Limb remote ischemic postconditioning is effective but also time-course-limited in protecting the brain from I/R injury

Aim: To determine the effect of limb remote ischemic postconditioning (LIPoC) against cerebral ischemia reperfusionin rats and the relationship between cycle number or remote postconditioning episode duration and the protective function of LIPoC. Materials and methods: Transient focal ischemia/reperfusion was induced by 90 min of middle cerebral arteryocclusion (MCAO) with nylon monofilament and 22 h of reperfusion in male Sprague-Dawley rats. The animals underwent LIPoC consisting of 1, 2, or 3 cycles, with each occlusion or release lasting for 5 min (5/5), 10 min (10/10), or15 min (15/15) of bilateral femoral artery occlusion/release. Neurological score, infarct volume, water content, blood brain barrier permeability (BBB), neuronal analysis, immunohistochemical detection, and mitochondrial permeability transition pore opening were measured. Results: Infarct volume was significantly reduced in the groups with 2 cycles of 15/15, 3 cycles of 10/10, and 2 cycles of10/10. These 3 groups also had attenuated brain edema, BBB disruption, and apoptosis compared to both the MCAOand sham groups. Conclusion: This study affirmed the protective effect of LIPoC on cerebral reperfusion injury. Furthermore, it indicated that the accumulative time of limb occlusion/reperfusion might be crucial in remote postconditioning and that LIPoC exerted its maximum protective effect if the accumulative time of limb occlusion/reperfusion lasted from 40 to 60 min.