Progressive striatonigral degeneration in a transgenic mouse model of multiple system atrophy: translational implications for interventional therapies

A rapidly progressive multiple system atrophy-cerebellar variant model presenting marked glial reactions with inflammation and spreading of α-synuclein oligomers and phosphorylated α-synuclein aggregates

Multiple system atrophy (MSA) is a severe α-synucleinopathy facilitated by glial reactions; the cerebellar variant (MSA-C) preferentially involves olivopontocerebellar fibres with conspicuous demyelination. A lack of aggressive models that preferentially involve olivopontocerebellar tracts in adulthood has hindered our understanding of the mechanisms of demyelination and neuroaxonal loss, and thus the development of effective treatments for MSA. We therefore aimed to develop a rapidly progressive mouse model that recaptures MSA-C pathology. We crossed Plp1-tTA and tetO-SNCA*A53T mice to generate Plp1-tTA::tetO-SNCA*A53T bi-transgenic mice, in which human A53T α-synuclein-a mutant protein with enhanced aggregability-was specifically produced in the oligodendrocytes of adult mice using Tet-Off regulation. These bi-transgenic mice expressed mutant α-synuclein from 8 weeks of age, when doxycycline was removed from the diet. All bi-transgenic mice presented rapidly progressive motor deterioration, with wide-based ataxic gait around 22 weeks of age and death around 30 weeks of age. They also had prominent demyelination in the brainstem/cerebellum. Double immunostaining demonstrated that myelin basic protein was markedly decreased in areas in which SM132, an axonal marker, was relatively preserved. Demyelinating lesions exhibited marked ionised calcium-binding adaptor molecule 1-, arginase-1-, and toll-like receptor 2-positive microglial reactivity and glial fibrillary acidic protein-positive astrocytic reactivity. Microarray analysis revealed a strong inflammatory response and cytokine/chemokine production in bi-transgenic mice. Neuronal nuclei-positive neuronal loss and patchy microtubule-associated protein 2-positive dendritic loss became prominent at 30 weeks of age. However, a perceived decrease in tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta in bi-transgenic mice compared with wild-type mice was not significant, even at 30 weeks of age. Wild-type, Plp1-tTA, and tetO-SNCA*A53T mice developed neither motor deficits nor demyelination. In bi-transgenic mice, double immunostaining revealed human α-synuclein accumulation in neurite outgrowth inhibitor A (Nogo-A)-positive oligodendrocytes beginning at 9 weeks of age; its expression was further increased at 10 to 12 weeks, and these increased levels were maintained at 12, 24, and 30 weeks. In an α-synuclein-proximity ligation assay, α-synuclein oligomers first appeared in brainstem oligodendrocytes as early as 9 weeks of age; they then spread to astrocytes, neuropil, and neurons at 12 and 16 weeks of age. α-Synuclein oligomers in the brainstem neuropil were most abundant at 16 weeks of age and decreased thereafter; however, those in Purkinje cells successively increased until 30 weeks of age. Double immunostaining revealed the presence of phosphorylated α-synuclein in Nogo-A-positive oligodendrocytes in the brainstem/cerebellum as early as 9 weeks of age. In quantitative assessments, phosphorylated α-synuclein gradually and successively accumulated at 12, 24, and 30 weeks in bi-transgenic mice. By contrast, no phosphorylated α-synuclein was detected in wild-type, tetO-SNCA*A53T, or Plp1-tTA mice at any age examined. Pronounced demyelination and tubulin polymerisation, promoting protein-positive oligodendrocytic loss, was closely associated with phosphorylated α-synuclein aggregates at 24 and 30 weeks of age. Early inhibition of mutant α-synuclein expression by doxycycline diet at 23 weeks led to fully recovered demyelination; inhibition at 27 weeks led to persistent demyelination with glial reactions, despite resolving phosphorylated α-synuclein aggregates. In conclusion, our bi-transgenic mice exhibited progressively increasing demyelination and neuroaxonal loss in the brainstem/cerebellum, with rapidly progressive motor deterioration in adulthood. These mice showed marked microglial and astrocytic reactions with inflammation that was closely associated with phosphorylated α-synuclein aggregates. These features closely mimic human MSA-C pathology. Notably, our model is the first to suggest that α-synuclein oligomers may spread from oligodendrocytes to neurons in transgenic mice with human α-synuclein expression in oligodendrocytes. This model of MSA is therefore particularly useful for elucidating the in vivo mechanisms of α-synuclein spreading from glia to neurons, and for developing therapies that target glial reactions and/or α-synuclein oligomer spreading and aggregate formation in MSA.

Transcriptomic insights into multiple system atrophy from a PLP-α-synuclein transgenic mouse model

Multiple system atrophy (MSA) is a rare, neurodegenerative disorder with rapid motor and non-motor symptom progression. MSA is characterized by protein aggregations of α-synuclein found in the cytoplasm of oligodendrocytes. Despite this pathological hallmark, there is still little known about the cause of this disease, resulting in poor treatment options and quality of life post-diagnosis. In this study, we investigated differentially expressed genes (DEGs) via RNA-sequencing of brain samples from a validated PLP-α-synuclein transgenic mouse model, identifying a total of 40 DEGs in the PLP group compared to wild-type (WT), with top detected genes being Gm15446, Mcm6, Aldh7a1 and Gm3435. We observed a significant enrichment of immune pathways and endothelial cell genes among the upregulated genes, whereas downregulated genes were significantly enriched for oligodendrocyte and neuronal genes. We then calculated possible overlap of these DEGs with previously profiled human MSA RNA, resulting in the identification of significant downregulation of the Tsr2 gene. Identifying key gene expression profiles specific to MSA patients is crucial to further understanding the cause, and possible prevention, of this rapidly progressive neurodegenerative disorder.

Understanding the potential causes of gastrointestinal dysfunctions in multiple system atrophy

Multiple system atrophy (MSA) is a rare, progressive neurodegenerative disorder characterised by autonomic, pyramidal, parkinsonian and/or cerebellar dysfunction. Autonomic symptoms of MSA include deficits associated with the gastrointestinal (GI) system, such as difficulty swallowing, abdominal pain and bloating, nausea, delayed gastric emptying, and constipation. To date, studies assessing GI dysfunctions in MSA have primarily focused on alterations of the gut microbiome, however growing evidence indicates other structural components of the GI tract, such as the enteric nervous system, the intestinal barrier, GI hormones, and the GI-driven immune response may contribute to MSA-related GI symptoms. Here, we provide an in-depth exploration of the physiological, structural, and immunological changes theorised to underpin GI dysfunction in MSA patients and highlight areas for future research in order to identify more suitable pharmaceutical treatments for GI symptoms in patients with MSA.

Microglia in neurodegenerative diseases: mechanism and potential therapeutic targets

Microglia activation is observed in various neurodegenerative diseases. Recent advances in single-cell technologies have revealed that these reactive microglia were with high spatial and temporal heterogeneity. Some identified microglia in specific states correlate with pathological hallmarks and are associated with specific functions. Microglia both exert protective function by phagocytosing and clearing pathological protein aggregates and play detrimental roles due to excessive uptake of protein aggregates, which would lead to microglial phagocytic ability impairment, neuroinflammation, and eventually neurodegeneration. In addition, peripheral immune cells infiltration shapes microglia into a pro-inflammatory phenotype and accelerates disease progression. Microglia also act as a mobile vehicle to propagate protein aggregates. Extracellular vesicles released from microglia and autophagy impairment in microglia all contribute to pathological progression and neurodegeneration. Thus, enhancing microglial phagocytosis, reducing microglial-mediated neuroinflammation, inhibiting microglial exosome synthesis and secretion, and promoting microglial conversion into a protective phenotype are considered to be promising strategies for the therapy of neurodegenerative diseases. Here we comprehensively review the biology of microglia and the roles of microglia in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, multiple system atrophy, amyotrophic lateral sclerosis, frontotemporal dementia, progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies and Huntington's disease. We also summarize the possible microglia-targeted interventions and treatments against neurodegenerative diseases with preclinical and clinical evidence in cell experiments, animal studies, and clinical trials.

The characteristics and alteration of peripheral immune function in patients with multiple system atrophy

Objective

Multiple system atrophy (MSA) is a degenerative disease. Immune dysfunction found to play a crucial role in the pathogenesis of this disease in the literature, while the characteristics of peripheral immune function remain unclear. This study aimed to investigate the characteristics and alterations of peripheral immune function in patients with MSA.

Methods

A case-control study was conducted between January 2021 to December 2022 at SanBo Brain Hospital, Capital Medical University, Beijing, China. A total of 74 participants were recruited, including 47 MSA patients and 27 non-MSA participants. Peripheral blood samples were collected from each participant. A total of 29 types of immune cells were measured using the flow cytometry analysis technology. Single-factor analysis and multiple-factor analysis (multiple linear regression models) were performed to determine the differences and risk factors in immune cells between the MSA and non-MSA groups.

Results

Alterations of the count or percentage of CD19+ B lymphocytes and CD3-CD56+ B lymphocytes in MSA patients were found in this study. The reductions of the count and percentage of CD19+ B lymphocytes were still robust after adjusting for variables of age, gender, body mass index, albumin, and hemoglobin. Furthermore, the reductions in the count and percentage of CD19+ B lymphocytes in the MSA patients were more significant in women and individuals aged 60 years old or above than in the non-MSA participants.

Conclusion

Our findings suggested that MSA patients may be influenced by B lymphocytes, particularly CD19+ cells. Therefore, the reductions in immune cells should be considered in the diagnosis and treatment of MSA. Further studies are warranted to confirm and expand upon these findings.

Multiple system atrophy: at the crossroads of cellular, molecular and genetic mechanisms

Multiple system atrophy (MSA) is a rare oligodendroglial α-synucleinopathy characterized by neurodegeneration in striatonigral and olivopontocerebellar regions and autonomic brain centres. It causes complex cumulative motor and non-motor disability with fast progression and effective therapy is currently lacking. The difficulties in the diagnosis and treatment of MSA are largely related to the incomplete understanding of the pathogenesis of the disease. The MSA pathogenic landscape is complex, and converging findings from genetic and neuropathological studies as well as studies in experimental models of MSA have indicated the involvement of genetic and epigenetic changes; α-synuclein misfolding, aggregation and spreading; and α-synuclein strain specificity. These studies also indicate the involvement of myelin and iron dyshomeostasis, neuroinflammation, mitochondrial dysfunction and other cell-specific aspects that are relevant to the fast progression of MSA. In this Review, we discuss these findings and emphasize the implications of the complexity of the multifactorial pathogenic cascade for future translational research and its impact on biomarker discovery and treatment target definitions.

Development of a Novel Electrochemiluminescence ELISA for Quantification of α-Synuclein Phosphorylated at Ser129 in Biological Samples

Synucleinopathies are a group of neurodegenerative diseases including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). These diseases are characterized by the aggregation and deposition of α-synuclein (α-syn) in Lewy bodies (LBs) in PD and DLB or as glial cytoplasmic inclusions in MSA. In healthy brains, only ∼4% of α-syn is phosphorylated at Ser¹²⁹ (pS¹²⁹-α-syn), whereas >90% pS¹²⁹-α-syn may be found in LBs, suggesting that pS¹²⁹-α-syn could be a useful biomarker for synucleinopathies. However, a widely available, robust, sensitive, and reproducible method for measuring pS¹²⁹-α-syn in biological fluids is currently missing. We used Meso Scale Discovery (MSD)'s electrochemiluminescence platform to create a new assay for sensitive detection of pS¹²⁹-α-syn. We evaluated several combinations of capture and detection antibodies and used semisynthetic pS¹²⁹-α-syn as a standard for the assay at a concentration range from 0.5 to 6.6 × 10⁴ pg/mL. Using the antibody EP1536Y for capture and an anti-human α-syn antibody (MSD) for detection was the best combination in terms of assay sensitivity, specificity, and reproducibility. We tested the utility of the assay for the detection and quantification of pS¹²⁹-α-syn in human cerebrospinal fluid, serum, plasma, saliva, and CNS-originating small extracellular vesicles, as well as in mouse brain lysates. Our data suggest that the assay can become a widely used method for detecting pS¹²⁹-α-syn in biomedical studies including when only a limited volume of sample is available and high sensitivity is required, offering new opportunities for diagnostic biomarkers, monitoring disease progression, and quantifying outcome measures in clinical trials.

Development of Small Molecules Targeting α-Synuclein Aggregation: A Promising Strategy to Treat Parkinson’s Disease

Parkinson’s disease, the second most common neurodegenerative disorder worldwide, is characterized by the accumulation of protein deposits in the dopaminergic neurons. These deposits are primarily composed of aggregated forms of α-Synuclein (α-Syn). Despite the extensive research on this disease, only symptomatic treatments are currently available. However, in recent years, several compounds, mainly of an aromatic character, targeting α-Syn self-assembly and amyloid formation have been identified. These compounds, discovered by different approaches, are chemically diverse and exhibit a plethora of mechanisms of action. This work aims to provide a historical overview of the physiopathology and molecular aspects associated with Parkinson’s disease and the current trends in small compound development to target α-Syn aggregation. Although these molecules are still under development, they constitute an important step toward discovering effective anti-aggregational therapies for Parkinson’s disease.

Host oligodendrogliopathy and α-synuclein strains dictate disease severity in multiple system atrophy

Multiple system atrophy is a progressive neurodegenerative disease with prominent autonomic and motor features. During early stages, different subtypes of the disease are distinguished by their predominant parkinsonian or cerebellar symptoms, reflecting its heterogeneous nature. The pathognomonic feature of multiple system atrophy is the presence of α-synuclein (αSyn) protein deposits in oligodendroglial cells. αSyn can assemble in specific cellular or disease environments and form αSyn strains with unique structural features, but the ability of αSyn strains to propagate in oligodendrocytes remains elusive. Recently, it was shown that αSyn strains with related conformations exist in the brains of patients. Here, we investigated whether different αSyn strains can influence multiple system atrophy progression in a strain-dependent manner. To this aim, we injected two recombinant αSyn strains (fibrils and ribbons) in multiple system atrophy transgenic mice and found that they determined disease severity in multiple system atrophy via host-restricted and cell-specific pathology in vivo. αSyn strains significantly impact disease progression in a strain-dependent way via oligodendroglial, neurotoxic and immune-related mechanisms. Neurodegeneration and brain atrophy were accompanied by unique microglial and astroglial responses and the recruitment of central and peripheral immune cells. The differential activation of microglial cells correlated with the structural features of αSyn strains both in vitro and in vivo. Spectral analysis showed that ribbons propagated oligodendroglial inclusions that were structurally distinct from those of fibrils, with resemblance to oligodendroglial inclusions, in the brains of patients with multiple system atrophy. This study, therefore, shows that the multiple system atrophy phenotype is governed by both the nature of the αSyn strain and the host environment and that by injecting αSyn strains into an animal model of the disease, a more comprehensive phenotype can be established.

A Mouse Model of Multiple System Atrophy: Bench to Bedside

Multiple system atrophy (MSA) is a rare neurodegenerative disorder with unclear etiology, currently difficult and delayed diagnosis, and rapid progression, leading to disability and lethality within 6 to 9 years after symptom onset. The neuropathology of MSA classifies the disease in the group of a-synucleinopathies together with Parkinson's disease and other Lewy body disorders, but features specific oligodendroglial inclusions, which are pathognomonic for MSA. MSA has no efficient therapy to date. Development of experimental models is crucial to elucidate the disease mechanisms in progression and to provide a tool for preclinical screening of putative therapies for MSA. In vitro and in vivo models, based on selective neurotoxicity, a-synuclein oligodendroglial overexpression, and strain-specific propagation of a-synuclein fibrils, have been developed, reflecting various facets of MSA pathology. Over the years, the continuous exchange from bench to bedside and backward has been crucial for the advancing of MSA modelling, elucidating MSA pathogenic pathways, and understanding the existing translational gap to successful clinical trials in MSA. The review discusses specifically advantages and limitations of the PLP-a-syn mouse model of MSA, which recapitulates motor and non-motor features of the human disease with underlying striatonigral degeneration, degeneration of autonomic centers, and sensitized olivopontocerebellar system, strikingly mirroring human MSA pathology.

Microglia in Parkinson’s Disease

Microglia are the primary resident immune cells of the central nervous system. Neuropathological reports have identified augmented microglial activation in brains of patients with neurodegenerative disorders including Parkinson’s disease (PD). Extensive research over the years has strengthened the current view on microglia as a player in the pathogenesis of PD and other α-synucleinopathies. In this review, we summarize key findings of the recent three years on microglia in PD with specific relevance to understanding its heterogeneity, dual nature, and specific interactions with pathological α-synuclein strains to mediate its clearance and spreading. This review provides evidence on the relevance of microglia as a putative biomarker and therapeutic target in PD and related disorders.

Age and Gender Differences in Cardiovascular Autonomic Failure in the Transgenic PLP-syn Mouse, a Model of Multiple System Atrophy

Multiple system atrophy (MSA) is a rare and progressive neurodegenerative disorder. Autonomic failure (AF) is one main clinical feature which has a significant impact on health-related quality of life. The neuropathological hallmark of MSA is the abnormal accumulation of α-synuclein in oligodendrocytes forming glial cytoplasmic inclusions. Only little is known about gender and age differences in AF in MSA. This study was carried out in 6 and 12 months old transgenic PLP-α-syn and WT male and female mice. Heart rate variability (HRV) was assessed both in time, frequential and non-linear domains. Baroreflex sensitivity (BRS) was estimated by the sequence method. Duration of ventricular depolarization and repolarization (QT/QTc intervals) were evaluated from the ECG signals. Three-way ANOVA (genotype x gender x age) with Sidak's method post-hoc was used to analyze data. BRS was significantly changed in PLP-α-syn mice and was age-dependent. QT and QTc intervals were not significantly modified in PLP-α-syn mice. An impaired HRV was observed at 12 months of age in PLP-α-syn female but not in male mice, indicative of cardiovascular AF.

Brain injections of glial cytoplasmic inclusions induce a multiple system atrophy-like pathology

Synucleinopathies encompass several neurodegenerative diseases, which include Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. These diseases are characterized by the deposit of α-synuclein aggregates in intracellular inclusions in neurons and glial cells. Unlike Parkinson's disease and dementia with Lewy bodies, where aggregates are predominantly neuronal, multiple system atrophy is associated with α-synuclein cytoplasmic inclusions in oligodendrocytes. Glial cytoplasmic inclusions are the pathological hallmark of multiple system atrophy and are associated with neuroinflammation, modest demyelination and, ultimately, neurodegeneration. To evaluate the possible pathogenic role of glial cytoplasmic inclusions, we inoculated glial cytoplasmic inclusion-containing brain fractions obtained from multiple system atrophy patients into the striatum of non-human primates. After a 2-year in vivo phase, extensive histochemical and biochemical analyses were performed on the whole brain. We found loss of both nigral dopamine neurons and striatal medium spiny neurons, as well as loss of oligodendrocytes in the same regions, which are characteristics of multiple system atrophy. Furthermore, demyelination, neuroinflammation and α-synuclein pathology were also observed. These results show that the α-synuclein species in multiple system atrophy-derived glial cytoplasmic inclusions can induce a pathological process in non-human primates, including nigrostriatal and striatofugal neurodegeneration, oligodendroglial cell loss, synucleinopathy and gliosis. The present data pave the way for using this experimental model for MSA research and therapeutic development.

Spreading of Aggregated α-Synuclein in Sagittal Organotypic Mouse Brain Slices

The accumulation of α-synuclein (α-syn) in the brain plays a role in synucleinopathies and it is hypothesized to spread in a prion-like fashion between connected brain regions. In the present study, we aim to investigate this spreading in well-characterized sagittal organotypic whole brain slices taken from postnatal wild type (WT) and transgenic mice overexpressing human α-syn under the promoter of proteolipid protein (PLP). Collagen hydrogels were loaded with monomers of human α-syn, as well as human and mouse pre-formed fibrils (PFFs), to allow local application and slow release. The spreading of α-syn was evaluated in different brain regions by immunohistochemistry for total α-syn and α-syn phosphorylated at the serine129 position (α-syn-P). The application of human and mouse PFFs of α-syn caused the aggregation and spreading of α-syn-P in the brain slices, which was pronounced the most at the region of hydrogel application and surrounding striatum, as well as along the median forebrain bundle. The organotypic slices from transgenic mice showed significantly more α-syn pathology than those from WT mice. The present study demonstrates that seeding with α-syn PFFs but not monomers induced intracellular α-syn pathology, which was significantly more prominent in brain slices with α-syn overexpression. This is consistent with the prion-like spreading theory of α-syn aggregates. The sagittal whole brain slices characterized in this study carry the potential to be used as a novel model to study α-syn pathology.

Depression in multiple system atrophy: Views on pathological, clinical and imaging aspects

Multiple system atrophy (MSA) is a common atypical parkinsonism, characterized by a varying combination of autonomic, cerebellar, and pyramidal systems. It has been noticed that the patients with MSA can be accompanied by some neuropsychiatric disorders, in particular depression. However, there is limited understanding of MSA-related depression. To bridge existing gaps, we summarized research progress on this topic and provided a new perspective regarding pathological, clinical, and imaging aspects. Firstly, we synthesized corresponding studies in order to investigate the relationship between depression and MSA from a pathological perspective. And then, from a clinical perspective, we focused on the prevalence of depression in MS patients and the comparison with other populations. Furthermore, the associations between depression and some clinical characteristics, such as life quality and gender, have been reported. The available neuroimaging studies were too sparse to draw conclusions about the radiological aspect of depression in MSA patients but we still described them in the presence of paper. Finally, we discussed some limitations and shortcomings existing in the included studies, which call for more high-quality basic research and clinical research in this field.

The Compound ATH434 Prevents Alpha-Synuclein Toxicity in a Murine Model of Multiple System Atrophy

BACKGROUND

An elevation in iron levels, together with an accumulation of α-synuclein within the oligodendrocytes, are features of the rare atypical parkinsonian disorder, Multiple System Atrophy (MSA). We have previously tested the novel compound ATH434 (formally called PBT434) in preclinical models of Parkinson's disease and shown that it is brain-penetrant, reduces iron accumulation and iron mediated redox activity, provides neuroprotection, inhibits alpha synuclein aggregation and lowers the tissue levels of alpha synuclein. The compound was also well-tolerated in a first-in-human oral dosing study in healthy and older volunteers with a favorable, dose-dependent pharmacokinetic profile.

OBJECTIVE

To evaluate the efficacy of ATH434 in a mouse MSA model.

METHODS

The PLP-α-syn transgenic mouse overexpresses α-synuclein, demonstrates oligodendroglial pathology, and manifests motor and non-motor aspects of MSA. Animals were provided ATH434 (3, 10, or 30 mg/kg/day spiked into their food) or control food for 4 months starting at 12 months of age and were culled at 16 months. Western blot was used to assess oligomeric and urea soluble α-synuclein levels in brain homogenates, whilst stereology was used to quantitate the number of nigral neurons and glial cell inclusions (GCIs) present in the substantia nigra pars compacta.

RESULTS

ATH434 reduced oligomeric and urea soluble α-synuclein aggregation, reduced the number of GCIs, and preserved SNpc neurons. In vitro experiments suggest that ATH434 prevents the formation of toxic oligomeric species of synuclein.

CONCLUSION

ATH434 is a promising small molecule drug candidate that has potential to move forward to trial for treating MSA.

A historical review of multiple system atrophy with a critical appraisal of cellular and animal models

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA), and dysautonomia with cerebellar ataxia or parkinsonian motor features. Isolated autonomic dysfunction with predominant genitourinary dysfunction and orthostatic hypotension and REM sleep behavior disorder are common characteristics of a prodromal phase, which may occur years prior to motor-symptom onset. MSA is a unique synucleinopathy, in which alpha-synuclein (aSyn) accumulates and forms insoluble inclusions in the cytoplasm of oligodendrocytes, termed glial cytoplasmic inclusions (GCIs). The origin of, and precise mechanism by which aSyn accumulates in MSA are unknown, and, therefore, disease-modifying therapies to halt or slow the progression of MSA are currently unavailable. For these reasons, much focus in the field is concerned with deciphering the complex neuropathological mechanisms by which MSA begins and progresses through the course of the disease. This review focuses on the history, etiopathogenesis, neuropathology, as well as cell and animal models of MSA.

Therapeutic potential of iron modulating drugs in a mouse model of multiple system atrophy

Multiple System Atrophy (MSA) is a rare neurodegenerative synucleinopathy which leads to severe disability followed by death within 6-9 years of symptom onset. There is compelling evidence suggesting that biological trace metals like iron and copper play an important role in synucleinopathies like Parkinson's disease and removing excess brain iron using chelators could slow down the disease progression. In human MSA, there is evidence of increased iron in affected brain regions, but role of iron and therapeutic efficacy of iron-lowering drugs in pre-clinical models of MSA have not been studied. We studied age-related changes in iron metabolism in different brain regions of the PLP-αsyn mice and tested whether iron-lowering drugs could alleviate disease phenotype in aged PLP-αsyn mice. Iron content, iron-ferritin association, ferritin protein levels and copper-ceruloplasmin association were measured in prefrontal cortex, putamen, substantia nigra and cerebellum of 3, 8, and 20-month-old PLP-αsyn and age-matched non-transgenic mice. Moreover, 12-month-old PLP-αsyn mice were administered deferiprone or ceruloplasmin or vehicle for 2 months. At the end of treatment period, motor testing and stereological analyses were performed. We found iron accumulation and perturbed iron-ferritin interaction in substantia nigra, putamen and cerebellum of aged PLP-αsyn mice. Furthermore, we found significant reduction in ceruloplasmin-bound copper in substantia nigra and cerebellum of the PLP-αsyn mice. Both deferiprone and ceruloplasmin prevented decline in motor performance in aged PLP-αsyn mice and were associated with higher neuronal survival and reduced density of α-synuclein aggregates in substantia nigra. This is the first study to report brain iron accumulation in a mouse model of MSA. Our results indicate that elevated iron in MSA mice may result from ceruloplasmin dysfunction and provide evidence that targeting iron in MSA could be a viable therapeutic option.

ATH434 Reduces α-Synuclein-Related Neurodegeneration in a Murine Model of Multiple System Atrophy

BACKGROUND

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder characterized by aggregated α-synuclein (α-syn) in oligodendrocytes and accompanied by striatonigral and olivopontocerebellar degeneration and motor symptoms. Key features of MSA are replicated in the PLP-α-syn transgenic mouse, including progressive striatonigral degeneration and motor deterioration. There are currently no approved treatments for MSA. ATH434 is a novel, orally bioavailable brain penetrant small molecule inhibitor of α-syn aggregation.

OBJECTIVES

To characterize ATH434 for disease modification in a mouse model of MSA.

METHODS

Six-month-old PLP-α-syn mice (MSA mice) were ATH434-treated (ATH434 in food) or untreated (normal food) for 6 months. Motor behavior and numbers of nigral and striatal neurons were evaluated. α-syn aggregates and oligomers were quantified by immunohistochemical and western blot analyses. Microglial activation and neuroinflammation were assessed by histological and molecular analyses. Ferric iron in the Substantia nigra was evaluated with the Perls method.

RESULTS

ATH434-treated mice demonstrated preservation of motor performance in MSA mice that was associated with neuroprotection of nigral and striatal neurons. The rescue of the phenotype correlated with the reduction of α-syn inclusions and oligomers in animals receiving ATH434. ATH434-treated mice exhibited significantly increased lysosomal activity of microglia without increased pro-inflammatory markers, suggesting a role in α-syn clearing. ATH434-treatment was associated with lower intracellular nigral iron levels.

CONCLUSIONS

Our findings demonstrate the beneficial disease-modifying effect of ATH434 in oligodendroglial α-synucleinopathy on both the motor phenotype and neurodegenerative pathology in the PLP-α-syn transgenic mouse and support the development of ATH434 for MSA. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Reduced oligodendrocyte exosome secretion in multiple system atrophy involves SNARE dysfunction

Transportation of key proteins via extracellular vesicles has been recently implicated in various neurodegenerative disorders, including Parkinson's disease, as a new mechanism of disease spreading and a new source of biomarkers. Extracellular vesicles likely to be derived from the brain can be isolated from peripheral blood and have been reported to contain higher levels of α-synuclein (α-syn) in Parkinson's disease patients. However, very little is known about extracellular vesicles in multiple system atrophy, a disease that, like Parkinson's disease, involves pathological α-syn aggregation, though the process is centred around oligodendrocytes in multiple system atrophy. In this study, a novel immunocapture technology was developed to isolate blood CNPase-positive, oligodendrocyte-derived enriched microvesicles (OEMVs), followed by fluorescent nanoparticle tracking analysis and assessment of α-syn levels contained within the OEMVs. The results demonstrated that the concentrations of OEMVs were significantly lower in multiple system atrophy patients, compared to Parkinson's disease patients and healthy control subjects. It is also noted that the population of OEMVs involved was mainly in the size range closer to that of exosomes, and that the average α-syn concentrations (per vesicle) contained in these OEMVs were not significantly different among the three groups. The phenomenon of reduced OEMVs was again observed in a transgenic mouse model of multiple system atrophy and in primary oligodendrocyte cultures, and the mechanism involved was likely related, at least in part, to an α-syn-mediated interference in the interaction between syntaxin 4 and VAMP2, leading to the dysfunction of the SNARE complex. These results suggest that reduced OEMVs could be an important mechanism related to pathological α-syn aggregation in oligodendrocytes, and the OEMVs found in peripheral blood could be further explored for their potential as multiple system atrophy biomarkers.

Assessment of the Retina of Plp-α-Syn Mice as a Model for Studying Synuclein-Dependent Diseases

Purpose

Synucleinopathies such as multiple system atrophy (MSA) and Parkinson's disease are associated with a variety of visual symptoms. Functional and morphological retinal aberrations are therefore supposed to be valuable biomarkers for these neurodegenerative diseases. This study examined the retinal morphology and functionality resulting from human α-synuclein (α-Syn) overexpression in the transgenic Plp-α-Syn mouse model.

Methods

Immunohistochemistry on retinal sections and whole-mounts was performed on 8- to 11-week-old and 12-month-old Plp-α-Syn mice and C57BL/6N controls. Quantitative RT-PCR experiments were performed to study the expression of endogenous and human α-Syn and tyrosine hydroxylase (TH). We confirmed the presence of human α-Syn in the retina in western blot analyses. Multi-electrode array (MEA) analyses from light-stimulated whole-mounted retinas were used to investigate their functionality.

Results

Biochemical and immunohistochemical analyses showed human α-Syn in the retina of Plp-α-Syn mice. We found distinct staining in different retinal cell layers, most abundantly in rod bipolar cells of the peripheral retina. In the periphery, we also observed a trend toward a decline in the number of retinal ganglion cells. The number of TH+ neurons was unaffected in this human α-Syn overexpression model. MEA recordings showed that Plp-α-Syn retinas were functional but exhibited mild alterations in dim light conditions.

Conclusions

Together, these findings implicate an impairment of retinal neurons in the Plp-α-Syn mouse. The phenotype partly relates to retinal deficits reported in MSA patients. We further propose the suitability of the Plp-α-Syn retina as a biological model to study synuclein-mediated mechanisms.

L-DOPA regulates α-synuclein accumulation in experimental parkinsonism

AIMS

Widespread accumulation of misfolded α-synuclein aggregates is a key feature of Parkinson's disease (PD). Although the pattern and extent of α-synuclein accumulation through PD brains is known, the impact of chronic dopamine-replacement therapy (the gold-standard pharmacological treatment of PD) on the fate of α-synuclein is still unknown. Here, we investigated the distribution and accumulation of α-synuclein in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) non-human primate model of PD and determined the effect of chronic L-DOPA treatment on MPTP-induced α-synuclein pathology.

METHODS

We measured the density of α-synuclein and tau immuno-positive neurons in the substantia nigra, putamen, hippocampal CA1 region, temporal cortex and dentate nucleus of control, MPTP and MPTP+L-DOPA-treated monkeys. Moreover, we also extracted and quantified Triton-X (TX) soluble and insoluble α-synuclein in putamen and hippocampus samples from a separate cohort of control, MPTP and MPTP+L-DOPA-treated monkeys.

RESULTS

MPTP-induced α-synuclein accumulation in NHP model of PD was not limited to the substantia nigra but also occurred in the putamen, hippocampal CA1 region and temporal cortex. Tau was increased only in the temporal cortex. Moreover, increased intraneuronal TX insoluble α-synuclein was truncated, but not in the structural form of Lewy bodies. The MPTP-induced increase in α-synuclein levels was abolished in animals having received L-DOPA in all the brain regions, except in the substantia nigra.

CONCLUSIONS

Dopamine replacement therapy can dramatically ameliorate α-synuclein pathology in the MPTP NHP model of PD. Therefore, patient's dopaminergic medication should be systematically considered when assessing α-synuclein as a biomarker for diagnosis, monitoring disease progression and response to disease-modifying treatments.

Viral-based rodent and nonhuman primate models of multiple system atrophy: Fidelity to the human disease

Multiple system atrophy (MSA) is a rare and extremely debilitating progressive neurodegenerative disease characterized by variable combinations of parkinsonism, cerebellar ataxia, dysautonomia, and pyramidal dysfunction. MSA is a unique synucleinopathy, in which alpha synuclein-rich aggregates are present in the cytoplasm of oligodendroglia. The precise origin of the alpha synuclein (aSyn) found in the glial cytoplasmic inclusions (GCIs) as well the mechanisms of neurodegeneration in MSA remain unclear. Despite this fact, cell and animal models of MSA rely on oligodendroglial overexpression of aSyn. In the present study, we utilized a novel oligotrophic AAV, Olig001, to overexpress aSyn specifically in striatal oligodendrocytes of rats and nonhuman primates in an effort to further characterize our novel viral vector-mediated MSA animal models. Using two cohorts of animals with 10-fold differences in Olig001 vector titers, we show a dose-dependent formation of MSA-like pathology in rats. High titer of Olig001-aSyn in these animals were required to produce the formation of pS129+ and proteinase K resistant aSyn-rich GCIs, demyelination, and neurodegeneration. Using this knowledge, we injected high titer Olig001 in the putamen of cynomolgus macaques. After six months, histological analysis showed that oligodendroglial overexpression of aSyn resulted in the formation of hallmark GCIs throughout the putamen, demyelination, a 44% reduction of striatal neurons and a 12% loss of nigral neurons. Furthermore, a robust inflammatory response similar to MSA was produced in Olig001-aSyn NHPs, including microglial activation, astrogliosis, and a robust infiltration of T cells into the CNS. Taken together, oligodendroglial-specific viral vector-mediated overexpression of aSyn in rats and nonhuman primates faithfully reproduces many of the pathological disease hallmarks found in MSA. Future studies utilizing these large animal models of MSA would prove extremely valuable as a pre-clinical platform to test novel therapeutics that are so desperately needed for MSA.

Overexpression of α-Synuclein by Oligodendrocytes in Transgenic Mice Does Not Recapitulate the Fibrillar Aggregation Seen in Multiple System Atrophy

The synucleinopathy underlying multiple system atrophy (MSA) is characterized by the presence of abundant amyloid inclusions containing fibrillar α-synuclein (α-syn) aggregates in the brains of the patients and is associated with an extensive neurodegeneration. In contrast to Parkinson's disease (PD) where the pathological α-syn aggregates are almost exclusively neuronal, the α-syn inclusions in MSA are principally observed in oligodendrocytes (OLs) where they form glial cytoplasmic inclusions (GCIs). This is intriguing because differentiated OLs express low levels of α-syn, yet pathogenic amyloid α-syn seeds require significant amounts of α-syn monomers to feed their fibrillar growth and to eventually cause the buildup of cytopathological inclusions. One of the transgenic mouse models of this disease is based on the targeted overexpression of human α-syn in OLs using the PLP promoter. In these mice, the histopathological images showing a rapid emergence of S129-phosphorylated α-syn inside OLs are considered as equivalent to GCIs. Instead, we report here that they correspond to the accumulation of phosphorylated α-syn monomers/oligomers and not to the appearance of the distinctive fibrillar α-syn aggregates that are present in the brains of MSA or PD patients. In spite of a propensity to co-sediment with myelin sheath contaminants, the phosphorylated forms found in the brains of the transgenic animals are soluble (>80%). In clear contrast, the phosphorylated species present in the brains of MSA and PD patients are insoluble fibrils (>95%). Using primary cultures of OLs from PLP-αSyn mice we observed a variable association of S129-phosphorylated α-syn with the cytoplasmic compartment, the nucleus and with membrane domains suggesting that OLs functionally accommodate the phospho-α-syn deriving from experimental overexpression. Yet and while not taking place spontaneously, fibrillization can be seeded in these primary cultures by challenging the OLs with α-syn preformed fibrils (PFFs). This indicates that a targeted overexpression of α-syn does not model GCIs in mice but that it can provide a basis for seeding aggregation using PFFs. This approach could help establishing a link between α-syn aggregation and the development of a clinical phenotype in these transgenic animals.

Shared Genetics of Multiple System Atrophy and Inflammatory Bowel Disease

Background:

Multiple system atrophy (MSA) is a rare neurodegenerative disease characterized by intracellular accumulations of α-synuclein and nerve cell loss in striatonigral and olivopontocerebellar structures. Epidemiological and clinical studies have reported potential involvement of autoimmune mechanisms in MSA pathogenesis. However, genetic etiology of this interaction remains unknown. We aimed to investigate genetic overlap between MSA and 7 autoimmune diseases and to identify shared genetic loci.

Methods:

Genome-wide association study summary statistics of MSA and 7 autoimmune diseases were combined in cross-trait conjunctional false discovery rate analysis to explore overlapping genetic background. Expression of selected candidate genes was compared in transgenic MSA mice and wild-type mice. Genetic variability of candidate genes was further investigated using independent whole-exome genotyping data from large cohorts of MSA and autoimmune disease patients and healthy controls.

Results:

We observed substantial polygenic overlap between MSA and inflammatory bowel disease and identified 3 shared genetic loci with leading variants upstream of the DENND1B and RSP04 genes, and in intron of the C7 gene. Further, the C7 gene showed significantly dysregulated expression in the degenerating midbrain of transgenic MSA mice compared with wild-type mice and had elevated burden of protein-coding variants in independent MSA and inflammatory bowel disease cohorts.

Conclusion:

Our study provides evidence of shared genetic etiology between MSA and inflammatory bowel disease with an important role of the C7 gene in both phenotypes, with the implication of immune and gut dysfunction in MSA pathophysiology.

Targeting α-synuclein by PD03 AFFITOPE® and Anle138b rescues neurodegenerative pathology in a model of multiple system atrophy: clinical relevance

Background

Misfolded oligomeric α-synuclein plays a pivotal role in the pathogenesis of α-synucleinopathies including Parkinson’s disease and multiple system atrophy, and its detection parallels activation of microglia and a loss of neurons in the substantia nigra pars compacta. Here we aimed to analyze the therapeutic efficacy of PD03, a new AFFITOPE® immunotherapy approach, either alone or in combination with Anle138b, in a PLP-α-syn mouse model.

Methods

The PLP-α-syn mice were treated with PD03 immunotherapy, Anle138b, or a combination of two. Five months after study initiation, the mice underwent behavioral testing and were sacrificed for neuropathological analysis. The treatment groups were compared to the vehicle group with regard to motor performance, nigral neuronal loss, microglial activation and α-synuclein pathology.

Results

The PLP-α-syn mice receiving the PD03 or Anle138b single therapy showed improvement of gait deficits and preservation of nigral dopaminergic neurons associated with the reduced α-synuclein oligomer levels and decreased microglial activation. The combined therapy with Anle138b and PD03 resulted in lower IgG binding in the brain as compared to the single immunotherapy with PD03.

Conclusions

PD03 and Anle138b can selectively target oligomeric α-synuclein, resulting in attenuation of neurodegeneration in the PLP-α-syn mice. Both approaches are potential therapies that should be developed further for disease modification in α-synucleinopathies.

Nilotinib Fails to Prevent Synucleinopathy and Cell Loss in a Mouse Model of Multiple System Atrophy

BACKGROUND

Multiple system atrophy (MSA) is a rare, untreatable neurodegenerative disorder characterized by accumulation of α-synuclein in oligodendroglial inclusions. As such, MSA is a synucleinopathy along with Parkinson's disease (PD) and dementia with Lewy bodies. Activation of the abelson tyrosine kinase c-Abl leads to phosphorylation of α-synuclein at tyrosine 39, thereby promoting its aggregation and subsequent neurodegeneration. The c-Abl inhibitor nilotinib used for the treatment of chronic myeloid leukemia based on data collected in preclinical models of PD might interfere with pathogenic mechanisms that are relevant to PD and dementia with Lewy bodies, which motivated its assessment in an open-label clinical trial in PD and dementia with Lewy bodies patients. The objective of this study was to assess the preclinical efficacy of nilotinib in the specific context of MSA.

METHODS

Mice expressing human wild-type α-synuclein in oligodendrocytes received daily injection of nilotinib (1 or 10 mg/kg) over 12 weeks. Postmortem analysis included the assessment of c-Abl activation, α-synuclein burden, and dopaminergic neurodegeneration.

RESULTS

α-Synuclein phosphorylated at tyrosine 39 was detected in glial cytoplasmic inclusions in MSA patients. Increased activation of c-Abl and α-synuclein phosphorylation at tyrosine 39 were found in transgenic mice. Despite significant inhibition of c-Abl and associated reduction of α-synuclein phosphorylation at tyrosine 39 by 40%, nilotinib failed to reduce α-synuclein aggregate burden (including phosphorylation at serine 129) in the striatum and cortex or to lessen neurodegeneration in the substantia nigra.

CONCLUSIONS

This preclinical study suggests that partial inhibition of c-Abl and reduction of α-synuclein phosphorylation at tyrosine 39 may not be a relevant target for MSA. © 2020 International Parkinson and Movement Disorder Society.

Genes to treat excitotoxicity ameliorate the symptoms of the disease in mice models of multiple system atrophy

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder characterized by striatonigral degeneration and olivopontocerebellar atrophy. The main hallmark of MSA is the aggregation of alpha-synuclein in oligodendrocytes, which contributes to the dysfunction and death of the oligodendrocytes, followed by neurodegeneration. Studies suggested that oxidative-excitatory pathway is associated with the progression of the disease. The aim of the current study was to test this concept by overexpression of excitatory amino acid transporter 2, glutamate dehydrogenase and nuclear factor (erythroid-derived 2)-related factor 2 genes in the striatum of two established mouse models of MSA. To induce the first model, we injected the mitochondrial neurotoxin, 3-nitropropionic acid (3-NP), unilaterally into the right striatum in 2-month-old C57BL/6 male mice. We demonstrate a significant improvement in two drug-induced rotational behavior tests, following unilateral injection the three genes. For the second model, we used transgenic mice expressing the alpha-synuclein gene under the proteolipid protein, in the age of 7 months, boosted with 3-NP to enhance the motor deficits and neurodegeneration. We show that the overexpression of the three genes attenuated the motor-related deficit in the elevated bridge and pole tests. Thus, our study indicates that glutamate excito-oxidative toxicity plays a major role in this MSA model and our gene therapy approach might suggest a novel strategy for MSA treatment.

Insights into the pathogenesis of multiple system atrophy: focus on glial cytoplasmic inclusions

Multiple system atrophy (MSA) is a debilitating and fatal neurodegenerative disorder. The disease severity warrants urgent development of disease-modifying therapy, but the disease pathogenesis is still enigmatic. Neurodegeneration in MSA brains is preceded by the emergence of glial cytoplasmic inclusions (GCIs), which are insoluble α-synuclein accumulations within oligodendrocytes (OLGs). Thus, preventive strategies against GCI formation may suppress disease progression. However, although numerous studies have tried to elucidate the molecular pathogenesis of GCI formation, difficulty remains in understanding the pathological interaction between the two pivotal aspects of GCIs; α-synuclein and OLGs. The difficulty originates from several enigmas: 1) what triggers the initial generation and possible propagation of pathogenic α-synuclein species? 2) what contributes to OLG-specific accumulation of α-synuclein, which is abundantly expressed in neurons but not in OLGs? and 3) how are OLGs and other glial cells affected and contribute to neurodegeneration? The primary pathogenesis of GCIs may involve myelin dysfunction and dyshomeostasis of the oligodendroglial cellular environment such as autophagy and iron metabolism. We have previously reported that oligodendrocyte precursor cells are more prone to develop intracellular inclusions in the presence of extracellular fibrillary α-synuclein. This finding implies a possibility that the propagation of GCI pathology in MSA brains is mediated through the internalization of pathological α-synuclein into oligodendrocyte precursor cells. In this review, in order to discuss the pathogenesis of GCIs, we will focus on the composition of neuronal and oligodendroglial inclusions in synucleinopathies. Furthermore, we will introduce some hypotheses on how α-synuclein pathology spreads among OLGs in MSA brains, in the light of our data from the experiments with primary oligodendrocyte lineage cell culture. While various reports have focused on the mysterious source of α-synuclein in GCIs, insights into the mechanism which regulates the uptake of pathological α-synuclein into oligodendroglial cells may yield the development of the disease-modifying therapy for MSA. The interaction between glial cells and α-synuclein is also highlighted with previous studies of post-mortem human brains, cultured cells, and animal models, which provide comprehensive insight into GCIs and the MSA pathomechanisms.

High-salt diet does not boost neuroinflammation and neurodegeneration in a model of α-synucleinopathy

AIM

Pre-clinical studies in models of multiple sclerosis and other inflammatory disorders suggest that high-salt diet may induce activation of the immune system and potentiate inflammation. However, high-salt diet constitutes a common non-pharmacological intervention to treat autonomic problems in synucleinopathies such as Parkinson's disease and multiple system atrophy. Since neuroinflammation plays an important pathogenic role in these neurodegenerative disorders, we asked here whether high-salt diet may aggravate the disease phenotype in a transgenic model of multiple system atrophy.

METHODS

Nine-month-old PLP-hαSyn and matched wildtype mice received normal or high-salt diet for a period of 3 months. Behavioral, histological, and molecular analyses were performed to evaluate the effect of high-salt diet on motor decline, neuroinflammation, neurodegeneration, and α-synuclein accumulation in these mice.

RESULTS

Brain subregion-specific molecular and histological analyses showed no deleterious effects of high-salt diet on the level of microglial activation. Moreover, neuroinflammation-related cytokines and chemokines, T cell recruitment or astrogliosis were unaffected by high-salt diet exposure. Behavioral testing showed no effect of diet on motor decline. High-salt diet was not related to the deterioration of neurodegeneration or α-synuclein accumulation in PLP-hαSyn mice.

CONCLUSIONS

Here, we demonstrate that high-salt diet does not aggravate neuroinflammation and neurodegeneration in PLP-hαSyn mice. Our findings discard a deleterious pro-neuroinflammatory effect of high-salt diet in multiple system atrophy.

MSA: From basic mechanisms to experimental therapeutics

Multiple system atrophy (MSA) is a rare and fatal neurodegenerative disorder characterized by rapidly progressive autonomic and motor dysfunction. Pathologically, MSA is mainly characterized by the abnormal accumulation of misfolded α-synuclein in the cytoplasm of oligodendrocytes, which plays a major role in the pathogenesis of the disease. Striatonigral degeneration and olivopontecerebellar atrophy underlie the motor syndrome, while degeneration of autonomic centers defines the autonomic failure in MSA. At present, there is no treatment that can halt or reverse its progression. However, over the last decade several studies in preclinical models and patients have helped to better understand the pathophysiological events underlying MSA. The etiology of this fatal disorder remains unclear and may be multifactorial, caused by a combination of factors which may serve as targets for novel therapeutic approaches. In this review, we summarize the current knowledge about the etiopathogenesis and neuropathology of MSA, its different preclinical models, and the main disease modifying therapies that have been used so far or that are planned for future clinical trials.

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.

Models of multiple system atrophy

Multiple system atrophy (MSA) is a neurodegenerative disease with diverse clinical manifestations, including parkinsonism, cerebellar syndrome, and autonomic failure. Pathologically, MSA is characterized by glial cytoplasmic inclusions in oligodendrocytes, which contain fibrillary forms of α-synuclein. MSA is categorized as one of the α-synucleinopathy, and α-synuclein aggregation is thought to be the culprit of the disease pathogenesis. Studies on MSA pathogenesis are scarce relative to studies on the pathogenesis of other synucleinopathies, such as Parkinson’s disease and dementia with Lewy bodies. However, recent developments in cellular and animal models of MSA, especially α-synuclein transgenic models, have driven advancements in research on this disease. Here, we review the currently available models of MSA, which include toxicant-induced animal models, α-synuclein-overexpressing cellular models, and mouse models that express α-synuclein specifically in oligodendrocytes through cell type-specific promoters. We will also discuss the results of studies in recently developed transmission mouse models, into which MSA brain extracts were intracerebrally injected. By reviewing the findings obtained from these model systems, we will discuss what we have learned about the disease and describe the strengths and limitations of the models, thereby ultimately providing direction for the design of better models and future research.

A review of the models available for studying multiple system atrophy (MSA), a Parkinson’s-like disease, may help identify new treatment options. MSA is difficult to diagnose and unresponsive to drugs. Similar to Parkinson’s disease, it involves accumulation of protein aggregates in brain and spinal cord cells, but the causes are poorly understood. He-Jin Lee at Konkuk University, and Seung-Jae Lee at Seoul National University College of Medicine in South Korea and coworkers have reviewed the models available to study the disease, including toxin-induced and transgenic animal models, and recent evidence that transferring the protein aggregates into cells causes MSA symptoms. Each model mimics some aspects of the disease, but none captures the full range of symptoms. This review helps highlight research pathways that may illuminate treatments for this complex and debilitating adult-onset disease.

Transcription factor EB overexpression prevents neurodegeneration in experimental synucleinopathies

The synucleinopathies Parkinson’s disease (PD) and Multiple system atrophy (MSA) — characterized by α-synuclein intracytoplasmic inclusions into, respectively, neurons and oligodendrocytes — are associated with impairment of the autophagy-lysosomal pathways (ALP). Increased expression of the master regulator of ALP, transcription factor EB (TFEB), is hypothesized to promote the clearance of WT α-synuclein and survival of dopaminergic neurons. Here, we explore the efficacy of targeted TFEB overexpression either in neurons or oligodendrocytes to reduce the pathological burden of α-synuclein in a PD rat model and a MSA mouse model. While TFEB neuronal expression was sufficient to prevent neurodegeneration in the PD model, we show that only TFEB oligodendroglial overexpression leads to neuroprotective effects in the MSA model. These beneficial effects were associated with a decreased accumulation of α-synuclein into oligodendrocytes through recovery of the ALP machinery. Our study demonstrates that the cell type where α-synuclein aggregates dictates the target of TFEB overexpression in order to be protective, paving the way for adapted therapies.

Targeted overexpression of transcription factor EB (TFEB) decreases accumulation of α-synuclein and prevents neurodegeneration in animal models of synucleinopathies.

Induced pluripotent stem cells in multiple system atrophy: recent developments and scientific challenges

Multiple system atrophy (MSA) is a rare and fatal neurodegenerative disease, with no known genetic cause to date. Oligodendroglial α-synuclein accumulation, neuroinflammation, and early myelin dysfunction are hallmark features of the disease and have been modeled in part in various preclinical models of MSA, yet the pathophysiology of MSA remains elusive. Here, we review the role and scientific challenges of induced pluripotent stem cells in the detection of novel biomarkers and druggable targets in MSA.

The molecular tweezer CLR01 reduces aggregated, pathologic, and seeding-competent α-synuclein in experimental multiple system atrophy

Multiple system atrophy (MSA) is a fatal, adult-onset neurodegenerative disorder that has no cure and very limited treatment options. MSA is characterized by deposition of fibrillar α-synuclein (α-syn) in glial cytoplasmic inclusions in oligodendrocytes. Similar to other synucleinopathies, α-syn self-assembly is thought to be a key pathologic event and a prominent target for disease modification in MSA. Molecular tweezers are broad-spectrum nanochaperones that prevent formation of toxic protein assemblies and enhance their clearance. The current lead compound, CLR01, has been shown to inhibit α-syn aggregation but has not yet been tested in the context of MSA. To fill this gap, here, we conducted a proof-of-concept study to assess the efficacy of CLR01 in remodeling MSA-like α-syn pathology in the PLP-α-syn mouse model of MSA. Six-month-old mice received intracerebroventricular CLR01 (0.3 or 1 mg/kg per day) or vehicle for 32 days. Open-field test revealed a significant, dose-dependent amelioration of an anxiety-like phenotype. Subsequently, immunohistochemical and biochemical analyses showed dose-dependent reduction of pathological and seeding-competent forms of α-syn, which correlated with the behavioral phenotype. CLR01 treatment also promoted dopaminergic neuron survival in the substantia nigra. To our knowledge, this is the first demonstration of an agent that reduces formation of putative high-molecular-weight oligomers and seeding-competent α-syn in a mouse model of MSA, supporting the view that these species are key to the neurodegenerative process and its cell-to-cell progression in MSA. Our study suggests that CLR01 is an attractive therapeutic candidate for disease modification in MSA and related synucleinopathies, supporting further preclinical development.

Neuropathology and pathogenesis of extrapyramidal movement disorders: a critical update-I. Hypokinetic-rigid movement disorders

Extrapyramidal movement disorders include hypokinetic rigid and hyperkinetic or mixed forms, most of them originating from dysfunction of the basal ganglia (BG) and their information circuits. The functional anatomy of the BG, the cortico-BG-thalamocortical, and BG-cerebellar circuit connections are briefly reviewed. Pathophysiologic classification of extrapyramidal movement disorder mechanisms distinguish (1) parkinsonian syndromes, (2) chorea and related syndromes, (3) dystonias, (4) myoclonic syndromes, (5) ballism, (6) tics, and (7) tremor syndromes. Recent genetic and molecular-biologic classifications distinguish (1) synucleinopathies (Parkinson's disease, dementia with Lewy bodies, Parkinson's disease-dementia, and multiple system atrophy); (2) tauopathies (progressive supranuclear palsy, corticobasal degeneration, FTLD-17; Guamian Parkinson-dementia; Pick's disease, and others); (3) polyglutamine disorders (Huntington's disease and related disorders); (4) pantothenate kinase-associated neurodegeneration; (5) Wilson's disease; and (6) other hereditary neurodegenerations without hitherto detected genetic or specific markers. The diversity of phenotypes is related to the deposition of pathologic proteins in distinct cell populations, causing neurodegeneration due to genetic and environmental factors, but there is frequent overlap between various disorders. Their etiopathogenesis is still poorly understood, but is suggested to result from an interaction between genetic and environmental factors. Multiple etiologies and noxious factors (protein mishandling, mitochondrial dysfunction, oxidative stress, excitotoxicity, energy failure, and chronic neuroinflammation) are more likely than a single factor. Current clinical consensus criteria have increased the diagnostic accuracy of most neurodegenerative movement disorders, but for their definite diagnosis, histopathological confirmation is required. We present a timely overview of the neuropathology and pathogenesis of the major extrapyramidal movement disorders in two parts, the first one dedicated to hypokinetic-rigid forms and the second to hyperkinetic disorders.

Neuroinflammation and Glial Phenotypic Changes in Alpha-Synucleinopathies

The role of neuroinflammation has been increasingly recognized in the field of neurodegenerative diseases. Many studies focusing on the glial cells involved in the inflammatory responses of the brain, namely microglia and astroglia, have over the years pointed out the dynamic and changing behavior of these cells, accompanied by different morphologies and activation forms. This is particularly evident in diseased conditions, where glia react to any shift from homeostasis, acquiring different phenotypes. Particularly for microglia, it has soon become clear that such phenotypes are multiple, as multiple are the functions related to them. Several approaches have over time revealed different facets of microglial phenotypic diversity, and advanced genetic analyses, in recent years, have added new insights into microglial heterogeneity, opening novel scenarios that researchers have just started to explore. Among neurodegenerative diseases, an important section is represented by alpha-synucleinopathies. Here alpha-synuclein accumulates abnormally in the brain and, depending on its pattern of distribution, leads to the development of different clinical conditions. Also for these proteinopathies, neuroinflammation and glial activation have been identified as constant and crucial factors during disease development. In the present review we will address the current literature about glial phenotypic changes with respect to alpha-synucleinopathies, as well as consider the pathophysiological and therapeutic implications of such a dynamic cellular behavior.

L-dopa response pattern in a rat model of mild striatonigral degeneration

Background

Unresponsiveness to dopaminergic therapies is a key feature in the diagnosis of multiple system atrophy (MSA) and a major unmet need in the treatment of MSA patients caused by combined striatonigral degeneration (SND). Transgenic, alpha-synuclein animal models do not recapitulate this lack of levodopa responsiveness. In order to preclinically study interventions including striatal cell grafts, models that feature SND are required. Most of the previous studies focused on extensive nigral and striatal lesions corresponding to advanced MSA-P/SND. The aim of the current study was to replicate mild stage MSA-P/SND with L-dopa failure.

Methods and results

Two different striatal quinolinic acid (QA) lesions following a striatal 6-OHDA lesion replicating mild and severe MSA-P/SND, respectively, were investigated and compared to 6-OHDA lesioned animals. After the initial 6-OHDA lesion there was a significant improvement of motor performance after dopaminergic stimulation in the cylinder and stepping test (p<0.001). Response to L-dopa treatment declined in both MSA-P/SND groups reflecting striatal damage of lateral motor areas in contrast to the 6-OHDA only lesioned animals (p<0.01). The remaining striatal volume correlated strongly with contralateral apomorphine induced rotation behaviour and contralateral paw use during L-dopa treatment in cylinder and stepping test (p<0.001).

Conclusion

Our novel L-dopa response data suggest that L-dopa failure can be induced by restricted lateral striatal lesions combined with dopaminergic denervation. We propose that this sequential striatal double-lesion model replicates a mild stage of MSA-P/SND and is suitable to address neuro-regenerative therapies aimed at restoring dopaminergic responsiveness.

Cerebrospinal fluid cytokines in multiple system atrophy: A cross-sectional Catalan MSA registry study

INTRODUCTION

Neuroinflammation is a potential player in neurodegenerative conditions, particularly the aggressive ones, such as multiple system atrophy (MSA). Previous reports on cytokine levels in MSA using serum or cerebrospinal fluid (CSF) have been inconsistent, including small samples and a limited number of cytokines, often without comparison to Parkinson's disease (PD), a main MSA differential diagnosis.

METHODS

Cross-sectional study of CSF levels of 38 cytokines using a multiplex assay in 73 participants: 39 MSA patients (19 with parkinsonian type [MSAp], 20 with cerebellar type [MSAc]; 31 probable, 8 possible), 19 PD patients and 15 neurologically unimpaired controls. None of the participants was under non-steroidal anti-inflammatory drugs at the time of the lumbar puncture.

RESULTS

There were not significant differences in sex and age among participants. In global non-parametric comparisons FDR-corrected for multiple comparisons, CSF levels of 5 cytokines (FGF-2, IL-10, MCP-3, IL-12p40, MDC) differed among the three groups. In pair-wise FDR-corrected non-parametric comparisons 12 cytokines (FGF-2, eotaxin, fractalkine, IFN-α2, IL-10, MCP-3, IL-12p40, MDC, IL-17, IL-7, MIP-1β, TNF-α) were significantly higher in MSA vs. non-MSA cases (PD + controls pooled together). Of these, MCP-3 and MDC were the most significant ones, also differed in MSA vs. PD, and were significant MSA-predictors in binary logistic regression models and ROC curves adjusted for age. CSF levels of fractalkine and MIP-1α showed a strong and significant positive correlation with UMSARS-2 scores.

CONCLUSION

Increased CSF levels of cytokines such as MCP-3, MDC, fractalkine and MIP-1α deserve consideration as potential diagnostic or severity biomarkers of MSA.

Iron in Neurodegeneration - Cause or Consequence?

Iron dyshomeostasis can cause neuronal damage to iron-sensitive brain regions. Neurodegeneration with brain iron accumulation reflects a group of disorders caused by iron overload in the basal ganglia. High iron levels and iron related pathogenic triggers have also been implicated in sporadic neurodegenerative diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and multiple system atrophy (MSA). Iron-induced dyshomeostasis within vulnerable brain regions is still insufficiently understood. Here, we summarize the modes of action by which iron might act as primary or secondary disease trigger in neurodegenerative disorders. In addition, available treatment options targeting brain iron dysregulation and the use of iron as biomarker in prodromal stages are critically discussed to address the question of cause or consequence.

Anle138b modulates α-synuclein oligomerization and prevents motor decline and neurodegeneration in a mouse model of multiple system atrophy

Background

MSA is a fatal neurodegenerative disease characterized by autonomic failure and severe motor impairment. Its main pathological hallmark is the accumulation of α‐synuclein in oligodendrocytes, leading to glial and neuronal dysfunction and neurodegeneration. These features are recapitulated in the PLP‐hαSyn mouse model expressing human α‐synuclein in oligodendrocytes. At present, there is no effective disease‐modifying therapy. Previous experiments have shown that the aggregation inhibitor, anle138b, reduces neurodegeneration and behavioral deficits in mouse models of other proteinopathies.

Objectives

To test the therapeutic potential of anle138b in a mouse model of MSA.

Methods

Two‐month‐old PLP‐hαSyn mice were fed over a period of 4 months with pellets containing anle138b at two different doses (0.6 and 2 g/kg) and compared to healthy controls and PLP‐hαSyn mice fed with placebo pellets. At the end of the treatment, behavioral and histological analyses were performed.

Results

We observed a reversal of motor function to healthy control levels when PLP‐hαSyn mice were treated with both doses of anle138b. Histological and molecular analyses showed a significant reduction in α‐synuclein oligomers and glial cytoplasmic inclusions in animals fed with anle138b compared to nontreated mice. These animals also present preservation of dopaminergic neurons and reduction in microglial activation in SN correlating with the α‐synuclein reduction observed.

Conclusions

Anle138b reduces α‐synuclein accumulation in PLP‐hαSyn mice, leading to neuroprotection, reduction of microglial activation, and preservation of motor function supporting the use of anle138b in a future clinical trial for MSA. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Region-Specific Effects of Immunotherapy With Antibodies Targeting α-synuclein in a Transgenic Model of Synucleinopathy

Synucleinopathies represent a group of neurodegenerative disorders which are characterized by intracellular accumulation of aggregated α-synuclein. α-synuclein misfolding and oligomer formation is considered a major pathogenic trigger in these disorders. Therefore, targeting α-synuclein species represents an important candidate therapeutic approach. Our aim was to analyze the biological effects of passive immunization targeting α-synuclein and to identify the possible underlying mechanisms in a transgenic mouse model of oligodendroglial α-synucleinopathy. We used PLP-α-synuclein mice overexpressing human α-synuclein in oligodendrocytes. The animals received either antibodies that recognize α-synuclein or vehicle. Passive immunization mitigated α-synuclein pathology and resulted in reduction of total α-synuclein in the hippocampus, reduction of intracellular accumulation of aggregated α-synuclein, particularly significant in the spinal cord. Lowering of the extracellular oligomeric α-synuclein was associated with reduction of the density of activated iba1-positive microglia profiles. However, a shift toward phagocytic microglia was seen after passive immunization of PLP-α-synuclein mice. Lowering of intracellular α-synuclein was mediated by autophagy degradation triggered after passive immunization in PLP-α-synuclein mice. In summary, the study provides evidence for the biological efficacy of immunotherapy in a transgenic mouse model of oligodendroglial synucleinopathy. The different availability of the therapeutic antibodies and the variable load of α-synuclein pathology in selected brain regions resulted in differential effects of the immunotherapy that allowed us to propose a model of the underlying mechanisms of antibody-aided α-synuclein clearance.