| Objectives:With the renewal of the concept of anesthesia and the advancement of anesthesia technology,anesthesia is not limited to providing good surgical conditions and ensuring the safety of patients during surgery.The topic of general anesthesia-induced neurotoxicity has attracted wide attention and discussion.Due to the adjustment of the birth policy,the number of pregnant women in China has increased sharply,and the proportion of maternal maternal age has increased,which in turn has caused increasing fetal dysplasia and teratogenicity significantly.Thanks to the rapid development of intrauterine treatment technology,some fetal diseases can be intervened and treated before birth,thus there are more and more cases of non-obstetric surgery and anesthesia during pregnancy.At present,various studies have found that nearly all types of general anesthetics have potential neurotoxic effects on the central nervous system of the developing brain.Therefore,it is urgent to take corresponding measures to reduce by anesthesia-induced the neurotoxicity effectively.Clinical studies have shown that routine exercise during pregnancy is beneficial to offspring brain development.A number of rodent experiments have also confirmed that maternal exercises such as treadmill training,swimming,and voluntary wheel exercise during pregnancy are beneficial to improve cognitive function of offspring.Such beneficial effects may involve multiple mechanisms: enhancing neurogenesis,enhancing the expression of neurotrophin,enhancing long-term potentiation,and enhancing antioxidant capacity.However,the effects and mechanisms of maternal exercise on the neurotoxicity of offspring induced by anesthesia during pregnancy are still unclear.Epigenetic modification refers to the heritable change of gene expression in the absence of changes in DNA sequence,and it is one of the ubiquitous gene regulation methods in the body.Epigenetic modification plays an important role in the field of neuroscience,especially in brain development and neurodegenerative diseases.During brain development,the genome is susceptible to external environment and drugs,resulting in epigenetic modifications(such as DNA methylation,histone modifications,and non-coding RNA)in the cerebral cortex and hippocampus,affecting the expression of learning and memory-related genes and interferring with synaptic plasticity and cognitive function.Histone acetylation is one of the important ways of histone modifications.It promotes the transcriptional expression of learning and memory-related genes through loosing internal structure of chromatin,thereby enhancing synaptic plasticity and learning and memory.Histone acetylation is catalyzed by histone acetyltransferases(HATs).HATs play a positive regulatory role in synaptic plasticity by promoting gene transcriptional expression.It has been found that p300 is involved in the regulation of learning and memory function.It has been confirmed that p300 plays a key role in hippocampal-dependent spatial learning and memory.Among the various histone acetylation sites,the acetylation levels of H3K9,H3K14 and H3K27 sites are closely related to synaptic plasticity and learning and memory.Among the various learning and memory related genes involved in the regulation of cognitive function,the transcription of the brain-derived neurotrophic factor(BDNF)gene has been confirmed to be regulated by histone acetylation in previous studies.The tyrosine protein kinase receptor B(Trk B)is a high-affinity receptor for BDNF,which promotes the development of neuronal dendritic spines by activating downstream protein kinase B(PKB/Akt).In summary,this study firstly clarifies the effects of mid-gestational single and multiple sevoflurane anesthesia on the brain development of offspring,and initially explores whether the possible mechanism of sevoflurane-induced neurotoxicity during brain development is associated with abnormal histone acetylation and BDNF down-regulation;Secondly,this study explores whether maternal exercise ameliorated the postnatal neurocognitive impairment by activating downstream BDNF/Trk B/Akt signaling;finally,this study explores the mechanisms of p300-mediated acetylation in the benifical effects of maternal exercise.Materials and methods: 1.SD rats were selected as experimental animals,and the rats were caged.The pregnant rats received a single 2-h 3% sevoflurane exposureat G14 or three 2-h 3% sevoflurane exposures at G13,G14 and G15.The expression of Ace-H3K9/14/27 and BDNF were detected by Western Blot at 6 h,24 h after anesthesia and postnatal day 0(P0).Behavioral tests(including the open field test,balance beam test,suspension test,and Morris water maze tests)were started at postnatal day 25(P25)in order to test the neurobehavioral changes of the offspring rats.After behavioral tests,Nissl staining and Golgi staining were used to observe the density of neurons and dendritic spine in hippocampal CA1 area,respectively.Western Blot was used to detect synaptic proteins PSD95 and GAP43.2.Second experiment choose maternal-fetal rat model exposed to multiple sevoflurane anesthesia.Pregnant rats were trained in treadmills throughout the pregnancy.Trk B receptor blocker ANA-12 was injected before the treadmill training.The remaining groups were injected with vehicle.The expression of Ace-H3K14/27 and BDNF were detected in P0 of the offspring rats.The spatial learning and memory function of the offspring rats was detected by Moris water maze tests at P28.After behavioral tests,the neuron density and dendritic spine density in hippocampal CA1 area were observed by Nissl staining and Golgi staining,respectively.Changes in synaptic protein PSD95 and GAP43 expression were detected by Western Blot.3.Third experiment choose maternal-fetal rat model exposed to multiple sevoflurane anesthesia.Pregnant rats were trained on the treadmill during the whole pregnancy.The p300 inhibitor,Garcinol,was injected before the treadmill training.The other groups were injected with vehicle.At P0,the expressions of p300,Ace-H3K14 and Ace-H3K27 in hippocampal CA1 neurons of offspring rats were detected by P300/Neu N,Ace-H3K14/Neu N and Ace-H3K27/Neu N immunofluorescence double staining,respectively.Western blot was used to detect the changes of p300,Ace-H3K14/27,BDNF/Trk B/Akt signaling pathways.Morris water maze tests were used to detect the spatial learning and memory function of the offspring rats at P28.After the behavioral tests,the neuron density and dendritic spine density in hippocampal CA1 area were observed by Nissl staining and Golgi staining,respectively.Changes in synaptic protein PSD95 and GAP43 expression were detected by Western Blot.Results: 1.Multiple,but not single,sevoflurane anesthesia in the second trimester of pregnant rats reduced Ace-H3K14/27 and BDNF expressions in the brain tissue or hippocampus of the offspring.The spatial learning and memory ability was impaired in the offspring rats.The density of neurons and the density of dendritic spines in the hippocampal CA1 area decreased.Synaptic protein expressions were downregulated.2.Maternal treadmill training could improve the expression of BDNF in hippocampus,activate Trk B/Akt signaling pathway,improve spatial learning and memory function,increase neuron density and dendritic spine density in hippocampal CA1 region,and increase synaptic protein expressions.The Trk B receptor blocker ANA-12 was injected before the maternal treadmill training,and ANA-12 blocked the neuroprotection of maternal exercise.3.Maternal treadmill training could improve the sevoflurane-induced reduction in hippocampal p300 and histone acetylation,activate BDNF/Trk B/Akt signaling pathway,improve spatial learning and memory function,increase neuron density and dendritic spine density in hippocampal CA1 region,and increase synapse protein expressions.The p300 inhibitor Garcinol was injected before the maternal treadmill training,and Garcinol blocked the neuroprotection of maternal exercise.Conclusions: 1.Multiple,but not single,sevoflurane anesthesia in pregnant rats in the second trimester could reduce the acetylation and BDNF expression in the offspring.The spatial learning and memory ability was impaired in the offspring rats,accompanied by neuronal loss and dendritic spine density decline in hippocampal CA1 area.2.Maternal exercise ameliorated sevoflurane-induced postnatal neurocognitive impairments by activating downstream BDNF/Trk B/Akt signaling.3.Maternal exercise ameliorated sevoflurane-induced postnatal neurocognitive impairments by promoting p300 expression,enhancing histone acetylation modification,and activating downstream BDNF/Trk B/Akt signaling pathway. |
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