Ultrasensitive Detection of Aggregated α-Synuclein in Glial Cells, Human Cerebrospinal Fluid, and Brain Tissue Using the RT-QuIC Assay: New High-Throughput Neuroimmune Biomarker Assay for Parkinsonian Disorders

Adult-onset neurodegenerative disorders, like Parkinson's disease (PD) and dementia with Lewy bodies (DLB), that share the accumulation of aggregated α-synuclein (αSynagg) as their hallmark molecular pathology are collectively known as α-synucleinopathies. Diagnosing α-synucleinopathies requires the post-mortem detection of αSynagg in various brain regions. Recent efforts to measure αSynagg in living patients include quantifying αSynagg in different biofluids as a biomarker for PD. We adopted the real-time quaking-induced conversion (RT-QuIC) assay to detect very low levels of αSynagg. We first optimized RT-QuIC for sensitivity, specificity, and reproducibility by using monomeric recombinant human wild-type αSyn as a substrate and αSynagg as the seed. Next, we exposed mouse microglia to αSyn pre-formed fibrils (αSynPFF) for 24 h. RT-QuIC assay revealed that the αSynPFF is taken up rapidly by mouse microglia, within 30 min, and cleared within 24 h. We then evaluated the αSyn RT-QuIC assay for detecting αSynagg in human PD, DLB, and Alzheimer's disease (AD) post-mortem brain homogenates (BH) along with PD and progressive supranuclear palsy (PSP) cerebrospinal fluid (CSF) samples and then determined protein aggregation rate (PAR) for αSynagg. The PD and DLB BH samples not only showed significantly higher αSynagg PAR compared to age-matched healthy controls and AD, but RT-QuIC was also highly reproducible with 94% sensitivity and 100% specificity. Similarly, PD CSF samples demonstrated significantly higher αSynagg PAR compared to age-matched healthy controls, with 100% sensitivity and specificity. Overall, the RT-QuIC assay accurately detects αSynagg seeding activity, offering a potential tool for antemortem diagnosis of α-synucleinopathies and other protein-misfolding disorders. Graphical Abstract A schematic representation of αSyn RT-QuIC assay.

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.

Mass Spectrometric Analysis of Cerebrospinal Fluid Ubiquitin in Alzheimer's Disease and Parkinsonian Disorders

PURPOSE

Dysfunctional proteostasis, with decreased protein degradation and an accumulation of ubiquitin into aggregated protein inclusions, is a feature of neurodegenerative diseases. Identifying new potential biomarkers in cerebrospinal fluid (CSF) reflecting this process could contribute important information on pathophysiology.

EXPERIMENTAL DESIGN

A developed method combining SPE and PRM-MS is employed to monitor the concentration of ubiquitin in CSF from subjects with Alzheimer's disease (AD), Parkinson's disease (PD), and progressive supranuclear palsy (PSP). Four independent cross-sectional studies are conducted, studies 1-4, including controls (n = 86) and participants with AD (n = 60), PD (n = 15), and PSP (n = 11).

RESULTS

The method shows a repeatability and intermediate precision not exceeding 6.1 and 7.9%, respectively. The determined LOD is 0.1 nm and the LOQ range between 0.625 and 80 nm. The CSF ubiquitin concentration is 1.2-1.5-fold higher in AD patients compared with controls in the three independent AD-control studies (Study 1, p < 0.001; Study 2, p < 0.001; and Study 3, p = 0.003). In the fourth study, there is no difference in PD or PSP, compared to controls.

CONCLUSION AND CLINICAL RELEVANCE

CSF ubiquitin may reflect dysfunctional proteostasis in AD. The described method can be used for further exploration of ubiquitin as a potential biomarker in neurodegenerative diseases.

Distinct Lysosomal Network Protein Profiles in Parkinsonian Syndrome Cerebrospinal Fluid

BACKGROUND

Clinical diagnosis of parkinsonian syndromes like Parkinson's disease (PD), corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) is hampered by overlapping symptomatology and lack of diagnostic biomarkers, and definitive diagnosis is only possible post-mortem.

OBJECTIVE

Since impaired protein degradation plays an important role in many neurodegenerative disorders, we hypothesized that profiles of select lysosomal network proteins in cerebrospinal fluid could be differentially expressed in these parkinsonian syndromes.

METHODS

Cerebrospinal fluid samples were collected from PD patients (n = 18), clinically diagnosed 4-repeat tauopathy patients; corticobasal syndrome (CBS) (n = 3) and PSP (n = 8); and pathologically diagnosed PSP (n = 8) and CBD patients (n = 7). Each patient set was compared to its appropriate control group consisting of age and gender matched individuals. Select lysosomal network protein levels were detected via Western blotting. Factor analysis was used to test the diagnostic sensitivity, specificity and accuracy of the select lysosomal network protein expression profiles.

RESULTS

PD, CBD and PSP were markedly different in their cerebrospinal fluid lysosomal network protein profiles. Lysosomal-associated membrane proteins 1 and 2 were significantly decreased in PD; early endosomal antigen 1 was decreased and lysozyme increased in PSP; and lysosomal-associated membrane proteins 1 and 2, microtubule-associated protein 1 light chain 3 and lysozyme were increased in CBD. A panel of lysosomal-associated membrane protein 2, lysozyme and microtubule-associated protein 1 light chain discriminated between controls, PD and 4-repeat tauopathies.

CONCLUSIONS

This study offers proof of concept that select lysosomal network proteins are differentially expressed in cerebrospinal fluid of Parkinson's disease, corticobasal syndrome and progressive supranuclear palsy. Lysosomal network protein analysis could be further developed as a diagnostic fluid biomarker in parkinsonian syndromes.

CSF biomarker profiles do not differentiate between the cerebellar and parkinsonian phenotypes of multiple system atrophy

BACKGROUND

Multiple system atrophy (MSA) can clinically be divided into the cerebellar (MSA-C) and the parkinsonian (MSA-P) variants. It is unknown whether the variation in clinical expression is also reflected by a different underlying neurochemical profile.

METHODS

We analyzed brain specific proteins and neurotransmitter metabolites in cerebrospinal fluid (CSF) of 26 patients with MSA-C and 19 with MSA-P.

RESULTS

No differences were found between MSA-C and MSA-P.

CONCLUSION

Our results suggest that the clinical and in part pathological distinction between the two clinical MSA phenotypes is not reflected by the neurochemical composition of CSF.

Proteomic identification of biomarkers in the cerebrospinal fluid in a rat model of nigrostriatal dopaminergic degeneration

We have performed proteomic analysis in the cerebrospinal fluid in an animal model of Parkinson's disease induced by axotomy of the medial forebrain bundle. In this model, the degeneration of dopaminergic neurons was completed in 14 days, with a loss of about 50% dopaminergic neurons in the substantia nigra and a loss of more than 80% dopamine terminals in the striatum, with a similar diminution of dopamine levels in both structures. Proteins were separated by 2D electrophoresis and identified by matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF). We found significant increases of haptoglobin and transthyretin along with a decrease of Apo E concentrations in the cerebrospinal fluid of axotomized animals. Changes for haptoglobin and transthyretin were further confirmed in cerebrospinal fluid and plasma by Western blotting. These results suggest that monitoring plasma levels of these signals appears to be a promising biological marker of neuronal degeneration of the nigrostriatal dopaminergic system.

Neurofilament heavy-chain NfHSMI35 in cerebrospinal fluid supports the differential diagnosis of Parkinsonian syndromes

We aimed to evaluate the potential of the cerebrospinal fluid (CSF) axonal damage biomarker NfH(SMI35) in the laboratory-supported differential diagnosis of parkinsonian syndromes. Patients with idiopathic Parkinson's disease (PD; n = 22), multiple-system atrophy (MSA; n = 21), progressive supranuclear palsy (PSP; n = 21), corticobasal degeneration (CBD; n = 6), and age-matched controls (n = 45) were included. CSF levels of NfH(SMI35) were measured using ELISA. Levels of CSF NfH(SMI35) were elevated in PSP compared to PD and controls (P < 0.05 each). They were also significantly higher in MSA than in PD and controls (P < 0.05 each). NfH(SMI35) differentiated PD from PSP with a sensitivity of 76.5% and a specificity of 94.4%. Axonal damage as measured by CSF NfH(SMI35) is most prominent in the more rapidly progressive syndromes PSP and MSA as compared to PD or CBD. CSF NfH(SMI35) may therefore be of some value for the laboratory-supported differential diagnosis of atypical parkinsonian syndromes.

Parkinsonism in the course of HTLV-I-associated myelopathy

Parkinsonian syndromes may represent a complication of viral infection. Human T cell lymphotropic virus I (HTLV-I) is a cause of a chronic myelopathy in which encephalic involvement has been also found. We report on the case of a 60-year-old man with HTLV-I-associated myelopathy, complicated with bradykinesia, resting tremor, and cogwheel rigidity. These findings suggest that parkinsonian features may represent a neurological disorder associated with HTLV-I infection.

Parkinsonism with excessive daytime sleepiness

BACKGROUND

Parkinsonian patients with excessive daytime sleepiness (EDS), hallucinations, REM sleep behavior disorder (RBD), short mean sleep latencies, and sleep-onset REM periods (SOREMP) on multiple sleep latency tests (MSLT) have been reported. In these patients a narcolepsy-like pathophysiology of sleep-wake disturbances has been suggested.

PATIENTS AND METHODS

We studied 14 consecutive patients with Parkinsonism and EDS. Standard studies included assessment of duration and severity of Parkinsonism (Hoehn & Yahr score), Epworth sleepiness score (ESS), history of "REM-symptoms" (RBD/hallucinations/sleep paralysis/cataplexy-like episodes), polysomnography (PSG), MSLT, and measurement of cerebrospinal fluid (CSF) levels of hypocretin-1 (orexin A).

RESULTS

There were 12 men and 2 women (mean age 69 years; range 54-82). The mean duration and the Hoehn&Yahr score were 6.3 years and 2.2, respectively. Diagnoses included idiopathic Parkinson's disease (IPD, n = 10), dementia with diffuse Lewy bodies (n = 3), and multisystem atrophy (n = 1). The ESS was > or = 10 in all patients (mean 12; range 10-18). "REM-symptoms" were reported by all but two patients (hallucinations: n = 9; RBD: n = 9). None of the patients reported cataplexy-like symptoms or sleep paralysis. On PSG sleep apnea (apnea hypopnea index > 10/h, n = 7), periodic limb movements during sleep (PLMS-index > 10/h, n = 6), and features of RBD (n = 5) were found. On MSLT mean sleep latency was < 5 minutes in 10 patients, and SOREMP were found in two patients. When compared with controls (n = 20, mean 497 pg/ml; range 350-603), CSF hypocretin-1 levels were normal in 8 patients and low in 2 patients (221 and 307 pg/ml, respectively).

CONCLUSION

These findings do not support the hypothesis of a "final common pathway" in the pathophysiology of narcolepsy and Parkinsonism with EDS. Sleep apnea and PLMS may play a so-far underestimated role in the pathogenesis of EDS in Parkinsonian patients.

Liquid chromatography with amperometric detection at a nano crystalline Ce-doped lead dioxide film modified electrode for determination of (R)-Salsolinol, (R)-N-methylsalsolinol and monoamine neurotransmitters in Parkinsonian patients' cerebrospinal fluid

The fabrication and application of a novel electrochemical detector (ED) with nano crystalline Ce-doped lead dioxide film chemically modified electrode (CME) for liquid chromatography (LC) were described. The Ce-doped PbO(2) film was characterized by X-ray diffractometer (XRD) and scanning tunnel microscope (STM). The electrochemical behaviors of (R)-Salsolinol ((R)-Sal) at the CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the CME exhibited an efficiently electrocatalytic effect on the current responses of (R)-Sal, (R)-N-methylsalsolinol ((R)-NMSal) and monoamine neurotransmitters. In LC-ED, all (R)-Sal, (R)-NMSal, dopamine (DA), norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) had good and stable current responses at the CME. The linear ranges of the nine analytes were over three orders of magnitude (R(2) > 0.995). The application of this method coupled with microdialysis sampling for the determination of (R)-Sal, (R)-NMSal and monoamine neurotransmitters in Parkinsonian patients' cerebrospinal fluid (CSF) was satisfactory.

Cerebrospinal fluid 3,4-dihydroxyphenylacetic acid level after tolcapone administration as an indicator of nigrostriatal degeneration

The development of reliable biological markers of nigrostriatal degeneration has important implications from both experimental and clinical viewpoints, since such biomarkers could be used for diagnostic and monitoring purposes in models of parkinsonism as well as in Parkinson's disease patients. In this study, levels of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were measured in the cerebrospinal fluid (CSF) of normal and parkinsonian squirrel monkeys in order to assess their reliability as indicators of nigrostriatal injury. In particular, we tested the hypothesis that these measurements may become more accurate by inhibiting catecholamine-O-methyltransferase (COMT) activity and therefore blocking the conversion of DOPAC to homovanillic acid. Oral administration of the COMT inhibitor tolcapone (2 doses of 15 mg/kg each with a 4-h interval) significantly reduced enzyme activity in the monkey brain. Tolcapone treatment enhanced CSF DOPAC concentrations in unlesioned animals (by approximately four times) as well as monkeys rendered parkinsonian after severe nigrostriatal dopaminergic injury caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Importantly, however, COMT inhibition greatly magnified the differences in CSF DOPAC levels between control and parkinsonian monkeys, since MPTP-induced DOPAC depletion was 35% in the absence vs >60% in the presence of tolcapone. Thus, tolcapone administration enhances the detection of DOPAC in the CSF and, by doing so, improves the reliability of CSF DOPAC as a marker of nigrostriatal degeneration.

Voxel-based morphometry detects cortical atrophy in the Parkinson variant of multiple system atrophy

To determine magnetic resonance imaging (MRI) patterns of brain atrophy in parkinsonian syndromes, we applied voxel-based morphometry (VBM) to segmented gray matter, white matter, and cerebrospinal fluid compartments of T(1)-weighted brain volumes of 12 patients with probable multiple system atrophy-parkinson variant (MSA-P) and 12 Parkinson's disease patients, comparing them with 12 normal controls matched for age. In comparison to controls, a cortical atrophy pattern was observed in MSA-P patients with significant clusters of volume loss in primary sensorimotor cortices bilateral, supplementary motor areas bilateral, right premotor cortex, prefrontal cortex bilateral (middle frontal gyri) and insular cortices bilateral; subcortical atrophy occurred bilaterally in caudate nuclei and putamen as well as in the midbrain. Furthermore, an enlargement of the cerebrospinal fluid compartment was found in the lateral ventricles, third ventricle, perimesencephalic and cerebellomedullar cavities. In PD patients, significant atrophy only occurred in left caudate head with enlargement of left lateral ventricle. Comparing MSA-P to PD patients, MSA-P showed a similar cortical pattern of atrophy as compared to controls. We conclude that VBM reveals selective cortical atrophy in patients with MSA-P affecting primary and higher order motor areas as well as prefrontal and insular cortices. Further studies are required to determine clinical and/or subclinical correlates of cortical atrophy in MSA-P.

CSF-neurofilament and levodopa tests combined with discriminant analysis may contribute to the differential diagnosis of Parkinsonian syndromes

The differentiation between Parkinson's disease (PD), progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) is important for prognostic and therapeutic purposes. In order to evaluate the diagnostic capability of two tests reflecting these items, patients fulfilling strict clinical criteria for PD (n=35), MSA (n=36) and PSP (n=14), were consecutively included. An analysis of neurofilament protein (NFL), a marker of axonal degeneration in the cerebrospinal fluid (CSF) and a levodopa test, recorded with optoelectronic technique were performed. Using discriminant analyses, the test's abilities to predict the clinical PD or non-PD (MSA and PSP) diagnoses were compared. Whereas the CSF-NFL and levodopa tests predicted 79 and 85% correct diagnoses respectively, the combined test predicted 90% correct diagnoses. We conclude that the CSF-NFL and levodopa tests provide detailed information of clinical variables on which the clinical diagnostic criteria are based. As they are pathologically unrelated, the diagnostic precision increases compared to clinical diagnoses when they are combined.

Extrapontine myelinolysis with parkinsonism after rapid correction of hyponatremia: high cerebrospinal fluid level of homovanillic acid and successful dopaminergic treatment

Extrapontine myelinolysis (EPM) is a demyelinating process of the brain. We report the case of an 11-year-old girl who developed EPM with parkinsonism. Magnetic resonance imaging revealed demyelinating patterns in the basal ganglia without central pontine lesions. The cerebrospinal fluid levels of homovanillic acid and 5-hydroxyindoleacetic acid were high at the time of onset and normalized upon complete recovery from extrapyramidal symptoms after a dopaminergic treatment. We speculated that demyelination of nerve fibers containing dopamine receptors in the striatum might be a main cause of these symptoms.