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Palytoxin is considered one of the most potent biotoxins. As palytoxin-induced cancer cell death mechanisms remain to be elucidated, we investigated this effect on various leukemia and solid tumor cell lines at low picomolar concentrations. As palytoxin did not affect the viability of peripheral blood mononuclear cells (PBMC) from healthy donors and did not create systemic toxicity in zebrafish, we confirmed excellent differential toxicity. Cell death was characterized by a multi-parametric approach involving the detection of nuclear condensation and caspase activation assays. zVAD-sensitive apoptotic cell death was concomitant with a dose-dependent downregulation of antiapoptotic Bcl-2 family proteins Mcl-1 and Bcl-xL. Proteasome inhibitor MG-132 prevented the proteolysis of Mcl-1, whereas the three major proteasomal enzymatic activities were upregulated by palytoxin. Palytoxin-induced dephosphorylation of Bcl-2 further exacerbated the proapoptotic effect of Mcl-1 and Bcl-xL degradation in a range of leukemia cell lines. As okadaic acid rescued cell death triggered by palytoxin, protein phosphatase (PP)2A was involved in Bcl-2 dephosphorylation and induction of apoptosis by palytoxin. At a translational level, palytoxin abrogated the colony formation capacity of leukemia cell types. Moreover, palytoxin abrogated tumor formation in a zebrafish xenograft assay at concentrations between 10 and 30 pM. Altogether, we provide evidence of the role of palytoxin as a very potent and promising anti-leukemic agent, acting at low picomolar concentrations in cellulo and in vivo. [ABSTRACT FROM AUTHOR]

The frequent occurrence of marine dinoflagellates producing palytoxin (PLTX) or okadaic acid (OA) raises concern for the possible co-presence of these toxins in seafood, leading to additive or synergistic adverse effects in consumers. Thus, the acute oral toxicity of PLTX and OA association was evaluated in mice: groups of eight female CD-1 mice were administered by gavage with combined doses of PLTX (30, 90 or 270 μg/kg) and OA (370 μg/kg), or with each individual toxin, recording signs up to 24 h (five mice) and 14 days (three mice). Lethal effects occurred only after PLTX (90 or 270 μg/kg) exposure, alone or combined with OA, also during the 14-day recovery. PLTX induced scratching, piloerection, abdominal swelling, muscle spasms, paralysis and dyspnea, which increased in frequency or duration when co-administered with OA. The latter induced only diarrhea. At 24 h, PLTX (90 or 270 μg/kg) and OA caused wall redness in the small intestine or pale fluid accumulation in its lumen, respectively. These effects co-occurred in mice co-exposed to PLTX (90 or 270 μg/kg) and OA, and were associated with slight ulcers and inflammation at forestomach. PLTX (270 μg/kg alone or 90 μg/kg associated with OA) also decreased the liver/body weight ratio, reducing hepatocyte glycogen (270 μg/kg, alone or combined with OA). No alterations were recorded in surviving mice after 14 days. Overall, the study suggests additive effects of PLTX and OA that should be considered for their risk assessment as seafood contaminants. [ABSTRACT FROM AUTHOR]

Benthic dinoflagellates have attracted increasing attention in recent years because of their toxicity and ability to form extensive harmful algal blooms. Ostreopsis producing palytoxin and its analogs, Gambierdiscus producing ciguatera toxins, and Prorocentrum producing okadaic acid and dinophysis toxins, have been concerned as serious human poisonings. We explored the benthic dinoflagellate biodiversity and distribution characteristics of a series of tropical reefs in 20–40-m water depth in wet season in the Zhongsha Islands in South China Sea using morphological, phylogenetic, and cell counting methods. Results show that benthic dinoflagellates in the islands are rich in biodiversity and 15 species from genera Amphidinium, Coolia, Ostreopsis, and Prorocentrum were identified: Amphidinium carterae, A. magnum, A. massartii, A. operculatum, Coolia canariensis, C. malayensis, C. palmyrensis, C. tropicalis, Ostreopsis cf. ovata, Prorocentrum concavum, P. cf. sculptile, P. emarginatum, P. hoffmannianum, P. lima, and P. rhathymum. Among them, A. magnum is reported for the first time in Chinese waters. The abundance of benthic dinoflagellates was relatively low at 88–4 345 cells/100 cm2 on sediment and 10–91 cells/g on macroalgae. Prorocentrum and Amphidinium were the dominant and subdominant genera, respectively. It is speculated that the low abundance of benthic dinoflagellates is closely related to the scarcity of macroalgae and stronger water motion at the depth >15 m in Zhongsha Islands. This study expanded the study in biodiversity of benthic dinoflagellates in Chinese waters, and revealed the distribution characteristics of harmful benthic microalgae in reef habitats. [ABSTRACT FROM AUTHOR]

Intense blooms of the toxic dinoflagellate Ostreopsis producing palytoxin (PlTX) analogs, mainly ovatoxins (OVTXs), have been a recurrent phenomenon along several Mediterranean coasts. Although there is evidence of seafood contamination by these toxins, the dynamics of their bioaccumulation during Ostreopsis blooms is not yet clear. Toxin concentrations in wild mussels at two sites in the Conero Riviera, along the northern Adriatic Sea (Portonovo and Passetto), were analyzed from August to October 2021, throughout an Ostreopsis cf. ovata bloom, to investigate their relationships with the bloom pattern and abundances. Contaminated mussels showed the typical toxin profile dominated by OVTX-a and -b, with levels lower than the threshold considered unsafe for human consumption (30 µg PlTX-equivalent kg−1 soft tissue). The toxin content reached 36.4 µg PlTX kg−1 soft tissue only in a single sampling date. A clear correlation between the bioaccumulation of OVTXs in mussels and the abundance of Ostreopsis was observed. Our results highlighted, however, that bioaccumulation in the mussels is not affected merely by the abundance of toxic microalgae, since higher toxin levels were recorded at Portonovo, where the cell abundances were lower than at Passetto. The results from this study indicate that the Italian guidelines for the management of Ostreopsis blooms in bathing waters are also useful in managing the risks of human intoxication through ingestion, as mussel contamination was detected only during the alert phase (10,000–30,000 cells L−1). [ABSTRACT FROM AUTHOR]

Palytoxin (PTX) is produced by corals such as zoanthid corals. Here we present a case of bilateral PTX-induced keratoconjunctivitis. A 63-year-old man presented to the emergency department with symptoms of red eye, purulent discharge, and foreign body sensation in both eyes. On slit lamp examination, epithelial defects in both eyes with a ring-shaped corneal stromal infiltrate in the right eye and a marginal stromal infiltrate in the left eye were noted. High-resolution anterior segment optical coherence tomography (HR-AS-OCT) showed stromal hyperreflectivity and Descemet folds. Bacterial, fungal, and amoebic cultures were taken. Empirical treatment with topical dexamethasone as well as antibiotics and systemic doxycycline was started. The next day the patient stated that he had been handling zoanthid coral without gloves and had rubbed his eyes afterward. Bilateral PTX-induced keratoconjunctivitis was diagnosed. His eyes were irrigated abundantly with saline solution, and umbilical cord serum eye drops were added to the treatment. Treatment was tapered according to improvement of the corneal infiltrates and epithelial defects. After four months, the stromal infiltrates were resolved but corneal scars persisted in both eyes. HR-AS-OCT showed anterior stromal hyperreflectivity corresponding to corneal leucomas. PTX can cause ocular adverse effects such as keratolysis and corneal inflammation, and in some cases can lead to corneal perforation. It can also produce systemic adverse effects, hence the importance of the preventive measures when handling corals that can produce this toxin.

Anemone-like animals belonging to the order Zoantharia are common anthozoans widely distributed from shallow to deep tropical and subtropical waters. Some species are well-known because of their high toxicity due to the presence of palytoxin (PLTX) in their tissues. PLTX is a large polyhydroxylated compound and one of the most potent toxins known. Currently, the PLTX biosynthetic pathway in zoantharians and the role of the host or the putative symbiotic organism(s) involved in this pathway are entirely unknown. To better understand the presence of PLTX in some Zoantharia, twenty-nine zoantharian colonies were analysed in this study. All zoantharian samples and their endosymbiotic dinoflagellates (Symbiodiniaceae = Zooxanthellae) were identified using DNA barcoding and phylogenetic reconstructions. Quantification of PLTX and its analogues showed that the yields contained in Palythoa heliodiscus, Palythoa aff. clavata and one potentially undescribed species of Palythoa are among the highest ever found (up to > 2 mg/g of wet zoantharian). Mass spectrometry imaging was used for the first time on Palythoa samples and revealed that in situ distribution of PLTX is mainly located in ectodermal tissues such as the epidermis of the body wall and the pharynx. Moreover, high levels of PLTX have been detected in histological regions where few or no Symbiodiniaceae cells could be observed. Finally, issues such as host‐specificity and environmental variables driving biogeographical patterns of hosted Symbiodiniaceae in zoantharian lineages were discussed in light of our phylogenetic results as well as the patterns of PLTX distribution. It was concluded that (1) the variability of Symbiodiniaceae diversity may be related to ecological divergence in Zoantharia, (2) all Palythoa species hosted Cladocopium Symbiodiniaceae (formerly clade C), (3) the sole presence of Cladocopium is not sufficient to explain the presence of high concentrations of PLTX and/or its analogues, and (4) the ability to produce high levels of PLTX and/or its analogues highlighted in some Palythoa species could be a plesiomorphic character inherited from their last common ancestor and subsequently lost in several lineages. [ABSTRACT FROM AUTHOR]

Palytoxin (PLTX) and its analogues are marine polyethers identified in Palythoa and Zoanthus corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. Humans can be exposed to these toxins by different routes with a series of adverse effects but the most severe risk is associated with poisonings by the consumption of edible marine organisms accumulating these toxins, as occurs in (sub)-tropical areas. In temperate areas, adverse effects ascribed to PLTXs have been recorded after inhalation of marine aerosols and/or cutaneous contact with seawater during Ostreopsis blooms, as well as during cleaning procedures of Palythoa-containing home aquaria. Besides instrumental analytical methods, in the last years a series of alternative or complementary methods based on biological/biochemical tools have been developed for the rapid and specific PLTX detection required for risk assessment. These methods are usually sensitive, cost- and time-effective, and do not require highly specialized operators. Among them, structural immunoassays and functional cell-based assays are reviewed. The availability of specific anti-PLTX antibodies allowed the development of different sensitive structural assays, suitable for its detection also in complex matrices, such as mussels. In addition, knowing the mechanism of PLTX action, a series of functional identification methods has been developed. Despite some of them being limited by matrix effects and specificity issues, biological methods for PLTX detection represent a feasible tool, suitable for rapid screening. [ABSTRACT FROM AUTHOR]

Ostreopsis cf. ovata, a benthic/epiphytic marine dinoflagellate, is currently spreading in tropical, sub-tropical and temperate areas, causing periodic Harmful Algal Blooms (HABs). It produces a wide array of palytoxin-like compounds named ovatoxins (OVTXs), with OVTX-a generally the most abundant congener. Despite numerous cases of human poisonings and environmental damage associated with the presence of OVTXs and O. cf. ovata proliferations, a complete characterization of the toxicity of this class of molecules cannot be performed until Reference Material (RM) for individual congeners is available. This, in turn, requires the availability of sufficient amounts of toxin at a high purity grade. To achieve this goal, herein an analytical re-evaluation of critical-steps of OVTX-a isolation from O. cf. ovata cell pellets is reported. The overall procedure consists of four steps, namely an extraction, a Medium Pressure Liquid Chromatography (MPLC) separation, and two preparative High Performance Liquid Chromatography (HPLC) steps. Particular attention was paid to the extraction step to evaluate the repeatability in OVTX-a yields. For subsequent steps, loading sample preparation and chromatographic conditions were refined. As a result, a significant increase in recovery yields (from 12.5 to 20 ± 3%) and in purity grade (from 51% to 94%) of the isolated OVTX-a was achieved in comparison to previous studies. The improved procedure can easily be applied to isolate sufficient quantities of a good candidate RM for OVTX-a., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Zoantharia is an order among the Hexacorallia (Anthozoa: Cnidaria), and includes at least 300 species. Previously reported genomes from scleractinian corals and actiniarian sea anemones have illuminated part of the hexacorallian diversification. However, little is known about zoantharian genomes and the early evolution of hexacorals. To explore genome evolution in this group of hexacorals, here, we report de novo genome assemblies of the zoantharians Palythoa mizigama (Pmiz) and Palythoa umbrosa (Pumb), both of which are members of the family Sphenopidae, and uniquely live in comparatively dark coral reef caves without symbiotic Symbiodiniaceae dinoflagellates. Draft genomes generated from ultra-low input PacBio sequencing totaled 373 and 319 Mbp for Pmiz and Pumb, respectively. Protein-coding genes were predicted in each genome, totaling 30,394 in Pmiz and 24,800 in Pumb, with each set having ∼93% BUSCO completeness. Comparative genomic analyses identified 3,036 conserved gene families, which were found in all analyzed hexacoral genomes. Some of the genes related to toxins, chitin degradation, and prostaglandin biosynthesis were expanded in these two Palythoa genomes and many of which aligned tandemly. Extensive gene family loss was not detected in the Palythoa lineage and five of ten putatively lost gene families likely had neuronal function, suggesting biased gene loss in Palythoa. In conclusion, our comparative analyses demonstrate evolutionary conservation of gene families in the Palythoa lineage from the common ancestor of hexacorals. Restricted loss of gene families may imply that lost neuronal functions were effective for environmental adaptation in these two Palythoa species., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

A 25-year-old woman presented with right eye pain, lid edema, conjunctival injection and chemosis, and mild corneal epitheliopathy after exposure to fluid content from an aquarium coral reef. Topical moxifloxacin and prednisolone were started 4 times daily, with full clinical resolution after 2 weeks. Toxin-mediated keratoconjunctivitis may occur after exposure to zoanthid coral reef, particularly in aquarium enthusiasts. Topical corticosteroids in tandem with topical antibiotics appear to be effective in mild disease. However, in severe cases that exhibit corneal infiltrates and stromal thinning, close observation is warranted in case of possible keratolysis.

The dinoflagellate genus Prorocentrum includes several harmful toxigenic species, predominantly benthic ones. In the past, fast-acting toxicity in mice has been observed in extracts of the epibenthic species P. borbonicum, with the finding of two compounds termed as borbotoxins-A and -B. The presence of palytoxin-like compounds was also suggested from electrophysiological experiments. In the present study, a strain of P. borbonicum was isolated in the continental coast of Colombian Caribbean, in seagrass beds of Thalassia testudinum in Bonito Gordo, Tayrona National Natural Park (PNNT). The morphological and molecular characteristics were consistent with the original and former descriptions for this species. Typical haemolytic activity due to palytoxin was confirmed in P. borbonicum extracts in presence of ouabain, the toxin contents being estimated as 1.9 pg palytoxin equivalents cell-1. HPLC-HRMS analyses of these extracts unambiguously identified the presence of borbotoxins and 42-hidroxy-palytoxin (42-OH-PLTX). This is the first report of palytoxin-like compounds in another dinoflagellate genus than Ostreopsis and the first record of P. borbonicum in Colombia and the Caribbean region.

Palytoxin is considered one of the most potent biotoxins. As palytoxin-induced cancer cell death mechanisms remain to be elucidated, we investigated this effect on various leukemia and solid tumor cell lines at low picomolar concentrations. As palytoxin did not affect the viability of peripheral blood mononuclear cells (PBMC) from healthy donors and did not create systemic toxicity in zebrafish, we confirmed excellent differential toxicity. Cell death was characterized by a multi-parametric approach involving the detection of nuclear condensation and caspase activation assays. zVAD-sensitive apoptotic cell death was concomitant with a dose-dependent downregulation of antiapoptotic Bcl-2 family proteins Mcl-1 and Bcl-xL. Proteasome inhibitor MG-132 prevented the proteolysis of Mcl-1, whereas the three major proteasomal enzymatic activities were upregulated by palytoxin. Palytoxin-induced dephosphorylation of Bcl-2 further exacerbated the proapoptotic effect of Mcl-1 and Bcl-xL degradation in a range of leukemia cell lines. As okadaic acid rescued cell death triggered by palytoxin, protein phosphatase (PP)2A was involved in Bcl-2 dephosphorylation and induction of apoptosis by palytoxin. At a translational level, palytoxin abrogated the colony formation capacity of leukemia cell types. Moreover, palytoxin abrogated tumor formation in a zebrafish xenograft assay at concentrations between 10 and 30 pM. Altogether, we provide evidence of the role of palytoxin as a very potent and promising anti-leukemic agent, acting at low picomolar concentrations in cellulo and in vivo.

Palytoxin (PLTX) is a polyether marine toxin isolated from sea anemones. It is one of the most toxic nonprotein substances, causing many people to be poisoned every year and to die in severe cases. Despite its known impact on Na+,K+-ATPase, much still remains unclear about PLTX's mechanism of action. Here, we tested different concentrations of PLTX on HaCaT cells and studied its distributions in cells, its impact on gene expression, and the associated pathways via proteomics combined with bioinformatics tools. We found that PLTX could cause ferroptosis in HaCaT cells, a new type of programmed cell death, by up-regulating the expression of VDAC3, ACSL4 and NCOA4, which lead to the occurrence of ferroptosis. PLTX also acts on the MAPK pathway, which is related to cell apoptosis, proliferation, division and differentiation. Different from its effect on ferroptosis, PLTX down-regulates the expression of ERK, and, as a result, the expressions of MAPK1, MAP2K1 and MAP2K2 are also lower, affecting cell proliferation. The genes from these two mechanisms showed interactions, but we did not find overlap genes between the two. Both ferroptosis and MAPK pathways can be used as anticancer targets, so PLTX may become an anticancer drug with appropriate modification. [ABSTRACT FROM AUTHOR]

Ryan T Barrett,1 Jordan P Hastings,2 Yasmyne C Ronquillo,3 Phillip C Hoopes,3 Majid Moshirfar3– 5 1Hollingshead Eye Center, Boise, ID, USA; 2California Northstate University College of Medicine, Elk Grove, CA, USA; 3Hoopes Vision Research Center, Draper, UT, USA; 4John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, USA; 5Utah Lions Eye Bank, Murray, UT, USACorrespondence: Majid MoshirfarHDR Research Center, Hoopes Vision, 11820 S. State Street Suite #200, Draper, UT, USATel +1 801-568-0200Email Cornea2020@me.comAbstract: Palytoxin is one of the most lethal natural toxins ever discovered. This molecule has been isolated from various marine animals, including zoanthid corals. This popular organism is commonly found in many home saltwater aquariums due to its beauty and survivability. As a result of an increase in popularity, an increased number of individuals are at risk for exposure to this potentially deadly toxin. Affected patients may experience various symptoms based on the route of exposure (ie, cutaneous contact, inhalation of aerosolized toxin, ocular exposure, or ingestion). Ocular exposure can occur in various ways (eg, contact with contaminated water, rubbing the eye with a dirtied hand, or direct spraying into the eye), and incidence rates have dramatically risen in recent years. In this review, we discuss a case of systemic toxicity from inhalation and ocular exposure to presumed palytoxin on a zoanthid coral which resulted in an intensive care unit (ICU) stay, and corneal perforation which required a corneal transplant. Additionally, we review what is known about the mechanism of action of this toxin, propose a comprehensive hypothesis of its effects on corneal cells, and discuss the prognosis and clinical management of patients with systemic symptoms secondary to other routes of exposure.Keywords: coral keratitis, zoanthid, palytoxin, corneal perforation, case report

Purpose: This case report describes the therapeutic management of a 61-year-old male who experienced aquarium coral keratoconjunctivitis caused by exposure to palytoxin and provides an additional resource to raise awareness and treat patients with ocular exposure to palytoxin. Observations: A 61-year-old male inadvertently touched his left eye while cleaning an aquarium. Within 24 hours, pain, redness and visual blurring was noted. After 48 hours his best corrected visual acuity was measured at 20/25 on the right eye and 20/200 on the left. A thick mucopurulent discharge was present with associated conjunctival edema. The corneal epithelium was denuded centrally and inferiorly with subepithelial infiltrates peripherally. The patient was treated with topical moxifloxacin (0.5%) drops 6x/day and prednisolone acetate (1%) 4x/day. He was seen for follow up 48 hours later with a significant improvement in discomfort. Vision had improved to 20/60 with resolution of conjunctival edema, partial corneal epithelialization and reduced erythema. Cultures for culture and sensitivity returned as normal. The patient's steroid regime was gradually tapered during reassessments at four and ten days by which time the left eye acuity had returned to 20/25 with no symptoms. Therapy was discontinued with the exception of artificial tears. The patient continued to do well at his 42-day follow-up appointment with persistent corneal epithelialization, absence of infiltrates and a stable visual acuity of 20/25 in the affected eye. His local optometrist confirmed that the acuity was consistent with measurements obtained prior to the insult. Conclusions: The combination of moxifloxacin eye drops and prednisolone acetate eye drops were effective in treating the patient's aquarium coral keratoconjunctivitis as after being treated the patient regained his baseline visual acuity in the affected eye (best corrected visual acuity of 20/25). Importance: Currently, there are only a handful of case-reports published on ocular exposure to palytoxin. This case report will add to the literature by providing an additional resource for health care providers, in the treatment of patients with ocular exposure to palytoxin and increasing awareness to this rare condition.

Summary: Background: From late 2016 to early 2021, cases of Haff disease, a rare cause of rhabdomyolysis, possibly due to poisoning by palytoxin-like compounds in seafood, were detected in Salvador, Brazil. Surveillance was established to detect additional cases aiming at describing the clinical characteristics of the cases, identifying associated factors, estimating disease attack rate, and investigating the presence of biotoxins and trace metals in selected fish specimens obtained from cases. Method: Between December/2016-January/2021, surveillance investigated Haff disease suspected cases, and obtained clinical and fish samples to test. Findings: Of 65 cases investigated during the 2016-2017 outbreak, 43 (66%) had high creatine phosphokinase (CPK) levels. Among those with laboratory-confirmed rhabdomyolysis, 38 (88%) were hospitalized, 11 (26%) required intensive care, and three (7%) dialysis. Ingestion of marine fish 24h before disease onset was reported by 74% of the cases with elevated CPK and by 41% of those without CPK measurement (P=0·02). Attack rate for individuals who ate fish related to the outbreak was 55%. Following this outbreak, surveillance identified 12 suspected cases between 2017-2019, and a second outbreak in 2020-2021, with 16 laboratory-confirmed rhabdomyolysis patients (five required intensive care; one died). No traces of ciguatoxins and metals were detected in fish specimens obtained in 2016, found to be Seriola rivoliana. Some fish samples from 2020 were screened for palytoxin (PlTX)-like compounds and contained detectable levels of molecule fragments characteristics of isobaric PlTX, ovatoxin-a (OVTX-a), OVTX-b and OVTX-d. Interpretation: These findings support the hypothesis that compounds related to PlTX accumulated in marine fish may be the toxic agent causing the disease. Haff disease is a life-threatening condition, requiring clinical suspicion for patients with sudden-onset myalgia following fish ingestion. Suspected cases should be reported to health authorities for investigation.

Palytoxin (PTX) is produced by corals such as zoanthid corals. Here we present a case of bilateral PTX-induced keratoconjunctivitis. A 63-year-old man presented to the emergency department with symptoms of red eye, purulent discharge, and foreign body sensation in both eyes. On slit lamp examination, epithelial defects in both eyes with a ring-shaped corneal stromal infiltrate in the right eye and a marginal stromal infiltrate in the left eye were noted. High-resolution anterior segment optical coherence tomography (HR-AS-OCT) showed stromal hyperreflectivity and Descemet folds. Bacterial, fungal, and amoebic cultures were taken. Empirical treatment with topical dexamethasone as well as antibiotics and systemic doxycycline was started. The next day the patient stated that he had been handling zoanthid coral without gloves and had rubbed his eyes afterward. Bilateral PTX-induced keratoconjunctivitis was diagnosed. His eyes were irrigated abundantly with saline solution, and umbilical cord serum eye drops were added to the treatment. Treatment was tapered according to improvement of the corneal infiltrates and epithelial defects. After four months, the stromal infiltrates were resolved but corneal scars persisted in both eyes. HR-AS-OCT showed anterior stromal hyperreflectivity corresponding to corneal leucomas. PTX can cause ocular adverse effects such as keratolysis and corneal inflammation, and in some cases can lead to corneal perforation. It can also produce systemic adverse effects, hence the importance of the preventive measures when handling corals that can produce this toxin. [ABSTRACT FROM AUTHOR]

The frequent occurrence of marine dinoflagellates producing palytoxin (PLTX) or okadaic acid (OA) raises concern for the possible co-presence of these toxins in seafood, leading to additive or synergistic adverse effects in consumers. Thus, the acute oral toxicity of PLTX and OA association was evaluated in mice: groups of eight female CD-1 mice were administered by gavage with combined doses of PLTX (30, 90 or 270 μg/kg) and OA (370 μg/kg), or with each individual toxin, recording signs up to 24 h (five mice) and 14 days (three mice). Lethal effects occurred only after PLTX (90 or 270 μg/kg) exposure, alone or combined with OA, also during the 14-day recovery. PLTX induced scratching, piloerection, abdominal swelling, muscle spasms, paralysis and dyspnea, which increased in frequency or duration when co-administered with OA. The latter induced only diarrhea. At 24 h, PLTX (90 or 270 μg/kg) and OA caused wall redness in the small intestine or pale fluid accumulation in its lumen, respectively. These effects co-occurred in mice co-exposed to PLTX (90 or 270 μg/kg) and OA, and were associated with slight ulcers and inflammation at forestomach. PLTX (270 μg/kg alone or 90 μg/kg associated with OA) also decreased the liver/body weight ratio, reducing hepatocyte glycogen (270 μg/kg, alone or combined with OA). No alterations were recorded in surviving mice after 14 days. Overall, the study suggests additive effects of PLTX and OA that should be considered for their risk assessment as seafood contaminants.

Intense blooms of the toxic dinoflagellate Ostreopsis producing palytoxin (PlTX) analogs, mainly ovatoxins (OVTXs), have been a recurrent phenomenon along several Mediterranean coasts. Although there is evidence of seafood contamination by these toxins, the dynamics of their bioaccumulation during Ostreopsis blooms is not yet clear. Toxin concentrations in wild mussels at two sites in the Conero Riviera, along the northern Adriatic Sea (Portonovo and Passetto), were analyzed from August to October 2021, throughout an Ostreopsis cf. ovata bloom, to investigate their relationships with the bloom pattern and abundances. Contaminated mussels showed the typical toxin profile dominated by OVTX-a and -b, with levels lower than the threshold considered unsafe for human consumption (30 µg PlTX-equivalent kg−1 soft tissue). The toxin content reached 36.4 µg PlTX kg−1 soft tissue only in a single sampling date. A clear correlation between the bioaccumulation of OVTXs in mussels and the abundance of Ostreopsis was observed. Our results highlighted, however, that bioaccumulation in the mussels is not affected merely by the abundance of toxic microalgae, since higher toxin levels were recorded at Portonovo, where the cell abundances were lower than at Passetto. The results from this study indicate that the Italian guidelines for the management of Ostreopsis blooms in bathing waters are also useful in managing the risks of human intoxication through ingestion, as mussel contamination was detected only during the alert phase (10,000–30,000 cells L−1).

Palytoxin (PLTX) and its analogues are marine polyethers identified in Palythoa and Zoanthus corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. Humans can be exposed to these toxins by different routes with a series of adverse effects but the most severe risk is associated with poisonings by the consumption of edible marine organisms accumulating these toxins, as occurs in (sub)-tropical areas. In temperate areas, adverse effects ascribed to PLTXs have been recorded after inhalation of marine aerosols and/or cutaneous contact with seawater during Ostreopsis blooms, as well as during cleaning procedures of Palythoa-containing home aquaria. Besides instrumental analytical methods, in the last years a series of alternative or complementary methods based on biological/biochemical tools have been developed for the rapid and specific PLTX detection required for risk assessment. These methods are usually sensitive, cost- and time-effective, and do not require highly specialized operators. Among them, structural immunoassays and functional cell-based assays are reviewed. The availability of specific anti-PLTX antibodies allowed the development of different sensitive structural assays, suitable for its detection also in complex matrices, such as mussels. In addition, knowing the mechanism of PLTX action, a series of functional identification methods has been developed. Despite some of them being limited by matrix effects and specificity issues, biological methods for PLTX detection represent a feasible tool, suitable for rapid screening.

This study revealed the dynamics of the genus Ostreopsis in the south-western Mediterranean Sea fish farm during the 2016 and 2017 summers. This phytoplankton is known to produce palytoxin-like compounds, listed among the most potent marine toxins known, and can pose a serious concern for humans in the Mediterranean area. Principal component analysis (PCA) explained the significance of temperature, salinity, and dissolved inorganic nitrogen in the proliferation of this toxic dinoflagellate. The peak of the Ostreopsis sp. (6.34 × 103 cells L−1) was recorded at 28.4 °C, at a salinity of 38.3 PSU, and the dissolved inorganic nitrogen had a value of 0.60 μmol L−1. Our results highlight the importance of monitoring the proliferation of this harmful dinoflagellate in southern Mediterranean waters. [ABSTRACT FROM AUTHOR]

A 25-year-old woman presented with right eye pain, lid edema, conjunctival injection and chemosis, and mild corneal epitheliopathy after exposure to fluid content from an aquarium coral reef. Topical moxifloxacin and prednisolone were started 4 times daily, with full clinical resolution after 2 weeks. Toxin-mediated keratoconjunctivitis may occur after exposure to zoanthid coral reef, particularly in aquarium enthusiasts. Topical corticosteroids in tandem with topical antibiotics appear to be effective in mild disease. However, in severe cases that exhibit corneal infiltrates and stromal thinning, close observation is warranted in case of possible keratolysis. [ABSTRACT FROM AUTHOR]

Blooms of the dinoflagellate Ostreopsis cf. ovata are regularly associated with human intoxications that are attributed to ovatoxins (OVTXs), the main toxic compounds produced by this organism and close analogs to palytoxin (PlTX). Unlike for PlTX, information on OVTXs'toxicity are scarce due to the absence of commercial standards. Extracts from two cultures of Mediterranean strains of O. cf. ovata (MCCV54 and MCCV55), two fractions containing or not OVTXs (prepared from the MCCV54 extract) and OVTX-a and -d (isolated from the MCCV55 extract) were generated. These chemical samples and PlTX were tested on a panel of cell types from several organs and tissues (skin, intestine, lung, liver and nervous system). The MCCV55 extract, containing a 2-fold higher amount of OVTXs than MCCV54 extract, was shown to be more cytotoxic on all the cell lines and more prone to increase interleukin-8 (IL-8) release in keratinocytes. The fraction containing OVTXs was also cytotoxic on the cell lines tested but induced IL-8 release only in liver cells. Unexpectedly, the cell lines tested showed the same sensitivity to the fraction that does not contain OVTXs. With this fraction, a pro-inflammatory effect was shown both in lung and liver cells. The level of cytotoxicity was similar for OVTX-a and –d, except on intestinal and skin cells where a weak difference of toxicity was observed. Among the 3 toxins, only PlTX induced a pro-inflammatory effect mostly on keratinocytes. These results suggest that the ubiquitous Na+/K+ ATPase target of PlTX is likely shared with OVTX-a and -d, although the differences in pro-inflammatory effect must be explained by other mechanisms. [Display omitted] • Extracts of Ostreopsis cf. ovata were cytotoxic to a broad range of cell lines. • The fraction not containing ovatoxins induced IL-8 release on liver and lung cells. • PlTX was more cytotoxic than OVTX-a and –d on cells from intestine and the nervous system. • A similar IC 50 was observed on lung cells for the three toxins. • OVTX-a and –d did not induce IL-8 release on intestinal, lung and skin cells. [ABSTRACT FROM AUTHOR]

We describe a case of a young male who presented to the emergency department with unilateral eye pain, blurred vision, conjunctival injection, and ocular pH of 9, one day after direct ocular exposure to palytoxin (PTX) from coral in a home saltwater fish tank. Although uncommon, ocular PTX toxicity is a potentially vision-threatening condition that requires prompt recognition. This case report documents the successful management of presumed ocular PTX exposure and suggests additional workup and treatment considerations for future patients. [ABSTRACT FROM AUTHOR]

Palytoxin (PLTX) is a polyether marine toxin isolated from sea anemones. It is one of the most toxic nonprotein substances, causing many people to be poisoned every year and to die in severe cases. Despite its known impact on Na+,K+-ATPase, much still remains unclear about PLTX’s mechanism of action. Here, we tested different concentrations of PLTX on HaCaT cells and studied its distributions in cells, its impact on gene expression, and the associated pathways via proteomics combined with bioinformatics tools. We found that PLTX could cause ferroptosis in HaCaT cells, a new type of programmed cell death, by up-regulating the expression of VDAC3, ACSL4 and NCOA4, which lead to the occurrence of ferroptosis. PLTX also acts on the MAPK pathway, which is related to cell apoptosis, proliferation, division and differentiation. Different from its effect on ferroptosis, PLTX down-regulates the expression of ERK, and, as a result, the expressions of MAPK1, MAP2K1 and MAP2K2 are also lower, affecting cell proliferation. The genes from these two mechanisms showed interactions, but we did not find overlap genes between the two. Both ferroptosis and MAPK pathways can be used as anticancer targets, so PLTX may become an anticancer drug with appropriate modification.

Palytoxin (PLTX) is a highly toxic polyether identified in various marine organisms, such as Palythoa soft corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. In addition to adverse effects in humans, negative impacts on different marine organisms have been often described during Ostreopsis blooms and the concomitant presence of PLTX and its analogues. Considering the increasing frequency of Ostreopsis blooms due to global warming, PLTX was investigated for its effects on Artemia franciscana, a crustacean commonly used as a model organism for ecotoxicological studies. At concentrations comparable to those detected in culture media of O. cf. ovata (1.0–10.0 nM), PLTX significantly reduced cysts hatching and induced significant mortality of the organisms, both at larval and adult stages. Adults appeared to be the most sensitive developmental stage to PLTX: significant mortality was recorded after only 12 h of exposure to PLTX concentrations > 1.0 nM, with a 50% lethal concentration (LC50) of 2.3 nM (95% confidence interval = 1.2–4.7 nM). The toxic effects of PLTX toward A. franciscana adults seem to involve oxidative stress induction. Indeed, the toxin significantly increased ROS levels and altered the activity of the major antioxidant enzymes, in particular catalase and peroxidase, and marginally glutathione-S-transferase and superoxide dismutase. On the whole, these results indicate that environmentally relevant concentrations of PLTX could have a negative effect on Artemia franciscana population, suggesting its potential ecotoxicological impact at the marine level.

Palytoxin is an emergent toxin in Europe and one of the most toxic substances know to date. The toxin disrupts the physiological functioning of the Na+/K+-ATPase converting the enzyme in a permeant cation channel. Human intoxications by PLTX after consumption of contaminated fishery products are a serious health issue and can be fatal. Several reports have previously investigated the oral and intraperitoneal toxicity of PLTX in mice. However, in all cases short observation periods (24 and 48 h) after toxin administration were evaluated. In this work, single oral or intraperitoneal doses of PLTX were administered to healthy mice and surviving animals were followed up for 96 h. The data obtained here allowed us to calculate the oral and intraperitoneal lethal doses 50 (LD 50) which were in the range of the values previously described. Surprisingly, the oral NOAEL for PLTX was more than 10 times lower than that previously described, a fact that indicates the need for the reevaluation of the levels of the toxin in edible fishery products. • Human intoxications by palytoxin are a serious health issue and can be fatal. • In 2009 EFSA concluded that the toxicological database for palytoxin was limited. • Single oral or intraperitoneal palytoxin was administered to mice and animals monitored for 96 h. • The oral NOAEL was more than 10 times lower than that previously described. • The intraperitoneal and oral LD 50 did not increase with the longer observation times. [ABSTRACT FROM AUTHOR]

Palytoxin (PLTX) and its congeners are emerging toxins held responsible for a number of human poisonings following the inhalation of toxic aerosols, skin contact, or the ingestion of contaminated seafood. Despite the strong structural analogies, the relative toxic potencies of PLTX congeners are quite different, making it necessary to isolate them individually in sufficient amounts for toxicological and analytical purposes. Previous studies showed poor PLTX recoveries with a dramatic decrease in PLTX yield throughout each purification step. In view of a large-scale preparative work aimed at the preparation of PLTX reference material, we have investigated evaporation as a critical—although unavoidable—step that heavily affects overall recoveries. The experiments were carried out in two laboratories using different liquid chromatography-mass spectrometry (LC-MS) instruments, with either unit or high resolution. Palytoxin behaved differently when concentrated to a minimum volume rather than when evaporated to complete dryness. The recoveries strongly depended on the solubility as well as on the material of the used container. The LC-MS analyses of PLTX dissolved in aqueous organic blends proved to give a peak intensity higher then when dissolved in pure water. After drying, the PLTX adsorption appeared stronger on glass surfaces than on plastic materials. However, both the solvents used to dilute PLTX and that used for re-dissolution had an important role. A quantitative recovery (97%) was achieved when completely drying 80% aqueous EtOH solutions of PLTX under N2-stream in Teflon. The stability of PLTX in acids was also investigated. Although PLTX was quite stable in 0.2% acetic acid solutions, upon exposure to stronger acids (pH < 2.66), degradation products were observed, among which a PLTX methyl-ester was identified.

Marine isolates such as palytoxin (PTX) are of concern within the Caribbean region due to their toxicity. PTX for example has been described as a one of the most known potent marine toxins, known to prevent predation from larger species (e.g. vertebrates) as well as the prevention of being overgrown from other coral species. PTX is a polyhydroxylated polyether toxin with a very large and complex chemical structure that possesses both hydrophilic and lipophilic properties. Previous acute toxicity tests using brine shrimp (Artemia salina) and PTX extract had shown it to be moderately toxic. In humans, PTX has been credited to be responsible for extreme symptoms such anaphylactic shock, rapid cardiac failure and eventual death occurring within minutes. Extrapolation for human dose ranges has therefore been suggested to be between 2.3 and 31.5 μg. This study isolates a potentially PTX-enriched extract from Palythoa caribaeorum and examines its organic extract toxicity from a biogeography perspective from a within-colony to a variety of reef sites around Trinidad and Tobago that are popular for marine visitors. This research represents an acute study with a high level of crude organic extract toxicity on A. salina whilst postulating potential factors which may contribute to its extreme toxicity and the risk posed to users of these environments. • Crude organic extracts (COE) isolated from Palythoa caribaeorum were classed as highly toxic. • COE toxicity on Artemia salina had an LC 50 between 3.57 and 28.52 μl/ml. • COE toxicity on A. salina was highest at the P. caribaeorum colony edge and lowest at its center. • Flying Reef had the highest COE % yield and most potent toxicity compared to the other sites. • P. caribaeorum COE toxicity from Trinidad and Tobago is higher than previous studies. [ABSTRACT FROM AUTHOR]

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Graphical abstract Highlights • A truncated palytoxin analogue was isolated from a red alga, Chondria armata. • This compound showed half of lethal activity of palytoxin against cockroaches. • The physicochemical properties of this compound were characterized. Abstract Palytoxin (PTX) has been widely studied owing to its outstanding toxic properties and complex structural features. It is a great challenge to identify and isolate analogues of PTX from various organisms and reveal their physiological activities. We previously reported the isolation of PTX as an insecticidal compound from the red alga, Chondria armata. In this study, we investigate another active compound from C. armata , which has similar toxicity and chromatographic behavior as PTX. Our detailed structural analysis reveals that this compound is palytoxin carboxylic acid. We characterized its physicochemical properties and conducted extensive NMR studies. This analogue has a structure devoid of the terminus of PTX, such that its presence in the alga implies the role of symbiotic microorganisms in marine ecosystems. [ABSTRACT FROM AUTHOR]

Palytoxin has been found in several soft coral species which are popular for in-home reef aquariums. Although a limited number of case reports describing acute respiratory distress after inhalational exposure to palytoxin have been reported, there have been no reports regarding the potential long-term effects of inhalational exposure to palytoxin in the literature. This case follows an aquatic specialist in the U.S. over a period of seven years after a single intense occupational exposure to the aerosolized toxin from cleaning of a residential aquarium. • Occupational exposure to palytoxin from home aquarium maintenance. • Inhalational exposure to presumed aerosols generated during the handling of zoanthids. • Long-term cognitive and respiratory impairments from one-time exposure to palytoxin. [ABSTRACT FROM AUTHOR]

The marine polyether palytoxin (PLTX) is one of the most toxic natural compounds, and is involved in human poisonings after oral, inhalation, skin and/or ocular exposure. Epidemiological and molecular evidence suggest different inter-individual sensitivities to its toxic effects, possibly related to genetic-dependent differences in the expression of Na+/K+-ATPase, its molecular target. To identify Na+/K+-ATPase subunits, isoforms correlated with in vitro PLTX cytotoxic potency, sensitivity parameters (EC50: PLTX concentration reducing cell viability by 50%; Emax: maximum effect induced by the highest toxin concentration; 10−7 M) were assessed in 60 healthy donors’ monocytes by the MTT (methylthiazolyl tetrazolium) assay. Sensitivity parameters, not correlated with donors’ demographic variables (gender, age and blood group), demonstrated a high inter-individual variability (median EC50 = 2.7 × 10−10 M, interquartile range: 0.4–13.2 × 10−10 M; median Emax = 92.0%, interquartile range: 87.5–94.4%). Spearman’s analysis showed significant positive correlations between the β2-encoding ATP1B2 gene expression and Emax values (rho = 0.30; p = 0.025) and between Emax and the ATP1B2/ATP1B3 expression ratio (rho = 0.38; p = 0.004), as well as a significant negative correlation between Emax and the ATP1B1/ATP1B2 expression ratio (rho = −0.30; p = 0.026). This toxicogenetic study represents the first approach to define genetic risk factors that may influence the onset of adverse effects in human PLTX poisonings, suggesting that individuals with high gene expression pattern of the Na+/K+-ATPase β2 subunit (alone or as β2/β1 and/or β2/β3 ratio) could be highly sensitive to PLTX toxic effects.

Palytoxin (PLTX) is one of the most poisonous substances known to date and considered as an emergent toxin in Europe. Palytoxin binds to the Na+-K+ ATPase, converting the enzyme in a permeant cation channel. This toxin is known for causing human fatal intoxications associated with the consumption of contaminated fish and crustaceans such as crabs, groupers, mackerel, and parrotfish. Human intoxications by PLTX after consumption of contaminated fishery products are a serious health issue and can be fatal. Different reports have previously explored the acute oral toxicity of PLTX in mice. Although the presence of palytoxin in marine products is currently not regulated in Europe, the European Food Safety Authority expressed its opinion on PLTX and demanded assessment for chronic toxicity studies of this potent marine toxin. In this study, the chronic toxicity of palytoxin was evaluated after oral administration to mice by gavage during a 28-day period. After chronic exposure of mice to the toxin, a lethal dose 50 (LD50) of 0.44 µg/kg of PLTX and a No-Observed-Adverse-Effect Level (NOAEL) of 0.03 µg/kg for repeated daily oral administration of PLTX were determined. These results indicate a much higher chronic toxicity of PLTX and a lower NOAEL than that previously described in shorter treatment periods, pointing out the need to further reevaluate the levels of this compound in marine products.

The sodium–potassium pump (Na+/K+ pump) is crucial for cell physiology. Despite great advances in the understanding of this ionic pumping system, its mechanism is not completely understood. We propose the use of a statistical model checker to investigate palytoxin (PTX)-induced Na+/K+ pump channels. We modelled a system of reactions representing transitions between the conformational substates of the channel with parameters, concentrations of the substates and reaction rates extracted from simulations reported in the literature, based on electrophysiological recordings in a whole-cell configuration. The model was implemented using the UPPAAL-SMC platform. Comparing simulations and probabilistic queries from stochastic system semantics with experimental data, it was possible to propose additional reactions to reproduce the single-channel dynamic. The probabilistic analyses and simulations suggest that the PTX-induced Na+/K+ pump channel functions as a diprotomeric complex in which protein–protein interactions increase the affinity of the Na+/K+ pump for PTX.

The emergence of marine toxins in water and seafood may have a considerable impact on public health. Although the tendency in Europe is to consolidate, when possible, official reference methods based on instrumental analysis, the development of alternative or complementary methods providing functional or toxicological information may provide advantages in terms of risk identification, but also low cost, simplicity, ease of use and high-throughput analysis. This article gives an overview of the immunoassays, cell-based assays, receptor-binding assays and biosensors that have been developed for the screening and quantification of emerging marine toxins: palytoxins, ciguatoxins, cyclic imines and tetrodotoxins. Their advantages and limitations are discussed, as well as their possible integration in research and monitoring programs.

Preparations of palytoxin (PLTX, derived from Japanese Palythoa tuberculosa ) and the congeners 42-OH-PLTX (from Hawaiian P. toxica ) and ovatoxin-a (isolated from a Japanese strain of Ostreopsis ovata ), as well as a 50:50 mixture of PLTX and 42-OH-PLTX derived from Hawaiian P. tuberculosa were characterized as to their concentration, composition, in-vitro potency and interaction with an anti-PLTX monoclonal antibody (mAb), after which they were evaluated for lethality and tissue histopathology after intraperitoneal (IP) and aerosol administration to rats. Once each preparation was characterized as to its toxin composition by LC-HRMS and normalized to a total PLTX/OVTX concentration using HPLC-UV, all four preparations showed similar potency towards mouse erythrocytes in the erythrocyte hemolysis assay and interactions with the anti-PLTX mAb. The IP LD 50 values derived from these experiments (0.92, 1.93, 1.81 and 3.26 μg/kg, for the 50:50 mix, 42-OH-PLTX, PLTX, and ovatoxin-a, respectively) were consistent with published values, although some differences from the published literature were seen. The aerosol LD 50 values (0.063, 0.045, 0.041, and 0.031 μg/kg for the 50:50 mix, 42-OH PLTX, PLTX, and ovatoxin-a, respectively) confirmed the exquisite potency of PLTX suggested by the literature. The tissue histopathology of the different toxin preparations by IP and aerosol administration were similar, albeit with some differences. Most commonly affected tissues were the lungs, liver, heart, salivary glands, and adrenal glands. Despite some differences, these results suggest commonalities in potency and mechanism of action among these PLTX congeners. [ABSTRACT FROM AUTHOR]

Palytoxin, isolated from a zoanthid of the genus Palythoa, is the most potent marine toxin known. Intoxication by palytoxin leads to vasoconstriction, hemorrhage, ataxia, muscle weakness, ventricular fibrillation, pulmonary hypertension, ischemia and death. Palytoxin and its numerous derivatives (congeners) may enter the food chain and accumulate mainly in fishes and crabs, causing severe human intoxication and death following ingestion of contaminated products. Furthermore, toxic effects in individuals exposed via inhalation or skin contact to marine aerosol in coincidence with Ostreopsis blooms, have been reported. Blooms of the benthic dinoflagellate Ostreopsis cf. ovata are a concern in the Mediterranean Sea, since this species produces a wide range of palytoxin-like compounds listed among the most potent marine toxins. Thus, the formerly unsuspected broad distribution of the benthic dinoflagellate Ostreopsis spp. has recently posed a problem of risk assessment for human health. Palytoxin has a strong potential for toxicity in humans and animals, and currently this toxin is of great concern worldwide. This review summarized and discussed the pharmacology and toxicology data of palytoxin and its congeners, including their cytotoxicity, human and animal toxicities. Moreover, the risk assessment and their control strategies including prevention and treatment assays were evaluated. [ABSTRACT FROM AUTHOR]

An expedition to North Meyer Island, Kermadec Islands, in November 2015, resulted in the isolation of twoGambierdiscusspecies,G. australesand a previously unknownGambierdiscusspecies maintained in the Cawthron Institute Culture Collection of Micro-algae as CAWD242. Identifications were based on morphology and DNA sequence data analysis. Nine isolates ofG. australesproduced maitotoxin-1 (MTX-1) ranging from present (detectable but below the confidence level) to 36.6 pg per cell. One further isolate did not produce MTX-1, but allG. australesisolates produced putative MTX-3. Isolate CAWD242 was negative for MTX-1 but produced MTX-3.Ostreopsissp. 3 isolated from samples collected during an earlier expedition in 2013 produced low concentrations of palytoxin (PLTX)-like compounds (0.013 pg per cell), but an isolate of the same species from samples collected in 2015 was non-toxic. Other dinoflagellates isolated and identified wereCoolia malayensis,Amphidinium carteraeandProrocentrum hoffmannianum. [ABSTRACT FROM AUTHOR]