Alpha‐synuclein and familial Parkinson's disease

Whole gene duplications and triplications of alpha‐synuclein (SNCA) can cause Parkinson's disease (PD), and variation in the promoter region (Rep1) and 3' region of SNCA has been reported to increase disease susceptibility. Within our cohort, one affected individual from each of 92 multiplex PD families showing the greatest evidence of linkage to the region around SNCA was screened for dosage alterations and sequence changes; no dosage or non‐synonymous sequence changes were found. In addition, 737 individuals (from 450 multiplex PD families) that met strict diagnostic criteria for PD and did not harbor a known causative mutation, as well as 359 neurologically normal controls, were genotyped for the Rep1 polymorphism and four SNPs in the 3′ region of SNCA. The four SNPs were in high LD (r² > 0.95) and were analyzed as a haplotype. The effects of the Rep1 genotype and the 3′ haplotype were evaluated using regression models employing only one individual per family. Cases had a 3% higher frequency of the Rep1 263 bp allele compared with controls (OR = 1.54; empirical P‐value = 0.02). There was an inverse linear relationship between the number of 263 bp alleles and age of onset (empirical P‐value = 0.0004). The 3′ haplotype was also associated with disease (OR = 1.29; empirical P‐value = 0.01), but not age of onset (P = 0.40). These data suggest that dosage and sequence changes are a rare cause of PD, but variation in the promoter and 3′ region of SNCA convey an increased risk for PD. © 2009 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     

Alpha‐synuclein in colonic submucosa in early untreated Parkinson's disease

The diagnosis of Parkinson's disease rests on motor signs of advanced central dopamine deficiency. There is an urgent need for disease biomarkers. Clinicopathological evidence suggests that α‐synuclein aggregation, the pathological signature of Parkinson's disease, can be detected in gastrointestinal tract neurons in Parkinson's disease. We studied whether we could demonstrate α‐synuclein pathology in specimens from unprepped flexible sigmoidoscopy of the distal sigmoid colon in early subjects with Parkinson's disease. We also looked for 3‐nitrotyrosine, a marker of oxidative stress. Ten subjects with early Parkinson's disease not treated with dopaminergic agents (7 men; median age, 58.5 years; median disease duration, 1.5 years) underwent unprepped flexible sigmoidoscopy with biopsy of the distal sigmoid colon. Immunohistochemistry studies for α‐synuclein and 3‐nitrotyrosine were performed on biopsy specimens and control specimens from a tissue repository (23 healthy subjects and 23 subjects with inflammatory bowel disease). Nine of 10 Parkinson's disease samples were adequate for study. All showed staining for α‐synuclein in nerve fibers in colonic submucosa. No control sample showed this pattern. A few showed light α‐synuclein staining in round cells. 3‐Nitrotyrosine staining was seen in 87% of Parkinson's disease cases but was not specific for Parkinson's disease. This study suggests a pattern of α‐synuclein staining in Parkinson's disease that was distinct from healthy subjects and those with inflammatory bowel disease. The absence of this pattern in subjects with inflammatory bowel disease suggests it is not a sequel of inflammation or oxidative stress. 3‐Nitrotyrosine immunostaining was common in all groups studied, suggesting oxidative stress in the colonic submucosa. © 2011 Movement Disorder Society.     

Alpha‐synuclein in the appendiceal mucosa of neurologically intact subjects

Parkinson's disease is characterized by the pathological aggregation of Alpha‐synuclein. The dual‐hit hypothesis proposed by Braak implicates the enteric nervous system as an initial site of α‐synuclein aggregation with subsequent spread to the central nervous system. Regional variations in the spatial pattern or levels of α‐synuclein along the enteric nervous system could have implications for identifying sites of onset of this pathogenic cascade. We performed immunohistochemical staining for α‐synuclein on gastrointestinal tissue from patients with no history of neurological disease using the established LB509 antibody and a new clone, MJFR1, characterized for immunohistochemistry here. We demonstrate that the vermiform appendix is particularly enriched in α‐synuclein–containing axonal varicosities, concentrated in its mucosal plexus rather than the classical submucosal and myenteric plexuses. Unexpectedly, intralysosomal accumulations of α‐synuclein were detected within mucosal macrophages of the appendix. The abundance and accumulation of α‐synuclein in the vermiform appendix implicate it as a candidate anatomical locus for the initiation of enteric α‐synuclein aggregation and permits the generation of testable hypotheses for Parkinson's disease pathogenesis. © 2013 International Parkinson and Movement Disorder Society     

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.     

Multiple organ involvement by alpha‐synuclein pathology in Lewy body disorders

Lewy body (LB) diseases are characterized by alpha‐synuclein (AS) aggregates in the central nervous system (CNS). Involvement of the peripheral autonomic nervous system (pANS) is increasingly recognized, although less studied. The aim of this study was to systematically analyze the distribution and severity of AS pathology in the CNS and pANS. Detailed postmortem histopathological study of brain and peripheral tissues from 28 brain bank donors (10 with Parkinson's disease [PD], 5 with dementia with LB [DLB], and 13 with non‐LB diseases including atypical parkinsonism and non‐LB dementia). AS aggregates were found in the pANS of all 15 LB disease cases (PD, DLB) in stellate and sympathetic ganglia (100%), vagus nerve (86.7%), gastrointestinal tract (86.7%), adrenal gland and/or surrounding fat (53.3%), heart (100%), and genitourinary tract (13.3%), as well as in 1 case of incidental Lewy body disease (iLBD). A craniocaudal gradient of AS burden in sympathetic chain and gastrointestinal tract was observed. DLB cases showed higher amounts of CNS AS aggregates than PD cases, but this was not the case in the pANS. No pANS AS aggregates were detected in Alzheimer's disease (AD) cases with or without CNS AS aggregates. All pathologically confirmed LB disease cases including 1 case of iLBD had AS aggregates in the pANS with a craniocaudal gradient of pathology burden in sympathetic chain and gastrointestinal tract. AS was not detected in the pANS of any AD case. These findings may help in the search of peripheral AS aggregates in vivo for the early diagnosis of PD. © 2014 International Parkinson and Movement Disorder Society     

Plasma α‐synuclein in patients with Parkinson's disease with and without treatment

Alpha‐synuclein (α‐syn) is an intracellular protein with a high tendency to aggregation. It is the major component of Lewy bodies and may play a key role in the pathogenesis of Parkinson's disease (PD). α‐Syn is also released by neurons and can be detected in biological fluids, such as plasma. The purpose of this study was to determine whether plasma α‐syn concentrations are elevated in newly diagnosed PD patients before treatment (nontreated PD group, ntPD; n = 53) and to compare them with concentrations in PD patients with at least 1 year of specific treatment (tPD; n = 42) and in healthy controls (n = 60). Plasma α‐syn concentrations in the ntPD and tPD groups were similar and significantly higher than in healthy controls. In conclusion, α‐syn was elevated early in the development of PD and specific PD treatment did not change plasma α‐syn levels. © 2010 Movement Disorder Society     

Exercise modifies α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor expression in striatopallidal neurons in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐lesioned mouse

The α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic‐acid‐type glutamate receptor (AMPAR) plays a critical role in modulating experience‐dependent neuroplasticity, and alterations in AMPAR expression may underlie synaptic dysfunction and disease pathophysiology. Using the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of dopamine (DA) depletion, our previous work showed exercise increases total GluA2 subunit expression and the contribution of GluA2‐containing channels in MPTP mice. The purpose of this study was to determine whether exercise‐dependent changes in AMPAR expression after MPTP are specific to the striatopallidal (D₂R) or striatonigral (D₁R) medium spiny neuron (MSN) striatal projection pathways. Drd₂‐eGFP‐BAC transgenic mice were used to delineate differences in AMPAR expression between striatal D₂R‐MSNs and D₁R‐MSNs. Striatal AMPAR expression was assessed by immunohistochemical (IHC) staining, Western immunoblotting (WB) of preparations enriched for postsynaptic density (PSD), and alterations in the current–voltage relationship of MSNs. We found DA depletion results in the emergence of GluA2‐lacking AMPARs selectively in striatopallidal D₂R‐MSNs and that exercise reverses this effect in MPTP mice. Exercise‐induced changes in AMPAR channels observed after DA depletion were associated with alterations in GluA1 and GluA2 subunit expression in postsynaptic protein, D₂R‐MSN cell surface expression, and restoration of corticostriatal plasticity. Mechanisms regulating experience‐dependent changes in AMPAR expression may provide innovative therapeutic targets to increase the efficacy of treatments for basal ganglia disorders, including Parkinson's disease. © 2013 Wiley Periodicals, Inc.     

Sensitive and specific detection of α‐synuclein in human plasma

α‐Synuclein (αsyn) mutations, overexpression, misfolding, and aggregation are associated with Parkinson's disease. This protein has been intensively studied in neuronal systems. However, αsyn is also present in extracellular fluids, such as cerebrospinal fluid and blood plasma. Recent studies have attempted to quantify its levels and compare these in various extracellular fluids of control and Parkinson's disease subjects. Data from these studies have been difficult to interpret, suggesting that more sensitive, standardized, and well‐characterized assays of larger cohorts are required. Here, we describe the development of a new ELISA specifically for quantifying αsyn in human plasma. An initial assay, using a commercial anti‐αsyn monoclonal antibody (211; Santa Cruz Biotechnology, Santa Cruz, CA) and based on a published protocol, was adapted for use in human plasma. In addition, we have developed a novel αsyn‐specific antibody for the assay that has very high sensitivity and signal:noise characteristics. Assays with either antibody showed high specificity for αsyn, and detected it in a variety of sample types, including plasma. These assays can now be employed on large cohorts of patients and control subjects to determine whether plasma levels are altered in disease. Although measuring extracellular αsyn levels may prove to be a useful biomarker of Parkinson's disease, it should also be a powerful tool for basic research aimed at understanding the normal and pathological physiology of αsyn secretion. © 2010 Wiley‐Liss, Inc.     

Parkinson's disease,cortical dysfunction,and alpha‐synuclein

The ability to understand how Parkinson's disease neurodegeneration leads to cortical dysfunction will be critical for developing therapeutic advances in Parkinson's disease dementia. The overall purpose of this project was to study the small‐amplitude cortical myoclonus in Parkinson's disease as an in vivo model of focal cortical dysfunction secondary to Parkinson's disease neurodegeneration. The objectives were to test the hypothesis that cortical myoclonus in Parkinson's disease is linked to abnormal levels of α‐synuclein in the primary motor cortex and to define its relationship to various biochemical, clinical, and pathological measures. The primary motor cortex was evaluated for 11 Parkinson's disease subjects with and 8 without electrophysiologically confirmed cortical myoclonus (the Parkinson's disease + myoclonus group and the Parkinson's disease group, respectively) who had premortem movement and cognitive testing. Similarly assessed 9 controls were used for comparison. Measurements for α‐synuclein, Aβ‐42 peptide, and other biochemical measures were made in the primary motor cortex. A 36% increase in α‐synuclein was found in the motor cortex of Parkinson's disease + myoclonus cases when compared with Parkinson's disease without myoclonus. This occurred without significant differences in insoluble α‐synuclein, phosphorylated to total α‐synuclein ratio, or Aβ‐42 peptide levels. Higher total motor cortex α‐synuclein levels significantly correlated with the presence of cortical myoclonus but did not correlate with multiple clinical or pathological findings. These results suggest an association between elevated α‐synuclein and the dysfunctional physiology arising from the motor cortex in Parkinson's disease + myoclonus cases. Alzheimer's disease pathology was not associated with cortical myoclonus in Parkinson's disease. Cortical myoclonus arising from the motor cortex is a model to study cortical dysfunction in Parkinson's disease. © 2011 Movement Disorder Society     

Intermittent theta‐burst stimulation rescues dopamine‐dependent corticostriatal synaptic plasticity and motor behavior in experimental parkinsonism: Possible role of glial activity

Background : Recent studies support the therapeutic utility of repetitive transcranial magnetic stimulation in Parkinson's disease (PD), whose progression is correlated with loss of corticostriatal long‐term potentiation and long‐term depression. Glial cell activation is also a feature of PD that is gaining increasing attention in the field because astrocytes play a role in chronic neuroinflammatory responses but are also able to manage dopamine (DA) levels. Methods : Intermittent theta‐burst stimulation protocol was applied to study the effect of therapeutic neuromodulation on striatal DA levels measured by means of in vivo microdialysis in 6‐hydroxydopamine‐hemilesioned rats. Effects on corticostriatal synaptic plasticity were studied through in vitro intracellular and whole‐cell patch clamp recordings while stepping test and CatWalk were used to test motor behavior. Immunohistochemical analyses were performed to analyze morphological changes in neurons and glial cells. Results : Acute theta‐burst stimulation induced an increase in striatal DA levels in hemiparkinsonian rats, 80 minutes post‐treatment, correlated with full recovery of plasticity and amelioration of motor performances. With the same timing, immediate early gene activation was restricted to striatal spiny neurons. Intense astrocytic and microglial responses were also significantly reduced 80 minutes following theta‐burst stimulation. Conclusion : Taken together, these results provide a first glimpse on physiological adaptations that occur in the parkinsonian striatum following intermittent theta‐burst stimulation and may help to disclose the real potential of this technique in treating PD and preventing DA replacement therapy‐associated disturbances. © 2017 International Parkinson and Movement Disorder Society     

Mice expressing the A53T mutant form of human alpha‐synuclein exhibit hyperactivity and reduced anxiety‐like behavior

Genetic mutations associated with α‐synuclein (α‐Syn) are implicated in the pathogenesis of Parkinson's disease (PD). PD is primarily a movement disorder, but patients are known to experience anxiety and other mood disorders. In this study, we examined the effect of the hA53T mutation during development by analyzing the protein expression of norepinephrine (NET), serotonin (SERT), and dopamine (DAT) transporters in addition to assessing locomotor and anxiety‐like behavior. We observed significant decreases in DAT expression at 8 months in transgenic animals compared with normal and younger mice. We used the elevated plus maze, open‐field test, and rotarod apparatus to evaluate wild‐type and hA53T hemizygous mice at 2, 8, and 12 months of age. Our results showed that 12‐month‐old transgenic mice spend more time in the open arms and display a greater number of open entries of the elevated plus maze compared with wild‐type controls and younger mice. Open‐field test results showed that 12‐month‐old mice travel a greater distance overall and travel more in the inner zone than either wild‐type or younger mice. Rotarod testing showed that 8‐ and 12‐month‐old transgenic mice perform better than either wild‐type controls or younger mice. Overall, 8–12‐month‐old transgenic mice showed a trend toward reduced anxiety‐like behavior and increased hyperactivity. These results indicate a possible role of the A53T α‐Syn mutation in anxiety‐like and hyperactive behaviors in a PD mouse model, suggesting that these behaviors might be comorbid with this disease. © 2010 Wiley‐Liss, Inc.