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OBJECTIVE Aberrant neutrophil activation occurs during the advanced stages of atherosclerosis. Once primed, neutrophils can undergo apoptosis or release neutrophil extracellular traps (NETs). This extracellular DNA exerts potent pro-inflammatory, prothrombotic and cytotoxic properties. The goal of this study was to examine the relationships between extracellular DNA formation, coronary atherosclerosis and the presence of a prothrombotic state. APPROACH AND RESULTS In a prospective, observational, cross-sectional cohort of 282 individuals with suspected coronary artery disease (CAD), we examined the severity, extent, and phenotype of coronary atherosclerosis by using coronary computed tomographic angiography (CCTA). Double-stranded DNA, nucleosomes, citrullinated histone H4 and myeloperoxidase (MPO)-DNA complexes, considered in vivo markers of cell death and NETosis, respectively, were established. We further measured various plasma markers of coagulation activation and inflammation. Plasma double-stranded DNA, nucleosomes and MPO-DNA complexes were positively associated with thrombin generation and significantly elevated in patients with severe coronary atherosclerosis or extremely calcified coronary arteries. Multinomial regression analysis, adjusted for confounding factors, identified high plasma nucleosome levels as an independent risk factor of severe coronary stenosis (OR: 2.14, 95% CI 1.26-3.63; p=0.005). Markers of NETs, such as MPO-DNA complexes, predicted the number of atherosclerotic coronary vessels and the occurrence of major adverse cardiac events. CONCLUSIONS Our report provides evidence demonstrating that markers of cell death and NET formation are independently associated with CAD, prothrombotic state and occurrence of adverse cardiac events. These biomarkers could potentially aid in the prediction of cardiovascular risk in patients with chest discomfort.

• PAD4-mediated chromatin decondensation and release by neutrophils exacerbate injury after MI/R. • Combining reduction of neutrophil recruitment with extracellular DNA cleavage could be a new approach to reduce cardiac damage after MI.Innate immune cells play a major role in the early response to myocardial ischemia/ reperfusion (MI/R) injury. Recombinant human ADAMTS13 (rhADAMTS13), cleaving von Willebrand factor (VWF), reduces leukocyte recruitment in mice. Death of cardiomyocytes and the possible formation of neutrophil extracellular traps (NETs) may result in chromatin release that is prothrombotic and cytotoxic. We investigated the pathophysiological role of extracellular chromatin during MI/R to evaluate the therapeutic potential of targeting extracellular DNA and VWF by using DNase I with/without rhADAMTS13. Finally, we examined the impact of histone citrullination and NETosis by peptidylarginine deiminase 4 (PAD4) on MI/R. We used a 24-hour MI/R mouse surgical model. MI/R injury caused an increase in plasma nucleosomes, abundant neutrophil infiltration, and the presence of citrullinated histone H3 at the site of injury. Both monotherapies and coadministration of DNase I and rhADAMTS13 revealed a cardioprotective effect, resulting in subsequent improvement of cardiac contractile function. PAD4 2/2 mice, which do not produce NETs, were also significantly protected from MI/R and DNase I treatment had no further beneficial effect. We demonstrate that extracellular chromatin released through NETosis exacerbates MI/R injury. Targeting both VWF-mediated leukocyte recruitment and chromatin removal may be a new therapeutic strategy to reduce ischemia-related cardiac damage. (Blood. 2014;123(1):141-148)

Background A growing health problem, venous thromboembolism (VTE), including pulmonary embolism (PE) and deep vein thrombosis (DVT), requires refined diagnostic and therapeutic approaches. Neutrophils contribute to thrombus initiation and development in experimental DVT. Recent animal studies recognized neutrophil extracellular traps (NETs) as an important scaffold supporting thrombus stability. However, the hypothesis that human venous thrombi involve NETs has not undergone rigorous testing. Objective To explore the cellular composition and the presence of NETs within human venous thrombi at different stages of development. Patients and Methods We examined sixteen thrombi obtained from 11 patients during surgery or at autopsy using histomorphological, immunohistochemical and immunofluorescence analyses. Results We classified thrombus regions as unorganized, organizing, and organized according to their morphological characteristics. We then evaluated them focusing on neutrophil and platelet deposition as well as micro-vascularization of the thrombus body. We observed evidence of NET accumulation, including the presence of citrullinated histone H3 (H3Cit)-positive cells. NETs, defined as extracellular diffuse H3Cit areas associated with myeloperoxidase and DNA, localized predominantly during the phase of organization in human venous thrombi. Conclusions NETs are present in organizing thrombi in patients with VTE. They are associated with thrombus maturation in humans. Dissolution of NETs might thus facilitate thrombolysis. This finding provides new insights into the clinical development and pathology of thrombosis and provides new perspectives for therapeutic advances.