Probing the xeno-oestrogenic impact of sediment cores contaminated by the pulp and paper industry: induction of aromatase cyp19a1b in late larval zebrafish

Abstract

To assess xenoestrogenicity, the 20 days-post-fertilization zebrafish (20dpfZF) life-stage was experimentally exposed to known model chemicals as well as to environmentally contaminated samples. From a selection of key responsive genes, molecular responses associated with the steroidogenic impact (brain aromatase, cyp19a1b and vitellogenin isoform 1, vtg1) were used to assess the endocrinic modulation by xenoestrogenic samples. This work showed diverse in vivo responses by the 20dpfZF, from pure chemicals (bisphenol A, BPA; 17 -ethinylestradiol, EE2; nonylphenol, NP; octylphenol, OP), and their mixture combinations, and to industrially contaminated sediment samples. Gene expression analysis of cyp19a1b and vtg1 in exposed 20dpfZF showed the estrogenic potencies of chemicals in the order: EE2 > OP > BPA > NP. Transcriptional up-regulation of vtg1 in early juvenile fish exposed to mixtures (BPA + NP + OP), relative to individual concentrations, suggest in minimum the additive in vivo effect of a mixture of very low sublethal doses of single xenoestrogens. Complementary expression of cyp19a1b and vtg1 in 20dpfZF, exposed to artificially-spiked sediment with EE2 established the estrogenresponsiveness of the model. In contrast, the lack of simple estrogenic or antiestrogenic trait of correspondence in biomarker transcription was evident from exposure to two types of industrially contaminated sediments, suggesting common non-linearity of in vivo response by the model. The results also highlight the applicability of 20dpfZF in the assessment of remediation and monitoring of historically polluted sites. This study showed that the 20dpfZF addressed the regulatory requirement of a multi-purpose and cost-effective ecotoxicological model capable of in vivo genomic assessment of endocrineactive substances in aquatic samples.