In vitro evaluation of potential oestrogenic compounds on oestrogen receptors of European sea bass, Dicentrarchus labrax (L.)

Trabajo presentado en el 8th Young environmental scientists meeting, celebrado en Ghent (Bélgica) del 5 al 10 de febrero de 2019Oestrogens are important regulators of multiple physiological processes. Across vertebrates, the oestrogenic action is mediated by the binding to several oestrogen receptors. Specific transcription factors designated nuclear oestrogen receptors (Esrs) have been mainly associated with the classical activation of gene expression by oestrogens or structurally similar compounds. More recently,membrane receptors, such as the G protein-coupled oestrogen receptor (Gper), have been related to rapid, non-genomic responses. Both signaling pathways are present in fish, which express additional gene duplicates for both receptor types. Using the human embryonic kidney cell line HEK293, transient transfections were performed (1) to study the effects of two chemicals, genistein - a phytoestrogen - and fluoxetine (Prozac®) – an antidepressant - on the activation of the sea bass Esrs, using an ERE-luciferase reporter gene assay; and (2) to characterize the sea bass Gper duplicates, using a cAMP response element-luciferase reporter gene assay. Results indicate that genistein and fluoxetine affect each nuclear receptor in a different manner: Fluoxetine rather triggers an anti-oestrogenic response, while genistein behaves as an oestrogen mimic in the transactivation of the three Esrs. Oestradiol was able to induce luciferase activity in cells transfected with both membrane receptors, confirming, for the first time, that both teleost gene duplicates are functional. This study also demonstrates the suitability of the luciferase reporter assay as a tool to assess the oestrogenic potency and mechanisms of action of a wide variety of chemicals. Potential risks of the exposure of fish to various compounds in the environment or in aquaculture can be identified efficiently