicity of dexamethasone on rat neurosensory retinal cells. Methods: Rat neurosensory retinal cells (R28) grown in tissue culture were treated with four different concentrations of dexamethasone sodium phosphate (American Regent Laboratories Inc., Shirley, NY ) : 0.125mg/ml, 0.25mg/ml, 0.50mg/ml and 1mg/ml. Cell viability was measured using the trypan blue dye exclusion assay (Beckman Coulter Inc., Fullerton, CA) after 24 hours. Statistical analysis was done by ANOVA using GraphPad Prism^TM 3.0 version statistics program (Graphpad Software Inc., San Diego, CA). Newman–Keuls multiple comparison test was done to compare the data within each experiment. P values less than 0.05 were considered statistically significant. Results: The mean cell viabilities of R28 cells after exposure to dexamethasone concentrations of 0.125mg/ml, 0.25mg/ml, 0.50mg/ml and 1mg/ml were 84.9 ± 4.4 %, 86.0 ± 4.1 %, 87.5 ± 2.6 % and 28.1 ± 10.5 % respectively. Untreated R28 cells (controls) had a mean cell viability of 90.7± 1.9%. As compared to controls, R28 cells exposed to 0.125mg/ml, 0.25mg/ml and 0.50mg/ml of dexamethasone did not show any significant decrease in cell viability (p>0.05). Cells exposed to dexamethasone concentration of 1mg/ml showed significant decrease in cell viability (p<0.001) as compared with dexamethasone concentrations of 0.125mg/ml, 0.25mg/ml and 0.50mg/ml and untreated controls. Conclusions: This study suggests that dexamethasone is toxic to rat neurosensory retinal cells in vitro at a concentration of 1mg/ml. Lower concentrations including doses normally used in clinical practice are not toxic in vitro. A previous study on human retinal pigment epithelial cells (ARPE 19) did not find any toxicity of dexamethasone at 24 hours even with 1mg/ml concentration. Thus, rat neurosensory retina cells may be more sensitive to dexamethasone than human RPE cells.Recent studies have shown in vitro toxicity of triamcinolone acetonide at doses used clinically. This suggests that dexamethasone might be a reasonable alternative to triamcinolone by combining decreased cellular toxicity as shown in the study here with the well established higher potency of dexamethasone compared to triamcinolone. However, given the short half life of dexamethasone, extended release formulations of dexamethasone may be required for clinical utility.

Keywords: retinal culture • corticosteroids • drug toxicity/drug effects