Intersex occurrence in rainbow trout (Oncorhynchus mykiss) male fry chronically exposed to ethynylestradiol

Multiple biomarker responses in female Clarias gariepinus exposed to acetaminophen

Several authors have documented the presences of acetaminophen (APAP) in both surface and groundwater and have received attention from government agencies and basic authorities across the globe. The impacts of such pharmaceutical products on non-target organism like fish are underestimated as a result of selected investigation using few biomarkers. We evaluated the sub-chronic impacts of APAP in female catfish (Clarias gariepinus) using multiple biomarkers. The exposure of female catfish to APAP induced oxidative stress. Markers such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and total antioxidant capacity (TAC) were significantly higher in all exposed groups. Exposure of Clarias gariepinus to APAPA caused histological alterations in the gills (fusion and shortening of some filaments, hyperplasia of the epithelial gill cells, aneurism, congestion, and epithelial rupture of the gills), liver (apoptotic hyperplasia, sinusoidal congestion, and necrosis of the hepatocytes), and gonad (degenerated follicles and ovarian apoptosis). Furthermore, multivariate results indicated that there was a distinct response from the acetaminophen-exposed female catfish, with over 95% of the biomarkers significantly contributing to the discrimination between the acetaminophen-exposed female catfish and the control groups. Our research provides evidence supporting the use of a multiple biomarker approach to evaluate the impacts of drugs on the health status of exposed fish.

Standardized tissue sampling guidelines for histopathological and molecular analyses of rainbow trout (Oncorhynchus mykiss) in ecotoxicological studies

In ecotoxicology, evaluation of toxicities and no observed effect concentrations (NOEC) of test compounds in experimental fish is commonly based on molecular-, biochemical- and analytical chemistry analyses of organ/tissue samples and the assessment of (histo-) pathological lesions. Standardization of organ/tissue sampling locations, sample numbers, and sample processing contributes to warrant the reproducibility and inter- and intra-study comparability of analysis results. The present article provides the first comprehensive tissue sampling guidelines specifically adapted to rainbow trout (Oncorhynchus mykiss) as a frequently used fish species in ecotoxicological studies. A broad spectrum of ~40 different organs and tissues is covered. Appropriate sampling locations, sample sizes and sample numbers for subsequent routine histopathological evaluation (all organs/tissue) and for molecular analyses (~30 organs/tissues) are described in detail and illustrated with schematic drawings and representative macroscopic and histological images. These field-proven sampling guidelines were developed based on the pertinent literature and practical experience in ecotoxicological fish studies. They are intended to serve as a standard reference for any routine ecotoxicological study using rainbow trout as a test system. A broad application of the featured tissue sampling procedures will help to improve the reproducibility of analyses and to reduce inter- and intra-study variability induced by sampling bias and (normal) inter-sample morphological variation, and will therefore provide a robust basis for reliable characterization of toxicity and NOEC identification of diverse test substances and aquatic pollutants.

Does dietary exposure to 17α-ethinylestradiol alter biomarkers related with endocrine disruption and oxidative stress in the adult triploid of Danio rerio?

This study was conducted to investigate a comprehensive effect of 17α-ethinylestradiol (EE2) in zebrafish (Danio rerio) with the emphasis on endocrine disruption, oxidative stress and detoxification processes at different levels. Adult male triploid zebrafish were exposed to EE2 administered in feed at two concentrations - 10 and 1000 μg/kg for six weeks. The estrogenic potential of EE2 was evaluated using an analysis of vitellogenin, gene expression focused on reproductive disorders and gonad histological examination. The alterations in antioxidant and detoxification status were assessed using analyses of enzyme activities and changes in transcriptional levels of selected genes. The most significant changes were observed especially in fish exposed to a high concentration of EE2 (i.e., 1000 μg/kg). Such high concentration caused extensive mortality (25 %) mainly in the second half of the experiment followed by a highly significant decrease in the length and body weight. Similarly, highly significant induction of vitellogenin level and vtg1 mRNA expression (about 43,000-fold compared to the control) as well as a significant downregulation of gonad aromatase expression (cyp19a1a) and histological changes in testicular tissue were confirmed in this group. In the group exposed to environmentally relevant concentration of EE2 (i.e., 10 μg/kg), no significant differences in vitellogenin were observed, although all fish were positive in the detection of vitellogenin compared to control, where only 40 % of individuals were positive. In addition, the high concentration of EE2 resulted in significant alterations in most monitored antioxidant and detoxifying enzymes with the exception of catalase, followed by strongly significant upregulation in mRNA expression of gsr, gpx1a, cat and cyp1a genes. Furthermore, a significant decrease in the glutathione reductase activity was recorded in fish exposed to 10 μg EE2/kg. To our knowledge, this is the first study which reports the effects of subchronic per oral exposure to EE2 in adult triploid zebrafish.

Integrative study of the reproductive biology and growth of Acestrorhynchus pantaneiro Menezes, 1992 (Characiformes, Acestrorhynchidae)

We studied the reproductive strategy, sexual system and growth of dientudo paraguayo Acestrorhynchus pantaneiro. After 2 years of monitoring in shallow areas of a floodplain lake from the lower Paraná basin (Argentina), it was evidenced that water temperature modulated gonadal maturation, but it was the river water level the synchronising stimulus that triggered spawning. This species exhibited a single annual breeding period from October to January, with most spawning activity in November. According to the von Bertalanffy growth curve, fish would reach autumn to winter months with L_S of ~120 mm, already mature males. The first mature females were found at L_S of 210 mm, becoming sexually mature between the second and third breeding seasons. This is the first integrative study that includes the body-length frequency distribution and sex differential size at first maturity and growth, and reports the presence of intersex gonads questioning its sexual pattern from gonochoristic to sequential hermaphrodite species. The sexual pattern, the multiple spawning behaviour and a medium to high absolute fecundity support the opportunistic and invasive behavior observed in previous contributions for this characiform species.

A case study: temporal trends of environmental stressors and reproductive health of smallmouth bass (Micropterus dolomieu) from a site in the Potomac River Watershed, Maryland, USA

Decades of poor reproductive success and young-of-the-year survival, combined with adult mortality events, have led to a decline in the smallmouth bass (SMB; Micropterus dolomieu) population in sections of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stressors, this study was conducted at the confluence of Antietam Creek and the Potomac River from 2013 to 2019 to identify temporal changes associated with SMB reproductive health. Surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. Numerous agriculture-related contaminants or land use patterns were associated with gene transcript abundance in both male and female SMB. Positive associations between pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males were identified. In males, the prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts (vtg) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when spawning and early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of these economically important sportfishes.

Gonadal Development in Smallmouth Bass (Micropterus Dolomieu) Reared in the Absence and Presence of 17-α-Ethinylestradiol

Testicular oocytes in wild adult bass (Micropterus spp.) are considered a potential indication of exposure to estrogenic compounds in municipal, agricultural, or industrial wastewater. However, our ability to interpret links between testicular oocyte occurrence in wild fish species and environmental pollutants is limited by our understanding of normal and abnormal gonadal development. We previously reported low-to-moderate testicular oocyte prevalence (7%-38%) among adult male bass collected from Minnesota waters with no known sources of estrogenic compounds. In the present study, two experiments were conducted in which smallmouth bass (Micropterus dolomieu) fry were exposed to control water or 17-α-ethinylestradiol (EE2) during gonadal differentiation, then reared in clean water for an additional period. Histological samples were evaluated at several time points during the exposure and grow-out periods, and the sequence and timing of gonadal development in the presence of estrogen were compared with that of control fish. Testicular oocytes were not observed in any control or EE2-exposed fish. Among groups exposed to 1.2 or 5.1 ng/L EE2 in Experiment 1 or 3.0 ng/L EE2 in Experiment 2, ovaries were observed in 100% of fish up to 90 days after exposure ceased, and approximately half of those ovaries had abnormal characteristics, suggesting that they likely developed in sex-reversed males. Groups exposed to 0.1, 0.4, or 1.0 ng/L in Experiment 2 developed histologically normal ovaries and testes in proportions not significantly different from 1:1. These findings suggest that, while presumably able to cause sex reversal, juvenile exposure to EE2 may not be a unique cause of testicular oocytes in wild bass, although the long-term outcomes of exposure are unknown. Environ Toxicol Chem 2022;41:1416-1428. © 2022 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Reproductive health and endocrine disruption in smallmouth bass (Micropterus dolomieu) from the Lake Erie drainage, Pennsylvania, USA

Smallmouth bass Micropterus dolomieu were sampled from three sites within the Lake Erie drainage (Elk Creek, Twentymile Creek, and Misery Bay, an embayment in Presque Isle Bay). Plasma, tissues for histopathological analyses, and liver and testes preserved in RNALater® were sampled from 30 smallmouth bass (of both sexes) at each site. Liver and testes samples were analyzed for transcript abundance with Nanostring nCounter® technology. Evidence of estrogenic endocrine disruption was assessed by the presence and severity of intersex (testicular oocytes; TO) and concentrations of plasma vitellogenin in male fish. Abundance of 17 liver transcripts associated with reproductive function, endocrine activity, and contaminant detoxification pathways and 40 testes transcripts associated with male and female reproductive function, germ cell development, and steroid biosynthesis were also measured. Males with a high rate of TO (87-100%) and plasma vitellogenin were noted at all sites; however, TO severity was greatest at the site with the highest agricultural land cover. Numerous transcripts were differentially regulated among the sites and patterns of transcript abundance were used to better understand potential risk factors for estrogenic endocrine disruption. The results of this study suggest endocrine disruption is prevalent in this region and further research would benefit to identify the types of contaminants that may be associated with the observed biological effects.

Growth and gonadal development retardations after long-term exposure to estradiol in little yellow croaker, Larimichthys polyactis

Endocrine disrupting chemicals (EDCs) including 17β-estradiol (E2) are widely distributed in the aquatic environment and are known to negatively affect the reproductive system of many animals, including fish. EDCs leading to feminization, altered sex ratio and reduced fecundity, it is possibly posing potential risks to the ecosystems. To investigate the potentially toxic effects of E2 exposure on little yellow croaker (Larimichthys polyactis, L. poliactis) who have a unique gonadal development pattern that males undergo a hermaphroditic stage. An experiment was set up where L. poliactis were maintained in tanks and exposed to E2 concentrations of 10 μg/L or no E2 exposure (the ethanol and control groups) from 30 to 90 days post-hatching (dph). After exposure, the E2 withdrawal and continual cultured to 150 and 365 dph. The morphological and histological analyses were used to compare the changes in the fish body and gonad under E2 exposure. The results showed that E2 exposure caused three major phenotypes at 30 and 60 days after treatment (dat), including ovary, ovotestis and gonadal development retardation compared with the control groups. The average ratio of these three phenotypes is 60.6%, 11.97% and 27.43%, respectively. The body length and weight of E2 exposure groups were repressed during the E2 exposure period, while it can recover after E2 withdrawal. However, the gonadal development (Gonadosomatic Index) of E2 exposure groups testis were retarded at 60 dat and doesn't recover until 365 dph. The sex determination/differentiation-related genes erα, erβI, erβII, fshβ and cyp11b2 were significantly decreased in E2-exposure male fish. This research highlights the E2 leads to feminization, disrupts testis maturation and spermatogenesis, this effect persisted into the stage of sexual maturity. Collectively, our findings provide insights into the molecular mechanisms underlying E2 disturbance of a marine economic fish reproduction.

Assessing the Toxicity of 17α-Ethinylestradiol in Rainbow Trout Using a 4-Day Transcriptomics Benchmark Dose (BMD) Embryo Assay

There is an urgent demand for more efficient and ethical approaches in ecological risk assessment. Using 17α-ethinylestradiol (EE2) as a model compound, this study established an embryo benchmark dose (BMD) assay for rainbow trout (RBT; Oncorhynchus mykiss) to derive transcriptomic points-of-departure (tPODs) as an alternative to live-animal tests. Embryos were exposed to graded concentrations of EE2 (measured: 0, 1.13, 1.57, 6.22, 16.3, 55.1, and 169 ng/L) from hatch to 4 and up to 60 days post-hatch (dph) to assess molecular and apical responses, respectively. Whole proteome analyses of alevins did not show clear estrogenic effects. In contrast, transcriptomics revealed responses that were in agreement with apical effects, including excessive accumulation of intravascular and hepatic proteinaceous fluid and significant increases in mortality at 55.1 and 169 ng/L EE2 at later time points. Transcriptomic BMD analysis estimated the median of the 20th lowest geneBMD to be 0.18 ng/L, the most sensitive tPOD. Other estimates (0.78, 3.64, and 1.63 ng/L for the 10th percentile geneBMD, first peak geneBMD distribution, and median geneBMD of the most sensitive over-represented pathway, respectively) were within the same order of magnitude as empirically derived apical PODs for EE2 in the literature. This 4-day alternative RBT embryonic assay was effective in deriving tPODs that are protective of chronic effects of EE2.

DNA methylation and expression of estrogen receptor alpha in fathead minnows exposed to 17α-ethynylestradiol

The gene expression response thought to underlie the negative apical effects resulting from estrogen exposure have been thoroughly described in fish. Although epigenetics are believed to play a critical role translating environmental exposures into the development of adverse apical effects, they remain poorly characterized in fish species. This study investigated alterations of DNA methylation of estrogen receptor alpha (esr1) in brain and liver tissues from 8 to 10 month old male fathead minnows (Pimephales promelas) after a 2d exposure to either 2.5 ng/L or 10 ng/L 17α-ethynylestradiol (EE2). Changes in the patterns of methylation were evaluated using targeted deep sequencing of bisulfite treated DNA in the 5' region of esr1. Methylation and gene expression were assessed at 2d of exposure and after a 7 and 14d depuration period. After 2d EE2 exposure, males exhibited significant demethylation in the 5' upstream region of esr1 in liver tissue, which was inversely correlated to gene expression. This methylation pattern reflected what was seen in females. No gene body methylation (GBM) was observed for liver of exposed males. Differential methylation was observed for a single upstream CpG site in the liver after the 14d depuration. A less pronounced methylation response was observed in the upstream region in brain tissue, however, several CpGs were necessarily excluded from the analysis. In contrast to the liver, a significant GBM response was observed across the entire gene body, which was sustained until at least 7d post-exposure. No differential expression was observed in the brain, limiting functional interpretation of methylation changes. The identification of EE2-dependent changes in methylation levels strongly suggests the importance of epigenetic mechanisms as a mediator of the organismal response to environmental exposures and the need for further characterization of the epigenome. Further, differential methylation following depuration indicates estrogenic effects persist well after the active exposure, which has implications for the risk posed by repeated exposures..

Health Effects and Life Stage Sensitivities in Zebrafish Exposed to an Estrogenic Wastewater Treatment Works Effluent

A wide range of health effects in fish have been reported for exposure to wastewater treatment work (WwTW) effluents including feminized responses in males. Most of these exposure studies, however, have assessed acute health effects and chronic exposure effects are less well established. Using an Estrogen Responsive Element-Green Fluorescent Protein (ERE-GFP)-Casper transgenic zebrafish, we investigated chronic health effects and life stage sensitivities for exposure to an estrogenic WwTW effluent and the synthetic estrogen 17α-ethinylestradiol (EE2). Exposure to the WwTW effluent (at full strength;100%) and to 10 ng/L (nominal) EE2 delayed testis maturation in male fish but accelerated ovary development in females. Exposure to 50% and 100% effluent, and to 10 ng/L EE2, also resulted in skewed sex ratios in favor of females. Differing patterns of green fluorescent protein (GFP) expression, in terms of target tissues and developmental life stages occurred in the ERE-GFP- zebrafish chronically exposed to 100% effluent and reflected the estrogenic content of the effluent. gfp and vitellogenin (vtg) mRNA induction were positively correlated with measured levels of steroidal estrogens in the effluent throughout the study. Our findings illustrate the importance of a fish's developmental stage for estrogen exposure effects and demonstrate the utility of the ERE-GFP zebrafish for integrative health analysis for exposure to estrogenic chemical mixtures.

Pharmaceuticals as emerging contaminants in the aquatic environment of Latin America: a review

Pharmaceutical active compounds (PhACs) are environmentally ubiquitous around the world, and the countries of Latin America (LATAM) are not the exception; however there is still little knowledge of the magnitude and conditions of their occurrence in LATAM and of the environmental consequences of their presence. The present work reviews 79 documents published from 2007 to 2019 on the occurrence, concentrations, and sources of PhACs and hormones in surface water (SW), wastewater (WW), and treated wastewater (TWW) in LATAM and on the circumstances of their release to the environment. Research efforts are reported in only ten countries and confirm the presence of 159 PhACs, mainly analgesics and anti-inflammatories, although extraordinarily high concentrations of carbamazepine (830 μg/L) and ethinylestradiol (6.8 μg/L) were found in Ecuador and Brazil, respectively. The analysis of maximum concentrations and the ecotoxicological risk assessment corroborate that (1) these values exceed the environmental concentrations found in other parts of the world, (2) the environmental risk posed by these concentrations is remarkably high, and (3) there is no statistically significant difference between the maximum concentrations found in WW and those found in TWW. The main source of PhACs in LATAM's aquatic environment is WW; hence, these countries should direct substantial efforts to develop efficient and cost-effective treatment technologies and plan and apply WW management strategies and regulations. This analysis presents the current states of occurrence, concentrations, and sources of PhACs in the aquatic environment of LATAM and outlines the magnitude of the environmental problem in that part of the world.

Impact of Endocrine Disruptors on Vitellogenin Concentrations in Wild Brown Trout (Salmo trutta trutta)

The adverse effects of endocrine disruptors (EDs) on aquatic wildlife and human health represent a current issue of high public concern. Substantial knowledge of the level of estrogenic EDs in fish has accumulated from field surveys. For this purpose, a survey of wild brown trout (Salmo trutta trutta) was carried out to assess the incidence of EDs in the feral fish population living in the Liri river (Abruzzi, Italy). The results of this study show that this aquatic environment possesses an estrogenic potency that triggered the increase of vitellogenin levels in both female and male trouts. Fish exposed to different pesticides and urban waste in downstream river showed higher vitellogenin levels in comparison to the headwater site. Furthermore, some trouts coming from the downstream reported the presence of several pesticides and fungicides, some of these banned several years ago.

Twenty years of transcriptomics, 17alpha-ethinylestradiol, and fish

In aquatic toxicology, perhaps no pharmaceutical has been investigated more intensely than 17alpha-ethinylestradiol (EE2), the active ingredient of the birth control pill. At the turn of the century, the fields of comparative endocrinology and endocrine disruption research witnessed the emergence of omics technologies, which were rapidly adapted to characterize potential hazards associated with exposures to environmental estrogens, such as EE2. Since then, significant advances have been made by the scientific community, and as a result, much has been learned about estrogen receptor signaling in fish from environmental xenoestrogens. Vitellogenin, the egg yolk precursor protein, was identified as a major estrogen-responsive gene, establishing itself as the premier biomarker for estrogenic exposures. Omics studies have identified a plethora of estrogen responsive genes, contributing to a wealth of knowledge on estrogen-mediated regulatory networks in teleosts. There have been ~40 studies that report on transcriptome responses to EE2 in a variety of fish species (e.g., zebrafish, fathead minnows, rainbow trout, pipefish, mummichog, stickleback, cod, and others). Data on the liver and testis transcriptomes dominate in the literature and have been the subject of many EE2 studies, yet there remain knowledge gaps for other tissues, such as the spleen, kidney, and pituitary. Inter-laboratory genomics studies have revealed transcriptional networks altered by EE2 treatment in the liver; networks related to amino acid activation and protein folding are increased by EE2 while those related to xenobiotic metabolism, immune system, circulation, and triglyceride storage are suppressed. EE2-responsive networks in other tissues are not as comprehensively defined which is a knowledge gap as regulated networks are expected to be tissue-specific. On the horizon, omics studies for estrogen-mediated effects in fish include: (1) Establishing conceptual frameworks for incorporating estrogen-responsive networks into environmental monitoring programs; (2) Leveraging in vitro and computational toxicology approaches to identify chemicals associated with estrogen receptor-mediated effects in fish (e.g., male vitellogenin production); (3) Discovering new tissue-specific estrogen receptor signaling pathways in fish; and (4) Developing quantitative adverse outcome pathway predictive models for estrogen signaling. As we look ahead, research into EE2 over the past several decades can serve as a template for the array of hormones and endocrine active substances yet to be fully characterized or discovered.

Bioavailability of estrogenic compounds from sediment in the context of flood events evaluated by passive sampling

Studies worldwide have demonstrated through in vitro bioassays and chemical analysis that endocrine-disrupting chemicals (EDCs) can accumulate in river sediments. However, remobilization of sediment-bound EDCs due to bioturbation or re-suspension during flood events remains poorly understood. The aim of this study was to evaluate the bioavailability of EDCs, more specifically estrogenic compounds (EC), from sediment under turbulent conditions using a passive sampling approach. Sediment was sampled along the Luppe River, Germany, previously described as a "hotspot" for ECs. The concentration of target ECs and estrogenic activity were investigated using chemical analysis (LC MS/MS) in addition to a novel screening tool (planar Yeast Estrogen Screen; p-YES) that utilizes high performance thin-layer chromatography plates in combination with an in vitro bioassay (YES). Estrone (50%, E1) and nonylphenol (35%, NP) accounted for the majority of estrogenic activity reported of up to 20 ± 2.4 μg E2 equivalents per kg dry weight in the Luppe sediments. Two types of passive samplers (polar organic chemical integrative sampler (POCIS) and Chemcatcher) were used to investigate the bioavailability of ECs from suspended sediment under laboratory conditions. NP, E1, E2 and ethynylestradiol (EE2) were remobilized from Luppe sediment when subjected to turbulent conditions, such as in a flood event, and were readily bioavailable at ecotoxicologically relevant concentrations (NP 18 μg/L, E1 14 ng/L, E2 0.2 ng/L, EE2 0.5 ng/L).

Gonad pathology and intersex severity in pelagic (Tilapia zilli) and benthic (Neochanna diversus and Clarias gariepinus) species from a pesticide-impacted agrarian catchment, south-south Nigeria

Pesticides are distributed to different degrees in surface water and sediment, thus, risks of toxicity and adverse impacts to physiology of resident species could be determined by their microhabitat (sub-habitat) associations, either water column or sediment. River Owan receives pesticide input from diffuse sources from adjacent farmlands. Surface water, sediment and fish samples [(Pelagic: Tilapia zilli (n = 92) and benthic: Neochanna diversus (n = 59), Clarias gariepinus (n = 68) were collected within the catchment area across seasons for 18-months (August 2016-January 2018) and measured for pesticide levels. Testicular and Ovarian tissue samples across the three species were also examined for pathological alterations. Individual pesticide concentrations in surface water and sediment exceeded international allowable limits, while concentration of pesticide residues in tissues of benthic species was higher compared to pelagic fish. Histopathological assessment revealed a higher incidence of ovarian disruption including atretic follicles, intersex and disorganization of ovarian structure in benthic (bottom-dwelling) fish (C. gariepinus and N. diversus) compared to pelagic (water-column) fish (T. zilli). Males benthic fish species also recorded more severe anomalies, compared to pelagic fish. The damages and anomalies observed in ovarian and testicular tissue indicate chronic responses to pollutant exposure, and implicates the elevation of pesticide concentrations in surface water and sediment above permissible limits. The higher incidence of anomalies recorded for benthic species compared to pelagic species, indicates greater risks of reproductive disruption and could be associated with the microhabitat preferences (water-column or sediment).

Occurrence, removal and risk assessment of steroid hormones in two wastewater stabilization pond systems in Morogoro, Tanzania

The present study investigated the occurrence and removal of 10 steroid hormones (4 androgens, 3 progestagens and 3 estrogens) in two WSP systems, Mafisa and Mzumbe in Morogoro, Tanzania. All 10 steroid hormones were detected in the influent of both WSP systems in the dry as well as in the rainy season. The concentrations of steroids in influent wastewater ranged from 0.1 ng/L for 17-OH-pregnenolone to 445 ng/L for estrone and from below limit of detection for 17-OH-pregnenolone to 45 ng/L for estrone in effluent. During dry season, the overall mean ± standard deviation removal efficiency for the 10 steroids were 70 ± 21% for Mzumbe WSP and 97 ± 3% for Mafisa WSP. During the rainy season the overall mean removal efficiency for all the steroid hormones were 52 ± 32% for Mzumbe WSP and 94 ± 8% for Mafisa WSP. Risk was characterized by calculating the risk quotients (RQs) for fish and humans. 46% of the total RQs calculated were above one, indicating high risk. Low RQs were estimated for androgens and progestagens but the estrogen concentrations measured in the WSP systems and Morogoro River indicated a high risk for fish. However, estrogens appeared not to pose an appreciable risk to human health from water intake and fish consumption. The results indicated that WSP systems are quite effective in removing steroid hormones from wastewater. Thus, low technology systems such as WSP systems are suitable techniques in low income counties due to relatively low costs of building, operating and maintaining these systems.

Environmentally-relevant mixture of pharmaceutical drugs stimulates sex-steroid hormone production and modulates the expression of candidate genes in the ovary of juvenile female rainbow trout

Because of their intrinsic biological activity and ubiquitous environmental occurrence, human pharmaceutical compounds have received increasing attention from health and environmental agencies. In the present study, all-female juvenile rainbow trout (Oncorhynchus mykiss) were exposed to environmentally-realistic concentrations of a mixture of nonsteroidal pharmaceuticals for 42 days, and the effects on plasma levels of sex-steroids and the expression of genes encoding key proteins involved in ovarian development were assessed. Paracetamol, carbamazepine, diclofenac, irbesartan and naproxen were selected, as these have been detected in the Meuse River in Belgium. Fish were exposed to three concentrations of the mixture including the environmental concentration, 10- and 100-times the environmental concentration. Plasma levels of sex-steroid hormones, particularly 11-ketotestosterone, increased in a concentration-dependent way in exposed females. In addition, some key genes involved in ovarian steroidogenesis were significantly overexpressed after 7 days of exposure, such as key genes involved in the maintenance of the ovary. The steady-state mRNA level of genes implicated in germ cell fate were especially affected, such as that of foxl3 which increased by 5 fold at the highest concentration of the mixture. In conclusion, this study highlights that combined occurrence of common pharmaceutical drugs at concentrations present in surface water environments may act as endocrine-disrupting compounds in rainbow trout.

Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt (Hypomesus transpacificus)

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.

Temporal patterns of induction and recovery of biomarker transcriptional responses to 4-Nonylphenol and 17β-estradiol in the estuarine arrow goby, Clevelandia ios

Several estuaries along the Pacific Ocean coast of North America were identified recently as having elevated 4-nonylphenol (4-NP) in sediments and biota, raising concerns about reproductive impacts for wildlife given 4-NP's established estrogenic activity as an endocrine-disrupting compound. Here we characterize 4-NP mediated induction and recovery of estrogen-sensitive gene transcripts in the arrow goby (Clevelandia ios), an intertidal fish abundant in estuarine mud flats on the west coast of North America. Male gobies were exposed to waterborne 4-NP at 10 μg/L or 100 μg/L for 20 days followed by a 20 day depuration period. Additional males were treated with 17β-estradiol (E2; 50 ng/L). 4-NP at 100 μg/L elevated hepatic mRNAs encoding vitellogenins A (vtgA) and C (vtgC) and choriogenin L (chgL) within 72 h, and choriogenin H minor (chgHm) within 12 days. Hepatic mRNAs encoding estrogen receptor alpha (esr1) were also elevated after 12 days of 4-NP exposure, but returned to pre-exposure levels at 20 days even under continuing 4-NP treatment. 4-NP did not alter mRNA levels of estrogen receptor gamma (esr2a) in the liver, or of esr1, esr2a, and cytochrome P450 aromatase B (cyp19a1b) in the brain. The temporal pattern of initial induction for hepatic vtgA, vtgC, and chgL transcripts by 4-NP mirrored the pattern by E2, while chgHm and esr1 mRNA induction by 4-NP lagged 2-11 days behind the responses of these transcripts to E2. These findings establish 4-NP concentration- and time-dependent induction patterns of choriogenin and vitellogenin transcription following exposure to environmentally relevant 4-NP concentrations, while concurrently demonstrating tissue-specific induction patterns for esr1 by estrogenic compounds. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1513-1529, 2017.

Influence of the Gastrointestinal Environment on the Bioavailability of Ethinyl Estradiol Sorbed to Single-Walled Carbon Nanotubes

Recent evidence suggests that, because of their sorptive nature, if single-walled carbon nanotubes (SWCNTs) make their way into aquatic environments, they may reduce the toxicity of other waterborne contaminants. However, few studies have examined whether contaminants remain adsorbed following ingestion by aquatic organisms. The objective of this study was to examine the bioavailability and bioactivity of ethinyl estradiol (EE2) sorbed onto SWCNTs in a fish gastrointestinal (GI) tract. Sorption experiments indicated that SWCNTs effectively adsorbed EE2, but the chemical was still able to bind and activate soluble estrogen receptors (ERs) in vitro. However, centrifugation to remove SWCNTs and adsorbed EE2 significantly reduced ER activity compared to that of EE2 alone. Additionally, the presence of SWCNTs did not reduce the extent of EE2-driven induction of vitellogenin 1 in vivo compared to the levels in organisms exposed to EE2 alone. These results suggest that while SWCNTs adsorb EE2 from aqueous solutions, under biological conditions EE2 can desorb and retain bioactivity. Additional results indicate that interactions with gastrointestinal proteins may decrease the level of adsorption of estrogen to SWCNTs by 5%. This study presents valuable data for elucidating how SWCNTs interact with chemicals that are already present in our aquatic environments, which is essential for determining their potential health risk.

Molecular initiating events of the intersex phenotype: Low-dose exposure to 17α-ethinylestradiol rapidly regulates molecular networks associated with gonad differentiation in the adult fathead minnow testis

Intersex, or the presence of oocytes in the testes, has been documented in fish following exposure to wastewater effluent and estrogenic compounds. However, the molecular networks underlying the intersex condition are not completely known. To address this, we exposed male fathead minnows to a low, environmentally-relevant concentration of 17alpha-ethinylestradiol (EE2) (15ng/L) and measured the transcriptome response in the testis after 96h to identify early molecular initiating events that may proceed the intersex condition. The short-term exposure to EE2 did not affect gonadosomatic index and proportion of gametes within the testes. However, the production of 11-ketotestosterone and testosterone from the testis in vitro was decreased relative to controls. Expression profiling using a 8×60K fathead minnow microarray identified 10 transcripts that were differentially expressed in the testes, the most dramatic change being that of coagulation factor XIII A chain (20-fold increase). Transcripts that included guanine nucleotide binding protein (Beta Polypeptide 2), peroxisome proliferator-activated receptor delta, and WNK lysine deficient protein kinase 1a, were down-regulated by EE2. Subnetwork enrichment analysis revealed that EE2 suppressed transcriptional networks associated with steroid metabolism, hormone biosynthesis, and sperm mobility. Most interesting was that gene networks associated with doublesex and mab-3 related transcription factor 1 (dmrt1) were suppressed in the adult testis, despite the fact that dmrt1 itself was not different in expression from control males. Transcriptional networks involving forkhead box L2 (foxl2) (transcript involved in ovarian follicle development) were increased in expression in the testis. Noteworthy was that a gene network associated to granulosa cell development was increased over 100%, suggesting that this transcriptome network may be important for monitoring estrogenic exposures. Other cell processes rapidly downregulated by EE2 at the transcript level included glucose homeostasis, response to heavy metal, amino acid catabolism, and the cyclooxygenase pathway. Conversely, lymphocyte chemotaxis, intermediate filament polymerization, glucocorticoid metabolism, carbohydrate utilization, and anterior/posterior axis specification were increased. These data provide new insight into the transcriptional responses that are perturbed prior to gonadal remodeling and intersex following exposure to estrogens. These data demonstrate that low concentrations of EE2 (1) rapidly suppresses male hormone production, (2) down-regulate molecular networks related to male sex differentiation, and (3) induce transcriptional networks related to granulosa cell development in the adult testis. These responses are hypothesized to be key molecular initiating events that occur prior to the development of the intersex phenotype following estrogenic exposures.

Equol Induces Gonadal Intersex in Japanese Medaka (Oryzias latipes) at Environmentally Relevant Concentrations: Comparison with 17β-Estradiol

Equol is present in the aquatic environment via livestock waste and runoff discharge; however, it remains unclear whether it can induce gonadal intersex in fish at environmentally relevant concentrations. This study evaluated adverse effects of equol on gonadal development by exposing transgenic Japanese medaka (Oryzias latipes) from hatching for 100 days. Equol induced intersex incidence in male medaka in a dose-dependent manner, and the benchmark dose corresponding to 10% intersex incidence (BMD10) was 11.5 ng/L (95% confidence interval (CI): 5.8 ng/L, 19.8 ng/L), which was comparable to the required dose of 17β-estradiol (E2β) (9.0 ng/L, 95% CI: 6.6 ng/L, 11.0 ng/L). Equol exposure resulted in reduced plasma 11-ketotestosterone (11-KT) concentrations in male medaka at 1.3 ng/L, while reduced plasma 11-KT concentrations were observed at a relatively high concentration (6.4 ng/L) of E2β. Such antiandrogenic property could partly explain the comparable potency of equol with that of E2β to induce intersex at relatively low concentrations, although the binding affinity of equol to medaka estrogen receptor α (EC50 939.4 nM) was 230-fold lower than that (4.07 nM) of E2β. This study for the first time demonstrated that equol could induce intersex in medaka fish at environmentally relevant concentrations.

Morphology, sex steroid level and gene expression analysis in gonadal sex reversal of triploid female (XXX) rainbow trout (Oncorhynchus mykiss)

In non-mammalian vertebrates, estrogens and expressions of cyp19a1 and foxl2 play critical roles in maintaining ovary differentiation and development, while dmrt1 and sox9 are male-specific genes in testicular differentiation and are highly conserved. In order to deeply understand the morphological change, sex steroids level and molecular mechanism of triploid female gonadal reversal in rainbow trout, we studied the ovary morphology, tendency of estradiol-17β (E2) and testosterone (T) levels and the relative expressions of dmrt1, cyp19a1, sox9 and foxl2 in juvenile and adult fish. Our results demonstrated that the development of triploid female gonads in rainbow trout went through arrested development, oocytes dedifferentiation, ovary reconstruction and sex reversal finally. During early gonadal development (154-334 days post-fertilization), the expressions of foxl2 and cyp19a1 increased linearly, while expressions of dmrt1 and sox9 were extremely suppressed, and E2 level was higher, while T level was lower. During the mid-to-late period of triploid female gonadal development (574-964 days post-fertilization), the expressions of dmrt1 and sox9 remained high and were very close to the quantity of diploid male genes, and T levels were even reaching diploid male plasma concentrations, while expressions of cyp19a1 and foxl2 were decreased, leading to decrease in E2 level. We realized that the development model of rainbow trout triploid female gonads was extremely rare, and the regulatory mechanism was very special. Genes involved in gonadal development and endogenous estrogens are pivotal factors in fish natural sex reversal.

Steroids in teleost fishes: A functional point of view

Steroid hormones are involved in the regulation of a variety of processes like embryonic development, sex differentiation, metabolism, immune responses, circadian rhythms, stress response, and reproduction in vertebrates. Teleost fishes and humans show a remarkable conservation in many developmental and physiological aspects, including the endocrine system in general and the steroid hormone related processes in particular. This review provides an overview of the current knowledge about steroid hormone biosynthesis and the steroid hormone receptors in teleost fishes and compares the findings to the human system. The impact of the duplicated genome in teleost fishes on steroid hormone biosynthesis and perception is addressed. Additionally, important processes in fish physiology regulated by steroid hormones, which are most dissimilar to humans, are described. We also give a short overview on the influence of anthropogenic endocrine disrupting compounds on steroid hormone signaling and the resulting adverse physiological effects for teleost fishes. By this approach, we show that the steroidogenesis, hormone receptors, and function of the steroid hormones are reasonably well understood when summarizing the available data of all teleost species analyzed to date. However, on the level of a single species or a certain fish-specific aspect of physiology, further research is needed.

Meta-Analysis of Microarray Data of Rainbow Trout Fry Gonad Differentiation Modulated by Ethynylestradiol

Sex differentiation in fish is a highly labile process easily reversed by the use of exogenous hormonal treatment and has led to environmental concerns since low doses of estrogenic molecules can adversely impact fish reproduction. The goal of this study was to identify pathways altered by treatment with ethynylestradiol (EE2) in developing fish and to find new target genes to be tested further for their possible role in male-to-female sex transdifferentiation. To this end, we have successfully adapted a previously developed bioinformatics workflow to a meta-analysis of two datasets studying sex reversal following exposure to EE2 in juvenile rainbow trout. The meta-analysis consisted of retrieving the intersection of the top gene lists generated for both datasets, performed at different levels of stringency. The intersecting gene lists, enriched in true positive differentially expressed genes (DEGs), were subjected to over-representation analysis (ORA) which allowed identifying several statistically significant enriched pathways altered by EE2 treatment and several new candidate pathways, such as progesterone-mediated oocyte maturation and PPAR signalling. Moreover, several relevant key genes potentially implicated in the early transdifferentiation process were selected. Altogether, the results show that EE2 has a great effect on gene expression in juvenile rainbow trout. The feminization process seems to result from the altered transcription of genes implicated in normal female gonad differentiation, resulting in expression similar to that observed in normal females (i.e. the repression of key testicular markers cyp17a1, cyp11b, tbx1), as well as from other genes (including transcription factors) that respond specifically to the EE2 treatment. The results also showed that the bioinformatics workflow can be applied to different types of microarray platforms and could be generalized to (eco)toxicogenomics studies for environmental risk assessment purposes.

Ovarian structure protein 1: A sensitive molecular biomarker of gonadal intersex in female Japanese medaka after androgen exposure

Intersex in gonochoristic fish can be induced after exposure to androgens and estrogens. The main objective of the present study was to identify biomarkers that would be predictive of intersex in Japanese medaka (Oryzias latipes) after exposure to synthetic hormones. First a gene was identified, ovarian structure protein 1 (osp1), with strong female-specific expression during gonadal differentiation. The authors hypothesized that osp1 expression would decrease to male levels in females after the exposure of larvae (15-25 d postfertilization [dpf]) to 17β-trenbolone (TRB; 5 ng/L) and would increase to female levels in males exposed to 17α-ethinylestradiol (EE2; 5 ng/L) and that gonadal intersex would be induced later in life (60 dpf). Tissue distribution and cellular localization of OSP1 was investigated using Western blot and immunohistochemistry. The results indicate that this exposure regime delays testicular maturation in males and development of ovarian intersex in females. Although decreased osp1 expression in females exposed to TRB correlated to changes in ovarian phenotype, up-regulation of osp1 was not observed in males exposed to EE2. In addition, OSP1 was only observed in ovaries and localized in the cytoplasm and follicular layer of immature and mature oocytes. The authors conclude that osp1 is a promising biomarker of androgen exposure and gonadal intersex in female medaka.

Adaptation of a Bioinformatics Microarray Analysis Workflow for a Toxicogenomic Study in Rainbow Trout

Sex steroids play a key role in triggering sex differentiation in fish, the use of exogenous hormone treatment leading to partial or complete sex reversal. This phenomenon has attracted attention since the discovery that even low environmental doses of exogenous steroids can adversely affect gonad morphology (ovotestis development) and induce reproductive failure. Modern genomic-based technologies have enhanced opportunities to find out mechanisms of actions (MOA) and identify biomarkers related to the toxic action of a compound. However, high throughput data interpretation relies on statistical analysis, species genomic resources, and bioinformatics tools. The goals of this study are to improve the knowledge of feminisation in fish, by the analysis of molecular responses in the gonads of rainbow trout fry after chronic exposure to several doses (0.01, 0.1, 1 and 10 μg/L) of ethynylestradiol (EE2) and to offer target genes as potential biomarkers of ovotestis development. We successfully adapted a bioinformatics microarray analysis workflow elaborated on human data to a toxicogenomic study using rainbow trout, a fish species lacking accurate functional annotation and genomic resources. The workflow allowed to obtain lists of genes supposed to be enriched in true positive differentially expressed genes (DEGs), which were subjected to over-representation analysis methods (ORA). Several pathways and ontologies, mostly related to cell division and metabolism, sexual reproduction and steroid production, were found significantly enriched in our analyses. Moreover, two sets of potential ovotestis biomarkers were selected using several criteria. The first group displayed specific potential biomarkers belonging to pathways/ontologies highlighted in the experiment. Among them, the early ovarian differentiation gene foxl2a was overexpressed. The second group, which was highly sensitive but not specific, included the DEGs presenting the highest fold change and lowest p-value of the statistical workflow output. The methodology can be generalized to other (non-model) species and various types of microarray platforms.