Neutrophil extracellular traps: a new source of tissue factor in atherothrombosis

The clonal hematopoiesis mutation Jak2V617F aggravates endothelial injury and thrombosis in arteries with erosion-like intimas

BACKGROUND

Superficial plaque erosion causes many acute coronary syndromes. However, mechanisms of plaque erosion remain poorly understood, and we lack directed therapeutics for thrombotic complication. Human eroded plaques can harbor neutrophil extracellular traps (NETs) that propagate endothelial damage at experimental arterial lesions that recapitulate superficial erosion. Clonal Hematopoiesis of Indeterminate Potential (CHIP) denotes age-related clonal expansion of bone marrow-derived cells harboring somatic mutations in the absence of overt hematological disease. CHIP heightens the risk of cardiovascular disease, with the greatest increase seen in individuals with JAK2V617F. Neutrophils from mice and humans with JAK2V617F undergo NETosis more readily than Jak2WT (wild-type) cells. We hypothesized that JAK2V617F, by increasing propensity to NETosis, exacerbates aspects of superficial erosion.

METHODS AND RESULTS

We generated Jak2V617F and Jak2WT mice with heterozygous Jak2V617F in myeloid cells. We induced areas of denuded endothelium that recapitulate features of superficial erosion and assessed endothelial integrity, cellular composition of the erosion, thrombosis rates, and response to ruxolitinib, a clinically available JAK1/2 inhibitor, in relation to genotype. Following experimental erosion, Jak2V617F mice have greater impairment of endothelial barrier function and increased rates of arterial thrombosis. Neointimas in Jak2V617F mice exhibit increased apoptosis, NETosis, and platelet recruitment. Jak2V617F mice treated with ruxolitinib show increased endothelial continuity and reduced apoptosis in the neointima comparable to levels in Jak2WT.

CONCLUSIONS

These observations provide new mechanistic insight into the pathophysiology of superficial erosion, the heightened risk for myocardial infarction in JAK2V617F CHIP, and point the way to personalized therapeutics based on CHIP status.

Cellular metabolism changes in atherosclerosis and the impact of comorbidities

Cell activation and nutrient dysregulation are common consequences of atherosclerosis and its preceding risk factors, such as hypertension, dyslipidemia, and diabetes. These diseases may also impact cellular metabolism and consequently cell function, and the other way around, altered cellular metabolism can impact disease development and progression through altered cell function. Understanding the contribution of altered cellular metabolism to atherosclerosis and how cellular metabolism may be altered by co-morbidities and atherosclerosis risk factors could support the development of novel strategies to lower the risk of CVD. Therefore, we briefly review disease pathogenesis and the principles of cell metabolic pathways, before detailing changes in cellular metabolism in the context of atherosclerosis and comorbidities. In the hypoxic, inflammatory and hyperlipidemic milieu of the atherosclerotic plaque riddled with oxidative stress, metabolism shifts to increase anaerobic glycolysis, the pentose-phosphate pathway and amino acid use. We elaborate on metabolic changes for macrophages, neutrophils, vascular endothelial cells, vascular smooth muscle cells and lymphocytes in the context of atherosclerosis and its co-morbidities hypertension, dyslipidemia, and diabetes. Since causal relationships of specific key genes in a metabolic pathway can be cell type-specific and comorbidity-dependent, the impact of cell-specific metabolic changes must be thoroughly explored in vivo, with a focus on also systemic effects. When cell-specific treatments become feasible, this information will be crucial for determining the best metabolic intervention to improve atherosclerosis and its interplay with co-morbidities.

The fluorochrome-to-protein ratio is crucial for the flow cytometric detection of tissue factor on extracellular vesicles

Extracellular vesicles (EVs) have crucial roles in hemostasis and coagulation. They sustain coagulation by exposing phosphatidylserine and initiate clotting by surface expression of tissue factor (TF) under inflammatory conditions. As their relevance as biomarkers of coagulopathy is increasingly recognized, there is a need for the sensitive and reliable detection of TF+ EVs, but their flow cytometric analysis is challenging and has yielded controversial findings for TF expression on EVs in the vascular system. We investigated the effect of different fluorochrome-to-protein (F/P) ratios of anti-TF-fluorochrome conjugates on the flow cytometric detection of TF+ EVs from activated monocytes, mesenchymal stem cells (MSCs), and in COVID-19 plasma. Using a FITC-labeled anti-TF antibody (clone VD8), we show that the percentage of TF+ EVs declined with decreasing F/P ratios. TF was detected on 7.6%, 5.4%, and 1.1% of all EVs derived from activated monocytes at F/P ratios of 7.7:1, 6.6:1, and 5.2:1. A similar decline was observed for EVs from MSCs and for EVs in plasma, whereas the detection of TF on cells remained unaffected by different F/P ratios. We provide clear evidence that next to the antibody clone, the F/P ratio affects the flow cytometric detection of TF+ EVs and should be carefully controlled.

Dipeptidyl peptidase 1 inhibition as a potential therapeutic approach in neutrophil-mediated inflammatory disease

Neutrophils have a critical role in the innate immune response to infection and the control of inflammation. A key component of this process is the release of neutrophil serine proteases (NSPs), primarily neutrophil elastase, proteinase 3, cathepsin G, and NSP4, which have essential functions in immune modulation and tissue repair following injury. Normally, NSP activity is controlled and modulated by endogenous antiproteases. However, disruption of this homeostatic relationship can cause diseases in which neutrophilic inflammation is central to the pathology, such as chronic obstructive pulmonary disease (COPD), alpha-1 antitrypsin deficiency, bronchiectasis, and cystic fibrosis, as well as many non-pulmonary pathologies. Although the pathobiology of these diseases varies, evidence indicates that excessive NSP activity is common and a principal mediator of tissue damage and clinical decline. NSPs are synthesized as inactive zymogens and activated primarily by the ubiquitous enzyme dipeptidyl peptidase 1, also known as cathepsin C. Preclinical data confirm that inactivation of this protease reduces activation of NSPs. Thus, pharmacological inhibition of dipeptidyl peptidase 1 potentially reduces the contribution of aberrant NSP activity to the severity and/or progression of multiple inflammatory diseases. Initial clinical data support this view. Ongoing research continues to explore the role of NSP activation by dipeptidyl peptidase 1 in different disease states and the potential clinical benefits of dipeptidyl peptidase 1 inhibition.

Beta 2 glycoprotein I and neutrophil extracellular traps: Potential bridge between innate and adaptive immunity in anti-phospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by recurrent vascular thrombosis and miscarriages in the absence of known causes. Antibodies against phospholipid-binding proteins (aPL) are pathogenic players in both clotting and pregnancy APS manifestations. There is sound evidence that antibodies specific for beta2 glycoprotein I (β2GPI) trigger thrombotic and pregnancy complications by interacting with the molecule on the membranes of different cell types of the coagulation cascade, and in placenta tissues. In addition to the humoral response against β2GPI, both peripheral and tissue CD4⁺ β2GPI-specific T cells have been reported in primary APS as well as in systemic lupus erythematosus (SLE)-associated APS. While adaptive immunity plays a clear role in APS, it is still debated whether innate immunity is involved as well. Acute systemic inflammation does not seem to be present in the syndrome, however, there is sound evidence that complement activation is crucial in animal models and can be found also in patients. Furthermore, neutrophil extracellular traps (NETs) have been documented in arterial and venous thrombi with different etiology, including clots in APS models. Keeping in mind that β2GPI is a pleiotropic glycoprotein, acting as scavenger molecule for infectious agents and apoptotic/damaged body constituents and that self-molecules externalized through NETs formation may become immunogenic autoantigens, we demonstrated β2GPI on NETs, and its ability to stimulate CD4⁺β2GPI-specific T cells. The aim of this review is to elucidate the role of β2GPI in the cross-talk between the innate and adaptive immunity in APS.

Neutrophil extracellular traps: from physiology to pathology

At the frontline of the host defence response, neutrophil antimicrobial functions have adapted to combat infections and injuries of different origins and magnitude. The release of web-like DNA structures named neutrophil extracellular traps (NETs) constitutes an important mechanism by which neutrophils prevent pathogen dissemination or deal with microorganisms of a bigger size. At the same time, nuclear and granule proteins with microbicidal activity bind to these DNA structures promoting the elimination of entrapped pathogens. However, these toxic properties may produce unwanted effects in the host, when neutrophils uncontrollably release NETs upon persistent inflammation. As a consequence, NET accumulation can produce vessel occlusion, tissue damage, and prolonged inflammation associated with the progression and exacerbation of multiple pathologic conditions. This review outlines recent advances in understanding the mechanisms of NET release and functions in sterile disease. We also discuss mechanisms of physiological regulation and the importance of neutrophil heterogeneity in NET formation and composition.

Cardiovascular disease and COVID-19: a consensus paper from the ESC Working Group on Coronary Pathophysiology & Microcirculation, ESC Working Group on Thrombosis and the Association for Acute CardioVascular Care (ACVC), in collaboration with the European Heart Rhythm Association (EHRA)

The cardiovascular system is significantly affected in coronavirus disease-19 (COVID-19). Microvascular injury, endothelial dysfunction, and thrombosis resulting from viral infection or indirectly related to the intense systemic inflammatory and immune responses are characteristic features of severe COVID-19. Pre-existing cardiovascular disease and viral load are linked to myocardial injury and worse outcomes. The vascular response to cytokine production and the interaction between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and angiotensin-converting enzyme 2 receptor may lead to a significant reduction in cardiac contractility and subsequent myocardial dysfunction. In addition, a considerable proportion of patients who have been infected with SARS-CoV-2 do not fully recover and continue to experience a large number of symptoms and post-acute complications in the absence of a detectable viral infection. This conditions often referred to as 'post-acute COVID-19' may have multiple causes. Viral reservoirs or lingering fragments of viral RNA or proteins contribute to the condition. Systemic inflammatory response to COVID-19 has the potential to increase myocardial fibrosis which in turn may impair cardiac remodelling. Here, we summarize the current knowledge of cardiovascular injury and post-acute sequelae of COVID-19. As the pandemic continues and new variants emerge, we can advance our knowledge of the underlying mechanisms only by integrating our understanding of the pathophysiology with the corresponding clinical findings. Identification of new biomarkers of cardiovascular complications, and development of effective treatments for COVID-19 infection are of crucial importance.

Cathepsin C inhibition as a potential treatment strategy in cancer

Epidemiological studies established an association between chronic inflammation and higher risk of cancer. Inhibition of proteolytic enzymes represents a potential treatment strategy for cancer and prevention of cancer metastasis. Cathepsin C (CatC) is a highly conserved lysosomal cysteine dipeptidyl aminopeptidase required for the activation of pro-inflammatory neutrophil serine proteases (NSPs, elastase, proteinase 3, cathepsin G and NSP-4). NSPs are locally released by activated neutrophils in response to pathogens and non-infectious danger signals. Activated neutrophils also release neutrophil extracellular traps (NETs) that are decorated with several neutrophil proteins, including NSPs. NSPs are not only NETs constituents but also play a role in NET formation and release. Although immune cells harbor large amounts of CatC, additional cell sources for this protease exists. Upregulation of CatC expression was observed in different tissues during carcinogenesis and correlated with metastasis and poor patient survival. Recent mechanistic studies indicated an important interaction of tumor-associated CatC, NSPs, and NETs in cancer development and metastasis and suggested CatC as a therapeutic target in a several cancer types. Cancer cell-derived CatC promotes neutrophil recruitment in the inflammatory tumor microenvironment. Because the clinical consequences of genetic CatC deficiency in humans resulting in the elimination of NSPs are mild, small molecule inhibitors of CatC are assumed as safe drugs to reduce the NSP burden. Brensocatib, a nitrile CatC inhibitor is currently tested in a phase 3 clinical trial as a novel anti-inflammatory therapy for patients with bronchiectasis. However, recently developed CatC inhibitors possibly have protective effects beyond inflammation. In this review, we describe the pathophysiological function of CatC and discuss molecular mechanisms substantiating pharmacological CatC inhibition as a potential strategy for cancer treatment.

Erythrocyte interaction with neutrophil extracellular traps in coronary artery thrombosis following myocardial infarction

Cardiovascular disease, including myocardial infarction (MI), is the leading cause of death globally. Current antithrombotic medications used during MI treatment are predominantly directed towards platelet inhibition and, to a lesser extent, anticoagulation. Bleeding is a major risk of such treatment and could be circumvented by targeting other causative factors essential for arterial thrombus formation. We sought to re-evaluate the cellular composition of arterial thrombus in order to better understand mechanisms that lead to coronary artery thrombosis in acute MI. We performed detailed histological and immunohistochemical analysis of coronary artery thrombi aspirated from 26 patients undergoing emergency percutaneous coronary intervention for acute ST elevated myocardial infarction (STEMI). Coronary arterial thrombi had an unanticipated cellular heterogeneity. Neutrophil extracellular traps (NETs) were observed in thrombi as identified by anti-citrullinated histone 3 and anti-myeloperoxidase staining. Increased abundance of NETs was seen directly surrounding erythrocytes. Extracellular iron and erythrocyte fragments were also associated with areas of NETs suggesting a possible link. Our results shed light on potential involvement of erythrocytes in coronary arterial thrombosis through activation of platelets and induction of NETs. If supported by further in vitro and in vivo studies, novel therapies to inhibit NET formation or coagulation activation by erythrocyte release products, could bolster current myocardial infarction treatment.

Involvement of Inflammation in Venous Thromboembolic Disease: An Update in the Age of COVID-19

The inflammatory process is strongly involved in the pathophysiology of venous thromboembolism (VTE) and has a significant role in disease prediction. Inflammation most probably represents a common denominator through which classical and nonclassical risk factors stimulate thrombotic process. Inflammation of the venous wall promotes the release of tissue factor, inhibits the release of anticoagulant factors, and hampers endogenous fibrinolysis. Systemic inflammatory response also inhibits restoration of blood flow in the occluded vessel. Recent studies indicate that increased inflammatory response ("cytokine storm") is related to prothrombotic state and thromboembolic events in patients with coronavirus disease 2019 (COVID-19). The growing evidence of involvement of inflammation in the pathogenesis of VTE indicates the importance of anti-inflammatory treatment and prevention of VTE. While aspirin was shown to be effective in prevention of recurrent venous thrombosis after treatment with anticoagulant drugs, some other anti-inflammatory drugs like nonsteroidal anti-inflammatory agents may have prothrombotic effect, thus potentially increasing the risk of VTE. Recently, new specific anti-inflammatory drug inhibitors of inflammatory markers that have been shown to be involved in the pathogenesis of VTE are being searched. As thrombogenesis is based on activation of coagulation provoked by inflammation, then prevention and treatment of VTE should include both anticoagulant and anti-inflammatory agents. Combined treatment is related to increased risk of bleeding complications, therefore subtherapeutic doses of both drugs should be used to improve the efficacy of management of VTE without increasing the risk of bleeding.

Metoprolol exerts a non-class effect against ischaemia-reperfusion injury by abrogating exacerbated inflammation

Aims

Clinical guidelines recommend early intravenous β-blockers during ongoing myocardial infarction; however, it is unknown whether all β-blockers exert a similar cardioprotective effect. We experimentally compared three clinically approved intravenous β-blockers.

Methods and results

Mice undergoing 45 min/24 h ischaemia–reperfusion (I/R) received vehicle, metoprolol, atenolol, or propranolol at min 35. The effect on neutrophil infiltration was tested in three models of exacerbated inflammation. Neutrophil migration was evaluated in vitro and in vivo by intravital microscopy. The effect of β-blockers on the conformation of the β1 adrenergic receptor was studied in silico. Of the tested β-blockers, only metoprolol ameliorated I/R injury [infarct size (IS) = 18.0% ± 0.03% for metoprolol vs. 35.9% ± 0.03% for vehicle; P < 0.01]. Atenolol and propranolol had no effect on IS. In the three exacerbated inflammation models, neutrophil infiltration was significantly attenuated only in the presence of metoprolol (60%, 50%, and 70% reductions vs. vehicle in myocardial I/R injury, thioglycolate-induced peritonitis, and lipopolysaccharide-induced acute lung injury, respectively). Migration studies confirmed the particular ability of metoprolol to disrupt neutrophil dynamics. In silico analysis indicated different intracellular β1 adrenergic receptor conformational changes when bound to metoprolol than to the other two β-blockers.

Conclusions

Metoprolol exerts a disruptive action on neutrophil dynamics during exacerbated inflammation, resulting in an infarct-limiting effect not observed with atenolol or propranolol. The differential effect of β-blockers may be related to distinct conformational changes in the β1 adrenergic receptor upon metoprolol binding. If these data are confirmed in a clinical trial, metoprolol should become the intravenous β-blocker of choice for patients with ongoing infarction.

The key contribution of platelet and vascular arachidonic acid metabolism to the pathophysiology of atherothrombosis

Arachidonic acid is one of the most abundant and ubiquitous ω-6 polyunsaturated fatty acid, present in esterified form in the membrane phospholipids of all mammalian cells and released from phospholipids by several phospholipases in response to various activating or inhibitory stimuli. Arachidonic acid is the precursor of a large number of enzymatically and non-enzymatically derived, biologically active autacoids, including prostaglandins (PGs), thromboxane (TX) A2, leukotrienes, and epoxyeicosatetraenoic acids (collectively called eicosanoids), endocannabinoids and isoprostanes, respectively. Eicosanoids are local modulators of the physiological functions and pathophysiological roles of blood vessels and platelets. For example, the importance of cyclooxygenase (COX)-1-derived TXA2 from activated platelets in contributing to primary haemostasis and atherothrombosis is demonstrated in animal and human models by the bleeding complications and cardioprotective effects associated with low-dose aspirin, a selective inhibitor of platelet COX-1. The relevance of vascular COX-2-derived prostacyclin (PGI2) in endothelial thromboresistance and atheroprotection is clearly shown by animal and human models and by the adverse cardiovascular effects exerted by COX-2 inhibitors in humans. A vast array of arachidonic acid-transforming enzymes, downstream synthases and isomerases, transmembrane receptors, and specificity in their tissue expression make arachidonic acid metabolism a fine-tuning system of vascular health and disease. Its pharmacological regulation is central in human cardiovascular diseases, as demonstrated by biochemical measurements and intervention trials.

β-Conglycinin induces the formation of neutrophil extracellular traps dependent on NADPH oxidase-derived ROS, PAD4, ERK1/2 and p38 signaling pathways in mice

β-Conglycinin is one of the key thermostable anti-nutritional factors in soybean, which has strong immunogenicity that usually leads to weaning in some young animals such as piglets and calves and allergic reaction in rats. Neutrophils are involved in the pathogenesis of an allergy. However, the contribution of functional neutrophils to allergy needs to be clarified. The formation of neutrophil extracellular traps is a novel effector mechanism of neutrophils and has been extensively investigated in recent years. To the best of our knowledge, there is no information available on β-conglycinin-induced NETs. In this study, β-conglycinin-induced NET formation in mice was examined via immunofluorescence analysis and fluorescence microplate reader. The mechanism of β-conglycinin-induced NETs was investigated using inhibitors and fluorescent microplate methods. The results showed that β-conglycinin induced the classical characteristics of NETs, which mainly consist of DNA as the backbone and decorated with histones, myeloperoxidase (MPO) and neutrophil elastase (NE). Moreover, β-conglycinin significantly induced the formation of NETs in a dose-dependent way. NET degrading enzyme DNase I markedly reduced β-conglycinin-induced NETs, which suggests that β-conglycinin indeed triggered the release of NETs. Further investigation showed that the quantitation of NETs was markedly decreased by the inhibitors of reactive oxygen species (ROS)-derived-NADPH oxidase, ERK1/2, p38, Rac and PAD4 signaling pathways, indicating the crucial role of these signaling pathways in β-conglycinin-induced NETs. Furthermore, our findings revealed that β-conglycinin induced the formation of NETs, which is dependent on NADPH oxidase-derived ROS, ERK1/2, p38, Rac and PAD4 signaling pathways. This study is the first to demonstrate the underlying mechanisms of β-conglycinin-induced NET formation, and it could be helpful to understand diarrhea caused by β-conglycinin overexposure in young animals and provides the corresponding theoretical basis for clinical applications.

New prediction tools and treatment for ACS patients with plaque erosion

For decades, we have known from autopsy observations that the proximate cause of the majority of acute coronary syndromes ( ACS) is occlusive thrombosis generated by plaque rupture or, less frequently, superficial erosion. Patients with ACS caused by plaque erosion seem to have a better long-term prognosis compared to those with plaque rupture, and may be stabilized by dual antiplatelet therapy without the need for stenting in a non-trivial proportion of cases, limiting the expenses and potential complications of invasive procedures. The accurate prediction of plaque erosion and the identification of specific biomarkers that could be used at the point-of-care without the need of invasive imaging would take us a step closer to the holy grail of precision medicine in patients with ACS.

COVID-19 in the Healthy Patient Population: Demographic and Clinical Phenotypic Characterization and Predictors of In-Hospital Outcomes

OBJECTIVE

Coronavirus disease 2019 (COVID-19) can infect patients in any age group including those with no comorbid conditions. Understanding the demographic, clinical, and laboratory characteristics of these patients is important toward developing successful treatment strategies. Approach and Results: In a retrospective study design, consecutive patients without baseline comorbidities hospitalized with confirmed COVID-19 were included. Patients were subdivided into ≤55 and >55 years of age. Predictors of in-hospital mortality or mechanical ventilation were analyzed in this patient population, as well as subgroups. Stable parameters in overall and subgroup models were used to construct a cluster model for phenotyping of patients. Of 1207 COVID-19-positive patients, 157 met the study criteria (80≤55 and 77>55 years of age). Most reliable predictors of outcomes overall and in subgroups were age, initial and follow-up d-dimer, and LDH (lactate dehydrogenase) levels. Their predictive cutoff values were used to construct a cluster model that produced 3 main clusters. Cluster 1 was a low-risk cluster and was characterized by younger patients who had low thrombotic and inflammatory features. Cluster 2 was intermediate risk that also consisted of younger population that had moderate level of thrombosis, higher inflammatory cells, and inflammatory markers. Cluster 3 was a high-risk cluster that had the most aggressive thrombotic and inflammatory feature.

CONCLUSIONS

In healthy patient population, COVID-19 remains significantly associated with morbidity and mortality. While age remains the most important predictor of in-hospital outcomes, thromboinflammatory interactions are also associated with worse clinical outcomes regardless of age in healthy patients.

Surrogate Markers of Neutrophil Extracellular Trap Formation are Associated with Ischemic Outcomes and Platelet Activation after Peripheral Angioplasty and Stenting

Neutrophil extracellular traps (NETs) are supposed to play a central role in atherothrombosis. We measured circulating citrullinated histone H3 (H3Cit) and cell-free DNA (cfDNA), which serve as surrogate markers of NET formation, in 79 patients with peripheral artery disease (PAD) following infrainguinal angioplasty with stent implantation. Analysis of cfDNA and H3Cit was performed using Quant-iT™ PicoGreen® dsDNA Assay Kit or an ELISA, respectively. Within two years of follow-up, the primary endpoint defined as nonfatal myocardial infarction, stroke or transient ischemic attack, cardiovascular death, and >80% target vessel restenosis occurred in 34 patients (43%). Both H3Cit (HR per 1-SD: 2.72; 95% CI: 1.2-6.3; p = 0.019) and cfDNA (HR per 1-SD: 2.15; 95% CI: 1.1-4.2; p = 0.028) were associated with the primary endpoint in a univariate Cox regression analysis. Multivariate linear regression analyses showed associations between cfDNA and platelet surface expression of P-selectin (p = 0.006) and activated glycoprotein IIb/IIIa (p < 0.001) in response to arachidonic acid (AA) after adjustment for age, sex, clinical risk factors, and inflammatory markers. H3Cit was also associated with P-selectin expression in response to thrombin-receptor activating peptide (p = 0.048) and AA (p = 0.032). Circulating H3Cit and cfDNA predict ischemic outcomes after peripheral angioplasty with stent implantation, and are associated with on-treatment platelet activation in stable PAD.

Extracellular traps derived from macrophages, mast cells, eosinophils and neutrophils are generated in a time-dependent manner during atherothrombosis

Extracellular traps generated by neutrophils contribute to thrombus progression in coronary atherosclerotic plaques. It is not known whether other inflammatory cell types in coronary atherosclerotic plaque or thrombus also release extracellular traps. We investigated their formation by macrophages, mast cells, and eosinophils in human coronary atherosclerosis, and in relation to the age of thrombus of myocardial infarction patients. Coronary arteries with thrombosed or intact plaques were retrieved from patients who died from myocardial infarction. In addition, thrombectomy specimens from patients with myocardial infarction were classified histologically as fresh, lytic or organised. Neutrophil and macrophage extracellular traps were identified using sequential triple immunostaining of CD68, myeloperoxidase, and citrullinated histone H3. Eosinophil and mast cell extracellular traps were visualised using double immunostaining for eosinophil major basic protein or tryptase, respectively, and citrullinated histone H3. Single‐ and double‐stained immunopositive cells in the plaque, adjacent adventitia, and thrombus were counted. All types of leucocyte‐derived extracellular traps were present in all thrombosed plaques, and in all types of the in vivo‐derived thrombi, but only to a much lower extent in intact plaques. Neutrophil traps, followed by macrophage traps, were the most prominent types in the autopsy series of atherothrombotic plaques, including the adventitia adjacent to thrombosed plaques. In contrast, macrophage traps were more numerous than neutrophil traps in intact plaques (lipid cores) and organised thrombi. Mast cell and eosinophil extracellular traps were also present, but sparse in all instances. In conclusion, not only neutrophils but also macrophages, eosinophils, and mast cells are sources of etosis involved in evolving coronary thrombosis. Neutrophil traps dominate numerically in early thrombosis and macrophage traps in late (organising) thrombosis, implying that together they span all the stages of thrombus progression and maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

New insights into the role of adipose tissue in thrombosis

Central obesity is independently associated with an elevated risk of cardiovascular disease, particularly thrombotic complications. Increasing data supports a link between excess body weight and the risk to suffer acute myocardial infarction, stent thrombosis after percutaneous interventions, ischemic stroke and vein thrombosis. Experimental and in vitro data have provided insights as to the mechanisms currently presumed to increase the thrombotic risk in obese subjects. Obesity is characterized by a chronic low grade inflammation and systemic oxidative stress that eventually damage the endothelium losing its antithrombotic properties. Obesity also stimulates the expression of leptin and attenuates adiponectin release, a protective adipokine. Although the contribution of adipokines to thrombosis has been questioned, recent work has suggested that they enhance platelet activation and, although to a lesser extent, induce the coagulation cascade through tissue factor (TF) expression. Increased body weight also impairs platelet sensitivity to insulin signaling and enhances the production of bioactive isoprostanes further promoting platelet reactivity. Finally, obese subjects have shown elevated circulating levels of von Willebrand factor, TF, factor VII and VIII, and fibrinogen, favoring a mild-to-moderate hypercoagulable state, and, on the other hand, increased secretion of plasminogen activator inhibitor (PAI)-1 and thrombin activatable fibrinolysis inhibitor (TAFI) contributing to impair the fibrinolytic system. In the present review, we provide an overview of the impact of excess body weight on thrombosis. We will focus on the link between dysfunctional adipose tissue and endothelial damage, platelet reactivity, enhanced coagulation and impaired fibrinolysis; mechanisms currently recognized to increase arterial thrombotic risk in obese subjects.

Noncanonical intercellular communication in immune response

The classical view of signaling between cells of immune system includes two major routes of intercellular communication: Through the release of extracellular molecules or a direct interaction between membrane bound receptor and its membrane bound ligand, which initiate a cascade of signaling in target cell. However, recent studies indicate that besides these canonical modes of signaling there are also noncanonical routs of intercellular communications through membrane stripping/membrane exchange/trogocytosis, extracellular traps, exosomes and ectososmes/microparticles. In this review we discuss what are the components of noncanonical pathways of signaling and what role they play in immune cells interactions.