Evidence of increased oxidative stress in hippocampal primary cultures of trisomy 16 mouse. Studies on metallothionein-I/II.

In the trisomy 16 mouse the increased gene dosage of SOD-1 increases H2O2 production that results in increased oxidative stress. We report here that in hippocampal primary cultures, metallothionein (MT)-I/II immunoreactivity was present mainly in glial fibrillary acidic protein-immunolabeled cells. Western blot analysis showed a two-fold higher level of MT-I/II in trisomy 16 mice then in euploid littermates. In contrast, the immunoreactivity of glutamine synthetase, another glia-expressed protein, was similar in hippocampal cultures of trisomy 16 mouse and euploid littermates. Oxyblot analysis of hippocampal cultures showed that the carbonyl content in several protein bands was higher in trisomy 16 mice than in euploid littermates giving evidence for increased oxidative stress in trisomy 16 mouse cultures. To evaluate the responsiveness of MT-I/II to agents that increase the level of reactive oxygen species in cells we measured the effect of H2O2, kainic acid, (+/-) ACPD, and beta-amyloid peptide 1-42. Western blot analysis documented that in hippocampal cultures of euploid littermates MT-I/II was maximally increased by 50 micro M H2O2, 100 micro M kainic acid, 10 micro M (+/-)ACPD, or 1.0 mM beta-amyloid peptide 1-42, whereas in those of trisomy 16 mice no further increase above the elevated level was observed. Our data suggest that in the trisomy 16 mouse the production of reactive oxygen species may have shifted the intracellular redox environment that could have alerted the susceptibility of MT-I/II transcription. The possibility that transcription factors whose activation may be essential to initiate MT-I/II transcription get oxidized has yet to be examined.