Sevoflurane preconditioning protects experimental ischemic stroke by enhancing anti-inflammatory microglia/macrophages phenotype polarization through GSK-3β/Nrf2 pathway

Aims: Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro-inflammatory state to anti-inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition. Methods: Mouse primary microglia with SPC were challenged by oxygen-glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro-inflammatory/anti-inflammatory factors were analyzed. GSK-3 beta phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro-inflammatory/anti-inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro-inflammatory/anti-inflammatory microglia/macrophages, and the generation of super-oxidants were examined after SPC or GSK-3 beta inhibitor TDZD treatment with or without Nrf2 deficiency. Results: Sevoflurane preconditioning promoted anti-inflammatory and inhibited pro-inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK-3 beta phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro-inflammatory microglia/macrophages markers expression, promoted anti-inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti-inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro-inflammatory positive cells and super-oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown. Conclusions: Our results indicated that SPC exerts brain ischemic tolerance and promotes anti-inflammatory microglia/macrophages polarization by GSK-3 beta-dependent Nrf2 activation, which provides a novel mechanism for SPC-induced neuroprotection.