Sevoflurane decreases self-renewal capacity and causes c-Jun N-terminal kinase-mediated damage of rat fetal neural stem cells

A Scoping Review of the Mechanisms Underlying Developmental Anesthetic Neurotoxicity

Although anesthesia makes painful or uncomfortable diagnostic and interventional health care procedures tolerable, it may also disrupt key cellular processes in neurons and glia, harm the developing brain, and thereby impair cognition and behavior in children. Many years of studies using in vitro, animal behavioral, retrospective database studies in humans, and several prospective clinical trials in humans have been invaluable in discerning the potential toxicity of anesthetics. The objective of this scoping review was to synthetize the evidence from preclinical studies for various mechanisms of toxicity across diverse experimental designs and relate their findings to those of recent clinical trials in real-world settings.

Overexpression of endothelial S1pr2 promotes blood-brain barrier disruption via JNK/c-Jun/MMP-9 pathway after traumatic brain injury in both in vivo and in vitro models

Objectives

The disruption of blood-brain barrier (BBB) is associated with poor outcomes of TBI patients. Sphingosine-1-phosphate receptor 2 (S1pr2), a member of the G protein-coupled receptor family, is involved in endothelial activation and the regulation of vascular integrity. We hypothesized that the inhibition of S1pr2 may alleviate BBB disruption and explored potential underlying molecular mechanisms.

Methods

Lesion volumes were assessed utilizing Nissl staining; neurological outcomes were evaluated through a battery of neurobehavioral assessments; phenotype-associated proteins were scrutinized via Western blot analysis; levels of reactive oxygen species (ROS), neuronal apoptosis, and S1pr2 expression were determined using immunofluorescence staining. The impact of S1pr2 inhibition after TBI and its underlying mechanism were elucidated using the selective S1pr2 inhibitor JTE-013, the JNK phosphorylation inhibitor SP600125, and cellular models. Chip-qPCR was employed to further elucidate the binding sites of the transcription factor c-Jun.

Results

The expression of S1pr2 significantly increased following TBI in mice. Pharmacological inhibition of S1pr2 alleviated secondary injury with reduced lesion volume, ROS generation, cerebral oedema, neurological deficits, and neuronal apoptosis; BBB disruption was also mitigated, accompanied by reduced degradation of tight junction proteins and decreased induction of matrix metalloproteinases-9 (MMP-9) post-TBI. Mechanistically, TBI induces an increase in S1pr2 specifically in endothelial cells, leading to the promotion of MMP-9 transactivation by enhancing JNK/c-Jun signaling. This results in the degradation of tight junction proteins and increased BBB permeability. Through in vitro and in vivo Chip-qPCR experiments, we verified that AP-1a and AP-1b of MMP-9 promoter function as binding sites for phosphorylated c-Jun.

Conclusion

Our findings identify a previously undisclosed role of S1pr2 in the pathophysiology of TBI. The S1pr2 inhibition presents a novel approach to alleviate BBB disruption after TBI through regulating the JNK/c-Jun/MMP-9 pathway.

Inhalation Anesthetics Play a Janus-Faced Role in Self-Renewal and Differentiation of Stem Cells

Inhalation anesthesia stands as a pivotal modality within clinical anesthesia practices. Beyond its primary anesthetic effects, inhaled anesthetics have non-anesthetic effects, exerting bidirectional influences on the physiological state of the body and disease progression. These effects encompass impaired cognitive function, inhibition of embryonic development, influence on tumor progression, and so forth. For many years, inhaled anesthetics were viewed as inhibitors of stem cell fate regulation. However, there is now a growing appreciation that inhaled anesthetics promote stem cell biological functions and thus are now regarded as a double-edged sword affecting stem cell fate. In this review, the effects of inhaled anesthetics on self-renewal and differentiation of neural stem cells (NSCs), embryonic stem cells (ESCs), and cancer stem cells (CSCs) were summarized. The mechanisms of inhaled anesthetics involving cell cycle, metabolism, stemness, and niche of stem cells were also discussed. A comprehensive understanding of these effects will enhance our comprehension of how inhaled anesthetics impact the human body, thus promising breakthroughs in the development of novel strategies for innovative stem cell therapy approaches.

Sevoflurane Induces a Cyclophilin D-Dependent Decrease of Neural Progenitor Cells Migration

Clinical studies have suggested that repeated exposure to anesthesia and surgery at a young age may increase the risk of cognitive impairment. Our previous research has shown that sevoflurane can affect neurogenesis and cognitive function in young animals by altering cyclophilin D (CypD) levels and mitochondrial function. Neural progenitor cells (NPCs) migration is associated with cognitive function in developing brains. However, it is unclear whether sevoflurane can regulate NPCs migration via changes in CypD. To address this question, we treated NPCs harvested from wild-type (WT) and CypD knockout (KO) mice and young WT and CypD KO mice with sevoflurane. We used immunofluorescence staining, wound healing assay, transwell assay, mass spectrometry, and Western blot to assess the effects of sevoflurane on CypD, reactive oxygen species (ROS), doublecortin levels, and NPCs migration. We showed that sevoflurane increased levels of CypD and ROS, decreased levels of doublecortin, and reduced migration of NPCs harvested from WT mice in vitro and in WT young mice. KO of CypD attenuated these effects, suggesting that a sevoflurane-induced decrease in NPCs migration is dependent on CypD. Our findings have established a system for future studies aimed at exploring the impacts of sevoflurane anesthesia on the impairment of NPCs migration.

Sevoflurane Exposure of Clinical Doses in Pregnant Rats Induces Vcan Changes without Significant Neural Apoptosis in the Offspring

Background and Objectives: Sevoflurane is a commonly used inhalational anaesthetic in clinics. Prolonged exposure to sevoflurane can induce significant changes in lipid metabolism and neuronal damage in the developing brain. However, the effect of exposure of pregnant rats to clinical doses of sevoflurane remains unclear. Materials and Methods: Twenty-eight pregnant rats were randomly and equally divided into sevoflurane exposure (S) group, control (C) and a blank group at gestational day (G) 18; Rats in S group received 2% sevoflurane with 98% oxygen for 6 h in an anesthetizing chamber, while C group received 100% oxygen at an identical flow rate for 6 h in an identical chamber. Partial least squares discriminant analysis (PLS-DA), ultra performance liquid chromatography/time-of-flight mass spectrometry(UPLC/TOF-MS) and MetaboAnalyst were used to analysis acquire metabolomics profiles, and immunohistochemical changes of neuronalapoptosis in hippocampus and cortex of neonatal rats were also analyzed. Results: This study aimed to explore lipidomics and transcriptomics changes related to 2% sevoflurane exposure for 6 h in the developing brains of newborn offspring rats. Ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOF-MS) and RNA sequencing (RNA-seq) analyses were used to acquire metabolomics and transcriptomics profiles. We used RNA-seq to analyse the expression of the coding and non-coding transcripts in neural cells of the cerebral cortex. No significant differences in arterial oxygen tension (PaO₂), arterial carbon dioxide tension (PaCO₂), or arterial blood gas were found between the groups. The relative standard deviation (RSD) of retention times was <1.53%, and the RSDs of peak areas ranged from 2.13% to 8.51%. Base peak chromatogram (BPC) profiles showed no differences between the groups. We evaluated the partial least square-discriminant analysis (PLS-DA) model. In negative ion mode, R2X was over 70%, R2Y was over 93%, and Q2 (cum) was over 80%. Cell apoptosis was not remarkably enhanced by TUNEL and haematoxylin and eosin (HE) staining in the sevoflurane-exposed group compared to the control group (p > 0.05). Glycerophospholipid (GP) and sphingolipid metabolism disturbances might adversely influence neurodevelopment in offspring. The expression of mRNAs (Vcan gene, related to neuronal development, function and repair) of the sevoflurane group was significantly increased in the differential genes by qRT-PCR verification. Conclusions: GP and sphingolipid metabolism homeostasis may be potential therapeutic approaches against inhalational anaesthetic-induced neurodegenerative disorders. Meanwhile, sevoflurane-induced Vcan changes indicated some lipidomic and transcriptomic changes, even if neural cell apoptosis was not significantly changed in the usual clinical dose of sevoflurane exposure.

Effects of Sevoflurane Exposure on Fetal Brain Development Using Cerebral Organoids

Sevoflurane is a safe and well-known inhaled anesthetic. Given that sevoflurane can be delivered to developing fetuses through the mother, it is critical to determine whether this agent affects fetal neurodevelopment. Recent research has sought to determine whether sevoflurane affects fetal brain development when the mother is exposed during the second to third trimester of pregnancy, considered to be the crucial period for the development of nervous system. However, even though the first trimester is a critical period for fetal organogenesis and the most susceptible time to teratogen exposure, research regarding the effects of sevoflurane on organogenesis, especially on brain development, is insufficient. In the present study, human embryonic stem cells (hESC)-derived cerebral organoids were exposed to sevoflurane during the time corresponding to the first trimester to investigate the effect of early sevoflurane exposure on fetal brain development, specifically the processes of neuronal differentiation and maturation. Organoid size exposed to the intermediate concentration of sevoflurane did not differ from control, immunofluorescence demonstrated that sevoflurane temporarily decreased the size of SOX2 + /N-cad + ventricular zone structures only during the mid-time point, and upregulated expression of TUJ1 and MAP2 only during the early time point. However, all markers returned to normal levels, and organoids formed normal cortical structures at the late time point. Our results suggest that maternal sevoflurane exposure during the first trimester of pregnancy can cause abnormal neuronal differentiation in the fetal brain. However, considering the recovery observed in later periods, sevoflurane exposure might not have lasting impacts on fetal brain development.

Research progress on the effects and mechanisms of anesthetics on neural stem cells

Exposure to anesthetic drugs has been proven to seriously affect developing animals in terms of neural stem cells' (NSCs') proliferation, differentiation, and apoptosis. This can severely hamper the development of physiological learning and memory skills. Studies on the effects of anesthetics on NSCs' proliferation and differentiation are thus reviewed here, with the aim to highlight which specific drug mechanisms are the least harmful to NSCs. PubMed has been used as the preferential searching database of relevant literature to identify studies on the effects and mechanisms of NSCs' proliferation and differentiation. It was concluded that propofol and sevoflurane may be the safest options for NSCs during pregnancy and in pediatric clinical procedures, while dexmedetomidine has been found to reduce opioid-related damage in NSCs. It was also found that the growth environment may impact neurodevelopment even more than narcotic drugs. Nonetheless, the current scientific literature available further highlights how more extensive clinical trials are absolutely required for corroborating the conclusion drawn here.

Carnosol alleviates sevoflurane-induced cognitive dysfunction by mediating NF-κB pathway in aged rats

Postoperative Cognitive Dysfunction (POCD) is a neurological disorder of unconsciousness due to cognitive regression after surgical anesthesia. However, the specific mechanism has not yet been clarified. Sevoflurane (SEV) is one of the most commonly used anesthetics in clinical practice, and how SEV mediates the generation of POCD is unclear. Carnosol, a natural ingredient, has been reported to have various beneficial effects such as anti-inflammatory, immune enhancement, and so forth, but how it ameliorates SEV-mediated neurotoxicity remains unclear. This study aimed to induce a POCD model in aged rats by SEV and to elucidate how Carnosol ameliorated SEV-mediated neurotoxicity. The effects of Carnosol on the expression of inflammatory factors in rat hippocampus mediated by SEV were determined by enzyme-linked immunoassay and polymerase chain reaction experiments; the effects of Carnosol on the expressions of Iba-1 and glial fibrillary acidic protein after SEV-mediated activation of rat microglia were clarified by immunofluorescence and Western blotting (WB); The effects of Carnosol on SEV-mediated neuronal apoptosis were studied by terminal deoxynucleotidyl transferase dUTP nick end labeling and WB; the specific signaling pathways regulated by Carnosol were elucidated by WB. The results showed that Carnosol can improve the cognitive dysfunction and reduce neuroinflammation in aged rats induced by SEV; Carnosol can reduce the activation of microglia and inhibit neuronal apoptosis in aged rats induced by SEV; Carnosol can phosphorylate p65 and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha regulates the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Carnosol can attenuate SEV-induced neuroinflammation, prevent microglial activation and inhibit neuronal apoptosis by modulating the NF-κB pathway.

LncRNA Rian ameliorates sevoflurane anesthesia-induced cognitive dysfunction through regulation of miR-143-3p/LIMK1 axis

Sevoflurane could stimulate neurotoxicity and result in postoperative cognitive dysfunction (POCD). Long non-coding RNAs (lncRNAs) have been implicated in the regulation of nervous system disease. This study was performed to investigate role and mechanism of lncRNA Rian (RNA imprinted and accumulated in nucleus) in sevoflurane anesthesia-induced cognitive dysfunction. Mice post-sevoflurane anesthesia showed cognitive impairments and neuronal damage and apoptosis. However, intracerebroventricularly injection with Adenovirus (Ad) for the over-expression of Rian ameliorated sevoflurane-induced neuronal damage and apoptosis. Cognitive impairments induced by sevoflurane were attenuated by injection with Ad-Rian. Moreover, transfection with Ad-Rian also protected isolated primary hippocampal neurons against sevoflurane-induced decrease of cell viability and increase of lactic acid dehydrogenase (LDH) and apoptosis. Mechanistically, Rian bind to miR-143-3p, and decreased expression of LIMK1 (Lim kinase 1) through negative regulation of miR-143-3p. Knockdown of LIMK1 aggravated sevoflurane-induced decrease of cell viability and increase of LDH and apoptosis in neurons, while over-expression attenuated LIMK1 silence-induced neuronal damage post-sevoflurane anesthesia. In conclusion, Rian demonstrated neuroprotective effects against sevoflurane anesthesia-induced cognitive dysfunction through regulation of miR-143-3p/LIMK1 axis, providing promising target for sevoflurane anesthesia-induced cognitive dysfunction.

Induced pluripotent stem cells as a platform to understand patient-specific responses to opioids and anaesthetics

Recent advances in human induced pluripotent stem cell (iPSC) technology may provide unprecedented opportunities to study patient-specific responses to anaesthetics and opioids. In this review, we will (1) examine the advantages and limitations of iPSC technology, (2) summarize studies using iPSCs that have contributed to our current understanding of anaesthetics and opioid action on the cardiovascular system and central nervous system (CNS), and (3) describe how iPSC technology can be used to further develop personalized analgesic and sedative pharmacotherapies with reduced or minimal detrimental cardiovascular effects.

Glioma-derived exosomes drive the differentiation of neural stem cells to astrocytes

Exosomes appear to be effective inter-cellular communicators delivering several types of molecules, such as proteins and RNAs, suggesting that they could influence neural stem cell (NSC) differentiation. Our RNA sequencing studies demonstrated that the RNAs related to cell proliferation and astrocyte differentiation were upregulated in human mesenchymal stem cells (hMSC) when co-cultured with exosomes obtained from the culture medium of human glioma cells (U87). Metallothionein 3 and elastin genes, which are related to cell proliferation, increased 10 and 7.2 fold, respectively. Expression of genes for astrocyte differentiation, such as tumor growth factor alpha, induced protein 3 of the NOTCH1 family, colony stimulating factor and interleukin 6 of the STAT3 family and Hes family bHLH transcription factor 1 also increased by 2.3, 10, 4.7 and 2.9 fold, respectively. We further examined the effects of these exosomes on rat fetal neural stem cell (rNSC) differentiation using the secreted exosomes from U87 glioma cells or exosomes from U87 cells that were stimulated with interleukin 1β (IL-1β). The rNSCs, extracted from rat brains at embryonic day 14 (E14), underwent a culture protocol that normally leads to predominant (~90%) differentiation to ODCs. However, in the presence of the exosomes from untreated or IL-1β-treated U87 cells, significantly more cells differentiated into astrocytes, especially in the presence of exosomes obtained from the IL-1β-challenged glioma cells. Moreover, glioma-derived exosomes appeared to inhibit rNSC differentiation into ODCs or astrocytes as indicated by a significantly increased population of unlabeled cells. A portion of the resulting astrocytes co-expressed both CD133 and glial fibrillary acidic protein (GFAP) suggesting that exosomes from U87 cells could promote astrocytic differentiation of NSCs with features expected from a transformed cell. Our data clearly demonstrated that exosomes secreted by human glioma cells provide a strong driving force for rat neural stem cells to differentiate into astrocytes, uncovering potential pathways and therapeutic targets that might control this aggressive tumor type.

Role of the GABAA receptors in the long-term cognitive impairments caused by neonatal sevoflurane exposure

Sevoflurane is a widely used inhalational anesthetic in pediatric surgeries, which is considered reasonably safe and reversible upon withdrawal. However, recent preclinical studies suggested that peri-neonatal sevoflurane exposure may cause developmental abnormalities in the brain. The present review aimed to present and discuss the accumulating experimental data regarding the undesirable effects of sevoflurane on brain development as revealed by the laboratory studies. First, we summarized the long-lasting side effects of neonatal sevoflurane exposure on cognitive functions. Subsequently, we presented the structural changes, namely, neuroapoptosis, neurogenesis and synaptogenesis, following sevoflurane exposure in the immature brain. Finally, we also discussed the potential mechanisms underlying subsequent cognitive impairments later in life, which are induced by neonatal sevoflurane exposure and pointed out potential strategies for mitigating sevoflurane-induced long-term cognitive impairments. The type A gamma-amino butyric acid (GABAA) receptor, the main targets of sevoflurane, is excitatory rather than inhibitory in the immature neurons. The excitatory effects of the GABAA receptors have been linked to increased neuroapoptosis, elevated serum corticosterone levels and epigenetic modifications following neonatal sevoflurane exposure in rodents, which might contribute to sevoflurane-induced long-term cognitive abnormalities. We proposed that the excitatory GABAA receptor-mediated HPA axis activity might be a novel mechanism underlying sevoflurane-induced long-term cognitive impairments. More studies are needed to investigate the effectiveness and mechanisms by targeting the excitatory GABAA receptor as a prevention strategy to alleviate cognitive deficits induced by neonatal sevoflurane exposure in future.

Dexmedetomidine Alleviates Neurogenesis Damage Following Neonatal Midazolam Exposure in Rats through JNK and P38 MAPK Pathways

Midazolam, a widely used anesthetic, inhibits proliferation of neural stem cells (NSCs) and induces neuroapoptosis in neonates. Dexmedetomidine, an effective auxiliary medicine in clinical anesthesia, protects the developing brain against volatile anesthetic-induced neuroapoptosis. Whether dexmedetomidine protects against neurogenesis damage induced by midazolam remains unknown. This study aims to clarify the protective effect of dexmedetomidine on midazolam-induced neurogenesis damage and explore its potential mechanism. Postnatal 7-day-old Sprague-Dawley (SD) rats and cultured NSCs were treated with either normal saline, midazolam, or dexmedetomidine combined with midazolam. The rats were sacrificed at 1, 3, and 7 days after treatment. Cell proliferation was assessed by 5-bromodeoxyurdine (BrdU) incorporation. Cell viability was determined using MTT assay. Cell differentiation and apoptosis were detected by immunofluorescent staining and terminal dUTP nick-end labeling (TUNEL), respectively. The protein levels of p-JNK, p-P38, and cleaved caspase-3 were quantified using Western blotting. Midazolam decreased cell proliferation and increased cell apoptosis in the subventricular zone (SVZ), the subgranular zone (SGZ) of the hippocampus, and cultured NSCs. Moreover, midazolam decreased cell viability and increased the expression of p-JNK and p-P38 in cultured NSCs. Co-treatment with dexmedetomidine attenuated midazolam-induced changes in cell proliferation, viability, apoptosis, and protein expression of p-JNK and p-P38 in cultured NSCs. Midazolam and dexmedetomidine did not affect the differentiation of the cultured NSCs. These results indicate that dexmedetomidine alleviated midazolam-induced neurogenesis damage via JNK and P38 MAPK pathways.

Plasmonic nano surface for neuronal differentiation and manipulation

Neurodegenerative diseases and traumatic brain injuries can destroy neurons, resulting in sensory and motor function loss. Transplantation of differentiated neurons from stem cells could help restore such lost functions. Plasmonic gold nanorods (AuNR) were integrated in growth surfaces to stimulate and modulate neural cells in order to tune cell physiology. An AuNR nanocomposite system was fabricated, characterized, and then utilized to study the differentiation of embryonic rat neural stem cells (NSCs). Results demonstrated that this plasmonic surface 1) accelerated differentiation, yielding almost twice as many differentiated neural cells as a traditional NSC culture surface coated with poly-D-lysine and laminin for the same time period; and 2) promoted differentiation of NSCs into neurons and astrocytes in a 2:1 ratio, as evidenced by the expression of relevant marker proteins. These results indicate that the design and properties of this AuNR plasmonic surface would be advantageous for tissue engineering to address neural degeneration.

Sevoflurane induces neurotoxicity in the developing rat hippocampus by upregulating connexin 43 via the JNK/c-Jun/AP-1 pathway

As one of the most popular anesthetics, sevoflurane is widely used in pediatric anesthesia. Unfortunately, an increasing number of studies have demonstrated that sevoflurane has potential neurotoxic effects on the developing brain and cognition, even in adolescence. Connexin 43 (Cx43) has been documented to contribute to cognitive dysfunction. The present study hypothesized that Cx43 may participate in sevoflurane-induced neuroinjury and investigated the underlying mechanisms in young Sprague Dawley (SD) rats. Seven-day-old SD rats (P7) were exposed to 3% sevoflurane for 4 h. The levels of Cx43,mitogen-activated protein kinase (MAPK) signaling pathway components(including total and phosphorylated p38, extracellular signal-regulated kinase (ERK), and c-Jun n-terminal kinase (JNK) and activator protein 1(AP-1) transcription factors (including total and phosphorylated c-Fos, and c-Jun) were assessed by Western blot analysis. Neuronal apoptosis was detected using immunohistochemistry (IHC). The Morris water maze (MWM) was performed to evaluate cognitive function from P28 to P33. The results showed that anesthesia with 3% sevoflurane for 4 h increased Cx43 levels in the rat hippocampus from 6 h to 3 d, and compared with sevoflurane exposure in the control group rats, exposure in P7 SD rats also increased the ratios of phosphorylated JNK to JNK and, phosphorylated c-Jun to c-Jun in the hippocampus from 6 h to 3 d. All these effects could be alleviated by pretreatment with the JNK inhibitor SP600125 (10 mg/kg). Neuroapoptosis was similarly increased from 6 h to 1 d after inhaled sevoflurane exposure. Finally, the MWM indicated that sevoflurane could increase the escape latency and, decrease the number of platform crossings from P28 to P33. Overall, our findings suggested that sevoflurane increased Cx43 expression and induced to apoptosis by activating the JNK/c-Jun signaling pathway in the hippocampus of P7 rats. This finding may reveal a new strategy for preventing sevoflurane-induced neuronal dysfunction.

Sevoflurane anesthesia represses neurogenesis of hippocampus neural stem cells via regulating microRNA-183-mediated NR4A2 in newborn rats

Sevoflurane has been commonly utilized in nonobstetric surgeries in pregnant women, and its impacts on fetal brain are still not completely known. Ectopic NR4A2 expression has been reported to be related with familial Parkinson disease, and through dual luciferase we found that NR4A2 is a target gene of microRNA-183 (miR-183). We proposed a hypothesis that miR-183 may participate in the process by targeting NR4A2 in neurons after sevoflurane anesthesia. To verify the effect of sevoflurane on hippocampal neural stem cells (NSCs) proliferation and differentiation, we conducted EdU assay and immunofluorescence staining. Next, for better understanding of the impact of miR-183, we altered the miR-183 expression using mimic and inhibitor. Meanwhile, the targeting relationship between miR-183 and NR4A2 was validated by a bioinformatics website and dual-luciferase reporter gene assay. Finally, expressions of miR-184, NR4A2, SRY (sex-determining region Y)-box 2 (Sox2), and brain-derived neurotrophic factor (BDNF) were determined and evaluated by reverse transcription quantitative polymerase chain reaction and western blot analysis. First, sevoflurane was determined a crucial factor in biological behaviors of hippocampal NSCs. Moreover, upregulated miR-183 expression by mimic inhibited the proliferation and differentiation of NSCs. Sevoflurane negatively regulated NR4A2 and Sox2 expressions but positively regulated miR-183 and BDNF expressions. Our findings revealed the underlying novel mechanism by which sevoflurane inhibits hippocampal NSC proliferation and differentiation through interaction with miR-183 and NR4A2. The study provides reliable reference for safe application of sevoflurane anesthesia in neonates.

Sevoflurane affects neurogenesis through cell cycle arrest via inhibiting wnt/β-catenin signaling pathway in mouse neural stem cells

AIMS

The development of central nervous system requires proliferation of neural stem cells followed by differentiation. Cell cycle parameters are closely related with cell fate specification and differentiation. Recent researches indicated that wnt/β-catenin signaling pathway might cause proliferation inhibition and differentiation abnormality through interfering NSCs cell cycle. Our previous research also showed that multiple sevoflurane exposure to neural stem cells inhibited proliferation via repressing transcription factor Pax6 and cyclin D1 through inhibiting wnt/β-catenin pathway. All above encouraged us to figure out the effect of sevoflurane on cell cycle and neurogenesis.

MAIN METHODS

Primary mouse cultured neural stem cells were used and exposed to 4.1% sevoflurane for 6 h in this study. The expression of β-catenin, GSK-3β, c-myc and cyclin D1 were determined by western blot and qRT-PCR. FACS was used to measure the cell cycle. The proliferation of NSCs was evaluated by EdU staining while the differentiation was evaluated by Tuj1 and GFAP staining on immunocytochemistry.

KEY FINDINGS

We found that exposure to sevoflurane at a concentration of 4.1% for 6 h induced inhibition of wnt/β-catenin pathway, cell cycle arrest at G0/G1 phase and an earlier switch from proliferation to differentiation. GSK-3β specific inhibitor, CHIR99021, attenuated sevoflurane-induced cell cycle arrest and abnormality of neurogenesis in neural stem cells.

SIGNIFICANCE

Our research suggested that sevoflurane arrested cell cycle at G0/G1 phase through inhibition of wnt/β-catenin signaling pathway thus resulting in a premature differentiation in NSCs. This study presents a deeper understanding of the mechanism on cognitive impairment by sevoflurane exposure.

Neonatal Exposure to Low-Dose (1.2%) Sevoflurane Increases Rats' Hippocampal Neurogenesis and Synaptic Plasticity in Later Life

The increasing usage of general anesthetics on young children and infants has drawn extensive attention to the effects of these drugs on cognitive function later in life. Recent animal studies have revealed improvement in hippocampus-dependent performance after lower concentrations of sevoflurane exposure. However, the long-term effects of low-dose sevoflurane on the developing brain remain elusive. On postnatal day (P) 7, rats were treated with 1.2% sevoflurane (1.2% sevo group), 2.4% sevoflurane (2.4% sevo group), and air control (C group) for 6 h. On P35-40, rats' hippocampus-dependent learning and memory was tested using the Morris water maze. Cognition-related and synapse-related proteins in the hippocampus were measured using Western blotting on P35. On the same day, neurogenesis and synapse ultrastructure were evaluated using immunofluorescence and transmission electron microscopy (TEM). On P35, the rats neonatally exposed to 1.2% sevoflurane showed better behavioral results than control rats, but not in the 2.4% sevo group. Exposure to 1.2% sevoflurane increased the number of 5'-bromo-2-deoxyuridine (BrdU)-positive cells in the dentate gyrus and improved both synaptic number and ultrastructure in the hippocampus. The expression levels of BDNF, TrkB, postsynaptic density (PSD)-95, and synaptophysin in the hippocampus were also increased in the 1.2% sevo group. In contrast, no significant changes in neurogenesis or synaptic plasticity were observed between the C group and the 2.4% sevo group on P35. These results showed that exposure of the developing brain to a low concentration of sevoflurane for 6 h could promote spatial learning and memory function, along with increased hippocampal neurogenesis and synaptic plasticity, in later life.

MicroRNA-188-3p is involved in sevoflurane anesthesia-induced neuroapoptosis by targeting MDM2

Sevoflurane is a commonly used inhalation anesthetic. Sevoflurane-induced neuroapoptosis and cognitive impairments in animals are widely reported, however, the underlying molecular mechanisms remain largely unknown. The results of the present study demonstrated that sevoflurane anesthesia induced spatial memory impairments in rats, as determined by the Morris water maze test. Mechanistically, the current study demonstrated that sevoflurane administration significantly enhanced the expression of microRNA (miR)-188-3p. Furthermore, inhibition of miR-188-3p using lentiviral miR-188-3p inhibitors attenuated sevoflurane-induced cognitive impairments in rats. The present study also demonstrated that miR-188-3p targeted MDM2 proto-oncogene (MDM2) and negatively regulated the expression of MDM2, as determined by luciferase assays, reverse transcription-quantitative polymerase chain reaction and western blot analysis. Furthermore, decreased abundance of MDM2 following transfection with miR-188-3p mimics was associated with increased stability of p53 protein. Suppression of p53 activity using the specific p53 inhibitor pifithrin-α alleviated sevoflurane-induced neuroapoptosis. These results indicate that the miR-188-3p-MDM2-p53 axis may have a critical role in sevoflurane-induced cognitive dysfunction. Therefore, miR-188-3p may be a potential target for the treatment of sevoflurane-induced cognitive impairment.