Metabolism of benzophenone-2 in novel in vitro and in vivo zebrafish bio-assays
Résumé
Contamination of aquatic environment by xeno-estrogens present in personal care products causes raising concerns. Benzophenones are used as UV filters in sunscreens. They can be detected in rivers, lakes, sewages and sediments with increasing concentrations during the summer season. A number of reports have demonstrated that rivers contamination with xeno-estrogens can result in hormonal dysfunctions in aquatic organisms, which have been characterized through histopathological changes at the level of gonads, developmental disorders and reproductive inability. In fish, benzophenone-2 (BP2) was reported to cause alterations such as the induction of plasmatic vitellogenin and decrease in spermatozoa production (males), as well as reduced spawning (females). Several bioassays, including aquatic vertebrate models, have been designed over the last years with the aim to characterize the estrogeno-mimetic potential of chemicals. However, the characterization of the biotransformation capability of these biological models which allows to take into account bio-activation/detoxification processes in effect assessment, is rarely reported. We have recently developed in vitro bio-assays based on the expression of zebrafish estrogenic receptors in an hepatic cell line (ZFL), and an in vivo zebrafish assay based on the expression of the Green Fluorescent Protein (GFP) under the control of the cyp19a1b promoter (an estrogeno-regulated gene located in the brain). These bioassays were used to investigate the estrogenic potency of benzophenone derivatives. Contrary to other chemicals, BP2 elicited a different response depending on the bio-assay we used. We hypothesized that this difference could rely on a different metabolic capability expressed by our models (i.e. detoxification/bio-activation ratio), which would explain the observed differences in the respective estrogenic responses. To examine this hypothesis, the in vitro and in vivo zebrafish systems were exposed to BP2 at various concentrations, using a tritium-labeled molecule (3H-BP2). BP2 metabolism was explored using radio-HPLC (metabolite profiling) and metabolite characterization was investigated using biochemical tools and high resolution mass spectrometry (HRMS).