Plasma exosomal α-synuclein is likely CNS-derived and increased in Parkinson's disease

Plasma alpha-synuclein detected by single molecule array is increased in PD

We utilized ultrasensitive single molecule technology to measure plasma alpha-synuclein in 221 subjects (51 controls, 170 PD). Plasma alpha-synuclein levels were significantly higher in PD than controls (15506.3 vs. 13057.0 pg/mL, P = 0.037), adjusting for age and gender. In PD, alpha-synuclein levels did not vary by H&Y stage or UPDRS motor scores but were significantly higher in PD patients with poorer cognition (MMSE ≤ 25) than controls (P = 0.016, Bonferroni corrected P = 0.047). Alpha-synuclein levels quantified using ultrasensitive single molecule technology discriminate PD from controls and correlate with cognitive severity. These preliminary findings require independent validation to determine the utility of this assay.

Long Non-coding RNAs Associated With Neurodegeneration-Linked Genes Are Reduced in Parkinson's Disease Patients

Transcriptome analysis has identified a plethora of long non-coding RNAs (lncRNAs) expressed in the human brain and associated with neurological diseases. However, whether lncRNAs expression levels correlate with Parkinson's disease (PD) pathogenesis remains unknown. Herein, we show that a number of lncRNA genes encompassing transcriptional units in close proximity to PD-linked protein-coding genes, including SNCA, LRRK2, PINK1, DJ-1, UCH-L1, MAPT and GBA1, are expressed in human dopaminergic cells and post-mortem material, such as cortex, Substantia Nigra and cerebellum. Interestingly, these lncRNAs are upregulated during neuronal differentiation of SH-SY5Y cells and of dopaminergic neurons generated from human fibroblast-derived induced pluripotent stem cells. Importantly, six lncRNAs are found under-expressed in the nigra and three in the cerebellum of PD patients compared to controls. Simultaneously, SNCA mRNA levels are increased in the nigra, while LRRK2 and PINK1 mRNA levels are decreased both in the nigra and the cerebellum of PD subjects compared to controls, indicating a possible correlation between the expression profile of the respective lncRNAs with their adjacent coding genes. Interestingly, all dysregulated lncRNAs are also detected in human peripheral blood mononuclear cells and four of them in exosomes derived from human cerebrospinal fluid, providing initial evidence for their potential use as diagnostic tools for PD. Our data raise the intriguing possibility that these lncRNAs may be involved in disease pathogenesis by regulating their neighboring PD-associated genes and may thus represent novel targets for the diagnosis and/or treatment of PD or related diseases.

Extracellular Vesicles: Mechanisms in Human Health and Disease

SIGNIFICANCE

Secreted extracellular vesicles (EVs) are now considered veritable entities for diagnosis, prognosis, and therapeutics. These structures are able to interact with target cells and modify their phenotype and function. Recent Advances: Since composition of EVs depends on the cell type of origin and the stimulation that leads to their release, the analysis of EV content remains an important input to understand the potential effects of EVs on target cells.

CRITICAL ISSUES

Here, we review recent data related to the mechanisms involved in the formation of EVs and the methods allowing specific EV isolation and identification. Also, we analyze the potential use of EVs as biomarkers in different pathologies such as diabetes, obesity, atherosclerosis, neurodegenerative diseases, and cancer. Besides, their role in these diseases is discussed. Finally, we consider EVs enriched in microRNA or drugs as potential therapeutic cargo able to deliver desirable information to target cells/tissues.

FUTURE DIRECTIONS

We underline the importance of the homogenization of the parameters of isolation of EVs and their characterization, which allow considering EVs as excellent biomarkers for diagnosis and prognosis.

Microglia as modulators of exosomal alpha-synuclein transmission

Recent researches regarding to exosomal involvement in alpha-synuclein (α-syn) transmission relating to the pathological process of Parkinson's disease (PD) have attracted considerable attention. It is highly desirable to make clear the diffusion process and cellular uptake of α-syn-associated exosomes and the underlying mechanism of exosomes-involved communication in the synucleinopathy pathogenesis. To determine the contribution of α-syn-associated exosomes to the initiation and progression of PD, plasma exosomes derived from PD patients were stereotaxically injected into the striatum of mice brains. Exosomes extracted from plasma diagnosed with PD contained monomeric and oligomeric α-syn. Here, we found that microglia display a high potency for uptake of plasma exosomes derived from PD patients, and therefore could be activated by exogenous exosomes in vitro and in vivo. In addition, immunofluorescent double staining verified the transfer of exogenous human exosomal α-syn to neurons. The release of human exosomal α-syn from microglia may facilitate this propagation. Finally, we described a mechanism underlying this potential role of microglia in the transmission of exosomal α-syn. Specifically, exogenous exosomes were found to dysregulate autophagy of the BV2 mouse microglia cell line with presentation of increased accumulation of intracellular α-syn and accelerated secretion of α-syn into extracellular space. These results suggest that microglia play a crucial role in the transmission of α-syn via exosomal pathways, in additional to idea that the progression of PD may be altered by the modulation of exosome secretion and/or microglial states.

Exosomes in Parkinson's Disease: Current Perspectives and Future Challenges

Exosomes, which are lipid bilayer membrane vesicles, have been implicated as carriers of biological macromolecules. In recent years, the functions of exosomes in the spreading of pathological conversion of proteins among neurons have drawn particular attention in Parkinson's disease research. Extracellular α-synuclein is proven to be associated with exosomes in vivo and in vitro. The contents of these exosomes may be altered during the pathological and clinical processes, serving as a potential target for biomarker development in Parkinson's disease. This Review highlights the current understanding of biogenesis and pathophysiological roles of exosomes. Meanwhile, exosomes are promising delivery vehicles. Artificial exosomes can be loaded with defined therapeutically active molecules, such as drugs, small interfering RNAs, long noncoding RNAs, and proteins to the brain, ensuring the site-specific targeting strategy to the recipient cells. Therefore, we will also discuss the potential applications of exosomes in developing modified exosome-based drug carrier systems to halt the pathologic propagation of Parkinson's disease.

Mass spectrometry: A platform for biomarker discovery and validation for Alzheimer's and Parkinson's diseases

Accurate, reliable, and objective biomarkers for Alzheimer's disease (AD), Parkinson's disease (PD), and related age-associated neurodegenerative disorders are urgently needed to assist in both diagnosis, particularly at early stages, and monitoring of disease progression. Technological advancements in protein detection platforms over the last few decades have resulted in a plethora of reported molecular biomarker candidates for both AD and PD; however, very few of these candidates are developed beyond the discovery phase of the biomarker development pipeline, a reflection of the current bottleneck within the field. In this review, the expanded use of selected reaction monitoring (SRM) targeted mass spectrometry will be discussed in detail as a platform for systematic verification of large panels of protein biomarker candidates prior to costly validation testing. We also advocate for the coupling of discovery-based proteomics with modern targeted MS-based approaches (e.g., SRM) within a single study in future workflows to expedite biomarker development and validation for AD and PD. It is our hope that improving the efficiency within the biomarker development process by use of an SRM pipeline may ultimately hasten the development of biomarkers that both decrease misdiagnosis of AD and PD and ultimately lead to detection at early stages of disease and objective assessment of disease progression. This article is part of the special issue "Proteomics".

New windows into the brain: Central nervous system-derived extracellular vesicles in blood

Extracellular vesicles (EVs), including exosomes and (shedding) microvesicles, are released by nearly all cell types and carry a cargo of proteins and nucleic acids that varies by the cell of origin. They are thought to play critical roles in normal central nervous system (CNS) function and neurological disorders. A recently revealed key characteristic of EVs is that they may travel between the CNS and peripheral circulation. This property has led to intense interest in how EVs might serve as a vehicle for toxic protein clearance and as a readily accessible source of biomarkers for CNS disorders. Furthermore, by bypassing the blood-brain barrier, modified EVs could serve as a unique drug delivery system that targets specific neuronal populations. Further work is necessary to develop and optimize techniques that enable high-yield capture of relevant EV populations, analyze individual EVs and their cargos, and validate preliminary results of EV-derived biomarkers in independent cohorts.

Characterization of Plasma-Derived Extracellular Vesicles Isolated by Different Methods: A Comparison Study

Extracellular vesicles (EV) are small membrane structures released by cells that act as potent mediators of intercellular communication. The study of EV biology is important, not only to strengthen our knowledge of their physiological roles, but also to better understand their involvement in several diseases. In the field of biomedicine they have been studied as a novel source of biomarkers and drug delivery vehicles. The most commonly used method for EV enrichment in crude pellet involves serial centrifugation and ultracentrifugation. Recently, different protocols and techniques have been developed to isolate EV that imply less time and greater purification. Here we carry out a comparative analysis of three methods to enrich EV from plasma of healthy controls: ultracentrifugation, ExoQuick^TM precipitation solution (System Biosciences), and Total Exosome Isolation kit (Invitrogen). Our results show that commercial precipitation reagents are more efficient and enable higher EV enrichment factors compared with traditional ultracentrifugation, although subsequent imaging analysis is not possible with some of them. We hope that this work will contribute to the current research on isolation techniques to assist the progress of clinical applications with diagnostic or therapeutic objectives.

Increased DJ-1 and α-Synuclein in Plasma Neural-Derived Exosomes as Potential Markers for Parkinson's Disease

The diagnosis of PD might be in difficulty, especially in the early stages. Therefore, the identification of novel biomarkers is imperative for the diagnosis and monitoring disease progression in PD. DJ-1 and α-synuclein, are two proteins that are critically involved in the pathogenesis of PD, and they have been examined as disease biomarkers in studies. However, no study exists regarding DJ-1 in plasma neural-derived exosomes. In the present study, the levels of DJ-1 and α-synuclein in plasma neural-derived exosomes were studied together in order to investigate novel biomarkers for PD. DJ-1 and α-synuclein in plasma and plasma neural-derived exosomes of the patients with PD and controls were quantified by ELISAs. The data revealed that the levels of DJ-1 and α-synuclein in plasma neural-derived exosomes and the ratio of plasma neural-derived exosomal DJ-1 to total DJ-1 were significantly higher in patients with PD, compared with controls, while levels of the two proteins in plasma exhibited no difference between the patients with PD and controls. However, no relationship was identified between biomarkers and disease progression. In addition, significant positive correlations between DJ-1 and α-synuclein in plasma neural-derived exosomes were found in the patients with PD and in healthy individuals. We hypothesize that DJ-1 in plasma neural-derived exosomes may be used as a potential biomarker as α-synuclein in PD and they might participate in the mechanism of PD together.

Contributions of Drug Transporters to Blood-Brain Barriers

Blood-brain interfaces comprise the cerebral microvessel endothelium forming the blood-brain barrier (BBB) and the epithelium of the choroid plexuses forming the blood-cerebrospinal fluid barrier (BCSFB). Their main functions are to impede free diffusion between brain fluids and blood; to provide transport processes for essential nutrients, ions, and metabolic waste products; and to regulate the homeostasis of central nervous system (CNS), all of which are attributed to absent fenestrations, high expression of tight junction proteins at cell-cell contacts, and expression of multiple transporters, receptors, and enzymes. Existence of BBB is an important reason that systemic drug administration is not suitable for the treatment of CNS diseases. Some diseases, such epilepsy, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and diabetes, alter BBB function via affecting tight junction proteins or altering expression and function of these transporters. This chapter will illustrate function of BBB, expression of transporters, as well as their alterations under disease status.

Shotgun Proteomic Profiling of Bloodborne Nanoscale Extracellular Vesicles

Analyses of bloodborne nanoscale extracellular vesicles (nsEVs) have shown tremendous promise in enabling the development of noninvasive blood-based clinical diagnostic tests, predicting and monitoring the efficacy of treatment programs, and identifying new drug targets in the context of health conditions such as cancer and Alzheimer's disease. In this chapter we present a protocol for generating global nsEV proteomic profiles that can further the utility of nsEV analysis for the above biomedical applications by enlightening us of differences in protein abundance across normal and disease state nsEVs. This protocol features the use of magnetic particle-based immunoprecipitation to enrich highly purified populations of nsEVs directly from plasma or serum samples. The constituent proteins of these vesicles are subsequently characterized using a comparative shotgun proteomics approach that entails bottom-up, tandem mass spectrometric analysis of peptides generated by proteolytic digestion of nsEV-derived proteins. The methods described here are compatible with parallel processing of dozens of plasma or serum samples and can be valuable tools in enabling nsEV biomarker discoveries that have high translational relevance in the development of both novel therapeutics and blood sample diagnostic assays.

Blood-Brain Barrier: From Physiology to Disease and Back

The blood-brain barrier (BBB) prevents neurotoxic plasma components, blood cells, and pathogens from entering the brain. At the same time, the BBB regulates transport of molecules into and out of the central nervous system (CNS), which maintains tightly controlled chemical composition of the neuronal milieu that is required for proper neuronal functioning. In this review, we first examine molecular and cellular mechanisms underlying the establishment of the BBB. Then, we focus on BBB transport physiology, endothelial and pericyte transporters, and perivascular and paravascular transport. Next, we discuss rare human monogenic neurological disorders with the primary genetic defect in BBB-associated cells demonstrating the link between BBB breakdown and neurodegeneration. Then, we review the effects of genes underlying inheritance and/or increased susceptibility for Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and amyotrophic lateral sclerosis (ALS) on BBB in relation to other pathologies and neurological deficits. We next examine how BBB dysfunction relates to neurological deficits and other pathologies in the majority of sporadic AD, PD, and ALS cases, multiple sclerosis, other neurodegenerative disorders, and acute CNS disorders such as stroke, traumatic brain injury, spinal cord injury, and epilepsy. Lastly, we discuss BBB-based therapeutic opportunities. We conclude with lessons learned and future directions, with emphasis on technological advances to investigate the BBB functions in the living human brain, and at the molecular and cellular level, and address key unanswered questions.

α-Synuclein in salivary extracellular vesicles as a potential biomarker of Parkinson's disease

BACKGROUND

Detection of α-synuclein (α-syn) in biological fluids such as saliva may serve as potential biomarker of PD. α-syn pertaining to extracellular vesicles (EVs) has been recently studied in plasma, but not in other biological fluids such as saliva.

AIM

1) To investigate the presence of exosomes in PD saliva; 2) to explore the value of α-syn in salivary EVs as potential biomarker in PD.

METHODS

Saliva samples were obtained from 74 PD and 60 healthy controls (HCs). The EVs were extracted from saliva by XYCQ EV Enrichment KIT. Western blot and Nanosight 300 were used to validate the existence of exosomes in EVs and to analyze the size of salivary EVs. Salivary EVs α-syn levels, including total α-syn (α-syn_Total), oligomeric α-syn (α-syn_Olig) and phosphorylated-ser129 α-syn (α-syn_PS129), were measured by Electrochemiluminescence (ECL) assays. Diagnostic value and clinical relevance of salivary EVs α-syn were assessed by Receiver Operator Characteristic (ROC) curve and Spearman correlation.

RESULTS

Alix and CD9 positive EVs, representing the presence of exosomes, was detected in PD salivary samples. Size of salivary EVs was about 30-400 nm. The levels of α-syn_Olig and α-syn_Olig/α-syn_Total in the salivary EVs were higher in PD than in HCs (10.39 ± 1.46 pg/ng vs.1.37 ± 0.24 pg/ng, p＜0.001;1.70 ± 0.52 pg/ng vs.0.67 ± 0.26 pg/ng, p＜0.001). There was no significant difference in α-syn_Total、α-syn_PS129、 α-syn_PS129/α-syn_Total ratio between PD and HCs (P = 0.723, 0.634, 0.734, respectively). α-syn_Olig 2.05 pg/ng distinguished PD from HCs with sensitivity 92% and specificity 86%; α-syn_Olig /α-syn_Total 0.18 pg/ng differentiated PD from HCs with sensitivity 81% and specificity 71%. No significant correlation between salivary EVs α-syn_Olig, α-syn_Olig/α-syn_Total and disease severity was found.

CONCLUSIONS

Exosomes are present in PD saliva. The α-syn_Olig and α-syn_Olig/α-syn_Total ratio in salivary EVs may serve as potential diagnostic biomarkers for PD.

Toward Exosome-Based Neuronal Diagnostic Devices

Targeting exosome for liquid biopsy has gained significant attention for its diagnostic and therapeutic potential. For detecting neuronal disease diagnosis such as Alzheimer's disease (AD), the main technique for identifying AD still relies on positron-emission tomography (PET) imaging to detect the presence of amyloid-β (Aβ). While the detection of Aβ in cerebrospinal fluid has also been suggested as a marker for AD, the lack of quantitative measurements has compromised existing assays. In cerebrospinal fluid, in addition to Aβ, T-Tau, and P-Tau, alpha-synuclein has been considered a biomarker of neurodegeneration. This review suggests that and explains how the exosome can be used as a neuronal diagnostic component. To this end, we summarize current progress in exosome preparation/isolation and quantification techniques and comment on the outlooks for neuronal exosome-based diagnostic techniques.

New Perspectives on Roles of Alpha-Synuclein in Parkinson's Disease

Parkinson’s disease (PD) is one of the synucleinopathies spectrum of disorders typified by the presence of intraneuronal protein inclusions. It is primarily composed of misfolded and aggregated forms of alpha-synuclein (α-syn), the toxicity of which has been attributed to the transition from an α-helical conformation to a β-sheetrich structure that polymerizes to form toxic oligomers. This could spread and initiate the formation of “LB-like aggregates,” by transcellular mechanisms with seeding and subsequent permissive templating. This hypothesis postulates that α-syn is a prion-like pathological agent and responsible for the progression of Parkinson’s pathology. Moreover, the involvement of the inflammatory response in PD pathogenesis has been reported on the excessive microglial activation and production of pro-inflammatory cytokines. At last, we describe several treatment approaches that target the pathogenic α-syn protein, especially the oligomers, which are currently being tested in advanced animal experiments or are already in clinical trials. However, there are current challenges with therapies that target α-syn, for example, difficulties in identifying varying α-syn conformations within different individuals as well as both the cost and need of long-duration large trials.

Quantification of brain-derived extracellular vesicles in plasma as a biomarker to diagnose Parkinson's and related diseases

INTRODUCTION

There is still a substantial unmet need for blood-based biomarkers to make an objective diagnosis of Parkinson's disease (PD) and the parkinsonism-plus syndromes. This study is aimed to determine whether enumeration of brain-derived exosomes (BDEs) in plasma is informative in the diagnosis of those diseases.

METHODS

We have developed a specific method to enumerate the plasma levels of neuron-derived, astrocyte-derived, and oligodendrocyte-derived exosomes (NDEs, ADEs and ODEs, respectively), and quantified them individually in patients with PD (n = 15), multiple system atrophy (MSA, n = 15), progressive supranuclear palsy (PSP, n = 7) and disease controls (n = 15). Our assays employ specific antibodies against molecules expressed by neurons, astrocytes and oligodendrocytes, respectively, combined with an antibody to the exosome common marker CD81.

RESULTS

The plasma levels of NDEs showed significant increase in PD compared to control (p < 0.01) and MSA (p < 0.05) (one-way ANOVA, Bonferroni post hoc test). The plasma levels of ODEs and the ratio of ODE/NDE showed a significant correlation with UPDRS part III scores in the patients with MSA with predominant parkinsonism (MSA-P) (r² = 0.57, n = 6, p = 0.048) and in the patients with PD (r² = 0.51, n = 14, p = 0.0041), respectively.

CONCLUSIONS

This is the first paper that enumerated NDE, ADE, and ODE in human plasma and showed the usefulness of those levels as biomarkers for PD. Our results suggest the capability of the plasma levels of NDE and ODE as a diagnostic and surrogate biomarker for PD and MSA-P, respectively.

Diagnostic biomarkers for Parkinson's disease: focus on α-synuclein in cerebrospinal fluid

Diagnostic biomarkers are measures that detect or confirm the presence of a disease or identify individuals with a subtype of the disease. For Parkinson's disease, unlike other neurodegenerative diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease, diagnostic biomarkers remain elusive as none are yet available or approved for clinical use. A biomarker to diagnose early or prodromal Parkinson's disease with high accuracy would significantly enhance clinical practice as well as advance clinical therapeutic trials. Multiple lines of evidence support a role of α-synuclein in the pathophysiology of Parkinson's disease and hence major ongoing efforts to identify biomarkers for Parkinson's disease are aimed at measuring α-synuclein in peripheral tissues and biofluids, including cerebrospinal fluid. This work is still in the early stages of biomarker development and has been accompanied by both losses and victories. Here, α-synuclein in cerebrospinal fluid as a diagnostic marker for Parkinson's disease is reviewed, including measures of total α-synuclein, oligomeric and phosphorylated α-synuclein, and seeding activity of α-synuclein.

Secretion and Uptake of α-Synuclein Via Extracellular Vesicles in Cultured Cells

In Parkinson’s disease and other Lewy body disorders, the propagation of pathology has been accredited to the spreading of extracellular α-synuclein (α-syn). Although the pathogenic mechanisms are not fully understood, cell-to-cell transfer of α-syn via exosomes and other extracellular vesicles (EVs) has been reported. Here, we investigated whether altered molecular properties of α-syn can influence the distribution and secretion of α-syn in human neuroblastoma cells. Different α-syn variants, including α-syn:hemi-Venus and disease-causing mutants, were overexpressed and EVs were isolated from the conditioned medium. Of the secreted α-syn, 0.1–2% was associated with vesicles. The major part of EV α-syn was attached to the outer membrane of vesicles, whereas a smaller fraction was found in their lumen. For α-syn expressed with N-terminal hemi-Venus, the relative levels associated with EVs were higher than for WT α-syn. Moreover, such EV-associated α-syn:hemi-Venus species were internalized in recipient cells to a higher degree than the corresponding free-floating forms. Among the disease-causing mutants, A53T α-syn displayed an increased association with EVs. Taken together, our data suggest that α-syn species with presumably lost physiological functions or altered aggregation properties may shift the cellular processing towards vesicular secretion. Our findings thus lend further support to the tenet that EVs can mediate spreading of harmful α-syn species and thereby contribute to the pathology in α-synucleinopathies.

Physiological clearance of tau in the periphery and its therapeutic potential for tauopathies

Accumulation of pathological tau is the hallmark of Alzheimer's disease and other tauopathies and is closely correlated with cognitive decline. Clearance of pathological tau from the brain is a major therapeutic strategy for tauopathies. The physiological capacity of the periphery to clear brain-derived tau and its therapeutic potential remain largely unknown. Here, we found that cisterna magna injected ¹³¹I-labelled synthetic tau dynamically effluxed from the brain and was mainly cleared from the kidney, blood, and liver in mice; we also found that plasma tau levels in inferior vena cava were lower than those in femoral artery in humans. These findings suggest that tau proteins can efflux out of the brain and be cleared in the periphery under physiological conditions. Next, we showed that lowering blood tau levels via peritoneal dialysis could reduce interstitial fluid (ISF) tau levels in the brain, and tau levels in the blood and ISF were dynamically correlated; furthermore, tau efflux from the brain was accelerated after the addition of another set of peripheral system in a parabiosis model. Finally, we established parabiosis mouse models using tau transgenic mice and their wild-type littermates and found that brain tau levels and related pathologies in parabiotic transgenic mice were significantly reduced after parabiosis, suggesting that chronic enhancement of peripheral tau clearance alleviates pathological tau accumulation and neurodegeneration in the brain. Our study provides the first evidence of physiological clearance of brain-derived pathological tau in the periphery, suggesting that enhancing peripheral tau clearance is a potential therapeutic strategy for tauopathies.

Proteomic Profiling of Exosomal Proteins for Blood-based Biomarkers in Parkinson's Disease

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder and is characterized by loss of dopaminergic neurons. Biomarkers for tracking disease progression are useful indicators of the pathological conditions or the effects of therapeutic interventions on disease progression, but there are currently no known biomarkers in the blood that correlate with the progression of PD. Several studies have suggested that exosomes reflect intracellular changes that occur in response to pathological conditions and are an effective source of biomarkers for disease progression. To identify candidate biomarkers of disease progression in PD, we isolated exosomes from plasma of PD patients at Hoehn and Yahr (HY) stages II and III and performed protein profiling of the exosomes using two-dimensional differential gel electrophoresis (2D-DIGE). The expression levels of three proteins (clusterin, complement C1r subcomponent, and apolipoprotein A1) in PD patients at HY stages II and III were significantly decreased compared to healthy subjects (p < 0.05). Apolipoprotein A1 in PD patients at HY stage III was significantly decreased compared to HY stage II and correlated with progression of PD (r < -0.77, p < 0.01). Fibrinogen gamma chain in plasma was also decreased in PD patients at HY stages II and III compared to healthy subjects. Therefore, these three exosomal proteins (clusterin, complement C1r subcomponent, and apolipoprotein A1) and fibrinogen gamma chain in plasma may be biomarker candidates for the diagnosis of PD. In particular, the expression levels of apolipoprotein A1 in exosomes may be useful for tracking the progression of PD.

Potential of Extracellular Vesicles in Neurodegenerative Diseases: Diagnostic and Therapeutic Indications

Extracellular vesicles (EVs) are membrane-bound vesicles, including exosomes and microvesicles. EVs are nanometer sized, found in physiological fluids such as urine, blood, cerebro-spinal fluid (CSF), with a capacity of transferring various biological materials such as microRNAs, proteins, and lipids among cells without direct cell-to-cell contact. Many cells in the nervous system have been shown to release EVs. These vesicles are involved in intercellular communication and a variety of biological processes such as modulation of immune response, signal transduction, and transport of genetic materials with low immunogenicity; therefore, they have also been recently investigated for the delivery of therapeutic molecules such as siRNAs and drugs in the treatment of diseases. In addition, since EV components reflect the physiological status of the cells and tissues producing them, they can be utilized as biomarkers for early detection of various diseases. In this review, we summarize EV application, in diagnosis as biomarker sources and as a carrier tool for drug delivery in EV-based therapies in neurodegenerative diseases.

The role of T cells in the pathogenesis of Parkinson's disease

Recent evidence has shown that neuroinflammation plays a key role in the pathogenesis of Parkinson's disease (PD). However, different components of the brain's immune system may exert diverse effects on neuroinflammatory events in PD. The adaptive immune response, especially the T cell response, can trigger type 1 pro-inflammatory activities and suppress type 2 anti-inflammatory activities, eventually resulting in deregulated neuroinflammation and subsequent dopaminergic neurodegeneration. Additionally, studies have increasingly shown that therapies targeting T cells can alleviate neurodegeneration and motor behavior impairment in animal models of PD. Therefore, we conclude that abnormal T cell-mediated immunity is a fundamental pathological process that may be a promising translational therapeutic target for Parkinson's disease.

Exosomes and their implications in central nervous system tumor biology

Exosomes are 20-100 nm cellular derived vesicles that upon discovery, were thought to be a form of cellular recycling of intracellular contents. More recently, these vesicles are under investigation for their purported significant roles in intercellular communication in both healthy and diseased states. Herein, we focus on the secretion of exosomes associated with glioblastoma, as most exosome studies on brain tumors have been performed in this tumor type. However, we included exosomes secreted from other forms of brain tumors for comparison as available. Exosomes contain intracellular content that can be transferred to other cells in the tumor or to cells of the immune system and endothelial cells. These recipient cells may subsequently take on oncogenic properties, including therapeutic resistance, cancer progression, and angiogenesis. Genetic components (DNA, RNA and miRNA) of the cell of origin may be included in the secreted exosomes. The presence of genetic material in the exosomes could serve as a biomarker for mutations in tumors, potentially leading to novel treatment strategies. In the last decade, exosomes have been identified as having a major impact on multiple aspects of medicine and tumor biology, and appear to be primed for a critical position in cancer diagnosis, prognosis, and treatment.

A Critical Assessment of Exosomes in the Pathogenesis and Stratification of Parkinson's Disease

Extracellular vesicles including exosomes are released by a variety of cell types including neurons and exhibit molecular profiles that reflect normal and disease states. As their content represents a snapshot of the intracellular milieu, they could be exploited as biomarkers of the otherwise inaccessible brain microenvironment. In addition they may contribute to the progression of neurodegenerative disorders by facilitating the spread of misfolded proteins at distant sites or activating immune cells. This review summarizes recent advances in the study of exosomes in Parkinson’s disease pathophysiology and their potential as disease biomarkers.

Protective Effects of Fibroblast Growth Factor 21 Against Amyloid-Beta1-42-Induced Toxicity in SH-SY5Y Cells

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the progressive loss of cholinergic neurons. Amyloid beta is a misfolded protein that represents one of the key pathological hallmarks of AD. Numerous studies have shown that Aβ_1-42 induces oxidative damage, neuroinflammation, and apoptosis, leading to cognitive decline in AD. Recently, fibroblast growth factor 21 (FGF21) has been suggested to be a potential regulator of oxidative stress in mammalian cells. FGF21 has been shown to improve insulin sensitivity, reduce hyperglycemia, increase adipose tissue glucose uptake and lipolysis, and decrease body fat and weight loss by enhancing energy expenditure. In this study, we investigated the effect of FGF21 Aβ_1-42 toxicity in SH-SY5Y neuroblastoma cells. Our data shows that FGF21 significantly decreased Aβ_1-42-induced toxic effects and repressed oxidative stress and apoptosis in cells exposed to Aβ_1-42 peptide. Our investigation also confirmed that FGF21 pretreatment favorably affects HSP90/TLR4/NF-κB signaling pathway. Therefore, FGF21 represents a viable therapeutic strategy to abrogate Aβ_1-42-induced cellular inflammation and apoptotic death in the SH-SY5Y neuroblastoma cells.

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force takes now the opportunity to extend and update the original paper. New concepts of Alzheimer's disease (AD) and the conceptual interactions between AD and dementia due to AD were developed, resulting in two sets for diagnostic/research criteria. Procedures for pre-analytical sample handling, biobanking, analyses and post-analytical interpretation of the results were intensively studied and optimised. A global quality control project was introduced to evaluate and monitor the inter-centre variability in measurements with the goal of harmonisation of results. Contexts of use and how to approach candidate biomarkers in biological specimens other than cerebrospinal fluid (CSF), e.g. blood, were precisely defined. Important development was achieved in neuroimaging techniques, including studies comparing amyloid-β positron emission tomography results to fluid-based modalities. Similarly, development in research laboratory technologies, such as ultra-sensitive methods, raises our hopes to further improve analytical and diagnostic accuracy of classic and novel candidate biomarkers. Synergistically, advancement in clinical trials of anti-dementia therapies energises and motivates the efforts to find and optimise the most reliable early diagnostic modalities. Finally, the first studies were published addressing the potential of cost-effectiveness of the biomarkers-based diagnosis of neurodegenerative disorders.

The Exosomal/Total α-Synuclein Ratio in Plasma Is Associated With Glucocerebrosidase Activity and Correlates With Measures of Disease Severity in PD Patients

Intensive research efforts in the field of Parkinson’s disease (PD) are focusing on identifying reliable biomarkers which possibly help physicians in predicting disease onset, diagnosis, and progression as well as evaluating the response to disease-modifying treatments. Given that abnormal alpha-synuclein (α-syn) accumulation is a primary component of PD pathology, this protein has attracted considerable interest as a potential biomarker for PD. Alpha-synuclein can be detected in several body fluids, including plasma, where it can be found as free form or in association with exosomes, small membranous vesicles secreted by virtually all cell types. Together with α-syn accumulation, lysosomal dysfunctions seem to play a central role in the pathogenesis of PD, given the crucial role of lysosomes in the α-syn degradation. In particular, heterozygous mutations in the GBA1 gene encoding lysosomal enzyme glucocerebrosidase (GCase) are currently considered as the most important risk factor for PD. Different studies have found that GCase deficiency leads to accumulation of α-syn; whereas at the same time, increased α-syn may inhibit GCase function, thus inducing a bidirectional pathogenic loop. In this study, we investigated whether changes in plasma total and exosome-associated α-syn could correlate with disease status and clinical parameters in PD and their relationship with GCase activity. We studied 39 PD patients (mean age: 65.2 ± 8.9; men: 25), without GBA1 mutations, and 33 age-matched controls (mean age: 61.9 ± 6.2; men: 15). Our results showed that exosomes from PD patients contain a greater amount of α-syn compared to healthy subjects (25.2 vs. 12.3 pg/mL, p < 0.001) whereas no differences were found in plasma total α-syn levels (15.7 vs. 14.8 ng/mL, p = 0.53). Moreover, we highlighted a significant increase of plasma exosomal α-syn/total α-syn ratio in PD patients (1.69 vs. 0.89, p < 0.001), which negatively correlates with disease severity (p = 0.014). Intriguingly, a significant inverse correlation between GCase activity and this ratio in PD subjects was found (p = 0.006). Additional and large-scale studies comparing GCase activity and pathological protein levels will be clearly needed to corroborate these data and determine whether the association between key players in the lysosomal system and α-syn can be used as diagnostic or prognostic biomarkers for PD.

Plasma α-synuclein and cognitive impairment in the Parkinson's Associated Risk Syndrome: A pilot study

Plasma total and nervous system derived exosomal (NDE) α-synuclein have been determined as potential biomarkers of Parkinson's disease (PD). To explore the utility of plasma α-synuclein in the prodromal phase of PD, plasma total and NDE α-synuclein were evaluated in baseline and 2-year follow-up samples from 256 individuals recruited as part of the Parkinson's Associated Risk Syndrome (PARS) study. The results demonstrated that baseline and longitudinal increases in total α-synuclein predicted progression of cognitive decline in hyposmic individuals with dopamine transporter (DAT) binding reduction. On the other hand, a longitudinal decrease in NDE α-synuclein predicted worsening cognitive scores in hyposmic individuals with DAT binding reduction. Finally, in individuals with faster DAT progression, decreasing NDE/total α-synuclein ratio was associated with a larger reduction in DAT from baseline to follow-up. These results suggest that, though underlying mechanisms remain to be defined, alterations in plasma total and NDE α-synuclein concentrations are likely associated with PD progression, especially in the aspect of cognitive impairment, at early stages of the disease.

Cerebrospinal fluid α-synuclein contributes to the differential diagnosis of Alzheimer's disease

INTRODUCTION

The ability of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers (amyloid β peptide 1-42, total tau, and phosphorylated tau) to discriminate AD from related disorders is limited. Biomarkers for other concomitant pathologies (e.g., CSF α-synuclein [α-syn] for Lewy body pathology) may be needed to further improve the differential diagnosis.

METHODS

CSF total α-syn, phosphorylated α-syn at Ser129, and AD CSF biomarkers were evaluated with Luminex immunoassays in 367 participants, followed by validation in 74 different neuropathologically confirmed cases.

RESULTS

CSF total α-syn, when combined with amyloid β peptide 1-42 and either total tau or phosphorylated tau, improved the differential diagnosis of AD versus frontotemporal dementia, Lewy body disorders, or other neurological disorders. The diagnostic accuracy of the combined models attained clinical relevance (area under curve ∼0.9) and was largely validated in neuropathologically confirmed cases.

DISCUSSION

Combining CSF biomarkers representing AD and Lewy body pathologies may have clinical value in the differential diagnosis of AD.

Extracellular Vesicles: Multimodal Envoys in Neural Maintenance and Repair

The physiology of the central nervous system (CNS) is built on a foundation of connection, integration, and the exchange of complex information among brain cells. Emerging evidence indicates that extracellular vesicles (EVs) are key players in the intercellular communication that underlies physiological processes such as synaptic plasticity and the maintenance of myelination. Furthermore, upon injury to the CNS, EVs may propagate inflammation across the blood-brain barrier and beyond, and also appear to mediate neuroprotection and modulate regenerative processes. In neurodegenerative diseases, EVs may play roles in the formation, spreading, and clearance of toxic protein aggregates. Here, we discuss the physiological roles of EVs in the healthy and the diseased CNS, with a focus on recent findings and emerging concepts.

Exogenous α-synuclein hinders synaptic communication in cultured cortical primary rat neurons

Amyloid aggregates of the protein α-synuclein (αS) called Lewy Bodies (LB) and Lewy Neurites (LN) are the pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. We have previously shown that high extracellular αS concentrations can be toxic to cells and that neurons take up αS. Here we aimed to get more insight into the toxicity mechanism associated with high extracellular αS concentrations (50-100 μM). High extracellular αS concentrations resulted in a reduction of the firing rate of the neuronal network by disrupting synaptic transmission, while the neuronal ability to fire action potentials was still intact. Furthermore, many cells developed αS deposits larger than 500 nm within five days, but otherwise appeared healthy. Synaptic dysfunction clearly occurred before the establishment of large intracellular deposits and neuronal death, suggesting that an excessive extracellular αS concentration caused synaptic failure and which later possibly contributed to neuronal death.

Tat controls transcriptional persistence of unintegrated HIV genome in primary human macrophages

In HIV infected macrophages, a large population of viral genomes persists as the unintegrated form (uDNA) that is transcriptionally active. However, how this transcriptional activity is controlled remains unclear. In this report, we investigated whether Tat, the viral transactivator of transcription, is involved in uDNA transcription. We demonstrate that de novo Tat activity is generated from uDNA, and this uDNA-derived Tat (uTat) transactivates the uDNA LTR. In addition, uTat is required for the transcriptional persistence of uDNA that is assembled into repressive episomal minichromatin. In the absence of uTat, uDNA minichromatin is gradually silenced, but remains highly inducible by HDAC inhibitors (HDACi). Therefore, functionally, uTat antagonizes uDNA minichromatin repression to maintain persistent viral transcription in macrophages. uTat-mediated viral persistence may establish a viral reservoir in macrophages where uDNA were found to persist.

Blood-brain barrier breakdown in Alzheimer disease and other neurodegenerative disorders

The blood-brain barrier (BBB) is a continuous endothelial membrane within brain microvessels that has sealed cell-to-cell contacts and is sheathed by mural vascular cells and perivascular astrocyte end-feet. The BBB protects neurons from factors present in the systemic circulation and maintains the highly regulated CNS internal milieu, which is required for proper synaptic and neuronal functioning. BBB disruption allows influx into the brain of neurotoxic blood-derived debris, cells and microbial pathogens and is associated with inflammatory and immune responses, which can initiate multiple pathways of neurodegeneration. This Review discusses neuroimaging studies in the living human brain and post-mortem tissue as well as biomarker studies demonstrating BBB breakdown in Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, multiple sclerosis, HIV-1-associated dementia and chronic traumatic encephalopathy. The pathogenic mechanisms by which BBB breakdown leads to neuronal injury, synaptic dysfunction, loss of neuronal connectivity and neurodegeneration are described. The importance of a healthy BBB for therapeutic drug delivery and the adverse effects of disease-initiated, pathological BBB breakdown in relation to brain delivery of neuropharmaceuticals are briefly discussed. Finally, future directions, gaps in the field and opportunities to control the course of neurological diseases by targeting the BBB are presented.

New Technologies for Analysis of Extracellular Vesicles

Extracellular vesicles (EVs) are diverse, nanoscale membrane vesicles actively released by cells. Similar-sized vesicles can be further classified (e.g., exosomes, microvesicles) based on their biogenesis, size, and biophysical properties. Although initially thought to be cellular debris, and thus under-appreciated, EVs are now increasingly recognized as important vehicles of intercellular communication and circulating biomarkers for disease diagnoses and prognosis. Despite their clinical potential, the lack of sensitive preparatory and analytical technologies for EVs poses a barrier to clinical translation. New analytical platforms including molecular ones are thus actively being developed to address these challenges. Recent advances in the field are expected to have far-reaching impact in both basic and translational studies. This article aims to present a comprehensive and critical overview of emerging analytical technologies for EV detection and their clinical applications.

Tau Proteins Cross the Blood-Brain Barrier

Tauopathies are a hallmark of many neurodegenerative diseases, including Alzheimer's disease and traumatic brain injuries. It has been demonstrated that amyloid-beta peptides, alpha-synuclein, and prion proteins cross the blood-brain barrier (BBB), contributing to their abilities to induce disease. Very little is known about whether tau proteins can cross the BBB. Here we systematically characterized several key forms of tau proteins to cross the BBB, including Tau-441 (2N4R), Tau-410 (2N3R), truncated tau 151-391 (0N4R), and truncated tau 121-227. All of these tau proteins crossed the BBB readily and bidirectonally; however, only Tau-410 had a saturable component to its influx. The tau proteins also entered the blood after their injection into the brain, with Tau 121-227 having the slowest exit from brain. The tau proteins varied in regards to their enzymatic stability in brain and blood and in their peripheral pharmacokinetics. These results show that blood-borne tau proteins could contribute to brain tauopathies. The result also suggest that the CNS can contribute to blood levels of tau, raising the possibility that, as suggested for other misfolded proteins, blood levels of tau proteins could be used as a biomarker of CNS disease.

Astroglial major histocompatibility complex class I following immune activation leads to behavioral and neuropathological changes

In the central nervous system, major histocompatibility complex class I (MHCI) molecules are mainly expressed in neurons, and neuronal MHCI have roles in synapse elimination and plasticity. However, the pathophysiological significance of astroglial MHCI remains unclear. We herein demonstrate that MHCI expression is up-regulated in astrocytes in the medial prefrontal cortex (mPFC) following systemic immune activation by an intraperitoneal injection of polyinosinic-polycytidylic acid (polyI:C) or hydrodynamic interferon (IFN)-γ gene delivery in male C57/BL6J mice. In cultured astrocytes, MHCI/H-2D largely co-localized with exosomes. To investigate the role of astroglial MHCI, H-2D, or sH-2D was expressed in the mPFC of male C57/BL6J mice using an adeno-associated virus vector under the control of a glial fibrillary acidic protein promoter. The expression of astroglial MHCI in the mPFC impaired sociability and recognition memory in mice. Regarding neuropathological changes, MHCI expression in astrocytes significantly activated microglial cells, decreased parvalbumin-positive cell numbers, and reduced dendritic spine density in the mPFC. A treatment with GW4869 that impairs exosome synthesis ameliorated these behavioral and neuropathological changes. These results suggest that the overexpression of MHCI in astrocytes affects microglial proliferation as well as neuronal numbers and spine densities, thereby leading to social and cognitive deficits in mice, possibly via exosomes created by astrocytes.

Alpha-Synuclein as a Biomarker for Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disorder, characterized pathologically by the presence of α-synuclein (α-syn)-rich Lewy bodies. As clinical diagnosis of PD is challenging, misdiagnosis is common, highlighting the need for disease-specific and early stage biomarkers. Both early diagnosis of PD and adequate tracking of disease progression could significantly improve outcomes for patients, particularly in regard to existing and future disease modifying treatments. Given its critical roles in PD pathogenesis, α-syn may be useful as a biomarker of PD. The aim of this review is, therefore, to summarize the efficacy of tissue and body fluid α-syn measurements in the detection of PD as well as monitoring disease progression. In comparison to solid tissue specimens and biopsies, biofluid α-syn levels may be the most promising candidates in PD diagnosis and progression based on specificity, sensitivity and availability. Although α-syn has been tested most extensively in cerebrospinal fluid (CSF), the relatively invasive procedure for collecting CSF is not suitable in most clinical settings, leading to investigation of plasma, blood and saliva as alternatives. The exploration of combined biomarkers, along with α-syn, to improve diagnostic accuracy is also likely required.

Diagnostic Potential of Neural Exosome Cargo as Biomarkers for Acute Brain Injury

Objective

Neuronal exosomes purified from peripheral blood samples have been proposed as diagnostic tool in the setting of acute brain injury but never tested clinically. We hypothesized that exosome protein biomarkers would change over time following acute hypoxic brain injury and would predict response to therapy.

Methods

Synaptopodin (SYNPO), an actin-associated protein present in postsynaptic spines, was evaluated as a potential biomarker as well as: synaptophysin, neuron-specific enolase, and mitochondrial cytochrome c oxidase. A secondary analysis was performed on neonatal samples collected at 8, 10, and 14 h after the initiation of therapeutic-controlled hypothermia for acute hypoxic-ischemic encephalopathy (n = 14). Neuronal exosomes were purified from serum and protein levels were quantified using standard ELISA methods. The primary study outcomes were length of stay (LOS), discharge on seizure medication (DCMED), and composite neuroimaging score (NIS).

Results

The slope of change in neuronal exosome SYNPO between 8 and 14 h appeared to be the most promising biomarker for all three clinical study outcomes. SYNPO was highly correlated with LOS (-0.91, P < 0.001). SYNPO increased in 6/8 without DCMED and was worse or neutral in 5/5 with DCMED (P = 0.02). All four neonates with an abnormal NIS had neutral or decreasing SYNPO (P = 0.055). Other candidate biomarkers were not associated with outcomes.

Interpretation

This report provides the first clinical evidence that neural exosomes turn over rapidly enough in the peripheral circulation to be used as a "troponin-like" test following acute brain injury. Optimal sampling and biomarkers likely vary with type of brain injury.

Magnetic Particle-Based Immunoprecipitation of Nanoscale Extracellular Vesicles from Biofluids

Analysis of nanoscale extracellular vesicles (nsEVs) present in blood, cell culture media, and other biofluids has shown tremendous promise in enabling the development of noninvasive blood-based clinical diagnostic tests, predicting and monitoring the efficacy of treatment programs, and providing molecular level insights into pathology that can enlighten new drug targets in the contexts of health conditions such as cancer and Alzheimer's Disease (AD). In this chapter, we present methods for using magnetic particle-based immunoprecipitation to enrich highly purified populations of nsEVs directly from plasma, serum, and other biofluids. These methods enable downstream analysis of nsEV protein and nucleic acid constituents in the contexts of both global omics profiling and quantification of individual protein or nucleic acid species of interest. Additionally, these methods allow the researcher to either enrich total nsEV populations or enrich nsEVs derived from a particular tissue type from the overall nsEV population. The methods described here are compatible with parallel processing of dozens of biofluid samples and can be valuable tools for enabling nsEV analyses that have high translational relevance in the development of both novel therapeutics and noninvasive diagnostic assays.

Cerebrospinal fluid, plasma, and saliva in the BioFIND study: Relationships among biomarkers and Parkinson's disease Features

OBJECTIVE

Examine relationships among neurodegenerative biomarkers and PD motor and nonmotor symptoms.

BACKGROUND

CSF alpha-synuclein is decreased in PD versus healthy controls, but whether plasma and saliva alpha-synuclein differentiate these groups is controversial. Correlations of alpha-synuclein among biofluids (CSF, plasma, saliva) or biomarkers (eg, beta-amyloid, tau [total, phosphorylated]) are not fully understood. The relationships of these biomarkers with PD clinical features remain unclear.

METHODS

BioFIND, a cross-sectional, observational study, examines clinical and biomarker characteristics in moderate-advanced PD and matched healthy controls. We compared alpha-synuclein concentrations across diagnosis, biofluids, and CSF biomarkers. Correlations of CSF biomarkers and MDS-UPDRS, motor phenotype, MoCA, and rapid eye movement sleep behavior disorder questionnaire scores in PD were examined.

RESULTS

CSF alpha-synuclein was lower in PD versus controls (P = .01), controlling for age, gender, and education. Plasma and saliva alpha-synuclein did not differ between PD and controls, and alpha-synuclein did not significantly correlate among biofluids. CSF beta-amyloid_1-42 was lower in PD versus controls (P < .01), and correlated weakly with MoCA recall scores (r = 0.23, P = .02). CSF alpha-synuclein was lower in the postural instability/gait difficulty phenotype than other motor phenotypes (P < .01). No CSF biomarkers predicted or correlated with total motor or rapid eye movement sleep behavior disorder scores. CSF alpha-synuclein correlated with beta-amyloid_1-42 , total-tau, and phosphorylated-tau (r = 0.41, 0.81, 0.43, respectively; Ps < .001).

CONCLUSION

Lower CSF alpha-synuclein is associated with diagnosis and motor phenotype in moderate-advanced PD. Plasma and saliva alpha-synuclein neither correlate with CSF alpha-synuclein, nor distinguish PD from controls. CSF beta-amyloid_1-42 remains a potential biomarker for cognitive impairment in PD. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Extracellular vesicles in neurodegenerative diseases

Extracellular vesicles (EVs) are released by all neural cells, including neurons, oligodendrocytes, astrocytes, and microglia. The lack of adequate technology has not halted neuroscientists from investigating EVs as a mean to decipher neurodegenerative disorders, still in search of comprehensible pathogenic mechanisms and efficient treatment. EVs are thought to be one of ways neurodegenerative pathologies spread in the brain, but also one of the ways the brain tries to displace toxic proteins, making their meaning in pathogenesis uncertain. EVs, however do reach biological fluids where they can be analyzed, and might therefore constitute clinically decisive biomarkers for neurodegenerative diseases in the future. Finally, if they constitute a physiological inter-cell communication system, they may represent also a very specific drug delivery tool for a difficult target such as the brain. We try to resume here available information on the role of EVs in neurodegeneration, with a special focus on Alzheimer's disease, progressive multiple sclerosis, amyotrophic lateral sclerosis, and Huntington's disease.

The relation between plasma α-synuclein level and clinical symptoms or signs of Parkinson's disease

INTRODUCTION

Parkinson disease (PD) is the common neurodegenerative disease. α-Synuclein (ASN), main aggregating protein in neural cells of CNS in PD, was found in peripheral fluids. Testing ASN in plasma is potential test for diagnose PD, but previous studies are controversial. The aim of this study was to investigate if plasma ASN level may be a valuable biomarker, is the level of plasma ASN concentration different in various motor subtypes of diseases, is there a relation between the level of plasma ASN and the severity of motor symptoms.

METHODS

Patients with PD hospitalized in Neurology Department, Medical College were performed sequencing the 8th and 9th exon of GBA gene. Next plasma ASN level was tested in 58 patients with sequenced GBA gene and in 38 healthy volunteers (HV), matched by the age (respectively 68.43 vs. 64.57 years of age) and sex (female %, respectively: 43.10 vs.44.74). Patients were assessed with the scales: UPDRS (II, III, IV), Hoehn-Yahr (HY) and qualified to PIGD or TD subtype. For homogeneity of the group patients with GBA mutation were excluded from the analysis.

RESULTS

The ASN level did not differ between patients and HV (respectively: 4.53 vs. 3.73ng/ml) and between patients with different subtypes. There was inverse correlation between ASN and HY in PIGD subtype.

CONCLUSIONS

Plasma ASN level is not valuable marker of the disease. It does not differ in subtypes of the disease. There is relation between plasma ASN level and the severity of the disease in PIGD subtype.

Autoimmunity as a Driving Force of Cognitive Evolution

In the last decades, increasingly robust experimental approaches have formally demonstrated that autoimmunity is a physiological process involved in a large range of functions including cognition. On this basis, the recently enunciated “brain superautoantigens” theory proposes that autoimmunity has been a driving force of cognitive evolution. It is notably suggested that the immune and nervous systems have somehow co-evolved and exerted a mutual selection pressure benefiting to both systems. In this two-way process, the evolutionary-determined emergence of neurons expressing specific immunogenic antigens (brain superautoantigens) has exerted a selection pressure on immune genes shaping the T-cell repertoire. Such a selection pressure on immune genes has translated into the emergence of a finely tuned autoimmune T-cell repertoire that promotes cognition. In another hand, the evolutionary-determined emergence of brain-autoreactive T-cells has exerted a selection pressure on neural genes coding for brain superautoantigens. Such a selection pressure has translated into the emergence of a neural repertoire (defined here as the whole of neurons, synapses and non-neuronal cells involved in cognitive functions) expressing brain superautoantigens. Overall, the brain superautoantigens theory suggests that cognitive evolution might have been primarily driven by internal cues rather than external environmental conditions. Importantly, while providing a unique molecular connection between neural and T-cell repertoires under physiological conditions, brain superautoantigens may also constitute an Achilles heel responsible for the particular susceptibility of Homo sapiens to “neuroimmune co-pathologies” i.e., disorders affecting both neural and T-cell repertoires. These may notably include paraneoplastic syndromes, multiple sclerosis as well as autism, schizophrenia and neurodegenerative diseases. In the context of this theoretical frame, a specific emphasis is given here to the potential evolutionary role exerted by two families of genes, namely the MHC class II genes, involved in antigen presentation to T-cells, and the Foxp genes, which play crucial roles in language (Foxp2) and the regulation of autoimmunity (Foxp3).