Toxicity and fate of chiral insecticide pyriproxyfen and its metabolites in zebrafish (Danio rerio)

A review on the enantioselective distribution and toxicity of chiral pesticides in aquatic environment

Chiral pesticides account for about 40% of the total pesticides. In the process of using pesticides, it will inevitably flow into the surface water and even penetrate into the groundwater through surface runoff and other means, as a consequence, it affects the water environment. Although the enantiomers of chiral pesticides have the same physical and chemical properties, their distribution, ratio, metabolism, toxicity, etc. in the organism are often different, and sometimes even show completely opposite biological activities. In this article, the selective fate of different types of chiral pesticides such as organochlorine, organophosphorus, triazole, pyrethroid and other chiral pesticides in natural water bodies and sediments, acute toxicity to aquatic organisms, chronic toxicity and other aspects are summarized to further reflect the risks between the enantiomers of chiral pesticides to non-target organisms in the water environment. In this review, we hope to further explore its harm to human society through the study of the toxicity of chiral pesticide enantiomers, so as to provide data support and theoretical basis for the development and production of biochemical pesticides.

Embryotoxic Effects of Pesticides in Zebrafish (Danio rerio): Diflubenzuron, Pyriproxyfen, and Its Mixtures

Diflubenzuron (DFB) and pyriproxyfen (PPF) are larvicides used in crops to control insect plagues. However, these pesticides are known to impact non-target organisms like fish and mammals. Here, we aimed at assessing the embryotoxicity of purified DFB, PPF, and their mixtures in a non-target organism-zebrafish. Zebrafish embryos were exposed to different concentrations for 120 h: 0.025, 0.125, 0.25, 1.25, 2.5, and 10 mg/L of purified PPF and purified DFB, while we used 0.025 mg/L PPF + 10 mg/L DFB (Mix A), 0.125 mg/L PPF + 10 mg/L DFB (Mix B), and 0.25 mg/L PPF + 10 mg/L DFB (Mix C) for the mixtures of PPF + DFB. We observed mortality, teratogenicity, and cardiotoxicity. For the neurotoxicity tests and evaluation of reactive oxygen species (ROS) levels in the brain, embryos were exposed for 120 h to 0.379 and 0.754 mg/L of PPF and 0.025 and 0.125 mg/L of DFB. We established the LC50 for PPF as 3.79 mg/L, while the LC50 for DFB was not determinable. Survival and hatching were affected by PPF concentrations above 0.125 mg/L, DFB concentrations above 1.25 mg/L, and the lower pesticide mixtures. PPF exposure and mixtures induced different types of malformations, while a higher number of malformations were observed for the mixtures, suggesting a potentiating effect. Pesticides diminished avoidance responses and increased the levels of ROS across all concentrations, indicating neurotoxicity. Our findings underscore the detrimental impact of PPF and DFB exposure, spanning from biochemistry to morphology. There is a critical need to reconsider the global use of these pesticides and transition to more ecologically friendly forms of pest control, raising an alarm regarding repercussions on human and animal health and well-being.

Multi-omics and gut microbiome: Unveiling the pathogenic mechanisms of early-life pesticide exposure

The extensive application of pesticides in agricultural production has raised significant concerns about its impact on human health. Different pesticides, including fungicides, insecticides, and herbicides, cause environmental pollution and health problems for non-target organisms. Infants and young children are so vulnerable to the harmful effects of pesticide exposure that early-life exposure to pesticides deserves focused attention. Recent research lays emphasis on understanding the mechanism between negative health impacts and early-life exposure to various pesticides. Studies have explored the impacts of exposure to these pesticides on model organisms (zebrafish, rats, and mice), as well as the mechanism of negative health effects, based on advanced methodologies like gut microbiota and multi-omics. These methodologies help comprehend the pathogenic mechanisms associated with early-life pesticide exposure. In addition to presenting health problems stemming from early-life exposure to pesticides and their pathogenic mechanisms, this review proposes expectations for future research. These proposals include focusing on identifying biomarkers that indicate early-life pesticide exposure, investigating transgenerational effects, and seeking effective treatments for diseases arising from such exposure. This review emphasizes how to understand the pathogenic mechanisms of early-life pesticide exposure through gut microbiota and multi-omics, as well as the adverse health effects of such exposure.

Vitamin B12 Ameliorates Pesticide-Induced Sociability Impairment in Zebrafish (Danio rerio): A Prospective Controlled Intervention Study

Constant exposure to a variety of environmental factors has become increasingly problematic. A variety of illnesses are initiated or aided by the presence of certain perturbing factors. In the case of autism spectrum disorder, the environmental component plays an important part in determining the overall picture. Moreover, the lack of therapies to relieve existing symptoms complicates the fight against this condition. As a result, animal models have been used to make biomedical research easier and more suited for disease investigations. The current study used zebrafish as an animal model to mimic a real-life scenario: acute exposure to an increased dose of pesticides, followed by prospective intervention-based therapy with vitamin B12 (vit. B12). It is known that vit. B12 is involved in brain function nerve tissue, and red blood cell formation. Aside from this, the role of vit. B12 in the redox processes is recognized for its help against free radicals. To investigate the effect of vit. B12, fish were divided into four different groups and exposed to a pesticide mixture (600 μg L-1 fipronil + 600 μg L-1 pyriproxyfen) and 0.24 μg L-1 vit. B12 for 14 days. The impact of the compounds was assessed daily with EthoVision XT 11.5 software for behavioral observations, especially for sociability, quantified by the social interaction test. In addition, at the end of the study, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) were measured. The results showed significant improvements in locomotor activity parameters and a positive influence of the vitamin on sociability. Regarding the state of oxidative stress, high activity was found for SOD and GPx in the case of vit. B12, while fish exposed to the mixture of pesticides and vit. B12 had a lower level of MDA. In conclusion, the study provides new data about the effect of vit. B12 in zebrafish, highlighting the potential use of vitamin supplementation to maintain and support the function of the organism.

Biochemical and teratogenic effects of a mixture of pyriproxyfen and glyphosate

The mixture of agrochemicals can be made to improve pest control or accidentally. In this way, the effects on non-target organisms are a critical aspect of the environment and heath. Thus, this work aimed to show how a mixture of pyriproxyfen, and glyphosate can impair biochemical routes and embryonic development. Zebrafish embryos 0-72 hpf were exposed to 0.001-1 μg/mL of pyriproxyfen, glyphosate, and a mixture of both pesticides. The ADMETox was evaluated in silico. The FET-test was used to estimate teratogenic effects. The biochemical effects were estimated using AChE, SOD, and CAT as parameters. ROS generation was estimated using 30 μM H2DCF-DA and 5 μM DHE. The ADMETox reveals that intestinal absorption and P-glycoprotein are the main sites for PPx and Gly adsorption. The distribution parameters were diverse. PPx + Gly at 0.1 μg/mL leads to 50 % of lethality and at 1 μg/mL 100 % of lethality. PPx + Gly leads to a 22 % of lack of somite formation at 1 μg/mL. The heart rate was reduced by >10 % in all concentrations tested. The AChE has a decrease with IC20 19.6 μM and IC50 261.5 μM. SOD showed a reduction of 28 % to PPx and CAT was reduced by 58 % to PPx + Gly and Gly at 1 μg/mL. Glyphosate does not increase unspecific ROS generation. The superoxide generation was 2× higher in the PPx + Gly at 1 μg/mL. Summarily, was observed that the mixture of PPx + Gly potentiated the toxic effects. This finding suggests a possible synergism between the PPx and Gly even at lower concentrations.

In vitro screening of genotoxicity and mutagenicity of pyriproxyfen in human lymphocytes and Salmonella typhimurium TA98 and TA100 strains

Pyriproxyfen (PPX) is a pesticide/larvicide used to increase productivity in agriculture against insects by inhibiting development of insects' larvae. In this study, cytotoxic, genotoxic, and mutagenic effects of PPX were investigated in human peripheral lymphocytes and Salmonella typhimurium strains by performing chromosomal aberration, micronucleus (MN) tests, and Ames test, respectively. For the chromosome aberration (CA) and MN methods, blood from four healthy donors (two men and two women, nonsmokers) were used. Two hundred microliters of blood was inoculated into PbMax medium and prepared according to International Guidelines. For the Ames test, S. typhimurium TA98 and TA100 strains were used to detect frameshift and base pair substitution mutagens, respectively. PPX induced both the CA percentage and MN frequency in human peripheral lymphocytes and exhibited cytotoxic effects. In addition, it showed a mutagenic effect at all doses in TA98 and TA100 strains in the presence of S9mix; however, no such effect was observed in the absence of S9mix. According to the obtained results, it can be said that PPX has genotoxic and mutagenic potentials.

Degradation of the Novel Heterocyclic Insecticide Pyraquinil in Water: Kinetics, Degradation Pathways, Transformation Products Identification, and Toxicity Assessment

As new pesticides are continuously introduced into agricultural systems, it is essential to investigate their environmental behavior and toxicity effects to better evaluate their potential risks. In this study, the degradation kinetics, pathways, and aquatic toxicity of the new fused heterocyclic insecticide pyraquinil in water under different conditions were investigated for the first time. Pyraquinil was classified as an easily degradable pesticide in natural water, and hydrolyzes faster in alkaline conditions and at higher temperatures. The formation trends of the main transformation products (TPs) of pyraquinil were also quantified. Fifteen TPs were identified in water using ultrahigh-performance liquid chromatography coupled to quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Orbitrap-HRMS) and Compound Discoverer software, which adopted suspect and nontarget screening strategies. Among them, twelve TPs were reported for the first time and 11 TPs were confirmed by synthesis of their standards. The proposed degradation pathways have demonstrated that the 4,5-dihydropyrazolo[1,5-a]quinazoline skeleton of pyraquinil is stable enough to retain in its TPs. ECOSAR prediction and laboratory tests showed that pyraquinil was "very toxic" or "toxic" to aquatic organisms, while the toxicities of all of the TPs are substantially lower than that of pyraquinil except for TP484, which was predicted to pose a higher toxicity. The results are important for elucidating the fate and assessing the environmental risks of pyraquinil, and provide guidance for scientific and reasonable use.

Ecological threat caused by malathion and its chiral metabolite in a honey bee-rape system: Stereoselective exposure risk and the mechanism revealed by proteome

Honey bees play an important role in the ecological environment. Regrettably, a decline in honey bee colonies caused by chemical insecticides has occurred throughout the world. Potential stereoselective toxicity of chiral insecticides may be a hidden source of danger to bee colonies. In this study, the stereoselective exposure risk and mechanism of malathion and its chiral metabolite malaoxon were investigated. The absolute configurations were identified using an electron circular dichroism (ECD) model. Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for chiral separation. In pollen, the initial residues of malathion and malaoxon enantiomers were 3571-3619 and 397-402 μg/kg, respectively, and R-malathion degraded relatively slowly. The oral LD₅₀ values of R-malathion and S-malathion were 0.187 and 0.912 μg/bee with 5 times difference, respectively, and the malaoxon values were 0.633 and 0.766 μg/bee. The Pollen Hazard Quotient (PHQ) was used to evaluate exposure risk. R-malathion showed a higher risk. An analysis of the proteome, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular localization, indicated that energy metabolism and neurotransmitter transport were the main affected pathways. Our results provide a new scheme for the evaluation of the stereoselective exposure risk of chiral pesticides to honey bees.

The metabolites could not be ignored: A comparative study of the metabolite norfluoxetine with its parent fluoxetine on zebrafish (Danio rerio)

The ubiquitous pharmaceuticals in aquatic environments have attracted huge attention due to their significant risks to humans and ecosystems. However, even though the knowledge of the negative effects induced by the parent pharmaceuticals is quite extensive, little is known about their metabolites for a long time. This study provides systematical knowledge about the potential toxicity of metabolite norfluoxetine and its parent fluoxetine on zebrafish (Danio rerio) at the early life stage. The results showed that the metabolite norfluoxetine had similar acute toxicity in fish with the parent fluoxetine. For the altered fish development, there was no significant difference in most cases between the two pharmaceuticals. Compared to the control, the metabolite markedly inhibited the locomotor behavior under light-to-dark transitions, which was comparable to the parent. Norfluoxetine could easily accumulate but hardly eliminate from fish, relative to fluoxetine. In addition, the accumulated fluoxetine in zebrafish may rapidly metabolize to norfluoxetine and then be eliminated through different metabolic pathways. The functional genes related to serotonergic process (5-ht1aa, 5-ht2c, slc6a4b, and vmat), early growth (egr4), and circadian rhythm (per2) were downregulated by both the norfluoxetine and fluoxetine, indicative of the same mode-of-action of norfluoxetine with its parent in these functions. Meanwhile, the alterations caused by norfluoxetine were more pronounced than that of fluoxetine in the genes of 5-ht2c, slc6a4b, vmat, and per2. The molecular docking also confirmed that norfluoxetine could bind with serotonin transporter protein in the same as fluoxetine with a lower binding free energy. Overall, the metabolite norfluoxetine could induce similar and even more toxic effects on zebrafish with the same mode of action. The different and binding energy of the metabolite norfluoxetine and its parent fluoxetine on zebrafish may be responsible for the differentiated effects. It highlights the risks of the metabolite norfluoxetine in the aquatic environment could not be ignored.

Syringol, a wildfire residual methoxyphenol causes cytotoxicity and teratogenicity in zebrafish model

Natural toxicants, particularly methoxy phenols (MPs) generated by wildfire lignin, can accumulate in the environment, and cause serious health hazards in living organisms. Although the toxicity of MPs such as guaiacol and catechol has recently been described, there is minimal evidence of ecotoxicological effects of syringol. As a result, this study focuses on determining the toxicity by evaluating the cytotoxic and teratogenic effects of syringol in vitro and in vivo in human embryonic kidney (HEK-293) cells and zebrafish embryos, respectively. The ecotoxicity of syringol was predicted to be 63.8 mg/L using the ECOSAR (ECOlogical Structure Activity Relationship) prediction tool, and molecular docking analysis was used to determine the interaction and binding affinities of syringol with human apoptotic proteins in silico. In HEK-293 cells, exposure of syringol (0.5-2 mg/L) has induced cytotoxicity in a concentration-dependent manner. In zebrafish larvae, exposure of syringol (0.5-2 mg/L) has induced dose-dependent embryo toxic effects (or growth abnormalities such as yolk sac edema, pericardial edema, skeletal abnormality, and hyperemia), and changes in growth morphometrics (head height, eye, yolk sac, and pericardial area, heart rate) in particular, the heart rate of larvae was found to be significantly decreased (p<0.001). After a 4-day experimental trial, the accumulated concentration of syringol in zebrafish larvae was confirmed both qualitatively (HPLC-MS - High Performance Liquid Chromatography-Mass spectrometry) and quantitatively (LC-QTOF-HRMS - Liquid Chromatography-Quadrupolar Time of Flight-High Resolution Mass spectrometry). The craniofacial abnormalities induced by syringol exposure (0.5-2 mg/L) were detected as anomalies in cartilaginous development and locomotor deficits using alcian blue staining and locomotor analyses, respectively. Significant increase in oxidative stress parameters (including reactive oxygen species generation, lipid peroxidation, superoxide dismutase, catalase, lactate dehydrogenase and nitric oxide production) (p<0.001) and substantial decrease in glutathione levels were observed (p<0.05) in syringol exposed zebrafish larvae through enzymatic analysis. Additionally, through acridine orange staining and gene expression analyses, syringol (2 mg/L) was found to activate apoptosis in zebrafish larvae. Considering the cytotoxic, embryotoxic (teratogenicity), and oxidative stress-related apoptotic effects of syringol in the zebrafish model, syringol has the potential to emerge as a potent environmental toxicant posing serious health hazards in many living systems; however, further research on its toxicological effects on the actual ecosystem and in higher animal models is required to confirm its consequences.

Comprehensive evaluation of chiral penflufen metabolite (penflufen-3-hydroxy-butyl): Identification, synthesis, enantioseparation, toxicity and enantioselective metabolism

Identification and evaluations of pesticide metabolites are necessary for risk assessment and toxicological research. In this study, the metabolites of penflufen (a widely used chiral pesticide) in rat liver microsomes were identified using liquid chromatography Q-Exactive Plus mass spectrometry. In total, 17 penflufen metabolites were identified, and most of them were hydroxylation products, which were generated by oxygenation at different candidate sites of penflufen. The relative abundance of metabolite M12 (penflufen-3-hydroxy-butyl, 32 %) was the largest, followed by M8 (15.6 %) and M2 (12.8 %). The major metabolite penflufen-3-hydroxy-butyl was first synthesized by 11 reactions with a 99.73 % purity. The absolute configuration of M12 enantiomers were confirmed after preparing enantiomers, and establishing the enantioseparation method. The M12 enantiomers toxicity to Danio rerio (LC₅₀, >10 mg/L) and four kinds of phytopathogens (EC₅₀, 148-34969 mg/L) were significantly lower than parents (LC₅₀, 0.449-24.3 mg/L; EC₅₀, 0.027-92.0 mg/L). In rat liver microsomes, approximately 40-47 % of the penflufen enantiomers were metabolized to M12 enantiomers, and R-penflufen was preferentially metabolized. The generation concentrations of S-M12 were higher than R-M12 after 10 min, and the metabolic half-lives of R-M12 (29.0-32.5 min) were shorter than S-M12 (35.2-38.1 min), and were approximately 4 times longer than parent penflufen enantiomers (4.5-9.5 min). Simultaneously, the generated contents (relative contents) of M8 (27.1-57 %) and M10 (2.22-8.36 %) from S-penflufen were lower than those from R-penflufen (M8, 24.7-92.4 %; M10, 27.4-69.5 %). The enantioselective evaluations of M12, M10 and M8 deserve further study. These findings were helpful in understanding the fate and risks of chiral penflufen.

Stereoselective toxicity, bioaccumulation, and metabolic pathways of triazole fungicide cyproconazole in zebrafish

Cyproconazole (CPZ) is a broad-spectrum fungicide that is widely used around the world. CPZ can persist in water which raised concerns about its potential adverse effects on aquatic life. In this study, the stereoselective toxicity, bioaccumulation, elimination, and kinetic biotransformation in zebrafish were investigated. The LC₅₀ of 96 h acute toxicity was 15.88, 19.68, 26.99, and 17.10 mg/L for SR-, SS-, RS-, and RR-CPZ, respectively. The uptake and elimination experiment showed the bioconcentration factor in order of SR- > RR- > SS- > RS-CPZ at the exposure concentration of 0.1 and 1 mg/L. In the depuration stage, CPZ isomers were rapidly eliminated by 99% within 24 h. Moreover, the oxidative stress responses (POD, SOD, and CAT) were stereoselectively induced by CPZ stereoisomers, the activity of POD was significantly increased in all CPZ treatment groups compared to the control while the activity of CAT exhibited a concentration-dependent decrease in the CPZ treatment group. Multiple metabolic pathways of CPZ in zebrafish were proposed for the first time and 7 phase I metabolites and 25 phase II conjugates were found. This study determined the potential toxicity of CPZ to zebrafish and provided a strategy for the risk evaluation of CPZ stereoisomers in aquatic ecosystems.

Comprehensive study of pydiflumetofen in Danio rerio: Enantioselective insight into the toxic mechanism and fate

Pydiflumetofen (PYD) is primarily used to control fungal disease. The potential risks posed by PYD enantiomers to the aquatic ecosystem are currently unclear. In this study, the enantioselective toxicity and fate of PYD in Danio rerio were investigated, and the enantioselective toxic mechanism and metabolic pathway were explored. The acute toxicity of R-PYD was 10.7-14.7-fold than that of S-PYD against Danio rerio embryos, larvae, and adults. Meanwhile, R-PYD presented a stronger effect on embryo hatching and abnormalities, adult tissue damage and oxidative stress. R-PYD inhibited the succinate dehydrogenase (SDH) activity more than S-PYD because of its better interaction with SDH with a lower binding free energy (-59.35 kcal/mol), explaining the mechanism of enantioselective toxicity. Remarkable enantioselectivity was observed in uptake, distribution, and elimination. R-PYD showed preferential uptake with the higher uptake rate constants and slow metabolism with a longer half-life, resulting in the bioaccumulation of R-PYD with higher BCF_k (7.37 at 0.05 mg/L and 14.69 at 0.2 mg/L). Besides, muscle is an important tissue for PYD accumulation, existing potential food risk. Eleven PYD metabolites were qualitatively identified, and the metabolic pathway was proposed, including hydroxylation, N-demethylation, demethoxylation, hydrolysation (phase Ⅰ), and acetylation and glucuronidation (phase Ⅱ). The predicted toxicity of the metabolite indicated that several highly toxic metabolites need to be considered in the future. This study provides a new perspective for evaluating the ecological and human health risks of chiral pesticides.

Systemic assessment of the chiral insecticide pyriproxyfen in a citrus nectar source system: Stereoselective degradation, biological effect and exposure risk

BACKGROUND

Balancing the safety and efficiency of chiral pesticides can help protect pollinators. We evaluated the stereoselective behavior, bioactivity, toxicity and exposure risk of the chiral insecticide pyriproxyfen in a citrus nectar system.

RESULTS

Density functional theory (DFT) and ultra-performance liquid chromatography tandem mass spectroscopy (UPLC-MS/MS) were applied for absolute configuration appraisal and chiral analysis validation, respectively. The recoveries ranged from 72.3% to 100.5% with an relative standard deviation (RSD) ranging from 1.2% to 9.7%. In a field trial, we determined insecticide half-lives in citrus leaves and flowers, which were 7.0 and 8.6 days for R-(+)-pyriproxyfen, and 11.7 and 14.7 days for S-(-)-pyriproxyfen, respectively. We found that the bioactivity of R-(+)-pyriproxyfen was 3.39 and 2.37 times higher than S-(-)-pyriproxyfen against Unaspis yanonensis and Diaphorina citri nymphs, respectively. S-(-)-pyriproxyfen had 3.8 times higher acute toxicity than R-(+)-pyriproxyfen on Apis mellifera L., and its exposure risk was moderate based on the hazard quotient.

CONCLUSION

The phenomenon of stereoselective degradation and biological effect demonstrated that the high-risk stereoisomer of S-(-)-pyriproxyfen degraded more slowly than R-(+)-pyriproxyfen, but R-(+)-pyriproxyfen with better efficiency for target. Therefore, an increased duration of R-(+)-pyriproxyfen activity on citrus was beneficial for efficacy. Our results could guide the scientific application and evaluation of chiral pesticides on nectar plants. © 2022 Society of Chemical Industry.

Evaluation of DNA Damage, Biomarkers of Oxidative Stress, and Status of Antioxidant Enzymes in Freshwater Fish (Labeo rohita) Exposed to Pyriproxyfen

Pyriproxyfen (PPF) mimics a natural hormone in insects and disrupts their growth. It is a well-known synthetic insecticide and aromatic juvenile hormone analog frequently used in agriculture and vegetable crops to control various insect species. At present, scanty information is available about the possible potential threats of PPF in aquatic organisms. Therefore, in this study, different toxico-pathologic endpoints of PPF like DNA damage, biomarkers of oxidative stress, and status of antioxidant enzymes were determined in Labeo rohita (freshwater fish). In our study, 60 active, free from any external obvious ailments, same size, age, and body mass were randomly allocated to four glass aquaria (T0-T3) separately containing 100 L water. The fish present in groups T1, T2, and T3 were administered PPF dissolved in water 300, 600, and 900 μg/L for 30 days. Different tissues including the blood and visceral organs were obtained from each fish on days 10, 20, and 30 of the experiment. Results on various morphological and nuclear changes in red blood cells of PPF-exposed Labeo rohita fish including pear-shaped erythrocytes, spherocytes, red blood cells with a blebbed nucleus, micronucleus, and nuclear remnants were significantly increased. Our results on genotoxicity (comet assay) recorded significantly (P ≤ 0.05) increased DNA damage in various tissues of insecticide-exposed fish. The results on oxidative stress profile (reactive oxygen species and thiobarbituric acid reactive substances) and antioxidant enzymes (reduced glutathione superoxide dismutase, peroxidase, and catalase) in multiple tissues of Labeo rohita fish concluded significantly (P ≤ 0.05) higher quantity of biomarkers of oxidative stress and lower concentrations of different antioxidant enzymes in treated fish. Hence, the findings of our experimental research determine that PPF could induce adverse toxic impacts on multiple tissues of Labeo rohita fish.

Sex-related deposition and metabolism of vanisulfane, a novel vanillin-derived pesticide, in rats and its hepatotoxic and gonadal effects

A series of vanillin derivatives have recently been synthesized as effective candidate antiviral agents, with vanisulfane exhibiting pronounced curative and protective activities against cucumber mosaic virus and potato virus Y. However, research on some new pesticides usually ignores their various metabolites and sex-related toxicity. Assisted by ¹⁴C labeling, a trial was conducted to investigate the tissue distribution, excretion, and metabolism of vanisulfane in male and female rats for the first time. The results showed that 83.30-87.51% of applied ¹⁴C activity was excreted in urine and feces within 24 h of oral administration, and ¹⁴C was most abundant in the liver and kidney in both sexes. Interestingly, sex differences were observed in the experiment, with lower body clearance in males than in females 24 h after treatment and preferences for biliary and renal excretion of the pesticide in male and female rats, respectively. A high degradation rate was found for vanisulfane in the plasma; thus, the metabolites of vanisulfane were investigated using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) combined with ¹⁴C labeling. One glucuronic acid conjugate and two oxidation metabolites were detected, supporting the monitoring of vanisulfane in vivo. Additionally, rats exposed to vanisulfane exhibited hepatic steatosis in both sexes, along with mild gonadal effects in males. This research offers an effective method for conducting environmental behavioral research and provides new insights for evaluating the potential risks of novel pesticides in mammals from a sex perspective.

Low-dose cadmium affects the enantioselective bioaccumulation and dissipation of chiral penflufen in zebrafish (Danio rerio)

Pesticides are currently extensively used in agriculture, forestry, animal husbandry, and environmental hygiene, and their residues have become a global environmental problem, which can easily form combined pollution with heavy metals. The present study examined the effects of chronic (28 days) aqueous exposure of chiral penflufen (rac-penflufen, R-(-)-penflufen and S-(+)-penflufen), a widely used fungicide, with/without cadmium (Cd), a highly toxic heavy metal in zebrafish (Danio rerio). After rac-penflufen individual or combined exposure with Cd, the bioaccumulation and residual levels of S-(+)-penflufen were significantly higher than R-(-)-penflufen, and the effects of Cd were insignificantly. But for penflufen enantiomer, the effects of Cd were more serious for R-(-)-penflufen, which could increase the bioaccumulation (up to1.73 times), inhibit the dissipation (up to 32.3%) and enhance the residue (up to 5.35 times) of R-(-)-penflufen in zebrafish, decreasing the enantioselectivity. However, significant increase of S-(+)-penflufen concentrations was only found in viscera under co-exposure of Cd. The tissue distribution of penflufen enantiomers were not affected by the presence of Cd, and no interconversion of the two enantiomers occurred regardless of the presence of Cd. These findings indicated that co-contamination with Cd could increase the persistence of R-(-)-penflufen in zebrafish, thus increasing the environmental risks. The significant differences of Cd effects on chiral pesticide enantiomer and racemate indicated that the combined pollution of heavy metal and chiral pesticide might have enantiomer-specific, which should raise concern, and the enantioselective mechanism deserve further study.