IL-1β stimulates iNOS and COX-2 expression. Temporal profile of IL-1β on (a) iNOS, (b) COX-2, (c) aggrecan and (d) collagen type II expression by chondrocyte/agarose constructs cultured under free-swelling conditions with 0 or 10 ng/ml IL-1β and/or 10 μmol/l SB203580. Bars represent the mean and standard error of the mean of six replicates from three separate experiments. The ratio of the relative expression level for the target gene was calibrated to the mean value at time = 0 and normalized to the reference gene GAPDH. Ratios were expressed on a logarithmic scale (arbitrary units). Two-way analysis of variance with post hoc Bonferroni-corrected t-tests was used to compare data under the different treatments: *P < 0.05, **P < 0.01 and ***P < 0.001 for comparisons between time zero with IL-1β; +P < 0.05, ++P < 0.01 and +++P < 0.001 for comparisons between untreated with IL-1β or IL-1β with IL-1β plus SB203580. COX, cyclo-oxygenase; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; iNOS, inducible isoforms of the nitric oxide synthase.