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Induction of PML immunoreactivity in rat brain neurons after transient middle cerebral artery occlusion
1Department of Neurology, Okayama University School of Medicine, Japan. thayashi@cc.okayama-u.ac.jp
Abstract:
Promyelocytic leukemia (PML) protein is involved in apoptotic death of cultured neuronal cells, but its role in ischemic brain damage remains uncertain. In this study, we investigated change of immunoreactivity for PML protein in rat brain after transient middle cerebral artery occlusion, and compared the results with that of terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL). Western blotting analysis revealed that PML immunoreactivity was only scant in the sham-control brain, but it increased at 1 h and 1 day after reperfusion, and decreased in density thereafter. Immunohistochemical analysis revealed that nuclei of neurons were most densely stained. TUNEL positive cells appeared at 1 day and peaked at 3 days of reperfusion, indicating that PML protein induction preceded DNA fragmentation in neurons. The present results suggest that PML protein may be one of the key molecules in ischemic neuronal cell death.
Insights
Promyelocytic leukemia (PML) protein increases in rat brains after ischemic injury, preceding DNA fragmentation in neurons. This suggests PML protein is crucial in ischemic neuronal cell death.
Area of Science:
- Neuroscience
- Molecular Biology
- Pathology
Background:
- The role of Promyelocytic leukemia (PML) protein in ischemic brain damage is not well understood.
- PML protein is known to be involved in the apoptotic death of cultured neuronal cells.
Purpose of the Study:
- To investigate changes in PML protein immunoreactivity in the rat brain following transient middle cerebral artery occlusion (MCAO).
- To compare the temporal expression of PML protein with DNA fragmentation (TUNEL) in ischemic brain injury.
Main Methods:
- Transient middle cerebral artery occlusion (MCAO) was performed on rats.
- Western blotting was used to analyze PML protein levels.
- Immunohistochemistry was employed to visualize PML protein distribution.
- Terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) was used to detect DNA fragmentation.
Main Results:
- PML immunoreactivity was low in sham-control brains but increased significantly at 1 hour and 1 day post-reperfusion after MCAO.
- PML protein staining was most prominent in the nuclei of neurons.
- TUNEL-positive cells, indicating DNA fragmentation, appeared at 1 day and peaked at 3 days post-reperfusion.
- The induction of PML protein was observed to precede DNA fragmentation in neurons.
Conclusions:
- PML protein expression is upregulated in the rat brain following ischemic injury.
- The temporal pattern suggests that PML protein induction occurs before significant neuronal DNA fragmentation.
- These findings indicate that PML protein may play a key role in the mechanisms of ischemic neuronal cell death.