The chronic effects of lignin-derived bisphenol and bisphenol A in Japanese medaka Oryzias latipes

Long-term exposure to bisphenol-A causes oxidative stress-related alterations at the genetic and cellular levels in the mature ovary of adult zebrafish

Bisphenol-A (BPA) is categorized as a major endocrine-disrupting chemical (EDC) used to manufacture many plastic products. BPA affects reproductive performance and promotes infertility by causing hormonal imbalance, mitochondrial dysfunction, and altered gene expression. The present investigation aimed to evaluate the effects of BPA exposure for 28 days on the activity or level of antioxidant response elements (AREs), mRNA expressions of antioxidant genes, and histomorphological changes in the ovary of adult zebrafish. The adult female zebrafish were randomly divided into four experimental groups, viz. control, vehicle (0.01% ethanol), low dose (BPA: 350 µg/L), and high dose (BPA: 700 µg/L) exposure groups. After BPA exposure in both groups, superoxide dismutase (SOD) activity and total antioxidant capacity (TAC) level were significantly (p < 0.05) decreased in the zebrafish ovary. Whereas, catalase (CAT) activity and malondialdehyde (MDA) level were significantly (p < 0.05) increased in both treatment groups. The sod mRNA expression was significantly (p < 0.05) down-regulated in the high-dose BPA-exposed group. Whereas, cat and nuclear factor erythroid 2-related factor 2 (nrf2) mRNA expressions were significantly (p < 0.05) up-regulated in both BPA-treated groups. Noticeable histomorphological alterations were recorded in the ovary of zebrafish exposed to low and high doses of BPA. The alterations in the activity of ARE, mRNA expressions of antioxidant genes, and histopathological changes suggest that exposure to BPA can cause endocrine disruption and damage to the ovary of adult zebrafish caused by oxidative stress.

Correlation of oxidative stress enzymes and histological alteration in the gastrointestinal tract of Clarias gariepinus induced with alpha olefin sulfonate

This study examined antioxidant system responses and gastrointestinal pathological changes related to alpha olefin sulfonate (α-OS) toxicity in generated oxidative stress. Clarias gariepinus, self-bred fish, including the control, were exposed to α-OS concentrations observed in the field (0.05, 0.10, 0.15, and 0.20 mg/l) for 30 days. Sigma-Aldrich test kits were used to assess reduced glutathione S-transferase (GST) spectrophotometrically, while abnormal changes or damage in the gastrointestinal tract (GIT) were examined under a microscope. In plasma, α-OS exposure increased GST activities by 73%, varying with dose and duration. Glutathione (GSH) activity decreased by 26% but had few impacts. Increasing α-OS concentration and exposure duration led to histopathologic damage in the GIT, while the control fish had a normal GIT architecture. Fish absorb surfactants easily through their skin and gills, and blood circulates them to their organs. Fish contamination lowers human resistance by altering numerous enzymes through the food chain. When other contaminants are present in high amounts, the combined toxicity damages biota more than either pollutant alone. Any detergent contamination in coastal waters should be addressed seriously because the organisms that are low on the food chain and other sensitive ones will be eliminated even at low concentrations.

Exposure and hazard of bisphenol A, S and F: a multi-biomarker approach in three-spined stickleback

Due to the estrogenic behavior of bisphenol (BP) A, industries have developed many substitutes, such as BPS and BPF. However, due to their structural similarities, adverse effects on reproduction are currently observed in various organisms, including fish. Even if new results have shown impacts of these bisphenols on many other physiological functions, their mode of action remains unclear. In this context, we proposed to better understand the impact of BPA, BPS, and BPF on immune responses (leucocyte sub-populations, cell death, respiratory burst, lysosomal presence, and phagocytic activity) and on biomarkers of metabolic detoxification (ethoxyresorufin-O-deethylase, EROD, and glutathione S-transferase, GST) and oxidative stress (glutathione peroxidase, GPx, and lipid peroxidation with thiobarbituric acid reactive substance method, TBARS) in an adult sentinel fish species, the three-spined stickleback. In order to enhance our understanding of how biomarkers change over time, it is essential to determine the internal concentration responsible for the observed responses. Therefore, it is necessary to explore the toxicokinetics of bisphenols. Thus, sticklebacks were exposed either to 100 μg/L of BPA, BPF or BPS for 21 days, or for seven days to 10 and 100 μg/L of BPA or BPS followed by seven days of depuration. Although BPS has very different TK, due to its lower bioaccumulation compared to BPA and BPF, BPS affect oxidative stress and phagocytic activity in the same way. For those reasons, the replacement of BPA by any substitute should be made carefully in terms of risk assessment on aquatic ecosystems.

Growth and reproductive toxicity of bisphenol A in Oikopleura dioica at environmentally relevant concentrations

Bisphenol A (BPA), a known endocrine disruptor, is ubiquitous in various aquatic environments. Appendicularians are among the most abundant mesozooplankton populations and occupy a crucial niche in marine ecosystems. However, no toxicological data are available concerning the effects of BPA on this functional group. In this study, an evaluation of the toxicity of environmentally relevant levels of BPA (2.5-150 μg/L) on the appendicularian Oikopleura dioica, including its morphology and transcriptome, was conducted. Our results demonstrated the high sensitivity of O. dioica to BPA, with a LC50 of 142 μg/L. Exposure to 125 μg/L BPA significantly inhibited the somatic growth, gonadal development and reproduction of individuals, whereas exposure to an environmentally safe concentration (2.5 μg/L) affected female fecundity and fitness as well as male gene expression. The results of the transcriptomic analysis suggest that males were more sensitive to BPA stress at the molecular level. BPA exposure not only led to abnormal secretion of digestive enzymes and phospholipase A2, affecting the function of the digestive system and arachidonic acid but also significantly down-regulated the expression of mRNAs related to enzymes involved in carbohydrate and energy metabolism in males. These findings suggest that the current safe environmental concentrations may not be safe.

Negligible additive effect of environmental concentrations of fragmented polyethylene terephthalate microplastics on the growth and reproductive performance of Java medaka exposed to 17β-estradiol and bisphenol A

To investigate whether environmental concentrations of fragmented polyethylene terephthalate (PET) microplastics (MPs) have additional or combined effects on endocrine-disrupting activity, Java medaka (Oryzias javanicus) were exposed to 17β-estradiol (E2; 5, 10, 50, and 100 ng L-1), bisphenol A (BPA; 5, 10, 50, and 100 µg L-1), and E2 and BPA combined with PET MPs (1 and 100 particles L-1) for 200 days. The growth parameters, such as body length and weight, were significantly decreased by the highest concentrations of E2 and BPA. A significant reduction in egg production was observed in female fish exposed to BPA, with an additive toxic effect of PET MPs. A female-biased sex ratio was observed in fish exposed to both chemicals. Exposure to E2 significantly increased the hepatosomatic index (HSI) in both sexes, while no significant effect was observed in the gonadosomatic index (GSI). Exposure to BPA significantly increased the HSI in female fish and decreased the GSI in both sexes of fish. An additive effect of PET MPs was observed on the GSI value of female exposed to BPA. Significant elevations in vitellogenin (VTG) levels were observed in both sexes due to exposure to E2 and BPA. Additive effects of PET MPs were observed on VTG levels in males exposed to E2 and BPA. Taken together, even long-term treatment with PET MPs induced only a negligible additive effect on the endocrine-disrupting activity in Java medaka at environmentally relevant concentrations.

Multiple-biomarker approach in the assessment of bisphenol A effect on the grooved carpet clam Ruditapes decussatus (Linnaeus, 1758)

BACKGROUND

Bisphenol A (BPA), a plastic additive monomer, is among the most highly produced chemicals worldwide, and is broadly used in many industries, such as food and beverage containers, milk bottles, and paper products. Previous studies demonstrated that BPA has potential toxicity to aquatic organisms, causing endocrine disturbance and behavioural disorders. The current work aimed to determine the toxic impacts of BPA on the edible marine clam Ruditapes decussatus considering a multi-biomarker approach (mortality, biochemical studies, DNA strand breaks using comet assay, and histopathological examinations with semi-quantitative and quantitative histopathological analyses). The clams were exposed under laboratory conditions to three concentrations of BPA (0 "control", 1, and 5 µg/L) for a period of 21 days. After the exposure period, BPA impacts were assessed in the digestive gland as a versatile and environmentally relevant organ for ecotoxicological studies.

RESULTS

In BPA-treated clams, mortality (10%) occurred only at the highest BPA concentration (5 µg/L). Biochemical impairments were detected in a concentration-dependent manner as a consequence of BPA exposure. There were significant increases in malondialdehyde (MDA) and glutathione (GSH) levels, while catalase (CAT) activity was significantly reduced. Our results revealed that BPA induced neurotoxicity in R. decussatus, as evidenced by the inhibition of acetylcholinesterase (AChE) activity in a dose-dependent manner. Furthermore, DNA damage was strongly induced as BPA levels increased. Additionally, our results have been affirmed by alterations in digestive gland tissues at BPA treatments, which consequently can impair the clam's ability for food absorption; these alterations included mainly atrophic and necrotic digestive tubules, epithelial cell vacuolization, hemocyte infiltration, and intertubular fibrosis. Based on the data obtained from the semi-quantitative and quantitative histopathological analyses, the exposure of the clam's digestive gland to BPA with concentrations of 1 and 5 µg/L for 21 days showed significant histopathological alterations compared with the control clams.

CONCLUSION

The multi-biomarker approach used in the current study proved to be a useful tool for assessing the impact of diphenylmethane compounds, such as BPA. Water-borne BPA causes oxidative stress, neurotoxicity, genotoxicity, and deleterious effects on the clam digestive gland; all of these could deteriorate clam performance and health, causing tissue dysfunction.

Toxicological Impact of Bisphenol A on Females' Reproductive System: Review Based on Experimental and Epidemiological Studies

The study encompassing research papers documented in the last two decades pertaining to the possible influence of bisphenol A (BPA) on the fertility of females are appraised with emphasis on the influence of BPA in reproductive organs (uterus and ovaries) and pregnancy outcomes including discussion on the reproductive process (implantation, estrous cycle, hormone secretion); outcomes reveal a connection amongst BPA and female infertility. Ovary, uterus, and its shape as well as function can alter a person's ability to become pregnant by influencing the hypothalamus-pituitary axis in the ovarian model. Additionally, implantation and the estrous cycle may be affected by BPA. However, more research is warranted to comprehend the underlying action mechanisms and to promptly identify any imminent reproductive harm.

Spatiotemporal distribution, source apportionment, and ecological risk of bisphenol analogues in a highly urbanized river basin

Bisphenol analogues (BPs), as one of the endocrine disruptors, have received wide attention due to their adverse impacts on ecosystems. However, the seasonal spatiotemporal distribution, source apportionment, and ecological risk of BPs in natural basins are poorly understood. Especially in highly urbanized river basins with the extensive economic development and anthropogenic activities threaten these critical but ecologically fragile regions. In this study, field investigations of BPs in the waters of the entire Qinhuai River Basin (QRB) were conducted in June (before the annual flood period) and August (after the annual flood period) 2023. The Qinhuai River, an important primary tributary of the lower Yangtze River, is located in eastern China and the QRB is characterized by a high population density and dense urbanization. Thirty-two sites were sampled for six types of BPs known to be ubiquitous in the surface water of the QRB. Significant differences in the concentrations of those BPs were found. Specifically, the concentration of total BPs (ΣBPs) was significantly higher before than after the flood period: 20.3-472 ng/L (mean = 146 ng/L) and 14.1-105 ng/L (mean = 35.9 ng/L), respectively. BPA was the main contributor to ΣBPs before the flood, and BPB followed by BPA after the flood. ΣBP concentrations were 12-241 % higher downstream than upstream of wastewater treatment plants (WWTPs). The results of a principal component analysis followed by multiple linear regression (PCA-MLR) suggested that untreated wastewater discharge from the WWTPs is an important source of BPs in the basin, with urban rainfall runoff as another potential source after the flood period. An assessment of the ecological risk of BPs, based on a calculation of the risk quotient, showed that BPA and BPS should be given due attention, and overall ecological risk of BPs pose a low risk to local algae but high and medium risks to invertebrates and fish, respectively.

The concentration of dissolved organic matter impacts the neurobehavior in female zebrafish exposed to cyclophosphamide

Cyclophosphamide (CP) is a broad-spectrum anticancer drug for various cancers and frequently detected in aquatic environments, reaching concentrations up to 22 μg/L. However, there is limited understanding of the toxicities of CP with the presence of dissolved organic matter, a ubiquitous component in aquatic environments, in fish. In this study, we investigated the behaviors, morphological alterations of retina, and related gene transcripts in zebrafish exposed to CP (0 and 50 μg/L) and Humic acid (HA, a main component of DOM) at concentrations of 0, 3, 10, and 30 mg-C/L for 30 days. The results showed that, relative to the zebrafish in CP treatment, HA at 30 mg-C/L increased the locomotion (12.1 % in the light and 7.2 % in the dark) and startle response (9.7 %), while inhibiting the anxiety (12.5 %) and cognition of female zebrafish (24.6 %). The levels of transcripts of neurotransmitter- (tph1b and ache), neuroinflammation-(il-6 and tnfα) and antioxidant-(gpx) related genes in the brain of female adult were also altered by CP with the presence of HA. In addition, HA promoted the transgenerational effects of CP on the neurobehaviors. Therefore, HA can enhance potential neurotoxicity of CP in female fish through alteration neurotransmission related genes. Our findings provide new insights into the toxicity and underlying mechanisms of CP with the presence of dissolved organic matter, thereby contribute to a deeper understanding of the risks posed by CP in aquatic ecosystems.

Exposure of male adult zebrafish (Danio rerio) to triphenyl phosphate (TPhP) induces eye development disorders and disrupts neurotransmitter system-mediated abnormal locomotor behavior in larval offspring

Triphenyl phosphate (TPhP) is a widely used organophosphorus flame retardant, which has become ubiquitous in the environment. However, little information is available regarding its transgenerational effects. This study aimed to investigate the developmental toxicity of TPhP on F1 larvae offspring of adult male zebrafish exposed to various concentrations of TPhP for 28 or 60 days. The findings revealed significant morphological changes, alterations in locomotor behavior, variations in neurotransmitter, histopathological changes, oxidative stress levels, and disruption of Retinoic Acid (RA) signaling in the F1 larvae. After 28 and 60 days of TPhP exposure, the F1 larvae exhibited a myopia-like phenotype with pathological alterations in the lens and retina. The genes involved in the RA signaling pathway were down-regulated following parental TPhP exposure. Swimming speed and total distance of F1 larvae were significantly reduced by TPhP exposure, and long-term exposure to environmental levels of TPhP had more pronounced effects on locomotor behavior and neurotransmitter levels. In conclusion, TPhP induced histological and morphological alterations in the eyes of F1 larvae, leading to visual dysfunction, disruption of RA signaling and neurotransmitter systems, and ultimately resulting in neurobehavioral abnormalities. These findings highlight the importance of considering the impact of TPhP on the survival and population reproduction of wild larvae.

Nonspecific immune, histology and accumulation of marine worm, Urechis unicinctus in response to bisphenol A (BPA)

Bisphenol A (BPA) is one of the environmental endocrine disruptors, due to its chemical stability it exists in abundant concentrations in water and soil consequently accumulating in the food chain and causing many endocrine-related health problems. So far, studies on the effects of BPA on marine invertebrates have focused on acute toxicity, endocrine regulation, reproduction, and development. However, fewer studies have been conducted on marine benthos. The current study aimed to detect the accumulation of BPA and its impact on tissue structure, antioxidant capacity, and immune indexes in marine worm, Urechis unicinctus. U. unicinctus, as a common marine benthic animal, were exposed to different concentrations of BPA. Blood cells and intestinal tract were taken for tissue structure inspection, and supernatant of the coelomic fluid was collected for oxidative and antioxidant biomarkers. Results showed that the accumulation of BPA in muscles of U. unicinctus tended to increase with exposure time. BPA induced a rise in H2O2 and MDA content, and altered the activities of CAT, T-SOD, GST, LSZ and ACP, weaken the immune system functions. Moreover, pathological observation showed that BPA caused severe histopathology in the respiratory intestine, stomach, and midgut. These results will be helpful to understand the response mechanism of U. unicinctus under BPA exposure and provide a reference for controlling the aquaculture conditions and marine water quality of U. unicinctus.

A systematic review of the evaluation of endocrine-disrupting chemicals in the Japanese medaka (Oryzias latipes) fish

Japanese medaka (Oryzias latipes) is an acceptable small laboratory fish model for the evaluation and assessment of endocrine-disrupting chemicals (EDCs) found in the environment. In this research, we used this fish as a potential tool for the identification of EDCs that have a significant impact on human health. We conducted an electronic search in PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and Google Scholar (https://scholar.google.com/) using the search terms, Japanese medaka, Oryzias latipes, and endocrine disruptions, and sorted 205 articles consisting of 128 chemicals that showed potential effects on estrogen-androgen-thyroid-steroidogenesis (EATS) pathways of Japanese medaka. From these chemicals, 14 compounds, namely, 17β-estradiol (E2), ethinylestradiol (EE2), tamoxifen (TAM), 11-ketotestosterone (11-KT), 17β-trenbolone (TRB), flutamide (FLU), vinclozolin (VIN), triiodothyronine (T3), perfluorooctanoic acid (PFOA), tetrabromobisphenol A (TBBPA), terephthalic acid (TPA), trifloxystrobin (TRF), ketoconazole (KTC), and prochloraz (PCZ), were selected as references and used for the identification of apical endpoints within the EATS modalities. Among these endpoints, during classification, priorities are given to sex reversal (masculinization of females and feminization of males), gonad histology (testis-ova or ovotestis), secondary sex characteristics (anal fin papillae of males), plasma and liver vitellogenin (VTG) contents in males, swim bladder inflation during larval development, hepatic vitellogenin (vtg) and choriogenin (chg) genes in the liver of males, and several genes, including estrogen-androgen-thyroid receptors in the hypothalamus-pituitary-gonad/thyroid axis (HPG/T). After reviewing 205 articles, we identified 108 (52.68%), 46 (22.43%), 19 (9.26%), 22 (17.18%), and 26 (12.68%) papers that represented studies on estrogen endocrine disruptors (EEDs), androgen endocrine disruptors (AEDs), thyroid endocrine disruptors (TEDs), and/or steroidogenesis modulators (MOS), respectively. Most importantly, among 128 EDCs, 32 (25%), 22 (17.18%), 15 (11.8%), and 14 (10.93%) chemicals were classified as EEDs, AEDs, TEDs, and MOS, respectively. We also identified 43 (33.59%) chemicals as high-priority candidates for tier 2 tests, and 13 chemicals (10.15%) show enough potential to be considered EDCs without any further tier-based studies. Although our literature search was unable to identify the EATS targets of 45 chemicals (35%) studied in 60 (29.26%) of the 205 articles, our approach has sufficient potential to further move the laboratory-based research data on Japanese medaka for applications in regulatory risk assessments in humans.

Assessment of single and combined effects of bisphenol-A and its analogue bisphenol-S on biochemical and histopathological responses of sea cucumber Holothuria poli

Bisphenols (BPs) are among emerging pollutants that have been frequently detected in different compartments of marine ecosystems and elicited great concern due to their potential toxicity to marine organisms. This work aimed to investigate the toxicity of bisphenol A (BPA) and bisphenol S (BPS) on oxidative stress markers, neurotoxicity and histopathological alterations in sea cucumbers (Holothuria poli). The results showed that exposure to 200 μg/L of BPA and BPS produced oxidative stress, neurotoxicity in the digestive tract and respiratory tree, and several types of histopathological lesions in tissues of the respiratory tree of the sea cucumber, posing a health hazard to this aquatic organism. In addition, BPA has greater effects than BPS on the generation of oxidative stress marked by the inductions of catalase (CAT), glutathione S-transferase (GST) and malondialdehyde (MDA) levels and neurotoxicity shown by the decrease in acetylcholinesterase activity (AChE). The respiratory tree of sea cucumbers might be an appropriate tissue for assessing CAT, MDA and AChE activity levels, which are reliable biomarkers that may be useful in marine biomonitoring studies. Evaluation of histopathological lesions of the respiratory tree suggests that BPA and BPS and their mixture cause various tissue alterations that may be associated with oxidative stress damage and neurotoxicity. In conclusion, this study showed that oxidative stress (CAT and MDA) and neurotoxicity (AChE) markers, as well as respiratory tree lesions, are sensitive biomarkers for the assessment of BPA and BPS toxicity in sea cucumbers.

Continuous and discontinuous multi-generational disturbances of tetrabromobisphenol A on longevity in Caenorhabditis elegans

Tetrabromobisphenol A (TBBPA) is one of the most prevalently used brominated flame retardants. Due to its persistence, it is predominantly found in environmental matrices and has the potential to generate multi-generational toxicity. However, knowledge of its adaptive response or long-term residual effect in multi-generations, and molecular mechanisms remain understudied. In the current study, the model animal nematode Caenorhabditis elegans (C. elegans) was exposed to TBBPA at environmentally realistic concentrations (0.1-1000 μg L^-1) for four consecutive generations (G₀ to G₃). Degenerative age-related multiple endpoints including lifespan, locomotion behaviors, growth, reproduction, oxidative stress-related biochemical responses, cell apoptosis, and stress related gene expressions were assessed in the continuous exposure generations (G₀ and G₃) and the discontinuously exposed generations (T₃ and T'₃). The results showed that changes in degenerative age-related response monitored four generations varied in direction and magnitude depending on the TBBPA concentrations, and the response intensify ranked as G₀ > T'₃/G₃ > T₃. TBBPA at 1 μg L^-1 dosage was detected as the lowest observed effect concentration in multi-biomarkers. The underlying mechanism of aging phenotypes was that reactive oxygen species accumulation led to cell apoptosis regulated by gene ape-1, and confirmed catalase enzyme and superoxide dismutase activity played a crucial role in the detoxification process of TBBPA at the molecular level. This study provided insights into the underlying mechanism of TBBPA-interfered longevity and its environmental multi-generational potential risks.

Investigation of long-term bisphenol A exposure on rainbow trout (Oncorhynchus mykiss): Hematological parameters, biochemical indicator, antioxidant activity, and histopathological examination

As an industrial synthetic chemical, bisphenol A (BPA) has the potential to have physiologically and histologically adverse effects on aquatic organisms. BPA causes the reproductive disrupting of all vertebrates due to its degradation on endocrine system. Therefore, the effect of BPA on fish with high economic value is an important issue. This study focused weekly on long-term BPA exposure on rainbow trout (Oncorhynchus mykiss). Hematological, biochemical, antioxidant activity and histopathological examinations were performed on O. mykiss exposed to 1000 μg/L BPA concentration. Mortality was observed in the BPA group during the first three weeks. As a result of hematological studies, leukocyte count and hemoglobin in the BPA group were significantly higher in the first three weeks compared to the control group. Plasma cortisol level as a biochemical indicator showed a similar trend to leukocyte and hemoglobin. There was no significant difference between BPA and control groups in terms of superoxide dismutase and catalase. However, glutathione peroxidase activity in the BPA group was significantly lower than in the control group for four weeks. At the end of the study, many alterations were observed histologically in the gill tissues. While more intense hyperplasia and epithelial lifting were observed in the tissues in the BPA group compared to the control group, vacuolization, necrosis and hypertrophy were observed infrequently. In conclusion, this study argues that BPA causes negative effects on O. mykiss in terms of fish welfare and future study should be focused on its environmental adaptation with color preference patterns.

Assessing the toxic effects of bisphenol A in consumed crayfish Astacus leptodactylus using multi biochemical markers

Bisphenol A (BPA), an endocrine-disrupting chemical (EDC), has strong potential for daily exposure to humans and animals due to its persistence and widespread in the environment, so its effects directly concern public health. Although invertebrates represent important components of aquatic ecosystems and are at significant risk of exposure, there is little information about the biological effects of EDCs in these organisms. Astacus leptodactylus used in this study is one of the most consumed and exported freshwater species in Europe. In this study, the 96-h effect of BPA on A. leptodactylus was examined using various biomarkers. The LC₅₀ value of BPA was determined as 96.45 mg L^-1. After 96 h of exposure to BPA, there were increases in superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities and levels of malondialdehyde (MDA), and total oxidant status context (TOSC), and there were decreases in the activity of glutathione reductase (GR), carboxylesterase (CaE), acetylcholinesterase (AChE), Na⁺/K⁺ ATPase, Mg²⁺ ATPase, Ca²⁺ ATPase, and total ATPase and the total antioxidant context (TAC). From the results of this study, it can be concluded that BPA has significant toxic effects on A. leptodactylus based on the selected biochemical parameters of antioxidant, cholinergic, detoxification, and metabolic systems in crayfish even at low doses. Thus, it can be said that BPA can seriously threaten the aquatic ecosystem and public health.

Cyclophosphamide affects eye development and locomotion in zebrafish (Danio rerio)

Cyclophosphamide (CP) is a broad-spectrum anticancer drug and has been frequently detected in aquatic environments due to its incomplete removal by wastewater treatment facilities and slow degradation in waters. Its toxicity in fish remains largely unknown. In this study, zebrafish eggs <4 h post fertilization (hpf) were exposed to CP at the concentrations from 0.5 to 50.0 μg/L until 168 hpf, and its toxicity was evaluated by biochemical, transcriptomic, and behavioral approaches. The results showed that malformation and mortality rates increased with CP concentrations. The 7-day malformation EC₅₀ and mortality (LC₃₀) by CP were calculated to be 86.8 μg/L and 7.5 mg/L, respectively. Inhibited startle response (light to dark) (a minimal of 19%) and reduced swimming velocity (a minimal of 30%) were observed in the CP-exposed larvae. The thicknesses of retinal ganglion layer, inner plexiform layer, and inner nuclear layer in the retina were increased after exposure to CP. Meanwhile, exposure to CP increased karyorrhexis and karyolysis in the liver tissue. Transcriptomic analysis identified 607 differentially expressed genes (DEGs) (159 up-regulated and 448 down-regulated). A significant reduction in the transcripts of sgk1 (the FoxO pathway), jun (the MAPK pathway), and diabloa (apoptosis pathway) were observed in the CP-treated larvae. This study has demonstrated that low concentrations of CP cause malformation, reduced swimming capacity, histopathological alterations in the retina and liver tissues, and interference on transcriptional expressions of key genes associated with different pathways. The ecological risk of CP and other anticancer drugs to aquatic organisms merits future investigation.

Bisphenol S leads to cytotoxicity-induced antioxidant responses and oxidative stress in isolated rainbow trout (Oncorhyncus mykiss) hepatocytes

BACKGROUND

Bisphenol S (BPS) is a chemical compound that is utilized in the plastic industry as an alternative to bisphenol A (BPA). The toxic effects of BPS in fish is less known and limited. Therefore, in the present study, the influence of BPS on rainbow trout (Oncorhyncus mykiss) hepatocytes in vitro was investigated.

METHODS AND RESULTS

For this purpose the fish hepatocytes were isolated, and then the cultured cells were treated with increasing concentrations of BPS (0, 15.63, 31.25, 62.50, 125, 250, and 500 µM) for 24 h. The cytotoxic impact of BPS was determined in the culture media using lactate dehydrogenase assay and then, the antioxidant defence indicators were assayed. The results showed that concentration-dependent increases were observed in the percentage of cytotoxicity. The superoxide dismutase activity was reduced, while the catalase and glutathione peroxidase activity increased with all of the BPS concentrations. The glutathione S-transferase (GST) activity significantly increased after a BPS concentration of 31.25 µM or higher, while GST Theta 1-1 activity was decreased by the same concentrations of BPS. The reduced glutathione content significantly decreased with a BPS concentration of 31.25 µM or higher, and the malondialdehyde content increased after BPS concentrations of 125, 250, and 500 µM.

CONCLUSIONS

The findings determined herein suggested that BPS causes cytotoxicity in fish hepatocytes and can lead to oxidative stress, resulting hepatotoxic in fish. Thus, the utilization of BPS instead of BPA as safe alternative in industry should be re-evaluated in the future for environmental health.

Evaluation of the oestrogenic potential of oestrone and bisphenol-A on the reproduction of Astyanax bimaculatus males after subacute exposure

In the last decades, oestrogenic compounds have often been reported in environmentally relevant concentrations in aquatic environments around the world. Most laboratory studies of oestrogens try to understand the effects of a single contaminant, but in natural environments, the effects may be quite different due to interactions with other compounds. The present study aimed to compare the action of oestrone (E1) and bisphenol-A (BPA), acting singularly and in combination, on the spermatogenesis of Astyanax bimaculatus. After exposure to 100 ng/L of E1, BPA and a mixture of the two for 15 days, our results showed that E1 and the E1 + BPA mixture significantly altered the number of spermatogenic cells. BPA presented high cytotoxicity when compared to other treatments. Analysis of the two oestrogenic compounds suggests that the E1 + BPA mixture has no additive or synergistic effects. Together, the results of the present study indicate that endocrine-disrupting chemicals (EDCs) analysed alone may behave differently than when administered with other substances.

Detrimental Effects of Bisphenol Compounds on Physiology and Reproduction in Fish: A Literature Review

Bisphenol-A is one of the most studied endocrine-chemicals, which is widely used all over the world in plastic manufacture. Because of its extensive use, it has become one of the most abundant chemical environmental pollutants, especially in aquatic environments. BPA is known to affect fish reproduction via estrogen receptors but many studies advocate that BPA affects almost all aspects of fish physiology. The possible modes of action include genomic, as well as and non-genomic mechanisms, estrogen, androgen, and thyroid receptor-mediated effects. Due to the high detrimental effects of BPA, various analogs of BPA are being used as alternatives. Recent evidence suggests that the analogs of BPA have similar modes of action, with accompanying effects on fish physiology and reproduction. In this review, a detailed comparison of effects produced by BPA and analogs and their mode of action is discussed.

Occurrence, mass loads and risks of bisphenol analogues in the Pearl River Delta region, South China: Urban rainfall runoff as a potential source for receiving rivers

Bisphenol (BP) analogues are widely used as industrial materials and various product additives and are inevitably released into environment. However, knowledge on the sources of different BPs, especially those from urban rainfall runoff to the receiving rivers is very limited. In this study, 15 BPs were determined in surface water, sediments, wastewater treatment plant (WWTP) and rainfall runoff samples in the Pearl River region, South China. Eleven BPs were detected in surface water and sediments of the Pearl Rivers. BPA was the dominant compound up to 2080 ng/L in surface and 1970 ng/g in sediments, followed by BPF, BPS, BPTMC and BPAF. In WWTPs, 10, 9 and 8 BPs were detected in influents, effluents and excess sludges, respectively, with total BPs (ΣBPs) concentrations in effluents still at thousands ng/L, suggesting incompletely removal of BPs. Five BPs were detected in urban rainfall runoff samples, with the ΣBPs concentrations up to 7740 ng/L. Mass loads of ΣBPs from the rainfall runoff (5800 kg/y) were almost equivalent to the source from WWTPs (7370 kg/y) in the region, implying that the urban rainfall runoff was a potential source for BPs into the receiving river. The calculated estrogenic activity contributed by BPs showed low to median risks in sources and receiving rivers. But BPs are always as mixtures with other potential endocrine disrupting chemicals (EDCs) which probably pose high estrogenic activity risks. Hence, effective measures should be taken to decrease the input of EDCs from sources to receiving rivers.

Bisphenol-A induced antioxidants imbalance and cytokines alteration leading to immune suppression during larval development of Labeo rohita

Recently, the oxidative stress and immunotoxicity biomarkers have been extensively used in embryotoxicity using fish embryos as promising models especially after exposure to chemical-like environmental estrogens. Bisphenol-A (BPA) is an estrogenic endocrine disruptor and is ubiquitous in the aquatic environment. Larvae of Labeo rohita were exposed to low concentrations of BPA (10, 100, 1000 μg/l) for 21 days. Innate immune system, antioxidants parameters, and developmental alterations were used as biomarkers. Exposure to BPA caused developmental abnormalities including un-inflated swim bladder, delayed yolk sac absorption, spinal curvature, and edema of pericardium. Lipid peroxidation increased and activity of catalase (p < 0.05), superoxide dismutase (p < 0.05), and glutathione peroxidase (p < 0.01) decreased after exposure to BPA. Level of reduced glutathione also decreased (p < 0.05) in BPA-exposed group. Lower expression of tumor necrosis factor-α (p < 0.05) and interferon-γ (p < 0.001) was observed in BPA-exposed groups while expression of interleukin-10 increased (p < 0.05) in larvae exposed to 10 μg/l BPA. Moreover, exposure of BPA caused a concentration-dependent increase in expression of heat shock protein 70 (p < 0.05). The present study showed that the exposure to BPA in early life stages of Labeo rohita caused oxidative stress and suppress NF-κB signaling pathway leading to immunosuppression. The results presented here demonstrate the cross talk between heat shock protein 70 and cytokines expression.

Subchronic effects of dietary selenium yeast and selenite on growth performance and the immune and antioxidant systems in Nile tilapia Oreochromis niloticus

Selenium is an essential element but toxic at high levels in animals. The effects of Se on growth performance and the immune system in Nile tilapia remain inconclusive. In this study, Nile tilapia Oreochromis niloticus was fed on selenium yeast (Se(Y))- and selenite (Se(IV))-enriched feed at 0, 3, 6, and 12 μg/g (dry wt) for 45 and 90 d. The growth, bioaccumulation, biochemical markers related to antioxidant, immunological, nervous and digestive systems were evaluated in various fish tissues (liver, intestine, kidney, muscle, brain, spleen, gills). The results showed that the accumulation of Se(Y) was 1.3-2 folds of Se(IV) in most tissues. The growth of tilapia was enhanced by both Se(Y) and Se(IV) at 3 μg/g after 90 d, with Se(Y) better than Se(IV) in tilapia feed. After 45 d, the levels of lipid peroxidation, the activity of the antioxidant enzymes, and the transcriptional levels of the immune related genes (IL-1β, IFN-γ and TNF-α) and stress proteins (HSP70 and MT) were enhanced in all treatments, except that of MT in the 12 μg/g Se(Y) group. In addition, both Se species inhibited the activity of acetylcholinesterase (AChE) in the brain and one digestive enzyme α-glucosidase (α-Glu) in the intestine at 12 μg/g. However, after 90 d, the effects on most biochemical markers were less pronounced, implying a possible acclimation after prolonged duration. The results demonstrate Se is beneficial to O. niloticus at low levels and toxic at elevated levels. The immunostimulation by Se might be greatly weakened after long term feeding Se-enriched feed. This study helps to better understand the effects of Se on the antioxidant and immune systems and to establish the optimal Se levels in the feed and duration for O. niloticus.

Assessment of the Effects of Bisphenol A on Dopamine Synthesis and Blood Vessels in the Goldfish Brain

Bisphenol A (BPA) is an abundant contaminant found in aquatic environments. While a large number of toxicological studies have investigated the effects of BPA, the potential effects of BPA exposure on fish brain have rarely been studied. To understand how BPA impacts goldfish brains, we performed a transcriptome analysis of goldfish brains that had been exposed to 50 μg L⁻¹ and 0 μg L⁻¹ BPA for 30 days. In the analysis of unigene expression profiles, 327 unigenes were found to be upregulated and 153 unigenes were found to be downregulated in the BPA exposure group compared to the control group. Dopaminergic signaling pathway-related genes were significantly downregulated in the BPA exposure group. Furthermore, we found that serum dopamine concentrations decreased and TUNEL (terminal deoxynucleotidyl transferase 2-deoxyuridine, 5-triphosphate nick end labeling) staining was present in dopamine neurons enriched regions in the brain after BPA exposure, suggesting that BPA may disrupt dopaminergic processes. A KEGG analysis revealed that genes involved in the fluid shear stress and atherosclerosis pathway were highly significantly enriched. In addition, the qRT-PCR results for fluid shear stress and atherosclerosis pathway-related genes and the vascular histology of the brain showed that BPA exposure could damage blood vessels and induce brain atherosclerosis. The results of this work provide insights into the biological effects of BPA on dopamine synthesis and blood vessels in goldfish brain and could lay a foundation for future BPA neurotoxicity studies.

Effects of Bisphenol A on redox balance in red blood and sperm cells and spermatic quality in zebrafish Danio rerio

Bisphenol-A (BPA) is a potential endocrine disruptor besides being associated with oxidative damage in several vertebrate classes. In the present study we investigated oxidative effects in erythrocytes and sperm cells as well as spermatic quality in Danio rerio exposed to 14 days at BPA concentrations of 2, 10 and 100 μg/L. Organelles structure, reactive species of oxygen (ROS) and lipoperoxidation (LPO) on erythrocytes and sperm cells were measured by flow cytometry and spermatic parameters were analyzed by the computer-assisted sperm analysis (CASA) system. For both cell types, when compared with control BPA treatment induced a significant increase in ROS and LPO production causing the membrane fluidity disorder, loss of membrane integrity and mitochondrial functionality. Furthermore, it was found a significant increase in DNA fragmentation in erythrocytes of zebrafish BPA exposed. Regarding the spermatic quality, results showed lower sperm motility in animals exposed to BPA, and alterations on velocity parameters of spermatozoa. Thus, the present study concludes that BPA affects the oxidative balance of both cell types, and that can directly affects the reproductive success of the adult Danio rerio. The sensitivity of erythrocytes to oxidative damage induced by BPA was similar to sperm cells, indicating a potential use of blood cells as indicators of oxidative damage present in fish sperm.

Bisphenol P activates hormonal genes and introduces developmental outcomes in Chironomus tentans

The endocrine disrupting properties of bisphenol A (BPA) discharged to the environment have been newly identified by the European Chemicals Agency, increasing the need to assess the environmental endocrine disrupting potentials of its alternatives with which it shares close structural features. However, few investigations of the environmental endocrine disrupting functions of BPA analogs have been conducted to date. In this study, the endocrine disrupting effects of a BPA analog of bisphenol P (BPP) were investigated in the nonbiting midge (Chironomus tentans), a model organism in ecotoxicology. An initial ex vivo test using salivary gland cells explanted from the larvae and a subsequent in vivo test using embryos and larvae revealed the upregulatory effects of BPP on ecdysone receptor genes encoding the ecdysone receptor (EcR) and the early responsive gene E74, with a similar temporal pattern of gene activation. Partial life cycle and full life cycle toxicity tests demonstrated BPP altered embryo hatching, larval emergence, and adult sex ratio at concentrations close to the effective concentrations for hormonal genetic endpoints in embryos and larvae after 48 h of exposure. Although embryos appeared to be more sensitive to BPP than the fourth instar larvae, the impact on neither life stage seemed enough to estimate the developmental impairment of the insects. These results demonstrate the ecdysone pathway is a target of BPP, and that long-term exposure could cause apical effects on the development of C. tentans. The endocrine disrupting effects towards aquatic organisms, as well as the high persistence and bioconcentration potential, indicate an urgent need to assess the environmental risks associated with BPP.

Bisphenol A disturbed the lipid metabolism mediated by sterol regulatory element binding protein 1 in rare minnow Gobiocypris rarus

Bisphenol A (BPA), a representative endocrine disrupting compound, exists ubiquitously in the aquatic environment. Several studies on fish have validated the role of BPA in the lipid metabolism. However, the action mechanisms of BPA on lipid metabolism have been little studied. To clarify how BPA regulates lipid metabolism, Gobiocypris rarus were exposed to 15 μg/L BPA for 3 and 6 weeks. Results showed that BPA altered lipid content by regulating some metabolism-related genes. The BPA's inhibiting effect on fatty acid β-oxidation might be stronger than on lipid synthesis. BPA disturbed the expression of acaca (acetyl-CoA carboxylase), fasn (fatty acid synthase) and cpt1α (carnitine palmitoyltransferase 1α) by altering the sterol regulatory element binding protein 1 (SREBP-1) binding to their sterol regulatory elements (SREs). Our result also revealed that DNA methylation in the 5' flanking regions of cpt1α could perturb the SREBP-1 binding adjacent to its SRE in females under BPA exposure. Besides, BPA exposure led to gender-specific effect on fatty acid β-oxidation in G. rarus. This will contribute to our understanding of the regulation mechanisms of BPA on lipid metabolism in fish.

Selenium accumulation and the effects on the liver of topmouth gudgeon Pseudorasbora parva exposed to dissolved inorganic selenium

Selenite(IV) and selenate(VI) are the major forms of Se in aquatic ecosystem. In this study, Pseudorasbora parva were exposed to 10, 200 and 1000 μg L^-1 selenite and selenate for 28 days. Selenium accumulation, antioxidant enzyme levels, glutathione concentrations, lipid peroxidation and histology were evaluated in livers following exposure. Our results showed that Se(IV) and Se(VI) caused different accumulation patterns in the liver, with a more rapid accumulation of Se with Se(IV) treatment. Both Se species increased hepatic lipid peroxidation after 14 and 28 d (~ 30%). Among the antioxidants examined, the activity of SOD (except day 28) and the cellular levels of GSH were induced by 72-137% at lower concentrations, while the activity of GST was at least 24% lower than that of the control at 200 and 1000 μg L^-1 for both Se species at all sampling points. Both forms of Se reduced the hepatosomatic index at 1000 μg L^-1 after 28 d. In addition, marked histopathological alterations (10-31%) were observed in the liver of P. parva after exposure to both Se species, with higher frequency in the Se(IV) exposed fish. Liver local necrosis was observed only in the liver of fish exposed to 1000 μg L^-1 of Se(IV) (~ 20%). Our results suggest that the ecological impacts of dissolved Se in this freshwater species may also contribute to overall toxicity.

Effects of acute and chronic exposures of fluoxetine on the Chinese fish, topmouth gudgeon Pseudorasbora parva

Fluoxetine is a selective serotonin reuptake inhibitor used as an antidepressant and has been frequently detected in aquatic environments. However, its effects in fish from Asia remain relatively less studied. In this study, the topmouth gudgeon Pseudorasbora parva was exposed to 0, 50, and 200 µg/L of fluoxetine for 4 h and 42 d. The effects of fluoxetine on biometrics were compared to biochemical endpoints indicative of stress in different fish tissues (brain, liver, gills and intestine) following exposures. In fish exposed for 42 d, lipid peroxidation endpoints were enhanced 80% in the liver and gills. Acetylcholinesterase (AChE) activity was increased 40% after exposure to 50 µg/L and 55% at 200 µg/L following 4 h exposure. In contrast AChE was increased 26% (at 50 µg/L) after 42 d of exposures. Enhanced ethoxyresorufin-O-deethylase activity (EROD) was detected only in fish exposed to 50 µg/L of fluoxetine for 4 h. The activity of α-glucosidase (α-Glu) was also induced (at 200 µg/L) after 4 h of exposure. After 4 h of exposure, the activities of proteases in the intestine were generally inhibited at 200 µg/L. Both 4 h and 42 d exposures resulted in an increased hepatosomatic index (HSI) but did not affect the condition factor (CF). Our results demonstrate that fluoxetine significantly altered biochemical endpoints in P. parva after acute exposure and the morphological changes in liver size were not observed until 42 d of exposure.

The differences in bioaccumulation and effects between Se(IV) and Se(VI) in the topmouth gudgeon Pseudorasbora parva

Selenium (Se) might be protective against oxidative stress at nutritional levels, but elevated Se concentrations in the diet has been revealed as the main culprit for the extinction of natural fish populations in Se-contaminated lakes. Though Se predominate as waterborne selenite (IV) and selenate (VI) in the water, the differences in bioaccumulation, effects (e.g., oxidative stress, antioxidants etc.) and molecular mechanisms between Se(IV) and Se(VI) have been relatively understudied in wild fish. In this study, the P. parva were exposed to waterborne Se (10, 200 and 1000 μg/L of Se(IV) or Se(VI)) and sampled at 4, 14 and 28 days. Bioaccumulation, tissue distributions of Se and following effects in different tissues were evaluated. The results showed that the levels of Se in the gills and intestine were significantly elevated with a seemingly concentration-dependent pattern in the Se(IV) treatment, with respectively 173.3% and 57.2% increase after 28 days of exposure, relative to that of Se(VI) treatment. Additionally, significant accumulation of Se was also observed in the muscle of Se(IV) treated fish. Se exposure increased the MDA levels in the brain and gills in the Se(IV) treatment, but less apparent in the Se(VI) treatment. Meanwhile, Se exposure lowered (at least 56%) the activity of GST in the gills, but increased the activity of AChE in the muscle (~69%) and brain (~50%) after 28 d. Most importantly, after 28 d of exposure, Se exposure caused significant decrease in GSH levels in the gills (at least 35%) and in all tissues examined at the highest test concentration. In general, the results showed that Se(IV) led to faster accumulation of Se than Se(VI) in P. parva, and the resulted lipid peroxidation was closely related to the levels of antioxidants, especially GSH. Our results suggest that the ecotoxicological effects of waterborne selenite and selenate differ in this freshwater species in the field.

Acetylcholinesterase Is a Potential Biomarker for a Broad Spectrum of Organic Environmental Pollutants

Acetylcholinesterase (AChE, EC 3.1.1.7) is a classical biomarker for monitoring contamination and intoxication of organophosphate (OP) and carbamate pesticides. In addition to these classical environmental AChE inhibitors, other organic toxic substances have been found to alter AChE activity in various species. These emerging organic AChE disruptors include certain persistent organic pollutants (POPs), polycyclic aromatic hydrocarbons (PAHs), and wildly used chemicals, most of which have received considerable public health concern in recent years. It is necessary to re-evaluate the environmental significances of AChE in terms of these toxic substances. Therefore, the present review is aiming to summarize correlations of AChE activity of certain organisms with the level of the contaminants in particular habitats, disruptions of AChE activity upon treatment with the emerging disruptors in vivo and in vitro, and action mechanisms underlying the effects on AChE. Over 40 chemicals belonging to six main categories were reviewed, including 12 POPs listed in the Stockholm Convention. AChE activity in certain organisms has been found to be well correlated with the contamination level of certain persistent pesticides and PAHs in particular habitats. Moreover, it has been documented that most of the listed toxic chemicals could inhibit AChE activity in diverse species ranging from invertebrates to mammals. Besides directly inactivating AChE, the mechanisms in terms of interference with the biosynthesis have been recognized for some emerging AChE disruptors, particularly for dioxins. The collected evidence suggests that AChE could serve as a potential biomarker for a diverse spectrum of organic environmental pollutants.

Individual and binary mixture effects of bisphenol A and lignin-derived bisphenol in Daphnia magna under chronic exposure

In recent years, many new chemicals have been synthesized from biomass with an aim for sustainable development by replacing the existing toxic chemicals with those having similar properties and applications. However, the effects of these new chemicals on aquatic organisms remain relatively unknown. In this study, the effects of bisphenol A (BPA) and lignin-derived bisphenol (LD-BP, a BPA analogue) on Daphnia magna were evaluated. The animals were exposed to BPA, LD-BP, and their binary mixture at concentrations (2-2000 μg L^-1) for 21 days. The expression of various biochemical markers and the effects on growth, molting, and reproduction parameters were examined. The results showed that the weight of daphnids significantly increased after exposure to BPA, LD-BP, and the binary mixture relative to that of the control animals. The activity of superoxide dismutase was significantly inhibited by LD-BP and the binary mixture. At the highest exposure concentration of the binary mixture, the activities of acetylcholinesterase and α-glucosidase, fecundity, and the number of neonates per brood were significantly altered. Our results showed that the effects of BPA and LD-BP on D. magna were generally comparable, except for the effect on the weight at their environmentally relevant concentrations (e.g., <20 μg L^-1). The effects on the reproduction of D. magna could be mainly due to the shift in energy redistribution under BPA and LD-BP exposures. Our results implied that exposures to both BPA and LD-BP could potentially cause deleterious effects at the population level in D. magna.

Enhanced uptake of BPA in the presence of nanoplastics can lead to neurotoxic effects in adult zebrafish

Plastic particles have been proven to be abundant in the aquatic environment, raising concerns about their potential toxic effects. In the present study, we determined the bioaccumulation potential of bisphenol A (BPA) in adult zebrafish (Danio rerio) in the absence and presence of nano-sized plastic particles (nanoplastics, NPPs). Results show that BPA can accumulate in the viscera, gill, head and muscle of zebrafish with 85, 43, 20, and 3μg/g ww after 1d exposure. NPPs were also found to accumulate in different tissues of the fish. Relative equilibrium was reached after 1d exposure in different tissues with 39 to 636mg/kg ww. Co-exposure of NPPs and BPA led to a 2.2 and 2.6-fold significant increment of BPA uptake in the head and viscera, if compared with BPA alone treatment after 3d exposure. As such, we further investigated several neurotoxic biomarker alterations in the fish head. It was found that either BPA or NPPs can cause myelin basic protein (MBP)/gene up-regulation in the central nervous system (CNS); meanwhile, both contaminants exhibited significant inhibition of acetylcholinesterase (AChE) activity, which is a well-known representative biomarker for neurotoxicity. Moreover, for the co-exposure treatment, biomarkers of myeline and tubulin protein/gene expressions, dopamine content, and the mRNA expression of mesencephalic astrocyte derived neurotrophic factor (MANF) were all significantly up-regulated, suggesting that an enhanced neurotoxic effects in both CNS and dopaminergic system occurred. However, AChE activity was no more inhibited in the co-exposure treatment, which implies that solely AChE measurement may not be sufficient to identify neurotoxic effects in the cholinergic system. Overall, the present study demonstrates that the presence of NPPs can increase BPA bioavailability and cause neurotoxicity in adult zebrafish.

Juvenile exposure to bisphenol A promotes ovarian differentiation but suppresses its growth - Potential involvement of pituitary follicle-stimulating hormone

Bisphenol A (BPA), a plastic monomer and plasticizer, is commonly used in plastics industry, and it has been well documented to be an estrogenic endocrine disrupter. In the present study, we investigated the effect of early (juvenile) exposure to BPA on the hypothalamic-pituitary-gonad (HPG) axis in the zebrafish. Estradiol (E2) and testosterone (T) were also included as positive and negative controls respectively. Juvenile zebrafish were exposed to BPA (1 and 10μM), E2 (10nM) and T (10nM) from 20 to 40 dpf (days post-fertilization), the period of sex/gonadal differentiation, followed by histological and expression analyses at 40 dpf. The ovary and hepatic proteomes were also analyzed by mass spectrometry. Our results showed that 20day exposure to BPA and E2 increased the ratio of females; however, they both significantly suppressed ovarian growth. Meanwhile, BPA and E2 significantly suppressed fshb but stimulated lhb expression in the pituitary. These effects did not seem to involve the hypothalamus because neither BPA nor E2 altered the expression of kiss1, kiss2, gnrh2 and gnrh3 in the hypothalamus. At the ovary level, BPA and E2 both decreased lhcgr expression. Interestingly, E2 and BPA displayed different effects in the liver. E2 induced a significant hepatic hypertrophy; however, BPA had no such effect. Analysis of hepatic proteomes revealed distinct protein profiles in the E2 group as compared with the others, especially fructose-bisphospahte aldolase B. These results indicated that BPA has estrogenic effects on female reproduction, but it does not mimic all E2 actions. Our data in the zebrafish suggest that sex differentiation involves estrogens and it is a sensitive window for evaluating estrogenic activities of compounds and their impacts on wildlife reproduction.

Different effects of bisphenol a and its halogenated derivatives on the reproduction and development of Oryzias melastigma under environmentally relevant doses

Bisphenol A (BPA) and its halogenated compounds (H-BPAs) are widely detected in the environmental media and organisms. However, their toxicological effects, especially chronic exposure at low doses, have not been fully compared. In this study, the effects of BPA and H-BPAs on the reproduction and development of Oryzias melastigma were systematically assessed and compared at various developmental stages. BPA and its derivatives tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) elicited the acceleration of embryonic heartbeat. BPA did not show any significant impact on the hatching time and rate of embryos. In contrast, both TBBPA and TCBPA led to the delayed hatching and decreased hatching rate. Accordingly, the expressions of hatching enzyme significantly decreased upon exposure and TCBPA was found to be more toxic than TBBPA. The body weight and gonadsomatic index (GSI) of the treated fish were relatively lower than the control fish upon long-term (four months from larvae to adult) exposure to BPA rather than H-BPAs. Slowed oocyte development occurred in the ovary, and the estrogen level decreased after exposure to BPA rather than H-BPAs. In male fish, no significant alteration was observed in the testis for all groups. The concentration of testosterone significantly decreased upon exposure to BPA rather than H-BPAs. The effects of these three chemicals on the estrogen-related gene expressions were different under various developmental stages. Our study indicated the importance of considering both the exposure stages and structure-activity relationship when assessing the eco-toxicological impact of pollutants.

The acute toxicity of bisphenol A and lignin-derived bisphenol in algae, daphnids, and Japanese medaka

Risk assessing newly synthesized chemicals prior to their applications is extremely important, if we want to ensure substitution of risky chemicals with more benign ones. During the past two decades, many analogs of bisphenol A (BPA) have been manufactured, while their toxicity remains less studied. The aim of this study was to compare the acute toxicity of a synthesized lignin-derived BPA (LD-BP) with that of BPA in representative aquatic organisms including two algal species (Chlorella pyrenoidosa and Scenedesmus obliquus), a cladoceran species (Daphnia magna), and the Japanese medaka (Oryzias latipes). The results revealed that the two algal species showed different responses to the two chemicals. For C. pyrenoidosa, both BPA and LD-BP stimulated growth within 48 h of exposure, except for the 50 mg L^-1 of LD-BP treatment. After 96 and 144 h of exposures, BPA stimulated the growth of C. pyrenoidosa at low-exposure concentrations but inhibited its growth at high concentrations, while LD-BP caused a concentration-dependent response in C. pyrenoidosa. S. obliquus exhibited a monotonic concentration-response curve for both BPA and LD-BP exposures. For both D. magna and O. latipes, concentration-responses were monotonic with 96 h-LC₅₀ of BPA and LD-BP of 11.7 and 5.0 mg L^-1 and 9.4 and 4.1 mg L^-1, respectively. Our results demonstrate that LD-BP is more toxic than BPA in the representative aquatic organisms, and it can pose higher ecological risk to the aquatic ecosystem than BPA.

Evidence for bisphenol A-induced female infertility: a review (2007-2016)

We summarized the scientific literature published from 2007 to 2016 on the potential effects of bisphenol A (BPA) on female fertility. We focused on overall fertility outcomes (e.g., ability to become pregnant, number of offspring), organs that are important for female reproduction (i.e., oviduct, uterus, ovary, hypothalamus, and pituitary), and reproductive-related processes (i.e., estrous cyclicity, implantation, and hormonal secretion). The reviewed literature indicates that BPA may be associated with infertility in women. Potential explanations for this association can be generated from experimental studies. Specifically, BPA may alter overall female reproductive capacity by affecting the morphology and function of the oviduct, uterus, ovary, and hypothalamus-pituitary-ovarian axis in animal models. In addition, BPA may disrupt estrous cyclicity and implantation. Nevertheless, further studies are needed to better understand the exact mechanisms of action and to detect potential reproductive toxicity at earlier stages.

Accumulation and effects of Cr(VI) in Japanese medaka (Oryzias latipes) during chronic dissolved and dietary exposures

Chromium (Cr) is an essential metal and a nutritional supplement for both human and agricultural uses. It is also a pollutant from a variety of industrial uses. These uses can lead to elevated Cr levels in aquatic environments, where it can enter and affect aquatic organisms. Its accumulation and subsequent effects in fish have received relatively little attention, especially for chronic exposure. In the present study, Japanese medaka were chronically exposed to dissolved or dietary Cr(VI) for 3 months. Cr accumulation in liver, gills, intestine, and brain was evaluated. Effects on the antioxidant system, nervous system (acetylcholinesterase, AChE), digestive system (α-glucosidase, α-Glu), and tissue histology (liver and gills) were also assessed. Cr accumulation was observed in the intestine and liver of fish exposed to Cr-contaminated brine shrimp. However, chronic dissolved Cr exposure led to significant Cr accumulation in all organs tested. Analysis of the subcellular distribution of Cr in medaka livers revealed that 37% of the Cr was present in the heat stable protein fraction. The dissolved Cr exposure had pronounced effects on the antioxidant system in the liver, with an elevated ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and decreases in GSH and glutathione S-transferase (GST). The α-Glu activity in the intestine was significantly inhibited. In addition, Cr exposure caused histopathological alterations in the gills and liver. In general, the effects of dietary Cr were relatively minor, possible due to the much lower accumulation in the fish. Our results imply that Japanese medaka accumulate Cr mainly via uptake of dissolved Cr(VI).