Circulating Microparticles from Patients with Septic Shock Exert Protective Role in Vascular Function

Lymphocyte-derived microparticles induce bronchial epithelial cells' pro-inflammatory cytokine production and apoptosis

OBJECTIVE

The aim of this study was to determine if human CEM (human lymphoblastoma) T cell-derived microparticles (LMPs) could directly induce human bronchial epithelial cells (BECs) apoptosis and cytokine production. We also tested if LMPs phagocytosis by BECs played a role in mediating these effects.

METHODS

We generated LMPs from CEM (human lymphoblastoma) T cells to investigate their effects on a human BEC cell line (16HBE) in vitro.

RESULTS

BECs (16HBE cells) incubation with LMPs resulted in significant production of inflammation-associated cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and IL-8, in a dose- and time-dependent manner. LMPs also induced increased activities of caspase-3, caspase-8, and caspase-9 in BECS, which resulted in increased BECs apoptosis as assessed by flow cytometry (Annexin V and propidium iodide staining) and transmission electronic microscopy (TEM). Interestingly, LMPs effects on BECS were inhibited by the phagocytosis inhibitors cytochalasin D and chloroquine.

CONCLUSIONS

These results suggest that phagocytosis plays an important role in mediating the effects of LMPs on BECs. Thus, increased LMP concentrations may contribute to increased respiratory inflammatory responses and innate immune response maintenance in airway epithelium after LMPs engulfment by endothelial cells.

Microparticle release in remote ischemic conditioning mechanism

Remote ischemic conditioning (RCond) induced by short periods of ischemia and reperfusion of an organ or tissue before myocardial reperfusion is an attractive strategy of cardioprotection in the context of acute myocardial infarction. Nonetheless, its mechanism remains unknown. A humoral factor appears to be involved, although its identity is currently unknown. We hypothesized that the circulating microparticles (MPs) are the link between the remote tissue and the heart. MPs from rats and healthy humans undergoing RCond were characterized. In rats, RCond was induced by 10 min of limb ischemia. In humans, RCond was induced by three cycles of 5-min inflation and 5-min deflation of a blood-pressure cuff. In the second part of the study, rats underwent 40 min myocardial ischemia followed by 2 h reperfusion. Infarct size was measured and compared among three groups of rats: 1) myocardial infarction alone (MI) ( n = 6); 2) MI + RCond started 20 min after coronary ligation ( n = 6); and 3) MI + injection of RCond-derived rat MPs (MI + MPs) ( n = 5). MPs from endothelial cells (CD54+ and CD146+ for rats and humans, respectively) and procoagulant MPs (Annexin V+) markedly increased after RCond, both in rats and humans. RCond reduced infarct size (24.4 ± 5.9% in MI + RCond vs. 54.6 ± 4.7% in MI alone; P < 0.01). Infarct size did not decrease in MI + MPs compared with MI alone (50.2 ± 6.4% vs. 54.6 ± 4.7%, not significantly different). RCond increased endothelium-derived and procoagulant MPs in both rats and humans. However, MP release did not appear to be a biological vector of RCond in our model.

Microparticles and acute renal dysfunction in septic patients

PURPOSE

The role of microparticles (MPs) in the pathogenesis of sepsis is not completely elucidated. We aimed to assess changes in the number of MPs during severe sepsis to follow the effect of sepsis-related organ failures, particularly renal impairment, an independent mortality factor of sepsis.

MATERIALS AND METHODS

Thirty-seven severe septic patients and 20 controls were enrolled. Patient status as well as organ failure-related laboratory markers was followed up to 5 consecutive days. Microparticles (annexin V+ events in MP size gate) of platelet (CD41, CD42a, and PAC1), monocyte (CD14), and myeloid cell line (CD13) origin were measured using flow cytometry.

RESULTS

Significantly increased total MP and CD41-, CD42a-, and PAC1-positive particle numbers were found in septic patients compared with controls. Actual number of organ dysfunctions on sample collection showed no correlation with MP numbers. Septic patients with renal dysfunction showed an increase in total MP, CD41(+), and CD13(+) particle numbers on admission. Amounts of platelet-derived CD42a(+) particles from patients with sepsis-related renal injury correlated negatively with actual blood urea nitrogen and creatinine concentrations.

CONCLUSION

The increased numbers of platelet-derived MPs in severe septic patients emphasize the possible contribution of the hemostasis system in the development of sepsis-related renal impairments.

Microparticles and acute lung injury

The pathophysiology of acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), is characterized by increased vascular and epithelial permeability, hypercoagulation and hypofibrinolysis, inflammation, and immune modulation. These detrimental changes are orchestrated by cross talk between a complex network of cells, mediators, and signaling pathways. A rapidly growing number of studies have reported the appearance of distinct populations of microparticles (MPs) in both the vascular and alveolar compartments in animal models of ALI/ARDS or respective patient populations, where they may serve as diagnostic and prognostic biomarkers. MPs are small cytosolic vesicles with an intact lipid bilayer that can be released by a variety of vascular, parenchymal, or blood cells and that contain membrane and cytosolic proteins, organelles, lipids, and RNA supplied from and characteristic for their respective parental cells. Owing to this endowment, MPs can effectively interact with other cell types via fusion, receptor-mediated interaction, uptake, or mediator release, thereby acting as intrinsic stimulators, modulators, or even attenuators in a variety of disease processes. This review summarizes current knowledge on the formation and potential functional role of different MPs in inflammatory diseases with a specific focus on ALI/ARDS. ALI has been associated with the formation of MPs from such diverse cellular origins as platelets, neutrophils, monocytes, lymphocytes, red blood cells, and endothelial and epithelial cells. Because of their considerable heterogeneity in terms of origin and functional properties, MPs may contribute via both harmful and beneficial effects to the characteristic pathological features of ALI/ARDS. A better understanding of the formation, function, and relevance of MPs may give rise to new promising therapeutic strategies to modulate coagulation, inflammation, endothelial function, and permeability either through removal or inhibition of "detrimental" MPs or through administration or stimulation of "favorable" MPs.

Leukocyte-derived microparticles in vascular homeostasis

Leukocyte-derived microparticles (LMPs) may originate from neutrophils, monocytes/macrophages, and lymphocytes. They express markers from their parental cells and harbor membrane and cytoplasmic proteins as well as bioactive lipids implicated in a variety of mechanisms, maintaining or disrupting vascular homeostasis. When they carry tissue factor or coagulation inhibitors, they participate in hemostasis and pathological thrombosis. Both proinflammatory and anti-inflammatory processes can be affected by LMPs, thus ensuring an appropriate inflammatory response. LMPs also play a dual role in the endothelium by either improving the endothelial function or inducing an endothelial dysfunction. LMPs are implicated in all stages of atherosclerosis. They circulate at a high level in the bloodstream of patients with high atherothrombotic risk, such as smokers, diabetics, and subjects with obstructive sleep apnea, where their prolonged contact with the vessel wall may contribute to its overall deterioration. Numbering microparticles, including LMPs, might be useful in predicting cardiovascular events. LMPs modify the endothelial function and promote the recruitment of inflammatory cells in the vascular wall, necessary processes for the progression of the atherosclerotic lesion. In addition, LMPs favor the neovascularization within the vulnerable plaque and, in the ruptured plaque, they take part in coagulation and platelet activation. Finally, LMPs participate in angiogenesis. They might represent a novel therapeutic tool to reset the angiogenic switch in pathologies with altered angiogenesis. Additional studies are needed to further investigate the role of LMPs in cardiovascular diseases. However, large-scale studies are currently difficult to set up because microparticle measurement still requires elaborate techniques which lack standardization.

Calpastatin controls polymicrobial sepsis by limiting procoagulant microparticle release

RATIONALE

Sepsis, a leading cause of death worldwide, involves widespread activation of inflammation, massive activation of coagulation, and lymphocyte apoptosis. Calpains, calcium-activated cysteine proteases, have been shown to increase inflammatory reactions and lymphocyte apoptosis. Moreover, calpain plays an essential role in microparticle release.

OBJECTIVES

We investigated the contribution of calpain in eliciting tissue damage during sepsis.

METHODS

To test our hypothesis, we induced polymicrobial sepsis by cecal ligation and puncture in wild-type (WT) mice and transgenic mice expressing high levels of calpastatin, a calpain-specific inhibitor.

MEASUREMENTS AND MAIN RESULTS

In WT mice, calpain activity increased transiently peaking at 6 hours after cecal ligation and puncture surgery. Calpastatin overexpression improved survival, organ dysfunction (including lung, kidney, and liver damage), and lymphocyte apoptosis. It decreased the sepsis-induced systemic proinflammatory response and disseminated intravascular coagulation, by reducing the number of procoagulant circulating microparticles and therefore delaying thrombin generation. The deleterious effect of microparticles in this model was confirmed by transferring microparticles from septic WT to septic transgenic mice, worsening their survival and coagulopathy.

CONCLUSIONS

These results demonstrate an important role of the calpain/calpastatin system in coagulation/inflammation pathways during sepsis, because calpain inhibition is associated with less severe disseminated intravascular coagulation and better overall outcomes in sepsis.

Microparticles as immune regulators in infectious disease - an opinion

Despite their clear relationship to immunology, few existing studies have examined the potential role of microparticles (MP) in infectious disease. MP have a different size range from exosomes and apoptotic bodies, with which they are often grouped and arise by different mechanisms in association with inflammatory cytokine action or stress on the source cell. Infection with pathogens usually leads to the expression of a range of inflammatory cytokines and chemokines, as well as significant stress in both infected and uninfected cells. It is thus reasonable to infer that infection-associated inflammation also leads to MP production. MP are produced by most of the major cell types in the immune system, and appear to be involved at both innate and adaptive levels, potentially serving different functions in each. Thus, they do not appear to have a universal function; instead their functions are source- or stimulus-dependent, although likely to be primarily either pro- or anti-inflammatory. We argue that in infectious diseases, MP may be able to deliver antigen, derived from the biological cargo acquired from their cells of origin, to antigen-presenting cells. Another potential benefit of MP would be to transfer and/or disseminate phenotype and function to target cells. However, MP may also potentially be manipulated, particularly by intracellular pathogens, for survival advantage.

Microparticles from patients with metabolic syndrome induce vascular hypo-reactivity via Fas/Fas-ligand pathway in mice

Microparticles are membrane vesicles with pro-inflammatory properties. Circulating levels of microparticles have previously been found to be elevated in patients with metabolic syndrome (MetS). The present study aimed to evaluate the effects of in vivo treatment with microparticles, from patients with MetS and from healthy subjects (HS), on ex vivo vascular function in mice. Microparticles isolated from MetS patients or HS, or a vehicle were intravenously injected into mice, following which vascular reactivity in response to vasoconstrictor agonists was assessed by myography with respect to cyclo-oxygenase pathway, oxidative and nitrosative stress. Injection of microparticles from MetS patients into mice induced vascular hypo-reactivity in response to serotonin. Hypo-reactivity was associated with up-regulation of inducible NO-synthase and increased production of NO, and was reversed by the NO-synthase inhibitor (N^G-nitro-L-arginine). The selective COX-2 inhibitor (NS398) reduced the contractile effect of serotonin in aortas from mice treated with vehicle or HS microparticles; however, this was not observed within mice treated with MetS microparticles, probably due to the ability of MetS microparticles to enhance prostacyclin. MetS microparticle-mediated vascular dysfunction was associated with increased reactive oxygen species (ROS) and enhanced expression of the NADPH oxidase subunits. Neutralization of the pro-inflammatory pathway Fas/FasL completely prevented vascular hypo-reactivity and the ability of MetS microparticles to enhance both inducible NO-synthase and monocyte chemoattractant protein-1 (MCP-1). Our data provide evidence that microparticles from MetS patients induce ex vivo vascular dysfunction by increasing both ROS and NO release and by altering cyclo-oxygenase metabolites and MCP-1 through the Fas/FasL pathway.

Microparticles as biological vectors of activated protein C treatment in sepsis

Activated protein C (APC), a physiological coagulation inhibitor, has been shown to reduce mortality in patients with severe sepsis. APC exerts pleiotropic cytoprotection by a mechanism that requires its interaction with endothelial cell protein C receptor and protease-activated receptor-1 on target cells. In the previous issue, Pérez-Casal and colleagues elegantly demonstrate that APC, using its recombinant form (rhAPC), can communicate to target cells through release of microparticles (MPs), small membrane vesicles released from activated cells, to induce anti-apoptotic and anti-inflammatory properties that might participate in the improvement of patient outcome. Of interest is the fact that APC itself promotes the release of MPs from target cells including endothelial cells and monocytes. These MPs bear the endothelial cell protein C receptor/APC molecules and can transfer the message to target cells including those of origin to induce cytoprotection. The long-range APC signal can thus be mediated by MPs in vivo upon pharmacological treatment using rhAPC in severe septic patients. A novel pharmacological approach targeting MP production and properties could therefore be used to treat severe sepsis in addition to other well-known actions of APC via direct interaction with the cells of interest.

The clinical and functional relevance of microparticles induced by activated protein C treatment in sepsis

INTRODUCTION

Activated protein C (APC) induces release of microparticles (MP) from primary physiological cells, which are found in patients undergoing treatment with recombinant human APC (rhAPC) for severe sepsis. We hypothesised that APC on these circulating MPs activate endothelial protease-activated receptor 1 (PAR1) to induce anti-apoptotic and anti-inflammatory properties that can improve patient outcome.

METHODS

This was an experimental study on clinical samples in an intensive care setting, and included patients with severe sepsis who fulfilled criteria for treatment with rhAPC. The number of CD13+ MPs from the patients were analysed to determine their origin. They were also quantified for endothelial protein C receptor (EPCR) and APC expression. Clinical relevance of these MPs were ascertained by comparing survival between the group receiving rhAPC (n = 25) and a control group of untreated patients (n = 25). MPs were also incubated with endothelial cells to analyse apoptotic gene expression, cytoprotection and anti-inflammatory effects.

RESULTS

rhAPC treatment induced a significant increase in circulating MP-associated EPCR by flow cytometry (P < 0.05) and by quantitative ELISA (P < 0.005). APC expression also showed significant increases (P < 0.05). Numerically, CD13+ MPs were higher in rhAPC-treated survivors versus non-survivors. However, the number of non-survivors was low and this was not significantly different. APC on MPs was demonstrated to induce anti-apoptotic and endothelial barrier effects through the activation of endothelial PAR1.

CONCLUSIONS

rhAPC treatment in patients with sepsis significantly increases circulating EPCR + MPs. These MPs were noted to express APC, which has specific anti-apoptotic and anti-inflammatory effects, with a non-significant correlative trend towards survival. This suggests that MPs could disseminate APC function and activate endothelial PAR1 at distal vascular sites.

Microparticles in Angiogenesis

Considered during the past decades as cell dust, microparticles are now deemed true biomarkers and vectors of biological information between cells. Depending on their origin, the composition of microparticles varies and the subsequent message transported by them, such as proteins, mRNA, or miRNA, can differ. Recent studies have described microparticles as “cargos” of deleterious information in blood vessel wall under pathological situations such as hypertension, myocardial infarction, and metabolic syndrome. In addition, it has been reported that depending on their origin, microparticles also possess a therapeutic potential regarding angiogenesis. Microparticles can act directly through the interaction ligand/receptor or indirectly on angiogenesis by modulating soluble factor production involved in endothelial cell differentiation, proliferation, migration, and adhesion; by reprogramming endothelial mature cells; and by inducing changes in levels, phenotype, and function of endothelial progenitor cells. This results in an increase in formation of in vitro capillary-like tubes and the generation of new vessels in vivo under ischemic conditions, for instance. Taking into consideration these properties of microparticles, recent evidence provides new basis to expand the possibility that microparticles might be used as therapeutic tools in pathologies associated with an alteration of angiogenesis.

Effects of progesterone and estradiol sex hormones on the release of microparticles by RAW 264.7 macrophages stimulated by Poly(I:C)

Microparticles (MPs) are small membrane-bound vesicles that display proinflammatory and prothrombotic properties. These particles can be released by macrophages stimulated by ligands of the Toll-like receptors (TLRs) in a process that depends on nitric oxide (NO) production. Since sex hormones can modulate macrophage responses, we investigated the effects of progesterone and estradiol on macrophage particle release in vitro, comparing the responses with those induced by the glucocorticoid dexamethasone. As a model system for particle release, RAW 264.7 cells were stimulated in vitro with poly(I:C), a ligand of TLR3. Microparticles were measured by flow cytometry, while NO was measured by the Griess reaction. As the results of these studies showed, progesterone but not estradiol can block particle release by RAW264.7 cells treated with poly(I:C); dexamethasone was also active. Furthermore, while progesterone and dexamethasone inhibited NO production under the same culture conditions, neither agent blocked the production of particles stimulated by the NO donors dipropylenetriamine NONOate {(z)-1-[N-(3-aminopropyl)-N-(3-ammoniopropyl)amino] diazen-1-ium-1,2-diolate} and (z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-1-ium-1,2-diolate. Studies using RU486 to assess the role of hormone receptors indicated that while this agent blocked the inhibition of particle and NO production by dexamethasone, it did not affect the inhibition by progesterone. Together, these results indicate that progesterone but not estradiol can inhibit particle release by stimulated macrophages and suggest a mechanism that may contribute to the immunomodulatory effects of this sex hormone.

Endothelial microparticle formation by angiotensin II is mediated via Ang II receptor type I/NADPH oxidase/ Rho kinase pathways targeted to lipid rafts

OBJECTIVE

Circulating microparticles are increased in cardiovascular disease and may themselves promote oxidative stress and inflammation. Molecular mechanisms underlying their formation and signaling are unclear. We investigated the role of reactive oxygen species (ROS), Rho kinase, and lipid rafts in microparticle formation and examined their functional significance in endothelial cells (ECs).

METHODS AND RESULTS

Microparticle formation from angiotensin II (Ang II)-stimulated ECs and apolipoprotein E(-/-) mice was assessed by annexin V or by CD144 staining and electron microscopy. Ang II promoted microparticle formation and increased EC O(2)(-) generation and Rho kinase activity. Ang II-stimulated effects were inhibited by irbesartan (Ang II receptor type I blocker) and fasudil (Rho kinase inhibitor). Methyl-β-cyclodextrin and nystatin, which disrupt lipid rafts/caveolae, blocked microparticle release. Functional responses, assessed in microparticle-stimulated ECs, revealed increased O(2)(-) production, enhanced vascular cell adhesion molecule/platelet-EC adhesion molecule expression, and augmented macrophage adhesion. Inhibition of epidermal growth factor receptor blocked the prooxidative and proinflammatory effects of microparticles. In vitro observations were confirmed in apolipoprotein E(-/-) mice, which displayed vascular inflammation and high levels of circulating endothelial microparticles, effects that were reduced by apocynin.

CONCLUSIONS

We demonstrated direct actions of Ang II on endothelial microparticle release, mediated through NADPH oxidase, ROS, and Rho kinase targeted to lipid rafts. Microparticles themselves stimulated endothelial ROS formation and inflammatory responses. Our findings suggest a feedforward system whereby Ang II promotes EC injury through its own endothelial-derived microparticles.

Membrane vesicles, current state-of-the-art: emerging role of extracellular vesicles

Release of membrane vesicles, a process conserved in both prokaryotes and eukaryotes, represents an evolutionary link, and suggests essential functions of a dynamic extracellular vesicular compartment (including exosomes, microparticles or microvesicles and apoptotic bodies). Compelling evidence supports the significance of this compartment in a broad range of physiological and pathological processes. However, classification of membrane vesicles, protocols of their isolation and detection, molecular details of vesicular release, clearance and biological functions are still under intense investigation. Here, we give a comprehensive overview of extracellular vesicles. After discussing the technical pitfalls and potential artifacts of the rapidly emerging field, we compare results from meta-analyses of published proteomic studies on membrane vesicles. We also summarize clinical implications of membrane vesicles. Lessons from this compartment challenge current paradigms concerning the mechanisms of intercellular communication and immune regulation. Furthermore, its clinical implementation may open new perspectives in translational medicine both in diagnostics and therapy.

Circulating microparticles from septic shock patients exert differential tissue expression of enzymes related to inflammation and oxidative stress

OBJECTIVE

Septic shock is characterized by hypotension and multiple organ failure after infection of microorganisms. Septic shock patients display high levels of circulating microparticles. These are small vesicles released from the plasma membrane of activated or apoptotic cells. Here, we have investigated the effects of in vivo injection of microparticles from nonseptic or septic subjects on protein expression in mouse tissues.

DESIGN

Prospective, controlled experiments.

SETTING

Animal basic science laboratory.

SUBJECTS

Male Swiss mice were randomly assigned to one of two groups: 11 animals injected with microparticles isolated from healthy subjects and 15 animals injected with microparticles isolated from septic patients.

INTERVENTIONS

Microparticles were extracted from whole blood of septic and nonseptic subjects and were intravenously injected in mice. After 24 hrs, mice were killed and heart, lungs, liver, and kidneys were isolated for Western blot assays. Organs were also used for direct measurements of nitric oxide and superoxide anion production by electron paramagnetic resonance.

MEASUREMENTS AND MAIN RESULTS

In heart and lungs, microparticles from septic shock patients increased the expression of endothelial and inducible nitric oxide synthases, cyclooxygenase-2, and nuclear factor-κB. However, extracellular superoxide dismutase was only increased in the heart. These effects were associated either with a greater oxidative or nitrative stress in heart and lungs, without affecting nitric oxide production. The liver exhibited an increase in oxidative stress linked to decreased endothelial nitric oxide synthase and manganese superoxide dismutase expression. However, cyclooxygenase-2 expression and IκBα phosphorylation were decreased. Septic microparticles did not change superoxide anion and nitric oxide productions in kidneys.

CONCLUSIONS

Results suggest that microparticles from septic shock patients exert pleiotropic and differential effects depending on target tissues with regard to the expression of proinflammatory proteins related with nitrative and oxidative stresses. Thus, microparticles might participate in organ dysfunction observed in septic shock patients.

High levels of circulating leukocyte microparticles are associated with better outcome in acute respiratory distress syndrome

Introduction

The current study has addressed the presence and the cellular origin of microparticles (MP) isolated from bronchoalveolar lavage (BAL) fluid and from blood samples from patients with acute respiratory distress syndrome (ARDS). Their prognostic interest was also investigated.

Methods

Fifty-two patients were included within the first 24 hours of ARDS. They were compared to spontaneous breathing (SB) and ventilated control (VC) groups. Bronchoalveolar lavage (BAL) and blood samples were obtained on Day 1 and Day 3 in an ARDS group. Leukocyte microparticles (LeuMP), neutrophil microparticles (NeuMP), endothelial microparticles (EMP), and platelet microparticles (PMP) were measured in arterial blood and in BAL samples by flow cytometry. Mortality from all causes was recorded at Day 28.

Results

All MP subpopulations were detected in BAL. However, only LeuMP and NeuMP were elevated in ARDS patients compared to the SB group (P = 0.002 for both). Among ARDS patients, higher levels of LeuMP were detected in blood (Day 1) and in BAL (Day 3) in survivors as compared with the non survivors. Circulating LeuMP >60 elements/microliter detectable on Day 1 of ARDS, was associated with a higher survival rate (odds ratio, 5.26; 95% confidence interval, 1.10 to 24.99; P = 0.037).

Conclusions

The identification of the cellular origin of microparticles at the onset of ARDS has identified LeuMP as a biomarker of prognostic significance. The higher levels of LeuMP in survivors could be associated with a protective role of this MP subpopulation. This hypothesis needs further investigations.

Cell-Derived Microparticles in the Pathogenesis of Cardiovascular Disease

Microparticles are ascribed important roles in coagulation, inflammation, and endothelial function. These processes are mandatory to safeguard the integrity of the organism, and their derangements contribute to the development of atherosclerosis and cardiovascular disease. More recently, the presumed solely harmful role of microparticles has been challenged because microparticles may also be involved in the maintenance and preservation of cellular homeostasis and in promoting defense mechanisms. Here, we summarize recent studies revealing these 2 faces of microparticles in cardiovascular disease.

PPARalpha is essential for microparticle-induced differentiation of mouse bone marrow-derived endothelial progenitor cells and angiogenesis

Background

Bone marrow-derived endothelial progenitor cells (EPCs) are critical for neovascularization. We hypothesized that microparticles (MPs), small fragments generated from the plasma membrane, can activate angiogenic programming of EPCs.

Methodology/Principal Findings

We studied the effects of MPs obtained from wild type (MPs^PPARα+/+) and knock-out (MPs^{PPARα−/−}) mice on EPC differentiation and angiogenesis. Bone marrow-derived cells were isolated from WT or KO mice and were cultured in the presence of MPs^PPARα+/+ or MPs^{PPARα−/−} obtained from blood of mice. Only MPs^PPARα+/+ harboring PPAR^α significantly increased EPC, but not monocytic, differentiation. Bone marrow-derived cells treated with MPs^PPARα+/+ displayed increased expression of pro-angiogenic genes and increased in vivo angiogenesis. MPs^PPARα+/+ increased capillary-like tube formation of endothelial cells that was associated with enhanced expressions of endothelial cell-specific markers. Finally, the effects of MPs^PPARα+/+ were mediated by NF-κB-dependent mechanisms.

Conclusions/Significance

Our results underscore the obligatory role of PPARα carried by MPs for EPC differentiation and angiogenesis. PPARα-NF-κB-Akt pathways may play a pivotal stimulatory role for neovascularization, which may, at least in part, be mediated by bone marrow-derived EPCs. Improvement of EPC differentiation may represent a useful strategy during reparative neovascularization.

Isolation and characterization of microparticles in sputum from cystic fibrosis patients

Background

Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis. MPs have different biological effects depending on the cell from they originate. Cystic fibrosis (CF) lung disease is characterized by massive neutrophil granulocyte influx in the airways, their activation and eventually apoptosis. We investigated on the presence and phenotype of MPs in the sputum, a rich non-invasive source of inflammation biomarkers, of acute and stable CF adult patients.

Methods

Spontaneous sputum, obtained from 21 CF patients (10 acute and 11 stable) and 7 patients with primary ciliary dyskinesia (PCD), was liquefied with Sputasol. MPs were counted, visualized by electron microscopy, and identified in the supernatants of treated sputum by cytofluorimetry and immunolabelling for leukocyte (CD11a), granulocyte (CD66b), and monocyte-macrophage (CD11b) antigens.

Results

Electron microscopy revealed that sputum MPs were in the 100-500 nm range and did not contain bacteria, confirming microbiological tests. CF sputa contained higher number of MPs in comparison with PCD sputa. Levels of CD11a⁺-and CD66b⁺-, but not CD11b⁺-MPs were significantly higher in CF than in PCD, without differences between acute and stable patients.

Conclusions

In summary, MPs are detectable in sputa obtained from CF patients and are predominantly of granulocyte origin. This novel isolation method for MPs from sputum opens a new opportunity for the study of lung pathology in CF.

Endothelial dysfunction and circulating microparticles from patients with obstructive sleep apnea

Endothelial dysfunction is involved in vascular complications of obstructive sleep apnea (OSA). In this study, circulating microparticles (MPs) from patients with OSA-induced nocturnal desaturations were characterized and their effects on endothelial function were evaluated. Two age-matched groups of patients undergoing polysomnography for OSA were compared: 35 desaturators with a 3% oxyhemoglobin desaturation index (ODI) > or = 10 events per hour of sleep and 27 nondesaturators with ODI <10 events per hour. MPs were characterized by flow cytometry and then either used to treat in vitro human endothelial cells or to study endothelial function in mice. Circulating MPs did not differ between groups, but MPs from granulocytes and activated leukocytes (CD62L(+)) were found at higher levels in desaturators. In vitro, MPs from desaturators reduced endothelial nitric oxide (NO) production by enhancing phosphorylation of endothelial NO synthase at the site of inhibition and expression of caveolin-1. CD62L(+) MPs positively correlated with ODI. Endothelial NO production negatively correlated with both CD62L(+) MPs and ODI. MPs from desaturators increased expression of endothelial adhesion molecules including E-selectin, ICAM-1 and ITGA5, and cyclooxygenase 2. Moreover, injection of MPs from desaturators into mice impaired endothelium-dependent relaxation in aorta and flow-induced dilation in small mesenteric arteries. This study demonstrates an association between endothelial dysfunction and increased circulating levels of CD62L(+) MPs. This may initiate atherogenic processes in patients with OSA and severe nighttime hypoxia.

Estrogen receptor alpha as a key target of red wine polyphenols action on the endothelium

Background

A greater reduction in cardiovascular risk and vascular protection associated with diet rich in polyphenols are generally accepted; however, the molecular targets for polyphenols effects remain unknown. Meanwhile evidences in the literature have enlightened, not only structural similarities between estrogens and polyphenols known as phytoestrogens, but also in their vascular effects. We hypothesized that alpha isoform of estrogen receptor (ERα) could be involved in the transduction of the vascular benefits of polyphenols.

Methodology/Principal Findings

Here, we used ERα deficient mice to show that endothelium-dependent vasorelaxation induced either by red wine polyphenol extract, Provinols™, or delphinidin, an anthocyanin that possesses similar pharmacological profile, is mediated by ERα. Indeed, Provinols™, delphinidin and ERα agonists, 17-beta-estradiol and PPT, are able to induce endothelial vasodilatation in aorta from ERα Wild-Type but not from Knock-Out mice, by activation of nitric oxide (NO) pathway in endothelial cells. Besides, silencing the effects of ERα completely prevented the effects of Provinols™ and delphinidin to activate NO pathway (Src, ERK 1/2, eNOS, caveolin-1) leading to NO production. Furthermore, direct interaction between delphinidin and ERα activator site is demonstrated using both binding assay and docking. Most interestingly, the ability of short term oral administration of Provinols™ to decrease response to serotonin and to enhance sensitivity of the endothelium-dependent relaxation to acetylcholine, associated with concomitant increased NO production and decreased superoxide anions, was completely blunted in ERα deficient mice.

Conclusions/Significance

This study provides evidence that red wine polyphenols, especially delphinidin, exert their endothelial benefits via ERα activation. It is a major breakthrough bringing new insights of the potential therapeutic of polyphenols against cardiovascular pathologies.

Circulating microparticles and procoagulant activity in elderly patients

BACKGROUND

Microparticles (MP) are shed membrane vesicles released from activation or apoptosis of several cell types and carry a procoagulant activity. Age is associated with a procoagulant state, but the role of MP in this setting is unknown, as the relationship of MP to aging in humans. We tested the hypotheses that elderly persons compared with young persons may have different patterns of expression of MP and procoagulant activity in stable or septic conditions.

METHODS

Patients from Emergency and Geriatric Departments were divided into four groups according to their age (< 50 or > or = 75 years old) and the presence of systemic infection (yes or no). The diagnosis of infection was reached when it was classified as certain or possible by an expert panel. Circulating MP were isolated from venous citrated blood. Cytofluorometry using specific antibodies was performed to determine the origins of MP (endothelial microparticles [EMP], red blood cell microparticles, or platelet microparticles). Procoagulant activity was determined using annexin V (prothrombinase activity) and tissue factor (TF) assays.

RESULTS

One hundred and eleven patients were included. Elderly patients expressed a decrease in EMP in stable conditions, associated with a decrease in procoagulant annexin V MP in septic conditions (p < .05), and higher EMP levels were found in elderly infected patients who died during hospital stay than in survivors (p = .04). Compared with young patients, response to sepsis was altered in elders concerning EMP, annexin V MP, and TF-bearing MP.

CONCLUSION

Elderly patients expressed a different pattern of MP in stable conditions, with a different response to sepsis in procoagulant activity modification.

Microparticles harbouring Sonic Hedgehog: role in angiogenesis regulation

Sonic Hedgehog (Shh) is a morphogen involved in embryonic development of nervous system. Also, it has been shown that recombinant Shh can modulate angiogenesis under ischemic conditions. However, angiogenic effects of endogenous Shh have not been completely elucidated. Using small membrane-derived vesicles expressing Shh (MPs(Shh+)), we have shown that, although MPs(Shh+) decrease endothelial cell proliferation and migration, they are able to favour angiogenesis through the increase of both endothelial cell adhesion and expression of pro-angiogenenic factors. Activation of proteins implicated in cell adhesion, such as Rho A, as well as upregulation of pro-angiogenic factors were sensitive to inhibition of Shh pathway. Although whole composition of MPs(Shh+) needs to be characterized to understand potential effects of MPs(Shh+), these results highlight a new role of MPs(Shh+) in vascular pathophysiology and may have significant implication for therapy in pathologies associated with altered angiogenesis in order to re-address angiogenic switch.

Therapeutic potential of plasma membrane-derived microparticles

In the past, plasma membrane-derived microparticles were considered "cellular dust." According to the literature, circulating levels of microparticles are increased in several cardiovascular diseases associated with inflammation, suggesting that microparticles are linked to deleterious effects such as endothelial dysfunction or thrombosis. However, very recent studies have shown that under several conditions microparticles can transfer biological messages between cells. Indeed, microparticles act as vectors of key information to maintain cell homeostasis or to favor cell repair and induce angiogenesis. For instance, microparticles of platelet origin are able to repair myocardial injury after myocardial infarction. Also, we have shown that engineered microparticles generated from human activated/apoptotic T cells promote angiogenesis through the up-regulation of adhesion proteins and pro-angiogenic factors in human endothelial cells. Interestingly, the effects induced by these microparticles on the formation of capillary-like structures, expression of adhesion molecules, and pro-angiogenic factors are reversed after silencing of the Sonic Hedgehog (Shh) morphogen pathway. In addition, the same type of microparticles is able to induce neo-vascularization in an ischemic hindlimb model. These effects are, at least in part, mediated by Shh and nitric oxide production. Taking into consideration these results and the most recent data concerning the ability of microparticles to transmit genetic information between cells through mRNA transfer, it is plausible that plasma membrane-derived microparticles could serve as tools with veritable therapeutic potential.