Transfer of the chemokine receptor CCR5 between cells by membrane-derived microparticles: a mechanism for cellular human immunodeficiency virus 1 infection

Extracellular Vesicles: Packages Sent With Complement

Cells communicate with other cells in their microenvironment by transferring lipids, peptides, RNA, and sugars in extracellular vesicles (EVs), thereby also influencing recipient cell functions. Several studies indicate that these vesicles are involved in a variety of critical cellular processes including immune, metabolic, and coagulatory responses and are thereby associated with several inflammatory diseases. Furthermore, EVs also possess anti-inflammatory properties and contribute to immune regulation, thus encouraging an emerging interest in investigating and clarifying mechanistic links between EVs and innate immunity. Current studies indicate complex interactions of the complement system with EVs, with a dramatic influence on local and systemic inflammation. During inflammatory conditions with highly activated complement, including after severe tissue trauma and during sepsis, elevated numbers of EVs were found in the circulation of patients. There is increasing evidence that these shed vesicles contain key complement factors as well as complement regulators on their surface, affecting inflammation and the course of disease. Taken together, interaction of EVs regulates complement activity and contributes to the pro- and anti-inflammatory immune balance. However, the molecular mechanisms behind this interaction remain elusive and require further investigation. The aim of this review is to summarize the limited current knowledge on the crosstalk between complement and EVs. A further aspect is the clinical relevance of EVs with an emphasis on their capacity as potential therapeutic vehicles in the field of translational medicine.

Role of Extracellular Vesicles in Viral and Bacterial Infections: Pathogenesis, Diagnostics, and Therapeutics

Extracellular vesicles (EVs), or exosomes, are nanovesicles of endocytic origin that carry host and pathogen-derived protein, nucleic acid, and lipid cargos. They are secreted by most cell types and play important roles in normal cell-to-cell communications but can also spread pathogen- and host-derived molecules during infections to alter immune responses and pathophysiological processes. New research is beginning to decipher how EVs influence viral and bacterial pathogenesis. In this review, we will describe how EVs influence viral and bacterial pathogenesis by spreading pathogen-derived factors and how they can promote and inhibit the immune response to these pathogens. We will also discuss the emerging potential of EVs as diagnostic and therapeutic tools.

Extracellular vesicles as modulators of wound healing

Impaired healing of cutaneous wounds and ulcers continues to have a major impact on the quality of life of millions of people. In recent years, the capacity for stem and progenitor cells to promote wound repair has been investigated with evidence that secreted factors are responsible for the observed therapeutic benefits. This review addresses current evidence in support of stem/progenitor cell-derived extracellular vesicles (EVs) as a regenerative therapy for acceleration of wound healing. Encouraging results for local or systemic administration of EVs have been reported in a range of clinically-relevant animal models of cutaneous wounds. Furthermore, a number of plausible mechanisms involving EV-mediated transfer of proteins and RNAs that trigger pro-repair pathways in target cells have been demonstrated experimentally. However, for successful clinical translation in the coming years, further emphasis on standardized experimental protocols, detailed methodological reporting and clear definition of EV-based therapeutic products will be required.

Extracellular vesicles as mediators of immunopathology in infectious diseases

In the last decades, extracellular vesicles have emerged as important elements in cell-cell communication and as key players in disease pathogenesis via transmission of their cargo between different cells. Various works have described different subpopulations of these membrane structures, based on their cell of origin, biogenesis, size, biophysical properties and cargo. In addition to their pathophysiological role in the development and progression of different diseases including infectious diseases, neurodegenerative disorders and cancer, extracellular vesicles are now recognized for their potential as novel therapeutic targets and intelligent drug delivery system. Here, we have reviewed the most recent data on different subtypes of extracellular vesicles, focusing on microvesicles and exosomes and their subpopulations, their involvement in immune-mediated pathogenesis of various infectious diseases and their role as potential therapeutic targets.

Tetraspanin blockage reduces exosome-mediated HIV-1 entry

HIV-1 is one of the most studied retroviruses. The role of exosomes in HIV-1 entry and pathogenesis are beginning to be appreciated. Exosomes can incorporate host proteins that are also contained in viruses (e.g., tetraspanins).

Extracellular Vesicles and the Promise of Continuous Liquid Biopsies

The rapid and accurate diagnosis of patients with minimally invasive procedures was once only found in science fiction. However, the discovery of extracellular vesicles (EVs) and their near ubiquity in body fluids, coupled with the advent of inexpensive next generation sequencing techniques and EV purification protocols, promises to make science fiction a reality. Purifying and sequencing the RNA content of EV from routine blood draws and urine samples are likely to enable pathologists and physicians to diagnose and track the progress of diseases in many inaccessible tissues in the near future. Here we present the evolutionary background of EV, summarize the biology of EV formation and cargo selection, and discuss the current barriers to making continuous liquid biopsies through the use of EV a science reality.

Exosome Theranostics: Biology and Translational Medicine

Exosomes are common membrane-bound nanovesicles that contain diverse biomolecules, such as lipids, proteins, and nucleic acids. Exosomes are derived from cells through exocytosis, are ingested by target cells, and can transfer biological signals between local or distant cells. Exosome secretion is a constitutive phenomenon that is involved in both physiological and pathological processes and determines both the exosomal surface molecules and the contents. Hence, we can exploit exosomes as biomarkers, vaccines and drug carriers and modify them rationally for therapeutic interventions. However, it is still a challenge to identify, isolate and quantify exosomes accurately, efficiently and selectively. Further studies on exosomes will explore their potential in translational medicine and provide new avenues for the creation of effective clinical diagnostics and therapeutic strategies; the use of exosomes in these applications can be called exosome theranostics. This review describes the fundamental processes of exosome formation and uptake. In addition, the physiological and pathological roles of exosomes in biology are also illustrated with a focus on how exosomes can be exploited or engineered as powerful tools in translational medicine.

Role of L-Particles during Herpes Simplex Virus Infection

Infection of eukaryotic cells with α-herpesviruses results in the formation and secretion of infectious heavy particles (virions; H-particles) and non-infectious light particles (L-particles). Herpes simplex virus type 1 (HSV-1) H-particles consist of a genome-containing capsid surrounded by tegument proteins and a glycoprotein-rich lipid bilayer. Non-infectious L-particles are composed mainly of envelope and tegument proteins and are devoid of capsids and viral DNA. L-particles were first described in the early nineties and from then on investigated for their formation and role during virus infection. The development and secretion of L-particles occur simultaneously to the assembly of complete viral particles. HSV-1 L-particles are assembled by budding of condensed tegument into Golgi-delivered vesicles and are capable of delivering their functional content to non-infected cells. Thereby, HSV-1 L-particles contribute to viral pathogenesis within the infected host by enhancing virion infectivity and providing immune evasion functions. In this review we discuss the emergence of HSV-1 L-particles during virus replication and their biological functions described thus far.

Microvesicle Involvement in Shiga Toxin-Associated Infection

Shiga toxin is the main virulence factor of enterohemorrhagic Escherichia coli, a non-invasive pathogen that releases virulence factors in the intestine, causing hemorrhagic colitis and, in severe cases, hemolytic uremic syndrome (HUS). HUS manifests with acute renal failure, hemolytic anemia and thrombocytopenia. Shiga toxin induces endothelial cell damage leading to platelet deposition in thrombi within the microvasculature and the development of thrombotic microangiopathy, mostly affecting the kidney. Red blood cells are destroyed in the occlusive capillary lesions. This review focuses on the importance of microvesicles shed from blood cells and their participation in the prothrombotic lesion, in hemolysis and in the transfer of toxin from the circulation into the kidney. Shiga toxin binds to blood cells and may undergo endocytosis and be released within microvesicles. Microvesicles normally contribute to intracellular communication and remove unwanted components from cells. Many microvesicles are prothrombotic as they are tissue factor- and phosphatidylserine-positive. Shiga toxin induces complement-mediated hemolysis and the release of complement-coated red blood cell-derived microvesicles. Toxin was demonstrated within blood cell-derived microvesicles that transported it to renal cells, where microvesicles were taken up and released their contents. Microvesicles are thereby involved in all cardinal aspects of Shiga toxin-associated HUS, thrombosis, hemolysis and renal failure.

Exosomes Derived from HIV-1 Infected DCs Mediate Viral trans-Infection via Fibronectin and Galectin-3

Exosomes are membrane enclosed nano-sized vesicles actively released into the extracellular milieu that can harbor genomic, proteomic and lipid cargos. Functionally, they are shown to regulate cell-cell communication and transmission of pathogens. Though studies have implicated a role for exosomes in HIV-1 pathogenesis, their mechanisms are not well defined. Here, we characterized exosomes derived from uninfected or HIV-1 infected T-cells and DCs. We demonstrate substantial differences in morphological, molecular and biogenesis machinery between exosomes derived from these two immune cell types. In addition, exosomes derived from HIV-1 infected DCs were 4 fold more infective than either cell free HIV-1 or exosomes derived from T-cells. Molecular analysis of exosomes detected the presence of fibronectin and galectin-3 in those derived from DCs, whereas T-cell exosomes lacked these molecules. Addition of anti-fibronectin antibody and β-lactose, a galectin-3 antagonist, significantly blocked DC exosome-mediated HIV-1 infection of T-cells. We also observed increased gene expression of the pro-inflammatory cytokines IFN-γ, TNF-α, IL-1β and RANTES and activation of p38/Stat pathways in T-cells exposed to exosomes derived from HIV-1 infected DCs. Our study provides insight into the role of exosomes in HIV pathogenesis and suggests they can be a target in development of novel therapeutic strategies against viral infection.

Transcellular communication at the immunological synapse: a vesicular traffic-mediated mutual exchange

The cell’s ability to communicate with the extracellular environment, with other cells, and with itself is a crucial feature of eukaryotic organisms. In the immune system, T lymphocytes assemble a specialized structure upon contact with antigen-presenting cells bearing a peptide-major histocompatibility complex ligand, known as the immunological synapse (IS). The IS has been extensively characterized as a signaling platform essential for T-cell activation. Moreover, emerging evidence identifies the IS as a device for vesicular traffic-mediated cell-to-cell communication as well as an active release site of soluble molecules. Here, we will review recent advances in the role of vesicular trafficking in IS assembly and focused secretion of microvesicles at the synaptic area in naïve T cells and discuss the role of the IS in transcellular communication.

Signal Peptide Peptidase, Encoded by HM13, Contributes to Tumor Progression by Affecting EGFRvIII Secretion Profiles in Glioblastoma

BACKGROUND AND AIMS

EGFRvIII is the most prevalent glioblastoma mutation, occurring in more than 25% of glioblastomas. EGFRvIII cells release microvesicles that contain proteins, miRNAs, and mRNAs that enhance the growth and survival of surrounding tumor cells. However, little is known about the maturation process and regulatory mechanisms of secreted vesicles in EGFRvIII cells.

METHODS

Signal peptide peptidase (SPP) provides a fascinating mechanism for protein cleavage and subsequent dislocation in the endoplasmic reticulum transmembrane domain.

RESULTS

In this study, we reported that SPP facilitates the secretion of cytokines in vitro and promotes tumor progression in mice. Human cytokine antibody arrays revealed that EGFRvIII secreted higher levels of cytokines, but these levels were significantly reduced following SPP knockdown, suggesting that cytokines in EGFRvIII secretion profiles play important roles in GBM development. Identical results were confirmed in intracellular maturation tracking of TGF-β1 in mouse serum. Clinically, analyses of GBM patient data from the database revealed that HM13 expression was closely related to patient prognosis and survival, suggesting an influence by the secreted vesicles of EGFRvIII tumor cells.

CONCLUSIONS

Collectively, our study identifies that SPP affects EGFRvIII secretion profiles and thus promotes tumor progression, providing further understanding of the formation of secreted vesicles and driving role of EGFRvIII in GBM.

Extracellular vesicles from KSHV-infected endothelial cells activate the complement system

Extracellular vesicles (EVs), released by cells, are associated with cell-to-cell communication and regulate various cellular processes. EVs draw parallels with viruses for their similar structures and functions. Increasing evidences from recent studies indicate that cells infected with viruses release a variety of EVs. Delineating the functions and mechanisms of EVs released during virus infection is essential for understanding the molecular basis of viral infection and replication as well as associated pathogenesis. The most challenging obstacle for these studies is the separation of EVs from viruses. In this study, we successfully isolated the EVs from de novo Kaposi’s sarcoma-associated herpesvirus (KSHV) infected-human endothelial cells during the period between virus entry and production. Intriguingly, a proteomics analysis of these EVs has revealed alterations of the complement system. Additionally, we have discovered that the EVs from KSHV-infected endothelial cells are potent activators of an alternative pathway of the complement system via exploitation of the endogenous C3 complement protein and properdin. Furthermore, we have found that complement activation promotes KSHV persistent latent infection by activating the NF-κB pathway, which enhances the survival of KSHV-infected cells and inhibits viral lytic replication. Our work identifies a novel role of EVs induced by KSHV during de novo infection and the underlying mechanism of complement activation by EVs.

Reproducible and scalable purification of extracellular vesicles using combined bind-elute and size exclusion chromatography

Extracellular vesicles (EVs) play a pivotal role in cell-to-cell communication and have been shown to take part in several physiological and pathological processes. EVs have traditionally been purified by ultracentrifugation (UC), however UC has limitations, including resulting in, operator-dependant yields, EV aggregation and altered EV morphology, and moreover is time consuming. Here we show that commercially available bind-elute size exclusion chromatography (BE-SEC) columns purify EVs with high yield (recovery ~ 80%) in a time-efficient manner compared to current methodologies. This technique is reproducible and scalable, and surface marker analysis by bead-based flow cytometry revealed highly similar expression signatures compared with UC-purified samples. Furthermore, uptake of eGFP labelled EVs in recipient cells was comparable between BE-SEC and UC samples. Hence, the BE-SEC based EV purification method represents an important methodological advance likely to facilitate robust and reproducible studies of EV biology and therapeutic application.

Trypanosoma cruzi Evades the Complement System as an Efficient Strategy to Survive in the Mammalian Host: The Specific Roles of Host/Parasite Molecules and Trypanosoma cruzi Calreticulin

American Trypanosomiasis is an important neglected reemerging tropical parasitism, infecting about 8 million people worldwide. Its agent, Trypanosoma cruzi, exhibits multiple mechanisms to evade the host immune response and infect host cells. An important immune evasion strategy of T. cruzi infective stages is its capacity to inhibit the complement system activation on the parasite surface, avoiding opsonizing, immune stimulating and lytic effects. Epimastigotes, the non-infective form of the parasite, present in triatomine arthropod vectors, are highly susceptible to complement-mediated lysis while trypomastigotes, the infective form, present in host bloodstream, are resistant. Thus T. cruzi susceptibility to complement varies depending on the parasite stage (amastigote, trypomastigotes or epimastigote) and on the T. cruzi strain. To avoid complement-mediated lysis, T. cruzi trypomastigotes express on the parasite surface a variety of complement regulatory proteins, such as glycoprotein 58/68 (gp58/68), T. cruzi complement regulatory protein (TcCRP), trypomastigote decay-accelerating factor (T-DAF), C2 receptor inhibitor trispanning (CRIT) and T. cruzi calreticulin (TcCRT). Alternatively, or concomitantly, the parasite captures components with complement regulatory activity from the host bloodstream, such as factor H (FH) and plasma membrane-derived vesicles (PMVs). All these proteins inhibit different steps of the classical (CP), alternative (AP) or lectin pathways (LP). Thus, TcCRP inhibits the CP C3 convertase assembling, gp58/68 inhibits the AP C3 convertase, T-DAF interferes with the CP and AP convertases assembling, TcCRT inhibits the CP and LP, CRIT confers ability to resist the CP and LP, FH is used by trypomastigotes to inhibit the AP convertases and PMVs inhibit the CP and LP C3 convertases. Many of these proteins have similar molecular inhibitory mechanisms. Our laboratory has contributed to elucidate the role of TcCRT in the host-parasite interplay. Thus, we have proposed that TcCRT is a pleiotropic molecule, present not only in the parasite endoplasmic reticulum, but also on the trypomastigote surface, participating in key processes to establish T. cruzi infection, such as inhibition of the complement system and serving as an important virulence factor. Additionally, TcCRT interaction with key complement components, participates as an anti-angiogenic and anti-tumor molecule, inhibiting at least in important part, tumor growth in infected animals.

Neural glycoprotein M6a is released in extracellular vesicles and modulated by chronic stressors in blood

Membrane neuronal glycoprotein M6a is highly expressed in the brain and contributes to neural plasticity promoting neurite growth and spine and synapse formation. We have previously showed that chronic stressors alter hippocampal M6a mRNA levels in rodents and tree shrews. We now show that M6a glycoprotein can be detected in mouse blood. M6a is a transmembrane glycoprotein and, as such, unlikely to be free in blood. Here we demonstrate that, in blood, M6a is transported in extracellular vesicles (EVs). It is also shown that M6a-containing EVs are delivered from cultured primary neurons as well as from M6a-transfected COS-7 cells. Released EVs containing M6a can be incorporated into COS-7 cells changing its phenotype through formation of membrane protrusions. Thus, M6a-containing EVs might contribute to maintain cellular plasticity. M6a presence in blood was used to monitor stress effects. Chronic restraint stress modulated M6a protein level in a sex dependent manner. Analysis of individual animals indicated that M6a level variations depend on the stressor applied. The response to stressors in blood makes M6a amenable to further studies in the stress disorder field.

Extracellular Vesicles in Cardiovascular Disease: Potential Applications in Diagnosis, Prognosis, and Epidemiology

Extracellular vesicles originate from diverse subcellular compartments and are released in the extracellular space. By transferring their cargoes into target cells and tissues, they now emerge as novel regulators of intercellular communication between adjacent and remote cells. Because vesicle composition and biological content are specific signatures of cellular activation and injury, their potential as diagnostic and prognostic biomarkers has raised significant interest in cardiovascular diseases. Characterization of circulating vesicles- or nonvesicles-bound nucleic acids represents a valuable tool for diagnosing and monitoring cardiovascular diseases, recently referred to as a liquid biopsy. Circulating extracellular vesicles offer a noninvasive and almost continuous access to circulating information on the disease state in epidemiological investigations. Finally, genetic engineering and cell-specific application of extracellular vesicles could display a novel therapeutic option for the treatment of cardiovascular diseases. In this review, we summarize the current knowledge about extracellular vesicles as diagnostic and prognostic biomarkers, as well as their potential applications for longitudinal epidemiological studies in cardiovascular diseases.

Mechanisms of HIV Neuropathogenesis: Role of Cellular Communication Systems

BACKGROUND

One of the major complications of Human Immunodeficiency Virus (HIV) infection is the development of HIV-Associated Neurocognitive Disorders (HANDs) in approximately 50-60% of HIV infected individuals. Despite undetectable viral loads in the periphery owing to anti-retroviral therapy, neuroinflammation and neurocognitive impairment are still prevalent in HIV infected individuals. Several studies indicate that the central nervous system (CNS) abnormalities observed in HIV infected individuals are not a direct effect of viral replication in the CNS, rather these neurological abnormalities are associated with amplification of HIV specific signals by unknown mechanisms. We propose that some of these mechanisms of damage amplification are mediated by gap junction channels, pannexin and connexin hemichannels, tunneling nanotubes and microvesicles/exosomes.

OBJECTIVE

Our laboratory and others have demonstrated that HIV infection targets cell to cell communication by altering all these communication systems resulting in enhanced bystander apoptosis of uninfected cells, inflammation and viral infection. Here we discuss the role of these communication systems in HIV neuropathogenesis.

CONCLUSION

In the current manuscript, we have described the mechanisms by which HIV "hijacks" these host cellular communication systems, leading to exacerbation of HIV neuropathogenesis, and to simultaneously promote the survival of HIV infected cells, resulting in the establishment of viral reservoirs.

Extracellular vesicles in renal disease

Extracellular vesicles, such as exosomes and microvesicles, are host cell-derived packages of information that allow cell-cell communication and enable cells to rid themselves of unwanted substances. The release and uptake of extracellular vesicles has important physiological functions and may also contribute to the development and propagation of inflammatory, vascular, malignant, infectious and neurodegenerative diseases. This Review describes the different types of extracellular vesicles, how they are detected and the mechanisms by which they communicate with cells and transfer information. We also describe their physiological functions in cellular interactions, such as in thrombosis, immune modulation, cell proliferation, tissue regeneration and matrix modulation, with an emphasis on renal processes. We discuss how the detection of extracellular vesicles could be utilized as biomarkers of renal disease and how they might contribute to disease processes in the kidney, such as in acute kidney injury, chronic kidney disease, renal transplantation, thrombotic microangiopathies, vasculitides, IgA nephropathy, nephrotic syndrome, urinary tract infection, cystic kidney disease and tubulopathies. Finally, we consider how the release or uptake of extracellular vesicles can be blocked, as well as the associated benefits and risks, and how extracellular vesicles might be used to treat renal diseases by delivering therapeutics to specific cells.

Mesenchymal stem/stromal cell extracellular vesicles: From active principle to next generation drug delivery system

It has been demonstrated that the biological effector of mesenchymal stem/stromal cells (MSCs) is their secretome, which is composed of a heterogeneous pool of bioactive molecules, partially enclosed in extracellular vesicles (EVs). Therefore, the MSC secretome (including EVs) has been recently proposed as possible alternative to MSC therapy. The secretome can be considered as a protein-based biotechnological product, it is probably safer compared with living/cycling cells, it presents virtually lower tumorigenic risk, and it can be handled, stored and sterilized as an Active Pharmaceutical/Principle Ingredient (API). EVs retain some structural and technological analogies with synthetic drug delivery systems (DDS), even if their potential clinical application is also limited by the absence of reproducible/scalable isolation methods and Good Manufacturing Practice (GMP)-compliant procedures. Notably, EVs secreted by MSCs preserve some of their parental cell features such as homing, immunomodulatory and regenerative potential. This review focuses on MSCs and their EVs as APIs, as well as DDS, considering their ability to reach inflamed and damaged tissues and to prolong the release of encapsulated drugs. Special attention is devoted to the illustration of innovative therapeutic approaches in which nanomedicine is successfully combined with stem cell therapy, thus creating a novel class of "next generation drug delivery systems."

Role of TIM-4 in exosome-dependent entry of HIV-1 into human immune cells

Exosomes, 30–200 nm nanostructures secreted from donor cells and internalized by recipient cells, can play an important role in the cellular entry of some viruses. These microvesicles are actively secreted into various body fluids, including blood, urine, saliva, cerebrospinal fluid, and breast milk. We successfully isolated exosomes from human breast milk and plasma. The size and concentration of purified exosomes were measured by nanoparticle tracking, while Western blotting confirmed the presence of the exosomal-associated proteins CD9 and CD63, clathrin, and T cell immunoglobulin and mucin proteins (TIMs). Through viral infection assays, we determined that HIV-1 utilizes an exosome-dependent mechanism for entry into human immune cells. The virus contains high amounts of phosphatidylserine (PtdSer) and may bind PtdSer receptors, such as TIMs. This mechanism is supported by our findings that exosomes from multiple sources increased HIV-1 entry into T cells and macrophages, and viral entry was potently blocked with anti-TIM-4 antibodies.

Macrophage Proresolving Mediators-the When and Where

Macrophages and neutrophils orchestrate acute inflammation and host defense as well as the resolution phase and return to homeostasis. In this article, we review the contribution of macrophages to local lipid mediator (LM) levels and the regulation of macrophage LM profiles by polymorphonuclear neutrophils and neutrophil-derived microparticles. We carried out LM metabololipidomics, profiling distinct phagocytes: neutrophils (PMNs), apoptotic PMNs, and macrophages. Efferocytosis increased specialized proresolving mediator (SPM) biosynthesis, including resolvin D1 (RvD1), RvD2, and RvE2, which were further elevated by PMN microparticles. In studies using deuterium-labeled precursors (d8-arachidonic acid, d5-eicosapentaenoic acid, and d5-docosahexaenoic acid), apoptotic PMNs and microparticles contributed to SPM biosynthesis during efferocytosis. Assessment of macrophage LM profiles in M2 macrophages demonstrated higher SPM levels in this macrophage subset, including maresin 1 (MaR1), and lower amounts of leukotriene B4 (LTB4) and prostaglandins than in M1. Apoptotic PMN uptake by both macrophage subtypes led to modulation of their LM profiles. LTB4 was downregulated in M2, whereas SPMs including lipoxin A4 were increased. Conversely, uptake of apoptotic PMNs by M2 macrophages reduced (∼25%) overall LMs. MaR1 displays potent tissue-regenerative and antinociceptive actions in addition to its proresolving and anti-inflammatory actions. In addition, the MaR1 biosynthetic intermediate 13S,14S-epoxy-maresin is also bioactive, inhibiting LTB4 biosynthesis and switching macrophage phenotypes from M1 to M2. Together, these results establish LM signature profiles of human phagocytes and related subpopulations. They demonstrate microparticle regulation of macrophage-specific endogenous LMs during defined stages of acute inflammation and their dynamic changes in human primary phagocytes.

The effects of indoxyl sulfate-induced endothelial microparticles on neointimal hyperplasia formation in an ex vivo model

Purpose

Neointimal hyperplasia (NH) is considered to be one of the main causes of vascular access occlusion in patients receiving hemodialysis. Endothelial injury and TGF-β-mediated proliferation of vascular smooth muscle cells (VSMCs) induce NH. Endothelial microparticles (EMPs) are also increased by endothelial injury. We aimed to investigate the effects of EMPs and TGF-β expression on VSMC proliferation and their contributions to NH formation in an ex vivo model.

Methods

EMPs were collected from the culture media of human umbilical vein endothelial cells treated with indoxyl sulfate (IS, 250 µg/mL) after ultracentrifugation at 100,000 × g. Porcine internal jugular veins were isolated and treated with EMPs (2 × 10⁶ /mL) or left untreated for 12 days and subsequently compared with TGF-β (10 ng/mL)-treated venous tissue. Intima-media thickness and NH area were assessed using a digital program. Masson's trichrome staining and immunohistochemistry (IHC) analysis for α-smooth muscle actin, phosphorylated Akt, ERK1/2, p38 mitogen-activated protein kinase (MAPK), and Smad3 were performed on each vein sample.

Results

NH and VSMC proliferation developed to a significantly greater degree in EMP-treated veins compared to controls, with similar patterns seen in TGF-β-stimulated samples. IHC analysis demonstrated that EMPs markedly increased phosphorylation of Akt, ERK1/2, p38 MAPK, and Smad3 in areas of venous NH formation.

Conclusion

Our results showed that IS-induced EMPs provoked massive VSMC proliferation and NH formation via activation of the TGF-β signaling pathways. Further investigation is needed to elucidate the precise mechanism of EMP activity on vascular access stenosis in vivo.

M2 Monocyte Microparticles Are Increased in Intracerebral Hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is a severe neurologic condition with no proven treatment. Recent evidence suggests that monocytes, a heterogenous group of cells with M1 and M2 phenotypes, contribute to secondary damage following ICH. Microparticles are vesicles .1-1 µm in size that are released from cells. We hypothesized that M1 and M2 monocyte microparticles (mMP) would be differentially expressed in ICH cases and controls.

METHODS

In a single-center, prospective, observational study, consecutive ICH cases were enrolled within 12 hours of symptom onset. Age (±5 years)-, race-, and sex-matched controls were recruited. M1 and M2 mMP numbers were determined in plasma samples using flow cytometry and protein biomarkers using standardized assays. The Mann-Whitney U test compared M1 and M2 mMP counts between cases and controls. Standardized regression coefficients compared M1 and M2 mMP with C-reactive protein (CRP) and serum amyloid A (SAA).

RESULTS

Nineteen ICH case-control pairs were enrolled. The median number of M1 mMP was not significantly different between ICH cases (8.63 × 10⁷/milliliter (mL)) compared with controls (8.64 × 10⁷/mL), (P = .525). The median number of M2 mMP was significantly higher in ICH cases (1.61 × 10⁶/mL) compared with controls (4.46 × 10⁵/mL) (P = .027). There were no significant associations for M1 or M2 mMP with CRP or SAA.

CONCLUSION

Higher numbers of M2 mMP in ICH cases compared with controls is hypothesis generating. It may represent differences in the chronic inflammatory status in patients susceptible to ICH, such as cellular activation or apoptosis. Further research is needed, including serial plasma samples, to elucidate the pathophysiology of monocytes and mMP following ICH.

Extracellular Microvesicles as Game Changers in Better Understanding the Complexity of Cellular Interactions-From Bench to Clinical Applications

Recent research has led to wide acceptance and better understanding of a novel mechanism for cell-cell communication that employs a network of extracellular microvesicles (ExMVs). Derived from the plasma membrane or the endosomal membrane compartment, these small, spherical membrane fragments are secreted from the cell surface or in the process of exocytosis from endosomal membrane compartment and (1) with ligands expressed on their surface directly stimulate target cells in a paracrine manner, (2) transfer cell membrane receptors to target cells or (3) deliver encapsulated messenger RNA, microRNA, proteins and bioactive lipids to target cells. This represents an evolutionarily ancient mechanism by which cells signal their presence in the microenvironment, communicate with each other and affect the biology of neighboring cells. Evidence suggests the pivotal role of ExMVs in almost all biological processes within the body as well as their involvement in certain pathologies. Moreover, liquid biopsies based on deciphering the molecular signature of ExMVs promise to revolutionize laboratory diagnostics. At the same time, there are ongoing attempts to employ them as delivery vehicles for drugs as well as therapeutics in regenerative medicine, oncology and immunotherapy.

Cellular microparticles and pathophysiology of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. The finding that cellular microparticles (MPs) generated by injured cells profoundly impact on pathological courses of TBI has paved the way for new diagnostic and therapeutic strategies. MPs are subcellular fragments or organelles that serve as carriers of lipids, adhesive receptors, cytokines, nucleic acids, and tissue-degrading enzymes that are unique to the parental cells. Their sub-micron sizes allow MPs to travel to areas that parental cells are unable to reach to exercise diverse biological functions. In this review, we summarize recent developments in identifying a casual role of MPs in the pathologies of TBI and suggest that MPs serve as a new class of therapeutic targets for the prevention and treatment of TBI and associated systemic complications.

Association of Extracellular Membrane Vesicles with Cutaneous Wound Healing

Extracellular vesicles (EVs) are membrane-enclosed vesicles that are released into the extracellular environment by various cell types, which can be classified as apoptotic bodies, microvesicles and exosomes. EVs have been shown to carry DNA, small RNAs, proteins and membrane lipids which are derived from the parental cells. Recently, several studies have demonstrated that EVs can regulate many biological processes, such as cancer progression, the immune response, cell proliferation, cell migration and blood vessel tube formation. This regulation is achieved through the release and transport of EVs and the transfer of their parental cell-derived molecular cargo to recipient cells. This thereby influences various physiological and sometimes pathological functions within the target cells. While intensive investigation of EVs has focused on pathological processes, the involvement of EVs in normal wound healing is less clear; however, recent preliminarily investigations have produced some initial insights. This review will provide an overview of EVs and discuss the current literature regarding the role of EVs in wound healing, especially, their influence on coagulation, cell proliferation, migration, angiogenesis, collagen production and extracellular matrix remodelling.

Review: the Multiple Roles of Monocytic Microparticles

Monocytic microparticles (mMP) are microparticles derived from human monocytes either under in vivo or in vitro conditions. The size of mMP is between 0.1 and 1.0 μm. Apart from the size range, mMPs are also identified based on phosphatidylserine and CD14 expression on their surface, though this is not always the case. Monocytic MP are critical players in inflammation, endothelial cell function, and blood coagulation. They exhibit dual function by either helping the progression of such conditions or limiting it, depending on certain factors. Furthermore, the numbers of mMP are elevated in some autoimmune diseases, infectious diseases, and metabolic disorders. However, it is unknown whether mMP play an active role in these diseases or are simply biomarkers. The mechanism of mMP modulation is yet to be identified. In this review, we highlight the mechanism of mMP formation and the roles that they play in inflammation, blood coagulation, and different disease settings.

Microglial-derived microparticles mediate neuroinflammation after traumatic brain injury

BACKGROUND

Local and systemic inflammatory responses are initiated early after traumatic brain injury (TBI), and may play a key role in the secondary injury processes resulting in neuronal loss and neurological deficits. However, the mechanisms responsible for the rapid expansion of neuroinflammation and its long-term progression have yet to be elucidated. Here, we investigate the role of microparticles (MP), a member of the extracellular vesicle family, in the exchange of pro-inflammatory molecules between brain immune cells, as well as their transfer to the systemic circulation, as key pathways of inflammation propagation following brain trauma.

METHODS

Adult male C57BL/6 mice were subjected to controlled cortical impact TBI for 24 h, and enriched MP were isolated in the blood, while neuroinflammation was assessed in the TBI cortex. MP were characterized by flow cytometry, and MP content was assayed using gene and protein markers for pro-inflammatory mediators. Enriched MP co-cultured with BV2 or primary microglial cells were used for immune propagation assays. Enriched MP from BV2 microglia or CD11b-positive microglia from the TBI brain were stereotactically injected into the cortex of uninjured mice to evaluate MP-related seeding of neuroinflammation in vivo.

RESULTS

As the neuroinflammatory response is developing in the brain after TBI, microglial-derived MP are released into the circulation. Circulating enriched MP from the TBI animals can activate microglia in vitro. Lipopolysaccharide stimulation increases MP release from microglia in vitro and enhances their content of pro-inflammatory mediators, interleukin-1β and microRNA-155. Enriched MP from activated microglia in vitro or CD11b-isolated microglia/macrophage from the TBI brain ex vivo are sufficient to initiate neuroinflammation following their injection into the cortex of naïve (uninjured) animals.

CONCLUSIONS

These data provide further insights into the mechanisms underlying the development and dissemination of neuroinflammation after TBI. MP loaded with pro-inflammatory molecules initially released by microglia following trauma can activate additional microglia that may contribute to progressive neuroinflammatory response in the injured brain, as well as stimulate systemic immune responses. Due to their ability to independently initiate inflammatory responses, MP derived from activated microglia may provide a potential therapeutic target for other neurological disorders in which neuroinflammation may be a contributing factor.

Proceedings of the ISEV symposium on "HIV, NeuroAIDS, drug abuse & EVs"

Extracellular vesicles (EVs) are globular, membrane bound nanovesicles (30-100 nm range) that are shed both during normal cellular functioning and under pathological conditions by most cell types. In recent years, there has been significant interest in the study of these vesicles as conduits for the delivery of information between cells from both analogous and disparate tissues. Their ability to carry specialised cargo including signalling mediators, proteins, messenger RNA and miRNAs characterises these vesicles as primary facilitators of cell-to-cell communication and regulation. EVs have also been demonstrated to play important roles in the field of cancer biology and metastasis. However, significant knowledge gaps exist in the role these vesicles play in the context of HIV infection and drug abuse. To foster discussion in this area a satellite symposium on "HIV, NeuroAIDS, Drug Abuse & EVs", was held in conjunction with the annual meeting of the International Society for Extracellular Vesicles (ISEV) in Bethesda, in April 2015. Experts in HIV and drug abuse fields were invited to share their findings on the role of EVs in HIV-1 infection and drug addiction. Additional discussion included current areas of research in EV biology in HIV infection and drug abuse.

The role of exosomes in hepatitis, liver cirrhosis and hepatocellular carcinoma

Exosomes are small vesicles that were initially thought to be a mechanism for discarding unneeded membrane proteins from reticulocytes. Their mediation of intercellular communication appears to be associated with several biological functions. Current studies have shown that most mammalian cells undergo the process of exosome formation and utilize exosome‐mediated cell communication. Exosomes contain various microRNAs, mRNAs and proteins. They have been reported to mediate multiple functions, such as antigen presentation, immune escape and tumour progression. This concise review highlights the findings regarding the roles of exosomes in liver diseases, particularly hepatitis B, hepatitis C, liver cirrhosis and hepatocellular carcinoma. However, further elucidation of the contributions of exosomes to intercellular information transmission is needed. The potential medical applications of exosomes in liver diseases seem practical and will depend on the ingenuity of future investigators and their insights into exosome‐mediated biological processes.

Extracellular vesicle communication pathways as regulatory targets of oncogenic transformation

Pathogenesis of human cancers bridges intracellular oncogenic driver events and their impact on intercellular communication. Among multiple mediators of this 'pathological connectivity' the role of extracellular vesicles (EVs) and their subsets (exosomes, ectosomes, oncosomes) is of particular interest for several reasons. The release of EVs from cancer cells represents a unique mechanism of regulated expulsion of bioactive molecules, a process that also mediates cell-to-cell transfer of lipids, proteins, and nucleic acids. Biological effects of these processes have been implicated in several aspects of cancer-related pathology, including tumour growth, invasion, angiogenesis, metastasis, immunity and thrombosis. Notably, the emerging evidence suggests that oncogenic mutations may impact several aspects of EV-mediated cell-cell communication including: (i) EV release rate and protein content; (ii) molecular composition of cancer EVs; (iii) the inclusion of oncogenic and mutant macromolecules in the EV cargo; (iv) EV-mediated release of genomic DNA; (v) deregulation of mechanisms responsible for EV biogenesis (vesiculome) and (vi) mechanisms of EV uptake by cancer cells. Intriguingly, EV-mediated intercellular transfer of mutant and oncogenic molecules between subpopulations of cancer cells, their indolent counterparts and stroma may exert profound biological effects that often resemble (but are not tantamount to) oncogenic transformation, including changes in cell growth, clonogenicity and angiogenic phenotype, or cause cell stress and death. However, several biological barriers likely curtail a permanent horizontal transformation of normal cells through EV-mediated mechanisms. The ongoing analysis and targeting of EV-mediated intercellular communication pathways can be viewed as a new therapeutic paradigm in cancer, while the analysis of oncogenic cargo contained in EVs released from cancer cells into biofluids is being developed for clinical use as a biomarker and companion diagnostics. Indeed, studies are underway to further explore the multiple links between molecular causality in cancer and various aspects of cellular vesiculation.

The Emerging Roles of Extracellular Vesicles As Communication Vehicles within the Tumor Microenvironment and Beyond

Tumors evolve in complex and dynamic microenvironments that they rely on for sustained growth, invasion, and metastasis. Within this space, tumor cells and non-malignant cells are in frequent communication. One specific mode of communication that has gained recent attention is the release of extracellular vesicles (EVs). EVs are lipid bilayer-bound vehicles that are released from the cell membrane and carry nucleic acids, proteins, and lipids to neighboring or distant cells. EVs have been demonstrated to influence a multitude of processes that aid in tumor progression including cellular proliferation, angiogenesis, migration, invasion, metastasis, immunoediting, and drug resistance. The ubiquitous involvement of EVs on cancer progression makes them very suitable targets for novel therapeutics. Furthermore, they are being studied as specific markers for cancer diagnostics, prognosis, and even as chemotherapy drug-delivery systems. This review focuses on the most recent advances in EV knowledge, some current and potential problems with their use, and some proposed solutions to consider for the future.

Characterization of extracellular vesicles by IR spectroscopy: Fast and simple classification based on amide and CH stretching vibrations

Extracellular vesicles isolated by differential centrifugation from Jurkat T-cell line were investigated by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). Amide and CH stretching band intensity ratios calculated from IR bands, characteristic of protein and lipid components, proved to be distinctive for the different extracellular vesicle subpopulations. This proposed 'spectroscopic protein-to-lipid ratio', combined with the outlined spectrum-analysis protocol is valid also for low sample concentrations (0.15-0.05mg/ml total protein content) and can carry information about the presence of other non-vesicular formations such as aggregated proteins, lipoproteins and immune complexes. Detailed analysis of IR data reveals compositional changes of extracellular vesicles subpopulations: second derivative spectra suggest changes in protein composition from parent cell towards exosomes favoring proteins with β-turns and unordered motifs at the expense of intermolecular β-sheet structures. The IR-based protein-to-lipid assessment protocol was tested also for red blood cell derived microvesicles for which similar values were obtained. The potential applicability of this technique for fast and efficient characterization of vesicular components is high as the investigated samples require no further preparations and all the different molecular species can be determined in the same sample. The results indicate that ATR-FTIR measurements provide a simple and reproducible method for the screening of extracellular vesicle preparations. It is hoped that this sophisticated technique will have further impact in extracellular vesicle research.

Mycobacterium tuberculosis Infection Manipulates the Glycosylation Machinery and the N-Glycoproteome of Human Macrophages and Their Microparticles

Tuberculosis (TB) remains a prevalent and lethal infectious disease. The glycobiology associated with Mycobacterium tuberculosis infection of frontline alveolar macrophages is still unresolved. Herein, we investigated the regulation of protein N-glycosylation in human macrophages and their secreted microparticles (MPs) used for intercellular communication upon M. tb infection. LC-MS/MS-based proteomics and glycomics were performed to monitor the regulation of glycosylation enzymes and receptors and the N-glycome in in vitro-differentiated macrophages and in isolated MPs upon M. tb infection. Infection promoted a dramatic regulation of the macrophage proteome. Most notably, significant infection-dependent down-regulation (4-26 fold) of 11 lysosomal exoglycosidases, e.g., β-galactosidase, β-hexosaminidases and α-/β-mannosidases, was observed. Relative weak infection-driven transcriptional regulation of these exoglycosidases and a stronger augmentation of the extracellular hexosaminidase activity demonstrated that the lysosome-centric changes may originate predominantly from infection-induced secretion of the lysosomal content. The macrophages showed heterogeneous N-glycan profiles and displayed significant up-regulation of complex-type glycosylation and concomitant down-regulation of paucimannosylation upon infection. Complementary intact N-glycopeptide analysis supported a subcellular-specific manipulation of the glycosylation machinery and altered glycosylation patterns of lysosomal N-glycoproteins within infected macrophages. Interestingly, the corresponding macrophage-derived MPs displayed unique N-glycome and proteome signatures supporting a preferential packaging from plasma membranes. The MPs were devoid of infection-dependent N-glycosylation signatures, but interestingly displayed increased levels of the glyco-initiating oligosaccharyltransferase complex and associated α-glucosidases that correlated with increased formation, N-glycan precursor levels and N-glycan density of infected MPs. In conclusion, this system-wide study provides new insight into the host- and pathogen-driven N-glycoproteome manipulation of macrophages in TB.

Human NK Cell Subsets Redistribution in Pathological Conditions: A Role for CCR7 Receptor

Innate and adaptive immunity has evolved complex molecular mechanisms regulating immune cell migration to facilitate the dynamic cellular interactions required for its function involving the chemokines and their receptors. One important chemokine receptor in the immune system is represented by CCR7. Together with its ligands CCL19 and CCL21, this chemokine receptor controls different arrays of migratory events, both in innate and adaptive immunity, including homing of CD56^bright NK cells, T cells, and DCs to lymphoid compartments, where T cell priming occurs. Only recently, a key role for CCR7 in promoting CD56^dim NK cell migration toward lymphoid tissues has been described. Remarkably, this event can influence the shaping and polarization of adaptive T cell responses. In this review, we describe recent progress in understanding the mechanisms and the site where CD56^dim KIR⁺ NK cells can acquire the capability to migrate toward lymph nodes. The emerging significance of this event in clinical transplantation is also discussed.

The biology of extracellular vesicles with focus on platelet microparticles and their role in cancer development and progression

Extracellular vesicles (EVs) are a heterogeneous group of structures which can be classified into smaller in size and relatively homogenous exosomes (EXSMs)—spherical fragments of lipid bilayers from inner cell compartments—and bigger in size ectosomes (ECSMs)—a direct consequence of cell-membrane blebbing. EVs can be found in body fluids of healthy individuals. Their number increases in cancer and other pathological conditions. EVs can originate from various cell types, including leukocytes, erythrocytes, thrombocytes, and neoplastic cells. Platelet microparticles (PMPs) are the most abundant population of EVs in blood. It is well documented that PMPs, being a crucial element of EVs signaling, are involved in tumor growth, metastasis, and angiogenesis and may participate in the development of multidrug resistance by tumor cells. The aim of this review is to present the role of PMPs in carcinogenesis. The biology and functions of PMPs with a particular emphasis on the most recent scientific reports on EV properties are also characterized.

Modification of tumor cell exosome content by transfection with wt-p53 and microRNA-125b expressing plasmid DNA and its effect on macrophage polarization

Exosomes are responsible for intercellular communication between tumor cells and others in the tumor microenvironment. These microvesicles promote oncogensis and can support towards metastasis by promoting a pro-tumorogenic environment. Modifying the exosomal content and exosome delivery are emerging novel cancer therapies. However, the clinical translation is limited due to feasibility of isolating and delivery of treated exosomes as well as an associated immune response in patients. In this study, we provide proof-of-concept for a novel treatment approach for manipulating exosomal content by genetic transfection of tumor cells using dual-targeted hyaluronic acid-based nanoparticles. Following transfection with plasmid DNA encoding for wild-type p53 (wt-p53) and microRNA-125b (miR-125b), we evaluate the transgene expression in the SK-LU-1 cells and in the secreted exosomes. Furthermore, along with modulation of wt-p53 and miR-125b expression, we also show that the exosomes (i.e., wt-p53/exo, miR-125b/exo and combination/exo) have a reprogramed global miRNA profile. The miRNAs in the exosomes were mainly related to the activation of genes associated with apoptosis as well as p53 signaling. More importantly, these altered miRNA levels in the exosomes could mediate macrophage repolarization towards a more pro-inflammatory/antitumor M1 phenotype. However, further studies, especially in vivo studies, are warranted to assess the direct influence of such macrophage reprogramming on cancer cells and oncogenesis post-treatment. The current study provides a novel platform enabling the development of therapeutic strategies affecting not only the cancer cells but also the tumor microenvironment by utilizing the 'bystander effect' through genetic transfer with secreted exosomes. Such modification could also support antitumor environment leading to decreased oncogenesis.

Leishmania exosomes and other virulence factors: Impact on innate immune response and macrophage functions

Leishmania parasites are the causative agents of the leishmaniases, a collection of vector-borne diseases that range from simple cutaneous to fatal visceral forms. Employing potent immune modulation mechanisms, Leishmania is able to render the host macrophage inactive and persist inside its phagolysosome. In the last few years, the role of exosomes in Leishmania-host interactions has been increasingly investigated. For instance, it was reported that Leishmania exosome release is augmented following temperature shift, a condition mimicking parasite's entry into its mammalian host. Leishmania exosomes were found to strongly affect macrophage cell signaling and functions, similarly to whole parasites. Importantly, these vesicles were shown to be pro-inflammatory, capable to recruit neutrophils at their inoculation site exacerbating the pathology. In this review, we provide the most recent insights on the role of exosomes and other virulence factors, especially the surface protease GP63, in Leishmania-host interactions, deepening our knowledge on leishmaniasis and paving the way for the development of new therapeutics.

Extracellular vesicles and viruses: Are they close relatives?

Extracellular vesicles (EVs) released by various cells are small phospholipid membrane-enclosed entities that can carry miRNA. They are now central to research in many fields of biology because they seem to constitute a new system of cell-cell communication. Physical and chemical characteristics of many EVs, as well as their biogenesis pathways, resemble those of retroviruses. Moreover, EVs generated by virus-infected cells can incorporate viral proteins and fragments of viral RNA, being thus indistinguishable from defective (noninfectious) retroviruses. EVs, depending on the proteins and genetic material incorporated in them, play a significant role in viral infection, both facilitating and suppressing it. Deciphering the mechanisms of EV-cell interactions may facilitate the design of EVs that inhibit viral infection and can be used as vehicles for targeted drug delivery.

Activated Stat5 trafficking Via Endothelial Cell-derived Extracellular Vesicles Controls IL-3 Pro-angiogenic Paracrine Action

Soluble factors and cell-derived extracellular vesicles (EVs) control vascular cell fate during inflammation. The present study investigates the impact of Interleukin 3 (IL-3) on EV release by endothelial cells (ECs), the mechanisms involved in EV release and paracrine actions. We found that IL-3 increases EV release, which is prevented by IL-3Ralpha blockade. EVs released upon IL-3 stimulation were able to induce pro-angiogenic signals as shown by chromatin immunoprecipitation (ChIP) assay performed on the promoter region of cyclin D1 and tridimensional tube-like structure formation. We herein demonstrate that these effects rely on the transfer of miR-126-3p, pre-miR-126 and, more importantly, of activated signal transduction and activator of transcription 5 (pSTAT5) from IL-3-EV cargo into recipient ECs. We show, using the dominant negative form (ΔN)STAT5 and an activated STAT5 (1*6STAT5) constructs, that STAT5 drives IL-3-mediated EV release, miR-126-3p and pSTAT5 content. Finally, using EVs recovered from ΔNSTAT5 expressing ECs, we provide evidence that miR-126-3p and pSTAT5 trafficking is relevant for IL-3-mediated paracrine pro-angiogenic signals. These results indicate that IL-3 regulates EC-EV release, cargo and IL-3 angiogenic paracrine action via STAT5. Moreover, these results provide evidence that EC-derived IL-3-EVs can serve as pro-angiogenic clinical delivery wound healing devices.

The Potential of HLA-G-Bearing Extracellular Vesicles as a Future Element in HLA-G Immune Biology

The HLA-G molecule is a member of the non-classical HLA class I family. Its surface expression is physiologically restricted to the maternal–fetal interface and to immune privileged adult tissues. Despite the restricted tissue expression, HLA-G is detectable in body fluids as secreted soluble molecules. A unique feature of HLA-G is the structural diversity as surface expressed and as secreted molecules. Secreted HLA-G can be found in various body fluids either as free soluble HLA-G or as part of extracellular vesicles (EVs), which are composed of various antigens/ligands/receptors, bioactive lipids, cytokines, growth factors, and genetic information, such as mRNA and microRNA. Functionally, HLA-G and its secreted forms are considered to play a crucial role in the network of immune-regulatory tolerance mechanisms, preferentially interacting with the cognate inhibitory receptors LILRB1 and LILRB2. The HLA-G mediated tolerance is described in processes of pregnancy, inflammation, and cancer. However, almost all functional and clinical implications of HLA-G in vivo and in vitro have been established based on simple single ligand/receptor interactions at the cell surface, whereas HLA-G-bearing EVs were in minor research focus. Indeed, cytotrophoblast cells, mesenchymal stem cells, and cancer cells were recently described to secrete HLA-G-bearing EVs, displaying immunosuppressive effects and modulating the tumor microenvironment. However, numerous functional and clinical open questions persist. Here, we (i) introduce basic aspects of EVs biology, (ii) summarize the functional knowledge, clinical implications and open questions of HLA-G-bearing EVs, and (iii) discuss HLA-G-bearing EVs as a future element in HLA-G biology.

Phenotyping of Leukocytes and Leukocyte-Derived Extracellular Vesicles

Extracellular vesicles (EVs) have a demonstrated involvement in modulating the immune system. It has been proposed that EVs could be used as biomarkers for detection of inflammatory and immunological disorders. Consequently, it is of great interest to investigate EVs in more detail with focus on immunological markers. In this study, five major leukocyte subpopulations and the corresponding leukocyte-derived EVs were phenotyped with focus on selected immunological lineage-specific markers and selected vesicle-related markers. The leukocyte-derived EVs displayed phenotypic differences in the 34 markers investigated. The majority of the lineage-specific markers used for identification of the parent cell types could not be detected on EVs released from monocultures of the associated cell types. In contrast, the vesicular presentation of CD9, CD63, and CD81 correlated to the cell surface expression of these markers, however, with few exceptions. Furthermore, the cellular expression of CD9, CD63, and CD81 varied between leukocytes present in whole blood and cultured leukocytes. In summary, these data demonstrate that the cellular and vesicular presentation of selected lineage-specific and vesicle-related markers may differ, supporting the accumulating observations that sorting of molecular cargo into EVs is tightly controlled.

Extracellular vesicles during Herpes Simplex Virus type 1 infection: an inquire

Extracellular vesicles are defined as a heterogeneous group of vesicles that are released by prokaryotic to higher eukaryotic cells and by plant cells in an evolutionary conserved manner. The significance of these vesicles lies in their capacity to transfer selected cargo composed of proteins, lipids and nucleic acids to both recipient and parent cells and to influence various physiological and pathological functions. Microorganisms such as parasites, fungi and protozoa and even single cell organisms such as bacteria generate extracellular vesicles. In addition, several viruses have evolved strategies to hijack the extracellular vesicles for egress or to alter the surrounding environment. The thesis of this article is that: a) during HSV-1 infection vesicles are delivered from infected to uninfected cells that influence the infection; b) the cargo of these vesicles consists of viral and host transcripts (mRNAs, miRNAs and non-coding RNAs) and proteins including innate immune components, such as STING; and c) the viral vesicles carry the tetraspanins CD9, CD63 and CD81, which are considered as markers of exosomes. Therefore, we assume that the STING-carrying vesicles, produced during HSV-1 infection, are reminiscent to exosomes. The presumed functions of the exosomes released from HSV-1 infected cells include priming the recipient cells and accelerating antiviral responses to control the dissemination of the virus. This may be one strategy used by the virus to prevent the elimination by the host and establish persistent infection. In conclusion, the modification of the cargo of exosomes appears to be part of the strategy that HSV-1 has evolved to establish lifelong persistent infections into the human body to ensure successful dissemination between individuals.

Circulating microRNAs as a Novel Class of Potential Diagnostic Biomarkers in Neuropsychiatric Disorders

Neuropsychiatric diseases, such as schizophrenia, bipolar disorder (BD), major depressive disorder (MDD) and autism spectrum disorder (ASD), are a huge burden on society, impairing the health of those affected, as well as their ability to learn and work. Biomarkers that reflect the dysregulations linked to neuropsychiatric diseases may potentially assist the diagnosis of these disorders. Most of these biomarkers are found in the brain tissue, which is not easily accessible. This is the challenge for the search of novel biomarkers that are present in various body fluids, including serum or plasma. As a group of important endogenous small noncoding RNAs that regulate gene expression at post-transcriptional level, microRNAs (miRNAs) play a crucial role in many physiological and pathological processes. Previously, researchers discovered that miRNAs contribute to the neurodevelopment and maturation, including neurite outgrowth, dendritogenesis and dendritic spine formation. These developments underline the significance of miRNAs as potential biomarkers for diagnosing and prognosing central nervous system diseases. Accumulated evidence indicates that there are considerable differences between the cell-free miRNA expression profiles of healthy subjects and those of patients. Therefore, circulating miRNAs are likely to become a new class of noninvasive, sensitive biomarkers. Despite the fact that little is known about the origin and functions of circulating miRNAs, their essential roles in the clinical diagnosis and prognosis of neuropsychiatric diseases make them attractive biomarkers. In this review we cover the increasing amounts of dataset that have accumulated in the last years on the use of circulating miRNAs and their values as potential biomarkers in most areas of neuropsychiatric diseases.