Enantioselective disruption of the endocrine system by Cis-Bifenthrin in the male mice

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.

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.

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.

Bifenthrin reduces pregnancy potential via induction of oxidative stress in porcine trophectoderm and uterine luminal epithelial cells

Exposure to pesticides has become a serious concern for the environment and human health. Bifenthrin, a synthetic pyrethroid pesticide, is one of the most frequently used pesticides worldwide. Despite the toxic potential of bifenthrin, no studies have elucidated the cytotoxic response of bifenthrin in maternal and fetal cells that are involved in the implantation process. In this study, the cytotoxic effect of bifenthrin was investigated using porcine trophectoderm (pTr) and uterine luminal epithelial (pLE) cells. The results showed that bifenthrin suppressed cell proliferation and viability in pTr and pLE cells. In particular, bifenthrin induced cell cycle arrest, resulting in apoptosis in both cell lines. We found that bifenthrin damaged the mitochondria and induced the production of reactive oxygen species, causing endoplasmic reticulum stress and calcium dysregulation in pTr and pLE cells. Finally, bifenthrin altered the MAPK/PI3K signaling pathway and pregnancy-related gene expression. Collectively, our results suggest that bifenthrin reduces the implantation potential of embryos and may help elucidate the mechanisms underlying toxin-derived cytotoxicity in maternal and fetal cells.

Enantioselectivity effects of imazethapyr enantiomers to metabolic responses in mice

Imazethapyr (IMZT) is a typical chiral pesticide with two enantiomers with the R-IMZT having the main herbicidal activity. However, the enantioselectivity of the effects of IMZT enantiomers on human and animals is still unclear. In this study, a nuclear magnetic resonance (NMR)-based metabolomics method and determination of oxidative stress were used to evaluate the enantioselectivity of IMZT enantiomers in mice. The results showed that the R-IMZT caused larger disturbances of endogenous metabolites and the S-IMZT had stronger interferences to oxidation defense system. The significantly perturbed metabolic pathways in mice exposed to the R-enantiomer were the valine, leucine and isoleucine biosynthesis pathway as well as the phenylalanine, tyrosine and tryptophan biosynthesis pathway. However, exposure of mice to the S-enantiomer did not significantly affect the metabolic pathways, but exposure led to an increase of catalase (CAT) activity and an increase in malondialdehyde (MDA) content in the liver. These results indicate that we need to conduct a more comprehensive assessment of the health risks of pesticide monomers in the future. In a word, these results provide more evidence for assessing the differences in health risks of IMZT enantiomers to mammals as well as provide more references for the promotion and use of pesticide monomers in the future.

Imidacloprid disrupts the endocrine system by interacting with androgen receptor in male mice

In the current study, six-week-old male ICR mice were administered imidacloprid (IMI) at concentrations of 3, 10 and 30 mg/L for a duration of 10 weeks to investigate the toxicity of IMI on the endocrine system. We observed that testicular morphology was severely impaired and damaged, and the levels of serum testosterone (T) and the expression of androgen receptor (AR) decreased significantly. Molecular docking analysis suggested that IMI docks into the active site of AR successfully and that three key hydrogen bonds were formed with the active site residues Glu11, Gln41 and Lys138. The binding free energy value of the AR-IMI complex suggested a stable binding between IMI and AR. All these results indicated that IMI could interact with AR. In addition, major genes in the testis involved in the synthesis of cholesterol and T were generally inhibited, and the serum cholesterol sources were also reduced. Moreover, the aromatase in male mice was lacking after subchronic IMI exposure. The data acquired from the present study indicated that IMI could lead to endocrine disruption by interacting with AR and influence the expression of genes involved in the production of T in male mice.

Coexposure to environmental concentrations of cis-bifenthrin and graphene oxide: Adverse effects on the nervous system during metamorphic development of Xenopus laevis

Despite the great concerns associated with the combined biological effects of nanoparticles and insecticides, the current understanding of the corresponding ecological risks remains limited. Xenopus laevis (X. laevis) tadpoles were exposed to various concentrations of typical pyrethroid (cis-bifenthrin; cis-BF), either alone or in combination with graphene oxide (GO), for 21 days. The presence of GO resulted in increased bioconcentration of cis-BF and a higher 1S-enantiomer fraction. Exposure to cis-BF and GO caused further reduction in pre-metamorphic developmental rates and activated dopaminergic, noradrenergic, and serotonergic neurotransmitter systems. Reduced tadpole activity and levels of genomic DNA methylation at cytosine nucleotides (5hmC) were observed in the coexposure groups. These results indicate that GO enhance the bioconcentration of cis-BF and promote the conversion of its 1R-enantiomer to the 1S form, which lead to disruption of neurotransmitter systems as well as interference in metamorphic development.

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.

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.

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.

Stereoselective degradation and thyroid endocrine disruption of lambda-cyhalothrin in lizards (Eremias argus) following oral exposure

The disturbance of the thyroid system and elimination of chiral pyrethroid pesticides with respect to enantioselectivity in reptiles have so far received limited attention by research. In this study, bioaccumulation, thyroid gland lesions, thyroid hormone levels, and hypothalamus-pituitary-thyroid axis-related gene expression in male Eremias argus were investigated after three weeks oral administration of lambda-cyhalothrin (LCT) enantiomers. In the lizard liver, the concentration of LCT was negatively correlated with the metabolite-3-phenoxybenzoic acid (PBA) level during 21 days of exposure. (+)-LCT exposure induced a higher thyroid follicular epithelium height than (-)-LCT exposure. The thyroxine levels were increased in both treated groups while only (+)-LCT exposure induced a significant change in the triiodothyronine (T3) level. In addition, the expressions of hypothalamus-pituitary-thyroid axis-related genes including thyroid hormone receptors (trs), deiodinases (dios), uridinediphosphate glucuronosyltransferase (udp), and sulfotransferase (sult) were up-regulated after exposure to the two enantiomers. (+)-LCT treatment resulted in higher expression of trs and (-)-LCT exposure led to greater stimulation of dios in the liver, which indicated PBA-induced antagonism on thyroid hormone receptors and LCT-induced disruption of thyroxine (T4) deiodination. The results suggest the (-)-LCT exposure causes higher residual level in lizard liver while induces less disruption on lizard thyroid activity than (+)-LCT.

Allethrin toxicity causes reproductive dysfunction in male rats

Pyrethroids are widely used for domestic and agricultural purposes and their use is increasing, especially in developing countries. Uncontrolled use of these insecticides resulted in their entry into the food chain thereby causing toxicity to different organ systems. Allethrin is one of the widely used pyrethroids, but its toxicological effects are underreported when compared to other pyrethroids. Further, its effects on the male reproductive tract remain uncharacterized. In this study, its toxicity on the male reproductive tract was evaluated by administering 25-150 mg/kg body weight allethrin to adult rats for 60 days. The mRNA expression of factors that are important in spermatogenesis (Scf, c-Kit, Hsf2, Ovol1, Brdt, Kdm3A, Ybx-2, and Grth) and steroidogenesis (StAR, 3β-HSD, 17β-HSD) was significantly downregulated. Decreased levels of testosterone, reduced sperm count and daily sperm production was also observed due to allethrin toxicity. However, sperm quality parameters assessed by computer-assisted sperm analyzer were not affected. Spermatozoa obtained from allethrin-treated rats failed to undergo acrosome reaction. Results of this study indicate that allethrin affects spermatogenesis and sperm function, thus lending further support to the growing evidence of its toxicity.