Astrocyte-mediated enhancement of neuronal survival is abolished by glutathione deficiency

Astrocytes promote the survival of neurons. Conditions characterized by loss of neurons, such as aging and aging-related neurodegenerative disorders, are accompanied by both disturbances in astrocyte-neuron interactions and signs of oxidative damage. Neuronal glutathione, a major antioxidant in the brain, is maintained by astrocytes and brain levels of glutathione are reduced in named conditions. Therefore, we focused on a possible link between glutathione deficiency and loss of astrocyte-derived neuronal support. For this purpose, we used a coculture system consisting of rat striatal astrocytes and mesencephalic, dopaminergic (DAergic) neurons. Using tyrosine hydroxylase immunocytochemistry and radiolabeled dopamine uptake as parameters, an increase in the number and outgrowth of DAergic neurons was noted in cocultures as compared to cultures of mesencephalic neurons alone. This enhanced survival of DAergic neurons in cocultures was abolished following depletion of glutathione with buthionine sulfoximine. As demonstrated by glial fibrillary acidic protein immunocytochemistry and a microtiter tetrazolium assay, under these conditions no change in astrocyte survival occurred. However, glutathione depletion in cocultures was accompanied by loss of astrocyte-mediated neuroprotection against hydrogen peroxide toxicity. Thus, our results indicate that glutathione is important for the maintenance of the neuronal support function of astrocytes and that glutathione deficiency in the brain may lead to enhanced vulnerability of neurons to (oxidative) damage.