Zebrafish embryos as bioanalytical tools for detection of estrogenic and dioxin-like chemicals in environmental matrices
Résumé
Recent studies have reported the use of fish embryos as in vivo mechanism-based screening bioassays for the specific detection of biologically active compounds. In this study, we aimed at evaluating the use of zebrafish embryos for the detection of estrogenic and dioxin-like compounds in environmental matrices. Effect on phase I xenobiotic metabolism was assessed using EROD (Cyp1A-like) and BFCOD (Cyp3-like) assays in living embryos; estrogenic activity was measured using a transgenic zebrafish line expressing green fluorescence protein reporter gene under the control of the aromatase-B promoter (AroB-GFP). A panel of standards chemicals was first tested in order to calibrate the bioassays. One significant result was the finding that dioxin-like compounds were strongly active on the BFCOD assay. Then, these bioassays were applied to a multi-contaminated sediment extract, which has been shown to exert multiple toxicological activities as determined by a panel of in vitro bioassays. Both the crude extract and four fractions of increasing polarity (F1 to F4) and obtained from normal phase solid phase extraction were tested on the bioassays. Overall, crude and/or fractions were active on all endpoints, demonstrating the suitability of the bioassay to detect biologically active compounds. While no estrogenic activity could be detected in crude extract, weak activities were detected in F1, F2 and F3 fractions whereas in vitro estrogenic activity was only detected in F2 and F3. F2 and F3 are known to contain estrogenic compounds such as alkylphenols, parabens and steroids (data not shown). EROD and BFCOD gave parallel results, with significant activities in crude, and F1=F2>F3fractions. Altogether these preliminary data show the suitability of zebrafish embryos-based assays to detect estrogenic and dioxin-like chemicals in environmental matrices and could serve as useful tools for effect-directed analysis approaches. Fundings: P189-ECOPI and ITN EDA-EMERGE.