Enantioselectivity in estrogenic potential and uptake of bifenthrin

Dopaminergic and anti-estrogenic responses in juvenile steelhead (Oncorhynchus mykiss) exposed to bifenthrin

The frequency of detection and concentrations of bifenthrin, a pyrethroid insecticide, in the waterways inhabited by the endangered species, steelhead trout (Oncorhynchus mykiss), has become a significant concern for regulatory agencies. Endocrine disruption has been observed with estrogenic and anti-estrogenic responses in fish species at different life stages. Since several studies have indicated alterations in dopaminergic signaling associated with endocrine responses, juvenile steelhead were exposed to environmentally relevant concentrations of 60 or 120 ng/L bifenthrin for two weeks. Fish brains were assessed for dopamine levels and the expression of genes involved in dopaminergic and estrogenic processes, such as catechol-o-methyltransferase (comt) and monoamine oxidase (mao). Vitellogenin (vtg) and estrogenic receptors (ERα1, ERβ1, and ERβ2) were also evaluated in livers of the animals. Dopamine concentrations were significantly higher in fish brains following bifenthrin exposure. Consistent with a reduction in dopamine clearance, there was a significant decrease in the mRNA expression of comt with increased bifenthrin concentration. Hepatic expression of ERα1 and ERβ2 mRNA was significantly decreased with increased bifenthrin concentration. These data support the possible mechanism of bifenthrin altering the dopaminergic pathway at low ng/L concentrations, in juvenile steelhead, which could interfere with endocrine feedback loops. These findings support the need for and importance of identifying species and life stage differences in pesticide modes of action to reduce uncertainties in risk assessments.

Enantioselective toxicity effect and mechanisms of bifenthrin enantiomers on normal human hepatocytes

In recent decades, the toxicity of chiral pesticides to non-target organisms has attracted increasing attention. Cellular metabolic disorders are essential sensitive molecular initiating event for toxicological effects. BF is a typical chiral pesticide, and the liver is the main organ for BF accumulation. This study aimed to investigate the potential molecular mechanism of BF enantiomers' different toxic effects on L02 by a non-targeted metabolomic approach. Results revealed that the BF enantiomers exhibited different metabolic responses. In total, 51 and 36 differential metabolites were perturbed by 1S-cis-BF and 1R-cis-BF at the value of variable importance, respectively. When L02 were exposed to 1R-cis-BF, the significantly disturbed metabolic pathways were nicotinate and nicotinamide metabolism and pyrimidine metabolism. By comparison, more significantly perturbed metabolic pathways were received when the L02 were exposed to 1S-cis-BF, including glycine, serine and threonine metabolism, nicotinate and nicotinamide metabolism, arginine and proline metabolism, cysteine and methionine metabolism, glycerolipid metabolism, histidine metabolism, pyrimidine metabolism, amino sugar and nucleotide sugar metabolism and arginine biosynthesis. The results offer a new perspective in understanding the role of selective cytotoxicity of BF enantiomers, and help to evaluate the risk to human health at the enantiomeric level.

Insights into the Enantiomeric Uptake, Translocation, and Distribution of Triazole Chiral Pesticide Mefentrifluconazole in Wheat (Triticum aestivum L.)

The uptake, translocation, and accumulation of mefentrifluconazole (MFZ), an innovative chiral triazole fungicide, in plants at the enantiomeric level are still unclear. Herein, we investigated the patterns and mechanisms of enantiomeric uptake, bioaccumulation, and translocation through several experiments. Rac-MFZ shows the strongest uptake and bioaccumulation capacity in wheat compared with its enantiomers, while S-(+)-MFZ has the highest translocation potential. Molecular docking provided evidence of the stronger translocation ability of S-(+)-MFZ than R-(-)-MFZ. Split-root experiments showed that MFZ and its enantiomers could undergo long-distance transport within the wheat. Active transport or facilitated and simple diffusion may be involved in the wheat uptake of MFZ. The limited acropetal translocation capability of MFZ may be attributed to the dominant uptake pathway of apoplastic. The concentrations of Rac-MFZ in different subcellular fractions varied greatly. In summary, this study provides novel insights for further understanding the behaviors of MFZ and its enantiomers in plants.

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.

Enantioselective bioaccumulation and toxicological effects of chiral neonicotinoid sulfoxaflor in rats

Sulfoxaflor is a widely used fourth-generation neonicotinoid pesticide, which has been detected in biological and environmental samples. Sulfoxaflor can potentially be exposed to humans via the food chain, thus understanding its toxic effects and enantioselective bioaccumulation is crucial. In this study, toxicokinetics, bioaccumulation, tissue distribution and enantiomeric profiles of sulfoxaflor in rats were investigated through single oral exposure and 28-days continuous exposure experiment. Sulfoxaflor mainly accumulated in liver and kidney, and the (-)-2R,3R-sulfoxaflor and (-)-2S,3R-sulfoxaflor had higher enrichment than their enantiomers in rats. The toxicological effects were evaluated after 28-days exposure. Slight inflammation in liver and kidney were observed by histopathology. Sphingolipid, amino acid, and vitamin B6 metabolism pathways were significantly disturbed in metabonomics analysis. These toxicities were in compliance with dose-dependent effects. These results improve understanding of enantioselective bioaccumulation and the potential health risk of sulfoxaflor.

Expanding the insight of ecological risk on the novel chiral pesticide mefentrifluconazole: Mechanism of enantioselective toxicity to earthworms (Eisenia fetida)

Continued application of new chiral fungicide mefentrifluconazole (MFZ) increases its risk to soil ecosystem. However, the toxicity of MFZ enantiomers to soil fauna and whether stereoselectivity exists remains poorly elucidated. Based on multilevel toxicity endpoints and transcriptomics, we investigated the negative effects of racemic, R-(-)-, and S-(+)-MFZ on Eisenia fetida. After exposure to S-(+) configuration at 4 mg/kg for 28 day, its reactive oxygen species levels were elevated by 15.4% compared to R-(-) configuration, inducing enantiospecific oxidative stress and transcriptional aberrations. The S-(+) isomer induced more severe cell membrane damage and apoptosis than the R-(-) isomer, and notably, the selectivity of apoptosis is probably dominated by the mitochondrial pathway. Mechanistically, differential mitochondrial stress lies in: S-(+) isomer specifically up-regulated mitochondrial cellular component compared to R-(-) isomer and identified more serious mitochondrial fission. Furthermore, S-(+) conformation down-regulated biological processes associated with ATP synthesis and metabolism, with specific inhibition of mitochondrial respiratory electron transport chain complex I and IV activity resulting in more severe electron flow disturbances. These ultimately mediated enantioselective ontogenetic process disorders, which were supported at phenotypic (weight loss), genetic, and protein (reverse modulate TCTP and Sox2 expression) levels. Our findings offer an important reference for elucidating the enantioselective toxicological mechanism of MFZ in soil fauna.

Adverse effects of bifenthrin exposure on neurobehavior and neurodevelopment in a zebrafish embryo/larvae model

Bifenthrin, a third-generation synthetic pyrethroid, is widely used as an agricultural insecticide. However, it can flow into surface and groundwater, leading to adverse consequences such as immunotoxicity, hepatotoxicity, hormone dysregulation, or neurotoxicity. Nevertheless, the entire range of its neurotoxic consequences, particularly in aquatic organisms, remains unclear. In this study, we conducted an extensive examination of how exposure to bifenthrin affects the behavior and nervous system function of aquatic vertebrates, using a zebrafish model and multiple-layered assays. We exposed wild-type and transgenic lines [tg(elavl3:eGFP) and tg(mbp:mGFP)] to bifenthrin from <3 h post-fertilization (hpf) to 120 hpf. Our findings indicate that bifenthrin exposure concentrations of 103.9 and 362.1 μg/L significantly affects the tail-coiling response at 24 hpf and the touch-evoked responses at 72 hpf. Moreover, it has a significant effect on various aspects of behavior such as body contact, distance between subjects, distance moved, and turn angle. We attribute these effects to changes in acetylcholinesterase and dopamine levels, which decrease in a concentration-dependent manner. Furthermore, neuroimaging revealed neurogenesis defects, e.g., shortened brain and axon widths, and demyelination of oligodendrocytes and Schwann cells. Additionally, the transcription of genes related to neurodevelopment (e.g., gap43, manf, gfap, nestin, sox2) were significantly upregulated and neurotransmitters (e.g., nlgn1, drd1, slc6a4a, ache) was significantly downregulated. In summary, our data shows that bifenthrin exposure has detrimental effects on neurodevelopmental and neurotransmission systems in the zebrafish embryo/larvae model.

Galaxolide and Irgacure 369 are novel environmental androgens

Endocrine disruptors are environmental chemicals that can interfere with the endocrine system. However, research on endocrine disruptors that interfere with androgen's actions is still limited. The purpose of this study is to use in silico computation, i.e., molecular docking to facilitate the identification of environmental androgens. Computational docking was used to study the binding interactions of environmental/industrial compounds with the three dimensional structure of human androgen receptor (AR). Then reporter assay and cell proliferation assay using AR-expressing LNCaP prostate cancer cells were used to determine their in vitro androgenic activity. Animal studies using immature male rats were also carried out to test their in vivo androgenic activity. Two novel environmental androgens were identified. As a photoinitiator, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (Irgacure 369, abbreviated as IC-369) is widely used in the packaging and electronics industries. Galaxolide (HHCB) is widely used in the production of perfume, fabric softeners and detergents. We found that both IC-369 and HHCB could activate AR transcriptional activity and promote cell proliferation in AR-sensitive LNCaP cells. Furthermore, IC-369 and HHCB could induce cell proliferation and histological changes of seminal vesicles in immature rats. RNA sequencing and qPCR analysis showed that androgen-related genes in seminal vesicle tissue were up-regulated by IC-369 and HHCB. In conclusion, IC-369 and HHCB are new environmental androgens that bind AR and induce AR transcriptional activity, thereby exerting toxicological effects on the development of male reproductive organs.

Enantioselectivity in the toxicological effects of chiral pesticides: A review

As a special category of pesticides, chiral pesticides have increased the difficulty in investigating pesticide toxicity. Based on their usage, chiral pesticides can be divided into insecticides, herbicides, and fungicides. Over the past decades, great efforts have been made on elucidating their toxicological effects. However, no literature has reviewed the enantioselective toxicity of chiral pesticides since 2014. In recent years, more chiral pesticides have been registered for application. As such, huge research progresses have been achieved in enantioselective toxicity of chiral pesticides. Generally, more researches have remedied the knowledge gap in toxicological effects of old and new chiral pesticides. And the toxicological endpoints being evaluated have become more specific rather than centering on basic toxicity and target organisms. Besides, the underlying mechanisms accounting for the enantioselectivity in toxicological effects of chiral pesticides have been discussed as well. All in all, this review provides the critical knowledge for risk assessments, and help to drive the green-technology of single- or enriched-enantiomer pesticides and formulation of relevant laws and regulations.

Systematic Stereoselectivity Evaluations of Tetramethrin Enantiomers: Stereoselective Cytotoxicity, Metabolism, and Environmental Fate in Earthworms, Soils, Vegetables, and Fruits

Tetramethrin is a widely applied type I chiral pyrethroid insecticide that exists as a mixture of four isomers. In the present study, its stereoselective cytotoxicity, bioaccumulation, degradation, and metabolism were investigated for the first time at the enantiomeric level in detail by using a sensitive chiral high-performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS) method. Results showed that among rac-tetramethrin and its four enantiomers, the trans (+)-1R,3R-tetramethrin had the strongest inhibition effect on the PC12 cells. In the earthworm exposure trial, the concentration of trans (-)-1S,3S-tetramethrin was 0.94-8.92 times in earthworms (cultivated in natural soil) and 1.67-5.01 times (cultivated in artificial soil) higher than trans (+)-1R,3R-tetramethrin, respectively. In the greenhouse experiment, the trans (+)-1R,3R-tetramethrin and cis (+)-1R,3S-tetramethrin were preferentially degraded. Furthermore, for rat liver microsome in vitro incubation, the maximum metabolism rate of cis (-)-1S,3R-tetramethrin was 1.50 times higher than its antipodes. Altogether, the aim of this study was to provide a scientific and reasonable reference for the possibility of developing a single enantiomer to replace the application of rac-tetramethrin, which could possess better bioactivity and lower ecotoxicity, and thus permit more reliable and accurate environmental monitoring and risk assessment.

Multi-walled carbon nanotubes impact on the enantioselective bioaccumulation and toxicity of the chiral insecticide bifenthrin to zebrafish (Danio rerio)

The effects of different multi-walled carbon nanotubes on the enantioselective bioaccumulation and toxicity of the chiral pesticide bifenthrin to zebrafish were investigated in this work. The results showed that MWCNTs and MWCNTs-COOH did not affect the preferential bioaccumulation of 1R-cis-BF in zebrafish following exposure to cis-BF enantiomers for 28 days, but which increased cis-BF accumulation amount by 1.03-1.48 times. Further research demonstrated that the genes related to immunity, endocrine activity and neurotoxicity showed enantioselective expression in different zebrafish tissues, and sex-specific differences were observed. The levels of c-fos, th, syn2a, 17β-hsd and cc-chem were expressed as 1.09-2.84 times higher in females and males treated with 1R-cis-BF than in the 1S-cis-BF-treated groups. However, in the presence of MWCNTs or MWCNTs-COOH, c-fos, th, syn2a, 17β-hsd and cc-chem levels were expressed as 1.53-14.92 times higher in females and males treated with 1S-cis-BF than in 1R-cis-BF-treated groups, which indicated that enantioselective expression was altered. The effects of different types of MWCNTs on the enantioselective bioaccumulation and toxicity of BF in zebrafish have little difference. In summary, the presence of MWCNTs or MWCNTs-COOH increased the impact of BF on zebrafish. Therefore, the risks posed by coexisting nanomaterials and chiral pesticides in aquatic environments should be considered.

Systemic Stereoselectivity Study of Fenobucarb: Environmental Behaviors in Greenhouse Vegetables, Fruits, Earthworms, and Soils and Its Cytotoxicity

Fenobucarb (2-sec-butylphenyl methylcarbamate, BPMC) is a potent carbamate pesticide with high insecticidal activity. In this study, the enantioselective accumulation of BPMC in earthworms (Eisenia foetida) and dissipation in cabbage, Chinese cabbage, strawberry, and soils were investigated. The samples were prepared using the QuEChERS method and analyzed using fast and sensitive chiral high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis. The stereoselective accumulation of BPMC enantiomers revealed that S-(+)-BPMC was preferentially accumulated in earthworms rather than its antipode. However, the dissipation studies showed that S-(+)-BPMC degraded faster than the R-(-)-isomer in cabbage, Chinese cabbage, strawberry, and soils. Furthermore, the cytotoxic effect of BPMC enantiomers toward PC12 and N9 neuronal, A549 lung cancer, and MRC5 lung fibroblast cell lines was evaluated using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Compared with R-(-)- and rac-isomers, S-(+)-BPMC exhibited lower cytotoxicity in neuronal cells and a weaker proliferating effect on lung cancer and lung fibroblast cells. Altogether, the findings suggest the use of the pure S-(+)-enantiomer in agricultural management rather than the use of the racemate or the R-(-)-isomer, which might reduce the environmental risk.

Old pesticide, new use: Smart and safe enantiomer of isocarbophos in locust control

Locust plagues are still worldwide problems. Selecting active enantiomers from current chiral insecticides is necessary for controlling locusts and mitigating the pesticide pollution in agricultural lands. Herein, two enantiomers of isocarbophos (ICP) were separated and the enantioselectivity in insecticidal activity against the pest Locusta migratoria manilensis (L. migratoria) and mechanisms were investigated. The significant difference of LD₅₀ between (+)-ICP (0.609 mg/kg bw) and (-)-ICP (79.412 mg/kg bw) demonstrated that (+)-ICP was a more effective enantiomer. The enantioselectivity in insecticidal activity of ICP enantiomers could be attributed to the selective affinity to acetylcholinesterase (AChE). Results of in vivo and in vitro assays suggested that AChE was more sensitive to (+)-ICP. In addition, molecular docking showed that the -CDOKER energies of (+)-ICP and (-)-ICP were 25.6652 and 24.4169, respectively, which suggested a stronger affinity between (+)-ICP and AChE. Significant selectivity also occurred in detoxifying enzymes activities (carboxylesterases (CarEs) and glutathione S-transferases (GSTs)) and related gene expressions. Suppression of detoxifying enzymes activities with (+)-ICP treatment suggested that (-)-ICP may induce the detoxifying enzyme-mediated ICP resistance. A more comprehensive understanding of the enantioselectivity of ICP is necessary for improving regulation and risk assessment of ICP.

Characterization of diphenyl phthalate as an agonist for estrogen receptor: an in vitro and in silico study

Phthalate esters (PAEs) are important pollutants in the environment, which can interfere with the endocrine system by mimicking estrogen. However, limited information is available on modulating the estrogen receptor (ER) of five PAEs including di (2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), benzyl butyl phthalate (BBP), diphenyl phthalate (DPhP) and dicyclohexyl phthalate (DCHP). This study evaluated the agonistic effects of PAEs on human ER. The cytotoxicity assay showed that there were a significant inhibition of the cell proliferation with treatment of five PAEs. Moreover, DPhP does-dependently enhanced ER-mediated transcriptional activity in the reporter gene assay. The increased expression of estrogen-responsive genes (TFF1, CTSD, and GREB1) was also observed in MCF-7 cells treated with DPhP. The result of molecular docking showed that DPhP tended to bind to the agonist conformation of ER compared with the antagonist conformation of ER, demonstrating its agonist characteristic that has been confirmed in the reporter gene assay. Thus, we found that DPhP may be evaluated as an ER agonist in vitro and it can interfere with the normal function of human ER.

Stage Dependent Enantioselective Metabolism of Bifenthrin in Embryos of Zebrafish (Danio rerio) and Japanese Medaka (Oryzias latipes)

Bifenthrin (BF) is a widely used pyrethroid that has been frequently detected in surface waters. Previous studies indicated that BF had antiestrogenic activity in zebrafish embryos but estrogenic activity in posthatch fish. To determine whether age-related differences in metabolism contribute to the endocrine effects in developing fish, embryos from zebrafish and Japanese medaka were exposed to BF before and after liver development. Since the commercial mixture of BF is an isomer-enriched product containing two enantiomers (1R-cis-BF and 1S-cis-BF), enantioselective metabolism was also evaluated. The estrogenic metabolite, 4-hydroxybifenthrin (4-OH-BF) was identified in zebrafish embryos, and formation was higher in animals after liver development (>48 hpf). Treatments with β-glucuronidase indicated that 4-OH-BF underwent conjugation in embryos. Formation was reduced by cotreatment of the cytochrome P450 (CYP450) inhibitor, ketoconazole. Formation of 4-OH-BF was greater when treated with 1R-cis-BF compared to the S-enantiomer. However, metabolites were not observed in medaka embryos. These data indicate enantioselective oxidation of BF to an estrogenic metabolite occurs in zebrafish embryos and, since it is increased after liver development, may partially explain estrogenic activity observed in older animals. The lack of activity in medaka suggests species-specific effects with BF metabolism and may influence risk assessment strategies in wildlife.

Transcriptomic and Histopathological Effects of Bifenthrin to the Brain of Juvenile Rainbow Trout (Oncorhynchus mykiss)

The increased global use of pyrethroids raises concern for non-target aquatic species. Bifenthrin, among the most predominantly detected pyrethroids in the environment, is frequently measured in water samples above concentrations reported to induce neuroendocrine and neurotoxic effects to several threatened and endangered fish species, such as the Chinook salmon and steelhead trout. To better characterize the neurotoxic effect of bifenthrin to salmonids, rainbow trout were treated with environmentally relevant concentrations of bifenthrin (15 and 30 ng/L) for two weeks and assessed for changes in transcriptomic profiles and histopathological alterations. The top bioinformatic pathways predicted to be impaired in bifenthrin-exposed trout were involved in gonadotropin releasing hormone signaling, the dysregulation of iron homeostasis, reduced extracellular matrix stability and adhesion, and cell death. Subsequent histopathological analysis showed a significant increase in TUNEL positive cells in the cerebellum and optic tectum of bifenthrin-treated trout, relative to controls (p < 0.05). These findings suggest that low, ng/L concentrations of bifenthrin are capable of dysregulating proper neuroendocrine function, impair the structural integrity of the extracellular matrix and cell signaling pathways in the brain, and induce apoptosis in neurons of juvenile salmonids following bifenthrin treatment, which is consistent with metabolomic profiles demonstrating a common target and mechanism.

Uptake, Acropetal Translocation, and Enantioselectivity of Perfluorooctane Sulfonate in Maize Coexisting with Copper

Plant uptake and translocation of perfluorooctane sulfonate (PFOS) are critical for food safety and raise major concerns. However, those processes are associated with many undisclosed mechanisms, especially when PFOS coexist with heavy metals. In this study, we investigated the effect of copper (Cu) on PFOS distribution in maize tissues by assessing the PFOS concentration and enantioselectivity. The presence of <100 μmol/L Cu exerted a limited effect on PFOS bioaccumulation, while >100 μmol/L Cu damaged the root cell membrane and increased root permeability, resulting in a higher PFOS concentration in roots. The suppression of acropetal translocation might be attributed to Cu inhibition of carrier proteins. The enantiomer fraction (EF) of 1m-PFOS at <100 μmol/L Cu was higher than that in a commercial product (0.5). Racemic PFOS was detected at >100 μmol/L Cu in roots and the EF variation changed from positive to negative in shoots. These EF results evidenced the existence of a protein-mediated uptake pathway. Besides, this study indicated the challenge of chiral signature application in PFOS source identification, given the effects of heavy metals and plants on PFOS enantioselectivity. The findings provide insight into PFOS bioaccumulation in plants cocontaminated with Cu and will facilitate environmental risk assessment.

Variability of urinary pyrethroid biomarkers in Chinese young-aged men and women over one year

Pyrethroids are a class of the most commonly used insecticides. The urinary metabolites are usually used as biomarkers of pyrethroid exposures in humans. In this study, the temporal variability of urinary pyrethroid biomarkers was investigated among 114 Chinese young-aged adults who provided up to 4-11 urine samples over one year. The detection rates of four urinary pyrethroid biomarkers, 3-phenoxybenzoic acid (3PBA), 4-fluoro-3-phenoxybenzoic acid (4F-3PBA), trans-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (trans-DCCA) and cis-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (cis-DCCA) were 100%, 8%, 69% and 44%, respectively. The intraclass correlation coefficient (ICC) estimates for 3PBA indicated poor reproducibility (<0.15) in the spot urine samples of young-aged adults over a week, month and year. Log-transformed 3PBA used the least number of random spot urine samples (≥4) per person, which would provide a reliable biomarker estimate (ICC≥0.40) over a year. As the predictors of the top 33% yearly average 3PBA concentrations, the sensitivity and specificity of 3PBA ranged from 0.25 to 0.89, 0.58 to 0.96, respectively. Based on the results of this study, we recommend at least 4 urine samples collected 3 months apart for prospective assessment of pyrethroid exposure in the epidemiological studies to estimate exposure-response relationships between pyrethroids and health outcomes with relative long-term exposure periods.

Metabolomic Profiles in the Brains of Juvenile Steelhead (Oncorhynchus mykiss) Following Bifenthrin Treatment

The pyrethroid insecticide, bifenthrin, is frequently measured at concentrations exceeding those that induce acute and chronic toxicity to several invertebrate and fish species residing in the Sacramento-San Joaquin Delta of California. Since the brain is considered to be a significant target for bifenthrin toxicity, juvenile steelhead trout (Oncorhynchus mykiss) were treated with concentrations of bifenthrin found prior to (60 ng/L) and following (120 ng/L) major stormwater runoff events with nontargeted metabolomics used to target transcriptomic alterations in steelhead brains following exposure. Predicted responses were involved in cellular apoptosis and necrosis in steelhead treated with 60 ng/L bifenthrin using the software Ingenuity Pathway Analysis. These responses were predominately driven by decreased levels of acetyl-l-carnitine (ALC), docosahexaenoic acid (DHA), and adenine. Steelhead treated with 120 ng/L bifenthrin had reductions of lysophosphatidylcholines (LPC), lysophosphatidylethanolamines (LPE), and increased levels of betaine, which were predicted to induce an inflammatory response. Several genes predicted to be involved in apoptotic (caspase3 and nrf2) and inflammatory (miox) pathways had altered expression following exposure to bifenthrin. There was a significantly increased expression of caspase3 and miox in fish treated with 120 ng/L bifenthrin with a significant reduction of nrf2 in fish treated with 60 ng/L bifenthrin. These data indicate that bifenthrin may have multiple targets within the brain that affect general neuron viability, function, and signaling potentially through alterations in signaling fatty acids.

Structure-based Identification of Endocrine Disrupting Pesticides Targeting Breast Cancer Proteins

Endocrine disrupting pesticides (EDPs) are exogenous compounds that disrupt endocrine activity. Human exposure to EDPs can occur through occupational contact, and through the consumption of food, milk and water with trace amounts of these pollutants. Several EDPs are epidemiologically linked to breast cancer or are considered as possible carcinogens. However, current evidence is not fully conclusive and their mechanisms of action remain unknown. Thus, the potential interactions between 262 EDPs and 189 proteins associated with breast cancer were evaluated by using a virtual high-throughput screening approach, with AutoDock Vina 1.1.1. The molecular coordinates were previously downloaded from Protein Data Bank and EDCs DataBank, and used for preparation and optimization in Sybyl X-2.0. The best affinity score (-11.0 kcal/mol) was obtained for flucythrinate with the nuclear receptor for vitamin D (VDR). This synthetic pyrethroid, along with other EDPs, such as fluvalinate, bifenthrin, cyhalothrin and cypermethrin, are proposed as multi-target ligands of several proteins related to breast cancer. In addition, the validation of our protocol showed a good accuracy in terms of binding pose prediction and affinity estimation. This study provides a guide to prioritize EDPs for which further in vitro and in vivo analysis could be done to evaluate the risk and possible mechanisms of action of these contaminants and their potential association with breast cancer.

Bifenthrin Induces Fat Deposition by Improving Fatty Acid Uptake and Inhibiting Lipolysis in Mice

Chemical residues in the environment are considered to be important factors that cause obesity. Bifenthrin is one of the pyrethroid pesticides and is widely used worldwide. However, its effect on adipose tissue is ill-defined. Here, we administered bifenthrin/corn oil to adult C57BL/6 mice by gavage. After 6 weeks, the bifenthrin treatment significantly increased their body weight (P = 0.015) and fat mass (P < 0.001). Then we identified 246 differently expressed proteins by proteomic analysis, and they were highly involved in fatty acid uptake and lipid metabolism processes. Interestingly, protein hormone-sensitive lipase and adipose triacylglyceride lipase were downregulated while lipoprotein lipase is upregulated after bifenthrin treatment. Similar effects in 3T3-L1 cells treated with bifenthrin validated the in vivo results. Thus, this study suggests that long-term exposure to low-dose bifenthrin induces fat deposition in mice by improving fatty acid uptake and inhibiting lipolysis, and it may cause obesity in humans.

Mechanisms behind interactive effects of temperature and bifenthrin on the predator avoidance behaviors in parr of chinook salmon (Oncorhynchus tshawytscha)

Many coastal systems have been experiencing the effects of non-chemical and chemical anthropological stressors through respective increases in surface water temperatures and rainstorm-derived runoff events of pyrethroid pesticide movement into waterways such as the San Francisco Bay-Delta. Salmonid populations in the Bay-Delta have been dramatically declining in recent decades. Therefore, the aim of this study was to investigate the interactive effects of bifenthrin, a pyrethroid insecticide, and increasing water temperatures on targeted neuroendocrine and behavioral responses in Chinook salmon (Oncorhynchus tshawytscha) parr (10- month post-hatch). Parr were reared at 11 °C, 16.4 °C, or 19 °C for 14 days and, in the final 96 h of rearing, exposed to nominal concentrations of 0, 0.15, or 1.5 μg/L bifenthrin. A predatory avoidance Y-Maze behavioral assay was conducted immediately following exposures. Parr were presented a choice of clean or odorant zones, and locomotive behavior was recorded. Thyroid hormones (T3 and T4), estradiol, and testosterone were quantified within plasma using ELISAs, and the expression of brain hormone and dopamine receptor genes were also evaluated by qPCR. Brain dopamine levels were analyzed by LC/MS. No significant changes were observed in brain transcripts or plasma hormone concentrations with bifenthrin or increasing temperature. However, temperature did significantly lower brain dopamine levels in fish reared at 19 °C compared to 11 °C controls, but was unaltered by bifenthrin treatment. In contrast, parr reared at 11 °C and exposed to 1.5 μg/L bifenthrin spent significantly less time avoiding a predatory odorant compared to vehicle controls reared at 11 °C. The 16.4 °C and 1.5 μg/L-treated fish spent significantly more time in the neutral arm compared to the odorant and clean arms, as well as spending significantly less time in the clean arm compared to the 11 °C control fish. These results suggest that the interaction of temperature and bifenthrin may be adversely impacting predator-avoidance behavior, which may not be related to dopaminergic responses.

Effects of bifenthrin on sex differentiation in Japanese Medaka (Oryzias latipes)

Bifenthrin (BF) is a pyrethroid insecticide used in urban and agricultural applications. Previous studies in early life stages of fish have indicated anti-estrogenic activity; however, estrogenic activity has been observed in adults. To test the hypothesis that BF impairs sex differentiation, larval Japanese Medaka were exposed to BF during a critical developmental window for phenotypic sexual differentiation. Fish were exposed to environmentally relevant concentrations of BF (0.15 μg/L and 1.5 μg/L), a single concentration (0.3 mg/L) of an estrogen receptor (ER) antagonist (ICI 182,780), and an ER agonist (0.2 ug/L) (17β-estradiol). Fish were exposed at 8 days post hatch (dph) larvae for 30 days. Phenotypic sex, secondary sexual characteristics (SSC) and genotypic sex were investigated at sexual maturity (8 weeks). A trend towards masculinization (p = 0.06) based on the presence of papillary processes in anal fin rays of Japanese Medaka was observed in fish exposed to the lowest concentration of BF. However, genotypic gender ratios were not altered. These results show sex differentiation was not significantly altered by larval exposure to BF in Japanese medaka.

In vitro assessment of corticosteroid effects of eight chiral herbicides

Information regarding the enantioselective endocrine disruption of chiral herbicides is scarce. This study assessed the disrupting effects of eight typical chiral herbicides on corticosteroids (including glucocorticoids and mineralocorticoids). Enantioselectivity of eight chiral herbicides were evaluated for their agonistic/antagonistic effects on glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) with CHOK1 cell line using reporter gene assay. Their influence on the production of corticosteroids were further investigated in H295R cell line using enzyme-linked immunosorbent assay (ELISA). None of the racemates or enantiomers of eight chiral herbicides exhibited GR or MR agonistic activity at non-cytotoxic concentrations. However, rac-propisochlor and S-imazamox antagonized cortisol-induced transactivation of GR by 21.79% and 38.73% at the concentration of 1.0 × 10^-7 M and 1.0 × 10^-6 M, respectively, and R-napropamide remarkably attenuated aldosterone-induced MR transactivation by 68.78% at 1.0 × 10^-6 M. The secretion of cortisol was significantly restrained after treated with 1.0 × 10^-6 M rac-propisochlor and rac-/R-napropamide at the concentration of 1.0 × 10^-6 M by 26.49%, 30.10% and 35.27%, respectively, while this glucocorticoid was remarkably induced by 1.0 × 10^-5 M rac-diclofop-methyl and its two enantiomers at the concentration of 1.0 × 10^-5 M by 75.60%, 100.1% and 68.78%, respectively. Exposure to rac-propisochlor (1.0 × 10^-6 M), S-diclofop-methyl (1.0 × 10^-5 M) or rac-/S-/R- acetochlor (1.0 × 10^-6 M) and rac-/S-/R-lactofen (1.0 × 10^-6 M) inhibited the secretion of aldosterone by approximately 40%. Our findings suggested that chiral herbicides disrupted corticosteroid homeostasis in an enantioselective way. Therefore, more comprehensive screening is required to better understand the ecological and health risks of chiral pesticides.

Effects of cis-bifenthrin enantiomers on the growth, behavioral, biomarkers of oxidative damage and bioaccumulation in Xenopus laevis

Chirality should be taken into consideration when assessing the effect of synthetic pyrethroids to aquatic environmental safety. In our study, 96 h acute toxicity assay showed that enantiomers of cis-BF had an addictive effect of toxicity on Xenopus laevis and R-cis-bifenthrin(R-cis-BF) had higher acute toxicity than S-cis-BF. In chronic assay, R-cis-BF exerted more toxic effect on behavior and development of tadpoles than S-cis-BF, and there was also enantioselective effect of cis-BF on antioxidant enzyme and LDH activity. Besides, thyroid development was also affected at the gene and hormone level, with varied effects observed with different exposure enantiomers. Moreover, in the enantioselective accumulation and tissue distribution of enantiomer assays, results showed that R-cis-BF had higher affinity to organisms than S-cis-BF. This study provided the evidence that chiral pesticides enantioselectively affected development of amphibians, and also shed light on the understanding of enantioselectivity in both acute and chronic eco-toxicities to improve risk assessment and regulation of chiral pesticides.

Chronic exposure to environmental levels of cis-bifenthrin: Enantioselectivity and reproductive effects on zebrafish (Danio rerio)

Synthetic pyrethroids (SPs) are broadly used to control pests and have been widely detected in aquatic environments, prompting concern over its risk to the health of non-target organisms. The present study evaluated whether long-term (60 d) exposure to low doses (0, 20, 100, and 500 ng/L) of cis-BF enantiomers (1S-cis-BF and 1R-cis-BF) could cause reproductive endocrine disturbance to zebrafish. Exposure to 1S-cis-BF has stronger reproductive impairment effect than 1R-enantiomer, indicating that the enantioselectivity of cis-BF on fish reproduction. Significant decrease of cumulative spawning of zebrafish was observed as a result of cis-BF exposure. And the retardations of testis and ovaries development found in histopathological section were suggested to be important cause for the decreased fecundity. Cis-BF decreased the total motility of sperm but did not affect sperm density. Relatively high levels of cis-BF detected in the gonads of males and females may directly impair gametogenesis. In addition, alterations in the expression of key genes (cyp17, cyp19a and 17β-hsd) associated with reproductive endocrine pathways were correlated well with the significant changes in sex hormone contents (E2 and T) and these results may relate to gonadal development and maturation of germ cells in females or/and males which were suspected to be a likely underlying mechanism. Furthermore, the reduction of quality of F1 embryo derived from the unexposed females and exposed males (UE♀ × E♂) demonstrated that male exposure had greater adverse effects on offspring. Our results indicate that long term, low dose exposure to cis-BF can enantioselectively impair the reproduction system of fish, and induce toxicity related abnormalities in non-exposed offspring. This study has important implications for environmental risk assessment of chiral pesticides that are concurrently present in aquatic systems.

Enantioselectivity of toxicological responses induced by maternal exposure of cis-bifenthrin enantiomers in zebrafish (Danio rerio) larvae

The maternal transfer and developmental toxicity of chiral contaminants with respect to enantioselectivity have rarely been investigated. Here, the residues and toxicological responses of cis-BF, a typical chiral pesticide, were studied in the progeny of adult zebrafish exposed to cis-BF (0, 20, 100, and 500 ng/L) for 60 days. Cis-BF enantiomers exhibited the equal maternal transfer potentials. GC/MSD analysis showed that parental 1S-cis-BF exposure could disrupt the components of fatty acids in offspring embryos. In transcriptional expression, the whole differentially expressed genes were significantly enriched in GO categories, including the processes related to lipid biosynthesis/metabolism. The perturbations of fatty acids suggested that cis-BF has potential negative impacts on embryos' development. Furthermore, enantioselective growth inhibition and developmental neurotoxicity in larvae were also observed. The mRNA expressions of neuronal development genes were significantly changed in 1S-exposed offspring, so were the levels of the neurotransmitters and larval locomotion. Our results show that the cis-BF induced the growth inhibition and neurotoxicity in zebrafish larvae, which may be mediated by the development interference in embryos related to the disrupted fatty acid composition. Furthermore, the toxicological response to 1S-cis-BF was greater than that to the 1R-enantiomer in the offspring of exposed adults.

The effects of bifenthrin and temperature on the endocrinology of juvenile Chinook salmon

The San Francisco Bay delta (USA) is experiencing seasonally warmer waters attributable to climate change and receives rainstorm runoff containing pyrethroid pesticides. Chinook salmon (Oncorhynchus tshawytscha) inhabit the affected waterways from hatch through smoltification, and thus juvenile fish may experience both pyrethroid and warmer water exposures. The effects of higher temperatures and pesticide exposure on presmolt Chinook are unknown. To improve understanding of the potential interaction between temperature and pesticide exposure on salmonid development, juvenile alevin and fry were reared in 11, 16.4, and 19 °C freshwater for 11 d and 2 wk, respectively, and exposed to nominal concentrations of 0, 0.15, and 1.5 µg/L bifenthrin for the final 96 h of rearing. Estradiol-17β (E2), testosterone, triiodothyronine, and thyroxine levels were measured in whole-body homogenates using hormone-specific enzyme-linked immunosorbent assays. Brain gonadotropin-releasing hormone receptor (GnRH2), dopamine receptor 2A, and growth hormone 1 (GH1) mRNA levels were measured using quantitative PCR. Results showed significantly decreased survival and condition factors observed with increasing temperature in alevin. Alevin thyroid hormones increased significantly with temperature, but fry thyroid hormones trended toward a decrease at lower temperatures with increasing bifenthrin exposure. There were significant reductions in fry testosterone and E2 at 11 °C with increasing bifenthrin treatments and significant changes in GnRH2 and GH1 gene expression in both alevin and fry, indicating potential disruption of hormonal and signaling pathways. Environ Toxicol Chem 2019;38:852-861. © 2019 SETAC.

Evaluation of the estrogen receptor alpha as a possible target of bifenthrin effects in the estrogenic and dopaminergic signaling pathways in zebrafish embryos

Bifenthrin (BF) is a pyrethroid insecticide widely used in urban and agricultural applications. Previous studies in embryos of zebrafish have shown that BF can affect estradiol biosynthesis and the dopaminergic system. To examine the role of the estrogen receptor (ER) in the endocrine effects of BF, embryos were exposed for 96 h to a mixture of 0.15 and 1.5 μg/L BF and an ER agonist (17α-ethynylestradiol - EE2) at 0.09 μg/L. Transcripts related to estrogenic (vitellogenin VTG) and dopaminergic (tyrosine hydroxylase (TH), dopamine receptor 1 (DR1), monoamine oxidase (MAO), and catechol-O-methyltransferase b (COMTb)) signaling pathways were investigated by qRT-PCR. Dopamine (DA) and its metabolites (homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC)) were also measured. There was a significant increase in VTG, DR1, MAO and COMTb mRNA levels and HVA-DA ratios within all zebrafish embryos exposed to EE2, including EE2 alone, 0.15 μg/L BF + EE2 and 1.5 μg/L BF + EE2. A significant decrease in homogenate concentrations of DA was observed within all zebrafish embryos exposed to EE2, which included EE2 alone, 0.15 μg/L BF + EE2 and 1.5 μg/L BF + EE2. Co-exposure of BF with EE2 failed to diminish estrogenic or dopaminergic signaling in embryos. Additionally, embryos with diminished ERα expression by morpholino injection were exposed to 0.15 μg/L BF, 1.5 μg/L BF and 0.09 μg/L EE2, with subsequent gene expression measurements. ERα knockdown did not prevent the effects of BF, indicating ERα may have a limited role in the estrogenic and dopaminergic effects caused by BF in zebrafish embryos.

Effects of pyrethroid insecticides on hypothalamic-pituitary-gonadal axis: A reproductive health perspective

Pyrethroids, a class of ubiquitous insecticides, have been recognized as endocrine-disrupting chemicals (EDCs). A lot of studies have implied the endocrine-disrupting effects of pyrethroids on the hypothalamic-pituitary-gonadal (HPG) axis. However, there are few review articles regarding the effects of pyrethroids on the HPG axis of mammal and human, especially new research progress made in this area. The present review sums up the effects of pyrethroids on the HPG axis-related reproductive outcomes, including epidemiological investigations based on human biomonitoring, animal studies and in vitro tests. Mechanisms have described that the endocrine-disrupting effects of pyrethroids on mammal can be mediated via the interaction with steroid receptors, the direct action on ion channels and signaling molecules. Finally, we summarize the current research gaps and suggest future directions in this topic.

Chiral pharmaceuticals: Environment sources, potential human health impacts, remediation technologies and future perspective

Chiral pharmaceuticals (CPs), including non-steroid anti-inflammatory drugs (NSAIDs), β-blockers and some herbicide and pesticides, are widely used in aquaculture, clinical treatment and many other fields. However, people are increasingly concerned about such ubiquitous pollutants, which can frequently be detected in contaminated soil and water. In large part, the significant sources of chiral pharmaceuticals stem from industrial processes, such as the direct discharge of untreated or incompletely treated wastewaters containing chiral pharmaceuticals, incorrect storage and use, animal wastes and biosolids. The main ways for human exposure to chiral pharmaceuticals are the disease treatment process and chiral pharmaceuticals contaminants. According to the results of a series of toxic studies, some diseases, even cancers, may be associated with exposure to certain chiral pharmaceuticals. Therefore, the treatment of chiral pharmaceuticals has become an important issue. The current advanced remediation techniques for chiral pharmaceuticals include the conventional method (sorption and sonolysis), biotransformation (an aerobic granular sludge-sequencing batch reactor and constructed wetland system) and advanced oxidation processes (ozonation and photocatalysis). Herein, in this review, we summarize the current status and sources of chiral pharmaceuticals, potential effects on human health, as well as the superiority, disadvantages and prospects of current advanced remediation technologies. Moreover, we also anticipate the prospect of the future research needed for chiral pharmaceuticals pollutant remediation.

Enantioselectivity in biotransformation and bioaccumulation processes of typical chiral contaminants

Chirality is a critical topic in the medicinal and agrochemical fields. One quarter of all agrochemicals was chiral in 1996, and this proportion has increased remarkably with the introduction of new compounds over time. Despite scientists have made great efforts to probe the enantiomeric selectivity of chiral chemicals in the environment since early 1990s, the different behaviours of individual enantiomers in biologically mediated processes are still unclear. In the present review, we highlight state-of-the-knowledge on the stereoselective biotransformation and accumulation of chiral contaminants in organisms ranging from invertebrates to humans. Chiral insecticides, fungicides, and herbicides, polychlorinated biphenyls (PCBs), pharmaceuticals, flame retardants hexabromocyclododecane (HBCD), and perfluorooctane sulfonate (PFOS) are all included in the target compounds. Key findings included: a) Changes in the enantiomeric fractions in vitro and in vivo models revealed that enantioselectivity commonly occurs in biotransformation and bioaccumulation. b) Emerging contaminants have become more important in the field of enantioselectivity together with their metabolites in biological transformation process. c) Chiral signatures have also been regarded as powerful tools for tracking pollution sources when the contribution of precursor is unknown. Future studies are needed in order to understand not only preliminary enrichment results but also detailed molecular mechanisms in diverse models to comprehensively understand the behaviours of chiral compounds.

Estimation of soil-specific microbial degradation of alpha-cypermethrin by compound-specific stable isotope analysis

In this study, the microbial degradation of alpha-cypermethrin was investigated in 14 different soil samples by compound-specific stable isotope analysis. After 40 and 80 days of microbial degradation, the stable carbon isotope ratios of alpha-cypermethrin shifted from - 32.18 to - 31.87‰ ~ - 31.12 and - 31.45‰ ~ - 29.75‰ in the soils, respectively. The microbial degradation percentages of alpha-cypermethrin were calculated as 15.6~44.3% after 40 days of incubation and 33.3~73.9% after 80 days of incubation. The effects of physicochemical properties of soil samples were then explored on the microbial degradation of alpha-cypermethrin. The results revealed that the microbial degradation percentages were positively correlated with the contents of organic carbon in soils with Pearson correlation coefficients of 0.794 and 0.843 for 40 and 80 days of microbial degradation, respectively, indicating that the microbial degradation of alpha-cypermethrin was faster in the soil with higher content of organic carbon. Accordingly, soil-specific use should be considered in practical agricultural application of alpha-cypermethrin to reduce the residue of the pesticide.

Effects of pyrethroid pesticide cis-bifenthrin on lipogenesis in hepatic cell line

Mounting evidence suggests there is a link between exposure to synthetic pyrethroids (SPs) and the development of obesity. The information presented in this study suggests that cis-bifenthrin (cis-BF) could activate pregnane X receptor (PXR) mediated pathway and lead to the lipid accumulation of human hepatoma (HepG2) cells. Cells were incubated in the control or different concentrations of cis-BF for 24 h. The 1 × 10^-7 M and 1 × 10^-6 M cis-BF exposure were found to induce cellular triglyceride (TG) accumulation significantly. This phenomenon was further supported by Oil Red O Staining assay. The cis-BF exposure caused upregulation of PXR gene and protein. Correspondingly, we also observed the increased expression of downstream genes involved in lipid formation and the inhibition of the expression of β-oxidation. As chiral pesticide，cis-BF was further conformed to behave enantioselectivity in the lipid metabolism. Rather than 1R-cis-BF, HepG2 cells incubated with 1S-cis-BF exhibited a significant TG accumulation. 1S-cis-BF also showed a higher binding level, of which the KD value was 9.184 × 10^-8 M in the SPR assay, compared with 1R-cis-BF (3.463 × 10^-6 M). In addition, the molecular docking simulation analyses correlated well with the KD values measured by the SPR, indicating that 1S-cis-BF showed a better binding affinity with PXR. The results in this study also elucidates the differences between the two enantiomers of pyrethroid-induced toxicity in lipid metabolism of non-target organism.

Direct Detection of Potential Pyrethroids in Yangtze River via an Imprinted Multilayer Phosphorescence Probe

A novel tailored multilayer probe for monitoring potential pyrethroids in the Yangtze River was proposed. The room-temperature phosphorescence method was applied to realize a detection strategy that is superior to the fluorescence method. Efficient Mn-doped ZnS quantum dots with uniform size of 4.6 nm were firstly coated with a mesoporous silica to obtain a suitable intermediate transition layer, then an imprinted layer containing bifenthrin specific recognition sites was anchored. Characterizations verified the multilayer structure convincingly and the detection process relied on the electron transfer-induced fluorescence quenching mechanism. Optional detection time and standard detection curve were obtained within a concentration range from 5.0 to 50 μmol L^-1. The stability was verified to be good after 12 replicates. Feasibility of the probe was proved by monitoring water samples from the Zhenjiang reach of the Yangtze River. The probe offers promise for direct bifenthrin detection in unknown environmental water with an accurate and stable phosphorescence analysis strategy.

Enantioselective Effects of Metalaxyl Enantiomers in Adolescent Rat Metabolic Profiles Using NMR-Based Metabolomics

More than 30% of the registered pesticides are chiral with one or more chiral centers and exist as two or more enantiomers. The frequency of chiral chemicals and their environmental safety has been considered in their risk assessment in recent decades. Despite the fact that metabolic disturbance is an important sensitive molecular initiating event of toxicology effects, the potential mechanisms of how chiral compounds affect metabolism phenotypes in organisms remain unclear. As a typical chiral pesticide, metalaxyl is an acylalanine fungicide with systemic function. Although the fungicidal activity almost comes from the R-enantiomer, the toxicity of both enantiomers in animals and human beings is not yet clear. In this study, a nuclear magnetic resonance (NMR)-based metabolomics approach was adopted to evaluate the enantioselectivity in metabolic perturbations in adolescent rats. On the basis of multivariate statistical results, stable and evident metabolic profiles of the enantiomers were obtained. When rats were exposed to R-metalaxyl, the significantly perturbed metabolic pathways were biosynthesis of valine, leucine, and isoleucine, synthesis and degradation of ketone bodies, and metabolism of glycerolipid. In contrast, more significantly perturbed metabolic pathways were obtained when the rats were exposed to S-metalaxyl, including glycolysis, biosynthesis of valine, leucine, and isoleucine, metabolism of glycine, serine, and threonine, synthesis and degradation of ketone bodies, metabolism of glycerophospholipid and glycerolipid. These abnormal metabolic pathways were closely related to liver metabolism. These results offer more detailed information about the enantioselective metabolic effects of metalaxyl in adolescent development and provide data for the health risk assessment of metalaxyl at molecular level.

Pyrethroid Pesticide Exposure and Risk of Primary Ovarian Insufficiency in Chinese Women

Pyrethroids are a class of widely used insecticides. Female animal studies suggested that pyrethroid exposure impaired ovarian function, which resulted in similar symptoms of primary ovarian insufficiency (POI). However, it is still unknown whether this association applies to women. In this case-control study, a total of 172 POI patients and 247 control women were recruited in Zhejiang, China. The urinary concentrations of metabolites of pyrethroids, 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), as well as the serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and anti-Mullerian hormone (AMH) were determined. The associations of pyrethroid metabolites with POI and POI-related hormones were accessed using unconditional logistic regression. Higher urinary levels of 3-PBA were significantly associated with increased risk of POI [adjusted odds ratio (OR) = 2.344, 95% CI: 1.193-4.607 for the highest vs lowest quartile of 3-PBA, p = 0.013]. Stratified analyses showed that each log increase in urinary 3-PBA concentration was significantly associated with an induction in odds of 51.0% being in the highest quartile of FSH and 28.6% being in the highest quartile of LH levels, whereas a 25.9% reduction in odds of being in the highest quartile of AMH levels (All p for trend <0.05). To our knowledge, this is the first case-control study to report an association of pyrethroid exposure with increased risk of POI in women.

Effects of bifenthrin exposure on the estrogenic and dopaminergic pathways in zebrafish embryos and juveniles

Bifenthrin is a pyrethroid insecticide used in urban and agricultural applications. Previous studies have shown that environmentally relevant (ng/L) concentrations of bifenthrin increased plasma concentrations of 17β-estradiol (E2) and altered the expression of dopaminergic pathway components. The dopaminergic neurons can indirectly regulate E2 biosynthesis, suggesting that bifenthrin may disrupt the hypothalamic-pituitary-gonadal (HPG) axis. Because embryos do not have a complete HPG axis, the hypothesis that bifenthrin impairs dopamine regulation was tested in embryonic and 1-mo-old juvenile zebrafish (Danio rerio) with exposure to measured concentrations of 0.34 and 3.1 µg/L bifenthrin for 96 h. Quantitative reverse transcriptase polymerase chain reaction was used to investigate transcripts of tyrosine hydroxylase (TH), dopamine receptor 1 (DR1) and 2A (DR2A), dopamine active transporter (DAT), estrogen receptor α (ERα), ERβ1, ERβ2, luteinizing hormone β (LHβ), follicle-stimulating hormone β (FSHβ), vitellogenin (VTG), cytochrome P450 cyp19a1a, and cyp19a1b. Levels of E2 were measured by enzyme-linked immunosorbent assay (ELISA). Dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) concentrations were measured by liquid chromatrography-tandem mass spectrometry (LC-MS/MS). Significant decreases in TH and DR1 transcripts and HVA levels, as well as ratios of HVA/dopamine and HVA+DOPAC/dopamine, in zebrafish embryos were observed after bifenthrin treatment. In juveniles, a significant increase in the expression of ERβ1 and the DOPAC to dopamine ratio was noted. These results show a possible antiestrogenic effect of bifenthrin in embryos, and estrogenicity in juveniles, indicating life-stage-dependent toxicity in developing fish. Environ Toxicol Chem 2018;37:236-246. © 2017 SETAC.

Effects of metals on enantioselective toxicity and biotransformation of cis-bifenthrin in zebrafish

Co-occurrence of pyrethroids and metals in watersheds previously has been reported to pose great risk to aquatic species. Pyrethroids are a class of chiral insecticides that have been shown to have enantioselective toxicity and biotransformation. However, the influence of metals on enantioselectivity of pyrethroids has not yet been evaluated. In the present study, the effects of cadmium (Cd), copper (Cu), and lead (Pb) on the enantioselective toxicity and metabolism of cis-bifenthrin (cis-BF) were investigated in zebrafish at environmentally relevant concentrations. The addition of Cd, Cu, or Pb significantly increased the mortality of zebrafish in racemate and R-enantiomer of cis-BF-treated groups. In rac-cis-BF- or 1R-cis-BF-treated groups, the addition of Cd, Cu, or Pb caused a decrease in enantiomeric fraction (EF) and an increased ratio of R-enantiomer residues in zebrafish. In 1S-cis-BF-treated groups, coexposure to Cd led to a lower EF and decreased residue levels of S-enantiomer. In addition, coexposure to the 3 metals resulted in different biodegradation characteristics of each enantiomer accompanied with differential changes in the expression of cytochrome P450 (CYP)1, CYP2, and CYP3 genes, which might be responsible for the enantioselective biodegradation of cis-BF in zebrafish. These results suggest that the influence of coexistent metals should be considered in the ecological risk assessment of chiral pyrethroids in aquatic environments. Environ Toxicol Chem 2017;36:2139-2146. © 2017 SETAC.

Association of pyrethroids exposure with onset of puberty in Chinese girls

Pyrethroids, a class of ubiquitous insecticides, have been considered as endocrine-disrupting chemicals (EDCs). Female animal studies suggested that early-life pyrethroids exposure might delay puberty onset. However, it remains unclear whether this association applies to human populations. A total of 305 girls at the ages of 9-15 years old were recruited in Hangzhou, China in this study. The concentration of the common metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), was analyzed in urine samples to reflect the exposure level of pyrethroids. The associations of 3-PBA with pubertal stages were evaluated using a multinomial logistic regression model. The geometric mean level of 3-PBA was 1.11 μg/L (1.42 μg/g for creatinine-adjusted concentration). There was a significant 45% reduction in odds of being in breast stage 3 (B3) per one-unit increase in the log-transformed 3-PBA levels [OR = 0.55 (95%CI: 0.31-0.98), p = 0.042]. A similar negative association was found between urinary 3-PBA levels with later onset by pubic hair stage 2 (P2) [OR = 0.56 (95%CI: 0.36-0.90), p = 0.015]. Similar negative association was also observed between urinary 3-PBA levels and pubertal onset indicated by menarche [OR = 0.51 (95%CI: 0.28-0.93), p = 0.029]. For the first time to our knowledge, this work reveals that pyrethroids exposure may increase the risk of delayed pubertal onset in girls.

Fluorescent aptasensor for 17β-estradiol determination based on gold nanoparticles quenching the fluorescence of Rhodamine B

In this paper, we developed a fluorescent aptasensor for 17β-estradiol (E2) determination in aqueous solution using label-free E2-specific aptamer, gold nanoparticles (AuNPs) and Rhodamine B (RhoB) as sensing probe, fluorescent quencher and fluorescent indicator respectively. In the absence of E2, AuNPs were wrapped by E2 aptamer and maintained dispersed in NaCl solution basically. These dispersed AuNPs could effectively impair the originally high fluorescence of RhoB. Contrarily, in the presence of E2, E2 aptamer could specifically combine with E2 to form E2-aptamer complex, so the AuNPs were released by E2 aptamer and aggregated under the influence of NaCl. The aggregated AuNPs have a weak influence on RhoB fluorescence. Therefore, the E2 concentration can be determined by the change of fluorescence intensity of RhoB. This fluorescent assay has a detection limit as low as 0.48 nM, a linear range from 0.48 to 200 nM, and high selectivity over other disrupting chemicals. It was applied to determine E2 in water samples with recoveries in the range of 94.3-111.7%. The fluorescent aptasensor holds great potential for E2 detection in environmental water samples.

Bifenthrin Causes Trophic Cascade and Altered Insect Emergence in Mesocosms: Implications for Small Streams

Direct and indirect ecological effects of the widely used insecticide bifenthrin on stream ecosystems are largely unknown. To investigate such effects, a manipulative experiment was conducted in stream mesocosms that were colonized by aquatic insect communities and exposed to bifenthrin-contaminated sediment; implications for natural streams were interpreted through comparison of mesocosm results to a survey of 100 Midwestern streams, USA. In the mesocosm experiment, direct effects of bifenthrin exposure included reduced larval macroinvertebrate abundance, richness, and biomass at concentrations (EC₅₀'s ranged from 197.6 to 233.5 ng bifenthrin/g organic carbon) previously thought safe for aquatic life. Indirect effects included a trophic cascade in which periphyton abundance increased after macroinvertebrate scrapers decreased. Adult emergence dynamics and corresponding terrestrial subsidies were altered at all bifenthrin concentrations tested. Extrapolating these results to the Midwestern stream assessment suggests pervasive ecological effects, with altered emergence dynamics likely in 40% of streams and a trophic cascade in 7% of streams. This study provides new evidence that a common pyrethroid might alter aquatic and terrestrial ecosystem function at the regional scale.

Tissue distribution, metabolism and hepatic tissue injury in Chinese lizards (Eremias argus) after a single oral administration of lambda-cyhalothrin

Lambda-cyhalothrin (LCT) is a widely used pyrethroid with neurotoxicity. However, little is known about the toxicokinetics of LCT in reptiles. In this study, the absorption, distribution, metabolism and excretion of LCT in Chinese lizards (Eremias Argus) were determined following a single dose (10 mg kg^-1) treatment. In the liver, brain, gonads and skin, LCT levels peaked within several hours and then decreased rapidly. However, the concentration of LCT gradually increased in the fat tissue. More than 90% of the LCT dose was excreted in the faeces. One LCT metabolite, 3-phenoxybenzoic acid (PBA), was detected in lizard plasma and tissues. PBA preferentially accumulates in the brain and plasma. The half-life of PBA in the brain was 3.2 days, which was 35.4-fold greater than that of LCT. In the plasma, the concentration of PBA was significantly higher than that of LCT. The bioaccumulation of LCT in tissues was enantioselective, and the enantiomeric fractions (EF) ranged from 0.72 to 0.26. The preferential accumulation of enantiomers changed according to exposure time, but the reasons behind this phenomenon were not clear. For pathological analysis, vacuolation of the cytoplasm and large areas of necrosis were observed in the liver sections after 168 h of dosing. The liver tissues exhibited both decreases in the hepatosomatic index and histopathological lesions during the exposure period. In this study, the effect concentration of LCT in lizards was 200-fold lower than its LD₅₀ value used in risk assessments for birds. These results may provide additional information for the risk assessment of LCT for reptiles and indicate that birds may not be an ideal surrogate for reptile toxicity evaluation.

Enantioselective metabolism and toxic effects of metalaxyl on primary hepatocytes from rat

Enantiomers of chiral compounds often exhibit enantioselective adverse effects and biochemical processes in non-target organisms. In this study, enantioselective metabolism and toxic effects of metalaxyl enantiomers on primary rat hepatocytes were investigated. Stereoselectivity was observed on both degradation of metalaxyl and formation of metabolites. (-)-R-metalaxyl eliminated faster than (+)-S-metalaxyl, while the hydroxylmetalaxyl, demethylmetalaxyl, and didemethylmetalaxyl metabolites derived from 50-μM (+)-S-metalaxyl after 24 h of incubation were approximately 1.57, 1.43, and 1.86 times more than that of (-)-R-metalaxyl, respectively. According to the methyl tetrazolium (MTT) assay, the EC50 values (24 h) for rac-, (+)-S-, and (-)-R-metalaxyl were 1788.22, 2066.73, and 2263.71 μM, respectively. An accordant enantioselective effect on oxidative stress suggested that the enantioselective cytotoxicity induced by metalaxyl enantiomers may partly contribute to enantioselective oxidative damage and mitochondrial dysfunction. Such results could be of great importance for credible environmental and toxicological risk assessment of metalaxyl.

Comparative toxicity and bioaccumulation of fenvalerate and esfenvalerate to earthworm Eisenia fetida

More attention is being paid to the enantioselective toxicity of chiral pesticides. However, limited investigations have been done to assess the ecological risks of chiral pesticides to soil community. Fenvalerate (FV), an extensively used synthetic pyrethroid, is a typical chiral pesticide. The most insecticidally active enantiomer of FV, esfenvalerate (ESFV), also has been marketed and widely used. In this study, the toxicological sensitivity and bioaccumulation of FV and ESFV in earthworms were assessed. The results showed that FV was less toxic than ESFV, but more accumulated in earthworms. ESFV was at least 4 times more toxic to earthworms than FV according to the filter paper contact toxicity test and the artificial soil test. Enantiospecific induction in oxidative stress was observed in earthworms exposed to FV and ESFV. The bioaccumulation of FV and ESFV in earthworm tissues was also enantioselective, preferentially accumulating FV. The uptake of ESFV by earthworms was lower than that of FV, so that the biota to soil accumulation factor (BSAF) value of ESFV was lower than that of FV. Our findings suggest that the enantioselective toxicity and bioaccumulation of chiral pesticides should be considered for evaluating ecological risks of these compounds to non-target organisms.

Triazole fungicide tebuconazole disrupts human placental trophoblast cell functions

Triazole fungicides are one of the top ten classes of current-use pesticides. Although exposure to triazole fungicides is associated with reproductive toxicity in mammals, limited information is available regarding the effects of triazole fungicides on human placental trophoblast function. Tebuconazole (TEB) is a common triazole fungicide that has been extensively used for fungi control. In this work, we showed that TEB could reduce cell viability, disturb normal cell cycle distribution and induce apoptosis of human placental trophoblast cell line HTR-8/SVneo (HTR-8). Bcl-2 protein expression decreased and the level of Bax protein increased after TEB treatment in HTR-8 cells. The results demonstrated that this fungicide induced apoptosis of trophoblast cells via mitochondrial pathway. Importantly, we found that the invasive and migratory capacities of HTR-8 cells decreased significantly after TEB administration. TEB altered the expression of key regulatory genes involved in the modulation of trophoblast functions. Taken together, TEB suppressed human trophoblast invasion and migration through affecting the expression of protease, hormones, angiogenic factors, growth factors and cytokines. As the invasive and migratory abilities of trophoblast are essential for successful placentation and fetus development, our findings suggest a potential risk of triazole fungicides to human pregnancy.