Neutrophil Extracellular Traps In Systemic Lupus Erythematosus Research Articles

The first clinical experience with selective DNA plasmasorption using the NucleoCapture Device in the treatment of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease of unknown etiology characterized by the overproduction of autoantibodies against various components of the nucleus of the patient's own cells with the development of immunoinflammatory tissue damage. In recent years, more and more data have accumulated on the involvement of neutrophils in the development of the clinical symptoms of SLE, and DNA-containing structures and neutrophil extracellular traps (NETs) playing an important role in this process. Effective neutralization of NETs in SLE can be achieved by removing circulating proteins and molecules associated with NETs from the bloodstream by selective plasma sorption of DNA using the NucleoCapture Device.This article describes the case of a patient who underwent three plasma sorption sessions aiming to suppress the activity of SLE. During the therapy, significant positive dynamics were achieved: the SLEDAI-2K index decreased from 32 to 12 points, the number of leukocytes in the blood normalized, renal function improved, and the immunological activity of the disease decreased.

Caught in a Trap? Proteomic Analysis of Neutrophil Extracellular Traps in Rheumatoid Arthritis and Systemic Lupus Erythematosus.

Neutrophil Extracellular Traps (NETs) are implicated in the development of auto-immunity in diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) through the externalization of intracellular neoepitopes e.g., dsDNA and nuclear proteins in SLE and citrullinated peptides in RA. The aim of this work was to use quantitative proteomics to identify and measure NET proteins produced by neutrophils from healthy controls, and from patients with RA and SLE to determine if NETs can be differentially-generated to expose different sets of neoepitopes. Ultra-pure neutrophils (>99%) from healthy individuals (n = 3) and patients with RA or SLE (n = 6 each) were incubated ± PMA (50 nM, PKC super-activator) or A23187 (3.8 μM, calcium ionophore) for 4 h. NETs were liberated by nuclease digestion and concentrated onto Strataclean beads prior to on-bead digestion with trypsin. Data-dependent LC-MS/MS analyses were conducted on a QExactive HF quadrupole-Orbitrap mass spectrometer, and label-free protein quantification was carried out using Progenesis QI. PMA-induced NETs were decorated with annexins, azurocidin and histone H3, whereas A23187-induced NETs were decorated with granule proteins including CAMP/LL37, CRISP3, lipocalin and MMP8, histones H1.0, H1.4, and H1.5, interleukin-8, protein-arginine deiminase-4 (PADI4), and α-enolase. Four proteins were significantly different between PMA-NETs from RA and SLE neutrophils (p < 0.05): RNASE2 was higher in RA, whereas MPO, leukocyte elastase inhibitor and thymidine phosphorylase were higher in SLE. For A23187-NETs, six NET proteins were higher in RA (p < 0.05), including CAMP/LL37, CRISP3, interleukin-8, MMP8; Thirteen proteins were higher in SLE, including histones H1.0, H2B, and H4. This work provides the first, direct comparison of NOX2-dependent (PMA) and NOX2-independent (A23187) NETs using quantitative proteomics, and the first direct comparison of RA and SLE NETs using quantitative proteomics. We show that it is the nature of the stimulant rather than neutrophil physiology that determines NET protein profiles in disease, since stimulation of NETosis in either a NOX2-dependent or a NOX2-independent manner generates broadly similar NET proteins irrespective of the disease background. We also use our proteomics pipeline to identify an extensive range of post-translationally modified proteins in RA and SLE, including histones and granule proteins, many of which are known targets of auto-antibodies in each disease.

REDD1/autophagy pathway promotes thromboinflammation and fibrosis in human systemic lupus erythematosus (SLE) through NETs decorated with tissue factor (TF) and interleukin-17A (IL-17A)

ObjectivesThe release of neutrophil extracellular traps (NETs) represents a novel neutrophil effector function in systemic lupus erythematosus (SLE) pathogenesis. However, the molecular mechanism underlying NET release and how NETs mediate...

Active NET formation in Libman–Sacks endocarditis without antiphospholipid antibodies: A dramatic onset of systemic lupus erythematosus

Although neutrophil extracellular traps (NETs) have been highlighted in several systemic inflammatory diseases, their clinical correlates and potential pathological role remain obscure. Herein, we describe a dramatic onset of systemic lupus erythematosus (SLE) with clear-cut pathogenic implications for neutrophils and NET formation in a young woman with cardiac (Libman–Sacks endocarditis) and central nervous system (psychosis and seizures) involvement. Despite extensive search, circulating antiphospholipid autoantibodies, a hallmark of Libman–Sacks endocarditis, could not be detected. Instead, we observed active NET formation in the tissue of the mitral valve, as well as in the circulation. Levels of NET remnants were significantly higher in serially obtained sera from the patient compared with sex-matched blood donors (p = .0011), and showed a non-significant but substantial correlation with blood neutrophil counts (r = 0.65, p = .16). The specific neutrophil elastase activity measured in serum seemed to be modulated by the provided immunosuppressive treatment. In addition, we found anti-Ro60/SSA antibodies in the cerebrospinal fluid of the patient but not NET remnants or increased elastase activity. This case illustrates that different disease mechanisms mediated via autoantibodies can occur simultaneously in SLE. NET formation with release of cytotoxic NET remnants is a candidate player in the pathogenesis of this non-canonical form of Libman–Sacks endocarditis occurring in the absence of traditional antiphospholipid autoantibodies. The case description includes longitudinal results with clinical follow-up data and a discussion of the potential roles of NETs in SLE.

Mlkl Pores Release Neutrophil Extracellular Traps in Necroptotic Neutrophils

Neutrophil extracellular traps (NETs) are networks of extracellular nuclear DNA and microbicidal proteins released from neutrophils in response to tissue damage and infection. Despite evidence of pathogenic roles for NETs in systemic lupus erythematosus, rheumatoid arthritis, diabetes, artherosclerosis and Alzheimer's disease, the major biochemical pathways controlling their formation remains poorly understood. Apoptosis does not contribute to NET formation but the role of regulated non-apoptotic cell death pathways such as necroptosis is not known. We have investigated the role of positive and negative regulators of necroptosis including receptor-interacting protein kinase-3 (RIPK3), mixed lineage kinase domain-like (MLKL), receptor-interacting protein kinase-1 (RIPK1) and Caspase-8. Using immunogold electron microscopy, flow cytometry, imaging flow cytometry and fluorescence microscopy, we demonstrate that necroptosis can drive NET formation via MLKL pore formation at the cell surface. This process is caspase-independent but reactive oxygen species-dependent. Genetically-modified mouse peripheral blood and bone marrow neutrophils were used to show that Caspase-8 and RIPK1 negatively regulate NET formation driven by RIPK3 and MLKL. Mice that lack MLKL are deficient in necroptosis and NET formation, and were sensitive to methicillin-resistant Staphylococcus aureus (MRSA). Neutrophil-specific Caspase-8-deficiency also leads to increased susceptibility to MRSA due to increased rates of necroptotic neutrophil death. Killing of MRSA by necroptotic neutrophils is sensitive to DNase, and is dependent on MLKL, suggesting that necroptosis-driven NET formation contributes to the bactericidal activity of neutrophils. Human peripheral blood neutrophils also generate NETs that are sensitive to pharmacological inhibitors of necroptosis, suggesting that targeting necroptosis in general may help combat autoimmune responses to DNA. This study provides a framework to investigate the role of extracellular DNA release and cell death in the setting of infection, autoimmunity and autoinflammatory disease. DisclosuresNo relevant conflicts of interest to declare.

Acetylated histones contribute to the immunostimulatory potential of neutrophil extracellular traps in systemic lupus erythematosus.

In addition to disturbed apoptosis and insufficient clearance of apoptotic cells, there is recent evidence for a role of neutrophils in the aetiopathogenesis of systemic lupus erythematosus (SLE). In response to various stimuli, neutrophils can rapidly release DNA fibres decorated with citrullinated histones and anti-microbial peptides. These structures are referred to as neutrophil extracellular traps (NETs). In addition to apoptotic cell-derived microparticles, these NETs may comprise a further source of autoantigens, able to drive the autoimmune response in SLE. Our group recently identified specific histone modifications occurring during apoptosis that play an important role in the autoimmune response in SLE. In the current study, we evaluated the presence and immunostimulatory potential of these previously identified histone modifications in NETs. Compared to NETs from healthy donors, the histones present in NETs formed by SLE-derived neutrophils contain increased amounts of acetylated and methylated residues, which we previously observed to be associated with apoptosis and SLE. Treatment of neutrophils with histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), prior to induction of NETosis, induced NETs containing hyperacetylated histones, endowed with an increased capacity to activate macrophages. This implies that specific histone modifications, in particular acetylation, might enhance the immunostimulatory potential of NETs in SLE.

Ligation of Signal Inhibitory Receptor on Leukocytes-1 Suppresses the Release of Neutrophil Extracellular Traps in Systemic Lupus Erythematosus

Neutrophil extracellular traps (NETs) have been implicated in the pathogenesis of systemic Lupus erythematosus (SLE), since netting neutrophils release potentially immunogenic autoantigens including histones, LL37, human neutrophil peptide (HNP), and self-DNA. In turn, these NETs activate plasmacytoid dendritic cells resulting in aggravation of inflammation and disease. How suppression of NET formation can be targeted for treatment has not been reported yet. Signal Inhibitory Receptor on Leukocytes-1 (SIRL-1) is a surface molecule exclusively expressed on phagocytes. We recently identified SIRL-1 as a negative regulator of human neutrophil function. Here, we determine whether ligation of SIRL-1 prevents the pathogenic release of NETs in SLE. Peripheral blood neutrophils from SLE patients with mild to moderate disease activity and healthy donors were freshly isolated. NET release was assessed spontaneously or after exposure to anti-neutrophil antibodies or plasma obtained from SLE patients. The formation of NETs was determined by microscopic evaluation using DNA dyes and immunostaining of NET components, as well as by live cell imaging. We show that SLE neutrophils spontaneously release NETs. NET formation is enhanced by stimulation with antibodies against LL37. Inhibition of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and MEK-ERK signaling prevents NET release in response to these antibodies. Signaling via the inhibitory receptor SIRL-1 was induced by ligation with anti-SIRL-1 specific antibodies. Both spontaneous and anti-neutrophil antibody-induced NET formation is suppressed by engagement of SIRL-1. Furthermore, NET release by healthy neutrophils exposed to SLE plasma is inhibited by SIRL-1 ligation. Thus, SIRL-1 engagement can dampen spontaneous and anti-neutrophil antibody-induced NET formation in SLE, likely by suppressing NAPDH oxidase and MEK-ERK activity. Together, these findings reveal a regulatory role for SIRL-1 in NET formation, potentially providing a novel therapeutic target to break the pathogenic loop in SLE.