Abstract
Purpose: :
To evaluate the toxicity of betamethasone and benzalkonium chloride (BAK) on retinal cells in vitro.
Methods: :
Human retinal pigment epithelial cells (ARPE–19) and rat neurosensory retinal cells (R28) were grown in tissue culture and treated for 2, 6 and 24 hours with betamethasone (Celestone/Soluspan; Schering–Plough; Kenilworth, NJ) at four concentrations (180, 90, 45, and 30mcg/ml), and with the corresponding four concentrations (6, 3, 1.5, 1mcg/ml) of BAK (Alfa Aesar, Ward Hill, MA). Cell viability was measured by the trypan blue dye–exclusion assay (Beckman–Coulter, Fullerton, CA).
Results: :
In both cell lines, betamethasone 180mcg/ml caused a significant decrease in cell viability at all timepoints. In ARPE–19 cells treated with 180mcg/ml, viability was 51.4 ± 2.8%, 51.0 ± 5.4%, and 18.1 ± 3.6% compared to control untreated ARPE–19 cells (95.0%, 93.0% and 92.2% at 2, 6 and 24 hours respectively, p<0.001). In R28 cells treated with 180 mcg/ml viability was 68.1 ± 6.6%, 52.4 ± 5.6% and 40.9 ± 1.6 % compared to control untreated R28 cells (89.3%, 86.0%, and 89.4% viability at 2, 6, and 24 hours respectively; p<0.001). Betamethasone 90 mcg/ml was toxic at 24 and 6 hours in both cell lines. ARPE cells showed values of 69.9 ± 11.1% and 71.1 ± 3.9% at 24 and 6 hours respectively and mean cell viability in R28 cells was 57.8 ± 2.3% and 77.1 ± 5.3% (p<0.001) respectively. BAK was not toxic at any dose or timepoint in both ARPE–19 and R28 cells with the exception of mild toxicity at the highest dose (6mcg/ml) and longest timepoint (24 hours) in R28 cells only (73.0 ± 2.6%; p<0.001). Mean cell viability of ARPE–19 cells after exposure to the highest concentration of BAK were 89.9 ± 1.6%, 91.8 ± 1.7% and 89.3 ± 1.9% at 2, 6 and 24 hour (p>0.05 for all).
Conclusions: :
Betamethasone is toxic for ARPE–19 and R28 cells in vitro in a dose–dependent fashion at levels comparable to clinical doses (90 mcg/ml intravitreally). Corresponding concentrations of the vehicle (BAK) were relatively non–toxic. Based on these studies, betamethasone does not appear to be a good candidate as an alternative to triamcinolone acetonide.
Keywords: drug toxicity/drug effects • retinal culture • corticosteroids