Functional Study of SNCA p.V15A Variant: Further Linking α-Synuclein and Glucocerebrosidase.

BACKGROUND: SNCA p.V15A was reported in five families. In vitro models showed increased aggregation and seeding activity, mitochondrial damage, and apoptosis. Mutant flies had reduced flying ability and survival. OBJECTIVES: To clinically and functionally evaluate SNCA p.V15A in a large Italian family with Parkinson's disease (PD). METHODS: Genetic diagnosis was reached through next-generation sequencing. Pathogenicity was assessed by molecular dynamics simulation and biochemical studies on peripheral blood mononuclear cells (PBMCs). RESULTS: Five siblings carried SNCA p.V15A; three developed bradykinetic-rigid PD in their 50s with rapid motor progression and variable cognitive impairment. A fourth sibling had isolated mood disturbance, whereas the fifth was still unaffected at age 47. The mutant protein showed decreased stability and an unstable folded structure. Proband's PBMCs showed elevated total and phosphorylated α-synuclein (α-syn) levels and significantly reduced glucocerebrosidase activity. CONCLUSION: This study demonstrates accumulation of α-synV15A in PBMCs and strengthens the link between α-syn pathophysiology and glucocerebrosidase dysfunction. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Impaired Mitochondrial Respiration in REM-Sleep Behavior Disorder: A Biomarker of Parkinson's Disease?

BACKGROUND: Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is associated with prodromal Parkinson's disease (PD), but the mechanisms linking phenoconversion of iRBD to PD have not yet been clarified. Considering the association between mitochondrial dysfunction and sleep disturbances in PD, we explored mitochondrial activity in fibroblasts derived from iRBD patients to identify a biochemical profile that could mark the presence of impending neurodegeneration. METHODS: The study involved 28 participants, divided into three groups: patients diagnosed with iRBD, PD patients converted from iRBD (RBD-PD), and healthy controls. We performed a comprehensive assessment of mitochondrial function, including an examination of mitochondrial morphology, analysis of mitochondrial protein expression levels by western blot, and measurement of mitochondrial respiration using the Seahorse XFe24 analyzer. RESULTS: In basal conditions, mitochondrial respiration did not differ between iRBD and control fibroblasts, but when cells were challenged with a higher energy demand, iRBD fibroblasts exhibited a significant (P = 0.006) drop in maximal and spare respiration compared to controls. Interestingly, RBD-PD patients showed the same alterations with a further significant reduction in oxygen consumption linked to adenosine triphosphate production (P = 0.032). Moreover, RBD-PD patients exhibited a significant decrease in protein levels of complexes III (P = 0.02) and V (P = 0.002) compared to controls, along with fragmentation of the mitochondrial network. iRBD patients showed similar, but milder alterations. CONCLUSIONS: Altogether, these findings suggest that mitochondrial dysfunctions in individuals with iRBD might predispose to worsening of the bioenergetic profile observed in RBD-PD patients, highlighting these alterations as potential predictors of phenoconversion to PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Ambroxol as a disease-modifying treatment to reduce the risk of cognitive impairment in GBA-associated Parkinson's disease: a multicentre, randomised, double-blind, placebo-controlled, phase II trial. The AMBITIOUS study protocol.

Background: Heterozygous mutations in the GBA gene, encoding the lysosomal enzyme ß-glucocerebrosidase (GCase), are the most frequent genetic risk factor for Parkinson's disease (PD). GBA-related PD (GBA-PD) patients have higher risk of dementia and reduced survival than non-carriers. Preclinical studies and one open-label trial in humans demonstrated that the chaperone ambroxol (ABX) increases GCase levels and modulates α-synuclein levels in the blood and cerebrospinal fluid (CSF). Methods and analysis: In this multicentre, double-blind, placebo-controlled, phase II clinical trial, we randomise patients with GBA-PD in a 1:1 ratio to either oral ABX 1.2 g/day or placebo. The duration of treatment is 52 weeks. Each participant is assessed at baseline and weeks 12, 26, 38, 52 and 78. Changes in the Montreal Cognitive Assessment score and the frequency of mild cognitive impairment and dementia between baseline and weeks 52 are the primary outcome measures. Secondary outcome measures include changes in validated scales/questionnaires assessing motor and non-motor symptoms. Neuroimaging features and CSF neurodegeneration markers are used as surrogate markers of disease progression. GCase activity, ABX and α-synuclein levels are also analysed in blood and CSF. A repeated-measures analysis of variance will be used for elaborating results. The primary analysis will be by intention to treat. Ethics and dissemination: The study and protocols have been approved by the ethics committee of centres. The study is conducted according to good clinical practice and the Declaration of Helsinki. The trial findings will be published in peer-reviewed journals and presented at conferences. Trial registration numbers: NCT05287503, EudraCT 2021-004565-13.

Neuroprotective and Symptomatic Effects of Cannabidiol in an Animal Model of Parkinson's Disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the Substantia Nigra pars compacta, leading to classical PD motor symptoms. Current therapies are purely symptomatic and do not modify disease progression. Cannabidiol (CBD), one of the main phytocannabinoids identified in Cannabis Sativa, which exhibits a large spectrum of therapeutic properties, including anti-inflammatory and antioxidant effects, suggesting its potential as disease-modifying agent for PD. The aim of this study was to evaluate the effects of chronic treatment with CBD (10 mg/kg, i.p.) on PD-associated neurodegenerative and neuroinflammatory processes, and motor deficits in the 6-hydroxydopamine model. Moreover, we investigated the potential mechanisms by which CBD exerted its effects in this model. CBD-treated animals showed a reduction of nigrostriatal degeneration accompanied by a damping of the neuroinflammatory response and an improvement of motor performance. In particular, CBD exhibits a preferential action on astrocytes and activates the astrocytic transient receptor potential vanilloid 1 (TRPV1), thus, enhancing the endogenous neuroprotective response of ciliary neurotrophic factor (CNTF). These results overall support the potential therapeutic utility of CBD in PD, as both neuroprotective and symptomatic agent.

GBA Mutations Influence the Release and Pathological Effects of Small Extracellular Vesicles from Fibroblasts of Patients with Parkinson's Disease.

Heterozygous mutations in the GBA gene, encoding the lysosomal enzyme glucocerebrosidase (GCase), are the strongest known genetic risk factor for Parkinson's disease (PD). The molecular mechanisms underlying the increased PD risk and the variable phenotypes observed in carriers of different GBA mutations are not yet fully elucidated. Extracellular vesicles (EVs) have gained increasing importance in neurodegenerative diseases since they can vehiculate pathological molecules potentially promoting disease propagation. Accumulating evidence showed that perturbations of the endosomal-lysosomal pathway can affect EV release and composition. Here, we investigate the impact of GCase deficiency on EV release and their effect in recipient cells. EVs were purified by ultracentrifugation from the supernatant of fibroblast cell lines derived from PD patients with or without GBA mutations and quantified by nanoparticle tracking analysis. SH-SY5Y cells over-expressing alpha-synuclein (α-syn) were used to assess the ability of patient-derived small EVs to affect α-syn expression. We observed that defective GCase activity promotes the release of EVs, independently of mutation severity. Moreover, small EVs released from PD fibroblasts carrying severe mutations increased the intra-cellular levels of phosphorylated α-syn. In summary, our work shows that the dysregulation of small EV trafficking and alpha-synuclein mishandling may play a role in GBA-associated PD.

Profiling the Biochemical Signature of GBA-Related Parkinson's Disease in Peripheral Blood Mononuclear Cells.

BACKGROUND: GBA mutations are the commonest genetic risk factor for Parkinson's disease (PD) and also impact disease progression. OBJECTIVE: The objective of this study was to define a biochemical profile that could distinguish GBA-PD from non-mutated PD. METHODS: 29 GBA-PD, 37 non-mutated PD, and 40 controls were recruited; α-synuclein levels in plasma, exosomes, and peripheral blood mononuclear cells were analyzed, GCase and main GCase-related lysosomal proteins in peripheral blood mononuclear cells were measured. RESULTS: Assessment of plasma and exosomal α-synuclein levels did not allow differentiation between GBA-PD and non-mutated PD; conversely, measurements in peripheral blood mononuclear cells clearly distinguished GBA-PD from non-mutated PD, with the former group showing significantly higher α-synuclein levels, lower GCase activity, higher LIMP-2, and lower Saposin C levels. CONCLUSION: We propose peripheral blood mononuclear cells as an easily accessible and manageable model to provide a distinctive biochemical profile of GBA-PD, potentially useful for patient stratification or selection in clinical trials. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.