Elevated serum pesticide levels and risk for Alzheimer disease

Impact of long-term deltamethrin exposure on Alzheimer's-related neurodegeneration in rats

In recent years, epidemiological studies have emerged indicating a potential association between chronic exposure to pesticides and the development of chronic neurodegenerative nervous system diseases such as Alzheimer's disease. In this study, we aimed to investigate the potential role of long-term nonfatal exposure to Deltamethrin in spreading this disease. To this end, a range of aspects of brain damage were discussed in rats administered deltamethrin in oral doses of 0.65 mg/kg b.w. and 1.3 mg/kg b.w. for 30 days. The activation of beta-amyloid, the primary component of plaques characteristic of Alzheimer's disease, and the NG2, a type 1 transmembrane protein, was assessed by immunohistochemistry and western blot methods in rat brain. In addition, the expression level of the APP, GFAP, NfL, TNF-alpha, CXCL9, CCL5, and IL-1 alpha genes in deltamethrin-exposed brain tissue was measured using qRT-PCR. In addition, levels of pTau181 and Abeta42 were measured with ELISA. A strong positive immunohistochemical reaction for beta-amyloid was detected in the deltamethrin-exposed brain tissues. A decrease in NG2 immunofluorescence positivity was found in the application groups compared to the control group. It was demonstrated that deltamethrin exposure significantly up-regulated the expressions of APP, GFAP, NfL, TNF-alpha, CXCL9, CCL5, and IL-1 alpha genes, also significantly higher the levels of pTau181 and Abeta42 (pg/ml) in rat brain tissues. This study provides scientific evidence that exposure to chronic doses of deltamethrin may play a positive role in the development of diseases such as Alzheimer's. Future studies should investigate similar projects and expand knowledge on the topic.

Concentrations of DDT metabolites in different food items and public health risk in Africa regions: systematic review and metal analysis

Background

DDT (Dichlorodiphenyltrichloroethane) is a synthetic organochlorine pesticide used in agriculture and mosquito control but later banned due to its harmful effects on humans. It persists in the environment, biomagnified through the food chain, and poses serious health risks, including reproductive defect, cancer, and nervous system disorders. DDT has a long half-life and potential of long-range transport and continuing to contaminate long after use and remains to pose a global environmental and health concern. Therefore, this review was designed to assess the concentration of DDT metabolites (p,p'-DDT, p,p'-DDD, and p,p'-DDE) in various food items and evaluate the health risk to consumers in the African.

Methods

The preferred reporting item for systematic reviews and meta-analysis (PRISMA) protocol was used to conduct this work. SCOPUS, PubMed, Web of Science, Google Scholar, DOAJ, national repository, and MedNar were used to retrieve articles from October 1, 2023, to January 20, 2024. Meta-analysis data visualized using a forest plot. A random-effects model was applied when heterogeneity existed in overall mean concentration of DDT metabolites. The subgroup analysis, meta-regression, and sensitivity analysis was conducted and the Joanna Briggs Institute Critical Assessment tool to assess the quality of the studies.

Results

The overall mean concentrations of p,p'-DDT, p,p'-DDD and p,p'-DDE, regardless of the types of food items, were 0.188, 0.22, and 0.0878 mg/kg, respectively. Based on the type of food items, The current study found that residue levels of DDT metabolites in vegetables, milk, and cereals exceeded the Maximum Residue Limits (MRLs) set by FAO/WHO/EU (0.05, 0.02, and 0.05 mg/kg, respectively), while residue levels in meat, khat, and fruit were below the MRLs (5, 0.5, and 0.05 mg/kg, respectively). The findings of the health risk assessment revealed that consumers are prone to both carcinogenic and non-carcinogenic risks from DDT metabolites. The persistence and bioaccumulation of these metabolites, along with multiple exposure routes and improper handling, may increase long-term health risks, even at low doses. DDT metabolite levels in most food categories exceed recommended limits, posing significant health risks to consumers. To reduce reliance on DDT, effective and cost-efficient alternative insecticides and vector-control strategies must be developed. Promoting environmental management, improving housing, and implementing farm-to-fork risk-based actions, such as Hazard Analysis and Critical Control Points (HACCP), across the food chain are crucial to mitigating the adverse effects of DDT exposure in the African region.

Effects of Pesticide Exposure on Neuroinflammation and Microglial Gene Expression: Relevance to Mechanisms of Alzheimer's Disease Risk

Background

Alzheimer's disease (AD) is characterized by the presence of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation. Previously, we reported serum levels of dichlorodiphenyldichloroethylene (DDE), the primary metabolite of the pesticide dichlorodiphenyltrichloroethane (DDT), were significantly higher in AD patients compared to age-matched controls and that DDT exposure worsened AD pathology in animal models.

Objective

Here, we investigated the effect of DDT on neuroinflammation in primary mouse microglia (PMG) and C57BL/6J mice.

Methods

Effects of DDT on inflammation and disease-associated microglia were determined in primary mouse microglia and C57BL/6J mice.

Results

PMG exposed to DDT (0.5-5.0 µM) elicited a ∼2-3-fold increase in Il-1b mRNA levels, with similar concentration-dependent upregulation in Il-6, Nos2, and Tnfa . These effects were blocked by the sodium channel antagonist tetrodotoxin, demonstrating the role of DDT-microglial sodium channel interactions in mediating this response. Additionally, NOS2 protein levels increased by ∼1.5-2-fold, while TNFa was elevated by 2-4-fold. C57BL/6J male and female mice exposed to DDT (30 mg/kg) demonstrated significantly increased mRNA levels of Nos2 , Il-1b , and Il-6 in the frontal cortex (1.5-2.3-fold), and Nos2 , Il-1b, and Tnfa (1.5-1.8-fold) in the hippocampus. Furthermore, microglial homeostatic genes, Cx3cr1 , P2ry12, and Tmem119 , were downregulated, while stage 1 disease-associated microglia genes were upregulated both in vitro and in vivo . Notably, Apoe and Trem2 were only upregulated in the frontal cortex and hippocampus of females.

Conclusion

These data indicate that DDT increases neuroinflammation, which may result from direct actions of DDT on microglia, providing a novel pathway by which DDT may contribute to AD risk.

Massive changes in gene expression and their cause(s) can be a unifying principle in the pathobiology of Alzheimer's disease

Understanding of the biology of Alzheimer's disease (AD) has long been fragmented, with various investigators concentrating on amyloid beta (Aβ) or tau, inflammation, cell death pathways, misfolded proteins, glia, and more. Yet data from multiple authors has repeatedly shown altered expression of myriad genes related to these seemingly disparate phenomena. In 2022, Morgan et al. organized the massive data on changes in AD in a meticulous survey of the literature and related these changes to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Their data showed that 91% of the known KEGG pathways are involved in AD and that many of these pathways are represented by the known cellular/molecular phenomena of AD. Such data then raise the fundamental question: What mechanism(s) may be responsible for such widespread changes in gene expression? We review evidence for a unifying model based on sequestrations in stress granules and alteration of nucleocytoplasmic transport in AD. HIGHLIGHTS: In Alzheimer's disease (AD), critical changes take place in neurons before the appearance of plaques or tangles. Addressing these early changes provides a path to early detection and effective intervention in AD.

The Role of Genetic, Environmental, and Dietary Factors in Alzheimer's Disease: A Narrative Review

Alzheimer's disease (AD) is one of the most common and severe forms of dementia and neurodegenerative disease. As life expectancy increases in line with developments in medicine, the elderly population is projected to increase in the next few decades; therefore, an increase in the prevalence of some diseases, such as AD, is also expected. As a result, until a radical treatment becomes available, AD is expected to be more frequently recorded as one of the top causes of death worldwide. Given the current lack of a cure for AD, and the only treatments available being ones that alleviate major symptoms, the identification of contributing factors that influence disease incidence is crucial. In this context, genetic and/or epigenetic factors, mainly environmental, disease-related, dietary, or combinations/interactions of these factors, are assessed. In this review, we conducted a literature search focusing on environmental factors such as air pollution, toxic elements, pesticides, and infectious agents, as well as dietary factors including various diets, vitamin D deficiency, social factors (e.g., tobacco and alcohol use), and variables that are affected by both environmental and genetic factors, such as dietary behavior and gut microbiota. We also evaluated studies on the beneficial effects of antibiotics and diets, such as the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) and Mediterranean diets.

Dietary interventions in mitigating the impact of environmental pollutants on Alzheimer's disease - A review

Numerous studies linking environmental pollutants to oxidative stress, inflammation, and neurotoxicity have assigned pollutants to several neurodegenerative disorders, including Alzheimer's disease (AD). Heavy metals, pesticides, air pollutants, and endocrine disruptor chemicals have been shown to play important roles in AD development, with some traditional functions in amyloid-β formation, tau kinase action, and neuronal degeneration. However, pharmacological management and supplementation have resulted in limited improvement. This raises the interesting possibility that activities usually considered preventive, including diet, exercise, or mental activity, might be more similar to treatment or therapy for AD. This review focuses on the effects of diet on the effects of environmental pollutants on AD. One of the primary issues addressed in this review is a group of specific diets, including the Mediterranean diet (MeDi), Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH intervention for Neurodegenerative Delay (MIND), which prevent exposure to these toxins. Such diets have been proven to decrease oxidative stress and inflammation, which are unfavorable for neuronal growth. Furthermore, they contribute to positive changes in the composition of the human gut microbiota and thus encourage interactions in the Gut-Brain Axis, reducing inflammation caused by pollutants. This review emphasizes a multi-professional approach with reference to nutritional activities that would lower the neurotoxic load in populations with a high level of exposure to pollutants. Future studies focusing on diet and environment association plans may help identify preventive measures aimed at enhancing current disease deceleration.

Melatonin attenuates affective disorders and cognitive deficits induced by perinatal exposure to a glyphosate-based herbicide via antioxidant pathway in adult male and female rats

The massive use of herbicides, particularly glyphosate-based herbicides (GBHs), raises several worries, notably their neurotoxic effects. Several studies have explored the consequences of developmental exposure. Our work aims to determine the impact of maternal exposure to GBH on behavioral disorders and memory deficits, as well as the involvement of oxidative stress in the hippocampus and prefrontal cortex. In addition, our study explores the neuroprotective properties of melatonin in male and female offspring. Pregnant Wistar rats were injected with GBH 75 mg/kg during gestation and lactation. After weaning, the offspring were treated with melatonin (4 mg/kg) from postnatal days 30-58. Our results show that GBH increases anxiety-like behavior levels in offspring, as well as depression-like behavior. GBH also impairs working memory in progeny. While markers of oxidative stress show a disturbance in lipid peroxidation and catalase activity, with a more pronounced effect in females, on the other hand, melatonin considerably attenuated the neurotoxic impact observed in the offspring, with higher efficacy in females. The oxidative stress results confirm the antioxidant power of melatonin to counteract the damaging effects of exposure to environmental contaminants such as glyphosate-based pesticides. It will then be interesting to further our work to fully understand the sex-dependent effect of melatonin.

Salvianolic acids modulate lifespan and gut microbiota composition in amyloid-β-expressing Drosophila melanogaster

Alzheimer's disease (AD), a form of neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ), hyperphosphorylated Tau, and neuroinflammation. The increasing population affected by AD urges for the development of effective treatments. The correlation between AD and gut microbiome remains underexplored, potentially providing a better understanding of the disease. Salvianolic acid A (Sal A) and salvianolic acid B (Sal B) are the active components extracted from Salvia miltiorrhiza (Danshen), and their antioxidant, anti-inflammation and Aβ inhibition activities were shown previously. In this study, these compounds were used to investigate their effects on Aβ toxicity, using Drosophila melanogaster expressing human Aβ42 as the model organism, by examining their lifespan and changes in gut bacterial communities. The study used two batches of flies, reared on food with or without methylparaben (MP) supplementation to evaluate the influence of MP on this animal model during pharmacological studies. MP is a common antimicrobial agent used in flies' food. The treatment of Sal A prolonged the lifespan of Aβ-expressing flies reared on MP-supplemented food significantly (P < 0.001), but not those without MP. The lifespan of Sal B-treated flies did not show a significant difference compared to untreated flies for both groups reared on food with and without MP. Sal A-treated flies in the presence of MP exhibited a lower abundance of Corynebacterium and Enterococcus than the untreated flies, while Lactiplantibacillus was the most dominant taxa. Urea cycle was predicted to be predominant in this group compared to the untreated group. The control group, Aβ-expressing flies treated with Sal A and Sal B on MP-supplemented food had improved lifespan compared to their respective groups reared on food without MP, while untreated Aβ-expressing flies was the exception. The gut microbiota composition of flies reared on MP-supplemented food was also significantly different from those without MP (P < 0.001).

Association between dietary exposure to chemical contaminants and risk of dementia in older persons

BACKGROUND

Diet is a major route of exposure to potentially neurotoxic chemicals, yet the epidemiological association of diet contaminants with dementia is unknown. We studied the link between dietary exposure to multiple chemicals and dementia risk in older persons, considering interaction with dietary fat content, which may modify the bioavailability and toxicity of (lipophilic) chemicals.

METHODS

We included 1,288 non-demented participants from the French Three-City cohort who answered a food frequency questionnaire and 24-hour recall at baseline and were followed for incident dementia. Dietary exposure to 167 contaminants was assessed by combining food intakes with food chemical content from the French second Total Diet Study. We assessed the relation of each individual contaminant with dementia risk using multivariable-adjusted Cox models, exploring effect modification by high-fat diet (>35 % energy from fat). Among high-fat diet consumers, we looked for a signature of contaminants associated with dementia using elastic-net penalization and assess their joint effect.

RESULTS

Participants were 76 years-old on average at baseline and 62 % were women. In total, 314 individuals developed dementia over a median 10 years. No contaminant was associated with dementia in the whole population. However, having a high-fat diet was a strong effect modifier for 85 contaminants (FDR-corrected p < 0.05 for interactions) in single-chemical analyses, so that higher intakes were significantly associated with higher dementia risk among high-fat consumers only (n = 386). Among them, a multi-chemical approach revealed a signature of 9 contaminants related to dementia, including 4 perfluoroalkyl substances, 2 flame retardants hexabromocyclododecane (HBCDD) congeners, 2 mycotoxins, and nitrites. This selection included two top hits from the single-chemical analyses (α-HBCDD and perfluorooctanesulfonic acid [PFOS]), and was mainly provided by delicatessen meat, seafood and bread/crispbread.

CONCLUSION

In this large population-based study, dietary exposure to several chemicals was associated with higher dementia risk among older persons consuming > 35 % energy from fat in diet.

Impact of glyphosate-based herbicide exposure through maternal milk on offspring's antioxidant status, neurodevelopment, and behavior

Glyphosate-based Herbicide (GBH) is a widely used pesticide that functions as a broad-spectrum, non-selective herbicide. Despite advanced research to describe the neurotoxic potential of GBH, the harmful effects on maternal behavior and neurodevelopment of offspring remain unclear. This study was conducted to highlight the effects of GBH on the antioxidant system, anxiety traits, social interaction, and cognitive and sensorimotor functions in pups exposed to 25 or 50 mg/l daily via their mother's milk. Concerning the biochemical biomarkers, GBH administered during the early stages of development negatively affected the status of antioxidant enzymes and lipid peroxidation in the brain structures of the pups. Furthermore, our results showed a significant decrease in acetylcholinesterase (AChE) specific activity within the brains of treated pups. The results of the behavioral tests indicated that the treated offspring developed anxiety, memory, and sociability disorders, as evidenced by the Open Field, Y-maze, object recognition task, and social interaction tests. Through neurodevelopmental testing, we also showed sensorimotor impairment (righting reflex and negative geotaxis) and abnormal maternal behavior. Altogether, our study clearly demonstrates that the developing brain is sensitive to GBH.

Widespread occurrence of pesticides in low-income housing

BACKGROUND

Low socioeconomic status (SES) residents living in social housing, which is subsidized by government or government-funded agencies, may have higher exposures to pesticides used in indoor residences since pesticides are applied due to structural deficiencies, poor maintenance, etc. OBJECTIVE: To estimate exposure of residents in low-SES social housing built in the 1970s to legacy and current-use pesticides and to investigate factors related to exposures.

METHODS

Twenty-eight particle-phase pesticides were measured in the indoor air of 46 units in seven low-income social housing, multi-unit residential buildings (MURBs) in Toronto, Canada using portable air cleaners deployed for 1 week in 2017. Pesticides analyzed were legacy and current use in the classes: organochlorines, organophosphates, pyrethroids, and strobilurins.

RESULTS

At least one pesticide was detected in 89% of the units with detection frequencies (DF) for individual pesticides of up to 50%, including legacy organochlorines and current-use pesticides. Current-use pyrethroids had the highest DF and concentrations, with the highest particle-phase concentration for pyrethrin I at 32,000 pg/m3. Heptachlor, restricted for use in Canada in 1985, had the highest estimated maximum total air (particle plus gas phase) concentration of 443,000 pg/m3. Heptachlor, lindane, endosulfan I, chlorothalonil, allethrin, and permethrin (except in one study) had higher concentrations than those measured in low-income residences reported elsewhere. In addition to the intentional use of pesticides to control pests and their use in building materials and paints, tobacco smoking was significantly correlated with the concentrations of five pesticides used on tobacco crops. The distribution of pesticides with high DF in individual buildings suggested that pest eradication programs by the building management and/or pesticide use by residents were the major sources of measured pesticides.

IMPACT

Low-income social housing fills a much-needed demand, but the residences are prone to pest infestation and hence pesticide use. We found exposure to at least 1 of 28 particle-phase pesticides in 89% of all 46 units tested, with the highest DF and concentrations for current-use pyrethroids and long-banned organochlorines (e.g., DDT, heptachlor) due to very high persistence indoors. Also measured were several pesticides not registered for use indoors, e.g., strobilurins used to treat building materials and pesticides used on tobacco crops. These results, which are the first Canadian data for most pesticides indoors, show widespread exposure to numerous pesticides.

Sesamin Exerts an Antioxidative Effect by Activating the Nrf2 Transcription Factor in the Glial Cells of the Central Nervous System in Drosophila Larvae

Sesame seeds are abundant in sesamin, which exerts health-promoting effects such as extending the lifespan of adult Drosophila and suppressing oxidative stress by activating the Nrf2 transcription factor. Here, we investigated whether sesamin activated Nrf2 in larval tissues and induced the expression of Nrf2 target genes. In the sesamin-fed larvae, Nrf2 was activated in the central nervous system (CNS), gut, and salivary glands. The ectopic expression of Keap1 in glial cells inhibited sesamin-induced Nrf2 activation in the whole CNS more than in the neurons, indicating that sesamin activates Nrf2 in glia efficiently. We labeled the astrocytes as well as cortex and surface glia with fluorescence to identify the glial cell types in which Nrf2 was activated; we observed their activation in both cell types. These data suggest that sesamin may stimulate the expression of antioxidative genes in glial cells. Among the 17 candidate Nrf2 targets, the mRNA levels of Cyp6a2 and Cyp6g1 in cytochrome P450 were elevated in the CNS, gut, and salivary glands of the sesamin-fed larvae. However, this elevation did not lead to resistance against imidacloprid, which is detoxified by these enzymes. Our results suggest that sesamin may exert similar health-promoting effects on the human CNS and digestive tissues.

Enhancing of cerebral Abeta clearance by modulation of ABC transporter expression: a review of experimental approaches

Clearance of amyloid-beta (Aβ) from the brain is impaired in both early-onset and late-onset Alzheimer's disease (AD). Mechanisms for clearing cerebral Aβ include proteolytic degradation, antibody-mediated clearance, blood brain barrier and blood cerebrospinal fluid barrier efflux, glymphatic drainage, and perivascular drainage. ATP-binding cassette (ABC) transporters are membrane efflux pumps driven by ATP hydrolysis. Their functions include maintenance of brain homeostasis by removing toxic peptides and compounds, and transport of bioactive molecules including cholesterol. Some ABC transporters contribute to lowering of cerebral Aβ. Mechanisms suggested for ABC transporter-mediated lowering of brain Aβ, in addition to exporting of Aβ across the blood brain and blood cerebrospinal fluid barriers, include apolipoprotein E lipidation, microglial activation, decreased amyloidogenic processing of amyloid precursor protein, and restricting the entrance of Aβ into the brain. The ABC transporter superfamily in humans includes 49 proteins, eight of which have been suggested to reduce cerebral Aβ levels. This review discusses experimental approaches for increasing the expression of these ABC transporters, clinical applications of these approaches, changes in the expression and/or activity of these transporters in AD and transgenic mouse models of AD, and findings in the few clinical trials which have examined the effects of these approaches in patients with AD or mild cognitive impairment. The possibility that therapeutic upregulation of ABC transporters which promote clearance of cerebral Aβ may slow the clinical progression of AD merits further consideration.

Peripheral HMGB1 is linked to O3 pathology of disease-associated astrocytes and amyloid

INTRODUCTION

Ozone (O3) is an air pollutant associated with Alzheimer's disease (AD) risk. The lung-brain axis is implicated in O3-associated glial and amyloid pathobiology; however, the role of disease-associated astrocytes (DAAs) in this process remains unknown.

METHODS

The O3-induced astrocyte phenotype was characterized in 5xFAD mice by spatial transcriptomics and proteomics. Hmgb1fl/fl LysM-Cre+ mice were used to assess the role of peripheral myeloid cell high mobility group box 1 (HMGB1).

RESULTS

O3 increased astrocyte and plaque numbers, impeded the astrocyte proteomic response to plaque deposition, augmented the DAA transcriptional fingerprint, increased astrocyte-microglia contact, and reduced bronchoalveolar lavage immune cell HMGB1 expression in 5xFAD mice. O3-exposed Hmgb1fl/fl LysM-Cre+ mice exhibited dysregulated DAA mRNA markers.

DISCUSSION

Astrocytes and peripheral myeloid cells are critical lung-brain axis interactors. HMGB1 loss in peripheral myeloid cells regulates the O3-induced DAA phenotype. These findings demonstrate a mechanism and potential intervention target for air pollution-induced AD pathobiology.

HIGHLIGHTS

Astrocytes are part of the lung-brain axis, regulating how air pollution affects plaque pathology. Ozone (O3) astrocyte effects are associated with increased plaques and modified by plaque localization. O3 uniquely disrupts the astrocyte transcriptomic and proteomic disease-associated astrocyte (DAA) phenotype in plaque associated astrocytes (PAA). O3 changes the PAA cell contact with microglia and cell-cell communication gene expression. Peripheral myeloid cell high mobility group box 1 regulates O3-induced transcriptomic changes in the DAA phenotype.

Assessing the contribution of the chemical exposome to neurodegenerative disease

Over the past few decades, numerous environmental chemicals from solvents to pesticides have been suggested to be involved in the development and progression of neurodegenerative diseases. Most of the evidence has accumulated from occupational or cohort studies in humans or laboratory research in animal models, with a range of chemicals being implicated. What has been missing is a systematic approach analogous to genome-wide association studies, which have identified dozens of genes involved in Alzheimer's disease, Parkinson's disease and other neurodegenerative diseases. Fortunately, it is now possible to study hundreds to thousands of chemical features under the exposome framework. This Perspective explores how advances in mass spectrometry make it possible to generate exposomic data to complement genomic data and thereby better understand neurodegenerative diseases.

Environmental pesticide exposure and Alzheimer's disease in southern Spain: A cross-sectional study

The intensive cultivation under plastic in southern Spain has made the agricultural model highly productive. Although strict regulations on pesticide usage exist, exposure to pesticides in the environment has been associated with an increased appearance of neurodegenerative diseases including Alzheimer's disease (AD). A cross-sectional study was performed to examine the prevalence and risk of AD related to pesticide exposure in Andalusia (Spain). We utilized the Odds Ratio statistical test to compare the prevalence rate of AD in the exposed and unexposed areas. 40,044 cases were collected from computerized hospital records between 2000 and 2021. Districts with higher pesticide use showed significantly higher prevalence rates and increased risk of developing AD, compared to those with lower pesticide use. These findings provide further evidence supporting an increased risk of AD following environmental exposure to pesticides at the level of the general population.

Pesticides impacts on human health and the environment with their mechanisms of action and possible countermeasures

Pesticides are chemical constituents used to prevent or control pests, including insects, rodents, fungi, weeds, and other unwanted organisms. Despite their advantages in crop production and disease management, the use of pesticides poses significant hazards to the environment and public health. Pesticide elements have now perpetually entered our atmosphere and subsequently contaminated water, food, and soil, leading to health threats ranging from acute to chronic toxicities. Pesticides can cause acute toxicity if a high dose is inhaled, ingested, or comes into contact with the skin or eyes, while prolonged or recurrent exposure to pesticides leads to chronic toxicity. Pesticides produce different types of toxicity, for instance, neurotoxicity, mutagenicity, carcinogenicity, teratogenicity, and endocrine disruption. The toxicity of a pesticide formulation may depend on the specific active ingredient and the presence of synergistic or inert compounds that can enhance or modify its toxicity. Safety concerns are the need of the hour to control contemporary pesticide-induced health hazards. The effectiveness and implementation of the current legislature in providing ample protection for human health and the environment are key concerns. This review explored a comprehensive summary of pesticides regarding their updated impacts on human health and advanced safety concerns with legislation. Implementing regulations, proper training, and education can help mitigate the negative impacts of pesticide use and promote safer and more sustainable agricultural practices.

Educating the public about toxic chemicals that we unknowingly consume: A potential important role for the practicing pharmacists

Although lifestyle factors are important in determining the overall health of the general public, the impact of endocrine-disrupting chemicals and other environmental toxins is often underestimated. There is growing evidence indicating that these substances have a significant influence on metabolic health, cancer risks, and fertility. Therefore, it is the shared responsibility of public health officials and health care professionals, including pharmacists, to educate the public about the potential exposure to harmful toxins present in our immediate surroundings, particularly toxic chemicals that we unknowingly consume. Pharmacists play a crucial role in promoting and maintaining public health. This article reviews a selection of common toxins and their significant health risks. Pharmacists can prepare educational materials, hold presentations at public libraries, and participate in scientific meetings to disseminate knowledge about the potential exposure to these toxins, their detrimental impact on health, and strategies and recommendations to minimize exposure.

[The exposome in the context of preventive measures for Alzheimer's and Parkinson's diseases]

BACKGROUND

Preventive measures addressing the exposome can counteract neurodegenerative diseases.

OBJECTIVE

This article gives an overview on the influence of general and individual exogenous factors (environmental influences and lifestyle changes) as well as endogenous factors (e.g. metabolic alterations) on the development and progression of Alzheimer's disease (AD) and Parkinson's disease (PD).

METHODS

Summary and evaluation of current scientific studies and evidence regarding the exposome and prevention of AD and PD.

RESULTS

Numerous studies could demonstrate a potential influence of environmental influences associated with industrialization (general exogenous factors), such as pesticides, solvents or air pollution on the development of AD and PD. Additionally, individually addressable changes of lifestyle (individual exogenous factors, e.g. physical activity, cognitive stimulation, nutrition and sleep) contribute to disease protection and modification and are becoming increasingly more important in light of still limited therapeutic interventions. Moreover, other exogenous factors (medication, noise pollution, head trauma and heavy metals) are discussed as risk factors for AD and/or PD. Endogenous factors (e.g., changes of the enteral microbiome, systemic inflammation and neuroinflammation, metabolic changes) can contribute to disease development by a higher potential for interacting with exogenous factors.

CONCLUSION

Despite the comprehensive scientific evidence confirming the significance of the exposome for the pathogenesis of AD and PD, the great potential of preventive measures has not yet been exploited. A clarification of the high potential of lifestyle changes should be a therapeutic standard not only for individuals with manifest PD/AD but also for individuals with a risk profile or with suspected prodromal disease. Further investigations on the influence of environmental factors and the implementation of preventive strategies to avoid exposure should be the focus of international efforts.

Effect of pesticides on phosphorylation of tau protein, and its influence on Alzheimer's disease

Alzheimer's disease (AD) is a progressive and neurodegenerative illness which results in alterations in cognitive development. It is characterized by loss/dysfunction of cholinergic neurons, and formation of amyloid plaques, and formation of neurofibrillary tangles, among other changes, due to hyperphosphorylation of tau-protein. Exposure to pesticides in humans occurs frequently due to contact with contaminated food, water, or particles. Organochlorines, organophosphates, carbamates, pyrethroids and neonicotinoids are associated with the most diagnosed incidents of severe cognitive impairment. The aim of this study was to determine the effects of these pesticides on the phosphorylation of tau protein, and its cognitive implications in the development of AD. It was found that exposure to pesticides increased the phosphorylation of tau protein at sites Ser198, Ser199, Ser202, Thr205, Ser396 and Ser404. Contact with these chemicals altered the enzymatic activities of cyclin-dependent kinase 5 and glycogen synthase kinase 3 beta, and protein phosphatase-2A. Moreover, it altered the expression of the microtubule associated protein tau gene, and changed levels of intracellular calcium. These changes affected tau protein phosphorylation and neuroinflammation, and also increased oxidative stress. In addition, the exposed subjects had poor level of performance in tests that involved evaluation of novelty, as test on verbal, non-verbal, spatial memory, attention, and problem-solving skills.

The herbicides glyphosate and glufosinate and the cyanotoxin β-N-methylamino-l-alanine induce long-term motor disorders following postnatal exposure: the importance of prior asymptomatic maternal inflammatory sensitization

Background

Prenatal maternal immune activation (MIA) and/or perinatal exposure to various xenobiotics have been identified as risk factors for neurological disorders, including neurodegenerative diseases. Epidemiological data suggest an association between early multi-exposures to various insults and neuropathologies. The "multiple-hit hypothesis" assumes that prenatal inflammation makes the brain more susceptible to subsequent exposure to several kinds of neurotoxins. To explore this hypothesis and its pathological consequences, a behavioral longitudinal procedure was performed after prenatal sensitization and postnatal exposure to low doses of pollutants.

Methods

Maternal exposure to an acute immune challenge (first hit) was induced by an asymptomatic lipopolysaccharide (LPS) dose (0.008 mg/kg) in mice. This sensitization was followed by exposing the offspring to environmental chemicals (second hit) postnatally, by the oral route. The chemicals used were low doses of the cyanotoxin β-N-methylamino-l-alanine (BMAA; 50 mg/kg), the herbicide glufosinate ammonium (GLA; 0.2 mg/kg) or the pesticide glyphosate (GLY; 5 mg/kg). After assessing maternal parameters, a longitudinal behavioral assessment was carried out on the offspring in order to evaluate motor and emotional abilities in adolescence and adulthood.

Results

We showed that the low LPS immune challenge was an asymptomatic MIA. Even though a significant increase in systemic pro-inflammatory cytokines was detected in the dams, no maternal behavioral defects were observed. In addition, as shown by rotarod assays and open field tests, this prenatal LPS administration alone did not show any behavioral disruption in offspring. Interestingly, our data showed that offspring subjected to both MIA and post-natal BMAA or GLA exposure displayed motor and anxiety behavioral impairments during adolescence and adulthood. However, this synergistic effect was not observed in the GLY-exposed offspring.

Conclusion

These data demonstrated that prenatal and asymptomatic immune sensitization represents a priming effect to subsequent exposure to low doses of pollutants. These double hits act in synergy to induce motor neuron disease-related phenotypes in offspring. Thus, our data strongly emphasize that multiple exposures for developmental neurotoxicity regulatory assessment must be considered. This work paves the way for future studies aiming at deciphering cellular pathways involved in these sensitization processes.

Bioelectrochemical platform with human monooxygenases: FMO1 and CYP3A4 tandem reactions with phorate

It is highly advantageous to devise an in vitro platform that can predict the complexity of an in vivo system. The first step of this process is the identification of a xenobiotic whose monooxygenation is carried out by two sequential enzymatic reactions. Pesticides are a good model for this type of tandem reactions since in specific cases they are initially metabolised by human flavin-containing monooxygenase 1 (hFMO1), followed by cytochrome P450 (CYP). To assess the feasibility of such an in vitro platform, hFMO1 is immobilised on glassy carbon electrodes modified with graphene oxide (GO) and cationic surfactant didecyldimethylammonium bromide (DDAB). UV-vis, contact angle and AFM measurements support the effective decoration of the GO sheets by DDAB which appear as 3 nm thick structures. hFMO1 activity on the bioelectrode versus three pesticides; fenthion, methiocarb and phorate, lead to the expected sulfoxide products with K_M values of 29.5 ± 5.1, 38.4 ± 7.5, 29.6 ± 4.1 µM, respectively. Moreover, phorate is subsequently tested in a tandem system with hFMO1 and CYP3A4 resulting in both phorate sulfoxide as well as phoratoxon sulfoxide. The data demonstrate the feasibility of using bioelectrochemical platforms to mimic the complex metabolic reactions of xenobiotics within the human body.

Metabolic Consequences of the Water We Drink: A Study Based on Field Evidence and Animal Model Experimentation

The effect of the chronic consumption of water contaminated with residual concentrations of DDT's metabolites (DDD-dichlorodiphenyldichloroethane and DDE-dichlorodiphenyldichloroethylene) found in the environment were evaluated on the biometric, hematological and antioxidant system parameters of the hepatic, muscular, renal and nervous tissues of Wistar rats. The results showed that the studied concentrations (0.002 mg.L^-1 of DDD plus 0.005 mg.L^-1 of DDE) could not cause significant changes in the hematological parameters. However, the tissues showed significant alteration in the activity of the antioxidant system represented by the increase in the activity of the enzymes gluthathione S-transferases in the liver, superoxide dismutase in the kidney, gluthathione peroxidase in the brain, and several changes in enzymatic activity in muscle (SOD, GPx and LPO). The enzymes alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) were also evaluated for the amino acids' metabolism in the liver, with ALT showing a significant increase in the exposed animals. In the integrative analysis of biomarkers (Permanova and PCOA), the studied concentrations showed possible metabolic changes and damage to cellular structures evidenced by increased oxidative stress and body weight gain among the treated animals. This study highlights the need for further studies on the impact of banned pesticides still present in soils that may induce adverse effects in organisms that may prevail in future generations and the environment.

Assessment of risks, implications, and opportunities of waterborne neurotoxic pesticides

Pesticides are a well-known family of chemicals that have contaminated water systems globally. Four common subfamilies of pesticides include organochlorines, organophosphates, pyrethroids, and carbamate insecticides which have been shown to adversely affect the human nervous system. Studies have shown a link between pesticide exposure and decreased viability, proliferation, migration, and differentiation of murine neural stem cells. Besides human exposure directly through water systems, additional factors such as pesticide bioaccumulation, biomagnification and potential synergism due to co-exposure to other environmental contaminants must be considered. A possible avenue to investigate the molecular mechanisms and biomolecules impacted by the various classes of pesticides includes the field of -omics. Discovery of the precise molecular mechanisms behind pesticide-mediated neurodegenerative disorders may facilitate development of targeted therapeutics. Likewise, discovery of pesticide biodegradation pathways may enable novel approaches for water system bioremediation using genetically engineered microorganisms. In this mini-review, we discuss recently established harmful impacts of various categories of pesticides on the nervous system and the application of -omics field for discovery, validation, and mitigation of pesticide neurotoxicity.

Validation of a Modified QuEChERS Method for the Determination of Selected Organochlorine Compounds in Honey

Honey is considered to be a health-promoting food product. Therefore, it is assumed that it should be free of contaminants. Although the use of organochlorine pesticides (OCPs) was banned a few decades ago in developed countries, persistent organic pollutants (POPs) are still detected in various environmental and biological matrices, including food. These contaminants exhibit toxic properties and bioaccumulate in some food chains. The validation of a modified QuEChERS extraction method was successfully performed for o,p'-DDT, o,p'-DDE, o,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD, heptachlor and dieldrin. 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) was used as an internal standard. The modification involved changing the solvent from acetonitrile to n-hexane after extraction. Quantitation was carried out using gas chromatography with an electron capture detector (µECD). The mean recovery values for o,p'-DDT, o,p'-DDE, o,p'-DDD, p,p'-DDT, p,p'-DDE, p,p'-DDD and dieldrin, spiked at 2.9 ng/g and 20 ng/g, ranged from 64.7% to 129.3%, and, for heptachlor spiked at 5.6 ng/g and 20 ng/g, ranged from 68.0% to 88.3%. The relative standard deviation (RSD) for these concentrations did not exceed 20%, and the within-laboratory reproducibility was below 20%, except o,p'-DDE and p,p'-DDT, which were 25.2% and 20.7%, respectively. This modified QuEChERS extraction method for selected organochlorine compounds was demonstrated as effective for routine testing in honey.

Neurotoxicity of pesticides in the context of CNS chronic diseases

Following the introduction and application of pesticides in human life, they have always been along with health concerns both in acute poisoning and chronic toxicities. Neurotoxicity of pesticides in chronic exposures has been known as one of the most important human health problems, as most of these chemicals act through interacting with some elements of nervous system. Pesticide-induced neurotoxicity can be defined in different categories of neurological disorders including neurodegenerative (Alzheimer, Parkinson, amyotrophic lateral sclerosis, multiple sclerosis), neurodevelopmental (attention deficit hyperactivity disorder, autism spectrum disorders, developmental delay, and intellectual disability), neurobehavioral and neuropsychiatric (depression/suicide attempt, anxiety/insomnia, and cognitive impairment) disorders some of which are among the most debilitating human health problems. In this review, neurotoxicity of pesticides in the mentioned categories and sub-categories of neurological diseases have been systematically presented in relation to different route of exposures including general, occupational, environmental, prenatal, postnatal, and paternal.

Dementia Prevention in Clinical Practice

Over 55 million people globally are living with dementia and, by 2050, this number is projected to increase to 131 million. This poses immeasurable challenges for patients and their families and a significant threat to domestic and global economies. Given this public health crisis and disappointing results from disease-modifying trials, there has been a recent shift in focus toward primary and secondary prevention strategies. Approximately 40% of Alzheimer's disease (AD) cases, which is the most common form of dementia, may be prevented or at least delayed. Success of risk reduction studies through addressing modifiable risk factors, in addition to the failure of most drug trials, lends support for personalized multidomain interventions rather than a "one-size-fits-all" approach. Evolving evidence supports early intervention in at-risk patients using individualized interventions directed at modifiable risk factors. Comprehensive risk stratification can be informed by emerging principals of precision medicine, and include expanded clinical and family history, anthropometric measurements, blood biomarkers, neurocognitive evaluation, and genetic information. Risk stratification is key in differentiating subtypes of dementia and identifies targetable areas for intervention. This article reviews a clinical approach toward dementia risk stratification and evidence-based prevention strategies, with a primary focus on AD.

Gene-environment interactions in Alzheimer disease: the emerging role of epigenetics

With the exception of a few monogenic forms, Alzheimer disease (AD) has a complex aetiology that is likely to involve multiple susceptibility genes and environmental factors. The role of environmental factors is difficult to determine and, until a few years ago, the molecular mechanisms underlying gene-environment (G × E) interactions in AD were largely unknown. Here, we review evidence that has emerged over the past two decades to explain how environmental factors, such as diet, lifestyle, alcohol, smoking and pollutants, might interact with the human genome. In particular, we discuss how various environmental AD risk factors can induce epigenetic modifications of key AD-related genes and pathways and consider how epigenetic mechanisms could contribute to the effects of oxidative stress on AD onset. Studies on early-life exposures are helping to uncover critical time windows of sensitivity to epigenetic influences from environmental factors, thereby laying the foundations for future primary preventative approaches. We conclude that epigenetic modifications need to be considered when assessing G × E interactions in AD.

Impact of Environmental Risk Factors on Mitochondrial Dysfunction, Neuroinflammation, Protein Misfolding, and Oxidative Stress in the Etiopathogenesis of Parkinson's Disease

As a prevalent progressive neurodegenerative disorder, Parkinson's disease (PD) is characterized by the neuropathological hallmark of the loss of nigrostriatal dopaminergic (DAergic) innervation and the appearance of Lewy bodies with aggregated α-synuclein. Although several familial forms of PD have been reported to be associated with several gene variants, most cases in nature are sporadic, triggered by a complex interplay of genetic and environmental risk factors. Numerous epidemiological studies during the past two decades have shown positive associations between PD and several environmental factors, including exposure to neurotoxic pesticides/herbicides and heavy metals as well as traumatic brain injury. Other environmental factors that have been implicated as potential risk factors for PD include industrial chemicals, wood pulp mills, farming, well-water consumption, and rural residence. In this review, we summarize the environmental toxicology of PD with the focus on the elaboration of chemical toxicity and the underlying pathogenic mechanisms associated with exposure to several neurotoxic chemicals, specifically 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, paraquat (PQ), dichloro-diphenyl-trichloroethane (DDT), dieldrin, manganese (Mn), and vanadium (V). Our overview of the current findings from cellular, animal, and human studies of PD provides information for possible intervention strategies aimed at halting the initiation and exacerbation of environmentally linked PD.

Contribution of insect gut microbiota and their associated enzymes in insect physiology and biodegradation of pesticides

Synthetic pesticides are extensively and injudiciously applied to control agriculture and household pests worldwide. Due to their high use, their toxic residues have enormously increased in the agroecosystem in the past several years. They have caused many severe threats to non-target organisms, including humans. Therefore, the complete removal of toxic compounds is gaining wide attention to protect the ecosystem and the diversity of living organisms. Several methods, such as physical, chemical and biological, are applied to degrade compounds, but as compared to other methods, biological methods are considered more efficient, fast, eco-friendly and less expensive. In particular, employing microbial species and their purified enzymes makes the degradation of toxic pollutants more accessible and converts them into non-toxic products by several metabolic pathways. The digestive tract of insects is usually known as a superior organ that provides a nutrient-rich environment to hundreds of microbial species that perform a pivotal role in various physiological and ecological functions. There is a direct relationship between pesticides and insect pests: pesticides reduce the growth of insect species and alter the phyla located in the gut microbiome. In comparison, the insect gut microbiota tries to degrade toxic compounds by changing their toxicity, increasing the production and regulation of a diverse range of enzymes. These enzymes breakdown into their derivatives, and microbial species utilize them as a sole source of carbon, sulfur and energy. The resistance of pesticides (carbamates, pyrethroids, organophosphates, organochlorines, and neonicotinoids) in insect species is developed by metabolic mechanisms, regulation of enzymes and the expression of various microbial detoxifying genes in insect guts. This review summarizes the toxic effects of agrochemicals on humans, animals, birds and beneficial arthropods. It explores the preferential role of insect gut microbial species in the degradation process and the resistance mechanism of several pesticides in insect species. Additionally, various metabolic pathways have been systematically discussed to better understand the degradation of xenobiotics by insect gut microbial species.

Chlorpyrifos and parathion regulate oxidative stress differentially through the expression of paraoxonase 2 in human neuroblastoma cell

Organophosphate (OP) compounds are frequently linked to both chronic and acute forms of nervous system disorders. Chlorpyrifos (CPF) and parathion (PA) are two of the most widely used OP insecticides throughout the world. These compounds are acetylcholinesterase inhibitors and cause a cholinergic crisis. However, there are other non-cholinergic effects of the OP compounds as well. The role of Paraoxonase 1 (PON1) in the metabolism of OP compounds is well established owing to its significant organophosphatase activity. Since PON2 has no paraoxonase activity and the level of its expression is 20-40 fold higher in the brain, in this article the role of PON2 in response to CPF and PA exposure concerning both cholinergic and non-cholinergic effects are explored. The effect of these OPs on cell viability, reactive oxygen species (ROS), PON2 gene expression, and function was studied. Glutathione level, esterase activity, and paraoxonase activity were also measured in CPF- and PA-treated IMR-32 cells. At these levels, both CPF and PA showed different impacts on IMR-32 cells. PA at higher concentrations (50-200µM) proved to be less toxic than CPF. Interestingly, induction of ROS was also lower in the case of PA-treated cells as compared to the CPF. However, PON2 protein expression was increased with the increasing concentration of PA and decreased with the increasing concentration of CPF. To explore the possible mechanism of the differential regulation of PON2 gene expression by CPF and PA, we investigated the possible binding and signaling through the human M2 muscarinic acetylcholine receptor (M2AChR). Since M2AChRs are similar to G-protein coupled receptors and function through cAMP signalling, we measured the cAMP level after CPF and PA treatment CPF- and PA-treated IMR-32 cells can be used as a model to study the mechanism by which PON2 acts as a ROS scavenger in response to xenobiotics stimulation in the brain.

Neurotoxicological Profiling of Paraquat in Zebrafish Model

Paraquat is a polar herbicide protecting plant products against invasive species, it requires careful manipulation and restricted usage because of its harmful potentials. Exposure to paraquat triggers oxidative damage in dopaminergic neurons and subsequently causes a behavioral defect in vivo. Thereby, persistent exposure to paraquat is known to increase Parkinson's disease risk by dysregulating dopaminergic systems in humans. Therefore, most studies have focused on the dopaminergic systems to elucidate the neurotoxicological mechanism of paraquat poisoning, and more comprehensive neurochemistry including histaminergic, serotonergic, cholinergic, and GABAergic systems has remained unclear. Therefore, in this study, we investigated the toxicological potential of paraquat poisoning using a variety of approaches such as toxicokinetic profiles, behavioral effects, neural activity, and broad-spectrum neurochemistry in zebrafish larvae after short-term exposure to paraquat and we performed the molecular modeling approach. Our results showed that paraquat was slowly absorbed in the brain of zebrafish after oral administration of paraquat. In addition, paraquat toxicity resulted in behavioral impairments, namely, reduced motor activity and led to abnormal neural activities in zebrafish larvae. This locomotor deficit came with a dysregulation of dopamine synthesis induced by the inhibition of tyrosine hydroxylase activity, which was also indirectly confirmed by molecular modeling studies. Furthermore, short-term exposure to paraquat also caused simultaneous dysregulation of other neurochemistry including cholinergic and serotonergic systems in zebrafish larvae. The present study suggests that this neurotoxicological profiling could be a useful tool for understanding the brain neurochemistry of neurotoxic agents that might be a potential risk to human and environmental health.

Effects of DDT on Amyloid Precursor Protein Levels and Amyloid Beta Pathology: Mechanistic Links to Alzheimer's Disease Risk

BACKGROUND

The interaction of aging-related, genetic, and environmental factors is thought to contribute to the etiology of late-onset, sporadic Alzheimer's disease (AD). We previously reported that serum levels of p,p'-dichlorodiphenyldichloroethylene (DDE), a long-lasting metabolite of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT), were significantly elevated in patients with AD and associated with the risk of AD diagnosis. However, the mechanism by which DDT may contribute to AD pathogenesis is unknown.

OBJECTIVES

This study sought to assess effects of DDT exposure on the amyloid pathway in multiple in vitro and in vivo models.

METHODS

Cultured cells (SH-SY5Y and primary neurons), transgenic flies overexpressing amyloid beta (Aβ), and C57BL/6J and 3xTG-AD mice were treated with DDT to assess impacts on the amyloid pathway. Real time quantitative polymerase chain reaction, multiplex assay, western immunoblotting and immunohistochemical methods were used to assess the effects of DDT on amyloid precursor protein (APP) and other contributors to amyloid processing and deposition.

RESULTS

Exposure to DDT revealed significantly higher APP mRNA and protein levels in immortalized and primary neurons, as well as in wild-type and AD-models. This was accompanied by higher levels of secreted Aβ in SH-SY5Y cells, an effect abolished by the sodium channel antagonist tetrodotoxin. Transgenic flies and 3xTG-AD mice had more Aβ pathology following DDT exposure. Furthermore, loss of the synaptic markers synaptophysin and PSD95 were observed in the cortex of the brains of 3xTG-AD mice.

DISCUSSION

Sporadic Alzheimer's disease risk involves contributions from genetic and environmental factors. Here, we used multiple model systems, including primary neurons, transgenic flies, and mice to demonstrate the effects of DDT on APP and its pathological product Aβ. These data, combined with our previous epidemiological findings, provide a mechanistic framework by which DDT exposure may contribute to increased risk of AD by impacting the amyloid pathway. https://doi.org/10.1289/EHP10576.

Titanium dioxide and carbon black nanoparticles disrupt neuronal homeostasis via excessive activation of cellular prion protein signaling

Background

Epidemiological emerging evidence shows that human exposure to some nanosized materials present in the environment would contribute to the onset and/or progression of Alzheimer’s disease (AD). The cellular and molecular mechanisms whereby nanoparticles would exert some adverse effects towards neurons and take part in AD pathology are nevertheless unknown.

Results

Here, we provide the prime evidence that titanium dioxide (TiO₂) and carbon black (CB) nanoparticles (NPs) bind the cellular form of the prion protein (PrP^C), a plasma membrane protein well known for its implication in prion diseases and prion-like diseases, such as AD. The interaction between TiO₂- or CB-NPs and PrP^C at the surface of neuronal cells grown in culture corrupts PrP^C signaling function. This triggers PrP^C-dependent activation of NADPH oxidase and subsequent production of reactive oxygen species (ROS) that alters redox equilibrium. Through PrP^C interaction, NPs also promote the activation of 3-phosphoinositide-dependent kinase 1 (PDK1), which in turn provokes the internalization of the neuroprotective TACE α-secretase. This diverts TACE cleavage activity away from (i) TNFα receptors (TNFR), whose accumulation at the plasma membrane augments the vulnerability of NP-exposed neuronal cells to TNFα -associated inflammation, and (ii) the amyloid precursor protein APP, leading to overproduction of neurotoxic amyloid Aβ40/42 peptides. The silencing of PrP^C or the pharmacological inhibition of PDK1 protects neuronal cells from TiO₂- and CB-NPs effects regarding ROS production, TNFα hypersensitivity, and Aβ rise. Finally, we show that dysregulation of the PrP^C-PDK1-TACE pathway likely occurs in the brain of mice injected with TiO₂-NPs by the intra-cerebro-ventricular route as we monitor a rise of TNFR at the cell surface of several groups of neurons located in distinct brain areas.

Conclusion

Our in vitro and in vivo study thus posits for the first time normal cellular prion protein PrP^C as being a neuronal receptor of TiO₂- and CB-NPs and identifies PrP^C-coupled signaling pathways by which those nanoparticles alter redox equilibrium, augment the intrinsic sensitivity of neurons to neuroinflammation, and provoke a rise of Aβ peptides. By identifying signaling cascades dysregulated by TiO₂- and CB-NPs in neurons, our data shed light on how human exposure to some NPs might be related to AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00490-x.

Far infrared light irradiation enhances Aβ clearance via increased exocytotic microglial ATP and ameliorates cognitive deficit in Alzheimer's disease-like mice

Background

Exposure to sunlight may decrease the risk of developing Alzheimer’s disease (AD), and visible and near infrared light have been proposed as a possible therapeutic strategy for AD. Here, we investigated the effects of the visible, near infrared and far infrared (FIR) light on the cognitive ability of AD mice, and found that FIR light also showed potential in the improvement of cognitive dysfunction in AD. However, the related mechanism remains to be elucidated.

Methods

Morris water maze was used to evaluate the cognitive ability of APPswe/PSEN1dE9 double-transgenic AD mice after light treatment. Western blot was carried out to detect the expression of protein involved in synaptic function and amyloid-β (Aβ) production. The protein amount of interleukin (IL)-1β, IL-6, Aβ_1-40 and Aβ_1-42 were determined using enzyme-linked immunosorbent assay. The mRNA level of receptors was performed using real-time quantitative polymerase chain reaction. Immunostaining was performed to characterize the Aβ burden and microglial Aβ phagocytosis in the brain of AD mice. The Aβ phagocytosis of primary cultured microglia and BV2 were assessed by flow cytometry. The energy metabolism changes were evaluated using related assay kits, including adenosine triphosphate (ATP), lactate content, mitochondrial respiratory chain complex enzymatic activity and oxidized/reduced nicotinamide adenine dinucleotide assay kits.

Results

Our results showed that FIR light reduced Aβ burden, a hallmark of AD neuropathology, alleviated neuroinflammation, restored the expression of the presynaptic protein synaptophysin, and ameliorated learning and memory impairment in the AD mice. FIR light enhanced mitochondrial oxidative phosphorylation pathway to increase ATP production. This increased intracellular ATP promoted the extracellular ATP release from microglia stimulated by Aβ, leading to the enhanced Aβ phagocytosis through phosphoinositide 3-kinase/mammalian target of rapamycin pathways for Aβ clearance.

Conclusions

Our findings have uncovered a previously unappreciated function of FIR light in inducing microglial phagocytosis to clean Aβ, which may be the mechanisms for FIR light to improve cognitive dysfunction in AD mice. These results suggest that FIR light treatment is a potential therapeutic strategy for AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02521-y.

Role of Environmental Toxicants on Neurodegenerative Disorders

Neurodegeneration leads to the loss of structural and functioning components of neurons over time. Various studies have related neurodegeneration to a number of degenerative disorders. Neurological repercussions of neurodegeneration can have severe impacts on the physical and mental health of patients. In the recent past, various neurodegenerative ailments such as Alzheimer’s and Parkinson’s illnesses have received global consideration owing to their global occurrence. Environmental attributes have been regarded as the main contributors to neural dysfunction-related disorders. The majority of neurological diseases are mainly related to prenatal and postnatal exposure to industrially produced environmental toxins. Some neurotoxic metals, like lead (Pb), aluminium (Al), Mercury (Hg), manganese (Mn), cadmium (Cd), and arsenic (As), and also pesticides and metal-based nanoparticles, have been implicated in Parkinson’s and Alzheimer’s disease. The contaminants are known for their ability to produce senile or amyloid plaques and neurofibrillary tangles (NFTs), which are the key features of these neurological dysfunctions. Besides, solvent exposure is also a significant contributor to neurological diseases. This study recapitulates the role of environmental neurotoxins on neurodegeneration with special emphasis on major neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease.

Cross-species metabolomic analysis of tau- and DDT-related toxicity

Exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) has been associated with increased risk of Alzheimer's disease (AD), a disease also associated with hyperphosphorylated tau (p-tau) protein aggregation. We investigated whether exposure to DDT can exacerbate tau protein toxicity in Caenorhabditiselegans using a transgenic strain that expresses human tau protein prone to aggregation by measuring changes in size, swim behavior, respiration, lifespan, learning, and metabolism. In addition, we examined the association between cerebrospinal fluid (CSF) p-tau protein-as a marker of postmortem tau burden-and global metabolism in both a human population study and in C. elegans, using the same p-tau transgenic strain. From the human population study, plasma and CSF-derived metabolic features associated with p-tau levels were related to drug, amino acid, fatty acid, and mitochondrial metabolism pathways. A total of five metabolites overlapped between plasma and C. elegans, and four between CSF and C. elegans. DDT exacerbated the inhibitory effect of p-tau protein on growth and basal respiration. In the presence of p-tau protein, DDT induced more curling and was associated with reduced levels of amino acids but increased levels of uric acid and adenosylselenohomocysteine. Our findings in C. elegans indicate that DDT exposure and p-tau aggregation both inhibit mitochondrial function and DDT exposure can exacerbate the mitochondrial inhibitory effects of p-tau aggregation. Further, biological pathways associated with exposure to DDT and p-tau protein appear to be conserved between species.

Endocrine disruptors: Challenges and future directions in epidemiologic research

Public concern about the impact of endocrine disrupting chemicals (EDCs) on both humans and the environment is growing steadily. Epidemiologic research provides key information towards our understanding of the relationship between environmental exposures like EDCs and human health outcomes. Intended for researchers in disciplines complementary to epidemiology, this paper highlights the importance and challenges of epidemiologic research in order to present the key elements pertaining to the design and interpretation of an epidemiologic study on EDCs. The conduct of observational studies on EDCs derives from a thoughtful research question, which will help determine the subsequent methodological choices surrounding the careful selection of the study population (including the comparison group), the adequate ascertainment of exposure(s) and outcome(s) of interest, and the application of methodological and statistical concepts more specific to epidemiology. The interpretation of epidemiologic results may be arduous due to the latency occurring between EDC exposure and certain outcome(s), the complexity in capturing EDC exposure(s), and traditional methodological and statistical issues that also deserve consideration (e.g., confounding, effect modification, non-monotonic responses). Moving forward, we strongly advocate for an integrative approach of expertise in the fields of epidemiology, exposure science, risk assessment and toxicology to adequately study the health risks associated with EDCs while tackling their challenges.

Transfer of Tumor-Bearing Mice Intestinal Flora Can Ameliorate Cognition in Alzheimer's Disease Mice

BACKGROUND

Fecal microbiota transplant (FMT) is a potential treatment approach for many diseases. Alzheimer's disease (AD) and cancer have been proven to have a specific antagonistic relationship to FMT.

OBJECTIVE

This article aims to explore whether intestinal flora transplantation from cancer individuals can ameliorate cognitive impairment.

METHODS

Morris water maze and object recognition tests were performed to assess cognitive function after the fecal flora from tumor-bearing and WT mice were transplanted into AD mice by gavage. The effect of flora transplantation on AD was analyzed by thioflavin T staining, western blot, and 16S RNA sequencing.

RESULTS

AD mice with FMT significantly improved short-term memory level and cognitive ability compared with Tg + NaCl group. Inflammatory factors in the plasma were regulated, and Aβ plaques burden in the hippocampus and cortex were decreased. FMT in the tumor-bearing group showed a higher significant amelioration in symptoms compared to the healthy group. 16S RNA sequencing revealed that FMT treatments could reverse the increased Firmicutes and Prevotella and the decreased Bacteroidetes, Bacteroides, and Sutterella in AD mice. AD mice transplanted with tumor-bearing mice feces additionally increased the density of Oscillospira, Odoribacter, and AF12. Furthermore, the predicted functional analyses showed that the metabolism of inorganic and organic salts in the intestinal flora of AD mice was also reversed by FMT.

CONCLUSION

Intestinal flora transplantation from tumor-bearing mice can ameliorate the cognitive impairment of AD mice.

High Pesticide Exposure Events and Dream‐Enacting Behaviors Among US Farmers

BACKGROUND

Dream-enacting behavior is a characteristic feature of rapid eye movement sleep behavior disorder, the most specific prodromal marker of synucleinopathies. Pesticide exposure may be associated with dream-enacting behaviors, but epidemiological evidence is limited.

OBJECTIVES

To examine high pesticide exposure events in relation to dream-enacting behaviors among farmers in the Agricultural Health Study.

METHODS

We conducted multivariable logistic regression analyses to examine high pesticide exposure events reported from 1993 to 1997 in relation to dream-enacting behaviors assessed from 2013 to 2015 among 11,248 farmers (age 47 ± 11 years).

RESULTS

A history of dream-enacting behaviors was reported by 939 (8.3%) farmers. Compared with farmers who did not report any high pesticide exposure event, those who reported were more likely to endorse dream-enacting behaviors 2 decades later (odds ratio = 1.75; 95% confidence interval [CI], 1.49-2.05). The association appeared stronger when there was a long delay in washing with soap and water after the event (2.63 [95% CI, 1.62-4.27] for waiting >6 hours vs. 1.71 [95% CI, 1.36-2.15] for washing within 30 minutes) and when the exposure involved the respiratory or digestive tract (2.04 [95% CI, 1.62-2.57] vs. 1.58 [95% CI, 1.29-1.93] for dermal contact only). In the analyses of specific pesticides involved, we found positive associations with two organochlorine insecticides (dichlorodiphenyltrichloroethane and lindane), four organophosphate insecticides (phorate, ethoprop, terbufos, and parathion), two herbicides (alachlor and paraquat), and fungicides as a group.

CONCLUSIONS

This study provides the first epidemiological evidence that high pesticide exposures may be associated with a higher risk of dream-enacting behaviors. © 2022 International Parkinson and Movement Disorder Society.

Oxidative Stress and Metabolism: A Mechanistic Insight for Glyphosate Toxicology

Glyphosate (GLYP) is a widely used pesticide; it is considered to be a safe herbicide for animals and humans because it targets 5-enolpyruvylshikimate-3-phosphate synthase. However, there has been increasing evidence that GLYP causes varying degrees of toxicity. Moreover, oxidative stress and metabolism are highly correlated with toxicity. This review provides a comprehensive introduction to the toxicity of GLYP and, for the first time, systematically summarizes the toxicity mechanism of GLYP from the perspective of oxidative stress, including GLYP-mediated oxidative damage, changes in antioxidant status, altered signaling pathways, and the regulation of oxidative stress by exogenous substances. In addition, the metabolism of GLYP is discussed, including metabolites,metabolic pathways, metabolic enzymes, and the toxicity of metabolites. This review provides new ideas for the toxicity mechanism of GLYP and proposes effective strategies for reducing its toxicity.

Epigenetics in neurodegenerative disorders induced by pesticides

Neurodegenerative diseases are becoming major socio-economic burdens. However, most of them still have no effective treatment. Growing evidence indicates excess exposure to pesticides are involved in the development of various forms of neurodegenerative and neurological diseases through trigger epigenetic changes and inducing disruption of the epigenome. This review summaries studies on epigenetics alterations in nervous systems in relation to different kinds of pesticides, highlighting potential mechanism in the etiology, precision prevention and target therapy of various neurodegenerative diseases. In addition, the current gaps in research and future areas for study were also discussed.

Analysis of serum levels of organochlorine pesticides and related factors in Parkinson's disease

BACKGROUND

There is evidence that environmental factors contribute to the onset and progression of Parkinson's disease (PD). Pesticides are a class of environmental toxins that are linked to increased risk of developing PD. However, few studies have investigated the association between specific pesticides and PD, especially in China, which was one of the first countries to adopt the use of pesticides.

METHODS

In this study, serum levels of 19 pesticides were measured in 90 patients with PD and 90 healthy spouse controls. We also analyzed the interaction between specific pesticides and PD. In addition, the association between pesticides and clinical features of PD was also investigated. Finally, we investigated the underlying mechanism of the association between pesticides and PD.

RESULTS

Serum levels of organochlorine pesticides, which included α-hexachlorocyclohexane (HCH), β-HCH, γ-HCH, δ-HCH, propanil, heptachlor, dieldrin, hexachlorobenzene, p,p'-dichlorodiphenyltrichloroethane and o,p'-dichloro-diphenyl-trichloroethane were higher in PD patients than controls. Moreover, α-HCH and propanil levels were associated with PD. Serum levels of dieldrin were associated with Hamilton Depression Scale and Montreal Cognitive Assessment scores in PD patients. In SH-SY5Y cells, α-HCH and propanil increased level of reactive oxygen species and decreased mitochondrial membrane potential. Furthermore, propanil, but not α-HCH, induced the aggregation of α-synuclein.

CONCLUSIONS

This study revealed that elevated serum levels of α-HCH and propanil were associated with PD. Serum levels of dieldrin were associated with depression and cognitive function in PD patients. Moreover, propanil, but not α-HCH, induced the aggregation of α-synuclein. Further research is needed to fully elucidate the effects of pesticides on PD.

Environmental Substances Associated with Alzheimer's Disease-A Scoping Review

Alzheimer's disease (AD) is the most common form of dementia, prevalent in approximately 50-70% of the dementia cases. AD affects memory, and it is a progressive disease interfering with cognitive abilities, behaviour and functioning of the person affected. In 2015, there were 47 million people affected by dementia worldwide, and the figure was estimated to increase to 75 million in 2030 and to 132 million by 2050. In the framework of European Human Biomonitoring Initiative (HBM4EU), 18 substances or substance groups were prioritized for investigation. For each of the priority substances, a scoping document was prepared. Based on these scoping documents and complementary review of the recent literature, a scoping review of HBM4EU-priority substances which might be associated with AD was conducted. A possible association between risk of AD and pesticides was detected. For mercury (Hg), association is possible but inconsistent. Regarding cadmium (Cd) and arsenic (As), the results are inconsistent but inclined towards possible associations between the substances and the risk of disease. The evidence regarding lead (Pb) was weaker than for the other substances; however, possible associations exist. Although there is evidence of adverse neurological effects of environmental substances, more research is needed. Environmental chemical exposure and the related hazards are essential concerns for public health, and they could be preventable.

Is the Exposome Involved in Brain Disorders through the Serotoninergic System?

Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic monoamine acting as a neurotransmitter in the central nervous system (CNS), local mediator in the gut, and vasoactive agent in the blood. It has been linked to a variety of CNS functions and is implicated in many CNS and psychiatric disorders. The high comorbidity between some neuropathies can be partially understood by the fact that these diseases share a common etiology involving the serotoninergic system. In addition to its well-known functions, serotonin has been shown to be a mitogenic factor for a wide range of normal and tumor cells, including glioma cells, in vitro. The developing CNS of fetus and newborn is particularly susceptible to the deleterious effects of neurotoxic substances in our environment, and perinatal exposure could result in the later development of diseases, a hypothesis known as the developmental origin of health and disease. Some of these substances affect the serotoninergic system and could therefore be the source of a silent pandemic of neurodevelopmental toxicity. This review presents the available data that are contributing to the appreciation of the effects of the exposome on the serotoninergic system and their potential link with brain pathologies (neurodevelopmental, neurodegenerative, neurobehavioral disorders, and glioblastoma).

The potential roles of genetic factors in predicting ageing-related cognitive change and Alzheimer's disease

Alzheimer's disease (AD) is a complex neurological disorder of uncertain aetiology, although substantial research has been conducted to explore important factors related to risk of onset and progression. Both lifestyle (e.g., complex mental stimulation, vascular health) and genetic factors (e.g., APOE, BDNF, PICALM, CLU, APP, PSEN1, PSEN2, and other genes) have been associated with AD risk. Despite more than thirty years of genetic research, much of the heritability of AD is not explained by measured loci. This suggests that the missing heritability of AD might be potentially related to rare variants, gene-environment and gene-gene interactions, and potentially epigenetic modulators. Moreover, while ageing is the most substantial factor risk for AD, there are limited longitudinal studies examining the association of genetic factors with decline in cognitive function due to ageing and the preclinical stages of this condition. This review summarises findings from currently available research on the genetic factors of ageing-related cognitive change and AD and suggests some future research directions.

Factors Influencing Practice of Pesticide Use and Acute Health Symptoms among Farmers in Nakhon Sawan, Thailand

Information on knowledge (K), attitude (A), and practice (P) in terms of pesticide use is essential for an effective exposure control program. The objectives of this study were to survey the level of knowledge, attitude, and practice in terms of pesticide use, and the prevalence of acute health symptoms (AHSs) among farmers in Nakhon Sawan Province, Thailand. The study also tried to identify factors affecting the practice of pesticide use. Data from 680 farmers were collected using a face-to-face interview questionnaire. The relationship between safety practices and related factors was analyzed using ordinal logistic regression. This study found about 40% of the farmers had a good level of practice. Factors affecting practice were education, work experience, level of knowledge, or attitudes. Many participants experienced acute health symptoms in the past 24 h, and these symptoms were significantly associated with poor practice (p < 0.05). Public health organizations should provide farmers with more information, especially on chronic effects of pesticides.

Chemosensory Dysfunction Induced by Environmental Pollutants and Its Potential As a Novel Neurotoxicological Indicator: A Review

Air pollution composed of the complex interactions among particular matter, chemicals, and pathogens is an emerging and global environmental issue that closely correlates with a variety of diseases and adverse health effects, especially increasing incidences of neurodegenerative diseases. However, as one of the prevalent health outcomes of air pollution, chemosensory dysfunction has not attracted enough concern until recently. During the COVID-19 pandemic, multiple scientific studies emphasized the plausibly essential roles of the chemosensory system in the airborne transmission airway of viruses into the human body, which can also be utilized by pollutants. In this Review, in addition to summarizing current progress regarding the contributions of traditional air pollutants to chemosensory dysfunction, we highlight the roles of emerging contaminants. We not only sum up clarified mechanisms, such as inflammation and apoptosis but also discuss some not yet completely identified mechanisms, e.g., disruption of olfactory signal transduction. Although the existing evidence is not overwhelming, the chemosensory system is expected to be a useful indicator in neurotoxicology and neural diseases based on accumulating studies that continually excavate the deep link between chemosensory dysfunction and neurodegenerative diseases. Finally, we argue the importance of studies concerning chemosensory dysfunction in understanding the health effects of air pollution and provide comments for some future directions of relevant research.