A novel contact assay for testing aryl hydrocarbon receptor (AhR)-mediated toxicity of chemicals and whole sediments in zebrafish (Danio rerio) embryos

Abstract

The European Water Framework Directive aims to achieve a good ecological and chemical status in surface waters until 2015. Sediment toxicology plays a major role in this intention as sediments can act as a secondary source of pollution. In order to fulfill this legal obligation, there is an urgent need to develop whole-sediment exposure protocols, since sediment contact assays represent the most realistic scenario to simulate in situ exposure conditions. Therefore, in the present study, a vertebrate sediment contact assay to determine aryl hydrocarbon receptor (AhR)-mediated activity of particle-bound pollutants was developed. Furthermore, the activity and the expression of the CYP1 family in early life stages of zebrafish after exposure to freeze-dried sediment samples were investigated. In order to validate the developed protocol, effects of β-naphthoflavone and three selected sediment on zebrafish embryos were investigated. Results documented clearly AhR-mediated toxicity after exposure to β-naphthoflavone (β-NF) and to the sediment from the Vering canal. Upregulation of mRNA levels was observed for all investigated sediment samples. The highest levels of all investigated cyp genes (cyp1a, cyp1b1, cyp1c1, and cyp1c2) were recorded after exposure to the sediment sample of the Vering canal. In conclusion, the newly developed sediment contact assay can be recommended for the investigation of dioxin-like activities of single substances and the bioavailable fraction of complex environmental samples. Moreover, the exposure of whole zebrafish embryos to native (freeze-dried) sediment samples represents a highly realistic and ecologically relevant exposure scenario.

The value of zebrafish as an integrative model in effect-directed analysis - a review

“…That is in fact a great advantage since mechanism-specific toxicity methods with zebrafish are broadly developed, as for AhR-mediated toxicity [72], genotoxicity [73] and neurotoxicity [74]. Furthermore, EDA guided by such zebrafish bioassays could integrate broader environmental assessment strategies, complementing effect-based approaches [7] and weightof-evidence frameworks [30].…”

Linking Ah receptor mediated effects of sediments and impacts on fish to key pollutants in the Yangtze Three Gorges Reservoir, China — A comprehensive perspective

“…In comparison, Wu et al (2010) determined mortalities between 3 to 16% for sediment extracts (concentration: 60 mg mL −1 ) from the Yangtze Estuary after 96 h exposure, whereas in this study mean mortalities (±SD) ranged from b10% in most of the samples up to 80 ± 10% (concentration: 60 mg mL −1 ) in the Long River (FEN-T) and 80 ± 17% (concentration: 50 mg mL − 1 ) in the Hanfeng Lake. Schiwy et al (2014) determined LC50 values of 160 mg mL − 1 and 355 mg mL −1 for sediment extracts from Altrip and Ehrenbreitstein, respectively, in the FET after 96 h exposure. Both are sampling sites at the German Rhine River and have been classified previously to be moderately and low contaminated.…”

The ecotoxic potential of a new zero-valent iron nanomaterial, designed for the elimination of halogenated pollutants, and its effect on reductive dechlorinating microbial communities

“…The assay with zebrafish (Danio rerio) was carried out based on OECD guideline 236 (OECD, 2013) with modifications given by Peddinghaus et al (2012) and Schiwy et al (2015). The nanomaterials were tested in duplicates in seven concentrations (16,31,63,125,250,500 and 1000 mg/L) prepared with artificial water with a static test design.…”