Selective anesthesia-induced neuroinflammation in developing mouse brain and cognitive impairment

Isoflurane Exposure Induces Cell Death, Microglial Activation and Modifies the Expression of Genes Supporting Neurodevelopment and Cognitive Function in the Male Newborn Piglet Brain

Exposure of the brain to general anesthesia during early infancy may adversely affect its neural and cognitive development. The mechanisms mediating this are complex, incompletely understood and may be sexually dimorphic, but include developmentally inappropriate apoptosis, inflammation and a disruption to cognitively salient gene expression. We investigated the effects of a 6h isoflurane exposure on cell death, microglial activation and gene expression in the male neonatal piglet brain. Piglets (n = 6) were randomised to: (i) naive controls or (ii) 6h isoflurane. Cell death (TUNEL and caspase-3) and microglial activation were recorded in 7 brain regions. Changes in gene expression (microarray and qPCR) were assessed in the cingulate cortex. Electroencephalography (EEG) was recorded throughout. Isoflurane anesthesia induced significant increases in cell death in the cingulate and insular cortices, caudate nucleus, thalamus, putamen, internal capsule, periventricular white matter and hippocampus. Dying cells included both neurons and oligodendrocytes. Significantly, microglial activation was observed in the insula, pyriform, hippocampus, internal capsule, caudate and thalamus. Isoflurane induced significant disruption to the expression of 79 gene transcripts, of these 26 are important for the control of transcription and 23 are important for the mediation of neural plasticity, memory formation and recall. Our observations confirm that isoflurane increases apoptosis and inflammatory responses in the neonatal piglet brain but also suggests novel additional mechanisms by which isoflurane may induce adverse neural and cognitive development by disrupting the expression of genes mediating activity dependent development of neural circuits, the predictive adaptive responses of the brain, memory formation and recall.

Etanercept, an inhibitor of TNF-a, prevents propofol-induced neurotoxicity in the developing brain

Propofol can induce acute neuronal apoptosis, neuronal loss or long-term cognitive impairment when exposed in neonatal rodents, but the mechanisms by which propofol induces developmental neurotoxicity are unclear. Recent studies have demonstrated that propofol can increase the TNF-α level in the developing brain, but there is a lack of direct evidence to show whether TNF-α is partially or fully involved in propofol-induced neurotoxicity. The present study shows that propofol exposure in neonatal rats induces an increase of TNF-α in the cerebral spinal fluid, hippocampus and prefrontal cortex (PFC). Etanercept, a TNF-α inhibitor, prevents propofol-induced short- or long-term neuronal apoptosis, neuronal loss, synaptic loss and long-term cognitive impairment. Furthermore, mTNF-α (precursor of TNF-α) expression in microglia cells is increased after propofol anaesthesia in either the hippocampus or PFC, but mTNF-α expression in neurons is only increased in the PFC. These findings suggest that TNF-α may mediate propofol-induced developmental neurotoxicity, and etanercept can provide neural protection. Microglia are the main cellular source of TNF-α after propofol exposure, while the synthesis of TNF-α in neurons is brain-region selective.

Aberrantly expressed long noncoding RNAs are involved in sevoflurane-induced developing hippocampal neuronal apoptosis: a microarray related study

The commonly used volatile anesthetic sevoflurane has been shown to induce widespread apoptosis in the developing brain, yet the underlying molecular mechanisms are not fully understood. Accumulating research has demonstrated that long noncoding RNAs (lncRNAs) regulate multiple biological processes, including neural development, differentiation and apoptosis. They are aberrantly expressed in multiple neurodegenerative diseases. In this study, we employed a lncRNA-mRNA microarray analysis to determine whether and how lncRNAs are involved in sevoflurane-induced hippocampal neuronal apoptosis in neonatal mice. Our data showed that a single 6-h sevoflurane exposure of P7 mice resulted in significant morphological changes and apoptosis in the hippocampus. Moreover, the microarray simultaneously revealed 817 lncRNAs and 856 of their potential coding targets that related to apoptosis, of which 31 lncRNAs (19 up and 12 down) and 25 mRNAs were significantly differentially expressed (P < 0.05) after sevoflurane exposure. Importantly, we found that Bcl2l11 (BIM), which potentiates mitochondria-dependent apoptosis and its nearby enhancer-like lncRNA ENSMUST00000136025, were both more highly expressed in sevoflurane-treated samples compared with control samples. Subsequent qRT-PCR results confirmed the changes. Further CNC network indicated that lncRNA ENSMUST00000136025 was positively correlated with Bim. Moreover, sevoflurane induced a significant increase of pro-apoptotic protein BIM and Bax but a reduction of anti-apoptotic proteins Bcl-2 in the hippocampus. Our study first demonstrates that aberrantly expressed lncRNAs play a role in sevoflurane-induced hippocampal apoptosis. We noted that up-regulated ENSMUST00000136025 highly likely induced the over-expression of BIM, which eventually promoted mitochondria-mediated apoptosis. Such findings further broaden the understanding of molecular mechanisms responsible for sevoflurane-induced neurotoxicity.

Sevoflurane-Induced Endoplasmic Reticulum Stress Contributes to Neuroapoptosis and BACE-1 Expression in the Developing Brain: The Role of eIF2α

Neonatal exposure to volatile anesthetics causes apoptotic neurodegeneration in the developing brain, possibly leading to neurocognitive deficits in adulthood. Endoplasmic reticulum (ER) stress might be associated with sevoflurane (sevo)-induced neuroapoptosis. However, the signaling pathway regulating sevo-induced neuroapoptosis is not understood. We investigated the effects of neonatal sevo exposure on ER signaling pathway activation. Seven-day-old mouse pups were divided into control (C) and sevo (S; 3 % sevo exposure, 6 h) groups. ER stress marker [protein kinase RNA-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), activating transcription factor 4 (ATF4), CHOP, and caspase-12] levels were determined by western blotting. To understand the role of eIF2α in sevo-induced ER stress and caspase-3 activation, pups were pretreated with an eIF2α dephosphorylation inhibitor, salubrinal, and a potent and selective inhibitor of PERK, GSK2656157, before sevo exposure, and the effects on ER stress signaling and neuroapoptosis were examined. We investigated whether neonatal exposure to sevo increased β-site APP-cleaving enzyme 1 (BACE-1) expression. Neonatal sevo exposure elevated caspase-3 activation. ER stress signaling was activated, along with increased PERK and eIF2α phosphorylation, and upregulation of proapoptotic proteins (ATF4 and CHOP) in the cerebral cortex of the developing brain. Pretreatment with salubrinal augmented sevo-induced eIF2α phosphorylation, which inhibited ER stress-mediated ATF4 and caspase-3 activation. Inhibition of PERK phosphorylation due to GSK2656157 pretreatment reduced the sevo-induced increase in eIF2α phosphorylation. Sevo increased BACE-1 expression, which was attenuated by GSK2656157 and salubrinal pretreatment. Our data suggested that neonatal sevo exposure-induced neuroapoptosis is mediated via the PERK-eIF2α-ATF4-CHOP axis of the ER stress signaling pathway. Modulation of eIF2α phosphorylation may play a key role in sevo-induced neurotoxicity in the developing brain.

Long-lasting behavioral effects in neonatal mice with multiple exposures to ketamine-xylazine anesthesia

Anesthetic agents are often administered in the neonatal period, a time of rapid brain development and synaptogenesis. Mounting evidence suggests that anesthetics can disrupt neurocognitive development, particularly in cases of multiple or prolonged anesthetic exposure. Previous studies have shown that administering multiple doses of ketamine-xylazine (KX) anesthesia to neonatal mice can induce long-term changes to synaptic plasticity in the cortex, but the effect on neurocognitive function remains unclear. In this study, we exposed neonatal mice to single dose and multiple doses of KX anesthesia in the neonatal period (postnatal days 7, 9, 11), and conducted a series of behavioral tests in young adulthood (1month of age). Mice receiving multiple doses of KX anesthesia showed deficits in novel object recognition, sociability, preference for social novelty and contextual fear response, but no effect on auditory-cued fear response. Single dose of KX anesthesia had no effect on these behaviors except for contextual fear response. We also observed that multiple exposures to KX anesthesia were associated with decreased CaMKII phosphorylation, which is known to play a role in synapse development and long-term potentiation, likely contributing to learning impairment.

Early-life single-episode sevoflurane exposure impairs social behavior and cognition later in life

BACKGROUND

Single-episode anesthetic exposure is the most prevalent surgery-related incidence among young children in the United States. Although numerous studies have used animals to model the effects of neonatal anesthetics on behavioral changes later on in life, our understanding of the functional consequences to the developing brain in a comprehensive and clinically relevant manner is unclear.

METHODS

The volatile anesthetic, sevoflurane (sevo) was administered to C57BL6 postnatal day 7 (P7) mice in a 40% oxygen and 60% nitrogen gas mixture. In order to examine the effects of sevo alone on the developing brain in a clinically relevant manner, mice were exposed to an average of 2.38 ± 0.11% sevo for 2 h. No sevo (control) mice were treated in an identical manner without sevo exposure. Mice were examined for cognition and neuropsychiatric-like behavioral changes at 1-5 months of age.

RESULTS

Using the active place avoidance (APA) test and the novel object recognition (NOR) test, we demonstrated that P7 sevo-treated mice showed a deficit in learning and memory both during periadolescence and adulthood. We then employed a battery of neuropsychiatric-like behavioral tests to examine social interaction, communication, and repetitive behavior. Interestingly, compared to the no-sevo-treated group, sevo-treated mice showed significant reductions in the time interacting with a novel mouse (push-crawl and following), time and interaction in a chamber with a novel mouse, and time sniffing a novel social odor.

CONCLUSIONS

Our study established that single-episode, 2-h sevo treatment during early life impairs cognition later on in life. With this approach, we also observed neuropsychiatric-like behavior changes such as social interaction deficits in the sevo-treated mice. This study elucidated the effects of a clinically relevant single-episode sevo application, given during the neonatal period, on neurodevelopmental behavioral changes later on in life.

From the Cover: Volatile Anesthetics Transiently Disrupt Neuronal Development in Neonatal Rats

Volatile anesthetics can cause neuronal and glial toxicity in the developing mammalian brain, as well as long-term defects in learning and memory. The goals of this study were to compare anesthetics using a clinically relevant exposure paradigm, and to assess the anesthetic effects on hippocampal development and behavior. Our hypothesis was that volatile anesthetics disrupt hippocampal development, causing neurobehavioral defects later in life. Bromodeoxyuridine (BrdU) was administered to rats on postnatal day (P)1, and the rats were exposed to volatile anesthetics (isoflurane, sevoflurane, or desflurane) for 2 h on P2. On days P7 and P14, the BrdU-labeled cells were quantified in the hippocampal dentate gyrus using immunohistochemical assays and fluorescent microscopy. Caspase-3 positive cells were quantified on P2 to evaluate apoptosis. The remaining animals underwent behavioral testing at ages 6 weeks and 6 months, using the Morris Water Maze. Significantly fewer BrdU-positive cells were detected in the hippocampal dentate gyrus in both isoflurane and desflurane-treated animals compared with controls at P7, but there were no changes in cell numbers after sevoflurane exposure. Cell counts for all three anesthetics compared with controls were equivalent at P14. Isoflurane or desflurane exposure yielded slight differences in the behavioral tests at 6 weeks, but no differences at 6 months post-exposure. We conclude that a single 2-h exposure at P2 to either isoflurane or desflurane causes a transient disruption of hippocampal neuronal development with no significant detectable long-term effects on learning and memory, whereas the same exposure to sevoflurane has no effects.

Sevoflurane represses the self-renewal ability by regulating miR-7a,7b/Klf4 signalling pathway in mouse embryonic stem cells

Sevoflurane is a frequently-used clinical inhalational anaesthetic and can cause toxicity to embryos during foetal development. Embryonic stem cells (ESCs) are derived from the inner cell mass of blastospheres and can be used as a useful model of early development. Here, we found that sevoflurane significantly influenced self-renewal ability of mESCs on stemness maintenance and cell proliferation. The cell cycle was arrested via G1 phase delay. We further found that sevoflurane upregulated expression of miR-7a,7b to repress self-renewal. Next we performed rescue experiments and found that after adding miR-7a,7b inhibitor into mESCs treated with sevoflurane, its influence on self-renewal could be blocked. Further we identified stemness factor Klf4 as the direct target of miR-7a,7b. Overexpression of Klf4 restored self-renewal ability repressed by miR-7a,7b or sevoflurane. In this work, we determined that sevoflurane repressed self-renewal ability by regulating the miR-7a,7b/Klf4 signalling pathway in mESCs. Our study demonstrated molecular mechanism underlying the side effects of sevoflurane during early development, laying the foundation for studies on safe usage of inhalational anaesthetic during non-obstetric surgery.

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.

Anesthetic Sevoflurane Causes Rho-Dependent Filopodial Shortening in Mouse Neurons

Early postnatal anesthesia causes long-lasting learning and memory impairment in rodents, however, evidence for a specific neurotoxic effect on early synaptogenesis has not been demonstrated. Drebrin A is an actin binding protein whose localization in dendritic protrusions serves an important role in dendritic spine morphogenesis, and is a marker for early synaptogenesis. We therefore set out to investigate whether clinically-relevant concentrations of anesthetic sevoflurane, widely- used in infants and children, alters dendritic morphology in cultured fetal day 16 mouse hippocampal neurons. After 7 days in vitro, mouse hippocampal neurons were exposed to four hours of 3% sevoflurane in 95% air/5% CO₂ or control condition (95% air/5% CO₂). Neurons were fixed in 4% paraformaldehyde and stained with Alexa Fluor555-Phalloidin, and/or rabbit anti-mouse drebrin A/E antibodies which permitted subcellular localization of filamentous (F)-actin and/or drebrin immunoreactivity, respectively. Sevoflurane caused acute significant length-shortening in filopodia and thin dendritic spines in days-in-vitro 7 neurons, an effect which was completely rescued by co-incubating neurons with ten micromolar concentrations of the selective Rho kinase inhibitor Y27632. Filopodia and thin spine recovered in length two days after sevoflurane exposure. Yet cluster-type filopodia (a precursor to synaptic filopodia) were persistently significantly decreased in number on day-in-vitro 9, in part owing to preferential localization of drebrin immunoreactivity to dendritic shafts versus filopodial stalks. These data suggest that sevoflurane induces F-actin depolymerization leading to acute, reversible length-shortening in dendritic protrusions through a mechanism involving (in part) activation of RhoA/Rho kinase signaling and impairs localization of drebrin A to filopodia required for early excitatory synapse formation.

Effect of sevoflurane anesthesia on the comprehensive mRNA expression profile of the mouse hippocampus

Postoperative nausea and vomiting (PONV) is a common complication after general anesthesia. Recent studies suggested that the hippocampus is involved in PONV. Hypothesising that hippocampal dopaminergic neurons are related to PONV, we examined the comprehensive mRNA profile of the hippocampus, using a sevoflurane-treated mouse model to confirm this. This study was conducted after approval from our institutional animal ethics committee, the Animal Research Center of Sapporo Medical University School of Medicine (project number: 12-033). Eight mice were assigned to two groups: a naïve group and a sevoflurane group (Sev group). In the Sev group, four mice were anesthetised with 3.5% sevoflurane for 1 hour. Subsequently, mRNA was isolated from their hippocampal cells and RNA sequencing was performed on an Illumina HiSeq 2500 platform. Mapping of the quality-controlled, filtered paired-end reads to mouse genomes and quantification of the expression levels of each gene were performed using R software. The Rtn4rl2 gene that encodes the Nogo receptor was the most up-regulated gene in the present study. The expression levels of dopamine receptor genes and the tachykinin gene were increased by sevoflurane exposure, while the genes related to serotonin receptors were not altered by sevoflurane exposure. The expression levels of LIM-homeodomain-related genes were highly down-regulated by sevoflurane. These findings suggest that sevoflurane exposure induces dopaminergic stimulation of hippocampal neurons and triggers PONV, while neuronal inflammation caused by LIM-homeodomain-related genes is down-regulated by sevoflurane.

Central Nervous System Delivery of Intranasal Insulin: Mechanisms of Uptake and Effects on Cognition

Intranasal insulin has shown efficacy in patients with Alzheimer's disease (AD), but there are no preclinical studies determining whether or how it reaches the brain. Here, we showed that insulin applied at the level of the cribriform plate via the nasal route quickly distributed throughout the brain and reversed learning and memory deficits in an AD mouse model. Intranasal insulin entered the blood stream poorly and had no peripheral metabolic effects. Uptake into the brain from the cribriform plate was saturable, stimulated by PKC inhibition, and responded differently to cellular pathway inhibitors than did insulin transport at the blood-brain barrier. In summary, these results show intranasal delivery to be an effective way to deliver insulin to the brain.

Epigenetic Manipulation of Brain-derived Neurotrophic Factor Improves Memory Deficiency Induced by Neonatal Anesthesia in Rats

BACKGROUND

Although neonatal exposure to anesthetic drugs is associated with memory deficiency in rodent models and possibly in pediatric patients, the underlying mechanisms remain elusive. The authors tested their hypothesis that exposure of the developing brain to anesthesia triggers epigenetic modification, involving the enhanced interaction among transcription factors (histone deacetylase 2, methyl-cytosine-phosphate-guanine-binding protein 2, and DNA methyltransferase 1) in Bdnf promoter region(s) that inhibit brain-derived neurotrophic factor (BDNF) expression, resulting in insufficient drive for local translation of synaptic mRNAs. The authors further hypothesized that noninvasive environmental enrichment (EE) will attenuate anesthesia-induced epigenetic inhibition of BDNF signaling and memory loss in rodent models.

METHODS

Seven days after birth (P7), neonatal rats were randomly assigned to receive either isoflurane anesthesia for 6 h or sham anesthesia. On P21, pups were weaned, and animals were randomly assigned to EE or a standard cage environment (no EE). Behavioral, molecular, and electrophysiological studies were performed on rats on P65.

RESULTS

The authors found a substantial reduction of hippocampal BDNF (n = 6 to 7) resulting from the transcriptional factors-mediated epigenetic modification in the promoter region of Bdnf exon IV in rats exposed postnatally to anesthetic drugs. This BDNF reduction led to the insufficient drive for the synthesis of synaptic proteins (n = 6 to 8), thus contributing to the hippocampal synaptic (n = 8 to 11) and cognitive dysfunction (n = 10) induced by neonatal anesthesia. These effects were mitigated by the exposure to an enriched environment.

CONCLUSIONS

The findings of this study elucidated the epigenetic mechanism underlying memory deficiency induced by neonatal anesthesia and propose EE as a potential therapeutic approach.

Exposure to Sevoflurane Affects the Development of Parvalbumin Interneurons in the Main Olfactory Bulb in Mice

Sevoflurane is widely used in adult and pediatric patients during clinical surgeries. Although studies have shown that exposure to sevoflurane impairs solfactory memory after an operation, the neuropathological changes underlying this effect are not clear. This study detected the effect of sevoflurane exposure on the development of calcium-binding proteins-expressing interneurons in the main olfactory bulb (MOB). We exposed neonatal mice to 2% sevoflurane at two different developmental time points and found that exposing mice to sevoflurane at postnatal day (PD) 7 significantly decreased the expression of GAD67 and parvalbumin (PV) in the olfactory bulb (OB) but did not alter the expression of calretinin (CR) or calbindin D28k (CB). The number and dendritic morphology of PV-expressing interneurons in the MOB were impaired by exposure to sevoflurane at PD7. However, exposure to sevoflurane at PD10 had no effect on calcium-binding protein expression or the number and dendritic morphology of PV-expressing interneurons in the MOB. These results suggest that exposing neonatal mice to sevoflurane during a critical period of olfactory development affects the development of PV-expressing interneurons in the MOB.

The Fas Ligand/Fas Death Receptor Pathways Contribute to Propofol-Induced Apoptosis and Neuroinflammation in the Brain of Neonatal Rats

A number of experimental studies have reported that exposure to common, clinically used anesthetics induce extensive neuroapoptosis and cognitive impairment when applied to young rodents, up to 2 weeks old, in phase of rapid synaptogenesis. Propofol is the most used general anesthetic in clinical practice whose mechanisms of neurotoxicity on the developing brain remains to be examined in depth. This study investigated effects of different exposures to propofol anesthesia on Fas receptor and Fas ligand expressions, which mediate proapoptotic and proinflammation signaling in the brain. Propofol (20 mg/kg) was administered to 7-day-old rats in multiple doses sufficient to maintain 2-, 4- and 6-h duration of anesthesia. Animals were sacrificed at 0, 4, 16 and 24 h after termination of anesthesia. It was found that propofol anesthesia induced Fas/FasL and downstream caspase-8 expression more prominently in the thalamus than in the cortex. Opposite, Bcl-2 and caspase-9, markers of intrinsic pathway activation, were shown to be more influenced by propofol treatment in the cortex. Further, we have established upregulation of caspase-1 and IL-1β cytokine transcription as well as subsequent activation of microglia that is potentially associated with brain inflammation. Behavioral analyses revealed that P35 and P60 animals, neonatally exposed to propofol, had significantly higher motor activity during three consecutive days of testing in the open field, though formation of the intersession habituation was not prevented. This data, together with our previous results, contributes to elucidation of complex mechanisms of propofol toxicity in developing brain.

Inhibiting NADPH oxidase protects against long-term memory impairment induced by neonatal sevoflurane exposure in mice

BACKGROUND

Neonatal exposure to anaesthetics such as sevoflurane has been reported to result in behavioural deficits in rodents. However, while oxidative injury is thought to play an underlying pathological role, the mechanisms of neurotoxicity remain unclear. In the present study, we investigated whether the NADPH oxidase inhibitor apocynin protects against long-term memory impairment produced by neonatal sevoflurane exposure in mice.

METHODS

Postnatal day six mice were divided into four groups; (1) non-anaesthesia, (2) intraperitoneal apocynin (50 mg kg(-1)) treatment, (3) 3% sevoflurane exposure for 6 h, and (4) apocynin treatment combined with sevoflurane exposure. Superoxide concentrations and NADPH oxidase expression in the brain were determined using dihydroethidium fluorescence and immunoblotting, respectively. Cleaved caspase-3 immunoblotting was used for the detection of apoptosis, and cytochrome c immunoblotting was performed to evaluate mitochondrial function. Long-term cognitive impairment was evaluated using the fear conditioning test in adulthood.

RESULTS

Sevoflurane exposure increased concentrations of superoxide (109%) and the NADPH oxidase subunit p22phox (39%) in the brain, and apocynin abolished these increases. Neonatal sevoflurane exposure caused learning deficits in adulthood. Apocynin also maintained long-term memory function in mice given neonatal sevoflurane exposure, and it reduced apoptosis and decreased cytochrome c concentrations in the brains of these mice.

CONCLUSIONS

Apocynin reduces neuronal apoptosis and protects against long-term memory impairment in mice, neonatally exposed to sevoflurane by reducing superoxide concentrations. These findings suggest that NADPH oxidase inhibitors may protect against cognitive dysfunction resulting from neonatal anaesthesia.

Autophagy activation prevents sevoflurane-induced neurotoxicity in H4 human neuroglioma cells

AIM

The inhaled anesthetic sevoflurane may induce cognitive impairment in both animals and humans. Previous study has shown that sevoflurane triggers ER stress and may lead to apoptosis in rat hippocampal neurons. In this study, we examined whether sevoflurane caused autophagy and its contributions to sevoflurane induced neuronal cell injury.

METHODS

H4 human neuroglioma cells were exposed to 4.1% sevoflurane for 6 h. Cell viability and apoptosis ratio were assessed using a CCK8 kit and flow cytometry, respectively. Autophagosomes in the cells were detected using GFP-LC3 plasmid transfection or transmission electronic microscopy. The expression of LC3B, p62/SQSTM, C/EBP homologous protein (CHOP) and glucose-related protein 78 (GRP78) was assessed with Western blotting.

RESULTS

Sevoflurane treatment induced apoptosis and markedly increased the LC3-II level and GFP-LC3 puncta number, decreased p62 expression in H4 cells. Activation of autophagy by rapamycin (1 μmol/L) significantly reduced sevoflurane-induced apoptosis and increased cell viability, whereas inhibition of autophagy with 3-MA (5 mmol/L) caused the opposite effects. Furthermore, sevoflurane treatment markedly increased the expression of CHOP and GRP78, two hallmark proteins of ER stress. Inhibition of ER stress by 4-phenylbutyrate (500 μmol/L) abrogated sevoflurane-induced autophagy and apoptosis, and improved the viability. Moreover, sevoflurane-stimulated expression of CHOP and GRP78 was inhibited by rapamycin, but further enhanced by 3-MA.

CONCLUSION

Sevoflurane treatment induces ER stress and activates autophagy, which antagonizes sevoflurane-induced apoptosis in H4 human neuroglioma cells. The results suggest that autophagy may be a potential therapeutic target in preventing sevoflurane-induced neurotoxicity.

Minocycline attenuates post-operative cognitive impairment in aged mice by inhibiting microglia activation

Although it is known that isoflurane exposure or surgery leads to post‐operative cognitive dysfunction in aged rodents, there are few clinical interventions and treatments available to prevent this disorder. Minocycline (MINO) produces neuroprotection from several neurodegenerative diseases and various experimental animal models. Therefore, we set out to investigate the effects of MINO pre‐treatment on isoflurane or surgery induced cognitive impairment in aged mice by assessing the hippocampal‐dependent spatial memory performance using the Morris water maze task. Hippocampal tissues were isolated from mice and evaluated by Western blot analysis, immunofluorescence procedures and protein array system. Our results elucidate that MINO down‐regulated the isoflurane‐induced and surgery‐induced enhancement in the protein levels of pro‐inflammatory cytokine tumour necrosis factor alpha, interleukin (IL)‐1β, interferon‐γ and microglia marker Iba‐1, and up‐regulated protein levels of the anti‐inflammatory cytokine IL‐4 and IL‐10. These findings suggest that pre‐treatment with MINO attenuated isoflurane or surgery induced cognitive impairment by inhibiting the overactivation of microglia in aged mice.

Anaesthesia in early childhood - is the development of the immature brain in danger?

Experimental studies performed on immature animal brains had demonstrated a neurotoxic effect following sedation and general anaesthetics administration. The same magnitude of neurotoxicity has been suggested but not been proven to neonates, infants and small children who have undergone anaesthesia. There is a justified and increasing inquiry regarding the administration of general anaesthesia to paediatric patients.

Sevoflurane prevents stroke-induced depressive and anxiety behaviors by promoting cannabinoid receptor subtype I-dependent interaction between β-arrestin 2 and extracellular signal-regulated kinases 1/2 in the rat hippocampus

One of the most frequent psychological consequences of stroke is depression. Previous animal studies have demonstrated that post-conditioning with sevoflurane protects against focal cerebral ischemia and reperfusion injury. Thus, we hypothesized that repeated exposure to sevoflurane after transient ischemia can prevent the development of depressive-like behavior. To test this hypothesis, we induced transient cerebral ischemia via transient occlusion of bilateral common carotid arteries and examined the effects of subsequent repeated exposure to sevoflurane on sucrose preference, locomotor activity, and rearing activity in rats. To explore the putative neurobiological mechanisms, we further investigated the roles of hippocampal CB1 receptor in the behavioral effects of sevoflurane. We found that repeated sevoflurane exposures reversed ischemia-induced depressive-like behaviors. Furthermore, CB1 receptor inhibition in the dorsal hippocampus (DH) abolished the effects of sevoflurane exposures on ischemia-induced depressive-like behaviors. In addition, repeated sevoflurane exposures increased CB1 receptor expression and endocannabinoids levels in the DH of ischemic rats. Moreover, repeated sevoflurane exposures enhanced the expression of β-arrestin 2, increased the activation of extracellular signal-regulated kinases (ERK)1/2, and promoted the interaction of β-arrestin 2 and ERK1/2 in the DH, and such effects were reversed by CB1 receptor antagonism in the DH. Finally, β-arrestin 2 expression and ERK1/2 activation in the DH were critical for the preventative effects of sevoflurane exposures on ischemia-induced depressive-like behaviors. Taken together, our results suggested that sevoflurane exposure after brain ischemia may prevent the development of depression, and such preventative effects of sevoflurane are likely ascribed to the activation of CB1 receptor-mediated β-arrestin 2-ERK1/2 signaling pathways. We propose that the following mechanisms are critical for the preventative effects of sevoflurane against post-stroke depressive and anxiety behaviors: repeated sevoflurane exposure after transient brain ischemia enhances N-arachidonoylethanolamine (AEA) and 2-Arachidonoylglycerol (2-AG) levels and normalize cannabinoid receptor type 1 (CB1) receptor expression in the dorsal hippocampus, which results in enhanced interaction of β-arrestin 2 and extracellular signal-regulated kinases (ERK1/2) and increased ERK1/2 activation, leading to decreased depressive and anxiety behaviors. We think these findings should provide a new strategy for treatment of post-stroke depression.

Sevoflurane inhibits embryonic stem cell self-renewal and subsequent neural differentiation by modulating the let-7a-Lin28 signaling pathway

The commonly used inhalational anesthetic, sevoflurane, can cause toxicity to the central nervous system of the developing fetus. Lin28 has been reported to regulate let-7a, thereby modulating embryo development, neurodegeneration, and even neuron-related tumorigenesis. We demonstrate that pregnant mice receiving sevoflurane treatment during the early stage of pregnancy give birth to fewer offspring presenting a lower birth weight. We have also treated mouse embryonic stem cells (mESCs) with sevoflurane for 6 h and determined that mESCs self-renewal is repressed, and that differentiation is initiated earlier than in controls. We have induced neural differentiation in the treated mESCs and determined that their neurogenesis is weakened. Furthermore, sevoflurane upregulates the level of let-7a, which might repress mESC self-renewal by directly targeting the Lin28 3'-untranslated region. Lin28 overexpression attenuates the influence of sevoflurane or of let-7a on the self-renewal of mESCs and their subsequent neural differentiation. The let-7a inhibitor also abolishes the influence of sevoflurane. Thus, the let-7a-Lin28 pathway is involved in the sevoflurane-induced inhibition of ESC self-renewal and subsequent neurogenesis. Our study demonstrates the molecular mechanism underlying the side effects of sevoflurane during early development, laying the foundation for studies on the safe and reasonable usage of other inhalational anesthetics.

Role of histone acetylation in long-term neurobehavioral effects of neonatal Exposure to sevoflurane in rats

Human studies, and especially laboratory studies, provide evidence that early life exposure to general anesthesia may affect neurocognitive development via largely unknown mechanisms. We explored whether hippocampal histone acetylation had a role in neurodevelopmental effects of sevoflurane administered to neonatal rats. Male Sprague-Dawley rats were exposed to 3% sevoflurane or were subjected to maternal separation only for 2h daily at postnatal days 6, 7, and 8. The histone deacetylase inhibitor, sodium butyrate (250mg/kg, intraperitoneally), or saline was administered starting 2h prior to anesthesia or maternal separation and continued daily until the end of behavioral tests, which were performed between postnatal days 33 and 50. Upon completion of the behavioral tests, the brain tissues were harvested for further analysis. Rats neonatally exposed to sevoflurane exhibited decreased freezing time in the fear conditioning contextual test and increased escape latency, decreased time in target quadrant, and number of platform crossings in the Morris water maze test. The sevoflurane-exposed rats had lower hippocampal density of dendritic spines, reduced levels of the brain-derived neurotrophic factor, c-fos protein, microtubule-associated protein 2, synapsin1, postsynaptic density protein 95, pCREB/CREB, CREB binding protein, and acetylated histones H3 and H4, and increased levels of histone deacetylases 3 and 8. These neurobehavioral abnormalities were normalized in the sevoflurane-exposed rats treated with sodium butyrate. Our findings provide evidence that neonatal exposure to sevoflurane induces neurobehavioral abnormalities and long-lasting alterations in histone acetylation; normalization of histone acetylation may alleviate the neurodevelopmental side effects of the anesthetic.

Suppression of ERK phosphorylation through oxidative stress is involved in the mechanism underlying sevoflurane-induced toxicity in the developing brain

In animal models, neonatal exposure to general anesthetics significantly increased neuronal apoptosis with subsequent behavioral deficits in adulthood. Although the underlying mechanism is largely unknown, involvement of extracellular signal-regulated kinases (ERKs) is speculated since ERK phosphorylation is decreased by neonatal anesthetic exposure. Importance of ERK phosphorylation for neuronal development is underscored by our recent finding that transient suppression of ERK phosphorylation during the neonatal period significantly increased neuronal apoptosis and induced behavioral deficits. However, it is still unknown as to what extent decreased ERK phosphorylation contributes to the mechanism underlying anesthetic-induced toxicity. Here we investigated the causal relationship of decreased ERK phosphorylation and anesthetic-induced toxicity in the developing brain. At postnatal day 6 (P6), mice were exposed to sevoflurane (2%) or the blood-brain barrier-penetrating MEK inhibitor, α-[amino[(4-aminophenyl)thio]methylene]-2-(trifluoromethyl)benzeneacetonitrile (SL327) (50 mg/kg). Transient suppression of ERK phosphorylation by an intraperitoneal injection of SL327 at P6 significantly increased apoptosis similar to sevoflurane-induced apoptosis. Conversely, SL327 administration at P14 or P21 did not induce apoptosis, even though ERK phosphorylation was inhibited. Restoring ERK phosphorylation by administration of molecular hydrogen ameliorated sevoflurane-induced apoptosis. Together, our results strongly suggests that suppressed ERK phosphorylation is critically involved in the mechanism underlying anesthetic-induced toxicity in the developing brain.

Intranasal Insulin Prevents Anesthesia-Induced Spatial Learning and Memory Deficit in Mice

Elderly individuals are at increased risk of cognitive decline after anesthesia. General anesthesia is believed to be a risk factor for Alzheimer’s disease (AD). At present, there is no treatment that can prevent anesthesia-induced postoperative cognitive dysfunction. Here, we treated mice with daily intranasal administration of insulin (1.75 U/day) for one week before anesthesia induced by intraperitoneal injection of propofol and maintained by inhalation of sevoflurane for 1 hr. We found that the insulin treatment prevented anesthesia-induced deficit in spatial learning and memory, as measured by Morris water maze task during 1–5 days after exposure to anesthesia. The insulin treatment also attenuated anesthesia-induced hyperphosphorylation of tau and promoted the expression of synaptic proteins and insulin signaling in the brain. These findings show a therapeutic potential of intranasal administration of insulin before surgery to reduce the risk of anesthesia-induced cognitive decline and AD.

Multiple sevoflurane exposures in infant monkeys do not impact the mother-infant bond

Exposure to general anesthesia during the postnatal period is associated with death of brain cells as well as long-term impairments in cognitive and emotional behavior in animal models. These models are critical for investigating mechanisms of pediatric anesthetic neurotoxicity as well as for testing potential strategies for preventing or mitigating this toxicity. Control conditions for anesthesia exposure involve separation of conscious infants from their mothers for variable periods of time, which could have its own effect on subsequent behavior because of stress to the mother and/or infant as a consequence of separation.We are conducting a long-term study of infant rhesus monkeys exposed three times for 4h each to sevoflurane anesthesia during the first six postnatal weeks, with a comparison condition of control infant monkeys that undergo brief maternal separations on the same schedule, to equate the period of time each infant is conscious and separated from its mother. Because mothers are separated from their infants longer for infants in the anesthesia condition, this could modify maternal behavior toward the infant, which may influence subsequent socioemotional behavior in the infants. In this study, we analyzed maternal behavior immediately after the first post-anesthesia (or control) reunion, as well as during reintroduction of the mother-infant pair to the larger social group 24 hpost-anesthesia or control separation, and found no differences between the conditions with mothers spending most of their time in contact with infants in all conditions analyzed. This indicates that the different durations of maternal separation in this study design do not impact the mother-infant bond, strengthening conclusions that subsequent differences in behavior between monkeys exposed to anesthesia compared to controls are a consequence of anesthesia exposure and not differential maternal behavior in the two conditions.

Isoflurane Is More Deleterious to Developing Brain Than Desflurane: The Role of the Akt/GSK3β Signaling Pathway

Demand is increasing for safer inhalational anesthetics for use in pediatric anesthesia. In this regard, researchers have debated whether isoflurane is more toxic to the developing brain than desflurane. In the present study, we compared the effects of postnatal exposure to isoflurane with those of desflurane on long-term cognitive performance and investigated the role of the Akt/GSK3β signaling pathway. Postnatal day 6 (P6) mice were exposed to either isoflurane or desflurane, after which the phosphorylation levels of Akt/GSK3β and learning and memory were assessed at P8 or P31. The phosphorylation levels of Akt/GSK3β and learning and memory were examined after intervention with lithium. We found that isoflurane, but not desflurane, impaired spatial learning and memory at P31. Accompanied by behavioral change, only isoflurane decreased p-Akt (ser473) and p-GSK3β (ser9) expressions, which led to GSK3β overactivation. Lithium prevented GSK3β overactivation and alleviated isoflurane-induced cognitive deficits. These results suggest that isoflurane is more likely to induce developmental neurotoxicity than desflurane in context of multiple exposures and that the Akt/GSK3β signaling pathway partly participates in this process. GSK3β inhibition might be an effective way to protect against developmental neurotoxicity.

Neurobehavioural abnormalities induced by repeated exposure of neonatal rats to sevoflurane can be aggravated by social isolation and enrichment deprivation initiated after exposure to the anaesthetic

BACKGROUND

We tested the hypothesis that developmental effects of repeated neonatal exposure to sevoflurane in rats are exacerbated by stressful experiences received later in life.

METHODS

Sprague-Dawley male rats received sequential exposures to 3% sevoflurane for two h on postnatal days (P) six, seven, and eight. After weaning at P21, rats were housed either in pairs in an enriched environment (EE) or singly in an enrichment-deprived environment (an adverse environment, AE). The hippocampal concentrations of brain-derived neurotrophic factor (BDNF), and synaptic markers were assessed at P8 and P53. The dentate gyrus neural progenitor proliferation was evaluated at P11 and P53 after administration of bromodeoyuridine (BrdU) at P8 to P10 and at P22 to P27, respectively. Neurobehavioural evaluations were performed at P49 to P53.

RESULTS

Repeated sevoflurane exposure acutely reduced concentrations of BDNF, synaptic markers and neural progenitor proliferation. The sevoflurane group housed in the AE conditions (sevoflurane+AE) had decreased concentrations of BDNF and synaptic markers, and survival of new granule cells and impaired cognitive function compared with the control+AE, control+EE, and sevoflurane+EE groups. The neurobehavioural parameters in the sevoflurane+EE and control+EE groups were similar.

CONCLUSIONS

Neurocognitive abnormalities induced by repeated neonatal exposure to sevoflurane can be aggravated by stressful conditions such as social isolation and enrichment deprivation.

Impact of propofol anaesthesia on cytokine expression profiles in the developing rat brain: a randomised placebo-controlled experimental in-vivo study

BACKGROUND

Recent experimental data indicate that volatile anaesthetics can induce a neuroinflammatory response in the central nervous system. The questions of to what extent this occurs in the developing brain and whether nonvolatile anaesthetics are also involved remain unanswered.

OBJECTIVES

The objective of this study is to investigate the impact of propofol anaesthesia on cytokine mRNA expression profiles in the neonatal brain at defined stages of the brain growth spurt.

DESIGN

A randomised placebo-controlled experimental in-vivo study.

SETTING

Translational research laboratories at the University of Geneva Medical School.

METHODS

Wistar rats received 6-h propofol anaesthesia at postnatal day 10 or 20. A quantitative real-time PCR was used to evaluate the impact of this treatment paradigm on mRNA expression profiles of selected members of the cytokine family in the prefrontal cortex and hippocampus.

RESULTS

Propofol anaesthesia induced a transient 1.8-fold (interquartile range, IQR 1.7 to 2.2) increase (P = 0.004) in prefrontal but not hippocampal tumour necrosis factor mRNA concentrations in 10-day-old animals. No such effect was detected in 20-day-old animals. No changes in mRNA concentrations of two other pro-inflammatory cytokines, interleukins IL-6 and IL-1β, were detected following drug exposure at any developmental stages or in any studied brain regions. In contrast, propofol anaesthesia at postnatal day 10 induced a transient increase in the mRNA expression patterns of two chemokines: Ccl2 and Ccl3 [for Ccl2 mRNA: 4.4-fold (3.8 to 5.6) increase in the prefrontal cortex, P = 0.0002 and a 3.5-fold (2.8 to 5.3) increase in the hippocampus, P = 0.0001; for Ccl3 mRNA: 2.9-fold (2.6 to 4.31) increase in the prefrontal cortex, P = 0.0001, and a 2.7-fold (2.2 to 3.6) increase in the hippocampus, P = 0.0003]. Propofol did not affect Ccl2 and Ccl3 mRNA concentrations in 20-day-old animals. In addition, it did not impact on two other members of the chemokine family, Cxcl1 and Cx3cl1, at any time points or in any brain regions investigated.

CONCLUSION

This study suggests that propofol anaesthesia does not have a major impact on pro-inflammatory cytokine expression profiles in the developing central nervous system during the brain growth spurt. These results raise arguments against the involvement of neuroinflammatory pathways in propofol-related neurotoxicity observed following the administration of this drug in the early postnatal period.

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.

Cerebral oxygen saturation after multiple perioperative influential factors predicts the occurrence of postoperative cognitive dysfunction

Background

Postoperative cognitive dysfunction (POCD) is a frequent complication in elderly patients undergoing major non-cardiac surgery, but its etiology is still unclear. Cerebral oxygen saturation (ScO₂) represents the balance of cerebral oxygen supply and demand. The aim of present study was to evaluate the relationship between perioperative ScO₂ and POCD, and to verify the hypothesis that the value of ScO₂ after multiple perioperative influential factors could predict POCD in elderly patients undergoing total knee arthroplasty (TKA).

Methods

Seventy eight Patients aged more than 65 years undergoing elective TKA with intrathecal anesthesia were enrolled. Cognitive functions were assessed one day before and 6 days after surgery, and POCD were defined according to ISPOCD. Demographics were recorded. Perioperative ScO₂, blood pressure (BP), blood gas analysis and other clinical data were monitored and recorded, then the decrease of ScO₂, BP and PaO₂ after influential factors were calculated.

Results

POCD occurred in 15 patients (19.2 %). BP decreased after anesthesia induction and tourniquet deflation, and PaO₂ decreased after cement implantation, then percentage decrease of BP was higher in POCD group. ScO₂ of POCD group is significantly lower than non-POCD group (P < 0.05), and the absolute value and percentage decrease of ScO₂ became significant between two groups after multiple influential factors. ScO₂ after all influential factors (anesthesia induction, cement implantation and tourniquet deflation) had the best predictive performance for POCD (AUC = 0.742), and the optimal threshold was 66.5 %.

Conclusions

Perioperative ScO₂ of patients with POCD is lower than patients without POCD. ScO₂ after multiple perioperative influential factors could be an effective predictor for POCD, which reveal an important role of ScO₂ decrease in the development of POCD and provide possible treatment target.

Acute and Long-Term Effects of Brief Sevoflurane Anesthesia During the Early Postnatal Period in Rats

The possibility that exposure to general anesthetics during early life results in long-term impairment of neural function attracted considerable interest over the past decade. Extensive laboratory data suggest that administration of these drugs during critical stages of central nervous system development can lead to cell death, impaired neurogenesis, and synaptic growth as well as cognitive deficits. These observations are corroborated by several recent human epidemiological studies arguing that such cognitive impairment might also occur in humans. Despite the potential public health importance of this issue, several important questions remain open. Amongst them, how the duration of anesthesia exposure impact on outcome is as yet not fully elucidated. To gain insight into this question, here we focused on the short- and long-term impact of a 30-min-long exposure to clinically relevant concentrations of sevoflurane in rat pups at 2 functionally distinct stages of the brain growth spurt. We show that this treatment paradigm induced developmental stage-dependent and brain region-specific acute but not lasting changes in dendritic spine densities. Electrophysiological recordings in hippocampal brain slices from adult animals exposed to anesthesia in the early postnatal period revealed larger paired-pulse facilitation but no changes in the long-term potentiation paradigm when compared with nonanesthetized controls. 5-bromo-2-deoxyuridine pulse and pulse-chase experiments demonstrated that neither proliferation nor differentiation and survival of hippocampal progenitors were affected by sevoflurane exposure. In addition, behavioral testing of short- and long-term memory showed no differences between control and sevoflurane-exposed animals. Overall, these results suggest that brief sevoflurane exposure during critical periods of early postnatal development, although it does not seem to exert major long-term effects on brain circuitry development, can induce subtle changes in synaptic plasticity and spine density of which the physiological significance remains to be determined.

A Mitochondrion-Targeted Antioxidant Ameliorates Isoflurane-Induced Cognitive Deficits in Aging Mice

Isoflurane possesses neurotoxicity and can induce cognitive deficits, particularly in aging mammals. Mitochondrial reactive oxygen species (mtROS) have been linked to the early pathogenesis of this disorder. However, the role of mtROS remains to be evaluated due to a lack of targeted method to treat mtROS. Here, we determined in aging mice the effects of the mitochondrion-targeted antioxidant SS-31, on cognitive deficits induced by isoflurane, a general inhalation anesthetic. We further investigated the possible mechanisms underlying the effects of SS-31 on hippocampal neuro-inflammation and apoptosis. The results showed that isoflurane induced hippocampus-dependent memory deficit, which was associated with mitochondrial dysfunction including reduced ATP contents, increased ROS levels, and mitochondrial swelling. Treatment with SS-31 significantly ameliorated isoflurane-induced cognitive deficits through the improvement of mitochondrial integrity and function. Mechanistically, SS-31 treatment suppressed pro-inflammatory responses by decreasing the levels of NF-κB, NLRP3, caspase 1, IL-1β, and TNF-α; and inhibited the apoptotic pathway by decreasing the Bax/Bcl-2 ratio, reducing the release of cytochrome C, and blocking the cleavage of caspase 3. Our results indicate that isoflurane-induced cognitive deficits may be attenuated by mitochondrion-targeted antioxidants, such as SS-31. Therefore, SS-31 may have therapeutic potentials in preventing injuries from oxidative stresses that contribute to anesthetic-induced neurotoxicity.

Efficacy of rutin in inhibiting neuronal apoptosis and cognitive disturbances in sevoflurane or propofol exposed neonatal mice

Sevoflurane and propofol are widely used in pediatric anesthesia. Neurotoxicity of sevoflurane and propofol in developing brain has been reported and these effects raise concerns on the usage of the drugs. We investigated the influence of rutin, a flavonoid on the neurodegenerative effects of sevoflurane and propofol and on memory and cognition in neonatal rodent model. Separate groups of neonatal mice (C57BL/6) were administered with rutin at 25 or 50 mg/kg body weight (b.wt) from post natal day 2 (P1) to P21. P7 mice were exposed to 2.9% sevoflurane and/or propofol (150 mg/kg b.wt). Neuroapoptosis was assessed by measuring activated caspase-3 and by Fluoro-Jade C staining. Plasma S100β levels were detected by ELISA. Morris water maze test was performed to test learning and memory impairments in the animals. General behaviour of the mice was also assessed. Anesthesia exposure caused severe neuroapoptosis and also raised the levels of plasma S100β. Neuroapoptosis, memory and cognitive deficits observed following anesthetics were comparatively more profound in mice on exposure to combined drug (sevoflurane and propofol) than in those exposed to either of the anesthetics. Rutin at both the doses was effective in reducing the apoptotic cell counts and enhanced the memory and cognitive abilities. Rutin supplementation offered significant protection against anesthetic induced neurodegeneration and learning and memory disturbances.

Isoflurane inhibits embryonic stem cell self-renewal through retinoic acid receptor

The commonly used inhalation anesthetic isoflurane could permeate rapidly through the placental barrier and induce toxicity to the central nervous system of the developing fetus. However, the effects of isoflurane in utero during early gestation are unknown. We therefore treated pregnant mice with 1.4% isoflurane for 2h per day for three days at day3.5 (E3.5) to day6.5 (E6.5) to investigated the toxicity of isoflurane. Pregnant mice were executed and the fetal mice were weighed and observed. Mouse ESCs (E14) was exposed to 2% isoflurane for 6h. Twenty-four hours later, self-renewal was examined with AP staining. Effects of isoflurane on the expression of RAR-γ were examined using Western blot. As a result, anesthesia with 1.4% isoflurane for 2 hour per day for 3 days reduced fetal growth and development. Isoflurane decreased self-renewal and the expression stemness genes (Nanog, Oct4, Sox2, and Lin28) in mESCs. Vitamin A attenuated the effects of isoflurane inducing self-renewal inhibition. In summary, Anesthesia with 1.4% isoflurane for 2h per day for 3 days reduced fetal growth and development. Moreover, isoflurane inhibits mESCs self-renewal through retinoic acid receptor.

Environmental Enrichment Ameliorates Neonatal Sevoflurane Exposure-Induced Cognitive and Synaptic Plasticity Impairments

Early exposure to sevoflurane, an inhalation anesthetic, induces neurodegeneration in the developing brain and subsequent long-term neurobehavioral abnormalities. Here, we investigated whether an enriched environment could mitigate neonatal sevoflurane exposure-induced long-term cognitive and synaptic plasticity impairments. Male C57BL/6 mice were exposed to 3 % sevoflurane 2 h daily for 3 days from postnatal day 6 (P6) to P8. The exposed mice were randomly allocated to an enriched environment for 2 h daily between P8 and P42 or to a standard environment. Their behavior and cognition were assessed using open field (P35) and fear conditioning tests (P41-P42). Hematoxylin-eosin staining was used to study morphological changes in pyramidal neurons of hippocampal CA1 and CA3 regions. Synaptic plasticity alternations were assessed using western blotting, Golgi staining, and electrophysiological recording. We found that sevoflurane-exposed mice housed in a standard environment exhibited a reduced freezing response in the contextual test, decreased number of dendritic spines on pyramidal neurons and synaptic plasticity-related proteins in the hippocampus, and impaired long-term potentiation. However, in an enriched environment, some of these abnormities induced by repeated sevoflurane exposure. In conclusion, neonatal sevoflurane exposure-induced cognitive and synaptic plasticity impairments are ameliorated by an enriched environment.

Therapeutic effects of intravenous administration of bone marrow stromal cells on sevoflurane-induced neuronal apoptosis and neuroinflammation in neonatal rats

Background

Sevoflurane exposure during the early postnatal period causes neuroinflammation and neuronal apoptosis in rodents. Bone marrow stromal cells (BMSCs) have been shown to protect and repair the damaged central nervous system, for example in ischemic stroke models. In this study, we investigated whether intravenous administration of BMSCs ameliorated neurodegeneration, induced by sevoflurane exposure, in neonatal rats.

Methods

Sprague-Dawley rat pups (postnatal day 7) were exposed to 2% sevoflurane for 6 h (vehicle group, n = 7). BMSCs were administered 30 min after induction of sevoflurane anesthesia (BMSCs group, n = 7). The pups were exposed to carrier gas only, as a negative control (mock anesthesia group, n = 4). We assessed the therapeutic effects of BMSC treatment by measuring expression of the pro-inflammatory cytokine interleukin-6 (IL-6), and levels of cleaved caspase-3, in brain tissues immediately following sevoflurane anesthesia.

Results

Analysis of the cleaved caspase-3 bands revealed that levels of activated caspase-3 were elevated in the vehicle group compared with the mock anesthesia group, indicating that a single exposure to sevoflurane at subclinical concentrations can precipitate neuronal apoptosis. BMSC treatment did not suppress apoptosis induced by sevoflurane exposure (compared with the vehicle group). The vehicle group had higher proinflammatory cytokine IL-6 protein levels compared with the mock anesthesia group, indicating that sevoflurane exposure induces IL-6 expression. BMSC treatment suppressed sevoflurane-induced increases in IL-6 expression, indicating that these cells can inhibit the neuroinflammation induced by sevoflurane exposure (vehicle group vs. BMSC group).

Conclusions

Intravenous administration of BMSCs reduces neuroinflammation, but does not attenuate apoptosis induced by sevoflurane exposure.

Toxic and protective effects of inhaled anaesthetics on the developing animal brain: systematic review and update of recent experimental work

BACKGROUND

Accumulating preclinical data indicate that neonatal exposure to general anaesthetics is detrimental to the central nervous system. Some studies, however, display potential protective effects of exactly the same anaesthetic agents on the immature brain. The effects of inhaled anaesthetics on the developing brain have received close attention from researchers, clinicians and the public in recent decades.

OBJECTIVES

To summarise the preclinical evidence reported in the last 5 years on both the deleterious effects and the neuroprotective potential in special indications, of inhaled anaesthetics on the developing brain.

DESIGN

A systematic review.

DATA SOURCES

PubMed search performed in June 2013.

ELIGIBILITY CRITERIA

Search terms included brain, development, inhaled anaesthetic, toxicity and protection within the scope of the last 5 years with animals. The reference lists of relevant articles and recent reviews were also hand-searched for additional studies. The type, dose and exposure duration of anaesthetics, species and age of animals, histopathologic indicators, outcomes and affected brain areas, neuro developmental test modules and outcomes, as well as other outcomes and comments were summarised.

RESULTS

Two hundred and nineteen relevant titles were initially revealed. In total, 81 articles were identified, with 68 articles assessing the detrimental effects induced by inhaled anaesthetics in the immature brain along with possible treatments. The remaining 13 articles focused on the protective profile of inhaled anaesthetics on perinatal hypoxic-ischaemic brain injury. Administration of inhaled anaesthetic agents to the immature brain was shown to be deleterious in several preclinical studies. In perinatal hypoxic-ischaemic brain injury models, pre- and postconditioning of inhalational anaesthetics exerted neuroprotective effects.

CONCLUSION

The majority of studies have linked inhaled anaesthetics to toxic effects in the neonatal brain of rodents, piglets and primates. Only a few studies, however, could demonstrate long-lasting cognitive impairment. The results of inhalational anaesthetic-induced neuroprotection in perinatal hypoxic-ischaemic brain injury are a promising basis for more research in this field. In general, prospective clinical trials are needed to further differentiate the effects of inhaled anaesthetics on the immature brain.

Long-term action of propofol on cognitive function and hippocampal neuroapoptosis in neonatal rats

Propofol is a short-acting anesthetic and generally is utilized for the induction and maintenance of anesthesia in pediatrics and adults. However, whether repeated use of propofol affects long-term cognitive function remains unclear. This study investigated the effects of propofol on cognitive function and hippocampal neuroapoptosis in neonatal rat. A total of 112 male newborn 7-day old Sprague-Dawley rats were randomly divided into 8 groups (n=14 rats per group) and intraperitoneally injected either with saline or propofol at 50, 100, and 150 mg/kg/day for 5 consecutive days. Four non-surgical groups were assigned as Con1, P50, P100, and P150. Four surgical groups were received an appendicectomy under propofol anesthesia and assigned as Con2, SP50, SP100, SP150. After 2 months raising, cognitive function, hippocampal neuroapoptosis, and intracephalic inflammatory cytokines were evaluated. There was no obvious effect on the cognitive function and neuroapoptosis after repeated use of propofol at a low dose for 5 days, whereas repeated use of propofol at a middle/high dose significantly increase the expression of apoptotic factors (caspase-3 and Bax), pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), and impair the cognitive function. Thus, our data suggest that repeated use of propofol at a low dose may be safe during the period of brain growth spurt. Using propofol at a recommended or higher dose for anaesthesia may lead to the cognitive defects, attributed to hippocampal neuroapoptosis and the overexpression of pro-inflammatory cytokines in the brain.

Environmental Enrichment Attenuated Sevoflurane-Induced Neurotoxicity through the PPAR-γ Signaling Pathway

Sevoflurane is the most widely used inhaled anesthetic. Environmental enrichment (EE) can reverse sevoflurane-induced learning and memory impairment in young mice. However, the mechanism by which EE elicits this effect is unclear. The peroxisome proliferator-activated receptor (PPAR) regulatory pathway plays a critical role in the regulation of inflammation in central nervous system diseases. In this study, we investigated whether EE attenuates sevoflurane-induced learning and memory disability via the PPAR signaling pathway. Six-day-old mice were treated with 3% sevoflurane for 2 hours daily from postnatal day 6 (P6) to P8. Then, the mice were treated with EE. The effects of sevoflurane on learning and memory function, PPAR-γ expression in the brain, and the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells and 5-bromodeoxyuridine-positive cells in the hippocampus were determined. Sevoflurane induced neuronal apoptosis and neurogenesis inhibition, which may impair learning and memory in young mice. Furthermore, sevoflurane downregulated PPAR-γ expression. Both EE and the PPAR-γ agonist, rosiglitazone, attenuated sevoflurane-induced neuronal apoptosis, neurogenesis inhibition, and learning and memory impairment. Our findings suggest that EE ameliorated sevoflurane-induced neurotoxicity and learning and memory impairment through the PPAR-γ signaling pathway. PPAR-γ may be a potential therapeutic target for preventing or treating sevoflurane-induced neurotoxicity.