Effect of zinc, copper and glucocorticoids on metallothionein levels of cultured neurons and astrocytes from rat brain

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Abstract

The knowledge of brain metallothionein (MT) regulation and especially of MT presence in specific cell types is scarce. Therefore, the effect of several well-known MT inducers, measured by radioimmunoassays using antibodies that cross-react with MT-I and MT-II or specific for MT-I and which do not cross-react with human growth inhibitory factor (GIF or MT-III), has been studied in primary cultures of neurons or astrocytes obtained from rat cerebrum. MT-I levels in glial cells were about ten times higher than those in neuronal cells (538 ± 194 vs. 49 ± 16 pg MT-I/μg protein, mean ± SD from three separate cell preparations). Increasing the concentration of Zn in the bovine serum albumin (BSA)-containing culture medium up to 50 μM significantly increased MT-I levels by up to 3.5-fold in neurons and 2.5-fold in astrocytes. In contrast, Cu up to 50 μM increased MT-I levels in a saturable manner in both neurons (up to 5-fold) and astrocytes (up to 1.5-fold), the maximum effect occurring at 5 μM Cu. In general, the combination of Zn and Cu further increased MT-I levels. The effect of the metals on MT-I appeared to reflect metal uptake, since MT-I induction was less marked when the BSA concentration in the medium was increased from 2 to 10 mg/ml. Dexamethasone increased MT-I levels in both neurons and astrocytes in vitro in a concentration-dependent manner. Endotoxin, IL-1 and IL-6 did not have a significant effect on glial MT levels at the concentrations studied. The administration of dexamethasone to rats increased MT-I levels in non-frontal cortex, cerebellum, pons + medulla, midbrain and hippocampus, but not in hypothalamus, frontal cortex and striatum. Endotoxin increased liver but not brain MT-I levels. Immunocytochemical studies in adult rat brain preparations with a polyclonal antibody that cross-reacts with MT-I and MT-II indicated that immunostaining was always nuclear in glial cells, whereas in neurons it was nuclear in the cerebral cortex, hippocampus and the granular layer of the cerebellum, and nuclear plus cytoplasmic in Purkinje cells in the cerebellum, hypothalamic nuclei and gigantocellular reticular nucleus in the brain stem. Meninges, choroidal plexus, ependymal and endothelial cells were also MT-immunoreactive.

References (58)

  • M.L. Failla et al.

    Zinc uptake by isolated rat liver parenchymal cells

    Biochim. Biophys. Acta

    (1978)
  • A.L. Weiner et al.

    Copper-accumulation and metabolism in primary monolayer cultures of rat liver parenchymal cells

    Biochim. Biophys. Acta

    (1980)
  • K. Nakajima et al.

    Detection of metallothionein in brain

    Methods Enzymol.

    (1991)
  • M. Panemangalore et al.

    Changes in the intracellular accumulation and distribution of metallothionein in rat liver and kidney during postnatal development

    Dev. Biol.

    (1983)
  • Y. Itano et al.

    Bacterial endotoxin-induced expression of metallothionein genes in rat brain, as revealed by in situ hybridization

    Neurosci. Lett.

    (1991)
  • I. Bremner et al.

    Effects of changes in dietary zinc, copper and selenium and of endotoxin administration on metallothionein I concentrations in blood cells and urine in the rat

    J. Nutr.

    (1987)
  • J. Liu et al.

    Endotoxin induction of hepatic metallothionein is mediated through cytokines

    Toxicol. Appl. Pharmacol.

    (1991)
  • S.K. De et al.

    Endotoxin induction of murine metallothionein gene expression

    J. Biol. Chem.

    (1990)
  • J.E. Churchich et al.

    Activation of pyridoxal kinase by metallothionein

    Biochim. Biophys. Acta

    (1989)
  • P. Szerdahelyi et al.

    Partial depletion and altered distribution of synaptic zinc in the rat hippocampus after treatment with sodium diethyldithiocarbamate

    Brain Res.

    (1987)
  • K. Gulya et al.

    Partial depletion of endogenous zinc levels by (D-Pen2, D-Pen5) Enkephalin in the rat brain

    Life Sci.

    (1991)
  • Y. Uchida et al.

    The growth inhibitory factor that is deficient in the Alzheimer's disease brain is a 68 amino acid metallothionein-like protein

    Neuron

    (1991)
  • R.J. Cousins

    Absorption, transport and hepatic metabolism of copper and zinc: special reference to metallothionein and ceruloplasmin

    Physiol. Rev.

    (1985)
  • D.H. Hamer

    Metallothionein

    Annu. Rev. Biochem.

    (1986)
  • R.M. Nalbandyan

    Copper in brain

    Neurochem. Res.

    (1983)
  • C.J. Frederickson et al.

    The Neurobiology of Zinc

    (1984)
  • M. Ebadi

    Biochemical characterization of a metallothionein-like protein in rat brain

    Biol. Trace Elem. Res.

    (1986)
  • V.K. Paliwall et al.

    Regulation of zinc metallothionein II mRNA level in rat rain

    Neurochem. Int.

    (1990)
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    Present address: Medical Academy of Wroclaw, Department of Toxicology, Traugutta 57/59, Wroclaw 50-417, Poland.

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