Occurrence and sequestration of toxins in food chains

History and Toxinology of Palytoxins

Palytoxins are a group of highly potent and structurally complex marine toxins that rank among some of the most toxic substances known to science. Palytoxins are naturally synthesized by a variety of marine organisms, including Palythoa zoanthids, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria, and are widely distributed in tropical and temperate regions where they can bioaccumulate in marine life. The evolution of research on palytoxins has been an intricate exchange between interdisciplinary fields, drawing insights from chemistry, biology, medicine, and environmental science in efforts to better understand and mitigate the health risks associated with this family of toxins. In this review, we begin with a brief history covering the discovery of this group of toxins and the events that led to its isolation. We then focus on the chemical structure of these compounds and their proposed mechanism of action. Finally, we review in vitro, ex vivo, and in vivo studies related to their toxicity, with the aim to provide a broad overview of the current knowledge on palytoxin toxinology.

Molecular game theory for a toxin-dominant food chain model

Animal toxins that are used to subdue prey and deter predators act as the key drivers in natural food chains and ecosystems. However, the predators of venomous animals may exploit feeding adaptation strategies to overcome toxins their prey produce. Much remains unknown about the genetic and molecular game process in the toxin-dominant food chain model. Here, we show an evolutionary strategy in different trophic levels of scorpion-eating amphibians, scorpions and insects, representing each predation relationship in habitats dominated by the paralytic toxins of scorpions. For scorpions preying on insects, we found that the scorpion α-toxins irreversibly activate the skeletal muscle sodium channel of their prey (insect, BgNa_V1) through a membrane delivery mechanism and an efficient binding with the Asp/Lys-Tyr motif of BgNa_V1. However, in the predatory game between frogs and scorpions, with a single point mutation (Lys to Glu) in this motif of the frog's skeletal muscle sodium channel (fNa_V1.4), fNa_V1.4 breaks this interaction and diminishes muscular toxicity to the frog; thus, frogs can regularly prey on scorpions without showing paralysis. Interestingly, this molecular strategy also has been employed by some other scorpion-eating amphibians, especially anurans. In contrast to these amphibians, the Asp/Lys-Tyr motifs are structurally and functionally conserved in other animals that do not prey on scorpions. Together, our findings elucidate the protein-protein interacting mechanism of a toxin-dominant predator-prey system, implying the evolutionary game theory at a molecular level.

Bioremediation of waste under ocean acidification: Reviewing the role of Mytilus edulis

Waste bioremediation is a key regulating ecosystem service, removing wastes from ecosystems through storage, burial and recycling. The bivalve Mytilus edulis is an important contributor to this service, and is used in managing eutrophic waters. Studies show that they are affected by changes in pH due to ocean acidification, reducing their growth. This is forecasted to lead to reductions in M. edulis biomass of up to 50% by 2100. Growth reduction will negatively affect the filtering capacity of each individual, potentially leading to a decrease in bioremediation of waste. This paper critically reviews the current state of knowledge of bioremediation of waste carried out by M. edulis, and the current knowledge of the resultant effect of ocean acidification on this key service. We show that the effects of ocean acidification on waste bioremediation could be a major issue and pave the way for empirical studies of the topic.

Airborne Microalgae: Insights, Opportunities, and Challenges

Airborne dispersal of microalgae has largely been a blind spot in environmental biological studies because of their low concentration in the atmosphere and the technical limitations in investigating microalgae from air samples. Recent studies show that airborne microalgae can survive air transportation and interact with the environment, possibly influencing their deposition rates. This minireview presents a summary of these studies and traces the possible route, step by step, from established ecosystems to new habitats through air transportation over a variety of geographic scales. Emission, transportation, deposition, and adaptation to atmospheric stress are discussed, as well as the consequences of their dispersal on health and the environment and state-of-the-art techniques to detect and model airborne microalga dispersal. More-detailed studies on the microalga atmospheric cycle, including, for instance, ice nucleation activity and transport simulations, are crucial for improving our understanding of microalga ecology, identifying microalga interactions with the environment, and preventing unwanted contamination events or invasions.

Assessing health in agriculture--towards a common research framework for soils, plants, animals, humans and ecosystems

In agriculture and food systems, health-related research includes a vast diversity of topics. Nutritional, toxicological, pharmacological, epidemiological, behavioural, sociological, economic and political methods are used to study health in the five domains of soils, plants, livestock, humans and ecosystems. An idea developed in the early founding days of organic agriculture stated that the health of all domains is one and indivisible. Here we show that recent research reveals the existence and complex nature of such health links among domains. However, studies of health aspects in agriculture are often separated by disciplinary boundaries. This restrains the understanding of health in agricultural systems. Therefore we explore the opportunities and limitations of bringing perspectives together from the different domains. We review current approaches to define and assess health in agricultural contexts, comparing the state of the art of commonly used approaches and bringing together the presently disconnected debates in soil science, plant science, veterinary science and human medicine. Based on a qualitative literature analysis, we suggest that many health criteria fall into two paradigms: (1) the Growth Paradigm, where terms are primarily oriented towards continued growth; (2) the Boundary Paradigm, where terms focus on maintaining or coming back to a status quo, recognising system boundaries. Scientific health assessments in agricultural and food systems need to be explicit in terms of their position on the continuum between Growth Paradigm and Boundary Paradigm. Finally, we identify areas and concepts for a future direction of health assessment and research in agricultural and food systems.

Complex toxin profile of French Mediterranean Ostreopsis cf. ovata strains, seafood accumulation and ovatoxins prepurification

Ostreopsis cf. ovata produces palytoxin analogues including ovatoxins (OVTXs) and a putative palytoxin (p-PLTX), which can accumulate in marine organisms and may possibly lead to food intoxication. However, purified ovatoxins are not widely available and their toxicities are still unknown. The aim of this study was to improve understanding of the ecophysiology of Ostreopsis cf. ovata and its toxin production as well as to optimize the purification process for ovatoxin. During Ostreopsis blooms in 2011 and 2012 in Villefranche-sur-Mer (France, NW Mediterranean Sea), microalgae epiphytic cells and marine organisms were collected and analyzed both by LC-MS/MS and hemolysis assay. Results obtained with these two methods were comparable, suggesting ovatoxins have hemolytic properties. An average of 223 μg·kg-1 of palytoxin equivalent of whole flesh was found, thus exceeding the threshold of 30 μg·kg-1 in shellfish recommended by the European Food Safety Authority (EFSA). Ostreopsis cells showed the same toxin profile both in situ and in laboratory culture, with ovatoxin-a (OVTX-a) being the most abundant analogue (~50%), followed by OVTX-b (~15%), p-PLTX (12%), OVTX-d (8%), OVTX-c (5%) and OVTX-e (4%). Ostreopsis cf. ovata produced up to 2 g of biomass per L of culture, with a maximum concentration of 300 pg PLTX equivalent cell-1. Thus, an approximate amount of 10 mg of PLTX-group toxins may be produced with 10 L of this strain. Toxin extracts obtained from collected biomass were purified using different techniques such as liquid-liquid partition or size exclusion. Among these methods, open-column chromatography with Sephadex LH20 phase yielded the best results with a cleanup efficiency of 93% and recovery of about 85%, representing an increase of toxin percentage by 13 fold. Hence, this purification step should be incorporated into future isolation exercises.

Cephalopods as vectors of harmful algal bloom toxins in marine food webs

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.

Toxicity of palytoxin after repeated oral exposure in mice and in vitro effects on cardiomyocytes

Palytoxin (PLTX) is a highly toxic hydrophilic polyether detected in several edible marine organisms from intra-tropical areas, where seafood poisoning were reported. Symptoms usually start with gastro-intestinal malaise, often accompanied by myalgia, muscular cramps, dyspnea and, sometimes, arrhythmias. Monitoring programs in the Mediterranean Sea have detected PLTX-like molecules in edible mollusks and echinoderms. Despite the potential exposure of the human population and its high toxic potential, the toxicological profile of the molecule is still an issue. Thus, the effects of repeated oral administration of PLTX in mice were investigated. Seven days of PLTX administration caused lethality and toxic effects at doses ≥ 30 μg/kg/day. A NOAEL was estimated equal to 3 μg/kg/day, indicating a quite steep dose-response curve. This value, due to the limited number of animal tested, is provisional, although represents a sound basis for further testing. Macroscopic alterations at gastrointestinal level (gastric ulcers and intestinal fluid accumulation) were observed in mice dead during the treatment period. Histological analysis highlighted severe inflammation, locally associated with necrosis, at pulmonary level, as well as hyper-eosinophilia and fiber separation in myocardium. A cardiac damage was supported by the in vitro effect of the toxin on cardiomyocytes, indicating a severe and irreversible impairment of their electrical properties: electrophysiological recordings detected a progressive cell depolarization, arrest of action potentials and beating.

Community ecology and the evolution of molecules of keystone significance

Molecules of keystone significance are vital in structuring ecological communities. Select bioactive compounds can cause disproportionately large effects by connecting such seemingly disparate processes as microbial loop dynamics and apex predation. Here, we develop a general theory and propose mechanisms that could lead to the evolution of keystone molecules. Introduced into a respective community by one, or only a few, autotrophic or microbial species, these compounds often originate as chemical defenses. When co-opted by resistant consumer species, however, they are used either in chemical defense against higher-order predators or as chemosensory cues that elicit courtship and mating, alarm, and predatory search. Requisite to these multifunctional properties, biosynthetic capacity evolves along with mechanisms for resistance and/or toxin storage in primary producers. Subsequently, consumers acquire resistances or tolerances, and the toxins are transferred through food webs via trophic interactions. In consumers, mechanisms eventually evolve for recognizing toxins as feeding cues and, ultimately, as signals or pheromones in chemical communication within or between species. One, or a few, active compounds can thus mediate a vast array of physiological traits, expressed differentially across many species in a given community. Through convergent evolution, molecules of keystone significance provide critical information to phylogenetically diverse species, initiate major trophic cascades, and structure communities within terrestrial, freshwater, coastal-ocean and open-ocean habitats.

Ovatoxin-a and palytoxin accumulation in seafood in relation to Ostreopsis cf. ovata blooms on the French Mediterranean coast

Dinoflagellates of the genus Ostreopsis are known to cause (often fatal) food poisoning in tropical coastal areas following the accumulation of palytoxin (PLTX) and/or its analogues (PLTX group) in crabs, sea urchins or fish. Ostreopsis spp. occurrence is presently increasing in the northern to north western Mediterranean Sea (Italy, Spain, Greece and France), probably in response to climate change. In France, Ostreopsis. cf. ovata has been associated with toxic events during summer 2006, at Morgiret, off the coast of Marseille, and a specific monitoring has been designed and implemented since 2007. Results from 2008 and 2009 showed that there is a real danger of human poisoning, as these demonstrated bioaccumulation of the PLTX group (PLTX and ovatoxin-a) in both filter-feeding bivalve molluscs (mussels) and herbivorous echinoderms (sea urchins). The total content accumulated in urchins reached 450 µg PLTX eq/kg total flesh (summer 2008). In mussels, the maximum was 230 µg eq PLTX/kg (summer 2009) compared with a maximum of 360 µg found in sea urchins during the same period at the same site. This publication brings together scientific knowledge obtained about the summer development of Ostreopsis spp. in France during 2007, 2008 and 2009.

Case definitions for human poisonings postulated to palytoxins exposure

A series of case reports and anecdotal references describe the adverse effects on human health ascribed to the marine toxin palytoxin (PLTX) after different exposure routes. They include poisonings after oral intake of contaminated seafood, but also inhalation and cutaneous/systemic exposures after direct contact with aerosolized seawater during Ostreopsis blooms and/or through maintaining aquaria containing cnidarian zoanthids. The symptoms commonly recorded during PLTX intoxication are general malaise and weakness, associated with myalgia, respiratory effects, impairment of the neuromuscular apparatus and abnormalities in cardiac function. Systemic symptoms are often recorded together with local damages whose intensity varies according to the route and length of exposure. Gastrointestinal malaise or respiratory distress is common for oral and inhalational exposure, respectively. In addition, irritant properties of PLTX probably account for the inflammatory reactions typical of cutaneous and inhalational contact. Unfortunately, the toxin identification and/or quantification are often incomplete or missing and cases of poisoning are indirectly ascribed to PLTXs, according only to symptoms, anamnesis and environmental/epidemiological investigations (i.e. zoanthid handling or ingestion of particular seafood). Based on the available literature, we suggest a "case definition of PLTX poisonings" according to the main exposure routes, and, we propose the main symptoms to be checked, as well as, hemato-clinical analysis to be carried out. We also suggest the performance of specific analyses both on biological specimens of patients, as well as, on the contaminated materials responsible for the poisoning. A standardized protocol for data collection could provide a more rapid and reliable diagnosis of palytoxin-poisoning, but also the collection of necessary data for the risk assessment for this family of toxins.

Occurrence of palytoxin-group toxins in seafood and future strategies to complement the present state of the art

Palytoxin (PlTX) and palytoxin-like (PlTX-like) compounds in seafood have been raising scientific concern in the last years. The constant increase in record numbers of the causative dinoflagellates of the genus Ostreopsis together with the large spatial expansion of this genus has led to intensification of research towards optimization of methods for determination of PlTX presence and toxicity. In this context, identification of seafood species which could possibly contain PlTXs constitutes an important issue for public health protection. In the present paper, worldwide occurrence of PlTX-like compounds in seafood is reviewed, while potential future strategies are discussed. PlTX has been reported to be present in several species of fish, crustaceans, molluscs and echinoderms. In one occasion, PlTX has been identified in freshwater puffer fish whereas all other records of PlTXs refer to marine species and have been recorded in latitudes approximately between 43°N and 15°S. PlTX determination in seafood has relied on different methodologies (mainly LC-MS, mouse bioassay and hemolysis neutralization assay) that have evolved over time. Future recommendations include systematic screening of PlTX in those species and areas where PlTX has already been recorded implementing updated methodologies.

Palytoxin and analogs: biological and ecological effects

Palytoxin (PTX) is a potent marine toxin that was originally found in soft corals from tropical areas of the Pacific Ocean. Soon after, its occurrence was observed in numerous other marine organisms from the same ecological region. More recently, several analogs of PTX were discovered, remarkably all from species of the dinoflagellate genus Ostreopsis. Since these dinoflagellates are also found in other tropical and even in temperate regions, the formerly unsuspected broad distribution of these toxins was revealed. Toxicological studies with these compounds shows repeatedly low LD50 values in different mammals, revealing an acute toxic effect on several organs, as demonstrated by different routes of exposure. Bioassays tested for some marine invertebrates and evidences from environmental populations exposed to the toxins also give indications of the high impact that these compounds may have on natural food webs. The recognition of its wide distribution coupled with the poisoning effects that these toxins can have on animals and especially on humans have concerned the scientific community. In this paper, we review the current knowledge on the effects of PTX and its analogs on different organisms, exposing the impact that these toxins may have in coastal ecosystems.

Extracellular signal regulated kinase 5 mediates signals triggered by the novel tumor promoter palytoxin

Palytoxin is classified as a non-12-O-tetradecanoylphorbol-13-acetate (TPA)-type skin tumor because it does not bind to or activate protein kinase C. Palytoxin is thus a novel tool for investigating alternative signaling pathways that may affect carcinogenesis. We previously showed that palytoxin activates three major members of the mitogen activated protein kinase (MAPK) family, extracellular signal regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38. Here we report that palytoxin also activates another MAPK family member, called ERK5, in HeLa cells and in keratinocytes derived from initiated mouse skin (308 cells). By contrast, TPA does not activate ERK5 in these cell lines. The major cell surface receptor for palytoxin is the Na+,K+-ATPase. Accordingly, ouabain blocked the ability of palytoxin to activate ERK5. Ouabain alone did not activate ERK5. ERK5 thus represents a divergence in the signaling pathways activated by these two agents that bind to the Na+,K+-ATPase. Cycloheximide, okadaic acid, and sodium orthovanadate did not mimic the effect of palytoxin on ERK5. These results indicate that the stimulation of ERK5 by palytoxin is not simply due to inhibition of protein synthesis or inhibition of serine/threonine or tyrosine phosphatases. Therefore, the mechanism by which palytoxin activates ERK5 differs from that by which it activates ERK1/2, JNK, and p38. Finally, studies that used pharmacological inhibitors and shRNA to block ERK5 action indicate that ERK5 contributes to palytoxin-stimulated c-Fos gene expression. These results suggest that ERK5 can act as an alternative mediator for transmitting diverse tumor promoter-stimulated signals.

Detection of hemolytic bacteria from Palythoa caribaeorum (Cnidaria, Zoantharia) using a novel palytoxin-screening assay

Palytoxin (PTX), one of the most potent and chemically complex marine toxins, is predominantly found in zoanthid corals and sporadically in dinoflagellates. Its biosynthesis and metabolic pathways are largely unknown. However, the widespread occurrence of the toxin in phylogenetically distinct marine organisms is consistent with its production by microorganisms and subsequent accumulation in the food chain. To investigate a possible microbial origin, bacteria from two zoanthid corals (Palythoa caribaeorum, Zoanthus pulchellus) and one sponge (Neofibularia nolitangere) were isolated. More than 250 bacteria were screened for hemolysis using a newly developed PTX-screening assay of which 7% showed PTX-like hemolytic activity. 16S rRNA gene sequencing revealed that these bacterial isolates belonged to strains of Bacillus cereus group (n = 11) as well as the genera Brevibacterium (n = 4) and Acinetobacter (n = 2). The results indicate the presence of Na+/K+-ATPase toxins and possibly PTX in hemolytic bacteria from P. caribaeorum.

Human risk associated with palytoxin exposure

Palytoxin (PTX) was first isolated from the zoanthid Palythoa toxica. Evaluation of PTX toxicity using various animal models determined that PTX was extremely potent through intravenous, intraperitoneal, and intratracheal exposure. PTX was less potent by direct intragastric exposure. PTX also caused significant, non-lethal effects through dermal and ocular exposure. PTX and PTX-like compounds have now been found in additional zoanthid species, red alga, a sea anemone, and several dinoflagellates. PTXs are found throughout certain reef associated food webs, including in fish and crabs responsible for human illness and death. Many of the organisms found to contain PTXs in the environment are also sold in the home aquarium trade, and recent evidence suggests poisonings have occurred through exposure to these organisms. Due to co-occurrence with other seafood toxins, such as ciguatoxins, saxitoxins, and tetrodotoxin, it has been difficult to assess the true risk of PTX poisoning through seafood consumption in humans, but limited cases have been well documented, some involving human fatalities. Recent evidence also suggests that humans are negatively impacted through PTX exposure by inhalation and dermal routes. Continued research into the distribution and occurrence of PTX and PTX-like compounds both in seafood and marine organisms sold in the aquarium trade appears warranted.

Marine toxins and the cytoskeleton: a new view of palytoxin toxicity

Palytoxin is a marine toxin first isolated from zoanthids (genus Palythoa), even though dinoflagellates of the genus Ostreopsis are the most probable origin of the toxin. Ostreopsis has a wide distribution in tropical and subtropical areas, but recently these dinoflagellates have also started to appear in the Mediterranean Sea. Two of the most remarkable properties of palytoxin are the large and complex structure (with different analogs, such as ostreocin-D or ovatoxin-a) and the extreme acute animal toxicity. The Na(+)/K(+)-ATPase has been proposed as receptor for palytoxin. The marine toxin is known to act on the Na(+) pump and elicit an increase in Na(+) permeability, which leads to depolarization and a secondary Ca(2+) influx, interfering with some functions of cells. Studies on the cellular cytoskeleton have revealed that the signaling cascade triggered by palytoxin leads to actin filament system distortion. The activity of palytoxin on the actin cytoskeleton is only partially associated with the cytosolic Ca(2+) changes; therefore, this ion represents an important factor in altering this structure, but it is not the only cause. The goal of the present minireview is to compile the findings reported to date about: (a) how palytoxin and analogs are able to modify the actin cytoskeleton within different cellular models; and (b) what signaling mechanisms could be involved in the modulation of cytoskeletal dynamics by palytoxin.

Influence of Palythoa caribaeorum (Anthozoa, Cnidaria) zonation on site-attached reef fishes

This work aimed to test the influence of Palythoa caribeorum, a widely distributed zoanthid in the Atlantic, on site-attached reef fish in a subtropical rocky shore. Density, richness and vertical distribution of reef fish inside (ID) and outside (OD) previously chosen P. caribaeorum dominance patches were compared through stationary visual censuses along three different periods. Fishes were grouped in different trophic guilds to evidence differences in resources uses in both treatments. A complexity index was estimated by the chain link method and percentage covering of benthic organisms was obtained analyzing random points from replicated photo-quadrats. We observed thirty-eight species of fishes, belonging to twenty-five families. Reef fish communities between studied patches were similar,both in terms of species composition and vertical distribution. Considering only the most site-attached fishes, which were the most frequent and abundant species, data showed that ID sustains higher diversity and abundance than OD. Results showed that benthic composition differ significantly among patches whereas complexity remained without differences. Otherwise, results indicated that these areas might play an important role in space limitation, structuring neighboring benthic community and consequently reef fish assemblages.

First egg protein with a neurotoxic effect on mice

While many invertebrates sequester toxic compounds to endow eggs with chemical defences, here we show, for the first time to our knowledge, the identification of a neurotoxin of proteinaceous nature localized inside an egg. Egg extracts from the freshwater apple snail Pomacea canaliculata displayed a neurotoxic effect in mice upon intraperitoneal injection (i.p.) (LD50, 96h 2.3mg/kg). Egg protein and total lipids were analysed separately and the only fraction displaying a highly toxic effect (LD50, 96h 0.25mg/kg, i.p.) was further purified to homogeneity as an oligomeric glyco-lipoprotein of 400kDa and two subunits biochemically and immunologically indistinguishable from the previously described perivitellin PV2. The neurotoxin was heat sensitive and there was evidence of circulating antibody response to sublethal i.p. doses on mice. Clinical signs, histopathological and immunocytochemical studies revealed damage mostly in mice spinal cord. Experiments showed chromatolysis and a decreased response to calbindin D-28K associated with a significant increase of TUNEL-positive cells in the dorsal horn neurons. These results suggest that calcium buffering and apoptosis may play a role in the neurological disorders induced by the toxin in mammalian central nervous system. This is the first report of a mollusc neurotoxin genetically encoded outside the cone-snail species.

Comparative analysis of purified Pacific and Caribbean ciguatoxin congeners and related marine toxins using a modified ELISA technique

The monoclonal antibody to ciguatoxin (CTX) produced from a hybridoma cell line was assayed for the detection of four congeners of CTX: Pacific ciguatoxin-1 (P-CTX-1), Pacific ciguatoxin-2 (P-CTX-2), Pacific ciguatoxin-3 (P-CTX-3), and Caribbean ciguatoxin-1 (C-CTX-1) and related marine toxins, including domoic acid, palytoxin, and okadaic acid, using a modified enzyme-linked immunosorbent assay (ELISA). Lower detection limits were assessed and linearity was statistically established (P<0.05) for P-CTX-1, P-CTX-2, and P-CTX-3 and C-CTX-1 at concentrations ranging from 0 to 5.00 ng, while the other marine toxins showed statistically insignificant cross-reactivities at similar concentrations. Thus, the monoclonal antibody to CTX is able to specifically detect various CTX congeners at levels comparable to those naturally occurring in ciguatoxic fish.

Cytotoxic actions of palytoxin on aortic smooth muscle cells in culture

Palytoxin (PTX), isolated from a zoanthid of the genus Palythoa, is the most potent marine toxin known. Intoxication by PTX leads to vasoconstriction, hemorrhage, ataxia, muscle weakness, ventricular fibrillation, pulmonary hypertension, ischemia and death. In this study, clonal A7r5 rat aortic smooth muscle cells were used to study the mechanism of PTX-mediated cytotoxicity. A7r5 cells exposed to PTX for > or = 15 min exhibited surface granularities, vacuoles and rounding. These alterations culminated in a loss of viability as indicated by marked increases in the release of lactate dehydrogenase. Electrophysiological recording from A7r5 cells disclosed a profound membrane depolarization and an increase in conductance to Na+ and K+. PTX-mediated cytotoxicity could not be reversed by washout or by the addition of 10 microM verapamil but was antagonized by 100 microM ouabain or by removal of extracellular Na+ or Ca2+. In light of the involvement of vascular smooth muscle in PTX poisoning, A7r5 cells could serve as a useful model to test specific drugs for treatment of PTX intoxication.

Distribution and sequestration of palytoxin in coral reef animals

In the reefs off the Colombian coast (Caribbean Sea) and around Lizard Island, Australia (Pacific), palytoxin (PTX), which has been detected in zoanthid species of the genus Palythoa, also occurred in various other marine organisms living in close association with zoanthid colonies, e.g. sponges (Porifera), soft corals (Alcyonaria), gorgonians (Gorgonaria), mussels, and crustaceans. Predators, e.g. polychaete worms (Hermodice carunculata), a starfish (Acanthaster planci) and fish (Chaetodon species) feeding on Palythoa colonies, accumulate high toxin concentrations in their organs, where PTX is stored in its active form. The high level of toxin tolerance observed in marine animals may enable the wide distribution of PTX in marine biota and its transport and sequestration in food chains.