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Enhanced production of superoxide anion by microglia from trisomy 16 mice
C A Colton1, J B Yao, D Gilbert
1Department of Physiology and Biophysics, Georgetown University Medical School, Washington, DC 20007.
Abstract:
Disruption of normal oxygen radical metabolism in the CNS may contribute to the neuropathological changes associated with Down syndrome (trisomy 21) and its mouse counterpart, the trisomy 16 (Ts16) mouse. One potent source of oxyradicals is the CNS-specific macrophage, the microglial cell. We prepared primary glial cultures from the cerebral cortices of Ts16 and normal littermate mice taken at day 15 of gestation. Microglia were isolated from confluent cultures after 14 days in vitro and assayed for superoxide anion production using a cytochrome C reduction assay. Stimulation by either opsonized zymosan (OPZ) or phorbol myristate acetate (PMA), produced significantly higher levels (2.8-20 fold) of superoxide per mg protein in Ts16 microglial cultures. Resting, i.e. unstimulated secretion, was not significantly different from littermate controls. Astrocyte enriched cultures, stimulated by OPZ, exhibited low levels of superoxide production which was higher in Ts16 mice than normal littermates. Microglial enriched cultures from rat neonatal cerebral cortices were exposed for 24 h to medium from the Ts16 glial cultures. Superoxide production in the Ts16 media treated rat microglia was significantly higher than in those treated with littermate conditioned media.
Insights
Mice with trisomy 16 (Ts16) show increased superoxide production in microglia, suggesting a link between oxygen radical metabolism disruption and Down syndrome neuropathology.
Area of Science:
- Neuroscience
- Immunology
- Genetics
Background:
- Down syndrome (trisomy 21) is associated with central nervous system (CNS) neuropathology.
- Disrupted oxygen radical metabolism in the CNS may contribute to these changes.
- Microglia, the CNS-specific macrophages, are a significant source of oxygen radicals.
Purpose of the Study:
- To investigate superoxide anion production in microglia from trisomy 16 (Ts16) mice, a model for Down syndrome.
- To determine if Ts16 microglia exhibit altered oxygen radical metabolism compared to normal littermates.
Main Methods:
- Primary glial cultures were prepared from E15 Ts16 and normal littermate mouse cerebral cortices.
- Microglia were isolated after 14 days in vitro.
- Superoxide anion production was measured using a cytochrome C reduction assay after stimulation with opsonized zymosan (OPZ) or phorbol myristate acetate (PMA).
- Rat microglial cultures were exposed to conditioned media from Ts16 or control glial cultures.
Main Results:
- Ts16 microglia produced significantly higher levels (2.8-20 fold) of superoxide anion per mg protein upon stimulation compared to normal littermate microglia.
- Resting superoxide secretion was not significantly different between Ts16 and control microglia.
- Astrocyte-enriched cultures from Ts16 mice also showed higher stimulated superoxide production.
- Rat microglia exposed to Ts16 glial conditioned media exhibited increased superoxide production.
Conclusions:
- Ts16 microglia display heightened stimulated superoxide production, indicating altered oxygen radical metabolism.
- These findings support the hypothesis that disrupted oxygen radical metabolism in microglia contributes to neuropathology in Down syndrome models.
- Further research into microglial function in Down syndrome is warranted.