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

Pretreatment with tetramethylpyrazine alleviated the impairment of learning and memory induced by sevoflurane exposure in neonatal rats

Sevoflurane impairs learning and memory of the developing brain. However, strategies to mitigate these detrimental effects have been scarce. Herein, we investigated whether tetramethylpyrazine pretreatment could alleviate the impairment of learning and memory and its underlying mechanism in sevoflurane-exposed neonatal rats. Postnatal 7-day Sprague-Dawley (SD) rats or primary hippocampal neurons were pretreated with tetramethylpyrazine and then exposed to sevoflurane. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and lactate dehydrogenase (LDH) assays were used to detect neuronal injury. Learning and memory function were evaluated by novel object recognition and Morris water maze tests. Long-term potentiation (LTP) was recorded to evaluate synaptic plasticity electrophysiologically in the hippocampal slices. Golgi-Cox staining or PSD95 immunochemistry was used to detect the morphology of dendritic spines. Western blotting was employed to assess the expressions of cleaved Caspase-3, PSD95, N-methyl-D-aspartate receptor (NMDAR) subunits NMDAR1, NMDAR2A and NMDAR2B in the hippocampus or cultured neurons. It was found that neonatal exposure of sevoflurane impaired learning and memory, increased neuronal apoptosis, altered the morphology of dendritic spines, upregulated the expressions of NMDAR2A and PSD95, and induced LTP deficits. Pretreatment with tetramethylpyrazine not only alleviated impairment of learning and memory, but also improved sevoflurane-induced changes in neuronal damage, dendritic spine morphology, NMDAR2A and PSD95 expressions, as well as LTP. These findings indicated that pretreatment with tetramethylpyrazine alleviated the impairment of learning and memory induced by sevoflurane through improvement of hippocampal synaptic plasticity in neonatal rats.

Research advances on CaMKs-mediated neurodevelopmental injury

Calcium/calmodulin-dependent protein kinases (CaMKs) are important proteins in the calcium signaling cascade response pathway, which can broadly regulate biological functions in vivo. Multifunctional CaMKs play key roles in neural development, including neuronal circuit building, synaptic plasticity establishment, and neurotrophic factor secretion. Currently, four familial proteins, calcium/calmodulin-dependent protein kinase I (CaMKI), calcium/calmodulin-dependent protein kinase II (CaMKII), eukaryotic elongation factor 2 kinase (eEF2K, popularly known as CaMKIII) and calcium/calmodulin-dependent protein kinase IV (CaMKIV), are thought to have been the most extensively studied during neurodevelopment. Although their spatial structures are extremely similar, as well as the initial starting point of activation, both require the activation of calcium and calmodulin (CaM) complexes to be involved in the process, and the phosphorylation sites and modes of each member are different. Furthermore, due to the high structural similarity of CaMKs, their members may play synergistic roles in the regulation of neural development, but different CaMKs also have their own means of regulating neural development. In this review, we first describe the visualized protein structural forms of CaMKI, CaMKII, eEF2K and CaMKIV, and then describe the functions of each kinase in neurodevelopment. After that, we focus on four main mechanisms of neurodevelopmental damage caused by CaMKs: CaMKI/ERK/CREB pathway inhibition leading to dendritic spine structural damage; Ca2+/CaM/CaMKII through induction of mitochondrial kinetic disorders leading to neurodevelopmental damage; CaMKIII/eEF2 hyperphosphorylation affects the establishment of synaptic plasticity; and CaMKIV/JNK/NF-κB through induction of an inflammatory response leading to neurodevelopmental damage. In conclusion, we briefly discuss the pathophysiological significance of aberrant CaMK family expression in neurodevelopmental disorders, as well as the protective effects of conventional CaMKII and CaMKIII antagonists against neurodevelopmental injury.

IL-17A is a key regulator of neuroinflammation and neurodevelopment in cognitive impairment induced by sevoflurane

Increasing numbers of animal studies have shown that repeat sevoflurane exposure during developmental stage may lead to long-term cognitive impairment. Nevertheless, the exact pathogenesis remains unclear. Interleukin 17A (IL-17A) has been associated with cognitive decline in various neurological disorders. Here we found that the expression of IL-17A was up-regulated in hippocampus of sevoflurane exposed neonatal mice. Genetic deletion of IL-17A or inhibition of IL-17A improved behavioral function and down-regulated neuroinflammation related genes, interleukin 1β (IL-1β), interleukin 6 (IL-6), Nicotinamide adenine dinucleotide phosphate(NADPH) oxidase 2 (NOX2) and NADPH oxidase 4 (NOX4) in hippocampus of sevoflurane exposed neonatal mice. Moreover, negative regulation of IL-17A/Interleukin 17A receptor(IL-17RA) promoted the extracellular signal-regulated protein kinase (ERK) signaling pathway and nucleation of cyclic adenosine monophosphate (cAMP) response element-binding (CREB) in neurons of cognitive impaired mice. Knockdown of IL-17A in vivo identified neurons-localized IL-17A as a major factor in neuroinflammation and neurodevelopment. Collectively, our results suggested that IL-17A was required for the pathogenesis of neuroinflammatory response and identify IL-17A as a potential therapeutic target for cognitive impairment exposed by general anesthetics during infancy.

Exploring the role of Cdk5 on striatal synaptic plasticity in a 3-NP-induced model of early stages of Huntington's disease

Impaired mitochondrial function has been associated with the onset of neurodegenerative diseases. Specifically, certain mitochondrial toxins, such as 3-nitropropionic acid (3-NP), initiate cellular changes within the striatum that closely resemble the pathology observed in Huntington's disease (HD). Among the pivotal signaling molecules contributing to neurodegeneration, cyclin-dependent kinase 5 (Cdk5) stands out. In particular, Cdk5 has been implicated not only in cellular pathology but also in the modulation of synaptic plasticity. Given its widespread presence in the striatum, this study seeks to elucidate the potential role of Cdk5 in the induction of corticostriatal synaptic plasticity in murine striatal cells subjected to subchronic doses of 3-NP in vivo, aiming to mimic the early stages of HD. Immunostaining analyses revealed an increase in Cdk5 in tissues from animals treated with 3-NP, without a significant change in protein levels. Regarding striatal plasticity, long-term depression (LTD) was induced in both control and 3-NP cells when recorded in voltage clamp mode. The Cdk5 inhibitor roscovitine-reduced LTD in most cells. A minority subset of cells exhibited long-term potentiation (LTP) generation in the presence of roscovitine. The inhibitor of D1 receptors SCH23390 prevented LTP in three of nine cells, implying that MSN cells lacking D1/PKA activation were capable of LTP induction when Cdk5 was also blocked. Nevertheless, the co-administration of H89, a PKA inhibitor, along with roscovitine, prevented the generation of any type of plasticity in all recorded cells. These findings show the impact of 3-NP treatment on striatal plasticity and suggest that Cdk5 during early neurodegeneration may attenuate signaling pathways that lead neurons to increase their activity.

Neonatal anesthesia with remimazolam Reduces the expression of synaptic proteins and increases depressive behavior in adult mice

The demand for pediatric anesthesia has risen in decades, raising concerns about the neurotoxic potential of anesthetics like remimazolam, which may impact neurodevelopment and later cognitive function. This study utilized a neonatal mouse model to assess remimazolam's neurodevelopmental effects. Results indicate that remimazolam-exposed mice displayed cognitive impairment and depressive behaviors in adulthood. Acute reductions in synaptic protein expression post-anesthesia were observed, along with long-term decreases in hippocampal choline acetyltransferase levels, reduced dendritic spine density in the CA1 region, and microglial proliferation. Collectively, these findings suggest that remimazolam can induce neurotoxicity and neuroinflammation, leading to synaptic dysfunction and associated cognitive and behavioral deficits.

Effects of esketamine on depression-like behavior and dendritic spine plasticity in the prefrontal cortex neurons of spared nerve injury-induced depressed mice

The present study utilized the spared nerve injury (SNI) to create a mouse model of depression to investigate the impact of esketamine on depressive-like behaviors, on the expression of PSD-95 and CRMP2 proteins, and on changes in neuronal dendritic spine plasticity in the prefrontal cortex (PFC). Depressive-like behavioral tests were performed 1 h after esketamine treatment, and the PFC tissues were obtained on the fourth day after completing the behavioral tests. Then, dendritic spine density and morphology in the PFC were measured using Golgi staining, and CRMP2 and PSD-95 proteins were obtained from PFC tissue by western blotting. The results of this study showed that esketamine significantly increased the immobility time in the forced swimming test and tail suspension test. In the open field test, esketamine increased the time spent in the open arms, the time spent in the central area, and the total distance covered. It also increased the protein expression levels of CRMP2 and PSD-95 in addition to the total and mature dendritic spine density of the PFC in SNI-depressed mice. Esketamine can significantly improve depression-like behaviors in SNI-depressed mice and promote an increase in dendritic spine density and maturation in the PFC. These effects may be associated with changes in CRMP2 and PSD-95 expression.

Astrocyte-derived exosomes-transported miRNA-26a-5p ameliorates sevoflurane-induced cognitive dysfunction in aged mice

Prolonged sevoflurane anesthesia is the primary factor contributing to the development of perioperative neurocognitive disorders (PND). Recent studies have highlighted neuronal apoptosis and abnormal dendritic structures as crucial features of PND. Astrocytes-derived exosomes (ADEs) have been identified as carriers of microRNAs (miRNAs), playing a vital role in cell-to-cell communication through transmitting genetic material. Nevertheless, the specific mechanisms by which miRNAs in ADEs contribute to sevoflurane-induced cognitive deficit are currently unknown. Through a series of in vivo and in vitro experiments, we demonstrated that ADEs contributed to improved neurocognitive outcomes by reducing neuronal apoptosis and promoting dendritic development. Our miRNA microarray analysis revealed a significant increase in the expression level of miR-26a-5p within ADEs. Furthermore, we identified NCAM as the downstream target gene of miR-26a-5p. Subsequent gain- and loss-of-function experiments were conducted to validate the role of the miR-26a-5p/NCAM axis. Finally, we found that the AKT/GSK3-β/CRMP2 signaling pathway was involved in regulating neurons through exosomal miR-26a-5p. Taken together, our findings suggest that the treatment with miR-26a-5p in ADEs can improve neurocognitive outcomes induced by long-term sevoflurane anesthesia, suggesting a promising approach for retarding the progress of PND.

Cyclin-dependent kinase 5 (CDK5) inhibitors in Parkinson disease

Cyclin-dependent kinase 5 (Cdk5) is a protein expressed in postmitotic neurons in the central nervous system (CNS). Cdk5 is activated by p35 and p39 which are neuron regulatory subunits. Cdk5/p35 complex is activated by calpain protease to form Cdk5/p35 which has a neuroprotective effect by regulating the synaptic plasticity and memory functions. However, exaggerated Cdk5 is implicated in different types of neurodegenerative diseases including Parkinson disease (PD). Therefore, modulation of Cdk5 signalling may mitigate PD neuropathology. Therefore, the aim of the present review was to discuss the critical role of Cdk5 in the pathogenesis of PD, and how Cdk5 inhibitors are effectual in the management of PD. In conclusion, overactivated Cdk5 is involved the development of neurodegeneration, and Cdk5/calpain inhibitors such as statins, metformin, fenofibrates and rosiglitazone can attenuate the progression of PD neuropathology.

Effects of Cyfluthrin Exposure on Neurobehaviour, Hippocampal Tissue and Synaptic Plasticity in Wistar Rats

This experiment was conducted to study the effects of Cyfluthrin (Cy) exposure on neurobehaviour, hippocampal tissue and synaptic plasticity in Wistar rats. First, it was found that high-dose Cy exposure could cause nerve injury, resulting in symptoms such as deficits in learning and memory ability, spatial exploration and autonomic motor function. Moreover, it was found that medium- and high-dose Cy exposure could cause an abnormal release of the neurotransmitter Glu. Second, brain tissue pathology showed that the middle and high doses of Cy caused tissue deformation, reduced the number of hippocampal puramidal cells, caused a disorder of these cells, decreased the number of Nissl bodies, and caused pyknosis of the hippocampal cell nuclear membrane and serious damage to organelles, indicating that exposure to these doses of Cy may cause hippocampal tissue damage in rats. Third, as the exposure dose increased, morphological changes in hippocampal synapses, including blurred synaptic spaces, a decreased number of synaptic vesicles and a decreased number of synapses, became more obvious. Moreover, the expression levels of the key synaptic proteins PSD-95 and SYP also decreased in a dose-dependent manner, indicating obvious synaptic damage. Finally, the study found that medium and high doses of Cy could upregulate the expression of A2AR in the hippocampus and that the expression levels of inflammatory factors and apoptosis-related proteins increased in a dose-dependent manner. Moreover, the expression of A2AR mRNA was correlated with neurobehavioural indicators and the levels of inflammatory factors, synaptic plasticity-related factors and apoptosis-related factors, suggesting that Cy may cause nerve damage in rats and that this effect is closely related to A2AR.

Inhibitory neuron map of sevoflurane induced neurotoxicity model in young primates

Introduction

Sevoflurane, one of the most commonly used anesthetic agents in children, may induce neuronal dysfunction and cognitive impairment. Exposure to sevoflurane might induce an imbalance between neural excitation and inhibition which could be a mechanism behind anesthesia-induced cognitive and affective dysfunctions. However, the underlying mechanisms remain unclear.

Methods

In this study, we used two rhesus macaques in the control group, and one rhesus macaques in the anesthesia group. We employed single-nucleus RNA sequencing (snRNA-seq) technology to explore alterations in distinct types of inhibitory neurons involved in the long-term cognitive impairment caused by sevoflurane in young macaques.

Results

Following sevoflurane treatment, an upregulation was observed in the SST+ inhibitory neuron in the LHX6+ neighborhood in the hippocampus of rhesus macaques. This alteration might impact brain development by influencing interneuron migration and maturation. Additionally, we proposed a novel classification of inhibitory neurons, defined by CNR1 and LHX6 applicable to both humans and macaques.

Discussion

Our study proposed a novel classification of inhibitory neurons defined by LHX6 and CNR1, relevant in macaques and humans. We also provide evidence that sevoflurane upregulated the SST+ inhibitory neuron in the LHX6+ neighborhood in the hippocampus of rhesus macaques, which may underlie the potential neurotoxic effects induced by general anesthetics. Our results also offer a more reliable approach for studying the structure and function of the human brain.

Inhibition of hippocampal cyclin-dependent kinase 5 activity ameliorates learning and memory dysfunction in a mouse model of bronchopulmonary dysplasia

AIMS

Oxygen therapy plays a vital role in the development of bronchopulmonary dysplasia (BPD), which is the independent risk factor for neurodevelopment deficits in premature infants. However, the effect of hippocampal cyclin-dependent kinase 5 (CDK5) on BPD-associated neurodevelopment deficits is not fully understood.

METHODS

Mice were placed in a hyperoxia chamber from postnatal Day 1 to Day 7. Hematoxylin and eosin staining was used to evaluate the lung histomorphological characteristics. Learning and memory functions of mice were detected by Morris water maze. TUNEL staining was applied to measure the number of apoptotic cells. The expression of CDK5, apoptosis-related protein, and neuroplasticity-related proteins were analyzed by Western blot. Golgi staining was used to assess the structure of dendritic spines.

RESULTS

Hyperoxia-induced BPD mice showed a long-term learning and memory dysfunction, more severe neuronal apoptosis, and a decline of synaptic plasticity. Inhibition of CDK5 overactivation ameliorated cognitive deficits, neuronal apoptosis, and synaptic plasticity disorders in BPD mice.

CONCLUSIONS

This study first found a vital role of CDK5 in BPD-associated neurodevelopmental disorders. Inhibition of CDK5 overexpression could effectively improve cognitive dysfunctions in BPD mice, which indicated that hippocampal CDK5 may be a new target for prevention and treatment in learning and memory dysfunction of BPD.

CircUBE3B High Expression Participates in Sevoflurane-Induced Human Hippocampal Neuron Injury via Targeting miR-326 and Regulating MYD88 Expression

The clinical application of Sevoflurane (Sevo) brings about non-negligible neuron injury, leading to postoperative cognitive dysfunction (POCD). However, related pathogenesis is complex and not fully established. We aimed to disclose the role of circRNA UBE3B (circUBE3B) in neuron injury induced by Sevo. Cell viability and apoptosis were determined by CCK-8 and flow cytometry experiments. Inflammation production was monitored by ELISA. The expression of circUBE3B, miR-326, and myeloid differentiation factor 88 (MYD88) mRNA was assessed by quantitative real-time PCR (qPCR). Apoptosis-associated markers and MYD88 protein were quantified by western blot. The putative binding site between miR-326 and circUBE3B or MYD88 was verified by a dual-luciferase reporter experiment, and their binding was validated by a pull-down assay. Sevo treatment weakened cell viability and promoted cell apoptosis and inflammatory response. CircUBE3B expression was elevated in Sevo-treated neurons. Sevo-induced neuron injury was alleviated by circUBE3B downregulation but aggravated by circUBE3B overexpression. MiR-326 was targeted by circUBE3B, and miR-326 inhibition recovered neuron injury that was repressed by circUBE3B absence in Sevo-treated neurons. MiR-326 interacted with MYD88. MiR-326 enrichment attenuated Sevo-induced neuron injury, while these effects were reversed by MYD88 overexpression. CircUBE3B dysregulation was involved in Sevo-induced human hippocampal neuron injury via targeting the miR-326/MYD88 network.

Maternal sevoflurane exposure induces neurotoxicity in offspring rats via the CB1R/CDK5/p-tau pathway

Sevoflurane is widely used for maternal anesthesia during pregnancy. Sevoflurane exposure of rats at mid-gestation can cause abnormal development of the central nervous system in their offspring. Sevoflurane is known to increase the expression of cannabinoid 1 receptor (CB1R) in the hippocampus. However, the effect of cannabinoid 1 receptor on fetal and offspring rats after maternal anesthesia is still unclear. At gestational day 14, pregnant rats were subjected to 2-h exposure to 3.5% sevoflurane or air. Rats underwent intraperitoneal injection with saline or rimonabant (1 mg/kg) 30 min prior to sevoflurane or air exposure. cannabinoid 1 receptor, cyclin-dependent kinase 5 (CDK5), p35, p25, tau, and p-tau expression in fetal brains was measured at 6, 12, and 24 h post-sevoflurane/air exposure. Neurobehavioral and Morris water maze tests were performed postnatal days 3-33. The expression of cannabinoid 1 receptor/cyclin-dependent kinase 5/p-tau and histopathological staining of brain tissues in offspring rats was observed. We found that a single exposure to sevoflurane upregulated the activity of cyclin-dependent kinase 5 and the level of p-tau via cannabinoid 1 receptor. This was accompanied by the diminished number of neurons and dendritic spines in hippocampal CA1 regions. Finally, these effects induced lower scores and platform crossing times in behavioral tests. The present study suggests that a single exposure to 3.5% sevoflurane of rats at mid-gestation impairs neurobehavioral abilities and cognitive memory in offspring. cannabinoid 1 receptor is a possible target for the amelioration of postnatal neurobehavioral ability and cognitive memory impairments induced by maternal anesthesia.

Sevoflurane exposure may cause dysplasia of dendritic spines and result in fine motor dysfunction in developing mouse through the PI3K/AKT/mTOR pathway

Sevoflurane has become one of the most widely used volatile anesthetics in pediatric surgery. However, sevoflurane exposure may interfere with dendritic development and synaptogenesis, resulting in brain function impairment. The PI3K/AKT/mTOR pathway plays an important role in dendritic development and synaptic plasticity. Here we investigated whether sevoflurane exposure would affect the morphological proportions of dendritic spines in developing mouse and explored the role of the change of plasticity of dendritic spines in sevoflurane-induced neurodevelopmental toxicity. The related signaling pathway was also examined. C57BL/6 mice at postnatal day (PND) 7 were exposed to 2% sevoflurane for 3 h. The PI3k/AKT/mTOR agonist IGF-1 or the mTOR phosphorylation inhibitor KU0063794 was intraperitoneally injected 30 min before sevoflurane or O₂ exposure at PND7. Hippocampi were harvested 6 h after sevoflurane exposure. Western blotting was applied to measure the protein expression of PI3K/AKT/mTOR pathway phosphorylation. At PND14, brains from all groups were harvested for Golgi staining, and the morphology of dendritic spines of hippocampal neurons was observed by an oil immersion lens. When the mice grew to adolescence (PND48), fine motor function was measured by the Beam walking test. Here we showed that exposure to 2% sevoflurane for 3 h decreased the proportion of thin dendritic spines and increased the proportion of mushroom dendritic spines, but not changed the density of the dendritic spines. Sevoflurane exposure also suppressed the phosphorylation of the PI3K/AKT/mTOR pathway in immature mice hippocampi, and eventually led to long-term fine motor dysfunction. Meanwhile, IGF-1 pretreatment could rescue and KU0063794 pretreatment could aggravate the impairment induced by sevoflurane. In conclusion, sevoflurane exposure may cause a change of proportions of the types of dendritic spines through impacting the phosphorylation expression of the PI3K/AKT/mTOR pathway, and eventually led to long-term fine motor dysfunction in developing mouse.

Mechanistic insight into sevoflurane-associated developmental neurotoxicity

With the development of technology, more infants receive general anesthesia for surgery, other interventions, or clinical examination at an early stage after birth. However, whether general anesthetics can affect the function and structure of the developing infant brain remains an important, complex, and controversial issue. Sevoflurane is the most-used anesthetic in infants, but this drug is potentially neurotoxic. Short or single exposure to sevoflurane has a weak effect on cognitive function, while long or repeated exposure to general anesthetics may cause cognitive dysfunction. This review focuses on the mechanisms by which sevoflurane exposure during development may induce long-lasting undesirable effects on the brain. We review neural cell death, neural cell damage, impaired assembly and plasticity of neural circuits, tau phosphorylation, and neuroendocrine effects as important mechanisms for sevoflurane-induced developmental neurotoxicity. More advanced technologies and methods should be applied to determine the underlying mechanism(s) and guide prevention and treatment of sevoflurane-induced neurotoxicity.

1. We discuss the mechanisms underlying sevoflurane-induced developmental neurotoxicity from five perspectives: neural cell death, neural cell damage, assembly and plasticity of neural circuits, tau phosphorylation, and neuroendocrine effects. 2. Tau phosphorylation, IL-6, and mitochondrial dysfunction could interact with each other to cause a nerve damage loop. 3. miRNAs and lncRNAs are associated with sevoflurane-induced neurotoxicity.

A National Population Cohort Study Showed That Exposure to General Anesthesia in Early Childhood Is Associated with an Increase in the Risk of Developmental Delay

This study investigated the relationship between exposure to general anesthesia (GA) and the risk of cognitive and mental disorders. This study has thus investigated the relationships between exposure to GA before the age of 3 and subsequent cognitive and mental disorders in a national-wide research sample. We obtained our subjects from the National Health Insurance Research Database (NHIRD) of Taiwan, which was based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). Children in the hospital aged less than 3 years old were included if there was GA exposure or not during the period of year 1997 to 2008. Cox proportional hazard regression models adjusted for potential confounding factors were used to estimate the relative magnitude of the risk associated with GA exposure. The cohort contained 2261 subjects with GA and 4522 children without GA as a comparison group. GA exposure group had a higher rate of developmental delay than in the without GA group (hazard ratio 1.46, p < 0.0001). There was no significant difference in the overall incidence of ADHD, autism and intellectual disability between the GA-exposed group and the comparison cohort. In conclusion, this study reported that children exposed to GA early before the age of three had a small association with increased risk of development delay thereafter.