A77 1726 inhibits IL-1β-induced prostaglandin E2 (PGE2) productionin human synovial fibroblasts and articular chondrocytes. (a) Human osteoarthritis (OA) synovial fibroblasts (passage 1), (b) de-differentiated human OA articular chondrocytes (passage 4), and (c) freshly isolated human OA articular chondrocytes were stimulated or not (control; white bars) with 1 ng/ml IL-1β (hatched bars), the combination of 1 ng/ml IL-1β and 100 μmol/l A77 1726 (black bars), or the combination of 1 ng/ml IL-1β and 5 μg/ml indomethacin (grey bars) for 48 hours. A77 1726 or indomethacin was added 2 hours before stimulation with IL-1β. PGE2 concentrations in culture supernatants were measured as described elsewhere . Results are represented as means ± SEM of three determinations in one representative experiment. Similar results were obtained with cells from two different donors (two OA samples) for synovial fibroblasts, three different donors (three OA samples) for de-differentiated chondrocytes and five different donors (three normal and two OA samples) for freshly isolated chondrocytes. *P < 0.01 versus control; &P < 0.01 versus IL-1β.