Novel Insights on the Toxicity of Phycotoxins on the Gut through the Targeting of Enteric Glial Cells

International audienceIn vitro and in vivo studies have shown that phycotoxins can impact intestinal epithelial cells and can cross the intestinal barrier to some extent. Therefore, phycotoxins can reach cells underlying the epithelium, such as enteric glial cells (EGCs), which are involved in gut homeostasis, motility, and barrier integrity. This study compared the toxicological effects of pectenotoxin-2 (PTX2), yessotoxin (YTX), okadaic acid (OA), azaspiracid-1 (AZA1), 13-desmethyl-spirolide C (SPX), and palytoxin (PlTX) on the rat EGC cell line CRL2690. Cell viability, morphology, oxidative stress, inflammation, cell cycle, and specific glial markers were evaluated using RT-qPCR and high content analysis (HCA) approaches. PTX2, YTX, OA, AZA1, and PlTX induced neurite alterations, oxidative stress, cell cycle disturbance, and increase of specific EGC markers. An inflammatory response for YTX, OA, and AZA1 was suggested by the nuclear translocation of NF-κB. Caspase-3-dependent apoptosis and induction of DNA double strand breaks (γH2AX) were also observed with PTX2, YTX, OA, and AZA1. These findings suggest that PTX2, YTX, OA, AZA1, and PlTX may affect intestinal barrier integrity through alterations of the human enteric glial system. Our results provide novel insight into the toxicological effects of phycotoxins on the gut

Simultaneous Quantification and Visualization of Titanium Dioxide Nanomaterial Uptake at the Single Cell Level in an In Vitro Model of the Human Small Intestine

International audienceUseful properties render titanium dioxide nanomaterials (NMs) to be one of the most commonly used NMs worldwide. TiO2 powder is used as food additives (E171), which may contain up to 36% nanoparticles. Consequently, humans could be exposed to comparatively high amounts of NMs that may induce adverse effects of chronic exposure conditions. Visualization and quantification of cellular NM uptake as well as their interactions with biomolecules within cells are key issues regarding risk assessment. Advanced quantitative imaging tools for NM detection within biological environments are therefore required. A combination of the label-free spatially resolved dosimetric tools, microresolved particle induced X-ray emission and Rutherford backscattering, together with high resolution imaging techniques, such as time-of-flight secondary ion mass spectrometry and transmission electron microscopy, are applied to visualize the cellular translocation pattern of TiO2 NMs and to quantify the NM-load, cellular major, and trace elements in differentiated Caco-2 cells as a function of their surface properties at the single cell level. Internalized NMs are not only able to impair the cellular homeostasis by themselves, but also to induce an intracellular redistribution of metabolically relevant elements such as phosphorus, sulfur, iron, and copper

Maitotoxin-4, a Novel MTX Analog Produced by Gambierdiscus excentricus

Maitotoxins (MTXs) are among the most potent toxins known. These toxins are produced by epi-benthic dinoflagellates of the genera Gambierdiscus and Fukuyoa and may play a role in causing the symptoms associated with Ciguatera Fish Poisoning. A recent survey revealed that, of the species tested, the newly described species from the Canary Islands, G. excentricus, is one of the most maitotoxic. The goal of the present study was to characterize MTX-related compounds produced by this species. Initially, lysates of cells from two Canary Island G. excentricus strains VGO791 and VGO792 were partially purified by (i) liquid-liquid partitioning between dichloromethane and aqueous methanol followed by (ii) size-exclusion chromatography. Fractions from chromatographic separation were screened for MTX toxicity using both the neuroblastoma neuro-2a (N2a) cytotoxicity and Ca2+ flux functional assays. Fractions containing MTX activity were analyzed using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) to pinpoint potential MTX analogs. Subsequent non-targeted HRMS analysis permitted the identification of a novel MTX analog, maitotoxin-4 (MTX4, accurate mono-isotopic mass of 3292.4860 Da, as free acid form) in the most toxic fractions. HRMS/MS spectra of MTX4 as well as of MTX are presented. In addition, crude methanolic extracts of five other strains of G. excentricus and 37 other strains representing one Fukuyoa species and ten species, one ribotype and one undetermined strain/species of Gambierdiscus were screened for the presence of MTXs using low resolution tandem mass spectrometry (LRMS/MS). This targeted analysis indicated the original maitotoxin (MTX) was only present in one strain (G. australes S080911_1). Putative maitotoxin-2 (p-MTX2) and maitotoxin-3 (p-MTX3) were identified in several other species, but confirmation was not possible because of the lack of reference material. Maitotoxin-4 was detected in all seven strains of G. excentricus examined, independently of their origin (Brazil, Canary Islands and Caribbean), and not detected in any other species. MTX4 may therefore serve as a biomarker for the highly toxic G. excentricus in the Atlantic area

Hazard characterization of Alternaria toxins to identify data gaps and improve risk assessment for human health

Fungi of the genus Alternaria are ubiquitous plant pathogens and saprophytes which are able to grow under varying temperature and moisture conditions as well as on a large range of substrates. A spectrum of structurally diverse secondary metabolites with toxic potential has been identified, but occurrence and relative proportion of the different metabolites in complex mixtures depend on strain, substrate, and growth conditions. This review compiles the available knowledge on hazard identification and characterization of Alternaria toxins. Alternariol (AOH), its monomethylether AME and the perylene quinones altertoxin I (ATX-I), ATX-II, ATX-III, alterperylenol (ALP), and stemphyltoxin III (STTX-III) showed in vitro genotoxic and mutagenic properties. Of all identified Alternaria toxins, the epoxide-bearing analogs ATX-II, ATX-III, and STTX-III show the highest cytotoxic, genotoxic, and mutagenic potential in vitro. Under hormone-sensitive conditions, AOH and AME act as moderate xenoestrogens, but in silico modeling predicts further Alternaria toxins as potential estrogenic factors. Recent studies indicate also an immunosuppressive role of AOH and ATX-II; however, no data are available for the majority of Alternaria toxins. Overall, hazard characterization of Alternaria toxins focused, so far, primarily on the commercially available dibenzo-α-pyrones AOH and AME and tenuazonic acid (TeA). Limited data sets are available for altersetin (ALS), altenuene (ALT), and tentoxin (TEN). The occurrence and toxicological relevance of perylene quinone-based Alternaria toxins still remain to be fully elucidated. We identified data gaps on hazard identification and characterization crucial to improve risk assessment of Alternaria mycotoxins for consumers and occupationally exposed workers.The European Partnership for the Assessment of Risks from Chemicals has received funding from the European Union’s Horizon Europe research and innovation program under Grant Agreement No 101057014 and has received co-funding of the authors’ institutions. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the Health and Digital Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.info:eu-repo/semantics/publishedVersio

From Basic Research to New Tools and Challenges for the Genotoxicity Testing of Nanomaterials

Genotoxicity is one of the key endpoints investigated as early as possible before marketing a product [...

Évaluation des effets génotoxiques et cancérogènes de la cylindrospermopsine, une cyanotoxine d'eau douce

La cylindrospermopsine (CYN), une hépatotoxine principalement produite par la cyanobactérie Cylindrospermopsis raciborskii, est un agent responsable d intoxications humaine et animale pouvant aller jusqu à la mort. En raison de l expansion géographique des efflorescences à cyanobactéries et de la contamination croissante des eaux douces par cette toxine en particulier en Europe y compris en France, l évaluation de la toxicité chronique de la CYN constitue un sujet incontournable en sécurité alimentaire. Les objectifs de ce projet de thèse étaient de caractériser le danger de la CYN pour l homme, sur les aspects de génotoxicité et de cancérogenèse. Ce travail met en évidence la génotoxicité de la CYN in vitro sur deux lignées cellulaires représentant des entérocytes et des hépatocytes humains, les Caco-2 et les HepaRG. La CYN serait un composé progénotoxique nécessitant au moins une étape de métabolisation par un cytochrome P450. In vivo, sur souris, la CYN induit, 24h après administration ip ou orale, des dommages primaires au niveau de l ADN dans le colon ainsi que la mort cellulaire, probablement par apoptose, dans les reins et le foie. De plus, suite au traitement par gavage, la CYN induit des altérations primaires de l ADN dans la moelle osseuse. Le test du micronoyau réalisé sur moelle osseuse et sur colon n indique cependant aucune altération chromosomique induite par la CYN. Enfin concernant la cancérogénicité, la CYN induit la transformation cellulaire des cellules SHE (Syrian Hamster Embryo) à très faibles doses ce qui atteste de son potentiel cancérogène. Afin d appréhender les mécanismes sous jacents à ces effets, les paramètres toxicocinétiques et toxicodynamiques de la CYN seraient à déterminer.AbstractRENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Contribution à l évaluation de la génotoxicité par des tests in vitro et in vivo (application à des toxines de cyanobactéries, les microcystines -LR et -RR)

Les microcystines sont des toxines de cyanobactéries responsables d intoxications animales et humaines répertoriées à travers le monde. La microcystine-LR (MCLR) vient d être classée comme potentiellement cancérogène pour l homme . En effet, une activité de promotion tumorale a été observée. Cependant, la génotoxicité de la MCLR reste controversée. Ce travail a contribué à l évaluation de la génotoxicité in vitro et in vivo de deux variants, les MCLR et -RR. Trois tests détectant des dommages à l ADN ont été choisis: le test des comètes, le test UDS et le test du micronoyau. Nous avons démontré que la MCLR est un composé génotoxique in vitro, mais ces données n ont pas été confirmées in vivo. Par ailleurs, la MCLR a induit un stress oxydant pouvant être impliqué dans le processus de formation des dommages à l ADN. Avec la MCRR, nos résultats suggèrent que le remplacement d un seul acide aminé au sein de la structure moléculaire induit une variation du potentiel toxique et génotoxique.Microcystins are toxins of cyanobacteria responsible for humans and animals poisonings throughout the world. Recently, microcystin-LR (MCLR) was considered like possibly carcinogenic to humans . In fact, MCLR is a potent tumour promoter. However, the genotoxic status of MCLR remains unclear. This work contributes to the evaluation of the in vitro and in vivo genotoxicity of two variants, MCLR and -RR. Three assays detecting DNA damages were chosen: the comet, the UDS and the micronucleus assays. We demonstrated that MCLR is a genotoxic compound in vitro, but these data were not confirmed in vivo. Otherwise, MCLR induced an oxidative stress, which could be implicated into the process of the formation of DNA damages. With MCRR, ours results suggested that the replacement of one amino acid into the molecular structure induces a variation of the toxic and genotoxic potential.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF