Multiple system atrophy: a sporadic synucleinopathy

Distinct ultrastructural phenotypes of glial and neuronal alpha-synuclein inclusions in multiple system atrophy

Multiple system atrophy is characterized pathologically by the accumulation of alpha-synuclein (aSyn) into glial cytoplasmic inclusions (GCIs). The mechanism underlying the formation of GCIs is not well understood. In this study, correlative light and electron microscopy was employed to investigate aSyn pathology in the substantia nigra and putamen of post-mortem multiple system atrophy brain donors. Three distinct types of aSyn immuno-positive inclusions were identified in oligodendrocytes, neurons and dark cells presumed to be dark microglia. Oligodendrocytes contained fibrillar GCIs that were consistently enriched with lysosomes and peroxisomes, supporting the involvement of the autophagy pathway in aSyn aggregation in multiple system atrophy. Neuronal cytoplasmic inclusions exhibited ultrastructural heterogeneity resembling both fibrillar and membranous inclusions, linking multiple systems atrophy and Parkinson's disease. The novel aSyn pathology identified in the dark cells, displayed GCI-like fibrils or non-GCI-like ultrastructures suggesting various stages of aSyn accumulation in these cells. The observation of GCI-like fibrils within dark cells suggests these cells may be an important contributor to the origin or spread of pathological aSyn in multiple system atrophy. Our results suggest a complex interplay between multiple cell types that may underlie the formation of aSyn pathology in multiple system atrophy brain and highlight the need for further investigation into cell-specific disease pathologies in multiple system atrophy.

Role of the Gut Microbiome and Bacterial Amyloids in the Development of Synucleinopathies

Less than ten years ago, evidence began to accumulate about association between the changes in the composition of gut microbiota and development of human synucleinopathies, in particular sporadic form of Parkinson's disease. We collected data from more than one hundred and thirty experimental studies that reported similar results and summarized the frequencies of detection of different groups of bacteria in these studies. It is important to note that it is extremely rare that a unidirectional change in the population of one or another group of microorganisms (only an elevation or only a reduction) was detected in the patients with Parkinson's disease. However, we were able to identify several groups of bacteria that were overrepresented in the patients with Parkinson's disease in the analyzed studies. There are various hypotheses about the molecular mechanisms that explain such relationships. Usually, α-synuclein aggregation is associated with the development of inflammatory processes that occur in response to the changes in the microbiome. However, experimental evidence is accumulating on the influence of bacterial proteins, including amyloids (curli), as well as various metabolites, on the α-synuclein aggregation. In the review, we provided up-to-date information about such examples.

Frequency of Comorbid Pathologies and Their Clinical Impact in Multiple System Atrophy

BACKGROUND

Mixed pathology is common at autopsy for a number of age-associated neurodegenerative disorders; however, the frequency of comorbid pathologies in multiple system atrophy (MSA) and their clinical correlations are poorly understood.

OBJECTIVE

We determined the frequency of comorbid pathologic processes in autopsy-confirmed MSA and assessed their clinical correlates.

METHODS

This study included 160 neuropathologically established MSA from the Mayo Clinic brain bank. Clinical information, including age at onset or death, clinical subtype, initial symptoms, antemortem clinical diagnosis, and cognitive dysfunction was collected. We assessed comorbid pathologies including Alzheimer's disease neuropathologic change, Lewy-related pathology, argyrophilic grain disease, age-related τ astrogliopathy, transactive DNA-binding protein 43 pathology, cerebral amyloid angiopathy, and cerebrovascular small vessel disease and examined their clinical impact.

RESULTS

The majority of MSA patients (62%) had no significant comorbid pathologies. There was a positive correlation between age at onset or death with the number of comorbid pathologies; however, even in the highest quartile group (average age at death 78 ± 6 years), the average number of comorbid pathologies was <2. Logistic regression analysis revealed that none of the assessed variables, including sex, age at onset, and the presence or absence of each comorbid pathology, were significantly associated with cognitive dysfunction.

CONCLUSIONS

The majority of MSA patients do not have comorbid pathologies, even in advanced age, indicating that MSA is unique among neurodegenerative disorders in this regard. There was minimal clinical impact of comorbid pathologies in MSA. These findings warrant focusing on α-synuclein for the treatment strategy for MSA. © 2023 International Parkinson and Movement Disorder Society.

Development and validation of an expanded antibody toolset that captures alpha-synuclein pathological diversity in Lewy body diseases

The abnormal aggregation and accumulation of alpha-synuclein (aSyn) in the brain is a defining hallmark of synucleinopathies. Various aSyn conformations and post-translationally modified forms accumulate in pathological inclusions and vary in abundance among these disorders. Relying on antibodies that have not been assessed for their ability to detect the diverse forms of aSyn may lead to inaccurate estimations of aSyn pathology in human brains or disease models. To address this challenge, we developed and characterized an expanded antibody panel that targets different sequences and post-translational modifications along the length of aSyn, and that recognizes all monomeric, oligomeric, and fibrillar aSyn conformations. Next, we profiled aSyn pathology across sporadic and familial Lewy body diseases (LBDs) and reveal heterogeneous forms of aSyn pathology, rich in Serine 129 phosphorylation, Tyrosine 39 nitration and N- and C-terminal tyrosine phosphorylations, scattered both to neurons and glia. In addition, we show that aSyn can become hyperphosphorylated during processes of aggregation and inclusion maturation in neuronal and animal models of aSyn seeding and spreading. The validation pipeline we describe for these antibodies paves the way for systematic investigations into aSyn pathological diversity in the human brain, peripheral tissues, as well as in cellular and animal models of synucleinopathies.

Evaluation of ferritin and TfR level in plasma neural-derived exosomes as potential markers of Parkinson's disease

Introduction

Early diagnosis of Parkinson's disease (PD) remains challenging. It has been suggested that abnormal brain iron metabolism leads to excessive iron accumulation in PD, although the mechanism of iron deposition is not yet fully understood. Ferritin and transferrin receptor (TfR) are involved in iron metabolism, and the exosome pathway is one mechanism by which ferritin is transported and regulated. While the blood of healthy animals contains a plentiful supply of TfR-positive exosomes, no studies have examined ferritin and TfR in plasma neural-derived exosomes.

Methods

Plasma exosomes were obtained from 43 patients with PD and 34 healthy controls. Neural-derived exosomes were isolated with anti-human L1CAM antibody immunoabsorption. Transmission electron microscopy and western blotting were used to identify the exosomes. ELISAs were used to quantify ferritin and TfR levels in plasma neural-derived exosomes of patients with PD and controls. Receivers operating characteristic (ROC) curves were applied to map the diagnostic accuracy of ferritin and TfR. Independent predictors of the disease were identified using logistic regression models.

Results

Neural-derived exosomes exhibited the typical exosomal morphology and expressed the specific exosome marker CD63. Ferritin and TfR levels in plasma neural-derived exosomes were significantly higher in patients with PD than controls (406.46 ± 241.86 vs. 245.62 ± 165.47 ng/μg, P = 0.001 and 1728.94 ± 766.71 vs. 1153.92 ± 539.30 ng/μg, P < 0.001, respectively). There were significant positive correlations between ferritin and TfR levels in plasma neural-derived exosomes in control group, PD group and all the individuals (rs = 0.744, 0.700, and 0.752, respectively). The level of TfR was independently associated with the disease (adjusted odds ratio 1.002; 95% CI 1.000-1.003). ROC performances of ferritin, TfR, and their combination were moderate (0.730, 0.812, and 0.808, respectively). However, no relationship was found between the biomarkers and disease progression.

Conclusion

It is hypothesized that ferritin and TfR in plasma neural-derived exosomes may be potential biomarkers for PD, and that they may participate in the mechanism of excessive iron deposition in PD.

Pathology vs pathogenesis: Rationale and pitfalls in the clinicopathology model of neurodegeneration

In neurodegenerative disorders, the term pathology is often implicitly referred to as pathogenesis. Pathology has been conceived as a window into the pathogenesis of neurodegenerative disorders. This clinicopathologic framework posits that what can be identified and quantified in postmortem brain tissue can explain both premortem clinical manifestations and the cause of death, a forensic approach to understanding neurodegeneration. As the century-old clinicopathology framework has yielded little correlation between pathology and clinical features or neuronal loss, the relationship between proteins and degeneration is ripe for revisitation. There are indeed two synchronous consequences of protein aggregation in neurodegeneration: the loss of the soluble/normal proteins on one; the accrual of the insoluble/abnormal fraction of these proteins on the other. The omission of the first part in the protein aggregation process is an artifact of the early autopsy studies: soluble, normal proteins have disappeared, with only the remaining insoluble fraction amenable to quantification. We here review the collective evidence from human data suggesting that protein aggregates, known collectively as pathology, are the consequence of many biological, toxic, and infectious exposures, but may not explain alone the cause or pathogenesis of neurodegenerative disorders.

Diagnostic accuracy of quantitative susceptibility mapping in multiple system atrophy: The impact of echo time and the potential of histogram analysis

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We performed histogram analysis on χ maps at different TEs on MSA patients and HC.

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We found altered χ distribution in Pu, SN, GP, CN for MSAp and in SN, DN for MSAc.

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QSM diagnostic accuracy is TE-dependent and is enhanced at short TEs.

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Short TEs capture rapidly-decaying contributions of high χ sources.

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Histogram features detect χ spatial heterogeneities improving diagnostic accuracy.

The non-invasive quantification of iron stores via Quantitative Susceptibility Mapping (QSM) could play an important role in the diagnosis and the differential diagnosis of atypical Parkinsonisms. However, the susceptibility (χ) values measured via QSM depend on echo time (TE). This effect relates to the microstructural organization within the voxel, whose composition can be altered by the disease. Moreover, pathological iron deposition in a brain area may not be spatially uniform, and conventional Region of Interest (ROI)-based analysis may fail in detecting alterations. Therefore, in this work we evaluated the impact of echo time on the diagnostic accuracy of QSM on a population of patients with Multiple System Atrophy (MSA) of either Parkinsonian (MSAp) or cerebellar (MSAc) phenotypes. In addition, we tested the potential of histogram analysis to improve QSM classification accuracy.

We enrolled 32 patients (19 MSAp and 13 MSAc) and 16 healthy controls, who underwent a 7T MRI session including a gradient-recalled multi-echo sequence for χ mapping. Nine histogram features were extracted from the χ maps computed for each TE in atlas-based ROIs covering deep brain nuclei, and compared among groups.

Alterations of susceptibility distribution were found in the Putamen, Substantia Nigra, Globus Pallidus and Caudate Nucleus for MSAp and in the Substantia Nigra and Dentate Nucleus for MSAc. Increased iron deposition was observed in a larger number of ROIs for the two shortest TEs and the standard deviation, the 75^th and the 90^th percentile were the most informative features yielding excellent diagnostic accuracy with area under the ROC curve > 0.9.

In conclusion, short TEs may enhance QSM diagnostic performances, as they can capture variations in rapidly-decaying contributions of high χ sources. The analysis of histogram features allowed to reveal fine heterogeneities in the spatial distribution of susceptibility alteration, otherwise undetected by a simple evaluation of ROI χ mean values.

Regional Selectivity of Neuromelanin Changes in the Substantia Nigra in Atypical Parkinsonism

BACKGROUND

Neurodegeneration in the substantia nigra pars compacta (SNc) in parkinsonian syndromes may affect the nigral territories differently.

OBJECTIVE

The objective of this study was to investigate the regional selectivity of neurodegenerative changes in the SNc in patients with Parkinson's disease (PD) and atypical parkinsonism using neuromelanin-sensitive magnetic resonance imaging (MRI).

METHODS

A total of 22 healthy controls (HC), 38 patients with PD, 22 patients with progressive supranuclear palsy (PSP), 20 patients with multiple system atrophy (MSA, 13 with the parkinsonian variant, 7 with the cerebellar variant), 7 patients with dementia with Lewy body (DLB), and 4 patients with corticobasal syndrome were analyzed. volume and signal-to-noise ratio (SNR) values of the SNc were derived from neuromelanin-sensitive MRI in the whole SNc. Analysis of signal changes was performed in the sensorimotor, associative, and limbic territories of the SNc.

RESULTS

SNc volume and corrected volume were significantly reduced in PD, PSP, and MSA versus HC. Patients with PSP had lower volume, corrected volume, SNR, and contrast-to-noise ratio than HC and patients with PD and MSA. Patients with PSP had greater SNR reduction in the associative region than HC and patients with PD and MSA. Patients with PD had reduced SNR in the sensorimotor territory, unlike patients with PSP. Patients with MSA did not differ from patients with PD.

CONCLUSIONS

This study provides the first MRI comparison of the topography of neuromelanin changes in parkinsonism. The spatial pattern of changes differed between PSP and synucleinopathies. These nigral topographical differences are consistent with the topography of the extranigral involvement in parkinsonian syndromes. © 2022 International Parkinson and Movement Disorder Society.

Neuropathology and molecular diagnosis of Synucleinopathies

Synucleinopathies are clinically and pathologically heterogeneous disorders characterized by pathologic aggregates of α-synuclein in neurons and glia, in the form of Lewy bodies, Lewy neurites, neuronal cytoplasmic inclusions, and glial cytoplasmic inclusions. Synucleinopathies can be divided into two major disease entities: Lewy body disease and multiple system atrophy (MSA). Common clinical presentations of Lewy body disease are Parkinson's disease (PD), PD with dementia, and dementia with Lewy bodies (DLB), while MSA has two major clinical subtypes, MSA with predominant cerebellar ataxia and MSA with predominant parkinsonism. There are currently no disease-modifying therapies for the synucleinopathies, but information obtained from molecular genetics and models that explore mechanisms of α-synuclein conversion to pathologic oligomers and insoluble fibrils offer hope for eventual therapies. It remains unclear how α-synuclein can be associated with distinct cellular pathologies (e.g., Lewy bodies and glial cytoplasmic inclusions) and what factors determine neuroanatomical and cell type vulnerability. Accumulating evidence from in vitro and in vivo experiments suggests that α-synuclein species derived from Lewy body disease and MSA are distinct "strains" having different seeding properties. Recent advancements in in vitro seeding assays, such as real-time quaking-induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA), not only demonstrate distinct seeding activity in the synucleinopathies, but also offer exciting opportunities for molecular diagnosis using readily accessible peripheral tissue samples. Cryogenic electron microscopy (cryo-EM) structural studies of α-synuclein derived from recombinant or brain-derived filaments provide new insight into mechanisms of seeding in synucleinopathies. In this review, we describe clinical, genetic and neuropathologic features of synucleinopathies, including a discussion of the evolution of classification and staging of Lewy body disease. We also provide a brief discussion on proposed mechanisms of Lewy body formation, as well as evidence supporting the existence of distinct α-synuclein strains in Lewy body disease and MSA.

The stimulator of interferon genes (STING) pathway is upregulated in striatal astrocytes of patients with multiple system atrophy

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by the accumulation of pathogenic phosphorylated α-synuclein in oligodendrocytes. In brains affected by MSA, severe astrogliosis is also observed, but its precise role in MSA pathogenesis remains largely unknown. Recently, the stimulator of interferon genes (STING) pathway and type I interferons, its downstream molecules, have been reported to be involved in the neurodegenerative process and to be activated in astrocytes. This study aimed to investigate the role of the STING pathway in the pathogenesis of MSA using postmortem brains. Samples used for immunohistochemical analysis included 6 cases of MSA parkinsonism type (MSA-P), 6 cases of MSA cerebellar type (MSA-C), and 7 age-matched controls. In MSA-P cases, astrocytes immunopositive for STING and TANK-binding kinase 1 (TBK1), its downstream molecule, were abundantly observed in the putamen and the substantia nigra. Moreover, these molecules colocalized with glial fibrillary acidic protein (GFAP) in reactive astrocytes, and the density of STING-positive astrocytes correlated with that of GFAP-positive reactive astrocytes in the brains of patients with MSA-P. These results suggest that the upregulated expression of STING pathway-related proteins in astrocytes and the subsequent inflammation may contribute to the pathogenesis in MSA-P and could provide novel therapeutic targets for the treatment of MSA.

Neuropathological correlation supports automated image-based differential diagnosis in parkinsonism

PURPOSE

Up to 25% of patients diagnosed as idiopathic Parkinson's disease (IPD) have an atypical parkinsonian syndrome (APS). We had previously validated an automated image-based algorithm to discriminate between IPD, multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). While the algorithm was accurate with respect to the final clinical diagnosis after long-term expert follow-up, its relationship to the initial referral diagnosis and to the neuropathological gold standard is not known.

METHODS

Patients with an uncertain diagnosis of parkinsonism were referred for ¹⁸F-fluorodeoxyglucose (FDG) PET to classify patients as IPD or as APS based on the automated algorithm. Patients were followed by a movement disorder specialist and subsequently underwent neuropathological examination. The image-based classification was compared to the neuropathological diagnosis in 15 patients with parkinsonism.

RESULTS

At the time of referral to PET, the clinical impression was only 66.7% accurate. The algorithm correctly identified 80% of the cases as IPD or APS (p = 0.02) and 87.5% of the APS cases as MSA or PSP (p = 0.03). The final clinical diagnosis was 93.3% accurate (p < 0.001), but needed several years of expert follow-up.

CONCLUSION

The image-based classifications agreed well with autopsy and can help to improve diagnostic accuracy during the period of clinical uncertainty.

Molecular Imaging of Neurodegenerative Parkinsonism

Advances in molecular PET imaging of neurodegenerative parkinsonism are reviewed with focus on neuropharmacologic radiotracers depicting terminals of selectively vulnerable neurons in these conditions. Degeneration and losses of dopamine, norepinephrine, serotonin, and acetylcholine imaging markers thus far do not differentiate among the parkinsonian conditions. Recent studies performed with [¹⁸F]fluorodeoxyglucose PET are limited by the need for automated image analysis tools and by lack of routine coverage for this imaging indication in the United States. Ongoing research engages use of novel molecular modeling and in silico methods for design of imaging ligands targeting these specific proteinopathies.

Prevention of multiple system atrophy using human bone marrow-derived mesenchymal stem cells by reducing polyamine and cholesterol-induced neural damages

Background

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder of unknown etiology, but is closely associated with damage to dopaminergic neurons. MSA progression is rapid. Hence, long-term drug treatments do not have any therapeutic benefits. We assessed the inhibitory effect of mesenchymal stem cells (MSCs) on double-toxin-induced dopaminergic neurodegenerative MSA.

Results

Behavioral disorder was significantly improved and neurodegeneration was prevented following MSC transplantation. Proteomics revealed lower expression of polyamine modulating factor-binding protein 1 (PMFBP1) and higher expression of 3-hydroxymethyl-3-methylglutaryl-CoA lyase (HMGCL), but these changes were reversed after MSC transplantation. In the in vitro study, the 6-OHDA-induced effects were reversed following co-culture with MSC. However, PMFBP1 knockdown inhibited the recovery effect due to the MSCs. Furthermore, HMGCL expression was decreased following co-culture with MSCs, but treatment with recombinant HMGCL protein inhibited the recovery effects due to MSCs.

Conclusions

These data indicate that MSCs protected against neuronal loss in MSA by reducing polyamine- and cholesterol-induced neural damage.

FTY720-Mitoxy reduces synucleinopathy and neuroinflammation, restores behavior and mitochondria function, and increases GDNF expression in Multiple System Atrophy mouse models

Multiple system atrophy (MSA) is a fatal disorder with no effective treatment. MSA pathology is characterized by α-synuclein (aSyn) accumulation in oligodendrocytes, the myelinating glial cells of the central nervous system (CNS). aSyn accumulation in oligodendrocytes forms the pathognomonic glial cytoplasmic inclusions (GCIs) of MSA. MSA aSyn pathology is also associated with motor and autonomic dysfunction, including an impaired ability to sweat. MSA patients have abnormal CNS expression of glial-cell-line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF). Our prior studies using the parent compound FTY720, a food and drug administration (FDA) approved immunosuppressive for multiple sclerosis, reveal that FTY720 protects parkinsonian mice by increasing BDNF. Our FTY720-derivative, FTY720-Mitoxy, is known to increase expression of oligodendrocyte BDNF, GDNF, and nerve growth factor (NGF) but does not reduce levels of circulating lymphocytes as it is not phosphorylated so cannot modulate sphingosine 1 phosphate receptors (S1PRs). To preclinically assess FTY720-Mitoxy for MSA, we used mice expressing human aSyn in oligodendrocytes under a 2,' 3'-cyclic nucleotide 3'-phosphodiesterase (CNP) promoter. CNP-aSyn transgenic (Tg) mice develop motor dysfunction between 7 and 9 mo, and progressive GCI pathology. Using liquid chromatography-mass spectrometry (LC-MS/MS) and enzymatic assays, we confirmed that FTY720-Mitoxy was stable and active. Vehicle or FTY720-Mitoxy (1.1 mg/kg/day) was delivered to wild type (WT) or Tg littermates from 8.5-11.5 mo by osmotic pump. We behaviorally assessed their movement by rotarod and sweat production by starch‑iodine test. Postmortem tissues were evaluated by qPCR for BDNF, GDNF, NGF and GDNF-receptor RET mRNA and for aSyn, BDNF, GDNF, and Iba1 protein by immunoblot. MicroRNAs (miRNAs) were also assessed by qPCR. FTY720-Mitoxy normalized movement, sweat function and soleus muscle mass in 11.5 mo Tg MSA mice. FTY720-Mitoxy also increased levels of brain GDNF and reduced brain miR-96-5p, a miRNA that acts to decrease GDNF expression. Moreover, FTY720-Mitoxy blocked aSyn pathology measured by sequential protein extraction and immunoblot, and microglial activation assessed by immunohistochemistry and immunoblot. In the 3-nitropropionic acid (3NP) toxin model of MSA, FTY720-Mitoxy protected movement and mitochondria in WT and CNP-aSyn Tg littermates. Our data confirm potent in vivo protection by FTY720-Mitoxy, supporting its further evaluation as a potential therapy for MSA and related synucleinopathies.

Quantifying iron deposition in the cerebellar subtype of multiple system atrophy and spinocerebellar ataxia type 6 by quantitative susceptibility mapping

We used quantitative susceptibility mapping (QSM) to assess the brain iron deposition in 28 patients with the cerebellar subtype of multiple system atrophy (MSA-C), nine patients with spinocerebellar ataxia type 6 (SCA6), and 23 healthy controls. Two reviewers independently measured the mean QSM values in brain structures including the putamen, globus pallidus, caudate nucleus, red nucleus, substantia nigra, and cerebellar dentate nucleus. A receiver operating characteristics (ROC) analysis was performed to assess the diagnostic usefulness of the QSM measurements. The QSM values in the substantia nigra were significantly higher in the MSA-C group compared to the HC group (p = .007). The QSM values in the cerebellar dentate nucleus were significantly higher in MSA-C than those in the SCA6 and HC groups (p < .001), and significantly lower in the SCA6 patients compared to the HCs (p = .027). The QSM values in the cerebellar dentate nucleus were correlated with disease duration in MSA-C, but inversely correlated with disease duration in SCA6. In the ROC analysis, the QSM values in the cerebellar dentate nucleus showed excellent accuracy for differentiating MSA-C from SCA6 (area under curve [AUC], 0.925), and good accuracy for differentiating MSA-C from healthy controls (AUC 0.834). QSM can identify increased susceptibility of the substantia nigra and cerebellar dentate nucleus in MSA-C patients. These results suggest that an increase in iron accumulation in the cerebellar dentate nucleus may be secondary to the neurodegeneration associated with MSA-C.

FTY720-Mitoxy reduces toxicity associated with MSA-like α-synuclein and oxidative stress by increasing trophic factor expression and myelin protein in OLN-93 oligodendroglia cell cultures

Multiple system atrophy (MSA) is a fatal demyelinating disorder lacking any disease-modifying therapies. MSA pathology stems from aggregated α-synuclein (aSyn) accumulation in glial cytosolic inclusions of oligodendroglial cell (OLGs), the myelinating cells of brain. In MSA brains and in MSA animal models with aSyn accumulation in OLGs, aberrant expression of brain-derived neurotrophic factor (BDNF) and glial-cell-line-derived neurotrophic factor (GDNF) occur. Nerve growth factor (NGF) expression can also be altered in neurodegenerative diseases. It is unclear if oxidative stress impacts the viability of aSyn-accumulating OLG cells. Here, we show that OLN-93 cells stably expressing human wild type aSyn or the MSA-associated-aSyn-mutants G51D or A53E, are more vulnerable to oxidative stress. In dose response studies we found that OLN-93 cells treated 48 h with 160 nM FTY720 or our new non-immunosuppressive FTY720-C2 or FTY720-Mitoxy derivatives sustained normal viability. Also, FTY720, FTY720-C2, and FTY720-Mitoxy all stimulated NGF expression at 24 h. However only FTY720-Mitoxy also increased BDNF and GDNF mRNA at 24 h, an effect paralleled by increases in histone 3 acetylation and ERK1/2 phosphorylation. Myelin associated glycoprotein (MAG) levels were also increased in OLN-93 cells after 48 h treatment with FTY720-Mitoxy. FTY720, FTY720-C2, and FTY720-Mitoxy all prevented oxidative-stress-associated-cell-death of OLN-93 cells that lack any aSyn expression. However, only FTY720-Mitoxy protected MSA-like aSyn-expressing-OLN-93-cells against oxidative-cell-death. These data identify potent protective effects for FTY720-Mitoxy with regard to trophic factors as well as MAG expression by OLG cells. Testing of FTY720-Mitoxy in mice is thus a judicious next step for neuropharmacological preclinical development.

FDG-PET patterns associated with underlying pathology in corticobasal syndrome

OBJECTIVE

To evaluate brain ¹⁸Fluorodeoxyglucose PET (FDG-PET) differences among patients with a clinical diagnosis of corticobasal syndrome (CBS) and distinct underling primary pathologies.

METHODS

We studied 29 patients with a diagnosis of CBS who underwent FDG-PET scan and postmortem neuropathologic examination. Patients were divided into subgroups on the basis of primary pathologic diagnosis: CBS-corticobasal degeneration (CBS-CBD) (14 patients), CBS-Alzheimer disease (CBS-AD) (10 patients), and CBS-progressive supranuclear palsy (CBS-PSP) (5 patients). Thirteen age-matched healthy patients who underwent FDG-PET were the control group (HC). FDG-PET scans were compared between the subgroups and the HC using SPM-12, with a threshold of p _FWE < 0.05.

RESULTS

There were no differences in Mattis Dementia Rating Scale or finger tapping scores between CBS groups. Compared to HC, the patients with CBS presented significant hypometabolism in frontoparietal regions, including the perirolandic area, basal ganglia, and thalamus of the clinically more affected hemisphere. Patients with CBS-CBD showed a similar pattern with a more marked, bilateral involvement of the basal ganglia. Patients with CBS-AD presented with posterior, asymmetric hypometabolism, including the lateral parietal and temporal lobes and the posterior cingulate. Finally, patients with CBS-PSP disclosed a more anterior hypometabolic pattern, including the medial frontal regions and the anterior cingulate. A conjunction analysis revealed that the primary motor cortex was the only common area of hypometabolism in all groups, irrespective of pathologic diagnosis.

DISCUSSION AND CONCLUSIONS

In patients with CBS, different underling pathologies are associated with different patterns of hypometabolism. Our data suggest that FDG-PET scans could help in the etiologic diagnosis of CBS.

ABI3 and PLCG2 missense variants as risk factors for neurodegenerative diseases in Caucasians and African Americans

BACKGROUND

Rare coding variants ABI3_rs616338-T and PLCG2_rs72824905-G were identified as risk or protective factors, respectively, for Alzheimer's disease (AD).

METHODS

We tested the association of these variants with five neurodegenerative diseases in Caucasian case-control cohorts: 2742 AD, 231 progressive supranuclear palsy (PSP), 838 Parkinson's disease (PD), 306 dementia with Lewy bodies (DLB) and 150 multiple system atrophy (MSA) vs. 3351 controls; and in an African-American AD case-control cohort (181 AD, 331 controls). 1479 AD and 1491 controls were non-overlapping with a prior report.

RESULTS

Using Fisher's exact test, there was significant association of both ABI3_rs616338-T (OR = 1.41, p = 0.044) and PLCG2_rs72824905-G (OR = 0.56, p = 0.008) with AD. These OR estimates were maintained in the non-overlapping replication AD-control analysis, albeit at reduced significance (ABI3_rs616338-T OR = 1.44, p = 0.12; PLCG2_rs72824905-G OR = 0.66, p = 0.19). None of the other cohorts showed significant associations that were concordant with those for AD, although the DLB cohort had suggestive findings (Fisher's test: ABI3_rs616338-T OR = 1.79, p = 0.097; PLCG2_rs72824905-G OR = 0.32, p = 0.124). PLCG2_rs72824905-G showed suggestive association with pathologically-confirmed MSA (OR = 2.39, p = 0.050) and PSP (OR = 1.97, p = 0.061), although in the opposite direction of that for AD. We assessed RNA sequencing data from 238 temporal cortex (TCX) and 224 cerebellum (CER) samples from AD, PSP and control patients and identified co-expression networks, enriched in microglial genes and immune response GO terms, and which harbor PLCG2 and/or ABI3. These networks had higher expression in AD, but not in PSP TCX, compared to controls. This expression association did not survive adjustment for brain cell type population changes.

CONCLUSIONS

We validated the associations previously reported with ABI3_rs616338-T and PLCG2_rs72824905-G in a Caucasian AD case-control cohort, and observed a similar direction of effect in DLB. Conversely, PLCG2_rs72824905-G showed suggestive associations with PSP and MSA in the opposite direction. We identified microglial gene-enriched co-expression networks with significantly higher levels in AD TCX, but not in PSP, a primary tauopathy. This co-expression network association appears to be driven by microglial cell population changes in a brain region affected by AD pathology. Although these findings require replication in larger cohorts, they suggest distinct effects of the microglial genes, ABI3 and PLCG2 in neurodegenerative diseases that harbor significant vs. low/no amyloid ß pathology.

3,4-Dihydroxyphenylacetaldehyde-Induced Protein Modifications and Their Mitigation by N-Acetylcysteine

The catecholaldehyde hypothesis posits that 3,4-dihydroxyphenylacetaldehyde (DOPAL), an obligate intermediary metabolite of dopamine, is an autotoxin that challenges neuronal homeostasis in catecholaminergic neurons. DOPAL toxicity may involve protein modifications, such as oligomerization of α-synuclein (AS). Potential interactions between DOPAL and other proteins related to catecholaminergic neurodegeneration, however, have not been systemically explored. This study examined DOPAL-induced protein-quinone adduct formation ("quinonization") and protein oligomerization, ubiquitination, and aggregation in cultured MO3.13 human oligodendrocytes and PC12 rat pheochromocytoma cells and in test tube experiments. Using near-infrared fluorescence spectroscopy, we detected spontaneous DOPAL oxidation to DOPAL-quinone, DOPAL-induced quinonization of intracellular proteins in both cell lines, and DOPAL-induced quinonization of several proteins related to catecholaminergic neurodegeneration, including AS, the type 2 vesicular monoamine transporter, glucocerebrosidase, ubiquitin, and l-aromatic-amino-acid decarboxylase (LAAAD). DOPAL also oligomerized AS, ubiquitin, and LAAAD; inactivated LAAAD (IC50 54 μM); evoked substantial intracellular protein ubiquitination; and aggregated intracellular AS. Remarkably, N-acetylcysteine, which decreases DOPAL-quinone formation, attenuated or prevented all of these protein modifications and functional changes. The results fit with the proposal that treatments based on decreasing the formation and oxidation of DOPAL may slow or prevent catecholaminergic neurodegeneration.

Tau Positron Emission Tomography Imaging in Degenerative Parkinsonisms

In recent years, several radiotracers that selectively bind to pathological tau proteins have been developed. Evidence is emerging that binding patterns of in vivo tau positron emission tomography (PET) studies in Alzheimer’s disease (AD) patients closely resemble the distribution patterns of known neurofibrillary tangle pathology, with the extent of tracer binding reflecting the clinical and pathological progression of AD. In Lewy body diseases (LBD), tau PET imaging has clearly revealed cortical tau burden with a distribution pattern distinct from AD and increased cortical binding within the LBD spectrum. In progressive supranuclear palsy, the globus pallidus and midbrain have shown increased binding most prominently. Tau PET patterns in patients with corticobasal syndrome are characterized by asymmetrical uptake in the motor cortex and underlying white matter, as well as in the basal ganglia. Even in the patients with multiple system atrophy, which is basically a synucleinopathy, ¹⁸F-flortaucipir, a widely used tau PET tracer, also binds to the atrophic posterior putamen, possibly due to off-target binding. These distinct patterns of tau-selective radiotracer binding in the various degenerative parkinsonisms suggest its utility as a potential imaging biomarker for the differential diagnosis of parkinsonisms.

The Relevance of Iron in the Pathogenesis of Multiple System Atrophy: A Viewpoint

Iron is essential for cellular development and maintenance of multiple physiological processes in the central nervous system. The disturbance of its homeostasis leads to abnormal iron deposition in the brain and causes neurotoxicity via generation of free radicals and oxidative stress. Iron toxicity has been established in the pathogenesis of Parkinson's disease; however, its contribution to multiple system atrophy (MSA) remains elusive. MSA is characterized by cytoplasmic inclusions of misfolded α-synuclein (α-SYN) in oligodendrocytes referred to as glial cytoplasmic inclusions (GCIs). Remarkably, the oligodendrocytes possess high amounts of iron, which together with GCI pathology make a contribution toward MSA pathogenesis likely. Consistent with this observation, the GCI density is associated with neurodegeneration in central autonomic networks as well as olivopontocerebellar and striatonigral pathways. Iron converts native α-SYN into a β-sheet conformation and promotes its aggregation either directly or via increasing levels of oxidative stress. Interestingly, α-SYN possesses ferrireductase activity and α-SYN expression underlies iron mediated translational control via RNA stem loop structures. Despite a correlation between progressive putaminal atrophy and iron accumulation as well as clinical decline, it remains unclear whether pathologic iron accumulation in MSA is a secondary event in the cascade of neuronal degeneration rather than a primary cause. This review summarizes the current knowledge of iron in MSA and gives evidence for perturbed iron homeostasis as a potential pathogenic factor in MSA-associated neurodegeneration.

The neuropathology of multiple system atrophy and its therapeutic implications

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder characterized by the abnormal accumulation of toxic forms of the synaptic protein alpha-synuclein (α-syn) within oligodendrocytes and neurons. The presence of α-syn within oligodendrocytes in the form of glial cytoplasmic inclusions is the diagnostic hallmark of MSA. However, it has been postulated that α-syn is produced in neurons and propagates to oligodendrocytes, where unknown mechanisms lead to its accumulation. The presence of α-syn within neurons in MSA has not been so extensively studied, but it may shed light into neuropathological mechanisms leading to oligodendroglial accumulation. Here we summarize the principal neuropathological events of MSA, and discuss how a deeper knowledge of these mechanisms may help develop effective therapies targeting α-syn accumulation and spreading.

MicroRNA-101 Modulates Autophagy and Oligodendroglial Alpha-Synuclein Accumulation in Multiple System Atrophy

Synucleinopathies, neurodegenerative disorders with alpha-synuclein (α-syn) accumulation, are the second leading cause of neurodegeneration in the elderly, however no effective disease-modifying alternatives exist for these diseases. Multiple system atrophy (MSA) is a fatal synucleinopathy characterized by the accumulation of toxic aggregates of α-syn within oligodendroglial cells, leading to demyelination and neurodegeneration, and the reduction of this accumulation might halt the fast progression of MSA. In this sense, the involvement of microRNAs (miRNAs) in synucleinopathies is yet poorly understood, and the potential of manipulating miRNA levels as a therapeutic tool is underexplored. In this study, we analyzed the levels of miRNAs that regulate the expression of autophagy genes in MSA cases, and investigated the mechanistic correlates of miRNA dysregulation in in vitro models of synucleinopathy. We found that microRNA-101 (miR-101) was significantly increased in the striatum of MSA patients, together with a reduction in the expression of its predicted target gene RAB5A. Overexpression of miR-101 in oligodendroglial cell cultures resulted in a significant increase in α-syn accumulation, along with autophagy deficits. Opposite results were observed upon expression of an antisense construct targeting miR-101. Stereotaxic delivery of a lentiviral construct expressing anti-miR-101 into the striatum of the MBP-α-syn transgenic (tg) mouse model of MSA resulted in reduced oligodendroglial α-syn accumulation and improved autophagy. These results suggest that miRNA dysregulation contributes to MSA pathology, with miR-101 alterations potentially mediating autophagy impairments. Therefore, therapies targeting miR-101 may represent promising approaches for MSA and related neuropathologies with autophagy dysfunction.

Anti-α-synuclein immunotherapy reduces α-synuclein propagation in the axon and degeneration in a combined viral vector and transgenic model of synucleinopathy

Neurodegenerative disorders such as Parkinson's Disease (PD), PD dementia (PDD) and Dementia with Lewy bodies (DLB) are characterized by progressive accumulation of α-synuclein (α-syn) in neurons. Recent studies have proposed that neuron-to-neuron propagation of α-syn plays a role in the pathogenesis of these disorders. We have previously shown that antibodies against the C-terminus of α-syn reduce the intra-neuronal accumulation of α-syn and related deficits in transgenic models of synucleinopathy, probably by abrogating the axonal transport and accumulation of α-syn in in vivo models. Here, we assessed the effect of passive immunization against α-syn in a new mouse model of axonal transport and accumulation of α-syn. For these purpose, non-transgenic, α-syn knock-out and mThy1-α-syn tg (line 61) mice received unilateral intra-cerebral injections with a lentiviral (LV)-α-syn vector construct followed by systemic administration of the monoclonal antibody 1H7 (recognizes amino acids 91-99) or control IgG for 3 months. Cerebral α-syn accumulation and axonopathy was assessed by immunohistochemistry and effects on behavior were assessed by Morris water maze. Unilateral LV-α-syn injection resulted in axonal propagation of α-syn in the contra-lateral site with subsequent behavioral deficits and axonal degeneration. Passive immunization with 1H7 antibody reduced the axonal accumulation of α-syn in the contra-lateral side and ameliorated the behavioral deficits. Together this study supports the notion that immunotherapy might improve the deficits in models of synucleinopathy by reducing the axonal propagation and accumulation of α-syn. This represents a potential new mode of action through which α-syn immunization might work.

Combination of alpha-synuclein immunotherapy with anti-inflammatory treatment in a transgenic mouse model of multiple system atrophy

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder characterized by the pathological accumulation of alpha-synuclein (α-syn) in oligodendrocytes. Therapeutic efforts to stop or delay the progression of MSA have yielded suboptimal results in clinical trials, and there are no efficient treatments currently available for MSA patients. We hypothesize that combining therapies targeting different aspects of the disease may lead to better clinical outcomes. To test this hypothesis, we combined the use of a single-chain antibody targeting α-syn modified for improved central nervous system penetration (CD5-D5) with an unconventional anti-inflammatory treatment (lenalidomide) in the myelin basic protein (MBP)-α-syn transgenic mouse model of MSA. While the use of either CD5-D5 or lenalidomide alone had positive effects on neuroinflammation and/or α-syn accumulation in this mouse model of MSA, the combination of both approaches yielded better results than each single treatment. The combined treatment reduced astrogliosis, microgliosis, soluble and aggregated α-syn levels, and partially improved behavioral deficits in MBP-α-syn transgenic mice. These effects were associated with an activation of the Akt signaling pathway, which may mediate cytoprotective effects downstream tumor necrosis factor alpha (TNFα). These results suggest that a strategic combination of treatments may improve the therapeutic outcome in trials for MSA and related neurodegenerative disorders.

Review: Novel treatment strategies targeting alpha-synuclein in multiple system atrophy as a model of synucleinopathy

Neurodegenerative disorders with alpha-synuclein (α-syn) accumulation (synucleinopathies) include Parkinson's disease (PD), PD dementia, dementia with Lewy bodies and multiple system atrophy (MSA). Due to the involvement of toxic α-syn aggregates in the molecular origin of these disorders, developing effective therapies targeting α-syn is a priority as a disease-modifying alternative to current symptomatic treatments. Importantly, the clinical and pathological attributes of MSA make this disorder an excellent candidate as a synucleinopathy model for accelerated drug development. Recent therapeutic strategies targeting α-syn in in vivo and in vitro models of MSA, as well as in clinical trials, have been focused on the pathological mechanisms of α-syn synthesis, aggregation, clearance, and/or cell-to-cell propagation of its neurotoxic conformers. Here we summarize the most relevant approaches in this direction, with emphasis on their potential as general synucleinopathy modifiers, and enumerate research areas for potential improvement in MSA drug discovery.

Profile of cognitive impairment and underlying pathology in multiple system atrophy

BACKGROUND

The objectives of this study were to elucidate any potential association between α-synuclein pathology and cognitive impairment and to determine the profile of cognitive impairment in multiple system atrophy (MSA) patients. To do this, we analyzed the clinical and pathologic features in autopsy-confirmed MSA patients.

METHODS

We retrospectively reviewed medical records, including neuropsychological test data, in 102 patients with autopsy-confirmed MSA in the Mayo Clinic brain bank. The burden of glial cytoplasmic inclusions and neuronal cytoplasmic inclusions were semiquantitatively scored in the limbic regions and middle frontal gyrus. We also assessed concurrent pathologies potentially causing dementia including Alzheimer's disease, hippocampal sclerosis, and cerebrovascular pathology.

RESULTS

Of 102 patients, 33 (32%) were documented to have cognitive impairment. Those that received objective testing, deficits primarily in processing speed and attention/executive functions were identified, which suggests a frontal-subcortical pattern of dysfunction. Of these 33 patients with cognitive impairment, 8 patients had concurrent pathologies of dementia. MSA patients with cognitive impairment had a greater burden of neuronal cytoplasmic inclusions in the dentate gyrus than patients without cognitive impairment, both including and excluding patients with concurrent pathologies of dementia.

CONCLUSIONS

The cognitive deficits observed in this study were more evident on neuropsychological assessment than with cognitive screens. Based on these findings, we recommend that clinicians consider more in-depth neuropsychological assessments if patients with MSA present with cognitive complaints. Although we did not identify the correlation between cognitive deficits and responsible neuroanatomical regions, a greater burden of neuronal cytoplasmic inclusions in the limbic regions was associated with cognitive impairment in MSA. © 2016 International Parkinson and Movement Disorder Society.

A Rapid, Semi-Quantitative Assay to Screen for Modulators of Alpha-Synuclein Oligomerization Ex vivo

Alpha synuclein (αsyn) aggregates are associated with the pathogenesis of Parkinson's disease and others related disorders. Although modulation of αsyn aggregation is an attractive therapeutic target, new powerful methodologies are desperately needed to facilitate in vivo screening of novel therapeutics. Here, we describe an in vivo rodent model with the unique ability to rapidly track αsyn-αsyn interactions and thus oligomerization using a bioluminescent protein complementation strategy that monitors spatial and temporal αsyn oligomerization ex vivo. We find that αsyn forms oligomers in vivo as early as 1 week after stereotactic AAV injection into rat substantia nigra. Strikingly, although abundant αsyn expression is also detected in striatum at 1 week, no αsyn oligomers are detected at this time point. By 4 weeks, oligomerization of αsyn is detected in both striatum and substantia nigra homogenates. Moreover, in a proof-of-principle experiment, the effect of a previously described Hsp90 inhibitor known to prevent αsyn oligomer formation, demonstrates the utility of this rapid and sensitive animal model to monitor αsyn oligomerization status in the rat brain.

DOPAL is transmissible to and oligomerizes alpha-synuclein in human glial cells

INTRODUCTION

Glial cytoplasmic inclusions (GCIs) containing alpha-synuclein (AS) are a neuropathologic hallmark of multiple system atrophy (MSA). Oligomerized AS is thought to be the pathogenic form of the protein. Glial cells normally express little AS, but they can take up AS from the extracellular fluid. 3,4-Dihydroxyphenylacetaldehyde (DOPAL), an obligate intermediate in the intra-neuronal metabolism of dopamine (DA), potently oligomerizes AS. In this study we tested whether DOPAL is taken up by human glial cells and augments intracellular oligomerization of AS.

METHODS

DOPAL (exogenous or endogenous from co-incubation with PC12 cells) and AS (native or A53T mutant form) were added to the incubation medium of glial cells (glioblastoma or MO3.13 oligodendrocytes). Glial cellular contents of DOPAL and its intracellular metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were measured at up to 180 min of incubation. Glial cellular AS oligomers were quantified by Western blotting.

RESULTS

Neither glioblastoma nor MO3.13 cells contained endogenous catecholamines or AS. Co-incubation of the cells with DA-producing PC12 cells produced time-related increases in DOPAL and DOPAC contents. Similarly, glial cellular DOPAL and DOPAC contents increased rapidly after addition of DOPAL to the medium. After addition of native or A53T-AS, intracellular AS also increased. Incubation of glial cells with both DOPAL and AS enhanced the intracellular oligomerization of native and A53T-AS.

CONCLUSIONS

DOPAL is transmissible to glial cells and enhances intracellular oligomerization of AS. An interaction of DOPAL with AS might help explain the formation of CGIs in MSA.

Neuropathology and Cellular Pathogenesis of Spinocerebellar Ataxia Type 12

OBJECTIVE

SCA12 is a progressive autosomal-dominant disorder, caused by a CAG/CTG repeat expansion in PPP2R2B on chromosome 5q32, and characterized by tremor, gait ataxia, hyperreflexia, dysmetria, abnormal eye movements, anxiety, depression, and sometimes cognitive impairment. Neuroimaging has demonstrated cerebellar and cortical atrophy. We now present the neuropathology of the first autopsied SCA12 brain and utilize cell models to characterize potential mechanisms of SCA12 neurodegeneration.

METHODS

A fixed SCA12 brain was examined using gross, microscopic, and immunohistochemical methods. The effect of the repeat expansion on PPP2R2B Bβ1 expression was examined in multiple cell types by transient transfection of constructs containing the PPP2R2B Bβ1 promoter region attached to a luciferase reporter. The neurotoxic effect of PPP2R2B overexpression was examined in transfected rat primary neurons.

RESULTS

Neuropathological investigation revealed enlarged ventricles, marked cerebral cortical atrophy and Purkinje cell loss, less-prominent cerebellar and pontine atrophy, and neuronal intranuclear ubiquitin-positive inclusions, consistent with Marinesco bodies, which did not stain for long polyglutamine tracts, alpha-synuclein, tau, or transactive response DNA-binding protein 43. Reporter assays demonstrated that the region of PPP2R2B containing the repeat functions as a promoter, and that promoter activity increases with longer repeat length and is dependent on cell type, repeat sequence, and sequence flanking the repeat. Overexpression of PPP2R2B in primary cortical neurons disrupted normal morphology.

CONCLUSIONS

SCA12 involves extensive, but selective, neurodegeneration distinct from Alzheimer's disease, synucleinopathies, tauopathies, and glutamine expansion diseases. SCA12 neuropathology may arise from the neurotoxic effect of repeat-expansion-induced overexpression of PPP2R2B.

Atypical parkinsonism: diagnosis and treatment

Atypical parkinsonism comprises typically progressive supranuclear palsy, corticobasal degeneration, and mutilple system atrophy, which are distinct pathologic entities; despite ongoing research, their cause and pathophysiology are still unknown, and there are no biomarkers or effective treatments available. The expanding phenotypic spectrum of these disorders as well as the expanding pathologic spectrum of their classic phenotypes makes the early differential diagnosis challenging for the clinician. Here, clinical features and investigations that may help to diagnose these conditions and the existing limited treatment options are discussed.

Expanding the spectrum of neuronal pathology in multiple system atrophy

Multiple system atrophy is a sporadic alpha-synucleinopathy that typically affects patients in their sixth decade of life and beyond. The defining clinical features of the disease include progressive autonomic failure, parkinsonism, and cerebellar ataxia leading to significant disability. Pathologically, multiple system atrophy is characterized by glial cytoplasmic inclusions containing filamentous alpha-synuclein. Neuronal inclusions also have been reported but remain less well defined. This study aimed to further define the spectrum of neuronal pathology in 35 patients with multiple system atrophy (20 male, 15 female; mean age at death 64.7 years; median disease duration 6.5 years, range 2.2 to 15.6 years). The morphologic type, topography, and frequencies of neuronal inclusions, including globular cytoplasmic (Lewy body-like) neuronal inclusions, were determined across a wide spectrum of brain regions. A correlation matrix of pathologic severity also was calculated between distinct anatomic regions of involvement (striatum, substantia nigra, olivary and pontine nuclei, hippocampus, forebrain and thalamus, anterior cingulate and neocortex, and white matter of cerebrum, cerebellum, and corpus callosum). The major finding was the identification of widespread neuronal inclusions in the majority of patients, not only in typical disease-associated regions (striatum, substantia nigra), but also within anterior cingulate cortex, amygdala, entorhinal cortex, basal forebrain and hypothalamus. Neuronal inclusion pathology appeared to follow a hierarchy of region-specific susceptibility, independent of the clinical phenotype, and the severity of pathology was duration-dependent. Neuronal inclusions also were identified in regions not previously implicated in the disease, such as within cerebellar roof nuclei. Lewy body-like inclusions in multiple system atrophy followed the stepwise anatomic progression of Lewy body-spectrum disease inclusion pathology in 25.7% of patients with multiple system atrophy, including a patient with visual hallucinations. Further, the presence of Lewy body-like inclusions in neocortex, but not hippocampal alpha-synuclein pathology, was associated with cognitive impairment (P = 0.002). However, several cases had the presence of isolated Lewy body-like inclusions at atypical sites (e.g. thalamus, deep cerebellar nuclei) that are not typical for Lewy body-spectrum disease. Finally, interregional correlations (rho ≥ 0.6) in pathologic glial and neuronal lesion burden suggest shared mechanisms of disease progression between both discrete anatomic regions (e.g. basal forebrain and hippocampus) and cell types (neuronal and glial inclusions in frontal cortex and white matter, respectively). These findings suggest that in addition to glial inclusions, neuronal pathology plays an important role in the developmental and progression of multiple system atrophy.

Active immunization against alpha-synuclein ameliorates the degenerative pathology and prevents demyelination in a model of multiple system atrophy

Background

Multiple system atrophy (MSA) is a neurodegenerative disease characterized by parkinsonism, ataxia and dysautonomia. Histopathologically, the hallmark of MSA is the abnormal accumulation of alpha-synuclein (α-syn) within oligodendroglial cells, leading to neuroinflammation, demyelination and neuronal death. Currently, there is no disease-modifying treatment for MSA. In this sense, we have previously shown that next-generation active vaccination technology with short peptides, AFFITOPEs®, was effective in two transgenic models of synucleinopathies at reducing behavioral deficits, α-syn accumulation and inflammation.

Results

In this manuscript, we used the most effective AFFITOPE® (AFF 1) for immunizing MBP-α-syn transgenic mice, a model of MSA that expresses α-syn in oligodendrocytes. Vaccination with AFF 1 resulted in the production of specific anti-α-syn antibodies that crossed into the central nervous system and recognized α-syn aggregates within glial cells. Active vaccination with AFF 1 resulted in decreased accumulation of α-syn, reduced demyelination in neocortex, striatum and corpus callosum, and reduced neurodegeneration. Clearance of α-syn involved activation of microglia and reduced spreading of α-syn to astroglial cells.

Conclusions

This study further validates the efficacy of vaccination with AFFITOPEs® for ameliorating the neurodegenerative pathology in synucleinopathies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-015-0008-9) contains supplementary material, which is available to authorized users.

Glia and alpha-synuclein in neurodegeneration: A complex interaction

α-Synucleinopathies (ASP) comprise adult-onset, progressive neurodegenerative disorders such as Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) that are characterized by α-synuclein (AS) aggregates in neurons or glia. PD and DLB feature neuronal AS-positive inclusions termed Lewy bodies (LB) whereas glial cytoplasmic inclusions (GCIs, Papp-Lantos bodies) are recognized as the defining hallmark of MSA. Furthermore, AS-positive cytoplasmic aggregates may also be seen in astroglial cells of PD/DLB and MSA brains. The glial AS-inclusions appear to trigger reduced trophic support resulting in neuronal loss. Moreover, microgliosis and astrogliosis can be found throughout the neurodegenerative brain and both are key players in the initiation and progression of ASP. In this review, we will highlight AS-dependent alterations of glial function and their impact on neuronal vulnerability thereby providing a detailed summary on the multifaceted role of glia in ASP.

Candidate biomarkers of multiple system atrophy in cerebrospinal fluid

Multiple system atrophy (MSA) is a neurodegenerative disease that presents as an autonomic dysfunction in combination with varying degrees of parkinsonism and cerebellar ataxia. It comprises a pathologically widespread neuronal loss accompanied by gliosis in the basal ganglia, cerebellum, pons, inferior olivary nuclei, and spinal cord. As a rapidly progressive disorder, MSA develops with autonomic dysfunction and mobility problems in several years. These autonomic and motor function impairments severely disrupt the patients' daily lives. Currently, the therapeutic management of this disease is only symptomatic. An early and accurate diagnosis is helpful not only in the clinical field but also in the research for new therapies. The biomarkers in cerebrospinal fluid (CSF) and serum facilitate the differential diagnosis of MSA when the disease is difficult to recognize based on the clinical features or even presymptomatic. This review will summarize the biomarkers present in CSF that are potential candidates to accurately differentiate MSA from other similar neurodegenerative disorders.

Immunotherapy targeting α-synuclein, with relevance for future treatment of Parkinson's disease and other Lewy body disorders

Immunotherapy targeting α-synuclein has evolved as a potential therapeutic strategy for neurodegenerative diseases, such as Parkinson's disease, and initial studies on cellular and animal models have shown promising results. α-synuclein vaccination of transgenic mice reduced the number of brain inclusions, whereas passive immunization studies demonstrated that antibodies against the C-terminus of α-synuclein can pass the blood-brain barrier and affect the pathology. In addition, preliminary evidence suggests that transgenic mice treated with an antibody directed against α-synuclein oligomers/protofibrils resulted in reduced levels of such species in the CNS. The underlying mechanisms of immunotherapy are not yet fully understood, but may include antibody-mediated clearance of pre-existing aggregates, prevention of protein propagation between cells and microglia-dependent protein clearance. Thus, immunotherapy targeting α-synuclein holds promise, but needs to be further developed as a future disease-modifying treatment in Parkinson's disease and other α-synucleinopathies.

Visual signs and symptoms of multiple system atrophy

Multiple system atrophy (MSA) is a rare movement disorder and a member of the 'parkinsonian syndromes', which also include Parkinson's disease (PD), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB) and corticobasal degeneration (CBD). Multiple system atrophy is a complex syndrome, in which patients exhibit a variety of signs and symptoms, including parkinsonism, ataxia and autonomic dysfunction. It can be difficult to separate MSA from the other parkinsonian syndromes but if ocular signs and symptoms are present, they may aid differential diagnosis. Typical ocular features of MSA include blepharospasm, excessive square-wave jerks, mild to moderate hypometria of saccades, impaired vestibular-ocular reflex (VOR), nystagmus and impaired event-related evoked potentials. Less typical features include slowing of saccadic eye movements, the presence of vertical gaze palsy, visual hallucinations and an impaired electroretinogram (ERG). Aspects of primary vision such as visual acuity, colour vision or visual fields are usually unaffected. Management of the disease to deal with problems of walking, movement, daily tasks and speech problems is important in MSA. Optometrists can work in collaboration with the patient and health-care providers to identify and manage the patient's visual deficits. A more specific role for the optometrist is to correct vision to prevent falls and to monitor the anterior eye to prevent dry eye and control blepharospasm.

Visuoperception test predicts pathologic diagnosis of Alzheimer disease in corticobasal syndrome

OBJECTIVE

To use the Visual Object and Space Perception Battery (VOSP) to distinguish Alzheimer disease (AD) from non-AD pathology in corticobasal syndrome (CBS).

METHODS

This clinicopathologic study assessed 36 patients with CBS on the VOSP. All were autopsied. The primary dependent variable was a binary pathologic outcome: patients with CBS who had primary pathologic diagnosis of AD (CBS-AD, n = 10) vs patients with CBS without primary pathologic diagnosis of AD (CBS-nonAD, n = 26). We also determined sensitivity and specificity of individual VOSP subtests.

RESULTS

Patients with CBS-AD had younger onset (54.5 vs 63.6 years, p = 0.001) and lower memory scores on the Mattis Dementia Rating Scale-2 (16 vs 22 points, p = 0.003). Failure on the VOSP subtests Incomplete Letters (odds ratio [OR] 11.5, p = 0.006), Position Discrimination (OR 10.86, p = 0.008), Number Location (OR 12.27, p = 0.026), and Cube Analysis (OR 45.71 p = 0.0001) had significantly greater odds of CBS-AD than CBS-nonAD. These associations remained when adjusting for total Mattis Dementia Rating score, disease laterality, education, age, and sex. Receiver operating characteristic curves demonstrated significant accuracy for Incomplete Letters and all VOSP spatial subtests, with Cube Analysis performing best (area under the curve 0.91, p = 0.0004).

CONCLUSIONS

In patients with CBS, failure on specific VOSP subtests is associated with greater odds of having underlying AD. There may be preferential involvement of the dorsal stream in CBS-AD.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that some subtests of the VOSP accurately distinguish patients with CBS-AD from those without AD pathology (e.g., Cube Analysis sensitivity 100%, specificity 77%).

Mechanisms of action of brain insulin against neurodegenerative diseases

Insulin, a pancreatic hormone, is best known for its peripheral effects on the metabolism of glucose, fats and proteins. There is a growing body of evidence linking insulin action in the brain to neurodegenerative diseases. Insulin present in central nervous system is a regulator of central glucose metabolism nevertheless this glucoregulation is not the main function of insulin in the brain. Brain is known to be specifically vulnerable to oxidative products relative to other organs and altered brain insulin signaling may cause or promote neurodegenerative diseases which invalidates and reduces the quality of life. Insulin located within the brain is mostly of pancreatic origin or is produced in the brain itself crosses the blood-brain barrier and enters the brain via a receptor-mediated active transport system. Brain Insulin, insulin receptor and insulin receptor substrate-mediated signaling pathways play important roles in the regulation of peripheral metabolism, feeding behavior, memory and maintenance of neural functions such as neuronal growth and differentiation, neuromodulation and neuroprotection. In the present review, we would like to summarize the novel biological and pathophysiological roles of neuronal insulin in neurodegenerative diseases and describe the main signaling pathways in use for therapeutic strategies in the use of insulin to the cerebral tissues and their biological applications to neurodegenerative diseases.

Prodegenerative IκBα expression in oligodendroglial α-synuclein models of multiple system atrophy

Multiple system atrophy is a progressive, neurodegenerative disease characterized by parkinsonism, ataxia, autonomic dysfunction, and accumulation of α-synuclein in oligodendrocytes. To understand how α-synuclein aggregates impact oligodendroglial homeostasis, we investigated an oligodendroglial cell model of α-synuclein dependent degeneration and identified responses linked to the NF-κB transcription factor stress system. Coexpression of human α-synuclein and the oligodendroglial protein p25α increased the expression of IκBα mRNA and protein early during the degenerative process and this was dependent on both aggregation and Ser129 phosphorylation of α-synuclein. This response was prodegenerative because blocking IκBα expression by siRNA rescued the cells. IκBα is an inhibitor of NF-κB and acts by binding and retaining NF-κB p65 in the cytoplasm. The protection obtained by silencing IκBα was accompanied by a strong increase in nuclear p65 translocation indicating that NF-κB activation protects against α-synuclein aggregate stress. In the cellular model, two different phenotypes were observed; degenerating cells retracting their microtubules and resilient cells tolerating the coexpression of α-synuclein and p25α. The resilient cells displayed a significant higher nuclear translocation of p65 and activation of the NF-κB system relied on stress elicited by aggregated and Ser129 phosphorylated α-synuclein. To validate the relationship between oligodendroglial α-synuclein expression and IκBα, we analyzed two different lines of transgenic mice expressing human α-synuclein under the control of the oligodendrocytic MBP promotor (intermediate-expresser line 1 and high-expresser line 29). IκBα mRNA expression was increased in both lines and immunofluorescence microscopy and in situ hybridization revealed that IκBα mRNA and protein is expressed in oligodendrocytes. IκBα mRNA expression was demonstrated prior to activation of microglia and astrocytes in line 1. Human brain tissue affected by MSA displayed increased expression of IκBα and NF-κB p65 in some oligodendrocytes containing glial cytoplasmic inclusions. Our data suggest that oligodendroglial IκBα expression and NF-κB are activated early in the course of MSA and their balance contributes to the decision of cellular demise. Favoring oligodendroglial NF-κB activation may represent a therapeutic strategy for this devastating disease.

Antidepressants reduce neuroinflammatory responses and astroglial alpha-synuclein accumulation in a transgenic mouse model of multiple system atrophy

Multiple system atrophy (MSA) is a neurodegenerative disease characterized by the pathological accumulation of alpha-synuclein (α-syn) within oligodendroglial cells. This accumulation is accompanied by neuroinflammation with astrogliosis and microgliosis, that leads to neuronal death and subsequent parkinsonism and dysautonomia. Antidepressants have been explored as neuroprotective agents as they normalize neurotrophic factor levels, increase neurogenesis and reduce neurodegeneration, but their anti-inflammatory properties have not been fully characterized. We analyzed the anti-inflammatory profiles of three different antidepressants (fluoxetine, olanzapine and amitriptyline) in the MBP1-hα-syn transgenic (tg) mouse model of MSA. We observed that antidepressant treatment decreased the number of α-syn-positive cells in the basal ganglia of 11-month-old tg animals. This reduction was accompanied with a similar decrease in the colocalization of α-syn with astrocyte markers in this brain structure. Consistent with these results, antidepressants reduced astrogliosis in the hippocampus and basal ganglia of the MBP1-hα-syn tg mice, and modulated the expression levels of key cytokines that were dysregulated in the tg mouse model, such as IL-1β. In vitro experiments in the astroglial cell line C6 confirmed that antidepressants inhibited NF-κB translocation to the nucleus and reduced IL-1β protein levels. We conclude that the anti-inflammatory properties of antidepressants in the MBP1-hα-syn tg mouse model of MSA might be related to their ability to inhibit α-syn propagation from oligodendrocytes to astroglia and to regulate transcription factors involved in cytokine expression. Our results suggest that antidepressants might be of interest as anti-inflammatory and α-syn-reducing agents for MSA and other α-synucleinopathies.

Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder

OBJECTIVE

To determine the pathologic substrates in patients with rapid eye movement (REM) sleep behavior disorder (RBD) with or without a coexisting neurologic disorder.

METHODS

The clinical and neuropathologic findings were analyzed on all autopsied cases from one of the collaborating sites in North America and Europe, were evaluated from January 1990 to March 2012, and were diagnosed with polysomnogram (PSG)-proven or probable RBD with or without a coexisting neurologic disorder. The clinical and neuropathologic diagnoses were based on published criteria.

RESULTS

172 cases were identified, of whom 143 (83%) were men. The mean±SD age of onset in years for the core features were as follows - RBD, 62±14 (range, 20-93), cognitive impairment (n=147); 69±10 (range, 22-90), parkinsonism (n=151); 68±9 (range, 20-92), and autonomic dysfunction (n=42); 62±12 (range, 23-81). Death age was 75±9 years (range, 24-96). Eighty-two (48%) had RBD confirmed by PSG, 64 (37%) had a classic history of recurrent dream enactment behavior, and 26 (15%) screened positive for RBD by questionnaire. RBD preceded the onset of cognitive impairment, parkinsonism, or autonomic dysfunction in 87 (51%) patients by 10±12 (range, 1-61) years. The primary clinical diagnoses among those with a coexisting neurologic disorder were dementia with Lewy bodies (n=97), Parkinson's disease with or without mild cognitive impairment or dementia (n=32), multiple system atrophy (MSA) (n=19), Alzheimer's disease (AD)(n=9) and other various disorders including secondary narcolepsy (n=2) and neurodegeneration with brain iron accumulation-type 1 (NBAI-1) (n=1). The neuropathologic diagnoses were Lewy body disease (LBD)(n=77, including 1 case with a duplication in the gene encoding α-synuclein), combined LBD and AD (n=59), MSA (n=19), AD (n=6), progressive supranulear palsy (PSP) (n=2), other mixed neurodegenerative pathologies (n=6), NBIA-1/LBD/tauopathy (n=1), and hypothalamic structural lesions (n=2). Among the neurodegenerative disorders associated with RBD (n=170), 160 (94%) were synucleinopathies. The RBD-synucleinopathy association was particularly high when RBD preceded the onset of other neurodegenerative syndrome features.

CONCLUSIONS

In this large series of PSG-confirmed and probable RBD cases that underwent autopsy, the strong association of RBD with the synucleinopathies was further substantiated and a wider spectrum of disorders which can underlie RBD now are more apparent.

Diffusivity of cerebellar hemispheres enables discrimination of cerebellar or parkinsonian multiple system atrophy from progressive supranuclear palsy-Richardson syndrome and Parkinson disease

PURPOSE

To explore the usefulness of histogram analysis of mean diffusivity (MD) derived from diffusion-weighted imaging of large infratentorial structures to distinguish parkinsonian syndromes.

MATERIALS AND METHODS

Local research ethics committee approval and informed consent were obtained. Ten patients with Parkinson disease (PD), nine with the parkinsonian variant of multiple system atrophy (MSA-P), seven with the cerebellar variant of MSA (MSA-C), 17 with progressive supranuclear palsy-Richardson syndrome (PSP-RS), and 10 healthy subjects were recruited. Histograms of MD values were generated for all pixels in the whole infratentorial compartment and separately for the whole brainstem, vermis, and cerebellar hemispheres. To assess the differences in MD values among groups, the Kruskal-Wallis test was used, followed by the Mann-Whitney U test for pairwise comparisons. All P values resulting from pairwise comparisons were corrected with the Bonferroni method.

RESULTS

MSA-P and MSA-C groups had higher median MD values (P < .01) in the brainstem and cerebellum when compared with other groups; this finding was in line with the known consistent neurodegenerative damage in posterior cranial fossa structures in these diseases. Median MD values from cerebellar hemispheres were used to discriminate patients with MSA-C and those with MSA-P from patients with PD and those with PSP-RS (P < .01; sensitivity, specificity, and positive predictive value equaled 100%). Furthermore, patients with PSP-RS had significantly higher MD values in the vermis than did healthy subjects (P < .05) and patients with PD (P < .001).

CONCLUSION

These findings support the clinical usefulness of diffusion imaging in the differential diagnosis of parkinsonism, suggesting that the minimally operator-dependent histogram analysis of the infratentorial structures and particularly of the whole cerebellar hemispheres can be used to distinguish patients with MSA-P and those with MSA-C from patients with PSP-RS and those with PD.

Glial cell inclusions and the pathogenesis of neurodegenerative diseases

In this review, we discuss examples that show how glial-cell pathology is increasingly recognized in several neurodegenerative diseases. We also discuss the more provocative idea that some of the disorders that are currently considered to be neurodegenerative diseases might, in fact, be due to primary abnormalities in glia. Although the mechanism of glial pathology (i.e. modulating glutamate excitotoxicity) might be better established for amyotrophic lateral sclerosis (ALS), a role for neuronal-glial interactions in the pathogenesis of most neurodegenerative diseases is plausible. This burgeoning area of neuroscience will receive much attention in the future and it is expected that further understanding of basic neuronal-glial interactions will have a significant impact on the understanding of the fundamental nature of human neurodegenerative disorders.

Iron-induced damage in corpus striatal cells of neonatal rats: attenuation by folic acid

BACKGROUND

Iron supplementation is recommended during pregnancy to meet the needs of the rapidly growing fetus. However, its intake is associated with the generation of destructive free radicals, i.e., oxidative damage to the fetal brain. Folic acid supplementation is needed during pregnancy to reduce the risk of neural tube defects.

HYPOTHESIS

Intake of folic acid can ameliorate the morphological features of cell damage in the striatal tissue (brain of neonatal rats) associated with the intake of iron.

OBJECTIVES AND METHODS

To test this hypothesis, an animal model (pregnant Albino rats) was established. The animals were divided into three groups: group A, control animals treated with saline only; group B, animals treated with iron gluconate; and group C, animals treated concomitantly with iron gluconate and folic acid. The striatal brain tissues of the neonates were examined for features of cellular damage, using immunohistological and ultrastructural methods.

RESULTS

The authors found significant variations among the three groups. The intake of iron (group B) and its deposition in the striatal tissue (neurons and glial cells) was associated with changes indicative of both cellular injury and regeneration. The former includes neuronal apoptosis and necrosis, and destruction of the organelles, including the mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes of the neurons and glial cells. The latter includes microgliosis, astrogliosis, upregulation of glial fibrillary acidic protein, and inducible nitric oxide synthase. These changes were absent in the striatal tissue of the control group (group A) and in animals treated concomitantly with both iron gluconate and folic acid (group C).

CONCLUSION

Intake of folic acid can protect the neonatal striatal tissue against iron-induced oxidative stress damage.