LRRK2 Quantification in Cerebrospinal Fluid of Patients with Parkinson's Disease and Atypical Parkinsonian Syndromes.

BACKGROUND: The alteration of leucine-rich repeat kinase 2 (LRRK2) kinase activity is thought to be involved in Parkinson's disease (PD) pathogenesis beyond familiar cases, and LRRK2 inhibitors are currently under investigation. Preliminary data suggest a relationship between LRRK2 alteration and cognitive impairment in PD. OBJECTIVE: To investigate cerebrospinal fluid (CSF) LRRK2 levels in PD and other parkinsonian disorders, also correlating them with cognitive impairment. METHODS: In this study, we retrospectively investigated by means of a novel highly sensitive immunoassay the levels of total and phosphorylated (pS1292) LRRK2 in CSF of cognitively unimpaired PD (n = 55), PD with mild cognitive impairment (n = 49), PD with dementia (n = 18), dementia with Lewy bodies (n = 12), atypical parkinsonian syndromes (n = 35), and neurological controls (n = 30). RESULTS: Total and pS1292 LRRK2 levels were significantly higher in PD with dementia with respect to PD with mild cognitive impairment and PD, and also showed a correlation with cognitive performances. CONCLUSIONS: The tested immunoassay may represent a reliable method for assessing CSF LRRK2 levels. The results appear to confirm an association of LRRK2 alteration with cognitive impairment in PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

α-Synuclein real-time quaking-induced conversion in the cerebrospinal fluid of uncertain cases of parkinsonism.

A reliable biomarker is needed for accurate and early differentiation between Parkinson disease and the various forms of atypical parkinsonism. We used a novel real-time quaking-induced conversion (RT-QuIC) assay to detect α-synuclein (α-syn) aggregates in cerebrospinal fluid (CSF) of 118 patients with parkinsonism of uncertain clinical etiology and 52 controls. Diagnostic accuracy to distinguish α-synucleinopathies from non-α-synucleinopathies and controls was 84% (sensitivity = 75%, specificity = 94%, area under the curve = 0.84, 95% confidence interval = 0.78-0.91, p < 0.0001, positive predictive value = 93%). CSF α-syn RT-QuIC could be a useful diagnostic tool to help clinicians differentiate α-synucleinopathies from other forms of parkinsonism when the clinical picture is uncertain. Ann Neurol 2019;85:777-781.

Inflammation biomarker discovery in Parkinson's disease and atypical parkinsonisms.

BACKGROUND: Parkinson's disease (PD) and atypical parkinsonisms (APD) have overlapping symptoms challenging an early diagnosis. Diagnostic accuracy is important because PD and APD have different prognosis and response to treatment. We aimed to identify diagnostic inflammatory biomarkers of PD and APD in cerebrospinal fluid (CSF) using the multiplex proximity extension assay (PEA) technology and to study possible correlations of biomarkers with disease progression. METHODS: CSF from a longitudinal cohort study consisting of PD and APD patients (PD, n = 44; multiple system atrophy (MSA), n = 14; vascular parkinsonism (VaP), n = 9; and PD with VaP, n = 7) and controls (n = 25) were analyzed. RESULTS: Concentrations of CCL28 were elevated in PD compared to controls (p = 0.0001). Five other biomarkers differentiated both MSA and PD from controls (p < 0.05) and 10 biomarkers differentiated MSA from controls, of which two proteins, i.e. beta nerve growth factor (ß-NGF) and Delta and Notch like epidermal growth factor-related receptor (DNER), were also present at lower levels in MSA compared to PD (both p = 0.032). Two biomarkers (MCP-1 and MMP-10) positively correlated with PD progression (rho > 0.650; p < 0.01). CONCLUSIONS: PEA technique identified potential new CSF biomarkers to help to predict the prognosis of PD. Also, we identified new candidate biomarkers to distinguish MSA from PD.

Proximity extension assay testing reveals novel diagnostic biomarkers of atypical parkinsonian syndromes.

OBJECTIVE: The high degree of clinical overlap between atypical parkinsonian syndromes (APS) and Parkinson's disease (PD) makes diagnosis challenging. We aimed to identify novel diagnostic protein biomarkers of APS using multiplex proximity extension assay (PEA) testing. METHODS: Cerebrospinal fluid (CSF) samples from two independent cohorts, each consisting of APS and PD cases, and controls, were analysed for neurofilament light chain (NF-L) and Olink Neurology and Inflammation PEA biomarker panels. Whole-cohort comparisons of biomarker concentrations were made between APS (n=114), PD (n=37) and control (n=34) groups using logistic regression analyses that included gender, age and disease duration as covariates. RESULTS: APS versus controls analyses revealed 11 CSF markers with significantly different levels in cases and controls (p<0.002). Four of these markers also reached significance (p<0.05) in APS versus PD analyses. Disease-specific analyses revealed lower group levels of FGF-5, FGF-19 and SPOCK1 in multiple system atrophy compared with progressive supranuclear palsy and corticobasal syndrome. Receiver operating characteristic curve analyses suggested that the diagnostic accuracy of NF-L was superior to the significant PEA biomarkers in distinguishing APS, PD and controls. The biological processes regulated by the significant proteins include cell differentiation and immune cell migration. Delta and notch-like epidermal growth factor-related receptor (DNER) had the strongest effect size in APS versus controls and APS versus PD analyses. DNER is highly expressed in substantia nigra and is an activator of the NOTCH1 pathway which has been implicated in the aetiology of other neurodegenerative disorders including Alzheimer's disease. CONCLUSIONS: PEA testing has identified potential novel diagnostic biomarkers of APS.

The biomarker potential of cell-free microRNA from cerebrospinal fluid in Parkinsonian Syndromes.

BACKGROUND: MicroRNAs are small noncoding RNAs involved in the post-transcriptional regulation of protein synthesis. Extracellular microRNAs are accessible in a stable form in biofluids. OBJECTIVES: The aim was to identify individual microRNAs and/or subsets of microRNAs in CSF with biomarker potential and thus identify specific putative pathophysiological pathways. METHODS: In a two-step exploratory study design of PD, MSA, PSP, and controls, we initially profiled CSF microRNAs in a pilot cohort (n = 40) by screening for 372 microRNAs. Subsequently, we attempted to validate findings in an independent study cohort in CSF (n = 118) and ethylenediaminetetraacetic acid plasma (n = 114). This study cohort encompassed 46 microRNAs, of which 26 were singled out from the pilot cohort, and an additional 20 microRNAs were added based on previous publications. The most accurate diagnostic microRNA classifiers were identified in a multivariable logistic regression model adjusted for age and sex. RESULTS: A set of three microRNAs in CSF discriminated PD and MSA from controls with good diagnostic accuracy by receiver operating characteristics curve evaluation. The microRNAs were for PD versus controls: miR-7-5p, miR-331-5p, and miR-145-5p (area under the curve = 0.88) and MSA versus controls: miR-7-5p, miR-34c-3p, and miR-let-7b-5p (area under the curve = 0.87). The classifier that best distinguished MSA and PD consisted of two microRNAs: miR-9-3p and miR-106b-5p (area under the curve = 0.73). A single microRNA, miR-106b-5p, provided the best discrimination between PD and PSP (area under the curve = 0.85) in the CSF. CONCLUSIONS: Levels of specific trios of CSF-microRNAs discriminate well between α-synucleinopathies (PD and MSA) and controls. The results need to be validated in larger, independent cohorts. © 2018 International Parkinson and Movement Disorder Society.

Cerebrospinal fluid neurofilament light and tau protein as mortality biomarkers in parkinsonism.

BACKGROUND: Mortality is increased in parkinsonian disorders, moderately in Parkinson's disease (PD) but markedly in atypical parkinsonian disorders (APD), including multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Still, there are no reliable quantitative biomarkers for mortality. The cerebrospinal fluid (CSF) neurodegeneration biomarkers such as neurofilament light chain (NF-L), total tau (t-tau), and the tau pathology marker phosphorylated tau (p-tau) are related to mortality in other neurological disorders (eg, amyotrophic lateral sclerosis, Alzheimer's disease), but have not been investigated in this respect in parkinsonian disorders. AIMS: To investigate the CSF biomarkers' (NF-L, t-tau, and p-tau) relationship to mortality in parkinsonian disorders. METHODS: Demographic, mortality, and CSF data were collected from 68 PD and 83 APD patients. Survival analysis was conducted using Cox regression, with age at lumbar puncture, gender, diagnosis, and levels of CSF biomarkers as predictors. RESULTS: NF-L in CSF was associated with increased mortality in synucleinopathies (PD, MSA; HR 3.698 [2.196-6.228, 95% confidence interval (CI)], P < 0.001), in PSP (HR 2.767 [1.126-6.802 95% CI], P = 0.027), and in the entire cohort (HR 1.661 [1.082-2.55, 95% CI], P = 0.02). t-Tau in CSF was associated with increased mortality in PSP (HR 9.587 [1.143-80.418], P = 0.037). p-Tau in CSF was associated with decreased mortality in synucleinopathies (HR 0.196 [0.041-0.929, 95% CI], P = 0.040). Atypical parkinsonian disorders and tauopathies were associated with higher mortality (HR 8.798 [4.516-17.14, 95% CI] and HR 3.040 [1.904-4.854], respectively, P < 0.001). CONCLUSION: NF-L and tau protein in CSF might be useful for mortality prognosis in patients with parkinsonian disorders and should be investigated in larger studies.

Cerebrospinal fluid pro-inflammatory cytokines differentiate parkinsonian syndromes.

INTRODUCTION: Neuroinflammation has been established to be part of the neuropathological changes in Parkinson's disease (PD) and atypical parkinsonism (APD). Activated microglia play a key role in neuroinflammation by release of cytokines. Evidence of the disparity, if any, in the neuroinflammatory response between PD and APD is sparse. In this study, we investigated CSF cytokine profiles in patients with PD, multiple system atrophy (MSA), or progressive supranuclear palsy (PSP). METHODS: On a sensitive electrochemiluminescence-based platform (Quickplex, Meso Scale Discovery®), we examined a panel of C-reactive protein (CRP) and eight selected cytokines, IFN-γ, IL-10, IL-18, IL-1ß, IL-4, IL-6, TGF-ß1, and TNF-α, among patients with PD (n = 46), MSA (n = 35), and PSP (n = 39) or controls (n = 31). Additionally, CSF total tau protein levels were measured as a marker of nonspecific neurodegeneration for correlation estimates. RESULTS: CRP and the pro-inflammatory cytokines TNF-α, IL-1ß, and Il-6 were statistically significantly elevated in MSA and PSP patients compared to PD patients but not compared to control patients. No analytes differed statistically significantly between MSA and PSP patients. The best diagnostic discrimination, evaluated by ROC curve (AUC 0.77, p = 007, 95% CI 0.660-0.867), between PD and MSA patients was seen for a subset of analytes: CRP, TNF-α, IL-1ß, and IFN-γ. CONCLUSION: Among the investigated cytokines and CRP, we found a statistically significant increase of microglia-derived cytokines in MSA and PSP patients compared to PD patients.

Estimating the Evolution of Disease in the Parkinson's Progression Markers Initiative.

Parkinson's disease is the second most common neurological disease and affects about 1% of persons over the age of 60 years. Due to the lack of approved surrogate markers, confirmation of the disease still requires postmortem examination. Identifying and validating biomarkers are essential steps toward improving clinical diagnosis and accelerating the search for therapeutic drugs to ameliorate disease symptoms. Until recently, statistical analysis of multicohort longitudinal studies of neurodegenerative diseases has usually been restricted to a single analysis per outcome with simple comparisons between diagnostic groups. However, an important methodological consideration is to allow the modeling framework to handle multiple outcomes simultaneously and consider the transitions between diagnostic groups. This enables researchers to monitor multiple trajectories, correctly account for the correlation among biomarkers, and assess how these associations may jointly change over the long-term course of disease. In this study, we apply a latent time joint mixed-effects model to study biomarker progression and disease dynamics in the Parkinson's Progression Markers Initiative (PPMI) and examine which markers might be most informative in the earliest phases of disease. The results reveal that, even though diagnostic category was not included in the model, it seems to accurately reflect the temporal ordering of the disease state consistent with diagnosis categorization at baseline. In addition, results indicated that the specific binding ratio on striatum and the total Unified Parkinson's Disease Rating Scale (UPDRS) show high discriminability between disease stages. An extended latent time joint mixed-effects model with heterogeneous latent time variance also showed improvement in model fit in a simulation study and when applied to real data.

Vascular parkinsonism or idiopathic NPH? New insights from CSF pressure analysis.

Differential diagnosis between vascular parkinsonism (VP) and idiopathic normal pressure hydrocephalus (iNPH) is particularly challenging due to similar clinical and neuroradiological features. The objective of this study is to differentiate VP with radiological evidence of ventricular enlargement (REVE) from iNPH on the basis of cerebrospinal fluid (CSF) hydrodynamics. CSF pressure components were investigated in patients with a clinical diagnosis of VP and REVE. Data of eight patients (seven men; age 76 ± 3.9 years; disease duration 26.5 ± 15.6 months) were evaluated. CSF opening pressure values were normal in all patients. Also, mean CSF pressure values during short-term monitoring were normal, except in one patient. Four out of the eight patients had raised values of pulse wave amplitude (PWA) during the opening phase (mean ± SD 57.1 ± 19.9 mmH2O), meanwhile during short-term monitoring, seven out of the eight patients showed raised values of mean PWA (76.8 ± 23 mmH2O). We found that most of patients with clinical characteristics of VP and REVE showed elevated PWA during the short-term monitoring of CSF pressure as observed in iNPH patients. Patients clinically identified as VP may be part of the clinical spectrum of iNPH.

A panel of nine cerebrospinal fluid biomarkers may identify patients with atypical parkinsonian syndromes.

BACKGROUND: Patients presenting with parkinsonian syndromes share many clinical features, which can make diagnosis difficult. This is important as atypical parkinsonian syndromes (APSs) such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and corticobasal syndrome (CBS) carry a poor prognosis, compared with patients with Parkinson's disease (PD). In addition, there is overlap between APS and dementia diseases, such as Alzheimer's disease (AD) and frontotemporal dementia (FTD). OBJECTIVE: To use a panel of cerebrospinal fluid (CSF) biomarkers to differentiate patients with APS from PD and dementia. METHODS: A prospective cohort of 160 patients and 30 control participants were recruited from a single specialist centre. Patients were clinically diagnosed according to current consensus criteria. CSF samples were obtained from patients with clinical diagnoses of PD (n=31), PSP (n=33), CBS (n=14), MSA (n=31), AD (n=26) and FTD (n=16). Healthy, elderly participants (n=30) were included as controls. Total τ (t-τ), phosphorylated τ (p-τ), ß-amyloid 1-42 (Aß42), neurofilament light chain (NFL), α-synuclein (α-syn), amyloid precursor protein soluble metabolites α and ß (soluble amyloid precursor protein (sAPP)α, sAPPß) and two neuroinflammatory markers (monocyte chemoattractant protein-1 and YKL-40) were measured in CSF. A reverse stepwise regression analysis and the false discovery rate procedure were used. RESULTS: CSF NFL (p<0.001), sAPPα (p<0.001) and a-syn (p=0.003) independently predicted diagnosis of PD versus APS. Together, these nine biomarkers could differentiate patients with PD from APS with an area under the curve of 0.95 and subtypes of APS from one another. There was good discriminatory power between parkinsonian groups, dementia disorders and healthy controls. CONCLUSIONS: A panel of nine CSF biomarkers was able to differentiate APS from patients with PD and dementia. This may have important clinical utility in improving diagnostic accuracy, allowing better prognostication and earlier access to potential disease-modifying therapies.

Striatal Injury with 6-OHDA Transiently Increases Cerebrospinal GFAP and S100B.

Both glial fibrillary acidic protein (GFAP) and S100B have been used as markers of astroglial plasticity, particularly in brain injury; however, they do not necessarily change in the same time frame or direction. Herein, we induced a Parkinson's disease (PD) model via a 6-OHDA intrastriatal injection in rats and investigated the changes in GFAP and S100B using ELISA in the substantia nigra (SN), striatum, and cerebrospinal fluid on the 1st, 7th, and 21st days following the injection. The model was validated using measurements of rotational behaviour induced by methylphenidate and tyrosine hydroxylase in the dopaminergic pathway. To our knowledge, this is the first measurement of cerebrospinal fluid S100B and GFAP in the 6-OHDA model of PD. Gliosis (based on a GFAP increase) was identified in the striatum, but not in the SN. We identified a transitory increment of cerebrospinal fluid S100B and GFAP on the 1st and 7th days, respectively. This initial change in cerebrospinal fluid S100B was apparently related to the mechanical lesion. However, the 6-OHDA-induced S100B secretion was confirmed in astrocyte cultures. Current data reinforce the idea that glial changes precede neuronal damage in PD; however, these findings also indicate that caution is necessary regarding the interpretation of data in this PD model.

Cerebrospinal fluid biomarkers in parkinsonian conditions: an update and future directions.

Parkinsonian diseases comprise a heterogeneous group of neurodegenerative disorders, which show significant clinical and pathological overlap. Accurate diagnosis still largely relies on clinical acumen; pathological diagnosis remains the gold standard. There is an urgent need for biomarkers to diagnose parkinsonian disorders, particularly in the early stages when diagnosis is most difficult. In this review, several of the most promising cerebrospinal fluid candidate markers will be discussed. Their strengths and limitations will be considered together with future developments in the field.

Flt3 ligand does not differentiate between Parkinsonian disorders.

BACKGROUND: Differential diagnosis of parkinsonian disorders is challenging because of overlapping symptoms, especially during early stages of disease. No validated biomarkers are available for early and accurate diagnosis of multiple system atrophy and other parkinsonian disorders. It has been reported that flt3 ligand levels in cerebrospinal fluid could clearly differentiate patients with Parkinson's disease from patients with multiple system atrophy, with 99% sensitivity and 95% specificity. METHODS: We measured flt3 ligand levels in cerebrospinal fluid of subjects with Parkinson's disease (n = 37), multiple system atrophy (n = 30), and progressive supranuclear palsy (n = 19). RESULTS: In our cohort, no significant difference was found in flt3 ligand levels between Parkinson's disease, multiple system atrophy, and progressive supranuclear palsy. CONCLUSIONS: Our results suggest that cerebrospinal fluid flt3 ligand levels do not differentiate between parkinsonian disorders.

Cerebrospinal fluid biomarkers of central catecholamine deficiency in Parkinson's disease and other synucleinopathies.

Central catecholamine deficiency characterizes α-synucleinopathies such as Parkinson's disease. We hypothesized that cerebrospinal fluid levels of neuronal metabolites of catecholamines provide neurochemical biomarkers of these disorders. To test this hypothesis we measured cerebrospinal fluid levels of catechols including dopamine, norepinephrine and their main respective neuronal metabolites dihydroxyphenylacetic acid and dihydroxyphenylglycol in Parkinson's disease and two other synucleinopathies, multiple system atrophy and pure autonomic failure. Cerebrospinal fluid catechols were assayed in 146 subjects-108 synucleinopathy patients (34 Parkinson's disease, 54 multiple system atrophy, 20 pure autonomic failure) and 38 controls. In 14 patients cerebrospinal fluid was obtained before or within 2 years after the onset of parkinsonism. The Parkinson's disease, multiple system atrophy and pure autonomic failure groups all had lower cerebrospinal fluid dihydroxyphenylacetic acid [0.86 ± 0.09 (SEM), 1.00 ± 0.09, 1.32 ± 0.12 nmol/l] than controls (2.15 ± 0.18 nmol/l; P < 0.0001; P < 0.0001; P = 0.0002). Dihydroxyphenylglycol was also lower in the three synucleinopathies (8.82 ± 0.44, 7.75 ± 0.42, 5.82 ± 0.65 nmol/l) than controls (11.0 ± 0.62 nmol/l; P = 0.009, P < 0.0001, P < 0.0001). Dihydroxyphenylacetic acid was lower and dihydroxyphenylglycol higher in Parkinson's disease than in pure autonomic failure. Dihydroxyphenylacetic acid was 100% sensitive at 89% specificity in separating patients with recent onset of parkinsonism from controls but was of no value in differentiating Parkinson's disease from multiple system atrophy. Synucleinopathies feature cerebrospinal fluid neurochemical evidence for central dopamine and norepinephrine deficiency. Parkinson's disease and pure autonomic failure involve differential dopaminergic versus noradrenergic lesions. Cerebrospinal fluid dihydroxyphenylacetic acid seems to provide a sensitive means to identify even early Parkinson's disease.

In vivo comparison of Richardson's syndrome and progressive supranuclear palsy-parkinsonism.

Richardson's syndrome (RS) and progressive supranuclear palsy-parkinsonism (PSP-P) are the most common subtypes of PSP. Post-mortem data suggests that the clinical presentation of the two subtypes differs especially in the first 2 years of disease and then converges. This hypothesis has, to our knowledge, never been confirmed in a living cohort. Medical history was used to define subtypes retrospectively in 23 consecutive PSP patients from our outpatient clinic specialized in movement disorders. 14 patients suffered from RS, and 9 from PSP-P. Using a prospective cross-sectional approach, clinical, cognitive, behavioral, speech and biochemical (cerebrospinal fluid tau levels) features were compared. RS patients showed shorter time from disease onset to diagnosis and more neuropsychological and neurobehavioral deficits than PSP-P patients, but differed not significantly with regard to clinical and biochemical features. RS and PSP-P show considerable symptoms overlap during the disease course when using routine assessments, with persisting differences regarding non-motor symptoms. Shorter disease duration of the comparably affected RS patients indicates that this subtype has an accelerated disease progression at early disease stages.

Differential pattern of brain-specific CSF proteins tau and amyloid-ß in Parkinsonian syndromes.

To evaluate cerebrospinal fluid (CSF) proteins reflecting processes of neurodegeneration and glial activation in progressive supranuclear palsy (PSP; Richardson's syndrome, n = 20; PSP-Parkinsonism, n = 7) and multiple system atrophy (MSA, n = 25), we analyzed tau, phosphorylated tau, amyloid-beta(1-42) (Abeta1-42), Abeta1-40, glial fibrillary acidic protein (GFAP), and CSF routine variables. Individuals with PSP-Parkinsonism and MSA had elevated tau levels when compared with Richardson's syndrome, Parkinson's disease (PD), and age-matched controls (P

Familial paroxysmal exercise-induced dystonia: atypical presentation of autosomal dominant GTP-cyclohydrolase 1 deficiency.

Paroxysmal exercise-induced dystonia (PED) is one of the rarer forms of paroxysmal dyskinesia, and can occur in sporadic or familial forms. We report a family (male index case, mother and maternal grandfather) with autosomal dominant inheritance of paroxysmal exercise-induced dystonia. The dystonia began in childhood and was only ever induced after many minutes of exercise, and was never present at rest, or on initiation of movements. In addition, family members suffered restless legs syndrome (RLS), depression, and adult-onset Parkinsonism. The index case had low cerebrospinal fluid neurotransmitters and pterins. The PED and RLS stopped on initiation of L-Dopa therapy. Both live family members were found to have a nonsense mutation (p.E84X) in exon 1 of the GTP-cyclohydrolase 1 (GCH-1) gene. We propose that GCH-1 mutations should be considered a genetic cause of familial PED, especially if additional clinical features of monoaminergic deficiency are present in affected individuals.

Molecular profiling in Parkinsonian syndromes: CSF biomarkers.

An accurate and early diagnosis of degenerative parkinsonian syndromes is a major need for their correct and timely therapeutic management. The current diagnostic criteria are mostly based on clinical features and molecular imaging. However, diagnostic doubts often persist especially in the early stages of diseases when signs are slight, ambiguous and overlapping among different syndromes. Molecular imaging may not be altered in the early stages of diseases, also failing to discriminate among different syndromes. Cerebrospinal fluid (CSF) represents an ideal source of biomarkers reflecting different pathways of neuropathological changes taking place in the brain and preceding the clinical onset. The aim of this review is to provide un update on CSF biomarkers in parkinsonian disorders, discussing in detail their association with neuropathological correlates. Their potential contribution in differential diagnosis and prognostic assessment of different parkinsonian syndromes is also discussed. Before entering the clinical use both for diagnostic and prognostic purposes, these CSF biomarkers need to be thoroughly assessed in terms of pre-analytical and analytical variability, as well as to clinical validation in independent cohorts.

Alpha-Synuclein Protofibrils in Cerebrospinal Fluid: A Potential Biomarker for Parkinson's Disease.

BACKGROUND: Currently, there is no established biomarker for Parkinson's disease (PD) and easily accessible biomarkers are crucial for developing disease-modifying treatments. OBJECTIVE: To develop a novel method to quantify cerebrospinal fluid (CSF) levels of α-synuclein protofibrils (α-syn PF) and apply it to clinical cohorts of patients with PD and atypical parkinsonian disorders. METHODS: A cohort composed of 49 patients with PD, 12 with corticobasal degeneration (CBD), 22 with progressive supranuclear palsy, and 33 controls, that visited the memory clinic but had no biomarker signs of Alzheimer's disease (AD, tau<350 pg/mL, amyloid-beta 42 (Aß42)>530 pg/mL, and phosphorylated tau (p-tau)<60 pg/mL) was used in this study. The CSF samples were analyzed with the Single molecule array (Simoa) technology. Total α-synuclein (α-syn) levels were analyzed with a commercial ELISA-kit. RESULTS: The assay is specific to α-syn PF, with no cross-reactivity to monomeric α-syn, or the ß- and γ-synuclein variants. CSF α-syn PF levels were increased in PD compared with controls (62.1 and 40.4 pg/mL, respectively, p = 0.03), and CBD (62.1 and 34.2 pg/mL, respectively, p = 0.02). The accuracy of predicting PD using α-syn PF is significantly different from controls (area under the curve 0.68, p = 0.0097) with a sensitivity of 62.8% and specificity of 67.7%. Levels of total α-syn were significantly different between the PD and CBD groups (p = 0.04). CONCLUSION: The developed method specifically quantifies α-syn PF in human CSF with increased concentrations in PD, but with an overlap with asymptomatic elderly controls.

Cerebrospinal Fluid Galectin-1 Levels Discriminate Patients with Parkinsonism from Controls.

Parkinson's disease (PD) is the second most common neurodegenerative disorder in elderly people. Currently, the diagnosis of PD is based on neurological examination, neuroimaging, and the response to dopaminergic medication. The diagnosis can be challenging, especially at early disease stages, when the symptoms of patients with atypical parkinsonism (APD) may strongly overlap. Therefore, reliable biomarkers that are able to identify patients with PD are much needed. Here, we aimed to identify and validate new biomarkers for PD in cerebrospinal fluid (CSF). We performed a profiling experiment using mass spectrometry (MS) of CSF from ten PD patients and ten matched non-neurological controls. We selected one protein, galectin-1 (Gal-1), which was differentially expressed in PD vs. controls, and quantified its concentrations in CSF by enzyme-linked immunosorbent assay (ELISA) in three new cohorts of 37 PD patients, 21 APD patients, and 44 controls. CSF levels of Gal-1 were lower in PD in both the discovery and validation experiments and discriminated PD from controls with moderate-high accuracy levels (ELISA: area under the curve = 0.7). Similar levels of Gal-1 were found in PD and APD. Gal-1 levels were correlated to age in all groups and correlated in the PD patients to CSF levels of total tau, phosphorylated tau, neurofilament light chain (NFL), and the mini-mental state examination (MMSE) score. We conclude that MS profiling of proteins may be a useful tool to identify novel biomarkers of neurological diseases and that CSF Gal-1 levels may discriminate PD from non-neurological controls.