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

Toxicity effects of pesticides based on zebrafish (Danio rerio) models: Advances and perspectives

Pesticides inevitably enter aquatic environments, posing potential risks to organisms. The common aquatic model organism, zebrafish (Danio rerio), are widely used to evaluate the toxicity of pesticides. In this review, we searched the Web of Science database for articles published between 2012 and 2022, using the keywords "pesticide", "zebrafish", and "toxicity", retrieving 618 publications. Furthermore, we described the main pathways by which pesticides enter aquatic environments and the fate of their residues in these environments. We systematically reviewed the toxicity effects of pesticides on zebrafish, including developmental toxicity, endocrine-disrupting effects, reproductive toxicity, neurotoxicity, immunotoxicity, and genotoxicity. Importantly, we summarized the latest research progress on the toxicity mechanism of pesticides to zebrafish based on omics technologies, including transcriptomics, metabolomics, and microbiomics. Finally, we discussed future research prospects, focusing on the combined exposure of multiple pollutants including pesticides, the risk of multigenerational exposure to pesticides, and the chronic toxicity of aquatic nanopesticides. This review provides essential data support for ecological risk assessments of pesticides in aquatic environments, and has implications for water management in the context of pesticide pollution.

NMR-based metabolomics applied to ecotoxicology with zebrafish (Danio rerio) as a prominent model for metabolic profiling and biomarker discovery: Overviewing the most recent approaches

Metabolomics is an innovative approach used in the medical, toxicological, and biological sciences. As an interdisciplinary topic, metabolomics and its relation with the environment and toxicological research are extensive. The use of substances, such as drugs and pesticides, contributes to the continuous releasing of xenobiotics into the environment, harming organisms and their habitats. In this context, fish are important bioindicators of the environmental condition and have often been used as model species. Among them, zebrafish (Danio rerio) presents itself as a versatile and straightforward option due to its unique attributes for research. Zebrafish proves to be a valuable model for toxicity assays and also for metabolomics profiling by analytical tools. Thus, NMR-based metabolomics associated with statistical analysis can reasonably assist researchers in critical factors related to discovering and validating biomarkers through accurate diagnosis. Therefore, this review aimed to report the studies that applied zebrafish as a model for (eco)toxicological assays and essentially utilized NMR-based metabolomics analysis to assess the biochemical profile and thus suggest the potential biological marker.

Dissecting the Enantioselective Neurotoxicity of Isocarbophos: Chiral Insight from Cellular, Molecular, and Computational Investigations

Chiral organophosphorus pollutants are found abundantly in the environment, but the neurotoxicity risks of these asymmetric chemicals to human health have not been fully assessed. Using cellular, molecular, and computational toxicology methods, this story is to explore the static and dynamic toxic actions and its stereoselective differences of chiral isocarbophos toward SH-SY5Y nerve cells mediated by acetylcholinesterase (AChE) and further dissect the microscopic basis of enantioselective neurotoxicity. Cell-based assays indicate that chiral isocarbophos exhibits strong enantioselectivity in the inhibition of the survival rates of SH-SY5Y cells and the intracellular AChE activity, and the cytotoxicity of (S)-isocarbophos is significantly greater than that of (R)-isocarbophos. The inhibitory effects of isocarbophos enantiomers on the intracellular AChE activity are dose-dependent, and the half-maximal inhibitory concentrations (IC₅₀) of (R)-/(S)-isocarbophos are 6.179/1.753 μM, respectively. Molecular experiments explain the results of cellular assays, namely, the stereoselective toxic actions of isocarbophos enantiomers on SH-SY5Y cells are stemmed from the differences in bioaffinities between isocarbophos enantiomers and neuronal AChE. In the meantime, the modes of neurotoxic actions display that the key amino acid residues formed strong noncovalent interactions are obviously different, which are related closely to the molecular structural rigidity of chiral isocarbophos and the conformational dynamics and flexibility of the substrate binding domain in neuronal AChE. Still, we observed that the stable "sandwich-type π-π stacking" fashioned between isocarbophos enantiomers and aromatic Trp-86 and Tyr-337 residues is crucial, which notably reduces the van der Waals' contribution (ΔG_vdW) in the AChE-(S)-isocarbophos complexes and induces the disparities in free energies during the enantioselective neurotoxic conjugations and thus elucidating that (S)-isocarbophos mediated by synaptic AChE has a strong toxic effect on SH-SY5Y neuronal cells. Clearly, this effort can provide experimental insights for evaluating the neurotoxicity risks of human exposure to chiral organophosphates from macroscopic to microscopic levels.

Serum metabolomics strategy for investigating the hepatotoxicity induced by different exposure times and doses of Gynura segetum (Lour.) Merr. in rats based on GC-MS

Gynura segetum (Lour.) Merr. (GS), has been widely used in Chinese folk medicine and can promote circulation, relieve pain and remove stasis. In recent years, the hepatotoxicity caused by GS has been reported, however its mechanism is not fully elucidated. Metabolomic techniques are powerful means to explore the toxicological mechanism and therapeutic effects of traditional Chinese medicine. The purpose of this study was to establish a serum metabolomics method based on Gas Chromatography-Mass Spectrometry (GC-MS) to explore the hepatotoxicity mechanism of different exposure times and doses of GS in rats. Sprague Dawley (SD) rats were administered daily with distilled water, 7.5 g kg^-1 GS, or 15 g kg^-1 GS by intragastrical gavage for either 10 or 21 days. The methods adopted included enzyme-linked immunosorbent assay (ELISA), Hematoxylin and Eosin (H&E) staining and GC-MS-based serum metabolomics. Serum biochemistry analysis showed that the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycerides (TG), total bilirubin (TBIL) and total bile acid (TBA) significantly (P < 0.05) increased while the levels of albumin (ALB) and high-density lipoprotein (HDL) significantly (P < 0.05) decreased in GS-treated groups, compared with the control group. Interestingly, the ALT, AST, TG and ALB levels changed in a time- and dose-dependent manner. The results of H&E staining showed the degree of liver damage after administration of GS gradually deepened with the extension of administration time and the increase of the dose. According to the results of metabolomics analysis, 26 differential metabolites were identified, which were involved in 8 metabolic pathways including phenylalanine metabolism, glyoxylic acid and dicarboxylic acid metabolism and so on. Meanwhile, the number of differential metabolites in different GS-treated groups was associated with GS exposure time and dose. Therefore, we concluded that GS might induce hepatotoxicity depending on the exposure time and dose.

Insight into the differences in the toxicity mechanisms of dinotefuran enantiomers in zebrafish by UPLC-Q/TOF-MS

Dinotefuran is a chiral insecticide widely used to control Nilaparvata lugens in agriculture. However, little is known about the toxic effects of dinotefuran enantiomers on aquatic organisms. In this study, zebrafish were exposed to 1.00 and 10.00 mg/L dinotefuran enantiomers for 96 h, after which multivariate pattern recognition, metabolite identification, and pathway analysis were performed. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were then conducted to reveal the metabolic perturbations caused by dinotefuran enantiomers. Metabolic pathway analysis revealed the perturbation of five main pathways, including phenylalanine, tyrosine and tryptophan biosynthesis; phenylalanine metabolism; retinol metabolism; arginine and proline metabolism; and glycerophospholipid metabolism. These disturbed metabolic pathways were strongly correlated with energy, amino acid metabolism, and lipid metabolism. Pathway analysis also indicated that the metabolic pathway changes induced by the same level of R and S-dinotefuran were enantioselective. Our research may provide better insight into the risk of chiral dinotefuran in aquatic organisms in the environment.

A multidimensional metabolomics workflow to image biodistribution and evaluate pharmacodynamics in adult zebrafish

An integrated evaluation of the tissue distribution and pharmacodynamic properties of a therapeutic is essential for successful translation to the clinic. To date, however, cost-effective methods to measure these parameters at the systems level in model organisms are lacking. Here, we introduce a multidimensional workflow to evaluate drug activity that combines mass spectrometry-based imaging, absolute drug quantitation across different biological matrices, in vivo isotope tracing and global metabolome analysis in the adult zebrafish. As a proof of concept, we quantitatively determined the whole-body distribution of the anti-rheumatic agent hydroxychloroquine sulfate (HCQ) and measured the systemic metabolic impacts of drug treatment. We found that HCQ distributed to most organs in the adult zebrafish 24 h after addition of the drug to water, with the highest accumulation of both the drug and its metabolites being in the liver, intestine and kidney. Interestingly, HCQ treatment induced organ-specific alterations in metabolism. In the brain, for example, HCQ uniquely elevated pyruvate carboxylase activity to support increased synthesis of the neuronal metabolite, N-acetylaspartate. Taken together, this work validates a multidimensional metabolomics platform for evaluating the mode of action of a drug and its potential off-target effects in the adult zebrafish. This article has an associated First Person interview with the first author of the paper.

Imazalil and its metabolite imazalil-M caused developmental toxicity in zebrafish (Danio rerio) embryos via cell apoptosis mediated by metabolic disorders

Imazalil (IMZ) is a highly effective fungicide employed in crop production. It has been consistently detected in aquatic environments. The main environmental metabolite of IMZ is imazalil-M (IMZ-M). Limited studies have focused on the toxicity of IMZ and IMZ-M in aquatic organisms. This study systematically evaluated the developmental toxicity of IMZ and IMZ-M on zebrafish (Danio rerio) embryos and explored the potential mechanisms involved. The results showed that IMZ and IMZ-M caused developmental toxicity, characterized by decreased heart rate, hatching inhibition, and pericardial cyst in zebrafish embryos. Subsequently, acridine orange (AO) staining revealed cell apoptosis in the area around the heart regions of zebrafish larvae. Besides, the expression levels of apoptosis-related genes also varied significantly. Furthermore, ¹H NMR-based metabolomics analysis showed that IMZ and IMZ-M exposure could induce metabolic profiles disorder in zebrafish larvae. Importantly, zebrafish exposure to IMZ and IMZ-M significantly affected the metabolism of branched - chain amino acids, energy, and ketone bodies, which are related to cell apoptosis. Overall, the toxicity of IMZ and IMZ-M in zebrafish embryos and larvae was characterized, suggesting a theoretical basis for the potential environmental risks of IMZ and its metabolite IMZ-M on non-target organisms.

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.

Effects of penconazole enantiomers exposure on hormonal disruption in zebrafish Danio rerio (Hamilton, 1822)

PEN is a widely used triazole fungicide, usually used to control grape white rot. In the process of agricultural use, PEN will be scattered to the soil and water environment, which brings certain environmental safety risks. In this study, we used a 200-μg/L solution of Rac-PEN, (+)-PEN, and (-)-PEN to perform a 28-day exposure test on zebrafish. The results showed that long-term low-dose PEN exposure did not significantly change the growth factor K and the number of spawning of zebrafish. However, the content of four important hormones vitellogenin, 17β-estradiol, testosterone, and 11-ketotestosterone in zebrafish has changed significantly. Furthermore, we measured the expression of hypothalamus-pituitary-gonads-liver (HPGL) axis-related genes, and the results showed that the expressions of related genes in the brain, gonads, and liver all changed significantly. Combining the above results, we can conclude that PEN has obvious endocrine disrupting effect on zebrafish, and has gender-specific endocrine effects. Meanwhile, Rac-PEN and (+)-PEN had stronger effects on the endocrine system of zebrafish than (-)-PEN.

Metabolomic Studies for the Evaluation of Toxicity Induced by Environmental Toxicants on Model Organisms

Environmental pollution causes significant toxicity to ecosystems. Thus, acquiring a deeper understanding of the concentration of environmental pollutants in ecosystems and, clarifying their potential toxicities is of great significance. Environmental metabolomics is a powerful technique in investigating the effects of pollutants on living organisms in the environment. In this review, we cover the different aspects of the environmental metabolomics approach, which allows the acquisition of reliable data. A step-by-step procedure from sample preparation to data interpretation is also discussed. Additionally, other factors, including model organisms and various types of emerging environmental toxicants are discussed. Moreover, we cover the considerations for successful environmental metabolomics as well as the identification of toxic effects based on data interpretation in combination with phenotype assays. Finally, the effects induced by various types of environmental toxicants in model organisms based on the application of environmental metabolomics are also discussed.

Occurrence of pesticides in white tea and a corresponding risk exposure assessment for the different residents in Fujian, China

White tea has been of increasing public interest worldwide owing to its health benefits. Based on 2 years of surveillance, the long-term and cumulative chronic exposure risks of pesticide residues through white tea drinking were assessed for different subpopulations in Fujian, China. Twenty-five different pesticides were found, and 74.8% of samples contained at least one pesticide residue. The most frequently detected pesticide was bifenthrin with detection rates of 61.6%. Risk assessment was performed using both the deterministic approach and semiprobabilistic model under the best-case and the worst-case scenarios. The results demonstrated that the dietary risks were extremely low for six different subpopulations in which the risks for adults over the age of 41 were relatively higher. The risk ranking scheme indicated that isocarbophos and triazophos were considered to be of medium risk. The different use suggestions for the 25 positive pesticides are proposed to further minimize the exposure risk to consumer health. PRACTICAL APPLICATION: Tea is the second most popular nonalcoholic beverage throughout the world. Pesticides are used to improve the yield of tea. Pesticide residues in tea could be one of the exposure pathways for consumers. Monitoring residual levels and assessing the health risk assessment in tea are thus in an urge.

Asymmetric Synthesis of Stereogenic Phosphorus P(V) Centers Using Chiral Nucleophilic Catalysis

Organophosphates have been widely used in agrochemistry, as reagents for organic synthesis, and in biochemistry. Phosphate mimics possessing four unique substituents, and thereby a chirality center, are useful in transition metal catalysis and as nucleotide therapeutics. The catalytic, stereocontrolled synthesis of phosphorus-stereogenic centers is challenging and traditionally depends on a resolution or use of stochiometric auxiliaries. Herein, enantioenriched phosphorus centers have been synthesized using chiral nucleophilic catalysis. Racemic H-phosphinate species were coupled with nucleophilic alcohols under halogenating conditions. Chiral phosphonate products were synthesized in acceptable yields (33-95%) and modest enantioselectivity (up to 62% ee) was observed after identification of an appropriate chiral catalyst and optimization of the solvent, base, and temperature. Nucleophilic catalysis has a tremendous potential to produce enantioenriched phosphate mimics that could be used as prodrugs or chemical biology probes.

Anti-pesticide DNA aptamers fail to recognize their targets with asserted micromolar dissociation constants

Herein, we originally aimed at developing fluorescence anisotropy biosensor platforms devoted to the homogeneous-phase detection of isocarbophos and phorate pesticides by using previously isolated DNA aptamers. To achieve this, two reporting approaches displaying very high generalizability features were implemented, based on either the complementary strand or the SYBR green intercalator displacement strategies. Unfortunately, none of the transduction methods led to phorate-dependent signals. Only the SYBR green displacement method provided a small output in the presence of isocarbophos, but at an analyte concentration greater than 100 μM. In order to identify the origin of such data, isothermal titration calorimetry (ITC) experiments were subsequently performed. It was shown that aptamers bind neither isocarbophos nor phorate in free solution with the claimed micromolar dissociation constants. This work puts forward some doubts about the previously described aptasensors that rely on the use of these functional DNA molecules. It also highlights the need to carefully investigate the binding capabilities of aptamers after their isolation and to include appropriate control experiments with scrambled or mutated oligonucleotides.

Toxicological effects of microplastics and phenanthrene to zebrafish (Danio rerio)

The toxicology of microplastics in combination with other pollutants has attracted widespread attention. In this study, zebrafish were exposed to 3 mg/L polystyrene microplastic, 0.2 mg/L phenanthrene, and a combination of both. Zebrafish microplastic uptake, phenanthrene accumulation, antioxidant-associated enzyme activity and related gene expression, immune-associated gene expression, and the gut microflora were measured after 12 and 24 days of exposure. Phenanthrene and microplastic accumulation increased with exposure time and was also greater in the combined exposure group than in the single exposure group. Combined analysis of antioxidant enzyme activity and immune and antioxidant-related genes shows that exposure alone causes oxidative stress in zebrafish, ultimately increasing immunity and the expression of oxidative stress genes, while combined exposure exacerbates these changes. Fusobacteria decreased and Proteobacteria and Bacteroidetes increased in the three exposure groups of gut microorganisms. Overall, our study demonstrates that microplastics enhance the toxicity of phenanthrene and that the two have a synergistic effect.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

Occurrence, source and ecotoxicological risk assessment of pesticides in surface water of Wujin District (northwest of Taihu Lake), China

This study investigated the occurrence and distribution of pesticides in surface water (lakes, major rivers and tributaries) and potential discharge sources (fish ponds, livestock and poultry farms, and sewage treatment plants) in Wujin District (northwest of Taihu Lake), Jiangsu province, China. An analytical liquid chromatography-tandem mass spectrometry method was developed for 38 pesticides, which was applied in the monitoring of 240 surface water samples and 76 potential discharge source samples. Eleven insecticides and five fungicides with temporal and spatial variation were detected in surface water. The total pesticide concentrations in surface water in different seasons were as follows: March > August > June > November. The two most polluting and widespread pesticides were carbendazim (maximum concentration 508 ng L^-1, detection rate 100%) and imidacloprid (maximum concentration 438 ng L^-1, detection rate 88%). Gehu Lake (S46) and Sanshangang River (S12) were seriously polluted water bodies. Seven insecticides and four fungicides were detected in the potential discharge sources; and their composition changed significantly with the seasons. The concentrations of detected organophosphorus pesticides and neonicotinoids (e.g. acetamiprid in March and dichlorvos in November) in a few non-agricultural planting sources were far greater than those detected in surface water, and hence a few fish ponds, livestock and poultry farms, and sewage treatment plants might be the potential discharge sources of pesticides in the surrounding surface water. The estimated input flux of the studied pesticides from upstream rivers to Taihu Lake was 141.95 kg a^-1. Furthermore, more attention should be paid to the medium or high aquatic ecotoxicological risk presented by the levels of organophosphorus pesticides, carbamates, and benzimidazoles.

A comprehensive analysis of metabolomics and transcriptomics reveals new biomarkers and mechanistic insights on DEHP exposures in MCF-7 cells

Di-(2-ethylhexyl) phthalate (DEHP) is one of the most important environmental pollutants and affects multiple pathways upon human exposure. DEHP could induce MCF-7 cell proliferation at a very low dose; however, the possible linkage between DEHP and the cell proliferation effect is still unclear. Here, we carried out a comprehensive metabolome and transcriptome analysis to depict the possible molecular mechanisms of the effect of DEHP exposure on MCF-7 proliferation. In this paper, MCF-7 cells treated with DEHP at a dose of 1 μM for 48 h were selected for metabolome and transcriptome analysis. Untargeted and targeted metabolomics identified 8 differential metabolites, including amino acids, purine, pyrimidine and nucleotides. The metabolite changes were associated with 9 metabolic pathways. Disorders in riboflavin, histidine, beta-alanine metabolism, and nitrogen metabolism caused by DEHP exposure are important concerns for MCF-7 proliferation. Moreover, a transcriptomics study of the MCF-7 cells found a total of 500 differentially expressed genes (DEGs). KEGG enrichment analyses showed that pathways in cancer had stronger responses. The results of integrated analysis of the interactions between the DEGs and metabolites revealed significant changes in the purine metabolism pathway, which will shed light on the mechanism of MCF-7 cell proliferation after DEHP exposure. Overall, this study depicts the possible contribution of DEHP exposure to MCF-7 cell proliferation and highlights the power of omics platforms to deepen the mechanistic understanding of toxicity caused by endocrine disrupting chemicals.

Metabolomics Reveals Antioxidant Stress Responses of Wheat (Triticum aestivum L.) Exposed to Chlorinated Organophosphate Esters

In this study, wheat (Triticum aestivum L.) was exposed to three of the most typical chlorinated organophosphate esters (OPEs), which are widely present in farmland soil, at environmental concentrations to assess their accumulation, disruption on metabolism, and oxidative stress in wheat. The three OPEs accumulated distinctly in the root and then translocated to the shoot. After exposure for 7 days, the content of chlorophyll b decreased, while the levels of carotenoid and activities of antioxidases, malonaldehyde, and reactive oxygen species increased significantly in both the root and shoot, indicating that the target OPEs caused significant oxidative stresses and affected photosynthesis in wheat. Untargeted metabolomics revealed concentration- and species-dependent metabolic responses of the three OPEs. Saccharides were downregulated, which might be due to the reduced photosynthesis activities. On the other hand, the chlorinated OPEs induced increases in respiration and antioxidative metabolites, revealing that the antioxidant system of wheat was active in scavenging ROS. The disturbance of tris(1,3-dichloro-2-propyl)phosphate on the metabolisms in wheat tissues was the strongest. These results contribute to the food safety and crop quality assessment of chlorinated OPEs and clarify the underlying mechanisms of their phytotoxicities.

Targeted toxicometabolomics of endosulfan sulfate in adult zebrafish (Danio rerio) using GC-MS/MS in multiple reaction monitoring mode

Endosulfan sulfate is a major oxidative metabolite of the chlorinated insecticide endosulfan. In this study, a targeted metabolomics approach was used to investigate the toxic mechanisms of endosulfan sulfate in adult zebrafish using the multiple reaction monitoring mode of a GC-MS/MS. The LC₅₀ of endosulfan sulfate in adult zebrafish was determined and then zebrafish were exposed to endosulfan sulfate at one-tenth the LC₅₀ (0.1LC₅₀) or the LC₅₀ for 24 and 48 h. After exposure, the fish were extracted, derivatized and analyzed by GC-MS/MS for 379 metabolites to identify 170 metabolites. Three experimental groups (control, 0.1LC₅₀ and LC₅₀) were clearly separated in PLS-DA score plots. Based on the VIP, ANOVA, and fold change results, 40 metabolites were selected as biomarkers. Metabolic pathways associated with those metabolites were identified using MetaboAnalyst 4.0 as follows: aminoacyl-tRNA biosynthesis, valine/leucine/isoleucine biosynthesis, citrate cycle, glycerolipid metabolism, and arginine/proline metabolism. Gene expression studies confirmed the activation of citrate cycle and glycerolipids metabolism. MDA levels of the exposed group significantly increased in oxidative toxicity assay tests. Such significant perturbations of important metabolites within key biochemical pathways must result in biologically hazardous effects in zebrafish.

Evaluating the effects of the tebuconazole on the earthworm, Eisenia fetida by H-1 NMR-Based untargeted metabolomics and mRNA assay

Tebuconazole, a widely used fungicide, can severely disrupt the reproductive process of various organisms. In this study, we investigated the subacute effects of tebuconazole on the earthworm to fully understand its toxic implications. Herein, untargeted metabolomics, mRNA assay and biochemical approaches were adopted to evaluate the subacute effects of Eisenia fetida earthworms, when exposed to tebuconazole at three different concentrations (0.5, 5 and 50 mg/kg) for seven days. SOD enzyme activity test displayed that tebuconazole exposure interfered with the earthworms' ROS. ANN mRNA expression was down-regulated after tebuconazole exposure. ¹H nuclear magnetic resonance (¹H-NMR)-based untargeted metabolomics study showed that 5 mg/kg tebuconazole exposure interfered with earthworms' metabolism. Twelve significantly changed metabolites were identified. The pathway analyses indicate that tebuconazole can disrupt the earthworm's metabolism, particularly in the AMP pathway, which impact the reproduction. This may explain the tebuconazole's mechanism of action behind the down-regulation of the expression of ANN mRNA, which is related to the earthworm's reproductive process. We comprehensively evaluated the mRNA expression, enzyme activity, and metabolomics, and acquired sufficient information for evaluating the toxicity of tebuconazole.

Toxicity testing of pesticides in zebrafish-a systematic review on chemicals and associated toxicological endpoints

The use of zebrafish (Danio rerio) has arisen as a promising biological platform for toxicity testing of pesticides such as herbicides, insecticides, and fungicides. Therefore, it is relevant to assess the use of zebrafish in models of exposure to investigate the diversity of pesticide-associated toxicity endpoints which have been reported. Thus, this review aimed to assess the recent literature on the use of zebrafish in pesticide toxicity studies to capture data on the types of pesticide used, classes of pesticides, and zebrafish life stages associated with toxicity endpoints and phenotypic observations. A total of 352 articles published between September 2012 and May 2019 were curated. The results show an increased trend in the use of zebrafish for testing the toxicity of pesticides, with a great diversity of pesticides (203) and chemical classes (58) with different applications (41) being used. Furthermore, experimental outcomes could be clustered in 13 toxicity endpoints, mainly developmental toxicity, oxidative stress, and neurotoxicity. Organophosphorus, pyrethroid, azole, and triazine were the most studied classes of pesticides and associated with various toxicity endpoints. Studies frequently opted for early life stages (embryos and larvae). Although there is an evident lack of standardization of nomenclatures and phenotypic alterations, the information gathered here highlights associations between (classes of) pesticides and endpoints, which can be used to relate mechanisms of action specific to certain classes of chemicals.

A potential biomarker of isofenphos-methyl in humans: A chiral view

Isofenphos-methyl (IFP) is a very active and persistent chiral insecticide. However, IFP has lower activity against acetylcholinesterases (AChEs). Previously, it was confirmed that phosphorothioate organophosphorus pesticides with N-alkyl (POPN) require activation by oxidative desulfuration and N-dealkylation. In this work, we demonstrated that IFP could be metabolized in human liver microsomes to isofenphos-methyl oxon (IFPO, 52.7%), isocarbophos (ICP, 14.2%) and isocarbophos oxon (ICPO, 11.2%). It was found that (R)-IFP was preferentially degraded compared to the (S)-enantiomer, and the enantiomeric fraction (EF) value reached 0.61 at 60 min. However, (S)-enantiomers of the three metabolites, were degraded preferentially, and the EF values ranged from 0.34 to 0.45. Cytochrome P450 (CYP) isoforms CYP3A4, CYP2E1, and CYP1A2 and carboxylesterase enzyme have an essential role in the enantioselective metabolism of IFP; but, the enzymes that participate in the degradation of IFP metabolites are different. The AChE inhibition bioassay indicated that ICPO is the only effective inhibitor of AChE. The covalent molecular docking has proposed that the metabolites of IFP and its analogs after N-dealkylation and oxidative desulfuration will possess the highest inhibitory activity against AChE. This study is the first to demonstrate that ICPO can be regarded as a potential biomarker for the biomonitoring of IFP and ICP exposure in humans.