Well-water consumption and Parkinson's disease in rural California

Cropland associated with risk of Parkinson's disease in the northern Great Plains

INTRODUCTION

We sought to identify regional associations between cropland density and crop types and PD in the U.S.

METHODS

We conducted a population-based study of 21,639,190 Medicare beneficiaries, 89,790 with incident PD in 2009. We used county-level geographic weighted regression (GWR) to identify region(s) of the U.S. where the association between PD RR and cropland density was strongest. In a broad region identified by GWR in which cropland density was associated with PD, we performed logistic regression using individual-level beneficiary data (2733 cases and 805,984 non-cases) with high-resolution cropland density data. We adjusted for age, sex, race, smoking, healthcare utilization, and PM2.5 (particulate matter <2.5 μm). We then explored PD-cropland associations for each type of crop within a subregion, in which the association was the strongest.

RESULTS

GWR identified a 9-state region in the Great Plains in which county-level cropland density and PD RR were associated. Within this region, the strongest GWR coefficients centered around the Williston Basin. High-resolution analysis demonstrated an association between cropland density within a 5-mile radius of residential zip+4 and PD. When comparing the highest to lowest quartile of cropland density, the odds ratio (OR) for PD was 1.14 (95 % confidence interval [CI] 1.01-1.27) in the 9-state region and 1.99 (95 % CI 1.09-3.61) in the Williston Basin. In the Williston Basin, percentage of sunflowers, winter wheat, and alfalfa within 5 miles of a beneficiary's zip+4 was associated with PD.

CONCLUSION

We identified a region-specific association between cropland and crop type and PD in the Williston Basin.

Environmental Risk Factors for Parkinson's Disease: A Critical Review and Policy Implications

The age-standardized prevalence of Parkinson's disease (PD) has increased substantially over the years and is expected to increase further. This emphasizes the need to identify modifiable risk factors of PD, which could form a logical entry point for the prevention of PD. The World Health Organization (WHO) has recommended reducing exposure to specific environmental factors that have been reported to be associated with PD, in particular pesticides, trichloroethylene (TCE), and air pollution. In this review we critically evaluate the epidemiological and biological evidence on the associations of these factors with PD and review evidence on whether these putative associations are causal. We conclude that when considered in isolation, it is difficult to determine whether these associations are causal, in large part because of the decades-long lag between relevant exposures and the incidence of manifest PD. However, when considered in tandem with evidence from complementary research lines (such as animal models), it is increasingly likely that these associations reflect harmful causal effects. Fundamentally, whilst we highlight some evidence gaps that require further attention, we believe the current evidence base is sufficiently strong enough to support our call for stronger policy action. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Chlorpyrifos-oxon induced neuronal cell death via endoplasmic reticulum stress-triggered apoptosis pathways

Chlorpyrifos (CPF) is one of the organophosphorus pesticides widely used throughout the world. Epidemiological studies suggested a link between CPF exposure and neurologic disorders, while the molecular mechanisms remain inconclusive. In the present study, we investigated the impacts of chlorpyrifos-oxon (CPO), the major toxic CPF metabolite, on cell apoptosis, and explored possible mechanism associated with endoplasmic reticulum (ER) stress in SH-SY5Y cells. Results showed that CPO exposure induced dose-dependent apoptosis and expression of ER stress-related proteins in SH-SY5Y cells. Pretreatment with 4-PBA (an ER stress inhibitor) effectively inhibited the expression of GRP78, GRP94, p-IRE1α, and XBP1-s, and apoptotic events. Pretreatment with STF-083010 (an IRE1α inhibitor) partially attenuated CPO-induced apoptosis. In addition, CPO exposure significantly evoked the generation of reactive oxygen species (ROS) which could be eliminated by pretreatment of 4-PBA. Of note, buffering the ROS generation with antioxidant NAC had little impact on the expression of p-IRE1α, and only partially attenuated CPO-induced apoptosis. In contrast, co-pretreatment with NAC and STF-083010 effectively inhibited CPO-induced apoptotic events. Collectively, our results indicate that CPO exposure exerts neuronal cytotoxicity via ER stress downstream-regulated IRE1α/XBP1 signaling pathway and ROS generation-triggered apoptosis. These findings highlight the role of ER stress in CPF-induced neurotoxicity, and provide a promising target for the intervention of organophosphate-associated neurodegenerative diseases.

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.

Emamectin benzoate-induced toxicity affects intestinal epithelial integrity involving apoptosis

The frequency presence of emamectin benzoate in agricultural production highlights the need for studying their toxicity against human intestinal epithelial barrier (IEB). Herein, we combined a Caco-2 cell model with transcriptome analysis to assess the intestinal toxicity of emamectin benzoate and its disease-causing potential. Results showed that the half maximal inhibitory concentration (IC50) of emamectin benzoate on Caco-2 cell viability after 24, 48, and 72 h of exposure were 18.1, 9.9, and 8.3 μM, respectively. Emamectin benzoate exposure enhanced the Caco-2 monolayer paracellular permeability, damaged the IEB, and increased cellular apoptosis. Key driver gene analysis of 42 apoptosis - related DEGs, identified 10 genes (XIAP, KRAS, MCL1, NRAS, PIK3CA, CYCS, MAPK8, CASP3, FADD, and TNFRSF10B) with the strongest correlation with emamectin benzoate - induced apoptosis. Transcriptomics identified 326 differentially expressed genes (DEGs, 204 upregulated and 122 downregulated). The functional terms of neurodegeneration - multiple diseases was enriched with the most number of DEGs, and the Parkinson disease pathway had the highest enrichment degree. Our findings provided support for environmental toxicology studies and the health risk assessment of emamectin benzoate.

Literature review and meta-analysis of environmental toxins associated with increased risk of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder and leading cause of death worldwide, whose pathogenesis has been linked to toxic environmental exposures. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (i) to compile, and group by exposure setting (non-specified general; residential; occupational), environmental factors reported to modulate the risk of developing PD and (ii) to map and geospatially analyze global regions of both research activity and paucity. Among the broader environmental settings, occupational exposures had the highest average odds ratio value at 3.82, followed by general (non-specified or mixed) exposures at 3.07, and residential exposures at 2.36. Occupational exposure to industrial toxins was the highest ranked subset of exposures with an odds ratio of 10.74. Among the studies meeting the inclusion criteria, 75 % were conducted in Europe or the Western United States. The number of individuals partaking per study ranged from a high of 55,585 (Taiwan) to a low of 233 (Faroe Islands), with a mean of n = 14,462. The top three environmental factors associated with high odds ratios for increased risk of developing PD were (i) exposure to dyes (25.33), (ii) methylene chloride (16.5) and specifically in adult men (iii) consumption of fatty whale meat (10.57), which is known to harbor a broad spectrum of so called persistent, bioaccumulative, toxic (PBT) pollutants. Geospatially, the highest odds ratio values were identified in European countries, whereas notable data gaps were revealed for South America, Australia, Africa, and the majority of Asia with the exception of Taiwan. Whereas occupational exposures to industrial chemicals, such as harmful dyes and methylene chloride, ranked highest in risk values, available data suggest notable opportunities for reducing PD cases globally by limiting harmful environmental exposures to a spectrum of toxic chemicals, particularly via the food intake route. Thus, current efforts in improving environmental quality globally by limiting toxic emission may deliver the added benefit of helping to reign in PD. Agents of concern in this respect include pesticides (e.g., paraquat, demeton, monocrotophos), particulate matter associated with air pollution, and a spectrum of organic and inorganic neurotoxins including heavy metals.

Role of the Gut Microbiome and Bacterial Amyloids in the Development of Synucleinopathies

Less than ten years ago, evidence began to accumulate about association between the changes in the composition of gut microbiota and development of human synucleinopathies, in particular sporadic form of Parkinson's disease. We collected data from more than one hundred and thirty experimental studies that reported similar results and summarized the frequencies of detection of different groups of bacteria in these studies. It is important to note that it is extremely rare that a unidirectional change in the population of one or another group of microorganisms (only an elevation or only a reduction) was detected in the patients with Parkinson's disease. However, we were able to identify several groups of bacteria that were overrepresented in the patients with Parkinson's disease in the analyzed studies. There are various hypotheses about the molecular mechanisms that explain such relationships. Usually, α-synuclein aggregation is associated with the development of inflammatory processes that occur in response to the changes in the microbiome. However, experimental evidence is accumulating on the influence of bacterial proteins, including amyloids (curli), as well as various metabolites, on the α-synuclein aggregation. In the review, we provided up-to-date information about such examples.

A study on possible risk factors for progressive supranuclear palsy in southern part of India

Background: The etiological factors leading to progressive supranuclear palsy (PSP) are poorly understood. This study aims to evaluate the role of various risk factors in patients with PSP. Methods: A case-control study was conducted over a period of two years from March 2016 to March 2018. The cases were recruited independently by two senior neurologists and a consensus was then reached after discussion for their inclusion. The controls were free of parkinsonian features or dementia and matched by age (± 3 years), sex, and race with the cases. The study population was then interviewed using a standard questionnaire for various possible risk factors. Variables with a significance (P ≤ 0.05) in univariate analysis were considered for bivariate analysis, multivariate analysis, and logistic-regression analysis. Results: A total of 51 cases with an equal number of controls were included in this study. Ten separate variables that included poor educational status, well water, smoking, tapioca, bakery/fast food, tea ≥ 5 cups/day, personality, exposure to pets, exposure to cattle, and family history of stroke were found to show statistical significance after univariate analysis. Among these, tapioca consumption, fast food and bakery items consumption, type A personality, and family history of stroke were found significant after adjusting for the confounding factors. Conclusion: The possible etiological factors that have a relevance in the causation of PSP as borne out in our study include dietary habits such as tapioca, fast food, and bakery items consumption, family history of stroke, and type A personality trait.

The Body, the Brain, the Environment, and Parkinson's Disease

The brain- and body-first models of Lewy body disorders predict that aggregated alpha-synuclein pathology usually begins in either the olfactory system or the enteric nervous system. In both scenarios the pathology seems to arise in structures that are closely connected to the outside world. Environmental toxicants, including certain pesticides, industrial chemicals, and air pollution are therefore plausible trigger mechanisms for Parkinson's disease and dementia with Lewy bodies. Here, we propose that toxicants inhaled through the nose can lead to pathological changes in alpha-synuclein in the olfactory system that subsequently spread and give rise to a brain-first subtype of Lewy body disease. Similarly, ingested toxicants can pass through the gut and cause alpha-synuclein pathology that then extends via parasympathetic and sympathetic pathways to ultimately produce a body-first subtype. The resulting spread can be tracked by the development of symptoms, clinical assessments, in vivo imaging, and ultimately pathological examination. The integration of environmental exposures into the brain-first and body-first models generates testable hypotheses, including on the prevalence of the clinical conditions, their future incidence, imaging patterns, and pathological signatures. The proposed link, though, has limitations and leaves many questions unanswered, such as the role of the skin, the influence of the microbiome, and the effects of ongoing exposures. Despite these limitations, the interaction of exogenous factors with the nose and the gut may explain many of the mysteries of Parkinson's disease and open the door toward the ultimate goal -prevention.

Towards improved screening of toxins for Parkinson's risk

Parkinson's disease (PD) is a chronic, progressive and disabling neurodegenerative disorder. The prevalence of PD has risen considerably over the past decades. A growing body of evidence suggest that exposure to environmental toxins, including pesticides, solvents and heavy metals (collectively called toxins), is at least in part responsible for this rapid growth. It is worrying that the current screening procedures being applied internationally to test for possible neurotoxicity of specific compounds offer inadequate insights into the risk of developing PD in humans. Improved screening procedures are therefore urgently needed. Our review first substantiates current evidence on the relation between exposure to environmental toxins and the risk of developing PD. We subsequently propose to replace the current standard toxin screening by a well-controlled multi-tier toxin screening involving the following steps: in silico studies (tier 1) followed by in vitro tests (tier 2), aiming to prioritize agents with human relevant routes of exposure. More in depth studies can be undertaken in tier 3, with whole-organism (in)vertebrate models. Tier 4 has a dedicated focus on cell loss in the substantia nigra and on the presumed mechanisms of neurotoxicity in rodent models, which are required to confirm or refute the possible neurotoxicity of any individual compound. This improved screening procedure should not only evaluate new pesticides that seek access to the market, but also critically assess all pesticides that are being used today, acknowledging that none of these has ever been proven to be safe from a perspective of PD. Importantly, the improved screening procedures should not just assess the neurotoxic risk of isolated compounds, but should also specifically look at the cumulative risk conveyed by exposure to commonly used combinations of pesticides (cocktails). The worldwide implementation of such an improved screening procedure, would be an essential step for policy makers and governments to recognize PD-related environmental risk factors.

Naringenin, a Functional Food Component, Improves Motor and Non-Motor Symptoms in Animal Model of Parkinsonism Induced by Rotenone

Parkinson's disease (PD) and other age-related neurodegenerative ailments have a strong link to oxidative stress. Bioflavonoid naringenin has antioxidant properties. The effects of pre- and post-naringenin supplementation on a rotenone-induced PD model were examined in this work. Naringenin (50 mg/kg, p.o.) was administered to rats for two weeks before the administration of rotenone in the pre-treatment phase. In contrast, rotenone (1.5 mg/kg, s.c.) was administered for eight days before naringenin (50 mg/kg, p.o.) was supplemented for two weeks in the post-treatment phase. During behavioral investigation, the motor and non-motor signs of PD were observed. Additionally, estimation of neurochemical and biochemical parameters was also carried out. Compared to controls, rotenone treatment substantially increased oxidative stress, altered neurotransmitters, and caused motor and non-motor impairments. Rotenone-induced motor and non-motor impairments were considerably reduced by naringenin supplementation. The supplementation also increased antioxidant enzyme activities and restored the changes in neurotransmitter levels. The findings of this work strongly imply that daily consumption of flavonoids such as naringenin may have a therapeutic potential to combat PD.

The susceptibility of humans to neurodegenerative and neurodevelopmental toxicities caused by organophosphorus pesticides

The toxicology field is concerned with the impact of organophosphorus (OP) compounds on human health. These compounds have been linked to an increased risk of neurological disorders, including neurodegenerative and neurodevelopmental diseases. This article aims to review studies on the role of OP compounds in developing these neurological disorders and explore how genetic variations can affect susceptibility to the neurotoxicity of these pesticides. Studies have shown that exposure to OP compounds can lead to the development of various neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), attention deficit hyperactivity disorder (ADHD), autism, intellectual disability, and other developmental neurotoxicities. Apart from inhibiting the cholinesterase enzyme, OP compounds are believed to cause other pathological mechanisms at both the extracellular level (cholinergic, serotonergic, dopaminergic, glutamatergic, and GABAergic synapses) and the intracellular level (oxidative stress, mitochondrial dysfunction, inflammation, autophagy, and apoptosis) that contribute to these disorders. Specific genetic polymorphisms, including PON1, ABCB1, NOS, DRD4, GST, CYP, and APOE, have increased the risk of developing OP-related neurological disorders.

Ecotoxicology of the herbicide paraquat: effects on wildlife and knowledge gaps

Paraquat (PQ) is an organic herbicide introduced to the commercial market in 1962 and since linked to a variety of human health effects, including lung fibrosis, liver tumors, and Parkinson's disease. Although PQ is banned in the European Union, it is still frequently used in agricultural areas of the United States and Asia. The general mechanism of PQ's toxicity is the disruption of the redox cycle in cells. This mini-review summarizes our current understanding of PQ toxicity in non-target plants and animals. Among vertebrates, PQ sensitivity tends follow the pattern of fish > amphibians > mammals > birds. Aquatic plants are particularly vulnerable to PQ, with EC50 values ranging from ~28-280 μg/L. A number of convenient but non-specific biomarkers have been identified for non-target species, including the activities of antioxidant enzymes such as superoxide dismutase and catalase, histological changes in the gill structures of fish, and the upregulation of genes associated with the cytochrome p450 monooxygenase system. Significant literature gaps include a lack of data for environmentally realistic conditions (i.e., chronic, low concentration, multi-stressor), toxicity in reptiles, and population- and ecosystem-level effects. Although PQ is a useful herbicide, considering the many human and ecological health impacts, it may be time for regulators and the agricultural industry to reconsider its use.

Overlapping Neuroimmune Mechanisms and Therapeutic Targets in Neurodegenerative Disorders

Many potential immune therapeutic targets are similarly affected in adult-onset neurodegenerative diseases, such as Alzheimer's (AD) disease, Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD), as well as in a seemingly distinct Niemann-Pick type C disease with primarily juvenile onset. This strongly argues for an overlap in pathogenic mechanisms. The commonly researched immune targets include various immune cell subsets, such as microglia, peripheral macrophages, and regulatory T cells (Tregs); the complement system; and other soluble factors. In this review, we compare these neurodegenerative diseases from a clinical point of view and highlight common pathways and mechanisms of protein aggregation, neurodegeneration, and/or neuroinflammation that could potentially lead to shared treatment strategies for overlapping immune dysfunctions in these diseases. These approaches include but are not limited to immunisation, complement cascade blockade, microbiome regulation, inhibition of signal transduction, Treg boosting, and stem cell transplantation.

Prevalence of neonicotinoid insecticides in paired private-well tap water and human urine samples in a region of intense agriculture overlying vulnerable aquifers in eastern Iowa

A pilot study among farming households in eastern Iowa was conducted to assess human exposure to neonicotinoids (NEOs). The study was in a region with intense crop and livestock production and where groundwater is vulnerable to surface-applied contaminants. In addition to paired outdoor (hydrant) water and indoor (tap) water samples from private wells, urine samples were collected from 47 adult male pesticide applicators along with the completions of dietary and occupational surveys. Estimated Daily Intake (EDI) were then calculated to examine exposures for different aged family members. NEOs were detected in 53% of outdoor and 55% of indoor samples, with two or more NEOs in 13% of samples. Clothianidin was the most frequently detected NEO in water samples. Human exposure was ubiquitous in urine samples. A median of 10 different NEOs and/or metabolites were detected in urine, with clothianidin, nitenpyram, thiamethoxam, 6-chloronicotinic acid, and thiacloprid amide detected in every urine samples analyzed. Dinotefuran, imidaclothiz, acetamiprid-N-desmethyl, and N-desmethyl thiamethoxam were found in ≥70% of urine samples. Observed water intake for study participants and EDIs were below the chronic reference doses (CRfD) and acceptable daily intake (ADI) standards for all NEOs indicating minimal risk from ingestion of tap water. The study results indicate that while the consumption of private well tap water provides a human exposure pathway, the companion urine results provide evidence that diet and/or other exposure pathways (e.g., occupational, house dust) may contribute to exposure more than water contamination. Further biomonitoring research is needed to better understand the scale of human exposure from different sources.

Development of a Qualitative Test to Detect the Presence of Organophosphate Pesticides on Fruits and Vegetables

BACKGROUND

In recent decades, the use of pesticides in agriculture has increased at a fast pace, highlighting safety problems for the environment and human health, which in turn has made it necessary to develop new detection and decontamination systems for pesticides.

METHODS

A new qualitative test capable of detecting the presence of pesticides on fruits and vegetables by using thermostable enzymes was discovered, and the test was carried out on apples and aubergines. The contaminating pesticides were extracted from fruits with acetonitrile and analyzed with a biosensor system based on the thermostable esterase EST2 immobilized on a nitrocellulose filter. This enzyme is irreversibly inhibited mainly in the presence of organophosphates pesticides. Therefore, by observing esterase activity inhibition, we revealed the presence of residual pesticides on the fruits and vegetables.

RESULTS

By analyzing the rate of esterase activity inhibition, we predicted that residual pesticides are present on the surface of the fruits. When we cleaned the fruits by washing them in the presence of the phosphotriesterase SsoPox before the detection of the esterase activity on filters, we observed a full recovery of the activity for apples and 30% for aubergines, indicating that the enzymatic decontamination of organophosphates pesticides took place.

CONCLUSIONS

The reported method permitted us to assess the pesticides present on the vegetables and their decontamination.

Oxidative Stress and Aging as Risk Factors for Alzheimer's Disease and Parkinson's Disease: The Role of the Antioxidant Melatonin

Aging and neurodegenerative diseases share common hallmarks, including mitochondrial dysfunction and protein aggregation. Moreover, one of the major issues of the demographic crisis today is related to the progressive rise in costs for care and maintenance of the standard living condition of aged patients with neurodegenerative diseases. There is a divergence in the etiology of neurodegenerative diseases. Still, a disturbed endogenous pro-oxidants/antioxidants balance is considered the crucial detrimental factor that makes the brain vulnerable to aging and progressive neurodegeneration. The present review focuses on the complex relationships between oxidative stress, autophagy, and the two of the most frequent neurodegenerative diseases associated with aging, Alzheimer's disease (AD) and Parkinson's disease (PD). Most of the available data support the hypothesis that a disturbed antioxidant defense system is a prerequisite for developing pathogenesis and clinical symptoms of ADs and PD. Furthermore, the release of the endogenous hormone melatonin from the pineal gland progressively diminishes with aging, and people's susceptibility to these diseases increases with age. Elucidation of the underlying mechanisms involved in deleterious conditions predisposing to neurodegeneration in aging, including the diminished role of melatonin, is important for elaborating precise treatment strategies for the pathogenesis of AD and PD.

Multiple neurological effects associated with exposure to organophosphorus pesticides in man

This article reviews available data regarding the possible association of organophosphorus (OP) pesticides with neurological disorders such as dementia, attention deficit hyperactivity disorder, neurodevelopment, autism, cognitive development, Parkinson's disease and chronic organophosphate-induced neuropsychiatric disorder. These effects mainly develop after repeated (chronic) human exposure to low doses of OP. In addition, three well defined neurotoxic effects in humans caused by single doses of OP compounds are discussed. Those effects are the cholinergic syndrome, the intermediate syndrome and organophosphate-induced delayed polyneuropathy. Usually, the poisoning can be avoided by an improved administrative control, limited access to OP pesticides, efficient measures of personal protection and education of OP pesticide applicators and medical staff.

Early-Onset Parkinson's Disease: Creating the Right Environment for a Genetic Disorder

Parkinson's disease (PD) by its common understanding is a late-onset sporadic movement disorder. However, there is a need to recognize not only the fact that PD pathogenesis expands beyond (or perhaps to) the brain but also that many early-onset patients develop motor signs before the age of 50 years. Indeed, studies have shown that it is likely the protein aggregation observed in the brains of patients with PD precedes the motor symptoms by perhaps a decade. Studies on early-onset forms of PD have shown it to be a heterogeneous disease with multiple genetic and environmental factors determining risk of different forms of disease. Genetic and neuropathological evidence suggests that there are α-synuclein centric forms (e.g., SNCA genomic triplication), and forms that are driven by a breakdown in mitochondrial function and specifically in the process of mitophagy and clearance of damaged mitochondria (e.g., PARKIN and PINK1 recessive loss-of-function mutations). Aligning genetic forms with recognized environmental influences will help better define patients, aid prognosis, and hopefully lead to more accurately targeted clinical trial design. Work is now needed to understand the cross-talk between these two pathomechanisms and determine a sense of independence, it is noted that autopsies studies for both have shown the presence or absence of α-synuclein aggregation. The integration of genetic and environmental data is critical to understand the etiology of early-onset forms of PD and determine how the different pathomechanisms crosstalk.

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.

Epidemiology meets toxicogenomics: Mining toxicologic evidence in support of an untargeted analysis of pesticides exposure and Parkinson's disease

BACKGROUND

Pesticides have been widely used in agriculture for more than half a century. However, with thousands currently in use, most have not been adequately assessed for influence Parkinson's disease (PD).

OBJECTIVES

Here we aimed to assess biologic plausibility of 70 pesticides implicated with PD through an agnostic pesticide-wide association study using a data mining approach linking toxicology and toxicogenomics databases.

METHODS

We linked the 70 targeted pesticides to quantitative high-throughput screening assay findings from the Toxicology in the 21st Century (Tox21) program and pesticide-related genetic/disease information with the Comparative Toxicogenomics Database (CTD). We used the CTD to determine networks of genes each pesticide has been linked to and assess enrichment of relevant gene ontology (GO) annotations. With Tox21, we evaluated pesticide induced activity on a series of 43 nuclear receptor and stress response assays and two cytotoxicity assays.

RESULTS

Overall, 59 % of the 70 pesticides had chemical-gene networks including at least one PD gene/gene product. In total, 41 % of the pesticides had chemical-gene networks enriched for ≥ 1 high-priority PD GO terms. For instance, 23 pesticides had chemical-gene networks enriched for response to oxidative stress, 21 for regulation of neuron death, and twelve for autophagy, including copper sulfate, endosulfan and chlorpyrifos. Of the pesticides tested against the Tox21 assays, 79 % showed activity on ≥ 1 assay and 11 were toxic to the two human cell lines. The set of PD-associated pesticides showed more activity than expected on assays testing for xenobiotic homeostasis, mitochondrial membrane permeability, and genotoxic stress.

CONCLUSIONS

Overall, cross-database queries allowed us to connect a targeted set of pesticides implicated in PD via epidemiology to specific biologic targets relevant to PD etiology. This knowledge can be used to help prioritize targets for future experimental studies and improve our understanding of the role of pesticides in PD etiology.

Parkinson's Disease: Risk Factor Modification and Prevention

The global burden of Parkinson's disease (PD) has increased from 2.5 to 6.1 million since the 1990s. This is expected to rise as the world population ages and lives longer. With the current consensus on the existence of a prediagnostic phase of PD, which can be divided into a preclinical stage and a prodromal stage, we can better define the risk markers and prodromal markers of PD in the broader context of PD pathogenesis. Here, we review this pathogenetic process, and discuss the evidence behind various heritability factors, exposure to pesticides and farming, high dairy consumption, and traumatic brain injuries that have been known to raise PD risk. Physical activity, early active lifestyle, high serum uric acid, caffeine consumption, exposure to tobacco, nonsteroidal anti-inflammatory drugs, and calcium channel blockers, as well as the Mediterranean and the MIND diets are observed to lower PD risk. This knowledge, when combined with ways to identify at-risk populations and early prodromal PD patients, can help the clinician make practical recommendations. Most importantly, it helps us set the parameters for epidemiological studies and create the paradigms for clinical trials.

Neurotoxicity of pesticides - A link to neurodegeneration

Parkinson's disease (PD) is a neurodegenerative disorder which mainly targets motor symptoms such as tremor, rigidity, bradykinesia and postural instability. The physiological changes occur due to dopamine depletion in basal ganglia region of the brain. PD aetiology is not yet elucidated clearly but genetic and environmental factors play a prominent role in disease occurrence. Despite of various environmental factors, pesticides exposure has been convicted as major candidate in PD pathogenesis. Among various pesticides 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been widely investigated in PD following with paraquat (PQ), maneb (MB), organochlorines (OC) and rotenone. Effect of these pesticides has been suggested to be involved in oxidative stress, alterations in dopamine transporters, mitochondrial dysfunction, α-synuclein (αSyn) fibrillation, and neuroinflammation in PD. The present review discusses the influence of pesticides in neurodegeneration and its related epidemiological studies conducted in PD. Furthermore, we have deliberated the common pesticides involved in PD and its associated genetic alterations and the probable mechanism of them behind PD pathogenesis. Hence, we conclude that pesticides play a prominent role in PD pathogenesis and advance research is needed to investigate the alterations in genetic and mechanistic aspects of PD.

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

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

Risk Factors of Parkinson’s Disease: A Case-Control Study in Moroccan Patients

Background: Parkinson’s disease (PD) remains a significant health concern in Morocco. Multivariate analysis was not used in any study to evaluate the role of various factors that contributed to the onset of the disease. Objectives: This study investigates the role of family, environmental, and professional factors in PD development. Methods: The present study is an age-matched case-control study with risk estimation based on odds ratios (OR) with a 95% confidence interval (CI). In total, 180 cases were matched with 360 controls. Results: The average age of participants was 68.3 ± 11.2 years. Adjusted logistic regression analysis showed that the family history of PD (ORa = 7.19, CI 95% 3.41 - 15.13), male sex (ORa = 1.92, CI 95% 1.16 - 3.16), spring water consumption (ORa = 3.31, CI 95% 2.05 - 5.34), drug use (ORa = 2.12, CI 95% 1.33 - 3.38), a history of head injury (ORa = 3.38, CI 95% 1.16 - 9.83) and non - consumption of coffee (ORa = 3.04, CI 95% 1.56 - 5.90) were significantly associated with the onset of the disease. In a univariate analysis, well water consumption was observed as a significant risk factor but could not be shown to be significant in a multivariate analysis. Previous work on a farm (ORa = 0.30, CI 95% 0.16 - 0.54) and history of general anesthesia (ORa = 0.47, CI 95% 0.27 - 0.83) were inversely associated with PD risk. No statistical significance was observed in the data on occupational exposure and disease risk, although there was a 30% decrease in risk for the service occupations (ORa = 0.05, CI 95% 0.01 - 0.18). Conclusions: As a result, further research is needed to determine additional risk factors.

Exploring the multifactorial aspects of Gut Microbiome in Parkinson's Disease

Advanced research in health science has broadened our view in approaching and understanding the pathophysiology of diseases and has also revolutionised diagnosis and treatment. Ever since the establishment of Braak’s hypothesis in the propagation of alpha-synuclein from the distant olfactory and enteric nervous system towards the brain in Parkinson’s Disease (PD), studies have explored and revealed the involvement of altered gut microbiota in PD. This review recapitulates the gut microbiome associated with PD severity, duration, motor and non-motor symptoms, and antiparkinsonian treatment from recent literature. Gut microbial signatures in PD are potential predictors of the disease and are speculated to be used in early diagnosis and treatment. In brief, the review also emphasises on implications of the prebiotic, probiotic, faecal microbiota transplantation, and dietary interventions as alternative treatments in modulating the disease symptoms in PD.

Environmental neurotoxicants and inflammasome activation in Parkinson's disease - A focus on the gut-brain axis

Inflammasomes are multi-protein complexes expressed in immune cells that function as intracellular sensors of environmental, metabolic and cellular stress. Inflammasome activation in the brain, has been shown to drive neuropathology and disease progression by multiple mechanisms, making it one of the most attractive therapeutic targets for disease modification in Parkinson's Disease (PD). Extensive inflammasome activation is evident in the brains of people with PD at the sites of dopaminergic degeneration and synuclein aggregation. While substantial progress has been made on validating inflammasome activation as a therapeutic target for PD, the mechanisms by which inflammasome activation is triggered and sustained over the disease course remain poorly understood. A growing body of evidence point to environmental and occupational chemical exposures as possible triggers of inflammasome activation in PD. The involvement of the gastrointestinal system and gut microbiota in PD pathophysiology is beginning to be elucidated, especially the profound link between gut dysbiosis and immune activation. While large cohort studies confirmed specific changes in the gut microbiota in PD patients compared to age-matched healthy controls, recent research suggest that synuclein pathology could be initiated in the gastrointestinal tract. In this review, we present a summarized perspective on current understanding on inflammasome activation and the gut-brain-axis link during PD pathophysiology. We discuss multiple environmental toxicants that are implicated as the etiological agents in causing idiopathic PD and their mechanistic underpinnings during neuroinflammatory events. We additionally present future directions that needs to address the research questions related to the gut-microbiome-brain mechanisms in PD.

Gut microbiota in Parkinson’s disease patients: hospital-based study

Background

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. There is accumulating evidence that link gut microbiota to symptomatology and pathophysiology of PD. The aim of this study was to describe the pattern of gut microbiota and its association with PD and identify the effect of environmental factors on gut microbiota. This case–control study included 46 patients diagnosed as Parkinson’s disease (PD) and 31 healthy volunteers age and sex matched. Detailed history including age of onset, duration of disease, environmental risk factors, diet data, treatment, Unified Parkinson’s Disease Rating Scale (UPDRS), and gastrointestinal tract (GIT) domain of Non‐Motor Symptoms Scale (NMSS) were assessed. After extraction of bacterial DNA from the fecal samples, bacterial abundance was quantified by qPCR using 16S rRNA group-specific primers.

Results

Significant high abundance of Clostridium cluster IV, Akkermansia, Bifidobacterium, and lactic acid bacteria were found in the PD group compared with the control group (P < 0.001, 0.04, 0.02 and < 0.001, respectively), while Firmicutes were significantly less abundant in the PD group (P < 0.001) compared with the control group. The naive PD patients had significant abundance of Bifidobacterium, and lactic acid compared with control group. Interestingly, Akkermansia was more abundant in treated than untreated patients. There were significant associations between pesticide exposure and Bifidobacterium (P = 0.002), while no significant correlations between different gut microbiota and demographic, environment data, different rating scores or dominant type of PD. There was a significant negative correlation between the Bifidobacterium with the duration of illness (P = 0.012).

Conclusion

The present study highlighted a significant connection between PD and levels of certain types of gut microbiota, in support of a possible link between gut microbiota and a neurodegenerative cascade of PD.

Area-Based Geocoding: An Approach to Exposure Assessment Incorporating Positional Uncertainty

While the spatial resolution of exposure surfaces has greatly improved, our ability to locate people in space remains a limiting factor in accurate exposure assessment. In this case-control study, two approaches to geocoding participant locations were used to study the impact of geocoding uncertainty on the estimation of ambient pesticide exposure and breast cancer risk among women living in California's Central Valley. Residential and occupational histories were collected and geocoded using a traditional point-based method along with a novel area-based method. The standard approach to geocoding uses centroid points to represent all geocoded locations, and is unable to adapt exposure areas based on geocode quality, except through the exclusion of low-certainty locations. In contrast, area-based geocoding retains the complete area to which an address matched (the same area from which the centroid is returned), and therefore maintains the appropriate level of precision when it comes to assessing exposure by geography. Incorporating the total potential exposure area for each geocoded location resulted in different exposure classifications and resulting odds ratio estimates than estimates derived from the centroids of those same areas (using a traditional point-based geocoder). The direction and magnitude of these differences varied by pesticide, but in all cases odds ratios differed by at least 6% and up to 35%. These findings demonstrate the importance of geocoding in exposure estimation and suggest it is important to consider geocode certainty and quality throughout exposure assessment, rather than simply using the best available point geocodes.

Pesticides applied to crops and amyotrophic lateral sclerosis risk in the U.S

BACKGROUND

Environmental exposures are implicated in the etiology of amyotrophic lateral sclerosis (ALS). Application of insecticides, herbicides, and fungicides with neurotoxic properties to crops is permitted in the U.S., however reporting of the quantities is government mandated.

OBJECTIVE

To identify pesticides that may be associated with ALS etiology for future study.

METHODS

We geospatially estimated exposure to crop-applied pesticides as risk factors for ALS in a large de-identified medical claims database, the SYMPHONY Integrated Dataverse®. We extracted residence at diagnosis of ∼26,000 nationally distributed ALS patients, and matched non-ALS controls. We mapped county-level U.S. Geological Survey data on applications of 423 pesticides to estimate local residential exposure. We randomly broke the SYMPHONY dataset into two groups to form independent discovery and validation cohorts, then confirmed top hits using residential history information from a study of NH, VT, and OH.

RESULTS

Pesticides with the largest positive statistically significant associations in both the discovery and the validation studies and evidence of neurotoxicity in the literature were the herbicides 2,4-D (OR 1.25 95 % CI 1.17-1.34) and glyphosate (OR 1.29 95 %CI 1.19-1.39), and the insecticides carbaryl (OR 1.32 95 %CI 1.23-1.42) and chlorpyrifos (OR 1.25 95 %CI 1.17-1.33).

SIGNIFICANCE

Our geospatial analysis results support potential neurotoxic pesticide exposures as risk factors for sporadic ALS. Focused studies to assess these identified potential relationships are warranted.

Association between water and sanitation, air and emission pollution and climate change and neurological disease distribution: A study based on GBD data

Along with the urbanization and industrialization of countries, the prevalence of chronic diseases has increased. There is ample evidence that ambient pollution can play a major role in these diseases. This study aimed to investigate the association between neurological disorders (NDs) and their subtypes with environmental factors. In this country-level study, we used the age-standardized prevalence and incidence rate (per 100,000 populations) of NDs and its subtypes that have been taken from the Global Burden of Disease (GBD) database in 2019. We used correlation and regression analysis to assess the association between variables. Also, multivariable regression analysis was performed to identify the most important variables in NDs distribution. Age-adjusted NDs incidence rate was significantly higher in developed countries compared to developing countries (11345.25 (95% CI: 11634.88-11055.62) and 9956.37 (95% CI: 10138.66-9774.08)). Association results indicated that the impact of water and sanitation could be more effective than air pollution on NDs. The increase in water and sanitation index levels was positively correlated with NDs incidence rate and prevalence (regression coefficient (b) = 38.011 (SE = 6.50) and b = 118.84 (SE = 20.64), p < 0.001, respectively) after adjusting socio-economic and demographic factors. Furthermore, the incidence of NDs was negatively correlated with the increase in air quality (b = -16.30 (SE = 7.25), p = 0.008). Water and sanitation and their related factors are plausible factors in the distribution of NDs, which may be linked to the potential role of air and water pollution, such as heavy metals and particle matters. These results can be used by politicians and municipal service planners for future planning.

Review of Metabolomics-Based Biomarker Research for Parkinson's Disease

Parkinson's disease (PD), as the second most common neurodegenerative disease, is seriously affecting the life quality of the elderly. However, there is still a lack of efficient medical methods to diagnosis PD before apparent symptoms occur. In recent years, clinical biomarkers including genetic, imaging, and tissue markers have exhibited remarkable benefits in assisting PD diagnoses. Due to the advantages of high-throughput detection of metabolites and almost non-invasive sample collection, metabolomics research of PD is widely used for diagnostic biomarker discovery. However, there are also a few shortages for those identified biomarkers, such as the scarcity of verifications regarding the sensitivity and specificity. Thus, reviewing the research progress of PD biomarkers based on metabolomics techniques is of great significance for developing PD diagnosis. To comprehensively clarify the progress of current metabolic biomarker studies in PD, we reviewed 20 research articles regarding the discovery and validation of biomarkers for PD diagnosis from three mainstream academic databases (NIH PubMed, ISI Web of Science, and Elsevier ScienceDirect). By analyzing those materials, we summarized the metabolic biomarkers identified by those metabolomics studies and discussed the potential approaches used for biomarker verifications. In conclusion, this review provides a comprehensive and updated overview of PD metabolomics research in the past two decades and particularly discusses the validation of disease biomarkers. We hope those discussions might provide inspiration for PD biomarker discovery and verification in the future.

Preventing Parkinson's Disease: An Environmental Agenda

Fueled by aging populations and continued environmental contamination, the global burden of Parkinson's disease (PD) is increasing. The disease, or more appropriately diseases, have multiple environmental and genetic influences but no approved disease modifying therapy. Additionally, efforts to prevent this debilitating disease have been limited. As numerous environmental contaminants (e.g., pesticides, metals, industrial chemicals) are implicated in PD, disease prevention is possible. To reduce the burden of PD, we have compiled preclinical and clinical research priorities that highlight both disease prediction and primary prevention. Though not exhaustive, the "PD prevention agenda" builds upon many years of research by our colleagues and proposes next steps through the lens of modifiable risk factors. The agenda identifies ten specific areas of further inquiry and considers the funding and policy changes that will be necessary to help prevent the world's fastest growing brain disease.

Bbc3 Loss Enhances Survival and Protein Clearance in Neurons Exposed to the Organophosphate Pesticide Chlorpyrifos

Exposure to environmental toxicants can increase the risk of developing age-related neurodegenerative disorders. Exposure to the widely used organophosphate pesticide chlorpyrifos (CPF) is associated with increased risk of developing Alzheimer's disease and Parkinson's disease, but the cellular mechanisms underlying CPF toxicity in neurons are not completely understood. We evaluated CPF toxicity in mouse primary cortical neuronal cultures, using RNA-sequencing to identify cellular pathways modulated by CPF. CPF exposure altered the expression of genes associated with intrinsic apoptosis, significantly elevating expression of the pro-apoptotic mediator Bbc3/Puma. Bbc3 loss attenuated CPF driven neurotoxicity, induction of other intrinsic apoptosis regulatory genes including Trp53 and Pmaip1 (encoding the NOXA protein), and cleavage of apoptosis executors caspase 3 and poly (ADP-ribose) polymerase (PARP). CPF exposure was associated with enhanced expression of endoplasmic reticulum stress-related genes and proteins and the accumulation of high molecular weight protein species in primary neuronal cultures. No evidence of alterations in the ubiquitin-proteosome system were observed, however, autophagy-related proteins were upregulated in CPF-treated Bbc3-/- neuronal cultures compared with identically exposed WT cultures. Elevated autophagy-related protein expression in Bbc3-/- neuronal cultures was associated with a reduction in CPF-induced high molecular weight alpha-synuclein and tau immunoreactive protein aggregates. Studies indicate that Bbc3-/- neuronal cultures enhance the endoplasmic reticulum stress response and upregulate protein clearance mechanisms as a component of resistance to CPF-mediated toxicity.

Perinatal exposure to a glyphosate-based herbicide causes dysregulation of dynorphins and an increase of neural precursor cells in the brain of adult male rats

Glyphosate, the most used herbicide worldwide, has been suggested to induce neurotoxicity and behavioral changes in rats after developmental exposure. Studies of human glyphosate intoxication have reported adverse effects on the nervous system, particularly in substantia nigra (SN). Here we used matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) to study persistent changes in peptide expression in the SN of 90-day-old adult male Wistar rats. The animals were perinatally exposed to 3 % GBH (glyphosate-based herbicide) in drinking water (corresponding to 0.36 % of glyphosate) starting at gestational day 5 and continued up to postnatal day 15 (PND15). Peptides are present in the central nervous system before birth and play a critical role in the development and survival of neurons, therefore, observed neuropeptide changes could provide better understanding of the GBH-induced long term effects on SN. The results revealed 188 significantly altered mass peaks in SN of animals perinatally exposed to GBH. A significant reduction of the peak intensity (P < 0.05) of several peptides from the opioid-related dynorphin family such as dynorphin B (57 %), alpha-neoendorphin (50 %), and its endogenous metabolite des-tyrosine alpha-neoendorphin (39 %) was detected in the GBH group. Immunohistochemical analysis confirmed a decreased dynorphin expression and showed a reduction of the total area of dynorphin immunoreactive fibers in the SN of the GBH group. In addition, a small reduction of dynorphin immunoreactivity associated with non-neuronal cells was seen in the hilus of the hippocampal dentate gyrus. Perinatal exposure to GBH also induced an increase in the number of nestin-positive cells in the subgranular zone of the dentate gyrus. In conclusion, the results demonstrate long-term changes in the adult male rat SN and hippocampus following a perinatal GBH exposure suggesting that this glyphosate-based formulation may perturb critical neurodevelopmental processes.

Baicalein alleviates depression-like behavior in rotenone- induced Parkinson's disease model in mice through activating the BDNF/TrkB/CREB pathway

BACKGROUND

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder in the world. In addition to motor symptoms, a variety of non-motor symptoms seriously affect the life quality of PD patients. Baicalein, a flavonoid extracted from the herb Scutellaria baicalensis Georgi, exhibits anti-PD activity through alleviation of its motor symptoms. However, its effects on non-motor symptoms were barely reported. This study aimed to investigate the therapeutic effects of baicalein on PD-related depression.

METHODS

After a 2-week injection of rotenone, mice with PD-related depression behavior were selected, divided into three groups, and administrated saline, baicalein, or madopar orally for four weeks. Behavior, neuroinflammation, neurotransmitters, and synaptic plasticity were evaluated.

RESULTS

Our results showed that 4-week baicalein treatment significantly alleviated the depression-like behavior in the rotenone-induced mice model. Repeated baicalein treatment reduced α-synuclein aggregation, inhibited neuroinflammation, and maintained neurotransmitters homeostasis. Moreover, we found that baicalein treatment could remarkably protect the synaptic plasticity and activate the BDNF/TrkB/CREB pathway in the PD-related depression mice model. As traditional dopamine replacement therapy unleashed few effects on depression-like symptom amelioration and synaptic function protection, baicalein might be a more appropriate choice for PD-related depression.

CONCLUSIONS

The current results suggested that baicalein could act as a treatment for PD-related depression.

Ubisol-Q10, a Nanomicellar and Water-Dispersible Formulation of Coenzyme-Q10 as a Potential Treatment for Alzheimer's and Parkinson's Disease

The world continues a desperate search for therapies that could bring hope and relief to millions suffering from progressive neurodegenerative diseases such as Alzheimer’s (AD) and Parkinson’s (PD). With oxidative stress thought to be a core stressor, interests have long been focused on applying redox therapies including coenzyme-Q₁₀. Therapeutic use has failed to show efficacy in human clinical trials due to poor bioavailability of this lipophilic compound. A nanomicellar, water-dispersible formulation of coenzyme-Q₁₀, Ubisol-Q₁₀, has been developed by combining coenzyme-Q₁₀ with an amphiphilic, self-emulsifying molecule of polyoxyethanyl α-tocopheryl sebacate (derivatized vitamin E). This discovery made possible, for the first time, a proper assessment of the true therapeutic value of coenzyme-Q₁₀. Micromolar concentrations of Ubisol-Q₁₀ show unprecedented neuroprotection against neurotoxin exposure in in vitro and in vivo models of neurodegeneration and was extremely effective when delivered either prior to, at the time of, and most significantly, post-neurotoxin exposure. These findings indicate a possible way forward for clinical development due to effective doses well within Federal Drug Administration guidelines. Ubisol-Q₁₀ is a potent mobilizer of astroglia, antioxidant, senescence preventer, autophagy activator, anti-inflammatory, and mitochondrial stabilizer. Here we summarize the work with oil-soluble coenzyme-Q₁₀, its limitations, and focus mainly on efficacy of water-soluble coenzyme-Q₁₀ in neurodegeneration.

Combined Ubisol-Q10 and Ashwagandha Root Extract Target Multiple Biochemical Mechanisms and Reduces Neurodegeneration in a Paraquat-Induced Rat Model of Parkinson's Disease

Parkinson’s disease (PD) is characterized by progressive neurodegeneration in the substantia nigra (SN) region resulting in loss of movement coordination. Current therapies only provide symptomatic relief, and there is no agent to halt the progression of PD. Previously, Ubisol-Q₁₀, a water-soluble formulation of coenzyme-Q_10, and ethanolic root extract of ashwagandha (ASH) have been shown to inhibit PD pathology in rodent models when used alone. Here, we evaluated the neuroprotective efficacy of oral administration of ASH and Ubisol-Q₁₀ alone and in combination in a paraquat-induced PD rat model. The combined treatment resulted in better-preserved neuron morphology compared to Ubsiol-Q₁₀ or ASH alone. The combination treatment enhanced activation of pro-survival astroglia and inhibited pro-inflammatory microglia. While anti-oxidative effects were seen with both agents, Ubisol-Q₁₀ activated autophagy, whereas ashwagandha showed a better anti-inflammatory response. Thus, the combined treatment caused inhibition of oxidative stress, autophagy activation, inhibition of pro-inflammatory microglia, and activation of pro-survival astroglia. Consequently, paraquat (PQ)-treated rats given the combination treatment in drinking water did not show motor impairment. Based on these interesting observations, the combined treatment containing two well-tolerated natural compounds could be a more effective strategy to halt the progression of PD.

Alpha-Synuclein: The Interplay of Pathology, Neuroinflammation, and Environmental Factors in Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is a multifactorial, chronic, and progressive neurodegenerative disease. α-Synuclein (α-syn), which is the main protein component of Lewy bodies, plays an important role in the pathological hallmarks of PD. However, the pathological function of α-syn and the molecular mechanisms responsible for the degeneration of dopaminergic neurons are still elusive.

SUMMARY

Cumulative evidence implicates that abnormal processing of α-syn will be predicted to lead to pathological changes in PD. Key Messages: In this review, we summarize the structure and physiological function of α-syn, and further discuss the interplay of pathology, neuroinflammation, and environmental factors in PD. Additionally, we suggest future directions for understanding the toxicity of α-syn to neurons, which may ultimately encourage us to better design disease-modifying therapeutic strategies for PD.

Well-Water Consumption and Risk of Parkinson's Disease: A Meta-Analysis of 15 Observational Studies

INTRODUCTION

The relationship between the risk of Parkinson disease and well-water consumption has been extensively studied, but the results have been contradictory. Therefore, we conducted a meta-analysis of observational studies to systematically assess the relationship between well-water consumption and Parkinson disease risk.

METHODS

We followed the PRISMA checklist in completing the meta-analysis. We searched two electronic databases (PubMed, EBSCO, EMBASE and Cochrane) from establishment to October, 2021, to identify relevant studies linking well-water drinking to Parkinson risk. We used a random-effects model to calculate the overall odds ratio (OR) with 95% confidence interval (CI). To reduce intragroup heterogeneity, we conducted subgroup analyses according to the research design and geographic area.

RESULTS

After careful review, a total of 15 case-control-designed studies included data suitable for our meta-analysis. The total number of cases and total controls that contribute to the combined OR were 2182 and 2456. The combined OR for ever well-water drinkers versus non-drinkers was 1.16 (95% CI: 0.97-1.39, I² = 44.52%). In subgroup analysis by geographic area, a significant association was observed in studies conducted in Asia (OR 1.29, 95% CI: 1.05-1.58, I² = 0.0%, p for heterogeneity = 0.460) but not in studies conducted in America (OR 0.97, 95% CI: 0.76-1.24, I² = 41.2%, p for heterogeneity = 0.164). In subgroup analysis by study design, a borderline significant association emerged in hospital-based case-control studies (OR 1.31, 95% CI: 1.04-1.65, I² = 40.9%, p for heterogeneity = 0.118) but not in population-based case-control studies (OR 0.96, 95% CI: 0.73-1.26, I² = 41.1%, p for heterogeneity = 0.165).

DISCUSSION

Our results indicate that there is no significant correlation between well-water consumption and PD risk.

Pesticide use and incident Parkinson's disease in a cohort of farmers and their spouses

BACKGROUND

Extensive literature suggests an association between general pesticide use and Parkinson's disease (PD). However, with few exceptions, little is known about associations between specific pesticides and PD.

OBJECTIVE

We evaluated use of pesticides and incident PD in 38,274 pesticide applicators and 27,836 of their spouses in the Agricultural Health Study cohort followed over 20 years.

METHODS

We used self-reported information on ever-use of 50 specific pesticides as of enrollment for both applicators and spouses, and considered intensity-weighted lifetime days (IWLD) reported at enrollment and through the first 5-year follow-up among applicators. We estimated covariate-adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression. We also examined heterogeneity in associations by history of head injury and chemical resistant glove use.

RESULTS

A total of 373 applicators and 118 spouses self-reported incident doctor-diagnosed PD. Ever-use of the insecticide terbufos (HR:1.31, 95%CI:1.02-1.68) and the herbicides trifluralin (HR:1.29, 95%CI: 0.99-1.70) and 2,4,5-T (HR:1.57, 95%CI:1.21-2.04) was associated with elevated PD risk. On the other hand, diazinon (HR:0.73, 95%CI: 0.58-0.94) and 2,4,5-TP (HR:0.39, 95%CI:0.25-0.62) were associated with reduced risk. We observed heterogeneity in ever-use associations by head injury and chemical-resistant glove use for some pesticides, with higher risk among those who reported a history of head injury, or who did not use gloves. PD risk was also elevated for applicators in the highest category of IWLD for dichlorvos, permethrin (animal use), and benomyl.

CONCLUSIONS

We found evidence of increased PD risk for some pesticides. Our results also suggest higher susceptibility for pesticide-associated PD among individuals with head injury as well as protection with use of chemical resistant gloves, although further research is needed to understand the impact of head injury. Research on current and newer pesticides, including mechanisms relevant to PD, is important given widespread pesticide use.

A critical review on the potential impacts of neonicotinoid insecticide use: current knowledge of environmental fate, toxicity, and implications for human health

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.

The gut microbiome in Parkinson's disease: A culprit or a bystander?

In recent years, large-scale metagenomics projects such as the Human Microbiome Project placed the gut microbiota under the spotlight of research on its role in health and in the pathogenesis several diseases, as it can be a target for novel therapeutical approaches. The emerging concept of a microbiota modulation of the gut-brain axis in the pathogenesis of neurodegenerative disorders has been explored in several studies in animal models, as well as in human subjects. Particularly, research on changes in the composition of gut microbiota as a potential trigger for alpha-synuclein (α-syn) pathology in Parkinson's disease (PD) has gained increasing interest. In the present review, we first provide the basis to the understanding of the role of gut microbiota in healthy subjects and the molecular basis of the gut-brain interaction, focusing on metabolic and neuroinflammatory factors that could trigger the alpha-synuclein conformational changes and aggregation. Then, we critically explored preclinical and clinical studies reporting on the changes in gut microbiota in PD, as compared to healthy subjects. Furthermore, we examined the relationship between the gut microbiota and PD clinical features, discussing data consistently reported across studies, as well as the potential sources of inconsistencies. As a further step toward understanding the effects of gut microbiota on PD, we discussed the relationship between dysbiosis and response to dopamine replacement therapy, focusing on Levodopa metabolism. We conclude that further studies are needed to determine whether the gut microbiota changes observed so far in PD patients is the cause or, instead, it is merely a consequence of lifestyle changes associated with the disease. Regardless, studies so far strongly suggest that changes in microbiota appears to be impactful in pathogenesis of neuroinflammation. Thus, dysbiotic microbiota in PD could influence the disease course and response to medication, especially Levodopa. Future research will assess the impact of microbiota-directed therapeutic intervention in PD patients.

Parkinson's Disease in Louisiana, 1999-2012: Based on Hospital Primary Discharge Diagnoses, Incidence, and Risk in Relation to Local Agricultural Crops, Pesticides, and Aquifer Recharge

The two major causes of Parkinson's disease (PD) are genetic susceptibility and exposure to agricultural pesticides. Access to 23,224 individuals' hospital primary discharge diagnoses of PD allowed the mapping of cases against known crop distributions and pesticides. Our main objective was to map PD risks (cases per 10,000 people) against crops and their pesticides. The ZIP Code address locations, and the 2000 and 2010 census data, were used to map the risks of PD throughout Louisiana and in relation to United States Department of Agriculture (USDA)-recorded crops. The introduction of glyphosate-resistant crops appears to have initiated the PD disappearance from northeastern parishes on the west bank of the Mississippi river. Rice and sugar cane are seemingly unassociated with PD, as is the Mississippi itself, except for Jefferson and St. Charles Parishes, which are essentially urban or industrial. The present major PD-affected areas are associated with commercial forests, woodlands, and pastures, and thus with certain arbor-pastoral pesticides, 2,4-D, chlorpyrifos, and paraquat. Human populations at maximum risk are those living in areas of moderate and high aquifer-recharge potential. The levels of estimated pesticide exposure in these recharge areas we were able to access were of variable use, but significant amounts of 2,4-D were being used.

Well Water and Parkinson's Disease in Medicare Beneficiaries: A Nationwide Case-Control Study

BACKGROUND

Well water frequently is considered a risk factor for Parkinson's disease (PD), but few studies were designed appropriately to test whether geographic factors affect PD risk.

OBJECTIVE

To determine the risk of PD in relation to residential use of private well water.

METHODS

In a nationwide, population-based case-control study, we identified all incident PD cases (N = 89,790) and all comparable controls (N = 21,549,400) age 66-90 who solely relied on Medicare coverage in the U.S. in 2009. We estimated the probability of use of private well water using zip code of residence at diagnosis/reference and U.S. Census data on household water source. We modeled this exposure linearly in logistic regression to calculate the odds ratio (OR) and 95% confidence interval (CI) of PD risk in relation to well water use. We adjusted for age, sex and race/ethnicity, and verified that smoking and use of medical care did not confound results. We repeated analyses with a 2-year exposure lag and separately within each U.S. state.

RESULTS

Use of well water was inversely associated with PD risk (OR = 0.87, 95% CI 0.85-0.89). We confirmed this association in a Cox survival analysis in which we followed controls for 5 years, death or PD diagnosis. There was little evidence that well water use increased risk of PD in any individual state.

CONCLUSIONS

Although it remains possible that exposures in well water in more narrow geographic regions increase PD risk, in general these results suggest that exposures more common in urban/suburban areas might also be relevant.

Validity and Reliability of an Assessment Tool for the Screening of Neurotoxic Effects in Agricultural Workers in Chile

There is a substantial use of pesticides within the agricultural industry of Chile, with neurotoxic effects through mechanisms of acetylcholinesterase inhibition. These pesticides result in deterioration in health, increasing the risk of diseases such as Parkinson's and Alzheimer's in highly exposed occupational population. To date, there are no brief assessment tools to monitor cognitive impairment in agricultural workers chronically exposed to these pesticides. Method. 234 agricultural workers and 305 nonagricultural workers were assessed two times (test-retest) through a brief tool which comprised three tests (clock-drawing test (CDT); frontal assessment battery (FAB); trail making tests (TMT) A and B). The full scale of WAIS-IV was administered as a gold standard to 18% of the sample of agricultural workers. Factor analysis was used to evaluate the factor structure, and validity and test-retest reliability were assessed concurrently. Results. Cronbach's alpha values were satisfactory or above (>0.60). Test-retest correlations were all significantly correlated (p < 0.001). All the tests had a significant correlation with the full scale IQ score of WAIS-IV (p < 0.05). The Kaiser-Meyer-Olkin (KMO) measure was 0.74, and the Bartell sphericity test = p < 0.001. Three factors explaining 61.62% of the variance were extracted. Two items of the FAB test were dropped of the final factor solution. Normative data transformed into percentile scores and stratified by age and educational level were obtained for Chilean agricultural workers. Conclusion. The brief assessment tool has adequate metric properties as a screening instrument. This allows for a simple administration test (10 to 15 minutes) that can potentially be used for the rapid monitoring of cognitive deterioration in the face of occupational exposure to pesticides in agricultural workers.

Inflammasomes: An Emerging Mechanism Translating Environmental Toxicant Exposure Into Neuroinflammation in Parkinson's Disease

Evidence indicates that complex gene-environment interactions underlie the incidence and progression of Parkinson's disease (PD). Neuroinflammation is a well-characterized feature of PD widely believed to exacerbate the neurodegenerative process. Environmental toxicants associated with PD, such as pesticides and heavy metals, can cause cellular damage and stress potentially triggering an inflammatory response. Toxicant exposure can cause stress and damage to cells by impairing mitochondrial function, deregulating lysosomal function, and enhancing the spread of misfolded proteins. These stress-associated mechanisms produce sterile triggers such as reactive oxygen species (ROS) along with a variety of proteinaceous insults that are well documented in PD. These associations provide a compelling rationale for analysis of sterile inflammatory mechanisms that may link environmental exposure to neuroinflammation and PD progression. Intracellular inflammasomes are cytosolic assemblies of proteins that contain pattern recognition receptors, and a growing body of evidence implicates the association between inflammasome activation and neurodegenerative disease. Characterization of how inflammasomes may function in PD is a high priority because the majority of PD cases are sporadic, supporting the widely held belief that environmental exposure is a major factor in disease initiation and progression. Inflammasomes may represent a common mechanism that helps to explain the strong association between exposure and PD by mechanistically linking environmental toxicant-driven cellular stress with neuroinflammation and ultimately cell death.

Gene-environment interaction and Mendelian randomisation

Genetic factors only account for up to a third of the cases of Parkinson's disease (PD), while the remaining cases are of unknown aetiology. Environmental exposures (such as pesticides or heavy metals) and the interaction with genetic susceptibility factors (summarized in the concept of impaired xenobiotic metabolism) are believed to play a major role in the mechanisms of neurodegeneration. Beside of the classical association studies (e.g. genome-wide association studies), a novel approach to investigate environmental risk factors are Mendelian randomisation studies. This review explores the gene-environment interaction and the gain of Mendelian randomisation studies in assessing causalities of modifiable risk factors for PD.