In cortical cultures of trisomy 16 mouse brain the upregulated metallothionein-I/II fails to respond to H2O2 exposure or glutamate receptor stimulation.
To assess whether a defective oxidative defense may contribute to Down's syndrome, we studied the regulation of the metallothionein(MT)-I/II isoforms in primary cultures of cerebral cortex from fetal trisomy 16 mice and their euploid littermates. Western blot analysis showed that MT-I/II was upregulated and the protein carbonyl content was higher in trisomy 16 compared with euploid cultures. Addition of N-acetyl-l-cysteine to the culture medium reduced the increment of MT-I/II in trisomy 16 cortical cells. In euploid, but not trisomic cortical cultures, kainic acid, trans-(+/-)-ACPD, or H2O2 exposure elicited a dose-dependent increase of the MT-I/II immunoblots. In trisomic cells, the MT-I/II immunoblot densities were not increased beyond their elevated basal levels. In contrast, 25 microM Pb induced MT-I/II, to a similar extent, in cortical cultures from euploid and trisomy 16 mice. This suggests that the antioxidant-but not the metal-response element of the MT-I/II promoter was altered by increased oxidative stress. Our data suggest that, in the trisomy 16 mouse, the effects of increased production of reactive oxygen species, due to the increased SOD-1, GluR5, or amyloid precursor protein gene dosage, is exacerbated by an insufficient or missing antioxidant response.
Scortegagna
M
M
Laboratory of Molecular Immunology, NHLBI, Bethesda, MD 20892, USA.
Galdzicki
Z
Z
Rapoport
S I
SI
Hanbauer
I
I
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D015153:Blotting, Western; D002540:Cerebral Cortex / Q000166:cytology / Q000473:pathology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007854:Lead / Q000494:pharmacology; D008297:Male; D008668:Metallothionein / Q000096:biosynthesis* / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D016877:Oxidants / Q000494:pharmacology*; D010084:Oxidation-Reduction; D017470:Receptors, Glutamate / Q000187:drug effects*; D013268:Stimulation, Chemical; D014314:Trisomy / Q000473:pathology*; D015854:Up-Regulation / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D016166:Free Radical Scavengers; D016877:Oxidants; D017470:Receptors, Glutamate; D007854:Lead; D008668:Metallothionein; D006861:Hydrogen Peroxide; D000111:Acetylcysteine