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

Emerging contaminants: A One Health perspective

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.

A Pretty Kettle of Fish: A Review on the Current Challenges in Mediterranean Teleost Reproduction

The Mediterranean region is facing several environmental changes and pollution issues. Teleosts are particularly sensitive to these challenges due to their intricate reproductive biology and reliance on specific environmental cues for successful reproduction. Wild populations struggle with the triad of climate change, environmental contamination, and overfishing, which can deeply affect reproductive success and population dynamics. In farmed species, abiotic factors affecting reproduction are easier to control, whereas finding alternatives to conventional diets for farmed teleosts is crucial for enhancing broodstock health, reproductive success, and the sustainability of the aquaculture sector. Addressing these challenges involves ongoing research into formulating specialized diets, optimizing feeding strategies, and developing alternative and sustainable feed ingredients. To achieve a deeper comprehension of these challenges, studies employing model species have emerged as pivotal tools. These models offer advantages in understanding reproductive mechanisms due to their well-defined physiology, genetic tractability, and ease of manipulation. Yet, while providing invaluable insights, their applicability to diverse species remains constrained by inherent variations across taxa and oversimplification of complex environmental interactions, thus limiting the extrapolation of the scientific findings. Bridging these gaps necessitates multidisciplinary approaches, emphasizing conservation efforts for wild species and tailored nutritional strategies for aquaculture, thereby fostering sustainable teleost reproduction in the Mediterranean.

Sub-acute exposure of male guppies (Poecilia reticulata) to environmentally relevant concentrations of PFOA and GenX induces significant changes in the testis transcriptome and reproductive traits

Poly- and perfluoroalkyl substances (PFAS) are frequently detected in the environment and are linked to adverse reproductive health outcomes in humans. Although legacy PFAS have been phased out due to their toxicity, alternative PFAS are increasingly used despite the fact that information on their toxic effects on reproductive traits is particularly scarce. Here, we exposed male guppies (Poecilia reticulata) for a short period (21 days) to an environmentally realistic concentration (1 ppb) of PFOA, a legacy PFAS, and its replacement compound, GenX, to assess their impact on reproductive traits and gene expression. Exposure to PFAS did not impair survival but instead caused sublethal effects. Overall, PFAS exposure caused changes in male sexual behaviour and had detrimental effects on sperm motility. Sublethal variations were also seen at the transcriptional level, with the modulation of genes involved in immune regulation, spermatogenesis, and oxidative stress. We also observed bioaccumulation of PFAS, which was higher for PFOA than for GenX. Our results offer a comprehensive comparison of these two PFAS and shed light on the toxicity of a newly emerging alternative to legacy PFAS. It is therefore evident that even at low concentrations and with short exposure, PFAS can have subtle yet significant effects on behaviour, fertility, and immunity. These findings underscore the potential ramifications of pollution under natural conditions and their impact on fish populations.

The Effects of Wastewater Reuse on Smallmouth Bass (Micropterus dolomieu) Relative Abundance in the Shenandoah River Watershed, USA

Municipal and industrial wastewater effluent is an important source of water for lotic systems, especially during periods of low flow. The accumulated wastewater effluent flows-expressed as a percentage of total streamflow (ACCWW%)-contain chemical mixtures that pose a risk to aquatic life; fish may be particularly vulnerable when chronically exposed. Although there has been considerable focus on individual-level effects of exposure to chemical mixtures found in wastewater effluent, scaling up to population-level effects remains a challenging component needed to better understand the potential consequences of exposure in wild populations. This may be particularly important under a changing climate in which wastewater reuse could be essential to maintain river flows. We evaluated the effects of chronic exposure to wastewater effluent, as measured by ACCWW%, on the relative abundance of young-of-year (YOY), juvenile, and adult smallmouth bass (Micropterus dolomieu) populations in the Shenandoah River Watershed (USA). We found that increases in ACCWW% in the previous year and during the prespawn period were negatively correlated with the relative abundance of YOY, resulting in an average 41% predicted decrease in abundance (range = 0.5%-94% predicted decrease in abundance). This lagged effect suggests that adult fish reproductive performance may be compromised by chemical exposure during periods of high ACCWW%. No relationships between ACCWW% and juvenile or adult relative abundance were found, suggesting that negative effects of ACCWW% on YOY abundance may be offset due to compensatory mechanisms following higher ACCWW% exposure. Understanding the effects of wastewater effluent exposure at multiple levels of biological organization will help in the development of management strategies aimed at protecting aquatic life. Environ Toxicol Chem 2024;00:1-11. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Reproductive toxicity of bisphenol A, at environmentally relevant concentrations, on ovarian redox balance, maturational response, and intra-oocyte signalling events in Labeo bata

Bisphenol A (BPA) is a widely used plastic monomer that potentially interferes with ovarian neuroendocrine, endocrine, and autocrine/paracrine factors, causing reproductive dysfunction. However, the influence of BPA on redox balance, estrogen receptor (ER) expression vis-à-vis meiotic cell cycle progression, and intra-oocyte signalling events has not been extensively investigated. The present study examines the impact of BPA on reproductive toxicity in female Labeo bata (Order Cypriniformes, Family Cyprinidae), a freshwater teleost preferred as a food fish in the Indian subcontinent. Our results show that while ovarian weight (gonadosomatic index, GSI) and dynamics of follicular growth undergo pronounced changes during the annual reproductive cycle, chronic BPA exposure at environmentally relevant concentrations promotes follicular atresia concomitant with reduced GSI during the spawning phase, the highest response being observed due to low-dose (0.1 μg/L, 0.438 nM) BPA exposure in vivo. Furthermore, BPA perturbation of ovarian StAR expression and ERα/ERβ homeostasis corroborates with elevated oxidative stress in BPA-treated ovary, FG follicles, and follicular cells. A sharp increase in ROS accumulation and nitric oxide (NO) levels in BPA-treated full-grown (FG) follicles coupled with loss of redox balance, elevated follicular cell death, and activation of apoptotic markers (caspase -8, -9, -3, Bax) indicate poor oocyte health and reproductive toxicity. Importantly, maturational steroid (MIS, 17,20β-P)-induced cyclin B-p34cdc2 activation and elevated GVBD (germinal vesicle breakdown) response require protein kinase A (PKA) inhibition and participation of Mos/MAPK- and cdc25-mediated signalling events. While the adenylate cyclase activator forskolin (FK) abrogates, priming with a PKA inhibitor (H89) promotes the meiotic G2-M1 transition, confirming the role of PKA in meiotic cell cycle progression in this species. Furthermore, the negative influence of BPA priming on 17,20β-P-induced oocyte maturation involves elevated PKAc phosphorylation (activation) and significant alteration in Mos/MAPK signalling, indicating derailed meiotic maturational competence and disrupted oocyte quality.

Single and mixture toxicity evaluation of avobenzone and homosalate to male zebrafish and H295R cells

Avobenzone and homosalate are widely used in sunscreens to provide ultraviolet (UV) protection, either as single compounds or in combination. Some UV filters exhibit estrogenic or anti-androgenic activities, however, studies regarding their interactions and toxicity in mixtures are limited. In this study, the effect of the toxicity of a binary mixture comprising avobenzone (0.72 μg L-1) and homosalate (1.02 and 103 μg L-1) on steroid hormone biosynthesis were investigated using male zebrafish and human adrenocortical carcinoma (H295R) cells. In fish exposed to homosalate, a significant decrease in the gonadosomatic index, testosterone level, and transcription of several genes (e.g, hsd3b2, cyp17a1, and hsd17b1) and a significant increase in the hepatosomatic index, liver steatosis, 17β-estradiol level, and transcription of vtg gene were observed. These results suggest that estrogenic and anti-androgenic effects of homosalate were mediated by the steroidogenic pathway. The presence of 0.72 μg L-1 of avobenzone augmented the anti-androgenic responses in male fish. The testosterone level in the H295R cells were significantly decreased after they were exposed to homosalate alone or in combination with avobenzone, which is consistent with observations in male zebrafish. Further studies need to be conducted to understand the endocrine disrupting properties of long-term exposure to substances typically used in sunscreens.

Persistent Organic Pollutants (POPs) in three bathyal chondrichthyes from the North-Western Mediterranean Sea

The deep-sea can act as a sink for legacy contaminants such as organochlorines (OCs), causing damages in its inhabitants for their persistence and their prolonged effects in the organisms. HCB, DDT and its isomers, and 28 PCBs congeners were detected in muscle and embryonic tissues of three deep-sea chondrichthyes Chimaera monstrosa (n = 16), Dalatias licha (n = 12) and Etmopterus spinax (n = 51) sampled in Ligurian and Tyrrhenian Sea (Mediterranean Sea). Contaminant distribution in E. spinax and C. monstrosa was PCBs > DDTs ≫ HCB while in D. licha was DDTs > PCBs ≫ HCB. Statistically significant differences were highlighted in OC levels among the species, but no such differences were found among sexes. Ratios between DDT isomers highlighted an historical input of the pesticide in the environment. For the first time was also demonstrated maternal transfer in deep water chondrichthyes, specifically in E. spinax where was highlighted that transfer of contaminants increases with increasing compound's Log Kow.

Impairment of oocyte maturation as a mechanism of decreased fecundity in Japanese medaka (Oryzias latipes) exposed to the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO)

Inhibition of oocyte maturation is an understudied mechanism by which chemical stressors can impair fecundity of female fishes. The primary objective of the present study was to develop an assay to assess oocyte maturation disruption by chemical stressors in Japanese medaka (Oryzias latipes). First, an in vitro assay to assess maturation inducing hormone (MIH)-stimulated oocyte maturation in zebrafish was validated for use with Japanese medaka. Next, using the brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO), which previously was shown to decrease fecundity of Japanese medaka and inhibit oocyte maturation in zebrafish, effects on oocyte maturation were quantified using in vitro and in vivo exposure. Adaptation of the protocol for in vitro MIH-stimulated maturation of stage IV oocytes from zebrafish was successful in inducing greater than 80% of stage IX oocytes from female Japanese medaka to mature. To assess effects of in vitro exposure, stage IX oocytes were exposed to 0, 2, 20, and 200 μg/L of TBCO, followed by exposure to MIH. The in vitro exposure caused a significant decrease in maturation of oocytes exposed to 20 and 200 μg/L of TBCO. To assess effects of TBCO on fecundity and oocyte maturation following in vivo exposure, sexually mature fish were fed a control, 100 μg/g, or 1000 μg/g concentration of TBCO-spiked fish food for 21 days, where fecundity was measured daily, and following the exposure, stage IX oocytes were excised to assess MIH-stimulated maturation. Fecundity and oocyte maturation were significantly decreased at either concentration of TBCO. Plasma concentrations of 17β-estradiol (E2) and hepatic abundances of transcripts of vitellogenin (vtgI and vtgII) were quantified, but there were no significant differences between treatments. Results suggest that inhibition of oocyte maturation is a mechanism by which TBCO decreases fecundity, and that in vitro assays of oocyte maturation might be predictive of fecundity in this species.

Endocrine disruptor responses in the embryos of marine medaka (Oryzias melastigma) after exposure to aged plastic leachates

The issue of the additives leached from plastics has attracted widespread attention. More crucially, endocrine disruptor status for several leached additives has been established. However, little is known about the overall endocrine disrupting effects of aged plastic leachates. Therefore, the transcriptional responses of endocrine-related genes were assessed in the embryos of marine medaka (Oryzias melastigma), which were exposed to the leachates from aged plastics that were immersed into the simulated seawater (SW) or fish digest (FD). The results revealed that there was a great difference between the SW and FD leachates in the transcripts of endocrine-related genes. With the exception of cyp1a, all target genes had their transcripts potentially down-regulated by the FD leachates. Chgl (a biomarker for estrogens), pparβ (related to lipid metabolism), and cyp19a (related to sexual differentiation and reproduction) transcripts tended to be repressed by the SW leachates, while pparα, pparγ and cyp1a (mediating metabolism of xenobiotics) transcripts were stimulated. In addition, a redundancy analysis was carried out to determine the relationship between the leached additives and the transcriptional changes. However, the additives only partially explained the variation in the transcripts of endocrine-related genes (24.8%), indicating that other leached additives may have an impact on target gene transcription. This study provided molecular evidence of the aged plastic leachates' endocrine disrupting effects. Exploring the primary factors that affect the transcriptional alterations would require more research.

Estrogenic potency of endocrine disrupting chemicals and their mixtures detected in environmental waters and wastewaters

Endocrine disrupting chemicals such as natural and synthetic steroid hormones and bisphenols are among the most important pollutants in the aquatic environment. We performed an environmental chemical analysis of five Slovenian water samples, two rivers, one groundwater, and the influent and effluent of wastewater treatment plants, with a highly sensitive analysis of twenty-five endocrine-disrupting compounds belonging to the groups of natural hormones, synthetic hormones, and bisphenols. Since these compounds are simultaneously present in the environment, it is important to study their individual effects as well as the effects of mixtures. We investigated in vitro the estrogenic potency of selected natural and synthetic steroid hormones and bisphenols detected in surface, ground and waste water in Slovenia using the OECD-validated transactivation assay on the cell line Hela9903. We predicted their mixture effects using the concentration addition model and compared them with experimentally determined values. Two mixing designs were used: a balanced design in which chemicals were combined in proportion to their individual EC₅₀ values, and an unbalanced design with compounds in proportion to their measured concentrations in the environmental samples. The estrogenic effects of the experimental mixtures followed the concentration addition model. Real water samples exhibited weaker estrogenic effects, showing the great heterogeneity of the real water samples.

Experimentally exposed toxic effects of long-term exposure to environmentally relevant concentrations of CIP in males and females of the silver catfish Rhamdia quelen

Ciprofloxacin (CIP) is an antibiotic commonly used in human and veterinary medicine. It is present in the aquatic environment, but we still know very little about its effect on non-targeted organisms. This study aimed to evaluate the effects of long-term exposure to environmental CIP concentrations (1, 10, and 100 μg.L^-1) in males and females of Rhamdia quelen. After 28 days of exposure, we collected the blood for the analysis of hematological and genotoxic biomarkers. Additionally, we measured 17 β-estradiol and 11 keto-testosterone levels. After the euthanasia, we collected the brain and the hypothalamus to analyze acetylcholinesterase (AChE) activity and neurotransmitters, respectively. The liver and gonads were assessed for biochemical, genotoxic, and histopathological biomarkers. At 100 μg.L^-1 CIP, we observed genotoxicity in the blood, nuclear morphological changes, apoptosis, leukopenia, and a reduction of AChE in the brain. In the liver was observed oxidative stress and apoptosis. At 10 μg.L^-1 CIP, leukopenia, morphological changes, and apoptosis were presented in the blood and a reduction of AChE in the brain. Apoptosis, leukocyte infiltration, steatosis, and necrosis occurred in the liver. Even at the lowest concentration (1 μg.L^-1), adverse effects such as erythrocyte and liver genotoxicity, hepatocyte apoptosis, oxidative stress, and a decrease in somatic indexes were observed. The results showed the importance of monitoring CIP concentrations in the aquatic environment that cause sublethal effects on fish.

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.

Effects of Dietary Cholesterol Regulation on Spermatogenesis of Gobiocypris rarus Rare Minnow

Cholesterol is an important component of cell membranes, and also a precursor for the synthesis of sex hormones, playing an important role in reproduction. However, few studies have focused on cholesterol and reproductive health. To investigate the toxic effects of different cholesterol levels on the spermatogenesis of rare minnows, we regulate the cholesterol content in fish by feeding them a high-cholesterol diet and cholesterol inhibitor pravastatin, and cholesterol levels, sex hormone (T and 11KT) levels, testis histology, sperm morphology and function, and the expression of genes related to sex hormone synthesis were investigated. The research findings indicate that increasing cholesterol levels significantly increases the liver weight and hepatic-somatic index, as well as the total cholesterol and free cholesterol levels in the testis, liver, and plasma of rare minnow, while inhibiting cholesterol has the opposite effect (p < 0.05). However, both increasing and decreasing cholesterol levels can suppress rare minnow testicular development, as evidenced by a decrease in testis weight, lowered gonadosomatic index, suppressed sex hormone levels, and reduced mature sperm count. Further exploration revealed that the expression of sex hormone synthesis-related genes, including star, cyp19a1a, and hsd11b2, was significantly affected (p < 0.05), which may be an important reason for the decrease in sex hormone synthesis and consequent inhibition of testicular development. At the same time, the fertilization ability of mature sperm in both treatment groups significantly decreased. Scanning electron microscopy and fluorescence polarization tests showed that reducing cholesterol levels significantly increased the rate of sperm head cell membrane damage, while both increasing and decreasing cholesterol levels led to a reduction in sperm cell membrane fluidity, which may be the main reason for the decrease in sperm fertilization ability. This study demonstrates that both increasing and decreasing the levels of cholesterol are detrimental to the fish spermatogenesis, providing fundamental information for the study of fish reproduction and also a reference for the causes of male reproductive dysfunction.

A transcriptomic-based analysis predicts the neuroendocrine disrupting effect on adult male and female zebrafish (Danio rerio) following long-term exposure to tetrabromobisphenol A bis(2-hydroxyethyl) ether

Endocrine-disrupting chemicals (EDCs) are now ubiquitously distributed in the environment. Tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) pollution in environment media poses a significant threat to humans and aquatic organisms as a result of its potential neurotoxicity and endocrine-disrupting effect. The endocrine-disrupting effects of TBBPA-DHEE on aquatic organisms, however, have received limited attention. In this study, the neurotoxicity and reproductive endocrine-disruptive effect of TBBPA-DHEE was evaluated by observing the neurobehavioral changes, vitellogenin (VTG), testosterone, 17β-estradiol and gene expression levels in adult male and female zebrafish exposed to TBBPA-DHEE (0.05, 0.2 and 0.3 mg/L) for 100 days. Furthermore, transcriptomic analysis was conducted to unravel other potential neuroendocrine-disrupting mechanism. Our result showed TBBPA-DHEE significantly (p < 0.05) altered the locomotor behavior and motor coordination abilities in both sexes. Steroid hormone and VTG levels were also altered indicating the neuroendocrine-disrupting effect of TBBPA-DHEE on the hypothalamic-pituitary-gonadal-axis. A total of 1568 genes were upregulated and 542 genes downregulated in males, whereas, 1265 upregulated and 535 downregulated genes were observed in females. The KEGG enrichment analysis showed that cell cycle and p55 signaling pathways were significantly enriched due to TBBPA-DHEE exposure. These pathways and its component genes are potential target of EDCs. The significant upregulation of genes in these pathways could partly explain the neuroendocrine disrupting effect of TBBPA-DHEE. The observed toxic effects of TBBPA-DHEE observed in this study is confirmation of the endocrine-disrupting toxicity of this chemical which would be valuable in biosafety evaluation and biomonitoring of TBBPA-DHEE for public health purposes.

Using zebrafish embryo bioassays to identify chemicals modulating the regulation of the epigenome: a case study with simvastatin

Contaminants of emerging concern have been increasingly associated with the modulation of the epigenome, leading to potentially inherited and persistent impacts on apical endpoints. Here, we address the performance of the OECD Test No. 236 FET (fish embryo acute toxicity) in the identification of chemicals able to modulate the epigenome. Using zebrafish (Danio rerio) embryos, acute and chronic exposures were performed with the pharmaceutical, simvastatin (SIM), a widely prescribed hypocholesterolemic drug reported to induce inter and transgenerational effects. In the present study, the epigenetic effects of environmentally relevant concentrations of SIM (from 8 ng/L to 2000 ng/L) were addressed following (1) an acute embryo assay based on OECD Test No. 236 FET, (2) a chronic partial life-cycle exposure using adult zebrafish (90 days), and (3) F1 embryos obtained from parental exposed animals. Simvastatin induced significant effects in gene expression of key epigenetic biomarkers (DNA methylation and histone acetylation/deacetylation) in the gonads of exposed adult zebrafish and in 80 hpf zebrafish embryos (acute and chronic parental intergenerational exposure), albeit with distinct effect profiles between biological samples. In the chronic exposure, SIM impacted particularly DNA methyltransferase genes in males and female gonads, whereas in F1 embryos SIM affected mostly genes associated with histone acetylation/deacetylation. In the embryo acute direct exposure, SIM modulated the expression of both genes involved in DNA methylation and histone deacetylase. These findings further support the use of epigenetic biomarkers in zebrafish embryos in a high throughput approach to identify and prioritize epigenome-modulating chemicals.

Roundup in the Reproduction of Crucian Carp (Carassius carassius): An In Vitro Effect on the Pituitary Gland and Ovary

Roundup, the most popular herbicide in global agriculture, is regarded as an endocrine disruptor causing alterations of important hormones at the hypothalamic-pituitary-gonadal axis as well as impairment of gametogenesis. The whole pituitary glands of crucian carp (Carassius carassius) were incubated for 3 h in the medium containing Roundup (0-control, 1 and 10 ng/mL). The level of luteinizing hormone (LH), and mRNA transcript abundance of kisspeptin (kiss-1) and its receptor (gpr54), were determined. The isolated ovarian fragments were incubated for 24 h in the presence of Roundup and the following effects on reproductive parameters were determined: the final oocyte maturation and ovulation, structural changes in follicles, secretion of 17,20β-progesterone (17,20β-P) as well as mRNA transcript abundance of the luteinizing hormone receptor (lhr), estrogen receptors (erα, erβ1, erβ2), and zona radiata (chorion) proteins (zp2 and zp3). Roundup inhibited final oocyte maturation and decreased the percentage of ovulated eggs, and furthermore, caused structural changes in the ovarian follicular components. There were no significant changes in the measured hormone levels and analyzed genes mRNA transcript abundance. Summing up, obtained results indicate that Roundup may adversely affect oocyte maturation and the quality of eggs, suggesting that exposure to this herbicide can lead to reproductive disorders in fish.

Generation of Endogenous Promoter-Driven Luciferase Reporter System Using CRISPR/Cas9 for Investigating Transcriptional Regulation of the Core Clock Gene BMAL1

Humans and other organisms are continuously exposed to thousands of chemicals through the atmosphere, drinking water, food, or direct contact. A large proportion of such chemicals are present in very low concentrations and may have synergistic effects, even at their no-observed-adverse-effect level (NOAEL). Complex mixtures of contaminants are very difficult to assess by traditional toxicological methods. There is increasing attention on how different pollutants induce adverse physiological functions in the human body through effects on the circadian rhythm. However, it is very difficult to screen for compounds with circadian-rhythm-disrupting effects from a large number of chemicals or their complex mixtures. We established a stable firefly luciferase reporter gene knock-in U2-OS cell line by CRISPR/Cas9 to screen circadian-rhythm-disrupting pollutants. The luciferase gene was inserted downstream of the core clock gene BMAL1 and controlled by an endogenous promoter. Compared to detection systems using exogenous promoters, these cells enable the detection of compounds that interfere with the circadian rhythm system mediated by BMAL1 gene expression. The U2-OS knock-in cells showed BMAL1 and luciferase activity had parallel changes when treated with BMAL1 inhibitor and activator. Furthermore, the luciferase reporter gene has high sensitivity and is faster and more cost-effective than classic toxicology methods. The knock-in cell line can be used for high-throughput and efficient screening of circadian-rhythm-disrupting chemicals such as drugs and pollutants.

Changes in thyroid histomorphology and thyroglobulin immunostaining upon exposure to thiourea in Triturus newts

Amphibians are useful bioindicators for monitoring aquatic health and the influence of xenobiotics such as endocrine disrupting chemicals. Because aquatic ecosystems experience the majority of global pollution, aquatic organisms are most exposed and vulnerable to endocrine disruptors. Furthermore, penetration of endocrine disruptors into aquatic organisms especially in amphibians is even easier because of more permeable skin, resulting in high bioavailability and bioaccumulation of chemicals. One of the most potent endocrine disruptors is thiourea, which chemically blocks the synthesis of thyroid hormones and prevents metamorphosis in amphibians. We investigated the influence of thiourea on histomorphology of the thyroid gland in Triturus newts at the metamorphic stage, when thyroid hormone concentrations should reach their maximum level. Chronic exposure to thiourea induced hypertrophy and hyperplasia of follicular cells as well as a significant reduction of interstitial tissue. The intensity of the thyroglobulin immunostaining signal significantly decreases upon chronic exposure to thiourea. Successful cross-reactivity of human primary antibody in immunochemical detection of thyroglobulin in Urodela confirms potential homology in thyroglobulin structure throughout the vertebrates.

Accounting for transgenerational effects of toxicant exposure in population models alters the predicted long-term population status

Acute environmental stressors such as short-term exposure to pollutants can have lasting effects on organisms, potentially impacting future generations. Parental exposure to toxicants can result in changes to the epigenome (e.g., DNA methylation) that are passed down to subsequent, unexposed generations. However, it is difficult to gauge the cumulative population-scale impacts of epigenetic effects from laboratory experiments alone. Here, we developed a size- and age-structured delay-coordinate population model to evaluate the long-term consequences of epigenetic modifications on population sustainability. The model emulated changes in growth, mortality, and fecundity in the F0, F1, and F2 generations observed in experiments in which larval Menidia beryllina were exposed to environmentally relevant concentrations of bifenthrin (Bif), ethinylestradiol (EE2), levonorgestrel (LV), or trenbolone (TB) in the parent generation (F0) and reared in clean water up to the F2 generation. Our analysis suggests potentially dramatic population-level effects of repeated, chronic exposures of early-life stage fish that are not captured by models not accounting for those effects. Simulated exposures led to substantial declines in population abundance (LV and Bif) or near-extinction (EE2 and TB) with the exact trajectory and timeline of population decline dependent on the combination of F0, F1, and F2 effects produced by each compound. Even acute one-time exposures of each compound led to declines and recovery over multiple years due to lagged epigenetic effects. These results demonstrate the potential for environmentally relevant concentrations of commonly used compounds to impact the population dynamics and sustainability of an ecologically relevant species and model organism.

Impacts of endocrine disrupting chemicals on reproduction in wildlife and humans

Endocrine disrupting chemicals (EDCs) are ubiquitous in aquatic and terrestrial environments. The main objective of this review was to summarize the current knowledge of the impacts of EDCs on reproductive success in wildlife and humans. The examples selected often include a retrospective assessment of the knowledge of reproductive impacts over time to discern how the effects of EDCs have changed over the last several decades. Collectively, the evidence summarized here within reinforce the concept that reproduction in wildlife and humans is negatively impacted by anthropogenic chemicals, with several altering endocrine system function. These observations of chemicals interfering with different aspects of the reproductive endocrine axis are particularly pronounced for aquatic species and are often corroborated by laboratory-based experiments (i.e. fish, amphibians, birds). Noteworthy, many of these same indicators are also observed in epidemiological studies in mammalian wildlife and humans. Given the vast array of reproductive strategies used by animals, it is perhaps not surprising that no single disrupted target is predictive of reproductive effects. Nevertheless, there are some general features of the endocrine control of reproduction, and in particular, the critical role that steroid hormones play in these processes that confer a high degree of susceptibility to environmental chemicals. New research is needed on the implications of chemical exposures during development and the potential for long-term reproductive effects. Future emphasis on field-based observations that can form the basis of more deliberate, extensive, and long-term population level studies to monitor contaminant effects, including adverse effects on the endocrine system, are key to addressing these knowledge gaps.

The effect of nonylphenol exposure on the stimulation of melanomacrophage centers, estrogen and testosterone level, and ERα gene expression in goldfish

The present study tried to measure the formation of melanomacrophage centers (MMCs) in various organs of male and female goldfish exposed to nonylphenol (NP) and aimed to assess its relationship with the main sexual hormones, estrogen receptor expression, and the pigment content of the MMCs. Immature goldfish were exposed to 10^-6 and 10^-7 M NP for 25 days. After obtaining blood for measuring testosterone and estrogen (E2) levels, tissue samples were collected from various organs for histological studies, quantifying pigments using ImageJ software and chemical analysis, and measuring ERα gene expression. Results showed that the order of forming MMCs in various organs exposed to NP was liver > spleen > kidney, and the order of ERα gene expression was liver > testes > spleen > kidney in the male, and liver > spleen > kidney > ovaries in the female. Among the three pigments present in MMCs after exposure to the two doses of NP, melanin was more obvious (especially in the liver) and increased mostly in a dose-dependent manner in both sexes (especially in the male). Chemical analyses confirmed these results. Measurement of testosterone and E2 level in male and female goldfish showed that NP had more effect on the concentration of these hormones in male fish, indicating more endocrine-disrupting potential of NP against the male fish. Generally, the increase of melanin content of melanomacrophage centers coincided with the increase of ERα gene expression and decrease of testosterone level in goldfish after exposure to NP.

Haemolymphatic Parameters in Two Aquaculture Crustacean Species Cherax destructor (Clark, 1836) and Cherax quadricarinatus (Von Martens, 1868)

Simple Summary

The spread of freshwater crustacean farms, in particular of the Australian species Cherax, has been widespread in recent years and has aroused particular interest at an economic level. Knowledge of the basic levels of some biochemical parameters becomes particularly important to understanding the health status of the animals and, therefore, for the maintenance of aquaculture facilities. In this study, the values of some biochemical parameters of two species of Cherax, Cherax destructor and Cherax quadricarinatus, reared in an Italian aquaculture plant, were evaluated for the first time. These parameters should contribute to assessing the health status of these animals on a farm and to understanding if they will be affected by stressful conditions or not.

Abstract

In the last few years, there has been a notable development in the breeding of freshwater shrimp (astaciculture), which involved various species and in particular, the two Australian Parastacidae species, Cherax destructor and Cherax quadricarinatus. Information about the haemolymphatic parameters of these two species is fragmentary, and filling these gaps becomes important given their importance in aquaculture. Cellular and biochemical parameters were analyzed in both species to create a reference baseline for these parameters to identify the state of welfare or suffering of these animals. The results showed that the total haemocyte count, haemocyte subpopulations, enzymatic activities and pH are similar between the two species, while total protein and osmolality are higher in C. destructor than C. quadricarinatus. Knowledge of these parameters could assist in evaluating the good health status of these species kept in aquaculture facilities.

Reprotoxic Impact of Environment, Diet, and Behavior

Reproductive health is progressively declining due to multiples endogenous and exogenous factors, such as environmental contaminants, diet and behavior. Accumulated evidences confirm that fertility and reproductive function have been adversely affected by exposure to chemical contaminants released in the environment. Today, the impact of diet and behavior on reproductive processes is also receiving special attention from the scientific community. Indeed, a close relationship between diet and fertility has been proven. Furthermore, a combination of unhealthy behavior, such as exposure to hazardous compounds and stress factors, poses living organisms at higher risk of reprotoxic effects. In particular, it has been described that poor life behaviors are associated with reduced male and female fertility due to decreased gamete quality and function. Most of the erroneous behaviors are, furthermore, a source of oxidative stress that, leading to epigenetic alterations, results in an impaired reproductive fitness. This review reports the detrimental impact of the most common environmental chemical stressors, diet, and behavior on reproductive functionality and success. Although clear evidences are still scarce, reassuring data are provided that a healthy diet and reverting unhealthy lifestyles may be of help to recover physiological reproductive conditions.

The interactive effects of ethinylestradiol and progesterone on transcriptional expression of genes along the hypothalamus-pituitary-thyroid axis in embryonic zebrafish (Danio rerio)

Progestins and estrogens are widespread in various aquatic environments and their potential endocrine disruption effects to aquatic organisms have drawn growing concern. However, their combined effects in aquatic organisms remain elusive. The aim of the present study was to assess the effects of the binary mixtures of gestodene (GES) and 17α-ethinylestradiol (EE2) on the hypothalamic-pituitary-thyroid (HPT) axis of zebrafish (Danio rerio) using the eleuthero-embryos. Embryos were exposed to GES and EE2 alone or in combination at concentrations ranging from 41 to 5329 ng L^-1 (nominal ones from 50 to 5000 ng L^-1) for 48 h, 96 h and 144 h post fertilization (hpf). The results showed that the transcripts of the genes along the HPT axis displayed pronounced alterations. There was no clear pattern in the change of the transcripts of these genes over time and with concentrations. However, in general, the transcripts of the genes were inversely affected by EE2 (increase 0.5 to 4.2-folds) and GES (inhibition 0.4 to 4.9-folds), and their mixtures showed interactive effects in embryonic zebrafish. In addition, physiological data (mortality, malformation, body length and heart rate etc.) denoted higher toxicity of the two chemicals in combination than alone based on the developmental toxicity and neurotoxicity (locomotor behavior). These results indicated that the interactive effects of these two chemicals might be different between at the transcriptional level and at the whole organismal level. In summary, GES and EE2 affect the HPT axis (related genes expression and thyroid hormones (THs) levels) and exhibit developmental toxicity and neurotoxicity.

Prediction of adverse effects of effluents containing phenolic compounds in the Ba River on the ovary of fish (Hemiculter leucisculus) using transcriptomic and metabolomic analyses

The aim of this work was to evaluate the endocrine disrupting effects on the ovarian development of sharpbelly (Hemiculter leucisculus) caused by effluents containing phenolic compounds. This was achieved using integrated transcriptomic and metabolomic analyses, along with histopathological examinations. Sharpbelly, an indigenous freshwater fish widely distributed in East Asia, were collected by pole fishing from three sampling sites in the Ba River. These sampling sites include a mid-stream site near a wastewater outfall and a reference site located upstream and a far field comparison site located downstream. In sharpbelly collected near the wastewater discharge, the oocyte development was activated, compared to the other two sites. Histopathological alterations in the fish ovaries were likely due to the upregulated steroid hormone biosynthesis process, as suggested by the differentially expressed genes (e.g., hsd3b, hsd17b1) and differentially accumulated metabolites (e.g., pregnenolone). Additionally, under the stress of effluents containing phenolic compounds, genes related to the signaling pathways for oxidative phosphorylation and leukocyte transendothelial migration were dysregulated, suggesting the potential induction of inflammation and several ovarian diseases. Overall, these findings suggest that effluents containing phenolic compounds influence ovary development and reproductive function of female sharpbelly. Whether there is any resulting dysfunction of folliculogenesis, abnormality of ovulation, production of premature eggs and/or potential induction of ovarian cancers remains to be determined by further studies, for a better evaluation on effluents containing phenolic compounds to the fish fertility and the health of their offspring, and even the stability of the wild fish population. Notably, the integration of transcriptomics and metabolomics can complement the routine chemical analysis to comprehensively monitor the effects of wastewater treatment plant effluents on the health of wild fish.

Cylindrospermopsin directly disrupts spermatogenesis in isolated male zebrafish testis

Cylindrospermopsin (CYN) is a cytotoxin, and its documented effects in mammals include damage to several organs. CYN also has hormone-disrupting properties, including estrogenic activity, progesterone production inhibition, and apoptosis induction. While CYN has been reported to exert reproductive toxicity in mice, little is known about its effect on fish reproductive function. Using ex vivo organ culture, we investigated the direct action of CYN on the male reproductive system. Isolated zebrafish testis was exposed to 250, 500, and 1000 µg/L CYN for 24 h and 7 d, followed by histo-morphological analysis. The results demonstrate that exposure to CYN led to a decrease in cell types from all three phases of spermatogenesis in zebrafish testis. There were also significant changes in fshr, lhr, and igf3 transcript levels, as well as testosterone secretion following exposure to CYN. In summary, this study provides novel information on the adverse effects of CYN on testicular spermatogenesis and male reproduction in zebrafish. These results provide a framework for a better understanding of CYN toxicity and the mechanism underlying the adverse action of CYN on male reproduction in fish.

Bioremediation of heavy metals from industrial effluents by endophytes and their metabolic activity: Recent advances

Worldwide, heavy metals pollution is mostly caused by rapid population growth and industrial development which is accumulated in food webs causing a serious public health risk. Endophytic microorganisms have a variety of mechanisms for metal sequestration having metal biosorption capacities.Endophytic organisms like bacteria and fungi provide beneficial qualities that help plants to improve their health, reduce stress, and detoxify metals. Endophytes have a higher proclivity for improving metal and mineral solubility by cells that secrete low-molecular-weight organic acids and metal-specific ligands like siderophores, which change the pH of the soil and improve binding activity. Protein-related approaches like chromatin immunoprecipitation sequencing (ChIP-Seq) and modified enzyme-linked immunosorbent assay (ELISA test) can represent endophytic bacterial community and DNA-protein interactions during metal reduction. This review explored the role of endophytes in bioremediation approaches that can help in analyzing the potential and prospects in response to industrial effluents' detoxification.

A Review on Environmental Contaminants-Related Fertility Threat in Male Fishes: Effects and Possible Mechanisms of Action Learned from Wildlife and Laboratory Studies

Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.

Effects of polycyclic aromatic hydrocarbons on biomarker responses in Gambusia yucatana, an endemic fish from Yucatán Peninsula, Mexico

Polycyclic aromatic hydrocarbons (PAHs) are petroleum components that, when dissolved in the aquatic environment, can disrupt normal animal physiological functions and negatively affect species populations. Gambusia yucatana is an endemic fish of the Yucatán Peninsula that seems to be particularly sensitive to the presence of PAHs dissolved in the water. Here, we examined PAH effects on gene expressions linked to endocrine disruption and biotransformation in this species. Specifically, we examined the expression of vitellogenin I (vtg1), vitellogenin II (vtg2), oestrogen receptor α (esr1), oestrogen receptor β (esr2), aryl hydrocarbon receptor (AhR) and the cytochrome P4503A (CYP3A) genes. We exposed G. yucatana to different concentrations of PAHs (3.89, 9.27, 19.51 μg/L) over a period of 72 h and found changes associated with reproduction, such as increases in hepatic expression of vtg, esr, AhR and CYP3A, mainly at concentrations of 9.27 and 19.51 μg/L. Our results also indicate that benzo[a]pyrene was probably the main PAH responsible for the observed effects. The genes examined here can be used as molecular markers of endocrine-disrupting compounds, as the PAHs, present in the environment, as gene expression increases could be observed as early as after 24 h. These biomarkers can help researchers and conservationists rapidly identify the impacts of oil spills and improve mitigation before the detrimental effects of environmental stressors become irreversible.

Probiotic Administration Mitigates Bisphenol A Reproductive Toxicity in Zebrafish

Although the use of bisphenol A (BPA) has been banned in a number of countries, its presence in the environment still creates health issues both for humans and wildlife. So far, BPA toxicity has been largely investigated on different biological processes, from reproduction to development, immune system, and metabolism. In zebrafish, Danio rerio, previous studies revealed the ability of environmentally relevant concentrations of this contaminant to significantly impair fertility via epigenetic modification. In addition, several studies demonstrated the ability of different probiotic strains to improve organism health. This study provides information on the role of the probiotic mixture SLAb51 to counteract adverse BPA effects on reproduction. A 28-day trial was set up with different experimental groups: BPA, exposed to 10 µg/L BPA; P, receiving a dietary supplementation of SLAb51 at a final concentration of 10⁹ CFU/g; BPA+P exposed to 10 µg/L BPA and receiving SLAb51 at a final concentration of 10⁹ CFU/g and a C group. Since oocyte growth and maturation represent key aspects for fertility in females, studies were performed on isolated class III (vitellogenic) and IV (in maturation) follicles and liver, with emphasis on the modulation of the different vitellogenin isoforms. In males, key signals regulating spermatogenesis were investigated. Results demonstrated that in fish exposed to the combination of BPA and probiotic, most of the transcripts were closer to C or P levels, supporting the hypothesis of SLAb51 to antagonize BPA toxicity. This study represents the first evidence related to the use of SLAb51 to improve reproduction and open new fields of investigation regarding its use to reduce endocrine disrupting compound impacts on health.

Summary of reference chemicals evaluated by the fish short-term reproduction assay, OECD TG229, using Japanese Medaka, Oryzias latipes

Under the Organisation for Economic Co-operation and Development (OECD), the Ministry of the Environment of Japan (MOE) added Japanese medaka (Oryzias latipes) to the test guideline fish short-term reproduction assay (FSTRA) developed by the United States Environmental Protection Agency (US EPA) using fathead minnow (Pimephales promelas). The FSTRA was designed to detect endocrine disrupting effects of chemicals interacting with the hypothalamic-pituitary-gonadal axis (HPG axis) such as agonists or antagonists on the estrogen receptor (Esr) and/or the androgen receptor (AR) and steroidogenesis inhibitors. We conducted the FSTRA with Japanese medaka, in accordance with OECD test guideline number 229 (TG229), for 16 chemicals including four Esr agonists, two Esr antagonists, three AR agonists, two AR antagonists, two steroidogenesis inhibitors, two progesterone receptor agonists, and a negative substance, and evaluated the usability and the validity of the FSTRA (TG229) protocol. In addition, in vitro reporter gene assays (RGAs) using Esr1 and ARβ of Japanese medaka were performed for the 16 chemicals, to support the interpretation of the in vivo effects observed in the FSTRA. In the present study, all the test chemicals, except an antiandrogenic chemical and a weak Esr agonist, significantly reduced the reproductive status of the test fish, that is, fecundity or fertility, at concentrations where no overt toxicity was observed. Moreover, vitellogenin (VTG) induction in males and formation of secondary sex characteristics (SSC), papillary processes on the anal fin, in females was sensitive endpoints to Esr and AR agonistic effects, respectively, and might be indicators of the effect concentrations in long-term exposure. Overall, it is suggested that the in vivo FSTRA supported by in vitro RGA data can adequately detect effects on the test fish, O. latipes, and probably identify the mode of action (MOA) of the chemicals tested.

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.

Endocrine Disruptors Acting on Estrogen and Androgen Pathways Cause Reproductive Disorders through Multiple Mechanisms: A Review

Increasing contamination of the environment by toxic compounds such as endocrine disrupting chemicals (EDCs) is one of the major causes of reproductive defects in both sexes. Estrogen/androgen pathways are of utmost importance in gonadal development, determination of secondary sex characteristics and gametogenesis. Most of the EDCs mediate their action through respective receptors and/or downstream signaling. The purpose of this review is to highlight the mechanism by which EDCs can trigger antagonistic or agonistic response, acting through estrogen/androgen receptors causing reproductive defects that lead to infertility. In vitro, in vivo and in silico studies focusing on the impact of EDCs on estrogen/androgen pathways and related proteins published in the last decade were considered for the review. PUBMED and PUBCHEM were used for literature search. EDCs can bind to estrogen receptors (ERα and ERβ) and androgen receptors or activate alternative receptors such as G protein-coupled receptors (GPCR), GPR30, estrogen-related receptor (ERRγ) to activate estrogen signaling via downstream kinases. Bisphenol A, dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, polychlorinated biphenyls and phthalates are major toxicants that interfere with the normal estrogen/androgen pathways leading to infertility in both sexes through many ways, including DNA damage in spermatozoids, altered methylation pattern, histone modifications and miRNA expression.

Integrated use of biomarkers to evaluate the reproductive physiology of Astyanax fasciatus and Hoplias malabaricus males (Teleostei: Characiformes) in polluted reservoirs

The reproductive physiology of fish can be changed by the presence of pollutants in the water, which act as endocrine disrupting compounds (EDC). We evaluated the impacts of water contaminants in polluted reservoirs acting as possible EDC on the reproductive physiology of Astyanax fasciatus and Hoplias malabaricus males. We used biomarkers with different levels of biological organization. Hoplias malabaricus adult males were collected in the summer and winter at five different sites in the Tietê River Basin: the Ponte Nova reservoir (PN), considered a reference site due to the low anthropogenic influence; the Billings reservoir (BIL) at two different branches; and the Guarapiranga reservoir (GUA) at two different branches. Astyanax fasciatus adult males were collected at PN and BIL. BIL and GUA are subjected to great anthropogenic action. We analyzed gonadal histomorphology, testosterone (T), 11-ketotestosterone (11-KT), estradiol (E₂) plasma levels, and gene expression of hepatic vitellogenin (vtgA) and pituitary follicle stimulating hormone (fshβ). In the PN reservoir (reference), the biomarkers analyzed in both species did not differ between the periods analyzed. This is an evidence that the animals keep the same reproductive activity during both seasons. The changes in the plasma concentration of gonadal steroids in both species in polluted reservoirs suggest the presence of EDC compounds in the water and/or adjusts of the physiological setpoint to allow the reproduction in such adverse conditions. The use of vtgA as biomarker suggests the presence of estrogenic compounds, mainly in BIL, but with a more evident response of H. malabaricus. However, even considering physiological changes, both species present testes during the maturation phase that allow the reproduction in an environment with a high degree of pollution.

Effects of Di-Isononyl Phthalate (DiNP) on Follicular Atresia in Zebrafish Ovary

Di-isononyl phthalate (DiNP) is a plasticizer reported to elicit hormone-like activity and disrupt metabolism and reproduction in fish and other vertebrates. In general, phthalates have been used at high concentrations beyond reported environmental levels to assess their adverse effects on fish gonadal physiology. The present study exposed adult female zebrafish to a wide range of DiNP concentrations [0.42 µg L^-1 (10^-9 M), 4.2 µg L^-1 (10^-8 M), and 42 µg L^-1 (10^-7 M)] for 21 days. We evaluated gene expression profiles related to apoptosis, autophagy, and oxidative stress; DNA fragmentation (TUNEL assay: terminal deoxynucleotidyl transferase dUTP nick end labeling) and caspase activity (CAS3) were also examined. Exposure to 0.42 and 4.2 µg L^-1 upregulated the genes coding for tnfa and baxa, sod1, prkaa1, respectively. CAS3 immunohistochemistry revealed a higher number of positive vitellogenic oocytes in ovaries exposed to 0.42 µg L^-1. Subsequently, we examined the relationship between CAS3 signaling and DNA fragmentation. Accordingly, DNA fragmentation was observed in vitellogenic follicles of fish exposed to 0.42 and 4.2 μg L^-1. Our results demonstrate that follicular atresia can occur after exposure to environmental levels of DiNP for 21 days, which may adversely affect the reproductive performance of female zebrafish in a non-monotonic manner.

Fish reproductive biology - Reflecting on five decades of fundamental and translational research

Driven by the broad diversity of species and physiologies and by reproduction-related bottlenecks in aquaculture, the field of fish reproductive biology has rapidly grown over the last five decades. This review provides my perspective on the field during this period, integrating fundamental and applied developments and milestones. Our basic understanding of the brain-pituitary-gonadal axis led to overcoming the failure of farmed fish to ovulate and spawn in captivity, allowing us to close the fish life cycle and establish a predictable, year-round production of eggs. Dissecting the molecular and hormonal mechanisms associated with sex determination and differentiation drove technologies for producing better performing mono-sex and reproductively-sterile fish. The growing contingent of passionate fish biologists, together with the availability of innovative platforms such as transgenesis and gene editing, as well as new models such as the zebrafish and medaka, have generated many discoveries, also leading to new insights of reproductive biology in higher vertebrates including humans. Consequently, fish have now been widely accepted as vertebrate reproductive models. Perhaps the best testament of the progress in our discipline is demonstrated at the International Symposia on Reproductive Physiology of Fish (ISRPF), at which our scientific family has convened every four years since the grandfather of the field, the late Ronald Billard, organized the inaugural 1977 meeting in Paimpont, France. As the one person who has been fortunate enough to attend all of these meetings since their inception, I have witnessed first-hand the astounding evolution of our field as we capitalized on the molecular and biotechnological revolutions in the life sciences, which enabled us to provide a higher resolution of fish reproductive and endocrine processes, answer more questions, and dive into deeper comprehension. Undoubtedly, the next (five) decades will be similarly exciting as we continue to integrate physiology with genomics, basic and translational research, and the small fish models with the aquacultured species.

Bisphenol A impairs reproductive fitness in zebrafish ovary: Potential involvement of oxidative/nitrosative stress, inflammatory and apoptotic mediators

Bisphenol A (BPA) is a highly pervasive chemical in consumer products with its ascribed endocrine-disrupting properties. Several studies have shown the cytotoxic, genotoxic, and carcinogenic property of BPA over a multitude of tissues. Although BPA exposure has earlier been implicated in female infertility, the underlying molecular mechanisms explaining the toxicity of BPA in the ovary remains less understood. In the present study, a plausible correlation between redox balance or inflammatory signaling and reproductive fitness upon BPA exposure has been examined in zebrafish (Danio rerio) ovary. Congruent with significant alteration of major antioxidant enzymes (SOD1, SOD2, catalase, GPx1α, GSTα1) at the transcript level, 30 d BPA exposure at environmentally relevant concentrations (1, 10 and 100 μg L^-1) promotes ovarian ROS/RNS synthesis, lipid peroxidation but attenuates catalase activity indicating elevated stress response. BPA promotes a sharp increase in ovarian p38 MAPK, NF-κB phosphorylation (activation), inducible nitric oxide synthase (Nos2a), and pro-inflammatory cytokines (TNF-α and IL-1β) expression, the reliable markers for inflammatory response. Congruent to an increased number of atretic follicles, BPA-exposed zebrafish ovary reveals elevated Bax/Bcl2 ratio, activation of caspase-8, -3 and DNA breakdown suggesting heightened cell death. Importantly, significant alteration in nuclear estrogen receptor (ER) transcripts (esr1, esr2a, and esr2b) and proteins (ERα, ERβ), gonadotropin receptors, and markers associated with steroidogenesis and growth factor gene expression in BPA-exposed ovary correlates well with impaired ovarian functions and maturational response. Collectively, elevated oxidative/nitrosative stress-mediated inflammatory response and altered ER expression can influence ovarian health and reproductive fitness in organisms exposed to BPA environment.

An integrated approach to evaluate port sediment quality: From chemical characterization to multispecies bioassays

Management of dredged sediments results in an environmental and social cost. Based on their level of contamination, they can be intended for beach nourishment or for alternative uses. Sediment quality is established considering their specific chemical contamination level and setting up bioassays to evaluate their toxic effects on living organisms. The integration of these different Line of Evidence (LOE) generates toxicity indexes, the Hazard Chemical Quotient (HQc), and the Hazard Ecotoxicological Quotient (HQe), which are further elaborated using the SediQualSoft software, finally providing evidence on the levels of sediment contamination. In this study, four different dredged sediments were analysed. Except for one, which was sampled in a reference area, the others were assigned to the same class of toxicity, despite they presented different levels of chemical and ecotoxicological toxicity. As a novelty, this study introduces transcriptomics as a new LOE, to provide a new tool to better categorize sediment toxicity. C. gigas embryos were exposed to sediment elutriates, sampled at 5 and 18 h post-fertilization (hpf), and the expression of a set of genes involved in immune and stress response (hsp70, gpx, sod, dehf1, galectin, lysozyme, tg) was analysed by Real-time PCR. Molecular results suggested that the 18 hpf stage represents a sensitive window of exposure during development and can be suggested as a critical time point for ecotoxicity studies. Finally, by multivariate statistical analysis, integrating the well-established LOEs with molecular data, it was demonstrated that transcriptomics could be a useful and novel LOE with the ability to provide greater accuracy in the assessment of sediment toxicity.

Exposure to 4-nonylphenol induces a shift in the gene expression of gsdf and testis-ova formation and sex reversal in Japanese medaka (Oryzias latipes)

The branched isomer mixture 4-nonylphenol (4-NP) has been used worldwide as a surfactant, and can have endocrine-disrupting effects on aquatic organisms. For instance, 4-NP induces the formation of testis-ova (i.e., testicular and ovarian tissue in the same gonad) or male to female sex reversal of various teleost fishes. Recently, our group revealed that altered gsdf gene expression is associated with disruption of gonadal differentiation in Japanese medaka (Oryzias latipes) embryos exposed to methyltestosterone or bisphenol A, suggesting that gsdf might be useful as a biomarker for predicting the impact of endocrine-disrupting chemicals (EDCs) on gonadal differentiation. Here, we used 4-NP to examine further whether gsdf expression at the embryo stage is useful for predicting EDC impact on gonadal sex differentiation. When fertilized medaka eggs were exposed to 32 or 100 μg/L 4-NP, testis-ova in genetic males and sex reversal from genetic male to phenotypic female were observed. At stage 38 (just before hatching), 4-NP exposure at 1-100 μg/L did not affect gsdf expression in XX embryos compared with the nontreated control; however, in XY embryos, the gsdf expression in the 100 μg/L-exposed group was significantly lower than that in the controls. The 4-NP concentration at which gsdf expression was suppressed was equal to that at which testis-ova and sex reversal were induced. These results indicate that expression of the gsdf gene at the embryonic stage in medaka is a useful biomarker for predicting the impact of EDCs on sexual differentiation.

Occurrence of selected endocrine disrupting compounds in the eastern cape province of South Africa

Endocrine-disrupting compounds are attracting attention worldwide because of their effects on living things in the environment. Ten endocrine disrupting compounds: 4-nonylphenol, 2,4-dichlorophenol, estrone, 17β-estradiol, bisphenol A, 4-tert-octylphenol, triclosan, atrazine, imidazole and 1,2,4-triazole were investigated in four rivers and wastewater treatment plants in this study. Rivers were sampled at upstream, midstream and downstream reaches, while the influent and effluent samples of wastewater were collected from treatment plants near the receiving rivers. Sample waters were freeze-dried followed by extraction of the organic content and purification by solid-phase extraction. Concentrations of the compounds in the samples were determined with ultra-high performance liquid chromatography-tandem mass spectrometry. The instrument was operated in the positive electrospray ionization (ESI) mode. The results showed that these compounds are present in the samples with nonylphenol > dichlorophenol > bisphenol A > triclosan > octylphenol > imidazole > atrazine > triazole > estrone > estradiol. Nonylphenol has its highest concentration of 6.72 μg/L in King Williams Town wastewater influent and 2.55 μg/L in midstream Bloukrans River. Dichlorophenol has its highest concentration in Alice wastewater influent with 2.20 μg/L, while it was 0.737 μg/L in midstream Bloukrans River. Uitenhage wastewater effluent has bisphenol A concentration of 1.684 μg/L while it was 0.477 μg/L in the downstream samples of the Bloukrans River. Generally, the upstream samples of the rivers had lesser concentrations of the compounds. The wastewater treatment plants were not able to achieve total removal of the compounds in the wastewater while runoffs and wastes dump from the cities contributed to the concentrations of the compounds in the rivers.

Gamete quality in a multistressor environment

Over the past few decades, accumulated evidence confirms that the global environment conditions are changing rapidly. Urban industrialization, agriculture and globalization have generated water, air and soil pollution, giving rise to an environment with a growing number of stress factors, which has a serious impact on the fitness, reproduction and survival of living organisms. The issue raises considerable concern on biodiversity conservation, which is now at risk: it is estimated that a number of species will be extinct in the near future. Sexual reproduction is the process that allows the formation of a new individual and is underpinned by gamete quality defined as the ability of spermatozoa and oocytes to interact during fertilization leading to the creation and development of a normal embryo. This review aimed to provide the current state of knowledge regarding the impact of a broad spectrum of environmental stressors on diverse parameters used to estimate and evaluate gamete quality in humans and in canonical animal models used for experimental research. Effects of metals, biocides, herbicides, nanoparticles, plastics, temperature rise, ocean acidification, air pollution and lifestyle on the physiological parameters that underlie gamete fertilization competence are described supporting the concept that environmental stressors represent a serious hazard to gamete quality with reproductive disorders and living organism failure. Although clear evidence is still limited, gamete capacity to maintain and/or recover physiological conditions is recently demonstrated providing further clues about the plasticity of organisms and their tolerance to the pressures of pollution that may facilitate the reproduction and the persistence of species within the scenario of global change. Changes in the global environment must be urgently placed at the forefront of public attention, with a massive effort invested in further studies aimed towards implementing current knowledge and identifying new methodologies and markers to predict impairment of gamete quality.

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.

Androgen signaling in male fishes: Examples of anti-androgenic chemicals that cause reproductive disorders

Similar to other vertebrates, androgens regulate spermatogenesis in fishes. In teleosts, the main androgen is 11-Ketotestosterone (11-KT), which is oxidized testosterone (T) at the C₁₁ position. Compared to T, 11-KT is a nonaromatizable steroid, and does not convert to 17β-estradiol. However, circulatory levels of both T and 11-KT undergo seasonal variations along with testicular development. Physiological functions of androgens are mediated via androgen receptor (Ar). So far, nuclear Ar and membrane Ar have been identified in fishes. In the present study, we reviewed androgen biosynthesis in fishes, compared molecular structure of nuclear Ar in models of mammals and fishes, and investigated the mechanisms of action of environmental contaminants that differentially disrupt androgen signaling in fish reproduction. In the latter case, the adverse effects of vinclozolin (VZ) and bis(2-ethylhexyl) phthalate (DEHP) are compared. Both VZ and DEHP are capable of decreasing sperm quality in males. Vinclozolin causes an increase in 11-KT production associated with increases in kisspeptin (kiss-1) and salmon gonadotropin-releasing hormone (gnrh3) mRNA levels as well as circulatory levels of luteinizing hormone (Lh). In contrast, DEHP inhibits 11-KT production associated with a decrease in circulatory Lh levels. However, DEHP-inhibited 11-KT production is not associated with changes in kiss-1 and gnrh3 mRNA levels. Studies also show that VZ alters ar mRNA levels, while DEHP is without effect. These suggest that VZ and DEHP act differentially to cause androgen-dependent reproductive disorder in male fishes. Molecular analyses of the nuclear AR show that both DNA and ligand binding domains (DBD and LBD, respectively) are highly conserved within models of mammals and fishes. A phylogeny tree of the AR shows distinct clusters between mammals and fishes. In fishes, subtypes of Arα and Arβ are also separated in distinct clusters. Thus, further studies need to generate ar knockout fish model to better elucidate androgen regulation of reproduction in fishes via Ar.

Toxic effects of single animal hormones and their mixtures on the growth of Chlorella vulgaris and Scenedesmus armatus

In their environments, aquatic organisms are simultaneously exposed to mixtures of several endocrine disrupting compounds, including hormones. However, most of the toxicity studies so far focused on effects of single contaminants. The available information on the potential toxicity of combined hormones on microalgae is extremely limited. For these reasons the aim of this study was to evaluate the individual and mixture effect of estrone (E1), ß-estradiol (E2), estriol (E3), 17-α-ethinylestradiol (EE2), progesterone (PRO), 5-pregnen-3β-ol-20-one (PRE), levonorgestrel (LG) and testosterone (TST) on Chlorella vulgaris and Scenedesmus armatus. Green algae cells were exposed to different concentrations (0.1-100 mg L^-1) of hormones for 14 days. Biomass in the form of dry weight and chlorophyll a was examined. The decreasing order of toxicity (based on EC₅₀, 14d) to Chlorella vulgaris and Scenedesmus armatus was: EE2>PRO > E2>PRE > TST > E3>LG > E1 and EE2>PRO > TST > E2>PRE > LG > E1>E3, respectively. Chlorella vulgaris was more sensitive to the effects of hormones than Scenedesmus armatus. Although mixed hormones were more toxic to green algae than single hormones, in the ecosystem mixtures can pose higher ecological risk than single pollutants. Therefore, data on the toxicology of both single and mixed hormones is very valuable for assessment of the possibility of adverse ecological effects caused by these pollutants. Furthermore, these results suggest that environmental exposure to hormone mixtures may cause toxicity levels different to the sum of those of the single hormones and provides a basic understanding of their toxic effect on algae.

Lipid Metabolism Alteration by Endocrine Disruptors in Animal Models: An Overview

Exposure to potential Endocrine Disrupting Chemicals (EDCs) pose a documented risk to both wildlife and human health. Many studies so far described declining sperm counts, genital malformations, early puberty onset, highlighting the negative impact on reproduction caused by the exposure to many anthropogenic chemicals. In the last years, increasing evidence suggested that these compounds, other than altering reproduction, affect metabolism and induce the onset of obesity and metabolic disorders. According to the "environmental obesogens" hypothesis, evidence exists that exposure to potential EDCs during critical periods when adipocytes are differentiating, and organs are developing, can induce diseases that manifest later in the life. This review summarizes the effects occurring at the hepatic level in different animal models, describing morphological alterations and changes of molecular pathways elicited by the toxicant exposure. Results currently available demonstrated that these chemicals impair normal metabolic processes via interaction with members of the nuclear receptor superfamily, including steroid hormone receptors, thyroid hormone receptors, retinoid X receptors, peroxisome proliferator-activated receptors, liver X receptors, and farnesoid X receptors. In addition, novel results revealed that EDC exposure can either affect circadian rhythms as well as up-regulate the expression of signals belonging to the endocannabinoid system, in both cases leading to a remarkable increase of lipid accumulation. These results warrant further research and increase the interest toward the identification of new mechanisms for EDC metabolic alterations. The last part of this review article condenses recent evidences on the ability of potential EDCs to cause "transgenerational effects" by a single prenatal or early life exposure. On this regard, there is compelling evidence that epigenetic modifications link developmental environmental insults to adult disease susceptibility. This review will contribute to summarize the mechanisms underlying the insurgence of EDC-induced metabolic alterations as well as to build integrated strategies for their better management. In fact, despite the large number of results obtained so far, there is still a great demand for the development of frameworks that can integrate mechanistic and toxicological/epidemiological observations. This would increase legal and governmental institution awareness on this critical environmental issue responsible for negative consequences in both wild species and human health.

Differential Hepatic Gene Expression Profile of Male Fathead Minnows Exposed to Daily Varying Dose of Environmental Contaminants Individually and in Mixture

Environmental contaminants are known to impair reproduction, metabolism and development in wild life and humans. To investigate the mechanisms underlying adverse effects of contaminants, fathead minnows were exposed to a number of endocrine disruptive chemicals (EDCs) including Nonylphenol (NP), bisphenol-A (BPA), Di(2-ethylhexyl) phthalate (DEHP), and a mixture of the three chemicals for 21 days, followed by determination of the liver transcriptome by expression microarrays. Pathway analysis revealed a distinct mode of action for the individual chemicals and their mixture. The results showed expression changes in over 980 genes in response to exposure to these EDC contaminants individually and in mixture. Ingenuity Pathway core and toxicity analysis were used to identify the biological processes, pathways and the top regulators affected by these compounds. A number of canonical pathways were significantly altered, including cell cycle & proliferation, lipid metabolism, inflammatory, innate immune response, stress response, and drug metabolism. We identified 18 genes that were expressed in all individual and mixed treatments. Relevant candidate genes identified from expression microarray data were verified using quantitative PCR. We were also able to identify specific genes affected by NP, BPA, and DEHP individually, but were also affected by exposure to the mixture of the contaminants. Overall the results of this study provide novel information on the adverse health impact of contaminants tested based on pathway analysis of transcriptome data. Furthermore, the results identify a number of new biomarkers that can potentially be used for screening environmental contaminants.