Miaomiao Teng

Enantioselective bioaccumulation of hexaconazole and its toxic effects in adult zebrafish (Danio rerio).

Little is known about the bioaccumulation and toxicity of hexaconazole (HEX) in spite of the fact that they are indispensable parts for a comprehensive assessment of its environmental behavior and toxic effects in organisms of freshwater ecosystems. In this study, adult zebrafish were used to study the enantioselective bioaccumulation of HEX and its effect endpoints in liver, including oxidative stress and the regulation of apoptosis-related gene expression. Significant enantioselective bioaccumulation was demonstrated when exposed to HEX of 100 and 200 μg L(-)(1), finding that the (-)-enantiomer tended to accumulate in zebrafish more easily than (+)-enantiomer. Activities of antioxidant enzymes (SOD, CAT and GPx) and GSH content were all significantly decreased when zebrafish were exposed to 50 and 200 μg L(-1) HEX for 21 d. A series of genes of the apoptosis pathway were examined in groups treated with 50 and 200 μg L(-)(1) HEX for 21 d using real-time PCR. Significant up-regulation of p53, Puma, Apaf-1, caspase-3 and caspase-9 expression and down-regulation of Bcl-2/Bax expression ratio were proved. The overall results indicated that waterborne HEX was able to produce oxidative stress and induce apoptosis through the involvement of caspases in adult zebrafish. The above information will play a vital role in the integrated environmental risk assessment of HEX and make its toxic mechanism in fish clear.

Effects of the bioconcentration and parental transfer of environmentally relevant concentrations of difenoconazole on endocrine disruption in zebrafish (Danio rerio)

Difenoconazole, a typical triazole fungicide, inhibits lanosterol-14R-demethylase (CYP51) to prevent fungal sterol synthesis and its residues are frequently detected in the environment due to its wide application. Previous studies have demonstrated that difenoconazole altered the triglyceride levels, and gene expression relevant to cholesterol biosynthesis in zebrafish. However, endocrine-disruption in the hypothalamus-pituitary-gonadal-liver (HPGL) axis, the effects of transferring to offspring, and the underlying mechanisms of difenoconazole in aquatic organisms are still unknown. In this study, we defined the effects of difenoconazole at environmental concentrations on endocrine disturbance using zebrafish as an experimental model. The results indicated that difenoconazole induced a significant change in the somatic index, and pathological variations in tissues, and steroid hormone levels. RT-PCR experiments further confirmed that difenoconazole significantly induced expression alteration of lhr, hsd3β, hsd11β, cyp19a in the ovary and star, cyp19a, cyp3c1 in the testis, and erα genes in livers. In addition, difenoconazole exposure in parental zebrafish affected the hatchability and length of its offspring. Moreover, the burdens of difenoconazole and difenoconazole alcohol in females were higher than in males. These findings highlighted that difenoconazole exposure at environmentally relevant concentrations elicited estrogenic endocrine-disruption effects via altering homeostasis of sex steroid hormones in the HPGL axis and the adverse effects can be transferred to the offspring.

Neonicotinoid insecticides imidacloprid, guadipyr, and cycloxaprid induce acute oxidative stress in Daphnia magna

Cycloxaprid (CYC) and guadipyr (GUA) are two new and promising neonicotinoid insecticides whose effects on Daphnia magna are as yet unknown. In this study, the acute toxicities of CYC and GUA to D. magna, including immobilization and embryo-hatching inhibition, and their effects on antioxidant enzymes and related gene expression were determined after a 48-h exposure. Imidacloprid (IMI) was evaluated at the same time as a reference agent. The 48-h EC50 values of IMI, GUA, and CYC for neonate immobilization were 13.0-16.5mg/L and for embryo hatching were 11.3-16.2mg/L. The specific activity of the enzymes superoxide dismutase (SOD) and catalase (CAT) were interfered by IMI, but not by GUA and CYC, while the activity of acetylcholinesterase (AChE) was significantly increased by IMI, but inhibited by GUA and CYC. The relative expressions of the Sod-Cu/Zn, Sod-Mn, Cat, and Ache genes were usually inhibited by IMI, GUA, and CYC, except for Cat by CYC, Ache by GUA, and Sods by IMI. For vitellogenin genes with a SOD-like domain (Vtg1/2-sod), relative expression was increased by IMI and inhibited by GUA and CYC, indicating that IMI, GUA, and CYC have potential toxicity toward reproduction. CYC and GUA are highly active against IMI-resistant pests, and considering the similar toxicity of IMI to D. magna, CYC and GUA are suitable for use in future integrated pest management systems.

Sex-specific effects of difenoconazole on the growth hormone endocrine axis in adult zebrafish (Danio rerio)

Difenoconazole, as one of the most widely used triazole fungicides, is applied to protect crops, fruits, and vegetables. It has been reported that difenoconazole can enter the environment and impair aquatic organisms, but whether difenoconazole can disrupt the growth hormone (GH) balance in adult zebrafish (Danio rerio) is still unclear. In this study, adult female and male zebrafish were exposed to difenoconazole (0, 5, 50, and 500µg/L) for seven days. The results revealed that the bioaccumulation of difenoconazole and its primary metabolite difenoconazole alcohol in females were both larger than that in males. In females, the growth of the liver and ovary were inhibited, which may be due to the decreased transcription of the key genes igf1a, igf2a, and igf2b in both organs. Male fish growth was promoted in response to the increased expression of genes relevant to the GH/insulin-like growth factor axis (GH/IGF) axis in the brain, liver, and testis as well as increased GH levels. It was found that difenoconazole interfered with the growth endocrine system and sex-specifically altered the expression of GH/IGF axis related genes in adult zebrafish after a short-term exposure.

Developmental toxicity, oxidative stress and immunotoxicity induced by three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) in zebrafish embryos

Strobilurins is the most widely used class of fungicides, but is reported highly toxic to some aquatic organisms. In this study, zebrafish embryos were exposed to a range concentrations of three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) for 96 h post-fertilization (hpf) to assess their aquatic toxicity. The 96-h LC50 values of pyraclostrobin, trifloxystrobin and picoxystrobin to embryos were 61, 55, 86 μg/L, respectively. A series of symptoms were observed in developmental embryos during acute exposure, including decreased heartbeat, hatching inhibition, growth regression, and morphological deformities. Moreover, the three fungicides induced oxidative stress in embryos through increasing reactive oxygen species (ROS) and malonaldehyde (MDA) contents, inhibiting superoxide dismutase (SOD) activity and glutathione (GSH) content as well as differently changing catalase (CAT) activity and mRNA levels of genes related to antioxidant system (Mn-sod, Cu/Zn-sod, Cat, Nrf2, Ucp2 and Bcl2). In addition, exposure to the three strobilurins resulted in significant upregulation of IFN and CC-chem as well as differently changed expressions of TNFa, IL-1b, C1C and IL-8, which related to the innate immune system, suggesting that these fungicides caused immunotoxicity during zebrafish embryo development. The different response of enzymes and genes in embryos exposed to the three fungicides might be the cause that leads to the difference of their toxicity. This work made a comparison of the toxicity of three strobilurins to zebrafish embryos on multi-levels and would provide a better understanding of the toxic effects of strobilurins on aquatic organisms.

Metabolomics and transcriptomics reveal the toxicity of difenoconazole to the early life stages of zebrafish ( Danio rerio )

Difenoconazole is widely used to inhibit the growth of fungi, but its residue in the water environment may threaten ecosystem and human health. Here, 1H nuclear magnetic resonance (NMR) and LC-MS/MS based metabolomics and transcriptomics approaches were used to assess the response of zebrafish to difenoconazole exposure. Early life stages of zebrafish were exposed to difenoconazole at environmentally relevant concentrations for 168h. Their comparison with the control group suggested an adverse development and disturbance of steroid hormones and VTG. KEGG pathway analysis identified five biological processes on the basis of differentially expressed genes (DEGs), as well as altered metabolites and amino acids in zebrafish following difenoconazole exposure. These affected processes included energy metabolism, amino acids metabolism, lipid metabolism, nucleotide metabolism, and an immune-related pathway. Collectively, these results bring us closer to an incremental understanding of the toxic effects of difenoconazole on zebrafish in its early development, and lend support to the continued use of the early life stages of zebrafish as a classical model to evaluate underlying environmental risks of xenobiotics in aquatic organisms.

Neonatal triphenyl phosphate and its metabolite diphenyl phosphate exposure induce sex- and dose-dependent metabolic disruptions in adult mice

The widespread application of organophosphorous flame retardants (OPFRs) has led to considerable human exposure, with major concerns regarding their health risks. Herein, we investigate the effects of triphenyl phosphate (TPP), one of the most widely used OPFRs, and one of its main metabolite diphenyl phosphate (DPP) on the endocrine systems and metabolic profiles after neonatal exposure from postnatal days 1-10 at two dosages (2 and 200 μg per day). Both TPP and DPP had no negative effect on uterine weight, glucose tolerance, and estradiol. 1H-NMR-based metabolomics revealed a sex-specific metabolic disturbance of TPP. Specifically, low dose of TPP altered the metabolic profiles of male mice while exerting no significant effects on female ones. Furthermore, a dose-dependent effect of TPP in male mice was observed, where a low toxicity dose up-regulated lipid-related metabolites, while a high toxicity dose down-regulated the pyruvate metabolism and TCA cycles. These results highlight the importance of carefully assessing the health impact of TPP on infants.

Acute exposure of zebrafish embryo (Danio rerio) to flutolanil reveals its developmental mechanism of toxicity via disrupting the thyroid system and metabolism

Flutolanil, an amide fungicide, had been detected frequently in aquatic environments; it is thus potentially a great risk to aquatic organisms and human health. Therefore, we investigated the developmental toxicity and the potential mechanism of thyroid endocrine disruption induced by flutolanil based on 1H NMR metabolomics analysis using a zebrafish model. Hatching of zebrafish embryo exposed to flutolanil was inhibited at 72 hpf (hour post-fertilization) and survival and body length at 96 hpf. In addition, increased teratogenic effects on embryos were observed, including pericardial edema, spine deformation, and tail malformation. Furthermore, flutolanil induced slower heartbeat and larger pericardial area in the treated groups than control group. Transcription levels of TRH, TSHR, TPO, Dio1, TRα, and UGT1ab were significantly altered after flutolanil exposure. Metabolomics analysis further indicated that flutolanil induced alterations of energy, amino acids, nucleotide, lipids, and fatty acid metabolism. Our study also indicated that flutolanil exposure led to alterations of endogenous metabolites, which induced the thyroid endocrine disruption in zebrafish. Ultimately, embryonic developmental toxicity was caused by flutolanil.

Perinatal exposure to low-dose decabromodiphenyl ethane increased the risk of obesity in male mice offspring

Decabromodiphenyl Ethane (DBDPE), a kind of new brominated flame retardants (NBFRs) used to replace DecaBDE, has been frequently detected in the environment and human samples. In this study, we explored its toxic effects on male mouse offspring after perinatal exposure to DBDPE. During the perinatal period, pregnant ICR mice were exposed to DBDPE (100 μg/kg body weight) via oral gavage. After weaning, male offspring were fed on a low-fat diet and a high-fat diet, respectively. We measured and recorded body weight, liver weight, and epididymis fat mass, blood biochemical markers, metabolites changes in liver, and gene expression involved in lipid and glucose homeostasis. The results showed that perinatal exposure to DBDPE increased the risk of obesity in mouse offspring and affected triglyceride synthesis, bile secretion, purine synthesis, mitochondrial function and glucose metabolism, furthermore, the use of HFD feeding may further exacerbate these effects. All of these results show that early-life exposure to low doses of DBDPE can promote the development of metabolic dysfunction, which in turn induces obesity.

Toxicity and metabolomics study of isocarbophos in adult zebrafish (Danio rerio)

Although isocarbophos is a widely used insecticide, its toxicity to aquatic organisms has not been well characterized. In this study, zebrafish were exposed to isocarbophos at concentrations of 50 µg L-1 and 200 µg L-1 to assess its bioaccumulation, metabolic disruption, and oxidative stress. Metabolomics analysis based on 1H NMR spectroscopy showed that 50 µg L-1 and 200 µg L-1 isocarbophos exposure induced increases in leucine, isoleucine, valine, and alanine compared to levels in the control. Lactate, creatine, and taurine were reduced in the 50 µg L-1 isocarbophos exposure group, and only lactate decreased in response to 200 µg L-1 isocarbophos. After zebrafish were exposed to 50 and 200 µg L-1 isocarbophos for 28 days, the activities of antioxidant enzymes (SOD, CAT, and GPx) and GSH contents decreased significantly in the liver. This result indicates that there was significant oxidative stress in the liver. Furthermore, changes in metabolite profiles significantly covaried with changes in several oxidative stress endpoints based on partial least squares regression. These results will contribute to the environmental risk assessment of isocarbophos and clarify the mechanism underlying its toxicity in zebrafish.