Chlorination of microcystin-LR and cylindrospermopsin: Identification of byproducts and characterization of the residual toxicity

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Characterization of cylindrospermopsin chlorination by-products

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Identification of key pathways involved in the toxic response of the cyanobacterial toxin cylindrospermopsin in human hepatic HepaRG cells

International audienceThe hepatotoxin cylindrospermopsin (CYN) has been involved in cases of poisoning in humans following ingestion. As its liver toxicity process is complex, we studied the transcriptomic profile of HepaRG cells exposed to CYN. The affected pathways were confirmed through the expression of key genes and the investigation of toxicity markers. In addition, CYP450 activities and cell redox homeostasis were investigated following acute and repeated exposure. CYN induced the down-regulation of genes involved in xenobiotic metabolism and cell cycle progression. There was cell cycle disturbance characterised by an accumulation of G1/S and G2/M cells and an increase in phospho-H3-positive cells. This was linked to the induction of DNA damage demonstrated by an increase in γH2AX-positive cells as well as an accumulation of sub-G1 cells indicating apoptosis but not involving caspase-3. While glutathione (GSH) content sharply decreased following acute exposure to CYN, it increased following repeated exposure, reflecting an adaptive response of cell redox homeostasis. However, our data also suggested that CYN induced the down-regulation of phase I and II metabolism gene products, and CYP450 activities were affected following both acute and repeated exposure to CYN. Our study indicated that repeated exposure of liver cells to low concentrations of CYN may affect their detoxification capacities

DNA Adducts of the Tobacco Carcinogens 2‑Amino‑9<i>H</i>‑pyrido[2,3‑<i>b</i>]indole and 4‑Aminobiphenyl Are Formed at Environmental Exposure Levels and Persist in Human Hepatocytes

Aromatic amines and structurally related heterocyclic aromatic amines (HAAs) are produced during the combustion of tobacco or during the high-temperature cooking of meat. Exposure to some of these chemicals may contribute to the etiology of several common types of human cancers. 2-Amino-9<i>H</i>-pyrido­[2,3-<i>b</i>]­indole (AαC) is the most abundant HAA formed in mainstream tobacco smoke: it arises in amounts that are 25–100 times greater than the levels of the arylamine, 4-aminobiphenyl (4-ABP), a human carcinogen. 2-Amino-3,8-dimethylimidazo­[4,5-<i>f</i>]­quinoxaline (MeIQx) is a prevalent HAA formed in cooked meats. AαC and MeIQx are rodent carcinogens; however, their carcinogenic potency in humans is unknown. A preliminary assessment of the carcinogenic potential of these HAAs in humans was conducted by examining the capacity of primary human hepatocytes to form DNA adducts of AαC and MeIQx, in comparison to 4-ABP, followed by the kinetics of DNA adduct removal by cellular enzyme repair systems. The principal DNA adducts formed were <i>N</i>-(deoxyguanosin-8-yl) (dG-C8) adducts. Comparable levels of DNA adducts were formed with AαC and 4-ABP, whereas adduct formation was ∼5-fold lower for MeIQx. dG-C8-AαC and dG-C8-4-ABP were formed at comparable levels in a concentration-dependent manner in human hepatocytes treated with procarcinogens over a 10,000-fold concentration range (1 nM–10 μM). Pretreatment of hepatocytes with furafylline, a selective inhibitor of cytochrome P450 1A2, resulted in a strong diminution of DNA adducts signifying that P450 1A2 is a major P450 isoform involved in bioactivation of these procarcinogens. The kinetics of adduct removal varied for each hepatocyte donor. Approximately half of the DNA adducts were removed within 24 h of treatment; however, the remaining lesions persisted over 5 days. The high levels of AαC present in tobacco smoke and its propensity to form persistent DNA adducts in human hepatocytes suggest that AαC can contribute to DNA damage and the risk of hepatocellular cancer in smokers

Review and analysis of occurrence, exposure and toxicity of cyanobacteria toxins in food

Rapport paru dans EFSA Supporting Publications, 2016, vol13, n°2This report presents the extensive literature search conducted on 1) the occurrence of different cyanotoxins in food matrices; 2) the analytical methods for their detection; 3) their toxicological profile; 3) the environmental factors affecting toxicity of cyanobacterial population and 4) the combined effects of mixtures of cyanotoxins and other chemicals. It also includes a review of guidelines values or health-alert levels for cyanotoxins in food (or drinking water) adopted worldwide. The methodological aspects and the queries used in the extensive literature search, the collection and screening of retrieved papers and the inventory are briefly described in the report; all details are available in 3 supplementary appendices to this report. The analysis of collected papers indicated that most of them are focused on a single microcystin (MC) variant (MC-LR) out of the almost 100 MC known. Many studies on occurrence are affected by limited quality, due to analytical drawbacks in the detection methods and were not considered in the exposure assessment. Toxicity studies useful for the derivation of health based reference values are few, being many of them carried out using i.p. injection, which is poorly representative of actual human exposure. In addition, those toxicological studies carried out with poorly characterised cyanobacterial extracts or focused on single parameters, using a single dose, devoted to elucidation of mechanism of action, reporting qualitative description of effects were not used for data extraction. The relevant exposure scenarios are also described, although being the available data on exposure very limited, no definite conclusion on the health risks for the exposed population could be drawn. However, the possibility of risky exposure is evidenced for fish and shellfish consumers and for blue-green algae supplements (BGAS) as well in relation to MC contamination. Finally, many data gaps were identified

Le dioxyde de titane sous forme nanoparticulaire. Valeurs toxicologiques de référence. Le dioxyde de titane sous forme nanoparticulaire. Valeurs toxicologiques de référence. Avis de l’Anses. Collective expert appraisal report

Le dioxyde de titane sous forme nanoparticulaire est utilisé dans de nombreuses applications industrielles et commerciales. Dans le cadre de sa mission nationale d’élaboration de valeurs sanitaires de référence, l’Anses a été chargée de définir une Valeur Toxicologique de Référence (VTR) pour le dioxyde de titane sous forme nanoparticulaire (TiO2 -NP). Suite à une analyse approfondie de l’ensemble des données de toxicité disponibles, l’Agence recommande une VTR chronique par inhalation pour la forme P25 du TiO2-NP de 0,12 µg.m-3. A partir de cette valeur de référence, des évaluations de risques sanitaires seront menées dans le cadre des actions de gestion des installations et sites industriels en France. Il s’agit par ailleurs, de la première VTR élaborée pour un nanomatériau en France

DNA Adduct Formation of 4-Aminobiphenyl and Heterocyclic Aromatic Amines in Human Hepatocytes.

DNA adduct formation of the aromatic amine, 4-aminobiphenyl (4-ABP), a known human carcinogen present in tobacco smoke, and the heterocyclic aromatic amines (HAAs), 2-amino-9H-pyrido[2,3-b]indole (AαC), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), potential human carcinogens, which are also present in tobacco smoke or formed during the high-temperature cooking of meats, was investigated in freshly cultured human hepatocytes. The carcinogens (10 μM) were incubated with hepatocytes derived from eight different donors for time periods up to 24 h. The DNA adducts were quantified by liquid chromatography-electrospray ionization mass spectrometry with a linear quadrupole ion trap mass spectrometer. The principal DNA adducts formed for all of the carcinogens were N-(deoxyguanosin-8-yl) (dG-C8) adducts. The levels of adducts ranged from 3.4 to 140 adducts per 10(7) DNA bases. The highest level of adduct formation occurred with AαC, followed by 4-ABP, then by PhIP, MeIQx, and IQ. Human hepatocytes formed dG-C8-HAA-adducts at levels that were up to 100-fold greater than the amounts of adducts produced in rat hepatocytes. In contrast to HAA adducts, the levels of dG-C8-4-ABP adduct formation were similar in human and rat hepatocytes. These DNA binding data demonstrate that the rat, an animal model that is used for carcinogenesis bioassays, significantly underestimates the potential hepatic genotoxicity of HAAs in humans. The high level of DNA adducts formed by AαC, a carcinogen produced in tobacco smoke at levels that are up to 100-fold higher than the amounts of 4-ABP, is noteworthy. The possible causal role of AαC in tobacco-associated cancers warrants investigation

Genotoxic impact of aluminum-containing nanomaterials in human intestinal and hepatic cells

International audienceExposure of consumers to aluminum-containing nanomaterials (Al NMs) is an area of concern for public health agencies. As the available data on the genotoxicity of AlO and Al NMs are inconclusive or rare, the present study investigated their in vitro genotoxic potential in intestinal and liver cell models, and compared with the ionic form AlCl. Intestinal Caco-2 and hepatic HepaRG cells were exposed to Al and AlO NMs (0.03 to 80 μg/cm). Cytotoxicity, oxidative stress and apoptosis were measured using High Content Analysis. Genotoxicity was investigated through γH2AX labelling, the alkaline comet and micronucleus assays. Moreover, oxidative DNA damage and carcinogenic properties were assessed using the Fpg-modified comet assay and the cell transforming assay in Bhas 42 cells respectively. The three forms of Al did not induce chromosomal damage. However, although no production of oxidative stress was detected, AlO NMs induced oxidative DNA damage in Caco-2 cells but not likely related to ion release in the cell media. Considerable DNA damage was observed with Al NMs in both cell lines in the comet assay, likely due to interference with these NMs. No genotoxic effects were observed with AlCl. None of the Al compounds induced cytotoxicity, apoptosis, γH2AX or cell transformation