Mononuclear cell factors stimulate the concomitant secretion of distinct latent proteoglycan, gelatin and collagen degrading enzymes from human skin fibroblasts and synovial cells.

Human skin fibroblasts or synovial cells exposed to conditioned medium from human peripheral blood mononuclear cells release distinct latent enzymes capable of degrading collagen, proteoglycan (PG) and gelatin at neutral pH. The PG-degrading activity also degrades casein. These enzymes require calcium, are activated by 4-aminophenylmercuric acetate and can be inhibited by ethylenediamine tetraacetic acid, but not by phenylmethylsulfonyl fluoride, iodoacetamide or pepstatin. Simultaneous secretion of these proteinases after exposure to conditioned medium from peripheral blood mononuclear cells may be an important mechanism by which connective tissue extracellular matrix is destroyed during chronic inflammation in diseases such as rheumatoid arthritis.