Use of zebrafish cell lines to assess estrogenic compounds in environmental samples
Résumé
Aquatic endocrine disrupting chemicals (EDCs) encompass a great diversity of chemicals that affect exposed organisms through different molecular mechanisms, including their ability to bind to estrogen receptors (ERs) and to modulate the transcription of target genes. Till date, most of in vitro assays used to assess xeno-estrogens have been established using human ER in either yeast or mammalian cell lines. However, cross-species differences due to cellular context (metabolic capacities, transcription) or different receptor sequences may lead to significant differences between-assay in estrogenic potency of chemicals and eventually influence the response of complex environmental mixtures. We recently established an in vitro luciferase assay based on stable expression of zebrafish ER subtypes (zfERa, zfERß1, zfERß2) in the ZFL zebrafish liver cell line (Cosnefroy et al 2012). Luciferase induction by 17ß-estradiol (E2) in zfERa and zfERß2 cell lines results in EC 50 s of 0.2 and 0.03 nM, respectively. In the present study, we have implemented this assay to screen and characterize the individual effect of different chemical contaminants, including bisphenols, zearalenone, alkylphenols, parabens and phthalates. Comparison with the response in the human cell based MELN assay revealed differences in both sensitivity (i.e. EC50) and receptor binding potency (i.e. full versus partial agonists). In addition, the ability of the zebrafish in vitro assays to detect active compounds in complex mixtures will be tested by screening organic extracts of river sediment, effluents and surface waters. These results will be compared with those obtained with the MELN assay which will provide new information on fish specific effects of environmental xenoestrogens present in aquatic ecosystems.