Differential expression of two major cytokines produced by neutrophils, interleukin-8 and the interleukin-1 receptor antagonist, in neutrophils isolated from the synovial fluid and peripheral blood of patients with rheumatoid arthritis

The forgotten key players in rheumatoid arthritis: IL-8 and IL-17 - Unmet needs and therapeutic perspectives

Despite the relevant advances in our understanding of the pathogenetic mechanisms regulating inflammation in rheumatoid arthritis (RA) and the development of effective therapeutics, to date, there is still a proportion of patients with RA who do not respond to treatment and end up progressing toward the development of joint damage, extra-articular complications, and disability. This is mainly due to the inter-individual heterogeneity of the molecular and cellular taxonomy of the synovial membrane, which represents the target tissue of RA inflammation. Tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) are crucial key players in RA pathogenesis fueling the inflammatory cascade, as supported by experimental evidence derived from in vivo animal models and the effectiveness of biologic-Disease Modifying Anti-Rheumatic Drugs (b-DMARDs) in patients with RA. However, additional inflammatory soluble mediators such as IL-8 and IL-17 exert their pathogenetic actions promoting the detrimental activation of immune and stromal cells in RA synovial membrane, tendons, and extra-articular sites, as well as blood vessels and lungs, causing extra-articular complications, which might be excluded by the action of anti-TNFα and anti-IL6R targeted therapies. In this narrative review, we will discuss the role of IL-8 and IL-17 in promoting inflammation in multiple biological compartments (i.e., synovial membrane, blood vessels, and lung, respectively) in animal models of arthritis and patients with RA and how their selective targeting could improve the management of treatment resistance in patients.

Increased circulating interleukin-8 levels in systemic lupus erythematosus patients: a meta-analysis

AIM

We performed this meta-analysis in order to evaluate circulating interleukin-8 (IL-8) levels in systemic lupus erythematosus (SLE) patients more accurately and explore its related influencing factors.

METHODS

The related literature was systematically searched in PubMed, Embase and The Cochrane Library database (up to 28 March 2018). All data analysis was performed by Stata 12.0 software.

RESULTS

The results showed SLE patients had a higher circulating IL-8 levels than normal controls (pooled standardized mean difference = 0.963; 95% CI: 0.416-1.511). Subgroup analyses indicated SLE patients with age <40 years, Asia group and disease duration <10 years had higher IL-8 levels.

CONCLUSION

Compared with normal controls, circulating IL-8 levels in SLE patients are elevated and affected by age, region and disease duration.

Gene Expression Deconvolution for Uncovering Molecular Signatures in Response to Therapy in Juvenile Idiopathic Arthritis

Gene expression-based signatures help identify pathways relevant to diseases and treatments, but are challenging to construct when there is a diversity of disease mechanisms and treatments in patients with complex diseases. To overcome this challenge, we present a new application of an in silico gene expression deconvolution method, ISOpure-S1, and apply it to identify a common gene expression signature corresponding to response to treatment in 33 juvenile idiopathic arthritis (JIA) patients. Using pre- and post-treatment gene expression profiles only, we found a gene expression signature that significantly correlated with a reduction in the number of joints with active arthritis, a measure of clinical outcome (Spearman rho = 0.44, p = 0.040, Bonferroni correction). This signature may be associated with a decrease in T-cells, monocytes, neutrophils and platelets. The products of most differentially expressed genes include known biomarkers for JIA such as major histocompatibility complexes and interleukins, as well as novel biomarkers including α-defensins. This method is readily applicable to expression datasets of other complex diseases to uncover shared mechanistic patterns in heterogeneous samples.

RNA-seq reveals activation of both common and cytokine-specific pathways following neutrophil priming

Neutrophils are central to the pathology of inflammatory diseases, where they can damage host tissue through release of reactive oxygen metabolites and proteases, and drive inflammation via secretion of cytokines and chemokines. Many cytokines, such as those generated during inflammation, can induce a similar “primed” phenotype in neutrophils, but it is unknown if different cytokines utilise common or cytokine-specific pathways to induce these functional changes. Here, we describe the transcriptomic changes induced in control human neutrophils during priming in vitro with pro-inflammatory cytokines (TNF-α and GM-CSF) using RNA-seq. Priming led to the rapid expression of a common set of transcripts for cytokines, chemokines and cell surface receptors (CXCL1, CXCL2, IL1A, IL1B, IL1RA, ICAM1). However, 580 genes were differentially regulated by TNF-α and GM-CSF treatment, and of these 58 were directly implicated in the control of apoptosis. While these two cytokines both delayed apoptosis, they induced changes in expression of different pro- and anti-apoptotic genes. Bioinformatics analysis predicted that these genes were regulated via differential activation of transcription factors by TNF-α and GM-CSF and these predictions were confirmed using functional assays: inhibition of NF-κB signalling abrogated the protective effect of TNF-α (but not that of GM-CSF) on neutrophil apoptosis, whereas inhibition of JAK/STAT signalling abrogated the anti-apoptotic effect of GM-CSF, but not that of TNF-α (p<0.05). These data provide the first characterisation of the human neutrophil transcriptome following GM-CSF and TNF-α priming, and demonstrate the utility of this approach to define functional changes in neutrophils following cytokine exposure. This may provide an important, new approach to define the molecular properties of neutrophils after in vivo activation during inflammation.

Cytokine mRNA profiling identifies B cells as a major source of RANKL in rheumatoid arthritis

Objectives

In rheumatoid arthritis (RA), a complex cytokine network drives chronic inflammation and joint destruction. So far, few attempts have been made to identify the cellular sources of individual cytokines systematically. Therefore, the primary objective of this study was systematically to assess the cytokine messenger RNA expression profiles in the five largest cell populations in the synovial fluid and peripheral blood of RA patients. To reflect the in vivo situation as closely as possible, the cells were neither cultured nor stimulated ex vivo.

Methods

Inflammatory cells from 12 RA patients were sorted into CD4 and CD8 T cells, B cells, macrophages and neutrophils. mRNA expression for 41 cytokines was determined by real-time PCR using microfluidic cards. Receptor activator nuclear factor kappa B ligand (RANKL) (TNFSF11) expression by B cells was further confirmed by flow cytometry and by immunofluorescence staining of frozen sections of synovial tissue from patients with RA.

Results

The detection of cytokines characteristic for T cells and myeloid cells in the expected populations validated this methodology. Beyond the expected cytokine patterns, novel observations were made. Striking among these was the high expression of mRNA for RANKL in B cells from synovial fluid. This observation was validated at the protein level in synovial tissue and fluid.

Conclusions

RANKL, the key cytokine driving bone destruction by osteoclast activation, is produced by synovial B cells in RA. This observation is of importance for our understanding of the role of B cells in RA and their therapeutic targeting.

Cytotoxic effects of Kingella kingae outer membrane vesicles on human cells

Kingella kingae is an emerging pathogen causing osteoarticular infections in pediatric patients. Electron microscopy of K. kingae clinical isolates revealed the heterogeneously-sized membranous structures blebbing from the outer membrane that were classified as outer membrane vesicles (OMVs). OMVs purified from the secreted fraction of a septic arthritis K. kingae isolate were characterized. Among several major proteins, K. kingae OMVs contained virulence factors RtxA toxin and PilC2 pilus adhesin. RtxA was also found secreted as a soluble protein in the extracellular environment indicating that the bacterium may utilize different mechanisms for the toxin delivery. OMVs were shown to be hemolytic and possess some leukotoxic activity while high leukotoxicity was detected in the non-hemolytic OMV-free component of the secreted fraction. OMVs were internalized by human osteoblasts and synovial cells. Upon interaction with OMVs, the cells produced increased levels of human granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 6 (IL-6) suggesting that these cytokines might be involved in the signaling response of infected joint and bone tissues during natural K. kingae infection. This study is the first report of OMV production by K. kingae and demonstrates that OMVs are a complex virulence factor of the organism causing cytolytic and inflammatory effects on host cells.

Implication of granulocyte-macrophage colony-stimulating factor induced neutrophil gelatinase-associated lipocalin in pathogenesis of rheumatoid arthritis revealed by proteome analysis

Introduction

In rheumatoid arthritis (RA), synovial fluid (SF) contains a large number of neutrophils that contribute to the inflammation and destruction of the joints. The SF also contains granulocyte-macrophage colony-stimulating factor (GM-CSF), which sustains viability of neutrophils and activates their functions. Using proteomic surveillance, we here tried to elucidate the effects of GM-CSF on neutrophils.

Methods

Neutrophils stimulated by GM-CSF were divided into four subcellular fractions: cytosol, membrane/organelle, nuclei, and cytoskeleton. Then, proteins were extracted from each fraction and digested by trypsin. The produced peptides were detected using matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF MS).

Results

We detected 33 peptide peaks whose expression was upregulated by more than 2.5-fold in GM-CSF stimulated neutrophils and identified 11 proteins out of the 33 peptides using MALDI-TOF/TOF MS analysis and protein database searches. One of the identified proteins was neutrophil gelatinase-associated lipocalin (NGAL). We confirmed that the level of NGAL in SF was significantly higher in patients with RA than in those with osteoarthritis. We next addressed possible roles of the increased NGAL in RA. We analysed proteome alteration of synoviocytes from patients with RA by treatment with NGAL in vitro. We found that, out of the detected protein spots (approximately 3,600 protein spots), the intensity of 21 protein spots increased by more than 1.5-fold and the intensity of 10 protein spots decreased by less than 1 to 1.5-fold as a result of the NGAL treatment. Among the 21 increased protein spots, we identified 9 proteins including transitional endoplasmic reticulum ATPase (TERA), cathepsin D, and transglutaminase 2 (TG2), which increased to 4.8-fold, 1.5-fold and 1.6-fold, respectively. Two-dimensional electrophoresis followed by western blot analysis confirmed the upregulation of TERA by the NGAL treatment and, moreover, the western blot analysis showed that the NGAL treatment changed the protein spots caused by post-translational modification of TERA. Furthermore, NGAL cancelled out the proliferative effects of fibroblast growth factor (FGF)-2 and epidermal growth factor (EGF) on chondrocytes from a patient with RA and proliferative effect of FGF-2 on chondrosarcoma cells.

Conclusions

Our results indicate that GM-CSF contributes to the pathogenesis of RA through upregulation of NGAL in neutrophils, followed by induction of TERA, cathepsin D and TG2 in synoviocytes. NGAL and the upregulated enzymes may therefore play an important role in RA.

Difference in gene expression of macrophage between normal spleen and portal hypertensive spleen idendified by cDNA microarray

AIM: To identify the difference in gene expression of microphage (Mφ) between normal spleen and portal hypertensive spleen using cDNA microarrays and find new gene functions associated with hypersplenism in portal hypertension.

METHODS: The Biostar-H140s chip containing 14 112 spots of cDNAs were used to investigate the difference of the expression. The total RNA extracted from macrophages isolated from both normal spleen and portal hypertensive spleen was reversely transcribed to cDNA with the incorporation of fluorescent (cy3 and cy5) labeled dCTP to prepare the hybridization probes. After hybridization, the gene chip was scanned for the fluorescent intensity. The differentially expressed genes were screened. That was repeated three times, and only the genes which had differential expression in all three chips were considered to be associated with hypersplenism in portal hypertension.

RESULTS: Eight hundred and ninety-six, 1330 and 898 genes were identified to be differentially expressed in three chips, respectively. One hundred and twenty-one genes (0.86%) were identified to be differentially expressed in all three chips, including 21 up-regulated genes and 73 down-regulated genes. The differentially expressed genes were related to ionic channel and transport protein, cyclin, cytoskeleton, cell receptor, cell signal conduct, metabolism, immune, and so on. These genes might be related to the hypersplenism in portal hypertension.

CONCLUSION: The investigations based on cDNA microarray can screen differentially expressed genes of macrophages between normal spleen and portal hypertensive spleen, thus may provide a new idea in studying the pathogenesis of hypersplenism in portal hypertension.

Neutrophil gene expression in rheumatoid arthritis

There is now a growing awareness that infiltrating neutrophils play an important role in the molecular pathology of rheumatoid arthritis. In part, this arises from the fact that neutrophils have potent cytotoxic activity, but additionally from the fact that inflammatory neutrophils can generate a number of cytokines and chemokines that can have a direct influence on the progress of an inflammatory episode. Furthermore, the molecular properties of inflammatory neutrophils are quite different from those normally found in the circulation. For example, inflammatory neutrophils, but not blood neutrophils, can express cell surface receptors (such as MHC Class II molecules and FcgammaRI) that dramatically alter the way in which these cells can interact with ligands to modulate immune function. Cytokine/chemokine expression and surface expression of these novel cell surface receptors is dependent upon the neutrophil responding to local environmental factors to selectively up-regulate the expression of key cellular components via signalling pathways coupled to transcriptional activation. However, major changes in the expression levels of some proteins are also regulated by post-translational modifications that alter rates of proteolysis, and hence changes in the steady-state levels of these molecules.

Secretion of oncostatin M by neutrophils in rheumatoid arthritis

OBJECTIVE

Neutrophils are known to express and release a large number of proinflammatory cytokines when they are stimulated by inflammatory stimuli. The objective of this study was to determine whether neutrophils express oncostatin M (OSM), a member of the interleukin-6 family of cytokines that has been implicated in the pathogenesis of inflammatory joint disease.

METHODS

Neutrophils were isolated from the blood of healthy volunteer donors and from the blood and synovial fluid of patients with rheumatoid arthritis (RA). OSM levels were measured in cell extracts and in culture supernatants by Western blotting. Total RNA was isolated from control and granulocyte-macrophage colony-stimulating factor (GM-CSF)-treated neutrophils, and OSM messenger RNA levels were quantified by hybridization of a radiolabeled probe.

RESULTS

GM-CSF stimulated a rapid and transient expression and release of OSM from blood neutrophils, which was more rapid than the expression and release from blood monocytes. A 28-kd protein was identified in cell extracts, but an additional 25-kd isoform was detected in culture supernatants. Synovial fluid neutrophils could not be stimulated to express OSM, but this cytokine was detected in cell-free supernatants at various levels.

CONCLUSION

Blood neutrophils can be stimulated to express and rapidly release large quantities of OSM. We propose that this important cytokine is released from neutrophils as they infiltrate rheumatoid joints and, thus, contribute to the complex cytokine network that characterizes RA.

The balance between IL-1 and IL-1Ra in disease

IL-1 is an important mediator of inflammation and tissue damage in multiple organs, both in experimental animal models of disease and in human diseases. The IL-1 family consists of two agonists, IL-1alpha and IL-1beta, two receptors, biologically active IL-1RI and inert IL-1RII, and a specific receptor antagonist, IL-1Ra. The balance between IL-1 and IL-1Ra in local tissues plays an important role in the susceptibility to and severity of many diseases. An allelic polymorphism in the IL-1Ra gene has been associated with a variety of human diseases primarily of epithelial and endothelial cell origin. This association may be secondary to an imbalance in the IL-1 system with enhanced production of IL-1beta and reduced production of the major intracellular isoform of IL-1Ra. Treatment of RA with daily subcutaneous injections of recombinant IL-1Ra protein has been shown to be efficacious. Gene therapy approaches with IL-1Ra are being evaluated for the treatment of RA and other human diseases.

Differential role of neutrophil Fcgamma receptor IIIB (CD16) in phagocytosis, bacterial killing, and responses to immune complexes

OBJECTIVE

To determine the roles played by the neutrophil Fcgamma receptor type II (FcgammaRII) (CD32) and FcgammaRIIIb (CD16) in phagocytosis, bacterial killing, and activation by immune complexes (ICs) and to test the hypothesis that inhibition of pathologic effector neutrophil function is possible without compromising host defense.

METHODS

Receptor function was probed by enzymic removal of FcgammaRIIIb from the cell surface and by use of Fab/F(ab')(2) fragments of monoclonal antibodies to block receptor-ligand binding. Cells were challenged with (a) serum-opsonized Staphylococcus aureus, (b) serum- and IgG-opsonized latex particles, and (c) synthetic soluble and insoluble ICs to mimic bacterial and inflammatory stimuli.

RESULTS

Phosphatidylinositol-phospholipase C treatment removed >97% of surface FcgammaRIIIb from neutrophils previously treated with tumor necrosis factor alpha to mobilize intracellular stores of receptor. This treatment profoundly inhibited activation of primed neutrophils by soluble ICs of the type found in diseased rheumatoid joints, but had no effect on phagocytosis and killing of serum-opsonized S aureus.

CONCLUSION

FcgammaRIIIb plays a major role in the secretion of toxic products in response to ICs, but little or no role in the phagocytosis and killing of serum-opsonized bacteria. The selective suppression of effector neutrophil function is therefore possible. FcgammaRIIIb, or its intracellular signaling pathway, is a potential therapeutic target in inflammatory diseases such as rheumatoid arthritis, because disruption of its function should decrease inflammatory tissue damage, but not jeopardize host protection against infection.

Differential binding of chemokines to macrophages and neutrophils in the human inflamed synovium

In chronic inflammatory foci, such as the rheumatoid joint, there is enhanced recruitment of phagocytes from the blood into the tissues. Chemokines are strongly implicated in directing the migration of these cells, although little is known regarding the chemokine receptors that could mediate their chemotaxis into the joint tissue. Therefore the objective of the study was to identify chemokine binding sites on macrophages and neutrophils within the rheumatoid synovium using radiolabeled ligand binding and in situ autoradiography. Specific binding sites for CCL3 (macrophage inflammatory protein-1alpha), CCL5 (RANTES), CCL2 (monocyte chemoattractant protein-1) and CXCL8 (IL-8) were demonstrated on CD68+ macrophages in the subintimal and intimal layers. The number and percentage of intimal cells that bound chemokines were greater in inflamed regions compared to noninflamed regions. The intensity of intimal binding varied between chemokines with the rank order, CCL3 > CCL5 > CCL2 > CXCL8. Neutrophils throughout the synovium bound CXCL8 but did not show any signal for binding CCL2, CCL3 or CCL5. Immunohistochemistry showed that both CXCR1 and CXCR2 are expressed by macrophages and neutrophils in the rheumatoid and nonrheumatoid synovia, suggesting that both of these receptors are responsible for the CXCL8 binding. The chemokine binding sites described on phagocytes may be involved in the migration of these cells into the inflamed joint.

Insoluble and soluble immune complexes activate neutrophils by distinct activation mechanisms: changes in functional responses induced by priming with cytokines

BACKGROUND

Rheumatoid synovial fluid contains both soluble and insoluble immune complexes that can activate infiltrating immune cells such as neutrophils.

OBJECTIVES

To determine if these different complexes activate neutrophils through similar or different receptor signalling pathways. In particular, to determine the circumstances which result in the secretion of tissue damaging reactive oxygen metabolites and granule enzymes.

METHODS

Blood neutrophils were incubated with synthetic soluble and insoluble immune complexes and the ability to generate reactive oxidants tested by luminescence or spectrophotometric assays that distinguished between intracellular and extracellular production. Degranulation of myeloperoxidase and lactoferrin was determined by western blotting. The roles of FcgammaRII (CD32) and FcgammaRIIIb (CD16) were determined by incubation with Fab/F(ab')(2) fragments before activation. The effect of cytokine priming was determined by incubation with GM-CSF.

RESULTS

Insoluble immune complexes activated unprimed neutrophils, but most of the oxidants produced were intracellular. This activation required FcgammaRIIIb, but not FcgammaRII function. Soluble complexes failed to activate unprimed neutrophils but generated a rapid and extensive secretion of reactive oxygen metabolites when the cells were primed with granulocyte-macrophage colony stimulating factor (GM-CSF). This activity required both FcgammaRII and FcgammaRIIIb function. Insoluble immune complexes activated the release of granule enzymes from primed or unprimed neutrophils, but the kinetics of release did not parallel those of secretion of reactive oxygen metabolites. Only primed neutrophils released enzymes in response to soluble complexes.

CONCLUSIONS

Soluble and insoluble immune complexes activate neutrophils by separate receptor signalling pathways. Profound changes in neutrophil responsiveness to these complexes occur after cytokine priming.

The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8)

Paired synovial tissue samples were obtained from both clinically uninvolved (CU) and clinically involved (CI) knee joints of eight rheumatoid arthritis (RA) patients. In addition, biopsies were taken from five control subjects. We observed the expression of the chemokines CXCL8, CXCL9, CXCL10, CCL2 and CCL4 in CI and CU joints of RA patients. In particular, CXCL8 protein levels were specifically increased in CI joints compared with CU joints, which was confirmed by immunohistochemistry and in situ hybridization.

Distribution of novel polymorphisms of the interleukin-8 and CXC receptor 1 and 2 genes in systemic sclerosis and cryptogenic fibrosing alveolitis

OBJECTIVE

To search for single-nucleotide polymorphisms in the interleukin-8 (IL-8) and IL-8 receptor CXCR-1 and CXCR-2 genes, and to compare their distribution among patients with systemic sclerosis (SSc) with fibrosing alveolitis (FASSc) or without fibrosing alveolitis (NFASSc), or patients with cryptogenic fibrosing alveolitis (CFA), and normal healthy subjects.

METHODS

Fifty control subjects were screened for potential polymorphisms by using polymerase chain reaction in association with sequence-specific primers incorporating mismatches at the 3' end. The novel polymorphisms were subsequently examined in British Caucasian subjects, including 194 healthy controls, 71 patients with CFA, and 128 patients with SSc who were further subdivided into 78 FASSc patients and 50 NFASSc patients.

RESULTS

Three novel biallelic polymorphisms were identified in the IL-8 gene (all in noncoding areas of the gene), 1 was found in the CXCR-1 gene (resulting in a conservative amino acid change), and 3 were observed in the CXCR-2 gene, of which the first resulted in a silent codon change and the others were in the 3' untranslated area of exon 3. Compared with controls, a significant increase in the frequency of the CXCR-2 +785 CC homozygote and of the CXCR-2 +1208 TT homozygote was found in the SSc patients (37% versus 22% [P = 0.01] and 33% versus 17% [P = 0.003], respectively). A subgroup analysis revealed this association to be significant both in the FASSc patients and in the NFASSc patients.

CONCLUSION

This report describes an association between SSc and 2 polymorphisms occurring close to each other in the CXCR-2 gene. This finding and its functional significance need to be confirmed and analyzed in future studies.

On the edge: the physiological and pathophysiological role of chemokines during inflammatory and immunological responses

Most, if not all, chemokines bind to seven transmembrane spanning G protein-coupled receptors and activate cellular migration. Stimulated chemokine expression is essential for directing leukocyte emigration from the circulation into sites of inflammation and tissue damage. In contrast, constitutive chemokine expression plays a role in the development of lymphoid cells, organs, and tissues. The present review examines rheumatoid arthritis and transplantation rejection as two examples of pathological conditions where chemokine directed leukocyte infiltration aids in the pathogenesis of the disease. We further discuss insights into leukocyte trafficking gained by chemokine and chemokine receptor transgenic and null mutant mice.

Chemotactic Migration Triggers IL-8 Generation in Neutrophilic Leukocytes

Neutrophils recovered from inflammatory exudates possess increased levels of IL-8, but exposure of neutrophils to chemoattractants results in only a modest stimulation of IL-8 generation. This study was undertaken to explore the hypothesis that IL-8 generation in these cells is dependent upon the process of migration. Neutrophils synthesized up to 30 times as much IL-8 during migration in response to a gradient of diverse chemoattractants than they did when stimulated directly by the attractants in the absence of a gradient. This IL-8 response was dependent on migration since it was not observed in cells exposed to concentration gradients of chemoattractants under conditions that prevented cell movement. While actinomycin-D (1 μg/ml) had little influence on the generation of IL-8 during chemotaxis, the protein synthesis inhibitor cycloheximide (10 μg/ml) markedly blunted the accumulation of cell-associated IL-8, suggesting that new protein synthesis from preexisting mRNA was responsible for the effect. Consistent with this interpretation, migrating cells incorporated over 10 times as much [3H]leucine into IL-8 as did nonmotile neutrophils exposed to chemoattractants. A substantial portion of the IL-8 generated during chemotaxis was released upon subsequent metabolic stimulation. Thus, the IL-8 synthesized during chemotaxis is uniquely positioned to exert a regulatory influence on inflammatory processes governed by neutrophilic leukocytes responding to inflammatory and infectious stimuli.

RANTES expression and contribution to monocyte chemotaxis in arthritis

Rheumatoid arthritis (RA) is characterized by recruitment of leukocytes from the vasculature into inflamed synovial tissue (ST) and synovial fluid (SF), which depends, in part, upon the continued maintenance of chemotactic stimuli. RANTES is a potent chemoattractant for leukocytes including monocytes and CD45RO+ memory T lymphocytes. The aim of this study was to determine the production, the source, and the function of antigenic RANTES in arthritis. We detected antigenic RANTES in SFs from RA and OA patients (100 +/- 22.7 and 72 +/- 30.7 pg/ml, respectively). CM from RA ST fibroblasts stimulated with interleukin-1beta or tumor necrosis factor-alpha contained significantly more antigenic RANTES than unstimulated CM (452 +/- 181.6 and 581 +/- 200.2 pg/ml, respectively, versus 12 +/- 4.4 pg/ml, P < 0.05). PHA-stimulated RA SF mononuclear cells secreted 5- to 15-fold more antigenic RANTES than did nonstimulated mononuclear cells, while LPS induced secretion up to 4-fold. We immunolocalized antigenic RANTES to sublining macrophages (28 +/- 3.7 and 8 +/- 2.0% immunopositive cells), perivascular macrophages (56 +/- 6.9 and 19 +/- 3.4%), and synovial lining cells (37 +/- 5.8 and 60 +/- 10.4%) in RA and OA tissue, respectively. Anti-RANTES neutralized 20.2 +/- 1.3% of the RA SF chemotactic activity for normal peripheral blood monocytes (P < 0.05). These results demonstrate antigenic RANTES in RA and OA ST and SF and identify RANTES as a chemoattractant for monocytes in the RA joint.

The Differential Production of Three Forms of IL-1 Receptor Antagonist by Human Neutrophils and Monocytes

IL-1R antagonist (IL-1Ra) exists as three well-characterized isoforms. The 17-kDa secretory IL-1Ra (sIL-1Ra) and 18-kDa intracellular IL-1Ra (icIL-1RaI) arise by alternative transcription of the same IL-1Ra gene. The recently described 16-kDa intracellular IL-1Ra (icIL-1RaII) is formed by alternative translation initiation of sIL-1Ra mRNA. Transcription and translation of IL-1Ra isoforms were examined in LPS-stimulated human neutrophils and PBMC using RT-PCR, ELISA, and Western blot analysis. LPS stimulation of neutrophils resulted in elevated sIL-1Ra mRNA levels by 1 h, whereas icIL-1RaI mRNA remained undetectable through 22 h of culture. Extracellular glycosylated sIL-1Ra protein and intracellular icIL-1RaII were observed in LPS-stimulated neutrophils by 3 h of culture; no icIL-1RaI protein was detected by immunoblot. LPS stimulation of PBMC resulted in elevated sIL-1Ra mRNA levels by 1 h and detectable icIL-1RaI mRNA at 8 h of culture. LPS-stimulated PBMC demonstrated extracellular glycosylated sIL-1Ra protein and intracellular icIL-1RaII within 3 h of stimulation, whereas detection of icIL-1RaI protein was delayed until 15 h of culture. Subcellular localization experiments established that both icIL-1RaI and icIL-1RaII were present primarily within the cytoplasmic compartment, as expected by their lack of a signal peptide. These results demonstrate that although both LPS-stimulated neutrophils and PBMC synthesize sIL-1Ra and icIL-1RaII, only PBMC transcribe and translate icIL-1RaI. Furthermore, sIL-Ra transcription and translation (and translation of icIL-1RaII) are early events, whereas icIL-1RaI transcription in PBMC is delayed.

Heparan sulfate proteoglycan on endothelium efficiently induces integrin-mediated T cell adhesion by immobilizing chemokines in patients with rheumatoid synovitis

OBJECTIVE

To clarify the role of heparan sulfate proteoglycan (HSPG) and chemokines in integrin-mediated T cell adhesion to endothelial cells in the synovium of patients with rheumatoid arthritis (RA).

METHODS

Endothelial cells were purified from RA synovium. Expression of heparan sulfate, chemokines, and adhesion molecules on the endothelium was assessed by immunohistochemical analysis or flow cytometry. The effects of chemokines and heparan sulfate on T cell adhesion to RA endothelium were estimated with relevant antibodies and signaling inhibitors. Production of chemokines from synovial T cells was detected by Northern blotting and enzyme-linked immunosorbent assay.

RESULTS

The endothelium in RA synovium highly expressed HSPG. The soluble form of chemokines, macrophage inflammatory protein 1beta (MIP-1beta), induced T cell adhesion to the endothelial cells. When MIP-lalpha and MIP-1beta were immobilized on RA endothelial cells, a more efficient integrin-mediated adhesion of T cells was induced compared with their soluble form. The induced T cell adhesion was reduced by pretreatment with either heparitinase, anti-MIP-lalpha antibody, or anti-MIP-lbeta antibody, indicating that these chemokines were bound to heparan sulfate on the cells. T cell adhesion was also inhibited by pertussis toxin, wortmannin, and cytochalasin B. MIP-lalpha and MIP-1beta were found on vessels in RA synovium in vivo, which were spontaneously produced from T cells purified from RA synovium.

CONCLUSION

Endothelial cells in RA synovium characteristically express HSPG, which is involved in T cell integrin triggering by "posting" chemokines, which are produced by synovial T cells, and by "relaying" them to their receptors on T cells, which activate G protein-dependent phosphoinositide 3-kinase and actin-dependent integrin triggering.

Activation of transcription factors and IL-8 expression in neutrophils stimulated with lipopolysaccharide from Porphyromonas gingivalis

DNA binding activity of NF-kappa B and AP-1 were examined in neutrophils stimulated with LPS purified from P. gingivalis, a major pathogenic bacteria of periodontitis lesion. Porphyromonas gingivalis LPS enhanced the activity reaching a peak at a concentration of 500 ng/ml in the absence of serum. The NF-kappa B activation stimulated with 10 ng/ml of P. gingivalis LPS was suppressed approximately 44% by treatment of neutrophils with anti-CD14 antibody under the presence of serum. Increase in the steady-state IL-8 mRNA level was concomitantly observed by stimulation of neutrophils with 500 ng/ml of P. gingivalis LPS under the absence of serum. These results indicate that P. gingivalis LPS activates NF-kappa B and AP-1 in both serum-dependent and -independent manners, followed by increased IL-8 transcription in neutrophils, and suggested a role for P. gingivalis LPS in IL-8 synthesis by neutrophils in inflamed gingiva and GCF.

Interleukin-1 receptor antagonist: role in biology

The interleukin-1 receptor antagonist (IL-1Ra) is a member of the IL-1 family that binds to IL-1 receptors but does not induce any intracellular response. Two structural variants of IL-1Ra have previously been described: a 17-kDa form that is secreted from monocytes, macrophages, neutrophils, and other cells (sIL-1Ra) and an 18-kDa form that remains in the cytoplasm of keratinocytes and other epithelial cells, monocytes, and fibroblasts (icIL-1Ra). An additional 16-kDa intracellular isoform of IL-1Ra has recently been described in neutrophils, monocytes, and hepatic cells. Both of the major isoforms of IL-1Ra are transcribed from the same gene through the use of alternative first exons. The two promoters regulating transcription of the secreted and intracellular forms have been cloned, and some of the functional cis-acting DNA regions have been characterized. The production of IL-1Ra is stimulated by many substances including adherent IgG, other cytokines, and bacterial or viral components. The tissue distribution of IL-1Ra in mice indicates that sIL-1Ra is found predominantly in peripheral blood cells, lungs, spleen, and liver, while icIL-1Ra is found in large amounts in skin. Studies in transgenic and knockout mice indicate that IL-1Ra is important in host defense against endotoxin-induced injury. IL-1Ra is produced by hepatic cells with the characteristics of an acute phase protein. Endogenous IL-1Ra is produced in numerous experimental animal models of disease as well as in human autoimmune and chronic inflammatory diseases. The use of neutralizing anti-IL-1Ra antibodies has demonstrated that endogenous IL-1Ra is an important natural antiinflammatory protein in arthritis, colitis, and granulomatous pulmonary disease. Treatment of human diseases with recombinant human IL-1Ra showed an absence of benefit in sepsis syndrome. However, patients with rheumatoid arthritis treated with IL-1Ra for six months exhibited improvements in clinical parameters and in radiographic evidence of joint damage.

Regulation of Chemokine Gene Expression in Human Peripheral Blood Neutrophils Phagocytosing Microbial Pathogens

Production of chemokines (chemotactic cytokines) by neutrophils is likely to be important in the regulation of inflammation and the control of infection. In this study we show that exposure of human neutrophils to various microbial pathogens leads to the production of both macrophage inflammatory protein 1α (MIP-1α) and IL-8. The bacterial microbes, Salmonella typhimurium and Pseudomonas aeruginosa, and Staphylococcus aureus all strongly induced both IL-8 and MIP-1α secretion, whereas Streptococcus pneumoniae, Staphylococcus epidermidis, and the opportunistic yeast Candida albicans were less potent. Saccharomyces cerevisiae and zymosan both induced IL-8 secretion but failed to stimulate that of MIP-1α. Coincubation of neutrophils with the proinflammatory cytokine TNF-α and the micro-organisms also led to differential expression of MIP-1α and IL-8. Significant enhancement of the induction of both MIP-1α and IL-8 by S. typhimurium, P. aeruginosa, and S. pneumoniae as well as by C. albicans was observed. In contrast, while IL-8 production in response to S. cerevisiae and zymosan was enhanced in the presence of TNF-α, no MIP-1α was produced. These combined results indicate that while neutrophils exposed to some micro-organisms alone or in the presence of inflammatory cytokines such as TNF-α will produce both MIP-1α and IL-8, resulting in generation of signals for the recruitment of mononuclear leukocytes and neutrophils, respectively, certain types of micro-organisms can skew this response toward synthesis of IL-8.

Epstein-Barr virus induces GM-CSF synthesis by monocytes: effect on EBV-induced IL-1 and IL-1 receptor antagonist production in neutrophils

Neutrophils play an important role in the control of viral infections by releasing a variety of potent agents. We previously demonstrated that Epstein-Barr virus (EBV) binds to human neutrophils and stimulates cytokine synthesis including interleukin-1 (IL-1) and IL-1 receptor antagonist (IL-1Ra). Since neutrophil functions are known to be modulated by the priming effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), we therefore investigated the cellular source of GM-CSF synthesis following treatment of leukocytes with EBV and the effect of GM-CSF on the production of IL-1, IL-1Ra, and superoxide by EBV-treated neutrophils. In enriched-cell populations, only monocytes were found to produce GM-CSF in response to EBV, which was maximal after 12 h of incubation. The results obtained with UV-irradiated particles or EBV neutralized with monoclonal antibody 72A1 suggest that contact between the cell and the gp350 of the viral envelope is sufficient to induce the release of GM-CSF. On the other hand, GM-CSF differentially upregulated EBV-induced IL-1 and IL-1Ra production by neutrophils. Pretreatment of neutrophils with GM-CSF prior to EBV activation synergistically enhanced the production of IL-1 alpha and IL-1 beta, but only marginally affected IL-1Ra synthesis. In addition, GM-CSF was also found to synergistically enhance the superoxide production by neutrophils in response to EBV. Molecular analysis showed that GM-CSF did not alter the IL-1 beta and IL-1Ra mRNA synthesis induced by EBV, suggesting that GM-CSF could act at a posttranslational level. Local production of GM-CSF by monocytes in tissues invaded by EBV could serve to potentiate the host defense mechanisms directed toward the destruction of the infectious virus.

Elevated concentrations of interleukin-1 beta and interleukin-1 receptor antagonist in plasma of women with silicone breast implants

Plasma from 27 women with silicone breast implants (SBIs) and 50 age-matched control women without SBIs were examined by enzyme immunoassay for the presence of interleukin-1 beta (IL-1 beta) and its naturally occurring receptor antagonist, IL-1ra. The results show that 74% (20 of 27) of women with SBIs had elevated concentrations of IL-1ra, whereas only 2% (1 of 50) of controls without SBIs had elevated concentrations of IL-1ra. In contrast to the IL-1ra results, the frequency of elevated IL-1 beta concentrations among women with SBIs was only 40% (11 of 27), but this was significantly higher than the 0% (0 of 50) in control women without SBIs. These findings suggest that there is a chronic ongoing inflammatory process in some women with SBIs, the implications of which are discussed in the context of silicone as an antigenic stimulant of the immune system.

Interleukin-1 expression by neutrophils in rheumatoid arthritis

OBJECTIVE

To determine if neutrophils from blood and synovial fluid of patients with rheumatoid arthritis and other joint arthropathies express interleukin-1 beta mRNA.

METHODS

RNA was isolated from neutrophils from patient and control blood, and synovial fluid of patients, probed in northern blots, and quantified by densitometry. It was also isolated and analysed from control blood neutrophils after incubation in vitro with granulocyte macrophage colony stimulating factor (GM-CSF).

RESULTS

Neutrophils from the synovial fluid of patients with rheumatoid arthritis contained low levels of mRNA for interleukin-1 beta--between 0.1 and 2% of those observed during stimulation of control neutrophils with GM-CSF for one hour. Higher levels (4-40% of the maximal GM-CSF values) were observed in blood neutrophils from patients with rheumatoid arthritis.

CONCLUSIONS

Neutrophils contribute to the cytokine network in rheumatoid arthritis. In some circumstances, activation of transcription may occur within the circulation of these patients.

Lipopolysaccharide-induced interleukin-8 gene expression in human granulocytes: transcriptional inhibition by interferon-gamma

We recently showed that lipopolysaccharide (LPS) is a potent inducer of interleukin-8 (IL-8) expression in human polymorphonuclear leucocytes (PMN), at the level of both mRNA and protein, and that interferon-gamma (IFN gamma) inhibits IL-8 mRNA accumulation in stimulated PMN. To further define the molecular basis of the regulation of IL-8 gene expression in PMN, we investigated the effects of LPS and IFN gamma at both the transcriptional and post-transcriptional levels. As determined by Northern blot analysis, new protein synthesis was not required for the induction of IL-8 mRNA expression by LPS. Neither did the half-life of IL-8 mRNA in LPS-treated PMN differ from that observed in untreated cells. However, nuclear run-on analysis revealed that LPS increased the transcription of the IL-8 and IL-1 beta genes and that, in LPS-activated cells, IFN gamma markedly inhibited the rate of IL-8 gene transcription, but not that of IL-1 beta. IFN gamma did not affect IL-8 mRNA stability in LPS-treated PMN, indicating that the cytokine does not regulate LPS-induced IL-8 gene expression through post-transcriptional events. These results provide the first evidence that human granulocytes can actively transcribe the IL-8 gene, and that transcriptional inhibition is the mechanism by which IFN gamma inhibits IL-8 gene expression in PMN.