Abstract
The effects of prostaglandin E2(PGE2) on the degradation of collagen and noncollagenous peptides in clonal osteoblastic MC3T3-E1 cells were investigated by using highly sensitive assay methods for PZ-peptidase, collagenase-like peptidase (CL-peptidase), dipeptidyl-aminopeptidase (DAP), leucine aminopeptidase (LAP), and post-proline cleaving enzyme (PPCE). PGE2, at concentrations of 0.1 to 4.0 μg/ml, doubled the PZ-peptidase and CL-peptidase activities in the cells on 24h culturing in a dose-dependent manner. PGE2, at a concentration of 2.0 μg/ml, enhanced the specific activities of PZ-peptidase, CL-peptidase, DAP, LAP, and PPCE for 75h after the start of PGE2 stimulation. The time dependent changes in PZ-peptidase and CL-peptidase activities showed similar patterns, and 3- and 2-fold increases were seen after 48h, respectively. The protein and DNA contents gradually increased after addition of PGE2. Since the PZ-peptidase and CL-peptidase, involved in degradation of collagen peptides, were significantly induced by PGE2 in comparison with LAP and PPCE, involved in the degradation of noncollagenous peptides, these results show that PGE2 specifically stimulates induction of collagen catabolizing enzymes in clonal osteoblasts.
