Bisphenol A in Eggs Impairs the Long-Term Stress Performance of Rainbow Trout in Two Generations

Salmonids are ecologically, economically, and culturally important fish species in North America, but whether contaminants in the environment play a role in their population decline is unclear. We tested the hypothesis that bisphenol A (BPA) deposition in eggs, mimicking a maternal transfer scenario, compromises the stress axis functioning and target tissues stress response in two generations of a model salmonid species, rainbow trout ( Oncorhynchus mykiss). Eggs were enriched with 0, 4, or 40 ng of BPA, fertilized, and reared in clean water for two generations. The fish were subjected to an acute stressor after a year in both generations to test their stress performances. Trout raised from BPA-enriched eggs showed impaired stressor-mediated plasma cortisol and lactate response in the F1 and F2 generations, respectively. Key genes involved in cortisol biosynthesis in the head kidney, as well as stress- and growth-related transcripts in the liver and muscle, were impacted either in the F1 and/or F2 generations. Our results underscore the long-term impact associated with BPA in eggs, mimicking a maternal transfer scenario, on the stress performance of trout in two generations. The results highlight the need for developing novel biomarkers to predict long-term and generational toxicities in salmonids.

Effects of the bioconcentration and parental transfer of environmentally relevant concentrations of difenoconazole on endocrine disruption in zebrafish (Danio rerio)

Difenoconazole, a typical triazole fungicide, inhibits lanosterol-14R-demethylase (CYP51) to prevent fungal sterol synthesis and its residues are frequently detected in the environment due to its wide application. Previous studies have demonstrated that difenoconazole altered the triglyceride levels, and gene expression relevant to cholesterol biosynthesis in zebrafish. However, endocrine-disruption in the hypothalamus-pituitary-gonadal-liver (HPGL) axis, the effects of transferring to offspring, and the underlying mechanisms of difenoconazole in aquatic organisms are still unknown. In this study, we defined the effects of difenoconazole at environmental concentrations on endocrine disturbance using zebrafish as an experimental model. The results indicated that difenoconazole induced a significant change in the somatic index, and pathological variations in tissues, and steroid hormone levels. RT-PCR experiments further confirmed that difenoconazole significantly induced expression alteration of lhr, hsd3β, hsd11β, cyp19a in the ovary and star, cyp19a, cyp3c1 in the testis, and erα genes in livers. In addition, difenoconazole exposure in parental zebrafish affected the hatchability and length of its offspring. Moreover, the burdens of difenoconazole and difenoconazole alcohol in females were higher than in males. These findings highlighted that difenoconazole exposure at environmentally relevant concentrations elicited estrogenic endocrine-disruption effects via altering homeostasis of sex steroid hormones in the HPGL axis and the adverse effects can be transferred to the offspring.

Exposure to wastewater effluent affects fish behaviour and tissue-specific uptake of pharmaceuticals

Pharmaceutical active compounds (PhACs) are increasingly being reported in wastewater effluents and surface waters around the world. The presence of these products, designed to modulate human physiology and behaviour, has created concern over whether PhACs similarly affect aquatic organisms. Though laboratory studies are beginning to address the effects of individual PhACs on fish behaviour, few studies have assessed the effects of exposure to complex, realistic wastewater effluents on fish behaviour. In this study, we exposed a wild, invasive fish species-the round goby (Neogobius melanostomus)-to treated wastewater effluent (0%, 50% or 100% effluent dilutions) for 28days. We then determined the impact of exposure on fish aggression, an important behaviour for territory acquisition and defense. We found that exposure to 100% wastewater effluent reduced the number of aggressive acts that round goby performed. We complimented our behavioural assay with measures of pharmaceutical uptake in fish tissues. We detected 11 of 93 pharmaceutical compounds that we tested for in round goby tissues, and we found that concentration was greatest in the brain followed by plasma, then gonads, then liver, and muscle. Fish exposed to 50% and 100% effluent had higher tissue concentrations of pharmaceuticals and concentrated a greater number of pharmaceutical compounds compare to control fish exposed to no (0%) effluent. Exposed fish also showed increased ethoxyresorufin-O-deethylase (EROD) activity in liver tissue, suggesting that fish were exposed to planar halogenated/polycyclic aromatic hydrocarbons (PHHs/PAHs) in the wastewater effluent. Our findings suggest that fish in effluent-dominated systems may have altered behaviours and greater tissue concentration of PhACs. Moreover, our results underscore the importance of characterizing exposure to multiple pollutants, and support using behaviour as a sensitive tool for assessing animal responses to complex contaminant mixtures, like wastewater effluent.

Bisphenol A in eggs causes development-specific liver molecular reprogramming in two generations of rainbow trout

Bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins and is prevalent in the aquatic environment. BPA disrupts endocrine pathways in fish, but the long-term developmental implications are unknown. We demonstrate that BPA deposition in the eggs of rainbow trout (Oncorhynchus mykiss), an ecologically and economically important species of fish, reprograms liver metabolism in the offspring and alters the developmental growth trajectory in two generations. Specifically, BPA reduces growth during early development, followed by a catch-up growth post-juveniles. More importantly, we observed a developmental shift in the liver transcriptome, including an increased propensity for protein breakdown during early life stages to lipid and cholesterol synthesis post- juveniles. The liver molecular responses corresponded with the transient growth phenotypes observed in the F1 generation, and this was also evident in the F2 generation. Altogether, maternal and/or ancestral embryonic exposure to BPA affects liver metabolism leading to development-distinct effects on growth, underscoring the need for novel risk assessment strategies for this chemical in the aquatic environment. This is particularly applicable to migratory species, such as salmon, where distinct temporal changes in growth and physiology during development are critical for their spawning success.

Maternal transfer of bisphenol A impacts the ontogeny of cortisol stress response in rainbow trout

Bisphenol A (BPA) is widespread in the aquatic environment, and early life-stage exposure to this chemical affects growth and development in fish. We tested the hypothesis that BPA accumulation in eggs, mimicking maternal transfer, impacts the development and function of the hypothalamus-pituitary-interrenal (HPI) axis in rainbow trout (Oncorhynchus mykiss). To mimic maternal transfer, oocytes were loaded with 0 (control), 1, 4 and 40ng BPA embryo(-1). We measured the temporal changes in whole body cortisol content, transcript levels of corticosteroidogenesis-related genes and glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) protein expressions during early development. In addition, trout larvae were subjected to an acute stressor at key developmental stages (at hatch, just prior to first feed and post hatch) and whole body cortisol levels measured to assess the functional integrity of the HPI axis. The developmental profile of whole body cortisol content was altered in the 1 and 40ng BPA groups compared to the control group. Also, the two key rate-limiting steps in steroidogenesis, the steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage (P450scc) enzyme transcript levels were disrupted in the larvae originating from BPA accumulated eggs prior to first feed. Whole body GR and MR protein expressions were higher in the 40ng BPA group compared to other groups prior to first feed. Stressor-induced elevation in whole body cortisol levels were evident at 65 days post-fertilization (dpf) and later, but not at 42 dpf in trout larvae. This cortisol response to a stressor exposure was attenuated in the 4 and 40ng BPA groups at 65 dpf, but not at 140 dpf. Together, accumulation of BPA in eggs, mimicking maternal transfer of this chemical, disrupts the ontogeny of cortisol stress response in trout larvae and may compromise the target tissue responsiveness to cortisol stimulation during early development.

Global Assessment of Bisphenol A in the Environment: Review and Analysis of Its Occurrence and Bioaccumulation

Because bisphenol A (BPA) is a high production volume chemical, we examined over 500 peer-reviewed studies to understand its global distribution in effluent discharges, surface waters, sewage sludge, biosolids, sediments, soils, air, wildlife, and humans. Bisphenol A was largely reported from urban ecosystems in Asia, Europe, and North America; unfortunately, information was lacking from large geographic areas, megacities, and developing countries. When sufficient data were available, probabilistic hazard assessments were performed to understand global environmental quality concerns. Exceedances of Canadian Predicted No Effect Concentrations for aquatic life were >50% for effluents in Asia, Europe, and North America but as high as 80% for surface water reports from Asia. Similarly, maximum concentrations of BPA in sediments from Asia were higher than Europe. Concentrations of BPA in wildlife, mostly for fish, ranged from 0.2 to 13 000 ng/g. We observed 60% and 40% exceedences of median levels by the US Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey in Europe and Asia, respectively. These findings highlight the utility of coordinating global sensing of environmental contaminants efforts through integration of environmental monitoring and specimen banking to identify regions for implementation of more robust environmental assessment and management programs.

Bisphenol A accumulation in eggs disrupts the endocrine regulation of growth in rainbow trout larvae

Bisphenol A (BPA), a monomer used in the production of plastics and epoxy resins, is ubiquitously present in the aquatic environment. BPA is considered a weak estrogen in fish, but the effects of this chemical on early developmental events are far from clear. We tested the hypothesis that BPA accumulation in eggs, mimicking maternal transfer, disrupts growth hormone/insulin-like growth factor (GH/IGF) axis function, leading to defects in larval growth in rainbow trout. Trout oocytes were exposed to 0 (control), 0.3, 3, and 30 μg ml(-1) BPA for 3h, which led to an accumulation of around 0, 1, 4 and 40 ng BPA per egg, respectively. All treatment groups were fertilized with clean milt and reared in clean water for the rest of the experiment. The embryo BPA content declined over time in all groups and was completely eliminated by 42 days post-fertilization (dpf). Hatchlings from BPA accumulated eggs had higher water content and reduced total energy levels prior to first feed. There was an overall reduction in the specific growth rate and food conversion ratio in larvae reared from BPA-laden eggs. BPA accumulation disrupted the mRNA abundance of genes involved in GH/IGF axis function, including GH isoforms and their receptors, IGF-1 and -2 and IGF receptors, in a life stage-dependent manner. Also, there was a temporal disruption in the mRNA levels of thyroid hormone receptors in the larvae raised from BPA-laden eggs. Altogether, BPA accumulation in eggs, mimicking maternal transfer, affects larval growth and the mode of action involves disruption of genes involved in the GH/IGF and thyroid axes function in trout.

Distribution of feminizing compounds in the aquatic environment and bioaccumulation in wild tilapia tissues

This study sampled six times of river water, sediment, and tilapia (Oreochromis niloticus) in the Dan-Shui River, Taipei, Taiwan; 10 feminizing compounds were analyzed using ultra-performance liquid chromatography-tandem mass spectrometry. Bisphenol A (508 ± 634 ng/L, geometric mean (GM) 303 ng/L) and nonylphenol (491 ± 570 ng/L, GM 328 ng/L) were the most abundant among analytes in the river water. Nonylphenol (770 ± 602 ng/g wet weight, GM 617 ng/g wet weight) was also the highest in sediment. Fish may uptake nonylphenol and nonylphenol ethoxylates from river water and sediment because there were significant correlations between the concentrations in these matrixes and those in fish tissues (r s ranged from 0.21 to 0.49, p < 0.05). The bioaccumulation of nonylphenol, nonylphenol ethoxylates and bisphenol A in gonad, eggs, and liver was much higher than that in muscle (e.g. mean bioaccumulation factors of nonylphenol were 27,287, 20,971, 9,576 and 967, respectively) and might result in low liver fractions in fish body weights (0.66 % ± 0.39 %, GM 0.55 %) and the skewed sex ratio of fish (male to female = 0.52). This innovative study linked the environmental and internal doses statistically in the globally distributed wild fish by analyzing feminizing compounds in water, sediment, and four fish tissues including gonad and eggs.

Effects of bisphenol s exposure on endocrine functions and reproduction of zebrafish

While bisphenol S (BPS) has been frequently detected both in environment and biota, limited information is available on their effects of endocrine system. In the present study, adult zebrafish pairs were exposed to 0.5, 5, and 50 μg/L of BPS for 21 d, and the effects on reproduction, sex steroid hormones, and transcription of the genes belonging to the hypothalamic-pituitary-gonad (HPG) axis were investigated. The adverse effects on performances of F1 generation were further examined with or without subsequent exposure to BPS. Egg production and the gonadosomatic index in female fish were significantly decreased at ≥0.5 μg/L BPS. Plasma concentrations of 17β-estradiol were significantly increased in both male and female fish. In male fish, however, significant decreases of testosterone concentration were observed along with up-regulation of cyp19a and down-regulation of cyp17 and 17βhsd transcripts. Parental exposure to BPS resulted in delayed and lesser rates of hatching even when they were hatched in clean water. Continuous BPS exposure in the F1 embryos resulted in worse hatchability and increased malformation rates compared to those without BPS exposure. Our observations showed that exposure to low level BPS could affect the feedback regulatory circuits of HPG axis and impair the development of offspring.