Effect of Dexamethasone on Mitochondrial Function and Cell Viability in Human Retinal Pigment Epithelial and Rat Neurosensory Retinal Cells in vitro

Abstract

Purpose:: To evaluate the in vitro toxicity of dexamethasone (DEX) on human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28).

Methods:: ARPE-19 and R28 cells were treated with DEX at concentrations of 0.125, 0.25, 0.50 or 1mg/ml, or with DEX’s preservative, benzyl alcohol (BA) at equivalent doses. Mean cell viability was measured after 2, 6 or 24 hours. The mitochondrial dehydrogenase activity was also determined using the WST-1 assay.

Results:: For ARPE-19 and R28 cells, cell viability of DEX and corresponding dose of preservative BA at concentrations of 0.125, 0.25 and 0.50mg/ml (1, 2, and 5 times clinical dose of free DEX injections) for all time points were not significantly different than controls. Decreased cell viability of ARPE-19 and R28 cells exposed to 1mg/ml DEX (10X clinical dose, 41.2±5.2% and 25.4±3.7%) or the corresponding preservative (64.6±1.7% and 38.8±2.9%) for 24 hs was observed compared to untreated controls ( 93.2±2.6%, 95.1±0.2%; p<0.001). Additionally, for R28 cells, cell viablilty for 1mg/ml DEX was lower than the corresponding preservative alone (25.4±3.7%, 38.8±2.9%; p<0.05). WST-1 was significantly reduced in ARPE-19 and R28 cells treated with 0.25, 0.50, and 1mg/ml DEX (0.92±0.09, 0.46±0.04, 0.33±0.01 absorbance at 490nm for ARPE-19; 0.70±0.02, 0.36±0.02, 0.41±0.03 for R28) or corresponding preservative (0.38±0.03, 0.21±0.02, 0.19±0.01) for 24 hours compared to untreated controls (1.57±0.03; p<0.001). Additionally, at 24 hours in R 28 cells, 0.125mg/ml DEX and its corresponding preservative showed reduced WST-1 (1.02±0.04, 1.09±0.04 versus 1.58±0.09; p<0.001).

Conclusions:: DEX at concentrations of 0.125, 0.25 and 0.50mg/ml (up to 5x the clinical dose of free DEX) does not cause decreased cell viability in ARPE19 and R-28 cells in-vitro. However, the more sensitive WST-1 assay shows that there may be some reduced mitochondrial function in response to DEX at the doses tested here (which are at least 40x the DEX dose achieved with the Posurdex^TM drug delivery system).

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