Comparative effect of adiponectin and interleukin (IL)-1β on the production of IL-6, IL-8, and prostaglandin E2 (PGE2) in rheumatoid arthritis fibroblast-like synoviocytes. IL-1β at 1 ng/mL stimulates the production of (a) IL-6, (b) IL-8, and (c) PGE2 more than 10 μg/mL adiponectin. (d) The expression of cycloxygenase-2 (COX-2) increased only in the presence of IL-1β in proportion to the level of PGE2. The data shown are representative of three independent experiments, and similar results were obtained from all three. Values are expressed as mean ± standard error of the mean. * P < 0.05, ** P < 0.01 versus nontreated group. ns, not significant.