The Neuronal Apoptosis And Its Relation To The Expression Of Bcl-2 And Caspase-3 After Focal Cerebral Ischemia Reperfusion In Rats

Objective: To study the apoptosis and and its relation to the expression of Bcl-2 and Caspase-3 genes of neurons after focal cerebral ischemia/reperfusion in rats. Methods: Adult Wistar rats were subjected to 1 h of transient focal cerebral ischemia induced by intraluminal blockade of the left middle cerebral artery. After 2h, 6h, 12h, 24h, 2d, 3d, 7d and 14d of reperfusion, the numbers and anatomic distribution of apoptotic or necrotic cells were examined with terminal deoxynucleotidyl tranferase mediated dUTP-flourescein nick end-labeling (TUNEL) assay in adjacent sections. The expression of Bcl-2 mRNA and Caspase-3 mRNA were examined by in situ hybridization. Results: (1) TUNEL-positive cells were preferentially located in the inner boundary zone of the infarction and progressively increased up to and peaked at 24h after reperfusion, and then decreased at 48h, but still in high level. The number of TUNEL-positive cells at every adjacent time are greatly different. (2) The expression of Bcl-2 mRNA was begun after reperfusion 2h, peaked at 12h~24h, and then decreased at 48h, but still in high level. The time-phase pattern of Bcl-2 is similar to that of apoptosis. (3) Caspase-3 mRNA was expressed after 2h-14d of reperfusion, mainly in the inner boundary zone of the infarction, with a peak at 24h of reperfusion. The temporal and spatial profile of Caspase-3 mRNA expression consistent is with those ofapoptosis. Conclusions: (1) These results suggest that the neuronal cell death is a dynamic ongoing process. After the onset of ischemia, reperfusion as soon as possible may not only ameliorate brain damage but also extend the therapeutic"time window"and enhance the therapeutic effect. It may play a beneficial role in salvaging neuronal cells from ischemic damage to intervene the mechanism of apoptosis as soon as possible up to 24 h after reperfusion. (2) The expression of Bcl-2 might correlate with the neuronal apoptosis and play an important role in protecting brain from cerebral ischemic reperfusive injury. (3) Caspase-3 plays a key role in neuronal apoptosis and ischemic brain injury. Caspase-3 inhibitors may provide a promising opportunity for stroke.