Sevoflurane causes neuronal apoptosis and adaptability changes of neonatal rats

Unraveling the signaling network between dysregulated microRNA and mRNA expression in sevoflurane-induced developmental neurotoxicity in rat

Research has indicated that general anesthesia may cause neuroapoptosis and long-term cognitive dysfunction in developing animals, however, the precise mechanisms orchestrating these outcomes remain inadequately elucidated within scholarly discourse. The purpose of this study was to investigate the impact of sevoflurane on the hippocampus of developing rats by analyzing the changes in microRNA and mRNA and their interactions. Rats were exposed to sevoflurane for 4 h on their seventh day after birth, and the hippocampus was collected for analysis of neuroapoptosis by Western blot and immunohistochemistry. High-throughput sequencing was conducted to analyze the variances in miRNA and mRNA expression levels, and the Morris water maze was employed to assess long-term memory in rats exposed to sevoflurane after 8 weeks. The results showed that sevoflurane exposure led to dysregulation of 5 miRNAs and 306 mRNAs in the hippocampus. Bioinformatic analysis revealed that these dysregulated miRNA-mRNA target pairs were associated with pathological neurodevelopment and developmental disorders, such as regulation of axonogenesis, regulation of neuron projection development, regulation of neuron differentiation, transmission of nerve impulse, and neuronal cell body. Further analysis showed that these miRNAs formed potential network interactions with 44 mRNAs, and two important nodes were identified, miR-130b-5p and miR-449c-5p. Overall, this study suggests that the dysregulation of the miRNA-mRNA signaling network induced by sevoflurane may contribute to neurodevelopmental toxicity in the hippocampus of rats and be associated with long-term cognitive dysfunction.

Efficacy of melatonin in alleviating disorders arising from repeated exposure to sevoflurane in males and females of the Wistar rats during preadolescence

Pediatricians use sevoflurane due to its fast action and short recovery time. However, studies have shown that repeated exposure to anesthesia can affect learning and memory. Melatonin, an indole-type neuroendocrine hormone, has significant anti-inflammatory, and neuroprotective properties. Melatonin's impact on cognitive behavior in sevoflurane-anesthetized males and females of the Wistar rats during preadolescence was examined in this research. The cognitive function was evaluated by shuttle box and morris water maze tests, while interleukin-10, Catalase (CAT), Malondialdehyde (MDA), and Tumor Necrosis Factor-α (TNF-α) were evaluated using ELISA kits. The expression levels of the apoptosis-linked proteins, Bax, Bcl-2, and caspase-3, were determined using the western blotting technique. The learning and memory latencies of the rats were more significant in the sevoflurane groups than in the control group; however, the latencies were significantly shorter in the sevoflurane and melatonin groups than in the control group. The levels of MDA, TNF-α, Bax, and caspase-3 were significantly higher in the sevoflurane groups than in the control group. We also found that the levels of CAT and Bcl-2 were significantly reduced in the sevoflurane groups compared to the control group. Increasing levels of CAT, Bcl-2, and decreasing levels of MDA, TNF-α, Bax, and caspase-3 in response to melatonin indicate a possible contribution to the recovery from the sevoflurane impairment. Melatonin shows neuroprotective effects in male and female rats with sevoflurane-induced cognitive impairment. This suggests melatonin could be a valuable treatment for learning and memory deficits resulting from repeated exposure to sevoflurane, possibly by controlling apoptosis, oxidative stress, and inflammation.

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

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

Sevoflurane Exposure Induces Neuronal Cell Ferroptosis Initiated by Increase of Intracellular Hydrogen Peroxide in the Developing Brain via ER Stress ATF3 Activation

Neuronal cell death is acknowledged as the primary pathological basis underlying developmental neurotoxicity in response to sevoflurane exposure, but the exact mechanism remains unclear. Ferroptosis is a form of programmed cell death characterized by iron-dependent lipid peroxidation that is driven by hydrogen peroxide (H2O2) and ferrous iron through the Fenton reaction and participates in the pathogenesis of multiple neurological diseases. As stress response factor, activating transcription factor 3 (ATF3) can be activated by the PERK/ATF4 pathway during endoplasmic reticulum (ER) stress, followed by increased intracellular H2O2, which is involved in regulation of apoptosis, autophagy, and ferroptosis. Here, we investigated whether ferroptosis and ATF3 activation were implicated in sevoflurane-induced neuronal cell death in the developing brain. The results showed that sevoflurane exposure induced neuronal death as a result of iron-dependent lipid peroxidation damage secondary to H2O2 accumulation and ferrous iron increase, which was consistent with the criteria for ferroptosis. Furthermore, we observed that increases in iron and H2O2 induced by sevoflurane exposure were associated with the upregulation and nuclear translocation of ATF3 in response to ER stress. Knockdown of ATF3 expression alleviated iron-dependent lipid peroxidation, which prevented sevoflurane-induced neuronal ferroptosis. Mechanistically, ATF3 promoted sevoflurane-induced H2O2 accumulation by activating NOX4 and suppressing catalase, GPX4, and SLC7A11 expression. Additionally, an increase in H2O2 was accompanied by the upregulation of TFR and TF and downregulation of FPN, which linked iron overload to ferroptosis induced by sevoflurane. Taken together, our results demonstrated that ER stress-mediated ATF3 activation contributed to sevoflurane-induced neuronal ferroptosis via H2O2 accumulation and the resultant iron overload.

Whole-brain characterization of apoptosis after sevoflurane anesthesia reveals neuronal cell death patterns in the mouse neonatal neocortex

In the last two decades, safety concerns about general anesthesia (GA) arose from studies documenting brain cell death in various pharmacological conditions and animal models. Nowadays, a thorough characterization of sevoflurane-induced apoptosis in the entire neonatal mouse brain would help identify and further focus on underlying mechanisms. We performed whole-brain mapping of sevoflurane-induced apoptosis in post-natal day (P) 7 mice using tissue clearing and immunohistochemistry. We found an anatomically heterogenous increase in cleaved-caspase-3 staining. The use of a novel P7 brain atlas showed that the neocortex was the most affected area, followed by the striatum and the metencephalon. Histological characterization in cortical slices determined that post-mitotic neurons were the most affected cell type and followed inter- and intracortical gradients with maximal apoptosis in the superficial layers of the posterodorsal cortex. The unbiased anatomical mapping used here allowed us to confirm sevoflurane-induced apoptosis in the perinatal period, neocortical involvement, and indicated striatal and metencephalic damage while suggesting moderate hippocampal one. The identification of neocortical gradients is consistent with a maturity-dependent mechanism. Further research could then focus on the interference of sevoflurane with neuronal migration and survival during development.

Anesthetics inhibit phosphorylation of the ribosomal protein S6 in mouse cultured cortical cells and developing brain

Introduction

The development and maintenance of neural circuits is highly sensitive to neural activity. General anesthetics have profound effects on neural activity and, as such, there is concern that these agents may alter cellular integrity and interfere with brain wiring, such as when exposure occurs during the vulnerable period of brain development. Under those conditions, exposure to anesthetics in clinical use today causes changes in synaptic strength and number, widespread apoptosis, and long-lasting cognitive impairment in a variety of animal models. Remarkably, most anesthetics produce these effects despite having differing receptor mechanisms of action. We hypothesized that anesthetic agents mediate these effects by inducing a shared signaling pathway.

Methods

We exposed cultured cortical cells to propofol, etomidate, or dexmedetomidine and assessed the protein levels of dozens of signaling molecules and post-translational modifications using reverse phase protein arrays. To probe the role of neural activity, we performed separate control experiments to alter neural activity with non-anesthetics. Having identified anesthetic-induced changes in vitro, we investigated expression of the target proteins in the cortex of sevoflurane anesthetized postnatal day 7 mice by Western blotting.

Results

All the anesthetic agents tested in vitro reduced phosphorylation of the ribosomal protein S6, an important member of the mTOR signaling pathway. We found a comparable decrease in cortical S6 phosphorylation by Western blotting in sevoflurane anesthetized neonatal mice. Using a systems approach, we determined that propofol, etomidate, dexmedetomidine, and APV/TTX all similarly modulate a signaling module that includes pS6 and other cell mediators of the mTOR-signaling pathway.

Discussion

Reduction in S6 phosphorylation and subsequent suppression of the mTOR pathway may be a common and novel signaling event that mediates the impact of general anesthetics on neural circuit development.

Long-term sevoflurane exposure resulted in temporary rather than lasting cognitive impairment in Drosophila

Sevoflurane is the primary inhaled anesthetic used in pediatric surgery. It has been the focus of research since animal models studies found that it was neurotoxic to the developing brain two decades ago. However, whether pediatric general anesthesia can lead to permanent cognitive deficits remained a subject of heated debate. Therefore, our study aims to determine the lifetime neurotoxicity of early long-time sevoflurane exposure using a short-life-cycle animal model, Drosophila melanogaster. To investigate this question, we measured the lifetime changes of two-day-old flies' learning and memory abilities after anesthesia with 3 % sevoflurane for 6 h by the T-maze memory assay. We evaluated the apoptosis, levels of ATP and ROS, and related genes in the fly head. Our results suggest that 6 h 3 % sevoflurane exposure at a young age can only induce transient neuroapoptosis and cognitive deficits around the first week after anesthesia. But this brain damage recedes with time and vanishes in late life. We also found that the mRNA level of caspases and Bcl-2, ROS level, and ATP level increased during this temporary neuroapoptosis process. And mRNA levels of antioxidants, such as SOD2 and CAT, increased and decreased simultaneously with the rise and fall of the ROS level, indicating a possible contribution to the recovery from the sevoflurane impairment. In conclusion, our results suggest that one early prolonged sevoflurane-based general anesthesia can induce neuroapoptosis and learning and memory deficit transiently but not permanently in Drosophila.

Sevoflurane induces neurotoxic effects on developing neurons through the WNK1/NKCC1/Ca2+ /Drp-1 signalling pathway

Children repeatedly exposed to anaesthesia have a high risk of cognitive impairment, but the mechanism of its regulation in this context is unknown. The objective of this study was to investigate the possible toxic mechanism of sevoflurane through the WNK1/NKCC1/Ca²⁺ /Drp-1 signalling pathway. The hippocampal neuronal HT22 cell line was used in this study. The intervention group was treated with the WNK1 inhibitor WNK-463, CaN inhibitor FK506 and Drp-1 inhibitor Mdivi-1 respectively in the medium for 30 min before sevoflurane anaesthesia. The sevofluane group and all intervention group treated with 4.1% sevoflurane for 6 h. Compared with the control group, sevoflurane treatment decreased cell viability and increased cellular apoptosis. Our study found that WNK-463, FK506 and Mdivi-1 can all alleviate the sevoflurane-induced reduction in cell viability, decrease the cell apoptosis. In addition, WNK-463 pretreatment could inhibit the increase of WNK1 kinase and NKCC1 protein concentration caused by sevoflurane. Further, sevoflurane anaesthesia causes intracellular calcium overload, increases the expression of CaN and induces the dephosphorylation of Drp-1 protein at ser637, while CaN inhibitor FK506 pretreatment could reduce the dephosphorylation of Drp-1. Therefore, the WNK1/NKCC1/Ca²⁺ /Drp-1 signalling pathway plays an important role in sevoflurane-related neurotoxicity. Reducing intracellular calcium influx may be one of the important mechanism to ameliorate sevoflurane toxicity.

Sevoflurane induces microRNA-18a to delay rat neurodevelopment via suppression of the RUNX1/Wnt/β-catenin axis

Sevoflurane anesthesia is reported to repress neurogenesis of neural stem cells (NSCs), thereby affecting the brain development, but the underlying mechanism of sevoflurane on the proliferation of NSCs remains unclear. Thus, this study aims to discern the relationship between sevoflurane and NSC proliferation. Bioinformatics tools were employed to predict the expression of microRNA-18a (miR-18a) in 9-day-old neonatal rat hippocampal tissues after sevoflurane treatment and the downstream genes of miR-18a, followed by a series of assays to explore the relationship among miR-18a, runt related transcription factor 1 (RUNX1), and β-catenin in the hippocampal tissues. NSCs were isolated from the hippocampal tissues and subjected to gain-/loss-of-function assays to investigate the interactions among miR-18a, RUNX1, and β-catenin in NSCs and their roles in NSC development. Bioinformatics analysis and experimental results confirmed high expression of miR-18a in rat hippocampal tissues and NSCs after sevoflurane treatment. Next, we found that miR-18a downregulated RUNX1 expression, while RUNX1 promoted NSC proliferation by activating the Wnt/β-catenin signaling pathway. The behavioral experiments also showed that sevoflurane caused nerve injury in rats, whilst RUNX1 overexpression protected rat neurodevelopment. Our findings uncovered that sevoflurane attenuated NSC proliferation via the miR-18a-meidated RUNX1/Wnt/β-catenin pathway, thereby impairing rat neurodevelopment.

MicroRNA-17-5p Protects against Propofol Anesthesia-Induced Neurotoxicity and Autophagy Impairment via Targeting BCL2L11

Background. Propofol (PPF) has been shown in studies to cause cognitive impairment and neuronal cell death in developing animals. PPF has been demonstrated to decrease the expression of microRNA-17-5p (miR-17-5p) in a recent study. Nonetheless, the function of miR-17-5p in PPF-induced neurotoxicity and related mechanisms is uncharacterized. Methods. After the induction of neurotoxicity by treating the SH-SY5Y cells with PPF, qRT-PCR was conducted to evaluate the level of miR-17-5p. Using MTT and flow cytometry, cell viability and apoptosis rate were assessed, respectively. Interaction between miR-17-5p and BCL2 like 11 was (BCL2L11) studied using a Luciferase reporter assay. With the help of western blot analysis, we determined the level of proteins of apoptosis-related genes and autophagy-related markers. Results. In SH-SY5Y cells, PPF treatment induced neurotoxicity and downregulated miR-17-5p expression. In SH-SY5Y cells post-PPF exposure, overexpression of miR-17-5p increased cell viability and decreased apoptosis. Consistently, miR-17-5p mimics mitigated PPF-generated autophagy via inhibition of Atg5, Beclin1, and LC3II/I level and elevation of p62 protein expression. In addition, BCL2L11, which was highly expressed in PPF-treated SH-SY5Y cells, was directly targeted by miR-17-5p. Further, in PPF-treated SH-SY5Y cells, overexpressed BCL2L11 counteracted the suppressing behavior of miR-17-5p elevation on PPF-induced apoptosis. Conclusion. Overexpressed miR-17-5p alleviates PPF exposure-induced neurotoxicity and autophagy in SH-SY5Y cells via binding to BCL2L11, suggesting the possibility that miR-17-5p can serve as a candidate in the treatment of neurotoxicity (caused by PPF).

Safety of general anaesthetics on the developing brain: are we there yet?

Thirty years ago, neurotoxicity induced by general anaesthetics in the developing brain of rodents was observed. In both laboratory-based and clinical studies, many conflicting results have been published over the years, with initial data confirming both histopathological and neurodevelopmental deleterious effects after exposure to general anaesthetics. In more recent years, animal studies using non-human primates and new human cohorts have identified some specific deleterious effects on neurocognition. A clearer pattern of neurotoxicity seems connected to exposure to repeated general anaesthesia. The biochemistry involved in this neurotoxicity has been explored, showing differential effects of anaesthetic drugs between the developing and developed brains. In this narrative review, we start with a comprehensive description of the initial concerning results that led to recommend that any non-essential surgery should be postponed after the age of 3 yr and that research into this subject should be stepped up. We then focus on the neurophysiology of the developing brain under general anaesthesia, explore the biochemistry of the observed neurotoxicity, before summarising the main scientific and clinical reports investigating this issue. We finally discuss the GAS trial, the importance of its results, and some potential limitations that should not undermine their clinical relevance. We finally suggest some key points that could be shared with parents, and a potential research path to investigate the biochemical effects of general anaesthesia, opening up perspectives to understand the neurocognitive effects of repetitive exposures, especially in at-risk children.

Solasonine relieves sevoflurane-induced neurotoxicity via activating the AMP-activated protein kinase/FoxO3a pathway

BACKGROUND

Solasonine (SS), the main active ingredient of Solanumnigrum L, has been reported to boast extensive anti-tumor, anti-oxidant, and anti-inflammatory properties. This study is committed to exploring whether solasonine can alleviate neurotoxicity resulting from sevoflurane.

MATERIALS AND METHODS

The mouse hippocampal neuron cell line HT22 was treated with sevoflurane and/or solasonine of different doses. The proliferation, inflammation, oxidative stress response, and apoptosis of HT22 cells were examined. The AMP-activated protein kinase (AMPK)/FoxO3a signaling pathway was ascertained through Western blot and cellular immunofluorescence. In in-vivo experiments, Morris water maze figured out the changes in learning and memory abilities of mice treated with 8 mg/kg solasonine and exposed to SEV.

RESULTS

Sevoflurane induced apoptosis and hampered proliferation in HT22 cells. It also aggravated the release of inflammatory factors and oxidative stress mediators. Solasonine weakened neuron damage mediated by sevoflurane in a concentration-dependent pattern. Mechanically, sevoflurane clogged AMPK/FoxO3a signaling pathway activation, which was strengthened by solasonine. AMPK inhibition greatly influenced solasonine's protective effect on HT22 cells. Invivo, solasonine prominently ameliorated learning and memory disorders and nerve damage in mice exposed to sevoflurane.

CONCLUSIONS

Solasonine alleviates sevoflurane-induced neurotoxicity through activating the AMPK/FoxO3a signaling pathway.

Evaluation of neurotoxicity and long-term function and behavior following intrathecal 1 % 2-chloroprocaine in juvenile rats

Spinally-administered local anesthetics provide effective perioperative anesthesia and/or analgesia for children of all ages. New preparations and drugs require preclinical safety testing in developmental models. We evaluated age-dependent efficacy and safety following 1 % preservative-free 2-chloroprocaine (2-CP) in juvenile Sprague-Dawley rats. Percutaneous lumbar intrathecal 2-CP was administered at postnatal day (P)7, 14 or 21. Mechanical withdrawal threshold pre- and post-injection evaluated the degree and duration of sensory block, compared to intrathecal saline and naive controls. Tissue analyses one- or seven-days following injection included histopathology of spinal cord, cauda equina and brain sections, and quantification of neuronal apoptosis and glial reactivity in lumbar spinal cord. Following intrathecal 2-CP or saline at P7, outcomes assessed between P30 and P72 included: spinal reflex sensitivity (hindlimb thermal latency, mechanical threshold); social approach (novel rat versus object); locomotor activity and anxiety (open field with brightly-lit center); exploratory behavior (rearings, holepoking); sensorimotor gating (acoustic startle, prepulse inhibition); and learning (Morris Water Maze). Maximum tolerated doses of intrathecal 2-CP varied with age (1.0 μL/g at P7, 0.75 μL/g at P14, 0.5 μL/g at P21) and produced motor and sensory block for 10-15 min. Tissue analyses found no significant differences across intrathecal 2-CP, saline or naïve groups. Adult behavioral measures showed expected sex-dependent differences, that did not differ between 2-CP and saline groups. Single maximum tolerated in vivo doses of intrathecal 2-CP produced reversible spinal anesthesia in juvenile rodents without detectable evidence of developmental neurotoxicity. Current results cannot be extrapolated to repeated dosing or prolonged infusion.

Sevoflurane-Induced miR-211-5p Promotes Neuronal Apoptosis by Inhibiting Efemp2

Sevoflurane exposure can result in serious neurological side effects including neuronal apoptosis and cognitive impairment. Although the microRNA miR-211-5p is profoundly upregulated following sevoflurane exposure in neonatal rodent models, the impact of miR-211-5p on neuronal apoptosis and cognitive impairment postsevoflurane exposure has not yet been elucidated. Here, we found that sevoflurane upregulated miR-211-5p and downregulated EGF-Containing Fibulin Extracellular Matrix Protein 2 (Efemp2, Fibulin-4) levels in vitro and in vivo. Sevoflurane's effect on miR-211-5p expression was based on enhancing primary miR-211 transcription. miR-211-5p targets Efemp2's mRNA 3′-untranslated region, reducing Efemp2 expression. RNA immunoprecipitation revealed significant enrichment of the miR-211-5p:Efemp2 mRNA dyad in the RNA-induced silencing complex. miR-211-5p mimics downregulated Efemp2, leading to phosphorylation of Smad2 and Smad3, upregulation of pro-apoptotic Bim, and mitochondrial release of allograft inflammatory factor 1 and cytochrome C. In contrast, miR-211-5p hairpin inhibitor (AntimiR-211-5p) negatively regulated this apoptotic pathway and reduced neuronal apoptosis in an Efemp2-dependent manner. Sevoflurane-exposed mice administered AntimiR-211-5p displayed reduced cortical apoptosis levels and near-term cognitive impairment. In conclusion, sevoflurane-induced miR-211-5p promotes neuronal apoptosis via Efemp2 inhibition. Summary statement: This study revealed the significance of sevoflurane-induced increases in miR-211-5p on the promotion of neuronal apoptosis via inhibition of Efemp2 and its downstream targets.

Repeated exposure to sevoflurane in neonatal rats impairs cognition in adulthood via the PKA-CREB-BDNF signaling pathway

Sevoflurane (Sev) anesthesia is widely used in pediatrics due to its low blood-gas partition coefficient and lack of pungency. However, Sev treatment may lead to cognitive dysfunction in later life. The current study administered Sev to neonatal rats to investigate the effects of Sev treatment on cognitive performance in adulthood. In total, 6-day-old rats received 3% Sev for 2 h daily for 3 consecutive days. The cognitive function of rats in adulthood was evaluated in 56-day-old rats by Morris water maze test. The hippocampal neuron morphology was observed by Nissl staining. Hippocampal brain-derived neurotrophic factor (BDNF) levels were measured by ELISA. The protein expression of protein kinase A (PKA), cAMP response element binding protein (CREB), phosphorylated-CREB (p-CREB) and BDNF in hippocampus were assessed by western blotting. The water maze results demonstrated that neonatal treatment with Sev resulted in a significant impairment of cognition in 56-day-old adult rats. Behavioral analysis revealed that Sev treatment increased latency to first pass the platform and decreased residence in target quadrants and across platform frequency compared with the control group in Morris water maze tests. Furthermore, compared with the control group, neonatal exposure to Sev reduced the number of neurons and the concentration of BDNF in the hippocampus, a brain region important for learning and memory. Additionally, Sev significantly decreased the expression of PKA, p-CREB, BDNF and the p-CREB/CREB ratio. Treatment with bucladesine, a selective PKA agonist, partially reversed the deleterious effects of Sev. In summary, the results indicated that PKA-CREB-BDNF signaling served an important role in the cognitive decline caused by neonatal exposure to Sev.

The Role of Klotho Protein Against Sevoflurane-Induced Neuronal Injury

The effects of general anesthetics on the developing brain have aroused much attention in recent years. Sevoflurane, a commonly used inhalation anesthetic especially in pediatric anesthesia, can induce developmental neurotoxicity. In this study, the differentially expressed mRNAs in the hippocampus of newborn rats exposed to 3% sevoflurane for 6 h were detected by RNA-Sequencing. Those data indicated that the mRNA of Klotho was increased after exposure to sevoflurane. Moreover, the protein expression of Klotho was assayed by Western Blot. Besides over-expression and under-expression of Klotho protein, we also detected changes of cell proliferation, ROS, JC-1, and Bcl-2/Bax ratio in PC12 cells exposed to sevoflurane. After exposure to 3% sevoflurane, the expression of Klotho protein increased in the hippocampus of neonatal rats. In PC12 cells, exposure to sevoflurane could increase cellular ROS level, reduce mitochondrial membrane potential and Bcl-2/Bax ratio. While overexpression of Klotho alleviated the above changes, knockdown of Klotho aggravated the injury of sevoflurane. Klotho protein could reduce oxidative stress and mitochondrial injury induced by sevoflurane in the neuron.

RIP3-mediated necroptosis increases neuropathic pain via microglia activation: necrostatin-1 has therapeutic potential

Neuropathic pain (NP) is a clinical symptom that accompanies many diseases. We investigated the effect of receptor‐interacting protein kinase 3 (RIP3)‐regulated necroptosis on NP and explored its relationship with microglia, in order to provide a theoretical basis for further research and provide new insights into the treatment of NP. In this study, the spared nerve injury (SNI) model was used along with intervention with necrostatin and the inhibitor of necroptosis necrostatin‐1 (Nec‐1). Pain behavior tests were performed 1 and 3 days before the nerve injury (or sham) operation, and on days 1, 3, 5, 7, 10, and 14 after the operation. The spinal cord tissues were collected for detection of RIP3 expression and distribution, changes in the number of microglia cells, activation of necroptosis, and the level of proinflammatory factors. Collected spinal cord tissues were analyzed using western blot, immunohistochemistry, immunofluorescence, immunoprecipitation assays, and ELISA, respectively. We found that, compared with the sham group, the expression of RIP3 protein in the spinal cord of rats in the SNI group increased from 3 to 14 days after surgery. Immunofluorescence staining showed that RIP3 was coexpressed with the microglia and the number of microglia increased significantly in the SNI model group. The results of immunoprecipitation assays suggested that a RIP3‐mediated necroptosis pathway promotes NP. After treatment with Nec‐1, the expression of RIP3 protein and the number of microglia were significantly reduced, and the expression levels of TNF‐α, IL‐1β, and IL‐6 in spinal dorsal horns were significantly decreased. These results indicate that RIP3 promotes necroptosis to increase the occurrence of NP via microglia.

Downregulation of HOTAIR reduces neuronal pyroptosis by targeting miR-455-3p/NLRP1 axis in propofol-treated neurons in vitro

Propofol is one of the most common intravenous anesthetics which may cause neuronal cell death in young mice. HOX transcript antisense RNA (HOTAIR) was abnormally expressed in neurodegenerative diseases. However, the effect of HOTAIR on propofol-induced pyroptosis of neurons and related mechanisms are still unknown. In this study, propofol treatment significantly reduced neuronal the viability of neurons, and promoted the expression of inflammation-related factors. Propofol treatment also promoted neuron death and neuronal pyroptosis. All the above effects might be related to the propofol-induced overexpression of HOTAIR. Interestingly, knockdown of HOTAIR by shRNA (sh-HOTAIR) significantly inhibited neuronal pyroptosis, but increased neuronal viability. Further analysis showed that HOTAIR and Nod-like receptor protein1 (NLRP1) were the targets of miR-455-3p, respectively. Notably, propofol treatment decreased the level of miR-455-3p, while increased the level of NLRP1. In addition, sh-HOTAIR increased the level of miR-455-3p, which further inhibited the expression of NLRP1 and the activation of NLRP1 inflammasome, thereby inhibiting neuronal pyroptosis. More importantly, NLRP1 overexpression decreased neuronal viability, and reactivated NLRP1 inflammasome, thus reversing the inhibitory effect of sh-HOTAIR on pyroptosis. Our findings indicated that HOTAIR inhibited propofol-induced pyroptosis of neurons by regulating miR-455-3p/NLRP1 axis, indicating that HOTAIR may be a potential therapeutic target for propofol-induced neurotoxicity.

Propofol impairs specification of retinal cell types in zebrafish by inhibiting Zisp-mediated Noggin-1 palmitoylation and trafficking

Background

Propofol can have adverse effects on developing neurons, leading to cognitive disorders, but the mechanism of such an effect remains elusive. Here, we aimed to investigate the effect of propofol on neuronal development in zebrafish and to identify the molecular mechanism(s) involved in this pathway.

Methods

The effect of propofol on neuronal development was demonstrated by a series of in vitro and in vivo experiments. mRNA injections, whole-mount in situ hybridization and immunohistochemistry, quantitative real-time polymerase chain reaction, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, 5-ethynyl-2′-deoxyuridine labeling, co-immunoprecipitation, and acyl–biotin exchange labeling were used to identify the potential mechanisms of propofol-mediated zisp expression and determine its effect on the specification of retinal cell types.

Results

Propofol impaired the specification of retinal cell types, thereby inhibiting neuronal and glial cell formation in retinas, mainly through the inhibition of Zisp expression. Furthermore, Zisp promoted the stabilization and secretion of a soluble form of the membrane-associated protein Noggin-1, a specific palmitoylation substrate.

Conclusions

Propofol caused a severe phenotype during neuronal development in zebrafish. Our findings established a direct link between an anesthetic agent and protein palmitoylation in the regulation of neuronal development. This could be used to investigate the mechanisms via which the improper use of propofol might result in neuronal defects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02204-0.

Effects of sevoflurane general anesthesia during early pregnancy on AIM2 expression in the hippocampus and parietal cortex of Sprague-Dawley offspring rats

The aim of the present study was to investigate the effect of exposure to sevoflurane general anesthesia during early pregnancy on interferon-inducible protein AIM2 (AIM2) expression in the hippocampus and parietal cortex of the offspring Sprague-Dawley (SD) rats. A total of 18 SD rats at a gestational age of 5-7 days were randomly divided into three groups: i) A control group (control); ii) 2-h sevoflurane general anesthesia, group 1 (S1); and iii) 4-h sevoflurane general anesthesia, group 2 (S2). The six offspring rats in each group were maintained for 30 days and assessed by Morris water maze testing. Brain specimens were collected from offspring rats 30 days after birth. Changes in the structural morphology of neurons in the hippocampus and parietal cortex were observed using hematoxylin and eosin staining. Nissl bodies in the hippocampus and parietal cortex were observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), AIM2, CD45 and IL-1β was detected by immunohistochemistry and the protein levels of CD45, IL-1β, pro-caspase-1 and caspase-1 p10 were detected by western blotting. Compared with the control group, offspring rats in the S1 and S2 groups exhibited poor long-term learning and memory ability and experienced different degrees of damage to both the hippocampus and parietal cortex. The expression levels of GFAP, AIM2, CD45, IL-1β, caspase-1 and caspase-1 p10 in the offspring of both the S1 and the S2 groups were significantly increased (P<0.05) compared with offspring of the control group. Moreover, compared with the offspring of the S1 group, hippocampal and parietal cortex injury in the offspring of the S2 group was further aggravated, and the expression of GFAP, AIM2, CD45, IL-1β, pro-caspase-1 and cleaved-caspase-1 was significantly increased (P<0.05). In conclusion, sevoflurane general anesthesia in SD rat early pregnancy promoted the expression of AIM2 and the inflammatory response in the hippocampus and parietal cortex of offspring rats.

Neuroprotective Effects of Carnitine and Its Potential Application to Ameliorate Neurotoxicity

Carnitine is an essential metabolite that is absorbed from the diet and synthesized in the kidney, liver, and brain. It ferries fatty acids across the mitochondrial membrane to undergo β-oxidation. Carnitine has been studied as a therapy or protective agent for many neurological diseases and neurotoxicity (e.g., prolonged anesthetic exposure-induced developmental neurotoxicity in preclinical models). Preclinical and clinical data support the notion that carnitine or acetyl carnitine may improve a patient's quality of life through increased mitochondrial respiration, release of neurotransmitters, and global gene expression changes, showing the potential of carnitine beyond its approved use to treat primary and secondary carnitine deficiency. In this review, we summarize the beneficial effects of carnitine or acetyl carnitine on the central nervous system, highlighting protective effects against neurotoxicity-induced damage caused by various chemicals and encouraging a thorough evaluation of carnitine use as a therapy for patients suffering from neurotoxicant exposure.

Sevoflurane-Induced Neuroapoptosis in Rat Dentate Gyrus Is Activated by Autophagy Through NF-κB Signaling on the Late-Stage Progenitor Granule Cells

OBJECTIVE

The mechanisms by which exposure of the late-stage progenitor cells to the anesthesia sevoflurane alters their differentiation are not known. We seek to query whether the effects of sevoflurane on late-stage progenitor cells might be regulated by apoptosis and/or autophagy.

METHODS

To address the short-term impact of sevoflurane exposure on granule cell differentiation, we used 5-bromo-2-deoxyuridine (BrdU) to identify the labeled late-stage progenitor granule cells. Male or female rats were exposed to 3% sevoflurane for 4 h when the labeled granule cells were 2 weeks old. Differentiation of the BrdU-labeled granule cells was quantified 4 and 7 days after exposure by double immunofluorescence. The expression of apoptosis and autophagy in hippocampal dentate gyrus (DG) was determined by western blot and immunofluorescence. Western blot for the expression of NF-κB was used to evaluate the mechanism. Morris water maze (MWM) test was performed to detect cognitive function in the rats on postnatal 28-33 days.

RESULTS

Exposure to sevoflurane decreased the differentiation of the BrdU-labeled late-stage progenitor granule cells, but increased the expression of caspase-3, autophagy, and phosphorylated-P65 in the hippocampus of juvenile rats and resulted in cognitive deficiency. These damaging effects of sevoflurane could be mitigated by inhibitors of autophagy, apoptosis, and NF-κB. The increased apoptosis could be alleviated by pretreatment with the autophagy inhibitor 3-MA, and the increased autophagy and apoptosis could be reduced by pretreatment with NF-κB inhibitor BAY 11-7085.

CONCLUSION

These findings suggest that a single, prolonged sevoflurane exposure could impair the differentiation of late-stage progenitor granule cells in hippocampal DG and cause cognitive deficits possibly via apoptosis activated by autophagy through NF-κB signaling. Our results do not preclude the possibility that the affected differentiation and functional deficits may be caused by depletion of the progenitors pool.

Sevoflurane Exposure Induces Neuronal Cell Parthanatos Initiated by DNA Damage in the Developing Brain via an Increase of Intracellular Reactive Oxygen Species

The safety of volatile anesthetics in infants and young children has been drawing increasing concern due to its potential neurotoxicity in the developing brain. Neuronal death is considered a major factor associated with developmental neurotoxicity after exposure to volatile anesthetics sevoflurane, but its mechanism remains elusive. Parthanatos, a new type of programmed cell death, resulting from poly (ADP-ribose) polymerase 1 (PARP-1) hyperactivation in response to DNA damage, was found to account for the pathogenesis of multiple neurological disorders. However, the role of Parthanatos in sevoflurane-induced neonatal neuronal cell death has not been investigated. To test it, neuronal cells treated with 2, 4, and 8% sevoflurane for 6, 12, and 24 h and postnatal day 7 rats exposed to 2.5% sevoflurane for 6 h were used in the present study. Our results found sevoflurane exposure induced neuronal cell death, which was accompanied by PARP-1 hyperactivation, cytoplasmic polymerized ADP-ribose (PAR) accumulation, mitochondrial depolarization, and apoptosis-inducing factor (AIF) nuclear translocation in the neuronal cells and hippocampi of rats. Pharmacological or genetic inhibition of PAPR-1 significantly alleviated sevoflurane-induced neuronal cell death and accumulation of PAR polymer and AIF nuclear translocation, which were consistent with the features of Parthanatos. We observed in vitro and in vivo that sevoflurane exposure resulted in DNA damage, given that 8-hydroxydeoxyguanosine (8-OHdG) and phosphorylation of histone variant H2AX (γH2AX) were improved. Moreover, we detected that sevoflurane exposure was associated with an overproduction of intracellular reactive oxygen species (ROS). Inhibition of ROS with antioxidant NAC markedly alleviated DNA damage caused by sevoflurane, indicating that ROS participated in the regulation of sevoflurane-induced DNA damage. Additionally, sevoflurane exposure resulted in upregulation of Parthanatos-related proteins and neuronal cell death, which were significantly attenuated by pretreatment with NAC. Therefore, these results suggest that sevoflurane exposure induces neuronal cell Parthanatos initiated by DNA damage in the developing brain via the increase of intracellular ROS.

General anesthesia activates the mitochondrial unfolded protein response and induces age-dependent, long-lasting changes in mitochondrial function in the developing brain

General anesthesia induces changes in dendritic spine number and synaptic transmission in developing mice. These changes are rather disturbing, as similar changes are seen in animal models of neurodevelopmental disorders. We previously suggested that mTor-dependent upregulation of mitochondrial function may be involved in such changes. To further understand the significance of mitochondrial changes after general anesthesia during neurodevelopment, we exposed young mice to 2.5 % sevoflurane for 2 h followed by injection of rotenone, a mitochondrial complex I inhibitor. In postnatal day 17 (PND17) mice, intraperitoneal injection of rotenone not only blocked sevoflurane-induced increases in mitochondrial function, it also prevented sevoflurane-induced changes in excitatory synaptic transmission. Interestingly, similar changes were not observed in younger, neonatal mice (PND7). We next assessed whether the mitochondrial unfolded protein response (UPR^mt) acted as a link between anesthetic exposure and mitochondrial function. Expression of UPR^mt proteins, which help maintain protein-folding homeostasis and increase mitochondrial function, was increased 6 h after sevoflurane exposure. Our results show that a single, brief sevoflurane exposure induces age-dependent changes in mitochondrial function that constitute an important mechanism for the increase in excitatory synaptic transmission in late postnatal mice, and also suggest mitochondria and UPR^mt as potential targets for preventing anesthesia toxicity.

TrkC Overexpression Protects Sevoflurane-Induced Neurotoxicity in Human Induced Pluripotent Stem Cell-Derived Neurons

BACKGROUND

Inhaled anesthetic sevoflurane (SEVO) may induce cortical neurotoxicity and memory dysfunction in both animals and humans. In this study, we investigated the toxic effects of SEVO on human induced pluripotent stem cell (iPS)-derived neurons.

METHODS

Human iPS-derived neurons were exposed to SEVO in vitro. SEVO-induced toxic effects were examined with the viability, live caspase 3/7, and neurite density assays, respectively. The effects of SEVO on the receptors of the tyrosine kinases TrkA, TrkB, and TrkC were assessed by qRT-PCR. TrkA, TrkB, and TrkC were ectopically overexpressed in human iPS-derived neurons. Their functional effects on SEVO-induced human iPS-derived neuron toxicity were further investigated.

RESULTS

SEVO induced dose-dependent cell death, caspase 3/7 elevation, neurite degeneration, and the downregulation of Trk receptors in human iPS-derived neurons. Adenovirus-mediated Trk receptor overexpression selectively upregulated endogenous TrkA, TrkB, or TrkC gene expressions in human iPS-derived neurons. Specifically, TrkC overexpression, but not TrkA or TrkB overexpression was found to overcome the neurotoxic effects of SEVO in human iPS-derived neurons.

CONCLUSIONS

SEVO may induce neurotoxicity in human iPS-derived neurons, and its neurotoxic damage could be protected by the overexpression of TrkC.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

Notoginsenoside R1 attenuates sevoflurane-induced neurotoxicity

Background

Sevoflurane, a volatile anesthetic, is known to induce widespread neuronal degeneration and apoptosis. Recently, the stress-inducible protein sestrin 2 and adenosine monophosphate-activated protein kinase (AMPK) have been found to regulate the levels of intracellular reactive oxygen species (ROS) and suppress oxidative stress. Notoginsenoside R1 (NGR1), a saponin isolated from Panax notoginseng, has been shown to exert neuroprotective effects. The effects of NGR1 against neurotoxicity induced by sevoflurane were assessed.

Methods

Sprague-Dawley rat pups on postnatal day 7 (PD7) were exposed to sevoflurane (3%) anesthesia for 6 h. NGR1 at doses of 12.5, 25, or 50 mg/kg body weight was orally administered to pups from PD2 to PD7.

Results

Pretreatment with NGR1 attenuated sevoflurane-induced generation of ROS and reduced apoptotic cell counts. Western blotting revealed decreased cleaved caspase 3 and Bad and Bax pro-apoptotic protein expression. NGR1 substantially upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) expression along with increased heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 levels, suggesting Nrf2 signaling activation. Enhanced sestrin-2 and phosphorylated AMPK expression were noticed following NGR1 pretreatment.

Conclusion

This study revealed the neuroprotective effects of NGR1 through effective suppression of apoptosis and ROS via regulation of apoptotic proteins and activation of Nrf2/HO-1 and sestrin 2/AMPK signaling cascades.

Regions of the basal ganglia and primary olfactory system are most sensitive to neurodegeneration after extended sevoflurane anesthesia in the perinatal rat

Extended general anesthesia early in life is neurotoxic in multiple species. However, little is known about the temporal progression of neurodegeneration after general anesthesia. It is also unknown if a reduction in natural cell death, or an increase in cell creation, occurs as a form of compensation after perinatal anesthesia exposure. The goal of this study was to evaluate markers of neurodegeneration and cellular division at 2, 24, or 72 h after sevoflurane (Sevo) exposure (6 h) in fully oxygenated postnatal day (PND) 7 rats. Neurodegeneration was observed in areas throughout the forebrain, while the largest changes (fold increase above vehicle) were observed in areas associated with either the primary olfactory learning pathways or the basal ganglia. These regions included the indusium griseum (IG, 25-fold), the posterior dorso medial hippocampal CA1 (17-fold), bed nucleus of the stria terminalis (Bed Nuclei STM, 5-fold), the shell of the nucleus accumbens (Acb, 5-fold), caudate/putamen (CPu, 5-fold), globus pallidus (GP, 9-fold) and associated thalamic (11-fold) and cortical regions (5-fold). Sevo neurodegeneration was minimal or undetectable in the ventral tegmentum, substantia nigra, and most of the hypothalamus and frontal cortex. In most brain regions where neurodegeneration was increased 2 h post Sevo exposure, the levels returned to <4-fold above control levels by 24 h. However, in the IG, CA1, GP, anterior thalamus, medial preoptic nucleus of the hypothalamus (MPO), anterior hypothalamic area (AHP), and the amygdaloid nuclei, neurodegeneration at 24 h was double or more than that at 2 h post exposure. Anesthesia exposure causes either a prolonged period of neurodegeneration in certain brain regions, or a distinct secondary degenerative event occurs after the initial insult. Moreover, regions most sensitive to Sevo neurodegeneration did not necessarily coincide with areas of new cell birth, and new cell birth was not consistently affected by Sevo. The profile of anesthesia related neurotoxicity changes with time, and multiple mechanisms of toxicity may exist in a time-dependent fashion.

Acetyl-l-carnitine does not prevent neurodegeneration in a rodent model of prolonged neonatal anesthesia

Many studies have shown that prolonged or repeated use of general anesthesia early in life can cause an increase in neurodegeneration and lasting changes in behavior. While short periods of general anesthesia appear to be safe, there is a concern about the neurotoxic potential of prolonged or repeated general anesthesia in young children. Unfortunately, the use of general anesthesia in children cannot be avoided. It would be a great benefit to develop a strategy to reduce or reverse anesthesia mitigated neurotoxicity. The mechanisms behind anesthesia related neurotoxicity are unknown, but evidence suggests that mitochondrial dysfunction and abnormal energy utilization are involved. Recent research suggests that a class of compounds known as carnitines may be effective at preventing anesthesia related neurotoxicity by influencing fatty acid metabolism in the mitochondria. However, it is unknown if carnitines can provide protection against changes in behavior associated with early life exposure to anesthesia. Accordingly, we evaluated the neuroprotective potential of acetyl-l-carnitine in 7-day old rats. Rat pups were exposed to 6 h of general anesthesia with sevoflurane or a control condition, with and without acetyl-l-carnitine. The oxygenation level of animals was continuously monitored during sevoflurane exposure, and any animal showing signs of hypoxia was removed from the study. Animals exposed to sevoflurane showed clear signs of neurodegeneration 2 h after sevoflurane exposure. The hippocampus, cortex, thalamus, and caudate putamen all had elevated levels of Fluoro-Jade C staining. Despite the elevated levels of Fluoro-Jade C, few behavioral changes were observed in an independent cohort of animals treated with sevoflurane. Furthermore, acetyl-l-carnitine had little impact on levels of Fluoro-Jade C staining in animals treated with sevoflurane. These data suggest that acetyl-l-carnitine may offer little protection again anesthesia related neurotoxicity in fully oxygenated animals.

PDE-7 Inhibitor BRL-50481 Reduces Neurodegeneration and Long-Term Memory Deficits in Mice Following Sevoflurane Exposure

Sevoflurane, one of the most commonly used anesthetic agents, has been demonstrated to induce widespread neurodegeneration in the developing brain. We aimed to evaluate the protective effects of a PDE-7 inhibitor (BRL-50481) against the neurotoxic effects of sevoflurane on the developing nervous system. Spatial learning and memory in sevoflurane-treated mice were examined using the Morris water maze test, and neuroprotective effects of PDE-7 inhibitor (BRL-50481) against sevoflurane-induced impairments were evaluated. Our results showed that sevoflurane treatment markedly induced neurodegeneration and impaired long-term memory in neonatal mice. Notably, BRL-50481 coadministration could significantly attenuate sevoflurane-induced learning and memory defects, prevent deterioration of recognition memory, and protect against neuron apoptosis. Mechanistically, BRL-50481 administration suppressed sevoflurane-induced neurodegenerative disorders through restoring cAMP and activating cAMP/CREB signaling in the hippocampus. PDE7 inhibitor may be a potential therapeutic agent for sevoflurane-induced neurodegeneration and long-term memory deficits.

The Effects of Hesperidin on Neuronal Apoptosis and Cognitive Impairment in the Sevoflurane Anesthetized Rat are Mediated Through the PI3/Akt/PTEN and Nuclear Factor-κB (NF-κB) Signaling Pathways

BACKGROUND Hesperidin (HPD) is a bioflavonoid found in citrus fruits. This study aimed to investigate the effects of HPD on cerebral morphology and cognitive behavior in sevoflurane anesthetized neonatal rats and the molecular mechanisms involved. MATERIAL AND METHODS Sixty neonatal Sprague-Dawley rats were divided into five groups, including the untreated control group, and the sevoflurane anesthesia groups untreated and treated with 25 mg/kg/day of HPD (HPD25), 50 mg/kg/day of HPD (HPD50), and 100 mg/kg/day of HPD (HPD100). The rat model was created by the administration of sevoflurane on the sixth postnatal day (P6) and for a further three days. Neonatal rats pre-treated with HPD for 19 days were given sevoflurane 30 minutes beforehand (P3 to P21). Rat hippocampal tissue specimens were investigated using the TUNEL assay for apoptosis. Hippocampal tissue homogenates underwent Western blot for the quantification of markers of neuroinflammation and oxidative stress. The neonatal rats were also investigated for behavior, learning, and memory. RESULTS HPD significantly reduced sevoflurane-induced neuronal apoptosis and protein expression of cleaved caspase-3, BAD, BAX, NF-kappaB, TNF-alpha, IL-6, and IL-1ß (p<0.05). HPD significantly increased the expression of Bcl-xL and Bcl-2 (p<0.05), and activated the PI3/Akt pathway. Learning and memory were significantly improved following HPD treatment (p<0.05). HPD treatment modulated the PI3/Akt/PTEN and NF-kappaB signaling pathways, and reduced oxidative stress (p<0.05). CONCLUSIONS In the sevoflurane anesthetized neonatal rat model, treatment with HPD reduced neuronal degeneration, hippocampal inflammation, and improvised memory, learning, and cognitive responses by modulating the PI3/Akt/PTEN and NF-kappaB signaling pathways.

Sevoflurane Induces Learning and Memory Impairment in Young Mice Through a Reduction in Neuronal Glucose Transporter 3

Sevoflurane, which is widely used in paediatric anaesthesia, induces neural apoptosis in the developing brain and cognitive impairment in young mammals. Glucose hypometabolism is the key pathophysiological modulator of cognitive dysfunction. However, the effects and mechanism of sevoflurane on cerebral glucose metabolism after its use as an anaesthetic and its complete elimination are still unknown. We therefore investigated the influence of sevoflurane on neuronal glucose transporter isoform 3 (GLUT3) expression, glucose metabolism and apoptosis in vivo and in vitro and on neurocognitive function in young mice 24 h after the third exposure to sevoflurane. Postnatal day 14 (P14) mice and neural cells were exposed to 3% sevoflurane 2 h daily for three days. We found that sevoflurane anaesthesia decreased GLUT3 gene and protein expression in the hippocampus and temporal lobe, consistent with a decrease in glucose metabolism in the hippocampus and temporal lobe observed by [18F] fluorodeoxyglucose positron emission tomography (18F-FDG PET). Moreover, sevoflurane anaesthesia increased the number of TUNEL-positive cells and the levels of Bax, cleaved caspase 3 and cleaved PARP and reduced Bcl-2 levels in the hippocampus and temporal lobe. Young mice exposed to sevoflurane multiple times also showed learning and memory impairment. In addition, sevoflurane inhibited GLUT3 expression in primary hippocampal neurons and PC12 cells. GLUT3 overexpression in cultured neurons ameliorated the sevoflurane-induced decrease in glucose utilization and increase in the apoptosis rate. These data indicate that GLUT3 deficiency may contribute to sevoflurane-induced learning and memory deficits in young mice.

Sevoflurane impairs learning and memory of the developing brain through post-transcriptional inhibition of CCNA2 via microRNA-19-3p

The molecular mechanisms underlying sevoflurane (SEVO)-induced impairment of learning and memory remain unclear. Specifically, a role of microRNAs (miRNAs) in the control of the neuron proliferation in the developing brain exposed to SEVO has not been reported previously. Here, we studied the effects of SEVO exposure on the neural cell proliferation, and on the learning and memory of neonatal rats. We found that SEVO exposure significantly decreased neuron cell proliferation, reduced BDNF levels in brain, and impaired learning and memory of neonatal rats in Morris water maze test and Plus-Maze discriminative avoidance task (PM-DAT), likely through downregulation of CCNA2 protein. Next, we used bioinformatic tools to predict CCNA2-binding microRNAs (miRNAs), and found that miR-19-3p was upregulated in neurons exposed to SEVO. Moreover, miR-19-3p functionally inhibited the protein translation of CCNA2 in a human neural cell line, HCN-2. Furthermore, intracranial injection of adeno-associated virus carrying antisense of miR-19-3p under a CMV promoter into the neonatal rats significantly alleviated SEVO exposure-induced impairment of neuron cell proliferation, as well as the learning and memory of the rats. Together, our data suggest that SEVO-induced upregulation of miR-19-3p post-transcriptionally inhibits CCNA2, which contributes to the SEVO-associated impairment of learning and memory of the neonatal rats.

Using animal models to evaluate the functional consequences of anesthesia during early neurodevelopment

Fifteen years ago Olney and colleagues began using animal models to evaluate the effects of anesthetic and sedative agents (ASAs) on neurodevelopment. The results from ongoing studies indicate that, under certain conditions, exposure to these drugs during development induces an acute elevated apoptotic neurodegenerative response in the brain and long-term functional impairments. These animal models have played a significant role in bringing attention to the possible adverse effects of exposing the developing brain to ASAs when few concerns had been raised previously in the medical community. The apoptotic degenerative response resulting from neonatal exposure to ASAs has been replicated in many studies in both rodents and non-human primates, suggesting that a similar effect may occur in humans. In both rodents and non-human primates, significantly increased levels of apoptotic degeneration are often associated with functional impairments later in life. However, behavioral deficits following developmental ASA exposure have not been consistently reported even when significantly elevated levels of apoptotic degeneration have been documented in animal models. In the present work, we review this literature and propose a rodent model for assessing potential functional deficits following neonatal ASA exposure with special reference to experimental design and procedural issues. Our intent is to improve test sensitivity and replicability for detecting subtle behavioral effects, and thus enhance the translational significance of ASA models.

Cognitive impairment and transcriptomic profile in hippocampus of young mice after multiple neonatal exposures to sevoflurane

Children with repeated inhalational anesthesia may develop cognitive disorders. This study aimed to investigate the transcriptome-wide response of hippocampus in young mice that had been exposed to multiple sevoflurane in the neonatal period. Mice received 3% sevoflurane for 2 h on postnatal day (PND) 6, 8, and 10, followed by arterial blood gas test on PND 10, behavioral experiments on PND 31–36, and RNA sequencing (RNA-seq) of hippocampus on PND 37. Functional annotation and protein-protein interaction analyses of differentially expressed genes (DEGs) and quantitative reverse transcription polymerase chain reaction (qPCR) were performed. Neonatal sevoflurane exposures induced cognitive and social behavior disorders in young mice. RNA-seq identified a total of 314 DEGs. Several enriched biological processes (ion channels, brain development, learning, and memory) and signaling pathways (oxytocin signaling pathway and glutamatergic, cholinergic, and GABAergic synapses) were highlighted. As hub-proteins, Pten was involved in nervous system development, synapse assembly, learning, memory, and behaviors, Nos3 and Pik3cd in oxytocin signaling pathway, and Cdk16 in exocytosis and phosphorylation. Some top DEGs were validated by qPCR. This study revealed a transcriptome-wide profile in mice hippocampus after multiple neonatal exposures to sevoflurane, promoting better understanding of underlying mechanisms and investigation of preventive strategies.

Theaflavins alleviate sevoflurane-induced neurocytotoxicity via Nrf2 signaling pathway

Aim: Sevoflurane could induce apoptosis of rat hippocampal neurons, while theaflavins (TFs) have antioxidant and anti-inflammatory properties. This study aims to explore whether TFs could alleviate sevoflurane-induced neuronal cell injury.Materials and methods: Cells were treated by concentration gradient of sevoflurane and TFs. Cell viability, level of reactive oxygen species (ROS) and apoptosis rate were determined by cell counting kit-8 (CCK-8) and flow cytometry, respectively. Quantitative PCR (qPCR) and western blot were performed to determine mRNA and protein expressions.Results: TFs promoted viability of cells under the treatment of sevoflurane, while it suppressed apoptosis and down-regulated ROS level in a concentration-dependent manner. TFs could also down-regulate expression levels of caspase-3 and caspase-9 and cytosol and intranuclear nuclear factor E2-related factor 2 (Nrf2) in rat hippocampal nerve cells, while it up-regulated those of heme oxygenase 1 (HO-1), NADPH quinine oxidoreductase 1 (NQO1), glutamate cysteine ligase (GCL) and peroxiredoxin 1 (Prx1).Conclusions: Our study suggests that TFs exert protective effects on sevoflurane-induced neurocytotoxicity and therefore could be used as a potential drug for treatment of neuronal injury.

Anesthetics disrupt growth cone guidance cue sensing through actions on the GABAA α2 receptor mediated by the immature chloride gradient

BACKGROUND

General anesthetics (GAs) may exert harmful effects on the developing brain by disrupting neuronal circuit formation. Anesthetics that act on γ-aminobutyric acid (GABA) receptors can interfere with axonal growth cone guidance, a critical process in the assembly of neuronal circuitry. Here we investigate the mechanism by which isoflurane prevents sensing of the repulsive guidance cue, Semaphorin 3A (Sema3A).

METHODS

Growth cone sensing was assayed by measuring growth cone collapse in dissociated neocortical cultures exposed to recombinant Sema3A in the presence or absence of isoflurane and/or a panel of reagents with specific actions on components of the GABA receptor and chloride ion systems.

RESULTS

Isoflurane exposure prevents Sema3A induced growth cone collapse. A GABA_A α2 specific agonist replicates this effect (36.83 ± 3.417% vs 70.82 ± 2.941%, in the Sema3A induced control group, p < 0.0001), but an α1-specific agonist does not. Both a Na-K-Cl cotransporter 1 antagonism (bumetanide, BUM) and a chloride ionophore (IONO) prevent isoflurane from disrupting growth cone sensing of Sema3A. (65.67 ± 3.775% in Iso + BUM group vs 67.45 ± 3.624% in Sema3A induced control group, 65.34 ± 1.678% in Iso + IONO group vs 68.71 ± 2.071% in Sema3A induced control group, no significant difference) (n = 96 growth cones per group).

CONCLUSION

Our data suggest that the effects of isoflurane on growth cone sensing are mediated by the α2 subunit of the GABA_A receptor and also that they are dependent on the developmental chloride gradient, in which Cl^- exhibits a depolarizing effect. These findings provide a rationale for why immature neurons are particularly susceptible to anesthetic toxicity.

Dexmedetomidine reduced sevoflurane-induced neurodegeneration and long-term memory deficits in neonatal rats

Exposure to sevoflurane and other inhalational anesthetics can induce neurodegeneration in the developing brain. Although dexmedetomidine (DEX) has provided neuroprotection against hypoxic ischemic injury, relatively little is known about whether it has the neuroprotective effects against anesthetic-induced neurodegeneration. This study examined whether DEX improves the long-term cognitive dysfunction observed after exposure of neonatal rats to 3% sevoflurane. Seven-day-old rats received intraperitoneal saline (DEX 0) or DEX (6.6, 12.5, 25 μg/kg) 30 min before exposure to 3% sevoflurane with 21% oxygen for 4 h (n = 10 per group). The pups in the control group received only DEX 25 μg/kg without anesthesia. The escape latency in the Morris water maze was significantly increased in the DEX 0 group compared with the sham and control group, and the escape latency, but not the swimming path length, was significantly shorter at post-natal day 47 in the DEX 25 than in the DEX 0 group. The percent time spent in the quadrant was significantly decreased in the DEX 0 group compared with the sham and control group, and the percent time spent in the quadrant was significantly increased in the DEX 25 group compared with the DEX 0 groups. The freezing times of the DEX 0 and 6.6 groups were significantly decreased compared with those in the sham, control and DEX 25 groups. The number of NeuN-positive cells in the CA1 region was significantly decreased in the DEX 0 and 6.6 groups compared with the sham, control and DEX 25 groups. These findings indicate pre-treatment with DEX may improve long-term cognitive function and ameliorate the neuronal degeneration induced by sevoflurane exposure in neonatal rats.

Sevoflurane-induced learning deficits and spine loss via nectin-1/corticotrophin-releasing hormone receptor type 1 signaling

In recent years, the neurotoxicity of general anesthetics in the developing brain has been studied and raised great concern as a major health issue to the public and physicians. Sevoflurane inhalation may induce neurotoxicity expressed as memory and learning impairment in young animals. In the current study, we investigated the role of nectin-1 and corticotrophin-releasing hormone receptor type 1 (CRHR1) in sevoflurane-induced learning deficits and dendritic spines loss in neonatal mice. Neonatal mice (P7) were treated with 3% sevoflurane with 60% O₂ or 60% O₂ for 6 h. Cognitive function was evaluated by Y Maze, Object recognition test, and Morris Water Maze. Hippocampal nectin-1 and L-afadin expression assessed using western blot analysis. The dendritic spines morphology of the hippocampus was determined using Golgi impregnation on 7 d and 2 months old. Sevoflurane exposed to neonatal mice decreased hippocampal nectin-1 levels from 1 h to 2 months after sevoflurane inhalation and attenuated working and spatial memory and spinal number in adulthood, which could be reversed by nectin-1 overexpression and CRHR1 antagonist Antalarmin. Nectin-1 knockdown caused spatial learning deficits and dendritic spine loss and lower L-afadin protein expression. Sevoflurane-induced nectin-1 and L-afadin expression decrease was mediated by CRHR1 signaling in the hippocampus. This information can be used to develop targeted intervention aimed at decreasing the neurotoxicity of sevoflurane inhalation.

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.

Signaling network between the dysregulated expression of microRNAs and mRNAs in propofol-induced developmental neurotoxicity in mice

Mounting evidence has demonstrated that general anesthetics could induce acute neuroapoptosis in developing animals followed by long-term cognitive dysfunction, with the mechanisms remaining largely unknown. The aim of this study was to investigate the effect of the intravenous anesthetic propofol on the profiles of microRNAs (miRNAs) and messenger RNAs (mRNAs), and their interactive signaling networks in the developing mouse hippocampus. Postnatal day 7 (P7) mice were exposed to propofol for 3 hours. Hippocampi were harvested from both P7 (3 hours after exposure) and P60 mice for the analysis of the expression of 726 miRNAs and 24,881 mRNAs, and apoptosis. Long-term memory ability of P60 mice was analyzed using the Morris Water Maze. Propofol induced acute apoptosis in the hippocampus, and impaired memory function of mice. There were 100 altered mRNAs and 18 dysregulated miRNAs in the propofol-treated hippocampi compared with the intralipid-treated control tissues on P7. Bioinformatics analysis of these abnormally expressed genes on P7 indicated that 34 dysregulated miRNA-mRNA target pairs were related to pathological neurological and developmental disorder processes such as cell viability, cell morphology and migration, neural stem cell proliferation and neurogenesis, oligodendrocyte myelination, reactive oxygen species, and calcium signaling. Neonatal propofol exposure also resulted in the abnormal expression of 49 mRNAs and 4 miRNAs in P60 mouse hippocampi. Specifically, bioinformatics analysis indicates that among these dysregulated mRNAs and miRNAs, there were 2 dysregulated miRNA-mRNA targets pairs (Fam46a/miR-363-3p and Rgs3/miR-363-3p) that might be related to the effect of propofol on long-term cognitive function. Collectively, our novel investigation indicates that acute and long-term dysregulated miRNA-mRNA signaling networks potentially participate in propofol-induced developmental neurotoxicity.

Baicalein Inhibits Neuroapoptosis Via Pathways in Sevoflurane Induced Rats

Background

Baicalein, a bioactive flavonoid was explored for its capability to attenuate sevoflurane induced neuronal apoptosis and to improve behavioural and cognitive impairments. Sevoflurane is a frequently used inhalation anesthetic in neonates and children. Neonatal sevoflurane exposure causes widespread neurodegeneration and cognitive impairments. Development of compounds that could effectively prevent/reduce the adverse effects is of tremendous medical value.

Methods

Isolated groups of neonatal rats were regulated with baicalein (25, 50 or 100 mg/kg b.wt) from postnatal day 3 (P3) to P21 and were exposed to sevoflurane (3%; 6 h) on P7. Results: Baicalein inhibited sevoflurane induced neuroapoptosis significantly as assessed by TUNEL assay. The raised levels of cleaved caspase-3, Bad and Bax were down-regulated by baicalein with enhanced Bcl-2, Bcl-xL, xIAP, c-IAP-1, c-IAP-2 and survivin expression. Baicalein regulated JNK/ERK signalling and also activated the PI3K/Akt pathway effectively as evident from the increased Akt, phospho-Akt, GSK-3β, phospho-GSK-3β levels. Baicalein, also improved the behaviour of animals in open filed and olfactory tests. The freezing responses and the performance in Morris Water Maze tests were enhanced.

Conclusion

Baicalein reduced neurodegeneration and improved learning and memory retention of rats and as well modulated PI3/Akt/GSK-3β and JNK/ERK signalling pathways.

Influence of sevoflurane exposure on mitogen-activated protein kinases and Akt/GSK-3β/CRMP-2 signaling pathways in the developing rat brain

Prolonged exposure to volatile anesthetics causes neurodegeneration in developing animal brains. However, their underlying mechanisms of action remain unclear. The current study investigated the expression of proteins associated with the mitogen-activated protein kinases (MAPK) and protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β)/collapsin response mediator protein 2 (CRMP-2) signaling pathways in the cortices of neonatal mice following exposure to sevoflurane. Seven-day-old (P7) neonatal C57BL/6 mice were randomly divided into 2 groups and either exposed to 2.6% sevoflurane or air for 6 h. Terminal deoxyribonucleotide transferase mediated dUTP nick end labeling (TUNEL) staining, as well as the expression of activated caspase-3 and α-fodrin, was used to detect neuronal apoptosis in the cortices of mice. MAPK signaling pathways were investigated by detecting the expression of phosphorylated (p-) extracellular signal-regulated kinase 1/2 (ERK1/2), p-cyclic adenosine monophosphate response element-binding protein (CREB), p-p38, p-nuclear factor (NF-κB) and p-c-Jun N-terminal kinase (p-JNK). Akt/GSK-3β/CRMP-2 signaling pathways were assessed by detecting the expression of p-Akt, p-GSK-3β and p-CRMP-2 in the cortices of P7 mice 2 h following exposure to sevoflurane. The results demonstrated that sevoflurane significantly increased the apoptosis of cells in the retrosplenial cortex (RS), frontal cortex (FC) and parietal association cortex (PtA), increased the expression of cleaved caspase-3 expression and promoted the formation of 145 kDa and 120 kDa fragments from α-fodrin. Sevoflurane inhibited the phosphorylation of ERK1/2 and CREB, stimulated the phosphorylation of p38 and NF-κB, but did not significantly affect the phosphorylation of JNK. Furthermore, sevoflurane inhibited the phosphorylation of Akt, decreased the phosphorylation of GSK-3β at ser9 and increased the phosphorylation of CRMP2 at Thr514. These results suggest that multiple signaling pathways, including ERK1/2, P38 and Akt/GSK-3β/CRMP-2 may be involved in sevoflurane-induced neuroapoptosis in the developing brain.

Sevoflurane Impairs Growth Cone Motility in Dissociated Murine Neurons

BACKGROUND

Early postnatal exposure to general anesthetic agents causes a lasting impairment in learning and memory in animal models. One hypothesis to explain this finding is that exposure to anesthetic agents during critical points in neural development disrupts the formation of brain circuitry. Here, we explore the effects of sevoflurane on the neuronal growth cone, a specialization at the growing end of axons and dendrites that is responsible for the targeted growth that underlies connectivity between neurons.

METHODS

Dissociated neuronal cultures were prepared from embryonic mouse neocortex. Time-lapse images of live growth cones exposed to anesthetics were taken using differential interference contrast microscopy, and the rate of change of the area of the lamellipodia and the speed of the filopodial tip were quantified as measures of motility. The involvement of the p75 neurotropin receptor (p75NTR) was tested using inhibitors applied to the media and by a coimmunoprecipitation assay.

RESULTS

The rate of lamellipodial area change and filopodial tip velocity in both axonal and dendritic growth cones was significantly reduced with sevoflurane exposure between 2% and 6%. Motility could be substantially restored by treatment with Y27632 and TAT-peptide 5, which are inhibitors of Rho Kinase and p75NTR, respectively. Sevoflurane results in reduced coimmunoprecipitation of Rho-Guanosine-5'-diphosphate dissociation inhibitor after pulldown with p75NTR.

CONCLUSIONS

Sevoflurane interferes with growth cone motility, which is a critical process in brain circuitry formation. Our data suggest that this may occur through an action on the p75NTR, which promotes growth inhibitory signaling by the Rho pathway.