Developmental toxicity and estrogenic potency of zearalenone in zebrafish (Danio rerio)

Thermo-Alkali-Tolerant Recombinant Laccase from Bacillus swezeyi and Its Degradation Potential against Zearalenone and Aflatoxin B1

The enzymatic biodegradation of mycotoxins in food and feed has attracted the most interest in recent years. In this paper, the laccase gene from Bacillus swezeyi was cloned and expressed in Escherichia coli BL 21(D3). The sequence analysis indicated that the gene consisted of 1533 bp. The purified B. swezeyi laccase was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis -12% with an estimated molecular weight of 56.7 kDa. The enzyme is thermo-alkali-tolerant, displaying the optimal degradation of zearalenone (ZEN) and aflatoxin B1 (AFB1) at pH 8 and 9, with incubation temperatures of 55 and 50 °C, respectively, within 24 h. The degradation potentials of the 50 μg of the enzyme against ZEN (5.0 μg/mL) and AFB1 (2.5 μg/mL) were 99.60 and 96.73%, respectively, within 24 h. To the best of our knowledge, this is the first study revealing the recombinant production of laccase from B. swezeyi, its biochemical properties, and potential use in ZEN and AFB1 degradation in vitro and in vivo.

Assessment of developmental toxicity and the potential mode of action underlying single and binary exposure to estrogenic endocrine disrupting chemicals in zebrafish (Danio rerio)

The current study investigated the effect of single and binary exposure to distinct xenoestrogens, including diethylstilbestrol (DES) and zearalenone (ZEN), on zebrafish embryos subjected to continuous exposure for 4 days starting from 4 h post fertilization. Noteworthy impact on cumulative mortality, hatchability, spinal and tail curvature, pericardial edema, and reduction in blood circulation were observed in DES-treated embryos, with lower incidence and intensity shown for ZEN at the same nominal concentration (3 μM). An interactive effect was seen for the combined exposure to DES and ZEN, in which deformities and circulatory failure mediated by DES were mitigated by co-treatment with low concentrations of ZEN. Similarly, ZEN-induced spinal and tail curvature, pericardial edema, and blood flow reduction declined dramatically following DES co-exposure at low concentrations. A significant counteracting effect has been observed against DES- and ZEN-induced developmental anomalies following co-treatment with an estrogen receptor (ER) antagonist, fulvestrant (FUL). The assessment of the aromatase gene (CYP19A1b) showed that DES strongly upregulated mRNA expression of CYP19A1b with a lower EC50 (1.1 × 10-3 nM) than a natural estrogen, 17β-estradiol (2.5 nM). Similarly, ZEN induced CYP19A1b mRNA expression with an EC50 of 57 nM. Exposure to 10 or 20 μM FUL inhibited the expression of CYP19A1b induced by a single treatment of DES or ZEN. Overall, the competitive action against ER could be the main mechanism underlying the developmental toxicity induced by DES and ZEN.

Zebrafish as model organisms for toxicological evaluations in the field of food science

Food safety has long been an area of concern. The selection of stable and efficient model organisms is particularly important for food toxicology studies. Zebrafish (Danio rerio) are small model vertebrates, and 70% of human genes have at least one zebrafish ortholog. Zebrafish have advantages as model organisms due to their short life cycle, strong reproductive ability, easy rearing, and low cost. Zebrafish embryos have the advantage of being sensitive to the breeding environment and thus have been used as biosensors. Zebrafish and their embryos have been widely used for food toxicology assessments. This review provides a systematic and comprehensive summary of food toxicology studies using zebrafish as model organisms. First, we briefly introduce the multidimensional mechanisms and structure-activity relationship studies of food toxicological assessment. Second, we categorize these studies according to eight types of hazards in foods, including mycotoxins, pesticides, antibiotics, heavy metals, endocrine disruptors, food additives, nanoparticles, and other food-related ingredients. Finally, we list the applications of zebrafish in food toxicology studies in line with future research prospects, aiming to provide a valuable reference for researchers in the field of food science.

High-Resolution Magic Angle Spinning (HRMAS) NMR Identifies Oxidative Stress and Impairment of Energy Metabolism by Zearalenone in Embryonic Stages of Zebrafish (Danio rerio), Olive Flounder (Paralichthys olivaceus) and Yellowtail Snapper (Ocyurus chrysurus)

Zearalenone (ZEA) is a mycotoxin, commonly found in agricultural products, linked to adverse health impacts in humans and livestock. However, less is known regarding effects on fish as both ecological receptors and economically relevant "receptors" through contamination of aquaculture feeds. In the present study, a metabolomics approach utilizing high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) was applied to intact embryos of zebrafish (Danio rerio), and two marine fish species, olive flounder (Paralichthys olivaceus) and yellowtail snapper (Ocyurus chrysurus), to investigate the biochemical pathways altered by ZEA exposure. Following the assessment of embryotoxicity, metabolic profiling of embryos exposed to sub-lethal concentrations showed significant overlap between the three species and, specifically, identified metabolites linked to hepatocytes, oxidative stress, membrane disruption, mitochondrial dysfunction, and impaired energy metabolism. These findings were further supported by analyses of tissue-specific production of reactive oxygen species (ROS) and lipidomics profiling and enabled an integrated model of ZEA toxicity in the early life stages of marine and freshwater fish species. The metabolic pathways and targets identified may, furthermore, serve as potential biomarkers for monitoring ZEA exposure and effects in fish in relation to ecotoxicology and aquaculture.

Impacts of co-exposure to zearalenone and trifloxystrobin on the enzymatic activity and gene expression in zebrafish

Although humans and animals are usually exposed to combinations of toxic substances, little is known about the interactive toxicity of mycotoxins and farm chemicals. Therefore, we can not precisely evaluate the health risks of combined exposure. In the present work, using different approaches, we examined the toxic impacts of zearalenone and trifloxystrobin on zebrafish (Danio rerio). Our findings showed that the lethal toxicity of zearalenone to embryonic fish with a 10-day LC₅₀ of 0.59 mg L^-1 was lower than trifloxystrobin (0.037 mg L^-1). Besides, the mixture of zearalenone and trifloxystrobin triggered acute synergetic toxicity to embryonic fish. Moreover, the contents of CAT, CYP450, and VTG were distinctly altered in most single and combined exposures. Transcriptional levels of 23 genes involved in the oxidative response, apoptosis, immune, and endocrine systems were determined. Our results implied that eight genes (cas9, apaf-1, bcl-2, il-8, trb, vtg1, erβ1, and tg) displayed greater changes when exposed to the mixture of zearalenone and trifloxystrobin compared with the corresponding individual chemicals. Our findings indicated that performing the risk assessment based on the combined impact rather than the individual dosage response of these chemicals was more accurate. Nevertheless, further investigations are still necessary to reveal the modes of action of mycotoxin and pesticide combinations and alleviate their effects on human health.

Combined effects of zearalenone and deoxynivalenol on oxidative stress, hepatotoxicity, apoptosis, and inflammation in zebrafish embryos

Co-existence of mycotoxins may pose a greater risk. It remains less known about the toxic effect of co-exposure of zearalenone (ZEA) and deoxynivalenol (DON) on aquatic life. In the present study, the toxic effects of the combine treatment of ZEA and DON on zebrafish (Danio rerio) embryos were investigated. The results showed that the combined treatment of ZEA (200, 400, 800 μg/L) and DON (4000 μg/L) did not cause apparent deaths, but induced a developmental toxicity as indicated by decreased movement times and heartbeat. At 96 h post-fertilization (hpf), co-exposure of ZEA and DON (Z400 + D4000 and Z800 + D4000 group) led to significant oxidative stress as evidenced by the increased ROS level and MDA content, as well as the changes of antioxidant enzymes (SOD, CAT and GPX) and their genes. Besides, the combined treatment of ZEA and DON triggered hepatotoxicity as shown by the changes of Fabp10a, Gclc, Gsr, Nqo1 genes, apoptosis through upregulating apoptosis-related genes (p53, Caspase-9, Caspase-3) and downregulating Bcl-2 gene, as well as inflammation by promoting the expression of IL-1β, IL-6, TNF-α, TLR4, MyD88, NF-κBp65 genes. These results indicated the co-exposure of ZEA and DON caused oxidative stress, leading to stronger potential toxic effects to zebrafish embryos than their respective single treatment. Therefore, more attention should be paid to risk management of the co-contamination of mycotoxins.

Chronic exposure to zearalenone induces intestinal inflammation and oxidative injury in adult Drosophila melanogaster midgut

In the past decade, mycotoxin zearalenone (ZEN)-induced gastrointestinal adverse effects have been increasingly attracting worldwide attention. This study aimed to determine the gastrointestinal adverse effects of ZEN in Drosophila melanogaster (D. melanogaster) and reveal possible mechanisms of action of ZEN in insects. Here, chronic exposure of D. melanogaster to ZEN killed flies in a dose-dependent manner (2-20 µM). ZEN (20 µM) decreased the survival rates and climbing ability of flies, and activated immune deficiency-mediated intestinal immunity in midgut, leading to the production of antimicrobial peptides. Meanwhile, ZEN exposure induced morphological alteration of adult midgut. Further study suggested that high levels of oxidative stress was observed in ZEN-treated midgut due to the imbalance between the production of reactive oxygen species and the expression and activities of cellular antioxidant enzyme, including superoxide dismutase and catalase. ZEN-induced oxidative stress then caused cell death, impaired gut barrier function and increased gut permeability, leading to oxidative injury in midgut. Subsequently, ZEN-induce midgut injury further disrupted intestinal stem cell (ISC) homeostasis, stimulating ISC proliferation and tissue regeneration, but did not alter cell fate specification of ISC. Additionally, activation of Jun N-terminal kinase pathway was involved in ZEN-induced oxidative injury and tissue regeneration in midgut. Antioxidant vitamin E alleviated ZEN-induced oxidative injury to midgut epithelium. Collectively, this study provided additional evidences for ZEN-induced gastrointestinal adverse effects from an invertebrate model, extended our understanding of the mechanisms mediating mycotoxin toxicity in organisms.

Microbial and enzymatic battle with food contaminant zearalenone (ZEN)

Zearalenone (ZEN) contamination of various foods and feeds is an important global problem. In some animals and humans, ZEN causes significant health issues in addition to massive economic losses, annually. Therefore, removal or degradation of the ZEN in foods and feeds is required to be done. The conventional physical and chemical methods have some serious issues including poor efficiency, decrease in nutritional value, palatability of feed, and use of costly equipment. Research examined microbes from diverse media for their ability to degrade zearalenone and other toxins, and the findings of several investigations revealed that enzymes produced from microbes play a significant role in the degradation of mycotoxins. In established bacterial hosts, genetically engineered technique was used to enhance heterologously produced degrading enzymes. Then, the bio-degradation of ZEN by the use of micro-organisms or their enzymes is much more advantageous and is close to nature and ecofriendly. Furthermore, an effort is made to put forward the work done by different scientists on the biodegradation of ZEN by the use of fungi, yeast, bacteria, and/or their enzymes to degrade the ZEN to non-toxic products. KEY POINTS: •Evolved microbial strains degraded ZEA more quickly •Different degrading properties were studied.

Statistical Analysis and Machine Learning Used in the Case of Two Behavioral Tests Applied in Zebrafish Exposed to Mycotoxins

Machine learning is a branch of artificial intelligence that allows computer systems to learn directly from examples, data, and experience. Statistical modeling is more about finding connections between variables and consequently the impact of these relationships, while also catering for prediction. It should be clear that these two methodologies are different in terms of their purpose, despite the fact that they use similar means to get there. The evaluation of the machine learning algorithm uses a set of tests to validate its accuracy. Although, for a statistical model, the analysis of regression parameters by confidence intervals, significance tests and other tests can be used to assess the legitimacy of the model. To demonstrate the applications and usefulness of this theory, an experimental study was conducted on zebrafish exposed to mycotoxin. Methods: Patulin (70 µg/L) and kojic acid (100 mg/L, 204 mg/L, and 284 mg/L) were administered by immersion to zebrafish once daily for a period of 7 days before the behavior testing. The following behavioral tests were performed: a novel tank test (NTT) (to assess the explorative behavior and anxiety); and a Y-maze test (which measures the spontaneous explorative behavior). Behavioral tests were performed on separate days. For the behavior tests, the statistical analysis was performed using ANOVA variation analysis (two-way ANOVA). All results are expressed as the mean ± standard error of the mean. The values of the general index F for which p < 0.05 were considered statistically significant. Results: Y-maze—patulin exposure led to an intensification of the locomotor activity and an increased traveled distance and number of arm entries. By increasing the spontaneous alternation between the aquarium’s arms, patulin has shown a stimulating effect on spatial memory. In the case of zebrafish exposed to 100 mg/L kojic acid, the traveled distance was shorter by 27% than the distance attained by those in the control group. The higher doses of kojic acid (204 mg/L and 284 mg/L) led to an increased locomotor activity, distance traveled, number of arm entries, and the spontaneous alternation. The increase in spontaneous alternation demonstrates that 204 mg/L and 284 mg/L kojic acid doses had a stimulating effect on spatial memory. Novel tank test—compared to the control group, the traveled distance of the patulin-exposed fish is slightly reduced. Compared to the control group, the traveled distance of the kojic acid-exposed fish is reduced, due to a shorter mobile time (by 25–27% in the case of fish exposed to 204 mg/L and 284 mg/L kojic acid). Patulin and kojic acid exhibit toxic effects on zebrafish liver, kidney, and myocardium and leads to severe alteration. We continued the analysis by trying some machine learning algorithms on the classification problems in the case of the two behavioral tests MAZE and NTT, after which we concluded that the results were better in the case of the NTT test relative to the MAZE test and that the use of decision tree algorithms leads to amazing results, knowing that their hierarchical structure allows them to learn signals from both classes. Conclusions: The groups exposed to patulin and kojic acid show histological changes in the liver, kidneys, and myocardial muscle tissue. The novel tank test, which assesses exploratory behavior, has been shown to be conclusive in the behavioral analysis of fish that have been given toxins, demonstrating that the intoxicated fish had a decreased explorative behavior and increased anxiety. We were able to detect a machine learning algorithm in the category of decision trees, which can be trained to classify the behavior of fish that were given a toxin in the category of those used in the experiment, only by analyzing the characteristic features of the NTT Behavior Test.

Estrogen Receptors Mediated Negative Effects of Estrogens and Xenoestrogens in Teleost Fishes-Review

Estrogen receptors (ERs) play a key role in many biochemical and physiological processes, that are involved in maintaining organism homeostasis. At the most basic level, they can be divided into nuclear estrogen receptors and membrane estrogen receptors that imply their effect in two ways: slower genomic, and faster non-genomic. In these ways, estrogens and xenoestrogens can negatively affect animal health and welfare. Most of the available literature focuses on human and mammalian physiology, and clearly, we can observe a need for further research focusing on complex mutual interactions between different estrogens and xenoestrogens in aquatic animals, primarily fishes. Understanding the mechanisms of action of estrogenic compounds on the ERs in fishes and their negative consequences, may improve efforts in environmental protection of these animals and their environment and benefit society in return. In this review, we have summarized the ER-mediated effects of xenoestrogens and estrogens on teleost fishes metabolism, their carcinogenic potential, immune, circulatory, and reproductive systems.

Zearalenone induces immuno-compromised status via TOR/NF/κB pathway and aggravates the spread of Aeromonas hydrophila to grass carp gut (Ctenopharyngodon idella)

The occurrence of immuno-compromised status in animals with zearalenone (ZEA) exposure may be a critical contributor to associated mucosal (gastrointestinal tract) diseases. However, it is difficult to assess the associated risks with limited reference data. This study comprehensively discussed the effects of ZEA on intestinal immune components, cytokines and molecular mechanism of juvenile grass carp infected with Aeromonas hydrophila. Specifically, the fish were fed six graded levels of dietary ZEA (0-2507 μg kg^-1 diet) for 70 d. The results pointed out that the average residual amount of ZEA in the intestines increased with dose level after ZEA feeding. We further performed an infection assay using A. hydrophila. After 14 d, ZEA groups increased enteritis morbidity rate compared with controls. The acid phosphatase (ACP), lysozyme (LZ) activities and immunoglobulin M (IgM) content were significantly decreased in three intestinal segments. Furthermore, ZEA could reduce the transcription of β-defensin-1, Hepcidin, liver expressed antimicrobial peptide 2A/2B (LEAP-2A/2B) and Mucin-2. We next confirmed the loss of these immune components accompanied by the invasion of the intestinal barrier by bacteria, as indicated by activation of the nuclear factor κB (NF-κB) and the expression of downstream cytokines. Notably, the phosphorylated target of rapamycin (TOR) plays an important role in regulating these genes, thus indicating a possible target caused by ZEA. In summary, the extensive inhibition of immune components by ZEA promotes the spread of pathogens, which may increase the possibility of intestinal mucosa exposure and the risk of transforming disease.

Variations of enzymatic activity and gene expression in zebrafish (Danio rerio) embryos co-exposed to zearalenone and fumonisin B1

The natural co-occurrence of multiple mycotoxins has been reported in cereals and cereal products worldwide. Even though the dietary exposure to mycotoxins constitutes a serious human health, most reports are limited to the toxic effect of individual mycotoxins. The purpose of the present study was to assess the combined toxic effects of zearalenone (ZEN) and fumonisin B1 (FB1) and the potential interaction of their mixture on zebrafish (Danio rerio) embryos. Our results showed that ZEN possessed the higher toxicity to embryonic zebrafish (7-day LC₅₀ value of 0.78 mg a.i. L^-1) compared with FB1 (7-day LC₅₀ value of 227.7 mg a.i. L^-1). The combination of ZEN and FB1 exerted an additive effect on zebrafish embryos. Meanwhile, the activities of antioxidant CAT, caspase-3, and detoxification enzyme CYP450, as well as the expressions of six genes (Mn-sod, cas9, bax, cc-chem, ERα, and crh) associated with oxidative stress, cellular apoptosis, immune system, and endocrine system were prominently altered in the mixture exposure compared with the corresponding single treatment group of ZEN or FB1. Taken together, the regulatory standards of mycotoxins in food and feed should be updated based on the mixture effects of mycotoxins, and there is an increased need on effective detoxification methods for controlling and reducing the toxicity of multiple mycotoxins in animal feed and throughout the food supply chain.

Dietary garlic and chitosan enhanced the antioxidant capacity, immunity, and modulated the transcription of HSP70 and Cytokine genes in Zearalenone-intoxicated European seabass

The present study was performed to evaluate the toxic effects of feed-born zearalenone (ZEN) on antioxidative status, immunity, transcriptomic responses of European seabass, and the modulating roles of dietary garlic and/or chitosan powders. Fish (30.7 ± 0.6 g) were randomly arranged in five experimental groups (in triplicates), whereas the first group was fed on the control diet only without any supplements (control), and the second group was fed on the basal diet contaminated with ZEN (0.725 mg/kg diet). Three other groups were fed on ZEN-contaminated diets and simultaneously supplemented with garlic powder (GP) (30 g/kg diet) (ZEN + GP), chitosan powder (CH) (10 g/kg diet) (ZEN + CH), and a mixture of GP and CH (ZEN + GP + CH). Fish were fed on the experimental diets thrice a day for 4 weeks. Two-way ANOVA revealed a gradual decline in serum superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities in the ZEN group reaching their lowest levels at the 4th week. Contrariwise, malondialdehyde levels were markedly higher in the ZEN group reaching their highest values at the end of the experiment. A significant decline of total immunoglobulins (P < 0.05) was observed in the serum of the ZEN group, especially after the 4th week. Moreover, significant down-regulation of interleukin-4 (IL-4) and interleukin 1 beta (IL-1β) genes (P < 0.05) alongside significant up-regulation of tumor necrosis factor-alpha (TNF-α) and heat shock protein 70 (HSP70) genes (P < 0.05) in the liver and anterior kidney of ZEN-intoxicated group. Interestingly, dietary supplementation with GP and CH significantly attenuated ZEN-induced oxidative stress, immunosuppression, and modulated transcriptomic responses of ZEN-exposed fish. Moreover, combined dietary supplementation of both feed additives resulted in better effects than each one alone.

Occurrence and distribution of estrogenic substances in the northern South China Sea

Estrogenic substances are today among the contaminants of emerging concern. Besides naturally occurring estrogens, other natural and synthetic substances can mimic a hormonal action due to their structural resemblance to hormones, possibly affecting the endocrine system of living organisms. Estrogens have been detected in inland water bodies such as influents and effluents of waste water treatment plants as well as in rivers, but data on their distribution and variability in the marine ecosystem are still limited. Surface water samples obtained during two research cruises on the northern shelf of the South China Sea (SCS) near the Pearl River Estuary, in September 2018 and in August 2019, were investigated for estrogenic substances, namely estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), genistein (GEN), daidzein (DAI) and zearalenone (ZEN). Among the target analytes, the natural hormones E1 and E2, as well as the synthetic EE2, were the most abundant with maximum concentrations of 1.1 ng L^-1, 0.7 ng L^-1 and 0.6 ng L^-1, respectively. Of substances produced by plants and fungi, GEN, DAI and ZEN, only GEN was detected (1.2 ng L^-1). High concentrations occurred predominantly close to the coast, which was also reflected in the calculated estradiol equivalent quotients (up to 1.4 ng L^-1). In general, the distribution of estrogenic substances observed in both years shows a regional and inter-annual variability consistent with the modeled surface current data for the SCS. Regarding single estrogenic compounds and estradiol equivalents, marine organisms in the northern SCS might be exposed to high potential risk.

Environmental risks to freshwater organisms from the mycotoxins deoxynivalenol and zearalenone using Species Sensitivity Distributions

In this study, laboratory experiments have addressed the acute toxicity of two common mycotoxins, deoxynivalenol (DON) and zearalenone (ZON), in a range of freshwater organisms (including rotifers Brachionus calyciflorus, insects Chironomus riparius (larvae), crustaceans Daphnia pulex and Thamnocephalus platyurus, cnidarians Hydra vulgaris, molluscs Lymnaea stagnalis (embryos) and Protozoa Tetrahymena thermophila). Acute EC₅₀ values highlight crustaceans as the most sensitive organisms to DON, with T. platyurus having a 24 h EC₅₀ of 0.14 and D. magna having a 48 h EC₅₀ of 0.13 mg DON/L. During exposures to ZON, H. vulgaris and L. stagnalis embryos showed the highest sensitivity; mortality EC₅₀ values were 1.1 (96 h) and 0.42 mg ZON/L (7 d), respectively. Combining these novel invertebrate toxicity results, along with recent published data for freshwater plant and fish toxicity for analysis of Species Sensitivity Distributions, provides freshwater HC₅ values of 5.2 μg DON/L and 43 μg ZON/L, respectively. Using highest reported environmental concentrations and following REACH guidelines, risk ratios calculated here show the risk of ZON to freshwater organisms is low. In contrast, DON may periodically because for concern in streams subject to high agricultural run-off, likely during certain times of year where cereal crops are susceptible to higher fungal infections rates and may pose increased risks due to climate change.

Evaluation of the Multimycotoxin-Degrading Efficiency of Rhodococcus erythropolis NI1 Strain with the Three-Step Zebrafish Microinjection Method

The multimycotoxin-degrading efficiency of the Rhodococcus erythropolis NI1 strain was investigated with a previously developed three-step method. NI1 bacterial metabolites, single and combined mycotoxins and their NI1 degradation products, were injected into one cell stage zebrafish embryos in the same doses. Toxic and interaction effects were supplemented with UHPLC-MS/MS measurement of toxin concentrations. Results showed that the NI1 strain was able to degrade mycotoxins and their mixtures in different proportions, where a higher ratio of mycotoxins were reduced in combination than single ones. The NI1 strain reduced the toxic effects of mycotoxins and mixtures, except for the AFB1+T-2 mixture. Degradation products of the AFB1+T-2 mixture by the NI1 strain were more toxic than the initial AFB1+T-2 mixture, while the analytical results showed very high degradation, which means that the NI1 strain degraded this mixture to toxic degradation products. The NI1 strain was able to detoxify the AFB1, ZEN, T-2 toxins and mixtures (except for AFB1+T-2 mixture) during the degradation experiments, which means that the NI1 strain degraded these to non-toxic degradation products. The results demonstrate that single exposures of mycotoxins were very toxic. The combined exposure of mycotoxins had synergistic effects, except for ZEN+T-2 and AFB1+ZEN +T-2, whose mixtures had very strong antagonistic effects.

Fumonisin B1 Production by Fusarium Species and Mycotoxigenic Effect on Larval Zebrafish

Fumonisin B₁ (FB₁) is a common mycotoxin produced by Fusarium species particularly F. proliferatum and F. verticillioides. The toxin produced can cause adverse effects on humans and animals. The objectives of this study were to detect the production of FB₁ based on the amplification of FUM1 gene, to quantify FB₁ produced by the isolates using Ultra-fast Liquid Chromatography (UFLC) analysis, to examine the embryotoxicity effect of FB₁ and to determine EC₅₀ toward the larvae of zebrafish (Danio rerio). Fifty isolates of Fusarium species were isolated from different hosts throughout Malaysia. Successful amplification of the FUM1 gene showed the presence of this gene (800 bp) in the genome of 48 out of 50 isolates. The highest level of FB₁ produced by F. proliferatum isolate B2433 was 6677.32 ppm meanwhile F. verticillioides isolate J1363 was 954.01 ppm. From the assessment of embryotoxicity test of FB₁ on larvae of zebrafish, five concentrations of FB₁ (0.43 ppm, 0.58 ppm, 0.72 ppm, 0.87 ppm and 1.00 ppm) were tested. Morphological changes of the FB₁ exposed-larvae were observed at 24 to 168 hpf. The mortality rate and abnormality of zebrafish larvae were significantly increased at 144 hpf exposure. Meanwhile, the spontaneous tail coiling showed a significant difference. There were no significant differences in the heartbeat rate. As a conclusion, the presence of FUM1 in every isolate can be detected by FUM1 gene analysis and both of the species produced different concentrations of FB₁. This is the first report of FB₁ produced by Fusarium species gave a significant effect on zebrafish development.

Larval zebrafish as an in vitro model for evaluating toxicological effects of mycotoxins

The presence of mycotoxins in food has created concern. Mycotoxin prevalence in our environment has changed in the last few years maybe due to climatic and other environmental changes. Evidence has emerged from in vitro and in vivo models: some mycotoxins have been found to be potentially carcinogenic, embryogenically harmful, teratogenic, and to generate nephrotoxicity. The risk assessment of exposures to mycotoxins at early life stages became mandatory. In this regard, the effects of toxic compounds on zebrafish have been widely studied, and more recently, mycotoxins have been tested with respect to their effects on developmental and teratogenic effects in this model system, which offers several advantages as it is an inexpensive and an accessible vertebrate model to study developmental toxicity. External post-fertilization and quick maturation make it sensitive to environmental effects and facilitate the detection of endpoints such as morphological deformities, time of hatching, and behavioral responses. Therefore, there is a potential for larval zebrafish to provide new insights into the toxicological effects of mycotoxins. We provide an overview of recent mycotoxin toxicological research in zebrafish embryos and larvae, highlighting its usefulness to toxicology and discuss the strengths and limitations of this model system.

Sources, quantification techniques, associated hazards, and control measures of mycotoxin contamination of aquafeed

With the productive intensification of fish farming, the partial or total replacement of fishmeal by ingredients of plant origin became a reality within the feed industry, with the aim of reducing costs. However, this practice increased the impact of mycotoxin contamination. Studies have shown that mycotoxins can induce various disorders in fish, such as cellular and organic alterations, as well as impair functional and morphological development, and, in more severe cases, mortality. Thus, studies have been conducted to evaluate and develop strategies to prevent the formation of mycotoxins, as well as to induce their elimination, inactivation or reduction of their availability in feed.

Risk assessment for mycotoxin contamination in fish feeds in Europe

Mycotoxins are difficult to monitor continuously, and a tool to assess the risk would help to judge if there is a particular risk due to the inclusion of certain feed ingredients. For this, the toxin contents of 97 commercial fish feeds have been estimated, and the most prominent toxins in fish feed are calculated to be deoxynivalenol, zearalenone, fumonisins and enniatins. These pose a risk to fish well-being, as can be calculated by the Bayesian models for determining the critical concentrations 5% (CC5) for the different toxins. Besides fishmeal, wheat, soybean products and corn are regularly used as fish feed ingredients. The calculated scenarios show that fish are at high risk of toxin contamination if feed ingredients of low quality are chosen for feed production. Due to this, specific maximum allowable levels for several mycotoxins in fish feeds should be established.

Occurrence of Fungi and Mycotoxins in Fish Feeds and Their Impact on Fish Health

The rapid population growth in developing countries has led to strong pressure on capture fisheries. However, capture fisheries have reached their maximal limits of fish production and are supplemented by farmed fish. The growth in aquaculture has led to high demand for fish feeds, which play a very important role in fish nutrition and health. Use of animal protein in fish feeds is expensive; hence, a majority of farmers from developing countries use local feed ingredients from plant origin as a source of dietary protein. However, these ingredients of plant origin provide the best natural substrates for fungi, which can be easily accompanied by mycotoxin development under suitable conditions. The locally made feed comprises ingredients such as soybeans, cottonseed cake, and wheat and maize bran which are mixed together and ground after which the compounded feed is pelleted and stored. Among the ingredients, maize and oilseeds are more susceptible for mycotoxigenic fungi compared to other ingredients. The outcomes of mycotoxin contamination in fish feeds are not different from other animal species intended for human consumption, and they are directly associated with production losses, particularly decreased weight gain and feed conversion, impaired immune system and reproductive performance, and increased fish mortality. Fish may also carry mycotoxin residues along the food chain, thus compromising human health. Hence, it is important to ensure the control of mycotoxin contamination in fish feeds, especially during the production and storage.

Effects of Dietary Zearalenone on Oxidative Stress, Cell Apoptosis, and Tight Junction in the Intestine of Juvenile Grass Carp (Ctenopharyngodon idella)

Zearalenone (ZEA) is a prevalent mycotoxin with high toxicity in animals. In order to study its effect on juvenile grass carp (Ctenopharyngodon idella), six diets supplemented with different levels of ZEA (0, 535, 1041, 1548, 2002, and 2507 μg/kg diet) for 10 weeks were studied to assess its toxicity on intestinal structural integrity and potential mechanisms of action. Our report firstly proved that ZEA led to growth retardation and body deformity, and impaired the intestinal structural integrity of juvenile grass carp, as revealed by the following findings: (1) ZEA accumulated in the intestine and caused histopathological lesions; (2) ZEA resulted in oxidative injury, apoptosis, and breached tight junctions in the fish intestine, which were probably associated with Nuclear factor-erythroid 2-related factor 2 (Nrf2), p38 mitogen activated protein kinases (p38MAPK), and myosin light chain kinase (MLCK) signaling pathways, respectively. ZEA had no influence on the antioxidant gene levels of Kelch-like ECH associating protein 1 (Keap1)b (rather than Keap1a), glutathione-S-transferase (GST)P1, GSTP2 (not in the distal intestine (DI)), tight junctions occludin, claudin-c (not in the proximal intestine (PI)), or claudin-3c (not in the mid intestine (MI) or DI).

Zearalenone Induces Estrogen-Receptor-Independent Neutrophil Extracellular Trap Release in Vitro

Zearalenone (ZEA) is a non-steroidal estrogenic mycotoxin synthesized in Fusarium species, mainly Fusarium graminearum and Fusarium culmorum, and it has strong estrogenic activity and causes genotoxic effects, reproductive disorders, and immunosuppressive effects. Neutrophil extracellular trap (NET) has been studied for many years. Initially, NET was considered a form of the innate response that combats invading microorganisms. However, NET is involved in a series of pathophysiological mechanisms, including thrombosis, tissue necrosis, autoinflammation, and even autoimmunity. We recently found that polymorphonuclear neutrophils response to ZEA exposure by undergoing NET formation. However, the molecular mechanisms involved in this process remain poorly characterized. Here, we analyze whether estrogen receptors (ERs) can affect NET formation after ZEA stimulation. The involvement of ERs is investigated with the selective ER antagonists. Moreover, we investigate the mechanisms of NET formation using immunofluorescence staining, fluorescence microplate, and western blot analysis. Our results show that ERs (ERα and ERβ) are not involved in ZEA-induced NET formation, but reactive oxygen species (ROS), extracellular signal-regulated kinase (ERK), and p38 are postulated to be involved. Specifically, we provide data demonstrating that ZEA-induced ROS may promote activation of ERK and p38 as well as subsequent NET release. We are the first to demonstrate this new mechanism of ZEA-induced NET formation, which may help in understanding the role of ZEA in overexposure diseases and provide a relevant basis for therapeutic applications.

Impacts of the mycotoxin zearalenone on growth and photosynthetic responses in laboratory populations of freshwater macrophytes (Lemna minor) and microalgae (Pseudokirchneriella subcapitata)

Mycotoxins are an important class of chemicals of emerging concern, recently detected in aquatic environments, potentially reflecting the influence of fungicide resistance and climatic factors on fungal diseases in agricultural crops. Zearalenone (ZON) is a mycotoxin formed by Fusarium spp. and is known for its biological activity in animal tissues; both in vitro and in vivo. ZON has been reported in US and Polish surface waters at 0.7 - 96 ng/L, with agricultural run-off and wastewater treatment plants being the likely sources of mycotoxins. As some mycotoxins can induce phytotoxicity, laboratory studies were conducted to evaluate the toxicity of ZON (as measured concentrations) to freshwater algae (Pseudokirchneriella subcapitata) and macrophytes (Lemna minor) following OECD test guidelines 201 and 221, respectively. Zinc sulphate was used as a positive control. In the OECD 201 algal static study (72 h at 24 ± 1 °C), exposure to ZON gave average specific growth rate (cell density) EC₅₀ and yield (cell density) EC₅₀ values of > 3.1 and 0.92 (0.74 - 1.8) mg/L, respectively. ZON was less toxic in the OECD 221 static study and after 7 d at 24 ± 1 °C. L. minor growth was significantly reduced based on frond number and frond area at 11.4 mg ZON/L, showing a higher tolerance than reported for other mycotoxins with Lemna spp. Chlorophyll fluorescence parameters were used as biomarkers of impacts on photosystem II efficiency, with no effect seen in algae but, with responses being observed in L. minor between 5.2 - 14.4 mg ZON/L. ZON toxicity seen here is not of immediate concern in context with environmental levels, but this study highlights that other freshwater organisms including algae are more sensitive to mycotoxins than Lemna sp., the only current source of toxicity data for freshwater plants.

Effect of grape seed extract on maternal toxicity and in utero development in mice treated with zearalenone

The aims of this study were to determine the polyphone content of grape seed extract (GSE) and to assess their protective effects against zearalenone (ZEN)-induced maternal toxicity and in utero development defects in mice. Five groups of pregnant mice were treated orally during days 6-13 of gestation as follows: control group, corn oil as vehicle (0.1 ml/mice)-treated group, ZEN-treated group (25 mg/kg b.w), GSE-treated group (150 mg/kg b.w.), and ZEN plus GSE-treated group. All animals were sacrificed on the 19th day of gestation and samples of bone marrow were collected for the micronucleus assay. The maternal and developmental toxicity were carried out. The HPLC analyses revealed that GES is rich in gallic acid, syringic acid, vanillin, quercetin, and coumaric acid. ZEN administration resulted in severe maternal and developmental toxicity which included an increase of micronuclei formation in bone marrow, decreased maternal weight gain, and litter weight. It also induces fetal growth retardation, increased number of the aborted dams and resorbed fetuses, abnormality of fetal bone ossification, and number of fetuses with a hematoma. GSE showed positive effects on the pregnant mice and the developing fetuses. Moreover, it counteracted the detrimental effects of ZEN in dams and fetuses. It could be concluded that polyphenols in GSE are a promising candidate to protect against ZEN toxicity in highly endemic areas.

Mycotoxins induce developmental toxicity and behavioural aberrations in zebrafish larvae

Mycotoxins are secondary metabolites produced by varieties of fungi that contaminate food and feed resources and are capable of inducing a wide range of toxicity. In the current study, we investigated developmental and behavioural toxicity in zebrafish larvae after exposure to six different mycotoxins; ochratoxin A (OTA), type A trichothecenes mycotoxin (T-2 toxin), type B trichothecenes mycotoxin (deoxynivalenol - DON), and zearalenone (ZEN) and its metabolites alpha-zearalenol (α-ZOL) and beta-zearalenol (β-ZOL). Developmental defects, hatching time, and survival were monitored until 96 h post fertilisation (hpf). The EC₅₀, LC₅₀, and IC₅₀ values were calculated. Subsequently, to assess behavioural toxicity, new sets of embryos were exposed to a series of non-lethal doses within the range of environmental and/or developmental concern. Results indicated that all the tested mycotoxins were toxic, they all induced developmental defects, and with the exception of OTA, all affected hatching time. Behavioural effects were only observed following exposure to OTA and ZEN and its metabolites, α ZOL and β ZOL. These results demonstrate that mycotoxins are teratogenic and can influence behaviour in a vertebrate model.

Mycotoxin zearalenone induced gonadal impairment and altered gene expression in the hypothalamic-pituitary-gonadal axis of adult female zebrafish (Danio rerio)

In the present study, we aimed to assess the adverse effects of zearalenone (ZEA) at environmentally relevant concentrations (0.5, 1, 5 and 10 μg l^-1 ) on hypothalamic-pituitary-gonadal axis associated reproductive function using zebrafish model. ZEA was exposed to female zebrafish for 21 days to assess growth indices such as condition factor, hepatosomatic index, gonadosomatic index and caspase 3 activity. Further, expression of estrogen receptor (ER) α and CYP19a1b genes in the brain, ERα and vitellogenin (Vtg) genes in the liver and follicle-stimulating hormone receptor, luteinizing hormone receptor, ERα, steroidogenic acute regulatory protein, 3β-hydroxysteroid dehydrogenase (HSD), 17-βHSD and CYP19a1 genes in the ovary were also investigated. Our results showed that there were no significant changes in the condition factor and hepatosomatic index, whereas a significant (P < .05) reduction in the gonadosomatic index, increase in caspase 3 activities and Vtg expression was observed at higher concentration. However, no significant changes were observed at lower treatment levels. Further, we also observed significant (P < .05) upregulation in ERα, Vtg, luteinizing hormone receptor, steroidogenic acute regulatory protein, 3β-HSD, 17β-HSD, CYP19a1 and CYP19a1b genes in treatment groups with higher levels of ZEA. Moreover, in histopathological examination, we observed oocyte atresia and oocyte membrane detachment in ovaries at the highest concentration. In conclusion, the present study revealed the negative impact of ZEA on zebrafish reproductive system by involvement of the hypothalamic-pituitary-gonadal axis-associated reproductive function.

Zearalenone induced embryo and neurotoxicity in zebrafish model (Danio rerio): Role of oxidative stress revealed by a multi biomarker study

In the present study, we evaluated the zearalenone induced adverse effects in zebrafish embryos using various endpoints like embryo toxicity, heart rate, oxidative stress indicators (reactive oxygen species (ROS), lipid peroxidation (LPO), Nitric oxide (NO)), antioxidant responses (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase enzyme (GST) and reduced glutathione (GSH), metabolic biomarkers (lactate dehydrogenase (LDH) and Nitric oxide (NO)), neurotoxicity (acetylcholinesterase (AChE)), genotoxicity (comet assay and acridine orange staining (AO)) and histological analysis. In this study, four concentrations 350, 550, 750 and 950 μg/L of ZEA were chosen based on LC10 and LC50 values of the previous report. The results shows that ZEA induces developmental defects like pericardial edema, hyperemia, yolk sac edema, spine curvature and reduction in heart rate from above 550 μg/L exposure and the severity was increased with concentration and time dependent manner. Significant induction in oxidative stress indices (ROS, LPO and NO), reduction in antioxidant defence system (SOD, CAT, GPx, GST and GSH) and changes in metabolic biomarkers (LDH and AP) were observed at higher ZEA exposed concentration. Neurotoxic effects of ZEA were observed with significant inhibition of AChE activity at higher exposure groups (750 and 950 μg/L). Moreover, we also noticed DNA damage, apoptosis and histological changes in the higher ZEA treatments at 96 h post fertilization (hpf) embryos. Hence, in the present study we concluded that oxidative stress is the main culprit in ZEA induced developmental, genotoxicity and neurotoxicity in zebrafish embryos.

Fish as a model to assess chemical toxicity in bone

Environmental toxicology has been expanding as growing concerns on the impact of produced and released chemical compounds over the environment and human health are being demonstrated. Among the toxic effects observed in organisms exposed to pollutants, those affecting skeletal tissues (osteotoxicity) have been somehow overlooked in comparison to hepato-, immune-, neuro- and/or reproductive toxicities. Nevertheless, sub-lethal effects of toxicants on skeletal development and/or bone maintenance may result in impaired growth, reduced survival rate, increased disease susceptibility and diminished welfare. Osteotoxicity may occur by acute or chronic exposure to different environmental insults. Because of biologically and technically advantagous features - easy to breed and inexpensive to maintain, external and rapid rate of development, translucent larvae and the availability of molecular and genetic tools - the zebrafish (Danio rerio) has emerged in the last decade as a vertebrate model system of choice to evaluate osteotoxicity. Different experimental approaches in fish species and analytical tools have been applied, from in vitro to in vivo systems, from specific to high throughput methodologies. Current knowledge on osteotoxicity and underlying mechanisms gained using fish, with a special emphasis on zebrafish systems, is reviewed here. Osteotoxicants have been classified into four categories according to the pathway involved in the transduction of the osteotoxic effects: activation/inhibition of membrane and/or nuclear receptors, alteration of redox condition, mimicking of bone constituents and unknown pathways. Knowledge on these pathways is also reported here as it may provide critical insights into the development, production and release of future chemical compounds with none or low osteotoxicity, thus promoting the green/environmental friendly chemistry.

The mycoestrogen zearalenone in Portuguese flowing waters and its potential environmental impact

This study provides the first environmental risk assessment (ERA) for zearalenone (ZEN), the only known mycoestrogen, based on a broad-scale investigation on its occurrence in rivers and creeks from Portugal. Water sample filtration and immunoaffinity columns (IAC) clean-up followed by liquid chromatograph with tandem mass spectrometry (LC/MS ⁿ ) provided an analytical method with good analytical performance. ZEN levels were determined for seven Portuguese rivers and one creek, during two different seasons, in a total of 38 samples collected upstream wastewater treatment plants (WWTPs). Overall, 23.7% were contaminated with ZEN at levels ranging between 5.6 and 82.6 ng/L. The highest concentration was observed during spring, although no statistically significant differences were observed between spring and autumn sampling campaigns. The potential ecotoxicological risk from ZEN to different trophic levels of aquatic organisms was evaluated by means of risk quotients (RQs) calculation. Although all the RQs obtained were lower than 1, our results confirm that ZEN is a relatively frequent contaminant in flowing waters in Portugal and might contribute to the overall estrogenic activity in the environment.

Bisphenol A and di(2-ethylhexyl) phthalate exert divergent effects on apoptosis and the Wnt/β-catenin pathway in zebrafish embryos: A possible mechanism of endocrine disrupting chemical action

Polyethylene terephthalate (PET) and polycarbonate (PC) are the most commonly used plastics in water bottles. Di(2-ethylhexyl) phthalate (DEHP) is used as a plasticizer in PET plastics, and bisphenol A (BPA) is used to produce PC. Both DEHP and BPA are known for their potential endocrine disrupting effects. The Wnt/β-catenin signaling pathway has important roles in cell proliferation, cell specification and cell fate determination during embryonic development. Recent reports suggest a link between the Wnt/β-catenin signaling pathway and apoptosis. The aim of this study was to investigate the relation between Wnt/β-catenin signaling and apoptosis in the case of BPA and DEHP exposure in zebrafish embryos. Accordingly, in vivo cell death was assessed using acridine orange staining, and reverse transcription polymerase chain reaction was used to determine the expressions of wnt3a, gsk3β and ccnd1. Proliferative cell nuclear antigen, β-catenin and Wnt3a expressions were determined immunohistochemically. Vitellogenin levels were determined using Enzyme Linked ImmunoSorbent Assay (ELISA). Increased vitellogenin levels, apoptosis, and wnt3a and gsk3β expressions were observed in BPA-exposed zebrafish embryos. Increased apoptosis in the BPA-exposed embryos may be due to the pro-apoptotic changes induced by Wnt3a, whereas DEHP might be suggested to have a minor effect as Wnt3a expression; vitellogenin levels and apoptosis did not increase significantly following exposure to DEHP.

Physiological responses of carp (Cyprinus carpio L.) to dietary exposure to zearalenone (ZEN)

Zearalenone (ZEN) is a frequent contaminant of animal feeds, but systemic effects on fish and possible metabolic costs have not yet been investigated. In order to fill this gap a feeding trial with juvenile carp was conducted. The fish were fed ZEN-contaminated diets at three concentrations (low: 332μgkg(-1), medium: 621μgkg(-1), and high: 797μgkg(-1) final feed, respectively) for four weeks. Possible reversible effects of ZEN were evaluated by feeding an additional group with the mycotoxin for four weeks period and the uncontaminated diet for further two weeks. After that possible ZEN effects on enzyme activities in kidney, spleen, liver and muscle tissue were investigated to get an organism-wide aspect of ZEN effects. Most organs appeared to (over)compensate ZEN effects during the exposure to this mycotoxin, which caused metabolic costs. Oxygen consumption increased in fish treated with the two higher ZEN concentrations via the diet. The differences between the treatments persisted also after the recovery phase of two weeks. Thus, the present study provided evidence of effects of ZEN on carbohydrate metabolism, lipid peroxidation in organs and metabolic oxygen demand. This is the first evidence for increased metabolic costs in a fish species due to exposure to the mycotoxin ZEN.

Comparative Developmental Toxicity of Flavonoids Using an Integrative Zebrafish System

Flavonoids are a large, structurally diverse class of bioactive naturally occurring chemicals commonly detected in breast milk, soy based infant formulas, amniotic fluid, and fetal cord blood. The potential for pervasive early life stage exposures raises concerns for perturbation of embryogenesis, though developmental toxicity and bioactivity information is limited for many flavonoids. Therefore, we evaluated a suite of 24 flavonoid and flavonoid-like chemicals using a zebrafish embryo-larval toxicity bioassay-an alternative model for investigating developmental toxicity of environmentally relevant chemicals. Embryos were exposed to 1-50 µM of each chemical from 6 to 120 h postfertilization (hpf), and assessed for 26 adverse developmental endpoints at 24, 72, and 120 hpf. Behavioral changes were evaluated in morphologically normal animals at 24 and 72 hpf, at 120 hpf using a larval photomotor response (LPR) assay. Gene expression was comparatively evaluated for all compounds for effects on biomarker transcripts indicative of AHR (cyp1a) and ER (cyp19a1b, esr1, lhb, vtg) pathway bioactivity. Overall, 15 of 24 flavonoids elicited adverse effects on one or more of the developmental or behavioral endpoints. Hierarchical clustering and principle component analyses compared toxicity profiles and identified 3 distinct groups of bioactive flavonoids. Despite robust induction of multiple estrogen-responsive biomarkers, co-exposure with ER and GPER antagonists did not ameliorate toxicity, suggesting ER-independence and alternative modes of action. Taken together, these studies demonstrate that development is sensitive to perturbation by bioactive flavonoids in zebrafish that are not related to traditional estrogen receptor mode of action pathways. This integrative zebrafish platform provides a useful framework for evaluating flavonoid developmental toxicity and hazard prioritization.

Interpretation of fish biomarker data for identification, classification, risk assessment and testing of endocrine disrupting chemicals

Chemical induced changes in fish biomarkers vitellogenin (VTG), secondary sex characteristics (SSC), and sex ratio indicate modes/mechanisms of action (MOAs) of EAS (estrogen, androgen and steroidogenesis) pathways. These biomarkers could be used for defining MOAs and the causal link between MOAs and adverse effects in fish for the identification of endocrine disrupting chemicals (EDCs). This paper compiled data sets of 150 chemicals for VTG, 57 chemicals for SSC and 38 chemicals for sex ratio in fathead minnow, medaka and zebrafish. It showed 1) changes in fish biomarkers can indicate the MOAs as anticipated; 2) in addition to EAS pathways, chemicals with non-EAS pathways induced changes in fish biomarkers; 3) responses of fish biomarkers did not always follow the anticipated patterns of EAS pathways. These responses may result from the interaction of chemical-induced multiple MOAs and confounding factors like fish diet, infection, culture conditions, general toxicity and stress response. The complex response of fish biomarkers to a chemical of interest requires EDC testing at multiple biological levels. Interpretation of fish biomarker data should be combined with relevant information at different biological levels, which is critical for defining chemical specific MOAs. The utility of fish biomarker data for identification, classification, PBT assessment, risk assessment, and testing of EDCs in the regulatory context was discussed. This paper emphasizes the importance of fish biomarker data in the regulatory context, a weight of evidence approach for the interpretation of fish biomarker data and the need for defining levels of evidence for the identification of EDCs.

Zebrafish reproductive toxicity induced by chronic perfluorononanoate exposure

Perfluoroalkyl acids (PFAAs) are a group of anthropogenic compounds that have been widely used in consumer products for over 50 years. One of the most dominant PFAAs is perfluorononanoate (PFNA), a compound detected ubiquitously in aquatic ecosystems. While PFNA is suspected of being an endocrine disruptor, the mechanisms behind PFNA-induced reproductive disorders are poorly understood. The aim of this study was to investigate the reproduction-related effects and possible mechanisms of PFNA on adult zebrafish (Danio rerio) following 180 days of exposure at different concentrations (0.01, 0.1, 1mg/L). PFNA concentration in the gonads of zebrafish was tested by HPLC-MS/MS after chronic exposure to study possible inconsistent accumulation between the genders. The results showed that the accumulation of PFNA in the male gonads was almost one-fold higher than that in the female gonads, indicating a possible higher PFAA gonad burden for male zebrafish. Significant reductions in the male gonadosomatic index (GSI) and female egg production were observed. In addition, the decreased 72h hatching rate displayed an evident dosage effect, indicating that maternal exposure to PFNA might impair offspring developmental success. To investigate how PFNA exposure affects the hypothalamic-pituitary-gonadal-liver axis (HPGL axis), the transcriptional levels of genes were measured by real-time PCR. The disrupted expression of genes, such as ERα, ERβ, FSHR, LHR, StAR, and 17βHSD, indicated the possible interference of PFNA on the HPGL axis function and sex hormone synthesis. Furthermore, testosterone (T) and estradiol (E2) levels in serum and VTG content in the liver were detected to clarify the influences of PFNA on sex hormone levels. Except for the increase in serum estrogen levels, as an estrogen analogue, PFNA also induced the synthesis of biomarker protein vitellogenin (VTG) in the adult male liver. The results of this study indicate that chronic exposure to PFNA can lead to dysfunction in the HPGL axis and sex hormone synthesis and cause adverse effects on fish reproduction.

Immunomodulation by Zearalenone in Carp (Cyprinus carpio L.)

The mycotoxin zearalenone (ZEN) is a frequent contaminant of animal feeds, but its effects on fish have not yet been investigated extensively. In order to fill this gap a feeding trial with juvenile carp was conducted. Three groups of fish were fed feeds contaminated with ZEN at three concentrations (low: 332 μg kg⁻¹, medium: 621 μg kg⁻¹, and high: 797 μg kg⁻¹ feed) for four weeks. Possible reversible effects of ZEN were evaluated by feeding additional groups with the ZEN-contaminated feeds for four weeks, followed by the uncontaminated diet for two weeks. Immune function of isolated leukocytes from head kidney and trunk kidney was assessed using the assessment of NO production, the respiratory burst assay, the chemiluminescence assay, and the measurement of arginase activities. These investigations frequently revealed increased immune responses after exposure of fish to low ZEN concentrations and reduced immune responses after exposure to high mycotoxin concentrations. Moreover, the feeding of the uncontaminated diet for further two weeks did not improve the immune responses in most cases. These results indicate that cellular immune functions in ZEN-contaminated carp are influenced which may be relevant for fish health in aquaculture.

Effects of Dietary Exposure to Zearalenone (ZEN) on Carp (Cyprinus carpio L.)

The mycotoxin zearalenone (ZEN) is frequently contaminating animal feeds including feed used in aquaculture. In the present study, the effects of dietary exposure to ZEN on carp (Cyprinus carpio L.) were investigated. ZEN at three different concentrations (low dose: 332 µg kg⁻¹, medium dose: 621 µg kg⁻¹ and high dose: 797 µg kg⁻¹ final feed, respectively) was administered to juvenile carp for four weeks. Additional groups received the mycotoxin for the same time period but were fed with the uncontaminated diet for two more weeks to examine the reversibility of the ZEN effects. No effects on growth were observed during the feeding trial, but effects on haematological parameters occurred. In addition, an influence on white blood cell counts was noted whereby granulocytes and monocytes were affected in fish treated with the medium and high dose ZEN diet. In muscle samples, marginal ZEN and α-zearalenol (α-ZEL) concentrations were detected. Furthermore, the genotoxic potential of ZEN was confirmed by analysing formation of micronuclei in erythrocytes. In contrast to previous reports on other fish species, estrogenic effects measured as vitellogenin concentrations in serum samples were not increased by dietary exposure to ZEN. This is probably due to the fact that ZEN is rapidly metabolized in carp.

Natural occurrence of emerging Fusarium mycotoxins in feed and fish from aquaculture

A new analytical method for the simultaneous determination of enniatins (ENs) and beauvericin (BEA) in fish feed and fish tissues by liquid chromatography coupled to mass spectrometry with linear ion trap (LC-MS/MS-LIT) was developed. Results showed that the developed method is precise and sensitive. The presence of emerging Fusarium mycotoxins, ENs and BEA, was determined in samples of aquaculture fish and feed for farmed fish, showing that all feed samples analyzed were contaminated with mycotoxins, with 100% coexistence. In aquacultured fish samples, the highest incidence was found in edible muscle and liver. As for the exposure assessment calculated, it was found that average consumer intake was lower than tolerable daily intake (TDI) values for other Fusarium mycotoxins.

Unraveling the mechanisms involved in zearalenone-mediated toxicity in permanent fish cell cultures

The world-wide occurrence of zearalenone (ZEN) as a contaminant in feed for farm animals and fish requires the evaluation of toxicity mechanisms of action of ZEN. The present study investigates possible metabolization of ZEN in fish cell lines suggesting that mainly glucuronidation takes place. It demonstrates that concentrations up to 20,000 ng ml(-1) ZEN are capable of influencing cell viability in permanent fish cell cultures in a dose-response manner with different response patterns between the five tested cell lines, whereby lysosomes appeared to be the main target of ZEN. ZEN toxicity is often discussed in the context of oxidative stress. Our study shows a biphasic response of the cell lines when reactive oxygen species (ROS) production is monitored. Damage in cells was observed by measuring lipid peroxidation, DNA strand breaks, and alterations of intracellular glutathione levels. Metabolization of ZEN, especially at concentrations above 7500 ng ml(-1) ZEN, does not prevent cytotoxicity. ZEN as an estrogenic compound may involve processes mediated by binding to estrogen receptors (ER). Since one cell line showed no detectable expression of ER, an ER-mediated pathway seems to be unlikely in these cells. This confirms a lysosomal pathway as a main target of ZEN in fish cells.

Mycotoxins: diffuse and point source contributions of natural contaminants of emerging concern to streams

To determine the prevalence of mycotoxins in streams, 116 water samples from 32 streams and three wastewater treatment plant effluents were collected in 2010 providing the broadest investigation on the spatial and temporal occurrence of mycotoxins in streams conducted in the United States to date. Out of the 33 target mycotoxins measured, nine were detected at least once during this study. The detections of mycotoxins were nearly ubiquitous during this study even though the basin size spanned four orders of magnitude. At least one mycotoxin was detected in 94% of the 116 samples collected. Deoxynivalenol was the most frequently detected mycotoxin (77%), followed by nivalenol (59%), beauvericin (43%), zearalenone (26%), β-zearalenol (20%), 3-acetyl-deoxynivalenol (16%), α-zearalenol (10%), diacetoxyscirpenol (5%), and verrucarin A (1%). In addition, one or more of the three known estrogenic compounds (i.e. zearalenone, α-zearalenol, and β-zearalenol) were detected in 43% of the samples, with maximum concentrations substantially higher than observed in previous research. While concentrations were generally low (i.e. < 50 ng/L) during this study, concentrations exceeding 1,000 ng/L were measured during spring snowmelt conditions in agricultural settings and in wastewater treatment plant effluent. Results of this study suggest that both diffuse (e.g. release from infected plants and manure applications from exposed livestock) and point (e.g. wastewater treatment plants and food processing plants) sources are important environmental pathways for mycotoxin transport to streams. The ecotoxicological impacts from the long-term, low-level exposures to mycotoxins alone or in combination with complex chemical mixtures are unknown.