Permanent cerebral ischemia induces sustained procaspase 9L increase not controlled by Bcl-2.
We have investigated how transgenic overexpression of human Bcl-2 (Hu-Bcl-2) modifies cell death proteins activation in the long-term in a model of permanent cerebral ischemia induced by middle cerebral artery occlusion. Hu-Bcl-2, cytochrome c, caspases 9 and 3 expression were examined by immunoblotting and immunohistochemistry. In wild type mice, 1 day after middle cerebral artery occlusion, cytochrome c released from the mitochondria was detected. Middle cerebral artery occlusion induces a lasting activation of caspases in WT mice from day 3 post-injury. Increased level of caspase 3 is accompanied by a decrease in procaspase 3. In contrast, middle cerebral artery occlusion induced a sustained increase of procaspase 9L and a decrease in procaspase 9S concomitant to caspase 9 production. These events were observed in the operated but not in the unoperated hemisphere. Bcl-2 overexpression blocks cytochrome c release and delays caspases activation. Consequently procaspase 3 decrease was no more observed. However, Bcl-2 overexpression did not influence the middle cerebral artery occlusion-induced changes in procaspases 9 L and S. Fourteen days after middle cerebral artery occlusion the apoptotic cascade was no longer blocked in transgenic mice. Caspases 9 and 3 were increased, procaspase 3 was decreased but procaspase 9L and procaspase 9S remained increased and decreased respectively. Hu-Bcl-2 overexpression delays the activation of the cell death molecular machinery but does not control the ischemia-induced change in procaspase 9 L and S. Procaspase 9L increase is a potentially harmful event threatening cells of a rapid destruction when anti-apoptotic treatments by Bcl-2, or caspases inhibitors, are overrun.
Pfister
Y
Y
University Hospital Geneva, Belle-Idée, Department of Psychiatry, Geneva, Switzerland.
Savioz
A
A
Vallet
P G
PG
Dubois-Dauphin
M
M
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D053453:Caspase 9; D020169:Caspases / Q000032:analysis / Q000096:biosynthesis*; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism*; D004790:Enzyme Induction / Q000502:physiology; D004792:Enzyme Precursors / Q000032:analysis / Q000096:biosynthesis*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics
D004792:Enzyme Precursors; D019253:Proto-Oncogene Proteins c-bcl-2; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse; D053453:Caspase 9; D020169:Caspases