Proteomic changes in the human cerebrovasculature in Alzheimer's disease and related tauopathies linked to peripheral biomarkers in plasma and cerebrospinal fluid.

INTRODUCTION: Cerebrovascular dysfunction is a pathological hallmark of Alzheimer's disease (AD). Nevertheless, detecting cerebrovascular changes within bulk tissues has limited our ability to characterize proteomic alterations from less abundant cell types. METHODS: We conducted quantitative proteomics on bulk brain tissues and isolated cerebrovasculature from the same individuals, encompassing control (N = 28), progressive supranuclear palsy (PSP) (N = 18), and AD (N = 21) cases. RESULTS: Protein co-expression network analysis identified unique cerebrovascular modules significantly correlated with amyloid plaques, cerebrovascular amyloid angiopathy (CAA), and/or tau pathology. The protein products within AD genetic risk loci were concentrated within cerebrovascular modules. The overlap between differentially abundant proteins in AD cerebrospinal fluid (CSF) and plasma with cerebrovascular network highlighted a significant increase of matrisome proteins, SMOC1 and SMOC2, in CSF, plasma, and brain. DISCUSSION: These findings enhance our understanding of cerebrovascular deficits in AD, shedding light on potential biomarkers associated with CAA and vascular dysfunction in neurodegenerative diseases.

SCRN1: A cerebrospinal fluid biomarker correlating with tau in Alzheimer's disease.

INTRODUCTION: Secernin-1 (SCRN1) is a neuronal protein that co-localizes with neurofibrillary tangles in Alzheimer's disease (AD), but not with tau inclusions in corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), or Pick's disease. METHODS: We measured SCRN1 concentration in cerebrospinal fluid (CSF) using a novel mass spectrometric parallel reaction monitoring method in three clinical cohorts comprising patients with neurochemically characterized AD (n = 25) and controls (n = 28), clinically diagnosed Parkinson's disease (PD; n = 38), multiple system atrophy (MSA; n = 31), PSP (n = 20), CBD (n = 8), healthy controls (n = 37), and neuropathology-confirmed AD (n = 47). RESULTS: CSF SCRN1 was significantly increased in AD (P < 0.01, fold change = 1.4) compared to controls (receiver operating characteristic area under the curve = 0.78) but not in CBD, PSP, PD, or MSA. CSF SCRN1 positively correlated with CSF total tau (R = 0.78, P = 1.1 × 10-13 ), phosphorylated tau181 (R = 0.64, P = 3.2 × 10-8 ), and Braak stage and negatively correlated with Mini-Mental State Examination score. DISCUSSION: CSF SCRN1 is a candidate biomarker of AD, reflecting tau pathology. HIGHLIGHTS: We developed a parallel reaction monitoring assay to measure secernin-1 (SCRN1) in cerebrospinal fluid (CSF). CSF SCRN1 was increased in Alzheimer's disease compared to healthy controls. CSF SCRN1 remained unchanged in Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, or corticobasal degeneration compared to controls. CSF SCRN1 correlated strongly with CSF phosphorylated tau and total tau. CSF SCRN1 increased across Braak stages and negatively correlated with Mini-Mental State Examination score.

Comparison of Amyloid in Cerebrospinal Fluid, Brain Imaging, and Autopsy in a Case of Progressive Supranuclear Palsy.

Cerebrospinal fluid (CSF) amyloid-beta 1-42 (Aß1-42) and amyloid positron emission tomography (PET) are the 2 main Alzheimer disease amyloid biomarkers that have been validated in neuropathologically confirmed Alzheimer disease cases. Although many studies have shown concordance of amyloid positivity or negativity between CSF Aß1-42 and amyloid PET, several studies also reported discrepancies between these 2 Aß biomarkers. We conducted a comparison of CSF Aß1-42 level, amyloid PET, and autopsy findings in a case with progressive supranuclear palsy in which biomarker acquisition and postmortem pathologic examination were conducted almost at the same time. Our case with antemortem CSF Aß1-42 (+)/amyloid PET (-) who was pathologically confirmed with Aß pathology in the cerebral cortex may indicate CSF Aß1-42 is more sensitive for assessing in vivo Aß than amyloid PET.

CSF biomarkers distinguish idiopathic normal pressure hydrocephalus from its mimics.

OBJECTIVE: To examine the differential diagnostic significance of cerebrospinal fluid (CSF) biomarkers reflecting Alzheimer's disease-related amyloid ß (Aß) production and aggregation, cortical neuronal damage, tau pathology, damage to long myelinated axons and astrocyte activation, which hypothetically separates patients with idiopathic normal pressure hydrocephalus (iNPH) from patients with other neurodegenerative disorders. METHODS: The study included lumbar CSF samples from 82 patients with iNPH, 75 with vascular dementia, 70 with Parkinson's disease, 34 with multiple system atrophy, 34 with progressive supranuclear palsy, 15 with corticobasal degeneration, 50 with Alzheimer's disease, 19 with frontotemporal lobar degeneration and 54 healthy individuals (HIs). We analysed soluble amyloid precursor protein alpha (sAPPα) and beta (sAPPß), Aß species (Aß38, Aß40 and Aß42), total tau (T-tau), phosphorylated tau, neurofilament light and monocyte chemoattractant protein 1 (MCP-1). RESULTS: Patients with iNPH had lower concentrations of tau and APP-derived proteins in combination with elevated MCP-1 compared with HI and the non-iNPH disorders. T-tau, Aß40 and MCP-1 together yielded an area under the curve of 0.86, differentiating iNPH from the other disorders. A prediction algorithm consisting of T-tau, Aß40 and MCP-1 was designed as a diagnostic tool using CSF biomarkers. CONCLUSIONS: The combination of the CSF biomarkers T-tau, Aß40 and MCP-1 separates iNPH from cognitive and movement disorders with good diagnostic sensitivity and specificity. This may have important implications for diagnosis and clinical research on disease mechanisms for iNPH.

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.

Symptomatic cerebrospinal fluid HIV-1 escape with no resistance-associated mutations following low-level plasma viremia.

The majority of neurologically symptomatic cerebrospinal fluid HIV-1 escape cases are connected with resistance-associated mutations and potentially explained by low cerebrospinal fluid antiretroviral concentrations. However, there are still significant knowledge gaps regarding the physiopathology and long-term management of neurosymptomatic viral escape. We report a case of Parkinson-like syndrome following cerebrospinal fluid HIV-1 escape in a 40-year-old female patient with an history of persistent low-level plasma viremia under treatment. No resistance-associated mutations, high viral diversity (env deep sequencing), adequate pharmacokinetics, atypical CD3-CD14-CD4+CD5-CD2-/+CD7-/+ lymphocytes, low-level Epstein-Barr virus replication, and white matter autoimmune reactivity were observed in the cerebrospinal fluid. Antiretroviral regimen modification led to rapid clinical and radiological improvements. This case may increase the current uncertain knowledge on the origin of cerebrospinal fluid HIV-1 and illustrates the consequences of uncontrolled compartmental viral replication; it also highlights the relevance and persistence of immune activation and the possibility of various detrimental mechanisms underlying neurosymptomatic viral escape.

Clinical value of CSF amyloid-beta-42 and tau proteins in Progressive Supranuclear Palsy.

Progressive Supranuclear Palsy (PSP) is a four-repeat tauopathy with high phenotypic and neuropathological variability, highlighting the urgent need for effective disease biomarkers. Quantitative analysis of cerebrospinal fluid (CSF) proteins reflecting pathological changes of CNS is currently used as biomarkers of multiple neurodegenerative disorders for both early differential diagnosis and prognostic clustering of patients. In this study, we thus assessed the clinical usefulness of a panel of CSF biomarker in PSP patients presenting with Richardson's Syndrome. CSF levels of 42-beta-amyloid, total-tau, phosphorylated-tau, and both 42-beta-amyloid/phosphorylated-tau and phosphorylated-tau/total-tau ratios were comparatively evaluated in 39 PSP patients, 31 patients with Parkinson's Disease (PD) and 58 gender-/age-matched healthy controls. Specific gold-standard clinical scores were obtained. Diagnostic accuracy and clinical correlates of each biomarker were measured with receiver operating curve analysis and Spearman's test/linear regression, respectively. In PSP, 42-beta-amyloid was lower than either controls or PD; total-tau and phosphorylated-tau were instead reduced compared to controls, but similar to PD. At the cut-off value of 623 pg/ml, 42-beta-amyloid significantly distinguished PSP from controls and PD. Likewise, phosphorylated-tau/total-tau ratio also supported differential diagnosis between PSP and PD (cut-off = 0.185). 42-beta-amyloid was inversely associated with PSP severity, as measured with PSP Rating Scale. Our study demonstrates that CSF 42-beta-amyloid is reduced in PSP patients, proportionally to clinical severity, thus suggesting a potential use as disease biomarker. Moreover, phosphorylated-tau/total-tau ratio resulted helpful in the early differential diagnosis between PSP and PD.

Ultrasensitive and selective detection of 3-repeat tau seeding activity in Pick disease brain and cerebrospinal fluid.

The diagnosis and treatment of diseases involving tau-based pathology such as Alzheimer disease and certain frontotemporal dementias is hampered by the inability to detect pathological forms of tau with sufficient sensitivity, specificity and practicality. In these neurodegenerative diseases, tau accumulates in self-seeding filaments. For example, Pick disease (PiD) is associated with frontotemporal degeneration and accumulation of 3-repeat (3R) tau isoforms in filaments constituting Pick bodies. Exploiting the self-seeding activity of tau deposits, and using a 3R tau fragment as a substrate, we have developed an assay (tau RT-QuIC) that can detect tau seeds in 2 µl aliquots of PiD brain dilutions down to 10-7-10-9. PiD seeding activities were 100-fold higher in frontal and temporal lobes compared to cerebellar cortex. Strikingly, this test was 103- to 105-fold less responsive when seeded with brain containing predominant 4-repeat (4R) tau aggregates from cases of corticobasal degeneration, argyrophilic grain disease, and progressive supranuclear palsy. Alzheimer disease brain, with 3R + 4R tau deposits, also gave much weaker responses than PiD brain. When applied to cerebrospinal fluid samples (5 µl), tau RT-QuIC analyses discriminated PiD from non-PiD cases. These findings demonstrate that abnormal tau aggregates can be detected with high sensitivity and disease-specificity in crude tissue and fluid samples. Accordingly, this tau RT-QuIC assay exemplifies a new approach to diagnosing tauopathies and monitoring therapeutic trials using aggregated tau itself as a biomarker.

Tracking and predicting disease progression in progressive supranuclear palsy: CSF and blood biomarkers.

Progressive supranuclear palsy (PSP) is a rare and progressive neurodegenerative condition characterised pathologically by neuronal cell loss due to abnormal tau deposits. Clinically, the condition manifests as parkinsonism with the addition of progressive balance, speech, swallowing, eye movement and cognitive impairment, ultimately leading to death. Measuring change over time in neurodegenerative conditions is central to defining the effects of therapeutic intervention and disease biology. The current gold standard for measuring clinical disease progression in PSP is the PSP Rating Scale score. However, such scales may be affected by intrarater and inter-rater variability. In addition, their use in clinical trials may be hindered by differences in the time interval between pathological disease progression/response to therapeutics and change in clinical state. Therefore, the need for reliable disease progression biomarkers to complement clinical rating scales is clear. Here we discuss the benefits of using biomarkers to predict and track disease progression in both clinical and research settings. Through reviewing the literature to date on the role of cerebrospinal fluid (CSF) and blood biomarkers, we highlight data that reveals the ability of CSF and plasma neurofilament light chain (NF-L) to predict and track clinical disease progression in PSP. We also discuss the need for large-scale longitudinal studies to identify novel biomarkers.

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.

Divergent CSF τ alterations in two common tauopathies: Alzheimer's disease and progressive supranuclear palsy.

BACKGROUND: Elevated CSF τ is considered a biomarker of neuronal injury in newly developed Alzheimer's disease (AD) and mild cognitive impairment (MCI) criteria. However, previous studies have failed to detect alterations of τ species in other primary tauopathies. We assessed CSF τ protein abnormalities in AD, a tauopathy with prominent Aß pathology, and progressive supranuclear palsy (PSP), a primary tauopathy characterised by deposition of four microtubule-binding repeat (4R) τ with minimal Aß pathology. METHODS: 26 normal control (NC), 37 AD, and 24 patients with PSP participated in the study. AD and PSP were matched for severity using the clinical dementia rating sum of boxes (CDR-sb) scores. The INNO BIA AlzBio3 multiplex immunoassay was used to measure CSF Aß, total τ, and ptau181. Additional, novel ELISAs targeting different N-terminal and central τ epitopes were developed to examine CSF τ components and to investigate interactions between diagnostic group, demographics and genetic variables. RESULTS: PSP had lower CSF N-terminal and C-terminal τ concentrations than NC and AD measured with the novel τ ELISAs and the standard AlzBio3 τ and ptau assays. AD had higher total τ and ptau levels than NC and PSP. There was a gender by diagnosis interaction in AD and PSP for most τ species, with lower concentrations for male compared to female patients. CONCLUSIONS: CSF τ fragment concentrations are different in PSP compared with AD despite the presence of severe τ pathology and neuronal injury in both disorders. CSF τ concentration likely reflects multiple factors in addition to the degree of neuronal injury.

Proteinase-activated receptor 2 and disease biomarkers in cerebrospinal fluid in cases with autopsy-confirmed prion diseases and other neurodegenerative diseases.

BACKGROUND: Proteinase-activated receptor 2 (PAR-2) has been shown to promote both neurotoxic and neuroprotective effects. Similarly, other routinely used nonspecific markers of neuronal damage can be found in cerebrospinal fluid (CSF) and can be used as biomarkers for different neurodegenerative disorders. METHODS: Using enzyme-linked immunosorbent assays and western blotting we assessed PAR-2, total-tau, phospho-tau, beta-amyloid levels, and protein 14-3-3 in the CSF of former patients who had undergone a neuropathological autopsy after death and who had been definitively diagnosed with a prion or other neurodegenerative disease. RESULTS: We did not find any significant correlation between levels of PAR-2 and other biomarkers, nor did we find any differences in PAR-2 levels between prion diseases and other neurodegenerative conditions. However, we confirmed that very high total-tau levels were significantly associated with definitive prion diagnoses and exhibited greater sensitivity and specificity than protein 14-3-3, which is routinely used as a marker. CONCLUSIONS: Our study showed that PAR-2, in CSF, was not specifically altered in prion diseases compared to other neurodegenerative conditions. Our results also confirmed that very high total-tau protein CSF levels were significantly associated with a definitive Creutzfeldt-Jakob disease (CJD) diagnosis and should be routinely tested as a diagnostic marker. Observed individual variability in CSF biomarkers provide invaluable feedback from neuropathological examinations even in "clinically certain" cases.

Intact protein analysis of ubiquitin in cerebrospinal fluid by multiple reaction monitoring reveals differences in Alzheimer's disease and frontotemporal lobar degeneration.

The impairment of the ubiquitin-proteasome system (UPS) is thought to be an early event in neurodegeneration, and monitoring UPS alterations might serve as a disease biomarker. Our aim was to establish an alternate method to antibody-based assays for the selective measurement of free monoubiquitin in cerebrospinal fluid (CSF). Free monoubiquitin was measured with liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MS/MS) in CSF of patients with Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), behavioral variant of frontotemporal dementia (bvFTD), Creutzfeldt-Jakob disease (CJD), Parkinson's disease (PD), primary progressive aphasia (PPA), and progressive supranuclear palsy (PSP). The LC-MS/MS method showed excellent intra- and interassay precision (4.4-7.4% and 4.9-10.3%) and accuracy (100-107% and 100-106%). CSF ubiquitin concentration was increased compared with that of controls (33.0 ± 9.7 ng/mL) in AD (47.5 ± 13.1 ng/mL, p < 0.05) and CJD patients (171.5 ± 103.5 ng/mL, p < 0.001) but not in other neurodegenerative diseases. Receiver operating characteristic curve (ROC) analysis of AD vs control patients revealed an area under the curve (AUC) of 0.832, and the specificity and sensitivity were 75 and 75%, respectively. ROC analysis of AD and FTLD patients yielded an AUC of 0.776, and the specificity and sensitivity were 53 and 100%, respectively. In conclusion, our LC-MS/MS method may facilitate ubiquitin determination to a broader community and might help to discriminate AD, CJD, and FTLD patients.

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.

Reduced alpha-synuclein in cerebrospinal fluid in synucleinopathies: evidence from a meta-analysis.

Alpha-synuclein plays a key role in the pathology of synucleinopathies including Parkinson's disease (PD) and multiple system atrophy (MSA). However, whether alpha-synuclein level in cerebrospinal fluid (CSF) could distinguish synucleinopathies from progressive supranuclear palsy (PSP) is still a contentious issue. A comprehensive literature search yielded nine eligible studies. We expressed the between-group difference of the concentration of alpha-synuclein in CSF as the standardized mean difference. The proportion of variation attributable to heterogeneity was computed and expressed as I(2) . Nine studies involved 537 controls, 843 PD, 130 MSA, and 98 PSP patients. The overall effect of PD on alpha-synuclein in CSF was significantly different from normal control or disease control (standardized mean difference = -0.67, P < 0.00001). These studies were heterogeneous (I(2) = 40%). Alpha-synuclein in CSF in MSA was significantly reduced relative to controls with heterogeneous studies (standardized mean difference = -0.75, P < 0.0001; I(2) = 62%). In contrast, no significant difference of alpha-synuclein in CSF was observed between PSP and controls with heterogeneous studies (standardized mean difference = -0.28, P = 0.13; I(2) = 53%). Alpha-synuclein in CSF was significantly reduced in synucleinopathies compared with PSP ("PD vs. PSP": standardized mean difference = -0.38, P = 0.001; "MSA vs. PSP": standardized mean difference = -0.66, P < 0.00001). The included studies were homogeneous (I(2) = 0%). Our study showed that alpha-synuclein levels in CSF in synucleinopathies was significantly lower than in PSP. This finding provides insights into the pathophysiological difference between synucleinopathies and PSP as well as possibility of development of a tool for differential diagnosis between MSA and PSP using enzyme-linked immunosorbent assay (ELISA) and similar methods.

CSF Proteomics in Patients With Progressive Supranuclear Palsy.

BACKGROUND AND OBJECTIVES: Identification of fluid biomarkers for progressive supranuclear palsy (PSP) is critical to enhance therapeutic development. We implemented unbiased DNA aptamer (SOMAmer) proteomics to identify novel CSF PSP biomarkers. METHODS: This is a cross-sectional study in original (18 clinically diagnosed PSP-Richardson syndrome [PSP-RS], 28 cognitively healthy controls]), validation (23 PSP-RS, 26 healthy controls), and neuropathology-confirmed (21 PSP, 52 non-PSP frontotemporal lobar degeneration) cohorts. Participants were recruited through the University of California, San Francisco, and the 4-Repeat Neuroimaging Initiative. The original and neuropathology cohorts were analyzed with the SomaScan platform version 3.0 (5026-plex) and the validation cohort with version 4.1 (7595-plex). Clinical severity was measured with the PSP Rating Scale (PSPRS). CSF proteomic data were analyzed to identify differentially expressed targets, implicated biological pathways using enrichment and weighted consensus gene coexpression analyses, diagnostic value of top targets with receiver-operating characteristic curves, and associations with disease severity with linear regressions. RESULTS: A total of 136 participants were included (median age 70.6 ± 8 years, 68 [50%] women). One hundred fifty-five of 5,026 (3.1%), 959 of 7,595 (12.6%), and 321 of 5,026 (6.3%) SOMAmers were differentially expressed in PSP compared with controls in original, validation, and neuropathology-confirmed cohorts, with most of the SOMAmers showing reduced signal (83.1%, 95.1%, and 73.2%, respectively). Three coexpression modules were associated with PSP across cohorts: (1) synaptic function/JAK-STAT (ß = -0.044, corrected p = 0.002), (2) vesicle cytoskeletal trafficking (ß = 0.039, p = 0.007), and (3) cytokine-cytokine receptor interaction (ß = -0.032, p = 0.035) pathways. Axon guidance was the top dysregulated pathway in PSP in original (strength = 1.71, p < 0.001), validation (strength = 0.84, p < 0.001), and neuropathology-confirmed (strength = 0.78, p < 0.001) cohorts. A panel of axon guidance pathway proteins discriminated between PSP and controls in original (area under the curve [AUC] = 0.924), validation (AUC = 0.815), and neuropathology-confirmed (AUC = 0.932) cohorts. Two inflammatory proteins, galectin-10 and cytotoxic T lymphocyte-associated protein-4, correlated with PSPRS scores across cohorts. DISCUSSION: Axon guidance pathway proteins and several other molecular pathways are downregulated in PSP, compared with controls. Proteins in these pathways may be useful targets for biomarker or therapeutic development.

CSF α-Synuclein Seed Amplification Assay in Patients With Atypical Parkinsonian Disorders.

BACKGROUND AND OBJECTIVES: There is no disease-modifying treatment of corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), 2 disorders characterized by their striking phenotypic, and, in CBS, pathologic heterogeneity. Seed amplification assays (SAAs) could enable the detection of neuropathologic processes, such as α-synuclein (αSyn) copathology, that affect the success of future disease-modifying treatment strategies. The primary objective was to assess possible αSyn copathology in CBS and PSP, as detected in CSF using an αSyn SAA (αSyn-SAA). Secondary objectives were to evaluate the association of αSyn-SAA positivity with other biomarkers including of Alzheimer disease (AD), and with clinical presentation. We hypothesized that αSyn-SAA positivity would be detectable in CBS and PSP and that it would be associated with AD biomarker positivity and ß-amyloid (Aß) 42 levels, neurodegeneration as assessed by neurofilament light chain (NfL) levels, and symptoms associated with synucleinopathies. METHODS: This cross-sectional observational study included patients clinically diagnosed with CBS and PSP who underwent a lumbar puncture between 2012 and 2021 (Toronto Western Hospital, Canada). CSF was tested for αSyn-SAA positivity, AD biomarkers, and NfL levels. Clinical data were derived from medical records. RESULTS: We tested the CSF of 40 patients with CBS (19 female patients, 65.9 ± 8.6 years) and 28 with PSP (13 female patients, 72.5 ± 8.7 years old), mostly White (n = 50) or Asian (n = 14). αSyn-SAA positivity was observed in 35.9% patients with CBS and 28.6% with PSP. In young-onset, but not late-onset patients, αSyn-SAA positivity and AD positivity were associated (odds ratio [OR] 8.8, 95% CI 1.2-82.6, p < 0.05). A multivariable linear regression analysis showed a significant interaction of αSyn-SAA status by age at onset on CSF Aß42 levels (ß = 0.3 ± 0.1, p < 0.05). Indeed, age at onset was positively related to Aß42 levels only in αSyn-SAA-positive patients, as shown by slope comparison. A logistic regression analysis also suggested that REM sleep behavior disorder was associated with αSyn-SAA positivity (OR 60.2, 95% CI 5.2-1,965.8; p < 0.01). DISCUSSION: We detected a frequency of αSyn-SAA positivity in CBS and PSP in line with pathologic studies, highlighting the usefulness of SAAs for in vivo detection of otherwise undetectable neuropathologic processes. Our results also suggest that AD status (specifically low Aß42) and older age at onset may contribute to αSyn-SAA positivity. This opens new perspectives for the stratification of patients in clinical trials.

The associations between common neuroimaging parameters of Progressive Supranuclear Palsy in magnetic resonance imaging and non-specific inflammatory factors - pilot study.

Progressive Supranuclear Palsy is an atypical parkinsonism based on tauopathic pathology. Growing interest is associated with the pathomechanism of this disease. Among theories analyzing this issue can be mentioned the one highlighting the significance of inflammation. In this study authors examined 14 patients with PSP-Richardson syndrome (PSP-RS) and 13 healthy volunteers using laboratory testing based on the analysis of interleukins 1 and 6 (IL-1 and IL-6), tau in the cerebrospinal fluid (CSF) and non-specific parameters of peripheral inflammation in the serum (IL-1, IL-6, neutrophils, lymphocytes, monocytes, platelets and the ratios based on the factors). All of the patients underwent neuroimaging using magnetic resonance imaging using 3 Tesla. The serum levels of IL-1 were positively correlated with the area of the mesencephalon, suggesting that higher levels of IL-1 are not linked with atrophic changes in this region, whereas serum levels IL-6 was positively correlated with frontal horn width and negatively correlated with superior cerebellar area. Additionally IL-6 in the serum was found to be correlated with neutrophil-to-high density lipoprotein ratio. The observations were not confirmed in the analysis of the levels of interleukins in the CSF. To the best of our knowledge this work is one of the first analyzing this issue. The outcome of the work shows that the role of interleukins associated with microglial activation may possibly differ in the context of neurodegenerative changes, moreover the role of peripheral inflammation in PSP requires further analysis.

Serum and cerebrospinal fluid urate levels in synucleinopathies versus tauopathies.

BACKGROUND: Low levels of serum urate are associated with a higher risk of Parkinson's disease (PD). Higher serum and cerebrospinal fluid (CSF) urate levels are associated with slower rates of clinical decline in PD and in multiple system atrophy (MSA). AIMS: To compare CSF and blood urate levels in healthy controls, patients with synucleinopathies and with tauopathies. METHODS: We investigated urate levels in serum and CSF from 18 healthy controls, 19 patients with synucleinopathies (six patients with PD and 13 with MSA), and 24 patients with tauopathies (18 with progressive supranuclear palsy and six with corticobasal degeneration). None of the patients were treated with dopaminergic medications. RESULTS: No significant differences were seen when comparing serum and CSF urate levels from controls across the parkinsonian diagnostic groups. However, in men, serum urate levels were significantly lower in the synucleinopathy group compared with the tauopathy group (P = 0.046), although with a broad overlap. CONCLUSION: Our study suggests that urate levels might provide new insights into the potential pathophysiological mechanisms underlying Parkinsonism and thereby contribute to the future management of these disorders.

Neurofilament Light Chain Levels in Frontotemporal Dementia and Progressive Supranuclear Palsy: A Systematic Review.

BACKGROUND: It can be challenging to discriminate between progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD). However, a correct diagnosis is a precondition for targeted treatment strategies and proper patient counseling. There has been a growing interest to identify cerebrospinal fluid (CSF) biomarkers, including neurofilament light chain (NfL). OBJECTIVE: This systematic review evaluates the existing literature on neurofilament light in CSF aiming to validate its utility for differentiating FTD from PSP. METHODS: A systematic literature search was conducted. A broad range of synonyms for PSP, NfL, and FTD as well as associated MeSH terms, were combined and used as keywords when searching. Relevant data were extracted and assessed for risk of bias. RESULTS: Nine studies including a total of 671 patients with FTD, 254 patients with PSP, 523 healthy controls, and 1,771 patients with other disorders were included in the review. Four studies found a significantly higher level of CSF NfL in FTD (n = 445) compared to PSP (n = 124); however, in three of these studies the difference was only significant in certain FTD variants. Four studies found no significant difference in CSF NfL between PSP (n = 98) and FTD (n = 248). One study found a significantly higher level of NfL in PSP (n = 33) compared to FTD (n = 16). CONCLUSION: In the majority of patients in the studies included in this review, a higher level of NfL in CSF was found in patients with FTD compared to patients with PSP; however, results were inconsistent and prospective studies including large study cohorts are needed.