The Mechanism Study Of Sevoflurane Developmental Neurotoxicity In Mice-GSK3β Activation And Tau Protein Hyperphosphorylation

Objective In this study,we determined the effects of single or multiple sevoflurane anesthesia on cognition of young mice.At the same time,we also assessed the effects of sevoflurane anesthesia on Tau hyperphosphorylation and its up-stream mechanisms and down-stream consequences in young mice.Methods 1.P6 wild-type mice were singly or multiply exposed to sevoflurane.Immediately or 2 days after treatment,the hippocampus tissues of mice were harvested for detecting the Tau phosphorylation,total Tau protein,levels of the kinases[GSK3β、P-GSK3β(Ser9)、JNK1/2、P-JNK1/2、ERK1/2、P-ERK1/2、CDK5、P35、P25]and phosphatase related to Tau dephosphorylation(PP1)with Western-blot analysis.After growing up,the spatial cognition of mice were determined with Morris Water Maze test.2.P6 Tau knockout mice were multiply exposed to sevoflurane.Immediately after treatment,the hippocampus tissues of mice were harvested for detecting the levels of GSK3βand P-GSK3β(Ser9)with Western-blot analysis,and IL-6 with Western-blot analysis and ELISA study.After growing up,the cognition of mice were determined with Morris Water Maze test.3.For the intervention studies,lithium(100mg/kg)or same volume saline was intraperitoneally administrated to young mice 30 minutes before each sevoflurane anesthesia.Immediately after anesthesia,the hippocampus tissues of mice were harvested for detecting the levels of Tau phosphorylation,T-Tau,GSK3β,P-GSK3β(Ser9)with Western-blot analysis,and IL-6 with Western-blot analysis a nd ELISA study.After growing up,the cognition of mice were determined with Morris Water Maze test.Results 1.Multiply sevoflurane treatment induced cognition dysfunction in young mice.In place navigation test,multiple sevoflurane anesthesia increased the escape latency from P31 to P37 as compared to control.In spatial probe test,multiple sevoflurane anesthesia decreased the crossing times as compared to control.However,singly sevoflurane treatment had no significant effects in young mice.2.Western-blot analysis showed there was a significant increase in the levels of AT8(detected Tau-PS202 and Tau-PT205)in the hippocampus of young mice Immediately or 2 days after multiply sevoflurane treatment as compared to control,and T-Tau levels had no significant difference between two groups.However,singly sevoflurane treatment didn’t affect Tau phosphorylation and T-Tau levels.3.Phosphorylated P-GSK3β(Ser9)immunoblotting showed that there was a visible reduction in the levels of P-GSK3β,but not total GSK3βin the hippocampus of young mice immediately after multiply sevoflurane treatment as compared to control.Multiple sevoflurane anesthesia did not significantly alter the levels of CDK5,P25 and P35,the ratios of P-JNK/JNK and P-ERK/ERK.4.Multiply sevoflurane treatment didn’t alter the level of PP1 in the hippocampus of young mice.5.Immunoblotting showed that there was a visible reduction in the levels of P-GSK3β,but not total GSK3βin the hippocampus of Tau KO young mice immediately after multiply sevoflurane treatment as compared to control.Sevoflurane anesthesia did not induce an elevation of IL-6 levels in the hippocampus,or cognitive impairment after growing up in Tau KO young mice.6.Lithium attenuated multiple sevoflurane anesthesia-induced GSK3β activation,Tau hyperphosphorylation,elevated level of IL-6 and cognitive impairment in young WT mice.Conclusions Multiple sevoflurane anesthesia might induce hippcampus Tau hyperphosphorylation via activation of GSK3β,which then caused elevation of IL-6 levels,leading to cognitive impairment in young mice.GSK3β may be a target for preventing sevoflurane developmental neurotoxcity.