Yessotoxin triggers ribotoxic stress

First report of epiphytic dinoflagellate Coolia malayensis (Dinophyceae) in the southeastern Pacific Ocean

Coolia species are epiphytic and benthic dinoflagellates with a cosmopolitan distribution in tropical and subtropical areas. In the austral summer of 2016, during a survey in Bahía Calderilla, a dinoflagellate of the genus Coolia was detected in macroalgae samples, and a clonal culture was established. Subsequently, the cultured cells were observed by scanning electron microscopy (SEM) and identified as C. malayensis based on their morphological characteristics. Phylogenetic analyses based on the LSU rDNA D1/D2 regions confirmed that strain D005-1 corresponded to C. malayensis and clustered with strains isolated from New Zealand, Mexico, and Asia Pacific countries. Although the strain D005-1 culture did not contain yessotoxin (YTX), cooliatoxin, 44-methyl gambierone, or its analogs in detectable amounts by LC-MS/MS, more research is needed to evaluate its toxicity and to determine the possible impact of C. malayensis in northern Chilean waters.

Shiga Toxins as Antitumor Tools

Shiga toxins (Stxs), also known as Shiga-like toxins (SLT) or verotoxins (VT), constitute a family of structurally and functionally related cytotoxic proteins produced by the enteric pathogens Shigella dysenteriae type 1 and Stx-producing Escherichia coli (STEC). Infection with these bacteria causes bloody diarrhea and other pathological manifestations that can lead to HUS (hemolytic and uremic syndrome). At the cellular level, Stxs bind to the cellular receptor Gb3 and inhibit protein synthesis by removing an adenine from the 28S rRNA. This triggers multiple cellular signaling pathways, including the ribotoxic stress response (RSR), unfolded protein response (UPR), autophagy and apoptosis. Stxs cause several pathologies of major public health concern, but their specific targeting of host cells and efficient delivery to the cytosol could potentially be exploited for biomedical purposes. Moreover, high levels of expression have been reported for the Stxs receptor, Gb3/CD77, in Burkitt's lymphoma (BL) cells and on various types of solid tumors. These properties have led to many attempts to develop Stxs as tools for biomedical applications, such as cancer treatment or imaging, and several engineered Stxs are currently being tested. We provide here an overview of these studies.

Blue-Print Autophagy in 2020: A Critical Review

Autophagy is an elegant and complex biological process that has recently attracted much attention from the scientific community. The compounds which are capable of control and modulation of this process have a promising potential as therapeutics for a number of pathological conditions, including cancer and neurodegenerative disorders. At the same time, due to the relatively young age of the field, there are still some pitfalls in the autophagy monitoring assays and interpretation of the experimental data. This critical review provides an overview of the marine natural compounds, which have been reported to affect autophagy. The time period from the beginning of 2016 to the middle of 2020 is covered. Additionally, the published data and conclusions based on the experimental results are re-analyzed with regard to the guidelines developed by Klionsky and colleagues (Autophagy. 2016; 12(1): 1–222), which are widely accepted by the autophagy research community. Remarkably and surprisingly, more than half of the compounds reported to be autophagy activators or inhibitors could not ultimately be assigned to either category. The experimental data reported for those substances could indicate both autophagy activation and inhibition, requiring further investigation. Thus, the reviewed molecules were divided into two groups: having validated and non-validated autophagy modulatory effects. This review gives an analysis of the recent updates in the field and raises an important problem of standardization in the experimental design and data interpretation.

Single-Cell Tracking of A549 Lung Cancer Cells Exposed to a Marine Toxin Reveals Correlations in Pedigree Tree Profiles

Long-term video-based tracking of single A549 lung cancer cells exposed to three different concentrations of the marine toxin yessotoxin (YTX) reveals significant variation in cytotoxicity, and it confirms the potential genotoxic effects of this toxin. Tracking of single cells subject to various toxic exposure, constitutes a conceptually simple approach to elucidate lineage correlations and sub-populations which are masked in cell bulk analyses. The toxic exposure can here be considered as probing a cell population for properties and change which may include long-term adaptation to treatments. Ranking of pedigree trees according to a measure of "size," provides definition of sub-populations. Following single cells through generations indicates that signaling cascades and experience of mother cells can pass to their descendants. Epigenetic factors and signaling downstream lineages may enhance differences between cells and partly explain observed heterogeneity in a population. Signaling downstream lineages can potentially link a variety of observations of cells making resulting data more suitable for computerized treatment. YTX exposure of A549 cells tends to cause two main visually distinguishable classes of cell death modalities ("apoptotic-like" and "necrotic-like") with approximately equal frequency. This special property of YTX enables estimation of correlation between cell death modalities for sister cells indicating impact downstream lineages. Hence, cellular responses and adaptation to treatments might be better described in terms of effects on pedigree trees rather than considering cells as independent entities.

Biotechnological and Pharmacological Applications of Biotoxins and Other Bioactive Molecules from Dinoflagellates

The long-lasting interest in bioactive molecules (namely toxins) produced by (microalga) dinoflagellates has risen in recent years. Exhibiting wide diversity and complexity, said compounds are well-recognized for their biological features, with great potential for use as pharmaceutical therapies and biological research probes. Unfortunately, provision of those compounds is still far from sufficient, especially in view of an increasing demand for preclinical testing. Despite the difficulties to establish dinoflagellate cultures and obtain reasonable productivities of such compounds, intensive research has permitted a number of advances in the field. This paper accordingly reviews the characteristics of some of the most important biotoxins (and other bioactive substances) produced by dinoflagellates. It also presents and discusses (to some length) the main advances pertaining to dinoflagellate production, from bench to large scale-with an emphasis on material published since the latest review available on the subject. Such advances encompass improvements in nutrient formulation and light supply as major operational conditions; they have permitted adaptation of classical designs, and aided the development of novel configurations for dinoflagellate growth-even though shearing-related issues remain a major challenge.

Mitotic Catastrophe in BC3H1 Cells following Yessotoxin Exposure

The marine toxin yessotoxin (YTX) can cause various cytotoxic effects depending on cell type and cell line. It is well known to trigger distinct mechanisms for programmed cell death which may overlap or cross-talk. The present contribution provides the first evidence that YTX can cause genotoxicity and induce mitotic catastrophe which can lead to different types of cell death. This work also demonstrates potential information gain from non-intrusive computer-based tracking of many individual cells during long time. Treatment of BC3H1 cells at their exponential growth phase causes atypical nuclear alterations and formation of giant cells with multiple nuclei. These are the most prominent morphological features of mitotic catastrophe. Giant cells undergo slow cell death in a necrosis-like manner. However, apoptotic-like cell death is also observed in these cells. Electron microscopy of treated BC3H1 cells reveal uncondensed chromatin and cells with double nuclei. Activation of p-p53, p-H2AX, p-Chk1, p-ATM, and p-ATR and down-regulation of p-Chk2 indicate DNA damage response and cell cycle deregulation. Micronuclei formation further support this evidence. Data from tracking single cells reveal that YTX treatment suppresses a second round of cell division in BC3H1 cells. These findings suggest that YTX can induce genomic alterations or imperfections in chromosomal segregation leading to permanent mitotic failure. This understanding extends the list of effects from YTX and which are of interest to control cancer and tumor progression.

Subacute Cardiotoxicity of Yessotoxin: In Vitro and in Vivo Studies

Yessotoxin (YTX) is a marine phycotoxin produced by dinoflagellates and accumulated in filter feeding shellfish. Although no human intoxication episodes have been reported, YTX content in shellfish is regulated by many food safety authorities due to their worldwide distribution. YTXs have been related to ultrastructural heart damage in vivo, but the functional consequences in the long term have not been evaluated. In this study, we explored the accumulative cardiotoxic potential of YTX in vitro and in vivo. Preliminary in vitro evaluation of cardiotoxicity was based on the effect on hERG (human ether-a-go-go related gene) channel trafficking. In vivo experiments were performed in rats that received repeated administrations of YTX followed by recordings of electrocardiograms, arterial blood pressure, plasmatic cardiac biomarkers, and analysis of myocardium structure and ultrastructure. Our results showed that an exposure to 100 nM YTX for 12 or 24 h caused an increase of extracellular surface hERG channels. Furthermore, remarkable bradycardia and hypotension, structural heart alterations, and increased plasma levels of tissue inhibitor of metalloproteinases-1 were observed in rats after four intraperitoneal injections of YTX at doses of 50 or 70 μg/kg that were administered every 4 days along a period of 15 days. Therefore, and for the first time, YTX-induced subacute cardiotoxicity is supported by evidence of cardiovascular function alterations related to its repeated administration. Considering international criteria for marine toxin risk estimation and that the regulatory limit for YTX has been recently raised in many countries, YTX cardiotoxicity might pose a health risk to humans and especially to people with previous cardiovascular risk.

New scenario for speciation in the benthic dinoflagellate genus Coolia (Dinophyceae)

In this study, inter- and intraspecific genetic diversity within the marine harmful dinoflagellate genus Coolia Meunier was evaluated using isolates obtained from the tropics to subtropics in both Pacific and Atlantic Ocean basins. The aim was to assess the phylogeographic history of the genus and to clarify the validity of established species including Coolia malayensis. Phylogenetic analysis of the D1-D2 LSU rDNA sequences identified six major lineages (L1-L6) corresponding to the morphospecies Coolia malayensis (L1), C. monotis (L2), C. santacroce (L3), C. palmyrensis (L4), C. tropicalis (L5), and C. canariensis (L6). A median joining network (MJN) of C. malayensis ITS2 rDNA sequences revealed a total of 16 haplotypes; however, no spatial genetic differentiation among populations was observed. These MJN results in conjunction with CBC analysis, rDNA phylogenies and geographical distribution analyses confirm C. malayensis as a distinct species which is globally distributed in the tropical to warm-temperate regions. A molecular clock analysis using ITS2 rDNA revealed the evolutionary history of Coolia dated back to the Mesozoic, and supports the hypothesis that historical vicariant events in the early Cenozoic drove the allopatric differentiation of C. malayensis and C. monotis.

Yessotoxin, a Promising Therapeutic Tool

Yessotoxin (YTX) is a polyether compound produced by dinoflagellates and accumulated in filter feeding shellfish. No records about human intoxications induced by this compound have been published, however it is considered a toxin. Modifications in second messenger levels, protein levels, immune cells, cytoskeleton or activation of different cellular death types have been published as consequence of YTX exposure. This review summarizes the main intracellular pathways modulated by YTX and their pharmacological and therapeutic implications.

Autophagic activity in BC3H1 cells exposed to yessotoxin

The marine toxin yessotoxin (YTX) can induce programmed cell death through both caspase-dependent and -independent pathways in various cellular systems. It appears to stimulate different forms of cellular stress causing instability among cell death mechanisms and making them overlap and cross-talk. Autophagy is one of the key pathways that can be stimulated by multiple forms of cellular stress which may determine cell survival or death. The present work evaluates a plausible link between ribotoxic stress and autophagic activity in BC3H1 cells treated with YTX. Such treatment produces massive cytoplasmic compartments as well as double-membrane vesicles termed autophagosomes which are typically observed in cells undergoing autophagy. The observed autophagosomes contain a large amount of ribosomes associated with the endoplasmic reticulum (ER). Western blotting analysis of Atg proteins and detection of the autophagic markers LC3-II and SQSTM1/p62 by flow cytometry and immunofluorescence verified autophagic activity during YTX-treatment. The present work supports the idea that autophagic activity upon YTX exposure may represent a response to ribotoxic stress.

Lifetime Distributions from Tracking Individual BC3H1 Cells Subjected to Yessotoxin

This work shows examples of lifetime distributions for individual BC3H1 cells after start of exposure to the marine toxin yessotoxin (YTX) in an experimental dish. The present tracking of many single cells from time-lapse microscopy data demonstrates the complexity in individual cell fate and which can be masked in aggregate properties. This contribution also demonstrates the general practicality of cell tracking. It can serve as a conceptually simple and non-intrusive method for high throughput early analysis of cytotoxic effects to assess early and late time points relevant for further analyzes or to assess for variability and sub-populations of interest. The present examples of lifetime distributions seem partly to reflect different cell death modalities. Differences between cell lifetime distributions derived from populations in different experimental dishes can potentially provide measures of inter-cellular influence. Such outcomes may help to understand tumor-cell resistance to drug therapy and to predict the probability of metastasis.