Imidacloprid Exposure Suppresses Neural Crest Cells Generation during Early Chick Embryo Development

Developmental toxicity of formulated insecticide mixture containing imidacloprid and beta-cyfluthrin in fish: Insights using zebrafish

Insecticides are critical in controlling pests and disease vectors. However, there is still a lack of ecotoxicological studies using commercial formulations of insecticides containing active ingredients. The study aimed to evaluate the developmental toxicity of a commercial insecticide mixture (imidacloprid [IMI] + beta-cyfluthrin [β-CYF]). Mortality, hatching rate, spontaneous contraction, heartbeat, morphological changes, reactive oxygen species (ROS), skeletal development, and locomotor behavior of zebrafish were analyzed. Embryos were exposed to imidacloprid (IMI) and β-cyfluthrin (β-CYF) in the following ratios: 0.001 mg IMI·L-1 + 0.000125 mg β-CYF·L-1 (C1); 0.01 mg IMI·L-1 + 0.00125 mg β-CYF·L-1 (C2); 0.1 mg IMI·L-1 + 0.0125 mg β-CYF·L-1 (C3); 1.0 mg IMI·L-1 + 0.125 mg β-CYF·L-1 (C4); 10.0 mg IMI·L-1 + 1.25 mg β-CYF·L-1 (C5) for 144 h. The results showed a mortality of 50 % of organisms in the C5 concentration. Embryos exposed to C1 and C3 showed tachycardia and hatched early compared to the negative control, indicating cardiotoxic and embryotoxic effects. The two highest concentrations tested (C4 and C5) induced evident morphological changes (yolk sac and pericardial edema, and spine alterations), and skeletal toxicity (absence of cartilage and bone formation), along with decreased larval swimming behavior. Also, the formulated insecticide (C1) increased ROS levels in zebrafish larvae. Results showed that the formulated insecticide containing IMI and β-CYF induces several toxic effects on developing zebrafish, indicating its environmental risk to aquatic organisms.

Pilot study on neonicotinoids in Finnish waterbirds: no detectable concentrations in common goldeneye (Bucephala clangula) plasma

Neonicotinoids have been detected in farmland-associated birds and exposure to these insecticides has been linked to adverse effects. Even though neonicotinoids are mobile and persistent and have been detected in surface waters and aquatic invertebrates, there is a considerable lack of knowledge on their occurrence in waterbirds. Here we investigated the occurrence of seven neonicotinoids and some of their transformation products (imidacloprid, thiacloprid, thiamethoxam, acetamiprid, clothianidin, dinotefuran, nitenpyram, 6-chloronicotinic acid, hydroxy-imidacloprid, imidacloprid-urea, imidacloprid-olefin, thiamethoxam-urea, thiacloprid-amide, acetamiprid-acetate, and acetamiprid-desmethyl) in blood plasma of 51 incubating female common goldeneyes (Bucephala clangula). We collected samples from five different regions from southern to northern Finland encompassing rural and urban settings in coastal and inland areas. Surprisingly, none of the targeted neonicotinoids was found above the limit of detection in any of the samples. As neonicotinoid concentrations in wild birds can be very low, a likely reason for the nil results is that the LODs were too high; this and other possible reasons for the lack of detection of neonicotinoids in the goldeneyes are discussed. Our results suggest that neonicotinoid exposure in their breeding areas is currently not of major concern to female goldeneyes in Finland. Even though this study did not find any immediate danger of neonicotinoids to goldeneyes, further studies including surface water, aquatic invertebrates, and other bird species could elucidate potential indirect food chain effects.

Comparing the effects of three neonicotinoids on embryogenesis of the South African clawed frog Xenopus laevis

Neonicotinoids (NEOs) are widely used insecticides that are ubiquitous in agricultural use. Since NEOs are found in natural waters as well as in tap water and human urine in regions where NEOs are widely used, NEOs pose a potential hazard to non-target organisms such as animals and humans. Some of the commonly detected NEOs are imidacloprid (IMD), thiamethoxam (TMX), and its metabolite clothianidin (CLO). Although previously published scientific information, including an assessment of the environmental risks, particularly for bees, had resulted in a ban on the outdoor use of these three NEOs in the EU - their use is now only permitted in closed greenhouses - these NEOs continue to be used in agriculture in many other parts of the world. Therefore, a detailed study and comparison of the effects of NEOs on the embryonic development of non-target organisms is needed to further define the risk profiles. Embryos of the South African clawed frog Xenopus laevis, a well-established aquatic model, were exposed to different concentrations of IMD, TMX, or CLO (0.1-100 mg/L) to study and compare the possible effects of a single contaminant in natural water bodies on early embryogenesis. The results included a reduced body length, a smaller orbital space, impaired cranial cartilage and nerves, and an altered heart structure and function. At the molecular level, NEO exposure partially resulted in an altered expression of tissue-specific factors, which are involved in eye, cranial placode, and heart development. Our results suggest that the NEOs studied negatively affect the embryonic development of the non-target organism X. laevis. Since pesticides, especially NEOs, pollute the environment worldwide, it is suggested that they are strictly controlled and monitored in the areas where they are used. In addition, the question arises as to whether pesticide metabolites also pose a risk to the environment and need to be investigated further so that they can be taken into account when registering ingredients.

Assessing developmental neurotoxicity of emerging environmental chemicals using multiple in vitro models: A comparative analysis

Newly synthesized chemicals are being introduced into the environment without undergoing proper toxicological evaluation, particularly in terms of their effects on the vulnerable neurodevelopment. Thus, it is important to carefully assess the developmental neurotoxicity of these novel environmental contaminants using methods that are closely relevant to human physiology. This study comparatively evaluated the potential developmental neurotoxicity of 19 prevalent environmental chemicals including neonicotinoids (NEOs), organophosphate esters (OPEs), and synthetic phenolic antioxidants (SPAs) at environment-relevant doses (100 nM and 1 μM), using three commonly employed in vitro neurotoxicity models: human neural stem cells (NSCs), as well as the SK-N-SH and PC12 cell lines. Our results showed that NSCs were more sensitive than SK-N-SH and PC12 cell lines. Among all the chemicals tested, the two NEOs imidaclothiz (IMZ) and cycloxaprid (CYC), as well as the OPE tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), generated the most noticeable perturbation by impairing NSC maintenance and neuronal differentiation, as well as promoting the epithelial-mesenchymal transition process, likely via activating NF-κB signaling. Our data indicate that novel NEOs and OPEs, particularly IMZ, CYC, and TDCIPP, may not be safe alternatives as they can affect NSC maintenance and differentiation, potentially leading to neural tube defects and neuronal differentiation dysplasia in fetuses.

Baicalin administration could rescue high glucose-induced craniofacial skeleton malformation by regulating neural crest development

Hyperglycemia in pregnancy can increase the risk of congenital disorders, but little is known about craniofacial skeleton malformation and its corresponding medication. Our study first used meta-analysis to review the previous findings. Second, baicalin, an antioxidant, was chosen to counteract high glucose-induced craniofacial skeleton malformation. Its effectiveness was then tested by exposing chicken embryos to a combination of high glucose (HG, 50 mM) and 6 μM baicalin. Third, whole-mount immunofluorescence staining and in situ hybridization revealed that baicalin administration could reverse HG-inhibited neural crest cells (NCC) delamination and migration through upregulating the expression of Pax7 and Foxd3, and mitigate the disordered epithelial-mesenchymal transition (EMT) process by regulating corresponding adhesion molecules and transcription factors (i.e., E-cadherin, N-cadherin, Cadherin 6B, Slug and Msx1). Finally, through bioinformatic analysis and cellular thermal shift assay, we identified the AKR1B1 gene as a potential target. In summary, these findings suggest that baicalin could be used as a therapeutic agent for high glucose-induced craniofacial skeleton malformation.

The impact of the insecticide acetamiprid on the embryogenesis of the aquatic model organism Xenopus laevis

Acetamiprid (ACT) is used extensively in agriculture worldwide, although data on ACT concentrations in natural water bodies and its impact on aquatic organisms are limited. To study whether ACT influences the embryogenesis of the South African clawed frog Xenopus laevis, embryos were incubated in ACT solutions from 0.01 to 100 mg/L. The low concentrations were chosen on the basis of concentrations already found in nature. ACT treatment leads to shorter embryo lengths, intestine malformation and reduced eye areas. It also affects the cranial cartilage and cardiac development as well as the embryo's mobility. The expression of tissue-specific marker genes is affected as well. Thus, our study suggests that pesticides may lead to an increased mortality of non-target organisms and emphasizes the importance of regular testing for ACT concentrations in nature. Our study provides an overview of ACT effects and can therefore be used as a basis for an ACT risk assessment.

Veterinary pharmaceuticals and declining Cape Griffon Vulture (Gyps coprotheres) numbers: A potential threat to developing embryos

Cape Vultures (Gyps coprotheres) are a vulnerable Old-World Vulture species in southern Africa. Of the numerous threats to their survival, malicious and accidental poisonings remain a major concern. Despite the dangers of poisonings little is however known about the more insidious effects of toxins on egg survival, despite the species known to have a long generational length. For this study, an extensive literature review focusing on veterinary pharmaceuticals was undertaken. Literature for vultures was scarce, with most studies focusing on the domestic chicken. Using information for domestic chickens, the risk was characterised from likely vulture exposure to production animal carcasses with residues of said drugs. From this various antibiotics, medetomidine and albendazole were identified with embryotoxic or teratogenic effects. We suggest that these drugs be tested to elucidate their dose-response relationship and/or mitigation measures to minimise vulture exposure.

Endocrine Disruptor-Induced Bone Damage Due to Hormone Dysregulation: A Review

Hormones are indispensable for bone development, growth, and maintenance. While many of the genes associated with osteogenesis are well established, it is the recent findings in endocrinology that are advancing the fields of bone biology and toxicology. Endocrine-disrupting chemicals (EDCs) are defined as chemicals that interfere with the function of the endocrine system. Here, we report recent discoveries describing key hormone pathways involved in osteogenesis and the EDCs that alter these pathways. EDCs can lead to bone morphological changes via altering hormone receptors, signaling pathways, and gene expression. The objective of this review is to highlight the recent discoveries of the harmful effects of environmental toxicants on bone formation and the pathways impacted. Understanding the mechanisms of how EDCs interfere with bone formation contributes to providing a comprehensive toxicological profile of a chemical.

Dynamic light scattering and zeta-potential as a tool for understanding the mechanism of pesticides binding toward individual components of transition metal nanoparticles and graphene oxide hybrids

Pesticides present in their commercial formulations are studied for their preferable binding toward carbon-based graphene oxide (GO) or transition metal nanoparticles (Fe, Co, Ni, and Cu), present as hybrids. This simple study also reveals the mechanism of interaction of few selected different classes of pesticides, namely, λ-cyhalothrin, imidacloprid, and metsulfuron-methyl toward these hybrids. Individually, to study this comparative binding when hybrids are not used, the understanding of preferred binding toward any of these selected compounds could be challenging, costly, and time-consuming. Dynamic light scattering (DLS) is used to study the changes observed for hydrodynamic radius and zeta potential for the stability of the resulting products. This simple method can also be extended to identify the binding mechanism for other diverse set of combinations. These studies are supported by binding of GO with nanoparticles in batch adsorption and the best fit using Langmuir and Freundlich isotherms is presented. Moreover, pesticide adsorption toward GO-nanoparticle composites is also evidenced.

Metabolomic profiling to assess the effects of chlordanes and its bioaccumulation characteristics in chicken embryo

Although chlordane-related compounds (CHLs) have been regulated, a variety of CHLs are still identified and detected in wild birds and eggs. Embryo is one of fragile periods and is very susceptible to toxic effects of pollutants. In this study, the fate of CHLs during embryo development and degradation of CHLs in neonatal chick were investigated. During embryo development, CHLs were mainly distributed to the liver and muscle, in which trans-nonachlor and an octachlorochlordane (MC5) were hardly metabolized and showed the high persistence, implying a greater risk to birds' offspring. CHLs with the lower K_ow were found to be higher uptake efficiency in embryo, implying contaminants with the lower lipophilicity may contribute to their transport to embryo. Furthermore, the effects of CHLs on the metabolome of neonatal chicks was evaluated. The ether lipid metabolism and glycerophospholipid metabolism were found to be significantly affected, which may disturb the angiogenesis and endothelial cell migration in embryogenesis. Taken together, the lipophilicity of contaminants might be a main factor influencing their transport to embryo, and metabolomics results improve understanding of the effects of CHLs on embryo.

Urinary neonicotinoid insecticides in children from South China: Concentrations, profiles and influencing factors

Neonicotinoid insecticides can selectively interact with the unique nicotinic acetylcholine receptor subtypes in insects and are considered to be low toxic to mammals. However, there is still insufficient knowledge on human exposure to neonicotinoid insecticides, especially for children. This study aimed to investigate urinary concentrations and profiles of neonicotinoid insecticides in South China children and to analyze potential influencing factors. Six neonicotinoid insecticides, including imidacloprid (IMI), thiamethoxam (THM), acetamiprid (ACE), clothianidin (CLO), thiacloprid (THD) and dinotefuran (DIN), exhibited high detection frequencies (>90%) in urine samples collected from 305 children, suggesting broad exposure in South China children. The median concentrations were determined to be 0.13, 0.21, 0.01, 0.19, 0.002 and 1.64 μg/L, respectively. Among the target neonicotinoids, urinary concentrations of CLO and THM exhibited a significant and positive correlation between each other (p < 0.05), suggesting similar sources of these two chemicals.

The double-edged sword role of TGF-β signaling pathway between intrauterine inflammation and cranial neural crest development

Intrauterine infection would harm a developing embryo/fetus, thereby increasing the risk of developmental malformation. But, whether or not the infection-induced inflammation affects neural crest development still remains obscure. In this study, we employed meta-analysis to demonstrate the potential correlation between infection-induced inflammation and craniofacial anomalies, which was usually derived from the problems in neural crest cell development. The correlation was further verified by inflammatory cytokine release and the activation of nuclear factor kappa-light-chain enhancer of activated B cells signaling in lipopolysaccharide-treated HH10 chicken embryos. In such an inflammatory condition, AP-2α- and Pax7-labeled pre-migratory and migratory neural crest cells in HH10 chicken embryos were significantly less than the ones in control. The bioinformatics analysis of RNA-seq data demonstrated that the principal differential gene expression occurred in transforming growth factor-beta (TGF-β) signaling pathway, which was confirmed by the subsequent experimental results of quantitative PCR and immunofluorescent staining. Under this inflammatory circumstance, whole-mount in situ hybridization, immunofluorescence, and quantitative PCR showed the gene expression changes of key EMT-related transcription factors including upregulated Msx1, downregulated Slug, and FoxD3, as well as adhesion molecules and extracellular matrix protein including upregulated Cadherrin6B, E-cadherin, N-cadherin, and Laminin at the dorsal portion of neural tube of HH10 chicken embryos. Meanwhile, the bioinformatics analysis of RNA-seq data also manifested the differential gene expressions relevant to cell proliferation, which was confirmed by proliferating cell nuclear antigen Western blot data and co-immunofluorescence staining of human natural killer-1 and phosphorylated histone H3. In brief, this study revealed for the first time that the double-edged sword role of TGF-β signaling pathway between intrauterine inflammation (protective role) and cranial neural crest development (harmful role).

Novel immunochromatographic strip assay based on up-conversion nanoparticles for sensitive detection of imidacloprid in agricultural and environmental samples

Neonicotinoid insecticides are widely used in agriculture for pest control, but the pesticide residues in environmental and agricultural products were a big threat to the health of non-target organisms. In this study, a new immunochromatographic strip test was established for the rapid detection of imidacloprid residue, a neonicotinoid insecticide, based on up-conversion nanoparticles (UCNPs) coupled with the monoclonal antibody against imidacloprid. Under optimal conditions, the half inhibitory concentration (IC₅₀), detection limit, and the linear range of this strip were 8.37 ng/mL, 0.45 ng/mL, and 0.97-250 ng/mL. The strip test could be completed in 30 min. The average recoveries of imidacloprid spiked in water, Chinese cabbages, cucumber, honey, and tea samples were 70.1~101.8%, with coefficient of variations less than 18.9%. The strip was used to test real samples and verified by UPLC-MS/MS method with the good agreement (R² was 0.9825), indicating this novel strip immunoassay is accurate and reliable.

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems

New information on the lethal and sublethal effects of neonicotinoids and fipronil on organisms is presented in this review, complementing the previous Worldwide Integrated Assessment (WIA) in 2015. The high toxicity of these systemic insecticides to invertebrates has been confirmed and expanded to include more species and compounds. Most of the recent research has focused on bees and the sublethal and ecological impacts these insecticides have on pollinators. Toxic effects on other invertebrate taxa also covered predatory and parasitoid natural enemies and aquatic arthropods. Little new information has been gathered on soil organisms. The impact on marine and coastal ecosystems is still largely uncharted. The chronic lethality of neonicotinoids to insects and crustaceans, and the strengthened evidence that these chemicals also impair the immune system and reproduction, highlights the dangers of this particular insecticidal class (neonicotinoids and fipronil), with the potential to greatly decrease populations of arthropods in both terrestrial and aquatic environments. Sublethal effects on fish, reptiles, frogs, birds, and mammals are also reported, showing a better understanding of the mechanisms of toxicity of these insecticides in vertebrates and their deleterious impacts on growth, reproduction, and neurobehaviour of most of the species tested. This review concludes with a summary of impacts on the ecosystem services and functioning, particularly on pollination, soil biota, and aquatic invertebrate communities, thus reinforcing the previous WIA conclusions (van der Sluijs et al. 2015).

Lead exposure affects cephalic morphogenesis and neural crest cells in Gallus gallus embryo

The morphogenesis of the head of vertebrates is a process that involves rapid growth and dynamic movements of various cell populations, including the neural crest cells (NCC). These pluripotent cells generated during neurulation have high proliferative and migratory capacity but xenobiotic agents can affect these migratory periods and cause congenital malformations. Lead (Pb) is the most common toxic metal in the environment and a potent teratogen that can affect growth and induce malformations. Despite the known toxic effects of Pb, there is a gap in knowledge about the impact of realistic concentrations of Pb at critical periods of early development. Here, we evaluated mortality, embryonic morphology, NCC migration, and the amount of Pb deposition in chicken embryos after 3 to 4 days of exposure. One of the most interesting observations in this study is that only about 34% of the injected Pb was present in the embryos after 4 days. We observed that exposure to Pb, even under low concentrations, increased mortality and the occurrence of malformations during embryonic development, especially in the cephalic region (CR). Although Pb was found widely distributed in the CR, no relation between its presence and the migration routes of cephalic NCC was observed. But the number of NCC and their migratory distance were reduced. These changes are consistent and explain the morphological anomalies described in this study, which also correlates with the morphofunctional abnormalities reported in the literature. Therefore, this study highlights the concern of exposure to low concentrations of this metal.

Toxicity of imidacloprid to collembolans in two tropical soils under different soil moisture

Shifts in precipitation regimes due to the predicted climate changes can alter the water content in tropical soils and, consequently, may influence the toxicity of pesticides to soil fauna. This study assessed the influence of soil moisture content on the toxicity of the insecticide imidacloprid to the collembolans Folsomia candida in two tropical soils and evaluated the risk of this active ingredient for this species in the soils tested through the toxicity exposure ratio approach. Acute and chronic toxicity tests with F. candida were performed using an Entisol and an Oxisol. The soils were spiked with increasing imidacloprid concentrations while simulating normal water availability (60% of the water holding capacity [WHC]) and water restriction (30 or 45% WHC) for the tests. In the Oxisol, the reduction of soil moisture content significantly increased the toxic effects of imidacloprid on F. candida's survival (LC₅₀ at 45% WHC = 23.8 vs. LC₅₀ at 60% WHC >64 mg kg^-1) and reproduction (effective concentration causing reductions in species reproduction of 50% [EC₅₀] at 45% WHC = 0.32 vs. EC₅₀ at 60% WHC = 2.83 mg kg^-1), but in the Entisol no clear influence of the soil moisture on the toxicity of imidacloprid for collembolans was found. A significant risk for F. candida was observed in the Oxisol only when in water restriction, whereas in the Entisol it occurred regardless of soil moisture, suggesting that the imidacloprid hazard and risk for F. candida may be increased if soil moisture decreases due to climate changes, depending on the soil type.

Wildlife consumption of neonicotinoid-treated seeds at simulated seed spills

The most likely route of exposure to high concentrations of neonicotinoids capable of producing lethal or sublethal effects in birds and mammals is consumption of treated seeds. We placed trail cameras at simulated seed spills to document wildlife consuming treated seeds during the spring planting season. We simulated 4 types of spills, corn treated with 2 concentrations of clothiandin (0.50 or 0.25 mg/seed), corn treated with thiamethoxam (0.25 mg/seed), and soybean treated with imidacloprid (0.15 mg/seed). We documented 16 species of birds and 14 species of mammals eating neonicotinoid-treated seeds at spills. Of these, we quantified consumption of treated seeds by 12 species of birds and 13 species of mammals. Birds and mammals did not consume enough seeds to exceed published LD50s in related taxa, but most species did consume enough seeds to reach or exceed thresholds for sublethal effects based on currently available studies. Birds and mammals did not increase the amount of seeds consumed over time, as would be expected if responsive to the concentration of neonicotinoids on seeds, but more birds and mammals consumed seeds over time, as a proportion of the number at spills each day. More birds also consumed seeds after a soaking rain event, which likely reduced the amount of treatment on the seeds. Importantly, wildlife are consuming seeds while neonicotinoids are still concentrated on seeds. Our findings indicate that previously held assumptions about the safety of neonicotinoid seed treatments for vertebrate wildlife need to be revisited.

Dimethylacetamide-induced toxic hepatitis in spandex workers: clinical presentation and treatment outcomes

BACKGROUND

Dimethylacetamide (DMAc) exposure has been associated with toxic hepatitis, and no clinical treatment has been reported.

AIM

To investigate the clinical manifestations of DMAc-induced symptoms and how to rescue the functional loss due to occupational exposure.

DESIGN

Clinical observations of 60 spandex factory workers with the exposure to DMAc from January, 2017-19.

METHODS

Chinese drugs (reduced glutathione, polyene phosphatidylcholine, glycyrrhizin compound, Hugan tablets and ornithine aspartate) were used to evaluate the therapeutic improvements in DMAc-exposed patients.

RESULTS

Our data found that 58.3% patients had no distinct clinical symptoms, but 41.7% patients felt fatigue, and 21.7% patients suffered abdominal discomfort and appetite loss, and 8.3% patients had yellow skin and sclera. The ultrasonic and CT imaging revealed that some patients have fatty livers, intrahepatic calcifications, hepatomegaly, gallbladder wall edema and abdominal effusions. Biochemical analysis showed that the alanine aminotransferase (ALT) (P < 0.001), aspartate aminotransferase (AST) (P < 0.001), lactate dehydrogenase (LDH) (P < 0.001) and bilirubin (P < 0.01) statistically decreased after the drug treatment, but alkaline phosphatase (P >0.05) and glutamyl transpeptidase (P> 0.05) did not decrease. Twenty-nine out of the thirty-one patients' abnormal blood ammonia recovered. The risk factor of ALT on hospitalization time was significantly related (P < 0.01).

CONCLUSIONS

The drugs above are sufficient to rescue functional loss in DMAc-induced toxic hepatitis, in part via the regulations of ALT, AST, LDH, bilirubin and ammonia. Workers with the exposure to DMAc should receive specific drugs to maintain the health and prevent functional loss in the long term.

The role of teratogens in neural crest development

The neural crest (NC), discovered by Wilhelm His 150 years ago, gives rise to a multipotent migratory embryonic cell population that generates a remarkably diverse and important array of cell types during the development of the vertebrate embryo. These cells originate in the neural plate border (NPB), which is the ectoderm between the neural plate and the epidermis. They give rise to the neurons and glia of the peripheral nervous system, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies are a class of congenital diseases resulting from the abnormal induction, specification, migration, differentiation or death of NC cells (NCCs) during embryonic development and have an important medical and societal impact. In general, congenital defects affect an appreciable percentage of newborns worldwide. Some of these defects are caused by teratogens, which are agents that negatively impact the formation of tissues and organs during development. In this review, we will discuss the teratogens linked to the development of many birth defects, with a strong focus on those that specifically affect the development of the NC, thereby producing neurocristopathies. Although increasing attention is being paid to the effect of teratogens on embryonic development in general, there is a strong need to critically evaluate the specific role of these agents in NC development. Therefore, increased understanding of the role of these factors in NC development will contribute to the planning of strategies aimed at the prevention and treatment of human neurocristopathies, whose etiology was previously not considered.

EMT is the major target for okadaic acid-suppressed the development of neural crest cells in chick embryo

As a main marine phycotoxin, okadaic acid (OA) is mainly responsible for diarrheic shellfish poisoning (DSP), through specifically inhibiting phosphatase (PP1 and PP2A). It has been shown that isotope labelled-OA could cross the placental barrier in mice. However, it remains obscure how OA exposure could affect the formation of neural crest cells (NCCs), especially cranial NCCs in early embryo development. Here, we explored the effects of OA exposure on the generation of neural crest cells during embryonic development using the classic chick embryo model. We found that OA exposure at 100 nM (80.5 μg/L) could cause craniofacial bone defects in the developing chick embryo and delay the development of early chick embryos. Immunofluorescent staining of HNK-1, Pax7, and Ap-2α demonstrated that cranial NCC generation was inhibited by OA exposure. Double immunofluorescent staining with Ap-2α/PHIS3 or Pax7/c-Caspase3 manifested that both NCC proliferation and apoptosis were restrained by OA exposure. Furthermore, the expression of Msx1 and BMP4 were down-regulated in the developing chick embryonic neural tubes, which could contribute the inhibitive production of NCCs. We also discovered that expression of EMT-related adhesion molecules, such as Cadherin 6B (Cad6B) and E-cadherin, was altered following OA exposure. In sum, OA exposure negatively affected the development of embryonic neural crest cells, which in turn might result in cranial bone malformation.

Distribution, metabolism and metabolic disturbances of alpha-cypermethrin in embryo development, chick growth and adult hens

Alpha-cypermethrin (Alpha-CP), an important pyrethroid pesticide, has been widely used for pest control in agriculture and parasite control in livestock farms. Thus, alpha-CP is easily exposed to wild birds and poultry, which may pose a potential risk to birds. Alpha-CP and its metabolites have been detected in many environmental samples, including poultry and wild birds. We studied the distribution and metabolism of alpha-CP and its metabolites in embryo development and newborn chick. The results showed that metabolites were the main residual forms of alpha-CP in different stages of life and might increase the exposure risk of bird and its offspring. Metabolomics investigation of newborn chick exhibited that the metabolic profiles of chicks were disturbed, especially lipid metabolism. The concentrations of cis-DCCA and trans-DCCA were high in the first and second weeks of chick growth, indicating that chicks have limited ability to further metabolize and excrete cis-DCCA and trans-DCCA during the early stages of chicks. Toxicokinetics of alpha-CP in adult hens showed that alpha-CP was rapidly metabolized to acid metabolites, which could be further metabolized and excreted. The results about metabolism of alpha-CP in different stages of chicken indicate that the ability of the embryo and early chick to metabolize alpha-CP and its metabolites was the weakest. Therefore, it is of important significance to focus on evaluating the ecological risk of cypermethrin on birds at different stages of life cycle.

The neonicotinoids acetamiprid and imidacloprid impair neurogenesis and alter the microglial profile in the hippocampal dentate gyrus of mouse neonates

Acetamiprid (ACE) and imidacloprid (IMI) are widely used neonicotinoid pesticides. They bind selectively to insect nicotinic acetylcholine receptors (nAChRs) and are considered non-hazardous to mammals. Few studies have assessed the activation of vertebrate nAChRs and the neurodevelopmental toxicity following in utero or neonatal exposure to neonicotinoids; therefore, we evaluated the effects of ACE or IMI exposure on neurogenesis and microglial profiles in the developing hippocampal dentate gyrus (DG) of mouse neonates. Mice were exposed to ACE, IMI (both 5 mg/kg/day) or nicotine (0.5 mg/kg/day) from postnatal day (P)12 to P26 by oral gavage. On P27, brains were removed, and neurogenesis and microglial activation in the hippocampal DG were examined via immunohistochemistry. A reduction in neurogenesis in the hippocampal DG of neonates following ACE, IMI and nicotine treatment was found. Additionally, neonicotinoid-exposed newborns showed an increase in the number of amoeboid-type and activated M1-type microglia. These results suggest that exposure to ACE and IMI impairs neurogenesis and alters microglial profiles in the developing hippocampal DG following oral dosing in an early postnatal period. A better understanding of the potential effects of these pesticides on human infant health is an important goal of our research.

Imidacloprid Impacts on Neurobehavioral Performance, Oxidative Stress, and Apoptotic Events in the Brain of Adolescent and Adult Rats

Currently, imidacloprid (IMI) is the first insecticide and the second agrochemical highly applied all over the world. Here, we report on the impacts of IMI on neurobehavioral performance, oxidative stress, and apoptotic changes in the brain in either adult or adolescent rats. Forty male rats (adult and adolescent) were allocated to four groups. IMI groups were orally given 1 mg IMI/kg b.wt. dissolved in corn oil, whereas the controls were orally administered corn oil daily for 60 days. The obtained results demonstrated that IMI exposure resulted in less exploratory activity, deficit sensorimotor functions, and high depression. Levels of neurotransmitter including serotonin, gamma-aminobutyric acid, and dopamine were significantly reduced. Oxidative damage of brain tissues was evident following IMI exposure represented by the high levels of protein carbonyl, 8-hydroxyguanosine, and malondialdehyde, but total antioxidant capacity was reduced. Histopathological investigations of the brain tissues of IMI treated group revealed varying degrees of degeneration of the neuron. The immunohistochemical evaluation revealed a strong presence of glial fibrillary acidic protein (GFAP) and Bax positive cells, but a low expression of Bcl-2. These injurious impacts of IMI were very prominent in the adult rats than in the adolescent rats. Conclusively, exposure to IMI even at very low concentration could induce multiple neurobehavioral aberrations and neurotoxic impacts, especially in adults.

Head skeleton malformations in zebrafish (Danio rerio) to assess adverse effects of mixtures of compounds

The EU-EuroMix project adopted the strategy of the European Food Safety Authority (EFSA) for cumulative risk assessment, which limits the number of chemicals to consider in a mixture to those that induce a specific toxicological phenotype. These so-called cumulative assessment groups (CAGs) are refined at several levels, including the target organ and specific phenotype. Here, we explore the zebrafish embryo as a test model for quantitative evaluation in one such CAG, skeletal malformations, through exposure to test compounds 0-120 hpf and alcian blue cartilage staining at 120 hpf, focusing on the head skeleton. Reference compounds cyproconazole, flusilazole, metam, and thiram induced distinctive phenotypes in the head skeleton between the triazoles and dithiocarbamates. Of many evaluated parameters, the Meckel's-palatoquadrate (M-PQ) angle was selected for further assessment, based on the best combination of a small confidence interval, an intermediate maximal effect size and a gentle slope of the dose-response curve with cyproconazole and metam. Additional test compounds included in the CAG skeletal malformations database were tested for M-PQ effects, and this set was supplemented with compounds associated with craniofacial malformations or cleft palate to accommodate otherwise organized databases. This additional set included hexaconazole, all-trans-retinoic acid, AM580, CD3254, maneb, pyrimethanil, imidacloprid, pirimiphos-methyl, 2,4-dinitrophenol, 5-fluorouracil, 17alpha-ethynylestradiol (EE2), ethanol, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), PCB 126, methylmercury, boric acid, and MEHP. Most of these compounds produced a dose-response for M-PQ effects. Application of the assay in mixture testing was provided by combined exposure to cyproconazole and TCDD through the isobole method, supporting that in this case the combined effect can be modeled through concentration addition.

Exposure to neonicotinoid insecticides induces embryotoxicity in mice and rabbits

The potential toxicity of neonicotinoids (thiacloprid, acetamiprid, thiamethoxam and clothianidin) as well as related commercial products Calypso 480SC (thiacloprid mixture), Mospilan 20SP (acetamiprid mixture) and Agita 10WG (thiamethoxam mixture) on developmental capacities and quality of preimplantation embryos was evaluated. During in vitro tests, isolated 2-cell stage mice embryos were cultured in media with various concentrations of active compounds or commercial products until blastocyst formation. As found using stereomicroscopic examination, all neonicotinoids at highest (100μM) concentration negatively affected embryonic development (P<0.001). Fluorescence staining revealed that the blastocysts obtained displayed lower numbers of blastomeres and elevated incidence of cell death. Thiacloprid and acetamiprid decreased quality of blastocysts also at 10μM concentration. From the tested products only Calypso 480SC containing 10μM of thiacloprid showed harmful impact on embryo quality. In an experiment using rabbit embryos, similar negative effect of thiacloprid in vitro was recorded. In vivo testing confirmed that blastocysts collected from thiacloprid-treated mice displayed lower total cell counts than blastocysts from controls. The sensitivity of embryonic cells to neonicotinoids is in the order of thiacloprid>acetamiprid, thiomethoxam>clothianidin. Thiacloprid impairs development and quality of both mouse and rabbit preimplantation embryos, and shows embryotoxicity even at acute reference dose.

Imidacloprid Promotes High Fat Diet-Induced Adiposity and Insulin Resistance in Male C57BL/6J Mice

Imidacloprid, a neonicotinoid insecticide widely used in agriculture worldwide, has been reported to promote adipogenesis and cause insulin resistance in vitro. The purpose of the current study was to determine the effects of imidacloprid and its interaction with dietary fat in the development of adiposity and insulin resistance using male C57BL/6J mice. Imidacloprid (0.06, 0.6, or 6 mg/kg bw/day) was mixed in a low-fat (4% w/w) or high-fat (20% w/w) diet and given to mice ad libitum for 12 weeks. Imidacloprid significantly promoted high fat diet-induced body weight gain and adiposity. In addition, imidacloprid treatment with the high fat diet resulted in impaired glucose metabolism. Consistently, there were significant effects of imidacloprid on genes regulating lipid and glucose metabolisms, including the AMP-activated protein kinase-α (AMPKα) pathway in white adipose tissue and liver. These results suggest that imidacloprid may potentiate high fat diet-induced adiposity and insulin resistance in male C57BL/6J mice.

Excess Imidacloprid Exposure Causes the Heart Tube Malformation of Chick Embryos

As a neonicotinoid pesticide, imidacloprid is widely used to control sucking insects on agricultural planting and fleas on domestic animals. However, the extent to which imidacloprid exposure has an influence on cardiogensis in early embryogenesis is still poorly understood. In vertebrates, the heart is the first organ to be formed. In this study, to address whether imidacloprid exposure affects early heart development, the early chick embryo has been used as an experimental model because of its accessibility at its early developmental stage. The results demonstrate that exposure of the early chick embryo to imidacloprid caused malformation of heart tube. Furthermore, the data reveal that down-regulation of GATA4, NKX2.5, and BMP4 and up-regulation of Wnt3a led to aberrant cardiomyocyte differentiation. In addition, imidacloprid exposure interfered with basement membrane breakdown, E-cadherin/laminin expression, and mesoderm formation during the epithelial-mesenchymal transition (EMT) in gastrula chick embryos. Finally, the DiI-labeled cell migration trajectory indicated that imidacloprid restricted the cell migration of cardiac progenitors to primary heart field in gastrula chick embryos. A similar observation was also obtained from the cell migration assay of scratch wounds in vitro. Additionally, imidacloprid exposure negatively affected the cytoskeleton structure and expression of corresponding adhesion molecules. Taken together, these results reveal that the improper EMT, cardiac progenitor migration, and differentiation are responsible for imidacloprid exposure-induced malformation of heart tube during chick embryo development.