Down regulation of interleukin 1beta production in human osteoarthritic synovial tissue and cartilage cultures by aminoguanidine

Aminoguanidine inhibits IL-1β-induced protein expression of iNOS and COX-2 by blocking the NF-κB signaling pathway in rat articular chondrocytes

Osteoarthritis is a chronic joint disease which has a serious impact on the health and quality of life of affected humans and animals. As an inhibitor of inducible nitric oxide synthase (iNOS), aminoguanidine (AG) displays anti-inflammatory effects. The purpose of the present study was to investigate the effect of AG on the expression of iNOS and cyclooxygenase-2 (COX-2), and the activity of the NF-κB signaling pathway in rat chondrocytes stimulated by interleukin-1β (IL-1β). The viability of chondrocytes treated with AG (0.3, 1 or 3 mM) alone was determined using a Cell Counting Kit-8 assay. Subsequently, the chondrocytes were treated with either 10 ng/ml IL-1β alone, or co-treated with increasing concentrations of AG (0.3, 1 or 3 mM) and 10 ng/ml IL-1β. The protein levels of COX-2, iNOS, phosphorylated (p)-p65, p65, p-NF-κβ inhibitor α (IκBα), IκBα, p-inhibitor of NF-κβ-β (IKKβ) and IKKβ were evaluated by western blotting. NF-κB translocation was determined by immunofluorescence analysis. Western blotting and reverse transcription-quantitative PCR were used to detect expression levels of relevant proteins/genes. The results suggested that the inhibitory effect of AG on the protein and gene expression levels of iNOS and COX-2 in IL-1β-treated chondrocytes was dose-dependent. In addition, AG decreased the level of phosphorylation of IKKβ, IκBα and NF-κB p65, the degradation of IKKβ, IκBα and p65, and the translocation of NF-κB in IL-1β-stimulated chondrocytes. The most significant inhibitory effect of AG was observed at a concentration of 1 mM. Therefore, the present study suggested that AG may serve as a potential agent to reduce the inflammatory response of chondrocytes stimulated by IL-1β.

Effect of Glucosamine Sulfate on Osteoarthritis in the Cruciate-Deficient Canine Model of Osteoarthritis

Objective Osteoarthritis (OA) is a major cause of musculoskeletal pain and disability worldwide. The investigation of disease-modifying treatment options for OA has become an important aspect of orthopedic care. To assess the effect of intra-articular and oral glucosamine sulfate (GS) versus placebo on osteoarthritis in a canine model. Materials In this randomized, placebo-controlled, double-blinded study, OA was induced by anterior cruciate ligament transection (ACLT) according to the Pond-Nuki model in 32 canines. All canines were allocated into 4 treatment subgroups with treatment administered for 8 weeks: GS (400 mg) intra-articular, placebo intra-articular, GS (200 mg/kg body weight) oral, and placebo oral. The contralateral nonoperated stifle (knee) served as control. After 8 weeks, the medial and lateral femoral condyles, the medial and lateral tibial plateau and patella were histologically examined and anatomic changes quantified by light microscopy using the modified Mankin score. Results After 8 weeks, mean Mankin score values significantly ( P < 0.002) decreased in the intra-articular GS group (8.1; range 7.9-8.8) compared with the intra-articular placebo group (13.9; range 11.6-15.9) and again significantly ( P < 0.002) in the oral GS group (12.1; range 9.9-12.7) compared with the oral placebo group (15.1; range 12.5-17.0). Mean Mankin score values were significantly ( P < 0.002) lower in the intra-articular GS group compared with the oral GS group. Conclusion Both, intra-articular and oral administered GS significantly reduced histological signs of OA in the Pond-Nuki model, with the intra-articular application being more effective compared to oral administration.

Evaluation of the inflammatory response in experimentally induced synovitis in the horse: a comparison of recombinant equine interleukin 1 beta and lipopolysaccharide

OBJECTIVE

To compare two transient models of synovitis-osteoarthritis (OA) in horses by characterizing biological changes in synovial fluid and joint tissue.

METHOD

Twelve skeletally mature mares were utilized in a block design. Synovitis was induced by an intra-articular injection of 100 ng recombinant equine interleukin 1 beta (reIL-1β) or 0.5 ng lipopolysaccharide (LPS) into a middle carpal joint in 1 ml volumes. One ml of saline was injected into the contra-lateral control joint. Lameness evaluations were conducted through post-injection hour (PIH) 8 (at which time arthroscopic removal of synovium and articular biopsies was done), and at PIH 240. Arthrocentesis collection of synovial fluid occurred between PIH 0 and 48. An arthroscopic examination at PIH 8 included synovium and articular cartilage biopsies for gene expression analysis.

RESULTS

Synovial fluid analysis indicated that single injections of reIL-1β or LPS increased synovial white blood cell (WBC), neutrophil count, total protein, prostaglandin E(2) (PGE(2)) concentrations and general matrix metalloproteinase (MMP) activity relative to control joints through PIH 8. Injections of either reIL-1β or LPS increased mRNA expression for MMP-1 and a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-4 in synovium and for MMP-1, ADAMTS-4, ADAMTS-5 in articular cartilage collected at PIH 8 compared to saline injections.

CONCLUSION

Injections of reIL-1β into equine carpal joints resulted in a transient inflammatory response that was similar in severity to the LPS injection, causing increased expression of certain deleterious mediators in joint tissues at 8 h. Given that IL-1β is a known critical mediator of traumatic arthritis and OA, this humane and temporary model may be useful in evaluating therapeutics that act against early stages of joint disease.

Experimental pharmacology of glucosamine sulfate

Several clinical studies demonstrated that glucosamine sulfate (GS) is effective in controlling osteoarthritis (OA), showing a structure-modifying action. However, little is known about the molecular mechanism(s) by which GS exerts such action and about the effects of GS at a tissue level on osteoarthritic cartilage and other joint structures. Here we provide mechanistic evidence suggesting that in vitro GS attenuates NF-κB activation at concentrations in the range of those observed after GS administration to volunteers and patients, thus strengthening previous findings. Furthermore, we describe the effects of GS at a tissue level on the progression of the disease in a relevant model of spontaneous OA, the STR/ort mouse. In this model, the administration of GS at human corresponding doses was associated with a significant decrease of OA scores. Histomorphometry showed that the lesion surface was also significantly decreased, while the number of viable chondrocytes within the matrix was significantly increased. GS improved the course of OA in the STR/Ort mouse, by delaying cartilage breakdown as assessed histologically and histomorphometrically.

A novel tumor necrosis factor alpha-responsive CCAAT/enhancer binding protein site regulates expression of the cartilage-derived retinoic acid-sensitive protein gene in cartilage

OBJECTIVE

Inflammatory processes in rheumatoid arthritis are primarily regulated by the cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta). Previous studies in our laboratory have shown that IL-1beta represses expression of the cartilage characteristic genes, cartilage-derived retinoic acid-sensitive protein (cd-rap) and type II collagen (COL2A1); this mechanism of repression involves activation of a CCAAT/enhancer binding protein (c/EBP) site within promoter regions. The aim of this study was to investigate novel TNFalpha-mediated mechanisms that regulate the expression of cd-rap.

METHODS

Rat chondrosarcoma cells were transiently transfected with complementary DNA constructs encoding cd-rap, in the presence of TNFalpha. The expression of c/EBPbeta, SOX9, and p300 in rat chondrosarcoma cells and primary human articular chondrocytes after treatment with TNFalpha was examined by reverse transcription-polymerase chain reaction and Western blotting. The effect of TNFalpha on endogenous binding of c/EBPbeta or SOX9 to the cd-rap promoter was examined by chromatin immunoprecipitation assays.

RESULTS

We identified a new c/EBP binding site in the cd-rap promoter (from position -1059 bp to position -1046 bp). Binding of c/EBP to this site was regulated by TNFalpha but not IL-1beta, resulting in down-regulation of cd-rap expression. This effect was reversed by mutational inactivation of the c/EBP motif. In addition, the activation potential of SOX9 and CREB binding protein/p300 on the cd-rap promoter was enhanced after mutation of the new c/EBP binding site, indicating that blockage of this site would increase transcription.

CONCLUSION

TNFalpha regulates the expression and/or DNA-binding potential of key positive-acting and negative-acting transcription factors that control the expression of the cartilage matrix gene, cd-rap.

Opiate regulation of IL-1β and TNF-α in cultured human articular chondrocytes

In order to investigate if beta-endorphins anti-inflammatory effect in cartilage-damaging states is mediated via tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta), we examined its influence on these two cytokines in vitro. Human articular chondrocytes were obtained from patients undergoing total knee arthroplasty and stimulated with beta-endorphin (60-6000 ng/ml). Protein levels of TNF-alpha and IL-1 beta were measured by ELISA in supernatants from articular chondrocyte cultures. beta-Endorphin significantly increased the levels of IL-1 beta for all concentrations used after 15 min incubation, and when stimulated with 600 and 6000 ng/ml after 24 h incubation. The opioid-induced increase in IL-1 beta was blocked by naltrexone in the group tested. TNF-alpha expression was also significantly stimulated by 60 and 600 ng/ml beta-endorphin after 15 min, an effect blocked by naltrexone in the group tested. These findings indicate that the mechanism of beta-endorphins anti-inflammatory influence in cartilage-damaging states is not apparently mediated via these two cytokines modulation.

Advanced glycation endproducts and osteoarthritis

Non-enzymatic glycation of proteins, such as collagen, results in the formation of advanced glycation endproducts (AGE). Advanced glycation endproducts result in pathologic stiffening of cartilage and extracellular matrix and accumulate with age. Pentosidine, an AGE, is present in serum, synovial fluid, and articular cartilage from patients with osteoarthritis (OA). However, AGE levels are not always increased, and may be decreased locally, in association with osteoarthritic pathology. The finding of pentosidine in articular cartilage of individuals with OA may not be specific for that disease, independent of chronologic age. Advanced glycation endproduct modification of normal articular cartilage increases its stiffness, increases chondrocyte-mediated proteoglycan degradation, reduces its susceptibility to matrix metalloproteinase-mediated degradation, and decreases proteoglycan synthesis by chondrocytes. These observations parallel findings in osteoarthritic cartilage, which suggests that AGE modification could contribute to the pathogenesis of OA. However, a causative link between AGEs and OA has not yet been established.