ISGylation controls exosome secretion by promoting lysosomal degradation of MVB proteins

Proteomics Mapping of the ISGylation Landscape in Innate Immunity

During infection, pathogen sensing and cytokine signaling by the host induce expression of antimicrobial proteins and specialized post-translational modifications. One such protein is ISG15, a ubiquitin-like protein (UBL) conserved among vertebrates. Similar to ubiquitin, ISG15 covalently conjugates to lysine residues in substrate proteins in a process called ISGylation. Mice deficient for ISGylation or lacking ISG15 are strongly susceptible to many viral pathogens and several intracellular bacterial pathogens. Although ISG15 was the first UBL discovered after ubiquitin, the mechanisms behind its protective activity are poorly understood. Largely, this stems from a lack of knowledge on the ISG15 substrate repertoire. To unravel the antiviral activity of ISG15, early studies used mass spectrometry-based proteomics in combination with ISG15 pulldown. Despite reporting hundreds of ISG15 substrates, these studies were unable to identify the exact sites of modification, impeding a clear understanding of the molecular consequences of protein ISGylation. More recently, a peptide-based enrichment approach revolutionized the study of ubiquitin allowing untargeted discovery of ubiquitin substrates, including knowledge of their exact modification sites. Shared molecular determinants between ISG15 and ubiquitin allowed to take advantage of this technology for proteome-wide mapping of ISG15 substrates and modification sites. In this review, we provide a comprehensive overview of mass spectrometry-based proteomics studies on protein ISGylation. We critically discuss the relevant literature, compare reported substrates and sites and make suggestions for future research.

Exosomes: Potential Disease Biomarkers and New Therapeutic Targets

Exosomes are extracellular vesicles released by cells, both constitutively and after cell activation, and are present in different types of biological fluid. Exosomes are involved in the pathogenesis of diseases, such as cancer, neurodegenerative diseases, pregnancy disorders and cardiovascular diseases, and have emerged as potential non-invasive biomarkers for the detection, prognosis and therapeutics of a myriad of diseases. In this review, we describe recent advances related to the regulatory mechanisms of exosome biogenesis, release and molecular composition, as well as their role in health and disease, and their potential use as disease biomarkers and therapeutic targets. In addition, the advantages and disadvantages of their main isolation methods, characterization and cargo analysis, as well as the experimental methods used for exosome-mediated drug delivery, are discussed. Finally, we present potential perspectives for the use of exosomes in future clinical practice.

Characterization and regulation of extracellular vesicles in the lumen of the ovine uterus†

Secretions of the endometrium are vital for peri-implantation growth and development of the sheep conceptus. Extracellular vesicles (EVs) are present in the uterine lumen, emanate from both the endometrial epithelia of the uterus and trophectoderm of the conceptus, and hypothesized to mediate communication between those cell types during pregnancy establishment in sheep. Size-exclusion chromatography and nanoparticle tracking analysis determined that total EV number in the uterine lumen increased from days 10 to 14 of the cycle but was lower on days 12 and 14 of pregnancy in sheep. Intrauterine infusions of interferon tau (IFNT) did not affect total EV number in the uterine lumen. Quantitative mass spectrometric analyses defined proteins and lipids in EVs isolated from the uterine lumen of day 14 cyclic and pregnant sheep. In vitro analyses found that EVs decreased ovine trophectoderm cell proliferation and increased IFNT production without effects on gene expression as determined by RNA-seq. Collective results support the idea EVs impact conceptus growth during pregnancy establishment via effects on trophectoderm cell growth.

Extracellular Vesicles in neural cell interaction and CNS homeostasis

Central nervous system (CNS) homeostasis critically depends on the interaction between neurons and glia cells. Extracellular vesicles (EVs) recently emerged as versatile messengers in CNS cell communication. EVs are released by neurons and glia in activity-dependent manner and address multiple target cells within and outside the nervous system. Here, we summarize the recent advances in understanding the physiological roles of EVs in the nervous system and their ability to deliver signals across the CNS barriers. In addition to the disposal of cellular components via EVs and clearance by phagocytic cells, EVs are involved in plasticity-associated processes, mediate trophic support and neuroprotection, promote axonal maintenance, and modulate neuroinflammation. While individual functional components of the EV cargo are becoming progressively identified, the role of neural EVs as compound multimodal signaling entities remains to be elucidated. Novel transgenic models and imaging technologies allow EV tracking in vivo and provide further insight into EV targeting and their mode of action. Overall, EVs represent key players in the maintenance of CNS homeostasis essential for the lifelong performance of neural networks and thus provide a wide spectrum of biomedical applications.

The role of Extracellular Vesicles during CNS development

With a diverse set of neuronal and glial cell populations, Central Nervous System (CNS) has one of the most complex structures in the body. Intercellular communication is therefore highly important to coordinate cell-to-cell interactions. Besides electrical and chemical messengers, CNS cells also benefit from another communication route, what is known as extracellular vesicles, to harmonize their interactions. Extracellular Vesicles (EVs) and their subtype exosomes are membranous particles secreted by cells and contain information packaged in the form of biomolecules such as small fragments of DNA, lipids, miRNAs, mRNAs, and proteins. They are able to efficiently drive changes upon their arrival to recipient cells. EVs actively participate in all stages of CNS development by stimulating neural cell proliferation, differentiation, synaptic formation, and mediating reciprocal interactions between neurons and oligodendrocyte for myelination process. The aim of the present review is to enlighten the presence and contribution of EVs at each CNS developmental milestone.

Glycometabolism regulates hepatitis C virus release

HCV cell-culture system uses hepatoma-derived cell lines for efficient virus propagation. Tumor cells cultured in glucose undergo active aerobic glycolysis, but switch to oxidative phosphorylation for energy production when cultured in galactose. Here, we investigated whether modulation of glycolysis in hepatocytes affects HCV infection. We showed HCV release, but not entry, genome replication or virion assembly, is significantly blocked when cells are cultured in galactose, leading to accumulation of intracellular infectious virions within multivesicular body (MVB). Blockade of the MVB-lysosome fusion or treatment with pro-inflammatory cytokines promotes HCV release in galactose. Furthermore, we found this glycometabolic regulation of HCV release is mediated by MAPK-p38 phosphorylation. Finally, we showed HCV cell-to-cell transmission is not affected by glycometabolism, suggesting that HCV cell-to-supernatant release and cell-to-cell transmission are two mechanistically distinct pathways. In summary, we demonstrated glycometabolism regulates the efficiency and route of HCV release. We proposed HCV may exploit the metabolic state in hepatocytes to favor its spread through the cell-to-cell transmission in vivo to evade immune response.

Hepatitis C virus (HCV) is a positive-stranded RNA virus that causes acute and chronic hepatitis and hepatocellular carcinoma. HCV infectious cycle comprises viral entry, uncoating, translation and replication of viral RNA, assembly into new virions and release. Establishment of HCV cell culture system (HCVcc) has yielded many insights into complete HCV infectious cycle in Huh7 cell and Huh7-derived human hepatoma cell lines. However, because hepatoma-derived cell lines and hepatocytes vary in metabolism, HCV infectious cycle in tumor cell lines and the patient’s liver may also be different. Therefore, we explored the alterations of HCV infectious cycle by forcing the tumor cell lines to switch their glycometabolic pathways. We found that HCV release can be blocked by culturing cells in galactose-containing medium, leading to accumulation of intracellular infectious virions within MVB. Moreover, we provided new evidence to suggest that HCV cell-to-cell transmission may be mechanistically distinct from cell-to-supernatant release. Finally, we proposed a new concept that HCV release from hepatocytes into circulation may be naturally inefficient due to the metabolic state in liver that may favor more HCV cell-to-cell transmission. This strategy would allow HCV to effectively evade neutralizing antibodies to establish persistent infection.

Heparan sulfate analogues regulate tumor-derived exosome formation that attenuates exosome functions in tumor processes

Heparan sulfate (HS) is involved in many biological activities, including the biogenesis and uptake of exosomes, which are related to the occurrence and development of tumors. This study investigated the role of HS analogues (heparin, low molecular weight heparin, and 6-O-desulfated heparin) in modulating exosome secretion, composition and functions. Exosomes derived from B16F10 cells exposed to different HS analogues were isolated and characterized by TEM, western blotting and Nanosight analyses. The number, size and protein cargo of exosomes secreted by HS analogues-induced B16F10 cells were detected. The findings indicated the reduced tumor-derived exosome secretion and protein cargo as reflected by lower levels of CD63, TSG101, heparinase and IL-6 in exosomes derived from heparin-induced B16F10 cells as compared with 6-O-desulfated heparin-induced tumor cells. Further functional assays demonstrated that exosomes from tumor cells exposed to heparin weakened tumor proliferation, migration and invasion most significantly among various exosomes derived from B16F10 cells treated with different HS analogues. Moreover, the sulfate group at 6-O position of heparan sulfate has been proved to play an important role in tumor-derived exosome formation and functions. This study suggested a vital view to develop more specific and efficient HS-based strategies in cancer treatment for targeting tumor-derived exosomes.

Strategies to Enhance Extracellular Vesicle Production

Extracellular vesicles (EVs) are sub-micrometer lipid vesicles secreted from parental cells with their information such as DNA, RNA, and proteins. EVs can deliver their cargo to recipient cells and regulate the signaling pathway of the recipient cells to determine their destiny. Depending on the cargo of EVs, the recipient cells can be changed into abnormal state or be relieved from diseases. Therefore, EVs has been spotlighted as emerging therapeutics in biomedical research. However, slow EV secretion rate is the major limitation for the clinical applications of EVs. EV secretion is highly environmental dependent and can be regulated by various stimulants such as chemicals, oxygen levels, pH, radiation, starvation, and culture methods. To overcome the limitation of low productivity of EVs, EV stimulation methods have been widely studied and applied to massive EV productions. Another strategy is the synthesis of artificial EVs from cells by physical methods such as nitrogen cavitation, extrusion via porous membrane, and sonication. These physical methods disrupt cellular membrane and reassemble the membrane to lipid vesicles containing proteins or drugs. In this review, we will focus on how EV generation can be enhanced and recent advances in large scale EV generation strategies.

The emerging role of exosomes in Alzheimer's disease

Alzheimer's disease (AD), manifested by memory loss and a decline in cognitive functions, is the most prevalent neurodegenerative disease accounting for 60-80 % of dementia cases. But, to-date, there is no effective treatment available to slow or stop the progression of AD. Exosomes are small extracellular vesicles that carry constituents, such as functional messenger RNAs, non-coding RNAs, proteins, lipids, DNA, and other bioactive substances of their source cells. In the brain, exosomes are likely to be sourced by almost all cell types and involve in cell communication to regulate cellular functions. The yet, accumulated evidence on the roles of exosomes and their constituents in the AD pathological process suggests their significance as additional biomarkers and therapeutic targets for AD. This review summarizes the current reported research findings on exosomes roles in the pathogenesis, diagnosis, and treatment of AD.

Cell-Secreted Vesicles: Novel Opportunities in Cancer Diagnosis, Monitoring and Treatment

Extracellular vesicles (EVs) are important mediators of intercellular communication playing a pivotal role in the regulation of physiological and pathological processes, including cancer. In particular, there is significant evidence suggesting that tumor-derived EVs exert an immunosuppressive activity during cancer progression, as well as stimulate tumor cell migration, angiogenesis, invasion and metastasis. The use of EVs as a liquid biopsy is currently a fast-growing area of research in medicine, with the potential to provide a step-change in the diagnosis and treatment of cancer, allowing the prediction of both therapy response and prognosis. EVs could be useful not only as biomarkers but also as drug delivery systems, and may represent a target for anticancer therapy. In this review, we attempted to summarize the current knowledge about the techniques used for the isolation of EVs and their roles in cancer biology, as liquid biopsy biomarkers and as therapeutic tools and targets.

Analysis of the uterine lumen in fertility-classified heifers: I. Glucose, prostaglandins, and lipids†

Survival and growth of the bovine conceptus (embryo and associated extraembryonic membranes) are dependent on endometrial secretions or histotroph found in the uterine lumen. Previously, serial embryo transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components [glucose, prostaglandins (PGs), and lipids] in the uterine lumen of day 17 pregnant and open fertility-classified heifers. Concentrations of glucose in the uterine lumen were increased by pregnancy but did not differ among fertility-classified heifers. Differences in expression of genes encoding glucose transporters and involved with glycolysis and gluconeogenesis were observed between conceptuses collected from HF and SF heifers. In the uterine lumen, PGE2 and PGF2α were increased by pregnancy, and HF heifers had higher concentrations of PGE2, PGF2α, and 6-keto-PFG1α than SF heifers. Differences were found in expression of genes regulating PG signaling, arachidonic acid metabolism, and peroxisome proliferator-activated receptor signaling among conceptuses and endometrium from fertility-classified heifers. Lipidomics was conducted exclusively in samples from HF heifers, and phosphatidylcholine was the main lipid class that increased in the uterine lumen by pregnancy. Expression of several lipid metabolism genes differed between HF and SF conceptuses, and a number of fatty acids were differentially abundant in the uterine lumen of pregnant HF and SF heifers. These results support the ideas that uterine luminal histotroph impacts conceptus survival and programs its development and is a facet of dysregulated conceptus-endometrial interactions that result in loss of the conceptus in SF cattle during the implantation period of pregnancy establishment.

Critical Review of the Evolution of Extracellular Vesicles' Knowledge: From 1946 to Today

Extracellular vesicles (EVs) are a family of particles/vesicles present in blood and body fluids, composed of phospholipid bilayers that carry a variety of molecules that can mediate cell communication, modulating crucial cell processes such as homeostasis, induction/dampening of inflammation, and promotion of repair. Their existence, initially suspected in 1946 and confirmed in 1967, spurred a sharp increase in the number of scientific publications. Paradoxically, the increasing interest for EV content and function progressively reduced the relevance for a precise nomenclature in classifying EVs, therefore leading to a confusing scientific production. The aim of this review was to analyze the evolution of the progress in the knowledge and definition of EVs over the years, with an overview of the methodologies used for the identification of the vesicles, their cell of origin, and the detection of their cargo. The MISEV 2018 guidelines for the proper recognition nomenclature and ways to study EVs are summarized. The review finishes with a “more questions than answers” chapter, in which some of the problems we still face to fully understand the EV function and potential as a diagnostic and therapeutic tool are analyzed.

Oncogene-regulated release of extracellular vesicles

Oncogenes can alter metabolism by changing the balance between anabolic and catabolic processes. However, how oncogenes regulate tumor cell biomass remains poorly understood. Using isogenic MCF10A cells transformed with nine different oncogenes, we show that specific oncogenes reduce the biomass of cancer cells by promoting extracellular vesicle (EV) release. While MYC and AURKB elicited the highest number of EVs, each oncogene selectively altered the protein composition of released EVs. Likewise, oncogenes alter secreted miRNAs. MYC-overexpressing cells require ceramide, whereas AURKB requires ESCRT to release high levels of EVs. We identify an inverse relationship between MYC upregulation and activation of the RAS/MEK/ERK signaling pathway for regulating EV release in some tumor cells. Finally, lysosome genes and activity are downregulated in the context of MYC and AURKB, suggesting that cellular contents, instead of being degraded, were released via EVs. Thus, oncogene-mediated biomass regulation via differential EV release is a new metabolic phenotype.

An Examination of the Putative Role of Melatonin in Exosome Biogenesis

During the last two decades, melatonin has been found to have pleiotropic effects via different mechanisms on its target cells. Data are abundant for some aspects of the signaling pathways within cells while other casual mechanisms have not been adequately addressed. From an evolutionary perspective, eukaryotic cells are equipped with a set of interrelated endomembrane systems consisting of intracellular organelles and secretory vesicles. Of these, exosomes are touted as cargo-laden secretory vesicles that originate from the endosomal multivesicular machinery which participate in a mutual cross-talk at different cellular interfaces. It has been documented that cells transfer various biomolecules and genetic elements through exosomes to sites remote from the original cell in a paracrine manner. Findings related to the molecular mechanisms between melatonin and exosomal biogenesis and cargo sorting are the subject of the current review. The clarification of the interplay between melatonin and exosome biogenesis and cargo sorting at the molecular level will help to define a cell's secretion capacity. This review precisely addresses the role and potential significance of melatonin in determining the efflux capacity of cells via the exosomal pathway. Certain cells, for example, stem cells actively increase exosome efflux in response to melatonin treatment which accelerates tissue regeneration after transplantation into the injured sites.

Biogenesis, Membrane Trafficking, Functions, and Next Generation Nanotherapeutics Medicine of Extracellular Vesicles

Extracellular vesicles (EVs) are a heterogeneous group of membrane-limited vesicles and multi-signal messengers loaded with biomolecules. Exosomes and ectosomes are two different types of EVs generated by all cell types. Their formation depends on local microdomains assembled in endocytic membranes for exosomes and in the plasma membrane for ectosomes. Further, EV release is a fundamental process required for intercellular communication in both normal physiology and pathological conditions to transmit/exchange bioactive molecules to recipient cells and the extracellular environment. The unique structure and composition of EVs enable them to serve as natural nanocarriers, and their physicochemical properties and biological functions can be used to develop next-generation nano and precision medicine. Knowledge of the cellular processes that govern EVs biology and membrane trafficking is essential for their clinical applications. However, in this rapidly expanding field, much remains unknown regarding EV origin, biogenesis, cargo sorting, and secretion, as well as EV-based theranostic platform generation. Hence, we present a comprehensive overview of the recent advances in biogenesis, membrane trafficking, and functions of EVs, highlighting the impact of nanoparticles and oxidative stress on EVs biogenesis and release and finally emphasizing the role of EVs as nanotherapeutic agents.

Proteostatic imbalance and protein spreading in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder whose exact causative mechanisms are still under intense investigation. Several lines of evidence suggest that the anatomical and temporal propagation of pathological protein species along the neural axis could be among the main driving mechanisms for the fast and irreversible progression of ALS pathology. Many ALS-associated proteins form intracellular aggregates as a result of their intrinsic prion-like properties and/or following impairment of the protein quality control systems. During the disease course, these mutated proteins and aberrant peptides are released in the extracellular milieu as soluble or aggregated forms through a variety of mechanisms. Internalization by recipient cells may seed further aggregation and amplify existing proteostatic imbalances, thus triggering a vicious cycle that propagates pathology in vulnerable cells, such as motor neurons and other susceptible neuronal subtypes. Here, we provide an in-depth review of ALS pathology with a particular focus on the disease mechanisms of seeding and transmission of the most common ALS-associated proteins, including SOD1, FUS, TDP-43, and C9orf72-linked dipeptide repeats. For each of these proteins, we report historical, biochemical, and pathological evidence of their behaviors in ALS. We further discuss the possibility to harness pathological proteins as biomarkers and reflect on the implications of these findings for future research.

Insights Into Extracellular Vesicle/Exosome and miRNA Mediated Bi-Directional Communication During Porcine Pregnancy

Spontaneous fetal loss is one of the most important challenges that commercial pig industry is still facing in North America. Research over the decade provided significant insights into some of the associated mechanisms including uterine capacity, placental efficiency, deficits in vasculature, and immune-inflammatory alterations at the maternal-fetal interface. Pigs have unique epitheliochorial placentation where maternal and fetal layers lay in opposition without any invasion. This has provided researchers opportunities to accurately tease out some of the mechanisms associated with maternal-fetal interface adaptations to the constantly evolving needs of a developing conceptus. Another unique feature of porcine pregnancy is the conceptus derived recruitment of immune cells during the window of conceptus attachment. These immune cells in turn participate in pregnancy associated vascular changes and contribute toward tolerance to the semi-allogeneic fetus. However, the precise mechanism of how maternal-fetal cells communicate during the critical times in gestation is not fully understood. Recently, it has been established that bi-directional communication between fetal trophoblasts and maternal cells/tissues is mediated by extracellular vesicles (EVs) including exosomes. These EVs are detected in a variety of tissues and body fluids and their role has been described in modulating several physiological and pathological processes including vascularization, immune-modulation, and homeostasis. Recent literature also suggests that these EVs (exosomes) carry cargo (nucleic acids, protein, and lipids) as unique signatures associated with some of the pregnancy associated pathologies. In this review, we provide overview of important mechanisms in porcine pregnancy success and failure and summarize current knowledge about the unique cargo containing biomolecules in EVs. We also discuss how EVs (including exosomes) transfer their contents into other cells and regulate important biological pathways critical for pregnancy success.

In situ self-assembled Ag-Fe3O4 nanoclusters in exosomes for cancer diagnosis

Recently, exosomes have gained attention as an effective tool for early cancer detection. Almost all types of cells release exosomes, making them substantially important for disease diagnosis. In this study, we have utilized HepG2 cancer cells for the in situ biosynthesis of silver and iron oxide nanoclusters (NCs) from their respective salts (i.e., AgNO3 and FeCl2, respectively) in the presence of glutathione (GSH). The self-assembled biosynthesized silver and iron NCs were readily loaded on exosomes as payloads and secreted into the cell culture medium. The cargo loaded exosomes were then isolated and characterized by electron microscopy for nano-silver and iron oxide NC confirmation. Ag NCs have potential as a fluorescent probe and Fe3O4 NCs as a contrast agent for CT and MRI. Furthermore, these isolated exosomes from HepG2 cancer cells have a significant influence on cellular uptake and cell viability when exposed to both HepG2 and U87 cancer cells. These findings demonstrate that the biocompatible nature of these self-assembled NCs loaded on exosomes could be utilized to bioimage cancer in the initial stages through fluorescence imaging.

Polychlorinated biphenyl quinone regulates MLKL phosphorylation that stimulates exosome biogenesis and secretion via a short negative feedback loop

Polychlorinated biphenyls (PCBs) are one of the most refractory organic environmental pollutants that ubiquitous existence in nature. Due to the polymorphism of their metabolic pathway and corresponding downstream metabolites, PCBs' toxicities are complicated and need extended investigation. In the present study, we discovered a novel regulatory mechanism of PCB quinone metabolite-driven programmed cell death (PCD), namely, necroptosis. We first confirmed that PCB quinone induces cancerous HeLa and MDA-MB-231 cells necroptosis via the phosphorylation of mixed lineage kinase domain-like MLKL (p-MLKL). Then, we found that PCB quinone-stimulated p-MLKL enhances exosome biogenesis and secretion. Exosome interacts with p-MLKL and releases p-MLKL to the outside of the cell, and ultimately alleviating PCB quinone-induced necroptosis. The inhibition of exosome secretion by GW4869 significantly elevated necroptotic level, indicating the establishment of a short negative feedback loop of MLKL-exosome secretion upon PCB quinone challenge. Since exosome-mediated signaling showed great implications in various human diseases, this work may provide a new mechanism for PCBs-associated toxicity.

Native and Bioengineered Exosomes for Ischemic Stroke Therapy

Exosomes are natural cells-derived vesicles, which are at the forefront toward clinical success for various diseases, including cerebral ischemia. Exosomes mediate cell-to-cell communication in different brain cells during both physiological and pathological conditions. Exosomes are an extensively studied type of extracellular vesicle, which are considered to be the best alternative for stem cell-based therapy. They can be secreted by various cell types and have unique biological properties. Even though native exosomes have potential for ischemic stroke therapy, some undesirable features prevent their success in clinical applications, including a short half-life, poor targeting property, low concentration at the target site, rapid clearance from the lesion region, and inefficient payload. In this review, we highlight exosome trafficking and cellular uptake and survey the latest discoveries in the context of exosome research as the best fit for brain targeting owing to its natural brain-homing abilities. Furthermore, we overview the methods by which researchers have bioengineered exosomes (BioEng-Exo) for stroke therapy. Finally, we summarize studies in which exosomes were bioengineered by a third party for stroke recovery. This review provides up-to-date knowledge about the versatile nature of exosomes with a special focus on BioEng-Exo for ischemic stroke. Standard exosome bioengineering techniques are mandatory for the future and will lead exosomes toward clinical success for stroke therapy.

Small Extracellular Vesicles: A Novel Avenue for Cancer Management

Extracellular vesicles are small membrane particles derived from various cell types. EVs are broadly classified as ectosomes or small extracellular vesicles, depending on their biogenesis and cargoes. Numerous studies have shown that EVs regulate multiple physiological and pathophysiological processes. The roles of small extracellular vesicles in cancer growth and metastasis remain to be fully elucidated. As endogenous products, small extracellular vesicles are an ideal drug delivery platform for anticancer agents. However, several aspects of small extracellular vesicle biology remain unclear, hindering the clinical implementation of small extracellular vesicles as biomarkers or anticancer agents. In this review, we summarize the utility of cancer-related small extracellular vesicles as biomarkers to detect early-stage cancers and predict treatment outcomes. We also review findings from preclinical and clinical studies of small extracellular vesicle-based cancer therapies and summarize interventional clinical trials registered in the United States Food and Drug Administration and the Chinese Clinical Trials Registry. Finally, we discuss the main challenges limiting the clinical implementation of small extracellular vesicles and recommend possible approaches to address these challenges.

[Significance of exosomes in cardiology: heralds of cardioprotection]

Los exosomas tienen un papel clave en la comunicación intercelular. Debido a sus múltiples interacciones, estas estructuras cumplen con el papel de «mensajeros» de forma dinámica, transportando su contenido a células blanco específicas y generando nuevas señales celulares. En este artículo se describen algunas de las proteínas, lípidos y ácidos nucleicos que son transportados por estas vesículas y que se han relacionado con cardioprotección, con la finalidad de proporcionar información y generar interés sobre la relevancia de los exosomas como posibles blancos diagnósticos y terapéuticos.

The effect of the WKYMVm peptide on promoting mBMSC secretion of exosomes to induce M2 macrophage polarization through the FPR2 pathway

Background

When multicystic vesicles (precursors of exosomes) are formed in cells, there are two results. One is decomposition by lysosomes, and the other is the generation of exosomes that are transported out through the transmembrane. On the other hand, M2 macrophages promote the formation of local vascularization and provide necessary support for the repair of bone defects. To provide a new idea for the treatment of bone defects, the purpose of our study was to investigate the effect of WKYMVm (Trp-Lys-Tyr-Met-Val-D-Met-NH2) peptide on the secretion of exosomes from murine bone marrow-derived MSCs (mBMSCs) and the effect of exosomes on the polarization of M2 macrophages.

Methods

The WKYMVm peptide was used to activate the formyl peptide receptor 2 (FPR2) pathway in mBMSCs. First, we used Cell Counting Kit-8 (CCK-8) to detect the cytotoxic effect of WKYMVm peptide on mBMSCs. Second, we used western blotting (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) to detect the expression of interferon stimulated gene 15 (ISG15) and transcription factor EB (TFEB) in mBMSCs. Then, we detected lysosomal activity using a lysozyme activity assay kit. Third, we used an exosome extraction kit and western blotting to detect the content of exosomes secreted by mBMSCs. Fourth, we used immunofluorescence and western blotting to count the number of polarized M2 macrophages. Finally, we used an inhibitor to block miRNA-146 in exosomes secreted by mBMSCs and counted the number of polarized M2 macrophages.

Results

We first found that the WKYMVm peptide had no toxic effect on mBMSCs at a concentration of 1 μmol/L. Second, we found that when the FPR2 pathway was activated by the WKYMVm peptide in mBMSCs, ISG15 and TFEB expression was decreased, leading to increased secretion of exosomes. We also found that lysosomal activity was decreased when the FPR2 pathway was activated by the WKYMVm peptide in mBMSCs. Third, we demonstrated that exosomes secreted by mBMSCs promote the polarization of M2 macrophages. Moreover, all these effects can be blocked by the WRWWWW (WRW4, H-Trp-Arg-Trp-Trp-Trp-Trp-OH) peptide, an inhibitor of the FPR2 pathway. Finally, we confirmed the effect of miRNA-146 in exosomes secreted by mBMSCs on promoting the polarization of M2 macrophages.

Conclusion

Our findings demonstrated the potential value of the WKYMVm peptide in promoting the secretion of exosomes by mBMSCs and eventually leading to M2 macrophage polarization. We believe that our study could provide a research basis for the clinical treatment of bone defects.

Emerging roles for the autophagy machinery in extracellular vesicle biogenesis and secretion

Autophagy classically functions to maintain cell health during stressful conditions by targeting cytosolic components for degradation and recycling via lysosomal pathways. However, accumulating evidence also supports roles for autophagy-related genes (ATGs) in non-degradative processes including cellular secretion. Here, we review emerging roles for the autophagy machinery in regulating extracellular vesicle loading and secretion and discuss how functional coupling of these pathways may impact normal physiology and disease.

Autophagy and Extracellular Vesicles in Colorectal Cancer: Interactions and Common Actors?

Autophagy is a homeostatic process involved in the degradation of disabled proteins and organelles using lysosomes. This mechanism requires the recruitment of specialized proteins for vesicle trafficking, that may also be involved in other types of machinery such as the biogenesis and secretion of extracellular vesicles (EVs), and particularly small EVs called exosomes. Among these proteins, Rab-GTPases may operate in both pathways, thus representing an interesting avenue for further study regarding the interaction between autophagy and extracellular vesicle machinery. Both mechanisms are involved in the development of colorectal cancer (CRC), particularly in cancer stem cell (CSC) survival and communication, although they are not specific to CRC or CSCs. This highlights the importance of studying the crosstalk between autophagy and EVs biogenesis and release.

Hypoxia enhances the production and antitumor effect of exosomes derived from natural killer cells

Background

Exosomes are a subgroup of extracellular vesicles that are naturally released by almost all types of cells. However, the factors that promote the capacity of natural killer (NK) cells to release exosomes are unclear. In this study, we investigated whether hypoxia can enhance the yield of NK cell-derived exosomes and improve the immunotherapeutic effects of these cells.

Methods

Exosomes from NK92 or NK92-hIL-15 cells were isolated from culture medium under normoxic (NK92-Exo and NK92-hIL-15-Exo) or hypoxic (hypoxic NK92-Exo and hypoxic NK92-hIL-15-Exo) conditions. NK92-Exo and hypoxic NK92-Exo were characterized by transmission electron microscopy (TEM), nanoparticle-tracking analysis (NTA), and western blot. Real-time cell assay, wound healing assay, flow cytometry, and western blot were then performed to assess cytotoxicity, cell proliferation, cell migration, apoptosis, and the expression levels of cytotoxicity-associated proteins.

Results

After 48 hours of hypoxic treatment, NK92-Exo exhibited significantly increased cytotoxicity, enhanced inhibition of cell proliferation, and elevated levels of molecules associated with NK cell cytotoxicity. The hypoxia-treated NK92-Exo and NK92-hIL-15-Exo showed increased expression of three functional proteins of NK cells-specifically FasL, perforin, and granzyme B-as compared with their NK92-Exo counterparts exposed to normoxia.

Conclusions

As an approach that supports overproduction of exosomes, hypoxic treatment of NK cells may serve as a promising therapeutic option for cancer immunotherapy.

Biocompatible exosomes nanodrug cargo for cancer cell bioimaging and drug delivery

Therapy against cancer remains a daunting issue for human health, despite remarkable innovations in many areas of pathology. In situ biosynthesized nanoclusters bestow a novel remedy for carcinogenic cell imaging. Exosomes have received special attention as an efficient tool for the diagnosis of various diseases, including cancers. All types of cells (healthy or diseased) generate exosomes, making them significantly unique for relevant disease diagnosis and treatment. In this contribution, we exploit the possibility of utilizing the exosomes to facilitate chemotherapeutics, viz. the combination of doxorubicin (Dox) and biosynthesized silver nanoclusters in cancer cells. Our study showed a new facile way for bioimaging of cancer cells using biosynthesized silver-DNA nanoclusters, and thus further targeting cancer cells using the relevant cancer exosomes as drug delivery cargo. After isolating exosomes from neoplastic cells, i.e. HeLa, loaded with the drug, and treating other neoplastic cells with cargo-loaded isolated exosomes, we found that cargo-loaded isolated exosomes can readily enter into the targeted cancer cells and efficiently kill these neoplastic cells. This raises the possibility of acting as a novel facile modality for target cancer theranostics with high efficiency and biocompability.

Diverse Populations of Extracellular Vesicles with Opposite Functions during Herpes Simplex Virus 1 Infection

Extracellular vesicles (EVs) are released by all types of cells as a means of intercellular communication. Their significance lies in the fact that they can alter recipient cell functions, despite their limited capacity for cargo. We have previously demonstrated that herpes simplex virus 1 (HSV-1) infection influences the cargo and functions of EVs released by infected cells and that these EVs negatively impact a subsequent HSV-1 infection. In the present study, we have implemented cutting-edge technologies to further characterize EVs released during HSV-1 infection. We identified distinct EV populations that were separable through a gradient approach. One population was positive for the tetraspanin CD63 and was distinct from EVs carrying components of the endosomal sorting complexes required for transport (ESCRT). Nanoparticle tracking analysis (NTA) combined with protein analysis indicated that the production of CD63⁺ EVs was selectively induced upon HSV-1 infection. The ExoView platform supported these data and suggested that the amount of CD63 per vesicle is larger upon infection. This platform also identified EV populations positive for other tetraspanins, including CD81 and CD9, whose abundance decreased upon HSV-1 infection. The stimulator of interferon genes (STING) was found in CD63⁺ EVs released during HSV-1 infection, while viral components were found in ESCRT⁺ EVs. Functional characterization of these EVs demonstrated that they have opposite effects on the infection, but the dominant effect was negative. Overall, we have identified the dominant population of EVs, and other EV populations produced during HSV-1 infection, and we have provided information about potential roles.IMPORTANCE Extracellular vesicles mediate cell-to-cell communication and convey messages important for cell homeostasis. Pathways of EV biogenesis are often hijacked by pathogens to facilitate their dissemination and to establish a favorable microenvironment for the infection. We have previously shown that HSV-1 infection alters the cargo and functions of the released EVs, which negatively impact the infection. We have built upon our previous findings by developing procedures to separate EV populations from HSV-1-infected cells. We identified the major population of EVs released during infection, which carries the DNA sensor STING and has an antiviral effect. We also identified an EV population that carries selected viral proteins and has a proviral role. This is the first study to characterize EV populations during infection. These data indicate that the complex interactions between the virus and the host are extended to the extracellular environment and could impact HSV-1 dissemination and persistence in the host.

High expression of tumor susceptibility gene 101 (TSG101) is associated with more aggressive behavior in colorectal carcinoma

INTRODUCTION

Identification of genetic determinants such as exosomal content that drives progression and metastasis of colorectal cancer (CRC) has received considerable attention. The present study aims to identify a suitable biomarker in CRC tissues and exosomes based on bioinformatics data to evaluate its expression patterns in CRC tissues as well as its clinicopathological significance.

MATERIALS AND METHODS

Protein-protein interaction (PPI) network and enrichment analysis were applied to identify up-regulated genes that contributed in CRC exosomes to select the marker. The expression patterns and clinical significance of selected exosomal marker were evaluated in tissue microarrays (TMAs) of 445 CRC tumors and 39 adjacent normal tissues using immunohistochemistry method.

RESULTS

Based on bioinformatics data, TSG101 gene was prominent amongst the tumor tissues and exosomes. Expression of TSG101 was significantly up-regulated in tumor cells compared to adjacent normal tissues (p-value = 0.04). Moreover, higher expressions of TSG101 (cytoplasmic and nuclear) were significantly associated with tumor differentiation (p-value = 0.042) and distant metastasis (p-value = 0.027). A significant association was found in the cytoplasmic expression of TSG101 between well and moderate tumor differentiation (p-value = 0.005) as well as moderate and poor differentiation (p-value = 0.050).

CONCLUSION

These findings indicate that the exploration of crosstalk between exosome content and CRC may be valuable for the development of novel exosomal biomarkers. Increased expression of TSG101, as a promising exosome marker, is more associated with more aggressive tumor behaviors, metastasis, and progression of CRC, which paves the way for therapeutic strategies and CRC management. However, further investigations are warranted to clarify the molecular mechanisms of TSG101 in CRC.

Exosomes and Lung Cancer: Roles in Pathophysiology, Diagnosis and Therapeutic Applications

Lung cancer is a malignancy with a high morbidity and mortality rate, and affected patients have low survival and poor prognosis. The therapeutic approaches for the treatment of this cancer, including radiotherapy and chemotherapy, are not particularly effective partly due to late diagnosis. Therefore, the search for new diagnostic and prognostic tools is a critical issue. Novel biomarkers, such as exosomes, could be considered as potential diagnostic tools for malignancies, particularly lung cancer. Exosomes are nanovesicles, which are associated with different physiological and pathological conditions. It has been shown that these particles are released from many cells, such as cancer cells, immune cells and to some degree normal cells. Exosomes could alter the behavior of target cells through intercellular transfer of their cargo (e.g. DNA, mRNA, long non-coding RNAs, microRNAs and proteins). Thus, these vehicles may play pivotal roles in various physiological and pathological conditions. The current insights into lung cancer pathogenesis suggest that exosomes are key players in the pathogenesis of this cancer. Hence, these nanovesicles and their cargos could be used as new diagnostic, prognostic and therapeutic biomarkers in the treatment of lung cancer. Besides the diagnostic roles of exosomes, their use as drug delivery systems and as cancer vaccines is under investigation. The present review summarizes the current information on the diagnostic and pathogenic functions of exosomes in lung cancer.

Carbon monoxide-triggered health effects: the important role of the inflammasome and its possible crosstalk with autophagy and exosomes

Carbon monoxide (CO) has long been known as a "silent killer" because of its ability to bind hemoglobin (Hb), leading to reduced oxygen carrying capacity of Hb, which is the main cause of CO poisoning (COP) in humans. Emerging studies suggest that mitochondria is a key target of CO action that can impact key biological processes, including apoptosis, cellular proliferation, inflammation, and autophagy. Despite its toxicity at high concentrations, CO also exhibits cyto- and tissue-protective effects at low concentrations in animal models of organ injury and disease. Specifically, CO modulates the production of pro- or anti-inflammatory cytokines and mediators by regulating the NLRP3 inflammasome. Given that human diseases are strongly associated with inflammation, a deep understanding of the exact mechanism is helpful for treatment. Autophagic factors and inflammasomes interact in various situations, including inflammatory disease, and exosomes might function as the bridge between the inflammasome and autophagy activation. Thus, the interplay among autophagy, mitochondrial dysfunction, exosomes, and the inflammasome may play pivotal roles in the health effects of CO. In this review, we summarize the latest research on the beneficial and toxic effects of CO and their underlying mechanisms, focusing on the important role of the inflammasome and its possible crosstalk with autophagy and exosomes. This knowledge may lead to the development of new therapies for inflammation-related diseases and is essential for the development of new therapeutic strategies and biomarkers of COP.

The Role of Exosomes and Exosomal MicroRNA in Cardiovascular Disease

Exosomes are small vesicles (30–150 nm in diameter) enclosed by a lipid membrane bilayer, secreted by most cells in the body. They carry various molecules, including proteins, lipids, mRNA, and other RNA species, such as long non-coding RNA, circular RNA, and microRNA (miRNA). miRNAs are the most numerous cargo molecules in the exosome. They are endogenous non-coding RNA molecules, approximately 19–22-nt-long, and important regulators of protein biosynthesis. Exosomes can be taken up by neighboring or distant cells, where they play a role in post-transcriptional regulation of gene expression by targeting mRNA. Exosomal miRNAs have diverse functions, such as participation in inflammatory reactions, cell migration, proliferation, apoptosis, autophagy, and epithelial–mesenchymal transition. There is increasing evidence that exosomal miRNAs play an important role in cardiovascular health. Exosomal miRNAs are widely involved in the occurrence and development of cardiovascular diseases, such as atherosclerosis, acute coronary syndrome, heart failure (HF), myocardial ischemia reperfusion injury, and pulmonary hypertension. In this review, we present a systematic overview of the research progress into the role of exosomal miRNAs in cardiovascular diseases, and present new ideas for the diagnosis and treatment of cardiovascular diseases.

Autophagy and Exosomes Relationship in Cancer: Friends or Foes?

Autophagy is an intracellular degradation process involved in the removal of proteins and damaged organelles by the formation of a double-membrane vesicle named autophagosome and degraded through fusion with lysosomes. An intricate relationship between autophagy and the endosomal and exosomal pathways can occur at different stages with important implications for normal physiology and human diseases. Recent researches have revealed that extracellular vesicles (EVs), such as exosomes, could have a cytoprotective role by inducing intracellular autophagy; on the other hand, autophagy plays a crucial role in the biogenesis and degradation of exosomes. Although the importance of these processes in cancer is well established, their interplay in tumor is only beginning to be documented. In some tumor contexts (1) autophagy and exosome-mediated release are coordinately activated, sharing the molecular machinery and regulatory mechanisms; (2) cancer cell-released exosomes impact on autophagy in recipient cells through mechanisms yet to be determined; (3) exosome-autophagy relationship could affect drug resistance and tumor microenvironment (TME). In this review, we survey emerging discoveries relevant to the exosomes and autophagy crosstalk in the context of cancer initiation, progression and recurrence. Consequently, we discuss clinical implications by targeting autophagy-exosomal pathway interaction and how this could lay a basis for the purpose of novel cancer therapeutics.

Alcohol-and-HIV-Induced Lysosomal Dysfunction Regulates Extracellular Vesicles Secretion in Vitro and in Liver-Humanized Mice

BACKGROUND

Alcohol abuse is common in people living with HIV-1 and dramaticallyenhances the severity of HIV-induced liver damage by inducing oxidative stress and lysosomaldysfunction in the liver cells. We hypothesize that the increased release of extracellular vesicles(EVs) in hepatocytes and liver humanized mouse model is linked to lysosome dysfunction.

METHODS

The study was performed on primary human hepatocytes and human hepatoma RLWXP-GFP (Huh7.5 cells stably transfected with CYP2E1 and XPack-GFP) cells and validated on ethanol-fed liverhumanizedfumarylacetoacetate hydrolase (Fah)-/-, Rag2-/-, common cytokine receptor gamma chainknockout (FRG-KO) mice. Cells and mice were infected with HIV-1ADA virus.

RESULTS

We observedan increase in the secretion of EVs associated with a decrease in lysosomal activity and expressionof lysosomal-associated membrane protein 1. Next-generation RNA sequencing of primary humanhepatocytes revealed 63 differentially expressed genes, with 13 downregulated and 50 upregulatedgenes in the alcohol-HIV-treated group. Upstream regulator analysis of differentially expressedgenes through Ingenuity Pathway Analysis identified transcriptional regulators affecting downstreamgenes associated with increased oxidative stress, lysosomal associated disease, and function andEVs biogenesis. Our in vitro findings were corroborated by in vivo studies on human hepatocytetransplantedhumanized mice, indicating that intensive EVs' generation by human hepatocytes andtheir secretion to serum was associated with increased oxidative stress and reduction in lysosomalactivities triggered by HIV infection and ethanol diet.

CONCLUSION

HIV-and-ethanol-metabolisminducedEVs release is tightly controlled by lysosome status in hepatocytes and participates in thedevelopment of double-insult-induced liver injury.

Circulating exosomes in cardiovascular disease: Novel carriers of biological information

Exosomes are a group of nanosized extracellular vesicles that include various bioactive nucleic acids, lipids, and proteins. They originate from membrane invagination and are released by exocytosis, which can transmit signals to target cells to achieve cell-to-cell communication and maintain homeostasis. The heart is a complex multicellular organ that contains resident cell types such as fibroblasts, endothelial cells, and smooth muscle cells. Communication between different cell types and immune systems is essential for the dynamic equilibrium of the cardiac internal environment. Intercellular communication is a universal phenomenon mediated by exosomes and their contents during several pathological processes in cardiovascular diseases, such as cardiomyocyte hypertrophy, apoptosis, and angiogenesis. Therefore, exosomes can be used as novel invasive diagnostic biomarkers in multiple diseases, including atherosclerosis, myocardial ischemia, cardiac fibrosis, and ischemia-reperfusion injury. In addition, the biocompatible nature and low immunogenicity of exosomes make them high-quality nanoparticle drug carriers with potential applications in translational medicine and therapeutic strategies. Here, we focus on the biogenesis, isolation, biological functions, and future application prospects of exosomes in cardiovascular disease.

Extracellular Vesicles and Their Roles in Cancer Progression

Extracellular vesicles (EVs) produced by cancer cells function as a unique form of intercellular communication that can promote cell growth and survival, help shape the tumor microenvironment, and increase invasive and metastatic activity. There are two major classes of EVs, microvesicles (MVs) and exosomes, and they differ in how they are formed. MVs are generated by the outward budding and fission of the plasma membrane. On the other hand, exosomes are derived as multivesicular bodies (MVBs) fuse with the plasma membrane and release their contents. What makes EVs especially interesting is how they mediate their effects. Both MVs and exosomes have been shown to contain a wide-variety of bioactive cargo, including cell surface, cytosolic, and nuclear proteins, as well as RNA transcripts, micro-RNAs (miRNAs), and even fragments of DNA. EVs, and their associated cargo, can be transferred to other cancer cells, as well as to normal cell types, causing the recipient cells to undergo phenotypic changes that promote different aspects of cancer progression. These findings, combined with those demonstrating that the amounts and contents of EVs produced by cancer cells can vary depending on their cell of origin, stage of development, or response to therapies, have raised the exciting possibility that EVs can be used for diagnostic purposes. Moreover, the pharmaceutical community is aggressively pursuing the use of EVs as a potential drug delivery platform. Here, in this chapter, we will highlight what is currently known about how EVs are generated, how they impact cancer progression, and the different ways they are being exploited for clinical applications.

The Role of Post-Translational Modifications in Targeting Protein Cargo to Extracellular Vesicles

Extracellular vesicles (EVs) are naturally occurring nanoparticles that contain proteins and nucleic acids. It is speculated that cells release EVs loaded with a selective cargo of proteins through highly regulated processes. Several proteomic and biochemical studies have highlighted phosphorylated, glycosylated, ubiquitinated, SUMOylated, oxidated and palmitoylated proteins within the EVs. Emerging evidences suggest that post-translational modifications (PTMs) can regulate the sorting of specific proteins into EVs and such proteins with specific PTMs have also been identified in clinical samples. Hence, it has been proposed that EV proteins with PTMs could be used as potential biomarkers of disease conditions. Among the other cellular mechanisms, the endosomal sorting complex required for transport (ESCRT) is also implicated in cargo sorting into EVs. In this chapter, various PTMs that are shown to regulate protein cargo sorting into EVs will be discussed.

Role of Exosomes for Delivery of Chemotherapeutic Drugs

Exosomes are endogenous extracellular vesicles (30-100 nm) composed with membrane lipid bilayer which carry vesicular proteins, enzymes, mRNA, miRNA and nucleic acids. They act as messengers for intra- and inter-cellular communication. In addition to their physiological roles, exosomes have the potential to encapsulate and deliver small chemotherapeutic drugs and biological molecules such as proteins and nucleic acid-based drugs to the recipient tissue or organs. Due to their biological properties, exosomes have better organotropism, homing capacity, cellular uptake and cargo release ability than other synthetic nano-drug carriers such as liposomes, micelles and nanogels. The secretion of tumor-derived exosomes is increased in the hypoxic and acidic tumor microenvironment, which can be used as a target for nontoxic and nonimmunogenic drug delivery vehicles for various cancers. Moreover, exosomes have the potential to carry both hydrophilic and hydrophobic chemotherapeutic drugs, bypass RES effect and bypass BBB. Exosomes can be isolated from other types of EVs and cell debris based on their size, density and specific surface proteins through ultracentrifugation, density gradient separation, precipitation, immunoaffinity interaction and gel filtration. Drugs can be loaded into exosomes at the biogenesis stage or with the isolated exosomes by incubation, electroporation, extrusion or sonication methods. Finally, exosomal cargo vehicles can be characterized by ultrastructural microscopic analysis. In this review we intend to summarize the inception, structure and function of the exosomes, role of exosomes in immunological regulation and cancer, methods of isolation and characterization of exosomes and products under clinical trials. This review will provide an inclusive insight of exosomes in drug delivery.

Regulation of exosome production and cargo sorting

Cellular communication can be mediated by the exchange of biological information, mainly in the form of proteins and RNAs. This can occur when extracellular vesicles, such as exosomes, secreted by a donor cell are internalized by an acceptor cell. Exosomes bear specific repertoires of proteins and RNAs, indicating the existence of mechanisms that control the sorting of molecules into them. Knowledge about loadings and processes and mechanisms of cargo sorting of exosomes is essential to shed light on the physiological and pathological functions of these vesicles as well as on clinical applications involving their use and/or analysis. In this review, we will discuss the molecular mechanisms associated with exosome secretion and their specific cargo sorting, with special attention to the sorting of RNAs and proteins, and thus the outcome and the emerging therapeutic opportunities of the communication between the exosome-producer and recipient cells.

Expression of miRNA-29 in Pancreatic β Cells Promotes Inflammation and Diabetes via TRAF3

Type 2 diabetes mellitus (T2DM) is recognized as a chronic, low-grade inflammatory disease characterized by insulin resistance and pancreatic β cell dysfunction; however, the underlying molecular mechanism remains unclear. Here, we report a key β cell-macrophage crosstalk pathway mediated by the miRNA-29-TNF-receptor-associated factor 3 (TRAF3) axis. β cell-specific transgenic miR-29a/b/c mice are predisposed to develop glucose intolerance and insulin resistance when fed a high-fat diet (HFD). The metabolic effect of β cell miR-29 is largely mediated through macrophages because either depletion of macrophages or reconstitution with miR-29-signaling defective bone marrow improves metabolic parameters in the transgenic mice. Mechanistically, our data show that miR-29 promotes the recruitment and activation of circulating monocytes and macrophages and, hence, inflammation, via miR-29 exosomes in a TRAF3-dependent manner. Our results demonstrate the ability of β cells to modulate the systemic inflammatory tone and glucose homeostasis via miR-29 in response to nutrient overload.

The forces driving cancer extracellular vesicle secretion

The discovery that cancer cells discharge vast quantities of extracellular vesicles (EVs), underscored the explosion of the EV field. A large body of evidence now supports their onco-functionality in an array of contexts; stromal crosstalk, immune evasion, metastatic site priming, and drug resistance - justifying therapeutic intervention. The current bottleneck is a lack of clear understanding of why and how EV biogenesis ramps up in cancer cells, and hence where exactly avenues for intervention may reside. We know that EVs also play an array of physiological roles, therefore effective anticancer inhibition requires a target distinct enough from physiology to achieve efficacy. Taking the perspective that EV upregulation may be a consequence of the tumor landscape, we examine classic mutational events and tumor characteristics for EV regulators. All the while, aiming to illuminate topics worth further research in therapeutic development.

Extracellular Vesicles from Red Blood Cells and Their Evolving Roles in Health, Coagulopathy and Therapy

Red blood cells (RBCs) release extracellular vesicles (EVs) including both endosome-derived exosomes and plasma-membrane-derived microvesicles (MVs). RBC-derived EVs (RBCEVs) are secreted during erythropoiesis, physiological cellular aging, disease conditions, and in response to environmental stressors. RBCEVs are enriched in various bioactive molecules that facilitate cell to cell communication and can act as markers of disease. RBCEVs contribute towards physiological adaptive responses to hypoxia as well as pathophysiological progression of diabetes and genetic non-malignant hematologic disease. Moreover, a considerable number of studies focus on the role of EVs from stored RBCs and have evaluated post transfusion consequences associated with their exposure. Interestingly, RBCEVs are important contributors toward coagulopathy in hematological disorders, thus representing a unique evolving area of study that can provide insights into molecular mechanisms that contribute toward dysregulated hemostasis associated with several disease conditions. Relevant work to this point provides a foundation on which to build further studies focused on unraveling the potential roles of RBCEVs in health and disease. In this review, we provide an analysis and summary of RBCEVs biogenesis, composition, and their biological function with a special emphasis on RBCEV pathophysiological contribution to coagulopathy. Further, we consider potential therapeutic applications of RBCEVs.

Enhancement of HIV-1 Env-Specific CD8 T Cell Responses Using Interferon-Stimulated Gene 15 as an Immune Adjuvant

Induction of the endogenous innate immune system by interferon (IFN) triggers the expression of many proteins that serve like alarm bells in the body, activating an immune response. After a viral infection, one of the genes activated by IFN induction is the IFN-stimulated gene 15 (ISG15), which encodes a ubiquitin-like protein that undergoes a reversible posttranslational modification (ISGylation). ISG15 protein can also act unconjugated, intracellularly and secreted, acting as a cytokine. Although ISG15 has an essential role in host defense responses to microbial infection, its role as an immunomodulator in the vaccine field remains to be defined. In this investigation, we showed that ISG15 exerts an immunomodulatory role in human immunodeficiency virus (HIV) vaccines. In mice, after priming with a DNA-ISG15 vector mixed with a DNA expressing HIV-1 gp120 (DNA-gp120), followed by a booster with a modified vaccinia virus Ankara (MVA) vector expressing HIV-1 antigens, both wild-type ISG15-conjugated (ISG15-wt) and mutant unconjugated (ISG15-mut) proteins act as immune adjuvants by increasing the magnitude and quality of HIV-1-specific CD8 T cells, with ISG15-wt providing better immunostimulatory activity than ISG15-mut. The HIV-1 Env-specific CD8 T cell responses showed a predominant T effector memory (TEM) phenotype in all groups. Moreover, the amount of DNA-gp120 used to immunize mice could be reduced 5-fold after mixing with DNA-ISG15 without affecting the potency and the quality of the HIV-1 Env-specific immune responses. Our study clearly highlights the potential use of the IFN-induced ISG15 protein as immune adjuvant to enhance immune responses to HIV antigens, suggesting that this molecule might be exploitable for prophylactic and therapeutic vaccine approaches against pathogens.IMPORTANCE Our study described the potential role of ISG15 as an immunomodulatory molecule in the optimization of HIV/AIDS vaccine candidates. Using a DNA prime-MVA boost immunization protocol, our results indicated an increase in the potency and the quality of the HIV-1 Env-specific CD8 T cell response. These results highlight the adjuvant potency of ISG15 to elicit improved viral antigen presentation to the immune system, resulting in an enhanced HIV-1 vaccine immune response. The DNA-ISG15 vector could find applicability in the vaccine field in combination with other nucleic acid-based vector vaccines.

Nonmuscle Myosin Heavy Chain ⅡA-Mediated Exosome Release via Regulation of the Rho-Associated Kinase 1/Myosin Light Chains/Actin Pathway

Nonmuscle myosin ⅡA, a kind of ATP-dependent molecular motor, binds actin to form the molecular motors of the cell. We found that interfering with nonmuscle myosin heavy chain (NMMHC) ⅡA could affect the exosome release from microglial cells stimulated by LPS. LPS could enhance exosome release from microglial cells by increasing exosome concentration, elevating the rate of positively labeled CD9 and CD81 proteins and protein expression. The myosin inhibitor, blebbistatin, could decrease the concentration of released exosome and reduce CD9 and CD81 protein expression on the exosome surface compared with that in the LPS group. To further determine the exact subtype of myosin Ⅱ responsible for these effects, we transfected microglial cells with siRNA for MYH9, MYH10, and MYH14. The data showed that only the transfection of siRNA-MYH9, but not MYH10 or MYH14 could decrease the released exosome concentration and particle size compared with those in the LPS group. siRNA-MYH9 would also weaken the CD9 and CD81 protein positive rate and protein expression compared with that in the LPS group by the quantification of CD9 and CD81 fluorescence intensities and by western blotting. Western blots and immunofluorescence assays indicated that NMMHC ⅡA might trigger the ROCK1/MLC/actin signaling pathway of microglial cells upon stimulation by LPS, which might be the potential mechanism of exosome release. These observations demonstrated that NMMHC ⅡA might be the potential target required for exosome release.

Potential Roles of Tumor Cell- and Stroma Cell-Derived Small Extracellular Vesicles in Promoting a Pro-Angiogenic Tumor Microenvironment

Simple Summary

In this review, we focus on the distinct functions of tumor-cell-derived small extracellular vesicles in promotion of angiogenesis and describe their potential as a therapeutic target for anti-angiogenic therapies. Also, we focus on extracellular vesicles derived from non-cancer cells and their potential role in stimulating a pro-angiogenic tumor microenvironment. The article describes the biogenesis of small extracellular vesicles and refers to their proteomic cargo components that play a role in promoting angiogenesis. Moreover, we explain how small extracellular vesicles derived from tumors and non-cancer cells can interact with recipient cells and alter their functions. We particularly focus on phenotypical and functional changes in endothelial cells, macrophages, and neutrophils that result in proangiogenic signaling.

Abstract

Extracellular vesicles (EVs) are produced and released by all cells and are present in all body fluids. They exist in a variety of sizes, however, small extracellular vesicles (sEVs), the EV subset with a size range from 30 to 150 nm, are of current interest. They are characterized by a distinct biogenesis and complex cargo composition, which reflects the cytosolic contents and cell-surface molecules of the parent cells. This cargo consists of proteins, nucleic acids, and lipids and is competent in inducing signaling cascades in recipient cells after surface interactions or in initiating the generation of a functional protein by delivering nucleic acids. Based on these characteristics, sEVs are now considered as important mediators of intercellular communication. One hallmark of sEVs is the promotion of angiogenesis. It was shown that sEVs interact with endothelial cells (ECs) and promote an angiogenic phenotype, ultimately leading to increased vascularization of solid tumors and disease progression. It was also shown that sEVs reprogram cells in the tumor microenvironment (TME) and act in a functionally cooperative fashion to promote angiogenesis by a paracrine mechanism involving the differential expression and secretion of angiogenic factors from other cell types. In this review, we will focus on the distinct functions of tumor-cell-derived sEVs (TEX) in promotion of angiogenesis and describe their potential as a therapeutic target for anti-angiogenic therapies. Also, we will focus on non-cancer stroma-cell-derived small extracellular vesicles and their potential role in stimulating a pro-angiogenic TME.

Dexosomes as a cell-free vaccine for cancer immunotherapy

Dendritic cells (DCs) secrete vast quantities of exosomes termed as dexosomes. Dexosomes are symmetric nanoscale heat-stable vesicles that consist of a lipid bilayer displaying a characteristic series of lipid and protein molecules. They include tetraspanins and all established proteins for presenting antigenic material such as the major histocompatibility complex class I/II (MHC I/II) and CD1a, b, c, d proteins and CD86 costimulatory molecule. Dexosomes contribute to antigen-specific cellular immune responses by incorporating the MHC proteins with antigen molecules and transferring the antigen-MHC complexes and other associated molecules to naïve DCs. A variety of ex vivo and in vivo studies demonstrated that antigen-loaded dexosomes were able to initiate potent antitumor immunity. Human dexosomes can be easily prepared using monocyte-derived DCs isolated by leukapheresis of peripheral blood and treated ex vivo by cytokines and other factors. The feasibility of implementing dexosomes as therapeutic antitumor vaccines has been verified in two phase I and one phase II clinical trials in malignant melanoma and non small cell lung carcinoma patients. These studies proved the safety of dexosome administration and showed that dexosome vaccines have the capacity to trigger both the adaptive (T lymphocytes) and the innate (natural killer cells) immune cell recalls. In the current review, we will focus on the perspective of utilizing dexosome vaccines in the context of cancer immunotherapy.

Comparative proteome analysis reveals VPS28 regulates milk fat synthesis through ubiquitylation in bovine mammary epithelial cells

In our previous study, we found that VPS28 (vacuolar protein sorting 28 homolog) could alter ubiquitylation level to regulate milk fat synthesis in bovine primary mammary epithelial cells (BMECs). While the information on the regulation of VPS28 on proteome of milk fat synthesis is less known, we explored its effect on milk fat synthesis using isobaric tags for relative and absolute quantitation assay after knocking down VPS28 in BMECs. A total of 2,773 proteins in three biological replicates with a false discovery rate of less than 1.2% were identified and quantified. Among them, a subset of 203 proteins were screened as significantly down-(111) and up-(92) regulated in VPS28 knockdown BMECs compared with the control groups. According to Gene Ontology analysis, the differentially expressed proteins were enriched in the "proteasome," "ubiquitylation," "metabolism of fatty acids," "phosphorylation," and "ribosome." Meanwhile, some changes occurred in the morphology of BMECs and an accumulation of TG (triglyceride) and dysfunction of proteasome were identified, and a series of genes associated with milk fat synthesis, ubiquitylation and proteasome pathways were analyzed by quantitative real-time PCR. The results of this study suggested VPS28 regulated milk fat synthesis was mediated by ubiquitylation; it could be an important new area of study for milk fat synthesis and other milk fat content traits in bovine.

More than Meets the ISG15: Emerging Roles in the DNA Damage Response and Beyond

Maintenance of genome stability is a crucial priority for any organism. To meet this priority, robust signalling networks exist to facilitate error-free DNA replication and repair. These signalling cascades are subject to various regulatory post-translational modifications that range from simple additions of chemical moieties to the conjugation of ubiquitin-like proteins (UBLs). Interferon Stimulated Gene 15 (ISG15) is one such UBL. While classically thought of as a component of antiviral immunity, ISG15 has recently emerged as a regulator of genome stability, with key roles in the DNA damage response (DDR) to modulate p53 signalling and error-free DNA replication. Additional proteomic analyses and cancer-focused studies hint at wider-reaching, uncharacterised functions for ISG15 in genome stability. We review these recent discoveries and highlight future perspectives to increase our understanding of this multifaceted UBL in health and disease.

Conformational changes in myeloperoxidase induced by ubiquitin and NETs containing free ISG15 from systemic lupus erythematosus patients promote a pro-inflammatory cytokine response in CD4+ T cells

Background

Neutrophil extracellular traps (NETs) from patients with systemic lupus erythematosus (SLE) are characterized by lower ubiquitylation and myeloperoxidase (MPO) as a substrate. The structural and functional effect of such modification and if there are additional post-translational modifications (PTMs) are unknown.

Methods

To assess the expression and functional role of PTMs in NETs of patients with SLE; reactivation, proliferation and cytokine production was evaluated by flow cytometry using co-cultures with dendritic cells (DC) and CD4⁺ from SLE patients and healthy controls. The impact of ubiquitylation on MPO was assessed by molecular dynamics. The expression of ISG15 in NETs was evaluated by immunofluorescence and Western Blot.

Results

Fifteen patients with SLE and ten healthy controls were included. In the co-cultures of CD4⁺ lymphocytes with DC stimulated with ubiquitylated MPO or recombinant MPO, a higher expression of IFNγ and IL-17A was found in CD4⁺ from SLE patients (p < 0.05). Furthermore, with DC stimulated with ubiquitylated MPO a trend towards increased expression of CD25 and Ki67 was found in lupus CD4⁺ lymphocytes, while the opposite was documented in controls (p < 0.05). Through molecular dynamics we found the K129-K488-K505 residues of MPO as susceptible to ubiquitylation. Ubiquitylation affects the hydration status of the HEME group depending on the residue to which it is conjugated. R239 was found near by the HEME group when the ubiquitin was in K488-K505. In addition, we found greater expression of ISG15 in the SLE NETs vs controls (p < 0.05), colocalization with H2B (r = 0.81) only in SLE samples and increased production of IFNγ in PBMCs stimulated with lupus NETs compared to healthy controls NETs.

Conclusion

The ubiquitylated MPO has a differential effect on the induction of reactivation of CD4⁺ lymphocytes in patients with SLE, which may be related to structural changes by ubiquitylation at the catalytic site of MPO. Besides a lower ubiquitylation pattern, NETs of patients with SLE are characterized by the expression of ISG15, and the induction of IFNγ by Th1 cells.