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1.
PLoS Negl Trop Dis ; 14(3): e0008060, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32163415

RESUMO

The northeast (NE) region of Brazil commonly goes through drought periods, which favor cyanobacterial blooms, capable of producing neurotoxins with implications for human and animal health. The most severe dry spell in the history of Brazil occurred between 2012 and 2016. Coincidently, the highest incidence of microcephaly associated with the Zika virus (ZIKV) outbreak took place in the NE region of Brazil during the same years. In this work, we tested the hypothesis that saxitoxin (STX), a neurotoxin produced in South America by the freshwater cyanobacteria Raphidiopsis raciborskii, could have contributed to the most severe Congenital Zika Syndrome (CZS) profile described worldwide. Quality surveillance showed higher cyanobacteria amounts and STX occurrence in human drinking water supplies of NE compared to other regions of Brazil. Experimentally, we described that STX doubled the quantity of ZIKV-induced neural cell death in progenitor areas of human brain organoids, while the chronic ingestion of water contaminated with STX before and during gestation caused brain abnormalities in offspring of ZIKV-infected immunocompetent C57BL/6J mice. Our data indicate that saxitoxin-producing cyanobacteria is overspread in water reservoirs of the NE and might have acted as a co-insult to ZIKV infection in Brazil. These results raise a public health concern regarding the consequences of arbovirus outbreaks happening in areas with droughts and/or frequent freshwater cyanobacterial blooms.


Assuntos
Morte Celular/efeitos dos fármacos , Microcefalia/patologia , Envenenamento/complicações , Envenenamento/patologia , Saxitoxina/toxicidade , Infecção por Zika virus/complicações , Infecção por Zika virus/patologia , Animais , Toxinas Bacterianas/análise , Toxinas Bacterianas/toxicidade , Encéfalo/patologia , Brasil/epidemiologia , Células Cultivadas , Modelos Animais de Doenças , Surtos de Doenças , Feminino , Humanos , Incidência , Toxinas Marinhas/análise , Toxinas Marinhas/toxicidade , Camundongos Endogâmicos C57BL , Microcistinas/análise , Microcistinas/toxicidade , Modelos Teóricos , Neurotoxinas/análise , Neurotoxinas/toxicidade , Saxitoxina/análise , Água/química
2.
Artigo em Inglês | MEDLINE | ID: mdl-31638869

RESUMO

There are two official PSP detection methods (mouse bioassay and HLPC-FLD) and a number of alternative methods. Ethical considerations have led to regulations being adopted in some countries that limit or prohibit the application of mouse bioassay. Analytical methodologies (e.g. HPLC-FLD or LC-MSMS) have the disadvantages of not being able to detect new toxins or analogues or reflecting the overall toxicity of the sample. In addition, they require highly trained personnel and expensive equipment, which are not always available. In this work, we have evaluated a method based on the Neuro-2a cell-based assay to detect substances that inhibit voltage-dependent sodium channels (Manger's method). We tested PSP standards and natural samples contaminated with PSP. Here we demonstrate that the adapted Manger's method is suitable for calculating Toxicity Equivalency Factors (TEF) for STX-analogues. The method was shown to be useful for screening contaminated natural samples in concentrations above the regulatory limit for these toxins (80 µg STX equivalents/100 g shellfish). We were able to detect PSP in 19 natural mollusc samples from South Chile despite the presence of other marine toxins. These preliminary results suggest that the method could be used as a first step in screening programmes.


Assuntos
Análise de Alimentos , Contaminação de Alimentos/análise , Saxitoxina/análise , Saxitoxina/toxicidade , Alimentos Marinhos/análise , Alimentos Marinhos/toxicidade , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Chile , Relação Dose-Resposta a Droga , Camundongos , Frutos do Mar , Intoxicação por Frutos do Mar
3.
Aquat Toxicol ; 218: 105371, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31790939

RESUMO

Harmful algal bloom (HAB) toxins have severe negative impacts on marine mammals, particularly for Florida bottlenose dolphins (Tursiops truncatus) which frequently experience mass mortality events. Dolphins on the Florida Atlantic coast inhabit a region endemic to two HAB species, Karenia brevis and Pyrodinium bahamense, which produce the neurotoxins brevetoxin (PbTx) and saxitoxin (STX), respectively. Although toxic HABs and associated dolphin mortality events have been reported from this region, there is a lack of available data necessary for comparing toxin exposure levels between bloom ('exposed') conditions and non-bloom ('baseline') conditions. Here we present a 10-year dataset of PbTx and STX concentrations detected in dolphins stranding in this region, and compare the toxin loads from HAB-exposed dolphins to those detected in dolphins recovered in the absence of a HAB. We analyzed liver tissue samples from dead-stranded dolphins (n = 119) recovered and necropsied between 2002-2011, using an enzyme-linked immunosorbent assay (ELISA) modified for use with mammalian tissues. For dolphins recovered during baseline conditions, toxin-positive samples ranged in concentration from 0.27 to 1.2 ng/g for PbTx and from 0.41 to 1.9 ng/g for STX. For K. brevis-exposed dolphins, concentrations of up to 12.1 ng PbTx/g were detected, and for P. bahamense-exposed dolphins, concentrations of up to 9.9 ng STX/g were detected. Baseline PbTx values were similar to those reported in other regions where K. brevis blooms are more frequent and severe, but HAB-exposed PbTx values were considerably lower relative to these other regions. Since no baseline STX dolphin data exist for any region, our data serve as a first step towards establishing reference STX values for potential dolphin mortality events associated with STX-producing blooms in the future. This study demonstrates that although HABs in eastern Florida are only infrequently associated with dolphin mortalities, the presence of toxins in these animals may pose significant health risks in this region.


Assuntos
Golfinho Nariz-de-Garrafa/metabolismo , Monitoramento Ambiental/métodos , Proliferação Nociva de Algas , Toxinas Marinhas/análise , Oxocinas/análise , Saxitoxina/análise , Poluentes Químicos da Água/análise , Animais , Dinoflagelados/crescimento & desenvolvimento , Ensaio de Imunoadsorção Enzimática , Florida , Fígado/química , Fígado/metabolismo , Toxinas Marinhas/toxicidade , Oxocinas/toxicidade , Rios/química , Saxitoxina/toxicidade , Poluentes Químicos da Água/toxicidade
4.
Chemosphere ; 238: 124661, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31472350

RESUMO

Toxicities of the marine algae Alexandrium minutum and its excreted gonyautoxins (GTXs) to the marine crustacean Artemia salina were investigated. Mortality was observed for neither larvae nor adult A. salina exposed to A. minutum at a density of 5000 cells/mL or 0.5 µM GTX2/3. After exposure, the full transcriptome of adult A. salina was assembled and functionally annotated. A total of 599,286 transcripts were obtained, which were clustered into 515,196 unigenes. Results of the transcriptional effect level index revealed that direct exposure to the toxic algae A. minutum caused greater alterations in the transcriptome than did exposure to the extracellular product GTX2/3. Mechanisms of effects were different between exposure of A. salina to A. minutum cells or GTX2/3. Exposure to A. minutum modulated formation of the ribonucleoprotein complex and metabolism of amino acids and lipids in A. salina. Exposure to GTX2/3 exposure inhibited expression of genes related to metabolism of chitin, which might result in disruption of molting process or disturbed sheath morphogenesis. Overall, effects on transcription observed in this study represent the first report based on application of next generation sequencing techniques to investigate the transcriptomic response of A. salina exposed to an environmentally realistic level of A. minutum or GTX2/3.


Assuntos
Artemia/genética , Saxitoxina/análogos & derivados , Transcriptoma/efeitos dos fármacos , Animais , Artemia/fisiologia , Quitina/genética , Quitina/metabolismo , Dinoflagelados/citologia , Dinoflagelados/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Saxitoxina/farmacologia , Saxitoxina/toxicidade
5.
Mar Drugs ; 17(12)2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31766477

RESUMO

Paralytic shellfish toxins (PSTs) are the major neurotoxic contaminants of edible bivalves in Japan. Tetrodotoxin (TTX) was recently detected in bivalve shellfish around the world, drawing widespread attention. In Japan, high levels of TTX were reported in the digestive gland of the scallop, Patinopecten yessoensis, in 1993; however, no new data have emerged since then. In this study, we simultaneously analyzed PSTs and TTX in scallops cultured in a bay of east Japan using hydrophilic interaction chromatography (HILIC)-MS/MS. These scallops were temporally collected from April to December 2017. The highest concentration of PSTs (182 µmol/kg, total congeners) in the hepatopancreas was detected in samples collected on May 23, lined to the cell density of the dinoflagellate, Alexandrium tamarense, in seawater around the scallops, whereas the highest concentration of TTX (421 nmol/kg) was detected in samples collected on August 22. Contrary to the previous report, temporal variation of the PSTs and TTX concentrations did not coincide. The highest concentration of TTX in the entire edible tissues was 7.3 µg/kg (23 nmol/kg) in samples obtained on August 22, which was lower than the European Food Safety Authority (EFSA)-proposed threshold, 44 µg TTX equivalents/kg shellfish meat. In addition, 12ß-deoxygonyautoxin 3 was firstly identified in scallops.


Assuntos
Dinoflagelados/química , Pectinidae/química , Saxitoxina/análogos & derivados , Alimentos Marinhos/análise , Tetrodotoxina/análise , Animais , Aquicultura , Baías , Cromatografia Líquida de Alta Pressão , Japão , Saxitoxina/análise , Saxitoxina/toxicidade , Estações do Ano , Água do Mar/microbiologia , Intoxicação por Frutos do Mar/etiologia , Intoxicação por Frutos do Mar/prevenção & controle , Espectrometria de Massas em Tandem , Tetrodotoxina/toxicidade , Fatores de Tempo
6.
Mar Environ Res ; 148: 46-56, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31085422

RESUMO

The effects of co-occurring harmful algal blooms (HABs) on marine organisms is largely unknown. We assessed the individual and combined impacts of the toxin producing HABs, Alexandrium catenella and Dinophysis acuminata, and a non-toxin-producing HAB (Gymnodinium instriatum) on early life stages of two estuarine fish species (Menidia beryllina and Cyprinodon variegatus). Lethal (i.e. time to death) and sublethal (i.e. growth, grazing rate, and swimming activity) effects of cultured HABs were investigated for eleutheroembryo and larval life stages. Mixed algal treatments (i.e. A. catenella and D. acuminata mixtures) were often equally toxic as A. catenella monoculture treatments alone, although responses depended on the fish species and life stage. Fish exposed to toxin producing HABs died significantly sooner (i.e. <1-3 days) than controls. Significant differences in sublethal effects were also found between fed controls and toxic HAB treatments, although responses were often similar to G. instriatum or starved controls. Collectively, the results demonstrate that HABs may reduce fish productivity and fitness.


Assuntos
Ecotoxicologia , Embrião não Mamífero/efeitos dos fármacos , Peixes/embriologia , Proliferação Nociva de Algas , Toxinas Marinhas/toxicidade , Animais , Dinoflagelados , Embrião não Mamífero/patologia , Estuários , Peixes/crescimento & desenvolvimento , Peixes Listrados/embriologia , Peixes Listrados/crescimento & desenvolvimento , Larva , Ácido Okadáico/toxicidade , Saxitoxina/toxicidade
7.
Toxins (Basel) ; 10(11)2018 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-30360529

RESUMO

Tetrodotoxin (TTX) is a potent neurotoxin associated with human poisonings through the consumption of pufferfish. More recently, TTX has been identified in bivalve molluscs from diverse geographical environments, including Europe, and is therefore recognised as an emerging threat to food safety. A recent scientific opinion of the EFSA Panel on Contaminants in the Food Chain recognised the need for further data on the acute oral toxicity of TTX and suggested that, since saxitoxin (STX) and TTX had similar modes of action, it was possible that their toxicities were additive so could perhaps be combined to yield one health-based guideline value. The present study determined the toxicity of TTX by various routes of administration. The testing of three different mixtures of STX and TTX and comparing the experimentally determined values to those predicted on the basis of additive toxicity demonstrated that the toxicities of STX and TTX are additive. This illustrates that it is appropriate to treat TTX as a member of the paralytic shellfish group of toxins. Since the toxicity of TTX was found to be the same as STX by feeding, a molar toxicity equivalence factor of 1.0 for TTX can be applied.


Assuntos
Saxitoxina/toxicidade , Tetrodotoxina/toxicidade , Animais , Vias de Administração de Medicamentos , Interações Medicamentosas , Feminino , Dose Letal Mediana , Camundongos , Saxitoxina/administração & dosagem , Tetrodotoxina/administração & dosagem , Testes de Toxicidade Aguda
8.
Aquat Toxicol ; 202: 196-206, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30075308

RESUMO

Blooms of Alexandrium spp., the causative agent of paralytic shellfish poisoning (PSP), recur with varying frequency and intensity on the Northwest Atlantic coast of North America, from New York, USA, to northern Canadian waters. Along this latitudinal range blooms co-occur with abundant, intertidal populations of softshell clams, Mya arenaria. Prior work identified a naturally-occurring genetic mutation in Domain II α-subunit of the clams' voltage-gated sodium channels (NaV), which significantly reduces the binding affinity of the paralytic shellfish toxin, saxitoxin (STX). This mutation provides clams with resistance to the deleterious effects of STX, allowing them to continue feeding during Alexandrium spp. blooms and attain very high tissue toxicities. This study used genetic sequencing of the NaV mutation locus in clams from four coastal regions of the Bay of Fundy-Gulf of Maine and the mid-Atlantic to determine the percentage of clams in each region that possess the resistant NaV mutation. The genotype composition was related to the occurrence and magnitude of PSP outbreaks based on shellfish toxicity, primarily that of mussels, Mytilus edulis, used as a proxy for the prevalence and severity of Alexandrium blooms in each region. As hypothesized, the proportion of clams bearing the resistant mutation generally matched up well with the historical incidence and intensity of Alexandrium spp. blooms. The highest percentage of homozygote resistant clams (RR = 70.0%), and the lowest percentage of sensitive clams (SS = 4.5%) were found in eastern Gulf of Maine populations. Exceptions at a few sites where anomalously high numbers of M. arenaria with the resistant mutation were found despite the absence of blooms, may be attributable to larval gene flow. There was no evidence that Alexandrium blooms occurring in Northport Harbor, Long Island, have resulted in a shift in genotypic composition of the local clam population, presumably due to their low cell toxicity. Seasonal mismatch of highly vulnerable M. arenaria postset with toxic blooms at this latitude may also partly explain this result. This study provides strong supporting evidence that Alexandrium blooms can select for resistance to PSP-toxins in M. arenaria populations and proposes a mechanism for the persistence of the sensitive allele throughout the region. Implications for clam aquaculture (seeding) efforts, as well as for shellfish toxicity monitoring are discussed.


Assuntos
Mya/efeitos dos fármacos , Saxitoxina/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Genótipo , Larva/efeitos dos fármacos , Larva/genética , Mutação , Mya/genética , Mya/crescimento & desenvolvimento , América do Norte , Intoxicação por Frutos do Mar , Canais de Sódio Disparados por Voltagem/genética
9.
Aquat Toxicol ; 199: 127-137, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29621672

RESUMO

Harmful Algal Blooms are worldwide occurrences that can cause poisoning in human seafood consumers as well as mortality and sublethal effets in wildlife, propagating economic losses. One of the most widespread toxigenic microalgal taxa is the dinoflagellate Genus Alexandrium, that includes species producing neurotoxins referred to as PST (Paralytic Shellfish Toxins). Blooms cause shellfish harvest restrictions to protect human consumers from accumulated toxins. Large inter-individual variability in toxin load within an exposed bivalve population complicates monitoring of shellfish toxicity for ecology and human health regulation. To decipher the physiological pathways involved in the bivalve response to PST, we explored the whole transcriptome of the digestive gland of the Pacific oyster Crassostrea gigas fed experimentally with a toxic Alexandrium minutum culture. The largest differences in transcript abundance were between oysters with contrasting toxin loads (1098 transcripts), rather than between exposed and non-exposed oysters (16 transcripts), emphasizing the importance of toxin load in oyster response to toxic dinoflagellates. Additionally, penalized regressions, innovative in this field, modeled accurately toxin load based upon only 70 transcripts. Transcriptomic differences between oysters with contrasting PST burdens revealed a limited suite of metabolic pathways affected, including ion channels, neuromuscular communication, and digestion, all of which are interconnected and linked to sodium and calcium exchanges. Carbohydrate metabolism, unconsidered previously in studies of harmful algal effects on shellfish, was also highlighted, suggesting energy challenge in oysters with high toxin loads. Associations between toxin load, genotype, and mRNA levels were revealed that open new doors for genetic studies identifying genetically-based low toxin accumulation.


Assuntos
Cálcio/metabolismo , Crassostrea/genética , Digestão/efeitos dos fármacos , Dinoflagelados/fisiologia , Metabolismo Energético/efeitos dos fármacos , Exposição Ambiental , Saxitoxina/toxicidade , Sódio/metabolismo , Transcriptoma/genética , Animais , Cromatografia Líquida de Alta Pressão , Crassostrea/efeitos dos fármacos , Crassostrea/metabolismo , Metabolismo Energético/genética , Genótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Estatística como Assunto , Poluentes Químicos da Água/toxicidade
10.
Toxins (Basel) ; 10(4)2018 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-29597338

RESUMO

Paralytic shellfish poisoning (PSP) is caused by a group of marine toxins with saxitoxin (STX) as the reference compound. Symptoms in humans after consumption of contaminated shellfish vary from slight neurological and gastrointestinal effects to fatal respiratory paralysis. A systematic review was conducted to identify reported cases of human poisoning associated with the ingestion of shellfish contaminated with paralytic shellfish toxins (PSTs). Raw data were collected from 143 exposed individuals (113 with symptoms, 30 without symptoms) from 13 studies. Exposure estimates were based on mouse bioassays except in one study. A significant relationship between exposure to PSTs and severity of symptoms was established by ordinal modelling. The critical minimal dose with a probability higher than 10% of showing symptoms is 0.37 µg STX eq./kg b.w. This means that 10% of the individuals exposed to this dose would have symptoms (without considering the severity of the symptoms). This dose is four-fold lower than the lowest-observed-adverse-effect-level (LOAEL) established by the European Food Safety Authority (EFSA, 2009) in the region of 1.5 µg STX eq./kg b.w. This work provides critical doses that could be used as point of departure to update the acute reference dose for STX. This is the first time a dose-symptoms model could be built for marine toxins using epidemiological data.


Assuntos
Modelos Biológicos , Saxitoxina/toxicidade , Intoxicação por Frutos do Mar , Animais , Bioensaio , Relação Dose-Resposta a Droga , Humanos , Camundongos
11.
Toxicol Mech Methods ; 28(5): 335-344, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29228856

RESUMO

The potent neurotoxin saxitoxin produced by both marine and freshwater phytoplankton causes paralytic shellfish poisoning syndrome. The toxicity and mode of action of the acute exposure of high-dose saxitoxin have been intensively studied for decades; however, the potential risk of exposure of low-dose saxitoxin remained to be uncovered. Here we present a proteomics study of murine neuroblastoma N2A cell with low-dose saxitoxin exposure (1 nM and 10 nM, 24-h intoxication). Differential proteins were profiled by two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) coupled with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). A total of 9 proteins, including 14-3-3 beta (1433B), alpha enolase (ENO1) and cofilin 2 (CFL2), were altered by the low-dose saxitoxin exposure. We further validated the expressions of 1433B, ENO1 and CFL2 by Western blot analysis and the enzyme-linked immunosorbent assay. These 9 proteins involve cell apoptotic pathways, cell skeleton maintenance, membrane potentials and mitochondrial functions. Modulation of these 9 proteins by low-dose saxitoxin exposure could correlate to the reports on genotoxicity and neurotoxicity induced by saxitoxin. This study also suggested other potential risks of saxitoxin.


Assuntos
Neuroblastoma/metabolismo , Neurônios/efeitos dos fármacos , Proteoma/efeitos dos fármacos , Saxitoxina/toxicidade , Proteínas 14-3-3/metabolismo , Animais , Western Blotting , Linhagem Celular Tumoral , Cofilina 2/metabolismo , Relação Dose-Resposta a Droga , Ensaio de Imunoadsorção Enzimática , Camundongos , Neuroblastoma/patologia , Neurônios/metabolismo , Neurônios/patologia , Fosfopiruvato Hidratase/metabolismo , Proteoma/metabolismo , Proteômica/métodos , Medição de Risco , Transdução de Sinais/efeitos dos fármacos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Testes de Toxicidade/métodos , Eletroforese em Gel Diferencial Bidimensional
12.
Environ Pollut ; 234: 779-787, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29247940

RESUMO

Toxic cyanobacterial blooms have been implicated for their negative consequences on many terrestrial and aquatic organisms. Water birds belong to the most common members of the freshwater food chains and are most likely to be affected by the consumption of toxic cyanobacteria as food. However, the contribution of cyanotoxins in bird mortalities is under-studied. The aim of the study was to investigate the likely role of cyanotoxins in a mass mortality event of the Dalmatian pelican (Pelecanus crispus) in the Karla Reservoir, in Greece. Water, scum, tissues and stomach content of dead birds were examined for the presence of microcystins, cylindrospermopsins and saxitoxins by an enzyme-linked immunosorbent assay. High abundances of potential toxic cyanobacterial species and significant concentrations of cyanotoxins were recorded in the reservoir water. All examined tissues and stomach content of the Dalmatian pelicans contained significant concentrations of microcystins and saxitoxins. Cylindrospermopsin concentrations were detected in all tissues except from the brain. Our results suggest that cyanotoxins are a plausible cause for this bird mass mortality episode in the Karla Reservoir.


Assuntos
Toxinas Bacterianas/toxicidade , Doenças das Aves/etiologia , Cianobactérias/metabolismo , Animais , Toxinas Bacterianas/metabolismo , Doenças das Aves/mortalidade , Aves , Cianobactérias/química , Água Doce/microbiologia , Grécia , Microcistinas/metabolismo , Microcistinas/toxicidade , Saxitoxina/toxicidade , Uracila/análogos & derivados , Uracila/metabolismo , Uracila/toxicidade
13.
J Helminthol ; 92(2): 244-249, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28349851

RESUMO

Cylindrospermopsis raciborskii (Woloszynska) is a photosynthetic cyanobacterium that can produce cytotoxic (cylindrospermopsin) and neurotoxic cyanotoxins (saxitoxins). In Brazil the strains of C. raciborskii are reported to produce only saxitoxins (STX) and their effect on fish parasites has not been tested to date. The fish Poecilia vivipara Bloch and Schneider is a common host for the trematode Pygidiopsis macrostomum Travassos off the coast of Rio de Janeiro, and this fish-parasite interaction is a model for behavioural and ecotoxicological studies. The aim of this work was to evaluate the motility of metacercariae of P. macrostomum from P. vivipara exposed to 40 mg l-1 and 400 mg l-1 of crude lyophilized extract of the cyanobacterium C. raciborskii (CYRF-01) for 48 h. The fish were separated into groups of ten individuals and, after exposure, five fish from each group were dissected for counting and checking the motility of metacercariae. The other five fish were dissected after 48 h in clean water. The detection and quantification of STX in the solutions of cyanobacteria, and the gills and guts of fish, were performed by an enzyme-linked immunosorbent assay. The crude extract of C. raciborskii caused temporary paralysis in metacercariae of P. macrostomum after exposure of fish to both concentrations, and the motility recovered after the fish were kept for 48 h in clean water. STX was detected in the guts and gills of all fish analysed, suggesting that this toxin is involved in the paralysis of metacercariae. This is the first report on the action of neurotoxins in metacercariae of fish.


Assuntos
Cylindrospermopsis/química , Metacercárias/efeitos dos fármacos , Saxitoxina/toxicidade , Extratos de Tecidos/toxicidade , Trematódeos/efeitos dos fármacos , Infecções por Trematódeos/parasitologia , Animais , Interações Hospedeiro-Parasita/efeitos dos fármacos , Movimento/efeitos dos fármacos , Neurotoxinas/farmacologia , Neurotoxinas/toxicidade , Poecilia/parasitologia , Saxitoxina/farmacologia , Extratos de Tecidos/química , Extratos de Tecidos/farmacologia , Trematódeos/fisiologia
14.
Toxicology ; 393: 171-184, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-29128272

RESUMO

Saxitoxins (STXs) are potent neurotoxins that block voltage-gated channels in neurons and induce cytotoxicity. These toxins not only can generate reactive oxygen species but also can alter antioxidant levels, promoting oxidative stress. Under this pro-oxidant situation, the use of the antioxidant lipoic acid (LA) can represent a chemoprotective alternative to minimize the deleterious effects induced by neurotoxins as STXs. P-glycoprotein (P-gp) is a well-known ATP-binding cassette (ABC) transporter that plays a crucial role in the extrusion of toxic substances, decreasing their accumulation and potential intracellular effects in virtue of its broad substrate specificity, its expression in many excretory tissues and its large efflux capacity. The interaction of STXs with LA was evaluated by ab initio simulation, molecular docking and bioassays using the cell line HT-22. The interaction of STXs with LA occurs by physisorption. Molecular docking indicated that STXs can be a substrate of P-gp and, estimating the Free Energy of Binding (FEB), LA has lower amino acids residues binding sites, similar to verapamil, while STX and STX+LA_1 have similar amino acids residues and binding sites with similar FEB between this ligands.Cells were exposed to STXs and LA for 30min and 24h. LA treatment minimizes STX cytotoxicity, evaluated by trypan blue and MTT assay and both STX and STX-LA treatments were efficient to induce P-gp activity measured by rhodamine 123 dye extrusion. LA and STX+LA treatments induced low reactive oxygen species levels and low oxygen consumption. Based on our results, it can be concluded that LA was able to induce cytoprotection, including induction of cellular glutathione levels, and that STX+LA interaction reduced toxicity effects induced by STX. Overall, the in vitro results corroborated the semi-empirical evidences found using density functional theory ab initio simulation and molecular docking.


Assuntos
Antioxidantes/farmacologia , Saxitoxina/toxicidade , Ácido Tióctico/farmacologia , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Glutationa/metabolismo , Hipocampo/citologia , Camundongos , Simulação de Acoplamento Molecular , Consumo de Oxigênio/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo
15.
Chemosphere ; 192: 66-74, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29100123

RESUMO

Saxitoxin (STX), a paralytic shellfish toxin (PST) produced from toxic bloom-forming dinoflagellates, was selected to comparatively investigate the induction of cytotoxicity and apoptosis and a possible mechanism based on changes in the antioxidant defence system of two cellular strains: the mouse neuroblastoma cell line Neuro-2a and the rainbow trout fish cell line RTG-2. Increasing concentrations of STX (0-256 nM) presented little cytotoxic or apoptotic effects on the two cell lines. Measurements of cellular viability, lethal ratio and LDH leakage showed slight changes in Neuro-2a and RTG-2 cells (p > 0.05), and similar results were observed for cellular morphology and apoptotic rates. The contents of the main reactive oxygen species (ROS) components, superoxide anion (O2-) and hydrogen peroxide (H2O2), were markedly increased in Neuro-2a cell with STX exposure at middle (15 nM) and high (150 nM) concentrations (p < 0.05), and the simultaneous increase of the ratio of reduced/oxidized glutathione (GSH/GSSG) (p < 0.05) inferred the occurrence of oxidative stress. However, little difference was observed in all treated groups of RTG-2 cells. The activities of three antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), were significantly enhanced in Neuro-2a cells in the middle and high concentration groups (p < 0.05), while glutathione peroxidase (GPX) obviously decreased (p < 0.05) in all treated groups. Little change was found in RTG-2 cells with the same exposures. These results provided evidence that STX exposure altered the redox status of Neuro-2a cells and resulted in oxidative stress, but the same exposure exerted little effect on RTG-2 cells. Therefore, Neuro-2a cells are more sensitive than reproductive cells to STX exposure, and the antioxidant systems appears to be partly responsible for this differentiation response.


Assuntos
Espécies Reativas de Oxigênio/metabolismo , Saxitoxina/toxicidade , Animais , Antioxidantes/metabolismo , Apoptose/efeitos dos fármacos , Catalase/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Glutationa Peroxidase/metabolismo , Camundongos , Oncorhynchus mykiss , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Superóxido Dismutase/metabolismo
16.
Sci Rep ; 7(1): 14201, 2017 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-29079725

RESUMO

Toxin resistance is a recurring evolutionary response by predators feeding on toxic prey. These adaptations impact physiological interaction and community ecology. Mechanisms for resistance vary depending on the predator and the nature of the toxin. Potent neurotoxins like tetrodotoxin (TTX) and saxitoxin (STX) that are highly toxic to humans and other vertebrates, target conserved voltage-gated sodium channels (NaV) of nerve and muscle, causing paralysis. The copepod Calanus finmarchicus consumes the STX-producing dinoflagellate, Alexandrium fundyense with no effect on survival. Using transcriptomic approaches to search for the mechanism that confers resistance in C. finmarchicus, we identified splice variants of NaVs that were predicted to be toxin resistant. These were co-expressed with putatively non-resistant form in all developmental stages. However its expression was unresponsive to toxin challenge nor was there any up-regulation of genes involved in multi-xenobiotic resistance (MXR) or detoxification (phases I or II). Instead, adults consistently regulated genes encoding digestive enzymes, possibly to complement channel resistance by limiting toxin assimilation via the digestive process. The nauplii, which were more susceptible to STX, did not regulate these enzymes. This study demonstrates how deep-sequencing technology can elucidate multiple mechanisms of toxin resistance concurrently, revealing the linkages between molecular/cellular adaptations and the ecology of an organism.


Assuntos
Copépodes/efeitos dos fármacos , Copépodes/genética , Resistência a Medicamentos/genética , Perfilação da Expressão Gênica , Neurotoxinas/toxicidade , Saxitoxina/toxicidade , Alveolados/metabolismo , Sequência de Aminoácidos , Animais , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Mutação , Saxitoxina/metabolismo , Canais de Sódio Disparados por Voltagem/química , Canais de Sódio Disparados por Voltagem/genética
17.
Aquat Toxicol ; 190: 133-141, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28711010

RESUMO

Exposure of the toxin-producing dinoflagellate Alexandrium catenella (A. catenella) was previously demonstrated to cause apoptosis of hemocytes in the oyster species Crassostrea gigas. In this work, a coumarin-labeled saxitoxin appeared to spread throughout the cytoplasm of the hemocytes. PSTs, including saxitoxin, were also shown to be directly responsible for inducing apoptosis in hemocytes, a process dependent on caspase activation and independent of reactive oxygen species (ROS) production. A series of in vitro labelling and microscopy experiments revealed that STX and analogs there of induced nuclear condensation, phosphatidylserine exposure, membrane permeability, and DNA fragmentation of hemocytes. Unlike in vertebrates, gonyautoxin-5 (GTX5), which is present in high concentrations in A. catenella, was found to be more toxic than saxitoxin (STX) to oyster immune cells. Altogether, results show that PSTs produced by toxic dinoflagellates enter the cytoplasm and induce apoptosis of oyster immune cells through a caspase-dependent pathway. Because of the central role of hemocytes in mollusc immune defense, PST-induced death of hemocytes could negatively affect resistance of bivalve molluscs to microbial infection.


Assuntos
Apoptose/efeitos dos fármacos , Caspases/metabolismo , Crassostrea/efeitos dos fármacos , Citoplasma/efeitos dos fármacos , Hemócitos/efeitos dos fármacos , Saxitoxina/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Crassostrea/imunologia , Crassostrea/metabolismo , Citoplasma/metabolismo , Dinoflagelados/metabolismo , Hemócitos/metabolismo , Hemócitos/ultraestrutura , Espécies Reativas de Oxigênio/metabolismo , Saxitoxina/metabolismo , Frutos do Mar , Poluentes Químicos da Água/metabolismo
18.
Proc Natl Acad Sci U S A ; 114(19): 4975-4980, 2017 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-28439007

RESUMO

Global ocean temperatures are rising, yet the impacts of such changes on harmful algal blooms (HABs) are not fully understood. Here we used high-resolution sea-surface temperature records (1982 to 2016) and temperature-dependent growth rates of two algae that produce potent biotoxins, Alexandrium fundyense and Dinophysis acuminata, to evaluate recent changes in these HABs. For both species, potential mean annual growth rates and duration of bloom seasons significantly increased within many coastal Atlantic regions between 40°N and 60°N, where incidents of these HABs have emerged and expanded in recent decades. Widespread trends were less evident across the North Pacific, although regions were identified across the Salish Sea and along the Alaskan coastline where blooms have recently emerged, and there have been significant increases in the potential growth rates and duration of these HAB events. We conclude that increasing ocean temperature is an important factor facilitating the intensification of these, and likely other, HABs and thus contributes to an expanding human health threat.


Assuntos
Dinoflagelados/crescimento & desenvolvimento , Eutrofização , Aquecimento Global , Ácido Okadáico/metabolismo , Saxitoxina/biossíntese , Oceano Atlântico , Humanos , Ácido Okadáico/toxicidade , Oceano Pacífico , Saxitoxina/toxicidade
19.
Environ Toxicol Chem ; 36(10): 2689-2697, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28409869

RESUMO

Cyanobacteria produce different toxic compounds that affect animal life, among them hepatotoxins and neurotoxins. Because cyanobacteria are able to produce a variety of toxic compounds at the same time, organisms may be, generally, subjected to their combined action. In the present study, we demonstrate the single and combined effects on cladocerans of cyanobacteria that produce microcystins (hepatotoxins) and saxitoxins (neurotoxins). Animals were exposed (either singly or combined) to 2 strains of cyanobacteria isolated from the same environment (Funil Reservoir, Rio de Janeiro, Brazil). The effects on clearance rate, mobility, survivorship, fecundity, population increase rate (r), and the antioxidant enzymes glutathione-S-transferase (GST) and catalase (CAT) were measured. Cladoceran species showed a variety of responses to cyanobacterial exposures, going from no effect to impairment of swimming movement, lower survivorship, fecundity, and general fitness (r). Animals ingested cyanobacteria in all treatments, although at lower rates than good food (green algae). Antioxidant defense responses were in accordance with fitness responses, suggesting that oxidative stress may be related to such effects. The present study emphasizes the need for testing combined actions of different classes of toxins, because this is often, and most likely, the scenario in a more eutrophic world with global climatic changes. Environ Toxicol Chem 2017;36:2689-2697. © 2017 SETAC.


Assuntos
Antioxidantes/metabolismo , Cladóceros/efeitos dos fármacos , Cianobactérias/metabolismo , Microcistinas/toxicidade , Saxitoxina/toxicidade , Animais , Catalase/metabolismo , Cladóceros/metabolismo , Daphnia/efeitos dos fármacos , Daphnia/fisiologia , Glutationa Transferase/metabolismo , Microcistinas/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Saxitoxina/metabolismo , Natação , Testes de Toxicidade
20.
Toxicon ; 129: 36-43, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28209476

RESUMO

Diamondback terrapins (Malaclemys terrapin) are a threatened or endangered species in much of their range along the U.S. Atlantic and Gulf coasts. Over an approximately three-week period from late April to mid-May 2015, hundreds of adult diamondback terrapins were found dead on the shores of Flanders Bay, Long Island, New York, USA. Concurrent with the mortality event, elevated densities of the paralytic shellfish toxin (PST)-producing dinoflagellate, Alexandrium fundyense (>104 cells L-1) and high levels of PST in bivalves (maximal levels = 540 µg STX eq. 100 g-1 shellfish tissue) were observed in the Flanders Bay region, resulting in shellfish bed closures in regional tributaries. Gross and histologic postmortem examinations of terrapins revealed no physical trauma to individuals or a common, underlying disease process to explain the deaths. PST compounds (0.2-12.5 µg STX eq. 100 g-1) were present in various M. terrapin tissues collected over the duration of the mortality event. High-throughput sequencing revealed that the ribbed mussel (Geukensia demissa, a PST vector) was present in the gastrointestinal tracks of all terrapin samples tested. While the potential of PST to cause mortality in chelonians has not been well-characterized, in the absence of other significant findings from necropsies and pathological analyses, we provide evidence that PST in shellfish was likely high enough to cause or contribute to the mortality in these small (<2.0 kg) animals.


Assuntos
Doenças dos Animais/mortalidade , Dinoflagelados/química , Proliferação Nociva de Algas , Toxinas Marinhas/toxicidade , Intoxicação por Frutos do Mar/veterinária , Tartarugas , Doenças dos Animais/induzido quimicamente , Animais , Baías/química , Bivalves , Complexo IV da Cadeia de Transporte de Elétrons/genética , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , New York , Saxitoxina/toxicidade , Frutos do Mar
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