Astrocyte-enhanced neuronal survival is mediated by scavenging of extracellular reactive oxygen species

The survival of cultured neurons is promoted by the presence of antioxidants or astrocytes. This indicates that extracellular reactive oxygen species (ROS) impair neuronal survival and suggests that astrocytes exert their survival-enhancing effect through inactivation of these toxicants. However, to our knowledge, data supporting this hypothesis are lacking. Previously, we showed that loss of the antioxidant glutathione abolishes the neuronal survival-stimulating action of astrocytes in cocultures, consisting of rat striatal astrocytes and mesencephalic, dopaminergic neurons. Using uptake of [3H]dopamine as marker of neuronal survival, we presently investigated whether this effect of glutathione depletion is mediated by extracellular ROS. For this purpose, we incubated glutathione-depleted cocultures with superoxide dismutase, catalase or both. Whereas superoxide dismutase had no effect and catalase only partially protected, addition of the enzymes together completely prevented the impairment of neuronal survival caused by glutathione loss. No change in neuronal survival occurred upon exposure of control cocultures to superoxide dismutase and/or catalase. These data strongly implicate scavenging of extracellular ROS in astrocyte-stimulated neuronal survival and moreover suggest a crucial role for glutathione in this process.