Oxidative stress, ion concentration change and immune response in gills of common carp (Cyprinus carpio) under long-term exposure to bisphenol A

Acute exposure to realistic concentrations of Bisphenol-A trigger health damage in fish: Blood parameters, gene expression, oxidative stress

Despite much information regarding BPA toxicity in fish and other aquatic organisms, data is still misleading as most studies have utilized concentrations several orders of magnitude higher than those typically found in the environment. As an illustration, eight of the ten studies investigating the impact of BPA on the biochemical and hematological parameters of fish have employed concentrations on the order of mg/L. Therefore, the results may not accurately represent the effects observed in the natural environment. Considering the information above, our study aimed to 1) determine whether or not realistic concentrations of BPA might alter the biochemical and blood parameters of Danio rerio and trigger an inflammatory response in the fish liver, brain, gills, and gut and 2) determine which organ could be more affected after exposure to this chemical. Findings pinpoint that realistic concentrations of BPA prompted a substantial increase in antioxidant and oxidant biomarkers in fish, triggering an oxidative stress response in all organs. Likewise, the expression of different genes related to inflammation and apoptosis response was significantly augmented in all organs. Our Pearson correlation shows gene expression was closely associated with the oxidative stress response. Regarding blood parameters, acute exposure to BPA generated biochemical and hematological parameters increased concentration-dependent. Thus, it can be concluded that BPA, at environmentally relevant concentrations, threatens aquatic species, as it prompts polychromasia and liver dysfunction in fish after acute exposure.

Bisphenol A (BPA) Directly Activates the G Protein-Coupled Estrogen Receptor 1 and Triggers the Metabolic Disruption in the Gonadal Tissue of Apostichopus japonicus

The sea cucumber, Apostichopus japonicus, is a marine benthic organism that feeds on small benthic particulate matter and is easily affected by pollutants. Bisphenol A (BPA, 4,4'-isopropylidenediphenol) has been identified as an endocrine disruptor. It is ubiquitously detectable in oceans and affects a variety of marine animals. It functions as an estrogen analog and typically causes reproductive toxicity by interfering with the endocrine system. To comparatively analyze the reproductive effects of estradiol (E₂) and BPA on sea cucumbers, we identified a G protein-coupled estrogen receptor 1 (GPER1) in A. japonicus and investigated its effects on reproduction. The results showed that BPA and E₂ exposure activated A. japonicus AjGPER1, thereby mediating the mitogen-activated protein kinase signaling pathways. High-level expression of AjGPER1 in the ovarian tissue was confirmed by qPCR. Furthermore, metabolic changes were induced by 100 nM (22.83 μg/L) BPA exposure in the ovarian tissue, leading to a notable increase in the activities of trehalase and phosphofructokinase. Overall, our findings suggest that AjGPER1 is directly activated by BPA and affects sea cucumber reproduction by disrupting ovarian tissue metabolism, suggesting that marine pollutants pose a threat to the conservation of sea cucumber resources.

Determination of the Oxidative Stress Biomarkers of 8-Hydroxydeoxyguanosine and Dityrosine in the Gills, Skin, Dorsal Fin, and Liver Tissue of Atlantic Salmon (Salmo salar) Parr

Oxidative stress is a condition caused by an imbalance in the occurrence of reactive oxygen species in the cells and tissues of organisms. An ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed for the simultaneous determination of two oxidative stress biomarkers, 8-hydroxydeoxyguanosine (8OHDG) and dityrosine (DIY), in the gills, skin, dorsal fin, and liver tissue of Atlantic salmon (Salmo salar) parr. The use of target analyte-specific ¹³C and ¹⁵N internal standards allowed quantification of each target analyte to be performed through the standard solvent calibration curve. The relative recoveries [mean ± (relative standard deviation%)] of 8OHDG and DIY were 101 ± 11 and 104 ± 13% at a fortified concentration of 10 ng/mL (8OHDG) and 500 ng/mL (DIY), respectively, ensuring the accuracy of the extraction and quantification. The chromatographic separation was carried out using a gradient elution program with a total run time of 5 min. The limits of detection (LODs) were 0.11 and 1.37 ng/g wet weight (w.w.) for 8OHDG and DIY, respectively. To demonstrate the applicability of the developed method, it was applied in 907 tissue samples that were collected from Atlantic salmon parr individuals reared in an experimental land-based recirculating aquaculture system (RAS) treated with peracetic acid. Moreover, the possibility of using the dorsal fin as an alternative matrix for the minimally invasive assessment of oxidative stress in Atlantic salmon parr was introduced. To our knowledge, 8OHDG and DIY were used for the first time as biomarkers for biomonitoring the fish health (oxidative stress) of Atlantic salmon parr in RAS.

The toxicokinetics of bisphenol A and its metabolites in fish elucidated by a PBTK model

Bisphenol A (BPA) is a chemical of major concern due to its endocrine disrupting function, high production volume, and persistence in the aquatic environment. Consequently, organisms such as fish are subject to chronic exposure to BPA. However, physiologically-based toxicokinetic (PBTK) models, which are valuable tools to improve the understanding of a chemical's fate in an organism, have never been specifically adapted to model BPA toxicokinetics (TK) in fish. In our work, an existing PBTK developed for four different fish species was modified to model BPA ADME processes (absorption, distribution, metabolization and excretion). The metabolization of BPA into BPA-monoglucuronide (BPA gluc) and BPA-monosulfate (BPA sulf) and their TK in various organs was taking into account in the model. Experiments were performed to generate BPA TK data in a model species commonly used in ecotoxicology, the stickleback. The model structure had to include two sites of metabolization to simulate BPA TK accurately in stickleback organs. Thus, the fish liver may not be the only site of the metabolization of BPA: plasma or gills could also play a role in BPA metabolization. The PBTK model predictive performance evaluated on literature data in zebrafish and rainbow trout concurs with this conclusion. Finally, a calibration mixing data from the three species was compared to the calibration on stickleback data only.

Exploring the toxic interactions between Bisphenol A and glutathione peroxidase 6 from Arabidopsis thaliana

As primary industrial raw material, the widespread usage of bisphenol A (BPA) has resulted in sustained release and accumulation in the environment. Besides its endocrine-disrupting character, BPA was reported to generate excessive reactive oxygen species (ROS). However, the potential toxic mechanisms of the BPA-induced oxidative damage to plants were poorly understood. In this study, glutathione peroxidase 6 from Arabidopsis thaliana (AtGPX6) was regarded as biomarker to investigate the toxic effects of BPA on plants by multi-spectroscopic techniques and molecular docking method. Firstly, BPA effectively quenched the intrinsic fluorescence of AtGPX6 via static quenching mechanism, and a single binding site of AtGPX6 towards BPA was presumed. Moreover, the binding force was mainly driven by van der Waals forces and hydrogen bonding based on the negative values of ΔH⁰ and ΔS⁰, which was consistent with the molecular docking result. In addition, the conformational changes of AtGPX6 accompanied with the enhancement of the hydrophilicity around the tryptophan residues upon the combination with BPA, were evaluated through the combination of the fluorescence, UV-visible absorption and Circular dichroism (CD) spectroscopy. Finally, the inhibitory impact on the development of Arabidopsis seedling roots was observed under BPA exposure. Therefore, the exploration of the molecular mechanism of AtGPX6 with BPA would provide valuable assessments on the toxic effects of BPA on plants.

Enhanced Immune Response Improves Resistance to Cadmium Stress in Triploid Crucian Carp

Previous research has indicated that triploid crucian carp (3n fish) have preferential resistance to cadmium (Cd) compared to Carassius auratas red var. (2n fish). In this article, comparative research is further conducted between the 2n and 3n fish in terms of the immune response to Cd-induced stress. Exposure to 9 mg/L Cd for 96 h changed the hepatic function indexes remarkably in the 2n fish, but not in the 3n fish. In the serum of Cd-treated 2n fish, the levels of alanine amino transferase, aspartate aminotransferase, adenosine deaminase, and total bilirubin significantly increased, while the levels of total protein, albumin, lysozyme, and anti-superoxide anion radicals decreased demonstrating hepatotoxicity. By analysis of transcriptome profiles, many immune-related pathways were found to be involved in the response of 3n fish to the Cd-induced stress. Expression levels of the immune genes, including the interleukin genes, tumor necrosis factor super family member genes, chemokine gene, toll-like receptor gene, and inflammatory marker cyclooxygenase 2 gene were significantly enhanced in the hepatopancreas of the Cd-treated 3n fish. In contrast, the expression levels of these genes decreased in the 2n fish. This research provides a theoretical basis for polyploid fish breeding and is helpful for the ecological restoration of water due to pollution.

Physiological and metabolic approach of plastic additive effects: Immune cells responses

Human and wildlife are continually exposed to a wide range of compounds and substances, which reach the body through the air, water, food, or personal care products. Plasticizers are compounds added to plastics and can be released to the environment under certain conditions. Toxicological studies have concluded that plasticizers, phthalates, and bisphenols are endocrine disruptors, alter the endocrine system and functioning of the immune system and metabolic process. A functional immune response indicates favourable living conditions for an organism; conversely, a weak immune response could reveal a degraded environment that requires organisms to adapt. There is growing concern about the presence of plastic debris in the environment. In this review, the current knowledge of the action of plasticizers on leukocyte cells will be itemized. We also point out critically the role of some nuclear and membrane receptors as key players in the action of plasticizers on cells possess immune function. We discuss the role of erythrocytes within the immune responses and the alteration caused by plasticizers. Finally, we highlight data evidencing mitochondrial dysfunctions triggered by plasticizing toxic action, which can lead to immunosuppression.

The heart of the adult goldfish Carassius auratus as a target of Bisphenol A: a multifaceted analysis

Bisphenol A (BPA) is a contaminant whose presence in aquatic environments is increasing. In fish embryos and larvae, it severely affects cardiac development; however, its influence on the heart function of adult fish has been scarcely analyzed. This study investigated the effects of the in vivo exposure to BPA on heart physiology, morphology, and oxidative balance in the goldfish Carassius auratus. Adult fish were exposed for 4 and 10 days to two BPA concentrations (10 μM and 25 μM). Ex vivo working heart preparations showed that high concentrations of BPA negatively affected cardiac hemodynamics, as revealed by an impaired Frank-Starling response. This was paralleled by increased cardio-somatic indices and by myocardial structural changes. An altered oxidative status and a modulation of stress (HSPs) and pro-apoptotic (Bax and Cytochrome C) proteins expression were also observed in the heart of animals exposed to BPA, with detrimental effects at the highest concentration and the longest exposure time. Results suggest that, in the adult goldfish, BPA may induce stressful conditions to the heart with time- and concentration-dependent deleterious morpho-functional alterations.

Biotoxicity of landfill leachate effluent treated by two-stage acclimatized sludge AS system and antioxidant enzyme activity in Cyprinus carpio

This research comparatively investigates the biotoxicity of landfill leachate effluent from acclimatized and non-acclimatized sludge two-stage activated sludge (AS) systems. Both AS systems were operated with two leachate influent concentrations: moderate (condition 1) and elevated (condition 2). The biotoxicity of AS effluent of variable concentrations (10, 20, and 30% (v/v)) was assessed by the mortality rates of common carp (Cyprinus carpio) and glutathione-S-transferase (GST) enzyme activity. The treatment efficiency of the acclimatized sludge AS system for organic and inorganic compounds and nutrients (BOD, COD, TKN, NH₄⁺, PO₄^3-) were 75-96% under condition 1 and 79-93% under condition 2. The non-acclimatized sludge AS system achieved the treatment efficiency of 70-91% under condition 1 and 66-90% under condition 2. The acclimatized sludge AS system also achieved higher biodegradation of trace organic compounds, especially under condition 1. The effluent from acclimatized sludge AS system was less toxic to the common carp, as evidenced by lower mortality rates and higher GST activity. The findings revealed that the acclimatized sludge two-stage AS system could be deployed to effectively treat landfill leachate with moderate concentrations of compounds and trace organic contaminants. The acclimatized sludge AS is an efficient wastewater treatment solution for developing countries with limited technological and financial resources.