Failure in neuroprotection of remote limb ischemic postconditioning in the hippocampus of a gerbil model of transient cerebral ischemia

Remote ischemic postconditioning (RIPoC) has been proven to provide potent protection of the heart and brain against ischemia-reperfusion injury. However, despite the evidence of cerebral protection with RIPoC is compelling, RIPoC-mediated neuroprotection against transient cerebral ischemic insult is still mired in controversy. In this study, we examined the effect of RIPoC induced by sublathal transient hind limb ischemia on neuronal death in the hippocampus following 5 min of transient cerebral ischemia in gerbils. Animals were randomly assigned to sham-, ischemia-, sham plus (+) RIPoC- and ischemia + RIPoC-groups. RIPoC was induced by three cycles of 5-min and 10-min occlusion-reperfusion of both femoral arteries at predetermined points in time (0, 1, 3, 6, 12 and 24 h after transient cerebral ischemia). CV staining, F-J B histofluorescence staining and NeuN immunohistochemistry were carried out to examine neuroprotection in the RIPoC-mediated hippocampus 5 days after ischemia-reperfusion. In the ischemia-group, we found a significant loss of pyramidal cells in the stratum pyramidale (SP) of the hippocampal CA1 region at 5 days post-ischemia compared with the sham-group. In all of the ischemia + RIPoC-groups, the loss of pyramidal cells in the CA1 region at 5 days post-ischemia was not different from that in the ischemia-group. Our present findings indicate that RIPoC does not prevent hippocampal CA1 pyramidal cells from neuronal death induced by transient cerebral ischemia.