The cytotoxicity and genotoxicity of okadaic acid are cell-line dependent.

Okadaic acid (OA) is a polyether fatty acid produced mainly by dinoflagellates causing diarrhoeic shellfish poisoning (DSP) in humans. To resolve the controversies concerning its genotoxicity in vitro, we have investigated eventual specific cellular response in DOK, Caco-2 (Deltap53/p53(-)), HepG-2 and C6 glioma cells using the DNA damage detection test (3d DNA repair test: nucleotide excision repair (NER) and base excision repair (BER)), caspase-3-triggered apoptosis, neutral red (NR) and lactate dehydrogenase (LDH) release tests. At low concentrations of OA (10nM), cytotoxicity measured by LDH release is more marked in DOK cells, indicating necrotic cell death that occurs only slightly in HepG-2 cells. At the same concentration, caspase-3 activation-dependent apoptosis and DNA damage caused by OA were only detected in HepG-2 cells. This apoptosis appears to be p53 gene dependent. Cell death occurs in the other cell types only by necrosis at OA concentrations amended to cultures. Among the tested cell lines, HepG-2 cells are the most sensitive to OA (10-50nM) at 12 and 72h as revealed by the NR test. The 3D test shows that only HepG-2 cells bear damaged DNA at tested concentrations. It is concluded that the genotoxicity of OA is chiefly cell type dependent and concentration dependent, giving sense to controversial genotoxicity data found in the literature.

Evaluation of the cytotoxicity and genotoxicity of extracts of mussels originating from Moroccan Atlantic coast, in human colonic epithelial cells Caco-2.

Industrial processing of phosphates generates chemical wastes which are, without any treatment, discharged directly into the Atlantic Ocean at Jorf Lasfar (JL), located 120 km south of Casablanca (Morocco) were shellfish are also collected by people without any control. Marine bivalves concentrate these pollutants by filtration and serve as vectors in human's exposure. The objective of this study was to test and compare in vitro on human intestinal cells (Caco-2) the cytotoxicity and genotoxicity of mussels (Mytilus galloprovincialis) extracts (either hydrophilic or lipophilic) collected at two coastal sites; JL (neighboring a phosphate processing plat-form) and Oualidia (OL) (a vegetable growing area) located 160 km south of Casablanca (i.e. 40 km south of JL). Using Caco-2 cells, the following end-points have been evaluated, cytotoxicity as measured by MTS test, inhibition of cellular macromolecules syntheses (DNA and protein) and genotoxicity evaluated by DNA fragmentation in agarose gel electrophoresis. The results indicated, that hydrophilic and lipophilic OL mussels extracts are cytotoxic and inhibit cellular macromolecules syntheses. Moreover these extracts damage the DNA in Caco-2 cells. The lipophilic JL mussels extract is cytotoxic, inhibits cellular macromolecules syntheses, and damages the DNA in Caco-2 cells whereas the hydrophilic extract of JL mussels fails to inhibit protein synthesis and does not damage the DNA. This extract rather enhances protein synthesis, suggesting possible metallothioneins induction by metal ions. Altogether these in vitro data indicate that mussels collected from OL could be more harmful than those from JL even though the later is closer to the pollution site than OL. Nevertheless consumption of mussels from all these areas may present a risk for humans. Epidemiological studies will be needed for global risk assessment in humans living in these areas especially those consuming see food regularly.

Effects of combinations of Fusarium mycotoxins on the inhibition of macromolecular synthesis, malondialdehyde levels, DNA methylation and fragmentation, and viability in Caco-2 cells.

We studied the interactive effects of either binary or tertiary mixtures of Fusarium mycotoxins, deoxynivalenol (DON), zearalenone (ZEA), and fumonisin B1 (FB1) on the human intestinal cell line, Caco-2, using the endpoints including malonedialdehyde (MDA) production, inhibition of protein and DNA syntheses, DNA methylation, DNA fragmentation, and cell viability as measured by the neutral red (NR) test. The mixtures of mycotoxins reduce cellular viability in increasing order: [FB1+ZEA]<[FB1+DON]<[ZEA+DON]<[FB1+DON+ZEA] in NR test. Because FB1 antagonizes the effects of estrogenic Zearalenone, FB1 was assayed against estradiol. In NR assay, mixture of FB1 and estradiol and/or ZEA improves Caco-2 cells viability in contrast to individual effects. Mixtures of ZEA or FB1 and DON, display synergistic effects in lipid peroxidation. The ability of the toxins to inhibit DNA synthesis is 45%, 70%, and 43% for 10 microM of ZEA, DON, and FBI, respectively. Their binary mixtures (at 10 microM each), inhibit DNA synthesis by 35%, 62%, and 65%, far less than additive effects. Surprisingly, the tertiary mixture (10 microM each) only inhibits DNA synthesis by 25%. ZEA, DON, and FB1 induce DNA fragmentation individually. However, mixtures of these mycotoxins always damage DNA to a greater extent. Each individual mycotoxin (10 microM) raises the percentage of 5-methylcytosine (m5dC) in DNA from 4.5% to 9%, while the combination does not increase this rate any further. Altogether, the data indicate that mixtures of Fusarium toxins are able to induce lipid peroxidation, DNA damage, DNA fragmentation, DNA methylation, and cytotoxicity in Caco-2 cells, and suggest a potential promoter effect in human intestinal cells.

Survey of air pollution in Cotonou, Benin--air monitoring and biomarkers.

Exposure to genotoxic compounds present in ambient air has been studied in Cotonou, Benin, a city where two-stroke motorbikes are the major form of transportation and gasoline quality is poor. Personal monitoring and biomarkers were used to assess the exposure. Non-smoking taxi-moto drivers (city) and village residents were the study subjects. Benzene exposure was significantly higher in the city, as compared to the village (76.0+/-26.8 microg/m(3) versus 3.4+/-3.0, p=0.0004). Urinary excretion of benzene and S-phenylmercapturic acid (S-PMA) were also highest in subjects living in the city, whereas 1-hydroxypyrene was not different. The level of total polycyclic aromatic hydrocarbons (PAHs), associated with particles, ranged from 76.21 to 103.23 in Cotonou versus 1.55 ng/m(3) for the village. Determination of DNA damage in lymphocytes showed that subjects from the city had elevated number of lesions compared to subjects in the village in terms of bulky DNA adducts, 8-hydroxy-2'-deoxyguanosine and 5-methylcytosine, whereas DNA fragmentations analysed by alkaline gel electrophoresis was not different between the subjects. In conclusion, this study shows that air pollution is pronounced in Cotonou, Bénin and is associated with elevated levels of DNA damage in residents of the city compared to people living in a non-polluted rural village.

Comparative study of cytotoxicity and oxidative stress induced by deoxynivalenol, zearalenone or fumonisin B1 in human intestinal cell line Caco-2.

Fusarium species infestations of cereals crops occur worldwide. Fusarium toxins such as, deoxynivalenol (DON), zearalenone (ZEN) and fumonisin B1 (FB1) have been shown to cause diverse toxic effects in animals and also suspected of disease causation in humans. From the literature and mechanistic point of view, DON binds to the ribosomal peptidyl-transferase and inhibits protein synthesis specifically and DNA synthesis consequently. ZEN known to be genotoxic, binds to 17-beta-estradiol receptors, induces lipid peroxidation, cell death and inhibits protein and DNA synthesis. FB1 disrupts sphingolipid metabolism, induces lipid peroxidation altering the cell membrane and causing cell death. We intended to compare DON, ZEN and FB1 (1-150 microM) cytotoxic effect and the pathways leading to cell death and related to oxidative stress and macromolecules syntheses in a human intestinal cell line in order to tentatively classify them according to their respective potential toxicity. The comparison reveals that all three mycotoxins bear, at variable degree, the capability of inducing lipid peroxidation (MDA production) and could be classified above 10 microM in decreasing potency order FB1>DON>ZEN. This effect seems to be related to their common target that is the mitochondria as revealed by MTT test and seemingly not related to sphingoids accumulation concerning FB1. DON and ZEN also adversely affect lysosomes in contrast to FB1. The three mycotoxins inhibit protein synthesis with respective IC50 of 5, 8.8 and 19 microM for DON, FB1 and ZEN confirming that protein synthesis is a specific target of DON. DNA synthesis is inhibited by DON, ZEN and FB1 with respective IC50 of 1.7, 10 and 20 microM. However at higher concentrations DNA synthesis seems to be restored for FB1 and DON suggesting a promoter activity. Altogether the potency of the three mycotoxins in macromolecules inhibition is DON>ZEN>FB1 in Caco-2 cells. It appears then that FB1 acts rather through lipid peroxidation while DON affects rather DNA and protein synthesis.

DNA fragmentation, apoptosis and cell cycle arrest induced by zearalenone in cultured DOK, Vero and Caco-2 cells: prevention by Vitamin E.

Zearalenone (ZEN) is a non-steroidal oestrogenic mycotoxin produced by several Fusarium species growing on cereals. ZEN and its metabolites bind to human oestrogen receptors and hence display oestrogenic and anabolic properties. Several lines of investigation suggest that ZEN may be genotoxic in vivo. ZEN damages DNA in Bacillus subtilis recombination tests, and it induces sister chromatid exchange and chromosomal aberration in CHO cells. ZEN also induces DNA-adduct formation in mouse tissues and SOS repair process in lysogenic bacteria. In the present study, ZEN genotoxicity has been confirmed in three cell-lines, Vero, Caco-2 and DOK at concentrations of 10, 20 and 40 microM. Under these conditions, ZEN induces concentration-dependent DNA fragmentation resulting in DNA laddering patterns on agarose gel electrophoresis. This observation is consistent with apoptosis, which was confirmed by observations of formation of apoptotic bodies. Moreover, ZEN induces cell cycle arrest in the three cell-lines characterised by an increase of the number of cells in the G2/M phase of the cell cycle. Vitamin E (25 microM) added simultaneously with ZEN partially reduces DNA fragmentation and apoptotic body formation after 24h incubation. Vitamin E may act by maintaining prolonged cell cycle arrest during which time DNA repair takes place.

Comparative study of the toxic effects of fumonisin B1 in rat C6 glioma cells and p53-null mouse embryo fibroblasts.

The present experiments have been carried out in order to study (comparatively) oxidative stress and its consequences (i.e. modifications of DNA bases and/or DNA fragmentation), cell cycle progression (through two generations) and apoptosis in C6 glioma cells (with normal p53 status) and p53-null mouse embryonic fibroblasts (MEF) after incubation with fumonisin B(1) (FB(1)). Further endpoints, including protein and DNA syntheses as well as cytotoxicity, have been also studied. The results show that FB(1) (incubation) produced a significant increase of malondialdehyde (MDA) production (suggestive of lipid peroxidation) which was prevented by antioxidant agents in both cell types. Moreover, FB(1) induced a significant and dose-related increase of 8-OH-dG and DNA fragmentation in both C6 glioma and MEF cells. Unlike MEF cells, apoptotic C6 glioma cells were observed after FB(1) incubation. Moreover, suppression of cell cycle progression was observed in C6 glioma but not in MEF cell incubated with FB(1). The results suggest a possible loss of protective mechanisms (such as p53-dependent apoptosis and cell cycle arrest) in FB(1)-damaged MEF cells and confirm that cells lacking of mechanisms governed by p53 gene would be more susceptible to neoplastic cascade or mutation following DNA lesions induced by this mycotoxin.