Circulating and platelet-derived microparticles in human blood enhance thrombosis on atherosclerotic plaques

Platelet-, monocyte-derived and tissue factor-carrying circulating microparticles are related to acute myocardial infarction severity

Objective

Circulating microparticles (cMPs) are phospholipid-rich vesicles released from cells when activated or injured, and contribute to the formation of intracoronary thrombi. Tissue factor (TF, CD142) is the main trigger of fibrin formation and TF-carrying cMPs are considered one of the most procoagulant cMPs. Similar types of atherosclerotic lesions may lead to different types of AMI, although the mechanisms behind are unresolved. Therefore, we aimed to investigate the phenotype of cMPs found in plasma of ACS patients and its relation to AMI severity and thrombotic burden.

Methods

In a cross-sectional study, two hundred patients aged 75±4 years were included in the study 2–8 weeks after suffering an AMI. Annexin V positive (AV⁺)-cMPs derived from blood and vascular cells were measured by flow cytometry. Plasma procoagulant activity (TF-PCA) was measured through a chromogenic assay.

Results

STEMI patients (n = 75) showed higher levels of platelet-derived cMPs [CD61⁺/AV⁺, CD31⁺/AV⁺, CD42b⁺/AV⁺ and CD31⁺/CD42b⁺/AV⁺, P = 0.048, 0.038, 0.009 and 0.006, respectively], compared to NSTEMI patients (n = 125). Patients who suffered a heart failure during AMI (n = 17) had increased levels of platelet (CD61⁺)-and monocyte (CD14⁺)-derived cMPs carrying TF (CD142⁺) (P<0.0001 and 0.004, respectively). Additionally, NYHA class III (n = 23) patients showed higher levels of CD142⁺/AV⁺, CD14⁺/AV⁺ and CD14⁺/CD142⁺/AV⁺ cMPs than those in class I/II (P = 0.001, 0.015 and 0.014, respectively). The levels of these cMPs positively correlated with TF-PCA (r≥0.166, P≤0.027, all).

Conclusions

Platelets and monocytes remain activated in AMI patients treated as per guidelines and release cMPs that discriminate AMI severity. Therefore, TF-MPs, and platelet- and monocyte-MPs may reflect thrombotic burden in AMI patients.

Extracellular vesicles in coronary artery disease

Membrane vesicles released in the extracellular space are composed of a lipid bilayer enclosing soluble cytosolic material and nuclear components. Extracellular vesicles include apoptotic bodies, exosomes, and microvesicles (also known previously as microparticles). Originating from different subcellular compartments, the role of extracellular vesicles as regulators of transfer of biological information, acting locally and remotely, is now acknowledged. Circulating vesicles released from platelets, erythrocytes, leukocytes, and endothelial cells contain potential valuable biological information for biomarker discovery in primary and secondary prevention of coronary artery disease. Extracellular vesicles also accumulate in human atherosclerotic plaques, where they affect major biological pathways, including inflammation, proliferation, thrombosis, calcification, and vasoactive responses. Extracellular vesicles also recapitulate the beneficial effect of stem cells to treat cardiac consequences of acute myocardial infarction, and now emerge as an attractive alternative to cell therapy, opening new avenues to vectorize biological information to target tissues. Although interest in microvesicles in the cardiovascular field emerged about 2 decades ago, that for extracellular vesicles, in particular exosomes, started to unfold a decade ago, opening new research and therapeutic avenues. This Review summarizes current knowledge on the role of extracellular vesicles in coronary artery disease, and their emerging potential as biomarkers and therapeutic agents.

Microparticles in Chronic Heart Failure

Heart failure (HF) continues to have a sufficient impact on morbidity, mortality, and disability in developed countries. Growing evidence supports the hypothesis that microparticles (MPs) might contribute to the pathogenesis of the HF development playing a pivotal role in the regulation of the endogenous repair system, thrombosis, coagulation, inflammation, immunity, and metabolic memory phenomenon. Therefore, there is a large body of data clarifying the predictive value of MP numerous in circulation among subjects with HF. Although the determination of MP signature is better than measurement of single MP circulating level, there is not yet close confirmation that immune phenotype of cells produced MPs are important for HF prediction and development. The aim of the chapter is to summarize knowledge regarding the role of various MPs in diagnosis and prognosis of HF. The role of MPs as a delivery vehicle for drugs attenuated cardiac remodeling is considered.

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.

Lipid profile of platelets and platelet-derived microparticles in ovarian cancer

Background

Ovarian cancer patients have a high risk of developing venous thrombosis. The membrane lipid bilayer of platelets and platelet-derived microparticles (PMP) provides a platform for assembly of coagulation proteins and generation of blood clots.

Methods

We compared the lipid composition of platelets and PMPs in patients with ovarian cancer to those in healthy subjects. We used shotgun lipidomics to quantify 12 classes and 177 species of lipids.

Results

We found a significant change in 2 classes of lipids in platelets and PMPs isolated from ovarian cancer patients: higher phosphatidylinositol and lower lyso-phosphatidylcholine. The level of 28 species of lipids was also significantly altered in the direction of an increase in the pro-coagulant and a reduction in the anticoagulant lipids. We found that cancer platelets expressed less lipid phosphate phosphatase 1 (LPP1), a key enzyme in phospholipid biosynthesis pathways, than normal platelets. The reduction in LPP1 might contribute to the changes in the lipid profile of cancer platelets.

Conclusion

Our results support a procoagulant lipid profile of platelets in ovarian cancer patients that can play a role in the increased risk of venous thrombosis in these patients.

General significance

As far as we are aware, our study is the first study on platelet lipidomics in ovarian cancer. The importance of our findings for the future studies are: 1) a similar change in lipid profile of platelets and PMP may be responsible for hypercoagulability in other cancers, and 2) plasma level of high-risk lipids for venous thrombosis may be useful biomarkers.

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Lipid composition of platelet and PMP is altered in ovarian cancer.

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The change in lipid composition of platelet and PMP is in a procoagulant direction.

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LPP1 enzyme is reduced in cancer platelets.

Adropin as a potential marker of enzyme-positive acute coronary syndrome

Aim

Enzyme-positive acute coronary syndrome (EPACS) can cause injury to or death of the heart muscle owing to prolonged ischaemia. Recent research has indicated that in addition to liver and brain cells, cardiomyocytes also produce adropin. We hypothesised that adropin is released into the bloodstream during myocardial injury caused by acute coronary syndrome (ACS), so serum and saliva levels rise as the myocytes die. Therefore, it could be useful to investigate how ACS affects the timing and significance of adropin release in human subjects

Methods

Samples were taken over three days after admission, from 22 EPACS patients and 24 age- and gendermatched controls. The three major salivary glands (submandibular, sublingual and parotid) were immunohistochemically screened for adropin production, and serum and saliva adropin levels were measured by an enzyme-linked immunosorbent assay (ELISA). Salivary gland cells produce and secrete adropin locally.

Results

Serum adropin, troponin I, CK and CK-MB concentrations in the EPACS group became gradually higher than those in the control group up to six hours (p < 0.05), and troponin I continued to rise up to 12 hours after EPACS. The same relative increase in adropin level was observed in the saliva. Troponin I, CK and CK-MB levels started to decrease after 12 hours, while saliva and serum adropin levels started to decrease at six hours after EPACS. In samples taken four hours after EPACS, when the serum adropin value averaged 4.43 ng/ml, the receiver operating characteristic curve showed that the serum adropin concentration indicated EPACS with 91.7% sensitivity and 50% specificity, while when the cut-off adropin value in saliva was 4.12 ng/ml, the saliva adropin concentration indicated EPACS with 91.7% sensitivity and 57% specificity.

Conclusion

In addition to cardiac troponin and CK-MB assays, measurement of adropin level in saliva and serum samples is a potential marker for diagnosing EPACS.

Microparticle Shedding by Erythrocytes, Monocytes and Vascular Smooth Muscular Cells Is Reduced by Aspirin in Diabetic Patients

INTRODUCTION AND OBJECTIVES

Diabetes mellitus is associated with an enhanced risk for cardiovascular disease and its prevalence is increasing. Diabetes induces metabolic stress on blood and vascular cells, promoting platelet activation and vascular dysfunction. The level of vascular cell activation can be measured by the number and phenotype of microparticles found in the circulation. The aim of this study was to investigate the effect of a platelet-inhibitory dose of aspirin on the number and type of microparticles shed to the circulation.

METHODS

Forty-three diabetic patients were enrolled in the study and received a daily dose of 100mg of aspirin for 10 days to cover the average platelet life-span in the circulation. Before and after the intervention period, circulating microparticles were characterized and quantified by flow cytometry.

RESULTS

Type 1 diabetic patients had about twice the number of tissue factor-positive circulating microparticles (derived both from platelets and monocytes) and endothelial-derived E-selectin positive microparticles than type 2 diabetic patients. Aspirin therapy significantly inhibited platelets since cyclooxygenase 1 derived thromboxane generation levels were reduced by 99%. Microparticles derived from erythrocytes, activated monocytes, and smooth muscle cells were significantly reduced after 10 days of aspirin administration.

CONCLUSIONS

These results indicate that: a) vascular and blood cells in type 1 diabetic patients are exposed to more sustained stress shown by their specific microparticle origin and levels; b) aspirin therapy inhibits vascular wall cell activation and microparticle shedding, and c) the effects of aspirin are similar in type 1 and 2 diabetes.

CD142+/CD61+, CD146+ and CD45+ microparticles predict cardiovascular events in high risk patients following a Mediterranean diet supplemented with nuts

Circulating microparticles (cMPs) are small phospholipid-rich microvesicles shed by activated cells that play a pivotal role in cell signalling related to the pathogenesis of atherothrombosis. We aimed to investigate the prognostic value of cMPs released from different vascular cells for cardiovascular event (CVE) presentation in asymptomatic patients at high cardiovascular risk factors under nutritional and pharmacologic treatment. This is a nested case-control study of 50 patients from the five-year follow-up prospective PREDIMED trial enrolled in the nuts arm of the Mediterranean diet (MedDiet-nuts). We randomly selected 25 patients who had suffered a CVE during follow-up and pair-matched them for sex, age, and classical CV risk factors to 25 patients who remained asymptomatic (no-CVE). Total Annexin V-(AV)+ cMPs and cMPs from cells of the vascular compartment were quantified by flow cytometry at baseline and after one year follow-up. MedDiet-nuts and pharmacological treatment neither modified levels nor source of MP shedding in CVE patients. However, no-CVE patients showed 40-86 % decreased total AV+, PAC-1+/AV+, CD61+/AV+, CD142+/CD61+/AV+, CD62P+/AV+, CD146+/AV+, CD63+/AV+ and CD11a+/AV+ cMPs at one year follow-up (p≤0.046, all). CD142+/CD61+/AV+, CD146+/AV+ and CD45+/AV+ cMPs were decreased in no-CVE patients compared to CVE patients. A ROC-curve clustered model for CD142+/CD61+/AV+, CD45+/AV+ and CD146+/AV+ cMPs predicted a future CVE [p<0.0001, AUC=0.805 (0.672 to 0.938)]. In patients at high CV risk profile treated with a controlled MedDiet supplemented with nuts and receiving up-to-date CV drug treatment, reduced cMPs derived from activated platelets, leukocytes and endothelial cells are predictive of protection against CVE within the next four years.

Plasma Levels of Endothelial Microparticles Bearing Monomeric C-reactive Protein are Increased in Peripheral Artery Disease

C-reactive protein (CRP) as an indicator of cardiovascular disease (CVD) has shown limited sensitivity. We demonstrate that two isoforms of CRP (pentameric, pCRP and monomeric, mCRP) present in soluble form or on microparticles (MPs) have different biological effects and are not all measured by clinical CRP assays. The high-sensitivity CRP assay (hsCRP) did not measure pCRP or mCRP on MPs, whereas flow cytometry did. MPs derived from endothelial cells, particularly those bearing mCRP, were elevated in peripheral artery disease (PAD) patients compared to controls. The numbers of mCRP(+) endothelial MPs did not correlate with hsCRP measurements of soluble pCRP, indicating their independent modulation. In controls, statins lowered mCRP(+) endothelial MPs. In a model of vascular inflammation, mCRP induced endothelial shedding of MPs and was proinflammatory, while pCRP was anti-inflammatory. mCRP on endothelial MPs may be both an unmeasured indicator of, and an amplifier of, vascular disease, and its detection might improve risk sensitivity.

Association Between Platelet to Lymphocyte Ratio and Saphenous Vein Graft Disease

Atherosclerosis plays an important role in saphenous vein graft disease (SVGD). Previous trials showed that inflammatory blood cells play a role in this process. The platelet to lymphocyte ratio (PLR) has been proposed as a novel predictor for cardiovascular risk and indicator of atherosclerosis. The aim of this study was to assess the relationship between SVGD and PLR. A total of 220 patients with SVG were enrolled (n = 87 with SVGD and n = 133 with patent SVG). A ≥ 50% stenosis within the SVG was defined as clinically significant. Median PLR (P < .001) and mean platelet volume (MPV; P = .043) were significantly higher in patients with SVGD. Also, PLR showed significantly positive correlation with age of SVG (P < .05). Median age of SVGs was also higher in the SVGD group (P = .025). In multivariate logistic regression analyses, the PLR and MPV were independent predictors of SVGD. Using a cutoff level of 106.3, the PLR predicted SVGD with a sensitivity of 87.4% and a specificity of 80.3%. To the best of our knowledge, this study showed, for the first time, that PLR was independently associated with SVGD. Both PLR and MPV might predict SVGD.

Microparticle Shedding from Neural Progenitor Cells and Vascular Compartment Cells Is Increased in Ischemic Stroke

Purpose

Ischemic stroke has shown to induce platelet and endothelial microparticle shedding, but whether stroke induces microparticle shedding from additional blood and vascular compartment cells is unclear. Neural precursor cells have been shown to replace dying neurons at sites of brain injury; however, if neural precursor cell activation is associated to microparticle shedding, and whether this activation is maintained at long term and associates to stroke type and severity remains unknown. We analyzed neural precursor cells and blood and vascular compartment cells microparticle shedding after an acute ischemic stroke.

Methods

Forty-four patients were included in the study within the first 48h after the onset of stroke. The cerebral lesion size was evaluated at 3–7 days of the stroke. Circulating microparticles from neural precursor cells and blood and vascular compartment cells (platelets, endothelial cells, erythrocytes, leukocytes, lymphocytes, monocytes and smooth muscle cells) were analyzed by flow cytometry at the onset of stroke and at 7 and 90 days. Forty-four age-matched high cardiovascular risk subjects without documented vascular disease were used as controls.

Results

Compared to high cardiovascular risk controls, patients showed higher number of neural precursor cell- and all blood and vascular compartment cell-derived microparticles at the onset of stroke, and after 7 and 90 days. At 90 days, neural precursor cell-derived microparticles decreased and smooth muscle cell-derived microparticles increased compared to levels at the onset of stroke, but only in those patients with the highest stroke-induced cerebral lesions.

Conclusions

Stroke increases blood and vascular compartment cell and neural precursor cell microparticle shedding, an effect that is chronically maintained up to 90 days after the ischemic event. These results show that stroke induces a generalized blood and vascular cell activation and the initiation of neuronal cell repair process after stroke. Larger cerebral lesions associate with deeper vessel injury affecting vascular smooth muscle cells.

Growing thrombi release increased levels of CD235a(+) microparticles and decreased levels of activated platelet-derived microparticles. Validation in ST-elevation myocardial infarction patients

BACKGROUND

Local fluid dynamics and exposed atherosclerotic lesions regulate thrombus formation. Activated cells in the attached thrombi release microparticles to the circulation (circulating microparticles [cMPs]); however, their phenotype is unknown.

OBJECTIVES

To investigate the specific phenotype of the cMPs released by growing thrombi.

METHODS/PATIENTS

cMPs released by thrombi growing in different well-characterized thrombogenic conditions were investigated. cMP contents just before and immediately after perfusion of the thrombogenic surfaces were analyzed by triple-labeling flow cytometry. cMPs were tested for their thrombin-generating capacity. The cMPs identified in the ex vivo perfusion experiments were validated in blood of ST-elevation myocardial infarction (STEMI) patients undergoing thrombectomy and percutaneous coronary intervention. Culprit coronary blood (STEMI-CCB) and peripheral artery blood (STEMI-PAB) were simultaneously analyzed and compared with peripheral artery blood from age-matched controls (C-PAB) and peripheral artery blood from patients who had recovered from acute coronary syndrome (ACS) (pSTEMI-PAB).

RESULTS

The levels of annexin V(+) cMPs significantly increased in blood collected after perfusion of the exposed thrombogenic surfaces. cMP release was directly related to the formed thrombus mass and the plasma procoagulant activity. Post-thrombus blood showed higher thrombin generation potential and contained higher levels of cMPs carrying glycophorin-A (CD235a(+) ; erythrocyte-derived microparticles [ErMPs]) than preperfusion blood (P < 0.05), whereas the levels of cMPs carrying activated and adhesion platelet markers were decreased. STEMI-CCB and STEMI-PAB had significantly higher ErMP levels than control blood (P < 0.005). ErMP levels were also significantly higher in STEMI-PAB than in pSTEMI-PAB, validating the experimental mechanistic studies and suggesting that ErMPs are markers of ongoing coronary thrombosis (C-statistics: 0.950; 95% confidence interval 0.889-1.000; P < 0.001).

CONCLUSION

Glycophorin-A-rich microparticles are released from evolving growing thrombi into the distal perfusing blood, and can be measured in peripheral blood. CD235a(+) cMPs may constitute a novel systemic biomarker of ongoing thrombosis.

Platelet to Lymphocyte Ratio Can be a Predictor of Infarct-Related Artery Patency in Patients With ST-Segment Elevation Myocardial Infarction

Patency of infarct-related artery (IRA) in patients with ST-segment elevation myocardial infarction (STEMI) before primary percutaneous coronary intervention (pPCI) is associated with lower mortality and better clinical outcome. However, there were little data regarding the predictors of IRA patency before pPCI in the setting of STEMI. We aimed to assess the association of platelet to lymphocyte ratio (PLR) with IRA patency in STEMI. A total of 452 patients were enrolled and categorized as occluded or patent IRA. Patency IRA was assessed by the thrombolysis in myocardial infarction (TIMI) flow grade. Blood samples were obtained on admission to calculate PLR. Of all patients, 92 (20.4%) patients revealed pre-pPCI TIMI 3 flow in IRA. The PLR was significantly higher in occluded IRA group (138.4 ± 51.4 vs 95.4 ± 43.5, P < .001). Glucose, troponin I, and neutrophil to lymphocyte ratio (NLR) levels were also higher in occluded IRA group (P < .05). Multivariate regression analysis demonstrated the PLR (odds ratio [OR]: 0.987; 95% confidence interval [CI]: 0.978-0.995, P = .002) and NLR (OR: 0.758; 95% CI: 0.584-0.985, P = .038) on admission as independent predictors of IRA patency. In conclusion, a higher PLR is a powerful and independent predictor of IRA patency in patients with STEMI before pPCI.

Extracellular vesicles as new pharmacological targets to treat atherosclerosis

Extracellular vesicles released by most cell types, include apoptotic bodies (ABs), microvesicles (MVs) and exosomes. They play a crucial role in physiology and pathology, contributing to "cell-to-cell" communication by modifying the phenotype and the function of target cells. Thus, extracellular vesicles participate in the key processes of atherosclerosis from endothelial dysfunction, vascular wall inflammation to vascular remodeling. The purpose of this review is to summarize recent findings on extracellular vesicle formation, structure, release and clearance. We focus on the deleterious and beneficial effects of extracellular vesicles in the development of atherosclerosis. The potential role of extracellular vesicles as biomarkers and pharmacological targets, their innate therapeutic capacity, or their use for novel drug delivery devices in atherosclerotic cardiovascular diseases will also be discussed.

Elevated Level of Circulating Platelet-derived Microparticles in Oral Cancer

Numerous studies have demonstrated that circulating microparticles (MPs) play important roles in a variety of diseases (e.g., atherosclerosis, hypertension, and diabetes), but the association between circulating MPs and oral squamous cell carcinoma (OSCC) remains largely unknown. In the present study, the circulating platelet-derived MPs (PMPs) in 63 patients with OSCC, 22 patients with infected keratocystic odontogenic tumor, and 31 healthy volunteers were characterized and quantified by flow cytometric analysis. The coagulation function of patients with OSCC was correspondingly evaluated. Meanwhile, the inflammation-related cytokines were detected in plasma by enzyme-linked immunosorbent assay and in tumor tissues by immunohistochemistry. Our results showed that the plasma level of circulating PMPs was significantly higher in OSCC patients compared with healthy volunteers and patients with infected keratocystic odontogenic tumor, and they showed positive correlation with the increased level of fibrinogen. Moreover, the coagulation time was significantly shorter after the MPs were added to the MP-free plasma. Most important, the levels of interleukin 6 and tumor necrosis factor α in plasma and tumor tissues were significantly increased in OSCC patients, which were closely correlated with the elevated level of circulating PMPs. In summary, this study suggests that the elevated level of circulating PMPs, showing close correlation with the secretion of inflammation-related factors, may contribute to the increased procoagulant activity in patients with OSCC.

The relationship between platelet to lymphocyte ratio and the clinical outcomes in ST elevation myocardial infarction underwent primary coronary intervention

The platelet to lymphocyte ratio (PLR) has been investigated as a new predictor for cardiovascular risk. The aim of the present study was to investigate the prognostic role admission PLRat admission in predicting in-hospital and early mortality in patients presenting with ST segment elevation myocardial infarction (STEMI). A total of 639 consecutive patients with STEMI who underwent primary percutaneous coronary intervention (PCI) were included. The study population was divided into tertiles on the basis of PLR values at the admission. A high PLR (N = 213) was defined as a value in the upper third tertile (PLR >174.9) and a low PLR (N = 426) was defined as any value in the lower two tertiles (PLR ≤ 174.9). The patients were followed for clinical outcomes for up to 6 months after discharge. In Kaplan-Meier survival analysis, the rate of 6-month all-cause deaths was 7% in the high PLR group versus 3% in the low PLR group (P = 0.03). In multivariate analyses, a significant association was noted between high PLR levels and the adjusted risk of 6-month all-cause deaths (odds ratio = 2.51, 95% confidence interval = 1.058-5.95; P = 0.03). PLR is a readily available clinical laboratory value associated with 6-month all-cause death in patients with STEMI who undergo primary PCI.

Acute and persistent platelet and coagulant activities in atherothrombosis

The potential relevance of murine atherothrombosis models for understanding human disease has been debated in the past. Despite this, in the last decade, many thrombosis studies with atherogenic Apoe(-/-) mice have been performed, which provide novel insight into the molecular mechanisms by which platelet and coagulation processes accomplish acute thrombus formation after plaque disruption in vivo. Support for these mechanisms has come from whole blood flow perfusion studies over plaque material in vitro, which are also reviewed in this study. The main plaque-derived triggers for thrombus formation appear to be collagen and tissue factor, next to bioactive mediators such as prostaglandin E2. The atherothrombotic process relies on collagen- and ADP-receptor-induced platelet activation as well as on thrombin/fibrin generation via the extrinsic and intrinsic coagulation pathways. Less is known of the persistent effects of a thrombus on atherosclerosis progression, but evidence suggests roles herein of activated platelets and ongoing thrombin generation.

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.

Global assays of hemostasis in the diagnostics of hypercoagulation and evaluation of thrombosis risk

Thrombosis is a deadly malfunctioning of the hemostatic system occurring in numerous conditions and states, from surgery and pregnancy to cancer, sepsis and infarction. Despite availability of antithrombotic agents and vast clinical experience justifying their use, thrombosis is still responsible for a lion’s share of mortality and morbidity in the modern world. One of the key reasons behind this is notorious insensitivity of traditional coagulation assays to hypercoagulation and their inability to evaluate thrombotic risks; specific molecular markers are more successful but suffer from numerous disadvantages. A possible solution is proposed by use of global, or integral, assays that aim to mimic and reflect the major physiological aspects of hemostasis process in vitro. Here we review the existing evidence regarding the ability of both established and novel global assays (thrombin generation, thrombelastography, thrombodynamics, flow perfusion chambers) to evaluate thrombotic risk in specific disorders. The biochemical nature of this risk and its detectability by analysis of blood state in principle are also discussed. We conclude that existing global assays have a potential to be an important tool of hypercoagulation diagnostics. However, their lack of standardization currently impedes their application: different assays and different modifications of each assay vary in their sensitivity and specificity for each specific pathology. In addition, it remains to be seen how their sensitivity to hypercoagulation (even when they can reliably detect groups with different risk of thrombosis) can be used for clinical decisions: the risk difference between such groups is statistically significant, but not large.

Thrombosis formation on atherosclerotic lesions and plaque rupture

Atherosclerosis is a silent chronic vascular pathology that is the cause of the majority of cardiovascular ischaemic events. The evolution of vascular disease involves a combination of endothelial dysfunction, extensive lipid deposition in the intima, exacerbated innate and adaptive immune responses, proliferation of vascular smooth muscle cells and remodelling of the extracellular matrix, resulting in the formation of an atherosclerotic plaque. High-risk plaques have a large acellular lipid-rich necrotic core with an overlying thin fibrous cap infiltrated by inflammatory cells and diffuse calcification. The formation of new fragile and leaky vessels that invade the expanding intima contributes to enlarge the necrotic core increasing the vulnerability of the plaque. In addition, biomechanical, haemodynamic and physical factors contribute to plaque destabilization. Upon erosion or rupture, these high-risk lipid-rich vulnerable plaques expose vascular structures or necrotic core components to the circulation, which causes the activation of tissue factor and the subsequent formation of a fibrin monolayer (coagulation cascade) and, concomitantly, the recruitment of circulating platelets and inflammatory cells. The interaction between exposed atherosclerotic plaque components, platelet receptors and coagulation factors eventually leads to platelet activation, aggregation and the subsequent formation of a superimposed thrombus (i.e. atherothrombosis) which may compromise the arterial lumen leading to the presentation of acute ischaemic syndromes. In this review, we will describe the progression of the atherosclerotic lesion along with the main morphological characteristics that predispose to plaque rupture, and discuss the multifaceted mechanisms that drive platelet activation and subsequent thrombus formation. Finally, we will consider the current scientific challenges and future research directions.

Low level of procoagulant platelet microparticles is associated with impaired coagulation and transfusion requirements in trauma patients

BACKGROUND

Following activation, platelets release small vesicles called platelet-derived microparticles (PMPs). PMPs accelerate thrombin generation and thus clot formation at sites of injury by exposing the procoagulant membrane phospholipid phosphatidylserine (PS). The role of PMPs in coagulopathy and hemorrhage following trauma remains elusive. We hypothesized that low levels of PS-positive PMPs (PS + PMPs) would be associated with impaired clot formation.

METHODS

This is a prospective observational study of 210 trauma patients admitted directly to a Level 1 trauma center. Plasma levels of PS + PMPs were determined by flow cytometry. Coagulation status was assessed by rotational thrombelastometry, and impaired clot formation was defined by an α angle less than 63 degrees using the tissue factor-based EXTEM reagent. Transfusion requirement was assessed by number of units of red blood cells (RBCs) transfused within 24 hours of admission; platelet aggregation capacity was evaluated by the Multiplate assay; and injury severity was determined by the Injury Severity Score (ISS).

RESULTS

The median ISS was 17, and blood samples were obtained after a median of 65 minutes following injury. Significantly lower levels of PS + PMPs were found in patients with impaired clot formation (p < 0.001). A low level of PS + PMPs was associated with a higher number of RBCs transfused during the initial 24 hours after admission (p < 0.03) when corrected for risk factors, for example, platelet count, hemoglobin level, and ISS. Platelet aggregation and PS + PMPs did not correlate significantly.

CONCLUSION

Low levels of PMPs were associated with impaired clot formation in trauma patients at admission and also with the number of RBC transfusions. This suggests that PMPs may play an important and not previously investigated role in trauma-induced coagulopathy.

LEVEL OF EVIDENCE

Prognostic study, level III.

Graphene oxide-based biosensor for detection of platelet-derived microparticles: A potential tool for thrombus risk identification

We report here design of a graphene oxide-based electrochemical biosensor for detection of platelet-derived microparticles (PMPs), a major risk factor for arterial pro-thrombotic pathologies like acute myocardial infarction and stroke. Electrodes were fabricated with immobilized layers of graphene oxide and a specific antibody targeted against active conformation of integrin αIIbβ3 on PMP surface. Results showed progressive rise in impedance in Nyquist plots with increasing number of PMPs in analyte. The sensor was highly specific for PMPs and did not identify microparticles originating from other cells. Blood obtained from patients diagnosed with acute myocardial infarction exhibited significantly higher values of impedance, consistent with larger number of circulating PMPs in these patients, as compared to samples from healthy individuals, thus validating biosensor as a specific, sensitive, label-free and cost-effective tool for rapid point-of-care detection of PMPs at bedside. Our biosensor is most ideal for mass population screening programs at periphery-level healthcare units with limited resources. It is aimed at early detection of individuals having higher imminent cardiovascular risk, as well as for routine analysis, which in turn would contribute to better management and survival of screened 'high-risk' subjects.

Roflumilast-induced Local Vascular Injury Is Associated with a Coordinated Proteome and Microparticle Change in the Systemic Circulation in Pigs

Drug-induced vascular injury (DIVI) is commonly associated with phosphodiesterase (PDE) inhibitors. Despite histological characterization, qualified biomarkers for DIVI detection are lacking. We investigated whether a single administration of roflumilast (PDE-IV inhibitor) induces vascular damage and identified novel surrogate biomarkers of acute vascular injury. Pigs received postoperative 250, 375, or 500 μg of roflumilast or placebo/control. After 1.5 hr, coronary reactivity was determined by catheter-based administration of acetylcholine and sodium nitroprusside (SNP) in the coronary sinus. Immunohistochemical analysis of vessel integrity (von Willebrand factor [vWF]) and fibrin(ogen) deposition was performed in the coronary artery and aorta. Peripheral blood was collected for differential proteomics and microparticles analysis. Circulating interleukin (IL)-6 was analyzed. Roflumilast-treated animals displayed higher vasodilation to acetylcholine and SNP versus controls (p < .05). Roflumilast-treated animals showed a dose-dependent (p < .05) decrease in vessel integrity and dose-dependent increase in fibrin deposition forming a continuous layer at roflumilast-500 μg. Peripheral blood of roflumilast-500-μg-treated animals showed increased levels of total and endothelial-derived microparticles and exhibited a coordinated change in proteins kininogen-1, endothelin-1, gelsolin, apolipoprotein A-I, and apolipoprotein-J associated with vascular injury (p < .05 vs. controls). IL-6 remained unaltered. Roflumilast-induced vascular injury can be detected by novel markers in peripheral blood. Validation of these surrogate markers in human samples seems required.

Association between platelet reactivity and circulating platelet-derived microvesicles in patients with acute coronary syndrome

High on-treatment platelet reactivity (HPR) to clopidogrel has been shown to increase the risk of cardiovascular events. Platelet-derived microvesicles (PMVs) may be prothrombotic and contribute to the risk of recurrent events observed in patients with HPR. However, PMVs may also serve as biomarkers and be used to assess platelet function. We investigated the association between platelet responses to clopidogrel (measured by whole blood impedance aggregometry) and circulating PMVs in patients with acute coronary syndrome (ACS). Blood samples were obtained at discharge from 200 patients with ACS who had undergone percutaneous coronary intervention (PCI). All patients were loaded with aspirin and clopidogrel before PCI. ADP-induced whole blood impedance aggregometry and measurement of PMVs were performed. Cut-off values for HPR and other reactivity (i.e. normal on-treatment reactivity, NPR and low on-treatment reactivity, LPR) to clopidogrel were set according to data from large prospective studies. We measured PMVs as phosphatidylserine and CD42a positive vesicles, together with CD62P or CD40L, using flow cytometry. ADP-induced platelet aggregation revealed that approximately 20% of patients had HPR. Levels of PMVs were almost two-fold higher in the HPR group compared with patients without HPR (for both CD42a- and CD62P-positive PMVs, p < 0.01). Furthermore, patients with LPR to clopidogrel had significantly fewer PMVs exposing CD62P than patients with HPR or those with NPR to clopidogrel. Patients with HPR during clopidogrel treatment have elevated levels of circulating PMVs, indicating ongoing platelet activation despite clopidogrel treatment. Moreover, in patients with LPR to clopidogrel, circulating PMV numbers are decreased. Taken together, our data suggest that PMVs are potential biomarkers of antiplatelet responses to clopidogrel. If PMVs also have prognostic value after, ACS should be tested in future studies.

Identification of a circulating microvesicle protein network involved in ST-elevation myocardial infarction

Membrane microvesicles (MVs) are released from activated cells, most notably platelets, into the circulation. They represent an important mode of intercellular communication, and their number is increased in patients with acute coronary syndromes. We present here a differential proteomic analysis of plasma MVs from ST-elevation myocardial infarction (STEMI) patients and stable coronary artery disease (SCAD) controls. The objective was the identification of MVs biomarkers/drug targets that could be relevant for the pathogenesis of the acute event. Proteome analysis was based on 2D-DIGE, and mass spectrometry. Validations were by western blotting in an independent cohort of patients and healthy individuals. A systems biology approach was used to predict protein-protein interactions and their relation with disease. Following gel image analysis, we detected 117 protein features that varied between STEMI and SCAD groups (fold change cut-off ≥2; p<0.01). From those, 102 were successfully identified, corresponding to 25 open-reading frames (ORFs). Most of the proteins identified are involved in inflammatory response and cardiovascular disease, with 11 ORFs related to infarction. Among others, we report an up-regulation of α2-macroglobulin isoforms, fibrinogen, and viperin in MVs from STEMI patients. Interestingly, several of the proteins identified are involved in thrombogenesis (e.g. α2-macroglobulin, and fibrinogen). In conclusion, we provide a unique panel of proteins that vary between plasma MVs from STEMI and SCAD patients and that might constitute a promising source of biomarkers/drug targets for myocardial infarction.

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

This study aimed to examine the mechanisms of cellular activation by small-size platelet microparticles (sPMP) and to present the performance of high-resolution flow cytometry for the analysis of subcellular entities from different origins. Plasma counts of sPMP were analysed in coronary artery disease patients (n = 40) and healthy controls (n = 40). The effect of sPMP and platelet debris (PD) in pathophysiologically relevant doses on platelet and monocyte activation parameters and thrombogenesis was investigated via flow cytometry and thromboelastometry. New generation flow cytometry identifies differences in size, levels and surface molecules of sPMP derived in the absence of stimulus, thrombin activation and platelet disruption. Addition of sPMP resulted in platelet degranulation and P-selectin redistribution to the membrane (P = 0·019) in a dose and time-dependent manner. Blood clotting time decreased after addition of sPMP (P = 0·005), but was not affected by PD. Blocking P-selectin (CD62P) in sPMP markedly reverted the effect on thrombus kinetics (P = 0·035). Exposure to sPMP stimulated monocyte expression of intercellular adhesion molecule-1 (P < 0·03) and decreased monocyte interleukin-6 receptor density (P < 0·01). These results implicate sPMP as a direct source of downstream platelet and monocyte activation. In pathological coronary artery disease conditions, higher levels of sPMP favour a prothrombotic state, partly through P-selectin expression.

Platelet microparticles: detection and assessment of their paradoxical functional roles in disease and regenerative medicine

There is increasing research on and clinical interest in the physiological role played by platelet microparticles (PMPs). PMPs are 0.1-1-μm fragments shed from plasma membranes of platelets that are undergoing activation, stress, or apoptosis. They have a phospholipid-based structure and express functional receptors from platelet membranes. As they are the most abundant microparticles in the blood and they express the procoagulant phosphatidylserine, PMPs likely complement, if not amplify, the functions of platelets in hemostasis, thrombosis, cancer, and inflammation, but also act as promoters of tissue regeneration. Their size and structure make them instrumental in platelet-cell communications as a delivery tool of platelet-borne bioactive molecules including growth factors, other signaling molecules and micro (mi)RNA. PMPs can therefore be a pathophysiological threat or benefit to the cellular environment when interacting with the blood vasculature. There is also increasing evidence that PMP generation is triggered during blood collection, separation into components, and storage, a phenomenon potentially leading to thrombotic and inflammatory side effects in transfused patients. Evaluating PMPs requires strict pre-analytical and analytical procedures to avoid artifactual generation and ensure accurate assessment of the number, size repartitioning, and functional properties. This review describes the physical and functional methods developed for analyzing and quantifying PMPs. It then presents the functional roles of PMPs as markers or triggers of diseases like thrombosis, atherosclerosis, and cancer, and discusses the possible detrimental immunological impact of their generation in blood components. Finally we review the potential function of PMPs in tissue regeneration and the prospects for their use in therapeutic strategies for human health.

Endothelial microparticles as conveyors of information in atherosclerotic disease

Endothelial microparticles (EMPs) are complex submicron membrane-shed vesicles released into the circulation following endothelium cell activation or apoptosis. They are classified as either physiological or pathological, with anticoagulant or pro-inflammatory effects respectively. Endothelial dysfunction caused by inflammation is a key initiating event in atherosclerotic plaque formation. Athero-emboli, resulting from ruptured carotid plaques are a major cause of stroke. Current clinical techniques for arterial assessment, angiography and carotid ultrasound, give accurate information about stenosis but limited evidence on plaque composition, inflammation or vulnerability; as a result, patients with asymptomatic, or fragile carotid lesions, may not be identified and treated effectively. There is a need to discover novel biomarkers and develop more efficient diagnostic approaches in order to stratify patients at most risk of stroke, who would benefit from interventional surgery. Increasing evidence suggests that EMPs play an important role in the pathogenesis of cardiovascular disease, acting as a marker of damage, either exacerbating disease progression or triggering a repair response. In this regard, it has been suggested that EMPs have the potential to act as biomarkers of disease status. In this review, we will present the evidence to support this hypothesis and propose a novel concept for the development of a diagnostic device that could be implemented in the clinic.

A Quest to Identify Prostate Cancer Circulating Biomarkers with a Bench-to-Bedside Potential

Prostate cancer (PCA) is a major health concern in current times. Ever since prostate specific antigen (PSA) was introduced in clinical practice almost three decades ago, the diagnosis and management of PCA have been revolutionized. With time, concerns arose as to the inherent shortcomings of this biomarker and alternatives were actively sought. Over the past decade new PCA biomarkers have been identified in tissue, blood, urine, and other body fluids that offer improved specificity and supplement our knowledge of disease progression. This review focuses on superiority of circulating biomarkers over tissue biomarkers due to the advantages of being more readily accessible, minimally invasive (blood) or noninvasive (urine), accessible for sampling on regular intervals, and easily utilized for follow-up after surgery or other treatment modalities. Some of the circulating biomarkers like PCA3, IL-6, and TMPRSS2-ERG are now detectable by commercially available kits while others like microRNAs (miR-21, -221, -141) and exosomes hold potential to become available as multiplexed assays. In this paper, we will review some of these potential candidate circulating biomarkers that either individually or in combination, once validated with large-scale trials, may eventually get utilized clinically for improved diagnosis, risk stratification, and treatment.

Management of hemorrhage in cardiothoracic surgery

Bleeding is an important issue in cardiothoracic surgery, and about 20% of all blood products are transfused in this clinical setting worldwide. Transfusion practices, however, are highly variable among different hospitals and more than 25% of allogeneic blood transfusions have been considered inappropriate. Furthermore, both bleeding and allogeneic blood transfusion are associated with increased morbidity, mortality, and hospital costs. In the past decades, several attempts have been made to find a universal hemostatic agent to ensure hemostasis during and after cardiothoracic surgery. Most drugs studied in this context have either failed to reduce bleeding and transfusion requirements or were associated with severe adverse events, such as acute renal failure or thrombotic/thromboembolic events and, in some cases, increased mortality. Therefore, an individualized goal-directed hemostatic therapy ("theranostic" approach) seems to be more appropriate to stop bleeding in this complex clinical setting. The use of point-of-care (POC) transfusion and coagulation management algorithms guided by viscoelastic tests such as thromboelastometry/thromboelastography in combination with POC platelet function tests such as whole blood impedance aggregometry, and based on first-line therapy with fibrinogen and prothrombin complex concentrate have been associated with reduced allogeneic blood transfusion requirements, reduced incidence of thrombotic/thromboembolic and transfusion-related adverse events, and improved outcomes in cardiac surgery. This article reviews the current literature dealing with the management of hemorrhage in cardiothoracic surgery based on POC diagnostics and with specific coagulation factor concentrates and its impact on transfusion requirements and patients' outcomes.

Increased levels of circulating microparticles are associated with increased procoagulant activity in patients with cutaneous malignant melanoma

Microparticles (MPs) are known to be increased in various malignancies and are involved in tumor invasion, angiogenesis, coagulation, and metastasis. We investigated the plasma levels of annexin-V MPs (AV(+)MPs), platelet-derived MPs (PMPs), and endothelial-derived MPs (EMPs) in patients with melanoma (n=129) and in healthy controls (n=49). A functional coagulation test STA Procoag-PPL measuring the clotting time was performed on samples containing MPs to evaluate their procoagulant potential. The plasma levels of PMPs, EMPs, and AV(+)MPs were significantly higher, and the clotting time-PPL was significantly lower in melanoma patients than in healthy controls. The plasma levels of PMPs, EMPs, and AV(+)MPs were higher in stage IV than in the other stages of melanoma, but with no significant difference. In addition, we observed an inverse correlation between PMPs, AV(+)MPs, and clotting times. Our data suggest that MPs are involved in the progression of melanoma and may be associated to melanoma-associated thrombogenesis.

Circulating CD45+/CD3+ lymphocyte-derived microparticles map lipid-rich atherosclerotic plaques in familial hypercholesterolaemia patients

Circulating microparticles (cMPs) seem to play important roles in vascular function. Beyond markers of activated cells, cMPs may have potential paracrine functions and influence atherosclerosis. Here, our objective was to characterise a) the abundance and phenotype of cMPs in stable statin-treated heterozygous familial hypercholesterolaemia (FH) patients exposed to life-long hypercholesterolaemia and b) the principal phenotype associated to lipid-rich atherosclerotic plaques in hFH-patients with significant atherosclerotic plaque burden. An age/gender/treatment-matched group of adult-onset non-FH hypercholesterolaemic patients (n=37/group) was comparatively analysed. cMPs were characterised by flow cytometry using annexin-V and cell surface-specific antibodies. Our study shows that LLT-FH patients had higher overall cMP-numbers (p<0.005) than LLT-non-FH patients. Endothelial cell-shed cMPs were also significantly higherin FH (p<0.0005). Within the leukocyte-derived cMP-subpopulations, FH-patients had significantly higher lymphocyte- and monocyte-derived cMP-numbers as well as cMPs carrying leukocyte-activation markers. Normalisation of cMPs by LDL levels did not affect cMP number or phenotype, indicating that the proinflammatory effect was derived from chronic vascular damage. Levels of AV+-total, CD45+-pan-leukocyte and CD45+/CD3+-lymphocyte-derived cMPs were significantly higher in FH-patients with subclinical lipid-rich atherosclerotic plaques than fibrous plaques. Levels of CD45+/CD3+-lymphocyte-MPs above 20,000/ml could differentiate between FH-patients with lipidic or non-lipidic plaques (area under the ROC curve of 0.803, 95%CI: 0.641-0.965, p=0.008). In summary, in this snapshot cross-sectional study cMP concentration and phenotype in FH differed markedly from non-FH hypercholesterolaemia. Patients with life-long high LDL exposure have higher endothelial activation and higher proinflammatory profile, even under current state-of-the-art LLT. cMPs carrying lymphocyte-epitopes appear as markers of lipid-rich atherosclerotic plaques in FH.

Proteomic analysis of venous thromboembolism: an update

Venous thromboembolism is a complex, multifactorial disorder, the pathogenesis of which typically involves a variety of inherited or acquired factors. The multifactorial etiology of this disease and the partial correlation between genotype and prothrombotic phenotype limit greatly the value of genetic analysis in assessing thrombotic risk. The integration of several new 'omics' techniques enables a multifaceted and holistic approach to the study of venous thrombotic processes and pave the way to the search and identification of novel blood biomarkers and/or effectors of thrombus formation that can also be the possible future target of new anticoagulant and thrombolytic therapies for more personalized medicine. This review provides a comprehensive overview of the latest candidate proteomic biomarkers of venous thrombosis and of the proteomics studies relevant to its pathophysiology, some of which seem to confirm the existence of a common physiopathological basis for venous thromboembolism and atherothrombosis.

Platelet-to-lymphocyte ratio: a novel marker for critical limb ischemia in peripheral arterial occlusive disease patients

Background

Platelet-to-Lymphocyte Ratio (PLR) is an easily applicable blood test. An elevated PLR has been associated with poor prognosis in patients with different oncologic disorder. As platelets play a key role in atherosclerosis and atherothrombosis, we investigated PLR and its association with critical limb ischemia (CLI) and other vascular endpoints in peripheral arterial occlusive disease (PAOD) patients.

Methods and Findings

We evaluated 2121 PAOD patients treated at our institution from 2005 to 2010. PLR was calculated and the cohort was categorized into tertiles according to the PLR. An optimal cut-off value for the continuous PLR was calculated by applying a receiver operating curve analysis to discriminate between CLI and non-CLI. In our cohort occurrence of CLI significantly increased with an increase in PLR. As an optimal cut-off value, a PLR of 150 was identified. Two groups were categorized, one containing 1228 patients (PLR≤150) and a second group with 893 patients (PLR>150). CLI was more frequent in PLR>150 patients (410(45.9%)) compared to PLR≤150 patients (270(22.0%)) (p<0.001), as was prior myocardial infarction (51(5.7%) vs. 42(3.5%), p = 0.02). Regarding inflammatory parameters, C-reactive protein (median 7.0 mg/l (3.0–24.25) vs. median 5.0 mg/l (2.0–10.0)) and fibrinogen (median 457 mg/dl (359.0–583.0) vs. 372 mg/dl (317.25–455.75)) also significantly differed in the two patient groups (both p<0.001). Finally, a PLR>150 was associated with an OR of 1.9 (95%CI 1.7–2.1) for CLI even after adjustment for other well-established vascular risk factors.

Conclusions

An increased PLR is significantly associated with patients at high risk for CLI and other cardiovascular endpoints. The PLR is a broadly available and cheap marker, which could be used to highlight patients at high risk for vascular endpoints.

Differences in platelet indices between healthy Han population and Tibetans in China

Introduction

The present data on the evaluation of platelet (PLT) parameters in Chinese Han population and Tibetans are still limited. The objective of this study was to determine the differences in common PLT indices between Han population and Tibetans in China, through a large-scale investigation of healthy people.

Methods

2131 Han people from Chengdu Plain, 1099 Tibetans from Qinghai-Tibet Plateau and 956 Plateau Han migrants were included in this study. All the subjects were healthy people through the health screening. PLT indices were measured with Sysmex XE-2100 and XT-1800i blood cell automatic analyzer.

Results

Compared with Han people in Chendu Plain, Tibetans had higher PLT count (P<0.01) but lower mean platelet volume (MPV), platelet distribution width (PDW) and platelet-large cell ratio (P-LCR) (P<0.01); while Plateau Han migrants had lower PLT count, MPV and P-LCR (P<0.05). When compared with Tibetans, Plateau Han migrants had lower levels of mean PLT count but higher PDW and P-LCR (P<0.05).

Conclusions

There are ethnic differences in PLT indices between Chinese Han population and Tibetans. Based on this finding, it would be reasonable to conduct formal prospective studies to determine the clinical significance of these differences and to explore the effects of genetic background on these indices.

Lipid-lowering therapy with statins reduces microparticle shedding from endothelium, platelets and inflammatory cells

Hyperlipidaemia is a causal factor in the ethiopathogenesis of atherosclerosis. Statins are the cornerstone drug therapy for LDL-cholesterol (LDL-c) lowering, that exert beneficial effects beyond lipid lowering. Circulating microparticles (cMPs), microvesicles released by activated cells into the bloodstream, are markers of vascular and inflammatory cell activation with tentative role in disease progression. However, the role of statins on cMPs seems controversial. We aimed at the evaluation of the effects of lipid-lowering treatment (LLT) on cMP generation in patients in primary prevention of atherosclerosis. A case-control study was conducted in hypercholesterolaemic patients receiving LLT with statins and normocholesterolaemic controls (LLT+ and LLT-, respectively, n=37/group), matched by age, gender and LDL-c levels. cMPs were characterised by flow cytometry using annexin-V and cell-specific antibodies. In LLT+-patients overall numbers of cMPs (p<0.005) were lower than in controls. Levels of cMPs carrying parental cell markers from vascular and circulating cell origin (platelet, endothelial cell, pan-leukocyte and specific-leukocyte subsets) were significantly lower in blood of LLT+ compared to LLT--patients. Moreover, MPs from LLT+-patients had reduced markers of activated platelets (αIIbβ3-integrin), activated inflammatory cells (αM-integrin) and tissue factor. The effect of LLT on cMP shedding was found to be accumulative in years. cMP shedding associated to cardiovascular risk in LLT+-patients. In summary, at similar plasma cholesterol levels patients on statin treatment had a significant lower number of cMPs carrying markers of activated cells. These findings indicate that statins protect against vascular cell activation.