Regulation by reactive oxygen species of interleukin-1beta, nitric oxide and prostaglandin E(2) production by human chondrocytes.

peer reviewedOBJECTIVES: To determine the effects of two drugs, N-monomethyl-L-arginine (L-NMMA) and N-acetylcysteine (NAC), on interleukin-1beta (IL-1beta), nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production by human chondrocytes. The effect of aceclofenac (ACECLO), a non-steroidal antiinflammatory drug (NSAID), was also examined. METHODS: Human chondrocytes were enzymatically isolated from osteoarthritic knee cartilage and then maintained in culture in suspension for 48h in the absence or in the presence of lipopolysaccharide (LPS) (10 microg/ml), L-NMMA (0.5mM), NAC (1mM) or ACECLO (6.10(-6)M). IL-1beta and PGE(2) productions were quantified by specific immunoassays. Nitrite was measured in the culture supernatants by a spectrophotometric method based upon the Griess reaction. Cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS) and IL-1beta gene expressions were quantified by transcription of mRNA followed by real time and quantitative polymerase chain reaction. COX-2 protein expression was analysed by Western blot. RESULTS: LPS markedly increased the expression of IL-1beta, iNOS and COX-2 genes. In parallel, NO(2) and PGE(2) amounts found in the culture supernatants were significantly enhanced whereas IL-1beta was immunologically undetectable. The addition of L-NMMA (0.5mM) fully blocked LPS-induced NO production but greatly increased PGE(2) production, suggesting a negative effect of NO on PGE(2) synthesis. Inversely, NO production was stimulated by NAC while PGE(2) production was not affected. Interestingly, NAC increased the IL-1beta and iNOS mRNA levels but did not significantly modify COX-2 mRNA expression. L-NMMA did not significantly affect the expression of IL-1beta, iNOS and COX-2. The amount of COX-2 protein did not change in the presence of the antioxidants. Finally, ACECLO fully blocked the production of PGE(2) by chondrocytes without affecting the levels of COX-2 mRNA. CONCLUSIONS: The stimulation of IL-1beta, NO and PGE(2) production by LPS is differentially controlled by reactive oxygen species (ROS). In fact, L-NMMA and NAC have different mechanisms of action on the regulation of NO and PGE(2) productions. L-NMMA fully inhibits NO but increases PGE(2) production whereas NAC up-regulates NO but does not modify PGE(2) synthesis. The stimulating effect of L-NMMA on PGE(2) production is not controlled at the transcriptional level. These findings suggest that antioxidant therapy could have different effects according to the oxygen radical species targeted

Pathology

SummaryObjectiveTo investigate the association between urinary biomarker Coll2-1NO2 (uColl2-1NO2) and incident knee OA after 2.5 years follow-up in middle-aged overweight and obese women at high risk for knee osteoarthritis (OA).DesignData were used from PROOF, a randomized controlled trial with 2.5 years follow-up evaluating the preventive effects of a diet and exercise program and oral glucosamine sulphate (double blind and placebo controlled), on development of incident knee OA in women with body mass index ≥ 27 kg/m2 without signs of knee OA at baseline. Baseline and 2.5 years uColl2-1NO2 concentrations were assessed with enzyme-linked immunosorbent assay (ELISA). Primary outcome measure was incidence of knee OA in one or both knees, defined as incidence of either Kellgren & Lawrence grade ≥2, joint space narrowing of ≥1.0 mm or knee OA according to the combined clinical and radiographic ACR-criteria. We used binary logistic regression for the association analyses.Results254 women were available for analyses. At 2.5 years follow-up, incident knee OA was present in 72 of 254 women (28.3%). An inversed association was found between baseline uColl2-1NO2 and incident knee OA at 2.5 years (OR 0.74, 95% CI 0.55–0.99). The concentration at 2.5 years and the change in concentration over 2.5 years did not show significant associations with the outcome.ConclusionsIn overweight and obese middle-aged women, not higher but lower baseline uColl2-1NO2 concentration was significantly associated with an increased risk for incident knee OA. This interesting but counterintuitive outcome makes further validation of this biomarker warranted

The role of reactive oxygen species in homeostasis and degradation of cartilage.

OBJECTIVES: The metabolism of cells in articular joint tissues in normal and pathological conditions is subject to a complex environmental control. In addition to soluble mediators such as cytokines and growth factors, as well as mechanical stimuli, reactive oxygen species (ROS) emerge as major factors in this regulation. ROS production has been found to increase in joint diseases, such as osteoarthritis and rheumatoid arthritis, but their role in joint diseases initiation and progression remains questionable. METHOD: This review is focused on the role of ROS, mainly nitric oxide, peroxynitrite and superoxide anion radicals, in the signaling mechanisms implied in the main cellular functions, including synthesis and degradation of matrix components. The direct effects of ROS on cartilage matrix components as well as their inflammatory and immunomodulatory effects are also considered. RESULTS: Some intracellular signaling pathways are redox sensitive and ROS are involved in the regulation of the production of some biochemical factors involved in cartilage degradation and joint inflammation. Further, ROS may cause damage to all matrix components, either by a direct attack or indirectly by reducing matrix components synthesis, by inducing apoptosis or by activating latent metalloproteinases. Finally, we have highlighted the uncoupling effect of ROS on tissue remodeling and synovium inflammation, suggesting that antioxidant therapy could be helpful to treat structural changes but not to relieve symptoms. CONCLUSIONS: This review of the literature supports the concept that ROS are not only deleterious agents involved in cartilage degradation, but that they also act as integral factors of intracellular signaling mechanisms. Further investigation is required to support the concept of antioxidant therapy in the management of joint diseases

Correlation between radiographic severity of knee osteoarthritis and future disease progression. Results from a 3-year prospective, placebo-controlled study evaluating the effect of glucosamine sulfate.

OBJECTIVE: To investigate the relationship between baseline radiographic severity of knee osteoarthritis (OA) and the importance of long-term joint space narrowing. DESIGN: Sub-analysis from a three-year randomized, placebo-controlled, prospective study, of 212 patients with knee OA, recruited in an osteoarthritic outpatient clinic and having been part of a study evaluating the effect of glucosamine sulfate on symptom and structure modification in knee OA. MATERIAL AND METHODS: Measurements of mean joint space width (JSW), assessed by a computer-assisted method, were performed at baseline and after 3 years, on weightbearing anteroposterior knee radiographs. RESULTS: In the placebo group, baseline JSW was significantly and negatively correlated with the joint space narrowing observed after 3 years (r=-0.34, P=0.003). In the lowest quartile of baseline mean JSW (6.2mm), a joint space narrowing of 14.9% (17.9) occurred in the placebo group after 3 years while patients from the glucosamine sulfate group only experienced a narrowing of 6.0% (15.1). Patients with the most severe OA at baseline had a RR of 0.42 (0.17-1.01) to experience a 0.5mm joint space narrowing over 3 years, compared to those with the less affected joint. In patients with mild OA, i.e. in the highest quartile of baseline mean JSW, glucosamine sulfate use was associated with a trend (P=0.10) towards a significant reduction in joint space narrowing. CONCLUSION: These results suggest that patients with the less severe radiographic knee OA will experience, over 3 years, the most dramatic disease progression in terms of joint space narrowing. Such patients may be particularly responsive to structure-modifying drugs