Organophosphorus Compounds at 80: Some Old and New Issues

Serum albumin and liver dysfunction mediate the associations between organophosphorus pesticide exposure and hypertension among US adults

BACKGROUND

Human health is commonly threatened by organophosphorus pesticides (OPPs) due to their widespread use and biological characteristics. However, the combined effect of mixtures of OPPs metabolites on the risk of hypertension and potential mechanism remain limited.

OBJECTIVES

To comprehensively investigate the effects between OPPs exposure on hypertension risk and explore and underlying mechanism among US general population.

METHODS

This cross-sectional study collected US adults who had available data on urine OPPs metabolites (dialkyl phosphate compounds, DAPs) from the National Health and Nutrition Examination Survey (NHANES) to assess the relationships of DAPs with hypertension risk. Survey-weighted logistic regression, restricted cubic spline (RCS), and mixed exposure analysis models [weighted quantile sum regression (WQS) and Bayesian kernel machine regression (BKMR)] were used to analyze individual, dose-response and combined associations between urinary DAPs metabolites and hypertension risk, respectively. Mediation analysis determined the potential intermediary role of serum albumin and liver function in the above associations.

RESULTS

Compared with the reference group, participants with the highest tertile levels of DEP, DMTP, DETP, and DMDTP experienced increased risk of hypertension by 1.21-fold (95%CI: 1.02-1.36), 1.20-fold (95%CI: 1.02-1.42), 1.19-fold (95%CI: 1.01-1.40), and 1.17-fold (95%CI: 1.03-1.43), respectively. RCS curve also showed positive exposure-response associations of individual DAPs with hypertension risk. WQS and BKMR analysis further confirmed DAP mixtures were significantly associated with increased risk of hypertension, with DEP identified as a major contributor to the combined effect. Mediation analysis indicated that serum albumin and AST/ALT ratios played crucial mediating roles in the relationships between individual and mixed urinary DAPs and the prevalence of hypertension.

CONCLUSION

Our findings provided more comprehensive and novel perspectives into the individual and combined effects of urinary OPPs matabolites on the increased risk of hypertension and the possible driving mechanism, which would be of great significance for environmental control and early prevention of hypertension.

Bioaccumulation of Deltamethrin and Piperonyl butoxide in Labeo rohita fish

Deltamethrin (DLM), in combination with the synergist piperonyl butoxide (PBO), is extensively used in pest control programs due to its potent pesticidal properties and appreciable safety margin. However, various research studies report their adverse effects on non-target organisms. In this study, we investigated the toxicity of DLM, PBO, and a DLM-PBO (3:1) combination on Labeo rohita (L. rohita) fish fingerlings. Fish behavior and mortality rates were recorded at different time intervals up to 96 h for concentrations of 0.003, 0.007, 0.015, 0.031, and 0.062 µg/mL, respectively. Biochemical, hematological, and histopathological studies were carried out. High-performance liquid chromatography (HPLC) was used to detect and quantify residues in fish samples. The LC50 values after 48 h for DLM, PBO, and DLM-PBO exposed fish fingerlings were found to be 0.028, 0.066, and 0.007 µg/mL, respectively. At a concentration of 0.003 µg/mL of DLM, PBO, and DLM-PBO, the treated fish fingerlings exhibited similar behavior to the control group. Hematological parameters, such as red blood cell (RBC) and white blood cell (WBC) counts, were reduced in the treated groups compared to the control. Biochemical parameters showed increased levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), while total serum protein levels decreased in DLM, PBO, and DLM-PBO treated fingerlings. Histopathological examination of liver, gill, and heart tissues revealed lesions with hydropic degeneration in the liver and fusions of gill lamellae in the treated tissues. Fish fingerlings exposed to the DLM-PBO combination appeared highly prone to toxicity compared to those treated with DLM and PBO separately.

N-methyl-d-aspartate receptors: Structure, function, and role in organophosphorus compound poisoning

Acute organophosphorus compound (OP) poisoning induces symptoms of the cholinergic crises with the occurrence of severe epileptic seizures. Seizures are induced by hyperstimulation of the cholinergic system, but are enhanced by hyperactivation of the glutamatergic system. Overstimulation of muscarinic cholinergic receptors by the elevated acetylcholine causes glutamatergic hyperexcitation and an increased influx of Ca2+ into neurons through a type of ionotropic glutamate receptors, N-methyl-d-aspartate (NMDA) receptors (NMDAR). These excitotoxic signaling processes generate reactive oxygen species, oxidative stress, and activation of the neuroinflammatory response, which can lead to recurrent epileptic seizures, neuronal cell death, and long-term neurological damage. In this review, we illustrate the NMDAR structure, complexity of subunit composition, and the various receptor properties that change accordingly. Although NMDARs are in normal physiological conditions important for controlling synaptic plasticity and mediating learning and memory functions, we elaborate the detrimental role NMDARs play in neurotoxicity of OPs and focus on the central role NMDAR inhibition plays in suppressing neurotoxicity and modulating the inflammatory response. The limited efficacy of current medical therapies for OP poisoning concerning the development of pharmacoresistance and mitigating proinflammatory response highlights the importance of NMDAR inhibitors in preventing neurotoxic processes and points to new avenues for exploring therapeutics for OP poisoning.

Association between organophosphorus pesticides and obesity among American adults

OBJECTIVE

To investigate any connections between urinary organophosphorus pesticide (OPP) metabolites and adiposity measures.

METHODS

In this study, data from the National Health and Nutrition Examination Survey (NHANES) projects from 2003 to 2008, 2011 to 2012, and 2015 to 2018 were analysed. Obesity was defined as a body mass index (BMI) of 30 kg/m² or higher. Abdominal obesity was defined as a waist circumference (WC) over 102 cm for men and 88 cm for women. Four urinary OPP metabolites (dimethyl phosphate [DMP], diethyl phosphate [DEP], dimethyl phosphorothioate [DMTP], and diethyl phosphorothioate [DETP]) and adiposity measures were examined using multiple linear regression and logistic regression analyses. The correlations between a variety of urinary OPP metabolites and the prevalence of obesity were investigated using weighted quantile sum regression and quantile g-computation regression.

RESULTS

In this analysis, a total of 9,505 adults were taken into account. There were 49.81% of male participants, and the average age was 46.00 years old. The median BMI and WC of the subjects were 27.70 kg/m2 and 97.10 cm, respectively. Moreover, 35.60% of the participants were obese, and 54.42% had abdominal obesity. DMP, DMTP, and DETP were discovered to have a negative correlation with WC and BMI in the adjusted models. DMP (OR = 0.93 [95% CI: 0.89-0.98]), DEP (OR = 0.94 [95% CI: 0.90-0.99]), DMTP (OR = 0.91 [95% CI: 0.86-0.95]), and DETP (OR = 0.85 [95% CI: 0.80-0.90]) exhibited negative associations with obesity prevalence. Similar correlations between the prevalence of abdominal obesity and the urine OPP metabolites were discovered. Moreover, the mixture of urinary OPP metabolites showed negative associations with adiposity measures, with DMTP and DETP showing the most significant effects.

CONCLUSION

Together, higher levels of urinary OPP metabolites in the urine were linked to a decline in the prevalence of obesity.

Understanding role of pesticides in development of Parkinson's disease: Insights from Drosophila and rodent models

Parkinson's disease is a neurodegenerative illness linked to ageing, marked by the gradual decline of dopaminergic neurons in the midbrain. The exact aetiology of Parkinson's disease (PD) remains uncertain, with genetic predisposition and environmental variables playing significant roles in the disease's frequency. Epidemiological data indicates a possible connection between pesticide exposure and brain degeneration. Specific pesticides have been associated with important characteristics of Parkinson's disease, such as mitochondrial dysfunction, oxidative stress, and α-synuclein aggregation, which are crucial for the advancement of the disease. Recently, many animal models have been developed for Parkinson's disease study. Although these models do not perfectly replicate the disease's pathology, they provide valuable insights that improve our understanding of the condition and the limitations of current treatment methods. Drosophila, in particular, has been useful in studying Parkinson's disease induced by toxins or genetic factors. The review thoroughly analyses many animal models utilised in Parkinson's research, with an emphasis on issues including pesticides, genetic and epigenetic changes, proteasome failure, oxidative damage, α-synuclein inoculation, and mitochondrial dysfunction. The text highlights the important impact of pesticides on the onset of Parkinson's disease (PD) and stresses the need for more research on genetic and mechanistic alterations linked to the condition.

Bioremediation and bioscavenging for elimination of organophosphorus threats: An approach using enzymatic advancements

Organophosphorus compounds (OP) are highly toxic pesticides and nerve agents widely used in agriculture and chemical warfare. The extensive use of these chemicals has severe environmental implications, such as contamination of soil, water bodies, and food chains, thus endangering ecosystems and biodiversity. Plants absorb pesticide residues, which then enter the food chain and accumulate in the body fat of both humans and animals. Numerous human cases of OP poisoning have been linked to both acute and long-term exposure to these toxic OP compounds. These compounds inhibit the action of the acetylcholinesterase enzyme (AChE) by phosphorylation, which prevents the breakdown of acetylcholine (ACh) neurotransmitter into choline and acetate. Thus, it becomes vital to cleanse the environment from these chemicals utilizing various physical, chemical, and biological methods. Biological methods encompassing bioremediation using immobilized microbes and enzymes have emerged as environment-friendly and cost-effective approaches for pesticide removal. Cell/enzyme immobilized systems offer higher stability, reusability, and ease of product recovery, making them ideal tools for OP bioremediation. Interestingly, enzymatic bioscavengers (stoichiometric, pseudo-catalytic, and catalytic) play a vital role in detoxifying pesticides from the human body. Catalytic bioscavenging enzymes such as Organophosphate Hydrolase, Organophosphorus acid anhydrolase, and Paraoxonase 1 show high degradation efficiency within the animal body as well as in the environment. Moreover, these enzymes can also be employed to decontaminate pesticides from food, ensuring food safety and thus minimizing human exposure. This review aims to provide insights to potential collaborators in research organizations, government bodies, and industries to bring advancements in the field of bioremediation and bioscavenging technologies for the mitigation of OP-induced health hazards.

Poison to Promise: The Resurgence of Organophosphorus Fluoride Chemistry

Organophosphorus(V) fluorides have a long and tumultuous history, with early applications as toxins and nerve agents reflecting their poisonous past. Behind these very real safety considerations, there is also growing potential in a wide range of fields, from chemical biology to drug development. The recent inclusion of organophosphorus(V) fluorides in click chemistry exemplifies the promise these compounds possess and brings these molecules to the brink of a resurgence. In this Perspective, we delve into the history of P(V)-F compounds, discuss the precautions needed to work with them safely, and explore recent advancements in their synthesis and application. We conclude by discussing how this field can continue on a path toward innovation.

Organophosphate toxicity patterns: A new approach for assessing organophosphate neurotoxicity

Organophosphorus compounds or organophosphates (OPs) are widely used as flame retardants, plasticizers, lubricants and pesticides. This contributes to their ubiquitous presence in the environment and to the risk of human exposure. The persistence of OPs and their bioaccumulative characteristics raise serious concerns regarding environmental and human health impacts. To address the need for safer OPs, this study uses a New Approach Method (NAM) to analyze the neurotoxicity pattern of 42 OPs. The NAM consists of a 4-step process that combines computational modeling with in vitro and in vivo experimental studies. Using spherical harmonic-based cluster analysis, the OPs were grouped into four main clusters. Experimental data and quantitative structure-activity relationships (QSARs) analysis were used in conjunction to provide information on the neurotoxicity profile of each group. Results showed that one of the identified clusters had a favorable safety profile, which may help identify safer OPs for industrial applications. In addition, the 3D-computational analysis of each cluster was used to identify meta-molecules with specific 3D features. Toxicity was found to correspond to the level of phosphate surface accessibility. Substances with conformations that minimize phosphate surface accessibility caused less neurotoxic effect. This multi-assay NAM could be used as a guide for the classification of OP toxicity, helping to minimize the health and environmental impacts of OPs, and providing rapid support to the chemical regulators, whilst reducing reliance on animal testing.

The influence of the model pesticides parathion and paraoxon on human cytochrome P450 and associated oxygenases in HepaRG cells

INTRODUCTION

Intentional and unintentional organophosphorus pesticide exposure is a public health concern. Organothiophosphate compounds require metabolic bioactivation by the cytochrome P450 system to their corresponding oxon analogues to act as potent inhibitors of acetylcholinesterase. It is known that interactions between cytochrome P450 and pesticides include the inhibition of major xenobiotic metabolizing cytochrome P450 enzymes and changes on the genetic level.

METHODS

In this in vitro study, the influence of the pesticides parathion and paraoxon on human cytochrome P450 and associated oxygenases was investigated with a metabolically competent cell line (HepaRG cells). First, the viability of the cells after exposure to parathion and paraoxon was evaluated. The inhibitory effect of both pesticides on cytochrome P450 3A4, which is a pivotal enzyme in the metabolism of xenobiotics, was examined by determining the dose-response curve. Changes on the transcription level of 92 oxygenase associated genes, including those for important cytochrome P450 enzymes, were evaluated.

RESULTS

The exposure of HepaRG cells to parathion and paraoxon at concentrations up to 100 µM resulted in a viability of 100 per cent. After exposure for 24 hours, pronounced inhibition of cytochrome P450 3A4 enzyme activity was shown, indicating 50 per cent effective concentrations of 1.2 µM (parathion) and 2.1 µM (paraoxon). The results revealed that cytochrome P450 involved in parathion metabolism were significantly upregulated.

DISCUSSION

Relevant changes of the cytochrome P450 3A4 enzyme activity and significant alteration of genes associated with cytochrome P450 suggest an interference of pesticide exposure with numerous metabolic processes. The major limitations of the work involve the use of a single pesticide and the in vitro model as surrogate to human hepatocytes.

CONCLUSION

The data of this study might be of relevance after survival of acute, life-threatening intoxications with organophosphorus compounds, particularly for the co-administration of drugs, which are metabolized by the affected cytochrome P450.

A comparative study on targeted gene expression in zebrafish and its gill cell line exposed to chlorpyrifos

Chlorpyrifos (CPF) is an organophosphorus-based insecticide, which is known to pose a serious risk to aquatic animals. However, the mechanisms of CPF toxicity in animals still remain unclear. The present investigation aimed to compare the potential effects of CPF in zebrafish (Danio rerio) and its gill cell line (DrG cells). Based on the in vivo study, the LC50 was calculated as 18.03 µg/L and the chronic toxic effect of CPF was studied by exposing the fish to 1/10th (1.8 µg/L) and 1/5th (3.6 µg/L) of the LC50 value. Morphological changes were observed in fish and DrG cells which were exposed to sublethal concentrations of CPF. The results of MTT and NR assays showed significant decline in the survival of cells exposed to CPF at 96 h. The production of reactive oxygen species in DrG cells and expression levels of antioxidant markers, inflammatory response genes (cox2a and cox2b), cyp1a, proapoptotic genes (bax), antiapoptotic gene (bcl2), apoptotic genes (cas3 and p53), and neuroprotective gene (ache) were determined in vivo using zebrafish and in vitro using DrG cells after exposure to CPF. Significant changes were found in the ROS production (DrG cells) and in the expression of inflammatory, proapoptotic, and apoptotic genes. This study showed that DrG cells are potential alternative tools to replace the use of whole fish for toxicological studies.

The α4 Nicotinic Acetylcholine Receptor Is Necessary for the Initiation of Organophosphate-Induced Neuronal Hyperexcitability

Acute intoxication with organophosphorus (OP) cholinesterase inhibitors can produce seizures that rapidly progress to life-threatening status epilepticus. Significant research effort has been focused on investigating the involvement of muscarinic acetylcholine receptors (mAChRs) in OP-induced seizure activity. In contrast, there has been far less attention on nicotinic AChRs (nAChRs) in this context. Here, we address this data gap using a combination of in vitro and in vivo models. Pharmacological antagonism and genetic deletion of α4, but not α7, nAChR subunits prevented or significantly attenuated OP-induced electrical spike activity in acute hippocampal slices and seizure activity in mice, indicating that α4 nAChR activation is necessary for neuronal hyperexcitability triggered by acute OP exposures. These findings not only suggest that therapeutic strategies for inhibiting the α4 nAChR subunit warrant further investigation as prophylactic and immediate treatments for acute OP-induced seizures, but also provide mechanistic insight into the role of the nicotinic cholinergic system in seizure generation.

Recent Advances in the Application of P(III)-Nucleophiles to Create New P-C Bonds through Michaelis-Arbuzov-Type Rearrangement

Organophosphorus compounds have long been considered valuable in both organic synthesis and life science. P(III)-nucleophiles, such as phosphites, phosphonites, and diaryl/alkyl phosphines, are particularly noteworthy as phosphorylation reagents for their ability to form new P-C bonds, producing more stable, ecofriendly, and cost-effective organophosphorus compounds. These nucleophiles follow similar phosphorylation routes as in the functionalization of P-H bonds and P-OH bonds. Activation can occur through photocatalytic, electrocatalytic, or thermo-driven reactions, often in coordination with a Michaelis-Arbuzov-trpe rearrangement process, to produce the desired products. As such, this review offers a thorough overview of the phosphorylated transformation and potential mechanisms of P(III)-nucleophiles, specifically focusing on developments since 2010. Notably, this review may provide researchers with valuable insights into designing and synthesizing functionalized organophosphorus compounds from P(III)-nucleophiles, guiding future advancements in both research and practical applications.

Toxic effects of organophosphate pesticide monocrotophos in aquatic organisms: A review of challenges, regulations and future perspectives

In recent times, usage of pesticide, herbicides and synthetic fertilizers in farming lands has made the environment worse. The pesticide residues and toxic byproducts from agricultural lands were found to contaminate the aquatic ecosystem. The misuse of synthetic pesticide not only affects the environment, but also affects the health status of aquatic organisms. The organophosphate pesticide pollutants are emerging contaminants, which threatens the terrestrial and aquatic ecosystem. Monocrotophos (MCP) is an organophosphate insecticide, utilized on crops including rice, maize, sugarcane, cotton, soybeans, groundnuts and vegetables. MCP is hydrophilic in nature and their solubilizing properties reduce the soil sorption which leads to groundwater contamination. The half-life period of MCP is 17-96 and the half-life period of technical grade MCP is 2500 days if held stable at 38 °C in a container. MCP causes mild to severe confusion, anxiety, hyper-salivation, convulsion and respiratory distress in mammals as well as aquatic animals. The MCP induced toxicity including survival rate, behavioural changes, reproductive toxicity and genotoxicity in different aquatic species have been discussed in this review. Furthermore, the ultimate aim of this review is to highlight the international regulations, future perspectives and challenges involved in using the MCP.

Ketamine Produces Antidepressant Effects by Inhibiting Histone Deacetylases and Upregulating Hippocampal Brain-Derived Neurotrophic Factor Levels in a Diisopropyl Fluorophosphate-Based Rat Model of Gulf War Illness

Approximately one-third of Gulf War veterans suffer from Gulf War Illness (GWI), which encompasses mood disorders and depressive symptoms. Deployment-related exposure to organophosphate compounds has been associated with GWI development. Epigenetic modifications have been reported in GWI veterans. We previously showed that epigenetic histone dysregulations were associated with decreased brain-derived neurotrophic factor (BDNF) expression in a GWI rat model. GWI has no effective therapies. Ketamine (KET) has recently been approved by the Food and Drug Administration for therapy-resistant depression. Interestingly, BDNF upregulation underlies KET's antidepressant effect in GWI-related depression. Here, we investigated whether KET's effect on histone mechanisms signals BDNF upregulations in GWI. Male Sprague-Dawley rats were injected once daily with diisopropyl fluorophosphate (DFP; 0.5 mg/kg, s.c., 5 days). At 6 months following DFP exposure, KET (10 mg/kg, i.p.) was injected, and brains were dissected 24 hours later. Western blotting was used for protein expression, and epigenetic studies used chromatin immunoprecipitation methods. Dil staining was conducted for assessing dendritic spines. Our results indicated that an antidepressant dose of KET inhibited the upregulation of histone deacetylase (HDAC) enzymes in DFP rats. Furthermore, KET restored acetylated histone occupancy at the Bdnf promoter IV and induced BDNF protein expression in DFP rats. Finally, KET treatment also increased the spine density and altered the spine diversity with increased T-type and decreased S-type spines in DFP rats. Given these findings, we propose that KET's actions involve the inhibition of HDAC expression, upregulation of BDNF, and dendritic modifications that together ameliorates the pathologic synaptic plasticity and exerts an antidepressant effect in DFP rats. SIGNIFICANCE STATEMENT: This study offers evidence supporting the involvement of epigenetic histone pathways in the antidepressant effects of ketamine (KET) in a rat model of Gulf War Illness (GWI)-like depression. This effect is achieved through the modulation of histone acetylation at the Bdnf promoter, resulting in elevated brain-derived neurotrophic factor expression and subsequent dendritic remodeling in the hippocampus. These findings underscore the rationale for considering KET as a potential candidate for clinical trials aimed at managing GWI-related depression.

Chronic Epilepsy and Mossy Fiber Sprouting Following Organophosphate-Induced Status Epilepticus in Rats

Organophosphate (OP) compounds are highly toxic and include pesticides and chemical warfare nerve agents. OP exposure inhibits the acetylcholinesterase enzyme, causing cholinergic overstimulation that can evolve into status epilepticus (SE) and produce lethality. Furthermore, OP-induced SE survival is associated with mood and memory dysfunction and spontaneous recurrent seizures (SRS). In male Sprague-Dawley rats, we assessed hippocampal pathology and chronic SRS following SE induced by administration of OP agents paraoxon (2 mg/kg, s.c.), diisopropyl fluorophosphate (4 mg/kg, s.c.), or O-isopropyl methylphosphonofluoridate (GB; sarin) (2 mg/kg, s.c.), immediately followed by atropine and 2-PAM. At 1-hour post-OP-induced SE onset, midazolam was administered to control SE. Approximately 6 months after OP-induced SE, SRS were evaluated using video and electroencephalography monitoring. Histopathology was conducted using hematoxylin and eosin (H&E), while silver sulfide (Timm) staining was used to assess mossy fiber sprouting (MFS). Across all the OP agents, over 60% of rats that survived OP-induced SE developed chronic SRS. H&E staining revealed a significant hippocampal neuronal loss, while Timm staining revealed extensive MFS within the inner molecular region of the dentate gyrus. This study demonstrates that OP-induced SE is associated with hippocampal neuronal loss, extensive MFS, and the development of SRS, all hallmarks of chronic epilepsy. SIGNIFICANCE STATEMENT: Models of organophosphate (OP)-induced SE offer a unique resource to identify molecular mechanisms contributing to neuropathology and the development of chronic OP morbidities. These models could allow the screening of targeted therapeutics for efficacious treatment strategies for OP toxicities.

A Pralidoxime Nanocomplex Formulation Targeting Transferrin Receptors for Reactivation of Brain Acetylcholinesterase After Exposure of Mice to an Anticholinesterase Organophosphate

Introduction

Organophosphates are among the deadliest of known chemicals based on their ability to inactivate acetylcholinesterase in neuromuscular junctions and synapses of the central and peripheral nervous systems. The consequent accumulation of acetylcholine can produce severe acute toxicities and death. Oxime antidotes act by reactivating acetylcholinesterase with the only such reactivator approved for use in the United States being 2-pyridine aldoxime methyl chloride (a.k.a., pralidoxime or 2-PAM). However, this compound does not cross the blood-brain barrier readily and so is limited in its ability to reactivate acetylcholinesterase in the brain.

Methods

We have developed a novel formulation of 2-PAM by encapsulating it within a nanocomplex designed to cross the blood-brain barrier via transferrin receptor-mediated transcytosis. This nanocomplex (termed scL-2PAM) has been subjected to head-to-head comparisons with unencapsulated 2-PAM in mice exposed to paraoxon, an organophosphate with anticholinesterase activity.

Results and Discussion

In mice exposed to a sublethal dose of paraoxon, scL-2PAM reduced the extent and duration of cholinergic symptoms more effectively than did unencapsulated 2-PAM. The scL-2PAM formulation was also more effective than unencapsulated 2-PAM in rescuing mice from death after exposure to otherwise-lethal levels of paraoxon. Improved survival rates in paraoxon-exposed mice were accompanied by a higher degree of reactivation of brain acetylcholinesterase.

Conclusion

Our data indicate that scL-2PAM is superior to the currently used form of 2-PAM in terms of both mitigating paraoxon toxicity in mice and reactivating acetylcholinesterase in their brains.

Screening of Indoor Transformation Products of Organophosphates and Organophosphites with an in Silico Spectral Database

Numerous transformation products are formed indoors, but they are outside the scope of current chemical databases. In this study, an in silico spectral database was established to screen previously unknown indoor transformation products of organophosphorus compounds (OPCs). An R package was developed that incorporated four indoor reactions to predict the transformation products of 712 seed OPCs. By further predicting MS2 fragments, an in silico spectral database was established consisting of 3509 OPCs and 28,812 MS2 fragments. With this database, 40 OPCs were tentatively detected in 23 indoor dust samples. This is the greatest number of OPCs reported to date indoors, among which two novel phosphonates were validated using standards. Twenty-four of the detected OPCs were predicted transformation products in which oxidation from organophosphites plays a major role. To confirm this, the in silico spectral database was expanded to include organophosphites for suspect screening in five types of preproduction plastics. A broad spectrum of 14 organophosphites was detected, with a particularly high abundance in polyvinyl chloride plastics and indoor end-user goods. This demonstrated the significant contribution of organophosphites to indoor organophosphates via oxidation, highlighting the strength of in silico spectral databases for the screening of unknown indoor transformation products.

Association of urinary organophosphate metabolites with adult asthma patients: a cross-sectional population-based study

Human health is adversely affected by exposure to organophosphate (OP) pesticides. This study aims to investigate the correlation between urinary OP metabolites and the prevalence of asthma. In cross-sectional studies, data from the National Health and Nutrition Examination Survey (NHANES) projects conducted between 2003-2008, 2011-2012, and 2015-2018 were analyzed. Multiple logistic regressions and restricted cubic spline (RCS) regressions were utilized to examine the relationship between four urinary OP metabolites, namely dimethyl phosphate (DMP), diethyl phosphate (DEP), dimethyl phosphorothioate (DMTP), and diethyl phosphorothioate (DETP), and the prevalence of asthma. Additionally, quantile g-computation (QG-C) regression was employed to evaluate the association between urinary OP metabolites (both individual and combined exposures) and asthma prevalence. The results showed that a total of 9316 adults, including 1298 participants with asthma, were included in the analysis. The median age of the participants was 47.37 years, and 50.27% were female. In the comprehensive model, the third tertile of DMP and DEP exhibited a positive association with asthma prevalence compared to the first tertile (odds ratio [95% confidence interval]: 1.26 [1.01-1.57], Ptrend = 0.036; and 1.25 [1.07-1.51], Ptrend = 0.008, respectively). Moreover, a linear relationship was observed between DMP, DEP, and asthma prevalence (P for nonlinearity = 0.320 and 0.553, respectively). The QG-C regression revealed a positive association between the mixture of urinary OP metabolites and asthma prevalence (OR = 1.04 [1.01-1.07], P = 0.025), with DEP contributing the most substantial effect (weight = 0.564). Our findings suggest that exposure to OP pesticides is associated with an increased prevalence of asthma, with DEP demonstrating the strongest impact.

Short-Term Transcriptomic Points of Departure Are Consistent with Chronic Points of Departure for Three Organophosphate Pesticides across Mouse and Fathead Minnow

New approach methods (NAMs) can reduce the need for chronic animal studies. Here, we apply benchmark dose (concentration) (BMD(C))-response modeling to transcriptomic changes in the liver of mice and in fathead minnow larvae after short-term exposures (7 days and 1 day, respectively) to several dose/concentrations of three organophosphate pesticides (OPPs): fenthion, methidathion, and parathion. The mouse liver transcriptional points of departure (TPODs) for fenthion, methidathion, and parathion were 0.009, 0.093, and 0.046 mg/Kg-bw/day, while the fathead minnow larva TPODs were 0.007, 0.115, and 0.046 mg/L, respectively. The TPODs were consistent across both species and reflected the relative potencies from traditional chronic toxicity studies with fenthion identified as the most potent. Moreover, the mouse liver TPODs were more sensitive than or within a 10-fold difference from the chronic apical points of departure (APODs) for mammals, while the fathead minnow larva TPODs were within an 18-fold difference from the chronic APODs for fish species. Short-term exposure to OPPs significantly impacted acetylcholinesterase mRNA abundance (FDR p-value <0.05, |fold change| ≥2) and canonical pathways (IPA, p-value <0.05) associated with organism death and neurological/immune dysfunctions, indicating the conservation of key events related to OPP toxicity. Together, these results build confidence in using short-term, molecular-based assays for the characterization of chemical toxicity and risk, thereby reducing reliance on chronic animal studies.

Biomarkers of organophosphate insecticides exposure and asthma in general US adults: findings from NHANES 1999-2018 data

The limited evidence linking exposure to organophosphate insecticides (OPIs) and asthma in the general population prompted us to investigate this association. Our study focused on US adults and utilized representative samples from the National Health and Nutrition Examination Survey (NHANES). From the 7 NHANES waves (1999-2018), we detected OPIs exposure using the urinary concentrations of six metabolites of dialkyl phosphates (DAPs). To evaluate the relationship between these OPIs and asthma, we employed three statistical methods: survey-multivariable logistic regression (SMLR), generalized weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR). Stratified analyses were done based on the relevant variable subgroups, and sensitivity analyses were carried out to evaluate the robustness of findings. A total of 6009 adults aged from 20 to 85 years old, representing the 313.5 million adults in the non-institutionalized US population, were included in our analyses. Among them, 842 participants were determined as asthma patients with an age-adjusted prevalence of 14.2%. Our results showed that dimethyl phosphate (DMP) (adjusted odd ratio (AOR) = 1.471, 95% CI: 1.086, 1.993), diethyl phosphate (DEP) (AOR = 1.453, 95% CI: 1.118, 1.888), dimethyl thiophosphate (DMTP) (AOR = 1.454, 95% CI: 1.071, 1.973), and dimethyl dithiophosphate (DMDTP) (AOR = 1.478, 95% CI: 1.119, 1.953) had a positive correlation with asthma in adults. This association was stronger in females, non-Hispanic White populations and those with a small amount of physical activity. Our study findings indicated that exposure to OPIs may elevate the risk of asthma in US general adults. Specifically, females, individuals from non-Hispanic White backgrounds, and those with lower levels of physical activity are more susceptible to developing asthma when exposed to OPIs.

Urinary Cypermethrin Metabolites among Conventional and Organic Farmers in Thailand

Cypermethrin, a pyrethroid insecticide, is frequently spread on agricultural farmlands and is also used in households in Thailand. Conventional pesticide-using farmers (n = 209) were recruited from the Phitsanulok and Nakornsawan provinces. Certified organic farmers (n = 224) were also recruited in the Yasothorn province. The farmers were interviewed via a questionnaire and the urine from their first morning void was collected. The urine samples were analyzed for 3-phenoxybenzoic acid (3-PBA), cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA), and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (trans-DCCA). The results showed no significant difference in the urinary cypermethrin metabolites between the conventional farmers and the organic farmers, for whom the usage of cypermethrin was not accounted for. However, when conventional farmers who used cypermethrin on the farm and in the home were compared with conventional farmers who did not use any cypermethrin or with organic farmers, a significant difference was noted for all metabolites except for trans-DCCA. These findings show that the most significant exposures to cypermethrin are among conventional farmers who use the insecticide on their farms or in their homes. However, measurable levels of all metabolites were found among both conventional and organic farmers who only used cypermethrin in the home or not at all, suggesting that the at-home use of pyrethroids and other possible exposures from pyrethroid residues on market-bought food may contribute to urinary levels of pyrethroids that exceed those of the general population in the US and Canada.

Health consequences of exposure to aircraft contaminated air and fume events: a narrative review and medical protocol for the investigation of exposed aircrew and passengers

Thermally degraded engine oil and hydraulic fluid fumes contaminating aircraft cabin air conditioning systems have been well documented since the 1950s. Whilst organophosphates have been the main subject of interest, oil and hydraulic fumes in the air supply also contain ultrafine particles, numerous volatile organic hydrocarbons and thermally degraded products. We review the literature on the effects of fume events on aircrew health. Inhalation of these potentially toxic fumes is increasingly recognised to cause acute and long-term neurological, respiratory, cardiological and other symptoms. Cumulative exposure to regular small doses of toxic fumes is potentially damaging to health and may be exacerbated by a single higher-level exposure. Assessment is complex because of the limitations of considering the toxicity of individual substances in complex heated mixtures.There is a need for a systematic and consistent approach to diagnosis and treatment of persons who have been exposed to toxic fumes in aircraft cabins. The medical protocol presented in this paper has been written by internationally recognised experts and presents a consensus approach to the recognition, investigation and management of persons suffering from the toxic effects of inhaling thermally degraded engine oil and other fluids contaminating the air conditioning systems in aircraft, and includes actions and investigations for in-flight, immediately post-flight and late subsequent follow up.

Recent Advancements in Liquid Chromatographic Techniques to Estimate Pesticide Residues Found in Medicinal Plants around the Globe

In the present review article, different advanced liquid chromatographic techniques and the advanced techniques other than liquid chromatography that are used to estimate the pesticide residues from different plant-based samples are presented. In the beginning of the article, details of pesticides, their health effects and various cell lines used for the related study has been outlined. Afterward, detailed descriptions regarding pesticides classification are inscribed. In the end, recent advancements in the area of analysis of pesticides for herbal drugs are explained. Solid phase micro extraction (SPME) and solid-phase extraction (SPE) are considered as most common method of sample preparation for pesticides and its residual analysis. The most commonly used analytical separation technique for pesticide analysis is liquid chromatography (LC) integrated with mass spectrometry (MS) and MS/MS as Triple Quadrupole Mass Spectrometer (QqQ) for the samples analysis where high level of sensitivity and accuracy is required in quantification.

Co-exposure of organophosphorus pesticides is associated with increased risk of type 2 diabetes mellitus in a Chinese population

OBJECTIVE

The epidemiological evidence of human exposure to organophosphorus pesticides (OPPs) with type 2 diabetes mellitus (T2DM) and prediabetes (PDM) is scarce. We aimed to examine the association of T2DM/PDM risk with single OPP exposure and multi-OPP co-exposure.

METHODS

Plasma levels of ten OPPs were measured using the gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) among 2734 subjects from the Henan Rural Cohort Study. We used generalized linear regression to estimate odds ratios (ORs) or β with 95% confidence intervals (CIs), and constructed quantile g-computation and Bayesian kernel machine regression (BKMR) models to investigate the association of OPPs mixture with the risk of T2DM and PDM.

RESULTS

High detection rates ranged from 76.35% (isazophos) to 99.17% (malathion and methidathion) for all OPPs. Several plasma OPPs concentrations were in positive correlation with T2DM and PDM. Additionally, positive associations of several OPPs with fasting plasma glucose (FPG) values and glycosylated hemoglobin (HbA1c) levels were observed. In the quantile g-computation, we identified significantly positive associations between OPPs mixtures and T2DM as well as PDM, and fenthion had the greatest contribution for T2DM, followed by fenitrothion and cadusafos. As for PDM, the increased risk was largely explained by cadusafos, fenthion, and malathion. Furthermore, BKMR models suggested that co-exposure to OPPs was linked to an increased risk of T2DM and PDM.

CONCLUSION

Our findings suggested that the individual and mixture of OPPs co-exposure were associated with an increased risk of T2DM and PDM, implying that OPPs might act an important role in the development of T2DM.

Quorum sensing system effectively enhances DegU-mediated degradation of pyrethroids by Bacillus subtilis

The contamination of the natural environment is a growing concern that threatens all life forms, including microorganisms. Bacteria protect themselves by initiating quorum sensing (QS), a bacterial cell-cell communication, to generate adaptive responses to these pollutants. Bacillus subtilis has a typical QS ComQXPA system that regulates the phosphorylation of the transcription factor DegU (DegU-P), and thus can mediate the expression of various downstream genes under different stress conditions. Herein, we found that cesB, a gene of Bacillus subtilis 168, plays a key role in pyrethroid degradation, and cesB-mediated degradation could be enhanced by coordinating with the ComX communication system. Using β-cypermethrin (β-CP) as a paradigm, we demonstrated that DegU-P increased upon exposure to β-CP, thus facilitating β-CP degradation by binding to the upstream regulatory regions of cesB, leading to the activation of the expression of cesB. Further, we showed that the expression of different levels of phosphorylated DegU in a degU deletion strain resulted in varying degrees of β-CP degradation efficiency, with phosphorylated DegU^H12L achieving 78.39% degradation efficiency on the first day, surpassing the 56.27% degradation efficiency in the wild type strain. Consequently, based on the conserved regulatory mechanism of ComQXPA system, we propose that DegU-P-dependent regulation serves as a conserved defense mechanism owing to its ability to fine-tune the expression of genes involved in the degradation of pollutants upon exposure to different pesticides.

In vitro neurotoxicity screening of engine oil- and hydraulic fluid-derived aircraft cabin bleed-air contamination

In most airplanes, cabin air is extracted from the turbine compressors, so-called bleed air. Bleed air can become contaminated by leakage of engine oil or hydraulic fluid and possible neurotoxic constituents, like triphenyl phosphate (TPhP) and tributyl phosphate (TBP). The aim of this study was to characterize the neurotoxic hazard of TBP and TPhP, and to compare this with the possible hazard of fumes originating from engine oils and hydraulic fluids in vitro. Effects on spontaneous neuronal activity were recorded in rat primary cortical cultures grown on microelectrode arrays following exposure for 0.5h (acute), and 24h and 48h (prolonged) to TBP and TPhP (0.01 - 100µM) or fume extracts (1 - 100µg/mL) prepared from four selected engine oils and two hydraulic fluids by a laboratory bleed air simulator. TPhP and TBP concentration-dependently reduced neuronal activity with equal potency, particularly during acute exposure (TPhP IC₅₀: 10 - 12µM; TBP IC₅₀: 15 - 18µM). Engine oil-derived fume extracts persistently reduced neuronal activity. Hydraulic fluid-derived fume extracts showed a stronger inhibition during 0.5h exposure, but the degree of inhibition attenuates during 48h. Overall, fume extracts from hydraulic fluids were more potent than those from engine oils, in particular during 0.5h exposure, although the higher toxicity is unlikely to be due only to higher levels of TBP and TPhP in hydraulic fluids. Our combined data show that bleed air contaminants originating from selected engine oils or hydraulic fluids exhibit neurotoxic hazard in vitro, with fumes derived from the selected hydraulic fluids being most potent.

Differentiated Neurons Are More Vulnerable to Organophosphate and Carbamate Neurotoxicity than Undifferentiated Neurons Due to the Induction of Redox Stress and Accumulate Oxidatively-Damaged Proteins

Organophosphate (OP) and carbamate pesticides are toxic to pests through targeted inhibition of acetylcholinesterase (AChE). However, OPs and carbamates may be harmful to non-target species including humans and could induce developmental neurotoxicity if differentiated or differentiating neurons are particularly vulnerable to neurotoxicant exposures. Hence, this study compared the neurotoxicity of OPs, chlorpyrifos-oxon (CPO), and azamethiphos (AZO) and the carbamate pesticide, aldicarb, to undifferentiated versus differentiated SH-SY5Y neuroblastoma cells. OP and carbamate concentration-response curves for cell viability were undertaken using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and cellular bioenergetic capacity assessed via quantitation of cellular ATP levels. Concentration-response curves for inhibition of cellular AChE activity were also generated and the production of reactive oxygen species (ROS) was monitored using a 2',7'-dichlorofluorescein diacetate (DCFDA) assay. The OPs and aldicarb reduced cell viability, cellular ATP levels, and neurite outgrowth in a concentration-dependent fashion, from a threshold concentration of ≥10 µM. Neurotoxic potency was in the order AZO > CPO > aldicarb for undifferentiated cells but CPO > AZO > aldicarb for differentiated cells and this toxic potency of CPO reflected its more extensive induction of reactive oxygen species (ROS) and generation of carbonylated proteins that were characterized by western blotting. Hence, the relative neurotoxicity of the OPs and aldicarb in part reflects non-cholinergic mechanisms that are likely to contribute to developmental neurotoxicity.

Chemical exposures and suspected impact on Gulf War Veterans

Gulf War Illness (GWI) encompass a spectrum of maladies specific to troops deployed during the Persian Gulf War (1990-1991). There are several hypothesized factors believed to contribute to GWI, including (but not limited to) exposures to chemical agents and a foreign environment (e.g., dust, pollens, insects, and microbes). Moreover, the inherent stress associated with deployment and combat has been associated with GWI. While the etiology of GWI remains uncertain, several studies have provided strong evidence that chemical exposures, especially neurotoxicants, may be underlying factors for the development of GWI. This mini style perspective article will focus on some of the major evidence linking chemical exposures to GWI development and persistence decades after exposure.

Complexification of In Vitro Models of Intestinal Barriers, A True Challenge for a More Accurate Alternative Approach

The use of cell models is common to mimic cellular and molecular events in interaction with their environment. In the case of the gut, the existing models are of particular interest to evaluate food, toxicants, or drug effects on the mucosa. To have the most accurate model, cell diversity and the complexity of the interactions must be considered. Existing models range from single-cell cultures of absorptive cells to more complex combinations of two or more cell types. This work describes the existing solutions and the challenges that remain to be solved.

Acetylcholinesterase Activity Staining in Freshwater Planarians

The serine hydrolase acetylcholinesterase (AChE) is an important neuronal enzyme which catalyzes the hydrolysis of the neurotransmitter acetylcholine and other choline esters. The breakdown of acetylcholine by AChE terminates synaptic transmission and regulates neuromuscular communication. AChE inhibition is a common mode of action of various insecticides, such as carbamates and organophosphorus pesticides. Freshwater planarians, especially the species Dugesia japonica, have been shown to possess AChE activity and to be a suitable alternative model for studying the effects of pesticides in vivo. AChE activity can be quantified in homogenates using the Ellman assay. However, this biochemical assay requires specialized equipment and large numbers of planarians. Here, we present a protocol for visualizing AChE activity in individual planarians. Activity staining can be completed in several hours and can be executed using standard laboratory equipment (a fume hood, nutator, and light microscope with imaging capability). We describe the steps for preparing the reagents, and the staining and imaging of the planarians. Planarians are treated with 10% acetic acid and fixed with 4% paraformaldehyde and then incubated in a staining solution containing the substrate acetylthiocholine. After incubation in the staining solution for 3.5 hr on a nutator at 4°C, or stationary on ice, planarians are washed and mounted for imaging. Using exposure to an organophosphorus pesticide as an example, we show how AChE inhibition leads to a loss of staining. Thus, this simple method can be used to qualitatively evaluate AChE inhibition due to chemical exposure or RNA interference, providing a new tool for mechanistic studies of effects on the cholinergic system. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Preparing the staining solution Basic Protocol 2: Fixing, staining, and imaging whole-mount planarian specimens for visualization of acetylcholinesterase activity.

Neurotoxicity evoked by organophosphates and available countermeasures

Organophosphorus compounds (OP) are a constant problem, both in the military and in the civilian field, not only in the form of acute poisoning but also for their long-lasting consequences. No antidote has been found that satisfactorily protects against the toxic effects of organophosphates. Likewise, there is no universal cure to avert damage after poisoning. The key mechanism of organophosphate toxicity is the inhibition of acetylcholinesterase. The overstimulation of nicotinic or muscarinic receptors by accumulated acetylcholine on a synaptic cleft leads to activation of the glutamatergic system and the development of seizures. Further consequences include generation of reactive oxygen species (ROS), neuroinflammation, and the formation of various other neuropathologists. In this review, we present neuroprotection strategies which can slow down the secondary nerve cell damage and alleviate neurological and neuropsychiatric disturbance. In our opinion, there is no unequivocal approach to ensure neuroprotection, however, sooner the neurotoxicity pathway is targeted, the better the results which can be expected. It seems crucial to target the key propagation pathways, i.e., to block cholinergic and, foremostly, glutamatergic cascades. Currently, the privileged approach oriented to stimulating GABA_AR by benzodiazepines is of limited efficacy, so that antagonizing the hyperactivity of the glutamatergic system could provide an even more efficacious approach for terminating OP-induced seizures and protecting the brain from permanent damage. Encouraging results have been reported for tezampanel, an antagonist of GluK1 kainate and AMPA receptors, especially in combination with caramiphen, an anticholinergic and anti-glutamatergic agent. On the other hand, targeting ROS by antioxidants cannot or already developed neuroinflammation does not seem to be very productive as other processes are also involved.

Identification of azukisapogenol triterpenoid saponins from Oxytropis hirta Bunge and their aphicidal activities against pea aphid Acyrthosiphon pisum Harris

BACKGROUND

Acyrthosiphon pisum Harris is the most destructive pest worldwide because of its ability to feed on plants directly and transmit plant viruses as a vector. This study aims to identify triterpenoid saponins from Oxytropis hirta Bunge as biopesticides to control aphids.

RESULTS

Three new azukisapogenol triterpenoid saponins (1-3), a new pinoresinol lignan glycoside (8), and four known saponins (4-7) were identified from the root of O. hirta. Compounds 4-7 displayed significant aphicidal activities against A. pisum with oral toxicities (LC₅₀  = 51.10-147.43 μg/mL, 72 h), deterrent effects (deterrence index = 1.00, 100-200 μg/mL, 24 h), and aphid reproduction inhibitory effects (inhibition rates = 75.91-86.73%, 400 μg/mL, 24 h), respectively. The carboxyl groups at C-3 GlcA and C-30 were functional groups for their aphicidal activities. The toxic symptoms caused by the optimal 5 involved insect body-color changes from light green to dark or gray-green, and then brown until death. The intestinal cavity, apical microvilli, nuclei, mitochondria, and electron dense granules in the midgut tissues of A. pisum were the target sites showing aphicidal activity. The suppression of pepsin and α-amylase, and the activation of lipase and trypsin could be the signs of organelle damage in the midgut tissues.

CONCLUSION

Azukisapogenol triterpenoid saponins from O. hirta could be used as biopesticides to control aphids for their multiple efficacies, including oral toxicity, deterrent activity, and reproduction inhibitory activity. The toxic symptoms involved insect body-color changes. Midgut tissues and their related enzymes were the targets for saponins showing aphicidal activities. © 2022 Society of Chemical Industry.

Developmental toxicity of chlorpyrifos-methyl and its primary metabolite, 3,5,6-trichloro-2-pyridinol to early life stages of zebrafish (Danio rerio)

Chlorpyrifos-methyl (CPM) is one of the thiophosphate insecticides, and it is mainly metabolized to 3,5,6-trichloro-2-pyridinol (TCP) in the environment. As CPM is a strongly toxic and TCP is persistent in the environment, CPM and TCP need to be evaluate their toxicities using animal model organisms. With this regard, CPM and TCP were treated on zebrafish (Danio rerio) embryos and LC₅₀ values were determined as over 2000 μg/L and 612.5 μg/L, respectively. For the hatchability, CPM did not exhibit any interference, while TCP showed weak inhibition. In the CPM-treated embryos, pericardial edema and bleeding were observed at 48 hpf, but recovered afterwards. The pericardial edema and yolk sac edema were observed in TCP-treated zebrafish embryos at the concentration of 500 μg/L after 72 hpf. TCP induced abnormal heart development and the heartbeat was dramatically decreased in Tg(cmlc2:EGFP) embryos at the level of 500 μg/L. The expression level of heart development-related genes such as gata, myl7, and cacna1c was significantly decreased in the TCP 500 μg/L-treated embryos at the 96 hpf. Taken together, TCP appears to be more toxic than the parent compound towards the zebrafish embryos. It is highly requested that TCP needs to be monitored with a strong public concern because it affects presumably heart development in early-stage aquatic vertebrates.

New Worm on the Block: Planarians in (Neuro)Toxicology

Traditional mammalian testing is too time- and cost-intensive to keep up with the large number of environmental chemicals needing assessment. This has led to a dearth of information about the potential adverse effects of these chemicals, especially on the developing brain. Thus, there is an urgent need for rapid and cost-effective neurotoxicity and developmental neurotoxicity testing. Because of the complexity of the brain, metabolically competent organismal models are necessary to understand the effects of chemicals on nervous system development and function on a systems level. In this overview, we showcase asexual freshwater planarians as an alternative invertebrate ("non-animal") organismal model for neurotoxicology research. Planarians have long been used to study the effects of chemicals on regeneration and behavior. But they have only recently moved back into the spotlight because modern molecular and computational approaches now enable quantitative high-content and high-throughput toxicity studies. Here, we present a short history of the use of planarians in toxicology research, highlight current techniques to measure toxicity qualitatively and quantitatively in planarians, and discuss how to further promote this non-animal organismal system into mainstream toxicology research. The articles in this collection will help work towards this goal by providing detailed protocols that can be adopted by the community to standardize planarian toxicity testing. © 2022 Wiley Periodicals LLC.

Developmental exposure to chlorpyrifos causes neuroinflammation via necroptosis in mouse hippocampus and human microglial cell line

Neurodevelopmental exposure to chlorpyrifos (CPF) could increase risks for neurological disorders, such as autism spectrum disorder, cognitive impairment, or attention deficit hyperactivity disorder. The potential involvement of microglia reactive to inflammatory stimuli in these neurological disorders has been generally reported. However, the concrete effects and potential mechanisms of microglia dysfunction triggered by developmental CPF exposure remain unclear. Therefore, we established mouse and human embryonic microglial cells (HMC3 cell) models of developmental CPF exposure to evaluate the effects of developmental CPF exposure on neuroinflammation and underlying mechanisms. The results showed that developmental exposure to CPF enhanced the expression of Iba1 in hippocampus. CPF treatment increased inflammatory cytokines levels and TSPO expression in hippocampus and HMC3 cells. The levels of necroptosis and necroptosis-related signaling RIPK/MLKL were increased in hippocampus and HMC3 cells following CPF exposure. Furthermore, the expression of TLR4/TRIF signaling was increased in hippocampus and HMC3 cells subjected to CPF exposure. Notably, the increased levels of TLR4/TRIF signaling, RIPK/MLKL signaling, necroptosis and pro-inflammatory cytokines induced by CPF treatment were remarkably inhibited by TAK-242 (a specific TLR4 inhibitor). Additionally, the necroptosis and pro-inflammatory cytokines production induced by CPF treatment were significantly relieved by Nec-1 (a specific RIPK1 inhibitor). In general, the above results suggested that activated microglia in hippocampus subjected to developmental CPF exposure underwent RIPK1/MLKL-mediated necroptosis regulated by TLR4/TRIF signaling.

Organophosphate pesticide exposure and biomarkers of liver injury/liver function

BACKGROUND AND AIMS

There is little epidemiological evidence linking the exposure of organophosphate pesticides (OPs) to liver function or liver injury in the general population. We used data from the National Health and Nutrition Examination Survey 1999-2012 to investigate the relationship of urinary OPs with biomarkers of liver function/liver injury.

METHODS

The exposures were the concentrations of urinary OP metabolites (dimethyl phosphate [DMP], dimethyl thiophosphate [DMTP], diethyl phosphate [DEP] and diethyl thiophosphate [DETP]). The health outcomes were biomarkers of liver function/liver injury. The multivariable linear regression model, restricted cubic splines (RCSs) analysis and weighted quantile sum (WQS) regression were used to evaluate the relationship between individual or overall exposure of OPs and outcomes.

RESULTS

Regressions of RCSs suggested linear and positive associations of OP metabolites with aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio (DMP and DEP) and fibrosis-4 (FIB-4) index (DMP, DEP and DMTP) (all p-non-linear values >.05). However, L-shaped relationships were found between OP metabolites (DMTP and DETP) and blood albumin and total protein (TP) concentrations (both p and non-linear values <.05). The positive associations of urinary DMP, DEP and DMTP with AST/ALT ratio, and with FIB-4 score were more pronounced among non-smokers than smokers, among alcohol drinkers than non-drinkers and among those with a body mass index (BMI) of ≥25 than participants with a BMI of <25. However, most of the interaction p values were more than .05, indicating no significant interactions between covariates and OPs on outcomes mainly including AST/ALT, FIB-4, ALB and TP levels. Finally, the WQS indices were positively associated with AST/ALT ratio (p = .014) and FIB-4 score (p = .002).

CONCLUSIONS

Our study added novel evidence that exposures to OPs might be adversely associated with the biomarkers of liver function/liver injury. These findings indicated the potential toxic effect of OP exposures on the human liver.

Associations of organophosphate metabolites with thyroid hormone and antibody levels: findings from U.S. National Health and Nutrition Examination Survey (NHANES)

Studies have shown that organophosphate pesticides (OPs) exposure may disrupt thyroid endocrine functions in animal models, agricultural population, occupational workers, and work-related population. However, the relationships between OPs exposure and thyroid hormone levels in the general population are unclear. This study aimed to explore the relationships of OPs exposure with thyroid hormone and antibody levels in the general population. We analyzed a sample of 1089 US adults from the National Health and Nutrition Examination Survey (NHANES) 2001-2002. OPs exposure was estimated using measures of six non-specific dialkyl phosphate metabolites (DAPs), e.g., dimethylphosphate (DMP). Multiple linear regression models were used to examine the associations of OPs exposure with thyroid hormone and antibody levels. The medians of urinary ∑DAPs detected in males and females were 32.98 nmol/g creatinine and 40.77 nmol/g creatinine, with statistical significance (p = 0.001). After controlling for sociodemographic factors, we found that concentrations of urinary OPs metabolites were positively associated with the serum thyroid stimulating hormone (TSH) in the general US population, particularly in males; OPs metabolites were associated with the serum TgAb, tT3, fT3, and TSH. These findings showed that thyroid hormone and antibody disruption are probably associated with OPs exposure in the general population; more studies are needed to confirm our findings.

Mitochondrial dysfunction from malathion and chlorpyrifos exposure is associated with degeneration of GABAergic neurons in Caenorhabditis elegans

Toxicity resulting from off-target effects, beyond acetylcholine esterase inhibition, for the commonly used organophosphate (OP) insecticides chlorpyrifos (CPS) and malathion (MA) was investigated using Saccharomyces cerevisiae and Caenorhabditis elegans model systems. Mitochondrial damage and dysfunction were observed in yeast following exposure to CPS and MA, suggesting this organelle is a major target. In the C. elegans model, the mitochondrial unfolded protein response pathway showed the most robust induction from CPS and MA treatment among stress responses examined. GABAergic neurodegeneration was observed with CPS and MA exposure. Impaired movement observed in C. elegans exposed to CPS and MA may be the result of motor neuron damage. Our analysis suggests that stress from CPS and MA results in mitochondrial dysfunction, with GABAergic neurons sensitized to these effects. These findings may aid in the understanding of toxicity from CPS and MA from high concentration exposure leading to insecticide poisoning.

Molecular and Cellular Interactions in Pathogenesis of Sporadic Parkinson Disease

An increasing number of the population all around the world suffer from age-associated neurodegenerative diseases including Parkinson’s disease (PD). This disorder presents different signs of genetic, epigenetic and environmental origin, and molecular, cellular and intracellular dysfunction. At the molecular level, α-synuclein (αSyn) was identified as the principal molecule constituting the Lewy bodies (LB). The gut microbiota participates in the pathogenesis of PD and may contribute to the loss of dopaminergic neurons through mitochondrial dysfunction. The most important pathogenetic link is an imbalance of Ca²⁺ ions, which is associated with redox imbalance in the cells and increased generation of reactive oxygen species (ROS). In this review, genetic, epigenetic and environmental factors that cause these disorders and their cause-and-effect relationships are considered. As a constituent of environmental factors, the example of organophosphates (OPs) is also reviewed. The role of endothelial damage in the pathogenesis of PD is discussed, and a ‘triple hit hypothesis’ is proposed as a modification of Braak’s dual hit one. In the absence of effective therapies for neurodegenerative diseases, more and more evidence is emerging about the positive impact of nutritional structure and healthy lifestyle on the state of blood vessels and the risk of developing these diseases.

Predicting Resistance: Quantifying the Relationship between Urban Development, Agricultural Pesticide Use, and Pesticide Resistance in a Nontarget Amphipod

Resistance alleles within the voltage-gated sodium channel (vgsc) have been correlated with pyrethroid resistance in wild populations of the nontarget amphipod, Hyalella azteca from California (CA), U.S.A. In the present study, we expand upon the relationship between land use and the evolution of pesticide resistance in H. azteca to develop a quantitative methodology to target and screen novel populations for resistance allele genotypes in a previously uninvestigated region of the U.S. (New England: NE). By incorporating urban land development and toxicity-normalized agricultural pesticide use indices into our site selection, we successfully identified three amino acid substitutions associated with pyrethroid resistance. One of the resistance mutations has been described in H. azteca from CA (L925I). We present the remaining two (vgsc I936F and I936V) as novel pyrethroid-resistance alleles in H. azteca based on previous work in insects and elevated cyfluthrin resistance in one NE population. Our results suggest that urban pesticide use is a strong driver in the evolution of resistance alleles in H. azteca. Furthermore, our method for resistance allele screening provides an applied framework for detecting ecosystem impairment on a nationwide scale that can be incorporated into ecological risk assessment decisions.

Differences in neurotoxic outcomes of organophosphorus pesticides revealed via multi-dimensional screening in adult and regenerating planarians

Organophosphorus pesticides (OPs) are a chemically diverse class of commonly used insecticides. Epidemiological studies suggest that low dose chronic prenatal and infant exposures can lead to life-long neurological damage and behavioral disorders. While inhibition of acetylcholinesterase (AChE) is the shared mechanism of acute OP neurotoxicity, OP-induced developmental neurotoxicity (DNT) can occur independently and/or in the absence of significant AChE inhibition, implying that OPs affect alternative targets. Moreover, different OPs can cause different adverse outcomes, suggesting that different OPs act through different mechanisms. These findings emphasize the importance of comparative studies of OP toxicity. Freshwater planarians are an invertebrate system that uniquely allows for automated, rapid and inexpensive testing of adult and developing organisms in parallel to differentiate neurotoxicity from DNT. Effects found only in regenerating planarians would be indicative of DNT, whereas shared effects may represent neurotoxicity. We leverage this unique feature of planarians to investigate potential differential effects of OPs on the adult and developing brain by performing a comparative screen to test 7 OPs (acephate, chlorpyrifos, dichlorvos, diazinon, malathion, parathion and profenofos) across 10 concentrations in quarter-log steps. Neurotoxicity was evaluated using a wide range of quantitative morphological and behavioral readouts. AChE activity was measured using an Ellman assay. The toxicological profiles of the 7 OPs differed across the OPs and between adult and regenerating planarians. Toxicological profiles were not correlated with levels of AChE inhibition. Twenty-two "mechanistic control compounds" known to target pathways suggested in the literature to be affected by OPs (cholinergic neurotransmission, serotonin neurotransmission, endocannabinoid system, cytoskeleton, adenyl cyclase and oxidative stress) and 2 negative controls were also screened. When compared with the mechanistic control compounds, the phenotypic profiles of the different OPs separated into distinct clusters. The phenotypic profiles of adult vs. regenerating planarians exposed to the OPs clustered differently, suggesting some developmental-specific mechanisms. These results further support findings in other systems that OPs cause different adverse outcomes in the (developing) brain and build the foundation for future comparative studies focused on delineating the mechanisms of OP neurotoxicity in planarians.

Protective activities of ellagic acid and urolithins against kidney toxicity of environmental pollutants: A review

Oxidative stress and inflammation are two possible mechanisms related to nephrotoxicity caused by environmental pollutants. Ellagic acid, a powerful antioxidant phytochemical, may have great relevance in mitigating pollutant-induced nephrotoxicity and preventing the progression of kidney disease. This review discusses the latest findings on the protective effects of ellagic acid, its metabolic derivatives, the urolithins, against kidney toxicity caused by heavy metals, pesticides, mycotoxins, and organic air pollutants. We describe the chelating, antioxidant, anti-inflammatory, antifibrotic, antiautophagic, and antiapoptotic properties of ellagic acid to attenuate nephrotoxicity. Furthermore, we present the molecular targets and signaling pathways that are regulated by these antioxidants, and suggest some others that should be explored. Nevertheless, the number of reports is still limited to establish the efficacy of ellagic acid against kidney damage induced by environmental pollutants. Therefore, additional preclinical studies on this topic are required, as well as the development of well-designed clinical trials.

Cognitive Impairment and Neurodegenerative Diseases Development Associated with Organophosphate Pesticides Exposure: a Review Study

A significant body of literature emphasizes the role of insecticide, particularly organophosphates (OPs), as the major environmental factor in the etiology of neurodegenerative diseases. This review aims to study the relationship between OP insecticide exposure, cognitive impairment, and neurodegenerative disease development. Human populations, especially in developing countries, are frequently exposed to OPs due to their extensive applications. The involvement of various signaling pathways in OP neurotoxicity are reported, but the OP-induced cognitive impairment and link between OP exposure and the pathophysiology of neurodegenerative diseases are not clearly understood. In the present review, we have therefore aimed to come to new conclusions which may help to find protective and preventive strategies against OP neurotoxicity and may establish a possible link between organophosphate exposure, cognitive impairment, and OP-induced neurotoxicity. Moreover, we discuss the findings obtained from animal and human research providing some support for OP-induced cognitive impairment and neurodegenerative disorders.

Association between exposure to organophosphorus pesticides and the risk of diabetes among US Adults: Cross-sectional findings from the National Health and Nutrition Examination Survey

OBJECTIVE

Organophosphorus pesticides (OPPs) are commonly used pesticides across the world, however there is little epidemiological evidence linking their exposure to diabetes. Hence, this study aimed at investigating the effect of OPP exposure on the prevalence of diabetes in American adults.

METHODS

Adults (≥20 years old) were eligible for this study from the National Health and Nutrition Examination Survey (NHANES). Multivariate logistic regression model was employed to explore the associations of six main urinary OPPs metabolites with diabetes. Subgroup analyses were performed by age and gender. Combined effect of OPPs metabolites on the overall association with diabetes was evaluated by weighted quantile sum regression (WQS). Furthermore, Bayesian kernel machine regression (BKMR) model was implemented to explore joint effect of multiple OPPs metabolites on diabetes.

RESULTS

Ultimately, 6,593 adults were included in our analysis. Of them, 1,044 participants were determined as diabetes patients. The results of logistic regression shown that urinary OPPs metabolites concentrations, whether taken as continuous variables or quantiles, were in positive correlation with diabetes. Notably, the p for trend of diethylphosphate (DEP), a kind of OPPs metabolites, was less than 0.05 indicated that a linear trend may exist between levels of DEP and prevalence of diabetes among adults while this trend was not obversed in other OPPs metabolites. In the WQS model, combined exposure of OPPs metabolites had a significantly positive association with diabetes (OR: 1.057; 95% CI: 1.002, 1.114) and diethylphosphate (36.84%) made the largest contributor to the WQS index. The result of BKMR also suggested a positive trend of association between mixed OPPs metabolites and diabetes.

CONCLUSION

Our results add credibility to the argument that OPP exposure might trigger diabetes. Certainly, prospective data are required to corroborate our findings.

An Investigation of the Neurotoxic Effects of Malathion, Chlorpyrifos, and Paraquat to Different Brain Regions

Acute or chronic exposures to pesticides have been linked to neurotoxicity and the potential development of neurodegenerative diseases (NDDs). This study aimed to consider the neurotoxicity of three widely utilized pesticides: malathion, chlorpyrifos, and paraquat within the hippocampus (HC), corpus striatum (CS), cerebellum (CER), and cerebral cortex (CC). Neurotoxicity was evaluated at relatively low, medium, and high pesticide dosages. All pesticides inhibited acetylcholinesterase (AChE) and neuropathy target esterase (NTE) in each of the brain regions, but esterase inhibition was greatest in the HC and CS. Each of the pesticides also induced greater disruption to cellular bioenergetics within the HC and CS, and this was monitored via inhibition of mitochondrial complex enzymes I and II, reduced ATP levels, and increased lactate production. Similarly, the HC and CS were more vulnerable to redox stress, with greater inhibition of the antioxidant enzymes catalase and superoxide dismutase and increased lipid peroxidation. All pesticides induced the production of nuclear Nrf2 in a dose-dependent manner. Collectively, these results show that pesticides disrupt cellular bioenergetics and that the HC and CS are more susceptible to pesticide effects than the CER and CC.

Prenatal Exposure to Organophosphorus Pesticides and Preschool ADHD in the Norwegian Mother, Father and Child Cohort Study

Prenatal organophosphorus pesticide (OPP) exposure has been associated with child attention-deficit/hyperactivity disorder (ADHD) in agricultural communities and those that are exposed to residentially applied insecticides. To examine this association in populations that are exposed primarily through diet, we estimate the associations between prenatal OPP exposure and preschool ADHD in the Norwegian Mother, Father and Child Cohort Study (MoBa), and describe modification by paraoxonase 1 (PON1) gene variants. We used participants from the MoBa Preschool ADHD Sub-study (n = 259 cases) and a random sample of MoBa sub-cohort participants (n = 547) with birth years from 2004 to 2008. Prenatal urinary dialkylphosphate (DAP) metabolites (total diethylphosphate [∑DEP] and total dimethylphosphate [∑DMP]) were measured by an ultra-performance liquid chromatography-time-of-flight system and summed by molar concentration. Maternal DNA was genotyped for coding variants of PON1 (Q192R and L55M). We used a multivariable logistic regression to calculate the odds ratios (OR) and 95% confidence intervals, adjusted for maternal education, parity, income dependency, age, marital status, ADHD-like symptoms, pesticide use, produce consumption, and season. We found no associations between DAP metabolite concentrations and preschool ADHD. The adjusted ORs for exposure quartiles 2-4 relative to 1 were slightly inverse. No monotonic trends were observed, and the estimates lacked precision, likely due to the small sample size and variation in the population. We found no evidence of modification by PON1 SNP variation or child sex. Maternal urinary DAP concentrations were not associated with preschool ADHD.

The growing concern of chlorpyrifos exposures on human and environmental health

Chlorpyrifos (CP) and its highly electrophilic intermediates are principal toxic metabolites. The active form of CP i.e. chlorpyrifos oxon (CP-oxon) is responsible for both the insecticidal activity and is also of greater risk when present in the atmosphere. Thus, the combined effects of both CP, CP-oxan, and other metabolites enhance our understanding of the safety and risk of the insecticide CP. They cause major toxicities such as AChE inhibition, oxidative stress, and endocrine disruption. Further, it can have adverse hematological, musculoskeletal, renal, ocular, and dermal effects. Excessive use of this compound results in poisoning and potentially kills a non-target species upon exposure including humans. Several examples of reactive metabolites toxicities on plants, aquatic life, and soil are presented herein. The review covers the general overview on reactive metabolites of CP, chemistry and their mechanism through toxic effects on humans as well as on the environment. Considerable progress has been made in the replacement or alternative to CP. The different strategies including antidote mechanisms for the prevention and treatment of CP poisoning are discussed in this review. The approach analyses also the active metabolites for the pesticide activity and thus it becomes more important to know the pesticide and toxicity dose of CP as much as possible.

Studying Lipophilicity Trends of Phosphorus Compounds by 31P-NMR Spectroscopy: A Powerful Tool for the Design of P-Containing Drugs

Systematically studying the lipophilicity of phosphorus compounds is of great importance for many chemical and biological fields and particularly for medicinal chemistry. Here, we report on the study of trends in the lipophilicity of a wide set of phosphorus compounds relevant to drug design including phosphates, thiophosphates, phosphonates, thiophosphonates, bis-phosphonates, and phosphine chalcogenides. This was enabled by the development of a straightforward log P determination method for phosphorus compounds based on ³¹P-NMR spectroscopy. The log P values measured ranged between -3.2 and 3.6, and the trends observed were interpreted using a DFT study of the dipole moments and by H-bond basicity (pK_HB) measurements of selected compounds. Clear signal separation in ³¹P-NMR spectroscopy grants the method high tolerability to impurities. Moreover, the wide range of chemical shifts for the phosphorus nucleus (250 to -250 ppm) enables a direct simultaneous log P determination of phosphorus compound mixtures in a single shake-flask experiment and ³¹P-NMR analysis.

A Novel Organophosphorus Acid Anhydrolase from Deep Sea Sediment with High Degradation Efficiency for Organophosphorus Pesticides and Nerve Agent

Organophosphorus compounds (OPCs), including highly toxic nerve agents and pesticides, have been used widely in agricultural and military applications. However, they have aroused widespread concern because they persistently pollute the environment and threaten human life. Organophosphorus acid anhydrolase (OPAA) is a promising enzyme that can detoxify OPCs. Here, a novel OPAA (OPAA114644) was isolated and characterized from deep-sea sediment (−3104 m). It exhibited excellent alkaline stability, and the loss of activity was less than 20% in the pH range 5.0–9.0, even after being incubated for 30 d at 4 °C. It also exhibited high salt tolerance, and its enzymatic activity increased by approximately fourfold in the presence of 20% NaCl (w/v). Additionally, OPAA114644 exhibited high degradation efficiency for soman, dichlorvos, paraoxon, coumaphos, and chlorpyrifos with a concentration of up to 250 mg/L, with the degradation rate being 100%, 100%, 100%, 80% and 51%, respectively, in 20 min under optimal conditions. Notably, OPAA114644 dissolved in different solutions, such as 20% NaCl, 1 mM SDS, 0.05% soap, 10% methanol, and tap water, could efficiently decontaminate the residual paraoxon on the surfaces of glasses, cotton tissues, and apples. These results indicate that OPAA114644 has excellent potential for the biodegradation and bioremediation of OPCs pollution and represents a real application of OPAA in the decontamination and detoxification of foods and clothes, and in the remediation of sites such as floors. Deep-sea sediment might also be an abundant resource for various functional microorganisms and enzymes.