Synovial fluid from patients with rheumatoid arthritis inhibits neutrophil apoptosis: role of adenosine and proinflammatory cytokines

The intricate relationship between autoimmunity disease and neutrophils death patterns: a love-hate story

Autoimmune diseases are pathological conditions that result from the misidentification of self-antigens in immune system, leading to host tissue damage and destruction. These diseases can affect different organs and systems, including the blood, joints, skin, and muscles. Despite the significant progress made in comprehending the underlying pathogenesis, the complete mechanism of autoimmune disease is still not entirely understood. In autoimmune diseases, the innate immunocytes are not functioning properly: they are either abnormally activated or physically disabled. As a vital member of innate immunocyte, neutrophils and their modes of death are influenced by the microenvironment of different autoimmune diseases due to their short lifespan and diverse death modes. Related to neutrophil death pathways, apoptosis is the most frequent cell death form of neutrophil non-lytic morphology, delayed or aberrant apoptosis may contribute to the development anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). In addition, NETosis, necroptosis and pyroptosis which are parts of lytic morphology exacerbate disease progression through various mechanisms in autoimmune diseases. This review aims to summarize recent advancements in understanding neutrophil death modes in various autoimmune diseases and provide insights into the development of novel therapeutic approaches for autoimmune diseases.

Seasonal variation and disease distribution of cytophagocytic mononuclear cells in synovial fluid: A medical record study

Cytophagocytic mononuclear (CPM) cells, previously known as Reiter's cells, are macrophages containing apoptotic polymorphonuclear leucocytes. Although they can be found in synovial fluid (SF) from different arthropathies, their role remains unclear. This study was performed to determine the frequency and disease distribution of CPM cells in SF in a large cohort of patients with rheumatic diseases over a 12-year period. We also investigated the seasonal variation in their incidence. This record review study included the reports pertaining to SF analyses performed between January 2010 and December 2021. Data were retrieved from the charts of inpatients and outpatients at Rheumatology and Emergency Departments of Padova. The total number of SF samples containing CPM cells was 189: 69% was from patients with seronegative spondyloarthritis (SpA), thus indicating a strong association between CPM cells and SpA. SF samples containing CPM cells were predominantly inflammatory. Our analyses demonstrated a 6-month cyclical fluctuation in concentrations of CPM cells, with an increase in spring and autumn. The presence of CPM cells in SF might offer diagnostic insight into the definition of SpA. Further studies are warranted to ascertain the link between CPM cells and the apoptotic process, shedding light on the mechanisms leading to their formation.

Hyaluronic Acid in Synovial Fluid Prevents Neutrophil Activation in Spondyloarthritis

Spondyloarthritis (SpA) patients suffer from joint inflammation resulting in tissue damage, characterized by the presence of numerous neutrophils in the synovium and synovial fluid (SF). As it is yet unclear to what extent neutrophils contribute to the pathogenesis of SpA, we set out to study SF neutrophils in more detail. We analyzed the functionality of SF neutrophils of 20 SpA patients and 7 disease controls, determining ROS production and degranulation in response to various stimuli. In addition, the effect of SF on neutrophil function was determined. Surprisingly, our data show that SF neutrophils in SpA patients have an inactive phenotype, despite the presence of many neutrophil-activating stimuli such as GM-CSF and TNF in SF. This was not due to exhaustion as SF neutrophils readily responded to stimulation. Therefore, this finding suggests that one or more inhibitors of neutrophil activation may be present in SF. Indeed, when blood neutrophils from healthy donors were activated in the presence of increasing concentrations of SF from SpA patients, degranulation and ROS production were dose-dependently inhibited. This effect was independent of diagnosis, gender, age, and medication in the patients from which the SF was isolated. Treatment of SF with the enzyme hyaluronidase strongly reduced the inhibitory effect of SF on neutrophil activation, indicating that hyaluronic acid that is present in SF may be an important factor in preventing SF neutrophil activation. This finding provides novel insights into the role of soluble factors in SF regulating neutrophil function and may lead to the development of novel therapeutics targeting neutrophil activation via hyaluronic acid or associated pathways.

Synovial fluid neutrophils in oligoarticular juvenile idiopathic arthritis have an altered phenotype and impaired effector functions

Background

Neutrophils are the most prevalent immune cells in the synovial fluid in inflamed joints of children with oligoarticular juvenile idiopathic arthritis (JIA). Despite this, little is known about neutrophil function at the site of inflammation in JIA and how local neutrophils contribute to disease pathogenesis. This study aimed to characterize the phenotype and function of synovial fluid neutrophils in oligoarticular JIA.

Methods

Neutrophils obtained from paired blood and synovial fluid from patients with active oligoarticular JIA were investigated phenotypically (n = 17) and functionally (phagocytosis and oxidative burst, n = 13) by flow cytometry. In a subset of patients (n = 6), blood samples were also obtained during inactive disease at a follow-up visit. The presence of CD206-expressing neutrophils was investigated in synovial biopsies from four patients by immunofluorescence.

Results

Neutrophils in synovial fluid had an activated phenotype, characterized by increased CD66b and CD11b levels, and most neutrophils had a CD16^hi CD62L^lowaged phenotype. A large proportion of the synovial fluid neutrophils expressed CD206, a mannose receptor not commonly expressed by neutrophils but by monocytes, macrophages, and dendritic cells. CD206-expressing neutrophils were also found in synovial tissue biopsies. The synovial fluid neutrophil phenotype was not dependent on transmigration alone. Functionally, synovial fluid neutrophils had reduced phagocytic capacity and a trend towards impaired oxidative burst compared to blood neutrophils. In addition, the effector functions of the synovial fluid neutrophils correlated negatively with the proportion of CD206⁺ neutrophils.

Conclusions

Neutrophils in the inflamed joint in oligoarticular JIA were altered, both regarding phenotype and function. Neutrophils in the synovial fluid were activated, had an aged phenotype, had gained monocyte-like features, and had impaired phagocytic capacity. The impairment in phagocytosis and oxidative burst was associated with the phenotype shift. We speculate that these neutrophil alterations might play a role in the sustained joint inflammation seen in JIA.

Neutrophils in the Pathogenesis of Rheumatoid Arthritis and Systemic Lupus Erythematosus: Same Foe Different M.O

Dysregulated neutrophil activation contributes to the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Neutrophil-derived reactive oxygen species (ROS) and granule proteases are implicated in damage to and destruction of host tissues in both conditions (cartilage in RA, vascular tissue in SLE) and also in the pathogenic post-translational modification of DNA and proteins. Neutrophil-derived cytokines and chemokines regulate both the innate and adaptive immune responses in RA and SLE, and neutrophil extracellular traps (NETs) expose nuclear neoepitopes (citrullinated proteins in RA, double-stranded DNA and nuclear proteins in SLE) to the immune system, initiating the production of auto-antibodies (ACPA in RA, anti-dsDNA and anti-acetylated/methylated histones in SLE). Neutrophil apoptosis is dysregulated in both conditions: in RA, delayed apoptosis within synovial joints contributes to chronic inflammation, immune cell recruitment and prolonged release of proteolytic enzymes, whereas in SLE enhanced apoptosis leads to increased apoptotic burden associated with development of anti-nuclear auto-antibodies. An unbalanced energy metabolism in SLE and RA neutrophils contributes to the pathology of both diseases; increased hypoxia and glycolysis in RA drives neutrophil activation and NET production, whereas decreased redox capacity increases ROS-mediated damage in SLE. Neutrophil low-density granulocytes (LDGs), present in high numbers in the blood of both RA and SLE patients, have opposing phenotypes contributing to clinical manifestations of each disease. In this review we will describe the complex and contrasting phenotype of neutrophils and LDGs in RA and SLE and discuss their discrete roles in the pathogenesis of each condition. We will also review our current understanding of transcriptomic and metabolomic regulation of neutrophil phenotype in RA and SLE and discuss opportunities for therapeutic targeting of neutrophil activation in inflammatory auto-immune disease.

Macrophage migration inhibitory factor inhibits neutrophil apoptosis by inducing cytokine release from mononuclear cells

The chemokine-like inflammatory cytokine macrophage migration inhibitory factor (MIF) is a pivotal driver of acute and chronic inflammatory conditions, cardiovascular disease, autoimmunity, and cancer. MIF modulates the early inflammatory response through various mechanisms, including regulation of neutrophil recruitment and fate, but the mechanisms and the role of the more recently described MIF homolog MIF-2 (D-dopachrome tautomerase; D-DT) are incompletely understood. Here, we show that both MIF and MIF-2/D-DT inhibit neutrophil apoptosis. This is not a direct effect, but involves the activation of mononuclear cells, which secrete CXCL8 and other prosurvival mediators to promote neutrophil survival. Individually, CXCL8 and MIF (or MIF-2) did not significantly inhibit neutrophil apoptosis, but in combination they elicited a synergistic response, promoting neutrophil survival even in the absence of mononuclear cells. The use of receptor-specific inhibitors provided evidence for a causal role of the noncognate MIF receptor CXCR2 expressed on both monocytes and neutrophils in MIF-mediated neutrophil survival. We suggest that the ability to inhibit neutrophil apoptosis contributes to the proinflammatory role ascribed to MIF, and propose that blocking the interaction between MIF and CXCR2 could be an important anti-inflammatory strategy in the early inflammatory response.

Proteomic analysis of synovial fluid from rheumatic arthritis and spondyloarthritis patients

Background

The aetiologies and pathogeneses of the joint diseases rheumatoid arthritis (RA) and spondyloarthritis (SpA) are still not fully elucidated. To increase our understanding of the molecular pathogenesis, we analysed the protein composition of synovial fluid (SF) from rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients.

Methods

Fifty-six synovial fluid samples (RA, n = 32; SpA, n = 24) were digested with trypsin, and the resulting peptides were separated by liquid chromatography and analysed by tandem mass spectrometry. Additionally, the concentration of cell-free DNA (cfDNA) in the synovial fluid was measured, and plasma C-reactive protein (CRP) was determined.

Results

Three hundred thirty five proteins were identified within the SF. The more abundant proteins seen in RA SF were inflammatory proteins, including proteins originating from neutrophil granulocytes, while SpA SF had less inflammatory proteins and a higher concentration of haptoglobin. The concentration of cell-free DNA in the SF increased together with proteins that may have originated from neutrophils. Plasma CRP levels in both RA and SpA, correlated to other acute phase reactants.

Conclusions

The proteomic results underline that neutrophils are central in the RA pathology but not in SpA, and even though inhibitors of neutrophils (migration, proteinase inhibitors) were present in the SF it was not sufficient to interrupt the disease process.

Cell death in chronic inflammation: breaking the cycle to treat rheumatic disease

Cell death is a vital process that occurs in billions of cells in the human body every day. This process helps maintain tissue homeostasis, supports recovery from acute injury, deals with infection and regulates immunity. Cell death can also provoke inflammatory responses, and lytic forms of cell death can incite inflammation. Loss of cell membrane integrity leads to the uncontrolled release of damage-associated molecular patterns (DAMPs), which are normally sequestered inside cells. Such DAMPs increase local inflammation and promote the production of cytokines and chemokines that modulate the innate immune response. Cell death can be both a consequence and a cause of inflammation, which can be difficult to distinguish in chronic diseases. Despite this caveat, excessive or poorly regulated cell death is increasingly recognized as a contributor to chronic inflammation in rheumatic disease and other inflammatory conditions. Drugs that inhibit cell death could, therefore, be used therapeutically for the treatment of these diseases, and programmes to develop such inhibitors are already underway. In this Review, we outline pathways for the major cell death programmes (apoptosis, necroptosis, pyroptosis and NETosis) and their potential roles in chronic inflammation. We also discuss current and developing therapies that target the cell death machinery.

Neutrophil Function in an Inflammatory Milieu of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by the presence of autoantibodies against citrullinated protein antigens and proinflammatory cytokines which cause chronic synovitis, bone erosion, and eventual deformity; however, the precise etiology of RA is unclear. In the early stage of RA, neutrophils migrate into the articular cavity, become activated, and exert their function in an inflammatory process, suggesting an essential role of neutrophils in the initial events contributing to the pathogenesis of RA. Solid evidence exists that supports the contribution of neutrophil extracellular traps (NETs) to the production of autoantibodies against citrullinated proteins which can trigger the immune reaction in RA. Concurrently, proinflammatory cytokines regulate the neutrophil migration, apoptosis, and NET formation. As a result, the inflammatory neutrophils produce more cytokines and influence other immune cells thereby perpetuating the inflammatory condition in RA. In this review, we summarize the advances made in improving our understanding of neutrophil migration, apoptosis, and NET formation in the presence of an RA inflammatory milieu. We will also discuss the most recent strategies in modulating the inflammatory microenvironment that have an impact on neutrophil function which may provide alternative novel therapies for RA.

The Development of Benzimidazole-Based Clickable Probes for the Efficient Labeling of Cellular Protein Arginine Deiminases (PADs)

Citrullination is the post-translational hydrolysis of peptidyl-arginines to form peptidyl-citrulline, a reaction that is catalyzed by the protein arginine deiminases (PADs), a family of calcium-regulated enzymes. Aberrantly increased protein citrullination is associated with a slew of autoimmune diseases (e.g., rheumatoid arthritis (RA), multiple sclerosis, lupus, and ulcerative colitis) and certain cancers. Given the clear link between increased PAD activity and human disease, the PADs are therapeutically relevant targets. Herein, we report the development of next generation cell permeable and "clickable" probes (BB-Cl-Yne and BB-F-Yne) for covalent labeling of the PADs both in vitro and in cell-based systems. Using advanced chemoproteomic technologies, we also report the off targets of both BB-Cl-Yne and BB-F-Yne. The probes are highly specific for the PADs, with relatively few off targets, especially BB-F-Yne, suggesting the preferential use of the fluoroacetamidine warhead in next generation irreversible PAD inhibitors. Notably, these compounds can be used in a variety of modalities, including the identification of off targets of the parent compounds and as activity-based protein profiling probes in target engagement assays to demonstrate the efficacy of PAD inhibitors.

Role of amino acids in rheumatoid arthritis studied by metabolomics

BACKGROUND

Rheumatoid arthritis (RA) is a complex, chronic autoimmune disease characterized by various inflammatory symptoms, including joint swelling, joint pain, and both structural and functional joint damage. The most commonly used animal model for studying RA is mice with collagen-induced arthritis (CIA); the wide use of this model is due primarily to many similarities with RA in human patients. Metabolomics is used increasingly in biological studies for diagnosing disease and for predicting and evaluating drug interventions, as a large number of disease-associated metabolites can be analyzed and interpreted from a biological perspective.

AIM

To profile free amino acids and their biogenic metabolites in CIA mice plasma.

METHOD

Ultra-high-performance liquid chromatography/tandem mass spectrometry coupled with multiple reaction monitoring (MRM) was used for metabolomics study.

RESULTS

Profile of 45 amine metabolites, including free amino acids and their biogenic metabolites in plasma was obtained from CIA mice. We found that the plasma levels of 20 amine metabolites were significantly decreased in the CIA group.

CONCLUSION

The results suggest that a disordered amine response is linked to RA-associated muscle wasting and energy expenditure.

Complement C5a Receptor is the Key Initiator of Neutrophil Adhesion Igniting Immune Complex-induced Arthritis

The deposition of immune complexes (IC) in tissues induces a "type III hypersensitivity" that results in tissue damage and underlies the pathogenesis of many autoimmune diseases. The neutrophil is the first immune cell recruited into sites of IC deposition and plays a critical role in shaping the overall tissue response. However, the mechanism by which IC initiate and propagate neutrophil infiltration into tissue is not known. Here, using intravital multiphoton joint imaging of IC-induced arthritis in live mice, we found that the complement C5a receptor (C5aR) was the key initiator of neutrophil adhesion on joint endothelium. C5a presented on joint endothelium induced β2 integrin-dependent neutrophil arrest, facilitating neutrophil spreading and transition to crawling, and subsequent leukotriene B₄ receptor (BLT1)-mediated extravasation of the first neutrophils. The chemokine receptor CCR1 promoted neutrophil crawling on the joint endothelium while CXCR2 amplified late neutrophil recruitment and survival once in the joint. Thus, imaging arthritis has defined a new paradigm for type III hypersensitivity where C5a directly initiates neutrophil adhesion on the joint endothelium igniting inflammation.

Adenosine and adenosine receptors in the pathogenesis and treatment of rheumatic diseases

Adenosine, a nucleoside derived primarily from the extracellular hydrolysis of adenine nucleotides, is a potent regulator of inflammation. Adenosine mediates its effects on inflammatory cells by engaging one or more cell-surface receptors. The expression and function of adenosine receptors on different cell types change during the course of rheumatic diseases, such as rheumatoid arthritis (RA). Targeting adenosine receptors directly for the treatment of rheumatic diseases is currently under study; however, indirect targeting of adenosine receptors by enhancing adenosine levels at inflamed sites accounts for most of the anti-inflammatory effects of methotrexate, the anchor drug for the treatment of RA. In this Review, we discuss the regulation of extracellular adenosine levels and the role of adenosine in regulating the inflammatory and immune responses in rheumatic diseases such as RA, psoriasis and other types of inflammatory arthritis. In addition, adenosine and its receptors are involved in promoting fibrous matrix production in the skin and other organs, and the role of adenosine in fibrosis and fibrosing diseases is also discussed.

The soluble cytoplasmic tail of CD45 (ct-CD45) in human plasma contributes to keep T cells in a quiescent state

The cytoplasmic tail of CD45 (ct‐CD45) is proteolytically cleaved and released upon activation of human phagocytes. It acts on T cells as an inhibitory, cytokine‐like factor in vitro. Here, we show that ct‐CD45 is abundant in human peripheral blood plasma from healthy adults compared with plasma derived from umbilical cord blood and plasma from patients with rheumatoid arthritis or systemic lupus erythematosus. Plasma depleted of ct‐CD45 enhanced T‐cell proliferation, while addition of exogenous ct‐CD45 protein inhibited proliferation and reduced cytokine production of human T lymphocytes in response to TCR signaling. Inhibition of T‐cell proliferation by ct‐CD45 was overcome by costimulation via CD28. T‐cell activation in the presence of ct‐CD45 was associated with an upregulation of the quiescence factors Schlafen family member 12 (SLFN12) and Krueppel‐like factor 2 (KLF2) as well as of the cyclin‐dependent kinase (CDK) inhibitor p27kip1. In contrast, positive regulators of the cell cycle such as cyclin D2 and D3 as well as CDK2 and CDK4 were found to be downregulated in response to ct‐CD45. In summary, we demonstrate that ct‐CD45 is present in human plasma and sets the threshold of T‐cell activation.

Inhibition of CDK9 as a therapeutic strategy for inflammatory arthritis

Rheumatoid arthritis is characterised by synovial inflammation and proliferation of fibroblast-like synoviocytes. The induction of apoptosis has long been proposed as a target for proliferative autoimmune diseases, and has further been shown to act as a successful treatment of experimental models of arthritis, such as collagen-induced arthritis. Here we examined the effects of specific oral small-molecule inhibitors of the transcription regulating cyclin-dependent kinase 9 on the development and progression of collagen-induced arthritis. DBA/1 mice were immunised with bovine collagen type II and treated orally with specific CDK9 inhibitors. The effects of CDK9 inhibition on RNA levels and protein expression, apoptosis induction, caspase activation and lymphocyte phenotype were further analysed. Mice showed a significant delay in disease onset and a reduction in disease severity following treatment with CDK9 inhibitors. Inhibiting CDK9 activity in peripheral blood mononuclear cells resulted in the loss of Mcl-1 expression at both the protein and RNA levels, along with a subsequent increase in apoptosis. CDK9 specific inhibitors may be a potential alternative treatment not only of cancer, but also for autoimmune- and inflammatory diseases. Taken together, these results show that transient inhibition of CDK9 induces apoptosis in leukocyte subsets and modulates the immune response.

Repeated Electroacupuncture Persistently Elevates Adenosine and Ameliorates Collagen-Induced Arthritis in Rats

The aim of this paper was to investigate the effect of repeated electroacupuncture (EA) over 21 days on the adenosine concentration in peripheral blood of rats with collagen-induced arthritis (CIA). Wistar rats were divided into three groups of 6 animals each: sham-control, CIA-control, and CIA-EA. We determined the adenosine concentration in peripheral blood and assessed pathological changes of ankle joints. Quantitative reverse-transcription-polymerase chain reaction was used to determine mRNA levels of ecto-5'-nucleotidase (CD73), adenosine deaminase (ADA), and tumor necrosis factor-alpha (TNF-α). Immunohistochemical staining was used to detect expression of ADA and CD73 in synovial tissue. Repeated EA treatment on CIA resulted in the persistence of high concentrations of adenosine in peripheral blood, significantly reduced pathological scores, TNF-α mRNA concentrations, and synovial hyperplasia. Importantly, EA treatment led to a significant increase in CD73 mRNA levels in peripheral blood but was associated with a decrease of CD73 immunostaining in synovial tissue. In addition, EA treatment resulted in a significant decrease of both ADA mRNA levels in peripheral blood and ADA immunostaining in synovial tissue. Thus, repeated EA treatment exerts an anti-inflammatory and immunoregulatory effect on CIA by increasing the concentration of adenosine. The mechanism of EA action may involve the modulation of CD73 and ADA expression levels.

Collagen Induced Arthritis in DBA/1J Mice Associates with Oxylipin Changes in Plasma

Oxylipins play important roles in various biological processes and are considered as mediators of inflammation for a wide range of diseases such as rheumatoid arthritis (RA). The purpose of this research was to study differences in oxylipin levels between a widely used collagen induced arthritis (CIA) mice model and healthy control (Ctrl) mice. DBA/1J male mice (age: 6-7 weeks) were selected and randomly divided into two groups, namely, a CIA and a Ctrl group. The CIA mice were injected intraperitoneally (i.p.) with the joint cartilage component collagen type II (CII) and an adjuvant injection of lipopolysaccharide (LPS). Oxylipin metabolites were extracted from plasma for each individual sample using solid phase extraction (SPE) and were detected with high performance liquid chromatography/tandem mass spectrometry (HPLC-ESI-MS/MS), using dynamic multiple reaction monitoring (dMRM). Both univariate and multivariate statistical analyses were applied. The results in univariate Student's t-test revealed 10 significantly up- or downregulated oxylipins in CIA mice, which were supplemented by another 6 additional oxylipins, contributing to group clustering upon multivariate analysis. The dysregulation of these oxylipins revealed the presence of ROS-generated oxylipins and an increase of inflammation in CIA mice. The results also suggested that the collagen induced arthritis might associate with dysregulation of apoptosis, possibly inhibited by activated NF-κB because of insufficient PPAR-γ ligands.

Platelet microparticles are internalized in neutrophils via the concerted activity of 12-lipoxygenase and secreted phospholipase A2-IIA

Platelets are anucleated blood elements highly potent at generating extracellular vesicles (EVs) called microparticles (MPs). Whereas EVs are accepted as an important means of intercellular communication, the mechanisms underlying platelet MP internalization in recipient cells are poorly understood. Our lipidomic analyses identified 12(S)-hydroxyeicosatetranoic acid [12(S)-HETE] as the predominant eicosanoid generated by MPs. Mechanistically, 12(S)-HETE is produced through the concerted activity of secreted phospholipase A2 IIA (sPLA2-IIA), present in inflammatory fluids, and platelet-type 12-lipoxygenase (12-LO), expressed by platelet MPs. Platelet MPs convey an elaborate set of transcription factors and nucleic acids, and contain mitochondria. We observed that MPs and their cargo are internalized by activated neutrophils in the endomembrane system via 12(S)-HETE. Platelet MPs are found inside neutrophils isolated from the joints of arthritic patients, and are found in neutrophils only in the presence of sPLA2-IIA and 12-LO in an in vivo model of autoimmune inflammatory arthritis. Using a combination of genetically modified mice, we show that the coordinated action of sPLA2-IIA and 12-LO promotes inflammatory arthritis. These findings identify 12(S)-HETE as a trigger of platelet MP internalization by neutrophils, a mechanism highly relevant to inflammatory processes. Because sPLA2-IIA is induced during inflammation, and 12-LO expression is restricted mainly to platelets, these observations demonstrate that platelet MPs promote their internalization in recipient cells through highly regulated mechanisms.

Optimized "in vitro" culture conditions for human rheumatoid arthritis synovial fibroblasts

The composition of synovial fluid in rheumatoid arthritis (RA) is complex and strongly influences the microenvironment of joints and it is an inseparable element of the disease. Currently, “in vitro” studies are performed on RA cells cultured in the presence of either recombinant proinflammatory cytokines-conditioned medium or medium alone. In this study, we evaluated the use of synovial fluid, derived from RA patients, as optimal culture condition to perform “in vitro” studies on RA synovial fibroblasts. We observed that synovial fluid is more effective in inducing cell proliferation with respect to TNF-alpha or culture medium alone. Spontaneous apoptosis in fibroblasts was also decreased in response to synovial fluid. The expression of proinflammatory cytokines in the presence of synovial fluid was significantly elevated with respect to cells cultured with TNF-alpha or medium, and the overall morphology of cells was also modified. In addition, modulation of intracellular calcium dynamics elicited in response to synovial fluid or TNF-alpha exposure is different and suggests a role for the purinergic signalling in the modulation of the effects. These results emphasize the importance of using RA synovial fluid in “in vitro” studies involving RA cells, in order to reproduce faithfully the physiopathological environmental characteristic of RA joints.

Apoptosis and the FLIP and NF-kappa B proteins as pharmacodynamic criteria for biosimilar TNF-alpha antagonists

Various criteria are necessary to assess the efficacy and safety of biological medications in order to grant companies the right to register these medications with the appropriate bodies that regulate their sale. The imminent expiration of the patents on reference biological products which block the cytokine TNF-α (tumor necrosis factor-α) raises the possibility of bringing so-called biosimilars to the market (similar to the biologicals of reference products). This occurrence is inevitable, but criteria to adequately evaluate these medications are now needed. Even among controversy, there is a demand from publications correlating the pro-apoptotic mechanism of the original TNF-α antagonists (etanercept, infliximab, adalimumab, golimumab, and certolizumab pegol) in the treatment of rheumatoid arthritis and other diseases. In this article, the authors discuss the possibility of utilizing the pro-apoptotic effect correlated with the regulation of the anti-apoptotic proteins FLIP and NF-κB as new criteria for analyzing the pharmacodynamics of possible biosimilar TNF-α antagonists which should be submitted to regulatory agencies for evaluation.

Inhibition of LPS-induced TNF-α and NO production in mouse macrophage and inflammatory response in rat animal models by a novel Ayurvedic formulation, BV-9238

Rheumatoid arthritis is a chronic crippling disease, where protein-based tumor necrosis factor-alpha (TNF-α) inhibitors show significant relief, but with potentially fatal side effects. A need for a safe, oral, cost-effective small molecule or phyto-pharmaceutical is warranted. BV-9238 is an Ayurvedic poly-herbal formulation containing specialized standardized extracts of Withania somnifera, Boswellia serrata, Zingiber officinale and Curcuma longa. The anti-inflammatory and anti-arthritic effects of BV-9238 were evaluated for inhibition of TNF-α and nitric oxide (NO) production, in lipopolysaccharide-stimulated, RAW 264.7, mouse macrophage cell line. BV-9238 reduced TNF-α and NO production, without any cytotoxic effects. Subsequently, the formulation was tested in adjuvant-induced arthritis (AIA) and carrageenan-induced paw edema (CPE) rat animal models. AIA was induced in rats by injecting Freund's complete adjuvant intra-dermally in the paw, and BV-9238 and controls were administered orally for 21 days. Arthritic scores in AIA study and inflamed paw volume in CPE study were significantly reduced upon treatment with BV-9238. These results suggest that the anti-inflammatory and anti-arthritic effects of BV-9238 are due to its inhibition of TNF-α, and NO, and this formulation shows promise as an alternate therapy for inflammatory disorders where TNF-α and NO play important roles.

Protein engineering and preclinical development of a GM-CSF receptor antibody for the treatment of rheumatoid arthritis

BACKGROUND AND PURPOSE

For antibody therapies against receptor targets, in vivo outcomes can be difficult to predict because of target-mediated clearance or antigen 'sink' effects. The purpose of this work was to engineer an antibody to the GM-CSF receptor α (GM-CSFRα) with pharmacological properties optimized for chronic, s.c. treatment of rheumatoid arthritis (RA) patients.

EXPERIMENTAL APPROACH

We used an in silico model of receptor occupancy to guide the target affinity and a combinatorial phage display approach for affinity maturation. Mechanism of action and internalization assays were performed on the optimized antibody in vitro before refining the modelling predictions of the eventual dosing in man. Finally, in vivo pharmacology studies in cynomolgus monkeys were carried out to inform the predictions and support future clinical development.

KEY RESULTS

Antibody potency was improved 8600-fold, and the target affinity was reached. The refined model predicted pharmacodynamic effects at doses as low as 1 mg kg(-1) and a study in cynomolgus monkeys confirmed in vivo efficacy at 1 mg kg(-1) dosing.

CONCLUSIONS AND IMPLICATIONS

This rational approach to antibody drug discovery enabled the isolation of a potent molecule compatible with chronic, s.c. self-administration by RA patients. We believe this general approach enables the development of optimal biopharmaceuticals.

Characterization of pathogenic human monoclonal autoantibodies against GM-CSF

The origin of pathogenic autoantibodies remains unknown. Idiopathic pulmonary alveolar proteinosis is caused by autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). We generated 19 monoclonal autoantibodies against GM-CSF from six patients with idiopathic pulmonary alveolar proteinosis. The autoantibodies used multiple V genes, excluding preferred V-gene use as an etiology, and targeted at least four nonoverlapping epitopes on GM-CSF, suggesting that GM-CSF is driving the autoantibodies and not a B-cell epitope on a pathogen cross-reacting with GM-CSF. The number of somatic mutations in the autoantibodies suggests that the memory B cells have been helped by T cells and re-entered germinal centers. All autoantibodies neutralized GM-CSF bioactivity, with general correlations to affinity and off-rate. The binding of certain autoantibodies was changed by point mutations in GM-CSF that reduced binding to the GM-CSF receptor. Those monoclonal autoantibodies that potently neutralize GM-CSF may be useful in treating inflammatory disease, such as rheumatoid arthritis and multiple sclerosis, cancer, and pain.

Regulation of neutrophil apoptosis differs after in vivo transmigration to skin chambers and synovial fluid: a role for inflammasome-dependent interleukin-1β release

Short-lived neutrophils are major players in inflammation, arriving early to infected and/or injured tissues. After performed duty, neutrophils are programmed to die by apoptosis and are thereafter rapidly cleared by other phagocytes. In vitro, modulation of the apoptotic process has been thoroughly investigated in neutrophils isolated from peripheral blood, but less is known about the regulation of this process in neutrophils derived from extravascular tissues. We recently demonstrated that neutrophils having transmigrated in vivo, obtained from experimental skin chambers of healthy human subjects, are resistant to the death-delaying signals induced by a range of antiapoptotic stimuli. In the current study, we show that skin chamber neutrophils spontaneously secrete high levels of antiapoptotic interleukin (IL)-1β which delays neutrophil apoptosis. Contrary to skin chamber fluid, synovial fluid from patients with rheumatic arthritis contained only moderate levels of IL-1β, and neutrophils taken from this site were fully responsive to antiapoptotic stimulation during in vitro culture. Our data demonstrate that resistance to antiapoptotic stimulation is not a general feature of tissue neutrophils and imply that autocrine IL-1β signaling could be an important factor in determining how life and death of neutrophils is regulated in inflamed tissues.

Fas-associated death domain protein and adenosine partnership: fad in RA

Inflammation is the principal hallmark of RA. Different pathways are implicated in the production of pro-inflammatory cytokines, the bona fide mediators of this inflammation. Among them are the TNF pathway and the IL-1 receptor/Toll-like receptor (IL-1R/TLR4) pathway. One of the potential negative regulators of IL-1R/TLR4 signalling is the Fas-associated death domain protein (FADD), which is the pivotal adaptor of the apoptotic signal mediated by death receptors of the TNF family. FADD can sequester myeloid differentiation primary response gene 88 (MyD88), the common adaptor of most TLRs, and hence hinder the activation of nuclear factor κB (NF-κB), the downstream transcription factor. We recently described a new regulatory mechanism of FADD expression, via the shedding of microvesicles, mediated by adenosine receptors. Interestingly, adenosine is found in high concentrations in the joints of RA patients and has been largely reported as a regulator of inflammation. This review discusses the possible link that could exist between the adenosine-dependent regulation of FADD in the inflammatory context of RA and the potential role of FADD as a therapeutic target in the treatment of RA. We will see that the modulation of FADD expression may be a double-edged sword by increasing apoptosis and at the same time limiting NF-κB activation.

Acipimox reduces circulating levels of insulin and associated neutrophilic inflammation in metabolic syndrome

Metabolic syndrome is a proatherosclerotic condition clustering cardiovascular risk factors, including glucose and lipid profile alterations. The pathophysiological mechanisms favoring atherosclerotic inflammation in the metabolic syndrome remain elusive. Here, we investigated the potential role of the antilipolytic drug acipimox on neutrophil- and monocyte-mediated inflammation in the metabolic syndrome. Acipimox (500 mg) was orally administered to metabolic syndrome patients (n = 11) or healthy controls (n = 8). Serum and plasma was collected before acipimox administration (time 0) as well as 2-5 h afterward to assess metabolic and hematologic parameters. In vitro, the effects of the incubation with metabolic syndrome serum were assessed on human neutrophil and monocyte migration toward the proatherosclerotic chemokine CCL3. Two to five hours after acipimox administration, a significant reduction in circulating levels of insulin and nonesterified fatty acid (NEFA) was shown in metabolic syndrome patients. At time 0 and 2 h after acipimox administration, metabolic syndrome serum increased neutrophil migration to CCL3 compared with healthy controls. No effect was shown in human monocytes. At these time points, serum-induced neutrophil migration positively correlated with serum levels of insulin and NEFA. Metabolic syndrome serum or recombinant insulin did not upregulate CCR5 expression on neutrophil surface membrane, but it increased intracellular JNK1/2 phosphorylation. Insulin immunodepletion blocked serum-induced neutrophil migration and associated JNK1/2 phosphorylation. Although mRNA expression of acipimox receptor (GPR109) was shown in human neutrophils, 5-500 μM acipimox did not affect insulin-induced neutrophil migration. In conclusion, results suggest that acipimox inhibited neutrophil proatherosclerotic functions in the metabolic syndrome through the reduction in circulating levels of insulin.

Anti-apolipoprotein A-1 IgG predicts major cardiovascular events in patients with rheumatoid arthritis

OBJECTIVE

To determine whether anti-apolipoprotein A-1 (anti-Apo A-1) IgG are associated with major cardiovascular events in patients with rheumatoid arthritis (RA).

METHODS

We determined anti-Apo A-1 IgG levels and the concentrations of cytokines, oxidized low-density lipoprotein (LDL), and matrix metalloproteinase 1 (MMP-1) MMP-2, MMP-3, and MMP-9 in sera from 133 patients with RA who did not have cardiovascular disease at baseline, all of whom were longitudinally followed up over a median period of 9 years. A major cardiovascular event was defined as a fatal or nonfatal stroke or acute coronary syndrome. The proinflammatory effects of anti-Apo A-1 IgG were assessed on human macrophages in vitro.

RESULTS

During followup, the overall incidence of major cardiovascular events was 15% (20 of 133 patients). At baseline, anti-Apo A-1 IgG positivity was 17% and was associated with a higher incidence of major cardiovascular events (adjusted hazard ratio 4.2, 95% confidence interval 1.5-12.1). Patients who experienced a subsequent major cardiovascular event had higher circulating levels of anti-Apo A-1 IgG at baseline compared with those who did not have a major cardiovascular event. Receiver operating curve analysis showed that anti-Apo A-1 IgG was the strongest of all tested biomarkers for the prediction of a subsequent major cardiovascular event, with an area under the curve value of 0.73 (P = 0.0008). At the predefined and previously validated cutoff levels, the specificity and sensitivity of anti-Apo A-1 IgG to predict major cardiovascular events were 50% and 90%, respectively. Anti-Apo A-1 IgG positivity was associated with higher median circulating levels of interleukin-8 (IL-8), oxidized LDL, and MMP-9 and higher proMMP-9 activity as assessed by zymography. On human macrophages, anti-Apo A-1 IgG induced a significant dose-dependent increase in IL-8 and MMP-9 levels and proMMP-9 activity.

CONCLUSION

Anti-Apo A-1 IgG is an independent predictor of major cardiovascular events in RA, possibly by affecting vulnerability to atherosclerotic plaque.

Cytokine-activated NK cells inhibit PMN apoptosis and preserve their functional capacity

Natural killer (NK) cells and polymorphonuclear cells (PMNs) play a critical role in the first line of defense against microorganisms. Upon host infection, PMNs phagocytose invading pathogens with subsequent killing by oxidative or nonoxidative mechanisms. NK cells are known to have immunoregulatory effects on T cells, B cells, dendritic cells (DCs), and monocytes through secretion of various soluble products and cell-cell contact. However, their impact on PMN survival and function is not well known. We found that soluble factors derived from cytokine-activated NK cells delay PMN apoptosis and preserve their ability to perform phagocytosis and produce reactive oxygen species (ROS). The expression patterns of CD11b and CD62L on PMNs differed according to the cytokine combination used for NK-cell stimulation. Irrespective of the NK-cell treatment, however, PMN survival was prolonged with sustained functional capacity. We found that interferon γ, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor α produced by NK cells upon stimulation with cytokines played a crucial role in NK cell–mediated effects on PMNs. Our study demonstrates that soluble factors derived from cytokine-activated NK cells send survival signals to PMNs, which would promote their accumulation and function at the site of inflammation in vivo.

Anti-inflammatory activity and neutrophil reductions mediated by the JAK1/JAK3 inhibitor, CP-690,550, in rat adjuvant-induced arthritis

Background

The Janus kinase (JAK) family of tyrosine kinases includes JAK1, JAK2, JAK3 and TYK2, and is required for signaling through Type I and Type II cytokine receptors. CP-690,550 is a potent and selective JAK inhibitor currently in clinical trials for rheumatoid arthritis (RA) and other autoimmune disease indications. In RA trials, dose-dependent decreases in neutrophil counts (PBNC) were observed with CP-690,550 treatment. These studies were undertaken to better understand the relationship between JAK selectivity and PBNC decreases observed with CP-690,550 treatment.

Methods

Potency and selectivity of CP-690,550 for mouse, rat and human JAKs was evaluated in a panel of in vitro assays. The effect of CP-690,550 on granulopoiesis from progenitor cells was also assessed in vitro using colony forming assays. In vivo the potency of orally administered CP-690,550 on arthritis (paw edema), plasma cytokines, PBNC and bone marrow differentials were evaluated in the rat adjuvant-induced arthritis (AIA) model.

Results

CP-690,550 potently inhibited signaling through JAK1 and JAK3 with 5-100 fold selectivity over JAK2 in cellular assays, despite inhibiting all four JAK isoforms with nM potency in in vitro enzyme assays. Dose-dependent inhibition of paw edema was observed in vivo with CP-690,550 treatment. Plasma cytokines (IL-6 and IL-17), PBNC, and bone marrow myeloid progenitor cells were elevated in the context of AIA disease. At efficacious exposures, CP-690,550 returned all of these parameters to pre-disease levels. The plasma concentration of CP-690,550 at efficacious doses was above the in vitro whole blood IC50 of JAK1 and JAK3 inhibition, but not that of JAK2.

Conclusion

Results from this investigation suggest that CP-690,550 is a potent inhibitor of JAK1 and JAK3 with potentially reduced cellular potency for JAK2. In rat AIA, as in the case of human RA, PBNC were decreased at efficacious exposures of CP-690,550. Inflammatory end points were similarly reduced, as judged by attenuation of paw edema and cytokines IL-6 and IL-17. Plasma concentration at these exposures was consistent with inhibition of JAK1 and JAK3 but not JAK2. Decreases in PBNC following CP-690,550 treatment may thus be related to attenuation of inflammation and are likely not due to suppression of granulopoiesis through JAK2 inhibition.

A semi-mechanistic model of CP-690,550-induced reduction in neutrophil counts in patients with rheumatoid arthritis

CP-690,550, a selective inhibitor of the Janus kinase family, is being developed as an oral disease-modifying antirheumatic drug for the treatment of rheumatoid arthritis (RA). A semi-mechanistic model was developed to characterize the time course of drug-induced absolute neutrophil count (ANC) reduction in a phase 2a study. Data from 264 RA patients receiving 6-week treatment (placebo, 5, 15, 30 mg bid) followed by a 6-week off-treatment period were analyzed. The model included a progenitor cell pool, a maturation chain comprising transit compartments, a circulation pool, and a feedback mechanism. The model was adequately described by system parameters (BASE(h), ktr(h), gamma, and k(circ)), disease effect parameters (DIS), and drug effect parameters (k(off) and k(D)). The disease manifested as an increase in baseline ANC and reduced maturation time due to increased demand from the inflammation site. The drug restored the perturbed system parameters to their normal values via an indirect mechanism. ANC reduction due to a direct myelosuppressive drug effect was not supported. The final model successfully described the dose- and time-dependent changes in ANC and predicted the incidence of neutropenia at different doses reasonably well.

Reprogramming of a subpopulation of human blood neutrophils by prolonged exposure to cytokines

Essential cells of innate immunity, neutrophils are often considered to be a homogenous population of terminally differentiated cells. During inflammation, neutrophils are extravasated cells exposed to local factors that prolong their survival and activate their production of mediators implicated in disease progression. In this study, a phenotypically distinct subset of human neutrophils that appear after prolonged exposure to cytokines was characterized. Freshly isolated neutrophils from healthy donors were incubated with granulocyte-macrophage colony-stimulating factor, tumor necrosis factor-alpha and interleukin (IL)-4, three cytokines that are locally present in various inflammatory conditions. Eight to 17% of neutrophils survived beyond 72 h. This subset of non-apoptotic neutrophils, as evaluated by three different markers, was enriched by discontinuous Percoll gradient centrifugation before studying their phenotype. These viable neutrophils showed neoexpression of HLA-DR, CD80 and CD49d. Compared with freshly isolated neutrophils, they responded differentially to second signals similar to formyl-methionyl-leucyl-phenylalanine with three- to four-fold increases in production of superoxide anions and leukotrienes. These cells augmented their phagocytic index by 141%, increased their adhesion to human primary fibroblasts, but reduced their migration in response to chemotactic stimuli and decreased exocytosis of primary and secondary granules. In addition, they produced substantial amounts of IL-8, IL-1Ra and IL-1beta. This neutrophil subset had a unique profile of phosphorylation of intracellular signaling molecules. In conclusion, the present identification of a novel neutrophil phenotype highlights the reprogammable character of the neutrophil. This aspect is crucial for our understanding of its contribution to disease pathogenesis and host defense.

Cell death and stress signaling in glycogen storage disease type I

Cell death has been traditionally classified in apoptosis and necrosis. Apoptosis, known as programmed cell death, is an active form of cell death mechanism that is tightly regulated by multiple cellular signaling pathways and requires ATP for its appropriate process. Apoptotic death plays essential roles for successful development and maintenance of normal cellular homeostasis in mammalian. In contrast to apoptosis, necrosis is classically considered as a passive cell death process that occurs rather by accident in disastrous conditions, is not required for energy and eventually induces inflammation. Regardless of different characteristics between apoptosis and necrosis, it has been well defined that both are responsible for a wide range of human diseases. Glycogen storage disease type I (GSD-I) is a kind of human genetic disorders and is caused by the deficiency of a microsomal protein, glucose-6-phosphatase-α (G6Pase-α) or glucose-6-phosphate transporter (G6PT) responsible for glucose homeostasis, leading to GSD-Ia or GSD-Ib, respectively. This review summarizes cell deaths in GSD-I and mostly focuses on current knowledge of the neutrophil apoptosis in GSD-Ib based upon ER stress and redox signaling.

Breaking old paradigms: Th17 cells in autoimmune arthritis

Aberrant helper T cell activation has been implicated in the pathogenesis of an array of autoimmune diseases. In this review, we summarize evidence that suggests the involvement of a novel T cell subset, the Th17 lineage, in rheumatoid arthritis. In particular, we focus on the role of Th17 cells in inducing and perpetuating the chronic inflammation, cartilage damage, and bone erosion that are hallmark phases of joint destruction and consider current and emerging therapies that seek to disrupt the inflammatory Th17 network and shift the immune system back towards homeostasis.

The impact of cytokines on the expression of drug transporters, cytochrome P450 enzymes and chemokine receptors in human PBMC

BACKGROUND AND PURPOSE

The function of transporters in peripheral blood mononuclear cells (PBMC) has been characterized, but less is known about cytochrome P450 (CYP) enzyme function in these cells. Given that cytokines are dysregulated in many diseases, the purpose of this work was to assess the impact of cytokines on the expression of CYPs, transporters and chemokine receptors in PBMC.

EXPERIMENTAL APPROACH

Human PBMC were incubated with cytokines for 48 h. ATP-binding cassette (ABC)B1, ABCC1, ABCC2, CYP2B6, CYP3A4, CXCR4 and CCR5 expression were measured by quantitative polymerase chain reaction and flow cytometry at 0, 4, 8, 24 and 48 h. Enzyme activity was assessed using fluorescent probes.

KEY RESULTS

We show here functional activity of CYP3A4 and CYP2B6 in PBMC. Furthermore, cytokines had a significant impact on the mRNA and protein expression of all proteins. For example, interleukin-2 (IL-2) had a marked impact on ABCB1 mRNA (% control 4745 +/- 11961) and protein (% control 200 +/- 57). Increases in drug efflux transporter expression, in response to cytokines, resulted in reduced cellular accumulation of digoxin [decrease of 17% and 26% for IL-2 and interferon-gamma (IFNgamma) respectively] and saquinavir (decrease of 28% and 30% for IL-2 and IFNgamma respectively). The degree to which drug transporter and chemokine receptor expression changed in response to cytokines was positively correlated (e.g. ABCB1 and CXCR4, r(2) = 0.545).

CONCLUSIONS AND IMPLICATIONS

These data have important implications for diseases in which cytokines are dysregulated and for which pharmacological intervention targets immune cells.

A single nucleotide polymorphism in the Mdm2 promoter and risk of sepsis

BACKGROUND

The Mdm2-SNP309(T/G) polymorphism has been shown to upregulate transcription of Mdm2 and subsequently attenuate the p53 pathway. Its role in regulating the human response to acute illness has not been reported.

METHODS

Patients from the surgical intensive care unit were prospectively enrolled. SNP309 genotype was determined, and a genotype-based comparison of clinical outcomes was performed.

RESULTS

Of the 85 enrolled patients, 41 had wild type (T/T) and 44 had mutant (32 T/G and 12 G/G) genotypes. The mutant-genotype group tended to have a longer LOS in both the surgical intensive care unit (P = .40) and the hospital (P = .08), but these trends did not reach significance. No observable genotype-based differences were noted in any other measured parameters.

CONCLUSIONS

The Mdm2-SNP309(G) allele may be associated with longer LOS. However, it does not appear to influence any other clinical characteristics, nor can it be used to predict clinical outcome.

Lactoferrin is a survival factor for neutrophils in rheumatoid synovial fluid

OBJECTIVES

Lactoferrin is an iron-binding protein that is released from activated neutrophils at sites of inflammation and has anti-microbial as well as anti-inflammatory properties. This study set out to determine whether lactoferrin can delay neutrophil apoptosis and could act as a survival factor for neutrophils in SF.

METHODS

Human peripheral blood and SF neutrophils were incubated with iron-free lactoferrin and apoptosis determined after 9 h. SF from patients with RA was added to isolated neutrophils, with or without immunodepletion of lactoferrin, and effects on neutrophil apoptosis determined. Levels of lactoferrin in SF were assessed and related to disease duration and markers of disease activity.

RESULTS

Iron-free lactoferrin significantly delayed apoptosis of peripheral blood neutrophils, in a concentration-dependent manner after 9 h in culture (P < 0.04). Lactoferrin could also delay apoptosis of neutrophils isolated from SF of patients with RA. SF from patients with established RA delayed apoptosis of peripheral blood neutrophils and this effect was significantly reduced by depletion of lactoferrin (P < 0.03). Lactoferrin levels in SF from patients with established RA did not correlate with disease severity, but did correlate with markers of inflammation (CRP) and with the presence of RF. SF from patients with arthritis of <12 weeks duration did not contain significant levels of lactoferrin.

CONCLUSION

Lactoferrin contributes to extended neutrophil survival in the rheumatoid joint in the established phase of RA but not in very early arthritis.

Neutrophil apoptosis: selective regulation by different ligands of integrin alphaMbeta2

Neutrophils undergo spontaneous apoptosis, but their survival can be extended during inflammatory responses. alpha(M)beta(2) is reported either to delay or accelerate neutrophil apoptosis, but the mechanisms by which this integrin can support such diametrically opposed responses are poorly understood. The abilities of closely related alpha(M)beta(2) ligands, plasminogen and angiostatin, derived from plasminogen, as well as fibrinogen and its two derivative alpha(M)beta(2) recognition peptides, P1 and P2-C, differed markedly in their effects on neutrophil apoptosis. Plasminogen, fibrinogen, and P2-C suppressed apoptosis via activation of Akt and ERK1/2 kinases, while angiostatin and P1 failed to activate these prosurvival pathways and did not prevent neutrophil apoptosis. Using cells transfected with alpha(M)beta(2) or its individual alpha(M) or beta(2) subunits, and purified receptors and its constituent chains, we show that engagement of both subunits with prosurvival ligands is essential for induction of the prosurvival response. Hence, engagement of a single integrin by closely related ligands can induce distinct signaling pathways, which can elicit distinct cellular responses.

In vitro affinity maturation of human GM-CSF antibodies by targeted CDR-diversification

The mammalian immune system applies somatic hypermutation to select for antibodies with improved dissociation rates in vivo up to an intrinsic limit, previously termed as affinity ceiling. However, for certain therapeutic applications it may be desirable to further improve antibody affinities beyond that limit. In this study the selection of antibodies specific for the pro-inflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) from the HuCAL GOLD human antibody library is described. In order to increase affinity and also functional activity, in vitro affinity maturation of a pool of lead Fab candidates was carried out. CDR-L3 and parallel CDR-H2 diversification using trinucleotide consensus cassettes were followed by the combination of optimized CDR-L3 and CDR-H2 leading to a 5000-fold improved affinity finally reaching a K(D) of 400 fM. Cytokine neutralizing potential of MOR04357 was evaluated in a TF-1 proliferation assay. Along with affinity optimization a 2000-fold increase in potency was observed compared to the parental antibody. Due to species cross-reactivity MOR04357 also blocks rat GM-CSF induced proliferation of FDCP-1 cells. Receptor inhibition studies showed that MOR04357 prevents the interaction of GM-CSF with the GM-CSF receptor alpha chain. As a consequence this leads to a blockade in signal transduction as measured by abolished STAT5 phosphorylation in the presence of GM-CSF and antibody. Due to its pro-inflammatory role GM-CSF has been implicated in the pathophysiology of inflammatory diseases like rheumatoid arthritis or asthma. Based on the mode of action described herein MOR04357 shows favourable antibody features as a potential drug candidate.

Purinergic regulation of neutrophil chemotaxis

Chemotaxis allows polymorphonuclear neutrophils (PMN) to rapidly reach infected and inflamed sites. However, excessive influx of PMN damages host tissues. Better knowledge of the mechanisms that control PMN chemotaxis may lead to improved treatments of inflammatory diseases. Recent findings suggest that ATP and adenosine are involved in PMN chemotaxis. Therefore, these purinergic signaling processes may be suitable targets for novel therapeutic approaches to ameliorate host tissue damage.

C-reactive protein (CRP) induces chemokine secretion via CD11b/ICAM-1 interaction in human adherent monocytes

Several studies support C-reactive protein (CRP) as a systemic cardiovascular risk factor. The recent detection of CRP in arterial intima suggests a dual activity in atherosclerosis as a circulating and tissue mediator on vascular and immune cells. In the present paper, we focused on the inflammatory effects of CRP on human monocytes, which were isolated by Ficoll-Percoll gradients and cultured in adherence to polystyrene, endothelial cell monolayer, or in suspension. Chemokine levels, adhesion molecule, and chemokine receptor expression were detected by ELISA, flow cytometry, and real-time RT-PCR. Migration assays were performed in a Boyden chamber. Stimulation with CRP induced release of CCL2, CCL3, and CCL4 in adherent monocytes through the binding to CD32a, CD32b, and CD64, whereas no effect was observed in suspension culture. This was associated with CRP-induced up-regulation of adhesion molecules membrane-activated complex 1 (Mac-1) and ICAM-1 on adherent monocytes. Blockade of Mac-1/ICAM-1 interaction inhibited the CRP-induced chemokine secretion. In addition, CRP reduced mRNA and surface expression of corresponding chemokine receptors CCR1, CCR2, and CCR5 in adherent monocytes. This effect was a result of chemokine secretion, as coincubation with neutralizing anti-CCL2, anti-CCL3, and anti-CCL4 antibodies reversed the effect of CRP. Accordingly, a reduced migration of CRP-treated monocytes to CCL2 and CCL3 was observed. In conclusion, our data suggest an in vitro model to study CRP activities in adherent and suspension human monocytes. CRP-mediated induction of adhesion molecules and a decrease of chemokine receptors on adherent monocytes might contribute to the retention of monocytes within atherosclerotic lesions and recruitment of other circulating cells.

Influência do exercício na indução da apoptose e necrose das células do líquido sinovial de eqüinos atletas

Examinaram-se os efeitos do estresse mecânico na resposta inflamatória e adaptativa dos tecidos articulares de cavalos atletas. O líquido sinovial foi colhido das articulações metacarpofalangeanas de eqüinos atletas antes, 3, 6 e 24 horas após o exercício, assim como de um grupo controle (cavalos não exercitados). A porcentagem de apoptose/necrose, o TNF-a e a PGE2 foram determinados pelo ensaio de AnexinaV/Iodeto de Propídeo, bioensaio (L929) e ELISA, respectivamente. Os resultados mostraram que a contagem total de células nucleadas foi sempre menor no grupo controle em relação ao grupo atleta (P<0,05). Observaram-se aumentos na porcentagem de células em apoptose (P<0,05) e necrose (P<0,05), concentração de PGE2 (P<0,05) e proteína sinovial (P<0,05), e diminuição da concentração de TNF-a (P<0,05) após 3 horas do término do exercício. O grupo atleta apresentou grau moderado de inflamação articular após o exercício intenso. Esta resposta dos tecidos articulares frente ao insulto mecânico do exercício, com maior intensidade às 3 horas após término da atividade esportiva e retornando à normalidade 24 horas após, revela a capacidade da adaptação articular ao estresse físico, em eqüinos atletas.

Taurine chloramine differentially inhibits matrix metalloproteinase 1 and 13 synthesis in interleukin-1beta stimulated fibroblast-like synoviocytes

It has been suggested that taurine chloramine (TauCl) plays an important role in the downregulation of proinflammatory mediators. However, little is known about its effect on the expression of matrix metalloproteinases (MMPs). In this study, we investigated the effects of TauCl on synovial expression of MMPs. The effects of TauCl on MMP expression in IL-1β stimulated fibroblast-like synoviocytes (FLSs) were studied using the following techniques. Real-time PCR and semi-quantitative PCR were employed to analyze the mRNA expression of MMPs. ELISA was used to determine protein levels of MMPs. Western blot analyses were performed to analyze the mitogen-activated protein kinase and inhibitor of nuclear factor-κB (IκB) kinase signalling pathways. Finally, electrophoretic mobility shift assay and immunohistochemistry were used to assess localization of transcription factors. IL-1β increased the transcriptional and translational levels of MMP-1 and MMP-13 in rheumatoid arthritis FLSs, whereas the levels of MMP-2 and MMP-9 were unaffected. TauCl at a concentration of 400 to 600 μmol/l greatly inhibited the transcriptional and translational expression of MMP-13, but the expression of MMP-1 was significantly inhibited at 800 μmol/l. At a concentration of 600 μmol/l, TauCl did not significantly inhibit phosphorylation of mitogen-activated protein kinase or IκB degradation in IL-1β stimulated rheumatoid arthritis FLSs. The degradation of IκB was significantly inhibited at a TauCl concentration of 800 μmol/l. The inhibitory effect of TauCl on IκB degradation was confirmed by electrophoretic mobility shift assay and immunochemical staining for localization of nuclear factor-κB. TauCl differentially inhibits the expression of MMP-1 and MMP-13, and inhibits expression of MMP-1 primarily through the inhibition of IκB degradation, whereas it inhibits expression of MMP-13 through signalling pathways other than the IκB pathway.

Constitutive neutrophil apoptosis: mechanisms and regulation

Neutrophil constitutive death is a critical cellular process for modulating neutrophil number and function, and it plays an essential role in neutrophil homeostasis and the resolution of inflammation. Neutrophils die due to programmed cell death or apoptosis. In this article, we review recent studies on the mechanism of neutrophil apoptosis. The involvement of caspase, calpain, reactive oxygen species, cellular survival/death signaling pathways, mitochondria, and BCL-2 family member proteins are discussed. The fate of neutrophils can be influenced within the inflammatory microenvironment. We summarize the current understanding regarding the modulation of neutrophil apoptotic death by various extracellular stimuli such as proinflammatory cytokines, cell adhesion, phagocytosis, red blood cells, and platelets. The involvement of neutrophil apoptosis in infectious and inflammatory diseases is also addressed.

Anti-type II collagen antibody accelerates arthritisvia CXCR2-expressing cells in IL-1 receptor antagonist-deficient mice

Arthritis can be induced in mice by the injection of anti-type II collagen (anti-CII) Ab and LPS. To elucidate the role of IL-1 receptor antagonist (IL-1ra) in Ab-induced arthritis, WT and IL-1ra(-/-) mice were administered anti-CII Ab and LPS. These IL-1ra(-/-) mice developed severe arthritis even at low doses of anti-CII Ab and LPS, while WT mice did not. The cells that invaded the arthritic joints were mainly Gr-1(+) neutrophils, and the number of the cells in the joints remained high over 4 weeks in the IL-1ra(-/-) mice. KC, a ligand for CXCR2, is found in higher levels in the arthritic paws of IL-1ra(-/-) mice compared with the WT, and most of the cells that infiltrated into the joints of the IL-1ra(-/-) mice were CXCR2-expressing neutrophils. Administration of anti-CXCR2 Ab completely inhibited arthritis development. The anti-CXCR2 Ab decreased the number of neutrophils in the blood and also inhibited the migration of neutrophils to KC. These results suggested that the high susceptibility of IL-1ra(-/-) mice to anti-CII Ab-induced arthritis was due to the higher expression of chemotactic factors like KC and the sustained infiltration of CXCR2-expressing neutrophils into the joints.

Synovial fluid leukocyte apoptosis is inhibited in patients with very early rheumatoid arthritis

Synovial leukocyte apoptosis is inhibited in established rheumatoid arthritis (RA). In contrast, high levels of leukocyte apoptosis are seen in self-limiting crystal arthritis. The phase in the development of RA at which the inhibition of leukocyte apoptosis is first apparent, and the relationship between leukocyte apoptosis in early RA and other early arthritides, has not been defined. We measured synovial fluid leukocyte apoptosis in very early arthritis and related this to clinical outcome. Synovial fluid was obtained at presentation from 81 patients with synovitis of ≤ 3 months duration. The percentages of apoptotic neutrophils and lymphocytes were assessed on cytospin preparations. Patients were assigned to diagnostic groups after 18 months follow-up. The relationship between leukocyte apoptosis and patient outcome was assessed. Patients with early RA had significantly lower levels of neutrophil apoptosis than patients who developed non-RA persistent arthritis and those with a resolving disease course. Similarly, lymphocyte apoptosis was absent in patients with early RA whereas it was seen in patients with other early arthritides. The inhibition of synovial fluid leukocyte apoptosis in the earliest clinically apparent phase of RA distinguishes this from other early arthritides. The mechanisms for this inhibition may relate to the high levels of anti-apoptotic cytokines found in the early rheumatoid joint (e.g. IL-2, IL-4, IL-15 GMCSF, GCSF). It is likely that this process contributes to an accumulation of leukocytes in the early rheumatoid lesion and is involved in the development of the microenvironment required for persistent RA.

Adenosine protects against suicidal erythrocyte death

Suicidal death of erythrocytes or eryptosis is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine exposure at the erythrocyte surface. The cell membrane scrambling is triggered by an increase in cytosolic Ca(2+) activity and activation of protein kinase C (PKC). Phosphatidylserine exposure fosters adherence of affected erythrocytes to the vascular wall. Thus, microcirculation in ischemic tissues may be impaired by the appearance of eryptotic erythrocytes. Ischemia leads to release of adenosine, which in most tissues leads to vasodilation and protects against cell injury. The present experiments explored whether adenosine influences mechanisms underlying eryptosis. Erythrocyte phosphatidylserine exposure was estimated from annexin V binding, cell volume from forward scatter and cytosolic Ca(2+) activity from Fluo3 fluorescence. Glucose depletion (for 24 or 48 h) significantly increased annexin binding and decreased forward scatter, effects partially reversed by adenosine. The protective effect of adenosine reached statistical significance (s.d.) at > =30 microM. Low Cl(-) solution (Cl(-) exchanged by gluconate for 24 h) similarly increased annexin binding and decreased forward scatter, effects again reversed by adenosine (s.d. at > or =10 and 30 microM, respectively). Similarly, phosphatase inhibitor okadaic acid (OA, 1 microM) and PKC activator phorbol 12-myristate-13-acetate (PMA, 3 microM) significantly enhanced annexin binding and decreased forward scatter. Adenosine significantly blunted the effects of OA and PMA on annexin V binding (s.d. at > or =30 and 10 microM, respectively) and the effect of OA on forward scatter (s.d. at > or =10 microM). In conclusion, adenosine inhibits eryptosis by a mechanism presumably effective downstream of PKC. The effect may participate in the maintenance of microcirculation in ischemic tissue.