Sevoflurane Neurotoxicity Research Articles

ADAR1 prevents ZBP1-dependent PANoptosis via A-to-I RNA editing in developmental sevoflurane neurotoxicity

It is well established that sevoflurane exposure leads to widespread neuronal cell death in the developing brain. Adenosine deaminase acting on RNA-1 (ADAR1) dependent adenosine-to-inosine (A-to-I) RNA editing is dynamically regulated throughout brain development. The current investigation is designed to interrogate the contributed role of ADAR1 in developmental sevoflurane neurotoxicity. Herein, we provide evidence to show that developmental sevoflurane priming triggers neuronal pyroptosis, apoptosis and necroptosis (PANoptosis), and elicits the release of inflammatory factors including IL-1β, IL-18, TNF-α and IFN-γ. Additionally, ADAR1-P150, but not ADAR1-P110, depresses cellular PANoptosis and inflammatory response by competing with Z-DNA/RNA binding protein 1 (ZBP1) for binding to Z-RNA in the presence of sevoflurane. Further investigation demonstrates that ADAR1-dependent A-to-I RNA editing mitigates developmental sevoflurane-induced neuronal PANoptosis. To restore RNA editing, we utilize adeno-associated virus (AAV) to deliver engineered circular ADAR-recruiting guide RNAs (cadRNAs) into cells, which is capable of recruiting endogenous adenosine deaminases to promote cellular A-to-I RNA editing. As anticipated, AAV-cadRNAs diminishes sevoflurane-induced cellular Z-RNA production and PANoptosis, which could be abolished by ADAR1-P150 shRNA transfection. Moreover, AAV-cadRNAs delivery ameliorates developmental sevoflurane-induced spatial and emotional cognitive deficits without influence on locomotor activity. Taken together, these results illustrate that ADAR1-P150 exhibits a prominent role in preventing ZBP1-dependent PANoptosis through A-to-I RNA editing in developmental sevoflurane neurotoxicity. Application of engineered cadRNAs to rectify the compromised ADAR1-dependent A-to-I RNA editing provides an inspiring direction for possible clinical preventions and therapeutics.

The effect of N-acetylcysteine on the neurotoxicity of sevoflurane in developing hippocampus cells

Sevoflurane, a common pediatric anesthetic, has been linked to neurodegeneration, raising safety concerns. This study explored N-acetylcysteine's protective potential against sevoflurane-induced neurotoxicity in rat hippocampi. Four groups were examined: Control: Received 6 hours of 3 l/min gas (air and 30 % O2) and intraperitoneal saline. NAC: Received 6 hours of 3 l/min gas and 150 mg/kg NAC intraperitoneally. Sev: Exposed to 6 hours of 3 l/min gas and 3 % sevoflurane. Sev+NAC: Received 6 hours of 3 l/min gas, 3 % sevoflurane, and 150 mg/kg NAC. Protein levels of NRF-2, NLRP3, IL-1β, caspase-1, Beclin 1, p62, LC3A, and apoptosis markers were assessed. Sevoflurane and NAC alone reduced autophagy, while Sev+NAC group maintained autophagy levels. Sev group had elevated NRF-2, NLRP3, pNRF2, Caspase-1, and IL-1β, which were reduced in Sev+NAC. Apoptosis was higher in Sev, but Sev+NAC showed reduced apoptosis compared to the control. In summary, sevoflurane induced neurotoxicity in developing hippocampus, which was mitigated by N-acetylcysteine administration.

Dysregulation of iron homeostasis and ferroptosis in sevoflurane and isoflurane associated perioperative neurocognitive disorders.

In recent years, sevoflurane and isoflurane are the most popular anesthetics in general anesthesia for their safe, rapid onset, and well tolerant. Nevertheless, many studies reported their neurotoxicity among pediatric and aged populations. This effect is usually manifested as cognitive impairment such as perioperative neurocognitive disorders. The wide application of sevoflurane and isoflurane during general anesthesia makes their safety a major health concern. Evidence indicates that iron dyshomeostasis and ferroptosis may establish a role in neurotoxicity of sevoflurane and isoflurane. However, the mechanisms of sevoflurane- and isoflurane-induced neuronal injury were not fully understood, which poses a barrier to the treatment of its neurotoxicity. We, therefore, reviewed the current knowledge on mechanisms of iron dyshomeostasis and ferroptosis and aimed to promote a better understanding of their roles in sevoflurane- and isoflurane-induced neurotoxicity.

Sevoflurane upregulates neuron death process-related Ddit4 expression by NMDAR in the hippocampus.

Postoperative cognitive dysfunction (POCD) is a serious and common complication induced by anesthesia and surgery. Neuronal apoptosis induced by general anesthetic neurotoxicity is a high-risk factor. However, a comprehensive analysis of general anesthesia-regulated gene expression patterns and further research on molecular mechanisms are lacking. Here, we performed bioinformatics analysis of gene expression in the hippocampus of aged rats that received sevoflurane anesthesia in GSE139220 from the GEO database, found a total of 226 differentially expressed genes (DEGs) and investigated hub genes according to the number of biological processes in which the genes were enriched and performed screening by 12 algorithms with cytoHubba in Cytoscape. Among the screened hub genes, Agt, Cdkn1a, Ddit4, and Rhob are related to the neuronal death process. We further confirmed that these genes, especially Ddit4, were upregulated in the hippocampus of aged mice that received sevoflurane anesthesia. NMDAR, the core target receptor of sevoflurane, rather than GABAAR, mediates the sevoflurane regulation of DDIT4 expression. Our study screened sevoflurane-regulated DEGs and focused on the neuronal death process to reveal DDIT4 as a potential target mediated by NMDAR, which may provide a new target for the treatment of sevoflurane neurotoxicity.

Dexmedetomidine-mediated neuroprotection against sevoflurane-induced brain development abnormality in fetal mice brain.

Brain development is susceptible to external influences during the gestation period so the neurotoxicity of anesthetics has gained a lot of attention. We aimed to investigate the neurotoxicity of sevoflurane to fetal mice brain as well as the neuroprotective effects of dexmedetomidine. Pregnant mice were treated with 2.5% sevoflurane for 6 hours. The changes in fetal brain development were assayed with immunofluorescence and western blot. The pregnant mice were intraperitoneally injected with dexmedetomidine or vehicle from gestation day (G) 12.5 to G15.5. Our results showed maternal sevoflurane exposure could not only inhibit neurogenesis but also lead to precocious generation of astrocytes in fetal mice brains. The fetal mice brain of sevoflurane group exhibited a significant inhibition in the activity of Wnt signaling and the expression of CyclinD1, Ngn2. Chronic dexmedetomidine administration could minimize the negative effects caused by sevoflurane by activating the Wnt signaling pathway. This study has uncovered a Wnt signaling-related mechanism of the neurotoxicity of sevoflurane and confirmed the neuroprotective effect of dexmedetomidine, which could provide pre-clinical evidence for clinical decision-making.

MTORC1-Dependent and GSDMD-Mediated Pyroptosis in Developmental Sevoflurane Neurotoxicity.

Developmental sevoflurane exposure leads to neuronal cell death, and subsequent learning and memory cognitive defects. The underlyi\ng mechanism remains to be elucidated. Gasdermin D (GSDMD)-mediated pyroptosis is a form of inflammatory cell death and participates in a variety of neurodegenerative diseases. Several studies illustrated that dysregulation of mTOR activity is involved in pyroptotic cell death. The current study was designed to interrogate the role of GSDMD-mediated pyroptosis and mTOR activity in developmental sevoflurane exposure. We found that inhibition of GSDMD pore formation with Disulfiram (DSF) or Necrosulfonamide (NSA) significantly attenuated sevoflurane neurotoxicity in vitro. In addition, treatment with DSF or NSA also mitigated damage-associated molecular patterns (DAMPs) release and subsequent plasma membrane rupture (PMR) induced by sevoflurane challenge. Further investigation showed that the overactivation of mTOR signaling is involved in sevoflurane induced pyroptosis both in vivo and in vitro. Intriguingly, we found that the DAMPs release and subsequent PMR triggered by developmental sevoflurane priming were compromised by knocking down the expression of mTORC1 component Raptor, but not mTORC2 component Rictor. Moreover, sevoflurane induced pyroptosis could also be restored by suppressing mTOR activity or knocking down the expressions of Ras-related small GTPases RagA or RagC. Finally, administration of DSF or NSA dramatically improved the spatial and emotional cognitive disorders without alternation of locomotor activity. Taken together, these results indicate that mTORC1-dependent and GSDMD-mediated pyroptosis contributes to the developmental sevoflurane neurotoxicity. Characterizing these processes may provide experimental evidence for the possible prevention of developmental sevoflurane neurotoxicity.

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.

Neuroglobin alleviates the neurotoxicity of sevoflurane to fetal rats by inhibiting neuroinflammation and affecting microglial polarization

Sevoflurane, a commonly used inhaled anesthetic, causes endogenous apoptosis in fetal rats. Microglia polarization is associated with inflammation, and the IL-10/STAT3/SOCS3 pathway is involved in this process. Neuroglobin (Ngb) is a neuroprotective protein which exhibits an anti-inflammatory effect. The purpose of this study was to investigate whether neurotoxicity induced by sevoflurane exposure in prenatal rats correlates with neuroinflammation and microglia polarization and whether Ngb can moderate this response. We found that exposure to sevoflurane on the 20th day of gestation (G20) induced discernable inflammation in postnatal day 0 (P0) rats, promoted M1 polarization of microglia, and inhibited M2 polarization. Hemin-mediated Ngb elevation inhibited sevoflurane-induced neuroinflammation. Additionally, elevated Ngb inhibited M1 polarization and promoted M2 polarization of microglia. We also found that elevated Ngb could alleviate the effect of sevoflurane on the expression of Interleukin-10 (IL-10), phosphorylated-signal transduction and activators of transcription 3 (P-STAT3), and suppressor of cytokine signaling 3 (SOCS3). Furthermore, we found that elevated Ngb ameliorated the effects of sevoflurane on long-term exploratory behavior and learning and memory in the offspring. Our results show that Ngb alleviates the neurotoxicity of sevoflurane to fetal rats by inhibiting neuroinflammation and affecting microglial polarization, a process which may involve the IL-10/STAT3/SOCS3 pathway.

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.

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

AimsAnaesthesia-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 methodsHippocampi 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 findingsSevoflurane 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. SignificanceOur 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.

Toxicity mechanism of sevoflurane in neural stem cells of rats through DNA methylation.

The present study investigated the influence of sevoflurane on the cytotoxicity of neural stem cells of rats and deoxyribonucleic acid (DNA) methylation, and analyzed the correlation between degree of methylation and neurotoxicity of sevoflurane. Ten healthy Sprague-Dawley rats aged 6–8 weeks were randomly selected. The neural stem cells in the hippocampus of rats were isolated, followed by multiplication culture and induced differentiation. The nerve-related factors were observed and detected under a microscope. Moreover, the neural stem cells were treated with sevoflurane in different concentrations. Three wells were only added with the normal medium as the control group (C0), 3 wells were added with the low-concentration sevoflurane (0.2 g/ml) prepared by the medium as the low-concentration group (C1), 3 wells were added with the moderate-concentration of sevoflurane (0.5 g/ml) as the moderate-concentration group (C2), and 3 wells were added with the high-concentration sevoflurane (1 g/ml) as the high-concentration group (C3). The apoptosis rate was detected and calculated via Cell Counting Kit-8 (CCK-8) assay, the content of genomic DNA methylation in neural stem cells in each group was detected via high-performance liquid chromatography (HPLC), and the distribution of methylation in the chromosome in each group was compared. During the culture, neurospheres were produced, and the expression levels of four neural markers were increased. With the increase of sevoflurane concentration and the prolongation of time, the apoptosis rate of stem cells was increased. The content of methylation in cells treated with sevoflurane in a higher concentration was higher than that in other groups (P<0.05). According to the Pearsons correlation analysis, the content of methylation in neural stem cells was directly proportional to the concentration of sevoflurane. Methylation mostly occurred in the autosome, and the content of methylation in the high-concentration group was higher than those in the moderate-concentration, low-concentration and control groups (P<0.05). In conclusion, the concentration of sevoflurane can affect the degree of methylation in neural stem cells of rats and produce certain cytotoxicity.

Hydrogen gas attenuates sevoflurane neurotoxicity through inhibiting nuclear factor κ-light-chain-enhancer of activated B cells signaling and proinflammatory cytokine release in neonatal rats.

Anesthesia neurotoxicity in developing brain has gained increasing attention. However, knowledge regarding its mitigating strategies remains scant. Sevoflurane, a commonly used anesthetic, is responsible for learning and memory deficits in neonates. Molecular hydrogen is reported to be a potential neuroprotective agent because of its antioxidative and anti-inflammatory activities. This study aimed to investigate the effect of hydrogen gas on sevoflurane neurotoxicity. The newborn rats were treated with sevoflurane and/or hydrogen gas for 2 h. Spatial recognition memory and fear memory were determined by Y-maze and fear conditioning tests at 10 weeks of age. Nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and proinflammatory cytokine levels were detected using western blot analysis. The data showed that the spatial recognition memory and fear memory of the rats treated with sevoflurane decreased compared with the control, and the cognitive function of the rats treated with sevoflurane and hydrogen gas significantly increased in comparison with treatment with sevoflurane alone. Moreover, hydrogen gas suppressed NF-κB phosphorylation and nuclear translocation and reduced the production of interleukin-1β, interleukin-6, and tumor necrosis factor-α following sevoflurane administration. Thus, the results proposed that hydrogen gas might protect against sevoflurane neurotoxicity by inhibiting NF-κB activation and proinflammatory cytokine release, providing a novel therapeutic strategy for anesthesia neurotoxicity.

Sevoflurane neurotoxicity in neonatal rats is related to an increase in the GABAA R α1/GABAA R α2 ratio.

Exposure of neonatal rat to sevoflurane leads to neurodegeneration and deficits of spatial learning and memory in adulthood. However, the underlying mechanisms remain unclear. The type A γ-aminobutyric acid receptor (GABAA R) is a target receptor for sevoflurane. The present study intends to investigate the changes in GABAA R α1/α2 expression and its relationship with the neurotoxicity effect due to sevoflurane in neonatal rats. After a dose-response curve was constructed to determine minimum alveolar concentration (MAC) and safety was guaranteed in our 7-day-old neonatal rat pup mode, we conducted two studies among the following groups: (A) the control group; (B) the sham anesthesia group; and (C) the sevoflurane anesthesia group and all three groups were treated in the same way as the model. First, poly(ADP-ribose) polymerase-1 protein (PARP-1) expression was determined in the different brain areas at 6 hr after anesthesia. Second, the expression of PARP-1 and GABAA R α1/GABAA R α2 in the hippocampus area was tested by Western blotting at 6 hr, 24 hr, and 72 hr after anesthesia in all three groups. After 4 hr, with 0.8 MAC (2.1%) sevoflurane anesthesia, the PARP-1 expression was significantly higher in the hippocampus than the other brain areas (p < .05). Compared with Groups A and B, the expression of PARP-1 in the hippocampus of Group C significantly increased at 6 hr after sevoflurane exposure (216% ± 15%, p < .05), and the ratio of the α1/α2 subunit of GABAA R surged at 6 hr (126% ± 6%), 24 hr (127% ± 8%), and 72 hr (183% ± 22%) after sevoflurane exposure in the hippocampus (p < .05). Our study showed that sevoflurane exposure of 0.8 MAC (2.1%)/4 hr was a suitable model for 7-day-old rats. And the exposure to sevoflurane could induce the apoptosis of neurons in the early stage, which may be related to the transmission from GABAA R α2 to GABAA R α1.

Erythropoietin rescues primary rat cortical neurons from pyroptosis and apoptosis via Erk1/2-Nrf2/Bach1 signal pathway.

The most commonly used inhalation anesthetics, sevoflurane, is reported to be a risk for development of learning disability. Erythropoietin (EPO) administration might be involved an effective therapy for sevoflurane neurotoxicity. EPO-EPO receptor-extracellular signal-related kinases 1/2 (Erk1/2) signal pathway plays a pivotal role in the neuroprotective effect. Nuclear factor erythroid 2-related factor (Nrf2)/BTB and CNC homology 1 (Bach1) ratio altering by Erk1/2 could ameliorate oxidative stress occurred in human macrophages. Primary cortical neuron cultures exposed to sevoflurane were assessed for cleaved caspase-1, cleaved caspase-3, Nrf2, Bach1, total Erk1/2, and phosphorylated Erk1/2 with the following: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT); propidium iodide uptake (PI); lactate dehydrogenase (LDH); malondialdehyde (MDA); superoxide dismutase (SOD); Real-time PCR; and Western blot. We found that sevoflurane exposure increased cell pyroptosis, apoptosis, injury, and MDA (n=9, P<0.05), but decreased cell viability (n=9, P<0.05) and down-regulated SOD (n=9, P<0.05), while EPO partially rescued the neurotoxicity induced by sevoflurane (n=9, P<0.05), as well as increase the expression of Nrf2 mRNA and Nrf2/Bach1 ratio (n=9, P<0.05). Inhibition of Erk1/2 phosphorylation via PD98059 reversed the protective effect of EPO (n=9, P<0.05). Thus, protection of EPO markedly attenuated pyroptosis and apoptosis of neurons exposed to sevoflurane via Erk1/2-Nrf2/Bach1 signal pathway.

Beta-arrestin1 and 2 differently modulate metabotropic glutamate receptor 7 signaling in rat developmental sevoflurane-induced neuronal apoptosis

Beta-arrestins (β-arrs) are initially known as negative regulators of G protein-coupled receptors (GPCRs). Recently, there is increasing evidence suggesting that β-arrs also serve as scaffolds and adapters that mediate distinct intracellular signal transduction initiated by GPCR activation. In the previous study, we have shown that metabotropic glutamate receptor 7 (mGluR7) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling may be involved in the developmental sevoflurane neurotoxicity. In the present study, we showed that activation of mGluR7 with a group III mGluRs orthosteric agonist LAP4 or an atypical mGluR7 allosteric agonist N,N′-bis(diphenylmethyl)-1,2-ethanediamine dihydrochloride (AMN082) significantly attenuated sevoflurane-induced neuronal apoptosis. Interestingly, this neuroprotective role of LAP4 could be partially reduced by β-arr1 small interfering RNA (siRNA) or β-arr2 siRNA transfection. In contrast, β-arr2 siRNA transfection alone abolished the effects of AMN082 on sevoflurane neurotoxicity. In addition, administration of LAP4 or AMN082 significantly enhanced Phospho-ERK1/2 in sevoflurane neurotoxicity, which could be abrogated by β-arr2 siRNA transfection, but not by β-arr1 siRNA transfection. Increased β-arr2-dependent Phospho-ERK1/2 signaling alleviated sevoflurane neurotoxicity by inhibiting bad phosphorylation. We also found that the neuroprotective role of AMN082 was completely reversed by ERK1/2 inhibitor 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene (U0126). Alternatively, treatment with U0126 partially suppressed the neuroprotective of LAP4, suggesting that other mechanisms may be implicated in this process. Further investigation indicated that, in the scenario of sevoflurane neurotoxicity, application of LAP4 (but not AMN082) increased the interaction of β-arrs with transcriptional factors CREB binding protein (CBP) and p300. LAP4 also enhanced the β-arr1-dependent H3 and H4 acetylation in sevoflurane neurotoxicity. For the behavior study, treatment with LAP4 or AMN082 significantly improved the emotional and spatial learning and memory disorders induced by postnatal sevoflurane exposure. These results suggested that β-arr1 and 2 may differently modulate mGluR7 signaling in developmental sevoflurane neurotoxicity. This study also reveals a β-arr-biased agonism at GPCRs (e.g. mGluR7).

Location- and Subunit-Specific NMDA Receptors Determine the Developmental Sevoflurane Neurotoxicity Through ERK1/2 Signaling.

It is well established that developmental exposure of sevoflurane (an inhalational anesthetic) is capable of inducing neuronal apoptosis and subsequent learning and memory disorders. Synaptic NMDA receptors activity plays an essential role in cell survival, while the extra-synaptic NMDA receptors activation is usually associated with cell death. However, whether synaptic or extra-synaptic NMDA receptors mediate developmental sevoflurane neurotoxicity is largely unknown. Here, we show that developmental sevoflurane treatment decreased NR2A, but increased NR2B subunit expression both in vitro and in vivo. Sevoflurane-induced neuronal apoptosis was attenuated by synaptic NMDA receptors activation or low dose of exogenous NMDA in vitro. Interestingly, these effects could be abolished by NR2A inhibitor PEAQX, but not NR2B inhibitor Ifenprodil in vitro. In contrast, activation of extra-synaptic NMDA receptors alone had no effects on sevoflurane neurotoxicity. In the scenario of extra-synaptic NMDA receptors stimulation, however, sevoflurane-induced neuronal apoptosis could be prevented by addition of Ifenprodil, but not by PEAQX in vitro. In addition, sevoflurane neurotoxicity could also be rescued by memantine, an uncompetitive antagonist for preferential blockade of extra-synaptic NMDA receptors both in vitro and in vivo. Furthermore, we found that developmental sevoflurane-induced phospho-ERK1/2 inhibition was restored by synaptic NMDA receptor activation (in vitro), low dose of NMDA (in vitro) or memantine (in vivo). And the neuroprotective role of synaptic NMDA activity was able to be reversed by MEK1/2 inhibitor U0126 in vitro. Finally, administration of memantine or NMDA significantly improved spatial learning and memory dysfunctions induced by developmental sevoflurane exposure without influence on locomotor activity. These results indicated that activation of synaptic NR2A-containing NMDA receptors, or inhibition of extra-synaptic NR2B-containing NMDA receptors contributed to the relief of sevoflurane neurotoxicity, and the ERK1/2 MAPK signaling may be involved in this process.

Sevoflurane in combination with propofol, not thiopental, induces a more robust neuroapoptosis than sevoflurane alone in the neonatal mouse brain

Sevoflurane is the most widely used volatile anesthetic of general anesthesia. In children and neonates, it is commonly used alone or in combination with thiopental or propofol. A few recent studies reported that sevoflurane induced neuronal death in the developing rodent brain. We measured the neurotoxicity of these anesthetics at clinical doses, alone and in combination, in the developing mouse brain. Seven-day-old C57BL/6 mice were randomly assigned to 6 treatment groups. Three groups were exposed to 3% sevoflurane for 6 h after injection of saline, thiopental (5 mg/kg), or propofol (10 mg/kg), whereas three groups were exposed to room air for 6 h after injection of equal doses of saline, thiopental, or propofol. Apoptosis in the hippocampal CA1 region (CA1) and retrosplenial cortex (RC) was assessed using caspase-3 immunostaining. Sevoflurane alone caused significantly higher apoptosis in the CA1 compared with saline plus air (P = 0.04). Sevoflurane in combination with propofol resulted in significantly greater numbers of apoptotic neurons than sevoflurane alone in both the CA1 and the RC (P = 0.04). However, there was no significant difference in apoptotic neuron density in both the regions between the groups treated with sevoflurane alone and in combination with thiopental (P = 0.683). Sevoflurane alone can induce neuronal apoptosis, and this effect is enhanced by propofol. Thiopental did not exacerbate the neurotoxicity of sevoflurane. There is the possibility that the combination of sevoflurane and propofol is a more harmful anesthetic technique than sevoflurane alone in pediatric patients.

Advances in neurotoxicity of sevoflurane on the developing central nervous system

Background Sevoflurane has been widely used in the obstetric and pediatric surgery.The neurotoxicity effects of sevoflurane on developing central nervous system (CNS) has become the focus of attention.Objective This article reviews the advances in the neurotoxicity of sevoflurane published in recent years.Content The neurotoxicity and neuroprotection of sevoflurane.The contrast of neurotoxicity to the developing CNS between sevoflurane and isoflurane.The mechanism and preventive measures.Trend Future researches are proposed to focus on differentiate the advantages or disadvantages among different inhaled anesthetics for pediatric anesthesia with clinical trials,and explicating the effects of sevoflurane on the developing CNS,and providing possible preventive and therapeutic measures for the neurotoxicity of sevoflurane. Key words: Sevoflurane; Inhaled anesthetic; Neurotoxicity; The developing brain

N-stearoyl-l-tyrosine ameliorates sevoflurane induced neuroapoptosis via MEK/ERK1/2 MAPK signaling pathway in the developing brain

N-arachidonoylethanolamine (AEA) plays a crucial neuroprotective role in certain neurodegenerative diseases. Our recent studies suggested that AEA analog N-stearoyl-l-tyrosine (NsTyr) could protect neurons from apoptosis and improve hippocampus-dependent learning and memory deficits. The present study was designed to determine the neuroprotective effect of NsTyr on developmental sevoflurane neurotoxicity using primary hippocampal neuronal cultures and rat pups. We found that NsTyr could decrease cell viability and reduce apoptosis in sevoflurane treated neuronal cultures. In addition, NsTyr attenuated sevoflurane-induced apoptosis by modulating Caspase-3 and Bcl-2 in vivo. Moreover, sevoflurane exposure led to an inhibition of phospho-ERK1/2, which was rescued by NsTyr. Administration of U0126 (an inhibitor of MEK) abolished the neuroprotective effect of NsTyr on sevoflurane neurotoxicity both in vitro and in vivo. Finally, administration of NsTyr improved the learning and memory disorders induced by postnatal sevoflurane exposure without alteration in locomotor activity. These results indicated that AEA analog NsTyr protects developing brain against developmental sevoflurane neurotoxicity possibly through MEK/ERK1/2 MAPK signaling pathway.

The effects of metabotropic glutamate receptor 7 allosteric agonist N,N′-dibenzhydrylethane-1,2-diamine dihydrochloride on developmental sevoflurane neurotoxicity: role of extracellular signal-regulated kinase 1 and 2 mitogen-activated protein kinase signaling pathway

The present study was designed to evaluate the possible neuroprotective effects of metabotropic glutamate receptor (mGluR7) allosteric agonist N,N′-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) on developmental sevoflurane neurotoxicity. To achieve the objective, hippocampal cultures (7 DIV, 7 day in vitro) were treated with different doses of l-(+)-2-Amino-4-phosphonobutyric acid (l-AP4, an agonist of group III mGluRs), (RS)-α-Methylserine-O-phosphate (MSOP, an antagonist of group III mGluRs), AMN082 or cis-2-[[(3,5-Dichlorophenyl)amino]carbonyl]cyclohexanecarboxylic acid (VU0155041, an agonist of mGluR4) before exposed to sevoflurane. Cell apoptosis were determined by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL)-staining. For in vivo study, rat pups (7 PND, 7 postnatal day) were injected with AMN082, l-AP4 or saline before sevoflurane exposure. Extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, caspase-3, Bcl-2, and Bax were detected by Western blot. The locomotor activity and cognitive functions were evaluated by open-field test and Morris water maze (MWM), respectively. We found that l-AP4 prevented sevoflurane-induced cell apoptosis, but MSOP promoted. Specially, application of AMN082 contributed to the relief of sevoflurane-induced apoptosis in vitro, whereas VU0155041 did not. In addition, sevoflurane treatment led to a decrease of Bcl-2 and an increase of caspase-3 and Bax, which were mitigated by AMNO82 in vivo. Moreover, we showed that sevoflurane treatment resulted in a remarkable suppression of phospho-ERK1/2, which was restored by AMN082. Application of U0126 (an inhibitor of MEK) abolished the neuroprotective effects of AMN082 on sevoflurane neurotoxicity both in vitro and in vivo. In addition, sevoflurane exposure also led to an increase of phospho-JNK, but SP600125 (an inhibitor of JNK) did not attenuate sevoflurane-induced apoptosis. The total and phosphorylated p38 remained unchanged in sevoflurane-treated rat pups. Finally, AMN082 improved the learning and memory defects caused by postnatal sevoflurane exposure without alternations in emotion or locomotor activity. These preliminary data indicate that AMN082 may protect immature brain against sevoflurane neurotoxicity, and the ERK1/2 MAP kinase signaling is likely to be involved. Further studies are needed to fully assess the neuroprotective role of mGluR7 agonist AMN082 in developmental anesthetic neurotoxicity.