Bcl‐2 overexpression protects against neuron loss within the ischemic margin following experimental stroke and inhibits cytochrome c translocation and caspase‐3 activity

Abstract

Bcl‐2 protects against both apoptotic and necrotic death induced by several cerebral insults. We and others have previously demonstrated that defective herpes simplex virus vectors expressing Bcl‐2 protect against various insults in vitro and in vivo, including cerebral ischemia. Because the infarct margin may be a region that is most amenable to treatment, we first determined whether gene transfer to the infarct margin is possible using a focal ischemia model. Since ischemic injury with and without reperfusion may occur by different mechanisms, we also determined whether Bcl‐2 protects against focal cerebral ischemic injury either with or without reperfusion in rats. Bax expression, cytochrome c translocation and activated caspase‐3 expression were also assessed. Viral vectors overexpressing Bcl‐2 were delivered to the infarct margin. Reperfusion resulted in larger infarcts than permanent occlusion. Bcl‐2 overexpression significantly improved neuron survival in both ischemia models. Bcl‐2 overexpression did not alter overall Bax expression, but inhibited cytosolic accumulation of cytochrome c and caspase‐3 activation. Thus, we provide the first evidence that gene transfer to the infarct margin is feasible, that overexpression of Bcl‐2 protects against damage to the infarct margin induced by ischemia with and without reperfusion, and that Bcl‐2 overexpression using gene therapy attenuates apoptosis‐related proteins. This suggests a potential therapeutic strategy for stroke.