A novel transgenic cy19a1b-GFP in vivo zebrafish embryo assay (EASZY assay) to assess the estrogenic potency of chemicals and complex environmental mixtures

Abstract : One major challenge to ecotoxicology is to develop species-specific biological tools that allow rapid and cost-efficient assessment of EDCs for environmental hazard and risk assessment but also for monitoring the contamination of aquatic systems by EDCs. In this context, the use of zebrafish (Danio rerio) embryo assay appears as usefulness and relevant. We recently developed a mechanism-based in vivo zebrafish assay called EASZY that allows the detection of Endocrine Active Substance, acting through zebrafish estrogen receptors, using transgenic cyp19a1b-GFP Zebrafish embryos. The Cyp19a1b gene is a strictly ER-regulated gene that codes for the brain aromatase which is mainly expressed in radial glial cells of the brain of fish. In the present work the relevance of the EASZY assay for assessing the estrogenic potency of substance was evaluated by testing more than 50 different compounds belonging to various chemical classes. We found that in EASZY GFP is induced in a ERspecific manner by (i) compounds that bind directly to estrogen receptors as agonists (ii) compounds that require metabolic activation into estrogenic metabolites (iii) aromatizable androgens as well as some non aromatizable androgens. By studying combined effects of estrogenic chemicals, we showed that mixtures of estrogenic compounds generally acted in an additive manner on the expression of GFP expression, their combined effects being predicted by the CA model although antagonism was observed in a specific case. Finally, POCIS-based bio-monitoring using EASZY allowed screening the estrogenic activity of various surface waters from French rivers resulting in the detection of estrogenic activities at some sites. Overall, our studies show that EASZY assay clearly emerges as a simple, fast and reliable in vivo assay for screening the capacity of chemical, alone or in combination, as well as complex environmental mixtures. The sensitivity of EASZY assay to activate ER-signalling by chemicals and complex mixtures at very early critical developmental stages makes it an outstanding screening in vivo tool for hazard assessment of chemicals and EDCs detection in aquatic environment.
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François Brion. A novel transgenic cy19a1b-GFP in vivo zebrafish embryo assay (EASZY assay) to assess the estrogenic potency of chemicals and complex environmental mixtures. Colloque Adebiotech / INERIS "Perturbateurs endocriniens : enjeux industriels, de santé et d'environnement", Jul 2014, Romainville, France. ⟨ineris-01852884⟩

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