Widespread occurrence of argyrophilic glial inclusions in Parkinson's disease.

Argyrophilic glial inclusions, which are immunohistochemically positive for alpha-synuclein but negative for tau protein, were examined in the brain of Parkinson's disease (PD) patients. Autopsied brains of 10 individuals who died from PD, of two incidental Lewy body disease cases and of five age-matched individuals whose deaths were caused by non-neurological diseases were studied, histopathologically, by Gallyas-Braak staining and, immunohistochemically, with anti-alpha-synuclein antibody, anti-ubiquitin, and anti-tyrosine hydroxylase. All postmortem PD brains showed a significant number of argyrophilic glial inclusions, but no glial inclusions were found in control brains. The inclusions were found not only in the regions showing neuronal loss and gliosis, such as the substantia nigra, locus ceruleus and dorsal vagal nucleus, but also in regions without neuronal loss and gliosis, such as the cerebral cortex, cerebral white matter, striatum, globus pallidus, thalamus, cerebellum and spinal cord. The distribution and density of glial inclusions in PD brains varied from case to case but, in the cerebral cortex, the number of glial inclusions were fairly well correlated with the number of Lewy bodies. The distribution pattern of glial inclusions also showed a striking resemblance to that of catecholaminergic neurones and fibres. The abnormal accumulation of alpha-synuclein in glial cells was more widespread than neurone loss, and appears to be an important pathological feature of PD.     

The cellular pathology of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder of unknown cause that occurs in adults. The presence of Lewy bodies (LB) in association with nerve cell loss in the substantia nigra and various other regions of the nervous system is a diagnostic hallmark of the disease. In 1997, a mutation was identified in the α‐synuclein gene in families with autosomal dominant PD. Subsequent immunohistochemical studies have revealed that all of the LB in familial and sporadic PD contain the gene product α‐synuclein: abnormal filaments that constitute LB were clearly recognized by antibodies against α‐synuclein. Moreover, it was shown that the glial cells, both astrocytes and oligodendrocytes, are also affected by α‐synuclein pathology. Recently, a novel protein, synphilin‐1, has been identified that interacts with α‐synuclein. Interestingly, synphilin‐1 immunohistochemistry has demonstrated that this protein is present in the central core of classical (brainstem) LB, which are composed mainly of densely packed vesicular structures. The role of both α‐synuclein and synphilin‐1 in normal conditions has yet to be clarified.     

Lowered cardiac sympathetic nerve performance in response to exercise in Parkinson's disease

We examined whether cardiac sympathetic denervation influences the cardiovascular response to exercise in Parkinson's disease (PD). Sixteen patients with PD were divided into two groups, according to their cardiac uptake of ¹²³I‐metaiodobenzylguanidine (denervated group, 10 patients with heart to mediastinum (H/M) ratio < 1.7; innervated group, six patients with H/M ratio > 1.7) and compared changes in blood pressure (BP), heart rate (HR), and cardiac contractility with 13 control subjects during ergometric exercise stress. Velocity index (VI), an indicator of cardiac contractility, was measured using impedance cardiography and recorded every minute. Exercise began at a power output of 20 W for the first 2 min and increased 10 W every 2 min to a maximal intensity of 60 W. All control subjects accomplished the procedure while six patients with PD could not continue after the first minute of 50 W loading. There were no significant differences in BP or HR change between the three groups. However, a significant reduction in VI was observed from the first minute of the 30 W workload in the denervated group compared to the control group. This lowered response continued till 50 W loading and was significantly different to the innervated group at 50 W loading. No significant VI changes were observed between the control and innervated groups throughout the exercise test. Patients with PD with reduced MIBG uptake had a lowered cardiac contractility than innervated subjects during exercise, suggesting that this response represents theimpaired exercise capacity of patients with PD with cardiac sympathetic denervation. © 2010 Movement Disorder Society     

Genetics of parkinsonism.

Parkinson's disease (PD) was noted to have a familial component as early as 1880 (Leroux, 1880). More recently, the discovery of several genetic factors influencing parkinsonism has emphasized the importance of heredity in PD. The clinical spectrum of familial parkinsonism is wide; it includes not only PD, but also dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), essential tremor, and other disorders. In the general population, it is likely that PD results from combined genetic and environmental factors, most of which are not yet known. The discovery of causal mutations in the gene for alpha-synuclein, parkin, and of genetic linkages to chromosomes 2p4, 4p5, and three loci on 1q6-8 have revolutionized PD research. This review focuses on recent progress in the Mendelian genetics of PD and those diseases in which parkinsonism is a prominent feature, and considers how these discoveries modify our beliefs regarding the etiology and pathogenesis of these disorders.     

Microglial phagocytosis is enhanced by monomeric alpha-synuclein, not aggregated alpha-synuclein: implications for Parkinson's disease

Gathering evidence has associated activation of microglia with the pathogenesis of numerous neurodegenerative diseases of the central nervous system (CNS) such as Alzheimer's disease and Parkinson's disease. Microglia are the resident macrophages of the CNS whose functions include chemotaxis, phagocytosis, and secretion of a variety of cytokines and proteases. In this study, we examined the possibility that alpha-synuclein (alpha-syn), which is associated with the pathogenesis of Parkinson's disease, may affect the phagocytic function of microglia. We found that extracellular monomeric alpha-syn enhanced microglial phagocytosis in both a dose- and time-dependent manner, but beta- and gamma- syn did not. We also found that the N-terminal and NAC region of alpha-syn, especially the NAC region, might be responsible for the effect of alpha-syn on microglial phagocytosis. In contrast to monomeric alpha-syn, aggregated alpha-syn actually inhibited microglial phagocytosis. The different effects of monomeric and aggregated alpha-syn on phagocytosis might be related to their localization in cells. This study indicates that alpha-syn can modulate the function of microglia and influence inflammatory changes such as those seen in neurodegenerative disorders.     

The Lewy body in Parkinson's disease: Molecules implicated in the formation and degradation of α‐synuclein aggregates

The histological hallmark of Parkinson's disease (PD) is the presence of fibrillar aggregates called Lewy bodies (LBs). LB formation has been considered to be a marker for neuronal degeneration, because neuronal loss is found in the predilection sites for LBs. To date, more than 70 molecules have been identified in LBs, in which α‐synuclein is a major constituent of LB fibrils. α‐synuclein immunohistochemistry reveals that diffuse cytoplasmic staining develops into pale bodies via compaction, and that LBs arise from the peripheral portion of pale bodies. This α‐synuclein abnormality is found in 10% of pigmented neurons in the substantia nigra and more than 50% of those in the locus ceruleus in PD. Recent studies have suggested that oligomers and protofibrils of α‐synuclein are cytotoxic, and that LBs may represent a cytoprotective mechanism in PD.     

Advanced glycation end products induce in vitro cross-linking of alpha-synuclein and accelerate the process of intracellular inclusion body formation

Cross-linking of alpha-synuclein and Lewy body formation have been implicated in the dopaminergic neuronal cell death observed in Parkinson's disease (PD); the mechanisms responsible, however, are not clear. Reactive oxygen species and advanced glycation end products (AGEs) have been found in the intracellular, alpha-synuclein-positive Lewy bodies in the brains of both PD as well as incidental Lewy body disease patients, suggesting a role for AGEs in alpha-synuclein cross-linking and Lewy body formation. The aims of the present study were to determine 1) whether AGEs can induce cross-linking of alpha-synuclein peptides, 2) the progressive and time-dependent intracellular accumulation of AGEs and inclusion body formation, and 3) the effects of extracellular or exogenous AGEs on intracellular inclusion formation. We first investigated the time-dependent cross-linking of recombinant human alpha-synuclein in the presence of AGEs in vitro, then used a cell culture model based on chronic rotenone treatment of human dopaminergic neuroblastoma cells (SH-SY5Y) over a period of 1-4 weeks, in the presence of different doses of AGEs. Cells (grown on coverslips) and cell lysates, collected at the end of every week, were analyzed for the presence of intracellular reactive oxygen species, AGEs, alpha-synuclein proteins, and intracellular alpha-synuclein- and AGE-positive inclusion bodies by using immunocytochemical, biochemical, and Western blot techniques. Our results show that AGEs promote in vitro cross-linking of alpha-synuclein, that intracellular accumulation of AGEs precedes alpha-synuclein-positive inclusion body formation, and that extracellular AGEs accelerate the process of intracellular alpha-synuclein-positive inclusion body formation.     

Alpha‐synuclein in peripheral tissues and body fluids as a biomarker for Parkinson's disease – a systematic review

Parkinson's disease (PD) is neuropathologically characterized as an alpha‐synucleinopathy. Alpha‐synuclein‐containing inclusions are stained as Lewy bodies and Lewy neurites in the brain, which are the pathological hallmark of PD. However, alpha‐synuclein‐containing inclusions in PD are not restricted to the central nervous system, but are also found in peripheral tissues. Alpha‐synuclein levels can also be measured in body fluids. The aim of this study was to conduct a systematic review of available evidence to determine the utility of alpha‐synuclein as a peripheral biomarker of PD. We searched PubMed (1948 to 26 May 2013), Embase (1974 to 26 May 2013), the Cochrane Library (up to 26 May 2013), LILACS (up to 26 May 2013) and CINAHL (up to 26 May 2013) for the studies of alpha‐synuclein in peripheral tissues or body fluids in PD. A total of 49 studies fulfilled the search criteria. Peripheral tissues such as colonic mucosa showed a sensitivity of 42–90% and a specificity of 100%; submandibular salivary glands showed sensitivity and specificity of 100%; skin biopsy showed 19% sensitivity and 80% specificity in detecting alpha‐synuclein pathology. CSF alpha‐synuclein had 71–94% sensitivity and 25–53% specificity for distinguishing PD from controls. Plasma alpha‐synuclein had 48–53% sensitivity and 69–85% specificity. Neither plasma nor CSF alpha‐synuclein is presently a reliable marker of PD. This differs from alpha‐synuclein in solid tissue samples of the enteric and autonomic nervous system, which offer some potential as a surrogate marker of brain synucleinopathy.     

Alpha-synuclein and Parkinson's disease: implications from the screening of more than 1,900 patients.

Data on the frequency of alpha-synuclein mutations in Parkinson's disease (PD) are limited. Screening the entire coding region in 1,921 PD patients with denaturing high performance liquid chromatography and subsequent sequencing we only detected silent mutations (g.2654A>G, g.10151G>A, and g.15986A>T) and the c.209G>A substitution corresponding to the p.A53T mutation. These results demonstrate that mutations in the alpha-synuclein gene are rare and suggest that other factors contribute to alpha-synuclein aggregation in the majority of PD patients.     

Autosomal recessive juvenile parkinsonism: A key to understanding nigral degeneration in sporadic Parkinson's disease

The contribution of genetic factors to the pathogenesis of Parkinson's disease (PD) is supported by the demonstration of the high concordance in twins studies using positron emission tomography (PET), the increased risk among relatives of PD patients in case–control and family studies, and the existence of familial PD and parkinsonism by single gene defect. Recently several genes have been mapped and/or identified. α‐Synuclein is involved in a rare dominant form of familial PD with dopa‐responsive parkinsonism features and Lewy body‐positive pathology. In contrast, parkin is responsible for the autosomal recessive form (AR‐JP) of early onset PD with Lewy body‐negative pathology. The clinical features of this form include early onset (in the 20s), levodopa‐responsive parkinsonism, diurnal fluctuation, and slow progression of the disease. Parkin consists of 12 exons and the estimated size is over 1.5 Mb. To date, variable mutations such as deletions or point mutations resulting in missense and nonsense changes have been reported in AR‐JP patients. In addition, the localization of parkin indicates that parkin may be involved in the axonal transport system. More recently we have found that parkin interacts with the ubiquitin‐conjugating enzyme E2 and is functionally linked to the Ub‐proteasome pathway as a ubiquitin ligase, E3. These findings fit the characteristics of a lack of Lewy bodies (these are cytoplasmic inclusions that are considered to be a pathological hallmark). Our findings should enhance the exploration of the mechanisms of neuronal death in PD as well as other neurodegenerative disorders of which variable inclusion bodies are observed.     

Neuropathology of sporadic Parkinson's disease: evaluation and changes of concepts

Parkinson's disease (PD), one of the most frequent neurodegenerative disorders, is no longer considered a complex motor disorder characterized by extrapyramidal symptoms, but a progressive multisystem or-more correctly-multiorgan disease with variegated neurological and nonmotor deficiencies. It is morphologically featured not only by the degeneration of the dopaminergic nigrostriatal system, responsible for the core motor deficits, but by multifocal involvement of the central, peripheral and autonomic nervous system and other organs associated with widespread occurrence of Lewy bodies and dystrophic Lewy neurites. This results from deposition of abnormal α-synuclein (αSyn), the major protein marker of PD, and other synucleinopathies. Recent research has improved both the clinical and neuropathological diagnostic criteria of PD; it has further provided insights into the development and staging of αSyn and Lewy pathologies and has been useful in understanding the pathogenesis of PD. However, many challenges remain, for example, the role of Lewy bodies and the neurobiology of axons in the course of neurodegeneration, the relation between αSyn, Lewy pathology, and clinical deficits, as well as the interaction between αSyn and other pathologic proteins. Although genetic and experimental models have contributed to exploring the causes, pathomechanisms, and treatment options of PD, there is still a lack of an optimal animal model, and the etiology of this devastating disease is far from being elucidated.     

Stanley Fahn Lecture 2005: The staging procedure for the inclusion body pathology associated with sporadic Parkinson's disease reconsidered.

The synucleinopathy known as sporadic Parkinson's disease (PD) is a multisystem disorder that severely damages predisposed nerve cell types in circumscribed regions of the human nervous system. A recent staging procedure for the inclusion body pathology associated with PD proposes that, in the brain, the pathological process (formation of proteinaceous intraneuronal Lewy bodies and Lewy neurites) begins at two sites and continues in a topographically predictable sequence in six stages, during which components of the olfactory, autonomic, limbic, and somatomotor systems become progressively involved. In stages 1 to 2, the Lewy body pathology is confined to the medulla oblongata/pontine tegmentum and anterior olfactory structures. In stages 3 to 4, the substantia nigra and other nuclei of the basal mid- and forebrain become the focus of initially subtle and, then, severe changes. During this phase, the illness probably becomes clinically manifest. In the final stages 5 to 6, the lesions appear in the neocortex. This cross-sectional study originally was performed on 168 autopsy cases using material from 69 incidental cases and 41 clinically diagnosed PD patients as well as 58 age- and gender-matched controls. Here, the staging hypothesis is critically reconsidered and discussed.     

Lysosomal pathology associated with alpha-synuclein accumulation in transgenic models using an eGFP fusion protein

Disorders with Lewy body (LB) formation, such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB), are characterized by alpha-synuclein accumulation in the neuronal cell body. Recent studies have suggested that in addition to LBs, alpha-synuclein might accumulate more widely throughout the neurons and their processes, leading to neurodegeneration and functional impairment. The precise patterns of alpha-synuclein accumulation in vivo, however, and its relationship with subcellular neuronal alterations such as lysosomal pathology are not completely clear. To this end, we developed transgenic (tg) in vivo and in vitro models expressing a stable enhanced green fluorescent protein (eGFP) tagged in the C-terminal site of a human (h)alpha-synuclein construct under the regulatory control of the platelet-derived growth factor-beta (PDGFbeta) promoter and carried out confocal, ultrastructural, and biochemical studies. In tg mice, confocal studies demonstrated a wide distribution of halpha-synuclein-eGFP in the neuronal cell bodies, axons, and presynaptic terminals. In several neuronal cell bodies and their neurites, halpha-synuclein-eGFP was found not only as inclusions but also as discrete granular structures that in double-labeling studies colocalized with antibodies against halpha-synuclein and the lysosomal marker cathepsin D. Consistent with these findings, ultrastructural analysis showed that halpha-synuclein-eGFP overexpression resulted in the accumulation of electrodense inclusions and laminated bodies suggestive of lysosomal pathology, and that the halpha-synuclein-eGFP protein was more abundant in the lysosomal fractions of the tg animals. Taken together, these findings support the notion that enhanced visualization of alpha-synuclein utilizing a hybrid eGFP molecule reveals a more widespread accumulation of this molecule in several neuronal compartments, promoting lysosomal dysfunction. Furthermore, the PDGFbeta-halpha-synuclein-eGFP tg model might be a valuable tool in testing new treatments for LBD in a fast and reliable manner.     

Association of alpha-synuclein Rep1 polymorphism and Parkinson's disease: influence of Rep1 on age at onset.

The alpha-synuclein Rep1 polymorphism was studied in patients and controls in an ethnic Greek population. There was an association of allele 2 with risk of Parkinson's disease (PD; adjusted odd ratio = 3.25; 95% CI = 1.80-5.87). Survival analyses (Cox proportional hazards models) were employed to explore the influence of genotypes on age at onset of PD. Age at onset of carriers of at least one Rep1 allele 2 was earlier (3.6 years) compared to noncarriers (adjusted hazard ratio = 2.21; 95% CI = 1.58-3.10). Kaplan-Meier analysis also supported a dosage effect of Rep1 allele 2 on age at onset. For Rep1 allele 1, there was neither association with risk of PD nor influence on age at onset. This is the first study showing an influence of Rep1 polymorphism on age at onset of PD.     

Milestones in Parkinson's disease—Clinical and pathologic features

The identification of the widespread deposition of fibrillized α‐synuclein in Lewy bodies and Lewy neurites in the brains of patients with Parkinson's disease in 1997 has had a profound impact on how the disease is now conceptualized. The previous focus on the loss of the dopaminergic nigrostriatal system, the concept of subcortical dementia, and the idea that Parkinson's disease was dominated by motor impairment have all given way to research assessing more diverse brain regions, clinical symptoms, and phenotypes. It is now recognized that Parkinson's disease is more than just a loss of midbrain dopaminergic neurons in association with Lewy bodies. There are now several theories on how the disease develops and progresses currently being validated in a variety of studies, although many of these theories have yet to incorporate the phenotypic clinical and pathological changes associated with age. A particularly exciting new area of research involves the cell‐to‐cell transmission of pathogenic proteins. The recent consensus definition of Parkinson's disease dementia will allow its pathologic substrates to be determined. These advances have progressed to a stage where the preclinical stages of Parkinson's disease and its specific signs and symptoms are being predicted and tested clinically. Such strategies herald a future wave of preventive strategies for Parkinson's disease and its clinical symptoms. © 2011 Movement Disorder Society     

Comparison of neuropathology in Parkinson's disease subjects with and without deep brain stimulation

Background : The aim of this postmortem study was to compare, in Parkinson's disease subjects with and without bilateral subthalamic nucleus deep brain stimulation (STN‐DBS), the loss of pigmented neurons within the substantia nigra and pathological alpha‐synuclein density within the SN and other brain regions. Methods : PD subjects were identified from the Arizona Study of Aging and Neurodegenerative Disorders database (STN‐DBS = 11, non‐DBS = 156). Pigmented neuron loss scores within the substantia nigra as well as alpha‐synuclein density scores within the substantia nigra and 9 other brain regions were compared, the latter individually and in summary as the Lewy body brain load score. Results : DBS subjects had higher alpha‐synuclein density scores within the substantia nigra, olfactory bulb, and locus ceruleus, as well as higher total Lewy body brain load scores when compared with non‐DBS subjects. No differences in substantia nigra pigmented neuron loss scores were found. Conclusions : STN‐DBS subjects tend to have higher alpha‐synuclein density scores, but do not have a differential loss of substantia nigra pigmented neurons. © 2016 International Parkinson and Movement Disorder Society     

Alpha‐synuclein polymorphisms are associated with Parkinson's disease in a Saskatchewan population

Alpha‐synuclein gene (SNCA) mutations cause familial Parkinsonism but the role of SNCA variability in idiopathic Parkinson's disease (PD) remains incompletely defined. We report a study of SNCA genetic variation in 452 idiopathic PD cases and 245 controls. SNCA copy number mutations were not associated with early‐onset disease in this population. The minor allele “G” at rs356165 was associated with increased odds of PD (P = 0.013) and genetic variation in D4S3481 (Rep1) was associated with age of disease onset (P = 0.007). There was a trend toward association between variation at rs2583988 and rapid PD progression. © 2009 Movement Disorder Society     

α‐Synuclein pathology in the cranial and spinal nerves in Lewy body disease

Accumulation of phosphorylated α‐synuclein in neurons and glial cells is a histological hallmark of Lewy body disease (LBD) and multiple system atrophy (MSA). Recently, filamentous aggregations of phosphorylated α‐synuclein have been reported in the cytoplasm of Schwann cells, but not in axons, in the peripheral nervous system in MSA, mainly in the cranial and spinal nerve roots. Here we conducted an immunohistochemical investigation of the cranial and spinal nerves and dorsal root ganglia of patients with LBD. Lewy axons were found in the oculomotor, trigeminal and glossopharyngeal‐vagus nerves, but not in the hypoglossal nerve. The glossopharyngeal‐vagus nerves were most frequently affected, with involvement in all of 20 subjects. In the spinal nerve roots, Lewy axons were found in all of the cases examined. Lewy axons in the anterior nerves were more frequent and numerous in the thoracic and sacral segments than in the cervical and lumbar segments. On the other hand, axonal lesions in the posterior spinal nerve roots appeared to increase along a cervical‐to‐sacral gradient. Although Schwann cell cytoplasmic inclusions were found in the spinal nerves, they were only minimal. In the dorsal root ganglia, axonal lesions were seldom evident. These findings indicate that α‐synuclein pathology in the peripheral nerves is axonal‐predominant in LBD, whereas it is restricted to glial cells in MSA.     

Olfactory dysfunction in incidental Lewy body disease and Parkinson's disease

BackgroundOlfactory dysfunction in Parkinson's disease (PD) is well-established and may represent one of the earliest signs of the disease.Objective & methodsThe objective of this study was to evaluate the relationship of olfactory dysfunction, using the University of Pennsylvania Smell Identification Test (UPSIT), to clinical and pathological parameters of clinicopathologically diagnosed PD (n = 10), incidental Lewy body disease (ILBD) (n = 13), and identically assessed controls who lacked a neurodegenerative disease (n = 69).ResultsMean UPSIT scores were significantly lower in PD (16.3, p < 0.001) and ILBD (22.2, p = 0.004) compared to controls (27.7). Using an UPSIT cutoff score of <22 (the 15th percentile) the sensitivity for detecting PD was 9/10 (90%) and ILBD 6/13 (46%), while the specificity was 86% (Controls with score of <22 = 10/69).ConclusionsThese results add to the growing body of evidence suggesting that olfactory testing could be useful as a screening tool for identifying early, pre-motor PD.     

Incidental Lewy body disease: Clinical comparison to a control cohort

Limited clinical information has been published on cases pathologically diagnosed with incidental Lewy body disease (ILBD). Standardized, longitudinal movement and cognitive data was collected on a cohort of subjects enrolled in the Sun Health Research Institute Brain and Body Donation Program. Of 277 autopsied subjects who had antemortem clinical evaluations within the previous 3 years, 76 did not have Parkinson's disease, a related disorder, or dementia of which 15 (20%) had ILBD. Minor extrapyramidal signs were common in subjects with and without ILBD. Cognitive testing revealed an abnormality in the ILBD group in the Trails B test only. ILBD cases had olfactory dysfunction; however, sample size was very small. This preliminary report revealed ILBD cases have movement and cognitive findings that for the most part were not out of proportion to similarly assessed and age‐similar cases without Lewy bodies. Larger sample size is needed to have the power to better assess group differences. © 2010 Movement Disorder Society