Ioxynil and diethylstilbestrol disrupt vascular and heart development in zebrafish

The Relationship Between Maternal Exposure to Endocrine-Disrupting Chemicals and the Incidence of Congenital Heart Diseases: A Systematic Review and Meta-Analysis

BACKGROUND

Congenital heart diseases are among the most common birth defects, significantly impacting infant health. Recent evidence suggests that exposure to endocrine-disrupting chemicals may contribute to the incidence of congenital heart diseases. This study systematically reviews and analyzes the association between maternal endocrine-disrupting chemicals exposure and congenital heart diseases.

METHODOLOGY

This systematic review and meta-analysis followed the Cochrane Handbook and PRISMA guidelines. We included studies assessing the link between maternal exposure to various endocrine-disrupting chemicals and the incidence of congenital heart diseases without restricting the study design or exposure assessment methods. Data were extracted from four databases, including PubMed, Scopus, Web of Science, and Cochrane Library, up to June 2024. Quality assessment of observational studies was conducted using the Newcastle-Ottawa Scale. Statistical analysis was performed using RevMan software version 5.3, presenting results as odds ratios with 95% confidence intervals.

RESULTS

Fifty-nine studies were included in the meta-analysis. The pooled analysis revealed a significant association between maternal endocrine-disrupting chemical exposure and the incidence of congenital heart diseases when measured using human samples (odds ratio = 1.63, 95% confidence interval [1.35-1.97], p < 0.00001). Notably, exposure to heavy metals, polycyclic aromatic hydrocarbons, and perfluoroalkyl compounds was strongly associated with congenital heart diseases. However, non-sample-based methods showed no significant overall correlation (odds ratio = 1.08, 95% confidence interval [0.93-1.26], p = 0.30), except for housing renovation compounds, which were linked to a higher incidence of congenital heart diseases.

CONCLUSIONS

Maternal exposure to specific endocrine-disrupting chemicals, particularly heavy metals and polycyclic aromatic hydrocarbons, significantly increases the risk of congenital heart diseases. These findings underscore the need for preventive measures to reduce endocrine-disrupting chemicals exposure during pregnancy and further research to elucidate the underlying mechanisms.

Insights into the developmental and cardiovascular toxicity of bixafen using zebrafish embryos and larvae

Bixafen (BIX), a member of the succinate dehydrogenase inhibitor (SDHI) class of fungicides, has seen a surge in interest due to its expanding market presence and positive development outlook. However, there is a growing concern about its potential harm to aquatic life, largely due to its resistance to breaking down in the environment. In this study, we thoroughly examined the toxicological impact of BIX on zebrafish as a model organism. Our results revealed that BIX significantly hindered the development of zebrafish embryos, leading to increased mortality, hatching failures, and oxidative stress. Additionally, we observed cardiovascular abnormalities, including dilated cardiac chambers, reduced heart rate, sluggish blood circulation, and impaired vascular function. Notably, BIX also altered the expression of key genes involved in cardiovascular development, such as myl7, vmhc, nkx2.5, tbx5, and flt1. In summary, BIX was found to induce developmental and cardiovascular toxicity in zebrafish, underscoring the risks associated with SDHI pesticides and emphasizing the need for a reassessment of their impact on human health. These findings are crucial for the responsible use of BIX.

Exposure to Endocrine-Disrupting Chemicals and Congenital Heart Diseases: The Pooled Results Based on the Current Evidence

The relationships between maternal exposure to endocrine-disrupting chemicals (EDCs) and congenital heart diseases (CHD) are not elucidated yet. The exposure levels of EDCs are generally estimated based on self-reported questionnaires or occupational exposure evaluations in the literature. Therefore, a study based on epidemiological data from human biospecimens is required to provide stronger evidence between maternal exposure to EDC and CHD. Embase, Pubmed, Scopus, and the Cochrane Library databases were searched for related research which provided risk estimates regarding the relationships between maternal EDC exposure and CHD in human offspring. Baseline characteristics and outcomes of CHD were extracted from each included study. Odds ratios (ORs) with 95% confidence intervals (CIs) were pooled to calculate the overall estimates of CHD. Subgroup and meta-regression analyses were performed to identify the sources of heterogeneity. Bootstrapping techniques were used in analyses where several studies originated from a similar population. A total of seventeen studies were involved in the meta-analyses. Maternal EDC exposure was significantly related to CHD in offspring (OR 2.15; 95%CI 1.64 to 2.83). EDC exposure was significantly associated with septal defects (OR 2.34; 95%CI 1.77 to 3.10), conotruncal defects (OR 2.54; 95%CI 1.89 to 3.43), right ventricular outflow tract obstruction (OR 2.65; 95%CI 1.73 to 4.07), left ventricular outflow tract obstruction (OR 3.58; 95%CI 2.67 to 4.79), anomalous pulmonary venous return (OR 2.31; 95%CI 1.34 to 4.00), and other heart defects (OR 2.49; 95%CI 1.75 to 3.54). In addition, maternal exposure to heavy metals, which included lead (OR 2.19; 95%CI 1.29 to 3.71), cadmium (OR 1.81; 95%CI 1.28 to 2.56), mercury (OR 2.23; 95%CI 1.13 to 4.44), and manganese (OR 2.65; 95%CI 1.48 to 4.74), increased risks for CHD significantly. In conclusion, based on the latest evidence, maternal EDC exposure may increase CHD risks in human offspring, especially in heavy metal exposure conditions.

Emerging disinfection byproducts 3-bromine carbazole induces cardiac developmental toxicity via aryl hydrocarbon receptor activation in zebrafish larvae

3-bromine carbazole (3-BCZ) represents a group of emerging aromatic disinfection byproducts (DBP) detected in drinking water; however, limited information is available regarding its potential cardiotoxicity. To assess its impacts, zebrafish embryos were exposed to 0, 0.06, 0.14, 0.29, 0.58, 1.44 or 2.88 mg/L of 3-BCZ for 120 h post fertilization (hpf). Our results revealed that ≥1.44 mg/L 3-BCZ exposure induced a higher incidence of heart malformation and an elevated pericardial area in zebrafish larvae; it also decreased the number of cardiac muscle cells and thins the walls of the ventricle and atrium while increasing cardiac output and impeding cardiac looping. Furthermore, 3-BCZ exposure also exhibited significant effects on the transcriptional levels of genes related to both cardiac development (nkx2.5, vmhc, gata4, tbx5, tbx2b, bmp4, bmp10, and bmp2b) and cardiac function (cacna1ab, cacna1da, atp2a1l, atp1b2b, atp1a3b, and tnnc1a). Notably, N-acetyl-L-cysteine, a reactive oxygen species scavenger, may alleviate the failure of cardiac looping induced by 3-BCZ but not the associated cardiac dysfunction or malformation; conversely, the aryl hydrocarbon receptor agonist CH131229 can completely eliminate the cardiotoxicity caused by 3-BCZ. This study provides new evidence for potential risks associated with ingesting 3-BCZ as well as revealing underlying mechanisms responsible for its cardiotoxic effects on zebrafish embryos.

Developmental cardiotoxicity of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in marine medaka (Oryzias melastigma)

The application of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as an antifouling biocide causes high toxicity to non-target marine organisms. To examine the developmental cardiotoxicity and mechanisms of DCOIT, we concurrently performed sub-chronic exposure and life-cycle exposure experiments using marine medaka embryos. After sub-chronic exposure to DCOIT at 1, 3, 10, and 33 μg/L, cardiac defects were caused by upregulation of cardiac gene transcriptions, decreasing heart size, and accelerating heartbeat. Hyperthyroidism in medaka larvae was identified as the cause of developmental cardiotoxicity of DCOIT sub-chronic exposure. In addition, parental life-cycle exposure to 1, 3, and 10 μg/L DCOIT led to transgenerational impairment of cardiogenesis in offspring medaka. A crossbreeding strategy discriminated a concentration-dependent mechanism of transgenerational cardiotoxicity. At 1 μg/L, the DCOIT-exposed female parent transferred a significantly higher amount of triiodothyronine (T3) hormone to offspring, corresponding to an accelerated heart rate. However, DCOIT at higher exposure concentrations modified the methylome imprinting in larval offspring, which was associated with cardiac dysfunction. Overall, the findings provide novel insights into the developmental cardiotoxicity of DCOIT. The high risks of DCOIT-even at environmentally realistic concentrations-raise concerns about its applicability as an antifoulant in a marine environment.

6-benzylaminopurine causes endothelial dysfunctions to human umbilical vein endothelial cells and exacerbates atorvastatin-induced cerebral hemorrhage in zebrafish

6-benzylaminopurine (6-BA), a multifunctional plant growth regulator, which is frequently used worldwide to improve qualities of various crops, is an important ingredient in production of "toxic bean sprouts." Although there is no direct evidence of adverse effects, its hazardous effects, as well as joint toxicity with other chemicals, have received particular attention and aroused furious debate between proponents and environmental regulators. By use of human umbilical vein endothelial cells (HUVECs), adverse effects of 6-BA to human-derived cells were first demonstrated in this study. A total of 25-50 mg 6-BA/L inhibited proliferation, migration, and formation of tubular-like structures by 50% in vitro. Results of Western blot analyses revealed that exposure to 6-BA differentially modulated the MAPK signal transduction pathway in HUVECs. Specifically, 6-BA decreased phosphorylation of MEK and ERK, but increased phosphorylation of JNK and P38. In addition, 6-BA exacerbated atorvastatin-induced cerebral hemorrhage via increasing hemorrhagic occurrence by 60% and areas by 4 times in zebrafish larvae. In summary, 6-BA elicited toxicity to the endothelial system of HUVECs and zebrafish. This was due, at least in part, to discoordination of MAPK signaling pathway, which should pose potential risks to the cerebral vascular system.

Stereoselective cardiotoxic effects of metconazole on zebrafish (Danio rerio) based on AGE-RAGE signalling pathway

Metconazole (MEZ) is a novel chiral triazole fungicide that is widely used to prevent and control soil-borne fungal pathogens and other fungal diseases. However, it has a long half-life in aquatic environments and thus poses potential environmental risks. This study evaluates the acute and stereoselective cardiotoxicity of MEZ in zebrafish (Danio rerio) embryos. In addition, transcriptomics, real-time quantitative PCR, enzyme activity determination, and molecular docking are performed to evaluate the molecular mechanisms underlying the cardiotoxicity of MEZ in zebrafish. MEZ decreases the heart rate while increasing the pericardial oedema rate; additionally, it induces stereoselective cardiotoxicity. 1S,5S-MEZ exhibits stronger cardiotoxicity than 1R,5R-MEZ. Furthermore, MEZ increases the expression of Ahr-associated genes and the transcription factors il6st, il1b, and AP-1. Heart development-related genes, including fbn2b, rbm24b, and tbx20 are differentially expressed. MEZ administration alters the activities of catalase, peroxidase, and glutathione-S-transferase in zebrafish larvae. Molecular docking indicates that 1R,5R-MEZ binds more strongly to the inhibitor-binding sites of p38 in the AGE-RAGE signalling pathway than to other MEZ enantiomers. Studies conducted in vivo and in silico have established the enantioselective cardiotoxicity of MEZ and its underlying mechanisms, highlighting the need to evaluate the environmental risk of chiral MEZ in aquatic organisms at the enantiomeric level.

Crosstalk between aryl hydrocarbon receptor and Wnt/β-catenin signaling pathway: Possible culprit of di (2-ethylhexyl) phthalate-mediated cardiotoxicity in zebrafish larvae

Typical plasticizer di (2-ethylhexyl) phthalate (DEHP) has been demonstrated to induce cardiotoxicity in zebrafish, but the potential molecular mechanisms involved have not been fully elucidated. Aryl hydrocarbon receptor (AhR), an essential protein for inducing developmental abnormalities, has been demonstrated to be activated by DEHP in other species, but whether the AhR signaling pathway also contributes to DEHP-mediated cardiac developmental toxicity in zebrafish remains unclear. Firstly, molecular docking simulations initially confirmed the possibility that DEHP has AhR agonistic activity. To further confirm this conjecture, this work analyzed the changes of cardiac-related indexes in zebrafish stressed by DEHP at individual, protein, and gene levels. The results showed that DEHP mediated cardiac phenotypic developmental defects, increased CYP1A1 activity, and oxidative stress as well as significant changes in the expression levels of key proteins and genes of AhR, Wnt/β-catenin, and Nrf2-Keap1 signaling pathways. Notably, the addition of AhR inhibitors effectively alleviated the above negative effects, indicating that the AhR signaling pathway and its crosstalk with the Wnt/β-catenin signaling pathway is an essential pathway for DEHP-mediated cardiac developmental toxicity. Overall, this work enriches the molecular mechanism of DEHP-mediated cardiac developmental defects in zebrafish and provides a reliable biomarker for future environmental risk assessment of DEHP.

Effects of butyl benzyl phthalate on zebrafish (Danio rerio) brain and the underlying molecular mechanisms revealed by transcriptome analysis

Butyl benzyl phthalate (BBP), a widely used class of plasticizers, has caused considerable concerns due to its widespread detection in various environmental media. However, the potential impact of BBP on the brain and its underlying molecular mechanisms remain poorly understood. In this study, adult zebrafish (Danio rerio) were exposed to 0, 5, 50, and 500 μg/L BBP for 28 days. Elevated levels of both reactive oxygen species and 8-hydroxydeoxyguanosine were observed, indicating the occurrence of oxidative stress and DNA damage. Furthermore, exposure to BBP resulted in neurotoxicity, apoptosis, and histopathological damage within the zebrafish brain. Transcriptome analysis further revealed that Gene Ontology terms associated with muscle contraction were specifically expressed in the brain after BBP exposure. In addition, BBP altered the transcriptome profile of the brain, with 293 genes induced and 511 genes repressed. Kyoto Encyclopedia of Genes and Genomes analysis highlighted the adverse effects of BBP on the complement and coagulation cascades and two cardiomyopathy-related pathways. Taken together, our results revealed that BBP resulted in brain oxidative stress, histological damage, and transcriptome alterations. These findings have the potential to offer novel insights into the adverse outcome pathways of key events in the brain.

Ioxynil and diethylstilbestrol impair cardiac performance and shell growth in the mussel Mytilus coruscus

The herbicide ioxynil (IOX) and the synthetic estrogen diethylstilbestrol (DES) are environmentally relevant contaminants that act as endocrine disruptors (EDCs) and have recently been shown to be cardiovascular disruptors in vertebrates. Mussels, Mytilus coruscus, were exposed to low doses of IOX (0.37, 0.037 and 0.0037 mg/L) and DES (0.27, 0.027 and 0.0027 mg/L) via the water and the effect monitored by generating whole animal transcriptomes and measuring cardiac performance and shell growth. One day after IOX (0.37 and 0.037 mg/L) and DES (0.27 and 0.027 mg/L) exposure heart rate frequency was decreased in both groups and 0.27 mg/L DES significantly reduced heart rate frequency with increasing time of exposure (P < 0.05) and no acclimatization occurred. The functional effects were coupled to significant differential expression of genes of the serotonergic synapse pathway and cardiac-related genes at 0.027 mg/L DES, which suggests that impaired heart function may be due to interference with neuroendocrine regulation and direct cardiac effect genes. Multiple genes related to detoxifying xenobiotic substances were up regulated and genes related to immune function were down regulated in the DES group (vs. control), indicating that detoxification processes were enhanced, and the immune response was depressed. In contrast, IOX had a minor disrupting effect at a molecular level. Of note was a significant suppression (P < 0.05) by DES of shell growth in juveniles and lower doses (< 0.0027 mg/L) had a more severe effect. The shell growth depression in 0.0027 mg/L DES-treated juveniles was not accompanied by abundant differential gene expression, suggesting that the effect of 0.0027 mg/L DES on shell growth may be direct. The results obtained in the present study reveal for the first time that IOX and DES may act as neuroendocrine disrupters with a broad spectrum of effects on cardiac performance and shell growth, and that DES exposure had a much more pronounced effect than IOX in a marine bivalve.

Bisphenol A (BPA) and Cardiovascular or Cardiometabolic Diseases

Bisphenol A (BPA; 4,4'-isopropylidenediphenol) is a well-known endocrine disruptor. Most human exposure to BPA occurs through the consumption of BPA-contaminated foods. Cardiovascular or cardiometabolic diseases such as diabetes, obesity, hypertension, acute kidney disease, chronic kidney disease, and heart failure are the leading causes of death worldwide. Positive associations have been reported between blood or urinary BPA levels and cardiovascular or cardiometabolic diseases. BPA also induces disorders or dysfunctions in the tissues associated with these diseases through various cell signaling pathways. This review highlights the literature elucidating the relationship between BPA and various cardiovascular or cardiometabolic diseases and the potential mechanisms underlying BPA-mediated disorders or dysfunctions in tissues such as blood vessels, skeletal muscle, adipose tissue, liver, pancreas, kidney, and heart that are associated with these diseases.

Characterization of glyphosate-induced cardiovascular toxicity and apoptosis in zebrafish

Glyphosate, the most widely used herbicide, presents new hazards to human health. The developmental toxicity of glyphosate, especially its cardiovascular toxicity, needs to be closely monitored. To understand how glyphosate affects development, we performed toxicity tests on zebrafish embryos that were continuously exposed to glyphosate. The results indicated that glyphosate affected the overall development of zebrafish embryos, including mortality, hatching abnormalities, and decreased body length. At the same time, zebrafish embryos exposed to glyphosate exhibited cardiac malformations, including enlarged chambers, thinned ventricular walls, and rhythm disturbances. In addition, defective intersegmental vasculature occurred after glyphosate exposure, indicating impaired angiogenesis. Mechanistically, apoptosis clustered in the heart and vascular regions and levels of ATP and apoptosis-related genes including caspase-3, caspase-9, bax, and bcl-2 were altered. In summary, the data showed that cardiovascular toxicity caused by glyphosate exposure may be related to apoptosis. Our study provides evidence for a link between glyphosate exposure and cardiovascular developmental toxicity. This raises concerns regarding the health risks of the glyphosate.

Influence of hypomagnetic field on the heartbeat in zebrafish embryos

The magnetic environment may influence the functioning of the cardiovascular system. It was reported that low-frequency and static magnetic fields affect hemodynamics, heart rate, and heart rate variability in animals and humans. Moreover, recent data suggest that magnetic fields affect the circadian rhythms of physiological processes. The influence of the magnetic environment on heart functionating during early development has been studied insufficiently. We utilized transparent zebrafish embryos to evaluate the effect of the hypomagnetic field on the characteristics of cardiac function using a noninvasive optical approach based on photoplethysmographic microscopic imaging. The embryos were exposed to the geomagnetic and hypomagnetic fields from the second to the 116th hour post fertilization under a 16 h light/8 h dark cycle or constant illumination. The exposure of embryos to the hypomagnetic field in both lighting modes led to increased embryo mortality, the appearance of abnormal phenotypes, and a significant increase in the embryo’s heartbeat rate. The difference between maximal and minimal heartbeat intervals, maximal to minimal heartbeat intervals ratio, and the coefficient of variation of heartbeat rate were increased in the embryos exposed to the hypomagnetic field under constant illumination from 96 to 116 h post fertilization. The dynamics of heartbeat rate changes followed a circadian pattern in all studied groups except zebrafish exposed to the hypomagnetic field under constant illumination. The results demonstrate the importance of natural magnetic background for the early development of zebrafish. The possible mechanisms of observed effects are discussed.

Ioxynil and diethylstilbestrol increase the risks of cardiovascular and thyroid dysfunction in zebrafish

Endocrine disruption results from exposure to chemicals that alter the function of the endocrine system in animals. Chronic 60 days of exposure to a low dose (0.1 μM) of ioxynil (IOX) or diethylstilbestrol (DES) via food was used to determine the effects of these chemicals on the physiology of the heart and thyroid follicles in juvenile zebrafish. Immunofluorescence analysis and subsequent 3D morphometric analysis of the zebrafish heart revealed that chronic exposure to IOX induced ventricle deformation and significant volume increase (p < 0.001). DES exposure caused a change in ventricle morphology, but volume was unaffected. Alongside, it was found that DES exposure upregulated endothelial related genes (angptl1b, mhc1lia, mybpc2a, ptgir, notch1b and vwf) involved in vascular homeostasis. Both IOX and DES exposure caused a change in thyroid follicle morphology. Notably, in IOX exposed juveniles, thyroid follicle hypertrophy was observed; and in DES-exposed fish, an enlarged thyroid field was present. In summary, chronic exposure of juvenile zebrafish to IOX and DES affected the heart and the thyroid. Given that both chemicals are able to change the morphology of the thyroid it indicates that they behave as endocrine disruptive chemicals (EDCs). Heart function dynamically changes thyroid morphology, and function and hence it is likely that the observed cardiac effects of IOX and DES are the source of altered thyroid status in these fish.

Spironolactone affects cardiovascular and craniofacial development in zebrafish embryos (Danio rerio)

Spironolactone, a potassium-sparing diuretic and aldosterone antagonist, is a mineralocorticoid hormone commonly prescribed to patients suffering from heart failure, hirsutism, dermatological afflictions, and hypertension. Interestingly, relatively little work has been done on the development of vertebrate embryos after exposure to this compound. Here, we treat zebrafish embryos with spironolactone at 10^-6 M, 10^-7 M, or 10^-8 M, and observe them after three to seven days of exposure. While no effect was observed in mortality, we did detect differences in cardiovascular development at 3 dpf and craniofacial development at 5 dpf. At 10^-6 M, smaller atria, ventricles, and blood vessels were observed. The highest concentrations also caused a longer ceratohyal/Meckel's distance, longer palatoquadrate, and smaller angles between the palatoquadrate and both the ceratohyal and Meckel's. Further research of spironolactone's effects on embryonic development could lead to a better understanding of the compound resulting in improved public and environmental health.

Developmental Exposure to Endocrine Disrupting Chemicals and Its Impact on Cardio-Metabolic-Renal Health

Developmental origin of health and disease postulates that the footprints of early life exposure are followed as an endowment of risk for adult diseases. Epidemiological and experimental evidence suggest that an adverse fetal environment can affect the health of offspring throughout their lifetime. Exposure to endocrine disrupting chemicals (EDCs) during fetal development can affect the hormone system homeostasis, resulting in a broad spectrum of adverse health outcomes. In the present review, we have described the effect of prenatal EDCs exposure on cardio-metabolic-renal health, using the available epidemiological and experimental evidence. We also discuss the potential mechanisms of their action, which include epigenetic changes, hormonal imprinting, loss of energy homeostasis, and metabolic perturbations. The effect of prenatal EDCs exposure on cardio-metabolic-renal health, which is a complex condition of an altered biological landscape, can be further examined in the case of other environmental stressors with a similar mode of action.

Integration of transcriptomics and metabolomics reveals damage and recovery mechanisms of fish gills in response to nanosilver exposure

Toxic effects of silver nanoparticles (AgNPs) on fish gills have been widely reported but the recoverability of AgNPs-induced fish gill injuries is still unknown. In this study, combined multiomics and conventional toxicological analytical methods were used to investigate the changes in the gills of common carp responses to AgNPs (0.1 mg/L) toxicity after 24 h exposure and 7-day recovery. Conventional toxicological results showed that AgNPs exposure significantly increased silver content in gills and caused epithelial hyperplasia and lamellar fusion. After the recovery period, the silver content in fish gills significantly decreased; accompanied by the disappearance of histopathological characteristics in fish gills. Multiomics results revealed that AgNPs exposure resulted in the differential expression of 687 genes and 96 metabolites in fish gills. These differentially expressed genes (DEGs) and metabolites mainly participate in amino acid, carbohydrate, and lipid metabolisms, and are significantly enriched in the tricarboxylic acid (TCA) cycle. After the recovery period, the number of DEGs and metabolites in gills decreased to 33 and 90, respectively. Moreover, DEGs and metabolites in the TCA cycle recovered to control levels. In summary, the present study found that AgNPs-induced fish gill toxicity showed potential recoverability at molecular and phenotype levels.

Zebrafish as the toxicant screening model: Transgenic and omics approaches

The production of large amounts of synthetic industrial and biomedical compounds, together with environmental pollutants, poses a risk to our ecosystem and induces negative effects on the health of wildlife and human beings. With the emergence of the global problem of chemical contamination, the adverse biological effects of these chemicals are gaining attention among the scientific communities, industry, governments, and the public. Among these chemicals, endocrine disrupting chemicals (EDCs) are regarded as one of the major global issues that potentially affecting our health. There is an urgent need of understanding the potential hazards of such chemicals. Zebrafish have been widely used in the aquatic toxicology. In this review, we first discuss the strategy of transgenic lines that used in the toxicological studies, followed by summarizing the current omics approaches (transcriptomics, proteomics, metabolomics, and epigenomics) on toxicities of EDCs in this model. We will also discuss the possible transgenerational effects in zebrafish and future prospective of the integrated omics approaches with customized transgenic organism. To conclude, we summarize the current findings in the field, and provide our opinions on future environmental toxicity research in the zebrafish model.

Forchlorfenuron (CPPU) causes disorganization of the cytoskeleton and dysfunction of human umbilical vein endothelial cells, and abnormal vascular development in zebrafish embryos

Forchlorfenuron (CPPU) has been used worldwide, to boost size and improve quality of various agricultural products. CPPU and its metabolites are persistent and have been detected frequently in fruits, water, sediments, and organisms in aquatic systems. Although the public became aware of CPPU through the exploding watermelon scandal of 2011 in Zhenjiang, China, little was known of its potential effects on the environment and wildlife. In this study, adverse effects of CPPU on developmental angiogenesis and vasculature, which is vulnerable to insults of persistent toxicants, were studied in vivo in zebrafish embryos (Danio rerio). Exposure to 10 mg CPPU/L impaired survival and hatching, while development was hindered by exposure to 2.5 mg CPPU/L. Developing vascular structure, including common cardinal veins (CCVs), intersegmental vessels (ISVs) and sub-intestinal vessels (SIVs), were significantly restrained by exposure to CPPU, in a dose-dependent manner. Also, CPPU caused disorganization of the cytoskeleton. In human umbilical vein endothelial cells (HUVECs), CPPU inhibited proliferation, migration and formation of tubular-like structures in vitro. Results of Western blot analyses revealed that exposure to CPPU increased phosphorylation of FLT-1, but inhibited phosphorylation of FAK and its downstream MAPK pathway in HUVECs. In summary, CPPU elicited developmental toxicity to the developing endothelial system of zebrafish and HUVECs. This was do, at least in part due to inhibition of the FAK/MAPK signaling pathway rather than direct interaction with the VEGF receptor (VEGFR).

Assessment of the in vitro developmental toxicity of diethylstilbestrol and estradiol in the zebrafish embryotoxicity test

The present study investigated the developmental toxicity of diethylstilbestrol (DES) in the zebrafish embryotoxicity test (ZET). This was done to investigate whether the ZET would better capture the developmental toxicity of DES than the embryonic stem cells test (EST) that was previously shown to underpredict the DES-induced developmental toxicity as compared to in vivo data, potentially because the EST does not capture late events in the developmental process. The ZET results showed DES-induced growth retardation, cumulative mortality and dysmorphisms (i.e. induction of pericardial edema) in zebrafish embryos while the endogenous ERα agonist 17β-estradiol (E2) showed only growth retardation and cumulative mortality with lower potency compared to DES. Furthermore, the DES-induced pericardial edema formation in zebrafish embryos could be counteracted by co-exposure with ERα antagonist fulvestrant, indicating that the ZET captures the role of ERα in the mode of action underlying the developmental toxicity of DES. Altogether, it is concluded that the ZET differentiates DES from E2 with respect to their developmental toxicity effects, while confirming the role of ERα in mediating the developmental toxicity of DES. Furthermore, comparison to in vivo data revealed that, like the EST, in a quantitative way also the ZET did not capture the relatively high in vivo potency of DES as a developmental toxicant.

Differential susceptibility to endocrine disruptor-induced epimutagenesis

There is now considerable evidence indicating the potential for endocrine disrupting chemicals to alter the epigenome and for subsets of these epigenomic changes or "epimutations" to be heritably transmitted to offspring in subsequent generations. While there have been many studies indicating how exposure to endocrine disrupting chemicals can disrupt various organs associated with the body's endocrine systems, there is relatively limited information regarding the relative susceptibility of different specific organs, tissues, or cell types to endocrine disrupting chemical-induced epimutagenesis. Here we review available information about different organs, tissues, cell types, and/or cell lines which have been shown to be susceptible to specific endocrine disrupting chemical-induced epimutations. In addition, we discuss possible mechanisms that may be involved, or impacted by this tissue- or cell type-specific, differential susceptibility to different endocrine disrupting chemicals. Finally, we summarize available information indicating that certain periods of development display elevated susceptibility to endocrine disrupting chemical exposure and we describe how this may affect the extent to which germline epimutations can be transmitted inter- or transgenerationally. We conclude that cell type-specific differential susceptibility to endocrine disrupting chemical-induced epimutagenesis is likely to directly impact the extent to, or manner in, which endocrine disrupting chemical exposure initially induces epigenetic changes to DNA methylation and/or histone modifications, and how these endocrine disrupting chemical-induced epimutations can then subsequently impact gene expression, potentially leading to the development of heritable disease states.

Risk assessment of cardiotoxicity to zebrafish (Danio rerio) by environmental exposure to triclosan and its derivatives

Triclosan (TCS) and its two derivatives (2,4-dichlorophenol and 2,4,6-trichlorophenol) are priority pollutants that coexist in aquatic environments. Joint exposure of TCS, 2,4-dichlorophenol and 2,4,6-trichlorophenol, hereafter referred to as TCS-DT, contributes severe toxicity to aquatic organisms. There is currently a paucity of data regarding TCS-DT molecular toxicity, especially on cardiac diseases. We used zebrafish (Danio rerio) as a model organism, and evaluated the molecular-level cardiotoxicity induced by TCS-DT from embryonic to adult stages. TCS-DT exposure prominently led to phenotypic malformations, such as pericardial cysts, cardiac bleeding, increased SV-BA distance, decreased heart rate and reduced ejection fraction, as well as abnormal swimming behavior. Analyses of the GO and KEGG pathways revealed enrichment pathways related to cardiac development and screened for significantly down-regulated adrenaline signaling in cardiomyocytes. The cardiac marker genes (amhc, cmlc2, vmhc, and nkx2.5) were obtained through protein-protein interaction (PPI) networks, and expressed as down-regulation by WISH. After chronic exposure to TCS-DT from 30 to 90-dpf, both body mass and heart indexes prominently increased, showing myocardial hypertrophy, abnormal heart rate and histopathological injury. Heart tissue damage included disordered and ruptured myocardial fibers, broken and dissolved myofilaments, nuclear pyknosis, mitochondrial injury and inflammatory cell infiltration. Further, abnormal changes in a series of cardiac functions-related biomarkers, including superoxide dismutase, triglyceride, lactate dehydrogenase and creatinine kinase MB, provided evidence for cardiac pathological responses. These results highlight the molecular mechanisms involving TCS-DT induced cardiac toxicity, and provide theoretical data to guide prevention and treatment of pollutant-induced cardiac diseases.

Near-future levels of ocean temperature weaken the byssus production and performance of the mussel Mytilus coruscus

Marine mussels are key ecological engineers that form dense aggregations to maintain the vital habitat in benthic systems. It is essential to understand the consequences of mussel byssus attachment in elevated temperatures associated with ocean warming. We evaluated byssus production and the mechanical performance of threads in the mussel Mytilus coruscus at 21° (control), 27 °C (average temperature in the M. coruscus habitat during the summer season) and 31 °C (4 °C raised) for 72 h. We quantified byssus secretion and shedding number, measured byssal breaking force, byssal polyphenol oxidase (PPO) activity, byssal thread length and diameter. Expression of byssus foot protein genes was analyzed by quantitative real-time PCR in foot tissue. High seawater temperature decreased the number of newly secreted byssus and the diameter of byssal threads, leading to the reduction of byssal breaking force and the alteration of the weakest part of the thread. Increased breakpoints in the upper part of the thread (proximal region) were higher at 27 °C than at 21 °C. High-temperature stress significantly reduced the PPO activity in byssus at 31 °C in comparison to 21 °C. The expression of mussel foot protein genes was affected by elevated temperature. The increased gene expression of byssus collagen-like protein 2 (Mccol2) at 31 °C conflicted with the number of byssuses produced. Suggesting the reduction of mussel foot protein abundance is not the cause of decreased byssus production at 31 °C. These results show that byssus, as an extracellular structure of mussels, may be highly susceptible to the adverse effects of ocean warming.