Anesthetic sevoflurane reduces levels of hippocalcin and postsynaptic density protein 95

Translatome and transcriptome profiling of neonatal mice hippocampus exposed to sevoflurane anesthesia

Exposure to anesthesia in early life may cause severe damage to the brain and lead to cognitive impairment. The underlying mechanisms, which have only been investigated in a limited scale, remains largely elusive. We performed translatome and transcriptome sequencing together for the first time in hippocampus of neonatal mice that were exposed to sevoflurane. We treated a group of neonatal mice with 2.5 % sevoflurane for 2 h on day 6, 7, 8, 9 and treated another group on day 6, 7. We performed behavioral study after day 30 for both groups and the control to evaluate the cognitive impairment. On day 36, we collected translatome and transcriptome from the hippocampus in the two groups, compared the gene expression levels between the groups and the control, and validated the results with RT-qPCR. We identified 1750 differentially expressed genes (DEGs) from translatome comparison and 1109 DEGs from transcriptome comparison. As expected, translatome-based DEGs significantly overlapped with transcriptome-based DEGs, and functional enrichment analysis generated similar enriched cognition-related GO terms and KEGG pathways. However, for many genes like Hspa5, their alterations in translatome differed remarkably from those in transcriptome, and Western blot results were largely concordant with the former, suggesting that translational regulation plays a significant role in cellular response to sevoflurane. Our study revealed global alterations in translatome and transcriptome of mice hippocampus after neonatal exposure to sevoflurane anesthesia and highlighted the importance of translatome analysis in understanding the mechanisms responsible for anesthesia-induced cognitive impairment.

TMT-based quantitative proteomics analysis of neuroprotective effects of Forsythoside A on the MPTP-induced Parkinson's disease mouse model

Parkinson's disease (PD) is a prevalent neurodegenerative disorder characteristized by the presence of dyskinesia and the progressive loss of dopaminergic neurons. Although certain drugs can mitigate the symptoms of PD, they are unable to delay the disease progression, and their prolonged use may result in complications. Therefore, there exists an urgent necessity to identify potential agents that can effectively delay PD progression with fewer side effects. Recent research has unveiled that several traditional Chinese medicines (TCM) exhibit neuroprotective properties in various models pertinent to PD. Forsythoside A (FSA), the primary bioactive compound derived from TCM Lianqiao, has undergone extensive research in animal models of Alzheimer's disease and cerebral ischemia. However, the investigation into the impact of FSA on PD is limited in existing research. In this study, we aimed to evaluate the neuroprotective effects of FSA on MPTP-induced PD mouse model. FSA demonstrated significant improvements in the behavioral and neuropathological changes triggered by MPTP in mice. Furthermore, it exerted a suppressive effect on the activations of astrocyte and microglia. Meanwhile, Tandem mass tag (TMT)-based quantitative proteomics of striatal tissue and bioinformatics analysis were performed to elucidate the underlying mechanisms of FSA on PD mouse model. Proteomics demonstrated a total of 68 differentially expressed proteins (DEPs) were identified between HFSA and MPTP groups including 26 upregulated and 42 downregulated. Systematic bioinformatics analysis of the 68 DEPs illustrated that they were predominantly related to estrogen signaling pathway and calcium signaling pathway. The related DEPs (PLCβ4, Grm2, HPAC and Cox4i1) expression levels were verified by Western blot. FSA effectively restored the altered expression of the four DEPs induced by MPTP. Summarily, FSA exerted remarkable neuroprotective effects in MPTP-induced mice. Further, our research may provide proteomics insights that contribute to the further exploration of FSA as a potential treatment for PD.

Circular RNA DLGAP4 alleviates sevoflurane-induced neurotoxicity by regulating miR-9-5p/Sirt1/BDNF pathway

BACKGROUND

Sevoflurane is a widely used anesthetic in infants. However, long and repeated exposure to this drug can cause developmental neurotoxicity. This study aimed to investigate the role and mechanism of circular RNA DLGAP4 (circDLGAP4) in sevoflurane-induced neurotoxicity.

METHODS

Neonatal mice and mouse hippocampal neuronal cell line HT22 were used to construct sevoflurane-induced nerve injury models. The role of circDLGAP4 in sevoflurane-induced neurotoxicity was evaluated by gain-and/or loss-of-function methods. Pathological alterations in hippocampus were analyzed by hematoxylin-eosin and Tunel staining. Cell injury was assessed by cell viability and apoptosis, which was detected by CCK-8 and flow cytometry. The expression of circDLGAP4 and miR-9-5p was determined by real-time PCR. Sirt1 and BDNF levels were measured by Western blot. Productions of TNF-α and IL-6 were examined by ELISA. Dual-luciferase reporter assay and/or RNA pull-down assay were used to confirm the direct binding among circDLGAP4, miR-9-5p, and Sirt1. Rescue experiments were used to further verify the mechanism of circDLGAP4.

RESULTS

CircDLGAP4 expression was decreased by sevoflurane both in vivo and in vitro. Overexpression of circDLGAP4 elevated cell viability, reduced apoptosis and levels of TNF-α and IL-6, while circDLGAP4 knockdown showed the opposite effects in sevoflurane-induced HT22 cells. Mechanically, circDLGAP4 functioned via directly binding to and regulating miR-9-5p, followed by targeting the Sirt1/BDNF pathway. Additionally, circDLGAP4 upregulation relieved sevoflurane-induced nerve injury, reduced levels of TNF-α, IL-6 and miR-9-5p, but increased the expression of Sirt1 and BDNF in hippocampus.

CONCLUSIONS

Our studies found that circDLGAP4 relieved sevoflurane-induced neurotoxicity by sponging miR-9-5p to regulate Sirt1/BDNF pathway.

Ac-YVAD-cmk ameliorated sevoflurane-induced cognitive dysfunction and revised mitophagy impairment

It is common for elderly patients to develop postoperative cognitive dysfunction (POCD), but the pathophysiological mechanisms have not yet been fully explored. NLRP3 inflammasome activation and mitophagy impairment was involved in neurodegenerative disease. This study investigated the interaction of NLRP3 inflammasome and mitophagy in sevoflurane-induced cognitive dysfunction. We found that sevoflurane induced cleaved caspase-1 level, IL-1β and IL-18 maturation, and activated NLRP3 inflammasome in aged mice and the primary hippocampus neuron. The cleaved caspase-1 was demonstrated in microglia of hippocampus. Ac-YVAD-cmk, a selected caspase-1 inhibitor, reduced the expression of cleaved caspase-1, IL-1β, IL-18 and NLRP3 inflammasome activation induced by sevoflurane. Ac-YVAD-cmk ameliorated learning ability impairment in aged mice induced by sevoflurane using Morris water maze. Moreover, Ac-YVAD-cmk reversed the mitophagy flux dysfunction induced by sevoflurane in aged mice by western blotting, immunostaining and mt-Keima reporters. For the first time, we found caspase-1 inhibitor mitigated mitochondria dysfunction and revised mitophagy impairment induced by sevoflurane.

Sevoflurane-Induced Neurotoxicity in the Developing Hippocampus via HIPK2/AKT/mTOR Signaling

Sevoflurane (Sev) is a widely used inhalational anesthetic for general anesthesia in children. Previous studies have confirmed that multiple exposures to inhaled anesthetic can induce long-term neurotoxicity in newborn mice. However, the underlying mechanisms remain elusive. In this study, we investigated the role of homeodomain interacting protein kinase 2 (HIPK2), a stress activating kinase involved in neural survival and synaptic plasticity, and its underlying mechanism in sevoflurane-induced neurotoxicity. Empirical study showed that neuronal apoptosis was elevated after exposure to sevoflurane. Meanwhile, up-regulation of HIPK2 and AKT/mTOR signaling was observed in primary hippocampal neurons and hippocampus in mice upon anesthetic exposure. A64, antagonist of HIPK2, could significantly reduce increased apoptosis and activation of AKT/mTOR induced by sevoflurane. AKT antagonist MK2206 partially alleviated neuronal apoptosis without affecting the expression of HIPK2. Experimental results demonstrated a crucial role of HIPK2/AKT/mTOR signaling in neurotoxicity of sevoflurane. Thus, HIPK2/AKT/mTOR signaling can serve as a potential target for the protection of inhalation anesthesia-induced cytotoxicity in the future.

Sevoflurane Promotes Neurodegeneration Through Inflammasome Formation in APP/PS1 Mice

Sevoflurane (SEVO) is a highly fluorinated methyl isopropyl ether used as an inhalational anesthetic for general anesthesia. Previous studies have shown that SEVO may induce impaired memory and recognition ability and may be associated with neurodegenerative disease, e.g., Alzheimer’s disease (AD). However, the underlying mechanism remains unknown. Here, we used a mouse AD model, APP/PS1, to study the effects of SEVO on neurodegeneration occurring in AD. We found that SEVO exposure significantly impaired the spatial reference memory, sensorimotor, and cognitive function of the mice. Mechanistically, we found that SEVO induced formation of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome and its downstream caspase 1-mediated production of IL-1β and IL-18, which subsequently deactivated brain-derived neurotrophic factor (BDNF) to promote neurodegeneration. Together, these data suggest that NLRP3 inflammasome is essential for SEVO-induced AD.

Testosterone attenuates sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice

BACKGROUND

Sevoflurane anaesthesia induces phosphorylation of the microtubule-associated protein tau and cognitive impairment in neonatal, but not adult, mice. The underlying mechanisms remain largely to be determined. Sex hormones can be neuroprotective, but little is known about the influence of testosterone on age-dependent anaesthesia effects.

METHODS

Six- and 60-day-old male mice received anaesthesia with sevoflurane 3% for 2 h daily for 3 days. Morris water maze, immunoassay, immunoblotting, co-immunoprecipitation, nanobeam technology, and electrophysiology were used to assess cognition; testosterone concentrations; tau phosphorylation; glycogen synthase kinase-3β (GSK3β) activation; binding or interaction between tau and GSK3β; and neuronal activation in mice, cells, and neurones.

RESULTS

Compared with 60-day-old male mice, 6-day-old male mice had lower testosterone concentrations (3.03 [0.29] vs 0.44 [0.12] ng ml^-1; P<0.01), higher sevoflurane-induced tau phosphorylation in brain (133 [20]% vs 100 [6]% in 6-day-old mice, P<0.01; 103 [8]% vs 100 [13]% in 60-day-old mice, P=0.77), and sevoflurane-induced cognitive impairment. Testosterone treatment increased brain testosterone concentrations (1.76 [0.10] vs 0.39 [0.05] ng ml^-1; P<0.01) and attenuated the sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice. Testosterone inhibited the interaction between tau and GSK3β, and attenuated sevoflurane-induced inhibition of excitatory postsynaptic currents in hippocampal neurones.

CONCLUSIONS

Lower brain testosterone concentrations in neonatal compared with adult male mice contributed to age-dependent tau phosphorylation and cognitive impairment after sevoflurane anaesthesia. Testosterone might attenuate the sevoflurane-induced tau phosphorylation and cognitive impairment by inhibiting the interaction between tau and GSK3β.

Resveratrol ameliorates sevoflurane-induced cognitive impairment by activating the SIRT1/NF-κB pathway in neonatal mice

Sevoflurane, the most commonly used inhaled anesthetic in pediatric anesthesia, has been reported to induce cognitive impairment in developing brain in preclinical and clinical settings. However, the mechanism and therapeutic measures of this developmental neurotoxicity need to be further investigated. Resveratrol, a natural polyphenolic agent, has been reported to improve cognitive function in neurological disorders and aging models through anti-inflammatory activity. However, its effect on sevoflurane-induced cognitive impairment in developing mice remains unknown. The present study was designed to investigate the therapeutic potential of resveratrol on sevoflurane-induced cognitive impairment. Six-day-old mice received anesthesia with 3% sevoflurane 2 h daily on postnatal days (P) 6, P7 and P8. About 100 mg/kg resveratrol were intraperitoneally administered for 6 consecutive days to neonatal mice before anesthesia. Sevoflurane exposure significantly suppressed the expression of Sirtuin 1 (SIRT1) and activated microglia in hippocampi. Furthermore, the levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were markedly increased after sevoflurane exposure. Strikingly, resveratrol pretreatment ameliorated sevoflurane-induced SIRT1 inhibition and microglial activation. Of note, resveratrol reversed sevoflurane-induced imbalance of M1/M2 microglia ratio revealed by increasing mRNA level of clusters of differentiation 206 (CD206) and decreasing mRNA levels of clusters of differentiation 86 (CD86) and suppressor of cytokine signaling 3 (SOCS3). Consequently, sevoflurane-induced cognitive impairment in developing mice was ameliorated by resveratrol pretreatment. Taken together, repeated sevoflurane exposure to the developing brain resulted in SIRT1 inhibition, NF-κB acetylation, and microglial activation. Resveratrol pretreatment ameliorated cognitive impairment in developing mice received sevoflurane exposure by modulating SIRT1-NF-κB pathway in microglia. In this regard, our findings open novel directions to explore promising therapeutic targets for preventing the developmental neurotoxicity of sevoflurane.

Sevoflurane increases intracellular calcium to induce mitochondrial injury and neuroapoptosis

Sevoflurane is commonly used in clinical anesthesia. However, some reports indicated that Sevoflurane could induce mitochondrial injury and neuroapoptosis. Although the mechanism remains unclear, evidence points to the increase of intracellular calcium after administration of Sevoflurane. Herein, we sought whether the increment of intracellular Ca2+ caused by Sevoflurane administration could induce mitochondrial injury and apoptosis in primary neurons of the hippocampus. Fluo-4-acetoxymethyl ester Ca2+ probe was used for measuring intracellular Ca2+ concentrations. LDH assay, CCK-8 assay, and Western blotting were performed to confirm Sevoflurane-induced neuroapoptosis. ROS, mPTP, and ATP production were assayed to reveal mitochondrial injury. Our results indicated that Sevoflurane increased intracellular Ca2+ and neuronal death. Sevoflurane also elevated ROS and the opening of mPTP, and decreased ATP production in neurons. The expression of cytochrome c, cleaved caspase-9, cleaved caspase-3, and the ratio of Bax/Bcl-2 were also increased. By using calcium channel blocker Nimodipine, the increase of intracellular Ca2+ was attenuated, and the death rate of neurons, the ROS and opening of mPTP, decreased ATP production, the expressions of cytochrome c, cleaved caspase-9, cleaved caspase-3 and the ratio of Bax/Bcl-2 were alleviated. Our study suggested that Sevoflurane could increase intracellular Ca2+ to induce mitochondrial injury and mitochondria-mediated neuroapoptosis in neurons.

Brief inhalation of sevoflurane can reduce glial scar formation after hypoxic-ischemic brain injury in neonatal rats

Previous studies have demonstrated that sevoflurane postconditioning can provide neuroprotection after hypoxic-ischemic injury and improve learning and memory function in developing rodent brains. The classical Rice-Vannucci model was used to induce hypoxic-ischemic injury, and newborn (postnatal day 7) rats were treated with 2.4% sevoflurane for 30 minutes after hypoxic-ischemic injury. Our results showed that sevoflurane postconditioning significantly improved the learning and memory function of rats, decreased astrogliosis and glial scar formation, increased numbers of dendritic spines, and protected the histomorphology of the hippocampus. Mechanistically, sevoflurane postconditioning decreased expression of von Hippel-Lindau of hypoxia-inducible factor-1α and increased expression of DJ-1. Injection of 1.52 μg of the hypoxia-inducible factor-1α inhibitor YC-1 (Lificiguat) into the left lateral ventricle 30 minutes before hypoxic-ischemic injury reversed the neuroprotection induced by sevoflurane. This finding suggests that sevoflurane can effectively alleviate astrogliosis in the hippocampus and reduce learning and memory impairments caused by glial scar formation after hypoxic-ischemic injury. The underlying mechanism may be related to upregulated DJ-1 expression, reduced ubiquitination of hypoxia-inducible factor-1α, and stabilized hypoxia-inducible factor-1α expression. This study was approved by the Laboratory Animal Care Committee of China Medical University, China (approval No. 2016PS337K) on November 9, 2016.

Prenatal sevoflurane exposure: Effects of iron metabolic dysfunction on offspring cognition and potential mechanism

For decades, the neurotoxicity caused by anesthetics in mammalian brain development has gained increasing attention. Exposure to anesthetics leads to neurotoxicity and apoptosis of nerve cells, which in turn induces cognitive dysfunction. Although most of the data came from animal studies, general anesthetics have been shown to have adverse effects on cognitive function in infants and young children in recent years. This concern has led to a number of retrospective studies that observed an association between general anesthesia in pregnant women and neurobehavioral problems in fetuses or offspring. Every year, many pregnant women undergo non-obstetric anesthesia due to various reasons such as traffic accidents, fetal interventions, acute appendicitis, symptomatic cholelithiasis, and trauma. A matter of concern for these pregnant women is whether anesthesia has a detrimental effect on fetal brain development in the womb and whether the fetus has cognitive impairment after birth. In humans, the association of anesthetic exposure in infants with the long-term impairment of neurologic functions has been reported in several retrospective clinical studies. Recently, we have found that sevoflurane anesthesia during pregnancy in mice-induced cognitive impairment in the offspring by causing iron deficiency and inhibiting myelinogenesis. Sevoflurane is a commonly used general anesthetic in the hospitals, which can induce neurotoxicity and cause cognitive impairment in fetuses, infants, children, and adults. However, the exact mechanism of sevoflurane-induced damage to the central nervous system (CNS) is not fully understood. Based on our recent results, this paper reviewed the effects of sevoflurane on cognitive impairment and pathological changes such as neurogenesis, neuronal apoptosis, and iron metabolism dysfunction in the offspring.

The differential effects of isoflurane and sevoflurane on neonatal mice

Previous research has shown that exposure to volatile anesthetics can induce acute neuroinflammation and neuroapoptopsis in neonatal rodents and that these events can lead to cognitive dysfunction at later stages. Isoflurane and sevoflurane are two of the most popular anesthetics used in the field of pediatrics. However, the relative impact of these two anesthetics on the developing brain at distinct time points after the induction of anesthesia has not been compared. In the present study, we exposed 7-day-old mice to clinically equivalent doses of isoflurane (1.5%) and sevoflurane (2.5%) for 4 h and then investigated consequential changes in the brains of these mice at six different time points. We analyzed the levels of proteins that are directly related to neuroapoptosis, neuroinflammation, synaptic function, and memory, in the brains of neonatal mice. Exposure of neonatal mice to isoflurane and sevoflurane resulted in acute neuronal apoptosis. Our analysis observed significant levels of neuroinflammation and changes in the expression levels of proteins associated with both synaptic transmission and memory in mice from the isoflurane group but not the sevoflurane group. Our results therefore indicate that isoflurane and sevoflurane induce differential effects in the brains of neonatal mice.

Maternal sevoflurane exposure affects differentiation of hippocampal neural stem cells by regulating miR-410-3p and ATN1

BACKGROUND

Currently, numerous animal studies have shown that exposure to commonly used general anesthetics during pregnancy may cause neurocognitive impairment in the offspring. Reportedly, exposure to sevoflurane during mid-trimester of pregnancy can inhibit proliferation of neural stem cells (NSCs) and lead to early apoptosis. Whether exposure to sevoflurane during pregnancy affects the differentiation of NSCs remains unclear.

METHODS

In the present study, pregnant rats were exposed to 3% sevoflurane once for 2 h on gestational day 14 (G14) or 3 times for 2 h on G13, G14, and G15. Next, the differentiation of NSCs was measured using neuron marker β-tubulin III and astrocyte marker glial fibrillary acidic protein (GFAP) in fetal brain tissues 24 h and 72 h after anesthesia and in hippocampus on postnatal day 28. Primary cultured rat NSCs were exposed to 4.1% sevoflurane to explore the mechanism.

RESULTS

The results showed that during mid-trimester, multiple exposures to sevoflurane can cause premature differentiation of NSCs in developing brains of offspring and lead to long-term neuron reduction and astrocyte proliferation in hippocampus. The data from the present study indicated that repeated exposure to sevoflurane downregulated atrophin-1 (ATN1) expression and caused early differentiation of NSCs. Overexpression of ATN1 via lentivirus transfection attenuated the influence of sevoflurane. Using dual luciferase assay, ATN1 was found to be a target gene of microRNA-410-3p (miR-410-3p). MiR-410-3p suppression via lentivirus transfection recovered the ATN1 expression and differentiation of NSCs.

CONCLUSIONS

The results from the present study demonstrated that repeated exposure to sevoflurane leads to early differentiation of NSCs and long-term effects via the miR-410-3p/ATN1 pathway.

Interaction of Tau, IL-6 and mitochondria on synapse and cognition following sevoflurane anesthesia in young mice

Tau phosphorylation is associated with cognitive impairment in young mice. However, the underlying mechanism and targeted interventions remain mostly unknown. We set out to determine the potential interactions of Tau, interleukin 6 (IL-6) and mitochondria following treatment of anesthetic sevoflurane and to assess their influences on synapse number and cognition in young mice. Sevoflurane (3% for 2 ​h) was given to wild-type, Tau knockout, IL-6 knockout, and cyclophilin D (CypD) knockout mice on postnatal (P) day 6, 7 and 8. We measured amounts of phosphorylated Tau, IL-6, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), ATP, postsynaptic density 95 (PSD-95), synaptophysin, N-cadherin, synapse number, and cognitive function in the mice, employing Western blot, electron microscope and Morris water maze among others. Here we showed that sevoflurane increased Tau phosphorylation and caused IL-6 elevation, mitochondrial dysfunction, synaptic loss and cognitive impairment in young wild-type, but not Tau knockout, mice. In young IL-6 knockout mice, sevoflurane increased Tau phosphorylation but did not cause mitochondrial dysfunction, synaptic loss or cognitive impairment. Finally, sevoflurane increased Tau phosphorylation and IL-6 amount, but did not induce synaptic loss and cognitive impairment, in young CypD knockout mice or WT mice pretreated with idebenone, an analog of co-enzyme Q10. In conclusion, sevoflurane increased Tau phosphorylation, which caused IL-6 elevation, leading to mitochondrial dysfunction in young mice. Such interactions caused synaptic loss and cognitive impairment in the mice. Idebenone mitigated sevoflurane-induced cognitive impairment in young mice. These studies would promote more research to study Tau in young mice.

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Research in context.•

Evidence before this studya.

Tau, a microtubule-associated protein that is predominantly expressed inside neurons, is associated with microtubule assembly and function. Tau phosphorylation, aggregation and spread all serve as the pathogenesis of age-dependent neurodegeneration in the old brain, as well as the neuropathogenesis of Alzheimer’s disease. However, the effects of Tau on the cellular changes and the function of the young brain are undetermined. Our previous studies showed that anesthetic sevoflurane induced Tau phosphorylation, IL-6 elevation, mitochondrial dysfunction and synaptic loss in brain tissues of neonatal mice, as well as cognitive impairment in the mice. However, the potential interactions of the Tau phosphorylation, IL-6 elevation and mitochondrial dysfunction and the influences of these interactions on synapse number and cognitive function in neonatal mice remains largely unknown.

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Added value of studyb.

Employing sevoflurane as a clinically relevant tool, and using the approaches including wild-type, Tau, IL-6, and CypD knockout neonatal mice, the present studies showed that Tau phosphorylation caused IL-6 elevation, which induced mitochondrial dysfunction, leading to synaptic loss and cognitive impairment in the neonatal mice. Idebenone, a synthetic analog of coenzyme Q10, mitigated the sevoflurane-induced cognitive impairment in the neonatal mice.

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Implications of all the available evidencec.

These findings demonstrated the role of Tau phosphorylation in cognitive impairment in neonatal mice, revealed the effects of the interactions of Tau phosphorylation, IL-6 elevation and mitochondrial dysfunction on the synapse number and cognitive function in the mice, and identified potential targeted intervention of the cognitive impairment in the neonatal mice.

Resveratrol Mitigates Sevoflurane-Induced Neurotoxicity by the SIRT1-Dependent Regulation of BDNF Expression in Developing Mice

Various lines of evidence suggest that neonatal exposure to general anesthetics, especially repeatedly, results in neuropathological brain changes and long-term cognitive impairment. Although progress has been made in experimental models, the exact mechanism of GA-induced neurotoxicity in the developing brain remains to be clarified. Sirtuin 1 (SIRT1) plays an important role in synaptic plasticity and cognitive performance, and its abnormal reduction is associated with cognitive dysfunction in neurodegenerative diseases. However, the role of SIRT1 in GA-induced neurotoxicity is unclear to date. In this study, we found that the protein level of SIRT1 was inhibited in the hippocampi of developing mice exposed to sevoflurane. Furthermore, the SIRT1 inhibition in hippocampi was associated with brain-derived neurotrophic factor (BDNF) downregulation modulated by methyl-cytosine-phosphate-guanine–binding protein 2 (MeCP2) and cAMP response element-binding protein (CREB). Pretreatment of neonatal mice with resveratrol nearly reversed the reduction in hippocampal SIRT1 expression, which increased the expression of BDNF in developing mice exposed to sevoflurane. Moreover, changes in the levels of CREB and MeCP2, which were considered to interact with BDNF promoter IV, were also rescued by resveratrol. Furthermore, resveratrol improved the cognitive performance in the Morris water maze test of the adult mice with exposure to sevoflurane in the neonatal stage, without changing motor function in the open field test. Taken together, our findings suggested that SIRT1 deficiency regulated BDNF signaling via regulation of the epigenetic activity of MeCP2 and CREB, and resveratrol might be a promising agent for mitigating sevoflurane-induced neurotoxicity in developing mice.

Cyclophilin D Contributes to Anesthesia Neurotoxicity in the Developing Brain

Anesthetic sevoflurane induces mitochondrial dysfunction, impairment of neurogenesis, and cognitive impairment in young mice, but the underlying mechanism remains to be determined. Cyclophilin D (CypD) is a modulatory factor for the mitochondrial permeability transition pore (mPTP). We, therefore, set out to evaluate the role of CypD in these sevoflurane-induced changes in vitro and in young mice. Wild-type (WT) and CypD knockout (KO) young (postnatal day 6, 7, and 8) mice received 3% sevoflurane 2 h daily and the neural progenitor cells (NPCs) harvested from the WT or CypD KO mice received 4.1% sevoflurane. We used immunohistochemistry and immunocytochemistry imaging, flow cytometry, Western blot, RT-PCR, co-immunoprecipitation, and Morris Water Maze to assess the interaction of sevoflurane and CypD on mitochondria function, neurogenesis, and cognition in vitro and in WT or CypD KO mice. We demonstrated that the sevoflurane anesthesia induced accumulation of CypD, mitochondrial dysfunction, impairment of neurogenesis, and cognitive impairment in WT mice or NPCs harvested from WT mice, but not in CypD KO mice or NPCs harvested from CypD KO mice. Furthermore, the sevoflurane anesthesia reduced the binding of CypD with Adenine nucleotide translocator, the other component of mPTP. These data suggest that the sevoflurane anesthesia might induce a CypD-dependent mitochondria dysfunction, impairment of neurogenesis, and cognitive impairment in young mice and NPCs.

Sevoflurane plays a reduced role in cognitive impairment compared with isoflurane: limited effect on fear memory retention

Isoflurane and sevoflurane are both inhalation anesthetics, but in clinical application, sevoflurane has been considered to be less suitable for long-term anesthesia because of its catabolic compounds and potential nephrotoxicity. Nevertheless, recent studies have shown that these two inhalation anesthetics are similar in hepatorenal toxicity, cost, and long-term anesthetic effect. Moreover, sevoflurane possibly has less cognitive impact on young mice. In this study, C57BL/6 mice aged 8–10 weeks were exposed to 1.2% isoflurane or 2.4% sevoflurane for 6 hours. Cognitive function and memory were examined in young mice using the novel object recognition, contextual fear conditioning, and cued-fear extinction tests. Western blot assay was performed to detect expression levels of D1 dopamine receptor, catechol-O-methyltransferase, phospho-glycogen synthase kinase-3β, and total glycogen synthase kinase-3β in the hippocampus. Our results show that impaired performance was not detected in mice exposed to sevoflurane during the novel object recognition test. Contextual memory impairment in the fear conditioning test was shorter in the sevoflurane group than the isoflurane group. Long-term sevoflurane exposure did not affect memory consolidation, while isoflurane led to memory consolidation and reduced retention. Downregulation of hippocampal D1 dopamine receptors and phosphorylated glycogen synthase kinase-3β/total glycogen synthase kinase-3β and upregulation of catechol-O-methyltransferase may be associated with differing memory performance after exposure to isoflurane or sevoflurane. These results confirm that sevoflurane has less effect on cognitive impairment than isoflurane, which may be related to expression of D1 dopamine receptors and catechol-O-methyltransferase and phosphorylation of glycogen synthase kinase-3β in the hippocampus. This study was approved by the Institutional Animal Care and Use Committee, Nanjing University, China on November 20, 2017 (approval No. 20171102).

Hemin treatment protects neonatal rats from sevoflurane-induced neurotoxicity via the phosphoinositide 3-kinase/Akt pathway

AIMS

Anaesthesia-related neurotoxicity in the developing brain is a controversial issue that has recently attracted much attention. Hemin plays a protective role in hypoxic and ischemic brain damage; however, its effects on sevoflurane-induced neurotoxicity remain unclear. Our aim was to investigate the mechanisms of sevoflurane neurotoxicity and potential neuroprotective roles of hemin upon sevoflurane exposure.

MAIN METHODS

Hippocampi were harvested 18 h after sevoflurane exposure. Haem oxygenase 1 (HMOX1), superoxide dismutase 2 (SOD2), discs large MAGUK scaffold protein 4 (DLG4), phosphorylated Akt, Akt, cleaved caspase 3, and neuroglobin were detected by western blotting. A water maze test was used to assess learning and memory ability in P30 rats.

KEY FINDINGS

Sevoflurane inhalation increased cleaved caspase 3 levels. Hemin treatment enhanced the antioxidant defence response, protecting rats from oxidative stress injury. Hemin plays its neuroprotective role via phosphoinositide 3-kinase (PI3K)/Akt signalling. A single inhalation of sevoflurane did not affect DLG4 expression, while hemin treatment did. Platform crossing increased in rats treated with hemin as well, which may be related to increased DLG4. Neuroglobin expression was not affected, suggesting that it may act upstream of PI3K/Akt signalling.

SIGNIFICANCE

Our study demonstrates that hemin plays a protective role in anaesthesia-induced neurotoxicity by both inhibiting apoptosis via the PI3K/Akt pathway and increasing the expression of antioxidant enzymes, reducing oxidative damage. The results provide mechanistic insight into the effects of sevoflurane anaesthesia on the developing brain and suggest that hemin could help avoid these effects.

Elamipretide (SS-31) improves mitochondrial dysfunction, synaptic and memory impairment induced by lipopolysaccharide in mice

Background

It is widely accepted that mitochondria have a direct impact on neuronal function and survival. Oxidative stress caused by mitochondrial abnormalities play an important role in the pathophysiology of lipopolysaccharide (LPS)-induced memory impairment. Elamipretide (SS-31) is a novel mitochondrion-targeted antioxidant. However, the impact of elamipretide on the cognitive sequelae of inflammatory and oxidative stress is unknown.

Methods

We utilized MWM and contextual fear conditioning test to assess hippocampus-related learning and memory performance. Molecular biology techniques and ELISA were used to examine mitochondrial function, oxidative stress, and the inflammatory response. TUNEL and Golgi-staining was used to detect neural cell apoptosis and the density of dendritic spines in the mouse hippocampus.

Results

Mice treated with LPS exhibited mitochondrial dysfunction, oxidative stress, an inflammatory response, neural cell apoptosis, and loss of dendritic spines in the hippocampus, leading to impaired hippocampus-related learning and memory performance in the MWM and contextual fear conditioning test. Treatment with elamipretide significantly ameliorated LPS-induced learning and memory impairment during behavioral tests. Notably, elamipretide not only provided protective effects against mitochondrial dysfunction and oxidative stress but also facilitated the regulation of brain-derived neurotrophic factor (BDNF) signaling, including the reversal of important synaptic-signaling proteins and increased synaptic structural complexity.

Conclusion

These findings indicate that LPS-induced memory impairment can be attenuated by the mitochondrion-targeted antioxidant elamipretide. Consequently, elamipretide may have a therapeutic potential in preventing damage from the oxidative stress and neuroinflammation that contribute to perioperative neurocognitive disorders (PND), which makes mitochondria a potential target for treatment strategies for PND.

Sevoflurane Impairs Short-Term Memory by Affecting PSD-95 and AMPA Receptor in the Hippocampus of a Mouse Model

Objective

To explore the effects of sevoflurane on the latency and error times of the passive avoidance and levels of PSD-95 and AMPA receptors in the hippocampus. We evaluated the effects of sevoflurane on short-term memory in adult mice and explored the possible mechanism.

Methods

144 Kunming mice (2-3 months, 30-35 g) were randomly divided into two groups A (n = 64) and B (n = 80) and received the dark-avoidance (DA) and step-down avoidance (SA) tests, respectively. The groups DA and SA were further divided into control (inhaled 40% O₂ 2 h) and sevoflurane (3.3% sevoflurane and 40% O₂ 2 h) subgroups. Before inhalation intervention, all mice were trained to be familiar with the Morris water maze (MWM). According to the test points of behavioral indicators, 8 mice were randomly selected from each subgroup at point 12 h (T1), 24 h (T2), 48 h (T3), and 72 h (T4) after inhalation intervention. The step-through latency and error times were measured in 5 min. After the behavioral test, the mice were killed and the tissues of the hippocampus were taken for hematoxylin and eosin (H&E) staining. The expression level of PSD-95 and AMPA receptors in the hippocampus was detected by immunohistochemistry and Western Blot. The changes of synaptic transmission were measured via electrophysiology analysis of hippocampal slices.

Results

The mice in the control subgroups found the platform in a shorter pathway than those in the sevoflurane subgroups during an MWM test. The step-through latency of T1 and T2 in the sevoflurane subgroup was shorter than baseline time, and the error times were increased in 5 min and higher than baseline time when compared with the control subgroup (P < 0.05) in the A and B groups. Compared with the control subgroup, the expression level of PSD-95 and AMPA receptors in the hippocampus was decreased at T1 and T2 in the sevoflurane subgroup (P < 0.05). The nerve cells were partially swelling. Electrophysiology analysis showed that the levels of PSD-95 and AMPA receptor expression were associated with synaptic transmission.

Conclusion

Sevoflurane impaired short-term memory in adult mice by inhibiting the expression of PSD-95 and AMPA receptors in the hippocampus, which led to the decrease in synaptic transmission.

Sevoflurane induces cognitive impairment in young mice via autophagy

Background

Anesthesia may induce neurotoxicity and neurocognitive impairment in young mice. However, the underlying mechanism remains largely to be determined. Meanwhile, autophagy is involved in brain development and contributes to neurodegenerative diseases. We, therefore, set out to determine the effects of sevoflurane on autophagy in the hippocampus of young mice and on cognitive function in the mice.

Methods

Six day-old mice received 3% sevoflurane, for two hours daily, on postnatal days (P) 6, 7 and 8. We then decapitated the mice and harvested the hippocampus of the young mice at P8. The level of LC3, the ratio of LC3-II to LC3-I, and SQSTM1/p62 level associated with the autophagy in the hippocampus of the mice were assessed by using Western blotting. We used different groups of mice for behavioral testing via the Morris Water Maze from P31 to P37.

Results

The anesthetic sevoflurane increased the level of LC3-II and ratio of LC3-II/LC3-I, decreased the p62 level in the hippocampus of the young mice, and induced cognitive impairment in the mice. 3-Methyladenine, the inhibitor of autophagy, attenuated the activation of autophagy and ameliorated the cognitive impairment induced by sevoflurane in the young mice.

Conclusion

These data showed that sevoflurane anesthesia might induce cognitive impairment in the young mice via activation of autophagy in the hippocampus of the young mice. These findings from the proof of concept studies have established a system and suggest the role of autophagy in anesthesia neurotoxicity and cognitive impairment in the young mice, pending further investigation.

Protective effects of TRPV1 inhibition against sevoflurane-induced cell death

Sevoflurane is a widely used inhalational anesthetic that can induce developmental neurotoxicity, leading to cognitive dysfunction. In this study, we assessed the role of transient receptor potential vanilloid 1 (TRPV1) in mediating sevoflurane activation and whether the TRPV1 antagonist could prevent anesthesia-induced cell death. Here, we demonstrated that the expression of TRPV1 was increased after sevoflurane treatment, and pretreatment with TRPV1 antagonist SB366791 could attenuate the effect of sevoflurane on TRPV1 expression. Moreover, the inhibition of TRPV1 could prevent sevoflurane-induced cell death. The findings of this study provide novel insights into the treatment of general anesthesia-induced developmental neurotoxicity and even cognitive impairment.

Disrupted folate metabolism with anesthesia leads to myelination deficits mediated by epigenetic regulation of ERMN

Background

Exposure to anesthetics during early life may impair cognitive functions. However, the underlying mechanisms remain largely unknown. We set out to determine effects of sevoflurane anesthesia on folate metabolism and myelination in young non-human primates, mice and children.

Methods

Young rhesus macaque and mice received 2.5 to 3% sevoflurane daily for three days. DNA and RNA sequencing and immunohistochemistry among others were used in the studies. We performed unbiased transcriptome profiling in prefrontal cortex of rhesus macaques and mice after the sevoflurane anesthesia. We constructed a brain blood barrier-crossing AAV-PHP.EB vector to harbor ERMN expression in rescue studies. We measured blood folate levels in children after anesthesia and surgery.

Findings

We found that thymidylate synthase (TYMS) gene was downregulated after the sevoflurane anesthesia in both rhesus macaque and mice. There was a reduction in blood folate levels in children after the anesthesia and surgery. Combined with transcriptome and genome-wide DNA methylation analysis, we identified that ERMN was the primary target of the disrupted folate metabolism. Myelination was compromised by the anesthesia in the young mice, which was rescued by systematic administration of folic acid or expression of ERMN in the brain through brain-specific delivery of the adeno-associated virus. Moreover, folic acid and expression of ERMN alleviated the cognitive impairment caused by the sevoflurane anesthesia in the mice.

Interpretation

General anesthesia leads to disrupted folate metabolism and subsequently defects in myelination in the developmental brain, and ERMN is the important target affected by the anesthesia via epigenetic mechanisms.

Effects of compound 21, a non‑peptide angiotensin II type 2 receptor agonist, on general anesthesia‑induced cerebral injury in neonatal rats

General anesthesia has a great impact on neurodevelopment. However, the mechanisms underlying this effect and therapeutic methods to address it remain limited. The present study aimed to investigate the effects of compound (C)21, a non-peptide angiotensin II type 2 receptor agonist, on general anesthesia-induced cerebral injury in neonatal rats. Neonatal Sprague Dawley rats (postnatal day 7) were randomly divided into three groups (n=6 per group): The control, isoflurane and C21+ isoflurane (C21) group. General anesthesia was induced through inhalation of 1.3% isoflurane. Apoptosis and synaptic structure were analyzed. The levels of peroxisome proliferator-activated receptor (PPAR)-α were detected using an enzyme-linked immunosorbent assay. BCL2, apoptosis regulator (Bcl-2) expression was also measured. Compared with the control group, the cerebral cortex, hippocampus, amygdala and hypothalamus in the isoflurane group had significantly more apoptotic cells (P<0.05). The nuclei of the control group were round and transparent, while shrunken nuclei and condensed chromatin were visible in the isoflurane group. A reduction in synapse number was observed in the isoflurane group compared with the control. By contrast, nuclei shrinkage and the decrease in synaptic number was improved in the C21 group. PPAR-α and Bcl-2 expression, at the mRNA and protein levels, was significantly reduced in the isoflurane group compared with the control (P<0.05). C21 treatment reduced the decrease in PPAR-α and Bcl-2 in the cerebral cortex, hippocampus, amygdala and hypothalamus (P<0.05). Collectively, it was demonstrated that C21 prevented apoptosis and synaptic loss induced by general anesthesia in neonatal rats by enhancing the expression of PPAR-α and Bcl-2.

Effects of Sevoflurane Exposure During Mid-Pregnancy on Learning and Memory in Offspring Rats: Beneficial Effects of Maternal Exercise

Fetal exposure to general anesthetics may pose significant neurocognitive risks but methods to mitigate against these detrimental effects are still to be determined. We set out, therefore, to assess whether single or repeated in utero exposure to sevoflurane triggers long-term cognitive impairments in rat offspring. Since maternal exercise during pregnancy has been shown to improve cognition in offspring, we hypothesized that maternal treadmill exercise during pregnancy would protect against sevoflurane-induced neurotoxicity. In the first experiment, pregnant rats were exposed to 3% sevoflurane for 2 h on gestational (G) day 14, or to sequential exposure for 2 h on G13, G14 and G15. In the second experiment, pregnant rats in the exercise group were forced to run on a treadmill for 60 min/day during the whole pregnancy. The TrkB antagonist ANA-12 was used to investigate whether the brain-derived neurotrophic factor (BDNF)/TrkB/Akt signaling pathway is involved in the neuroprotection afforded by maternal exercise. Our data suggest that repeated, but not single, exposure to sevoflurane caused a reduction in both histone acetylation and BDNF expression in fetal brain tissues and postnatal hippocampus. This was accompanied by decreased numbers of dendritic spines, impaired spatial-dependent learning and memory dysfunction. These effects were mitigated by maternal exercise but the TrkB antagonist ANA-12 abolished the beneficial effects of maternal exercise. Our findings suggest that repeated, but not single, exposure to sevoflurane in pregnant rats during the second trimester caused long-lasting learning and memory dysfunction in the offspring. Maternal exercise ameliorated the postnatal neurocognitive impairment by enhancing histone acetylation and activating downstream BDNF/TrkB/Akt signaling.

[Application of sevoflurane and laryngeal mask in cesarean section in women with heart disease]

OBJECTIVE

To compare the safety of sevoflurane anesthesia with laryngeal mask and tracheal intubation in cesarean section in women with heart disease.

METHODS

Fifty-two pregnant women with heart diseases undergoing cesarean section were randomized into laryngeal mask (LAM) group and tracheal intubation group. In LAM group, 6% sevoflurane was given at the rate of 6 L/min for induction with a maintenance sevoflurane concentration of 3%. In the intubation group, 1.5 mg/kg propofol and 1 µg/kg remifentanil were injected intravenously, and after achieving D0 with Narcotrend monitoring, 0.9 mg/kg rocuronium was injected and intubation was performed 1 min later. The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were recorded in the two groups before anesthesia induction (T₀), at intubation or laryngeal mask placement (T₁), skin incision (T₂), and extubation or laryngeal mask removal (T₃). The surgery to fetal birth time, uterine incision to fetal childbirth time, drug discontinuation to awake time, and newborn Apgar scores were also recorded. Sevoflurane consumption and maternal comfort during hospitalization were compared between the two groups.

RESULTS

In LAM group, HR and MBP at T₁ and T₃ were significantly lower than those in the intubation group (P<0.05). The drug discontinuation to extubation time and to awaken time were significantly shorter in LAM group than in the intubation group (P<0.05), but the operation time and fetal child birth time were comparable between the two groups (P>0.05). The women in LAM group reported better physical and psychological comforts than those in the intubation group (P<0.05). The neonatal Apgar scores and the scores of health education, satisfaction with hospital environment and service were all similar between the two groups (P>0.05).

CONCLUSION

Sevoflurane anesthesia with laryngeal mask can achieve satisfactory anesthetic effects in cesarean section in women with heart disease.

Sevoflurane Acts on Ubiquitination-Proteasome Pathway to Reduce Postsynaptic Density 95 Protein Levels in Young Mice

BACKGROUND

Children with multiple exposures to anesthesia and surgery may have an increased risk of developing cognitive impairment. Sevoflurane, a commonly used anesthetic in children, has been reported to decrease levels of postsynaptic density 95 protein. However, the upstream mechanisms and downstream consequences of the sevoflurane-induced reduction in postsynaptic density 95 protein levels remains largely unknown. We therefore set out to assess whether sevoflurane acts on ubiquitination-proteasome pathway to facilitate postsynaptic density 95 protein degradation.

METHODS

Six-day-old wild-type mice received anesthesia with 3% sevoflurane 2 h daily for 3 days starting on postnatal day 6. We determined the effects of the sevoflurane anesthesia on mRNA, protein and ubiquitinated levels of postsynaptic density 95 protein in neurons, and synaptosomes and hippocampus of young mice. Cognitive function in the mice was determined at postnatal day 31 by using a Morris water maze. Proteasome inhibitor MG132 and E3 ligase mouse double mutant 2 homolog inhibitor Nutlin-3 were used for the interaction studies.

RESULTS

The sevoflurane anesthesia decreased protein, but not mRNA, levels of postsynaptic density 95, and reduced ubiquitinated postsynaptic density 95 protein levels in neurons, synaptosomes, and hippocampus of young mice. Both MG132 and Nutlin-3 blocked these sevoflurane-induced effects. Sevoflurane promoted the interaction of mouse double mutant 2 homolog and postsynaptic density 95 protein in neurons. Finally, MG132 and Nutlin-3 ameliorated the sevoflurane-induced cognitive impairment in the mice.

CONCLUSIONS

These data suggest that sevoflurane acts on the ubiquitination-proteasome pathway to facilitate postsynaptic density 95 protein degradation, which then decreases postsynaptic density 95 protein levels, leading to cognitive impairment in young mice. These studies would further promote the mechanistic investigation of anesthesia neurotoxicity in the developing brain.

Anesthetic Isoflurane or Desflurane Plus Surgery Differently Affects Cognitive Function in Alzheimer's Disease Transgenic Mice

Anesthesia/surgery could be associated with cognitive impairment and Alzheimer's disease neuropathogenesis. However, whether surgery under different anesthetics has different effects on cognitive function remains largely unknown. We therefore set out to compare effects of anesthetic isoflurane or desflurane plus surgery on cognitive function and hippocampus levels of synaptic marker (postsynaptic density-95 and synaptophysin) and ATP. Five-month-old AD Transgenic (Tg) (FAD5X) and wild-type male mice received isoflurane or desflurane plus abdominal surgery. We assessed cognitive function in Barnes maze and measured hippocampus levels of postsynaptic density-95, synaptophysin, and ATP in the mice. We determined whether vitamin K₂ could mitigate these anesthesia/surgery-induced changes. Isoflurane, but not desflurane, plus surgery increased escape latency and escape distance in Barnes maze probe test and reduced postsynaptic density-95, synaptophysin, and ATP levels as compared to control condition in AD Tg mice. Vitamin K₂ attenuated the anesthesia/surgery-induced changes in the AD Tg mice. These findings suggest that isoflurane, but not desflurane, plus surgery might induce cognitive impairment via causing brain energy deficits. Pending confirmative studies in both animals and humans suggest desflurane could be a better choice for AD patients when surgery is needed. Moreover, vitamin K₂ could treat cognitive deficiency associated with anesthesia and surgery.

Voluntary exercise rescues sevoflurane-induced memory impairment in aged male mice

Postoperative cognitive impairment is especially common in older patients following major surgery. Although exposure to sevoflurane is known to cause memory deficits, few studies have examined the putative approaches to reduce such impairments. This study tested the hypotheses that sevoflurane exposure can decrease NR2B subunit-containing NMDA receptor activity in hippocampus of aged mice, and voluntary exercise may counteract the declining hippocampal functions. We found that long exposure (3 h/day for 3 days), but not short exposure (1 h/day for 3 days), to 3 % sevoflurane produced a long-lasting spatial memory deficits up to 3 weeks in aged mice, and such an effect was not due to the neuronal loss in the hippocampus, but was correlated with a long-term decrease in Fyn kinase expression and NR2B subunit phosphorylation in the hippocampus. Furthermore, voluntary exercise rescued sevoflurane-induced spatial memory deficits in aged mice and restored Fyn kinase expression and NR2B subunit phosphorylation in the hippocampus to a level comparable to control animals. Generally, our results suggested that Fyn-mediated NR2B subunit phosphorylation may play a critical role in sevoflurane-induced impairment in cognitive functions in aged animals, and voluntary exercise might be an important non-pharmacological approach to treatment of inhaled anesthetics-induced postoperative cognitive impairment in clinical settings.

Docosahexaenoic Acid Rescues Synaptogenesis Impairment and Long-Term Memory Deficits Caused by Postnatal Multiple Sevoflurane Exposures

Sevoflurane exposures were demonstrated to induce neurotoxicity in the developing brain in both human and animal studies. However, there is no effective approach to reverse it. The present study aimed to evaluate the feasibility of utilizing docosahexaenoic acid (DHA) to prevent sevoflurane-induced neurotoxicity. P6 (postnatal 6 days) mice were administrated DHA after exposure to 3% sevoflurane for two hours daily in three consecutive days. Molecular expressions of synaptic makers (PSD95, synaptophysin) and synaptic morphological changes were investigated by Western blot analysis and transmission electron microscopy, respectively. Meanwhile, Morris water maze test was used to assess spatial memory of mice at P31 (postnatal 31 days). DHA restored sevoflurane-induced decreased level of PSD95 and synaptophysin expressions and increased PSD areas and also improved long-term spatial memory. These results suggest that DHA could rescue synaptogenesis impairment and long-term memory deficits in postnatal caused by multiple sevoflurane exposures.

Learning, memory and synaptic plasticity in hippocampus in rats exposed to sevoflurane

PURPOSE

Developmental exposure to volatile anesthetics has been associated with cognitive deficits at adulthood. Rodent studies have revealed impairments in performance in learning tasks involving the hippocampus. However, how the duration of anesthesia exposure impact on hippocampal synaptic plasticity, learning, and memory is as yet not fully elucidated.

METHODS

On postnatal day 7(P7), rat pups were divided into 3 groups: control group (n=30), 3% sevoflurane treatment for 1h (Sev 1h group, n=30) and 3% sevoflurane treatment for 6h (Sev 6h group, n=28). Following anesthesia, synaptic vesicle-associated proteins and dendrite spine density and synapse ultrastructure were measured using western blotting, Golgi staining, and transmission electron microscopy (TEM) on P21. In addition, the effects of sevoflurane treatment on long-term potentiation (LTP) and long-term depression (LTD), two molecular correlates of memory, were studied in CA1 subfields of the hippocampus, using electrophysiological recordings of field potentials in hippocampal slices on P35-42. Rats' neurocognitive performance was assessed at 2 months of age, using the Morris water maze and novel-object recognition tasks.

RESULTS

Our results showed that neonatal exposure to 3% sevoflurane for 6h results in reduced spine density of apical dendrites along with elevated expression of synaptic vesicle-associated proteins (SNAP-25 and syntaxin), and synaptic ultrastructure damage in the hippocampus. The electrophysiological evidence indicated that hippocampal LTP, but not LTD, was inhibited and that learning and memory performance were impaired in two behavioral tasks in the Sev 6h group. In contrast, lesser structural and functional damage in the hippocampus was observed in the Sev 1h group.

CONCLUSION

Our data showed that 6-h exposure of the developing brain to 3% sevoflurane could result in synaptic plasticity impairment in the hippocampus and spatial and nonspatial hippocampal-dependent learning and memory deficits. In contrast, shorter-duration exposure (1h) results in less damage. These results provide further evidences that duration of anesthesia exposure could have differential effects on neuronal plasticity and neurocognitive performance.

Neurodevelopmental implications of the general anesthesia in neonate and infants

Each year, about six million children, including 1.5 million infants, in the United States undergo surgery with general anesthesia, often requiring repeated exposures. However, a crucial question remains of whether neonatal anesthetics are safe for the developing central nervous system (CNS). General anesthesia encompasses the administration of agents that induce analgesic, sedative, and muscle relaxant effects. Although the mechanisms of action of general anesthetics are still not completely understood, recent data have suggested that anesthetics primarily modulate two major neurotransmitter receptor groups, either by inhibiting N-methyl-D-aspartate (NMDA) receptors, or conversely by activating γ-aminobutyric acid (GABA) receptors. Both of these mechanisms result in the same effect of inhibiting excitatory activity of neurons. In developing brains, which are more sensitive to disruptions in activity-dependent plasticity, this transient inhibition may have longterm neurodevelopmental consequences. Accumulating reports from preclinical studies show that anesthetics in neonates cause cellular toxicity including apoptosis and neurodegeneration in the developing brain. Importantly, animal and clinical studies indicate that exposure to general anesthetics may affect CNS development, resulting in long-lasting cognitive and behavioral deficiencies, such as learning and memory deficits, as well as abnormalities in social memory and social activity. While the casual relationship between cellular toxicity and neurological impairments is still not clear, recent reports in animal experiments showed that anesthetics in neonates can affect neurogenesis, which could be a possible mechanism underlying the chronic effect of anesthetics. Understanding the cellular and molecular mechanisms of anesthetic effects will help to define the scope of the problem in humans and may lead to preventive and therapeutic strategies. Therefore, in this review, we summarize the current evidence on neonatal anesthetic effects in the developmental CNS and discuss how factors influencing these processes can be translated into new therapeutic strategies.

Pre-administration of curcumin prevents neonatal sevoflurane exposure-induced neurobehavioral abnormalities in mice

Sevoflurane, a commonly used inhaled anesthetic, can induce neuronal apoptosis in the developing rodent brain and correlate with functional neurological impairment later in life. However, the mechanisms underlying these deleterious effects of sevoflurane remain unclear and no effective treatment is currently available. Herein, the authors investigated whether curcumin can prevent the sevoflurane anesthesia-induced cognitive impairment in mice. Six-day-old C57BL/6 mice were exposed to 3% sevoflurane 2h daily for 3 consecutive days and were treated with curcumin at the dose of 20 mg/kg or vehicle 30 min before the sevoflurane anesthesia from postnatal days 6 (P6) to P8. Cognitive functions were evaluated by open field, Morris water maze, and fear conditioning tests on P61, P63-69, and P77-78, respectively. In another separate experiment, mice were killed on day P8 or P78, and the brain tissues were harvested and then subjected to biochemistry studies. Our results showed that repeated neonatal sevoflurane exposure led to significant cognitive impairment later in life, which was associated with increased neuronal apoptosis, neuroinflammation, oxidative nitrosative stress, and decreased memory related proteins. By contrast, pre-administration of curcumin ameliorated early neuronal apoptosis, neuroinflammation, oxidative nitrosative stress, memory related proteins, and later cognitive dysfunction. In conclusion, our data suggested that curcumin pre-administration can prevent the sevoflurane exposure-induced cognitive impairment later in life, which may be partly attributed to its ability to attenuate the neural apoptosis, inflammation, and oxidative nitrosative stress in mouse brain.