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Masahiro Hirama - One of the best experts on this subject based on the ideXlab platform.
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Transcriptomic Analysis of Ciguatoxin-Induced Changes in Gene Expression in Primary Cultures of Mice Cortical Neurons
MDPI AG, 2018Co-Authors: Juan Andrés Rubiolo, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Andrea Boente-juncal, Mercedes Camiña, Luis M. BotanaAbstract:Ciguatoxins are polyether marine toxins that act as sodium channel activators. These toxins cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents several symptoms in humans including long-term neurological alterations. Earlier work has shown that both acute and chronic exposure of primary cortical neurons to synthetic Ciguatoxin CTX3C have profound impacts on neuronal function. Thus, the present work aimed to identify relevant neuronal genes and metabolic pathways that could be altered by Ciguatoxin exposure. To study the effect of Ciguatoxins in primary neurons in culture, we performed a transcriptomic analysis using whole mouse genome microarrays, for primary cortical neurons exposed during 6, 24, or 72 h in culture to CTX3C. Here, we have shown that the effects of the toxin on gene expression differ with the exposure time. The results presented here have identified several relevant genes and pathways related to the effect of Ciguatoxins on neurons and may assist in future research or even treatment of ciguatera. Moreover, we demonstrated that the effects of the toxin on gene expression were exclusively consequential of its action as a voltage-gated sodium channel activator, since all the effects of CTX3C were avoided by preincubation of the neurons with the sodium channel blocker tetrodotoxin
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chronic Ciguatoxin treatment induces synaptic scaling through voltage gated sodium channels in cortical neurons
Chemical Research in Toxicology, 2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luis M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin inc...
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Chronic Ciguatoxin Treatment Induces Synaptic Scaling through Voltage Gated Sodium Channels in Cortical Neurons
2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luís M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin increased the mRNA levels of both Arc and Egr1, the effect of CTX 3C in NaV channels, membrane potential, firing activity, miniature excitatory postsynaptic currents (mEPSCs), and glutamate receptors expression in cortical neurons after a 24 h exposure was evaluated using electrophysiological and western blot approaches. The data presented here show that CTX 3C induced an upregulation of Arc and Egr1 that was prevented by previous coincubation of the neurons with the NaV channel blocker tetrodotoxin. In addition, chronic CTX 3C caused a concentration-dependent shift in the activation voltage of NaV channels to more negative potentials and produced membrane potential depolarization. Moreover, 24 h treatment of cortical neurons with 5 nM CTX 3C decreased neuronal firing and induced synaptic scaling mechanisms, as evidenced by a decrease in the amplitude of mEPSCs and downregulation in the protein level of glutamate receptors that was also prevented by tetrodotoxin. These findings identify an unanticipated role for Ciguatoxin in the regulation of homeostatic plasticity in central neurons involving NaV channels and raise the possibility that some of the neurological symptoms of ciguatera might be explained by these compensatory mechanisms
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differential effects of Ciguatoxin and maitotoxin in primary cultures of cortical neurons
Chemical Research in Toxicology, 2014Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Alvaro Antelo, Masahiro Hirama, Shuji Yamashita, Luis M. BotanaAbstract:Ciguatoxins (CTXs) and maitotoxins (MTXs) are polyether ladder shaped toxins derived from the dinoflagellate Gambierdiscus toxicus. Despite the fact that MTXs are 3 times larger than CTXs, part of the structure of MTXs resembles that of CTXs. To date, the synthetic Ciguatoxin, CTX 3C has been reported to activate voltage-gated sodium channels, whereas the main effect of MTX is inducing calcium influx into the cell leading to cell death. However, there is a lack of information regarding the effects of these toxins in a common cellular model. Here, in order to have an overview of the main effects of these toxins in mice cortical neurons, we examined the effects of MTX and the synthetic Ciguatoxin CTX 3C on the main voltage dependent ion channels in neurons, sodium, potassium, and calcium channels as well as on membrane potential, cytosolic calcium concentration ([Ca2+]c), intracellular pH (pHi), and neuronal viability. Regarding voltage-gated ion channels, neither CTX 3C nor MTX affected voltage-gated calci...
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A study on mechanisms of toxic actions of Ciguatoxins: existence of functional relationship between CTX3C and charged residues of voltage sensors in Na_v1.4 sodium channel
Forensic Toxicology, 2011Co-Authors: Kaoru Yamaoka, Masayuki Inoue, Masahiro HiramaAbstract:Ciguatoxins, a group of virulent marine toxins, are bound to "site 5" inside voltage-dependent sodium channels and alter their kinetics dramatically; this is probably responsible for clinical symptoms of Ciguatoxin poisoning or ciguatera. Although Ciguatoxins are known to affect the voltage dependency of both activation and inactivation kinetics, site 5 has not been functionally clarified. This study, therefore, targeted putative voltage sensors as a receptor for Ciguatoxins. We constructed mutants, in which 1 of 23 basic residues was substituted with glutamine in the S4 segment for each of four domains. We then examined the effects of a synthetic Ciguatoxin congener CTX3C on these mutants. Notably, the suppressive effect of CTX3C on the sodium current ( I _Na) amplitude of domain 2 mutants, which carried a mutation in the basic S4 residue of domain 2, was either reduced or eliminated. Kinetic analyses of domain 2 mutants in comparison with those of the wild type and other mutants revealed that the negative shift of the steady-state inactivation curve ( V _1/2inactΔ) was significantly decreased. The resistance of domain 2 mutants to CTX3C in terms of changes in V _1/2inact is suggested to be closely related to resistance to the suppressive effect of CTX3C on the I _Na amplitude. This is the first report to demonstrate the existence of a functional relationship between a Ciguatoxin congener and voltage sensor segments in domain 2 of the α-subunit of voltage-dependent sodium channels, although further studies are needed to locate a Ciguatoxin receptor.
Masayuki Inoue - One of the best experts on this subject based on the ideXlab platform.
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A study on mechanisms of toxic actions of Ciguatoxins: existence of functional relationship between CTX3C and charged residues of voltage sensors in Na_v1.4 sodium channel
Forensic Toxicology, 2011Co-Authors: Kaoru Yamaoka, Masayuki Inoue, Masahiro HiramaAbstract:Ciguatoxins, a group of virulent marine toxins, are bound to "site 5" inside voltage-dependent sodium channels and alter their kinetics dramatically; this is probably responsible for clinical symptoms of Ciguatoxin poisoning or ciguatera. Although Ciguatoxins are known to affect the voltage dependency of both activation and inactivation kinetics, site 5 has not been functionally clarified. This study, therefore, targeted putative voltage sensors as a receptor for Ciguatoxins. We constructed mutants, in which 1 of 23 basic residues was substituted with glutamine in the S4 segment for each of four domains. We then examined the effects of a synthetic Ciguatoxin congener CTX3C on these mutants. Notably, the suppressive effect of CTX3C on the sodium current ( I _Na) amplitude of domain 2 mutants, which carried a mutation in the basic S4 residue of domain 2, was either reduced or eliminated. Kinetic analyses of domain 2 mutants in comparison with those of the wild type and other mutants revealed that the negative shift of the steady-state inactivation curve ( V _1/2inactΔ) was significantly decreased. The resistance of domain 2 mutants to CTX3C in terms of changes in V _1/2inact is suggested to be closely related to resistance to the suppressive effect of CTX3C on the I _Na amplitude. This is the first report to demonstrate the existence of a functional relationship between a Ciguatoxin congener and voltage sensor segments in domain 2 of the α-subunit of voltage-dependent sodium channels, although further studies are needed to locate a Ciguatoxin receptor.
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The first F-ring modified Ciguatoxin analogue showing significant toxicity
Chemical communications (Cambridge England), 2010Co-Authors: Yuuki Ishihara, Shuji Yamashita, Masayuki Inoue, Nayoung Lee, Naomasa Oshiro, Shigeru Matsuoka, Masahiro HiramaAbstract:Ciguatoxins, the principal causative toxins of ciguatera seafood poisoning, are potent neurotoxic polycyclic ethers. We report herein the total synthesis of a 10-membered F-ring analogue of 51-hydroxyCTX3C, which constitutes the first example of an F-ring modified Ciguatoxin that exhibits potent cytotoxicity as well as mouse acute toxicity.
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production of monoclonal antibodies for sandwich immunoassay detection of Ciguatoxin 51 hydroxyctx3c
Toxicon, 2006Co-Authors: Takeshi Tsumuraya, Masayuki Inoue, Keisuke Miyazaki, Ikuo Fujii, Atsushi Tatami, Masahiro HiramaAbstract:Every year, more than 50,000 people in subtropical and tropical regions suffer from ciguatera seafood poisoning. The extremely low level of the causative neurotoxins (Ciguatoxins) in fish has hampered the preparation of antibodies for detection of the toxins. In this study, we produced a monoclonal antibody (8H4) against the right end of Ciguatoxin CTX1B (1) and 51-hydroxyCTX3C (3) by immunizing mice with the keyhole limpet hemocyanin-conjugate of the synthetic HIJKLM ring fragment (10). We used 8H4 and another previously reported monoclonal antibody (10C9) that recognizes the left end of 3 to develop a sandwich enzyme-linked immunosorbent assay (ELISA) to detect 3. The assay could detect 3 down to the ppb level and lacked cross-reactivity with other related marine toxins, including brevetoxin A, brevetoxin B, okadaic acid, and maitotoxin.
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Total synthesis of Ciguatoxin and 51-hydroxyCTX3C
Journal of the American Chemical Society, 2006Co-Authors: Masayuki Inoue, Shuji Yamashita, Keisuke Miyazaki, Yuuki Ishihara, Nayoung Lee, Kazuo Komano, Yuuya Kawada, Atsushi Tatami, Yuyu Ohnuma, Masahiro HiramaAbstract:Ciguatoxins, the principal causative toxins of ciguatera seafood poisoning, are large ladder-like polycyclic ethers with the 13 ether rings ranging from five- to nine-membered. In this paper, we describe the total synthesis of the two most toxic members of the Ciguatoxin family, Ciguatoxin 1 and 51-hydroxyCTX3C 2, based on a unified synthetic strategy. The key features in our syntheses were (i) direct construction of the O,S-acetal from the corresponding left and right wing fragments (3, 4, 14); (ii) stereo- and chemoselective radical reaction of the alpha-oxyradical with pentafluorophenyl acrylate to achieve cyclization of the seven-membered G-ring; (iii) ring-closing metathesis reaction to build the nine-membered F-ring; and (iv) an efficient protective group strategy using the oxidatively removable 2-naphthylmethyl groups.
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First- and second-generation total synthesis of Ciguatoxin CTX3C
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Masayuki Inoue, Hisatoshi Uehara, Megumi Maruyama, Keisuke Miyazaki, Masahiro HiramaAbstract:More than 20,000 people suffer annually from ciguatera seafood poisoning in subtropical and tropical regions. The extremely low content of the causative neurotoxins, designated as Ciguatoxins, in fish has hampered isolation, detailed biological studies, and preparation of anti-Ciguatoxin antibodies for detecting these toxins. Furthermore, the large (3 nm in length) and complex molecular structure of Ciguatoxins has impeded chemists from completing their total synthesis. In this article, the full details of studies leading to the total synthesis of Ciguatoxin CTX3C are provided. The key elements of the first-generation approach include O,O-acetal formation from the right and left wing fragments, conversion from O,O-acetal to O,S-acetal, a radical reaction to cyclize the G ring, a ring-closing metathesis reaction to close the F ring, and final removal of the 2-naphtylmethyl protective groups. Subsequent studies provided a second-generation total synthesis, which is more concise and results in a higher yield. Second-generation synthesis was accomplished by using a direct method of constructing the key intermediate O,S-acetal from α-chlorosulfide and a secondary alcohol. These syntheses ensure a practical supply of Ciguatoxin for biological applications.
Richard J. Lewis - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Food Toxins and Toxicants - Ciguatoxin Detection Methods and High‐Throughput Assays
Analysis of Food Toxins and Toxicants, 2017Co-Authors: Marco Inserra, Richard J. Lewis, Yelena Lavrukhina, Alun Jones, Irina VetterAbstract:Ciguatera, the most common form of ichthyosarcotoxism, is caused by consumption of fish contaminated with heat-stable polycyclic neurotoxins known as Ciguatoxins. Although ciguatera affects at least 50,000 people annually and is a serious public health concern, no effective treatments are available. Thus, identification of ciguatoxic fish and avoidance of consumption remain key to reducing the impact of ciguatera without restricting essential dietary sources of fish protein. However, while significant advances in detection and quantification of Ciguatoxins have been made, no single assay is available currently that can detect Ciguatoxins in a rapid, quantitative and highly sensitive manner. Here we review and summarise the pharmacology of Ciguatoxins and outline the advantages and disadvantages of in vivo assays, antibody-based assays, receptor binding assays, functional and cell-based assays, as well as mass spectrometry for detection and quantification of Ciguatoxins.
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Ciguatoxin detection methods and high throughput assays
2017Co-Authors: Marco Inserra, Richard J. Lewis, Yelena Lavrukhina, Alun Jones, Irina VetterAbstract:Ciguatera, the most common form of ichthyosarcotoxism, is caused by consumption of fish contaminated with heat-stable polycyclic neurotoxins known as Ciguatoxins. Although ciguatera affects at least 50,000 people annually and is a serious public health concern, no effective treatments are available. Thus, identification of ciguatoxic fish and avoidance of consumption remain key to reducing the impact of ciguatera without restricting essential dietary sources of fish protein. However, while significant advances in detection and quantification of Ciguatoxins have been made, no single assay is available currently that can detect Ciguatoxins in a rapid, quantitative and highly sensitive manner. Here we review and summarise the pharmacology of Ciguatoxins and outline the advantages and disadvantages of in vivo assays, antibody-based assays, receptor binding assays, functional and cell-based assays, as well as mass spectrometry for detection and quantification of Ciguatoxins.
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rapid extraction and identification of maitotoxin and Ciguatoxin like toxins from caribbean and pacific gambierdiscus using a new functional bioassay
PLOS ONE, 2016Co-Authors: Richard J. Lewis, Marco Inserra, Irina Vetter, William C Holland, Ransom D Hardison, Patricia A. Tester, Wayne R LitakerAbstract:Background Ciguatera is a circumtropical disease produced by polyether sodium channel toxins (Ciguatoxins) that enter the marine food chain and accumulate in otherwise edible fish. Ciguatoxins, as well as potent water-soluble polyethers known as maitotoxins, are produced by certain dinoflagellate species in the genus Gambierdiscus and Fukuyoa spp. in the Pacific but little is known of the potential of related Caribbean species to produce these toxins. Methods We established a simplified procedure for extracting polyether toxins from Gambierdiscus and Fukuyoa spp. based on the Ciguatoxin rapid extraction method (CREM). Fractionated extracts from identified Pacific and Caribbean isolates were analysed using a functional bioassay that recorded intracellular calcium changes (Ca2+) in response to sample addition in SH-SY5Y cells. Maitotoxin directly elevated Ca2+i, while low levels of Ciguatoxin-like toxins were detected using veratridine to enhance responses. Results We identified significant maitotoxin production in 11 of 12 isolates analysed, with 6 of 12 producing at least two forms of maitotoxin. In contrast, only 2 Caribbean isolates produced detectable levels of Ciguatoxin-like activity despite a detection limit of >30 pM. Significant strain-dependent differences in the levels and types of Ciguatoxins and maitotoxins produced by the same Gambierdiscus spp. were also identified. Conclusions The ability to rapidly identify polyether toxins produced by Gambierdiscus spp. in culture has the potential to distinguish Ciguatoxin-producing species prior to large-scale culture and in naturally occurring blooms of Gambierdiscus and Fukuyoa spp. Our results have implications for the evaluation of ciguatera risk associated with Gambierdiscus and related species.
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flow cytometric membrane potential detection of sodium channel active marine toxins application to Ciguatoxins in fish muscle and feasibility of automating saxitoxin detection
Journal of AOAC International, 2014Co-Authors: Ronald Manger, Robert Wayne Dickey, Richard J. Lewis, Edward L E Jester, Doug Woodle, Andrew Berger, Takeshi Yasumoto, Timothy Hawryluk, James M HungerfordAbstract:Ciguatoxins are potent neurotoxins with a significant public health impact. Cytotoxicity assays have allowed the most sensitive means of detection of Ciguatoxin-like activity without reliance on mouse bioassays and have been invaluable in studying outbreaks. An improvement of these cell-based assays is presented here in which rapid flow cytometric detection of Ciguatoxins and saxitoxins is demonstrated using fluorescent voltage sensitive dyes. A depolarization response can be detected directly due to Ciguatoxin alone; however, an approximate 1000-fold increase in sensitivity is observed in the presence of veratridine. These results demonstrate that flow cytometric assessment of Ciguatoxins is possible at levels approaching the trace detection limits of our earlier cytotoxicity assays, however, with a significant reduction in analysis time. Preliminary results are also presented for detection of brevetoxins and for automation and throughput improvements to a previously described method for detecting saxitoxins in shellfish extracts.
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Analgesic treatment of Ciguatoxin-induced cold allodynia
Pain, 2013Co-Authors: Katharina Zimmermann, Peter J. Cabot, Jennifer R. Deuis, Marco Inserra, Richard J. Lewis, Lindon S. Collins, Barbara Namer, Peter W. Reeh, Irina VetterAbstract:Ciguatera, the most common form of nonbacterial ichthyosarcotoxism, is caused by consumption of fish that have bioaccumulated the polyether sodium channel activator Ciguatoxin. The neurological symptoms of ciguatera include distressing, often persistent sensory disturbances such as paraesthesias and the pathognomonic symptom of cold allodynia. We show that intracutaneous administration of Ciguatoxin in humans elicits a pronounced axon-reflex flare and replicates cold allodynia. To identify compounds able to inhibit Ciguatoxin-induced Nav responses, we developed a novel in vitro Ciguatoxin assay using the human neuroblastoma cell line SH-SY5Y. Pharmacological characterisation of this assay demonstrated a major contribution of Nav1.2 and Nav1.3, but not Nav1.7, to Ciguatoxin-induced Ca2+ responses. Clinically available Nav inhibitors, as well as the Kv7 agonist flupirtine, inhibited tetrodotoxin-sensitive Ciguatoxin-evoked responses. To establish their in vivo efficacy, we used a novel animal model of Ciguatoxin-induced cold allodynia. However, differences in the efficacy of these compounds to reverse Ciguatoxin-induced cold allodynia did not correlate with their potency to inhibit Ciguatoxin-induced responses in SH-SY5Y cells or at heterologously expressed Nav1.3, Nav1.6, Nav1.7, or Nav1.8, indicating cold allodynia might be more complex than simple activation of Nav channels. These findings highlight the need for suitable animal models to guide the empiric choice of analgesics, and suggest that lamotrigine and flupirtine could be potentially useful for the treatment of ciguatera.
Shuji Yamashita - One of the best experts on this subject based on the ideXlab platform.
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Transcriptomic Analysis of Ciguatoxin-Induced Changes in Gene Expression in Primary Cultures of Mice Cortical Neurons
MDPI AG, 2018Co-Authors: Juan Andrés Rubiolo, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Andrea Boente-juncal, Mercedes Camiña, Luis M. BotanaAbstract:Ciguatoxins are polyether marine toxins that act as sodium channel activators. These toxins cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents several symptoms in humans including long-term neurological alterations. Earlier work has shown that both acute and chronic exposure of primary cortical neurons to synthetic Ciguatoxin CTX3C have profound impacts on neuronal function. Thus, the present work aimed to identify relevant neuronal genes and metabolic pathways that could be altered by Ciguatoxin exposure. To study the effect of Ciguatoxins in primary neurons in culture, we performed a transcriptomic analysis using whole mouse genome microarrays, for primary cortical neurons exposed during 6, 24, or 72 h in culture to CTX3C. Here, we have shown that the effects of the toxin on gene expression differ with the exposure time. The results presented here have identified several relevant genes and pathways related to the effect of Ciguatoxins on neurons and may assist in future research or even treatment of ciguatera. Moreover, we demonstrated that the effects of the toxin on gene expression were exclusively consequential of its action as a voltage-gated sodium channel activator, since all the effects of CTX3C were avoided by preincubation of the neurons with the sodium channel blocker tetrodotoxin
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chronic Ciguatoxin treatment induces synaptic scaling through voltage gated sodium channels in cortical neurons
Chemical Research in Toxicology, 2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luis M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin inc...
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Chronic Ciguatoxin Treatment Induces Synaptic Scaling through Voltage Gated Sodium Channels in Cortical Neurons
2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luís M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin increased the mRNA levels of both Arc and Egr1, the effect of CTX 3C in NaV channels, membrane potential, firing activity, miniature excitatory postsynaptic currents (mEPSCs), and glutamate receptors expression in cortical neurons after a 24 h exposure was evaluated using electrophysiological and western blot approaches. The data presented here show that CTX 3C induced an upregulation of Arc and Egr1 that was prevented by previous coincubation of the neurons with the NaV channel blocker tetrodotoxin. In addition, chronic CTX 3C caused a concentration-dependent shift in the activation voltage of NaV channels to more negative potentials and produced membrane potential depolarization. Moreover, 24 h treatment of cortical neurons with 5 nM CTX 3C decreased neuronal firing and induced synaptic scaling mechanisms, as evidenced by a decrease in the amplitude of mEPSCs and downregulation in the protein level of glutamate receptors that was also prevented by tetrodotoxin. These findings identify an unanticipated role for Ciguatoxin in the regulation of homeostatic plasticity in central neurons involving NaV channels and raise the possibility that some of the neurological symptoms of ciguatera might be explained by these compensatory mechanisms
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differential effects of Ciguatoxin and maitotoxin in primary cultures of cortical neurons
Chemical Research in Toxicology, 2014Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Alvaro Antelo, Masahiro Hirama, Shuji Yamashita, Luis M. BotanaAbstract:Ciguatoxins (CTXs) and maitotoxins (MTXs) are polyether ladder shaped toxins derived from the dinoflagellate Gambierdiscus toxicus. Despite the fact that MTXs are 3 times larger than CTXs, part of the structure of MTXs resembles that of CTXs. To date, the synthetic Ciguatoxin, CTX 3C has been reported to activate voltage-gated sodium channels, whereas the main effect of MTX is inducing calcium influx into the cell leading to cell death. However, there is a lack of information regarding the effects of these toxins in a common cellular model. Here, in order to have an overview of the main effects of these toxins in mice cortical neurons, we examined the effects of MTX and the synthetic Ciguatoxin CTX 3C on the main voltage dependent ion channels in neurons, sodium, potassium, and calcium channels as well as on membrane potential, cytosolic calcium concentration ([Ca2+]c), intracellular pH (pHi), and neuronal viability. Regarding voltage-gated ion channels, neither CTX 3C nor MTX affected voltage-gated calci...
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Stereoselective synthesis of the left wing of Caribbean Ciguatoxin
Tetrahedron, 2011Co-Authors: Shuji Yamashita, Ryohei Uematsu, Masahiro HiramaAbstract:Abstract Ciguatoxins, the principal causative toxins of ciguatera seafood poisoning, are potent toxic polycyclic ethers. In this paper, we report a stereoselective and secure route to the left wing of Caribbean Ciguatoxin on the basis of a 6-exo radical cyclization strategy.
Mercedes R. Vieytes - One of the best experts on this subject based on the ideXlab platform.
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Transcriptomic Analysis of Ciguatoxin-Induced Changes in Gene Expression in Primary Cultures of Mice Cortical Neurons
MDPI AG, 2018Co-Authors: Juan Andrés Rubiolo, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Andrea Boente-juncal, Mercedes Camiña, Luis M. BotanaAbstract:Ciguatoxins are polyether marine toxins that act as sodium channel activators. These toxins cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents several symptoms in humans including long-term neurological alterations. Earlier work has shown that both acute and chronic exposure of primary cortical neurons to synthetic Ciguatoxin CTX3C have profound impacts on neuronal function. Thus, the present work aimed to identify relevant neuronal genes and metabolic pathways that could be altered by Ciguatoxin exposure. To study the effect of Ciguatoxins in primary neurons in culture, we performed a transcriptomic analysis using whole mouse genome microarrays, for primary cortical neurons exposed during 6, 24, or 72 h in culture to CTX3C. Here, we have shown that the effects of the toxin on gene expression differ with the exposure time. The results presented here have identified several relevant genes and pathways related to the effect of Ciguatoxins on neurons and may assist in future research or even treatment of ciguatera. Moreover, we demonstrated that the effects of the toxin on gene expression were exclusively consequential of its action as a voltage-gated sodium channel activator, since all the effects of CTX3C were avoided by preincubation of the neurons with the sodium channel blocker tetrodotoxin
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chronic Ciguatoxin treatment induces synaptic scaling through voltage gated sodium channels in cortical neurons
Chemical Research in Toxicology, 2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luis M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin inc...
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Chronic Ciguatoxin Treatment Induces Synaptic Scaling through Voltage Gated Sodium Channels in Cortical Neurons
2015Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Masahiro Hirama, Shuji Yamashita, Juan A Rubiolo, Maria Roel, Luís M. BotanaAbstract:Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by Ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10–13 days in vitro (DIV) cortical neurons to the synthetic Ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin increased the mRNA levels of both Arc and Egr1, the effect of CTX 3C in NaV channels, membrane potential, firing activity, miniature excitatory postsynaptic currents (mEPSCs), and glutamate receptors expression in cortical neurons after a 24 h exposure was evaluated using electrophysiological and western blot approaches. The data presented here show that CTX 3C induced an upregulation of Arc and Egr1 that was prevented by previous coincubation of the neurons with the NaV channel blocker tetrodotoxin. In addition, chronic CTX 3C caused a concentration-dependent shift in the activation voltage of NaV channels to more negative potentials and produced membrane potential depolarization. Moreover, 24 h treatment of cortical neurons with 5 nM CTX 3C decreased neuronal firing and induced synaptic scaling mechanisms, as evidenced by a decrease in the amplitude of mEPSCs and downregulation in the protein level of glutamate receptors that was also prevented by tetrodotoxin. These findings identify an unanticipated role for Ciguatoxin in the regulation of homeostatic plasticity in central neurons involving NaV channels and raise the possibility that some of the neurological symptoms of ciguatera might be explained by these compensatory mechanisms
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differential effects of Ciguatoxin and maitotoxin in primary cultures of cortical neurons
Chemical Research in Toxicology, 2014Co-Authors: Víctor Martín, Carmen Vale, Mercedes R. Vieytes, Alvaro Antelo, Masahiro Hirama, Shuji Yamashita, Luis M. BotanaAbstract:Ciguatoxins (CTXs) and maitotoxins (MTXs) are polyether ladder shaped toxins derived from the dinoflagellate Gambierdiscus toxicus. Despite the fact that MTXs are 3 times larger than CTXs, part of the structure of MTXs resembles that of CTXs. To date, the synthetic Ciguatoxin, CTX 3C has been reported to activate voltage-gated sodium channels, whereas the main effect of MTX is inducing calcium influx into the cell leading to cell death. However, there is a lack of information regarding the effects of these toxins in a common cellular model. Here, in order to have an overview of the main effects of these toxins in mice cortical neurons, we examined the effects of MTX and the synthetic Ciguatoxin CTX 3C on the main voltage dependent ion channels in neurons, sodium, potassium, and calcium channels as well as on membrane potential, cytosolic calcium concentration ([Ca2+]c), intracellular pH (pHi), and neuronal viability. Regarding voltage-gated ion channels, neither CTX 3C nor MTX affected voltage-gated calci...
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A comparative study of the effect of Ciguatoxins on voltage-dependent Na+ and K+ channels in cerebellar neurons.
Chemical research in toxicology, 2011Co-Authors: Sheila Pérez, Carmen Vale, Masahiro Hirama, Eva Alonso, Carmen Alfonso, Paula Rodríguez, Paz Otero, Amparo Alfonso, Paulo Vale, Mercedes R. VieytesAbstract:Ciguatera is a global disease caused by the consumption of certain warm-water fish (ciguateric fish) that have accumulated orally effective levels of sodium channel activator toxins (Ciguatoxins) through the marine food chain. The effect of Ciguatoxin standards and contaminated Ciguatoxin samples was evaluated by electrophysiological recordings in cultured cerebellar neurons. The toxins affected both voltage-gated sodium (Nav) and potassium channels (Kv) although with different potencies. CTX 3C was the most active toxin blocking the peak inward sodium currents, followed by P-CTX 1B and 51-OH CTX 3C. In contrast, P-CTX 1B was more effective in blocking potassium currents. The analysis of six different samples of contaminated fish, in which a Ciguatoxin analogue of mass 1040.6, not identical with the standard 51-OH CTX 3C, was the most prevalent compound, indicated an additive effect of the different Ciguatoxins present in the samples. The results presented here constitute the first comparison of the potencies of three different purified Ciguatoxins on sodium and potassium channels in the same neuronal preparation and indicate that electrophysiological recordings from cultured cerebellar neurons may provide a valuable tool to detect and quantify Ciguatoxins in the very low nanomolar range.