l-DOPA Up-Regulates Glutathione and Protects Mesencephalic Cultures Against Oxidative Stress

Authors

  • Shan-Kuo Han,

    1. Department of Neurology, Center for Neurobiology, and Graduate School in Biomedical Science (Neurobiology), Mount Sinai School of Medicine of the City University of New York, New York, New York, U.S.A.
    Search for more papers by this author
  • Catherine Mytilineou,

    1. Department of Neurology, Center for Neurobiology, and Graduate School in Biomedical Science (Neurobiology), Mount Sinai School of Medicine of the City University of New York, New York, New York, U.S.A.
    Search for more papers by this author
  • Gerald Cohen

    Corresponding author
    1. Department of Neurology, Center for Neurobiology, and Graduate School in Biomedical Science (Neurobiology), Mount Sinai School of Medicine of the City University of New York, New York, New York, U.S.A.
      Address correspondence and reprint requests to Dr. G. Cohen at Department of Neurology (Box 1137), Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, U.S.A.
    Search for more papers by this author

Address correspondence and reprint requests to Dr. G. Cohen at Department of Neurology (Box 1137), Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, U.S.A.

Abstract

Abstract: Incubation with l-DOPA induced a rise in GSH level in cultures of fetal rat mesencephalon, mouse neuroblastoma (Neuro-2A), human neuroblastoma (SK-N-MC), pig kidney epithelial cells (LLC-PK1), and glia from newborn rat brain, but not C6 glioma cells or neuronal cultures (no glia) from the mesencephalon. The pure neuronal cultures were destroyed by incubation with l-DOPA; added ascorbic acid or superoxide dismutase protected the cells. Washout of l-DOPA after 48 h amplified the rise in GSH content in mixed cultures (neurons plus glia). Examination of structure-activity relationships for elevating GSH levels in responsive cell types revealed that autooxidizable compounds (α-methyl-DOPA, dopamine, apomorphine, catechol, and hydroquinone) behaved similarly to l-DOPA, whereas structural analogues that cannot undergo autooxidation (3-O-methyl-DOPA, tyrosine, 2,4-dihydroxyphenylalanine, and resorcinol) failed to elevate GSH levels. Therefore, up-regulation of GSH appears to be a response to a mild oxidative stress. When mixed mesencephalic cultures were exposed to a strong oxidant stress by incubation with tert-butyl hydroperoxide, a loss in viability was seen. Cultures pretreated with l-DOPA or hydroquinone were protected from loss of viability. However, when cultures were pretreated with both l-DOPA and ascorbate, which prevents the rise in GSH level, protection was lost, in accord with the failure to up-regulate GSH. These results show that the up-regulation of cellular GSH evoked by autooxidizable agents is associated with significant protection of cells. Glia play an essential role in the response of mesencephalic cell cultures. An ability to up-regulate GSH may serve a protective role in vivo.

Ancillary