Panagiotis Skendros

Neutrophil Extracellular Trap Formation Is Associated with IL-1β and Autophagy-Related Signaling in Gout

Background Gout is a prevalent inflammatory arthritis affecting 1–2% of adults characterized by activation of innate immune cells by monosodium urate (MSU) crystals resulting in the secretion of interleukin-1β (IL-1β). Since neutrophils play a major role in gout we sought to determine whether their activation may involve the formation of proinflammatory neutrophil extracellular traps (NETs) in relation to autophagy and IL-1β. Methodology/Principal Findings Synovial fluid neutrophils from six patients with gout crisis and peripheral blood neutrophils from six patients with acute gout and six control subjects were isolated. MSU crystals, as well as synovial fluid or serum obtained from patients with acute gout, were used for the treatment of control neutrophils. NET formation was assessed using immunofluorescence microscopy. MSU crystals or synovial fluid or serum from patients induced NET formation in control neutrophils. Importantly, NET production was observed in neutrophils isolated from synovial fluid or peripheral blood from patients with acute gout. NETs contained the alarmin high mobility group box 1 (HMGB1) supporting their pro-inflammatory potential. Inhibition of phosphatidylinositol 3-kinase signaling or phagolysosomal fusion prevented NET formation, implicating autophagy in this process. NET formation was driven at least in part by IL-1β as demonstrated by experiments involving IL-1β and its inhibitor anakinra. Conclusions/Significance These findings document for the first time that activation of neutrophils in gout is associated with the formation of proinflammatory NETs and links this process to both autophagy and IL-1β. Modulation of the autophagic machinery may represent an additional therapeutic study in crystalline arthritides.

Targeting IL-1β in disease; the expanding role of NLRP3 inflammasome

NLRP3 inflammasome activation and IL-1beta secretion have recently emerged as a central mechanism in the pathogenesis of disease. Genetically defined syndromes like cryopyrin-associated periodic syndromes (CAPS, cryopyrinopathies) and familial Mediterranean fever (FMF) or diseases associated with NLRP3 activation by danger signals like gout, pseudogout, Alzheimers disease or type 2 diabetes are included in this group of diseases. The contribution of anakinra, a recombinant, nonglycosylated human IL-1 receptor antagonist, in both the identification and treatment of such syndromes was considerable. Recently, rilonacept, a long-acting IL-1 receptor fusion protein, and canakinumab, a fully humanized anti-IL-1beta monoclonal antibody, have been developed, with the intention to further extent IL-1beta inhibition treatment strategies to a broader spectrum of disorders beyond the characterized autoinflammatory syndromes, offering a more favorable administration profile. On the other hand, the developed caspase-1 inhibitors, even though effective in experimental models, were not proven efficient in the treatment of inflammatory diseases.

Autophagy mediates the delivery of thrombogenic tissue factor to neutrophil extracellular traps in human sepsis.

Background Sepsis is associated with systemic inflammatory responses and induction of coagulation system. Neutrophil extracellular traps (NETs) constitute an antimicrobial mechanism, recently implicated in thrombosis via platelet entrapment and aggregation. Methodology/Principal Findings In this study, we demonstrate for the first time the localization of thrombogenic tissue factor (TF) in NETs released by neutrophils derived from patients with gram-negative sepsis and normal neutrophils treated with either serum from septic patients or inflammatory mediators involved in the pathogenesis of sepsis. Localization of TF in acidified autophagosomes was observed during this process, as indicated by positive LC3B and LysoTracker staining. Moreover, phosphatidylinositol 3-kinase inhibition with 3-MA or inhibition of endosomal acidification with bafilomycin A1 hindered the release of TF-bearing NETs. TF present in NETs induced thrombin generation in culture supernatants, which further resulted in protease activated receptor-1 signaling. Conclusions/Significance This study demonstrates the involvement of autophagic machinery in the extracellular delivery of TF in NETs and the subsequent activation of coagulation cascade, providing evidence for the implication of this process in coagulopathy and inflammatory response in sepsis.

Tissue factor expression in neutrophil extracellular traps and neutrophil derived microparticles in antineutrophil cytoplasmic antibody associated vasculitis may promote thromboinflammation and the thrombophilic state associated with the disease

Objectives Antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is characterised by neutrophil activation. An elevated prevalence of venous thromboembolic events has been reported in AAV. Because of the critical role of neutrophils in inflammation associated thrombosis, we asked whether neutrophil tissue factor (TF) may be implicated in the thrombotic diathesis in AAV. Methods Neutrophils from four patients and sera from 17 patients with ANCA associated vasculitis with active disease and remission were studied. TF expression was assessed by immunoblotting and confocal microscopy. Circulating DNA levels were evaluated. TF expressing microparticles (MPs) were measured by flow cytometry and thrombin–antithrombin complex levels by ELISA. Results Peripheral blood neutrophils from four patients with active disease expressed elevated TF levels and released TF expressing neutrophil extracellular traps (NETs) and MPs. TF positive NETs were released by neutrophils isolated from the bronchoalveolar lavage and were detected in nasal and renal biopsy specimens. Elevated levels of circulating DNA and TF expressing neutrophil derived MPs were further observed in sera from patients with active disease. Induction of remission attenuated the aforementioned effects. Control neutrophils treated with sera from patients with active disease released TF bearing NETs and MPs which were abolished after IgG depletion. Treatment of control neutrophils with isolated IgG from sera from patients with active disease also resulted in the release of TF bearing NETs. TF implication in MP dependent thrombin generation was demonstrated by antibody neutralisation studies. Conclusions Expression of TF in NETs and neutrophil derived MPs proposes a novel mechanism for the induction of thrombosis and inflammation in active AAV.

Expression of functional tissue factor by neutrophil extracellular traps in culprit artery of acute myocardial infarction

Neutrophils are involved in the pathophysiology of infracted coronary arteries in STEMI via NET structures. Platelets, activated by thrombin, are required for NET formation, while the integrity of NET scaffold contributes to the functionality of NET-bound TF. The blockage of NET formation or local neutralization of NET-mediated TF signalling constitutes candidate therapeutic targets.

Cell-mediated immunity in human brucellosis.

Brucella can parasitize within human antigen-presenting cells modifying phagocytosis, phagolysosome fusion, antigen presentation, cytokine secretion, and apoptosis. Subversion of innate immune mechanisms by Brucella leads to defective Th1 immune responses and T-cell anergy in chronic brucellosis patients. This review summarizes the cellular immune responses in brucellosis, based on data derived exclusively from human cells or cell lines.

The efficacy of canakinumab in the treatment of a patient with familial Mediterranean fever and longstanding destructive arthritis

Self-limited, non-destructive arthritis is a common clinical presentation of familial Mediterranean fever (FMF), while protracted, refractory to standard treatment arthritis is a rare manifestation of the disease, potentially resulting in severe damage and disability.1,–,3 We report on a 25-year-old woman with FMF, homozygous for the MEFV gene M694V mutation, and with longstanding articular involvement affecting her hips and her left knee, effectively treated with canakinumab. She had been under treatment with colchicine since the age of 5. In 2005, she experienced long-lasting arthritis of her right hip and treatment with anakinra (100 mg/day) was added. Anakinra was discontinued shortly afterwards due to severe injection site reactions, precluding the evaluation of its efficacy. She was switched to treatment with etanercept (25 mg twice weekly) and low dose prednisone (5–7.5 mg/day). In 2008, she developed destructive arthritis of the right hip, which lead to total hip replacement, and chronic arthritis of her left knee. Methotrexate (10 mg/week) was added to the existent treatment. Long-term remission was not achieved, as indicated by the clinical findings and the elevated inflammatory …

Neutrophil extracellular traps regulate IL-1β-mediated inflammation in familial Mediterranean fever

Objective Inflammatory attacks of familial Mediterranean fever (FMF) are characterised by circulation and influx of high number of polymorphonuclear neutrophils (PMN) in the affected sites and profound therapeutic effect of IL-1β inhibitors. We investigated the role of neutrophil extracellular traps (NET) in the pathogenesis of FMF, and their involvement in IL-1β production. Methods Blood samples were obtained from six FMF patients during remissions and from three patients during attacks. NET formation and NET components were studied by fluorescence techniques, immunobloting and MPO-DNA complex ELISA. Results PMNs from patients released NETs decorated with IL-1β during disease attacks. On the other hand, PMNs from patients during remission were resistant to inflammatory stimuli that induce NET release in PMNs from control subjects. Lower basal autophagy levels were identified in PMNs during remission, while induction of autophagy facilitated NET release, suggesting that autophagy is involved in the regulation of NET release. During the resolution of attacks, inhibition of NET formation by negative feedback mechanism was also observed. The anti-inflammatory agents, colchicine and DNAse I, inhibited IL-1β production in PMNs and IL-1β activity in NETs, respectively. Conclusions We suggest two additive events for triggering the FMF attack; the production of IL-1β by PMNs and its release through NETs. At the same time NETs, homeostatically, downregulate further NETosis, facilitating the resolution of attack. Compensatorly, lower basal autophagy of PMNs may protect from crises by attenuating the release of pro-inflammatory NETs.

Chronic Brucellosis Patients Retain Low Frequency of CD4+ T-Lymphocytes Expressing CD25 and CD28 after Escherichia coli LPS Stimulation of PHA-Cultured PBMCs

Chronic brucellosis patients display a defective Th1 response to PHA. We have previously shown that heat-killed B. abortus (HKBA) can downregulate the PHA-induced increase of CD4+/CD25+ and CD14+/CD80+ cells of brucellosis patients. In the present study, we investigate the effect of E. coli LPS, as a potent stimulant of monocytes and autologous T-lymphocytes, on the PHA-cultured PBMCs of the same groups of patients. Thirteen acute brucellosis (AB) patients, 22 chronic brucellosis (CB) patients, 11 “cured” subjects, and 15 healthy volunteers were studied. The percentage of CD4+/CD25+ and CD4+/CD28+ T-lymphocytes as well as CD14+/CD80+ monocytes were analyzed by flow cytometry after PBMCs culture with PHA plus E. coli LPS. A significant decrease in the percentage of CD4+/CD25+ and CD4+/CD28+ T-lymphocytes was observed in CB compared to AB. In HKBA cultures, compared to E. coli LPS-cultures, there was a significant reduction of CD4+/CD25+ T-lymphocytes in all groups and CD14+/CD80+ in patients groups. We suggest that Brucella can modulate host immune response, leading to T-cell anergy and chronic infection.

Effect of bacterial extracts on the immunologic profile in chronic relapsing brucellosis patients.

Brucellosis is an intracellular bacterial disease of common incidence in Greece. Existing therapy is inadequate and a considerable proportion of patients become chronically ill and are immunocompromised. Defects of the monocyte-macrophage system and T-lymphocytes have been described in chronic brucellosis and can be restored after immunopotentiation therapy. Bacterial (Klebsiella pneumoniae) extracts exert immunostimulating effects on the monocyte-macrophage system and have already been used successfully in the prevention of common infections of the respiratory track. So we decided to investigate: 1) Leukocyte Migration Index (LMI), 2) Monocyte-macrophage random and directed migration against both nonspecific leukoattractant (casein) and disease specific antigens (Brucella melitensis, Brucella abortus), 3) Monocyte-macrophage phagocytosis index, 4) Delayed-type hypersensitivity (skin tests) against seven antigens, before (TO), during (T2), and after (T3) oral administration of bacterial (Klebsiella pneumoniae) extracts at conventional doses plus antibiotics or not. Our results show that: 1) Concerning the LMI, 4 out of 19 remained anergic at time T3 of the study, 2) Random migration was not affected during treatment, 3) Directed migration increased significantly without reaching control group values, 4) Phagocytosis index increased significantly and reached normal values at T3, 5) Delayed type hypersensitivity reactions (skin tests) increased significantly at the end of the study period. Reaction against Tuberculin and Candida antigens showed the most pronounced increase in skin reactivity. In conclusion, bacterial (Klebsiella pneumoniae) extracts improve peripheral monocyte locomotion and restore phagocytosis index, thus enhancing cellular immunity parameters in immunocompromised chronic brucellosis patients.