key: cord-0885585-retb0p0a
authors: Caillon, Antoine; Trimaille, Antonin; Favre, Julie; Jesel, Laurence; Morel, Olivier; Kauffenstein, Gilles
title: Role of neutrophils, platelets, and extracellular vesicles and their interactions in COVID‐19‐associated thrombopathy
date: 2021-11-09
journal: J Thromb Haemost
DOI: 10.1111/jth.15566
sha: 34085de11133122c9deb68a7c557abb40ceafbdc
doc_id: 885585
cord_uid: retb0p0a

The COVID‐19 pandemic extended all around the world causing millions of deaths. In addition to acute respiratory distress syndrome, many patients with severe COVID‐19 develop thromboembolic complications associated to multiorgan failure and death. Here, we review evidence for the contribution of neutrophils, platelets, and extracellular vesicles (EVs) to the thromboinflammatory process in COVID‐19. We discuss how the immune system, influenced by pro‐inflammatory molecules, EVs, and neutrophil extracellular traps (NETs), can be caught out in patients with severe outcomes. We highlight how the deficient regulation of the innate immune system favors platelet activation and induces a vicious cycle amplifying an immunothrombogenic environment associated with platelet/NET interactions. In light of these considerations, we discuss potential therapeutic strategies underlining the modulation of purinergic signaling as an interesting target.

In December 2019, hospitals in Wuhan, China, admitted patients with a diagnosis of pneumonia from an unknown etiology, describing a new infection named coronavirus disease 2019 secondary to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 1 As the pandemic spread, more than half of infected people were found to be asymptomatic or develop mild symptoms with a rapid recovery. Nevertheless, a significant proportion of patients require hospitalization among who critical cases and death are not rare. 2 The infection has a significant impact on the cardiovascular system and patients with pre-existing cardiovascular disease have an increased risk of developing severe symptoms and death. [3] [4] [5] A majority of admission cases suffered from thromboinflammatory manifestations on admission to the intensive care unit (ICU) 2 including exaggerated cytokine release; profound, progressive hypoxemia; and coagulation abnormalities, leading to thrombotic complications 4,6,7 and finally, for the worst cases, multiorgan failure and death. Elevated biomarkers in critically ill COVID-19 patients include C-reactive protein (CRP), procalcitonin, ferritin, erythrocyte sedimentation rate, D-dimers, and many pro-inflammatory cytokines that are elevated or increase during the infection, and for some, highly correlate with fatal outcomes. This clinical picture points out a pathomechanism involving an outburst of the immune system leading to thrombotic manifestations. Coagulation and fibrinolytic parameter abnormalities during COVID-19 encompass elevated Ddimer and fibrinogen and thrombocytopenia, but moderate changes in prothrombin and activated partial thromboplastin time. 8 The hematology data also evidence an increase in white blood cell count with a high neutrophil-to-leukocyte ratio (NLR), characteristic of a strong inflammatory process. The analysis of this landscape is coherent with a participation of platelets and neutrophils in immune response, contributing to endothelial dysfunction (ED) and thrombosis, this being particularly pronounced in the pulmonary vascular field. 9 The catchall notions of thromboinflammation or immunothrombosis are key in COVID-19. These are hard-to-define concepts that involve a variety of systems and pathways such as CRP, factor (F)XII, complement, neutrophils and neutrophil extracellular traps (NETs), extracellular vesicles (EVs), von Willebrand factor (VWF), thrombin, and cytokines, and make a bridge between inflammation and thrombosis. This review presents data evidencing the cross-talk between neutrophils and platelets, in particular through their EVs, and how they accentuate the thromboinflammatory process in COVID- 19. In the light of these considerations, we discuss potential therapeutic strategies that particularly target some of these immunothrombotic pathways.

Antiviral responses are classically mediated through the type I interferon molecule (IFN α and β) associated with strong cytokine production. The major role of type I IFN is to activate cytotoxic natural killer (NK) cells and CD8+ T cells that eliminate infected cells through the action of perforin and granzyme. In a controlled antiviral response, myeloid cells (granulocytes and monocytes) are attracted and activated by the cytokine secretion/environment. In particular, interleukin 8 (IL-8), an early cytokine produced locally, is responsible for both chemotaxis and activation of neutrophils, initiating a strong pro-inflammatory pathway with occasional NET formation (also called NETosis). In a second step, plasmocytoid dendritic cells (pDCs) drive antiviral response with a robust production of IFNα and β that decreases IL-8 production. 10 It is noteworthy that in severe cases of COVID-19, the number of NK, CD8+ T cells as well as pDCs, but also plasmatic levels of IFNα2, were shown to be reduced due to low levels of type I IFN. 11 These observations point to a deficient antiviral response in COVID-19 due to decreased T cell number and disproportionate innate activity. In the absence of this efficient adaptive antiviral immune response, the blood neutrophil count stays elevated with sustained pro-inflammatory cytokine concentration. Together with the decrease of lymphocyte count, the NLR is particularly high in severe patients and has emerged as a robust predictor of bad outcomes. 12 Efficient antiviral response is associated with the release of pro-inflammatory cytokines to recruit and activate the immune system. Cytokines from which secretion is increased in COVID-19 defining the so-called "cytokine storm" have been reviewed by Costela-Ruiz et al. 13 These include an increase of macrophage colony-stimulating factor (M-CSF), granulocyte CSF (G-CSF), and granulocyte-macrophage CSF (GM-CSF) that participate in myeloid cell activation and survival for antigen processing and presentation to T cells. Also increased are the interleukins IL-2, IL-4, IL-13, IL-12,   and IL-7 that participate in T cell maintenance, activation, and polarization. IL-4 and IL-13 target Th2 function and favor B cell activation and immunoglobulin production against viral molecules. IL-12 induces Th1 response and IFNγ production. Together, IL-17 and IFNγ maintain a pro-inflammatory state to prime myeloid cells and activate chemokine release and adherence molecules from infected epithelia. IL-10, by contrast, decreases Th1 cell activation and is anti-inflammatory. 13, 14 Notably, some of these cytokines have been shown to directly or indirectly contribute to exert prothrombotic activity and correlate with bad outcomes. 15 In particular, IL-1β, IL-8, IL-6, and tumor necrosis factor alpha (TNFα), which participate in neutrophil, endothelial cell, and platelet activation and the release of pro-inflammatory molecules, and favor the recruitment of immune cells and in turn thrombosis.

Altogether, this argues in favor of a causal relationship among the immune imbalance (due to insufficient type I IFN production) encountered in COVID-19, a specific cytokine environment =, and the pathological involvement of neutrophils. Many of the abovementioned cytokines interact, activate, or can be secreted by neutrophils and platelets. Table 1 presents how the main cytokines are produced following neutrophil and platelet activation and participate in their activation in the context of COVID-19.

Neutrophils are the most abundant circulating leukocytes (40-70% of white blood cells) and the first responders to migrate toward the site of inflammation to fight infection and launch the immune response. They neutralize microbial agents through tissue-degrading and microbial-killing hydrolytic proteases and reactive oxygen species (ROS) production. Together with activated epithelium, neutrophils also produce chemokines and pro-inflammatory cytokines to enhance local inflammation and in the case of sustained activation, the release of NETs. In the context of COVID-19, primary pulmonary type-II pneumocyte viral infection initiates the inflammatory response including the secretion of inducers of neutrophil colony formation (GM-CSF 2 and 3) and CXC cytokines (including CXCL8/IL-8) potent neutrophils chemoattractant. This response, coupled with the weak type I IFN production (as detailed above) leads to early neutrophil recruitment and activation. 16 If neutrophil involvement in COVID-19 patients is evidenced by an elevated NLR and indirectly by neutrophil-derived cytokines such as IL-8, CCL2/MCP-1 (monocyte chemotactic protein-1), and CXCL10 (Table 1) Suicidal NETosis is initiated by oxidative stress-dependent signaling and leads to activation of peptidylarginine deiminase 4 (PAD4), histone 3/4 citrullination, and nucleosome dismantling. 20 In vitro studies evidenced that SARS-CoV-2 potentiated ROS and IL-8 production by healthy neutrophils and NETosis, suggesting that the virus triggers neutrophil activation through direct binding. 21 Corroborating these data, SARS-CoV-2 was shown to infect directly circulating neutrophils through ACE2-serine protease (viral cellular receptor) binding, virus replication, and PAD4 signaling. 18 Cytokines known to enhance NETosis such as IL-8, IL-1β, TNFα, and IL-6, were all found to be elevated in COVID- 19. 13 Attesting for NETosis in COVID-19 patients, early papers described an increase in free DNA, myeloperoxidase (MPO)-DNA complex, and citrullinated histone H3 in COVID-19 patients. 22 Infiltrated neutrophils emitting NETs were found in COVID-19 lung and heart samples after autopsy. 23, 24 It is noteworthy that NET-containing platelet microthrombi were evidenced in pulmonary autopsies of COVID-19 patients. 17 Importantly, NETs highly correlate with CRP, neutrophil count, and lactate dehydrogenase, three predictors of death at admission and, overall, with COVID-19 severity. 5 During disease progression, NET markers strongly associate to clinical outcomes, coagulation, fibrinolysis, and inflammatory markers and importantly returned to basal levels in convalescent patients. 25 Altogether, these data point to a strong Neutrophil activation is also associated with the release of danger-associated molecular patterns (DAMPs) such as ATP and ADP, histones (H3), the chromatin-associated protein high-mobility group box 1 (HMGB1), and S100 protein. Both NETs and DAMPs such as HMGB1 were proposed as valuable targets for treatment strategies to dampen thromboinflammation in the context of COVID-19. 27

Unleashed neutrophil activation and excessive NET formation can worsen the preexisting pathological environment driving ARDS in the lungs, and atherosclerosis and aortic aneurysms in the vascular system. Moreover, NETosis is commonly associated with acute organ failure through promoting thrombosis. 28 In the microcirculation of patients with a severe form of COVID-19, NET aggregates were found to enter into the composition of occlusive thrombi composed of platelets and neutrophils 29 and to co-stained with neutrophil granular enzymes. 24 In a small case series of patients with myocardial infarction, analyses of coronary thrombosis revealed a higher NET density in COVID-19 versus non COVID-19 patients. 30 The histology of thrombi did not evidence signs of increased plaque rupture suggesting a role of NETs in the pathogenesis of myocardial infarction during COVID-19. Several other papers reported the causative link existing between NET formation and thrombotic risk in COVID-19 patients. 31, 32 Activated neutrophils, and NETs in particular, contribute to generate a prothrombotic environment through several mechanisms. 28, 33, 34 DNA from NETs constitute a scaffold for a forming venous thrombus in addition to fibrin and VWF. 35 Negatively charged extracellular nucleic acids favor the assembly of coagulation factors and NETs contribute to enhance both intrinsic and extrinsic coagulation pathways. This is in agreement with an increase in FXIa, α1AT, FIXa, and thrombin/anti-thrombin complex on one hand and tissue factor (TF) on the other hand, according to the severity of the disease. 36 NETs were shown to directly favor the exposition of TF, the physiological activator of the coagulation cascade. 37 In addition, a previous paper has demonstrated that NETs may represent an assembly platform for neutrophil-derived EVs resulting in increased thrombin generation through the intrinsic pathway of coagulation in a sepsis model in mice. 38 In COVID-19 patients, high TF expression was measured in neutrophils and on NETs, this effect being dependent, at least in part, on complement, 39 

During The COVID-19 prothrombotic state leads to increased thrombin generation with patients presenting with ARDS being characterized by a thrombin burst. 64 Thrombin generation correlates with thromboinflammatory markers CRP, IL-6, and lactate dehydrogenase, and the D-dimer/endogenous thrombin potential ratio was shown to be an independent predictor of adverse events during COVID-19. 65 Thus, thrombin may be in the epicenter of a vicious circle with COVID-19 procoagulant state leading to thrombin generation, platelet activation (thrombin is the strongest platelet activator), and inflammation participating to thrombosis. The probable role of protease-activated receptors (PAR), which contribute to strong platelet activation, inflammation, and ED is likely in COVID-19 patients and has been reviewed elsewhere. 66 Several cytokines also attest for platelet activation in severe Importantly, platelets also amplify EV emission and TF expression on monocytes via the interaction of P-selectin with P-selectin gycoprotein ligand-1, its counter-receptor on monocytes and neutrophils. 53 Interaction with neutrophils and the dysfunctional endothelium is a critical point for full platelet but also neutrophil activation Figure 1 .

The origin of ED reported in COVID-19 seems to be multifacto- Increased levels of asymmetric dimethylarginine, the specific nitric oxide synthase (NOS) inhibitor, but also the marked reduction of arginine levels, an essential amino acid that can be converted to NO and citrulline by NOS has been documented in COVID-19. 85 The importance and nature of ED in COVID-19 have been reviewed elsewhere. 79, 86 Among the multiple endothelial aggressions during SARS-CoV-2 infection, neutrophils are pointed out as key players.

An important aspect to understand the role of neutrophils on ED is the effect of the strong local neutrophil degranulation close to endothelial cells, which, under the influence of pro-inflammatory cytokines, will release MPO, PR3, NE, and CG. Prolonged exposure to these enzymes induces endothelium permeabilization and apoptosis. 87, 88 The loss of endothelial cells by apoptosis is associated with a disruption of the endothelial barrier by cleavage of adherent junctions and extracellular matrix by proteolytic enzymes exposing subendothelium to platelets and leukocytes. 89 Even if endothelial TF production is controversial, 90 it has been shown that NETs could directly induce the production of TF as well as adhesion molecule (VCAM-1 and ICAM-1) by the endothelium, through IL-1α and cathepsin G-dependent mechanisms. 91 It is noteworthy that circulating neutrophil EVs constitute a bad prognosis marker for sepsis patients 111 and are responsible of matrix degradation in chronic lung diseases through NE exposure. 112 Altogether these data suggest that EVs likely enhance thromboinflammation in COVID-19 patients and cause major lung dysfunction.

In this context, a drug that reduces the release of EVs and/or their thrombogenic capacity may improve patients' outcomes during severe COVID-19 beyond available current therapeutics (anticoagulants, corticosteroids).

The 113 It has been documented that

On one hand, systemic inflammation induced by SARS-CoV-2 infection is associated with the release of pro-inflammatory cytokines and endothelial dysfunction. On the other hand, increase of innate immune activation without effective adaptive immune system response leads to neutrophil accumulation, which participates in neutrophil extracellular trap (NET) formation and pro-thrombotic mediators' production. Together with platelet activation, extracellular vesicle (EV) release and NET emission neutrophils and platelets aggregate, driving strong and sustained thrombosis. Therapeutic approaches targeting inflammation, NET formation, and platelet aggregation aiming at limiting thromboinflammation are represented in green activated platelets enhance NET formation 114, 115 giving a substratum for a thrombotic auto-amplification mechanism. The physical interaction of activated platelets with neutrophils through P-selectin induces platelet-derived HMGB1 which, in turn, triggers NET formation. 116, 117 Platelet aggregates, formed as a result of the NETplatelet interaction bind to neutrophils via glycoprotein Ib (GPIb) further amplifying NETosis. 118 Complement seems to play multiple roles enhancing NETosis (C5a) and TF release and potentially platelet activation (C3a), which together could induce thromboinflammation. 119 Interactions between NETs and activated platelets have been reported to enhance procoagulant activity in acute stroke patients with internal carotid artery occlusion. 120 

Numerous therapeutic approaches could limit COVID-19 consequences targeting neutrophils and neutrophil inflammationdependent cascade, platelet activation, and aggregates to restrain thromboinflammation.

In many countries, vaccination against COVID-19 is being deployed but its development requires time and SARS-CoV-2 variants could limit its efficacy. Antiviral treatments have so far proved to be relatively ineffective. Hence, various strategies have been tested to limit consequences of severe forms, including inflammation and thrombosis, and decrease morbi-mortality of COVID-19.

In the Randomized Evaluation of COVID-19 Therapy (RECOVERY) trial on hospitalized patients with COVID-19, dexamethasone was associated with a lower 28-day mortality compared to usual care in severe cases requiring mechanical ventilation at inclusion. 124 To date, it is the only treatment to have demonstrated a reduction of mortality rate during COVID-19. Steroids are commonly used as antiinflammatory treatments in diseases in which the immune system is abnormally activated. 125 Their anti-inflammatory effects arise from several pathways resulting in immunosuppressive actions mediated by interference with nuclear factor κB (NF-κB), the key inflammatory transcriptional regulator. 125 Steroids can curb neutrophil activation at different levels. Indeed, steroids reduce the expression of L-selectin and decrease neutrophil adhesion on the endothelium; 126 the oxidative stress in neutrophils by lowering superoxide release; 127 and inflammation as dexamethasone reduces transcription of IL-1β, TNFα, and IL-8 in neutrophils. 128 Steroids also have an impact on platelet activation. In a study on patients with immune thrombocytopenia, the positive effect of steroids was in part assigned to a reduction of platelet activation status. 129 These data may partially explain clinical effects of steroids during COVID-19. However, because the use of steroids is associated with an increased risk of venous thromboembolism, 130 further studies are required to confirm their efficacy without negative impact. All these results must be confirmed on larger cohorts and future studies should evaluate the susceptibility of developing thrombosis in patients taking these treatments.

Therapeutic anticoagulation during hospital stay is associated with improved outcomes among COVID-19 patients. 6, 138, 139 Hence, the International Society on Thrombosis and Haemostasis proposed to reinforced thromboprophylaxis (twice standard dose) in severe cases or in the presence of thrombotic risk factors. 140 However, intensified use of anticoagulants exposes patients to bleeding risks. 141 Several randomized controlled trials are investigating outcomes of COVID-19 patients with different anticoagulation including heparin and direct oral anticoagulants. 142 In the majority of these trials, anticoagulant intensity is proportional to the severity of COVID-19 and thus the expected thrombotic event rates. rior benefit compared to clopidogrel to prevent fatal thrombosis in patients with acute coronary syndrome. 146 Compared to clopidogrel, ticagrelor inhibited in a larger extent platelet and leukocyte EV emission. 147 Finally, ticagrelor was shown to reduce mortality secondary to bacterial lung infection and sepsis in the PLATO study. 148 These effects can be attributable, at least in part, to ENT (equilibrative nucleoside transporter)-1 inhibition, which increases local concentration of adenosine. 149 In turn, adenosine, through A2A receptor activation, limits platelet aggregation and secretion, exerts anti-inflammatory effects, and prevents the formation of platelet-neutrophils aggregates. Importantly, adenosine has recently been reported to inhibit emission of NETs in antiphospholipid syndrome. 150 Altogether these data strengthen the rationale of using 165 Moreover, following their sequential hydrolysis by CD39 and CD73 (ecto 5'-nucleotidase) adenylic nucleotide hydrolysis leads to the accumulation of adenosine.

Adenosine exerts an inhibitory/protective effect on platelet aggregation through a feedback loop involving A2B receptors.

Interestingly, a recent work evidenced a strong inhibition of neutrophil NETosis by adenosine. 150 Altogether, considering the inhibition of aggregation, NETosis, and the wide anti-inflammatory effect of adenosine, 166 

This work was supported by GERCA (Groupe pour l'étude et la recherche des maladies cardiovasculaires en Alsace).

Putative therapeutic strategies aiming at targeting deleterious involvement of platelets and neutrophils in COVID-19 167, 193 Abbreviations: NE, neutrophil elastase; NET, neutrophil extracellular trap; PAR-1, protease-activated receptor 1; PAD4, peptidylarginine deiminase 4.

A novel coronavirus from patients with pneumonia in China

Incidence of thrombotic complications in critically ill ICU patients with COVID-19

COVID-19 and the cardiovascular system: implications for risk assessment, diagnosis, and treatment options

COVID-19 related coagulopathy: a distinct entity?

High systolic blood pressure at hospital admission is an important risk factor in models predicting outcome of COVID-19 patients

Pulmonary embolism in COVID-19 patients: a French multicentre cohort study

High risk of thrombosis in patients with severe SARS-CoV-2 infection: a multicenter prospective cohort study

Abnormal coagulation parameters are associated with poor prognosis in patients with novel coronavirus pneumonia

Immune mechanisms of pulmonary intravascular coagulopathy in COVID-19 pneumonia

Type-I interferons are potent inhibitors of interleukin-8 production in hematopoietic and bone marrow stromal cells

Impaired type I interferon activity and inflammatory responses in severe COVID-19 patients

The diagnostic and predictive role of NLR, d-NLR and PLR in COVID-19 patients

SARS-CoV-2 infection: the role of cytokines in COVID-19 disease

Dysregulation of the immune response in coronavirus disease 2019 Leila Mohamed Khosroshahi, Nima Rezaei

Identification of key signaling pathways induced by SARS-CoV2 that underlie thrombosis and vascular injury in COVID-19 patients

Neutrophil extracellular traps contribute to immunothrombosis in COVID-19 acute respiratory distress syndrome

SARS-CoV-2-triggered neutrophil extracellular traps mediate COVID-19 pathology

NETosis: how vital is it?

Histone hypercitrullination mediates chromatin decondensation and neutrophil extracellular trap formation

The emerging role of neutrophil extracellular traps in severe acute respiratory syndrome coronavirus 2 (COVID-19)

Neutrophil extracellular traps in COVID-19

Targeting potential drivers of COVID-19: neutrophil extracellular traps

Neutrophil extracellular traps infiltrate the lung airway, interstitial, and vascular compartments in severe COVID-19

Circulating markers of neutrophil extracellular traps are of prognostic value in patients with COVID-19

Neutrophil extracellular traps and endothelial dysfunction in atherosclerosis and thrombosis

Neutrophil extracellular traps (NETs) and damage-associated molecular patterns (DAMPs): two potential targets for COVID-19 treatment

Thrombosis: tangled up in NETs

Vascular occlusion by neutrophil extracellular traps in COVID-19

Assessment of neutrophil extracellular traps in coronary thrombus of a case series of patients with COVID-19 and myocardial infarction

Neutrophil more than platelet activation associates with thrombotic complications in COVID-19 patients

Neutrophil extracellular traps and thrombosis in COVID-19

The role of neutrophils in thrombosis

Neutrophil extracellular traps: villains and targets in arterial, venous, and cancer-associated thrombosis

Neutrophil extracellular trap (NET) impact on deep vein thrombosis

Neutrophils and contact activation of coagulation as potential drivers of COVID-19

Tissue factor expression in neutrophil extracellular traps and neutrophil derived microparticles in antineutrophil cytoplasmic antibody associated vasculitis may promote thromboinflammation and the thrombophilic state associated with the disease

Neutrophil extracellular trapmicroparticle complexes enhance thrombin generation via the intrinsic pathway of coagulation in mice

Complement and tissue factor-enriched neutrophil extracellular traps are key drivers in COVID-19 immunothrombosis

Is COVID-19 associated thrombosis caused by overactivation of the complement cascade? A literature review

The role of extracellular histones in influenza virus pathogenesis

Extracellular DNA traps promote thrombosis

Extracellular DNA traps are associated with the pathogenesis of TRALI in humans and mice

Cancers predispose neutrophils to release extracellular DNA traps that contribute to cancer-associated thrombosis

The dual role of plateletinnate immune cell interactions in thrombo-inflammation

Platelets in neutrophil recruitment to sites of inflammation

Amicus or adversary revisited: platelets in acute lung injury and acute respiratory distress syndrome

Platelets in sepsis: an update on experimental models and clinical data

Platelets and multi-organ failure in sepsis

COVID-19 induces a hyperactive phenotype in circulating platelets

Platelets can associate with SARS-Cov-2 RNA and are hyperactivated in COVID-19

Platelet gene expression and function in patients with COVID-19

Platelet activation and platelet-monocyte aggregate formation trigger tissue factor expression in patients with severe COVID-19

Antibody-induced procoagulant platelets in severe COVID-19 infection

Pulmonary embolism or pulmonary thrombosis in COVID-19? Is the recommendation to use high-dose heparin for thromboprophylaxis justified?

Clinical features of 85 fatal cases of COVID-19 from Wuhan. A retrospective observational study

Thrombocytopenia is associated with severe coronavirus disease 2019 (COVID-19) infections: a meta-analysis

Thrombocytopenia is independently associated with poor outcome in patients hospitalized for COVID-19

Mechanisms involved in the development of thrombocytopenia in patients with COVID-19

The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors

Immune thrombocytopenia secondary to COVID-19: a systematic review

Disruption of the CCL5/RANTES-CCR5 pathway restores immune homeostasis and reduces plasma viral load in critical COVID-19. medRxiv

SARS-CoV-2 binds platelet ACE2 to enhance thrombosis in COVID-19

Covid-19-associated coagulopathy: biomarkers of thrombin generation and fibrinolysis leading the outcome

Prognostic value of thrombin generation parameters in hospitalized COVID-19 patients

Protease-activated receptor 1 as a potential therapeutic target for COVID-19

Mapping systemic inflammation and antibody responses in multisystem inflammatory syndrome in children (MIS-C)

Activation of NLRP3 inflammasome complex potentiates venous thrombosis in response to hypoxia

Novel path to IL-6 transsignaling through thrombin-induced soluble IL-6 receptor release by platelets

Hypercoagulability of COVID-19 patients in intensive care unit: a report of thromboelastography findings and other parameters of hemostasis

von Willebrand factor and inflammation

Platelets in immune response to virus and immunopathology of viral infections

Platelets fuel the inflammasome activation of innate immune cells

Search for SARS-CoV-2 RNA in platelets from COVID-19 patients

Impact of angiotensinconverting enzyme inhibition on platelet tissue factor expression in stroke-prone rats

COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensinaldosterone system

Elevation of plasma angiotensin II level is a potential pathogenesis for the critically ill COVID-19 patients

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

COVID-19 is, in the end, an endothelial disease

Complement and coagulation: key triggers of COVID-19-induced multiorgan pathology

Blood viscosity of COVID-19 patient: a preliminary report

Endotheliopathy in COVID-19-associated coagulopathy: evidence from a single-centre, crosssectional study

Intermediate-dose anticoagulation, aspirin, and in-hospital mortality in COVID-19: a propensity score-matched analysis

Role of endothelial dysfunction in the thrombotic complications of COVID-19 patients

Platelet and endothelial activation as potential mechanisms behind the thrombotic complications of COVID-19 patients

Endothelial cells orchestrate COVID-19 coagulopathy

Novel effects of neutrophil-derived proteinase 3 and elastase on the vascular endothelium involve in vivo cleavage of NF-kappaB and proapoptotic changes in JNK, ERK, and p38 MAPK signaling pathways

Apoptosis of endothelial cells induced by the neutrophil serine proteases proteinase 3 and elastase

Extracellular matrix proteins in hemostasis and thrombosis

Editorial commentary: tissue factor expression by the endothelium: coagulation or inflammation?

Neutrophil extracellular traps induce endothelial cell activation and tissue factor production through interleukin-1α and cathepsin G

Endothelial tissue factor stimulation by proteinase 3 and elastase

Microvesicles in vascular homeostasis and diseases. Position paper of the European society of cardiology (ESC) working group on atherosclerosis and vascular biology

Microparticles in hemostasis and thrombosis

Procoagulant microparticles: disrupting the vascular homeostasis equation?

Platelets promote thromboinflammation in SARS-CoV-2 pneumonia

Extracellular vesicle-mediated endothelial apoptosis and EVassociated proteins correlate with COVID-19 disease severity

COVID-19 patients exhibit reduced procoagulant platelet responses

Evidence for increased circulating procoagulant phospholipids in patients with COVID-19 pneumonia and their prognostic role

Tissue factor in blood cells and endothelial cells

Circulating tissue factor and thrombosis

Dissemination of extreme levels of extracellular vesicles: tissue factor activity in patients with severe COVID-19

Circulating microparticles and activated platelets as novel prognostic biomarkers in COVID-19; relation to cancer

Patients with COVID-19 have elevated levels of circulating extracellular vesicle tissue factor activity that is associated with severity and mortalitybrief report

Increased levels of procoagulant tissue factor-bearing microparticles within the occluded coronary artery of patients with ST-segment elevation myocardial infarction: role of endothelial damage and leukocyte activation

Significance of neutrophil microparticles in ischaemia-reperfusion: pro-inflammatory effectors of endothelial senescence and vascular dysfunction

Novel mediators and biomarkers of thrombosis

Microparticles: a critical component in the nexus between inflammation, immunity, and thrombosis

C-type lectins and extracellular vesicles in virus-induced NETosis

Neutrophil extracellular trap-microparticle complexes trigger neutrophil recruitment via high-mobility group protein 1 (HMGB1)-toll-like receptors(TLR2)/TLR4 signalling

Circulating neutrophil-derived microparticles associated with the prognosis of patients with sepsis

Activated PMN exosomes: pathogenic entities causing matrix destruction and disease in the lung

Measuring and interpreting platelet-leukocyte aggregates

Reciprocal coupling of coagulation and innate immunity via neutrophil serine proteases

Monocytes, neutrophils, and platelets cooperate to initiate and propagate venous thrombosis in mice in vivo

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

Platelet-derived HMGB1 is a critical mediator of thrombosis

Directed transport of neutrophil-derived extracellular vesicles enables plateletmediated innate immune response

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

Interactions between neutrophil extracellular traps and activated platelets enhance procoagulant activity in acute stroke patients with ICA occlusion

IL-1 induces throboxane-A2 (TxA2) in COVID-19 causing inflammation and micro-thrombi: inhibitory effect of the IL-1 receptor antagonist (IL-1Ra)

Ability of plateletderived extracellular vesicles to promote neutrophil-endothelial cell interactions

Platelet extracellular vesicles drive inflammasome-IL-1β-dependent lung injury in sickle cell disease

Dexamethasone in hospitalized patients with Covid-19 -preliminary report the RECOVERY collaborative group

Antiinflammatory action of glucocorticoidsnew mechanisms for old drugs

Glucocorticoid receptor regulates expression of L-selectin and CD11/CD18 on human neutrophils

Acute suppressive effect of hydrocortisone on p47 subunit of nicotinamide adenine dinucleotide phosphate oxidase

Neutrophils are not less sensitive than other blood leukocytes to the genomic effects of glucocorticoids

Effect of steroids on the activation status of platelets in patients with Immune thrombocytopenia (ITP)

Use of glucocorticoids and risk of venous thromboembolism: a nationwide population-based case-control study

Tocilizumab for treatment of mechanically ventilated patients with COVID-19

Association between early treatment with tocilizumab and mortality among critically Ill patients with COVID-19

Efficacy of tocilizumab in patients hospitalized with Covid-19

Interleukin-6 receptor antagonists in critically Ill patients with Covid-19

Infliximab against severe COVID-19-induced cytokine storm syndrome with organ failure-a cautionary case series

Continuous intravenous anakinra infusion to calm the cytokine storm in macrophage activation syndrome

Canakinumab in a subgroup of patients with COVID-19

Association of treatment dose anticoagulation with in-hospital survival among hospitalized patients with COVID-19

Venous thromboembolism in non-critically ill patients with COVID-19 infection

ISTH interim guidance on recognition and management of coagulopathy in COVID-19

Anticoagulation, bleeding, mortality, and pathology in hospitalized patients with COVID-19

Therapeutic anticoagulation with heparin in critically Ill patients with Covid-19

Association of mortality and aspirin prescription for COVID-19 patients at the veterans health administration

Therapeutic anticoagulation with heparin in noncritically Ill patients with Covid-19

Effect of P2Y12 inhibitors on inflammation and immunity

Ticagrelor versus clopidogrel in patients with acute coronary syndromes

Ticagrelor attenuates the increase of extracellular vesicle concentrations in plasma after acute myocardial infarction compared to clopidogrel

Lower mortality following pulmonary adverse events and sepsis with ticagrelor compared to clopidogrel in the PLATO study

Ticagrelor inhibits human platelet aggregation via adenosine in addition to P2Y12 antagonism

Adenosine receptor agonism protects against NETosis and thrombosis in antiphospholipid syndrome

Ticagrelor reduces thromboinflammatory markers in patients with pneumonia

New (re)purpose for an old drug: purinergic modulation may extinguish the COVID-19 thromboinflammatory firestorm

Dipyridamole augments the antiinflammatory response during human endotoxemia

Potential therapeutic effects of dipyridamole in the severely ill patients with COVID-19

Engineering human ACE2 to optimize binding to the spike protein of SARS coronavirus 2

Extracellular vesicles containing ACE2 efficiently prevent infection by SARS-CoV-2 Spike protein-containing virus

SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor

Colchicine for community-treated patients with COVID-19 (COLCORONA): a phase 3, randomised, double-blinded, adaptive, placebocontrolled, multicentre trial

Purinergic receptors in thrombosis and inflammation

A rationale for targeting the P2X7 receptor in Coronavirus disease 19

Liaisons dangereuses: P2X(7) and the inflammasome

Targeting the NLRP3 inflammasome in severe COVID-19

P2X7 receptors: an untapped target for the management of cardiovascular disease

CD39: interface between vascular thrombosis and inflammation

Stimulation of P2 (P2X7) receptors in human dendritic cells induces the release of tissue factor-bearing microparticles

Purinergic signaling during inflammation

Possible role of adenosine in COVID-19 pathogenesis and therapeutic opportunities

The role of interleukin 6 during viral infections

Interleukin-6 mediates the platelet abnormalities and thrombogenesis associated with experimental colitis

Interleukin-6: a potential target for post-thrombotic syndrome

IL-6 regulates neutrophil trafficking during acute inflammation via STAT3

IL-6 drives neutrophilmediated pulmonary inflammation associated with bacteremia in murine models of colitis

Antithrombotic activity of TNF-alpha

Macrophage interleukin-6 and tumour necrosis factor-alpha are induced by coronavirus fixation to Toll-like receptor 2/heparan sulphate receptors but not carcinoembryonic cell adhesion antigen 1a

Epidermal growth factor enhances TNF-alpha-induced priming of human neutrophils

Tumor necrosis factor alpha exerts powerful anti-influenza virus effects in lung epithelial cells

Promotion of neutrophil apoptosis by TNF-alpha

Contribution of the TNF-α (tumor necrosis factor-α)-TNF-Rp55 (tumor necrosis factor receptor p55) axis in the resolution of venous thrombus

The role of interleukin-1 in neutrophil leukocyte emigration induced by endotoxin

Influence of interleukin-1 beta on platelet-poor plasma clot formation: a potential impact on early bone healing

Ectonucleotidase tri(di)phosphohydrolase-1 (ENTPD-1) disrupts inflammasome/interleukin 1β-driven venous thrombosis

Interleukin 8 and venous thrombosis: evidence for a role of inflammation in thrombosis

Long-term increased factor VIII levels are associated to interleukin-6 levels but not to post-thrombotic syndrome in patients with deep venous thrombosis

Thrombolysis of deep vein thrombosis and inhibiting chemotaxis of macrophage by MCP-1 blockage

Chemokine CC-motif ligand 2 participates in platelet function and arterial thrombosis by regulating PKCα-P38MAPK-HSP27 pathway

Eculizumab as an emergency treatment for adult patients with severe COVID-19 in the intensive care unit: a proof-of-concept study

Complement C3 vs C5 inhibition in severe COVID-19: early clinical findings reveal differential biological efficacy

Proteinase-activated receptor 1: a target for repurposing in the treatment of COVID-19?

Long-acting nanoparticulate DNase-1 for effective suppression of SARS-CoV-2-mediated neutrophil activities and cytokine storm

Neutrophil elastase inhibitors: a potential prophylactic treatment option for SARS-CoV-2-induced respiratory complications?

Neutrophil elastase inhibitor (sivelestat) may be a promising therapeutic option for management of acute lung injury/acute respiratory distress syndrome or disseminated intravascular coagulation in COVID-19

Putative roles for peptidylarginine deiminases in COVID-19

Harnessing adenosine A2A receptors as a strategy for suppressing the lung inflammation and thrombotic complications of COVID-19: potential of pentoxifylline and dipyridamole

Role of neutrophils, platelets, and extracellular vesicles and their interactions in COVID-19-associated thrombopathy