In vitro dose-dependent inhibition of the intracellular spontaneous calcium oscillations in developing hippocampal neurons by ketamine

Astrocytic Calcium Signaling Toolkit (astroCaST): efficient analysis of dynamic astrocytic calcium events

The Astrocytic Calcium Signaling Toolkit (astroCaST) is a novel solution to a longstanding challenge in neuroscience research: the specialized analysis of astrocytic calcium events within fluorescence time-series imaging. Distinct from existing neuron-centric tools, astroCaST is adept at detecting and clustering astrocytic calcium events based on their unique spatiotemporal characteristics, thus filling a gap in astrocytic research methodologies. This toolkit not only facilitates the detection of such events but also extends its utility to provide comprehensive end-to-end analysis. This feature is absent in most tools targeting astrocytic activity. AstroCaST's development was motivated by the critical need for dedicated software that supports researchers in transitioning from raw video data to insightful experimental conclusions, efficiently managing large-scale datasets without compromising computational speed. It offers a user-friendly interface that caters to both novice and expert users, incorporating both a graphical user interface (GUI) for detailed explorations and a command-line interface (CLI) for extensive analyses. Expected outcomes from utilizing astroCaST include the ability to process and analyze a significantly larger volume of data. This enables a more profound and comprehensive analysis than previously possible, addressing the demands of large-scale astrocytic studies. In summary, astroCaST aims to advance astrocytic calcium imaging analysis, offering a tailored, efficient, and comprehensive toolset that enhances our understanding of astrocytic functions and their implications in neuroscience.

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.

Ketamine impairs growth cone and synaptogenesis in human GABAergic projection neurons via GSK-3β and HDAC6 signaling

The growth cone guides the axon or dendrite of striatal GABAergic projection neurons that protrude into the midbrain and cortex and form complex neuronal circuits and synaptic networks in a developing brain, aberrant projections and synaptic connections in the striatum related to multiple brain disorders. Previously, we showed that ketamine, an anesthetic, reduced dendritic growth, dendritic branches, and spine density in human striatal GABAergic neurons. However, whether ketamine affects the growth cone, the synaptic connection of growing striatal GABAergic neurons has not been tested. Using human GABAergic projection neurons derived from human inducible pluripotent stem cells (hiPSCs) and embryonic stem cells (ES) in vitro, we tested ketamine effects on the growth cones and synapses in developing GABAergic neurons by assessing the morphometry and the glycogen synthase kinase-3 (GSK-3) and histone deacetylase 6 (HDAC6) pathway. Ketamine exposure impairs growth cone formation, synaptogenesis, dendritic development, and maturation via ketamine-mediated activation of GSK-3 pathways and inhibiting HDAC6, an essential stabilizing protein for dendritic morphogenesis and synapse maturation. Our findings identified a novel ketamine neurotoxic pathway that depends on GSK-3β and HDAC6 signaling, suggesting that microtubule acetylation is a potential target for reducing ketamine's toxic effect on GABAergic projection neuronal development.

Ketamine-induced neurotoxicity is mediated through endoplasmic reticulum stress in vitro in STHdhQ7/Q7 cells

Ketamine has traditionally been used as a dissociative anesthetic agent and more recently as a treatment for treatment-resistant depression. However, there is growing concern over the increased use of ketamine in recreational and therapeutic settings due to the potential neurotoxic effects. Recent studies have demonstrated that ketamine is cytotoxic in several cell types, such as fibroblasts, hepatocytes, uroepithelial cells, and adult induced pluripotent stem cells (iPSCs). Ketamine has been shown to dysregulate calcium signalling, increase reactive oxygen species (ROS) production, and impair mitochondrial function, ultimately leading to apoptosis. However, it is unclear whether endoplasmic reticulum (ER) stress plays a role in ketamine associated neurotoxicity in striatal neurons. Disruption to ER homeostasis can initiate ER-mediated cell death, which has been implicated in several neurodegenerative diseases. Thus, the purpose of this study was to determine whether ketamine's neurotoxic effects involve an ER stress-dependent pathway and to elucidate the underlying mechanisms involved in its neurotoxic effects. Mouse striatal cells were treated with various concentrations of ketamine (10 μM, 100 μM, 1 mM) or DMEM for 9-72 hrs. Cell viability was assessed using the MTT assay, and changes in gene expression of ER stress markers were evaluated using RT-qPCR. MTT results revealed that 1 mM ketamine decreased cell viability in striatal cells after 24 h of treatment. Gene expression studies complemented these findings such that ketamine upregulated pro-apoptotic ER stress markers, including X-box binding protein 1 (XBP1), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP) and downregulated pro-survival ER stress proteins such as GRP78, MANF and CDNF. Ketamine activated all three stress sensing pathways including PERK, IRE1, and ATF6. Taken together, our results show that ketamine-induced neurotoxicity is mediated through an ER stress-dependent apoptotic pathway.

Early Developmental PMCA2b Expression Protects From Ketamine-Induced Apoptosis and GABA Impairments in Differentiating Hippocampal Progenitor Cells

PMCA2 is not expressed until the late embryonic state when the control of subtle Ca²⁺ fluxes becomes important for neuronal specialization. During this period, immature neurons are especially vulnerable to degenerative insults induced by the N-methyl-D-aspartate (NMDA) receptor blocker, ketamine. As H19-7 hippocampal progenitor cells isolated from E17 do not express the PMCA2 isoform, they constitute a valuable model for studying its role in neuronal development. In this study, we demonstrated that heterologous expression of PMCA2b enhanced the differentiation of H19-7 cells and protected from ketamine-induced death. PMCA2b did not affect resting [Ca²⁺]_c in the presence or absence of ketamine and had no effect on the rate of Ca²⁺ clearance following membrane depolarization in the presence of the drug. The upregulation of endogenous PMCA1 demonstrated in response to PMCA2b expression as well as ketamine-induced PMCA4 depletion were indifferent to the rate of Ca²⁺ clearance in the presence of ketamine. Yet, co-expression of PMCA4b and PMCA2b was able to partially restore Ca²⁺ extrusion diminished by ketamine. The profiling of NMDA receptor expression showed upregulation of the NMDAR1 subunit in PMCA2b-expressing cells and increased co-immunoprecipitation of both proteins following ketamine treatment. Further microarray screening demonstrated a significant influence of PMCA2b on GABA signaling in differentiating progenitor cells, manifested by the unique regulation of several genes key to the GABAergic transmission. The overall activity of glutamate decarboxylase remained unchanged, but Ca²⁺-induced GABA release was inhibited in the presence of ketamine. Interestingly, PMCA2b expression was able to reverse this effect. The mechanism of GABA secretion normalization in the presence of ketamine may involve PMCA2b-mediated inhibition of GABA transaminase, thus shifting GABA utilization from energetic purposes to neurosecretion. In this study, we show for the first time that developmentally controlled PMCA expression may dictate the pattern of differentiation of hippocampal progenitor cells. Moreover, the appearance of PMCA2 early in development has long-standing consequences for GABA metabolism with yet an unpredictable influence on GABAergic neurotransmission during later stages of brain maturation. In contrast, the presence of PMCA2b seems to be protective for differentiating progenitor cells from ketamine-induced apoptotic death.

Ketamine and Calcium Signaling-A Crosstalk for Neuronal Physiology and Pathology

Ketamine is a non-competitive antagonist of NMDA (N-methyl-D-aspartate) receptor, which has been in clinical practice for over a half century. Despite recent data suggesting its harmful side effects, such as neuronal loss, synapse dysfunction or disturbed neural network formation, the drug is still applied in veterinary medicine and specialist anesthesia. Several lines of evidence indicate that structural and functional abnormalities in the nervous system caused by ketamine are crosslinked with the imbalanced activity of multiple Ca²⁺-regulated signaling pathways. Due to its ubiquitous nature, Ca²⁺ is also frequently located in the center of ketamine action, although the precise mechanisms underlying drug’s negative or therapeutic properties remain mysterious for the large part. This review seeks to delineate the relationship between ketamine-triggered imbalance in Ca²⁺ homeostasis and functional consequences for downstream processes regulating key aspects of neuronal function.

Association Analysis of Neuronal Nitric Oxide Synthase 1 Gene Polymorphism With Psychopathological Symptoms in Chronic Ketamine Users

Objective: We previously found that chronic ketamine usages were associated with various psychotic and cognitive symptoms mimicking schizophrenia. The blockade of the NMDA receptor and subsequent nitric oxide synthase 1 (NOS1) dysfunction were found to be closely correlated with schizophrenia including NOS1 gene polymorphisms. We examined the allelic variants of the gene coding neuronal nitric oxide synthase 1 (NOS1) in chronic ketamine users in the Chinese population and analyzed the association between NOS1 gene polymorphism and psychopathological symptoms in chronic ketamine users. The association between the NOS1 polymorphism and ketamine use characteristics was also examined. Methods: One hundred ninety seven male chronic ketamine users and 82 controls were recruited. Four common SNPs of the NOS1 gene, rs6490121, rs41279104, rs3782206, and rs3782219, were examined by real-time PCR with the TaqMan® assay system. Psychopathological symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI), and the Beck Anxiety Inventory (BAI). Results: The genotype distribution of rs6490121 and rs41279104 in chronic ketamine users was significantly different from that in the control (p = 0.0001 and p = 0.002). The G allele frequency of rs6490121 in ketamine users was higher than that in the control (p = 2.23 * 10^-6, OR = 3.07, 95% CI = 1.93-4.90). The T allele frequency of rs41279104 in chronic ketamine users was higher than that in the control (p = 0.01, OR = 1.76, 95% CI = 1.14-2.72). The BAI score was significantly different among the three genotypic groups of rs6490121 (F = 6.21, p = 0.002) in ketamine users; subjects of genotype AG and GG had a lower score than subjects of genotype AA. The score of the negative symptom subscale of PANSS was significantly different among the three genotypic groups of rs41279104 (F = 5.39, p = 0.005); in ketamine users, subjects of genotype CT and TT had a higher score than subjects of genotype CC. There was no difference in drug use characteristics in different genotypes of the four NOS1 gene polymorphisms tested in ketamine users (p > 0.05).

N-methyl-D-aspartate (NMDA) receptor expression and function is required for early chondrogenesis

Background

In vitro chondrogenesis depends on the concerted action of numerous signalling pathways, many of which are sensitive to the changes of intracellular Ca²⁺ concentration. N-methyl-D-aspartate (NMDA) glutamate receptor is a cation channel with high permeability for Ca²⁺. Whilst there is now accumulating evidence for the expression and function of NMDA receptors in non-neural tissues including mature cartilage and bone, the contribution of glutamate signalling to the regulation of chondrogenesis is yet to be elucidated.

Methods

We studied the role of glutamatergic signalling during the course of in vitro chondrogenesis in high density chondrifying cell cultures using single cell fluorescent calcium imaging, patch clamp, transient gene silencing, and western blotting.

Results

Here we show that key components of the glutamatergic signalling pathways are functional during in vitro chondrogenesis in a primary chicken chondrogenic model system. We also present the full glutamate receptor subunit mRNA and protein expression profile of these cultures. This is the first study to report that NMDA-mediated signalling may act as a key factor in embryonic limb bud-derived chondrogenic cultures as it evokes intracellular Ca²⁺ transients, which are abolished by the GluN2B subunit-specific inhibitor ifenprodil. The function of NMDARs is essential for chondrogenesis as their functional knock-down using either ifenprodil or GRIN1 siRNA temporarily blocks the differentiation of chondroprogenitor cells. Cartilage formation was fully restored with the re-expression of the GluN1 protein.

Conclusions

We propose a key role for NMDARs during the transition of chondroprogenitor cells to cartilage matrix-producing chondroblasts.

Ketamine destabilizes growth of dendritic spines in developing hippocampal neurons in vitro via a Rho‑dependent mechanism

The safety of anesthetics on the developing brain has caused concern. Ketamine, an N-methyl-D-aspartate receptor antagonist, is widely used as a general pediatric anesthetic. Recent studies suggested that ketamine alters the plasticity of dendritic spines in the developing brain and may be an important contributing factor to learning and cognitive impairment. However, the underlying molecular mechanism remains poorly understood. Therefore, the aim of the present study was to investigate the effect of ketamine on the plasticity of dendritic spines in cultured hippocampal neurons and the potential underlying mechanisms. After 5 days in vitro, rat hippocampal neurons were exposed to different concentrations (100, 300 and 500 µM) of ketamine for 6 h. Ketamine decreased the number and length of dendritic spines in a dose-dependent manner. Ketamine at a concentration of 300 µM caused an upregulation of transforming protein RhoA (RhoA) and Rho-associated kinase (ROCK) protein. These effects were inhibited by the ROCK inhibitor Y27632. These results suggested that ketamine induces loss and shortening of dendritic spines in hippocampal neurons via activation of the RhoA/ROCK signaling pathway.

Ketamine induces hippocampal apoptosis through a mechanism associated with the caspase-1 dependent pyroptosis

Ketamine, a pediatric anesthetic, is widely used in clinical practice. There was growing evidence showing that ketamine can promote neuronal death in developing brains of both humans and animals. In this study, we used in vivo neonatal and juvenile mouse models to induce ketamine-related neurotoxicity in the hippocampus. Active caspase-3 and -9 proteins, which are responsible for the release of cytochrome C, and the mitochondrial translocation of p53, which is associated with mitochondrial apoptosis, were found to be significantly up-regulated in the ketamine-induced hippocampal neurotoxicity. Furthermore, we demonstrated that the levels of pyroptosis-related proteins, including caspase-1 and -11, NOD-like receptor family, pyrin domain containing 3 (NLRP3), and IL-1β and IL-18, significantly increased after multiple doses of ketamine administration. We speculated that ketamine triggered the formation of NLRP3 and caspase-1 complex and its translocation to the mitochondria. In consistent with this, ketamine treatment was found to induce pyroptosis in mouse primary hippocampal neurons, which was characterized by increased pore formation and elevated lactate dehydrogenase release in mitochondria. Silencing caspase-1 with lentivirus-mediated short hairpin RNA (shRNA) significantly decreased the levels of not only pyroptosis-related proteins but also mitochondrial apoptosis-associated proteins in mouse primary hippocampal neurons. We conclude that caspase-1-dependent pyroptosis is an important event which may be an essential pathway involved in the mitochondria-associated apoptosis in ketamine-induced hippocampal neurotoxicity.

Behavioral alterations of zebrafish larvae after early embryonic exposure to ketamine

RATIONALE

Ketamine has been associated with pediatric risks that include neurocognitive impairment and long-term behavioral disorders. However, the neurobehavioral effects of ketamine exposure in early development remain uncertain.

OBJECTIVES

This study aimed to test stage- and dose-dependent effects of ketamine exposure on certain brain functions by evaluating alterations in locomotion, anxiety-like and avoidance behaviors, as well as socialization.

METHODS

Embryos were exposed to different concentrations of ketamine (0, 0.2, 0.4, and 0.8 mg mL^-1) for 20 min during the 256-cell (2.5 h post fertilization-hpf), 50% epiboly (5.5 hpf), and 1-4 somites (10.5 hpf) stages. General exploratory activities, natural escape-like responses, and social interactions were analyzed under continuous light or under a moving light stimulus.

RESULTS

A dose-dependent decrease in the overall mean speed was perceived in the embryos exposed during the 256-cell stage. These results were related to previously observed head and eye malformations, following ketamine exposure at this stage and may indicate possible neurobehavioral disorders when ketamine exposure is performed at this stage. Results also showed that ketamine exposure during the 50% epiboly and 1-4 somites stages induced a significant increment of the anxiety-like behavior and a decrease in avoidance behavior in all exposed groups.

CONCLUSIONS

Overall, the results validate the neurodevelopmental risks of early-life exposure to ketamine.

Mobilization and removing of cadmium from kidney by GMDTC utilizing renal glucose reabsorption pathway

Chronic exposure to cadmium compounds (Cd(2+)) is one of the major public health problems facing humans in the 21st century. Cd(2+) in the human body accumulates primarily in the kidneys which leads to renal dysfunction and other adverse health effects. Efforts to find a safe and effective drug for removing Cd(2+) from the kidneys have largely failed. We developed and synthesized a new chemical, sodium (S)-2-(dithiocarboxylato((2S,3R,4R,5R)-2,3,4,5,6 pentahydroxyhexyl)amino)-4-(methylthio) butanoate (GMDTC). Here we report that GMDTC has a very low toxicity with an acute lethal dose (LD50) of more than 10,000mg/kg or 5000mg/kg body weight, respectively, via oral or intraperitoneal injection in mice and rats. In in vivo settings, up to 94% of Cd(2+) deposited in the kidneys of Cd(2+)-laden rabbits was removed and excreted via urine following a safe dose of GMDTC treatment for four weeks, and renal Cd(2+) level was reduced from 12.9μg/g to 1.3μg/g kidney weight. We observed similar results in the mouse and rat studies. Further, we demonstrated both in in vitro and in animal studies that the mechanism of transporting GMDTC and GMDTC-Cd complex into and out of renal tubular cells is likely assisted by two glucose transporters, sodium glucose cotransporter 2 (SGLT2) and glucose transporter 2 (GLUT2). Collectively, our study reports that GMDTC is safe and highly efficient in removing deposited Cd(2+) from kidneys assisted by renal glucose reabsorption system, suggesting that GMDTC may be the long-pursued agent used for preventive and therapeutic purposes for both acute and chronic Cd(2+) exposure.

Ketamine-induced oxidative stress at different developmental stages of zebrafish (Danio rerio) embryos

The changes induced by ketamine exposure were developmental stage-dependent, and related with the gradual development of the antioxidant defense system of the embryo, which is dependent on changes in energy-sensing pathways.

Vortioxetine promotes maturation of dendritic spines in vitro: A comparative study in hippocampal cultures

Cognitive dysfunction is prevalent in patients with major depressive disorder (MDD), and cognitive impairments can persist after relief of depressive symptoms. The multimodal-acting antidepressant vortioxetine is an antagonist at 5-HT3, 5-HT7, and 5-HT1D receptors, a partial agonist at 5-HT1B receptors, an agonist at 5-HT1A receptors, and an inhibitor of the serotonin (5-HT) transporter (SERT) and has pro-cognitive properties. In preclinical studies, vortioxetine enhances long-term potentiation (LTP), a cellular correlate of neuroplasticity, and enhances memory in various cognitive tasks. However, the molecular mechanisms by which vortioxetine augments LTP and memory remain unknown. Dendritic spines are specialized, actin-rich microdomains on dendritic shafts and are major sites of most excitatory synapses. Since dendritic spine remodeling is implicated in synaptic plasticity and spine size dictates the strength of synaptic transmission, we assessed if vortioxetine, relative to other antidepressants including ketamine, duloxetine, and fluoxetine, plays a role in the maintenance of dendritic spine architecture in vitro. We show that vortioxetine, ketamine, and duloxetine induce spine enlargement. However, only vortioxetine treatment increased the number of spines in contact with presynaptic terminals. In contrast, fluoxetine had no effect on spine remodeling. These findings imply that the various 5-HT receptor mechanisms of vortioxetine may play a role in its effect on spine dynamics and in increasing the proportion of potentially functional synaptic contacts.

The role of TNF-α in regulating ketamine-induced hippocampal neurotoxicity

INTRODUCTION

Ketamine is commonly used in pediatric anesthesia but recent studies have shown that it could induce neurotoxicity in the developing brain. The inflammatory cytokine, tumor necrosis factor α (TNF-α) is involved in the pathogenesis of various types of neurodegenerations. In the present study, we examined whether TNF-α may regulate ketamine-induced neurotoxicity in the hippocampus of neonatal mouse.

MATERIAL AND METHODS

The in vitro organotypic culture of hippocampal slices was used to investigate the gain-of-function and loss-of-function effect of TNF-α modulation on ketamine-induced hippocampal neurotoxicity. Also, western blotting analysis was used to examine the relative pathways associated with TNF-α modulation. In the in vivo Morris water maze test, TNF-α was genetically silenced to see if memory function was improved after anesthesia-induced memory impairment.

RESULTS

In in vitro experiments, adding TNF-α enhanced (112.99 ±5.4%, p = 0.015), whereas knocking down TNF-α ameliorated (46.8 ±11.6%, p = 0.003) ketamine-induced apoptosis in hippocampal CA1 neurons in the organotypic culture. Western blotting showed that addition of TNF-α reduced (67.1 ±3.7%, p = 0.022), whereas downregulation of TNF-α increased (126.87 ±8.5%, p = 0.004) the phosphorylation of PKC-ERK pathway in ketamine-treated hippocampus. In in vivo experiments, genetically silencing TNF-α markedly improved the ketamine-induced memory impairment through Morris water maze test.

CONCLUSIONS

Our results clearly demonstrated a protective mechanism of down-regulating TNF in ketamine-induced hippocampal neurotoxicity. This study may present a new target for pharmacological intervention to prevent anesthesia-related neurodegeneration in brain.

Region-specific effects of repeated ketamine administration on the presynaptic GABAergic neurochemistry in rat brain

A growing body of evidence indicates that clinical use of ketamine as a promising antidepressant can be accompanied by psychotic-like side effects. Although, the generation of such effects is thought to be attributed to dysfunction of prefrontal GABAergic interneurons, the mechanism underlying ketamine's propsychotic-like action is not fully understood. Due to wide spectrum of behavioral abnormalities, it is hypothesized that ketamine action is not limited to only cortical GABA metabolism but may also involve alterations in other functional brain areas. To test it, we treated rats with ketamine (30 mg/kg, i.p.) for 5 days, and next we analyzed GABA metabolizing enzymes in cortex, cerebellum, hippocampus and striatum. Our results demonstrated that diminished GAD67 expression in cortex, cerebellum (by ∼60%) and in hippocampus (by ∼40%) correlated with lowered protein level in these areas. The expression of GAD65 isoform decreased by ∼45% in striatum, but pronounced increase by ∼90% was observed in hippocampus. Consecutively, reduction in glutamate decarboxylase activity and GABA concentration were detected in cortex, cerebellum and striatum, but not in hippocampus. Ketamine administration decreased GABA transaminase protein in cortex and striatum (by ∼50% and 30%, respectively), which was reflected in diminished activity of the enzyme. Also, a significant drop in succinic semialdehyde dehydrogenase activity in cortex, cerebellum and striatum was present. These data suggest a reduced utilization of GABA for energetic purposes. In addition, we observed synaptic GABA release to be reduced by ∼30% from striatal terminals. It correlated with lowered KCl-induced Ca(2+) influx and decreased amount of L-type voltage-dependent calcium channel. Our results indicate that unique changes in GABA metabolism triggered by chronic ketamine treatment in functionally distinct brain regions may be involved in propsychotic-like effects of this drug.

Role of miR-34c in ketamine-induced neurotoxicity in neonatal mice hippocampus

Ketamine is a commonly used pediatric anesthetic, but it might affect development, or even induce neurotoxicity in the neonatal brain. We have used an in vivo neonatal mouse model to induce ketamine-related neurotoxicity in the hippocampus, and found that miR-34c, a microRNA associated with pathogenesis of Alzheimer's disease, was significantly upregulated during ketamine-induced hippocampal neurodegeneration. Functional assay of silencing miR-34c demonstrated that downregulation of miR-34c activated PKC-ERK pathway, upregulated anti-apoptotic protein BCL2, and ameliorated ketamine-induced apoptosis in the hippocampus. Cognitive examination with the Morris water maze test showed that ketamine-induced memory impairment was significantly improved by miR-34c downregulation. Thus, miR-34c is important in regulating ketamine-induced neurotoxicity in hippocampus.

Carbon monoxide augments electrical signaling in cultured neural networks of hippocampal neurons partly through activation of BKCa channels

Carbon monoxide (CO) is often viewed as a lethal gas in light of its capacity to prevent oxygen uptake in hemoglobin; however, it also functions to regulate a variety of proteins and physiological processes. Here we show that CO is an important chemical cue, to which neurons respond strongly, and this response is then integrated into neural network activity. In cultured mouse hippocampal neurons, CO enhanced synchronized spontaneous cytosolic Ca(2+) oscillations which arose from periodic action potentials through synaptic transmission. We used single-cell patch-clamp recording to investigate the neural network. Our results showed that the frequency of spontaneous and miniature post synaptic current was increased in neurons cultured for 14-18 days after addition of CO, with no change in current amplitude. BK channels have recently been demonstrated to be important in the action of CO. Our results showed that the effect of CO on neural network electrical activity was partly abolished after blocking the BK channels. Altogether, our results suggest that CO can influence neural network electrical activity and that BK channels participate in this regulation process.

The role of miR-124 in modulating hippocampal neurotoxicity induced by ketamine anesthesia

PURPOSE

Ketamine is widely used in pediatric anesthesia. Recent studies have demonstrated that excessive application of ketamine leads to cortical neurodegeneration in neonatal brains. The present study aims to characterize the functional role of neuronal microRNA, miR-124, in regulating ketamine-induced neurotoxicity in mouse hippocampus.

METHODS

Real-time quantitative PCR (RT-PCR) was used to examine the effect of high-dosage ketamine on the expression of miR-124 in murine hippocampus in vitro. Downregulation of hippocampal miR-124 was achieved by lentivirual transfection, and its effects on protecting ketamine-induced hippocampal neurodegeneration were examined both in vitro and in vivo.

RESULTS

Hippocampal miR-124 was upregulated by ketamine treatment. Knocking down miR-124 in vitro reduced ketamine-induced apoptosis in hippocampal CA1 neurons, upregulated AMPA receptors phosphorylation and activated the protein kinase C/extracellular signal-regulated kinases (PKC/ERK) pathway. In the in vivo Morris water maze test, following ketamine-induced hippocampal neurodegeneration, mice subjected to hippocampal miR-124 inhibition showed improved memory performance.

CONCLUSIONS

Our study demonstrated that miR-124 played an important role in regulating ketamine-induced hippocampal neurodegeneration. Inhibiting miR-124 may provide a molecular target to improve memory performance in both human and animals suffering from overanesthetizing-related neurotoxicity.

MicroRNA-34a negatively regulates anesthesia-induced hippocampal apoptosis and memory impairment through FGFR1

BACKGROUND

Mounting evidence has shown the toxic effects of anesthesia to neonatal hippocampus. We used an in vivo mouse model to explore the role of microRNA 34a (miR-34a) in regulating anesthesia-induced hippocampal neurotoxicity.

METHODS

One-month old C57/BL6 mice received daily intraperitoneal injection of anesthesia (ketamine, 50 mg/kg) for 7 days. One day after, apoptosis was evaluated by TUNEL staining in hippocampal CA1 region, and expression level of miR-34a assessed by real-time quantitative PCR (qPCR). Hippocampal miR-34a was then down-regulated through lentivirus mediated cortical injection prior to anesthesia. The effects of inhibiting hippocampal miR-34a on anesthesia-induced hippocampal apoptosis and memory impairment were further investigated by TUNEL staining and Morris water maze (MWM) test. The predicted molecular target of miR-34a, fibroblast growth factor receptor 1 (FGFR1) was down-regulated in hippocampus through siRNA-mediated cortical injection and its effect on hippocampal apoptosis was also examined.

RESULTS

Anesthesia caused severe apoptosis among hippocampal CA1 neurons and upregulated hippocampal miR-34a. On the other hand, lentivirual inhibition of miR-34a protected anesthesia-induced hippocampal apoptosis and memory impairment. Luciferase essay demonstrated FGFR1 was directly regulated by miR-34a in hippocampus. siRNA-induced FGFR1 downregulation further exaggerated anesthesia-induced apoptosis in hippocampus.

CONCLUSIONS

Overall, we showed that miR-34a negatively modulated anesthesia-induced hippocampal neurotoxicity.

Upregulation of miR-137 protects anesthesia-induced hippocampal neurodegeneration

PURPOSE

Ketamine is commonly used in pediatric anesthesia but may cause neurodegeneration in young brains. The aim of the study is to use an animal model to characterize the role of microRNA 137 (miR-137) in ketamine-induced neurodegeneration in neonatal hippocampus.

METHODS

Young Sprague-Dawley Rats (1 month old) was systemically administrated with ketamine (75 mg/kg) for 3 days. TUNEL assay was used to assess the ketamine-induced neurodegeneration of hippocampal CA1 neurons, quantitative real-time PCR (qRT-PCR) to assess the expression of miR-137 and Morris water maze test (MWM) to assess the damaged memory function. Alternatively, lentivirus over-expressing miR-137 was injected into hippocampus before ketamine administration, and the subsequent effects of miR-137 upregulation on ketamine-induced hippocampal neurodegeneration and memory dysfunction were investigated. Furthermore, the direct downstream target of miR-137, CDC42, was down-regulated by siRNA injection into hippocampus. The effects of CDC42 inhibition on hippocampal apoptosis and memory function were also investigated.

RESULTS

Excessive ketamine treatment resulted in severe apoptosis in hippocampal CA1 neurons, downregulation of miR-137 in hippocampus and significant long-term memory dysfunction. Conversely, pre-treatment of overexpressing miR-137 protected hippocampal neurodegeneration and memory loss. The molecular target of miR-137, CDC42 was down-regulated by ketamine in hippocampus. Knocking down hippocampal CDC42 exerted an apoptotic effect on hippocampal neurons and memory loss, similar to the effect of ketamine treatment.

CONCLUSIONS

Our results demonstrated that miR-137 played an important role in regulating ketamine induced hippocampal neurodegeneration, possibly through CDC42.