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Wang G, Qiu J, Li A, Ji Y, Zhang J. Apoptosis and oxidative stress of mouse breast carcinoma 4T1 and human intestinal epithelial Caco-2 cell lines caused by the phycotoxin gymnodimine-A. Chem Biol Interact 2023; 384:110727. [PMID: 37739050 DOI: 10.1016/j.cbi.2023.110727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 09/11/2023] [Accepted: 09/20/2023] [Indexed: 09/24/2023]
Abstract
Gymnodimine-A (GYM-A) is a cyclic imine phycotoxin produced by some marine dinoflagellates. It can cause rapid death of mice via intraperitoneal administration and frequently accumulate in shellfish potentially threatening human health. In this study, four different cell lines were exposed to GYM-A for the viability assessment. Results showed that GYM-A was cytotoxic with concentration-dependent pattern to each cell type, with mean IC50 values ranging from 1.39 to 2.79 μmol L-1. Results suggested that the loss of cell viability of 4T1 and Caco-2 cells was attributed to apoptosis. Furthermore, the collapse of mitochondrial membrane potential and caspases activation were observed in the GYM-A-treated cells. Reactive oxygen species (ROS) and lipid peroxides (LPO) levels were markedly increased in 4T1 and Caco-2 cells exposed to GYM-A at 2 μmol L-1, and the oxidative stress in 4T1 cells was more obvious than that in Caco-2 cells. Additionally, unusual ultrastructure impairment on mitochondria and mitophagosomes occurred in the GYM-A-treated cells. These results suggested that an ROS-mediated mitochondrial pathway for apoptosis and mitophagy was implicated in the cytotoxic effects induced by GYM-A. This is the first report to explore the cytotoxic mechanisms of GYM-A through apoptosis and oxidative stress, and it will provide theoretical foundations for the potential therapeutic applications of GYM-A.
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Affiliation(s)
- Guixiang Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China
| | - Jiangbing Qiu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao, 266100, China
| | - Aifeng Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao, 266100, China.
| | - Ying Ji
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China
| | - Jingrui Zhang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China
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2
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Tebben J, Zurhelle C, Tubaro A, Samdal IA, Krock B, Kilcoyne J, Sosa S, Trainer VL, Deeds JR, Tillmann U. Structure and toxicity of AZA-59, an azaspiracid shellfish poisoning toxin produced by Azadinium poporum (Dinophyceae). HARMFUL ALGAE 2023; 124:102388. [PMID: 37164556 DOI: 10.1016/j.hal.2023.102388] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/13/2023] [Accepted: 01/18/2023] [Indexed: 05/12/2023]
Abstract
To date, the putative shellfish toxin azaspiracid 59 (AZA-59) produced by Azadinium poporum (Dinophyceae) has been the only AZA found in isolates from the Pacific Northwest coast of the USA (Northeast Pacific Ocean). Anecdotal reports of sporadic diarrhetic shellfish poisoning-like illness, with the absence of DSP toxin or Vibrio contamination, led to efforts to look for other potential toxins, such as AZAs, in water and shellfish from the region. A. poporum was found in Puget Sound and the outer coast of Washington State, USA, and a novel AZA (putative AZA-59) was detected in low quantities in SPATT resins and shellfish. Here, an A. poporum strain from Puget Sound was mass-cultured and AZA-59 was subsequently purified and structurally characterized. In vitro cytotoxicity of AZA-59 towards Jurkat T lymphocytes and acute intraperitoneal toxicity in mice in comparison to AZA-1 allowed the derivation of a provisional toxicity equivalency factor of 0.8 for AZA-59. Quantification of AZA-59 using ELISA and LC-MS/MS yielded reasonable quantitative results when AZA-1 was used as an external reference standard. This study assesses the toxic potency of AZA-59 and will inform guidelines for its potential monitoring in case of increasing toxin levels in edible shellfish.
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Affiliation(s)
- Jan Tebben
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Section Ecological Chemistry, Am Handelshafen 12, Bremerhaven, 27570, Germany.
| | - Christian Zurhelle
- University of Bremen, Department of Biology and Chemistry, Marine Chemistry, Leobener Straße 6, Bremen, 28359, Germany
| | - Aurelia Tubaro
- Department of Life Sciences, University of Trieste, Via A. Valerio 6, Trieste, 34127, Italy
| | | | - Bernd Krock
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Section Ecological Chemistry, Am Handelshafen 12, Bremerhaven, 27570, Germany
| | - Jane Kilcoyne
- Marine Institute, Rinville, Oranmore, County Galway H91 R673, Ireland
| | - Silvio Sosa
- Department of Life Sciences, University of Trieste, Via A. Valerio 6, Trieste, 34127, Italy
| | - Vera L Trainer
- Olympic Natural Resources Center, University of Washington, 1455 S. Forks Ave, Forks, WA 98331, United States
| | - Jonathan R Deeds
- Center for Food Safety and Applied Nutrition, Office of Regulatory Science, U.S. Food and Drug Administration, 5001 Campus Drive, College Park, Maryland, 20740, United States of America
| | - Urban Tillmann
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Section Ecological Chemistry, Am Handelshafen 12, Bremerhaven, 27570, Germany.
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Qiu J, Zhang J, Li A. Cytotoxicity and intestinal permeability of phycotoxins assessed by the human Caco-2 cell model. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 249:114447. [PMID: 38321666 DOI: 10.1016/j.ecoenv.2022.114447] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 12/05/2022] [Accepted: 12/16/2022] [Indexed: 02/08/2024]
Abstract
Phycotoxins are a class of multiple natural metabolites produced by microalgae in marine and freshwater ecosystems that bioaccumulate in food webs, particularly in shellfish, having a great impact on human health. Phycotoxins are mainly leached and absorbed in the small intestine when human consumers accidentally ingest toxic aquatic products contaminated by them. To assess the intestinal uptake and damage of phycotoxins, a typical in vitro model was developed and widely applied using the human colorectal adenocarcinoma Caco-2 cell line. In this review, the application cases were summarized for multiple phycotoxins, including microcystins (MCs), cylindrospermopsins (CYNs), domoic acids (DAs), saxitoxins (STXs), palytoxins (PLTXs), okadaic acids (OAs), pectenotoxins (PTXs) and azaspiracids (AZAs). The results of the previous studies showed that each group of phycotoxins presented different cytotoxicity and mechanisms to Caco-2 cells, and significant discrepancies in the transport of phycotoxin across the Caco-2 cell monolayers. Therefore, this review describes the evaluation assays of the Caco-2 cell monolayer model, illustrates the principles of several primary cytotoxicity evaluation assays, and summarizes the cytotoxicity of each group of phycotoxins to Caco-2 cells line and their cellular transport, and finally proposes the development of multicellular intestinal models for future comprehensive studies on the toxicity and absorption of phycotoxins in the intestine. It will improve the understanding of Caco-2 cell monolayer models in the toxicology studies on phycotoxins and the potentially detrimental effects of microalgal toxins on the human intestine.
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Affiliation(s)
- Jiangbing Qiu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Jingrui Zhang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Aifeng Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China.
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Pradhan B, Ki JS. Phytoplankton Toxins and Their Potential Therapeutic Applications: A Journey toward the Quest for Potent Pharmaceuticals. Mar Drugs 2022; 20:md20040271. [PMID: 35447944 PMCID: PMC9030253 DOI: 10.3390/md20040271] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/12/2022] [Accepted: 04/16/2022] [Indexed: 02/04/2023] Open
Abstract
Phytoplankton are prominent organisms that contain numerous bioactive substances and secondary metabolites, including toxins, which can be valuable to pharmaceutical, nutraceutical, and biotechnological industries. Studies on toxins produced by phytoplankton such as cyanobacteria, diatoms, and dinoflagellates have become more prevalent in recent years and have sparked much interest in this field of research. Because of their richness and complexity, they have great potential as medicinal remedies and biological exploratory probes. Unfortunately, such toxins are still at the preclinical and clinical stages of development. Phytoplankton toxins are harmful to other organisms and are hazardous to animals and human health. However, they may be effective as therapeutic pharmacological agents for numerous disorders, including dyslipidemia, obesity, cancer, diabetes, and hypertension. In this review, we have focused on the properties of different toxins produced by phytoplankton, as well as their beneficial effects and potential biomedical applications. The anticancer properties exhibited by phytoplankton toxins are mainly attributed to their apoptotic effects. As a result, phytoplankton toxins are a promising strategy for avoiding postponement or cancer treatment. Moreover, they also displayed promising applications in other ailments and diseases such as Alzheimer’s disease, diabetes, AIDS, fungal, bacterial, schizophrenia, inflammation, allergy, osteoporosis, asthma, and pain. Preclinical and clinical applications of phytoplankton toxins, as well as future directions of their enhanced nano-formulations for improved clinical efficacy, have also been reviewed.
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Reale O, Huguet A, Fessard V. Co-culture model of Caco-2/HT29-MTX cells: A promising tool for investigation of phycotoxins toxicity on the intestinal barrier. CHEMOSPHERE 2020; 273:128497. [PMID: 34756374 DOI: 10.1016/j.chemosphere.2020.128497] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 09/23/2020] [Accepted: 09/28/2020] [Indexed: 06/13/2023]
Abstract
Most lipophilic phycotoxins have been involved in human intoxications but some of these toxins have never been proven to induce human gastro-intestinal symptoms, although intestinal damage in rodents has been documented. For investigating the in vitro toxicological profile of lipophilic phycotoxins on intestine, the epithelial Caco-2 cell line has been the most commonly used model. Nevertheless, considering the complexity of the intestinal epithelium, in vitro co-cultures integrating enterocyte-like and mucus-secreting cell types are expected to provide more relevant data. In this study, the toxic effects (viability, inflammation, cellular monolayer integrity, modulation of cell type proportion and production of mucus) of four lipophilic phycotoxins (PTX2, YTX, AZA1 and OA) were evaluated in Caco-2/HT29-MTX co-cultured cells. The four toxins induced a reduction of viability from 20% to 50% and affected the monolayer integrity. Our results showed that the HT29-MTX cells population were more sensitive to OA and PTX2 than Caco-2 cells. Among the four phycotoxins, OA induced inflammation (28-fold increase of IL-8 release) and also a slight increase of both mucus production (up-regulation of mucins mRNA expression) and mucus secretion (mucus area and density). For PTX2 we observed an increase of IL-8 release but weaker than OA. Intestinal cell models integrating several cell types can contribute to improve hazard characterization and to describe more accurately the modes of action of phycotoxins.
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Affiliation(s)
- Océane Reale
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35306, France.
| | - Antoine Huguet
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35306, France.
| | - Valérie Fessard
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35306, France.
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Biological Effects of the Azaspiracid-Producing Dinoflagellate Azadinium dexteroporum in Mytilus galloprovincialis from the Mediterranean Sea. Mar Drugs 2019; 17:md17100595. [PMID: 31652521 PMCID: PMC6835248 DOI: 10.3390/md17100595] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/17/2019] [Accepted: 10/18/2019] [Indexed: 12/11/2022] Open
Abstract
Azaspiracids (AZAs) are marine biotoxins including a variety of analogues. Recently, novel AZAs produced by the Mediterranean dinoflagellate Azadinium dexteroporum were discovered (AZA-54, AZA-55, 3-epi-AZA-7, AZA-56, AZA-57 and AZA-58) and their biological effects have not been investigated yet. This study aimed to identify the biological responses (biomarkers) induced in mussels Mytilus galloprovincialis after the bioaccumulation of AZAs from A. dexteroporum. Organisms were fed with A. dexteroporum for 21 days and subsequently subjected to a recovery period (normal diet) of 21 days. Exposed organisms accumulated AZA-54, 3-epi-AZA-7 and AZA-55, predominantly in the digestive gland. Mussels' haemocytes showed inhibition of phagocytosis activity, modulation of the composition of haemocytic subpopulation and damage to lysosomal membranes; the digestive tissue displayed thinned tubule walls, consumption of storage lipids and accumulation of lipofuscin. Slight genotoxic damage was also observed. No clear occurrence of oxidative stress and alteration of nervous activity was detected in AZA-accumulating mussels. Most of the altered parameters returned to control levels after the recovery phase. The toxic effects detected in M. galloprovincialis demonstrate a clear biological impact of the AZAs produced by A. dexteroporum, and could be used as early indicators of contamination associated with the ingestion of seafood.
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Effects of Temperature, Growth Media, and Photoperiod on Growth and Toxin Production of Azadinium spinosum. Mar Drugs 2019; 17:md17090489. [PMID: 31443393 PMCID: PMC6780083 DOI: 10.3390/md17090489] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/13/2019] [Accepted: 08/16/2019] [Indexed: 01/02/2023] Open
Abstract
Azaspiracids (AZAs) are microalgal toxins that can accumulate in shellfish and lead to human intoxications. To facilitate their study and subsequent biomonitoring, purification from microalgae rather than shellfish is preferable; however, challenges remain with respect to maximizing toxin yields. The impacts of temperature, growth media, and photoperiod on cell densities and toxin production in Azadinium spinosum were investigated. Final cell densities were similar at 10 and 18 °C, while toxin cell quotas were higher (~3.5-fold) at 10 °C. A comparison of culture media showed higher cell densities and AZA cell quotas (2.5-5-fold) in f10k compared to f/2 and L1 media. Photoperiod also showed differences, with lower cell densities in the 8:16 L:D treatment, while toxin cell quotas were similar for 12:12 and 8:16 L:D treatments but slightly lower for the 16:8 L:D treatment. AZA1, -2 and -33 were detected during the exponential phase, while some known and new AZAs were only detected once the stationary phase was reached. These compounds were additionally detected in field water samples during an AZA event.
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Kilcoyne J, McCarron P, Twiner MJ, Rise F, Hess P, Wilkins AL, Miles CO. Identification of 21,22-Dehydroazaspiracids in Mussels ( Mytilus edulis) and in Vitro Toxicity of Azaspiracid-26. JOURNAL OF NATURAL PRODUCTS 2018; 81:885-893. [PMID: 29488755 DOI: 10.1021/acs.jnatprod.7b00973] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Azaspiracids (AZAs) are marine biotoxins produced by the genera Azadinium and Amphidoma, pelagic marine dinoflagellates that may accumulate in shellfish resulting in human illness following consumption. The complexity of these toxins has been well documented, with more than 40 structural variants reported that are produced by dinoflagellates, result from metabolism in shellfish, or are extraction artifacts. Approximately 34 μg of a new AZA with MW 823 Da (AZA26 (3)) was isolated from blue mussels ( Mytilus edulis), and its structure determined by MS and NMR spectroscopy. AZA26, possibly a bioconversion product of AZA5, lacked the C-20-C-21 diol present in all AZAs reported thus far and had a 21,22-olefin and a keto group at C-23. Toxicological assessment of 3 using an in vitro model system based on Jurkat T lymphocyte cells showed the potency to be ∼30-fold lower than that of AZA1. The corresponding 21,22-dehydro-23-oxo-analogue of AZA10 (AZA28) and 21,22-dehydro analogues of AZA3, -4, -5, -6, -9, and -10 (AZA25, -48 (4), -60, -27, -49, and -61, respectively) were also identified by HRMS/MS, periodate cleavage reactivity, conversion from known analogues, and NMR (for 4 that was present in a partially purified sample of AZA7).
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Affiliation(s)
- Jane Kilcoyne
- Marine Institute , Rinville, Oranmore , Co. Galway H91 R673 , Ireland
| | - Pearse McCarron
- Measurement Science and Standards , National Research Council Canada , Halifax , NS B3H 3Z1 , Canada
| | - Michael J Twiner
- Department of Emergency Medicine, Detroit Receiving Hospital , Wayne State University , Detroit , Michigan 48202 , United States
| | - Frode Rise
- Department of Chemistry , University of Oslo , N-0315 Oslo , Norway
| | - Philipp Hess
- Ifremer, Laboratoire Phycotoxines , Rue de l'Ile d'Yeu , 44311 Nantes , France
| | - Alistair L Wilkins
- Norwegian Veterinary Institute , P.O. Box 750 Sentrum, 0106 Oslo , Norway
| | - Christopher O Miles
- Measurement Science and Standards , National Research Council Canada , Halifax , NS B3H 3Z1 , Canada
- Norwegian Veterinary Institute , P.O. Box 750 Sentrum, 0106 Oslo , Norway
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Schirone M, Berti M, Visciano P, Chiumiento F, Migliorati G, Tofalo R, Suzzi G, Di Giacinto F, Ferri N. Determination of Lipophilic Marine Biotoxins in Mussels Harvested from the Adriatic Sea by LC-MS/MS. Front Microbiol 2018; 9:152. [PMID: 29487576 PMCID: PMC5816572 DOI: 10.3389/fmicb.2018.00152] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 01/23/2018] [Indexed: 11/13/2022] Open
Abstract
Lipophilic marine biotoxins include okadaic acid, pectenotoxin, yessotoxin and azaspiracid groups. The consumption of contaminated molluscs can lead to acute food poisoning syndromes depending on the exposure level. Regulatory limits have been set by Regulation (European Community, 2004a) No 853/2004 and LC-MS/MS is used as the official analytical method according to Regulation (European Community, 2011) No 15/2011. In this study specimens of mussels (Mytilus galloprovincialis) were collected along the coasts of the central Adriatic Sea during the years 2015–2017 and analyzed by the European harmonized Standard Operating Procedure. The method was validated for linearity, specificity, repeatability and reproducibility and it revealed able to be used for the detection of the lipophilic marine biotoxins. Levels of okadaic acid, pectenotoxin, yessotoxin and its analogs were detected at different concentrations in 148 (37%) out of a total of 400 samples, always below the maximum limits, except for 11 (4.3%) of them that were non-compliant because they exceeded the regulatory limit. Moreover, some samples were exposed to a multi-toxin mixture with regards to okadaic acid, yessotoxin and 1-Homo yessotoxin. Following these results, the aquaculture farms from which the non-compliant samples derived were closed until the analytical data of two consecutive samplings returned favorable. Besides the potential risk of consumption of mussels contaminated by lipophilic marine biotoxins, these marine organisms can be considered as bio-indicators of the contamination status of the marine ecosystem.
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Affiliation(s)
- Maria Schirone
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Miriam Berti
- Biologia delle Acque Interne, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Pierina Visciano
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Francesco Chiumiento
- Bromatologia e Residui negli Alimenti per l'Uomo e gli Animali, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Giacomo Migliorati
- Bromatologia e Residui negli Alimenti per l'Uomo e gli Animali, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Rosanna Tofalo
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Giovanna Suzzi
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Federica Di Giacinto
- Biologia delle Acque Interne, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - Nicola Ferri
- Biologia delle Acque Interne, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
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Assunção J, Guedes AC, Malcata FX. Biotechnological and Pharmacological Applications of Biotoxins and Other Bioactive Molecules from Dinoflagellates. Mar Drugs 2017; 15:E393. [PMID: 29261163 PMCID: PMC5742853 DOI: 10.3390/md15120393] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/12/2017] [Accepted: 12/15/2017] [Indexed: 12/26/2022] Open
Abstract
The long-lasting interest in bioactive molecules (namely toxins) produced by (microalga) dinoflagellates has risen in recent years. Exhibiting wide diversity and complexity, said compounds are well-recognized for their biological features, with great potential for use as pharmaceutical therapies and biological research probes. Unfortunately, provision of those compounds is still far from sufficient, especially in view of an increasing demand for preclinical testing. Despite the difficulties to establish dinoflagellate cultures and obtain reasonable productivities of such compounds, intensive research has permitted a number of advances in the field. This paper accordingly reviews the characteristics of some of the most important biotoxins (and other bioactive substances) produced by dinoflagellates. It also presents and discusses (to some length) the main advances pertaining to dinoflagellate production, from bench to large scale-with an emphasis on material published since the latest review available on the subject. Such advances encompass improvements in nutrient formulation and light supply as major operational conditions; they have permitted adaptation of classical designs, and aided the development of novel configurations for dinoflagellate growth-even though shearing-related issues remain a major challenge.
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Affiliation(s)
- Joana Assunção
- LEPABE-Laboratory of Process Engineering, Environment, Biotechnology and Energy, Rua Dr. Roberto Frias, s/n, P-4200-465 Porto, Portugal.
| | - A Catarina Guedes
- Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos, s/n, P-4450-208 Matosinhos, Portugal.
| | - F Xavier Malcata
- LEPABE-Laboratory of Process Engineering, Environment, Biotechnology and Energy, Rua Dr. Roberto Frias, s/n, P-4200-465 Porto, Portugal.
- Department of Chemical Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, P-4200-465 Porto, Portugal.
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Botana LM, Hess P, Munday R, Nathalie A, DeGrasse SL, Feeley M, Suzuki T, van den Berg M, Fattori V, Garrido Gamarro E, Tritscher A, Nakagawa R, Karunasagar I. Derivation of toxicity equivalency factors for marine biotoxins associated with Bivalve Molluscs. Trends Food Sci Technol 2017. [DOI: 10.1016/j.tifs.2016.09.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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In vivo cardiomyocyte response to YTX- and AZA-1-induced damage: autophagy versus apoptosis. Arch Toxicol 2016; 91:1859-1870. [DOI: 10.1007/s00204-016-1862-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 09/28/2016] [Indexed: 10/20/2022]
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Doerr B, O'Halloran J, O'Brien N, van Pelt F. Investigation of the genotoxic potential of the marine biotoxins azaspiracid 1-3. Toxicon 2016; 121:61-69. [PMID: 27576062 DOI: 10.1016/j.toxicon.2016.08.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 08/19/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
Azaspiracids (AZAs) are the most recently discovered group of biotoxins and are the cause of azaspiracid shellfish poisoning (AZP) in humans. To date over thirty analogues have been identified. However, toxicological studies of AZAs are limited due to the lack of availability of toxins and toxin standards. Most data available are on acute toxicity and there are no data available on genotoxicity of AZAs. This study presents an integrated approach investigating the genotoxic potential of AZA1-3 in cell culture systems using the Comet assay combined with assays to provide information on possible apoptotic processes, cytotoxicity and changes in cell number. Results demonstrate a time and dose dependent increase in DNA fragmentation in most cell lines, indicating a genotoxic effect of AZA1-3. However, a significant reduction in cell number and a clear shift from early to late apoptosis was observed for all analogues in Jurkat T cells and HepG-2 cells; CaCo-2 cells did not show a clear apoptotic profile. Late apoptotic/necrotic cells correlate well with the percentage of tail DNA for all analogues in all three cell lines. All data taken together indicate that AZA1-3 is not genotoxic per se and demonstrate apoptotic/necrotic processes to be involved to some extent in AZAs toxicity. The sensitivities of cell lines and the different potencies of AZA1-3 are in agreement with the literature available. The order of sensitivity for all three AZAs tested in the present study is, in increasing order, CaCo-2 cells < HepG-2 cells < Jurkat T cells. The order of potency of AZA1-3 varies among the cell lines.
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Affiliation(s)
- Barbara Doerr
- Department of Pharmacology and Therapeutics, University College Cork, Cork, Ireland; Environmental Research Institute, University College Cork, Cork, Ireland.
| | - John O'Halloran
- Environmental Research Institute, University College Cork, Cork, Ireland; School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland.
| | - Nora O'Brien
- School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
| | - Frank van Pelt
- Department of Pharmacology and Therapeutics, University College Cork, Cork, Ireland; Environmental Research Institute, University College Cork, Cork, Ireland.
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Kilcoyne J, McCarron P, Hess P, Miles CO. Effects of Heating on Proportions of Azaspiracids 1-10 in Mussels (Mytilus edulis) and Identification of Carboxylated Precursors for Azaspiracids 5, 10, 13, and 15. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:10980-10987. [PMID: 26631586 DOI: 10.1021/acs.jafc.5b04609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Azaspiracids (AZAs) are marine biotoxins that induce human illness following the consumption of contaminated shellfish. European Union regulation stipulates that only raw shellfish are tested, yet shellfish are often cooked prior to consumption. Analysis of raw and heat-treated mussels (Mytilus edulis) naturally contaminated with AZAs revealed significant differences (up to 4.6-fold) in AZA1-3 (1-3) and 6 (6) values due to heat-induced chemical conversions. Consistent with previous studies, high levels of 3 and 6 were detected in some samples that were otherwise below the limit of quantitation before heating. Relative to 1, in heat-treated mussels the average (n = 40) levels of 3 (range, 11-502%) and 6 (range, 3-170%) were 62 and 31%, respectively. AZA4 (4) (range, <1-27%), AZA5 (5) (range, 1-21%), and AZA8 (8) (range, 1-27%) were each ∼5%, whereas AZA7 (7), AZA9 (9), and AZA10 (10) (range, <1-8%) were each under 1.5%. Levels of 5, 10, AZA13 (13), and AZA15 (15) increased after heating, leading to the identification of novel carboxylated AZA precursors in raw shellfish extracts, which were shown by deuterium labeling to be precursors for 5, 10, 13, and 15.
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Affiliation(s)
- Jane Kilcoyne
- Marine Institute , Rinville, Oranmore, Co. Galway, Ireland
| | - Pearse McCarron
- Measurement Science and Standards, National Research Council Canada , Halifax, Nova Scotia B3H 3Z1, Canada
| | - Philipp Hess
- Laboratoire Phycotoxines, Ifremer , Rue de l'Ile d'Yeu, 44311 Nantes, France
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15
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Hjørnevik LV, Frøyset AK, Grønset TA, Rungruangsak-Torrissen K, Fladmark KE. Algal Toxin Azaspiracid-1 Induces Early Neuronal Differentiation and Alters Peripherin Isoform Stoichiometry. Mar Drugs 2015; 13:7390-402. [PMID: 26694421 PMCID: PMC4699245 DOI: 10.3390/md13127072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 11/23/2015] [Accepted: 12/02/2015] [Indexed: 12/13/2022] Open
Abstract
Azaspiracid-1 is an algal toxin that accumulates in edible mussels, and ingestion may result in human illness as manifested by vomiting and diarrhoea. When injected into mice, it causes neurotoxicological symptoms and death. Although it is well known that azaspiracid-1 is toxic to most cells and cell lines, little is known about its biological target(s). A rat PC12 cell line, commonly used as a model for the peripheral nervous system, was used to study the neurotoxicological effects of azaspiracid-1. Azaspiracid-1 induced differentiation-related morphological changes followed by a latter cell death. The differentiated phenotype showed peripherin-labelled neurite-like processes simultaneously as a specific isoform of peripherin was down-regulated. The precise mechanism behind this down-regulation remains uncertain. However, this study provides new insights into the neurological effects of azaspiracid-1 and into the biological significance of specific isoforms of peripherin.
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Affiliation(s)
- Linda V Hjørnevik
- Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway.
| | - Ann K Frøyset
- Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway.
| | - Toril A Grønset
- Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway.
| | | | - Kari E Fladmark
- Department of Molecular Biology, University of Bergen, Thormøhlensgate 55, N-5008 Bergen, Norway.
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16
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Berdalet E, Fleming LE, Gowen R, Davidson K, Hess P, Backer LC, Moore SK, Hoagland P, Enevoldsen H. Marine harmful algal blooms, human health and wellbeing: challenges and opportunities in the 21st century. JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM. MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM 2015; 2015:10.1017/S0025315415001733. [PMID: 26692586 PMCID: PMC4676275 DOI: 10.1017/s0025315415001733] [Citation(s) in RCA: 175] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Microalgal blooms are a natural part of the seasonal cycle of photosynthetic organisms in marine ecosystems. They are key components of the structure and dynamics of the oceans and thus sustain the benefits that humans obtain from these aquatic environments. However, some microalgal blooms can cause harm to humans and other organisms. These harmful algal blooms (HABs) have direct impacts on human health and negative influences on human wellbeing, mainly through their consequences to coastal ecosystem services (fisheries, tourism and recreation) and other marine organisms and environments. HABs are natural phenomena, but these events can be favoured by anthropogenic pressures in coastal areas. Global warming and associated changes in the oceans could affect HAB occurrences and toxicity as well, although forecasting the possible trends is still speculative and requires intensive multidisciplinary research. At the beginning of the 21st century, with expanding human populations, particularly in coastal and developing countries, mitigating HABs impacts on human health and wellbeing is becoming a more pressing public health need. The available tools to address this global challenge include maintaining intensive, multidisciplinary and collaborative scientific research, and strengthening the coordination with stakeholders, policymakers and the general public. Here we provide an overview of different aspects of the HABs phenomena, an important element of the intrinsic links between oceans and human health and wellbeing.
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Affiliation(s)
- Elisa Berdalet
- Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta, 37-49, 08003 Barcelona, Catalonia, Spain
| | - Lora E Fleming
- European Centre for Environment and Human Health, University of Exeter Medical School, Truro, Cornwall TR1 3HD, UK
| | - Richard Gowen
- Fisheries and Aquatic Ecosystems Branch, Agri-Food and Biosciences Institute, Newforge Lane, Belfast BT9 5PX, UK ; Scottish Association for Marine Science (SAMS), Scottish Marine Institute, Oban, PA37 1QA, UK
| | - Keith Davidson
- Scottish Association for Marine Science (SAMS), Scottish Marine Institute, Oban, PA37 1QA, UK
| | - Philipp Hess
- Ifremer, Laboratoire Phycotoxines, BP21105, Rue de l'lle d'Yeu, 44311 Nantes Cedex 03, France
| | - Lorraine C Backer
- National Center for Environmental Health, 4770 Buford Highway NE, MS F-60, Chamblee, GA 30341
| | - Stephanie K Moore
- University Corporation for Atmospheric Research, Joint Office for Science Support. Visiting Scientist at Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd E, Seattle, WA 98112, USA
| | - Porter Hoagland
- Marine Policy Center, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Henrik Enevoldsen
- Intergovernmental Oceanographic Commission of UNESCO, IOC Science and Communication Centre on Harmful Algae, University of Copenhagen, Universitetsparken 4, 2100 Copenhagen Ø, Denmark
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17
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Kilcoyne J, Twiner MJ, McCarron P, Crain S, Giddings SD, Foley B, Rise F, Hess P, Wilkins AL, Miles CO. Structure Elucidation, Relative LC-MS Response and In Vitro Toxicity of Azaspiracids 7-10 Isolated from Mussels (Mytilus edulis). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:5083-5091. [PMID: 25909151 DOI: 10.1021/acs.jafc.5b01320] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Azaspiracids (AZAs) are marine biotoxins produced by dinoflagellates that can accumulate in shellfish, which if consumed can lead to poisoning events. AZA7-10, 7-10, were isolated from shellfish and their structures, previously proposed on the basis of only LC-MS/MS data, were confirmed by NMR spectroscopy. Purified AZA4-6, 4-6, and 7-10 were accurately quantitated by qNMR and used to assay cytotoxicity with Jurkat T lymphocyte cells for the first time. LC-MS(MS) molar response studies performed using isocratic and gradient elution in both selected ion monitoring and selected reaction monitoring modes showed that responses for the analogues ranged from 0.3 to 1.2 relative to AZA1, 1. All AZA analogues tested were cytotoxic to Jurkat T lymphocyte cells in a time- and concentration-dependent manner; however, there were distinct differences in their EC50 values, with the potencies for each analogue being: AZA6 > AZA8 > AZA1 > AZA4 ≈ AZA9 > AZA5 ≈ AZA10. This data contributes to the understanding of the structure-activity relationships of AZAs.
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Affiliation(s)
- Jane Kilcoyne
- †Marine Institute, Rinville, Oranmore, County Galway, Ireland
- ‡School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland
| | - Michael J Twiner
- §School of Medicine, Wayne State University, Detroit, Michigan 48202, United States
| | - Pearse McCarron
- ⊥Measurement Science and Standards, Biotoxin Metrology, National Research Council Canada, 1411 Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada
| | - Sheila Crain
- ⊥Measurement Science and Standards, Biotoxin Metrology, National Research Council Canada, 1411 Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada
| | - Sabrina D Giddings
- ⊥Measurement Science and Standards, Biotoxin Metrology, National Research Council Canada, 1411 Oxford Street, Halifax, Nova Scotia B3H 3Z1, Canada
| | - Barry Foley
- ‡School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland
| | - Frode Rise
- ∥Department of Chemistry, University of Oslo, N-0315 Oslo, Norway
| | - Philipp Hess
- ▽Ifremer, Laboratoire Phycotoxines, Rue de l'Ile d'Yeu, 44311 Nantes, France
| | | | - Christopher O Miles
- ○Norwegian Veterinary Institute, P.O. Box 750 Sentrum, 0106 Oslo Norway
- #Department of Pharmaceutical Chemistry, School of Pharmacy, University of Oslo, P.O. Box 1068 Blindern, N-0316 Oslo Norway
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O'Driscoll D, Škrabáková Z, James KJ. Confirmation of extensive natural distribution of azaspiracids in the tissue compartments of mussels (Mytilus edulis). Toxicon 2014; 92:123-8. [DOI: 10.1016/j.toxicon.2014.10.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 10/24/2022]
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19
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Kilcoyne J, Nulty C, Jauffrais T, McCarron P, Herve F, Foley B, Rise F, Crain S, Wilkins AL, Twiner MJ, Hess P, Miles CO. Isolation, structure elucidation, relative LC-MS response, and in vitro toxicity of azaspiracids from the dinoflagellate Azadinium spinosum. JOURNAL OF NATURAL PRODUCTS 2014; 77:2465-2474. [PMID: 25356854 DOI: 10.1021/np500555k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We identified three new azaspiracids (AZAs) with molecular weights of 715, 815, and 829 (AZA33 (3), AZA34 (4), and AZA35, respectively) in mussels, seawater, and Azadinium spinosum culture. Approximately 700 μg of 3 and 250 μg of 4 were isolated from a bulk culture of A. spinosum, and their structures determined by MS and NMR spectroscopy. These compounds differ significantly at the carboxyl end of the molecule from known AZA analogues and therefore provide valuable information on structure-activity relationships. Initial toxicological assessment was performed using an in vitro model system based on Jurkat T lymphocyte cytotoxicity, and the potencies of 3 and 4 were found to be 0.22- and 5.5-fold that of AZA1 (1), respectively. Thus, major changes in the carboxyl end of 1 resulted in significant changes in toxicity. In mussel extracts, 3 was detected at low levels, whereas 4 and AZA35 were detected only at extremely low levels or not at all. The structures of 3 and 4 are consistent with AZAs being biosynthetically assembled from the amino end.
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Affiliation(s)
- Jane Kilcoyne
- Marine Institute , Rinville, Oranmore, Galway, Ireland
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20
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Ferreiro SF, Vilariño N, Louzao MC, Nicolaou KC, Frederick MO, Botana LM. In vitro chronic effects on hERG channel caused by the marine biotoxin azaspiracid-2. Toxicon 2014; 91:69-75. [PMID: 25286396 DOI: 10.1016/j.toxicon.2014.09.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/16/2014] [Accepted: 09/25/2014] [Indexed: 11/27/2022]
Abstract
Azaspiracids (AZAs) are marine biotoxins produced by the dinoflagellate Azadinium spinosum that accumulate in many shellfish species. Azaspiracid poisoning caused by AZA-contaminated seafood consumption is primarily manifested by diarrhea in humans. To protect human health, AZA-1, AZA-2 and AZA-3 content in seafood has been regulated by food safety authorities in many countries. Recently AZAs have been reported as a low/moderate hERG channel blockers. Furthermore AZA-2 has been related to arrhythmia appearance in rats, suggesting potential heart toxicity. In this study AZA-2 in vitro effects on hERG channel after chronic exposure are analyzed to further explore potential cardiotoxicity. The amount of hERG channel in the plasma membrane, hERG channel trafficking and hERG currents were evaluated up to 12 h of toxin exposure. In these conditions AZA-2 caused an increase of hERG levels in the plasma membrane, probably related to hERG retrograde trafficking impairment. Although this alteration did not translate into an increase of hERG channel-related current, more studies will be necessary to understand its mechanism and to know what consequences could have in vivo. These findings suggest that azaspiracids might have chronic cardiotoxicity related to hERG channel trafficking and they should not be overlooked when evaluating the threat to human health.
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Affiliation(s)
- Sara F Ferreiro
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain
| | - Natalia Vilariño
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain.
| | - M Carmen Louzao
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain
| | - K C Nicolaou
- Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA; Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Michael O Frederick
- Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Luis M Botana
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain.
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21
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Kilcoyne J, McCarron P, Twiner MJ, Nulty C, Crain S, Quilliam MA, Rise F, Wilkins AL, Miles CO. Epimers of azaspiracids: Isolation, structural elucidation, relative LC-MS response, and in vitro toxicity of 37-epi-azaspiracid-1. Chem Res Toxicol 2014; 27:587-600. [PMID: 24506502 DOI: 10.1021/tx400434b] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Since azaspiracid-1 (AZA1) was identified in 1998, the number of AZA analogues has increased to over 30. The development of an LC-MS method using a neutral mobile phase led to the discovery of isomers of AZA1, AZA2, and AZA3, present at ~2-16% of the parent analogues in phytoplankton and shellfish samples. Under acidic mobile phase conditions, isomers and their parents are not separated. Stability studies showed that these isomers were spontaneous epimerization products whose formation is accelerated with the application of heat. The AZA1 isomer was isolated from contaminated shellfish and identified as 37-epi-AZA1 by nuclear magnetic resonance (NMR) spectroscopy and chemical analyses. Similar analysis indicated that the isomers of AZA2 and AZA3 corresponded to 37-epi-AZA2 and 37-epi-AZA3, respectively. The 37-epimers were found to exist in equilibrium with the parent compounds in solution. 37-epi-AZA1 was quantitated by NMR, and relative molar response studies were performed to determine the potential differences in LC-MS response of AZA1 and 37-epi-AZA1. Toxicological effects were determined using Jurkat T lymphocyte cells as an in vitro cell model. Cytotoxicity experiments employing a metabolically based dye (i.e., MTS) indicated that 37-epi-AZA1 elicited a lethal response that was both concentration- and time-dependent, with EC50 values in the subnanomolar range. On the basis of EC50 comparisons, 37-epi-AZA1 was 5.1-fold more potent than AZA1. This data suggests that the presence of these epimers in seafood products should be considered in the analysis of AZAs for regulatory purposes.
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Affiliation(s)
- Jane Kilcoyne
- Marine Institute, Rinville, Oranmore, County, Galway, Ireland
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22
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Twiner MJ, Doucette GJ, Rasky A, Huang XP, Roth BL, Sanguinetti MC. Marine algal toxin azaspiracid is an open-state blocker of hERG potassium channels. Chem Res Toxicol 2012; 25:1975-84. [PMID: 22856456 DOI: 10.1021/tx300283t] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Azaspiracids (AZA) are polyether marine dinoflagellate toxins that accumulate in shellfish and represent an emerging human health risk. Although human exposure is primarily manifested by severe and protracted diarrhea, this toxin class has been shown to be highly cytotoxic, a teratogen to developing fish, and a possible carcinogen in mice. Until now, AZA's molecular target has not yet been determined. Using three independent methods (voltage clamp, channel binding assay, and thallium flux assay), we have for the first time demonstrated that AZA1, AZA2, and AZA3 each bind to and block the hERG (human ether-à-go-go related gene) potassium channel heterologously expressed in HEK-293 mammalian cells. Inhibition of K(+) current for each AZA analogue was concentration-dependent (IC(50) value range: 0.64-0.84 μM). The mechanism of hERG channel inhibition by AZA1 was investigated further in Xenopus oocytes where it was shown to be an open-state-dependent blocker and, using mutant channels, to interact with F656 but not with Y652 within the S6 transmembrane domain that forms the channel's central pore. AZA1, AZA2, and AZA3 were each shown to inhibit [(3)H]dofetilide binding to the hERG channel and thallium ion flux through the channel (IC(50) value range: 2.1-6.6 μM). AZA1 did not block the K(+) current of the closely related EAG1 channel. Collectively, these data suggest that the AZAs physically block the K(+) conductance pathway of hERG1 channels by occluding the cytoplasmic mouth of the open pore. Although the concentrations necessary to block hERG channels are relatively high, AZA-induced blockage may prove to contribute to the toxicological properties of the AZAs.
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Affiliation(s)
- Michael J Twiner
- Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI 48128, USA.
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