Human cystatin C, a cysteine proteinase inhibitor, inhibits bone resorption in vitro stimulated by parathyroid hormone and parathyroid hormone-related peptide of malignancy

Open Access
Publisher Website
Google Scholar
Abstract
The effect of human recombinant cystatin C, a cysteine proteinase inhibitor, on bone resorption in vitro was evaluated. Bone resorption was assessed by analyzing the release of 45Ca and 3H from mouse calvarial bones prelabeled in vivo by injections with 45Ca or [3H]proline, respectively. In 24 h cultures, cystatin C (50 μg/ml) significantly inhibited the release of 45Ca and 3H stimulated by parathyroid hormone (PTH, 15 nmol/liter) or parathyroid hormone-related peptide of malignancy (PTHrP, 15 nmol/liter). The degree of inhibition caused by cystatin C in these 24 h cultures was similar to that caused by calcitonin (30 ng/ml). The inhibitory effect of cystatin C on 45Ca release induced by PTH was sustained in 96 h cultures, whereas the initial inhibition caused by calcitonin was transient. Cystatin C, 10–100 μg/ml, caused a dose-dependent inhibition of PTH (15 nmol/liter), and PTHrP (15 nmol/liter) stimulated 45Ca release. Addition of 50 μg/ml of cystatin C to mouse bone cultures inhibited the release of 45Ca induced by PTH and PTHrP at a wide range of submaximal and maximal concentrations of hormones (0.01–10 nmol/liter). No effect of cystatin C on 45Ca release in dead bones could be observed, nor did the inhibitor decrease the release of calcium in control bones. The inhibition by cystatin C on PTH-induced mineral mobilization was reversible. Cystatin C (1–100 μg/ml) did not affect protein synthesis or mitotic activities in mouse calvarial bones as assessed by the incorporation of I'HIproline and [3H]thymidine, respectively. These data show that cystatin C is a potent inhibitor of mineral mobilization and matrix degradation in cultured bones stimulated to resorb by PTH and PTHrP and that this effect is not due to general cytotoxicity.
Funding Information
  • Swedish Medical Research Council
  • Bergvall Foundation
  • Umei Foundation
  • Craaford Foundation
  • Österlund Foundation
  • Pihlsson Foundation
  • Kock Foundation
  • Lundgren Foundation
  • Lund Hospital Foundation
  • Lund Hospital Cancer Foundation
  • University of Lund

This publication has 22 references indexed in Scilit: