Cyclooxygenase expression in synovial tissue of patients with rheumatoid arthritis and rats with experimental arthritis.

Cyclooxygenase (COX) plays a role in inflammatory diseases, but limited data exist on the regulation of COXin vivo. We studied thein vivoexpression of COX in synovia from patients with rheumatoid arthritis (RA) as well as rats with streptococcal cell wall (SCW) and adjuvant arthritis. Extensive and intense COX immunostaining, which correlated with the intensity of mononuclear cell infiltration, was observed in RA synovia. Significantly less staining was noted in OA and normal human synovia. COX immunostaining was equivocal in the joints of normal and arthritis-resistant F344/N rats. In contrast, high level COX expression developed rapidly in female LEW/N rats throughout hindlimb joints preceeding or paralleling experimental arthritis.COX was expressed in the joints of athymic LEW. rnu/rnu rats 2-4 days after injection of SCW or adjuvant but was not sustained. Physiological doses of glucocorticoids suppressed both arthritis and COX expression in LEW/N rats injected with SCW or adjuvant.These observations suggest that, in vivo, (a) COX expression is upregulated in inflammatory joint diseases, (b) expression is a biochemical marker of disease activity, and (c) expression is down-regulated by antiinflammatory glucocorticoids.