Effects of (Anti) Androgenic Endocrine Disruptors (DEHP and Butachlor) on Immunoglobulin M (IgM) and Leukocytes Counts of Male Rainbow Trout (Oncorhynchus mykiss)

Environmental occurrence and ecotoxicity of aquaculture-derived plastic leachates

Plastic products such as fishing nets and foam buoys have been widely used in aquaculture. To enhance the desirable characteristics of the final equipment, plastic gear for aquaculture is mixed with a wide range of additives. Recent studies have shown that additives could be leached out to the environment with a long-term use of aquaculture plastics, forming aquaculture-derived plastic leachates. It should be emphasized that some leachates such as phthalic acid esters (PAEs) and organophosphate esters (OPEs) are endocrine disruptors, which could increase the exposure risk of aquatic products and subsequently display potential threats to human health via food chain. However, systematic studies on the release, occurrence, bioaccumulation, and toxic effects of aquaculture-derived plastic leachates are missing, overlooking their potential sources and ecotoxicological risks in aquatic environments. We have reviewed and compared the concentrations of major plastic leachates in the water environment and organisms of global aquaculture and non-farmed areas, confirming that aquaculture leachate is an important source of contaminants in the environment. Moreover, the toxic effects of aquaculture-derived plastic additives and the related mechanisms are summarized with fish as a representative, revealing their potential health risk. In addition, we proposed current challenges and future research needs, which provides scientific guidance for the use and management of plastic products in aquaculture industries.

Accumulation, functional and antioxidant responses to acute exposure to Di(2-ethylhexyl)phthalate (DEHP) in Mytilus galloprovincialis

Mussels were exposed to di-(2-ethylhexyl) phthalate (DEHP) (0.4 mg L^-1 and 4.0 mg L^-1) for 24 h and 48 h and its effect on hemocyte cellular composition and spontaneous reactive oxygen production (ROS) levels in hemocytes were evaluated. Exposure to DEHP induced a loss in spontaneous ROS production levels in hemocytes and decreased agranulocyte number in hemolymph. DEHP was found to accumulate in hepatopancreas of mussels and this process was associated with an increase of catalase (CAT) activity after 24 h incubation. At the end of the experimental period (48 h) CAT activity recovered up to control levels. Superoxide dismutase (SOD) activity in hepatopancreas increased following 48 h exposure to DEHP. The results indicated that DEHP could affect hemocyte immune properties, and also cause non-specific general stress-response of the antioxidant complex, which, in turn, was not associated with pronounced oxidative stress.

One-step synthesis of Bi2O2CO3/Bi2S3 S-scheme heterostructure with enhanced photoactivity towards dibutyl phthalate degradation under visible light

Bi₂O₂CO₃/Bi₂S₃ heterojunction was prepared by one-step hydrothermal method, where Bi(NO₃)₃ was employed as Bi source, Na₂S was used as a sulfur source, and CO(NH₂)₂ was adopted as C source. The load of Bi₂S₃ was adjusted by changing the content of Na₂S. The prepared Bi₂O₂CO₃/Bi₂S₃ illustrated strong photocatalytic activity towards dibutyl phthalate (DBP) degradation. The degradation rate was 73.6% under the irradiation of visible light for 3 h, which were 3.5 and 1.87 times for Bi₂O₂CO₃ and Bi₂S₃, respectively. In addition, the mechanism for the enhanced photoactivity was investigated. After combined with Bi₂S₃, the formed heterojunction structure inhibited the recombination of photogenerated electron-hole pair, improved the visible light adsorption, and accelerated the migration rate of the photogenerated electron. As a result, analysis of the radical formation and the energy band structure revealed that Bi₂O₂CO₃/Bi₂S₃ was consistent with the S-scheme heterojunction model. The S-scheme heterojunction allowed the Bi₂O₂CO₃/Bi₂S₃ to possess high photocatalytic activity. The prepared photocatalyst presented acceptable cycle application stability. This work not only develops a facile one-step synthesis technique for Bi₂O₂CO₃/Bi₂S₃, and also provides a good platform for the degradation of DBP.

Androgen and prolactin manipulation do not induce changes in immunocompetence measures in a fish with male parental care

Prolactin and 11-ketotestosterone (11-KT) are important reproductive hormones in fishes, which may also influence immunocompetence. The immunocompetence handicap hypothesis states that higher androgen concentrations that support secondary sex traits are traded off against a decrease in immune system function. To test the relationships between these hormones and immunocompetence, we experimentally manipulated 11-ketotestosterone and prolactin in the freshwater fish, bluegill (Lepomis macrochirus) during parental care using implants that contained either 11-KT, prolactin, or an inert control. We vaccinated individuals to stimulate the acquired immune response, then measured immunocompetence as the number of granulocytes, lymphocytes and monocytes, and the expression of interleukin 8 in each sample. We did not observe any significant differences in the immune measures among the hormone treatments. Our results indicate that in bluegill, there is no trade-off between androgens or prolactin and immunocompetence.

Crosstalk between reproductive and immune systems: the teleostean perspective

The bidirectional interaction between the hypothalamic-pituitary-gonadal (HPG) axis and the immune system plays a crucial role in the adaptation of an organism to its environment, its survival and the continuance of a species. Nonetheless, very little is known about this interaction among teleost, the largest group of extant vertebrates. Fishes being seasonal breeders, their immune system is exposed to seasonally changing levels of HPG hormones. On the contrary, the presence and infiltration of leukocytes, the expression of pattern recognition receptors as well as cytokines in gonads suggest their key role in teleostean gametogenesis as in the case of mammals. Moreover, the modulation of gametogenesis and steroidogenesis by lipopolysaccharide implicates the pathological significance of inflammation on reproduction. Thus, it is important to engage in the understanding of the interaction between these two important physiological systems, not only from a phylogenetic perspective but also due to the importance of fish as an important economic resource. In view of this, the authors have reviewed the crosstalk between the reproductive and immune systems in teleosts and tried to explore the importance of this interaction in their survival and reproductive fitness.

Quantification of differential tissue biomarker responses to microplastic ingestion and plasticizer bioaccumulation in aquaculture reared sea bream Sparus aurata

Marine aquaculture is considered a potential source of microplastics (MPs). MPs can induce oxidative stress and damage in marine species. In this study we evaluated the impact of MPs intake in the commercial fish, Sparus aurata, from aquaculture facilities and the antioxidant response associated to this MPs ingestion in caged specimens for 120 days. Sampling was carried out at the beginning of the study (T₀), at 60 days (T₆₀) and at 120 days (T₁₂₀). At each sampling stage, gastrointestinal tract, blood, plasma, liver and muscle samples were obtained to analyse MPs intake (gastrointestinal tract), oxidative stress markers (blood, plasma and liver) and plasticizers bioaccumulation (muscle). Fish sampled at T₆₀ presented the highest MPs intake and plasticizers accumulated in muscle over time, but with a different pattern according to type: bisphenols and phthalates. This indicates MPs ingestion induces a differential tissue response in S. aurata. Similarly, stress biomarkers presented a differential response throughout the study, depending on the analysed tissue. In the case of oxidative damage markers, for malondialdehyde (MDA) an increase throughout the study was observed both in liver and blood cells but with a progressive decrease in plasma. In the case of phase I detoxifying enzyme activities in liver, 7-ethoxyresorufin O-deethylase (EROD), 7-benzyloxy-4-[trifluoromethyl]-coumarin-O-debenzyloxylase (BFCOD) and carboxylesterases (CE), showed a comparable decrease at T₆₀ with a slight recovery at T₁₂₀. In contrast, glutathione-S-transferase (GST) activity was significantly enhanced at T₆₀ compared to the other sampling stages. In conclusion, MPs ingestion occurs in aquaculture reared seabream where potentially associated plasticizers accumulate in the muscle and both could be responsible for plasma and liver oxidative stress damage and alterations on detoxifying biomarkers responses.

Hazards of phthalates (PAEs) exposure: A review of aquatic animal toxicology studies

Phthalates (PAEs) are of wide concern because they are commonly used in various plastic products as plasticizers, and can found their way into the environment. However, their interaction with the environment and their toxicity in aquatic animals is still a matter of intense debate. In this review on PAEs in aquatic environments (lakes, rivers and seas), it is found that there is a large variety and abundance of PAEs in developing countries, and the total concentration of PAEs even exceeds 200 μg / L. The interaction between metabolic processes involved in the toxicity induced by various PAEs is summarized for the first time in the article. Exposure of PAEs can lead to activation of the detoxification system CYP450 and endocrine system receptors of aquatic animals, which in turn causes oxidative stress, metabolic disorders, endocrine disorders, and immunosuppression. Meanwhile, each system can activate / inhibit each other, causing genotoxicity and cell apoptosis, resulting in the growth and development of organisms being blocked. The mixed PAEs shows no cumulative toxicity changes to aquatic animals. For the combined pollution of other chemicals and PAEs, PAE can act as an agonist or antagonist, leading to combined toxicity in different directions. Phthalate monoesters (MPEs), the metabolites of PAEs, are also toxic to aquatic animals, however, the toxicity is weaker than the corresponding parent compounds. This review summarizes and analyzes the current ecotoxicological effects of PAEs on aquatic animals, and provides guidance for future research.

Current insights into the microbial degradation for butachlor: strains, metabolic pathways, and molecular mechanisms

The herbicide butachlor has been used in huge quantities worldwide, affecting various environmental systems. Butachlor residues have been detected in soil, water, and organisms, and have been shown to be toxic to these non-target organisms. This paper briefly summarizes the toxic effects of butachlor on aquatic and terrestrial animals, including humans, and proposes the necessity of its removal from the environment. Due to long-term exposure, some animals, plants, and microorganisms have developed resistance toward butachlor, indicating that the toxicity of this herbicide can be reduced. Furthermore, we can consider removing butachlor residues from the environment by using such butachlor-resistant organisms. In particular, microbial degradation methods have attracted much attention, with about 30 kinds of butachlor-degrading microorganisms have been found, such as Fusarium solani, Novosphingobium chloroacetimidivorans, Chaetomium globosum, Pseudomonas putida, Sphingomonas chloroacetimidivorans, and Rhodococcus sp. The metabolites and degradation pathways of butachlor have been investigated. In addition, enzymes associated with butachlor degradation have been identified, including CndC1 (ferredoxin), Red1 (reductase), FdX1 (ferredoxin), FdX2 (ferredoxin), Dbo (debutoxylase), and catechol 1,2 dioxygenase. However, few reviews have focused on the microbial degradation and molecular mechanisms of butachlor. This review explores the biochemical pathways and molecular mechanisms of butachlor biodegradation in depth in order to provide new ideas for repairing butachlor-contaminated environments. KEY POINTS: • Biodegradation is a powerful tool for the removal of butachlor. • Dechlorination plays a key role in the degradation of butachlor. • Possible biochemical pathways of butachlor in the environment are described.

Role of estrogen receptor alpha in MEHP-induced proliferation and invasion of SH-SY5Y cells

Estrogen receptors are involved in regulating the proliferation and invasion process of neuroblastoma. As a kind of estrogen-like environmental endocrine disruptors (EEDs), whether mono-2-ethylhexyl phthalate (MEHP) can affect the proliferation and invasion of neuroblastoma cells via ERs is unknown. The present study aimed to explore the role of ERα in MEHP-induced proliferation, migration, and invasion of SH-SY5Y cells. SH-SY5Y cells were cultured in DMEM with 10 % FBS. Wild-type SH-SY5Y cells and ERα-knockdown SH-SY5Y cells were treated with MEHP (0, 10, 50, and 250 μM) for 12 h and 24 h. The viability of SH-SY5Y cells was detected with a CCK8 kit and cell cycle was measured by flow cytometry. Cell migration was measured using a scratch assay, and cell invasion was tested using a Transwell migration assay. The expression levels of proliferating cell nuclear antigen (PCNA), matrix metalloproteinase 2 (MMP-2), matrix metalloproteinase 9 (MMP-9), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2), ERα, and ERβ were detected with real-time qPCR and western blotting. MEHP promoted the proliferation of SH-SY5Y cells. The results also showed that MEHP significantly increased the relative migration distance of wild-type SH-SY5Y cells. Conversely, MEHP treatment did not increase the relative migration distance of ERα-knockdown SH-SY5Y cells, suggesting that MEHP promotes the migration of neuroblastoma through ERα. Similarly, MEHP significantly increased the relative number of invaded wild-type SH-SY5Y cells, while the MEHP-induced invasion effect was significantly decreased in ERα-knockdown SH-SY5Y cells. Moreover, the expression levels of PCNA, MMP-2, MMP-9, and ERα cells were upregulated by MEHP in wild-type SH-SY5Y, and the expression level of its tissue inhibitor TIMP-2 was downregulated. In contrast, the expression of PCNA, MMP-2, MMP-9, and ERα was significantly downregulated in ERα-knockdown SH-SY5Y cells, while the expression of TIMP-2 was significantly upregulated. In conclusion, MEHP can upregulate PCNA, MMP-2, and MMP-9, and downregulate TIMP-2, further promoting proliferation, migration, and invasion of neuroblastoma through ERα.

Neural mechanisms underlying the deficit of learning and memory by exposure to Di(2-ethylhexyl) phthalate in rats

Di(2-ethylhexyl) phthalate (DEHP), as one of the most broadly representative phthalic acid esters, is used as a plasticizer in Polyvinyl chloride production. The exact neurotoxicologically effects of DEHP to human have not been adequately researched. In order to investigate the effects and mechanisms of DEHP exposure on neural circuit, the spatial learning and memory of Sprague Dawley (SD) rats was measured, and the cellular mechanisms underlying synaptic plasticity, cellular excitability and ion channels were detected. Our data showed that the spatial learning and memory was changed by DEHP (100 and 300 mg) treatment. Meanwhile, the frequency of mini Excitatory Postsynaptic Current (mEPSC) from CA3 pyramidal cells were significantly decreased by DEHP exposure (0.1 and 0.3 M); the firing threshold, membrane potential threshold, number, amplitude and latency of Action Potentials (Aps) of CA1 pyramidal cells were altered with the application of DEHP (0.1 and 0.3 M); furthermore, DEHP, both in 0.1 and 0.3 M could inhibit the voltage-gated potassium channel of CA1 pyramidal cells. Our results indicated that DEHP could impair the spatial learning and memory, and this impairment might due to the DEHP-induced suppression of the neuronal excitability and synaptic plasticity by inhibiting the voltage-gated potassium channel, supporting the hypothesis that DEHP could cause the disruption of neural function.

Estrogen-dependent seasonal adaptations in the immune response of fish

Clinical and experimental evidence shows that estrogens affect immunity in mammals. Less is known about this interaction in the evolutionary older, non-mammalian, vertebrates. Fish form an excellent model to identify evolutionary conserved neuroendocrine-immune interactions: i) they are the earliest vertebrates with fully developed innate and adaptive immunity, ii) immune and endocrine parameters vary with season, and iii) physiology is constantly disrupted by increasing contamination of the aquatic environment. Neuro-immuno-endocrine interactions enable adaption to changing internal and external environment and are based on shared signaling molecules and receptors. The presence of specific estrogen receptors on/in fish leukocytes, implies direct estrogen-mediated immunoregulation. Fish leukocytes most probably are also capable to produce estrogens as they express the cyp19a and cyp19b - genes, encoding aromatase cytochrome P450, the enzyme critical for conversion of C19 steroids to estrogens. Immunoregulatory actions of estrogens, vary among animal species, and also with dose, target cell type, or physiological condition (e.g., infected/non-infected, reproductive status). They moreover are multifaceted. Interestingly, season-dependent changes in immune status correlate with changes in the levels of circulating sex hormones. Whereas E2 circulating in the bloodstream is perhaps the most likely candidate to be the physiological mediator of systemic immune-reproductive trade-offs, leukocyte-derived hormones are hypothesized to be mainly involved in local tuning of the immune response. Contamination of the aquatic environment with estrogenic EDCs may violate the delicate and precise allostatic interactions between the endogenous estrogen system and the immune system. This has negative effects on fish health, but will also affect the physiology of its consumers.