Methylmercury-mediated inhibition of 3H-D-aspartate transport in cultured astrocytes is reversed by the antioxidant catalase

Jeffrey W. Allen, Lysette A. Mutkus, Michael Aschner

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

Astrocytes are essential for removal of glutamate from the extracellular space in the central nervous system. The neurotoxic heavy metal methylmercury potently and specifically inhibits the transport of glutamate in cultured astrocytes by an unknown mechanism. Glutamate transport in astrocytes is also inhibited by reactive oxygen species. A glutamate-induced transporter current is inhibited both by reactive oxygen species and thiol oxidizing agents. These observations suggest that oxidation of the transporter might mediate methylmercury-induced inhibition of glutamate transport. In the present study, we examined the ability of thiol reducing or oxidizing agents to inhibit transport of 3H-D-aspartate, a glutamate analog, in primary cultures of neonatal rat astrocytes. To assess if methylmercury-mediated inhibition of 3H-aspartate transport was due to overproduction of reactive oxygen species, we tested the ability of Trolox, α-phenyl-tert-butyl nitrone (PBN), or catalase to attenuate the methylmercury-induced inhibition of aspartate uptake. Neither the thiol reducing agent dithiothreitol (DTT), nor the thiol oxidizing agent 5,5′-dithio-bis(2-nitrobenzoic) acid (DTNB) had any effect on 3H-aspartate transport suggesting that the thiol redox state does not alter transporter function. In contrast, the antioxidant catalase (1000 U/ml) significantly attenuated methylmercury-induced inhibition of 3H-aspartate uptake, suggesting that excess reactive oxygen species, specifically H2O2, inhibit the function of an astrocytic excitatory amino acid transporter (EAAT1). Prolonged exposure (6 h) to inhibitors of glutamate transport significantly decreased EAAT1 mRNA levels suggesting that transporter expression is related to function. This study suggests that methylmercury-induced overproduction of H2O2 is a mechanism for inhibition of glutamate transport and transporter expression in cultured astrocytes.

Original languageEnglish (US)
Pages (from-to)92-100
Number of pages9
JournalBrain Research
Volume902
Issue number1
DOIs
StatePublished - May 25 2001
Externally publishedYes

Fingerprint

D-Aspartic Acid
Astrocytes
Catalase
Glutamic Acid
Sulfhydryl Compounds
Antioxidants
Aspartic Acid
Reactive Oxygen Species
Oxidants
Amino Acid Transport System X-AG
Reducing Agents
Nitrobenzoates
Dithionitrobenzoic Acid
Amino Acid Transport Systems
Excitatory Amino Acids
Dithiothreitol
Extracellular Space
Heavy Metals
Oxidation-Reduction
Central Nervous System

Keywords

  • Antioxidants
  • Astrocytes
  • Catalase
  • Glutamate transporter
  • Methylmercury
  • Reactive oxygen species

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Methylmercury-mediated inhibition of 3H-D-aspartate transport in cultured astrocytes is reversed by the antioxidant catalase. / Allen, Jeffrey W.; Mutkus, Lysette A.; Aschner, Michael.

In: Brain Research, Vol. 902, No. 1, 25.05.2001, p. 92-100.

Research output: Contribution to journalArticle

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