Peripubertal exposure to the neonicotinoid pesticide dinotefuran affects dopaminergic neurons and causes hyperactivity in male mice

An occupational health assessment of dinotefuran exposure in greenhouse vegetable workers: Metabolomic profiling and toxicokinetic analysis

This study aimed to explore the metabolite profiles of populations engaged in intensive vegetable cultivation and their exposure to pesticides. As urbanization progresses and eating habits evolve, intensive vegetable farming has rapidly expanded; however, this cultivation method poses potential health risks to farmers, particularly due to long-term exposure to "greenhouse gases" in enclosed environments. The study investigated the demographic characteristics of individuals in vegetable-growing areas, collected relevant biological samples, and assessed exposure levels by analyzing pesticide metabolites in urine. The results indicated that the types and concentrations of pesticide metabolites detected in the urine of the exposed group were significantly higher than those in the control group, with notable increases in neonicotinoid metabolites such as dinotefuran (DIN) and thiacloprid. Furthermore, the impact of these pesticides on mammalian organisms was examined through animal experiments, which revealed dynamic changes in the concentration of DIN in mouse serum and urine, providing valuable data on its biological metabolic characteristics. These findings underscore the importance of ongoing disease prevention, pollution control, and the need for enhanced health monitoring and protective measures for agricultural workers.

Effect of the neonicotinoid pesticide clothianidin at a no-observed-adverse-effect-level (NOAEL) dose on maternal behavior in pregnant mice and their female offspring

Our previous reports showed that exposure to the neonicotinoid pesticide clothianidin (CLO) at a no-observed-adverse-effect-level (NOAEL) dose during fetal development and lactation in mice led to higher rates of maternal neglect and infanticide. Although the demonstrated association between decreased oxytocin secretion and decreased maternal parenting behavior implies a link to declining oxytocin levels, no evidence has yet emerged in CLO to clearly establish such an association. This study investigated the effects of CLO on maternal behavior and oxytocin in C57BL/6N mice exposed during pregnancy and lactation (F0 mothers) as well as in their adult female offspring (F1 mothers). The effects were assessed using nest building assays during pregnancy and pup retrieval assessment after delivery. The results showed a decrease in oxytocin secretion and a marked decrease in pup retrieval behavior among the F0 mothers in the CLO exposure group compared to those in the control group. Their offspring, the F1 mothers, showed significantly lower nest-building scores during pregnancy. In conclusion, this study is the first to examine the potential mechanisms by which CLO exposure in mothers at the NOAEL dose during pregnancy and lactation results in reduced plasma oxytocin levels, subsequently leading to a decline in maternal behaviors such as pup retrieval. Furthermore, these effects may impair maternal behaviors in the next generation, when the offspring mice become mothers.

Role of brain monoamines in acetamiprid-induced anxiety-like behavior

Neonicotinoid (NN) pesticides have been linked to increased brain dysfunction in mammals, such as anxiety-like behavior; this is thought to involve monoamines (MA), neurotransmitters that control behavior, memory, and learning. However, the mechanism by which NNs affect the central nervous system is not fully understood. In this study, we aimed to investigate whether MAs affect NNs-induced anxiety-like behavior. Mice were orally administered acetamiprid (ACE), an NN, at the no observed adverse effect level (NOAEL) of mouse (20 mg/kg body mass) set by the Food Safety Commission of Japan, and the elevated zero-maze (EZM) test was performed 30 min after administration. After behavioral analysis, levels of four MA (dopamine, 3-MT, serotonin, and histamine) in selected brain regions were determined by liquid chromatography mass spectrometry (LC/MS/MS). In the exposed group, a trend toward increased anxiety-like behavior was observed, and at least one MA concentration was significantly increased in each region. Further, significant correlations were found between behavioral test results and hippocampal serotonin and striatal dopamine concentrations, as well as between dopamine and serotonin concentrations, in the exposed group. As anxiety can influence activity in the behavioral tests, the activity of neurons in the raphe nuclei (RN), a brain region greatly involved in anxiety via the serotonergic system, was examined by staining with anti-serotonin antibodies, and increased serotonergic activity was observed. Taken together, these results suggest that ACE regulates MA levels, notably serotonin levels in the hippocampus and that RN plays an important role in ACE-induced anxiety-like behavior.

No-observed-adverse-effect-level (NOAEL) clothianidin, a neonicotinoid pesticide, impairs hippocampal memory and motor learning associated with alteration of gene expression in cerebellum

Neonicotinoid pesticides (NNs) have been associated with numerous neurobehavioral effects in rodents, raising concerns about their impact on cognitive function. Clothianidin (CLO), a type of NN, was orally administered to male mice (10 weeks old, C57BL/6N) at the no-observed-adverse-effect level (NOAEL) of 50 mg/kg/day as indicated in the pesticide risk assessment report. Behavioral tests (novel location recognition and rotarod tests) evaluated hippocampal memory and cerebellar motor learning. After each test, plasma monoamines (3-methoxytyramine, histamine, serotonin, tryptamine) were measured by LC-ESI/MS/MS (Liquid chromatography-electrospray ionization/tandem mass spectrometry), and cerebellar mRNA expression was quantified by microarray and qRT-PCR analyses. The NOAEL of CLO was found to impair hippocampal memory, leading to decreased spontaneous locomotor activity and motor function. We reported, for the first time, multiple alterations of gene expression in the cerebellum associated with motor dysfunction.

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.

Quantification of the tissue distribution and accumulation of the neonicotinoid pesticide clothianidin and its metabolites in maternal and fetal mice

Neonicotinoids (NNs) are commonly used pesticides that have a selective agonistic action on insect nicotinic acetylcholine receptors. Recent evidence has shown that NNs have adverse effects in the next generation of mammals, but it remains unclear how NNs transferred from dams to fetuses are distributed and accumulated in fetal tissues. Here, we aimed to clarify the tissue distribution and accumulation properties of the NN clothianidin (CLO) and its 6 metabolites in 7 tissues and blood in both dams and fetuses of mice administered CLO for a single day or for 9 consecutive days. The results showed that the total concentrations of CLO-related compounds in the brain and kidney were higher in fetuses than in dams, whereas in the liver, heart, and blood they were lower in fetuses. The multi-day administration increased the total levels in heart and blood only in the fetuses of the single administration group. In addition, dimethyl metabolites of CLO showed fetus/dam ratios >1 in some tissues, suggesting that fetuses have higher accumulation property and are thus at higher risks of exposure to CLO-related compounds than dams. These findings revealed differences in the tissue-specific distribution patterns of CLO and its metabolites between dams and fetuses, providing new insights into the assessment of the developmental toxicity of NNs.

Ecotoxicological impact of dinotefuran insecticide and its metabolites on non-targets in agroecosystem: Harnessing nanotechnology- and bio-based management strategies to reduce its impact on non-target ecosystems

The class of insecticides known as neonicotinoid insecticides has gained extensive application worldwide. Two characteristics of neonicotinoid pesticides are excellent insecticidal activity and a wide insecticidal spectrum for problematic insects. Neonicotinoid pesticides can also successfully manage pest insects that have developed resistance to other insecticide classes. Due to its powerful insecticidal properties and rapid plant absorption and translocation, dinotefuran, the most recent generation of neonicotinoid insecticides, has been widely used against biting and sucking insects. Dinotefuran has a wide range of potential applications and is often used globally. However, there is growing evidence that they negatively impact the biodiversity of organisms in agricultural settings as well as non-target organisms. The objective of this review is to present an updated summary of current understanding regarding the non-target effects of dinotefuran; we also enumerated nano- and bio-based mitigation and management strategies to reduce the impact of dinotefuran on non-target organisms and to pinpoint knowledge gaps. Finally, future study directions are suggested based on the limitations of the existing studies, with the goal of providing a scientific basis for risk assessment and the prudent use of these insecticides.

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.

Reproductive and neurobehavioral effects of dinotefuran in an F1 -generation toxicity study in mice

BACKGROUND

Few studies were found for neurobehavioral toxicity of dinotefuran in mammals. This study was designed to evaluate the reproductive and neurobehavioral effects of dinotefuran exposure in mice.

METHODS

Dinotefuran was given in the diet to provide levels of 0% (control), 0.015%, 0.03%, and 0.06% from 5 weeks of age of the F0 generation to 11 weeks of age of the F1 generation in mice. Selected reproductive and neurobehavioral parameters were measured.

RESULTS

Movement time increased with a significant dose-related trend, and the related variables of rearing time decreased in significant dose-related trends in adult males in the F0 generation. Litter size and weight increased in significant dose-related trends, and sex ratio decreased in a significant dose-related trend. The average body weight of offspring increased in a significant dose-related trend on postnatal day (PND) 21 in both sexes. In the olfactory orientation on PND 14 in female offspring, the time required lengthened in a significant dose-related trend. In male offspring, total distance and the average speed decreased in significant dose-related trends, and the average time of rearing, number of defecations, and frequencies of mice with urination increased in a significant dose-related trend. In female offspring, the related variables of rearing increased in significant dose-related trends. In spontaneous behavior of males, the parallel lines during the control and treatment groups indicated a significant distance in the number of horizontal activities.

CONCLUSIONS

The dose levels of dinotefuran in the present study produced several adverse effects on reproductive and neurobehavioral parameters in mice.

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.

Detection of Changes in Monoamine Neurotransmitters by the Neonicotinoid Pesticide Imidacloprid Using Mass Spectrometry

Monoamine neurotransmitters (MAs), including dopamine (DA) and serotonin (5-HT), regulate brain functions such as behavior, memory, and learning. Neonicotinoids are pesticides that are being used more frequently. Neonicotinoid exposure has been observed to produce neurological symptoms, such as altered spontaneous movements and anxiety-like behaviors, which are suspected to be caused by altered MA levels. However, current neurotoxicity tests are not sufficiently sensitive enough to make these determinations. In this study, we performed some behavior tests, and derivatization reagents to improve the ionization efficiency, which was applied to liquid chromatography mass spectrometry (LC-MS/MS) to reveal the effect of neonicotinoid administration on MAs in the brain. We orally administered the neonicotinoid imidacloprid (0, 10, and 50 mg/kg body weight) to C57BL/6NCrSlc mice. In the behavior tests, a decrease in activity was observed. The LC-MS/MS quantification of MAs in various brain regions showed a decrease in some MA levels in the olfactory bulb and the striatum. These results showed, for the first time, that even a low dose of imidacloprid could alter MA levels in various parts of the brain.

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.

Elucidation of the neurological effects of clothianidin exposure at the no-observed-adverse-effect level (NOAEL) using two-photon microscopy in vivo imaging

Neonicotinoid pesticides (NNs) cause behavioral abnormalities in mammals, raising concerns about their effects on neural circuit activity. We herein examined the neurological effects of the NN clothianidin (CLO) by in vivo Ca²⁺ imaging using two-photon microscopy. Mice were fed the no-observed-adverse-effect-level (NOAEL) dose of CLO for 2 weeks and their neuronal activity in the primary somatosensory cortex (S1) was observed weekly for 2 weeks. CLO exposure caused a sustained influx of Ca²⁺ in neurons in the S1 2/3 layers, indicating hyperactivation of neurons. In addition, microarray gene expression analysis suggested the induction of neuroinflammation and changes in synaptic activity. These results demonstrate that exposure to the NOAEL dose of CLO can overactivate neurons and disrupt neuronal homeostasis.

Neurotoxic Effects of Neonicotinoids on Mammals: What Is There beyond the Activation of Nicotinic Acetylcholine Receptors?-A Systematic Review

Neonicotinoids are a class of insecticides that exert their effect through a specific action on neuronal nicotinic acetylcholine receptors (nAChRs). The success of these insecticides is due to this mechanism of action, since they act as potent agonists of insect nAChRs, presenting low affinity for vertebrate nAChRs, which reduces potential toxic risk and increases safety for non-target species. However, although neonicotinoids are considered safe, their presence in the environment could increase the risk of exposure and toxicity. On the other hand, although neonicotinoids have low affinity for mammalian nAChRs, the large quantity, variety, and ubiquity of these receptors, combined with its diversity of functions, raises the question of what effects these insecticides can produce in non-target species. In the present systematic review, we investigate the available evidence on the biochemical and behavioral effects of neonicotinoids on the mammalian nervous system. In general, exposure to neonicotinoids at an early age alters the correct neuronal development, with decreases in neurogenesis and alterations in migration, and induces neuroinflammation. In adulthood, neonicotinoids induce neurobehavioral toxicity, these effects being associated with their modulating action on nAChRs, with consequent neurochemical alterations. These alterations include decreased expression of nAChRs, modifications in acetylcholinesterase activity, and significant changes in the function of the nigrostriatal dopaminergic system. All these effects can lead to the activation of a series of intracellular signaling pathways that generate oxidative stress, neuroinflammation and, finally, neuronal death. Neonicotinoid-induced changes in nAChR function could be responsible for most of the effects observed in the different studies.

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

Recently, developmental exposure to clothianidin (CLO) has been shown to cause reproductive toxicity in male mice, but the effects in female mice remain to be clarified. Pregnant C57BL/6N mice were given a no-observed-adverse-effect-level (NOAEL) dose of CLO until weaning. We then examined ovaries of 3- or 10-week-old female offspring. In the CLO-administered group, morphological changes, a decrease in the immunoreactivity of the antioxidant enzyme glutathione peroxidase 4 (GPx4), and activation of genes in the steroid hormone biosynthesis pathway were observed in 3-week-old mice, and decreases of GPx4 immunoreactivity, 17OH-progesterone and corticosterone levels were observed in 10-week-old mice, along with high rates of infanticide and severe neglect, providing new evidence that developmental exposure to CLO affects juvenile and adult mice differently.

Fetal and lactational exposure to the no-observed-adverse-effect level (NOAEL) dose of the neonicotinoid pesticide clothianidin inhibits neurogenesis and induces different behavioral abnormalities at the developmental stages in male mice

Recently, it has been reported that neonicotinoid pesticides (NNs) are transferred from mother to child and are assumed to affect the next generation, but the behavioral effects of NN exposure at different developmental stages have not been investigated. We exposed mice to no-observed-adverse-effect level (NOAEL) doses of clothianidin (CLO) during the fetal and lactational period, and then evaluated the neurobehavioral effects in juvenile and adult mice. Significant increases in anxiety-like behavior and locomotor activity were observed in juveniles and adults, respectively, and neuronal activity and neurogenesis in the hippocampal dentate gyrus were affected in both stages. These results suggest that fetal and lactational exposure to CLO may inhibit neurogenesis and cause different behavioral abnormalities at different developmental stages.

Combined exposure to dinotefuran and chronic mild stress counteracts the change of the emotional and monoaminergic neuronal activity induced by either exposure singly despite corticosterone elevation in mice

Dinotefuran (DIN) belongs to the neonicotinoids (NNs), a class of globally applied pesticides originally developed to exhibit selective toxicity in insects. However, several reports have suggested that NNs also exert neurotoxic effects in mammals. We previously demonstrated neurobehavioral effects of DIN on mice under non-stressful conditions. For further toxicity assessments in the present study, we investigated the effects of DIN on mice exposed to stressful conditions. After subacutely administering a no-observed-effect-level (NOEL) dose of DIN and/or chronic unpredictable mild stress (CUMS) to mice, we conducted three behavioral tests (i.e., open field test [OFT], tail suspension test [TST] and forced swimming test [FST]). In addition, serotonin (5-HT) and tryptophan hydroxylase 2 (TPH2) of the dorsal raphe nuclei (DRN) and median raphe nuclei (MRN) and tyrosine hydroxylase (TH) of the ventral tegmental area and substantia nigra (SN) were evaluated immunohistochemically. A NOEL dose of DIN or CUMS alone increased of the total distance in OFT, decreased or increased the immobility time in TST or FST, respectively, and increased the positive intensity of 5-HT and TPH2 in the DRN/MRN, and TH in the SN. These changes were suppressed under the conditions of combined exposure to DIN and CUMS, though the blood corticosterone level was increased depending on the blood DIN values and the presence of CUMS. The present study suggests the multifaceted toxicity of the neurotoxin DIN.

Immunotoxicity evaluation by subchronic oral administration of clothianidin in Sprague-Dawley rats

Neonicotinoid pesticides (NNs) act as agonists on nicotinic acetylcholine receptors (nAChRs) of insects, and there have been concerns about the effects of NNs on the health of mammals. Since nAChRs are expressed in immune cells, it is possible that NNs disturb the immune system. However, few reports have examined the immunotoxicity of clothianidin (CLO), a widely-used NN. Here, we report the effects of CLO on immune organs and type IV allergic reactions in ear auricles. We orally administered CLO at 0, 30 and 300 mg/kg/day (CLO-0, 30 and 300) to Sprague-Dawley rats for 28 days. The effects were evaluated by organ and body weights, histopathology, and immunohistochemistry (TCRαβ, CD4, CD8, CD11b, CD68, CD103). In addition, some cecal contents were subjected to preliminary gut microbiota analysis, because microbiota contribute to host homeostasis, including the immunity. Our results showed loose stool, suppression of body weight gain, significant changes in organ weights (thymus: decreased; liver: increased) and changes of the gut microbiota in the CLO-300 group. There were no obvious histopathological changes in immune organs. Granulomas of the ear auricles were found in one rat of each of the CLO-30 and 300 groups, but CLO had no apparent effect on the thickness or immunohistochemistry in the ear auricles. We present new evidence that CLO affects the thymus and intestine, and might enhance the local inflammatory response. These findings should contribute to the appropriate evaluation of the safety of NNs in the future.

Quantitative elucidation of maternal-to-fetal transfer of neonicotinoid pesticide clothianidin and its metabolites in mice

Neonicotinoids (NNs), a widely used class of systemic pesticides, are regarded as exhibiting selective toxicity in insects. However, NNs are suspected of exerting adverse effects on mammals as well, including humans. To date, only adult male animal models have been subjected to general toxicity studies of NNs; fetuses have yet to be considered in this context. Here, we focused on the NN clothianidin (CLO) for the first quantitative LC-MS/MS analysis of maternal-to-fetal transfer and residual property of once-daily (single or multiple days), orally administered CLO and its metabolites in mice. The results revealed the presence of CLO and its five metabolites at approximately the same respective blood levels in both dams and fetuses. In the dams, CLO showed a peak value 1 h after administration, after which levels rapidly decreased at 3 and 6 h. In the fetuses of each group, levels of CLO were almost the same as those observed in the corresponding dams. The present results clearly demonstrated rapid passage of CLO through the placental barrier. However, metabolite-dependent differences observed in blood pharmacokinetics and residual levels. This is the first quantitative demonstration of the presence of CLO and its metabolites in fetal mouse blood.

Growth and neurite stimulating effects of the neonicotinoid pesticide clothianidin on human neuroblastoma SH-SY5Y cells

Neonicotinoids are one of most widely used pesticides targeting nicotinic acetylcholine receptors (nAChRs) of insects. Recent epidemiological evidence revealed increasing amounts of neonicotinoids detected in human samples, raising the critical question of whether neonicotinoids affect human health. We investigated the effects of a neonicotinoid pesticide clothianidin (CTD) on human neuroblastoma SH-SY5Y cells as in vitro models of human neuronal cells. Cellular and functional effects of micromolar doses of CTD were evaluated by changes in cell growth, intracellular signaling activities and gene expression profiles. We examined further the effects of CTD on neuronal differentiation by measuring neurite outgrowth. Exposure to CTD (1-100 μM) significantly increased the number of cells within 24 h of culture. The nAChRs antagonists, mecamylamine and SR16584, inhibited this effect, suggesting human α3β4 nAChRs could be targets of neonicotinoids. We observed a transient intracellular calcium influx and increased phosphorylation of extracellular signal-regulated kinase 1/2 shortly after exposure to CTD. Transcriptome analysis revealed that CTD down-regulated genes involved in neuronal function (e.g., formation of filopodia and calcium ion influx) and morphology (e.g., axon guidance signaling and cytoskeleton signaling); these changes were reflected by a finding of increased neurite length during neuronal differentiation. These findings provide novel insight into the potential risks of neonicotinoids to the human nervous system.

Mammalian Susceptibility to a Neonicotinoid Insecticide after Fetal and Early Postnatal Exposure

Neonicotinoids have become the most widely used class of insecticides world-wide. Although numerous studies have documented neonicotinoid toxicity in bees and other insects, the effects of exposure during early development in mammals remain largely unexplored. We assessed the effects of the neonicotinoid imidacloprid (IMI) in adult male and female mice after in utero and early postnatal exposure. Pregnant mice were infused with IMI (0.5 mg/kg/day) from gestational day 4 to the end of nursing at postnatal day 21. The young adult offspring were studied in a series of biochemical and behavioral tests. To assess reproducibility, the behavioral analyses were conducted in three separate studies using multiple exposed litters. Exposure to IMI reduced fecundity, and in adult offspring, decreased body weight in male but not female pups. Offspring from IMI-treated mothers displayed lower triglycerides, elevated motor activity, enhanced social dominance, reduced depressive-like behavior, and a diminution in social aggression compared to vehicle treated controls. Low levels of IMI were detected in the brains and livers of the treated mothers, while trace levels were detected in some offspring. Our results demonstrate that transient exposure to a neonicotinoid over the early developmental period induces long-lasting changes in behavior and brain function in mice.