title: Thiol oxidation by 2,2'-dithiodipyridine induced calcium mobilization in MG63 human osteosarcoma cells.
abstract: 2,2'-dithiodipyridine (2,2'-DTDP), a reactive disulphide that mobilizes Ca(2+) in muscle, induced an increase in cytoplasmic free Ca(2+)concentrations ([Ca(2+)](i)) in MG63 human osteosarcoma cells loaded with the Ca(2+)-sensitive dye fura-2. 2,2'-DTDP acted in a concentration-independent manner with an EC(50) of 50 microM. The Ca(2+) signal comprised an initial spike and a prolonged increase. Removing extracellular Ca(2+) did not alter the Ca(2+) signal, suggesting that the Ca(2+) signal was due to store Ca(2+) release. In Ca(2+)-free medium, the 2,2'-DTDP-induced [Ca(2+)](i) increase was not changed by depleting store Ca(2+) with 50 microM bredfeldin A (a Golgi apparatus permeabilizer), 2 microM carbonylcyanide m-chlorophenylhydrazone (CCCP, a mitochondrial uncoupler), 1 microM thapsigargin (an endoplasmic reticulum Ca(2+)pump inhibitor) or 5 microM ryanodine. Conversely, 2,2'-DTDP pretreatment abolished CCCP and thapsigargin-induced [Ca(2+)](i) increases. 2,2'-DTDP-induced Ca(2+) signals in Ca(2+)-containing medium were not affected by modulation of protein kinase C activity or suppression of phospholipase C activity. However, 2,2'-DTDP-induced Ca(2+) release was inhibited by a thiol-selective reducing reagent, dithiothreitol (5-25 microM) in a concentration-dependent manner. Collectively, this study shows that 2,2'-DTDP induced [Ca(2+)](i) increases in human osteosarcoma cells via releasing store Ca(2+)from multiple stores in a manner independent of protein kinase C or phospholipase C activity. The 2,2'-DTDP-induced store Ca(2+) release appeared to be dependent on oxidation of membranes.
authors.affiliation: Department of Medical Technology, Fooyin Institute of Technology, Kaohsiung 813, Taiwan.
authors.forename: Soong-Yu
authors.initials: SY
authors.lastname: Kuo
authors.forename: Bang-Ping
authors.initials: BP
authors.lastname: Jiann
authors.forename: Yih-Chau
authors.initials: YC
authors.lastname: Lu
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.forename: Wei-Chung
authors.initials: WC
authors.lastname: Chen
authors.forename: Jong-Khing
authors.initials: JK
authors.lastname: Huang
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000494:pharmacology*; D001859:Bone Neoplasms / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D004220:Disulfides / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D012516:Osteosarcoma / Q000378:metabolism*; D010084:Oxidation-Reduction; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D019163:Reducing Agents / Q000494:pharmacology; D015290:Second Messenger Systems / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D004220:Disulfides; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D011500:Protein Synthesis Inhibitors; D019163:Reducing Agents; D013438:Sulfhydryl Compounds; D020126:Brefeldin A; C001105:2,2'-dipyridyl disulfide; D015082:2,2'-Dipyridyl; D019284:Thapsigargin; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2