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Hepatic transcriptional responses of zebrafish to chronic, low dose pharmaceutical exposures

ABSTRACT: Our study makes use of zebrafish and has determined hepatic transcriptional changes after exposure to four single pharmaceuticals, a pharmaceutical mixture (MIX), and wastewater effluent (WWE) exposures. The pharmaceuticals chosen include acetaminophen, carbamazepine, gemfibrozil, and venlafaxine. We have performed chronic (6 week), low concentration (0.5 and 10 μgL-1 or 5 and 25% effluent) exposure of male and female fish and previously determined a range of effects (reproductive, histological, hormonal) after exposure to single compounds, a mixture of these compounds or wastewater effluent. Herein we determine by microarray the hepatic transcriptional responses of male and female zebrafish from the same exposures.

ORGANISM(S): Danio rerio

PROVIDER: GSE43491 | GEO | 2019/12/23

REPOSITORIES: GEO

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Project description:Despite recent knowledge of the potential environmental impact that compounds present in municipal wastewater effluents, including contaminants of emerging concern (CECs), may have, the implications of fish exposure to this contaminant mixtures are not completely understood. The effects caused by effluent CECs may be subtle and diverse, thus the need for sensitive and comprehensive tools such as gene expression to detect such responses. In this study, we conducted laboratory exposures that examined plasma concentrations of vitellogenin (VTG), changes in secondary sexual characteristics and gene expression in sexually mature male fathead minnows (Pimephales promelas) exposed to environmentally realistic (0.5%) and higher (5%) concentrations of municipal wastewater effluents. Secondary and primary treated effluents were used. Several of the 32 CECs investigated were detected, including pharmaceuticals, personal care products, hormones, current use pesticides and industrial compounds. The percent of males with detectable levels of VTG was higher in fish exposed to effluent treatments. An increased number of males with changes in secondary sexual characteristics (e.g. development of ovipositors), was observed in fish exposed to 5% effluent treatments. Gene expression data indicated that overall expression patterns were characteristic to each effluent. Higher numbers of differentially expressed genes were observed in fish exposed to primary treated effluent when compared to controls. Differentially expressed genes belonged to several functional categories, including xenobiotic metabolism, estogenicity and energy/metabolism processes. Gene expression data provided information to understand some of the mechanisms behind the effects observed at higher biological levels. To investigate gene expression responses resulting from exposure to POTW effluents, two laboratory experiments were conducted using effluent from San Diego (Point Loma; SD) and Los Angeles (Hyperion; LA). The LA effluent received secondary treatment and the SD effluent received advanced primary treatment. Treatments used during exposures consisted of negative controls (moderately hard water), positive controls (E2), and 0.5% and 5% effluent concentrations. The 0.5% concentration of effluent represented an environmentally realistic exposure level. The 5% effluent concentration represented a higher level at which we expected biological responses. The exposures lasted 14 days. Treatments: EFFHa = 5% primary treated effluent EFFHb = 5% secondary treated effluent EFFLa = 0.5% primary treated effluent E2a = Estradiol, positive control for primary effluent E2b = Estradiol, positive control for secondary effluent CTRLa = Moderately hard water, negative control for primary effluent CTRLb = Moderately hard water, negative control for secondary effluent

Project description:Wastewater treatment plant (WWTP) effluent-dominated streams provide critical habitat for aquatic and terrestrial organisms but also continually expose them to complex mixtures of pharmaceuticals that can potentially impair growth, behavior, and reproduction. Currently, few biomarkers are available that relate to pharmaceutical-specific mechanisms of action. In the experiment reported in this paper, zebrafish (Danio rerio) embryos at two developmental stages were exposed to water samples from three sampling sites (0.1 km upstream of the outfall, at the effluent outfall, and 0.1 km below the outfall) during base-flow conditions from two months (January and May) of a temperate-region effluent-dominated stream containing a complex mixture of pharmaceuticals and other contaminants of emerging concern. RNA-sequencing identified potential biological impacts and biomarkers of WWTP effluent exposure that extend past traditional markers of endocrine disruption. Transcriptomics revealed changes to a wide range of biological functions and pathways including cardiac, neurological, visual, metabolic, and signaling pathways. These transcriptomic changes varied by developmental stage and displayed sensitivity to variable chemical composition and concentration of effluent, thus indicating a need for stage-specific biomarkers. Some transcripts are known to be associated with genes related to pharmaceuticals that were present in the collected samples. Although traditional biomarkers of endocrine disruption were not enriched in either month, a high estrogenicity signal was detected upstream in May and implicates the presence of unidentified chemical inputs not captured by the targeted chemical analysis. This work reveals associations between bioeffects of exposure, stage of development, and the composition of chemical mixtures in effluent-dominated surface water. The work underscores the importance of measuring effects beyond the endocrine system when assessing the impact of bioactive chemicals in WWTP effluent and identifies a need for non-targeted chemical analysis when bioeffects are not explained by the targeted analysis.

Project description:Contaminants of emerging concern (CECs) in treated municipal effluents have the potential to adversely impact exposed organisms prompting elevated public concern. Using transcriptomic tools, we investigated changes in gene expression and cellular pathways in the liver of male fathead minnows (Pimephales promelas) exposed to 5% concentrations of full secondary-treated (HTP) or advanced primary-treated (PL) municipal wastewater effluents containing CECs. Gene expression changes were associated with apical endpoints (plasma vitellogenin and changes in secondary sexual characteristics). Of 32 effluent CECs analyzed, 28 were detected including pharmaceuticals, personal care products, hormones, and industrial compounds. Transcript patterns differed between effluents, however < 10% of these had agreement in the detected response (e.g. transcrips involved in xenobiotic detoxification, oxidative stress and apoptosis) in both effluents. Exposure to PL effluent caused changes in transcript levels of genes involved in metabolic pathways (e.g., lipid transport and steroid metabolism). Exposure to HTP effluent affected transcripts involved in signaling pathways (e.g., focal adhesion assembly and extracellular matrix). Exposure to both effluents produced significantly higher levels of plasma VTG and changes in secondary sexual characteristics (e.g., ovipositor development). Taken together the results suggest, a potential association between some transcriptomic changes and higher biological responses following effluent exposure; and a potential adverse outcome pathway following exposure to complex chemical mixtures containing CECs -. Furthermore, this study identified responses in key genes and pathways not previously implicated in exposure to CECS, , which could be consistent with effluent exposure (e.g., oxidative stress) in addition to other pathway responses specific to the effluent type. This may be useful for assessing the adverse health effects of fish by effluents exposure to CECs.

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Hepatic transcriptional responses of zebrafish to chronic, low dose pharmaceutical exposures

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