Oxidative stress has been proposed as a major injury mechanism in the central nervous system including the retina. In this study, as an initial attempt to study the mechanism of oxidative injury in the retina, we developed a cell culture model by utilizing the iron exposure paradigm. Exposure of rat retinal cultures for 24 hours to 10-40 μM ferrous or ferric chloride induced a concentration-dependent death of retinal neurons but not of photoreceptors or astrocytes. An antioxidant, trolox effectively attenuated the iron-induced death of neurons and photoreceptors in a dose-dependent manner whereas neither glutamate receptor antagonists nor cycloheximide were protective. Of retinal interneurons, GABAergic neurons were more vulnerable to the iron toxicity than calbindin (+) horizontal neurons. These findings show that iron exposure induces anti-oxidant-sensitive neuronal injury in retinal culture, independent of the excitotoxic or the apoptotic mechanisms. Of retinal neurons, different cell types exhibit differential vulnerabilities to the iron-induced oxidative injury. This simplified culture model system may be useful in elucidating mechanisms of oxidative injury in the retina.
MATERIALS AND METHODS