Estrogenic activities of diuron metabolites in female Nile tilapia (Oreochromis niloticus)

Interaction of different chloro-substituted phenylurea herbicides (diuron and chlortoluron) with bovine serum albumin: Insights from multispectral study

In this work, the interaction between different chloro-substituted phenylurea herbicides (diuron (DIU) and chlortoluron (CHL)) and BSA were investigated and compared at three different temperatures (283 K, 298 K and 310 K) adopting UV-vis, fluorescence, and circular dichroism spectra. The quenching mechanism of the interaction was also proposed. The energy transfer between BSA and DIU/CHL was investigated. The binding sites of DIU/CHL and BSA and the variations in the microenvironment of amino acid residues were studied. The changes of the secondary structure of BSA were analyzed. The results indicate that both DIU and CHL can significantly interact with BSA, and the degree of the interaction between DIU/CHL and BSA increases with the increase of the DIU/CHL concentration. The fluorescence quenching of BSA by DIU/CHL results from the combination of static and dynamic quenching. The DIU/CHL has a weak to moderate binding affinity for BSA, and the binding stoichiometry is 1:1. Their binding processes are spontaneous, and hydrophobic interaction, hydrogen bonds and van der Waals forces are the main interaction forces. DIU/CHL has higher affinity for subdomain IIA (Site I) of BSA than subdomain IIIA (Site II), and also interacts with tryptophan more than tyrosine residues. The energy transfer can occur from BSA to DIU/CHL. By comparison, the strength of the interaction of DIU-BSA is always greater than that of CHL-BSA, and DIU can destroy the secondary structure of BSA molecules greater than CHL and thus the potential toxicity of DIU is higher due to DIU with more chlorine substituents than CHL. It is expected that this study on the interaction can offer in-depth insights into the toxicity of phenylurea herbicides, as well as their impact on human and animal health at the molecular level.

Environmental DNA highlights the influence of salinity and agricultural run-off on coastal fish assemblages in the Great Barrier Reef region

Agricultural run-off in Australia's Mackay-Whitsunday region is a major source of nutrient and pesticide pollution to coastal and inshore ecosystems of the Great Barrier Reef. While the effects of run-off are well documented for the region's coral and seagrass habitats, the ecological impacts on estuaries, the direct recipients of run-off, are less known. This is particularly true for fish communities, which are shaped by the physico-chemical properties of coastal waterways that vary greatly in tropical regions. To address this knowledge gap, we used environmental DNA (eDNA) metabarcoding to examine fish assemblages at four locations (three estuaries and a harbour) subjected to varying levels of agricultural run-off during a wet and dry season. Pesticide and nutrient concentrations were markedly elevated during the sampled wet season with the influx of freshwater and agricultural run-off. Fish taxa richness significantly decreased in all three estuaries (F = 164.73, P = <0.001), along with pronounced changes in community composition (F = 46.68, P = 0.001) associated with environmental variables (largely salinity: 27.48% contribution to total variance). In contrast, the nearby Mackay Harbour exhibited a far more stable community structure, with no marked changes in fish assemblages observed between the sampled seasons. Among the four sampled locations, variation in fish community composition was more pronounced within the wet season (F = 2.5, P = 0.001). Notably, variation in the wet season was significantly correlated with agricultural contaminants (phosphorus: 6.25%, pesticides: 5.22%) alongside environmental variables (salinity: 5.61%, DOC: 5.57%). Historically contaminated and relatively unimpacted estuaries each demonstrated distinct fish communities, reflecting their associated catchment use. Our findings emphasise that while seasonal effects play a key role in shaping the community structure of fish in this region, agricultural contaminants are also important contributors in estuarine systems.

Diuron-induced fetal Leydig cell dysfunction in in vitro organ cultured fetal testes

Diuron is a phenylurea herbicide widely used in the agricultural industry. In recent years, the risk of infertility and developmental defects has increased due to exposure to environmental pollutants. In this study, we investigated the toxicity of diuron in fetal mouse testes using three-dimensional organ cultures. Fetal testes derived from embryonic day (E) 14.5 were cultured with 200 µM diuron for 5 days. The results revealed that diuron did not impair fetal germ cell proliferation or the expression levels of germ cell markers such as Ddx4, Dazl, Oct 4, Nanog, Plzf, and TRA 98. Similarly, the gene or protein expression of the Sertoli cell markers Sox9 and Wt1 in diuron-exposed fetal testes did not change after 5 days of culture. In contrast, diuron increased fetal Leydig cell markers (FLC), Cyp11a1, Cyp17a1, Thbs2, and Pdgf α, and decreased adult Leydig cell (ALC) markers, Sult1e1, Hsd173, Ptgds, and Vcam1. However, 3-βHSD, an FLC and ALC marker, was consistently maintained upon exposure to diuron in fetal testes compared to non-treated groups. In conclusion, our study demonstrates that diuron negatively impacts Fetal Leydig cell development, although it does not affect germ and Sertoli cells.

Tracking Targets of Dynamic Super-Enhancers in Vitro to Better Characterize Osteoclastogenesis and to Evaluate the Effect of Diuron on the Maturation of Human Bone Cells

BACKGROUND

Osteoclasts are major actors in the maintenance of bone homeostasis. The full functional maturation of osteoclasts from monocyte lineage cells is essential for the degradation of old/damaged bone matrix. Diuron is one of the most frequently encountered herbicides, particularly in water sources. However, despite a reported delayed ossification in vivo, its impact on bone cells remains largely unknown.

OBJECTIVES

The objectives of this study were to first better characterize osteoclastogenesis by identifying genes that drive the differentiation of CD14+ monocyte progenitors into osteoclasts and to evaluate the toxicity of diuron on osteoblastic and osteoclastic differentiation in vitro.

METHODS

We performed chromatin immunoprecipitation (ChIP) against H3K27ac followed by ChIP-sequencing (ChIP-Seq) and RNA-sequencing (RNA-Seq) at different stages of differentiation of CD14+ monocytes into active osteoclasts. Differentially activated super-enhancers and their potential target genes were identified. Then to evaluate the toxicity of diuron on osteoblasts and osteoclasts, we performed RNA-Seq and functional tests during in vitro osteoblastic and osteoclastic differentiation by exposing cells to different concentrations of diuron.

RESULTS

The combinatorial study of the epigenetic and transcriptional remodeling taking place during differentiation has revealed a very dynamic epigenetic profile that supports the expression of genes vital for osteoclast differentiation and function. In total, we identified 122 genes induced by dynamic super-enhancers at late days. Our data suggest that high concentration of diuron (50μM) affects viability of mesenchymal stem cells (MSCs) in vitro associated with a decrease of bone mineralization. At a lower concentration (1μM), an inhibitory effect was observed in vitro on the number of osteoclasts derived from CD14+ monocytes without affecting cell viability. Among the diuron-affected genes, our analysis suggests a significant enrichment of genes targeted by pro-differentiation super-enhancers, with an odds ratio of 5.12 (ρ=2.59×10-5).

DISCUSSION

Exposure to high concentrations of diuron decreased the viability of MSCs and could therefore affect osteoblastic differentiation and bone mineralization. This pesticide also disrupted osteoclasts maturation by impairing the expression of cell-identity determining genes. Indeed, at sublethal concentrations, differences in the expression of these key genes were mild during the course of in vitro osteoclast differentiation. Taken together our results suggest that high exposure levels of diuron could have an effect on bone homeostasis. https://doi.org/10.1289/EHP11690.

Synthetic microfiber exposure negatively affects reproductive parameters in male medaka (Oryzias latipes)

Microplastics not only accumulate in the bodies of fishes and cause damage to the organs, but also cause many other problems, such as reduced reproductive capacity, by acting directly or indirectly on the hypothalamus-pituitary-gonad axis (HPG axis). In this study, we investigated the changes in HPG axis-related genes in male medaka (Oryzias latipes) exposed to fiber-type microplastics. We confirmed the progression of vitellogenesis, a sign of endocrine disruption, in male fish. In the microfiber-exposed group, microfiber accumulation was confirmed in the gills and intestines. One week after exposure to two different concentrations of microfibers (500 and 1,000 fibers/L), the fish showed increased expression of gonadotropin-releasing hormone (GnRH) and luteinizing hormone receptor (LH-R) mRNA. From day 10 of exposure to the microfibers, there was an increase in the expression of the gonadotropin-inhibitory hormone (GnIH) mRNA and a decrease in the expression of GnRH and LH-R mRNA. There was an increase in the cytochrome P450 aromatase (CYP19a) mRNA expression and plasma estradiol (E₂) concentration in the 1,000 fibers/L exposure group. High vitellogenin (VTG) mRNA expression was confirmed seven days after exposure in the 1,000 fibers/L group, which was consistent with the VTG mRNA expression signals detected in the liver using in situ hybridization. These results suggest that microfiber ingestion may cause short-term endocrinal disruption of the HPG axis in male medaka, which in turn may interfere with their normal maturation process.

Chronic effects of environmental concentrations of antifoulant diuron on two marine fish: Assessment of hormone levels, immunity, and antioxidant defense system

The presence and toxicity of waterborne diuron in aquatic environments pose a severe threat to non-target organisms. However, the chronic impact of diuron in marine fish has been poorly investigated. In this study, we report the chronic effects (30 and 60 days) of environmentally relevant concentrations of diuron (0.1, 1, and 10 μg L^-1) on economically important marine fish, red seabream (Pagrus major), and black rockfish (Sebastes schlegelii) by evaluating several parameters, including hormone levels, immunity, hepatic function, and antioxidant defense. Significant decreases in 17β-estradiol and 11-ketotestosterone levels and gonadosomatic index were observed on day 60 in fish exposed to 10 μg L^-1 diuron. Parameters of immunity, such as alternative complement activity, lysozyme activity, and total immunoglobulin levels, were significantly lowered by 60-day exposure to 10 μg L^-1 diuron in both fish. Significant decreases in the hepatic enzyme activities of alanine transaminase and aspartate transaminase were observed with an induction of cortisol on day 60 in fish exposed to 10 μg L-¹ diuron. Intracellular malondialdehyde and glutathione levels were significantly increased by 10 μg L-¹ diuron at day 60 with an increase in the enzymatic activities of catalase and superoxide dismutase. Overall, black rockfish were more sensitive to diuron than red seabream. These results suggest that consistent exposure to environmentally relevant concentrations of diuron is detrimental to the reproduction, immunity, and health of marine fish.

South American National Contributions to Knowledge of the Effects of Endocrine Disrupting Chemicals in Wild Animals: Current and Future Directions

Human pressure due to industrial and agricultural development has resulted in a biodiversity crisis. Environmental pollution is one of its drivers, including contamination of wildlife by chemicals emitted into the air, soil, and water. Chemicals released into the environment, even at low concentrations, may pose a negative effect on organisms. These chemicals might modify the synthesis, metabolism, and mode of action of hormones. This can lead to failures in reproduction, growth, and development of organisms potentially impacting their fitness. In this review, we focused on assessing the current knowledge on concentrations and possible effects of endocrine disruptor chemicals (metals, persistent organic pollutants, and others) in studies performed in South America, with findings at reproductive and thyroid levels. Our literature search revealed that most studies have focused on measuring the concentrations of compounds that act as endocrine disruptors in animals at the systemic level. However, few studies have evaluated the effects at a reproductive level, while information at thyroid disorders is scarce. Most studies have been conducted in fish by researchers from Brazil, Argentina, Chile, and Colombia. Comparison of results across studies is difficult due to the lack of standardization of units in the reported data. Future studies should prioritize research on emergent contaminants, evaluate effects on native species and the use of current available methods such as the OMICs. Additionally, there is a primary focus on organisms related to aquatic environments, and those inhabiting terrestrial environments are scarce or nonexistent. Finally, we highlight a lack of funding at a national level in the reviewed topic that may influence the observed low scientific productivity in several countries, which is often negatively associated with their percentage of protected areas.

Aryl hydrocarbon receptor agonist diuron and its metabolites cause reproductive disorders in male marine medaka (Oryzias melastigma)

Diuron, a widely used phenylurea herbicide, has been frequently detected in marine organism and seawater all over the world. But the understanding of potential damage of diuron on reproduction in marine fish is currently not enough. Herein, marine medaka (Oryzias melastigma) were continuously exposed to 0, 5, 50, 500, and 5000 ng/L diuron from embryo (0 dpf) to adult (180 dpf) stage. The results suggested that diuron had an adverse influence on male reproduction for marine medaka, including decreased gonado somatic index, histological changes of testes, decreased mobility of sperm, and reduced fecundity through disrupting the balance of sex hormone and genes expression related to hypothalamus-pituitary-gonadal-liver (HPGL) axis. The reduced fecundity was reflected in abnormal sexual behaviors, further inhibited growth and development of F1 embryo and larvae. Moreover, the proportion of diuron metabolites (DCPMU and DCPU) was increased in fish, but the proportion of diuron was decreased with the increasing of exposure concentration. Diuron, DCPMU, and DCPU was identified as aryl hydrocarbon receptor agonist (AhR) agonist using in silico and in vivo models. DCPMU and DCPU induced the gene expression of AhR signaling and metabolizing enzymes (such as cyp1a1) in the livers. A great deal of major metabolites affected various organs related to HPGL axis of male marine medaka and led to serious reproductive disorders. Consequently, it reveals that long-term exposure to environmentally relevant concentrations of diuron and even AhR agonist pesticides pose a potential ecological risk for marine fish.

Atlantic cod (Gadus morhua) embryos are highly sensitive to short-term 3,4-dichloroaniline exposure

3,4-dichloroaniline (3,4-DCA) is one of the most widely produced anilines world-wide, used in plastic packaging, fabrics, pharmaceuticals, pesticides, dyes and paints as well as being a degradation product of several pesticides. 3,4-DCA has been detected in freshwater, brackish and marine environments. Although freshwater toxicity thresholds exist, very little toxicological information is available on marine and cold-water species. In this study, we exposed Atlantic cod (Gadus morhua) embryos (3-7 days post fertilization) to 3,4-DCA concentrations ranging from 8-747 μg/L for 4 days followed by a recovery period in clean sea water until 14 days post fertilization (dpf). The cod embryos were significantly more sensitive to acute 3,4-DCA exposure compared to other species tested and reported in the literature. At the highest concentration (747 μg/L), no embryos survived until hatch, and even at the lowest concentration (8 μg/L), a small, but significant increase in mortality was observed at 14 dpf. Delayed and concentration-dependent effects on surviving yolk-sac larvae, manifested as cardiac, developmental and morphometric alterations, more than a week after exposure suggest potential long-term effects of transient embryonic exposure to low concentrations of 3,4-DCA.

Protective effect of the Spirulina platensis against toxicity induced by Diuron exposure in Mytilus galloprovincialis

Diuron herbicide is widely used for weeds control in many kinds of cultivations. It reaches the waterbodies through various fate routes and can adversely threaten non-target organism. The current study was carried out to evaluate the antioxidant activity of Spirulina as feed additive against the toxicity of Diuron concentrations (40 and 80 µg/L) on the edible mollusk Mytilus galloprovincialis during seven days of exposure. Oxidative stress biomarkers were applied on mussel gills and digestive gland, investigating changes in enzymes activities such as catalase (CAT), Glutathione-S-transferase (GST) and Acetylcholinesterase (AChE) and the Malondialdehyde level (MDA). The obtained results show that diuron altered oxidative stress biomarkers in both organs, gills and digestive gland. Performed principle component analysis (PCA) highlighted relationship between biomarkers involved in functional response. Spirulina platensis supplemented diet (1 mg/L), completely ameliorated diuron-induced oxidative stress in mussel tissues. Thus, Spirulina seems to be a promising microalgae and eco-friendly tool helping the health recovery of aquatic animals subjected to environmental stressors.

Chronic exposure to environmentally realistic levels of diuron impacts the behaviour of adult marine medaka (Oryzias melastigma)

Diuron, a commonly used herbicide and antifouling biocide, has been frequently detected in seawater. The effects of diuron on fish behaviour are currently poorly understood. Herein, the marine medaka (Oryzias melastigma) was continuously exposed to environmentally realistic levels of diuron from the fertilised egg stage to the adult stage. Behavioural evaluation of adult marine medaka indicated that exposure to diuron increased anxiety in the light-dark test and increased predator avoidance. In addition, diuron exposure significantly reduced aggression, social interaction, shoaling, and learning and memory ability. However, only negligible variations in foraging behaviour and in behaviour in the novel tank test were observed. Marine medaka chronically exposed to diuron also showed decreased levels of dopamine in the brain, and changes were observed in the transcription of genes related to dopamine synthesis, degradation and receptors. Exposure to 5000 ng/L diuron caused significant downregulation of the expression of the genes of tyrosine hydroxylase and monoamine oxidase and significantly upregulated the expression of the genes of the D5 dopaminergic receptor. The relative expression of the D4 dopaminergic receptor was significantly upregulated in the 50, 500 and 5000 ng/L diuron-treated groups. These findings highlight the significant neurotoxic effects of diuron and the extent to which this may involve the dopaminergic system of the brain. More broadly, this study reveals the ecological risk associated with environmentally realistic levels of diuron in marine animals.

Effects of 3,4-dichloroaniline (3,4-DCA) and 4,4'-methylenedianiline (4,4'-MDA) on sex hormone regulation and reproduction of adult zebrafish (Danio rerio)

3,4-dichloroaniline (3,4-DCA) and 4,4'-methylenedianiline (4,4'-MDA) have been widely used in manufacture of many industrial and consumer products, and hence often detected in aquatic environment. Reproductive toxicity of aniline and its derivatives in aquatic organisms has been suggested, however, knowledge on the endocrine disruption potentials and toxicological consequences of both anilines are not well understood, especially in fish. In this study, we aimed to understand the effects of 3,4-DCA and 4,4'-MDA on sex hormone regulation and reproduction of adult zebrafish (Danio rerio). Following 21 d exposure, significant decreases of the reproduction were observed at 0.38 mg/L 3,4-DCA, and 4.6 mg/L 4,4'-MDA. Moreover, plasma concentrations of testosterone (T) and 17β-estradiol (E2) level were significantly decreased in both male and female fish following the exposure. The sex hormone changes could be explained by the regulatory changes of the genes along the hypothalamic-pituitary-gonadal (HPG) axis, including significant down-regulation of steroidogenic acute regulatory protein (star) and cytochrome P450 family 19 subfamily A (cyp19a) genes in the gonad. Moreover, inhibition of gonadotropin hormone signaling and prostaglandin-endoperoxide synthase 2 (ptgs2) gene expression were observed, suggesting potential disruption of oocyte maturation and ovulation by the exposure. Our observations indicate that 3,4-DCA and 4,4'-MDA can impair reproduction of zebrafish potentially through disruption of steroid hormone synthesis and ovulation.

Reproductive Toxicity of 3,4-dichloroaniline (3,4-DCA) on Javanese Medaka (Oryziasjavanicus, Bleeker 1854)

Compound 3,4-dichloroaniline (3,4-DCA) is a metabolite of several urea herbicides and intermediate chemical of several industrial products. Moreover, 3,4-DCA has been frequently detected in aquatic ecosystems around the world. This aniline is more toxic than the parent chemicals, and it affects non-target organisms. This study evaluated a 21-day reproductive response of an emerging aquatic vertebrate model, Javanese medaka (Oryzias javanicus), exposed to 3,4-DCA. Fecundity and gonads histopathology were observed. The spawning rate and fertilisation reduced significantly in the highest exposed-group (250 µg/L). Gonadosomatic index (GSI) was significantly low in females exposed to 250 µg/L. No substantial structural alteration of male gonads. However, oocyte development and ovarian cell structure were disrupted in 250 µg/L exposed females. The gonadal developmental was not affected in the males; however, a significant reduction in the developmental of female gonads was observed at 250 µg/L. These results show that 3,4-DCA interfere with the reproduction of Javanese medaka through fecundity and alteration of gonadal tissues.

Embryonic toxicity of 3,4-dichloroaniline (3,4-DCA) on Javanese medaka (Oryzias javanicus Bleeker, 1854)

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The 96 h LC₅₀ of 3,4-dichloroaniline in Javanese medaka embryo is 32.87 mg.L⁻¹.

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3,4-DCA lowers heart rate of developing Javanese medaka embryos.

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The sublethal concentration of 3,4-DCA delays hatching in Javanese medaka embryo.

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The LOEC for deformities in embryos of Javanese medaka was 0.5 mg.L⁻¹.

Early-life exposure to toxic chemicals causes irreversible morphological and physiological abnormalities that may last for a lifetime. The present study aimed to determine the toxicity effect of 3,4-Dichloroaniline (3,4-DCA) on Javanese medaka (Oryzias javanicus) embryos. Healthy embryos were exposed to various 3,4-DCA concentrations for acute toxicity (5, 10, 25, 50, and 100 mg.L⁻¹) and sublethal toxicity (0.10, 0.50, 1.25, 2.50, and 5.00 mg.L⁻¹) for 96 h and 20 days respectively. Acute toxicity test revealed that the median lethal concentration (96h-LC₅₀) was 32.87 mg.L⁻¹ (95 % CI = 27.90–38.74, R² = 0.95). Sublethal exposure revealed that 1.25 mg.L^-1 at 3 days post-exposure (3 dpe) has a significant lower heartrate (120 ± 12.3 beats/min., p < 0.01), while at 7 dpe those exposed to 5 mg.L⁻¹ (141.8 ± 8.3 beats/min) had significantly (p < 0.01) lower heart rate compared to other treatments. Likewise, at 13 dpe, 5.00 mg.L⁻¹ (110.4 ± 17.3 beats/min) and 2.5 mg.L^-1 (130.4 ± 8.3 beats/min) were significantly lower (p < 0.001) compared to control. None of the embryos in 5.00 mg.L⁻¹ and 2.50 mg.L^-1 treatment groups survived at the end of the experiment. The results indicated a concentration-dependent response. The lowest observed effect concentration (LOEC) that exerted developmental deformities was 0.5 mg.L⁻¹. Javanese medaka embryo have low sensitivity to acute toxicity of 3,4-DCA, but developmental abnormalities at sublethal concentrations were observed.

Environmental estrogens and progestins disturb testis and brood pouch development with modifying transcriptomes in male-pregnancy lined seahorse Hippocampus erectus

Exposure to environmental estrogens and progestins has contributed to adverse effects on the reproduction of many aquatic wildlife species. However, few reports have paid attention to fish species with specialized reproductive strategies, such as male-pregnancy seahorses. In this study, the potential effects on the behavior, gonad and brood pouch development, and transcriptomic profiles of lined seahorse Hippocampus erectus exposed to environmentally relevant concentrations of 17α-ethynyl estradiol (EE2, 5 ng/L, 50 ng/L, 10 ng/L, 100 ng/L) or progesterone (P4) for 60 days were examined. Both EE2 and P4 significantly inhibited male brood pouch development by disrupting the extracellular matrix and basement membrane pathways. In addition, both EE2 and P4 impaired the expression of genes associated with spermatogenesis in the testis, and even caused male feminization. We suggest that seahorses be regarded as a sensitive indicator for evaluating the potential effects of endocrine disrupting chemical (EDC) pollution on aquatic biotic communities.

Herbicide Diuron as Endocrine Disrupting Chemicals (EDCs) through Histopathalogical Analysis in Gonads of Javanese Medaka (Oryzias javanicus, Bleeker 1854)

The expeditious augmentation of the agriculture industry is leaving a significant negative impact on aquatic ecosystems. However, the awareness of the impacts of herbicide Diuron toxicities on the non-targeted aquatic organism, especially fish is still lacking. Javanese medaka, a new model fish species were exposed under sublethal levels and the long-term effects on gonads were investigated via histological studies. A total of 210 sexually mature fish were exposed to Diuron at seven different concentrations; control, solvent control, 1, 50, 100, 500, and 1000 μg/L for 21 days. In this study, Diuron caused histopathological alterations in gonads (ovary and testis) of Javanese medaka (Oryzias javanicus) by decreasing in gonadal staging and maturity of germ cells in oogenesis and spermatogenesis of female and male Javanese medaka. The results obtained in this study had proven our hypothesis that long-term exposure of herbicide Diuron can cause alterations in the gonadal histology of the adults of Javanese medaka.

Endocrine disruption by several aniline derivatives and related mechanisms in a human adrenal H295R cell line and adult male zebrafish

Aniline and aniline derivatives have been widely used in the production of pesticides, pharmaceuticals, cosmetic, dyes, rubber, and adhesives products. These chemicals can easily be released into the environment through industrial and municipal discharges or as degradation byproducts. Several studies have suggested that aniline and some of its derivatives could cause reproductive toxicity in aquatic organisms. However, knowledge on the endocrine disruption potentials of these chemicals is limited only to aniline and associated mechanisms are rarely investigated. The objective of this study was to investigate the potential of major aniline derivatives, i.e., 3,4-dichloroaniline (3,4-DCA), 1-naphthylamine (1-NPA), and 4,4'-methylenedianiline (4,4'-MDA), to disrupt sex steroid production and other biological processes. For this purpose, the human adrenal H295R cell line and adult male zebrafish (Danio rerio) were used. In the H295R cell line, all tested aniline derivatives decreased testosterone (T) levels. Regulatory changes of several steroidogenic genes, i.e., down-regulation of StAR or CYP17 genes, and up-regulation of CYP19A, observed in the H295R cells could explain the sex hormone disruption. In male zebrafish, generally similar directions of changes, i.e., decreases in T levels and increased E2/T ratios, were observed. Again, down-regulation of key steroidogenic genes such as cyp17 or 3β-hsd, but slight up-regulation of cyp19a gene observed in the fish could explain the sex hormone changes. The results of our study demonstrate that all tested aniline derivatives could influence steroidogenesis and disrupt sex hormone balance toward reduced androgenicity. Consequences of anti-androgenicity following long-term exposure warrant further investigation.

Endocrine-disrupting chemicals in aquatic environment: what are the risks for fish gametes?

Over the past 25 years, extensive research in vertebrate species has identified several genomic pathways altered by exposures to anthropogenic chemicals with hormone-like activity mediated by their interaction with nuclear receptors. In addition, many pollutants have been shown to interfere with non-genomic (non-classical) pathways, but this mechanism of endocrine disruption is still poorly understood. Recently, the number of publications describing the effects of Endocrine disrupting chemicals (EDCs) on fish reproduction, focusing on the deregulation of the hypothalamus-pituitary-gonadal axis as well as on gamete quality, significantly increased. Depending on their ability to mimic endogenous hormones, the may differently affect male or female reproductive physiology. Inhibition of gametogenesis, development of intersex gonads, alteration of the gonadosomatic index, and decreased fertility rate have been largely documented. In males, alterations of sperm density, motility, and fertility have been observed in several wild species. Similar detrimental effects were described in females, including negative outcomes on oocyte growth and maturation plus the occurrence of apoptotic/autophagic processes. These pathways may affect gamete viability considered as one of the major indicators of reproductive endocrine disruption. Pollutants act also at DNA level producing DNA mutations and changes in epigenetic pathways inducing specific mechanisms of toxicity and/or aberrant cellular responses that may affect subsequent generation(s) through the germline. In conclusion, this review summarizes the effects caused by EDC exposure on fish reproduction, focusing on gametogenesis, giving a general overview of the different aspects dealing with this issue, from morphological alteration, deregulation of steroidogenesis, hormonal synthesis, and occurrence of epigenetic process.

Visible-light photoelectrodegradation of diuron on WO3 nanostructures

The degradation of pesticide diuron has been explored by photoelectrocatalysis (PEC) under visible light illumination using two different WO₃ nanostructures, obtained by anodization of tungsten. The highest degradation efficiency (73%) was obtained for WO₃ nanosheets synthesized in the presence of small amounts of hydrogen peroxide (0.05 M). For that nanostructure, the kinetic coefficient for diuron degradation was 133% higher than that for the other nanostructure (anodized in the presence of fluoride anions). These results have been explained by taking into account the different architecture and dimensions of the two WO₃ nanostructures under study.

Polar pesticide contamination of an urban and peri-urban tropical watershed affected by agricultural activities (Yaoundé, Center Region, Cameroon)

Urban agriculture is crucial to local populations, but the risk of it contaminating water has rarely been documented. The aim of this study was to assess pesticide contamination of surface waters from the Méfou watershed (Yaoundé, Cameroon) by 32 selected herbicides, fungicides, and insecticides (mainly polar) according to their local application, using both grab sampling and polar organic compounds integrative samplers (POCIS). Three sampling campaigns were conducted in the March/April and October/November 2015 and June/July 2016 rainy seasons in urban and peri-urban areas. The majority of the targeted compounds were detected. The quantification frequencies of eight pesticides were more than 20% with both POCIS and grab sampling, and that of diuron and atrazine reached 100%. Spatial differences in contamination were evidenced with higher contamination in urban than peri-urban rivers. In particular, diuron was identified as an urban contaminant of concern because its concentrations frequently exceeded the European water quality guideline of 0.200 μg/L in freshwater and may thus represent an ecological risk due to a risk quotient > 1 for algae observed in 94% of grab samples. This study raises concerns about the impacts of urban agriculture on the quality of water resources and to a larger extent on the health of the inhabitants of cities in developing countries. Graphical abstract ᅟ.

Impacts of Salinity and Temperature on the Thyroidogenic Effects of the Biocide Diuron in Menidia beryllina

Diuron is a herbicide used in agricultural and urban settings and also as an antifouling agent. Recent studies have indicated sublethal responses of diuron in the endocrine system of fish and amphibians. Given the potential of climate change to also alter fish endocrinology, the combination of environmental stressors with diuron may contribute to its sublethal toxicity. In this study, the effects of temperature and salinity on thyroid targets of diuron were assessed in juveniles of the estuarine fish Menidia beryllina under different conditions of salinity (10 and 20‰) and temperature (10 and 20 °C). Environmentally relevant concentrations of diuron affected the growth, and the higher temperature reduced the condition factor of animals. Increased levels of T3 were observed in fish from all treatments, and at 10 °C, T4 levels were augmented at 10‰ but reduced at 20‰. Increased gene expression of deiodinases at 20‰ in both temperatures suggests the influence of salinity on the regulation of hormone imbalance via deiodination pathway activation. Decreased transcripts of thyroid and growth hormone receptors were also observed following diuron treatment. These results indicate that changes in environmental stressors may have significant impacts on the ecological risk of diuron in estuarine fish.

Isolated and mixed effects of diuron and its metabolites on biotransformation enzymes and oxidative stress response of Nile tilapia (Oreochromis niloticus)

Diuron is one of the most used herbicide in the world, and its field application has been particularly increased in Brazil due to the expansion of sugarcane crops. Diuron has often been detected in freshwater ecosystems and it can be biodegraded into three main metabolites in the environment, the 3,4-dichloroaniline (DCA), 3,4-dichlorophenylurea (DCPU) and 3,4-dichlorophenyl-N-methylurea (DCPMU). Negative effects under aquatic biota are still not well established for diuron, especially when considering its presence in mixture with its different metabolites. In this study, we evaluated the effects of diuron alone or in combination with its metabolites, DCPMU, DCPU and 3,4-DCA on biochemical stress responses and biotransformation activity of the fish Oreochromis niloticus. Results showed that diuron and its metabolites caused significant but dispersed alterations in oxidative stress markers and biotransformation enzymes, except for ethoxyresorufin-O-deethylase (EROD) activity, that presented a dose-dependent increase after exposure to either diuron or its metabolites. Glutathione S-transferase (GST) activity was significant lower in gills after exposure to diuron metabolites, but not diuron. Diuron, DCPMU and DCA also decreased the multixenobiotic resistance (MXR) activity. Lipid peroxidation levels were increased in gill after exposure to all compounds, indicating that the original compound and diuron metabolites can induce oxidative stress in fish. The integration of all biochemical responses by the Integrated Biomarker Response (IBR) model indicated that all compounds caused significant alterations in O. niloticus, but DCPMU caused the higher alterations in both liver and gill. Our findings imply that diuron and its metabolites may impair the physiological response related to biotransformation and antioxidant activity in fish at field concentrations. Such alterations could interfere with the ability of aquatic animals to adapt to environments contaminated by agriculture.

Diuron metabolites act as endocrine disruptors and alter aggressive behavior in Nile tilapia (Oreochromis niloticus)

Diuron and its biodegradation metabolites were recently reported to cause alterations in plasma steroid hormone concentrations with subsequent impacts on reproductive development in fish. Since steroid hormone biosynthesis is regulated through neurotransmission of the central nervous system (CNS), studies were conducted to determine whether neurotransmitters that control hormone biosynthesis could be affected after diuron and diuron metabolites treatment. As the same neurotransmitters and steroid hormones regulate behavioral outcomes, aggression was also evaluated in male Nile tilapia (Oreochromis niloticus). Male tilapias were exposed for 10 days to waterborne diuron and the metabolites 3,4-dichloroaniline (DCA), 3,4-dichlorophenyl-N-methylurea (DCPMU), at nominal concentrations of 100 ng L^-1. In contrast to Diuron, DCA and DCPMU significantly diminished plasma testosterone concentrations (39.4% and 36.8%, respectively) and reduced dopamine levels in the brain (47.1% and 44.2%, respectively). In addition, concentrations of the stress steroid, cortisol were increased after DCA (71.0%) and DCPMU (57.8-%) exposure. A significant decrease in aggressive behavior was also observed in animals treated with the metabolites DCA (50.9%) and DCPMU (68.8%). These results indicate that biotransformation of diuron to active metabolites alter signaling pathways of the CNS which may impact androgen and the stress response as well as behavior necessary for social dominance, growth, and reproduction.

Estrogenic and anti-androgenic effects of the herbicide tebuthiuron in male Nile tilapia (Oreochromis niloticus)

Tebuthiuron is a phenylurea herbicide widely used in agriculture that can reach the aquatic environments, possibly posing negative effects to the aquatic biota. Phenylurea herbicides, such as diuron, are known to cause estrogenic and anti-androgenic effects in fish, but no such effects were yet reported for tebuthiuron exposure. Thus, the aim of this study was to evaluate if tebuthiuron, at environmentally relevant concentrations (100 and 200ng/L) and after 25days of exposure have estrogenic and/or anti-androgenic effects on male of Nile tilapia (Oreochromis niloticus), through the evaluation of plasmatic testosterone (T) and estradiol (E₂) levels, brain aromatase (CYP19) levels (western-blot), and by evaluating the histology of the testicles. When compared to the control group, plasmatic T levels decreased about 76% in the animals exposed to 200ng/L of tebuthiuron, while E₂ levels increased about 94%, which could be related to a significant increase (77%) in CYP19A1 levels, an enzyme that catalyzes the conversion of androgens into estrogens. Histological analyses of the testicles also demonstrated that tebuthiuron at both tested concentrations caused a decrease in the diameter of the seminiferous tubules and in the diameter of the lumen. Therefore, the gonadosomatic index (GSI) was reduced by 36% % in the animals exposed 200ng/L to tebuthiuron. Indeed, the relative frequency of spermatocytes and spermatids increased respectively 73% (200ng/L) and 61% (100ng/L) in the tebuthiuron exposed animals, possibly due to the impairment of sperm release into the lumen, that was decreased 93% (200ng/L) in the treated animals compared to the control. These results confirm that tebuthiuron causes estrogenic and anti-androgenic effects in Nile tilapias at environmentally relevant concentrations.

Assessment of multiple hormone activities of a UV-filter (octocrylene) in zebrafish (Danio rerio)

In this study, zebrafish (Danio rerio) were exposed to a UV-filter-octocrylene (OCT) with elevated concentrations for 28 d. The total body accumulation of OCT in zebrafish was found to reach 2321.01 ("L" level), 31,234.80 ("M" level), and 70,593.38 ng g(-1) ("H" level) when the average OCT exposure concentration was controlled at 28.61, 505.62, and 1248.70 μg L(-1), respectively. Gross and histological observations as well as RT-qPCR analysis were conducted to determine the effects of OCT accumulation on zebrafish. After exposure, the gonad-somatic index and percentage of vitellogenic oocytes were found to increase significantly in the ovaries of female zebrafish at the H accumulation level. Significant up-regulation of esr1 and cyp19b were observed in the gonads, as well as vtg1 in the livers for both female and male zebrafish. At M and H accumulation levels, apparent down-regulation of ar was observed in the ovaries and testis of the female and male zebrafish, respectively. Although the extent of the effects on zebrafish differed at different accumulation levels, the induction of vtg1 and histological changes in the ovaries are indications of estrogenic activity and the inhibition of esr1 and ar showed antiestrogenic and antiandrogenic activity, respectively. Thus, as OCT could easily accumulate in aquatic life such as zebrafish, one of its most of concern hazards would be the disturbance of the histological development and its multiple hormonal activities.