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      Expression of functional tissue factor by neutrophil extracellular traps in culprit artery of acute myocardial infarction

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          Abstract

          Neutrophils are involved in the pathophysiology of infracted coronary arteries in STEMI via NET structures. Platelets, activated by thrombin, are required for NET formation, while the integrity of NET scaffold contributes to the functionality of NET-bound TF. The blockage of NET formation or local neutralization of NET-mediated TF signalling constitutes candidate therapeutic targets.

          Abstract

          Aims

          Neutrophil extracellular traps (NETs) are chromatin filaments released by activated polymorphonuclear neutrophils (PMNs) and decorated with granule proteins with various properties. Several lines of evidence implicate NETs in thrombosis. The functional significance and the in vivo relevance of NETs during atherothrombosis in humans have not been addressed until now.

          Methods and results

          Selective sampling of thrombotic material and surrounding blood from the infarct-related coronary artery (IRA) and the non-IRA was performed during primary percutaneous revascularization in 18 patients with ST-segment elevation acute myocardial infarction (STEMI). Thrombi isolated from IRA contained PMNs and NETs decorated with tissue factor (TF). Although TF was expressed intracellularly in circulating PMNs of STEMI patients, active TF was specifically exposed by NETs obtained from the site of plaque rupture. Treatment of NET structures with DNase I abolished TF functionality measurement. In vitro treatment of control PMNs with plasma obtained from IRA and non-IRA was further shown to induce intracellular up-regulation of TF but not NET formation. A second step consisting of the interaction between PMNs and thrombin-activated platelets was required for NET generation and subsequent TF exposure.

          Conclusion

          The interaction of thrombin-activated platelets with PMNs at the site of plaque rupture during acute STEMI results in local NET formation and delivery of active TF. The notion that NETs represent a mechanism by which PMNs release thrombogenic signals during atherothrombosis may offer novel therapeutic targets.

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          Most cited references16

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          Platelet TLR4 activates neutrophil extracellular traps to ensnare bacteria in septic blood.

          It has been known for many years that neutrophils and platelets participate in the pathogenesis of severe sepsis, but the inter-relationship between these players is completely unknown. We report several cellular events that led to enhanced trapping of bacteria in blood vessels: platelet TLR4 detected TLR4 ligands in blood and induced platelet binding to adherent neutrophils. This led to robust neutrophil activation and formation of neutrophil extracellular traps (NETs). Plasma from severely septic humans also induced TLR4-dependent platelet-neutrophil interactions, leading to the production of NETs. The NETs retained their integrity under flow conditions and ensnared bacteria within the vasculature. The entire event occurred primarily in the liver sinusoids and pulmonary capillaries, where NETs have the greatest capacity for bacterial trapping. We propose that platelet TLR4 is a threshold switch for this new bacterial trapping mechanism in severe sepsis.
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            Thrombin signalling and protease-activated receptors.

            S Coughlin (2000)
            How does the coagulation protease thrombin regulate cellular behaviour? The protease-activated receptors (PARs) provide one answer. In concert with the coagulation cascade, these receptors provide an elegant mechanism linking mechanical information in the form of tissue injury or vascular leakage to cellular responses. Roles for PARs are beginning to emerge in haemostasis and thrombosis, inflammation, and perhaps even blood vessel development.
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              Reciprocal coupling of coagulation and innate immunity via neutrophil serine proteases.

              Blood neutrophils provide the first line of defense against pathogens but have also been implicated in thrombotic processes. This dual function of neutrophils could reflect an evolutionarily conserved association between blood coagulation and antimicrobial defense, although the molecular determinants and in vivo significance of this association remain unclear. Here we show that major microbicidal effectors of neutrophils, the serine proteases neutrophil elastase and cathepsin G, together with externalized nucleosomes, promote coagulation and intravascular thrombus growth in vivo. The serine proteases and extracellular nucleosomes enhance tissue factor- and factor XII-dependent coagulation in a process involving local proteolysis of the coagulation suppressor tissue factor pathway inhibitor. During systemic infection, activation of coagulation fosters compartmentalization of bacteria in liver microvessels and reduces bacterial invasion into tissue. In the absence of a pathogen challenge, neutrophil-derived serine proteases and nucleosomes can contribute to large-vessel thrombosis, the main trigger of myocardial infarction and stroke. The ability of coagulation to suppress pathogen dissemination indicates that microvessel thrombosis represents a physiological tool of host defense.
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                Author and article information

                Journal
                Eur Heart J
                Eur. Heart J
                eurheartj
                ehj
                European Heart Journal
                Oxford University Press
                0195-668X
                1522-9645
                07 June 2015
                07 February 2015
                07 February 2015
                : 36
                : 22
                : 1405-1414
                Affiliations
                [1 ]Cardiology Department, Democritus University of Thrace , Alexandroupolis, Greece
                [2 ]Laboratory of Molecular Hematology, Democritus University of Thrace , Alexandroupolis, Greece
                [3 ]Department of Clinical Pathobiochemistry, and Institute for Clinical Chemistry and Laboratory Medicine , Faculty of Medicine Technische Universität Dresden, Dresden, Germany
                [4 ]Department of Pathology, University General Hospital of Alexandroupolis , Alexandroupolis, Greece
                [5 ]Center for Thrombosis and Hemostasis, University Medical Center Mainz , Mainz, Germany
                Author notes
                [* ]Corresponding author: Tel: +30 25513 51103, Fax: +30 25510 30378, Email: kritis@ 123456med.duth.gr
                [†]

                These authors contributed equally.

                Article
                ehv007
                10.1093/eurheartj/ehv007
                4458286
                25660055
                27283bc9-40f0-4837-a349-33caaf9a3f60
                © The Author 2015. Published by Oxford University Press on behalf of the European Society of Cardiology.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

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                Categories
                Basic Science

                Cardiovascular Medicine
                myocardial infarction,thrombosis,inflammation,neutrophil extracellular traps,tissue factor

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