title: Thimerosal-induced cytosolic Ca2+ elevation and subsequent cell death in human osteosarcoma cells.
abstract: The effect of the oxidizing agent thimerosal on cytosolic free Ca(2+) concentration ([Ca(2+)]i) and proliferation has not been explored in human osteoblast-like cells. This study examined whether thimerosal alters Ca(2+) levels and causes cell death in MG63 human osteosarcoma cells. [Ca(2+)]i and cell death were measured using the fluorescent dyes fura-2 and WST-1, respectively. Thimerosal at concentrations above 5 microM increased [Ca(2+)]i in a concentration-dependent manner. The Ca(2+) signal was reduced by 80% by removing extracellular Ca(2+). The thimerosal-induced Ca(2+) influx was sensitive to blockade of La(3+), and dithiothreitol (50 microM) but was insensitive to nickel and several L-type Ca(2+) channel blockers. After pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), thimerosal failed to induce [Ca(2+)]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change thimerosal-induced [Ca(2+)]i rises. At concentrations of 5, 10 and 20 microM thimerosal killed 33, 55 and 100% cells, respectively. The cytotoxic effect of 5 microM thimerosal was reversed by 54% by prechelating cytosolic Ca(2+) with BAPTA. Collectively, in MG63 cells, thimerosal induced a [Ca(2+)]i rise by causing Ca(2+) release from endoplasmic reticulum stores and Ca(2+) influx from extracellular space. Furthermore, thimerosal can cause Ca(2+)-related cytotoxicity in a concentration-dependent manner.
authors.affiliation: Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan.
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.forename: Chung-Shin
authors.initials: CS
authors.lastname: Liu
authors.forename: Chiang-Ting
authors.initials: CT
authors.lastname: Chou
authors.forename: Ching-Hong
authors.initials: CH
authors.lastname: Hsieh
authors.forename: Chih-Hung
authors.initials: CH
authors.lastname: Chang
authors.forename: Wei-Chuan
authors.initials: WC
authors.lastname: Chen
authors.forename: Shiuh-Inn
authors.initials: SI
authors.lastname: Liu
authors.forename: Shu-Shong
authors.initials: SS
authors.lastname: Hsu
authors.forename: Jin-Shyr
authors.initials: JS
authors.lastname: Chen
authors.forename: Bang-Ping
authors.initials: BP
authors.lastname: Jiann
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
mesh_terms: D001859:Bone Neoplasms; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016923:Cell Death; D045744:Cell Line, Tumor / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D012516:Osteosarcoma; D013849:Thimerosal / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D002121:Calcium Channel Blockers; D002614:Chelating Agents; D013849:Thimerosal; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D016257:Fura-2