Role of reactive oxygen species at reperfusion stage in isoflurane preconditioning-induced neuroprotection.

In this in vivo and in vitro study, we aimed to investigate whether isoflurane preconditioning-induced neuronal protection is mediated by reactive oxygen species (ROS) signaling at the reperfusion stage. In the in vivo study, Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) and in the in vitro study, rat pheochromocytoma (PC12) cells were subjected to oxygen glucose deprivation (OGD). Isoflurane preconditioning was carried out prior to MCAO or OGD and the ROS scavenger, N-2-mercaptopropiopylglycine (2-MPG), was administered at the start of reperfusion. Infarct volume, neurological severity score, and TUNEL staining were analyzed in the in vivo study and cell viability, Bcl-2/Bax ratio, cleaved caspase 3/caspase 3 ratio, and ROS fluorescence intensity were measured in the in vitro study. In the in vivo study, infarct volume, neurological severity score, and TUNEL-positive cell count were significantly decreased with preconditioning but were abrogated by administration of 2-MPG. In the in vitro study, cell viability and Bcl-2/Bax ratio were significantly increased with preconditioning, and cleaved caspase-3/caspase-3 ratio and ROS fluorescence intensity were significantly decreased. Administration of 2-MPG for 10 min abrogated this preconditioning effect, but it did not abolish the protection when administered for 60 min of reperfusion. Isoflurane preconditioning-induced protection was abolished by ROS scavengers at the start of reperfusion, indicating that ROS signaling can mediate the isoflurane preconditioning effect, which suggests that the time window can be important.