Edward D. Harris

Endogenous activation of latent collagenase by rheumatoid synovial cells evidence for a role of plasminogen activator

To elucidate the mechanism of synovial damage in rheumatoid arthritis, we studied the activation of latent collagenases released from adherent rheumatoid synovial cells in culture. Latent enzyme was not complexed with alpha2 macroglobulin, the prinicpal proteinase inhibitor in serum, and could be activated by trypsin in the presence of alpha2 macroglobulin if sufficient proteinase was added to saturate inhibitor. Latent collagenase bound half as effectively to collagen fibrils as active enzyme. Plasmin was a threefold better activator of latent enzyme than trypsin and could be generated by addition of plasminogen to synovial-cell cultures. Production of both collagenase and plasminogen activator was inhibited by dexamethasone (10(-9) M). These studies emphasize in importance of control of activation in regulation collagenase activity, It is likely that rheumatoid synovium produces both latent collagenase and plasminogen activator; plasmin is activated from its zymogen, plasminogen, present in inflamed tissues, and in turn activates collagenase.

Inhibition by Retinoic Acid of Collagenase Production in Rheumatoid Synovial Cells

IN rheumatoid arthritis, synovial cells produce many mediators of inflammation in response to stimuli generated within the inflamed joint. Collagenase and prostaglandin E2 are two of these mediator...

Activation in vitro of rheumatoid synovial collagenase from cell cultures.

Rheumatoid synovial cells dissociated from matrix and adherent to culture dishes released a latent form of collagenase into culture medium. Previous studies have shown that the latent enzyme does not complex with alpha2-macroglobulin and binds to fibrillar substrate. We now show that serum-free culture medium of the synovial cells contains an inhibitor of collagenase as well as latent enzyme; the two were separated on a column of acrylamide/agarose. Latent collagenase (estimated mol wt 45,000-49,000) was transformed by trypsin to active collagenase of approximately equal to mol wt 33,000. When mixed with inhibitor the active enzyme formed an inactive complex again with approximately equal to mol wt 45,000-49,000. The inhibitor(s) itself was found in one major peak of mol wt 33,000-35,000 and several minor peaks eluting with lower apparent molecular weight. Mersalyl, an organic mercurial compound, effectively activated latent collagenase producing an active enzyme with approximately equal to mol wt 33,000. Bacterial collagenase did not activate latent enzyme. We suggest that latent rheumatoid synovial collagenase, as it is harvested from synovial cells in culture, is an enzyme-inhibitor complex.

Collagenase release from synovial fibroblasts: relationship to fatty acid release and prostaglandin synthesis

Rheumatoid synovium has proliferative and destructive characteristics in vivo. These capabilities are also evident in tissue culture studies in which cultured expiants of rheumatoid synovium have been shown to invade normal tendon1 and release substances which stimulate bone resorption2. There are numerous biochemical differences between normal and inflamed synovia but it is likely that the destructive capacity of rheumatoid tissues is related in part to formation of high levels of prostaglandins (PGs) and collagenase3,4. PGE2, released from cultured rheumatoid synovium, stimulates bone resorption2 and collagenase is believed to be the major enzyme responsible for cartilage degradation associated with rheumatoid arthritis5,6.

Specificity of glucocorticoid inhibition of synovial prostaglandin synthesis

Inhibition of prostaglandin (PG) synthesis contributes to the antiinflammatory activity of a number of anti-rheumatic compounds. Inhibition of PG synthesis by non-steroidal anti-inflammatory drugs (e.g. aspirin, indomethacin) has been observed in experiments with cell-free preparations of PG synthase as well as in intact tissues and cells1–3. These agents appear to act primarily by blocking the enzyme cylo-oxygenase which catalyses the initial step in synthesis of PGs from their fatty acid precursor, arachidonic acid4.