Environmental occurrence and effects in fish of ligands of the progesterone receptor : current progress of the french national project proofs
Résumé
To date, most studies on endocrine disrupting compounds have focused on estrogenic compounds with a particular attention to natural (estradiol, estrone, estriol) and synthetic estrogens (17α-ethinylestradiol). However, there is a now emerging evidence for the occurrence of other natural and synthetic steroids in aquatic systems. Among them, the potential risk posed by synthetic progestins on aquatic species has been recently pointed out. These compounds are widely used in human medicine, especially in oral contraceptives and hormone replacement therapy. However, their occurrence, fate and effects have been poorly investigated. To fulfill these gaps, the national ANR project PROOFS aimed at investigating i) the mode of action of a broad range of progestins and their effects in fish and ii) the occurrence of (anti)-progestagenic activities in the aquatic environment. A broad range (24) of currently used progestins were screened using in vitro and in vivo reporter gene assays for their capacities to interact with human (h) or zebrafish (zf) nuclear progesterone receptor (PR) and to deregulate the tissue-specific expression of steroidogenic genes in zebrafish embryos. By using human reporter cell lines stably expressing either hPR or zfPR, we revealed marked interspecies differences on the ability of progestins to activate/antagonize PRs. In transgenic cyp19a1b-GFP zebrafish embryos, progestins derived from 19-nor-testosterone induced brain aromatase in radial glial cells through an ER-dependent mechanism. Finally, in vitro screening of a bank of environmental samples (including more than 100 wastewater effluents and surface waters) allowed the quantification of (anti)progestagenic activities, with noticeable zfPR agonistic activities in waste waters at several sites. The PROOFS project provides an extensive (eco)toxicological characterization of a large number of currently used (anti-)progestin pharmaceuticals on key molecular targets. We showed marked differences between hPR and zfPR in ivtro and ii) early developmental effects in brain of zf embryos. Furthermore, environmental bioanalysis revealed fish-specific activities in the aquatic ecosystems. The ANR PROOFS also depicted for the first time (anti)progestagenic activities in aquatic samples showing wastewaters as a source of contamination by zf-active compounds that still need to be identified. Overall, this study supports the need to further characterize ecotoxicological risks posed by progestins.