Synovial fluid neutrophils of patients with rheumatoid arthritis have membrane antigen changes that reflect activation

Ageing and interferon gamma response drive the phenotype of neutrophils in the inflamed joint

OBJECTIVE

Neutrophils are typically the most abundant leucocyte in arthritic synovial fluid. We sought to understand changes that occur in neutrophils as they migrate from blood to joint.

METHODS

We performed RNA sequencing of neutrophils from healthy human blood, arthritic blood and arthritic synovial fluid, comparing transcriptional signatures with those from murine K/BxN serum transfer arthritis. We employed mass cytometry to quantify protein expression and sought to reproduce the synovial fluid phenotype ex vivo in cultured healthy blood neutrophils.

RESULTS

Blood neutrophils from healthy donors and patients with active arthritis showed largely similar transcriptional signatures. By contrast, synovial fluid neutrophils exhibited more than 1600 differentially expressed genes. Gene signatures identified a prominent response to interferon gamma (IFN-γ), as well as to tumour necrosis factor, interleukin-6 and hypoxia, in both humans and mice. Mass cytometry confirmed that healthy and arthritic donor blood neutrophils are largely indistinguishable but revealed a range of neutrophil phenotypes in synovial fluid defined by downregulation of CXCR1 and upregulation of FcγRI, HLA-DR, PD-L1, ICAM-1 and CXCR4. Reproduction of key elements of this signature in cultured blood neutrophils required both IFN-γ and prolonged culture.

CONCLUSIONS

Circulating neutrophils from patients with arthritis resemble those from healthy controls, but joint fluid cells exhibit a network of changes, conserved across species, that implicate IFN-γ response and ageing as complementary drivers of the synovial fluid neutrophil phenotype.

Serum Calprotectin a Potential Biomarker in Juvenile Idiopathic Arthritis: A Meta-Analysis

Juvenile idiopathic arthritis (JIA) is the most common inflammatory chronic disease affecting children and adolescents. Today, there are no specific biomarkers of inflammation. Therefore, it is important to identify new markers as predictors of disease activity. Recently, some researchers have directed their interest toward a protein, calprotectin (CLP), as a potential biomarker. The primary objective of our systematic review and meta-analysis was to analyze the possible role of CLP in JIA. Method: A literature search was conducted using PubMed, EMBASE, Scopus, Science Direct on 10 August 2021. The selection of studies was made using the PRISMA 2020 guidelines. Cohen’s d with 95% CI and p-value were used as a measure of effect size. The random effects model was used to account for different sources of variation among studies. Heterogeneity was assessed using Q statistics and I². The publication bias was analyzed and represented by a funnel plot, and funnel plot symmetry was assessed with Egger’s test. Results: Our results at follow-up showed a statistically significant difference between patients with active disease compared to patients with inactive disease: 0.39 (0.16; 0.62), p = 0.001; without statistical heterogeneity. Another important aspect that emerged were the differences between the systemic disease form and any form of inactive disease showing a different concentration of calprotectin: 0.74 (0.40; 1.08), p < 0.001; without statistical heterogeneity. On the other hand, meta-regression analyses performed on gender, age, duration of disease, percentage of patients with ANA+ or RF+, medium value of ESR or CRP were not statistically significant. A statistically significant difference in serum calprotectin concentration between patients with JIA and healthy controls were observed. In fact, it presented lower values in the control group. Conclusions: The use of serum CLP could represent, in the future, a useful tool in JIA in order to stratify disease activity more accurately and may aid a more tailored approach to drug of choice in children with JIA. Further studies are needed to evaluate CLP as a predictor of flare in combination with other potential biomarkers of subclinical disease activity.

C5a and C5aR are elevated in joints of rheumatoid and psoriatic arthritis patients, and C5aR blockade attenuates leukocyte migration to synovial fluid

Complement activation correlates to rheumatoid arthritis disease activity, and increased amounts of the complement split product C5a is observed in synovial fluids from rheumatoid arthritis patients. Blockade of C5a or its receptor (C5aR) is efficacious in several arthritis models. The aim of this study was to investigate the role of C5a and C5aR in human rheumatoid arthritis and psoriatic arthritis–both with respect to expression and function. Synovial fluid, blood and synovial samples were obtained from rheumatoid arthritis, psoriatic arthritis and osteoarthritis patients as a less inflammatory arthritis type, and blood from healthy subjects. Cells infiltrating synovial tissue were analysed by immunohistochemistry and flow cytometry. SF and blood were analysed for biomarkers by flow cytometry or ELISA. The effect of a blocking anti-human C5aR mAb on leukocyte migration was determined using a Boyden chamber. Appropriate statistical tests were applied for comparisons. C5aR⁺ cells were detected in most rheumatoid arthritis, in all psoriatic arthritis, but not in non-inflammatory control synovia. C5aR⁺ cells were primarily neutrophils and macrophages. C5aR⁺ macrophages were mainly found in lymphoid aggregates in close contact with T cells. C5a levels were increased in both rheumatoid arthritis and psoriatic arthritis synovial fluid compared to osteoarthritis, and in blood from rheumatoid arthritis compared to healthy subjects. Neutrophil and monocyte migration to rheumatoid arthritis synovial fluid was significantly inhibited by anti-C5aR. The data support that the C5a-C5aR axis may be driving the infiltration of inflammatory cells into the synovial fluid and synovium in both rheumatoid and psoriatic arthritis, and suggest that C5a or C5aR may be a promising treatment target in both diseases.

Enhanced neutrophil phagocytic capacity in rheumatoid arthritis related to the autoantibodies rheumatoid factor and anti-cyclic citrullinated peptides

Background

There is no consensus on the mechanisms by which anti-cyclic citrullinated peptide antibodies (anti-CCP) and rheumatoid factor (RF) influence the pathogenesis of rheumatoid arthritis (RA). The current study verified if the presence of RF or anti-CCP is associated with phagocytic capacity and reactive oxygen species (ROS) production by phagocytes in RA patients to better clarify the role played by these antibodies in pathogenesis of the disease.

Methods

A cohort of 30 RA patients followed from early stages of the disease were characterized by positivity for RF or anti-CCP, disease activity score (DAS-28), health assessment questionnaire (HAQ), use of synthetic or biologic therapy, lifestyle, comorbidities and radiographic erosions. Phagocytic capacity against Saccharomyces cerevisiae and superoxide anion production were assessed in RA patients and compared with 20 healthy controls. Phagocytic capacity and superoxide anion production were also compared between RF- and anti-CCP-positive and -negative RA patients.

Results

Anti-CCP- and RF-positive RA patients had higher neutrophil phagocytic capacity than anti-CCP- (p = 0.005) and RF (p = 0.005)-negative individuals through pattern-recognition receptors. As assessed via pattern recognition or opsonin receptors, neutrophils and monocytes from RA patients presented overall higher phagocytic capacity than neutrophils and monocytes from healthy controls (p < 0.05). Furthermore, RA patients also showed a higher capacity for producing cytotoxic oxygen radicals (p = 0.0026). Phagocytosis and superoxide anion production did not correlate with any of the clinical variables analyzed in this study.

Conclusions

This study showed increased phagocytosis by neutrophils in RA patients who were positive for anti-CCP and RF autoantibodies. Furthermore, there was an overall hyperactivation of the phagocytes in RA patients. Our data suggest that anti-CCP and RF may indirectly enhance the inflammation cascade involving neutrophils and may indirectly sustain tissue damage in RA. Targeting the production of these autoantibodies may be a promising strategy in the management of RA.

Role of neutrophils in systemic autoimmune diseases

Neutrophils have emerged as important regulators of innate and adaptive immune responses. Recent evidence indicates that neutrophils display marked abnormalities in phenotype and function in various systemic autoimmune diseases, and may play a central role in initiation and perpetuation of aberrant immune responses and organ damage in these conditions. This review discusses the putative roles that neutrophils and aberrant neutrophil cell death play in the pathogenesis of various systemic autoimmune diseases, including systemic lupus erythematosus, small vessel vasculitis and rheumatoid arthritis.

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.

Phagocyte-specific calcium-binding S100 proteins as clinical laboratory markers of inflammation

The EF-hand homolog family of S100 proteins comprises the largest group of calcium-binding proteins. Within this S100 family, the phagocyte-specific calcium-binding proteins are pro-inflammatory molecules expressed and secreted by phagocytes, which play a pivotal role within the innate immune system. Although the exact biological functions of these proteins still remain to be defined in greater detail, there is evidence that they are involved in a pro-inflammatory axis associated with various inflammatory conditions. The three members of this group, S100A8, S100A9 and S100A12 are overexpressed at local sites of inflammation. High concentrations are found in synovial fluid, sputum, stool and blood plasma/serum during inflammation. Both the S100A8/S100A9 complex and S100A12 have been proven to be useful as diagnostic markers of inflammation especially in non-infectious inflammatory diseases such as arthritis, chronic inflammatory lung and bowel disease. They indicate phagocyte activation more sensitively than conventional parameters of inflammation. As a consequence, there is a strong correlation to the inflammation of various acute and chronic disorders, making these proteins sensitive parameters for the monitoring of disease activity and response to treatment in individual patients. The phagocyte-specific S100 proteins are able to indicate minimal residual inflammation, which is not detected by other diagnostic tests, and they may even be prospective markers for the outcome of patients. In this review, pro-inflammatory functions of S100 proteins and their usefulness as biomarkers of inflammation are presented.

Neutrophil function in pregnancy and rheumatoid arthritis

BACKGROUND

Pregnancy exerts suppressive effects on rheumatoid arthritis (RA). An attenuation in neutrophil function in late pregnancy which may explain this amelioration has previously been reported.

OBJECTIVE

A longitudinal investigation of neutrophil activity in healthy pregnant women (n=9) and pregnant patients with RA (n=9), compared with age matched non-pregnant patients with RA (n=12) and healthy controls (n=22).

METHODS

Neutrophil activation was measured in response to the physiological receptor agonists, n-formyl-methionyl-leucyl-phenylalanine (fMLP) and zymosan activated serum (ZAS). Superoxide anion production (respiratory burst) was determined by lucigenin enhanced chemiluminescence (LUCL); secondary granule lactoferrin release by enzyme linked immunosorbent assay (ELISA); and CD11b, CD18, and CD62L expression by flow cytometric analysis.

RESULTS

Stimulated neutrophil LUCL was significantly reduced in both pregnant women with RA and healthy pregnant women in the second (fMLP 43% and 69%, ZAS 43% and 59%, respectively) and third trimesters (fMLP 24% and 44%, ZAS 32% and 38%, respectively). Responses returned to normal within eight weeks of delivery and unstimulated levels remained unchanged throughout pregnancy. Basal and stimulated CD11b, CD18, and CD62L expression showed no variations throughout gestation for both pregnancy groups. Likewise, stimulated lactoferrin release and plasma lactoferrin remained unchanged. Certain morphological differences in RA neutrophils were highlighted by the flow cytometric analysis. Moreover, resting neutrophils and stimulated cells from patients with RA, including pregnant subjects, showed a marked increase in LUCL, but a reduction in CD11b, CD18, and CD62L. Low dose prednisolone and methylprednisolone had no effect on neutrophil parameters over the period of treatment with non-steroidal anti-inflammatory drugs.

CONCLUSION

The attenuation to neutrophil respiratory burst in both healthy and RA pregnancies may offer an explanation for the pregnancy induced remission of this inflammatory disorder.

A phase 1 study to address the safety and efficacy of granulocyte colony-stimulating factor for the mobilization of hematopoietic progenitor cells in active rheumatoid arthritis

OBJECTIVE

To examine the safety and efficacy of granulocyte colony-stimulating factor (G-CSF) alone for the mobilization of peripheral blood progenitor cells in patients with resistant active rheumatoid arthritis (RA).

METHODS

Five patients with resistant active RA were studied. A dose of 5 microg/kg of G-CSF (Filgrastim) was given subcutaneously each day for 5 days, and the number of stem cells mobilized into the peripheral blood was assessed by daily CD34 counts. RA disease activity was assessed by standard clinical methods.

RESULTS

The absolute numbers of peripheral blood CD34+ cells peaked on day 4, with a mean value of 0.025 x 10(9)/liter (range 0.013-0.048 x 10(9)/liter). There was no significant change in disease activity during the study or in the month following therapy.

CONCLUSION

Using G-CSF alone, CD34+ progenitor peripheral blood cells were mobilized in numbers suitable for leukopheresis. G-CSF therapy was well-tolerated in patients with active RA, and was not associated with a flare during treatment or in the month following treatment.

Stimulation of intracellular Ca2+ levels in human neutrophils by soluble immune complexes. Functional activation of FcgammaRIIIb during priming

Soluble immune complexes bind to unprimed neutrophils and generate intracellular Ca2+ transients but fail to activate the NADPH oxidase. Following priming of the neutrophils with either tumor necrosis factor alpha or granulocyte-macrophage colony-stimulating factor, stimulation of the cells with the soluble immune complexes leads to an enhanced Ca2+ signal and significant secretion of reactive oxidants. The enhanced Ca2+ signal observed in primed neutrophils results from the influx of Ca2+ from the external environment and is partly sensitive to tyrosine kinase inhibitors. This is in contrast to the Ca2+ signal observed in unprimed neutrophils, which arises from the mobilization of intracellular stores. When the surface expression of FcgammaRIIIb on primed neutrophils was decreased either through incubation with Pronase or phosphoinositide-specific phospholipase C, the extra enhanced Ca2+ mobilization seen in primed cells was significantly lowered, while the initial rise in intracellular Ca2+ was unaffected. Depletion of FcgammaRIIIb had no significant effect on the Ca2+ transients in unprimed neutrophils. Cross-linking FcgammaRII, but not FcgammaRIIIb, induced increases in intracellular Ca2+ in unprimed neutrophils, while cross-linking either of these receptors increased Ca2+ levels in primed neutrophils. The FcgammaRII-dependent intracellular Ca2+ rise in primed cells was unaffected by incubation in Ca2+-free medium, whereas the FcgammaRIIIb-dependent transient was significantly decreased when Ca2+ influx was prevented in Ca2+-free medium supplemented with EGTA. Cross-linking either FcgammaRII or FcgammaRIIIb in primed or unprimed cells failed to stimulate substantial levels of inositol 1,4,5-trisphosphate production. These results indicate that following stimulation of primed neutrophils with soluble immune complexes the enhanced Ca2+ mobilization observed is the result of a functional activation of the glycosylphosphatidylinositol-linked FcgammaRIIIb.

Neutrophils from the synovial fluid of patients with rheumatoid arthritis express the high affinity immunoglobulin G receptor, Fc gamma RI (CD64): role of immune complexes and cytokines in induction of receptor expression

Neutrophils isolated from the synovial fluid of 16/24 patients with rheumatoid arthritis expressed Fc gamma RI (CD64), the high-affinity receptor for monomeric immunoglobulin G (IgG), on their cell surface. Receptor expression ranged from 17% to 168% of the level of expression obtained after incubation of control blood neutrophils with 100 U/ml interferon-gamma (IFN-gamma) for 24 hr in vitro. Similarly, mRNA for Fc gamma RI was detected in synovial fluid neutrophils from 12/15 patients and transcript levels ranged from 5% to 200% of the values obtained after treatment of blood neutrophils with IFN-gamma for 4 hr in vitro. No surface expression nor mRNA were detected in freshly isolated blood neutrophils from either patients or from healthy controls. Addition of cell-free synovial fluid to control blood neutrophils induced both mRNA and surface expression of Fc gamma RI to levels that were comparable to those achieved after addition of IFN-gamma. Neither soluble nor insoluble immune complexes appeared to be involved in induction of Fc gamma RI expression in spite of the ability of these complexes to induce protein biosynthesis. Synovial fluid-induced expression of Fc gamma RI was partially blocked by incubation with neutralizing IFN-gamma antibodies, whilst neutralizing interleukin (IL)-6 antibodies had little effect. Levels of IFN-gamma measured within these synovial fluids ranged from 0 to 2.7 U/ml, well within the range known to induce neutrophil Fc gamma RI expression. These data thus indicate that gene expression in synovial fluid neutrophils is selectively activated as the cells enter the diseased joint. Furthermore, these data indicate that induced expression of Fc gamma RI may alter the ability of infiltrating neutrophils to respond to IgG-containing immune complexes present in these joints.

Neutrophil gelatinase levels in plasma and synovial fluid of patients with rheumatic diseases

To examine the clinical significance of neutrophil gelatinase in rheumatic diseases, plasma and synovial fluid (SF) gelatinase levels were determined in 62 patients with rheumatoid arthritis (RA), 12 patients with ankylosing spondylitis (AS), 18 patients with osteoarthritis (OA) and 17 healthy controls. The gelatinase level was measured by enzyme-linked immunoassay (ELISA). The assay had a sensitivity of 1 ng/ml and a working range of 5-25 ng/ml. Gelatinase levels were significantly higher in the plasma of patients with RA and of patients with RA complicated by amyloidosis or vasculitis as compared to those of healthy controls. Moreover, the mean value of gelatinase in the plasma of patients with RA complicated by vasculitis was found to be significantly higher than that of RA patients without vasculitis. A significant increase in gelatinase concentration was also observed in the plasma of AS patients but not in the plasma of patients with OA. The concentration of gelatinase in the RA SF samples was much higher (18-fold) than the level of the enzyme in the plasma of RA patients. There was also a higher concentration of gelatinase (four-fold) in OA SF compared with OA plasma. The results suggested that circulating gelatinase may reflect some degree of neutrophil activation in patients with inflammatory arthritis, especially in those with RA complicated by vasculitis. However, the results did not allow a differentiation between chronic and acute inflammation.

Specific human granulocyte-macrophage colony-stimulating factor antagonists

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic hemopoietic growth factor and activator of mature myeloid cell function. We have previously shown that residue 21 in the first helix of GM-CSF plays a critical role in both biological activity and high-affinity receptor binding. We have now generated analogues of GM-CSF mutated at residue 21, expressed them in Escherichia coli, and examined them for binding, agonistic, and antagonistic activities. Binding experiments showed that GM E21A, E21Q, E21F, E21H, E21R, and E21K bound to the GM-CSF receptor alpha chain with a similar affinity to wild-type GM-CSF and had lost high-affinity binding to the GM-CSF receptor alpha-chain-common beta-chain complex. From these mutants, only the charge reversal mutants E21R and E21K were completely devoid of agonistic activity. Significantly we found that E21R and E21K antagonized the proliferative effect of GM-CSF on the erythroleukemic cell line TF-1 and primary acute myeloid leukemias, as well as GM-CSF-mediated stimulation of neutrophil superoxide production. This antagonism was specific for GM-CSF in that no antagonism of interleukin 3-mediated TF-1 cell proliferation or tumor necrosis factor alpha-mediated stimulation of neutrophil superoxide production was observed. E. coli-derived GM E21R and E21K were effective antagonists of both nonglycosylated and glycosylated wild-type GM-CSF. These results show that low-affinity GM-CSF binding can be dissociated from receptor activation and have potential clinical significance for the management of inflammatory diseases and certain leukemias where GM-CSF plays a pathogenic role.

Stimulation of reactive oxidant production in neutrophils by soluble and insoluble immune complexes occurs via different receptors/signal transduction systems

Cell-free synovial fluid from patients with rheumatoid arthritis contains soluble and insoluble IgG-containing immune complexes which activate reactive oxidant production in human neutrophils. In this report we have measured the effects of inhibitors of signal transduction pathways on neutrophil activation by these complexes and also following activation by synthetic soluble and insoluble immune complexes made from human serum albumin (HSA) and anti-(HSA) antibodies. In all aspects studied, the soluble rheumatoid complexes and the soluble synthetic complexes were indistinguishable in the ways in which they activated neutrophils. Activation of reactive oxidant production in response to these soluble complexes was completely inhibited by pertussis toxin (indicating G-protein coupling of receptor occupancy), completely insensitive to staurosporine (indicating that oxidant production did not require protein kinase C activity), only marginally (< 30%) inhibited by butanol (indicating that dependence upon activity of phospholipase D was minimal), and completely inhibited by chloracysine, an inhibitor of phospholipase A2. In contrast, activation of reactive oxidant production in response to the insoluble rheumatoid or insoluble synthetic immune complexes was largely pertussis toxin insensitive, inhibited by > 50% by staurosporine, inhibited by > 50% by butanol, and completely inhibited by chloracysine. These results show that the receptor-mediated signal transduction systems activated by the soluble and insoluble immune complexes are different. Because the soluble complexes activate a transient burst of reactive oxidant secretion from primed neutrophils, the mechanisms regulating either the release or the intracellular production of oxidants within rheumatoid joints are distinct and hence may be pharmacologically modified independently of each other.

Up-regulation by tumor necrosis factor alpha of intercellular adhesion molecule 1 expression and function in synovial fibroblasts and its inhibition by glucocorticoids

OBJECTIVE

To examine the regulation of the intercellular adhesion molecule 1 (ICAM-1) gene in cultured human synovial fibroblasts in response to tumor necrosis factor alpha (TNF alpha), and investigate its modulation by the synthetic glucocorticoid, dexamethasone.

METHODS

Cell surface expression of ICAM-1 was determined by flow cytometry, enzyme immunoassay, and immunoprecipitation. ICAM-1 messenger RNA (mRNA) levels were monitored by Northern blot. ICAM-1 function was determined by measuring the adhesion of monocytes to synovial fibroblasts.

RESULTS

ICAM-1 expression on unstimulated cells was weak but was rapidly enhanced in both a time- and dose-dependent manner following exposure to TNF alpha. Treatment of the cells with TNF alpha also resulted in both a time- and dose-dependent increase in steady-state ICAM-1 mRNA levels, as determined by Northern blot. The increased expression of ICAM-1 was inhibited by cycloheximide and actinomycin D. Cultured synovial fibroblasts from patients with rheumatoid and nonrheumatoid arthropathies responded similarly to TNF alpha. Adhesion studies demonstrated that ICAM-1 is involved in the adherence of peripheral blood monocytes to TNF alpha-activated synovial fibroblasts. In addition, dexamethasone inhibited TNF alpha-induced surface expression of ICAM-1, accumulation of ICAM-1 mRNA, and adhesion of monocytes to TNF alpha-activated synovial fibroblasts.

CONCLUSION

These combined results provide further evidence of an important role of ICAM-1 in inflammatory synovitis, as well as a potentially novel site of antiinflammatory action of glucocorticoids.

Flow cytometric determination of CD11b upregulation in vivo

We describe a flow cytometric method to evaluate upregulation of peripheral blood neutrophil and monocyte integrin CD11b in vivo. To avoid spontaneous upregulation in vitro, buffy coat cells were separated on ice and all subsequent cell handling steps were carried out at 0-4 degrees C. Such leukocytes were 95-100% viable, as determined by PI staining. Buffy coat leukocytes were double-stained with CD11b PE-conjugated and CD14 FITC-conjugated monoclonal antibodies and, in addition, with the nucleic acid dye LDS-751. After staining, firstly, LDS-751 positive (+ve) leukocytes, and, secondly, CD14 +ve monocytes were collected in live mode. Aggregated and irrelevant cells were gated out on the basis of their LDS-751 staining pattern and cellular light scattering properties, and the CD11b expression on neutrophils and monocytes was determined. Upregulation of CD11b in vitro was significantly affected by factors such as cell handling temperature, pre-fixation of blood samples, and density gradient separation of the cells. Incubation of aliquots of buffy coat cell suspension supplemented with FMLP for 5 min or without FMLP supplement for 15 min at 37 degrees C significantly increased CD11b expression without affecting cell viability. We have demonstrated that CD11b is expressed at maximal levels on arthritic synovial fluid neutrophils and CD14 +ve cells, and at increased but submaximal levels on peripheral blood neutrophils and monocytes of patients recovering from sepsis. The results suggest that the method can be used to evaluate in vivo upregulation of CD11b.

Increased expression of neutrophil and monocyte adhesion molecules in unstable coronary artery disease

BACKGROUND

A rapid increase in leukocyte adhesion to endothelial cells is one of the first events in the acute inflammatory response and in the pathogenesis of vascular diseases. A subgroup of cell surface glycoproteins (the CD11/CD18 complex) play a major role in the leukocyte adhesion process; in particular, the CD11b/CD18 receptor can be upregulated severalfold in response to chemotactic factors. The purpose of this study was to assess whether upmodulation of granulocyte and monocyte CD11b/CD18 receptors takes place during the passage of blood through the coronary tree of patients with clinical manifestations of ischemic heart disease.

METHODS AND RESULTS

Thirty-nine patients who underwent diagnostic coronary arteriography were studied. Group 1 (15 patients) had a clinical diagnosis of unstable angina, group 2 (14 patients) had stable exertional angina, and group 3 (10 patients) had atypical chest pain. Simultaneous sampling from the coronary sinus and aorta was obtained before coronary arteriography. Cell surface receptors were detected by direct immunofluorescence evaluated by flow cytofluorimetry using monoclonal antibodies tagged with fluorescent markers. Leukocytes were stained in unseparated blood to avoid in vitro manipulation that could activate phagocytes. Group 1 and 2 patients had significant coronary artery disease (> 50% coronary narrowing in at least one major coronary vessel), whereas group 3 patients had normal coronary arteries. In group 1, granulocytes and monocytes showed a significantly higher expression of the CD11b/CD18 adhesion receptor in the coronary sinus than in the aorta (both P < .01), whereas no difference in CD11b/CD18 expression was seen in groups 2 and 3.

CONCLUSIONS

Patients with unstable angina have an increased expression of granulocyte and monocyte CD11b/CD18 adhesion receptors, indicating that an inflammatory reaction takes place within their coronary tree. Activation of these leukocytes may induce coronary vasoconstriction, favor thrombotic processes, and further activate platelets, thus having potential implications on the pathogenesis of unstable coronary artery disease.

Receptor expression in synovial fluid neutrophils from patients with rheumatoid arthritis

OBJECTIVES

The aim of this study was to determine if neutrophils isolated from the blood and synovial fluid of patients with rheumatoid arthritis had patterns of receptor expression resembling those of blood neutrophils from controls which had been activated and primed in vitro.

METHODS

Fluorescence activated cell sorting was used to measure receptor expression in paired blood and synovial fluid neutrophils from patients and in control neutrophils exposed to phorbol myristate acetate and granulocyte-macrophage colony stimulating factor.

RESULTS

There was no significant difference in the patterns of receptor expression in blood neutrophils from patients and healthy controls, but neutrophils in the synovial fluid had been primed and activated within the joint. About 50% of rheumatoid synovial fluid neutrophil samples expressed Fc gamma RI, a high affinity receptor for monomeric IgG, which is only expressed in neutrophils exposed to cytokines.

CONCLUSIONS

Synovial fluid neutrophils are activated and primed within the inflamed joint and hence their ability to respond to activating factors such as immune complexes will be modulated. As the expression of Fc gamma RI requires active biosynthesis, this work indicates that selective gene activation occurs when neutrophils are recruited into rheumatoid joints.

Increased expression of C1q receptors on neutrophils from inflammatory joint fluids

C1q receptor (C1qR) expression was determined by immunofluorescence flow cytometry on neutrophils from paired peripheral blood and synovial fluid samples from 21 patients with rheumatoid arthritis (RA) and 13 patients with other articular diseases (OAD). In both patient groups the levels of C1qR on circulating neutrophils were similar to that observed for normal control subjects, whereas on synovial fluid neutrophils significantly higher levels of receptor expression were observed. The mean percentage increases observed were: RA patients 47%, OAD patients 72%. C1q-bearing immune complexes were most prevalent in patients with RA, with the highest concentrations being found in synovial fluid samples. No correlation between immune complex levels and neutrophil C1qR expression was noted. Upregulation of C1qR expression is a feature of activated neutrophils from inflammatory joint fluids.

Activation of neutrophils by soluble and insoluble immunoglobulin aggregates from synovial fluid of patients with rheumatoid arthritis

OBJECTIVES

Previous work has shown that synovial fluid isolated from patients with active rheumatoid arthritis contains soluble (not sedimented by centrifugation at 11,600 g for two minutes) and insoluble (sedimented by centrifugation at 11,600 g for two minutes) immunoglobulin aggregates that are capable of activating reactive oxidant production by bloodstream neutrophils. The purpose of this study was to determine which of these types of immunoglobulin aggregates activated the secretion of reactive oxygen metabolites and granule enzymes from neutrophils.

METHODS

Cell free synovial fluid (from patients with rheumatoid arthritis) was added to neutrophils isolated from blood of healthy controls that had been incubated in the presence and absence of granulocyte-macrophage colony stimulating factor (GM-CSF). Reactive oxidant production was measured by luminol chemiluminescence (which detects both intracellular and extracellular oxidant production) and by cytochrome c reduction (which measures superoxide secretion).

RESULTS

The soluble aggregates only activated neutrophils that were previously primed, and activated a rapid and transient burst of reactive oxidant secretion. On the other hand, the insoluble aggregates activated primed and unprimed neutrophils with similar efficacy and most of the oxidants generated (especially in unprimed cells) were intracellular. The soluble aggregates, but not the insoluble aggregates, also activated the secretion of myeloperoxidase from neutrophils that had either been pretreated with cytochalasin B or primed with GM-CSF.

CONCLUSION

It is thus proposed that these soluble immunoglobulin aggregates are responsible for activation of the release of tissue damaging granule enzymes and reactive oxidants from primed neutrophils within the rheumatoid joint.

Possible clearance of effete polymorphonuclear leucocytes from synovial fluid by cytophagocytic mononuclear cells: implications for pathogenesis and chronicity in inflammatory arthritis

A feature common to all forms of chronic inflammatory arthritis, irrespective of the possible underlying cause, is the persistent exudation of large numbers of polymorphonuclear leucocytes (PMNL) into synovial fluid. These cells possess potent degradative enzymes and proinflammatory mediators, and their removal is vital to normal inflammatory resolution. A major route of disposal of extravasated PMNL appears to be programmed cell death (apoptosis), followed by their rapid recognition, and intact phagocytosis, by mature tissue macrophages. Such macrophages, containing PMNL (cytophagocytic mononuclear cells (CPM)), long recognised in synovial fluid as Reiter cells, are commonly found in reactive arthritis, spondyloarthritis, and crystal arthritides, but only rarely in rheumatoid disease. In a retrospective analysis of 187 knee synovial fluid cytospins, the relation between the formation of CPM and the presence of apoptotic (pyknotic) PMNL was investigated. As long as the synovial fluid examined was fresh there was a high correlation between numbers of CPM (as a percentage of macrophages) and pyknotic numbers of PMNL in fluids containing CPM. This suggests that the formation of CPM occurs in vivo and is involved in the disposal of PMNL. Numbers of pyknotic PMNL increased rapidly in stored synovial fluid without a significant change in numbers of CPM, and were highest in synovial fluid which did not contain CPM. The presence or absence of CPM, or their disease associations, could not be explained simply by limiting numbers of macrophages, or apoptotic PMNL in synovial fluid. These findings are consistent with a regulatory role for CPM in synovial fluid, where they may be important in preventing autolysis of PMNL, and thus local tissue damage.

Markers of inflammatory activation: upregulation of complement receptors CR1 and CR3 on synovial fluid neutrophils from patients with inflammatory joint disease

Expression of the C3 receptors CR1 and CR3 was investigated on neutrophils from paired peripheral blood and synovial fluid samples from 34 patients with inflammatory joint disease (21 patients with rheumatoid arthritis (RA) and 13 patients with other articular diseases (OAD)). Using monoclonal antibodies (anti-CD35, anti-CD11b) and immunofluorescence flow cytometric analyses the percentages of positively labeled cells and the relative fluorescence intensities (as a measure of receptor number) were determined. CR1 and CR3 were found to be present on the majority (> 85%) of circulating neutrophils from normal subjects, RA and OAD patients, and on synovial fluid neutrophils from both patient groups. A strong correlation between neutrophil CR1 and CR3 expression was observed in peripheral blood samples from normal subjects (r = 0.81; P = 0.001), RA (r = 0.79; P = 0.001), and OAD patients (r = 0.83; P = 0.001); in each case the levels of CR3 expression were approximately twice those recorded for CR1. Both CR1 and CR3 expression was upregulated on synovial fluid neutrophils compared with that observed on the corresponding peripheral blood cells. Mean percentage increases observed were: RA patients: CR1, 16.5% (P < 0.001) and CR3, 28.7% (P < 0.001); and OAD patients: CR1, 4.1% and CR3, 26.9% (P = 0.001). Correlation of serum and synovial fluid IL-6, IL-8, and immune complex levels with neutrophil CR1 and CR3 expression failed to demonstrate any significant relationship between the concentrations of these soluble factors and receptor expression. Upregulation of CR1 and CR3 receptors, reflecting neutrophil activation within the inflamed joint, is a consistent finding in patients with inflammatory arthropathies.

Gold complexes and activation of human polymorphonuclear leukocytes. Dissociation of changes in membrane potential and oxidative burst

The effects of the gold compounds on the alteration of membrane potential of polymorphonuclear leukocytes (PMN) in response to various stimulants have been compared with their effects on the oxidative burst. The present studies have shown that gold complexes [auranofin (AF), aurothiomalate (Autm), aurocyanide (Au(CN)2-)] have contrasting effects on the membrane potential of 3,3'-dipentyloxacarbocyanine [di-O-C5(3)] loaded PMN. Au(CN)2- at concentrations which inhibit the oxidative burst of PMN did not affect the membrane depolarization after activation of PMN by phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl phenylalanine (FMLP); Autm slightly stimulated the oxidative burst but had no effect on the depolarization of PMN. In contrast, AF inhibited the depolarization of stimulated PMN to an extent depending upon the concentration of AF, the time of preincubation and the stimulus. The membrane depolarization of PMN caused by PMA, FMLP and concanavalin A (ConA) was inhibited by AF (5 microM) but the depolarization induced by calcium ionophore (A23187) was not affected. AF at the same conditions inhibits the oxidative burst of PMN induced by all these single stimuli including the calcium ionophore. Dissociation of membrane depolarization and superoxide generation caused by AF was also seen in PMN activated by two stimuli. AF (5 microM) had little initial inhibitory effect on the oxidative burst of PMN stimulated by combinations of PMA and ConA or PMA and FMLP whereas it almost totally blocked the depolarization caused by these combinations. Preincubation of cells with 5 microM AF for less than 5 min prior to the addition of PMA allowed membrane depolarization which was followed rapidly by repolarization. None of the gold complexes studied had any effect on the resting membrane potential of PMN.

Activation of neutrophil reactive-oxidant production by synovial fluid from patients with inflammatory joint disease. Soluble and insoluble immunoglobulin aggregates activate different pathways in primed and unprimed cells

Cell-free synovial fluid from patients with rheumatoid arthritis stimulated the NADPH oxidase activity in human neutrophils, which reached a peak 15-20 min after addition. Insoluble immunoglobulin aggregates isolated from these fluids activated a similar pattern of oxidase activity. However, when synovial fluid was added to neutrophil suspensions which had been previously exposed to granulocyte-macrophage colony-stimulating factor, the stimulated oxidase activity was biphasic, in that an additional transient activity was observed which reached a peak within 5 min of addition. The additional neutrophil-stimulating activity could not be sedimented by centrifugation at 330,000 g-min, and only activated oxidase activity in neutrophils which had previously been primed. The neutrophil-stimulating activity in this soluble fraction was removed by Protein A affinity chromatography, and activity was recovered in eluates from this column. Thus activity in this soluble fraction from synovial fluid is attributed to the presence of soluble immunoglobulin aggregates. Whereas oxidase activity stimulated by the isoluble immunoglobulin aggregates was inhibited by staurosporine (and hence largely dependent on the activity of protein kinase C), the activity stimulated by the soluble immunoglobulin aggregates was staurosporine-insensitive. The soluble immunoglobulin aggregates were present at significantly higher levels in synovial fluids from patients with rheumatoid arthritis compared with those from other joint arthropathies. Thus rheumatoid synovial fluids possess heterogeneous immunoglobulin aggregates which activate neutrophils via distinct molecular pathways. As neutrophils within rheumatoid joints are primed, the soluble immunoglobulin aggregates are likely to be of importance in disease pathology.

Leucocyte integrin and CR1 expression on peripheral blood leucocytes of patients with rheumatoid arthritis

Expression of the leucocyte integrins (CD11a, b, c/CD18) and of CD35 (CR1) on leucocytes from the peripheral blood of patients with rheumatoid arthritis (RA) (n = 14) and control subjects (n = 12) was measured by flow cytometry using a rapid fixation and leucocyte preparation procedure. The mean (SE) percentages of lymphocytes expressing CD11a (RA 93.4 (1.7)%; controls 97.2 (1.8)%) and CD18 (RA 91.3 (2.3)%; controls 97.0 (2.6)%) were lower and the percentage of monocytes expressing CD11b (RA 86.9 (11.4)%; controls 78.4 (11.9)%) and CR1 (RA 62.6 (15.5)%; controls 36.6 (17.6)%) were higher in patients with RA than in controls. In addition, the mean fluorescence intensity of CD18 (RA 22.1 (2.3); controls 30.7 (2.5)) on lymphocytes was decreased and that of CD11b (RA 4.5 (0.8); controls 2.9 (0.9)) and CR1 (RA 2.4 (0.4); controls 1.5 (0.5)) on monocytes was increased in patients with RA compared with controls. The functional importance (if any) of the altered expression of the antigens on lymphocytes is not yet known. Altered expression on monocytes is consistent with activation within the circulation.

Analysis of function-associated receptor molecules on peripheral blood and synovial fluid granulocytes from patients with rheumatoid and reactive arthritis

In this study we report the expression pattern of 13 different function-associated surface molecules on synovial fluid and peripheral blood granulocytes from rheumatoid and reactive arthritis patients. We found increased expression of the complement receptors 1 (CD35) and 3 (CD11b) and of the activation-associated antigens CD67, CD24, and M5 on synovial fluid granulocytes from rheumatoid and/or reactive arthritis patients compared to autologous peripheral blood granulocytes. In addition, synovial fluid granulocytes expressed IgG Fc receptor 1 (CD64) and complement receptor 4 (CD11c), neither of which can be found on peripheral blood granulocytes. Peripheral blood granulocytes from rheumatoid and reactive arthritis patients expressed higher levels of leucocyte function-associated antigen 1 (CD11a) and of the membrane proteins CD31, CD24, M5, and M6 compared to peripheral blood granulocytes from healthy controls and patients with degenerative joint disease. No significant differences in the expression of any of the molecules studied could be observed between cells from rheumatoid and cells from reactive arthritis patients, suggesting a similar activation process for granulocytes in these two diseases.

Activation of the neutrophil myeloperoxidase-H2O2 system by synovial fluid isolated from patients with rheumatoid arthritis

Synovial fluid isolated from 16 patients with rheumatoid arthritis activated luminol dependent chemiluminescence in bloodstream neutrophils, and the maximal activity stimulated varied over a 50-fold range. In contrast, these same fluids only activated a much lower range (two- to threefold) of maximal rates of lucigenin dependent chemiluminescence and cytochrome c reduction, two assays which only measure oxidant secretion which is independent of myeloperoxidase. Over 95% of the luminol dependent chemiluminescence activated by all samples was inhibited by azide (indicating its dependence upon myeloperoxidase), but anti-(myeloperoxidase) IgG (which specifically inhibits only the extracellular activity of this enzyme) only inhibited the response stimulated by some samples: those fluids which activated the highest luminol dependent chemiluminescence also stimulated the greatest activity of an extracellular myeloperoxidase-H2O2 system. A clear correlation was shown to exist between the activity of myeloperoxidase already present in the fluids (after its secretion from neutrophils in situ within the rheumatoid joint) and the ability of the fluid to activate luminol dependent chemiluminescence. It is concluded, therefore, that all synovial fluid samples tested possess almost equivalent levels of a factor(s) which activated O2-/H2O2 secretion and that the variations in the measured activity of the extracellular myeloperoxidase-H2O2 system are dependent upon the level of degranulation which had occurred within the joint.

Neutrophils isolated from the synovial fluid of patients with rheumatoid arthritis: priming and activation in vivo

The oxidative metabolism of neutrophils isolated from the bloodstream and synovial fluid of 16 patients with rheumatoid arthritis was compared by measuring the ability of neutrophils to generate luminol dependent chemiluminescence and to secrete O2-. Measurements of receptor mediated--that is, N-formyl-methionyl-leucyl-phenylalanine stimulated--activation or receptor and second message independent--that is phorbol myristate acetate stimulated--activation showed that synovial fluid neutrophils had biochemical characteristics to suggest that they had been either up-regulated (primed) or down-regulated (activated) in vivo. These conclusions were confirmed by comparison of these responses with the changes in oxidative metabolism observed during in vitro priming and activation of control neutrophils: synovial fluid neutrophils possessed lower levels of myeloperoxidase than paired bloodstream cells, and unlike bloodstream cells could not be primed in vitro. These data thus suggest that synovial fluid neutrophils have been exposed to both priming and activating agents within rheumatoid joints.

The leukocyte protein L1 in plasma and synovial fluid from patients with rheumatoid arthritis and osteoarthritis

L1 is a major granulocyte and monocyte protein, released during activation and turnover of such cells. Blood and synovial fluid (SF) from 41 patients with rheumatoid arthritis (RA) and 6 patients with osteoarthritis (OA), were analyzed for L1 and the acute phase proteins C-reactive protein, orosomucoid, haptoglobin, alpha 1-antitrypsin and albumin as well as for differential leukocyte count. L1 levels in plasma and SF showed highly significant differences (p less than 0.0001), between the RA and OA patients. All the OA patients had normal plasma concentrations of L1 and low concentrations of L1 in SF. All the RA patients had elevated plasma levels of L1 and high L1 concentrations in SF. In the RA patients, the ratios between the protein concentrations in SF and blood were 3.29 for L1 and less than or equal to 0.64 for the acute phase proteins. In the SF, the L1 levels did not correlate with the monocyte count, while a low, positive correlation was found between L1 and the granulocyte count. The high L1 concentrations observed in SF from RA patients probably reflected an increased turnover of leukocytes in the inflamed joints. In SF from RA patients, high L1 concentrations were found in joints with a high amount of swelling. The present study suggests that L1 may represent a marker of both local and systemic inflammation.