Subacute Cardiotoxicity of Yessotoxin: In Vitro and in Vivo Studies

Effects of okadaic acid, azaspiracid-1, yessotoxin and their binary mixtures on human intestinal Caco-2 cells

Phycotoxins are responsible for foodborne intoxications. Symptoms depend on the ingested toxins but mostly imply gastro-intestinal and neurological disorders. Importantly, humans are exposed to combinations of several phycotoxins, resulting in possible mixture effects. Most previous studies, however, have been focused on single toxin effects. Thus, the aim of this study was to examine the effects of binary mixtures of three main phycotoxins, okadaic acid (OA), azaspiracid-1 (AZA1) and yessotoxin (YTX), on human intestinal Caco-2 cells. The focus was placed on cell viability studies and inflammation responses using a multi-parametric approach to assess cell population (nuclei staining), cell metabolism/viability (reductase activity and lysosomal integrity), and release of inflammation markers (e.g., interleukins). Mixture effects were evaluated using the concentration addition (CA) and independent action (IA) models. Our assays show that none of the toxins had an impact on the cell population in the tested concentration range. Only OA modulated reductase activity, while all three toxins had strong effects on lysosomal integrity. Furthermore, all toxins triggered the release of interleukin 8 (IL-8), with OA being most potent. Mixture effect analysis showed additivity in most cases. However, supra-additivity was observed in regards to IL-6 and IL-8 release for combinations implying high concentrations of OA. This study extends the knowledge on mixture effects of phycotoxins in human cells.

Red tides in the Galician rías: historical overview, ecological impact, and future monitoring strategies

The Galician rías (NW Iberia, Spain) are coastal embayments at the northern boundary of the Canary Current upwelling system. Their favourable conditions for phytoplankton growth turn them into a suitable area for the development of aquaculture activities and a site of most of the national shellfish production. Phytoplankton blooms, a natural phenomenon inside the rías, under certain conditions eventually lead to seawater discolourations (colloquially known as "red tides"). Because of their transient nature, available records derive mainly from opportunistic samplings or casual observations, and are scattered in the literature. As a rule of thumb, red tides in the NW Iberian Peninsula are of non-toxic nature and are not systematically monitored. However, in recent years striking exceptions such as those of the toxic dinoflagellate Alexandrium minutum, a producer of paralytic shellfish toxins, have been registered. The present study goes through a historical overview of red tides in the Galician rías, describing their colouring, responsible organisms, seasonal and geographical occurrence, and their association with other features (harmful algal blooms, biotoxins and shellfish harvesting closures, bioluminescence, etc.), ending with social challenges and proposals for improving the monitoring of red tides in the future.

Yessotoxins in Mollusks of the Galician Coast from 2014 to 2022: Variability, Biotransformation, and Resistance to Alkaline Hydrolysis

The presence of yessotoxins (YTXs) was analyzed in 10,757 samples of Galician bivalves from 2014 to 2022. Only YTX and 45-OH YTX were found. YTX was detected in 31% of the samples, while 45-OH YTX was found in 11.6% of them. Among the samples containing YTX, 45-OH YTX was detected in 37.3% of cases. The maximum recorded levels were 1.4 and 0.16 mg of YTX-equivalentsg-1, for YTX and 45-OH YTX, respectively, which are well below the regulatory limit of the European Union. The YTX and 45-OH YTX toxicities in the raw extracts and extracts subjected to alkaline hydrolysis were strongly and linearly related. Due to the lack of homo-YTX in Galician samples, the effect of alkaline hydrolysis on homo-YTX and 45OH-Homo-YTX was only checked in 23 additional samples, observing no negative effect but a high correlation between raw and hydrolyzed extracts. Hydrolyzed samples can be used instead of raw ones to carry out YTXs determinations in monitoring systems, which may increase the efficiency of those systems where okadaic acid episodes are very frequent and therefore a higher number of hydrolyzed samples are routinely analyzed. The presence of YTX in the studied bivalves varied with the species, with mussels and cockles having the highest percentages of YTX-detected samples. The presence of 45-OH YTX was clearly related to YTX and was detected only in mussels and cockles. Wild populations of mussels contained proportionally more 45-OH YTX than those that were raft-cultured. Spatially, toxin toxicities varied across the sampling area, with higher levels in raft-cultured mussels except those of Ría de Arousa. Ría de Ares (ARE) was the most affected geographical area, although in other northern locations, lower toxin levels were detected. Seasonally, YTX and 45-OH YTX toxicities showed similar patterns, with higher levels in late summer and autumn but lower toxicities of the 45-OH toxin in August. The relationship between the two toxins also varied seasonally, in general with a minimum proportion of 45-OH YTX in July-August but with different maximum levels for raft-cultured and wild mussel populations. Interannually, the average toxicities of YTX decreased from 2014 to 2017 and newly increased from 2018 to 2021, but decreased slightly in 2022. The relationship between 45-OH YTX and YTX also varied over the years, but neither a clear trend nor a similar trend for wild and raft mussels was observed.

Natural Polyketides Act as Promising Antifungal Agents

Invasive fungal infections present a significant risk to human health. The current arsenal of antifungal drugs is hindered by drug resistance, limited antifungal range, inadequate safety profiles, and low oral bioavailability. Consequently, there is an urgent imperative to develop novel antifungal medications for clinical application. This comprehensive review provides a summary of the antifungal properties and mechanisms exhibited by natural polyketides, encompassing macrolide polyethers, polyether polyketides, xanthone polyketides, linear polyketides, hybrid polyketide non-ribosomal peptides, and pyridine derivatives. Investigating natural polyketide compounds and their derivatives has demonstrated their remarkable efficacy and promising clinical application as antifungal agents.

Spatiotemporal distribution characteristics of yessotoxins and pectenotoxins in phytoplankton and shellfish collected from the southern coast of South Korea

The distribution characteristics of lipophilic marine biotoxins (LMTs), such as yessotoxins (YTXs) and pectenotoxins (PTXs) in phytoplankton, mussels, and commercial seafood were determined for the southern coast of South Korea. Gonyaulax spinifera and Dinophysis acuminata, which are the causative microalgae of YTXs and PTXs, were recorded during summer. Homo-YTX and PTX-2 were predominantly detected in phytoplankton (max: 5.7 μg g^-1 ww), whereas only YTXs were detected in mussels (max: 1.1 μg g^-1 ww). LMT concentrations in mussels were positively correlated with those in phytoplankton. However, there was a 1-month time gap in maximum LMT concentrations between mussels and phytoplankton. Homo-YTX was detected in commercial seafood, including red scallop and comb pen shell. However, homo-YTX concentrations in shellfish were below the recommended value of the European Food Safety Authority (3.75 mg YTX equivalents kg^-1); thus, the consumption of this seafood was not considered to be a significant risk for human health.

The occurrence of lipophilic toxins in shellfish from the Middle Adriatic Sea

The first survey of the phycotoxin profile in mussels (Mytilus galloprovincialis) from the coastal waters of Bosnia and Herzegovina (The Bay of Neum, Middle Adriatic Sea) in correlation to the Makarska City Bay (Croatia, Middle Adriatic Sea) was conducted in 2017. Throughout the monitoring period, occasions of gymnodimine (GYM) and azaspiracid (AZA2) shellfish toxicity were recorded in concentrations that do not endanger human health. The occurrence of yessotoxins (YTXs), the most common toxins found in the Adriatic Sea, was correlated to the presence of the Gonyaulax species, a potential source of YTX. The DSP group of toxins is represented by the ester-OA. Phytoplankton analysis confirmed the presence of dinoflagellates from the Prorocentrum genus, a species associated with DSP toxicity. Occurrence frequency and variability of toxin composition were investigated in conjunction to physico-chemical parameters in the surrounding sea water. In the central Adriatic Sea, the infestation period ranges in general from June to August. However, the depuration phase extended beyond September in the Bay of Neum, increasing the length of the decontamination period.

Structure Elucidation and Relative Toxicity of (24R)-24-Hydroxyyessotoxin from a Namibian Isolate of Gonyaulax spinifera

Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis of a Namibian strain of Gonyaulax spinifera showed the presence of a number of yessotoxins (YTXs). Principal among these were YTX (1), homoYTX (2), and a tentative hydroxylated analogue that did not correspond to any previously confirmed YTX structures. Culturing the G. spinifera strain afforded sufficient biomass for purification of the new analogue through a series of solvent partitioning and chromatographic steps, yielding ∼0.9 mg as a solid. NMR spectroscopy, ion-trap mass spectrometry, and HRMS identified the new analogue as 24-hydroxyYTX (7). Purified 24-hydroxyYTX was quantitated by NMR, and its relative toxicity evaluated using two embryonic zebrafish toxicity assays. 24-HydroxyYTX demonstrated reduced toxicity compared to YTX.

Determination of Lipophilic Marine Biotoxins in Mussels Harvested from the Adriatic Sea by LC-MS/MS

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.

How Safe Is Safe for Marine Toxins Monitoring?

Current regulation for marine toxins requires a monitoring method based on mass spectrometric analysis. This method is pre-targeted, hence after searching for pre-assigned masses, it identifies those compounds that were pre-defined with available calibrants. Therefore, the scope for detecting novel toxins which are not included in the monitoring protocol are very limited. In addition to this, there is a poor comprehension of the toxicity of some marine toxin groups. Also, the validity of the current approach is questioned by the lack of sufficient calibrants, and by the insufficient coverage by current legislation of the toxins reported to be present in shellfish. As an example, tetrodotoxin, palytoxin analogs, or cyclic imines are mentioned as indicators of gaps in the system that require a solid comprehension to assure consumers are protected.