The Role of SUMO-Conjugating Enzyme Ubc9 in the Neuroprotection of Isoflurane Preconditioning Against Ischemic Neuronal Injury.

Preconditioning with volatile anesthetics can create an ischemia tolerance against cerebral ischemia-reperfusion injury. We investigated whether ubiquitin conjugase 9 (Ubc9), the E2 conjugase for SUMOylation, is associated with neuroprotection induced by isoflurane preconditioning (IsoPC). In vitro, Ubc9 protein expression was evaluated at 4 and 24 h after reoxygenation. The role of Ubc9 in the neuroprotective effect was assessed in the presence or absence of Ubc9 small interfering RNA (siRNA). In vivo, rats were preconditionally exposed for 1 h to 2 % isoflurane for five consecutive days followed by middle cerebral artery occlusion. Neurobehavioral scores and infarction volume were determined at different times after reperfusion. The role of Ubc9 in ischemic tolerance was evaluated by intracerebroventricular microinjection with the Ubc9 siRNA. We showed that isoflurane preconditioning improved the cell viability of the SH-SY5Y cells that were challenged by oxygen-glucose deprivation. It also reduced brain infarct volumes and improved neurologic outcomes in the focal cerebral ischemic rat. The expression of Ubc9 was upregulated by isoflurane preconditioning. Knockdown of Ubc9 significantly attenuated the isoflurane preconditioning-induced neuroprotective effects. Isoflurane preconditioning-induced neuroprotection against ischemic injuries is mediated by Ubc9. These results suggest a novel mechanism for isoflurane preconditioning-induced tolerance to cerebral ischemia.