Inhibition of caspase-9 activation and apoptosis is involved in ischemic preconditioning-induced neuroprotection in rat brain.
OBJECTIVE
Cerebral ischemic pre-conditioning (IPC) is capable of protecting hippocampal neurons from ischemia/reperfusion (I/R) injury. In the current study, we investigated the role of activated caspase-9 in the protective process induced by IPC and related it to cytochrome c release and apoptosis.


METHODS
I/R injury was induced by a four-vessel occlusion model in Wistar rats which were randomly divided into ischemia/reperfusion group (I/R), ischemic pre-conditioning + I/R group (IPC + I/R) and control group. Histologic changes in the pyramidal layer of the hippocampal CA1 region were determined by hematoxylin and eosin (H&E) staining. The relative proportion of apoptotic neurons in this area was assessed with TUNEL staining. The redistribution of cytochrome c and activation of caspase-9 were detected in the same area with immunohistochemistry and Western blotting respectively.


RESULTS
Compared to the I/R group, IPC increased the number of surviving neurons in the hippocampal CA1 region (p<0.001), markedly reduced the number of apoptotic pyramidal neurons (p<0.001), inhibited the release of cytochrome c from mitochondria to cytoplasm (p<0.001 for positively stained neurons) and decreased the amount of activated caspase-9 (p<0.001).


CONCLUSIONS
These findings confirm that IPC is capable of protecting neurons from injury by apoptosis. The release of cytochrome c to the cytosol demonstrates that the mitochondrial pathway was involved, and the reduction in this release caused by IPC was clearly associated with reduced caspase-9 activation. Together, these results suggest that IPC protects neurons via action on the mitochondrial/caspase-9 pathway of apoptosis.
Liu
Yajun
Y
Institute of Physiology, School of Medicine, Shandong University, Jinan 250012, Shandong, China.
Sercombe
Richard
R
Xie
Dongping
D
Liu
Kejing
K
Chen
Lianbi
L
D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053453:Caspase 9 / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000502:physiology; D006624:Hippocampus / Q000473:pathology; D020287:In Situ Nick-End Labeling / Q000379:methods; D019194:Ischemic Preconditioning / Q000379:methods*; D008297:Male; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control
D045304:Cytochromes c; D053453:Caspase 9