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Late-onset lipid peroxidation and neuronal cell death following transient forebrain ischemia in rat brain
Y Kondo1, M Asanuma, S Nishibayashi
1Department of Neuroscience, Institute of Molecular and Cellular Medicine, Okayama University Medical School, Japan. konchan@cc.okayama-u.ac.jp
Insights
Iron deposition after brain ischemia contributes to lipid peroxidation, a process linked to delayed neuronal damage. This suggests iron-mediated damage may play a role in slowly progressive neurodegeneration.
Area of Science:
- Neuroscience
- Pathology
- Biochemistry
Background:
- Transient forebrain ischemia leads to iron deposition in specific brain regions.
- Iron deposition in the hippocampus correlates with neuronal death, but not in the cerebral cortex initially.
Purpose of the Study:
- To investigate the role of iron in lipid peroxidation and neuronal damage following transient forebrain ischemia.
- To determine if iron contributes to delayed neurodegeneration in the cerebral cortex.
Main Methods:
- Rats underwent transient forebrain ischemia (four-vessel occlusion).
- Lipid peroxidation products (malondialdehyde and 4-hydroxynonenal) were measured up to 6 months post-ischemia.
- Histological analysis using immunohistochemical methods was performed up to 1 year post-reperfusion.
Main Results:
- Significant increase in lipid peroxidation products observed in the cerebral cortex at 6 months and in the striatum from 1 week to 6 months post-ischemia.
- Severe neuronal cell death and atrophy in the cerebral cortex were observed much later (up to 1 year), unlike the hippocampus and striatum.
- Lipid peroxidation occurred both early and late after ischemia, particularly in iron-deposited areas.
Conclusions:
- Iron-mediated lipid peroxidation may contribute to slowly progressive neurodegeneration.
- Delayed neuronal damage in the cerebral cortex appears linked to ongoing lipid peroxidation in iron-rich regions.
- This highlights a potential mechanism for late-onset neurodegenerative processes after ischemic events.
Abstract:
We previously reported that iron deposition was seen in the cerebral cortex and hippocampal CA1 area late after transient forebrain ischemia generated by four-vessel occlusion in rats. Iron deposition in the hippocampal CA1 area was coupled with delayed pyramidal cell death, while that in the cerebral cortex was not accompanied by neuronal death or atrophy until 6 months after ischemia. Iron is involved in the formation of free radicals, thus contributing to lipid peroxidation. To elucidate whether this iron has deleterious effects on neurons, we investigated changes in the levels of lipid peroxidation and resulting neuronal damage in this ischemia model. The level of malondialdehyde plus 4-hydroxynonenal as major decomposition products of lipid peroxidation, monitored for 6 months beginning just after 30 min of transient forebrain ischemia, was significantly increased in the cerebral cortex at 6 months, and in the striatum from 1 week to 6 months compared to that in sham-operated controls. Histological changes were also examined up to 1 year after reperfusion by immunohistochemical methods. In contrast with the hippocampus and striatum, the cerebral cortex did not develop severe neuronal cell death and atrophy until 1 year after the ischemic insult. We showed that lipid peroxidation took place not only immediately after ischemia-reperfusion but also late after the ischemic insult in regions where iron was deposited, and we showed that neuronal cell death in the cerebral cortex appeared extremely late, suggesting that iron-mediated lipid peroxidation may be of importance in some slowly progressive forms of neurodegeneration.