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Poster

Nested interactions in the uranium and cadmium combined toxicity to the C. elegans.

Abstract : Uranium (U) is a natural ubiquitous radioelement whose occurrence may be magnified in the vicinity of some nuclear fuel cycle facilities or intensive farming areas. As mixtures are common in environment, U may be found associated with other contaminants such as cadmium (Cd). The exposure of organisms to these mixtures may result in unexpected synergism or antagonism that may be explained by interactions occurring at the exposure, toxicokinetics and/or toxicodynamic levels. The identification of these interactions and their underlying mechanisms may be of interest for a better risk characterization of multi-metallic polluted sites. In the present study, toxicity of binary mixture of U and Cd was assessed over time on physiological parameters, maximal length and brood size, in a partial lifespan experiment with the soil nematode Caenorhabditis elegans. A 49-condition fractional factorial design (extended design) was used with U and Cd concentrations, representative of some highly polluted soils, ranging from 0.95 to 1.30 mM and 0.006 to 0.040 mM, respectively. Combined effects were analyzed using MixTox tool (Jonker et al., 2005) to identify possible synergistic or antagonistic interactions. The best description of the toxic effects was met with the response addition concept and considering a dose-level dependent interaction model. An early significant antagonism was found at 1.2 d. Then, a continuous antagonism was identified for mixture levels upper than the EC36 or at low U concentrations. As diet is suspected to be the main route of exposure of C. elegans to contaminants, an investigation of the diffusion of U and Cd from agar to bacteria and their bioaccumulation by nematodes was achieved in a reduced design (8 conditions). A significant reduction of Cd internalization by C. elegans was observed in case of co-exposure with U and these results were correlated with the concentration of contaminants in bacteria. The observed antagonism of toxicity may thus be the resultant of an interaction at the exposure level where the diffusion or adsorption of Cd to bacteria is decreased by U. These findings underline the importance of studying chemical mixtures at various levels to fully understand the underlying mechanisms and thus, avoid misinterpretations in the prediction of combined toxicity. Measurements of U and Cd concentrations in bacteria are currently performed with the extended design in order to reinterpret the combined toxic effects on the basis of these concentrations.
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https://hal.umontpellier.fr/hal-02953530
Contributeur : Pascale Roussel Connectez-vous pour contacter le contributeur
Soumis le : mercredi 30 septembre 2020 - 11:39:40
Dernière modification le : mardi 19 octobre 2021 - 18:57:26

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  • HAL Id : hal-02953530, version 1

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A. Margerit, C. Lecomte-Pradines, C. Svendsen, S. Frelon, E. Gomez, et al.. Nested interactions in the uranium and cadmium combined toxicity to the C. elegans.. ICRER 3rd International Conference on Radioecology & Environmental Radioactivity, Sep 2014, Barcelone, Spain. ⟨hal-02953530⟩

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