The enantioselective toxicity and oxidative stress of beta-cypermethrin on zebrafish

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.

One step cleanup of 160 pesticides and veterinary drugs in aquatic products using melamine-based automatic pressure filtration purification method combined with HPLC-MS/MS

A 15-channel pressure filtration purification method was presented for high throughput sample preparation of aquatic products. A cost-effective device was constructed and melamine sponge was selected as the cleanup sorbent. Upon interfacing with HPLC-MS/MS, the analytical procedure demonstrated its suitability for quantifying 160 pesticides and veterinary drug residues in aquatic products such as fish, shrimp, and crab. The method achieved sample recoveries ranging from 61.3 to 124.9 %. The detection limits were established between 0.5 and 1.0 μg/kg, while the quantitation limits were confirmed to be within the range of 1.0-2.0 μg/kg. The method was applied to quantify the pesticide and veterinary drug residues in mostly consumed aquatic products from five coastal provinces in China. The results showed significant differences between different aquatic products in the concentrations of pesticide and veterinary drug residues, implying the necessity of supervision for the accurate determination of pesticides and veterinary drugs.

AhR agonists screening and identification in indoor dust based on non-target chemical analysis by GC-Q-TOFMS and biological effect evaluation referring to ToxCast/Tox21 database

Numerous studies reported the concentration of agonists of aryl hydrocarbon receptor (AhR) in indoor dust by target chemical analysis or the biological effects of activating the AhR by indoor extracts, but the major AhR agonists identification in indoor dust were rarely researched. In the present study, the indoor dust samples were collected for 7-ethoxyresorufin O-deethylase (EROD) assay and both non-targeted and targeted chemical analysis for AhR agonists by gas chromatography quadrupole time-of-flight mass spectrometry and gas chromatography-mass spectrometry analysis. Coupled with non-targeted analysis and toxicity Forecaster (ToxCast)/Tox21 database, 104 ToxCast chemicals were screened to be able to induce EROD response. The combination of targeted chemical analyses and biological effects evaluation indicated that PAHs, dibutyl phthalate (DBP) and Cypermethrin might be the important AhR-agonists in different indoor dust and mainly contributed in 1.84%-97.56 % (median: 26.62%) of total observed biological effects through comparing toxic equivalency quotient derived from chemical analysis with biological equivalences derived from bioassay. DBP and cypermethrin seldom reported in the analysis of AhR agonists should raise great concern. In addition, the present results in experiment of synthetic solution of 4 selected AhR-agonists pointed out that some unidentified AhR agonists existed in indoor dust.

Toxic effect and mechanism of β-cypermethrin and its chiral isomers on HTR-8/SVneo cells

Beta-cypermethrin (β-CYP) consists of four chiral isomers, acting as an environmental estrogen and causing reproductive toxicity, neurotoxicity, and dysfunctions in multiple organ systems. This study investigated the toxic effects of β-CYP, its isomers, metabolite 3-phenoxybenzoic acid (3-PBA), and 17β-estradiol (E2) on HTR-8/SVneo cells. We focused on the toxic mechanisms of β-CYP and its specific isomers. Our results showed that β-CYP and its isomers inhibit HTR-8/SVneo cell proliferation similarly to E2, with 100 μM 1S-trans-αR displaying significant toxicity after 48 h. Notably, 1S-trans-αR, 1R-trans-αS, and β-CYP were more potent in inducing apoptosis and cell cycle arrest than 1R-cis-αS and 1S-cis-αR at 48 h. AO/EB staining and flow cytometry indicated dose-dependent apoptosis in HTR-8/SVneo cells, particularly at 100 μM 1R-trans-αS. Scratch assays revealed that β-CYP and its isomers variably reduced cell migration. Receptor inhibition assays demonstrated that post-ICI 182780 treatment, which inhibits estrogen receptor α (ERα) or estrogen receptor β (ERβ), β-CYP, its isomers, and E2 reduced HTR-8/SVneo cell viability, whereas milrinone, a phosphodiesterase 3 A (PDE3A) inhibitor, increased viability. Molecular docking studies indicated a higher affinity of β-CYP, its isomers, and E2 for PDE3A than for ERα or ERβ. Consequently, β-CYP, its isomers, and E2 consistently led to decreased cell viability. Transcriptomics and RT-qPCR analyses showed differential expression in treated cells: up-regulation of Il24 and Ptgs2, and down-regulation of Myo7a and Pdgfrb, suggesting the PI3K-AKT signaling pathway as a potential route for toxicity. This study aims to provide a comprehensive evaluation of the cytotoxicity of chiral pesticides and their mechanisms.

Vitamin E alleviates pyraclostrobin-induced toxicity in zebrafish (Danio rerio) and its potential mechanisms

Strobilurin fungicides (SFs) are commonly used in agriculture worldwide and frequently detected in aquatic environments. High toxicity of SFs to aquatic organisms has caused great concerns. To explore whether vitamin E (VE) can relieve the toxicity caused by pyraclostrobin (PY), zebrafish were exposed to PY with or without VE supplementation. When co-exposure with VE (20 μM), the 96 h-LC50 values of PY to zebrafish embryos, adult, and the 24 h-LC50 value of PY to larvae increased from 43.94, 58.36 and 38.16 μg/L to 64.72, 108.62 and 72.78 μg/L, respectively, indicating that VE significantly decreased the toxicity of PY to zebrafish at different life stages. In addition, VE alleviated the deformity symptoms (pericardial edema and brain damage), reduced speed and movement distance, and decreased heart rate caused by 40 μg/L PY in zebrafish larvae. Co-exposure of PY with VE significantly reduced PY-caused larval oxidative stress and immunotoxicity via increasing the activities of superoxide dismutase, catalase and level of glutathione, as well as reducing the malondialdehyde production and the expression levels of Nrf2, Ucp2, IL-8, IFN and CXCL-C1C. Meanwhile, the expression levels of gria4a and cacng4b genes, which were inhibited by PY, were significantly up-regulated after co-exposure of PY with VE. Moreover, co-exposure with VE significantly reversed the increased mitochondrial DNA copies and reduced ATP content caused by PY in larvae, but had no effect on the expression of cox4i1l and activity of complex III that reduced by PY, suggesting VE can partially improve PY-induced mitochondrial dysfunction. In conclusion, the potential mechanisms of VE alleviating PY-induced toxicity may be ascribed to decreasing the oxidative stress level, restoring the functions of heart and nervous system, and improving the immunity and mitochondrial function in zebrafish.

Co-exposure to polystyrene microplastics and cypermethrin enhanced the effects on hepatic phospholipid metabolism and gut microbes in adult zebrafish

Microplastics (MPs) can absorb environmental pollutants from the aquatic environment to cause mixed toxicity, which has received widespread attention. However, studies on the joint effects of MPs and insecticides are limited. As one of the most widely used pyrethroids, there was a large amount of residual cypermethrin (CYP) in water due to insufficient decomposition. Here, adult female zebrafish were exposed to MPs, CYP, and their mixtures for 21 days, respectively. After exposures, the MPs and CYP caused tissue damage to the liver. Hepatic triglyceride (TG) level increased significantly after MPs + CYP exposure, and the expression of genes about glycolipids metabolism was significantly altered. Furthermore, metabolome results suggested that MPs + CYP exposure resulted in increased content of some glycerophospholipid, affecting phospholipid metabolism-related pathways. In addition, through 16 s rDNA sequencing, it was found that MPs + CYP led to significant changes in the proportion of dominant phyla. Interestingly, Cetobacterium which increased in CYP and the co-exposure group was positively correlated with most lipid metabolites. Our results suggested that co-exposure to MPs and CYP enhanced the disturbances in hepatic phospholipid metabolism by affecting the gut microbial composition, while these changes were not observed in separate treatment groups. These results emphasized the importance of studying the joint toxicity of MPs and insecticides.

Enantioselectivity in ecotoxicity of pharmaceuticals, illicit drugs, and industrial persistent pollutants in aquatic and terrestrial environments: A review

At present, there is a serious concern about the alarming number of recalcitrant contaminants that can negatively affect biodiversity threatening the ecological status of marine, estuarine, freshwater, and terrestrial ecosystems (e.g., agricultural soils and forests). Contaminants of emerging concern (CEC) such as pharmaceuticals (PHAR), illicit drugs (ID), industrial persistent pollutants, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and chiral ionic solvents are globally spread and potentially toxic to non-target organisms. More than half of these contaminants are chiral and have been measured at different enantiomeric proportions in diverse ecosystems. Enantiomers can exhibit different toxicodynamics and toxicokinetics, and thus, can cause different toxic effects. Therefore, the enantiomeric distribution in occurrence cannot be neglected as the toxicity and other adverse biological effects are expected to be enantioselective. Hence, this review aims to reinforce the recognition of the stereochemistry in environmental risk assessment (ERA) of chiral CEC and gather up-to-date information about the current knowledge regarding the enantioselectivity in ecotoxicity of PHAR, ID, persistent pollutants (PCBs and PBDEs) and chiral ionic solvents present in freshwater and agricultural soil ecosystems. We performed an online literature search to obtain state-of-the-art research about enantioselective studies available for assessing the impact of these classes of CEC. Ecotoxicity assays have been carried out using organisms belonging to different trophic levels such as microorganisms, plants, invertebrates, and vertebrates, and considering ecologically relevant aquatic and terrestrial species or models organisms recommended by regulatory entities. A battery of ecotoxicity assays was also reported encompassing standard acute toxicity to sub-chronic and chronic assays and different endpoints as biomarkers of toxicity (e.g., biochemical, morphological alterations, reproduction, behavior, etc.). Nevertheless, we call attention to the lack of knowledge about the potential enantioselective toxicity of many PHAR, ID, and several classes of industrial compounds. Additionally, several questions regarding key species, selection of most appropriate toxicological assays and ERA of chiral CEC are addressed and critically discussed.

Co-exposure to sodium hypochlorite and cadmium induced locomotor behavior disorder by influencing neurotransmitter secretion and cardiac function in larval zebrafish

Sodium hypochlorite (NaClO) and cadmium (Cd) are widely co-occurring in natural aquatic environment; however, no study has been conducted on effects of their combined exposure on aquatic organisms. To assess effects of exposure to NaClO and Cd in zebrafish larvae, we designed six treatment groups, as follows: control group, NaClO group (300 μg/L), 1/100 Cd group (48 μg/L), 1/30 Cd group (160 μg/L), NaClO+1/100 Cd group, and NaClO+1/30 Cd group analyzed behavior, neurological function and cardiac function. Results revealed that exposure to 1/30 Cd and NaClO+1/30 Cd caused abnormal embryonic development in larvae by altering body morphology and physiological indicators. Combined exposure to NaClO and 1/30 Cd affected the free-swimming activity and behavior of larvae in response to light-dark transition stimuli. Moreover, exposure to 1/30 Cd or NaClO+1/30 Cd resulted in a significant increase in tyrosine hydroxylase and acetylcholinesterase activities, as well as significant changes of various neurotransmitters. Lastly, exposure to 1/30 Cd or NaClO+1/30 Cd influenced the transcription of cardiac myosin-related genes and disturbed the myocardial contractile function. Altogether, our results suggested that combined exposure to NaClO and Cd induced oxidative damage in larvae, resulting in detrimental effects on nervous system and cardiac function, thus altering their swimming behavior.

Stereoselective metabolic disruption of cypermethrin by remolding gut homeostasis in rat

Cypermethrin (CYP), a prototypical synthetic pyrethroid, reportedly causes metabolic disruption, while its stereoselective impact remains elusive. This study initially revealed that only α-CYP caused significant weight loss at 8.5 mg/(kg•day) in rats. All three CYP isomers caused the accumulation of hepatic glycogen, and hyperlipemia phenotype as the increment of total triglyceride. Rats treated with α-CYP had markedly high blood glucose levels and homeostasis model assessment of insulin resistance index. The systematic inflammation of θ-CYP group rats was evidenced by high lipopolysaccharide-binding protein levels and abnormalities of leukocytes indices. By examining the gut microbiome, we found that α-CYP-treated rats had low contents of Firmicutes and high levels of Verrucomicrobia while Elusimicrobia was enriched in the β-CYP group. The increasing alpha diversity in the θ-CYP group may be due to the dominance of pathogenic bacteria and the increase of probiotics to counteract adverse effects. Exclusively, the α-CYP group enriched total short-chain fatty acids (SCFAs), whereas most SCFAs depleted in the θ-CYP group. The correlation analysis further found Firmicutes, an energy storage modulator, was positive to body weight (BW), while SCFAs exerted the opposite, confirming the low BW in α-CYP. Blood glucose that correlated well with SCFAs and Verrucomicrobia can be accounted for the discrepancy between α-CYP and θ-CYP. Overall, the three isomers exerted stereoselective glycolipid disruption in rats, and gut homeostasis acted as vital indicators.

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.

Effects of single and combined exposure to zinc and two tetracycline antibiotics on zebrafish at the early stage

Tetracycline antibiotics (TCs) and heavy metals are commonly used in livestock and poultry farming, leading to their coexistence in the aquatic environment. This coexistence causes combined toxicity to aquatic organisms. Here, zebrafish embryos were exposed to chlortetracycline (CTC), oxytetracycline (OTC), zinc chloride (ZnCl₂), and their combinations for 120 h to evaluate their adverse effects on the growth, antioxidant system, immune system, and endocrine system during the early stage of life. OTC/ZnCl₂ combined exposure significantly reduced the body weight, whereas the TCs/ZnCl₂ combination significantly increased the heart rate of zebrafish larvae, suggesting growth impairment induced by TCs and ZnCl₂. Further, combined groups showed more prominent toxicity to the antioxidant system than single groups, as revealed by related levels of enzyme activity and gene expression. In addition, the levels of most pro-inflammatory genes were downregulated, and those of NF-κB-related genes were upregulated in all treatment groups, indicating an immunosuppressive response and the potential role of NF-κB signaling, while the combined treatment was not more toxic than TCs or ZnCl₂ alone. Similarly, hormone and endocrine related gene levels were determined. Although both single and combined exposures caused certain endocrine-disrupting effects, the combined exposure did not result in higher toxicity than a single exposure. Our findings showed that a mixture of TCs and ZnCl₂ might exert greater toxic effects as compared to a single compound on some systems, providing fundamental data on the toxic effects of single and combined TC and ZnCl₂ exposure on aquatic organisms, although studies are needed to explore the underlying mechanisms.

In silico and in vivo assessment of developmental toxicity, oxidative stress response & Na+/K+-ATPase activity in zebrafish embryos exposed to cypermethrin

Cypermethrin (CYP), a synthetic type II pyrethroid pesticide, is extensively used to control pests in industrial, domestic, and agricultural environments. However, its indiscriminate use leads to a potential threat to aquatic organisms. Although several reports focussed on developmental toxicity effects, a concise study combining cardiotoxicity along with Na⁺/K⁺-ATPase activity and molecular docking of developmental proteins with CYP was lacking. This present study was designed to address this gap to comprehend the impact of CYP exposure (0, 25, 100 and 200 µg/L) on embryonic zebrafish. As a result, CYP delayed the hatching rate, reduced heart rate, increased mortality rate and induced numerous morphological abnormalities. Subsequently, CYP induced oxidative stress in treated zebrafish embryos with the concomitant increase in antioxidant enzymes (SOD and CAT) and malondialdehyde production. In addition, an alteration in AChE, NO content and Na⁺/K⁺-ATPase activity was observed, suggesting a disruption in cardiac development and ion regulation. Furthermore, AO staining showed notable apoptotic cells which are supported by alteration in apoptosis-related gene expressions. Moreover, to explore the putative targets of CYP, computational docking with developmental proteins (WNT3A, WNT8A, GATA-4, Nkx 2-5 and ZHE1) showed strong interactions and binding. Taken together, our findings provide a better understanding of assessing the ecotoxicological risk information and the mode of action underlying the development of teleost fishes following CYP exposure. Meanwhile, the pioneering nature of this study is to emphasize the future use of Na⁺/K⁺-ATPase activity as a potential toxicity biomarker and in silico molecular docking studies to complement developmental toxicity findings.

Bromuconazole exposure induces cardiotoxicity and lipid transport disorder in larval zebrafish

Bromuconazole (BRO), as one of the typical triazole fungicides, has not been reported on its effects on aquatic organisms. In this study, zebrafish embryos were used as experimental objects to evaluate the toxicity of BRO. In the acute embryo toxicity test, it was observed that the heart rate and growing development were affected by BRO in a concentration-dependent manner, and the half-lethal concentration (LC50) of BRO at 96 h post-fertilization (hpf) was about 11.83 mg/L. Then, low concentrations of BRO (50 ng/L, 0.075 mg/L, 0.3 mg/L, 1.2 mg/L), which were set according to the LC50 and environmental related concentrations, were used to analyze the toxic effects on the different endpoints in larval zebrafish. Interestingly, the transcriptomic analysis found that most different expressed genes (DEGs) could be focused on the pathways of lipid metabolism, myocardial function, glycometabolism, indicating that heart function and lipid metabolism in larval zebrafish were disrupted by BRO. For supporting this idea, we re-exposed the transgenic zebrafish and WT zebrafish embryos, proved that BRO caused damage to heart development and lipid transport on morphological and genetic level, which was consistent with transcriptomic results. In addition, BRO exposure caused oxidative damage in the larvae. Taken together, BRO exposure could affect the myocardial contraction function and lipid transport in larval zebrafish, accompanied by disturbances in the level of oxidative stress, which was of great significance for improving the biotoxicological information of BRO.

Integrated toxicity assessment of DEHP and DBP toward aquatic ecosystem based on multiple trophic model assays

To comprehensively understand the toxic risks of phthalates to aquatic ecosystems, we examined the acute toxicity of di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) on multiple trophic models, including algae (Chlorella vulgaris), Daphnia magna and fish (Danio rerio, Pseudorasbora parva). Thus, a 15-day zebrafish exposure was conducted to trace the dynamic changes of phthalate-induced toxic effects. Among the four species, D. magna exhibited the strongest sensitivity to both DEHP and DBP, followed by D. rerio and P. parva. C. vulgaris exhibited the lowest sensitivity to phthalates. The sub-chronic zebrafish assay demonstrated that 1000 μg/L DBP induced significant mortality at 15 days post-exposure (dpe), and DEHP exhibited no lethality at the tested concentrations (10-5000 μg/L). Zebrafish hepatic SOD activity and sod transcription levels were inhibited by DBP from 3 dpe, which was accompanied by increased malondialdehyde level, while zebrafish exposed to DEHP exhibited less oxidative damage. Both DEHP and DBP induced time-dependent alterations on Ache activity in zebrafish brains, thus indicating the potential neurotoxicity toward aquatic organisms. Additionally, 1000 μg/L and higher concentration of DBP caused hepatic DNA damage in zebrafish from 7 dpe. These results provide a better understanding of the health risks of phthalate to water environment.

Avermectin induces carp neurotoxicity by mediating blood-brain barrier dysfunction, oxidative stress, inflammation, and apoptosis through PI3K/Akt and NF-κB pathways

Avermectin, a "low toxicity insecticide", has been widely used in recent years, but its non-target toxicity, especially to aquatic organisms, has been neglected. In this study, we evaluated the neurotoxic effects of avermectin on carp by establishing a 96 h avermectin acute toxicity test, and its possible mechanism was discussed. The 96 h LC₅₀ of avermectin in carp was found to be 24.04 μg/L. Therefore, 3.005 μg/L and 12.02 μg/L were used as the low-dose and high-dose groups, respectively, to investigate the neurotoxic effects of avermectin on carp. The results of high-performance liquid chromatography (HPLC) analysis showed that avermectin accumulated in the carp brain. Histopathological observation and immunohistochemical analysis (IHC) of TNF-α and Bax showed that avermectin exposure led to inflammatory cell infiltration and neuronal necrosis. The mRNA levels of tight junction genes and the IHC results of ZO-1 and Occludin showed that the structure of the blood-brain barrier (BBB) was destroyed. Biochemical analysis showed that avermectin induced the accumulation of MDA in the brain and decreased the activity of antioxidant enzymes CAT and SOD, leading to oxidative stress. In addition, avermectin induces brain inflammation by activating NF-κB pathway and releasing inflammatory factors IL-1β, IL-6, TNF-α and iNOS. TEM and TUNEL assays showed that exposure to avermectin induced apoptosis in brain. what is more, the expression of apoptosis-related genes and proteins suggested that avermectin-induced apoptosis may be associated with inhibition of the PI3K/Akt signaling pathway. This study also showed that avermectin-induced NF-κB signaling activation was partially dependent on its upstream PI3K/Akt signaling pathway. Therefore, this study concludes that avermectin can induce neurotoxicity in carp by disrupting the blood-brain barrier structure and generating oxidative stress, inflammation, and apoptosis and that NF-κB and PI3K/Akt signaling pathways are involved in this process.

Combined ingestion of polystyrene microplastics and epoxiconazole increases health risk to mice: Based on their synergistic bioaccumulation in vivo

Microplastic and pesticide are two common environmental pollutants whose adverse effects have been widely reported, but it is unclear whether they cause combined toxicity in mammals. In this study, polystyrene microplastics (5 µm, 0.012 or 0.120 mg/kg) or/and epoxiconazole (0.080 mg/kg) were administered orally to mice for 6 weeks, their toxicity to liver and kidney was assessed from changes in histopathology, tissue function, oxidative defense system and metabolic profile. In addition, mechanism of combined toxicity was explored in terms of bioaccumulation levels, intestinal barrier, gut microbiota. Results showed that combined ingestion of polystyrene (0.120 mg/kg) and epoxiconazole caused more severe tissue damage, dysfunction, oxidative stress, and metabolic disorders compared to single exposure sources. Interestingly, occurrence of combined toxicity was associated with their increased accumulation in tissues. In-depth exploration found that epoxiconazole caused intestinal barrier damage by targeting the gut microbiota, leading to massive invasion and accumulation of polystyrene, which in turn interfered with the metabolic clearance of epoxiconazole in liver. In all, findings highlighted that polystyrene and epoxiconazole could cause combined toxicity in mice through the synergistic effect of their bioaccumulation in vivo, which provided new reference for understanding the health risks of microplastics and pesticides and sheds light on the potential risk to humans of their combined ingestion.

Enantioselective bioaccumulation, oxidative stress, and thyroid disruption assessment of cis-metconazole enantiomers in zebrafish (Danio rerio)

Chiral triazole pesticides may cause enantioselectively adverse effects to non-target organisms. In this work, we employed zebrafish as an aquatic organism model to explore stereoselective acute toxicity, bioaccumulation, oxidative stress, and thyroid disruption of cis-metconazole enantiomers. The median lethal concentration values of (1S, 5R)-metconazole, (1R, 5S)-metconazole, and the mixture of them against zebrafish were 4.01, 2.61 and 3.17 mg⋅L^-1, respectively. (1R, 5S)-Metconazole was preferentially bioaccumulated in zebrafish than (1S, 5R)-metconazole, and the bioconcentration factor of (1R, 5S)-metconazole was 1.28-fold larger than that of (1S, 5R)-metconazole. Then, the activity order of catalase, superoxide dismutase, and glutathione-S transferase enzymes in zebrafish was expressed as (1S, 5R)-metconazole > the mixture > (1R, 5S)-metconazole, while the order of malondialdehyde content in zebrafish was (1R, 5S)-metconazole > the mixture > (1S, 5R)-metconazole. Moreover, cis-metconazole exhibited enantioselective regulation effects on the levels of triiodothyronine and thyroxine in zebrafish, and (1R, 5S)-metconazole possessed stronger thyroid disruption ability to zebrafish than the others. By virtue of molecular docking methodology, the binding affair and docking energy results supported that interactions between (1R, 5S)-metconazole and thyroid hormone receptors were much stronger than those between (1S, 5R)-metconazole and same receptors. This study of enantioselective evaluation of cis-metconazole in zebrafish can provide favorable information for risk assessments of chiral pesticides toward environment and health of aquatic organisms.

Enantioselective acute toxicity, oxidative stress effects, neurotoxicity, and thyroid disruption of uniconazole in zebrafish (Danio rerio)

Uniconazole is a widely used plant growth retardant in the agricultural field. However, toxicological effects of uniconazole in aquatic ecosystem at chiral level are still unclear. Herein, acute toxicity, oxidative stress effects, neurotoxicity, and thyroid disruption of uniconazole enantiomers were investigated through using zebrafish as a model. (R)-Uniconazole possessed 1.16-fold greater acute toxicity to zebrafish than (S)-enantiomer. Then, integrated biomarker response values of oxidative stress parameters in zebrafish exposed to (R)-uniconazole were about 1.27~1.53 times greater than those treated by (S)-uniconazole, revealing that (R)-uniconazole could result in more significant adverse effects than (S)-uniconazole. Subsequently, the results of acetylcholinesterase activity of experimental fish demonstrated a state of inhibition-activation-inhibition after 14-day exposure to uniconazole, and a significant enantioselective neurotoxicity of uniconazole was observed in zebrafish after exposure for 4 and 7 days (p < 0.05). Moreover, thyroxine and triiodothyronine contents in (R)-uniconazole-exposed zebrafish were 0.89-fold (p=0.007) and 0.80-fold (p=0.007) than those in (S)-enantiomer-treated group, respectively. Furthermore, molecular docking results between uniconazole enantiomers and thyroid hormone receptors revealed that (R)-uniconazole was more tightly bound than (S)-uniconazole to the receptors. Briefly, our findings provide favorable information for ecological risk assessments of chiral agrochemicals in the environment and health of aquatic organisms.

Protective effects of 5-aminolevulinic acid against toxicity induced by alpha-cypermethrin to the liver-gut-microbiota axis in zebrafish

To explore whether and how 5-aminolevulinic acid (ALA) can relieve the toxicity to the liver-gut-microbiota axis caused by alpha-cypermethrin (α-CP), adult zebrafish were exposed to α-CP (1.0 µg L-1) with or without 5.0 mg L-1 ALA supplementation. In the present work, the calculated LC50 of α-CP+ALA was 1.15 μg L-1, increasing about 1.16-fold compared with that of α-CP group (0.99 μg L-1), which indicated that ALA can alleviate the toxicity of α-CP. ALA also alleviated the histopathological lesions in the liver and gut induced by α-CP. Transcriptome sequencing of the liver showed that ALA rescues the differential expression of genes involved in the oxidation-reduction, heme metabolism, and complement activation pathways associated with dysfunctions induced by α-CP, and these findings were verified by RT-qPCR analysis and detection of the activities of enzymes in the liver-gut axis. The gut microbiota 16S rRNA sequencing results showed that α-CP alone induced gut microbial dysbiosis, which was efficiently antagonized by ALA due to decreasing the relative abundances of Cetobacterium and 3 major pathogens, and increasing the relative abundances of beneficial genera. Taken together, the results indicate that ALA might be a promising candidate for attenuating the adverse effects caused by pesticide-induced environmental pollution.

Ecotoxicological evaluation of zebrafish liver (Danio rerio) induced by dibutyl phthalate

Dibutyl phthalate (DBP), one of the most commonly applied plasticizers, has been frequently detected in the aquatic environment, posing potential risks to aquatic organisms. Currently, reports about the toxicity of zebrafish liver with DBP exposure are rare, and the toxic mechanism is still not clear. In this study, zebrafish (Danio rerio) were used to explore the ecotoxicological effects of DBP from the physiological, biochemical, genetic, and molecular levels. The results showed oxidative stress, lipid peroxidation, and DNA damage occurred in zebrafish liver according to changes in antioxidant enzymes, MDA and 8-OHdG content. AchE activity was always active, and negatively correlated with the DBP concentration. The expression of Cu/Zn-sod and gpx genes were similar to that of antioxidant enzymes from 7 to 21 days, while in the end, the inconsistent result appeared due to the time lag effect in protein modification, gene transcription and translation. Besides, the mRNA abundance of Caspase-3 and p53 were upregulated, showing a "dose-response" relationship. The integrated biomarker reaction indicated that the effects of exposure time on zebrafish liver was 14th day> 28th day> 7th day> 21th day. These results are of great significance to evaluate the toxicological effects and explore the toxic mechanism of DBP on aquatic organisms.

A comprehensive review of 1,2,4-triazole fungicide toxicity in zebrafish (Danio rerio): A mitochondrial and metabolic perspective

In this critical review, we synthesize data from peer-reviewed literature reporting on triazole fungicide exposures in the zebrafish model. Based on their mode of action in plants (potent inhibitors of ergosterol synthesis), we focused attention on mechanisms related to cellular, lipid, and steroid metabolism. Evidence from several studies reveals that zebrafish exposed to triazoles present with impaired mitochondrial oxidative phosphorylation and oxidative stress, as well as dysregulation of lipid metabolism. Such metabolic disruptions are expected to underscore developmental delays, deformity, and aberrant locomotor activity and behaviors often observed following exposure. We begin by summarizing physiological and behavioral effects observed with triazole fungicide exposure in zebrafish. We then discuss mechanisms that may underlie adverse apical effects, focusing on mitochondrial bioenergetics and metabolism. Using computational approaches, we also identify novel biomarkers of triazole fungicide exposure. Extracting and analyzing data contained in the Comparative Toxicogenomics Database (CTD) revealed that transcriptional signatures responsive to different triazoles are related to metabolism of lipids and lipoproteins, biological oxidations, and fatty acid, triacylglycerol, and ketone body metabolism among other processes. Pathway and sub-network analysis identified several transcripts that are responsive in organisms exposed to triazole fungicides, several of which include lipid-related genes. Knowledge gaps and recommendations for future investigations include; (1) targeted metabolomics for metabolites in glycolysis, Krebs cycle, and the electron transport chain; (2) additional studies conducted at environmentally relevant concentrations to characterize the potential for endocrine disruption, given that studies point to altered cholesterol (precursor for steroid hormones), as well as altered estrogen receptor alpha and thyroid hormone expression; (3) studies into the potential role for lipid peroxidation and oxidation of lipid biomolecules as a mechanism of triazole-induced toxicity, given the strong evidence for oxidative damage in zebrafish following exposure to triazole fungicides.

Specnuezhenide reduces carbon tetrachloride-induced liver injury in mice through inhibition of oxidative stress and hepatocyte apoptosis

OBJECTIVES

This study aimed to investigate the hepatoprotective effects of specnuezhenide against carbon tetrachloride (CCl4)-induced liver injury in mice.

METHODS

Male C57BL/6 mice were intraperitoneally injected with 10 ml/kg body weight of CCl4 (0.5% diluted in arachis oil) for acute liver injury after oral administration of specnuezhenide for 7 days. Twenty-four hours after the final CCl4 injection, mice were euthanized and plasma and liver samples were collected.

KEY FINDINGS

The results showed that specnuezhenide markedly and dose-dependently reduced serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) activity and relative liver weight, as well as ameliorated histopathological damage caused by CCl4 and decreased malondialdehyde (MDA) levels, and increased the activity of antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Moreover, specnuezhenide promoted the expression and nuclear translocation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and increased the mRNA and protein expression of Nrf2 signalling-related genes heme oxygenase-1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC) and NAD(P)H:quinone oxidoreductase 1 (NQO1). Finally, TUNEL staining and immunohistochemistry indicated that specnuezhenide prevented CCl4-induced hepatocytic apoptosis by up-regulating B-cell lymphoma 2 (Bcl-2) expression and downregulating Bcl-2-associated X (Bax) expression.

CONCLUSIONS

Specnuezhenide reduced CCl4-induced liver injury in mice by inhibiting oxidative stress via activation of Nrf2 signalling and decreasing hepatocyte apoptosis.

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.

Evaluating Multiple Biochemical Markers in Xenopus laevis Tadpoles Exposed to the Pesticides Thiacloprid and Trifloxystrobin in Single and Mixed Forms

Pesticide exposure is thought to be one of the common reasons for the decline in amphibian populations, a phenomenon that is a major threat to global biodiversity. Although the single effects of pesticides on amphibians have been well studied, the effects of mixtures are not well known. The present study aimed to evaluate the acute toxicity of the insecticide thiacloprid and the fungicide trifloxystrobin on early developmental stages of Xenopus laevis using various biochemical markers (glutathione S-transferase, glutathione reductase, acetylcholinesterase, carboxylesterase, glutathione peroxidase, catalase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, Na⁺ K⁺ -adenosine triphosphatase [ATPase], Ca²⁺ -ATPase, Mg²⁺ -ATPase, and total ATPase). The median lethal concentrations (LC50s) of thiacloprid and trifloxystrobin were determined to be 3.41 and 0.09 mg a.i. L^-1 , respectively. Tadpoles were exposed to the LC50, LC50/2, LC50/10, LC50/20, LC50/50, and LC50/100 of these pesticides. Both pesticides significantly affected (inhibited/activated) the biomarkers even at low concentrations. The pesticides showed a synergistic effect when applied as a mixture and altered the biomarkers more than when applied individually. In conclusion, we can assume that tadpoles are threatened by these pesticides even at environmentally relevant concentrations. Our findings provide important data to guide management of the ecotoxicological effects of these pesticides on nontarget amphibians.  Environ Toxicol Chem 2021;40:2846-2860. © 2021 SETAC.

Bioaccumulation, Metabolism and the Toxic Effects of Chlorfenapyr in Zebrafish (Danio rerio)

Chlorfenapyr is widely used as an insecticide/miticide. Tralopyril, the active metabolite of chlorfenapyr, is used as an antifouling biocide in antifouling systems, and negatively affects aquatic environments. However, it is unclear whether tralopyril is a metabolite of chlorfenapyr in aquatic vertebrates, and there is little data on the bioaccumulation and toxicity of chlorfenapyr to aquatic vertebrates. In this study, the bioaccumulation and elimination of chlorfenapyr in zebrafish were assessed, and tralopyril, the active metabolite of chlorfenapyr, was determined. The effects of chronic exposure to chlorfenapyr on zebrafish liver and brain oxidative damage, apoptosis, immune response, and metabolome were investigated. These results showed that chlorfenapyr has a high bioaccumulation in zebrafish, with bioaccumulation factors of 864.6 and 1321.9 after exposure to 1.0 and 10 μg/L chlorfenapyr for 21 days, respectively. Chlorfenapyr at these concentrations also rapidly accumulated in zebrafish, reaching 615.5 and 10336 μg/kg on the second and third days of exposure, respectively. Chlorfenapyr was degraded to tralopyril in zebrafish; therefore, both chlorfenapyr and tralopyril should be considered when evaluating the risk of chlorfenapyr to aquatic organisms. In addition, chronic exposure caused oxidative damage, apoptosis, and immune disorders in zebrafish liver. Chronic exposure also altered the levels of endogenous metabolites in liver and brain. After 9 days of depuration, some indicators of oxidative damage, apoptosis, and immunity returned to normal levels, but the concentration of endogenous metabolites in zebrafish liver was still altered. Overall, these results provide useful information for evaluating the toxicity and environmental fate of chlorfenapyr in aquatic vertebrates.

ROS-Induced Hepatotoxicity under Cypermethrin: Involvement of the Crosstalk between Nrf2/Keap1 and NF-κB/iκB-α Pathways Regulated by Proteasome

Cypermethrin (CMN) is a man-made insecticide, and its abuse has led to potential adverse effects, particularly in sensitive populations such as aquatic organisms. The present study was focused on the toxic phenotype and detoxification mechanism in grass carp (Ctenopharyngodon idella) after treatment with waterborne CMN (0.651 μg/L) for 6 weeks in vivo or 6.392 μM for 24 h in vitro. In vivo, we describe the toxic phenotype of the liver of grass carp in terms of pathological changes, serum transaminase levels, oxidative stress indexes, and apoptosis rates. RNA-Seq analysis (2 × 3 cDNA libraries) suggested a compromise of proteasome and oxidative phosphorylation signaling pathways under CMN exposure. Thus, these two pathways were chosen for the in vitro study, which suggested that the CMN intoxication-induced proteasome pathway caused hepatotoxicity in the liver cell line of grass carp (L8824 cells). Moreover, pretreatment with MG132, a proteasome inhibitor, displayed protection against the toxic effects of CMN by enhancing antioxidative and anti-inflammatory capability by directly inhibiting the proteasomal degradation of nuclear factor erythroid-2 related factor (Nrf2) and IκB-α, thus turning on the transcription of downstream genes of Nrf2 and NF-κB, respectively. Taken together, these results suggest proteasome activity as a reason for CMN-induced hepatotoxicity.

Influence of multi-walled carbon nanotubes on enantioselective bioaccumulation and oxidative stress toxicity of indoxacarb in zebrafish(Danio rerio)

Carbon nanotubes (CNTs) have been widely used in various fields with the rapid development of nanotechnology. Pesticides have an irreplaceable role in agricultural production, which leads to their massive utilization and their inevitably penetrate into the aquatic environment. However, limited information is available regarding the impact of CNTs on the toxicity and enrichment of chiral compounds to organisms. Using zebrafish as a model to study whether the enantioselective bioaccumulation and oxidative stress of chiral pollutants may be altered in the presence of MWCNTs. Significant enantioselective bioaccumulation was observed in zebrafish with the preferential accumulation of R-(-)-indoxacarb during the 28-day bioaccumulation. The combined exposure of MWCNTs does not affect the enantioselectivity of zebrafish bioaccumulation, but increase the bioaccumulation amount of R-(-)-indoxacarb by 65%. Moreover, the average degradation half-life of indoxacarb enantiomers was 1.30 days. The indoxacarb causes oxidative stress toxicity in zebrafish liver and exhibited enantioselectivity, while the addition of MWCNTs did not significantly change the enantioselectivity of oxidative stress toxicity of indoxacarb, but enhanced the toxicity 20% with increased MWCNTs concentrations. This study suggests that the risk of the co-presence of nanomaterials and chiral pesticides in aquatic environments should be taken into consideration.

Chiral Recognition for Chromatography and Membrane-Based Separations: Recent Developments and Future Prospects

With the rapid development of global industry and increasingly frequent product circulation, the separation and detection of chiral drugs/pesticides are becoming increasingly important. The chiral nature of substances can result in harm to the human body, and the selective endocrine-disrupting effect of drug enantiomers is caused by differential enantiospecific binding to receptors. This review is devoted to the specific recognition and resolution of chiral molecules by chromatography and membrane-based enantioseparation techniques. Chromatographic enantiomer separations with chiral stationary phase (CSP)-based columns and membrane-based enantiomer filtration are detailed. In addition, the unique properties of these chiral resolution methods have been summarized for practical applications in the chemistry, environment, biology, medicine, and food industries. We further discussed the recognition mechanism in analytical enantioseparations and analyzed recent developments and future prospects of chromatographic and membrane-based enantioseparations.

New insight into the enantioselective cytotoxicity of cypermethrin: imbalance between cell cycle and apoptosis

Cypermethrin (CP) is a frequently used chiral pesticide comprised of different enantiomers that can induce a variable toxic response in biota, dependent on conformational change. However, the potential mechanism accounting for the enantioselective toxicity induced by CP enantiomers remains unknown. Herein, to shed light on the underlying mechanism of enantioselective cytotoxicity on cell cycle and apoptotic function, an MTT assay, flow cytometric (FCM) approach, and qPCR arrays combining bioinformatic analysis were conducted on HepG2 cell lines following exposure to CP enantiomers. Decreased cell viability in keeping with increased cell arrest and apoptosis was observed in cells exposed to (1S,3R,αR)-CP, relative to the (1R,3S,αS)-CP treatment group. PCR array also reflected an enantioselective difference in expression of cell cycle and apoptosis-related genes. Ingenuity pathway analysis (IPA) showed that cell cycle checkpoints, arrest in interphase, death receptor signaling, and apoptosis were among the top canonical and disease and functions predicted to be affected between CP enantiomers. Data presented here not only provide potential molecular endpoints for evaluating toxicity by cell cycle and apoptosis but also help to guide the scientific application of chiral pesticides.

Effects of exposure to prothioconazole and its metabolite prothioconazole-desthio on oxidative stress and metabolic profiles of liver and kidney tissues in male mice

Prothioconazole (PTC), a popular agricultural fungicide, and its main metabolite prothioconazole-desthio (PTCd) are receiving great attention due to their toxicological effects in the non-target organisms. This study investigated their dosage-dependent (1 and 5 mg/kg BW/day) toxicological effects on oxidative stress and metabolic profiles of liver and kidney tissues using male mice. PTC and PTCd significantly inhibited the growth phenotype including body weights gain, liver and kidney indices. Furthermore, these effects were deeply investigated using the biomarkers of oxidative stress, and metabolomics. Notably, these effects were dose and tissue-dependent. Specifically, the more serious impacts involving oxidative stress and metabolic disorders were observed in the high concentration treatment groups. Also, the liver tissue was more severely affected than the kidney tissue. Lastly, the change in oxidative stress biomarkers and metabolomics profile revealed that PTCd induced more severe toxic effects than the parent compound PTC. In brief, these results indicate that exposure to PTC and PTCd could cause potential health risks in mammals.

Molecular mechanism of reproductive toxicity induced by beta-cypermethrin in zebrafish

Beta-cypermethrin, a type II synthetic pyrethroid insecticide, is widely used in pest control. Several studies have demonstrated that beta-cypermethrin can affect the reproductive system of mammals. However, there is still a scarcity of information about the reproductive toxicity to fish induced by beta-cypermethrin and its molecular mechanism. Therefore, this study was conducted to address this scientific question, in which the adult zebrafish were exposed to 0 (blank control), 0 (acetone solvent control), 0.1, 0.5, and 2.5 μg/L of beta-cypermethrin for 21 days. A decrease in cumulative egg production of zebrafish was observed, indicating that beta-cypermethrin had a negative impact on reproductive capacity of zebrafish. Regarding the histomorphological analysis of gonads, the delay of gonadal development was observed after exposure for 21 days. In addition, significant changes in plasma 17β-estradiol (E2) and testosterone (T) were found in zebrafish. Further exploration showed that the transcription levels of hypothalamic-pituitary-gonadal (HPG) axis-related genes were remarkably changed, which corresponded well with the alterations of hormone levels. These results demonstrated that beta-cypermethrin might have an adverse effect on the reproduction system of zebrafish through delaying gonadal development, disturbing sex hormone secretion, and affecting HPG axis gene expression. This study suggests that beta-cypermethrin poses a potential threat to the reproduction of fish populations, and the toxicity assessment of beta-cypermethrin plays a vital role in the environmental risk assessment of pesticides.

Effects of cypermethrin on the hepatic transcriptome and proteome of the red claw crayfish Cherax quadricarinatus

Cypermethrin (CYP) is a synthetic pyrethroid broadly used for pest control, however, it is extremely toxic to aquatic organisms. To assess the toxicity of CYP in red claw crayfish Cherax quadricarinatus, transcriptional and proteomic approaches combining two-dimensional polyacrylamide gel electrophoresis and tandem mass spectrometry were used to compare the hepatic expression profiles. A total of 41,349 unigenes and 8839 differentially expressed genes (DEGs) were obtained, which were enriched in the process. The category of 779 (0.625 ng L^-1 CYP vs Con), 1963 (1.25 vs Con), and 2066 (1.25 vs 0.625) DEGs were screened. All findings suggested that CYP can induce antioxidant and biotransformation modulation variations in C. quadricarinatus to resist immunotoxicity and oxidative damages. The category of 196 (0.625 ng L^-1 CYP vs Con) specific proteins were differentially expressed: 24 proteins were upregulated, and 20 proteins were downregulated relative to CYP. Protein identification indicated the KEGG pathways of the human immunodeficiency virus 1 infection, insulin signaling pathway, and influenza A enriched. From the differential expression of the selected nine proteins, the increased Loc113824800, Rps19, Atp2, Rps10, Hsp40, Brafldraft_124327, and the decreased Loc117331934, Loc113213835, and Loc106806551 revealed. While for the verification of the eight genes in transcriptome and the above nine genes in proteomic, specifically, gpx5, ggt, loc106458463, chelonianin decreased in the 0.625 ng L^-1 CYP group. The transcripts of loc113816050, akr1d1 and gst, chelonianin and loc108675455 decreased and increased in the 1.25 ng L^-1 CYP group, respectively. The present study reflects the overall change in cellular structure and metabolism related to the resistance of pyrethroid insecticides.

Oxidative Stress in NAFLD: Role of Nutrients and Food Contaminants

Non-alcoholic fatty liver disease (NAFLD) is often the hepatic expression of metabolic syndrome and its comorbidities that comprise, among others, obesity and insulin-resistance. NAFLD involves a large spectrum of clinical conditions. These range from steatosis, a benign liver disorder characterized by the accumulation of fat in hepatocytes, to non-alcoholic steatohepatitis (NASH), which is characterized by inflammation, hepatocyte damage, and liver fibrosis. NASH can further progress to cirrhosis and hepatocellular carcinoma. The etiology of NAFLD involves both genetic and environmental factors, including an unhealthy lifestyle. Of note, unhealthy eating is clearly associated with NAFLD development and progression to NASH. Both macronutrients (sugars, lipids, proteins) and micronutrients (vitamins, phytoingredients, antioxidants) affect NAFLD pathogenesis. Furthermore, some evidence indicates disruption of metabolic homeostasis by food contaminants, some of which are risk factor candidates in NAFLD. At the molecular level, several models have been proposed for the pathogenesis of NAFLD. Most importantly, oxidative stress and mitochondrial damage have been reported to be causative in NAFLD initiation and progression. The aim of this review is to provide an overview of the contribution of nutrients and food contaminants, especially pesticides, to oxidative stress and how they may influence NAFLD pathogenesis.

Effect of Lambdacyhalothrin on Locomotor Activity, Memory, Selected Biochemical Parameters, Tumor Necrosis Factor α, and Interleukin 1ß in a Mouse Model

Background: Pyrethroids are synthetic insecticides used for plant protection. They are synthetic analogues of pyrethrins. Lambdacyhalothrin (LCH) is a type II pyrethroid used for wheat, potato, corn farming, and malaria control. There are data that pyrethroids may cause neurotoxicity, nephrotoxicity, hepatotoxicity, and immunotoxicity in non-target organisms. Methods: The experiment was carried on 32 Albino Swiss mice (16 females and 16 males). The animals were divided into four groups. Controls received canola oil; the rest received LCH orally in oil at a dose of 2 mg/kg bw for 7 days. Memory retention was assessed in a passive avoidance task on day 2 and 7, and spatial memory and motor activity in a Y-maze on day 1 and 7. Blood morphology, biochemical tests, tumor necrosis factor α, and interleukin 1ß were measured. Results: Decreased white blood cell count and red blood cell count, increased creatinine, and increased kidney and liver mass were observed in groups exposed to LCH. In LCH-exposed males’ kidneys and livers, interleukin 1ß was significantly elevated, and it was correlated with creatinine concentration. Conclusions: Subacute poisoning with a low dose of LCH does not significantly affect memory nor locomotor activity but increases proinflammatory interleukin 1ß in male livers and kidneys and reduces white and red blood cell counts.

Acute exposure to the fungicide penconazole affects some biochemical parameters in the crayfish (Astacus leptodactylus Eschscholtz, 1823)

Penconazole is one of the most widely used fungicides all over the world, and since it spreads to large environments, its toxic effects on non-target organisms are of great concern. The toxic effects of penconazole on crayfish (Astacus leptodactylus), which is a bioindicator in freshwater ecosystems and consumed economically, are not known. Therefore, in this study, the purpose was to contribute to the literature on the potential harmful effects of penconazole on a non-target species, Astacus leptodactylus. For this aim, the acute toxicity (96 h) of penconazole was examined. The 96-h LC₅₀ value of penconazole was detected as 18.7 mg L^-1. Four concentrations of penconazole (18.7 mg L^-1, 9.35 mg L^-1, 4.68 mg L^-1, 2.34 mg L^-1) were applied to crayfish for 96 h. The results showed that penconazole had destructive effects on esterase mechanisms by inhibiting acetylcholinesterase (AChE) and carboxylesterase (CaE) activities. Significant increases were observed in all antioxidant parameters (superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), reduced glutathione (GSH), malondialdehyde (MDA)) in all doses except the lowest concentration (2.34 mg L^-1). All adenosine triphosphatase (ATPase) activities (Na⁺/K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase, total ATPase) had significant dose-related inhibition in both gill and muscle tissues. In summary, our findings show that acute penconazole administration to crayfish causes significant toxic effects on esterase, antioxidative parameters, and metabolic enzymes.

Mediation of oxidative stress toxicity induced by pyrethroid pesticides in fish

Organophosphate and organochlorine pesticides are banned in most countries because they cause high toxicity and bioaccumulation in non-target organisms. Pyrethroid pesticides have been applied to agriculture and aquaculture since the 1970s to replace traditional pesticides. However, pyrethroids are approximately 1000 times more toxic to fish than to mammals and birds. Fish-specific organs such as the gills and their late metabolic action against this type of pesticide make fish highly susceptible to the toxicity of pyrethroid pesticides. Oxidative stress plays an important role in the neurological, reproductive, and developmental toxicity caused by pyrethroids. Deltamethrin, cypermethrin, and lambda-cyhalothrin are representative pyrethroid pesticides that induce oxidative stress in tissues such as the gills, liver, and muscles of fish and cause histopathological changes. Although they are observed in low concentrations in aquatic environments such as rivers, lakes, and surface water they induce DNA damage and apoptosis in fish. Pyrethroid pesticides cause ROS-mediated oxidative stress in fish species including carp, tilapia, and trout. They also cause lipid peroxidation and alter the state of DNA, proteins, and lipids in the cells of fish. Moreover, changes in antioxidant enzyme activity following pyrethroid pesticide exposure make fish more susceptible to oxidative stress caused by environmental pollutants. In this review, we examine the occurrence of pyrethroid pesticides in the aquatic environment and oxidative stress-induced toxicity in fish exposed to pyrethroids.

Four cypermethrin isomers induced stereoselective metabolism in H295R cells

Cypermethrin (CP) is widely used for controlling agricultural and indoor vermin. Previous studies have reported the stereoselective difference of CP in biological activities. However, little is known about their potential mechanisms between metabolic phenotypes and endocrine-disrupting effects. Herein, nuclear magnetic resonance (NMR)-based metabolomics combining metabolite identification and pathway analysis were applied to evaluate the stereoselective metabolic cdisorders induced by CP isomers in human adrenocortical carcinoma cells (H295R) culture medium. Then, gene expression levels related to disturbed metabolic pathways were assessed to verify according to metabolic phenotypes. Metabolomics profiles showed that [(S)-cyano(3-phenoxyphenyl)methyl](1R,3R)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate [(1R,3R,αS)-CP] induced the most significant changes in metabolic phenotypes than did the other stereoisomers. There are 10 differential metabolites (isoleucine, valine, leucine, ethanol, alanine, acetate, aspartate, arginine, lactate, and glucose) as well as two significantly disturbed pathways, including "pyruvate metabolism" and "alanine, aspartate, and glutamate metabolism," that were confirmed in H295R cells culture medium of (1R,3R,αS)-CP compared with other stereoisomers. Polymerase chain reaction (PCR) array also confirmed the results of metabolomics. Our results can help to understand the potential mechanisms between the isomer selectivity in metabolic phenotypes and endocrine-disrupting effects. Data provided here not only lend authenticity to the cautions issued by the scientists and researchers but also offer a solution for the balance between environment and political regulations.

Combined toxic effects of fludioxonil and triadimefon on embryonic development of zebrafish (Danio rerio)

Pesticides scarcely exist as individual compounds in the water ecosystem, but rather as mixtures of multiple chemicals at relatively low concentrations. In this study, we aimed to explore the mixture toxic effects of fludioxonil (FLU) and triadimefon (TRI) on zebrafish (Danio rerio) by employing different toxicological endpoints. Results revealed that the 96-h LC₅₀ values of FLU to D. rerio at multiple developmental stages ranged from 0.055 (0.039-0.086) to 0.61 (0.33-0.83) mg L^-1, which were less than those of TRI ranging from 3.08 (1.84-5.96) to 9.75 (5.99-14.78) mg L^-1. Mixtures of FLU and TRI exerted synergistic effects on embryonic zebrafish. Activities of total superoxide dismutase (T-SOD) and catalase (CAT) were markedly altered in most of the individual and pesticide mixture treatments compared with the control. The expressions of 16 genes involved in oxidative stress, cellular apoptosis, immune system and endocrine system displayed that embryonic zebrafish were affected by the individual pesticides and their mixtures, and greater variations of four genes (ERɑ, Tnf, IL and bax) were found when exposed to pesticide mixtures compared with their individual compounds. Therefore, more studies on mixture toxicities among different pesticides should be taken as a priority when evaluating their ecological risk.

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.

Lethal toxicity and gene expression changes in embryonic zebrafish upon exposure to individual and mixture of malathion, chlorpyrifos and lambda-cyhalothrin

Pesticides are usually present as mixtures in water environments. Evaluating the toxic effects of individual pesticide may not be enough for protecting ecological environment due to interactions among substances. In this study, we aimed to examine the lethal doses and gene expression changes in zebrafish (Danio rerio) upon exposure to individual and mixture pesticides [malathion (MAL), chlorpyrifos (CHL) and lambda-cyhalothrin (LCY)]. Individual pesticide toxicity evaluation manifested that the toxicity of the three pesticides to D. rerio at various developmental stages (embryonic, larval, juvenile and adult stages) followed the order of LCY > CHL > MAL. On the contrary, the least toxicity to the animals was discovered from MAL. Most of the tested pesticides displayed lower toxicities to the embryonic stage compared with other life stages of zebrafish. Synergistic effects were monitored from two binary mixtures of LCY in combination with MAL or CHL and ternary mixture of MAL + CHL + LCY. The expressions of 16 genes involved in oxidative stress, immunity system, cell apoptosis and endocrine disruption at the mRNA level revealed that embryonic zebrafish were influenced by the individual or mixture pesticides. The expressions of Tnf, P53, TRα, Crh and Cyp19a exerted greater variations upon exposure to pesticide mixtures compared with their individual compounds. Collectively, the transcriptional responses of these genes might afford early warning biomarkers for identifying pollutant exposure, and the data acquired from this study provided valuable insights into the comprehensive toxicity of pesticide mixtures to zebrafish.

Toxicity effects in zebrafish embryos (Danio rerio) induced by prothioconazole

Triazole fungicides are widely used in agriculture production and have adverse impacts on aquatic organisms. As one of the triazole fungicides, prothioconazole has been reported to cause many toxicological effects, but its risks to aquatic organisms are unknown. In this study, we systematically explored the toxicity effects of prothioconazole exposure on zebrafish embryos (Danio rerio) involving in developmental toxicity, oxidative damage and metabolism disorders. The results showed that prothioconazole exposure to zebrafish embryos produced a series of toxic symptoms, including hatching inhibition, shortening of body length, pericardial cyst and yolk cyst. In addition, prothioconazole exposure caused significant lipid peroxidation and oxidative damage. Particularly, we also found that metabolites and genes involved in lipid metabolism also showed significant changes. This study may provide theoretical basis for systematically assessing the potential risks of zebrafish embryos with prothioconazole exposure.

The immune responses of the Chinese rare minnow (Gobiocypris rarus) exposed to environmentally relevant concentrations of cypermethrin and subsequently infected by the bacteria Pseudomonas fluorescens

In the present study, to assess the immunotoxicity of cypermethrin (CYP) in fish, Chinese rare minnows (Gobiocypris rarus) were exposed to environmentally relevant concentrations (0.15, 0.5, and 1.5 μg/L) of CYP for 28 d and subjected to pathogen challenge trials for 2 d. After 28 d of CYP exposure, the levels of Immunoglobulin M (IgM), Alkaline phosphatase (ALP), and C-reactive protein (CRP) were significantly decreased (p < 0.05) after treatment with 1.5 μg/L CYP. Moreover, an induction of inflammatory cytokine transcripts (tnfa, il-6, il-8, and il-12) was observed (p < 0.05) after treatment with 1.5 μg/L CYP. After challenge with Pseudomonas fluorescens (P. fluorescens), plasma lysozyme (LYS) activity at 24 and 48 hours post-injection (hpi) was significantly decreased in the 0.5 and 1.5 μg/L CYP treatment groups (p < 0.05). Moreover, liver Complement component 3 (C3) and CRP contents at 24 hpi were significantly decreased in the 1.5 μg/L CYP treatment group (p < 0.05), whereas significant decreases in liver C3 and IgM contents were observed at 48 hpi (p < 0.05). Inhibition of expression of Toll-like receptor-nuclear factor kappa B (TLR-NF-kB) signaling pathway-related genes was observed in the CYP treatment groups and resulted in significant down-regulation of inflammatory cytokines (il-1β and il-12) in the 1.5 μg/L CYP treatment group at 48 hpi (p < 0.05). Interestingly, the mortality in the 0.5 and 1.5 μg/L CYP treatments was significantly increased at 48 hpi (p < 0.05). These results indicated that environmentally relevant concentrations of CYP suppressed the Chinese rare minnow immune system and reduced immune defense against bacterial infection, thereby causing subsequent mortality. Meanwhile, our results demonstrated that a subsequent host resistance challenge is an effective method for determining the immunotoxicity of chemicals (e.g., CYP).

Critical time window of fenvalerate-induced fetal intrauterine growth restriction in mice

Fenvalerate (FEN), a representative type II pyrethroid, is a widely used pyrethroid insecticide and a potential environmental contaminant. Several studies demonstrated that gestational FEN exposure induced intrauterine growth restriction (IUGR). However, the critical time window of FEN-induced fetal IUGR remains obscure. The present study aimed to identify the critical window of FEN-induced fetal IUGR. Pregnant mice were administered corn oil or FEN (20 mg/kg) by gavage daily at the early gestational stage (GD0-GD6), middle gestational stage (GD7-GD12) or late gestational stage (GD13-GD17). The results showed that the rates of fetal IUGR were markedly increased only in the mice exposed to FEN on GD13-GD17 but not in the mice exposed to FEN on GD7-GD12 or GD0-GD6. Further analysis showed that the blood sinusoid area in the placental labyrinth layer was reduced in the mice exposed to FEN on GD13-GD17. In addition, CD34⁺ microvessel density in the labyrinthine region was decreased in the male and female fetuses whose mothers were exposed to FEN on GD13-GD17. Mechanistic analysis found that the glutathione level was decreased in the FEN-exposed placentas. In contrast, the levels of 3-nitrotyrosine and malondialdehyde, two oxidative stress markers, were increased in FEN-exposed placentas. Heme oxygenase-1, inducible nitric oxide synthase, catalase and peroxiredoxin-3, which are antioxidant enzymes, were upregulated in the FEN-exposed placentas. The present study suggests that the late gestational stage is a critical time window of FEN-induced fetal IUGR. Placental oxidative stress may be, at least partially, involved in the process of FEN-induced placental damage and fetal IUGR.

Enantioselectivity in endocrine disrupting effects of four cypermethrin enantiomers based on in vitro models

Cypermethrin (CP) is a kind of chiral pesticides that has been defined as endocrine disrupting chemical. The diversity in bioactivity, toxicity, metabolism, bioaccumulation, and degradation behaviors of CP enantiomers as well as the research deficiency had made the risk assessment of CP enantiomers very complicated. Herein, four CP enantiomers were separated as target chemicals to investigate their enantioselective endocrine disrupting effects. Firstly, dual-luciferase reporter gene assays were adopted to investigate their potential endocrine disrupting effects via various receptors. The expression levels of steroid hormones related genes and hormone secretion levels in H295R cell were measured to verify the results. Results from the reporter gene assay showed that 1R-cis-αS-CP (CP11) exhibited glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and thyroid receptor (TR) antagonistic activity with the RIC₂₀ values of 9.22 × 10^-7, 3.33 × 10^-7, and 4.47 × 10^-7 M, respectively; 1R-trans-αS-CP (CP21) also showed androgen receptor (AR) agonist activity and estrogen receptor (ER) antagonistic activity with the REC₂₀ and RIC₂₀ values were 1.07 × 10^-4 M and 4.78 × 10^-6 M, respectively. Results of qRT-PCR and hormone measurement also showed that CP11 and CP21 could disturb the expression of steroid hormones related genes and hormone secretion accordingly. Results provided here can help to understand the enantioselective ecological and health risks of CP enantiomers comprehensively and provide constructive guidance for the safe use of chiral pesticides and the invention of green pesticides.

Behavioral, molecular and physiological responses of embryo-larval zebrafish exposed to types I and II pyrethroids

Pyrethroids are potent neurotoxicants that may elicit multiple pathways of toxicity in non-target organisms. Comparative studies on the mechanistic and developmental effects of types I and II pyrethroids against non-target aquatic species are limited. This study assessed the effects of the two pyrethroid types against embryo-larval zebrafish (Danio rerio) at environmentally relevant and laboratory concentrations. Zebrafish embryos were exposed to type-I (permethrin, bifenthrin) and type-II (deltamethrin, λ-cyhalothrin, fenvalerate, esfenvalerate) pyrethroids at 1000, 10, 0.1, 0.01, 0.0 μg/L, starting at 5-h post-fertilization (hpf) through 5-d post-fertilization (dpf) under static exposure conditions. Swimming behavior (distance traveled and velocity) was assessed at 5-dpf. The relative expression of Nrf2a, GST, Casp-9 and p53 mRNA transcripts, carboxyl esterase (CES) activity and total reactive oxygen species (ROS) were measured. The stability of the pyrethroids across 5 days was analyzed. Bifenthrin-(10 μg/L) and esfenvalerate-(1000 μg/L) significantly (p < 0.05) reduced total distance traveled by larvae while 1000 μg/L deltamethrin and λ-cyhalothrin were lethal causing body axis curvature and pericardial edema. At environmentally relevant concentrations-(μg/L) compared to control, permethrin-(0.122) upregulated Nrf2a and Casp-9 expressions while λ-cyhalothrin-(0.053) downregulated Nrf2a and fenvalerate-0.037 downregulated GST. At laboratory concentrations-(μg/L), permethrin-(1000) upregulated Nrf2a, Casp-9 and p53 expressions, bifenthrin-(10) upregulated Casp-9 while fenvalerate-(0.1) and esfenvalerate-(1000) downregulated GST. There was concentration dependent increase in CES activity which correlated positively with total ROS. Pyrethroid concentrations decreased significantly by day 5. This study showed disparity in the mechanistic effects across the pyrethroids types and their instability in aqueous media may underestimate toxicity against non-target aquatic species when exposed in their natural environment.

Effects of beta-cypermethrin and myclobutanil on some enzymes and changes of biomarkers between internal tissues and saliva in reptiles (Eremias argus)

Numerous studies suggested that reptiles are sensitive to environmental pollution and the abundance of many species are in decline. Our research is aim to assess the toxic effects of pesticide in reptiles. And we also want to supply some data about nondestructive samples for environmental risk assessment in reptiles. Lizards were orally administered a single-dose of beta-cypermethrin (BCP) or myclobutanil (MC) at the concentration of 20 mg/kg body weight (bw). The results showed that pesticides could induce changes in enzymatic activities (SOD, CAT, LDH, AChE) and MDA levels in organs or tissues of lizards. BCP could cause more severe oxidative damage than that of MC. Salivary enzymes activities showed sensitivity changes to the toxicity of pesticides. We could use saliva to reflect whether the reptiles are toxic by pesticides. We also agree that buccal swabs could be used as a tool for saliva sampling.

Macrolides induce severe cardiotoxicity and developmental toxicity in zebrafish embryos

Macrolide antibiotics (MALs) are widely used for both human and animal health. Most MALs and their metabolites transfer into aquatic organisms and environment resulting in violent consequences. Previous studies show that MALs cause cardiotoxicity in humans and mammals. However, the potential risk of these chemicals in aquatic organisms remains unclear. Here, we used zebrafish embryos as a model to evaluate the toxicity of MALs. Zebrafish embryos were exposed to four typical MALs including azithromycin (AZM), clarithromycin (CLR), tilmicosin (TMS) and tylosin (TYL) to study their cardiotoxicity. The heart rate of zebrafish embryos showed similar biphasic distribution in the presence of four MALs at 2 days post-fertilization (dpf). The heart rate increased significantly at low levels of MALs while decreased obviously at high levels. Subsequently, TMS was chose to study its acute toxicity and developmental toxicity, which caused pericardial edema and spinal curvature in zebrafish embryos at 4 dpf. Furthermore, we found that TMS triggered oxidative stress, with decreased SOD activities and increased MDA contents. Lastly, apoptosis was observed in zebrafish embryos under TMS treatment, with up-regulation of apoptosis associated genes such as p53, bcl 2, bax, caspase 3 and caspase 9, confirmed by increased protein expression based on Western blot analysis. Taken together, these data indicate that MALs can cause serious toxicity in the development of zebrafish. Great caution should be taken due to the huge consumption of MALs for food animal production and treatments with TMS for infections in aquaculture.

Enantioselective bioaccumulation and metabolism of lactofen in zebrafish Danio rerio and combined effects with its metabolites

Pesticide residue in agricultural land might led to contamination of fresh waters, creating potential risks to organisms. The environmental behavior of herbicide lactofen may be enantioselective and the metabolites may have high toxic effects in individual or in combination. In this work, the enantioselective bioaccumulation, metabolism and toxic effects of lactofen and three metabolites (desethyl lactofen, acifluorfene, and amino acifluorfene) in zebrafish were investigated. The antioxidase activity (superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase), lipid peroxidation content were measured after exposure, and genetic toxicity was evaluated by a micronucleus test. The integrated biomarker response (IBR) method was used to determine the effects of the lactofen and its metabolites as well as their combinations. The metabolites were found to have higher toxic effects, and enantioselective toxic effects of lactofen and desethyl lactofen were observed, with the S-enantiomer more toxic. Based on IBR values, synergistic effects existed in combination of lactofen and desethyl lactofen, while antagonistic effects of lactofen with acifluorfene or amino acifluorfene were observed. Zebrafish were exposed to 0.5 mg L^-1 lactofen and the bioaccumulation were measured during a 15 d period followed by a 7 d elimination. The half-lives of the metabolites varied between 0.66 and 5.21 d, with bioconcentration factors (BCFs) in the range of 39-120. The metabolic pathways of R- and S-lactofen were found to be significantly different. The results supported our hypothesis. Therefore, the assessment of enantiomers and metabolites in individual or in combination should be taken into consideration in evaluating chiral pesticide risks.