Tanshinone ?A Attenuates Sevoflurane Neurotoxicity In Neonatal Mice

[Objectives]Sevoflurane is the most widely used inhalational anesthetic in pediatric medicine.Despite this,sevoflurane has been reported to exert potentially neurotoxic effects on the developing brain.Clinical interventions and treatments for these effects are limited.Tanshinone ?A(Tan ?A),extracted from Salvia miltiorrhiza(Danshen),has been documented to alleviate cognitive decline in traditional applications.Therefore,we hypothesized that pre-administration of Tan ?A may attenuate sevoflurane-induced neurotoxicity.[Methods]1.To test this hypothesis,neonatal C57 mice(P6) were exposed to 3% sevoflurane for 2 hours with or without Tan ?A pre-treatment(dissolved in corn oil) for 3 consecutive days.Neonatal mice were randomly separated into 5 groups: Control;Sevoflurane;Sevoflurane+Tan ?A(10mg/kg);Sevoflurane+Tan ?A(20mg/kg)and Tan ?A(20 mg/kg).Open field and fear conditioning tests were performed to evaluate locomotor and cognitive function at P31 and P32.2.Neonatal mice were randomly separated into 4 groups: Control;Sevoflurane;Sevoflurane+Tan ?A(20mg/kg) and Tan ?A(20 mg/kg).Neuronal apoptosis was evaluated by TUNEL assay,immunohistochemistry and Western blotting.3.Levels of the neuroinflammatory factors IL-6 and IL-1? were analyzed by ELISA.4.Hippocampal synaptic ultrastructures were further assessed by electron microscopy.[Results]1.There were no significant differences in weight gain of P6-P8 mice and physiological status during anesthesia among groups.In the open field and cued(tone) test,no significant differences were observed among the five groups(p>0.05).However,in the contextual test,the percentage of freezing times were all decreased in the sevoflurane-treated groups(p<0.05).Interestingly,pre-administration with Tan ?A could ameliorate this neurocognitive deficits,as evidenced by increasing the freezing percentage in sevoflurane+Tan ?A(10mg/kg)group(18.52±1.76 vs.13.75±0.93,p=0.026) and the sevoflurane+Tan ?A(20mg/kg)group(32.63±1.67 vs.13.75±0.93,p<0.0001).2.Tan ?A administration also reduced the numbers of TUNEL-positive nuclei(4.41±0.54 vs.1.80±0.49,p<0.001) and cleaved caspase-3 expression.3.Moreover,it attenuated the relative release of neuroinflammatory mediators,IL-1? and IL-6(0.78±0.05 vs.1.52±0.06,p<0.001;1.24±0.06 vs.1.89±0.09,p<0.001).4.Finally,Tan ?A pre-treatment preserved synaptic ultrastructure by the measurement of postsynaptic density region(70.57±3.05 vs.27.92±3.43,p<0.001).[Conclusion]These results indicate that Tan ?A can alleviate sevoflurane-induced neurobehavioral abnormalities and may decrease neuroapoptosis and neuroinflammation.