Mechanistic studies on ketamine-induced mitochondrial toxicity in zebrafish embryos

Occurrence, ecotoxicity and ecological risks of psychoactive substances in surface waters

Psychoactive substances (PSs) represent a subset of emerging contaminants. Their widespread production and utilization contribute to a growing ecological burden and risk on a global scale. Conventional wastewater treatment methods have proven insufficient in adequately removing psychoactive substances, leading to their occurrence in surface water ecosystems worldwide. As of present, however, a thorough understanding of their geographical prevalence and distribution patterns remains elusive. Further, in the existing literature, there is a scarcity of comprehensive overviews that systematically summarize the toxicity of various psychoactive substances towards aquatic organisms. Through summarizing almost 140 articles, the present study provides an overview of the sources, pollution status, and biotoxicity of psychoactive substances in surface waters, as well as an assessment of their ecological risks. Concentrations of several psychoactive substances in surface waters were found to be as high as hundreds or even thousands of ng·L-1. In parallel, accumulation of psychoactive substances in the tissues or organs of aquatic organisms was found to potentially cause certain adverse effects, including behavioral disorders, organ damage, and DNA changes. Oxidative stress was found to be a significant factor in the toxic effects of psychoactive substances on organisms. The application of the risk quotient approach indicated that psychoactive substances posed a medium to high risk in certain surface water bodies, as well as the need for sustained long-term attention and management strategies.

Effects of carvacrol on ketamine-induced cardiac injury in rats: an experimental study

AIM

We aimed to investigate the preventive effects of carvacrol against ketamine-induced cardiotoxicity biochemically and histopathologically in an experimental model.

MATERIAL AND METHOD

The rats were divided into three groups; healthy control (HC), ketamine alone (KG), and ketamine + carvacrol (KCG) groups. Serum Creatine Kinase Myocardial Band (CK-MB) and Troponin I (TP I) levels were determined. Malondialdehyde (MDA), Glutathione (GSH), Superoxide Dismutase (SOD), Tumor Necrosis Factor α (TNF-α), Interleukin 1 beta (IL-1beta), and Interleukin 6 (IL-6) levels were measured in the heart tissues of the rats. Heart tissues were also evaluated histopathologically.

RESULTS

In the ketamine-treated group, tissue MDA, TNF-α, IL-1beta, and IL-6 levels increased while tissue GSH and SOD levels decreased significantly compared with the control group. However, in the ketamine plus carvacrol applied group, all those alterations were significantly less pronounced, close to the healthy controls. Severe mononuclear cell infiltrations, degenerated myocytes and hemorrhage were determined in the ketamine alone administered group, and these alterations were at a mild level in the carvacrol + ketamine administered group.

CONCLUSION

Prolonged exposure to ketamine resulted in induced oxidative stress in rat heart tissue; concomitant carvacrol application could counteract the negative effects of ketamine by protecting tissues from lipid peroxidation and decreasing the inflammatory response.

The neurotoxicity and mechanism of TBBPA-DHEE exposure in mature zebrafish (Danio rerio)

Tetrabromobisphenol A-bis (2-hydroxyethyl) ether (TBBPA-DHEE) has been detected in various environmental media and organisms, and its ecological risks and health hazards have attracted great attention, but sufficient toxicological data have not proved the toxic effects of TBBPA-DHEE exposure on aquatic organism. In this study, the neurotoxicity and mechanism of zebrafish (3-month-old) exposed to TBBPA-DHEE (0.86 μg/L, 12.9 μg/L, 193.5 μg/L) were studied. Furthermore, the neurotoxicity susceptibility of different sexes of zebrafish was revealed. Behavioral studies revealed that TBBPA-DHEE exposure has significant differences in average speed, duration of mania, the distance between objects, and ATP content between male and female zebrafish. Slight damage in brain tissue of male zebrafish was found. The transcriptome analysis revealed that the molecular mechanism of neurotoxicity in mature female and male zebrafish is different. For mature female zebrafish, TBBPA-DHEE significantly affected the expression of genes related to behavior and development, and its mechanism may be that it can produce neurotoxicity by affecting related genes in the hormone, synapse, and Ca²⁺ signaling pathway. For mature male zebrafish, TBBPA-DHEE can significantly affect their behavior and expression of nerve-related genes. Results from the transcriptomic analysis suggests that the possible molecular mechanism may be through the inhibition of Ca²⁺ signal transmission and produce neurotoxicity by affecting the expression of related genes in neural synapses, Ca²⁺ signal, and MAPK signal in brain tissue of zebrafish. The results suggested that exposure to low-dose TBBPA-DHEE could induce neurotoxicity in zebrafish, and female and male zebrafish showed different toxic effects and molecular mechanisms.

The potential mechanisms of TBBPA bis(2-hydroxyethyl) ether induced developmental neurotoxicity in juvenile zebrafish (Danio rerio)

TBBPA bis(2-hydroxyethyl) ether (TBBPA-DHEE), one of the main derivatives of TBBPA, has been widely detected in environmental samples and been discovered to be potential neurotoxic. In this study, the juvenile zebrafish were selected as the research subject to explore the neurotoxicity and its mechanism of low-dose TBBPA-DHEE exposure, and to reveal the neurotoxicity susceptibility in different sexes. Behavioral studies revealed that TBBPA-DHEE could significantly reduce the swimming velocity, maximum acceleration and cumulative duration of high-speed mobility, significantly increasing the cumulative duration of low-speed mobility and average social distance. It significantly reduced the contents of ATP, glutamate and Ca²⁺ in the whole brain. The histopathological study demonstrated that TBBPA-DHEE could cause brain tissue damage in female and male juvenile zebrafish. The comprehensive data analysis indicated that female zebrafish were more susceptible to TBBPA-DHEE exposure than male zebrafish. Transcriptomic analysis showed that TBBPA-DHEE could significantly affect the expressions of behavioral and development-related genes. Furthermore, female and male juvenile zebrafish have different molecular mechanisms of neurotoxicity. For female juvenile zebrafish, the potential mechanism of neurotoxicity could be that it interfered with the feedback regulation of nerves by affecting the related genes expressions in the signaling pathways such as Ca²⁺ signaling, Wnt signaling and synapses. For male juvenile zebrafish, the potential mechanism of neurotoxicity may be through affecting the expression of related genes in hormones and neuro-related genes. This research could reveal the potential neurotoxicity of TBBPA-DHEE to aquatic organisms, which will be helpful to reveal the health effects of the emerging environmental pollutants.

Zebrafish (Danio rerio): A potential model to assess developmental toxicity of ketamine

Ketamine is a non-competitive antagonist of NMDA glutamate receptor. It is used as an anesthetic, analgesic, sedative, and anti-depressive agent in clinical practice and also an illegal recreational drug. The increasing use has contributed to the measurable levels of ketamine in both wastewaters and hospital effluents, thereby classified as an emergent contaminant. Lately, the potential toxicity of ketamine has raised serious concerns about its iatrogenic or illicit use during pregnancy, neonatal and childhood stages. However, to assess its long-term toxicity potentially by the use of early life stages in human and rodents is limited. In this regard, the zebrafish has been considered as excellent model organism for biosafety assessments of ketamine due to it boasts an in vivo model with the advantages of an in vitro assay. In this review, we summarize the current understanding of the reported toxicity studies with ketamine in early life stage of zebrafish. The adverse effects of ketamine are known to cause overall developmental and multi-organ toxicity, including cardio-, neuro-, and skeletal toxicity. Furthermore, multiple mechanisms are found to be responsible for perpetrating toxicity of ketamine. The current findings confluence to emphasize the zebrafish embryo as an appealing model system for developmental toxicity testing in higher vertebrates.

Neuroprotective effect of hesperidin and its combination with coenzyme Q10 on an animal model of ketamine-induced psychosis: behavioral changes, mitochondrial dysfunctions, and oxidative stress

Background

Psychosis is a complex mental illness divided by positive symptoms, negative symptoms, and cognitive decline. Clinically available medicines are associated with some serious side effects which limit their use. Treatment with flavonoids has been associated with delayed onset and development, decreased risk, or increased improvement of various neuropsychiatric disorders including psychosis with negligible side effects. Therefore, the present study was aimed to investigate the protective effects of hesperidin (flavonoid) alone or its combination with coenzyme Q10 against ketamine-induced psychotic symptoms in mice.

Results

Ketamine (50 mg/kg, i.p.) was given for 21 days to induce psychosis in Laca mice of either sex. Locomotor activity and stereotypic behaviors, immobility duration (forced swim test), and increased transfer latency (elevated plus maze) were performed to test the effect of hesperidin (50 mg/kg, 100 mg/kg, 200 mg/kg, p.o.) and coenzyme Q10 (20 mg/kg, 40 mg/kg, p.o.) and combination of hesperidin + coenzyme Q10 followed by biochemical and mitochondrial complexes assays. For 21 days, ketamine (50 mg/kg, i.p.) administration significantly produced increased locomotor activity and stereotypic behaviors (positive symptoms), increased immobility duration (negative symptoms) and cognitive deficits (increases transfer latency) weakens oxidative defense and mitochondrial function. Further, 21 days’ administration of hesperidin and coenzyme Q10 significantly reversed the ketamine-induced psychotic behavioral changes and biochemical alterations and mitochondrial dysfunction in the discrete areas (prefrontal cortex and hippocampus) of mice brains. The potential effect of these drugs was comparable to olanzapine treatment. Moreover, the combination of hesperidin with coenzyme Q10 and or a combination of hesperidin + coenzyme Q10 + olanzapine treatment did not produce a significant effect compared to their per se effect in ketamine-treated animals.

Conclusions

The study revealed that hesperidin alone or in combination with coenzyme Q10 could reduce psychotic symptoms and improve mitochondrial functions and antioxidant systems in mice, suggesting neuroprotective effects against psychosis.

Ecotoxicological effects of pyraclostrobin on tilapia (Oreochromis niloticus) via various exposure routes

Pyraclostrobin is a widely used and highly efficient fungicide that also has high toxicity to aquatic organisms, especially fish. Although some research has reported the toxic effects of pyraclostrobin on fish, the main toxic pathways of pyraclostrobin in fish remain unclear. The present study has integrated histopathological, biochemical and hematological techniques to reveal the main toxic pathways and mechanisms of pyraclostrobin under different exposure routes. Our results indicated that pyraclostrobin entered fish mainly through the gills. The highest accumulation of pyraclostrobin was observed in the gills and heart compared with accumulation in other tissues and gill tissue showed the most severe damage. Hypoxia symptoms (water jacking, tummy turning and cartwheel formation) in fish were observed throughout the experiment. Taken together, our results suggested that the gills are important target organs. The high pyraclostrobin toxicity to gills might be associated with oxidative damage to the gills, inducing alterations in ventilation frequency, oxygen-carrying substances in blood and disorders of energy metabolism. Our research facilitates a better understanding of the toxic mechanisms of pyraclostrobin in fish, which can promote the ecotoxicological research of agrochemicals on aquatic organisms.

Effect of ketamine on gene expression in zebrafish embryos

Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist. Used as an anesthetic, potential neurotoxic and cardiotoxic effects of ketamine in animal models have been reported. The underlying mechanisms of ketamine-induced toxicity are not clear. The zebrafish is an ideal model for toxicity assays because of its predictive capability in chemical testing, which compares well with that of mammalian models. To gain insight into potential mechanisms of ketamine effects, we performed real-time quantitative polymerase chain reaction-based gene expression array analyses. Gene expression analysis was conducted for multiple genes (a total of 84) related to 10 major signaling pathways including the transforming growth factor β (TGFβ), Wingless and Int-1 (Wnt), nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), Janus kinase/signal transducers and activators of transcription (JAK/STAT), p53, Notch, Hedgehog, peroxisome proliferator-activated receptor (PPAR), oxidative stress, and hypoxia pathways. Our results show that ketamine altered the expression of specific genes related to hypoxia, p53, Wnt, Notch, TGFβ, PPAR, and oxidative stress pathways. Thus, we can further focus on these specific pathways to elucidate the mechanisms by which ketamine elicits a toxic response.

Neuroprotective Effects of Carnitine and Its Potential Application to Ameliorate Neurotoxicity

Carnitine is an essential metabolite that is absorbed from the diet and synthesized in the kidney, liver, and brain. It ferries fatty acids across the mitochondrial membrane to undergo β-oxidation. Carnitine has been studied as a therapy or protective agent for many neurological diseases and neurotoxicity (e.g., prolonged anesthetic exposure-induced developmental neurotoxicity in preclinical models). Preclinical and clinical data support the notion that carnitine or acetyl carnitine may improve a patient's quality of life through increased mitochondrial respiration, release of neurotransmitters, and global gene expression changes, showing the potential of carnitine beyond its approved use to treat primary and secondary carnitine deficiency. In this review, we summarize the beneficial effects of carnitine or acetyl carnitine on the central nervous system, highlighting protective effects against neurotoxicity-induced damage caused by various chemicals and encouraging a thorough evaluation of carnitine use as a therapy for patients suffering from neurotoxicant exposure.

Effects of acetyl L-carnitine on zebrafish embryos: Phenotypic and gene expression studies

Acetyl L-carnitine (ALCAR), a dietary supplement and an antioxidant, plays a vital role in the bioenergetic process that produces ATP. Although there are reports on antioxidant toxicity, there is no information on the potential toxicity of ALCAR. Here, using zebrafish embryos, we explored whether ALCAR modulated ATP synthesis, generation of reactive oxygen species (ROS) and expression of specific genes related to major signaling pathways that control metabolism, growth, differentiation, apoptosis and oxidative stress. First, we show that ALCAR elicits a physiologic response, as ATP levels increased after ALCAR treatment. Simultaneously, an increase in the expression of ROS, a by-product of ATP synthesis, was observed in the ALCAR-treated embryos. Consistent with higher ROS expression, the level of cysteine, a precursor of glutathione, was significantly reduced. ALCAR did not have any drastic effect on overall development and heart rate. Polymerase chain reaction-based gene expression array analyses showed no significant change in the expression of 83 genes related to 10 major signaling pathways including: the transforming growth factor β (TGFβ), Wingless and Int-1 (Wnt), nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), Janus kinase/signal transducers and activators of transcription (JAK/STAT), p53, Notch, Hedgehog, Peroxisome proliferator-activated receptor (PPAR), oxidative stress, and hypoxia pathways. Our results show that the expression of 83 genes related to these major signaling pathways did not change significantly.

Nifedipine toxicity is exacerbated by acetyl l-carnitine but alleviated by low-dose ketamine in zebrafish in vivo

Calcium channel blocker (CCB) poisoning is a common and sometimes life-threatening emergency. Our previous studies have shown that acetyl l-carnitine (ALCAR) prevents cardiotoxicity and developmental toxicity induced by verapamil, a CCB used to treat patients with hypertension. Here, we tested whether toxicities of nifedipine, a dihydropyridine CCB used to treat hypertension, can also be mitigated by co-treatment with ALCAR. In the zebrafish embryos at three different developmental stages, nifedipine induced developmental toxicity with pericardial sac edema in a dose-dependent manner, which were surprisingly exacerbated with ALCAR co-treatment. Even with low-dose nifedipine (5 μm), when the pericardial sac looked normal, ALCAR co-treatment showed pericardial sac edema. We hypothesized that toxicity by nifedipine, a vasodilator, may be prevented by ketamine, a known vasoconstrictor. Nifedipine toxicity in the embryos was effectively prevented by co-treatment with low (subanesthetic) doses (25-100 μm added to the water) of ketamine, although a high dose of ketamine (2 mm added to the water) partially prevented the toxicity.As expected of a CCB, nifedipine either in the presence or absence of ketamine-reduced metabolic reactive oxygen species (ROS), a downstream product of calcium signaling, in the rapidly developing digestive system. However, nifedipine induced ROS in the trunk region that showed significantly stunted growth indicating that the tissues under stress potentially produced pathologic ROS. To the best of our knowledge, these studies for the first time show that nifedipine and the dietary supplement ALCAR together induce adverse effects while providing evidence on the therapeutic efficacy of subanesthetic doses of ketamine against nifedipine toxicity in vivo.

Mitochondrial dysfunction-based cardiotoxicity and neurotoxicity induced by pyraclostrobin in zebrafish larvae

Pyraclostrobin is widely used to control crop diseases, and was reported to be highly toxic to aquatic organisms. The molecular target of pyraclostrobin to fungus is the mitochondrion, but its effect on mitochondria of aquatic organisms has rarely been investigated. In this study, zebrafish larvae at 4 days post fertilization (dpf) were exposed to a range of pyraclostrobin for 96 h to assess its acute toxicity and effects on mitochondria. Pyraclostrobin at 36 μg/L or higher concentrations caused significant influences on larval heart and brain including pericardial edema, brain damage malformations, histological and mitochondrial structural damage of the two organs. The results of RNA-Seq revealed that the transcripts of genes related to oxidative phosphorylation, cardiac muscle contraction, mitochondrion, nervous system development and glutamate receptor activity were significantly influenced by 36 μg/L pyraclostrobin. Further tests showed that pyraclostrobin at 18 and 36 μg/L reduced the concentrations of proteins related to cardiac muscle contraction, impaired cardiac function, inhibited glutamate receptors activities and suppressed locomotor behavior of zebrafish larvae. Negative changes in mitochondrial complex activities, as well as reduced ATP content were also observed in larvae treated with 18 and 36 μg/L pyraclostrobin. These results suggested that pyraclostrobin exposure caused cardiotoxicity and neurotoxicity in zebrafish larvae and mitochondrial dysfunction might be the underlying mechanism of pyraclostrobin toxicity.

Review on the use of zebrafish embryos to study the effects of anesthetics during early development

Over the years, the potential toxicity of anesthetics has raised serious concerns about its safe use during pregnancy. As evidence emerged from research in animal models, showing that some anesthetic drugs are potential teratogenic, the determination of the risk of exposures to anesthetic drugs at early life stages became mandatory. However, due to inaccessibility and ethical constrains related to experimental conditions, the use of early life stages in mammalian models is limited. In this regard, some animal and nonanimal models have been suggested to surpass mammalian use in experimentation. Among them, the zebrafish embryo test has been recognized as a promising alternative in toxicology research, as well as an inexpensive and practical test. Substantial information collected from developmental research following compounds exposure, has contributed to the application of zebrafish assays in research, although only a few studies have focused on the use of early life stages of zebrafish to evaluate the developmental effects of anesthetics. Based on the recent advances of science and technology, there is a clear potential for zebrafish early life stages to provide new insights into anesthetics teratogenicity. This review provides an overview of recent anesthesia research using zebrafish embryos, demonstrating its usefulness to the anesthesia field, discussing the recent findings on various aspects related to the effects of anesthetics during early life development and the strengths and limitations of this model system.

Ketamine-induced attenuation of reactive oxygen species in zebrafish is prevented by acetyl l-carnitine in vivo

Ketamine, an anesthetic, is a non-competitive antagonist of the calcium-permeable N-methyl-d-aspartate (NMDA) receptor. High concentrations of ketamine have been implicated in cardiotoxicity and neurotoxicity. Often, these toxicities are thought to be mediated by reactive oxygen species (ROS). However, findings to the contrary showing ketamine reducing ROS in mammalian cells and neurons in vitro, are emerging. Here, we determined the effects of ketamine on ROS levels in zebrafish larvae in vivo. Based on our earlier studies demonstrating reduction in ATP levels by ketamine, we hypothesized that as a calcium antagonist, ketamine would also prevent ROS generation, which is a by-product of ATP synthesis. To confirm that the detected ROS in a whole organism, such as the zebrafish larva, is specific, we used diphenyleneiodonium (DPI) that blocks ROS production by inhibiting the NADPH Oxidases (NOX). Upon 20 h exposure, DPI (5 and 10 μM) and ketamine at (1 and 2 mM) reduced ROS in the zebrafish larvae in vivo. Using acetyl l-carnitine (ALCAR), a dietary supplement, that induces mitochondrial ATP synthesis, we show elevated ROS generation with increasing ALCAR concentrations. Combined, ketamine and ALCAR counter-balanced ROS generation in the larvae suggesting that ketamine and ALCAR have opposing effects on mitochondrial metabolism, which may be key to maintaining ROS homeostasis in the larvae and affords ALCAR the ability to prevent ketamine toxicity. These results for the first time show ketamine's antioxidative and ALCAR's prooxidative effects in a live vertebrate.

Acetyl-L-carnitine as a putative candidate for the treatment of stress-related psychiatric disorders: Novel evidence from a zebrafish model

Stress-related psychiatric disorders are mental conditions that affect mood, cognition and behavior and arise because of the impact of prolonged stress on the central nervous system (CNS). Acetyl-L-carnitine (ALC) is an acetyl ester of L-carnitine that easily crosses the blood-brain barrier and was recently found to be decreased in patients with major depressive disorder. ALC plays a role in energy metabolism and is widely consumed as a nutritional supplement to improve physical performance. In this study, our objective was to evaluate the effects of ALC treatment (0.1 mg/L, 10 min) for 7 days on behavior and oxidative stress in zebrafish subjected to unpredictable chronic stress (UCS) protocol. Behavioral outcomes were assessed in the novel tank test, and parameters of oxidative status (lipid peroxidation and antioxidant defenses) were evaluated in the brain using colorimetric methods. According to our previous findings, UCS increased anxiety-like behavior and lipid peroxidation, while it decreased non-protein thiol levels and superoxide dismutase activity. However, ALC reversed the anxiety-like behavior and oxidative damage in stressed animals, while it was devoid of effect in control animals. Although our data reinforce the neuroprotective potential of ALC in the treatment of psychiatric disorders related to stress, further investigations are required to clarify its mechanisms of action and confirm its efficacy.