Neonatal anesthetic neurotoxicity: Insight into the molecular mechanisms of long-term neurocognitive deficits

A recommendation for the use of electrical biosensing technology in neonatology

Non-invasive cardiac output monitoring, via electrical biosensing technology (EBT), provides continuous, multi-parameter hemodynamic variable monitoring which may allow for timely identification of hemodynamic instability in some neonates, providing an opportunity for early intervention that may improve neonatal outcomes. EBT encompasses thoracic (TEBT) and whole body (WBEBT) methods. Despite the lack of relative accuracy of these technologies, as compared to transthoracic echocardiography, the use of these technologies in neonatology, both in the research and clinical arena, have increased dramatically over the last 30 years. The European Society of Pediatric Research Special Interest Group in Non-Invasive Cardiac Output Monitoring, a group of experienced neonatologists in the field of EBT, deemed it appropriate to provide recommendations for the use of TEBT and WBEBT in the field of neonatology. Although TEBT is not an accurate determinant of cardiac output or stroke volume, it may be useful for monitoring longitudinal changes of hemodynamic parameters. Few recommendations can be made for the use of TEBT in common neonatal clinical conditions. It is recommended not to use WBEBT to monitor cardiac output. The differences in technologies, study methodologies and data reporting should be addressed in ongoing research prior to introducing EBT into routine practice. IMPACT STATEMENT: TEBT is not recommended as an accurate determinant of cardiac output (CO) (or stroke volume (SV)). TEBT may be useful for monitoring longitudinal changes from baseline of hemodynamic parameters on an individual patient basis. TEBT-derived thoracic fluid content (TFC) longitudinal changes from baseline may be useful in monitoring progress in respiratory disorders and circulatory conditions affecting intrathoracic fluid volume. Currently there is insufficient evidence to make any recommendations regarding the use of WBEBT for CO monitoring in neonates. Further research is required in all areas prior to the implementation of these monitors into routine clinical practice.

Comparative analysis of two methods in circumcision: a new disposable device versus classic sleeve technique

PURPOSE

Circumcision is the most common surgical procedures performed in males. Medical circumcision is recommended for diseases such as phimosis, paraphimosis, balanoposthitis and common urinary tract infections, although there is no exact indication. Conversely, Jewish and Muslim individuals commonly undergo circumcision regardless of medical necessity. Circumcision devices are designed to shorten surgery time, achieve an aesthetic appearance and ensure safe surgery. The aim of this study is to evaluate the effectiveness of the NeoAlis clamp, a disposable circumcision device, by comparing it with the sleeve technique in children.

MATERIALS AND METHODS

Between 2017 and 2023, retrospective evaluation of 2626 patients who underwent circumcision using either the NeoAlis clamp (group 1) or the sleeve technique (group 2) was conducted. Operation time, results, cost, complications were compared between the two groups.

RESULTS

The study encompassed 2626 patients who fulfilled the inclusion criteria. Group 1 comprised 2403 patients, whereas Group 2 consisted of 223 patients. The overall complication rate, as denoted by n = 47, was 1.7%. Group 1 operation time was shorter than group 2. Bleeding, the most feared complication in the early period, was higher in the second group. No statistically significant difference was observed between the two groups regarding cost comparison.

CONCLUSION

The primary concern during circumcision is to avoid complications related to general anesthesia in newborns and infants. The use of disposable ring devices has been facilitated by the shorter operation time and the absence of the need for sutures when performing circumcision under local anesthesia. However, knowledge of advanced surgical circumcision techniques is necessary in cases of bleeding and inappropriate ring placement.

Impact of anesthetics on rat hippocampus and neocortex: A comprehensive proteomic study based on label-free mass spectrometry

Anesthesia is regarded as an important milestone in medicine. However, the negative effect on memory and learning has been observed. In addition, the impact of anesthetics on postoperative cognitive functions is still discussed. In this work, in vivo experiment simulating a general anesthesia and ICU sedation was designed to assess the impact of two intravenous (midazolam, dexmedetomidine) and two inhalational (isoflurane, desflurane) agents on neuronal centers for cognition (neocortex), learning, and memory (hippocampus). More than 3600 proteins were quantified across both neocortex and hippocampus. Proteomic study revealed relatively mild effects of anesthetics, nevertheless, protein dysregulation uncovered possible different effect of isoflurane (and midazolam) compared to desflurane (and dexmedetomidine) to neocortical and hippocampal proteins. Isoflurane induced the upregulation of hippocampal NMDAR and other proteins of postsynaptic density and downregulation of GABA signaling, whereas desflurane and dexmedetomidine rather targeted mitochondrial VDAC isoforms and protein regulating apoptotic activity.

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.

Nicotinamide ameliorates mitochondria-related neuronal apoptosis and cognitive impairment via the NAD+/SIRT3 pathway

Emerging evidence suggests that mitochondria play a central role in mental health disorders including schizophrenia. Here we investigated whether nicotinamide (NAM) normalized cognitive impairment via a mechanism involving the mitochondrial Sirtuin 3 (SIRT3) pathway. The 24 h maternal separation (MS) rat model was used to mimic schizophrenia-associate phenotypes. Schizophrenia-like behaviors and memory impairments were detected using the pre-pulse inhibition test, novel object recognition test, and Barnes maze test, and neuronal apoptosis was characterized using multiple assays. SIRT3 activity was inhibited pharmacologically or by knockdown in HT22 cells, and BV2 microglia and SIRT3-knockdown HT22 cells were co-cultured in vitro. Mitochondrial molecules were measured by western blotting, and mitochondrial damage was measured with reactive oxygen species and mitochondrial membrane potential assays. Proinflammatory cytokines were assayed by ELISA and microglial activation was detected by immunofluorescence. MS animals showed behavioral and cognitive impairment and increased neuronal apoptosis. Supplementation with NAM or administration of honokiol, a SIRT3 activator, reversed all of the changes in behavioral and neuronal phenotypes. Administration of the SIRT3 inhibitor 3-TYP in control and NAM-treated MS rats caused behavioral and neuronal phenotypes similar to MS. In vitro, inhibition of SIRT3 activity with 3-TYP or by knockdown in HT22 cells increased ROS accumulation and caused neuronal apoptosis in a single-culture system. In co-culture systems, SIRT3 knockdown in HT22 cells activated BV2 microglia and increased levels of TNF-α, IL-6, and IL-1β. The administration of NAM blocked these alterations. Taken together, these data suggest that NAM can rescue neuronal apoptosis and microglial over-activation through the nicotinamide adenine dinucleotide (NAD⁺)-SIRT3-SOD2 signaling pathway, furthering our understanding of the pathogenesis of schizophrenia and providing avenues for novel treatments.

Heart-brain axis: Association of congenital heart abnormality and brain diseases

Brain diseases are a major burden on human health worldwide, and little is known about how most brain diseases develop. It is believed that cardiovascular diseases can affect the function of the brain, and many brain diseases are associated with heart dysfunction, which is called the heart-brain axis. Congenital heart abnormalities with anomalous hemodynamics are common treatable cardiovascular diseases. With the development of cardiovascular surgeries and interventions, the long-term survival of patients with congenital heart abnormalities continues to improve. However, physicians have reported that patients with congenital heart abnormalities have an increased risk of brain diseases in adulthood. To understand the complex association between congenital heart abnormalities and brain diseases, the paper reviews relevant clinical literature. Studies have shown that congenital heart abnormalities are associated with most brain diseases, including stroke, migraine, dementia, infection of the central nervous system, epilepsy, white matter lesions, and affective disorders. However, whether surgeries or other interventions could benefit patients with congenital heart abnormalities and brain diseases remains unclear because of limited evidence.

Gastrodin improves neuroinflammation-induced cognitive dysfunction in rats by regulating NLRP3 inflammasome

Neuroinflammation is the main pathological mechanism of cognitive dysfunction caused by neurodegenerative diseases, and effective preventive and therapeutic measures are not available. We predicted the key targets of gastrodin's effects upon neuroinflammation through Network Pharmacology and molecular docking. Then the predicted targets were used to study how gastrodin affected cognitive dysfunction triggered by lipopolysaccharide-induced neuroinflammation in rats and its mechanisms. Three-month-old male rats were intraperitoneally injected with lipopolysaccharide for 3 days (d), 7 d and 14 d respectively. Gastrodin improved learning and memory ability of rats with neuroinflammation. Lipopolysaccharide enhanced the levels of pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6, in rat hippocampus, which could be reversed by gastrodin. Gastrodin also inhibited the activation of microglia. Our findings suggested that gastrodin exerted neuroprotective effects in rats with neuroinflammation by impacting the TLR4-NF-kB-NLRP3 pathway. Therefore, gastrodin may be a potential therapeutic agent for neuroinflammation-induced cognitive dysfunction.

Echinacoside alleviates sevoflurane-induced cognitive dysfunction by activating FOXO1-mediated autophagy

The current study aimed to examine the effects of echinacoside on cognitive impairment in mice after exposure to sevoflurane. To examine the role of FOXO1, si-FOXO1 and si-con were injected into the hippocampus through the left lateral cerebral ventricles. Sevoflurane-induced mice had serious cognitive dysfunction. However, pretreatment with echinacoside alleviated the cognitive dysfunction, as measured by a shortened escape latency time, and increased platform crossing times, the percentage of distance in the target quadrant and Y-maze spontaneous alternations. In addition, we found that echinacoside elevated FOXO1 expression in the hippocampus, increased the expression of autophagy-related proteins including Beclin 1, ATG5, ATG7 and LC3, and reduced P62 expression. Silencing of FOXO1 aggravated the cognitive deficits and reduced expression of the autophagy-related markers, while the effects of si-FOXO1 on memory were abrogated by echinacoside. Echinacoside attenuated the cognitive impairment in sevoflurane-induced mice through FOXO1-mediated autophagy.

Dopamine transporter in the ventral tegmental area modulates recovery from propofol anesthesia in rats

OBJECTIVE(S)

To investigate the role of the dopamine transporter (DAT) in the ventral tegmental area (VTA) in the recovery from propofol anesthesia in rats.

MATERIALS AND METHODS

A total of 150 Sprague-Dawley (SD) rats were randomly split into a normal control group (NC), saline group (S), propofol anesthesia group (P), adeno-associated viral-NC-mCherry (AAV-NC) group, and AAV-DAT-RNAi (DAT-RNAi) group (n = 30 per group). In rats in the AAV intervention group, AAV was injected into the VTA nucleus via a stereotaxer. The rats in each group were continuously pumped with propofol through the tail vein at a dose of 70mg/kg/h, and the control group was infused with the same dose of saline at the same speed for 30min. Immunofluorescence staining was used to observe the expression of c-fos protein in the prefrontal cortex (PFC). The induction and recovery time of propofol anesthesia were recorded based on the time of disappearance of the righting reflex (LORR) and recovery (RORR). The anesthesia depth score was performed on all rats 10min after starting the administration and 10min after withdrawal, which represented the depth of anesthesia during anesthesia and the degree of recovery during anesthesia recovery, respectively. electroencephalogram (EEG) was recorded during propofol anesthesia and recovery.

RESULTS

Compared to the NC group, the RORR of the DAT-RNAi group was shortened, and the anesthesia depth score was higher (P < 0.05). In the DAT-RNAi group, during the period of propofol anesthesia, the β wave frequencies increased, the θ wave frequencies decreased, and the expression of c-fos protein in PFC increased and during the recovery from propofol anesthesia, the α wave and β wave frequencies were increased (P < 0.05).

CONCLUSION

Knockdown of the DAT in the VTA region can enhance the activity of PFC neurons and promote the recovery of rats from propofol anesthesia.

Neuron-Glia Crosstalk Plays a Major Role in the Neurotoxic Effects of Ketamine via Extracellular Vesicles

Background: There is a compelling evidence from animal models that early exposure to clinically relevant general anesthetics (GAs) interferes with brain development, resulting in long-lasting cognitive impairments. Human studies have been inconclusive and are challenging due to numerous confounding factors. Here, we employed primary human neural cells to analyze ketamine neurotoxic effects focusing on the role of glial cells and their activation state. We also explored the roles of astrocyte-derived extracellular vesicles (EVs) and different components of the brain-derived neurotrophic factor (BDNF) pathway.

Methods: Ketamine effects on cell death were analyzed using live/dead assay, caspase 3 activity and PARP-1 cleavage. Astrocytic and microglial cell differentiation was determined using RT-PCR, ELISA and phagocytosis assay. The impact of the neuron-glial cell interactions in the neurotoxic effects of ketamine was analyzed using transwell cultures. In addition, the role of isolated and secreted EVs in this cross-talk were studied. The expression and function of different components of the BDNF pathway were analyzed using ELISA, RT-PCR and gene silencing.

Results: Ketamine induced neuronal and oligodendrocytic cell apoptosis and promoted pro-inflammatory astrocyte (A1) and microglia (M1) phenotypes. Astrocytes and microglia enhanced the neurotoxic effects of ketamine on neuronal cells, whereas neurons increased oligodendrocyte cell death. Ketamine modulated different components in the BDNF pathway: decreasing BDNF secretion in neurons and astrocytes while increasing the expression of p75 in neurons and that of BDNF-AS and pro-BDNF secretion in both neurons and astrocytes. We demonstrated an important role of EVs secreted by ketamine-treated astrocytes in neuronal cell death and a role for EV-associated BDNF-AS in this effect.

Conclusions: Ketamine exerted a neurotoxic effect on neural cells by impacting both neuronal and non-neuronal cells. The BDNF pathway and astrocyte-derived EVs represent important mediators of ketamine effects. These results contribute to a better understanding of ketamine neurotoxic effects in humans and to the development of potential approaches to decrease its neurodevelopmental impact.

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.

Anesthetic Exposure in Staged Versus Single-Stage Cleft Lip and Palate Repair: Can We Reduce Risk of Anesthesia-Induced Developmental Neurotoxicity?

ABSTRACT

Cleft lip and palate (CLP) repair is typically performed in a staged fashion, which requires multiple instances of anesthetic exposure during a critical period of infant neurodevelopment. One solution to this concern includes the implementation of a single-stage CLP repair performed between 6 and 12 months of age. This study aimed to compare total anesthetic exposure between single-stage and staged CLP repairs. A retrospective review of unilateral CLP repairs between 2013 and 2018 conducted at a single institution was performed. Patients underwent either traditional, staged lip and palate repair, or single-stage complete cleft repair, where palate, lip, alveolus, and nasal repair was performed simultaneously. Primary endpoints included: total surgical time and total anesthetic exposure. Secondary endpoints included: excess anesthesia time, recovery room time, length of stay, and type of anesthetic administered. Two hundred twenty-five (n = 225) unilateral CLP repairs were conducted at the Loma Linda University. Detailed anesthetic data for eighty-six (n = 86) single-stage and twenty-eight (n = 28) staged operations were available. There was a statistically significant decrease in anesthetic exposure in single-stage versus staged repairs (316 minutes versus 345 minutes, P = 0.017), despite similar procedure times (260 minutes versus 246 minutes, P = 0.224). This resulted in near double excess anesthetic exposure time in the staged group (98 minutes versus 56 minutes, P < 0.001), primarily occurring during induction. This analysis suggests that single-stage CLP repair can reduce wasted time under general anesthesia and potentially reduce harmful neuronal toxicity in the developmental period in this at-risk population.

[Inhalational anesthetics]

Inhalational anesthetics have been used for induction and maintenance of general anesthesia for more than 150 years. All of the currently used inhalational anesthetics are chlorinated and fluorinated derivatives of ether. Dosing is carried out using the minimal alveolar concentration (MAC) concept. The pharmacokinetic properties of the various inhalational anesthetics are governed by the specific distribution coefficients. Mechanisms of action include specific modulations of various receptors of the central nervous system as well as an unspecific interaction with the cell membrane. Organ toxicity of modern inhalational anesthetics is considered to be minimal. The role of inhalational anesthetics in the context of postoperative nausea and vomiting (PONV) has been reassessed in recent years. The superiority of inhalational anesthetics over intravenous hypnotics with respect to intraoperative awareness is undisputed. The organ protective mechanism of preconditioning is an exclusive property of inhalational anesthetics among all the currently available hypnotics.

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.

Naringenin Prevents Propofol Induced Neurodegeneration in Neonatal Mice Brain and Long-Term Neurocognitive Impacts on Adults

Background

Natural products have shown neuroprotective effects in neurodegenerative conditions. Naringenin is a natural flavonoid with various pharmacological activities especially antioxidant, anti-inflammatory and neuroprotective properties. We investigated the effects of naringenin on anesthetic propofol-induced impacts on neonatal mouse brain development and consequent long-term neurocognitive impacts during adulthood.

Materials and Methods

Female C57Bl/6 and male CD-1 mice and postnatal day 7 (P7) pups were exposed to propofol (2.5 mg/kg) and propofol with naringenin (50 mg/kg). Mice pups were allowed to grow until week 10 (adulthood), and memory and learning were assessed.

Results

Propofol caused neurodegeneration by inducing apoptosis in the neonatal mouse brains while naringenin administration prevented neuronal cell loss by preventing neuronal apoptosis in neonatal mouse brains. Propofol caused degenerative alterations in metabolic factors pH, PO₂, glucose and lactate, which were subsequently restored by naringenin treatment. Propofol-exposed mice, when developed into adults, showed long-term neuronal deficits, impaired neurocognitive functions, and memory and learning restrictions.

Conclusion

Administration of naringenin to propofol-exposed mice resulted in significant neuroprotective effects by restoring long-term neurocognitive functions. The molecular mechanism behind the effects of naringenin was mediated by suppressing apoptosis and preventing cellular inflammation. These findings suggest that propofol administration requires careful consideration and that naringenin may prevent neurodegeneration and neurocognitive functions.

Dexmedetomidine attenuates sevoflurane‑induced neurocognitive impairment through α2‑adrenoceptors

It has been reported that sevoflurane induces neurotoxicity in the developing brain. Dexmedetomidine is an α2 adrenoceptor agonist used for the prevention of sevoflurane‑induced agitation in children in clinical practice. The aim of the present study was to determine whether dexmedetomidine could prevent sevoflurane‑induced neuroapoptosis, neuroinflammation, oxidative stress and neurocognitive impairment. Additionally, the involvement of α2 adrenoceptors in the neuroprotective effect of dexmedetomidine was assessed. Postnatal day (P)6 C57BL/6 male mice were randomly divided into four groups (n=6 in each group). Mice were pretreated with dexmedetomidine, either alone or together with yohimbine, an α2 adrenoceptor inhibitor, then exposed to 3% sevoflurane in 25% oxygen. Control mice either received normal saline alone or with sevoflurane exposure. Following sevoflurane exposure, the expression of cleaved caspase‑3 was detected by immunohistochemistry in hippocampal tissue sections. In addition, the levels of tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β, IL‑6 and malondialdehyde, as well as superoxide dismutase (SOD) activity in the hippocampus were measured. At P35, the learning and memory abilities were assessed in each mouse using a Morris water maze test. Dexmedetomidine significantly decreased the expression of activated caspase‑3 following sevoflurane exposure. Moreover, dexmedetomidine significantly decreased the levels of TNF‑α, IL‑1β and IL‑6 in the hippocampus. SOD activity also increased in a dose‑dependent manner in dexmedetomidine‑treated mice. MDA decreased in a dose‑dependent manner in dexmedetomidine‑treated mice. Lastly, sevoflurane‑induced learning and memory impairment was reversed by dexmedetomidine treatment. By contrast, co‑administration of yohimbine significantly attenuated the neuroprotective effects of dexmedetomidine. These findings suggested that dexmedetomidine exerted a neuroprotective effect against sevoflurane‑induced apoptosis, inflammation, oxidative stress and neurocognitive impairment, which was mediated, at least in part, by α2 adrenoceptors.

Propofol Attenuates Isoflurane-Induced Neurotoxicity and Cognitive Impairment in Fetal and Offspring Mice

BACKGROUND

Anesthesia in pregnant rodents causes neurotoxicity in fetal and offspring rodents. However, the underlying mechanisms and targeted treatments remain largely to be determined. Isoflurane and propofol are among commonly used anesthetics. Thus, we set out to investigate whether propofol can mitigate the isoflurane-induced neurotoxicity in mice.

METHODS

Pregnant C57BL/6 mice at gestational day 15 (G15) were randomly assigned to 4 groups: control, isoflurane, propofol, and isoflurane plus propofol. Levels of interleukin (IL)-6 and poly-ADP ribose polymerase (PARP) fragment were measured in the brains of G15 embryos, and levels of postsynaptic density (PSD)-95 and synaptophysin were determined in the hippocampal tissues of postnatal day 31 (P31) offspring using Western blotting and immunohistochemical staining. Learning and memory functions in P31 offspring were determined using a Morris water maze test.

RESULTS

Isoflurane anesthesia in pregnant mice at G15 significantly increased brain IL-6 (222.6% ± 36.45% vs 100.5% ± 3.43%, P < .0001) and PARP fragment (384.2% ± 50.87% vs 99.59% ± 3.25%, P < .0001) levels in fetal mice and reduced brain PSD-95 (30.76% ± 2.03% vs 100.8% ± 2.25%, P < .0001) and synaptophysin levels in cornu ammonis (CA) 1 region (57.08% ± 4.90% vs 100.6% ± 2.20%, P < .0001) and dentate gyrus (DG; 56.47% ± 3.76% vs 99.76% ± 1.09%, P < .0001) in P31 offspring. Isoflurane anesthesia also impaired cognitive function in offspring at P31. Propofol significantly mitigated isoflurane-induced increases in brain IL-6 (117.5% ± 10.37% vs 222.6% ± 36.45%, P < .0001) and PARP fragment (205.1% ± 35.99% vs 384.2% ± 50.87%, P < .0001) levels in fetal mice, as well as reductions in PSD-95 (49.79% ± 3.43% vs 30.76% ± 2.03%, P < .0001) and synaptophysin levels in CA1 region (85.57% ± 2.97% vs 57.08% ± 4.90%, P < .0001) and DG (85.05% ± 1.87% vs 56.47% ± 3.76%, P < .0001) in hippocampus of P31 offspring. Finally, propofol attenuated isoflurane-induced cognitive impairment in offspring.

CONCLUSIONS

These findings suggest that gestational isoflurane exposure in mice induces neuroinflammation and apoptosis in embryos and causes cognitive impairment in offspring. Propofol can attenuate these isoflurane-induced detrimental effects.

Perioperative management of circumcision in children: Is there a difference between African and European hospitals?

CONTEXT

The circumcision is the most frequent procedure in paediatric surgery worldwide, performed for medical and ritual purposes. In developing countries, because of the difficult accessibility to healthcare, even a common procedure could be unsafe.

AIMS

The aim of the article is to compare the perioperative and anaesthesiological management of circumcision in children between two Italian and two sub-Saharan African hospitals.

MATERIALS AND METHODS

Medical records of paediatric circumcision from January 2014 to December 2016 have been reviewed. The involved hospitals were: Padua (Italy), Ferrara (Italy), Sao José em Bor (Guinea Bissau) and Yaoundé (Cameroun).

RESULTS

In Padua, 77 circumcisions were performed, 19 of these (24.6%) were ritual. In 75 children (97.4%), locoregional anaesthesia (LRA) together with sedation was used; only one complication (1.3%) occurred. In Ferrara, 200 interventions were done, 140 (70%) ritual; general anaesthesia was administered to 183 (93.5%) patients. There were five complications (2.5%). In Bissau, 53 procedures were performed, 21 (39.6%) ritual; in 34 children (64.1%), LRA with sedation was preferred. Two complications (3.8%) were reported. In Yaoundé, 60 children were circumcised, 15 (25%) for ritual purposes; in 51 (85%), only LRA was performed; there was only one (1.7%) complication. In the African hospital, no post-operative analgesia was administered.

CONCLUSION

Despite the different anaesthesiological techniques, the study shows no difference in rate of complications for the in-hospital setting. Training of the local medical team in pain management and post-operative care should be emphasised.

Analgesics and Sedatives in Critically Ill Newborns and Infants: The Impact on Long-Term Neurodevelopment

Inadequate pain and/or stress management in preterm- and term-born infants has been associated with increased morbidity and even mortality. However, exposure to analgosedatives during early infancy may also be one of the risk factors for subsequent neurodevelopmental impairment, at least in animal studies. Because infants admitted to neonatal or pediatric intensive care units may receive high amounts of these drugs for prolonged periods of time and the majority of these infants nowadays survive to discharge, this is of major concern. A balanced approach that incorporates the assessment and quantification of both wanted effects as well as unwanted side effects is therefore needed. In this article, the optimal dose determination of commonly used analgosedative drugs as well as their potential long-term effects on the developing human brain and neuropsychological functioning are reviewed.

Effects of Early Exposure of Isoflurane on Chronic Pain via the Mammalian Target of Rapamycin Signal Pathway

Persistent post-surgical pain (PPSP) is a chronic pain condition, often with neuropathic features, that occurs in approximately 20% of children who undergo surgery. The biological basis of PPSP has not been elucidated. Anesthetic drugs can have lasting effects on the developing nervous system, although the clinical impact of this phenomenon is unknown. Here, we used a mouse model to test the hypothesis that early developmental exposure to isoflurane causes cellular and molecular alteration in the pain perception circuitry that causes a predisposition to chronic, neuropathic pain via a pathologic upregulation of the mammalian target of the rapamycin (mTOR) signaling pathway. Mice were exposed to isoflurane at postnatal day 7 and select cohorts were treated with rapamycin, an mTOR pathway inhibitor. Behavioral tests conducted 2 months later showed increased evidence of neuropathic pain, which did not occur in rapamycin-treated animals. Immunohistochemistry showed neuronal activity was chronically increased in the insular cortex, anterior cingulate cortex, and spinal dorsal horn, and activity was attenuated by rapamycin. Immunohistochemistry and western blotting (WB) showed a co-incident chronic, abnormal upregulation in mTOR activity. We conclude that early isoflurane exposure alters the development of pain circuits and has the potential to contribute to PPSP and/or other pain syndromes.

Surgical interventions and anesthesia in the 1st year of life for lower urinary tract obstruction

BACKGROUND

Patients with a prenatal diagnosis of lower urinary tract obstruction (LUTO) may undergo prenatal interventions, such as vesicoamniotic shunt (VAS) placement, as a temporary solution for relieving urinary tract obstruction. A recent FDA communication has raised awareness of the potential neurocognitive adverse effects of anesthesia in children. We hypothesized as to whether a prenatal LUTO staging system was predictive of the number of anesthesia events for prenatally diagnosed LUTO patients.

METHODS

We retrospectively reviewed the prenatal and postnatal clinical records for patients with prenatally diagnosed LUTO from 2012 to 2015. Patients were stratified by prenatal VAS status and by LUTO disease severity according to Ruano et al. (Ultrasound Obstet Gynecol. 2016).

RESULTS

31 patients were identified with a prenatal LUTO diagnosis, and postnatal records were available for 21 patients (seven patients in each stage). When combining prenatal and postnatal anesthesia, there was a significant difference in the number of anesthesia encounters by stage (1.6, 3.7, and 6.7 for Stage I, II, and III respectively, p = .034). Upon univariate analysis, higher gestational age (GA) at birth was associated with a decreased number of anesthesia events in the first year (p = .031).

CONCLUSIONS

The majority of infants with prenatally diagnosed LUTO will undergo postnatal procedures with general anesthesia exposure in the first year of life. Patients with higher prenatal LUTO severity experienced a higher number of both prenatal and postnatal anesthesia encounters. In addition, higher GA at birth was associated with fewer anesthesia encounters in the first year.

LEVEL OF EVIDENCE

This is a prognostic study with Level IV evidence.

Neurotoxicity of Anesthesia in Children: Prevention and Treatment

PURPOSE OF REVIEW

The purpose of this review is to summarize the current evidence regarding the impact of the exposure to anesthetic and sedative agents on neurodevelopment during the period of rapid brain growth in the first 3 years of life. Though much of the definitive data demonstrating anesthesia-induced neurotoxicity has come from studies in young animals, the focus of this review is on emerging human data.

RECENT FINDINGS

In 2016, the first prospective trials investigating the neurodevelopmental impact of early anesthetic exposure (GAS and PANDA studies) were published, both showing no significant impact on IQ from a single brief anesthetic. More recent population cohort analyses have shown varying, but minimal, impacts from early anesthetic exposure on academic performance and IQ, much smaller than that of maternal education and other environmental factors. Animal and human data document that post-anesthetic neurotoxicity is a genuine phenomenon, but its long-term clinical significance is uncertain. Most experts would agree that a single, brief anesthetic likely has no significant impact on neurodevelopment, but it is yet to be determined whether longer exposures or multiple anesthetics are associated with subsequent learning issues. Future research is aimed at determining the mechanisms of neuronal injury from exposure to anesthetic and sedative agents, adjunctive medications that may prevent or ameliorate this injury, and therapeutic approaches such as early intervention that can enhance recovery. While these studies are underway, it is recommended that exposure to anesthetic and sedative agents be minimized in young children and consideration be given to alternative methods of immobilization for nonpainful procedures such as radiologic imaging.

Ablation of proliferating neural stem cells during early life is sufficient to reduce adult hippocampal neurogenesis

Environmental exposures during early life, but not during adolescence or adulthood, lead to persistent reductions in neurogenesis in the adult hippocampal dentate gyrus (DG). The mechanisms by which early life exposures lead to long-term deficits in neurogenesis remain unclear. Here, we investigated whether targeted ablation of dividing neural stem cells during early life is sufficient to produce long-term decreases in DG neurogenesis. Having previously found that the stem cell lineage is resistant to long-term effects of transient ablation of dividing stem cells during adolescence or adulthood (Kirshenbaum, Lieberman, Briner, Leonardo, & Dranovsky, ), we used a similar pharmacogenetic approach to target dividing neural stem cells for elimination during early life periods sensitive to environmental insults. We then assessed the Nestin stem cell lineage in adulthood. We found that the adult neural stem cell reservoir was depleted following ablation during the first postnatal week, when stem cells were highly proliferative, but not during the third postnatal week, when stem cells were more quiescent. Remarkably, ablating proliferating stem cells during either the first or third postnatal week led to reduced adult neurogenesis out of proportion to the changes in the stem cell pool, indicating a disruption of the stem cell function or niche following stem cell ablation in early life. These results highlight the first three postnatal weeks as a series of sensitive periods during which elimination of dividing stem cells leads to lasting alterations in adult DG neurogenesis and stem cell function. These findings contribute to our understanding of the relationship between DG development and adult neurogenesis, as well as suggest a possible mechanism by which early life experiences may lead to lasting deficits in adult hippocampal neurogenesis.

Early Developmental Exposure to General Anesthetic Agents in Primary Neuron Culture Disrupts Synapse Formation via Actions on the mTOR Pathway

Human epidemiologic studies and laboratory investigations in animal models suggest that exposure to general anesthetic agents (GAs) have harmful effects on brain development. The mechanism underlying this putative iatrogenic condition is not clear and there are currently no accepted strategies for prophylaxis or treatment. Recent evidence suggests that anesthetics might cause persistent deficits in synaptogenesis by disrupting key events in neurodevelopment. Using an in vitro model consisting of dissociated primary cultured mouse neurons, we demonstrate abnormal pre- and post-synaptic marker expression after a clinically-relevant isoflurane anesthesia exposure is conducted during neuron development. We find that pharmacologic inhibition of the mechanistic target of rapamycin (mTOR) pathway can reverse the observed changes. Isoflurane exposure increases expression of phospho-S6, a marker of mTOR pathway activity, in a concentration-dependent fashion and this effect occurs throughout neuronal development. The mTOR 1 complex (mTORC1) and the mTOR 2 complex (mTORC2) branches of the pathway are both activated by isoflurane exposure and this is reversible with branch-specific inhibitors. Upregulation of mTOR is also seen with sevoflurane and propofol exposure, suggesting that this mechanism of developmental anesthetic neurotoxicity may occur with all the commonly used GAs in pediatric practice. We conclude that GAs disrupt the development of neurons during development by activating a well-defined neurodevelopmental disease pathway and that this phenotype can be reversed by pharmacologic inhibition.

Anesthetics disrupt brain development via actions on the mTOR pathway

Experiments conducted in non-human primates have recently provided new evidence supporting a longstanding concern that exposure to general anesthesia during late intrauterine life or early childhood can cause lasting cognitive deficits through harmful effects on brain development. The mammalian target of rapamycin (mTOR) signaling system plays a key role in both normal brain development and in a wide range of developmental disorders that are characterized by cognitive deficits. Intriguingly, our recently published work shows that anesthetics can chronically alter mTOR signaling in the hippocampal dentate gyrus and that normalization of mTOR signaling can prevent anesthesia-induced perturbation of structure and function. In this addendum, we briefly discuss the putative role of mTOR in developmental anesthetic neurotoxicity.

KIF17 mediates the learning and memory impairment in offspring induced by maternal exposure to propofol during middle pregnancy

Preclinical studies suggest that propofol may cause neuronal injury to the developing brain. A previous study demonstrated that, in a rat model, maternal exposure to propofol during early or late pregnancy caused learning and memory impairment in the offspring. However, whether propofol exposure during middle pregnancy can cause long‑term behavioral deficits in the offspring remains to be elucidated. N‑methyl‑D‑aspartate receptor 2B subunit (NR2B) serves a critical role in memory modulation. To exert its function, NR2B must be transported to the neuronal membrane by kinesin family member 17 (KIF17). The aim of the present study was to investigate the role of KIF17 in learning and memory impairment in rat offspring caused by propofol exposure during middle pregnancy. Pregnant rats were exposed to propofol on gestational day 14 (G14) for 4 and 8 h, with control pregnant rats receiving an equal volume of normal saline. The learning and memory of the offspring was assessed using Morris water maze tests from postnatal day 30 (P30) to P36. The levels of KIF17 protein, total NR2B (T‑NR2B) and membrane NR2B (M‑NR2B) in the hippocampus were detected using western blotting. The results demonstrated that propofol exposure caused learning and memory deficits and decreased KIF17 and M‑NR2B protein levels in the hippocampus; however, no but changes in the expression of T‑NR2B were observed. These results indicate that maternal propofol exposure during middle pregnancy impairs learning and memory in offspring rats by suppressing the expression of KIF17 and inhibiting the translocation of NR2B to the neuronal membrane.

PTEN Inhibition in Human Disease Therapy

The tumor suppressor PTEN is a major homeostatic regulator, by virtue of its lipid phosphatase activity against phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3], which downregulates the PI3K/AKT/mTOR prosurvival signaling, as well as by its protein phosphatase activity towards specific protein targets. PTEN catalytic activity is crucial to control cell growth under physiologic and pathologic situations, and it impacts not only in preventing tumor cell survival and proliferation, but also in restraining several cellular regeneration processes, such as those associated with nerve injury recovery, cardiac ischemia, or wound healing. In these conditions, inhibition of PTEN catalysis is being explored as a potentially beneficial therapeutic intervention. Here, an overview of human diseases and conditions in which PTEN inhibition could be beneficial is presented, together with an update on the current status of specific small molecule inhibitors of PTEN enzymatic activity, their use in experimental models, and their limitations as research or therapeutic drugs.

Food and Drug Administration warning on anesthesia and brain development: implications for obstetric and fetal surgery

There has been growing concern about the detrimental effects of certain anesthetic agents on the developing brain. Preclinical studies in small animal models as well as nonhuman primates suggested loss or death of brain cells and consequent impaired neurocognitive function following anesthetic exposure in neonates and late gestation fetuses. Human studies in this area are limited and currently inconclusive. On Dec. 14, 2016, the US Food and Drug Administration issued a warning regarding impaired brain development in children following exposure to certain anesthetic agents used for general anesthesia, namely the inhalational anesthetics isoflurane, sevoflurane, and desflurane, and the intravenous agents propofol and midazolam, in the third trimester of pregnancy. Furthermore, this warning recommends that health care professionals should balance the benefits of appropriate anesthesia in young children and pregnant women against potential risks, especially for procedures that may last >3 hours or if multiple procedures are required in children <3 years old. The objective of this article is to highlight how the Food and Drug Administration warning may impact the anesthetic and surgical management of the obstetric patient. Neuraxial anesthesia (epidural or spinal anesthesia) is more commonly administered for cesarean delivery than general anesthesia. The short duration of fetal exposure to general anesthesia during cesarean delivery has not been associated with learning disabilities. However, the fetus can also be exposed to both intravenous and inhalation anesthetics during nonobstetric or fetal surgery in the second and third trimester; this exposure is typically longer than that for cesarean delivery. Very few studies address the effect of anesthetic exposure on the fetus in the second trimester when most nonobstetric and fetal surgical procedures are performed. It is also unclear how the plasticity of the fetal brain at this stage of development will modulate the consequences of anesthetic exposure. Strategies that may circumvent possible untoward long-term neurologic effects of anesthesia in the baby include: (1) use of nonimplicated (nongamma-aminobutyric acid agonist) agents for sedation such as opioids (remifentanil, fentanyl) or the alpha-2 agonist, dexmedetomidine, when appropriate; (2) minimizing the duration of exposure to inhalational anesthetics for fetal, obstetric, and nonobstetric procedures in the pregnant patient, as much as possible within safe limits; and (3) commencing surgery promptly and limiting the interval between induction of anesthesia and surgery start time will help decrease patient exposure to inhalational agents. While the Food and Drug Administration warning was based on duration and repetitive nature of exposure rather than concentration of inhalational agents, intravenous tocolytics can be considered for intraoperative use, to provide uterine relaxation for fetal surgery, in lieu of high concentrations of inhalational anesthetic agents. Practitioners should consider the type of anesthesia that will be administered and the potential risks when scheduling patients for nonobstetric and fetal surgery.

Activation of Autophagy Contributes to Sevoflurane-Induced Neurotoxicity in Fetal Rats

Numerous animal studies have demonstrated that commonly used general anesthetics may result in cognitive impairment in the immature brain. The prevailing theory is that general anesthetics could induce developmental neurotoxicity via enhanced apoptosis. In addition, inhibited proliferation induced by anesthetics has also been reported. So far, whether autophagy, a well-conserved cellular process that is critical for cell fate, also participates in anesthesia-induced neurotoxicity remains elusive. Here, we first examined autophagy-related changes after sevoflurane exposure and the effect of autophagy on apoptosis and proliferation, and we also explored the underlying mechanisms of autophagy activation. Pregnant rats were exposed to 2 or 3.5% sevoflurane for 2 h on gestational day 14 (G14); then, markers of autophagy and expression of autophagy pathway components were measured in fetal brains 2, 12, 24, and 48 h after anesthesia. Changes in neural stem cell (NSC) apoptosis, neurogenesis, neuron quantity and learning and memory function were examined after administration of an autophagy or PTEN inhibitor. The expression of microtubule-associated protein 1 light chain 3 (LC3)-II, Beclin-1 and phosphatase and tensin homolog on chromosome 10 (PTEN) were increased in the 3.5% sevoflurane group, while Sequestosome 1 (P62/SQSTM1), phospho-protein kinase B/protein kinase B (p-Akt/Akt) and mammalian target of rapamycin (mTOR) were decreased. 3-methyladenine (3-MA), an inhibitor of autophagy, or dipotassium bisperoxo-(5-hydroxypyridine-2-carboxyl)-oxovanadate (V) (bpV), a PTEN inhibitor, significantly attenuated the activation of autophagy, reversed the decreased expression of B-cell lymphoma-2 (Bcl-2) and reduced the number of terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) positive cells, ameliorated the decline of Nestin expression, Ki67 positive cell rate, neuron quantity and cross platform times, and shortened the prolonged escape latency. Our results demonstrated that 2 h 3.5% sevoflurane exposure at G14 induced excessive autophagy in the fetal brain via the PTEN/Akt/mTOR pathway. Autophagy inhibition reversed anesthesia-induced NSC apoptosis, proliferation decline and memory deficits.