17β-estradiol causes abnormal development in embryos of the viviparous eelpout

Developmental toxicity and estrogenicity of glyphosate in zebrafish in vivo and in silico studies

As the most heavily used herbicide globally, glyphosate (GLY) has been detected in a variety of environments and has raised concerns about its ecological and health effects. There is debate as to whether GLY may disrupt the endocrine system. Here, we investigated the developmental toxicity of GLY in zebrafish based on deep learning-enabled morphometric analysis (DLMA). In addition, the estrogenic activity of GLY was assessed by endocrine disruption prediction, docking study and in vivo experiments. Results showed that exposure to environmental concentrations of GLY negatively impacted zebrafish development, causing yolk edema and pericardial edema. Endocrine disruption prediction suggested that GLY may target estrogen receptors (ER). Molecular docking analysis revealed binding of GLY to three zebrafish ER. In vivo zebrafish experiment, GLY enhanced the protein levels of ERα and the mRNA levels of cyp19a, HSD17b1, vtg1, vtg2, esr1, esr2a and esr2b. These results suggest that GLY may act as an endocrine disruptor by targeting ER, which warrants further attention for its potential toxicity to aquatic animals.

Toxicity and Estrogenicity of Bisphenol TMC in Oryzias melastigma via In Vivo and In Silico Studies

Bisphenol 4-[1-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexyl] phenol (BPTMC), as a substitute for bisphenol A, has been detected in environments. However, the ecotoxicological data of BPTMC are extremely scarce. Here, the lethality, developmental toxicity, locomotor behavior, and estrogenic activity of BPTMC at different concentrations (0.25-2000 μg/L) in marine medaka (Oryzias melastigma) embryos were examined. In addition, the in silico binding potentials of O. melastigma estrogen receptors (omEsrs) with BPTMC were assessed by docking study. Low-concentration BPTMC exposure (including an environmentally relevant concentration, 0.25 μg/L) resulted in stimulating effects, including hatching rate, heart rate, malformation rate, and swimming velocity. However, elevated concentrations of BPTMC led to an inflammatory response, changed heart rate and swimming velocity in the embryos and larvae. In the meantime, BPTMC (including 0.25 μg/L) altered the concentrations of estrogen receptor, vitellogenin, and endogenous 17 β-estradiol as well as the transcriptional levels of estrogen-responsive genes in the embryos or/and larvae. Furthermore, elaborate tertiary structures of omEsrs were built by ab initio modeling, and BPTMC exerted potent binding potential with three omEsrs with -47.23, -49.23, and -50.30 kJ/mol for Esr1, Esr2a, and Esr2b, respectively. This work suggests that BPTMC has potent toxicity and estrogenic effects in O. melastigma.

Isolation of Environmental Bacteria Able to Degrade Sterols and/or Bile Acids: Determination of Cholesterol Oxidase and Several Hydroxysteroid Dehydrogenase Activities in Rhodococcus, Gordonia, and Pseudomonas putida

Interest about the isolation and characterization of steroid-catabolizing bacteria has increased over time due to the massive release of these recalcitrant compounds and their deleterious effects or their biotransformation derivatives as endocrine disruptors for wildlife, as well as their potential use in biotechnological approaches for the synthesis of pharmacological compounds. Thus, in this chapter, an isolation protocol to select environmental bacteria able to degrade sterols, bile acids, and androgens is shown. Moreover, procedures for the determination of cholesterol oxidase or different hydroxysteroid dehydrogenase activities in Pseudomonas putida DOC21, Rhodococcus sp. HE24.12, Gordonia sp. HE24.4J and Gordonia sp. HE24.3 are also detailed.

Mechanistic and phylogenetic insights into actinobacteria-mediated oestrogen biodegradation in urban estuarine sediments

Steroidal oestrogens are often accumulated in urban estuarine sediments worldwide at microgram per gram levels. These aromatic steroids have been classified as endocrine disruptors and group 1 carcinogens. Microbial degradation is a naturally occurring mechanism that mineralizes oestrogens in the biosphere; however, the corresponding genes in oestrogen-degrading actinobacteria remain unidentified. In this study, we identified a gene cluster encoding several putative oestrogen-degrading genes (aed; actinobacterial oestrogen degradation) in actinobacterium Rhodococcus sp. strain B50. Among them, the aedA and aedB genes involved in oestrogenic A-ring cleavage were identified through gene-disruption experiments. We demonstrated that actinobacterial oestrone 4-hydroxylase (AedA) is a cytochrome P450-type monooxygenase. We also detected the accumulation of two extracellular oestrogenic metabolites, including pyridinestrone acid (PEA) and 3aα-H-4α(3'-propanoate)-7aβ-methylhexahydro-1,5-indanedione (HIP), in the oestrone-fed strain B50 cultures. Since actinobacterial aedB and proteobacterial edcB shared < 40% sequence identity, 4-hydroxyestrone 4,5-dioxygenase genes (namely aedB and edcB) could serve as a specific biomarker to differentiate the contribution of actinobacteria and proteobacteria in environmental oestrogen degradation. Therefore, 4-hydroxyestrone 4,5-dioxygenase genes and the extracellular metabolites PEA and HIP were used as biomarkers to investigate oestrogen biodegradation in an urban estuarine sediment. Interestingly, our data suggested that actinobacteria are active oestrogen degraders in the urban estuarine sediment.

Effects of maternal exposure to environmentally relevant concentrations of 17α-ethinyloestradiol in a live bearing freshwater fish, Xenotoca eiseni (Cyprinodontiformes, Goodeidae)

The viviparous teleost Redtail Splitfin (Xenotoca eiseni) is a live bearing fish that presents a novel freshwater model for investigating the effects of maternally derived micropollutants on vulnerable early developmental life stages. Here, adult female X. eiseni were exposed to 17α-ethinyloestradiol (EE2), a potent contraceptive oestrogen, at environmentally relevant concentrations, to investigate for effects on sex partitioning and development. Pregnant and non-pregnant females were exposed for four weeks to EE2 at measured concentrations of 0.9 and 3.4 ng/L EE2 and offspring from gravid females were kept in clean water for a further four weeks. Only pregnant females were seen to respond to 3.4 ng/L EE2 with an increase in the transcription of hepatic vitellogenins (vtgA, vtgB and vtgC). Offspring of exposed mothers showed no obvious effects on somatic growth, gonadal development, sex partitioning or development. However, there was a higher rate of deformities and developmental abnormalities in offspring of EE2-exposed females. The work presented provides the foundation for the development of X. eiseni as a new freshwater model for studies on maternal transfer of chemical pollutants in live bearing animals.

Microbial degradation of steroid sex hormones: implications for environmental and ecological studies

Steroid hormones modulate development, reproduction and communication in eukaryotes. The widespread occurrence and persistence of steroid hormones have attracted public attention due to their endocrine-disrupting effects on both wildlife and human beings. Bacteria are responsible for mineralizing steroids from the biosphere. Aerobic degradation of steroid hormones relies on O2 as a co-substrate of oxygenases to activate and to cleave the recalcitrant steroidal core ring. To date, two oxygen-dependent degradation pathways - the 9,10-seco pathway for androgens and the 4,5-seco pathways for oestrogens - have been characterized. Under anaerobic conditions, denitrifying bacteria adopt the 2,3-seco pathway to degrade different steroid structures. Recent meta-omics revealed that microorganisms able to degrade steroids are highly diverse and ubiquitous in different ecosystems. This review also summarizes culture-independent approaches using the characteristic metabolites and catabolic genes to monitor steroid biodegradation in various ecosystems.

Alterations to embryonic development and teratogenic effects induced by a hospital effluent on Cyprinus carpio oocytes

Hospital functioning generates a great quantity of contaminants, among which organic materials, heavy metals, and diverse pharmaceuticals are noteworthy that can affect organisms if they are not properly removed from the effluents. The hospital effluent evaluated in the present study came from IMSS (Instituto Mexicano del Seguro Social) Clinic 221 in downtown Toluca, State of Mexico, a secondary care facility. The contaminants identified in hospitals have been associated with deleterious effects on aquatic organisms; however, it is necessary to continue with more studies in order to be able to regulate the production of said contaminants which are generally dumped into the city sewage system. The present study had the purpose of evaluating the alterations to embryonic development and teratogenic effects on oocytes Cyprinus carpio after exposure to different proportions of hospital effluent. For said purpose, the physicochemical properties of the effluent were determined. Concentrations of the main microcontaminants were also determined. An embryolethality study out and the determination of the main alterations to embryonic development and teratogenic effects produced, due to exposure of C. carpio at different proportions of the effluent, were carried out. The results showed that the physicochemical properties were within the values permitted by Mexican regulation; however, the presence of contaminants such as NaClO, metals, anti-biotics, anti-diabetics, non-steroidal anti-inflammatory drugs, hormones and beta-blockers, was detected. Lethal concentration 50 was 5.65% and the effective concentration for malformations was 3.85%, with a teratogenic index of 1.46. The main teratogenic alterations were yolk deformation, scoliosis, modified chorda structure, tail malformation, fin deformity and mouth hyperplasia. A high rate of hatching delay was observed. The results suggest that the hospital effluent under study is capable of inducing embryotoxicity and teratogenicity in oocytes of C. carpio.

Removal of estrone, 17β-estradiol, and estriol from sewage and cow dung by immobilized Novosphingobium sp. ARI-1

Immobilized bacterial agents (IBA) can increase the cell density and improve the environmental adaptability of bacteria. An estrogen-degrading bacterium, Novosphingobium sp. ARI-1, was immobilized in calcium alginate (CA) using an embedding method and applied to the removal of estrogens from natural sewage and cow dung. The optimum immobilization conditions were as follows: sodium alginate (SA) and CaCl₂·2H₂O concentrations of 5% (m/v) and 4% (m/v), respectively; a bacterial suspension to SA ratio of 1:2; and cross-linking for 6 h at 4°C. Immobilized strain ARI-1 mediated the biodegradation of estrone (E1), 17β-estradiol (E2), and estriol (E3) either individually or in combination and was tolerant of various temperatures and pH values. Immobilized ARI-1 removed 80.43%, 94.76%, and 100% of E1, E2, and E3 from sewage containing 1.75, 0.71, and 1.52 μg L^-1 of the three test estrogens within seven days, respectively. In cow dung containing initial E1, E2, and E3 concentrations of 0.71, 0.64, and 0.66 mg kg^-1, respectively, E1 and E2 concentrations were below the limit of detection, and 1.09% of E3 remained after incubation with immobilized ARI-1 for seven days. These results confirmed the utility of immobilized strain ARI-1 for the removal of estrogens from environmental matrices.

Development of ELISAs for the detection of vitellogenin in three marine fish from coastal areas of China

Estrogenic pollution has aroused great concern for its adverse effects on marine organisms. This study aimed to establish biomarker-based methods for detecting environmental estrogens using vitellogenin (Vtg) of teleost fishes inhabiting coastal areas of China. Firstly, Vtgs in marbled flounder (Pseudopleuronectes yokohamae), black rockfish (Sebastes schlegelii) and fat greenling (Hexagrammos otakii) were purified, characterized and used to prepare antibodies. Then, Vtg ELISA for each species was developed using purified Vtg and its antibody. Marbled flounder Vtg ELISA had a working range of 3.9-500 ng/mL and a detection limit of 2.1 ng/mL, and black rockfish Vtg ELISA had strong cross-reactivity with marbled flounder Vtg. Furthermore, Vtg induction in male marbled flounder exposed to pentadecafluorooctanoic acid (PFOA) was measured by developed ELISA. Plasma Vtg concentrations were significantly increased with PFOA concentrations in seawater and fish muscle. Therefore, Vtg ELISAs for these species might be useful tools for monitoring marine environmental estrogens.

Effects of 17β-estradiol and 17α-ethinylestradiol on the embryonic development of the clearhead icefish (Protosalanx hyalocranius)

Estrogenic effects of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) on animals have been widely reported. The high sensitivity of fish in the early-life stages to xenobiotics can be exploited to evaluate the developmental effects of environmentally relevant levels of E2 and EE2. In this work, clearhead icefish (Protosalanx hyalocranius) embryos (blastula stage) were exposed to E2 or EE2 at concentrations between 0.05 ng/L and 1 mg/L. The toxicity endpoints of mortality, teratogenesis, and hatching retardation were evaluated. The results showed that continuous exposure of the fish embryos/larvae to higher concentrations of E2 and EE2 dramatically increased mortality after 17 days, when the hatching period started. An E2 concentration of 8 μg/L (day 16) and an EE2 concentration of at 0.2 mg/L (day 18) induced maximum teratogenesis rates of 30% and 35%, respectively. Embryos exposed to 0.2 mg E2 or EE2/L had a significantly retarded hatching time compared to the control. Thus, although environmentally relevant concentrations E2 and EE2 are not lethal for P. hyalocranius embryos or larvae, their ability to induce teratogenesis and hatching retardation merits concern.

Current limitations and recommendations to improve testing for the environmental assessment of endocrine active substances

In the present study, existing regulatory frameworks and test systems for assessing potential endocrine active chemicals are described, and associated challenges are discussed, along with proposed approaches to address these challenges. Regulatory frameworks vary somewhat across geographies, but all basically evaluate whether a chemical possesses endocrine activity and whether this activity can result in adverse outcomes either to humans or to the environment. Current test systems include in silico, in vitro, and in vivo techniques focused on detecting potential endocrine activity, and in vivo tests that collect apical data to detect possible adverse effects. These test systems are currently designed to robustly assess endocrine activity and/or adverse effects in the estrogen, androgen, and thyroid hormone signaling pathways; however, there are some limitations of current test systems for evaluating endocrine hazard and risk. These limitations include a lack of certainty regarding: 1) adequately sensitive species and life stages; 2) mechanistic endpoints that are diagnostic for endocrine pathways of concern; and 3) the linkage between mechanistic responses and apical, adverse outcomes. Furthermore, some existing test methods are resource intensive with regard to time, cost, and use of animals. However, based on recent experiences, there are opportunities to improve approaches to and guidance for existing test methods and to reduce uncertainty. For example, in vitro high-throughput screening could be used to prioritize chemicals for testing and provide insights as to the most appropriate assays for characterizing hazard and risk. Other recommendations include adding endpoints for elucidating connections between mechanistic effects and adverse outcomes, identifying potentially sensitive taxa for which test methods currently do not exist, and addressing key endocrine pathways of possible concern in addition to those associated with estrogen, androgen, and thyroid signaling. Integr Environ Assess Manag 2017;13:302-316. © 2016 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Biomarker responses in eelpouts from four coastal areas in Sweden, Denmark and Germany

To increase our understanding of possible chemical impacts on coastal fish populations in the Baltic Sea, Kattegat and Skagerrak, the viviparous eelpout (Zoarces viviparus) was used as sentinel species in two major sampling campaigns (spring and autumn) in 16 different coastal sites. Condition factor (CF), liver somatic index (LSI), gonad somatic index (GSI) were measured and the activity of the hepatic enzymes ethoxyresorufin-O-deethylase (EROD), glutathione reductase GR), glutathione S-transferase (GST), catalase (CAT) and muscular activity of acetylcholinesterase (AChE) were assessed. PAH metabolites in bile were also analyzed. The most notable finding in the data set was the low EROD activity in eelpouts collected at the relatively polluted region in Germany compared to the other regions, which could be due to an inhibition of the CYP1A-system or to adaptation to chronic exposure of pollutants in this area. Additionally, low AChE activity was noted in the German region in the autumn campaign and low AChE activity detected in the Danish region in the spring campaign. These differences suggest possible season-specific differences in the use and release of AChE-inhibiting chemicals in the Danish and German regions. Clustering of biomarkers on site level indicated a relationship between CF and GSI and suggested that sites with a high CF contained eelpout that put a larger effort into their larvae development. Clustering of the oxidative stress markers GR, GST and CAT on the individual level reflected a possible coordinated regulation of these enzymes. Overall, the results support the importance of taking into account general regional differences and seasonal variation in biomarker activity when monitoring and assessing the effects of pollution. Despite the expected seasonal variation for most of the measured endpoint, several markers (GSI, EROD and CF) vary similarly between all selected sites in both spring and autumn. This suggests that the differences between sites for these endpoints are independent of season.

Severe malformations of eelpout (Zoarces viviparus) fry are induced by maternal estrogenic exposure during early embryogenesis

Pregnant eelpout were exposed via the water to known endocrine disrupting compounds (EDCs) to clarify if EDCs could be causing the increased eelpout fry malformation frequencies observed in coastal areas receiving high anthropogenic input. The presence of a teratogenic window for estrogen-induced malformations was also investigated by starting the exposure at different times during eelpout pregnancy. Both 17α-ethinylestradiol (EE2) (17.8 ng/L) and pyrene (0.5 μg/L) significantly increased fry malformation frequency whereas 4-t-octylphenol (4-t-OP) up to 14.3 μg/L did not. Vitellogenin was significantly induced by EE2 (5.7 and 17.8 ng/L) but not by 4-t-OP and pyrene. A critical period for estrogen-induced fry malformations was identified and closed between 14 and 22 days post fertilization (dpf). Exposure to 17β-estradiol (E2) between 0 and 14 dpf caused severe malformations and severity increased the closer exposure start was to fertilization, whereas malformations were absent by exposure starting later than 14 dpf. Data on ovarian fluid volume and larval length supported the suggested teratogenic window. Larval mortality also increased when exposure started right after fertilization.

A target-induced three-way G-quadruplex junction for 17β-estradiol monitoring with a naked-eye readout

A three-way G-quadruplex junction for 17β-estradiol monitoring has been constructed based on split G-quadruplex DNAzyme and toehold-mediated strand displacement.