The toxic effect of ketamine on SH-SY5Y neuroblastoma cell line and human neuron

The effects of ketamine on viability, primary DNA damage, and oxidative stress parameters in HepG2 and SH-SY5Y cells

Ketamine is a dissociative anaesthetic used to induce general anaesthesia in humans and laboratory animals. Due to its hallucinogenic and dissociative effects, it is also used as a recreational drug. Anaesthetic agents can cause toxic effects at the cellular level and affect cell survival, induce DNA damage, and cause oxidant/antioxidant imbalance. The aim of this study was to explore these possible adverse effects of ketamine on hepatocellular HepG2 and neuroblastoma SH-SY5Y cells after 24-hour exposure to a concentration range covering concentrations used in analgesia, drug abuse, and anaesthesia (0.39, 1.56, and 6.25 µmol/L, respectively). At these concentrations ketamine had relatively low toxic outcomes, as it lowered HepG2 and SH-SY5Y cell viability up to 30 %, and low, potentially repairable DNA damage. Interestingly, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH) remained unchanged in both cell lines. On the other hand, oxidative stress markers [superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT)] pointed to ketamine-induced oxidant/antioxidant imbalance.

Brain Changes Associated With Long-Term Ketamine Abuse, A Systematic Review

Recently, the abuse of ketamine has soared. Therefore, it is of great importance to study its potential risks. The effects of prolonged ketamine on the brain can be observationally studied in chronic recreational users. We performed a systematic review of studies reporting functional and structural brain changes after repeated ketamine abuse. We searched the following electronic databases: Medline, Embase and PsycINFO We screened 11,438 records and 16 met inclusion criteria, totaling 440 chronic recreational ketamine users (2–9.7 years; mean use 2.4 g/day), 259 drug-free controls and 44 poly-drug controls. Long-term recreational ketamine use was associated with lower gray matter volume and less white matter integrity, lower functional thalamocortical and corticocortical connectivity. The observed differences in both structural and functional neuroanatomy between ketamine users and controls may explain some of its long-term cognitive and psychiatric side effects, such as memory impairment and executive functioning. Given the effect that long-term ketamine exposure may yield, an effort should be made to curb its abuse.

Clozapine protects adult neural stem cells from ketamine-induced cell death in correlation with decreased apoptosis and autophagy

Adult neurogenesis, the production of newborn neurons from neural stem cells (NSCs) has been suggested to be decreased in patients with schizophrenia. A similar finding was observed in an animal model of schizophrenia, as indicated by decreased bromodeoxyuridine (BrdU) labelling cells in response to a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist. The antipsychotic drug clozapine was shown to counteract the observed decrease in BrdU-labelled cells in hippocampal dentate gyrus (DG). However, phenotypic determination by immunohistochemistry analysis could not reveal whether BrdU-positive cells were indeed NSCs. Using a previously established cell model for analysing NSC protection in vitro, we investigated a protective effect of clozapine on NSCs.

Primary NSCs were isolated from the mouse subventricular zone (SVZ), we show that clozapine had a NSC protective activity alone, as evident by employing an ATP cell viability assay. In contrast, haloperidol did not show any NSC protective properties. Subsequently, cells were exposed to the non-competitive NMDA-receptor antagonist ketamine. Clozapine, but not haloperidol, had a NSC protective/anti-apoptotic activity against ketamine-induced cytotoxicity. The observed NSC protective activity of clozapine was associated with increased expression of the anti-apoptotic marker Bcl-2, decreased expression of the pro-apoptotic cleaved form of caspase-3 and associated with decreased expression of the autophagosome marker 1A/1B-light chain 3 (LC3-II).

Collectively, our findings suggest that clozapine may have a protective/anti-apoptotic effect on NSCs, supporting previous in vivo observations, indicating a neurogenesis-promoting activity for clozapine. If the data are further confirmed in vivo, the results may encourage an expanded use of clozapine to restore impaired neurogenesis in schizophrenia.

Yes‑associated protein protects and rescues SH‑SY5Y cells from ketamine‑induced apoptosis

Ketamine is a widely used intravenous anesthetic; however, basic and clinical studies have demonstrated that prolonged exposure can cause irreversible injury to the immature human brain. Yes-associated protein (YAP) is the main effector of the Hippo signaling pathway, which serves an important role in regulating tissue homeostasis and organ size during development. However, whether YAP mediates ketamine-induced apoptosis is not completely understood. Based on the functions of YAP during apoptosis resistance and cell self-renewal regulation, the present study hypothesized that YAP serves a role during ketamine-induced apoptosis. An in vitro model was utilized to investigate the effects of ketamine on neurotoxicity and to further investigate the role of YAP in ketamine-induced apoptosis using techniques including CCK-8 assay, flow cytometry and western blotting. The present study assessed the effects of YAP overexpression and knockdown on the expression of typical apoptotic markers in SH-SY5Y cells. Ketamine induced apoptosis in a dose-dependent manner, which was regulated by YAP. Following YAP overexpression, ketamine-treated SH-SY5Y cells displayed increased activity and viability, whereas expression levels of the apoptotic markers were decreased compared with the negative control group. By contrast, ketamine-induced apoptosis was enhanced following YAP knockdown. Collectively, the results of the present study indicated that YAP may serve an important role during ketamine-induced neurotoxicity, and alterations to YAP signaling may counteract ketamine-induced apoptosis. The neuroprotective effect of YAP activation may serve as a novel pharmacological target for the treatment of ketamine-induced neurotoxicity via neurogenesis normalization.

Autoimmune Encephalitis: NMDA Receptor Encephalitis as an Example of Translational Neuroscience

Autoimmune encephalitis (AE) is a group of disorders causing synaptic receptor dysfunction with a broad range of neurological symptoms that has been historically difficult to differentiate clinically. Today, AE represents an excellent example of the rapid determination of the cause of a disease and the ability to identify potential treatments using relatively simple basic science techniques of investigation. Of the number of autoimmune encephalitides identified thus far, one of the best examples of the impact of basic science studies on disease management is NMDA receptor mediated autoimmune encephalitis (NMDAr-AE). In this review, we will provide an overview of the epidemiology of NMDAr-AE, clinical features and treatments, and the basic science tools and techniques that were used to identify the cause, correlate symptoms to underlying pathophysiology, and to understand the mechanism of disease pathology.

Inhibition of GSK-3beta Signaling Pathway Rescues Ketamine-Induced Neurotoxicity in Neural Stem Cell-Derived Neurons

Clinical application of anesthetic reagent, ketamine (Keta), may induce irreversible neurotoxicity in central nervous system. In this work, we utilized an in vitro model of neural stem cells-derived neurons (nSCNs) to evaluate the role of GSK-3 signaling pathway in Keta-induced neurotoxicity. Embryonic mouse-brain neural stem cells were differentiated into neurons in vitro. Keta (50 μM)-induced neurotoxicity in cultured nSCNs was monitored by apoptosis, immunohistochemical and western blot assays, respectively. GSK-3 signaling pathways, including GSK-3α and GSK-3β, were inhibited by siRNA in the culture. The subsequent effects of GSK-3α or GSK-3β downregulation on Keta-induced neurotoxicity, including apoptosis and neurite loss, were then evaluated in nSCNs. Finally, caspase and Akt/ERK signal pathways were further examined by western blot to evaluate the regulatory effect of GSK-3 signaling pathways on Keta-induced neural injury. Keta (50 μM) caused markedly nSCN apoptosis and neurite degeneration in vitro. Keta decreased GSK-3β phosphorylation, but had no effect on GSK-3α phosphorylation. SiRNA-induced GSK-3β downregulation rescued Keta-induced neurotoxicity in nSCNs by reducing neuronal apoptosis and preventing neurite degeneration. On the other hand, GSK-3α downregulation had no effect on Keta-induced neurotoxicity. Western blot showed that, in Keta-injured nSCNs, GSK-3β downregulation reduced Caspase-1/3 proteins, but left phosphorylated Akt/ERK unchanged. GSK-3β, not GSK-3α, was specifically involved in the process of Keta-induced neurotoxicity in nSCNs. Inhibiting GSK-3β may be an effective approach to counter toxic effect of ketamine on central neurons in clinical and experimental applications.

PACAP Protects Adult Neural Stem Cells from the Neurotoxic Effect of Ketamine Associated with Decreased Apoptosis, ER Stress and mTOR Pathway Activation

Ketamine administration is a well-established approach to mimic experimentally some aspects of schizophrenia. Adult neurogenesis dysregulation is associated with psychiatric disorders, including schizophrenia. The potential role of neurogenesis in the ketamine-induced phenotype is largely unknown. Recent results from human genetic studies have shown the pituitary adenylate cyclase-activating polypeptide (PACAP) gene is a risk factor for schizophrenia. Its potential role on the regulation of neurogenesis in experimental model of schizophrenia remains to be investigated. We aimed to determine whether ketamine affects the viability of adult neural stem cells (NSC). We also investigated whether the detrimental effect mediated by ketamine could be counteracted by PACAP. NSCs were isolated from the subventricular zone of the mouse and exposed to ketamine with/without PACAP. After 24 hours, cell viability, potential involvement of apoptosis, endoplasmic reticulum (ER) stress, mTOR and AMPA pathway activation were assessed by quantitative RT-PCR and Western blot analysis. We show that ketamine impairs NSC viability in correlation with increased apoptosis, ER stress and mTOR activation. The results also suggest that the effect of ketamine occurs via AMPA receptor activation. Finally, we show that PACAP counteracted the decreased NSC viability induced by ketamine via the specific activation of the PAC-1 receptor subtype. Our study shows that the NSC viability may be negatively affected by ketamine with putative importance for the development of a schizophrenia phenotype in the ketamine induced animal model of schizophrenia. The neuroprotective effect via PAC-1 activation suggests a potentially novel pharmacological target for the treatment of schizophrenia, via neurogenesis normalization.

Biological effect of ketamine in urothelial cell lines and global gene expression analysis in the bladders of ketamine‑injected mice

Ketamine is used clinically for anesthesia but is also abused as a recreational drug. Previously, it has been established that ketamine-induced bladder interstitial cystitis is a common syndrome in ketamine-abusing individuals. As the mechanisms underlying ketamine-induced cystitis have yet to be revealed, the present study investigated the effect of ketamine on human urothelial cell lines and utilized a ketamine-injected mouse model to identify ketamine-induced changes in gene expression in mice bladders. In the in vitro bladder cell line assay, ketamine induced cytotoxicity in a dose- and time-dependent manner. Ketamine arrested the cells in G1 phase and increased the sub-G1 population, and also increased the barrier permeability of these cell lines. In the ketamine-injected mouse model, ketamine did not change the body weight and bladder histology of the animals at the dose of 30 mg/kg/day for 60 days. Global gene expression analysis of the animals’ bladders following data screening identified ten upregulated genes and 36 downregulated genes induced by ketamine. A total of 52% of keratin family genes were downregulated, particularly keratin 6a, 13 and 14, which was confirmed by polymerase chain reaction analysis. Keratin 14 protein, one of the 36 ketamine-induced downregulated genes, was also reduced in the ketamine-treated mouse bladder, as determined by immunohistochemical analysis. This suggested that cytotoxicity and keratin gene downregulation may have a critical role in ketamine-induced cystitis.

Ketamine as antidepressant? Current state and future perspectives

Major depressive disorder (MDD) is a serious mental disorder that ranks among the major causes of disease burden. Standard medical treatment targeting cerebral monoamines often provides only insufficient symptom relief and fails in approximately every fifth patient. The complexity of MDD therefore, reflects more than monoaminergic dysregulation. Initial research argues the case for excessive glutamate levels, suggesting that antiglutamatergic drugs might be useful in treating MDD. Ketamine is a non-selective, high-affinity N-methyl-D-aspartate receptor (NMDAR) antagonist most commonly used in pediatric and animal surgery. In the past, ketamine has gained popularity because of its ability to rapidly elevate mood, even in treatment-resistant and bipolar depression. However, there are still many obstacles before widespread clinical approval of ketamine treatment could become reality. In this review, ketamine's powerful antidepressant effects are discussed and further research necessary for therapeutic application is outlined. NMDAR antagonists provide an entirely new way of treating the manifold appearances of depression that should not be left unused.

Brain damages in ketamine addicts as revealed by magnetic resonance imaging

Ketamine, a known antagonist of N-methyl-D-aspartic (NMDA) glutamate receptors, had been used as an anesthetic particularly for pediatric or for cardiac patients. Unfortunately, ketamine has become an abusive drug in many parts of the world while chronic and prolonged usage led to damages of many organs including the brain. However, no studies on possible damages in the brains induced by chronic ketamine abuse have been documented in the human via neuroimaging. This paper described for the first time via employing magnetic resonance imaging (MRI) the changes in ketamine addicts of 0.5–12 years and illustrated the possible brain regions susceptible to ketamine abuse. Twenty-one ketamine addicts were recruited and the results showed that the lesions in the brains of ketamine addicts were located in many regions which appeared 2–4 years after ketamine addiction. Cortical atrophy was usually evident in the frontal, parietal or occipital cortices of addicts. Such study confirmed that many brain regions in the human were susceptible to chronic ketamine injury and presented a diffuse effect of ketamine on the brain which might differ from other central nervous system (CNS) drugs, such as cocaine, heroin, and methamphetamine.

Modeling anesthetic developmental neurotoxicity using human stem cells

Mounting preclinical evidence in rodents and nonhuman primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, whereas ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward ensuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this article, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Ketamine enhances human neural stem cell proliferation and induces neuronal apoptosis via reactive oxygen species-mediated mitochondrial pathway

BACKGROUND

Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models, leading to a serious concern regarding the safety of pediatric anesthesia. However, if and how ketamine induces human neural cell toxicity is unknown. Recapitulation of neurogenesis from human embryonic stem cells (hESCs) in vitro allows investigation of the toxic effects of ketamine on neural stem cells (NSCs) and developing neurons, which is impossible to perform in humans. In the present study, we assessed the influence of ketamine on the hESC-derived NSCs and neurons.

METHODS

hESCs were directly differentiated into neurons via NSCs. NSCs and 2-week-old neurons were treated with varying doses of ketamine for different durations. NSC proliferation capacity was analyzed by Ki67 immunofluorescence staining and bromodeoxyuridine assay. Neuroapoptosis was analyzed by TUNEL staining and caspase 3 activity measurement. The mitochondria-related neuronal apoptosis pathway including mitochondrial membrane potential, cytochrome c distribution within cells, mitochondrial fission, and reactive oxygen species (ROS) production were also investigated.

RESULTS

Ketamine (100 µM) increased NSC proliferation after 6-hour exposure. However, significant neuronal apoptosis was only observed after 24 hours of ketamine treatment. In addition, ketamine decreased mitochondrial membrane potential and increased cytochrome c release from mitochondria into cytosol. Ketamine also enhanced mitochondrial fission as well as ROS production compared with no-treatment control. Importantly, Trolox, a ROS scavenger, significantly attenuated the increase of ketamine-induced ROS production and neuronal apoptosis.

CONCLUSIONS

These data for the first time demonstrate that (1) ketamine increases NSC proliferation and causes neuronal apoptosis; (2) mitochondria are involved in ketamine-induced neuronal toxicity, which can be prevented by Trolox; and (3) the stem cell-associated neurogenesis system may provide a simple and promising in vitro model for rapidly screening anesthetic neurotoxicity and studying the underlying mechanisms as well as prevention strategies to avoid this toxic effect.

Chronic ketamine administration modulates midbrain dopamine system in mice

Ketamine is an anesthetic and a popular abusive drug. As an anesthetic, effects of ketamine on glutamate and GABA transmission have been well documented but little is known about its long-term effects on the dopamine system. In the present study, the effects of ketamine on dopamine were studied in vitro and in vivo. In pheochromocytoma (PC 12) cells and NGF differentiated-PC 12 cells, ketamine decreased the cell viability while increasing dopamine (DA) concentrations in a dose-related manner. However, ketamine did not affect the expression of genes involved in DA synthesis. In the long-term (3 months) ketamine treated mice, significant increases of DA contents were found in the midbrain. Increased DA concentrations were further supported by up-regulation of tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. Activation of midbrain dopaminergic neurons could be related to ketamine modulated cortical-subcortical glutamate connections. Using western blotting, significant increases in BDNF protein levels were found in the midbrain, suggesting that perhaps BDNF pathways in the cortical-subcortical connections might contribute to the long-term ketamine induced TH upregulation. These data suggest that long-term ketamine abuse caused a delayed and persistent upregulation of subcortical DA systems, which may contribute to the altered mental status in ketamine abusers.

Ketamine induces toxicity in human neurons differentiated from embryonic stem cells via mitochondrial apoptosis pathway

Ketamine is widely used for anesthesia in pediatric patients. Growing evidence indicates that ketamine causes neurotoxicity in a variety of developing animal models. Our understanding of anesthesia neurotoxicity in humans is currently limited by difficulties in obtaining neurons and performing developmental toxicity studies in fetal and pediatric populations. It may be possible to overcome these challenges by obtaining neurons from human embryonic stem cells (hESCs) in vitro. hESCs are able to replicate indefinitely and differentiate into every cell type. In this study, we investigated the toxic effect of ketamine on neurons differentiated from hESCs. Two-week-old neurons were treated with different doses and durations of ketamine with or without the reactive oxygen species (ROS) scavenger, Trolox. Cell viability, ultrastructure, mitochondrial membrane potential (ΔΨm), cytochrome c distribution within cells, apoptosis, and ROS production were evaluated. Here we show that ketamine induced ultrastructural abnormalities and dose- and time-dependently caused cell death. In addition, ketamine decreased ΔΨm and increased cytochrome c release from mitochondria. Ketamine also increased ROS production and induced differential expression of oxidative stress-related genes. Specifically, abnormal ultrastructural and ΔΨm changes occurred earlier than cell death in the ketamine-induced toxicity process. Furthermore, Trolox significantly decreased ROS generation and attenuated cell death caused by ketamine in a dose-dependent manner. In conclusion, this study illustrates that ketamine time- and dose-dependently induces human neurotoxicity at supraclinical concentrations via ROS-mediated mitochondrial apoptosis pathway and that these side effects can be prevented by the antioxidant agent Trolox. Thus, hESC-derived neurons might provide a promising tool for studying anesthetic-induced developmental neurotoxicity and prevention strategies.

Gene expression changes in GABA(A) receptors and cognition following chronic ketamine administration in mice

Ketamine is a well-known anesthetic agent and a drug of abuse. Despite its widespread use and abuse, little is known about its long-term effects on the central nervous system. The present study was designed to evaluate the effect of long-term (1- and 3-month) ketamine administration on learning and memory and associated gene expression levels in the brain. The Morris water maze was used to assess spatial memory and gene expression changes were assayed using Affymetrix Genechips; a focus on the expression of GABA(A) receptors that mediate a tonic inhibition in the brain, was confirmed by quantitative real-time PCR and western blot. Compared with saline controls, there was a decline in learning and memory performance in the ketamine-treated mice. Genechip results showed that 110 genes were up-regulated and 136 genes were down-regulated. An ontology analysis revealed the most significant effects of ketamine were on GABA(A) receptors. In particular, there was a significant up-regulation of both mRNA and protein levels of the alpha 5 subunit (Gabra5) of the GABA(A) receptors in the prefrontal cortex. In conclusion, chronic exposure to ketamine impairs working memory in mice, which may be explained at least partly by up-regulation of Gabra5 subunits in the prefrontal cortex.

Hyperphosphorylated tau in the brains of mice and monkeys with long-term administration of ketamine

Ketamine, a non-competitive antagonist at the glutamatergic N-methyl-d-aspartate (NMDA) receptor, might impair memory function of the brain. Loss of memory is also a characteristic of aging and Alzheimer's disease. Hyperphosphorylation of tau is an early event in the aging process and Alzheimer's disease. Therefore, we aimed to find out whether long-term ketmaine administration is related to hyperphosphorylation of tau or not in the brains of mice and monkeys. Results showed that after 6 months' administration of ketamine, in the prefrontal and entorhinal cortical sections of mouse and monkey brains, there were significant increases of positive sites for the hyperphosphorylated tau protein as compared to the control animals receiving no ketamine administration. Furthermore, about 15% of hyperphosphorylated tau positive cells were also positively labeled by terminal dUTP nick end labeling (TUNEL) indicating there might be a relationship between hyperphosphorylation of tau and apoptosis. Therefore, the long-term ketamine toxicity might involve neurodegenerative process similar to that of aging and/or Alzheimer's disease.