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1.
Mar Drugs ; 18(2)2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32033403

RESUMO

Saxitoxin is an alkaloid neurotoxin originally isolated from the clam Saxidomus giganteus in 1957. This group of neurotoxins is produced by several species of freshwater cyanobacteria and marine dinoflagellates. The saxitoxin biosynthesis pathway was described for the first time in the 1980s and, since then, it was studied in more than seven cyanobacterial genera, comprising 26 genes that form a cluster ranging from 25.7 kb to 35 kb in sequence length. Due to the complexity of the genomic landscape, saxitoxin biosynthesis in dinoflagellates remains unknown. In order to reveal and understand the dynamics of the activity in such impressive unicellular organisms with a complex genome, a strategy that can carefully engage them in a systems view is necessary. Advances in omics technology (the collective tools of biological sciences) facilitated high-throughput studies of the genome, transcriptome, proteome, and metabolome of dinoflagellates. The omics approach was utilized to address saxitoxin-producing dinoflagellates in response to environmental stresses to improve understanding of dinoflagellates gene-environment interactions. Therefore, in this review, the progress in understanding dinoflagellate saxitoxin biosynthesis using an omics approach is emphasized. Further potential applications of metabolomics and genomics to unravel novel insights into saxitoxin biosynthesis in dinoflagellates are also reviewed.


Assuntos
Dinoflagelados/genética , Dinoflagelados/metabolismo , Saxitoxina/biossíntese , Saxitoxina/química , Vias Biossintéticas , Cianobactérias/metabolismo , Genômica , Metabolômica , Neurotoxinas/metabolismo , Biossíntese de Proteínas , Proteômica , Saxitoxina/metabolismo , Transcriptoma
2.
Chemosphere ; 243: 125318, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995862

RESUMO

Increased agricultural intensification goes with the widespread use of herbicides that adversely affect aquatic biodiversity. The effects of herbicides on toxin-producing cyanobacteria have been poorly studied. The present study aimed to investigate the toxicological and physiological effects of the herbicide clethodim on Raphidiopsis raciborskii (a.k.a. Cylindrospermopsis raciborskii) ITEPA1 and Microcystis aeruginosa BCCUSP232. On day four of the experiment, the exposure to 25 mg/L clethodim resulted in the highest cell density of R. raciborskii. Similarly, exposure to the 1, 5, 20, and 50 mg/L clethodim treatments resulted in the highest cell densities of M. aeruginosa on day 4 of the experiment. Medium effect concentrations (EC50) after 96 h of exposure of both strains to clethodim were 192.98 mg/L and 168.73 mg/L for R. raciborskii and M. aeruginosa, respectively. The presence of clethodim significantly increased the total microcystin content of M. aeruginosa compared to the control cultures. At 400 mg/L, total saxitoxins content of R. raciborskii was 27% higher than that of the control cultures on day 4. In contrast, cultures exposed to 100 mg/L clethodim had the lowest saxitoxins levels per cell quota. There was an increase in the levels of intracellular hydrogen peroxide in both species during exposure to clethodim, which was followed by significant changes (p < 0.05) in the activity of antioxidant enzymes such as peroxidase and superoxide dismutase. These results revealed that the presence of low levels of clethodim in the aquatic environment might lead to the excessive proliferation of cyanobacteria and alteration of their cyanotoxins content.


Assuntos
Cicloexanonas/farmacologia , Cylindrospermopsis/efeitos dos fármacos , Cylindrospermopsis/crescimento & desenvolvimento , Microcystis/efeitos dos fármacos , Microcystis/crescimento & desenvolvimento , Antioxidantes/metabolismo , Toxinas Bacterianas/metabolismo , Cylindrospermopsis/metabolismo , Herbicidas/farmacologia , Microcistinas/metabolismo , Microcystis/metabolismo , Peroxidases/metabolismo , Saxitoxina/metabolismo , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/farmacologia
3.
Chemistry ; 26(9): 2025-2033, 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-31769085

RESUMO

A novel series of C12-keto-type saxitoxin (STX) derivatives bearing an unusual nonhydrated form of the ketone at C12 has been synthesized, and their NaV -inhibitory activity has been evaluated in a cell-based assay as well as whole-cell patch-clamp recording. Among these compounds, 11-benzylidene STX (3 a) showed potent inhibitory activity against neuroblastoma Neuro 2A in both cell-based and electrophysiological analyses, with EC50 and IC50 values of 8.5 and 30.7 nm, respectively. Interestingly, the compound showed potent inhibitory activity against tetrodotoxin-resistant subtype of NaV 1.5, with an IC50 value of 94.1 nm. Derivatives 3 a-d and 3 f showed low recovery rates from NaV 1.2 subtype (ca 45-79 %) compared to natural dcSTX (2), strongly suggesting an irreversible mode of interaction. We propose an interaction model for the C12-keto derivatives with NaV in which the enone moiety in the STX derivatives 3 works as Michael acceptor for the carboxylate of Asp1717 .


Assuntos
Saxitoxina/química , Bloqueadores dos Canais de Sódio/síntese química , Canais de Sódio Disparados por Voltagem/metabolismo , Potenciais de Ação/efeitos dos fármacos , Sequência de Aminoácidos , Sítios de Ligação , Linhagem Celular Tumoral , Humanos , Concentração Inibidora 50 , Simulação de Acoplamento Molecular , Técnicas de Patch-Clamp , Isoformas de Proteínas/antagonistas & inibidores , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Teoria Quântica , Saxitoxina/metabolismo , Saxitoxina/farmacologia , Bloqueadores dos Canais de Sódio/metabolismo , Bloqueadores dos Canais de Sódio/farmacologia , Tetrodotoxina/química , Tetrodotoxina/metabolismo , Canais de Sódio Disparados por Voltagem/química , Canais de Sódio Disparados por Voltagem/genética
4.
Sci Adv ; 5(6): eaax2650, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31223657

RESUMO

Dinoflagelates and cyanobacteria produce saxitoxin (STX), a lethal bis-guanidinium neurotoxin causing paralytic shellfish poisoning. A number of metazoans have soluble STX-binding proteins that may prevent STX intoxication. However, their STX molecular recognition mechanisms remain unknown. Here, we present structures of saxiphilin (Sxph), a bullfrog high-affinity STX-binding protein, alone and bound to STX. The structures reveal a novel high-affinity STX-binding site built from a "proto-pocket" on a transferrin scaffold that also bears thyroglobulin domain protease inhibitor repeats. Comparison of Sxph and voltage-gated sodium channel STX-binding sites reveals a convergent toxin recognition strategy comprising a largely rigid binding site where acidic side chains and a cation-π interaction engage STX. These studies reveal molecular rules for STX recognition, outline how a toxin-binding site can be built on a naïve scaffold, and open a path to developing protein sensors for environmental STX monitoring and new biologics for STX intoxication mitigation.


Assuntos
Proteínas de Transporte/metabolismo , Saxitoxina/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação/efeitos dos fármacos , Sítios de Ligação/fisiologia , Linhagem Celular , Cianobactérias/metabolismo , Humanos , Peptídeo Hidrolases/metabolismo , Inibidores de Proteases/farmacologia , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Rana catesbeiana , Células Sf9 , Canais de Sódio/metabolismo , Tireoglobulina/metabolismo , Transferrina/metabolismo
5.
Mar Environ Res ; 144: 240-245, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30739812

RESUMO

The neurotoxic complex saxitoxin, is a group of marine toxins that historically has significantly impacted human health and the ability to utilize marine resources. A steady increase in the distribution and intensity of Alexandrium catenella blooms in Chile, and around the world, has caused major ecological and socioeconomic impacts, putting this type of dinoflagellate, and its toxicity, in the spotlight. Ostrea chilensis is a commercially and ecologically important resource harvested from wild populations and farmed in centers of southern Chile, where it is exposed to large harmful algal blooms of the type that can cause paralysis in humans. This study contributes to our understanding about the transfer of toxins from A. catenella cells to juvenile and adult Ostrea chilensis by tracking transformations of the neurotoxic complex until it reaches its most stable molecular form in the intracellular environment of O. chilensis tissues. These biotransformations are different in O. chilensis juveniles and adults, indicating a differentiated response for these two life stages of this bivalve species. These studies can be used for similar analyses in other ecologically and commercially important species of filter feeding organisms, providing greater understanding of the specific interactions of bivalves in scenarios of toxic dinoflagellate proliferations (e.g. A. catenella blooms).


Assuntos
Biotransformação , Dinoflagelados , Proliferação Nociva de Algas , Ostrea/metabolismo , Saxitoxina/metabolismo , Animais , Chile
6.
Toxins (Basel) ; 11(1)2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30646514

RESUMO

Cylindrospermopsis raciborskii is a potentially toxic freshwater cyanobacterium that can tolerate a wide range of light and temperature. Due to climatic changes, the interaction between light and temperature is studied in aquatic systems, but no study has addressed the effect of both variables on the saxitoxins production. This study evaluated the combined effect of light and temperature on saxitoxins production and cellular quota in C. raciborskii. Experiments were performed with three C. raciborskii strains in batch cultures under six light intensities (10, 40, 60, 100, 150, and 500 µmol of photons m-2 s-1) and four temperatures (15, 20, 25, and 30 °C). The growth of C. raciborskii strains was limited at lower temperatures and the maximum growth rates were obtained under higher light combined with temperatures equal or above 20 °C, depending on the strain. In general, growth was highest at 30 °C at the lower light intensities and equally high at 25 °C and 30 °C under higher light. Highest saxitoxins concentration and cell-quota occurred at 25 °C under high light intensities, but were much lower at 30 °C. Hence, increased temperatures combined with sufficient light will lead to higher C. raciborskii biomass, but blooms could become less toxic in tropical regions.


Assuntos
Cylindrospermopsis , Luz , Saxitoxina/metabolismo , Temperatura , Cylindrospermopsis/crescimento & desenvolvimento , Cylindrospermopsis/metabolismo , Cylindrospermopsis/efeitos da radiação
7.
Toxins (Basel) ; 10(11)2018 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-30373104

RESUMO

Paralytic shellfish poisoning (PSP) is a severe food-borne illness, caused by the ingestion of seafood containing paralytic shellfish toxins (PST), which are naturally produced by marine dinoflagellates and accumulate in shellfish during algae blooms. Novel PST, designated as hydroxybenzoate analogues (also known as GC toxins), was relatively recently discovered in Gymnodinium catenatum strains worldwide. However, to date, there have been no studies examining their accumulation in shellfish. In this study, mussels (Mytilus galloprovincialis) were exposed to G. catenatum for five days and then exposed to a non-toxic diet for 24 h, to investigate the toxin's accumulation/elimination dynamics. As determined by UHPLC-HILIC-MS/MS, the hydroxybenzoate analogues, GC1 to GC6, comprised 41% of the algae toxin profile and only 9% in mussels. Elimination of GC toxins after 24 h was not evident. This study highlights that a relevant fraction of PST in mussels are not routinely analysed in monitoring programs and that there is a need to better understand the toxicological potential of the hydroxybenzoate analogues, in order to properly address the risk of G. catenatum blooms.


Assuntos
Dinoflagelados , Hidroxibenzoatos/análise , Mytilus/metabolismo , Saxitoxina/análogos & derivados , Saxitoxina/análise , Animais , Cromatografia Líquida de Alta Pressão , Hidroxibenzoatos/metabolismo , Saxitoxina/metabolismo , Intoxicação por Frutos do Mar , Espectrometria de Massas em Tandem
8.
Toxicon ; 153: 58-61, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30170168

RESUMO

The pufferfish saxitoxin- and tetrodotoxin-binding protein 2 (PSTBP2), which is involved in toxin accumulation, was knocked out in Takifugu rubripes embryos by using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 genome-editing technology. Treating the embryos with one of two single-guide RNA (sgRNA) resulted in mutation rates of 57.1% and 62.5%, respectively, as estimated using a heteroduplex mobility assay at 3 days postfertilization. Both sgRNAs might induced frameshift mutations that knocked out the T. rubripes PSTBP2.


Assuntos
Proteínas de Peixes/genética , Saxitoxina/metabolismo , Canais de Sódio/genética , Takifugu/genética , Tetrodotoxina/metabolismo , Animais , Sistemas CRISPR-Cas , Proteínas de Peixes/metabolismo , Edição de Genes , Taxa de Mutação , RNA Guia , Canais de Sódio/química , Takifugu/embriologia , Takifugu/metabolismo
9.
Spectrochim Acta A Mol Biomol Spectrosc ; 204: 180-187, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-29933153

RESUMO

Aptamers could be used to construct simple and effective biosensor because the conformational switch of aptamer upon target binding is easy to be transferred to optical or electrochemical signals. Nevertheless, we found that the binding between saxitoxin (STX) and aptamer (M-30f) is not accompanied with conformational switch. Here, the circular dichroism spectra, fluorophore and quencher labeled aptamer, and crystal violet-based assays were used to identify the binding way between STX and aptamer. The results show that the conformation of aptamer is stabilized in PBS buffer (10 mM phosphate buffer, 2.7 mM KCl, 137 mM NaCl, pH 7.4) and this conformation may provide an exactly suitable cave for STX binding. Through the analysis of UV-melting curves and circular dichroism-melting curves, it is found that different concentrations of STX produce different unfolding extents of the aptamer under high temperature. Then, a simple temperature-assisted "turn-on" fluorescent aptasensor was developed to detect STX and the application in real sample detection demonstrates its feasibility. The proposed method provides not only an alternative for STX detection but also a strategy for simple aptasensor design using aptamers that do not switch conformation upon targets binding.


Assuntos
Aptâmeros de Nucleotídeos/metabolismo , Técnicas Biossensoriais/métodos , Corantes Fluorescentes/metabolismo , Saxitoxina/análise , Saxitoxina/metabolismo , Aptâmeros de Nucleotídeos/química , Corantes Fluorescentes/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Saxitoxina/química
10.
Toxicon ; 143: 44-50, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29326037

RESUMO

In October 2012, paralytic shellfish toxins (PST) were detected in the hepatopancreas of Southern Rock Lobsters (Jasus edwardsii) collected from the east coast of Tasmania, Australia. This resulted in the first commercial closure in Australia for this species. Questions were raised on how the toxins were transferred to the lobsters, how long the toxins would persist, whether PST-contaminated hepatopancreas posed a risk to human health, and what management strategies could be applied. The aim of this study was to investigate whether PST-contaminated mussels are a potential vector enabling toxin accumulation in J. edwardsii and to collect information on toxin uptake, distribution and depuration rates and toxin profiles under controlled experimental settings. Lobsters were fed mussels naturally contaminated with PST for a period of 28 days in an experimental setting; following this, lobsters were allocated to either fed or starved treatment groups. PST were not detected in the tail tissue of lobsters at any stage of the experiment. Lobster hepatopancreas contained mean levels of 2.4 mg STX.2HCl eq/kg after 28 days of uptake, although substantial variability in total toxicity was observed. The PST profile of the hepatopancreas was similar to that of the contaminated mussels used as feed. Significant differences were noted in the PST depuration rates between fed and starved treatment groups. The daily depuration rate for total PST was estimated to be 0.019 and 0.013 mg STX.2HCl eq/kg for the fed and starved treatment groups respectively using a constant-rate decay model. After 42 days of depuration, total PST (STX equivalents) levels in the hepatopancreas of all lobsters were below 0.8 mg STX.2HCl eq/kg, which represents the regulatory level applied to bivalves. This result indicates that long-term holding to depurate PST may potentially be used as a risk management tool.


Assuntos
Palinuridae/metabolismo , Saxitoxina/metabolismo , Animais , Bivalves/química , Cadeia Alimentar , Hepatopâncreas , Saxitoxina/análise , Frutos do Mar/análise , Intoxicação por Frutos do Mar/metabolismo , Tasmânia , Distribuição Tecidual
11.
Mar Drugs ; 16(1)2018 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-29316695

RESUMO

Although pufferfish of the family Tetraodontidae contain high levels of tetrodotoxin (TTX) mainly in the liver, some species of pufferfish, boxfish of the family Ostraciidae, and porcupinefish of the family Diodontidae do not. To clarify the mechanisms, uptake of TTX and saxitoxins (STXs) into liver tissue slices of pufferfish, boxfish and porcupinefish was examined. Liver tissue slices of the pufferfish (toxic species Takifugu rubripes and non-toxic species Lagocephalus spadiceus, L. cheesemanii and Sphoeroides pachygaster) incubated with 50 µM TTX accumulated TTX (0.99-1.55 µg TTX/mg protein) after 8 h, regardless of the toxicity of the species. In contrast, in liver tissue slices of boxfish (Ostracion immaculatus) and porcupinefish (Diodon holocanthus, D. liturosus, D. hystrix and Chilomycterus reticulatus), TTX content did not increase with incubation time, and was about 0.1 µg TTX/mg protein. When liver tissue slices were incubated with 50 µM STXs for 8 h, the STXs content was <0.1 µg STXs/mg protein, irrespective of the fish species. These findings indicate that, like the toxic species of pufferfish T. rubripes, non-toxic species such as L. spadiceus, L. cheesemanii and S. pachygaster, potentially take up TTX into the liver, while non-toxic boxfish and porcupinefish do not take up either TTX or STXs.


Assuntos
Fígado/metabolismo , Saxitoxina/metabolismo , Tetraodontiformes/metabolismo , Tetrodotoxina/metabolismo , Animais , Transporte Biológico , Saxitoxina/isolamento & purificação , Tetrodotoxina/isolamento & purificação , Fatores de Tempo , Distribuição Tecidual
12.
Toxicon ; 144: 14-22, 2018 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-29288682

RESUMO

This study was designed to assess the contribution of feeding behavior to inter-individual variability of paralytic shellfish toxin (PST) accumulation in the Pacific oyster Crassostrea gigas. For this purpose 42 oysters were exposed for 2 days to non-toxic algae and then for 2 other days to the PST producer Alexandrium minutum. Individual clearance rate (CR) of oysters was continuously monitored over the 4 days using an ecophysiological measurement system. Comparison of CR values when exposed to toxic and non toxic algae allowed to estimate a clearance rate inhibition index (CRII). Toxin concentration of oysters was quantified at the end of the experiment. These data allowed to estimate the toxin accumulation efficiency (TAE) as the ratio of toxin accumulated on toxin consumed. Changes of clearance rate during the experiment indicated that all individuals stopped feeding immediately after being exposed to A. minutum for at least 7 h. This fast response likely corresponded to a behavioral mechanism of avoidance rather to a toxin-induced response. Individuals also showed high inter-variability in their recovery of filtration after this period. Most of the inter-individual variability (78%) in PST accumulation in C. gigas could be explained by the consumption of A. minutum cells, thus emphasizing the importance of the feeding behavior in accumulation. Based on the toxin concentration in their tissues, oysters were clustered in 3 groups showing contrasted patterns of PST accumulation: the high accumulation group was characterized by high feeding rates both on non-toxic and toxic diet and subsequently a low CRII and high TAE. Inversely, the low accumulation group was characterized by low filtration rates, high CRII and low TAE. Both filtration capacity and sensitivity of oysters to toxins may account for the differences in their accumulation. The contribution of TAE in PST accumulation is discussed and might result from differences in assimilation and detoxification abilities among individuals.


Assuntos
Crassostrea/metabolismo , Dinoflagelados , Comportamento Alimentar , Saxitoxina/metabolismo , Animais , Crassostrea/fisiologia , Inativação Metabólica , Fenótipo , Intoxicação por Frutos do Mar
13.
Toxins (Basel) ; 9(10)2017 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-29027918

RESUMO

The cyanobacterium Aphanizomenon gracile is the most widely distributed producer of the potent neurotoxin saxitoxin in freshwaters. In this work, total and extracellular saxitoxin and the transcriptional response of three genes linked to saxitoxin biosynthesis (sxtA) and transport (sxtM, sxtPer) were assessed in Aphanizomenon gracile UAM529 cultures under temperatures covering its annual cycle (12 °C, 23 °C, and 30 °C). Temperature influenced saxitoxin production being maximum at high temperatures (30 °C) above the growth optimum (23 °C), concurring with a 4.3-fold increased sxtA expression at 30 °C. Extracellular saxitoxin transport was temperature-dependent, with maxima at extremes of temperature (12 °C with 16.9% extracellular saxitoxin; and especially 30 °C with 53.8%) outside the growth optimum (23 °C), coinciding with a clear upregulation of sxtM at both 12 °C and 30 °C (3.8-4.1 fold respectively), and yet with just a slight upregulation of sxtPer at 30 °C (2.1-fold). Nitrate depletion also induced a high extracellular saxitoxin release (51.2%), although without variations of sxtM and sxtPer transcription, and showing evidence of membrane damage. This is the first study analysing the transcriptional response of sxtPer under environmental gradients, as well as the effect of temperature on putative saxitoxin transporters (sxtM and sxtPer) in cyanobacteria in general.


Assuntos
Aphanizomenon/genética , Aphanizomenon/metabolismo , Saxitoxina/genética , Saxitoxina/metabolismo , Temperatura , Aphanizomenon/crescimento & desenvolvimento , Membrana Celular/metabolismo , Clorofila/metabolismo , Clorofila A , Genes Bacterianos
14.
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
15.
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
16.
J Agric Food Chem ; 65(27): 5494-5502, 2017 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-28616979

RESUMO

A seafood poisoning event occurred in Qinhuangdao, China, in April 2016. Subsequently, the causative mussels (Mytilus galloprovincialis) were harvested and analyzed to reveal a high concentration [∼10 758 µg of saxitoxin (STX) equiv kg-1] of paralytic shellfish toxins (PSTs), including gonyautoxin (GTX)1/4 and GTX2/3, as well as new metabolites 11-hydroxy-STX (M2), 11,11-dihydroxy-STX (M4), open-ring 11,11-dihydroxy-STX (M6), 11-hydroxy-neosaxitoxin (NEO) (M8), and 11,11-dihydroxy-NEO (M10). To understand the origin and biotransformation pathways of these new metabolites, uncontaminated mussels (M. galloprovincialis) were fed with either of two Alexandrium tamarense strains (ATHK and TIO108) under laboratory conditions. Similar PST metabolites were also detected in mussels from both feeding experiments. Results supposed that 11-hydroxy-C2 toxin (M1) and 11,11-dihydroxy-C2 (M3) are transformed from C2, while 11-hydroxy-C4 toxin (M7) and 11,11-dihydroxy-C4 (M9) are converted from C4. In addition, the metabolites M2, M4, and M6 appear to be products of GTX2/3, and the metabolites M8 and M10 are likely derived from GTX1/4.


Assuntos
Bivalves/química , Toxinas Marinhas/metabolismo , Intoxicação por Frutos do Mar/metabolismo , Frutos do Mar/análise , Animais , Biotransformação , Bivalves/metabolismo , Dinoflagelados/metabolismo , Toxinas Marinhas/química , Toxinas Marinhas/toxicidade , Estrutura Molecular , Saxitoxina/análogos & derivados , Saxitoxina/química , Saxitoxina/metabolismo , Frutos do Mar/toxicidade
17.
Toxins (Basel) ; 9(6)2017 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-28604648

RESUMO

The saxitoxin-group (STX-group) corresponds to toxic metabolites produced by cyanobacteria and dinoflagellates of the genera Alexandrium, Gymnodinium, and Pyrodinium. Over the last decade, it has been possible to extrapolate the areas contaminated with the STX-group worldwide, including Chile, a phenomenon that has affected ≈35% of the Southern Pacific coast territory, generating a high economic impact. The objective of this research was to study the toxicity of the STX-group in all aquatic organisms (bivalves, algae, echinoderms, crustaceans, tunicates, cephalopods, gastropods, and fish) present in areas with a variable presence of harmful algal blooms (HABs). Then, the toxic profiles of each species and dose of STX equivalents ingested by a 60 kg person from 400 g of shellfish were determined to establish the health risk assessment. The toxins with the highest prevalence detected were gonyautoxin-4/1 (GTX4/GTX1), gonyautoxin-3/2 (GTX3/GTX2), neosaxitoxin (neoSTX), decarbamoylsaxitoxin (dcSTX), and saxitoxin (STX), with average concentrations of 400, 2800, 280, 200, and 2000 µg kg-1 respectively, a species-specific variability, dependent on the evaluated tissue, which demonstrates the biotransformation of the analogues in the trophic transfer with a predominance of α-epimers in all toxic profiles. The identification in multiple vectors, as well as in unregulated species, suggests that a risk assessment and risk management update are required; also, chemical and specific analyses for the detection of all analogues associated with the STX-group need to be established.


Assuntos
Contaminação de Alimentos/análise , Saxitoxina/análise , Alimentos Marinhos/análise , Animais , Cianobactérias , Dinoflagelados , Cadeia Alimentar , Invertebrados/química , Invertebrados/metabolismo , Macrocystis/química , Macrocystis/metabolismo , Salmão/metabolismo , Saxitoxina/metabolismo
18.
Harmful Algae ; 65: 27-39, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28526117

RESUMO

We tested the hypothesis that a combination of coagulant and ballast could be efficient for removal of positively buoyant harmful cyanobacteria in shallow tropical waterbodies, and will not promote the release of cyanotoxins. This laboratory study examined the efficacy of coagulants [polyaluminium chloride (PAC) and chitosan (made of shrimp shells)] alone, and combined with ballast (lanthanum modified bentonite, red soil or gravel) to remove the natural populations of cyanobacteria collected from a shallow eutrophic urban reservoir with alternating blooms of Cylindrospermopsis and Microcystis. PAC combined with ballast was effective in settling blooms dominated by Microcystis or Cylindrospermopsis. Contrary to our expectation, chitosan combined with ballast was only effective in settling Cylindrospermopsis-dominated blooms at low pH, whereas at pH≥8 no effective flocculation and settling could be evoked. Chitosan also had a detrimental effect on Cylindrospermopsis causing the release of saxitoxins. In contrast, no detrimental effect on Microcystis was observed and all coagulant-ballast treatments were effective in not only settling the Microcystis dominated bloom, but also lowering dissolved microcystin concentrations. Our data show that the best procedure for biomass reduction also depends on the dominant species.


Assuntos
Hidróxido de Alumínio/farmacologia , Bentonita/farmacologia , Quitosana/farmacologia , Coagulantes/farmacologia , Cylindrospermopsis/efeitos dos fármacos , Microcystis/efeitos dos fármacos , Biomassa , Quitosana/efeitos adversos , Cylindrospermopsis/crescimento & desenvolvimento , Proliferação Nociva de Algas/efeitos dos fármacos , Microcistinas/metabolismo , Microcystis/crescimento & desenvolvimento , Saxitoxina/metabolismo , Solo/química
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 ; 130: 47-55, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28235579

RESUMO

Last decades, cyanobacterial blooms have been commonly reported in Russia. Among the boom-forming species, potential toxin producers have been identified. The aim of this paper was to study the presence of neurotoxic compounds - saxitoxins and anatoxin-a - in water bodies from different regions of Russia. We also made attempts to identify the neurotoxin-producing genera. The good convergence of the results obtained by light microscopy, PCR and LC-MS/MS analyses indicated the presence of active neurotoxin producing species in all investigated water bodies. Saxitoxin was detected in phytoplankton from 4 water bodies in Central European Russia and West Siberia, including lake and reservoirs used as a source for potable water. The water bodies differed with the respect of saxitoxin producers which belonged to Aphanizomenon and/or Dolichospermum genera. For the first time, we obtained quantitative data on the intracellular saxitoxin concentration in Russian freshwaters using LC-MS/MS. Anatoxin-a was detected only in lakes of Northwestern Russia. In the eutrophic shallow Lower Suzdal Lake, Aphanizomenon was the stated anatoxin-a-producing genus. In the large shallow artificial hypertrophic Sestroretskij Razliv Lake, it was very likely that both dominant species - Aphanizomenon flos-aquae and Dolichospermum planctonicum - were anatoxin-a producers.


Assuntos
Aphanizomenon/metabolismo , Cianobactérias/metabolismo , Água Doce/química , Neurotoxinas/metabolismo , Aphanizomenon/genética , Aphanizomenon/isolamento & purificação , Cromatografia Líquida , Cianobactérias/genética , Cianobactérias/isolamento & purificação , Monitoramento Ambiental , Água Doce/microbiologia , Espectrometria de Massas , Neurotoxinas/química , Neurotoxinas/isolamento & purificação , Federação Russa , Saxitoxina/química , Saxitoxina/isolamento & purificação , Saxitoxina/metabolismo , Tropanos/química , Tropanos/isolamento & purificação , Tropanos/metabolismo
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