General anesthesia causes long-lasting disturbances in the ultrastructural properties of developing synapses in young rats

Zika virus encephalitis causes transient reduction of functional cortical connectivity

Significance

Determining the long-term cognitive impact of infections is clinically challenging. Using functional cortical connectivity, we demonstrate that interhemispheric cortical connectivity is decreased in individuals with acute Zika virus (ZIKV) encephalitis. This correlates with decreased presynaptic terminals in the somatosensory cortex. During recovery from ZIKV infection, presynaptic terminals recover, which is associated with recovered interhemispheric connectivity. This supports the contribution of synapses in the cortex to functional networks in the brain, which can be detected by widefield optical imaging. Although myeloid cell and astrocyte numbers are still increased during recovery, RNA transcription of multiple proinflammatory cytokines that increase during acute infection decreases to levels comparable to mock-infected mice during recovery. These findings also suggest that the immune response and cytokine-mediated neuroinflammation play significant roles in the integrity of brain networks during and after viral encephalitis.

Aim

We hypothesized that widefield optical imaging would allow us to assess functional cortical network disruption by ZIKV, including hippocampal-cortical networks.

Approach

We use widefield optical imaging to measure cortical functional connectivity (FC) in mice during acute infection with, and recovery from, intracranial infection with a mouse-adapted strain of ZIKV.

Results

Acute ZIKV infection leads to high levels of myeloid cell activation, with loss of neurons and presynaptic termini in the cerebral cortex and associated loss of FC primarily within the somatosensory cortex. During recovery, neuron numbers, synapses, and FC recover to levels near those of healthy mice. However, hippocampal injury and impaired spatial cognition persist. The magnitude of activated myeloid cells during acute infection predicted both recovery of synapses and the degree of FC recovery after recovery from ZIKV infection.

Conclusions

These findings suggest that a robust inflammatory response may contribute to the health of functional brain networks after recovery from infection.

Effect of Anesthesia During Pregnancy, Delivery, and Childhood on Autism Spectrum Disorder: A Systematic Review and Meta-analysis

To investigate the association between exposure to anesthesia during three periods of pregnancy, delivery, and childhood and autism spectrum disorder (ASD). PubMed, Scopus, Web of Science, Embase, Google Scholar, PsycArticles, and PsycINFO were searched from the date of database inception to 1 December 2022. Studies reported the association between exposure to anesthesia during pregnancy, delivery, and childhood and ASD were included. Extracted variables included hazard ratio (HR), relative risk or odds ratio, standard error, and 95% confidence interval (CI). Effect estimates were pooled using random-effects meta-analysis. In total, 16 studies including 8,156,608 individuals were included in the meta-analysis. Labor epidural anesthesia during delivery was associated with ASD in the general population (adjusted HR = 1.16, 95% CI, 1.06-1.28) but not in the sibling population (adjusted HR = 1.06, 95% CI, 0.98-1.15). Other anesthesia during delivery was not associated with ASD (general population: adjusted HR = 1.08, 95% CI, 0.99-1.17; sibling population: adjusted HR = 1.20, 95% CI, 0.81-1.79). Three studies suggested that exposure to anesthesia during pregnancy was associated with ASD in offspring (adjusted HR = 2.15, 95% CI, 1.32-3.48). There was no significant association between exposure to general anesthesia during childhood and ASD (adjusted HR = 1.02, 95% CI, 0.60-1.72). This meta-analysis did not confirm the association between exposure to anesthesia during labour and ASD. Previous observational studies used the neurotoxicity of anesthesia to biologically explain significant associations, but in fact different controls for confounding factors led to differences in associations. The evidence for pregnancy and childhood was limited given the small number of studies in these periods.

Unraveling the role and mechanism of mitochondria in postoperative cognitive dysfunction: a narrative review

Postoperative cognitive dysfunction (POCD) is a frequent neurological complication encountered during the perioperative period with unclear mechanisms and no effective treatments. Recent research into the pathogenesis of POCD has primarily focused on neuroinflammation, oxidative stress, changes in neural synaptic plasticity and neurotransmitter imbalances. Given the high-energy metabolism of neurons and their critical dependency on mitochondria, mitochondrial dysfunction directly affects neuronal function. Additionally, as the primary organelles generating reactive oxygen species, mitochondria are closely linked to the pathological processes of neuroinflammation. Surgery and anesthesia can induce mitochondrial dysfunction, increase mitochondrial oxidative stress, and disrupt mitochondrial quality-control mechanisms via various pathways, hence serving as key initiators of the POCD pathological process. We conducted a review on the role and potential mechanisms of mitochondria in postoperative cognitive dysfunction by consulting relevant literature from the PubMed and EMBASE databases spanning the past 25 years. Our findings indicate that surgery and anesthesia can inhibit mitochondrial respiration, thereby reducing ATP production, decreasing mitochondrial membrane potential, promoting mitochondrial fission, inducing mitochondrial calcium buffering abnormalities and iron accumulation, inhibiting mitophagy, and increasing mitochondrial oxidative stress. Mitochondrial dysfunction and damage can ultimately lead to impaired neuronal function, abnormal synaptic transmission, impaired synthesis and release of neurotransmitters, and even neuronal death, resulting in cognitive dysfunction. Targeted mitochondrial therapies have shown positive outcomes, holding promise as a novel treatment for POCD.

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

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

Pre-adolescence repeat exposure to sub-anesthetic doses of ketamine induces long-lasting behaviors and cognition impairment in male and female rat adults

In pre-adolescence, repeated anesthesia may be required for therapeutic interventions. Adult cognitive and neurobehavioral problems may result from preadolescent exposure to anesthetics. This study examined the long-term morphological and functional effects of repeated sub-anesthetic doses of ketamine exposure on male and female rat adults during pre-adolescence. Weaned 48 pre-adolescent rats from eight mothers and were randomly divided into four equal groups: control group and the ketamine group of males and females (20 mg/kg daily for 14 days); then animals received care for 20-30 days. Repeated exposure to sub-anesthetic doses of ketamine on cognitive functions was assayed using Social discrimination and novel object tests. Besides, an elevated plus maze and fear conditioning apparatus were utilized to determine exploratory and anxiety-like behavior in adults. Toluidine blue stain was used to evaluate the number of dead neurons in the hippocampus, and the effects of ketamine on synaptic plasticity were compared in the perforant pathway of the CA1 of the hippocampus. Our study indicates that repeated exposure to sub-anesthetic doses of ketamine during pre-adolescence can result in neurobehavioral impairment in male and female rat adulthood but does not affect anxiety-like behavior. We found a significant quantifiable increase in dark neurons. Recorded electrophysiologically, repeat sub-anesthetic doses of ketamine resulted in hampering long-term potentiation and pair pulse in male adult animals. Our results showed that repeated exposure to sub-anesthetic doses of ketamine during pre-adolescence can induce hippocampus and neuroplasticity changes later in adulthood. This study opens up a new line of inquiry into potential adverse outcomes of repeated anesthesia exposure in pre-adolescent rats.

Fer-1 Protects against Isoflurane-Induced Ferroptosis in Astrocytes and Cognitive Impairment in Neonatal Mice

Early and prolonged exposure to anesthetic agents could cause neurodevelopmental disorders in children. Astrocytes, heavily outnumber neurons in the brain, are crucial regulators of synaptic formation and function during development. However, how general anesthetics act on astrocytes and the impact on cognition are still unclear. In this study, we investigated the role of ferroptosis and GPX4, a major hydroperoxide scavenger playing a pivotal role in suppressing the process of ferroptosis, and their underlying mechanism in isoflurane-induced cytotoxicity in astrocytes and cognitive impairment. Our results showed that early 6 h isoflurane anesthesia induced cognitive impairment in mice. Ferroptosis-relative genes and metabolic changes were involved in the pathological process of isoflurane-induced cytotoxicity in astrocytes. The level of GPX4 was decreased while the expression of 4-HNE and generation of ROS were elevated after isoflurane exposure. Selectively blocking ferroptosis with Fer-1 attenuated the abovementioned cytotoxicity in astrocytes, paralleling with the reverse of the changes in GPX4, ROS and 4-HNE secondary to isoflurane anesthesia. Fer-1 attenuated the cognitive impairment induced by prolonged isoflurane exposure. Thus, ferroptosis conduced towards isoflurane-induced cytotoxicity in astrocytes via suppressing GPX4 and promoting lipid peroxidation. Fer-1 was expected to be an underlying intervention for the neurotoxicity induced by isoflurane in the developing brain, and to alleviate cognitive impairment in neonates.

Exposure to Sedation and Analgesia Medications: Short-term Cognitive Outcomes in Pediatric Critical Care Survivors With Acquired Brain Injury

Background/Objective: Pediatric intensive care unit (PICU) survivors risk significant cognitive morbidity, particularly those with acquired brain injury (ABI) diagnoses. Studies show sedative and analgesic medication may potentiate neurologic injury, but few studies evaluate impact on survivor outcomes. This study aimed to evaluate whether exposures to analgesic and sedative medications are associated with worse neurocognitive outcome. Methods: A retrospective cohort study was conducted of 91 patients aged 8 to 18 years, undergoing clinical neurocognitive evaluation approximately 1 to 3 months after PICU discharge. Electronic health data was queried for sedative and analgesic medication exposures, including opioids, benzodiazepines, propofol, ketamine, and dexmedetomidine. Doses were converted to class equivalents, evaluated by any exposure and cumulative dose exposure per patient weight. Cognitive outcome was derived from 8 objective cognitive assessments with an emphasis on executive function skills using Principal Components Analysis. Then, linear regression was used to control for baseline cognitive function estimates to calculate a standardized residualized neurocognitive index (rNCI) z-score. Multivariable linear regression evaluated the association between rNCI and medication exposure controlling for covariates. Significance was defined as P < .05. Results: Most (n = 80; 88%) patients received 1 or more study medications. Any exposure and higher cumulative doses of benzodiazepine and ketamine were significantly associated with worse rNCI in bivariate analyses. When controlling for Medicaid, preadmission comorbid conditions, length of stay, delirium, and receipt of other medication classes, receipt of benzodiazepine was associated with significantly worse rNCI (β-coefficient = -0.48, 95% confidence interval = -0.88, -0.08). Conclusions: Exposure to benzodiazepines was independently associated with worse acute phase cognitive outcome using objective assessments focused on executive function skills when controlling for demographic and illness characteristics. Clinician decisions regarding medication regimens in the PICU may serve as a modifiable factor to improve outcomes. Additional inquiry into associations with long-term cognitive outcome and optimal medication regimens is needed.

Transcranial ultrasound neuromodulation facilitates isoflurane-induced general anesthesia recovery and improves cognition in mice

Delayed arousal and cognitive dysfunction are common, especially in older patients after general anesthesia (GA). Elevating central nervous system serotonin (5-HT) levels can promote recovery from GA and increase synaptic plasticity to improve cognition. Ultrasound neuromodulation has become a noninvasive physical intervention therapy with high spatial resolution and penetration depth, which can modulate neuronal excitability to treat psychiatric and neurodegenerative diseases. This study aims to use ultrasound to noninvasively modulate the brain 5-HT levels of mice to promote recovery from GA and improve cognition in mice. The dorsal raphe nucleus (DRN) of mice during GA was stimulated by the 1.1 MHz ultrasound with a negative pressure of 356 kPa, and the liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) method was used to measure the DRN 5-HT concentrations. The mice's recovery time from GA was assessed, and the cognition was evaluated through spontaneous alternation Y-maze and novel object recognition (NOR) tests. After ultrasound stimulation, the mice's DRN 5-HT levels were significantly increased (control: 554.0 ± 103.2 ng/g, anesthesia + US: 664.2 ± 84.1 ng/g, *p = 0.0389); the GA recovery time (return of the righting reflex (RORR) emergence latency time) of mice was significantly reduced (anesthesia: 331.6 ± 70 s, anesthesia + US: 223.2 ± 67.7 s, *p = 0.0215); the spontaneous rotation behavior score of mice was significantly increased (anesthesia: 59.46 ± 5.26 %, anesthesia + US: 68.55 ± 5.24 %; *p = 0.0126); the recognition index was significantly increased (anesthesia: 55.02 ± 6.23 %, anesthesia + US: 78.52 ± 12.21 %; ***p = 0.0009). This study indicates that ultrasound stimulation of DRN increases serotonin levels, accelerates recovery from anesthesia, and improves cognition, which could be an important strategy for treating delayed arousal, postoperative delirium, or even lasting cognitive dysfunction after GA.

The effects of general anesthetics on mitochondrial structure and function in the developing brain

The use of general anesthetics in modern clinical practice is commonly regarded as safe for healthy individuals, but exposures at the extreme ends of the age spectrum have been linked to chronic cognitive impairments and persistent functional and structural alterations to the nervous system. The accumulation of evidence at both the epidemiological and experimental level prompted the addition of a warning label to inhaled anesthetics by the Food and Drug Administration cautioning their use in children under 3  years of age. Though the mechanism by which anesthetics may induce these detrimental changes remains to be fully elucidated, increasing evidence implicates mitochondria as a potential primary target of anesthetic damage, meditating many of the associated neurotoxic effects. Along with their commonly cited role in energy production via oxidative phosphorylation, mitochondria also play a central role in other critical cellular processes including calcium buffering, cell death pathways, and metabolite synthesis. In addition to meeting their immense energy demands, neurons are particularly dependent on the proper function and spatial organization of mitochondria to mediate specialized functions including neurotransmitter trafficking and release. Mitochondrial dependence is further highlighted in the developing brain, requiring spatiotemporally complex and metabolically expensive processes such as neurogenesis, synaptogenesis, and synaptic pruning, making the consequence of functional alterations potentially impactful. To this end, we explore and summarize the current mechanistic understanding of the effects of anesthetic exposure on mitochondria in the developing nervous system. We will specifically focus on the impact of anesthetic agents on mitochondrial dynamics, apoptosis, bioenergetics, stress pathways, and redox homeostasis. In addition, we will highlight critical knowledge gaps, pertinent challenges, and potential therapeutic targets warranting future exploration to guide mechanistic and outcomes research.

Dexmedetomidine prevents spatial learning and memory impairment induced by chronic REM sleep deprivation in rats

The study was attempted to investigate the effect on and mechanisms of action of dexmedetomidine with regard to learning and memory impairment in rats with chronic rapid eye movement (REM) sleep deprivation. A total of 50 male Sprague Dawley rats were randomly divided into five groups. Modified multiple platform method was conducted to cause the sleep deprivation of rats. Dexmedetomidine and midazolam were administered by intraperitoneal injection. Learning and memory ability was assessed through Morris water maze. Morphological changes of rat hippocampal neurons and synaptic were detected by transmission electron microscope and Golgi staining. The gene expression in hippocampus of each group was detected by RNA-seq and verified by RT-PCR and western blot. REM Sleep-deprived rats exhibited spatial learning and memory deficits. Furthermore, there was decreased density of synaptic spinous in the hippocampal CA1 region of the sleep deprivation group compared with the control. Additionally, transmission electron microscopy showed that the synaptic gaps of hippocampal neurons in REM sleep deprivation group were loose and fuzzy. Interestingly, dexmedetomidine treatment normalized these events to control levels following REM sleep deprivation. Molecular biological methods showed that Alox15 expression increased significantly after REM sleep deprivation as compared to control, while dexmedetomidine administration reversed the expression of Alox15. Dexmedetomidine alleviated the spatial learning and memory dysfunction induced with chronic REM sleep deprivation in rats. This protective effect may be related to the down-regulation of Alox15 expression and thereby the enhancement of synaptic structural plasticity in the hippocampal CA1 area of rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-023-00450-8.

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.

Neonatal sevoflurane exposure induces long-term changes in dendritic morphology in juvenile rats and mice

General anesthetics are potent neurotoxins when given during early development, causing apoptotic deletion of substantial number of neurons and persistent neurocognitive and behavioral deficits in animals and humans. The period of intense synaptogenesis coincides with the peak of susceptibility to deleterious effects of anesthetics, a phenomenon particularly pronounced in vulnerable brain regions such as subiculum. With steadily accumulating evidence confirming that clinical doses and durations of anesthetics may permanently alter the physiological trajectory of brain development, we set out to investigate the long-term consequences on dendritic morphology of subicular pyramidal neurons and expression on genes regulating the complex neural processes such as neuronal connectivity, learning, and memory. Using a well-established model of anesthetic neurotoxicity in rats and mice neonatally exposed to sevoflurane, a volatile general anesthetic commonly used in pediatric anesthesia, we report that a single 6 h of continuous anesthesia administered at postnatal day (PND) 7 resulted in lasting dysregulation in subicular mRNA levels of cAMP responsive element modulator (Crem), cAMP responsive element-binding protein 1 (Creb1), and Protein phosphatase 3 catalytic subunit alpha, a subunit of calcineurin (Ppp3ca) (calcineurin) when examined during juvenile period at PND28. Given the critical role of these genes in synaptic development and neuronal plasticity, we deployed a set of histological measurements to investigate the implications of anesthesia-induced dysregulation of gene expression on morphology and complexity of surviving subicular pyramidal neurons. Our results indicate that neonatal exposure to sevoflurane induced lasting rearrangement of subicular dendrites, resulting in higher orders of complexity and increased branching with no significant effects on the soma of pyramidal neurons. Correspondingly, changes in dendritic complexity were paralleled by the increased spine density on apical dendrites, further highlighting the scope of anesthesia-induced dysregulation of synaptic development. We conclude that neonatal sevoflurane induced persistent genetic and morphological dysregulation in juvenile rodents, which could indicate heightened susceptibility toward cognitive and behavioral disorders we are beginning to recognize as sequelae of early-in-life anesthesia.

Effect of sevoflurane anesthesia to neonatal rat hippocampus by RNA-seq

BACKGROUND

Sevoflurane is an inhalational anesthetic for the induction and maintenance of general anesthesia in pediatric surgery. However, few studies have paid attention to the multiple organ toxicity and the mechanism behind it.

METHODS

Inhalation anesthesia neonatal rat model were realized by exposing to 3.5% sevoflurane. RNA-seq was performed to find out how inhalation anesthesia affects the lung, cerebral cortex, hippocampus, and heart. Validation of RNA-seq results by QPCR after animal model establishment. Tunel assay detects cell apoptosis in each group. CCK-8, cell apoptosis assay and western blot assay validation of the role of siRNA-Bckdhb in the action of sevoflurane on rat hippocampal neuronal cells.

RESULTS

There are significant differences between different groups, especially the hippocampus and cerebral cortex. Bckdhb was significantly up-regulated in the hippocampus with sevoflurane-treated. Pathway analysis revealed several abundant pathways related to DEGs, e.g., protein digestion and absorption and PI3K-Akt signaling pathway. A series of cellular and animal experiments showed that siRNA-Bckdhb can inhibit the reduction of cellular activity caused by sevoflurane.

CONCLUSION

Bckdhb interference experiments indicated that sevoflurane induces hippocampal neuronal cells apoptosis by regulating Bckdhb expression. Our study provided new insights into the molecular mechanism of sevoflurane-induced brain damage in pediatrics.

Practical and societal implications of the potential anesthesia-induced neurotoxicity: The safetots perspective

Key elements for safe and high-quality care in pediatric anesthesia are personal and institutional competence, perioperative maintenance of physiological homeostasis, prevention, prompt recognition, and appropriate treatment of critical situations as well as the reassurance of the parents and respecting the children's rights. Training in pediatric anesthesia should take place within the framework of harmonized curricular structures. International quality assessment and improvement projects should be encouraged and supported by collaborations. Healthy communication and providing information in a balanced way to the public and all stakeholders is an important task for pediatric anesthesia societies and individuals. The Safetots.org initiative was established to emphasize the role of the conduct of anesthesia to prevent harm, promote quality in the perioperative period, and provide safe and high-quality clinical care. This initiative considers that the prevention of complications and other well-known risk factors of perioperative care, as well as the quality of anesthesia management, have a far more important impact on outcomes following anesthesia and surgery than anesthetic drugs themselves.

Neonatal exposures to sevoflurane in rhesus monkeys alter synaptic ultrastructure in later life

Repeated or prolonged early life exposure to anesthesia is neurotoxic in animals and associated with neurocognitive impairment in later life in humans. We used electron microscopy with unbiased stereological sampling to assess synaptic ultrastructure in dorsolateral prefrontal cortex (dlPFC) and hippocampal CA1 of female and male rhesus monkeys, four years after three 4-h exposures to sevoflurane during the first five postnatal weeks. This allowed us to ascertain long-term consequences of anesthesia exposure without confounding effects of surgery or illness. Synapse areas were reduced in the largest synapses in CA1 and dlPFC, predominantly in perforated spinous synapses in CA1 and nonperforated spinous synapses in dlPFC. Mitochondrial morphology and localization changed subtly in both areas. Synapse areas in CA1 correlated with response to a mild social stressor. Thus, exposure to anesthesia in infancy can cause long-term ultrastructural changes in primates, which may be substrates for long-term alterations in synaptic transmission and behavioral deficits.

Neurotoxic Impact of Individual Anesthetic Agents on the Developing Brain

Concerns about the safety of anesthetic agents in children arose after animal studies revealed disruptions in neurodevelopment after exposure to commonly used anesthetic drugs. These animal studies revealed that volatile inhalational agents, propofol, ketamine, and thiopental may have detrimental effects on neurodevelopment and cognitive function, but dexmedetomidine and xenon have been shown to have neuroprotective properties. The neurocognitive effects of benzodiazepines have not been extensively studied, so their effects on neurodevelopment are undetermined. However, experimental animal models may not truly represent the pathophysiological processes in children. Multiple landmark studies, including the MASK, PANDA, and GAS studies have provided reassurance that brief exposure to anesthesia is not associated with adverse neurocognitive outcomes in infants and children, regardless of the type of anesthetic agent used.

Prolonged sevoflurane exposure causes abnormal synapse development and dysregulates beta-neurexin and neuroligins in the hippocampus in neonatal rats

BACKGROUND

The underlying molecular mechanisms of the excitatory/inhibitory (E/I) imbalance induced by sevoflurane exposure to neonates remain poorly understood. This study aimed to investigate the long-term effects of prolonged sevoflurane exposure to neonatal rats during the peak period of synaptogenesis on the changes of trans-synaptic neurexin-neuroligin interactions, synaptic ultrastructure in the hippocampus and cognition.

METHODS

A total of 30 rat pups at postnatal day (P) 7 was randomly divided into two groups: the control group (exposed to 30 % oxygen balanced with nitrogen) and the sevoflurane group (exposed to 2.5 % sevoflurane plus 30 % oxygen balanced with nitrogen) for 6 h. Neurocognitive behaviors were assessed with the Open field test at P23-25 and the Morris water maze test at P26-30. The expression of β-neurexin (β-NRX), N-methyl-d-aspartate receptor 2 subunit (NR2A and NR2B), neuroligin-1 (NLG-1), neuroligin-2 (NLG-2), postsynaptic density protein-95 (PSD-95), α1-subunit of the γ-aminobutyric acid A receptor (GABAAα1) and gephyrin in the hippocampus at P30 were measured by Western blot. The ultrastructure of synapses was examined under electron microscope.

RESULTS

Prolonged sevoflurane exposure at P7 resulted in cognitive deficiency in adolescence, as well as the downregulation of β-NRX, NR2A, NR2B, NLG-1, and PSD-95, and the upregulation of GABAAα1, NLG-2, and gephyrin in the hippocampal CA3 region. Sevoflurane anesthesia also increased the number of symmetric synapses in the hippocampus.

CONCLUSIONS

Prolonged sevoflurane exposure during the brain development leads to cognitive deficiency and disproportion of excitatory/inhibitory synapses which may be caused by dysregulated expression of synaptic adhesion molecules of β-NRX and neuroligins.

MiR-128-3p Attenuates the Neurotoxicity in Rats Induced by Isoflurane Anesthesia

Isoflurane (ISO) has been widely used in clinical anesthesia, and exposure to ISO leads to cognitive dysfunction. Our paper aimed to investigate the effect of miR-128-3p on cognitive impairment, inflammation, and oxidative stress elicited by ISO anesthesia in Sprague-Dawley (SD) rats. The SD rats were treated with ISO to mimic the ISO-injured situation, and the concentration of miR-128-3p was quantified utilizing real-time PCR. The miR-128-3p's impacts in ISO-engendered rat models on the respects of inflammatory condition and oxidative activities were measured by the commercial kits. The Morris water maze test was adopted to measure the neuro-function regarding miR-128-3p. Additionally, the target was tested by the alternation of luciferase activity. The irritation of ISO suppressed miR-128-3p expression in rats, which was enhanced by the injection of miR-128-3p agomir. The adverse roles of ISO on inflammation, oxidative stress, and cognitive disorders were partially abrogated by an increment of miR-128-3p. A miR-128-3p's interconnection with specificity protein 1 (SP1) was pinpointed, and aggrandized mRNA levels of SP1 were found under ISO state. MiR-128 acted as a regulator in ISO damage in the respects of cognition, inflammation, and oxidative stress. The SP1's link of miR-128-3p was showcased.

Differential Effects of Sevoflurane Exposure on Long-Term Fear Memory in Neonatal and Adult Rats

It remains unclear whether exposure to sevoflurane produces different effects on long-term cognitive function in developing and mature brains. In the present study, Sprague-Dawley neonatal rats at postnatal day (PND) 7 and adult rats (PND 56) were used in all experiments. We performed fear conditioning testing to examine long-term fear memory following 4-h sevoflurane exposure. We assessed hippocampal synapse ultrastructure with a transmission electron microscope. Moreover, we investigated the effect of sevoflurane exposure on the expression of postsynaptic protein 95 (PSD-95) and its binding protein kalirin-7 in the hippocampus. We observed that early exposure to sevoflurane in neonatal rats impairs hippocampus-dependent fear memory, reduces hippocampal synapse density, and dramatically decreases the expressions of PSD-95 and kalirin-7 in the hippocampus of the developing brain. However, sevoflurane exposure in adult rats has no effects on hippocampus-dependent fear memory and hippocampal synapse density, and the expressions of PSD-95 and kalirin-7 in the adult hippocampus are not significantly altered following sevoflurane treatment. Our results indicate that sevoflurane exposure produces differential effects on long-term fear memory in neonatal and adult rats and that PSD-95 signaling may be involved in the molecular mechanism for early sevoflurane exposure-caused long-term fear memory impairment.

General Anesthesia and the Young Brain: The Importance of Novel Strategies with Alternate Mechanisms of Action

Over the past three decades, we have been grappling with rapidly accumulating evidence that general anesthetics (GAs) may not be as innocuous for the young brain as we previously believed. The growing realization comes from hundreds of animal studies in numerous species, from nematodes to higher mammals. These studies argue that early exposure to commonly used GAs causes widespread apoptotic neurodegeneration in brain regions critical to cognition and socio-emotional development, kills a substantial number of neurons in the young brain, and, importantly, results in lasting disturbances in neuronal synaptic communication within the remaining neuronal networks. Notably, these outcomes are often associated with long-term impairments in multiple cognitive-affective domains. Not only do preclinical studies clearly demonstrate GA-induced neurotoxicity when the exposures occur in early life, but there is a growing body of clinical literature reporting similar cognitive-affective abnormalities in young children who require GAs. The need to consider alternative GAs led us to focus on synthetic neuroactive steroid analogues that have emerged as effective hypnotics, and analgesics that are apparently devoid of neurotoxic effects and long-term cognitive impairments. This would suggest that certain steroid analogues with different cellular targets and mechanisms of action may be safe alternatives to currently used GAs. Herein we summarize our current knowledge of neuroactive steroids as promising novel GAs.

Do We Have Viable Protective Strategies against Anesthesia-Induced Developmental Neurotoxicity?

Since its invention, general anesthesia has been an indispensable component of modern surgery. While traditionally considered safe and beneficial in many pathological settings, hundreds of preclinical studies in various animal species have raised concerns about the detrimental and long-lasting consequences that general anesthetics may cause to the developing brain. Clinical evidence of anesthetic neurotoxicity in humans continues to mount as we continue to contemplate how to move forward. Notwithstanding the alarming evidence, millions of children are being anesthetized each year, setting the stage for substantial healthcare burdens in the future. Hence, furthering our knowledge of the molecular underpinnings of anesthesia-induced developmental neurotoxicity is crucially important and should enable us to develop protective strategies so that currently available general anesthetics could be safely used during critical stages of brain development. In this mini-review, we provide a summary of select strategies with primary focus on the mechanisms of neuroprotection and potential for clinical applicability. First, we summarize a diverse group of chemicals with the emphasis on intracellular targets and signal-transduction pathways. We then discuss epigenetic and transgenerational effects of general anesthetics and potential remedies, and also anesthesia-sparing or anesthesia-delaying approaches. Finally, we present evidence of a novel class of anesthetics with a distinct mechanism of action and a promising safety profile.

Quantitative behavioural phenotyping to investigate anaesthesia induced neurobehavioural impairment

Anaesthesia exposure to the developing nervous system causes neuroapoptosis and behavioural impairment in vertebrate models. Mechanistic understanding is limited, and target-based approaches are challenging. High-throughput methods may be an important parallel approach to drug-discovery and mechanistic research. The nematode worm Caenorhabditis elegans is an ideal candidate model. A rich subset of its behaviour can be studied, and hundreds of behavioural features can be quantified, then aggregated to yield a 'signature'. Perturbation of this behavioural signature may provide a tool that can be used to quantify the effects of anaesthetic regimes, and act as an outcome marker for drug screening and molecular target research. Larval C. elegans were exposed to: isoflurane, ketamine, morphine, dexmedetomidine, and lithium (and combinations). Behaviour was recorded, and videos analysed with automated algorithms to extract behavioural features. Anaesthetic exposure during early development leads to persisting behavioural variation (in total, 125 features across exposure combinations). Higher concentrations, and combinations of isoflurane with ketamine, lead to persistent change in a greater number of features. Morphine and dexmedetomidine do not appear to lead to behavioural impairment. Lithium rescues the neurotoxic phenotype produced by isoflurane. Findings correlate well with vertebrate research: impairment is dependent on agent, is concentration-specific, is more likely with combination therapies, and can potentially be rescued by lithium. These results suggest that C. elegans may be an appropriate model with which to pursue phenotypic screens for drugs that mitigate the neurobehavioural impairment. Some possibilities are suggested for how high-throughput platforms might be organised in service of this field.

The importance of non-coding RNAs in environmental stress-related developmental brain disorders: A systematic review of evidence associated with exposure to alcohol, anesthetic drugs, nicotine, and viral infections

Brain development is a dynamic and lengthy process that includes cell proliferation, migration, neurogenesis, gliogenesis, synaptogenesis, and pruning. Disruption of any of these developmental events can result in long-term outcomes ranging from brain structural changes, to cognitive and behavioral abnormality, with the mechanisms largely unknown. Emerging evidence suggests non-coding RNAs (ncRNAs) as pivotal molecules that participate in normal brain development and neurodevelopmental disorders. NcRNAs such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are transcribed from the genome but not translated into proteins. Many ncRNAs have been implicated as tuners of cell fate. In this review, we started with an introduction of the current knowledge of lncRNAs and miRNAs, and their potential roles in brain development in health and disorders. We then reviewed and discussed the evidence of ncRNA involvement in abnormal brain development resulted from alcohol, anesthetic drugs, nicotine, and viral infections. The complex connections among these ncRNAs were also discussed, along with potential overlapping ncRNA mechanisms, possible pharmacological targets for therapeutic/neuroprotective interventions, and potential biomarkers for brain developmental disorders.

Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit

In the midst of concerns for potential neurodevelopmental effects after surgical anesthesia, there is a growing awareness that children who require sedation during critical illness are susceptible to neurologic dysfunctions collectively termed pediatric post-intensive care syndrome, or PICS-p. In contrast to healthy children undergoing elective surgery, critically ill children are subject to inordinate neurologic stress or injury and need to be considered separately. Despite recognition of PICS-p, inconsistency in techniques and timing of post-discharge assessments continues to be a significant barrier to understanding the specific role of sedation in later cognitive dysfunction. Nonetheless, available pediatric studies that account for analgesia and sedation consistently identify sedative and opioid analgesic exposures as risk factors for both in-hospital delirium and post-discharge neurologic sequelae. Clinical observations are supported by animal models showing neuroinflammation, increased neuronal death, dysmyelination, and altered synaptic plasticity and neurotransmission. Additionally, intensive care sedation also contributes to sleep disruption, an important and overlooked variable during acute illness and post-discharge recovery. Because analgesia and sedation are potentially modifiable, understanding the underlying mechanisms could transform sedation strategies to improve outcomes. To move the needle on this, prospective clinical studies would benefit from cohesion with regard to datasets and core outcome assessments, including sleep quality. Analyses should also account for the wide range of diagnoses, heterogeneity of this population, and the dynamic nature of neurodevelopment in age cohorts. Much of the related preclinical evidence has been studied in comparatively brief anesthetic exposures in healthy animals during infancy and is not generalizable to critically ill children. Thus, complementary animal models that more accurately "reverse translate" critical illness paradigms and the effect of analgesia and sedation on neuropathology and functional outcomes are needed. This review explores the interactive role of sedatives and the neurologic vulnerability of critically ill children as it pertains to survivorship and functional outcomes, which is the next frontier in pediatric intensive care.

Neonatal Anesthesia and dysregulation of the Epigenome

Each year, millions of infants and children are anesthetized for medical and surgical procedures. Yet, a substantial body of preclinical evidence suggests that anesthetics are neurotoxins that cause rapid and widespread apoptotic cell death in the brains of infant rodents and non-human primates. These animals have persistent impairments in cognition and behavior many weeks or months after anesthesia exposure, leading us to hypothesize that anesthetics do more than simply kill brain cells. Indeed, anesthetics cause chronic neuropathology in neurons that survive the insult, which then interferes with major aspects of brain development, synaptic plasticity, and neuronal function. Understanding the phenomenon of anesthesia-induced developmental neurotoxicity is of critical public health importance because clinical studies now report that anesthesia in human infancy is associated with cognitive and behavioral deficits. In our search for mechanistic explanations for why a young and pliable brain cannot fully recover from a relatively brief period of anesthesia, we have accumulated evidence that neonatal anesthesia can dysregulate epigenetic tags that influence gene transcription such as histone acetylation and DNA methylation. In this review, we briefly summarize the phenomenon of anesthesia-induced developmental neurotoxicity. We then discuss chronic neuropathology caused by neonatal anesthesia, including disturbances in cognition, socio-affective behavior, neuronal morphology, and synaptic plasticity. Finally, we present evidence of anesthesia-induced genetic and epigenetic dysregulation within the developing brain that may be transmitted intergenerationally to anesthesia-naïve offspring.

Astrogliosis in juvenile non-human primates 2 years after infant anaesthesia exposure

BACKGROUND

Infant anaesthesia causes acute brain cell apoptosis, and later in life cognitive deficits and behavioural alterations, in non-human primates (NHPs). Various brain injuries and neurodegenerative conditions are characterised by chronic astrocyte activation (astrogliosis). Glial fibrillary acidic protein (GFAP), an astrocyte-specific protein, increases during astrogliosis and remains elevated after an injury. Whether infant anaesthesia is associated with a sustained increase in GFAP is unknown. We hypothesised that GFAP is increased in specific brain areas of NHPs 2 yr after infant anaesthesia, consistent with prior injury.

METHODS

Eight 6-day-old NHPs per group were exposed to 5 h isoflurane once (1×) or three times (3×), or to room air as a control (Ctr). Two years after exposure, their brains were assessed for GFAP density changes in the primary visual cortex (V1), perirhinal cortex (PRC), hippocampal subiculum, amygdala, and orbitofrontal cortex (OFC). We also assessed concomitant microglia activation and hippocampal neurogenesis.

RESULTS

Compared with controls, GFAP densities in V1 were increased in exposed groups (Ctr: 0.208 [0.085-0.427], 1×: 0.313 [0.108-0.533], 3×: 0.389 [0.262-0.652]), whereas the density of activated microglia was unchanged. In addition, GFAP densities were increased in the 3× group in the PRC and the subiculum, and in both exposure groups in the amygdala, but there was no increase in the OFC. There were no differences in hippocampal neurogenesis among groups.

CONCLUSIONS

Two years after infant anaesthesia, NHPs show increased GFAP without concomitant microglia activation in specific brain areas. These long-lasting structural changes in the brain caused by infant anaesthesia exposure may be associated with functional alterations at this age.

Early Isoflurane Exposure Impairs Synaptic Development in Fmr1 KO Mice via the mTOR Pathway

General anesthetics (GAs) may cause disruptions in brain development, and the effect of GA exposure in the setting of pre-existing neurodevelopmental disease is unknown. We tested the hypothesis that synaptic development is more vulnerable to GA-induced deficits in a mouse model of fragile X syndrome than in WT mice and asked whether they were related to the mTOR pathway, a signaling system implicated in both anesthesia toxicity and fragile X syndrome. Early postnatal WT and Fmr1-KO mice were exposed to isoflurane and brain slices were collected in adulthood. Primary neuron cultures isolated from WT and Fmr1-KO mice were exposed to isoflurane during development, in some cases treated with rapamycin, and processed for immunohistochemistry at maturity. Quantitative immunofluorescence microscopy was conducted for synaptic markers and markers of mTOR pathway activity. Isoflurane exposure caused reduction in Synpasin-1, PSD-95, and Gephyrin puncta that was significantly lower in Fmr1-KO mice than in WT mice. Similar results were found in cell culture, where synapse loss was ameliorated with rapamycin treatment. Early developmental exposure to isoflurane causes more profound synapse loss in Fmr1- KO than WT mice, and this effect is mediated by a pathologic increase in mTOR pathway activity.

HDAC6 is critical for ketamine-induced impairment of dendritic and spine growth in GABAergic projection neurons

Ketamine is widely used in infants and children for anesthesia; both anesthetic and sub-anesthetic doses of ketamine have been reported to preferentially inhibit the GABAergic neurons. Medium spiny neurons (MSNs), the GABAergic projection neurons in the striatum, are vulnerable to anesthetic exposure in the newborn brain. Growth of dendrites requires a deacetylase to remove acetyl from tubulin in the growth cone to destabilize the tubulin. Histone deacetylase 6 (HDAC6) affects microtubule dynamics, which are involved in neurite elongation. In this study we used a human induced pluripotent stem cells (iPSCs)-derived striatal GABA neuron system to investigate the effects of ketamine on HDAC6 and the morphological development of MSNs. We showed that exposure to ketamine (1-500 μM) decreased dendritic growth, dendrite branches, and dendritic spine density in MSNs in a time- and concentration-dependent manner. We revealed that ketamine treatment concentration-dependently inhibited the expression of HDAC6 or aberrantly translocated HDAC6 into the nucleus. Ketamine inhibition on HDAC6 resulted in α-tubulin hyperacetylation, consequently increasing the stability of microtubules and delaying the dendritic growth of MSNs. Finally, we showed that the effects of a single-dose exposure on MSNs were reversible and lasted for at least 10 days. This study reveals a novel role of HDAC6 as a regulator for ketamine-induced deficits in the morphological development of MSNs and provides an innovative method for prevention and treatment with respect to ketamine clinical applications.

Inhibition of RhoA Activity Does Not Rescue Synaptic Development Abnormalities and Long-Term Cognitive Impairment After Sevoflurane Exposure

General anesthetics interfere with dendritic development and synaptogenesis, resulting in cognitive impairment in the developing animals. RhoA signal pathway plays important roles in dendritic development by regulating cytoskeleton protein such as tubulin and actin. However, it's not clear whether RhoA pathway is involved in inhaled general anesthetics sevoflurane-induced synaptic development abnormalities and long-term cognitive dysfunction. Rats at postnatal day 7 (PND7) were injected intraperitoneally with RhoA pathway inhibitor Y27632 or saline 20 min before exposed to 2.8% sevoflurane for 4 h. The apoptosis-related proteins and RhoA/CRMP2 pathway proteins in the hippocampus were measured 6 h after sevoflurane exposure. Cognitive functions were evaluated by the open field test on PND25 rats and contextual fear conditioning test on PND32-33 rats. The dendritic morphology and density of dendritic spines in the pyramidal neurons of hippocampus were determined by Golgi staining and the synaptic plasticity-related proteins were also measured on PND33 rats. Long term potentiation (LTP) from hippocampal slices was recorded on PND34-37 rats. Sevoflurane induced caspase-3 activation, decreased the ratio of Bcl-2/Bax and increased TUNEL-positive neurons in hippocampus of PND7 rats, which were attenuated by inhibition of RhoA. However, sevoflurane had no significant effects on activity of RhoA/CRMP2 pathway. Sevoflurane disturbed dendritic morphogenesis, reduced the number of dendritic spines, decreased proteins expression of PSD-95, drebrin and synaptophysin, inhibited LTP in hippocampal slices and impaired memory ability in the adolescent rats, while inhibition of RhoA activity did not rescue the changes above induced by sevoflurane. RhoA signal pathway did not participate in sevoflurane-induced dendritic and synaptic development abnormalities and cognitive dysfunction in developing rats.

A synthetic peptide rescues rat cortical neurons from anesthetic-induced cell death, perturbation of growth and synaptic assembly

Anesthetics are deemed necessary for all major surgical procedures. However, they have also been found to exert neurotoxic effects when tested on various experimental models, but the underlying mechanisms remain unknown. Earlier studies have implicated mitochondrial fragmentation as a potential target of anesthetic-induced toxicity, although clinical strategies to protect their structure and function remain sparse. Here, we sought to determine if preserving mitochondrial networks with a non-toxic, short-life synthetic peptide—P110, would protect cortical neurons against both inhalational and intravenous anesthetic-induced neurotoxicity. This study provides the first direct and comparative account of three key anesthetics (desflurane, propofol, and ketamine) when used under identical conditions, and demonstrates their impact on neonatal, rat cortical neuronal viability, neurite outgrowth and synaptic assembly. Furthermore, we discovered that inhibiting Fis1-mediated mitochondrial fission reverses anesthetic-induced aberrations in an agent-specific manner. This study underscores the importance of designing mitigation strategies invoking mitochondria-mediated protection from anesthetic-induced toxicity in both animals and humans.

Regulation of CRMP2 by Cdk5 and GSK-3β participates in sevoflurane-induced dendritic development abnormalities and cognitive dysfunction in developing rats

BACKGROUND

General anesthetics such as sevoflurane interfere with dendritic development and synaptogenesis, resulting in cognitive impairment. The collapsin response mediator protein2 (CRMP2) plays important roles in dendritic development and synaptic plasticity and its phosphorylation is regulated by cycline dependent kinase-5 (Cdk5) and glycogen synthase kinase-3β (GSK-3β). Here we investigated whether Cdk5/CRMP2 or GSK-3β/CRMP2 pathway is involved in sevoflurane-induced developmental neurotoxicity.

METHODS

Rats at postnatal day 7 (PND7) were i.p. injected with Cdk5 inhibitor roscovitine, GSK-3β inhibitor SB415286 or saline 20 min. before exposure to 2.8% sevoflurane for 4 h. Western-blotting was applied to measure the expression of Cdk5/CRMP2 and GSK-3β/CRMP2 pathway proteins in the hippocampus 6 h after the sevoflurane exposure. When rats grew to adolescence (from PND25), they were tested for open-field and contextual fear conditioning, and then long term potentiation (LTP) from hippocampal slices was recorded, and morphology of pyramidal neuron was examined by Golgi staining and synaptic plasticity-related proteins expression in hippocampus were measured by western-blotting. In another batch of experiment, siRNA-CRMP2 or vehicle control was injected into hippocampus on PND5.

RESULTS

Sevoflurane activated Cdk5/CRMP2 and GSK-3β/CRMP2 pathways in the hippocampus of neonatal rats, reduced dendritic length, branches and the density of dendritic spine in pyramidal neurons. It also reduced the expressions of PSD-95, drebrin and synaptophysin in hippocampus, impaired memory ability of rats and inhibited LTP in hippocampal slices. All the impairment effects by sevoflurane were attenuated by pretreatment with inhibitor of Cdk5 or GSK-3β. Furthermore, rat transfected with siRNA-CRMP2 eliminated the neuroprotective effects of Cdk5 or GSK-3β blocker in neurobehavioral and LTP tests.

CONCLUSION

Cdk5/CRMP2 and GSK-3β/CRMP2 pathways participate in sevoflurane-induced dendritic development abnormalities and cognitive dysfunction in developing rats.

Expression Signature of lncRNAs and mRNAs in Sevoflurane-Induced Mouse Brain Injury: Implication of Involvement of Wide Molecular Networks and Pathways

Sevoflurane, one of the most commonly used pediatric anesthetics, was found to cause developmental neurotoxicity. To understand specific risk groups and develop countermeasures, a better understanding of its mechanisms is needed. We hypothesize that, as in many other brain degeneration pathways, long non-coding RNAs (lncRNAs) are involved in the sevoflurane-induced neurotoxicity. Postnatal day 7 (PD7) mice were exposed to 3% sevoflurane for 6 h. To quantify neurotoxicity in these mice, we (1) detected neural apoptosis through analysis of caspase 3 expression level and activity and (2) assessed long-term learning ability via the Morris water maze at PD60. To elucidate specific mechanisms, profiles of 27,427 lncRNAs and 18,855 messenger RNAs (mRNAs) in mouse hippocampi were analyzed using microarray assays. Sevoflurane-induced abnormal lncRNA and mRNA expression-associated function pathways were predicted by bioinformatic analysis. We found that sevoflurane induced significant neurotoxicity, causing acute neuroapoptosis and abnormal expression of 148 mRNAs and 301 lncRNAs on PD7 in mouse hippocampus. Additionally, exposed mice exhibited impaired memory on PD60. Bioinformatic analysis predicted that the dysregulated mRNAs, which are highly correlated with their co-expressed dysregulated lncRNAs, might be involved in 34 neurodegenerative signaling pathways (e.g., brain cell apoptosis and intellectual developmental disorder). Our study reveals for the first time that neonatal exposure to 3% sevoflurane induces abnormal lncRNA and mRNA expression profiles. These dysregulated lncRNAs/mRNAs form wide molecular networks that might contribute to various functional neurological disease pathways in the hippocampus, resulting in the observed acute apoptosis and impaired long-term memory.

Attention deficit hyperactivity disorder and educational level in adolescent and adult individuals after anesthesia and abdominal surgery during infancy

AIM

Several studies in animal models have found that exposure to anesthetics in early life can cause cognitive dysfunction. Human studies show conflicting results and studies of cognitive function after anesthesia and neonatal surgery are scarce. The aim of this study was to investigate whether exposure to anesthesia and abdominal surgery during infancy was associated with cognitive dysfunction from the perspective of educational level, disposable income and attention deficit hyperactivity disorders (ADHD) in adolescent and adult individuals.

METHODS

A cohort study with patients born 1976 to 2002 that underwent abdominal surgery during infancy at a pediatric surgical center were matched by age, sex, and gestational age to ten randomly selected individuals from the Swedish Medical Birth Register. Individuals with chromosomal aberrations were excluded. Data on highest level of education and annual disposable income were attained from Statistics Sweden and the diagnosis of ADHD were retrieved from the Swedish National Patient Register.

RESULTS

485 individuals and 4835 controls were included. Median gestational age was 38 weeks (24-44) and median age at surgery was seven days (0-365). Three hundred sixty-six individuals (70.0%) underwent surgery during the neonatal period (< 44 gestational weeks). Median operating time was 80 minutes (10-430). The mean age at follow-up was 28 years. Fisher's exact test for highest level of education for the exposed and unexposed groups were respectively: university 35% and 33%, upper secondary 44% and 47%, compulsory 21% and 20% (p = 0.6718). The median disposable income was 177.7 versus 180.9 TSEK respectively (p = 0.7532). Exposed individuals had a prevalence of ADHD of 5.2% and unexposed 4.4% (p = 0.4191).

CONCLUSIONS

This study shows that exposure to anesthesia and abdominal surgery during infancy is not associated with cognitive dysfunction from the perspective of educational level, disposable income and ADHD in adolescent and adult individuals. Further studies in larger cohorts at earlier gestational ages are needed to verify these findings.

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

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

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Research in context.•

Evidence before this studya.

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

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Added value of studyb.

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

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Implications of all the available evidencec.

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

Neonatal Exposure to Anesthesia Leads to Cognitive Deficits in Old Age: Prevention with Intranasal Administration of Insulin in Mice

Recent pre-clinical and clinical studies suggest that general anesthesia in infants and children may increase the risk of learning disabilities. Currently, there is no treatment for preventing anesthesia-induced neurotoxicity and potential long-term functional impairment. Animal studies have shown that neonatal exposure to anesthesia can induce acute neurotoxicity and long-term behavioral changes that can be detected a few months later. It is currently unknown whether neonatal exposure, especially repeated exposures, to general anesthesia can induce or increase the risk for cognitive impairment during aging. Here, we report that repeated exposures of neonatal mice (P7-9 days old) to anesthesia with sevoflurane (3 h/day for 3 days) led to cognitive impairment that was detectable at the age of 18-19 months, as assessed by using novel object recognition, Morris water maze, and fear conditioning tests. The repeated neonatal exposures to anesthesia did not result in detectable alterations in neurobehavioral development, in tau phosphorylation, or in the levels of synaptic proteins in the aged mouse brains. Importantly, we found that treatment with intranasal insulin prior to anesthesia exposure can prevent mice from anesthesia-induced cognitive impairment. These results suggest that neonatal exposure to general anesthesia could increase the risk for cognitive impairment during aging. This study also supports pre-treatment with intranasal administration of insulin to be a simple, effective approach to prevent infants and children from the increased risk for age-related cognitive impairment induced by neonatal exposure to general anesthesia.

Potential Neurodevelopmental Effects of Pediatric Intensive Care Sedation and Analgesia: Repetitive Benzodiazepine and Opioid Exposure Alters Expression of Glial and Synaptic Proteins in Juvenile Rats

Sedatives are suspected contributors to neurologic dysfunction in PICU patients, to whom they are administered during sensitive neurodevelopment. Relevant preclinical modeling has largely used comparatively brief anesthesia in infant age-approximate animals, with insufficient study of repetitive combined drug administration during childhood. We hypothesized that childhood neurodevelopment is selectively vulnerable to repeated treatment with benzodiazepine and opioid. We report a preclinical model of combined midazolam and morphine in early childhood age-approximate rats.

Disruption of Rapid Eye Movement Sleep Homeostasis in Adolescent Rats after Neonatal Anesthesia

BACKGROUND

Previous studies suggest that rapid eye movement sleep rebound and disruption of rapid eye movement sleep architecture occur during the first 24 h after general anesthesia with volatile anesthetics in adult rats. However, it is unknown whether rapid eye movement sleep alterations persist beyond the anesthetic recovery phase in neonatal rats. This study tested the hypothesis that rapid eye movement sleep disturbances would be present in adolescent rats treated with anesthesia on postnatal day 7.

METHODS

Forty-four neonatal rats were randomly allocated to treatment with anesthesia consisting of midazolam, nitrous oxide, and isoflurane or control conditions for 2 h or 6 h. Electroencephalographic and electromyographic electrodes were implanted and recordings obtained between postnatal days 26 and 34. The primary outcome was time spent in rapid eye movement sleep. Data were analyzed using two-tailed unpaired t tests and two-way repeated measures analysis of variance.

RESULTS

Rats treated with midazolam, nitrous oxide, and isoflurane exhibited a significant increase in rapid eye movement sleep three weeks later when compared with control rats, regardless of whether they were treated for 2 h (174.0 ± 7.2 min in anesthetized, 108.6 ± 5.3 in controls, P < 0.0001) or 6 h (151.6 ± 9.9 min in anesthetized, 108.8 ± 7.1 in controls, P = 0.002).

CONCLUSIONS

Treatment with midazolam, nitrous oxide, and isoflurane on postnatal day 7 increases rapid eye movement sleep three weeks later in rats.

Cyclophilin D Contributes to Anesthesia Neurotoxicity in the Developing Brain

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

The impact of surgeon experience on perioperative complications and operative measures following thoracolumbar 3-column osteotomy for adult spinal deformity: overcoming the learning curve

OBJECTIVE

Posterior-based thoracolumbar 3-column osteotomy (3CO) is a formidable surgical procedure. Surgeon experience and case volume are known factors that influence surgical complication rates, but these factors have not been studied well in cases of adult spinal deformity (ASD). This study examines how surgeon experience affects perioperative complications and operative measures following thoracolumbar 3CO in ASD.

METHODS

A retrospective study was performed of a consecutive cohort of thoracolumbar ASD patients who underwent 3CO performed by the senior authors from 2006 to 2018. Multivariate analysis was used to assess whether experience (years of experience and/or number of procedures) is associated with perioperative complications, operative duration, and blood loss.

RESULTS

A total of 362 patients underwent 66 vertebral column resections (VCRs) and 296 pedicle subtraction osteotomies (PSOs). The overall complication rate was 29.4%, and the surgical complication rate was 8.0%. The rate of postoperative neurological deficits was 6.2%. There was a trend toward lower overall complication rates with greater operative years of experience (from 44.4% to 28.0%) (p = 0.115). Years of operative experience was associated with a significantly lower rate of neurological deficits (p = 0.027); the incidence dropped from 22.2% to 4.0%. The mean operative time was 310.7 minutes overall. Both increased years of experience and higher case numbers were significantly associated with shorter operative times (p < 0.001 and p = 0.001, respectively). Only operative years of experience was independently associated with operative times (p < 0.001): 358.3 minutes from 2006 to 2008 to 275.5 minutes in 2018 (82.8 minutes shorter). Over time, there was less deviation and more consistency in operative times, despite the implementation of various interventions to promote fusion and prevent construct failure: utilization of multiple-rod constructs (standard, satellite, and nested rods), bone morphogenetic protein, vertebroplasty, and ligament augmentation. Of note, the use of tranexamic acid did not significantly lower blood loss.

CONCLUSIONS

Surgeon years of experience, rather than number of 3COs performed, was a significant factor in mitigating neurological complications and improving quality measures following thoracolumbar 3CO for ASD. The 3- to 5-year experience mark was when the senior surgeon overcame a learning curve and was able to minimize neurological complication rates. There was a continuous decrease in operative time as the surgeon's experience increased; this was in concurrence with the implementation of additional preventative surgical interventions. Ongoing practice changes should be implemented and can be done safely, but it is imperative to self-assess the risks and benefits of those practice changes.

General Anesthetic-Induced Neurotoxicity in the Immature Brain: Reevaluating the Confounding Factors in the Preclinical Studies

General anesthetic (GA) is used clinically to millions of young children each year to facilitate surgical procedures, relieve perioperative stress, and provide analgesia and amnesia. During recent years, there is a growing concern regarding a causal association between early life GA exposure and subsequently long-term neurocognitive abnormalities. To address the increasing concern, mounting preclinical studies and clinical trials have been undergoing. Until now, nearly all of the preclinical findings show that neonatal exposure to GA causally leads to acute neural cell injury and delayed cognitive impairment. Unexpectedly, several influential clinical findings suggest that early life GA exposure, especially brief and single exposure, does not cause adverse neurodevelopmental outcome, which is not fully in line with the experimental findings and data from several previous cohort trials. As the clinical data have been critically discussed in previous reviews, in the present review, we try to analyze the potential factors of the experimental studies that may overestimate the adverse effect of GA on the developing brain. Meanwhile, we briefly summarized the advance in experimental research. Generally, our purpose is to provide some useful suggestions for forthcoming preclinical studies and strengthen the powerfulness of preclinical data.

General anesthetic neurotoxicity in the young: Mechanism and prevention

General anesthesia (GA) is usually considered to safely induce a reversible unconscious state allowing surgery to be performed without pain. A growing number of studies, in particular pre-clinical studies, however, demonstrate that general anesthetics can cause neuronal death and even long-term neurological deficits. Herein, we report our literature review and meta-analysis data of the neurological outcomes after anesthesia in the young. We also review available mechanistic and epigenetic data of GA exposure related to cognitive impairment per se and the potential preventive strategies including natural herbal compounds to attenuate those side effects. In summary, anesthetic-induced neurotoxicity may be treatable and natural herbal compounds and other medications may have great potential for such use but warrants further study before clinical applications can be initiated.

The Role of Free Oxygen Radicals in Lasting Hyperexcitability of Rat Subicular Neurons After Exposure to General Anesthesia During Brain Development

A large number of preclinical studies have established that general anesthetics (GAs) may cause neurodevelopmental toxicity in rodents and nonhuman primates, which is followed by long-term cognitive deficits. The subiculum, the main output structure of hippocampal formation, is one of the brain regions most sensitive to exposure to GAs at the peak of synaptogenesis (i.e., postnatal day (PND) 7). We have previously shown that subicular neurons exposed to GAs produce excessive amounts of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂), which is a known modulator of neuronal excitability. To further explore the association between GA-mediated increase in ROS levels and long-term functional changes within subicular neurons, we sought to investigate the effects of ROS on excitability of these neurons using patch-clamp electrophysiology in acute rat brain slices. We hypothesized that both acute application of H₂O₂ and an early exposure (at PND 7) to GA consisting of midazolam (9 mg/kg), 70% nitrous oxide, and 0.75% isoflurane can affect excitability of subicular neurons and that superoxide dismutase and catalase mimetic, EUK-134, may reverse GA-mediated hyperexcitability in the subiculum. Our results using whole-cell recordings demonstrate that acute application of H₂O₂ has bidirectional effects on neuronal excitability: lower concentrations (0.001%, 0.3 mM) cause an excitatory effect, whereas higher concentrations (0.01%, 3 mM) inhibited neuronal firing. Furthermore, 0.3 mM H₂O₂ increased the average action potential frequency of subicular neurons by almost twofold, as assessed using cell-attach configuration. Finally, we found that preemptive in vivo administration of EUK-134 reduced GA-induced long-lasting hyperexcitability of subicular neurons ex vivo when studied in neonatal and juvenile rats. This finding suggests that the increase in ROS after GA exposure may play an important role in regulating neuronal excitability, thus making it an attractive therapeutic target for GA-induced neurotoxicity in neonates.

Evaluation of Neurotoxicity of Multiple Anesthesia in Children Using Visual Evoked Potentials

Objectives:

Anesthetic applications may cause increased neuronal damage in infants and children. Commonly cognitive or learning disability tests were used to investigate the neurological progress in children. Visual Evoked Potential is a gross electrical signal generated by the occipital regions of the cerebral cortex in response to visual stimulation and an objective assessment of brain function. In this study, to acquire more objective results, Visual Evoked Potential responses of children who had multiple exposures to anesthesia during the treatment of corrosive esophagitis were compared to children who have never received anesthesia before.

Methods:

In this prospective, single-blinded, randomized, controlled study, 25 children, who were admitted to our pediatric surgery clinic because of corrosive esophagitis and who received general anesthesia more than 15 times composed Group-P; 25 children, who admitted to our well-child-clinic and who had never received anesthesia before consisted Group-C. The flash and pattern VEP responses of both groups were measured at the electrophysiology laboratory without any anesthetic drug application. The VEP responses of children in Group-P were recorded at least three days after the last exposure to anesthesia.

Results:

Latencies and amplitudes of the N2 and P2 components of the pattern and flash VEP responses were statistically significantly different between the two groups (p=0.000).

Conclusion:

This study shows that in children who had repeated anesthetic applications VEP parameters are significantly altered. We believe that VEP responses may be a reliable objective criterion for the evaluation of anesthesia neurotoxicity.

Exposure of Developing Brain to General Anesthesia: What Is the Animal Evidence?

Recently, the U.S. Food and Drug Administration issued an official warning to all practicing physicians regarding potentially detrimental behavioral and cognitive sequelae of an early exposure to general anesthesia during in utero and in early postnatal life. The U.S. Food and Drug Administration concern is focused on children younger than three years of age who are exposed to clinically used general anesthetics and sedatives for three hours or longer. Although human evidence is limited and controversial, a large body of scientific evidence gathered from several mammalian species demonstrates that there is a potential foundation for concern. Considering this new development in public awareness, this review focuses on nonhuman primates because their brain development is the closest to humans in terms of not only timing and duration, but in terms of complexity as well. The review compares those primate findings to previously published work done with rodents.

Early Developmental Exposure to Repetitive Long Duration of Midazolam Sedation Causes Behavioral and Synaptic Alterations in a Rodent Model of Neurodevelopment

There is a large body of preclinical literature suggesting that exposure to general anesthetic agents during early life may have harmful effects on brain development. Patients in intensive care settings are often treated for prolonged periods with sedative medications, many of which have mechanisms of action that are similar to general anesthetics. Using in vivo studies of the mouse hippocampus and an in vitro rat cortical neuron model we asked whether there is evidence that repeated, long duration exposure to midazolam, a commonly used sedative in pediatric intensive care practice, has the potential to cause lasting harm to the developing brain. We found that mice that underwent midazolam sedation in early postnatal life exhibited deficits in the performance on Y-maze and fear-conditioning testing at young adult ages. Labeling with a nucleoside analog revealed a reduction in the rate of adult neurogenesis in the hippocampal dentate gyrus, a brain region that has been shown to be vulnerable to developmental anesthetic neurotoxicity. In addition, using immunohistochemistry for synaptic markers we found that the number of presynaptic terminals in the dentate gyrus was reduced, while the number of excitatory postsynaptic terminals was increased. These findings were replicated in a midazolam sedation exposure model in neurons in culture. We conclude that repeated, long duration exposure to midazolam during early development has the potential to result in persistent alterations in the structure and function of the brain.

Neonatal anesthesia impairs synapsin 1 and synaptotagmin 1, two key regulators of synaptic vesicle docking and fusion

Early exposure to anesthetics may interfere with synaptic development and lead to cognitive deficits. We previously demonstrated a decrease in vesicles docked at and within 100 nm from the presynaptic membrane in hippocampal nerve terminals of neonatal rats after anesthesia. Hence, we designed this study to assess the effects of neonatal anesthesia on synapsin 1 (Syn1) and synaptotagmin 1 (Syt1), two key regulators of vesicle docking and fusion. To test the link between changes in Syn1 and Syt1 and behavioral deficits observed after neonatal anesthesia, we also assessed retention memory and fear conditioning in adolescent rats after neonatal anesthesia. Pups received a combination of clinical anesthetics, then Syn1 and Syt1 mRNA and protein expression were determined at the peak (postnatal day 8, P8), part-way through (P12) and end of synaptogenesis (P24) in the CA1-subiculum by qPCR and western blotting. Anesthesia decreased Syn1 and Syt1 mRNA expression at P8 (P<0.01 and <0.001) and P12 (P=0.001 and 0.017), but not P24 (P=0.538 and 0.671), and impaired Syn1, p-Syn1, and Syt1 protein levels at P8 (P=0.038, 0.041, and 0.004, respectively), P12 (P<0.001, P=0.001, and P<0.0001), and P24 (P=0.025, 0.031, and 0.001). Anesthetic-challenged rats displayed deficient long-term retention memory (P=0.019) and hippocampus-dependent fear conditioning (P<0.001). These results suggest that anesthetics alter Syn1 and Syt1 during synapse assembly and maturation, raising the possibility that anesthetic interference with Syn1 and Syt1 could initiate changes in synaptic function that contribute to the cognitive deficits observed after neonatal anesthesia.

General anesthetic exposure in adolescent rats causes persistent maladaptations in cognitive and affective behaviors and neuroplasticity

Accumulating evidence indicates that exposure to general anesthetics during infancy and childhood can cause persistent cognitive impairment, alterations in synaptic plasticity, and, to a lesser extent, increased incidence of behavioral disorders. Unfortunately, the developmental parameters of susceptibility to general anesthetics are not well understood. Adolescence is a critical developmental period wherein multiple late developing brain regions may also be vulnerable to enduring general anesthetic effects. Given the breadth of the adolescent age span, this group potentially represents millions more individuals than those exposed during early childhood. In this study, isoflurane exposure within a well-characterized adolescent period in Sprague-Dawley rats elicited immediate and persistent anxiety- and impulsive-like responding, as well as delayed cognitive impairment into adulthood. These behavioral abnormalities were paralleled by atypical dendritic spine morphology in the prefrontal cortex (PFC) and hippocampus (HPC), suggesting delayed anatomical maturation, and shifts in inhibitory function that suggest hypermaturation of extrasynaptic GABA_A receptor inhibition. Preventing this hypermaturation of extrasynaptic GABA_A receptor-mediated function in the PFC selectively reversed enhanced impulsivity resulting from adolescent isoflurane exposure. Taken together, these data demonstrate that the developmental window for susceptibility to enduring untoward effects of general anesthetics may be much longer than previously appreciated, and those effects may include affective behaviors in addition to cognition.