Impaired polymorphonuclear leucocyte chemotaxis in rheumatoid arthritis

RA-map: building a state-of-the-art interactive knowledge base for rheumatoid arthritis

Rheumatoid arthritis (RA) is a progressive, inflammatory autoimmune disease of unknown aetiology. The complex mechanism of aetiopathogenesis, progress and chronicity of the disease involves genetic, epigenetic and environmental factors. To understand the molecular mechanisms underlying disease phenotypes, one has to place implicated factors in their functional context. However, integration and organization of such data in a systematic manner remains a challenging task. Molecular maps are widely used in biology to provide a useful and intuitive way of depicting a variety of biological processes and disease mechanisms. Recent large-scale collaborative efforts such as the Disease Maps Project demonstrate the utility of such maps as versatile tools to organize and formalize disease-specific knowledge in a comprehensive way, both human and machine-readable. We present a systematic effort to construct a fully annotated, expert validated, state-of-the-art knowledge base for RA in the form of a molecular map. The RA map illustrates molecular and signalling pathways implicated in the disease. Signal transduction is depicted from receptors to the nucleus using the Systems Biology Graphical Notation (SBGN) standard representation. High-quality manual curation, use of only human-specific studies and focus on small-scale experiments aim to limit false positives in the map. The state-of-the-art molecular map for RA, using information from 353 peer-reviewed scientific publications, comprises 506 species, 446 reactions and 8 phenotypes. The species in the map are classified to 303 proteins, 61 complexes, 106 genes, 106 RNA entities, 2 ions and 7 simple molecules. The RA map is available online at ramap.elixir-luxembourg.org as an open-access knowledge base allowing for easy navigation and search of molecular pathways implicated in the disease. Furthermore, the RA map can serve as a template for omics data visualization.

Neutrophils activation can be diminished by apolipoprotein A-I

High density lipoprotein (HDL) has anti-inflammatory function. To investigate the effects of apolipoprotein A-I (ApoA-I), the major apolipoprotein of HDL, on activated neutrophils, we stimulated neutrophils in vitro with fMLP and PMA, as a receptor-binding and a nonreceptor-binding stimuli, respectively, and incubated ApoA-I with those neutrophils. Three conditions were utilized: 1) resting neutrophils + ApoA-I (0, 2.5,5, 10 microg/mL respectively), 2) fMLP(10(-7) mol/L)-activated neutrophils + ApoA-I (0, 2.5, 5, 10 microg/mL respectively), and 3) PMA(10(-7) mol/L)-activated neutrophils + ApoA-I (0, 2.5, 5, 10 microg/mL respectively). After incubation, we measured neutrophils adhesion to fibronectin, oxidative bust (O2- and H2O2 production), degranulation (release of MPO and elastase), and L929 cell mortality which were attacked by release-out of cytokines in activated neutrophils (using MTT). Our results showed that in vitro ApoA-I inhibits fMLP- and PMA- activated neutrophil adhesion, oxidative burst, degranulation and L929 cell mortality. These inhibition effects of ApoA-I on fMLP-activated neutrophils are more powerful than that on PMA-activated neutrophils. ApoA-I has no effect on resting neutrophils. We concluded that ApoA-I could diminish the function of activated neutrophils.

Abnormal directed migration of blood polymorphonuclear leukocytes in rheumatoid arthritis. Potential role in increased susceptibility to bacterial infections

Rheumatoid arthritis (RA) patients are at higher risks of bacterial infection than healthy subjects. Polymorphonuclear leukocytes (PMN) are the first line of nonspecific cellular defence against these infections. We tested the hypothesis that abnormal directed migration of PMN may be one reason for the increased infection rate of RA patients. PMN migration was investigated in 68 peripheral blood samples of 15 RA patients compared with 64 samples of healthy controls in a novel whole blood in vitro membrane filter assay. The migration of PMNs from RA patients and controls was stimulated using the bacterial chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMLP). Unstimulated PMN migration of RA patients was increased compared with healthy controls as measured by the following parameters: (a) absolute number of migrant PMNs (1954+/-87 vs. 1238 +/-58 PMN/mm2), (b) percentage of PMNs migrated into the filter (total migration index, TMI) (28.6+/-0.9 vs. 24.0+/-0.8%), (c) the distance half the migrating PMNs had covered (distribution characteristic, DC) (22.6+/-1.1 vs. 16.1+/-0.6 mm) and (d) the product of TMI and DC (neutrophil migratory activity, NMA) (669.0+/-45.0 vs. 389.0+/-18.9). fMLP stimulated PMNs of RA patients showed defective migration compared to unstimulated samples as shown by (a) a reduced number of migrant PMNs (1799+/-93 PMN/mm2), (b) lower TMI (26.1+/-0.9%), (c) unremarkable altered distribution characteristic (22.9+/-0.8 mm) and (d) significant reduced migratory activity (600.0+/-30.0). Our data suggest that the high incidence of infections in RA patients may partly be caused by defective migratory activity of PMNs to bacterial chemoattractants as demonstrated by fMLP.

Intracellular demonstration of active TGFbeta1 in B cells and plasma cells of autoimmune mice. IgG-bound TGFbeta1 suppresses neutrophil function and host defense against Staphylococcus aureus infection

Infection remains a leading cause of morbidity and mortality in patients with SLE. To investigate this, previously we assessed the host defense status of autoimmune MRL/lpr mice and found that elaboration of active TGFbeta suppressed neutrophil function and decreased survival in response to Staphylococcus aureus infection. The purpose of the present work was to elucidate the molecular form and the cellular source of the active TGFbeta involved. Here, we report for the first time that TGFbeta1 is found in the active form inside B cells and plasma cells and that it circulates in the plasma complexed with IgG in two murine models of systemic autoimmunity and in some patients with SLE. IgG-bound active TGFbeta1 is many times more potent than uncomplexed active TGFbeta1 for suppression of neutrophil function in vitro and host defense against S. aureus infection in vivo. These data indicate that TGFbeta1 is in the active form inside B cells and plasma cells, that the formation of a complex of IgG and active TGFbeta1 is greatly accelerated in autoimmunity, and that this complex is extremely potent for suppression of PMN function and host defense against bacterial infection.

Effects of methotrexate, sulphasalazine and aurothiomalate on polymorphonuclear leucocytes in rheumatoid arthritis

The aim of the study was to evaluate the effects of treatment with methotrexate, sulphasalazine and aurothiomalate on polymorphonuclear leucocytes (PMN) in rheumatoid arthritis (RA). Circulating PMNs from 58 RA patients treated with either methotrexate (n = 27), sulphasalazine (n = 16) or aurothiomalate (n = 15) were assayed for their chemotactic capacity and generation of superoxide anions. The expression of CD18/CD11b was measured for 17 RA patients treated with methotrexate. Chemotaxis and generation of superoxide anions were not affected by any of the three drugs. We found no difference in the expression of CD18/CD11b in RA patients treated with methotrexate compared to healthy subjects. Further methotrexate and aurothiomalate did not in vitro alter chemotaxis, generation of superoxide anion or expression of CD18/CD11b on normal PMNs. In conclusion we found no evidence that the effect of methotrexate, aurothiomalate or sulphasalazine in RA can be explained by modulation of chemotactic ability or superoxide anion generation of peripheral circulating PMNs.

Spontaneous elaboration of transforming growth factor beta suppresses host defense against bacterial infection in autoimmune MRL/lpr mice

Infection with gram-negative and gram-positive bacteria remains a leading cause of death in patients with systemic lupus erythematosis (SLE), even in the absence of immunosuppressive therapy. To elucidate the mechanisms that underly the increased risk of infection observed in patients with systemic autoimmunity, we have investigated host defense against bacterial infection in a murine model of autoimmunity, the MRL/Mp-lpr/lpr (MRL/lpr) mouse. Our previous study implicated transforming growth factor beta (TGF-beta) in a novel acquired defect in neutrophil function in MRL/lpr but not congenic MRL/Mp-+/+ (MRL/n) mice (Gresham, H.D., C.J. Ray, and F.K. O'Sullivan. 1991. J. Immunol. 146:3911). We hypothesized from these observations that MRL/lpr mice would have defects in host defense against bacterial infection and that they would have constitutively higher local and systemic levels of active TGF-beta which would be responsible, at least in part, for the defect in host defense. We show in this paper that spontaneous elaboration of active TGF-beta adversely affects host defense against both gram-negative and gram-positive bacterial infection in MRL/lpr mice. Our data indicate that MRL/lpr mice, as compared with congenic MRL/n mice, exhibit decreased survival in response to bacterial infection, that polymorphonuclear leukocytes (PMN) from MRl/lpr mice fail to migrate to the site of infection during the initial stages of infection, that MRL/lpr mice have a significantly increased bacterial burden at the site of infection and at other tissue sites, and that this increased bacterial growth occurs at a time (> 20 h after infection) when PMN influx is greatly enhanced in MRL/lpr mice. Most intriguingly, the alteration in PMN extravasation during the initial stages of infection and failure to restrict bacterial growth in vivo could be duplicated in MRL/n mice with a parenteral injection of active TGF-beta 1 at the time of bacterial challenge. Moreover, these alterations in host defense, including survival in response to lethal infection, could be ameliorated in MRL/lpr mice by the parenteral administration of a monoclonal antibody that neutralizes the activity of TGF-beta. These data indicate that elaboration of TGF-beta as a result of autoimmune phenomenon suppresses host defense against bacterial infection and that such a mechanism could be responsible for the increased risk of bacterial infection observed in patients with autoimmune diseases.

Migratory activity of blood polymorphonuclear leukocytes during juvenile rheumatoid arthritis, demonstrated with a new whole-blood membrane filter assay

Polymorphonuclear leukocyte (PMN) migration is measured in whole blood in a migration chamber consisting of a membrane filter (3-microns pores, 140 microns thick) with an integrated chemoattractant depot (FMLP in solid form) attached to a plastic container. Control chambers lack FMLP (blanks). One test unit requires 300 microliters blood. Numbers and distribution of the PMN immigrants into the filters are determined microscopically. Altogether 26 measurements of PMN migration in five juvenile rheumatoid arthritis (JRA) patients with varying disease activity were compared with the reactions of a healthy control group (N = 32). Correlations were calculated with conventional laboratory parameters (WBC, PLT, BSR, CRP, Hgb, serum Fe) and disease activity. In comparison with healthy controls, PMNs of JRA patients generally show a markedly increased penetration depth into the filters irrespective the presence of the chemoattractant or the disease activity. Increased migratory reactions to FMLP in comparison to blanks were found during high disease activity only. The PMN penetration depth correlates positively with the CRP, and reciprocally with the Hgb blood levels. The migration assay combines fast and simple processing with good preservation of the genuine PMN activation state.

Functions of polymorphonuclear leukocytes in early rheumatoid arthritis

We carried out a prospective study on clinical variables and functions of polymorphonuclear leukocytes (PMNs) of 20 patients with early rheumatoid arthritis (RA) and compared the results with the presence of erosions before treatment and at a one-year follow-up. Migration of PMNs determined by agarose and filter assays and respiratory burst of PMNs determined by luminol-enhanced chemiluminescence (CL) test were studied both before starting RA-modifying treatment and 6-12 (mean 7.3) months later. PMNs of the patients without erosions at one year, as compared to the patients with erosions, showed significantly depressed migration into filter and significantly depressed CL responses to N-formyl-methionyl-leucyl-phenylalanine, both before starting the treatment and at 7.3 months. Although causality remains uncertain, the results suggest that depressed functional capacity of PMNs is associated with low risk of joint destruction in early RA.

Chemotaxis and chemiluminescence responses of synovial fluid polymorphonuclear leucocytes during acute reactive arthritis

The chemotaxis and chemiluminescence responses of polymorphonuclear leucocytes (PMN) of synovial fluid and peripheral blood from patients with acute reactive arthritis were studied. Rates of chemotactic and chemokinetic migration of synovial fluid PMN were significantly decreased. In addition, chemiluminescence responses tended to be depressed, suggesting that the cells were deactivated for both chemotaxis and production of oxygen derived free radicals. Such deactivation has been described previously as a characteristic of synovial fluid PMN in rheumatoid arthritis. Compared with those with a mild disease, patients with severe acute reactive arthritis had higher chemiluminescence responses of synovial fluid PMN to phorbol myristate acetate during acute disease and developed increased migration of peripheral blood PMN towards zymosan treated serum after recovery from the disease. This supports the view that hyperreactive PMN contribute to the development of severe inflammatory symptoms in acute reactive arthritis.

Inhibition of leukotriene B4 synthesis in neutrophils from patients with rheumatoid arthritis by a single oral dose of methotrexate

We studied the effects of a single, oral dose of methotrexate (MTX) on arachidonic acid metabolism in neutrophils from 6 patients with rheumatoid arthritis, which were obtained 1 day before and 1 day after their usual weekly MTX dose. The 6 patients had received a mean weekly MTX dose of 9.6 mg (range 5-15) for a mean of 61.7 months (range 58-64), and none received concomitant corticosteroids. Total generation of leukotriene B4 (LTB4) in neutrophils stimulated ex vivo with 10 microM calcium ionophore A23187 for 20 minutes was significantly suppressed, by a mean of 53%, after the MTX dose compared with the predose levels (mean +/- SEM 13.0 +/- 1.4 ng/10(6) cells versus 6.0 +/- 0.9 ng/10(6) cells; P = 0.0019), reflecting a comparable suppression of both released and cell-retained LTB4. A 49% decrease in omega-oxidation products of LTB4 demonstrates that decreased LTB4 synthesis, rather than increased degradation, is responsible for the decrease in LTB4 generation. The absence of a significant change in either 3H-labeled arachidonic acid release or platelet-activating factor generation indicates that the observed decrease in LTB4 synthesis was apparently not caused by diminished phospholipase A2 activity. A 28% decrease in the total formation of the 5-lipoxygenase products 5-hydroxyeicosatetraenoic acid and the 6-trans-LTB4 diastereoisomers, and a 48% suppression of production of LTB4 plus its omega-oxidation metabolites after the MTX dose suggest inhibition of 5-lipoxygenase activity and possible suppression of leukotriene A4 epoxide hydrolase activity.

Changes in PMN leukocyte migration activity and complement C3d levels in RA patients with high disease activity during steroid treatment

We have investigated chemotaxis of polymorphonuclear granulocytes (PMN) from 7 well characterized RA patients with intense disease activity, before and after steroid treatment. Increased spontaneous and directed granulocyte migration was observed in 6 out of 7 patients before steroid treatment. In 5 patients these parameters were reduced after treatment. In contrast to this, decreased chemotaxis of polymorphonuclear granulocytes (PMN) from patients with Rheumatoid Arthritis (RA), have been reported earlier. This has been suggested as a partial explanation of the increased morbidity of these patients. Plasma levels of Complement C3d were initially increased in all patients and were slightly reduced following treatment. PMN migration in highly active RA cases is increased and responds markedly to steroid treatment, in contrast to the complement activation. The mainly unaffected, increased levels of plasma C3d might, in part, explain the early recurrence of symptoms often seen when steroid medication is withdrawn. Our results contrast with earlier findings and need to be confirmed in further studies.

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

The level of expression of surface antigens was studied on neutrophils from paired samples of blood and synovial fluid of patients with rheumatoid arthritis (RA). By measuring the immunofluorescence of labelled monoclonal antibodies it was shown that on joint neutrophils there was an increase in expression of complement receptor 3 (CR3) and granulocyte functional antigens 1 and 2 compared with blood neutrophils, whereas the expression of GpIIb-IIIa was reduced. The pattern of expression was the same as that seen with in vitro activation and strongly suggest that activation is occurring within the joint.

HLA-B51 may serve as an immunogenetic marker for a subgroup of patients with Behçet's syndrome

Epidemiologic data, family history, clinical data, HLA typing, neutrophilic chemotaxis, and immunofluorescence of clinically normal non-sun-exposed skin were studied in 46 Israeli non-Ashkenazi Jewish and Arab patients with Behçet's syndrome. HLA-B51 was present in 71 percent of the patient group as compared with 13 percent of the control group (relative risk = 17.1). In four of 30 families in the B51-positive group, there was a close relative of the proband with Behçet's syndrome who was carrying the HLA-B51 antigen. Neutrophilic chemotaxis in this group was enhanced in 80 percent of the patients, and in most patients no deposition of immunoglobulin in the dermo-epidermal junction was observed, whereas C3 was present in papillary vessels. In the B51-negative group, the family history was negative for Behçet's syndrome, neutrophilic chemotaxis was enhanced in only two of eight patients, and in four of six patients, IgM deposition was detected in the dermo-epidermal junction. It is concluded that in Israeli non-Ashkenazi Jews and Arabs, there is a significant association between HLA-B51 and the risk of developing Behçet's syndrome. The B51-positive patient group has a family history of the disease, enhanced neutrophilic chemotaxis, and a lack of immunoglobulin deposition in the dermo-epidermal junction.

Pathogenesis of rheumatoid arthritis

Many types of cells are activated and transformed in rheumatoid synovium, thereby contributing to amplification of the disease process. The immune response in rheumatoid arthritis is probably initiated by an antigen, although there is some evidence that anticollagen antibodies develop in response to tissue destruction, after rheumatoid arthritis has evolved clinically. Early inflammation in the synovium is characterized by a striking vascular proliferation, occurring in response to angiogenesis factors released by activated macrophages. Generalized activation of macrophages and lymphocytes typical of the immune reaction in the synovium generates antibody production, including production of rheumatoid factor. Data suggest that immune complexes deposited within cartilage attract polymorphonuclear leukocytes, which then release enzymes onto the cartilage surface. Many products of inflammation act as mediators, driving proliferation of synovial cells. Stellate cells, macrophages, and fibroblasts have been found along the pannus/cartilage junction; by various interactions, these contribute to destruction of cartilage and bone.

Changes in normal polymorphonuclear leucocyte motility after ingestion of IgG aggregates

Changes in normal polymorphonuclear leucocyte (PMN) motility after membrane-binding and internalisation of IgG aggregates (a model of soluble immune complexes) have been studied by the micropore filter assay. The results have confirmed that IgG aggregates stimulate as well as inhibit PMN chemotaxis. These effects are dependent on the size and concentration of the IgG aggregates in solution as well as the length of time of incubation. Stimulated chemotaxis was observed in a small subset of the whole PMN population which was apparent only when cell distribution through the filters was analysed. These results indicate the need for caution when drawing conclusions about PMN function from results obtained by these assay techniques.