Small-size platelet microparticles trigger platelet and monocyte functionality and modulate thrombogenesis via P-selectin

Exploring platelet-derived microvesicles in vascular regeneration: unraveling the intricate mechanisms and molecular mediators

Microvesicles (MVs) serve as biomarkers and transmitters for cell communication and also act as essential contributors to diseases. Platelets release microvesicles when activated voluntarily, making them a significant source. Platelet-derived microvesicles possess a range of characteristics similar to their parent cells and were shown to exert regulatory impacts on vascular and immunological cells. MVs can alter the activity of recipient cells by transferring their internal components. Furthermore, it has been identified that microvesicles derived from platelets possess the ability to exert immunomodulatory effects on different kinds of cells. Recent research has shown that microvesicles have a bidirectional influence of harming and preventing the receptor cells. Nevertheless, the specific characteristics of the active molecules responsible for this phenomenon are still unknown. The primary focus of this review was to explore the mechanism of vascular tissue regeneration and the specific molecules that play a role in mediating various biological effects throughout this process. These molecules exert their effects by influencing autophagy, apoptosis, and inflammatory pathways.

Platelet-derived microvesicles (PMVs) in cancer progression and clinical applications

Platelet-derived microvesicles (PMVs), the microvesicles with the highest concentration in the bloodstream, play a key role in the regulation of hemostasis, inflammation, and angiogenesis. PMVs have recently been identified as key factors in the link between platelets and cancer. PMVs bind to both cancer cells and nontransformed cells in the microenvironment of the tumor, and then transfer platelet-derived contents to the target cell. These contents have the potential to either stimulate or modulate the target cell's response. PMVs are encased in a lipid bilayer that contains surface proteins and lipids as well as components found inside the PMV. Each of these components participates in known and potential PMV roles in cancer. The complicated roles played by PMVs in the onset, development, and progression of cancer and cancer-related comorbidities are summarized in this study.

Interactions between Platelets and Tumor Microenvironment Components in Ovarian Cancer and Their Implications for Treatment and Clinical Outcomes

Platelets, the primary operatives of hemostasis that contribute to blood coagulation and wound healing after blood vessel injury, are also involved in pathological conditions, including cancer. Malignancy-associated thrombosis is common in ovarian cancer patients and is associated with poor clinical outcomes. Platelets extravasate into the tumor microenvironment in ovarian cancer and interact with cancer cells and non-cancerous elements. Ovarian cancer cells also activate platelets. The communication between activated platelets, cancer cells, and the tumor microenvironment is via various platelet membrane proteins or mediators released through degranulation or the secretion of microvesicles from platelets. These interactions trigger signaling cascades in tumors that promote ovarian cancer progression, metastasis, and neoangiogenesis. This review discusses how interactions between platelets, cancer cells, cancer stem cells, stromal cells, and the extracellular matrix in the tumor microenvironment influence ovarian cancer progression. It also presents novel potential therapeutic approaches toward this gynecological cancer.

A Phytoprostane from Gracilaria longissima Increases Platelet Activation, Platelet Adhesion to Leukocytes and Endothelial Cell Migration by Potential Binding to EP3 Prostaglandin Receptor

Plant phytoprostanes (PhytoPs) are lipid oxidative stress mediators that share structural similarities with mammal prostaglandins (PGs). They have been demonstrated to modulate inflammatory processes mediated by prostaglandins. The present study aims to test the effects of the most abundant oxylipin from Gracilaria longissima, ent-9-D1t-Phytoprostane (9-D1t-PhytoP), on platelet activation and vascular cells as well as clarify possible interactions with platelets and the endothelial EP3 receptor Platelet and monocyte activation was assessed by flow cytometry in the presence of purified 9-D1t-PhytoP. Cell migration was studied using the human Ea.hy926 cell line by performing a scratch wound healing assay. The RNA expression of inflammatory markers was evaluated by RT-PCR under inflammatory conditions. Blind docking consensus was applied to the study of the interactions of selected ligands against the EP3 receptor protein. The 9D1t-PhytoP exerts several pharmacological effects; these include prothrombotic and wound-healing properties. In endothelial cells, 9D1t-PhytP mimics the migration stimulus of PGE₂. Computational analysis revealed that 9D1t-PhytP forms a stable complex with the hydrophobic pocket of the EP3 receptor by interaction with the same residues as misoprostol and prostaglandin E₂ (PGE₂), thus supporting its potential as an EP3 agonist. The potential to form procoagulant platelets and the higher endothelial migration rate of the 9-D1t-PhytoP, together with its capability to interact with PGE₂ main target receptor in platelets suggest herein that this oxylipin could be a strong candidate for pharmaceutical research from a multitarget perspective.

The posttraumatic response of CD4+ regulatory T cells is modulated by direct cell-cell contact via CD40L- and P-selectin-dependent pathways

CD4+ FoxP3+ regulatory T cells (CD4+ Tregs) are important for the posttraumatic anti-inflammatory host response. As described previously, platelets are able to modulate CD4+ Treg activity in a reciprocally activating interaction following injury. The underlying mechanisms of the posttraumatic interaction between platelets and CD4+ Tregs remain unclear. We investigated the potential influence of CD40L and P-selectin, molecules known to be involved in direct cell contact of these cell types. In a murine burn injury model, the potential interaction pathways were addressed using CD40L- and P-selectin-deficient mice. Draining lymph nodes were harvested following trauma (1 h) and following a sham procedure. Early rapid activation of CD4+ Tregs was assessed by phospho-flow cytometry (signaling molecules (p)PKC-δ and (p)ZAP-70). Platelet function was analyzed performing rotational thromboelastometry (ROTEM). We hypothesized that disruption of the direct cell-cell contact via CD40L and P-selectin would affect posttraumatic activation of CD4+ Tregs and influence the hemostatic function of platelets. Indeed, while injury induced early activation of CD4+ Tregs in wild-type mice (ZAP-70: p = 0.13, pZAP-70: p < 0.05, PKC-δ: p < 0.05, pPKC-δ: p < 0.05), disruption of CD40L-dependent interaction (ZAP-70: p = 0.57, pZAP-70: p = 0.68, PKC-δ: p = 0.68, pPKC-δ: p = 0.9) or P-selectin-dependent interaction (ZAP-70: p = 0.78, pZAP-70: p = 0.58, PKC-δ: p = 0.81, pPKC-δ: p = 0.73) resulted in reduced posttraumatic activation. Furthermore, hemostatic function was impaired towards hypocoagulability in either deficiency. Our results suggest that the posttraumatic activation of CD4+ Tregs and hemostatic function of platelets are affected by direct cell-cell-signaling via CD40L and P-selectin.

Platelets and extracellular vesicles and their cross talk with cancer

Platelets play significant and varied roles in cancer progression, as detailed throughout this review series, via direct interactions with cancer cells and by long-range indirect interactions mediated by platelet releasates. Microvesicles (MVs; also referred to as microparticles) released from activated platelets have emerged as major contributors to the platelet-cancer nexus. Interactions of platelet-derived MVs (PMVs) with cancer cells can promote disease progression through multiple mechanisms, but PMVs also harbor antitumor functions. This complex relationship derives from PMVs' binding to both cancer cells and nontransformed cells in the tumor microenvironment and transferring platelet-derived contents to the target cell, each of which can have stimulatory or modulatory effects. MVs are extracellular vesicles of heterogeneous size, ranging from 100 nm to 1 µm in diameter, shed by living cells during the outward budding of the plasma membrane, entrapping local cytosolic contents in an apparently stochastic manner. Hence, PMVs are encapsulated by a lipid bilayer harboring surface proteins and lipids mirroring the platelet exterior, with internal components including platelet-derived mature messenger RNAs, pre-mRNAs, microRNAs, and other noncoding RNAs, proteins, second messengers, and mitochondria. Each of these elements engages in established and putative PMV functions in cancer. In addition, PMVs contribute to cancer comorbidities because of their roles in coagulation and thrombosis and via interactions with inflammatory cells. However, separating the effects of PMVs from those of platelets in cancer contexts continues to be a major hurdle. This review summarizes our emerging understanding of the complex roles of PMVs in the development and progression of cancer and cancer comorbidities.

Cell-derived microparticles and von Willebrand factor in Brazilian renal transplant recipients

AIM

This study was aimed at investigating platelet-derived microparticles (PMP), endothelium cell-derived microparticles (EMP) and von Willebrand factor (VWF) according to renal function and time post-transplant. We found this study relevant because unusual biomarkers seem to be a promising tool to evaluate chronic renal disease and post-transplant monitoring.

METHODS

Ninety-one renal transplant recipients (RTx) were allocated into groups according to creatinine plasma levels (C1 < 1.4 and C2 ≥ 1.4 mg/dL), estimated glomerular filtration rates (R1 < 60 and R2 ≥ 60 mL/min per 1.73 m² ) and time post-transplant (T1: 3-24; T2: 25-60; T3: 61-120; and T4 > 120 months). EMP and PMP levels were assessed by flow cytometry and VWF levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Platelet-derived microparticle levels were higher in C1 group compared with C2 (P = 0.00). According to diameter, small PMP and EMP (≤0.7 μm) were also higher in C1 group, all values of P less than 0.05. T1 and T2 groups have shown high EMP levels and a predominance of big microparticle (>0.7 μm) compared with T4 group, all values of P less than 0.05. Higher VWF levels were observed among RTx with creatinine ≥1.4 mg/dL compared with other RTx, P = 0.01.

CONCLUSION

The results showed that PMP, EMP and VWF are promising markers to evaluate endothelial function in RTx. These biomarkers could play a major role in monitoring patients after renal transplant.

Generation of platelet-derived microparticles through the activation of the toll-like receptor 4

Introduction

Infection from different bacterial may increase the risk of thrombosis and atherosclerosis risk by production and secretion of many proinflammatory factors. Human platelets have toll-like receptor 4 (TLR4), the principal receptor for lipopolysaccharide (LPS). The activation of platelet produces Platelet-derived Microparticles (PDMPs) measuring less than 1.0 micron (that are very abundant in circulation >90%), which are associated with the development of Cardiovascular Diseases (CVDs), the leading cause of death in the world.

Objectives

Experiments were designed to evaluate the generation of pro-thrombogenic microparticles in vitro on platelets via TLR4 activation.

Methods

Platelet-rich plasma and washed platelets from healthy volunteers were incubated for the generation of PDMPs. The best source for the generation of microparticles was washed platelets. Then the washed platelets were incubated for 15 minutes with ultrapure Escherichia coli LPS (0–9 μg/mL) followed by activation with ADP (1 μM, subaggregant concentration), centrifuged for 60 minutes and analyzed by flow cytometry.

Results

Incubating platelets with LPS (9 μg/mL) and ADP (1 μM) produced a 34-fold increase in PDMPs generation. Finally, we evaluated this protocol to detect the inhibition of PDMPs generation, washed platelets were incubated with acetylsalicylic acid (10 μM) and an inhibition of 7.7-fold in PDMPs generation for activation of TLR4 was found.

Conclusion

A new and easy protocol for PDMPs generation and analysis by Flow Cytometry is established. In the future it could be used to determine the association of PDMPs with different pathologies.

Application of Extracellular Vesicles Proteomics to Cardiovascular Disease: Guidelines, Data Analysis, and Future Perspectives

Extracellular vesicles (EVs) are a heterogeneous population of vesicles composed of a lipid bilayer that carry a large repertoire of molecules including proteins, lipids, and nucleic acids. In this review, some guidelines for plasma-derived EVs isolation, characterization, and proteomic analysis, and the application of the above to cardiovascular disease (CVD) studies are provided. For EVs analysis, blood samples should be collected using a 21-gauge needle, preferably in citrate tubes, and plasma stored for up to 1 year at -80°, using a single freeze-thaw cycle. For proteomic applications, differential centrifugation (including ultracentrifugation steps) is a good option for EVs isolation. EVs characterization is done by transmission electron microscopy, particle enumeration techniques (nanoparticle-tracking analysis, dynamic light scattering), and flow cytometry. Regarding the proteomics strategy, a label-free and gel-free quantitative method is a good choice due to its accuracy and because it minimizes the amount of sample required for clinical applications. Besides the above, main EVs proteomic findings in cardiovascular-related diseases are presented and analyzed in this review, paying especial attention to overlapping results between studies. The latter might offer new insights into the clinical relevance and potential of novel EVs biomarkers identified to date in the context of CVD.

Microparticles as new markers of cardiovascular risk in diabetes and beyond

The term microparticle (MP) identifies a heterogeneous population of vesicles playing a relevant role in the pathogenesis of vascular diseases, cancer and metabolic diseases such as diabetes mellitus. MPs are released by virtually all cell types by shedding during cell growth, proliferation, activation, apoptosis or senescence processes. MPs, in particular platelet- and endothelial-derived MPs (PMPs and EMPs), are increased in a wide range of thrombotic disorders, with an interesting relationship between their levels and disease pathophysiology, activity or progression. EMP plasma levels have been associated with several cardiovascular diseases and risk factors. PMPs are also shown to be involved in the progressive formation of atherosclerotic plaque and development of arterial thrombosis, especially in diabetic patients. Indeed, diabetes is characterised by an increased procoagulant state and by a hyperreactive platelet phenotype, with enhanced adhesion, aggregation, and activation. Elevated MP levels, such as TF+ MPs, have been shown to be one of the procoagulant determinants in patients with type 2 diabetes mellitus. Atherosclerotic plaque constitutes an opulent source of sequestered MPs, called “plaque” MPs. Otherwise, circulating MPs represent a TF reservoir, named “blood-borne” TF, challenging the dogma that TF is a constitutive protein expressed in minute amounts. “Blood-borne” TF is mainly harboured by PMPs, and it can be trapped within the developing thrombus. MP detection and enumeration by polychromatic flow cytometry (PFC) have opened interesting perspectives in clinical settings, particularly for the evaluation of MP numbers and phenotypes as independent marker of cardiovascular risk, disease and outcome in diabetic patients.

Standardization of a fast and effective method for the generation and detection of platelet-derived microparticles by a flow cytometer

The Flow Cytometry is the principal method used to measure platelet-derived microparticles (PDMPs), by fluorescent properties analysis. PDMPs (0.1-1.0 μm) are abundant in circulation, accounting for approximately 90% of the microparticles and are associated with Cardiovascular Disease, the leading cause of death in the world.

Extracellular vesicles: how they interact with endothelium, potentially contributing to metastatic cancer cell implants

Extracellular vesicles (EV) are blebs of cellular membranes, which entrap small portions of subjacent cytosol. They are released from a variety of cells, circulate in the blood for an unknown length of time and come to rest on endothelial surfaces. They contribute to an array of physiologic pathways, the complexity of which is still being investigated. They contribute to metastatic malignant cell implants and tumor-related angiogenesis, possibly abetted by the tissue factor that they carry. It is thought that the adherence of the EV to endothelium is dependent upon a combination of their P-selectin glycoprotein ligand-1 and exposed phosphatidylserine, the latter of which is normally hidden on the inner bilayer of the intact cellular membrane. This manuscript reviews what is known about EV origins, their clearance from the circulation and how they contribute to malignant cell implants upon endothelium surfaces and subsequent tumor growth.

The Effect of Regular Intake of Dry-Cured Ham Rich in Bioactive Peptides on Inflammation, Platelet and Monocyte Activation Markers in Humans

Background and aims: Dietary studies have shown that active biopeptides provide protective health benefits, although the mediating pathways are somewhat uncertain. To throw light on this situation, we studied the effects of consuming Spanish dry-cured ham on platelet function, monocyte activation markers and the inflammatory status of healthy humans with pre-hypertension. Methods: Thirty-eight healthy volunteers with systolic blood pressure of >125 mmHg were enrolled in a two-arm crossover randomized controlled trial. Participants received 80 g/day dry-cured pork ham of >11 months proteolysis or 100 g/day cooked ham (control product) for 4 weeks followed by a 2-week washout before “crossing over” to the other treatment for 4 more weeks. Soluble markers and cytokines were analyzed by ELISA. Platelet function was assessed by measuring P-selectin expression and PAC-1 binding after ADP (adenosine diphosphate) stimulation using whole blood flow cytometry. Monocyte markers of the pathological status (adhesion, inflammatory and scavenging receptors) were also measured by flow cytometry in the three monocyte subsets after the interventional period. Results: The mean differences between dry-cured ham and cooked ham followed by a time period adjustment for plasmatic P-selectin and interleukin 6 proteins slightly failed (p = 0.062 and p = 0.049, respectively), notably increased for MCP-1 levels (p = 0.023) while VCAM-1 was not affected. Platelet function also decreased after ADP stimulation. The expression of adhesion and scavenging markers (ICAM1R, CXCR4 and TLR4) in the three subsets of monocytes was significantly higher (all p < 0.05). Conclusions: The regular consumption of biopeptides contained in the dry-cured ham but absent in cooked ham impaired platelet and monocyte activation and the levels of plasmatic P-selectin, MCP-1 and interleukin 6 in healthy subjects. This study strongly suggests the existence of a mechanism that links dietary biopeptides and beneficial health effects.

Whole Blood Analysis of Leukocyte-Platelet Aggregates

In inflammatory and thrombotic syndromes, platelets aggregate with circulating leukocytes, especially monocytes and neutrophils. This leukocyte-platelet aggregate formation is initiated primarily through platelet surface expression of P-selectin (CD62P), following activation-dependent degranulation of α-granules, binding to its constitutively expressed counter-receptor, P-selectin glycoprotein ligand 1 (PSGL-1), on leukocytes. Monocyte-platelet aggregates are a more sensitive marker of platelet activation than platelet surface P-selectin. Detection of leukocyte-platelet aggregates is relatively simple by whole-blood flow cytometry. Light scatter and at least one leukocyte-specific antibody are used to gate the desired population, and the presence of associated platelets is detected by immunostaining for abundant platelet-specific markers. © 2016 by John Wiley & Sons, Inc.

Role of Platelet-Derived Microvesicles As Crosstalk Mediators in Atherothrombosis and Future Pharmacology Targets: A Link between Inflammation, Atherosclerosis, and Thrombosis

Reports in the last decade have suggested that the role of platelets in atherosclerosis and its thrombotic complications may be mediated, in part, by local secretion of platelet-derived microvesicles (pMVs), small cell blebs released during the platelet activation process. MVs are the most abundant cell-derived microvesicle subtype in the circulation. High concentrations of circulating MVs have been reported in patients with atherosclerosis, acute vascular syndromes, and/or diabetes mellitus, suggesting a potential correlation between the quantity of microvesicles and the clinical severity of the atherosclerotic disease. pMVs are considered to be biomarkers of disease but new information indicates that pMVs are also involved in signaling functions. pMVs evoke or promote haemostatic and inflammatory responses, neovascularization, cell survival, and apoptosis, processes involved in the pathophysiology of cardiovascular disease. This review is focused on the complex cross-talk between platelet-derived microvesicles, inflammatory cells and vascular elements and their relevance in the development of the atherosclerotic disease and its clinical outcomes, providing an updated state-of-the art of pMV involvement in atherothrombosis and pMV potential use as therapeutic agent influencing cardiovascular biomedicine in the future.

Microvesicles from platelets: novel drivers of vascular inflammation

Microvesicles are receiving increased attention not only as biomarkers but also as mediators of cell communication and as integral effectors of disease. Platelets present a major source of microvesicles and release these microvesicles either spontaneously or upon activation. Platelet-derived microvesicles retain many features of their parent cells and have been shown to exert modulatory effects on vascular and immune cells. Accordingly, microvesicles from platelets can be measured at increased levels in patients with cardiovascular disease or individuals at risk. In addition, isolated microvesicles from platelets were shown to exert immunomodulatory actions on various cell types. In this review the various aspects of platelet-derived microvesicles including release, clearance, measurement, occurrence during disease and relevance for the pathophysiology of vascular inflammation will be discussed.

Small-size Microparticles as Indicators of Acute Decompensated State in Ischemic Heart Failure

INTRODUCTION AND OBJECTIVES

Microparticles are markers for cell activation and apoptosis and could provide valuable information that is not available from clinical data. This study assesses the clinical and biological relationship of small-sized microparticles in different forms of ischemic systolic heart failure and their relation to markers of inflammation and repair.

METHODS

We compared 49 patients with acute heart failure, 39 with stable heart failure and 25 patients with stable coronary artery disease. Small-size microparticles counts were determined by high-resolution flow cytometry. Moreover, 3 different monocyte subpopulations and their expression of inflammatory and adhesive scavenger receptors were analyzed using a conventional flow cytometer.

RESULTS

Endothelial CD144+ microparticle counts were decreased in heart failure groups (P=.008). Annexin V-binding microparticle counts were found increased in heart failure (P=.024) and in patients with lower functional class (P=.013). Platelet CD42b+ microparticle counts positively correlated with left ventricular ejection fraction (P=.006), and annexin V-binding microparticle counts with interleukin-6 levels in stable heart failure (P=.034). Annexin V-binding microparticle counts in the acute status strongly correlated with toll-like receptor-4 expression on all monocyte subsets (all P<.01). Three months after admission with acute heart failure, annexin V-binding microparticle counts were positively correlated with receptors for interleukin-6, CD163 and CD204 (all P<.05).

CONCLUSIONS

Annexin V-binding microparticle counts constitute valuable hallmarks of acute decompensated state in systolic heart failure. The observed relationship between small-size annexin V-binding microparticles and scavenger receptors supports their involvement in the progression of the acute response to injury, and thus their contribution to the pathogenesis of acute decompensated heart failure.

Microparticles as potential biomarkers of cardiovascular disease

Primary prevention of cardiovascular disease is a choice of great relevance because of its impact on health. Some biomarkers, such as microparticles derived from different cell populations, have been considered useful in the assessment of cardiovascular disease. Microparticles are released by the membrane structures of different cell types upon activation or apoptosis, and are present in the plasma of healthy individuals (in levels considered physiological) and in patients with different pathologies. Many studies have suggested an association between microparticles and different pathological conditions, mainly the relationship with the development of cardiovascular diseases. Moreover, the effects of different lipid-lowering therapies have been described in regard to measurement of microparticles. The studies are still controversial regarding the levels of microparticles that can be considered pathological. In addition, the methodologies used still vary, suggesting the need for standardization of the different protocols applied, aiming at using microparticles as biomarkers in clinical practice.