Acetyl L‐carnitine targets adenosine triphosphate synthase in protecting zebrafish embryos from toxicities induced by verapamil and ketamine: An in vivo assessment

Verapamil is a Ca²⁺ channel blocker and is highly prescribed as an anti‐anginal, antiarrhythmic and antihypertensive drug. Ketamine, an antagonist of the Ca²⁺‐permeable N‐methyl‐d ‐aspartate‐type glutamate receptors, is a pediatric anesthetic. Previously we have shown that acetyl l ‐carnitine (ALCAR) reverses ketamine‐induced attenuation of heart rate and neurotoxicity in zebrafish embryos. Here, we used 48 h post‐fertilization zebrafish embryos that were exposed to relevant drugs for 2 or 4 h. Heart beat and overall development were monitored in vivo . In 48 h post‐fertilization embryos, 2 mm ketamine reduced heart rate in a 2 or 4 h exposure and 0.5 mm ALCAR neutralized this effect. ALCAR could reverse ketamine's effect, possibly through a compensatory mechanism involving extracellular Ca²⁺ entry through L‐type Ca²⁺ channels that ALCAR is known to activate. Hence, we used verapamil to block the L‐type Ca²⁺ channels. Verapamil was more potent in attenuating heart rate and inducing morphological defects in the embryos compared to ketamine at specific times of exposure. ALCAR reversed cardiotoxicity and developmental toxicity in the embryos exposed to verapamil or verapamil plus ketamine, even in the presence of 3,4,5‐trimethoxybenzoic acid 8‐(diethylamino)octyl ester, an inhibitor of intracellular Ca²⁺ release suggesting that ALCAR acts via effectors downstream of Ca²⁺. In fact, ALCAR's protective effect was blunted by oligomycin A, an inhibitor of adenosine triphosphate synthase that acts downstream of Ca²⁺ during adenosine triphosphate generation. We have identified, for the first time, using in vivo studies, a downstream effector of ALCAR that is critical in abrogating ketamine‐ and verapamil‐induced developmental toxicities. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

Assessment of sediment quality of Yangtze River estuary using zebrafish (Danio rerio) embryos

Yangtze River estuary is one of the largest estuaries worldwide. In this study, the sediment quality of Yangtze River estuary was evaluated using zebrafish (Danio rerio) embryos. Freshly fertilized zebrafish eggs (2 h after fertilization) were exposed to the whole sediment and its organic phase of extract, respectively. The parameters, including survival rate, abnormality, hatching rate, and heart rate of the zebrafish embryos, were recorded during the 96‐h exposure. The results demonstrated that the concentrations of heavy metals (Zn, Cu, Cd, Ni, Cr, and As) and low‐molecular weight PAHs (Fluorene) in the sediment of Yangtze River estuary exceeded their corresponding effects range low values. The maximum concentrations of Zn and Fluorene in the sediment samples were 239.6 μg/g and 45.9 ng/g, respectively. In both whole sediment test and organic extract test, the survival rate and heart rate of zebrafish embryos were reduced, as well as abnormalities and delayed hatching were induced. For example, the highest mortality of the embryos was 39% in the whole sediment exposure. Overall, the occurrence of toxic compounds in the sediment of Yangtze River estuary may have potentially teratogenic effect on biota. The sediment from the upstream of Yangtze River estuary have more observed toxic effects on zebrafish embryos than that form the downstream. Therefore, more attention should be paid to control these pollutants, especially heavy metals in the Yangtze River estuary. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

Behavioral and physiological effects of acute ketamine exposure in adult zebrafish

Ketamine is a non-competitive glutamatergic antagonist used to induce sedation and analgesia. In sub-anesthetic doses, it induces hyperlocomotion, impairs memory and evokes stereotypic circling in rodents. Zebrafish (Danio rerio) emerged as a promising new animal model to screen the effects of psychotropic compounds. Here, we investigated the effects of sub-anesthetic doses of ketamine on anxiety, locomotion, habituation and social behavior of adult zebrafish. Acute 20-min exposure to 20 and 40 mg/L (but not 2 mg/L) of ketamine reduced anxiety, impaired intra-session habituation, evoked circular swimming and disrupted zebrafish shoaling. Additionally, ketamine reduced whole-body cortisol levels and elevated brain c-fos expression in zebrafish. Our findings demonstrate the sensitivity of zebrafish to behavioral and physiological effects of sub-anesthetic doses of ketamine, further supporting the utility of this species as a model for neuropharmacological research, including testing ketamine and related drugs.     

Cyclosporine exacerbates ketamine toxicity in zebrafish: Mechanistic studies on drug–drug interaction

Cyclosporine A (CsA) is an immunosuppressive drug commonly used in organ transplant patients to prevent allograft rejections. Ketamine is a pediatric anesthetic that noncompetitively inhibits the calcium‐permeable N‐methyl‐d ‐aspartic acid receptors. Adverse drug–drug interaction effects between ketamine and CsA have been reported in mammals and humans. However, the mechanism of such drug–drug interaction is unclear. We have previously reported adverse effects of combination drugs, such as verapamil/ketamine and shown the mechanism through intervention by other drugs in zebrafish embryos. Here, we show that ketamine and CsA in combination produce developmental toxicity even leading to lethality in zebrafish larvae when exposure began at 24 h post‐fertilization (hpf), whereas CsA did not cause any toxicity on its own. We also demonstrate that acetyl l ‐carnitine (ALCAR) completely reversed the adverse effects. Both ketamine and CsA are CYP3A4 substrates. Although ketamine and CsA independently altered the expression of the hepatic marker CYP3A65 , a zebrafish ortholog of human CYP3A4 , both drugs together induced further increase in CYP3A65 expression. In the presence of ALCAR, however, CYP3A65 expression was normalized. ALCAR has been shown to prevent ketamine toxicity in mammal and zebrafish. In conclusion, CsA exacerbated ketamine toxicity and ALCAR reversed the effects. These results, providing evidence for the first time on the reversal of the adverse effects of CsA/ketamine interaction by ALCAR, would prove useful in addressing potential occurrences of such toxicities in humans. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.     

Toxicity and cardiac effects of carbaryl in early developing zebrafish (Danio rerio) embryos

Carbaryl, an acetylcholinesterase inhibitor, is known to be moderately toxic to adult zebrafish and has been reported to cause heart malformations and irregular heartbeat in medaka. We performed experiments to study the toxicity of carbaryl, specifically its effects on the heart, in early developing zebrafish embryos. LC50 and EC50 values for carbaryl at 28 h post-fertilization were 44.66 microg/ml and 7.52 microg/ml, respectively, and 10 microg/ml carbaryl was used in subsequent experiments. After confirming acetylcholinesterase inhibition by carbaryl using an enzymatic method, we observed red blood cell accumulation, delayed hatching and pericardial edema, but not heart malformation as described in some previous reports. Our chronic exposure data also demonstrated carbaryl-induced bradycardia, which is a common effect of acetylcholinesterase inhibitors due to the accumulation of acetylcholine, in embryos from 1 day post-fertilization (dpf) to 5 dpf. The distance between the sinus venosus, the point where blood enters the atrium, and the bulbus arteriosus, the point where blood leaves the ventricle, indicated normal looping of the heart tube. Immunostaining of myosin heavy chains with the ventricle-specific antibody MF20 and the atrium-specific antibody S46 showed normal development of heart chambers. At the same time, acute exposure resulted in carbaryl-induced bradycardia. Heart rate dropped significantly after a 10-min exposure to 100 microg/ml carbaryl but recovered when carbaryl was removed. The novel observation of carbaryl-induced bradycardia in 1- and 2-dpf embryos suggested that carbaryl affected cardiac function possibly through an alternative mechanism other than acetylcholinesterase inhibition such as inhibition of calcium ion channels, since acetylcholine receptors in zebrafish are not functional until 3 dpf. However, the exact nature of this mechanism is currently unknown, and thus further studies are required.     

雷公藤红素对斑马鱼胚胎心脏毒性的初步研究

目的研究雷公藤红素对斑马鱼胚胎的心脏毒性。方法以发育48 h的斑马鱼胚胎为心脏毒性模型,以不同浓度的雷公藤红素处理上述胚胎,分别于处理后6、12、24 h观察胚胎心脏形态和功能变化。结果1μmol.L-1雷公藤红素作用24 h未引起胚胎心脏中毒。而2、3、4μmol.L-1雷公藤红素均导致胚胎心脏中毒,出现心脏线性化、心膜出血、血细胞在心区堆积等现象,而且心率也随着浓度的升高和作用时间的延长而明显下降,引起心率下降的EC50(24 h)约为1.78μmol.L-1。结论雷公藤红素对斑马鱼胚胎具有心脏毒性作用。     

Up-regulation of noradrenaline transporter in response to prolonged exposure to ketamine

We previously reported that the intravenous anaesthetic ketamine acutely inhibits the activity of the noradrenaline transporter (NAT) by acting on a site partly overlapping the desipramine binding site. Here we report the effects of a prolonged exposure to ketamine on the functional activity and number of NAT and its mRNA in cultured bovine adrenal medullary cells. Treatment of cells with ketamine (10-1000 microM) for 1-24 h resulted in a transient decrease and subsequent increase in [(3)H]noradrenaline (NA) uptake by the cells. Saturation analysis showed that ketamine (100 microM, 12 h) increased the V(max) value of [(3)H]NA uptake without any change in the K(m) value. Ketamine also increased the specific binding of [(3)H]nisoxetine to plasma membranes isolated from the cells. Scatchard analysis of [(3)H]nisoxetine binding revealed that ketamine increased the B(max) value without altering the K(d) value, suggesting an increase in the number of NAT in the plasma membrane. The stimulatory effect of ketamine on [(3)H]NA uptake was blocked by cycloheximide, an inhibitor of protein synthesis. Treatment of cells with ketamine for 12-24 h enhanced the expression of NAT mRNA. The present findings demonstrated that prolonged exposure to ketamine increases the functional activity of NAT and its mRNA. This may imply that ketamine negatively modulates sympathetic nervous activity through an up-regulation of NAT during long anaesthesia.     

Contribution of CYP3A4, CYP2B6, and CYP2C9 isoforms to N-demethylation of ketamine in human liver microsomes.

Ketamine is a widely used drug for its anesthetic and analgesic properties; it is also considered as a drug of abuse, as many cases of ketamine illegal consumption were reported. Ketamine is N-demethylated by liver microsomal cytochrome P450 into norketamine. The identification of the enzymes responsible for ketamine metabolism is of great importance in clinical practice. In the present study, we investigated the metabolism of ketamine in human liver microsomes at clinically relevant concentrations. Liver to plasma concentration ratio of ketamine was taken into consideration. Pooled human liver microsomes and human lymphoblast-expressed P450 isoforms were used. N-demethylation of ketamine was correlated with nifedipine oxidase activity (CYP3A4-specific marker reaction), and it was also correlated with S-mephenytoin N-demethylase activity (CYP2B6-specific marker reaction). Orphenadrine, a specific inhibitor to CYP2B6, and ketoconazole, a specific inhibitor to CYP3A4, inhibited the N-demethylation of ketamine in human liver microsomes. In human lymphoblast-expressed P450, the activities of CYP2B6 were higher than those of CYP3A4 and CYP2C9 at three concentrations of ketamine, 0.005, 0.05, and 0.5 mM. When these results were extrapolated using the average relative content of these P450 isoforms in human liver, CYP3A4 was the major enzyme involved in ketamine N-demethylation. The present study demonstrates that CYP3A4 is the principal enzyme responsible for ketamine N-demethylation in human liver microsomes and that CYP2B6 and CYP2C9 have a minor contribution to ketamine N-demethylation at therapeutic concentrations of the drug.     

A representative retinoid X receptor antagonist UVI3003 induced teratogenesis in zebrafish embryos

Retinoid X receptor (RXR) interfering activity has been detected in different water resources. To study RXR disruptor‐induced toxicological effects on vertebrates, embryos of zebrafish (Danio rerio) were exposed to a representative RXR antagonist UVI3003. Results showed that the teratogenic index (LC₅₀/EC₅₀) of UVI3003 was as high as 5.4. UVI3003 induced multiple malformations of embryos, including deformed fins, reduced brains, small jaws, bent tails and edema in hearts, the degree of which became more severe with increasing exposure concentration. Although no significant difference was observed in the hatching rates between the exposure group and control, the whole body length was significantly reduced by 6.5% and 8.9% when exposed to 200 and 300 µg l^?1 of UVI3003, respectively. The heart rate also significantly decreased by 8.8–50.2% during exposure. Further experiments revealed that the pharyngula stage was the most sensitive development phase in terms of embryo response to UVI3003. The results demonstrated severe teratogenicity of RXR antagonist in zebrafish embryos and provided important data for ecotoxicological evaluation of RXR antagonists. Copyright © 2014 John Wiley & Sons, Ltd.     

Cardiotoxicity evaluation of anthracyclines in zebrafish (Danio rerio)

Drug‐induced cardiotoxicity is a leading factor for drug withdrawals, and limits drug efficacy and clinical use. Therefore, new alternative animal models and methods for drug safety evaluation have been given great attention. Anthracyclines (ANTs) are widely prescribed anticancer agents that have a cumulative dose relationship with cardiotoxicity. We performed experiments to study the toxicity of ANTs in early developing zebrafish embryos, especially their effects on the heart. LC₅₀ values for daunorubicin, pirarubicin, doxorubicin (DOX), epirubicin and DOX‐liposome at 72 h post‐fertilization were 122.7 μM, 111.9 μM, 31.2 μM, 108.3 μM and 55.8 μM, respectively. At the same time, zebrafish embryos were exposed to ANTs in three exposure stages and induced incomplete looping of the heart tube, pericardia edema and bradycardia in a dose‐dependent manner, eventually leading to death. DOX caused the greatest heart defects in the treatment stages and its liposome reduced the effects on the heart, while daunorubicin produced the least toxicity. Genes and proteins related to heart development were also identified to be sensitive to ANT exposure and downregulated by ANTs. It revealed ANTs could disturb the heart formation and development. ANTs induced cardiotoxicity in zebrafish has similar effects in mammalian models, indicating that zebrafish may have a potential value for assessment of drug‐induced developmental cardiotoxicity. Copyright © 2014 John Wiley & Sons, Ltd.     

Cytoskeleton interruption in human hepatoma HepG2 cells induced by ketamine occurs possibly through suppression of calcium mobilization and mitochondrial function

Ketamine is an intravenous anesthetic agent often used for inducing and maintaining anesthesia. Cytoskeletons contribute to the regulation of hepatocyte activity of drug biotransformation. In this study, we attempted to evaluate the effects of ketamine on F-actin and microtubular cytoskeletons in human hepatoma HepG2 cells and its possible molecular mechanisms. Exposure of HepG2 cells to ketamine at 相似文献   

The Vasodilatory Effects of Ketamine on Isolated Rabbit Portal Veins

Abstract: The vasodilation mechanism induced by ketamine was investigated in isolated smooth muscle strips of rabbit portal veins. Ketamine inhibited both the phasic and tonic components of K⁺-induced contraction at concentrations greater than 500 μM and 100 μM, respectively. This effect was reversible and concentration-dependent with concentrations up to 1 mM. These effects were similar to those producd by verapamil. In the presence of 60 mM K⁺, application of Ca²⁺ (2.5 mM) in the perfusing solution caused tonic contraction of the smooth muscle, and ketamine at concentrations larger than 10 μM strongly inhibited this Ca²⁺-induced contraction. Ketamine (100 μM) also inhibited the K⁺-induced contractions significantly in the absence and presence of guanethidine, tetrodotoxin and propranolol. Ketamine produced similar concentration-dependent relaxations in the tissues with and without endothelium. These results indicate that in rabbit portal vein, vasodilation produced by ketamine is not endothelium-dependent but is likely to be due to blockade of the voltage-gated influx of extracellular Ca²⁺.     

Neonatal ketamine exposure results in changes in biochemical substrates of neuronal growth and synaptogenesis, and alters adult behavior irreversibly

Ketamine, an anaesthetic agent used in newborns and toddlers, has been shown to induce neurodegeneration and alter adult behavior in mice, when administered during the neonatal period. Mammals have a marked period of rapid brain growth and development (BGS), which is postnatal in mice and rats, spanning the first 3-4 weeks of life and reaching its peak around postnatal day 10. CaMKII and GAP-43 play important roles during the BGS in mammals. In the present study, 10 days old mice were exposed to 5-25 mg ketamine/kg bw and 24 h later brains were analyzed for calcium/calmodulin-dependent protein kinase II (CaMKII) and growth associated protein-43 (GAP-43) and at an age of 2 and 4 months the animals were tested for spontaneous behavior. The protein analysis showed that CaMKII increased significantly in hippocampus, but not in cortex, in animals 24h after exposure to ketamine. GAP-43 showed a significant increase in hippocampus, but a significant decrease in cortex for the highest ketamine dose. When looking at the adult behavior it was clear that neonatal ketamine exposure affected spontaneous behavior and habituation in a dose-response-related manner and that these behavioral disturbances were not transient but still persisted 2 months later. Taken together, this shows that ketamine affects important proteins involved in normal maturation of the brain and induce functional deficits in the adult individual, which further strengthen our findings concerning ketamine as a developmental neurotoxicological agent.     

Signal-transducing mechanisms of ketamine-caused inhibition of interleukin-1β gene expression in lipopolysaccharide-stimulated murine macrophage-like Raw 264.7 cells

Ketamine may affect the host immunity. Interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) are pivotal cytokines produced by macrophages. This study aimed to evaluate the effects of ketamine on the regulation of inflammatory cytokine gene expression, especially IL-1β, in lipopolysaccharide (LPS)-activated murine macrophage-like Raw 264.7 cells and its possible signal-transducing mechanisms. Administration of Raw 264.7 cells with a therapeutic concentration of ketamine (100 μM), LPS, or a combination of ketamine and LPS for 1, 6, and 24 h was not cytotoxic to macrophages. Exposure to 100 μM ketamine decreased the binding affinity of LPS and LPS-binding protein but did not affect LPS-induced RNA and protein synthesis of TLR4. Treatment with LPS significantly increased IL-1β, IL-6, and TNF-α gene expressions in Raw 264.7 cells. Ketamine at a clinically relevant concentration did not affect the synthesis of these inflammatory cytokines, but significantly decreased LPS-caused increases in these cytokines. Immunoblot analyses, an electrophoretic mobility shift assay, and a reporter luciferase activity assay revealed that ketamine significantly decreased LPS-induced translocation and DNA binding activity of nuclear factor-kappa B (NFκB). Administration of LPS sequentially increased the phosphorylations of Ras, Raf, MEK1/2, ERK1/2, and IKK. However, a therapeutic concentration of ketamine alleviated such augmentations. Application of toll-like receptor 4 (TLR4) small interfering (si)RNA reduced cellular TLR4 amounts and ameliorated LPS-induced RAS activation and IL-1β synthesis. Co-treatment with ketamine and TLR4 siRNA synergistically ameliorated LPS-caused enhancement of IL-1β production. Results of this study show that a therapeutic concentration of ketamine can inhibit gene expression of IL-1β possibly through suppressing TLR4-mediated signal-transducing phosphorylations of Ras, Raf, MEK1/2, ERK1/2, and IKK and subsequent translocation and transactivation of NFκB.     

Developmental toxicity and alteration of gene expression in zebrafish embryos exposed to PFOS

Perfluorooctanesulfonate (PFOS) is a persistent organic pollutant, the potential toxicity of which is causing great concern. In the present study, we employed zebrafish embryos to investigate the developmental toxicity of this compound. Four-hour post-fertilization (hpf) zebrafish embryos were exposed to 0.1, 0.5, 1, 3 and 5 mg/L PFOS. Hatching was delayed and hatching rates as well as larval survivorship were significantly reduced after the embryos were exposed to 1, 3 and 5 mg/L PFOS until 132 hpf. The fry displayed gross developmental malformations, including epiboly deformities, hypopigmentation, yolk sac edema, tail and heart malformations and spinal curvature upon exposure to PFOS concentrations of 1 mg/L or greater. Growth (body length) was significantly reduced in the 3 and 5 mg/L PFOS-treated groups. To test whether developmental malformation was mediated via apoptosis, flow cytometry analysis of DNA content, acridine orange staining and TUNEL assay was used. These techniques indicated that more apoptotic cells were present in the PFOS-treated embryos than in the control embryos. Certain genes related to cell apoptosis, p53 and Bax, were both significantly up-regulated upon exposure to all the concentrations tested. In addition, we investigated the effects of PFOS on marker genes related to early thyroid development (hhex and pax8) and genes regulating the balance of androgens and estrogens (cyp19a and cyp19b). For thyroid development, the expression of hhex was significantly up-regulated at all concentrations tested, whereas pax8 expression was significantly up-regulated only upon exposure to lower concentrations of PFOS (0.1, 0.5, 1 mg/L). The expression of cyp19a and of cyp19b was significantly down-regulated at all exposure concentrations. The overall results indicated that zebrafish embryos constitute a reliable model for testing the developmental toxicity of PFOS, and the gene expression patterns in the embryos were able to reveal some potential mechanisms of developmental toxicity.     

Effects of ketamine on pulmonary inflammatory responses and survival in rats exposed to polymicrobial sepsis.

PURPOSE: Ketamine is reported to suppress production of proinflammatory cytokines and activity of nuclear factor-kappa B (NF-kappaB) after lipopolysaccharide (LPS) stimulation. Our study was designed to investigate the effects of ketamine on pulmonary inflammatory responses and survival in a clinically relevant model of polymicrobial sepsis, induced by cecal ligation and puncture (CLP). METHODS: After the induction of sepsis or sham-operation, animals were treated with ketamine (0.5, 5 or 10 mg/kg) or saline (10 ml/kg) at 3h after operation. At 6 h post-operation, the levels of tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-6, activity of NF-kappaB, expression of Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4) of the lungs were measured. And the mortality was recorded for 7 days. RESULTS: TNF-alpha and IL-6 production, NF-kappaB activity, TLR2 and TLR4 expression in rat lungs were increased after CLP. Ketamine at the doses of 5 mg/kg and 10 mg/kg suppressed CLP-induced elevation of TNF-alpha and IL-6 production, NF-kappaB activity and TLR2 expression. Ketamine 0.5, 5 and 10 mg/kg inhibited TLR4 expression in sepsis. Ketamine 5mg/kg and 10 mg/kg after CLP improved the survival of rats. CONCLUSIONS: Ketamine at sub-anesthetic doses could suppress the production of inflammatory cytokines such as TNF-alpha and IL-6, attenuate NF-kappaB activity, and inhibit TLR2 and TLR4 expression in polymicrobial sepsis. These anti-inflammatory effects of ketamine may correlate with improved survival in sepsis.