Monocyte-platelet aggregates affect local inflammation in patients with acute myocardial infarction

Association of elevated circulating monocyte-platelet aggregates with hypercoagulability in patients with nephrotic syndrome

BACKGROUND

Hypercoagulability emerges as a central pathological feature and clinical complication in nephrotic syndrome. Increased platelet activation and aggregability are closely related to hypercoagulability in nephrotic syndrome. Monocyte-platelet aggregates (MPAs) have been proposed to represent a robust biomarker of platelet activation. The aim of this study was to investigate levels of the circulating MPAs and MPAs with the different monocyte subsets to evaluate the association of MPAs with hypercoagulability in nephrotic syndrome.

METHODS

Thirty-two patients with nephrotic syndrome were enrolled. In addition, thirty-two healthy age and sex matched adult volunteers served as healthy controls. MPAs were identified by CD14 monocytes positive for CD41a platelets. The classical (CD14 + + CD16-, CM), the intermediate (CD14 + + CD16+, IM) and the non-classical (CD14 + CD16++, NCM) monocytes, as well as subset specific MPAs, were measured by flow cytometry.

RESULTS

Patients with nephrotic syndrome showed a higher percentage of circulating MPAs as compared with healthy controls (p < 0.001). The percentages of MPAs with CM, IM, and NCM were higher than those of healthy controls (p = 0.012, p < 0.001 and p < 0.001, respectively). Circulating MPAs showed correlations with hypoalbuminemia (r=-0.85; p < 0.001), hypercholesterolemia (r = 0.54; p < 0.001), fibrinogen (r = 0.70; p < 0.001) and D-dimer (r = 0.37; p = 0.003), but not with hypertriglyceridemia in nephrotic syndrome. The AUC for the prediction of hypercoagulability in nephrotic syndrome using MPAs was 0.79 (95% CI 0.68-0.90, p < 0.001). The sensitivity of MPAs in predicting hypercoagulability was 0.71, and the specificity was 0.78.

CONCLUSION

Increased MPAs were correlated with hypercoagulability in nephrotic syndrome. MPAs may serve as a potential biomarker for thrombophilic or hypercoagulable state and provide novel insight into the mechanisms of anticoagulation in nephrotic syndrome.

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.

Circulating monocyte-platelet aggregates with different monocyte subsets and their association with disease severity in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is usually considered an immune inflammatory disease. Interaction between platelets and monocytes is associated with immune inflammation. Cross-talk between platelets and monocytes is reflected by formation monocyte-platelet aggregates (MPAs). This study aims to test MPAs and MPAs with the different monocyte subsets to evaluate their association with disease severity in CKD.

METHODS

Forty-four hospitalized patients with CKD and twenty healthy volunteers were enrolled. The proportion of MPAs and MPAs with the different monocyte subsets were tested by flow cytometry.

RESULTS

The proportion of circulating MPAs in all patients with CKD were significantly higher than those of healthy controls (p<0.001). A higher proportion of MPAs with classical monocytes (CM) was found in CKD4-5 patients (p=0.007), while another higher proportion of MPAs with non-classical monocytes (NCM) was found CKD2-3 patients (p<0.001). The proportion of MPAs with intermediate monocytes (IM) in CKD 4-5 group was significantly higher in comparison to CKD2-3 group and healthy controls (p<0.001). Circulating MPAs were found to be correlated with serum creatinine (r=0.538, p<0.001) and eGFR (r=-0.864, p<0.001). The AUC for MPAs with IM was 0.942 (95% CI 0.890-0.994, p<0.001).

CONCLUSIONS

Study results highlight the interplay between platelets and inflammatory monocytes in CKD. There are alterations in circulating MPAs and MPAs with the different monocyte subsets in CKD patients compared to controls which change with CKD severity. The MPAs may have an important role in the development of CKD or as a predictive marker for monitoring disease severity.

Platelet, a key regulator of innate and adaptive immunity

Platelets, anucleate blood components, represent the major cell type involved in the regulation of hemostasis and thrombosis. In addition to performing haemostatic roles, platelets can influence both innate and adaptive immune responses. In this review, we summarize the development of platelets and their functions in hemostasis. We also discuss the interactions between platelet products and innate or adaptive immune cells, including neutrophils, monocytes, macrophages, T cells, B cells and dendritic cells. Activated platelets and released molecules regulate the differentiation and function of these cells via platelet-derived receptors or secreting molecules. Platelets have dual effects on nearly all immune cells. Understanding the exact mechanisms underlying these effects will enable further application of platelet transfusion.

Association of peak C-reactive protein with long-term clinical outcomes in patients with ST-segment elevation myocardial infarction

Peak C-reactive protein (CRP) levels following ST-segment elevation myocardial infarction (STEMI) are associated with left ventricular thrombus formation or cardiac rupture. However, the impact of peak CRP on long-term outcomes in patients with STEMI is not completely understood. The purpose of this retrospective study was to compare the long-term all-cause death after STEMI between patients with and without high peak CRP levels. We included 594 patients with STEMI, and divided them into the high CRP group (n = 119) and the low-moderate CRP group (n = 475) according to the quintile of peak CRP levels. The primary endpoint was all-cause death after the discharge of the index admission. The mean peak CRP level was 19.66 ± 5.14 mg/dL in the high CRP group, whereas that was 6.43 ± 3.86 mg/dL in the low-moderate CRP group (p < 0.001). During the median follow-up duration of 1045 days (Q1 284 days, Q3 1603 days), a total of 45 all-cause deaths were observed. The Kaplan-Meier curves showed that all-cause death was more frequently observed in the high CRP group than in the low-moderate CRP group (p = 0.002). The multivariate Cox hazard analysis revealed that high CRP was significantly associated with all-cause death (hazard ratio 2.325, 95% confidence interval 1.246-4.341, p = 0.008) after controlling for confounding factors. In conclusion, high peak CRP was significantly associated with all-cause death in patients with STEMI. Our results suggest that peak CRP may be useful to stratify patients with STEMI for the risk of future death.

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.

In-vivo platelet activation and aggregation during and after acute atherothrombotic myocardial infarction in patients with and without Type-2 diabetes mellitus treated with ticagrelor

INTRODUCTION

Patients with type-2 diabetes are twice as likely to suffer from acute myocardial infarction (AMI) and have a higher incidence of recurrent events than their non-diabetic counterparts. Ticagrelor is a platelet inhibitor known to reduce major adverse cardiovascular events (MACE) in AMI patients. This study measures the level and change in platelet activation and aggregation at the time of and following an AMI in patients with and without diabetes treated with ticagrelor.

MATERIALS/METHODS

P₂Y₁₂ receptor inhibitor naïve patients presenting with AMI were prospectively enrolled. Blood collection occurred before coronary angiography (baseline: T₀), 2, 4, 24, 48 h after baseline, and at a three-month follow-up. Ticagrelor was administered within five minutes of T₀. We assessed platelet activation via measurements of surface P-selectin and platelet activated glycoprotein IIb/IIIa-1 (PAC-1) and assessed platelet aggregation via monocyte, lymphocyte, and granulocyte aggregates. We hypothesize that platelet activation and aggregation will be proportionally impacted to the same degree by ticagrelor, regardless of diabetes status.

RESULTS

Ninety-seven patients were prospectively enrolled (diabetes, N = 33; no diabetes, N = 64). No difference was observed in the expression of P-selectin and PAC-1 at any given point between diabetes and non-diabetes groups (p > 0.05). No difference was observed in the percentage of platelet bound to leukocytes at any measured timepoint between patients with and without diabetes (p > 0.05). Platelet leukocyte aggregation was suppressed during the acute phase compared to quiescence equally among both groups.

DISCUSSION

Ticagrelor demonstrated similar in-vivo effects on platelet activation and aggregation regardless of diabetes status in patients presenting with AMI.

Protective Role of Platelets in Myocardial Infarction and Ischemia/Reperfusion Injury

Thrombotic occlusion of the coronary artery is a key component in the pathogenesis of myocardial ischemia and myocardial infarction (MI). The standard therapy for ischemia is revascularization and restoration of blood flow to previously ischemic myocardium. Paradoxically, reperfusion may result in further tissue damage called ischemia/reperfusion injury (IRI). Platelets play a major role in the pathogenesis of MI and IRI, since they contribute to the thrombus and microthrombi formation, inflammation, release of immunomodulatory mediators, and vasoconstrictive molecules. Antiplatelet therapies have proven efficacy in the prevention of thrombosis and play a protective role in cardiac IRI. Beyond the deterioration effect of platelets in MI and IRI, in the 90s the first reports on a protective effect of molecules released from platelets during MI appeared. However, the role of platelets in cardioprotection is still poorly understood. This review describes the involvement of platelets in MI, IRI, and inflammation. It mainly focuses on the protective role of platelets in MI and IRI. Platelets are involved in cardioprotection based on platelet-releasing molecules and antiplatelet therapy, apart from antiaggregatory effects. Additionally, the use of platelet-derived microparticles as possible markers of MI, with and without comorbidities, and their role in cardioprotection are discussed. This review is aimed at illustrating the present knowledge on the role of platelets in MI and IRI, especially in a context of cardioprotection.

Imaging Inflammation with Positron Emission Tomography

The impact of inflammation on the outcome of many medical conditions such as cardiovascular diseases, neurological disorders, infections, cancer, and autoimmune diseases has been widely acknowledged. However, in contrast to neurological, oncologic, and cardiovascular disorders, imaging plays a minor role in research and management of inflammation. Imaging can provide insights into individual and temporospatial biology and grade of inflammation which can be of diagnostic, therapeutic, and prognostic value. There is therefore an urgent need to evaluate and understand current approaches and potential applications for imaging of inflammation. This review discusses radiotracers for positron emission tomography (PET) that have been used to image inflammation in cardiovascular diseases and other inflammatory conditions with a special emphasis on radiotracers that have already been successfully applied in clinical settings.

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.

Measurement of leukocyte-platelet aggregates (LPA) by FACS: a comparative analysis

In addition to their role in hemostasis and coagulation platelets bear critical roles in modulation of the innate and adaptive immune system. Upon platelet activation in response to tissue injury, bacterial or viral infections, they secrete many soluble factors or directly interact with leukocytes. An increase of leukocyte-platelet aggregates (LPA) has been described for many pathological conditions. Nevertheless, a standardized method for the reliable measurement of PLAs is not securely established. This methodical study provides a comparison of four different protocols from the literature and summarizes major pitfalls of measuring and interpreting leukocyte-platelet aggregates. The different techniques vary in the workup of the blood samples, applying variable washing and centrifugation steps or the use of erythrocyte lysis. All samples were finally analyzed by flow cytometry. Leukocyte subsets were stained with specific antibodies and platelet aggregates were identified by additional expression of CD41. The different procedures generated very heterogeneous data from the same blood sample which highlight the abundance of error measuring LPA. The most reproducible technique turned out to be a two-color whole blood flow cytometry assay with erythrocyte lysis and without washing or centrifugation steps avoiding platelet activation and artificial aggregate formation to achieve data mirroring the true situation in peripheral blood.

Imaging inflammation after myocardial infarction: implications for prognosis and therapeutic guidance

Inflammation after myocardial infarction (MI) has been in the focus of cardiovascular research for several years as it influences the remodeling process of the ischemic heart and thereby critically determines the clinical outcome of the patient. Today, it is well appreciated that inflammation is a crucial necessity for the initiation of the natural wound healing process; however, excessive inflammation can have detrimental effects and might result in adverse ventricular remodeling which is associated with an increased risk of heart failure. Newly emerged imaging techniques facilitate the non-invasive assessment of immune cell infiltration into the ischemic myocardium and can provide greater insight into the underlying complex and dynamic repair mechanisms. Molecular imaging of inflammation in the context of MI may help with stratification of patients at high risk of adverse ventricular remodeling post-MI which may be of diagnostic, therapeutic, and prognostic value. Novel radiopharmaceuticals may additionally provide a way to combine patient monitoring and therapy. In spite of great advances in recent years in the field of imaging sciences, clinicians still need to overcome some obstacles to a wider implementation of inflammation imaging post-MI. This review focuses on inflammation as a molecular imaging target and its potential implication in prognosis and therapeutic guidance.

The role of P2Y6R in cardiovascular diseases and recent development of P2Y6R antagonists

As a member of the P2Y receptor family with a typical 7-transmembrane structure, P2Y₆ purinergic receptor (P2Y₆R) belongs to the G-protein-coupled nucleotide receptor activating the phospholipase-C signaling pathway. P2Y₆R is widely involved in a range of human diseases, including atherosclerosis and other cardiovascular diseases, gradually attracting attention owing to its inappropriate or excessive activation. In addition, it was reported that P2Y₆R might regulate inflammatory responses by governing the maturation and secretion of proinflammatory cytokines. Hence, several P2Y₆R antagonists have been subjected to evaluation as new therapeutic strategies in recent years. This review was aimed at summarizing the role of P2Y₆R in the pathogenesis of cardiovascular diseases, with an insight into the recent progress on discovery of P2Y₆R antagonists.