Endocrine disrupting chemicals in fish: Developing exposure indicators and predictive models of effects based on mechanism of action

doi:10.1016/j.aquatox.2009.01.013

Aquatic Toxicology

Volume 92, Issue 3, 5 May 2009, Pages 168-178

https://doi.org/10.1016/j.aquatox.2009.01.013 Get rights and content

Abstract

Knowledge of possible toxic mechanisms (or modes) of action (MOA) of chemicals can provide valuable insights as to appropriate methods for assessing exposure and effects, thereby reducing uncertainties related to extrapolation across species, endpoints and chemical structure. However, MOA-based testing seldom has been used for assessing the ecological risk of chemicals. This is in part because past regulatory mandates have focused more on adverse effects of chemicals (reductions in survival, growth or reproduction) than the pathways through which these effects are elicited. A recent departure from this involves endocrine-disrupting chemicals (EDCs), where there is a need to understand both MOA and adverse outcomes. To achieve this understanding, advances in predictive approaches are required whereby mechanistic changes caused by chemicals at the molecular level can be translated into apical responses meaningful to ecological risk assessment. In this paper we provide an overview and illustrative results from a large, integrated project that assesses the effects of EDCs on two small fish models, the fathead minnow (Pimephales promelas) and zebrafish (Danio rerio). For this work a systems-based approach is being used to delineate toxicity pathways for 12 model EDCs with different known or hypothesized toxic MOA. The studies employ a combination of state-of-the-art genomic (transcriptomic, proteomic, metabolomic), bioinformatic and modeling approaches, in conjunction with whole animal testing, to develop response linkages across biological levels of organization. This understanding forms the basis for predictive approaches for species, endpoint and chemical extrapolation. Although our project is focused specifically on EDCs in fish, we believe that the basic conceptual approach has utility for systematically assessing exposure and effects of chemicals with other MOA across a variety of biological systems.

Section snippets

Background

Prospective ecological risk assessments of most chemicals typically are conducted with little consideration for toxic mechanisms (or modes) of action (MOA). Testing for ecological effects usually includes a wide array of species and endpoints, with a focus primarily on apical responses. When little is known about the properties of a test chemical, this is a pragmatic approach; however, substantial benefits can be realized by basing testing and subsequent risk management decisions on known or

Experimental overview

The basic approach used for our work involves perturbation of the HPG axis with chemical probes known or hypothesized to impact different key control points, ranging from neurotransmitter receptors in the brain to steroid hormone receptors in gonads (Fig. 1). Following perturbation of the axis by chemicals with different MOA, information is collected at multiple biological levels of organization, ranging from molecular changes to apical responses (i.e., reproductive success), and even (via

Phase 1

Table 1 summarizes the fathead minnow 21-d reproduction tests that have been conducted to date and, where available, provides reference information for the completed studies. In terms of exposure concentrations that cause impacts on reproductive health, the test chemicals span a wide range of potency and efficacy, ranging from trenbolone which significantly decreased egg production at a water concentration of 0.05 μg/L (Ankley et al., 2003), to trilostane which affected egg production at a

Integrating the data: predictive modeling

To help design the Phase 1, 2 and 3 studies and subsequently interpret and integrate the large amounts of data collected, we are using a systems biology/toxicology approach. Villeneuve et al. (2007b) described development of a graphical systems model focused on defining the HPG axis of teleost fish, which enables consideration of the interactive nature of the system at multiple levels of biological organization, ranging from changes in gene, protein and metabolite expression profiles to effects

Prospectus

In this paper we describe a MOA/systems-based research effort with HPG-active chemicals that will help provide the technical basis for development of predictive toxicology tools (models, in vitro and short-term in vivo assays) which could improve the efficiency of current testing and monitoring programs for EDCs. As we contemplate informational needs for chemical risk assessments in the coming years, it is clear that historical toxicology approaches which focus mostly on generating empirical

Acknowledgements

We thank our many colleagues who have been involved in different aspects of this work, including L. Blake, J. Brodin, J. Cavallin, E. Durhan, K. Greene, M. Kahl, A. Linnum, E. Makynen and N. Mueller from the Duluth EPA lab; M. Henderson and Q. Teng from the Athens EPA lab; A. Biales, M. Kostich, D. Lattier and G. Toth from the Cincinnati EPA lab; X. Guan, C. Warner, L. Escalon, Y. Deng and S. Brasfield from the US Army Engineer Research and Development Center; J. Shoemaker, K. Gayen, and F. J.

References (54)

G.T. Ankley et al.
The fathead minnow in aquatic toxicology: past, present and future
Aquat. Toxicol.
(2006)
D.R. Ekman et al.
NMR analysis of fathead minnow urinary metabolites: a potential approach for studying impacts of chemical exposures
Aquat. Toxicol.
(2007)
A.L. Filby et al.
Gene expression profiles revealing the mechanisms of anti-androgen- and estrogen-induced feminization in fish
Aquat. Toxicol.
(2007)
H. Hao et al.
Modeling the VPAC₂-Activated cAMP/PKA signaling pathway: from receptor to circadian clock gene induction
Biophys. J.
(2006)
J.L. Hoffmann et al.
Hepatic gene expression profiling using GeneChips in zebrafish exposed to 17α-ethynylestradiol
Aquat. Toxicol.
(2006)
J.L. Hoffmann et al.
Hepatic gene expression profiling using GeneChips in zebrafish exposed to 17α-methyldihydrotestosterone
Aquat. Toxicol.
(2008)
S.E. Hook et al.
Gene expression patterns in rainbow trout, Oncorhynchus mykiss, exposed to a suite of model toxicants
Aquat. Toxicol.
(2006)
M.A. Hurley et al.
A model for environmental sex reversal in fish
J. Theoret. Biol.
(2004)
K.M. Jensen et al.
Characterization of responses to the antiandrogen flutamide in a short-term reproduction assay with the fathead minnow
Aquat. Toxicol.
(2004)
C.J. Martyniuk et al.
Microarray analysis in the zebrafish (Danio rerio) liver and telencephalon after exposure to low concentration of 17α-ethinylestradiol
Aquat. Toxicol
(2007)

A.R. Brown et al.

Predicting the effects of endocrine disrupting chemicals on fish populations

Hum. Ecol. Risk Assess.

(2003)

Y. Chen et al.

Variations in DNA elucidate molecular networks that cause disease

Nature

(2008)

Cited by (217)

Deconjugation potentials of natural estrogen conjugates in sewage and wastewater treatment plant: New insights from model prediction and on-site investigations
2024, Science of the Total Environment
Natural estrogen conjugates play important roles in municipal wastewater treatment plant (WWTP), but their deconjugation potentials are poorly understood. This work is the first to investigate the relationships between the enzyme activities of arylsulfatase/β-glucuronidase and deconjugation potentials of natural estrogen conjugates. This work led to three important findings. First, the enzyme activity of β-glucuronidase in sewage is far higher than that of arylsulfatase, while their corresponding activities in activated sludge were similar. Second, a model based on β-glucuronidase could successfully predict the deconjugation potentials of natural estrogen glucuronide conjugates in sewage. Third, the enzyme activity of arylsulfatase in sewage was too low to lead to evident deconjugation of sulfate conjugates, which means that the deconjugation rate of estrogen sulfates can be regarded as zero. By comparing their theoretical removal based on enzyme activity and on-site investigation, it is reasonable to conclude that reverse deconjugation of estrogen conjugates (i.e., conjugation of natural estrogens to form conjugated estrogens) likely exist in WWTP, which explains well why natural estrogen conjugates cannot be effectively removed in WWTP. Meanwhile, this work provides new insights how to improve the removal performance of WWTP on natural estrogen conjugates.
This work is the first to show how arylsulfatase/β-glucuronidase could affect deconjugation of natural estrogen conjugates and possible way to enhance their removal in wastewater treatment plant.
Identifying transcriptomic indicators of tertiary treated municipal effluent in longnose dace (Rhinichthys cataractae) caged under semi-controlled conditions in experimental raceways
2024, Science of the Total Environment
To evaluate effects of tertiary treated wastewater treatment plant effluent (MWWE) on transcriptomic responses in longnose dace (Rhinichthys cataractae; LND) we conducted a semi-controlled study in experimental raceways (Advancing Canadian Water Assets facility) imbedded in the Pine Creek treatment plant (Calgary, AB). LND collected from a reference site in the Bow River (REF) were caged in raceways containing either 5 % Pine Creek effluent (PC) or Bow River water (BR; control) over 28 d. Liver transcriptomes were analyzed in males and females sampled on days 7, 14 and 28 from BR and PC, and compared to REF fish on day 0. Concurrent with the caging, selected environmental substances of concern were analyzed in the BR and PC. Significantly different unigenes (SDUs) in females (vs males) within both BR and PC raceways increased over time and compared to REF fish. Moreover, SDUs in females and males within the same treatment (i.e., BR, PC) showed a temporal increase as well as compared to REF fish. Time was the dominant factor affecting SDUs, whereas sex and treatment had less of an impact on the transcriptome profiling. Gene Set Enrichment Analysis of BR vs PC over time revealed effects on genes involved in growth, metabolism of carbohydrates and lipids, and immune system on day 7; however, by day 28, 80–100 % of the transcripts localized to enriched biomarkers were associated with tissue immune responses in both sexes. Exposure to 5 % effluent had significant effects on female liver somatic index but no effects were observed on other phenotypic health indices in either sex. BR was used as the source of reference water, but analyses showed trace amounts of ESOCs. Analyses did not point towards definitive response patterns that could be used in field-based ecotoxicogenomic studies on the impacts of well-treated MWWE but suggested compromised adaptive immune responses.
Physiological responses on the reproductive, metabolism and stress endpoints of Astyanax lacustris females (Teleostei: Characiformes) after diclofenac and ibuprofen exposure
2024, Comparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology
Diclofenac (DCF) and ibuprofen (IBU) are pharmaceutical compounds frequently detected in aquatic compartments worldwide. Several hazard effects including developmental abnormalities and redox balance impairment have been elucidated in aquatic species, but multiple endocrine evaluations are scarce. Therefore, the present study aimed to assess the disruptive physiological effects and toxicity of DCF and IBU isolated and combined, using females of the native freshwater teleost Astyanax lacustris. In regards to NSAIDs bioavailability, the results showed absence of degradation of IBU and DCF after 7 days of exposure. IBU LC₅₀ for A. lacustris was 137 mgL⁻¹ and females exposed to IBU isolated increased thyroxine (T₄) concentration at 24 h and decreased after 96 h; DCF exposure decreased triiodothyronine (T3) concentration at 96 h. Circulating levels of 17β-estradiol (E₂), cortisol (F) and testosterone (T) were not affected by any treatment. HPG and HPI axis genes fshβ, pomc and vtg were upregulated after 24 h of IBU exposure, and dio2 was downregulated in DCF fish exposed group after 96 h compared to the mixture. Protein concentration was reduced in muscle and increased in the liver by DCF and mixtures exposures at 24 h; while liver lipids were increased in the mixture groups after 96 h. The study point out the capacity of NSAIDs to affect endocrine endpoints in A. lacustris females and induce changes in energetic substrate content after acute exposure to isolated and mixed NSAIDs treatments. Lastly, the present investigation brings new insights into the toxicity and endocrine disruptive activity of NSAIDs in Latin America teleost species and the aquatic environment.
Chlorothalonil as a potential endocrine disruptor in male zebrafish (Danio rerio): Impact on the hypothalamus-pituitary-gonad axis and sperm quality
2024, Chemosphere
Chlorothalonil is a broad-spectrum organochlorine fungicide widely employed in agriculture to control fungal foliar diseases. This fungicide enters aquatic environments through the leaching process, leading to toxicity in non-target organisms. Organic contaminants can impact organism reproduction as they have the potential to interact with the neuroendocrine system. Although there are reports of toxic effects of chlorothalonil, information regarding its impact on reproduction is limited. The aim of the present study was to evaluate the influence of chlorothalonil on male reproductive physiology using the zebrafish (Danio rerio) as ecotoxicological model. Zebrafish were exposed for 7 days to two concentrations of chlorothalonil (0.1 and 10 μg/L) along with a control group (with DMSO – 0.001%). Gene expression of hypothalamus-pituitary-gonad axis components (gnrh2, gnrh3, lhr, fshr, star, hsd17b1, hsd17b3, and cyp19a1), as well as hepatic vitellogenin concentration were assessed. In sperm cells, reactive oxygen species (ROS) content, lipid peroxidation (LPO), mitochondrial functionality, and membrane integrity and fluidity were evaluated. Results indicate that exposure to the higher concentration of chlorothalonil led to a reduction in brain gnr2 expression. In gonads, mRNA levels of lhr, star, and hsd17b1 were decreased at both chlorothalonil concentrations tested. Similarly, hepatic vitellogenin concentration was reduced. Regarding sperm cells, a decreased ROS level was observed, without significant difference in LPO level. Additionally, a higher mitochondrial potential and lower membrane fluidity were observed in zebrafish exposed to chlorothalonil. These findings demonstrate that chlorothalonil acts as an endocrine disruptor, influencing reproductive control mechanisms, as evidenced by changes in expression of genes HPG axis, as well as hepatic vitellogenin concentration. Furthermore, our findings reveal that exposure to this contaminant may compromise the reproductive success of the species, as it affected sperm quality parameters.
Comprehensive identification of gene expression fingerprints and biomarkers of sexual endocrine disruption in zebrafish embryo
2023, Ecotoxicology and Environmental Safety
Endocrine disruptors (EDs), capable of modulating the sex hormone system of an organism, can exert long-lasting negative effects on reproduction in both humans and the environment. For these reasons, the properties of EDs prevent a substance from being approved for marketing. However, regulatory testing to evaluate endocrine disruption is time-consuming, costly, and animal-intensive. Here, we combined sublethal zebrafish embryo assays with transcriptomics and proteomics for well-characterized endocrine disrupting reference compounds to identify predictive biomarkers for sexual endocrine disruption in this model. Using RNA and protein gene expression fingerprints from two different sublethal exposure concentrations, we identified specific signatures and impaired biological processes induced by ethinylestradiol, tamoxifen, methyltestosterone and flutamide 96 h post fertilization (hpf). Our study promotes vtg1 as well as cyp19a1b, fam20cl, lhb, lpin1, nr1d1, fbp1b, and agxtb as promising biomarker candidates for identifying and differentiating estrogen and androgen receptor agonism and antagonism. Evaluation of these biomarkers for pre-regulatory zebrafish embryo-based bioassays will help identify endocrine disrupting hazards of compounds at the molecular level. Such approaches additionally provide weight-of-evidence for the identification of putative EDs and may contribute significantly to a reduction in animal testing in higher tier studies.
Organophosphate esters cause thyroid dysfunction via multiple signaling pathways in zebrafish brain
2022, Environmental Science and Ecotechnology
Organophosphate esters (OPEs) are widespread in various environmental media, and can disrupt thyroid endocrine signaling pathways. Mechanisms by which OPEs disrupt thyroid hormone (TH) signal transduction are not fully understood. Here, we present in vivo-in vitro-in silico evidence establishing OPEs as environmental THs competitively entering the brain to inhibit growth of zebrafish via multiple signaling pathways. OPEs can bind to transthyretin (TTR) and thyroxine-binding globulin, thereby affecting the transport of TH in the blood, and to the brain by TTR through the blood–brain barrier. When GH3 cells were exposed to OPEs, cell proliferation was significantly inhibited given that OPEs are competitive inhibitors of TH. Cresyl diphenyl phosphate was shown to be an effective antagonist of TH. Chronic exposure to OPEs significantly inhibited the growth of zebrafish by interfering with thyroperoxidase and thyroglobulin to inhibit TH synthesis. Based on comparisons of modulations of gene expression with the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, signaling pathways related to thyroid endocrine functions, such as receptor–ligand binding and regulation of hormone levels, were identified as being affected by exposure to OPEs. Effects were also associated with the biosynthesis and metabolism of lipids, and neuroactive ligand–receptor interactions. These findings provide a comprehensive understanding of the mechanisms by which OPEs disrupt thyroid pathways in zebrafish.

View all citing articles on Scopus

¹: Current affiliation: Jackson State University, Jackson, MS, United States.

²: Current affiliation: University of St. Thomas, St. Paul, MN, United States.

View full text

Published by Elsevier B.V.

Endocrine disrupting chemicals in fish: Developing exposure indicators and predictive models of effects based on mechanism of action

Abstract

Section snippets

Background

Experimental overview

Phase 1

Integrating the data: predictive modeling

Prospectus

Acknowledgements

Aquat. Toxicol.

Aquat. Toxicol.

Aquat. Toxicol.

Biophys. J.

Aquat. Toxicol.

Aquat. Toxicol.

Aquat. Toxicol.

J. Theoret. Biol.

Aquat. Toxicol.

Aquat. Toxicol

Ecotoxicol. Environ. Safety

Repro. Toxicol.

Aquat. Toxicol.

J. Lipid Res.

Aquat. Toxicol.

Comp. Biochem. Physiol.

Small fish models for identifying and assessing the effects of endocrine-disrupting chemicals

Inst. Lab. Anim. Res. J.

Description and evaluation of a short-term reproduction test with the fathead minnow (Pimephales promelas)

Environ. Toxicol. Chem.

Evaluation of the aromatase inhibitor fadrozole in a short-term reproduction assay with the fathead minnow (Pimephales promelas)

Toxicol. Sci.

Effects of the androgenic growth promoter 17β-trenbolone on fecundity and reproductive endocrinology of the fathead minnow (Pimephales promelas)

Environ. Toxicol. Chem.

Effects of two fungicides with multiple modes of action on reproductive endocrine function in the fathead minnow (Pimephales promelas)

Toxicol. Sci.

Toxicogenomics in regulatory ecotoxicology

Environ. Sci. Technol.

Ketoconazole in the fathead minnow (Pimephales promelas): reproductive toxicity and biological compensation

Environ. Toxicol. Chem.

Meeting the scientific needs of ecological risk assessment in a regulatory context

Environ. Sci. Technol.

Mechanistic computational model of ovarian steroidogenesis to predict biochemical responses to endocrine active compounds

Ann. Biomed. Eng.

Predicting the effects of endocrine disrupting chemicals on fish populations

Hum. Ecol. Risk Assess.

Variations in DNA elucidate molecular networks that cause disease

Nature