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Early decrease of apurinic/apyrimidinic endonuclease expression after transient focal cerebral ischemia in mice
M Fujimura1, Y Morita-Fujimura, M Kawase
1Department of Neurosurgery, Stanford University School of Medicine, Palo Alto, California 94304, USA.
Abstract:
The authors examined the protein expression of apurinic/apyrimidinic endonuclease (APE/Ref-1), a multifunctional protein in the DNA base excision repair pathway, before and after transient focal ischemia in mice. Immunohistochemistry showed the nuclear expression of APE/Ref-1 in the entire region of the control brains. Nuclear immunoreactivity was decreased as early as 5 minutes after 60 minutes of ischemia in the ischemic core, which was followed by a significant reduction of APE/Ref-1-positive cells in the entire middle cerebral artery territory. Western blot analysis of the sample from the nonischemic brain showed a characteristic 37-kDa band, which was reduced after ischemia. A significant amount of DNA fragmentation was observed at 24 hours, but not at 4 hours, after ischemia. The authors' data provide the first evidence that APE/Ref-1 rapidly decreases after transient focal ischemia, and that this reduction precedes the peak of DNA fragmentation in the brain regions that are destined to show necrosis and apoptosis. Although further examination is necessary to elucidate the direct relationship between the APE/Ref-1 decrease and ischemic necrosis and apoptosis, our results suggest the possibility that rapid decrease of APE/Ref-1 and the failure of the DNA repair mechanism may contribute to necrosis or apoptosis after transient focal ischemia.
Insights
A rapid decrease in apurinic/apyrimidinic endonuclease (APE/Ref-1) occurs after transient focal ischemia in mice. This reduction precedes DNA fragmentation, suggesting a role in brain cell death following stroke.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Apurinic/apyrimidinic endonuclease (APE/Ref-1) is crucial for DNA base excision repair.
- APE/Ref-1 is a multifunctional protein involved in DNA repair and gene regulation.
- Transient focal ischemia can lead to significant cellular damage in the brain.
Purpose of the Study:
- To investigate the changes in APE/Ref-1 protein expression following transient focal ischemia in a mouse model.
- To determine if APE/Ref-1 reduction precedes DNA fragmentation and subsequent cell death.
Main Methods:
- Transient focal ischemia was induced in mice.
- Immunohistochemistry was used to assess APE/Ref-1 nuclear expression in brain tissue.
- Western blot analysis quantified APE/Ref-1 protein levels.
- DNA fragmentation was evaluated at different time points post-ischemia.
Main Results:
- Nuclear APE/Ref-1 expression decreased rapidly (within 5 minutes) in the ischemic core after 60 minutes of ischemia.
- A significant reduction in APE/Ref-1-positive cells was observed throughout the middle cerebral artery territory.
- Western blot confirmed a reduction in the 37-kDa APE/Ref-1 band after ischemia.
- Significant DNA fragmentation was detected at 24 hours, but not at 4 hours, post-ischemia.
Conclusions:
- APE/Ref-1 levels decrease rapidly following transient focal ischemia in mice.
- This reduction in APE/Ref-1 occurs before the peak of DNA fragmentation, suggesting a potential role in the pathogenesis of ischemic brain injury.
- The findings suggest that impaired DNA repair due to decreased APE/Ref-1 may contribute to necrosis and apoptosis after transient focal ischemia.