[Show abstract][Hide abstract] ABSTRACT: To study whether hypercholesterolemia increases articular damage in a rabbit model of chronic arthritis.
Hypercholesterolemia was induced in eighteen rabbits by administrating a high-fat diet (HFD). Fifteen rabbits were fed normal chow as controls. Chronic arthritis (AIA) was induced in half of the HFD and control rabbits, previously immunized, by intra-articular injections of ovalbumin. After sacrifice, lipid and systemic inflammation markers were analyzed in blood serum. Synovium was analyzed by Krenn score, multinucleated cell counting, immunohistochemistry of RAM11 and CD31, and TNF-alpha and MCP-1 gene expression. Active bone resorption was assessed by protein expression of RANKL, OPG and quantification of cathepsin K, contact surface and invasive area of pannus into bone.
Rabbits receiving HFD showed higher total serum cholesterol, HDL, triglycerides and CRP levels than rabbits fed normal diet. Synovitis score was increased in HFD, and particularly in AIA and AIA+HFD groups. AIA+HFD synovium was characterized by a massive infiltration of RAM11+ cells, higher presence of multinucleated foam cells and bigger vascularization than AIA. Cathepsin K+ osteoclasts and contact surface of bone resorbing pannus were also increased in rabbits with AIA+HFD compared with AIA alone. Synovial TNF-alpha and MCP-1 gene expression was increased in AIA and HFD rabbits compared with healthy animals. RANKL protein expression in AIA and AIA+HFD groups was higher compared with either HFD or normal groups.
This experimental model demonstrates that hypercholesterolemia increments joint tissue damage in chronic arthritis, being foam macrophages key players in this process.
[Show abstract][Hide abstract] ABSTRACT: The receptor activator nuclear factor-kappaB ligand (RANKL) diffuses from articular cartilage to subchondral bone. However, the role of chondrocyte-synthesized RANKL in rheumatoid arthritis-associated juxta-articular bone loss has not yet been explored. This study aimed to determine whether RANKL produced by chondrocytes induces osteoclastogenesis and juxta-articular bone loss associated with chronic arthritis.
Chronic antigen-induced arthritis (AIA) was induced in New Zealand (NZ) rabbits. Osteoarthritis (OA) and control groups were simultaneously studied. Dual X-ray absorptiometry of subchondral knee bone was performed before sacrifice. Histological analysis and protein expression of RANKL and osteoprotegerin (OPG) were evaluated in joint tissues. Co-cultures of human OA articular chondrocytes with peripheral blood mononuclear cells (PBMCs) from healthy donors were stimulated with macrophage-colony stimulating factor (M-CSF) and prostaglandin E2 (PGE2), then further stained with tartrate-resistant acid phosphatase.
Subchondral bone loss was confirmed in AIA rabbits when compared with controls. The expression of RANKL, OPG and RANKL/OPG ratio in cartilage were increased in AIA compared to control animals, although this pattern was not seen in synovium. Furthermore, RANKL expression and RANKL/OPG ratio were inversely related to subchondral bone mineral density. RANKL expression was observed throughout all cartilage zones of rabbits and was specially increased in the calcified cartilage of AIA animals. Co-cultures demonstrated that PGE2-stimulated human chondrocytes, which produce RANKL, also induce osteoclasts differentiation from PBMCs.
Chondrocyte-synthesized RANKL may contribute to the development of juxta-articular osteoporosis associated with chronic arthritis, by enhancing osteoclastogenesis. These results point out a new mechanism of bone loss in patients with rheumatoid arthritis.
[Show abstract][Hide abstract] ABSTRACT: Background and objectivesCytotoxic T lymphocyte antigen 4 (CTLA4) is a surface protein on T lymphocytes that binds to the surface of antigen-presenting cells through the CD80/86 molecules regulating their co-stimulation. The authors hypothesised that Abatacept (CTLA4-Ig) might bind to monocyte/macrophages regulating the differentiation of monocytes to macrophages, and the production of pro-inflammatory and anti-inflammatory cytokines by macrophages.Material and methodsHuman peripheral blood mononuclear cells were isolated from buffy coats from four normal donors by Ficoll gradient cell separation. Then, monocytes were purified by CD14 positive selection, and they were differentiated in vitro to classic and alternative macrophages by culturing in the presence of granulocyte-macrophage colony stimulating factor or macrophage-colony stimulating factor (M-CSF) respectively. The authors analysed the CTLA4-Ig binding to classic and alternative macrophages by flow cytometry. After demonstrating that CTLA4-Ig binds to classic and alternative macrophages, the effect of CTLA4-Ig on macrophage differentiation and cytokines production were tested.ResultsCTLA4-Ig binds to human macrophages. In addition, CTLA4-Ig reduced, in a dose-dependent fashion, the macrophage differentiation in monocytes cultures stimulated with M-CSF. This results did not evidence any effect of CTLA4-Ig on the IL-10 or tumour necrosis factor production by neither classical nor alternative macrophages.Conclusion
These data show that CTLA4-Ig directly affects macrophage differentiation in vitro. Therefore, the beneficial effect of Abatacept in rheumatoid arthritis patients could be achieved at least partially through a direct mechanism of action on the monocyte/macrophage line cell.
Annals of the Rheumatic Diseases 02/2011; 70(2). DOI:10.1136/ard.2010.149013.3 · 10.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-steroidal anti-inflammatory drugs improve inflammatory cachexia in several conditions. Thus, we have explored inhibition of cyclooxygenase-2 (COX-2) in an experimental model of rheumatoid cachexia in rabbits.
Chronic arthritis was induced in immunized rabbits by repeated intra-articular injections of ovalbumin. To increase the degree of systemic inflammation and also to induce atherosclerotic lesions, the animals were fed a hyperlipidaemic diet (2% cholesterol and 6% peanut oil) and were given an endothelial injury of the femoral artery. Rabbits were randomized to receive the COX-2 inhibitor celecoxib (10 mg·kg⁻¹ ·day⁻¹) or no treatment. After 4 weeks, sera, peripheral mononuclear cells and vessel specimens were collected.
Inhibition of COX-2 by celecoxib modulated the systemic inflammatory response and increased total cholesterol and triglyceride levels. Celecoxib also minimized weight loss and prevented serum albumin fall. At a vascular level, celecoxib reduced COX-2 protein in the femoral arterial wall, but did not modify size or the macrophage infiltration of femoral lesions nor the percentage of rabbits with spontaneous aortic plaques.
Our animal model induced a severe inflammatory cachexia, comparable to that of persistently active rheumatoid arthritis. The inhibition of COX-2 by celecoxib improves this state, suggesting that COX products play an important role in its development, without affecting the development or the progression of vascular lesions. Overall, these results suggest that celecoxib might be considered as a new therapeutic tool for the treatment of rheumatoid cachexia.
British Journal of Pharmacology 11/2010; 161(5):1012-22. DOI:10.1111/j.1476-5381.2010.00957.x · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Our aim was to explore the effect of chondroitin sulfate (CS), a natural glycosaminoglycan with attributed anti-inflammatory properties, on synovitis in a rabbit model of chronic arthritis with intense systemic inflammation bolstered by endothelial lesion and atherosclerotic diet.
Chronic arthritis was induced by intraarticular injections of ovalbumin in immunized rabbits. Systemic inflammation was boosted in these rabbits by receiving a hyperlipidemic diet after producing an endothelial lesion in the femoral arteries. A group of these rabbits were treated with CS (100mg/kg/day). At sacrifice, synovial membranes were isolated, and cyclooxygenase-2 (COX-2) and chemokine (C-C motif) ligand 2 (CCL2) mRNA, as well as protein expression were assayed by quantitative real-time polymerase chain reaction (RT-PCR) and western blot studies. Histological synovial examination was also carried out employing the histopathological synovitis score (Krenn scale).
CS diminished both gene expression and protein synthesis of COX-2 and CCL2, and the histopathological score of the synovial membrane, when compared to untreated rabbits. In fact, CS partially prevented the intimal layer proliferation and the inflammatory cell infiltration in the synovial membrane, which was observed in non-treated animals.
CS reduced the inflammatory response of the synovial membrane, as well as decreased the synovial histopathological lesions in our animal model. Further studies are warranted to demonstrate whether CS might be beneficial in the treatment of inflammatory arthritis.
[Show abstract][Hide abstract] ABSTRACT: The rheumatic diseases have been associated with accelerated atherosclerosis. Rheumatoid arthritis (RA) is a systemic inflammatory disease characterized by persistent synovial inflammation which leads to disability and structural changes in joints. Epidemiological studies have demonstrated an increased cardiovascular mortality in patients with RA. In these patients, atherosclerotic plaque occurs earlier, and it has a faster evolution than in general population. Atherosclerosis (AT) is also an inflammatory disease partly mediated by cytokines, many of them involved on chronic synovitis. Our group has developed a rabbit experimental model of AT aggravated by chronic arthritis to study inflammatory mechanisms involved on the progression of vascular lesions and their response to drugs. A preliminary study using this model suggests a beneficial effect of chondroitin sulphate (CS), a drug recommended for the treatment of osteoarthritis, in controlling AT lesions. Yet clinical trials should be conducted with this compound to address the same hypothesis in human studies.
[Show abstract][Hide abstract] ABSTRACT: Glucosamine sulfate (GS) is a glycosaminoglycan with anti-inflammatory and immunoregulatory properties. Here we set out to explore the effect of GS administration on markers of systemic and local inflammation in rabbits with atherosclerosis aggravated by chronic arthritis. Atherosclerosis was induced in rabbits by maintaining them on a hyperlipidemic diet after producing an endothelial lesion in the femoral arteries. Simultaneously, chronic arthritis was induced in these animals by repeated intra-articular injections of ovalbumin in previously immunized rabbits. A group of these rabbits was treated prophylactically with oral GS (500 mg.kg(-1).day(-1)), and, when the animals were killed, serum was extracted and peripheral blood mononuclear cells (PBMC) were isolated. Furthermore, the femoral arteries, thoracic aorta, and synovial membranes were examined in gene expression studies and histologically. GS administration reduced circulating levels of the C-reactive protein and of interleukin-6. GS also lowered nuclear factor-kappaB activation in PBMC, and it downregulated the expression of both the CCL2 (monocyte chemoattractant protein) and cyclooxygenase-2 genes in these cells. Lesions at the femoral wall were milder after GS treatment, as reflected by the intimal-to-media thickened ratio and the absence of aortic lesions. Indeed, GS also attenuated the histological lesions in synovial tissue. In a combined rabbit model of chronic arthritis and atherosclerosis, orally administered GS reduced the markers of inflammation in peripheral blood, as well as the femoral and synovial membrane lesions. GS also prevented the development of inflammation-associated aortic lesions. These results suggest an atheroprotective effect of GS.