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Although the concept of endocrine disruptors first appeared almost 30 years ago, the relatively recent involvement of these substances in the etiology of metabolic pathologies (obesity, diabetes, hepatic steatosis, etc.) has given rise to the concept of Metabolic Disrupting Chemicals (MDCs). Organs such as the liver and adipose tissue have been well studied in the context of metabolic disruption by these substances. The intestine, however, has been relatively unexplored despite its close link with these organs. In vivo models are useful for the study of the effects of MDCs in the intestine and, in addition, allow investigations into interactions with the rest of the organism. In the latter respect, the zebrafish is an animal model which is used increasingly for the characterization of endocrine disruptors and its use as a model for assessing effects on the intestine will, no doubt, expand. This review aims to highlight the importance of the intestine in metabolism and present the zebrafish as a relevant alternative model for investigating the effect of pollutants in the intestine by focusing, in particular, on cytochrome P450 3A (CYP3A), one of the major molecular players in endogenous and MDCs metabolism in the gut. [ABSTRACT FROM AUTHOR]

Secondary organic aerosols (SOA) formed by oxidation of typical precursors largely emitted by biomass burning, such as PAHs and furans, are still poorly characterized in terms of formation yields, physical and light absorption properties, particularly those generated at night following reaction with nitrate radicals (NO3). In the present study, we evaluated and compared the formation yields, effective density (ρeff), absorption Ångström exponent (α), and mass absorption coefficient (MAC) of laboratory-generated SOA from three furan compounds (furan, 2-methylfuran, and 2,5-dimethylfuran) and four PAHs (naphthalene, acenaphthylene, fluorene, and phenanthrene). SOA were generated in an oxidation flow reactor from the reaction between hydroxyl radicals (OH; 0.1–20 equivalent aging days) or NO3 radicals (0.05–6 equivalent aging nights of 14 h) with single furan or PAH. The ρeff, formation yields, α, and MAC of the generated SOA varied depending on the precursor and oxidant considered. The ρeff of SOA formed with OH and NO3 tended to increase with particle size before reaching a “plateau”. This was particularly evident for the nighttime chemistry experiments with NO3 radicals (1.2 to 1.6 on average for particles > 100 nm). Such results highlighted potential differences in the chemical composition of the SOA, as well as probably in their morphology, according to the particle size. Three times lower SOA formation yields were obtained with NO3 compared to OH. The yields of PAH SOA (18 to 76 %) were 5 to 6 times higher than those obtained for furans (3–12 %). While furan SOA showed low or negligible light absorption properties, PAH SOA was found to have a significant impact in the UV-Visible region, implying a significant contribution to atmospheric brown carbon (BrC). No increase in the MAC values was observed from OH to NO3 oxidation processes, probably due to a low formation of nitrogen-containing chromophores through homogeneous gas phase oxidation processes with NO3 only (without NOx). Overall, the results obtained in this work demonstrated that PAHs are significant precursors of SOA emitted by biomass burning, through both, day- and nighttime processes, and have a substantial impact on the aerosol light absorption properties and so probably on climate. [ABSTRACT FROM AUTHOR]

In vitro bioassays are increasingly used for water quality monitoring. Surface water samples often need to be enriched to observe an effect and solid-phase extraction (SPE) is commonly applied for this purpose. The applied methods are typically optimised for the recovery of target chemicals and not for effect recovery for bioassays. A review of the few studies that have evaluated SPE recovery for bioassays showed a lack of experimentally determined recoveries. Therefore, we systematically measured effect recovery of a mixture of 579 organic chemicals covering a wide range of physicochemical properties that were spiked into a pristine water sample and extracted using large volume solid-phase extraction (LVSPE). Assays indicative of activation of xenobiotic metabolism, hormone receptor-mediated effects and adaptive stress responses were applied, with non-specific effects determined through cytotoxicity measurements. Overall, effect recovery was found to be similar to chemical recovery for the majority of bioassays and LVSPE blanks had no effect. Multi-layer SPE exhibited greater recovery of spiked chemicals compared to LVSPE, but the blanks triggered cytotoxicity at high enrichment. Chemical recovery data together with single chemical effect data were used to retrospectively estimate with reverse recovery modelling that there was typically less than 30% effect loss expected due to reduced SPE recovery in published surface water monitoring studies. The combination of targeted experiments and mixture modelling clearly shows the utility of SPE as a sample preparation method for surface water samples, but also emphasizes the need for adequate controls when extraction methods are adapted from chemical analysis workflows. [ABSTRACT FROM AUTHOR]

A mixture of urban and hospital effluents (50 % v/ v) was evaluated for ecotoxicity with an advanced bioassay battery. Mixed effluents were tested before any treatment, after biological treatment alone, and after biological treatment followed by a tertiary ozonation (15 mg O/L). Laying a high value on the continuance of organisms' fitness, essential to preserve a healthy receiving ecosystem, the main objective of this study was to combine normalized bioassays with newly developed in vivo and in vitro tests in order to assess alteration of embryo development, growth and reproduction, as well as genotoxic effects in aquatic organisms exposed to complex wastewater effluents. Comparison of the bioassays sensitivity was considered. Contrary to the lack of toxicity observed with normalized ecotoxicity tests, endpoints measured on zebrafish embryos such as developmental abnormalities and genotoxicity demonstrated a residual toxicity in wastewater both after a biological treatment followed or not by a tertiary O treatment. However, the ozonation step allowed to alleviate the residual endocrine disrupting potential measure in the biologically treated effluent. This study shows that normalized bioassays are not sensitive enough for the ecotoxicological evaluation of wastewaters and that there is a great need for the development of suitable sensitive bioassays in order to characterize properly the possible residual toxicity of treated effluents. [ABSTRACT FROM AUTHOR]

Several human and fish bioassays have been designed to characterize the toxicity and the estrogenic activity of chemicals. However, their biotransformation capability (bioactivation/detoxification processes) is rarely reported, although this can influence the estrogenic potency of test compounds. The fate of two estrogenic chemicals, the UV filter benzophenone-2 (BP2) and the bisphenol A substitute bisphenol S (BPS) was deciphered in eight human and zebrafish in vitro cell models, encompassing hepatic and mammary cellular contexts. BP2 and BPS were metabolized into a variety of gluco- and sulfo-conjugated metabolites. Similar patterns of BP2 and BPS biotransformation were observed among zebrafish models (primary hepatocytes, ZFL and ZELH-zfER cell lines). Interestingly, metabolic patterns in zebrafish models and in the human hepatic cell line HepaRG shared many similarities, while biotransformation rates in cell lines widely used for estrogenicity testing (MELN and T47D-KBLuc) were quantitatively low and qualitatively different. This study provides new data on the comparative metabolism of BP2 and BPS in human and fish cellular models that will help characterize their metabolic capabilities, and underlines the relevance of using in vitro zebrafish-based bioassays when screening for endocrine disrupting chemicals. [ABSTRACT FROM AUTHOR]