Hippocampal subfield pathologic burden in Lewy body diseases vs. Alzheimer's disease.

AIMS: Lewy body diseases (LBD) are characterized by alpha-synuclein (SYN) pathology, but comorbid Alzheimer's disease (AD) pathology is common and the relationship between these pathologies in microanatomic hippocampal subfields is understudied. Here we use digital histological methods to test the association between hippocampal SYN pathology and the distribution of tau and amyloid-beta (Aß) pathology in LBD and contrast with AD subjects. We also correlate pathologic burden with antemortem episodic memory testing. METHODS: Hippocampal sections from 49 autopsy-confirmed LBD cases, 30 with no/low AD copathology (LBD - AD) and 19 with moderate/severe AD copathology (LBD + AD), and 30 AD patients were stained for SYN, tau, and Aß. Sections underwent digital histological analysis of subfield pathological burden which was correlated with antemortem memory testing. RESULTS: LBD - AD and LBD + AD had similar severity and distribution of SYN pathology (P > 0.05), CA2/3 being the most affected subfield (P < 0.02). In LBD, SYN correlated with tau across subfields (R = 0.49, P < 0.001). Tau burden was higher in AD than LBD + AD (P < 0.001), CA1/subiculum and entorhinal cortex (ERC) being most affected regions (P = 0.04 to <0.01). However, tau pathology in LBD - AD was greatest in CA2/3, which was equivalent to LBD + AD. Aß severity and distribution was similar between LBD + AD and AD. Total hippocampal tau and CA2/3 tau was inversely correlated with memory performance in LBD (R = -0.52, -0.69, P = 0.04, 0.009). CONCLUSIONS: Our findings suggest that tau burden in hippocampal subfields may map closely with the distribution of SYN pathology in subfield CA2/3 in LBD diverging from traditional AD and contribute to episodic memory dysfunction in LBD.

TDP-43 pathology occurs infrequently in multiple system atrophy.

AIMS AND METHODS: The α-synucleinopathy multiple system atrophy (MSA) and diseases defined by pathological 43-kDa transactive response DNA-binding protein (TDP-43) or fused in sarcoma (FUS) aggregates such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration show overlapping clinico-pathological features. Consequently, we examined MSA for evidence of TDP-43 or FUS pathology utilizing immunohistochemical studies in autopsy material from 29 MSA patients. RESULTS: TDP-43 pathology was generally rare, and there were no FUS lesions. The TDP-43 lesions were located predominantly in medio-temporal lobe and subcortical brain areas and were comprised mainly of dystrophic processes and perivascular (and subpial) lesions. CONCLUSIONS: The multisystem clinical symptoms and signs of MSA, and in particular the neurobehavioural/cognitive and pyramidal features, appear not to result from concomitant TDP-43 or FUS pathology, but rather from widespread white matter α-synuclein positive glial cytoplasmic inclusions and neurodegeneration in keeping with a primary α-synuclein-mediated oligodendrogliopathy. The gliodegenerative disease MSA evidently results from different pathogenetic mechanisms than neurodegenerative diseases linked to pathological TDP-43.

Oxidative damage linked to neurodegeneration by selective alpha-synuclein nitration in synucleinopathy lesions.

Aggregated alpha-synuclein proteins form brain lesions that are hallmarks of neurodegenerative synucleinopathies, and oxidative stress has been implicated in the pathogenesis of some of these disorders. Using antibodies to specific nitrated tyrosine residues in alpha-synuclein, we demonstrate extensive and widespread accumulations of nitrated alpha-synuclein in the signature inclusions of Parkinson's disease, dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and multiple system atrophy brains. We also show that nitrated alpha-synuclein is present in the major filamentous building blocks of these inclusions, as well as in the insoluble fractions of affected brain regions of synucleinopathies. The selective and specific nitration of alpha-synuclein in these disorders provides evidence to directly link oxidative and nitrative damage to the onset and progression of neurodegenerative synucleinopathies.

Immunohistochemical and biochemical studies demonstrate a distinct profile of alpha-synuclein permutations in multiple system atrophy.

Although alpha-synuclein (alpha-syn) has been implicated as a major component of the abnormal filaments that form glial cytoplasmic inclusions (GCIs) in multiple system atrophy (MSA), it is uncertain if GCIs are homogenous and contain full-length alpha-syn. Since this has implications for hypotheses about the pathogenesis of GCIs, we used a novel panel of antibodies to defined regions throughout alpha-syn in immunohistochemical epitope mapping studies of GCIs in MSA brains. Although the immunostaining profile of GCIs with these antibodies was similar for all MSA brains, there were significant differences in the immunoreactivity of the alpha-syn epitopes detected in GCIs. Notably, carboxy-terminal alpha-syn epitopes were immunodominant in GCIs, but the entire panel of antibodies immunostained cortical Lewy bodies (LBs) in dementia with LBs brain with similar intensity. While the distribution of alpha-syn labeled GCIs paralleled that previously reported using silver stains, antibodies to carboxy-terminal alpha-syn epitopes revealed a previously undescribed burden of GCIs in the MSA hippocampal formation. Finally, Western blots demonstrated detergent insoluble monomeric and high-molecular weight alpha-syn species in GCI rich MSA cerebellar white matter. Collectively, these data indicate that alpha-syn is a prominent component of GCIs in MSA, and that GCIs and LBs may result from cell type specific conformational or post-translational permutations in alpha-syn.

Atomoxetine for depression and other neuropsychiatric symptoms in Parkinson disease.

OBJECTIVES: Depression and antidepressant use, especially selective serotonin reuptake inhibitors (SSRIs), are common in Parkinson disease (PD). The objective of this clinical trial was to assess the efficacy of atomoxetine, a selective norepinephrine reuptake inhibitor (SNRI), for the treatment of clinically significant depressive symptoms and common comorbid neuropsychiatric symptoms in PD. METHODS: A total of 55 subjects with PD and an Inventory of Depressive Symptomatology-Clinician (IDS-C) score > or = 22 were randomized to 8 weeks of atomoxetine or placebo treatment (target dosage = 80 mg/day). Depression response (> 50% decrease in IDS-C score or Clinical Global Impression-Improvement [CGI-I] score of 1 or 2) was assessed using intention-to-treat modeling procedures. Secondary outcomes included global cognition, daytime sleepiness, anxiety, apathy, and motor function. RESULTS: There were no between-groups differences in a priori-defined response rates. Using a more liberal response criterion of > 40% decrease in IDS score from baseline, there was a trend (p = 0.08) favoring atomoxetine. Patients receiving atomoxetine experienced significantly greater improvement in global cognition (p = 0.003) and daytime sleepiness (p = 0.001), and atomoxetine was well-tolerated. CONCLUSIONS: Atomoxetine treatment was not efficacious for the treatment of clinically significant depressive symptoms in PD, but was associated with improvement in global cognitive performance and daytime sleepiness. Larger studies of SNRIs in PD for disorders of mood, cognition, and wakefulness are appropriate. CLASSIFICATION OF EVIDENCE: This interventional study provides Class II evidence that atomoxetine (target dosage = 80 mg/day) is not efficacious in improving clinically significant depression in PD.

Validity of the MoCA and MMSE in the detection of MCI and dementia in Parkinson disease.

BACKGROUND: Due to the high prevalence of mild cognitive impairment (MCI) and dementia in Parkinson disease (PD), routine cognitive screening is important for the optimal management of patients with PD. The Montreal Cognitive Assessment (MoCA) is more sensitive than the commonly used Mini-Mental State Examination (MMSE) in detecting MCI and dementia in patients without PD, but its validity in PD has not been established. METHODS: A representative sample of 132 patients with PD at 2 movement disorders centers was administered the MoCA, MMSE, and a neuropsychological battery with operationalized criteria for deficits. MCI and PD dementia (PDD) criteria were applied by an investigator blinded to the MoCA and MMSE results. The discriminant validity of the MoCA and MMSE as screening and diagnostic instruments was ascertained. RESULTS: Approximately one third of the sample met diagnostic criteria for a cognitive disorder (12.9% PDD and 17.4% MCI). Mean (SD) MoCA and MMSE scores were 25.0 (3.8) and 28.1 (2.0). The overall discriminant validity for detection of any cognitive disorder was similar for the MoCA and the MMSE (receiver operating characteristic area under the curve [95% confidence interval]): MoCA (0.79 [0.72, 0.87]) and MMSE (0.76 [0.67, 0.85]), but as a screening instrument the MoCA (optimal cutoff point = 26/27, 64% correctly diagnosed, lack of ceiling effect) was superior to the MMSE (optimal cutoff point = 29/30, 54% correctly diagnosed, presence of ceiling effect). CONCLUSIONS: The Montreal Cognitive Assessment, but not the Mini-Mental State Examination, has adequate psychometric properties as a screening instrument for the detection of mild cognitive impairment or dementia in Parkinson disease. However, a positive screen using either instrument requires additional assessment due to suboptimal specificity at the recommended screening cutoff point.

DLB and PDD boundary issues: diagnosis, treatment, molecular pathology, and biomarkers.

For more than a decade, researchers have refined criteria for the diagnosis of dementia with Lewy bodies (DLB) and at the same time have recognized that cognitive impairment and dementia occur commonly in patients with Parkinson disease (PD). This article addresses the relationship between DLB, PD, and PD with dementia (PDD). The authors agreed to endorse "Lewy body disorders" as the umbrella term for PD, PDD, and DLB, to promote the continued practical use of these three clinical terms, and to encourage efforts at drug discovery that target the mechanisms of neurodegeneration shared by these disorders of alpha-synuclein metabolism. We concluded that the differing temporal sequence of symptoms and clinical features of PDD and DLB justify distinguishing these disorders. However, a single Lewy body disorder model was deemed more useful for studying disease pathogenesis because abnormal neuronal alpha-synuclein inclusions are the defining pathologic process common to both PDD and DLB. There was consensus that improved understanding of the pathobiology of alpha-synuclein should be a major focus of efforts to develop new disease-modifying therapies for these disorders. The group agreed on four important priorities: 1) continued communication between experts who specialize in PDD or DLB; 2) initiation of prospective validation studies with autopsy confirmation of DLB and PDD; 3) development of practical biomarkers for alpha-synuclein pathologies; 4) accelerated efforts to find more effective treatments for these diseases.

Multiple pathologies in a patient with a progressive neurodegenerative syndrome.

A woman presenting with levodopa responsive Parkinsonism developed rapidly progressive bulbar signs, quadriparesis, and upper and lower motor neurone signs. At necropsy, she was found to have three pathological diagnoses: amyotrophic lateral sclerosis, Parkinson's disease, and abundant tau-positive argyrophilic neuritic pathology, known as argyrophilic grain disease. This case raises the possibility that three distinct neuropathological diagnoses share a common aetiology.

[99mTc]TRODAT-1 SPECT imaging correlates with odor identification in early Parkinson disease.

BACKGROUND: In vivo imaging of the dopamine transporter with [99mTc]TRODAT-1 (TRODAT) and olfactory testing have both been proposed as potential biomarkers in Parkinson disease (PD). OBJECTIVE: To evaluate the relationship between TRODAT SPECT imaging, odor identification skills, and motor function in patients with early PD. METHODS: Twenty-four patients with a clinical diagnosis of early-stage PD (mean Hoehn & Yahr stage = 1.4) underwent TRODAT imaging, Unified PD Rating Scale (UPDRS) ratings of motor function, and administration of the University of Pennsylvania Smell Identification Test (UPSIT). Brain images were obtained using a standardized processing protocol and specific uptake ratios for striatal regions of interest were calculated. Partial correlations between the imaging indices, disease duration, UPSIT scores, and UPDRS motor scores were then calculated. RESULTS: UPSIT scores were correlated with TRODAT uptake in the striatum as a whole (r = 0.66, p = 0.001). The putamen showed the strongest correlation with the UPSIT (r = 0.74; p < 0.001). The correlation between dopamine transporter density in the caudate and UPSIT was moderate (r = 0.36, p = 0.11), but was not significant. CONCLUSIONS: Olfactory function is highly correlated with dopamine transporter imaging abnormalities in early Parkinson disease (PD). Further studies are warranted to determine whether changes over time in these two measures are also correlated in early PD.

Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium.

The dementia with Lewy bodies (DLB) Consortium has revised criteria for the clinical and pathologic diagnosis of DLB incorporating new information about the core clinical features and suggesting improved methods to assess them. REM sleep behavior disorder, severe neuroleptic sensitivity, and reduced striatal dopamine transporter activity on functional neuroimaging are given greater diagnostic weighting as features suggestive of a DLB diagnosis. The 1-year rule distinguishing between DLB and Parkinson disease with dementia may be difficult to apply in clinical settings and in such cases the term most appropriate to each individual patient should be used. Generic terms such as Lewy body (LB) disease are often helpful. The authors propose a new scheme for the pathologic assessment of LBs and Lewy neurites (LN) using alpha-synuclein immunohistochemistry and semiquantitative grading of lesion density, with the pattern of regional involvement being more important than total LB count. The new criteria take into account both Lewy-related and Alzheimer disease (AD)-type pathology to allocate a probability that these are associated with the clinical DLB syndrome. Finally, the authors suggest patient management guidelines including the need for accurate diagnosis, a target symptom approach, and use of appropriate outcome measures. There is limited evidence about specific interventions but available data suggest only a partial response of motor symptoms to levodopa: severe sensitivity to typical and atypical antipsychotics in approximately 50%, and improvements in attention, visual hallucinations, and sleep disorders with cholinesterase inhibitors.

Neuropathology of synuclein aggregates.

Beginning with the isolation of the fragment of alpha-synuclein (alpha-syn) known as the non-Abeta component of amyloid plaques (NAC peptide) from Alzheimer's disease (AD) brains, alpha-syn has been increasingly implicated in the pathogenesis of neurodegenerative diseases, which now are classified as synucleinopathies. Indeed, unequivocal evidence linking abnormal alpha-syn to mechanisms of brain degeneration came from discoveries of missense mutations in the alpha-syn gene pathogenic for familial Parkinson's disease (PD) in rare kindreds. Shortly thereafter, alpha-syn was shown to be a major component of Lewy bodies (LBs) and Lewy neurites in sporadic PD, dementia with LBs (DLB) and the LB variant of AD. Also, studies of brains from patients with AD caused by genetic abnormalities demonstrated many alpha-syn positive LBs. Further, alpha-syn was implicated in the formation of the glial (GCIs) and neuronal cytoplasmic inclusions of multiple system atrophy, and the LBs, GCIs and neuraxonal spheroids of neurodegeneration with brain iron accumulation type 1. Recently, two other members of the synuclein family, beta- and gamma-synuclein, have also been recognized to play a role in the pathogenesis of novel axonal lesions in PD and DLB. Evidence for a role of alpha-syn in the formation of filamentous aggregates was reinforced by in vitro studies showing aggregation and fibrillogenesis of mutant and wild type alpha-syn. Indeed, since the aggregation of brain proteins into presumptively toxic lesions is emerging as a common but poorly understood mechanistic theme in sporadic and hereditary neurodegenerative diseases, clarification of the mechanism of synuclein aggregation could augment efforts to develop novel and more effective therapies for many neurodegenerative disorders.

The expression of alpha-, beta-, and gamma-synucleins in olfactory mucosa from patients with and without neurodegenerative diseases.

A family of homologous proteins known as alpha-, beta-, and gamma-synuclein are abundantly expressed in brain, especially in the presynaptic terminal of neurons. Although the precise function of these proteins remains unknown, alpha-synuclein has been implicated in synaptic plasticity associated with avian song learning as well as in the pathogenesis of Parkinson's disease (PD), dementia with LBs (DLB), some forms of Alzheimer's disease (AD), and multiple system atrophy (MSA). Since olfactory dysfunction is a common feature of these disorders and the olfactory receptor neurons (ORNs) of the olfactory epithelium (OE) regenerate throughout the lifespan, we used antibodies specific for alpha-, beta-, and gamma-synucleins to examine the olfactory mucosa of patients with PD, DLB, AD, MSA, and controls without a neurological disorder. Although antibodies to alpha- and beta-synucleins detected abnormal dystrophic neurites in the OE of patients with neurodegenerative disorders, similar pathology was also seen in the OE of controls. More significantly, we show here for the first time that alpha-, beta-, and gamma-synucleins are differentially expressed in cells of the OE and respiratory epithelium and that alpha-synuclein is the most abundant synuclein in the olfactory mucosa, where it is prominently expressed in ORNs. Moreover, alpha- and gamma-synucleins also were prominent in the OE basal cells, which include the progenitor cells of the ORNs in the OE. Thus, our data on synuclein expression within the OE may signify that synuclein plays a role in the regeneration and plasticity of ORNs in the adult human OE.

A panel of epitope-specific antibodies detects protein domains distributed throughout human alpha-synuclein in Lewy bodies of Parkinson's disease.

To facilitate studies of the normal biology of alpha-synuclein, a member of a family of neuronal proteins of unknown function, and to elucidate the role of alpha-synuclein pathologies in neurodegenerative diseases, we generated and characterized a panel of anti-synuclein antibodies. Here we demonstrate that these antibodies recognize defined epitopes spanning the entire length of human alpha-synuclein, and that some of these antibodies also cross-react with zebra finch and rodent synucleins. Since alpha-synuclein has been reported to be a major component of Lewy bodies (LBs) in Parkinson's disease (PD), dementia with LBs and common variants of Alzheimer's disease, we performed immunohistochemical studies showing that these antibodies label numerous LBs in the PD substantia nigra, thereby localizing protein domains throughout human alpha-synuclein in LBs. Taken together, our data indicate that this panel of antibodies can be exploited to probe the normal biology of alpha-synuclein as well as the role of pathological forms of this protein in PD and related neurodegenerative synucleinopathies.

Prominent perikaryal expression of alpha- and beta-synuclein in neurons of dorsal root ganglion and in medullary neurons.

Synucleins (syns) are a family of small, highly conserved proteins expressed predominantly in neurons. Although the normal function of syns is unknown, alpha-syn plays a pivotal role in several neurodegenerative diseases. The expression patterns of syns have been described in several studies, but much of this information was obtained before the cloning of all four members of this family of proteins and previous studies were limited to the analysis of single species. Here, we used antibodies specific for alpha-, beta-, and gamma-syn to study the patterns of expression in human, mouse, and rat nervous systems. Significant species-specific differences were detected in the expression of all three syns throughout the neuraxis. For example, gamma-syn is highly expressed in human cortex, while it is present only at low levels in mouse and rat cortex. Moreover, in contrast to previous reports that alpha- and beta-syns are normally localized predominantly at presynaptic terminals, we demonstrate that these proteins also are abundant in the perikarya of some neurons, such as in dorsal root ganglion. Intense alpha-syn immunoreactivity also was detected in the perikarya of human neurons in raphe, hypoglossal, and arcuate nuclei. These data underscore the need for additional studies to better understand the fundamental biological mechanism(s) targeting specific proteins to axonal terminals, as disruption of this process may be involved in the formation of pathological lesions.

Widespread nitration of pathological inclusions in neurodegenerative synucleinopathies.

Reactive nitrogen species may play a mechanistic role in neurodegenerative diseases by posttranslationally altering normal brain proteins. In support of this hypothesis, we demonstrate that an anti-3-nitrotyrosine polyclonal antibody stains all of the major hallmark lesions of synucleinopathies including Lewy bodies, Lewy neurites and neuraxonal spheroids in dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and neurodegeneration with brain iron accumulation type 1, as well as glial and neuronal cytoplasmic inclusions in multiple system atrophy. This antibody predominantly recognized nitrated alpha-synuclein when compared to other in vitro nitrated constituents of these pathological lesions, such as neurofilament subunits and microtubules. Collectively, these findings imply that alpha-synuclein is nitrated in pathological lesions. The widespread presence of nitrated alpha-synuclein in diverse intracellular inclusions suggests that oxidation/nitration is involved in the onset and/or progression of neurodegenerative diseases.