In vitro study of carbon black nanoparticles on human pulmonary artery endothelial cells: effects on calcium signaling and mitochondrial alterations.

Human exposure to manufactured nanoparticles (NPs) is a public health concern. Endothelial cells lining the inner surface of arteries could be one of the primary targets for inhaled nanoparticles. Moreover, it is well known that alteration in calcium signaling is a critical event involved in the physiopathology of cardiovascular diseases. The objective of this study was to assess the role of oxidative stress in carbon black FW2 NPs-induced alteration in calcium signaling and mitochondria in human pulmonary artery endothelial cells. To this end, cells were exposed for 4 or 24 h to FW2 NPs (1-10 µg/cm2) and the following endpoints were studied: (i) production of ROS by fluorimetry and electron paramagnetic resonance, (ii) variation in intracellular calcium concentration by confocal microscopy, and (iii) mitochondrial alteration and apoptosis by confocal microscopy and transmission electronic microscopy. Exposure to FW2 NPs concentration-dependently increases oxidative stress, evidenced by the production of superoxide anion leading to an alteration in calcium content of intracellular organelles, such as endoplasmic reticulum and mitochondria activating, in turn, intrinsic apoptosis. This study provides evidence that FW2 NPs exposure impairs calcium signaling and mitochondria triggered by oxidative stress, and, thus, could act as a cardiovascular disease risk owing to the key role of calcium homeostasis in the control of vascular tone.

Effects of FW2 Nanoparticles Toxicity in a New In Vitro Pulmonary Vascular Cells Model Mimicking Endothelial Dysfunction.

Several epidemiological studies have revealed the involvement of nanoparticles (NPs) in respiratory and cardiovascular mortality. In this work, the focus will be on the effect of manufactured carbon black NPs for risk assessment of consumers and workers, as human exposure is likely to increase. Since the pulmonary circulation could be one of the primary targets of inhaled NPs, patients suffering from pulmonary hypertension (PH) could be a population at risk. To compare the toxic effect of carbon black NPs in the pulmonary circulation under physiologic and pathological conditions, we developed a new in vitro model mimicking the endothelial dysfunction and vascular dynamics observed in vascular pathology such as PH. Human pulmonary artery endothelial cells were cultured under physiological conditions (static and normoxia 21% O2) or under pathological conditions (20% cycle stretch and hypoxia 1% O2). Then, cells were treated for 4 or 6 h with carbon black FW2 NPs from 5 to 10 µg/cm2. Different endpoints were studied: (i) NPs internalization by transmission electronic microscopy; (ii) oxidative stress by CM-H2DCFDA probe and electron paramagnetic resonance; (iii) NO (nitrites and nitrates) production by Griess reaction; (iv) inflammation by ELISA assay; and (v) calcium signaling by confocal microscopy. The present study characterizes the in vitro model mimicking endothelial dysfunction in PH and indicates that, under such pathological conditions, oxidative stress and inflammation are increased along with calcium signaling alterations, as compared to the physiological conditions. Human exposure to carbon black NPs could produce greater deleterious effects in vulnerable patients suffering from cardiovascular diseases.

[Involvement of the Piezo1 and TRPV4 stretch-activated channels in pulmonary hypertension]. / Implication des canaux mécanosensibles Piezo1 et TRPV4 dans l'hypertension pulmonaire.

Pulmonary hypertension is a pulmonary circulation pathology characterized by remodelling and hyperreactivity of the pulmonary arteries. Vasodilatation/vasoconstriction balance is modified in favour of constriction via, among other things, the proliferation of smooth muscle cells and the development of endothelial dysfunction. In addition, the pulmonary arteries undergo modification of mechanical forces, inducing modified activation of stretch-activated channels (SAC) such as Piezo1 and TRPV4. These ionic channels are sensitive to stretch and their activation can induce various cellular physiological responses, which strongly contribute to development and continuation of the pathology.

Involvement of oxidative stress and calcium signaling in airborne particulate matter - induced damages in human pulmonary artery endothelial cells.

Recent studies have revealed that particulate matter (PM) exert deleterious effects on vascular function. Pulmonary artery endothelial cells (HPAEC), which are involved in the vasomotricity regulation, can be a direct target of inhaled particles. Modifications in calcium homeostasis and oxidative stress are critical events involved in the physiopathology of vascular diseases. The objectives of this study were to assess the effects of PM2.5 on oxidative stress and calcium signaling in HPAEC. Different endpoints were studied, (i) intrinsic and intracellular production of reactive oxygen species (ROS) by the H2DCF-DA probe, (ii) intrinsic, intracellular and mitochondrial production of superoxide anion (O2-) by electronic paramagnetic resonance spectroscopy and MitoSOX probe, (iii) reactive nitrosative species (RNS) production by Griess reaction, and (vi) calcium signaling by the Fluo-4 probe. In acellular conditions, PM2.5 leads to an intrinsic free radical production (ROS, O2-) and a 4h-exposure to PM2.5 (5-15µg/cm2), induced, in HPAEC, an increase of RNS, of global ROS and of cytoplasmic and mitochondrial O2- levels. The basal intracellular calcium ion level [Ca2+]i was also increased after 4h-exposure to PM2.5 and a pre-treatment with superoxide dismutase and catalase significantly reduced this response. This study provides evidence that the alteration of intracellular calcium homeostasis induced by PM2.5 is closely correlated to an increase of oxidative stress.

Effect of piroxicam on the nephrotoxicity induced by ochratoxin A in rats.

Ochratoxin A (OTA) is a mycotoxin which contaminates animal feed and human food and is nephrotoxic for all animal species studied so far. It binds to plasma proteins and is transported into target organs, especially the kidney. An attempt to prevent its toxic effects has been made using piroxicam, a non-steroidal anti-inflammatory drug (NSAID). Piroxicam also binds strongly to plasma proteins and our hypothesis is that this drug could stop OTA-binding and transport into target organs, thereby preventing its nephrotoxicity. Our experiments on rats given OTA (289 micrograms/kg/48 h for 2 weeks) show that piroxicam prevents the enzymuria induced by OTA and increases renal elimination of OTA. In vivo, piroxicam could prove useful in preventing the chronic effects of ochratoxin A, mainly nephrotoxicity, at doses 5 mg/kg/48 h, which were not found to be nephrotoxic in experimental animals.

Effect of superoxide dismutase and catalase on the nephrotoxicity induced by subchronical administration of ochratoxin A in rats.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other molds. It is a natural contaminant of mouldy food and feed. OTA has a number of toxic effects, the most prominent being nephrotoxicity. Furthermore, OTA is immunosuppressive, genotoxic, teratogenic and carcinogenic. OTA inhibits protein synthesis by competition with phenylalanine in the phenylalanine-tRNA aminoacylation reaction. Recently, lipid peroxidation induced by OTA has been reported, indicating that the lesions induced by this mycotoxin could be also related to oxidative pathways. It was then interesting to study effects of the superoxide dismutase (SOD) and catalase on the nephrotoxicity induced by OTA in rats. The two enzymes (20 mg/kg body weight each) were given to rats by subcutaneous injection, every 48 h, 1 h before gavage by OTA (289 micrograms/kg b.w. every 48 h), for 3 weeks. SOD and catalase prevented most of the nephrotoxic effects induced by ochratoxin A, observed as enzymuria, proteinuria, creatinemia and increased urinary excretion of OTA. Altogether these results indicate (i) that superoxide radicals and hydrogen peroxide are likely to be involved in the damaging processes of OTA in vivo, (ii) that SOD and catalase might be used for prevention of renal lesions in cases of ochratoxicosis.

Prevention of lipid peroxidation induced by ochratoxin A in Vero cells in culture by several agents.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other moulds. This mycotoxin contaminates animal feed and food and is nephrotoxic for all animal species studied so far. OTA is immunosuppressive, genotoxic, teratogenic and carcinogenic. It is a structural analogue of phenylalanine and contains a chlorinated dihydroisocoumarinic moiety. Ochratoxin A inhibits protein synthesis by competition with phenylalanine in the phenylalanine-tRNA aminoacylation reaction. Recently lipid peroxidation induced by OTA has been reported, indicating that the lesions induced by this toxin could also be related to oxidative damage. An attempt to prevent its toxic effect, mainly the lipid peroxidation, has been made using aspartame (L-aspartyl-L-phenylalanine methyl ester) a structural analogue of both OTA and phenylalanine, piroxicam, a non steroidal anti-inflammatory drug and superoxide dismutase+catalase (endogenous oxygen radical scavengers). Lipid peroxidation was assayed in monkey kidney cells (Vero cells) treated by increasing concentrations of OTA (5-50 microM). After 24 h incubation OTA induced lipid peroxidation in Vero cells in a concentration dependent manner, as measured by malonaldehyde (MDA) production. The MDA production, in Vero cells, was significantly increased by 50.5% from 694.1 +/- 21.0 to 1041.5 +/- 23.5 pmol/mg of protein. In the presence of superoxide dismutase (SOD)+catalase (25 micrograms/ml each) the MDA production induced by OTA was significantly decreased. At 50 microM of OTA concentration (optimal production of MDA) the MDA production decreased from 1041.5 +/- 23.5 to 827.5 +/- 21.3 pmol/mg of protein. SOD and catalase, when applied prior to the toxin, seemed to prevent lipid peroxidation more efficiently than piroxicam (at a ten-fold higher concentration than OTA) and aspartame (at equimolar concentration). These molecules also partially prevented the OTA-induced leakage of MDA in the culture medium.

Formation of ochratoxin A metabolites and DNA-adducts in monkey kidney cells.

Monkey kidney cells (named Vero cells) were incubated with increasing doses of ochratoxin A (10-100 microM). The inhibiting concentration 50% (IC50) on protein synthesis was about 14 microM in the presence of 5% fetal calf serum and 37 microM in the presence of 10% fetal calf serum. Some metabolites of ochratoxin A, including the chlorinated dihydroisocoumarin moiety of OTA (OT alpha), 4-[S]-hydroxy-OTA and 4-[R]-hydroxy-OTA were detected by HPLC in the mixture of cell homogenate after a 24 h incubation with 10 and 25 microM of OTA. Using the 32P-postlabelling method, several DNA-adducts, similar to those formed in mouse kidney after OTA treatment, were detected in monkey kidney cells. Thus, Vero cells are suitable for genotoxic and cytotoxic studies in relation to the metabolism of nephrotoxic xenobiotics such as OTA.

Prevention of nephrotoxicity of ochratoxin A, a food contaminant.

Ochratoxin A (OTA) is a mycotoxin produced by ubiquitous Aspergilli, mainly by Aspergillus ochraceus and also by Penicilium verrucosum. It was found all over the world in feed and human food and blood as well as in animal blood and tissues. The most threatening effects of OTA are its nephrotoxicity and carcinogenicity, since this mycotoxin is nephrotoxic to all animal species studied so far and is increasingly involved in the Balkan endemic nephropathy (BEN), a human chronic interstitial nephropathy which is most of the time associated to urinary tract tumours. Since it seems impossible to avoid contamination of foodstuffs by toxigenic fungi, detoxification and detoxication for OTA are needed. To reduce or abolish the OTA-induced toxic effects, several mechanisms were investigated. The results of these investigations showed that some of the potential antidotes were efficient in preventing the main OTA toxic effects whereas some others were not. Promising compounds are structural analogues of OTA, and/or compounds having a high binding affinity for plasma proteins such as piroxicam, a non-steroidal anti-inflammatory drug (NSAID). Some enzymes such as superoxide dismutase (SOD) and catalase, radical scavengers, vitamins, prostaglandin (PG) synthesis inhibitors, (such as piroxicam), pH modificators, adsorbant resin such as cholestyramine etc. are efficient in vivo. Some of the results obtained in vivo were already confirmed in vitro and gave useful information on how to safely use these antidotes. The most generally acting compound seems to be A19 (Aspartame), a structural analogue of OTA and phenylalanine. When given to rats A19 (25 mg/kg/48 h) combined to OTA (289 micrograms/kg/48 h) for several weeks largely prevented OTA nephrotoxicity and genotoxicity. When given after intoxication of animals with OTA it washes out the toxin efficiently from the body. In vitro, A19 (10 micrograms/ml) prevents OTA (20-500 micrograms/ml) binding to plasma proteins. Its general action without any known side effect in humans and in animals, points at A19 to be the best candidate for preventing the OTA-induced subchronic effects.

Cytotoxicity, inhibition of DNA and protein syntheses and oxidative damage in cultured cells exposed to zearalenone.

Mycotoxins are toxic metabolites of various fungi commonly found in feed and foodstuff and can cause very serious health problems in animals as well as in humans. Zearalenone (ZEN), a mycotoxin produced by various Fusarium species has several adverse effects. Indeed, ZEN has strong estrogenic activity associated with hyperestrogenism and several physiological alterations of the reproductive tract. Moreover, ZEN was shown to be hepatotoxic, haematotoxic, immunotoxic and genotoxic. The exact mechanism of ZEN toxicity is not completely established. The observed strong estrogenic effect of ZEN resulting from its competition with 17beta-estradiol in the binding to estrogen receptors is generally considered to underline most toxic effects of ZEN, but estrogenic activity alone cannot explain the diverse and apparent adverse effects. The objective of the present study was to determine the involvement of other possible mechanisms in ZEN induced toxicity. Cytotoxicity, cell cycle perturbation, inhibition of protein and DNA synthesis as well as the presumed later marker of oxidative stress, malondialdehyde, were monitored in Vero and Caco-2 cells exposed to ZEN. Our results showed that ZEN reduces cell viability correlated to cell cycle perturbation, inhibits protein and DNA syntheses and increases MDA formation in both cell lines in concentration-dependant manner. We assumed that cytotoxicity and oxidative damage are additional mechanisms of ZEN mediated toxicity.

How aspartame prevents the toxicity of ochratoxin A.

The ubiquitous mycotoxin ochratoxin A (OTA) is found as a frequent contaminant of a large variety of food and feed and beverage such as beer, coffee and win. It is produced as a secondary metabolite of moulds from Aspergillus and Penicillium genera. Ochratoxin A has been shown experimentally to inhibit protein synthesis by competition with phenylalanine its structural analogue and also to enhance oxygen reactive radicals production. The combination of these basic mechanisms with the unusual long plasma half-life time (35 days in non-human primates and in humans), the metabolisation of OTA into still active derivatives and glutathione conjugate both potentially reactive with cellular macromolecules including DNA could explain the multiple toxic effects, cytotoxicity, teratogenicity, genotoxicity, mutagenicity and carcinogenicity. A relation was first recognised between exposure to OTA in the Balkan geographical area and Balkan Endemic Nephropathy (BEN) with a high incidence (nearly 50 times higher than normal) of urinary tract tumours. Exposure rates of OTA are measurable in blood of humans and animals and are established in several countries including Scandinavia, Germany, France, Italy, Canada, Japan and Northern Africa mainly Tunisia and Egypt. The impact of OTA exposure in non- endemic areas in the world is not known, the rates of exposure being not correlated with the disease records, especially in developed countries, due to lake of well- designed epidemiological studies, genetic polymorphism and maybe to dietary contents of radical scavengers and antioxidants. However the incidence and mortality rates of renal cancer are increasing in European countries and Northern Africa which could be a global resultant of human exposure to natural compounds in food such as mycotoxins and especially ochratoxin A. In addition to special care to prevent the growth of moulds and detoxification measures there was a need for the prevention of the OTA-induced toxic effects once the toxin is ingested. For this purpose several compound have been studied including some therapeutic agents such as piroxicam which cannot be proposed for a large scale use in humans for preventive purpose. Among other compounds, Aspartame, already used as sweetener has shown a real effectiveness in vivo confirmed largely in vitro. When rats exposed to OTA (289 micrograms/kg) by oral route every two days are given 25 mg/kg similarly for several weeks, all the toxic effects including genotoxicity are very efficiently prevented as shown for example by the disappearance of DNA- adducts in tissues excised from treated animals. Aspartame is also effective in washing out the toxin when given afterwards to animals intoxicated by the same oTA doses for several weeks. In vitro, provided that it is added in cell culture medium before OTA it prevent significantly the inhibition of protein synthesis and lipid peroxidation induced by the toxin. Obviously the molecular mechanism mediating the preventive effect of Aspartame is the delivery of phenylalanine by cleavage of the peptide but also the direct effect of the peptide on the bending capacity and transport of the toxin in vivo and in vitro. As a matter of fact when Aspartame is given to animals or added in culture medium the amount of peptide found unchanged (10-15%) may account for a preventive effect as entire peptide.

Ochratoxin A in human plasma in Morocco: a preliminary survey.

Available epidemiological information seems to indicate that Balkan endemic nephropathy is associated with consumption patterns involving foodstuffs contaminated with ochratoxin A (OTA) and with a higher frequency of OTA-positive blood samples. The aim of this preliminary study was to assess OTA concentrations in human plasma in Morocco. Therefore, samples from 309 healthy volunteers (213 males, 96 females) were analysed. The analyses revealed that 60% of the human plasma sampled was positive for OTA (61.5% in the male and 56% in the female population), and an average concentration of 0.29 ng/mL (0.31 ng/mL in males, 0.26 ng/mL in females). The highest concentration found was 6.59 ng/mL. The results suggest that the Moroccan population is exposed to OTA, even though the OTA plasma levels are lower than that reported in some North African countries.

Karyomegaly of tubular cells as early stage marker of the nephrotoxicity induced by ochratoxin A in rats.

Cases of karyomegaly were described by Sclare and by Mihatch in patients affected with tubular-interstitial nephropathy. The Karyomegalic cells showed enlarged nuclei with accumulation of genetic material. No aetiology was suggested. Our study of rats experimentally intoxicated by ochratoxin A, a well-known nephrotoxic compound, indicates the presence of karyomegaly with alteration of the tubular tissue. In control animals no karyomegalic cells were detected. These observations suggest that karyomegaly with megacytosis may be caused by the nephrotoxic ochratoxin A in the kidney. In addition abnormal mitosis together with karyomegalic cells were observed at an earlier stage of the intoxication (30 days) suggesting possible regeneration if the OTA insults are stopped. After 90 days of treatment, the degeneration increased and only karyomegalic and apoptotic-like cells were observed indicating that the regeneration no longer occurs and that the degeneration becomes irreversible.

Reduction of the ochratoxin A-induced cytotoxicity in Vero cells by aspartame.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other moulds. This mycotoxin contaminates animal feed and human food and is nephrotoxic for all animal species studied so far. OTA is immunosuppressive, genotoxic, teratogenic and carcinogenic. Recently lipid peroxidation induced by OTA has been reported. OTA, a structural analogue of phenylalanine, inhibits protein synthesis by competition with phenylalanine in the phenylalanine-tRNA aminoacylation reaction, constituting the main mechanism of OTA-induced cytotoxicity. Since it seems impossible to avoid contamination of foodstuffs by toxigenic fungi, investigation is required for preventing the toxicity of OTA. An attempt to prevent its toxic effect, mainly the inhibition of protein synthesis, has been made using aspartame (L-aspartyl-L-phenylalanine methyl ester) a structural analogue of both OTA and phenylalanine. Protein synthesis was assayed in monkey kidney cells (Vero cells) treated by increasing concentrations of OTA (10-100 microM). After 24 h incubation, protein synthesis was inhibited by OTA in a concentration dependent manner (the 50% inhibitory concentration, IC50, was c. 14.5 microM). Aspartame (A19), at tenfold higher concentrations than OTA (100-1000 microM), was found to partially protect against the OTA-induced inhibition of protein synthesis in Vero cells, and more efficiently when added 24 h prior to the toxin (IC50 34 microM) than together (IC50 22 microM). As expected A19(250 microM) prevented the OTA-induced leakage of certain enzymes, including lactate dehydrogenase, gamma-glutamyl transferase, alkaline phosphatase, into the culture medium, and the concomitant decrease of their intracellular activity in OTA (25 microM)-treated cells. In order to investigate the effect of aspartame (A19) on OTA-protein binding as explanation of the above results, the mycotoxin time- and concentration-dependent binding to human samples was studied in static diffusion cells with two compartments separated by a dialysis membrane. When A19 (34 microM) was added to the upper compartment containing plasma before installing OTA (50, 250, 1240 microM) in the lower one. OTA binding was largely prevented (95-98%). When A19 (34 microM) was added to the lower compartment simultaneously with the toxin (50, 250, 1240 microM), for the lowest concentration of OTA, the same efficiency was shown in preventing OTA binding, but at the two high concentrations A19 seemed less efficient.

DNA breaks and cell cycle arrest induced by okadaic acid in Caco-2 cells, a human colonic epithelial cell line.

Okadaic acid (OA) is a shellfish toxin produced by dinoflagellates, in mussels. It is a potent tumour promoter and represents a potential threat to human health even at low concentrations. OA targets mainly the gastrointestinal tract in acute poisoning, causing diarrhoea. Therefore the present investigations were designed to study the ability of okadaic acid to induce cytotoxicity and DNA lesions in a human colonic cell line (Caco-2). Incubation of Caco-2 cells with OA (3.75-60 ng/ml, i.e. 4.6 x 10(-3)-7.5 x 10(-2) microM) causes a significant reduction in cell viability. Moreover, okadaic acid inhibits protein and DNA synthesis with, respectively, IC50 of 16 and 6.5 ng/ml after 24 h incubation. It also provokes cell cycle arrest, characterised by an increase in the number of S phase cells, correlated with a significant decrease in G0/G1 phase cells at high concentration. One of the main results obtained in these investigations is the apoptosis induced by OA in Caco-2 cells of intestinal origin, shown by DNA laddering in agarose gel electrophoresis (250-1000 base pairs). OA also induces clastogenic effects evaluated by DNA fragmentation analysis using the method of Higuchi and Aggarwal (52% for 60 ng/ml) and comet assay (increase of the frequency of comets and their tails length). Therefore, the cell death induced by OA seems clearly to be concentration-dependent after 24 h of incubation. The cytotoxic properties of okadaic acid and its ability to damage DNA result in cell death, mainly by apoptosis. Since consumption of shellfish contaminated with acceptable okadaic acid concentrations exposes colonic cells to harmful concentrations of this toxin, the possibility that OA would display its toxic effects on intestinal cells in vivo should be evaluated in human primary intestinal cells and human intestinal slices for cytotoxic effects, DNA fragmentation and apoptosis.

Selective toxicity of ochratoxin A in primary cultures from different brain regions.

Ochratoxin A (OTA) is a mycotoxin produced by moulds from the Aspergillus and Penicillium genera. It is a natural contaminant of a wide variety of both human and animal foodstuffs. Via dietary intake, OTA passes into the blood of both humans and animals and accumulates in several organs, such as the kidney and the brain with selective toxicity in the ventral mesencephalon and in the cerebellum. In order to confirm the regional selectivity to OTA cytotoxicity in rat brain, investigations were designed to study the mechanism of the cytotoxicity of OTA in primary cultures of the above-mentioned structures (ventral mesencephalon and cerebellum), and to compare their sensitivity to the toxin. Protein and DNA synthases, lactate dehydrogenase (LDH) release and production of malondialdehyde (MDA) were assayed in astrocytes and neurones of the selected structures in the presence of OTA. After 48 h incubation, OTA (10-150 microM) induced an inhibition of protein and DNA syntheses in a concentration-dependent manner with a selective higher toxicity in the cells of the ventral mesencephalon [50% inhibitory concentrations (IC50) of protein and DNA syntheses were 14 +/- 2 microM for neurones and 40 +/- 5 microM for astrocytes] compared to the cerebellum values (24 +/- 7 microM for neurones and 69 +/- 9 microM for astrocytes). In parallel, a significant increase in levels of MDA and LDH release were noted. Altogether these results indicate that OTA is also a neurotoxic substance in addition to its well-documented nephrotoxicity and that the effects are likely to be restricted within particular structures of the brain.

Ochratoxin A in beverages from Morocco: a preliminary survey.

In a preliminary study, samples of Moroccan wines (n = 30), beers (n = 5) and fruit juices (n = 14) were assayed for ochratoxin A (OTA) by HPLC with fluorimetric detection, followed by confirmation by cleavage of the OTA molecule using carboxypeptidase with HPLC-fluorimetric determination of ochratoxin alpha (OT alpha). All the wine samples were contaminated, and the overall median OTA concentration was 0.65 microg/l (range 0.028-3.24 microg/l). One of the 14 samples of fruit juices was contaminated with a concentration of 1.16 microg/l, whereas none of the five beer samples was contaminated. This is the first report on the occurrence of OTA in various beverages from Morocco.

Combined effects of okadaic acid and cadmium on lipid peroxidation and DNA bases modifications (m5dC and 8-(OH)-dG) in Caco-2 cells.

Okadaic acid (OA) is a marine toxin, a tumour promoter and an inducer of apoptosis. It mainly inhibits protein-phosphatases, protein synthesis and enhances lipid peroxidation. Cadmium (Cd) is known to be carcinogenic in animals and humans (group 1 according to the International Agency for Research on Cancer (IARC) classification). Cd also induces oxidative stress in living organisms. Since they are sometimes found simultaneously in mussels, we have evaluated in the present investigation, the lipid peroxidation, as malondialdehyde (MDA) production, in the variation of the ratios of 8-(OH)-dG/10(5)dG and m5dC/(dC + m5dC) induced by OA and/or Cd in Caco-2 cells. When cells were treated exclusively by OA (15 ng/ml) or Cd (0.625 and 5 microg/ml) for 24 h, protein synthesis was inhibited (by 42 +/- 5%, 18 +/- 13%, and 90 +/- 4% respectively) while MDA production was 2,235 +/- 129, 1710 +/- 20, and 11,496 +/-1,624 pmol/mg protein respectively. In addition, each toxicant induced modified bases in DNA; increases in oxidised bases and methylated dC. The combination of OA and cadmium was more cytotoxic and caused more DNA base modifications; the ratio m(5)dC/(m(5)dC + dC) was increased from 3 +/- 0.15 to 9 +/- 0.15 and the ratio 8-(OH)-dG/10(5) dG also (from 36 +/- 2 to 76 +/- 6). The combination of OA and Cd also increased the level of MDA (1,6874 +/- 2,189 pmole/mg protein). The present results strongly suggest that DNA damage resulting from the oxidative stress induced by these two toxicants may significantly contribute to increasing their carcinogenicity via epigenetic processes.

Prevention by vitamin E of DNA fragmentation and apoptosis induced by fumonisin B1 in C6 glioma cells.

Fumonisin B1 (FB1), produced by the fungus Fusarium moniliforme, belongs to a class of sphingosine analogue mycotoxins that occur widely in the food chain. Epidemiological studies have associated consumption of Fusarium moniliforme-contaminated food with human oesophageal cancer in China and South Africa. FB1 also causes equine leucoencephalomalacia. Evidence for induction of apoptosis by FB1 was first obtained when C6 glioma cells were incubated with fumonisin B1 (3-27 microM) causing DNA fragmentation profiles showing DNA laddering in gel electrophoresis and apoptotic bodies revealed by chromatin staining with acridine orange and ethidium bromide. Further confirmation experiments and comet assays have been performed under similar conditions. The results of the comet test show that FB1 at 9 and 18 microM induces respectively 50 +/- 2% and 40 +/- 1% of cells with a comet with an increased tail length of 93 +/- 9 microm and 102 +/- 17 microm respectively. Under these concentrations, FB1 induced DNA fragmentation and laddering and many apoptotic bodies. Pre-incubation of the cells with vitamin E (25 microM) for 24 h before FB1 (18 microM) significantly reduced DNA fragmentation and apoptotic bodies induced by FB1.

Epigenetic properties of fumonisin B(1): cell cycle arrest and DNA base modification in C6 glioma cells.

Fumonisin B(1) produced by the fungus Fusarium moniliforme is a member of a new class of sphinganine analogue mycotoxins that occur widely in the food chain. Epidemiological studies associate FB(1) with human oesophageal cancer in China and South Africa. FB(1) also causes acute pulmonary edema in pigs and equine leucoencephalomalacia. This disease is thought to be a consequence of inhibition by FB(1) of cellular ceramide synthesis in cells. To investigate further on this pathogenesis, the effect of FB(1) was studied on cell viability (3 to 54 microM of FB(1)), protein (2.5 to 20 microM of FB(1)) and DNA syntheses (2.5 to 50 microM of FB(1)), and cellular cycle (3 to 18 microM of FB(1)) of rat C6 glioma cells after 24 h incubation. The results of the viability test show that FB(1) induces 10 +/- 2% and 47 +/- 4% cell death with, respectively, 3 and 54 microM, in C6 cells. This cytotoxicity induced by FB(1) was efficiently prevented when the cells were preincubated 24 h with vitamin E (25 microM). FB(1) displays epigenetic properties since it induced hypermethylation of the DNA (9-18 microM). Inhibition of protein synthesis was observed with FB(1) with an IC(50) of 6 microM showing that C6 glioma cells are very sensitive to FB(1); however, the synthesis of DNA was only slightly inhibited, up to 20 microM of FB1. The flow cytometry showed that the number of cells in phase S decreased significantly as compared to the control p = 0.01 from 18. 7 +/- 2.5% to 8.1 +/- 1.1% for 9 microM FB(1). The number of cells in phase G(2)/M increased significantly as compared to the control (p