Cathepsin B in osteoblasts.
Active cathepsin B has been found in cell extract and medium of human osteoblast-like cells and MG-63 cells. The released form is stable at neutral and alkaline pH and, in both cell types, intracellular and extracellular cathepsin B activities are increased by interleukin-1 beta (IL-1beta) and parathyroid hormone (PTH). To evaluate the physiological role of cathepsin B in osteoblasts, we investigated the production and secretion of this enzyme in normal human synovial fibroblasts and modulation by IL-1beta and PTH. Lactate secretion concurrent with release of cathepsin B and comparable responses in osteoblasts were also examined. Our data show that synovial fibroblasts respond differently to treatment with the two agents, suggesting a cell-specific regulation of cathepsin B and possible involvement in osteoblast physiology. Cathepsin B involvement was then evaluated in the activation of plasminogen activator (PA) in MG-63 cells using two specific inhibitors of cathepsin B, CA074 and CA074-Me, in constitutive conditions and after treatment with IL-1beta. As results of PA activity obtained in the presence of IL-beta were in contrast with previous reports, we examined the activities of PA, pro-PA activated with trypsin, and plasmin in cell extract and media of MG-63 cells after 24-h treatment with IL-1beta. Results show that in normal conditions and in the presence of IL-1beta, cathepsin B is involved in the activation of PA. Moreover, IL-1beta stimulates PA, pro-PA activated by trypsin, and plasmin activity in medium, whereas in cell extract it stimulates pro-PA activated by trypsin and plasmin activity. IL-1beta has no effect on cell extract-associated PA.
Department of Biochemical Science and Molecular Biotechnology, University of Perugia, Via del Giochetto, 06122 Perugia, Italy. cma.aisa@unipg.it
Maria Cristina
MC
Aisa
Tommaso
T
Beccari
Egidia
E
Costanzi
Dario
D
Maggio
D002401:Cathepsin B / Q000502:physiology*; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005341:Fibrinolysin / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism; D010006:Osteoblasts / Q000201:enzymology*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010960:Plasminogen Activators / Q000378:metabolism; D014357:Trypsin / Q000494:pharmacology
C400541:CA 074 methyl ester; D004151:Dipeptides; D007375:Interleukin-1; D010281:Parathyroid Hormone; C068250:N-(3-propylcarbamoyloxirane-2-carbonyl)-isoleucyl-proline; D019344:Lactic Acid; D010960:Plasminogen Activators; D014357:Trypsin; D005341:Fibrinolysin; D002401:Cathepsin B