Evidence for oxidised low density lipoprotein in synovial fluid from rheumatoid arthritis patients.

The oxidative modification of human LDL has been implicated in atherosclerosis, but the mechanisms by which such modification occurs in vivo are not fully understood. In the present study, we have isolated LDL from knee-joint synovial fluid of patients with rheumatoid arthritis. We demonstrate that such LDL is oxidatively modified as evidenced by an increased negative charge, distorted particulate nature and more rapid degradation by cultured macrophages. These results indicate that formation of oxidised LDL is associated with the local inflammatory response. Because the cellular interactions in rheumatoid arthritis have analogies with those in atherogenesis, we suggest that the rheumatoid joint is a useful model of atherosclerosis in which the in vivo process of LDL oxidation may be readily studied.