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A special issue of Marine Drugs (ISSN 1660-3397).

Deadline for manuscript submissions: closed (15 December 2014) | Viewed by 113910

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Dr. Alison Robertson

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Marine Toxicology & Chemistry, Department of Marine Sciences, University of South Alabama, Mobile, AL 36688, USA
Interests: marine and freshwater toxin chemistry; biochemical pathways; metabolism; biomarkers of exposure; and method development for detection of chemical hazards in seafood
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Special Issue Information

Dear Colleagues,

Shellfish toxins pose a significant public health concern worldwide. These toxins are potent bioactive metabolites produced by a variety of dinoflagellate, diatom, and cyanobacterial species in marine and freshwater ecosystems. Within each major class, these toxins include a vast array of congeners, differing greatly in terms of structure, pharmacological action, and toxicity. This combined special issue for Marine Drugs and Toxins is dedicated to recent advances in marine and freshwater shellfish toxin research. We encourage shellfish toxin research that reports on: 1) the discovery of novel shellfish toxins, metabolites and biochemical pathways relevant to human health, 2) the elucidation of biochemical or molecular targets for toxin detection, 3) research that enhances our understanding and linkage of ecological and functional roles of shellfish toxins, and 4) evaluation of new and emerging human health hazards on a regional and global scale including the evaluation of trophic pathways and toxicology.

I am honored to serve as a guest editor for this special issue and would encourage all scientists to submit their latest findings in an effort to enhance our collective knowledge and communication of marine and freshwater shellfish toxin research.

Dr. Alison Robertson
Guest Editor

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Keywords

shellfish toxins
harmful algal blooms
dinoflagellates
diatoms
cyanobacteria
cyanotoxins
bioaccumulation
biomolecular pathways
toxicology
trophic transfer
chemical ecology

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Published Papers (10 papers)

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821 KiB

Open AccessArticle

Toxin Profile of Gymnodinium catenatum (Dinophyceae) from the Portuguese Coast, as Determined by Liquid Chromatography Tandem Mass Spectrometry

by Pedro R. Costa, Alison Robertson and Michael A. Quilliam

Mar. Drugs 2015, 13(4), 2046-2062; https://doi.org/10.3390/md13042046 - 13 Apr 2015

Cited by 52 | Viewed by 8264

Abstract

The marine dinoflagellate Gymnodinium catenatum has been associated with paralytic shellfish poisoning (PSP) outbreaks in Portuguese waters for many years. PSP syndrome is caused by consumption of seafood contaminated with paralytic shellfish toxins (PSTs), a suite of potent neurotoxins. Gymnodinium catenatum was frequently reported along the Portuguese coast throughout the late 1980s and early 1990s, but was absent between 1995 and 2005. Since this time, G. catenatum blooms have been recurrent, causing contamination of fishery resources along the Atlantic coast of Portugal. The aim of this study was to evaluate the toxin profile of G. catenatum isolated from the Portuguese coast before and after the 10-year hiatus to determine changes and potential impacts for the region. Hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC-MS/MS) was utilized to determine the presence of any known and emerging PSTs in sample extracts. Several PST derivatives were identified, including the N-sulfocarbamoyl analogues (C1–4), gonyautoxin 5 (GTX5), gonyautoxin 6 (GTX6), and decarbamoyl derivatives, decarbamoyl saxitoxin (dcSTX), decarbamoyl neosaxitoxin (dcNeo) and decarbamoyl gonyautoxin 3 (dcGTX3). In addition, three known hydroxy benzoate derivatives, G. catenatum toxin 1 (GC1), GC2 and GC3, were confirmed in cultured and wild strains of G. catenatum. Moreover, two presumed N-hydroxylated analogues of GC2 and GC3, designated GC5 and GC6, are reported. This work contributes to our understanding of the toxigenicity of G. catenatum in the coastal waters of Portugal and provides valuable information on emerging PST classes that may be relevant for routine monitoring programs tasked with the prevention and control of marine toxins in fish and shellfish. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Open AccessArticle

Comparative Transcriptome Analysis of a Toxin-Producing Dinoflagellate Alexandrium catenella and Its Non-Toxic Mutant

by Yong Zhang, Shu-Fei Zhang, Lin Lin and Da-Zhi Wang

Mar. Drugs 2014, 12(11), 5698-5718; https://doi.org/10.3390/md12115698 - 24 Nov 2014

Cited by 66 | Viewed by 8678

Abstract

The dinoflagellates and cyanobacteria are two major kingdoms of life producing paralytic shellfish toxins (PSTs), a large group of neurotoxic alkaloids causing paralytic shellfish poisonings around the world. In contrast to the well elucidated PST biosynthetic genes in cyanobacteria, little is known about the dinoflagellates. This study compared transcriptome profiles of a toxin-producing dinoflagellate, Alexandrium catenella (ACHK-T), and its non-toxic mutant form (ACHK-NT) using RNA-seq. All clean reads were assembled de novo into a total of 113,674 unigenes, and 66,812 unigenes were annotated in the known databases. Out of them, 35 genes were found to express differentially between the two strains. The up-regulated genes in ACHK-NT were involved in photosynthesis, carbon fixation and amino acid metabolism processes, indicating that more carbon and energy were utilized for cell growth. Among the down-regulated genes, expression of a unigene assigned to the long isoform of sxtA, the initiator of toxin biosynthesis in cyanobacteria, was significantly depressed, suggesting that this long transcript of sxtA might be directly involved in toxin biosynthesis and its depression resulted in the loss of the ability to synthesize PSTs in ACHK-NT. In addition, 101 putative homologs of 12 cyanobacterial sxt genes were identified, and the sxtO and sxtZ genes were identified in dinoflagellates for the first time. The findings of this study should shed light on the biosynthesis of PSTs in the dinoflagellates. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Open AccessArticle

A Feedback Mechanism to Control Apoptosis Occurs in the Digestive Gland of the Oyster Crassostrea gigas Exposed to the Paralytic Shellfish Toxins Producer Alexandrium catenella

by Jean-Luc Rolland, Walid Medhioub, Agnes Vergnes, Celina Abi-khalil, Véronique Savar, Eric Abadie, Estelle Masseret, Zouher Amzil and Mohamed Laabir

Mar. Drugs 2014, 12(9), 5035-5054; https://doi.org/10.3390/md12095035 - 25 Sep 2014

Cited by 13 | Viewed by 7320

Abstract

To better understand the effect of Paralytic Shellfish Toxins (PSTs) accumulation in the digestive gland of the Pacific oyster, Crassostrea gigas, we experimentally exposed individual oysters for 48 h to a PSTs producer, the dinoflagellate Alexandrium catenella. In comparison to the effect of the non-toxic Alexandrium tamarense, on the eight apoptotic related genes tested, Bax and BI.1 were significantly upregulated in oysters exposed 48 h to A. catenella. Among the five detoxification related genes tested, the expression of cytochrome P450 (CYP1A) was shown to be correlated with toxin concentration in the digestive gland of oysters exposed to the toxic dinoflagellate. Beside this, we observed a significant increase in ROS production, a decrease in caspase-3/7 activity and normal percentage of apoptotic cells in this tissue. Taken together, these results suggest a feedback mechanism, which may occur in the digestive gland where BI.1 could play a key role in preventing the induction of apoptosis by PSTs. Moreover, the expression of CYP1A, Bax and BI.1 were found to be significantly correlated to the occurrence of natural toxic events, suggesting that the expression of these genes together could be used as biomarker to assess the biological responses of oysters to stress caused by PSTs. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Exposure to the Neurotoxic Dinoflagellate, Alexandrium catenella, Induces Apoptosis of the Hemocytes of the Oyster, Crassostrea gigas

by Walid Medhioub, Simon Ramondenc, Audrey Sophie Vanhove, Agnes Vergnes, Estelle Masseret, Veronique Savar, Zouher Amzil, Mohamed Laabir and Jean Luc Rolland

Mar. Drugs 2013, 11(12), 4799-4814; https://doi.org/10.3390/md11124799 - 2 Dec 2013

Cited by 31 | Viewed by 7978

Abstract

This study assessed the apoptotic process occurring in the hemocytes of the Pacific oyster, Crassostrea gigas, exposed to Alexandrium catenella, a paralytic shellfish toxins (PSTs) producer. Oysters were experimentally exposed during 48 h to the toxic algae. PSTs accumulation, the expression of 12 key apoptotic-related genes, as well as the variation of the number of hemocytes in apoptosis was measured at time intervals during the experiment. Results show a significant increase of the number of hemocytes in apoptosis after 29 h of exposure. Two pro-apoptotic genes (Bax and Bax-like) implicated in the mitochondrial pathway were significantly upregulated at 21 h followed by the overexpression of two caspase executor genes (caspase-3 and caspase-7) at 29 h, suggesting that the intrinsic pathway was activated. No modulation of the expression of genes implicated in the cell signaling Fas-Associated protein with Death Domain (FADD) and initiation-phase (caspase-2) was observed, suggesting that only the extrinsic pathway was not activated. Moreover, the clear time-dependent upregulation of five (Bcl2, BI-1, IAP1, IAP7B and Hsp70) inhibitors of apoptosis-related genes associated with the return to the initial number of hemocytes in apoptosis at 48 h of exposure suggests the involvement of strong regulatory mechanisms of apoptosis occurring in the hemocytes of the Pacific oyster. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Toxic C17-Sphinganine Analogue Mycotoxin, Contaminating Tunisian Mussels, Causes Flaccid Paralysis in Rodents

by Riadh Marrouchi, Evelyne Benoit, Jean-Pierre Le Caer, Nawel Belayouni, Hafedh Belghith, Jordi Molgó and Riadh Kharrat

Mar. Drugs 2013, 11(12), 4724-4740; https://doi.org/10.3390/md11124724 - 28 Nov 2013

Cited by 11 | Viewed by 7774

Abstract

Severe toxicity was detected in mussels from Bizerte Lagoon (Northern Tunisia) using routine mouse bioassays for detecting diarrheic and paralytic toxins not associated to classical phytoplankton blooming. The atypical toxicity was characterized by rapid mouse death. The aim of the present work was to understand the basis of such toxicity. Bioassay-guided chromatographic separation and mass spectrometry were used to detect and characterize the fraction responsible for mussels’ toxicity. Only a C17-sphinganine analog mycotoxin (C17-SAMT), with a molecular mass of 287.289 Da, was found in contaminated shellfish. The doses of C17-SAMT that were lethal to 50% of mice were 750 and 150 μg/kg following intraperitoneal and intracerebroventricular injections, respectively, and 900 μg/kg following oral administration. The macroscopic general aspect of cultures and the morphological characteristics of the strains isolated from mussels revealed that the toxicity episodes were associated to the presence of marine microfungi (Fusarium sp., Aspergillus sp. and Trichoderma sp.) in contaminated samples. The major in vivo effect of C17-SAMT on the mouse neuromuscular system was a dose- and time-dependent decrease of compound muscle action potential amplitude and an increased excitability threshold. In vitro, C17-SAMT caused a dose- and time-dependent block of directly- and indirectly-elicited isometric contraction of isolated mouse hemidiaphragms. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Cytotoxicity, Fractionation and Dereplication of Extracts of the Dinoflagellate Vulcanodinium rugosum, a Producer of Pinnatoxin G

by Marie Geiger, Gwenaëlle Desanglois, Kevin Hogeveen, Valérie Fessard, Thomas Leprêtre, Florence Mondeguer, Yann Guitton, Fabienne Hervé, Véronique Séchet, Olivier Grovel, Yves-François Pouchus and Philipp Hess

Mar. Drugs 2013, 11(9), 3350-3371; https://doi.org/10.3390/md11093350 - 2 Sep 2013

Cited by 12 | Viewed by 8040

Abstract

Pinnatoxin G (PnTX-G) is a marine toxin belonging to the class of cyclic imines and produced by the dinoflagellate Vulcanodinium rugosum. In spite of its strong toxicity to mice, leading to the classification of pinnatoxins into the class of “fast-acting toxins”, its hazard for human health has never been demonstrated. In this study, crude extracts of V. rugosum exhibited significant cytotoxicity against Neuro2A and KB cells. IC₅₀ values of 0.38 µg mL⁻¹ and 0.19 µg mL⁻¹ were estimated on Neuro2A cells after only 24 h of incubation and on KB cells after 72 h of incubation, respectively. In the case of Caco-2 cells 48 h after exposure, the crude extract of V. rugosum induced cell cycle arrest accompanied by a dramatic increase in double strand DNA breaks, although only 40% cytotoxicity was observed at the highest concentration tested (5 µg mL⁻¹). However, PnTX-G was not a potent cytotoxic compound as no reduction of the cell viability was observed on the different cell lines. Moreover, no effects on the cell cycle or DNA damage were observed following treatment of undifferentiated Caco-2 cells with PnTX-G. The crude extract of V. rugosum was thus partially purified using liquid-liquid partitioning and SPE clean-up. In vitro assays revealed strong activity of some fractions containing no PnTX-G. The crude extract and the most potent fraction were evaluated using full scan and tandem high resolution mass spectrometry. The dereplication revealed the presence of a major compound that could be putatively annotated as nakijiquinone A, N-carboxy-methyl-smenospongine or stachybotrin A, using the MarinLit™ database. Further investigations will be necessary to confirm the identity of the compounds responsible for the cytotoxicity and genotoxicity of the extracts of V. rugosum. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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1647 KiB

Open AccessReview

Dinophysis Toxins: Causative Organisms, Distribution and Fate in Shellfish

by Beatriz Reguera, Pilar Riobó, Francisco Rodríguez, Patricio A. Díaz, Gemita Pizarro, Beatriz Paz, José M. Franco and Juan Blanco

Mar. Drugs 2014, 12(1), 394-461; https://doi.org/10.3390/md12010394 - 20 Jan 2014

Cited by 308 | Viewed by 19834

Abstract

Several Dinophysis species produce diarrhoetic toxins (okadaic acid and dinophysistoxins) and pectenotoxins, and cause gastointestinal illness, Diarrhetic Shellfish Poisoning (DSP), even at low cell densities (<10³ cells·L⁻¹). They are the main threat, in terms of days of harvesting bans, to aquaculture in Northern Japan, Chile, and Europe. Toxicity and toxin profiles are very variable, more between strains than species. The distribution of DSP events mirrors that of shellfish production areas that have implemented toxin regulations, otherwise misinterpreted as bacterial or viral contamination. Field observations and laboratory experiments have shown that most of the toxins produced by Dinophysis are released into the medium, raising questions about the ecological role of extracelular toxins and their potential uptake by shellfish. Shellfish contamination results from a complex balance between food selection, adsorption, species-specific enzymatic transformations, and allometric processes. Highest risk areas are those combining Dinophysis strains with high cell content of okadaates, aquaculture with predominance of mytilids (good accumulators of toxins), and consumers who frequently include mussels in their diet. Regions including pectenotoxins in their regulated phycotoxins will suffer from much longer harvesting bans and from disloyal competition with production areas where these toxins have been deregulated. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Shellfish Toxins Targeting Voltage-Gated Sodium Channels

by Fan Zhang, Xunxun Xu, Tingting Li and Zhonghua Liu

Mar. Drugs 2013, 11(12), 4698-4723; https://doi.org/10.3390/md11124698 - 28 Nov 2013

Cited by 57 | Viewed by 16809

Abstract

Voltage-gated sodium channels (VGSCs) play a central role in the generation and propagation of action potentials in excitable neurons and other cells and are targeted by commonly used local anesthetics, antiarrhythmics, and anticonvulsants. They are also common targets of neurotoxins including shellfish toxins. Shellfish toxins are a variety of toxic secondary metabolites produced by prokaryotic cyanobacteria and eukaryotic dinoflagellates in both marine and fresh water systems, which can accumulate in marine animals via the food chain. Consumption of shellfish toxin-contaminated seafood may result in potentially fatal human shellfish poisoning. This article provides an overview of the structure, bioactivity, and pharmacology of shellfish toxins that act on VGSCs, along with a brief discussion on their pharmaceutical potential for pain management. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs

by Vanessa M. Lopes, Ana Rita Lopes, Pedro Costa and Rui Rosa

Mar. Drugs 2013, 11(9), 3381-3409; https://doi.org/10.3390/md11093381 - 6 Sep 2013

Cited by 47 | Viewed by 14045

Abstract

Here we summarize the current knowledge on the transfer and accumulation of harmful algal bloom (HAB)-related toxins in cephalopods (octopods, cuttlefishes and squids). These mollusks have been reported to accumulate several HAB-toxins, namely domoic acid (DA, and its isomers), saxitoxin (and its derivatives) and palytoxin (and palytoxin-like compounds) and, therefore, act as HAB-toxin vectors in marine food webs. Coastal octopods and cuttlefishes store considerably high levels of DA (amnesic shellfish toxin) in several tissues, but mainly in the digestive gland (DG)—the primary site of digestive absorption and intracellular digestion. Studies on the sub-cellular partitioning of DA in the soluble and insoluble fractions showed that nearly all DA (92.6%) is found in the cytosol. This favors the trophic transfer of the toxins since cytosolic substances can be absorbed by predators with greater efficiency. The available information on the accumulation and tissue distribution of DA in squids (e.g., in stranded Humboldt squids, Dosidicus gigas) is scarcer than in other cephalopod groups. Regarding paralytic shellfish toxins (PSTs), these organisms accumulate them at the greatest extent in DG >> kidneys > stomach > branchial hearts > posterior salivary glands > gills. Palytoxins are among the most toxic molecules identified and stranded octopods revealed high contamination levels, with ovatoxin (a palytoxin analogue) reaching 971 μg kg⁻¹ and palytoxin reaching 115 μg kg⁻¹ (the regulatory limit for PlTXs is 30 μg kg⁻¹ in shellfish). Although the impacts of HAB-toxins in cephalopod physiology are not as well understood as in fish species, similar effects are expected since they possess a complex nervous system and highly developed brain comparable to that of the vertebrates. Compared to bivalves, cephalopods represent a lower risk of shellfish poisoning in humans, since they are usually consumed eviscerated, with exception of traditional dishes from the Mediterranean area. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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Evolution and Distribution of Saxitoxin Biosynthesis in Dinoflagellates

by Russell J. S. Orr, Anke Stüken, Shauna A. Murray and Kjetill S. Jakobsen

Mar. Drugs 2013, 11(8), 2814-2828; https://doi.org/10.3390/md11082814 - 8 Aug 2013

Cited by 55 | Viewed by 13817

Abstract

Numerous species of marine dinoflagellates synthesize the potent environmental neurotoxic alkaloid, saxitoxin, the agent of the human illness, paralytic shellfish poisoning. In addition, certain freshwater species of cyanobacteria also synthesize the same toxic compound, with the biosynthetic pathway and genes responsible being recently reported. Three theories have been postulated to explain the origin of saxitoxin in dinoflagellates: The production of saxitoxin by co-cultured bacteria rather than the dinoflagellates themselves, convergent evolution within both dinoflagellates and bacteria and horizontal gene transfer between dinoflagellates and bacteria. The discovery of cyanobacterial saxitoxin homologs in dinoflagellates has enabled us for the first time to evaluate these theories. Here, we review the distribution of saxitoxin within the dinoflagellates and our knowledge of its genetic basis to determine the likely evolutionary origins of this potent neurotoxin. Full article

(This article belongs to the Special Issue Marine Shellfish Toxins)

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