Metallothionein Induction in Neonatal Rat Primary Astrocyte Cultures Protects Against Methylmercury Cytotoxicity

L. Rising, D. Vitarella, H. K. Kimelberg, M. Aschner

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

Abstract: Metallothionein (MT) protein and mRNA levels were monitored following exposure of rat neonatal primary astrocyte cultures to methylmercury (MeHg). MT‐I and MT‐II mRNAs were probed on northern blots with an [α‐32P]dCTP‐labeled synthetic cDNA probe specific for rat MT mRNA. MT‐I and MT‐II mRNAs were detected in untreated cells, suggesting constitutive MT expression in these cells. The probes hybridize to a single mRNA with a size appropriate for MT, ∼550 and 350 bp for MT‐I and MT‐II, respectively. Expression of MT‐I and MT‐II mRNA in astrocyte monolayers exposed to 2 × 10−6M MeHg for 6 h was increased over MT‐I and MT‐II mRNA levels in controls. Western blot analysis revealed a time‐dependent increase in MT protein synthesis through 96 h of exposure to MeHg. Consistent with the constitutive expression of MTs at both the mRNA level and the protein level, we have also demonstrated a time‐dependent increase in MT immunoreactivity in astrocytes exposed to MeHg. The cytotoxic effects of MeHg were measured by the rate of astrocytic d‐[3H]aspartate uptake. Preexposure of astrocytes to CdCl2, a potent inducer of MTs, completely reversed the inhibitory effect of MeHg on d‐[3H]aspartate uptake that occurs in MeHg‐treated astrocytes with constitutive MT levels. Associated with CdCl2 treatment was a time‐dependent increase in astrocytic MT levels. In summary, astrocytes constitutively express MTs; treatment with MeHg increases astrocytic MT expression, and increased MT levels (by means of CdCl2 pretreatment) attenuate MeHg‐induced toxicity. Increased MT expression may represent a generalized response to heavy metal exposure, thus protecting astrocytes and perhaps also, indirectly, juxtaposed neurons from the neurotoxic effects of heavy metals.

Original languageEnglish (US)
Pages (from-to)1562-1568
Number of pages7
JournalJournal of Neurochemistry
Volume65
Issue number4
DOIs
Publication statusPublished - Oct 1995
Externally publishedYes

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Keywords

  • Astrocytes
  • Cadmium chloride
  • Metallothionein
  • Methylmercury
  • Rat
  • d‐Aspartate

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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