The developmental effects of low-level procymidone towards zebrafish embryos and involved mechanism

A novel electrochemical aptasensor based on AgPdNPs/PEI-GO and hollow nanobox-like Pt@Ni-CoHNBs for procymidone detection

Herein, an aptasensor based on a signal amplification strategy was developed for the sensitive detection of procymidone (PCM). AgPd nanoparticles/Polenimine Graphite oxide (AgPdNPs/PEI-GO) was weaned as electrode modification material to facilitate electron transport and increase the active sites on the electrode surface. Besides, Pt@Ni-Co nanoboxes (Pt@Ni-CoHNBs) were utilized to be carriers for signaling tags, after hollowing ZIF-67 and growing Pt, the resulting Pt@Ni-CoHNBs has a tremendous amounts of folds occurred on the surface, enables it to carry a larger quantity of thionine, thus amplify the detectable electrochemical signal. In the presence of PCM, the binding of PCM to the signal probe would trigger a change in electrical signal. The aptasensor was demonstrated with excellent sensitivity and a low detection limit of 0.98 pg·mL-1, along with a wide linear range of 1 μg·mL-1 to 1 pg·mL-1. Meanwhile, the specificity, stability and reproducibility of the constructed aptasensor were proved to be satisfactory.

Enzymatic and transcriptional level changes induced by the co-presence of lead and procymidone in hook snout carp (Opsariichthys bidens)

Understanding the interactions between different environmental pollutants is necessary in ecotoxicology since environmental contaminants never appear as single components but rather in combination with other substances. Heavy metals and pesticides are commonly detected in the environment, but the characterization of their mixture toxicity has been inadequately explored. This research aimed to elucidate the mixture impacts of the heavy metal lead (Pb) and the pesticide procymidone (PCM) on the hook snout carp (Opsariichthys bidens) using an array of biomarkers. The data showed that Pb and PCM possessed almost equivalent acute toxicity to the animals, with 4-days LC50 values of 120.9 and 85.15 mg L-1, respectively. Combinations of Pb and PCM generated acute synergistic effects on O. bidens. The contents of malondialdehyde (MDA), antioxidative (SOD), apoptotic (caspase-9), and detoxifying enzymes glutathione S-transferase (GST) and cytochrome P450 (CYP450) significantly changed after most of the mixture exposures compared with the baseline level and the corresponding individual exposures. This suggests the induction of oxidative stress, cell damage, and detoxification dysfunction. The expressions of eight genes (mn-sod, cu-sod, p53, cas3, erβ1, esr, ap, and klf2α) associated with oxidative stress, cell apoptosis, immune response, and hormonal functions exhibited pronounced changes when challenged with the mixture compared to the individual treatments. This indicates the occurrence of immune dysregulation and endocrine disorder. These findings provide an overall understanding of fish upon the challenge of sublethal toxicity between Pb and PCM and can be adopted to evaluate the complicated toxic mechanisms in aquatic vertebrates when exposed to heavy metal and pesticide mixtures. Additionally, these results might guide environmental regulation tactics to protect the population of aquatic vertebrates in natural ecosystems.

Novel and portable test strip platform for rapid and sensitive on-site detection of procymidone pesticide

A novel and portable detection platform for procymidone (PRM) was developed by combining simple sample pretreatment, lateral flow test strips based on multi-branched gold nanoparticle (LFTS-MBGNP), and a smartphone. Based on the large surface area of MBGNPs, rapid detection of PRM was realized by simple naked eye observation. By utilizing a smartphone as a portable signal analyzer, ultrasensitive quantitative detection of PRM in red wine was realized with the limits of detection (LOD) of 1.60 ng/mL, which was 3000 times lower than the US limit (5 ppm). Moreover, rapid detection of four kinds of fruits and vegetables was achieved within 10 min, with LODs of 4.34 ng/g, 6.93 ng/g, 8.99 ng/g, and 5.03 ng/g, respectively, which could meet the PRM limit of the European Union (10 ng/g). Integrating the optimized QuEChERS pretreatment method, the developed platform realized a simple and sensitive on-site detection of PRM pesticide in foods and red wine within 45 min. This platform provides a useful tool and new idea for rapid screening and detection of pesticide residues in food.

Maternal procymidone exposure has lasting effects on murine gut-liver axis and glucolipid metabolism in offspring

There is increasing evidence that maternal exposure to environmental pollutants can cause intestinal and metabolic diseases, and these disease risks still exist in offspring. Here, female C57BL/6 mice were orally treated with procymidone (PRO) (10 and 100 mg/kg body weight/day) by dietary supplementation during the gestation and lactation periods. Then, we discovered PRO changed the physiology, intestinal barrier and metabolism both in the generations of F₀ and different developmental stages of F₁ (7 weeks and 30 weeks old, respectively). Maternal PRO exposure affected the growth phenotypes and the glucolipid metabolism related indicators and genes of mice, especially the male mice of F₁ generations. The changes in bile acids (BAs) metabolism demonstrated that PRO disordered glucolipid metabolism through enterohepatic circulation. Furthermore, PRO reduced mucus secretion in the gut and altered the composition of gut microbiota, leading more bacteria to disseminate in the gut and inflammatory responses both in F₀ and F₁ regenerations. And PRO-induced gut microbiota dysbiosis was tightly related to BAs metabolites. Together, the results indicated that PRO destructed the functional integrity of intestinal barrier and the inflammatory reaction was triggered. And then, the disorder of glucolipid metabolism was induced through the BAs enterohepatic circulation. This study indicated that the cross-generation effects of PRO could not be ignored.

Effects of maternal exposure to procymidone on hepatic metabolism in the offspring of mice

As an effective fungicide widely used in agricultural production, the excessive procymidone (PRO) residue has been detected in the environment and food. Our previous study demonstrated that PRO could destroy the intestinal barrier in mice and has a joint toxic effect. To explore the cross-generational impact of maternal exposure, 10-week-old C57BL/6 female mice were orally administrated to 10 and 100 mg/kg body weight/day of PRO during pregnancy and lactation. The offspring obtained nutrients from the maternal through the placenta and breast milk, and PRO residues were detected in the liver, intestine, and feces of F1 generation. Fecal examination found that the residual PRO had been completely metabolized when the offspring mice grew to 35 days. The drug residue of F1 generation male mice was higher than that of female mice. We attributed this result to the difference in cytochrome P450 (CYP450) enzyme expression between male and female mice. The transcriptional levels of CYP1A1, CYP1A2, CYP2D9, and CYP3A4, and CYP450 protein expression levels, were higher in female mice. Furthermore, targeted MS of plasma revealed abnormal amino acid levels. In addition, PRO-induced hepatic metabolite changes in F0 and F1-7w mice. KEGG pathway analysis further showed that PRO jointly changed the amino acid biosynthesis pathway of the maternal and offspring. In summary, these results indicated that maternal exposure to PRO during a special period would interfere with self metabolism, and offspring will also have metabolic disorders.

Toxicity of procymidone to Bombyx mori based on physiological and transcriptomic analysis

Procymidone is widely used in vegetables and fruits because of its broad-spectrum and high efficiency. However, it is unclear whether procymidone can affect silkworm (Bombyx mori) growth and cocoon production. This study investigated the effects of procymidone on the growth and cocoon production of silkworms. We analyzed the growth, and cocoon quality of fifth instar larvae fed on mulberry leaves saturated with different concentrations (2.5, 5, and 10 mg/ml) of procymidone and the control. Results showed that procymidone supplementation decreased the larval growth and cocoon quality compared to the control group, suggesting that procymidone had toxicity to silkworms. Additionally, after transcriptomic analysis, we identified 396 significantly differentially expressed genes (DEGs) in the presence of procymidone. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) illustrated that these DEGs were closely related to metabolism. Taken together, these results confirmed that procymidone could cause toxicity by affecting metabolism in silkworm larvae. We believed that these results could provide important materials for the effect of procymidone on silkworms and gave us some clues for pesticides used in the mulberry garden.

The effect of chlorophyll on the enzyme-linked immunosorbent assay (ELISA) of procymidone in vegetables and the way to overcome the matrix interference

BACKGROUND

There is now an increasing demand for the immunoassay of procymidone residue in foodstuffs. However, the matrix interference could significantly affect the analysis. Till now there is no detailed information on the source of the interference and the mechanism involved, which greatly limits the real application of these techniques.

RESULTS

Significant matrix effect was observed in the enzyme-linked immunosorbent assay (ELISA) of procymidone in negative vegetable samples (leek, broccoli and cucumber). By the investigation with both vegetable extracts and standard solutions, the chlorophyll was confirmed as an important source of the matrix effect. Therefore, a new strategy was proposed for the pretreatment based on the exploitation of 5-sulfosalicylic acid. It was demonstrated to effectively eliminate chlorophyll and exhibited little effect on procymidone and the competitive indirect ELISA (ci-ELISA) performance. The established technique was validated with different vegetables. With the spiking concentration of procymidone investigated, the recovery rate of ci-ELISA was 71.52-120.37%, and the relative standard deviation was 4.05-17.61%.

CONCLUSION

Chlorophyll was for the first time illuminated as an important source of matrix interference to the immunoassay of procymidone in vegetables. A new pretreatment based on 5-sulfosalicylic acid was established to remove chlorophyll and therefore eliminate the matrix effect. Validated with different vegetable samples, the new technique was demonstrated much better efficiency in comparison to conventional methods, which indicated its promising application for the development of immunoassays of herb-origin samples. © 2021 Society of Chemical Industry.

Effects of low-concentration glyphosate and aminomethyl phosphonic acid on zebrafish embryo development

Glyphosate (GLY) is the most widely used broad-spectrum, non-selective herbicide in the world, whose main degradation product is aminomethyl phosphonic acid (AMPA). Because of long-term and large-scale use, residual GLY and AMPA in the environment pose great environmental and human health threats. The purpose of this study is to evaluate the effects and mechanism of residual low-concentrations of GLY and AMPA in the environment on the development of zebrafish embryos. Zebrafish embryos were exposed to 0, 1, 10, 100, and 700 ng·mL-1 GLY and AMPA for 72 h (from 2 to 74 h post-fertilization). With increasing exposure dose, heart rates of both embryos and larvae showed a rising trend and obvious arrhythmia appeared. Defects in cardiac development and function of zebrafish juveniles may be related to altered transcription levels of cardiac development genes (TBX5, NKX2.5, BMP4) and apoptosis genes (Bcl-2, Bax). In addition, pericardial edema and bone deformation of zebrafish embryos may be caused by inhibition of Na+/K+-ATPase and Ca2+-ATPase after exposure to GLY and AMPA. The present results demonstrated that at typical environmental residual concentrations of GLY and AMPA had similar developmental toxicity in zebrafish embryos.

Evaluation of fentanyl toxicity and metabolism using a zebrafish model

The increased abuse of novel drugs has created a critical need for cheap and rapid in vivo models to understand whole organism drug-induced toxicity and metabolic impacts. One such model is zebrafish, which share many similarities to human. Assays have been developed for behavioral, toxicity, and metabolism elucidation following chemical exposure. The zebrafish model provides the advantage of assessing these parameters within a single study. Previous zebrafish studies have evaluated the behavioral effects of fentanyl, but not developmental toxicity and its relation to metabolism. In this study, we evaluate the effects of fentanyl on the development of wild-type (TL strain) zebrafish and its metabolism over 4 days. Fertilized eggs were exposed to six concentrations of fentanyl (0.01, 0.1, 1, 10, 50, and 100 μM) through embryo media incubated at 28-29°C. Observations included egg coagulation, somite formation, heartbeat, tail and yolk morphology, pericardial formation, and swim bladder inflation. The incubation media was analyzed for the presence of metabolites using a targeted metabolomics approach. Fentanyl concentration caused significant effects on survival and development, with notable defects to the tail, yolk, and pericardium at 50 and 100 μM. Despropionyl fentanyl (4-ANPP), β-hydroxy fentanyl, and norfentanyl were detected in zebrafish larvae. We present a single in vivo model to assess toxicity and metabolism of fentanyl exposure in a vertebrate model system. Our findings provide a foundation for further investigations into fentanyl's mechanism of action and translation to human drug exposure.

Developmental toxicity of procymidone to larval zebrafish based on physiological and transcriptomic analysis

As a broad-spectrum with low toxicity, procymidone (PCM), is widely used in agriculture and frequently observed in aquatic system, which may cause some impacts on aquatic organisms. Here, to determine the developmental toxicity of PCM, embryonic and larval zebrafish were exposed to PCM at 0, 1, 10, 100 μg/L in dehydrogenated natural water containing 0.01% acetone for 7 days. The results showed that high concentration of PCM could cause the pericardial edema and increase the heart rates in larval zebrafish, suggesting that PCM had developmental toxicity to zebrafish. We also observed that PCM exposure not only changed the physiological parameters including TBA, GLU and pyruvic acid, but also changed the transcriptional levels of glycolipid metabolism related genes. In addition, after transcriptomics analysis, a total of 1065 differentially expressed genes, including 456 up-regulated genes and 609 down-regulated genes, changed significantly in 100 μg/L PCM treated larval zebrafish. Interestingly, after GO (Gene Ontology) analysis, the different expression genes (DEGs) were mainly enriched to the three different biology processes including GABA-nervous, lipid Metabolism and response to drug. We also observed that the levels of GABA receptor related genes including gabrg2, gabbr1α, gabbr1 and gabra6α were inhibited by PCM exposure. Interestingly, the swimming distance of larval zebrafish had the tendency to decrease after PCM exposure, indicating that the nervous system was affected by PCM. Taken together, the results confirmed that the fungicide PCM could cause developmental toxicity by influencing the lipid metabolism and GABA mediated nervous system and behavior in larval zebrafish. We believed that the results could provide an important data for the influence of PCM on aquatic animals.

Toxicity effects of procymidone, iprodione and their metabolite of 3,5-dichloroaniline to zebrafish

Dicarboximide fungicides mainly including procymidone, iprodione, vinclozolin, and dimethachlon are often applied as protective fungicides, 3,5-dichloroaniline (3,5-DCA) is their common metabolite in plant and environment. In this study, the acute toxicity of procymidone, iprodione and their metabolite of 3,5-DCA toward zebrafish was evaluated by semi-static method. The enrichment and metabolism of procymidone and iprodione in zebrafish were also clarified. The results indicated that procymidone and iprodione exhibited moderately toxic to adult zebrafish with the LC₅₀ of 2.00 mg/L, 5.70 mg/L at 96 h. Both procymidone and iprodione could be metabolized to 3,5-DCA in zebrafish, which showed higher toxic to adult zebrafish with the LC₅₀ of 1.64 mg/L at 96 h. From the perspective of histomorphology, for all treatment groups, the brain of the zebrafish was significantly damaged, while the damage to gut and gills was lighter. For procymidone, the biological concentration factor (BCF_8d) were 236 and 246 at the exposure concentration of 0.2 mg/L and 0.04 mg/L, and the BCF_8d were 3.2 and 2.4 for iprodione at the exposure concentration of 0.5 mg/L and 0.1 mg/L. Therefore, the procymidone and iprodione were moderate-enriched and low-enriched in zebrafish, respectively.

Effects of chlorothalonil, prochloraz and the combination on intestinal barrier function and glucolipid metabolism in the liver of mice

Chlorothalonil (CHL) and procymidone (PRO) are fungicides that exhibit low toxicity and are widely used in many countries. And both fungicides are frequently detected in the food chain. However, the health risk posed by these fungicides is still unclear. Here, 8-week-old male C57BL/6 mice were orally treated with CHL (10, 50 mg/kg/day), PRO (20, 100 mg/kg/day) and CHL+PRO (5+10, 25+50 mg/kg/day) by dietary supplementation for 10 weeks. Hepatic pathological analysis showed that exposure to CHL, PRO and CHL+PRO could cause liver injury. The glucose, triglyceride (TG) levels and the related gene expression to glucolipid metabolism changed significantly. The significantly reduced acylcarnitine levels demonstrated that CHL, PRO and CHL+PRO exposure inhibited fatty acids (FAs) β-oxidation. In addition, CHL and PRO altered the structure of the gut microbiota and destroyed the integrity of the intestinal barrier function. In particular, AF12, Odoribacter, Prevotella and Lactobacillus were highly correlated with carnitine. The results showed that CHL, PRO and CHL+PRO exposure might inhibit FAs β-oxidation by decreasing cystic fibrosis transmembrane conductance regulator (CFTR)-mediated ion transport, indicating that these fungicides disturbed intestinal barrier function associated with glucolipid metabolism disorder. Here, the data also indicated that there was an additive effect between CHL and PRO in mice.

Network Pharmacology-Based Systematic Analysis of Molecular Mechanisms of Dingji Fumai Decoction for Ventricular Arrhythmia

Background

Dingji Fumai Decoction (DFD), a traditional herbal mixture, has been widely used to ventricular arrhythmia (VA) in clinical practice in China. However, research on the bioactive components and underlying mechanisms of DFD in VA is still scarce.

Methods

Components of DFD were collected from TCMSP, ETCM, and literature. The chemical structures of each component were obtained from PubChem. Next, SwissADME and SwissTargetPrediction were applied for compounds screening and targets prediction of DFD; meanwhile, targets of VA were collected from DrugBank and Online Mendelian Inheritance in Man (OMIM). Then, the H-C-T-D network and the protein-protein interaction (PPI) network were constructed based on the data obtained above. CytoNCA was utilized to filter hub genes and VarElect was used to analyze the relationship between genes and diseases. At last, Metascape was employed for systematic analysis on the potential targets of herbals against VA, and AutoDock was applied for molecular docking to verify the results.

Results

A total of 434 components were collected, 168 of which were qualified, and there were 28 shared targets between DFD and VA. Three function modules of DFD were found from the PPI network. Further systematic analysis of shared genes and function modules explained the potential mechanism of DFD in the treatment of VA; molecular docking has verified the interactions.

Conclusions

DFD could be employed for VA through mechanisms, including complex interactions between related components and targets, as predicted by network pharmacology and molecular docking. This work confirmed that DFD could apply to the treatment of VA and promoted the explanation of DFD for VA in the molecular mechanisms.

In silico and in vitro assessment of androgen receptor antagonists

There is a growing concern for male reproductive health as studies suggest that there is a sharp increase in prostate cancer and other fertility related problems. Apart from lifestyle, pollutants are also known to negatively affect the reproductive system. In addition to many other compounds that have been shown to alter androgen signaling, several environmental pollutants are known to disrupt androgen signaling via binding to androgen receptor (AR) or indirectly affecting the androgen synthesis. We analyzed here the molecular mechanism of the interaction between the human AR Ligand Binding Domain (hAR-LBD) and two environmental pollutants, linuron (a herbicide) and procymidone (a pesticide), and compared with the steroid agonist dihydrotestosterone (DHT) and well-known hAR antagonists bicalutamide and enzalutamide. Using molecular docking and dynamics simulations, we showed that the co-activator interaction site of the hAR-LBD is disrupted in different ways by different ligands. Binding free energies of the ligands were also ordered in increasing order as follows: linuron, procymidone, DHT, bicalutamide, and enzalutamide. These data were confirmed by in vitro assays. Reporter assay with MDA-kb2 cells showed that linuron, procymidone, bicalutamide and enzalutamide can inhibit androgen mediated activation of luciferase activity. Gene expression analysis further showed that these compounds can inhibit the expression of prostate specific antigen (PSA) and microseminoprotein beta (MSMB) in prostate cell line LNCaP. Comparative analysis showed that procymidone is more potent than linuron in inhibiting AR activity. Furthermore, procymidone at 10 μM dose showed equivalent and higher activity to AR inhibitor enzalutamide and bicalutamide respectively.

Comparison of developmental toxicity of different surface modified CdSe/ZnS QDs in zebrafish embryos

Quantum dots (QDs) are new types of nanomaterials. Few studies have focused on the effect of different surface modified QDs on embryonic development. Herein, we compared the in vivo toxicity of CdSe/ZnS QDs with carboxyl (-COOH) and amino (-NH₂) modification using zebrafish embryos. After exposure, the two CdSe/ZnS QDs decreased the survival rate, hatching rate, and embryo movement of zebrafish. Moreover, we found QDs attached to the embryo membrane before hatching and the eyes, yolk and heart after hatching. The attached amount of carboxyl QDs was more. Consistently, the Cd content in embryos and larvae was higher in carboxyl QD-treatment. We further observed that the two QDs caused zebrafish pericardial edema and cardiac dysfunction. In line with it, both carboxyl and amino QDs up-regulated the transcription levels of cardiac development-related genes, and the levels were higher in carboxyl QD-treated groups. Furthermore, the chelator of Cd²⁺ diethylene triamine pentacetate acid could partially rescued the developmental toxicity caused by the two types of QDs suggesting that both the nature of QDs and the release of Cd²⁺ contribute to the developmental toxicity. In conclusion, the two CdSe/ZnS QDs have developmental toxicity and affect the cardiac development, and the carboxyl QDs is more toxic possibly due to the higher affinity and more release to embryos and larvae. Our study provides new knowledge that the surface functional modification of QDs is critical on the development on aquatic species, which is beneficial to develop and applicate QDs more safely and environment-friendly.

Zebrafish (Danio rerio) as an excellent vertebrate model for the development, reproductive, cardiovascular, and neural and ocular development toxicity study of hazardous chemicals

In the past decades, the type of chemicals has gradually increased all over the world, and many of these chemicals may have a potentially toxic effect on human health. The zebrafish, as an excellent vertebrate model, is increasingly used for assessing chemical toxicity and safety. This review summarizes the efficacy of zebrafish as a model for the study of developmental toxicity, reproductive toxicity, cardiovascular toxicity, neurodevelopmental toxicity, and ocular developmental toxicity of hazardous chemicals, and the transgenic zebrafish as biosensors are used to detect the environmental pollutants.

A multi-omics approach reveals molecular mechanisms by which phthalates induce cardiac defects in zebrafish (Danio rerio)

The potential risks of phthalates affecting human and animal health as well as the environment are emerging as serious concerns worldwide. However, the mechanism by which phthalates induce developmental effects is under debate. Herein, we found that embryonic exposure of zebrafish to di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) increased the rate of heart defects including abnormal heart rate and pericardial edema. Changes in the transcriptional profile demonstrated that genes involved in the development of the heart, such as tbx5b, nppa, ctnt, my17, cmlc1, were significantly altered by DEHP and DBP at 50 μg/L, which agreed with the abnormal cardiac outcomes. Methylated DNA immunoprecipitation sequencing (MeDIP-Seq) further showed that significant hypomethylation of nppa and ctnt was identified after DEHP and DBP exposure, which was consistent with the up-regulation of these genes. Notably, hypermethylation on the promoter region (<1 kb) of tbx5b was found after DEHP and DBP exposure, which might be responsible for its decrease in transcription. In conclusion, phthalates have the potential to induce cardiac birth defects, which might be associated with the transcriptional regulation of the involved developmental factors such as tbx5b. These findings would contribute to understand the molecular pathways that mediated the cardiac defects caused by phthalates.

Exposure to the AhR agonist cyprodinil impacts the cardiac development and function of zebrafish larvae

Cyprodinil is a broad-spectrum pyrimidine amine fungicide that has been reportedly used worldwide. However, toxicity studies of cyprodinil on aquatic organisms, specifically zebrafish (Danio rerio), are lacking. In our present study, we predicted cyprodinil binding to the aryl hydrocarbon receptor (AhR) by using molecular docking simulation. Then, we used recombinant HepG2 cells and Tg(cyp1a1-12DRE:egfp) transgenic zebrafish to further assess the AhR agonistic activity of cyprodinil. Besides, the significant upregulation of cyp1a1 further verified that statement. Moreover, we found that zebrafish exposure to cyprodinil induced developmental toxicity in the larvae, particularly during cardiac development. The expression levels of cardiac development-related genes, namely tbx5, nkx2.5, gata4, and tnnt2, were markedly altered, which might cause the adverse effects of cyprodinil on cardiac function and development. In summary, we found that cyprodinil, as an AhR agonist, induced development toxicity in zebrafish larvae, especially on cardiac. Data here can assess the potential effects on organisms in the aquatic environment and promote the regulation and safe use of cyprodinil.

Teratogenic effects of environmentally relevant concentrations of phenanthrene on the early development of marine medaka (Oryzia melastigma)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in marine environments and have arouse great concern since they pose adverse effects to marine ecosystem. To determine the potential impacts of environmentally relevant PAHs on early life stages of marine fish, this study exposed embryos of marine medaka (Oryzias melastigma) to 0, 2, 10, 50, and 250 μg/L of phenanthrene (Phe), one of the most abundant PAHs. The results demonstrated that Phe exposure decreased hatching rates, delayed hatching time of embryos, and increased deformity rate of newly-hatched larvae. Exposure to 10 and 50 μg/L Phe decreased the survival rate of marine medaka larvae at 28 days post-fertilization (dpf), and no embryo successfully hatched in 250 μg/L Phe exposure group. Morphology results showed that 10, 50, and 250 μg/L Phe exposure significantly retarded the development of embryos, and 2, 10, and 50 μg/L caused yolk sac edema and pericardial edema in newly-hatched larvae, indicating that low concentrations of Phe could induce developmental cardiac toxicity. Furthermore, the changes in the expression of heart development-related genes were determined, and the results showed that Phe-induced cardiac malformation might be related with fgf8, bmp4, smyd1, ATPase and gata4 genes. Overall, environmentally relevant PAHs could disrupt heart morphogenesis and hatching process of marine medaka, which might have profound consequences for sustainability of fish population.

Evaluation of the spinal effects of phthalates in a zebrafish embryo assay

Phthalates (phthalate esters, PAEs) are commonly used as plasticizers and are emerging concerns worldwide for their potential influence on the environment and general public health. Thus, identification of the negative effects and involved mechanisms of PAEs is necessary. Herein, we found that embryonic exposure of zebrafish to di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) significantly induced spinal defects, such as inhibited spontaneous movement at 24 h post-fertilization (hpf), spine curvature and body length decrease at 96 hpf. The transcriptional level of the genes that are related to the development of the notochord (col8a1a and ngs), muscle (stac3, klhl41a and smyd2b) and skeleton (bmp2, spp1) were significantly altered by DEHP and DBP at 50 and 250 μg/L, which might be associated with the observed morphological changes. Notably, DBP and DEHP altered the locomotor activity of zebrafish larvae at 144 hpf, which might be due to the abnormal development of the spine and skeletal system. In conclusion, phthalates caused spinal birth defects in zebrafish embryos, induced transcriptional alterations of the spinal developmental genes, and led to abnormal behavior.

Aryl hydrocarbon receptor is required for immune response in Epinephelus coioides and Danio rerio infected by Pseudomonas plecoglossicida

Aryl hydrocarbon receptor (AhR), a ligand-dependent transcriptional factor that responds to environmental chemicals, has been recently found to be closely associated with immune response in mammals. Pseudomonas plecoglossicida (P. plecoglossicida) is a temperature-dependent bacterial pathogen of visceral white spot disease in fish. Using dual RNA-seq, we previously evaluated the expression levels of ahr1a, ahr1b, ahr2 and cyp1a in the spleen of Epinephelus coioides at different time points after infection with P. plecoglossicida. In the present study, the expression levels of ahr1a, ahr1b, ahr2 and cyp1a in different organs of E. coioides and Danio rerio showed similar trends after being infected by P. plecoglossicida. It also was noted that liver, intestine, spleen, and heart were the most obviously affected organs, and ahr2 particularly showed a dramatically increase in the spleen. Subsequently, macrophages of E. coioides were isolated, and then infected by P. plecoglossicida, followed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay, which revealed that the expression level of ahr1a in macrophages was significantly down-regulated, while expression levels of ahr1b, ahr2 and cyp1a were noticeably up-regulated. Eventually, it was noted that ahr1b and ahr2 were knocked-down in macrophages, and intracellular survival rate and immune escape rate of P. plecoglossicida were markedly improved. Taken together, ahr1a, ahr1b, ahr2 and cyp1a participate in the immune response to P. plecoglossicida in different organs of fish, while ahr1b and ahr2 may play pivotal roles in the immune response of spleen and macrophages.

Exposure to low-level metalaxyl impacts the cardiac development and function of zebrafish embryos

Metalaxyl is an anilide pesticide that is widely used to control plant diseases caused by Peronosporales species. In order to study the toxic effects, zebrafish embryos were exposed to metalaxyl at nominal concentrations of 5, 50 and 500 ng/L for 72 hr, and the cardiac development and functioning of larvae were observed. The results showed that metalaxyl exposure resulted in increased rates of pericardial edema, heart hemorrhage and cardiac malformation. The distance between the sinus venosus and bulbus arteriosus, stroke volume, cardiac output and heart rate were significantly increased in larvae exposed to 50 and 500 ng/L metalaxyl compared to solvent control larvae. Significant upregulation in the transcription of tbx5, gata4 and myh6 was observed in the 50 and 500 ng/L treatments, and that of nkx2.5 and myl7 was observed in the 5, 50 and 500 ng/L groups. These disturbances may be related to cardiac developmental and functional defects in the larvae. The activity of Na⁺/K⁺-ATPase and Ca²⁺-ATPase was significantly increased in zebrafish embryos exposed to 500 ng/L metalaxyl, and the mRNA levels of genes related to ATPase (atp2a11, atp1b2b, and atp1a3b) (in the 50 and 500 ng/L groups) and calcium channels (cacna1ab) (in the 500 ng/L group) were significantly downregulated; these changes might be associated with heart arrhythmia and functional failure.