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  • Title: Dynamic compression counteracts IL-1beta induced inducible nitric oxide synthase and cyclo-oxygenase-2 expression in chondrocyte/agarose constructs.
    Author: Chowdhury TT, Arghandawi S, Brand J, Akanji OO, Bader DL, Salter DM, Lee DA.
    Journal: Arthritis Res Ther; 2008; 10(2):R35. PubMed ID: 18348730.
    Abstract:
    BACKGROUND: Nitric oxide and prostaglandin E2 (PGE2play pivotal roles in both the pathogenesis of osteoarthritis and catabolic processes in articular cartilage. These mediators are influenced by both IL-1beta and mechanical loading, and involve alterations in the inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 enzymes. To identify the specific interactions that are activated by both types of stimuli, we examined the effects of dynamic compression on levels of expression of iNOS and COX-2 and involvement of the p38 mitogen-activated protein kinase (MAPK) pathway. METHODS: Chondrocyte/agarose constructs were cultured under free-swelling conditions with or without IL-1beta and/or SB203580 (inhibitor of p38 MAPK) for up to 48 hours. Using a fully characterized bioreactor system, constructs were subjected to dynamic compression for 6, 12 and 48 hours under similar treatments. The activation or inhibition of p38 MAPK by IL-1beta and/or SB203580 was analyzed by western blotting. iNOS, COX-2, aggrecan and collagen type II signals were assessed utilizing real-time quantitative PCR coupled with molecular beacons. Release of nitrite and PGE2 was quantified using biochemical assays. Two-way analysis of variance and the post hoc Bonferroni-corrected t-test were used to examine data. RESULTS: IL-1beta activated the phosphorylation of p38 MAPK and this effect was abolished by SB203580. IL-1beta induced a transient increase in iNOS expression and stimulated the production of nitrite release. Stimulation by either dynamic compression or SB203580 in isolation reduced the IL-1beta induced iNOS expression and nitrite production. However, co-stimulation with both dynamic compression and SB203580 inhibited the expression levels of iNOS and production of nitrite induced by the cytokine. IL-1beta induced a transient increase in COX-2 expression and stimulated the cumulative production of PGE2 release. These effects were inhibited by dynamic compression or SB203580. Co-stimulation with both dynamic compression and SB203580 restored cytokine-induced inhibition of aggrecan expression. This is in contrast to collagen type II, in which we observed no response with the cytokine and/or SB203580. CONCLUSION: These data suggest that dynamic compression directly influences the expression levels of iNOS and COX-2. These molecules are current targets for pharmacological intervention, raising the possibility for integrated pharmacological and biophysical therapies for the treatment of cartilage joint disorders.
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