Mathematical modeling for estrogenic activity prediction of 17β-estradiol and 17α-ethynylestradiol mixtures in wastewater treatment plants effluent

Full sexual maturity-cycle exposure to environmentally relevant concentrations of 17β-estradiol decreases reproductive capacity of zebrafish

17β-Estradiol (E2) has been widely detected in natural water and treatment with E2 induces potential endocrine disrupting effects in fish. However, effects on fish fecundity and steroid system after treatment with environmentally relevant concentrations of E2 for the full sexual maturation cycle remain unclear. In this study, zebrafish were treatment with 0, 10 or 100 ng/L E2 from embryo to adult stage, and effects on gonadal development and differentiation, steroid hormone levels, transcription of genes associated with the hypothalamic-pituitary-gonadal-liver (HPG) axis in adults and fertilization rate of offspring were assessed. The results showed that treatment with E2 lead to increased number of feminization in zebrafish. In females, E2 decreased cumulative amount of spawning and inhibited the maturation of oocyte. In males, E2 inhibited the maturation and motility of sperm, as well as decreased the movement speed of sperm. These adverse effects on sperm might be responsible for the reduced fertilization observed in offspring. In addition, treatment with E2 changed the levels of steroid hormones in zebrafish gonad and altered the transcriptional levels of genes associated with HPG axis, which is responsible for the regulation of germ cells maturation and gonadal development in zebrafish. Overall, these results suggested that treatment with environmentally relevant concentrations of E2 for the full sexual maturity cycle resulted in adverse effects on reproduction in zebrafish.

A Novel Estrone Degradation Gene Cluster and Catabolic Mechanism in Microbacterium oxydans ML-6

Global-scale estrone (E1) contamination of soil and aquatic environments results from the widespread use of animal manure as fertilizer, threatening both human health and environmental security. A detailed understanding of the degradation of E1 by microorganisms and the associated catabolic mechanism remains a key challenge for the bioremediation of E1-contaminated soil. Here, Microbacterium oxydans ML-6, isolated from estrogen-contaminated soil, was shown to efficiently degrade E1. A complete catabolic pathway for E1 was proposed via liquid chromatography-tandem mass spectrometry (LC-MS/MS), genome sequencing, transcriptomic analysis, and quantitative reverse transcription-PCR (qRT-PCR). In particular, a novel gene cluster (moc) associated with E1 catabolism was predicted. The combination of heterologous expression, gene knockout, and complementation experiments demonstrated that the 3-hydroxybenzoate 4-monooxygenase (MocA; a single-component flavoprotein monooxygenase) encoded by the mocA gene was responsible for the initial hydroxylation of E1. Furthermore, to demonstrate the detoxification of E1 by strain ML-6, phytotoxicity tests were performed. Overall, our findings provide new insight into the molecular mechanism underlying the diversity of E1 catabolism in microorganisms and suggest that M. oxydans ML-6 and its enzymes have potential applications in E1 bioremediation to reduce or eliminate E1-related environmental pollution. IMPORTANCE Steroidal estrogens (SEs) are mainly produced by animals, while bacteria are major consumers of SEs in the biosphere. However, the understanding of the gene clusters that participate in E1 degradation is still limited, and the enzymes involved in the biodegradation of E1 have not been well characterized. The present study reports that M. oxydans ML-6 has effective SE degradation capacity, which facilitates the development of strain ML-6 as a broad-spectrum biocatalyst for the production of certain desired compounds. A novel gene cluster (moc) associated with E1 catabolism was predicted. The 3-hydroxybenzoate 4-monooxygenase (MocA; a single-component flavoprotein monooxygenase) identified in the moc cluster was found to be necessary and specific for the initial hydroxylation of E1 to generate 4-OHE1, providing new insight into the biological role of flavoprotein monooxygenase.

Ecological risk assessment associated with five endocrine-disrupting compounds in wastewater treatment plants of Northeast Mexico

The ecological risk associated with five endocrine-disrupting compounds (EDCs) was studied in four wastewater treatment plants (WWTPs) in Monterrey, Mexico. The EDCs, 17β-estradiol (E2), 17α-ethinylestradiol (EE2), bisphenol A (BPA), 4-nonylphenol (4NP), and 4-tert-octylphenol (4TOP) were determined by SPE/GC-MS method, where EE2 and 4TOP were the most abundant in effluents at levels from 1.6 - 26.8 ng/L (EE2) and < LOD - 5.0 ng/L (4TOP), which corroborate that the wastewater discharges represent critical sources of EDCs to the aquatic environments. In this study, the potential risk associated with selected EDCs was assessed through the risk quotients (RQs) and by estimating the estrogenic activity (expressed as EEQ). This study also constitutes the first approach for the ecological risk assessment in effluents of WWTPs in Northeast Mexico. The results demonstrated that the effluents of the WWTPs represent a high risk for the organisms living in the receiving water bodies because the residual estrogens effect E2 and EE2 with RQ values up to 49.1 and 1165.2. EEQ values between 6.3 and 24.6 ngEE2/L were considered the most hazardous compounds among the target EDCs, capable of causing some alterations in the endocrine system of aquatic and terrestrial organisms due to chronic exposition.

Degradation of 17β-estradiol by UV/persulfate in different water samples

Sulfate radical (•SO₄^-)-based advanced oxidation processes are widely used for wastewater treatment. This study explored the potential use of UV/persulfate (UV/PS) system for the degradation of 17β-estradiol (E2). The pH of the reaction system can affect the degradation rate of E2 by UV/PS and the optimum pH was 7.0; Br^- and Cl^- in water can promote the degradation rate, HCO₃^- has an inhibitory effect on the reaction, SO₄^2- and cations (Na⁺, Mg²⁺, K⁺) have no effect on the degradation rate. The degradation of E2 by UV/PS was a mineralization process, with the mineralization rate reaching 90.97% at 8 h. E2 in the UV/PS system was mainly degraded by hydroxylation, deoxygenation, and hydrogenation. E2 reaction sites were mainly located on benzene rings, mainly carbonylation on quinary rings, and bond breakage between C10 and C5 resulted in the removal of benzene rings and carboxyl at C2 and C3 sites. In the presence of halogen ions, halogenated disinfection by-products were not formed in the degradation process of E2 by UV/PS. E2 in the UV/PS system could inhibit the formation of bromate. The results of this study suggest that UV/PS is a safe and reliable method to degrade E2.

Distribution and Potential Effects of 17β-Estradiol (E2) on <i>Aeromonas </i>Diversity in Wastewater and Fish Samples

BACKGROUND AND OBJECTIVE

Recently, there has been evidence for the accumulation of steroid hormones in the water environment with negative consequences on fish and humans. However, there is paucity of information on how the steroid hormones influence the microbial community in environmental waters. The objective of this study was to determine the occurrence of 17β-estradiol (E2) and its potential influence on the diversity of Aeromonas spp.

MATERIALS AND METHODS

Wastewater samples were obtained from sewage treatment plants in northern South Africa and fish samples were collected from the Nandoni dam. Aeromonas spp. were isolated using microbiological methods and PCR protocols were used for their identification. A commercial Elisa kit was used for measuring the concentration of 17β-estradiol (E2) from the wastewater samples as well as the fish samples.

RESULTS

17β-estradiol (E2) was found in high concentration in sewage samples varying from 0.32-348.6 pg mL-1 while in fish samples, it ranged from 1.1-73.6 pg mL-1. There was a tendency of samples with high E2 concentrations to have higher diversity of Aeromonas spp., implying that steroid hormones may serve as nutrient for Aeromonas spp. Aeromonas hydrophila was the most prevalent species (71%), followed by A. sobria with (68%).

CONCLUSION

The presence of Aeromonas spp. in environmental waters and fish that is consumed by the local community poses a serious health concern. The high content of E2 in treated wastewater is of serious concern as well. For the first time, the present study showed a positive impact of E2 on Aeromonas growth.

Development of a separation framework for effects-based targeted and non-targeted toxicological screening of water and wastewater

An environmental water sample fractionation framework was developed based on effects-directed analysis (EDA) to detect known and unknown compounds of concern in different waters. Secondary effluent from a wastewater treatment plant was used to demonstrate the effectiveness of the developed framework for characterizing estrogenic compounds in the effluent. The effluent was spiked with known estrogenic compounds to validate the framework in a targeted approach and an unspiked sample was also investigated in a non-targeted approach. The framework separated compounds based on polarity and adsorption using liquid-liquid extraction followed by solid phase extraction. The targeted and non-targeted effluents generated six fractions each, which were assessed for estrogenic activity using an in vitro bioassay (yeast estrogen screen - YES). Three out of the six fractions in each case, along with the raw effluent, showed estrogen equivalent concentrations (EEQs) ranging between 1.0 and 3.0 μg/L. Directed by the assay results, these estrogenic fractions were further analyzed using liquid- and gas-chromatography coupled with mass spectrometry for compound identification. The developed separation framework coupled with a bioassay aided in identification of both known and unknown compounds producing estrogenic effects in the water sample. The approach of fractionation followed by concentration helped isolate and elevate contaminant levels without necessarily concentrating potential matrix effects that could cause interfering cytotoxicity and inhibition in the bioassay. The targeted analysis showed consistency between predicted and observed results, while the non-targeted analysis revealed the presence of three estrogenic compounds in the unspiked effluent: di-isobutyl phthalate, diethyl phthalate and benzophenone, that were confirmed with standards. The study mainly aimed at development and validation of a simple yet effective EDA framework with low cost techniques for water and wastewater toxicity screening and evaluation, and the results suggested that the developed framework could be used as a screening tool for isolating and identifying unknown compounds in a complex water sample.

Mytilidae as model organisms in the marine ecotoxicology of pharmaceuticals - A review

Growing production and consumption of pharmaceuticals is a global problem. Due to insufficient data on the concentration and distribution of pharmaceuticals in the marine environment, there are no appropriate legal regulations concerning their emission. In order to understand all aspects of the fate of pharmaceuticals in the marine environment and their effect on marine biota, it is necessary to find the most appropriate model organism for this purpose. This paper presents an overview of the ecotoxicological studies of pharmaceuticals, regarding the assessment of Mytilidae as suitable organisms for biomonitoring programs and toxicity tests. The use of mussels in the monitoring of pharmaceuticals allows the observation of changes in the concentration and distribution of these compounds. This in turn gives valuable information on the amount of pharmaceutical pollutants released into the environment in different areas. In this context, information necessary for the assessment of risks related to pharmaceuticals in the marine environment are provided based on what effective management procedures can be developed. However, the accumulation capacity of individual Mytilidae species, the bioavailability of pharmaceuticals and their biological effects should be further scrutinized.

Testicular transcriptome alterations in zebrafish (Danio rerio) exposure to 17β-estradiol

The hormone 17β-estradiol (E₂) can be found in rivers, effluents, and even drinking water. Researches have demonstrated that E₂ affects various metabolic pathways through gene activation and may cause reproductive toxicity in fish. Therefore, the aim of this study was to evaluate E₂-induced toxicity via testicular transcriptome of zebrafish (Danio rerio) exposed to different concentrations (10 ng L^-1, and 100 ng L^-1) of E₂. A total of >600 significant differentially expressed genes (DEGs) were enriched among the three treatments. Short time-series expression miner analysis revealed five KEGG pathways including drug metabolism, other enzymes, calcium signaling pathway, ECM-receptor interaction, gap junction, and cell adhesion molecules. Twenty genes were selected to verify the accuracy of RNA-Seq. Other reported genes related to sex differentiation, development, energy metabolism, and other processes were found. One set of genes significantly increased/decreased/fluctuated over time, especially 12 h after E₂ exposure. Genes associated with ovaries (zp3c), and development (bmp15, gdf9, and sycp2l) were significantly upregulated with increasing E₂ concentration. E₂ and testosterone was significantly decreased by 10 (except for T) and 100 ng L^-1 E₂ exposure at 12 h. The current study demonstrated that sex differentiation, development, energy metabolism, immunity, and ribosome biogenesis in male zebrafish were all significantly affected by 17β-estradiol exposure through transcriptional alterations.