Circulating endothelial progenitor cell and platelet microparticle impact on platelet activation in hypertension associated with hypercholesterolemia

Impact of Breaking up of Sitting Time on Anti-inflammatory Response Induced by Extracellular Vesicles

Physical inactivity and sedentary behaviors (SB) have promoted a dramatic increase in the incidence of a host of chronic disorders over the last century. The breaking up of sitting time (i.e., sitting to standing up transition) has been proposed as a promising solution in several epidemiological and clinical studies. In parallel to the large interest it initially created, there is a growing body of evidence indicating that breaking up prolonged sedentary time (i.e., > 7 h in sitting time) could reduce overall mortality risks by normalizing the inflammatory profile and cardiometabolic functions. Recent advances suggest that the latter health benefits, may be mediated through the immunomodulatory properties of extracellular vesicles. Primarily composed of miRNA, lipids, mRNA and proteins, these vesicles would influence metabolism and immune system functions by promoting M1 to M2 macrophage polarization (i.e., from a pro-inflammatory to anti-inflammatory phenotype) and improving endothelial function. The outcomes of interrupting prolonged sitting time may be attributed to molecular mechanisms induced by circulating angiogenic cells. Functionally, circulating angiogenic cells contribute to repair and remodel the vasculature. This effect is proposed to be mediated through the secretion of paracrine factors. The present review article intends to clarify the beneficial contributions of breaking up sitting time on extracellular vesicles formation and macrophage polarization (M1 and M2 phenotypes). Hence, it will highlight key mechanistic information regarding how breaking up sitting time protocols improves endothelial health by promoting antioxidant and anti-inflammatory responses in human organs and tissues.

Subclinical markers of cardiovascular toxicity of benzene inhalation in mice

Benzene is a ubiquitous environmental pollutant. Recent population-based studies suggest that benzene exposure is associated with an increased risk for cardiovascular disease. However, it is unclear whether benzene exposure by itself is sufficient to induce cardiovascular toxicity. We examined the effects of benzene inhalation (50 ppm, 6 h/day, 5 days/week, 6 weeks) or HEPA-filtered air exposure on the biomarkers of cardiovascular toxicity in male C57BL/6J mice. Benzene inhalation significantly increased the biomarkers of endothelial activation and injury including endothelial microparticles, activated endothelial microparticles, endothelial progenitor cell microparticles, lung endothelial microparticles, and activated lung and endothelial microparticles while having no effect on circulating levels of endothelial adhesion molecules, endothelial selectins, and biomarkers of angiogenesis. To understand how benzene may induce endothelial injury, we exposed human aortic endothelial cells to benzene metabolites. Of the metabolites tested, trans,trans-mucondialdehyde (10 μM, 18h) was the most toxic. It induced caspases-3, -7 and -9 (intrinsic pathway) activation and enhanced microparticle formation by 2.4-fold. Levels of platelet-leukocyte aggregates, platelet macroparticles, and a proportion of CD4+ and CD8+ T-cells were also significantly elevated in the blood of the benzene-exposed mice. We also found that benzene exposure increased the transcription of genes associated with endothelial cell and platelet activation in the liver; and induced inflammatory genes and suppressed cytochrome P450s in the lungs and the liver. Together, these data suggest that benzene exposure induces endothelial injury, enhances platelet activation and inflammatory processes; and circulatory levels of endothelial cell and platelet-derived microparticles and platelet-leukocyte aggregates are excellent biomarkers of cardiovascular toxicity of benzene.

Extracellular Vesicles: Versatile Nanomediators, Potential Biomarkers and Therapeutic Agents in Atherosclerosis and COVID-19-Related Thrombosis

Cells convey information among one another. One instrument employed to transmit data and constituents to specific (target) cells is extracellular vesicles (EVs). They originate from a variety of cells (endothelial, immune cells, platelets, mesenchymal stromal cells, etc.), and consequently, their surface characteristics and cargo vary according to the paternal cell. The cargo could be DNA, mRNA, microRNA, receptors, metabolites, cytoplasmic proteins, or pathological molecules, as a function of which EVs exert different effects upon endocytosis in recipient cells. Recently, EVs have become important participants in a variety of pathologies, including atherogenesis and coronavirus disease 2019 (COVID-19)-associated thrombosis. Herein, we summarize recent advances and some of our own results on the role of EVs in atherosclerotic cardiovascular diseases, and discuss their potential to function as signaling mediators, biomarkers and therapeutic agents. Since COVID-19 patients have a high rate of thrombotic events, a special section of the review is dedicated to the mechanism of thrombosis and the possible therapeutic potential of EVs in COVID-19-related thrombosis. Yet, EV mechanisms and their role in the transfer of information between cells in normal and pathological conditions remain to be explored.

Intravenous Administration of Allogenic Cell-Derived Microvesicles of Healthy Origins Defend Against Atherosclerotic Cardiovascular Disease Development by a Direct Action on Endothelial Progenitor Cells

Atherosclerosis and cardiovascular disease development is the outcome of intermediate processes where endothelial dysfunction and vascular inflammation are main protagonists. Cell-derived microvesicles (MVs), endothelial progenitor cells (EPCs), and circulating microRNAs (miRNAs) are known as biomarkers and potential regulators for atherosclerotic vascular disease, but their role in the complexity of the inflammatory process and in the mechanism of vascular restoration is far from clear. We aimed to evaluate the biological activity and functional role of MVs, in particular of the EPCs-derived MVs (MVEs), of healthy origins in reducing atherosclerotic vascular disease development. The experiments were performed on hamsters divided into the following groups: simultaneously hypertensive–hyperlipidemic (HH group) by combining two feeding conditions for 4 months; HH with retro-orbital sinus injection containing 1 × 10⁵ MVs or MVEs from control hamsters, one dose per month for 4 months of HH diet, to prevent atherosclerosis (HH-MVs or HH-MVEs group); and controls (C group), age-matched normal healthy animals. We found that circulating MV and MVE transplantation of healthy origins significantly reduces atherosclerosis development via (1) the mitigation of dyslipidemia, hypertension, and circulating EPC/cytokine/chemokine levels and (2) the structural and functional remodeling of arterial and left ventricular walls. We also demonstrated that (1) circulating MVs contain miRNAs; this was demonstrated by validating MVs and MVEs as transporters of Ago2-miRNA, Stau1-miRNA, and Stau2-miRNA complexes and (2) MV and MVE administration significantly protect against atherosclerotic cardiovascular disease via transfer of miR-223, miR-21, miR-126, and miR-146a to circulating late EPCs. It should be mentioned that the favorable effects of MVEs were greater than those of MVs. Our findings suggest that allogenic MV and MVE administration of healthy origins could counteract HH diet-induced detrimental effects by biologically active miR-10a, miR-21, miR-126, and miR-146a transfer to circulating EPCs, mediating their vascular repair function in atherosclerosis processes.

Neuroimmune crosstalk in the pathophysiology of hypertension

Hypertension is an important risk factor for cardiovascular morbidity and mortality and for events such as myocardial infarction, stroke, heart failure and chronic kidney disease and is a major determinant of disability-adjusted life-years. Despite the importance of hypertension, the pathogenesis of essential hypertension, which involves the complex interaction of several mechanisms, is still poorly understood. Evidence suggests that interplay between bone marrow, microglia and immune mediators underlies the development of arterial hypertension, in particular through mechanisms involving cytokines and peptides, such as neuropeptide Y, substance P, angiotensin II and angiotensin-(1-7). Chronic psychological stress also seems to have a role in increasing the risk of hypertension, probably through the activation of neuroimmune pathways. In this Review, we summarize the available data on the possible role of neuroimmune crosstalk in the origin and maintenance of arterial hypertension and discuss the implications of this crosstalk for recovery and rehabilitation after cardiac and cerebral injuries.

Hypertension Associated With Hyperlipidemia Induced Different MicroRNA Expression Profiles in Plasma, Platelets, and Platelet-Derived Microvesicles; Effects of Endothelial Progenitor Cell Therapy

Aim: The aim of this study was to analyze the expressed profiles of miRNAs in plasma, platelets, and platelet-derived microvesicles (PMVs) obtained from experimental induced atherosclerosis animal model and to investigate the effect of EPC transplantation on these profiles. Methods: Seventeen selected circulating miRNAs (miR-19a,-21,-126,-146a,-223,-26b,-92a,-222,-210,-221,-143,-10a,-145,-155,-34a,-204, and miR-214) were individually analyzed in plasma, platelets, and PMVs isolated from peripheral blood of hypertensive-hyperlipidemic hamsters treated or not with endothelial progenitor cells (EPCs), and of healthy hamsters taken as control group. Results: Comparative with control group, in hypertension associated with hyperlipidemia the investigated miRNA expression profiles were different: (i) in plasma, the levels of all investigated miRNAs were significantly increased, the highest enhances being noticed for miR-21,-146a,-221,-143,-34a, and miR-204; (ii) in platelets, the expressions of almost all miRNAs were significantly elevated, remarkable for miR-126,-146a,-223,-222, and miR-214, while levels of miR-143, miR-10a, and miR-145 were significantly reduced; (iii) in PMVs, numerous miRNAs were found to have significantly increased levels, especially miR-222,-221,-210, and miR-34a, whereas expressions of various miRNAs as miR-223,-214,-146a,-143,-10a, and miR-145 were significantly decreased. The treatment with EPCs had the following reverse effects: (i) in plasma, significantly reduced the expression of miR-26b,-143,-34a,-204, and miR-214; (ii) in platelets, significantly decreased the levels of almost investigated miRNAs, with remarkably diminishing for miR-126 and miR-221; and (iii) in PMVs, significantly lowered the expression of some miRNAs, with considerably reductions for miR-222,-221,-210, and miR-19a, while the level of miR-214 was found elevated. Conclusions: The present study revealed that miRNAs have differential expression profiles in plasma, platelets, and PMVs under hypertension associated with hyperlipidemia conditions. The different miRNA profile in PMVs compared with platelets indicated an active mechanism of selective packing of miRNAs into PMVs from maternal cells; various miRNAs such as miR-19a,-21,-126,-26b,-92a,-155,-204,-210,-221,-222, and-34a delivered by PMVs may contribute to enrichment of circulating plasma miRNA expression. In addition, our study showed that the EPC-based therapy can regulate the expressions of investigated miRNAs into the three sources. These results provide novel information that could help in finding potential targets for the development of new therapeutic strategies in the cardiovascular disease.

Clinical Assessment of Intravenous Endothelial Progenitor Cell Transplantation in Dogs

Endothelial progenitor cells (EPCs) have been applied for cell therapy because of their roles in angiogenesis and neovascularization in ischemic tissue. However, adverse responses caused by EPC therapy have not been fully investigated. In this study, a human peripheral blood sample was collected from a healthy donor and peripheral blood mononuclear cells were separated using Ficoll-Hypaque. There were four experimental groups: 10 ml saline infusion group (injection rate; 3 ml/min), 10 ml saline bolus group (injection rate; 60 ml/min), 10 ml EPCs infusion group (2 x 10⁵ cells/ml, injection rate; 3 ml/min), 10 ml EPCs bolus group (2 × 10⁵ cells/ml, injection rate; 60 ml/min). Clinical assessment included physical examination and laboratory examination for intravenous human EPC transplantation in dogs. The results revealed no remarkable findings in vital signs among the dogs used. In blood analysis, platelet counts in saline infusion groups were significantly higher than in the EPC groups within normal ranges, and no significant differences were observed except K⁺, Cl^- and blood urea nitrogen/urea. In ELISA assay, no significant difference was observed in serum tumor necrosis factor alpha. The serum concentration of vascular endothelial growth factor was significantly higher in EPC groups than in saline groups, and interleukin 10 was significantly up-regulated in the EPC infusion group compared with other groups. In conclusion, we demonstrated that no clinical abnormalities were detected after intravenous transplantation of human EPCs in dogs. The transplanted xenogenic EPCs might be involved in anti-inflammatory and angiogenic functions in dogs.

Platelets of Healthy Origins Promote Functional Improvement of Atherosclerotic Endothelial Progenitor Cells

The purpose was to evaluate the effect of platelets on functional properties of late endothelial progenitor cells (EPCs), in the direct co-culture conditions, and to investigate the involved mediators, in experimental induced atherosclerosis. The late EPCs obtained from two animal groups, hypertensive-hyperlipidemic (HH) and control (C) hamsters, named late EPCs-HH and late EPCs-C, were co-incubated with or without platelets isolated from both groups. Our results have showed that exposure to platelets from control animals: (i) promoted the late EPCs-C capacity to form colonies and capillary-like structures, and also to proliferate and migrate; (ii) improved the functional properties of late EPCs-HH; (iii) strengthened the direct binding EPCs-platelets; (iv) increased SDF-1α,VEGF, PDGF, and reduced CD40L, IL-1β,-6,-8 levels; and (v) enhanced miR-223 and IGF-1R expressions. Platelets from HH group diminished functional abilities for both EPC types and had opposite effects on these pro-angiogenic and pro-inflammatory molecules. Furthermore, testing the direct effect of miR-223 and IGF-1R on late EPCs disclosed that these molecular factors improve late EPC functional properties in atherosclerosis in terms of stimulation of the proliferation and migration abilities. In conclusion, in vitro exposure to platelets of healthy origins had a positive effect on functional properties of atherosclerotic late EPCs. The most likely candidates mediating EPC-platelet interaction can be SDF-1α, VEGF, CD40L, PDGF, IL-1β,-6,-8, miR-223, and IGF-1R. The current study brings evidences that the presence of healthy origin platelets is of utmost importance on functional improvement of EPCs in atherosclerosis.

Endothelial Cells: From Dysfunction Mechanism to Pharmacological Effect in Cardiovascular Disease

Endothelial cells (ECs) are the innermost layer of blood vessels that play important roles in homeostasis and vascular function. However, recent evidence suggests that the onset of inflammation and the production of reactive oxygen species impair the function of ECs and are a main factor in the development of cardiovascular disease (CVD). In this study, we investigated the effects of inflammatory markers, oxidative stress, and treatment on ECs in CVD patients. This review article is based on the material obtained from PubMed up to 2018. The key search terms used were "Cardiovascular Disease," "Endothelial Cell Dysfunction," "Inflammation," "Treatment," and "Oxidative Stress." The generation of reactive oxygen species (ROS) as well as reduced nitric oxide (NO) production by ECs impairs the function of blood vessels. Therefore, treatment of CVD patients leads to the expression of transcription factors activating anti-oxidant mechanisms and NO production. In contrast, NO production by inflammatory agents can cause ECs repair due to differentiation of endothelial progenitor cells (EPCs). Therefore, identifying the molecular pathways leading to the differentiation of EPCs through mediation of factors induced by inflammatory factors can be effective in regenerative medicine for ECs repair.

Correlation between NADPH oxidase-mediated oxidative stress and dysfunction of endothelial progenitor cell in hyperlipidemic patients

BACKGROUND/AIMS

NADPH (nicotinamide adenine dinucleotide phosphate) oxidase (NOX)-mediated oxidative stress plays a key role in promotion of oxidative injury in the cardiovascular system. The aim of this study is to evaluate the status of NOX in endothelial progenitor cells (EPCs) of hyperlipidemic patients and to assess the correlation between NOX activity and the functions EPCs.

METHODS

A total of 30 hyperlipidemic patients were enrolled for this study and 30 age-matched volunteers with normal level of plasma lipids served as controls. After the circulating EPCs were isolated, the EPC functions (migration, adhesion and tube formation) were evaluated and the status of NOX (expression and activity) was examined.

RESULTS

Compared to the controls, hyperlipidemic patients showed an increase in plasma lipids and a reduction in EPC functions including the attenuated abilities in adhesion, migration and tube formation, concomitant with an increase in NOX expression (NOX2 and NOX4), NOX activity, and reactive oxygen species production. The data analysis showed negative correlations between NOX activity and EPC functions.

CONCLUSIONS

There is a positive correlation between the NOX-mediated oxidative stress and the dysfunctions of circulating EPCs in hyperlipidemic patients, and suppression of NOX might offer a novel strategy to improve EPCs functions in hyperlipidemia.

Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model

AIM

In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms.

METHODS

Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group.

RESULTS

The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer.

CONCLUSION

The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

Overexpression of the β2AR gene improves function and re-endothelialization capacity of EPCs after arterial injury in nude mice

Background

Proliferation and migration of endothelial progenitor cells (EPCs) play important roles in restoring vascular injuries. β2 adrenergic receptors (β2ARs) are widely expressed in many tissues and have a beneficial impact on EPCs regulating neoangiogenesis. The aim of the present study was to determine the effect of overexpressing β2ARs in infused peripheral blood (PB)-derived EPCs on the re-endothelialization in injured vessels.

Methods

Induction of endothelial injury was performed in male nude mice that were subjected to wire-mediated injury to the carotid artery. Human PB-derived EPCs were transfected with an adenovirus serotype 5 vector expressing β2AR (Ad5/β2AR-EPCs) and were examined 48 h later. β2AR gene expression in EPCs was detected by real-time polymerase chain reaction and Western blot analysis. In vitro, the proliferation, migration, adhesion, and nitric oxide production of Ad5/β2AR-EPCs were measured. Meanwhile, phosphorylated Akt and endothelial nitric oxide synthase (eNOS), which are downstream of β2AR signaling, were also elevated. In an in vivo study, CM-DiI-labeled EPCs were injected intravenously into mice subjected to carotid injury. After 3 days, cells recruited to the injury sites were detected by fluorescent microscopy, and the re-endothelialization was assessed by Evans blue dye.

Results

In vitro, β2AR overexpression augmented EPC proliferation, migration, and nitric oxide production and enhanced EPC adhesion to endothelial cell monolayers. In vivo, when cell tracking was used, the number of recruited CM-DiI-labeled EPCs was significantly higher in the injured zone in mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. The degree of re-endothelialization was also higher in the mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. We also found that the phosphorylation of Akt and eNOS was increased in Ad5/β2AR-EPCs. Preincubation with β2AR inhibitor (ICI118,551), Akt inhibitor (ly294002), or eNOS inhibitor (L-NAME) significantly attenuated the enhanced in vitro function and in vivo re-endothelialization capacity of EPCs induced by β2AR overexpression.

Conclusions

The present study demonstrates that β2AR overexpression enhances EPC functions in vitro and enhances the vascular repair abilities of EPCs in vivo via the β2AR/Akt/eNOS pathway. Upregulation of β2AR gene expression through gene transfer may be a novel therapeutic target for endothelial repair.

Effects of transplanted circulating endothelial progenitor cells and platelet microparticles in atherosclerosis development

BACKGROUND INFORMATION

Atherosclerosis is an inflammatory disease, in which risk factors such as hyperlipidemia and hypertension affect the arterial endothelium, resulting in dysfunction, cell damage or both. The number of circulating endothelial progenitor cells and microparticles provides invaluable outcome prediction for atherosclerosis disease. However, evidence for the therapeutic potential of endothelial progenitor cells and microparticles in atherosclerosis development is limited. Our study was designed to investigate the possible protective role of a cell therapy-based approach, using endothelial progenitor cells and the dual behaviour of circulating platelet microparticles, on atherosclerosis development in hypertensive-hypercholesterolemic hamster model. Consequently, control hamsters received four intravenous inoculations of: (1) 1×10(5) endothelial progenitor cells of healthy origins in one dose per month, during four months of diet-induced atherosclerosis, and after hypertensive-hypercholesterolemic diet for further four months; (2) in a second set of experiments, 1×10(5) endothelial progenitor cells of healthy origins or/and 1×10(5) platelet microparticles of atherosclerotic origins were inoculated every other month during hypertensive-hypercholesterolemic diet.

RESULTS

Endothelial progenitor cell treatment had the following effects: (1) re-established plasmatic parameters: cholesterol and triglyceride concentrations, blood pressure, heart rate, cytokine and chemokine profiles, platelet microparticle pro-thrombotic activity and endothelial progenitor cell paracrine activity reflected by cytokine/chemokine detection; (2) reduced lipid, macrophage and microparticle accumulation in liver; (3) reduced atherosclerosis development, revealed by decreased lipid, macrophage and microparticle content of arterial wall; (4) induced the recruitment and incorporation of endothelial progenitor cells into liver and arterial wall; (5) improved arterial dysfunction by increasing contraction and relaxation; (6) reduced the protein expression of specific pro-inflammatory molecules in liver and arterial wall. Platelet microparticle transplantation aggravated the above-mentioned biomarkers and atherosclerosis process, which were partially reverted with co-inoculation of platelet microparticles and endothelial progenitor cells.

CONCLUSIONS

With this study, we demonstrate in a hypertensive-hypercholesterolemic hamster model, that the endothelial progenitor cell-based therapy suppresses the development of atherosclerosis and reduces hepatic lipid and macrophage accumulation with the consequent alleviation of dyslipidaemia and hypertension.

SIGNIFICANCE

Our results support the notion that increasing the number of circulating endothelial progenitor cells by different ways could be a promising therapeutic tool for atherosclerosis.

Hypercholesterolemia and Hypertension: Two Sides of the Same Coin

The aim of this review article is to summarize the current knowledge about mechanisms that connect blood pressure regulation and hypercholesterolemia, the mutual interaction between hypertension and hypercholesterolemia, and their influence on atherosclerosis development. Our research shows that at least one-third of the population of Western Europe has hypertension and hypercholesterolemia. Several biohumoral mechanisms could explain the relationship between hypertension and hypercholesterolemia and the association between these risk factors and accelerated atherosclerosis. The most investigated mechanisms are the renin-angiotensin-aldosterone system, oxidative stress, endothelial dysfunction, and increased production of endothelin-1. Arterial hypertension is frequently observed in combination with hypercholesterolemia, and this is related to accelerated atherosclerosis. Understanding the mechanisms behind this relationship could help explain the benefits of therapy that simultaneously reduce blood pressure and cholesterol levels.

Early outgrowth cells versus endothelial colony forming cells functions in platelet aggregation

Background

Endothelial progenitor cells (EPCs) have been implicated in neoangiogenesis, endothelial repair and cell-based therapies for cardiovascular diseases. We have previously shown that the recruitment of EPCs to sites of vascular lesions is facilitated by platelets where EPCs, in turn, modulate platelet function and thrombosis. However, EPCs encompass a heterogeneous population of progenitor cells that may exert different effects on platelet function. Recent evidence suggests the existence of two EPC subtypes: early outgrowth cells (EOCs) and endothelial colony-forming cells (ECFCs). We aimed at characterizing these two EPC subtypes and at identifying their role in platelet aggregation.

Methods

EOCs and ECFCs were generated from human peripheral blood mononuclear cells (PBMCs) seeded in conditioned media on fibronectin and collagen, respectively. The morphological, phenotypical and functional characteristics of EOCs and ECFCs were assessed by optical and confocal laser scanning microscopes, cell surface markers expression, and Matrigel tube formation. The impact of EOCs and ECFCs on platelet aggregation was monitored in collagen-induced optical aggregometry and compared with PBMCs and human umbilical vein endothelial cells (HUVECs). The levels of the anti-platelet agents’ nitric oxide (NO) and prostacyclin (PGI₂) released from cultured cells as well as the expression of their respective producing enzymes NO synthases (NOS) and cyclooxygenases (COX) were also assessed.

Results

We showed that EOCs display a monocytic-like phenotype whereas ECFCs have an endothelial-like phenotype. We demonstrated that both EOCs and ECFCs and their supernatants inhibited platelet aggregation; however ECFCs were more efficient than EOCs. This could be related to the release of significantly higher amounts of NO and PGI₂ from ECFCs, in comparison to EOCs. Indeed, ECFCs, like HUVECs, constitutively express the endothelial (eNOS)—and inducible (iNOS)—NOS isoforms, and COX-1 and weakly express COX-2, whereas EOCs do not constitutively express these NO and PGI₂ producing enzymes.

Conclusion

The different morphological, phenotypic and more importantly the release of the anti-aggregating agents PGI₂ and NO in each EPC subtype are implicated in their respective roles in platelet function and thus, may be linked to the increased efficiency of ECFCs in inhibiting platelet aggregation as compared to EOCs.

Atherosclerosis: a chronic inflammatory disease mediated by mast cells

Inflammation is a process that plays an important role in the initiation and progression of atherosclerosis and immune disease, involving multiple cell types, including macrophages, T-lymphocytes, endothelial cells, smooth muscle cells and mast cells. The fundamental damage of atherosclerosis is the atheromatous or fibro-fatty plaque which is a lesion that causes several diseases. In atherosclerosis the innate immune response, which involves macrophages, is initiated by the arterial endothelial cells which respond to modified lipoproteins and lead to Th1 cell subset activation and generation of inflammatory cytokines and chemoattractant chemokines. Other immune cells, such as CD4+ T inflammatory cells, which play a critical role in the development and progression of atherosclerosis, and regulatory T cells [Treg], which have a protective effect on the development of atherosclerosis are involved. Considerable evidence indicates that mast cells and their products play a key role in inflammation and atherosclerosis. Activated mast cells can have detrimental effects, provoking matrix degradation, apoptosis, and enhancement as well as recruitment of inflammatory cells, which actively contributes to atherosclerosis and plaque formation. Here we discuss the relationship between atherosclerosis, inflammation and mast cells.

Reverse-D-4F Increases the Number of Endothelial Progenitor Cells and Improves Endothelial Progenitor Cell Dysfunctions in High Fat Diet Mice

Although high density lipoprotein (HDL) improves the functions of endothelial progenitor cells (EPCs), the effect of HDL ApoAI mimetic peptide reverse-D-4F (Rev-D4F) on EPC mobilization and repair of EPC dysfunctions remains to be studied. In this study, we investigated the effects of Rev-D4F on peripheral blood cell subpopulations in C57 mice treated with a high fat diet and the mechanism of Rev-D4F in improving the function of EPCs impaired by tumor necrosis factor-α (TNF-α). The high fat diet significantly decreased the number of EPCs, EPC migratory functions, and the percentage of lymphocytes in the white blood cells. However, it significantly increased the number of white blood cells, the percentage of monocytes in the white blood cells, and the level of vascular endothelial growth factor (VEGF) and TNF-α in the plasma. Rev-D4F clearly inhibited the effect of the high fat diet on the quantification of peripheral blood cell subpopulations and cytokine levels, and increased stromal cell derived factor 1α (SDF-1α) in the plasma. We provided in vitro evidence that TNF-α impaired EPC proliferation, migration, and tube formation through inactive AKT and eNOS, which was restored by Rev-D4F treatment. In contrast, both the PI3-kinase (PI3K) inhibitor (LY294002) and AKT inhibitor (perifosine) obviously inhibited the restoration of Rev-4F on EPCs impaired by TNF-α. Our results suggested that Rev-D4F increases the quantity of endothelial progenitor cells through increasing the SDF-1α levels and decreasing the TNF-α level of peripheral blood in high fat diet-induced C57BL/6J mice, and restores TNF-α induced dysfunctions of EPCs partly through stimulating the PI3K/AKT signal pathway.

Dysfunctional endothelial progenitor cells in cardiovascular diseases: role of NADPH oxidase

Endothelial progenitor cells (EPCs) play a critical role in maintenance of the endothelial integrity and vascular homeostasis, as well as in neovascularization. Dysfunctional EPCs are believed to contribute to the endothelial dysfunction and are closely related to the development of various cardiovascular diseases, such as hypertension, hyperlipidemia, and stroke. However, the underlying mechanisms of EPC dysfunction are complicated and remain largely elusive. Recent studies have demonstrated that reactive oxygen species (ROS) are key factors that involve in modulation of stem and progenitor cell function under various physiologic and pathologic conditions. It has been shown that NADPH oxidase (NOX)-derived ROS are the major sources of ROS in cardiovascular system. Accumulating evidence suggests that NOX-mediated oxidative stress can modulate EPC bioactivities, such as mobilization, migration, and neovascularization, and that inhibition of NOX has been shown to improve EPC functions. This review summarized recent progress in the studies on the correlation between NOX-mediated EPC dysfunction and cardiovascular diseases.

Platelets and neurovascular inflammation

Platelets participate in haemostasis and in thrombus formation in health and disease. Moreover, they contribute to inflammation and cooperate with immune cells in a magnitude of inflammatory/immune responses. Although the inflammatory response has been recognised to be critical in neuronal diseases such as Alzheimer's disease or multiple sclerosis and its mouse counterpart, experimental autoimmune encephalomyelitis, the participation of platelets in these diseases is poorly investigated so far. Emerging studies, however, point to an interesting crosstalk between platelets and neuroinflammation. For instance, when the integrity of the blood brain barrier is compromised, platelets may be relevant for endothelial inflammation, as well as recruitment and activation of inflammatory cells, thereby potentially contributing to central nervous tissue pathogenesis. This review summarises recent insights in the role of platelets for neurovascular inflammation and addresses potential underlying mechanisms, by which platelets may affect the pathophysiology of neurovascular diseases.