Complement activation in patients with rheumatoid arthritis mediated in part by C-reactive protein

Overview on the Link Between the Complement System and Auto-Immune Articular and Pulmonary Disease

Complement system (CS) dysregulation is a key factor in the pathogenesis of different autoimmune diseases playing a central role in many immune innate and adaptive processes. Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by ta breach of self-tolerance leading to a synovitis and extra-articular manifestations. The CS is activated in RA and seems not only to mediate direct tissue damage but also play a role in the initiation of RA pathogenetic mechanisms through interactions with citrullinated proteins. Interstitial lung disease (ILD) represents the most common extra-articular manifestation that can lead to progressive fibrosis. In this review, we focused on the evidence of CS dysregulation in RA and in ILD, and highlighted the role of the CS in both the innate and adaptive immune responses in the development of diseases, by using idiopathic pulmonary fibrosis as a model of lung disease. As a proof of concept, we dissected the evidence that several treatments used to treat RA and ILD such as glucocorticoids, pirfenidone, disease modifying antirheumatic drugs, targeted biologics such as tumor necrosis factor (TNF)-inhibitors, rituximab, tocilizumab, and nintedanib may act indirectly on the CS, suggesting that the CS might represent a potential therapeutic target in these complex diseases.

The complement system and human autoimmune diseases

Genetic deficiencies of early components of the classical complement activation pathway (especially C1q, r, s, and C4) are the strongest monogenic causal factors for the prototypic autoimmune disease systemic lupus erythematosus (SLE), but their prevalence is extremely rare. In contrast, isotype genetic deficiency of C4A and acquired deficiency of C1q by autoantibodies are frequent among patients with SLE. Here we review the genetic basis of complement deficiencies in autoimmune disease, discuss the complex genetic diversity seen in complement C4 and its association with autoimmune disease, provide guidance as to when clinicians should suspect and test for complement deficiencies, and outline the current understanding of the mechanisms relating complement deficiencies to autoimmunity. We focus primarily on SLE, as the role of complement in SLE is well-established, but will also discuss other informative diseases such as inflammatory arthritis and myositis.

Assessment of Serum Lipid Profiles and High-sensitivity C-reactive Protein Among Patients Suffering from Rheumatoid Arthritis at Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia: A Cross-Sectional Study

Background

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by severe joint pain, swelling, damage, and disability which leads to joint destruction and loss of function. The complication of RA is associated with cardiovascular diseases, particularly due to systemic inflammation and dyslipidemia. The purpose of this study was to assess the development of atherosclerosis, which acts as a major risk factor for cardiovascular complications in RA patients.

Methods

A hospital-based cross-sectional study was conducted at the Rheumatology Clinic of Tikur Anbessa Specialized Hospital. The study made a comparison of risk factors (dyslipidemia and inflammatory status) between individuals having RA as a case group and apparently healthy individuals as a control group. Simple descriptive statistics, one-way ANOVA, independent sample t-test and multivariate analysis were utilized for statistical analysis. p-value of <0.05 at the 95% confidence level was considered as statistically significant.

Results

The result of this study demonstrated that there was a significant elevation of mean ±SD of TC, TC/HDL, LDL/HDL, and lowered value of HDL-C was seen among RA patients than controls (P-value <0.05). The mean ±SD of inflammatory marker, high-sensitivity C-reactive protein (hsCRP), was significantly higher among RA patients compared to controls (P<0.05). HDL-C had a significant negative correlation with a hsCRP whereas TC/HDL-C and LDL/HDL-C had a significant positive correlation with hsCRP (P<0.05).

Conclusion

In this study, RA patients had lipid abnormalities and elevated systemic inflammation than controls. An increase in hsCRP and dyslipidemia status among RA patients indicates the possible development of an atherosclerotic event. Therefore, assessment of lipid profiles and hsCRP in early RA patients may be helpful to assess the possible development of cardiovascular complications.

Rheumatoid arthritis and systemic lupus erythematosus: Pathophysiological mechanisms related to innate immune system

Rheumatoid arthritis and systemic lupus erythematosus are two highly prevalent autoimmune diseases that generate disability and low quality of life. The innate immune system, a long-forgotten issue in autoimmune diseases, is becoming increasingly important and represents a new focus for the treatment of these entities. This review highlights the role that innate immune system plays in the pathophysiology of rheumatoid arthritis and systemic lupus erythematosus. The role of the innate immune system in rheumatoid arthritis and systemic lupus erythematosus pathophysiology is not only important in early stages but is essential to maintain the immune response and to allow disease progression. In rheumatoid arthritis, genetic and environmental factors are involved in the initial stimulation of the innate immune response in which macrophages are the main participants, as well as fibroblast-like synoviocytes. In systemic lupus erythematosus, all the cells contribute to the inflammatory response, but the complement system is the major effector of the inflammatory process. Detecting alterations in the normal function of these cells, besides its contribution to the understanding of the pathophysiology of autoimmune diseases, could help to establish new treatment strategies for these diseases.

Utility of Carotid Intima-Media Thickness as an Auxiliary Vascular Parameter of Structural Alteration in Ulcerative Colitis

Background

Ulcerative colitis (UC) is characterized by chronic relapsing-remitting inflammation of the gastrointestinal tract. The chronic inflammatory process may predispose to atherosclerosis. The aim of the study was to assess the carotid intima-media thickness (CIMT) and its relation to subclinical atherosclerosis and to follow up cardiovascular complications in patients with UC.

Methods

83 patients with proven UC in remission were enrolled in the study. 42 age- and sex-matched healthy controls were taken. Patients with known risk factors for atherosclerosis were excluded from the study. Baseline blood investigations along with C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and fasting lipid profile were done. CIMT was measured using B-mode Doppler imaging study.

Results

The mean age of the UC patients was 37.06 ± 14.87 years. Left-sided colitis (45.8%) was the commonest type of presentation according to the extent of the disease. Mean CIMT (0.55 ± 0.17) was significantly higher in UC patients when compared to mean CIMT (0.46 ± 0.13) in the control group (p = 0.002). In Pearson correlation analysis, age, ESR, and CRP were positive and significantly correlated with CIMT. Multiple linear regression analysis (R² = 0.18, p = 0.0026) revealed that age and CRP were significant independent predictors of mean CIMT. On following up for 6 months, 4 patients with UC had complications in the form of venous thrombosis.

Conclusion

CIMT is a simple, noninvasive, reliable and objective auxiliary vascular parameter of structural alteration in UC patients.

Activation status of peripheral blood neutrophils and the complement system in adult rheumatoid arthritis patients undergoing combined therapy with infliximab and methotrexate

We examined the functional activity of peripheral blood neutrophils and the complement system activation status in patients with rheumatoid arthritis (RA) undergoing infliximab/methotrexate combined therapy. We studied female RA patients under treatment with infliximab (3-5 mg/kg) and methotrexate (15-25 mg/week) who presented inactive (i-RA; n = 34, DAS-28 ≤ 2.6) or at least moderately active disease (a-RA; n = 29, DAS-28 > 3.2), and age-matched healthy women (n = 38). We measured the levels of reactive oxygen species (ROS) generation (chemiluminescence assay) and membrane expression of FcγRIIa/CD32, FcγRIIIb/CD16, CR1/CD35, and CR3/CD11b receptors (ELISA assay) in neutrophils. We also determined the hemolytic activity of the alternative and classical pathways of the complement system (spectrophotometry), serum levels of C5a and Bb (ELISA assay), and serum chemotactic activity (Boyden chamber). Compared with the control group, i-RA and a-RA patients exhibited: (1) increased neutrophil ROS production and membrane expression of FcγRIIa/CD32, FcγRIIIb/CD16, and CR1/CD35, indicating neutrophil activation; and (2) increased serum chemotactic activity and decreased activity of the alternative complement pathway, indicating systemic complement system activation. The levels of C-reactive protein in a-RA patients were augmented, compared with i-RA patients. Although infliximab/methotrexate combined therapy induced disease remission according to the DAS-28 criteria, both i-RA and a-RA patients still exhibited significant levels of systemic activation of neutrophils and the complement system.

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.

Anti-arthritic potential of marine macroalgae Turbinaria ornata in Complete Freund's Adjuvant induced rats

T. ornata a macroalgae rich in bioactive molecules possess various biological activities. Herein, the aim of the study is to evaluate the aqueous extract and the sulphated polysaccharide isolated from T. ornata for its anti-arthritic potential in Complete Freund's Adjuvant (CFA) induced arthritis in rats. Anti-arthritic potential of aqueous T. ornata (ATO) and T. ornata sulphated polysaccharide (TSP) was evidenced by the significant reduction in paw volume and arthritic score. Inflammatory and antioxidant markers were found to be restored in the drug treated groups which was found to be in line with dexamethasone a standard anti-inflammatory drug. The histopathological and radiological examination adds on the support to the above findings confirming the anti-arthritic potential of ATO and TSP. It is interesting to note that the sulphated polysaccharide inhibits inflammation and bone damage at very low dose itself. Hence, TSP could be considered as a better candidate in the management of chronic inflammatory diseases like rheumatoid arthritis.

Preclinical atherosclerosis in patients with inflammatory bowel diseases: a case-control study

BACKGROUND

An independent role of chronic inflammation in the atherosclerotic process in patients with inflammatory bowel diseases (IBD) has been suggested, but data are still contentious. We assessed pre-clinical atherosclerosis in the IBD patients without traditional risk factors.

METHODS

In this case-control study we assessed the early atherosclerotic alterations by carotid artery intima-media thickness (CIMT) measurement in IBD patients and matched controls. The normal CIMT values were ≤0.9 mm; moderate thickness when >0.9 and ≤1.2 mm, and pre-clinical atherosclerosis when >1.2 mm. We selected a homogeneous group of IBD patients, all in ongoing biologic therapy, without any traditional risk factor for atherosclerosis as well as controls.

RESULTS

The study enrolled 23 consecutive patients (16 with ulcerative colitis and 7 with Crohn's disease) and 20 controls matched for age and sex. The mean of CIMT values was not statistically different between patients and controls (0.68±0.21 vs. 0.82±0.2 mm; P=0.4). The prevalence of moderate CIMT thickness was significantly lower in cases than in controls (8.7% vs. 42.8%; P=0.01; OR: 0.15, 95% CI: 0.03-0.85).

CONCLUSIONS

This case-control study found that the atherosclerotic process is not more apparent in IBD patients without traditional risk factors.

Anti-rheumatoid arthritic effects of Saussurea involucrata on type II collagen-induced arthritis in rats

Saussurea involucrata (SI) has long been used under the herbal name "snow lotus" for treatment of inflammation and pain-related diseases in traditional Chinese medicine. The present study aimed to evaluate the pharmacological effects of SI on collagen II (CII)-induced arthritis in rats. Rats with collagen II (CII)-induced arthritis were orally administered SI (420 mg kg(-1)) for 40 consecutive days. Histopathological examination indicated that SI alleviates infiltration of inflammatory cells and synovial hyperplasia and slows joint destruction. SI intervention reduced the serum levels of RF, COMP, CRP and anti-CII IgG. Results also showed that SI is a potential therapeutic agent for alleviating the severity of the disease based on the reduced arthritic index. It was concluded that SI can ameliorate inflammation and joint destruction in CIA rats.

Long noncoding RNA expression profile in fibroblast-like synoviocytes from patients with rheumatoid arthritis

Background

Long noncoding RNAs (lncRNAs) have recently received wide attention as key molecules that mediate a variety of physiological and pathological processes by regulating gene expression; however, knowledge of lncRNAs in rheumatoid arthritis (RA) is limited. Thus, we investigated the lncRNA expression profile in fibroblast-like synoviocytes (FLSs) from patients with RA and explored the function of abundantly expressed lncRNAs.

Methods

LncRNA and mRNA microarrays were performed to identify differentially expressed lncRNAs in RA FLSs compared with normal FLSs. Quantitative polymerase chain reaction (qPCR) was used to validate the results, and correlation analysis was used to analyze the relationship between these aberrantly expressed lncRNAs and clinical characteristics. A receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic value of the lncRNAs identified.

Results

According to the gene expression profiles, 135 lncRNAs were differentially expressed between RA and normal FLSs. Furthermore, qPCR data showed that lncRNA ENST00000483588 was up-regulated and that three lncRNAs (ENST00000438399, uc004afb.1, and ENST00000452247) were down-regulated in RA FLSs. The expression level of ENST00000483588 was positively correlated with the level of C-reactive protein and the Simplified Disease Activity Index score. Moreover, the areas under the ROC curve were 0.85, 0.92, 0.97, and 0.92 for ENST00000483588, ENST00000438399, uc004afb.1, and ENST00000452247, respectively.

Conclusions

The results indicate that the dysregulation of ENST00000483588, ENST00000438399, uc004afb.1, and ENST00000452247 may be involved in the pathological processes of RA and that these lncRNAs may have potential value for the diagnosis and assessment of the disease activity of RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1129-4) contains supplementary material, which is available to authorized users.

Increased resistin levels in the serum and cerebrospinal fluid of patients with neuromyelitis optica

INTRODUCTION

Resistin, which acts as a pro-inflammatory cytokine, has been implicated in the pathogenesis of several autoimmune diseases. However, the involvement of resistin in neuromyelitis optica (NMO), a severe inflammatory central nervous system disorder that targets the optic nerve and spinal cord, remains unclear.

METHODS

We measured serum and cerebrospinal fluid (CSF) resistin levels in patients with NMO and controls matched by age and sex. The link between resistin levels and clinical variables in NMO was subsequently assessed.

RESULTS

The concentrations of serum and CSF resistin were significantly higher in patients with NMO than in controls, and decreased following treatment with methylprednisolone. High sensitivity C-reactive protein (hs-CRP) levels and annualized relapse rate positively correlated with resistin levels in patients with NMO.

CONCLUSION

Resistin might be a useful biomarker of inflammation in NMO, and a potential target for the treatment of NMO.

Early Components of the Complement Classical Activation Pathway in Human Systemic Autoimmune Diseases

The complement system consists of effector proteins, regulators, and receptors that participate in host defense against pathogens. Activation of the complement system, via the classical pathway (CP), has long been recognized in immune complex-mediated tissue injury, most notably systemic lupus erythematosus (SLE). Paradoxically, a complete deficiency of an early component of the CP, as evidenced by homozygous genetic deficiencies reported in human, are strongly associated with the risk of developing SLE or a lupus-like disease. Similarly, isotype deficiency attributable to a gene copy-number (GCN) variation and/or the presence of autoantibodies directed against a CP component or a regulatory protein that result in an acquired deficiency are relatively common in SLE patients. Applying accurate assay methodologies with rigorous data validations, low GCNs of total C4, and heterozygous and homozygous deficiencies of C4A have been shown as medium to large effect size risk factors, while high copy numbers of total C4 or C4A as prevalent protective factors, of European and East-Asian SLE. Here, we summarize the current knowledge related to genetic deficiency and insufficiency, and acquired protein deficiencies for C1q, C1r, C1s, C4A/C4B, and C2 in disease pathogenesis and prognosis of SLE, and, briefly, for other systemic autoimmune diseases. As the complement system is increasingly found to be associated with autoimmune diseases and immune-mediated diseases, it has become an attractive therapeutic target. We highlight the recent developments and offer a balanced perspective concerning future investigations and therapeutic applications with a focus on early components of the CP in human systemic autoimmune diseases.

Inflammatory biomarkers in osteoarthritis

Osteoarthritis (OA) is highly prevalent and a leading cause of disability worldwide. Despite the global burden of OA, diagnostic tests and treatments for the molecular or early subclinical stages are still not available for clinical use. In recent years, there has been a large shift in the understanding of OA as a "wear and tear" disease to an inflammatory disease. This has been demonstrated through various studies using MRI, ultrasound, histochemistry, and biomarkers. It would of great value to be able to readily identify subclinical and/or sub-acute inflammation, particularly in such a way as to be appropriate for a clinical setting. Here we review several types of biomarkers associated with OA in human studies that point to a role of inflammation in OA.

Results of a proof of concept, double-blind, randomized trial of a second generation antisense oligonucleotide targeting high-sensitivity C-reactive protein (hs-CRP) in rheumatoid arthritis

Introduction

This randomized, double-blind, phase II study evaluated the pharmacodynamics, safety and tolerability of ISIS 329993 (ISIS-CRP_Rx), an antisense oligonucleotide, in patients with active rheumatoid arthritis (RA).

Methods

Patients with active RA of at least six months duration were randomized into three cohorts to receive ISIS-CRP_Rx (100 mg, 200 mg or 400 mg) or placebo (3 active:1 placebo within each cohort) via subcutaneous (SC) injection on Days 1, 3, 5 and 8 and then once weekly for the next 11 weeks. The effects of study treatment on high-sensitivity C-reactive protein (hs-CRP) level were evaluated. An exploratory analysis on disease activity was assessed via the American College of Rheumatology 20% improvement criteria (ACR20). Safety was evaluated via adverse events and laboratory measures.

Results

Fifty-one patients received one of the following treatments: ISIS-CRP_Rx 100 mg, n = 12; 200 mg, n = 13, 400 mg, n = 14; placebo n = 12. In the ISIS-CRP_Rx treatment groups there were dose-dependent reductions in hs-CRP. At Day 36 the mean percent change from baseline was: placebo: −14.4%; ISIS-CRP_Rx 100 mg: −19.5%; 200 mg: −56.6% and 400 mg: −76.7%, (P = 0.0015 placebo compared to 400 mg). There were no differences between treatment groups and placebo in the ACR20 at Day 36 or Day 92. There were no serious infections and no elevations in liver function tests, lipids, creatinine or other lab abnormalities related to ISIS-CRP_Rx.

Conclusions

In this study, ISIS-CRP_Rx selectively reduced hs-CRP in a dose-dependent manner, and was well-tolerated in patients with RA. Its utility as a therapy in RA remains unclear.

Trial registration

Clinicaltrials.gov NCT01414101. Registered 21 July 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0578-5) contains supplementary material, which is available to authorized users.

Differential diagnosis of systemic lupus erythematosus and rheumatoid arthritis with complements C3 and C4 and C-reactive protein

The aim of this study was to analyze the changes in complements C3 and C4 and C-reactive protein (CRP) in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and to evaluate the role of these indices in the differential diagnosis of SLE and RA. The first 347 patients with SLE, 382 patients with RA and 66 patients with erythema nodosum were selected for the measurement of complement and CRP levels in the serum, the erythema nodosum patients were the control group. The roles of the complements and CRP in the differential diagnosis and disease activity evaluation of SLE and RA were analyzed with SPSS 13.0. Complement C3 and C4 levels were significantly reduced in patients with SLE compared with those in the control group. However, in RA patients, the CRP level was increased. In addition, the levels of complements C3 and C4 in patients with SLE were much lower than those in patients with RA and the level of CRP in RA patients was much higher than that in patients with SLE. The reduction of complement C3 levels in SLE patients, and increase of CRP and complement C4 in patients with RA were associated with a higher risk of joint pain, butterfly rash and oral ulcer. These results show that the disease activity of SLE was negatively correlated with complement C3 and C4, and the disease activity of RA was positively correlated with CRP. With the increase in disease activity, the levels of complements C3 and C4 in patients with SLE were gradually reduced and the level of CRP in patients with RA was increased. There were distinctive differences in the levels of complements C3 and C4 and CRP between SLE and RA patients. The differences are useful in disease activity evaluation and the differential diagnosis of the two diseases that have similar symptoms.

Tongue diagnosis of traditional Chinese medicine for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease with unknown aetiology that causes the immune system to attack the joints (synoviums), leading to chronic inflammation. According to the traditional Chinese medicine (TCM), RA falls into the category of Impediment disease ("Bi" syndrome), that is, poor circulation of qi and blood (stasis). Tongue diagnosis is an important method of TCM to detect blood stasis. In this study, 74 RA patients, meeting the pre-set criteria, were recruited via rheumatology outpatient clinic and examined by experienced rheumatology physicians. Two images-one of the tongue and the other, sublingual vessels-of the same patient were taken by a Canon digital camera in a darkroom with uniform lighting conditions. Relevant features of the tongue were extracted by utilising image processing techniques. Every tongue was classified into corresponding patterns based on the features identified. The subjects included 62 females and 12 males with an average age of 49.86 ± 13.81 years old, an average morbidity period of 4.56 ± 3.92 years, an average rheumatoid factor (RF) of 225.3 ± 373.8 IU/mL and an average erythrocyte sedimentation rate of (ESR) 40.9 ± 31.9 m/hr. According to our study, 86% of the patients with RA have tongues with sublingual vessels with a width of more than 2.7 mm, a length of more than 3/5 from tongue tipto sublingual caruncle, or a count of sublingual vessels more than 2. Moreover, since RA index is highly correlated with blood stasis in TCM, a logistic regression is conducted to predict the probability of presence of RA using RF and ESR as explanatory variables. Also, the logistic regression analysis of RA with respect to the conventional tongue diagnosis criteria was performed. Based on the aforementioned studies, we concluded that tongue diagnosis is helpful in detecting blood stasis of RA.

Atherogenic lipid profile and high sensitive C-reactive protein in patients with rheumatoid arthritis

OBJECTIVES

The objective of this study was to investigate the lipid profile and high sensitive C-reactive protein (hs-CRP) levels in rheumatoid arthritis (RA) patients, and compare them with healthy controls, and also compare the different patterns of these parameters during active RA between male and female patients.

DESIGN AND METHODS

We studied 60 RA patients and 65 controls matched by age and sex. All cases were selected from the Rheumatology Department of a tertiary care hospital, Delhi, India and fulfilled the 1987 American College of Rheumatology revised criteria for RA.

RESULTS

We found that male RA patients had significantly higher levels of hs-CRP (p<0.001), low density lipoprotein cholesterol (LDL-C)/high density lipoprotein cholesterol (HDL-C) (p<0.001), total cholesterol (TC)/HDL-C (p<0.05), and lower level of HDL-C (p<0.01), than male controls. The mean levels of HDL-C and TC were high (p<0.05), and LDL-C, LDL-C/HDL-C (p<0.01), and hs-CRP (p<0.001) were low in healthy females as compared to female RA patients. Between RA patients, females had significantly high level of HDL-C (p<0.001), and low levels of TC/HDL-C and LDL-C/HDL-C (p<0.001) as compared to RA males. Mean levels of TC and HDL-C were higher in healthy females (p<0.05) and triglyceride (TG) was lower (p<0.05) than in healthy males.

CONCLUSIONS

Results demonstrate that the RA patients have high levels of inflammatory marker hs-CRP and altered lipid profile, and these are affected by the gender of the RA patients. Lipid levels should be monitored and managed in patients with RA to minimize the long-term risk of cardiovascular disease.

A Selective Inhibitor of Human C-reactive Protein Translation Is Efficacious In Vitro and in C-reactive Protein Transgenic Mice and Humans

Observational studies of patients with established rheumatoid arthritis (RA) document a positive correlation between C-reactive protein (CRP) blood concentration and worsening of RA symptoms, but whether this association is causal or not is not known. Using CRP transgenic mice (CRPTg) with collagen-induced arthritis (CIA; a rodent model of RA), we explored causality by testing if CRP lowering via treatment with antisense oligonucleotides (ASOs) targeting human CRP mRNA was efficacious and of clinical benefit. We found that in CRPtg with established CIA, ASO-mediated lowering of blood human CRP levels improved the clinical signs of arthritis. In addition, in healthy human volunteers the ASO was well tolerated and efficacious i.e., treatment achieved significant CRP lowering. ASOs targeting CRP should provide a specific and effective way to lower human CRP levels, which might be an effective therapy in patients with established RA.

Collagen-induced arthritis is exacerbated in C-reactive protein-deficient mice

OBJECTIVE

Blood C-reactive protein (CRP) is routinely measured to gauge inflammation. In rheumatoid arthritis (RA), a heightened CRP level is predictive of a poor outcome, while a lowered CRP level is indicative of a positive response to therapy. CRP interacts with the innate and adaptive immune systems in ways that suggest it may be causal in RA and, although this is not proven, it is widely assumed that CRP makes a detrimental contribution to the disease process. Paradoxically, results from animal studies have indicated that CRP might be beneficial in RA. This study was undertaken to study the role of CRP in a mouse model of RA, the collagen-induced arthritis (CIA) model.

METHODS

We compared the impact of CRP deficiency with that of transgenic overexpression of CRP on inflammatory and immune responses in mice, using CRP-deficient (Crp-/-) and human CRP-transgenic (CRP-Tg) mice, respectively. Susceptibility to CIA, a disease that resembles RA in humans, was compared between wild-type, Crp-/-, and CRP-Tg mice.

RESULTS

CRP deficiency significantly altered the inflammatory cytokine response evoked by challenge with endotoxin or anti-CD3 antibody, and heightened some immune responses. Compared to that in wild-type mice, CIA in Crp-/- mice progressed more rapidly and was more severe, whereas CIA in CRP-Tg mice was dramatically attenuated. Despite these disparate clinical outcomes, anticollagen autoantibody responses during CIA did not differ among the genotypes.

CONCLUSION

CRP exerts an early and beneficial effect in mice with CIA. The mechanism of this effect remains unknown but does not involve improvement of the autoantibody profile. In humans, the presumed detrimental role of a heightened blood CRP level during active RA might be balanced by a beneficial effect of the baseline CRP (i.e., levels manifest during the preclinical stages of disease).

Association of body fat with C-reactive protein in rheumatoid arthritis

OBJECTIVE

The serum C-reactive protein (CRP) concentration is commonly used in rheumatoid arthritis (RA) as a surrogate marker of systemic inflammation, presumably induced by synovitis. However, other tissues, such as adipose tissue, can induce CRP production. This study was undertaken to explore the associations between measures of adiposity and CRP levels in RA.

METHODS

One hundred ninety-six men and women with RA underwent anthropometric assessment and total body dual-energy x-ray absorptiometry for measurement of total and regional body fat and lean mass. The associations between measures of fat and lean mass and serum levels of CRP and interleukin-6 (IL-6) were determined in analyses stratified by sex, with adjustment for pertinent demographic, lifestyle, and RA disease and treatment covariates as well as for the potential modifying effects of articular activity and biologic pharmacotherapeutic agents.

RESULTS

All measures of adiposity were significantly associated with the level of CRP in women, but not in men. In women, the measure of adiposity that showed the strongest association with the CRP level was truncal fat, in which, in adjusted analyses, each kilogram increase was associated with a 0.101-unit increase in the logarithmically transformed CRP level (P < 0.001). Neither the level of articular activity nor the use of biologic agents significantly modified this association in women. However, in men, elevated articular involvement was associated with a decreasing CRP level as truncal fat increased. For all analyses, substitution of IL-6 for CRP produced similar findings.

CONCLUSION

Adiposity is independently associated with CRP levels in women with RA, and thus may confound the estimation of RA disease activity when serum CRP concentration is used as a surrogate for systemic inflammation.

The soluble terminal complement complex (SC5b-9) up-regulates osteoprotegerin expression and release by endothelial cells: implications in rheumatoid arthritis

OBJECTIVE

Complement activation products contribute to a large number of inflammatory diseases, including RA. We have investigated whether osteoprotegerin (OPG) may concur with the soluble terminal complement complex (SC5b-9) to the inflammatory cascade characterizing RA.

METHODS

Levels of SC5b-9 and OPG in the plasma and SF of patients with active RA were determined by ELISA. The presence of SC5b-9 and OPG in RA synovial lesions was analysed by immunohistochemistry. Cultured endothelial cells were used for in vitro leucocyte/endothelial cell adhesion assays. In addition, endothelial cells were exposed to SC5b-9 in order to evaluate the effects on the production of OPG protein, as well as the activation of the OPG promoter.

RESULTS

Patients affected by active RA are characterized by elevated levels of both SC5b-9 and OPG in plasma and/or SF. Of note, we have observed a co-localization of SC5b-9 and OPG in endothelial cells of post-capillary venules of RA synovial lesions. Data on endothelial cell cultures showed that exposure to SC5b-9 induced the up-regulation of OPG expression/release, stimulating the transcriptional activity of the OPG promoter, and synergized with TNF-alpha in up-regulating OPG production.

CONCLUSIONS

Our findings demonstrate that SC5b-9 induces OPG production by endothelial cells and we propose that the SC5b-9-mediated up-regulation of OPG may be an important mechanism whereby complement contributes in promoting and/or enhancing the inflammation in RA.

Colocalization of C4d deposits/CD68+ macrophages in rheumatoid nodule and granuloma annulare: immunohistochemical evidence of a complement-mediated mechanism in fibrinoid necrosis

Rheumatoid nodule (RN) represents a palisading granuloma with central fibrinoid necrosis, which is not only a classical manifestation of rheumatoid arthritis (RA) and part of the American College of Rheumatology (ACR)-criteria, but also is its diagnostic hallmark. The pathogenesis of RN is still not fully understood. At present, only data on serum analyses indicating a complement-mediated pathogenesis in the development of RA are available. Equivalent examinations for RN have not yet been performed. Granuloma annulare (GA) represents another type of palisading granuloma. A special subtype of GA, subcutaneous GA (SGA), is an important differential diagnosis to RN. Therefore, our aim was to examine RN and SGA regarding the complement deposition (C4d) by immunohistochemical means. All RN and GA were stained by hematoxylin/eosin and different special stains. In addition, all specimens were stained immunohistochemically with antibodies against CD68. Five GA and five RN were analyzed immunohistochemically with antibodies against C4d and CD68, and evaluated using single- and doublestaining immunohistochemistry. All RN and GA displayed depositions of C4d within their central necroses and between the surrounding palisading macrophages. Most importantly, C4d/CD68 double staining was visible in the palisading macrophages next to the necroses, while macrophages in the periphery were negative for C4d but positive for CD68. The main difference between RN and GA was a quantitative phenomenon with less positively reacting macrophages in a more incomplete palisade in GA. The positive reactions of all central necroses to C4d and colocalization of CD68 and C4d suggest that a complement-mediated mechanism may be operative in the formation of fibrinoid necrosis. This mechanism may be involved in any form of "fibrinoid necrosis", since no different patterns of C4d/CD68 expression could be observed in GA. This may explain why RG/GA are not distinguishable morphologically.

[Differential diagnosis of rheumatoid granuloma]

Rheumatoid granuloma (RG) is histomorphologically defined as a subcutaneous palisading granuloma with central fibrinoid necrosis. Clinically, it presents as a nodule typically localized at pressure points near the joints. From the rheumatic pathological point of view, the main diagnostic challenge is the differentiation of RG from granuloma anulare, especially if clinical information on the site of removal, known diseases, duration of illness, medication and existing American College of Rheumatology (ACR) criteria are missing. Other granulomatous lesions, such as mycobacterial infections, foreign body granulomas, necrobiosis lipoidica or sarcoidosis, can be differentiated from RG by histopathological criteria or by additional examinations such as pathogen specification or PCR. An immunohistochemical marker for the differential diagnosis of granulomas is not yet available. Diagnosis is based on conventional H-E staining, alcian blue-PAS staining, polarizing analysis or PCR. In the following article, the most important granulomatous entities in the differential diagnosis of RG are introduced and the main diagnostic characteristics are discussed.

Evidence-based review of biologic markers as indicators of disease progression and remission in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, immune-mediated inflammatory disease characterised by inflammation resulting in structural joint damage and functional disability. Tumour necrosis factor-alpha (TNFalpha) is a pivotal mediator and driver of inflammation in RA. Inflammation is closely related to the production of C-reactive protein (CRP), and a close correlation exists between serum CRP and TNFalpha levels. CRP levels are therefore a convenient, objective biomarker of disease activity. CRP correlates closely with changes in inflammation/disease activity, radiological damage and progression and functional disability. Identification of TNFalpha as a driver of RA progression has led to the introduction of TNFalpha-blocking agents and, subsequently, improvement of disease management. TNFalpha-blocking agents provide rapid, profound and sustained suppression of disease activity in correspondence with a marked reduction in CRP levels. A reduction in CRP level correlates closely with the positive clinical response to TNFalpha-blocking therapy. Thus, CRP levels can be used to predict, assess and monitor response to treatment with TNFalpha-blocking agents, and may be helpful in determining the optimal TNFalpha-blocker dosage. Given the close correlation between inflammation and disease progression and the relation between inflammation and CRP, the latter, if used effectively in clinical practice, may be means to identify patients likely to progress rapidly and who require intensive anti-TNFalpha therapy. The purpose of this review is to identify how CRP levels may be useful for monitoring the effect of therapy on halting disease progression and why monitoring CRP levels at baseline and after treatment should become a routine part of clinical practice.

Selective therapeutic control of C5a and the terminal complement complex by anti-C5 single-chain Fv in an experimental model of antigen-induced arthritis in rats

OBJECTIVE

To determine the role of the terminal complement complex (TCC) in the development of experimental antigen-induced arthritis (AIA) and the therapeutic effects of human anti-C5 single-chain Fv (scFv).

METHODS

Two different anti-C5 scFv, one that inhibits both release of C5a and assembly of the TCC (TS-A 12/22) and another that selectively blocks formation of the TCC (TS-A 8), were injected at the onset of AIA. The effects of these scFv on disease severity were evaluated for up to 21 days and compared with the effects of injection of an unrelated scFv. AIA was also established in C6-deficient and C6-sufficient PVG rats to obtain further information on the role of the TCC in this model.

RESULTS

TS-A 12/22 and TS-A 8 proved to be equally effective in reducing joint swelling, cell counts and tumor necrosis factor alpha levels in synovial lavage fluids, and the degree of histomorphologic changes compared with the effects of the unrelated scFv. TS-A 12/22 and TS-A 8 prevented the deposition of C9 but not that of C3, confirming the ability of the 2 scFv to neutralize C5. Administration of the 2 anti-C5 scFv after AIA onset also reduced disease severity. In C6-deficient rats with AIA, disease activity was reduced markedly compared with that in C6-sufficient rats.

CONCLUSION

These 2 human anti-C5 scFv could represent potential therapeutic reagents to be used in patients with rheumatoid arthritis. In addition, the finding that TS-A 8 was as effective as TS-A 12/22 in reducing disease severity suggests that the TCC is mainly responsible for the joint inflammation and damage observed in AIA.

Solid-phase classical complement activation by C-reactive protein (CRP) is inhibited by fluid-phase CRP–C1q interaction

C-reactive protein (CRP) interacts with phosphorylcholine (PC), Fcgamma receptors, complement factor C1q and cell nuclear constituents, yet its biological roles are insufficiently understood. The aim was to characterize CRP-induced complement activation by ellipsometry. PC conjugated with keyhole limpet hemocyanin (PC-KLH) was immobilized to cross-linked fibrinogen. A low-CRP serum with different amounts of added CRP was exposed to the PC-surfaces. The total serum protein deposition was quantified and deposition of IgG, C1q, C3c, C4, factor H, and CRP detected with polyclonal antibodies. The binding of serum CRP to PC-KLH dose-dependently triggered activation of the classical pathway. Unexpectedly, the activation was efficiently down-regulated at CRP levels > 150 mg/L. Using radial immunodiffusion, CRP-C1q interaction was observed in serum samples with high CRP concentrations. We propose that the underlying mechanism depends on fluid-phase interaction between C1q and CRP. This might constitute another level of complement regulation, which has implications for systemic lupus erythematosus where CRP is often low despite flare-ups.

Evaluation of classical complement pathway activation in rheumatoid arthritis: measurement of C1q-C4 complexes as novel activation products

OBJECTIVE

Novel activation products that are stable and minimally susceptible to in vitro artefacts have recently been described in the classical complement pathway. The present study assessed circulating levels of these products, i.e., covalent complexes between the recognition molecule of the classical pathway (C1q) and activated C4, in plasma samples from patients with rheumatoid arthritis (RA) to establish the relationship between these levels and the clinical and immunologic parameters in these patients.

METHODS

C1q-C4 levels were measured in plasma samples from 41 patients with active RA and 43 patients with inactive RA. These levels were related to other complement activation products and to disease activity according to the Disease Activity Score in 28 joints (DAS28), using Spearman's rank correlations.

RESULTS

C1q-C4 plasma levels were significantly higher in patients with active RA as compared with patients with RA in clinical remission (median 3.3 arbitrary units [AU], range 0.4-13.4 versus 1.7 AU, range 0.2-5.5; P=0.0001), suggesting that activation of the classical complement pathway reflects disease activity. This was supported by a significant correlation between C1q-C4 levels and the DAS28 (r=0.398, P=0.0002). Levels of other complement activation products, such as activated C4 (C4b/c), were also significantly elevated in patients with active disease compared with patients with inactive disease (P=0.03), and were correlated with C1q-C4 levels (r=0.329, P=0.002). Levels of C1q-C4 complexes were higher in synovial fluid samples than in plasma samples from the 4 patients tested.

CONCLUSION

Systemic complement activation via the classical pathway in patients with RA correlates with disease activity. These results indicate that C1q-C4 complexes may be used as a biomarker for RA.

Evidence That Complement Protein C1q Interacts with C-Reactive Protein through Its Globular Head Region

C1q acts as the recognition unit of the first complement component, C1, and binds to immunoglobulins IgG and IgM, as well as to non-Ig ligands, such as C-reactive protein (CRP). IgG and IgM are recognized via the globular head regions of C1q (C1qGR), whereas CRP has been postulated to interact with the collagen-like region (C1qCLR). In the present study, we used a series of nine mAbs to C1q, five directed against C1qGR and four against C1qCLR, to inhibit the interaction of C1q with CRP. The F(ab')(2) of each of the five mAbs directed against C1qGR inhibited binding of C1q to polymerized IgG. These five mAbs also successfully inhibited the interaction of C1q with CRP. Moreover, these five mAbs inhibited C1 activation by CRP as well as by polymerized IgG in vitro. In contrast, none of the four mAbs against C1qCLR inhibited C1q interaction with CRP or IgG, or could reduce activation of complement by CRP or polymerized IgG. These results provide the first evidence that the interaction of C1q with CRP or IgG involves sites located in the C1qGR, whereas sites in the CLR do not seem to be involved in the physiological interaction of C1q with CRP.

Statin-induced expression of CD59 on vascular endothelium in hypoxia: a potential mechanism for the anti-inflammatory actions of statins in rheumatoid arthritis

Hypoxia, which leads to dysfunctional cell metabolism, and complement activation both play central roles in the pathogenesis of rheumatoid arthritis (RA). Recent studies have reported that mice deficient for the complement-inhibitory protein CD59 show enhanced susceptibility to antigen-induced arthritis and reported that statins have anti-inflammatory effects in RA. We hypothesized that the anti-inflammatory effect of statins in RA relates in part to their ability to increase CD59 expression in hypoxic conditions and therefore to reduce complement activation. Flow-cytometric analysis showed that CD59 expression on endothelial cells (EC) was unaffected by atorvastatin in normoxia (21% O2), whereas in hypoxic conditions (1% O2) an up to threefold dose-dependent increase in CD59 expression was seen. This effect of hypoxia was confirmed by treatment of EC with chemical mimetics of hypoxia. The upregulation of CD59 protein expression in hypoxia was associated with an increase in steady-state mRNA. L-Mevalonate and geranylgeraniol reversed the response, confirming a role for inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase and geranylgeranylation. Likewise, inhibition by NG-monomethyl-L-arginine and NG-nitro-L-arginine methyl ester confirmed that CD59 upregulation in hypoxia was nitric oxide dependent. The expression of another complement-inhibitory protein, decay-accelerating factor (DAF), is known to be increased by atorvastatin in normoxia; this response was also significantly enhanced under hypoxic conditions. The upregulation of CD59 and DAF by atorvastatin in hypoxia prevented the deposition of C3, C9 and cell lysis that follows exposure of reoxygenated EC to serum. This cytoprotective effect was abrogated by inhibitory anti-CD59 and anti-DAF mAbs. The modulation of EC CD59 and DAF by statins under hypoxic conditions therefore inhibits both early and late complement activation and may contribute to the anti-inflammatory effects of statins in RA.

Rheumatoid arthritis: a disease associated with accelerated atherogenesis

OBJECTIVES

Rheumatoid arthritis (RA) is a systemic inflammatory disease associated with an increased prevalence of coronary heart disease and a high cardiovascular (CV) mortality. In this article, a review of mechanisms implicated in the development of accelerated atherogenesis in RA was performed. The potential role of treatment to reduce the incidence of CV events in RA was also discussed.

METHODS

Retrospective review of the literature. The potential mechanisms implicated in the development of accelerated atherogenesis in RA, information on carotid ultrasonography, and the potential implication of treatment to prevent accelerated atherogenesis in individuals with RA were examined.

RESULTS

Endothelial dysfunction, which is an early step in the development of atherosclerosis, has been observed in patients with RA. Deleterious effects resulting from persistent chronic inflammation may lead to endothelial dysfunction, insulin resistance, and a dyslipidemic pattern in these patients. Other mechanisms different from those related to classic atherogenesis risk factors, such as hyperhomocysteinemia and increased oxidative stress, are considered to be implicated in the pathogenesis of atherosclerosis in RA. Increased carotid intima-media thickness and carotid plaques have been found in RA patients compared with matched controls. Active MTX treatment of the disease has been associated with decreased CV mortality. Additional drugs such as statins may be considered in the management of these patients.

CONCLUSIONS

The increased prevalence of CV mortality rate in RA cannot only be explained by the presence of traditional atherosclerotic risk factors. A chronic inflammatory response may promote the development of accelerated atherogenesis in these patients. Active treatment of the disease is required to reduce the risk of developing CV complications in individuals with RA.

Infliximab treatment reduces complement activation in patients with rheumatoid arthritis

BACKGROUND

Tumour necrosis factor (TNF) blocking agents decrease C reactive protein (CRP) levels in rheumatoid arthritis (RA). It has been shown that CRP may contribute to complement activation in RA.

OBJECTIVE

To assess the effect of intravenous infliximab treatment on complement activation, especially that mediated by CRP, in RA.

METHODS

35 patients with active RA (28 joint count Disease Activity Score (DAS28) >4.4) were treated with intravenous injections of infliximab (3 mg/kg, at weeks 0, 2, 6, 14, and 22). Clinical response and plasma levels of complement activation products, of CRP and of CRP-complement complexes, which are specific markers for CRP mediated complement activation, were assessed at the indicated time points up to 22 weeks. The relationship between CRP and CRP-complement complexes was analysed by paired t test between two time points and by generalised estimated equation, to test differences of variables over time.

RESULTS

At 2 weeks after the first dose, infliximab significantly reduced overall C3 and C4 activation and plasma levels of CRP and CRP-complement complexes were also significantly reduced at this time point. The effects of infliximab on CRP and complement continued throughout the observation period and were more pronounced in patients with a good response to infliximab treatment.

CONCLUSION

Treatment with infliximab decreases plasma levels of CRP and CRP dependent complement activation products and concomitantly may reduce complement activation in RA. Complement activation may be among the effector mechanisms of TNF in RA.

Complexes between C1q and C3 or C4: novel and specific markers for classical complement pathway activation

Classical pathway activation is often assessed by measuring circulating levels of activated C4. However, this parameter does not discriminate between activation through the classical or the lectin pathway. We hypothesized that during classical pathway activation, complexes are formed between C1q and activated C4 or C3. Using ELISA, we investigated whether such complexes constitute specific markers for classical pathway activation. In vitro, C1q-C3d/C4d complexes were generated upon incubation of normal recalcified plasma with aggregated IgG or an anti-C1q mAb that activates C1 (mAb anti-C1q-130). In contrast, during incubation with C1s or trypsin, C1q-C3d/C4d complexes were not generated, which excludes an innocent bystander effect. Additionally, C1q-C3d/C4d complexes were not generated during activation of the alternative or the lectin pathway. Repeated freezing and thawing did not influence levels of C1q-C3d/C4d complexes in recalcified plasma. To measure C1q-complement complexes in plasma samples, we separated unbound complement proteins from C1q-C3d/C4d complexes in the samples prior to testing with ELISA. In samples from patients undergoing cardiopulmonary bypass surgery or suffering from rheumatoid arthritis, we found higher levels of C1q-C4 complexes than in samples from healthy individuals. We conclude that complexes between C1q and C4 or C3 are specific markers of classical complement pathway activation.

A monoclonal antibody to high-molecular weight kininogen is therapeutic in a rodent model of reactive arthritis

We reported that high-molecular weight kininogen is proangiogenic by releasing bradykinin and that a monoclonal antibody to high-molecular weight kininogen, C11C1, blocked its binding to endothelial cells. We now test if this antibody can prevent arthritis and systemic inflammation in a Lewis rat model. We studied 32 animals for 16 days. Group I (negative control) received saline intraperitoneally. Group II (disease-treated) received peptidoglycan-polysaccharide simultaneously with C11C1. Group III (disease-untreated) received peptidoglycan-polysaccharide simultaneously with isotype-matched mouse IgG. Group IV (disease-free-treated) and group V (disease-free isotype-treated) received saline and C11C1 or mouse IgG. Analysis of joint diameter changes showed a decrease in the C11C1 disease-treated group compared to the disease-untreated group. The hind paw inflammatory score showed a decrease in the intensity and extent of inflammation between the disease-untreated and the C11C1 disease-treated group. Prekallikrein, high-molecular weight kininogen, factor XI, and factor XII were decreased in the disease-untreated group compared to the C11C1 disease-treated group. T-kininogen was increased in the disease-untreated group when compared with the C11C1 disease-treated group. Disease-free groups IV and V did not show any sign of inflammation at any time. This study shows that monoclonal antibody C11C1 attenuates plasma kallikrein-kinin system activation, local and systemic inflammation, indicating therapeutic potential in reactive arthritis.

Endothelial dysfunction in young patients with rheumatoid arthritis and low disease activity

BACKGROUND

Rheumatoid arthritis (RA) is associated with an increased risk of cardiovascular disease. Endothelial dysfunction represents the earliest stage of atherosclerosis.

OBJECTIVE

To evaluate the influence of chronic inflammatory state on endothelial function in patients with RA by measuring endothelial reactivity in young patients with RA with low disease activity and without traditional cardiovascular risk factors.

METHODS

Brachial flow mediated vasodilatation (FMV), assessed by non-invasive ultrasound, was evaluated in 32 young to middle aged patients with RA (age </=59 years), with DAS28 </=3.2 and without overt cardiovascular disease, and in 28 age and sex matched controls.

RESULTS

Mean (SD) FMV was significantly lower in patients than in controls (3.2 (1.3)% v 5.7 (2.0)%; p<0.001), inversely related to low density lipoprotein cholesterol (r = -0.45, p<0.05) and C reactive protein (CRP), expressed as the value at the moment of ultrasound evaluation (r = -0.44, p<0.05), as the average of CRP levels evaluated at different times during the disease (r = -0.47, p<0.05), or as the average of >/=4 determinations multiplied by the disease duration (r = -0.40, p<0.05). In a multivariate regression model, a lower brachial flow mediated vasodilatation was independently predicted by low density lipoprotein cholesterol (beta = -0.40, p<0.05), average CRP levels multiplied by the disease duration (beta = -0.44, p<0.05), and brachial artery diameter (beta = -0.28, p<0.05).

CONCLUSIONS

Young to middle aged patients with RA with low disease activity, free from cardiovascular risk factors and overt cardiovascular disease, have an altered endothelial reactivity that seems to be primarily related to the disease associated chronic inflammatory condition.

Rat C-reactive protein activates the autologous complement system

Activation of complement is a biological function of human C-reactive protein (hCRP), whereas rat CRP (rCRP) has been claimed to be unable to activate complement. As important biological functions of proteins are probably conserved among species, we re-evaluated, using various ligands, the capability of rCRP to activate complement. The activation of complement by hCRP and rCRP was investigated in solid- and fluid-phase systems. In the solid-phase system, purified CRP was fixed to enzyme-linked immunosorbent assay (ELISA) plates and incubated with human or rat recalcified plasma. Dose-dependent binding of human and rat C3 and C4 was observed to human and rat CRP, respectively. In the fluid-phase system, recalcified rat plasma, which contains about 500 mg/l of CRP, or human plasma supplemented with hCRP, were incubated with lyso-phosphatidylcholine. A dose-dependent activation of complement was observed upon incubation with this ligand, as reflected by the generation of activated C4 as well as of CRP-complement complexes. This activation was, in both cases, inhibited by preincubation of plasma with p-aminophosphorylcholine, a specific inhibitor of the interaction of CRP with its ligands, or by chelation of calcium ions. We conclude that rat CRP, similarly to human CRP, can activate autologous complement. These results support the notion that opsonization of ligands with complement is an important biological function of CRP.

Regulation of CCR5 expression and MIP-1alpha production in CD4+ T cells from patients with rheumatoid arthritis

Production of CCR5 expression and MIP-1alpha, a ligand of CCR5, by CD4+ T cells from patients with rheumatoid arthritis (RA) were studied. We analysed further the influence of IL-15 stimulation, CD40/CD40 ligand (CD40L) interaction and CCR5 promotor polymorphism. One hundred and fifty-five RA patients and another 155 age- and sex-matched healthy individuals were enrolled. Peripheral CD4+ and double negative (DN) T cells from patients had lower portions of CCR5, whereas synovial CD4+ and DN T cells showed a much higher CCR5 expression. IL-15 significantly up-regulated the expression of CCR5 on purified CD4+ T cells. CD40L expression on synovial CD4+ T cells was increased greatly in CCR5+ portions by IL-15. MIP-1alpha production by synovial CD4+ T cells was also enhanced by IL-15. Co-culture of CD40 expressing synovial fibroblasts with IL-15-activated synovial CD4+ T cells significantly increased MIP-1alpha production. Expression of CCR5 on patients' CD4+ T cells was not influenced by the promotor polymorphism of CCR5 gene. Taken together, these data suggest CCR5+CD4+ T cells infiltrate the inflamed synovium and IL-15 up-regulates CCR5 and CD40L expression further and enhance MIP-1alpha production in synovial CD4+ T cells. Production of MIP-1alpha by synovial fibroblasts is significantly increased by engagement of CD40 with CD40L. Synovial microenvironment plays a potential role in regulation of CCR5+CD4+ T cells in rheumatoid joints.

Identification of IgG subclasses and C-reactive protein in lupus nephritis: the relationship between the composition of immune deposits and FCgamma receptor type IIA alleles

OBJECTIVE

To characterize the subclass composition of IgG deposited in lupus glomeruli, to examine its relationship to allelic polymorphisms of IgG receptors (Fcgamma receptors [FcgammaR]), and to determine whether C-reactive protein (CRP), a ligand for FcgammaRIIa, is present in these immune deposits.

METHODS

Renal biopsy samples from 80 patients with lupus nephritis were examined by light microscopy and indirect immunofluorescence with IgG-subclass-specific monoclonal antibodies. FcgammaRIIA genotypes were determined using allele-specific polymerase chain reaction. Immunostaining for CRP was performed on lupus and nonlupus glomerulonephritis specimens.

RESULTS

IgG2 and IgG3 were the predominant subclasses in immune deposits in all World Health Organization classes of nephritis. The frequency of genotypes containing the low-binding IgG2 allele, FcgammaRIIa-R131, was significantly greater than expected in patients with class III or class IV nephritis and in patients with intense IgG2 deposition. CRP, a ligand with particular affinity for FcgammaRIIa-R131, was consistently present in the renal immune deposits of lupus nephritis specimens.

CONCLUSION

FcgammaRIIA genes are associated with proliferative renal disease and may contribute to disease pathogenesis. FcgammaRIIa-R131, the variant with low affinity for IgG2, has high affinity for CRP. Thus, FcgammaRIIa-R131 may contribute to impaired removal of circulating immune complexes, as well as efficiently triggering phagocyte activation and the release of inflammatory mediators within glomeruli.

Common promoter variant in cyclooxygenase-2 represses gene expression: evidence of role in acute-phase inflammatory response

OBJECTIVE

Cyclooxygenase (COX)-2 is a key regulatory enzyme in the synthesis of prostanoids associated with trauma and inflammation. We investigated the COX-2 gene for functional variants that may influence susceptibility to disease.

METHODS AND RESULTS

The promoter of COX-2 was screened for variants in healthy subjects by use of polymerase chain reaction-based methods. Promoter activity was investigated by using reporter expression experiments in human lung fibroblasts. Patients undergoing coronary artery bypass graft surgery, with measurements of plasma markers linked to COX-2 activity, were genotyped for association studies. A common COX-2 promoter variant, -765G>C, was found and shown to be carried by >25% of a group of healthy UK subjects. The -765C allele had significantly lower promoter activity compared with -765G, basally (28+/-3% lower, P<0.005) and in serum-stimulated cells (31+/-2% lower, P<0.005). In patients subjected to coronary artery bypass graft surgery, the magnitude of rise in levels of C-reactive protein (CRP) was strongly genotype dependent. Compared with -765G homozygotes, patients carrying the -765C allele had significantly lower plasma CRP levels at 1 to 4 days after surgery (14% lower at the peak of CRP levels on day 3, P<0.05 for all time points).

CONCLUSIONS

For several acute and chronic inflammatory diseases, -765G>C may influence the variability of response observed.

Use of complement inhibitors in tissue injury

A great deal of information has accumulated implicating the complement system in several human disease processes. Although some of this information is circumstantial, protein inhibitors of the complement system have been developed and applied successfully to experimental disease models in animals. Two inhibitors, soluble complement receptor 1 (sCR1) and anti-C5 monoclonal antibody, are now being investigated in a variety of clinical conditions such as systemic lupus erythematosus and rheumatoid arthritis (RA), diseases for which current therapy has changed little and remains unsatisfactory. Preliminary successes in Phase II clinical trials of RA have provided optimism that complement inhibition might prove useful in these diseases and become part of standard medical therapy.

Z39Ig is co-expressed with activated macrophage genes

Z39Ig is a recently-identified gene with immunoglobulin-like domains whose function is unknown. We examined expression of Z39Ig in 1432 human cDNA libraries, and found it primarily in synovium of patients with rheumatoid arthritis, in placenta, and in lung. We analyzed its co-expression pattern using the Guilt-by-Association (GBA) algorithm, and found that it is most similar in expression to early genes in the classical complement system (C1qA, C1qB, C1qC, C1r, and C1 inhibitor), MHC class II genes (HLA-DR alpha, HLA-DR beta 1, and HLA-DP alpha 1), Fc receptors (Fc gamma RIIa and Fc epsilon R1), lysosomal protein (LAPTm5), tissue transglutaminase, and macrophage receptors (MARCO and CD163/M130). The sequence and expression data suggest that Z39Ig is a cell surface receptor, expressed in activated macrophages, and linked with the classical complement system, most likely in phagocytosis preceding antigen presentation. Knowledge of this gene may contribute to better understanding of the role of complement and activated macrophages in rheumatoid arthritis and systemic lupus.