Effects of in utero and lactational exposure to the no-observed-adverse-effect level (NOAEL) dose of the neonicotinoid clothianidin on the reproductive organs of female mice

Urinary neonicotinoid concentrations and obesity: A cross-sectional study among Chinese adolescents

Epidemiological and toxicological studies on neonicotinoids and obesity have been relevant to adults and young children, but data are limited in adolescents. This study aimed to examine the association between urinary neonicotinoid concentrations and obesity measures among Chinese adolescent. A total of 524 urine samples from 300 boys (11.3-16.1 years) and 224 girls (12.1-15.8 years) were collected to detect the concentrations of eleven neonicotinoids. Generalized linear regression, weighted quantile sum regression (WQS) and Bayesian kernel machine regression (BKMR) were used to estimate covariate-adjusted associations between detectable neonicotinoids and ten indicators of obesity. Nitenpyram concentration was associated with increased body mass index z-score (β = 0.170, 95% CI: 0.041, 0.299) and greater odds of being general obesity (OR = 2.46, 95% CI: 1.11, 5.46). N-desmethyl- acetamiprid concentration was associated with an increase in waist-to-height ratio (β = 0.102, 95% CI: 0.029, 0.176) and waist-to-hip ratio (β = 0.083, 95% CI: 0.011, 0.155). The concentrations of clothianidin (OR = 2.06, 95% CI: 1.10, 3.88) and flonicamid (OR = 2.39, 95% CI: 1.07, 5.32) were associated with greater odds of being abdominal obesity. In contrast, the concentrations of imidacloprid (OR = 0.35, 95% CI: 0.14, 0.88) and thiacloprid (OR = 0.28, 95% CI: 0.08, 0.99) were associated with lower odds of being general obesity. The estimates of general obesity and abdominal obesity increased significantly when concentrations of neonicotinoids mixture were at or above the 55th and 65th percentiles, respectively, compared to the 50th percentile concentration. Sex modified the association between nitenpyram and clothianidin and the risk of obesity with a positive association among boys, and a nonsignificant inverse association among girls. The findings suggest that these associations may be mixed and sex-specific.

Effects of exposure to the neonicotinoid pesticide clothianidin on α-defensin secretion and gut microbiota in mice

The mechanism by which the neonicotinoid pesticide clothianidin (CLO) disrupts the intestinal microbiota of experimental animals is unknown. We focused on α-defensins, which are regulators of the intestinal microbiota. Subchronic exposure to CLO induced dysbiosis and reduced short-chain fatty acid-producing bacteria in the intestinal microbiota of mice. Levels of cryptdin-1 (Crp1, a major α-defensin in mice) in feces and cecal contents were lower in the CLO-exposed groups than in control. In Crp1 immunostaining, Paneth cells in the jejunum and ileum of the no-observed-adverse-effect-level CLO-exposed group showed a stronger positive signal than control, likely due to the suppression of Crp1 release. Our results showed that CLO exposure suppresses α-defensin secretion from Paneth cells as part of the mechanism underlying CLO-induced dysbiosis.

Non-acute exposure of neonicotinoids, health risk assessment, and evidence integration: a systematic review

Neonicotinoid pesticides are utilized against an extensive range of insects. A growing body of evidence supports that these neuro-active insecticides are classified as toxicants in invertebrates. However, there is limited published data regarding their toxicity in vertebrates and mammals. the current systematic review is focused on the up-to-date knowledge available for several neonicotinoid pesticides and their non-acute toxicity on rodents and human physiology. Oral lethal dose 50 (LD50) of seven neonicotinoids (i.e. imidacloprid, acetamiprid, clothianidin, dinotefuran, thiamethoxam, thiacloprid, and nitenpyram) was initially identified. Subsequently, a screening of the literature was conducted to collect information about non-acute exposure to these insecticides. 99 studies were included and assessed for their risk of bias and level of evidence according to the Office of Health and Translation (OHAT) framework. All the 99 included papers indicate evidence of reproductive toxicity, hepatotoxicity, nephrotoxicity, neurotoxicity, immunotoxicity, and oxidative stress induction with a high level of evidence in the health effect of rodents and a moderate level of evidence for human health. The most studied type of these insecticides among 99 papers was imidacloprid (55 papers), followed by acetamiprid (22 papers), clothianidin (21 papers), and thiacloprid (11 papers). While 10 of 99 papers assessed the relationship between clothianidin, thiamethoxam, dinotefuran, and nitenpyram, showing evidence of liver injury, dysfunctions of oxidative stress markers in the reproductive system, and intestinal toxicity. This systematic review provides a comprehensive overview of the potential risks caused by neonicotinoid insecticides to humans and rodents with salient health effects. However, further research is needed to better emphasize and understand the patho-physiological mechanisms of these insecticides, taking into account various factors that can influence their toxicity.

Effects of exposure to the neonicotinoid pesticide clothianidin on mouse intestinal microbiota under unpredictable environmental stress

Recent research has demonstrated the toxicity of neonicotinoid pesticides (NNs) in mammals through their interaction with nicotinic acetylcholine receptors (nAChRs). These effects are reported to extend to the intestinal microbiota as well. In addition, environmental stress affects the expression of nAChRs, which may alter sensitivity to NNs. In this study, we analyzed the intestinal microbiota of mice exposed to clothianidin (CLO), a type of NN, under environmental stress, and aimed to clarify the effects of such combined exposure on the intestinal microbiota. C57BL/6N male mice (9 weeks old) were subchronically administered a no-observed-adverse-effect-level (NOAEL) CLO-mixed rehydration gel for 29 days and simultaneously subjected to chronic unpredictable mild stress (CUMS). After the administration period, cecum contents were collected and analyzed by 16S rRNA sequencing for intestinal microbiota. CLO exposure alone resulted in alterations in the relative abundance of Alistipes and ASF356, which produce short-chain fatty acids. The addition of CUMS amplified these changes. On the other hand, CLO alone did not affect the relative abundance of Lactobacillus, but the abundance decreased when CUMS was added. This study revealed that the combined exposure to CLO and stress not only amplifies their individual effects on intestinal microbiota but also demonstrates combined and multifaceted toxicities.

Transgenerational effects of developmental neurotoxicity induced by exposure to a no-observed-adverse-effect level (NOAEL) of neonicotinoid pesticide clothianidin

Neonicotinoid pesticides (NNs) transfer rapidly from mother to offspring, which exhibit neurobehavioral effects. However, no studies have investigated NNs' transgenerational effects. We exposed F0 generation mice (mothers) to a no-observed-adverse-effect level (NOAEL) of clothianidin (CLO) during gestation and lactation, and examined the adult neurobehavioral effects of three generations of offspring (F1, F2, F3). F1 had lower birth weight, decreased locomotor activity, and increased anxiety-like behavior. In F2, body weight was affected, and there was a decreasing trend in locomotor activity and an increasing trend in anxiety-like behavior. In F3, locomotor activity tended to increase. Thus, even when only the mothers were exposed, the effects of CLOs were still observed in F1, F2, and F3 but the effects became smaller.

Reproductive effects of pubertal exposure to neonicotinoid thiacloprid in immature male mice

Thiacloprid (THIA) is a kind of neonicotinoid, a widely used insecticide class. Animal studies of adult and prenatal exposure to THIA have revealed deleterious effects on mammalian sperm fertility and embryonic development. A recent cross-sectional study linked higher THIA concentrations to delayed genitalia development stages in adolescent boys, suggesting that pubertal exposure to THIA may adversely affect reproductive development in immature males. Hence, this study aimed to investigate the effects of daily oral administration of THIA during puberty on the reproductive system of developing male mice. Young male C57 BL/6 J mice aged 21 days were administrated with THIA at concentrations of 10 (THIA-10), 50 (THIA-50) and 100 mg/kg (THIA-100) for 4 weeks by oral gavage. It is found that exposure to 100 mg/kg THIA diminished sexual behavior in immature male mice, caused a decrease in the spermatogenic cell layers and irregular arrangement of the seminiferous epithelium, and down-regulated the mRNA levels of spermatogenesis-related genes Ddx4, Scp3, Atg5, Crem, and Ki67, leading to an increase of sperm abnormality rate. In addition, THIA exposure at 50 and 100 mg/kg reduced the serum levels of testosterone and FSH, and decreased the expression levels of Star and Cyp11a1 related to testosterone biosynthesis. THIA exposure at 10 mg/kg did not produce any of the above significant changes. In conclusion, the high dose of THIA exposure impaired reproductive function in immature mice. It seems that THIA has no detrimental effects on the reproductive system of mice at low dose of 10 mg/kg.

Neurotoxicity and behavioral disorders induced in mice by acute exposure to the diamide insecticide chlorantraniliprole

Diamide insecticides activate ryanodine receptors expressed in lepidopteran skeletal muscle and promote Ca2+ release in the sarcoplasmic reticulum, causing abnormal contractions and paralysis, leading to death of the pest. Although they had been thought not to act on nontarget organisms, including mammals, adverse effects on vertebrates were recently reported, raising concerns about their safety in humans. We investigated the neurotoxicity of the acute no-observed-adverse-effect level of chlorantraniliprole (CAP), a diamide insecticide, in mice using clothianidin (CLO), a neonicotinoid insecticide, as a positive control. The CLO-administered group showed decreased locomotor activities, increased anxiety-like behaviors, and abnormal human-audible vocalizations, while the CAP-administered group showed anxiety-like behaviors but no change in locomotor activities. The CAP-administered group had greater numbers of c-fos-immunoreactive cells in the hippocampal dentate gyrus, and similar to the results in a CLO-administered group in our previous study. Blood corticosterone levels increased in the CLO-administered group but did not change in the CAP-administered group. Additionally, CAP was found to decreased 3-Methoxytyramine and histamine in mice at the time to maximum concentration. These results suggest that CAP-administered mice are less vulnerable to stress than CLO-administered mice, and the first evidence that CAP exposure increases neuronal activity and induces anxiety-like behavior as well as neurotransmitter disturbances in mammals.

Pesticides as endocrine disruptors: programming for obesity and diabetes

PURPOSE

Exposure to pesticides has been associated with obesity and diabetes in humans and experimental models mainly due to endocrine disruptor effects. First contact with environmental pesticides occurs during critical phases of life, such as gestation and lactation, which can lead to damage in central and peripheral tissues and subsequently programming disorders early and later in life.

METHODS

We reviewed epidemiological and experimental studies that associated pesticide exposure during gestation and lactation with programming obesity and diabetes in progeny.

RESULTS

Maternal exposure to organochlorine, organophosphate and neonicotinoids, which represent important pesticide groups, is related to reproductive and behavioral dysfunctions in offspring; however, few studies have focused on glucose metabolism and obesity as outcomes.

CONCLUSION

We provide an update regarding the use and metabolic impact of early pesticide exposure. Considering their bioaccumulation in soil, water, and food and through the food chain, pesticides should be considered a great risk factor for several diseases. Thus, it is urgent to reformulate regulatory actions to reduce the impact of pesticides on the health of future generations.

Quantitative elucidation of the transfer of the neonicotinoid pesticide clothianidin to the breast milk in mice

Neonicotinoid pesticides (NNs) have been reported to have neurobehavioral effects on offspring after fetal and lactational exposure. In this study, clothianidin (CLO), an NN, was administered orally as a single dose (6.5 mg/kg: 1/10 of the no-observed-adverse-effect level in the current Pesticide Evaluation Report) to 10-day post-partum ICR mice, and CLO and its metabolites desmethyl-CLO (dm-CLO) were quantified using liquid chromatography-electrospray ionization/tandem mass spectrometry (LC-ESI/MS/MS) after collecting maternal breast milk and blood samples over time (1, 3, 6, 9, 12, and 24 h after administration). CLO and dm-CLO were detected in the breast milk at 1 h after the administration, and their concentrations were significantly higher than those in blood at all time points. The concentrations of CLO and dm-CLO in the breast milk were at their highest levels at 1 and 3 h, respectively, and then decreased over time to become almost undetectable at 24 h after the administration. These results show that CLO is metabolized in the mother's body and is rapidly transferred to and concentrated in the breast milk. Since CLO concentrations in breast milk are higher than those in the blood, there is concern about the effects of CLO during lactation.

Effect of Neonicotinoid Pesticides on Japanese Water Systems: Review with Focus on Reproductive Toxicity

Neonicotinoid pesticides (NPs) are neurotoxic substances. They are highly effective as insecticides owing to their water solubility, permeability, and long-lasting activity. These molecules are structurally similar to nicotine and act as nicotinic acetylcholine receptor agonists. The administration of NPs to experimental animals reportedly causes neuromuscular and reproductive disorders. Moreover, recently reported problems caused by NPs include damage to land-dwelling creatures (such as mammals and birds), hydrobiology, and ecosystems. This review summarizes the recent reports on NP concentrations detected in river systems in several Japanese regions. These values were lower than the environmental standard values; however, seasonal variations were observed. Furthermore, reports on NP-induced testicular and ovarian toxicity were examined, revealing that the mechanism of injury is mainly driven by oxidative stress. The use of NPs is declining worldwide, except in Japan; therefore, continuous monitoring remains necessary.

Fetal programming: in utero exposure to acrylamide leads to intergenerational disrupted ovarian function and accelerated ovarian aging

In this study we investigated the effects of multigenerational exposures to acrylamide (ACR) on ovarian function. Fifty-day-old Wistar albino female rats were divided into the control and ACR-treated groups (2.5, 10, and 20 mg/kg/day) from day 6 of pregnancy until delivery. The obtained females of the first (AF1) and second generation (AF2) were euthanized at 4 weeks of age, and plasma and ovary samples were collected. We found that in utero multigenerational exposure to ACR reduced fertility and ovarian function in AF1 through inducing histopathological changes as evidenced by the appearance of cysts and degenerating follicles, oocyte vacuolization, and pyknosis in granulosa cells. TMR red positive cells confirmed by TUNEL assay were mostly detected in the stroma of the treated groups. Estradiol and IGF-1 concentrations significantly decreased as a result of decreased CYP19 gene and its protein expression. However, ACR exposure in AF2 led to early ovarian aging as evidenced by high estradiol and progesterone levels among all treated groups compared to control group, corresponding to the upregulation of the CYP19 gene and protein expression. The apoptotic cells of the stroma were greatly detected compared to that in the control group, whereas no significant difference was reported in ESR1 and ESR2 gene expression. This study confirms the developmental adverse effects of ACR on ovarian function and fertility in at least two consecutive generations. It emphasizes the need for more effective strategies during pregnancy, such as eating healthy foods and avoiding consumption of ACR-rich products, including fried foods and coffee.

Pre- and Postnatal Dietary Exposure to a Pesticide Cocktail Disrupts Ovarian Functions in 8-Week-Old Female Mice

Female infertility has a multifactorial origin, and exposure to contaminants, including pesticides, with endocrine-disrupting properties is considered to be involved in this reproductive disorder, especially when it occurs during early life. Pesticides are present in various facets of the environment, and consumers are exposed to a combination of multiple pesticide residues through food intake. The consequences of such exposure with respect to female fertility are not well known. Therefore, we aimed to assess the impact of pre- and postnatal dietary exposure to a pesticide mixture on folliculogenesis, a crucial process in female reproduction. Mice were exposed to the acceptable daily intake levels of six pesticides in a mixture (boscalid, captan, chlorpyrifos, thiacloprid, thiophanate and ziram) from foetal development until 8 weeks old. Female offspring presented with decreased body weight at weaning, which was maintained at 8 weeks old. This was accompanied by an abnormal ovarian ultrastructure, a drastic decrease in the number of corpora lutea and progesterone levels and an increase in ovary cell proliferation. In conclusion, this study shows that this pesticide mixture that can be commonly found in fruits in Europe, causing endocrine disruption in female mice with pre- and postnatal exposure by disturbing folliculogenesis, mainly in the luteinisation process.

Neurotoxicity of a pyrethroid pesticide deltamethrin is associated with the imbalance in proteolytic systems caused by mitophagy activation and proteasome inhibition

Pyrethroids are one of the most commonly used classes of synthetic pesticides in the world. Recent laboratory and epidemiological evidence suggested that pyrethroids have potential adverse effects in the mammalian brain; however, the underlying mechanisms of the neurotoxic effects of pyrethroids have not been fully elucidated. In the present study, we investigated the mechanisms of effects of a type II pyrethroid deltamethrin (DM) in a neuronal cell model focusing on the proteolytic function, including autophagy and the ubiquitin-proteasome system. We confirmed that a micromolar concentration of DM dose-dependently decreased the cell viability and induced apoptotic cell death. Our results showed that DM enhanced autophagy in association with an accumulation of autophagosomes and increase in the levels of autophagy markers LC3-II/LC3-I ratio and p62 which were much elevated in the presence of lysosomal inhibitors bafilomycin A1 and chloroquine. We also found that DM caused a dysfunction of mitochondria with a decrease of mitochondrial membrane potential and mitochondrial DNA copy number as well as colocalization with autophagosomes. Moreover, a decrease in the activities of three major proteasomal enzymes and an accumulation of ubiquitinated proteins were observed by the exposure to DM. Transcriptome analysis revealed that up-regulated genes supported the activation of autophagy with induction of cellular stress responses including oxidative stress and endoplasmic reticulum stress, while down-regulated genes related to the cell cycle and DNA replication. These findings provide novel insights into the neurotoxicity of DM which underlie the imbalance in proteolytic function caused by mitophagy activation and proteasome inhibition.