Plasma exosomal α-synuclein is likely CNS-derived and increased in Parkinson’s disease
TL;DR: It is discovered that CSF α-synuclein was readily transported to blood, with a small portion being contained in exosomes that are relatively specific to the central nervous system (CNS), which may lead to a more convenient and robust assessment of Parkinson’s disease clinically.
Abstract: Extracellular α-synuclein is important in the pathogenesis of Parkinson’s disease (PD) and also as a potential biomarker when tested in the cerebrospinal fluid (CSF). The performance of blood plasma or serum α-synuclein as a biomarker has been found to be inconsistent and generally ineffective, largely due to the contribution of peripherally derived α-synuclein. In this study, we discovered, via an intracerebroventricular injection of radiolabeled α-synuclein into mouse brain, that CSF α-synuclein was readily transported to blood, with a small portion being contained in exosomes that are relatively specific to the central nervous system (CNS). Consequently, we developed a technique to evaluate the levels of α-synuclein in these exosomes in individual plasma samples. When applied to a large cohort of clinical samples (267 PD, 215 controls), we found that in contrast to CSF α-synuclein concentrations, which are consistently reported to be lower in PD patients compared to controls, the levels of plasma exosomal α-synuclein were substantially higher in PD patients, suggesting an increased efflux of the protein to the peripheral blood of these patients. Furthermore, although no association was observed between plasma exosomal and CSF α-synuclein, a significant correlation between plasma exosomal α-synuclein and disease severity (r = 0.176, p = 0.004) was observed, and the diagnostic sensitivity and specificity achieved by plasma exosomal α-synuclein were comparable to those determined by CSF α-synuclein. Further studies are clearly needed to elucidate the mechanism involved in the transport of CNS α-synuclein to the periphery, which may lead to a more convenient and robust assessment of PD clinically.
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TL;DR: 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.
Abstract: 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
1,507 citations
TL;DR: This review examines molecular and cellular mechanisms underlying the establishment of the blood-brain barrier, and examines 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.
Abstract: 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 t...
1,033 citations
TL;DR: This article aims to present a comprehensive and critical overview of emerging analytical technologies for EV detection and their clinical applications.
Abstract: Extracellular vesicles (EVs) are diverse, nanoscale membrane vesicles actively released by cells Similar-sized vesicles can be further classified (eg, 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
902 citations
TL;DR: This article will focus on EV composition, mechanisms of uptake, and their biological effects on recipient cells, and established and recently developed methods used to study EVs, including isolation, quantification, labeling and imaging protocols, as well as RNA analysis.
Abstract: The release of extracellular vesicles (EVs), including exosomes and microvesicles, is a phenomenon shared by many cell types as a means of communicating with other cells and also potentially removing cell contents. The cargo of EVs includes the proteins, lipids, nucleic acids, and membrane receptors of the cells from which they originate. EVs released into the extracellular space can enter body fluids and potentially reach distant tissues. Once taken up by neighboring and/or distal cells, EVs can transfer functional cargo that may alter the status of recipient cells, thereby contributing to both physiological and pathological processes. In this article, we will focus on EV composition, mechanisms of uptake, and their biological effects on recipient cells. We will also discuss established and recently developed methods used to study EVs, including isolation, quantification, labeling and imaging protocols, as well as RNA analysis.
695 citations
TL;DR: This review serves as an introductory overview of EVs, their biogenesis and molecular composition, and their physiological roles are still ill-defined.
Abstract: Intercellular communication was long thought to be regulated exclusively through direct contact between cells or via release of soluble molecules that transmit the signal by binding to a suitable receptor on the target cell, and/or via uptake into that cell. With the discovery of small secreted vesicular structures that contain complex cargo, both in their lumen and the lipid membrane that surrounds them, a new frontier of signal transduction was discovered. These “extracellular vesicles” (EV) were initially thought to be garbage bags through which the cell ejected its waste. Whilst this is a major function of one type of EV, i.e., apoptotic bodies, many EVs have intricate functions in intercellular communication and compound exchange; although their physiological roles are still ill-defined. Additionally, it is now becoming increasingly clear that EVs mediate disease progression and therefore studying EVs has ignited significant interests among researchers from various fields of life sciences. Consequently, the research effort into the pathogenic roles of EVs is significantly higher even though their protective roles are not well established. The “Focus on extracellular vesicles” series of reviews highlights the current state of the art regarding various topics in EV research, whilst this review serves as an introductory overview of EVs, their biogenesis and molecular composition.
571 citations
References
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TL;DR: A mutation was identified in the α-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype.
Abstract: Parkinson's disease (PD) is a common neurodegenerative disorder with a lifetime incidence of approximately 2 percent. A pattern of familial aggregation has been documented for the disorder, and it was recently reported that a PD susceptibility gene in a large Italian kindred is located on the long arm of human chromosome 4. A mutation was identified in the α-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype. This finding of a specific molecular alteration associated with PD will facilitate the detailed understanding of the pathophysiology of the disorder.
7,387 citations
"Plasma exosomal α-synuclein is like..." refers background in this paper
...Mechanistically, α-syn clearly plays an important role in PD pathogenesis, as mutations or multiplications of the α-syn gene (SNCA) are known to be causative of some familial forms of PD [41, 55]....
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TL;DR: Tumour-derived microvesicles may provide diagnostic information and aid in therapeutic decisions for cancer patients through a blood test by incorporating an mRNA for a reporter protein into them, and it is demonstrated that messages delivered by microvesicle are translated by recipient cells.
Abstract: Glioblastoma tumour cells release microvesicles (exosomes) containing mRNA, miRNA and angiogenic proteins. These microvesicles are taken up by normal host cells, such as brain microvascular endothelial cells. By incorporating an mRNA for a reporter protein into these microvesicles, we demonstrate that messages delivered by microvesicles are translated by recipient cells. These microvesicles are also enriched in angiogenic proteins and stimulate tubule formation by endothelial cells. Tumour-derived microvesicles therefore serve as a means of delivering genetic information and proteins to recipient cells in the tumour environment. Glioblastoma microvesicles also stimulated proliferation of a human glioma cell line, indicating a self-promoting aspect. Messenger RNA mutant/variants and miRNAs characteristic of gliomas could be detected in serum microvesicles of glioblastoma patients. The tumour-specific EGFRvIII was detected in serum microvesicles from 7 out of 25 glioblastoma patients. Thus, tumour-derived microvesicles may provide diagnostic information and aid in therapeutic decisions for cancer patients through a blood test.
4,118 citations
TL;DR: The Skyline user interface simplifies the development of mass spectrometer methods and the analysis of data from targeted proteomics experiments performed using selected reaction monitoring (SRM).
Abstract: Summary: Skyline is a Windows client application for targeted proteomics method creation and quantitative data analysis. It is open source and freely available for academic and commercial use. The Skyline user interface simplifies the development of mass spectrometer methods and the analysis of data from targeted proteomics experiments performed using selected reaction monitoring (SRM). Skyline supports using and creating MS/MS spectral libraries from a wide variety of sources to choose SRM filters and verify results based on previously observed ion trap data. Skyline exports transition lists to and imports the native output files from Agilent, Applied Biosystems, Thermo Fisher Scientific and Waters triple quadrupole instruments, seamlessly connecting mass spectrometer output back to the experimental design document. The fast and compact Skyline file format is easily shared, even for experiments requiring many sample injections. A rich array of graphs displays results and provides powerful tools for inspecting data integrity as data are acquired, helping instrument operators to identify problems early. The Skyline dynamic report designer exports tabular data from the Skyline document model for in-depth analysis with common statistical tools. Availability: Single-click, self-updating web installation is available at http://proteome.gs.washington.edu/software/skyline. This web site also provides access to instructional videos, a support board, an issues list and a link to the source code project.
3,794 citations
Additional excerpts
...5) (McCoss Lab, University of Washington, Seattle, WA, USA) [45]....
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TL;DR: It is shown that exosomes—endogenous nano-vesicles that transport RNAs and proteins—can deliver short interfering (si)RNA to the brain in mice, and the therapeutic potential of exosome-mediated siRNA delivery was demonstrated by the strong mRNA and protein knockdown of BACE1, a therapeutic target in Alzheimer's disease, in wild-type mice.
Abstract: To realize the therapeutic potential of RNA drugs, efficient, tissue-specific and nonimmunogenic delivery technologies must be developed. Here we show that exosomes-endogenous nano-vesicles that transport RNAs and proteins-can deliver short interfering (si)RNA to the brain in mice. To reduce immunogenicity, we used self-derived dendritic cells for exosome production. Targeting was achieved by engineering the dendritic cells to express Lamp2b, an exosomal membrane protein, fused to the neuron-specific RVG peptide. Purified exosomes were loaded with exogenous siRNA by electroporation. Intravenously injected RVG-targeted exosomes delivered GAPDH siRNA specifically to neurons, microglia, oligodendrocytes in the brain, resulting in a specific gene knockdown. Pre-exposure to RVG exosomes did not attenuate knockdown, and non-specific uptake in other tissues was not observed. The therapeutic potential of exosome-mediated siRNA delivery was demonstrated by the strong mRNA (60%) and protein (62%) knockdown of BACE1, a therapeutic target in Alzheimer's disease, in wild-type mice.
3,442 citations
"Plasma exosomal α-synuclein is like..." refers background in this paper
...Evidence suggests exosomes may cross multiple layers of the blood– brain barrier [3], possibly by jumping from cell-to-cell via the multivesicular body (MVB) compartment [56]....
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TL;DR: Associated pathological findings suggest that cases of incidental Lewy body disease are presymptomatic cases of Parkinson's disease, and confirm the importance of age (time) in the evolution of the disease.
Abstract: The Lewy body is a distinctive neuronal inclusion that is always found in the substantia nigra and other specific brain regions in Parkinson's disease. It is mainly composed of structurally altered neurofilament, and occurs wherever there is excessive loss of neurons. It occurs in some elderly individuals and rarely in other degenerative diseases of the central nervous system. In 273 brains of patients dying from disorders other than Parkinson's disease, the age-specific prevalence of Lewy bodies increased from 3.8% to 12.8% between the sixth and ninth decades. Associated pathological findings suggest that these cases of incidental Lewy body disease are presymptomatic cases of Parkinson's disease, and confirm the importance of age (time) in the evolution of the disease. In view of the common and widespread occurrence of this disorder we propose that endogenous mechanisms operating in early life may be more important than environmental agents in the pathogenesis of Lewy bodies and Parkinson's disease.
3,223 citations
"Plasma exosomal α-synuclein is like..." refers methods in this paper
...Briefly, all PD patients met UK PD Society Brain Bank clinical diagnostic criteria for PD [25], except that having “more than one affected relative” was not considered an exclusion criterion....
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