Background and Purpose-Ischemic postconditioning (Postcond) is defined as a series of intermittent interruptions of blood flow in the early phase of reperfusion that mechanically alters the hydrodynamics of reperfusion. A recent study showed that Postcond reduced infarct size in cerebral ischemia/reperfusion (I/R) injury. However, little is known about the mechanisms of Postcond in cerebral I/R injury. In the present study, we investigated the effects of Postcond in focal cerebral I/R injury in the rat middle cerebral artery occlusion model. Methods-Adult male Sprague-Dawley rats were treated with Postcond after 60 minutes of occlusion (beginning of reperfusion). Neurologic scores and infarct volumes were assessed at 24 and 72 hours. Oxidative stress was evaluated by malondialdehyde assay, and apoptosis-related molecules were studied by Western blotting. Results-Postcond treatment upregulated Bcl-2 and heat-shock protein 70 expression and downregulated cytochrome c release to the cytosol, Bax translocation to the mitochondria, and caspase-3 activity. Postcond treatment also reduced infarct volumes and oxidative stress levels and improved neurologic scores compared with the I/R-only group. Conclusions-These findings indicate that Postcond inhibits focal cerebral I/R injury. This neuroprotective effect is likely achieved by antiapoptotic mechanisms.

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Summary Ischemic postconditioning is a phenomenon that intermittent interruptions of blood flow in the early phase of reperfusion can protect organ from ischemia/reperfusion (I/R) injury. In the present study, we investigated whether the protective effect of ischemic postconditioning was associated with modulation of apoptosis after renal I/R injury. Rats were subjected to 45 min of renal ischemia, both with and without treatment with ischemic postconditioning. Serum urea nitrogen and creatinine levels, phosphorylation of Akt and ERK1/2 and apoptosis were compared after renal injury. Our data showed that ischemic postconditioning attenuated the renal dysfunction and cell apoptosis induced by I/R and increased phosphorylation of Akt and ERK1/2. The results indicated that ischemic postconditioning decreased apoptosis and improved renal function. This protective effect may be related with the levels of Akt and ERK1/2 activation. These findings may have major implications in the treatment of renal transplantation.