Thrombosis: tangled up in NETs

Multifaceted roles of neutrophils in cardiac disease

Neutrophils, the most abundant leukocytes in human blood, have long been recognized as critical first responders in the innate immune system's defense against pathogens. Some of the more notable innate antimicrobial properties of neutrophils include generation of superoxide free radicals like myeloperoxidase, production of proteases that reshape the extracellular matrix allowing for easier access to infected tissues, and release of neutrophil extracellular traps, extruded pieces of DNA that ensnare bacterial and fungi. These mechanisms developed to provide neutrophils with a vast array of specialized functions to provide the host defense against infection in an acute setting. However, emerging evidence over the past few decades has revealed a far more complex and nuanced role for these neutrophil-driven processes in various chronic conditions, particularly in cardiovascular diseases. The pathophysiology of cardiac diseases involves a complex interplay of hemodynamic, neurohumoral, and inflammatory factors. Neutrophils, as key mediators of inflammation, contribute significantly to this intricate network. Their involvement extends far beyond their classical role in pathogen clearance, encompassing diverse functions that can both exacerbate tissue damage and contribute to repair processes. Here, we consider the contributions of neutrophils to myocardial infarction, heart failure, cardiac arrhythmias, and nonischemic cardiomyopathies. Understanding these complex interactions is crucial for developing novel therapeutic strategies aimed at modulating neutrophil functions in these highly morbid cardiac diseases.

Bacterial biofilm-derived H-NS protein acts as a defense against Neutrophil Extracellular Traps (NETs)

Extracellular DNA (eDNA) is crucial for the structural integrity of bacterial biofilms as they undergo transformation from B-DNA to Z-DNA as the biofilm matures. This transition to Z-DNA increases biofilm rigidity and prevents binding by canonical B-DNA-binding proteins, including nucleases. One of the primary defenses against bacterial infections are Neutrophil Extracellular Traps (NETs), wherein neutrophils release their own eDNA to trap and kill bacteria. Here we show that H-NS, a bacterial nucleoid associated protein (NAP) that is also released during biofilm development, is able to incapacitate NETs. Indeed, when exposed to human derived neutrophils, H-NS prevented the formation of NETs and lead to NET eDNA retraction in previously formed NETs. NETs that were exposed to H-NS also lost their ability to kill free-living bacteria which made H-NS an attractive therapeutic candidate for the control of NET-related human diseases. A model of H-NS release from biofilms and NET incapacitation is discussed.

M2 macrophages-derived exosomes for osteonecrosis of femoral head treatment: modulating neutrophil extracellular traps formation and endothelial phenotype transition

Exosomes have shown good potential in ischemic injury disease treatments. However, evidence about their effect and molecular mechanisms in osteonecrosis of femoral head (ONFH) treatment is still limited. Here, we revealed the cell biology characters of ONFH osteonecrosis area bone tissue in single cell scale and thus identified a novel ONFH treatment approach based on M2 macrophages-derived exosomes (M2-Exos). We further show that M2-Exos are highly effective in the treatment of ONFH by modulating the phenotypes communication between neutrophil and endothelium including neutrophil extracellular traps formation and endothelial phenotype transition. Additionally, we identified that M2-Exos' therapeutic effect is attributed to the high content of miR-93-5p and constructed miR-93-5p overexpression model in vitro and in vivo based on lentivirus and adeno-associated virus respectively. Then we found miR-93-5p can not only reduce neutrophil extracellular traps formation but also improve angiogenic ability of endothelial cells. These results provided a new theoretical basis for the clinical application of ONFH therapeutic exosomes.

The Role of Neutrophil Extracellular Traps in Atherosclerosis: From the Molecular to the Clinical Level

Atherosclerosis is a chronic inflammatory condition that is typified by the deposition of lipids and the subsequent inflammation of medium and large arteries. Neutrophil extracellular traps (NETs) are fibrous meshworks of DNA, histones, and granzymes expelled by activated neutrophils in response to a variety of pathogenic conditions. In addition to their role in pathogen eradication, NETs have been demonstrated to play a pivotal role in the development of atherosclerosis. This article presents a review of the bidirectional interactions in which atherosclerosis-related risk factors stimulate the formation of NETs, which in turn support disease progression. This article emphasizes the involvement of NETs in the various stages of atherogenesis and development, influencing multiple factors such as the vascular endothelium, platelets, the inflammatory milieu, and lipid metabolism. The findings of this study offer new insights and avenues for further investigation into the processes underlying the formation and regulation of the vascular inflammatory microenvironment in atherosclerosis. Finally, potential targeted therapeutic strategies for NETs are discussed to facilitate their progression to clinical practice (Graphical Abstract).

Neutrophil extracellular traps: potential thrombotic markers and therapeutic targets in colorectal cancer

Neutrophil extracellular traps (NETs) are promising promoters in venous thromboembolism (VTE). In the present study, we have investigated the potential thrombogenic role of NETs in colorectal cancer (CRC). A total of 583 patients with gastrointestinal malignancies who were diagnosed with or without VTE by extremities arteriovenous ultrasound and computed tomography were enrolled. The incidence of VTE in CRC was as high as 17.53%. In serological ELISA experiments, Cit-H3, myeloperoxidase, and cfDNA were significantly overexpressed in CRC patients with VTE compared with CRC patients without VTE and healthy individuals. Neutrophils from CRC patients with VTE produced appreciable amounts of NETs after stimulation with phorbol-12-myristate-13-acetate, which were lacking in CRC patients without VTE and healthy individuals. CfDNA was positively correlated with plasmin-α2-antiplasmin complex and tissue plasmin activator inhibitor-1 complex, and Cit-H3 was positively correlated with plasmin-α2-antiplasmin complex, suggesting that NETs are associated with increased fibrinolytic activity. We screened some NETs-related genes by analyzing several high-throughput sequencing datasets of VTE and NETs. FCGR1A was identified as the optimal target gene by pan-cancer expression analysis and survival analysis. FCGR1A was significantly overexpressed in the peripheral blood of CRC patients without VTE compared with healthy individuals and showed a positive correlation with cfDNA. Neutrophil-derived NETs were significantly reduced by FCGR1A inhibitor exposure. These findings indicate that NETs are actively involved in VTE in CRC. NETs are promising thrombotic marker and therapeutic target in CRC to prevent the thrombotic consequences of cancer.

Neutrophil Extracellular Traps in Atherosclerosis: Research Progress

Atherosclerosis (AS) is a disease characterised by the accumulation of atherosclerotic plaques on the inner walls of blood vessels, resulting in their narrowing. In its early stages, atherosclerosis remains asymptomatic and undetectable by conventional pathological methods. However, as the disease progresses, it can lead to a series of cardiovascular diseases, which are a leading cause of mortality among middle-aged and elderly populations worldwide. Neutrophil extracellular traps (NETs) are composed of chromatin and granular proteins released by neutrophils. Upon activation by external stimuli, neutrophils undergo a series of reactions, resulting in the release of NETs and subsequent cell death, a process termed NETosis. Research has demonstrated that NETosis is a means by which neutrophils contribute to immune responses. However, studies on neutrophil extracellular traps have identified NETs as the primary cause of various inflammation-induced diseases, including cystic fibrosis, systemic lupus erythematosus, and rheumatoid arthritis. Consequently, the present review will concentrate on the impact of neutrophil extracellular traps on atherosclerosis formation, analysing it from a molecular biology perspective. This will involve a systematic dissection of their proteomic components and signal pathways.

Thromboembolic Events in the Era of COVID-19: A Detailed Narrative Review

COVID-19, caused by the SARS-CoV-2 virus, is not only characterized by respiratory symptoms but is also associated with a wide range of systemic complications, including significant hematologic abnormalities. This is a comprehensive review of the current literature, using PubMed and Google Scholar, on the pathophysiology and incidence of thromboembolic events in COVID-19 patients and thromboprophylaxis. COVID-19 infection induces a prothrombotic state in patients through the dysregulation of the renin-angiotensin-aldosterone system (RAAS), endothelial dysfunction, elevated von Willebrand factor (vWF), and a dysregulated immune response involving the complement system and neutrophil extracellular traps (NETs). As a result, thromboembolic complications have emerged in COVID-19 cases, occurring more frequently in severe cases and hospitalized patients. These thrombotic events affect both venous and arterial circulation, with increased incidences of deep venous thrombosis (DVT), pulmonary embolism (PE), systemic arterial thrombosis, and myocardial infarction (MI). While DVT and PE are more common, the literature highlights the potential lethal consequences of arterial thromboembolism (ATE). This review also briefly examines the ongoing discussions regarding the use of anticoagulants for the prevention of thrombotic events in COVID-19 patients. While theoretically promising, current studies have yielded varied outcomes: Some suggest potential benefits, whereas others report an increased risk of bleeding events among hospitalized patients. Therefore, further large-scale studies are needed to assess the efficacy and safety of anticoagulants for thromboprophylaxis in COVID-19 patients.

PROGNOSTIC IMPLICATIONS OF CHANGES IN PLATELET TRAJECTORIES IN PATIENTS WITH SEPSIS: A RETROSPECTIVE ANALYSIS USING THE MEDICAL INFORMATION MART FOR INTENSIVE CARE IV DATABASE

ABSTRACT

Objective: Patients with sepsis often experience reductions or increases in platelet counts, but the implications of these temporal patterns on prognosis remain unclear. The aim of this study was to investigate the impact of changes in platelet trajectories on the clinical prognosis of sepsis. Methods: This study was a retrospective analysis using data from the Medical Information Mart for Intensive Care IV database. Patients with sepsis were identified from the database, and their platelet trajectories were categorized into four distinct models based on the changes in platelet counts over a period of 14 days after diagnosis of sepsis. The effect of these trajectories on patient prognosis was subsequently evaluated. Results: A total of 15,250 patients with sepsis were included to construct a model, and the following four distinct platelet count trajectories were identified: normal platelet levels (phenotype 1); persistently low platelet levels (phenotype 2); gradually increasing platelet levels exceeding the normal range (phenotype 3); and consistently significantly elevated platelet levels (phenotype 4). Statistically significant differences were found in the 28-day mortality, in-hospital mortality, and 90-day mortality among the four phenotypes. Multivariate regression analysis showed that compared to the group with normal platelet levels (phenotype 1), the group with persistently low platelet levels (phenotype 2) had higher in-hospital mortality (odds ratio [OR] = 1.34, 95% confidence interval [CI]: 1.16-1.54), 28-day mortality (OR = 1.69, 95% CI: 1.47-1.94), and 90-day mortality (OR = 1.50, 95% CI: 1.32-1.69). There was no difference in in-hospital mortality between phenotypes 3 and 4 compared to phenotype 1, although phenotype 4 showed an increase in 28-day mortality ( P < 0.05), and phenotype 3 showed a decreasing trend in 90-day mortality ( P < 0.05). The results of inverse probability weighting adjusted by regression were basically consistent with the above findings, except that there was no statistical difference in 28-day mortality between phenotype 4 and phenotype 1. In the subgroups based on age, weight, and antiplatelet drugs or therapies, there was an interaction between platelet levels and these factors. Conclusions: In patients with sepsis, a decrease in platelet count is associated with increased mortality, while a moderate increase in platelet count can reduce 90-day mortality. However, for patients with persistently elevated platelet counts, caution is advised when using antiplatelet drugs or therapies, as it may increase mortality.

COVID-19 patient serum-derived extracellular vesicles deliver miR-20b-5p induces neutrophil extracellular traps

BACKGROUND

Severe cases of COVID-19 are characterized by an excessive presence of neutrophils. Neutrophil extracellular traps (NETs), released by activated neutrophils due to SARS-CoV-2 infection, contribute to lung epithelial cell death and are key drivers in COVID-19-associated immunothrombosis. However, the mechanism underlying NET formation in COVID-19 remain unclear.

METHODS

Extracellular vesicles (EVs) were isolated from the serum of COVID-19 patients and healthy volunteers, while neutrophils were isolated from blood samples of healthy volunteers. Neutrophils were treated with EVs, and the formation of NETs was observed. To identify the components responsible for the COVID-19-EVs-induced NET formation, we analyzed the expression profiles of microRNA (miRNAs) in COVID-19-EVs. We identified eight highly expressed miRNAs in COVID-19-EVs and explored their potential roles in COVID-19-EVs-mediated NET formation. Additionally, we explored the role of miR-20b-5p in COVID-19-EVs-induced NET formation.

RESULTS

In this study, we demonstrate that patients with COVID-19 have a higher concentration of serum EVs (COVID-19-EVs) than healthy controls (Normal-EVs). We also found that COVID-19-EVs are internalized by neutrophils to induced NET formation. Through comprehensive miRNA profiling of COVID-19-EVs versus Normal-EVs, we identified 78 differentially expressed miRNAs, with 27 of these being upregulated and 51 being downregulated. Subsequently, we discovered that COVID-19-EVs that were highly abundant with certain miRNAs promote NET formation. Specifically, miR-20b-5p was found to be the strongest inducer of NET formation of the identified miRNAs. Inhibition of miR-20b-5p resulted in a significant decrease in COVID-19-EVs-mediated induction of NET formation.

CONCLUSION

Herein, we reveal a previously unknown role of COVID-19-EVs in NET formation, which contributes to COVID-19 progression. This study suggests that miR-20b-5p may serve as a potential therapeutic target for COVID-19 treatment.

"The NET effect": Neutrophil extracellular traps-a potential key component of the dysregulated host immune response in sepsis

Neutrophils release neutrophil extracellular traps (NETs) as part of a healthy host immune response. NETs physically trap and kill pathogens as well as activating and facilitating crosstalk between immune cells and complement. Excessive or inadequately resolved NETs are implicated in the underlying pathophysiology of sepsis and other inflammatory diseases, including amplification of the inflammatory response and inducing thrombotic complications. Here, we review the growing evidence implicating neutrophils and NETs as central players in the dysregulated host immune response. We discuss potential strategies for modifying NETs to improve patient outcomes and the need for careful patient selection.

Citrullination of tissue factor pathway inhibitor alpha by peptidylarginine deiminase 4 impairs its natural anticoagulant activity toward factors Xa and VIIa/tissue factor and reduces binding to its cofactor protein S

BACKGROUND

Neutrophils are known to externalize their DNA and intracellular contents to neutralize invading pathogens. This process may enhance blood coagulation during inflammation. Tissue factor (TF) pathway inhibitor (TFPI) binds to extracellular DNA and may be citrullinated by peptidylarginine deiminase 4. Citrullination of TFPI reduces its anticoagulant activity toward factor (F)Xa but appears to retain its inhibition of TF-triggered thrombin generation, indicating differential regulation of TFPI functions by peptidylarginine deiminase 4.

OBJECTIVES

This work aimed to study the effects of citrullination of TFPI-alpha on the inhibition of FXa, FVIIa/TF, and the cofactor activity of protein S.

METHODS

The effect of TFPI citrullination on the inhibition of FXa and FVIIa/TF was measured by chromogenic assays using purified components and by calibrated automated thrombography. Interaction with protein S was assessed by surface plasmon resonance and solid-phase binding assays using immobilized protein S, recombinant TFPI, and synthetic TFPI domains.

RESULTS

Citrullination of TFPI abolished its ability to inhibit FXa- and FXIa-triggered thrombin generation. However, its impaired inhibition of TF-triggered thrombin generation was still enhanced by protein S. Chromogenic assays revealed that citrullinated TFPI was essentially inactive as an inhibitor of the FVIIa-TF complex in the absence of protein S but partially restored by protein S. Interaction studies revealed that binding of citrullinated TFPI to protein S was reduced approximately 4-fold.

CONCLUSION

Citrullinated TFPI shows impaired natural anticoagulant activity. While anti-FXa activity is essentially absent, its anti-TF/FVIIa activity can still be enhanced by protein S. This enhancement is incomplete; however, protein S binding to citrullinated TFPI is impaired.

Immunopharmacological Insights into Cordyceps spp.: Harnessing Therapeutic Potential for Sepsis

Cordyceps spp. (CS), a well-known medicinal mushroom that belongs to Tibetan medicine and is predominantly found in the high altitudes in the Himalayas. CS is a rich reservoir of various bioactive substances including nucleosides, sterols flavonoids, peptides, and phenolic compounds. The bioactive compounds and CS extract have antibacterial, antioxidant, immunomodulatory, and inflammatory properties in addition to organ protection properties across a range of disease states. The study aimed to review the potential of CS, a medicinal mushroom, as a treatment for sepsis. While current sepsis drugs have side effects, CS shows promise due to its anti-inflammatory, antioxidant, and antibacterial properties. We have performed an extensive literature search based on published original and review articles in Scopus and PubMed. The keywords used were Cordyceps, sepsis, and inflammation. Studies indicate that CS extract and bioactive compounds target free radicals including oxidative as well as nitrosative stress, lower inflammation, and modulate the immune system, all of which are critical components in sepsis. The brain, liver, kidneys, lungs, and heart are among the organs that CS extracts may be able to shield against harm during sepsis. Traditional remedies with anti-inflammatory and protective qualities, such as Cordyceps mushrooms, are promising in sepsis. However, more research including clinical trials is required to validate the usefulness of CS metabolites in terms of organ protection and fight infections in sepsis.

Critical role for platelet Ral GTPases in regulating venous thrombosis in mice

BACKGROUND

Deep vein thrombosis is a major cause of morbidity and mortality globally. While its pathophysiology is complex, increasing evidence suggests a more prominent role for platelets than previously suspected. Genetic deletion of Ral GTPases, RalA and RalB, conditionally in mouse platelets (RalAB double knockout [DKO]), results in a near complete defect in P-selectin externalization upon activation, while other platelet activation responses and arterial thrombosis are preserved.

OBJECTIVES

Given the critical role of P-selectin in mediating platelet-neutrophil interaction and thromboinflammation, we sought to investigate whether platelet Rals would also play critical roles in venous thrombosis, a thromboinflammatory disease, using RalAB DKO mice.

METHODS

Deep vein thrombosis was induced by surgical partial ligation of the caudal (inferior) vena cava for 24 hours or 48 hours before venous thrombi were assessed by histology and immunofluorescence microscopy.

RESULTS

RalAB DKO mice showed a reduction in venous thrombus formation after 24 hours and near complete ablation of venous thrombosis by 48 hours post inferior vena cava ligation. Immunofluorescence microscopy revealed that cross-sections of thrombi from wild-type mice consisted of an organized scaffolded structure of platelets surrounding leukocytes/neutrophils producing neutrophil extracellular traps (NETs) to stabilize and propagate the thrombus. This organized structure was absent in platelet-specific conditional RalAB DKO thrombi. In vitro analysis of platelet-mediated NET formation was also significantly reduced when platelets lacked RalAB or when platelets were treated with the Ral inhibitor RBC8.

CONCLUSION

We identify platelet Rals as novel, potentially critical regulators of venous thrombus stability through their ability to regulate neutrophil NET formation via platelet P-selectin.

Neutrophil Extracellular Traps, Platelets and Endothelial Cells Cooperatively Contribute to Hypercoagulability in Non-Small Cell Lung Cancer

BACKGROUND

 Thromboembolism is the second leading cause of death among patients with non-small cell lung cancer (NSCLC), but the precise mechanisms of thrombogenesis in NSCLC remain largely unknown. Our objectives were to evaluate the definitive role of neutrophil extracellular traps (NETs) in the hypercoagulability in NSCLC and to explore its interactions with platelets and endothelial cells (ECs).

METHODS

 The levels of NET markers in samples from 100 NSCLC patients and 30 healthy controls were measured by ELISA. NET formation was detected using immunofluorescence. Procoagulant activity was assessed based on purified coagulation complex, thrombin, clotting time, and fibrin formation assays.

RESULTS

 The plasma levels of NETs were increased in a stage-dependent manner in NSCLC patients and were markedly higher than those in controls. Neutrophils from NSCLC patients were more prone to form NETs, resulting in shortened coagulation time, significantly increased thrombin-antithrombin complexes and fibrin compared to controls. Moreover, NETs generation was mediated by High Mobility Group Box 1 from activated platelets in NSCLC patients. Conversely, NETs from NSCLC patients also induce phosphatidylserine exposure on platelets, leading to markedly enhanced procoagulant activity (PCA). Furthermore, NETs can damage endothelial cells and convert them to a procoagulant phenotype. The administration of NETs inhibitors (DNase I/activated protein C) could markedly diminish the PCA of NETs, activated platelets, and ECs.

CONCLUSION

 Our results suggest that NETs contribute to hypercoagulability and may represent a potential therapeutic target to prevent cancer-associated thrombosis in NSCLC patients.

Circulating Levels of Low-Density Granulocytes and Cell-Free DNA as Predictors of Cardiovascular Disease and Bone Deterioration in SLE Patients

OBJECTIVE

 The present work evaluates the predictive value of low-density granulocytes (LDGs) for the development of cardiovascular disease (CVD) and/or bone deterioration (BD) in a 6-year prospective study in systemic lupus erythematosus (SLE). Considering the high SLE-LDG capacity to form neutrophil extracellular traps (NETs), circulating levels of total cell-free DNA (cirDNA) and relative amounts of mitochondrial and nuclear DNA (mtDNA and nDNA, respectively) were tested as LDG-associated biomarkers to identify SLE patients at risk of CVD and BD.

MATERIAL AND METHODS

 The frequency of total blood LDGs, as well as the CD16negCD14neg (nLDG) and CD16posCD14low (pLDG) subsets, was quantified by flow cytometry in 33 controls and 144 SLE patients. Total cirDNA and relative amounts of mitochondrial (mtDNA) and nuclear (nDNA) cell-free DNA were measured by fluorometry or qPCR in plasma from a subgroup of 117 patients and 23 controls at enrolment.

RESULTS AND CONCLUSION

 Our findings showed increased blood levels of SLE-nLDGs at enrolment associated with prospective CVD development (pCVD) and the presence of BD, thus revealing LDG expansion as a predictor of both comorbidities in SLE progression. The amounts of the different types of circulating DNA analyzed were increased in patients, especially those presenting with traditional CV risk factors or subclinical atheromatosis. Similar to nLDGs, the nDNA concentration could predict the development of pCVD in SLE, supporting the quantification of cirDNA levels as a surrogate marker of LDGs in clinical practice.

Fantastic proteins and where to find them - histones, in the nucleus and beyond

Animal genomes are packaged into chromatin, a highly dynamic macromolecular structure of DNA and histone proteins organised into nucleosomes. This accommodates packaging of lengthy genomic sequences within the physical confines of the nucleus while also enabling precise regulation of access to genetic information. However, histones existed before chromatin and have lesser-known functions beyond genome regulation. Most notably, histones are potent antimicrobial agents, and the release of chromatin to the extracellular space is a defence mechanism nearly as ancient and widespread as chromatin itself. Histone sequences have changed very little throughout evolution, suggesting the possibility that some of their 'non-canonical' functions are at play in parallel or in concert with their genome regulatory functions. In this Review, we take an evolutionary perspective of histone, nuclear chromatin and extracellular chromatin biology and describe the known extranuclear and extracellular functions of histones. We detail molecular mechanisms of chromatin release and extracellular chromatin sensing, and we discuss their roles in physiology and disease. Finally, we present evidence and give a perspective on the potential of extracellular histones to act as bioactive, cell modulatory factors.

Gender-specific relationships between hyperuricemia and idiopathic deep venous thrombosis in the Chinese population: a case‒control study

BACKGROUND

Many studies have indicated that hyperuricemia is positively correlated with secondary deep venous thrombosis (DVT); however, the risk factors for idiopathic DVT based on gender differences, such as serum uric acid (SUA) and hyperuricemia, have not been fully examined.

OBJECTIVES

To investigate the association between hyperuricemia and the occurrence of idiopathic lower extremity DVT based on gender differences.

METHODS

This was a retrospective analysis of 4299 patients who were hospitalized at the Affiliated Hospital of Qingdao University from January 2012 to October 2021 and who underwent ultrasound of the lower limbs. A total of 930 patients were diagnosed in the DVT group, and 3369 patients were diagnosed in the control group without DVT. The baseline SUA and other important baseline data were compared between the two groups, and sex was stratified. Multivariate logistic regression analysis models adjusted for potential confounders were used to investigate the associations between hyperuricemia and idiopathic lower extremity DVT.

RESULTS

The SUA level in patients with idiopathic DVT was significantly greater than that in patients without DVT (total: 6.00 ± 1.75 vs. 5.40 ± 1.56 mg/dL, respectively; male: 6.42 ± 1.60 vs. 5.87 ± 1.57 mg/dL, respectively; female: 5.58 ± 1.79 vs. 4.72 ± 1.27 mg/dL, respectively; all P < 0.001). The proportion of patients with hyperuricemia in the idiopathic DVT group was significantly greater than that in the control group (total: 29.03% vs. 16.10%, respectively; male: 35.26% vs. 23.19%, respectively; female: 22.73% vs. 5.74%, respectively; all P < 0.001). The incidence of DVT in patients with hyperuricemia was significantly greater than patients with normouricemia (33.29% vs. 18.92%, respectively), and this difference was particularly prominent among women (58.01%). According to the univariate model, hyperuricemia was significantly associated with a grester risk of idiopathic DVT. After adjustment for potential confounders, this association remained significant. The risk of idiopathic lower extremity DVT in patients with hyperuricemia was 2.643-fold greater than that in patients with normouricemia (Model 3: OR: 2.643, 95% CI: 2.165-3.228). After stratification by sex, the risk of idiopathic lower extremity DVT in female patients with hyperuricemia was 7.482-fold greater than that in patients with normouricemia (Model 3, OR: 7.482, 95% CI: 4.999-11.199).

CONCLUSION

In the Chinese population, hyperuricemia is closely related to an increased risk of idiopathic lower extremity DVT, especially in female patients.

Thrombosis in Paroxysmal Nocturnal Hemoglobinuria (PNH): From Pathogenesis to Treatment

Paroxysmal Nocturnal Hemoglobinuria (PNH) constitutes a rare bone marrow failure syndrome characterized by hemolytic anemia, thrombotic events (TEs), and bone marrow aplasia of variable degrees. Thrombosis is one of the major clinical manifestations of the disease, affecting up to 40% of individuals with PNH. Venous thrombosis is more prevalent, affecting mainly unusual sites, such as intrabdominal and hepatic veins. TEs might be the first clinical manifestation of PNH. Complement activation, endothelial dysfunction, hemolysis, impaired bioavailability of nitric oxide, and activation of platelets and neutrophils are implicated in the pathogenesis of TEs in PNH patients. Moreover, a vicious cycle involving the coagulation cascade, complement system, and inflammation cytokines, such as interleukin-6, is established. Complement inhibitors, such as eculizumab and ravulizumab (C5 inhibitors), have revolutionized the care of patients with PNH. C5 inhibitors should be initiated in patients with PNH and thrombosis, while they constitute a great prophylactic measure for TEs in those individuals. Anticoagulants, such as warfarin and low-molecular-weight heparin, and, in selected cases, direct oral anticoagulants (DOACs) should be used in combination with C5 inhibitors in patients who develop TEs. Novel complement inhibitors are considered an alternative treatment option, especially for those who develop extravascular or breakthrough hemolysis when terminal inhibitors are administered.

The roles of migrasomes in immunity, barriers, and diseases

Migrasomes are recently identified extracellular vesicles and organelles formed in conjunction with cell migration. They are situated at the rear of migrating cells, exhibit a circular or elliptical membrane-enclosed structure, and function as a new organelle. Migrasomes selectively sort intercellular components, mediating a cell migration-dependent release mechanism known as migracytosis and modulating cell-cell communication. Accumulated evidence clarifies migrasome formation processes and indicates their diverse functional roles. Migrasomes may also be potentially correlated with the occurrence, progression, and prognosis of certain diseases. Migrasomes' involvement in physiological and pathological processes highlights their potential for expanding our understanding of biological procedures and as a target in clinical therapy. However, the precise mechanisms and full extent of their involvement in immunity, barriers, and diseases remain unclear. This review aimed to provide a comprehensive overview of the roles of migrasomes in human immunity and barriers, in addition to providing insights into their impact on human diseases. STATEMENT OF SIGNIFICANCE: Migrasomes, newly identified extracellular vesicles and organelles, form during cell migration and are located at the rear of migrating cells. These circular or elliptical structures mediate migracytosis, selectively sorting intercellular components and modulating cell-cell communication. Evidence suggests diverse functional roles for migrasomes, including potential links to disease occurrence, progression, and prognosis. Their involvement in physiological and pathological processes highlights their significance in understanding biological procedures and potential clinical therapies. However, their exact mechanisms in immunity, barriers, and diseases remain unclear. This review provides an overview of migrasomes' roles in human immunity and barriers, and their impact on diseases.

Coagulopathy and acute pancreatitis: pathophysiology and clinical treatment

Coagulopathy is a critical pathophysiological mechanism of acute pancreatitis (AP), arising from the complex interplay between innate immune, endothelial cells and platelets. Although initially beneficial for the host, uncontrolled and systemic activation of coagulation cascade in AP can lead to thrombotic and hemorrhagic complications, ranging from subclinical abnormalities in coagulation tests to severe clinical manifestations, such as disseminated intravascular coagulation. Initiation of coagulation activation and consequent thrombin generation is caused by expression of tissue factor on activated monocytes and is ineffectually offset by tissue factor pathway inhibitor. At the same time, endothelial-associated anticoagulant pathways, in particular the protein C system, is impaired by pro-inflammatory cytokines. Also, fibrin removal is severely obstructed by inactivation of the endogenous fibrinolytic system, mainly as a result of upregulation of its principal inhibitor, plasminogen activator inhibitor type 1. Finally, increased fibrin generation and impaired break down lead to deposition of (micro) vascular clots, which may contribute to tissue ischemia and ensuing organ dysfunction. Despite the high burden of coagulopathy that have a negative impact on AP patients' prognosis, there is no effective treatment yet. Although a variety of anticoagulants drugs have been evaluated in clinical trials, their beneficial effects are inconsistent, and they are also characterized by hemorrhagic complications. Future studies are called to unravel the pathophysiologic mechanisms involved in coagulopathy in AP, and to test novel therapeutics block coagulopathy in AP.

LncRNA-mRNA co-expression analysis reveals aquaporin-9-promoted neutrophil extracellular trap formation and inflammatory activation in sepsis

Sepsis is a life-threatening condition caused by an excessive inflammatory response to an infection. However, the precise regulatory mechanism of sepsis remains unclear. Using a strand-specific RNA-sequencing, we identified 115 hub differentially expressed long noncoding RNAs (lncRNAs) and 443 mRNAs in septic patients, primarily participated in crucial pathways including neutrophil extracellular trap (NET) formation and toll-like receptor signaling. Notably, NETs related gene aquaporin-9 (AQP9) and its associated lncRNAs exhibited significant upregulation in septic neutrophils. Functional experiments revealed AQP9 interacts with its lncRNAs to augment the formation of neutrophil NETs. In murine sepsis models, AQP9 inhibition with phloretin reduced proinflammatory cytokine production and lung damage. These findings provide crucial insights into the regulatory role of AQP9 in sepsis, unraveling its interaction with associated lncRNAs in transmitting downstream signals, holding promise in informing the development of novel therapeutic strategies aimed at ameliorating the debilitating effects of sepsis.

Atomic Force Microscopy and Scanning Ion-Conductance Microscopy for Investigation of Biomechanical Characteristics of Neutrophils

Scanning probe microscopy (SPM) is a versatile tool for studying a wide range of materials. It is well suited for investigating living matter, for example, in single-cell neutrophil studies. SPM has been extensively utilized to analyze cell physical properties, providing detailed insights into their structural and functional characteristics at the nanoscale. Its long-standing application in this field highlights its essential role in cell biology and immunology research, significantly contributing to understanding cellular mechanics and interactions. In this review, we discuss the application of SPM techniques, specifically atomic force microscopy (AFM) and scanning ion-conductance microscopy (SICM), to study the fundamental functions of neutrophils. In addition, recent advances in the application of SPM in single-cell immunology are discussed. The application of these techniques allows for obtaining data on the morphology, topography, and mechanical and electrochemical properties of neutrophils with high accuracy.

Immunity and Coagulation in COVID-19

Discovered in late 2019, the SARS-CoV-2 coronavirus has caused the largest pandemic of the 21st century, claiming more than seven million lives. In most cases, the COVID-19 disease caused by the SARS-CoV-2 virus is relatively mild and affects only the upper respiratory tract; it most often manifests itself with fever, chills, cough, and sore throat, but also has less-common mild symptoms. In most cases, patients do not require hospitalization, and fully recover. However, in some cases, infection with the SARS-CoV-2 virus leads to the development of a severe form of COVID-19, which is characterized by the development of life-threatening complications affecting not only the lungs, but also other organs and systems. In particular, various forms of thrombotic complications are common among patients with a severe form of COVID-19. The mechanisms for the development of thrombotic complications in COVID-19 remain unclear. Accumulated data indicate that the pathogenesis of severe COVID-19 is based on disruptions in the functioning of various innate immune systems. The key role in the primary response to a viral infection is assigned to two systems. These are the pattern recognition receptors, primarily members of the toll-like receptor (TLR) family, and the complement system. Both systems are the first to engage in the fight against the virus and launch a whole range of mechanisms aimed at its rapid elimination. Normally, their joint activity leads to the destruction of the pathogen and recovery. However, disruptions in the functioning of these innate immune systems in COVID-19 can cause the development of an excessive inflammatory response that is dangerous for the body. In turn, excessive inflammation entails activation of and damage to the vascular endothelium, as well as the development of the hypercoagulable state observed in patients seriously ill with COVID-19. Activation of the endothelium and hypercoagulation lead to the development of thrombosis and, as a result, damage to organs and tissues. Immune-mediated thrombotic complications are termed "immunothrombosis". In this review, we discuss in detail the features of immunothrombosis associated with SARS-CoV-2 infection and its potential underlying mechanisms.

Clopidogrel Is Associated with Reduced Likelihood of Aneurysmal Subarachnoid Hemorrhage: a Multi-Center Matched Retrospective Analysis

Maladaptive inflammation underlies the formation and rupture of human intracranial aneurysms. There is a growing body of evidence that anti-inflammatory pharmaceuticals may beneficially modulate this process. Clopidogrel (Plavix) is a commonly used irreversible P2Y12 receptor antagonist with anti-inflammatory activity. In this paper, we investigate whether clopidogrel is associated with the likelihood of aneurysm rupture in a multi-institutional propensity-matched cohort analysis. Patients presenting for endovascular treatment of their unruptured intracranial aneurysms and those presenting with aneurysm rupture between 2015 and 2019 were prospectively identified at two quaternary referral centers. Patient demographics, comorbidities, and medication usage at the time of presentation were collected. Patients taking clopidogrel or not taking clopidogrel were matched in a 1:1 fashion with respect to location, age, smoking status, aneurysm size, aspirin usage, and hypertension. A total of 1048 patients with electively treated aneurysms or subarachnoid hemorrhages were prospectively identified. Nine hundred twenty-one patients were confirmed to harbor aneurysms during catheter-based diagnostic angiography. A total of 172/921 (19%) patients were actively taking clopidogrel at the time of presentation. Three hundred thirty-two patients were matched in a 1:1 fashion. A smaller proportion of patients taking clopidogrel at presentation had ruptured aneurysms than those who were not taking clopidogrel (6.6% vs 23.5%, p < .0001). Estimated treatment effect analysis demonstrated that clopidogrel usage decreased aneurysm rupture risk by 15%. We present, to the best of our knowledge, the first large-scale multi-institutional analysis suggesting clopidogrel use is protective against intracranial aneurysm rupture. It is our hope that these data will guide future investigation, revealing the pathophysiologic underpinning of this association.

Factors affecting neutrophil functions during sepsis: human microbiome and epigenetics

Sepsis is a severe disease that occurs when the body's immune system reacts excessively to infection. The body's response, which includes an intense antibacterial reaction, can damage its tissues and organs. Neutrophils are the major components of white blood cells in circulation, play a vital role in innate immunity while fighting against infections, and are considered a feature determining sepsis classification. There is a plethora of basic research detailing neutrophil functioning, among which, the study of neutrophil extracellular traps is providing novel insights into mechanisms and treatments of sepsis. This review explores their functions, dysfunctions, and influences in the context of sepsis. The interplay between neutrophils and the human microbiome and the impact of DNA methylation on neutrophil function in sepsis are crucial areas of study. The interaction between neutrophils and the human microbiome is complex, particularly in the context of sepsis, where dysbiosis may occur. We highlight the importance of deciphering neutrophils' functional alterations and their epigenetic features in sepsis because it is critical for defining sepsis endotypes and opening up the possibility for novel diagnostic methods and therapy. Specifically, epigenetic signatures are pivotal since they will provide a novel implication for a sepsis diagnostic method when used in combination with the cell-free DNA. Research is exploring how specific patterns of DNA methylation in neutrophils, detectable in cell-free DNA, could serve as biomarkers for the early detection of sepsis.

Inhibitors of Polyphosphate and Neutrophil Extracellular Traps

The contact pathway of blood clotting has received intense interest in recent years as studies have linked it to thrombosis, inflammation, and innate immunity. Because the contact pathway plays little to no role in normal hemostasis, it has emerged as a potential target for safer thromboprotection, relative to currently approved antithrombotic drugs which all target the final common pathway of blood clotting. Research since the mid-2000s has identified polyphosphate, DNA, and RNA as important triggers of the contact pathway with roles in thrombosis, although these molecules also modulate blood clotting and inflammation via mechanisms other than the contact pathway of the clotting cascade. The most significant source of extracellular DNA in many disease settings is in the form of neutrophil extracellular traps (NETs), which have been shown to contribute to incidence and severity of thrombosis. This review summarizes known roles of extracellular polyphosphate and nucleic acids in thrombosis, with an emphasis on novel agents under current development that target the prothrombotic activities of polyphosphate and NETs.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

Cyclic stretch enhances neutrophil extracellular trap formation

BACKGROUND

Neutrophils, the most abundant leukocytes circulating in blood, contribute to host defense and play a significant role in chronic inflammatory disorders. They can release their DNA in the form of extracellular traps (NETs), which serve as scaffolds for capturing bacteria and various blood cells. However, uncontrolled formation of NETs (NETosis) can lead to excessive activation of coagulation pathways and thrombosis. Once neutrophils are migrated to infected or injured tissues, they become exposed to mechanical forces from their surrounding environment. However, the impact of transient changes in tissue mechanics due to the natural process of aging, infection, tissue injury, and cancer on neutrophils remains unknown. To address this gap, we explored the interactive effects of changes in substrate stiffness and cyclic stretch on NETosis. Primary neutrophils were cultured on a silicon-based substrate with stiffness levels of 30 and 300 kPa for at least 3 h under static conditions or cyclic stretch levels of 5% and 10%, mirroring the biomechanics of aged and young arteries.

RESULTS

Using this approach, we found that neutrophils are sensitive to cyclic stretch and that increases in stretch intensity and substrate stiffness enhance nuclei decondensation and histone H3 citrullination (CitH3). In addition, stretch intensity and substrate stiffness promote the response of neutrophils to the NET-inducing agents phorbol 12-myristate 13-acetate (PMA), adenosine triphosphate (ATP), and lipopolysaccharides (LPS). Stretch-induced activation of neutrophils was dependent on calpain activity, the phosphatidylinositol 3-kinase (PI3K)/focal adhesion kinase (FAK) signalling and actin polymerization.

CONCLUSIONS

In summary, these results demonstrate that the mechanical forces originating from the surrounding tissue influence NETosis, an important neutrophil function, and thus identify a potential novel therapeutic target.

Low-Density Neutrophils and Neutrophil Extracellular Traps (NETs) Are New Inflammatory Players in Heart Failure

BACKGROUND

Heart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) is characterized by low-grade chronic inflammation. Circulating neutrophils regroup 2 subtypes termed high- and low-density neutrophils (HDNs and LDNs). LDNs represent less than 2% of total neutrophil under physiological conditions, but their counts increase in multiple pathologies, releasing more inflammatory cytokines and neutrophil extracellular traps (NETs). The aims of this study were to assess the differential count and role of HDNs, LDNs, and NETs-related activities in patients with heart failure (HF).

METHODS

HDNs and LDNs were isolated from human blood by density gradient and purified by fluorescence-activated cell sorting (FACS) and their counts obtained by flow cytometry. Formation of NETs (NETosis) was quantified by confocal microscopy. Circulating inflammatory and NETosis biomarkers were measured by enzyme-linked immunosorbent assay (ELISA). Neutrophil adhesion onto human extracellular matrix (hECM) was assessed by optical microscopy.

RESULTS

A total of 140 individuals were enrolled, including 33 healthy volunteers (HVs), 41 HFrEF (19 stable patients and 22 presenting acute decompensated HF [ADHF]), and 66 patients with HFpEF (36 stable patients and 30 presenting HF decompensation). HDNs and LDNs counts were significantly increased up to 39% and 2740%, respectively, in patients with HF compared with HVs. In patients with HF, the correlations among LDNs counts and circulating inflammatory (CRP, IL-6 and -8), troponin T, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and NETosis components were significant. In vitro, LDNs expressed more citrullinated histone H3 (H3Cit) and NETs and were more proadhesive, with ADHFpEF patients presenting the highest proinflammatory profile.

CONCLUSIONS

Patients with HFpEF present higher levels of circulating LDNs- and NETs-related activities, which are the highest in the context of acute HF decompensation.

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.

The significance of CD16+ monocytes in the occurrence and development of chronic thromboembolic pulmonary hypertension: insights from single-cell RNA sequencing

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious pulmonary vascular disease characterized by residual thrombi in the pulmonary arteries and distal pulmonary microvascular remodeling. The pathogenesis of CTEPH remains unclear, but many factors such as inflammation, immunity, coagulation and angiogenesis may be involved. Monocytes are important immune cells that can differentiate into macrophages and dendritic cells and play an important role in thrombus formation. However, the distribution, gene expression profile and differentiation trajectory of monocyte subsets in CTEPH patients have not been systematically studied. This study aims to reveal the characteristics and functions of monocytes in CTEPH patients using single-cell sequencing technology, and to provide new insights for the diagnosis and treatment of CTEPH.

Methods

Single-cell RNA sequencing (scRNA-seq) were performed to analyze the transcriptomic features of peripheral blood mononuclear cells (PBMCs) from healthy controls, CTEPH patients and the tissues from CTEPH patients after the pulmonary endarterectomy (PEA). We established a CTEPH rat model with chronic pulmonary embolism caused by repeated injection of autologous thrombi through a central venous catheter, and used flow cytometry to detect the proportion changes of monocyte subsets in CTEPH patients and CTEPH rat model. We also observed the infiltration degree of macrophage subsets in thrombus tissue and their differentiation relationship with peripheral blood monocyte subsets by immunofluorescence staining.

Results

The results showed that the monocyte subsets in peripheral blood of CTEPH patients changed significantly, especially the proportion of CD16+ monocyte subset increased. This monocyte subset had unique functional features at the transcriptomic level, involving processes such as cell adhesion, T cell activation, coagulation response and platelet activation, which may play an important role in pulmonary artery thrombus formation and pulmonary artery intimal remodeling. In addition, we also found that the macrophage subsets in pulmonary endarterectomy tissue of CTEPH patients showed pro-inflammatory and lipid metabolism reprogramming features, which may be related to the persistence and insolubility of pulmonary artery thrombi and the development of pulmonary hypertension. Finally, we also observed that CD16+ monocyte subset in peripheral blood of CTEPH patients may be recruited to pulmonary artery intimal tissue and differentiate into macrophage subset with high expression of IL-1β, participating in disease progression.

Conclusion

CD16+ monocytes subset had significant gene expression changes in CTEPH patients, related to platelet activation, coagulation response and inflammatory response. And we also found that these cells could migrate to the thrombus and differentiate into macrophages with high expression of IL-1β involved in CTEPH disease progression. We believe that CD16+ monocytes are important participants in CTEPH and potential therapeutic targets.

Deletion of pyruvate dehydrogenase kinases reduces susceptibility to deep vein thrombosis in mice

ABSTRACT

Neutrophils contribute to deep vein thrombosis (DVT) by releasing prothrombotic neutrophil extracellular traps (NETs). NET formation (known as NETosis) is an energy-intensive process that requires an increased rate of aerobic glycolysis. The metabolic enzymes pyruvate dehydrogenase kinases (PDKs) inhibit the pyruvate dehydrogenase complex to divert the pyruvate flux from oxidative phosphorylation toward aerobic glycolysis. Herein, we identified that the combined deletion of PDK2 and PDK4 (PDK2/4-/-) renders mice less susceptible to DVT (measured by thrombus incidence, weight, and length) in the inferior vena cava-stenosis model at day 2 after surgery. Compared with wild-type (WT) mice, the venous thrombus obtained from PDK2/4-/- mice exhibited reduced citrullinated histone content, a known marker of NETs. In line with in vivo observations, phorbol 12-myristate 13-acetate (PMA)-stimulated PDK2/4-/- neutrophils displayed reduced NETosis and secretion of cathepsin G and elastase compared with PMA-stimulated WT neutrophils. The formation of platelet aggregates mediated by PMA-stimulated PDK2/4-/- neutrophils were significantly reduced compared with PMA-stimulated WT neutrophils. Finally, PDK2/4-/- neutrophils exhibited reduced levels of intracellular Ca2+ concentration, extracellular signal-regulated kinase 1/2 (Erk1/2) phosphorylation, and glycolytic proton efflux rate (a measure of aerobic glycolysis), known to facilitate NETosis. Together, these findings elucidate, to our knowledge, for the first time, the fundamental role of PDK2/4 in regulating NETosis and acute DVT.

Atorvastatin combined with imipenem alleviates lung injury in sepsis by inhibiting neutrophil extracellular trap formation via the ERK/NOX2 signaling pathway

Sepsis is a systemic inflammatory response syndrome caused by the invasion of pathogenic microorganisms. Despite major advances in diagnosis and technology, morbidity and mortality remain high. The level of neutrophil extracellular traps (NETs) is closely associated with the progression and prognosis of sepsis, suggesting the regulation of NET formation as a new strategy in sepsis treatment. Owing to its pleiotropic effects, atorvastatin, a clinical lipid-lowering drug, affects various aspects of sepsis-related inflammation and immune responses. To align closely with clinical practice, we combined it with imipenem for the treatment of sepsis. In this study, we used a cecum ligation and puncture-induced lung injury mouse model and employed techniques including western blot, immunofluorescence, and enzyme-linked immunosorbent assay to measure the levels of NETs and other sepsis-related lung injury indicators. Our findings indicate that atorvastatin effectively inhibited the formation of NETs. When combined with imipenem, it significantly alleviated lung injury, reduced systemic inflammation, and improved the 7-day survival rate of septic mice. Additionally, we explored the inhibitory mechanism of atorvastatin on NET formation in vitro, revealing its potential action through the ERK/NOX2 pathway. Therefore, atorvastatin is a potential immunomodulatory agent that may offer new treatment strategies for patients with sepsis in clinical settings.

ADAMTS13 or Caplacizumab Reduces the Accumulation of Neutrophil Extracellular Traps and Thrombus in Whole Blood of COVID-19 Patients under Flow

BACKGROUND

 Neutrophil NETosis and neutrophil extracellular traps (NETs) play a critical role in pathogenesis of coronavirus disease 2019 (COVID-19)-associated thrombosis. However, the extents and reserve of NETosis, and potential of thrombus formation under shear in whole blood of patients with COVID-19 are not fully elucidated. Neither has the role of recombinant ADAMTS13 or caplacizumab on the accumulation of NETs and thrombus in COVID-19 patients' whole blood under shear been investigated.

METHODS

 Flow cytometry and microfluidic assay, as well as immunoassays, were employed for the study.

RESULTS

 We demonstrated that the percentage of H3Cit + MPO+ neutrophils, indicative of NETosis, was dramatically increased in patients with severe but not critical COVID-19 compared with that in asymptomatic or mild disease controls. Upon stimulation with poly [I:C], a double strain DNA mimicking viral infection, or bacterial shigatoxin-2, the percentage of H3Cit + MPO+ neutrophils was not significantly increased in the whole blood of severe and critical COVID-19 patients compared with that of asymptomatic controls, suggesting the reduction in NETosis reserve in these patients. Microfluidic assay demonstrated that the accumulation of NETs and thrombus was significantly enhanced in the whole blood of severe/critical COVID-19 patients compared with that of asymptomatic controls. Like DNase I, recombinant ADAMTS13 or caplacizumab dramatically reduced the NETs accumulation and thrombus formation under arterial shear.

CONCLUSION

 Significantly increased neutrophil NETosis, reduced NETosis reserve, and enhanced thrombus formation under arterial shear may play a crucial role in the pathogenesis of COVID-19-associated coagulopathy. Recombinant ADAMTS13 or caplacizumab may be explored for the treatment of COVID-19-associated thrombosis.

Neutrophil extracellular traps mediate neuro-immunothrombosis

Neutrophil extracellular traps are primarily composed of DNA and histones and are released by neutrophils to promote inflammation and thrombosis when stimulated by various inflammatory reactions. Neutrophil extracellular trap formation occurs through lytic and non-lytic pathways that can be further classified by formation mechanisms. Histones, von Willebrand factor, fibrin, and many other factors participate in the interplay between inflammation and thrombosis. Neuro-immunothrombosis summarizes the intricate interplay between inflammation and thrombosis during neural development and the pathogenesis of neurological diseases, providing cutting-edge insights into post-neurotrauma thrombotic events. The blood-brain barrier defends the brain and spinal cord against external assaults, and neutrophil extracellular trap involvement in blood-brain barrier disruption and immunothrombosis contributes substantially to secondary injuries in neurological diseases. Further research is needed to understand how neutrophil extracellular traps promote blood-brain barrier disruption and immunothrombosis, but recent studies have demonstrated that neutrophil extracellular traps play a crucial role in immunothrombosis, and identified modulators of neuro-immunothrombosis. However, these neurological diseases occur in blood vessels, and the mechanisms are unclear by which neutrophil extracellular traps penetrate the blood-brain barrier to participate in immunothrombosis in traumatic brain injury. This review discusses the role of neutrophil extracellular traps in neuro-immunothrombosis and explores potential therapeutic interventions to modulate neutrophil extracellular traps that may reduce immunothrombosis and improve traumatic brain injury outcomes.

Monocyte/macrophage-mediated venous thrombus resolution

Venous thromboembolism (VTE) poses a notable risk of morbidity and mortality. The natural resolution of the venous thrombus might be a potential alternative treatment strategy for VTE. Monocytes/macrophages merge as pivotal cell types in the gradual resolution of the thrombus. In this review, the vital role of macrophages in inducing inflammatory response, augmenting neovascularization, and facilitating the degradation of fibrin and collagen during thrombus resolution was described. The two phenotypes of macrophages involved in thrombus resolution and their dual functions were discussed. Macrophages expressing various factors, including cytokines and their receptors, adhesion molecules, chemokine receptors, vascular endothelial growth factor receptors, profibrinolytic- or antifibrinolytic-related enzymes, and other elements, are explored for their potential to promote or attenuate thrombus resolution. Furthermore, this review provides a comprehensive summary of new and promising therapeutic candidate drugs associated with monocytes/macrophages that have been demonstrated to promote or impair thrombus resolution. However, further clinical trials are essential to validate their efficacy in VTE therapy.

Taxifolin inhibits NETosis through activation of Nrf2 and provides protective effects in models of lupus and antiphospholipid syndrome

OBJECTIVES

Taxifolin (dihydroquercetin) is a bioactive plant flavonoid that exhibits anti-inflammatory and anti-oxidative properties. We hypothesized that taxifolin might be an effective dietary supplement to ameliorate symptoms arising from thrombo-inflammatory diseases such as lupus and APS.

METHODS

We used in vitro assays and a mouse model to determine mechanisms by which taxifolin inhibits neutrophil extracellular trap (NET) formation (i.e. NETosis) and venous thrombosis in lupus and APS.

RESULTS

At doses ranging from 0.1 to 1 µg/ml, taxifolin inhibited NETosis from control neutrophils stimulated with autoantibodies isolated from lupus and APS patients, and its suppressive effects were mitigated by blocking the antioxidant transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2). Furthermore, taxifolin at a dose as low as 20 mg/kg/day reduced in vivo NETosis in thrombo-inflammatory mouse models of lupus and APS while also significantly attenuating autoantibody formation, inflammatory cytokine production and large-vein thrombosis.

CONCLUSION

Our study is the first to demonstrate the protective effects of taxifolin in the context of lupus and APS. Importantly, our study also suggests a therapeutic potential to neutralize neutrophil hyperactivity and NETosis that could have relevance to a variety of thrombo-inflammatory diseases.

Glycosaminoglycans: Participants in Microvascular Coagulation of Sepsis

Sepsis represents a syndromic response to infection and frequently acts as a common pathway leading to fatality in the context of various infectious diseases globally. The pathology of severe sepsis is marked by an excess of inflammation and activated coagulation. A substantial contributor to mortality in sepsis patients is widespread microvascular thrombosis-induced organ dysfunction. Multiple lines of evidence support the notion that sepsis induces endothelial damage, leading to the release of glycosaminoglycans, potentially causing microvascular dysfunction. This review aims to initially elucidate the relationship among endothelial damage, excessive inflammation, and thrombosis in sepsis. Following this, we present a summary of the involvement of glycosaminoglycans in coagulation, elucidating interactions among glycosaminoglycans, platelets, and inflammatory cells. In this section, we also introduce a reasoned generalization of potential signal pathways wherein glycosaminoglycans play a role in clotting. Finally, we discuss current methods for detecting microvascular conditions in sepsis patients from the perspective of glycosaminoglycans. In conclusion, it is imperative to pay closer attention to the role of glycosaminoglycans in the mechanism of microvascular thrombosis in sepsis. Dynamically assessing glycosaminoglycan levels in patients may aid in predicting microvascular conditions, enabling the monitoring of disease progression, adjustment of clinical treatment schemes, and mitigation of both acute and long-term adverse outcomes associated with sepsis.

Role of inflammation and evidence for the use of colchicine in patients with acute coronary syndrome

Acute Coronary Syndrome (ACS) significantly contributes to cardiovascular death worldwide. ACS may arise from the disruption of an atherosclerotic plaque, ultimately leading to acute ischemia and myocardial infarction. In the pathogenesis of atherosclerosis, inflammation assumes a pivotal role, not solely in the initiation and complications of atherosclerotic plaque formation, but also in the myocardial response to ischemic insult. Acute inflammatory processes, coupled with time to reperfusion, orchestrate ischemic and reperfusion injuries, dictating infarct magnitude and acute left ventricular (LV) remodeling. Conversely, chronic inflammation, alongside neurohumoral activation, governs persistent LV remodeling. The interplay between chronic LV remodeling and recurrent ischemic episodes delineates the progression of the disease toward heart failure and cardiovascular death. Colchicine exerts anti-inflammatory properties affecting both the myocardium and atherosclerotic plaque by modulating the activity of monocyte/macrophages, neutrophils, and platelets. This modulation can potentially result in a more favorable LV remodeling and forestalls the recurrence of ACS. This narrative review aims to delineate the role of inflammation across the different phases of ACS pathophysiology and describe the mechanistic underpinnings of colchicine, exploring its purported role in modulating each of these stages.

Involvement of peptidylarginine deiminase 4 in eosinophil extracellular trap formation and contribution to citrullinated histone signal in thrombi

BACKGROUND

Extracellular traps formed by neutrophils (NETs) and eosinophils (EETs) have been described in coronary thrombi, contributing to thrombus stability. A key mechanism during NET formation is histone modification by the enzyme PAD4. Citrullinated histones, the product of PAD4 activity, are often attributed to neutrophils. Eosinophils also express high levels of PAD4.

OBJECTIVES

We aimed to explore the contribution of PAD4 to EET formation.

METHODS

We performed immunohistological analyses on thrombi, including a large, intact, and eosinophil-containing thrombus retrieved from the right coronary artery using an aspiration catheter and stroke thrombi from thrombectomy retrieval. We studied eosinophils for their capability to form PAD4-dependent EETs in response to strong ET-inducing agonists as well as activated platelets and bacteria.

RESULTS

Histopathology and immunofluorescence microscopy identified a coronary thrombus rich in platelets and neutrophils, with distinct areas containing von Willebrand factor and citrullinated histone H3 (H3Cit). Eosinophils were also identified in leukocyte-rich areas. The majority of the H3Cit+ signal colocalized with myeloperoxidase, but some colocalized with eosinophil peroxidase, indicating EETs. Eosinophils isolated from healthy volunteers produced H3Cit+ EETs, indicating an involvement of PAD4 activity. The selective PAD4 inhibitor GSK484 blocked this process, supporting PAD4 dependence of H3Cit+ EET release. Citrullinated histones were also present in EETs produced in response to live Staphylococci. However, limited evidence for EETs was found in mouse models of venous thrombosis or infective endocarditis.

CONCLUSION

As in NETosis, PAD4 can catalyze the formation of EETs. Inhibition of PAD4 decreases EET formation, supporting the future utility of PAD4 inhibitors as possible antithrombotic agents.

Poly (ADP-ribose) Polymerase-1 modulations in the genesis of thrombosis

Thrombosis, a coagulation disorder, occurs due to altered levels of coagulation, fibrinolytic and immune factors, which are otherwise known to maintain hemostasis in normal physiological conditions. Here, we review the direct and indirect participation of a multifunctional nuclear enzyme poly (ADP-ribose) polymerase-1 (PARP1) in the expression of key genes and cellular processes involved in thrombotic pathogenesis. PARP1 biological activities range from maintenance of genomic integrity, chromatin remodeling, base excision DNA repair, stress responses to cell death, angiogenesis and cell cycle pathways. However, under homeostatic imbalances, PARP1 activities are linked with the pathogenesis of diseases, including cancer, aging, neurological disorders, and cardiovascular diseases. Disease-associated distressed cells employ a variety of PARP-1 functions such as oxidative damage exacerbations, cellular energetics and apoptosis pathways, regulation of inflammatory mediators, promotion of endothelial dysfunction, and ERK-mediated signaling in pathogenesis. Thrombosis is one such pathogenesis that comprises exacerbation of coagulation cascade due to biochemical alterations in endothelial cells, platelet activation, overexpression of adhesion molecules, cytokines release, and leukocyte adherence. Thus, the activation of endothelial and inflammatory cells in thrombosis implicates a potential role of PARP1 activation in thrombogenesis. This review article explores the direct impact of PARP1 activation in the etiology of thrombosis and discusses PARP1-mediated endothelial dysfunction, inflammation, and epigenetic regulations in the disease manifestation. Understanding PARP1 functions associated with thrombosis may elucidate novel pathogenetic mechanisms and help in better disease management through newer therapeutic interventions targeting PARP1 activity.

CREB1 Silencing Protects Against Inflammatory Response in Rats with Deep Vein Thrombosis Through Reducing RPL9 Expression and Blocking NF-κB Signaling

Apoptosis and inflammation of vascular endothelial cells (VECs) are the most important causes of deep vein thrombosis (DVT). cAMP response element binding protein 1 (CREB1) encodes a transcription factor that binds as a homodimer to the cAMP-responsive element and can promote inflammation. CREB1 is found to be upregulated in the plasma of patients with venous thromboembolism. However, the biological functions of CREB1 in DVT remain unknown. We evaluated the effect of CREB1 in a rat model of inferior vena cava (IVA) stenosis-induced DVT. IVC stenosis resulted in stable thrombus, inflammatory response and CREB1 upregulation, whereas CREB1 knockdown inhibited thrombus and inflammation in DVT rats. In vitro analysis showed that CREB1 knockdown inhibited VEC apoptosis. Mechanistically, CREB1 knockdown reduced Ribosomal protein L9 (RPL9) expression and blocked the NF-κB pathway. Therefore, CREB1 may become a potential therapeutic target of DVT prevention.

Unraveling the Intricate Web: Complement Activation Shapes the Pathogenesis of Sepsis-Induced Coagulopathy

BACKGROUND

Sepsis-associated coagulopathy specifically refers to widespread systemic coagulation activation accompanied by a high risk of hemorrhage and organ damage, which in severe cases manifests as disseminated intravascular coagulation (DIC), or even develops into multiple organ dysfunction syndrome (MODS). The complement system and the coagulation system as the main columns of innate immunity and hemostasis, respectively, undergo substantial activation after sepsis.

SUMMARY

Dysfunction of the complement, coagulation/fibrinolytic cascades caused by sepsis leads to "thromboinflammation," which ultimately amplifies the systemic inflammatory response and accelerates the development of MODS. Recent studies have revealed that massive activation of the complement system exacerbates sepsis-induced coagulation and even results in DIC, which suggests that inhibition of complement activation may have therapeutic potential in the treatment of septic coagulopathy.

KEY MESSAGES

Sepsis-associated thrombosis involves the upregulation or activation of procoagulant factors, down-regulation or inactivation of anticoagulant factors, and impairment of the fibrinolytic mechanism. This review aims to summarize the latest literature and analyze the underlying molecular mechanisms of the activation of the complement system on the abnormal coagulation cascades in sepsis.

Interactions between integrin α9β1 and VCAM-1 promote neutrophil hyperactivation and mediate poststroke DVT

ABSTRACT

Venous thromboembolic events are significant contributors to morbidity and mortality in patients with stroke. Neutrophils are among the first cells in the blood to respond to stroke and are known to promote deep vein thrombosis (DVT). Integrin α9 is a transmembrane glycoprotein highly expressed on neutrophils and stabilizes neutrophil adhesion to activated endothelium via vascular cell adhesion molecule 1 (VCAM-1). Nevertheless, the causative role of neutrophil integrin α9 in poststroke DVT remains unknown. Here, we found higher neutrophil integrin α9 and plasma VCAM-1 levels in humans and mice with stroke. Using mice with embolic stroke, we observed enhanced DVT severity in a novel model of poststroke DVT. Neutrophil-specific integrin α9-deficient mice (α9fl/flMrp8Cre+/-) exhibited a significant reduction in poststroke DVT severity along with decreased neutrophils and citrullinated histone H3 in thrombi. Unbiased transcriptomics indicated that α9/VCAM-1 interactions induced pathways related to neutrophil inflammation, exocytosis, NF-κB signaling, and chemotaxis. Mechanistic studies revealed that integrin α9/VCAM-1 interactions mediate neutrophil adhesion at the venous shear rate, promote neutrophil hyperactivation, increase phosphorylation of extracellular signal-regulated kinase, and induce endothelial cell apoptosis. Using pharmacogenomic profiling, virtual screening, and in vitro assays, we identified macitentan as a potent inhibitor of integrin α9/VCAM-1 interactions and neutrophil adhesion to activated endothelial cells. Macitentan reduced DVT severity in control mice with and without stroke, but not in α9fl/flMrp8Cre+/- mice, suggesting that macitentan improves DVT outcomes by inhibiting neutrophil integrin α9. Collectively, we uncovered a previously unrecognized and critical pathway involving the α9/VCAM-1 axis in neutrophil hyperactivation and DVT.

NETosis in Surgery: Pathophysiology, Prevention, and Treatment

OBJECTIVE

To provide surgeons with an understanding of the latest research on NETosis, including the pathophysiology and treatment of conditions involving neutrophil extracellular traps (NETs) in the care of surgical patients.

BACKGROUND

A novel function of neutrophils, the formation of NETs, was described in 2004. Neutrophils form mesh-like structures of extruded decondensed chromatin, comprising DNA and histones decorated with bactericidal proteins. These NETs exert antimicrobial action by trapping microorganisms and preventing their wider dissemination through the body.

RESULTS

A narrative review of the existing literature describing NETosis was conducted, including NET pathophysiology, conditions related to NET formation, and treatments relevant to surgeons.

CONCLUSIONS

In addition to its canonical antimicrobial function, NETosis can exacerbate inflammation, resulting in tissue damage and contributing to numerous diseases. NETs promote gallstone formation and acute pancreatitis, impair wound healing in the early postoperative period and in chronic wounds, and facilitate intravascular coagulation, cancer growth, and metastasis. Agents that target NET formation or removal have shown promising efficacy in treating these conditions, although large clinical trials are required to confirm these benefits.

Association of neutrophil extracellular trap levels with Raynaud's phenomenon, glomerulonephritis and disease index score in SLE patients from Brazil

Neutrophil extracellular traps (NETs) are cell-extruded DNA strands coated with neutrophils' nuclear proteins and enzymes from cytotoxic granules, produced by NETosis, a cell death pathway. They perform an important defensive role in innate immunity, but their increased production and/or inefficient degradation expose new antigens, such as DNA or citrullinated histone peptides, triggering autoimmunity. This study aimed to access possible associations between serum NETs levels with epidemiological, clinical, and serological data from a well-characterized SLE Brazilian patients' cohort. NET levels were evaluated in one hundred seventy serum samples of patients with Systemic Lupus Erythematosus (SLE) using an Immunoassay. Univariate and multivariate binary logistic regression used clinical patients' data as independent variables. Parametric and non-parametric tests compared log10 base serum NET levels transformed between patients' groups. SLE patients were also dichotomized into "High serum NET levels" and "Low serum NET levels" groups. All analyses were performed in R language 4.1.2, and p < 0.05 were considered significant. Increased susceptibility for high serum NET levels was observed in SLE patients with Raynaud's phenomenon (OR = 2.30, 95 % CI = 1.06-5.21 and p = 0.039), independently of any other risk factor. Also, SLE patients with Raynaud's phenomenon presented higher mean NET serum levels (mean = -0.13 vs. -0.51, p = 0.01). In addition, higher mean NET serum levels were associated with glomerulonephritis (mean = -0.45 vs. -0.12, p = 0.03). Ultimately, the SLEDAI index scored higher in the high NETs serum levels group (median = 2.0 vs. 0.0, p = 6 × 10-3). The formation of NETs might be implicated in Raynaud's phenomenon, glomerulonephritis, and disease index score in SLE patients. Our results highlight the importance of serum NET levels as a possible therapeutical target to modulate the clinical course of SLE.

Neutrophil peptidylarginine deiminase 4 plays a systemic role in obesity-induced chronic inflammation in mice

BACKGROUND

Obesity is an increasing problem in our current society and is expected to keep rising in incidence. With its multiorigin, complex pathophysiology, it is difficult to treat and easy to acquire unnoticeably. During obesity, it has been established that the body is in a constant state of low-grade inflammation, thereby causing changes in immune cell physiology.

OBJECTIVES

Here, we investigated the influence of neutrophils, more specifically as a result of peptidylarginine deiminase 4 (PAD4) activity and the release of neutrophil extracellular traps (NETs), during obesity-induced chronic inflammation.

METHODS

Wild-type mice were placed on a high-fat diet (HFD) and investigated over a period of 10 weeks for NET formation and its impact on the heart. Neutrophil-selective PAD4 knockout (Ne-PAD4-/-) mice were studied in parallel.

RESULTS

As a result of high fat intake, we observed clear alteration in the priming status of isolated neutrophils toward NET release, including early stages of speck formation and histone citrullination of apoptosis-associated speck-like protein containing a CARD. Ne-PAD4-/- mice deficient in NET formation did not increase bodyweight to the same extent as their littermate controls, with Ne-PAD4-/- mice being leaner after 10 weeks of HFD feeding. Interestingly, obesity progression led to cardiac remodeling and diastolic dysfunction in wild-type mice after 10 weeks, while this remodeling and subsequent decrease in function were absent in Ne-PAD4-/- mice. Surprisingly, HFD did not alter NET content or thrombus formation in the inferior vena cava stenosis model.

CONCLUSION

Detrimental physiological effects, the result of obesity progression, can in part be attributed to neutrophil PAD4 and NETs in response to chronic inflammation.