Model Of Multiple System Atrophy Research Articles

CSF1R-mediated myeloid cell depletion shifts the ratio of motor cortical excitatory to inhibitory neurons in a multiple system atrophy model

Motor cortical circuit functions depend on the coordinated fine-tuning of two functionally diverse neuronal populations: glutamatergic pyramidal neurons providing synaptic excitation and GABAergic interneurons adjusting the response of pyramidal neurons through synaptic inhibition. Microglia are brain resident macrophages which dynamically refine cortical circuits by monitoring perineuronal extracellular matrix and remodelling synapses. Previously, we showed that colony-stimulating factor 1 receptor (CSF1R)-mediated myeloid cell depletion extended the lifespan, but impaired motor functions of MBP29 mice, a mouse model for multiple system atrophy. In order to better understand the mechanisms underlying these motor deficits we characterized the microglial involvement in the cortical balance of GABAergic interneurons and glutamatergic pyramidal neurons in 4-months-old MBP29 mice following CSF1R inhibition for 12 weeks. Lack of myeloid cells resulted in a decreased number of COUP TF1 interacting protein 2-positive (CTIP2+) layer V pyramidal neurons, however in a proportional increase of calretinin-positive GABAergic interneurons in MBP29 mice. While myeloid cell depletion did not alter the expression of important presynaptic and postsynaptic proteins, the loss of cortical perineuronal net area was attenuated by CSF1R inhibition in MBP29 mice. These cortical changes may restrict synaptic plasticity and potentially modify parvalbumin-positive perisomatic input. Collectively, this study suggests, that the lack of myeloid cells shifts the neuronal balance toward an increased inhibitory connectivity in the motor cortex of MBP29 mice thereby potentially deteriorating motor functions.

IFNγ drives neuroinflammation, demyelination, and neurodegeneration in a mouse model of multiple system atrophy

Multiple system atrophy (MSA) is a rare and fatal synucleinopathy characterized by insoluble alpha-synuclein (α-syn) cytoplasmic inclusions located within oligodendroglia. Neuroinflammation, demyelination, and neurodegeneration are correlated with areas of glia cytoplasmic inclusions (GCI) pathology, however it is not known what specifically drives disease pathogenesis. Recent studies have shown that disease pathologies found in post-mortem tissue from MSA patients can be modeled in rodents via a modified AAV overexpressing α-syn, Olig001-SYN, which has a 95% tropism for oligodendrocytes. In the Olig001-SYN mouse model, CD4+ T cells have been shown to drive neuroinflammation and demyelination, however the mechanism by which this occurs remains unclear. In this study we use genetic and pharmacological approaches in the Olig001-SYN model of MSA to show that the pro-inflammatory cytokine interferon gamma (IFNγ) drives neuroinflammation, demyelination, and neurodegeneration. Furthermore, using an IFNγ reporter mouse, we found that infiltrating CD4+ T cells were the primary producers of IFNγ in response to α-syn overexpression in oligodendrocytes. Results from these studies indicate that IFNγ expression from CD4+ T cells drives α-syn-mediated neuroinflammation, demyelination, and neurodegeneration. These results indicate that targeting IFNγ expression may be a potential disease modifying therapeutic strategy for MSA.

Sobetirome rescues α-synuclein-mediated demyelination in an in vitro model of multiple system atrophy.

Multiple system atrophy (MSA) is a rare and rapidly progressive atypical parkinsonian disorder characterized by oligodendroglial cytoplasmic inclusions containing α-synuclein (α-syn), demyelination, inflammation and neuronal loss. To date, no disease-modifying therapy is available. Targeting α-syn-driven oligodendroglial dysfunction and demyelination presents a potential therapeutic approach for restricting axonal dysfunction, neuronal loss and disease progression. The present study investigated the promyelinogenic potential of sobetirome, a blood-brain barrier permeable and central nervous system selective thyromimetic in the context of an in vitro MSA model. Oligodendrocyte precursor cells (OPCs) were obtained from transgenic mice overexpressing human α-syn specifically in oligodendrocytes (MBP29 mouse line), a well-described MSA model, and non-transgenic littermates. mRNA and protein expression analyses revealed a substantial rescue effect of sobetirome on myelin-specific proteins in control and α-syn overexpressing oligodendrocytes. Furthermore, myelination analysis using nanofibres confirmed that sobetirome increases both the length and number of myelinated segments per oligodendrocyte in primary murine α-syn overexpressing oligodendrocytes and their respective control. These results suggest that sobetirome may be a promising thyromimetic compound targeting an important neuropathological hallmark of MSA.

Activation of Pgk1 Results in Reduced Protein Aggregation in Diverse Neurodegenerative Conditions.

The prevention of protein condensates has emerged as a new drug target to treat diverse neurodegenerative disorders. We previously reported that terazosin (TZ), a prescribed antagonist of the α1 adrenergic receptor, is an activator of phosphoglycerate kinase 1 (Pgk1) and Hsp90. In this study, we aimed to determine whether TZ prevents the formation of diverse pathological condensates in cell cultures and animal disease models. In primary neuron culture, TZ treatment reduced both the protein density and abundance of fused in sarcoma (FUS)-P525L-GFP, a disease-associated mutant form of FUS. Regarding the mechanism, we found that increased intracellular ATP levels were critical for the reduction in protein aggregate density. In addition, Hsp90 activation by TZ enhanced Hsp90 interaction with ULK1, a master regulator of autophagy. Through in vivo studies, we examined neuron-specific overexpression of tau in Drosophila, mouse models of APP/PS1 Alzheimer's disease (AD), and a rat model of multiple system atrophy (MSA) via the viral expression of α-synuclein in the striatum. TZ prevented and reversed the formation of pathological protein condensates. Together, our results suggest that activation of Pgk1 in cytosol may dissolve pathological protein aggregates via increased ATP levels and degrade these proteins via autophagy; the FUS-P525L degradation pathway in nucleus is unclear.

GRK2-Targeted Knockdown as Therapy for Multiple System Atrophy.

Multiple system atrophy (MSA) is a sporadic adult-onset rare neurodegenerative synucleinopathy for which counteracting central nervous system insulin resistance bears the potential of being neuroprotective. G-protein-(heterotrimeric guanine nucleotide-binding protein)-coupled receptor kinase 2 (GRK2) is emerging as a physiologically relevant inhibitor of insulin signaling. We tested whether lowering brain GRK2 abundance may reverse insulin-resistance. We lowered brain GRK2 abundance through viral-mediated delivery of a GRK2-specific miRNA and quantified the reversion of a developing or an established insulin-resistant phenotype using the transgenic PLP-SYN mouse model of MSA. Viral vector delivery of a GRK2 miRNA demonstrated a neuroprotective capacity when administered (1) in utero intracerebroventricularly in developing PLP-SYN mice and (2) intrastriatally in adult PLP-SYN mice. Decreased striatal GRK2 levels correlated in both designs with neuroprotection of the substantia nigra dopamine neurons, reduction in high-molecular-weight species of α-synuclein, and reduced insulin resistance. These data support GRK2 as a potential therapeutic target in MSA. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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 currentlylacking. 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 geneticand neuropathological studiesas well as studies in experimental models of MSA have indicated the involvement ofgenetic and epigenetic changes; α-synuclein misfolding, aggregationand spreading; and α-synucleinstrain 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 itsimpact on biomarker discovery and treatment target definitions.

Parkinson's disease or multiple system atrophy: potential separation by quantitative susceptibility mapping.

Due to the absence of robust biomarkers, and the low sensitivity and specificity of routine imaging techniques, the differential diagnosis between Parkinson's disease (PD) and multiple system atrophy (MSA) is challenging. High-field magnetic resonance imaging (MRI) opened up new possibilities regarding the analysis of pathological alterations associated with neurodegenerative processes. Recently, we have shown that quantitative susceptibility mapping (QSM) enables visualization and quantification of two major histopathologic hallmarks observed in MSA: reduced myelin density and iron accumulation in the basal ganglia of a transgenic murine model of MSA. It is therefore emerging as a promising imaging modality on the differential diagnosis of Parkinsonian syndromes. To assess QSM on high-field MRI for the differential diagnosis of PD and MSA. We assessed 23 patients (nine PDs and 14 MSAs) and nine controls using QSM on 3T and 7T MRI scanners at two academic centers. We observed increased susceptibility in MSA at 3T in prototypical subcortical and brainstem regions. Susceptibility measures of putamen, pallidum, and substantia nigra reached excellent diagnostic accuracy to separate both synucleinopathies. Increase toward 100% sensitivity and specificity was achieved using 7T MRI in a subset of patients. Magnetic susceptibility correlated with age in all groups, but not with disease duration in MSA. Sensitivity and specificity were particularly high for possible MSA, and reached 100% in the putamen. Putaminal susceptibility measures, in particular on ultra-high-field MRI, may distinguish MSA patients from both, PD and controls, allowing an early and sensitive diagnosis of MSA.

Phosphorylation of Tau at Threonine 231 in Patients With Multiple System Atrophy and in a Mouse Model.

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder pathologically characterized by the presence of glial cytoplasmic inclusions (GCIs). Some MSA patients exhibit motor deficits with accompanying cognitive impairment. Of note, some patients suffering from MSA with longer disease duration have AT8-positive signals, which correspond to phosphorylated tau (P-tau) at 202/205 (P-tau202/205). However, P-tau sites other than the AT8 antibody epitope antibody are less well studied. Here, we focused on the effect of α-synuclein (Syn) expression on the phosphorylation of tau in MSA model mice. Among the 6 kinds of antibodies against P-tau, we confirmed that antibodies against P-tau at 231 (P-tau231) were phospho-specific and found that P-tau231 level was increased in parallel with disease progression in MSA model mice. Additional studies of human brains revealed that P-tau231 was mainly expressed in the temporal cortex in MSA brains and that its expression level was significantly higher in MSA patients than in controls. Immunohistochemical analysis showed that anti-P-tau231-, but not AT8, antibodies mainly immunolabeled hippocampal CA2/3 pyramidal neurons, and some GCIs in MSA. These data suggest that P-tau231 occurs in MSA differently from P-tau202/205.

CSF1R-Mediated Myeloid Cell Depletion Prolongs Lifespan But Aggravates Distinct Motor Symptoms in a Model of Multiple System Atrophy.

As the CNS-resident macrophages and member of the myeloid lineage, microglia fulfill manifold functions important for brain development and homeostasis. In the context of neurodegenerative diseases, they have been implicated in degenerative and regenerative processes. The discovery of distinct activation patterns, including increased phagocytosis, indicated a damaging role of myeloid cells in multiple system atrophy (MSA), a devastating, rapidly progressing atypical parkinsonian disorder. Here, we analyzed the gene expression profile of microglia in a mouse model of MSA (MBP29-hα-syn) and identified a disease-associated expression profile and upregulation of the colony-stimulating factor 1 (Csf1). Thus, we hypothesized that CSF1 receptor-mediated depletion of myeloid cells using PLX5622 modifies the disease progression and neuropathological phenotype in this mouse model. Intriguingly, sex-balanced analysis of myeloid cell depletion in MBP29-hα-syn mice revealed a two-faced outcome comprising an improved survival rate accompanied by a delayed onset of neurological symptoms in contrast to severely impaired motor functions. Furthermore, PLX5622 reversed gene expression profiles related to myeloid cell activation but reduced gene expression associated with transsynaptic signaling and signal release. While transcriptional changes were accompanied by a reduction of dopaminergic neurons in the SNpc, striatal neuritic density was increased upon myeloid cell depletion in MBP29-hα-syn mice. Together, our findings provide insight into the complex, two-faced role of myeloid cells in the context of MSA emphasizing the importance to carefully balance the beneficial and adverse effects of CSF1R inhibition in different models of neurodegenerative disorders before its clinical translation.SIGNIFICANCE STATEMENT Myeloid cells have been implicated as detrimental in the disease pathogenesis of multiple system atrophy. However, long-term CSF1R-dependent depletion of these cells in a mouse model of multiple system atrophy demonstrates a two-faced effect involving an improved survival associated with a delayed onset of disease and reduced inflammation which was contrasted by severely impaired motor functions, synaptic signaling, and neuronal circuitries. Thus, this study unraveled a complex role of myeloid cells in multiple system atrophy, which indicates important functions beyond the previously described disease-associated, destructive phenotype and emphasized the need of further investigation to carefully and individually fine-tune immunologic processes in different neurodegenerative diseases.

Pathological substrate of memory impairment in multiple system atrophy.

Synaptic dysfunction in Parkinson's disease is caused by propagation of pathogenic α-synuclein between neurons. Previously, in multiple system atrophy (MSA), pathologically characterised by ectopic deposition of abnormal α-synuclein predominantly in oligodendrocytes, we demonstrated that the occurrence of memory impairment was associated with the number of α-synuclein-positive neuronal cytoplasmic inclusions (NCIs) in the hippocampus. In the present study, we aimed to investigate how abnormal α-synuclein in the hippocampus can lead to memory impairment. We performed pathological and biochemical analyses using a mouse model of adult-onset MSA and human cases (MSA, N = 25; Parkinson's disease, N = 3; Alzheimer's disease, N = 2; normal controls, N = 11). In addition, the MSA model mice were examined behaviourally and physiologically. In the MSA model, inducible human α-synuclein was first expressed in oligodendrocytes and subsequently accumulated in the cytoplasm of excitatory hippocampal neurons (NCI-like structures) and their presynaptic nerve terminals with the development of memory impairment. α-Synuclein oligomers increased simultaneously in the hippocampus of the MSA model. Hippocampal dendritic spines also decreased in number, followed by suppression of long-term potentiation. Consistent with these findings obtained in the MSA model, post-mortem analysis of human MSA brain tissues showed that cases of MSA with memory impairment developed more NCIs in excitatory hippocampal neurons along with α-synuclein oligomers than those without. Our results provide new insights into the role of α-synuclein oligomers as a possible pathological cause of memory impairment in MSA.

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.

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.

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.

Prolyl oligopeptidase inhibition reduces alpha-synuclein aggregation in a cellular model of multiple system atrophy.

Multiple system atrophy (MSA) is a fatal neurodegenerative disease where the histopathological hallmark is glial cytoplasmic inclusions in oligodendrocytes, rich of aggregated alpha‐synuclein (aSyn). Therefore, therapies targeting aSyn aggregation and toxicity have been studied as a possible disease‐modifying therapy for MSA. Our earlier studies show that inhibition of prolyl oligopeptidase (PREP) with KYP‐2047 reduces aSyn aggregates in several models. Here, we tested the effects of KYP‐2047 on a MSA cellular models, using rat OLN‐AS7 and human MO3.13 oligodendrocyte cells. As translocation of p25α to cell cytosol has been identified as an inducer of aSyn aggregation in MSA models, the cells were transiently transfected with p25α. Similar to earlier studies, p25α increased aSyn phosphorylation and aggregation, and caused tubulin retraction and impaired autophagy in OLN‐AS7 cells. In both cellular models, p25α transfection increased significantly aSyn mRNA levels and also increased the levels of inactive protein phosphatase 2A (PP2A). However, aSyn or p25α did not cause any cellular death in MO3.13 cells, questioning their use as a MSA model. Simultaneous administration of 10 µM KYP‐2047 improved cell viability, decreased insoluble phosphorylated aSyn and normalized autophagy in OLN‐AS7 cells but similar impact was not seen in MO3.13 cells.

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

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

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.

Targeting \u03b1-synuclein by PD03 AFFITOPE\xae and Anle138b rescues neurodegenerative pathology in a model of multiple system atrophy: clinical relevance

BackgroundMisfolded 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.MethodsThe 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.ResultsThe 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.ConclusionsPD03 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.

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.

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

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. 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. 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. 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.

Quantitative susceptibility mapping depicts severe myelin deficit and iron deposition in a transgenic model of multiple system atrophy

Despite internationally established diagnostic criteria, multiple system atrophy (MSA) is frequently misdiagnosed, particularly at disease onset. While neuropathological changes such as demyelination and iron deposition are typically detected in MSA, these structural hallmarks were so far only demonstrated post-mortem. Here, we examine whether myelin deficit observed in a transgenic murine model of MSA can be visualized and quantified in vivo using specific magnetic resonance imaging (MRI) approaches. Reduced myelin content was measured histologically in prototypical white matter as well as mixed grey-white matter regions i.e. corpus callosum, anterior commissure, and striatum of transgenic mice overexpressing human α-synuclein under the control of the myelin basic protein promotor (MBP29-hα-syn mice). Correspondingly, in vivo quantitative susceptibility mapping (QSM) showed a strongly reduced susceptibility contrast in white matter regions and T2-weighted MR imaging revealed a significantly reduced grey-white matter contrast in MBP29-hα-syn mice. In addition, morphological analysis suggested a pronounced, white matter-specific deposition of iron in MBP29-hα-syn mice. Importantly, in vivo MRI results were matched by comprehensive structural characterization of myelin, iron, and axonal directionality. Taken together, our results provide strong evidence that QSM is a very sensitive tool measuring changes in myelin density in conjunction with iron deposition in MBP29-hα-syn mice. This multimodal neuroimaging approach may pave the way towards a novel non-invasive technique to detect crucial neuropathological changes specifically associated with MSA.