Neutrophil α-defensins promote thrombosis in vivo by altering fibrin formation, structure, and stability

Hot under the clot: venous thrombogenesis is an inflammatory process

ABSTRACT

Venous thrombosis (VT) is a serious medical condition in which a blood clot forms in deep veins, often causing limb swelling and pain. Current antithrombotic therapies carry significant bleeding risks resulting from targeting essential coagulation factors. Recent advances in this field have revealed that the cross talk between the innate immune system and coagulation cascade is a key driver of VT pathogenesis, offering new opportunities for potential therapeutic interventions without inducing bleeding complications. This review summarizes and discusses recent evidence from preclinical models on the role of inflammation in VT development. We highlight the major mechanisms by which endothelial cell activation, Weibel-Palade body release, hypoxia, reactive oxygen species, inflammasome, neutrophil extracellular traps, and other immune factors cooperate to initiate and propagate VT. We also review emerging clinical data describing anti-inflammatory approaches as adjuncts to anticoagulation in VT treatment. Finally, we identify key knowledge gaps and future directions that could maximize the benefit of anti-inflammatory therapies in VT. Identifying and targeting the inflammatory factors driving VT, either at the endothelial cell level or within the clot, may pave the way for new therapeutic possibilities for improving VT treatment and reducing thromboembolic complications without increasing bleeding risk.

Predictive value of baseline alpha defensin level in patients with stable coronary artery disease: A retrospective single center study

Background

Inflammation plays a central role in atherogenesis. The major neutrophilic peptide alpha-defensin is a promising evolving risk factor for atherosclerosis. The aim of the present study was to examine the role of alpha-defensin in predicting future major adverse cardiovascular events (MACE) occurrence in fully revascularized patients with stable CAD under optimal medical therapy.

Methods and results

We retrospectively examined the prognostic value of baseline plasma alpha-defensin levels in predicting MACE occurrence in 174 fully revascularized patients for stable CAD between March 2016 and January 2017. Alpha-defensin levels were found 20 % higher among demised patients (10,859 pg/ml, IQR [6,920 to 23,320] vs. 9,020 pg/ml, IQR [5,540 to 16,180] pg/ml, P = 0.15). The absolute increase in mortality risk in patients with alpha-defensin levels greater than the median values was 72.5 % (P = 0.33). Log-rank analysis proved both recurrent PCI for de novo lesions (14.9 % and 2.3 %) and the composite of mortality and recurrent PCI for de novo lesions (27.6 % vs. 9.2 %) were significantly related to alpha-defensin values greater than the median (>9200 pg/ml).

Conclusion

Baseline plasma alpha-defensin is an independent predictor of mortality and recurrent PCI among patients with stable CAD. Alpha-defensin may evolve as a promising factor in cardiovascular risk assessment beyond traditional risk factors. Targeting alpha-defensin to ameliorate MACE occurrence should be addressed in future studies.

Untargeted blood serum proteomics identifies novel proteins related to neurological recovery after human spinal cord injury

BACKGROUND

The discovery of new prognostic biomarkers following spinal cord injury (SCI) is a rapidly growing field that could help uncover the underlying pathological mechanisms of SCI and aid in the development of new therapies. To date, this search has largely focused on the initial days after the lesion. However, during the subacute stage of SCI (weeks to months after the injury), there remains potential for sensorimotor recovery, and numerous secondary events develop in various organs. Additionally, the confounding effects of early interventions after the injury are less likely to interfere with the results.

METHODS

In this study, we conducted an untargeted proteomics analysis to identify biomarkers of recovery in blood serum samples during the subacute phase of SCI patients, comparing those with strong recovery to those with no recovery between 30 and 120 days. We analyzed the fraction of serum that is depleted of the most abundant proteins to unmask proteins that would otherwise go undetected. Linear models were used to identify peptides and proteins related to neurological recovery and we validated changes in some of these proteins using Enzyme-linked Immunosorbent Assay (ELISA).

RESULTS

Our findings reveal that differences in subacute recovery after SCI (from 30 to 120 days) are associated with an enrichment in proteins involved in inflammation, coagulation, and lipid metabolism. Technical validation using commercial ELISAs further confirms that high levels of SERPINE1 and ARHGAP35 are associated with strong neurological recovery, while high levels of CD300a and DEFA1 are associated with a lack of recovery.

CONCLUSIONS

Our study identifies new candidates for biomarkers of neurological recovery and for novel therapeutic targets after SCI.

Proteomic Characterization of Plasma in Lemierre's Syndrome

BACKGROUND

 The underlying mechanisms of thrombosis in Lemierre's syndrome and other septic thrombophlebitis are incompletely understood. Therefore, in this case control study we aimed to generate hypotheses on its pathogenesis by studying the plasma proteome in patients with these conditions.

METHODS

 All patients with Lemierre's syndrome in the Skåne Region, Sweden, were enrolled prospectively during 2017 to 2021 as cases. Age-matched patients with other severe infections were enrolled as controls. Patient plasma samples were analyzed using label-free data-independent acquisition liquid chromatography tandem mass spectrometry. Differentially expressed proteins in Lemierre's syndrome versus other severe infections were highlighted. Functions of differentially expressed proteins were defined based on a literature search focused on previous associations with thrombosis.

RESULTS

 Eight patients with Lemierre's syndrome and 15 with other severe infections were compared. Here, 20/449 identified proteins were differentially expressed between the groups. Of these, 14/20 had functions previously associated with thrombosis. Twelve of 14 had a suggested prothrombotic effect in Lemierre's syndrome, whereas 2/14 had a suggested antithrombotic effect.

CONCLUSION

 Proteins involved in several thrombogenic pathways were differentially expressed in Lemierre's syndrome compared to other severe infections. Among identified proteins, several were associated with endothelial damage, platelet activation, and degranulation, and warrant further targeted studies.

Update on the Role of Colchicine in Cardiovascular Disease

PURPOSE OF REVIEW

This review focuses on the use of colchicine to target inflammation to prevent cardiovascular events among those at-risk for or with established coronary artery disease.

RECENT FINDINGS

Colchicine is an anti-inflammatory drug that reduces cardiovascular events through its effect on the IL-1β/IL-6/CRP pathway, which promotes the progression and rupture of atherosclerotic plaques. Clinical trials have demonstrated that colchicine reduces cardiovascular events by 31% among those with chronic coronary disease, and by 23% among those with recent myocardial infarction. Its ability to dampen inflammation during an acute injury may broaden its scope of use in patients at risk for cardiovascular events after major non-cardiac surgery. Colchicine is an effective anti-inflammatory therapy in the prevention of acute coronary syndrome. Ongoing studies aim to assess when, and in whom, colchicine is most effective to prevent cardiovascular events in patients at-risk for or with established coronary artery disease.

The Simplified Thrombo-Inflammatory Score as a Novel Predictor of All-Cause Mortality in Patients with Heart Failure: A Retrospective Cohort Study

Background

The simplified thrombo-inflammatory score (sTIPS) has recently emerged as a novel prognostic score. Hence, we investigated the prognostic value of sTIPS for predicting long-term mortality in patients with heart failure (HF).

Methods

A total of 3741 patients were analyzed in this study. The sTIPS was calculated based on the white blood cell count (WBC) and the mean platelet volume to platelet count (MPV/PC) ratio at admission. The mean follow-up time was 22.75 months. Multivariable Cox regression analyses were used to investigate the associations between the sTIPS and all-cause mortality (ACM).

Results

In the whole study population, multivariate Cox regression analysis showed that patients in both the sTIPS 2 and sTIPS 1 groups had significantly increased risk of ACM as compared with patients in the sTIPS 0 group (hazard ratio [HR]=1.706, 95% confidence interval [CI]: 1.405-2.072, P<0.001 and HR = 1.431, 95% CI 1.270-1.612, P<0.001). The same significant trend was observed in heart failure with preserved ejection fraction (HFpEF) patients (sTIPS1 vs sTIPS0: HR = 1.366, 95% CI 1.100-1.697, P = 0.005; sTIPS2 vs sTIPS0: HR = 1.995, 95% CI 1.460-2.725, P<0.001). However, only sTIPS 1 group had a significantly increased the risk of ACM compared to the sTIPS 0 group among patients with HFmrEF (sTIPS1 vs sTIPS0: HR = 1.648, 95% CI 1.238-2.194, P = 0.001) and HFrEF (sTIPS1 vs sTIPS0: HR = 1.322, 95% CI 1.021-1.712, P = 0.035).

Conclusion

sTIPS is useful in predicting risk for long-term mortality in patients with HF.

Glycosaminoglycans' Ability to Promote Wound Healing: From Native Living Macromolecules to Artificial Biomaterials

Glycosaminoglycans (GAGs) are important for the occurrence of signaling molecules and maintenance of microenvironment within the extracellular matrix (ECM) in living tissues. GAGs and GAG-based biomaterial approaches have been widely explored to promote in situ tissue regeneration and repair by regulating the wound microenvironment, accelerating re-epithelialization, and controlling ECM remodeling. However, most approaches remain unacceptable for clinical applications. To improve insights into material design and clinical translational applications, this review highlights the innate roles and bioactive mechanisms of native GAGs during in situ wound healing and presents common GAG-based biomaterials and the adaptability of application scenarios in facilitating wound healing. Furthermore, challenges before the widespread commercialization of GAG-based biomaterials are shared, to ensure that future designed and constructed GAG-based artificial biomaterials are more likely to recapitulate the unique and tissue-specific profile of native GAG expression in human tissues. This review provides a more explicit and clear selection guide for researchers designing biomimetic materials, which will resemble or exceed their natural counterparts in certain functions, thereby suiting for specific environments or therapeutic goals.

Fungi Fibrinolytic Compound 1 Plays a Core Role in Modulating Fibrinolysis, Altering Plasma Clot Structure, and Promoting Susceptibility to Lysis

Fibrin clot structure and function are major determinants of venous and arterial thromboembolic diseases, as well as the key determinants of the efficiency of clot lysis. Studies have revealed that fungi fibrinolytic compound 1 (FGFC1) is a novel marine pyranisoindolone natural product with fibrinolytic activity. Here, we explore the impacts of FGFC1 on clot structure, lysis, and plasminogen activation in vitro using turbidimetric, enzyme-linked immunosorbent assay, confocal and electron microscopy, urokinase, or plasmin chromogenic substrate. Clots formed in the presence of FGFC1 expressed reduced fibrin polymerization rate and maximum turbidity; however, they did not influence the lag phase of fibrin polymerization. In the absence of scu-PA (single-chain urokinase plasminogen activator), microscopy revealed that FGFC1 increased the number of protofibrils within fibrin fiber and the pore diameter between protofibrils, inducing clots to form a region of thinner and looser networks separated by large pores. The effects of FGFC1 on scu-PA-mediated plasma clot structure were similar to those in the absence of scu-PA. In addition, FGFC1 promoted the lysis of clots and increased the D-dimer concentration in lysate. FGFC1 increased the generation rate of p-nitroaniline in plasma. These results show that FGFC1 has fibrinolytic activity in plasma, leading to interference with the release of fibrinopeptide B to affect lateral aggregation of protofibrils and increase clot susceptibility to fibrinolysis by altering its structure.

NLRP3 inflammasome and interleukin-1 contributions to COVID-19-associated coagulopathy and immunothrombosis

Immunothrombosis-immune-mediated activation of coagulation-is protective against pathogens, but excessive immunothrombosis can result in pathological thrombosis and multiorgan damage, as in severe coronavirus disease 2019 (COVID-19). The NACHT-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome produces major proinflammatory cytokines of the interleukin (IL)-1 family, IL-1β and IL-18, and induces pyroptotic cell death. Activation of the NLRP3 inflammasome pathway also promotes immunothrombotic programs including release of neutrophil extracellular traps and tissue factor by leukocytes, and prothrombotic responses by platelets and the vascular endothelium. NLRP3 inflammasome activation occurs in patients with COVID-19 pneumonia. In preclinical models, NLRP3 inflammasome pathway blockade restrains COVID-19-like hyperinflammation and pathology. Anakinra, recombinant human IL-1 receptor antagonist, showed safety and efficacy and is approved for the treatment of hypoxaemic COVID-19 patients with early signs of hyperinflammation. The non-selective NLRP3 inhibitor colchicine reduced hospitalization and death in a subgroup of COVID-19 outpatients but is not approved for the treatment of COVID-19. Additional COVID-19 trials testing NLRP3 inflammasome pathway blockers are inconclusive or ongoing. We herein outline the contribution of immunothrombosis to COVID-19-associated coagulopathy, and review preclinical and clinical evidence suggesting an engagement of the NLRP3 inflammasome pathway in the immunothrombotic pathogenesis of COVID-19. We also summarize current efforts to target the NLRP3 inflammasome pathway in COVID-19, and discuss challenges, unmet gaps, and the therapeutic potential that inflammasome-targeted strategies may provide for inflammation-driven thrombotic disorders including COVID-19.

Inflammasome Signaling, Thromboinflammation, and Venous Thromboembolism

Venous thromboembolism (VTE) remains a major health burden despite anticoagulation advances, suggesting incomplete management of pathogenic mechanisms. The NLRP3 (NACHT-, LRR- and pyrin domain-containing protein 3) inflammasome, interleukin (IL)-1, and pyroptosis are emerging contributors to the inflammatory pathogenesis of VTE. Inflammasome pathway activation occurs in patients with VTE. In preclinical models, inflammasome signaling blockade reduces venous thrombogenesis and vascular injury, suggesting that this therapeutic approach may potentially maximize anticoagulation benefits, protecting from VTE occurrence, recurrence, and ensuing post-thrombotic syndrome. The nonselective NLRP3 inhibitor colchicine and the anti-IL-1β agent canakinumab reduce atherothrombosis without increasing bleeding. Rosuvastatin reduces primary venous thrombotic events at least in part through lipid-lowering independent mechanisms, paving the way to targeted anti-inflammatory strategies in VTE. This review outlines recent preclinical and clinical evidence supporting a role for inflammasome pathway activation in venous thrombosis, and discusses the, yet unexplored, therapeutic potential of modulating inflammasome signaling to prevent and manage VTE.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Colchicine efficacy comparison at varying time points in the peri-operative period for coronary artery disease: a systematic review and meta-analysis of randomized controlled trials

Objectives

Over the years, it has been found that colchicine offers substantial benefits in secondary prevention in patients with coronary artery disease (CAD). We studied the effects of colchicine timing because there are no guidelines about when to provide it during the perioperative period for patients with CAD.

Methods

Up to January 1, 2023, seven electronic literature databases were screened (including three English databases and four Chinese databases). Randomized controlled trials included only treatment with colchicine in the perioperative period of CAD. The Cochrane Evaluation Tool was used to judge the risk of bias in research. Statistical analysis was performed by Stata 16.0 software.

Results

We evaluated twelve studies that found colchicine to be effective in decreasing the occurrence of major adverse cardiac events (MACEs) (p < 0.00001), but it also raised the rate of adverse events (p = 0.001). Subgroup analysis showed the same benefit in lowering the incidence of MACE with continuous administration of a total daily dose of 0.5 mg postoperatively while minimizing drug-related side effects in the patients (p = 0.03). When it comes to preventing surgical stroke occurrences, postoperative administration is more effective (p = 0.006). While the effect of simultaneous preoperative and postoperative administration was marginally greater than other periods in reducing postoperative hs-CRP levels (p = 0.02).

Conclusion

Colchicine, a traditional anti-inflammatory drug, also reduces the risk of MACE by reducing inflammation after PCI. Administration at different periods had no significant effect on decreasing the occurrence of MACE, but when administered postoperatively, we advise continuous administration with a total daily dose of 0.5 mg to obtain the same benefit while minimizing the drug's side effects. Postoperative administration is the better measure to prevent postoperative stroke events. Due to the effective anti-inflammatory effect of colchicine, we recommend its use as early as possible in the perioperative period and its continued use at low doses in the postoperative period.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=316751, identifier CRD42022316751.

Endothelial dysfunction and immunothrombosis in sepsis

Sepsis is a life-threatening clinical syndrome characterized by multiorgan dysfunction caused by a dysregulated or over-reactive host response to infection. During sepsis, the coagulation cascade is triggered by activated cells of the innate immune system, such as neutrophils and monocytes, resulting in clot formation mainly in the microcirculation, a process known as immunothrombosis. Although this process aims to protect the host through inhibition of the pathogen’s dissemination and survival, endothelial dysfunction and microthrombotic complications can rapidly lead to multiple organ dysfunction. The development of treatments targeting endothelial innate immune responses and immunothrombosis could be of great significance for reducing morbidity and mortality in patients with sepsis. Medications modifying cell-specific immune responses or inhibiting platelet–endothelial interaction or platelet activation have been proposed. Herein, we discuss the underlying mechanisms of organ-specific endothelial dysfunction and immunothrombosis in sepsis and its complications, while highlighting the recent advances in the development of new therapeutic approaches aiming at improving the short- or long-term prognosis in sepsis.

A novel interaction between extracellular vimentin and fibrinogen in fibrin formation

INTRODUCTION

Thrombosis is frequently manifested in critically ill patients with systemic inflammation, including sepsis and COVID-19. The coagulopathy in systemic inflammation is often associated with increased levels of fibrinogen and D-dimer. Because elevated levels of vimentin have been detected in sepsis, we sought to investigate the relationship between vimentin and the increased fibrin formation potential observed in these patients.

MATERIALS AND METHODS

This hypothesis was examined by using recombinant human vimentin, anti-vimentin antibodies, plasma derived from healthy and critically ill patients, confocal microscopy, co-immunoprecipitation assays, and size exclusion chromatography.

RESULTS

The level of vimentin in plasma derived from critically ill subjects with systemic inflammation was on average two-fold higher than that of healthy volunteers. We determined that vimentin directly interacts with fibrinogen and enhances fibrin formation. Anti-vimentin antibody effectively blocked fibrin formation ex vivo and caused changes in the fibrin structure in plasma. Additionally, confocal imaging demonstrated plasma vimentin enmeshed in the fibrin fibrils. Size exclusion chromatography column and co-immunoprecipitation assays demonstrated a direct interaction between extracellular vimentin and fibrinogen in plasma from critically ill patients but not in healthy plasma.

CONCLUSIONS

The results describe that extracellular vimentin engages fibrinogen in fibrin formation. In addition, the data suggest that elevated levels of an apparent aberrant extracellular vimentin potentiate fibrin clot formation in critically ill patients with systemic inflammation; consistent with the notion that plasma vimentin contributes to the pathogenesis of thrombosis.

Neutrophils: As a Key Bridge between Inflammation and Thrombosis

Immunothrombosis is a mechanism of defense of the organism against pathogenic microorganisms that increases their recognition, limitation, and clearance and is part of the innate immune defense. Physiological immunothrombosis is beneficial to the body against the invasion of pathogenic microorganisms, but when immunothrombosis is out of control, it is easy to cause thrombotic diseases, thus, causing unpredictable consequences to the body. Neutrophils play a pivotal role in this process. Understanding the mechanism of neutrophils in immune thrombosis and out-of-control is particularly important for the treatment of related thrombotic diseases. In this review, we studied the role of neutrophils in immune thrombosis and each link out of control (including endothelial cell dysfunction; activation of platelets; activation of coagulation factor; inhibition of the anticoagulation system; and inhibition of the fibrinolysis system).

Neutrophil Recruitment in Arterial Thrombus and Characteristics of Stroke Patients with Neutrophil-Rich Thrombus

PURPOSE

Neutrophils contribute to thrombosis. However, there is limited information on the temporal course of neutrophil recruitment in thrombosis, the contribution of neutrophils to thrombus growth, and the characteristics of stroke patients with neutrophil-rich thrombi.

MATERIALS AND METHODS

After inducing carotid artery thrombosis in Institute of Cancer Research mice using ferric chloride, aged thrombi were produced by ligating the distal portion of the carotid artery in mice for 0.5, 1, 2, 3, 6, or 24 h. For thrombus analysis in stroke patients, we used registry data and thrombi that were obtained during intra-arterial thrombectomy. Immunohistochemistry was performed to determine thrombus composition.

RESULTS

In the thrombi of 70 mice, Ly6G positive cell counts (neutrophils) and histone H3-positive cell counts increased in a time-dependent manner (both p<0.001). Ly6G-positive cell count was strongly correlated with histone H3-positive cell counts (r=0.910, p<0.001), but not with thrombus size (p=0.320). In 75 stroke patients, atrial fibrillation and cardioembolism were more frequent in the higher neutrophil group (32/37, 86.5%) than in the lower neutrophil group (19/38, 50%) (p=0.002). The median erythrocyte fraction was higher [52.0 (interquartile range 39.9-57.8)] in the higher neutrophil group than in the lower neutrophil group [40.3 (interquartile range 23.5-53.2)]. The fraction of neutrophils was positively correlated with that of erythrocytes (R=0.35, p=0.002).

CONCLUSION

Neutrophils were recruited and increased in arterial thrombosis in a time-dependent manner; however, they were not associated with the growth of formed thrombi. Neutrophil fractions in the thrombi of stroke patients appeared to be associated with atrial fibrillation and erythrocyte fraction.

Association between tissue human neutrophil peptide 1-3 levels and cardiovascular phenotype: a prospective, longitudinal cohort study

Objective

Inflammation is associated with atherogenesis. Although a higher neutrophil count is associated with the plaque burden, the role of neutrophil activation is unclear. Human neutrophil peptides 1–3 (HNP1–3) are a risk factor for atherogenesis in bench models and are elevated in human atheromas. This study aimed to examine the association between skin HNP1–3 deposition and the severity of coronary artery disease (CAD), including long-term outcomes.

Methods

HNP1–3 levels were immunohistochemically quantified in skin biopsies, which were prospectively taken from 599 consecutive patients before clinically indicated coronary angiography. Established cardiovascular risk factors and blood markers for atheroinflammation were obtained. CAD severity and the incidence of repeat revascularization and mortality at 48 months of follow-up were assessed in relation to HNP1–3 levels.

Results

The risk of CAD was independently associated with age and HNP1–3 in the entire cohort (F = 0.71 and F = 7.4, respectively). Additionally, HNP1–3 levels were significantly associated with myocardial necrosis (R = 0.26). At the follow-up, high HNP1–3 levels negatively affected mortality (19.54%) and recurrent revascularization (8.05%).

Conclusion

HNP1–3 tissue deposition is positively associated with the severity of CAD, myonecrosis, and long-term sequelae. HNP1–3 levels may be suppressed using colchicine.

Human neutrophil peptides 1-3 protect the murine urinary tract from uropathogenic Escherichia coli challenge

Antimicrobial peptides (AMPs) are critical to the protection of the urinary tract of humans and other animals from pathogenic microbial invasion. AMPs rapidly destroy pathogens by disrupting microbial membranes and/or augmenting or inhibiting the host immune system through a variety of signaling pathways. We have previously demonstrated that alpha-defensins 1-3 (DEFA1A3) are AMPs expressed in the epithelial cells of the human kidney collecting duct in response to uropathogens. We also demonstrated that DNA copy number variations in the DEFA1A3 locus are associated with UTI and pyelonephritis risk. Because DEFA1A3 is not expressed in mice, we utilized human DEFA1A3 gene transgenic mice (DEFA^4/4) to further elucidate the biological relevance of this locus in the murine urinary tract. We demonstrate that the kidney transcriptional and translational expression pattern is similar in humans and the human gene transgenic mouse upon uropathogenic Escherichia coli (UPEC) stimulus in vitro and in vivo. We also demonstrate transgenic human DEFA^4/4 gene mice are protected from UTI and pyelonephritis under various UPEC challenges. This study serves as the foundation to start the exploration of manipulating the DEFA1A3 locus and alpha-defensins 1-3 expression as a potential therapeutic target for UTIs and other infectious diseases.

Human Neutrophil Defensins Disrupt Liver Interendothelial Junctions and Aggravate Sepsis

Human neutrophil peptides 1-3 (HNP1-3), also known as human α-defensins, are the most abundant neutrophil granule proteins. The genes that encode HNP1-3, DEFA1/DEFA3, exhibit extensive copy number variations, which correlate well with their protein levels. Human and mouse studies have shown that increased copy numbers of DEFA1/DEFA3 worsen sepsis outcomes. Additionally, high concentrations of HNP1-3 in body fluids have been reported in patients with sepsis. However, direct evidence for the pathogenic role of HNP1-3 proteins during sepsis progression is lacking. In current study, sepsis was induced by means of cecal puncture and ligation. Various doses of HNP-1 (low dose with 0.5 mg/kg body weight and high dose with 10 mg/kg body weight) or phosphate buffer saline were intraperitoneally administered to mice at six hours after sepsis onset. Survival rate was monitored, and vascular permeability, endothelial cell pyroptosis, and immunofluorescence of endothelial adherens junction protein vascular endothelial-cadherin were evaluated. The administration of a high dose of HNP-1 after sepsis onset led to increased mortality, more severe liver injury, and increased vascular permeability in the liver and mesentery. The injection of high dose of HNP-1 did not directly induce liver endothelial cell death but destroyed interendothelial junctions in the liver. Moreover, genetic deficiency of nucleotide-binding oligomerization domain-like receptor protein-3 or caspase-1 abrogated the high mortality and disrupted liver interendothelial junctions caused by high dose of HNP-1 during sepsis. This study directly demonstrates that neutrophil defensins play a key role in regulating endothelial stability during sepsis development.

Neutrophils Mediate Pulmonary Artery Thrombosis In Situ

Pulmonary embolism is a life-threatening condition, which can result in respiratory insufficiency and death. Blood clots occluding branches of the pulmonary artery (PA) are traditionally considered to originate from thrombi in deep veins (usually in legs). However, growing evidence suggests that occlusion of the vessels in the lungs can develop without preceding deep vein thrombosis (DVT). In this work, we used an inferior vena cava (IVC) complete ligation model of DVT in Wistar rats to explore the possibility and mechanisms of PA thrombosis under the conditions where all routes of thrombotic mass migration from peripheral veins are blocked. We demonstrate that rats both with normal and reduced neutrophil counts developed thrombi in the IVC, although, neutropenia caused a substantial decrease in thrombus size and a shift from fresh fibrin toward mature fibrin and connective tissue inside the thrombus. Massive fibrin deposition was found in the PA branches in the majority of DVT rats with normal neutrophil counts, but in none of the neutropenic animals. Neutrophil ablation also abolished macroscopic signs of lung damage. Altogether, the results demonstrate that thrombi in the lung vasculature can form in situ by mechanisms that require local neutrophil recruitment taking place in the DVT setting.

Colchicine Against SARS-CoV-2 Infection: What is the Evidence?

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a matter of concern worldwide and a huge challenge for rheumatologists. Indeed, several antirheumatic drugs are currently used at different stages of COVID-19, such as several cytokine inhibitors and colchicine. Colchicine is one of the oldest medicines with potent anti-inflammatory properties. In rheumatic diseases it is widely used for the treatment of gout, calcium pyrophosphate deposition disease, and familial Mediterranean fever. It is also used off-label in cardiology to treat atrial fibrillation, pericarditis, and myocardial infarction. Over the last few years, advances in the understanding of colchicine's mechanism of action and its pharmacology and safety have made colchicine a promising candidate agent for the fight against COVID-19. In this review, we discuss COVID-19 pathophysiology highlighting colchicine's mode of action, its pleiotropic effects on neutrophils, inflammasome inhibition, and its viral activity. Finally, we discuss the main clinical studies dealing with the use of colchicine in COVID-19. Given the large body of evidence that demonstrates its effectiveness, safety, and its simple way of administration, colchicine seems to be a promising drug to reduce the risk of severe COVID-19 disease.

Theta-Defensins to Counter COVID-19 as Furin Inhibitors: In Silico Efficiency Prediction and Novel Compound Design

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was characterized as a pandemic by the World Health Organization (WHO) in Dec. 2019. SARS-CoV-2 binds to the cell membrane through spike proteins on its surface and infects the cell. Furin, a host-cell enzyme, possesses a binding site for the spike protein. Thus, molecules that block furin could potentially be a therapeutic solution. Defensins are antimicrobial peptides that can hypothetically inhibit furin because of their arginine-rich structure. Theta-defensins, a subclass of defensins, have attracted attention as drug candidates due to their small size, unique structure, and involvement in several defense mechanisms. Theta-defensins could be a potential treatment for COVID-19 through furin inhibition and an anti-inflammatory mechanism. Note that inflammatory events are a significant and deadly condition that could happen at the later stages of COVID-19 infection. Here, the potential of theta-defensins against SARS-CoV-2 infection was investigated through in silico approaches. Based on docking analysis results, theta-defensins can function as furin inhibitors. Additionally, a novel candidate peptide against COVID-19 with optimal properties regarding antigenicity, stability, electrostatic potential, and binding strength was proposed. Further in vitro/in vivo investigations could verify the efficiency of the designed novel peptide.

Colchicine for COVID-19: targeting NLRP3 inflammasome to blunt hyperinflammation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is capable of inducing the activation of NACHT, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome, a macromolecular structure sensing the danger and amplifying the inflammatory response. The main product processed by NLRP3 inflammasome is interleukin (IL)-1β, responsible for the downstream production of IL-6, which has been recognized as an important mediator in coronavirus disease 2019 (COVID-19). Since colchicine is an anti-inflammatory drug with the ability to block NLRP3 inflammasome oligomerization, this may prevent the release of active IL-1β and block the detrimental effects of downstream cytokines, i.e. IL-6. To date, few randomized clinical trials and many observational studies with colchicine have been conducted, showing interesting signals. As colchicine is a nonspecific inhibitor of the NLRP3 inflammasome, compounds specifically blocking this molecule might provide increased advantages in reducing the inflammatory burden and its related clinical manifestations. This may occur through a selective blockade of different steps preceding NLRP3 inflammasome oligomerization as well as through a reduced release of the main cytokines (IL-1β and IL-18). Since most evidence is based on observational studies, definitive conclusion cannot be drawn and additional studies are needed to confirm preliminary results and further dissect how colchicine and other NLRP3 inhibitors reduce the inflammatory burden and evaluate the timing and duration of treatment.

Colchicine in Cardiovascular Disease: In-Depth Review

Inflammation plays a prominent role in the development of atherosclerosis and other cardiovascular diseases, and anti-inflammatory agents may improve cardiovascular outcomes. For years, colchicine has been used as a safe and well-tolerated agent in diseases such as gout and familial Mediterranean fever. The widely available therapeutic has several anti-inflammatory effects, however, that have proven effective in a broad spectrum of cardiovascular diseases as well. It is considered standard-of-care therapy for pericarditis, and several clinical trials have evaluated its role in postoperative and postablation atrial fibrillation, postpericardiotomy syndrome, coronary artery disease, percutaneous coronary interventions, and cerebrovascular disease. We aim to summarize colchicine's pharmacodynamics and the mechanism behind its anti-inflammatory effect, outline thus far accumulated evidence on treatment with colchicine in cardiovascular disease, and present ongoing randomized clinical trials. We also emphasize real-world clinical implications that should be considered on the basis of the merits and limitations of completed trials. Altogether, colchicine's simplicity, low cost, and effectiveness may provide an important addition to other standard cardiovascular therapies. Ongoing studies will address complementary questions pertaining to the use of low-dose colchicine for the treatment of cardiovascular disease.

Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx

The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.

Divergent impacts of tocilizumab and colchicine in COVID-19-associated coagulopathy: the role of alpha-defensins

Patients who are severely affected by coronavirus disease 2019 (COVID-19) may develop a delayed onset 'cytokine storm', which includes an increase in interleukin-6 (IL-6). This may be followed by a pro-thrombotic state and increased D-dimers. It was anticipated that tocilizumab (TCZ), an anti-IL-6 receptor monoclonal antibody, would mitigate inflammation and coagulation in patients with COVID-19. However, clinical trials with TCZ have recorded an increase in D-dimer levels. In contrast to TCZ, colchicine reduced D-dimer levels in patients with COVID-19. To understand how the two anti-inflammatory agents have diverse effects on D-dimer levels, we present data from two clinical trials that we performed. In the first trial, TCZ was administered (8 mg/kg) to patients who had a positive polymerase chain reaction test for COVID-19. In the second trial, colchicine was given (0·5 mg twice a day). We found that TCZ significantly increased IL-6, α-Defensin (α-Def), a pro-thrombotic peptide, and D-dimers. In contrast, treatment with colchicine reduced α-Def and Di-dimer levels. In vitro studies show that IL-6 stimulated the release of α-Def from human neutrophils but in contrast to colchicine, TCZ did not inhibit the stimulatory effect of IL-6; raising the possibility that the increase in IL-6 in patients with COVID-19 treated with TCZ triggers the release of α-Def, which promotes pro-thrombotic events reflected in an increase in D-dimer levels.

Neutrophil extracellular traps contribute to tissue plasminogen activator resistance in acute ischemic stroke

Circulating neutrophil extracellular traps (NETs) resistant to t-PA have not been studied completely although NETs in thrombi may contribute to tissue plasminogen activator (t-PA) resistance. This research intended to elucidate whether circulating NETs are associated with t-PA resistance and the underlying mechanism. The levels of NETs were detected in the circulating neutrophils, ischemic brain tissue of acute ischemic stroke (AIS) patients, and transient middle cerebral artery occlusion (tMCAO) models. NET formation in blood, thrombi, and ischemic brain tissue of mice were analyzed by immunofluorescence. Exposed phosphatidylserine (PS) was assessed using flow cytometry and confocal microscopy. Procoagulant activity (PCA) was evaluated using fibrin formation assays, thrombin, and purified coagulation complex. The plasma levels of NETs in AIS patients were significantly higher than those in healthy individuals. After thrombolysis, a significant increase was noted in NET markers in no-improvement patients, while the changes in improvement patients were not significant. Importantly, NETs were decorated with von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1) in the blood and thrombi, which could reverse the fibrinolytic effects. In addition, NETs activated platelets (PLTs) and endothelial cells (ECs), stimulating a procoagulant phenotype and facilitating vWF and PAI-1 release. DNase I, activated protein C (APC), and sivelestat markedly inhibited these effects. Furthermore, targeting NETs protected mice from tMCAO-induced cerebral ischemia, possibly by regulating vWF and PAI-1. In summary, NETs may contribute to t-PA resistance in AIS through activation of PLTs and ECs. Strategies against NETs may present a promising therapeutic approach to improve the thrombolysis efficiency of t-PA in AIS patients.

Engineering of magnetic nanoparticles as magnetic particle imaging tracers

Magnetic particle imaging (MPI) has recently emerged as a promising non-invasive imaging technique because of its signal linearly propotional to the tracer mass, ability to generate positive contrast, low tissue background, unlimited tissue penetration depth, and lack of ionizing radiation. The sensitivity and resolution of MPI are highly dependent on the properties of magnetic nanoparticles (MNPs), and extensive research efforts have been focused on the design and synthesis of tracers. This review examines parameters that dictate the performance of MNPs, including size, shape, composition, surface property, crystallinity, the surrounding environment, and aggregation state to provide guidance for engineering MPI tracers with better performance. Finally, we discuss applications of MPI imaging and its challenges and perspectives in clinical translation.

Alpha-defensins: risk factor for thrombosis in COVID-19 infection

The inflammatory response to SARS/CoV-2 (COVID-19) infection may contribute to the risk of thromboembolic complications. α-Defensins, antimicrobial peptides released from activated neutrophils, are anti-fibrinolytic and prothrombotic in vitro and in mouse models. In this prospective study of 176 patients with COVID-19 infection, we found that plasma levels of α-defensins were elevated, tracked with disease progression/mortality or resolution and with plasma levels of interleukin-6 (IL-6) and D-dimers. Immunohistochemistry revealed intense deposition of α-defensins in lung vasculature and thrombi. IL-6 stimulated the release of α-defensins from neutrophils, thereby accelerating coagulation and inhibiting fibrinolysis in human blood, imitating the coagulation pattern in COVID-19 patients. The procoagulant effect of IL-6 was inhibited by colchicine, which blocks neutrophil degranulation. These studies describe a link between inflammation and the risk of thromboembolism, and they identify a potential new approach to mitigate this risk in patients with COVID-19 and potentially in other inflammatory prothrombotic conditions.

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

BACKGROUND

Evidence suggests a role for excessive inflammation in COVID-19 complications. Colchicine is an oral anti-inflammatory medication beneficial in gout, pericarditis, and coronary disease. We aimed to investigate the effect of colchicine on the composite of COVID-19-related death or hospital admission.

METHODS

The present study is a phase 3, randomised, double-blind, adaptive, placebo-controlled, multicentre trial. The study was done in Brazil, Canada, Greece, South Africa, Spain, and the USA, and was led by the Montreal Heart Institute. Patients with COVID-19 diagnosed by PCR testing or clinical criteria who were not being treated in hospital were eligible if they were at least 40 years old and had at least one high-risk characteristic. The randomisation list was computer-generated by an unmasked biostatistician, and masked randomisation was centralised and done electronically through an automated interactive web-response system. The allocation sequence was unstratified and used a 1:1 ratio with a blocking schema and block sizes of six. Patients were randomly assigned to receive orally administered colchicine (0·5 mg twice per day for 3 days and then once per day for 27 days thereafter) or matching placebo. The primary efficacy endpoint was the composite of death or hospital admission for COVID-19. Vital status at the end of the study was available for 97·9% of patients. The analyses were done according to the intention-to-treat principle. The COLCORONA trial is registered with ClinicalTrials.gov (NCT04322682) and is now closed to new participants.

FINDINGS

Trial enrolment began in March 23, 2020, and was completed in Dec 22, 2020. A total of 4488 patients (53·9% women; median age 54·0 years, IQR 47·0-61·0) were enrolled and 2235 patients were randomly assigned to colchicine and 2253 to placebo. The primary endpoint occurred in 104 (4·7%) of 2235 patients in the colchicine group and 131 (5·8%) of 2253 patients in the placebo group (odds ratio [OR] 0·79, 95·1% CI 0·61-1·03; p=0·081). Among the 4159 patients with PCR-confirmed COVID-19, the primary endpoint occurred in 96 (4·6%) of 2075 patients in the colchicine group and 126 (6·0%) of 2084 patients in the placebo group (OR 0·75, 0·57-0·99; p=0·042). Serious adverse events were reported in 108 (4·9%) of 2195 patients in the colchicine group and 139 (6·3%) of 2217 patients in the placebo group (p=0·051); pneumonia occurred in 63 (2·9%) of 2195 patients in the colchicine group and 92 (4·1%) of 2217 patients in the placebo group (p=0·021). Diarrhoea was reported in 300 (13·7%) of 2195 patients in the colchicine group and 161 (7·3%) of 2217 patients in the placebo group (p<0·0001).

INTERPRETATION

In community-treated patients including those without a mandatory diagnostic test, the effect of colchicine on COVID-19-related clinical events was not statistically significant. Among patients with PCR-confirmed COVID-19, colchicine led to a lower rate of the composite of death or hospital admission than placebo. Given the absence of orally administered therapies to prevent COVID-19 complications in community-treated patients and the benefit of colchicine in patients with PCR-proven COVID-19, this safe and inexpensive anti-inflammatory agent could be considered for use in those at risk of complications. Notwithstanding these considerations, replication in other studies of PCR-positive community-treated patients is recommended.

FUNDING

The Government of Quebec, the Bill & Melinda Gates Foundation, the National Heart, Lung, and Blood Institute of the US National Institutes of Health, the Montreal Heart Institute Foundation, the NYU Grossman School of Medicine, the Rudin Family Foundation, and philanthropist Sophie Desmarais.

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

BACKGROUND

Evidence suggests a role for excessive inflammation in COVID-19 complications. Colchicine is an oral anti-inflammatory medication beneficial in gout, pericarditis, and coronary disease. We aimed to investigate the effect of colchicine on the composite of COVID-19-related death or hospital admission.

METHODS

The present study is a phase 3, randomised, double-blind, adaptive, placebo-controlled, multicentre trial. The study was done in Brazil, Canada, Greece, South Africa, Spain, and the USA, and was led by the Montreal Heart Institute. Patients with COVID-19 diagnosed by PCR testing or clinical criteria who were not being treated in hospital were eligible if they were at least 40 years old and had at least one high-risk characteristic. The randomisation list was computer-generated by an unmasked biostatistician, and masked randomisation was centralised and done electronically through an automated interactive web-response system. The allocation sequence was unstratified and used a 1:1 ratio with a blocking schema and block sizes of six. Patients were randomly assigned to receive orally administered colchicine (0·5 mg twice per day for 3 days and then once per day for 27 days thereafter) or matching placebo. The primary efficacy endpoint was the composite of death or hospital admission for COVID-19. Vital status at the end of the study was available for 97·9% of patients. The analyses were done according to the intention-to-treat principle. The COLCORONA trial is registered with ClinicalTrials.gov (NCT04322682) and is now closed to new participants.

FINDINGS

Trial enrolment began in March 23, 2020, and was completed in Dec 22, 2020. A total of 4488 patients (53·9% women; median age 54·0 years, IQR 47·0-61·0) were enrolled and 2235 patients were randomly assigned to colchicine and 2253 to placebo. The primary endpoint occurred in 104 (4·7%) of 2235 patients in the colchicine group and 131 (5·8%) of 2253 patients in the placebo group (odds ratio [OR] 0·79, 95·1% CI 0·61-1·03; p=0·081). Among the 4159 patients with PCR-confirmed COVID-19, the primary endpoint occurred in 96 (4·6%) of 2075 patients in the colchicine group and 126 (6·0%) of 2084 patients in the placebo group (OR 0·75, 0·57-0·99; p=0·042). Serious adverse events were reported in 108 (4·9%) of 2195 patients in the colchicine group and 139 (6·3%) of 2217 patients in the placebo group (p=0·051); pneumonia occurred in 63 (2·9%) of 2195 patients in the colchicine group and 92 (4·1%) of 2217 patients in the placebo group (p=0·021). Diarrhoea was reported in 300 (13·7%) of 2195 patients in the colchicine group and 161 (7·3%) of 2217 patients in the placebo group (p<0·0001).

INTERPRETATION

In community-treated patients including those without a mandatory diagnostic test, the effect of colchicine on COVID-19-related clinical events was not statistically significant. Among patients with PCR-confirmed COVID-19, colchicine led to a lower rate of the composite of death or hospital admission than placebo. Given the absence of orally administered therapies to prevent COVID-19 complications in community-treated patients and the benefit of colchicine in patients with PCR-proven COVID-19, this safe and inexpensive anti-inflammatory agent could be considered for use in those at risk of complications. Notwithstanding these considerations, replication in other studies of PCR-positive community-treated patients is recommended.

FUNDING

The Government of Quebec, the Bill & Melinda Gates Foundation, the National Heart, Lung, and Blood Institute of the US National Institutes of Health, the Montreal Heart Institute Foundation, the NYU Grossman School of Medicine, the Rudin Family Foundation, and philanthropist Sophie Desmarais.

Modulating the rate of fibrin formation and clot structure attenuates microvascular thrombosis in systemic inflammation

Systemic inflammation can lead to coagulopathy and disseminated intravascular coagulation (DIC). In prior studies, the recombinant A2 domain of human von Willebrand factor (VWF; A2 protein) attenuated DIC and decreased mortality in lipopolysaccharide (LPS)-treated mice. Here, we performed studies to dissect the mechanism by which the A2 protein moderates DIC. We used confocal microscopy to analyze the fibrin clot structure in plasma from healthy humans and endotoxemic mice, turbidity assays to examine fibrin polymerization, and a murine model for LPS-induced DIC and introduced a loss-of-function mutation into the A2 protein for fibrin. The mutation of the residue E1567 located in the α2 helix of the folded A2 domain of VWF inhibited binding activity for fibrin, possibly mapping a novel region containing a putative binding site for fibrin. The A2 protein increased the initial rate of change of fibrin polymerization, intercalated into the fibrin network, and modified the resultant clot structure in vitro. Furthermore, ex vivo experiments using plasma from mice with endotoxemia treated with the A2 protein revealed an increased rate of fibrin formation and an altered clot structure as compared with plasma from nontreated sick animals. Moreover, and in contrast to the A2 mutant, the A2 protein improved survival and reduced fibrin deposition and microvascular thrombosis in mice with endotoxemia-induced DIC. Importantly, in vivo and in vitro studies indicated that the A2 protein did not affect experimental thrombosis. Thus, we provide evidence for a novel treatment to attenuate systemic inflammation-induced coagulopathy/DIC via targeting fibrin formation, without an increased risk for bleeding.

Anti-inflammatory therapy for COVID-19 infection: the case for colchicine

The search for effective COVID-19 management strategies continues to evolve. Current understanding of SARS-CoV-2 mechanisms suggests a central role for exaggerated activation of the innate immune system as an important contributor to COVID-19 adverse outcomes. The actions of colchicine, one of the oldest anti-inflammatory therapeutics, target multiple mechanisms associated with COVID-19 excessive inflammation. While many COVID-19 trials have sought to manipulate SARS-CoV-2 or dampen the inflammatory response once patients are hospitalised, few examine therapeutics to prevent the need for hospitalisation. Colchicine is easily administered, generally well tolerated and inexpensive, and holds particular promise to reduce the risk of hospitalisation and mortality due to COVID-19 in the outpatient setting. Successful outpatient treatment of COVID-19 could greatly reduce morbidity, mortality and the demand for rare or expensive care resources (front-line healthcare workers, hospital beds, ventilators, biological therapies), to the benefit of both resource-replete and resource-poor regions.

It takes two to thrombosis: Hemolysis and complement

Thromboembolic events represent the most common complication of hemolytic anemias characterized by complement-mediated hemolysis such as paroxysmal nocturnal hemoglobinuria and autoimmune hemolytic anemia. Similarly, atypical hemolytic uremic syndrome is characterized by hemolysis and thrombotic abnormalities. The main player in the development of thrombosis in hemolytic diseases is suggested to be the complement system. However, the release of extracellular hemoglobin and heme by hemolysis itself can also drive procoagulant responses. Both, complement activation and hemolysis promote the activation of neutrophils resulting in the formation of neutrophil extracellular traps and induce inflammation and vascular damage which all together might (synergistically) lead to hypercoagulability. In this review we aim to summarize the current knowledge on the role of complement activation and hemolysis in the onset of thrombosis in hemolytic diseases. This review will discuss the interplay between different biological systems and neutrophil activation contributing to the pathogenesis of thrombosis. Finally, we will combine this fundamental knowledge and address the pathophysiology of hemolysis in prototypical complement-driven diseases.

Phosphatidylserine-exposing tumor-derived microparticles exacerbate coagulation and cancer cell transendothelial migration in triple-negative breast cancer

Background: Neoadjuvant chemotherapy is relevant to the formation of thromboembolism and secondary neoplasms in triple-negative breast cancer (TNBC). Chemotherapy-induced breast cancer cell-derived microparticles (BCMPs) may have important thrombogenic and pro-metastatic effects on platelets and endothelium, which may be related to the expression and distribution of phosphatidylserine (PS). However, investigating these interactions is challenging due to technical limitations. Methods: A study was conducted in 20 healthy individuals and 18 patients who had been recently diagnosed with TNBC and were undergoing neoadjuvant chemotherapy with doxorubicin and cyclophosphamide. BCMPs were isolated from patient blood samples and doxorubicin-treated breast cancer cell lines. Their structure and morphology were studied by electron microscopy and antigen levels were measured by fluorescence-activated cell sorting. In an inhibition assay, isolated BCMPs were pretreated with lactadherin or tissue factor antibodies. Platelets isolated from healthy subjects were treated with BCMPs and coagulation time, fibrin formation, and expression of intrinsic/extrinsic factor Xase (FXa) and thrombin were evaluated. The effects of BCMPs on endothelial thrombogenicity and integrity were assessed by confocal microscopy, electron microscopy, measurement of intrinsic/extrinsic FXa, prothrombinase assay, and transwell permeability assay. Results: Neoadjuvant chemotherapy significantly increased the expression of PS+ BCMPs in patient plasma. Its expression was associated with a rapid increase in procoagulant activity. Treatment with lactadherin, a PS-binding scavenging molecule, markedly reduced the adhesion of BCMPs and abolished their procoagulant activity, but this was not observed with tissue factor antibody treatment. Intravenous injection of BCMPs in mice induced a significant hypercoagulable state, reducing the extent of plasma fibrinogen and promoting the appearance of new thrombus. Cancer cells incubated with doxorubicin released large numbers of PS+ BCMPs, which stimulated and transformed endothelial cells into a procoagulant phenotype and increased the aggregation and activation of platelets. Moreover, cancer cells exploited this BCMP-induced endothelial leakiness and showed promoted metastasis. Pretreatment with lactadherin increased uptake of both PS+ BCMPs and cancer cells by endothelial cells and limited the transendothelial migration of cancer cells. Conclusion: Lactadherin, a biosensor that we developed, was used to study the extracellular vesicle distribution of PS, which revealed a novel PS+ BCMPs administrative axis that initiated a local coagulation cascade and facilitated metastatic colonization of circulating cancer cells.

Cystatin C is a potential predictor of unfavorable outcomes for cerebral ischemia with intravenous tissue plasminogen activator treatment: A multicenter prospective nested case-control study

BACKGROUND AND PURPOSE

The aim of this study was to explore whether cystatin C (CysC) could be used as a potential predictor of clinical outcomes in acute ischemic stroke (AIS) patients treated with intravenous tissue plasminogen activator (IV-tPA).

METHODS

We performed an observational study including a retrospective analysis of data from 125 AIS patients with intravenous thrombolysis. General linear models were applied to compare CysC levels between groups with different outcomes; logistic regression analysis and receiver-operating characteristic curves were adopted to identify the association between CysC and the therapeutic effects.

RESULTS

Compared with the "good and sustained benefit" (GSB) outcome group (defined as ≥4-point reduction in National Institutes of Health Stroke Scale or a score of 0-1 at 24 h and 7 days) and the "good functional outcome" (GFO) group (modified Rankin Scale score 0-2 at 90 days), serum CysC baseline levels were increased in the non-GSB and non-GFO groups. Logistic regression analysis found that CysC was an independent negative prognostic factor for GSB (odds ratio [OR] 0.010; p = 0.005) and GFO (OR 0.011; p = 0.021) after adjustment for potential influencing factors. Receiver-operating characteristic curves showed the CysC-involved combined models provided credible efficacy for predicting post-90-day favorable clinical outcome (area under the curve 0.86; p < 0.001).

CONCLUSIONS

Elevated serum CysC is independently associated with unfavorable clinical outcomes after IV-tPA therapy in AIS. Our findings provide new insights into discovering potential mediators for neuropathological process or treatment in stroke.

Thromboembolic complications in critically ill COVID-19 patients are associated with impaired fibrinolysis

BACKGROUND

There is emerging evidence for enhanced blood coagulation in coronavirus 2019 (COVID-19) patients, with thromboembolic complications contributing to morbidity and mortality. The mechanisms underlying this prothrombotic state remain enigmatic. Further data to guide anticoagulation strategies are urgently required.

METHODS

We used viscoelastic rotational thromboelastometry (ROTEM) in a single-center cohort of 40 critically ill COVID-19 patients.

RESULTS

Clear signs of a hypercoagulable state due to severe hypofibrinolysis were found. Maximum lysis, especially following stimulation of the extrinsic coagulation system, was inversely associated with an enhanced risk of thromboembolic complications. Combining values for maximum lysis with D-dimer concentrations revealed high sensitivity and specificity of thromboembolic risk prediction.

CONCLUSIONS

The study identifies a reduction in fibrinolysis as an important mechanism in COVID-19-associated coagulopathy. The combination of ROTEM and D-dimer concentrations may prove valuable in identifying patients requiring higher intensity anticoagulation.

Molecular Drivers of Platelet Activation: Unraveling Novel Targets for Anti-Thrombotic and Anti-Thrombo-Inflammatory Therapy

Cardiovascular diseases (CVDs) are the leading cause of death globally-partly a consequence of increased population size and ageing-and are major contributors to reduced quality of life. Platelets play a major role in hemostasis and thrombosis. While platelet activation and aggregation are essential for hemostasis at sites of vascular injury, uncontrolled platelet activation leads to pathological thrombus formation and provokes thrombosis leading to myocardial infarction or stroke. Platelet activation and thrombus formation is a multistage process with different signaling pathways involved to trigger platelet shape change, integrin activation, stable platelet adhesion, aggregation, and degranulation. Apart from thrombotic events, thrombo-inflammation contributes to organ damage and dysfunction in CVDs and is mediated by platelets and inflammatory cells. Therefore, in the past, many efforts have been made to investigate specific signaling pathways in platelets to identify innovative and promising approaches for novel antithrombotic and anti-thrombo-inflammatory strategies that do not interfere with hemostasis. In this review, we focus on some of the most recent data reported on different platelet receptors, including GPIb-vWF interactions, GPVI activation, platelet chemokine receptors, regulation of integrin signaling, and channel homeostasis of NMDAR and PANX1.

ACE2, COVID-19 Infection, Inflammation, and Coagulopathy: Missing Pieces in the Puzzle

Engulfed by the grave consequences of the coronavirus disease 2019 (COVID-19) pandemic, a better understanding of the unique pattern of viral invasion and virulence is of utmost importance. Angiotensin (Ang)-converting enzyme (ACE) 2 is a key component in COVID-19 infection. Expressed on cell membranes in target pulmonary and intestinal host cells, ACE2 serves as an anchor for initial viral homing, binding to COVID-19 spike-protein domains to enable viral entry into cells and subsequent replication. Viral attachment is facilitated by a multiplicity of membranal and circulating proteases that further uncover attachment loci. Inherent or acquired enhancement of membrane ACE2 expression, likely leads to a higher degree of infection and may explain the predisposition to severe disease among males, diabetics, or patients with respiratory or cardiac diseases. Additionally, once attached, viral intracellular translocation and replication leads to depletion of membranal ACE2 through degradation and shedding. ACE2 generates Ang 1-7, which serves a critical role in counterbalancing the vasoconstrictive, pro-inflammatory, and pro-coagulant effects of ACE-induced Ang II. Therefore, Ang 1-7 may decline in tissues infected by COVID-19, leading to unopposed deleterious outcomes of Ang II. This likely leads to microcirculatory derangement with endothelial damage, profound inflammation, and coagulopathy that characterize the more severe clinical manifestations of COVID-19 infection. Our understanding of COVID-ACE2 associations is incomplete, and some conceptual formulations are currently speculative, leading to controversies over issues such as the usage of ACE inhibitors or Ang-receptor blockers (ARBs). This highlights the importance of focusing on ACE2 physiology in the evaluation and management of COVID-19 disease.

Venous Thrombotic Events in ANCA-Associated Vasculitis: Incidence and Risk Factors

Background

The incidence of venous thromboembolism (VTE) is increased in ANCA-associated vasculitis (AAV). We assessed the frequency of VTE observed among patients with AAV evaluated at our center and identified risk factors.

Methods

Patients from the Johns Hopkins Vasculitis Center cohort who were evaluated between 1998 and 2018 and had a diagnosis of granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) were eligible for analysis. Baseline demographics and clinical and serologic data were extracted. Univariate and multivariate analyses were performed to identify factors associated with VTE in AAV.

Results

A total of 162 patients with AAV were identified, 105 (65%) with GPA; 22 (14%) of these patients had a recorded VTE with a median time to VTE of 1 month. The mean (SD) age in the VTE versus non-VTE groups was 54±20 versus 55±17 years (P=0.99), 64% versus 60% female (P=0.93), 82% versus 49% PR3-ANCA positive (P=0.01), with a total mean BMI of 33.3±5.7 versus 28.3±6.1 kg/m2, (P<0.001) respectively. The median Birmingham Vasculitis Activity Score (BVAS version 3) was 19 versus 14 (P=0.02). Univariate analyses identified PR3-ANCA, rapidly progressive GN (RPGN), and hypoalbuminemia. In multivariate analysis, the significant associations with VTE included PR3-ANCA (OR, 4.77; P=0.02), hypoalbuminemia (OR, 4.84; P=0.004), and BMI (OR, 1.18; P<0.001).

Conclusions

VTE is a surprisingly common complication of AAV. PR3-ANCA and hypoalbuminemia are risk factors for developing VTEs. Further studies are needed to confirm these findings.

Podcast

This article contains a podcast at https://www.asn-online.org/media/podcast/K360/2020_04_30_KID0000572019.mp3.

The distinctive structure and composition of arterial and venous thrombi and pulmonary emboli

Although arterial and venous thromboembolic disorders are among the most frequent causes of mortality and morbidity, there has been little description of how the composition of thrombi and emboli depends on their vascular origin and age. We quantified the structure and composition of arterial and venous thrombi and pulmonary emboli using high-resolution scanning electron microscopy. Arterial thrombi contained a surprisingly large amount of fibrin, in addition to platelets. The composition of pulmonary emboli mirrored the most distal part of venous thrombi from which they originated, which differed from the structure of the body and head of the same thrombi. All thrombi and emboli contained few biconcave red blood cells but many polyhedrocytes or related forms of compressed red blood cells, demonstrating that these structures are a signature of clot contraction in vivo. Polyhedrocytes and intermediate forms comprised the major constituents of venous thrombi and pulmonary emboli. The structures within all of the thrombi and emboli were very tightly packed, in contrast to clots formed in vitro. There are distinctive, reproducible differences among arterial and venous thrombi and emboli related to their origin, destination and duration, which may have clinical implications for the understanding and treatment of thrombotic disorders.

Heterogeneity in neutrophil responses to immune complexes

Immune complexes (ICs) can trigger inflammation and thrombosis, in part, by activating neutrophils. Much attention has focused on the serologic characteristics of ICs and Fc receptors associated with cellular activation, but few studies have examined host susceptibility to neutrophil activation by ICs. Here, we use a novel whole blood system to investigate the ability of ICs to cause neutrophil activation and degranulation. Using monoclonal anti-platelet factor 4/heparin (PF4/heparin), anti-protamine/heparin antibodies, patient-derived anti-PF4/heparin antibodies, and heat-aggregated immunoglobulin G as model ICs, we demonstrate that heparin-containing ICs cause robust, heparin-dependent neutrophil activation and degranulation which is mediated by both FcγRIIa and complement. Longitudinal testing over a 1-year period shows that an individual's neutrophil response to ICs represents a fixed phenotype resulting in high, intermediate, or low reactivity. Examination of individuals at the extremes of reactivity (high vs low) shows that phenotypic variation resides in the cellular compartment and is correlated with host white blood cell count and absolute neutrophil count, but not age, sex, race, polymorphisms in neutrophil Fcγ receptors, or CR1, CR3, and Fcγ receptor expression on neutrophils. Together, these studies demonstrate that susceptibility to neutrophil activation by ICs is intrinsic to the host and is likely genetic in origin. These findings may be relevant to the heterogeneous clinical outcomes seen in patients with heparin-induced thrombocytopenia and other IC-mediated disorders and could potentially identify patients at high risk for thrombotic and inflammatory complications.