Endothelial-Derived Extracellular Vesicles Induce Cerebrovascular Dysfunction in Inflammation

Extracellular vesicles: biological mechanisms and emerging therapeutic opportunities in neurodegenerative diseases

Extracellular vesicles (EVs) are membrane vesicles originating from different cells within the brain. The pathophysiological role of EVs in neurodegenerative diseases is progressively acknowledged. This field has advanced from basic biological research to essential clinical significance. The capacity to selectively enrich specific subsets of EVs from biofluids via distinctive surface markers has opened new avenues for molecular understandings across various tissues and organs, notably in the brain. In recent years, brain-derived EVs have been extensively investigated as biomarkers, therapeutic targets, and drug-delivery vehicles for neurodegenerative diseases. This review provides a brief overview of the characteristics and physiological functions of the various classes of EVs, focusing on the biological mechanisms by which various types of brain-derived EVs mediate the occurrence and development of neurodegenerative diseases. Concurrently, novel therapeutic approaches and challenges for the use of EVs as delivery vehicles are delineated.

Annexin A1 Mitigates Blood-Brain Barrier Disruption in a Sepsis-Associated Encephalopathy Model by Enhancing the Expression of Occludin and Zonula Occludens-1 (ZO-1)

AIMS

This study investigated the protective role of Annexin A1 (ANXA1) in sepsis-associated encephalopathy (SAE) by examining its effects on brain vascular endothelium and blood-brain barrier (BBB) integrity.

METHODS

Mice were divided into four groups: wild type (WT), cecal ligation and puncture (CLP), ANXA1 knockout (ANXA1[-/-]), and ANXA1(-/-) with CLP. Neurobehavioral changes were assessed using the Y-maze test, while BBB integrity was evaluated through Evans blue dye (EBD) staining and permeability tests with fluorescein isothiocyanate (FITC)-dextran.

RESULTS

Results showed that ANXA1 levels were reduced in septic mice, and its deficiency exacerbated cognitive impairment and survival rate reduction. ANXA1 deficiency also upregulated proinflammatory cytokines and adhesion molecules, worsened BBB impairment, and altered expression of tight junction proteins and VEGF-A/VEGF-R2. In vitro, ANXA1 Ac2-26 prevented LPS-induced increased permeability in bEnd.3 cells by restoring tight junction proteins and reducing VEGF-A/VEGF-R2 expression. Notably, VEGF-A negated the protective effects of ANXA1 Ac2-26.

CONCLUSION

The study concludes that ANXA1 reduces BBB permeability to protect against sepsis-induced brain dysfunction via VEGF-A/VEGF-R2 regulation of tight junction proteins, suggesting ANXA1 as a potential therapeutic for SAE.

Characteristic changes in the mRNA expression profile of plasma exosomes from patients with MPO-ANCA-associated vasculitis and its possible correlations with pathogenesis

To explore the expression patterns and potential roles of mRNAs in exosomes from patients with myeloperoxidase-specific anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (MPO-AAV). Plasma exosomes were isolated from MPO-AAV patients and healthy controls (HCs) to screen for differential mRNA expression via exosomal mRNA sequencing. The differentially expressed mRNAs in exosomes from the 2 groups were comparatively explored by bioinformatics analysis. The six most differentially expressed mRNAs were selected and validated in larger groups of MPO-AAV patients and HCs by real-time quantitative polymerase chain reaction (RT‒qPCR). The relationships between these selected mRNAs and patient characteristics were statistically analyzed. Compared with HCs, a total of 1077 mRNAs in exosomes from MPO-AAV patients were found to be significantly upregulated, including DEPDC1B and TPST1, while NSUN4 and AK4 were significantly downregulated. Statistical analysis did not reveal any correlation between the six selected mRNAs and clinical indicators, including disease activity. GO enrichment analysis revealed that these differentially expressed genes participate in various enzyme activities, protein synthesis, etc. KEGG pathway analysis revealed that metabolic pathways, cell adhesion molecules, epithelial signaling, and mitogen-activated protein kinase (MAPK) signaling pathways were significantly enriched in the exosomal mRNAs. There were significant differences in the expression of exosomal mRNAs between MPO-AAV patients and HCs, which may be related to the occurrence and development of MPO-AAV. These findings provide clues for further investigations of MPO-AAV pathogenesis and the identification of new potential therapeutic targets.

Insight into endothelial cell-derived extracellular vesicles in cardiovascular disease: Molecular mechanisms and clinical implications

The endothelium is crucial in regulating vascular function. Extracellular vesicles (EVs) serve as membranous structures released by cells to facilitate intercellular communication through the delivery of nucleic acids, lipids, and proteins to recipient cells in an paracrine or endocrine manner. Endothelial cell-derived EVs (EndoEVs) have been identified as both biomarkers and significant contributors to the occurrence and progression of cardiovascular disease (CVD). The impact of EndoEVs on CVD is complex and contingent upon the condition of donor cells, the molecular cargo within EVs, and the characteristics of recipient cells. Consequently, elucidating the underlying molecular mechanisms of EndoEVs is crucial for comprehending their contributions to CVD. Moreover, a thorough understanding of the composition and function of EndoEVs is imperative for their potential clinical utility. This review aims provide an up-to-date overview of EndoEVs in the context of physiology and pathophysiology, as well as to discuss their prospective clinical applications.

Primary Progressive Multiple Sclerosis-A Key to Understanding and Managing Disease Progression

Primary progressive multiple sclerosis (PPMS), the least frequent type of multiple sclerosis (MS), is characterized by a specific course and clinical symptoms, and it is associated with a poor prognosis. It requires extensive differential diagnosis and often a long-term follow-up before its correct recognition. Despite recent progress in research into and treatment for progressive MS, the diagnosis and management of this type of disease still poses a challenge. Considering the modern concept of progression "smoldering" throughout all the stages of disease, a thorough exploration of PPMS may provide a better insight into mechanisms of progression in MS, with potential clinical implications. The goal of this study was to review the current evidence from investigations of PPMS, including its background, clinical characteristics, potential biomarkers and therapeutic opportunities. Processes underlying CNS damage in PPMS are discussed, including chronic immune-mediated inflammation, neurodegeneration, and remyelination failure. A review of potential clinical, biochemical and radiological biomarkers is presented, which is useful in monitoring and predicting the progression of PPMS. Therapeutic options for PPMS are summarized, with approved therapies, ongoing clinical trials and future directions of investigations. The clinical implications of findings from PPMS research would be associated with reliable assessments of disease outcomes, improvements in individualized therapeutic approaches and, hopefully, novel therapeutic targets, relevant for the management of progression.

From Genesis to Old Age: Exploring the Immune System One Cell at a Time with Flow Cytometry

The immune system is a highly complex and tightly regulated system that plays a crucial role in protecting the body against external threats, such as pathogens, and internal abnormalities, like cancer cells. It undergoes development during fetal stages and continuously learns from each encounter with pathogens, allowing it to develop immunological memory and provide a wide range of immune protection. Over time, after numerous encounters and years of functioning, the immune system can begin to show signs of erosion, which is commonly named immunosenescence. In this review, we aim to explore how the immune system responds to initial encounters with antigens and how it handles persistent stimulations throughout a person's lifetime. Our understanding of the immune system has greatly benefited from advanced technologies like flow cytometry. In this context, we will discuss the valuable contribution of flow cytometry in enhancing our knowledge of the immune system behavior in aging, with a specific focus on T-cells. Moreover, we will expand our discussion to the flow cytometry-based assessment of extracellular vesicles, a recently discovered communication channel in biology, and their implications for immune system functioning.

Brain microvascular endothelial cell-derived exosomes transmitting circ_0000495 promote microglial M1-polarization and endothelial cell injury under hypoxia condition

Human brain microvascular endothelial cells (HBMVECs) and microglia play critical roles in regulating cerebral homeostasis during ischemic stroke. However, the role of HBMVECs-derived exosomes in microglia polarization after stroke remains unknown. We isolated exosomes (Exos) from oxygen glucose deprivation (OGD)-exposed HBMVECs, before added them into microglia. Microglia polarization markers were tested using RT-qPCR or flow cytometry. Inflammatory cytokines were measured with ELISA. Endothelial cell damage was assessed by cell viability, apoptosis, apoptosis-related proteins, oxidative stress, and angiogenic activity using CCK-8, flow cytometry, western blot, ELISA, and endothelial tube formation assay, respectively. We also established middle cerebral artery occlusion (MCAO) mice model to examine the function of circ_0000495 on stroke in vivo. Our study found that HBMVECs-Exos reduced M2 markers (IL-10, CD163, and CD206), increased M1 markers (TNF-α, IL-1β, and IL-12), CD86-positive cells, and inflammatory cytokines (TNF-α and IL-1β), indicating the promotion of microglial M1-polarization. Microglial M1-polarization induced by HBMVECs-Exos reduced viability and promoted apoptosis and oxidative stress, revealing the aggravation of endothelial cell damage. However, circ_0000495 silencing inhibited HBMVECs-Exos-induced alterations. Mechanistically, circ_0000495 adsorbed miR-579-3p to upregulate toll-like receptor 4 (TLR4) in microglia; miR-579-3p suppressed HBMVECs-Exos-induced alterations via declining TLR4; furthermore, Yin Yang 1 (YY1) transcriptionally activated circ_0000495 in HBMVECs. Importantly, circ_0000495 aggravated ischemic brain injury in vivo via activating TLR4/nuclear factor-κB (NF-κB) pathway. Collectively, OGD-treated HBMVECs-Exos transmitted circ_0000495 to regulate miR-579-3p/TLR4/NF-κB axis in microglia, thereby facilitating microglial M1-polarization and endothelial cell damage.

Cerebral microvascular endothelial cell-derived extracellular vesicles regulate blood - brain barrier function

Autoreactive T lymphocytes crossing the blood-brain barrier (BBB) into the central nervous system (CNS) play a crucial role in the initiation of demyelination and neurodegeneration in multiple sclerosis (MS). Recently, extracellular vesicles (EV) secreted by BBB endothelial cells (BBB-EC) have emerged as a unique form of cell-to-cell communication that contributes to cerebrovascular dysfunction. However, the precise impact of different size-based subpopulations of BBB-EC-derived EV (BBB-EV) on the early stages of MS remains unclear. Therefore, our objective was to investigate the content and function of distinct BBB-EV subpopulations in regulating BBB integrity and their role in T cell transendothelial migration, both in vitro and in vivo. Our study reveals that BBB-ECs release two distinct size based EV populations, namely small EV (sEV; 30-150 nm) and large EV (lEV; 150-300 nm), with a significantly higher secretion of sEV during inflammation. Notably, the expression patterns of cytokines and adhesion markers differ significantly between these BBB-EV subsets, indicating specific functional differences in the regulation of T cell migration. Through in vitro experiments, we demonstrate that lEV, which predominantly reflect their cellular source, play a major role in BBB integrity loss and the enhanced migration of pro-inflammatory Th1 and Th17.1 cells. Conversely, sEV appear to protect BBB function by inducing an anti-inflammatory phenotype in BBB-EC. These findings align with our in vivo data, where the administration of sEV to mice with experimental autoimmune encephalomyelitis (EAE) results in lower disease severity compared to the administration of lEV, which exacerbates disease symptoms. In conclusion, our study highlights the distinct and opposing effects of BBB-EV subpopulations on the BBB, both in vitro and in vivo. These findings underscore the need for further investigation into the diagnostic and therapeutic potential of BBB-EV in the context of MS.

Cerebral endothelial cell-derived extracellular vesicles regulate microglial polarization and promote autophagy via delivery of miR-672-5p

The interaction between cerebral endothelial cells (CEC) and brain parenchymal cells is critical to maintain neurovascular homeostasis, whereas extracellular vesicles (EVs) are essential to mediate the cell-cell communication. Previous researches demonstrated that CEC-derived EVs (CEC-EVs) confer neuroprotective actions. However, the molecular mechanisms remain unknown. In this study, we isolated EVs from CEC and assessed their immune-regulatory actions in microglial cells and mice following lipopolysaccharide (LPS) exposure. We found that CEC-EVs treatment significantly ameliorated LPS-induced inflammatory activation, shifting microglial polarization from pro-inflammatory phenotype to anti-inflammatory phenotype. Meanwhile, microglial cells can effectively internalize CEC-EVs and this process was further enhanced by immune activation. Next, the miRNA microarray analysis revealed that CEC-EVs increased expression of miR-672-5p, which was demonstrated to be the cargo of CEC-EVs. TGFβ-activated kinase 1 (TAK1)-binding proteins 2 (TAB2) was identified to be the target of miR-672-5p. Through inhibiting TAB2, miR-672-5p derived from CEC-EVs suppressed TAK1-TAB signaling and thereby mitigating the downstream NF-κB activation. Furthermore, we found that by delivering miR-672-5p, CEC-EVs promoted autophagy and hence stimulating autophagic degradation of NLRP3 inflammasome. Our work firstly revealed the neuroimmune-modulating actions of CEC-EVs and further demonstrated that miR-672-5p secreted from CEC-EVs inhibits microglial pro-inflammatory polarization and facilitates autophagic process via targeting TAB2.

Impact and Advances in the Role of Bacterial Extracellular Vesicles in Neurodegenerative Disease and Its Therapeutics

Bacterial Extracellular Vesicles (BEVs) possess the capability of intracellular interactions with other cells, and, hence, can be utilized as an efficient cargo for worldwide delivery of therapeutic substances such as monoclonal antibodies, proteins, plasmids, siRNA, and small molecules for the treatment of neurodegenerative diseases (NDs). BEVs additionally possess a remarkable capacity for delivering these therapeutics across the blood-brain barrier to treat Alzheimer's disease (AD). This review summarizes the role and advancement of BEVs for NDs, AD, and their treatment. Additionally, it investigates the critical BEV networks in the microbiome-gut-brain axis, their defensive and offensive roles in NDs, and their interaction with NDs. Furthermore, the part of BEVs in the neuroimmune system and their interference with ND, as well as the risk factors made by BEVs in the autophagy-lysosomal pathway and their potential outcomes on ND, are all discussed. To conclude, this review aims to gain a better understanding of the credentials of BEVs in NDs and possibly discover new therapeutic strategies.

Extracellular Vesicles as "Very Important Particles" (VIPs) in Aging

In recent decades, extracellular vesicles have been recognized as "very important particles" (VIPs) associated with aging and age-related disease. During the 1980s, researchers discovered that these vesicle particles released by cells were not debris but signaling molecules carrying cargoes that play key roles in physiological processes and physiopathological modulation. Following the International Society for Extracellular Vesicles (ISEV) recommendation, different vesicle particles (e.g., exosomes, microvesicles, oncosomes) have been named globally extracellular vesicles. These vesicles are essential to maintain body homeostasis owing to their essential and evolutionarily conserved role in cellular communication and interaction with different tissues. Furthermore, recent studies have shown the role of extracellular vesicles in aging and age-associated diseases. This review summarizes the advances in the study of extracellular vesicles, mainly focusing on recently refined methods for their isolation and characterization. In addition, the role of extracellular vesicles in cell signaling and maintenance of homeostasis, as well as their usefulness as new biomarkers and therapeutic agents in aging and age-associated diseases, has also been highlighted.

Extracellular vesicles as contributors in the pathogenesis of multiple sclerosis

Extracellular vesicles (EVs) are a heterogeneous family of extracellular structures bounded by a phospholipid bilayer, released by all cell types in various biological fluids, such as blood and cerebrospinal fluid (CSF), playing important roles in intercellular communication, both locally and systemically. EVs carry and deliver a variety of bioactive molecules (proteins, nucleic acids, lipids and metabolites), conferring epigenetic and phenotypic changes to the recipient cells and thus resulting as important mediators of both homeostasis and pathogenesis. In neurological diseases, such as multiple sclerosis (MS), the EV ability to cross Blood-Brain Barrier (BBB), moving from central nervous system (CNS) to the peripheral circulation and vice versa, has increased the interest in EV study in the neurological field. In the present review, we will provide an overview of the recent advances made in understanding the pathogenic role of EVs regarding the immune response, the BBB dysfunction and the CNS inflammatory processes.

Microscopic polyangiitis plasma-derived exosomal miR-1287-5p induces endothelial inflammatory injury and neutrophil adhesion by targeting CBL

Background

An inflammatory environment around the vessel wall caused by leukocyte infiltration is one of the characteristic histopathological features of microscopic polyangiitis (MPA); however, the pathogenic mechanisms are not fully understood. Studies have found that circulating microRNA (miRNA) can be used as potential biomarkers for the diagnosis and classification of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV), and the E3 ubiquitin ligase casitas B-lineage lymphoma (CBL) seems to be associated with inflammation. In addition, evidence indicates that miRNA can be tracked into exosomes and transferred into recipient cells to mediate the process of vascular endothelial injury. Herein, we aimed to identify the profiles of exosomal miRNA, and determine the effect of exosomal miR-1287-5p and its target gene CBL on vascular endothelial cells in MPA.

Method

We isolated plasma exosomes from patients with MPA (MPA-exo) and healthy controls (HC-exo) by ultracentrifugation and conducted exosome small-RNA sequencing to screen differential miRNA expression in MPA-exo (n = 3) compared to HC-exo (n = 3). We measured the expression levels of miR-1303, miR-1287-5p, and miR-129-1-3p using quantitative reverse transcription-polymerase chain reaction (qRT-PCR, n = 6) and performed dual luciferase reporter gene assays to confirm the downstream target gene of miR-1287-5p. In addition, we treated human umbilical vein endothelial cell (HUVEC) with MPA-exo, or transfected them with miR-1287-5p mimic/inhibitor or with CBL-siRNA/CBL-siRNA+ miR-1287-5p inhibitor. After cell culture, we evaluated the effects on vascular endothelial cells by examining the mRNA levels of IL-6, IL-8, MCP-1, ICAM-1 and E-selectin using qRT-PCR and performed neutrophil adhesion assay with haematoxylin staining.

Result

Transmission electron microscopy, Western blot and nanoparticle tracking analysis showed that we successfully purified exosomes and MPA-exo could be absorbed into HUVEC. We screened a total of 1,077 miRNA by sequencing and observed a high abundance of miR-1287-5p in the exosomes obtained from MPA plasma. The dual luciferase reporter assay identified CBL as a downstream target gene of miR-1287-5p, and the results revealed that MPA-exo decreased CBL protein expression in HUVEC. In addition, treatment with MPA-exo, up-regulating miR-1287-5p or silencing of CBL in HUVEC significantly increased the mRNA expression of inflammatory factors (including IL-6, IL-8, and MCP-1) and adhesion molecules (including ICAM-1 and E-selection) and promoted the adhesion of neutrophils to HUVEC. However, down-regulating miR-1287-5p had the opposite effect.

Conclusion

Our study revealed that MPA-exo was involved in the intercellular transfer of miR-1287-5p and subsequently promote the development of acute endothelial injury in MPA. MiR-1287-5p and CBL agonists may be promising therapeutic approach for MPA-induced vascular inflammatory injury.

Biomarkers involved in the pathogenesis of cerebral small-vessel disease

Cerebral small-vessel disease (CSVD) has been found to have a strong association with vascular cognitive impairment (VCI) and functional loss in elderly patients. At present, the diagnosis of CSVD mainly relies on brain neuroimaging markers, but they cannot fully reflect the overall picture of the disease. Currently, some biomarkers were found to be related to CSVD, but the underlying mechanisms remain unclear. We aimed to systematically review and summarize studies on the progress of biomarkers related to the pathogenesis of CSVD, which is mainly the relationship between these indicators and neuroimaging markers of CSVD. Concerning the pathophysiological mechanism of CSVD, the biomarkers of CSVD have been described as several categories related to sporadic and genetic factors. Monitoring of biomarkers might contribute to the early diagnosis and progression prediction of CSVD, thus providing ideas for better diagnosis and treatment of CSVD.

Lung-Based, Exosome Inhibition Mediates Systemic Impacts Following Particulate Matter Exposure

Particulate matter (PM) exposure is a global health issue that impacts both urban and rural communities. Residential communities in the Southwestern United States have expressed concerns regarding the health impacts of fugitive PM from rural, legacy mine-sites. In addition, the recent literature suggests that exosomes may play a role in driving toxicological phenotypes following inhaled exposures. In this study, we assessed exosome-driven mechanisms and systemic health impacts following inhaled dust exposure, using a rodent model. Using an exosome inhibitor, GW4869 (10 μM), we inhibited exosome generation in the lungs of mice via oropharyngeal aspiration. We then exposed mice to previously characterized inhaled particulate matter (PM) from a legacy mine-site and subsequently assessed downstream behavioral, cellular, and molecular biomarkers in lung, serum, and brain tissue. Results indicated that CCL-2 was significantly upregulated in the lung tissue and downregulated in the brain (p < 0.05) following PM exposure. Additional experiments revealed cerebrovascular barrier integrity deficits and increased glial fibrillary acidic protein (GFAP) staining in the mine-PM exposure group, mechanistically dependent on exosome inhibition. An increased stress and anxiety response, based on the open-field test, was noted in the mine-PM exposure group, and subsequently mitigated with GW4869 intervention. Exosome lipidomics revealed 240 and eight significantly altered positive-ion lipids and negative-ion lipids, respectively, across the three treatment groups. Generally, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) lipids were significantly downregulated in the PM group, compared to FA. In conclusion, these data suggest that systemic, toxic impacts of inhaled PM may be mechanistically dependent on lung-derived, circulating exosomes, thereby driving a systemic, proinflammatory phenotype.

Extracellular Vesicles at CNS barriers: Mode of action

The exchange of molecules between the brain and periphery is limited by cellular barriers such as the blood-brain barrier (BBB) and the blood-CSF barrier (BCB). Extracellular vesicles (EVs) secreted by brain cells or circulating in the blood stream interact with these barriers and provide a pathway for brain-periphery communication. This review briefly summarizes the main current concepts of EVs signaling over the BBB/BCB. EVs can either be released by barrier cells upon stimulation, act on barrier cells modulating barrier properties, or cross the barrier transferring cargo between the circulation and the brain. The mechanisms of EV signaling and passage over the BBB are increasingly being explored, with inflammation being a main driver. EVs acting at or through the barriers possess wide-ranging effects on brain-periphery communication in both healthy and pathological states. A deeper understanding of the mechanisms of action is important for translation into biomedical applications for brain diseases.

Lymphatic and Blood Endothelial Extracellular Vesicles: A Story Yet to Be Written

Extracellular vesicles (EVs), such as exosomes, microvesicles, and apoptotic bodies, are cell-derived, lipid bilayer-enclosed particles mediating intercellular communication and are therefore vital for transmitting a plethora of biological signals. The vascular endothelium substantially contributes to the circulating particulate secretome, targeting important signaling pathways that affect blood cells and regulate adaptation and plasticity of endothelial cells in a paracrine manner. Different molecular signatures and functional properties of endothelial cells reflect their heterogeneity among different vascular beds and drive current research to understand varying physiological and pathological effects of blood and lymphatic endothelial EVs. Endothelial EVs have been linked to the development and progression of various vascular diseases, thus having the potential to serve as biomarkers and clinical treatment targets. This review aims to provide a brief overview of the human vasculature, the biology of extracellular vesicles, and the current knowledge of endothelium-derived EVs, including their potential role as biomarkers in disease development.

The Blood-Brain Barrier, an Evolving Concept Based on Technological Advances and Cell-Cell Communications

The construction of the blood–brain barrier (BBB), which is a natural barrier for maintaining brain homeostasis, is the result of a meticulous organisation in space and time of cell–cell communication processes between the endothelial cells that carry the BBB phenotype, the brain pericytes, the glial cells (mainly the astrocytes), and the neurons. The importance of these communications for the establishment, maturation and maintenance of this unique phenotype had already been suggested in the pioneering work to identify and demonstrate the BBB. As for the history of the BBB, the evolution of analytical techniques has allowed knowledge to evolve on the cell–cell communication pathways involved, as well as on the role played by the cells constituting the neurovascular unit in the maintenance of the BBB phenotype, and more particularly the brain pericytes. This review summarises the key points of the history of the BBB, from its origin to the current knowledge of its physiology, as well as the cell–cell communication pathways identified so far during its development, maintenance, and pathophysiological alteration.