Increased platelet reactivity and circulating monocyte-platelet aggregates in patients with stable coronary artery disease

Non-severe burn injury causes sustained platelet hyperreactivity

Individuals who present to a hospital for treatment of a burn of any magnitude are more frequently hospitalised for ischemic heart disease, even decades after injury. Blood platelets are key mediators of cardiovascular disease. To investigate platelet involvement in post-burn cardiovascular risk, platelet reactivity was assessed in patients at 2- and 6-weeks after non-severe (TBSA < 20%) burn injury, and in a murine model 30 days after 8% TBSA full-thickness burn injury. Platelets were stimulated with canonical agonists and function reported by GPIIb/IIIa PAC1-binding site, CD62P expression, and formation of monocyte-platelet aggregates. In vivo thrombosis in a modified Folts model of vascular injury was assessed. Burn survivors had elevated frequencies of circulating monocyte-platelet aggregates, and platelets were hyperreactive, primarily to collagen stimulation. Burn plasma did not cause hyper-reactivity when incubated with control platelets. Platelets from burn injured mice also demonstrated increased response to collagen peptides but did not show any change in thrombosis following vascular injury. This study demonstrates the persistence of a small but significant platelet hyperreactivity following burn injury. Although our data does not suggest this heightened platelet sensitivity modulates thrombosis following vascular injury, the contribution of sub-clinical platelet hyperreactivity to accelerating atherogenesis merits further investigation.

Crosstalk of platelets with macrophages and fibroblasts aggravates inflammation, aortic wall stiffening, and osteopontin release in abdominal aortic aneurysm

AIMS

Abdominal aortic aneurysm (AAA) is a highly lethal disease with progressive dilatation of the abdominal aorta accompanied by degradation and remodelling of the vessel wall due to chronic inflammation. Platelets play an important role in cardiovascular diseases, but their role in AAA is poorly understood.

METHODS AND RESULTS

The present study revealed that platelets play a crucial role in promoting AAA through modulation of inflammation and degradation of the extracellular matrix (ECM). They are responsible for the up-regulation of SPP1 (osteopontin, OPN) gene expression in macrophages and aortic tissue, which triggers inflammation and remodelling and also platelet adhesion and migration into the abdominal aortic wall and the intraluminal thrombus (ILT). Further, enhanced platelet activation and pro-coagulant activity result in elevated gene expression of various cytokines, Mmp9 and Col1a1 in macrophages and Il-6 and Mmp9 in fibroblasts. Enhanced platelet activation and pro-coagulant activity were also detected in AAA patients. Further, we detected platelets and OPN in the vessel wall and in the ILT of patients who underwent open repair of AAA. Platelet depletion in experimental murine AAA reduced inflammation and ECM remodelling, with reduced elastin fragmentation and aortic diameter expansion. Of note, OPN co-localized with platelets, suggesting a potential role of OPN for the recruitment of platelets into the ILT and the aortic wall.

CONCLUSION

In conclusion, our data strongly support the potential relevance of anti-platelet therapy to reduce AAA progression and rupture in AAA patients.

Antiplatelet drugs do not protect from platelet-leukocyte aggregation in coronary artery disease

BACKGROUND

Despite advances in cardiovascular medicine, coronary artery disease (CAD) remains a leading cause of mortality. Among the pathophysiological features of this condition, platelet-leukocyte aggregates (PLAs) require further attention, either as diagnostic/prognostic disease markers or as potential interventional targets.

OBJECTIVES

In this study, we characterized PLAs in patients with CAD. Primarily, we investigated the association of PLA levels with CAD diagnosis. In addition, the basal levels of platelet activation and degranulation were assessed in patients with CAD and controls, and their correlation with PLA levels was analyzed. Finally, the effect of antiplatelet treatments on circulating PLA numbers, basal platelet activation, and degranulation was studied in patients with CAD.

METHODS

Participants were recruited at the Department of Cardiology of the University Heart and Vascular Centre Hamburg Eppendorf. Among patients admitted with severe chest pain, the diagnosis of CAD was made angiographically, and patients without CAD were used as controls. PLAs, platelet activation, and platelet degranulation were assessed by flow cytometry.

RESULTS

Circulating PLAs and basal platelet degranulation levels were significantly higher in patients with CAD than in controls. Surprisingly, there was no significant correlation between PLA levels and platelet degranulation (or any other measured parameter). In addition, patients with CAD on antiplatelet therapy did not display lower PLA or platelet degranulation levels compared with those in controls.

CONCLUSION

Overall, these data suggest a mechanism of PLA formation that is independent of platelet activation or degranulation and highlights the inefficiency of current antiplatelet treatments for the prevention of basal platelet degranulation and PLA formation.

Platelet-monocyte aggregates: molecular mediators of thromboinflammation

Platelets, key facilitators of primary hemostasis and thrombosis, have emerged as crucial cellular mediators of innate immunity and inflammation. Exemplified by their ability to alter the phenotype and function of monocytes, activated platelets bind to circulating monocytes to form monocyte-platelet aggregates (MPA). The platelet-monocyte axis has emerged as a key mechanism connecting thrombosis and inflammation. MPA are elevated across the spectrum of inflammatory and autoimmune disorders, including cardiovascular disease, systemic lupus erythematosus (SLE), and COVID-19, and are positively associated with disease severity. These clinical disorders are all characterized by an increased risk of thromboembolic complications. Intriguingly, monocytes in contact with platelets become proinflammatory and procoagulant, highlighting that this interaction is a central element of thromboinflammation.

P2Y12 Inhibition Suppresses Proinflammatory Platelet-Monocyte Interactions

BACKGROUND

 Monocyte-platelet aggregates (MPAs) represent the crossroads between thrombosis and inflammation, and targeting this axis may suppress thromboinflammation. While antiplatelet therapy (APT) reduces platelet-platelet aggregation and thrombosis, its effects on MPA and platelet effector properties on monocytes are uncertain.

OBJECTIVES

 To analyze the effect of platelets on monocyte activation and APT on MPA and platelet-induced monocyte activation.

METHODS

 Agonist-stimulated whole blood was incubated in the presence of P-selectin, PSGL1, PAR1, P2Y12, GP IIb/IIIa, and COX-1 inhibitors and assessed for platelet and monocyte activity via flow cytometry. RNA-Seq of monocytes incubated with platelets was used to identify platelet-induced monocyte transcripts and was validated by RT-qPCR in monocyte-PR co-incubation ± APT.

RESULTS

 Consistent with a proinflammatory platelet effector role, MPAs were increased in patients with COVID-19. RNA-Seq revealed a thromboinflammatory monocyte transcriptome upon incubation with platelets. Monocytes aggregated to platelets expressed higher CD40 and tissue factor than monocytes without platelets (p < 0.05 for each). Inhibition with P-selectin (85% reduction) and PSGL1 (87% reduction) led to a robust decrease in MPA. P2Y12 and PAR1 inhibition lowered MPA formation (30 and 21% reduction, p < 0.05, respectively) and decreased monocyte CD40 and TF expression, while GP IIb/IIIa and COX1 inhibition had no effect. Pretreatment of platelets with P2Y12 inhibitors reduced the expression of platelet-mediated monocyte transcription of proinflammatory SOCS3 and OSM. CONCLUSIONS:  Platelets skew monocytes toward a proinflammatory phenotype. Among traditional APTs, P2Y12 inhibition attenuates platelet-induced monocyte activation.

IRGM/Irgm1 deficiency inhibits neutrophil-platelet interactions and thrombosis in experimental atherosclerosis and arterial injury

BACKGROUND

Neutrophil extracellular traps (NETs) closely link inflammation and thrombosis. The immune-related GTPase family M protein (IRGM) and its ortholog of mouse IRGM1 are positively correlated with plaque rupture during atherosclerosis process. However, whether and how IRGM/IRGM1 affects NETs formation and atherosclerotic thrombosis remains unknown, which will further promote the development of antithrombotic treatment tools.

METHODS

The thrombi images, platelet activation makers and NETs makers were detected in the serum of STEMI patients and controls. To futher investigate IRGM/IRGM1 affects NETs formation and atherothrombosis in vivo, ApoE^-/-Irgm1^+/- and ApoE^-/- mice received diets rich in fat and 2.5% FeCl₃ was then used to induce experimental arterial thrombosis in an atherosclerosis background. In vitro, PMA and thrombin were used to stimulate neutrophils and platelets, respectively, and the expression of IRGM/IRGM1 were modified. To reveal the molecular mechanisms, MAPK-cPLA2 signals inhibitors were used.

RESULTS

Serum IRGM was positively correlated with PF4 and neutrophil elastase. Subsequently, Irgm1 deficient mice have a longer occlusion time and lower growth rate. In vitro, as expected, IRGM/Irgm1 deficiency inhibits platelet activation and platelet-neutrophil interaction. More importantly, IRGM promoted NETs production through activating MAPK-cPLA2 signals in PMA stimulated neuropils, whereas inhibiting the production of NETs eliminated the difference in platelet activation and thrombosis caused by IRGM/Irgm1 modification in vivo and vitro. Similarly, inhibition of platelet activation also eliminated the influence of IRGM/Irgm1 modification on NETs production.

CONCLUSIONS

Overall, our data indicate that IRGM/Irgm1 deficiency in neuropils inhibits the intense interaction between neutrophils and platelets, and ultimately inhibits thrombosis.

Extracellular Vesicles and Vascular Inflammation

Vascular inflammation is the most common pathological feature in the pathogenesis of human disease. It is a complex immune process involved with many different types of cells including platelet, monocytes, macrophages, endothelial cells, and others. It is widely accepted that both innate and adaptive immune responses are important for the initiation and progression of vascular inflammation. The cell-cell interaction constitutes an important aspect of those immune responses in the vascular inflammation. Extracellular vesicles (EVs) are nanometer-sized double-layer lipid membrane vesicles released from most types of cells. They have been proved to play critical roles in intercellular communication in the occurrence and development of multisystem diseases. With the advancement of basal medical science, the biological roles of EVs in vascular inflammation have been clearer today. In this chapter, we will summarize the advance progress of extracellular vesicles in regulating vascular inflammation and its potential application in the clinical.

Protease-activated receptors in health and disease

Proteases are signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation; from immune, inflammatory epithelial, and cancer cells; as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure, and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.

Stable CAD patients show higher levels of platelet-borne TGF-β1 associated with a superior pro-inflammatory state than the pro-aggregatory status; Evidence highlighting the importance of platelet-derived TGF-β1 in atherosclerosis

Activated platelets are involved in the atherogenic stage of atherosclerosis, while they can also progress it to atherothrombosis which may cause an ischemic state and organ failure. In general, coronary artery disease (CAD) is considered as common and severe clinical consequence of atherosclerosis, manifesting as a chronic inflammatory condition with the release of platelet mediators, among which the importance of platelet-borne TGF-β1 is not yet well understood. Hence, for the first time, this study aimed to examine platelet level of TGF-β1 (latent/mature) in CAD-patients and its association with the expression of platelet pro-inflammatory molecules. Platelet from stable CAD-patients candidate for CABG and healthy controls were subjected to flowcytometry analysis to evaluate P-selectin and CD40L expressions and PAC-1 binding. Platelet-borne and soluble TGF-β1, both mature/active and latent forms were also examined with western blotting. Higher expression levels of P-selectin and CD40L in patients with CAD than in controls were associated with comparable levels of PAC-1 binding in both groups. Platelet TGF-β1 levels were also significantly higher in patients, while their platelets showed clear bands of mature TGF-β1 that were barely visible in healthy individuals. Soluble TGF-β1 was also higher in patients. Significant correlations between mature/active TGF-β1 and platelet pro-inflammatory markers (P-selectin and CD40L) as well as common indicators of inflammation (CRP and ESR) were observed in CAD patients. In this study, given the insignificant changes in pro-aggregatory potentials in stable CAD, the pro-inflammatory state of platelets may be more involved in disease development and progression. Direct correlations between active platelet-borne TGF-β1 and pro-inflammatory markers with its presence in CAD-patients, which was almost absent in the platelets of healthy individuals, may also underscore the significant contribution of platelet-borne TGF-β1 to the pathogenesis of the disease.

Platelet-leukocyte aggregate formation and inflammation in patients with pulmonary arterial hypertension and CTEPH

Pulmonary hypertension (PH) is defined by increased mean pulmonary artery pressure, and the clinical classification includes five etiologies, of which we investigated subgroup 1, pulmonary arterial hypertension (PAH) and subgroup 4, chronic thrombotic and/or embolic disease (CTEPH). Platelets participate in both innate and adaptive immune responses and could possibly contribute to the suggested systemic inflammation associated with PAH. In this study, we utilized flow cytometry to analyze platelet activation and platelet-monocyte (PMA) and granulocyte (PGA) aggregates in PAH and CTEPH patients and healthy control subjects. The plasma concentration of proinflammatory cytokines was measured by multiplex electrochemiluminescence. Our main finding is that circulating platelets are activated in the circulation and form aggregates with both monocytes and granulocytes in patients with idiopathic PAH (IPAH), associated PAH (APAH) and pulmonary hypertension due to CTEPH. There was a strong correlation between the platelet activation, assessed as P-selectin, and the number of aggregates formed. IL-6, IL-8, IL-10 and TNF-α were increased in all PH subgroups as compared to healthy controls, and PMAs were associated with circulating IL-6, IL-8 and IL-10, whereas PGAs were associated with IL-6. The increased concentrations of platelet-leukocyte aggregates found in PAH/CTEPH patients might thus contribute to the inflammatory state in PH.

Value of the Neutrophil to Lymphocyte Ratio and Platelet to Lymphocyte Ratio in Predicting CPET Performance in Patients with Stable CAD and Recent Elective PCI

Background and Objectives: Functional capacity (FC) assessed via cardiopulmonary exercise testing (CPET) is a novel, independent prognostic marker for patients with coronary artery disease (CAD). Neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) are two readily available predictors of systemic inflammation and cardiovascular event risk, which could be used as cost-effective predictors of poor FC. The purpose of this study was to evaluate the utility of NLR and PLR in predicting poor FC in patients with CAD and recent elective percutaneous coronary intervention (PCI). Materials and Methods: Our cross-sectional retrospective analysis included 80 patients with stable CAD and recent elective PCI (mean age 55.51 ± 11.83 years, 71.3% male) who were referred to a cardiovascular rehabilitation center from January 2020 to June 2021. All patients underwent clinical examination, cardiopulmonary exercise testing on a cycle ergometer, transthoracic echocardiography and standard blood analysis. Results: Patients were classified according to percent predicted oxygen uptake (% VO2 max) in two groups—poor FC (≤70%, n = 35) and preserved FC (>70%, n = 45). There was no significant difference between groups regarding age, gender ratio, presence of associated comorbidities, left ventricular ejection fraction and NLR. PLR was higher in patients with poor FC (169.8 ± 59.3 vs. 137.4 ± 35.9, p = 0.003). A PLR cut-off point of 139 had 74% sensitivity and 60% specificity in predicting poor FC. After multivariate analysis, PLR remained a significant predictor of poor functional status. Conclusions: Although CPET is the gold standard test for assessing FC prior to cardiovascular rehabilitation, its availability remains limited. PLR, a cheap and simple test, could predict poor FC in patients with stable CAD and recent elective PCI and help prioritize referral for cardiovascular rehabilitation in high-risk patients.

Pathophysiology and mechanisms of Acute Coronary Syndromes: athero-thrombosis, immune-inflammation and beyond

INTRODUCTION

The pathophysiology of atherosclerosis and its acute complications, such as the Acute Coronary Syndromes (ACS), is continuously under investigation. Immunity and inflammation seem to play a pivotal role in promoting formation and grow of atherosclerotic plaques. At the same time, plaque rupture followed by both platelets' activation and coagulation cascade induction lead to intracoronary thrombus formation. Although these phenomena might be considered responsible of about 90% of ACS, in up to 5-10% of acute syndromes a non-obstructive coronary artery disease (MINOCA) might be documented. This paper gives an overview on athero-thrombosis and immuno-inflammation processes involved in ACS pathophysiology also emphasizing the pathological mechanisms potentially involved in MINOCA.

AREAS COVERED

The relationship between immuno-inflammation and atherothrombosis is continuously updated by recent findings. At the same time, pathophysiology of MINOCA still remains a partially unexplored field, stimulating the research of potential links between these two aspects of ACS pathophysiology.

EXPERT OPINION

Pathophysyiology of ACS has been extensively investigated; however, several grey areas still remain. MINOCA represents one of these areas. At the same time, many aspects of immune-inflammation processes are still unknown. Thus, research should be continued to shed a brighter light on both these sides of "ACS" moon.

Growth Differentiation Factor-15 Correlates Inversely with Protease-Activated Receptor-1-Mediated Platelet Reactivity in Patients with Left Ventricular Assist Devices

Growth differentiation factor (GDF)-15 inhibits platelet activation, prevents thrombus formation, and has been linked to bleeding events. This was a prospective study including 51 left-ventricular assist device (LVAD) patients on aspirin and phenprocoumon. Platelet surface expression of activated glycoprotein (GP) IIb/IIIa was assessed by flow cytometry, and platelet aggregation was measured by multiple electrode aggregometry (MEA) in response to arachidonic acid (AA), adenosine diphosphate (ADP), and thrombin receptor-activating peptide (TRAP), a protease-activated-receptor-1 (PAR-1) agonist. GDF-15 was determined with a commercially-available assay. There was a trend towards an inverse correlation of GDF-15 with activated GPIIb/IIIa in response to TRAP (r = −0.275, p = 0.0532) but not in response to AA and ADP. Moreover, GDF-15 correlated with MEA TRAP (r = −0.326, p = 0.0194), whereas it did not correlate with MEA ADP and MEA AA. In a second step, GDF-15 levels in the fourth quartile were defined as high GDF-15. Patients with high GDF-15 showed significantly lower TRAP-inducible platelet aggregation by MEA compared to patients in the first quartile (63 AU vs. 113 AU, p = 0.0065). In conclusion, in LVAD patients receiving state-of-the-art antithrombotic therapy, GDF-15 correlates inversely with residual platelet reactivity via PAR-1.

Beyond Hemostasis: Platelet Innate Immune Interactions and Thromboinflammation

There is accumulating evidence that platelets play roles beyond their traditional functions in thrombosis and hemostasis, e.g., in inflammatory processes, infection and cancer, and that they interact, stimulate and regulate cells of the innate immune system such as neutrophils, monocytes and macrophages. In this review, we will focus on platelet activation in hemostatic and inflammatory processes, as well as platelet interactions with neutrophils and monocytes/macrophages. We take a closer look at the contributions of major platelet receptors GPIb, α_IIbβ₃, TLT-1, CLEC-2 and Toll-like receptors (TLRs) as well as secretions from platelet granules on platelet-neutrophil aggregate and neutrophil extracellular trap (NET) formation in atherosclerosis, transfusion-related acute lung injury (TRALI) and COVID-19. Further, we will address platelet-monocyte and macrophage interactions during cancer metastasis, infection, sepsis and platelet clearance.

Comprehensive Landscape of Modules-Dysregulated Functions Reveals a Profound Role of ceRNAs in Coronary Heart Disease

Coronary heart disease (CHD) is one of the most common severe cardiovascular diseases. Competitive endogenous RNAs (ceRNA) play critical roles in complex diseases. However, our understanding of the dysregulated functions of ceRNAs in CHD remains limited. Here, we systematically analyzed the alterations of ceRNAs and identified the specific functions based on dysregulated modules from the ceRNA network. A total of 2457 significantly differential expressed genes and 212 differential expressed lncRNAs were identified. We got 76679 regulator relationship between different expression genes and miRNAs and 336 regulator relationship between differential expressed lncRNAs and miRNAs. We constructed the ceRNA network and selected five dysregulated modules. Furthermore, CHD specific functions based on dysregulated modules from the ceRNA network were identified, including histone acetylation, platelet degranulation, cAMP-dependent protein kinase complex, xenobiotic transport and so on. Our results will provide novel insight for a better understanding of the mechanism of ceRNAs and facilitate the identification of novel diagnostic and therapeutic biomarkers in CHD.

Neutrophil-Platelet Interactions as Novel Treatment Targets in Cardiovascular Disease

Neutrophils and platelets are among the most abundant cell types in peripheral blood and characterized by high plasticity and a readily available reservoir of surface proteins and secretable granule contents. Receptor-mediated activation and granule release predispose both cell types for rapid responses to various stimuli. While neutrophils provide the first line of defense to microbial infections and platelets are known for their aggregatory functions in hemostasis and thrombosis, research of the past decade has highlighted that both cell types jointly shape local and systemic immune responses and clot formation alike. Concomitant activation of neutrophils and platelets has been observed in a variety of cardiovascular diseases, including arterial and venous thrombosis, atherosclerosis as well as myocardial infarction and ischemia-reperfusion injury. In this review, we describe the mechanisms by which neutrophils and platelets interact physically, how release of granule contents and soluble molecules by either cell type affects the other and how this mutual activation supports the efficacy of immune responses. We go on to describe how activated platelets contribute to host defense by triggering neutrophil extracellular trap (NET) formation in a process termed immunothrombosis, which in turn promotes local platelet activation and coagulation. Further, we review current evidence of hazardous overactivation of either cell type and their respective role in cardiovascular disease, with a focus on thrombosis, myocardial infarction and ischemia-reperfusion injury, and describe how neutrophils and platelets shape thromboinflammation in COVID-19. Finally, we provide an overview of therapeutic approaches targeting neutrophil-platelet interactions as novel treatment strategy in cardiovascular disease.

Platelet-Leucocyte Aggregates as Novel Biomarkers in Cardiovascular Diseases

Simple Summary

Cardiovascular diseases are the most common cause of death worldwide. Hence, novel biomarkers are urgently needed to improve diagnosis and treatment. Platelet–leucocyte aggregates are conglomerates of platelets and leucocytes and are widely investigated as biomarkers in cardiovascular diseases. Platelet–leucocytes aggregates are present in health, but increase in patients with cardiovascular risk factors and acute or stable coronary syndromes, making them a potential diagnostic marker. Moreover, platelet–leucocyte aggregates predict outcomes after surgery or percutaneous treatment and could be used to monitor antiplatelet therapy. Emerging data about the participation of platelet–leucocyte aggregates in cardiovascular diseases pathogenesis make them an attractive target for novel therapies. Furthermore, simple detection with conventional flow cytometry provides accurate and reproducible results, although requires specific sample handling. The main task for the future is to determine the standardized protocol to measure blood concentrations of platelet–leucocyte aggregates and subsequently establish their normal range in health and disease.

Abstract

Platelet–leucocyte aggregates (PLA) are a formation of leucocytes and platelets bound by specific receptors. They arise in the condition of sheer stress, thrombosis, immune reaction, vessel injury, and the activation of leukocytes or platelets. PLA participate in cardiovascular diseases (CVD). Increased levels of PLA were revealed in acute and chronic coronary syndromes, carotid stenosis cardiovascular risk factors. Due to accessible, available, replicable, quick, and low-cost quantifying using flow cytometry, PLA constitute an ideal biomarker for clinical practice. PLA are promising in early diagnosing and estimating prognosis in patients with acute or chronic coronary syndromes treated by percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). PLA were also a reliable marker of platelet activity for monitoring antiplatelet therapy. PLA consist also targets potential therapies in CVD. All of the above potential clinical applications require further studies to validate methods of assay and proof clinical benefits.

Platelet-to-hemoglobin ratio as a valuable predictor of long-term all-cause mortality in coronary artery disease patients with congestive heart failure

BACKGROUND

The platelet-to-hemoglobin ratio (PHR) has emerged as a prognostic biomarker in coronary artery disease (CAD) patients after PCI but not clear in CAD complicated with congestive heart failure (CHF). Hence, we aimed to assess the association between PHR and long-term all-cause mortality among CAD patients with CHF.

METHODS

Based on the registry at Guangdong Provincial People's Hospital in China, we analyzed data of 2599 hospitalized patients who underwent coronary angiography (CAG) and were diagnosed with CAD complicated by CHF from January 2007 to December 2018. Low PHR was defined as ˂ 1.69 (group 1) and high PHR as ≥ 1.69 (group 2). Prognosis analysis was performed using Kaplan-Meier method. To assess the association between PHR and long-term all-cause mortality, a Cox-regression model was fitted.

RESULTS

During a median follow-up of 5.2 (3.1-7.8) years, a total of 985 (37.9%) patients died. On the Kaplan-Meier analysis, patients in high PHR group had a worse prognosis than those in low PHR group (log-rank, p = 0.0011). After adjustment for confounders, high PHR was correlated with an increased risk of long-term all-cause mortality in CAD patients complicated with CHF. (adjusted hazard ratio [aHR], 1.31; 95% confidence interval [CI], 1.13-1.52, p < 0.0001).

CONCLUSION

Elevated PHR is correlated with an increased risk of long-term all-cause mortality in CAD patients with CHF. These results indicate that PHR may be a useful prognostic biomarker for this population. Meanwhile, it is necessary to take effective preventive measures to regulate both hemoglobin levels and platelet counts in this population.

Increased Platelet-CD4+ T Cell Aggregates Are Correlated With HIV-1 Permissiveness and CD4+ T Cell Loss

Chronic HIV-1 infection is associated with persistent inflammation, which contributes to disease progression. Platelet-T cell aggregates play a critical role in maintaining inflammation. However, the phenotypic characteristics and clinical significance of platelet-CD4+ T cell aggregates remain unclear in different HIV-infected populations. In this study, we quantified and characterized platelet-CD4+ T cell aggregates in the peripheral blood of treatment-naïve HIV-1-infected individuals (TNs), immunological responders to antiretroviral therapy (IRs), immunological non-responders to antiretroviral therapy (INRs), and healthy controls (HCs). Flow cytometry analysis and immunofluorescence microscopy showed increased platelet-CD4+ T cell aggregate formation in TNs compared to HCs during HIV-1 infection. However, the frequencies of platelet-CD4+ T cell aggregates decreased in IRs compared to TNs, but not in INRs, which have shown severe immunological dysfunction. Platelet-CD4+ T cell aggregate frequencies were positively correlated with HIV-1 viral load but negatively correlated with CD4+ T cell counts and CD4/CD8 ratios. Furthermore, we observed a higher expression of CD45RO, HIV co-receptors, HIV activation/exhaustion markers in platelet-CD4+ T cell aggregates, which was associated with HIV-1 permissiveness. High levels of caspase-1 and caspase-3, and low levels of Bcl-2 in platelet-CD4+ T cell aggregates imply the potential role in CD4+ T cell loss during HIV-1 infection. Furthermore, platelet-CD4+ T cell aggregates contained more HIV-1 gag viral protein and HIV-1 DNA than their platelet-free CD4+ T cell counterparts. The platelet-CD4+ T cell aggregate levels were positively correlated with plasma sCD163 and sCD14 levels. Our findings demonstrate that platelet-CD4+ T cell aggregate formation has typical characteristics of HIV-1 permissiveness and is related to immune activation during HIV-1 infection.

Platelet-lymphocyte ratio as a new predictor of in-hospital mortality in cardiac intensive care unit patients

It has been discovered that both inflammation and platelet aggregation could cause crucial effect on the occurrence and development of cardiovascular diseases. As a combination of platelet and lymphocyte, platelet-lymphocyte ratio (PLR) was proved to be correlated with the severity as well as prognosis of cardiovascular diseases. Exploring the relationship between PLR and in-hospital mortality in cardiac intensive care unit (CICU) patients was the purpose of this study. PLR was calculated by dividing platelet count by lymphocyte count. All patients were grouped by PLR quartiles and the primary outcome was in-hospital mortality. The independent effect of PLR was determined by binary logistic regression analysis. The curve in line with overall trend was drawn by local weighted regression (Lowess). Subgroup analysis was used to determine the relationship between PLR and in-hospital mortality in different subgroups. We included 5577 CICU patients. As PLR quartiles increased, in-hospital mortality increased significantly (Quartile 4 vs. Quartile 1: 13.9 vs. 8.3, P < 0.001). After adjusting for confounding variables, PLR was proved to be independently associated with increased risk of in-hospital mortality (Quartile 4 vs. Quartile 1: OR 95% CI 1.55, 1.08–2.21, P = 0.016, P for trend < 0.001). The Lowess curves showed a positive relationship between PLR and in-hospital mortality. The subgroup analysis revealed that patients with low Acute Physiology and Chronic Health Evaluation IV (APACHE IV) or with less comorbidities had higher risk of mortality for PLR. Further, PLR quartiles had positive relation with length of CICU stay (Quartile 4 vs. Quartile 1: 2.7, 1.6–5.2 vs. 2.1, 1.3–3.9, P < 0.001), and the length of hospital stay (Quartile 4 vs. Quartile 1: 7.9, 4.6–13.1 vs. 5.8, 3.3–9.8, P < 0.001). PLR was independently associated with in-hospital mortality in CICU patients.

P2Y12 receptor blockers are anti-inflammatory drugs inhibiting both circulating monocytes and macrophages including THP-1 cells

P₂Y₁₂ blockade improves patient outcomes after myocardial infarction. As well as antithrombotic effects, anti-inflammatory effects may contribute to this beneficial clinical outcome. Here we aimed to identify potential anti-inflammatory effects of P₂Y₁₂ receptor blockers on monocytes and macrophages. Using flow cytometry, migration assays, flow chambers and RNA microarrays, we investigated the effects of adenosine diphosphate (ADP) and P₂Y₁₂ receptor blockers on blood monocytes, THP-1 monocytes and THP-1 monocytes after differentiation to macrophages. P₂Y₁₂ -expressing platelets can form aggregates with monocytes in circulating blood. Mediated by platelets, ADP results in activation of the integrin receptor Mac-1 on blood monocytes, as detected by the conformation-specific single-chain antibody MAN-1. Via the same association with platelets, THP-1 monocyte adhesion to the endothelial intercellular adhesion molecule 1 (ICAM-1) is induced by ADP. P₂Y₁₂ receptor blockers prevent these ADP effects on monocytes. Interestingly, in contrast to THP-1 monocytes, THP-1 monocytes, after differentiation to macrophages, directly expressed the P₂Y₁₂ receptor and consequently ADP was found to be a potent chemoattractant. Again, P₂Y₁₂ receptor blockers antagonised this effect. Accordingly, stimulation of THP-1 macrophages with ADP caused a substantial change in gene expression pattern and upregulation of several genes associated with inflammation and atherogenesis. These data establish novel anti-inflammatory effects of P₂Y₁₂ receptor blockers on monocytes and macrophages, which are expected to contribute to cardiovascular risk reduction.

Platelet-Like Fusogenic Liposome-Mediated Targeting Delivery of miR-21 Improves Myocardial Remodeling by Reprogramming Macrophages Post Myocardial Ischemia-Reperfusion Injury

Inflammatory modulations focusing on macrophage phenotype are promising candidates to promote better cardiac healing post myocardial ischemia-reperfusion (MI/R) injury. However, the peak of monocyte/macrophage recruitment is later than the time when enhanced permeability and retention effect disappears, which greatly increases the difficulty of reprogramming macrophages through systemic administration. Meanwhile, the inability of nanomaterials to release their contents to specific intracellular locations through reasonable cellular internalization pathways is another obstacle to achieving macrophage reprogramming. Here, inspired by the increase in circulating platelet-monocyte aggregates in patients' post-MI/R and the high efficiency of fusogenic liposomes to deliver contents to the cytoplasm of target cells, a platelet-like fusogenic liposome (PLPs) is constructed. Under the coating of PLPs, mesoporous silica nanospheres with a payload of miR-21, an anti-inflammatory agent, can be specifically delivered to inflammatory monocytes in the blood circulation of MI/R induced mice. Then it directly enters the cytoplasm of monocytes through membrane fusion, thereby realizing the reparative reprogramming of the inflamed macrophages derived from it. In vivo administration of the resulting formula can effectively preserve the cardiac function of mice undergone MI/R. Minimal invasiveness and biological safety make this nano-platform a promising approach of immunotherapy.

Human monocytes store and secrete preformed CCL5, independent of de novo protein synthesis

Monocytes are a subset of circulating peripheral blood mononuclear cells with diverse roles in immunity, including sentinel roles in cytokine secretion. Conventionally, cytokines require an inductive stimulus for their expression and secretion, resulting in a time lag from the time of stimulation to when the proteins are packaged and secreted. Because cytokines are the main communicators in the immune system, their temporal expression is a key factor in coordinating responses to efficiently resolve infection. Herein, we identify that circulating human monocytes contain preformed cytokines that are stored intracellularly, in both resting and activated states. Having preformed cytokines bypasses the time lag associated with de novo synthesis, allowing monocytes to secrete immune mediators immediately upon activation or sensing of microbe-associated molecular patterns. We demonstrate here that, out of several cytokines evaluated, human monocytes contain a previously undescribed reservoir of the preformed chemokine CCL5. Furthermore, we showed that CCL5 could be secreted from monocytes treated with the protein synthesis inhibitor (cycloheximide) and Golgi blocker (brefeldin A). We examined the possibility for uptake of extracellular CCL5 from platelet aggregates and observed no significant levels of platelet binding to our enriched monocyte preparations, indicating that the source of preformed CCL5 was not from platelets. Preformed CCL5 was observed to be distributed throughout the cytoplasm and partially colocalized with CD63+ and Rab11A+ membranes, implicating endosomal compartments in the intracellular storage and trafficking of CCL5.

Platelet Activation and Plasma Levels of Furin Are Associated With Prognosis of Patients With Coronary Artery Disease and COVID-19

[Figure: see text].

Extracellular vesicles from monocyte/platelet aggregates modulate human atherosclerotic plaque reactivity

Extracellular vesicles (EVs) are emerging as key players in different stages of atherosclerosis. Here we provide evidence that EVs released by mixed aggregates of monocytes and platelets in response to TNF‐α display pro‐inflammatory actions on endothelial cells and atherosclerotic plaques. Tempering platelet activation with Iloprost, Aspirin or a P2Y₁₂ inhibitor impacted quantity and phenotype of EV produced. Proteomics of EVs from cells activated with TNF‐α alone or in the presence of Iloprost revealed a distinct composition, with interesting hits like annexin‐A1 and gelsolin. When added to human atherosclerotic plaque explants, EVs from TNF‐α stimulated monocytes augmented release of cytokines. In contrast, EVs generated by TNF‐α together with Iloprost produced minimal plaque activation. Notably, patients with coronary artery disease that required percutaneous coronary intervention had elevated plasma numbers of monocyte, platelet as well as double positive EV subsets. In conclusion, EVs released following monocyte/platelet activation may play a potential role in the development and progression of atherosclerosis. Whereas attenuating platelet activation modifies EV composition released from monocyte/platelet aggregates, curbing their pro‐inflammatory actions may offer therapeutic avenues for the treatment of atherosclerosis.

Monocyte platelet aggregates in children with Kawasaki disease- a preliminary study from a tertiary care centre in North-West India

BACKGROUND

Platelet activation is an integral part of pathogenesis of Kawasaki disease (KD). However, there is paucity of literature on flow-cytometry based assessment of platelet activation in KD. We aimed to analyse monocyte-platelet aggregates (MPAs), one of the sensitive markers for platelet activation, by flow cytometry in children with KD.

FINDINGS

In this single-centre prospective study, we have enrolled 14 children with KD and results were compared with age-matched febrile (n = 15) and healthy (n = 13) controls. After gating monocytes in side-scatter plot, MPAs were identified based on CD14 and CD41 expression. Two (2) ml of blood samples for children with KD were collected at 3 phases of illness- acute stage before start of intravenous immunoglobulin or aspirin, 24 h after completion of IVIg infusion, and 3 months after acute episode of KD. Children with KD had a significantly higher MPA% values [Median (IQR)- 41.3% (26.6, 52.7)] when compared with febrile [Median (IQR)- 5.98% (2.98-9.72)] and normal [Median (IQR)- 4.48% (2.57-5.59)] controls, p<0.01. On follow-up, the MPA% showed a gradual decline in children with KD, but even at 3 months, the value [Median (IQR)- 7.55% (4.15-14.6)] was higher compared to healthy controls [Median (IQR)- 4.48% (2.57-5.59)].

CONCLUSIONS

Our results suggest that MPA% was significantly elevated in acute stages in children with KD and activated platelets may continue to persist even after systemic inflammation has subsided. Future studies are warranted whether objective evidence of platelet activation may guide the use of immunomodulatory and anti-platelet therapy in KD.

Anti-platelet Drug-loaded Targeted Technologies for the Effective Treatment of Atherothrombosis

Atherothrombosis results from direct interaction between atherosclerotic plaque and arterial thrombosis and is the most common type of cardiovascular disease. As a long term progressive disease, atherosclerosis frequently results in an acute atherothrombotic event through plaque rupture and platelet-rich thrombus formation. The pathophysiology of atherothrombosis involves cholesterol accumulation endothelial dysfunction, dyslipidemia, immuno-inflammatory, and apoptotic aspects. Platelet activation and aggregation is the major cause for stroke because of its roles, including thrombus, contributing to atherosclerotic plaque, and sealing off the bleeding vessel. Platelet aggregates are associated with arterial blood pressure and cardiovascular ischemic events. Under normal physiological conditions, when a blood vessel is damaged, the task of platelets within the circulation is to arrest the blood loss. Antiplatelet inhibits platelet function, thereby decreasing thrombus formation with complementary modes of action to prevent atherothrombosis. In the present scientific scenario, researchers throughout the world are focusing on the development of novel drug delivery systems to enhance patient's compliance. Immediate responding pharmaceutical formulations become an emerging trend in the pharmaceutical industries with better patient compliance. The proposed review provides details related to the molecular pathogenesis of atherothrombosis and recent novel formulation approaches to treat atherothrombosis with particular emphasis on commercial formulation and upcoming technologies.

Relationship Between Composition of Fatty Acid in Platelet Phospholipid Membrane and Markers of Oxidative Stress in Healthy Men and Men After a Myocardial Infarction

Background

Oxidative stress (OS) is known to be extremely damaging for phospholipids in cell membranes, especially their polyunsaturated fatty acids (PUFAs). OS is known to be associated with increased platelet activation and thrombosis, which lead to cardiovascular lesions. The aim of this study was to investigate how changes in the composition of fatty acids (FAs) in the platelet phospholipid membrane correlate with OS in healthy men and in men who have experienced a myocardial infarction (post-MI men).

Material/Methods

FA methyl esters from the platelet phospholipid membrane of 79 apparently healthy and 20 post-MI men were identified using gas chromatography/mass spectrometry. Malondialdehyde (MDA) was measured in the blood serum using high-performance liquid chromatography, and platelet-white blood cell aggregates (PWAs) were analysed based on whole-blood flow cytometry. The composition of platelet membrane FAs was compared to MDA concentration (μg/l) and the percentage of PWA formation between healthy men and individuals who had suffered a myocardial infarction (MI).

Results

Statistically, post-MI patients had a significantly higher concentration of blood serum MDA than those in the control group (p=0.000). The level of PUFAs was also higher in the platelet phospholipid membrane of post-MI patients than in healthy individuals (p=0.016). However, the percentage of PWA formation was lower in patients compared with the control group (p<0.05).

Conclusions

A higher level of blood serum MDA concentration due to OS stimulates platelets to incorporate more PUFAs into the phospholipid membrane, thereby affecting platelet activation. This may lead the individual to develop cardiovascular diseases in the future.

Circulating MicroRNAs and Monocyte-Platelet Aggregate Formation in Acute Coronary Syndrome

BACKGROUND

 Monocyte-platelet aggregates (MPAs) are a sensitive marker of in vivo platelet activation in acute coronary syndrome (ACS) and associated with clinical outcomes. MicroRNAs (miRs) play an important role in the regulation of platelet activation, and may influence MPA formation. Both, miRs and MPA, could be influenced by the type of P2Y12 inhibitor.

AIM

 To study the association of platelet-related miRs with MPA formation in ACS patients on dual antiplatelet therapy (DAPT), and to compare miRs and MPA levels between prasugrel- and ticagrelor-treated patients.

METHODS AND RESULTS

 We analyzed 10 circulating platelet-related miRs in 160 consecutive ACS patients on DAPT with low-dose aspirin and either prasugrel (n = 80) or ticagrelor (n = 80). MPA formation was measured by flow cytometry without addition of platelet agonists and after simulation with the toll-like receptor (TLR)-1/2 agonist Pam3CSK4, adenosine diphosphate (ADP), or arachidonic acid (AA). In multivariate regression analyses, we identified miR-21 (β = 9.50, 95% confidence interval [CI]: 1.60-17.40, p = 0.019) and miR-126 (β = 7.50, 95% CI: 0.55-14.44, p = 0.035) as independent predictors of increased MPA formation in vivo and after TLR-1/2 stimulation. In contrast, none of the investigated miRs was independently associated with MPA formation after stimulation with ADP or AA. Platelet-related miR expression and MPA formation did not differ significantly between prasugrel- and ticagrelor-treated patients.

CONCLUSION

 Platelet-related miR-21 and miR-126 are associated with MPA formation in ACS patients on DAPT. miRs and MPA levels were similar in prasugrel- and ticagrelor-treated patients.

Hemostatic changes by thrombopoietin-receptor agonists in immune thrombocytopenia patients

Thrombopoietin receptor agonist (TPO-RA) treatment increases the thrombosis rate in immune thrombocytopenia (ITP). We hypothesize that TPO-RAs influence platelet function, global and secondary hemostasis and/or fibrinolysis. A systematic review was performed. If possible, data were compared between responders (relevant increase in platelet count), and non-responders. Twelve observational studies with 305 patients were included (responders (127/150 (85%))). There were indications that TPO-RA treatment enhanced platelet function, with respect to platelet-monocyte aggregates, soluble P-selectin, GPVI expression, and adhesion under flow. Studies addressing global and secondary hemostasis and fibrinolysis were scarce. Overall, no changes were found during TPO-RA treatment, apart from an accelerated clot formation and conflicting data on levels of plasminogen activator inhibitor (PAI)-1. The parameters that increased have previously been associated with thrombosis in other patient groups, and might contribute to the increased rate of thrombosis observed in TPO-RA-treated ITP patients.

Extracellular tyrosyl-tRNA synthetase cleaved by plasma proteinases and stored in platelet α-granules: Potential role in monocyte activation

BACKGROUND

Tyrosyl-tRNA synthetase (YRS) belongs to the family of enzymes that catalyzes the tRNA aminoacylation reaction for protein synthesis, and it has been recently shown to exert noncanonical functions. Although database results indicate extremely low levels of YRS mRNA in platelets, YRS protein is abundantly present. The source of YRS in platelets, as well as the physiological role of platelet-stored YRS, remains largely unknown.

OBJECTIVES

To clarify how YRS accumulates in platelets and determine the potential role of platelet-stored YRS.

METHODS

Recombinant YRS proteins with epitope tags were prepared and tested in vitro for proteolytic cleavage in human plasma. Fluorescent-labeled YRS was examined for uptake by platelets, as demonstrated by western blotting and confocal microscopy analysis. Using RAW-Dual reporter cells, Toll-like receptor and type I interferon activation pathways were analyzed after treatment with YRS.

RESULTS

Full-length YRS was cleaved by both elastase and matrix metalloproteinases in the plasma. The cleaved, N-terminal YRS fragment corresponds to the endogenous YRS detected in platelet lysate by western blotting. Both full-length and cleaved forms of YRS were taken up by platelets in vitro and stored in the α-granules. The N-terminal YRS fragment generated by proteolytic cleavage had monocyte activation comparable to that of the constitutive-active mutant YRS (YRSY341A) previously reported.

CONCLUSION

Platelets take up both full-length YRS and the active form of cleaved YRS fragment from the plasma. The cleaved, N-terminal YRS fragment stored in α-granules may have potential to activate monocytes.

Platelet regulation of myeloid suppressor of cytokine signaling 3 accelerates atherosclerosis

Platelets are best known as mediators of hemostasis and thrombosis; however, their inflammatory effector properties are increasingly recognized. Atherosclerosis, a chronic vascular inflammatory disease, represents the interplay between lipid deposition in the artery wall and unresolved inflammation. Here, we reveal that platelets induce monocyte migration and recruitment into atherosclerotic plaques, resulting in plaque platelet-macrophage aggregates. In Ldlr ^-/- mice fed a Western diet, platelet depletion decreased plaque size and necrotic area and attenuated macrophage accumulation. Platelets drive atherogenesis by skewing plaque macrophages to an inflammatory phenotype, increasing myeloid suppressor of cytokine signaling 3 (SOCS3) expression and reducing the Socs1:Socs3 ratio. Platelet-induced Socs3 expression regulates plaque macrophage reprogramming by promoting inflammatory cytokine production (Il6, Il1b, and Tnfa) and impairing phagocytic capacity, dysfunctions that contribute to unresolved inflammation and sustained plaque growth. Translating our data to humans with cardiovascular disease, we found that women with, versus without, myocardial infarction have up-regulation of SOCS3, lower SOCS1:SOCS3, and increased monocyte-platelet aggregate. A second cohort of patients with lower extremity atherosclerosis demonstrated that SOCS3 and the SOCS1:SOCS3 ratio correlated with platelet activity and inflammation. Collectively, these data provide a causative link between platelet-mediated myeloid inflammation and dysfunction, SOCS3, and cardiovascular disease. Our findings define an atherogenic role of platelets and highlight how, in the absence of thrombosis, platelets contribute to inflammation.

Neutrophil/lymphocyte ratio predicts in-hospital complications in Takotsubo syndrome. Results from a prospective multi-center registry

Background

Several hematological indices including subtypes of leukocytes populations have been associated with cardiovascular outcome. Takotsubo syndrome (TTS) is a form of acute heart failure syndrome featured by several in‐hospital complications (IHCs).

Hypothesis

Hematological indices at admission may predict IHCs in TTS patients.

Methods

One hundred and sixty consecutive patients with TTS were enrolled in a multicenter prospective registry. Clinical data, admission hemogram, and IHCs were recorded.

Results

Incidence of IHCs was 37%, including pulmonary edema 9%, cardiogenic shock 9%, need of invasive ventilation 10%, death 8%, stroke 2.5%, and left ventricular thrombi 6%.

Patients with IHCs were older, more frequently male, with physical stressor‐induced TTS, lower left ventricular ejection fraction at admission. Neutrophil/lymphocyte ratio (NLr) (12 ± 12 vs 7 ± 8, P = .002) and white blood cells/mean platelet volume ratio (1.2 ± 0.5 vs 1.0 ± 0.5, P = .03) at admission were significantly higher in patients with IHCs.

NLr values were predictor of IHCs (Odds ratios [OR] 1.07, 95% CI 1.03‐1.11, P < .01). When stratified according to NLr into tertiles, the rate of IHCs was from first to third tertile was, respectively, 22%, 31%, and 58%. NLr values in the higher tertile were independent predictors of IHCs even at multivariate analysis (OR 3.7, 95% CI 1.5‐9.4, P < .01).

NLr values higher than 5 were able to predict IHCs with a sensitivity of 82% and specificity of 58%; negative predictive power was 84% (area under the ROC curve 0.73).

Conclusions

NLr is an independent predictor of IHCs in patients admitted with TTS. Admission hemogram may represent a potential tool for prediction of IHCs in TTS.

Acute exacerbations of COPD are associated with a prothrombotic state through platelet-monocyte complexes, endothelial activation and increased thrombin generation

INTRODUCTION

Patients with chronic obstructive pulmonary disease (COPD) are at increased risk for cardiovascular events, particularly following an acute exacerbation (AE-COPD). Exacerbations are associated with increased systemic inflammation, which may drive coagulation. This prospective cohort study aimed to determine how an AE-COPD affects platelet activation, the endothelium, plasmatic coagulation and fibrinolysis, and its association with systemic inflammation.

MATERIALS AND METHODS

Fifty-two patients with an AE-COPD were included. Blood samples at admission, at day 3 of treatment and at convalescence were available for 32 patients. Platelet-monocyte complex (PMC) formation, monocyte Mac-1 expression and platelet (re)activity (P-selectin expression, αIIbβ3 activation) were measured by flow cytometry. Von Willebrand Factor (VWF), thrombin generation (TG) and clot lysis time (CLT) were determined as measures of endothelial activation, plasmatic coagulation and fibrinolysis, respectively.

RESULTS

Exacerbations were associated with increased PMCs (MFI 31.3 vs 23.8, p = 0.004) and Mac-1 (MFI 38.2 vs 34.8, p = 0.006) compared to convalescence, but not with changes in platelet (re)activity. VWF (antigen, activity, active fraction) and TG (peak, ETP and velocity index) were all significantly higher during AE-COPD compared to convalescence. PMCs, Mac-1, VWF and TG were positively associated with systemic inflammation (CRP). CLT was prolonged in AE-COPD patients with systemic inflammation. Moreover, platelet hyperreactivity on admission was associated with an increased risk for exacerbation relapse.

CONCLUSIONS

Acute exacerbations are associated with an inflammation-associated prothrombotic state, characterized by increased PMCs, endothelial activation and plasmatic coagulation. Our findings provide direction for future studies on biomarkers predicting the risk of exacerbation relapse and cardiovascular events.

Platelet/lymphocyte ratio for prediction of no-reflow phenomenon in ST-elevation myocardial infarction managed with primary percutaneous coronary intervention

Background

Coronary no-reflow phenomenon in ST-segment elevation myocardial infarction (STEMI) is associated with a poor clinical outcome. Although its pathophysiology is not fully understood, a deregulated systemic inflammatory response plays an important role. We aimed to explore the relationship between platelet\lymphocyte ratio (PLR) and no-reflow in patients with acute STEMI who were treated with a primary percutaneous coronary intervention (PPCI).

Methods

A total of 200 patients with STEMI undergoing PPCI were included in the study. Transthoracic echocardiographic examination was performed to assess left ventricular (LV) ejection fraction (EF) and wall motion score index. Blood samples were assayed for platelet and lymphocyte count before PPCI. No-reflow was defined as coronary blood flow thrombolysis in myocardial infarction grade ≤II.

Results

No-reflow was observed in 58 (29%) of STEMI patients following PPCI. PLR was significantly higher in hypertensive patients compared to normotensive patients (144.7±91.6 vs. 109.1±47.1, respectively, P<0.001) and in the no-reflow group compared to the normal reflow group (214±93 vs. 101.6±51.3, respectively, P<0.0001). Logistic regression analysis revealed that PLR (β: 0.485, 95% CI: -0.006-0.001, P<0.002) and LV EF (β: 0.272, 95% CI: 0.009-0.034, P<0.001) were independent predictors of no-reflow after PPCI.

Conclusion

Pre-procedural increase in PLR is predictive of the no-reflow phenomenon following PPCI in STEMI patients.

Relevance for Patients

No reflow phenomenon is an unfavorable complication following PPCI in patients with acute STEMI. High pre-procedural PLR is an independent predictor of reperfusion failure and helps to identify patients who require prophylactic treatment.

Flow cytometric evaluation of platelet-leukocyte conjugate stability over time: methodological implications of sample handling and processing

Platelet activation and subsequent aggregation is a vital component of atherothrombosis resulting in acute myocardial infarction. Therefore, quantifying platelet aggregation is a valuable measure for elucidating the pathogenesis of acute coronary syndromes (ACS). Circulating platelet-monocyte conjugates (PMC) as determined by flow cytometry (FCM) are an important measure of in vivo platelet aggregation. However, the influence of sample handling on FCM measurement of PMC is not well-studied. The changes in FCM measurement of PMC with variation in sample handling techniques were evaluated. The stability of PMC concentrations over time with changes in fixation and immunolabeling intervals was assessed. The effect of Time-to-Fix and Time-to-Stain on FCM PMC measurements was investigated in five healthy volunteers. Time-to-Fix (i.e., interval between phlebotomy and sample fixation) was performed at 3, 30, and 60 min. Time-to-Stain (i.e., time of fixed sample storage to staining) was performed at 1, 24, and 48 h. Increasing Time-to-Stain from 1 to 24 or 48 h resulted in lower PMC measures (p < 0.0001). A statistically significant difference in PMC measurement with increasing Time-to-Fix was not observed (p < 0.41). Postponement of sample staining has deleterious effects on the measurement of PMC via FCM. Delays in immunolabeling of fixed samples compromised measurement of PMC by 30% over the first 24 h. Staining/FCM should be completed within an hour of collection.

The adipokine vaspin is associated with decreased coronary in-stent restenosis in vivo and inhibits migration of human coronary smooth muscle cells in vitro

BACKGROUND

Percutaneous coronary intervention represents the most important treatment modality of coronary artery stenosis. In-stent restenosis (ISR) is still a limitation for the long-term outcome despite the introduction of drug eluting stents. It has been shown that adipokines directly influence vessel wall homeostasis by influencing the function of endothelial cells and arterial smooth muscle cells. Visceral adipose tissue-derived serpin vaspin was recently identified as a member of serine protease inhibitor family and serveral studies could demonstrate a relation to metabolic diseases. The aim of this study was to investigate a role of vaspin in the development of in-stent restenosis in vivo and on migration of smooth muscle cells and endothelial cells in vitro.

METHODS

We studied 85 patients with stable coronary artery disease who underwent elective and successful PCI with implatation of drug eluting stents. Blood samples were taken directly before PCI. Vaspin plasma levels were measured by specific ELISA. ISR was evaluated eight months later by coronary angiography. Human coronary artery smooth muscle cells (HCASMC) and human umbilical vein endothelial cells (HUVEC) migration was analyzed by an in-vitro migration assay with different concentrations (0.004ng/mL up to 40ng/mL) of vaspin as well as by an scratch assay. For proliferation an impedance measurement with specialiced E-Plates was performed.

RESULTS

During the follow up period, 14 patients developed ISR. Patients with ISR had significantly lower vaspin plasma levels compared to patients without ISR (0.213 ng/ml vs 0.382 ng/ml; p = 0.001). In patients with plasma vaspin levels above 1.35 ng/ml we could not observe any restenosis. There was also a significant correlation of plasma vaspin levels and late lumen loss in the stented coronary segments. Further we could demonstrate that vaspin nearly abolishes serum induced migration of HCASMC (100% vs. 9%; p<0.001) in a biphasic manner but not migration of HUVEC. Proliferation of HCASMC and HUVEC was not modulated by vaspin treatment.

CONCLUSION

We were able to show that the adipokine vaspin selectively inhibits human coronary SMC migration in vitro and has no effect on HUVEC migration. Vaspin had no effect on proliferation of HUVEC which is an important process of the healing of the stented vessel. In addition, the occurrence of ISR after PCI with implantation of drug eluting stents was significantly associated with low vaspin plasma levels before intervention. Determination of vaspin plasma levels before PCI might be helpful in the identification of patients with high risk for development of ISR after stent implantation. In addition, the selective effects of vaspin on smooth muscle cell migration could potentially be used to reduce ISR without inhibition of re-endothelialization of the stented segment.

Increased platelet activation in sleep apnea subjects with intermittent hypoxemia

PURPOSE

Obstructive sleep apnea (OSA) is independently associated with increased risk for stroke and other cardiovascular diseases. Since activated platelets play an important role in cardiovascular disease, the objective of this study was to determine whether platelet reactivity was altered in OSA subjects with intermittent nocturnal hypoxemia.

METHODS

Thirty-one subjects, without hypertension or cardiovascular disease and not taking medication, participated in the study. Subjects were stratified based on OSA-related oxygen desaturation index (ODI) recorded during overnight polysomnography. Platelet reactivity to a broad panel of agonists (collagen, thrombin, protease-activated receptor1 hexapeptide, epinephrine, ADP) was measured by monitoring platelet aggregation and ATP secretion. Expression of platelet activation markers CD154 (CD40L) and CD62P (P-selectin) and platelet-monocyte aggregates (PMA) was quantified by flow cytometry.

RESULTS

Epinephrine-induced platelet aggregation was substantially decreased in OSA subjects with significant intermittent hypoxemia (ODI ≥ 15) compared with subjects with milder hypoxemia levels (ODI < 15) (area under curve, p = 0.01). In addition, OSA subjects with ODI ≥ 15 exhibited decreased thrombin-induced platelet aggregation (p = 0.02) and CD40L platelet surface expression (p = 0.05). Platelet responses to the other agonists, CD62P platelet surface expression, and PMA levels were not significantly different between groups. Reduction in platelet responses to epinephrine and thrombin, and decreased CD40L surface marker expression in significant hypoxemic OSA individuals, is consistent with their platelets being in an activated state.

CONCLUSIONS

Increased platelet activation was present in otherwise healthy subjects with intermittent nocturnal hypoxemia due to underlying OSA. This prothrombotic milieu in the vasculature is likely a key contributing factor toward development of thrombosis and cardiovascular disease.

TRIAL REGISTRATION

NCT00859950.

Impaired Glucose Tolerance is Associated with Enhanced Platelet-Monocyte Aggregation in Short-Term High-Fat Diet-Fed Mice

High-fat diet (HFD) feeding is known to induce metabolic dysregulation, however, less is known on its impact in promoting the hypercoagulable state. This current study aimed to evaluate platelet-monocyte aggregate (PMA) formation following short-term HFD feeding. This is particularly important for understanding the link between inflammation and the hypercoagulable state during the early onset of metabolic dysregulation. To explore such a hypothesis, mice were fed a HFD for 8 weeks, with body weights as well as insulin and blood glucose levels monitored on a weekly basis during this period. Basal hematological measurements were determined and the levels of spontaneous peripheral blood PMAs were assessed using whole blood flow cytometry. The results showed that although there were no significant differences in body weights, mice on HFD displayed impaired glucose tolerance and markedly raised insulin levels. These metabolic abnormalities were accompanied by elevated baseline PMA levels as an indication of hypercoagulation. Importantly, it was evident that baseline levels of monocytes, measured using the CD14 monocyte marker, were significantly decreased in HFD-fed mice when compared to controls. In summary, the current evidence shows that in addition to causing glucose intolerance, such as that identified in a prediabetic state, HFD-feeding can promote undesirable hypercoagulation, the major consequence implicated in the development of cardiovascular complications.

Platelet-Derived MRP-14 Induces Monocyte Activation in Patients With Symptomatic Peripheral Artery Disease

BACKGROUND

Peripheral artery disease (PAD), a diffuse manifestation of atherothrombosis, is a major cardiovascular threat. Although platelets are primary mediators of atherothrombosis, their role in the pathogenesis of PAD remains unclear.

OBJECTIVES

The authors sought to investigate the role of platelets in a cohort of symptomatic PAD.

METHODS

The authors profiled platelet activity, mRNA, and effector roles in patients with symptomatic PAD and in healthy controls. Patients with PAD and carotid artery stenosis were recruited into ongoing studies (NCT02106429 and NCT01897103) investigating platelet activity, platelet RNA, and cardiovascular disease.

RESULTS

Platelet RNA sequence profiling mapped a robust up-regulation of myeloid-related protein (MRP)-14 mRNA, a potent calcium binding protein heterodimer, in PAD. Circulating activated platelets were enriched with MRP-14 protein, which augmented the expression of the adhesion mediator, P-selectin, thereby promoting monocyte-platelet aggregates. Electron microscopy confirmed the firm interaction of platelets with monocytes in vitro and colocalization of macrophages with MRP-14 confirmed their cross talk in atherosclerotic manifestations of PAD in vivo. Platelet-derived MRP-14 was channeled to monocytes, thereby fueling their expression of key PAD lesional hallmarks and increasing their directed locomotion, which were both suppressed in the presence of antibody-mediated blockade. Circulating MRP-14 was heightened in the setting of PAD, significantly correlated with PAD severity, and was associated with incident limb events.

CONCLUSIONS

The authors identified a heightened platelet activity profile and unraveled a novel immunomodulatory effector role of platelet-derived MRP-14 in reprograming monocyte activation in symptomatic PAD. (Platelet Activity in Vascular Surgery and Cardiovascular Events [PACE]; NCT02106429; and Platelet Activity in Vascular Surgery for Thrombosis and Bleeding [PIVOTAL]; NCT01897103).

Plasma soluble C-type lectin-like receptor-2 is associated with the risk of coronary artery disease

Accumulating evidence suggests that C-type lectin-like receptor-2 (CLEC-2) plays an important role in atherothrombosis. In this case-control study, we investigated the association between CLEC-2 and incidence of coronary artery disease (CAD). A total of 216 patients, including 14 cases of stable angina pectoris (SAP, non-ACS) and 202 cases of acute coronary syndrome (ACS), and 89 non-CAD control subjects were enrolled. Plasma levels of soluble CLEC-2 (sCLEC-2) were measured using the enzyme-linked immunosorbent assay (ELISA). Compared with the control group (65.69 (55.36-143.22) pg/mL), the plasma levels of sCLEC-2 were significantly increased in patients with CAD (133.67 (88.76-220.09) pg/mL) and ACS (134.16 (88.88-225.81) pg/mL). The multivariate adjusted odds ratios (95% confidence interval) of CAD reached 2.01 (1.52-2.66) (P_trend < 0.001) for each 1-quartile increase in sCLEC-2. Restricted cubic splines showed a positive dose-response association between sCLEC2 and CAD incidence (P_linearity < 0.001). The addition of sCLEC-2 to conventional risk factors improved the C statistic (0.821 vs. 0.761, P = 0.004) and reclassification ability (net reclassification improvement: 57.45%, P < 0.001; integrated discrimination improvement: 8.27%, P < 0.001) for CAD. In conclusion, high plasma sCLEC-2 is independently associated with CAD risk, and the prognostic value of sCLEC-2 may be evaluated in future prospective studies.

Differences in Monocyte Subsets and Monocyte-Platelet Aggregates in Acute Myocardial Infarction-PreliminaryResults

BACKGROUND

Monocyte-platelet interaction may favor the development of a proatherogenic monocyte phenotype. It is still uncertain which of the 3 monocyte subpopulations interact with platelets to form monocyte-platelet aggregates (MPAs) in acute myocardial infarctions. The aim of our study was to evaluate the monocyte subsets, the percentage of MPAs and the involvement of monocyte subsets in MPA formation among patients with ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI), and compared to patients with stable angina (SA).

METHODS

Monocyte subsets and MPAs formation were measured in blood collected in 3.2% sodium citrate tubes by means of flow cytometry.

RESULTS

Classical, intermediate and nonclassical monocyte percentages were statistically different when comparing patients with STEMI and NSTEMI. Moreover, classical and intermediate monocytes were statistically different when comparing the STEMI and SA group; however, only the classical monocyte subset was found to be higher in the acute myocardial infarction group compared to the SA group. The percentage of MPAs was significantly higher in STEMI (50.1%) compared to NSTEMI (22.9%). We found no differences in the involvement of monocyte subsets in MPA formation between patients with STEMI and NSTEMI and in comparison with the SA group.

CONCLUSIONS

These findings suggest that the increase in circulating levels of classical monocytes in patients with STEMI as compared to NSTEMI reflects the severity of the acute event. The increased percentage of MPAs may favor the development of STEMI compared to NSTEMI.

Platelets Activation in Patients Undergoing PTCA and Their Responsiveness After in vitro Stimulation

We evaluated expression of platelet activation markers in blood samples of 15 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) by flow cytometry. Analysis was performed before the beginning of PTCA, during initial coronary angiography and after the end of PTCA or after a stent placement, respectively. We evaluated platelet-derived microparticles, platelet-leukocyte aggregates, platelet aggregates and a membrane expression of CD62P and CD63 molecules. Responsiveness of platelets to the activationin vitrowith thrombin-receptor activating protein – 6 (TRAP-6) was tested simultaneously. Statistically significant differences between patient samples were found only in the expression of the activation markers CD62P (before PTCA 0.22 %, during 0.39 %, after 0.67 %), CD63 (0.26 %/ 0.45 %/ 0.85 %) and platelet-leukocyte aggregates (13.57 %/ 18.39 %/ 23.63 %).In the same group the expression of all constitutive membrane markers was statistically significantly decreased: in patients undergoing PTCA was the expression of CD9:87.98 % (in comparison with control group 94.98 %), CD31: 87.10 % (92.78 %), CD36: 87.37 % (90.98 %), CD41: 88.09 % (95.62 %), CD42a: 88.54 % (94.98 %), CD42a: 88.31 % (94.13 %).

BloodSurf 2017: News from the blood-biomaterial frontier

From stents and large-diameter vascular grafts, to mechanical heart valves and blood pumps, blood-contacting devices are enjoying significant clinical success owing to the application of systemic antiplatelet and anticoagulation therapies. On the contrary, research into material and device hemocompatibility aimed at alleviating the need for systemic therapies has suffered a decline. This research area is undergoing a renaissance fueled by recent fundamental insights into coagulation and inflammation that are offering new avenues of investigation, the growing recognition of the limitations facing existing therapeutic approaches, and the severity of the cardiovascular disorders epidemic. This Opinion article discusses clinical needs for hemocompatible materials and the emerging research directions for fulfilling those needs. Based on the 2017 BloodSurf conference that brought together clinicians, scientists, and engineers from academia, industry, and regulatory bodies, its purpose is to draw the attention of the wider clinical and scientific community to stimulate further growth. STATEMENT OF SIGNIFICANCE: The article highlights recent fundamental insights into coagulation, inflammation, and blood-biomaterial interactions that are fueling a renaissance in the field of material hemocompatibility. It will be useful for clinicians, scientists, engineers, representatives of industry and regulatory bodies working on the problem of developing hemocompatible materials and devices for treating cardiovascular disorders.

Circulating monocyte-platelet aggregates are a robust marker of platelet activity in cardiovascular disease

BACKGROUND AND AIMS

Platelets are a major culprit in the pathogenesis of cardiovascular disease (CVD). Circulating monocyte-platelet aggregates (MPA) represent the crossroads between atherothrombosis and inflammation. However, there is little understanding of the platelets and monocytes that comprise MPA and the prevalence of MPA in different CVD phenotypes. We aimed to establish (1) the reproducibility of MPA over time in circulating blood samples from healthy controls, (2) the effect of aspirin, (3) the relationship between MPA and platelet activity and monocyte subtype, and (4) the association between MPA and CVD phenotype (coronary artery disease, peripheral artery disease [PAD], abdominal aortic aneurysm, and carotid artery stenosis).

METHODS AND RESULTS

MPA were identified by CD14⁺ monocytes positive for CD61⁺ platelets in healthy subjects and in patients with CVD. We found that MPA did not significantly differ over time in healthy controls, nor altered by aspirin use. Compared with healthy controls, MPA were significantly higher in CVD (9.4% [8.2, 11.1] vs. 21.8% [11.5, 44.1], p < 0.001) which remained significant after multivariable adjustment (β = 9.1 [SER = 3.9], p = 0.02). We found PAD to be associated with a higher MPA in circulation (β = 19.3 [SER = 6.0], p = 0.001), and among PAD subjects, MPA was higher in subjects with critical limb ischemia (34.9% [21.9, 51.15] vs. 21.6% [15.1, 40.6], p = 0.0015), and significance remained following multivariable adjustment (β = 14.77 (SE = 4.35), p = 0.001).

CONCLUSIONS

Circulating MPA are a robust marker of platelet activity and monocyte inflammation, unaffected by low-dose aspirin, and are significantly elevated in subjects with CVD, particularly those with PAD.