Rille Pullerits

Decreased levels of soluble receptor for advanced glycation end products in patients with rheumatoid arthritis indicating deficient inflammatory control.

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily being expressed as a cell surface molecule and binding a variety of ligands. One of these ligands is high-mobility group box chromosomal protein 1, a potent proinflammatory cytokine, expression of which is increased in synovial tissue and in synovial fluid of rheumatoid arthritis (RA) patients. The interaction of high-mobility group box chromosomal protein 1 with cell-surface RAGE leads to an inflammatory response. In contrast, the presence of soluble RAGE (sRAGE) may abrogate cellular activation since the ligand is bound prior to interaction with the surface receptor.Our aim was to analyse to what extent sRAGE is present in patients with chronic joint inflammation (RA) as compared with patients with non-inflammatory joint disease and with healthy subjects, and to assess whether there is an association between sRAGE levels and disease characteristics.Matching samples of blood and synovial fluid were collected from 62 patients with RA with acute joint effusion. Blood from 45 healthy individuals, synovial fluid samples from 33 patients with non-inflammatory joint diseases and blood from six patients with non-inflammatory joint diseases were used for comparison. sRAGE levels were analysed using an ELISA.RA patients displayed significantly decreased blood levels of sRAGE (871 ± 66 pg/ml, P < 0.0001) as compared with healthy controls (1290 ± 78 pg/ml) and with patients with non-inflammatory joint disease (1569 ± 168 pg/ml). Importantly, sRAGE levels in the synovial fluid of RA patients (379 ± 36 pg/ml) were lower than in corresponding blood samples and correlated significantly with blood sRAGE. Interestingly, a significantly higher sRAGE level was found in synovial fluid of RA patients treated with methotrexate as compared with patients without disease-modifying anti-rheumatic treatment.We conclude that a decreased level of sRAGE in patients with RA might increase the propensity towards inflammation, whereas treatment with methotrexate counteracts this feature.

Resistin in serum is associated with higher levels of IL-1Ra in post-menopausal women with rheumatoid arthritis

OBJECTIVES The aim of this study was to investigate associations between serum levels of resistin, an adipokine and markers of inflammation, bone metabolism, plasma lipids and kidney function in post-menopausal RA patients and to evaluate if HRT during 2 yrs affected resistin levels. METHODS Eighty-eight women were randomly allocated to receive HRT, vitamin D(3) and calcium or vitamin D(3) and calcium alone. Serum levels of resistin, IL-1beta, IL-1 receptor antagonist (IL-1Ra), IL-6, IL-6 soluble receptor, TNF-alpha were measured by ELISA, markers of bone metabolism, carboxyterminal cross-linked telopeptide of type I collagen (ICTP) and carboxyterminal propeptide of type I procollagen by RIA, ESR, CRP, Hb, creatinine and lipids by standard laboratory techniques, BMD and total lean mass (TLM) by DXA and joint destruction by Larsen score. Resistin was also measured in 42 healthy control women. RESULTS There was no difference in resistin concentration between patients and healthy controls. Resistin was significantly correlated with IL-1Ra, CRP, TNF-alpha, ICTP, glucocorticosteroids and Larsen score and inversely with BMD, hip and with TLM. In multiple regression analysis, IL-1Ra, TLM and use of corticosteroids remained determinants of resistin. Patients treated with HRT displayed significant increase in resistin compared with controls in the first but not the second year. CONCLUSIONS Resistin was associated with increased inflammation, particularly by the acute-phase reactant IL-1Ra antagonizing IL-1beta, joint destruction, glucocorticosteroids and with reduced BMD and TLM. These findings suggest resistin being a significant mediator in the inflammatory process in RA. Further studies examining the mechanisms behind the relation between resistin and IL-1Ra are encouraged. HRT does not seem to have important long-term effect on resistin.

The Combination of a Tumor Necrosis Factor Inhibitor and Antibiotic Alleviates Staphylococcal Arthritis and Sepsis in Mice

BACKGROUND Despite advances in medical practices, in recent decades permanent reductions in joint function have not been achieved, and the high mortality rate of patients with staphylococcal septic arthritis has not substantially improved. METHODS We evaluated the effects of a combined tumor necrosis factor (TNF) inhibitor and antibiotic therapy on the course of Staphylococcus aureus arthritis and sepsis in mice. RESULTS Treatment with the combination of a TNF inhibitor and an antibiotic resulted in a quicker relief of clinical arthritis in mice with septic arthritis, compared with an antibiotic monotherapy. Both histopathologically verified synovitis and the extent of joint destruction were reduced by this combined treatment. Importantly, anti-TNF treatment significantly improved the survival rate of mice with S. aureus sepsis and staphylococcal enterotoxin shock syndrome; this effect might be the result of a partial restoration of the hemostatic balance between coagulation and fibrinolysis. Finally, we demonstrated that anti-TNF treatment downregulates high-mobility group protein B1 in staphylococcal enterotoxin shock syndrome. CONCLUSIONS Thus, simultaneous systemic TNF inhibition and antibiotic therapy has beneficial effects on the outcome of S. aureus arthritis and sepsis in a mouse model, suggesting that the combination of a TNF inhibitor and antibiotics represents a novel therapeutic strategy for the treatment of staphylococcal infections.

HMGB1 levels are increased in patients with juvenile idiopathic arthritis, correlate with early onset of disease, and are independent of disease duration.

Objective. High mobility group box chromosomal protein 1 (HMGB1) has been implicated as a mediator of inflammation in rheumatoid arthritis (RA), while its role in juvenile idiopathic arthritis (JIA) has not been described. To evaluate the role of HMGB1 in the inflammatory process in JIA and its potential as a therapeutic target, we investigated whether extracellular HMGB1 is detectable in JIA and if so, to correlate the levels with established inflammatory markers and clinical measures. Methods. Matching samples of blood and synovial fluid (SF) were collected from 23 patients with JIA. Levels of HMGB1, soluble receptor for advanced glycation endproducts, S100A12, myeloid-related protein 8/14, and other inflammatory mediators were analyzed. Results. Significantly increased HMGB1 levels were recorded in SF compared to blood samples from patients with JIA. The amount of HMGB1 was highest in patients with early disease onset irrespective of disease duration. In contrast, the proinflammatory S100 protein and interleukin 8 were highest in patients in early phases of disease. Matrix metalloproteinase-3, a marker of cartilage destruction, was higher in patients with late disease onset, indicating similarities with RA in that patient subgroup. Conclusion. Levels of extracellular HMGB1 are increased in the inflamed joints of patients with JIA. This warrants further studies of HMGB1 as a mediator of JIA pathogenesis as well as a biomarker for inflammatory activity and as a target for therapy. The variation in levels of HMGB1 and S100 proteins in relation to disease onset indicates a difference in inflammatory phenotype during disease progression.

Antibiotic-killed Staphylococcus aureus induces destructive arthritis in mice.

Permanent reduction in joint function is a severe postinfectious complication in patients with Staphylococcus aureus septic arthritis. We undertook this study to determine whether this reduction in joint function might be caused by persistent joint inflammation after the adequate eradication of bacteria by antibiotics.

Induction of arthritis by high mobility group box chromosomal protein 1 is independent of tumour necrosis factor signalling

IntroductionTNFα and high mobility group box chromosomal protein 1 (HMGB1) are two potent proinflammatory cytokines implicated as important mediators of arthritis. Increased levels of these cytokines are found in the joints of rheumatoid arthritis patients, and the cytokines trigger arthritis when applied into the joints of naïve mice. HMGB1 is actively released from immune cells in response to TNFα; once released, HMGB1 in turn induces production of several proinflammatory cytokines – including IL-6 and TNFα – by macrophages. Whether HMGB1-induced arthritis is mediated via the TNFα pathway, however, is unknown. The purpose of the present study was to investigate whether the arthritis-inducing effect of HMGB1 is dependent on TNFα expression in vivo and to assess whether TNFα deficiency affects a proinflammatory cytokine response to HMGB1 in vitro.MethodsTNFα knockout mice and backcrossed control animals on a C57Bl6 background were injected intraarticularly with 5 μg HMGB1. Joints were dissected 3 days after intraarticular injection and were evaluated histologically by scoring the frequency and severity of arthritis. For in vitro studies, mouse spleen cultures from TNFα knockout mice and from control mice were incubated with different doses of HMGB1, and cell culture supernatants were collected at different time points for analysis of IL-6.ResultsIntraarticular injection of HMGB1 into healthy mouse joints resulted in an overall frequency of 32% to 39% arthritic animals. No significant differences were found with respect to the severity and incidence of synovitis between mice deficient for TNFα (seven out of 18 mice with arthritis) in comparison with control TNFα+/+ animals (six out of 19). No significant differences were detected between spleen cells from TNFα+/+ mice versus TNFα-/- mice regarding IL-6 production upon stimulation with highly purified HMGB1 after 24 hours and 48 hours. Upon stimulation with a suboptimal dose of recombinant HMGB1, however, the splenocytes from TNFα+/+ animals released significantly more IL-6 than cells from the knockout mice (602 ± 112 pg/ml and 304 ± 50 pg/ml, respectively; P < 0.05).ConclusionOur data show that HMGB1-triggered joint inflammation is not mediated via the TNF pathway. Combined with our previous study, we suggest that HMGB1-triggered arthritis is probably mediated through IL-1 activation.

IL-1 Receptor Antagonist Treatment Aggravates Staphylococcal Septic Arthritis and Sepsis in Mice

Background Interleukin-1 receptor antagonist (IL-1Ra) is the primary therapy against autoinflammatory syndromes with robust efficacy in reducing systemic inflammation and associated organ injury. However, patients receiving IL-1Ra might be at increased risk of acquiring serious infections. Aims To study whether IL-1Ra treatment deteriorates Staphylococcus aureus (S. aureus) septic arthritis and sepsis in mice. Method NMRI mice were treated with anakinra (IL-1Ra) daily for 7 days before intravenous inoculation with S. aureus strain Newman in both arthritogenic and lethal doses. The clinical course of septic arthritis, histopathological and radiological changes of the joints, as well as the mortality were compared between IL-1Ra treated and control groups. Results IL-1Ra treated mice developed more frequent and severe clinical septic arthritis. Also, the frequency of polyarthritis was significantly higher in the mice receiving IL-1Ra therapy. In line with the data from clinical arthritis, both histological and radiological signs of septic arthritis were more pronounced in IL-1Ra treated group compared to controls. Importantly, the mortality of IL-1Ra treated mice was significantly higher than PBS treated controls. Conclusion IL-1Ra treatment significantly aggravated S. aureus induced septic arthritis and increased the mortality in these mice.

Serum Levels of HMGB1 in Postmenopausal Patients with Rheumatoid Arthritis: Associations with Proinflammatory Cytokines, Acute-phase Reactants, and Clinical Disease Characteristics

To the Editor: High mobility group box 1 (HMGB1) chromosomal protein, an endogenous molecule with multiple intra- and extracellular effects, is also defined as a novel proinflammatory cytokine, proved to contribute to the pathogenesis of several rheumatic diseases1. Evidence grows showing that HMGB1 plays a role as an important endogenous mediator of arthritis. Significantly elevated levels of HMGB1 are reported in the sera and synovial fluid of patients with rheumatoid arthritis (RA) as compared to patients with osteoarthritis2. Levels of HMGB1 are increased in the synovial tissues of animals and humans with joint inflammation3. HMGB1 mediates the development of arthritis when applied into the joints of naive mice4 and treatment strategies directed against HMGB1 attenuate progression in collagen-induced arthritis1. In RA, characterized by chronic autoimmune destructive joint inflammation, extensive production of proinflammatory cytokines is known to mediate tissue damage. HMGB1, either released actively from myeloid and dendritic cells or passively during local cell death in the joint, could sustain chronic synovitis by several mechanisms including an augmentation of production of several proinflammatory mediators such as interleukin 1 (IL-1), tumor necrosis factor-α (TNF-α), and IL-6, all known to be important in the pathogenesis of arthritis5. In a cross-sectional study, we investigated the relationship between concentrations of HMGB1 and proinflammatory cytokines and disease characteristics in a cohort6 of 81 postmenopausal patients with RA. The … Address correspondence to Dr. R. Pullerits, The Sahlgrenska Academy, University of Gothenburg, Department of Rheumatology and Inflammation Research, Guldhedsgatan 10A, 41346, Gothenburg, Sweden. E-mail: rille.pullerits{at}rheuma.gu.se

CTLA4 Immunoglobulin but Not Anti–Tumor Necrosis Factor Therapy Promotes Staphylococcal Septic Arthritis in Mice

BACKGROUND The development of biologics has greatly increased the quality of life and the life expectancy of many patients with rheumatoid arthritis. However, a large number of these patients have an increased risk of developing serious infections. The aim of this study was to examine differential effects of anti-tumor necrosis factor (TNF) treatment and CTLA4 immunoglobulin (Ig) treatment on both immunological response and host defense in a murine model of septic arthritis. METHODS Abatacept (CTLA4-Ig), etanercept (anti-TNF), or phosphate-buffered saline were given to NMRI mice intravenously inoculated with Staphylococcus aureus. The clinical course of septic arthritis and histopathological and radiological changes of joints were compared among the groups. RESULTS Mice receiving CTLA4-Ig treatment had more-severe septic arthritis, compared with controls and mice receiving anti-TNF treatment. Anti-TNF treatment led to more-severe weight loss and kidney abscesses, as well as a higher bacterial burden in the kidneys. Mice receiving CTLA4-Ig therapy had lower serum levels of interleukin 4, whereas mice receiving anti-TNF therapy had higher levels of TNF-α. Both iNOS and arginase-1 expression were reduced in peritoneal macrophages from mice receiving CTLA4-Ig, compared with expression in the anti-TNF group. CONCLUSIONS CTLA4-Ig therapy significantly increased the susceptibility to S. aureus septic arthritis in mice, whereas anti-TNF therapy deteriorated host bacterial clearance, resulting in more-severe weight loss and kidney abscesses.

The decrease of soluble RAGE levels in rheumatoid arthritis patients following hormone replacement therapy is associated with increased bone mineral density and diminished bone/cartilage turnover: a randomized controlled trial

OBJECTIVE The aim of the study was to prospectively investigate the effects of HRT on serum soluble receptor for advanced glycation end product (sRAGE) levels in RA patients and to determine whether sRAGE production is related to bone/cartilage metabolism. METHODS Eighty-eight post-menopausal RA patients were randomized to receive vitamin D3 and calcium supplementation with or without HRT (oestradiol plus noretisterone acetate). The levels of total sRAGE in sera were measured before, 1 and 2 years after treatment initiation. Potential associations between sRAGE levels, bone/cartilage metabolic markers and BMD were investigated. RESULTS Patients receiving HRT displayed significantly decreased levels of serum sRAGE at 1 and 2 years as compared with levels at study entry. The increase in serum oestradiol was associated with the decline in sRAGE levels. Importantly, sRAGE levels at baseline significantly correlated with bone/cartilage turnover markers including C-terminal propeptide of type I procollagen, carboxyterminal telopeptide of type I collagen and cartilage oligomeric matrix protein, and the decrease of sRAGE levels paralleled with diminished concentration of these molecules. BMD in hip and femoral neck and progression of Larsen score at 1 year were associated with baseline sRAGE levels. The decline in sRAGE levels significantly correlated with an increase in total BMD following 2 years of treatment in patients receiving HRT but not in the control group. CONCLUSION Our findings suggest that HRT decreases the levels of endogenous sRAGE in post-menopausal RA patients implicating its role in sRAGE regulation. In addition, serum sRAGE was associated with BMD and markers of bone/cartilage metabolism. These data suggest that sRAGE is involved directly or indirectly in bone metabolism. Trial registration. Current Controlled Trials, ISRCTN46523456, http://www.controlled-trials.com/isrctn/search.html?srch=ISRCTN46523456.