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Permanent cerebral ischemia induces sustained procaspase 9L increase not controlled by Bcl-2
Y Pfister1, A Savioz, P G Vallet
1University Hospital Geneva, Belle-Idée, Department of Psychiatry, Geneva, Switzerland.
Brain Research
|March 21, 2003
Summary
Transgenic Bcl-2 overexpression delays cell death activation following cerebral ischemia but does not prevent long-term caspase changes. This suggests Bcl-2 offers temporary protection, but sustained ischemia can overcome its anti-apoptotic effects.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Permanent cerebral ischemia, induced by middle cerebral artery occlusion (MCAO), triggers cell death pathways.
- The anti-apoptotic protein Bcl-2 plays a crucial role in regulating programmed cell death.
- Understanding Bcl-2's long-term effects on cell death mediators in ischemia is vital for therapeutic development.
Purpose of the Study:
- To investigate the long-term impact of human Bcl-2 (Hu-Bcl-2) overexpression on cell death protein activation after permanent cerebral ischemia.
- To examine the expression and activation of key apoptosis-related proteins, including cytochrome c, caspase 9, and caspase 3, in a mouse model of MCAO.
Main Methods:
- Utilized a permanent middle cerebral artery occlusion (MCAO) model in transgenic mice overexpressing Hu-Bcl-2 and wild-type (WT) littermates.
- Analyzed protein expression and localization of Hu-Bcl-2, cytochrome c, procaspase 9, caspase 9, procaspase 3, and caspase 3 using immunoblotting and immunohistochemistry at various time points post-MCAO.
Main Results:
- In WT mice, MCAO induced cytochrome c release and sustained caspase activation (caspase 9 and 3) starting from day 3 post-injury.
- Hu-Bcl-2 overexpression blocked cytochrome c release and delayed caspase activation, preventing procaspase 3 decrease initially.
- However, Hu-Bcl-2 did not alter MCAO-induced changes in procaspase 9 isoforms (9L and 9S).
- By 14 days post-MCAO, the apoptotic cascade was no longer blocked in transgenic mice, with increased caspases 9 and 3, and altered procaspase levels.
Conclusions:
- Transgenic Hu-Bcl-2 overexpression provides temporary protection against ischemia-induced cell death by delaying the activation of the apoptotic machinery.
- The inability to control MCAO-induced changes in procaspase 9 isoforms suggests a limitation in Bcl-2's long-term efficacy.
- Sustained increase in procaspase 9L represents a potential threat, indicating that anti-apoptotic strategies may eventually be overcome by severe ischemic insults.