Thioredoxin protects against joint destruction in a murine arthritis model

Thioredoxin (TRX) is an oxidative stress-inducible biological antioxidant that is highly expressed in the synoviocytes of rheumatoid arthritis (RA) patients. There is much evidence that oxidative stress plays a key role in the inflammation and destruction of RA joints; the functional relationship between TRX and RA remains unknown, however. We therefore investigated the role played by TRX in the inflammatory and joint-damaging processes of RA using a murine model in which arthritis was induced by administering a mixture of anti-type II collagen monoclonal antibodies (mAb) and lipopolysaccharide (LPS). In Wt mice mAb/LPS injection induced neutrophil infiltration, cartilage destruction, and chondrocyte apoptosis within the joints, all of which were dramatically suppressed in TRX transgenic (TRX-Tg) mice. Moreover, the 8-hydoxy-2'-deoxyguanosine (8-OHdG) expression seen in Wt mice after mAb/LPS injection was almost completely inhibited in TRX-Tg mice. The administration of recombinant TRX also suppressed mAb/LPS-induced joint swelling in Wt mice. Taken together, these results suggest that TRX protects against arthritis and is a plausible candidate with which to develop novel therapies for the treatment of RA.     

Inhibition of HDAC activity by ITF2357 ameliorates joint inflammation and prevents cartilage and bone destruction in experimental arthritis

Inhibition of histone deacetylases (HDAC) has been shown to modulate gene expression and cytokine production after stimulation with several stimuli. In the present study, the antiinflammatory effect of a potent HDACi, ITF2357, was explored in different experimental models of arthritis. In addition, the bone protective effect of ITF2357 was investigated in vitro. Treatment of acute arthritis (Streptococcus pyogenes cell wall [SCW] arthritis) with ITF2357 showed that joint swelling and cell influx into the joint cavity were reduced. Furthermore, the chondrocyte metabolic function was improved by treatment of ITF2357. The production of proinflammatory cytokines by synovial tissue was reduced after ITF2357 treatment. To examine the effect of HDAC inhibition on joint destruction, ITF2357 was applied to both rat adjuvant arthritis and mouse collagen type II arthritis. ITF2357 treatment both ameliorates the severity scores in arthritis models and prevents bone destruction. In an in vitro bone destruction assay, ITF2357 was highly effective at a dose of 100 nmol/L. In conclusion, inhibition of HDAC prevents joint inflammation and cartilage and bone destruction in experimental arthritis.     

Combined treatment with dexamethasone and raloxifene totally abrogates osteoporosis and joint destruction in experimental postmenopausal arthritis

Introduction  

Postmenopausal patients with rheumatoid arthritis (RA) are often treated with corticosteroids. Loss of estrogen, the inflammatory disease and exposure to corticosteroids all contribute to the development of osteoporosis. Therefore, our aim was to investigate if addition of the selective estrogen receptor modulator raloxifene, or estradiol, could prevent loss of bone mineral density in ovariectomized and dexamethasone treated mice with collagen-induced arthritis (CIA).     

An experimental model for chronic lymphedema

Although a multitude of operations exist for the treatment of lymphedema, none is highly successful. An experimental model that reliably and easily produces chronic lymphedema in an extremity would be useful to study treatments in a controlled and comparative manner and would enhance our understanding of the physiology and treatment of lymphedema. Many models that simulate clinical lymphedema have been described, but they suffer from cumbersome protocols, high laboratory costs, and an inconsistent yield of permanent lymphedema. We describe an experimental model for chronic lymphedema in the lower extremity of the rat that creates a lymphatic block in the groin induced by radiation treatment and one operation--surgical division of the superficial and deep lymphatics. All animals develop stable chronic lymphedema of the lower extremity within days of operation, with swelling that persists for at least 9 months. A mortality rate of 8 percent was associated with this technique. Methods for quantification of limb swelling are described, as is analysis of the lymphatic block by lymphoscintigraphic imaging of lymph channels and nodes. This model has the advantages of simplicity of technique, cost-effective use of rodent subjects, reproducibility of lymphedema, and quantification of results.     

Suppression of macrophage infiltration into the conjunctiva by clodronate liposomes in experimental immune-mediated blepharoconjunctivitis

Macrophages infiltrate the conjunctiva in severe cases of allergic conjunctivitis (AC) such as atopic keratoconjunctivitis (AKC). We established experimental immune-mediated blepharoconjunctivitis (EC) in Brown Norway (BN) rats as a model for severe types of AC. We investigated whether macrophage infiltration in the conjunctiva in this EC model is inhibited by clodronate liposomes (CL2MDP-lip). The numbers of ED1-positive but not ED2-positive macrophages in the conjunctivas were increased by the induction of EC. Subconjunctival injection of CL2MDP-lip decreased the number of ED2-positive but not ED1-positive macrophages in the conjunctivas of naive rats. CL2MDP-lip did not affect macrophages in the spleen. Subconjunctival injection of CL2MDP-lip into EC-developing BN rats decreased the number of ED2-positive macrophages at all the time points. ED1-positive cell infiltration was inhibited when treatment was administered just prior to OVA challenge. Intravenous injection of CL2MDP-lip decreased the number of ED2-positive cells in the conjunctiva. Thus, we conclude that CL2MDP-lip inhibits infiltration of macrophages into the conjunctiva within 24 h of antigen challenge.     

C17 prevents inflammatory arthritis and associated joint destruction in mice

C17 was first described about ten years ago as a gene expressed in CD34+ cells. A more recent study has suggested a role for C17 in chondrogenesis and development of cartilage. However, based on sequence analysis, we believe that C17 has homology to IL-2 and hence we present the hypothesis that C17 is a cytokine possessing immune-regulatory properties. We provide evidence that C17 is a secreted protein preferentially expressed in chondrocytes, hence in cartilage-rich tissues. Systemic expression of C17 in vivo reduces disease in a collagen antibody-induced arthritis model in mice (CAIA). Joint protection is evident by delayed disease onset, minimal edema, bone protection and absence of diverse histological features of disease. Expression of genes typically associated with acute joint inflammation and erosion of cartilage or bone is blunted in the presence of C17. Consistent with the observed reduction in bone erosion, we demonstrate reduced levels of RANKL in the paws and sera of mice over-expressing C17. Administration of C17 at the peak of disease, however, had no effect on disease progression, indicating that C17's immune-regulatory activity must be most prominent prior to or at the onset of severe joint inflammation. Based on this data we propose C17 as a cytokine that s contributes to immune homeostasis systemically or in a tissue-specific manner in the joint.     

The role of interleukin-17 in mediating joint destruction in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, persistent inflammatory joint disease with systemic involvement that affects about 1% of the world’s population, that ultimately leads to the progressive destruction of joint. Effective medical treatment for joint destruction in RA is lacking because the knowledge about molecular mechanisms leading to joint destruction are incompletely understood. It has been confirmed that cytokine-mediated immunity plays a crucial role in the pathogenesis of various autoimmune diseases including RA. Recently, IL-17 was identified, which production by Th17 cells. IL-17 has proinflammatory properties and may promote bone and joint damage through induction of matrix metalloproteinases and osteoclasts. In mice, intra-articular injection of IL-17 into the knee joint results in joint inflammation and damage. In addition, it has been shown that blocking IL-17/IL-17R signaling is effective in the control of rheumatoid arthritis symptoms and in the prevention of joint destruction. In this article, we will briefly discuss the biological features of IL-17/IL-17R and summarize recent advances on the role of IL-17/IL-17R in the pathogenesis and treatment of joint destruction in RA.     

Serum IL-2 level in rheumatoid arthritis: correlation with joint destruction and disease progression.

Understanding of T cell dysfunctions in rheumatoid arthritis (RA) may help to elucidate the pathophysiology of this disease. Cytokines determinations may be a promising approach and could represent a simple mean of quantifying RA immunological dysfunctions. In this study, interleukin-2 (IL-2) measurements were performed in sera of 74 RA patients to evaluate the potential use of this method to monitor "disease activity" and/or prognosis. Although the serum IL-2 levels of patients in active disease stage proved to be somewhat lower than those from patients with inactive disease, the difference was not significant. In our study, however, the serum IL-2 concentration was correlated with the circulating immune complexes level. In addition, patients with the highest serum IL-2 levels exhibited the poorest radiological stages and these same patients were often not receiving any disease modifying antirheumatic drugs (DMARD). Our results demonstrate that serum IL-2 level may be elevated in certain RA conditions. A better understanding of this phenomenon, especially the consequences of disease duration, could be of interest in the follow up and the prognosis of the disease.     

Alternative complement pathway activation is essential for inflammation and joint destruction in the passive transfer model of collagen-induced arthritis

Activation of each complement initiation pathway (classical, alternative, and lectin) can lead to the generation of bioactive fragments with resulting inflammation in target organs. The objective of the current study was to determine the role of specific complement activation pathways in the pathogenesis of experimental anti-type II collagen mAb-passive transfer arthritis. C57BL/6 mice were used that were genetically deficient in either the alternative pathway protein factor B (Bf(-/-)) or in the classical pathway component C4 (C4(-/-)). Clinical disease activity was markedly decreased in Bf(-/-) compared with wild-type (WT) mice (0.5 +/- 0.22 (n = 6) in Bf(-/-) vs 8.83 +/- 0.41 (n = 6) in WT mice (p < 0.0001)). Disease activity scores were not different between C4(-/-) and WT mice. Analyses of joints showed that C3 deposition, inflammation, pannus, cartilage, and bone damage scores were all significantly less in Bf(-/-) as compared with WT mice. There were significant decreases in mRNA levels of C3, C4, CR2, CR3, C3aR, and C5aR in the knees of Bf(-/-) as compared with C4(-/-) and WT mice with arthritis; mRNA levels for complement regulatory proteins did not differ between the three strains. These results indicate that the alternative pathway is absolutely required for the induction of arthritis following injection of anti-collagen Abs. The mechanisms by which these target organ-specific mAbs bypass the requirements for engagement of the classical pathway remain to be defined but do not appear to involve a lack of alternative pathway regulatory proteins.     

IL-1-independent role of IL-17 in synovial inflammation and joint destruction during collagen-induced arthritis.

T cell IL-17 displays proinflammatory properties and is expressed in the synovium of patients with rheumatoid arthritis. Its contribution to the arthritic process has not been identified. Here, we show that blocking of endogenous IL-17 in the autoimmune collagen-induced arthritis model results in suppression of arthritis. Also, joint damage was significantly reduced. In contrast, overexpression of IL-17 enhanced collagen arthritis. Moreover, adenoviral IL-17 injected in the knee joint of type II collagen-immunized mice accelerated the onset and aggravated the synovial inflammation at the site. Radiographic and histologic analysis showed markedly increased joint destruction. Elevated levels of IL-1beta protein were found in synovial tissue. Intriguingly, blocking of IL-1alphabeta with neutralizing Abs had no effect on the IL-17-induced inflammation and joint damage in the knee joint, implying an IL-1 independent pathway. This direct potency of IL-17 was underscored in the unabated IL-17-induced exaggeration of bacterial cell wall-induced arthritis in IL-1beta(-/-) mice. In conclusion, this data shows that IL-17 contributes to joint destruction and identifies an IL-1-independent role of IL-17. These findings suggest IL-17 to be a novel target for the treatment of destructive arthritis and may have implications for tissue destruction in other autoimmune diseases.     

Perpetuation of inflammation associated with experimental arthritis: the role of macrophage activation by neutrophilic myeloperoxidase.

Rheumatoid arthritis (RA) is characterized by an abnormal cellular and cytokine infiltration of inflamed joints. This study addresses a previously unrecognized interaction between neutrophilic-myeloperoxidase (MPO) and macrophages (Mphi) which could explain the perpetuation of inflammation associated with RA. A monoarticular arthritis was induced in female Lewis rats by injection of streptococcal cell wall extracts (PG-APS). After swelling and erythema subsided, joints were re-injected with one of the following: porcine MPO or partially inactivated MPO (iMPO). Injection with either MPO or iMPO induced a ''flare'' of experimental RA. Blocking the Mphi-mannose receptor by mannans, ablated exacerbation of disease. These results indicate that MPO or iMPO can play a pivotal role in the perpetuation but not initiation of this RA model.     

Amelioration by menadione of the experimental chronic immune arthritis in the rabbit

The immunological induction of arthritis in the knee of the rabbit is well established as a model for human rheumatoid arthritis. It has the special advantage of allowing the development of the condition, and the effect of disease-modifying agents, to be followed. Attention has been focussed on the activity of glucose 6-phosphate dehydrogenase in the synovial lining cells since the fourfold elevation of this activity was shown to be fundamental in the human condition. An equal elevation of this activity has now been demonstrated in the rabbit model. Furthermore, it has been shown that the oral administration of menadione decreases this activity towards normality with a concomitant decrease in the degree of inflammation.     

A genetic variant in osteoprotegerin is associated with progression of joint destruction in rheumatoid arthritis

Introduction

Progression of joint destruction in rheumatoid arthritis (RA) is partly heritably; 45 to 58% of the variance in joint destruction is estimated to be explained by genetic factors. The binding of RANKL (Receptor Activator for Nuclear Factor κ B Ligand) to RANK results in the activation of TRAF6 (tumor necrosis factor (TNF) receptor associated factor-6), and osteoclast formation ultimately leading to enhanced bone resorption. This bone resorption is inhibited by osteoprotegerin (OPG) which prevents RANKL-RANK interactions. The OPG/RANK/RANKL/TRAF6 pathway plays an important role in bone remodeling. Therefore, we investigated whether genetic variants in OPG, RANK, RANKL and TRAF6 are associated with the rate of joint destruction in RA.

Methods

1,418 patients with 4,885 X-rays of hands and feet derived from four independent data-sets were studied. In each data-set the relative increase of the progression rate per year in the presence of a genotype was assessed. First, explorative analyses were performed on 600 RA-patients from Leiden. 109 SNPs, tagging OPG, RANK, RANKL and TRAF6, were tested. Single nucleotide polymorphisms (SNPs) significantly associated in phase-1 were genotyped in data-sets from Groningen (Netherlands), Sheffield (United Kingdom) and Lund (Switzerland). Data were summarized in an inverse weighted variance meta-analysis. Bonferonni correction for multiple testing was applied.

Results

We found that 33 SNPs were significantly associated with the rate of joint destruction in phase-1. In phase-2, six SNPs in OPG and four SNPs in RANK were associated with progression of joint destruction with P-value <0.05. In the meta-analyses of all four data-sets, RA-patients with the minor allele of OPG-rs1485305 expressed higher rates of joint destruction compared to patients without these risk variants (P = 2.35x10⁻⁴). This variant was also significant after Bonferroni correction.

Conclusions

These results indicate that a genetic variant in OPG is associated with a more severe rate of joint destruction in RA.     

Further evidence validating adjuvant arthritis as an experimental model of chronic pain in the rat

The experiments described here were aimed at further validating adjuvant arthritis as an animal model of chronic pain. It was found that the relative oral intake of a 0.008 mg/ml solution of fentanyl was higher in arthritic than in normal control rats; this difference was predicted by the notion that the analgesic effect of a substance may reinforce its intake in animals exposed to pain, more so than in normal pain-free animals. It was also found that body weight decreases and that vocalizations of aggregated rats increase as a result of the challenge; these effects suggest that the vegetative signs and the behavioral irritability which are characteristic of chronic pain in humans, also occur in arthritic animals. The pain which thus seems to be associated with adjuvant arthritis was estimated to have its onset on days 10–11, to peak on days 18–21, and to terminate on days 35–40 after inoculation with $\text{Mycobacterium butyricum}$.     

Alveolar macrophage activation in experimental legionellosis.

Legionella pneumophila is a facultative intracellular parasite of alveolar macrophages. In vitro studies have shown that lymphokine-activated mononuclear phagocytes inhibit intracellular replication of L. pneumophila. To determine if recovery from legionellosis is associated with activation of alveolar macrophages in vivo to resist L. pneumophila, we studied an animal model of Legionnaires' disease. Rats were exposed to aerosolized L. pneumophila and alveolar macrophages were harvested during the recovery phase of infection. We compared these alveolar exudate macrophages with normal resident alveolar macrophages for the capacity to support or inhibit the intracellular growth of L. pneumophila. We also measured Ia expression as a marker of immunologic activation, and studied binding of bacteria, superoxide release, and the expression of transferrin receptors as potential mechanisms of resistance to L. pneumophila. For perspective on the specificity of these responses, we also studied alveolar exudate cells elicited by inhalation of heat-killed L. pneumophila, live Listeria monocytogenes, and live Escherichia coli. We found that alveolar exudate macrophages elicited by live L. pneumophila, but not heat-killed L. pneumophila, resisted the intracellular growth of L. pneumophila. Exudate macrophages in resolving legionellosis exhibited increased Ia expression, diminished superoxide production, and downregulation of transferrin receptors. Binding of L. pneumophila to exudate macrophages was indistinguishable from that to resident macrophages in the presence of normal serum, and augmented in the presence of immune serum. Alveolar exudate macrophages elicited by E. coli also inhibited growth of L. pneumophila, and exhibited a modest increase in Ia expression without change in transferrin receptors. Exudate cells induced by L. monocytogenes exhibited up-regulation of Ia without diminution of superoxide release. Alveolar cells harvested after inhalation of heat-killed L. pneumophila did not differ from resident alveolar macrophages in the expression of surface markers. These findings suggest that alveolar macrophages are immunologically activated in vivo to serve as effector cells in resolving legionellosis, and that live bacteria are required to induce this expression of immunity. The mechanism of resistance to parasitism by L. pneumophila may entail restriction of the intracellular availability of iron, but does not involve diminished bacterial binding or an augmented respiratory burst.     

Adenoviral vector-mediated overexpression of IL-4 in the knee joint of mice with collagen-induced arthritis prevents cartilage destruction.

Rheumatoid arthritis is a chronic inflammatory joint disease, leading to cartilage and bone destruction. In this study, we investigated the effects of local IL-4 application, introduced by a recombinant human type 5 adenovirus vector, in the knee joint of mice with collagen-induced arthritis. One intraarticular injection with an IL-4-expressing virus caused overexpression of IL-4 in the mouse knee joint. Enhanced onset and aggravation of the synovial inflammation were found in the IL-4 group. However, despite ongoing inflammation, histologic analysis showed impressive prevention of chondrocyte death and cartilage erosion. In line with this, chondrocyte proteoglycan synthesis was enhanced in the articular cartilage. This was quantified with ex vivo 35S-sulfate incorporation in patellar cartilage and confirmed by autoradiography on whole knee joint sections. Reduction of cartilage erosion was further substantiated by lack of expression of the stromelysin-dependent cartilage proteoglycan breakdown neoepitope VDIPEN in the Ad5E1 mIL-4-treated knee joint. Reduced metalloproteinase activity was also supported by markedly diminished mRNA expression of stromelysin-3 in the synovial tissue. Histologic analysis revealed marked reduction of polymorphonuclear cells in the synovial joint space in the IL-4-treated joints. This was confirmed by immunolocalization studies on knee joint sections using NIMP-R14 staining and diminished mRNA expression of macrophage-inflammatory protein-2 in the synovium tissue. mRNA levels of TNF-alpha and IL-1beta were suppressed as well, and IL-1beta and nitric oxide production by arthritic synovial tissue were strongly reduced. Our data show an impressive cartilage-protective effect of local IL-4 and underline the feasibility of local gene therapy with this cytokine in arthritis.     

Metabolism of cholesteryl ester lipid droplets in a J774 macrophage foam cell model

J774 macrophages rapidly incorporated [3H]cholesteryl oleate droplets by a non-saturable phagocytic process. In less than 2 h, foam cell morphology was acquired. The extent of loading obtained after 2 h was a linear function of the mass of cholesteryl oleate provided to the cells. The cholesteryl oleate incorporated was hydrolyzed in the cells at a linear rate over 24 h and the fractional hydrolysis was constant over a wide range of cellular esterified cholesterol contents. The rate of hydrolysis was influenced by the physical state of the cholesteryl ester; cholesteryl oleate in isotropic droplets was hydrolyzed 2-3-fold more rapidly than cholesteryl oleate in anisotropic droplets. The hydrolysis of both types of droplets was inhibited by lysosomotropic agents, indicating that hydrolysis occurred in the lysosomes. Only a small fraction (less than 10% after 24 h) of the free [3H]cholesterol generated in the lysosomes was esterified by ACAT resulting in a doubling of the cell free cholesterol content. Electron microscopy of cells treated with digitonin revealed the accumulation of free cholesterol in lipid-laden lysosomes. ACAT was active as endogenous free [14C]cholesterol was esterified in a linear manner over 24 h and was responsive to the presence of lysosomally-derived cholesterol, as the extent of esterification of the endogenous pool was directly proportional to the mass of [3H]cholesterol generated in the lysosomes.