Cyclosporine A Protects RGC-5 Cells From Excitotoxic Cell Death

Purpose: Cyclosporine A (CSA) is a widely used immunosuppressive drug. Furthermore, CSA showed neuroprotective properties in several neurological disorders. However, nearly no data exist regarding CSA and its possible neuroprotective effect on retinal ganglion cells (RGCs). Methods: RGC-5 cells were stressed with 10 mM glutamate for 24 hours with or without adding varying concentrations of CSA (1, 3, 6, or 9 mu g/mL) to the medium. Cell viability and cell density were analyzed by MTS assay and crystal violet staining, respectively. Induction of apoptosis was determined through caspase 3/7 activity and Annexin V+/PI- flow cytometry. Results: The incubation of RGC-5 cells with 10 mM glutamate for 24 hours induced a 3.1-fold and a 3.4-fold decrease in overall cell viability and cell density, respectively, compared with controls. The supplementation of 9 mu g/mL CSA to 10 mM glutamate led to a 2.7-fold increase in overall cell viability (P < 0.0005) and a 2.5-fold increase in cell density (P < 0.0005) compared with RGC-5 cells treated only with 10 mM glutamate. Furthermore, the addition of 9 mu g/mL CSA to 10 mM glutamate significantly reduced caspase 3/7 activity by 1.3-fold (P < 0.0005) and the amount of Annexin V+/PI- cells by 2.8-fold compared with RGC-5 cells incubated with 10 mM glutamate alone. The neuroprotective effect of CSA dose-dependently decreased with lower concentrations. Conclusions: CSA can effectively protect RGC-5 cells against glutamate-induced excitotoxicity. Therefore, CSA should be tested in further experiments to evaluate its potential as a neuroprotective substance against RGC disorders.