Molecular mechanisms of developmental toxicities of azoxystrobin and pyraclostrobin toward zebrafish (Danio rerio) embryos: Visualization of abnormal development using two transgenic lines

Induction of oxidative stress and cardiac developmental toxicity in zebrafish embryos by arsenate at environmentally relevant concentrations

The contamination of water by arsenic (As) has emerged as a significant environmental concern due to its well-documented toxicity. Environmentally relevant concentrations of As have been reported to pose a considerable threat to fish. However, previous studies mainly focused on the impacts of As at environmentally relevant concentrations on adult fish, and limited information is available regarding its impacts on fish at early life stage. In this study, zebrafish embryos were employed to evaluate the environmental risks following exposure to different concentrations (0, 25, 50, 75 and 150 μg/L) of pentavalent arsenate (AsV) for 120 hours post fertilization. Our findings indicated that concentrations ≤ 150 μg/L AsV did not exert significant effects on survival or aberration; however, it conspicuously inhibited heart rate of zebrafish larvae. Furthermore, exposure to AsV significantly disrupted mRNA transcription of genes associated with cardiac development, and elongated the distance between the sinus venosus and bulbus arteriosus at 75 μg/L and 150 μg/L treatments. Additionally, AsV exposure enhanced superoxide dismutase (SOD) activity at 50, 75 and 150 μg/L treatments, and increased mRNA transcriptional levels of Cu/ZnSOD and MnSOD at 75 and 150 μg/L treatments. Concurrently, AsV suppressed metallothionein1 (MT1) and MT2 mRNA transcriptions while elevating heat shock protein70 mRNA transcription levels in zebrafish larvae resulting in elevated malondialdehyde (MDA) levels. These findings provide novel insights into the toxic effects exerted by low concentrations of AsV on fish at early life stage, thereby contributing to an exploration into the environmental risks associated with environmentally relevant concentrations.

Network analysis of toxic endpoints of fungicides in zebrafish

Zebrafish being the best animal model to study, every attempt has been made to decipher the toxic mechanism of every fungicide of usage and interest. It is important to understand the multiple targets of a toxicant to estimate the toxic potential in its totality. A total of 22 fungicides of different classes like amisulbrom, azoxystrobin, carbendazim, carboxin, chlorothalonil, difenoconazole, etridiazole, flusilazole, fluxapyroxad, hexaconazole, kresoxim methyl, mancozeb, myclobutanil, prochloraz, propiconazole, propineb, pyraclostrobin, tebuconazole, thiophanate-methyl, thiram, trifloxystrobin and ziram were reviewed and analyzed for their multiple explored targets in zebrafish. Toxic end points in zebrafish are highly informative when it comes to network analysis. They provide a window into the molecular and cellular pathways that are affected by a certain toxin. This can then be used to gain insights into the underlying mechanisms of toxicity and to draw conclusions on the potential of a particular compound to induce toxicity. This knowledge can then be used to inform decisions about drug development, environmental regulation, and other areas of research. In addition, the use of zebrafish toxic end points can also be used to better understand the effects of environmental pollutants on ecosystems. By understanding the pathways affected by a given toxin, researchers can determine how pollutants may interact with the environment and how this could lead to health or environmental impacts.

Stereo-selective cardiac toxicity induced by metconazole via oxidative stress and the wnt/β-catenin signaling pathway in zebrafish embryos

Metconazole (MEZ), a chiral triazole fungicide, produces enantioselective adverse effects in non-target organisms. Among MEZ's isomers, cis-MEZ displays robust antimicrobial properties. Evaluating MEZ and cis-MEZ's toxicity may mitigate fungicide usage and safeguard non-target organisms. Our study evaluated the toxicity of MEZ and its cis-isomers at concentrations of 0.02, 0.2, 2, and 4 mg L-1. We report stereoselectivity and severe cardiovascular defects in zebrafish, including pericardial oedema, decreased heart rate, increased sinus venous and bulbous arteries distances, intersegmental vessel defects, and altered cardiovascular development genes (hand2, gata4, nkx2.5, tbx5, vmhc, amhc, dll4, vegfaa, and vegfc). Further, MEZ significantly increased oxidative stress and apoptosis in zebrafish, primarily in the cardiac region. Isoquercetin, an antioxidant found in plants, partially mitigates MEZ-induced cardiac defects. Furthermore, MEZ upregulated the Wnt/β-catenin pathway genes (wnt3, β-catenin, axin2, and gsk-3β) and β-catenin protein expression. Inhibitor of Wnt Response-1 (IWR-1) rescued MEZ-induced cardiotoxicity. Our findings highlight oxidative stress, altered cardiovascular development genes, and upregulated Wnt/β-catenin signaling as contributors to cardiovascular toxicity in response to MEZ and cis-MEZ treatments. Importantly, 1R,5S-MEZ exhibited greater cardiotoxicity than 1S,5R-MEZ. Thus, our study provides a comprehensive understanding of cis-MEZ's cardiovascular toxicity in aquatic life.

Biodegradation of the strobilurin fungicide pyraclostrobin by Burkholderia sp. Pyr-1: Characteristics, degradation pathway, water remediation, and toxicity assessment

Pyraclostrobin, a widely used fungicide, poses significant risks to both the environment and human health. However, research on the microbial degradation process of pyraclostrobin was scarce. Here, a pyraclostrobin-degrading strain, identified as Burkholderia sp. Pyr-1, was isolated from activated sludge. Pyraclostrobin was efficiently degraded by strain Pyr-1, and completely eliminated within 6 d in the presence of glucose. Additionally, pyraclostrobin degradation was significantly enhanced by the addition of divalent metal cations (Mn2+ and Cu2+). The degradation pathway involving ether bond and N-O bond cleavage was proposed by metabolite identification. The sodium alginate-immobilized strain Pyr-1 had a higher pyraclostrobin removal rate from contaminated lake water than the free cells. Moreover, the toxicity evaluation demonstrated that the metabolite 1-(4-chlorophenyl)-1H-pyrazol-3-ol significantly more effectively inhibited Chlorella ellipsoidea than pyraclostrobin, while its degradation products by strain Pyr-1 alleviated the growth inhibition of C. ellipsoidea, which confirmed that the low-toxic metabolites were generated from pyraclostrobin by strain Pyr-1. The study provides a potential strain Pyr-1 for the bioremediation in pyraclostrobin-contaminated aquatic environments.

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.

Interaction mechanism of a pesticide, Azoxystrobin with bovine serum albumin: Assessments through fluorescence, UV-Vis absorption, electrochemical and molecular docking simulation techniques

The current study's objective was to investigate how an antifungal pesticide Azoxystrobin (AZO) interacts with bovine serum albumin (BSA) under conditions that simulate a physiological medium (pH 7.4). This investigation was carried out using various experimental (UV-Vis absorption, steady-state fluorescence and 3-D fluorescence spectroscopies, and electrochemical) and theoretical (molecular docking and molecular dynamics simulations) methods. The fluorescence quenching data demonstrated that AZO caused fluorescence quenching in BSA, and this quenching process was attributed to the static quenching mechanism. By examining the fluorescence quenching of BSA at three different temperatures, it was determined that the binding constants for the AZO-BSA complexes were approximately 104 M-1 in magnitude, while the same magnitude of the binding constant was found by the electrochemical method. This indicates that the interaction between AZO and BSA was of moderate strength. This was further validated by the changes observed in the UV-Vis spectrum of BSA following the addition of AZO. The thermodynamic information, including ΔH and ΔS, revealed that the interaction forces primarily involved van der Waals forces as well as hydrogen bonds. The negative Gibbs free energy indicated that the reaction is spontaneous. In the theoretical investigation, the comparison highlights a remarkable consistency in how AZO interacts with the BSA active site over various time points. Hydrogen bonding and hydrophobic interactions consistently play a role in ensuring the stable and specific binding of the ligand. Moreover, the 3-D fluorescence spectral findings revealed alterations in the surrounding microenvironment of protein fluorophores when AZO binds. Upon analyzing the electrochemical data, it was observed that there was a consistent decrease in the peak currents of AZO when BSA was added to solutions containing AZO. The primary cause of this decrease in the peak currents was the reduction in the equilibrium concentration of AZO due to the addition of BSA. Furthermore, the formation of a non-electroactive complex between BSA and AZO, which impedes electron transport between AZO and the working electrode, accounts for these decreases. As a result, it can be said that the understanding of how AZO binds to BSA offers valuable insights that can be applied in the food, human health, and environment sectors.

Impacts of pyraclostrobin on intestinal health and the intestinal microbiota in common carp (Cyprinus carpio L.)

Pyraclostrobin (PYR) is a strobilurin fungicide that is commonly used in agriculture, and its use in agriculture may lead to an increase in its residue in the aquatic environment and may have a deleterious influence on the intestinal health of aquatic creatures. Here, common carp were chronically exposed to PYR (0, 0.5, or 5.0 μg/L) for 30 d to determine its effect on the physical and immunological barrier and intestinal microbiota in the intestine. PYR exposure caused significant histological changes; altered the mRNA expression levels of occludin, claudin-2, and zonula occludens-1 (ZO-1); induced oxidative stress in the common carp intestine; and increased the serum D-lactate and diamine oxidase (DAO) levels. Moreover, PYR significantly increased the protein expression levels of tumour necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and IL-6 while decreasing the level of transforming growth factor beta (TGF-β). Further studies revealed that PYR significantly reduced lysozyme (LZM) and acid phosphatase (ACP) activities as well as complement 3 (C3) and immunoglobulin M (IgM) levels. Furthermore, PYR decreased gut microbial diversity while increasing the abundance of pathogenic bacteria such as Aeromonas and Shewanella, causing an intestinal microbial disturbances in common carp. These results imply that PYR has a negative impact on fish intestinal health and may pose serious health risks to fish by disrupting the intestinal microbiota, physical barrier, and immunological barrier in common carp.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

Single and joint toxicity of azoxystrobin and cyproconazole to Prochilodus lineatus: Bioconcentration and biochemical responses

Fungicides are widely used across the world to protect crops and their presence in freshwater systems is increasing. However, the evaluation of their potential impacts on non-target organisms is in the minority of studies related to pesticides. In the current research, the single and joint toxicity of azoxystrobin (AZX) and cyproconazole (CYP) was investigated in juvenile fish Prochilodus lineatus. In particular, we evaluated bioconcentration and biochemical responses following a short-term exposure to environmentally relevant concentrations of the fungicides (alone and in mixture). We also determined interactions between the biological responses when the two compounds were used in mixture. Our results demonstrate that AZX and CYP pose a risk to native freshwater fish by causing deleterious effects. Both compounds, alone and in mixture, bioaccumulated in P. lineatus and triggered neurotoxicity and changes in oxidative stress biomarkers in several organs. Moreover, muscle was a target tissue for these fungicides and a synergistic interaction was observed for the mixture. Due to the lack of studies in fish assessing the effects following exposure to AZX-CYP mixtures and considering a realistic exposure situation in agriculture-impacted water bodies, these findings provide new and relevant information for future studies.

Characterization of hepatotoxic effects induced by pyraclostrobin in human HepG2 cells and zebrafish larvae

Pyraclostrobin is a highly effective and broad-spectrum strobilurin fungicide. With the widespread use of pyraclostrobin to prevent and control crop diseases, its environmental pressure and potential safety risks to humans have attracted much attention. Herein, the toxicological risks of pyraclostrobin toward HepG2 cells and the mechanisms of intoxication in vitro were investigated. The liver toxicity of pyraclostrobin in zebrafish larvae was also evaluated. It was found that pyraclostrobin induced DNA damage and reactive oxygen species generation in HepG2 cells, indicating the potential genotoxicity of pyraclostrobin. The results of fluorescent staining experiments and the expression of cytochrome c, Bcl-2 and Bax demonstrated that pyraclostrobin induced mitochondrial dysfunction, resulting in cell apoptosis. Monodansylcadaverine staining and autophagy marker-related proteins LC3, p62, Beclin-1 protein expression showed that pyraclostrobin promoted cell autophagy. Furthermore, immunoblotting analysis suggested that pyraclostrobin induced autophagy accompanied with activation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/mTOR signaling pathway. Visualization of zebrafish liver and oil red staining indicated that pyraclostrobin could induce liver degeneration and liver steatosis in zebrafish. Collectively, these results help to better understand the hepatotoxicity of pyraclostrobin and provide a scientific basis for its safe applications and risk control.

Developmental toxicity of fipronil and its two metabolites towards zebrafish (Danio rerio) embryos

Fipronil (FIL) use is currently regulated in several countries due to its specific toxicity to bees. This study investigated the possible developmental toxicities as well as the acute toxicities of FIL, fipronil sulfide (FIL-SI), and fipronil sulfone (FIL-SO) to zebrafish (Danio rerio) embryos. At concentrations up to 5000 μg L-1, FIL- and FIL-SI-treated embryos exhibited significant mortality at 96 h postfertilization. Body length was significantly shortened with increasing concentrations in FIL- and FIL-SI-treated embryos. However, FIL-SO-treated embryos exhibited low mortality with high hatching rates. Body length was also significantly shortened in FIL-SO-treated embryos. Regarding the number of intersegmental vessels (ISVs), all chemical-treated embryos showed high ISV numbers with increasing concentrations of each chemical. FIL and FIL-SI induced abnormal heart formation with heart dysfunction in embryos, whereas FIL-SO did not induce any difference in heart development compared with the control. Abnormal heart formation may be related to the upregulation of nppa responsible for the expression of natriuretic peptides in embryos. Embryonic acetylcholinesterase activity was decreased gradually according to the increase in FIL and FIL-SI concentrations, whereas FIL-SO did not cause any change in enzyme activity. Il-1β responsible for the occurrence of injury or infection was highly upregulated in FIL-SI- and FIL-SO-treated embryos. Therefore, reduction to FIL-SI may be associated with FIL toxicity, whereas oxidation to FIL-SO may be a detoxification route in the environment.

An integrated approach for evaluating the interactive effects between azoxystrobin and ochratoxin A: Pathway-based in vivo analyses

Azoxystrobin (AZO) is a broad-spectrum strobilurin fungicide widely used in agriculture. However, its use increases the possibility of co-occurrence with mycotoxins such as ochratoxin A (OTA), which poses a significant risk to human health. Therefore, it is imperative to prioritize the evaluation of the combined toxicity of these two compounds. To assess the combined effects of AZO and OTA, the response genes and phenotypes for AZO or OTA exposure were obtained by utilizing Comparative Toxicogenomics Database, and Database for Annotation, Visualization and Integrated Discovery was used for GO and KEGG pathway enrichment analysis. In addition, we provided in-vivo evidence that AZO and OTA, in isolation and combination, could disrupt a variety of biological processes, such as oxidative stress, inflammatory response, apoptosis and thyroid hormone regulation under environmentally relevant concentrations. Notably, our findings suggest that the combined exposure group exhibited greater toxicity, as evidenced by the expression of various markers associated with the aforementioned biological processes, compared to the individual exposure group, which presents potential targets for the underlying mechanisms of induced toxicity. This study provides a novel methodological approach for exploring the mechanism of combined toxicity of a fungicide and a mycotoxin, which can shed light for conducting risk assessment of foodborne toxins.

Enantioselective effect of trifloxystrobin in early-stage zebrafish (Danio rerio) embryos: Cardiac abnormalities impacted by E,E-trifloxystrobin enantiomer

Trifloxystrobin (TFS) is one of the extensively used strobilurin fungicides, which is composed of four enantiomers and its active form is E,E-TFS. In this study, we assess the acute toxicity of four enantiomers, E,E-, E,Z-, Z,E-, and Z,Z-TFS in zebrafish (Danio rerio) embryos. Among the four enantiomers, only E,E-TFS was found to be acutely toxic, with an estimated LC₅₀ value of 0.68 mg/L. Treatment with E,E-TFS resulted in various phenotypic changes in the embryos, including pericardial and yolk-sac edema, spine curvature, and blood pooling. And it shortened the whole body length in the treated embryos by increasing the total intersegmental vessel numbers using a Tg(fli1a:EGFP) zebrafish line. Further study using Tg(cmlc2:EGFP) zebrafish line revealed that E,E-TFS treatment was associated with cardiac malformations, a failure of heart function, and a lowered heartbeat rate at the concentration of 0.25 mg/L. Also, the differential gene expression analysis identified significant down-regulation of vmhc and cacna1c genes encoding ventricular myosin heavy chain and calcium voltage-gated channel subunit alpha 1C, which are crucial for heart development. These results suggest the need for regular monitoring of E,E-TFS enantiomers after field application and further research into their potential chronic effects on environmental organisms.

Combined toxicity of 3,5,6-trichloro-2-pyridinol and 2-(bromomethyl)naphthalene in the early stages of zebrafish (Danio rerio) embryos: Abnormal heart development at lower concentrations via differential expression of heart forming-related genes

Combined toxicity can occur in the environment according to the combination of single substances, and the combination works additively or in a synergistic or antagonistic mode. In our study, 3,5,6-trichloro-2-pyridinol (TCP) and 2-(bromomethyl)naphthalene (2-BMN) were used to measure combined toxicity in zebrafish (Danio rerio) embryos. As the lethal concentration (LC) values were obtained through single toxicity, the lethal effects at all combinational concentrations were considered synergistic by the Independent Action model. At 96 hpf, the combined toxicity of TCP LC₁₀ + 2-BMN LC₁₀, the lowest combinational concentration, resulted in high mortality, strong inhibition of hatching, and various morphological changes in zebrafish embryos. Combined treatment resulted in the downregulation of cyp1a, leading to reduced detoxification of the treated chemicals in embryos. These combinations may enhance endocrine-disrupting properties via upregulation of vtg1 in embryos, and inflammatory responses and endoplasmic reticulum stress were found to upregulate il-β, atf4, and atf6. These combinations might induce severe abnormal cardiac development in embryos via downregulation of myl7, cacna1c, edn1, and vmhc expression, and upregulation of the nppa gene. Therefore, the combined toxicity of these two chemicals was observed in zebrafish embryos, which proves that similar substances can exhibit stronger combined toxicity than single toxicity.

Antimelanogenic Effects of Curcumin and Its Dimethoxy Derivatives: Mechanistic Investigation Using B16F10 Melanoma Cells and Zebrafish (Danio rerio) Embryos

Regulation of melanin production via the MC1R signaling pathway is a protective mechanism of the skin of living organisms against exposure to ultraviolet rays. The discovery of human skin-whitening agents has been one of the most intense pursuits of the cosmetic industry. The MC1R signaling pathway is activated by its agonist, alpha-melanocyte stimulating hormone (α-MSH), and mainly regulates melanogenesis. Here, we evaluated the antimelanogenic activities of curcumin (CUR) and its two derivatives, dimethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), in B16F10 mouse melanoma cells and zebrafish embryos. CUR and BDMC reduced the α-MSH-induced melanin production in B16F10 cells and also downregulated the expression of the melanin-production-related genes Tyr, Mitf, Trp-1, and Trp-2. Moreover, the biological activity of these two compounds against melanogenesis was confirmed in in vivo experiments using zebrafish embryos. However, the highest concentration of CUR (5 µM) resulted in slight malformations in zebrafish embryos, as indicated by acute toxicity tests. In contrast, DMC did not show any biological activity in vitro or in vivo. Conclusively, BDMC is a strong candidate as a skin-whitening agent.

Ferroptosis contributes to nickel-induced developmental neurotoxicity in zebrafish

Nickel (Ni) is a widely utilized heavy metal that can cause environmental pollution and health hazards. Its safety has attracted the attention of both the environmental ecology and public health fields. While the central nervous system (CNS) is one of the main targets of Ni, its neurotoxicity and the underlying mechanisms remain unclear. Here, by taking advantage of the zebrafish model for live imaging, genetic analysis and neurobehavioral studies, we reveal that the neurotoxic effects induced by exposure to environmentally relevant levels of Ni are closely related to ferroptosis, a newly-described form of iron-mediated cell death. In vivo two-photon imaging, neurobehavioral analysis and transcriptome sequencing consistently demonstrate that early neurodevelopment, neuroimmune function and vasculogenesis in zebrafish larvae are significantly affected by environmental Ni exposure. Importantly, exposure to various concentrations of Ni activates the ferroptosis pathway, as demonstrated by physiological/biochemical tests, as well as the expression of ferroptosis markers. Furthermore, pharmacological intervention of ferroptosis via deferoxamine (DFO), a classical iron chelating agent, strongly implicates iron dyshomeostasis and ferroptosis in these Ni-induced neurotoxic effects. Thus, this study elucidates the cellular and molecular mechanisms underlying Ni neurotoxicity, with implications for our understanding of the physiologically damaging effects of other environmental heavy metal pollutants.

Mechanism of bisphenol S exposure on color sensitivity of zebrafish larvae

Color vision, initiated from cone cells, is vitally essential for identifying environmental information in vertebrate. Although the retinotoxicity of bisphenol S (BPS) has been reported, data on the influence of BPS treatment on cone cells are scarce. In the present study, transgenic zebrafish (Danio rerio) labeling red and ultraviolet (UV) cones were exposed to BPS (0, 1, 10, and 100 μg/L) during the early stages of retinal development, to elucidate the mechanism underlying its retinal cone toxicity of BPS. The results showed that 10 and 100 μg/L BPS induced oxidative DNA damage, structural damage (decreased number of ribbon synapses), mosaic patterning disorder, and altered expression of genes involved in the phototransduction pathway in red and UV cones. Furthermore, BPS exposure also caused abnormal development of key neurons (retinal ganglion cells, optic nerve, and hypothalamus), responsible for transmitting the light-electrical signal to brain, and thereby resulted in inhibition of light-electrical signal transduction, finally diminishing the spectral sensitivity of zebrafish larvae to long- and short-type light signal at 5 day post fertilization. This study highlights the cone-toxicity of environmental relevant concentrations of BPS, and clarifies the mechanism of color vision impairment induced by BPS at the cellular level, updating the understanding of visual behavior driven by environmental factors.

Hepatopancreas toxicity and immunotoxicity of a fungicide, pyraclostrobin, on common carp

Pyraclostrobin (PYR), a strobilurin fungicide, has been widely used to control fungal diseases, posing potential risk to aquatic organisms. However, the toxic effects of PYR to fish remained largely unknown. In this study, common carp (Cyprinus carpio L.) was exposed to environmentally relevant levels of PYR (0, 0.5 and 5.0 μg/L) for 30 days to assess its chronic toxicity and potential toxicity mechanism. The results showed that long-term exposure to PYR induced hepatopancreas damage as evident by increased in serum transaminase activities (AST and ALT). Moreover, PYR exposure remarkably enhanced the expressions of hsp70 and hsp90, decreased the levels of antioxidant enzymes and biomarkers and promoted the reactive oxygen species (H₂O₂ and O₂^-) and MDA contents in carp hepatopancreas. PYR exposure also upregulated apoptosis-related genes (bax, apaf-1, caspase-3 and caspase-9) and reduced anti-apoptosis gene bcl-2 in fish hepatopancreas. Moreover, PYR exposure altered the expressions of inflammatory cytokines (IL-1β, IL-6, TNF-α and TGF-β) in the serum and hepatopancreas and the level of NF-κB p65 in the hepatopancreas. Further research indicated that PYR exposure markedly changed the levels of immune parameters (LYZ, C3, IgM, ACP and AKP) in the serum and/or hepatopancreas, indicating that chronic PYR exposure also has immunotoxicity on fish. Additionally, we found that PYR exposure upregulated p38 and jnk MAPK transcription levels, suggesting that MAPK may be play important role in PYR-induced apoptosis and inflammatory response in the hepatopancreas of common carp. In summary, PYR exposure induced oxidative stress, triggered apoptosis, inflammatory and immune response in common carp, which can help to elucidate the possible toxicity mechanism of PYR in fish.

Comprehensive study of the effects of strobilurin-based fungicide formulations on Enchytraeus albidus

Excessive application of fungicides in crop fields can cause adverse effects on soil organisms and consequently affect soil properties. Existing knowledge on the effects of strobilurin fungicides has been primarily based on toxicity tests with active ingredients, while the effects of fungicide formulations remain unclear. Therefore, this work aims to provide new data on the effects of three commercial formulations of strobilurin fungicides on the soil organism Enchytraeus albidus. The tested fungicide formulations were Retengo® (pyraclostrobin-PYR), Zato WG 50® (trifloxystrobin-TRI) and Stroby WG® (kresoxim-methyl-KM). In laboratory experiments, multiple endpoints were considered at different time points. The results showed that PYR had the greatest impact on survival and reproduction (LC₅₀ = 7.57 mg_a.i.kg_soil^-1, EC₅₀ = 0.98 mg_a.i.kg_soil^-1), followed by TRI (LC₅₀ = 72.98 mg_a.i.kg_soil^-1, EC₅₀ = 16.93 mg_a.i.kg_soil^-1) and KM (LC₅₀ = 73.12 mg_a.i.kg_soil^-1, EC₅₀ ≥ 30 mg_a.i.kg_soil^-1). After 7 days of exposure, MXR activity was inhibited at the highest concentration of all fungicides tested (6 mg_PYRkg_soil^-1, 15 mg_TRIkg_soil^-1 and 30 mg_KMkg_soil^-1). Furthermore, oxidative stress (induction of SOD, CAT and GST) and lipid peroxidation (increase in MDA) were also observed. In addition, there was a decrease in total available energy after exposure to PYR and KM. Exposure to fungicides resulted in a shift in the proportions of carbohydrates, lipids, and proteins affecting the amount of available energy. In addition to the initial findings on the effects of strobilurin formulations on enchytraeids, the observed results suggest that multiple and long-term exposure to strobilurin formulations in the field could have negative consequences on enchytraeid populations.

Titanium dioxide nanoparticles decreases bioconcentration of azoxystrobin in zebrafish larvae leading to the alleviation of cardiotoxicity

Interactions between titanium dioxide nanoparticles (n-TiO₂) and pollutants in the aquatic environment may alter the bioavailability of pollutants, and thus altering their toxicity and fate. In order to investigate the bioconcentration of azoxystrobin (AZ) and its mechanism of cardiotoxicity in the presence of n-TiO₂, the experiment was divided into control, n-TiO₂ (100 μg/L), AZ (40, 200 and 1000 μg/L) and AZ (40, 200, 1000 μg/L) + n-TiO₂ groups, and the zebrafish embryos were exposed to the exposure solution until 72 h post-fertilization. Results suggested the presence of n-TiO₂ notably reduced the accumulation of AZ in larvae compared with exposure to AZ alone, thereby significantly decreasing AZ-induced cardiotoxicity, including heart rate changes, pericardium edema, venous thrombosis, increased sinus venosus and bulbus arteriosus distance and changes in cardiac-related gene expression. Further studies showed that AZ + n-TiO₂ together restrained total-ATPase and Ca²⁺-ATPase activities, while the activity of Na⁺K⁺-ATPase increased at first and then decreased. Furthermore, there were significant changes in the expressions of oxidative phosphorylation and calcium channel-related genes, suggesting mitochondrial dysfunction may be the potential mechanism of cardiotoxicity induced by AZ and n-TiO₂. This study supplies a new perspective for the joint action of AZ and environmental coexisting pollutants and provides a basis for ecological risk management of pesticides.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

Antagonistic effects and mechanisms of carbendazim and chlorpyrifos on the neurobehavior of larval zebrafish

Residues from multiple pesticides are frequently detected on vegetables, which may produce combined toxicity not predicted by individual toxicity data. As these combined effects present additional dangers to food safety, we have compared individual to combined effects for a variety of pesticides. Carbendazim and chlorpyrifos are the two most commonly detected pesticides in vegetables, and previous studies reported that combined exposure results in synergistic developmental toxicity to zebrafish embryos. In this study, individual and combined effects on zebrafish motor activity were examined following individual and combined exposure to assess nervous system toxicity. Further, transcriptomics methods were used to identify potential molecular mechanisms for individual and combined toxicity. Carbendazim alone induced a disorganized swim pattern characterized by increased angular velocity, turn angle, meander, and acceleration during light-dark transition, while chlorpyrifos alone reduced average swim speed and light-dark acceleration. Combined treatment significantly reduced average swim velocity and total distance traveled. Combination indices indicated strong antagonism between compounds for average speed and light-dark acceleration. Transcriptomics (RNA-seq) showed that carbendazim significantly altered the expression of genes involved in antigen processing and presentation, apoptosis, autophagy, and metabolism, including ctslb, cyp7a1, hsp70l, and ugt1a1. Alternatively, chlorpyrifos significantly altered genes involved in various nervous system-related pathways, including glutamatergic, GABAergic, dopaminergic, and calcium signaling. Protein-protein interaction (PPI) network analysis suggested that chlorpyrifos significantly downregulated genes related to light transduction, resulting in decreased sensitivity to light-dark transitions, while antagonism mainly reflected divergent effects on phototransduction and retinol metabolism. Carbendazim had no significant effects on vision-related genes such as gnat1 and gngt1, while chlorpyrifos downregulated expression, an effect reversed by the combination. Comprehensive toxicity analyses must include joint effects of co-applied pesticides for enhanced food safety.

Dissipation and Residues of Pyraclostrobin in Rosa roxburghii and Soil under Filed Conditions

Rosa roxburghii has been widely planted in China. Powdery mildew is the most serious disease of R. roxburghii cultivation. Pyraclostrobin was widely used as a novel fungicide to control powdery mildew of R. roxburghii. To assess the safety of pyraclostrobin for use on R. roxburghii fruits, its residue rapid analysis as well as an investigation on its dissipation behaviors and terminal residues in R. roxburghii and soil under field conditions were carried out. The QuEChERS method was simplified using LC−MS/MS detection and combined with liquid−liquid extraction purification to allow determination of pyraclostrobin levels in R. roxburghii fruits and the soil. The fortified recoveries at 0.1~5.0 mg/kg were 93.48~102.48%, with the relative standard deviation of 0.64~3.21%. The limit of detection of the analytical method was 0.16 and 0.15 µg/kg for R. roxburghii fruit and soil, respectively. The effects of different spray equipment and formulations on the persistence of pyraclostrobin in R.roxburghii were as follows: gaston gasoline piggyback agricultural sprayer (5.38 d) > manual agricultural backpack sprayer (3.37 d) > knapsack multi-function electric sprayer (2.91 d), suspension concentrate (SC) (6.78 d) > wettable powder (WP) (5.64 d) > water dispersible granule (WG) (4.69 d). The degradation of pyraclostrobin followed the first-order kinetics and its half-lives in R.roxburghii and soil were 6.20~7.79 days and 3.86~5.95 days, respectively. The terminal residues of pyraclostrobin in R. roxburghii and soil were 0.169~1.236 mg/kg and 0.105~3.153 mg/kg, respectively. This study provides data for the establishment of the maximum residue limit (MRL) as well as the safe and rational use of pyraclostrobin in R. roxburghii production.