Effects of embryonic exposure to polychlorinated biphenyls on zebrafish (Danio rerio) retinal development

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that affect embryonic development. The purpose of this study was to examine the effects of embryonic exposure to PCBs on early retinal development in zebrafish, Danio rerio. Zebrafish embryos were immediately exposed to different concentrations (0, 0.125, 0.25, 0.5, 1.0 and 2.0 mg) of PCBs per liter of medium at 28.5 °C. Embryos were assessed at 30, 48, 72 and 96 h post‐fertilization (hpf) for changes in embryonic survival rate, development, larval retinal morphology and ultrastructure of the retina. The results show that PCB exposure decreased the survival rate of embryos in a time‐ and dose‐dependent manner. Embryos exposed to the higher concentrations of PCBs (0.5, 1.0 and 2.0 mg l^?1) displayed obvious gross morphological deformities. At 72 hpf, the retinal layer development of zebrafish was delayed at higher PCB concentrations (1.0 mg l^?1). At 96 hpf, irregularity of photoreceptor cells arrangement and thickening of photoreceptor and ganglionic layers were observed in PCB‐treated larvae at concentrations of 0.25–1 mg l^?1. Ultrastructural examination showed signs of growth inhibition of the photoreceptor outer segment at 0.25–1 mg l^?1 PCB exposure at 72 hpf, as well as the appearance of massive vacuoles and holes inside the outer segments in the PCB exposure group at 96 hpf. These results suggest that embryonic exposure to moderate and high levels of PCBs induced developmental deficits in zebrafish retinas, particularly in photoreceptor cells. Copyright © 2011 John Wiley & Sons, Ltd.     

AhR2-mediated, CYP1A-independent cardiovascular toxicity in zebrafish (Danio rerio) embryos exposed to retene

In the embryo-larval stages of fish, alkylphenanthrenes such as retene (7-isopropyl-1-methylphenanthrene) produce a suite of developmental abnormalities typical of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), including pericardial and yolk sac edema, cardiovascular dysfunction, and skeletal deformities. To investigate the mechanism and target tissue of retene toxicity, we used observational, histological, and protein knockdown techniques in zebrafish (Danio rerio) embryos. The primary overt signs of toxicity are pericardial edema and reduced blood flow, first observed at 36 h post-fertilization (hpf). The most pronounced effects at this stage are a reduced layer of cardiac jelly in the atrium and reduced diastolic filling. Conversely, an increased layer of cardiac jelly is observed at 72 hpf in retene-exposed embryos. Induction of cytochrome P4501A (CYP1A) is apparent in a subset of cardiomyocytes by 48 hpf suggesting that early cardiac effects may be due to AhR activation in the myocardium. Myocardial CYP1A induction is transient, with only endocardial induction observed at 72 hpf. Knockdown of cyp1a by morpholino oligonucleotides does not affect retene toxicity; however, ahr2 knockdown prevents toxicity. Thus, the mechanism of retene cardiotoxicity is AhR2-mediated and CYP1A-independent, similar to TCDD; however, the onset and proximate signs of retene toxicity differ from those of TCDD. Retene cardiotoxicity also differs mechanistically from the cardiac effects of non-alkylated phenanthrane, illustrating that alkyl groups can alter toxic action. These findings have implications for understanding the toxicity of complex mixtures containing alkylated and non-alkylated polycyclic aromatic hydrocarbons.     

多柔比星斑马鱼胚胎心脏发育毒性表现

目的通过观察多柔比星的斑马鱼胚胎心脏毒性表现,为其作为心脏毒性评价模型提供可靠的检测指标。方法选择发育正常的6hpf(hours post fertilization)斑马鱼胚胎暴露于多柔比星2.16～34.48μmol·L-148h。显微镜观察72hpf斑马鱼心血管系统的形态学改变。通过DVC摄像系统测定心率;测量静脉窦-动脉球(SV-BA)间距,HE染色观察斑马鱼心肌结构。结果多柔比星2.16μmol·L-1组斑马鱼心血管系统形态无改变,但心率下降,为(166±5)min-1;SV-BA间距增加,为(237±13)μm。多柔比星4.31μmol·L-1可引起斑马鱼出现心包水肿,心脏畸形,心率减低,为(166±5)min-1;SV-BA间距增加,为(268±13)μm。随着多柔比星浓度增加,斑马鱼出现体长缩短、体节发育异常、脊柱弯曲、卵黄囊水肿、出血、心脏缩小等多种表型改变。心脏组织切片显示,多柔比星8.62μmol·L-1可引起斑马鱼心包腔变大、心脏缩小、心肌层变薄和心肌细胞减少。结论多柔比星对斑马鱼胚胎心脏毒性作用的表现与对哺乳动物的毒性作用表现相同,有望成为评价药物心脏发育毒性的模型。     

Toxicity of parathion on embryo and yolk‐sac larvae of gilthead seabream (Sparus aurata l.): Effects on survival,cholinesterase, and carboxylesterase activity

This study was conducted to examine the acute toxicity of the organophosphorus pesticide (OP) parathion on embryos and yolk‐sac larvae of gilthead seabream (Sparus aurata), and to investigate the effects of this compound on cholinesterase and carboxylesterase activity of seabream larvae in the phase of endogenous feeding. The 72‐h LC50 for yolk‐sac larvae (0.523 mg L^?1) was about two‐fold lower than the 48‐h LC50 for embryos (1.005 mg L^?1). Parathion significantly inhibited the activity of ChE and CaE activity in yolk sac larvae but there were not significant differences in the sensitivity of both esterases to parathion as inferred by their 72‐h IC50 values. Larvae exposed to parathion for 72 h showed a 70% inhibition of the whole body acetylcholinesterase at approximately the LC50. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 601–607, 2010.     

Food colorant Sunset Yellow (E110) intervenes developmental profile of zebrafish (Danio rerio)

In this study, we tested the teratogenic/embryotoxic potentials of food colorant, Sunset Yellow (E110) using zebrafish embryos as a model. Laboratory‐raised developing embryos of Danio rerio were exposed to graded concentrations (00, 0.1, 1.0, 2.0, 3.0, 4.0, 5.0, 10, 20, 30, 40, 50 and 100 mm ) of E110 from gastrulation stage (~6 hours post‐fertilization [hpf]) up until hatching. The developmental trajectory of each embryo and post‐hatched larva was traced from 24 to 168 hpf. The no observed effect concentration (NOEC), median effective concentration (EC₅₀), median lethal concentration (LC₅₀) and teratogenic index were determined. In the 0.1 mm E110‐exposed embryos, the development proceeded as in controls (NOEC), while, exposure of embryos to 1‐5 mm of E110 led to a decrease in body size, dry body mass of resultant larvae along with appearance of morphological deformities such as, microphthalmia, pericardial edema, yolk sac edema and spinal curvature. Larvae of 10‐50 mm E110‐exposed embryos exhibited increased cellular apoptosis in the cardiac region with significantly declined heartbeats and elevated mortality rates, in addition to the above‐mentioned abnormalities. In the 100 mm exposure group, all embryos succumbed to death within 24 hpf. The NOEC and LC₅₀ recorded were at 0.1 and 42.57 mm respectively. EC₅₀ (96 hpf) recorded for pericardial edema and yolk sac edema was 19.41 and 39.84 mm with teratogenic index quotient 2.1 and 1.06 respectively The study provides direct evidence for the developmental toxicity/teratogenic potential of E110.     

Toxicity evaluation of β‐diketone antibiotics on the development of embryo‐larval zebrafish (Danio rerio)

This study evaluated the effects of β‐diketone antibiotics (DKAs) on the development of embryo‐larval zebrafish (Danio rerio). When exposure to DKAs, developmental malformations, such as hatching delay, curved body axis, pericardial edema, uninflated swim bladder and yolk sac edema, were observed at 120 h postfertilization (hpf). The estimated 120 hpf nominal concentrations of no observed effect concentration and lowest observed effect concentration for DKAs were 18.75 and 37.50 mg/L, respectively, suggesting that DKAs have much lower toxicity than other persistent pollutants. Following DKA exposure, embryonic heart rates were significantly reduced as compared to the controls at 48 and 60 hpf. The peak bending motion frequency appeared 1 h earlier than in control embryos. The 2.34 and 9.38‐mg/L treatment groups had a higher basal swim rate than control groups at 120 hpf in both light and light‐to‐dark photoperiod experiments. The occurrence of high speed swim rates was enhanced approximately threefold to sevenfold in the 2.34 and 9.38 mg/L treatments compared to the control. Glutathione (GSH) concentrations in the 2.34 and 9.38‐mg/L treatments were significantly higher than the control at 72 hpf, suggesting that GSH production was induced at the end of the hatching period. When exposed to DKAs, zebrafish superoxide dismutase enzyme (SOD) activities were significantly inhibited in the early embryonic period, demonstrating that the clearing ability in zebrafish was lower than the generation rate of free radicals. In summary, the combined DKAs were developmentally toxic to zebrafish in their early life stages and had the ability to impair individual behaviors that are of great importance in the assessment of their ecological fitness. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1134–1146, 2014.     

Toxicological assessment and developmental abnormalities induced by butylparaben and ethylparaben exposure in zebrafish early-life stages

Toxicological effects of butylparaben (BuP) and ethylparaben (EtP) on zebrafish (Danio rerio) early-life stages are not well established. The present study evaluated, using zebrafish embryos and larvae, the toxicity of BuP and EtP through benchmark dose (BMD) approach. BuP was more toxic than EtP to zebrafish larvae. In fact, Lethal Concentration 50 (LC50) values at 96 h post-fertilization (hpf) for BuP and EtP were 2.34 mg/L and 20.86 mg/L, respectively. Indeed, BMD confidence interval (lower bound (BMDL) - upper bound (BMDU) was 0.91–1.92 mg/L for BuP and 10.8–17.4 mg/L for EtP. Zebrafish embryos exposed to 1 mg/L, 2.5 mg/L of BuP and 5 mg/L, 10 mg/L, 20 mg/L, 30 mg/L of EtP showed several developmental abnormalities and teratological effects compared to negative control. Exposed zebrafish developed reduced heartbeat, reduction in blood circulation, blood stasis, pericardial edema, deformed notochord and misshaped yolk sac. Embryos exposed to the highest concentrations of the chemicals (2.5 mg/L of BuP, 10 mg/L, 20 mg/L and 30 mg/L of EtP) showed the developmental abnormalities at 48 hpf while those treated with 1 mg/L of BuP and 10 mg/L of EtP reported behavioral changes at 72 hpf, including trembling of head, pectoral fins and spinal cord. This research identified the lethal and sublethal effects of BuP and EtP in zebrafish early-life stages and could be helpful to elucidate the developmental pathways of toxicity of parabens.     

Developmental toxicity of auranofin in zebrafish embryos

Auranofin (AF) is used in clinic for the treatment of rheumatoid arthritis, repurposing of AF as an anticancer drug has just finished a phase I/II clinical trial, but the developmental toxicity of AF remains obscure. This study focused on its developmental toxicity by using zebrafish embryos. Zebrafish embryos were exposed to different concentrations (1, 2.5, 5, 10 μm ) of AF from 2 h post‐fertilization (hpf) to 72 hpf. At 72 hpf, two major developmental defects caused by AF were found, namely severe pericardial edema and hypopigmentation, when embryos were exposed to concentrations higher than 2.5 μm . Biochemical detection of oxidative stress enzyme combined with expressions of a series of genes related to oxidative stress, cardiac, metal stress and pigment formation were subsequently tested. The superoxide dismutase activity was decreased while malondialdehyde content was accumulated by AF treatment. The expression of oxidative stress‐related genes (sod1 , gpx1a , gst ), pigment‐related genes (mitfb , trp‐1a ) and one metal stress‐related gene ctr1 were all decreased by AF exposure. The expressions of cardiac‐related genes (amhc , vmhc ) and one metal‐related gene hsp70 were found to be significantly upregulated by AF exposure. These findings indicated the potential developmental toxicity of AF on zebrafish early development. Copyright © 2016 John Wiley & Sons, Ltd.     

β-氯氰菊酯对斑马鱼胚胎的发育毒性

目的以斑马鱼胚胎为模型,探讨一种高效氯氰菊酯β-氯氰菊酯对胚胎发育的影响。方法 丙酮为助溶剂,配制β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1,采用换水式每12 h更换一半β-氯氰菊酯溶液,对斑马鱼胚胎进行96 h暴露处理,采用显微镜观察β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1对斑马鱼胚胎发育形态,测定受精后24 h(24 hpf)自主抽动次数、48 hpf心率及孵化率、72和96 hpf体轴弯曲个体比例等。结果 与正常对照组比较,β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1组斑马鱼胚胎在24 hpf前形态上未出现明显异常,48 hpf以后表现出体轴弯曲、心包囊肿等不同程度的毒性反应症状,β-氯氰菊酯0.2 mg.L-1组幼鱼胸鳍发育即受到严重抑制且黑色素减少体色偏黄;随着β-氯氰菊酯浓度的增加,斑马鱼胚胎在24 hpf时每分钟自主抽动次数由正常对照组的(0.72±0.19)次增加至(3.83±1.07)次(P<0.05);48 hpf孵化率由对照组的(15.5±4.3)%升高至(98.9±1.2)%(P<0.05)。β-氯氰菊酯0.05 mg.L-1组72 hpf和96 hpf体轴弯曲个体比例分别为6.6%和10%,β-氯氰菊酯1 mg.L-1组分别为97.8%和100%。结论 β-氯氰菊酯对斑马鱼胚胎的神经及形态发育均有明显抑制作用,并且呈现一定的时间剂量依赖性。     

Exposure to the azo dye Direct blue 15 produces toxic effects on microalgae,cladocerans, and zebrafish embryos

Aquatic pollution caused by dyes has increased together with the growth of activities using colorants such as the textile, leather, food, and agrochemicals industries. Because most popular azo dyes are synthesized from benzidine, a carcinogenic compound, a threat to aquatic biota could be expected. The use of single species for toxicity assessment provides limited data, so a battery of test organisms, including representatives of different trophic levels such as algae, zooplankters, and fish, could undoubtedly provide more information. Therefore, our study was aimed at evaluating the toxic effect of the azo dye Direct blue 15 (DB15) on a battery of bioassays using a primary producer (Pseudokirchneriella subcapitata), a primary consumer (Ceriodaphnia dubia), and a secondary consumer (Danio rerio). P. subcapitata was more sensitive to DB15 (IC₅₀ = 15.99 mg L⁻¹) than C. dubia (LC₅₀: 450 mg L⁻¹). In the algae exposed to DB15, chlorophyll-a and -b were significantly increased, and carotenoids were reduced. The concentrations of protein, carbohydrates, and lipids per cell in P. subcapitata exposed to all DB15 concentrations were significantly higher than that measured in control. At 25 mg L⁻¹ of DB15, survival, total progeny, and the number of released clutches were significantly decreased, and the start of reproduction was delayed in C. dubia. DB15 did not induce lethal or sublethal effects in D. rerio embryos at any of the tested concentrations from 24 to 72 h post-fertilization (hpf), but from 96 to 144 hpf, the larvae exposed to 100 and 500 mg L⁻¹ developed yolk sac edema, curved tail, and skeletal deformations. After 144 hpf, DB15 produced a significant increase in embryos without a heartbeat, as the concentration of dye raised. The textile-used, azo dye DB15, caused toxic effects of different magnitude on microalgae, cladocerans, and zebrafish embryos; for this reason, the discharge of this colorant into waterbodies should be regulated to prevent environmental impacts.

     

Triphenyl phosphate-induced pericardial edema is associated with elevated epidermal ionocytes within zebrafish embryos

Triphenyl phosphate (TPHP) is an organophosphate ester-based plasticizer and flame retardant. The objective of this study was to identify the potential role of epidermal ionocytes in mediating TPHP-induced pericardial edema within zebrafish embryos. Exposure to TPHP from 24 to 72 h post fertilization (hpf) resulted in a significant increase in pericardial edema and the number of ionocytes at 72 hpf relative to time-matched embryos treated with vehicle. In addition, co-exposure of embryos to mannitol (an osmotic diuretic) blocked TPHP-induced pericardial edema and effects on ionocyte abundance. However, knockdown of ATPase1a1.4 – an abundant Na⁺/K⁺-ATPase localized to epidermal ionocytes – mitigated TPHP-induced effects on ionocyte abundance but not pericardial edema, whereas co-exposure of embryos to ouabain – a Na⁺/K⁺-ATPase inhibitor – enhanced TPHP-induced pericardial edema but not ionocyte abundance. Overall, our findings suggest that TPHP may have multiple mechanisms of toxicity leading to an increase in ionocyte abundance and pericardial edema within developing zebrafish embryos.     

MicroRNA expression changes during zebrafish development induced by perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS), a kind of widely distributed environmentally organic compound, has been found to cause developmental toxicity. Although microRNAs (miRNAs) play an important role in many metabolic tasks, whether and how they are involved in the process of PFOS‐induced toxicity is largely unknown. To address this problem, PFOS‐induced changes in miRNAs and target gene expression in zebrafish embryos, and the potential mechanism of PFOS‐induced toxic action were studied in this research. Zebrafish embryos were exposed to 1 µg ml^?1 PFOS or DMSO control from 6 h post‐fertilization (hpf) to 24 or 120 hpf. Subsequently, RNA was isolated from the embryo pool and the expression profiles of 219 known zebrafish miRNAs were analyzed using microarray. Finally, quantitative real‐time polymerase chain reaction was used to validate several miRNAs expression of microarray data. The analysis revealed that PFOS exposure induced significant changes in miRNA expression profiles. A total of 39 and 81 miRNAs showed significantly altered expression patterns after PFOS exposure 24 and 120 hpf. Of the changed miRNAs, 20 were significantly up‐regulated and 19 were significantly down‐regulated (p < 0.01) at 24 hpf, whereas 41 were significantly up‐regulated and 40 were significantly down‐regulated (p < 0.01) at 120 hpf. These miRNAs were involved in development, apoptosis and cell signal pathway, cell cycle progression and proliferation, oncogenesis, adipose metabolism and hormone secretion, whereas there is still little functional information available for 32 miRNAs. Our results demonstrate that PFOS exposure alters the expression of a suite of miRNAs and may induce developmental toxicity. Copyright © 2010 John Wiley & Sons, Ltd.     

Toxicity effects of captan on different life stages of zebrafish (Danio rerio)

The objective of this study was to evaluate the toxicity and developmental effects of captan on different life stages (embryo and adult) of zebrafish (Danio rerio). The results showed that the 96-h lethal concentration 50 (LC₅₀) values of embryo and adult zebrafish (exposed to captan) were 0.81(0.75−0.87) mg/L and 0.65(0.62−0.68) mg/L, respectively. The results of developmental effect experiment showed that captan can significantly decrease the heartbeats and inhibit the hatching rate and growth of zebrafish embryos. Moreover, captan exposure can induce a series of deformities, including pericardial edema, yolk sac edema, spine curvature, and tail bending, in zebrafish embryos during the developmental period. Among these, the most significant were tail bending and spine curvature.     

Role of AHR2 in the expression of novel cytochrome P450 1 family genes, cell cycle genes, and morphological defects in developing zebra fish exposed to 3,3',4,4',5-pentachlorobiphenyl or 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Halogenated agonists for the aryl hydrocarbon receptor (AHR), such as 3,3',4,4',5-pentachlorobiphenyl (PCB126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), cause developmental toxicity in fish. AHR dependence of these effects is known for TCDD but only presumed for PCB126, and the AHR-regulated genes involved are known only in part. We defined the role of AHR in regulation of four cytochrome P450 1 (CYP1) genes and the effect of PCB126 on cell cycle genes (i.e., PCNA and cyclin E) in zebra fish (Danio rerio) embryos. Basal and PCB126-induced expression of CYP1A, CYP1B1, CYP1C1, and CYP1C2 was examined over time as well as in relation to cell cycle gene expression and morphological effects of PCB126 in developing zebra fish. The four CYP1 genes differed in the time for maximal basal and induced expression, i.e., CYP1B1 peaked within 2 days postfertilization (dpf), the CYP1Cs around hatching (3 dpf), and CYP1A after hatching (14-21 dpf). These results indicate developmental periods when the CYP1s may play physiological roles. PCB126 (0.3-100nM) caused concentration-dependent CYP1 gene induction (EC50: 1.4-2.7nM, Lowest observed effect concentration [LOEC]: 0.3-1nM) and pericardial edema (EC50: 4.4nM, LOEC: 3nM) in 3-dpf embryos. Blockage of AHR2 translation significantly inhibited these effects of PCB126 and TCDD. PCNA gene expression was reduced by PCB126 in a concentration-dependent manner, suggesting that PCB126 could suppress cell proliferation. Our results indicate that the four CYP1 genes examined are regulated by AHR2 and that the effect of PCB126 on morphology in zebra fish embryos is AHR2 dependent. Moreover, the developmental patterns of expression and induction suggest that CYP1 enzymes could function in normal development and in developmental toxicity of PCB126 in fish embryos.     

Toxic effects of celastrol on embryonic development of zebrafish (Danio rerio)

Celastrol is a terpenoid purified from Tripterygium wilfordii Hook F. As a natural product with pharmacological activities, this compound is a promising candidate for drug development. To provide more information about its toxicity for clinical trials, toxicity assessment of celastrol was conducted with zebrafish model in vivo. 1hour post-fertilization (hpf) embryos were treated with various concentrations of celastrol for 120h. Developmental phenotypes were observed and survival rates were recorded. The results showed that the hatching rates of embryos treated with 1.0μM or higher celastrol were significantly lower. Embryos exposed to 1.0μM celastrol had no blood flow in trunk vessels at 48hpf with a median effect concentration (EC(50)) of 0.94μM. At 72hpf serious edema in pericardial sac was observed in the surviving larvae (hatched from embryos treated with 1.5μM celastrol). Bent tails or hook-like tails were seen as 0.5μM celastrol and the EC(50) for tail malformation was 0.66 μM at 72hpf. The lethal effect of celastrol on zebrafish embryos was dose-dependent and the LC(50) values of celastrol on 1hpf embryos were approximately 1.40μM. These results indicate that celastrol affects the normal development of zebrafish embryo in μM concentrations.