Induction of the synthesis of latent collagenase and latent neutral protease in chondrocytes by a factor synthesized by activated macrophages

Abstract

Abstract The spent medium of stimulated peritoneal macrophages contains a factor or factors that induce the de novo synthesis of collagenase and neutral protease(s) in primary cultures of articular chondrocytes. The synthesis of this inducing factor by stimulated macrophages is inhibited by cycloheximide, indicating that the factor is a protein. The inducing factor is heat stable and stable to tryspin treatment, but it is partially inactivated on treatment to pH 2.0. The inducing factor is not retained on concanavalin Sepharose, is stable to reductive alkylation, and has an apparent molecular weight of approximately 30,000. Addition of the inducing factor to cartilage slices also results in the synthesis of both collagenase and neutral protease by the slices. Both of these enzymes synthesized by chondrocytes are in the latent form and are activated by either trypsin or plasmin. The neutral protease (MW 22,000) is a metalloprotease and is inhibited by o‐phenanthroline and by D‐penicillamine but not by phenylmethane sulfonylfluoride or iodoacetic acid. Induction of these latent enzymes in chondrocytes occurs between 8 and 16 hours after exposure to the inducing factor and is completely blocked by cycloheximide. The spent medium of stimulated lymphocytes (concanavalin A) does not induce the synthesis of these enzymes in chondrocytes, suggesting that the synthesis of the inducing factor may be a property specific to stimulated macrophages.