Chronic Toxic Effects of Flutolanil on the Liver of Zebrafish ( Danio rerio)

Chronic exposure to palm oil mill effluent induces oxidative stress and histopathological changes in zebrafish (Danio rerio)

Several studies have revealed that Palm Oil Mill Effluent (POME) adversely affects fish health systems in various ways. However, further studies on oxidative stress and histopathological changes in fish tissues exposed to POME are essential so that a more comprehensive and detailed understanding of its toxicity is attained. Subsequently, this study investigated oxidative stress indicators, including malondialdehyde (MDA) content and activities of antioxidant enzymes, as well as histological changes in zebrafish (Danio rerio) tissues after chronic exposure to POME. The results showed a significant increase in MDA content by up to 122 % in gills and 351 % in liver, while catalase (CAT) activity rose by 70 % in gills and 170 % in liver. Glutathione S-transferase (GST) activity was significantly reduced by 50 % in both tissues, while superoxide dismutase (SOD) activity increased by 162 % in the liver, yet showed no significant change in gills. Histological analysis revealed mild to severe alterations in gills (e.g., hyperplasia, hypertrophy, hemorrhage, and necrosis) and liver (e.g., hepatocyte shrinkage, congestion, hydropic degeneration, and necrosis) at higher POME concentrations and longer exposure durations. These findings suggest that oxidative stress markers and histopathological changes potentially serve as early warning indicators for: firstly, assessing POME contamination in aquatic environments; and secondly, evaluating the effectiveness of wastewater treatment systems.

Ecotoxicological impact of succinate dehydrogenase inhibitor (SDHI) fungicides on non-targeted organisms: a review

As the global population continues to grow, the use of pesticides to increase food production is projected to escalate. Pesticides are critical in plant protection, offering a powerful defense against fungal diseases such as apple scab, leaf spot, sclerotinia rot, damping off, sheath blight, and root rot, which threaten crops like cereals, corn, cotton, soybean, sugarcane, tuberous vegetables, and ornamentals. Succinate Dehydrogenase Inhibitor (SDHI) fungicides represent a novel class essential for controlling fungal pathogens and bolstering food security. However, the impact of SDHIs on non-target organisms, including freshwater and terrestrial invertebrates, crustaceans, and oligochaetes, remains insufficiently understood. Empirical studies indicate that SDHIs can induce mortality, mitochondrial dysfunction, oxidative stress, and developmental delays in non-target organims. Additionally, the environmental persistence of these compounds raises concerns about their potential for ecological disruption. The effects of SDHIs on pollinating species and the possible transgenerational transmission of harmful effects warrant further investigation. Comprehensive transcriptomic analyses are necessary to elucidate the molecular disturbances and adverse outcome pathways triggered by SDHIs. Furthermore, there are emerging concerns about the endocrine-disrupting potential of SDHIs in aquatic organisms. For the first time, this review aims to synthesize existing knowledge on the ecotoxicological impacts of SDHIs on non-target organisms and identify critical research directions to address the ecological challenges posed by their use.

Growth disorders, respiratory distress and skin discoloration in zebrafish (Danio rerio) after chronic exposure to Palm Oil Mill Effluent

Understanding the environmental and health impacts of Palm Oil Mill Effluent (POME) contamination is essential for driving sustainable practices and innovation within the industry. In this study, we elaborated the chronic toxicity of POME on growth disorder, respiratory distress, and skin discoloration of zebrafish (Danio rerio). Zebrafish were exposed to three concentrations of POME (0 mL/L, 0.5 mL/L and 1.0 mL/L) for 28 days. Results revealed that an increase in POME concentration significantly reduced the weight gain, length gain, specific growth rate, specific length rate and oxygen consumption rate of zebrafish. In contrast, the opercular rate increased significantly. Skin discoloration in zebrafish exposed to POME were characterized by reduced red percentage value on the body and tail, increased green and blue percentages on the tail, and decreased brightness values. This result suggests crucial insights for the management and regulation of POME.

Morphological Alterations and Oxidative Stress Induction in Danio rerio Liver After Short-Term Exposure to the Strobilurin Fungicide Dimoxystrobin

Unlike many other fungicides, strobilurins are applied several times during the growing season for prophylactic purposes, thus heightening the risk of environmental contamination. In the EU, the dimoxystrobin approval period lasted for 17 years. It has been classified as moderately toxic to birds and highly toxic to earthworms, and it is suspected to be carcinogenic to humans. However, it is still commercialized in several countries. The effects of dimoxystrobin are still largely underexplored, with only three studies reporting sublethal alterations in fish. Here, we evaluated for the first time the effects of dimoxystrobin on zebrafish liver after short-term exposure (96 h) to two sublethal and environmentally relevant concentrations (6.56 and 13.13 μg/L), providing evidence of morphological, functional, and ultrastructural modifications. We revealed severe alterations encompassing three reaction patterns: circulatory disturbance, regressive and progressive changes, which also showed a dose-dependent trend. Furthermore, we revealed that dimoxystrobin induced a significant increase in lipid content, a decrease in glycogen granules and affected the defensive response against oxidative stress through a significant downregulation of SOD and CAT. The information presented here demonstrates that the hazardous properties of dimoxystrobin may result from several pathological events involving multiple targets. Our results also emphasize the importance of the combined use of morphological, ultrastructural and functional investigation in ecotoxicological studies.

Assessing the effects of cadmium on antioxidant enzymes and histological structures in rainbow trout liver and kidney

Cadmium contamination in aquatic environments poses severe risks to aquatic organisms, particularly fish, where cadmium accumulation in tissues can lead to compromised organ functionality and reproductive issues. The present study aimed to assess the effects of cadmium (Cd) exposure on key biomarkers of oxidative stress, DNA damage, apoptosis, and enzyme activity in the liver and kidney tissues of rainbow trout (Oncorhynchus mykiss). Specifically, the study measured 8-hydroxy-2-deoxyguanosine (8-OHdG) levels, caspase-3 activation, acetylcholinesterase (AChE) activity, and oxidative stress indicators (ONOO-, MDA, GSH, SOD, and CAT) following exposure to three Cd concentrations (1, 3, and 5 mg/L) over three time points (24, 48, and 96 h). Tissue samples were collected post-exposure, and the analysis revealed a significant decrease in MDA levels in both tissues. GSH concentrations declined with prolonged exposure, while SOD activity increased, indicating a response to oxidative stress, contrasted by a reduction in CAT activity. An initial increase in ONOO- levels was observed at 24 h, followed by a subsequent decrease at the 48 and 96 h marks. These results suggest that cadmium induces oxidative stress in the liver and kidney tissues of fish. Cadmium exposure also significantly elevated 8-OHdG levels, signaling DNA damage, and increased caspase-3 activity, indicative of apoptosis, across all doses and time points (p < 0.05). The histological examination of liver and kidney showed tissue injury. Additionally, a negative correlation between AChE activity and exposure duration was noted, with prolonged exposure resulting in substantial AChE inhibition. Given the role of AChE in behavior regulation, these findings underscore the importance of exploring time-dependent, tissue-specific changes in AChE activity to further elucidate the mechanisms underlying cadmium-induced behavioral abnormalities.

Pyridaben inhibits cell cycle progression and delays early embryonic development in zebrafish (Danio rerio)

Pyridaben is a broad-spectrum, contact-killing acaricide that can be used to control a variety of harmful food and plant mites. Pyridaben displays cardiotoxicity and liver toxicity toward fish, but the effects on fish embryonic development have not been characterized. We exposed early zebrafish embryos to 20, 30, and 40 μg/L concentrations of pyridaben. The exposure caused developmental abnormalities, including delayed embryonic shield formation, yolk sac resorption, decreases in body length, reduced pigmentation, and delays in hatching. Pyridaben caused a significant increase in the transcription level of the endoderm marker foxa2, but the transcription levels of the ectoderm development marker foxb1a and the mesoderm development marker snaila were not significantly altered. The transcription levels of the genes SOX17 in early embryos were significantly reduced. After exposure to pyridaben, catalase (CAT) activity and glutathione (GSH) content were increased, and cyclin D1, that is involved in early embryonic development, was abnormally expressed. This study shows that pyridaben causes anomalous development in zebrafish embryos by interfering with the cell cycle order of early embryonic development and inducing excessive oxidative stress. Colivelin, an agonist of the STAT3 signaling pathway, acted as a salvage drug to restore the cell cycle order during embryonic development following exposure to pyridaben. Thus, the toxic effects may be caused by pyridaben's regulation of the STAT3 signaling pathway.

Permethrin exposure impacts zebrafish lipid metabolism via the KRAS-PPAR-GLUT signaling pathway, which is mediated by oxidative stress

Permethrin (Per) is a widely used and frequently detected pyrethroid pesticide in agricultural products and the environment. It may pose potential toxicity to non-target organisms. Per has been reported to affect lipid homeostasis, although the mechanism is undefined. This study aims to explore the characteristic transcriptomic profiles and clarify the underlying signaling pathways of Per-induced lipid metabolism disorder in zebrafish liver. The results showed that environmental exposure to Per caused changes in the liver index, histopathology, and oxidative stress in zebrafish. Moreover, transcriptome results showed that Per heavily altered the pathways involved in metabolism, the immune system, and the endocrine system. We conducted a more in-depth analysis of the genes associated with lipid metabolism. Our findings revealed that exposure to Per led to a disruption in lipid metabolism by activating the KRAS-PPAR-GLUT signaling pathways through oxidative stress. The disruption of lipid homeostasis caused by exposure to Per may also contribute to obesity, hepatitis, and other diseases. The results may provide new insights for the risk of Permethrin to aquatic organisms and new horizons for the pathogenesis of hepatotoxicity.

Dessecting the toxicological profile of polysorbate 80 (PS80): comparative analysis of constituent variability and biological impact using a zebrafish model

Polysorbate 80, commonly abbreviated as PS80, is a widely used pharmaceutical excipient renowned for its role as a solubilizer and stabilizer in drug formulations. Although PS80 is essential for various pharmaceutical applications, particularly in the formulation of injectable drugs, it has been implicated in a range of adverse reactions. However, due to the complexity of the composition of PS80, the differences in the types and contents of the constituents of PS80 from different manufacturers increase the probability or likelihood of their uneven quality. Addressing the complete spectrum of PS80's components is challenging; thus, most studies to date have examined PS80 as a singular entity. This approach, however, carries a degree of uncertainty, as it overlooks the unique composition and concentration of components within the PS80 used in experiments, which may not reflect the actual diversity in commercially available PS80 products. Recognizing the critical need to understand how PS80's composition influences biological effects and toxicity, our study aims to bridge this knowledge gap. By doing so, we can clarify how different PS80 compositions from various manufacturers might affect the quality of pharmaceutical formulations, and also guide excipient manufacturers toward producing higher-quality PS80. Such insights could further facilitate a more targeted application of PS80 in drug development. Building on our previous work, we isolated and prepared two key components of PS80-polyoxyethylene sorbitan monooleate (PSM) and polyoxyethylene isosorbide monooleate (PIM)-and conducted a systematic comparison. We evaluated the acute, hemolytic, and target organ toxicity of two different PS80 samples, as well as PSM and PIM, using a zebrafish model. Our research also delved into the potential mechanisms behind the observed toxicological effects, providing an in-depth understanding of PS80's impact on biological systems.The results show that PS80, PSM, and PIM resulted in developmental anomalies in larval zebrafish. The primary organs of acute toxicity in zebrafish exposed to PS80 and its typical components PSM and PIM include the cardiovascular system, kidneys, intestines, skin, and liver. Notably, PIM further induced severe pericardial edema and erythrocyte hemolysis, thereby affecting blood flow. The samples also instigated oxidative damage by disrupting the redox equilibrium in the larvae. Compared to PS80, both PSM and PIM induced greater oxidative damage, with PIM notably causing significantly higher lipid oxidation, suggesting that oxidative stress may play a crucial role in polysorbate80-induced toxicity. Furthermore, our study found that PS80 could induce alterations in DNA conformation. The findings underscore the necessity for excipient regulators to establish comprehensive quality standards for Polysorbate 80 (PS80). By implementing such standards, it is possible to minimize the clinical risks associated with the variability in PS80 composition, ensuring safer pharmaceutical products for patients.

The role of miRNA-26a-5p and target gene socs1a in flutolanil induced hepatotoxicity of zebrafish at environmental relevant levels

Flutolanil has been detected worldwide in aquatic environment and fish, which has become an undeniable stressor on ecosystem and human health. Flutolanil has been reported to be toxic to aquatic organisms. However, the pathophysiological and molecular mechanism behind the detrimental effects remains obscure. Here we reported hepatotoxicity induced by flutolanil in HepG2 cells and zebrafish, as revealed by toxicokinetic, HE staining, miRNAs-mRNAs sequencing, molecular dynamic simulations and dual luciferase reporter assays. Collectively, our results indicated that flutolanil could be absorbed by and accumulated in the liver of zebrafish, causing hepatic vacuolar degeneration, steatosis and nuclear condensation and abnormal liver function, where its exposure at environmental levels disrupted the expressions of miRNA-26a-5p and its target gene socs1a by mediating JAK-STAT signaling pathway, which was partially responsible for hepatotoxicity, correlated with oxidative stress, cell apoptosis, inflammation, cell cycle disorder and mitochondrial dysfunction. These findings suggest that miRNA-26a-5p/socs1a can serve as potential biomarkers of hepatotoxicity in zebrafish following exposure to flutolanil. This uncovered route will provide a new tool for the risk assessment of flutolanil and a guide to proper use of flutolanil and environmental remedy, and open up a new horizon for liver disease assessment.

Bixafen causes hepatotoxicity and pancreas toxicity in zebrafish (Danio rerio)

Bixafen (BIX), a widely used succinate dehydrogenase inhibitor (SDHI) in agricultural disease control, has garnered significant attention due to its known hazardous effects on aquatic organisms. In this study, we exposed zebrafish embryos to 0.1, 0.2, and 0.3 μM BIX, to explore the impact of BIX on liver and pancreas. The results showed that BIX caused deformities and dysfunction in zebrafish embryos, including spinal curvature, pericardial edema, heart rate decrease, and hatching delay. Moreover, BIX significantly affected the development of the liver and pancreas in zebrafish and downregulated zebrafish fabp10a gene expression. Overall, this study presents strong evidence for BIX's potential toxicity to zebrafish liver and pancreas. The results may provide new insights into the evaluation of BIX'S impact on aquatic organisms.

Application and prospect of metabolomics-related technologies in food inspection

BACKGROUND

Food inspection covers a broad range of topics, including nutrient analysis, food pollutants, food auxiliary materials, additives, and food sensory identification. The foundation of diverse subjects like food science, nutrition, health research, and the food industry, as well as the desired reference for drafting trade and food legislation, makes food inspection highly significant. Because of their high efficiency, sensitivity, and accuracy, instrumental analysis methods have gradually replaced conventional analytical methods as the primary means of food hygiene inspection.

SCOPE AND APPROACH

Metabolomics-based analysis technology, such as nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and capillary electrophoresis-mass spectrometry (CE-MS), has become a widely used analytics platform. This research provides a bird's eye view of the application and future of metabolomics-related technologies in food inspection.

KEY FINDINGS AND CONCLUSIONS

We have provided a summary of the features and the application range of various metabolomics techniques, the strengths and weaknesses of different metabolomics platforms, and their implementation in specific inspection procedures. These procedures encompass the identification of endogenous metabolites, the detection of exogenous toxins and food additives, analysis of metabolite alterations during processing and storage, as well as the recognition of food adulteration. Despite the widespread utilization and significant contributions of metabolomics-based food inspection technologies, numerous challenges persist as the food industry advances and technology continues to improve. Thus, we anticipate addressing these potential issues in the future.

The Migration Mechanism of BTEX in Single- and Double-Lithology Soil Columns under Groundwater Table Fluctuation

The migration of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Groundwater table fluctuation can not only affect contaminant migration but also redox conditions, bacterial communities, and contaminant degradation. Understanding LNAPLs' (e.g., benzene, toluene, ethylbenzene, and xylene (BTEX)) behavior within porous media is critical for the high efficiency of most in situ remediation systems. A laboratory study of single- and double-lithology soil column investigation of the groundwater table fluctuation effect on BTEX transport, using benzene and toluene as typical compounds, in a typical representative model of aquifers subjected to water table fluctuation was undertaken in this study. The results show that benzene and toluene migration in single-lithology soil columns packed with sand was mainly affected by flushing due to the hydraulic force induced by water table fluctuations and that the double-lithology soil column packed with sand and silt was significantly affected by retention due to the higher adsorption induced by 10 cm of silt. The dissolution mainly correlated with the BTEX migration in saturated zones, and the contaminant concentration increased when the water table fell and decreased when the water table rose. For a contaminated site with a single-lithology structure consisting of sand, more attention should be paid to organic contaminant removal within the groundwater, and a double-lithology structure containing silt is more suited to the removal of organic contaminants from the silt layer. The difference in biodegradation kinetics between the groundwater table fluctuation (GTF) zone and the saturated zone should be better understood for the remediation of BTEX compounds.

Cyhalofop-butyl and pyribenzoxim-induced oxidative stress and transcriptome changes in the muscle of crayfish (Procambarus clarkii)

Cyhalofop-butyl and pyribenzoxim are commonly used herbicides in rice-crayfish co-culture fields. In actual production, weed control in paddy fields is inseparable from cyhalofop-butyl and pyribenzoxim, while its risk to P. clarkii is still unclear. The present study investigated the risk of acute and subchronic toxicity of cyhalofop-butyl and pyribenzoxim to P. clarkii. The results showed that cyhalofop-butyl and pyribenzoxim exposure for 28 days could accumulate in P. clarkii muscle and inhibit P. clarkii growth. Further research found that the malondialdehyde (MDA) level and glutathione-S-transferase (GST) activity in muscle of P. clarkii were significantly increased after exposure to cyhalofop-butyl and pyribenzoxim (4 days and 28 days), and the superoxide dismutase (SOD) and catalase (CAT) activities were significantly altered. Histological results also confirmed cyhalofop-butyl and pyribenzoxim-induced muscle damage in P. clarkii. Additionally, after 28 days exposure to 1.02 mg/L cyhalofop-butyl and 10.4 mg/L pyribenzoxim, transcriptome analysis identified 2029 and 4246 differentially expressed genes (DEGs), respectively. Exposure to 1.02 mg/L cyhalofop-butyl significantly altered metabolism-related pathways, such as drug metabolism-other enzymes, glutathione metabolism, drug metabolism-cytochrome P450, fatty acid biosynthesis and fatty acid degradation. While the pathways related to antioxidant system and nutrient substances synthesis and metabolic were significantly enriched after exposure to 10.4 mg/L pyribenzoxim. This research has significant implications for scientific and rational use of herbicides under rice-crayfish co-culture and will contribute to the development of the highly productive agricultural model.

Enantioselective toxic effects of the novel chiral antifungal agrochemical penthiopyrad in the early life stage of zebrafish (Danio rerio)

Penthiopyrad was extensively applied in agricultural production, however, the toxicities information of the penthiopyrad enantiomers on early life stages of aquatic organism were limited. This study investigated the enantioselective toxicity of penthiopyrad on the early life stage of zebrafish by acute toxicity, sublethal toxic effects and the mRNA relative expression levels of genes related to succinate dehydrogenase, cardiac development, and lipid metabolism. The results showed that the 96-h-LC₅₀ of penthiopyrad racemate and enantiomers to zebrafish embryos were Rac-: 2.784 mg/L; R-(-)-: 3.528 mg/L; S-(+)-: 1.882 mg/L. Penthiopyrad exposure induced autonomous movement abnormalities, slowed heart rate and delayed hatching in zebrafish embryos, and caused developmental toxic effects such as pericardial edema and yolk sac edema. The mRNA relative expression levels results showed that penthiopyrad exposure induced significant enantioselectivity effect for the expression of the Sdha, Pr1 and Nkx2.5 with a 1.94-4.98-fold difference between different enantiomers, and significantly affected succinate dehydrogenase (energy metabolism), lipid metabolism and cardiac development-related genes expression. In general, S-(+)-penthiopyrad induced higher toxic effects in zebrafish embryos, and mitochondrial dysfunction may be an important cause of abnormal development. This study contributed to improve the comprehensive risk assessment and enantiomeric research system of penthiopyrad to early life stage of zebrafish.

Toxic effects of pesticides on cellular and humoral immunity: an overview

People are exposed to pesticides through food, drinking water, and the environment. These compounds are associated with several disorders, such as inflammatory diseases, rheumatoid arthritis, cancer, and a condition related to metabolic syndrome. The immunotoxicants or immunotoxic compounds can cause a wide variety of effects on immune function, altering humoral immunity and cell-mediated immunity, resulting in adverse effects to the body. Here, immune system disorders are highlighted because they are closely linked to multiple organs, including the nervous, endocrine, reproductive, cardiovascular, and respiratory systems, leading to transient or permanent changes. Therefore, this study reviewed the mechanisms involved in the immunotoxicity of fungicides, herbicides, and insecticides in cells, animals, and humans in the past 11 years. According to the studies analyzed, the pesticides interfere with innate and adaptive immune functions, but the effects observed mainly on cellular and humoral immunity were highlighted. These compounds affected specific immune cells, causing apoptosis, changes in factor nuclear kappa B (NF-κB) expression, pro-inflammatory factors interleukin 6 (IL-6), interleukin 8 (IL-8), interferon-gamma (IFN-γ), chemokines (CXCL-c1c), and anti-inflammatory factor, such as interleukin 10 (IL-10). To verify the threats of these compounds, new evaluations with immunotoxicological biomarkers are necessary. HighlightsPesticides interfere with the innate and adaptive immune response.Cells, animals and human studies demonstrate the immunotoxicity of pesticides in the cellular and humoral immune response.Fungicides, herbicides, and insecticides alter the immune system by various mechanisms, such as pro-inflammatory and anti-inflammatory factors.

Toxicity effects of chlorantraniliprole in zebrafish (Danio rerio) involving in liver function and metabolic phenotype

Chlorantraniliprole (CAP), a representative bisamide insecticide, is widely used in rice fields around the world, posing potential toxicity risks to aquatic organisms. In this study, we examined the effects of exposure to CAP on growth and metabolic phenotype of zebrafish (Danio rerio) and oxidative stress and apoptosis in the liver of zebrafish (Danio rerio). First, we identified that CAP had a low bioaccumulation in zebrafish. Subsequently, growth phenotype analysis revealed that CAP could significantly increase liver weight and liver index in zebrafish. In addition, we found that CAP exposure could cause significant changes in indicators of oxidative stress, resulting in a significant increase in the content of malondialdehyde (MDA), causing oxidative stress in the liver of zebrafish. Meanwhile, the expression levels of apoptosis-related genes were also significantly changed and apoptosis was promoted in the liver of zebrafish with CAP exposure. Importantly, the results of metabolomics analysis shown that CAP exposure could significantly disrupt the metabolic phenotype of zebrafish, interfering with multiple metabolic pathways, mainly including valine, leucine and isoleucine biosynthesis and degradation, alanine, aspartate and glutamate metabolism and d-glutamine and D-glutamate metabolism. Last but not least, correlation analysis identified strong links between changes in liver function involving oxidative stress and apoptosis and changes in metabolic phenotype of zebrafish following CAP exposure. In brief, these results indicate that potential environmental risks of CAP to aquatic organisms should receive more attention.

Bioaccumulation and toxicity effects of flubendiamide in zebrafish (Danio rerio)

Flubendiamide is a widely used diamide insecticide with many adverse effects on environmental organisms. This study assessed its bioaccumulation and toxicity effects in zebrafish (Danio rerio) using LC-MS/MS. The concentrations of flubendiamide in the whole zebrafish increased in the early stages and achieved steady levels at 14 days. The bioconcentration factors (BCFs) of flubendiamide was 1.125-2.011. Although flubendiamide did not significantly affect the growth phenotypes of zebrafish, it significantly changed the hepatic somatic index (HSI) of zebrafish. Histopathological analysis showed that flubendiamide could cause structural damage to the liver tissue of zebrafish. Further physiological and biochemical analysis showed that flubendiamide significantly changed the activity of catalase (CAT) and the contents of malondialdehyde (MDA) and glutathione (GSH) in liver of zebrafish. Moreover, flubendiamide significantly changed the mRNA expression levels of cell apoptosis-related genes, including p53, puma, caspase-3, caspase-9, apaf-1, and bax in liver of zebrafish. In summary, these results indicate that flubendiamide can cause liver damage by inducing oxidative stress and apoptosis in the liver of zebrafish. This study provides a background for further safety evaluation of flubendiamide to aquatic organisms.

Effects of embryonic exposure to fluxapyroxad on zebrafish (Danio rerio) ocular development

Fluxapyroxad (FLU) is a succinate dehydrogenase inhibitor that protects crops from fungal diseases, however, it has been identified as toxicants to aquatic organisms. The objective of this study is to investigate the potential toxicity and underlying mechanisms of FLU on aquatic organisms. Herein, by using zebrafish embryos as a model organism, we demonstrated that FLU can cause microphthalmia in zebrafish embryos. The cell density in ganglion cell layer (GCL) is increased after exposure. Compared with the control, differentiation of the cells in ganglion cell layer, inner nuclear layer (INL), and outer nuclear layer (ONL) were severely disrupted in response to FLU treatment. The data show clear evidence that FLU exhibits development toxicity to zebrafish embryos by inducing retinal cell apoptosis, which causes microphthalmia. Our study provides comprehensive understanding to the underlying mechanism of FLU toxicity.

Combined lethal toxicity, biochemical responses, and gene expression variations induced by tebuconazole, bifenthrin and their mixture in zebrafish (Danio rerio)

Pesticides commonly occur as mixtures in an aqueous environment, causing deleterious effects on human health and the environment. However, the mechanism underlying the combined effects on aqueous organisms remains largely unknown, especially at low concentrations. In the current study, we inspected the interactive toxicity of tebuconazole (TEB), a triazole fungicide, and bifenthrin (BIF), a pyrethroid insecticide, to zebrafish (Danio rerio) using various toxicological assays. Our data revealed that the 96 h-LC50 (lethal concentration 50) values of BIF to fish at different life periods (embryonic, larval, juvenile, and adult periods) ranged from 0.013 (0.011-0.016) to 0.41 (0.35-0.48) mg a.i. L-1, which were lower than that of TEB ranging from 1.1 (0.88-1.3) to 4.8 (4.1-5.7) mg a.i. L-1. Combination of TEB and BIF induced synergetic acute toxicity to embryonic fish. Activities of T-SOD, POD, and GST were distinctly altered in most individual and joint administrations. Expressions of 16 genes associated with oxidative stress, cellular apoptosis, immune system, and endocrine system at the mRNA level were evaluated, and the information revealed that embryonic zebrafish were impacted by both individual compounds and their combinations. Six genes (cas9, P53, gr, TRα, IL-8, and cxcl-clc) exhibited greater changes when exposed to pesticide mixtures. Therefore, the joint effects induced by the pesticides at low concentrations should be considered in the risk assessment of mixtures and regulated as priorities for mixture risk management in the aqueous ecosystem. More research is needed to identify the threshold concentrations of the realistic pesticide mixtures above which synergistic interactions occur.

Study on toxicity effects of environmental pollutants based on metabolomics: A review

In the past few decades, the toxic effects of environmental pollutants on non-target organisms have received more and more attention. As a new omics technology, metabolomics can clarify the metabolic homeostasis of the organism at the overall level by studying the changes in the relative contents of endogenous metabolites in the organism. Recently, a large number of studies have used metabolomics technology to study the toxic effects of environmental pollutants on organisms. In this review, we reviewed the analysis processes and data processes of metabolomics and its application in the study of the toxic effects of environmental pollutants including heavy metals, pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and microplastics. In addition, we emphasized that the combination of metabolomics and other omics technologies will help to explore the toxic mechanism of environmental pollutants and provide new research ideas for the toxicological evaluation of environmental pollutants.

Dose-Dependent Molecular Responses of Labeo rohita to Triphenyl Phosphate

Triphenyl phosphate (TPhP) is a broad-spectrum organophosphate compound widely used as an additive in several products to prevent ignition. However, its utilization produces a hazardous impact on various organisms. So far, very few studies have investigated the acute toxicity of TPhP at environmentally relevant concentrations in nontarget aquatic species. This study aimed to assess whether the short-term exposure of TPhP (4, 20, and 100 μg L^-1) affects the oxidative stress, antioxidant activity, biomolecule metabolism, DNA stability, chromosomal integrity, apoptosis, and pathological changes in various organs of Labeo rohita fingerlings. The results illustrated that the reactive oxygen species (ROS) production and lipid peroxidation (LPO) rates were significantly higher in tissues (brain, liver, and kidney) of TPhP-treated groups. Interestingly, superoxide dismutase (SOD) and catalase (CAT) activities were remarkably decreased in tissues following TPhP exposure. The levels of protein, glucose, total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) in various tissues were also found to be significantly altered in TPhP-exposed fish fingerlings. These significant alterations in the antioxidant system and biochemical profile induced genotoxic responses such as DNA and chromosomal damage in the fish fingerlings. Furthermore, the incidence of the observed genotoxic responses was also found to be dose-dependent. Likewise, the apoptotic responses were also significantly altered following TPhP acute exposure in L. rohita fingerlings. The subsequent effects on oxidative stress, antioxidant inhibition, dysregulated biomolecule metabolism, and genotoxicity might be the possible reason for the observed pathological changes in various tissues of L. rohita. Taken together, the present findings showed that the toxicity of TPhP is principally associated with exposure concentrations. Therefore, this study illustrates the toxicity risks of TPhP to vertebrate organisms at real-world concentrations.

Enantioselective bioaccumulation and toxicity of the novel chiral antifungal agrochemical penthiopyrad in zebrafish (Danio rerio)

Succinate dehydrogenase inhibitor (SDHI) fungicides has been extensively used in agricultural production, which are not easily degrade in the environment and have various toxic effects on aquatic organisms. However, the toxic effects information to non-target organisms were mostly at the racemate level, which were poorly understood at the enantiomers level. Thus, this study aimed to investigate the enantioselective bioaccumulation behavior and toxic effects of penthiopyrad in zebrafish. Significant enantioselective bioaccumulation was observed when exposed to penthiopyrad at two dose levels: S-(+)-penthiopyrad was preferentially accumulated. Moreover, S-(+)-penthiopyrad caused oxidative stress in zebrafish liver. The results of real-time RT-PCR analyses revealed that exposure to penthiopyrad also enantioselectivity interfered with the expression of mitochondrial respiratory complexes, mtDNA synthesis, lipid metabolism and apoptosis-related genes. S-(+)-penthiopyrad significantly decreased most of the expression of the above gene, which showed higher toxic effects. We inferred that the toxicity mechanism of penthiopyrad was caused by lipid metabolism disorder and mitochondrial dysfunction in zebrafish, and further leads to apoptosis even DNA damage. This study provides more accurate data to investigate the environmental impact of penthiopyrad at the enantiomer level.

SDHI Fungicide Toxicity and Associated Adverse Outcome Pathways: What Can Zebrafish Tell Us?

Succinate dehydrogenase inhibitor (SDHI) fungicides are increasingly used in agriculture to combat molds and fungi, two major threats to both food supply and public health. However, the essential requirement for the succinate dehydrogenase (SDH) complex—the molecular target of SDHIs—in energy metabolism for almost all extant eukaryotes and the lack of species specificity of these fungicides raise concerns about their toxicity toward off-target organisms and, more generally, toward the environment. Herein we review the current knowledge on the toxicity toward zebrafish (Brachydanio rerio) of nine commonly used SDHI fungicides: bixafen, boscalid, fluxapyroxad, flutolanil, isoflucypram, isopyrazam, penthiopyrad, sedaxane, and thifluzamide. The results indicate that these SDHIs cause multiple adverse effects in embryos, larvae/juveniles, and/or adults, sometimes at developmentally relevant concentrations. Adverse effects include developmental toxicity, cardiovascular abnormalities, liver and kidney damage, oxidative stress, energy deficits, changes in metabolism, microcephaly, axon growth defects, apoptosis, and transcriptome changes, suggesting that glycometabolism deficit, oxidative stress, and apoptosis are critical in the toxicity of most of these SDHIs. However, other adverse outcome pathways, possibly involving unsuspected molecular targets, are also suggested. Lastly, we note that because of their recent arrival on the market, the number of studies addressing the toxicity of these compounds is still scant, emphasizing the need to further investigate the toxicity of all SDHIs currently used and to identify their adverse effects and associated modes of action, both alone and in combination with other pesticides.

Exposure to 2,4-D herbicide induces hepatotoxicity in zebrafish larvae

2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide is the main ingredient in over 1500 commercially available products such as Weedestroy® AM40 and DMA® 4 IVM. Although the liver has been identified as one of the organs that are affected by this herbicide, reports on its hepatotoxic effects available in the literature are restricted to rats. Thus, there is a gap in information on other organisms that may be vulnerable to 2,4-D exposure, such as fish. Therefore, the present work aimed to assess the hepatotoxic potential of 2,4-D in fish using zebrafish (Danio rerio) larvae as a model system. For this purpose, its acute toxicity to zebrafish embryos was assessed, as well as its sublethal effects (< LC₅₀) on the activity of enzymes related to oxidative (GST, CAT and GPX) and metabolic (LDH) stress and liver parameters (AST, ALT and ALP) after 48 h of exposure. Morphological analyses of the liver were also assessed in zebrafish larvae. As a result, 2,4-D reduced larvae survival (LC₅₀ 15.010 mg/L in 96 h of exposure), induced malformations, altered the activity of LDH, GST and CAT enzymes and significantly increased the activity of all biomarkers for liver damage. Although no changes in the color or size of larval liver were observed, histopathological analysis revealed that treatment with 2,4-D caused severe changes in liver tissue, such as vacuolization of the cytosol, eccentric cell nucleus, loss of tissue architecture and cellular boundaries. Thus, the results showed that 2,4-D altered the enzymatic profile related to oxidative stress, and induces liver damage.

In vivo assessment of dichlorvos induced histological and biochemical impairments coupled with expression of p53 responsive apoptotic genes in the liver and kidney of fish, Channa punctatus (Bloch, 1793)

Sub-lethal exposure of dichlorvos induces oxidative stress, consequent genetic instability and apoptosis coupled with impairments in biochemical, histopathological and transcription of genes in Channa punctatus. Exposure of 5% (0.041 mg/L; E2) and 10% (0.082 mg/L; E3) of 96 h-LC₅₀ of dichlorvos significantly (p < 0.05) elevated the reactive oxygen species (ROS) generation and activities of SOD and CAT, as compared to control (E1) after 30 d. The maximum reduction in reduced glutathione (GSH) was recorded in the liver (18.53 ± 0.81 μg/mg of protein) and kidney (19.32 ± 0.97 μg/mg of protein); while the total protein contents were also found reduced, 278.38 ± 8.40 μg/mL (liver) and 248.44 ± 7.28 μg/mL (kidney), after 30 days in E3, in comparison to respective controls. Further, significant (p < 0.05) induction in micronuclei (MN) and apoptotic cells (AC), in a dose- and exposure-based manner were also recorded. Moreover, a significant (p < 0.05) up-regulation of p53 (2.51-fold in liver), bax (2.03-fold in liver; 1.99-fold in kidney) and casp3a (2.26-fold in liver; 2.10-fold in kidney) together with an elevated expression of cat (1.73-fold in liver; 1.12-fold in kidney), p53 (1.27-fold in kidney) and apaf-1 (1.72-fold in liver) in fish exposed to higher dose of dichlorvos for 30 d evidently reflects geno-toxicological potential of referenced pesticide. Disturbed biochemical and molecular parameters evince that the fish experienced oxidative stress as is further supported by prominent pathological observations in liver and kidney. Findings are, thus, helpful in organ-specific molecular scanning against aquatic toxicants like dichlorvos.

Effects of Dufulin on Oxidative Stress and Metabolomic Profile of Tubifex

Dufulin is a highly effective antiviral pesticide used in plants. In this study, a seven-day experiment was conducted to evaluate the effects of Dufulin at five different concentrations (1 × 10⁻⁴, 1 × 10⁻³, 1 × 10⁻², 0.1, and 1 mg/L) on Tubifex. LC-MS-based metabolome analysis detected a total of 5356 features in positive and 9110 features in negative, of which 41 showed significant changes and were identified as differential metabolites. Four metabolic pathways were selected for further study. Detailed analysis revealed that Dufulin exposure affected the urea cycle of Tubifex, probably via argininosuccinate lyase (ASL) inhibition. It also affected the fatty acid metabolism, leading to changes in the concentration of free fatty acids in Tubifex. Furthermore, the changes in metabolites after exposure to Dufulin at 1 × 10⁻² mg/L were different from those at the other concentrations.

Fluxapyroxad induces developmental delay in zebrafish (Danio rerio)

Succinate dehydrogenase inhibitor (SDHI) fungicides are extensively used in agriculture. Some SDHI fungicides show developmental toxicity, immune toxicity and hepatotoxicity to fish. Fluxapyroxad (FLU) is a broad spectrum pyrazole-carboxamide SDHI fungicide and its potential impacts on fish embryonic development are unknown. We exposed zebrafish embryos to 1, 2 and 4 μM FLU. Developmental malformations, including yolk sac absorption disorder, decreased pigmentation and hatch delay were induced after FLU exposure. FLU caused significantly increased transcription levels in the ectoderm marker foxb1a but no significant changes in endoderm and mesoderm development markers (foxa2, ntl and eve1). Transcription levels of genes in the early stage embryos (gh, crx, neuroD and nkx2.4b) decreased significantly after FLU treatments. The content of glutathione (GSH) increased after FLU exposure. This study shows that FLU is toxic to zebrafish through its developmental effects and oxidative stress. FLU may pose risks to other non-target aquatic organisms.

Bixafen exposure induces developmental toxicity in zebrafish (Danio rerio) embryos

Bixafen (BIX), a new generation succinate dehydrogenase inhibitor (SDHI) fungicide commonly used in agriculture, is regarded as a potential aquatic pollutant because of its lethal and teratogenic effects on Xenopus tropicalis embryos. To evaluate the threat of BIX to aquatic environments, information concerning BIX's embryonic toxicity to aquatic organisms (especially fish) is important, yet such information remains scarce. The present study aimed to fill this knowledge gap by employing zebrafish embryos as model animals in exposure to 0.1, 0.3 and 0.9 μM BIX. Our results showed that BIX caused severe developmental abnormalities (hypopigmentation, tail deformity, spinal curvature and yolk sac absorption anomaly) and hatching delay in zebrafish embryos. The expression levels of early embryogenesis-related genes (gh, crx, sox2 and neuroD) were downregulated after BIX exposure, except for nkx2.4b, which was upregulated. Furthermore, transcriptome sequencing analysis showed that all the downregulated differentially expressed genes were enriched in cell cycle processes. Taken together, these results demonstrated that BIX has strong developmental toxicity to zebrafish that may be due to the downregulated expression of genes involved in embryonic development. These findings provide valuable reference for evaluating BIX's potential adverse effects on aquatic ecosystems.

Chronic exposure of zebrafish (Danio rerio) to flutolanil leads to endocrine disruption and reproductive disorders

The pesticide flutolanil has been detected in fish and aquatic environments, but its potential impact on the endocrine function is unknown. In this study, two-month zebrafish were exposed to the environmentally relevant concentrations of flutolanil for 60 days to examine the reproductive endpoints on the gonad endocrine system. Increased 17 beta-estradiol (17β-E2) content and 17β-E2/T ratio and decreased testosterone (T) in male suggested that flutolanil produces the estrogenic effect. In support of this view, vitellogene (vtg1, vtg2) and cytochrome P450 aromatase 19a (cyp19a) expression were up-regulated in the male liver. The levels of global DNA methylation were increased in ovary. Parental zebrafish exposure to different concentrations of flutolanil affected the offspring development as shown by short body length, and increased mortality. Thus, these results demonstrate that flutolanil exposure results in gonad endocrine disruption, decreased reproduction, and developmental toxicity in F1, highlighting the importance of assessing the potential environmental risks of flutolanil application.

Monobutyl phthalate (MBP) can dysregulate the antioxidant system and induce apoptosis of zebrafish liver

In this paper, the acute toxicity of monobutyl phthalate (MBP), the main hydrolysis product of dibutyl phthalate, on adult zebrafish liver antioxidant system was studied. Compared the toxicity effect of MBP and DBP by histopathology and apoptosis experiments, we speculated that the toxic effects of DBP on animals may be caused by its metabolite MBP. The results indicated that the antioxidant Nrf2-Keap1 pathway was insufficient to resist MBP-induced hepatotoxicity and led to an imbalance of membrane ion homeostasis and liver damage. Decreased cell viability, significant tissue lesions and early hepatocyte apoptosis were observed in the zebrafish liver in MBP exposure at high concentration (10 mg/L). The activities of antioxidant enzymes and ATPases in zebrafish liver were inhibited with increased malondialdehyde (MDA) content and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Integrated biomarker response (IBR) calculation results indicated that MBP mainly inhibited catalase (CAT) activity. Simultaneously, the expression of antioxidant-related genes (SOD, CAT, GPx, Nrf2, HO-1) was down-regulated, while apoptosis-related genes (p53, bax, cas3) were significantly up-regulated.

Impacts of Penconazole and Its Enantiomers Exposure on Gut Microbiota and Metabolic Profiles in Mice

Exposure to chiral pesticides poses many potential health risks. In this study, we examined the impacts of exposure to penconazole and its enantiomers on gut microbiota and metabolic profiles in mice. The relative abundance of microbiota in cecal content significantly changed following exposure to penconazole and its enantiomers. At the genus level, the relative abundances of seven gut microflora were altered following exposure to (-)-penconazole. Both (±)-penconazole and (+)-penconazole caused significant changes in the relative abundances of five gut microflora. In addition, targeted serum metabolomics analysis showed disturbed metabolic profiles following exposure. Respectively, (±)-penconazole, (+)-penconazole, and (-)-penconazole exposure significantly altered the relative levels of 29, 23, and 36 metabolites. In general, exposure to penconazole and its enantiomers caused disorders in gut microbiota and metabolic profiles of mice. The potential health risks of penconazole and its enantiomers now require further evaluation.