Effects of protease inhibitors and protein synthesis inhibitors on cartilage tissue-dependent bone resortpion

Abstract

We studied bone resorption of fetal rat femora in association with cartilage tissue. Some protease inhibitors, e.g., E-64, pepstatin A, phosphoramidon, amastatin, bestatin, foroxymithine, did not influence the bone resorption, but some serine protease inhibitors such as PMSF, TLCK, TPCK and elastatinal inhibited the bone resorption at 10-5 M, 10-4 M, 10-4 M, 10-4 M, respectively. A conditioned medium, obtained from cartilage tissue-cultured medium in the presence of 10-4 M TPCK, which was then excluded from the medium by dialysis after the culture, stimulated the bone resorption. Cycloheximide (0.1 to 10μ g/ml) and puromycin (0.3 to 30μg/ml) inhibited the cartilage tissue-dependent bone resorption. A transient treatment of the femora with cycloheximide (3μg/ml) for a day inhibited the bone resorption, but after the treatment, in the absence of cycloheximide, the femora gradually recovered the bone-resorbing activity. The conditioned medium, obtained from cartilage tissue-cultured medium in the presence of cycloheximide (3μ g/ml), which was then excluded from the medium by dialysis after the culture, failed to influence the bone resorption. These findings collectively suggest that cartilage tissue produces a bone resorption-stimulating factor(s) which is a serine protease or contains the protein as an inactive, latent form and then a certain serine protease converts it to an active form. © 1993, The Japanese Pharmacological Society. All rights reserved.