Anti-myeloperoxidase antibodies enhance phagocytosis, IL-8 production, and glucose uptake of polymorphonuclear neutrophils rather than anti-proteinase 3 antibodies leading to activation-induced cell death of the neutrophils

NETosis Secondary to the Use of Levamisole-Adulterated Cocaine: A Likely Underlying Mechanism of Vasculopathy

Background

Since 2010, several cases of a new vasculopathy induced by the use of levamisole-adulterated cocaine (LAC) have been reported. This vasculopathy is characterized by retiform purpura, earlobe necrosis, multisystem compromise, and multiple autoantibodies. Given its similarity to antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, LAC-associated vasculopathy is postulated to be mediated by pathophysiologic processes resulting from neutrophil cell death by NETosis, a phenomenon previously described in ANCA vasculitis. This study tries to establish the presence of NETosis induced by cocaine, levamisole, or both. Methodology. Neutrophils were isolated from the peripheral blood of healthy controls by Ficoll-Hystopaque density gradient centrifugation followed by dextran sedimentation. Cell viability and purity were evaluated by flow cytometry after staining with PI/DiOC6 and labeling with fluorescent anti-CD45/anti-CD3 monoclonal antibodies (mAbs), respectively. Neutrophils were exposed to levamisole, cocaine, a cocaine-levamisole mixture, and sera pools from healthy controls and patients with LAC-associated vasculopathy. NETosis was then assessed by flow cytometry after staining cells with Sytox Green, Hoechst-33342, and fluorescent antineutrophil elastase (NE) and antimyeloperoxidase (MPO) mAbs. In addition, NETosis was morphologically confirmed by fluorescence microscopy. Proinflammatory cytokine levels in culture supernatants and reactive oxygen species (ROS) synthesis were determined by flow cytometry. The involvement of calcium and muscarinic receptors in cell death induction was evaluated in parallel experiments carried out in the presence of 1,2-bis (o-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid (BAPTA) and hyoscine butylbromide (HBB), their respective inhibitors.

Results

Cocaine, levamisole, and a cocaine-levamisole mixture induced neutrophil cell death. DNA/MPO extrusion and cell morphology patterns were consistent with NETosis. Neither proinflammatory cytokines nor ROS behaved as proNETotic factors. Preliminary results suggested that muscarinic receptors and calcium-dependent signals were involved in LAC-induced NETosis.

Conclusions

Cocaine, levamisole, and a cocaine-levamisole mixture can induce NETosis through mechanisms involving muscarinic receptors and calcium-dependent pathways.

Longitudinal monitoring of circulating immune cell phenotypes in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a necrotizing multiorgan autoimmune disease that affects small- to medium-sized blood vessels. Despite the improvements in treatments, half of the patients with AAV still experience disease relapses. In this review, we focus on peripheral leukocyte properties and phenotypes in patients with AAV. In particular, we explore longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and treatment. The numbers and phenotypes of leukocytes in peripheral blood were differs between AAV and healthy controls, AAV in active versus inactive phase, AAV in treatment responders versus non-responders, and AAV with and without severe infection. Therefore, biomarkers detected in peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in AAV.

A proposed role of neutrophil extracellular traps and their interplay with fibroblasts in ANCA-associated vasculitis lung fibrosis

ANCA-associated vasculitides (AAV) comprise three diseases: granulomatosis with polyangiitis, microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis. They are characterised by small vessel inflammation and have a broad range of clinical manifestations and multiorgan involvement which endanger the patient's life. An increasingly recognised complication of AAV, especially in MPA is lung fibrosis, for which no clearcut therapy in this context is available. The release of neutrophil extracellular traps (NETs) in these diseases has been related to the development of fibrosis, but the precise mechanisms are not fully unravelled. This review provides an overview of some of the important proteins known to compose NETs, and proposes some mechanisms by which these remarkable components may exert an impact on the different fibroblastic phenotypes leading to lung fibrosis.

Neutrophil Extracellular Traps: Signaling Properties and Disease Relevance

Neutrophil extracellular traps (NETs) are characterized as extracellular DNA fibers comprised of histone and cytoplasmic granule proteins. NETs were first described as a form of innate response against pathogen invasion, which can capture pathogens, degrade bacterial toxic factors, and kill bacteria. Additionally, NETs also provide a scaffold for protein and cell binding. Protein binding to NETs further activate the coagulation system which participates in thrombosis. In addition, NETs also can damage the tissues due to the proteins they carry. Many studies have suggested that the excessive formation of NETs may contribute to a range of diseases, including thrombosis, atherosclerosis, autoimmune diseases, and sepsis. In this review, we describe the structure and components of NETs, models of NET formation, and detection methods. We also discuss the molecular mechanism of NET formation and their disease relevance. Modulation of NET formation may provide a new route for the prevention and treatment of releated human diseases.

Neutrophil hyperactivation correlates with Alzheimer's disease progression

OBJECTIVE

Recent studies have underlined the effect of systemic inflammation on the pathophysiology of Alzheimer's disease (AD). Neutrophils are key components of early innate immunity and contribute to uncontrolled systemic inflammation if not tightly regulated. The aim of our study was to fully characterize human circulating neutrophils at different disease stages in AD.

METHODS

We analyzed neutrophil phenotypes and functions in 42 patients with AD (16 with mild cognitive impairment and 26 with dementia), and compared them to 22 age-matched healthy subjects. This study was performed directly in whole blood to avoid issues with data interpretation related to cell isolation procedures.

RESULTS

Blood samples from AD patients with dementia revealed neutrophil hyperactivation associated with increased reactive oxygen species production and increased levels of intravascular neutrophil extravascular traps. The homeostasis of circulating neutrophils in these patients also changed: The ratio between the harmful hyperreactive CXCR4^high /CD62L^low senescent and the CD16^bright /CD62L^dim immunosuppressive neutrophil subsets rose in the later stage of the disease. These abnormalities were greater in fast-decliner than in slow-decliner patients.

INTERPRETATION

Our results indicate that the inflammatory properties of circulating neutrophils shift as the percentage of aged neutrophils expands in patients with AD-changes that may play an instrumental role in establishing systemic chronic inflammation. Most important, our data strongly suggest that the neutrophil phenotype may be associated with the rate of cognitive decline and may thus constitute an innovative and prognostic blood biomarker in patients with AD. Ann Neurol 2018;83:387-405.

Hydrogen peroxide promotes the activation of preeclampsia peripheral T cells

Preeclampsia (PE) is a pregnancy disorder with a high mortality rate. Patients with PE exhibit systemic high oxidative stress status and inflammatory immune activation. This study aims to define the role of H₂O₂ in the activation of neutrophils and T lymphocytes in PE patients. CD3⁺/HLA-DR⁺ cells in blood from PE patients are remarkably increased compared with those of normal non-pregnancies or normal pregnancies, while the percentage of CD3⁺/CD62L⁺ cells is significantly reduced in PE patients compared to normal pregnancies. Furthermore, CD62L levels in granulocytes of periphery blood of PE patients are significantly higher than non-pregnancies, but significantly lower than normal pregnancies. To characterize the effects of intracellular reactive oxygen species (ROS) on T lymphocyte activation in PE patients, PBMCs from normal pregnancies were challenged with H₂O₂, and intracellular ROS levels in neutrophil granulocytes, as well as T cell surface marker levels, have been determined. We confirm that H₂O₂ exposure increases intracellular ROS levels in neutrophil granulocytes, and increases the proportion of CD3⁺/HLA-DR⁺ cells, but does not alter the percentage of CD3⁺/CD62L⁺ cells in PBMCs. Our study has confirmed dysregulated CD3⁺/HLA-DR⁺ and CD3⁺/CD62L⁺ T lymphocytes in PE patient peripheral blood, and the dysregulative effects of H₂O₂ on T lymphocyte activation, suggesting a novel mechanism of immune activation in PE.

Neutrophil extracellular traps (NETs) in autoimmune diseases: A comprehensive review

Neutrophil extracellular traps (NETs) are fibrous networks which protrude from the membranes of activated neutrophils. NETs are found in a variety of conditions such as infection, malignancy, atherosclerosis, and autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV), psoriasis, and gout. Studies suggest that an imbalance between "NETosis," which is a process by which NETs are formed, and NET degradation may be associated with autoimmune diseases. Neutrophils, interleukin-8, ANCA and other inflammatory molecules are considered to play a key role in NET formation. Prolonged exposure to NETs-related cascades is associated with autoimmunity and increases the chance of systemic organ damage. In this review, we discuss the roles of various inflammatory molecules in relation to NETs. We also describe the role of NETs in the pathogenesis of autoimmune diseases and discuss the possibility of using targeted therapies directed to NETs and associated molecules to treat autoimmune diseases.

Churg-Strauss Syndrome: an evolving paradigm

The Churg-Strauss Syndrome is an ANCA-associated vasculitis, an inflammatory multisystem disease with preference to the respiratory tract. Peripheral and tissue eosinophilia are the pathological hallmarks of this condition. The etiopathogenesis is unknown but some cytokines appear to play a central role and could be targets for new therapies.

The human lactoferrin-derived peptide hLF1-11 exerts immunomodulatory effects by specific inhibition of myeloperoxidase activity

Because of their ability to eliminate pathogens and to modulate various host immune responses, antimicrobial peptides are considered as candidate agents to fight infections by (antibiotic-resistant) pathogens. We recently reported that hLF1-11 (GRRRRSVQWCA), an antimicrobial peptide derived from the N terminus of human lactoferrin, displays diverse modulatory activities on monocytes, thereby enhancing their actions in innate immune responses. The aim of this study was to identify the cellular target of hLF1-11 that mediates these effects. Results revealed that hLF1-11 binds and subsequently penetrates human monocytes, after which it inhibits the enzymatic activities of myeloperoxidase (MPO). Moreover, a chemical inhibitor of MPO (aminobenzoic acid hydrazide) mimicked the effects of hLF1-11 on the inflammatory response by monocytes and on monocyte-macrophage differentiation. Computer-assisted molecular modeling predicted that hLF1-11 can bind to the edge of and within the crevice of the active site of MPO. Experiments with a set of hLF1-11 peptides with amino acid substitutions identified the stretch of arginines and the cysteine at position 10 as pivotal in these immunomodulatory properties of hLF1-11. We conclude that hLF1-11 may exert its modulatory effects on human monocytes by specific inhibition of MPO activity.

Stable formyl peptide receptor agonists that activate the neutrophil NADPH-oxidase identified through screening of a compound library

The neutrophil formyl peptide receptors (FPR1 and FPR2) are G-protein coupled receptors that can induce pro-inflammatory as well as anti-inflammatory activities when activated. Accordingly, these receptors may become therapeutic targets for the development of novel drugs to be used for reducing the inflammation induced injuries in asthma, rheumatoid arthritis, Alzheimer's disease, cardiovascular diseases and traumatic shock. We screened a library of more then 50K small compounds for an ability of the compounds to induce a transient rise in intracellular Ca(2+) in cells transfected to express FPR2 (earlier called FPRL1 or the lipoxin A(4) receptor). Ten agonist hits were selected for further analysis representing different chemical series and five new together with five earlier described molecules were further profiled. Compounds 1-10 gave rise to a calcium response in the FPR2 transfectants with EC(50) values ranging from 4×10(-9)M to 2×10(-7)M. All 10 compounds activated human neutrophils to release superoxide, and based on the potency of their activity, the three most potent activators of the neutrophil NADPH-oxidase were further characterized. These three agonists were largely resistant to inactivation by neutrophil produced reactive oxygen species and shown to trigger the same functional repertoire in neutrophils as earlier described peptide agonists. Accordingly they induced chemotaxis, granule mobilization and secretion of superoxide. Interestingly, the oxidase activity was largely inhibited by cyclosporine H, an FPR1 selective antagonist, but not by PBP10, an FPR2 selective inhibitor, suggesting that FPR1 is the preferred receptor in neutrophils for all three agonists.

Spatiotemporal expression of chemokines and chemokine receptors in experimental anti-myeloperoxidase antibody-mediated glomerulonephritis

Myeloperoxidase (MPO)-anti-neutrophil cytoplasmic autoantibody (ANCA)-associated necrotizing crescentic glomerulonephritis (NCGN) is characterized by abundant leucocyte infiltration. Chemokines are chemotactic cytokines involved in receptor-mediated recruitment of leucocytes. Our objective was to analyse spatiotemporal gene expression of chemokines and chemokine receptors in anti-MPO-mediated NCGN, to find potential targets for intervening with leucocyte influx. NCGN was induced in mice by co-administration of anti-MPO immunoglobulin (Ig)G and lipopolysaccharide. mRNA expression levels of chemokines and chemokine receptors were analysed in whole kidney lysates as well as in laser microdissected glomeruli and tubulo-interstitial tissue 1 and 7 day(s) after NCGN induction. Several chemokines and chemokine receptors were induced or up-regulated in anti-MPO-mediated NCGN, both on day 1 (chemokines CCL3, 5; CXCL2, 5, 13; receptor CXCR2) and on day 7 (chemokines CCL2, 5, 7, 8, 17, 20; CXCL1, 2, 5, 10; CX(3)CL1; receptors CCR2, 8; CX(3)CR1). The expression levels of most chemokines and receptors were higher in glomeruli than in the tubulo-interstitium. Because of the temporal induction of CXCR2 on day 1, we hypothesized CXCR2 as a potential target for treatment in anti-MPO-induced NCGN. Inhibition of CXCR2 using a goat-anti-CXCR2 serum prior to NCGN induction increased glomerular neutrophil influx but did not affect crescent formation and albuminuria. In conclusion, expression levels of various chemokines and chemokine receptors were increased in anti-MPO NCGN, and expressed particularly in glomeruli. These chemokines and receptors may serve as potential targets for treatment. Inhibition of a single target, CXCR2, did not attenuate anti-MPO NCGN. Combinatorial interventions may be necessary to avoid redundancy.

The clinical value of neutrophil extracellular traps

Neutrophil extracellular traps (NETs) have recently been discovered as a central part of antimicrobial innate immunity. In the meanwhile, evidence accumulated that NETs are also generated upon non-infectious stimuli in various clinical settings. In acute or chronic inflammatory disorders aberrantly enhanced NET formation and/or decreased NET degradation seems to correlate with disease outcome. This review summarizes current knowledge about the relation of NETs in a broad spectrum of clinical settings. Specifically, we focus on the importance of NETs as a predictive marker in severely ill patients and further, we speculate about the potential pathophysiology of NETs.

Endothelial-derived thrombospondin-1 promotes macrophage recruitment and apoptotic cell clearance

Rapid apoptotic cell engulfment is crucial for prevention of inflammation and autoimmune diseases and is conducted by special immunocompetent cells like macrophages or immature dendritic cells. We recently demonstrated that endothelial cells (ECs) also participate in apoptotic cell clearance. However, in contrast to conventional phagocytes they respond with an inflammatory phenotype. To further confirm these pro-inflammatory responses human ECs were exposed to apoptotic murine ECs and changes in thrombospondin-1 (TSP-1) expression and in activation of intracellular signalling cascades were determined by real-time qPCR, immunoblotting and immunocytochemistry. Human primary macrophages or monocytic lymphoma cells (U937) were incubated with conditioned supernatant of human ECs exposed to apoptotic cells and changes in activation, migration and phagocytosis were monitored. Finally, plasma levels of TSP-1 in patients with anti-neutrophil cytoplasmic antibody(ANCA)-associated vasculitis (AAV) were determined by ELISA. We provided evidence that apoptotic cells induce enhanced expression of TSP-1 in human ECs and that this increase in TSP-1 is mediated by the mitogen-activated protein kinases (MAPK) ERK1 and 2 and their upstream regulators MEK and B-Raf. We also showed that plasma TSP-1 levels are increased in patients with AAV. Finally, we showed that conditioned supernatant of ECs exposed to apoptotic cells induces pro-inflammatory responses in monocytes or U937 cells and demonstrated that increased TSP-1 expression enhances migration and facilitates engulfment of apoptotic cells by monocyte-derived macrophages or U937 cells. These findings suggest that under pathological conditions with high numbers of uncleared dying cells in the circulation endothelial-derived elevated TSP-1 level may serve as an attraction signal for phagocytes promoting enhanced recognition and clearance of apoptotic cells.

The beta-galactoside binding immunomodulatory lectin galectin-3 reverses the desensitized state induced in neutrophils by the chemotactic peptide f-Met-Leu-Phe: role of reactive oxygen species generated by the NADPH-oxidase and inactivation of the agonist

Neutrophils interacting with a chemoattractant gradually become nonresponsive to further stimulation by the same agonist, a process known as desensitization. Receptor desensitization is a highly regulated process that involves different mechanisms depending on which receptor-ligand pair that is studied. Galectin-3, a member of a large family of beta-galactoside-binding lectins, has been suggested to be a regulator of the inflammatory process, augmenting or directly triggering the neutrophil functional repertoire. We show here that the desensitized state of neutrophils interacting with the chemotactic peptide fMLF is broken by galectin-3 and that this is achieved through an oxygen radical-mediated inactivation of the chemoattractant. The effect was inhibited by the competitor lactose and required the affinity of galectin-3 for N-acetyllactosamine, a saccharide typically found on cell surface glycoproteins. The latter was shown using a galectin-3 mutant that lacked N-acetyllactosamine binding activity, and this protein was not active. The mechanism behind the inactivation of the chemoattractant was found to depend on the ability of galectin-3 to induce a neutrophil generation/secretion of reactive oxygen species which in combined action with myeloperoxidase inactivated the peptides.

Renal expression of adhesion molecules in anca-associated disease

INTRODUCTION

Anti-neutrophil cytoplasmic autoantibodies (ANCA)-associated disease among other manifestations can underlie rapidly progressive glomerulonephritis (RPGN), with crescentic and necrotizing GN. Differences in pathogenic immune mechanisms in RPGN may provide differences in the renal expression of adhesion molecules mediating these lesions.

METHODS

Renal intercellular adhesion molecule 1 (ICAM-1; CD54) and vascular cell adhesion molecule 1 (VCAM-1; CD106) were assessed in 40 patients with type I RPGN (anti-glomerular basement membrane antibodies, n = 4), type II (immune complexes, n = 17), and type III (ANCA, n = 19). Enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin G antibodies against the Goodpasture's antigen and indirect immunofluorescence and ELISA for myeloperoxidase (MPO) and proteinase 3 (PR3) were performed for ANCA testing. Ten normal renal tissues were used as controls. Relationships between ICAM-1 and VCAM-1, histopathologic features, and CD18, CD14, and CD3 cells were analyzed.

RESULTS

Abnormal ICAM-1 and VCAM-1 in tubule was seen in >80% of biopsies with RPGN. Abnormal VCAM-1 in glomerular tuft was seen in >60% of biopsies with RPGN. Glomerular ICAM-1 was associated with less glomerulosclerosis (chi (2) = 6.719, p = 0.01), less interstitial fibrosis (chi (2) = 4.322, p < 0.05), and less tubular atrophy (chi (2) = 8.547, p < 0.005). Glomerular VCAM-1 was associated with glomerular leukocyte infiltration (chi (2) = 4.698, p < 0.05). Glomerular tuft stains of ++/+++ for VCAM-1 was observed in 10% from MPO-ANCA-GN patients but in 60% from PR3-ANCA-GN (Fi = 8.538, p = 0.03).

CONCLUSIONS

The following conclusions can be made from this study. (1) The renal expression of ICAM-1 and VCAM-1 is upregulated in RPGN, and this is associated with the histological activity. (2) De novo expression of VCAM-1 on glomerular tuft suggests that endothelial cells play a role in RPGN. (3) De novo tubular expression of ICAM-1 and VCAM-1 suggests that epithelial cells may participate in adhesive interactions in RPGN. (4) De novo expression of VCAM-1 at the glomerular tuft in PR3-ANCA positive patients seems greater than in MPO-ANCA positive patients, which suggests that testing specific immune activation mechanisms may play a role in ANCA-associated GN.

Two cases of acute exacerbation of interstitial pneumonia treated with polymyxin B-immobilized fiber column hemoperfusion treatment

The effect of polymixin B-immobilized fiber column (PMX) hemoperfusion treatment for acute exacerbation of interstitial pneumonia (IP) has been reported. Here, we report 2 cases of acute exacerbation of IP successfully treated with PMX hemoperfusion. One is a 55-year-old woman who was diagnosed as microscopic polyangiitis (MPA) with IP. The other is a 58-year-old man, diagnosed as having idiopathic pulmonary fibrosis. Both cases were treated with PMX hemoperfusion and other therapies. One died on day 44 and the other is still alive. The PMX hemoperfusion treatment decreased the serum levels of several cytokines and activated neutrophil percentage in bronchoalveolar lavage fluid.