Immature cortical neurons are uniquely sensitive to glutamate toxicity by inhibition of cystine uptake

Timothy H. Murphy, Ronald Lee Schnaar, Joseph T. Coyle

Research output: Contribution to journalArticle

Abstract

Using the N18-RE-105 neuroblastoma X retina cell line, we previously described Ca2+-dependent quisqualatetype glutamate toxicity caused by the inhibition of high-affinity cystine uptake, leading to glutathione depletion and accumulation of cellular oxidants. We now demonstrate that primary cultures of rat cortical neurons (E17; 24-72 h in culture), but not glia, also degenerate when exposed to culture medium with reduced cystine or containing competitive inhibitors of cystine uptake, including glutamate. At this developmental stage, neurotoxicity did not occur as a consequence of continuous exposure to glutamate receptor subtype agonists, N-methyl-D-aspartate, kainate, or 2(RS)-amino-3-hydroxy-5-methyl-4-isoxazolepropioniate. However, those that inhibited neuronal cystine uptake - quisqualate, glutamate, homocysteate, β-N-oxalyl-L-α,β-diaminopropionic acid, and ibotenate - were neurotoxic. Toxicity related to quisqualate did not correlate with the development of quisqualate-stimulated phosphatidylinositol turnover. The toxic potencies of glutamate, quisqualate, and homocysteate were inversely proportional to the concentration of cystine in the medium, suggesting that they competitively inhibit cystine uptake. Autoradiographic analysis of the cellular localization of L-[35S]cystine uptake indicated that embryonic neurons have a high-affinity transport system that is sensitive to quisqualate, whereas nonneuronal cells in the same cultures have a low-affinity system that is insensitive to quisqualate but potently blocked by D-aspartate and glutamate. Exposure to glutamate or homocysteate resulted in a time-dependent depletion of the cellular antioxidant glutathione. The centrally acting antioxidant idebenone and α-tocopherol completely blocked the neurotoxicity resulting from glutamate exposure. We propose that competitive inhibition of cystine transport and reduction of extracellular cystine levels result in neuronal cell death due to accumulation of cellular oxidants.

Original languageEnglish (US)
Pages (from-to)1624-1633
Number of pages10
JournalFASEB Journal
Volume4
Issue number6
StatePublished - Apr 1 1990

Fingerprint

Cystine
cystine
glutamates
Quisqualic Acid
Neurons
Toxicity
Glutamic Acid
neurons
immatures
toxicity
uptake mechanisms
neurotoxicity
aspartic acid
Oxidants
oxidants
Glutathione
glutathione
Antioxidants
D-Aspartic Acid
antioxidants

Keywords

  • Cystine
  • Glutamate
  • Neurotoxicity
  • Quisqualate

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology

Cite this

Immature cortical neurons are uniquely sensitive to glutamate toxicity by inhibition of cystine uptake. / Murphy, Timothy H.; Schnaar, Ronald Lee; Coyle, Joseph T.

In: FASEB Journal, Vol. 4, No. 6, 01.04.1990, p. 1624-1633.

Research output: Contribution to journalArticle

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