title: Interleukin-6 and cyclic AMP stimulate release of cathepsin B in human osteoblasts.
abstract: Previous studies have suggested that cathepsin B participates in the joint destruction associated with rheumatoid arthritis (RA). This study examined the activity of cathepsin B (a lysosomal cysteine protease) in human osteoblasts along with its regulation by cyclic AMP and Interleukin-6 (IL-6). Cyclic AMP elevating agents activate cathepsin B and stimulate the secretion of cathepsin B via the secretion of IL-6, a potent mediator of RA. This study investigated the induction of cathepsin B using the proinflammatory cytokine in human osteoblasts (MG-63) in relation to p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappa B transcription factor. When added to MG-63 cells, IL-6 stimulated the production of cathepsin B, which was reduced significantly by the addition of SB203580, a specific p38 MAPK inhibitor. In addition, the release of IL-6 was also inhibited by either pyrrolidine dithiocarbamate (PDTC) or NF-kappaB SN50, which are potent NF-kappaB inhibitors. Both NF-kappaB inhibitors had a larger inhibitory effect on the activity of cathepsin B in the presence of SB203580. IL-6 stimulated the NF-kappaB binding affinity as well as the activation of p38 MAP kinase, leading to the release of cathepsin B. However, SB203580 had no effect on the IL-6-induced activation of NF-kappaB, and neither of the NF-kappaB inhibitors decreased the level of p38 MAPK activation in the IL-6-stimulated osteoblasts. Moreover, IL-6 increased the activity of urokinase type plasminogen activator (uPA) in MG-63 cells, which was inhibited by SB203580, PDTC and NF-kappaB SN50. This strongly suggests that p38 MAPK and NF-kappaB are essential to the IL-6-induced activation of cathepsin B or uPA and that these two IL-6-activated pathways can act independently.
authors.affiliation: Department of Pharmacology and Institute of Cardiovascular Research, Medical School, Chonbuk National University, Jeonju, Chonbuk, South Korea.
authors.forename: Han-Jung
authors.initials: HJ
authors.lastname: Chae
authors.forename: Ki-Chan
authors.initials: KC
authors.lastname: Ha
authors.forename: Geun-Youn
authors.initials: GY
authors.lastname: Lee
authors.forename: Sun-Kyung
authors.initials: SK
authors.lastname: Yang
authors.forename: Ki-Jung
authors.initials: KJ
authors.lastname: Yun
authors.forename: Eun-Cheol
authors.initials: EC
authors.lastname: Kim
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Kim
authors.forename: Soo-Wan
authors.initials: SW
authors.lastname: Chae
authors.forename: Hyung-Ryong
authors.initials: HR
authors.lastname: Kim
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D015153:Blotting, Western; D002401:Cathepsin B / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005470:Fluorometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015290:Second Messenger Systems / Q000502:physiology; D013268:Stimulation, Chemical; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004791:Enzyme Inhibitors; D007093:Imidazoles; D015850:Interleukin-6; D016328:NF-kappa B; D011725:Pyridines; D000242:Cyclic AMP; D048051:p38 Mitogen-Activated Protein Kinases; D014568:Urokinase-Type Plasminogen Activator; D002401:Cathepsin B; C093642:SB 203580