Release of neutrophil extracellular traps by neutrophils stimulated with antiphospholipid antibodies: a newly identified mechanism of thrombosis in the antiphospholipid syndrome

NETosis: A key player in autoimmunity, COVID-19, and long COVID

NETosis, the process through which neutrophils release neutrophil extracellular traps (NETs), has emerged as a crucial mechanism in host defense and the pathogenesis of autoimmune responses. During the SARS-CoV-2 pandemic, this process received significant attention due to the central role of neutrophil recruitment and activation in infection control. However, elevated neutrophil levels and dysregulated NET formation have been linked to coagulopathy and endothelial damage, correlating with disease severity and poor prognosis in COVID-19. Moreover, it is known that SARS-CoV-2 can induce persistent low-grade systemic inflammation, known as long COVID, although the underlying causes remain unclear. It has been increasingly acknowledged that excessive NETosis and NET generation contribute to further pathophysiological abnormalities following SARS-CoV-2 infection. This review provides an updated overview of the role of NETosis in autoimmune diseases, but also the relationship between COVID-19 and long COVID with autoimmunity (e.g., latent and overt autoimmunity, molecular mimicry, epitope spreading) and NETosis (e.g., immune responses, NET markers). Finally, we discuss potential therapeutic strategies targeting dysregulated NETosis to mitigate the severe complications of COVID-19 and long COVID.

NETs activate AIM2 to mediate synovial fibroblast pyroptosis and promote acute gouty arthritis development

BACKGROUND

Acute gouty arthritis is a metabolic disease characterized by hyperuricemia, with acute attacks involving neutrophil-released NETs activating immune responses through their major component, DNA, as danger-associated molecular patterns (DAMPs).

OBJECTIVE

To investigate whether DNA from NETs activates the AIM2 inflammasome in synovial fibroblasts during acute gouty arthritis attacks, inducing pyroptosis and exacerbating inflammation.

METHODS

The AIM2 gene knockdown mouse model of acute gouty arthritis was constructed, the joint pathological changes were observed by H&E staining, the synovium fibroblasts and neutrophils were sorted by flow cytometry, and the expressions of AIM2, Caspase-1 and GSDMD related proteins were detected by Western blot. The levels of TNF-α, IL-6, IL-1β and IL-18 in serum and cell supernatant were detected by ELISA. Neutrophils were induced to release NETs by urate, and NETs markers (dsDNA, MPO-DNA, NE-DNA) were detected by immunofluorescence (Cit-H3, PAD4) and ELISA. NETs media were co-cultured with synovial fibroblasts, cell activity and migration were evaluated by CCK8 and scrape assay, markers of synovitis (Thy1, VCAM-1, PDPN) were detected by immunofluorescence, and pyroptosis was evaluated by TUNEL and LDH release. By silencing or overexpression of AIM2 gene, Western blot and ELISA, the role of AIM2 in NETs induced pyrodeath and inflammatory response was investigated.

RESULTS

AIM2 gene knockdown significantly alleviated the symptoms of MSU-induced acute gouty arthritis in mice, reducing joint swelling and pathological damage. Expression levels of inflammatory factors (TNF-α, IL-6, IL-1β, IL-18) and cleaved Caspase-1/Caspase-1, GSDMD-NT/GSDMD) were decreased. It was found that neutrophils released NETs in response to sodium urate stimulation, manifested by significant upregulation of Cit-H3 and PAD4, as well as increased dsDNA, MPO-DNA, and NE-DNA complexes. NETs can induce inflammatory response in synovial fibroblasts, which is manifested as decreased cell activity and migration ability, increased release of inflammatory factors, and significantly increased markers of synovitis (Thy1, VCAM-1, PDPN). In addition, NETs induce scorch death of synovium fibroblasts by activating AIM2 inflammatories, which aggravates the inflammatory response, and AIM2 gene knockdown can effectively inhibit the scorch death and inflammatory response induced by NETs, indicating that NETs play a key role in the occurrence and development of gout arthritis through AIM2-mediated scorch death of synovium fibroblasts.

CONCLUSION

NETs-activated AIM2-mediated synovial fibroblast pyroptosis plays a crucial role in acute gouty arthritis, providing a new therapeutic target.

A Mimetic Assay of Neutrophil Extracellular Trap Degradation Using YOYO-1-Stained DNA-Histone Surface Webs

Neutrophil extracellular traps (NETs) are not only promising biomarkers of disease, but also potential therapeutic targets. Overproduction or the improper clearance of NETs has been linked to disease severity. In vitro NET degradation assays can reveal mechanisms and degradation efficiency differences in diseased serum samples. There is a need for more convenient assays to increase the speed of NET degradation studies. This paper describes a simplified, lower variability mimetic assay with DNA-histone structures, referred to as surface webs, that performs functionally similarly to traditional NET degradation assays with increased scalability, ease of use, shorter preparation time, and lowered costs. The surface webs are created and dehydrated in a 96-well microplate that is shelf-stable, transportable, and viable for 30 days of storage at room temperature. The surface webs, compared to NETs, have similar shapes and distribution but lower intraplate variability while degrading with healthy serum and DNase I within the same timeframe. The assay can identify patient serum with reduced degradation capabilities. This assay opens new opportunities for NET-targeted drug discovery and studies on the role of NETs as modulators of disease.

Distinctive clinical traits of lupus-related myocarditis: a multicentre retrospective study

OBJECTIVES

Cardiovascular involvement in systemic lupus erythematosus (SLE) is frequent, but little is known about possible distinctive traits of SLE-related myocarditis (myoSLE) in comparison with patients with SLE (onlySLE) or myocarditis alone (onlyMyo).

METHODS

A retrospective analysis was performed comparing patients with myoSLE (n = 25) from three centres with consecutive patients with onlySLE (n = 279) and onlyMyo (n = 88). SLE patients were dichotomized by disease duration ≤1 vs >1 year into recent onlySLE/early myoSLE vs longstanding onlySLE/late myoSLE. Further stratification into disease duration of 1-5, 5-10 and >10 years was also performed. SLE disease activity index 2000 (SLEDAI-2K) was used to estimate disease activity. Myocarditis was diagnosed through biopsy or MRI.

RESULTS

Women were significantly more frequent among myoSLE than among onlyMyo (72% vs 43%; P = 0.013). Compared with onlyMyo, myoSLE patients had a higher frequency of conduction abnormalities (22% vs 5%; P = 0.046) and presented with numerically higher frequencies of left ventricular function compromise (48% vs 30%), along with higher pro-brain natriuretic peptide levels. Inflammation markers were higher in myoSLE compared with onlyMyo and with patients with onlySLE with >10 years of disease duration. SLEDAI-2K was significantly higher in late myoSLE than in longstanding onlySLE. Antiphospholipid syndrome was more frequent in myoSLE than in onlySLE. Multivariate analysis showed an association among myoSLE, anti-β-2-glycoprotein I antibodies (aB2GPI, P = 0.014) and a higher number of involved British Isles Lupus Assessment Group domains in patient history (P = 0.003).

CONCLUSION

myoSLE has unique clinical traits compared with other forms of myocarditis and is associated with aB2GPI and a more severe SLE course.

Therapeutic potential of DNases in immunothrombosis: promising succor or uncertain future?

Sepsis, a life-threatening condition characterized by systemic inflammation and multiorgan dysfunction, is closely associated with the excessive formation of neutrophil extracellular traps (NETs) and the release of cell-free DNA. Both play a central role in sepsis progression, acting as major contributors to immunothrombosis and associated complications. Endogenous DNases play a pivotal role in degrading NETs and cell-free DNA, yet their activity is often dysregulated during thrombotic disease. Although exogenous DNase1 administration has shown potential in reducing NET burden and mitigating the detrimental effects of immunothrombosis, its therapeutic efficacy upon intravenous administration remains uncertain. The development of engineered DNase formulations and combination therapies may further enhance its therapeutic effectiveness by modifying its pharmacodynamic properties and avoiding the adverse effects associated with NET degradation, respectively. Although NETs are well-established targets of DNase1, it remains uncertain whether the positive effects of DNase1 on immunothrombosis are exclusively related to it's targeting of NETs or if other components contributing to immunothrombosis are also affected. This review examines the endogenous regulation of NETs in circulation and the therapeutic potential of DNases in immunothrombosis, underscoring the necessity for further investigation to optimize their clinical application.

Statins as an Adjunctive Antithrombotic Agent in Thrombotic Antiphospholipid Syndrome: Mechanisms and Clinical Implications

The thrombotic physiopathology of antiphospholipid syndrome (APS) is complex, heterogeneous, and dynamic. While venous thromboembolism (VTE) is the most common initial presentation, arterial thrombotic events (ATE) become more frequent in advanced stages and are associated with high morbidity and mortality. Despite the use of oral anticoagulants (OACs), thrombotic APS remains associated with a high risk of recurrent thrombosis. Given their potential antithrombotic effects capable of reducing the risk of both VTE and ATE, statins have been proposed as an adjunctive therapy to OACs for patients with APS and recurrent thrombosis. However, this recommendation is primarily based on studies not specifically conducted in APS populations, with only preclinical data or evidence from retrospective observational studies available from APS patients cohorts. For these reasons, this narrative review aims to synthesise the studies evaluating the potential antithrombotic effects of statins in patients with APS, highlighting the progress made and identifying areas for future research.

Immunoglobulin therapy for infertility and the role of immune cells in pregnancy success: An extensive investigation and update

In the United States, roughly one out of every eight couples, or 7.5 million women, experience challenges related to conceiving or maintaining a pregnancy. The body's immune response is vital during pregnancy. T cells, natural killer (NK) cells, B cells, and macrophages (MQ) are immune cells in the female reproductive tract. They are in charge of maintaining tissue homeostasis and regulating the immune system's response to invasive pathogens. Failure to regulate these immune cells might result in inflammation, which reduces fertility. The immune system modulation of pregnancy loss has been studied with intralipid, intravenous immunoglobulin (IVIG), and paternal leukocyte vaccination. A concentrated antibody called intravenous immunoglobulin (IVIG) is utilized as a biological agent to treat autoimmune, viral, and inflammatory diseases and some immunodeficiencies. The main objective of this treatment is to restore a damaged immune system. IgGs, through binding to specific antigens, promote the innate immunity's cellular and humoral immune response by activating complements and binding to Fc receptors of several immune cells. Contrariwise, IVIG regulates pathogenic autoimmunity in animal models, including skin-blister diseases, nephrotoxic nephritis, and K/BxN arthritis. IVIG has, therefore, been of great interest as an immune modulator in several immune disorders. This review aims to investigate the immunological reasons of reproductive failure, focusing on the immunomodulatory effects of IVIG in its treatment.

Research progress on the relationship between neutrophil extra-cellular traps and autogenous arteriovenous fistula thrombosis

Autogenous arteriovenous fistula (AVF) is the preferred vascular access for long-term hemodialysis, and thrombosis is one of the most common complications. In recent years, it has been found that neutrophil extra-cellular traps (NETs) play an important role in thrombosis. NETs are a kind of network structure with DNA as a skeleton and intercalated with a variety of granule proteins, proteolytic enzymes, antimicrobial peptides and histone proteins, which are released into the extracellular space by neutrophils after stimulation. In this paper, the NETs in the role of AVF thrombus formation and NETs in the value of prevention and cure of AVF thrombus complications were reviewed.

Intrinsic pathway activation in patients with antiphospholipid syndrome and healthy controls

Background

Antiphospholipid syndrome (APS) is a thrombotic autoimmune disease. Activation of the intrinsic coagulation pathway contributes to inflammatory and cardiovascular diseases, but its role in APS is unknown. Increased release of neutrophil extracellular traps and reduced effectiveness of direct oral anticoagulants support the hypothesis of increased intrinsic pathway activation in patients with APS, which is relevant considering the ongoing development and clinical testing of intrinsic pathway inhibitors.

Objectives

To compare in vivo intrinsic pathway activation of patients with APS and healthy controls.

Methods

Patients with APS without recent thrombotic or obstetric events and healthy controls were investigated. ELISAs were used to measure activated coagulation factors in complex with the natural inhibitors antithrombin or C1-esterase inhibitor in plasma. The primary outcome of this study was factor (F)XII activation, which initiates the intrinsic pathway. Secondary outcomes included activation of downstream intrinsic coagulation FXI and FIX.

Results

Plasma of 73 patients with APS and 19 healthy controls showed no significant difference in activated FXII-inhibitor complexes. The concentrations of activated FXI and FIX and inhibitor complexes likewise did not differ between the groups. A subanalysis of patients with APS by anticoagulant use showed no difference for FXII and FXI activation.

Conclusion

Intrinsic pathway activation in patients with APS without recent thrombotic or obstetric events did not differ significantly compared with healthy controls.

Pediatric antiphospholipid syndrome: is it the same as an adult?

IMPORTANCE

Antiphospholipid syndrome in neonates and children is a rare, but in some cases life-threatening condition with arterial and/or venous thrombosis and/or non-thrombotic neurological, skin, ophthalmological and other manifestations.

OBSERVATIONS

This review highlights the available information about the features of pediatric APS, including the rare catastrophic form, the differences between pediatric and adult APS, and the role of genetic thrombophilia in APS manifestation.

CONCLUSIONS AND RELEVANCE

The clinical manifestations and treatment options for APS in children may differ from those in adults, and prescribing therapy can be challenging due to the unique clinical and morphological characteristics of the pediatric patient. Pediatric APS may be a predictor of the development of certain autoimmune diseases and classic manifestations of APS in adulthood, therefore, a revision of the existing criteria for the diagnosis and treatment of APS in children is necessary.

Progress in the field of animal models of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by recurrent arteriovenous thrombosis and pathological pregnancy, accompanied by persistent antiphospholipid antibodies, (aPL). The incidence of APS is increasing year by year, clinicians lack of understanding of this type of disease, easy to misdiagnose and miss the diagnosis. Therefore, it is extremely important to establish a suitable animal model to reduce the process of disease development as much as possible and improve clinicians' understanding and understanding. This review will summarize the animal models of APS from the aspects of modeling methods, modeling mechanism, evaluation indicators and advantages and disadvantages of methods, providing a reference for finding an animal model highly similar to human APS, helping researchers to further clarify the pathogenesis of APS and find potential therapeutic targets, so as to achieve early diagnosis, early intervention, and ultimately improve the prognosis of patients.

Transcriptomics analysis of differential gene expression and immune and inflammatory response mechanisms in patients with typical and non-criteria obstetric antiphospholipid syndrome (OAPS and NC-OAPS)

In this study, we investigated the molecular differences between patients with typical obstetric antiphospholipid syndrome (OAPS) and patients with non-criteria obstetric antiphospholipid syndrome (NC-OAPS) patients through transcriptome sequencing of peripheral blood samples from ten OAPS patients and ten NC-OAPS patients. Differentially expressed genes (DEGs) were identified, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, protein-protein interaction (PPI) analysis, and competitive endogenous RNA (ceRNA) network construction to identify hub genes. Verification was performed via Quantitative Real-time PCR (qPCR) in OAPS (n=9) and NC-OAPS (n=12) samples. We identified 240 DEGs in two groups. GO and KEGG analyses reviewed upregulated in pathways related to the inflammatory response; immune response; antigen processing and presentation; Th1, Th2, and Th17 cell differentiation; and NK cell-mediated cytotoxicity in OAPS patients. PPI and ceRNA network analyses identified key genes, with significant upregulation of CXCR2, JAK2, and MPO found in the OAPS group, which correlated with severe inflammation, JAK-STAT pathway activation, and increased NET activity in neutrophils. Other genes such as CD4, IL2RB, and NKG7, are involved in T-cell and NK cell regulation. Our results indicate enhanced inflammatory and immune responses in OAPS patients, suggesting more severe immune activity than in NC-OAPS patients, providing a basis for precise diagnostic and therapeutic strategies.

5-oxoETE promote thrombosis in antiphospholipid syndrome by triggering NETs formation through PLC/PKC/ERK pathway

BACKGROUND

One mechanism by which antiphospholipid syndrome (APS) IgG contribute to thrombotic events in patients with APS is through the potentiation of neutrophil extracellular traps (NETs) release. However, the exact mechanism by which APS IgG induces NETs formation and thrombosis has not been fully elucidated.

METHODS

We conducted untargeted metabolomics on serum samples from thrombotic APS patients to identify metabolic changes. The effect of 5-oxoETE on NETs formation and oxidative stress was evaluated in vitro by treating neutrophils with various concentrations of 5-oxoETE. The involvement of the PLC/PKC/ERK signaling pathway in 5-oxoETE-induced NETs formation was examined using pharmacological inhibitors. In vivo, we assessed the effects of inhibiting 5-oxoETE synthesis or blocking its receptor (OXE-R) on NETs formation and thrombosis in APS mouse models.

RESULTS

Serum metabolomics revealed significantly elevated levels of 5-oxoETE in APS patients. In vitro experiments demonstrated that 5-oxoETE, via OXE-R activation of the PLC/PKC/ERK signaling pathway, increased NETs formation and oxidative stress in a dose-dependent manner. In vivo, inhibiting 5-oxoETE synthesis or OXE-R reduced NETs formation and attenuated venous thrombosis in APS mice models.

CONCLUSION

This study identifies 5-oxoETE as a critical mediator of NET formation and thrombosis in APS. Targeting 5-oxoETE or OXE-R may offer a promising therapeutic approach for thrombotic APS and other NET-associated autoimmune diseases.

Can complement activation be the missing link in antiphospholipid syndrome?

APS is an autoimmune disorder with life-threatening complications that, despite therapeutic advantages, remains associated with thrombotic recurrences and treatment failure. The role of complement activation in APS pathogenesis is increasingly recognized, specifically in obstetric APS. However, its exact role in thrombotic APS and on the severity of the disease is not yet fully elucidated. Further mechanistic studies are needed to delineate the role of complement activation in the various APS clinical manifestations with aim to identify novel markers of disease severity, together with clinical trials to evaluate the efficacy of complement inhibition in APS. This could ultimately improve risk stratification in APS, patient-tailored targeted therapy with complement inhibition identified as an adjunctive treatment. This article reviews current findings and challenges about complement activation in APS, discusses the potential role of platelet-mediated complement activation in this setting and provides an overview of clinical implications and current therapeutics.

Antiphospholipid Antibodies as Key Players in Systemic Lupus Erythematosus: The Relationship with Cytokines and Immune Dysregulation

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by an overproduction of cytokines, such as interleukins and interferons, contributing to systemic inflammation and tissue damage. Antiphospholipid syndrome is a thrombo-inflammatory autoimmune disease affecting a third of SLE patients. We performed an in-depth analysis of the available literature, and we highlighted the complex interplay between immunity, inflammation, and thrombosis, the three major pathogenic pathways that are trapped in a mutually reinforcing destructive loop.

Parvovirus B19 Infection Is Associated with the Formation of Neutrophil Extracellular Traps and Thrombosis: A Possible Linkage of the VP1 Unique Region

Neutrophil extracellular traps (NETs) formation, namely NETosis, is implicated in antiphospholipid syndrome (APS)-related thrombosis in various autoimmune disorders such as systemic lupus erythematosus (SLE) and APS. Human parvovirus B19 (B19V) infection is closely associated with SLE and APS and causes various clinical manifestations such as blood disorders, joint pain, fever, pregnancy complications, and thrombosis. Additionally, B19V may trigger the production of autoantibodies, including those against nuclear and phospholipid components. Thus, exploring the connection between B19V, NETosis, and thrombosis is highly relevant. An in vitro NETosis model using differentiated HL-60 neutrophil-like cells (dHL-60) was employed to investigate the effect of B19V-VP1u IgG on NETs formation. A venous stenosis mouse model was used to test how B19V-VP1u IgG-mediated NETs affect thrombosis in vivo. The NETosis was observed in the dHL-60 cells treated with rabbit anti-B19V-VP1u IgG and was inhibited in the presence of either 8-Br-cAMP or CGS216800 but not GSK484. Significantly elevated reactive oxygen species (ROS), myeloperoxidase (MPO), and citrullinated histone (Cit-H3) levels were detected in the dHL60 treated with phorbol myristate acetate (PMA), human aPLs IgG and rabbit anti-B19V-VP1u IgG, respectively. Accordingly, a significantly larger thrombus was observed in a venous stenosis-induced thrombosis mouse model treated with PMA, human aPLs IgG, rabbit anti-B19V-VP1u IgG, and human anti-B19V-VP1u IgG, respectively, along with significantly increased amounts of Cit-H3-, MPO- and CRAMP-positive infiltrated neutrophils in the thrombin sections. This research highlights that anti-B19V-VP1u antibodies may enhance the formation of NETosis and thrombosis and implies that managing and treating B19V infection could lower the risk of thrombosis.

Metabolic regulation of neutrophil functions in homeostasis and diseases

Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.

Plasma cell-free DNA as a monitoring tool for high-risk pregnancies associated with antiphospholipid syndrome

INTRODUCTION

Despite thromboprophylaxis, women with antiphospholipid syndrome (APS) face high-risk pregnancies due to proinflammatory and prothrombotic states. This highlights the need for new monitoring and prognostic tools. Recent insights into the pathophysiological role of neutrophil activation and extracellular trap (NET) formation in this syndrome led to the exploration of plasma cell-free DNA (cfDNA), a derivative of NETosis, as a promising biomarker.

MATERIALS AND METHODS

cfDNA was isolated and quantified from plasma samples of healthy pregnant women (control group, HC) and women with APS (APS group). We assessed the physiological variability of cfDNA across the three trimesters in HC. Levels of cfDNA were compared between APS and HC by gestational trimester. ROC curve analysis was performed to evaluate the efficacy of cfDNA levels for classifying APS patients. Furthermore, cfDNA levels in pregnant women with APS with obstetric complications were compared to those from uncomplicated pregnancies.

RESULTS

Among HC, cfDNA significantly increased in the third trimester compared to the first and second. Elevated cfDNA levels in APS compared to HC were observed in the first and second trimesters. First-trimester cfDNA levels demonstrated the highest classification ability to discriminate between APS and HC patients (AUC: 0.906). Among APS, those with complicated pregnancies (fetal growth restriction, preeclampsia, placenta accreta) exhibited significantly elevated cfDNA levels in the second trimester.

CONCLUSIONS

Elevated levels of cfDNA in pregnant women with APS, particularly among those with obstetric complications, supports further investigation into the potential of cfDNA as a valuable tool in the obstetric management of women with APS.

The role of neutrophils in autoimmune diseases

Historically, neutrophils have been primarily regarded as short-lived immune cells that act as initial responders to antibacterial immunity by swiftly neutralizing pathogens and facilitating the activation of adaptive immunity. However, recent evidence indicates that their roles are considerably more complex than previously recognized. Neutrophils comprise distinct subpopulations and can interact with various immune cells, release granular proteins, and form neutrophil extracellular traps. These functions are increasingly recognized as contributing factors to tissue damage in autoimmune diseases. This review comprehensively examines the physiological functions and heterogeneity of neutrophils, their interactions with other immune cells, and their significance in autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome, antineutrophil cytoplasmic antibody-associated vasculitis, multiple sclerosis, and others. This review aims to provide a deeper understanding of the function of neutrophils in the development and progression of autoimmune disorders.

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.

Elevated neutrophil extracellular traps in systemic sclerosis-associated vasculopathy and suppression by a synthetic prostacyclin analog

OBJECTIVES

Neutrophils and neutrophil extracellular traps (NETs) contribute to the vascular complications of multiple diseases, but their role in systemic sclerosis (SSc) is understudied. We sought to test the hypothesis that NETs are implicated in SSc vasculopathy and that treatment with prostacyclin analogs may ameliorate SSc vasculopathy not only through vasodilation but also by inhibiting NET release.

METHODS

Blood from 125 patients with SSc (87 diffuse cutaneous SSc and 38 limited cutaneous SSc) was collected at a single academic medical center. Vascular complications such as digital ulcers, pulmonary artery hypertension, and scleroderma renal crisis were recorded. The association between circulating NETs and vascular complications was determined using in vitro and ex vivo assays. The impact of the synthetic prostacyclin analog epoprostenol on NET release was determined.

RESULTS

Neutrophil activation and NET release were elevated in patients with SSc-associated vascular complications compared to matched patients without vascular complications. Neutrophil activation and NETs positively correlated with soluble E-selectin and VCAM-1, circulating markers of vascular injury. Treatment of patients with digital ischemia with a synthetic prostacyclin analog boosted neutrophil cyclic AMP, which was associated with the blunting of NET release and reduced NETs in circulation.

CONCLUSION

Our study demonstrates an association between NETs and vascular complications in SSc. We also identified the potential for an additional therapeutic benefit of synthetic prostacyclin analogs, namely to reduce neutrophil hyperactivity and NET release in SSc patients.

CXCL8 and its cognate receptors CXCR1/CXCR2 in primary myelofibrosis

BCR::ABL1 negative myeloproliferative neoplasms (MPN) form a distinct group of hematologic malignancies characterized by sustained proliferation of cells from multiple myeloid lineages. With a median survival of 16-35 months in patients with high-risk disease, primary myelofibrosis (PMF) is considered the most aggressive entity amongst all BCR::ABL1 MPN. Additionally, for a significant subset of patients, MPN evolve into secondary acute myeloid leukemia (AML), which has an even poorer prognosis compared to de novo AML. As the exact mechanisms of disease development and progression remain to be elucidated, current therapeutic approaches fail to prevent disease progression or transformation into secondary AML. As each MPN entity is characterized by sustained activation of various immune cells and raised cytokine concentrations within bone marrow (BM) and peripheral blood (PB), MPN may be considered to be typical inflammation-related malignancies. However, the exact role and consequences of increased cytokine concentrations within BM and PB plasma has still not been completely established. Up-regulated cytokines can stimulate cellular proliferation, or contribute to the development of an inflammation-related BM niche resulting in genotoxicity and thereby supporting mutagenesis. The neutrophil chemoattractant CXCL8 is of specific interest as its concentration is increased within PB and BM plasma of patients with PMF. Increased concentration of CXCL8 negatively correlates with overall survival. Furthermore, blockage of the CXCR1/2 axis appears to be able to reduce BM fibrosis and megakaryocyte dysmorphia in murine models. In this review, we summarize available evidence on the role of the CXCL8-CXCR1/2 axis within the pathogenesis of PMF, and discuss potential therapeutic modalities targeting either CXCL8 or its cognate receptors CXCR1/2.

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.

Neutrophil glucose flux as a therapeutic target in antiphospholipid syndrome

Neutrophil hyperactivity and neutrophil extracellular trap release (NETosis) appear to play important roles in the pathogenesis of the thromboinflammatory autoimmune disease known as antiphospholipid syndrome (APS). The understanding of neutrophil metabolism has advanced tremendously in the past decade, and accumulating evidence suggests that a variety of metabolic pathways guide neutrophil activities in health and disease. Our previous work characterizing the transcriptome of APS neutrophils revealed that genes related to glycolysis, glycogenolysis, and the pentose phosphate pathway (PPP) were significantly upregulated. Here, we found that neutrophils from patients with APS used glycolysis more avidly than neutrophils from people in the healthy control group, especially when the neutrophils were from patients with APS with a history of microvascular disease. In vitro, inhibiting either glycolysis or the PPP tempered phorbol myristate acetate- and APS IgG-induced NETosis, but not NETosis triggered by a calcium ionophore. In mice, inhibiting either glycolysis or the PPP reduced neutrophil reactive oxygen species production and suppressed APS IgG-induced NETosis ex vivo. When APS-associated thrombosis was evaluated in mice, inhibiting either glycolysis or the PPP markedly suppressed thrombosis and circulating NET remnants. In summary, these data identify a potential role for restraining neutrophil glucose flux in the treatment of APS.

The role of neutrophils and neutrophil extracellular traps (NETs) in stages, outcomes and pregnancy complications

Neutrophils are the main components of innate immunity to eliminate infectious pathogens. Neutrophils play a role in several stages of the reproductive cycle, and their presence in the female reproductive system is highly regulated, so their function may change during pregnancy. Emerging evidence suggests that neutrophils are important at all stages of pregnancy, from implantation, placentation, and connective tissue regeneration to birth, as well as birth itself. Neutrophil extracellular traps (NETs) are defined as extracellular strands of unfolded DNA together with histone complexes and neutrophil granule proteins. NET formation is a new mechanism of these cells for their defense function. These strands containing DNA and antimicrobial peptides were initially recognized as one of the defense mechanisms of neutrophils, but later it was explained that they are involved in a variety of non-infectious diseases. Since the source of inflammation and tissue damage is the irregular activity of neutrophils, it is not surprising that NETosis are associated with a number of inflammatory conditions and diseases. The overexpression of NET components or non-principled NET clearance is associated with the risk of production and activation of autoantibodies, which results in participation in autoinflammatory and autoimmune disorders (SLE, RA), fibrosis, sepsis and other disorders such as vascular diseases, for example, thrombosis and atherosclerosis. Recent published articles have shown the role of neutrophils and extracellular traps (NETs) in pregnancy, childbirth and pregnancy-related diseases. The aim of this study was to identify and investigate the role of neutrophils and neutrophil extracellular traps (NETs) in the stages of pregnancy, as well as the complications caused by these cells.

Biological markers of high risk of thrombotic recurrence in patients with antiphospholipid syndrome: A literature review

OBJECTIVES

This review aims to identify biological markers associated with the risk of recurrence of thrombotic and/or obstetric events in patients with antiphospholipid syndrome (APS).

METHODS

A comprehensive review of literature was conducted to evaluate established and potential novel biological markers associated with thrombosis in APS. To this end, a PubMed literature search was conducted for the last twenty years using the following keywords or their combinations: thrombotic risk, recurrence of thrombosis, risk stratification, severity, predictive value.

RESULTS

Previous studies showed that multiple aPL positivity correlates with an increased risk of thrombosis in APS. Moreover, the analysis of N-glycosylation of antiphospholipid antibodies (aPL) revealed that low levels of IgG sialylation, fucosylation or galactosylation increases the pro-inflammatory activity of aPL, predisposing to thrombosis. In addition, quantification of neutrophil extracellular traps (NETs) and antibodies directed against NETs (anti-NETs) in serum demonstrates promising prognostic utility in assessing APS severity. Oxidative stress plays a role in the pathogenicity of APS and paraoxonase 1 (PON1) activity emerges as a promising biomarker of thrombotic risk in APS. Furthermore, identification of novel antigenic targets involved in the pathophysiology of APS, such as lysobisphosphatidic acid (LBPA), had led to the discovery of unconventional aPL, antibodies directed against the LBPA (aLBPA), whose clinical value could make it possible to identify APS patients at high risk of thrombotic recurrence.

CONCLUSION

The immunological profile of aPL, N-glycosylation of aPL, quantification of NETs and anti-NETs, analysis of biomarkers of oxidative stress and the discovery of aLBPA offer potential prognostic tools for risk stratification in APS patients.

Obstetric antiphospholipid syndrome carries an increased lifetime risk for obstetric and thrombotic complications-a population-based study

Background

Antiphospholipid syndrome (APS) can present with either a thromboembolic event (thrombotic APS, TAPS) or an obstetric complication (obstetric APS, OAPS). Data on long-term complications in the different APS phenotypes are limited.

Objectives

We aimed to compare obstetric history, antiphospholipid antibody profiles, obstetric and thromboembolic complications, and pregnancy outcomes between TAPS and OAPS.

Methods

This retrospective cohort study included women who delivered singleton pregnancies between 1998 and 2020. One hundred sixteen thousand four hundred nine women were included, resulting in 320,455 deliveries. Among the included patients, 71 were diagnosed with APS, 49 were classified as OAPS, and 22 as TAPS. The demographics, obstetric, neonatal, and thrombotic outcomes were compared among TAPS, OAPS, and the general obstetric population.

Results

OAPS patients had an increased risk of thrombotic events compared with the general obstetric population (odds ratio [OR] 18.0; 95% CI, 8.7-37.2). In pregnancies following the diagnosis of APS, despite standard antithrombotic treatment, OAPS patients exhibited an elevated risk of placenta-related and neonatal complications compared with the general obstetric population (late fetal loss [adjusted OR {aOR}, 15.3; 95% CI, 0.5-27.5], stillbirth [aOR, 5.9; 95% CI, 2.2-15.4], placental abruption [aOR, 4.8; 95% CI, 1.5-15.3], preeclampsia [aOR, 4.4; 95% CI, 2.5-7.7], fetal growth restriction [aOR, 4.3; 95% CI, 8.5-27.5], small for gestational age neonate [aOR, 4.0; 95% CI, 2.4-6.6], and low Apgar scores [Apgar'1: aOR, 2.6; 95% CI, 1.3-10.4; Apgar'5: aOR, 3.7; 95% CI, 1.3-10.4]). TAPS patients exhibited increased risk of preeclampsia (aOR, 3.1; 95% CI, 1.2-8).

Conclusion

OAPS patients exhibit a heightened risk of thrombotic events compared with the general obstetric population. Despite treatment, OAPS and TAPS still presented obstetric complications. These findings, after confirmation in prospective studies, need to be taken into consideration when planning the treatment approach for these patients.

Prothrombotic autoantibodies targeting platelet factor 4/polyanion are associated with pediatric cerebral malaria

BACKGROUNDFeatures of consumptive coagulopathy and thromboinflammation are prominent in cerebral malaria (CM). We hypothesized that thrombogenic autoantibodies contribute to a procoagulant state in CM.METHODSPlasma from children with uncomplicated malaria (UM) (n = 124) and CM (n = 136) was analyzed by ELISA for a panel of 8 autoantibodies including anti-platelet factor 4/polyanion (anti-PF4/P), anti-phospholipid, anti-phosphatidylserine, anti-myeloperoxidase, anti-proteinase 3, anti-dsDNA, anti-β-2-glycoprotein I, and anti-cardiolipin. Plasma samples from individuals with nonmalarial coma (NMC) (n = 49) and healthy controls (HCs) (n = 56) were assayed for comparison. Associations with clinical and immune biomarkers were determined using univariate and logistic regression analyses.RESULTSMedian anti-PF4/P and anti-PS IgG levels were elevated in individuals with malaria infection relative to levels in HCs (P < 0.001) and patients with NMC (PF4/P: P < 0.001). Anti-PF4/P IgG levels were elevated in children with CM (median = 0.27, IQR: 0.19-0.41) compared with those with UM (median = 0.19, IQR: 0.14-0.22, P < 0.0001). Anti-PS IgG levels did not differ between patients with UM and those with CM (P = 0.39). When patients with CM were stratified by malaria retinopathy (Ret) status, the levels of anti-PF4/P IgG correlated negatively with the peripheral platelet count in patients with Ret+ CM (Spearman's rho [Rs] = 0.201, P = 0.04) and associated positively with mortality (OR = 15.2, 95% CI: 1.02-275, P = 0.048). Plasma from patients with CM induced greater platelet activation in an ex vivo assay relative to plasma from patients with UM (P = 0.02), and the observed platelet activation was associated with anti-PF4/P IgG levels (Rs= 0.293, P = 0.035).CONCLUSIONSThrombosis mediated by elevated anti-PF4/P autoantibodies may be one mechanism contributing to the clinical complications of CM.

Non-criteria antiphospholipid antibodies and calprotectin as potential biomarkers in pediatric antiphospholipid syndrome

Our study aimed to evaluate the presence, clinical associations, and potential mechanistic roles of non-criteria antiphospholipid antibodies (aPL) and circulating calprotectin, a highly stable marker of neutrophil extracellular trap release (NETosis), in pediatric APS patients. We found that 79% of pediatric APS patients had at least one non-criteria aPL at moderate-to-high titer. Univariate logistic regression demonstrated that positive anti-beta-2 glycoprotein I domain 1 (anti-D1) IgG (p = 0.008), anti-phosphatidylserine/prothrombin (aPS/PT) IgG (p < 0.001), and aPS/PT IgM (p < 0.001) were significantly associated with venous thrombosis. Positive anti-D1 IgG (p < 0.001), aPS/PT IgG (p < 0.001), and aPS/PT IgM (p = 0.001) were also associated with non-thrombotic manifestations of APS, such as thrombocytopenia. Increased levels of calprotectin were detected in children with APS. Calprotectin correlated positively with absolute neutrophil count (r = 0.63, p = 0.008) and negatively with platelet count (r = -0.59, p = 0.015). Mechanistically, plasma from pediatric APS patients with high calprotectin levels impaired platelet viability in a dose-dependent manner.

Low ectonucleotidase activity and increased neutrophil-platelet aggregates in patients with antiphospholipid syndrome

ABSTRACT

Many patients with antiphospholipid syndrome had decreased ectonucleotidase activity on neutrophils and platelets, which enabled extracellular nucleotides to trigger neutrophil-platelet aggregates. This phenotype was replicated by treating healthy neutrophils and platelets with patient-derived antiphospholipid antibodies or ectonucleotidase inhibitors.

Neutrophil Extracellular DNA Traps in Response to Infection or Inflammation, and the Roles of Platelet Interactions

Neutrophils present the host's first line of defense against bacterial infections. These immune effector cells are mobilized rapidly to destroy invading pathogens by (a) reactive oxygen species (ROS)-mediated oxidative bursts and (b) via phagocytosis. In addition, their antimicrobial service is capped via a distinct cell death mechanism, by the release of their own decondensed nuclear DNA, supplemented with a variety of embedded proteins and enzymes. The extracellular DNA meshwork ensnares the pathogenic bacteria and neutralizes them. Such neutrophil extracellular DNA traps (NETs) have the potential to trigger a hemostatic response to pathogenic infections. The web-like chromatin serves as a prothrombotic scaffold for platelet adhesion and activation. What is less obvious is that platelets can also be involved during the initial release of NETs, forming heterotypic interactions with neutrophils and facilitating their responses to pathogens. Together, the platelet and neutrophil responses can effectively localize an infection until it is cleared. However, not all microbial infections are easily cleared. Certain pathogenic organisms may trigger dysregulated platelet-neutrophil interactions, with a potential to subsequently propagate thromboinflammatory processes. These may also include the release of some NETs. Therefore, in order to make rational intervention easier, further elucidation of platelet, neutrophil, and pathogen interactions is still needed.

Antiphospholipid syndrome pathogenesis in 2023: an update of new mechanisms or just a reconsideration of the old ones?

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (β2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). β2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating β2GPI tissue presentation. β2GPI/β2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

Transcriptionally activates CCL28 expression to inhibit M2 polarization of macrophages and prevent immune escape in colorectal cancer cells

OBJECTIVE

This study aimed to investigate the potential molecular mechanism of SPDEF in immune evasion of colorectal cancer (CRC) and examine its impact on macrophage M2 polarization using the TCGA and GEO databases.

METHODS

By combining TCGA and GEO databases, differential gene expression between CRC samples and standard tissue samples was analyzed to screen for immune-related genes (IRGs) associated with the prognosis of CRC patients. A predictive risk model was constructed based on 18 key IRGs, which were then validated using the GEO dataset. The relationship between transcription factors and IRGs was further explored to investigate their regulatory network in CRC. In vivo and in vitro experiments were carried out to validate these regulatory relationships and explore the function of SPDEF and CCL28 in CRC.

RESULTS

Twelve key IRGs associated with clinical and pathological characteristics of CRC patients were identified. Among them, CCL28 significantly impacted macrophage infiltration in CRC cells and may be a critical factor in immune evasion. In both in vitro and in vivo experiments, overexpression of SPDEF upregulated CCL28 expression, thereby suppressing M2 polarization of macrophages and inhibiting CRC cell proliferation and tumor growth. Notably, interference with CCL28 could reverse the effect of SPDEF overexpression.

CONCLUSION

SPDEF can suppress immune evasion of CRC cells by activating CCL28, which is achieved through the modulation of M2 polarization of macrophages. This provides a new research direction and potential therapeutic target for immunotherapy in CRC.

Platelets and Thrombotic Antiphospholipid Syndrome

Antiphospholipid antibody syndrome (APS) is an autoimmune disorder characterised by thrombosis and the presence of antiphospholipid antibodies (aPL): lupus anticoagulant and/or IgG/IgM anti-β2-glycoprotein I and anticardiolipin antibodies. APS carries significant morbidity for a relatively young patient population from recurrent thrombosis in any vascular bed (arterial, venous, or microvascular), often despite current standard of care, which is anticoagulation with vitamin K antagonists (VKA). Platelets have established roles in thrombosis at any site, and platelet hyperreactivity is clearly demonstrated in the pathophysiology of APS. Together with excess thrombin generation, platelet activation and aggregation are the common end result of all the pathophysiological pathways leading to thrombosis in APS. However, antiplatelet therapies play little role in APS, reserved as a possible option of low dose aspirin in addition to VKA in arterial or refractory thrombosis. This review outlines the current evidence and mechanisms for excessive platelet activation in APS, how it plays a central role in APS-related thrombosis, what evidence for antiplatelets is available in clinical outcomes studies, and potential future avenues to define how to target platelet hyperreactivity better with minimal impact on haemostasis.

Proteomics of Serum Samples for the Exploration of the Pathological Mechanism of Obstetric Antiphospholipid Syndrome

Obstetric antiphospholipid syndrome (OAPS) is a multisystem disorder characterized by thrombosis or recurrent fetal loss. In this study, we aim to explore the pathological mechanism of OAPS. Herein, we carried out data-independent acquisition (DIA) mass spectrometry quantitative proteomic analysis of serum samples from OAPS patients and healthy controls. A set of 93 differentially expressed proteins was identified, including 75 upregulated and 18 downregulated proteins compared with the levels in controls. Those proteins are enriched in KEGG pathways related to autoimmune diseases, allergic diseases, and pathogen infection. Interestingly, metabolic pathways such as fatty acid degradation and type I diabetes were enriched, indicating that OAPS is metabolic disease related. The significantly increased triglyceride also supported this idea. The differentially expressed proteins insulin-like growth factor-binding protein-1 (IGFBP-1), C-reactive protein (CRP), and ferritin light chain (FTL) were validated by ELISA. Our study presented a deep serum proteomics of OAPS and advanced our understanding of OAPS pathogenesis.

Can anticoagulation be withdrawn in APS patients after aPL negativization?

Long-term vitamin K antagonist (VKA) anticoagulation is the cornerstone of the management of subjects with thrombotic antiphospholipid syndrome (APS). Recent investigations have opened up new discussion points regarding the potential for stopping anticoagulant medication in patients with a history of thrombotic APS who no longer have detectable aPL (the so called aPL negativization). Despite the lack of unanimous agreement, some experts agreed on defining aPL negativization as the presence of two negative determinations, 1 year apart. What to do in order to optimize the management of these subjects with thrombotic APS when aPL turn negative is still a matter of debate. In this review, we aim to summarize the main evidence highlighting the magnitude of aPL negativizing among patients with APS and the features to keep in mind when considering (or not) stopping anticoagulation.

Natural supplements in antiphospholipid syndrome: A case for further study

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by thrombotic events and/or pregnancy complications in the presence of persistently positive antiphospholipid antibodies (aPL). Although long-term anticoagulation with vitamin K antagonists is considered standard of care, there is an unmet need for safe therapeutics as primary thromboprophylaxis or adjuncts to standard of care in APS. APS is driven by oxidative stress, procoagulant, proinflammatory and angiogenic pathways. For these reasons there has been an increased interest into the investigation of antithrombotic, anti-inflammatory and anti-oxidant properties of natural supplements in APS. The objective of this review is to summarize the mechanistic, epidemiologic and clinical evidence behind the use of natural supplements in APS, with a specific focus on vitamin D, omega-3 fatty acids, coenzyme Q10, gingerol, and isoquercetin. This review should serve as a compelling argument for the future study of natural supplements in APS.

An Emerging Role for Anti-DNA Antibodies in Systemic Lupus Erythematosus

Anti-DNA antibodies are hallmark autoantibodies produced in systemic lupus erythematosus (SLE), but their pathogenetic role is not fully understood. Accumulating evidence suggests that some anti-DNA antibodies enter different types of live cells and affect the pathophysiology of SLE by stimulating or impairing these cells. Circulating neutrophils in SLE are activated by a type I interferon or other stimuli and are primed to release neutrophil extracellular traps (NETs) on additional stimulation. Anti-DNA antibodies are also involved in this process and may induce NET release. Thereafter, they bind and protect extracellular DNA in the NETs from digestion by nucleases, resulting in increased NET immunogenicity. This review discusses the pathogenetic role of anti-DNA antibodies in SLE, mainly focusing on recent progress in the two research fields concerning antibody penetration into live cells and NETosis.

Comorbid association of obstructive sleep apnea (OSA) and thrombotic primary antiphospholipid syndrome (tPAPS): A more severe phenotype?

OBJECTIVE

We aimed to evaluate the frequency of obstructive sleep apnea (OSA) in patients with thrombotic primary antiphospholipid syndrome (tPAPS), to investigate the performance of screening tools for OSA in this scenario and to compare clinical/laboratorial differences in tPAPS patients with and without OSA.

METHODS

We consecutively enrolled patients with tPAPS to undergo sleep studies using a portable monitor. OSA was defined as apnea-hypopnea index ≥15 events/h. Frequency of OSA in tPAPS was evaluated and compared with age-, gender-, and BMI-matched controls (1:3 ratio) from the Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil). Next, we tested the performance of three different screening tools for assessing OSA in patients with tPAPS. Finally, patients with tPAPS were stratified according to OSA status comparing their clinical and laboratory characteristics (including damage burden measured by Damage Index for Antiphospholipid Syndrome [DIAPS] and biomarkers associated with thrombosis) using standard statistical procedures.

RESULTS

Fifty-two patients were included for analysis (females: 82.7%; mean age: 48 ± 14 years; body-mass index: 31.1 ± 6.5 Kg/m2; 25% with moderate-severe OSA). When compared to matched controls from ELSA-Brasil (n = 115), there was no significant differences in the frequencies of OSA (tPAPS: 12/42 [28.6%] vs. controls: 35/115 [30.4%], p = 0.821). Among screening tools, NoSAS had the highest area under ROC curve (AUC 0.806, CI 95% 0.672-0.939, p = 0.001), followed by STOP-Bang (AUC 0.772, CI 95% 0.607-0.938, p = 0.004). Patients with comorbid tPAPS and OSA presented higher levels of von Willebrand factor (vWF) (median 38.9 vs. 32.6, p = 0.038) and DIAPS (median 5 vs. 2, p = 0.020), when compared to those without OSA. OSA remained statistically associated with higher DIAPS, even after controlling for age, disease duration and BMI.

CONCLUSION

OSA is common in patients with tPAPS, with rates comparable to a non-referred population. Both NoSAS and STOP-Bang scores seems to be useful for screening OSA in these patients. Patients with tPAPS+OSA had higher damage burden and higher levels of vWF, which might suggest a more severe phenotype of tPAPS in this scenario.

Neutrophils, neutrophil extracellular traps, and rheumatoid arthritis: An updated review for clinicians

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by the presence of autoantibodies. Research on the pathogenic mechanisms involved in systemic autoimmune diseases has largely focused on the involvement of the adaptive immune system with dysregulated responses of T and B cells. However, in recent years, there is increasing evidence of the significant role played by the innate immune system, particularly neutrophils, in these diseases, particularly in RA. Neutrophil extracellular traps (NETs) are extracellular structures composed of remodeled and concentrated chromatin with DNA, histones, and neutrophil proteins, and were first described in 2004. It has been studied that NETs may play a pathogenic role in RA and could be a source of autoantigens, increasing the immune response in the form of autoantibodies in this disease. The possible role of NETs and other markers of neutrophil activation as biomarkers of activity in RA and other immune-mediated diseases has also been studied. This article reviews the role of NETs in RA. It discusses the role of neutrophils and the latest advances in NETs, especially their involvement in autoimmune phenomena in RA. Finally, a literature review is conducted on the determination of NETs in peripheral blood and their relationship as a biomarker of RA activity, as well as their potential role in disease monitoring.

Beyond the classics: The emerging value of anti-phosphatidylserine/prothrombin antibodies in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies (aPLs), which can lead to thrombosis and pregnancy complications. Within the diverse range of aPLs, anti-phosphatidylserine/prothrombin antibodies (aPS/PT) have gained significance in clinical practice. The detection of aPS/PT has proven valuable in identifying APS patients and stratifying their risk, especially when combined with other aPL tests like lupus anticoagulant (LA) and anti-β2-glycoprotein I (aβ2GPI). Multivariate analyses have confirmed aPS/PT as an independent risk factor for vascular thrombosis and obstetric complications, with its inclusion in the aPL score and the Global Anti-Phospholipid Syndrome Score (GAPSS) aiding in risk evaluation. However, challenges remain in the laboratory testing of aPS/PT, including the need for assay standardization and its lower sensitivity in certain patient populations. Further research is necessary to validate the clinical utility of aPS/PT antibodies in APS diagnosis, risk stratification, and management.

Role of Neutrophil Extracellular Traps in Health and Disease Pathophysiology: Recent Insights and Advances

Neutrophils are the principal trouper of the innate immune system. Activated neutrophils undergo a noble cell death termed NETosis and release a mesh-like structure called neutrophil extracellular traps (NETs) as a part of their defensive strategy against microbial pathogen attack. This web-like architecture includes a DNA backbone embedded with antimicrobial proteins like myeloperoxidase (MPO), neutrophil elastase (NE), histones and deploys in the entrapment and clearance of encountered pathogens. Thus NETs play an inevitable beneficial role in the host's protection. However, recent accumulated evidence shows that dysregulated and enhanced NET formation has various pathological aspects including the promotion of sepsis, pulmonary, cardiovascular, hepatic, nephrological, thrombotic, autoimmune, pregnancy, and cancer diseases, and the list is increasing gradually. In this review, we summarize the NET-mediated pathophysiology of different diseases and focus on some updated potential therapeutic approaches against NETs.

Philadelphia chromosome-negative myeloproliferative chronic neoplasms: is clonal hematopoiesis the main determinant of autoimmune and cardio-vascular manifestations?

In this article, we reviewed the possible mechanisms linking the clonal hematopoiesis of indeterminate potential (CHIP) to chronic myeloproliferative neoplasms (MPNs), autoimmune diseases (ADs), and cardiovascular diseases (CADs). CHIP is characterized by the presence of clonal mutations with an allelic frequency >2% in the peripheral blood without dysplasia, overt hematological neoplasms, or abnormalities in blood cell count. The prevalence may reach 20% of elderly healthy individuals and is considered a risk factor for myelodysplastic neoplasms and acute leukemia. In MPNs, CHIP is often associated with mutations such as JAK2V617F or DNMT3A, TET2, or ASXL1, which exhibit a 12.1- and 1.7-2-fold increase in CADs. Specifically, JAK2-mutated cells produce excessive cytokines and reactive oxygen species, leading to proinflammatory modifications in the bone marrow microenvironment. Consequently, the likelihood of experiencing thrombosis is influenced by the variant allele frequency (VAF) of the JAK2V617F mutation, which also appears to be correlated with anti-endothelial cell antibodies that sustain thrombosis. However, DNMT3A mutations induce pro-inflammatory T-cell polarization and activate the inflammasome complex, while TET2 downregulation leads to endothelial cell autophagy and inflammatory factor upregulation. As a result, in patients with TET2 and DNMT3A-related CHIP, the inflammasome hyperactivation represents a potential cause of CADs. CHIP also occurs in patients with large and small vessel vasculitis, while ADs are more frequently associated with MPNs. In these diseases, monocytes and neutrophils play a key role in the formation of neutrophil extracellular trap (NET) as well as anti-endothelial cell antibodies, resulting in a final procoagulant effect. ADs, such as systemic lupus erythematosus, psoriasis, and arthritis, are also characterized by an overexpression of the Rho-associated coiled-coil containing protein kinase 2 (ROCK2), a serine/threonine kinase that can hyperactivate the JAK-STAT pathway. Interestingly, hyperactivation of ROCK2 has also been observed in myeloid malignancies, where it promotes the growth and survival of leukemic cells. In summary, the presence of CHIP, with or without neoplasia, can be associated with autoimmune manifestations and thrombosis. In the presence of these manifestations, it is necessary to consider a "disease-modifying therapy" that may either reduce the clonal burden or inhibit the clonally activated JAK pathway.

The Role of the Oxidative State and Innate Immunity Mediated by TLR7 and TLR9 in Lupus Nephritis

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) and is considered one of the leading causes of mortality. Multiple immunological pathways are involved in the pathogenesis of SLE, which makes it imperative to deepen our knowledge about this disease's immune-pathological complexity and explore new therapeutic targets. Since an altered redox state contributes to immune system dysregulation, this document briefly addresses the roles of oxidative stress (OS), oxidative DNA damage, antioxidant enzymes, mitochondrial function, and mitophagy in SLE and LN. Although adaptive immunity's participation in the development of autoimmunity is undeniable, increasing data emphasize the importance of innate immunity elements, particularly the Toll-like receptors (TLRs) that recognize nucleic acid ligands, in inflammatory and autoimmune diseases. Here, we discuss the intriguing roles of TLR7 and TLR9 in developing SLE and LN. Also included are the essential characteristics of conventional treatments and some other novel and little-explored alternatives that offer options to improve renal function in LN.

Immune Thrombosis: Exploring the Significance of Immune Complexes and NETosis

Neutrophil extracellular traps (NETs) are major contributors to inflammation and autoimmunity, playing a key role in the development of thrombotic disorders. NETs, composed of DNA, histones, and numerous other proteins serve as scaffolds for thrombus formation and promote platelet activation, coagulation, and endothelial dysfunction. Accumulating evidence indicates that NETs mediate thrombosis in autoimmune diseases, viral and bacterial infections, cancer, and cardiovascular disease. This article reviews the role and mechanisms of immune complexes in NETs formation and their contribution to the generation of a prothrombotic state. Immune complexes are formed by interactions between antigens and antibodies and can induce NETosis by the direct activation of neutrophils via Fc receptors, via platelet activation, and through endothelial inflammation. We discuss the mechanisms by which NETs induced by immune complexes contribute to immune thrombotic processes and consider the potential development of therapeutic strategies. Targeting immune complexes and NETosis hold promise for mitigating thrombotic events and reducing the burden of immune thrombosis.

Assessing disease activity and damage in antiphospholipid syndrome

Antiphospholipid syndrome (APS) has been characterized by a variety of vascular and pregnancy manifestations related to an interplay between thrombotic and inflammatory mechanisms, a progressive accrual of irreversible organ damage and increased morbidity and mortality rates, supporting a high need of optimal treatment approach. The lack of standardized outcome measures is a significant barrier in the design of clinical studies in APS. Disease activity (in principle reversible) and its distinction from disease damage (in principle irreversible) needs to be evaluated by validated scores for use in clinical trials but also in daily clinical practice in APS. A disease damage score in APS, the DIAPS score, has been developed and validated in external cohorts. The development of a disease activity score that will provide an accurate and reproducible rating of each disease domain, can help clinicians and researchers to comprehensively assess the activity of disease and the response to treatment, in an attempt to prevent future damage.

The pathogenesis of obstetric APS: a 2023 update

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by the persistent presence of antibodies directed against phospholipids and phospholipid-binding proteins that are associated with thrombosis and pregnancy-related morbidity. The latter includes fetal deaths, premature birth and maternal complications. In the early 1990s, a distinct set of autoantibodies, termed collectively antiphospholipid antibodies (aPL), were identified as the causative agents of this disorder. Subsequently histological analyses of the placenta from APS pregnancies revealed various abnormalities, including inflammation at maternal-fetal interface and poor placentation manifested by reduced trophoblast invasion and limited uterine spiral artery remodeling. Further preclinical investigations identified the molecular targets of aPL and the downstream intracellular pathways of key placental cell types. While these discoveries suggest potential therapeutics for this disorder, definitive clinical trials have not been completed. This concise review focuses on the recent developments in the field of basic and translational research pursuing novel mechanisms underlying obstetric APS.

Activation of Platelet mTORC2/Akt Pathway by Anti-β2GP1 Antibody Promotes Thrombosis in Antiphospholipid Syndrome

BACKGROUND

Anti-β2GP1 (β2-glycoprotein 1) antibodies are the primary pathogenic antibody to promote thrombosis in antiphospholipid syndrome (APS), yet the underlying mechanism remains obscure. We aimed to explore the intracellular pathway that mediated platelet activation.

METHODS

Platelets were isolated from patients with APS and subjected to RNA sequencing. Platelet aggregation, the release of platelet granules, platelet spreading, and clot retraction were detected to evaluate platelet activation. We purified anti-β2GP1 antibodies from patients with APS and the total IgG from healthy donors to stimulate platelets with/without FcγRIIA (Fcγ receptor IIA) blocking antibody or Akt (protein kinase B) inhibitor. Platelet-specific Sin1 (stress-activated protein kinase-interacting protein) deficiency mice were established. The thrombus model of inferior vena cava flow restriction, ferric chloride-induced carotid injury model, and laser-induced vessel wall injury in cremaster arterioles model were constructed after administration of anti-β2GP1 antibodies.

RESULTS

Combined RNA sequencing and bioinformatics analysis suggested that APS platelets exhibited increased levels of mRNA associated with platelet activation, which was in line with the hyperactivation of APS platelets in response to stimuli. Platelet activation in APS platelets was accompanied by upregulation of the mTORC2 (mammalian target of the rapamycin complex 2)/Akt pathway and increased levels of SIN1 phosphorylation at threonine 86. Anti-β2GP1 antibody derived from patients with APS enhanced platelet activation and upregulated the mTORC2/Akt pathway. Moreover, the Akt inhibitor weakened the potentiating effect of the anti-β2GP1 antibody on platelet activation. Notably, Sin1 deficiency suppresses anti-β2GP1 antibody-enhanced platelet activation in vitro and thrombosis in all 3 models.

CONCLUSIONS

This study elucidated the novel mechanism involving the mTORC2/Akt pathway, which mediates the promotion of platelet activation and induction of thrombosis by the anti-β2GP1 antibody. The findings suggest that SIN1 may be a promising therapeutic target for the treatment of APS.

Antiphospholipid syndrome nephropathy: Current knowledge and unanswered questions

The definition of acute and chronic antiphospholipid syndrome (APS) nephropathy was recently updated using a multiphase methodology in the context of the development of the new APS classification criteria. Currently, there is no consensus for the treatment of APS nephropathy, which mainly relies on the general recommendations for the management of APS. Based on evidence from experimental studies and a few clinical studies and case series, targeted treatments such as B-cell depletion, anti-B-cell activating factor antibody, complement inhibition, mammalian target of rapamycin inhibition, and neutrophil extracellular traps or interferon targeting may show promise for the treatment of microvascular manifestations in APS, including APS nephropathy. Validation of the new APS nephropathy definition and/or efforts for improvement in proposed terminology, along with the assessment of the safety and efficacy of potential targeted treatments in randomized controlled trials, are major future research directions. In this review, we summarize the current knowledge of APS nephropathy and discuss unanswered questions.