Lethal and sublethal effects of aniline and chlorinated anilines on zebrafish embryos and larvae

Environmental risk assessments show increased attention to the sublethal effects of chemicals on aquatic organisms. The Organization for Economic Cooperation and Development (OECD) established the “Fish, Short‐term Toxicity Test on Embryo and Sac‐fry Stages” (OECD test 212) to predict lethal effects. It is still unclear, however, whether this test can predict sublethal effects. Although their sublethal effects are still unknown, chlorinated anilines are widely used in various fields. The purpose of this study, therefore, is to investigate sublethal effects of chlorinated anilines using OECD test 212 with zebrafish, and to examine the correlation of several sublethal effects between embryo and larval stages. Embryos were exposed to aniline and nine chlorinated anilines until 8 days post‐fertilization. A delayed lethal effect was observed from three of the 10 anilines tested. In the control group, the swim bladder inflated after hatching, but there was no swim‐bladder inflation after exposure to the chlorinated anilines. Fertilized eggs exposed to lower concentrations of test chemicals showed effects during embryogenesis that did not affect mortality rates, such as changes in body curvature and edema. Our results show that chlorinated anilines induce not only lethal effects but also a variety of sublethal effects. Moreover, a detailed estimate of these effects requires study during both embryonic and larval stages. OECD test 212 may therefore prove useful as a method for screening chemicals for lethal and sublethal effects. Copyright © 2017 John Wiley & Sons, Ltd.     

Summary of 17 chemicals evaluated by OECD TG229 using Japanese Medaka,Oryzias latipes in EXTEND 2016

In June 2016, the Ministry of the Environment of Japan announced a program “EXTEND2016” on the implementation of testing and assessment for endocrine active chemicals, consisting of a two-tiered strategy. The aim of the Tier 1 screening and the Tier 2 testing is to identify the impacts on the endocrine system and to characterize the adverse effects to aquatic animals by endocrine disrupting chemicals detected in the aquatic environment in Japan. For the consistent assessment of the effects on reproduction associated with estrogenic, anti-estrogenic, androgenic, and/or anti-androgenic activities of chemicals throughout Tier 1 screening to Tier 2 testing, a unified test species, Japanese medaka (Oryzias latipes), has been used. For Tier 1 screening, the in vivo Fish Short-Term Reproduction Assay (OECD test guideline No. 229) was conducted for 17 chemicals that were nominated based on the results of environmental monitoring, existing knowledge obtained from a literature survey, and positive results in reporter gene assays using the estrogen receptor of Japanese medaka. In the 17 assays using Japanese medaka, adverse effects on reproduction (i.e., reduction in fecundity and/or fertility) were suggested for 10 chemicals, and a significant increase of hepatic vitellogenin in males, indicating estrogenic (estrogen receptor agonistic) potency, was found for eight chemicals at the concentrations in which no overt toxicity was observed. Based on these results, and the frequency and the concentrations detected in the Japanese environment, estrone, 4-nonylphenol (branched isomers), 4-tert-octylphenol, triphenyl phosphate, and bisphenol A were considered as high priority candidate substances for the Tier 2 testing.     

The non‐steroidal anti‐inflammatory drug diclofenac sodium induces abnormal embryogenesis and delayed lethal effects in early life stage zebrafish (Danio rerio)

Diclofenac sodium, a non‐steroidal anti‐inflammatory drug widely used in both human and veterinary medicine, has been detected in aquatic environments; therefore, its ecotoxicological effects on aquatic organisms need to be clarified. Recently, toxicity testing using zebrafish (Danio rerio) embryos has been recommended from the point of view of animal welfare; therefore, we investigated the suitability of using sub‐lethal endpoints observed during embryogenesis for predicting lethal effects in early life stage zebrafish exposed to diclofenac sodium. After exposure to diclofenac sodium (0.4‐7.0 mg/L) from 2 hours post‐fertilization to 30 days post‐hatching, abnormal embryogenesis, characterized by the presence of edema and body curvature, was observed in the 7.0 mg/L exposure group but not in any other groups including controls. The body curvature was found to be the result of abnormal development of the spine. All abnormal embryos hatched without delay, but died within 1 week after hatching, suggesting that the combination of the sub‐lethal endpoints of edema and abnormal development of the spine during embryogenesis may predict lethal effects in early life stage zebrafish exposed to diclofenac sodium. Further investigations to verify these findings are needed. The value of the no observed effect concentrations for the embryogenesis, survival and growth endpoints were 3.5, 1.8 and >3.5 mg/L, respectively.     

Acute and sub‐lethal exposure to copper oxide nanoparticles causes oxidative stress and teratogenicity in zebrafish embryos

Nano‐copper oxides are a versatile inorganic material. As a result of their versatility, the immense applications and usage end up in the environment causing a concern for the lifespan of various beings. The ambiguities surround globally on the toxic effects of copper oxide nanoparticles (CuO‐NPs). Hence, the present study endeavored to study the sub‐lethal acute exposure effects on the developing zebrafish embryos. The 48 hpf LC₅₀ value was about 64 ppm. Therefore, we have chosen the sub‐lethal dose of 40 and 60 ppm for the study. Accumulation of CuO‐NPs was evidenced from the SEM‐EDS and AAS analyzes. The alterations in the AChE and Na⁺/K⁺‐ATPase activities disrupted the development process. An increment in the levels of oxidants with a concomitant decrease in the antioxidant enzymes confirmed the induction of oxidative stress. Oxidative stress triggered apoptosis in the exposed embryos. Developmental anomalies were observed with CuO‐NPs exposure in addition to oxidative stress in the developing embryos. Decreased heart rate and hatching delay hindered the normal developmental processes. Our work has offered valuable data on the connection between oxidative stress and teratogenicity leading to lethality caused by CuO‐NPs. A further molecular mechanism unraveling the uncharted connection between oxidative stress and teratogenicity will aid in the safe use of CuO‐NPs. Copyright © 2015 John Wiley & Sons, Ltd.     

Oxidative stress‐mediated developmental toxicity induced by isoniazide in zebrafish embryos and larvae

Isoniazide (INH) is an important first‐line drug that is used to treat tuberculosis. However, the effect of INH on fetal growth has not yet been elucidated, and the mechanism of INH‐induced developmental toxicity is still unknown. In the present study, we employed zebrafish embryos and larvae to investigate the developmental toxicity of INH. The survival rates of the embryos and larvae as well as the hatching rates of embryos were significantly reduced. Morphological abnormalities, including spinal curvature, yolk retention, swimming bladder absence, tail bending and shorter body lengths were induced by INH. Histopathological analysis showed loose cell‐to‐cell contacts and large vacuoles in the larval hepatocytes. Thin intestinal walls, frayed gut villi and widespread cell lysis were observed in the intestines of the larvae in the higher concentration (8, 16 mm ) exposure groups. In addition, exposure to high doses (≥ 6 mm ) of INH significantly reduced the locomotor capacity of the zebrafish larvae. INH significantly increased the levels of reactive oxygen species and malondialdehyde and decreased the superoxide dismutase activity in zebrafish larvae, which suggested that oxidative stress was induced and that the antioxidant capacity was inhibited. Superoxide dismutase 1 and liver fatty acid‐binding protein mRNA levels were significantly downregulated, while the GSTP2 and cytochrome P450 3A mRNA levels were significantly upregulated in the INH‐exposed zebrafish larvae. The overall results indicated that INH caused a dose‐ and time‐dependent increase in developmental toxicity and that oxidative stress played an important role in the developmental toxicity induced by INH in zebrafish larvae. Copyright © 2017 John Wiley & Sons, Ltd.     

Investigation into the sub‐lethal effects of the triazole fungicide triticonazole in zebrafish (Danio rerio) embryos/larvae

Global use of azole fungicides is expected to increase over the next several years. Triticonazole is a triazole fungicide that is used for turf protection, residential, and other commercial applications. As such, it can enter local rural and urban water systems via run‐off and rain events. Early life stages of aquatic organisms can be susceptible to pesticides that enter the water, but in the case of triticonazole, data on the potential for subacute toxicity are lacking. Here, we determined the effects of triticonazole on development, oxygen consumption rates, and locomotor activity in zebrafish to address this knowledge gap. Wild‐type zebrafish (ABTu strain) embryos and larvae were exposed to triticonazole (1‐100 μM) in early development for different lengths of time depending on the assay conducted. Triticonazole did not affect survival nor induce significant deformity (pericardial edema, skeletal defects) in zebrafish at doses up to 100 μM. Oxygen consumption rate was measured in embryos after 24 and 48 hour exposure to triticonazole beginning at ～6 hpf using the XF_e flux analyzer. Triticonazole did not affect basal respiration, oligomycin‐induced ATP linked respiration, FCCP‐induced maximum respiration, proton leak, spare capacity, nor non‐mitochondrial respiration at doses up to 100 μM for 24 hours, even for exposure up to 250 μM for 48 hours. To determine whether the fungicide affected larval swimming activity, the visual motor response test was conducted following triticonazole exposure for 6 days. Larval zebrafish exposed to triticonazole showed hypoactivity in the dark following a 100 μM treatment, suggesting that the fungicide can affect the locomotor activity of zebrafish, albeit at relatively high levels. Given the fact that sublethal biological responses were absent at lower environmentally relevant concentrations, we conclude that triticonazole, relative to other triazole fungicides and types of pesticides, exhibits a relatively low risk of toxicity to the early life stages of fish.     

Toxic effects of indoxacarb enantiomers on the embryonic development and induction of apoptosis in zebrafish larvae (Danio rerio)

Indoxacarb is a highly potent insecticide widely used to control Lepidoptera insects in vegetable, tea, cotton, and rice fields. It can run off into aquatic environments. It is consisted of two enantiomers. Environmental risks and aquatic toxicity of indoxacarb enantiomers have not been fully investigated. In this study, zebrafish (Danio rerio ) embryos were exposed to varying concentrations of (?)‐R‐indoxacarb and (+)‐S‐indoxacarb until 96‐h post‐fertilization (hpf) to assess the embryonic toxicity. (?)‐R‐indoxacarb was 1.3‐fold more toxic than (+)‐S‐isomer to zebrafish embryos at 96 hpf. (?)‐R‐indoxacarb exhibited reduction in body length and pericardial edema compared with (+)‐S‐indoxacarb. (?)‐R‐indoxacarb decreased the hatching rate sixfold greater than (+)‐S‐indoxacarb. The rate of pericardial edema induced by (?)‐R‐indoxacarb was 2.5 times greater than that by (+)‐S‐indoxacarb. The heart rate of the larvae exposed to (?)‐R‐indoxacarb was 30% lower than that to (+)‐S‐indoxacarb. In addition, exposure to the chiral isomers resulted in significant increases in apoptosis; interestingly (?)‐R‐indoxacarb induced apoptosis in the heart area, whereas (+)‐S‐indoxacarb induced apoptosis in the head area. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 7–16, 2017.     

Evaluation of toxicological and teratogenic effects of carbosilane glucose glycodendrimers in zebrafish embryos and model rodent cell lines

Abstract

Glycodendrimers (Glyco-DDMs) represent a rapidly growing class of nanoparticles with promising properties for biomedical applications but concerns regarding the impact on human health and environment are still justified. Here we report, for the first time, the comparative study of in vivo developmental toxicity of carbosilane Glyco-DDMs and their cytotoxicity in vitro. Carbosilane Glyco-DDMs (generation 1–3) containing 4, 8, and 16 β-d-glucopyranosyl units at the periphery (DDM₁Glu, DDM₂Glu, and DDM₃Glu) were synthesized and characterized by ¹H, ¹³C and ²⁹Si NMR, mass spectrometry, dynamic light scattering, atomic force microscopy (AFM), and computer modeling. In vitro cytotoxicity assay (MTT) of DDM_1–3Glu was performed on three different rodent cell lines (Cricetulus griseus) – B14 (ATCC, CCL-14.1), BRL 3A (ATCC, CRL-1442), and NRK 52E (ATCC, CRL-1571). Overall, very low cytotoxicity was observed with calculated IC₅₀ in mM range with slight difference between each cell line and DDM generation investigated. Modified fish embryo test (FET) was further used for DDM₃Glu developmental toxicity testing on zebrafish (Danio rerio) embryos. While seemingly harmless to intact embryos, adverse effects of DDMs on the embryonic development become evident after chorion removal (LD₅₀=2.78?µM at 96 hpe). We summarized that the modified FET test showed a two to three orders of magnitude difference between the in vitro cytotoxicity and in vivo developmental toxicity of DDM₃Glu. While, in general, the Glyco-DDMs show great promises as efficient vectors in targeted drug delivery or as therapeutic molecules itself, we suggest that their developmental toxicity should be thoroughly investigated to exclude safety risks associated with their potential biomedical use.     

Hemodynamic effects of anthrax toxins in the rabbit model and the cardiac pathology induced by lethal toxin

Anthrax lethal toxin (LeTx) and edema toxin (EdTx) have been shown to alter hemodynamics in the rodent model, while LeTx primarily is reported to induce extensive tissue pathology. However, the rodent model has limitations when used for comparison to higher organisms such as humans. The rabbit model, on the other hand, has gained recognition as a useful model for studying anthrax infection and its pathophysiological effects. In this study, we assessed the hemodynamic effects of lethal toxin (LeTx) and edema toxin (EdTx) in the rabbit model using physiologically relevant amounts of the toxins. Moreover, we further examine the pathological effects of LeTx on cardiac tissue. We intravenously injected Dutch-belted rabbits with either low-dose and high-dose recombinant LeTx or a single dose of EdTx. The animals' heart rate and mean arterial pressure were continuously monitored via telemetry until either 48 or 72 h post-challenge. Additional animals challenged with LeTx were used for cardiac troponin I (cTnI) quantitation, cardiac histopathology, and echocardiography. LeTx depressed heart rate at the lower dose and mean arterial pressure (MAP) at the higher dose. EdTx, on the other hand, temporarily intensified heart rate while lowering MAP. Both doses of LeTx caused cardiac pathology with the higher dose having a more profound effect. Lastly, left-ventricular dilation due to LeTx was not apparent at the given time-points. Our study demonstrates the hemodynamic effects of anthrax toxins, as well as the pathological effects of LeTx on the heart in the rabbit model, and it provides further evidence for the toxins' direct impact on the heart.     

Benomyl induction of brain aromatase and toxic effects in the zebrafish embryo

Benomyl is a benzimidazole fungicide that has been widely used on a variety of food crops and ornamental plants. It is known to cause adverse effects on reproductive systems, including decreased testicular and epididymal weights and reduced epididymal sperm counts and fertility. The brain aromatase gene is up‐regulated by estrogens and estrogen mimics and considered a target gene to screen estrogen mimics. This study was designed to test the estrogenic potential and toxic effects of benomyl in the zebrafish system, and validated this system as a model that may correspond to the effect of benomyl in rodents. Concentrations of 20 × 10^?6, 40 × 10^?6 and 80 × 10^?6 m of benomyl‐treated embryos showed decreased survival, hatching and heart rates, and increased incidence of malformations, such as pericardial edema, spinal lordosis, elongated heart, head edema, eye lens protrusion and caudal fin disappearance. Benomyl induced enhanced green fluorescent protein (EGFP) expression in the mediobasal hypothalamus (MBH) in transient zebrafish embryos with a brain aromatase‐based reporter gene. In this study, we determined that benomyl has estrogenic potential based on zebrafish brain aromatase gene induction, and that benomyl is toxic at 20 × 10^?6 m concentration and higher. These results demonstrate the usefulness of zebrafish embryos as an in vivo system to examine the estrogenic and developmental toxic potential of unknown compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

氨茶碱水分测定用溶剂的优化及与热分析法的比较

目的:为氨茶碱水分测定选择适宜溶剂;探讨氨茶碱分子中结晶水的数量.方法:采用费休氏水分测定法,以无吡啶卡氏试剂和含吡啶卡氏试剂为滴定液,以甲醇、氯仿-甲醇(1:1)、吡啶为溶剂测定氨茶碱的水分,用热重法测定氨茶碱的热失重.结果:以氯仿-甲醇(1:1)为溶剂测定氨茶碱水分,滴定终点易出现且样品能全部溶解;热分析结果表明:氨茶碱分子中可能含有不同数目的结晶水,实际样品可能是含不同数目结晶水的混合物.结论:以氯仿-甲醇(1:1)为溶剂测定氨茶碱水分结果准确;卡氏试剂中含有一定的吡啶可使测定结果灵敏度增加;<中国药典>2005年版收载的氨茶碱结构式中含有二分子结晶水似不够确切.     

Protective effects of folic acid on PM2.5‐induced cardiac developmental toxicity in zebrafish embryos by targeting AhR and Wnt/β‐catenin signal pathways

Our previous observations indicated that extractable organic matter (EOM) from PM2.5 induced malformations in the heart of zebrafish embryos by activating AhR and inhibiting canonical Wnt/β‐catenin signal pathway. As a nutritional factor, folic acid (FA) is reported to prevent cardiac defects during embryo development. Hence, we hypothesize that FA may prevent PM2.5‐induced heart defects by interfering with AhR and Wnt/β‐catenin signaling pathways. Our results showed that FA supplementation alleviated the EOM‐induced heart defects in zebrafish embryos, and both AhR inhibitor CH223191 and Wnt activator CHIR99021 enhanced the protective efficiency of FA. Furthermore, FA supplementation attenuated the EOM‐induced upregulation of AhR and its target genes including Cyp1a1, Cyp1b1, Ahrra, and Ahrrb. EROD assay confirmed that the EOM agonized Cyp1a1 activity was diminished by FA. The EOM‐induced downregulation of β‐catenin and its target genes including Nkx2.5, Axin2, Sox9b, and Cox2b were recovered or even overexpressed in embryos exposed to EOM plus FA. In conclusion, our study suggested that FA supplementation protected against PM2.5 cardiac development toxicity by targeting AhR and Wnt/β‐catenin signal pathways.     

Set‐up of an infrared fast behavioral assay using zebrafish (Danio rerio) larvae,and its application in compound biotoxicity screening

Zebrafish (Danio rerio) is increasingly employed for evaluating toxicity and drug discovery assays. Commonly experimental approaches for biotoxicity assessment are based on visual inspection or video recording. However, these techniques are limited for large‐scale assays, as they demand either a time‐consuming detailed inspection of the animals or intensive computing resources in order to analyze a considerable amount of screenshots. Recently, we have developed a simple methodology for tracking the locomotor activity of small animals cultured in microtiter plates. In this work, we implemented this automatic methodology, based on infrared (IR) microbeam scattering, for measuring behavioral activity in zebrafish larvae. We determined the appropriate culture conditions, number of animals and stage of development to get robust results. Furthermore, we validated this methodology as a rapid test for evaluating toxicity. By measuring the effects of reference compounds on larvae activity, we were able to estimate the concentration that could cause a 50% decrease in activity events values (AEC₅₀), showing a strong linear correlation (R² = 0.91) with the LC₅₀ values obtained with the standard DarT test. The toxicity order of the measured compounds was CuSO₄ > 2,4‐dinitrophenol > 3,4‐dichloroaniline > SDS > sodium benzoate > EDTA > K₂CrO₄; regarding solvents, EtOH ≈ DMSO. In this study, we demonstrate that global swimming behavior could be a simple readout for toxicity, easy to scale‐up in automated experiments. This approach is potentially applicable for fast ecotoxicity assays and whole‐organism high‐throughput compound screening, reducing the time and money required to evaluate unknown samples and to identify leading pharmaceutical compounds. Copyright © 2013 John Wiley & Sons, Ltd.     

Estrogenic effects of fluorinated diiodine alkanes in MCF‐7 cells,H295R cells and zebrafish embryo assays

Fluorinated diiodine alkanes (FDIAs), important industrial intermediates in the synthesis of various perfluorinated compounds, which are distributed widely in wildlife and humans. Recent studies showed that FDIAs had in vitro estrogenic effects. However, to date, little information is available regarding the in vivo estrogenic effects of FDIAs and the mechanisms are unclear. In this study, a combination of in vitro and in vivo assays was used to investigate the estrogenic effects of FDIAs. We tested the in vitro estrogenic effects and estrogen receptor‐related gene expression via MCF‐7 cell assay. The hormone level of estradiol and the expression of estrogenic synthesis genes were measured in the H295R cell assay. Finally, the in vivo effects of FDIAs on development and estrogen‐related gene expression were assessed in the zebrafish embryos assay. The results demonstrated that FDIAs could exhibit estrogenic activity through inducing cell proliferation (1.6‐6.7‐fold of the control) and estrogen receptor alpha gene expression (1.07‐1.39‐fold of the control), altering estradiol production (1.14‐1.22‐fold of the control) and the major estrogenic synthesis gene expression of CYP19 (1.22‐1.31‐fold of the control), disrupting the estrogen‐related genes (esr1 and cyp19b) levels in zebrafish (1.52‐2.99‐fold and 2.95‐5.00‐fold of the control for esr1 and cyp19b, respectively). The current findings indicated the potential estrogenic effects of FDIAs and provided novel information for human risk assessment.     

An in vivo assay of the mutagenic potential of imidacloprid using sperm head abnormality test and dominant lethal test

Objective: To assess the mutagenic effects of imidacloprid in germ cells of Swiss albino male mice by sperm head abnormality (SHA) assay and dominant lethal test (DLT). Methods: Swiss albino mice were exposed to imidacloprid (22, 11 and 5.5?mg/kg/day) along with 3% gum acacia as vehicle control through oral route for 7, 14 and 28 days for SHA assay and for 28 days for DLT. The epididymal sperm smear in 1% eosin stain was analyzed for SHAs. In DLT, male mice were allowed to mate with females after 1, 3 and 6 weeks of end of pesticide treatment. The uterine contents of the sacrificed females were observed for live and dead implants. The analysis of test and control groups data was done by one way ANOVA at p?Results: Exposure of all dose levels of imidacloprid (22, 11 and 5.5?mg/kg/day) for seven days did not induce significant SHAs while they induced significant SHAs compared with the control group following exposure for 14 and 28 days. The analysis of uterine content revealed a significant increase in the number of dead implants/female compared with the vehicle control in only those females which were mated with male mice after six weeks of treatment of highest dose level of imidacloprid. The dominant lethal mutations were observed only at spermatogonial stage. Conclusions: Long-term exposure of pesticide generated SHAs even at lowest dose level (5.5?mg/kg/day for 14 days) and mutagenic effects at spermatogonial stage at highest dose level (22?mg/kg/day for 28 days).     

Testing the protective effects of cyclodextrins vs. alternariol-induced acute toxicity in HeLa cells and in zebrafish embryos

Alternariol (AOH) is a mycotoxin produced by Alternaria fungi, it appears as a contaminant in tomatoes, grains, and grapes. The chronic exposure to AOH may cause carcinogenic and xenoestrogenic effects. Cyclodextrins (CDs) are cyclic oligosaccharides, they form host-guest complexes with apolar molecules. In this study, the interactions of AOH with CD monomers and polymers were examined employing fluorescence spectroscopy. Thereafter, the protective effects of certain CDs vs. AOH-induced toxicity were investigated on HeLa cells and on zebrafish embryos. Our major observations are the following: (1) Sugammadex forms highly stable complex with AOH (K = 4.8 ×10⁴ L/mol). (2) Sugammadex abolished the AOH-induced toxicity in HeLa cells, while native β-CD did not show relevant protective effect. (3) Each CD tested decreased the AOH-induced mortality and sublethal adverse effects in zebrafish embryos: Interestingly, native β-CD showed the strongest protective impact in this model. (4) CD technology may be suitable to relieve AOH-induced toxicity.     

Functional expressions of adenosine triphosphate‐binding cassette transporters during the development of zebrafish embryos and their effects on the detoxification of cadmium chloride and β‐naphthoflavone

Adenosine triphosphate‐binding cassette (ABC) transporters, including ABCB, ABCC and ABCG families represent general biological defenses against environmental toxicants in varieties of marine and freshwater organisms, but their physiological functions at differential developmental stages of zebrafish embryos remain undefined. In this work, functional expressions of typical ABC transporters including P‐glycoprotein (Pgp), multiresistance associated protein 1 (Mrp1) and Mrp2 were studied in zebrafish embryos at 4, 24, 48 and 72 h post‐fertilization (hpf). As a result, both the gene expressions and activities of Pgp and Mrps increased with the development of embryos. Correspondingly, 4–72 hpf embryos exhibited an increased tolerance to the toxicity caused by cadmium chloride (CdCl₂) and β‐naphthoflavone (BNF) with time. Such a correlation was assumed caused by the involvement of ABC transporters in the detoxification of chemicals. In addition, the assumption was supported by the fact that model efflux inhibitors of Pgp and Mrps such as reversine 205 and MK571 significantly inhibited the efflux of toxicants and increased the toxicity of Cd and BNF in zebrafish embryos. Moreover, exposure to CdCl₂ and BNF induced the gene expressions of Pgp and Mrp1 in 72 hpf embryos. Thus, functional expressions of Pgp and Mrps increased with the development of zebrafish embryos, which could cause an increasing tolerance of zebrafish embryos to CdCl₂ and BNF. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessment of thyroid endocrine system impairment and oxidative stress mediated by cobalt ferrite (CoFe2O4) nanoparticles in zebrafish larvae

Fascinating super paramagnetic uniqueness of iron oxide particles at nano‐scale level make them extremely useful in the state of the art therapies, equipments, and techniques. Cobalt ferrite (CoFe₂O₄) magnetic nanoparticles (MNPs) are extensively used in nano‐based medicine and electronics, results in extensive discharge and accumulation into the environment. However, very limited information is available for their endocrine disrupting potential in aquatic organisms. In this study, the thyroid endocrine disrupting ability of CoFe₂O₄ NPs in Zebrafish larvae for 168‐h post fertilization (hpf) was evaluated. The results showed the elevated amounts of T4 and T3 hormones by malformation of hypothalamus pituitary axis in zebrafish larvae. These elevated levels of whole body THs leads to delayed hatching, head and eye malformation, arrested development, and alterations in metabolism. The influence of THs disruption on ROS production and change in activities of catalase (CAT), mu‐glutathione s‐transferase (mu‐GST), and acid phosphatase (AP) were also studied. The production of significantly higher amounts of in vivo generation of ROS leads to membrane damage and oxidative stress. Presences of NPs and NPs agglomerates/aggregates were also the contributing factors in mechanical damaging the membranes and physiological structure of thyroid axis. The increased activities of CAT, mu‐GST, and AP confirmed the increased oxidative stress, possible DNA, and metabolic alterations, respectively. The excessive production of in vivo ROS leads to severe apoptosis in head, eye, and heart region confirming that malformation leads to malfunctioning of hypothalamus pituitary axis. ROS‐induced oxidative DNA damage by formation of 8‐OHdG DNA adducts elaborates the genotoxicity potential of CoFe₂O₄ NPs. This study will help us to better understand the risk and assessment of endocrine disrupting potential of nanoparticles. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2068–2080, 2016.