Pest toxicology: the primary mechanisms of pesticide action

The mode of action of different organochlorine pesticides families in mammalians

Organochlorine pesticides (OCPs) show differences in their chemical structure, mechanism of toxicity, and target organisms. However, OCPs also have some common characteristics such as high persistence in the environment, bioaccumulation, and toxicity which lead to health issues. Nowadays, the toxicity of OCPs is well known, but we still do not know all the specific molecular mechanisms leading to their toxicity in mammalians. Therefore, this review aims to collect data about the mode of action of various classes of OCPs, highlighting their differences and common behavioural reactions in the human and animal body. To discuss the OCPs molecular pathways and fate in different systems of the body, three organochlorine insecticides were selected (Dichlorodiphenyltrichloroethane, Hexachlorocyclohexane and Chlordecone), regarding to their widespread use, with consequent effects on the ecosystem and human health. Their common biological responses at the molecular scale and their different interactions in human and animal bodies were highlighted and presented.

Bifenox induces hepatotoxicity and vascular toxicity in zebrafish embryos via ROS production and alterations in signaling pathways

Existing evidence shows that currently used pesticides pose toxicological risks to exposed wildlife. Chemically, bifenox belongs to diphenyl ethers, a well-known group of herbicides. Its mechanism of action primarily involves inducing lipid peroxidation and blocking protoporphyrinogen oxidases. Toxicity of diphenyl ether herbicides has been elucidated in animal cells; however, in vivo toxicological evaluations of bifenox are required to determine its unexpected effects. This study aimed to determine the negative effects of bifenox, and its effects on higher eukaryotes. We found that early stages of zebrafish embryo exposed to bifenox demonstrated increased mortality and physiological defects, based on the LC50 value. Bifenox severely inhibited blood vessel growth by reducing key elements of complex connectivity; fluorescently tagged transgenic lines (fli1a:EGFP) showed morphological changes. Additionally, transgenic lines that selectively identified hepatocytes (fabp10a:DsRed) showed reduced fluorescence, indicating that bifenox may inhibit liver development. To evaluate the level of oxidative stress, we used 2',7'-dichlorofluorescein diacetate (DCFH-DA) probes in zebrafish embryos to identify the underlying mechanisms causing developmental damage. Our findings demonstrate that exposure to bifenox causes abnormalities in the hepatic and cardiovascular systems during zebrafish embryogenesis. Therefore, this study provides new information for the evaluation of toxicological risks of bifenox in vertebrates.

Key residues involved in the interaction between chlorpyrifos and a chemosensory protein in Rhopalosiphum padi: Implication for tracking chemical residues via insect olfactory proteins

The development of advanced biosensors for tracking chemical residues and detecting environmental pollution is of great significance. Insect chemical sensory proteins, including chemosensory proteins (CSPs), are easy to synthesize and purify and have been used to design proteins for specific biosensor applications. Chlorpyrifos is one of the most commonly used chemicals for controlling insect pests in agriculture. This organophosphate is harmful to aquatic species and has long-term negative consequences for the ecosystem. CSPs can bind and carry a variety of environmental chemicals, including insecticides. However, the mechanism by which CSPs bind to insecticides in aphids has not been clarified. In this study, we discovered that RpCSP1 from Rhopalosiphum padi has a higher affinity for chlorpyrifos, with a Ki value of 4.763 ± 0.491 μM. Multispectral analysis revealed the physicochemical binding mechanism between RpCSP1 and chlorpyrifos. Computational simulation analysis demonstrated that the main factor promoting the development of the RpCSP1-chlorpyrifos complex is polar solvation energy. Four residues (Arg33, Glu94, Gln145, Lys153) were essential in facilitating the interaction between RpCSP1 and chlorpyrifos. Our research has improved knowledge of the relationship between CSPs and organophosphorus pesticides. This knowledge contributes to the advancement of biosensor chips for tracking chemical residues and detecting environmental pollution through the use of CSPs.

Transfer and bioaccumulation of pesticides in terrestrial arthropods and food webs: State of knowledge and perspectives for research

Arthropods represent an entry point for pesticide transfers in terrestrial food webs, and pesticide accumulation in upper chain organisms, such as predators can have cascading consequences on ecosystems. However, the mechanisms driving pesticide transfer and bioaccumulation in food webs remain poorly understood. Here we review the literature on pesticide transfers mediated by terrestrial arthropods in food webs. The transfer of pesticides and their potential for bioaccumulation and biomagnification are related to the chemical properties and toxicokinetic of the substances, the resistance and detoxification abilities of the contaminated organisms, as well as by their effects on organisms' life history traits. We further identify four critical areas in which knowledge gain would improve future predictions of pesticides impacts on terrestrial food webs. First, efforts should be made regarding the effects of co-formulants and pesticides mixtures that are currently understudied. Second, progress in the sensitivity of analytical methods would allow the detection of low concentrations of pesticides in small individual arthropods. Quantifying pesticides in arthropods preys, their predators, and arthropods or vertebrates at higher trophic level would bring crucial insights into the bioaccumulation and biomagnification potential of pesticides in real-world terrestrial food webs. Finally, quantifying the influence of the trophic structure and complexity of communities on the transfer of pesticides could address several important sources of variability in bioaccumulation and biomagnification across species and food webs. This narrative review will inspire future studies aiming to quantify pesticide transfers in terrestrial food webs to better capture their ecological consequences in natural and cultivated landscapes.

Genetically encoded libraries and spider venoms as emerging sources for crop protective peptides

Agricultural crops are targeted by various pathogens (fungi, bacteria, and viruses) and pests (herbivorous arthropods). Antimicrobial and insecticidal peptides are increasingly recognized as eco-friendly tools for crop protection due to their low propensity for resistance development and the fact that they are fully biodegradable. However, historical challenges have hindered their development, including poor stability, limited availability, reproducibility issues, high production costs, and unwanted toxicity. Toxicity is a primary concern because crop-protective peptides interact with various organisms of environmental and economic significance. This review focuses on the potential of genetically encoded peptide libraries like the use of two-hybrid-based methods for antimicrobial peptides identification and insecticidal spider venom peptides as two main approaches for targeting plant pathogens and pests. We discuss some key findings and challenges regarding the practical application of each strategy. We conclude that genetically encoded peptide library- and spider venom-derived crop protective peptides offer a sustainable and environmentally responsible approach for addressing modern crop protection needs in the agricultural sector.

Dosage-sensitive and simultaneous detection of multiple small-molecule pollutants in environmental water and agriproducts using portable SERS-based lateral flow immunosensor

The co-contamination of pesticide residues and mycotoxins in agricultural products is a global concern, with the potential for cumulative and synergistic damaging effects, imposing substantial health and economic burdens to the public. The dosage-sensitive and simultaneous detection of multiple pollutants, with a heightened sensitivity in real samples, poses a significant demand and challenge. Herein, we propose a portable detection method integrating surface-enhanced Raman scattering (SERS)-with lateral flow immunoassay (LFIA), offering high sensitivity and multiplex analysis capabilities. This approach enables the simultaneous detection of imidacloprid (IMI), pyraclostrobin (PYR) and aflatoxin B1 (AFB1) through a single test strip. Utilizing the immune-specific binding between antigen and antibodies, we immobilised antibody- conjugated SERS nanotags on three test lines of the strips to generate Raman signal amplification in the proposed biosensor. Accurate quantitative analysis was performed by measuring the SERS signal intensity on the test lines. The limits of detection were 8.6 pg/mL for IMI, 97.4 pg/mL for PYR and 8.9 pg/mL for AFB1, exhibiting sensitivities 12-fold, 102-fold and11-fold higher than the colorimetric signals, respectively. Importantly, the SERS-LFIA immunosensor demonstrated robust performance when applied to real samples, yielding recoveries ranging from 86.16 % to 115.0 %, with relative standard deviation values below 8.67 %. These results underscore the excellent stability, high selectivity and reliability the proposed SERS-LFIA immunosensor. Consequently, it holds promise for the detection of multiple pesticides and mycotoxins in both environmental and agricultural samples.

On Disease Configurations, Black-Grass Blowback, and Probiotic Pest Management

This article explores approaches to managing pests that are being developed in response to the faltering effectiveness of antibiotic regimes of chemical control. It focuses on black-grass (Alopecurus myosuroides), an endemic plant in European agriculture that has emerged as a serious yield-robber with increasing levels of herbicidal resistance. Following farmers and agronomists who have developed "integrated" approaches to black-grass management, the article identifies approaches to biosecurity that do not target unwanted life so much as they modulate ecological systems in their entirety. Pathogenesis, in this relational understanding, follows not from breaches of dangerous life into healthy space, but from ecological intra-actions that enable the proliferation of some life to compromise the multispecies livability of the body in question. The article contributes to the literature by detailing how this configurational approach works in the world. It traces the polymorphic spatial imaginaries required to map pests well; the process of knowledge intensification needed to reveal which configurations can resist pathogenesis; and the probiotic biopolitical interventions used to safeguard farmland productivity. The article uses black-grass to present a temporal metanarrative of intensive farming causing ecological blowback, leading to the development of approaches to pest management predicated on a pragmatic tolerance toward unwanted life.

Investigating the prevalence of erectile dysfunction among men exposed to organophosphate insecticides

INTRODUCTION

Erectile dysfunction (ED) poses a significant disease morbidity and contributor to male infertility, where an estimated 20-40% of men are affected annually. While several risk factors have been identified in the etiology of ED (e.g., aging, heart disease, diabetes, and obesity), the complete pathogenesis remains to be elucidated. Over the last few decades, the contribution of environmental exposures to the pathogenesis of ED has gained some attention, though population studies are limited and results are mixed. Among environmental contaminants, organophosphate (OP) insecticides represent one of the largest chemical classes, and chlorpyrifos is the most commonly used OP in the U.S. OP exposure has been implicated in driving biological processes, including inflammation, reactive oxygen species production, and endocrine and metabolism disruption, which have been demonstrated to adversely affect the hypothalamus and testes and may contribute to ED. Currently, studies evaluating the association between OPs and ED within the U.S. general population are sparse.

METHODS

Data were leveraged from the National Health and Nutrition Examination Survey (NHANES), which is an annually conducted, population-based cross-sectional study. Urinary levels of 3,5,6-trichloro-2-pyridinol (TCPy), a specific metabolite of the most pervasive OP insecticide chlorpyrifos, were quantified as measures of OP exposure. ED was defined by responses to questionnaire data, where individuals who replied "sometimes able" or "never able" to achieve an erection were classified as ED. Chi-square, analysis of variance (ANOVA), and multivariable, weighted linear and logistic regression analyses were used to compare sociodemographic variables between quartiles of TCPy exposure, identify risk factors for TCPy exposure and ED, and to analyze the relationship between TCPy and ED.

RESULTS

A total of 671 adult men were included in final analyses, representing 28,949,379 adults after survey weighting. Approximately 37% of our cohort had ED. Smoking, diabetes, aging, Mexican-American self-identification, and physical inactivity were associated with higher ED prevalence. Analysis of TCPy modeled as a continuous variable revealed nonsignificant associations with ED (OR = 1.02 95% CI [0.95, 1.09]). Stratification of total TCPy into quartiles revealed increased odds of ED among adults in the second and fourth quartiles, using the first quartile as the reference (OR = 2.04 95% CI [1.11, 3.72], OR = 1.51 95% CI [0.58, 3.93], OR = 2.62 95% CI [1.18, 5.79], for quartiles 2, 3, and 4, respectively).

CONCLUSIONS

The results of our study suggest a potential role for chlorpyrifos and other OPs the pathogenesis of ED. Future studies are warranted to validate these findings, determine clinical significance, and to investigate potential mechanisms underlying these associations.

Fate of pesticides in agricultural runoff treatment systems: Occurrence, impacts and technological progress

The levels of pesticides in air, water, and soil are gradually increasing due to its inappropriate management. In particular, agricultural runoff inflicts the damages on the ecosystem and human health at massive scale. Present study summarizes 70 studies in which investigations on removal or treatment of pesticides/insecticides/herbicides are reported. A bibliometric analysis was also done to understand the recent research trends through the analysis of 2218 publications. The specific objectives of this study are as follows: i) to inventorize the characteristics details of agriculture runoff and analyzing the occurrence and impacts of pesticides, ii) analyzing the role and interaction of pesticides in different environmental segments, iii) investigating the fate of pesticides in agriculture runoff treatment systems, iv) summarizing the experiences and findings of most commonly technology deployed for pesticides remediation in agriculture runoff including target pesticide(s), specifications, configuration of technological intervention. Among the reported technologies for pesticide treatment in agriculture runoff, constructed wetland was at the top followed by algal or photobioreactor. Among various advanced oxidation processes, photo Fenton method is mainly used for pesticides remediation such as triazine, methyl parathion, fenuron and diuron. Algal bioreactors are extensively used for a wide range of pesticides treatment including 2,4-Dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, alachlor, diuron, chlorpyrifos, endosulfan, and imidacloprid; especially at lower hydraulic retention time of 2-6 h. This study highlights that hybrid approaches can offers potential opportunities for effective removal of pesticides in a more viable manner.

Effect of nanopesticides (azoxystrobin and bifenthrin) on the phenolic content and metabolic profiles of strawberries (Fragaria × ananassa)

BACKGROUND

Nanoencapsulation has opened promising fields of innovation for pesticides. Conventional pesticides can cause side effects on plant metabolism. To date, the effect of nanoencapsulated pesticides on plant phenolic contents has not been reported.

RESULTS

In this study, a comparative evaluation of the phenolic contents and metabolic profiles of strawberries was performed for plants grown under controlled field conditions and treated with two separate active ingredients, azoxystrobin and bifenthrin, loaded into two different types of nanocarriers (Allosperse® polymeric nanoparticles and SiO2 nanoparticles). There were small but significant decreases of the total phenolic content (9%) and pelargonidin 3-glucoside content (6%) in strawberries treated with the nanopesticides. An increase of 31% to 125% was observed in the levels of gallic acid, quercetin, and kaempferol in the strawberries treated with the nanoencapsulated pesticides compared with the conventional treatments. The effects of the nanocarriers on the metabolite and phenolic profiles was identified by principal component analysis.

CONCLUSION

Overall, even though the effects of nanopesticides on the phenological parameters of strawberry plants were not obvious, there were significant changes to the plants at a molecular level. In particular, nanocarriers had some subtle effects on plant health and fruit quality through variations in total and individual phenolics in the fruits. Further research will be needed to assess the impact of diverse nanopesticides on other groups of plant metabolites. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pesticide residues in agricultural end-products and risk assessment for consumers in North China

This study investigated pesticide residues in market-sold vegetables and fruits in Hebei Province, China, over 5 years (2018-2022). A modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was applied to gas chromatography with triple-quadrupole mass spectrometer (GC-MS/MS). The analytical methods were validated with respect to matrix effect (ME), recovery rate (78.9~105.5%), limit of quantitation (LOQ, 2.93~9.73 μg/kg), and linear correlation coefficient (0.9982~0.9997). Residues of 10 pesticides in 12 categories of vegetable and fruit were detected. 31.9% of the samples were detected pesticide residues; 15.5% of samples were detected multi-component pesticide residues. Twenty-seven positive detections of pesticide residues exceeded the corresponding maximum residue limit (MRL), accounting for 2.33%. The most types of pesticide residues were detected in cherry, with the number of 7. Procymidone was the most detected pesticide, and it was detected in 8 categories of samples. The hazard index (HI) of omethoate was the highest and the procymidone was the lowest. The HI of all the vegetables and fruits were less than 100%. The effects of pesticide residues are within an acceptable range for human. Adequate attention and further monitoring are still needed.

Non-target biotransformation enzymes as a target for triazole-zinc mixtures

Triazoles inhibit lanosterol 14α-demethylase and block ergosterol biosynthesis in fungal pathogens. However, they also interact with other cytochrome P450 enzymes and influence non-target metabolic pathways. Disturbingly, triazoles may interact with essential elements. The interaction of penconazole (Pen), cyproconazole (Cyp) and tebuconazole (Teb) with Zn2+ results in the formation of deprotonated ligands in their complexes or in the creation of complexes with Cl- as a counterion or doubly charged complexes. Triazoles, as well as their equimolar cocktails with Zn2+ (10-6 mol/L), decreased the activities of the non-target enzymes CYP19A1 and CYP3A4. Pen most decreased CYP19A1 activity and was best bound to its active centre to block the catalytic cycle in computational analysis. For CYP3A4, Teb was found to be the most effective inhibitor by both, activity assay and interaction with the active centre. Teb/Cyp/Zn2+ and Teb/Pen/Cyp/Zn2+ cocktails also decreased the CYP19A1 activity, which was in correlation with the formation of numerous triazole-Zn2+ complexes.

Triazoles as a Potential Threat to the Nutritional Quality of Tomato Fruits

Triazole fungicides can threaten plants as abiotic stressors but can also positively affect plant defense by inducing priming. Thus, plant yield is also both protected and endangered by triazoles that may influence several metabolic pathways during maturation processes, such as the biosynthesis of saccharides or secondary metabolites. Here, Solanum lycopersicum L. plants were exposed to foliar and soil applications of penconazole, tebuconazole, or their combination, and their resulting effect on tomato fruits was followed. The exposure to the equimolar mixture of both triazoles influenced the representation of free proteinogenic amino acids, especially Gln, Glu, Gly, Ile, Lys, Ser and Pro, saccharide content, and led to a significant increase in the contents of total phenolics and flavonoids as well as positive stimulation of the non-enzymatic antioxidant system. Among the identified secondary metabolites, the most abundant was naringenin, followed by chlorogenic acid in tomato peel. In turn, all triazole-treated groups showed a significantly lower content of rosmarinic acid in comparison with the control. Foliar application of penconazole affected the fruit more than other single triazole applications, showing a significant decrease in antioxidant capacity, the total content of secondary metabolites, and the activities of total membrane-bound peroxidases and ascorbate peroxidase.

Neurotoxicity in complex environmental mixtures-a case-study at River Danube in Novi Sad (Serbia) using zebrafish embryos

Acetylcholinesterase (AChE) inhibitors are an important class of neuroactive chemicals that are often detected in aquatic and terrestrial environments. The correct functionality of the AChE enzyme is linked to many important physiological processes such as locomotion and respiration. Consequently, it is necessary to develop new analytical strategies to identify harmful AChE inhibitors in the environment. It has been shown that mixture effects and oxidative stress may jeopardize the application of in vivo assays for the identification of AChE inhibitors in the environment. To confirm that in vivo AChE assays can be successfully applied when dealing with complex mixtures, an extract from river water impacted by non-treated wastewater was bio-tested using the acute toxicity fish embryo test (FET) and AChE inhibition assay with zebrafish. The zebrafish FET showed high sensitivity for the extract (LC10 = relative extraction factor 2.8) and we observed a significant inhibition of the AChE (40%, p < 0.01) after 4-day exposure. Furthermore, the extract was chromatographically fractionated into a total of 26 fractions to dilute the mixture effect and separate compounds according to their physico-chemical properties. As expected, non-specific acute effects (i.e., mortality) disappeared or evenly spread among the fractions, while AChE inhibition was still detected in five fractions. Chemical analysis did not detect any known AChE inhibitors in these active fractions. These results confirm that the AChE assay with Danio rerio can be applied for the detection of neuroactive effects induced in complex environmental samples, but also, they highlight the need to increase analytical and identification techniques for the detection of neurotoxic substances.

Ecotoxicity of Diazinon and Atrazine Mixtures after Ozonation Catalyzed by Na+ and Fe2+ Exchanged Montmorillonites on Lemna minor

The toxicity of two pesticides, diazinon (DAZ) and atrazine (ATR), before and after montmorillonite-catalyzed ozonation was comparatively investigated on the duckweed Lemna minor. The results allowed demonstrating the role of clay-containing media in the evolution in time of pesticide negative impact on L. minor plants. Pesticides conversion exceeded 94% after 30 min of ozonation in the presence of both Na+ and Fe2+ exchanged montmorillonites. Toxicity testing using L. minor permitted us to evaluate the change in pesticide ecotoxicity. The plant growth inhibition involved excessive oxidative stress depending on the pesticide concentration, molecular structure, and degradation degree. Pesticide adsorption and/or conversion by ozonation on clay surfaces significantly reduced the toxicity towards L. minor plants, more particularly in the presence of Fe(II)-exchanged montmorillonite. The results showed a strong correlation between the pesticide toxicity towards L. minor and the level of reactive oxygen species, which was found to depend on the catalytic activity of the clay minerals, pesticide exposure time to ozone, and formation of harmful derivatives. These findings open promising prospects for developing a method to monitor pesticide ecotoxicity according to clay-containing host-media and exposure time to ambient factors.

Comparison of disinfectants-induced gene expression profile: Potential adverse effects

Despite their importance in combating the spread of the COVID-19 pandemic, adverse effects of disinfectants on human health, especially the respiratory system, have been of continuing concern to researchers. Considering that bronchi are the main target of sprayed disinfectants, we here treated the seven major active ingredients in disinfectant products accepted by the US EPA to human bronchial epithelial cells and determined the subtoxic levels. Then, we performed microarray analysis using total RNA obtained at the subtoxic level and designed a network representing disinfectant-induced cellular response using the KEGG pathway analysis technique. Polyhexamethylguanidine phosphate, a lung fibrosis inducer, was used as a reference material to verify the relationship between cell death and pathology. The derived results reveal potential adverse effects along with the need for an effective application strategy for each chemical.

Evaluation of cadmium and mercury on cardiovascular and neurological systems: Effects on humans and fish

Chemicals are at the top of public health concerns and metals have received much attention in terms of toxicological studies. Cadmium (Cd) and mercury (Hg) are among the most toxic heavy metals and are widely distributed in the environment. They are considered important factors involved in several organ disturbances. Heart and brain tissues are not among the first exposure sites to Cd and Hg but they are directly affected and may manifest intoxication reactions leading to death. Many cases of human intoxication with Cd and Hg showed that these metals have potential cardiotoxic and neurotoxic effects. Human exposure to heavy metals is through fish consumption which is considered as an excellent source of human nutrients. In the current review, we will summarize the most known cases of human intoxication with Cd and Hg, highlight their toxic effects on fish, and investigate the common signal pathways of both Cd and Hg to affect heart and brain tissues. Also, we will present the most common biomarkers used in the assessment of cardiotoxicity and neurotoxicity using Zebrafish model.

Application of cell painting for chemical hazard evaluation in support of screening-level chemical assessments

'Cell Painting' is an imaging-based high-throughput phenotypic profiling (HTPP) method in which cultured cells are fluorescently labeled to visualize subcellular structures (i.e., nucleus, nucleoli, endoplasmic reticulum, cytoskeleton, Golgi apparatus / plasma membrane and mitochondria) and to quantify morphological changes in response to chemicals or other perturbagens. HTPP is a high-throughput and cost-effective bioactivity screening method that detects effects associated with many different molecular mechanisms in an untargeted manner, enabling rapid in vitro hazard assessment for thousands of chemicals. Here, 1201 chemicals from the ToxCast library were screened in concentration-response up to ~100 μM in human U-2 OS cells using HTPP. A phenotype altering concentration (PAC) was estimated for chemicals active in the tested range. PACs tended to be higher than lower bound potency values estimated from a broad collection of targeted high-throughput assays, but lower than the threshold for cytotoxicity. In vitro to in vivo extrapolation (IVIVE) was used to estimate administered equivalent doses (AEDs) based on PACs for comparison to human exposure predictions. AEDs for 18/412 chemicals overlapped with predicted human exposures. Phenotypic profile information was also leveraged to identify putative mechanisms of action and group chemicals. Of 58 known nuclear receptor modulators, only glucocorticoids and retinoids produced characteristic profiles; and both receptor types are expressed in U-2 OS cells. Thirteen chemicals with profile similarity to glucocorticoids were tested in a secondary screen and one chemical, pyrene, was confirmed by an orthogonal gene expression assay as a novel putative GR modulating chemical. Most active chemicals demonstrated profiles not associated with a known mechanism-of-action. However, many structurally related chemicals produced similar profiles, with exceptions such as diniconazole, whose profile differed from other active conazoles. Overall, the present study demonstrates how HTPP can be applied in screening-level chemical assessments through a series of examples and brief case studies.

Predictive liver lipid biomarker signature of Acetyl-coenzyme A carboxylase inhibitor related developmental toxicity in non-pregnant female Han Wistar rats – lipidomics biomarker discovery and validation

INTRODUCTION

Acetyl-coenzyme A carboxylase (ACCase) inhibition is an attractive herbicide target. However, issues with fetal developmental toxicity identified at the late stages of the development process can halt progression of previously promising candidates.

OBJECTIVES

To select and verify predictive lipid biomarkers of ACCase inhibition activity in vivo using liver samples obtained from early stage 7 day repeat dose studies in non-pregnant female Han Wistar rats that could be translated to developmental toxicity endpoints discovered during late-stage studies to provide an early screening tool.

METHODS

Liver samples from eight rat repeat dose studies, exposed to six ACCase inhibitors from three different chemistries and one alternative mode of action (MoA) that also perturbs lipid biochemistry, were analysed using liquid chromatography - high resolution accurate mass - mass spectrometry. Multivariate and univariate data analysis methods were used for biomarker discovery and validation.

RESULTS

A biomarker signature consisting of sixteen lipids biomarkers were selected. Verification of the signature as indicative of ACCase inhibition was established by demonstrating consistent perturbations in the biomarkers using two different ACCase inhibitor chemistries and the lack thereof with an alternate MoA. The fold change profile pattern was predictive of which test substance doses would or would not cause developmental toxicity.

CONCLUSION

A strategy for selecting and verifying a robust signature of lipid biomarkers for predicting a toxicological end point has been described and demonstrated. Differences in lipidomic profiles correlated with developmental toxicity suggesting that indicators of a molecular initiation event resulting in pup developmental toxicity can be predicted from short term, toxicity studies conducted in non-pregnant adult female Han Wistar rats.

Household based-pyrethroids on adult zebrafish (Danio rerio) exert behavioral and cholinergic changes in different brain regions

Pyrethroid-based insecticides are largely used for mosquito control. These compounds have household and agricultural applications with different formulations. Two important compounds used as household insecticides are prallethrin and transfluthrin, both from the pyrethroid chemical group. With the mode of action centered on sodium channels, pyrethroids keep the ionic sodium channels open for a long time causing the death of the insect by nervous hyperexcitability. Given the increased use of household insecticides by humans and the incidence of disease outbreaks with unknown etiology such as autism spectrum disease, schizophrenia, and Parkinson's disease we investigate some physiological inputs of these compounds on zebrafish. In this study, we evaluated the social interaction, shoaling formation, and anxiety-like behavior of zebrafish exposed chronically to transfluthrin- and prallthrin-based insecticides (T-BI and P-BI). In addition, we quantified the activity of the enzyme acetylcholinesterase (AChE) in different brain regions. We observed that both compounds caused anxiolytic behavior and reduced shoaling formation and social interaction. Their behavioral biomarkers indicated a harmful ecological effect on the specie as well as a possible impact of these compounds on autism spectrum disorder (ASD) and schizophrenia (SZP). In addition, the AChE activity would change its activity in different brain regions modulating the anxiety-like behavior and social behavior in zebrafish. We conclude that P-BI and T-BI make us alert about the relationship of these compounds with nervous diseases related to cholinergic signaling.

Biomarkers of imidacloprid toxicity in Japanese quail, Coturnix coturnix japonica

The in vivo effect of the oral sublethal doses of 3.014 mg kg^-1 of IMI (1/25 LD₅₀) for 1, 7, 14, and 28 days every other day on Japanese quail was investigated. The results revealed that certain biomarkers in the selected tissues of the quail such as acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), aminotransaminases (alanine aminotransferase, ALT, and aspartate aminotransaminase, AST), phosphatases (acid phosphatase, ACP, and alkaline phosphatase, ALP), lactate dehydrogenase (LDH), adenosine-triphosphatase (ATPase), glutathione-S-transferase (GST), lipid peroxidation (LPO), and blood glucose showed significant inductions, while significant reductions in the levels of glutathione-reduced (GSH), deoxyribonucleic acid (DNA), and ribonucleic acid (RNA) were noticed. In this study, the molecular mechanisms of the toxic effects of imidacloprid on quails were elucidated regarding neurotoxicity, hepatotoxicity, oxidative stress, lipid peroxidation, antioxidant activity, and genotoxicity. Because IMI induced alterations in the levels of these biomarkers in Japanese quail; therefore, Japanese quail as a wild avian can be used as a suite bioindicator to detect imidacloprid toxicity.

Comparative transcriptome analysis reveals the non-neuronal cholinergic system in the ovary of the oriental armyworm, Mythimna separata Walker (Lepidoptera: Noctuidae)

BACKGROUND

Acetylcholine (ACh), as a classical neurotransmitter, plays great roles in the nervous system. There is increasing evidence of its non-neuronal roles in regulating basic cell functions in vertebrates. However, knowledge about the non-neuronal cholinergic system in insects is scarce.

RESULTS

A comparative transcriptome analysis was performed to investigate differences in the key molecular components of the cholinergic system between the head and ovary. The results showed that expression levels of most cholinergic system-related genes were higher in the head than in the ovary, and some cholinergic components were absent in the ovary. ACh contents ranged from 0.1 to 1.3 μg mg^-1 of wet weight during the development of the ovary, and weak acetylcholinesterase activity was also detected. Moreover, the ovary has a capacity for ACh synthesis. Bromoacetylcarnitine (BrACar), a specific carnitine acetyltransferase (CarAT) inhibitor, greatly inhibits ACh synthesis by 83.83% in ovary homogenates, but bromoacetylcholine (BrACh), a specific choline acetyltransferase (ChAT) inhibitor, has no effect on ACh synthesis in the ovary. These findings indicate that non-neuronal ACh in the ovary is only catalyzed by CarAT.

CONCLUSION

This study reveals the existence of the non-neuronal cholinergic system in the ovary of M. separata, whose synthesis and release mechanisms are different from those of the head. These results provide novel insights into the non-neuronal cholinergic system in insects, and will be valuable in the discovery of new target genes and the future development of green pest control. © 2022 Society of Chemical Industry.

Comparative Insecticide Uptake Characteristics of Chlorfenapyr Suggests an Additional Reason Why Bed Bugs (Hemiptera: Cimicidae) are so Difficult to Control

Insecticides interact with biochemical sites, disrupting homeostasis, leading to moribundity and death. Considering this process of intoxication, investigating insecticide uptake ensures an understanding of exposure profile. This study evaluated insecticide uptake by bed bugs, Cimex lectularius L., as affected by time and formulation, and a comparative uptake by German cockroaches, Blattella germanica (L.). Insects exposed to chlorfenapyr residues from two Phantom insecticide formulations (i.e., Aerosol and Suspended Concentrate (SC)) were solvent extracted and analyzed by GC-ECD. Chlorfenapyr uptake by bed bugs significantly increased with time, but the rate of external chlorfenapyr adsorption between the two formulations was not significantly different. However, initial exposure and uptake to the aerosol-treated versus SC-treated surfaces were significantly greater by 2.7x. Absorption-rates of chlorfenapyr residues inside the insect, associated with internal insect tissues or exoskeleton-bound, were significantly lower compared with external adsorption, with aerosol and SC formulations accumulating at 4.8x and 14.4x less, respectively. An unexpected formulation effect occurred with aerosol-treated papers and aging of residues. A reformulation of the aerosol provided a greater adsorption of chlorfenapyr at 19.1x that of the original formula after 2 hr. External versus internal uptake of chlorfenapyr by cockroaches was inverse to that seen in bed bugs, with greater chlorfenapyr absorption. Obstructing cockroach mouthparts prevented an internal uptake of chlorfenapyr and provided a similar exposure profile to bed bugs. This work demonstrates a need to evaluate insecticide uptake with formulation and insect morphology to maximize dose, especially in such a morphologically and environmentally isolated insect as the bed bug.

Functional analysis reveals ionotropic GABA receptor subunit RDL is a target site of ivermectin and fluralaner in the yellow fever mosquito, Aedes aegypti

BACKGROUND

Ionotropic γ-aminobutyric acid (iGABA) receptors are involved in various physiological activities in insects, including sleep, olfactory memory, movement, and resistance to viruses. Ivermectin and fluralaner can disturb the insect nervous system by binding to iGABA receptors, and are therefore an effective means for controlling insect pests. However, the molecular mechanisms underlying the insecticidal effect of both the compounds on Aedes. aegypti remain unexplored.

RESULTS

In this study, we investigated the spatiotemporal expression profile of Ae. aegypti RDL (Ae-RDL), a subunit of iGABA receptor. RDL dsRNA suppressed the expression of Ae-RDL mRNA in Ae. aegypti larvae and adult by 60% and 50.67%,  resepectly. However, the physiology of Ae. aegypti larvae was not significantly affected. The mortality of Ae. aegypti larvae and adult females subjected to Ae-RDL knockdown significantly decreased after exposure to ivermectin and fluralaner. Additionally, Ae-RDL was cloned into Xenopus laevis oocytes and characterized using the two-electrode voltage-clamp method. The inward current was induced by GABA binding to the functional Ae-RDL homomeric receptors at a median effective concentration (EC₅₀ ) of 100.4 ± 59.95 μM (n > 3). The significant inhibitory effect of ivermectin and fluralaner on inward current indicated that both insecticides exerted a significant antagonistic effect on Ae-RDL. However, ivermectin also showed strong agonistic as well as weak activation effects on Ae-RDL. These contrasting effects of ivermectin on Ae-RDL depended on ivermectin concentration.

CONCLUSION

Our study revealed that Ae-RDL subunit is a target of ivermectin and fluralaner, providing new insights into the insecticidal mechanism of both compounds in Ae. aegypti. © 2022 Society of Chemical Industry.

Lethal, Sub-Lethal and Trans-Generational Effects of Chlorantraniliprole on Biological Parameters, Demographic Traits, and Fitness Costs of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Fall armyworm [Spodoptera frugiperda (J. E. Smith, 1797)] was first reported in the Americas, then spread to all the continents of the world. Chemical insecticides are frequently employed in managing fall armyworms. These insecticides have various modes of actions and target sites to kill the insects. Chlorantraniliprole is a selective insecticide with a novel mode of action and is used against Lepidopteran, Coleopteran, Isopteran, and Dipteran pests. This study determined chlorantraniliprole's lethal, sub-lethal, and trans-generational effects on two consecutive generations (F₀, F₁, and F₂) of the fall armyworm. Bioassays revealed that chlorantraniliprole exhibited higher toxicity against fall armyworms with a LC₅₀ of 2.781 mg/L after 48 h of exposure. Significant differences were noted in the biological parameters of fall armyworms in all generations. Sub-lethal concentrations of chlorantraniliprole showed prolonged larval and adult durations. The parameters related to the fitness cost in F₀ and F₁ generations showed non-significant differences. In contrast, the F₂ generation showed lower fecundity at lethal (71 eggs/female) and sub-lethal (94 eggs/female) doses of chlorantraniliprole compared to the control (127.5-129.3 eggs/female). Age-stage specific survival rate (S_xj), life expectancy (E_xj) and reproductive rate (V_xj) significantly differed among insecticide-treated groups in all generations compared to the control. A comparison of treated and untreated insects over generations indicated substantial differences in demographic parameters such as net reproduction rate (R₀), intrinsic rate of increase (r), and mean generation time (T). Several biological and demographic parameters were shown to be negatively impacted by chlorantraniliprole. We conclude that chlorantraniliprole may be utilized to manage fall armyworms with lesser risks.

Pesticide impacts on avian species with special reference to farmland birds: a review

For decades, we have observed a major biodiversity crisis impacting all taxa. Avian species have been particularly well monitored over the long term, documenting their declines. In particular, farmland birds are decreasing worldwide, but the contribution of pesticides to their decline remains controversial. Most studies addressing the effects of agrochemicals are limited to their assessment under controlled laboratory conditions, the determination of lethal dose 50 (LD₅₀) values and testing in a few species, most belonging to Galliformes. They often ignore the high interspecies variability in sensitivity, delayed sublethal effects on the physiology, behaviour and life-history traits of individuals and their consequences at the population and community levels. Most importantly, they have entirely neglected to test for the multiple exposure pathways to which individuals are subjected in the field (cocktail effects). The present review aims to provide a comprehensive overview for ecologists, evolutionary ecologists and conservationists. We aimed to compile the literature on the effects of pesticides on bird physiology, behaviour and life-history traits, collecting evidence from model and wild species and from field and lab experiments to highlight the gaps that remain to be filled. We show how subtle nonlethal exposure might be pernicious, with major consequences for bird populations and communities. We finally propose several prospective guidelines for future studies that may be considered to meet urgent needs.

Impairments in learning and memory performances associated with nicotinic receptor expression in the honeybee Apis mellifera after exposure to a sublethal dose of sulfoxaflor

Sulfoxaflor is a new insecticide which acts on the nicotinic acetylcholine receptor (nAChRs) in a similar way to neonicotinoids. However, sufloxaflor (SFX) is thought to act in a different manner and is thus proposed as an alternative in crop protection. The goal of this study is to evaluate the toxicity of SFX and its sublethal effect on the honeybee Apis mellifera after acute exposure. In toxicological assay studies, the LD₅₀ value and sublethal dose (corresponding to the NOEL: no observed effect level) were 96 and 15 ng/bee, respectively. Using the proboscis extension response paradigm, we found that an SFX dose of 15 ng/bee significantly impairs learning and memory retrieval when applied 12 h before conditioning or 24 h after olfactory conditioning. SFX had no effect on honeybee olfactory performance when exposure happened after the conditioning. Relative quantitative PCR experiments performed on the six nicotinic acetylcholine receptor subunits demonstrated that they are differently expressed in the honeybee brain after SFX exposure, whether before or after conditioning. We found that intoxicated bees with learning defects showed a strong expression of the Amelβ1 subunit. They displayed overexpression of Amelα9 and Amelβ2, and down-regulation of Amelα1, Amelα3 and Amelα7 subunits. These results demonstrated for the first time that a sublethal dose of SFX could affect honeybee learning and memory performance and modulate the expression of specific nAChR subunits in the brain.

Pesticide Research and Development: General Discussion and Spinosad Case

On average, it has taken approximately 10 years and $250 million to discover and develop one pesticide out of approximately 100 000 compounds. A successful pesticide researcher nowadays needs to be knowledgeable and skillful in multiple disciplines. As a result of the high costs and unique requirements, only a handful of companies in the world can afford to continue pesticide research and development (R/D) in the $70 billion pesticide market. Pesticide R/D is a high-risk yet high-reward business. In this perspective, pesticide R/D is briefly discussed and a case study is used to illustrate how spinosad was discovered and became a successful product, despite the many challenges facing pesticide R/D.

Molecular Physicochemical Properties of Selected Pesticides as Predictive Factors for Oxidative Stress and Apoptosis-Dependent Cell Death in Caco-2 and HepG2 Cells

In this work, three pesticides of different physicochemical properties: glyphosate (GLY, herbicide), imidacloprid (IMD, insecticide), and imazalil (IMZ, fungicide), were selected to assess their cytotoxicity against Caco-2 and HepG2 cells. Cell viability was assessed by the Alamar Blue assay, after 24 and 48 h exposure to different concentrations, and IC50 values were calculated. The mechanisms underlying toxicity, namely cellular reactive oxygen species (ROS), glutathione (GSH) content, lipid peroxidation, loss of mitochondrial membrane potential (MMP), and apoptosis/necrosis induction were assessed by flow cytometry. Cytotoxic profiles were further correlated with the molecular physicochemical parameters of pesticides, namely: water solubility, partition coefficient in an n-octanol/water (Log Pow) system, topological polar surface area (TPSA), the number of hydrogen-bonds (donor/acceptor), and rotatable bonds. In vitro outputs resulted in the following toxicity level: IMZ (Caco-2: IC50 = 253.5 ± 3.37 μM, and HepG2: IC50 = 94 ± 12 μM) > IMD (Caco-2: IC50 > 1 mM and HepG2: IC50 = 624 ± 24 μM) > GLY (IC50 >>1 mM, both cell lines), after 24 h treatment, being toxicity time-dependent (lower IC50 values at 48 h). Toxicity is explained by oxidative stress, as IMZ induced a higher intracellular ROS increase and lipid peroxidation, followed by IMD, while GLY did not change these markers. However, the three pesticides induced loss of MMP in HepG2 cells while in Caco-2 cells only IMZ produced significant MMP loss. Increased ROS and loss of MMP promoted apoptosis in Caco-2 cells subjected to IMZ, and in HepG2 cells exposed to IMD and IMZ, as assessed by Annexin-V/PI. The toxicity profile of pesticides is directly correlated with their Log Pow, as affinity for the lipophilic environment favours interaction with cell membranes governs, and is inversely correlated with their TPSA; however, membrane permeation is favoured by lower TPSA. IMZ presents the best molecular properties for membrane interaction and cell permeation, i.e., higher Log Pow, lower TPSA and lower hydrogen-bond (H-bond) donor/acceptor correlating with its higher toxicity. In conclusion, molecular physicochemical factors such as Log Pow, TPSA, and H-bond are likely to be directly correlated with pesticide-induced toxicity, thus they are key factors to potentially predict the toxicity of other compounds.

In Vitro Assessment of Pesticides Toxicity and Data Correlation with Pesticides Physicochemical Properties for Prediction of Toxicity in Gastrointestinal and Skin Contact Exposure

In this work, three pesticides of different physicochemical properties, namely, glyphosate (herbicide), imidacloprid (insecticide) and imazalil (fungicide), were selected to assess their cytotoxicity against distinct cell models (Caco-2, HepG2, A431, HaCaT, SK-MEL-5 and RAW 264.7 cells) to mimic gastrointestinal and skin exposure with potential systemic effect. Cells were subjected to different concentrations of selected pesticides for 24 h or 48 h. Cell viability was assessed by Alamar Blue assay, morphological changes by bright-field microscopy and the IC50 values were calculated. Cytotoxic profiles were analysed using the physico-chemical parameters of the pesticides, namely: molecular weight, water solubility, the partition coefficient in the n-octanol/water (Log Pow) system, the topological polar surface area (TPSA), and number of hydrogen-bonds (donor/acceptor) and rotatable bonds. Results showed that glyphosate did not reduce cell viability (up to 1 mM), imidacloprid induced moderate toxicity (IC50 > 1 mM for Caco-2 cells while IC50 = 305.9 ± 22.4 μM for RAW 264.7 cells) and imazalil was highly cytotoxic (IC50 > 253.5 ± 3.37 for Caco-2 cells while IC50 = 31.3 ± 2.7 μM for RAW 264.7 cells) after 24 h exposure. Toxicity was time-dependent as IC50 values at 48 h exposure were lower, and decrease in cell viability was accompanied by changes in cell morphology. Pesticides toxicity was found to be directly proportional with their Log Pow, indicating that the affinity to a lipophilic environment such as the cell membranes governs their toxicity. Toxicity is inverse to pesticides TPSA, but lower TPSA favours membrane permeation. The lower toxicity against Caco-2 cells was attributed to the physiology and metabolism of cell barriers equipped with various ABC transporters. In conclusion, physicochemical factors such as Log Pow, TPSA and H-bond are likely to be directly correlated with pesticide-induced toxicity, thus being key factors to potentially predict the toxicity of other compounds.

Discovery of a novel nucleoside immune signaling molecule 2'-deoxyguanosine in microbes and plants

INTRODUCTION

Beneficial microorganisms play essential roles in plant growth and induced systemic resistance (ISR) by releasing signaling molecules. Our previous study obtained the crude extract from beneficial endophyte Paecilomyces variotii, termed ZNC (ZhiNengCong), which significantly enhanced plant resistance to pathogen even at 100 ng/ml. However, the immunoreactive components of ZNC remain unclear. Here, we further identified one of the immunoreactive components of ZNC is a nucleoside 2'-deoxyguanosine (2-dG).

OBJECTIVES

This paper intends to reveal the molecular mechanism of microbial-derived 2'-deoxyguanosine (2-dG) in activating plant immunity, and the role of plant-derived 2-dG in plant immunity.

METHODS

The components of ZNC were separated using a high-performance liquid chromatography (HPLC), and 2-dG is identified using a HPLC-mass spectrometry system (LC-MS). Transcriptome analysis and genetic experiments were used to reveal the immune signaling pathway dependent on 2-dG activation of plant immunity.

RESULTS

This study identified 2'-deoxyguanosine (2-dG) as one of the immunoreactive components from ZNC. And 2-dG significantly enhanced plant pathogen resistance even at 10 ng/ml (37.42 nM). Furthermore, 2-dG-induced resistance depends on NPR1, pattern-recognition receptors/coreceptors, ATP receptor P2K1 (DORN1), ethylene signaling but not salicylic acid accumulation. In addition, we identified Arabidopsis VENOSA4 (VEN4) was involved in 2-dG biosynthesis and could convert dGTP to 2-dG, and vne4 mutant plants were more susceptible to pathogens.

CONCLUSION

In summary, microbial-derived 2-dG may act as a novel immune signaling molecule involved in plant-microorganism interactions, and VEN4 is 2-dG biosynthesis gene and plays a key role in plant immunity.

Methyl Eugenol Binds Recombinant Gamma-Aminobutyric Acid Receptor-Associated Protein from the Western Flower Thrips Frankliniella occidentalis

The western flower thrips (Frankliniella occidentalis) is a major pest insect in agriculture. However, few insecticides are effective for their control. The recombinant gamma-aminobutyric acid receptor-associated protein (rGABARAP) was examined as a potential target of the monoterpenoids responsible for their insecticidal activities. The insecticidal activity of anethole, linalool, and methyl eugenol (ME) was evaluated in the laboratory. The half-maximum lethal concentration (LC₅₀) of ME against second-instar nymphs of F. occidentalis was 5.5 mg/L using membrane and leaf immersion methods, while that of spinosyn A was 1.0 mg/L. The dissociation constants of ME binding to rGABARAP were 1.30 and 4.22 μmol/L, respectively, according to microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) measurements. A molecular docking study showed interactions between ME and Tyr174 via π-π stacking. The MST and ITC experiments showed loss of specific binding between ME and the rGABARAP^Y174A mutant. Therefore, Tyr174 is a key amino acid residue of rGABARAP involving ME binding. The results revealed GABARAP as a potential target for the development of monoterpenoid insecticides.

Methoxyacrylate Fungicide Candidate CL-15C Also Functions as a Plant Elicitor in Arabidopsis thaliana and Oryza sativa L

Unlike traditional fungicides targeting fungi, plant elicitors usually lack direct fungicidal activity but improve the plant immune system to resist fungi infection, which has gained increasing attention for better fungi resistance management and environment protection. (E)-methyl-2-(2-((((Z)-(amino-(3,4-dichloroisothiazol-5-yl)methylene)amino)oxy)methyl)phenyl)-2-(methoxyimino)acetate (CL-15C) was found to be a fungicide candidate with a broad spectrum. Here, we studied its immune-inducing ability and mechanism to strengthen the resistance of Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) and Oryza sativa L. against Magnaporthe oryzae. CL-15C promoted a 2.20- and 1.47-fold increase in phenylalanine ammonia-lyase (PAL) activity in A. thaliana and O. sativa, respectively. It also facilitated a 1.89- and 1.32-fold increase in accumulation of salicylic acid (SA) in A. thaliana and O. sativa, respectively. Differential genes were clustered in the SA signaling pathway at 24 h after a CL-15C treatment in A. thaliana. Because PAL is a rate-limiting enzyme in the phenylalanine metabolic pathway, after a CL-15C treatment, a pal1(PAL 1) mutant was more susceptible to Pst DC3000 when compared with the wild type. Bacterial counts in leaves after a CL-15C treatment showed a 1.11-fold reduction in the pal1 mutant and a 1.54-fold reduction in the wild type. The effect of CL-15C on the PAL enzyme activity and SA content was attenuated in the pal1 mutant. Present experimental data implied that the immune-inducing activity of CL-15C was dependent on PAL gene-mediated synthesis of SA.

Inhibition of neurite outgrowth and enhanced effects compared to baseline toxicity in SH-SY5Y cells

Early life exposure to environmental chemicals can cause developmental neurotoxicity (DNT). The impairment of key neurodevelopmental processes such as neurite outgrowth inhibition can be used as endpoints for screening of DNT effects. We quantified neurite-specific effects using the ratio of effect concentrations for cytotoxicity and neurite outgrowth inhibition (SR_cytotoxicity). Baseline cytotoxicity, the minimal toxicity of any chemical, was used to quantify enhanced cytotoxicity (toxic ratio, TR) and neuronal-specific toxicity (SR_baseline) by comparing baseline cytotoxicity with the effects on cell viability and neurite outgrowth, respectively. The effects on cell viability and neurite length were measured based on image analysis in human neuroblastoma SH-SY5Y cells. Baseline cytotoxicity was predicted from hydrophobicity descriptors using a previously published model for SH-SY5Y cells. Enhanced cytotoxicity and neuronal-specific toxicity were more often observed for hydrophilic chemicals, which indicates that they are more likely to act through specific modes of action (MOA) on cell viability and neurite outgrowth. Hydrophobic chemicals showed a tendency to act through baseline toxicity without showing specific or enhanced toxicity, but were highly potent considering their low effect concentrations for both cytotoxicity and neurite outgrowth inhibition. The endpoint-specific controls (narciclasine, colchicine, cycloheximide, and rotenone), two carbamates (3-hydroxycarbofuran and carbaryl), and two redox cyclers (diquat and paraquat) showed distinct neurite-specific effects (SR_cytotoxicity > 4). By comparing neurite-specific effects with enhanced cytotoxicity, one can explain whether the observed effects involve specific inhibition of neurite outgrowth, other specific MOAs, or merely baseline toxicity arising from hydrophobicity.

Are Pesticides Used to Control Thrips Harmonious with Soil-Dwelling Predatory Mite Cosmolaelaps sabelis (Mesostigmata: Laelapidae)?

Edaphic predatory mites could be introduced in pest management programs of pests that live, or spend part of their life cycle, in the soil. Some mesostigmatic mites have been widely used for the management of different species of thrips (Thysanoptera), especially in protected cultivation. The edaphic predator Cosmolaelaps sabelis (Mesostigmata: Laelapidae) was a model species in this study, being exposed to the most applied insecticides for the control of thrips in Brazil. After lethal, sublethal and transgenerational effects were evaluated. The pesticides acephate, acetamiprid + etofenprox, azadirachtin, spinetoram, formetanate hydrochloride, and imidacloprid were classified according to the IOBC/WPRS (International Organization for Biological Control-West Paleartic Regional Section) recommendation, considering the acute toxicity and the effects on adult females' reproduction, in the maternal and first generation. The pesticides acetamiprid + etofenprox and azadirachtin were classified as slightly harmful (Class 2), while spinetoram was classified as moderately harmful (Class 3). Acephate and formetanate hydrochloride were classified as harmful (Class 4). Only imidacloprid didn't cause negative effects on the females. Regarding effects on the first generation, acetamiprid + etofenprox, azadirachtin, and spinetoram caused reduction in the oviposition rates. Therefore, we suggest that complimentary bioassays should be done under semi-field and field conditions using the pesticides that were considered harmful in this study, to assess their effects on this predator in other environments prior to recommending not to use them in integrated programs to manage soil-based pests using chemical and biological tools.

Geographical Distribution and Pattern of Pesticides in Danish Drinking Water 2002-2018: Reducing Data Complexity

Pesticides are a large and heterogenous group of chemicals with a complex geographic distribution in the environment. The purpose of this study was to explore the geographic distribution of pesticides in Danish drinking water and identify potential patterns in the grouping of pesticides. Our data included 899,169 analyses of 167 pesticides and metabolites, of which 55 were identified above the detection limit. Pesticide patterns were defined by (1) pesticide groups based on chemical structure and pesticide-metabolite relations and (2) an exploratory factor analysis identifying underlying patterns of related pesticides within waterworks. The geographic distribution was evaluated by mapping the pesticide categories for groups and factor components, namely those detected, quantified, above quality standards, and not analysed. We identified five and seven factor components for the periods 2002-2011 and 2012-2018, respectively. In total, 16 pesticide groups were identified, of which six were representative in space and time with regards to the number of waterworks and analyses, namely benzothiazinone, benzonitriles, organophosphates, phenoxy herbicides, triazines, and triazinones. Pesticide mapping identified areas where multiple pesticides were detected, indicating areas with a higher pesticide burden. The results contribute to a better understanding of the pesticide pattern in Danish drinking water and may contribute to exposure assessments for future epidemiological studies.

Impact of Cymbopogon flexuosus (Poaceae) essential oil and primary components on the eclosion and larval development of Aedes aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L^-1 and larvae with 3 or 6 mg L^-1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L^-1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L^-1: 6 ± 0.0 mm; 6 mg L^-1: 6 ± 0.7 mm) and head width (3 mg L^-1: 0.8 ± 0 mm; 6 mg L^-1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

Use of the Species Sensitivity Distribution Approach to Derive Ecological Threshold of Toxicological Concern (eco-TTC) for Pesticides

The species sensitivity distribution (SSD) calculates the hazardous concentration at which 5% of species (HC5) will be potentially affected. For many compounds, HC5 values are unavailable impeding the derivation of SSD curves. Through a detailed bibliographic survey, we selected HC5 values (from acute toxicity tests) for freshwater aquatic species and 129 pesticides. The statistical distribution and variability of the HC5 values within the chemical classes were evaluated. Insecticides are the most toxic compounds in the aquatic communities (HC5 = 1.4 × 10-3 µmol L-1), followed by herbicides (HC5 = 3.3 × 10-2 µmol L-1) and fungicides (HC5 = 7.8 µmol L-1). Subsequently, the specificity of the mode of action (MoA) of pesticides on freshwater aquatic communities was investigated by calculating the ratio between the estimated baseline toxicity for aquatic communities and the HC5 experimental values gathered from the literature. Moreover, we proposed and validated a scheme to derive the ecological thresholds of toxicological concern (eco-TTC) of pesticides for which data on their effects on aquatic communities are not available. We proposed eco-TTCs for different classes of insecticides, herbicides, and fungicides with a specific MoA, and three eco-TTCs for those chemicals with unavailable MoA. We consider the proposed approach and eco-TTC values useful for risk management purposes.

Regulation of GSTu1-mediated insecticide resistance in Plutella xylostella by miRNA and lncRNA

The evolution of resistance to insecticides is well known to be closely associated with the overexpression of detoxifying enzymes. Although the role of glutathione S-transferase (GST) genes in insecticide resistance has been widely reported, the underlying regulatory mechanisms are poorly understood. Here, one GST gene (GSTu1) and its antisense transcript (lnc-GSTu1-AS) were identified and cloned, and both of them were upregulated in several chlorantraniliprole-resistant Plutella xylostella populations. GSTu1 was confirmed to be involved in chlorantraniliprole resistance by direct degradation of this insecticide. Furthermore, we demonstrated that lnc-GSTu1-AS interacted with GSTu1 by forming an RNA duplex, which masked the binding site of miR-8525-5p at the GSTu1-3′UTR. In summary, we revealed that lnc-GSTu1-AS maintained the mRNA stability of GSTu1 by preventing its degradation that could have been induced by miR-8525-5p and thus increased the resistance of P. xylostella to chlorantraniliprole. Our findings reveal a new noncoding RNA-mediated pathway that regulates the expression of detoxifying enzymes in insecticide-resistant insects and offer opportunities for the further understanding of the mechanisms of insecticide and drug resistance.

The development of insecticide resistance in insect pests is a worldwide concern and a major problem in agriculture. Understanding the genetics of insecticide resistance is critical for effective crop protection. Plutella. xylostella (L.), a major pest of cruciferous crops, has developed resistance to almost all kinds of insecticide, and has become one of the most resistant pests in the world. Overexpression of detoxification enzymes is closely associated with insecticide resistance, but researches on their regulatory mechanism are still very limited. Here, GSTu1 was identified to be upregulated in several chlorantraniliprole-resistant P. xylostella populations and was confirmed to be involved in chlorantraniliprole resistance by direct degradation of this insecticide. Further, lnc-GSTu1-AS transcribed from the opposite DNA strand to GSTu1 was identified to be able to enhance the mRNA stability of GSTu1 by blocking miRNA activity, and thus increased the resistance of P. xylostella to chlorantraniliprole. The results provide further insights into the mechanisms underlying metabolic resistance.

Mode of Action of Neonicotinoid Insecticides Imidacloprid and Thiacloprid to the Cockroach Pameα7 Nicotinic Acetylcholine Receptor

The functional expression of the cockroach Pameα7 nicotinic acetylcholine receptor subunit has been previously studied, and was found to be able to form a homomeric receptor when expressed in Xenopus laevis oocytes. In this study, we found that the neonicotinoid insecticide imidacloprid is unable to activate the cockroach Pameα7 receptor, although thiacloprid induces low inward currents, suggesting that it is a partial agonist. In addition, the co-application or 5 min pretreatment with 10 µM imidacloprid increased nicotine current amplitudes, while the co-application or 5 min pretreatment with 10 µM thiacloprid decreased nicotine-evoked current amplitudes by 54% and 28%, respectively. This suggesting that these two representatives of neonicotinoid insecticides bind differently to the cockroach Pameα7 receptor. Interestingly, the docking models demonstrate that the orientation and interactions of the two insecticides in the cockroach Pameα7 nAChR binding pocket are very similar. Electrophysiological results have provided evidence to suggest that imidacloprid and thiacloprid could act as modulators of the cockroach Pameα7 receptors.

Climate warming promotes pesticide resistance through expanding overwintering range of a global pest

Climate change has the potential to change the distribution of pests globally and their resistance to pesticides, thereby threatening global food security in the 21st century. However, predicting where these changes occur and how they will influence current pest control efforts is a challenge. Using experimentally parameterised and field-tested models, we show that climate change over the past 50 years increased the overwintering range of a global agricultural insect pest, the diamondback moth (Plutella xylostella), by ~2.4 million km² worldwide. Our analysis of global data sets revealed that pesticide resistance levels are linked to the species' overwintering range: mean pesticide resistance was 158 times higher in overwintering sites compared to sites with only seasonal occurrence. By facilitating local persistence all year round, climate change can promote and expand pesticide resistance of this destructive species globally. These ecological and evolutionary changes would severely impede effectiveness of current pest control efforts and potentially cause large economic losses.

Neurodevelopmental impact of the offspring by thyroid hormone system-disrupting environmental chemicals during pregnancy

Everyday use chemicals have been demonstrated to be endocrine disruptors. Since normal thyroid function during pregnancy is transcendental for the neurodevelopment of the offspring, knowledge of endocrine disrupting chemicals (EDC) is of main importance. The aim of our study is to recognize and describe EDC actions in pregnant women and focus on neurodevelopmental processes that can lead to neurotransmitter imbalance and cognitive impairment, and the possible clinical outcomes in the newborn and child. We searched PubMed databases for animal studies and clinical trials evaluating chemicals recognized as thyroid disruptors -perchlorate, phthalates, bisphenol A-, as well as chemicals with potential thyroid disruption activity -parabens, pesticides and persistent organic pollutants, on thyroid hormones (THs) levels and their bioavailability during pregnancy, and the outcome in newborns, infants and children. We also exhibit evidence from worldwide cohort studies to this regard. The publications reviewed show: 1) known endocrine disruptors have an association with hormonal thyroid levels, where an effect of increase or decrease in TH concentrations has been reported depending on the chemical exposed 2) associations between TH, EDCs and neurocognitive disorders have been addressed, such as ADHD, though no conclusive impact on potential related disorders as autism has been established, 3) perchlorate has demonstrated effects on thyroid levels on iodine uptake. In conclusion, detrimental risks and long-term consequences after in-utero exposure to EDCs are being reported in several cohort studies and further research must be conducted to establish a well-known cause-effect association.

Toxicological Comparison of Mancozeb and Zoxamide Fungicides at Environmentally Relevant Concentrations by an In Vitro Approach

Mancozeb (MZ) and zoxamide (ZOX) are fungicides commonly used in pest control programs to protect vineyards. Their toxic and genotoxic potential were investigated in vitro on HepG2 and A549 cell lines at environmentally relevant concentrations. Cytotoxicity, apoptosis, necrosis and intracellular reactive oxygen species (ROS), comet assay and a micronucleus test with CREST immunofluorescence were used. The expression of a panel of genes involved in apoptosis/necrosis (BAX/BCL2), oxidative stress (NRF2), drug metabolism (CYP1A1) and DNA repair (ERCC1/OGG1) was evaluated by real-time PCR. Both fungicides were cytotoxic at the highest tested concentrations (295.7 and 463.4 µM, respectively); MZ induced necrosis, ZOX did not increase apoptosis but modulated BAX and BCL2 expression, suggesting a different mechanism. Both compounds did not increase ROS, but the induction of CYP1A1 and NRF2 expression supported a pro-oxidant mechanism. The comet assay evidenced MZ genotoxicity, whereas no DNA damage due to ZOX treatment was observed. Positive micronuclei were increased in both cell lines treated with MZ and ZOX, supporting their aneugenic potential. ERCC1 and OGG1 were differently modulated, indicating the efficient activation of the nucleotide excision repair system by both fungicides and the inhibition of the base excision repair system by MZ. Overall, MZ confirmed its toxicity and new ZOX-relevant effects were highlighted.

Structural effects on the bromination rate and selectivity of alkylbenzenes and alkoxybenzenes in aqueous solution

Aqueous free bromine species (e.g., HOBr, BrCl, Br2, BrOCl, Br2O, and H2OBr+) can react with activated aromatic compounds via electrophilic aromatic substitution to generate products with industrial applications, environmental consequences, and potentially adverse biological effects. The relative contributions of these brominating agents to overall bromination rates can be calculated via nonlinear regression analyses of kinetic data collected under a variety of solution conditions, including variations in parameters (e.g., [Cl-], [Br-], and pH) known to influence free bromine speciation. Herein, kinetic experiments conducted in batch reactors were employed to evaluate the contributions of steric and electronic effects on bromination of monosubstituted alkylbenzenes (ethyl, isopropyl, tert-butyl) and alkoxybenzenes (ethoxy, isopropoxy, tert-butoxy) and to elucidate the inherent reactivities of aqueous brominating agents towards these aromatic compounds. For bromination at the para position of alkylbenzenes, overall reactivity increased from tert-butyl < ethyl ≈ isopropyl. For bromination at the para position of alkoxybenzenes, reactivity increased from tert-butoxy < ethoxy < isopropoxy. In going from ethyl to tert-butyl and ethoxy to isopropoxy, unfavorable steric effects attenuated the favorable electronic effects imparted by the substituents. When comparing unsubstituted benzene, alkyl-, and alkoxybenzenes, the structure of the substituent has a significant effect on bromination rates, nucleophile regioselectivity, and electrophile chemoselectivity. Hirshfeld charges were useful predictors of reactivity and regioselectivity. The experimental results were also modeled using Taft equations. Collectively, these findings indicate that steric effects, electronic effects, and brominating agents other than HOBr can influence aromatic compound bromination in solutions of free bromine.

The Foraging Gene, a New Environmental Adaptation Player Involved in Xenobiotic Detoxification

Foraging is vital for animals, especially for food. In Drosophila melanogaster, this behavior is controlled by the foraging gene (for) which encodes a cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG). In wild populations of Drosophila, rover individuals that exhibit long foraging trails and sitter individuals that exhibit short ones coexist and are characterized by high and low levels of PKG activity, respectively. We, therefore, postulated that rover flies are more exposed to environmental stresses, including xenobiotics contamination, than sitter flies. We then tested whether these flies differed in their ability to cope with xenobiotics by exposing them to insecticides from different chemical families. We performed toxicological tests and measured the activity and expression levels of different classes of detoxification enzymes. We have shown that a link exists between the for gene and certain cytochrome P450-dependent activities and that the expression of the insecticide-metabolizing cytochrome P450 Cyp6a2 is controlled by the for gene. An unsuspected regulatory pathway of P450s expression involving the for gene in Drosophila is revealed and we demonstrate its involvement in adaptation to chemicals in the environment. This work can serve as a basis for reconsidering adaptation to xenobiotics in light of the behavior of species, including humans.

Novel alternative splicing of GABA receptor RDL exon 9 from Laodelphax striatellus modulates agonist potency

The resistance to dieldrin gene (RDL) encodes the primary subunit of the insect ionotropic γ-aminobutyric acid (GABA) receptor (GABAR), which is the target of phenylpyrazole and isoxazoline insecticides. The splice variants in exons 3 and 6 of RDL, which have been widely explored in many insects, modulate the agonist potency of the homomeric RDL GABAR and potentially play an important role in the development of insects. In the present study, four splice variants of exon 9 were identified in RDL of the small brown planthopper, Laodelphax striatellus (LsRDL), resulting in LsRDL-9a, LsRDL-9a', LsRDL-9b, and LsRDL-9c. LsRDL-9a has one more amino acid (E, glutamic acid) compared with LsRDL-9a', and LsRDL-9b lacked two amino acids and had seven different amino acids compared with LsRDL-9c. Two-electrode voltage-clamp recording on LsRDLs expressed in Xenopus oocytes showed that alternative splicing of exon 9 has significant impact on LsRDL sensitivity to the agonists GABA and β-alanine, whereas no significant difference was observed in the potencies of the non-competitive antagonists (NCAs) ethiprole and fluralaner on the splice variants. Our results suggest that alternative splicing of RDL exon 9 broadens functional capabilities of the GABAR in L. striatellus by influencing the action of GABA.

Maternal Exposure to Pesticides and Risk of Autism Spectrum Disorders in Offspring: A Meta-analysis

This meta-analysis was conducted to estimate the overall association between maternal exposure to pesticides and risk of ASD in offspring. PubMed, EMBASE, Web of Science, and the PsycINFO were searched until December 30, 2020 to include eligible studies. Eight studies with 50,426 participants, 5810 of whom had ASD, were involved in the study. Overall, the summary OR (95% confidence interval) of ASDs in offspring for maternal exposure to pesticide estimated by residential proximity measures and self-report was 1.88 (1.10-3.20). However, maternal exposure to pesticide measured by biomarkers was not associated with an increased risk of ASDs (pooled OR 1.13; 95% CI 0.83-1.54). Further well-designed studies are needed to confirm our findings.

Approaches to Test the Neurotoxicity of Environmental Contaminants in the Zebrafish Model: From Behavior to Molecular Mechanisms

The occurrence of neuroactive chemicals in the aquatic environment is on the rise and poses a potential threat to aquatic biota of currently unpredictable outcome. In particular, subtle changes caused by these chemicals to an organism's sensation or behavior are difficult to tackle with current test systems that focus on rodents or with in vitro test systems that omit whole-animal responses. In recent years, the zebrafish (Danio rerio) has become a popular model organism for toxicological studies and testing strategies, such as the standardized use of zebrafish early life stages in the Organisation for Economic Co-operation and Development's guideline 236. In terms of neurotoxicity, the zebrafish provides a powerful model to investigate changes to the nervous system from several different angles, offering the ability to tackle the mechanisms of action of chemicals in detail. The mechanistic understanding gained through the analysis of this model species provides a good basic knowledge of how neuroactive chemicals might interact with a teleost nervous system. Such information can help infer potential effects occurring to other species exposed to neuroactive chemicals in their aquatic environment and predicting potential risks of a chemical for the aquatic ecosystem. In the present article, we highlight approaches ranging from behavioral to structural, functional, and molecular analysis of the larval zebrafish nervous system, providing a holistic view of potential neurotoxic outcomes. Environ Toxicol Chem 2021;40:989-1006. © 2020 SETAC.

A Cationic Surfactant-Decorated Liquid Crystal-Based Aptasensor for Label-Free Detection of Malathion Pesticides in Environmental Samples

We report a liquid crystal (LC)-based aptasensor for the detection of malathion using a cationic surfactant-decorated LC interface. In this method, LCs displayed dark optical images when in contact with aqueous cetyltrimethylammonium bromide (CTAB) solution due to the formation of a self-assembled CTAB monolayer at the aqueous/LC interface, which induced the homeotropic orientation of LCs. With the addition of malathion aptamer, the homeotropic orientation of LCs changed to a planar one due to the interactions between CTAB and the aptamer, resulting in a bright optical image. In the presence of malathion, the formation of aptamer-malathion complexes caused a conformational change of the aptamers, thereby weakening the interactions between CTAB and the aptamers. Therefore, CTAB is free to induce a homeotropic ordering of the LCs, which corresponds to a dark optical image. The developed sensor exhibited high specificity for malathion determination and a low detection limit of 0.465 nM was achieved. Moreover, the proposed biosensor was successfully applied to detect malathion in tap water, river water, and apple samples. The proposed LC-based aptasensor is a simple, rapid, and convenient platform for label-free monitoring of malathion in environmental samples.