Meeting report: consensus statement-Parkinson's disease and the environment: collaborative on health and the environment and Parkinson's Action Network (CHE PAN) conference 26-28 June 2007

STAT4 targets KISS1 to inhibit the oxidative damage, inflammation and neuronal apoptosis in experimental PD models by inactivating the MAPK pathway

BACKGROUND

Oxidative stress and neuroinflammation are proven to play critical roles in the pathogenesis of Parkinson's disease (PD). As reported, patients with PD have lower level of STAT4 compared with healthy subjects. However, the biological functions and mechanisms of STAT4 in PD pathogenesis remain uncertain. This study aimed to investigate the roles and related mechanisms of STAT4 in PD development.

METHODS

The intraperitoneal injection of MPTP (20 mg/kg) dissolved in physiological saline was performed to mimic PD-like conditions in vivo. MPP + solution was prepared for cell model of PD. Cell viability was measured by CCK-8. Griess reaction was conducted to measure NO concentrations. The mRNA and protein levels were evaluated by RT-qPCR and western blotting. ROS generation was assessed by DCFH-DA. The levels of inflammatory cytokines were measured by ELISA. Cell apoptosis was examined by flow cytometry and western blotting. Moreover, the SH-SY5Y cells were treated with conditioned medium from LPS-stimulated microglia and subjected to CCK-8 assays and ELISA. Mechanistically, CHIP assays and luciferase reporter assays were performed to verify the binding relationship between KISS1 and STAT4. For in vivo analysis, the histological changes of midbrain tissues of mice were determined by hematoxylin and eosin staining. The expression of tyrosine hydroxylase (TH) was detected by immunohistochemistry staining. Iba-1 positive microglial cells in the striatum were assessed by immunofluorescence staining.

RESULTS

For in vitro analysis, STAT4 level was downregulated after MPP+ treatment, and STAT4 upregulation inhibited the oxidative damage, inflammation and apoptosis in SH-SY5Y cells. STAT4 bound at +215-228 region of KISS1, and KISS1 upregulation counteracted the protection of STAT4 upregulation against cell damage. Moreover, STAT4 upregulation inhibited cell viability loss and inflammation induced by conditioned medium from LPS-treated microglia, whereas KISS1 upregulation had the opposite effect. For in vivo analysis, the protective effects of STAT4 upregulation against inflammatory response, oxidative stress, dopaminergic neuronal loss and microglia activation were attenuated by KISS1 upregulation. Moreover, the inactivation of MAPK pathway caused by STAT4 upregulation was reversed by KISS1 upregulation, and MAPK inhibition attenuated the MPP+-induced inflammation, oxidative stress and apoptosis in SH-SY5Y cells.

CONCLUSION

STAT4 inhibits KISS1 to attenuate the oxidative damage, inflammation and neuronal apoptosis in PD by inactivating the MAPK pathway.

Lifestyle Factors and Parkinson's Disease Risk in a Rural New England Case-Control Study

Introduction

Parkinson's disease (PD) is an age-related neurodegenerative disease likely caused by complex interactions between genetic and environmental risk factors. Exposure to pesticides, toxic metals, solvents, and history of traumatic brain injury have been implicated as environmental risk factors for PD, underscoring the importance of identifying risk factors associated with PD across different communities.

Methods

We conducted a questionnaire-based case-control study in a rural area on the New Hampshire/Vermont border, enrolling PD patients and age- and sex-matched controls from the general population between 2017 and 2020. We assessed frequent participation in a variety of recreational and occupational activities and surveyed potential chemical exposures.

Results

Suffering from “head trauma or a concussion” prior to diagnosis was associated with a fourfold increased risk of PD. Adjustment for head trauma negated any risk of participation in “strenuous athletic activities.” We observed a 2.7-fold increased risk of PD associated with activities involving lead (adjusted p=0.038).

Conclusion

Implicating these factors in PD risk favors public health efforts in exposure mitigation while also motivating future work mechanisms and intervention opportunities.

Discrimination between healthy and patients with Parkinson's disease from hand resting activity using inertial measurement unit

BACKGROUND

Parkinson's disease (PD) is a neurological disease that affects the motor system. The associated motor symptoms are muscle rigidity or stiffness, bradykinesia, tremors, and gait disturbances. The correct diagnosis, especially in the initial stages, is fundamental to the life quality of the individual with PD. However, the methods used for diagnosis of PD are still based on subjective criteria. As a result, the objective of this study is the proposal of a method for the discrimination of individuals with PD (in the initial stages of the disease) from healthy groups, based on the inertial sensor recordings.

METHODS

A total of 27 participants were selected, 15 individuals previously diagnosed with PD and 12 healthy individuals. The data collection was performed using inertial sensors (positioned on the back of the hand and on the back of the forearm). Different numbers of features were used to compare the values of sensitivity, specificity, precision, and accuracy of the classifiers. For group classification, 4 classifiers were used and compared, those being [Random Forest (RF), Support Vector Machine (SVM), K-Nearest Neighbor (KNN), and Naive Bayes (NB)].

RESULTS

When all individuals with PD were analyzed, the best performance for sensitivity and accuracy (0.875 and 0.800, respectively) was found in the SVM classifier, fed with 20% and 10% of the features, respectively, while the best performance for specificity and precision (0.933 and 0.917, respectively) was associated with the RF classifier fed with 20% of all the features. When only individuals with PD and score 1 on the Hoehn and Yahr scale (HY) were analyzed, the best performances for sensitivity, precision and accuracy (0.933, 0.778 and 0.848, respectively) were from the SVM classifier, fed with 40% of all features, and the best result for precision (0.800) was connected to the NB classifier, fed with 20% of all features.

CONCLUSION

Through an analysis of all individuals in this study with PD, the best classifier for the detection of PD (sensitivity) was the SVM fed with 20% of the features and the best classifier for ruling out PD (specificity) was the RF classifier fed with 20% of the features. When analyzing individuals with PD and score HY = 1, the SVM classifier was superior across the sensitivity, precision, and accuracy, and the NB classifier was superior in the specificity. The obtained result indicates that objective methods can be applied to help in the evaluation of PD.

Genes Implicated in Familial Parkinson's Disease Provide a Dual Picture of Nigral Dopaminergic Neurodegeneration with Mitochondria Taking Center Stage

The mechanism of nigral dopaminergic neuronal degeneration in Parkinson's disease (PD) is unknown. One of the pathological characteristics of the disease is the deposition of α-synuclein (α-syn) that occurs in the brain from both familial and sporadic PD patients. This paper constitutes a narrative review that takes advantage of information related to genes (SNCA, LRRK2, GBA, UCHL1, VPS35, PRKN, PINK1, ATP13A2, PLA2G6, DNAJC6, SYNJ1, DJ-1/PARK7 and FBXO7) involved in familial cases of Parkinson's disease (PD) to explore their usefulness in deciphering the origin of dopaminergic denervation in many types of PD. Direct or functional interactions between genes or gene products are evaluated using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. The rationale is to propose a map of the interactions between SNCA, the gene encoding for α-syn that aggregates in PD, and other genes, the mutations of which lead to early-onset PD. The map contrasts with the findings obtained using animal models that are the knockout of one of those genes or that express the mutated human gene. From combining in silico data from STRING-based assays with in vitro and in vivo data in transgenic animals, two likely mechanisms appeared: (i) the processing of native α-syn is altered due to the mutation of genes involved in vesicular trafficking and protein processing, or (ii) α-syn mutants alter the mechanisms necessary for the correct vesicular trafficking and protein processing. Mitochondria are a common denominator since both mechanisms require extra energy production, and the energy for the survival of neurons is obtained mainly from the complete oxidation of glucose. Dopamine itself can result in an additional burden to the mitochondria of dopaminergic neurons because its handling produces free radicals. Drugs acting on G protein-coupled receptors (GPCRs) in the mitochondria of neurons may hopefully end up targeting those receptors to reduce oxidative burden and increase mitochondrial performance. In summary, the analysis of the data of genes related to familial PD provides relevant information on the etiology of sporadic cases and might suggest new therapeutic approaches.

Microbiota and Other Preventive Strategies and Non-genetic Risk Factors in Parkinson's Disease

The exact cause of Parkinson’s disease (PD), the second most prevalent neurodegenerative disease in modern societies, is still unknown. Many scientists point out that PD is caused by a complex interaction between different factors. Although the main risk factor is age, there are other influences, genetic and environmental, that individually or in combination may trigger neurodegenerative changes leading to PD. Nowadays, research remains focused on better understanding which environmental factors are related to the risk of developing PD and why. In line with the knowledge on evidence on exposures that prevent/delay PD onset or that impact on disease progression, the aims of this review were: (i) to comment on the non-genetic risk factors that mainly affect idiopathic PD; and (ii) to comment on seemingly reliable preventive interventions. We discuss both environmental factors that may affect the central nervous system (CNS) or the intestinal tract, and the likely mechanisms underlying noxious or protective actions. Knowledge on risk, protective factors, and mechanisms may help to envisage why nigral dopaminergic neurons are so vulnerable in PD and, eventually, to design new strategies for PD prevention and/or anti-PD therapy. This article reviews the variety of the known and suspected environmental factors, such as lifestyle, gut microbiota or pesticide exposition, and distinguishes between those that are harmful or beneficial for the PD acquisition or progression. In fact, the review covers one of the most novel players in the whole picture, and we address the role of microbiota on keeping a healthy CNS and/or on preventing the “side-effects” related to aging.

Brain diseases in changing climate

Climate change is one of the biggest and most urgent challenges for the 21st century. Rising average temperatures and ocean levels, altered precipitation patterns and increased occurrence of extreme weather events affect not only the global landscape and ecosystem, but also human health. Multiple environmental factors influence the onset and severity of human diseases and changing climate may have a great impact on these factors. Climate shifts disrupt the quantity and quality of water, increase environmental pollution, change the distribution of pathogens and severely impacts food production - all of which are important regarding public health. This paper focuses on brain health and provides an overview of climate change impacts on risk factors specific to brain diseases and disorders. We also discuss emerging hazards in brain health due to mitigation and adaptation strategies in response to climate changes.

Genetic Defects in Mitochondrial Dynamics in Caenorhabditis elegans Impact Ultraviolet C Radiation- and 6-hydroxydopamine-Induced Neurodegeneration

Background: Parkinson’s disease (PD) is one of the most common neurodegenerative disorders involving devastating loss of dopaminergic neurons in the substantia nigra. Early steps in PD pathogenesis include mitochondrial dysfunction, and mutations in mitochondrial genes have been linked to familial forms of the disease. However, low penetrance of mutations indicates a likely important role for environmental factors in PD risk through gene by environment interactions. Herein, we study how genetic deficiencies in mitochondrial dynamics processes including fission, fusion, and mitophagy interact with environmental exposures to impact neurodegeneration. Methods: We utilized the powerful model organism Caenorhabditis elegans to study ultraviolet C radiation (UVC)- and 6-hydroxydopamine-induced degeneration of fluorescently-tagged dopaminergic neurons in the background of fusion deficiency (MFN1/2 homolog, fzo-1), fission deficiency (DMN1L homolog, drp-1), and mitochondria-specific autophagy (mitophagy) deficiency (PINK1 and PRKN homologs, pink-1 and pdr-1). Results: Overall, we found that deficiency in either mitochondrial fusion or fission sensitizes nematodes to UVC exposure (used to model common environmental pollutants) but protects from 6-hydroxydopamine-induced neurodegeneration. By contrast, mitophagy deficiency makes animals more sensitive to these stressors with an interesting exception—pink-1 deficiency conferred remarkable protection from 6-hydroxydopamine. We found that this protection could not be explained by compensatory antioxidant gene expression in pink-1 mutants or by differences in mitochondrial morphology. Conclusions: Together, our results support a strong role for gene by environment interactions in driving dopaminergic neurodegeneration and suggest that genetic deficiency in mitochondrial processes can have complex effects on neurodegeneration.

Parkinson's disease research: adopting a more human perspective to accelerate advances

Parkinson's disease (PD) affects 1% of the population over 60 years old and, with global increases in the aging population, presents huge economic and societal burdens. The etiology of PD remains unknown; most cases are idiopathic, presumed to result from genetic and environmental risk factors. Despite 200 years since the first description of PD, the mechanisms behind initiation and progression of the characteristic neurodegenerative processes are not known. Here, we review progress and limitations of the multiple PD animal models available and identify advances that could be implemented to better understand pathological processes, improve disease outcome, and reduce dependence on animal models. Lessons learned from reducing animal use in PD research could serve as guideposts for wider biomedical research.

Genetic differences in the aryl hydrocarbon receptor and CYP1A2 affect sensitivity to developmental polychlorinated biphenyl exposure in mice: relevance to studies of human neurological disorders

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that remain a human health concern with newly discovered sources of contamination and ongoing bioaccumulation and biomagnification. Children exposed during early brain development are at highest risk of neurological deficits, but highly exposed adults reportedly have an increased risk of Parkinson's disease. Our previous studies found allelic differences in the aryl hydrocarbon receptor and cytochrome P450 1A2 (CYP1A2) affect sensitivity to developmental PCB exposure, resulting in cognitive deficits and motor dysfunction. High-affinity Ahr ^b Cyp1a2(-/-) mice were most sensitive compared with poor-affinity Ahr ^d Cyp1a2(-/-) and wild-type Ahr ^b Cyp1a2(+/+) mice. Our follow-up studies assessed biochemical, histological, and gene expression changes to identify the brain regions and pathways affected. We also measured PCB and metabolite levels in tissues to determine if genotype altered toxicokinetics. We found evidence of AHR-mediated toxicity with reduced thymus and spleen weights and significantly reduced thyroxine at P14 in PCB-exposed pups. In the brain, the greatest changes were seen in the cerebellum where a foliation defect was over-represented in Cyp1a2(-/-) mice. In contrast, we found no difference in tyrosine hydroxylase immunostaining in the striatum. Gene expression patterns varied across the three genotypes, but there was clear evidence of AHR activation. Distribution of parent PCB congeners also varied by genotype with strikingly high levels of PCB 77 in poor-affinity Ahr ^d Cyp1a2(-/-) while Ahr ^b Cyp1a2(+/+) mice effectively sequestered coplanar PCBs in the liver. Together, our data suggest that the AHR pathway plays a role in developmental PCB neurotoxicity, but we found little evidence that developmental exposure is a risk factor for Parkinson's disease.

Editor's Highlight: Base Excision Repair Variants and Pesticide Exposure Increase Parkinson's Disease Risk

Exposure to certain pesticides induces oxidative stress and increases Parkinson's disease (PD) risk. Mitochondrial DNA (mtDNA) damage is found in dopaminergic neurons in idiopathic PD and following pesticide exposure in experimental models thereof. Base excision repair (BER) is the major pathway responsible for repairing oxidative DNA damage in cells. Whether single nucleotide polymorphisms (SNPs) in BER genes alone or in combination with pesticide exposure influence PD risk is unknown. We investigated the contributions of functional SNPs in 2 BER genes (APEX1 and OGG1) and mitochondrial dysfunction- or oxidative stress-related pesticide exposure, including paraquat, to PD risk. We also studied the effect of paraquat on levels of mtDNA damage and mitochondrial bioenergetics. 619 PD patients and 854 population-based controls were analyzed for the 2 SNPs, APEX1 rs1130409 and OGG1 rs1052133. Ambient pesticide exposures were assessed with a geographic information system. Individually, or in combination, the BER SNPs did not influence PD risk. Mitochondrial-inhibiting (OR = 1.79, 95% CI [1.32, 2.42]), oxidative stress-inducing pesticides (OR = 1.61, 95% CI [1.22, 2.11]), and paraquat (OR = 1.54, 95% CI [1.23, 1.93]) were associated with PD. Statistical interactions were detected, including for a genetic risk score based on rs1130409 and rs1052133 and oxidative stress inducing pesticides, where highly exposed carriers of both risk genotypes were at the highest risk of PD (OR = 2.21, 95% CI [1.25, 3.86]); similar interactions were estimated for mitochondrial-inhibiting pesticides and paraquat alone. Additionally, paraquat exposure was found to impair mitochondrial respiration and increase mtDNA damage in in vivo and in vitro systems. Our findings provide insight into possible mechanisms involved in increased PD risk due to pesticide exposure in the context of BER genotype variants.

Time Trends in the Incidence of Parkinson Disease

IMPORTANCE

Changes over time in the incidence of parkinsonism and Parkinson disease (PD) remain uncertain.

OBJECTIVE

To investigate secular trends (period effects) and birth cohort trends in the incidence of parkinsonism and PD over 30 years in a geographically defined American population.

DESIGN, SETTING, AND PARTICIPANTS

We used the medical records-linkage system of the Rochester Epidemiology Project to identify incidence cases of PD and other types of parkinsonism in Olmsted County, Minnesota, from 1976 to 2005. All cases were classified by a movement disorder specialist using defined criteria through the review of the complete medical records within the system. The analyses for this study were conducted between May 2015 and January 2016.

MAIN OUTCOMES AND MEASURES

Incidence rates of parkinsonism and PD over 30 years. We tested for secular trends (period effects) using negative binomial regression models and for birth cohort effects using age-period-cohort models.

RESULTS

Of 906 patients with parkinsonism, 501 were men, and the median age at onset was 74 years (interquartile range, 66-81 years). Of the 464 patients with PD, 275 were men, and the median age at onset was 73 years (interquartile range, 64-80 years). The overall incidence rates increased significantly over 30 years in men for both parkinsonism (relative risk [RR], 1.17 per decade; 95% CI, 1.03-1.33) and PD (RR, 1.24 per decade; 95% CI, 1.08-1.43). These trends were driven primarily by the older age groups. In particular, for men 70 years or older, incidence rates increased for both parkinsonism (RR, 1.24 per decade; 95% CI, 1.07-1.44) and PD (RR, 1.35 per decade; 95% CI, 1.10-1.65). The secular trends were not significant for women overall or in age strata. We observed an increased risk for both men and women born in the 1920 cohort (1915-1924). However, this birth cohort effect was significant only for PD and only in men.

CONCLUSIONS AND REVELANCE

Our study suggests that the incidence of parkinsonism and PD may have increased between 1976 and 2005, particularly in men 70 years and older. These trends may be associated with the dramatic changes in smoking behavior that took place in the second half of the 20th century or with other lifestyle or environmental changes. However, the trends could be spurious and need to be confirmed in other populations.

Linking Stress, Catecholamine Autotoxicity, and Allostatic Load with Neurodegenerative Diseases: A Focused Review in Memory of Richard Kvetnansky

In this Focused Review, we provide an update about evolving concepts that may link chronic stress and catecholamine autotoxicity with neurodegenerative diseases such as Parkinson's disease. Richard Kvetnansky's contributions to the field of stress and catecholamine systems inspired some of the ideas presented here. We propose that coordination of catecholaminergic systems mediates adjustments maintaining health and that senescence-related disintegration of these systems leads to disorders of regulation and to neurodegenerative diseases such as Parkinson's disease. Chronically repeated episodes of stress-related catecholamine release and reuptake, with attendant increases in formation of the toxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde, might accelerate this process.

Climate Justice in Rural Southeastern United States: A Review of Climate Change Impacts and Effects on Human Health

Climate justice is a local, national, and global movement to protect at-risk populations who are disproportionately affected by climate change. The social context for this review is the Southeastern region of the United States, which is particularly susceptible to climate change because of the geography of the area and the vulnerabilities of the inhabiting populations. Negative human health effects on variable and vulnerable populations within the Southeast region due to changing climate are concerning, as health threats are not expected to produce parallel effects among all individuals. Vulnerable communities, such as communities of color, indigenous people, the geographically isolated, and those who are socioeconomically disadvantaged and already experiencing poor environmental quality, are least able to respond and adapt to climate change. Focusing on vulnerable populations in the Southeastern United States, this review is a synthesis of the recent (2010 to 2015) literature-base on the health effects connected to climate change. This review also addresses local and regional mitigation and adaptation strategies for citizens and leaders to combat direct and indirect human health effects related to a changing climate.

Associations of Ozone and PM2.5 Concentrations With Parkinson's Disease Among Participants in the Agricultural Health Study

OBJECTIVE

This study describes associations of ozone and fine particulate matter with Parkinson's disease observed among farmers in North Carolina and Iowa.

METHODS

We used logistic regression to determine the associations of these pollutants with self-reported, doctor-diagnosed Parkinson's disease. Daily predicted pollutant concentrations were used to derive surrogates of long-term exposure and link them to study participants' geocoded addresses.

RESULTS

We observed positive associations of Parkinson's disease with ozone (odds ratio = 1.39; 95% CI: 0.98 to 1.98) and fine particulate matter (odds ratio = 1.34; 95% CI: 0.93 to 1.93) in North Carolina but not in Iowa.

CONCLUSIONS

The plausibility of an effect of ambient concentrations of these pollutants on Parkinson's disease risk is supported by experimental data demonstrating damage to dopaminergic neurons at relevant concentrations. Additional studies are needed to address uncertainties related to confounding and to examine temporal aspects of the associations we observed.

Exposure to mitochondrial genotoxins and dopaminergic neurodegeneration in Caenorhabditis elegans

Neurodegeneration has been correlated with mitochondrial DNA (mtDNA) damage and exposure to environmental toxins, but causation is unclear. We investigated the ability of several known environmental genotoxins and neurotoxins to cause mtDNA damage, mtDNA depletion, and neurodegeneration in Caenorhabditis elegans. We found that paraquat, cadmium chloride and aflatoxin B₁ caused more mitochondrial than nuclear DNA damage, and paraquat and aflatoxin B₁ also caused dopaminergic neurodegeneration. 6-hydroxydopamine (6-OHDA) caused similar levels of mitochondrial and nuclear DNA damage. To further test whether the neurodegeneration could be attributed to the observed mtDNA damage, C. elegans were exposed to repeated low-dose ultraviolet C radiation (UVC) that resulted in persistent mtDNA damage; this exposure also resulted in dopaminergic neurodegeneration. Damage to GABAergic neurons and pharyngeal muscle cells was not detected. We also found that fasting at the first larval stage was protective in dopaminergic neurons against 6-OHDA-induced neurodegeneration. Finally, we found that dopaminergic neurons in C. elegans are capable of regeneration after laser surgery. Our findings are consistent with a causal role for mitochondrial DNA damage in neurodegeneration, but also support non mtDNA-mediated mechanisms.

Catecholamine autotoxicity. Implications for pharmacology and therapeutics of Parkinson disease and related disorders

Several neurodegenerative diseases involve loss of catecholamine neurons-Parkinson disease is a prototypical example. Catecholamine neurons are rare in the nervous system, and why they are vulnerable in PD and related disorders has been mysterious. Accumulating evidence supports the concept of "autotoxicity"-inherent cytotoxicity of catecholamines and their metabolites in the cells in which they are produced. According to the "catecholaldehyde hypothesis" for the pathogenesis of Parkinson disease, long-term increased build-up of 3,4-dihydroxyphenylacetaldehyde (DOPAL), the catecholaldehyde metabolite of dopamine, causes or contributes to the eventual death of dopaminergic neurons. Lewy bodies, a neuropathologic hallmark of PD, contain precipitated alpha-synuclein. Bases for the tendency of alpha-synuclein to precipitate in the cytoplasm of catecholaminergic neurons have also been mysterious. Since DOPAL potently oligomerizes and aggregates alpha-synuclein, the catecholaldehyde hypothesis provides a link between alpha-synucleinopathy and catecholamine neuron loss in Lewy body diseases. The concept developed here is that DOPAL and alpha-synuclein are nodes in a complex nexus of interacting homeostatic systems. Dysfunctions of several processes, including decreased vesicular sequestration of cytoplasmic catecholamines, decreased aldehyde dehydrogenase activity, and oligomerization of alpha-synuclein, lead to conversion from the stability afforded by negative feedback regulation to the instability, degeneration, and system failure caused by induction of positive feedback loops. These dysfunctions result from diverse combinations of genetic predispositions, environmental exposures, stress, and time. The notion of catecholamine autotoxicity has several implications for treatment, disease modification, and prevention. Conversely, disease modification clinical trials would provide key tests of the catecholaldehyde hypothesis.

Mitochondrial DNA damage as a peripheral biomarker for mitochondrial toxin exposure in rats

Demonstrating or verifying a current or past exposure to an environmental mitochondrial toxin or toxicant is extraordinarily difficult. Thus, there is a pressing need to develop a biomarker for exposure to environmental mitochondrial inhibitors. Rotenone, an environmental toxicant, is a potent inhibitor of the mitochondrial electron transfer chain. Rotenone specifically inhibits complex I throughout the body and brain, thereby producing systemic mitochondrial impairment. As such, rotenone is a prototypical clinically relevant, environmental mitochondrial toxicant that may be used as an ideal initial platform to develop accessible biomarkers of exposure. The over-arching goal of this work is to explore and validate peripheral (blood and skeletal muscle) DNA damage as a biomarker of mitochondrial toxicant exposure using the rat rotenone model. In this effort, we utilized an extremely sensitive quantitative polymerase chain reaction (QPCR)-based assay that simultaneously allows the assessment of multiple forms of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage. We found mtDNA damage in blood is detected after subclinical rotenone exposure and the damage persists even after complex I activity has returned to normal. With a more sustained rotenone exposure, mtDNA damage is also detected in skeletal muscle, suggesting that mtDNA damage in this tissue simply lags behind blood. Using the QPCR-based assay, we have no evidence for nDNA damage in peripheral tissues after rotenone exposure either acutely or chronically. Overall, these data support the idea that mtDNA damage in peripheral tissues in the rotenone model may provide a biomarker of past or ongoing mitochondrial toxin exposure.

Sex differences in Parkinson's disease

Parkinson's disease (PD) displays a greater prevalence and earlier age at onset in men. This review addresses the concept that sex differences in PD are determined, largely, by biological sex differences in the NSDA system which, in turn, arise from hormonal, genetic and environmental influences. Current therapies for PD rely on dopamine replacement strategies to treat symptoms, and there is an urgent, unmet need for disease modifying agents. As a significant degree of neuroprotection against the early stages of clinical or experimental PD is seen, respectively, in human and rodent females compared with males, a better understanding of brain sex dimorphisms in the intact and injured NSDA system will shed light on mechanisms which have the potential to delay, or even halt, the progression of PD. Available evidence suggests that sex-specific, hormone-based therapeutic agents hold particular promise for developing treatments with optimal efficacy in men and women.

Depression and Parkinson's disease: current knowledge

Depressive disturbances are common in patients with Parkinson's disease (PD) and influence many other clinical aspects of the disease. In addition to causing inherent emotional distress, depressive disorders negatively impact quality of life, motor and cognitive deficits, functional disability, and other psychiatric comorbidities in patients with PD. Knowledge of the pathophysiology of PD depression remains limited. However, clinical studies demonstrate the efficacy of medications and psychotherapies for PD depression, underscoring the importance of their timely detection and concerted management.

Occupational health outcomes for workers in the agriculture, forestry and fishing sector: implications for immigrant workers in the southeastern US

BACKGROUND

Workers in the Agriculture, Forestry, and Fisheries (AgFF) sector experience exposures directly related to the work itself, as well as the physical environment in which the work occurs. Health outcomes vary from immediate to delayed, and from acute to chronic.

METHODS

We reviewed existing literature on the health outcomes of work in the AgFF sector and identified areas where further research is needed to understand the impact of these exposures on immigrant Latino workers in the southeastern US.

RESULTS

Outcomes related to specific body systems (e.g., musculoskeletal, respiratory) as well as particular exposure sources (e.g., pesticides, noise) were reviewed. The most extensive evidence exists for agriculture, with a particular focus on chemical exposures. Little research in the southeastern US has examined health outcomes of exposures of immigrant workers in forestry or fisheries.

CONCLUSION

As the AgFF labor force includes a growing number of Latino immigrants, more research is needed to characterize a broad range of exposures and health outcomes experienced by this population, particularly in forestry and fisheries.

Vesicular uptake blockade generates the toxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde in PC12 cells: relevance to the pathogenesis of Parkinson's disease

Parkinson's disease entails profound loss of nigrostriatal dopaminergic terminals, decreased vesicular uptake of intraneuronal catecholamines, and relatively increased putamen tissue concentrations of the toxic dopamine metabolite, 3,4-dihydroxyphenylacetaldehyde (DOPAL). The objective of this study was to test whether vesicular uptake blockade augments endogenous DOPAL production. We also examined whether intracellular DOPAL contributes to apoptosis and, as α-synuclein oligomers may be pathogenetic in Parkinson's disease, oligomerizes α-synuclein. Catechols were assayed in PC12 cells after reserpine to block vesicular uptake, with or without inhibition of enzymes metabolizing DOPAL-daidzein for aldehyde dehydrogenase and AL1576 for aldehyde reductase. Vesicular uptake was quantified by a method based on 6F- or (13) C-dopamine incubation; DOPAL toxicity by apoptosis responses to exogenous dopamine, with or without daidzein+AL1576; and DOPAL--induced synuclein oligomerization by synuclein dimer production during DOPA incubation, with or without inhibition of L-aromatic-amino-acid decarboxylase or monoamine oxidase. Reserpine inhibited vesicular uptake by 95-97% and rapidly increased cell DOPAL content (p = 0.0008). Daidzein+AL1576 augmented DOPAL responses to reserpine (p = 0.004). Intracellular DOPAL contributed to dopamine-evoked apoptosis and DOPA-evoked synuclein dimerization. The findings fit with the 'catecholaldehyde hypothesis,' according to which decreased vesicular sequestration of cytosolic catecholamines and impaired catecholaldehyde detoxification contribute to the catecholaminergic denervation that characterizes Parkinson's disease.

Clinical approach to Parkinson's disease: features, diagnosis, and principles of management

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. The condition causes a heavy burden both on those affected, as well as their families. Accurate diagnosis is critical and remains founded on clinical grounds as no specific diagnostic test is available so far. The clinical picture of PD is typical in many instances; however, features distinguishing it from other disorders should be thoroughly sought. Monogenic forms of PD also have some distinctive characteristics in many cases. This text is a roadmap to accurate diagnosis in PD, as it approaches clinical features, diagnostic methodology, and leading differential diagnoses. Therapeutic issues are also briefly discussed.

Pesticide exposure and Parkinson's disease: epidemiological evidence of association

It has been suggested that exposure to pesticides might be involved in the etiology of Parkinson's disease (PD). We conducted an updated systematic review of the epidemiologic literature over the past decade on the relationship between pesticide exposure and PD, using the MEDLINE database. Despite methodological differences, a significantly increased PD risk was observed in 13 out of 23 case-control studies that considered overall exposure to pesticides (risk estimates of 1.1-2.4) and in 10 out of 12 studies using other research designs (risk estimates of 2 or higher). Various studies found stronger associations in genetically susceptible individuals. Among a growing number of studies on the effects of exposure to specific pesticides (n=20), an increased PD risk has been associated with insecticides, especially chlorpyrifos and organochlorines, in six studies (odds ratios of 1.8-4.4), and with the herbicide paraquat, the fungicide maneb or the combination of both. Findings considerably strengthen the evidence that exposure to pesticides in well water may contribute to PD, whereas studies of farming and rural residence found inconsistent or little association with the disease. Taken together, this comprehensive set of results suggests that the hypothesis of an association between pesticide exposure and PD cannot be ruled out. However, inadequate data on consistent responses to exposure hinder the establishment of a causal relationship with PD. Given the extensive worldwide use of many pesticides, further studies are warranted in larger populations that include detailed quantitative data on exposure and determination of genetic polymorphisms.

A progressive mouse model of Parkinson's disease: the Thy1-aSyn ("Line 61") mice

Identification of mutations that cause rare familial forms of Parkinson's disease (PD) and subsequent studies of genetic risk factors for sporadic PD have led to an improved understanding of the pathological mechanisms that may cause nonfamilial PD. In particular, genetic and pathological studies strongly suggest that alpha-synuclein, albeit very rarely mutated in PD patients, plays a critical role in the vast majority of individuals with the sporadic form of the disease. We have extensively characterized a mouse model over-expressing full-length, human, wild-type alpha-synuclein under the Thy-1 promoter. We have also shown that this model reproduces many features of sporadic PD, including progressive changes in dopamine release and striatal content, alpha-synuclein pathology, deficits in motor and nonmotor functions that are affected in pre-manifest and manifest phases of PD, inflammation, and biochemical and molecular changes similar to those observed in PD. Preclinical studies have already demonstrated improvement with promising new drugs in this model, which provides an opportunity to test novel neuroprotective strategies during different phases of the disorder using endpoint measures with high power to detect drug effects.

Paraquat and Parkinson's disease: an overview of the epidemiology and a review of two recent studies

OBJECTIVE

This paper reviews and evaluates two recent epidemiologic studies focused on pesticides, and in particular, paraquat as a cause of PD. Both studies are derived primarily from the Agricultural Health Study (AHS). A review and evaluation is also provided on the AHS and several additional studies of paraquat and PD.

METHODS

The methods used to design and conduct the studies and analyze the data are described and evaluated.

RESULTS

Studies were inadequately designed and often underpowered with very few exposed individuals. They were not population-based, failed to distinguish incident from prevalent cases, relied on multiple comparisons, and may have reported results selectively. The results across the studies are inconsistent.

CONCLUSIONS

The inherent difficulties of studying Parkinson's disease in relation to paraquat or other pesticides are well illustrated by these studies. A conclusion regarding these relationships cannot be reached based on the current literature. Further research with higher methodological standards is needed to reach a definitive conclusion.

Epidemiology and etiology of Parkinson's disease: a review of the evidence

The etiology of Parkinson's disease (PD) is not well understood but likely to involve both genetic and environmental factors. Incidence and prevalence estimates vary to a large extent-at least partly due to methodological differences between studies-but are consistently higher in men than in women. Several genes that cause familial as well as sporadic PD have been identified and familial aggregation studies support a genetic component. Despite a vast literature on lifestyle and environmental possible risk or protection factors, consistent findings are few. There is compelling evidence for protective effects of smoking and coffee, but the biologic mechanisms for these possibly causal relations are poorly understood. Uric acid also seems to be associated with lower PD risk. Evidence that one or several pesticides increase PD risk is suggestive but further research is needed to identify specific compounds that may play a causal role. Evidence is limited on the role of metals, other chemicals and magnetic fields. Important methodological limitations include crude classification of exposure, low frequency and intensity of exposure, inadequate sample size, potential for confounding, retrospective study designs and lack of consistent diagnostic criteria for PD. Studies that assessed possible shared etiological components between PD and other diseases show that REM sleep behavior disorder and mental illness increase PD risk and that PD patients have lower cancer risk, but methodological concerns exist. Future epidemiologic studies of PD should be large, include detailed quantifications of exposure, and collect information on environmental exposures as well as genetic polymorphisms.

Assessment of fetal brain uptake of paraquat in utero using in vivo PET/CT imaging

Prenatal in utero conditions are thought to play a role in the development of adult diseases including Parkinson's disease (PD). Paraquat is a common herbicide with chemical structure similar to 1-methyl-4-phenyl 1,2,3,6-tetrahydropyridine, a neurotoxin known to induce parkinsonism. In order to assess the role of in utero paraquat exposure in PD, uptake in maternal and fetal brains were measured using positron emission tomography (PET)/computed tomography (CT) imaging. Two anesthetized pregnant rhesus macaques in the late second trimester of pregnancy were given bolus iv injections of ¹¹C-paraquat, and whole-body PET/CT imaging was performed. Using maternal ventricular blood pool as the input function, the unidirectional influx rate constants (K(i)s), a measure of the irreversible transport of paraquat from plasma to brain, were calculated for the maternal and fetal brains using Patlak graphical analysis. Results indicate minimal uptake of paraquat by both maternal and fetal brains with average K(i)s of 0.0009 and 0.0016 per minute, respectively. The highest regional cerebral uptake in the maternal brain (0.0009% injected dose) was seen in the pineal gland, a structure known to lack a blood brain barrier. The finding of minimal paraquat uptake in maternal and fetal brains is similar to previous findings in adult male macaques and extends the contention that a single acute paraquat exposure, prenatally or postnatally, is unlikely to play a role in PD.

Histopathological evaluation of the nervous system in National Toxicology Program rodent studies: a modified approach

This article outlines the changes and underlying rationale for modifications to the histopathological evaluation of the nervous system during toxicology and carcinogenesis studies conducted by the National Toxicology Program (NTP). In the past, routine evaluation of the nervous system was mostly limited to three sections of brain, and occasionally the spinal cord and peripheral nerves. Factors such as the increasing occurrence of human neurological diseases and associated economical cost burden, the role of unidentified environmental stressors in neurodegenerative disorders, multiple therapeutic drug-induced neuropathies noted in human clinical trials, and the exponential use of environmental chemicals with unknown neurotoxic potential necessitate a more extensive evaluation of the nervous system. The NTP has modified its protocol to include examination of key anatomic subsites related to neurodegenerative diseases such as Parkinson's disease. Modifications include four additional sections of the brain. Increasing the number of brain sections permits examination of a greater number of specific anatomic subsites with unique vulnerability. In addition, the spinal cord, peripheral nerves, trigeminal ganglion, and intestinal autonomic ganglia will be evaluated as needed. It is expected that this modified approach will increase the sensitivity of detecting neurotoxicants and neurocarcinogens important in human neurologic and neurodegenerative disorders.

The relation between type of farming and prevalence of Parkinson's disease among agricultural workers in five French districts

Retrospective assessment of pesticide exposure is complex; however, patterns of pesticide use strongly depend on farming type, which is easier to assess than pesticide exposure. Our aim was to estimate Parkinson's disease (PD) prevalence in five French districts in 2007 among affiliates of Mutualité Sociale Agricole (MSA) and to investigate the relation between PD prevalence and farming type. We identified PD cases from administrative files as persons who used levodopa and/or benefited from free health care for PD. Densities of 16 farming types were defined at the canton of residence level (1988 French agricultural census). We used logistic regression to study the relation between PD prevalence and density of farming types and a semi-Bayes approach to deal with correlated exposures. We identified 1,659 PD cases, yielding an age- and sex-standardized PD prevalence of 3.01/1,000. Prevalence increased with age and was higher in men than women. We found a higher PD prevalence among affiliates living in cantons characterized by a higher density of farms specialized in fruits and permanent crops (multivariable semi-Bayes model: OR(4+5 vs 1+2+3 quintiles) = 1.21, 95% CI = 1.08-1.36; test for trend, P = 0.035). In France, farms specialized in fruits and permanent crops rank first in terms of insecticide use per hectare. Our findings are consistent with studies reporting an association between PD and insecticide use and show that workers in farms specialized in fruits or permanent crops may be an occupational group at higher PD risk.

A dual-hit animal model for age-related parkinsonism

Parkinson's disease is a neurological disorder which afflicts an increasing number of individuals. If the wider complex of extrapyramidal symptoms referred to as "age-related parkinsonism" is included, the incidence is near 50% of the population above 80 years of age. This review summarizes recent studies from our laboratories as well as other research groups in the quest to explore the multi-faceted etiology of age-related neurodegeneration, in general, and degeneration of the substantia nigra dopaminergic neurons, in particular. Our work during recent years has focused on assessment of potential interactive effects of a reduction in glial cell line-derived neurotrophic factor (GDNF) and the aging process (intrinsic factors) and early neurotoxin exposure (an extrinsic factor) on dopamine (DA) systems and the behaviors they mediate. The guiding hypothesis directing the research to be described was that a combination of the two factors would exacerbate the decline in the DA transmitter system function that occurs during aging. The results obtained were consistent with the well-established aging-related decline in function and structure of neurons utilizing DA as a transmitter and motor function, and extended knowledge by establishing that the genetic reduction of Gdnf exacerbated these aging related changes. Thus, GDNF reduction appears to increase the vulnerability of the DA neurons to the many different challenges associated with the aging process. Assessment of methamphetamine effects on young Gdnf(+/-) mice indicated that reduced GDNF availability increased the vulnerability of DA systems to this well-established neurotoxin. The work discussed in this review is consistent with earlier work demonstrating the importance of GDNF for maintenance of DA neurons and also provides a novel model for progressive DA degeneration and motor dysfunction.

Mitochondrial dysfunction in the striatum of aged chronic mouse model of Parkinson's disease

Mitochondrial oxidative stress and dysfunction has been implicated as a possible mechanism for the onset and progression of Parkinson-like neurodegeneration. However, long-term mitochondrial defects in chronic animal neurodegenerative models have not been demonstrated. In this study, we investigated the function of striatal mitochondria 6 weeks after the induction of a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (MPD). Although severe depression of mitochondrial respiration was observed immediately after acute administrations of MPTP, we failed to detect a significant mitochondrial inhibition in presence of striatal dopamine (DA) deficit 6 weeks after the chronic MPD induction in young adult mice. In contrast, when aged mice were chronically treated with MPTP and at 6 weeks post-treatment, these animals suffered an inhibition of the basal (state 4) and adenosine 5′-diphosphate-stimulated (state 3) respiration and a fall in adenosine triphosphate level in the striatal mitochondria. The aged chronic MPD also brought about a sustained diminution of striatal anti-oxidant enzyme levels including that of superoxide dismutases and cytochrome c. The mitochondrial deficits in the striatum of aged chronic MPD 6 weeks after treatment were further correlated with significant losses of striatal DA, tyrosine hydroxylase, DA uptake transporter, and with impaired movement when tested on a challenging beam. Our findings suggest that MPTP may trigger the neurodegenerative process by obstructing the mitochondrial function; however, striatal mitochondria in young animals may potentially rejuvenate, whereas mitochondrial dysfunction is sustained in the aged chronic MPD. Therefore, the aged chronic MPD may serve as a suitable investigative model for further elucidating the integral relationship between mitochondrial dysfunction and neurodegenerative disorder, and for assessing the therapeutic efficacy of mitochondrial protective agents as potential neuroprotective drugs.

Disruption of microRNA expression in human airway cells by diesel exhaust particles is linked to tumorigenesis-associated pathways

BACKGROUND

Particulate matter (PM) is associated with adverse airway health effects; however, the underlying mechanism in disease initiation is still largely unknown. Recently, microRNAs (miRNAs; small noncoding RNAs) have been suggested to be important in maintaining the lung in a disease-free state through regulation of gene expression. Although many studies have shown aberrant miRNA expression patterns in diseased versus healthy tissue, little is known regarding whether environmental agents can induce such changes.

OBJECTIVES

We used diesel exhaust particles (DEP), the largest source of emitted airborne PM, to investigate pollutant-induced changes in miRNA expression in airway epithelial cells. We hypothesized that DEP exposure can lead to disruption of normal miRNA expression patterns, representing a plausible novel mechanism through which DEP can mediate disease initiation.

METHODS

Human bronchial epithelial cells were grown at air-liquid interface until they reached mucociliary differentiation. After treating the cells with 10 microg/cm(2) DEP for 24 hr, we analyzed total RNA for miRNA expression using microarray profile analysis and quantitative real-time polymerase chain reaction.

RESULTS

DEP exposure changed the miRNA expression profile in human airway epithelial cells. Specifically, 197 of 313 detectable miRNAs (62.9%) were either up-regulated or down-regulated by 1.5-fold. Molecular network analysis of putative targets of the 12 most altered miRNAs indicated that DEP exposure is associated with inflammatory responses pathways and a strong tumorigenic disease signature.

CONCLUSIONS

Alteration of miRNA expression profiles by environmental pollutants such as DEP can modify cellular processes by regulation of gene expression, which may lead to disease pathogenesis.