Assessment of deoxynivalenol (DON) adsorbents and characterisation of their efficacy using complementary in vitro tests.

Deoxynivalenol (DON) is a prevalent and resistant mycotoxin found in cereals and related products. Adsorbents appear to provide an opportunity to decrease DON absorption in animals but, due to their specificity, it is very difficult to evaluate their actual efficacy. It is pointless to extrapolate results obtained with one mycotoxin to another and even to extrapolate results obtained in vitro in buffer to an in vivo situation. We carried out experiments to characterize the properties of potential DON adsorbents. Initial tests in buffer pH 7 allowed us to focus on six adsorbents: activated charcoal, cholestyramin, Saccharomyces cerevisiae mannans, algal beta-glycan, fungal beta-glycan and leguminous plant. The use of equilibrium sorption models suggested a non-saturated phenomenon and involved variable mechanisms according to the specific material. Subsequent tests with a Caco-2 cell model showed a high reduction in DON cytotoxicity on proliferative intestinal cells and DON absorption by differentiated intestinal cells when adsorbent was added (except for cholestyramin). Otherwise, values were not always in accordance with those obtained in buffer. Our work allowed us to identify five potential DON adsorbents and to propose a complementary in vitro test allowing improved determination of adsorbent properties.

ABCC1, ABCC2 and ABCC3 are implicated in the transepithelial transport of the myco-estrogen zearalenone and its major metabolites.

The myco-estrogene zearalenone (ZEA) is a worldwide cereal contaminant, implicated in reproductive disorders in animals and humans. Intestinal cells constitute a first barrier to mycotoxins exposure, since they express membrane ABC transporters that may affect the bioavailability of food xenobiotics. In this study, we investigated the mechanisms involved in the transepithelial transfer of ZEA and its major metabolites alpha- and beta-zearalenols (ZOLs), first using human intestinal Caco-2 cells. When exposed to ZEA, alpha-ZOL or beta-ZOL either in the apical (AP) or basolateral (BL) compartment, cells showed asymmetry in the AP-BL and BL-AP transfer of mycotoxins. Metabolic inhibitors increased ZEA, alpha-ZOL and beta-ZOL intracellular accumulation. Caco-2 cells apically exposed to ZEA produced metabolites (ZOLs and glucuronides) whose distribution between AP, BL and intracellular compartments was significantly modified by ABCCs inhibitor MK571. ABCB1-, ABCC1-, ABCC2 and ABCC3-transfected cells were used for studies of intracellular accumulation of ZEA, alpha-ZOL and beta-ZOL with or without specific inhibitors, and for competitive studies using fluorescent substrates. The results showed that ZEA, alpha-ZOL and beta-ZOL were substrates for ABCC2. ABCC1 was also involved in ZEA and alpha-ZOL transport, whereas ABCC3 only interacted with beta-ZOL. These specific interactions suggest a role for ABCC1-3 transport proteins in zearalenone exposure and its resulting risk for human health.

Diazinon cytotoxicity and transfer in Caco-2 cells: Effect of long-term exposure to the pesticide.

The purpose of this work was to investigate the effect of prolonged exposure to diazinon (widely used organophosphorus pesticide) on the intestinal cell-line Caco-2. Cytotoxicity of the pesticide (50µM-6mM) significantly decreased in long-term exposed (20µM, 2 months) cells, compared to untreated control cells. In long-term exposed cells, the resistance to diazinon cytotoxicity was reversed in the presence of PSC-833, a P-glycoprotein (P-gp) inhibitor, but not in the presence of MK 571, a Multidrug Resistance Protein (MRP) inhibitor. Cell exposure to 25µM diazinon showed a secretory-directed transport of the molecule, which increased in long-term exposed cells. This efflux decreased significantly, for both long-term and non-exposed cells, in the presence of verapamil and PSC-833, but not MK 571. Furthermore, the total amount of P-gp increased in long-term exposed cells. These results suggest that ABC transporter P-gp is involved in the intestinal transfer of diazinon, and that repeated exposure to low doses of diazinon could strengthen the activity of ABC transporters in intestinal cells, thus increasing cell resistance to pesticide cytotoxicity.

Zebra mussels (Dreissena polymorpha) as indicators of freshwater contamination with lindane.

Zebra mussels are common freshwater mollusks in many European lakes and rivers. Their abundance, wide distribution, and filtering activity make them good candidates to evaluate the contamination of freshwaters with environmental contaminants. The purpose of this work was to determine the kinetics of lindane in zebra mussels and compare laboratory results with in situ measurements. Exposure was conducted in small tanks, under controlled experimental conditions. Our results indicated that mussels accumulated lindane with a bioconcentration factor around 10. They generally reached equilibrium within 4 days. Elimination was rapid but biphasic and the terminal elimination half-life was long (> 168 h). Age of the mussels and temperature also affected the kinetics of lindane in mussels. In the Lake of Geneva, zebra mussels were sampled and showed that mussels accumulated it to significant values (up to 900 ng/g fresh weight) depending on the site and period of sampling. The in situ results, together with the laboratory exposures, showed that freshwater mussels could be used to monitor point sources of pollutants such as lindane over short periods of time (< 1 week).

Difethialone (LM-2219): a new anticoagulant rodenticide for use against warfarin-resistant and -susceptible strains of Rattus norvegicus and Mus musculus.

Data on the efficacy of difethialone, a new anticoagulant rodenticide derived from 4-hydroxybenzothiopyranone against rats and mice, are reported. After one day of feeding with 25 mg/kg of bait, 100 and 85%, respectively, male and female warfarin-susceptible Rattus norvegicus were killed. With the resistant strain, mortality was 90 and 94% for males and females, respectively. 100 and 96% of warfarin-sensitive males and females, respectively, were killed after 3 days of feeding with the same bait. Those of the resistant strain were respectively, 100 and 93%. In Mus musculus, after one day of feeding, mortality was 97, 94, 95 and 93% for males and females of susceptible and resistant strains, respectively, and 100, 97, 100 and 91% after 3 days of feeding. No significant difference in bait intake was observed between 25 mg/kg difethialone bait and a control bait. Compared to other anticoagulant rodenticides, these results show that difethialone is a promising rodenticide.