A new paradigm for diagnosis of neurodegenerative diseases: peripheral exosomes of brain origin.

Neurodegenerative diseases are a heterogeneous group of maladies, characterized by progressive loss of neurons. These diseases involve an intricate pattern of cross-talk between different types of cells to maintain specific signaling pathways. A component of such intercellular cross-talk is the exchange of various types of extracellular vesicles (EVs). Exosomes are a subset of EVs, which are increasingly being known for the role they play in the pathogenesis and progression of neurodegenerative diseases, e.g., synucleinopathies and tauopathies. The ability of the central nervous system exosomes to cross the blood-brain barrier into blood has generated enthusiasm in their study as potential biomarkers. However, the lack of standardized, efficient, and ultra-sensitive methods for the isolation and detection of brain-derived exosomes has hampered the development of effective biomarkers. Exosomes mirror heterogeneous biological changes that occur during the progression of these incurable illnesses, potentially offering a more comprehensive outlook of neurodegenerative disease diagnosis, progression and treatment. In this review, we aim to discuss the challenges and opportunities of peripheral biofluid-based brain-exosomes in the diagnosis and biomarker discovery of Alzheimer's and Parkinson's diseases. In the later part, we discuss the traditional and emerging methods used for the isolation of exosomes and compare their advantages and disadvantages in clinical settings.

Selenium speciation analysis in the cerebrospinal fluid of patients with Parkinson's disease.

BACKGROUND: The aim of the study was to investigate if speciation analysis by liquid chromatography coupled to mass spectrometry could be used to detect organic and inorganic binding forms of selenium in the cerebrospinal fluid (CSF) of patients with Parkinson's disease (PD) and age-matched control subjects (AMC). METHODS: PD patients and control subjects were enrolled from three different neurological departments. CSF samples were collected according to standardized biomarker protocols and subjected to inductively coupled plasma mass spectrometry (ICP-MS) for total selenium determination and ion exchange chromatography (IEC) hyphenated to ICP-MS for selenium speciation analysis. RESULTS: 75 PD patients and 68 age-matched controls were enrolled for speciation analysis. 8 different species could be detected, but only selenoprotein P (SELENOP), human serum albumin-bound Se (Se-HSA), selenomethionine (Se-Met) and an unidentified Se-compound (U2) presented with more than 50% values above the limit of quantification, without showing significant differences between both groups (p > 0.05). The Se-HSA / Se-Met ratio yielded a significant difference between PD and AMC (p = 0.045). The inorganic species Se-IV and Se-VI were only detectable in a minor part of PD and AMC samples. A highly significant correlation between total selenium levels and SELENOP (PD p < 0.0001; AMC p < 0.0001) and Se-HSA (PD p < 0.0001; AMC p < 0.0001) could be demonstrated, respectively. CONCLUSIONS: Speciation analysis yielded new insight into selenium homeostasis in PD but cannot be used to establish a diagnostic biomarker. The small number of detectable values for Se-IV and Se-VI suggests an inferior role of these potentially neurotoxic binding forms in PD pathology in contrast to other neurodegenerative disorders.

Applications of the real-time quaking-induced conversion assay in diagnosis, prion strain-typing, drug pre-screening and other amyloidopathies.

INTRODUCTION: The development of in vitro protein misfolding amplification assays for the detection and analysis of abnormally folded proteins, such as proteinase K resistant prion protein (PrPres) was a major innovation in the prion field. In prion diseases, these types of assays imitate the pathological conversion of the cellular PrP (PrPC) into a proteinase resistant associated conformer or amyloid, called PrPres. Areas covered: The most prominent protein misfolding amplification assays are the protein misfolding cyclic amplification (PMCA), which is based on sonication and the real-time quaking-induced conversion (RT-QuIC) technique based on shaking. The more recently established RT-QuIC is fully automatic and enables the monitoring of misfolded protein aggregates in real-time by using a fluorescent dye. Expert commentary: RT-QuIC is a very robust and highly reproducible test system which is applicable in diagnosis, prion strain-typing, drug pre-screening and other amyloidopathies.

Identification of new molecular alterations in fatal familial insomnia.

Fatal familial insomnia is a rare disease caused by a D178N mutation in combination with methionine (Met) at codon 129 in the mutated allele of PRNP (D178N-129M haplotype). FFI is manifested by sleep disturbances with insomnia, autonomic disorders and spontaneous and evoked myoclonus, among other symptoms. This study describes new neuropathological and biochemical observations in a series of eight patients with FFI. The mediodorsal and anterior nuclei of the thalamus have severe neuronal loss and marked astrocytic gliosis in every case, whereas the entorhinal cortex is variably affected. Spongiform degeneration only occurs in the entorhinal cortex. Synaptic and fine granular proteinase K digestion (PrPres) immunoreactivity is found in the entorhinal cortex but not in the thalamus. Interleukin 6, interleukin 10 receptor alpha subunit, colony stimulating factor 3 receptor and toll-like receptor 7 mRNA expression increases in the thalamus in FFI. PrPc levels are significantly decreased in the thalamus, entorhinal cortex and cerebellum in FFI. This is accompanied by a particular PrPc and PrPres band profile. Altered PrP solubility consistent with significantly reduced PrP levels in the cytoplasmic fraction and increased PrP levels in the insoluble fraction are identified in FFI cases. Amyloid-like deposits are only seen in the entorhinal cortex. The RT-QuIC assay reveals that all the FFI samples of the entorhinal cortex are positive, whereas the thalamus is positive only in three cases and the cerebellum in two cases. The present findings unveil particular neuropathological and neuroinflammatory profiles in FFI and novel characteristics of natural prion protein in FFI, altered PrPres and Scrapie PrP (abnormal and pathogenic PrP) patterns and region-dependent putative capacity of PrP seeding.

Subtype-specific synaptic proteome alterations in sporadic Creutzfeldt-Jakob disease.

Sporadic Creutzfeldt-Jakob disease (sCJD) is characterized by wide clinical and pathological variability, which is mainly influenced by the conformation of the misfolded prion protein (PrPSc) and by methionine and valine polymorphism at codon 129 of the gene encoding PrP. This heterogeneity likely implies differences in the molecular cascades that lead to the development of certain disease phenotypes. Here, we investigated synaptic proteome patterns in two most common sCJD subtypes (MM1 and VV2) using 2D DIGE and mass spectrometry. We found that 23 distinct proteins were differentially expressed in at least one sCJD subtype when compared to age-matched controls. The majority of these proteins displayed significant subtype-specific alterations, with only up-regulated glial fibrillary acidic protein and down-regulated spectrin alpha chain in both sCJD subtypes. Differentially expressed proteins found in this study are mainly involved in synaptic structure and activity, mitochondrial function, or calcium metabolism. Moreover, several of them have been already linked to the pathophysiological processes occurring in Alzheimer's disease.

Proteome analysis of the thalamus and cerebrospinal fluid reveals glycolysis dysfunction and potential biomarkers candidates for schizophrenia.

Schizophrenia (SCZ) is the result of DNA alterations and environmental factors, which together lead to differential protein expression and ultimately to the development of the illness. The diagnosis is based on clinical symptoms, and the molecular background of SCZ is not completely understood. The thalamus, whose dysfunction has been associated with SCZ based in diverse lines of evidences, plays for instance a pivotal role in the central nervous system as a relay center by re-distributing auditory and visual stimuli from diverse brain regions to the cerebral cortex. We analyzed the proteome of postmortem mediodorsal thalamus (MDT) samples from 11 SCZ patients and 8 non-SCZ individuals by using quantitative shotgun-mass spectrometry and two-dimensional gel electrophoresis. Our analyses identified 551 proteins, 50 of which showed significant differential expression. The main pathways affected by the differentially expressed proteins include energy metabolism, oligodendrocyte metabolism, and cytoskeleton assembly. The potential protein biomarkers candidates myelin basic protein and myelin oligodendrocyte protein were validated by Western blot in the MDT samples and also in cerebrospinal fluid from a separate set of samples of 17 first-episode SCZ patients and 10 healthy controls. The differential expression of µ-crystallin, protein kinase C-gamma, and glial fibrillary acidic protein were confirmed in MDT. Because we found several glycolysis enzymes to be differentially expressed, we measured the levels of pyruvate and NADPH and found them to be altered in MDT. The protein changes described here corroborate the importance of myelin/oligodendrocyte and energy metabolism in SCZ and highlight new potential biomarkers candidates that may contribute to the understanding of the pathogenesis of this complex disease.

Clinical findings in sporadic Creutzfeldt-Jakob disease correlate with thalamic pathology.

The pathogenesis underlying the typical findings in Creutzfeldt-Jakob disease (CJD) such as periodic EEG changes or myoclonus is not fully understood. The thalamus possesses a high density of inhibitory neurones and serves as a crucial pacemaker of rhythmic EEG activity. As inhibitory neurones expressing parvalbumin (PV) are reduced in the cerebral cortex and hippocampus in sporadic CJD (sCJD), we studied the distribution and number of PV-immunoreactive neurones in sCJD thalami in order to determine whether damage to them could account for certain clinical findings. Immuno histochemical analysis was performed on the thalami from 21 sCJD patients and five controls. The number of PV+ neurones was counted in the thalamic nuclei and compared with clinical and molecular findings. In sCJD patients, PV+ neurones were significantly reduced in the ventrolateral posterior (VLp), ventrolateral anterior (VLa), anteroventral (AV), lateral dorsal (LD), mediodorsal (MD) and reticular (Re) thalamic nuclei (P < 0.05). The VLp was especially damaged in sCJD patients with homozygosity for methionine at codon 129 and scrapie prion protein (PrP(Sc)) type 1. Patients with typical EEG changes [periodic sharp wave complexes (PSWCs)] and myoclonus had a predominant loss of PV+ cells in the reticular thalamic nucleus. In conclusion, our data support the hypothesis that the damage to PV-immunoreactive neurones determines the generation of certain typical clinical features of CJD, i.e. PSWCs associated with myoclonus.