Natural history of multiple system atrophy in the USA: a prospective cohort study.

BACKGROUND: Multiple system atrophy is a rare, fatal neurodegenerative disorder with symptoms of autonomic failure plus parkinsonism, cerebellar ataxia, or both. We report results of the first prospective natural history study of multiple system atrophy in the USA, and the effects of phenotype and autonomic failure on prognosis. METHODS: We recruited participants with probable multiple system atrophy-of either the parkinsonism subtype (MSA-P) or the cerebellar ataxia subtype (MSA-C)-at 12 neurology centres in the USA specialising in movement or autonomic disorders. We followed up patients every 6 months for 5 years and assessed them with the Unified Multiple System Atrophy Rating Scale part I (UMSARS I; a functional score of symptoms and ability to undertake activities of daily living), UMSARS II (neurological motor evaluation), and the Composite Autonomic Symptoms Scale (COMPASS)-select (a measure of autonomic symptoms and autonomic functional status). We assessed potential predictors of outcome. We used Cox proportional hazards models to calculate univariate hazard ratios for shorter survival using age at disease onset as a continuous variable and sex, clinical phenotype, and early development of neurological and autonomic manifestations as categorical variables. FINDINGS: We recruited 175 participants. Mean age at study entry was 63·4 years (SD 8·6). Median survival from symptom onset was 9·8 years (95% CI 8·8-10·7) and median survival from enrolment was 1·8 years (0·9-2·7). Participants with severe symptomatic autonomic failure (symptomatic orthostatic hypotension, urinary incontinence, or both) at diagnosis (n=62) had a worse prognosis than those without severe disease (n=113; median survival 8·0 years, 95% CI 6·5-9·5 vs 10·3 years, 9·3-11·4; p=0·021). At baseline, patients with MSA-P (n=126) and MSA-C (n=49) had much the same symptoms and functional status: mean UMSARS I 25·2 (SD 8·08) versus 24·6 (8·34; p=0·835); mean UMSARS II 26·4 (8·8) versus 25·4 (10·5; p=0·764); COMPASS-select 43·5 (18·7) versus 42·8 (19·6; p=0·835). Progression over 5 years, assessed by change in UMSARS I, UMSARS II, and COMPASS-select, was modest. INTERPRETATION: Probable multiple system atrophy is a late-stage disease with short survival. The natural histories of MSA-P and MSA-C are similar and severe symptomatic autonomic failure at diagnosis is associated with worse prognosis. FUNDING: US National Institutes of Health, Mayo Clinic, and Kathy Shih Memorial Foundation.

Platelet mitochondrial activity and pesticide exposure in early Parkinson's disease.

BACKGROUND: Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD), but the cause of this dysfunction is unclear. METHODS: Platelet mitochondrial complex I and I/III (nicotinamide adenine dinucleotide cytochrome c reductase, NCCR) activities were measured in early PD patients and matched controls enrolled in a population-based case-control study. Ambient agricultural pesticide exposures were assessed with a geographic information system and California Pesticide Use Registry. RESULTS: In contrast to some previous reports, we found no differences in complex I and I/III activities in subjects with PD and controls. We did find that NCCR activity correlated with subjects' exposure to pesticides known to inhibit mitochondrial activity regardless of their diagnosis. CONCLUSIONS: Electron transport chain (ETC) activity is not altered in PD in this well-characterized cohort when compared with community-matched controls but appears to be affected by environmental toxins, such as mitochondria-inhibiting pesticides.

Prospective differentiation of multiple system atrophy from Parkinson disease, with and without autonomic failure.

OBJECTIVE: To report preliminary results of a prospective ongoing study of multiple system atrophy (MSA) and Parkinson disease (PD), with a large subset of patients with PD with autonomic failure (25%), to evaluate autonomic indices that distinguish MSA from PD. METHODS: We used consensus criteria, detailed autonomic studies (Composite Autonomic Symptom Scale, Composite Autonomic Scoring Scale, thermoregulatory sweat test, and plasma catecholamines), and functional scales (Unified MSA Rating Scale [UMSARS] I-IV and Hoehn-Yahr grading) on a prospective, repeated, and ongoing basis. RESULTS: We report the results of a study on 52 patients with MSA (mean [SD], age, 61.1 [7.8] years; body mass index (calculated as weight in kilograms divided by height in meters squared), 27.2 [4.6]; Hoehn-Yahr grade, 3.2 [0.9]; UMSARS I score, 21.5 [7.4]; and UMSARS II score, 22.7 [9.0]) and 29 patients with PD, including PD with autonomic failure (mean [SD], age, 66.0 [8.1] years; body mass index, 26.6 [5.5]; Hoehn-Yahr grade, 2.2 [0.8]; UMSARS I score, 10.4 [6.1]; and UMSARS II score, 13.0 [5.9]). Autonomic indices were highly significantly more abnormal in MSA than PD (P < .001) for the Composite Autonomic Scoring Scale (5.9 [1.9] vs 3.3 [2.3], respectively), Composite Autonomic Symptom Scale (54.4 [21.8] vs 24.7 [20.5], respectively), and thermoregulatory sweat test (percentage anhidrosis, 57.4% [35.2%] vs 9.9% [17.7%], respectively). These differences were sustained and greater at 1-year follow-up, indicating a greater rate of progression of dysautonomia in MSA than PD. CONCLUSIONS: The severity, distribution, and pattern of autonomic deficits at study entry will distinguish MSA from PD, and MSA from PD with autonomic failure. These differences continue and are increased at follow-up. Our ongoing conclusion is that autonomic function tests can separate MSA from PD. Autonomic indices support the notion that the primary lesion in PD is ganglionic and postganglionic, while MSA is preganglionic.

Dopamine depletion induces distinct compensatory gene expression changes in DARPP-32 signal transduction cascades of striatonigral and striatopallidal neurons.

Functional alterations in striatal projection neurons play a critical role in the development of motor symptoms in Parkinson's disease (PD), but their molecular adaptation to dopamine depletion remains poorly understood. In particular, type and extent of regulation in postsynaptic signal transduction pathways that determine the responsiveness of striatal projection neurons to incoming stimuli, are currently unknown. Using cell-type-specific transcriptome analyses in a rodent model of chronic dopamine depletion, we identified large-scale gene expression changes, including neurotransmitter receptors, signal transduction cascades, and target proteins of dopamine signaling in striatonigral and striatopallidal neurons. Within the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) cascade of enzymes that plays a central role in signal integration of dopaminoceptive neurons multiple catalytic and regulatory subunits change their mRNA expression levels. In addition to the number of genes the fact that the alterations occur at multiple levels stresses the biological relevance of transcriptional regulation for adaptations of postsynaptic signaling pathways. The overall pattern of changes in both striatonigral and striatopallidal neurons is compatible with homeostatic mechanisms. In accordance with the distinct biological effects of dopamine D(1) and D(2) receptor stimulation, the alterations of the transcriptional profiles most likely result in prodopaminergic phosphorylation patterns. Our data provide insight into the disease-related plasticity of functional genomic networks in vivo that might contribute to the protracted preclinical phase of PD. In addition, the data have potential implications for the symptomatic treatment of the disease.

Dopamine depletion induced up-regulation of HCN3 enhances rebound excitability of basal ganglia output neurons.

Motor symptoms in Parkinson's disease (PD) are associated with complex changes of firing properties in basal ganglia output neurons (BGON). The abnormalities are generally attributed to altered synaptic input and potential post-synaptic mechanisms are currently unknown. Our cell-type selective transcriptome analyses of BGON in the rat 6-hydroxydopamine (6-OHDA) model of PD identified the ion channel HCN3 as a likely contributor to altered neuronal excitability. Quantitative PCR experiments confirmed the HCN3 upregulation in the rat and mouse 6-OHDA models and also demonstrated selectivity of the effect for HCN3. In accordance with the mRNA expression data, in vitro whole cell patch-clamp recordings in BGON showed increased HCN3 current amplitudes and increased rebound excitability in BGON of 6-OHDA treated rats. These data establish HCN3 up-regulation as a novel candidate mechanism that might contribute to the in vivo changes of electrical activity in basal ganglia output neurons of the parkinsonian brain.

Potential outcome measures and trial design issues for multiple system atrophy.

Multiple system atrophy (MSA) is a neurodegenerative disorder exhibiting a combination of parkinsonism, cerebellar ataxia, and autonomic failure. A disease-specific scale, the Unified Multiple System Atrophy Rating Scale (UMSARS), has been developed and validated to measure progression of MSA, but its use as an outcome measure for therapeutic trials has not been evaluated. On the basis of twelve months of follow-up from an observational study of 67 patients with probable MSA, we evaluated three disease-specific scores: Activities of Daily Living, Motor Examination, and a combined score from the UMSARS and two general health scores, the Physical Health and Mental Health scores of the SF-36 health survey, for their use as outcome measures in a therapeutic trial. We discuss related design issues and provide sample size estimates. Scores based on the disease-specific UMSARS seemed to be equal or superior to scores based on the SF-36 health survey. They appeared to capture disease progression, were well correlated and required the smallest sample size. The UMSARS Motor Examination score exhibited the most favorable characteristics as an outcome measure for a therapeutic trial in MSA with 1 year of follow-up.

G2019S mutation in the leucine-rich repeat kinase 2 gene is not associated with multiple system atrophy.

Multiple system atrophy (MSA) is characterized clinically by Parkinsonism, cerebellar dysfunction, and autonomic impairment. Multiple mutations in the LRRK2 gene are associated with parkinsonian disorders, and the most common one, the G2019S mutation, has been found in approximately 1% of sporadic cases of Parkinsonism. In a well-characterized cohort of 136 subjects with probable MSA and 110 neurologically evaluated control subjects, none carried the G2019S mutation. We conclude that the G2019S mutation in the LRRK2 gene is unlikely to be associated with MSA.

R1514Q substitution in Lrrk2 is not a pathogenic Parkinson's disease mutation.

Mutations in LRRK2 were first reported as causing Parkinson's disease (PD) in late 2004. Since then, approximately a dozen LRRK2 substitutions have been identified that are believed to be pathogenic mutations. The substitution of adenine for guanine at nucleotide 4541 (4541G>A) in LRRK2 was recently reported. This substitution resulted in the replacement of an arginine at position 1514 with a glutamine (R1514Q). Although this substitution was not found in a large cohort of controls, its pathogenicity could not be verified. We have now genotyped the R1514Q substitution in a sample of 954 PD patients from 429 multiplex PD families. This substitution was identified in 1.8% of the PD patients; however, the majority of the PD sibships segregating this substitution were discordant for this putative mutation. In addition, the R1514Q substitution was detected in 1.4% of neurologically evaluated, control individuals. These data suggest that the R1514Q variant is not a pathogenic LRRK2 mutation. We believe it is imperative that the causative nature of any newly identified genetic variant be determined before it is included in any panel for diagnostic testing.

Mutations in LRRK2 other than G2019S are rare in a north American-based sample of familial Parkinson's disease.

A total of 956 individuals with Parkinson's disease (PD) from 430 multiplex PD pedigrees were screened for 12 previously reported, pathogenic LRRK2 mutations: R793M, L1114L, I1371V, R1441C, R1441G, R1441H, Y1699C, M1869T, I2012T, I2020T, G2385R, and IVS31 +3G > A. Previous screening identified the LRRK2 G2019S mutation in 5% of our families. Only 1 of the 12 newly screened mutations, R1441C, was detected in a single family in our patient cohort. These results indicate that, although the G2019S mutation remains the most common mutation identified in familial PD patients, other mutations in LRRK2 are infrequent.

Mutations in DJ-1 are rare in familial Parkinson disease.

Mutations in DJ-1 (PARK7) are one cause of early-onset autosomal-recessive parkinsonism. We screened for DJ-1 mutations in 93 affected individuals from the 64 multiplex Parkinson disease (PD) families in our sample that had the highest family-specific multipoint LOD scores at the DJ-1 locus. In addition to sequencing all coding exons for alterations, we used multiplex ligation-dependent probe amplification (MLPA) to examine the genomic copy number of DJ-1 exons. A known polymorphism (R98Q) was found in five PD subjects, once as a homozygote and in the other four cases as heterozygotes. No additional missense mutations and no exon deletions or duplications were detected. Our results, in combination with those of previous studies, suggest that alterations in DJ-1 are not a common cause of familial PD.

alpha-synuclein from platelets is not phosphorylated at serine 129 in Parkinson's disease and multiple system atrophy.

Parkinson's disease (PD) and multiple system atrophy (MSA) are characterized pathologically by inclusions in the brain containing alpha-synuclein, which is phosphorylated at serine 129. alpha-Synuclein is present not only in the brain but also in platelets; platelets have previously been used to study mitochondrial function in PD. We undertook to determine whether alpha-synuclein extracted from platelets of patients with PD and MSA is phosphorylated at serine 129 and could be used as a peripheral marker of these disorders. Immunoblots indicated that platelet alpha-synuclein is not phosphorylated at serine 129 in PD and MSA.

Lewy bodies.

Lewy bodies (LB) in the substantia nigra are a cardinal pathological feature of Parkinson's disease, but they occur in a number of neurodegenerative diseases and can be widespread in the nervous system. The characteristics, locations, and composition of LB are reviewed, with particular attention to alpha-synuclein (alpha-SYN), which appears to be the major component of LB. The propensity for alpha-SYN, a presynaptic protein widely expressed in the brain, to aggregate is because of an amyloidogenic central region. The factors that favor the aggregation of alpha-SYN and mechanisms of toxicity are examined, and a mechanism through which aggregates of alpha-SYN could induce mitochondrial dysfunction and/or release of proapoptotic molecules is proposed.

Presence of an APOE4 allele results in significantly earlier onset of Parkinson's disease and a higher risk with dementia.

The epsilon4 allele of the apolipoprotein E gene (APOE4) has been consistently associated with a greater risk of Alzheimer's disease (AD) as well as an earlier onset of AD. It is possible that APOE4 may also play a role in the etiology of other neurodegenerative disorders, such as Parkinson's disease (PD). APOE genotype, age of onset, disease duration, smoking history, and dementia status were collected for families with PD, yielding 324 Caucasian families with complete information. Logistic regression employing one individual per family and including age of onset and disease duration as covariates demonstrated a significantly increased risk of dementia for those individuals having inherited at least one epsilon4 allele (OR=3.37; P=0.002). Survival analyses also demonstrated a significantly earlier age of onset for those subjects with at least one epsilon4 allele (59.7 years) as compared with those homozygous for the more common epsilon3 allele (62.4 years; P=0.009). Thus, consistent with previous studies, we find evidence that the presence of an epsilon4 allele results in significantly earlier onset of PD and a greater likelihood of dementia. It appears the similarities between PD and AD may be due to an overlap in the diseases' genetic etiology.

Neurological and neurodegenerative alterations in a transgenic mouse model expressing human alpha-synuclein under oligodendrocyte promoter: implications for multiple system atrophy.

Multiple system atrophy (MSA) is a progressive, neurodegenerative disease characterized by parkinsonism, ataxia, autonomic dysfunction, and accumulation of alpha-synuclein (alpha-syn) in oligodendrocytes. To better understand the mechanisms of neurodegeneration and the role of alpha-syn accumulation in oligodendrocytes in the pathogenesis of MSA, we generated transgenic mouse lines expressing human (h) alpha-syn under the control of the murine myelin basic protein promoter. Transgenic mice expressing high levels of halpha-syn displayed severe neurological alterations and died prematurely at 6 months of age. Furthermore, mice developed progressive accumulation of halpha-syn-immunoreactive inclusions in oligodendrocytes along the axonal tracts in the brainstem, basal ganglia, cerebellum, corpus callosum, and neocortex. The inclusions also reacted with antibodies against phospho-serine (129) halpha-syn and ubiquitin, and halpha-syn was found in the detergent-insoluble fraction. In high-expresser lines, the white matter tracts displayed intense astrogliosis, myelin pallor, and decreased neurofilament immunostaining. Accumulation of halpha-syn in oligodendrocytes also leads to prominent neurodegenerative changes in the neocortex with decreased dendritic density and to loss of dopaminergic fibers in the basal ganglia. The oligodendrocytic inclusions were composed of fibrils and accompanied by mitochondrial alterations and disruption of the myelin lamina in the axons. Together, these studies support the contention that accumulation of alpha-syn in oligodendrocytes promotes neurodegeneration and recapitulates several of the key functional and neuropathological features of MSA.

Therapeutic role of coenzyme Q(10) in Parkinson's disease.

Mitochondrial dysfunction has been well established to occur in Parkinson's disease (PD) and appears to play a role in the pathogenesis of the disorder. A key component of the mitochondrial electron transport chain (ETC) is coenzyme Q(10), which not only serves as the electron acceptor for complexes I and II of the ETC but is also an antioxidant. In addition to being crucial to the bioenergetics of the cell, mitochondria play a central role in apoptotic cell death through a number of mechanisms, and coenzyme Q(10) can affect certain of these processes. Levels of coenzyme Q(10) have been reported to be decreased in blood and platelet mitochondria from PD patients. A number of preclinical studies in in vitro and in vivo models of PD have demonstrated that coenzyme Q(10) can protect the nigrostriatal dopaminergic system. A phase II trial of coenzyme Q(10) in patients with early, untreated PD demonstrated a positive trend for coenzyme Q(10) to slow progressive disability that occurs in PD.

Alpha-synuclein overexpression in oligodendrocytic cells results in impaired adhesion to fibronectin and cell death.

The cardinal pathological features of multiple system atrophy (MSA) are the presence of glial cytoplasmic inclusions (GCIs) in oligodendrocytes and loss of oligodendrocytes. To understand the mechanisms underlying MSA, we examined the effects of overexpression of human alpha-synuclein (halpha-syn) in CG-4 oligodendrocytic progenitor cells. CG-4 cells overexpressing halpha-syn (halpha-syn CG-4) demonstrated severely impaired adhesion and increased cell death when plated on fibronectin compared to laminin. The expression of the alphav integrin subunit in whole cell lysates was also significantly downregulated in halpha-syn CG-4. These results demonstrate a cytotoxic consequence of halpha-syn overexpression in CG-4. This cytotoxicity appears to be the result of alterations in cell-extracellular matrix interactions, where impaired adhesion to fibronectin is associated with downregulation of the alphav integrin subunit and increased cell death. It may, therefore, be one of the mechanisms underlying the loss of oligodendrocytes in MSA.

Genetic screening for a single common LRRK2 mutation in familial Parkinson's disease.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause some forms of autosomal dominant Parkinson's disease. We measured the frequency of a novel mutation (Gly2019 ser) in familial Parkinson's disease by screening genomic DNA of patients and controls. Of 767 affected individuals from 358 multiplex families, 35 (5%) individuals were either heterozygous (34) or homozygous (one) for the mutation, and had typical clinical findings of idiopathic Parkinson's disease. Thus, our results suggest that a single LRRK2 mutation causes Parkinson's disease in 5% of individuals with familial disease. Screening for this mutation should be a component of genetic testing for Parkinson's disease.