Manganese (Mn) is a neurotoxicant that is present in soil, air, and water. Investigations of occupationally- exposed groups, such as welders, provide an ideal opportunity to characterize dose-related dopaminergic system damage associated with Mn. Recent studies from our collaborating institutions demonstrate a high prevalence of Parkinsonism in workers with chronic exposure to Mn containing welding fumes and dopaminergic dysfunction on [18F] fluorodopa (FDOPA) PET. This study utilizes an established, well characterized cohort of welders with detailed exposure and clinical assessments, developed through NIEHS funded research projects. For this proposal, a cohort of 40 career welders with baseline FDOPA PET scans will undergo repeat PET imaging of the nigrostriatal dopamine system using FDOPA and first time imaging with the presynaptic dopaminergic radioligand [11C]dihydrotetrabenazine (DTBZ) and the post-synaptic dopamine D2 receptor selective radioligand [11C]N-methylbenperidol (NMB). These workers will be compared to a second group of non-welder reference subjects who will be imaged at baseline and four years. The specific goals of this project are: 1) to investigate progression of dopaminergic dysfunction in welding exposed workers as evidence of progressive neurotoxicity, 2) to use the radioligand DTBZ to investigate the dose-response relationship with welding fume exposure as an indicator of the underlying etiologic relationship between Mn and damage to the presynaptic dopaminergic system, and 3) to use the radioligand NMB to investigate the dose-response relationship with welding fume exposure as an indicator of the underlying etiologic relationship between Mn and damage to the postsynaptic dopamine system. This proposal uses state-of-the-art imaging methods to investigate the health effects of a common environmental and occupational health hazard. The results of this study will have broad implications for public and worker health worldwide and will inform future community based studies of metal neurotoxicity. In addition, this study, in conjunction with our previously published data, will provide converging evidence of the role of Mn as a nigrostriatal neurotoxin. The methods described in this application represent cutting edge molecular and MRI techniques and the institutions and investigators are ideally suited for this unique epidemiology and imaging proposal.

Project 2, which will be new to the UW SBRP, is an epidemiologic investigation of the roles of metals as determinants of the risk, severity, and progression of parkinsonism (PS) among professional welders. Previous epidemiologic and experimental research has demonstrated very plausible links between manganese (Mn) and other metals, individually and in combination, and PS. The study population includes 875 Wisconsin shipyard welders (775 actively employed, 100 retired) and 200 non-exposed shipyard workers with no welding exposure history previously enrolled in an ongoing NEIHS-funded R01 (ES013743; PI: B. Racette; Co-investigators: H. Checkoway, N. Seixas). The new features of this proposed study will be the refinement of exposure assessment to generate quantitative metal-specific levels, and repeated neurological examinations of longitudinal change of PS-related motor function. The scientific objectives of the project are to: 1) estimate dose-response relations between Mn and other metal exposures and PS risk and severity; 2) test the hypothesis that these metal exposures are associated with PS progression; 3) determine the predictive relations of PS proteomic biomarkers, characterized in Project 3 (Dr. Zhang), with PS risk, severity, and progression; 4) test dose-response relations for Mn and other metals with PS proteomic biomarker profiles as indicators of preclinical disease. To achieve these objects, we will perform repeated standardized neurological exams of motor function (Unified Parkinson's Disease Rating Scale Motor Subsection 3 [UPDRS3]) 3 years after enrollment exams for as many study subjects as can be enrolled (~75%). Addionally, in collaboration with Project 3, we will collect plasma samples for assays of proteomics that have been validated as strongly associated with PS for a sample of 150 subjects selected according to baseline UPDRS3 ('normal', borderline PS, probable/definite PS). Data on potentially important confounding factors, especially cigarette smoking and pesticide exposure, will be obtained by questionnaire. This project has great potential to quantify the extent of neurological effects of metals, which are widespread environmental contaminants, and thus could contribute to disease prevention strategies.

Environmental exposure to metals, including manganese, is an important risk factor for the development of parkinsonism (PS) in workers of welding or related industries. However, the relevance of metal-mediated PS to idiopathic Parkinson's disease (iPD) remains to be characterized. Clinically, differential diagnosis between metal-related PS and iPD is difficult, even in the best hands. This proposal is focused on discovering plasma biochemical markers unique to welders for differential diagnosis of various PS, monitoring PS progression, and identification of the population at risk for developing disabling PS. The techniques to be utilized are state-of-the-art proteomics that are actively employed currently in our laboratory in revealing biomarkers specific to iPD in both human brain tissue and cerebrospinal fluid (CSF). Three specific aims are designed for the current proposal: 1) to differentiate PS in the plasma samples of welders from those of iPD using brain/CSF specific markers identified in iPD patients, 2) to develop plasma biomarkers unique to PS progression as well as early stages in welders using targeted and nonbiased quantitative proteomics, and 3) to confirm and validate PS plasma biomarkers in welders, which is a key process of biomarker discovery. The significance of this investigation includes: 1) identification of markers unique to PS, both in symptomatic welders and those at risk for developing PS, will help diagnose and monitor these patients as well as make it possible to remove the subjects at risk from the environment, thereby preventing them from developing PS; 2) identification of protein markers unique to PS secondary to metal exposure likely suggests novel pathogenesis and therapeutic targets for the disease process; and 3) PS markers, if identified, can be widely utilized, given that plasma-based assays can be readily implemented in a clinical setting, even in developing countries or in remote areas of developed countries.

Parkinson's disease (PD) is a neurodegenerative disorder affecting one million people in North America. There is no known cause for most cases of PD although environmental factors have been implicated in the majority of cases. We have preliminary evidence that parkinsonism is three to ten times more common in career welders than the general population. We have an NIEHS and Michael J. Fox Foundation funded research program to investigate welding as a risk-factor for parkinsonism. For the funded research, we will perform a population based, epidemiology study of the prevalence of parkinsonism in career welders and controls. We will assemble a cohort of 875 active shipyard workers (and retirees) and 200 same-sex, nearest age, sibling controls. Movement disorders specialists will examine all subjects for parkinsonism. Prevalence of parkinsonism will be compared between shipyard welders, non-welder shipyard workers and the non-welder, same-sex, sibling controls. An industrial hygienist will reconstruct subject welding exposure from a detailed exposure questionnaire in all exposed subjects and subjects will be grouped into tertiles of exposure using a Job Exposure Matrix (JEM) to determine if there is a dose-response relationship between welding exposure and parkinsonism. New research to be supported by this proposal includes assessment of the relationship between blood manganese levels and increased Tl-weighted signal changes in globus pallidum. In addition, we will determine if lifetime welding exposure reconstructed from a validated questionnaire and categorized by a JEM is associated with a dose dependent decrease in [18F]FDOPA striatal uptake using PET and with greater severity of parkinsonism as measured by clinical examination and timed motor tasks. The team conducting this research represents a unique collaboration of movement disorders specialists, epidemiologists, occupational medicine specialists, industrial hygienists, and industry leaders. Demonstrating a definitive relationship between welding and parkinsonism will have substantial public health impact since the majority of these cases should be preventable through worksite modifications. This multi-institution and multi-discipline research program, in addition to the numerous educational (institutional K12, extensive lectures/seminar series) and collaborative resources in the Department of Neurology (P30), makes this research proposal an ideal environment to mentor trainees in patient-oriented neurological research.

Parkinson's disease (PD) is a neurodegenerative disorder affecting one million people in North America. There is no known cause for most cases of PD although environmental factors have been implicated in the majority of cases. We have preliminary evidence that parkinsonism is three to ten times more common in career welders than the general population. The purpose of this grant is to establish welding as a risk-factor for parkinsonism in a population based cohort and to establish a dose-response relationship between welding and parkinsonism. For our first specific aim we will perform a population based epidemiological study of the prevalence of parkinsonism in career welders and controls. We will assemble a cohort of 600 welders (boilermakers) and a non-exposed reference cohort of workers from the same union and same-sex, nearest age, sibling controls. Movement disorders specialists will perform all evaluations and ratings will be verified by a movement disorders specialist who will review each videotaped examination. Prevalence of parkinsonism will be compared between welders and the non-welder reference cohort For the second specific aim of this study, an industrial hygienist will reconstruct subject welding exposure from a detailed exposure questionnaire in all exposed subjects and subjects will be grouped into tertiles of exposure using a Job ExposureMatrix to determine if there is a dose-response relationship between welding exposure and parkinsonism. The team conducting this research represents a unique collaboration of movement disorders specialists, epidemiologists, industrial hygienists, and industry leaders. Demonstrating a definitive relationship between welding and parkinsonism will have substantial public health impact since the majority of these cases should be preventable through worksite modifications. The cohort assembled will provide unique opportunities for future research projects into specific toxins associated with parkinsonism in welders, gene-environment interactions, and exposure related neuroimaging changes.