Experimental studies on signal transduction pathways in rheumatoid arthritis

Reumatoïde artritis (RA) is een chronische ontstekingsziekte, die met name gelocaliseerd is in de gewrichten. De ziekte komt voor bij 0.5 - 1% van de bevolking, en komt meer voor bij vrouwen dan bij mannen. Door de ontsteking in de gewrichten raken kraakbeen en bot beschadigd en dit kan leiden tot handicaps en verminderde kwaliteit van leven. De behandeling van RA is er ten eerste op gericht om de verschijnselen van ontsteking (pijn en koorts) te bestrijden en in de tweede plaats om de schade aan de gewrichten te beperken. Uit onderzoek is gebleken dat de zogenaamde cytokines tumor necrosis factor (TNF-) en interleukine-1 (IL-1) een centrale rol spelen in het ontstekingsproces. De laatste jaren is gebleken dat het blokkeren van deze cytokines met antilichamen een goede therapie is voor RA. Helaas reageren niet alle patiënten op deze therapie en komen ook incidenteel ernstige bijwerkingen van deze therapie voor. Een andere manier om de produktie en activiteit van deze cytokines te remmen is door het blokkeren van intracellulaire signaal transductieroutes. Deze routes zijn mechanismen waarbij een prikkel buiten de cel omgezet wordt in een reactie in de cel, meestal in de vorm van de produktie van ontstekingseiwitten. In deze signaal transductie routes spelen de zogenaamde kinases een belangrijke rol, doordat ze het signaal in de vorm van een fosfaatgroep aan elkaar doorgeven. In dit proefschrift is onderzocht of het remmen van een belangrijke intracellulaire signaal transductie route (de p38 mitogen-activated protein kinase (MAPK) route) een goede therapie zou kunnen zijn voor RA. In ons onderzoek is gekeken naar de gevolgen van remming met een specifieke p38 MAPK remmer (RWJ 67657) in cellen, die een rol spelen bij ontsteking

From incomplete to complete systemic lupus erythematosus; A review of the predictive serological immune markers

Systemic lupus erythematosus (SLE) is a complex and heterogeneous autoimmune disease. A main challenge faced by clinicians is early identification of SLE, frequently resulting in diagnostic delay. Timely treatment, however, is important to limit disease progression, and prevent organ damage and mortality. Often, patients present with clinical symptoms and immunologic abnormalities suggestive of SLE, while not meeting classification criteria yet. This is referred to as incomplete SLE (iSLE). However, not all these patients will develop SLE. Therefore, there is need for predictive biomarkers that can distinguish patients at high risk of developing SLE, in order to allow early treatment. This article reviews the current literature on immunological changes in patients with stages preceding SLE, focusing on autoantibodies, type-I and -II interferons, and the complement system. We also provide an overview of possible predictive markers for progression to SLE that are applicable in daily clinical practice

Hydroxychloroquine Suppresses Interferon-inducible Genes and B Cell Activating Factor in Patients With Incomplete and New-onset Systemic Lupus Erythematosus

OBJECTIVE: Hydroxychloroquine (HCQ) is commonly used as first-line treatment for systemic lupus erythematosus (SLE). Interferon (IFN)-inducible gene expression, IFN-γ-induced protein 10 (IP-10) and B cell activating factor (BAFF) are early mediators in SLE. The purpose of this study was to analyze the effects of HCQ on these factors. METHODS: Patients with incomplete SLE (iSLE; antinuclear antibody titer ≥ 1:80, symptoms < 5 years, ≥ 1 objectified clinical American College of Rheumatology or SLE International Collaborating Clinics criteria), or new-onset, mild SLE were included when HCQ treatment was started for clinical reasons. Blood samples were taken at start and after 16 weeks. Three SLE-related IFN-inducible genes were measured in whole blood by real-time PCR, and an IFN score was calculated. Serum levels of IP-10 and BAFF were measured using ELISA. RESULTS: In total, 9 patients were included: 7 with iSLE and 2 with new-onset SLE. The median SLE Disease Activity Index (SLEDAI) was 4. After 16 weeks of treatment with HCQ, the expression of IFN-inducible genes decreased in 8 of 9 patients, and the IFN-3 score decreased significantly (P = 0.012). There was a trend towards lower IP-10 levels (P = 0.055), and a significant decrease in BAFF levels (P = 0.023). CONCLUSION: HCQ suppresses IFN score and BAFF levels in patients with iSLE or new-onset SLE, and there is a trend towards lowering IP-10 levels. As these biomarkers are early mediators in SLE, this might support the hypothesis that HCQ could influence disease progression. However, prospective research with a larger sample size and longer follow-up is needed

The periodontium of periodontitis patients contains citrullinated proteins which may play a role in ACPA (anti-citrullinated protein antibody) formation

Aim To determine the presence and location (stroma versus epithelium) of citrullinated proteins in periodontitis tissue as compared to non-periodontitis tissue and synovial tissue of RA patients. Materials & Methods Periodontitis, healthy periodontal and RA-affected synovial tissue samples were collected in addition to buccal swabs. These samples were stained for the presence of citrullinated proteins using polyclonal (Ab5612) and monoclonal (F95) antibodies. Furthermore, Western blotting with F95 was performed on lysates prepared from periodontal and synovial tissues. Results In periodontitis stroma, increased citrullinated protein presence (80%) was observed compared with control stroma (33%), the latter was associated with inflammation of non-periodontitis origin. Periodontal epithelium always stained positive for Ab5612. Noteworthy, only periodontitis-affected epithelium stained positive for F95. All buccal mucosal swabs and 3 of 4 synovial tissue samples stained positive for both Ab5612 and F95. Western blotting with F95 showed presence of similar citrullinated proteins in both periodontitis and RA-affected synovial tissue. Conclusion Within the periodontal stroma, citrullination is an inflammation-depended process. In periodontal epithelium, citrullination is a physiological process. Additional citrullinated proteins are formed in periodontitis, apparently similar to those formed in RA-affected synovial tissue. Periodontitis induced citrullination may play a role in the aetiology of rheumatoid arthritis

Incomplete Systemic Lupus Erythematosus:What Remains After Application of American College of Rheumatology and Systemic Lupus International Collaborating Clinics criteria?

Incomplete systemic lupus (iSLE) is an acknowledged condition of patients with clinical signs of lupus who do not fulfill classification criteria for SLE. Some patients with iSLE have persistent mild disease, but others have serious organ involvement, and up to 55% progress to established SLE. Research on this subject could reveal predictive or diagnostic biomarkers for SLE. Ideally, it would become possible to discern those patients with critical organ involvement or a high risk for progression to SLE. This high-risk group might benefit from early treatment, which would preferably be confirmed in randomized controlled trials. This process would, however, require agreement on a definition of iSLE. The Systemic Lupus International Collaborating Clinics (SLICC) classification criteria was composed in order to diagnose SLE earlier. The present review outlines the clinical characteristics of iSLE after introduction of SLICC criteria and furthermore proposes a definition of iSLE with the aim of discriminating the high-risk group from those with a lower risk

Lessons to be learned from periodontitis

Purpose of reviewThis article reviews the link between periodontitis and rheumatoid arthritis (RA) with regard to similarities in genetic risk factors and immunopathogenesis. Emphasis is paid to the potential role of the periodontal pathogen Porphyromonas gingivalis in the etiopathogenesis of both periodontitis and RA, in particular by post-translational modification of arginine into citrulline.Recent findingsP. gingivalis, a major periodontal pathogen, is presently known as the only bacterium in the oral flora which contains a peptidyl arginine deiminase enzyme (PAD). This enzyme is necessary for citrullination. As a result, citrullinated proteins and P. gingivalis PAD, PAD2 and PAD4 (expressed by infiltrating neutrophils) are found in periodontal tissues. Autoantibodies directed to citrullinated proteins, so-called anticitrullinated protein antibodies (ACPAs), are found to be present in gingival crevicular fluid originating from inflamed gingival tissue. Furthermore, treatment studies have revealed that nonsurgical periodontal treatment, that is removal of sub-gingival calculus and biofilm deposits, is accompanied by a reduction in the severity of RA.SummaryIn this study the similarities in immune response and tissue degradation between RA and periodontitis are reviewed. It is shown that the two diseases share the same environmental and genetic risk factors, apart from the fact that there is a link between both diseases via citrullination of proteins by human PAD and P. gingivalis PAD.</p

Biological Characteristics of HLA-G and Its Role in Solid Organ Transplantation

Organ transplantation is a lifesaving option for patients with advanced diseases. Rejection is regarded as one of the most severe risk factors post-transplantation. A molecule that contributes to immune tolerance and resisting rejection is human leukocyte antigen (HLA)-G, which belongs to the non-classical major histocompatibility complex class (MHC) I family. HLA-G was originally found to play a role during pregnancy to maintain immune tolerance between mother and child. It is expressed in the placenta and detected in several body fluids as soluble factor as well as different membrane isoforms on cells. Recent findings on HLA-G show that it can also play multifaceted roles during transplantation. This review will explain the general characteristics and biological function of HLA-G and summarize the views supporting the tolerogenic and other roles of HLA-G to better understand its role in solid organ transplantation (SOT) and its complications. Finally, we will discuss potential future research on the role of HLA-G in prevention, diagnosis, and treatment in SOT

High mobility group box 1 (HMGB1) and anti-HMGB1 antibodies and their relation to disease characteristics in systemic lupus erythematosus

Introduction: High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein. HMGB1, which is secreted by inflammatory cells and passively released from apoptotic and necrotic cells, may act as a pro-inflammatory mediator. As apoptotic cells accumulate in systemic lupus erythematosus (SLE), HMGB1 levels might be increased in SLE. HMGB1 may also serve as an autoantigen, leading to the production of anti-HMGB1 antibodies. In this study we determined levels of HMGB1 and anti-HMGB1 in SLE patients in comparison to healthy controls (HC) and analysed their relation with disease activity. Methods: The study population consisted of 70 SLE patients and 35 age-and sex-matched HC. Thirty-three SLE patients had quiescent disease, the other 37 patients were selected for having active disease. Nineteen of these had lupus nephritis. HMGB1 levels were measured with both Western blot and ELISA. Anti-HMGB1 levels were measured by ELISA. Clinical and serological parameters were assessed according to routine procedures. Results: HMGB1 levels in SLE patients could be measured reliably by Western blotting only, and were significantly increased compared to HC. During active disease HMGB1 levels increased, in particular in patients with renal involvement. Serum HMGB1 levels correlated with SLEDAI, proteinuria, and anti-dsDNA levels, and showed a negative correlation with complement C3. Anti-HMGB1 levels were significantly increased in SLE patients compared to HC, and positively correlated with HMGB1 levels. Conclusions: Levels of HMGB1 in the sera of SLE patients, in particular in those with active renal disease, are increased. Serum HMGB1 levels are related to SLEDAI scores and proteinuria, as well as to levels of anti-HMGB1 antibodies. These findings suggest that besides HMGB1, HMGB1-anti-HMGB1 immune complexes play a role in the pathogenesis of SLE, in particular in patients with renal involvement