Organophosphorus Compounds at 80: Some Old and New Issues

Associations between agricultural use of pyrethroid insecticides and asthma: AGRICAN cohort results

RATIONALE

Following the withdrawal of organochlorines and organophosphates, pyrethroids have become the most used insecticides in both agricultural and domestic settings.

OBJECTIVES

We analyzed data from the French AGRICAN agricultural cohort to assess associations of occupational pyrethroid exposures and allergic/non-allergic asthma.

METHODS

At enrollment, asthma diagnosed by a doctor was reported by 11 815 participants (7028 classified as non-allergic and 4458 as allergic based on the presence of eczema and/or hay fever). Individual exposures to 17 pyrethroids were defined in 124 992 participants, based on a combination of the history of pesticide treatment of 11 crops (grassland, vineyard, wheat/barley, corn, field peas, potatoes, tobacco, beets, sunflower, rape, fruits) and a crop-exposure matrix.

MEASUREMENTS AND MAIN RESULTS

In men, no association was observed for any of the pyrethroids regardless of asthma phenotype. In contrast, in ever-exposed women, asthma risk was increased with use of any pyrethroid, both for allergic (+80 %) and non-allergic asthma (+40 %). Highest increases were observed for allergic asthma with fenpropathrin (OR = 2.00; 95 %CI:1.38-2.90), tralomethrin (OR = 1.81; 95 %CI:1.28-2.56), fenvalerate (OR = 1.81; 95 %CI:1.38-2.38), permethrin (OR = 1.78; 95 %CI:1.26-2.50) and deltamethrin (OR = 1.76; 95 %CI:1.35-2.29). Stratified analyses on women who reported living on a farm in early life showed stronger associations for non-allergic asthma. For women who reported early life living on vineyards associations with pyrethroids were stronger for both allergic and non-allergic asthma. Associations for women who lived on cattle farms were reduced for some pyrethroids.

CONCLUSION

Occupational pyrethroid exposure was positively associated with both allergic and non-allergic asthma in women but not in men.

Expression of carboxylesterase and paraoxonase in the placenta and their association with chlorpyrifos exposure during pregnancy

Exposure to environmental chemicals during pregnancy, including organophosphate pesticides, can affect the health of both the mother and the fetus, and have repercussions later in life. The present study aimed to determine whether the A-esterases paraoxonases (PON) and the B-esterases carboxylesterases (CES) are modulated in the placenta of pregnant women residing in an intensive pesticide use scenario. A total of 104 healthy pregnant women were recruited between 2018 and 2022 and were classified according to their residential settings in rural (RG) and urban (UG) groups. Chlorpyrifos (CP) level in the placenta was determined by GC-ECD, and confirmed by GC-MS. To analyze possible impacts in esterases, the CES and PON activity, mRNA transcript and protein expression levels were studied. Significantly higher CP levels were detected in RG vs UG. Also, CES activity determined with 1-naphthyl acetate substrate was significantly lower in RG vs UG. In contrast, PON arylesterase and lactonase activities were up modulated in RG vs UG. Likewise, mRNA transcript levels of CES1, CES2 and PON2 were upregulated in the RG along with increases in CES2 and PON2 protein expressions. Moreover, a positive significant correlation was determined between CP concentration and CES1 and CES2 mRNA levels. Rural samples showed elevated CP concentrations and alterations in esterases, which elucidate the impact of CP exposure in mRNA CES and PON regulation. These findings highlight the need for further investigation into the effects of pesticide exposure during pregnancy and to deepen the knowledge about the function that esterases play in the placenta.

A sensitive and selective electrochemical detection and kinetic analysis of methyl parathion using Au nanoparticle-decorated rGO/CuO ternary nanocomposite

Detecting organophosphorus pesticide (OP) residues is essential for maintaining ecological integrity and monitoring public health concerns. This research developed a novel electrochemical sensor that employed composite materials based on copper oxide (CuO) nanostructures and reduced graphene oxide (rGO), customized with Au nanoparticles (AuNPs), to detect methyl parathion (MP) pesticide with high selectivity and sensitivity. The nanocomposite was synthesized in two facile steps, without the use of stabilizers or dispersants, utilizing a simple ultrasonication and photo-reduction process. Morphological analysis revealed a uniform distribution of AuNPs and rGO within the CuO nanostructure. Kinetic studies demonstrated that the electro-reduction of MP on a glassy carbon electrode (GCE) modified with Au@rGO/CuO exhibited irreversible, diffusion-controlled kinetics, with a transfer coefficient (α) value of 0.485. A sensing study employing the square wave voltammetry (SWV) technique exhibited exceptional sensitivity (3.46 μA μM-1 cm-2), with a limit of detection (LOD) of 0.045 μM. Moreover, the Au@rGO/CuO-based sensor electrode exhibited exceptional selectivity for MP in the presence of various organic and inorganic species, along with notable reproducibility, repeatability, and stability. Overall, this electrochemical method for effective MP detection suggests that the prepared nanocomposite could contribute to the development of viable electrocatalysts.

Identification and prioritisation of biomarkers of organophosphorus compounds-induced neurotoxicity

Organophosphorus compounds (OPCs), a diverse group of chemicals widely utilised as pesticides and flame retardants, pose significant neurotoxic risks, even during neurodevelopment. While their primary molecular and cellular targets are well characterised, growing evidence suggest additional mechanisms, particularly in developmental neurotoxicity. Despite extensive research, predictive biomarkers of OPC-induced neurotoxicity beyond acetylcholinesterase remain underexplored. This study conducted a comprehensive review of epidemiological, in vivo, and in vitro evidence to identify and prioritise biomarkers associated with OPC-induced neurotoxicity. Findings highlight the critical roles of non-cholinergic mechanisms, including neuroinflammation, mitochondrial dysfunction, oxidative stress, and epigenetic modifications. Biomarkers were categorised based on their biological function, mechanistic relevance, and feasibility for early, non-invasive detection. Current research efforts focus on validating sensitive and reliable biomarkers capable of predicting and monitoring nervous system damage and severity. Growing attention is being directed toward non-invasive biomarkers that correlate with behavioural, neuropathological, and imaging outcomes. This review addresses two main aspects. The first provides an overview of established and emerging biomarkers for assessing neurotoxicity in the general population and in individuals occupationally exposed to OPC. The second evaluates molecular biomarkers prioritised based on scientific robustness, clinical relevance, and regulatory applicability. A structured ranking of biomarkers across different levels of biological organisation is proposed to enhance mechanistic understanding and improve risk assessment. This study underscores the need for a standardised biomarker framework for neurotoxicity risk assessment and regulatory decision-making. Implementing these biomarkers in biomonitoring for predictive purposes will facilitate early detection and prevention strategies, ultimately mitigating neurotoxic effects in exposed individuals.

Concentration-time profiles of the nerve agent VX and the pesticide parathion in five different cell culture plates

Cell cultivation tools are usually not considered the primary factors influencing research results. In this study, we selected two organophosphorus compounds (OP) to examine possible compound absorption in five different commercially available cell culture plates. In addition, compound degradation processes were studied. The plates were exposed to the nerve agent VX or the OP pesticide parathion. Using analytical methods such as LC-ESI-MS/MS or GC-MS, the respective concentrations of VX and its degradation products O-ethyl methylphosphonic acid (EMPA) and S-[2-(diisopropylamino)ethyl]methylphosphonothioic acid (EA-2192) as well as parathion, paraoxon, diethyl thiophosphate (DETP), and diethyl phosphate (DEP) were determined up to 72 h. Our data showed that the choice of the cell culture plate can have an impact on the OP concentration and the degradation products. The balance of VX, EMPA, and EA-2192 resulted in about the initial VX concentration at all evaluated time points, indicating that VX absorption was not likely to occur in the cell culture plates. In contrast, relevant parathion concentrations were unaccounted for after 72 h suggesting absorption to the plates. In conclusion, it was shown for the model substance parathion that it is important to characterize cell culture tools, i.e., the respective plates, regarding possible compound interaction. The suitability of the cell cultivation tool for investigations with an OP should be evaluated in advance to obtain a high quality of the study and to improve the concordance with in vivo data.

GM1 and GD3 Gangliosides Attenuate NGF-TrkA and BDNF-TrkB Signaling Dysfunction Associated with Acute Diisopropylfluorophosphate Exposure in Mouse Brain

The prevalence of neurodegenerative diseases and mental health disorders has been increasing over the past few decades. While genetic and lifestyle factors are important to the etiology of these illnesses, the pathogenic role of environmental factors, especially toxicants such as pesticides encountered over the life span, is receiving increased attention. As an environmental factor, organophosphates pose a constant threat to human health due to their widespread use as pesticides, their deployment by rogue militaries, and their use in terrorist attacks. The standard organophosphate-antidotal regimen provides modest efficacy against lethality, although morbidity remains high, and there is little evidence that it attenuates long-term neurobehavioral sequelae. Here we show that a novel intranasally administered treatment strategy with specific gangliosides can prevent the organophosphate-related alterations in important neurotrophin pathways that are involved in cognition and depression. We found that a single toxic dose of the organophosphate diisopropylfluorophosphate (DFP) in mice leads to persistent decreases in the neurotrophins NGF and BDNF and their receptors, TrkA and TrkB. Moreover, seven days of repeated intranasal administration of gangliosides GM1 or GD3 24 hours after the DFP injection prevented the neurotrophin receptor alterations. As NGF and BDNF signaling are involved in cognitive function and depression symptoms, respectively, intranasal administration of GM1 or GD3 can prevent the organophosphate-related alterations in those brain functions. Our study thus supports the potential of a novel therapeutic strategy for neurological deficits associated with a class of poisons that endangers millions of people worldwide.

Highlights

A single exposure to DFP, which causes cognitive deficits, dysregulates NGF and BDNF signalingGM1 or GD3 24 hours after DFP injection prevents the alteration of the neurotrophin signalingIntranasal ganglioside treatment provides neuroprotective effects against persistent organophosphate toxicity.

Serum testosterone partially mediates the adverse effects of organophosphate pesticides exposure on growth indicators of children and adolescents

Environmental pollutants affect children's and adolescents' growth. However, the effect of organophosphate pesticides (OPPs) exposure on this population remains unclear. This study applied a comprehensive statistical framework to evaluate the effects of multiple OPP metabolites on growth indicators in individuals aged 6-19 using data from the National Health and Nutrition Examination Survey (NHANES). The framework integrated latent class analysis (LCA), survey-weighted generalized linear regression models (SWGLMs), weighted quantile sum (WQS) regression, and bayesian kernel machine regression (BKMR). The role of total testosterone (TT) as a mediator was assessed. Network pharmacology methods were used to identify key targets and therapeutic drugs. LCA identified three exposure patterns for OPP metabolites: High DMP-High DEP (N = 145), Low DMP-Low DEP (N = 689), and High DMP-Low DEP (N = 97). SWGLMs, WQS, and BKMR demonstrated a negative association between OPPs exposure and growth indicators, particularly in females and adolescents. TT mediated this association, with mediation proportions ranging from 8.7 % to 35.7 %. Network pharmacology analysis identified 120 key targets, and pterostilbene emerged as a potential therapeutic agent. These findings suggest that OPPs exposure adversely affects children's and adolescents' growth, partly mediated by TT. Adolescents and females may be particularly vulnerable. Pterostilbene supplementation represents a potential strategy to mitigate these adverse effects.

Recent perspectives on biotechnological production, modulation and applications of glycerophosphoryl diester phosphodiesterases

Organophosphate (OP) compounds have been extensively employed as pesticides, insecticides and nerve agents. Stockpiles of chemical warfare agents must be destroyed as recommended by Chemical Weapon Convention (CWC). Toxicity of OP compounds to insects and mammals is due to their ability to inhibit the activity of acetylcholinesterase. Accumulation of acetylcholine leads to overstimulation of nerves, leading to convulsion, paralysis or even death. There is a dire need to decontaminate OP contaminated sites by using inexpensive and eco-friendly agents. Recently, OP hydrolyzing enzymes such as glycerophosphoryl diester phosphodiesterases (GDPDs) emerged as appealing agents to clean-up OP contaminated environmental sites. GDPDs are well known for enzymatic generation of glycerol 3-phosphate and corresponding alcoholic moiety from glycerophosphodiesters. Additionally, they are also involved in hydrolysis of OP compounds and degradative products of nerve agents. In the current review, structural and functional characteristics of GDPDs have been elaborated. Production of GDPDs from natural sources is quiet low so the current study aims at recombinant production of GDPDs from various sources. Comparative analysis of biochemical characteristics of various GDPDs indicated that thermostable GDPDs are active over broad temperature and pH range. In addition, thermostable GDPDs are resistant to high concentrations of organic solvents as well as metal ions. In order to enhance their practical utility, different engineering approaches (directed evolution, rational design and site-saturation mutagenesis) as well as immobilization strategies can be utilized to improve catalytic properties of GDPDs. Thus, the current review highlights the utilization of recombinant engineered free or immobilized GDPDs as tools in OP bioremediation.

LC-MS/MS-Profiling of Human Serum Unveils Significant Increase in Neuroinflammation and Carcinogenesis Following Chronic Organophosphate Exposure

The utilization of organophosphate pesticides (OPs) has escalated in response to the growing global food demand driven by a rapidly increasing population and the environmental disruptions caused by climate change. While acute exposure leads to cholinergic poisoning, chronic OP exposure has been linked to organ dysfunction, inflammation, and carcinogenesis. Serum samples from healthy individuals (n = 11), patients with acute OP exposure (n = 12), and those with chronic OP exposure (n = 31) were analyzed to discern the differentially expressed pathways after acute and chronic OP exposure. Differential expression analysis identified 132 proteins altered in chronic exposure vs control, 86 in acute exposure vs control, and 124 in chronic vs acute exposure. Pathway analysis revealed increased blood coagulation and reduced LXR/RXR activation and DCHR24 signaling in both acute and chronic exposures. Elevated levels of pro-inflammatory proteins, such as S100A8, VWF, and GPIBA, were observed, particularly in chronic exposure, highlighting significant inflammatory effects of OP exposure. These findings provide insights into the pathological mechanisms underlying chronic OP exposure and its contribution to inflammation and long-term health risks.

Association between organophosphate pesticide exposure and atopic dermatitis: a cross-sectional study based on NHANES 1999-2007

Background

Organophosphate pesticides (OPPs) are widely used environmental chemicals with potential health impacts, but their relationship with atopic dermatitis (AD) remains unclear.

Methods

Using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2007, we investigated associations between urinary OPP metabolites and AD in 4,258 adults. Six dialkyl phosphate (DAP) metabolites were measured, and weighted quantile sum (WQS) regression was used to assess mixture effects.

Results

Both DMP (odds ratio [OR] = 1.17, 95% confidence interval [CI]: 1.05-1.31) and DMDTP (OR = 2.23, 95%CI: 1.08-4.60) showed significant positive associations with AD in fully adjusted models. WQS regression revealed significant associations between mixed OPP exposure and AD (OR = 1.25, 95%CI: 1.04-1.50), with DMP contributing most (45.8%) to the mixture effect. Stratified analyses indicated stronger associations in males, younger adults (<60 years), and smokers.

Conclusion

Our findings suggest that OPP exposure, particularly DMP, may be associated with increased AD risk in adults. These results provide new insights into environmental risk factors for AD.

Chlorine-substituted transformation products generated during chlorination of the organophosphorus insecticide disulfoton induce anti-acetylcholine esterase activity

Global concern regarding transformation products (TPs) derived from contaminants, including pesticides, in the environment and during water treatment has been growing markedly. In the present study, we investigated the anti-acetylcholinesterase (AChE) activity of an aqueous solution of the organophosphorus insecticide disulfoton, a toxicological endpoint for determining the acceptable daily intake of disulfoton, both in the presence and the absence of metabolism during chlorination. Disulfoton rapidly reacted with free chlorine and completely disappeared within 0.25 h. Although the aqueous disulfoton solution did not induce anti-AChE activity before chlorination, the chlorinated samples did induce anti-AChE activity, both with (indirect toxicity) and without (direct toxicity) metabolism. These observations clearly indicated that disulfoton was converted into toxic TPs through reactions with free chlorine. Liquid chromatographic fractionation followed by an anti-AChE activity assay revealed that three TPs were responsible for the observed direct toxicity. Further mass spectrometric analyses showed that these TPs were disulfoton-oxon-sulfone, and mono- and dichloro-substituted derivatives of disulfoton-oxon-sulfoxide (O-(1-chloroethyl) S-[2-(ethanesulfinyl)ethyl] O-ethyl phosphorothioate and O-(1,2-dichloroethyl) S-[2-(ethanesulfinyl)ethyl] O-ethyl phosphorothioate, respectively), none of which were simply oxon. Results of the anti-AChE activity assay on the chemical standard of disulfoton-oxon-sulfone after metabolism and quantification of the disulfoton-oxon-sulfone in the chlorinated samples revealed that the observed indirect toxicity was solely induced by this TP. It is recommend that drinking water treatment plants that use free chlorine as a disinfectant monitor the concentrations of at least disulfoton-oxon-sulfone, which is commercially available, in finished water in addition to disulfoton itself, to ensure the safety of tap water.

Impact of pesticide exposure on auditory health: Mechanisms, efferent system disruption, and public health implications

Pesticide exposure has been linked to adverse effects on auditory health, impacting both peripheral and central auditory systems. Studies suggest that organophosphate, carbamate, organochlorine, and pyrethroid pesticides disrupt auditory processing through oxidative stress, neuroinflammation, and interference with cholinergic signaling. These disruptions may compromise sensory hair cells, spiral ganglion neurons, and auditory pathways, impairing precise signal transmission. The auditory efferent system, responsible for cochlear protection and auditory signal modulation, appears particularly susceptible to pesticide-induced alterations. This system relies on cholinergic transmission to regulate cochlear amplification and selective attention, functions that may be disrupted by pesticide exposure. Evidence from epidemiological and experimental studies highlights the potential for long-term auditory dysfunction in populations exposed to pesticides, with agricultural workers and their families facing elevated risks due to prolonged contact with agrochemicals. This review integrates findings on pesticide exposure and its implications for auditory health, discussing potential peripheral and central ototoxicity pathways. The cumulative effects of chronic exposure are emphasized, including the gradual degradation of auditory processing capabilities. Additionally, the need for targeted interventions, such as audiological monitoring and enhanced safety protocols, is addressed. Further research is critical to elucidate the mechanisms underlying pesticide-induced auditory damage and identify protective strategies. Such investigations can inform evidence-based policies to mitigate the public health impact of pesticide exposure while maintaining agricultural productivity. A multidisciplinary approach is essential to safeguard auditory health in vulnerable populations exposed to these environmental hazards.

N-acetylcysteine prevents cholinergic and non-cholinergic toxic effects induced by nerve agent poisoning in rats

Objective

Organophosphorus Nerve Agent, VX [(O-Ethyl S-diisopropylaminomethyl) methylphosphonothioate] compound interferes with acetylcholine signaling by targeting the AChE enzyme. Studies suggest that in nerve agents poisoning, non-cholinergic effects are also responsible for damage in peripheral tissues including long term damage in brain. Present study reports cholinergic and non-cholinergic effects of VX poisoning and their prevention by use of N-acetylcysteine (NAC) in addition to conventional antidotes atropine sulphate and 2-PAM chloride as an antioxidant. NAC was chosen being an approved drug for medical conditions including oxidative damage and as mucolytic.

Results

Results of the study showed that after 1x LD 50 exposure to VX and standard atropine and oxime therapy resulted in recovery of cholinesterase activity up to 51%, while additional NAC administration resulted in increased recovery up to 89% in brain cholinesterase activity. NAC also helped in maintaining intracellular and tissue GSH level, reduced ROS generation and lipid peroxidation. NAC treatment could able to reduce the lipid peroxidation (MDA) levels in liver of NAC administered groups as compared to standard treatment of atropine sulphate and PAM chloride at 10 LD 50 VX. Likewise, a 20% higher level of GSH was found in NAC treated group at 1x LD 50 dose in brain. Cell cycle analysis and histopathological results showed that NAC prevents VX induced damage.

Conclusion

it was found that use of antioxidant agent NAC along with standard atropine-oxime treatment is helpful in reducing the cholinergic and oxidative stress mediated toxicity induced by VX.

Mitochondrial Gene Expression of Three Different Dragonflies Under the Stress of Chlorpyrifos

Chlorpyrifos (CPF) is an organophosphate insecticide that is extensively utilized globally due to its effectiveness against over 200 pest species. CPF exhibits its toxicity primarily through the inhibition of the acetylcholinesterase (AChE) enzyme, while mitochondrial damage and dysfunction have also been observed. The present study quantified the transcript levels of mitochondria protein-coding genes (mtPCGs) using quantitative real-time polymerase chain reaction (RT-qPCR) in samples of larvae of three dragonfly species (A. parthenope, E. elegans, and G. confluens) under different levels of CPF stress. By exposing larvae from uncontaminated populations to 0.05 μg/L CPF for 24 h, the transcript levels of seven mtPCGs in A. parthenope were significantly increased (p < 0.05) by 1.89 ± 0.42-fold for COI, 4.30 ± 0.24-fold for COIII, 5.94 ± 0.17-fold for ND1, 4.69 ± 0.56-fold for ND2, 3.44 ± 0.48-fold for ND4, 2.19 ± 0.53-fold for ND4L, and 5.05 ± 0.36-fold for Cytb, respectively. In E. elegans, the transcript levels of ND1, ND2, and ND4 increased by 1.23 ± 0.15, 1.48 ± 0.31, and 1.98 ± 0.25-fold, respectively (p < 0.05). In G. confluens, the transcript levels of COI, COIII, and ND4 increased by 1.56 ± 0.13, 1.50 ± 0.26, and 3.74 ± 0.40-fold, respectively (p < 0.01). It was demonstrated that the transcript levels of different mtPCGs showed significant up-regulation in the three different dragonfly larvae under CPF stress in the absence of mortality. ND4 was significantly increased in all three species, indicating that it is an important target gene. The present study underscores the response of mitochondrial gene expression in larvae of three different species in response to CPF pollutants, indicating that pesticide influences can potentially alter mitochondrial gene expression and potentially act as a method for assessing aquatic ecosystem health.

Associations of Depression Score with Dialkyl Phosphate Metabolites in Urine: A Cross-Sectional Study

OBJECTIVES

Growing evidence suggests a link between organophosphate insecticides and depression disorder. These chemicals are metabolized and subsequently expelled through the urinary tract. The present study aims to investigate whether dialkyl phosphate metabolites associate with depression score and severity among the general population.

METHODS

This cross-sectional study used data from the National Health and Nutrition Examination Survey (NHANES). Depression was evaluated by the Patient Health Questionnaire-9 (PHQ-9). All urinary dialkyl phosphate metabolites were quantitatively analyzed. The survey's complex design parameters and sampling weights were considered.

RESULTS

3035 eligible individuals were included. The estimated prevalence of mild and major depression was 18.3% (95% confidence interval [CI]: 16.9-19.7%) and 9.9% (95% CI: 8.7-11.0%). For each incremental unit in the level of urinary dimethyl phosphate (DMP), individuals were found to have a higher depression score of 0.77 and a significantly increased odds ratio (OR) of 1.13 (95% CI: 1.12-1.13) for mild depression and 2.75 (95% CI: 2.74-2.76) for major depression.

CONCLUSIONS

Our findings indicate positive and independent associations between urinary dialkyl phosphate metabolites and an elevated risk of depression among the general population.

The ameliorative effect of chrysin on ovarian toxicity caused by methidathion in female rats

Introduction: Methidathion (MD) is commonly used in agriculture and has adverse effects on reproduction. Chrysin (CHR) has several advantageous properties, such as anti-inflammatory, anti-cancer, and antioxidant properties. The purpose of the current investigation was to assess CHR's therapeutic efficacy in reducing ovarian toxicity brought on by MD. Methods: Twenty-four female rats were divided into four groups of six animals each. Group 1 served as a control, while group 2 rats received MD (5 mg/kg). Rats in Group 3 received CHR at a dose of 50 mg/kg. Rats in group 4 received treatment with CHR after MD intoxication. Results and Discussion: Our research revealed that MD significantly (p < 0.001) increased the levels of MDA, caspase-3, FSH, LH, CA-125, and TNF-α but significantly (p < 0.001) decreased the levels of SOD, GSH, E2, and progesterone when compared to the control and CHR groups. After receiving CHR therapy, damage induced by MD was significantly (p < 0.001) repaired. Conclusion: This study showed that CHR could mitigate the adverse effects that MD causes to the ovaries by decreasing oxidative stress, inflammation, and apoptosis; improving antioxidant status; and restoring the correct ratio of sex hormones.

Mechanisms of Neurotoxicity of Organophosphate Pesticides and Their Relation to Neurological Disorders

Organophosphates (OPs) refers to a diverse group of phosphorus-containing organic compounds; they are widely used all over the world and have had an important beneficial impact on industrial and agricultural production and control of vector transmission. Exposure to OPs of different toxicities (high, moderate, slight, and low toxicity) can all have negative consequences on the nervous system, such as nausea, vomiting, muscle tremors, and convulsions. In severe cases, it can lead to respiratory failure or even death. Notably, OPs induce neuropathy in the nervous system through specific interactions with nicotinic or muscarinic receptors, phosphorylating acetylcholinesterase, or neuropathic target esterases. This review summarizes the possible toxicological mechanisms and their interplay underlying OP pesticide poisoning, including cholinesterase inhibition and non-cholinesterase mechanisms. It outlines the possible links between OP pesticide poisoning and neurological disorders, such as dementia, neurodevelopmental diseases, and Parkinson's disease. Additionally, it explores OP interactions' potential therapeutic implications that may help mitigate the deleterious impact of OPs on the nervous system.

Acute exposure to diisopropylfluorophosphate in mice results in persistent cognitive deficits and alterations in senescence markers in the brain

Organophosphates (OPs) are found in hundreds of important products used worldwide; however, they have been associated with adverse long-term health consequences ranging from neurodevelopmental deficits to age-related neurological diseases. OP exposure has also been implicated in Gulf War Illness; a cluster of medically unexplained chronic symptoms estimated to affect 25-32% of veterans of the Persian Gulf war in 1991. The development of multiple types of chronic illnesses in these veterans at an early age compared to the general population has led to the suggestion that they are experiencing signs of premature or accelerated aging. The process of cellular senescence and the development of the senescence-associated secretory phenotype (SASP) is believed to lead to chronic inflammation, chronic illnesses, as well as accelerated biological aging, and a role of environmental exposures in these processes has been suggested, but not extensively studied to date. In the studies described here, we evaluated the persistent effects of a single (acute) exposure of a representative nerve agent OP, diisopropylfluorophosphate (DFP) 4.0 mg/kg on cognitive function, noncognitive behaviors, cellular senescence markers and proinflammatory cytokines in the mouse brain. The results indicated modest, but persistent DFP-related impairments in spatial learning and working memory, but not contextual or cued fear conditioning. DFP exposure was also not associated with negative effects on weight or impairments of the various noncognitive (e.g., motor function or exploratory activity) behavioral assessments. Both histology and quantitative PCR experiments indicated that DFP was associated with persistent alterations in several senescence markers and proinflammatory cytokines in brain regions that are relevant to the performance of the memory-related tasks (e.g., hippocampus, prefrontal cortex). The results thus suggest that single acute exposures to OPs like DFP can lead to persistent impairments in specific domains of cognition that may be related to alterations in cellular senescence and inflammaging in the brain.

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.

Rejection of malathion by nanofiltration and reverse osmosis membranes exposed to foulant and two clean-in-place procedures

This research tested the treatment efficacy of an Energy Savings Nanofiltration 1 Low Fouling (ESNA 1-LF) nanofiltration (NF) and an Energy Saving Polyamide 2 (ESPA2) reverse osmosis (RO) membrane for removing malathion from water. Both membranes are of composite polyamide construction. The study included measuring malathion rejection using both pristine membranes and membranes exposed to a simulated secondary wastewater effluent foulant before and after two types of clean-in-place procedures. Across all conditions studied, malathion rejection ranged from 84 to 95% for the ESNA1-LF NF membrane and 77 to 94% for the ESPA2 RO membrane. Contact angle measurements were also collected for each membrane exposure condition. While the contact angle measurements indicated changes to the hydrophobicity of the selective layer of the membranes, they did not correlate to changes in the performance of malathion rejection. As expected, it was observed that malathion rejection improved with the introduction of foulant. Also, the clean-in-place procedures helped restore flux while maintaining malathion rejection.

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.

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 exposure were associated with an increased risk of T2DM and PDM, implying that OPPs might act an important role in the development of T2DM.

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.

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.