Brain Microvascular Endothelial Cell-Derived Exosomes Protect Neurons from Ischemia–Reperfusion Injury in Mice

Regulation of blood-brain barrier integrity by brain microvascular endothelial cells in ischemic stroke: A therapeutic opportunity

Stroke is the second leading cause of death from cardiovascular diseases. Brain microvascular endothelial cells (BMECs) are crucial in the treatment of cerebral ischemic stroke, as their functional status directly affects the integrity of the blood-brain barrier (BBB). This review systematically discusses the central role of BMECs in ischemia. The mitochondrial dysfunction and activation of apoptosis/necrosis pathways in BMECs directly disrupt the integrity of the BBB and the degradation of junctional complexes (such as TJs and AJs) further exacerbates its permeability. In the neurovascular unit (NVU), astrocytes, microglia, and pericytes regulate the function of BMECs by secreting cytokines (such as TGF-β and VEGF), showing dual effects of promoting repair and damage. The dynamic changes of transporters, including those from the ATP-binding cassette and solute carrier families, as well as ion channels and exchangers, such as potassium and calcium channels, offer novel insights for the development of targeted drug delivery systems.

Progress of Exosomal MicroRNAs and Traditional Chinese Medicine Monomers in Neurodegenerative Diseases

Exosomes, extracellular vesicles secreted by various cells, actively participate in intercellular communication by facilitating the exchange of crucial molecular information such as DNA, RNA, and lipids. Within this intricate network, microRNAs, endogenous non-coding small RNAs, emerge as pivotal regulators of post-transcriptional gene expression, significantly influencing the development of neurodegenerative diseases. The historical prominence of traditional Chinese medicine (TCM) in clinical practice in China underscores its enduring significance. Notably, TCM monomers, serving as active constituents within herbal medicine, assume a critical role in the treatment of neurodegenerative diseases, particularly in mitigating oxidative stress, inhibiting apoptosis, and reducing inflammation. This comprehensive review aims to delineate the specific involvement of exosomal microRNAs in various neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke, and amyotrophic lateral sclerosis. Furthermore, the exploration extends to the application of TCM monomers, elucidating their efficacy as therapeutic agents in these conditions. Additionally, the review examines the utilization of exosomes as drug delivery carriers in the context of neurodegenerative diseases, providing a nuanced understanding of the potential synergies between TCM and modern therapeutic approaches. This synthesis of knowledge aims to contribute to the advancement of our comprehension of the intricate molecular mechanisms underlying neurodegeneration and the potential therapeutic avenues offered by TCcom interventions.

Exosomes as therapeutic and drug delivery vehicle for neurodegenerative diseases

Neurodegenerative disorders are complex, progressive, and life-threatening. They cause mortality and disability for millions of people worldwide. Appropriate treatment for neurodegenerative diseases (NDs) is still clinically lacking due to the presence of the blood-brain barrier (BBB). Developing an effective transport system that can cross the BBB and enhance the therapeutic effect of neuroprotective agents has been a major challenge for NDs. Exosomes are endogenous nano-sized vesicles that naturally carry biomolecular cargoes. Many studies have indicated that exosome content, particularly microRNAs (miRNAs), possess biological activities by targeting several signaling pathways involved in apoptosis, inflammation, autophagy, and oxidative stress. Exosome content can influence cellular function in healthy or pathological ways. Furthermore, since exosomes reflect the features of the parental cells, their cargoes offer opportunities for early diagnosis and therapeutic intervention of diseases. Exosomes have unique characteristics that make them ideal for delivering drugs directly to the brain. These characteristics include the ability to pass through the BBB, biocompatibility, stability, and innate targeting properties. This review emphasizes the role of exosomes in alleviating NDs and discusses the associated signaling pathways and molecular mechanisms. Furthermore, the unique biological features of exosomes, making them a promising natural transporter for delivering various medications to the brain to combat several NDs, are also discussed.

The science of exosomes: Understanding their formation, capture, and role in cellular communication

Extracellular vesicles (EVs) serve as a crucial method for transferring information among cells, which is vital in multicellular organisms. Among these vesicles, exosomes are notable for their small size, ranging from 20 to 150 nm, and their role in cell-to-cell communication. They carry lipids, proteins, and nucleic acids between cells. The creation of exosomes begins with the inward budding of the cell membrane, which then encapsulates various macromolecules as cargo. Once filled, exosomes are released into the extracellular space and taken up by target cells via endocytosis and similar processes. The composition of exosomal cargo varies, encompassing diverse macromolecules with specific functions. Because of their significant roles, exosomes have been isolated from various cell types, including cancer cells, endothelial cells, macrophages, and mesenchymal cells, with the aim of harnessing them for therapeutic applications. Exosomes influence cellular metabolism, and regulate lipid, glucose, and glutamine pathways. Their role in pathogenesis is determined by their cargo, which can manipulate processes such as apoptosis, proliferation, inflammation, migration, and other molecular pathways in recipient cells. Non-coding RNA transcripts, a common type of cargo, play a pivotal role in regulating disease progression. Exosomes are implicated in numerous biological and pathological processes, including inflammation, cancer, cardiovascular diseases, diabetes, wound healing, and ischemic-reperfusion injury. As a result, they hold significant potential in the treatment of both cancerous and non-cancerous conditions.

Current evidence of synaptic dysfunction after stroke: Cellular and molecular mechanisms

BACKGROUND

Stroke is an acute cerebrovascular disease in which brain tissue is damaged due to sudden obstruction of blood flow to the brain or the rupture of blood vessels in the brain, which can prompt ischemic or hemorrhagic stroke. After stroke onset, ischemia, hypoxia, infiltration of blood components into the brain parenchyma, and lysed cell fragments, among other factors, invariably increase blood-brain barrier (BBB) permeability, the inflammatory response, and brain edema. These changes lead to neuronal cell death and synaptic dysfunction, the latter of which poses a significant challenge to stroke treatment.

RESULTS

Synaptic dysfunction occurs in various ways after stroke and includes the following: damage to neuronal structures, accumulation of pathologic proteins in the cell body, decreased fluidity and release of synaptic vesicles, disruption of mitochondrial transport in synapses, activation of synaptic phagocytosis by microglia/macrophages and astrocytes, and a reduction in synapse formation.

CONCLUSIONS

This review summarizes the cellular and molecular mechanisms related to synapses and the protective effects of drugs or compounds and rehabilitation therapy on synapses in stroke according to recent research. Such an exploration will help to elucidate the relationship between stroke and synaptic damage and provide new insights into protecting synapses and restoring neurologic function.

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.

Endogenous Extracellular Vesicles Participate in Brain Remodeling after Ischemic Stroke

Brain remodeling after an ischemic stroke represents a promising avenue for exploring the cellular mechanisms of endogenous brain repair. A deeper understanding of these mechanisms is crucial for optimizing the safety and efficacy of neuroprotective treatments for stroke patients. Here, we interrogated the role of extracellular vesicles, particularly exosomes, as potential mediators of endogenous repair within the neurovascular unit (NVU). We hypothesized that these extracellular vesicles may play a role in achieving transient stroke neuroprotection. Using the established ischemic stroke model of middle cerebral artery occlusion in adult rats, we detected a surged in the extracellular vesicle marker CD63 in the peri-infarct area that either juxtaposed or co-localized with GFAP-positive glial cells, MAP2-labeled young neurons, and VEGF-marked angiogenic cells. This novel observation that CD63 exosomes spatially and temporally approximated glial activation, neurogenesis, and angiogenesis suggests that extracellular vesicles, especially exosomes, contribute to the endogenous repair of the NVU, warranting exploration of extracellular vesicle-based stroke therapeutics.

Exosomal miRNAs as Biomarkers of Ischemic Stroke

Exosomes are small lipid bilayer membrane particles released from all living cells into the extracellular environment. They carry several molecules and have a critical role in cell-cell communication under physiological and pathological conditions. In recent decades, exosomes, and especially their cargo, have emerged as a promising tool for several clinical conditions. However, the literature has become increasingly unambiguous in defining the role of exosomes in chronic cerebrovascular diseases. Because they can pass through the blood-brain barrier, they have great potential to reflect intracerebral changes. They can, thus, provide valuable insight into the mechanisms of central nervous system diseases. The purpose of this review is to describe the literature on the role of exosomal miRNA, which represents the most widely investigated exosomal biomarker, in strokes. First, we provide an overview of exosomes, from biology to isolation and characterization. Then, we describe the relationship between exosomes and stroke pathogenesis. Finally, we summarize the human studies evaluating exosomal miRNA biomarkers of stroke. Although the collective literature supports the potential use of exosomal miRNA as biomarkers of ischemic stroke, there are still several limitations hampering their introduction into clinical practice.

Natural Products for the Potential Use of Neuroprotective and Neurorestorative Effects in Stroke

Stroke is the second leading cause of death and the third leading cause of disability worldwide, with limited treatment options [...].

Expression analysis and targets prediction of microRNAs in OGD/R treated astrocyte-derived exosomes by smallRNA sequencing

Astrocytes activate and crosstalk with neurons influencing inflammatory responses following ischemic stroke. The distribution, abundance, and activity of microRNAs in astrocytes-derived exosomes after ischemic stroke remains largely unknown. In this study, exosomes were extracted from primary cultured mouse astrocytes via ultracentrifugation, and exposed to oxygen glucose deprivation/re‑oxygenation injury to mimic experimental ischemic stroke. SmallRNAs from astrocyte-derived exosomes were sequenced, and differentially expressed microRNAs were randomly selected and verified by stem-loop real time quantitative polymerase chain reaction. We found that 176 microRNAs, including 148 known and 28 novel microRNAs, were differentially expressed in astrocyte-derived exosomes following oxygen glucose deprivation/re‑oxygenation injury. In gene ontology enrichment, Kyoto encyclopedia of genes and genomes pathway analyses, and microRNA target gene prediction analyses, these alteration in microRNAs were associated to a broad spectrum of physiological functions including signaling transduction, neuroprotection and stress responses. Our findings warrant further investigating of these differentially expressed microRNAs in human diseases particularly ischemic stroke.