Matrix metalloproteinases in arthritis: towards precision medicine.

Proteolysis of structural molecules of the extracellular matrix (ECM) is an irreversible post-translational modification in all arthropathies. Common joint disorders, including osteoarthritis and rheumatoid arthritis, have been associated with increased levels of matrix remodelling enzymes, including matrix metalloproteinases (MMPs). MMPs, in concert with other host proteinases and glycanases, destroy proteoglycans, collagens and other ECM molecules. MMPs may also control joint remodelling indirectly by signalling through cell-surface receptors or by proteolysis of cytokines and receptor molecules. After synthesis as pro-forms, MMPs can be activated by various types of post-translational modifications, including proteolysis. Once activated, MMPs are controlled by general and specific tissue inhibitors of metalloproteinases (TIMPs). In rheumatoid arthritis, proteolysis of the ECM results in so-called remnant epitopes that enhance and perpetuate autoimmune processes in susceptible hosts. In osteoarthritis, the considerable production of MMP-13 by chondrocytes, often concurrent with mechanical overload, is a key event. Hence, information about the regulation, timing, localization and activities of MMPs in specific disease phases and arthritic entities will help to develop better diagnostics. Insights into beneficial and detrimental effects of MMPs on joint tissue inflammation are also necessary to plan and execute (pre)clinical studies for better therapy and precision medicine with MMP inhibitors. With the advances in proteomics and single-cell transcriptomics, two critical points need attention: neglected neutrophil MMP biology, and the analysis of net proteolytic activities as the result of balances between MMPs and their inhibitors.

Proteoform Analysis of Matrix Metalloproteinase-9/Gelatinase B and Discovery of Its Citrullination in Rheumatoid Arthritis Synovial Fluids.

Objectives: To explore posttranslational modifications (PTMs), including proteolytic activation, multimerization, complex formation and citrullination of gelatinases, in particular of gelatinase B/MMP-9, and to detect in gelatin-Sepharose affinity-purified synovial fluids, the presence of specific MMP proteoforms in relation to arthritis. Methods: Latent, activated, complexed and truncated gelatinase-A/MMP-2 and gelatinase B/MMP-9 proteoforms were detected with the use of zymography analysis to compare specific levels, with substrate conversion assays, to test net proteolytic activities and by Western blot analysis to decipher truncation variants. Citrullination was detected with enhanced sensitivity, by the use of a new monoclonal antibody against modified citrullines. Results: All MMP-9 and MMP-2 proteoforms were identified in archival synovial fluids with the use of zymography analysis and the levels of MMP-9 versus MMP-2 were studied in various arthritic diseases, including rheumatoid arthritis (RA). Secondly, we resolved misinterpretations of MMP-9 levels versus proteolytic activities. Thirdly, a citrullinated, truncated proteoform of MMP-9 was discovered in archival RA synovial fluid samples and its presence was corroborated as citrullinated hemopexin-less MMP-9 in a small prospective RA sample cohort. Conclusion: Synovial fluids from rheumatoid arthritis contain high levels of MMP-9, including its truncated and citrullinated proteoform. The combination of MMP-9 as analyte and its PTM by citrullination could be of clinical interest, especially in the field of arthritic diseases.

The Impact of a Group-Based Multidisciplinary Rehabilitation Program on the Quality of Life in Patients With Fibromyalgia: Results From the QUALIFIBRO Study.

BACKGROUND AND OBJECTIVE: Patients with fibromyalgia (FM) have a substantially reduced health-related quality of life (HRQoL). Their management should preferably focus on multidisciplinary nonpharmacological interventions. However, the long-term impact of such multicomponent therapies is not fully established. Waiting lists for patients seeking medical treatment are long, making individual-based approaches often unfeasible. The aim of our pragmatic study was to evaluate long-term HRQoL benefits of a comprehensive 8-week group-based multidisciplinary rehabilitation program focusing on patients' coping ability and self-care. METHODS: A total of 94 patients with clinically confirmed FM agreed to participate in this study. Before entering the program based on group-based cognitive behavioral therapy and graded activity training, patients completed questionnaires to screen for comorbidities. Health-related quality of life was assessed at the start, at 8 weeks, 6 months, and 1 year using the 36-Item Short-Form Health Survey instrument. Changes in HRQoL scores were analyzed according to linear mixed regression modeling. RESULTS: Baseline findings confirmed the substantially low physical and mental HRQoL in FM patients as well as high levels of depression, anxiety, and burnout. Only 2 patients left the program prematurely; 89% participated in the 1-year assessment. By the end of the program, HRQoL was significantly improved in all domains. This effect was maintained at 6 months and 1 year for all subscales. Changes at 1 year were greater in younger patients and those with depressive feelings before the start of treatment. CONCLUSIONS: Our group-based program offered to FM patients proved successful with significant improvements in their HRQoL both in the short and long term.

Clinical and radiological outcomes of 5-year drug-free remission-steered treatment in patients with early arthritis: IMPROVED study.

OBJECTIVES: To determine the 5-year outcomes of early remission induction therapy followed by targeted treatment aimed at drug-free remission (DFR) in patients with early arthritis. METHODS: In 12 hospitals, 610 patients with early (<2 years) rheumatoid arthritis (RA) or undifferentiated arthritis (UA) started on methotrexate (MTX) 25 mg/week and prednisone (60 mg/day tapered to 7.5 mg/day). Patients not in early remission (Disease Activity Score <1.6 after 4 months) were randomised (single blind) to arm 1, adding hydroxychloroquine 400 mg/day and sulfasalazine 2000 mg/day, or arm 2, switching to MTX plus adalimumab 40 mg/2 weeks. Treatment adjustments over time aimed at DFR. Outcomes were remission percentages, functional ability, toxicity and radiological damage progression after 5 years. RESULTS: After 4 months, 387 patients were in early remission, 83 were randomised to arm 1 and 78 to arm 2. After 5 years, 295/610 (48%) patients were in remission, 26% in sustained DFR (SDFR) (≥1 year) (220/387 (57%) remission and 135/387 (35%) SDFR in the early remission group, 50% remission, 11% SDFR in the randomisation arms without differences between the arms). More patients with UA (37% vs 23% RA, p=0.001) and more anticitrullinated protein antibody (ACPA)-negative patients (37% vs 18% ACPA-positive, p<0.001) achieved SDFR.Overall, mean Health Assessment Questionnaire was 0.6 (0.5), and median (IQR) damage progression was 0.5 (0-2.7) Sharp/van der Heijde points, with only five patients showing progression >25 points in 5 years. CONCLUSIONS: Five years of DFR-steered treatment in patients with early RA resulted in almost normal functional ability without clinically relevant joint damage across treatment groups. Patients who achieved early remission had the best clinical outcomes. There were no differences between the randomisation arms. SDFR is a realistic treatment goal.

Best cost-effectiveness and worker productivity with initial triple DMARD therapy compared with methotrexate monotherapy in early rheumatoid arthritis: cost-utility analysis of the tREACH trial.

OBJECTIVE: To evaluate direct and indirect costs per quality adjusted life year (QALY) for different initial treatment strategies in very early RA. METHODS: The 1-year data of the treatment in the Rotterdam Early Arthritis Cohort trial were used. Patients with a high probability (>70%) according to their likelihood of progressing to persistent arthritis, based on the prediction model of Visser, were randomized into one of following initial treatment strategies: (A) initial triple DMARD therapy (iTDT) with glucocorticoids (GCs) intramuscular (n = 91); (B) iTDT with an oral GC tapering scheme (n = 93); and (C) initial MTX monotherapy (iMM) with GCs similar to B (n = 97). Data on QALYs, measured with the Dutch EuroQol, and direct and indirect cost were used. Direct costs are costs of treatment and medical consumption, whereas indirect costs are costs due to loss of productivity. RESULTS: Average QALYs (sd) for A, B and C were, respectively, 0.75 (0.12), 0.75 (0.10) and 0.73 (0.13) for Dutch EuroQol. Highest total costs per QALY (sd) were, respectively, €12748 (€18767), €10 380 (€15 608) and €17 408 (€21 828) for strategy A, B and C (P = 0.012, B vs C). Direct as well as indirect costs were higher with iMM (strategy C) compared with iTDT (strategy B). Higher direct costs were due to ∼40% more biologic usage over time. Higher indirect costs, on the other hand, were caused by more long-term sickness and reduction in contract hours. iTDT was >95% cost-effective across all willingness-to-pay thresholds compared with iMM. CONCLUSION: iTDT was more cost-effective and had better worker productivity compared with iMM.

Two-year results of disease activity score (DAS)-remission-steered treatment strategies aiming at drug-free remission in early arthritis patients (the IMPROVED-study).

BACKGROUND: Early suppression of disease activity in (rheumatoid) arthritis (RA) patients may result in drug-free remission and prevent damage. We assessed 2-year clinical and radiological outcomes of two disease activity score (DAS)-remission-steered treatment strategies in early arthritis patients. METHODS: Patients (n = 610) with early RA or undifferentiated arthritis (UA) were treated with methotrexate (MTX) and tapered high dose of prednisone. Patients in early remission (44/53 joints DAS <1.6) after 4 months tapered and stopped medication. Patients who did not achieve early DAS-remission were randomized to either MTX plus hydroxychloroquine plus sulphasalazine plus low dose prednisone (arm 1) or to MTX + adalimumab (arm 2). At four-monthly intervals, medication was tapered and stopped if DAS was <1.6 but restarted, increased or switched if DAS was ≥1.6. Proportions of (drug-free) DAS-remission (DFR) after 2 years and Sharp-van der Heijde scores (SHS) were analyzed separately for the treatment strategies and patients with RA and UA. RESULTS: After 2 years, 301/610 (49 %) patients were in DAS-remission and 131/610 (21 %) in DFR. In the early remission group 241/387 patients (62 %) were in DAS-remission and 111/387 (29 %) DFR. In arm 1 22/83 (27 %) and in arm 2 24/78 (31 %) were in DAS-remission, and 6/83 (7 %) and 7/78 (9 %), respectively, were in DFR. RA and UA patients achieved DAS-remission in comparable percentages (RA: 234/479 (49 %), UA: 64/122 (52 %), p = 0.25). More UA patients achieved DFR (41/122 (34 %)) compared to RA patients (89/479 (19 %), p<0.001). Mean (SD) DAS over time was 1.74 (0.58) across all patients, and median (IQR) SHS progression was 0 (0-0). CONCLUSIONS: After 2 years remission-steered treatment in early RA and UA patients, DAS-remission and DFR percentages were relatively low. Patients who achieved early remission more often achieved (drug-free) remission after 2 years than patients who needed additional treatment steps in the randomization arms, and more UA than RA patients achieved DFR. Overall, disease activity and radiologic damage progression in all patients were well suppressed. TRIAL REGISTRATION: http://www.controlled-trials.com/ISRCTN11916566 Registered 07/11/2006 and EudraCT number 2006-06186-16 Registered 16/07/2007.

Do we need to lower the cut point of the 2010 ACR/EULAR classification criteria for diagnosing rheumatoid arthritis?

OBJECTIVE: In this study we aimed to evaluate the effect of lowering the cut point of the 2010 criteria to identify more patients with RA among early inflammatory arthritis patients. METHODS: We included early arthritis patients from the Rotterdam Early Arthritis Cohort with at least one joint with clinical synovitis and symptoms for <1 year, with no other explanation for their symptoms. The demographic and clinical characteristics of each patient were recorded at baseline. Patients were classified as case or non-case at the 1-year follow-up by the definition used in the development of the 2010 criteria (MTX initiation). To assess the diagnostic performance of the 2010 criteria, the sensitivity and specificity at each cut point were determined. RESULTS: We included 557 patients in our analysis. At the 1-year follow-up, 253 patients (45%) were classified as case (MTX use). In the group of patients who scored 0-5 points (n = 328), 98 patients (30%) were classified as case (MTX use). The sensitivity and specificity of the 2010 criteria using the cut point of 6 were 61% and 76%, respectively. With the cut point of 5, the sensitivity would increase to 76% and the specificity would decrease to 68%. CONCLUSION: By lowering the cut point of the 2010 criteria from 6 to 5 points, we were able to identify 15% more RA patients at the cost of 8% more false-positive patients.

Health-related quality of life and functional ability in patients with early arthritis during remission steered treatment: results of the IMPROVED study.

INTRODUCTION: The aim of this study was to investigate patient reported outcomes (PROs) of functional ability and health related quality of life (HRQoL) in patients with early (rheumatoid) arthritis during one year of remission steered treatment. METHODS: In this study, 610 patients with early rheumatoid arthritis (RA) or undifferentiated arthritis (UA) were treated with methotrexate (MTX) and tapered high dose of prednisone. Patients in early remission (Disease Activity Score (DAS) <1.6 after 4 months) tapered prednisone to zero and when in persistent remission, also tapered MTX. Patients not in early remission were randomized to either MTX + hydroxychloroquine + sulphasalazine + prednisone (arm 1) or to MTX + adalimumab (arm 2). Every 4 months, patients filled out the Health Assessment Questionnaire (HAQ) and the McMaster Toronto Arthritis Patient Preference Questionnaire (MACTAR), the Short Form 36 (SF-36) and visual analogue scales (VAS). Change scores were compared between treatment groups. The association with achieving remission was analyzed using linear mixed models. RESULTS: During year 1, patients who achieved early remission had the most improvement in PROs with scores comparable to the general population. Patients in the randomization arms showed less improvement. Scores were comparable between the arms. There was a significant association between achieving remission and scores of HAQ, MACTAR and physical HRQoL. CONCLUSIONS: In early arthritis, PROs of functional ability and HRQoL after one year of remission steered treatment reach normal values in patients who achieved early remission. In patients not in early remission, who were randomized to two strategy arms, PROs improved less, with similar scores in both treatment arms. TRIAL REGISTRATIONS: ISRCTN11916566 and EudraCT2006-006186-16.

Large-joint damage in patients with early rheumatoid arthritis and its association with treatment strategy and damage of the small joints.

OBJECTIVE: To determine the prevalence of large-joint damage and the association with small-joint damage in patients with RA after 8 years of low DAS (≤2.4)-targeted treatment with different treatment strategies. METHODS: Radiological data of 290 patients participating in the BeSt study, a randomized trial comparing initial monotherapy and initial combination therapy strategies, were used. Radiographs of large joints were scored using the Larsen score and of the small joints using the Sharp-van der Heijde score. With multivariate logistic regression analysis, an association between total damage of the small joints and of the large joints was investigated. RESULTS: After 8 years of treatment, damage was observed in 12% of shoulders, 10% of elbows, 26% of wrists, 13% of hips, 18% of knees and 7% of the ankles. Damage in one or more large joints was found in 64% of patients, with a median score of 1. No difference was found between initial monotherapy or combination therapy strategies. There was a significant association between damage progression in small joints and damage to one or more large joints (OR 1.02; 95% CI 1.00-1.04). CONCLUSION: After 8 years of DAS-targeted treatment in early RA patients, large-joint damage was found in 64% of patients and was associated with small-joint damage. Continued DAS-targeted treatment is probably more important in damage suppression than initial treatment strategy. Patients with more damage to hands and feet also have more damage to the large joints.

Remission induction therapy with methotrexate and prednisone in patients with early rheumatoid and undifferentiated arthritis (the IMPROVED study).

AIM: Classifying more patients as rheumatoid arthritis (RA) (2010 American College of Rheumatology/European League Against Rheumatism criteria for RA) may improve treatment outcomes but may cause overtreatment in daily practice. The authors determined the efficacy of initial methotrexate (MTX) plus prednisone treatment in patients with 1987 or 2010 classified RA and undifferentiated arthritis (UA). METHOD: 610 recent onset RA or UA patients started with MTX 25 mg/week and prednisone 60 mg/day tapered to 7.5 mg/day in 7 weeks. Percentage remissions after 4 months were compared between RA (1987 or 2010 criteria) and UA. Predictors for remission were identified. RESULTS: With the 2010 criteria, 19% more patients were classified as RA than with the 1987 criteria, but similar remission rates were achieved: 291/479 (61%) 2010 classified RA and 211/264 (58%) 1987 classified RA patients (p=0.52), and 79/122 (65%) UA patients (p=0.46). Anticitrullinated protein antibodies (ACPA) positive RA patients achieved more remission (66%) than ACPA negative RA patients (51%, p=0.001), but also had a lower mean baseline Disease Activity Score (DAS) (3.2 vs 3.6, p<0.001). Independent predictors for remission were male sex, low joint counts, DAS and Health Assessment Questionnaire, low body mass index and ACPA positivity. CONCLUSION: Initial treatment with MTX and a tapered high dose of prednisone results in similarly high remission percentages after 4 months (about 60%) in RA patients, regardless of fulfilling the 1987 or 2010 criteria, and in UA patients. Independent predictors indicate that initiating treatment while disease activity is relatively low results in more remission.

Patient preferences for treatment: report from a randomised comparison of treatment strategies in early rheumatoid arthritis (BeSt trial).

OBJECTIVE: To determine treatment preferences among patients with recent onset rheumatoid arthritis participating in a randomised controlled trial comparing four therapeutic strategies. METHODS: A questionnaire was sent to all 508 participants of the BeSt trial, treated for an average of 2.2 years with either sequential monotherapy (group 1), step-up combination therapy (group 2), initial combination therapy with tapered high-dose prednisone (group 3), or initial combination therapy with infliximab (group 4). Treatment adjustments were made every 3 months to achieve low disease activity (DAS < or =2.4). The questionnaire explored patients' preferences or dislikes for the initial therapy. RESULTS: In total, 440 patients (87%) completed the questionnaire. Despite virtually equal study outcomes at 2 years, more patients in group 4 reported much or very much improvement of general health: 50%, 56%, 46% and 74% in groups 1-4, respectively (overall, P<0.001). Almost half of the patients expressed no preference or aversion for a particular treatment group, 33% had hoped for assignment to group 4 and 38% had hoped against assignment to group 3. This negative perception was much less prominent in patients actually in group 3. Nevertheless, 50% of patients in group 3 disliked having to take prednisone, while only 8% in group 4 disliked going to the hospital for intravenous treatment. CONCLUSIONS: Within the limitations of our retrospective study, patients clearly preferred initial combination therapy with infliximab and disliked taking prednisone. After actual exposure, this preference remained, but the perception of prednisone improved. Patient perceptions need to be addressed when administering treatment.

Coexpression and interaction of CXCL10 and CD26 in mesenchymal cells by synergising inflammatory cytokines: CXCL8 and CXCL10 are discriminative markers for autoimmune arthropathies.

Leukocyte infiltration during acute and chronic inflammation is regulated by exogenous and endogenous factors, including cytokines, chemokines and proteases. Stimulation of fibroblasts and human microvascular endothelial cells with the inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor alpha (TNF-alpha) combined with either interferon-alpha (IFN-alpha), IFN-beta or IFN-gamma resulted in a synergistic induction of the CXC chemokine CXCL10, but not of the neutrophil chemoattractant CXCL8. In contrast, simultaneous stimulation with different IFN types did not result in a synergistic CXCL10 protein induction. Purification of natural CXCL10 from the conditioned medium of fibroblasts led to the isolation of CD26/dipeptidyl peptidase IV-processed CXCL10 missing two NH2-terminal residues. In contrast to intact CXCL10, NH2-terminally truncated CXCL10(3-77) did not induce extracellular signal-regulated kinase 1/2 or Akt/protein kinase B phosphorylation in CXC chemokine receptor 3-transfected cells. Together with the expression of CXCL10, the expression of membrane-bound CD26/dipeptidyl peptidase IV was also upregulated in fibroblasts by IFN-gamma, by IFN-gamma plus IL-1beta or by IFN-gamma plus TNF-alpha. This provides a negative feedback for CXCL10-dependent chemotaxis of activated T cells and natural killer cells. Since TNF-alpha and IL-1beta are implicated in arthritis, synovial concentrations of CXCL8 and CXCL10 were compared in patients suffering from crystal arthritis, ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis. All three groups of autoimmune arthritis patients (ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis) had significantly increased synovial CXCL10 levels compared with crystal arthritis patients. In contrast, compared with crystal arthritis, only rheumatoid arthritis patients, and not ankylosing spondylitis or psoriatic arthritis patients, had significantly higher synovial CXCL8 concentrations. Synovial concentrations of the neutrophil chemoattractant CXCL8 may therefore be useful to discriminate between autoimmune arthritis types.

TLR ligands and cytokines induce CXCR3 ligands in endothelial cells: enhanced CXCL9 in autoimmune arthritis.

CXC chemokines are potent attractants of neutrophil granulocytes, T cells or natural killer cells. Toll-like receptors (TLR) recognize microbial components and are also activated by endogenous molecules possibly implicated in autoimmune arthritis. In contrast to CXC chemokine ligand 8 (CXCL8), no CXC chemokine receptor 3 (CXCR3) ligand (ie CXCL9, CXCL10 and CXCL11) was induced by bacterial TLR ligands in human microvascular endothelial cells (HMVEC). However, peptidoglycan (PGN), double-stranded (ds) RNA or lipopolysaccharide (LPS) (TLR2, TLR3 or TLR4 ligands, respectively) synergized with interferon-gamma (IFN-gamma) at inducing CXCL9 and CXCL10. In contrast, enhanced CXCL11 secretion was only obtained when IFN-gamma was combined with TLR3 ligand. Furthermore, flagellin, loxoribine and unmethylated CpG oligonucleotide (TLR5, TLR7 and TLR9 ligands, respectively) did not enhance IFN-gamma-dependent CXCR3 ligand production in HMVEC. In analogy with TLR ligands, tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1beta), in combination with IFN-gamma, synergistically induced CXCL9 and CXCL11 in HMVEC and human fibroblasts, two fundamental cell types delineating the joint cavity. Etanercept, a humanized soluble recombinant p75 TNF-receptor/IgG(1)Fc fusionprotein, neutralized synergistic CXCL9 production induced by TNF-alpha plus IFN-gamma, but not synergy between IFN-gamma and the TLR ligands PGN or LPS. Synovial chemokine concentrations exemplify the physiopathological relevance of the observed in vitro chemokine production patterns. In synovial fluids of patients with spondylarthropathies (ie ankylosing spondylitis or psoriatic arthritis) or rheumatoid arthritis, significantly enhanced CXCL9, but not CXCL11 levels, were detected compared to concentrations in synovial fluids of patients with metabolic crystal-induced arthritis. Thus, CXCL9 is an important chemokine in autoimmune arthritis.

Synergistic induction of CXCL9 and CXCL11 by Toll-like receptor ligands and interferon-gamma in fibroblasts correlates with elevated levels of CXCR3 ligands in septic arthritis synovial fluids.

The synovial cavity constitutes the ideal stage to study the interplay between microbial Toll-like receptor (TLR) ligands and cytokines. Infiltrated leukocytes and synovial fibroblasts produce cytokine- and chemokine-induced proteases for remodeling the extracellular matrix. The regulation of chemokine function for attraction and activation of leukocytes constitutes a key feature in host immunity and resolution of inflammation after infection. Enhanced levels of the CXC chemokine ligand (CXCL9)/monokine induced by interferon-gamma (IFN-gamma) and CXCL11/IFN-inducible T cell alpha chemoattractant, two chemoattractants for activated T cells and natural killer cells, and ligands for CXC chemokine receptor 3 (CXCR3) were detected in the synovial fluid of septic arthritis compared with osteo- and crystal arthritis patients. In vitro, IFN-gamma and TLR3 ligation by double-stranded RNA (dsRNA) induced the expression of CXCL9 and CXCL11 in leukocytes and skin-muscle fibroblasts, whereas ligation of TLR2, TLR4, TLR5, and TLR9 by peptidoglycan (PGN), lipopolysaccharide (LPS), flagellin, and unmethylated CpG oligonucleotides, respectively, did not. PGN and LPS, but not unmethylated CpG oligonucleotides, even inhibited IFN-gamma-induced CXCL9 and CXCL11 expression in leukocytes. In sharp contrast, in fibroblasts, the TLR ligands PGN, dsRNA, LPS, and flagellin synergized with IFN-gamma for the production of CXCL9 and CXCL11. Although TLR ligands stimulate leukocytes to produce CXCL8/interleukin-8 during the early innate defense, they contribute less to the production of CXCR3 ligands, whereas fibroblasts are important sources of CXCR3 ligands. These results illustrate the complex interaction between cytokines and TLR ligands in infection.

Microbial Toll-like receptor ligands differentially regulate CXCL10/IP-10 expression in fibroblasts and mononuclear leukocytes in synergy with IFN-gamma and provide a mechanism for enhanced synovial chemokine levels in septic arthritis.

The CXC chemokine IFN-gamma-inducible protein-10 (IP-10/CXCL10) activates CXC chemokine receptor 3 (CXCR3) and attracts activated T cells and natural killer cells. Peripheral blood mononuclear cells (PBMC) produce low but significant amounts of IP-10/CXCL10 protein upon stimulation with double-stranded (ds) RNA, the Toll-like receptor 3 (TLR3) ligand. IFN-gamma is a superior IP-10/CXCL10inducer. The bacterial TLR4 and TLR2 ligands, LPS and peptidoglycan (PGN), inhibit IFN-gamma- or dsRNA-dependent IP-10/CXCL10 production in PBMC, whereas IL-8/CXCL8 production was enhanced. In fibroblasts a different picture emerges with IFN-gamma inducing moderate and dsRNA provoking strong IP-10/CXCL10 production. Furthermore, treatment of fibroblasts with IFN-gamma in combination with bacterial LPS or PGN results in a synergistic production of IP-10/CXCL10 and IL-8/CXCL8. The synergistic induction of IP-10/CXCL10 in fibroblasts is reflected by significantly enhanced IP-10/CXCL10 concentrations in synovial fluids of septic compared to osteoarthritis patients to reach on average higher levels than those of IL-8/CXCL8. These high amounts of IP-10/CXCL10 produced by connective tissue fibroblasts not only attract CXCR3 expressing activated Th1 cells and natural killer cells to sites of infection but may also antagonize the CCR3 dependent attraction of Th2 lymphocytes and exert CXCR3-independent, defensin-like antibacterial activity.

Cleavage of denatured natural collagen type II by neutrophil gelatinase B reveals enzyme specificity, post-translational modifications in the substrate, and the formation of remnant epitopes in rheumatoid arthritis.

During acute inflammation, leukocytes release proteolytic enzymes including matrix metalloproteinases (MMPs), but the physiopathological mechanisms and consequences of this process are not yet fully understood. Neutrophils, the predominant leukocyte type, produce neutrophil collagenase (MMP-8) and gelatinase B (MMP-9) but not the tissue inhibitors of MMPs. After stimulation, these cells also activate MMPs chemically. In arthritic diseases, neutrophils undergo great chemoattraction to the synovium, are activated by interleukin-8, and are stimulated to release gelatinase B in vivo. Production levels and net activities of gelatinase B were found to be absent in degenerative osteoarthritis but significantly increased in rheumatoid arthritis. The cleavage sites in cartilage type II collagen by gelatinase B were determined by a combination of reverse phase high-performance liquid chromatography, Edman degradation, and mass spectrometry analysis. The analysis revealed the site specificity of proline and lysine hydroxylations and O-linked glycosylation, the cleavage specificities by gelatinase B, and the preferential absence and presence of post-translational modifications at P2' and P5', respectively. Furthermore, gelatinase B leaves the immunodominant peptides intact, which are known from studies with (autoreactive) T cells. Lysine hydroxylation was detected at a critical position for T-cell activation. These data lend support to the thesis that extracellular proteolysis and other post-translational modifications of antigenic peptides may be critical in the establishment and perpetuation of autoimmune processes.