Phospholipase A2-independent Ca2+ entry and subsequent apoptosis induced by melittin in human MG63 osteosarcoma cells
Journal
Life Sciences
Journal Volume
80
Journal Issue
4
Pages
364-369
Date Issued
2007
Author(s)
Chu S.-T.
Cheng H.-H.
Huang C.-J.
Chi C.-C.
Su H.-H.
Hsu S.-S.
Wang J.-L.
Chen I.-S.
Liu S.-I.
Lu Y.-C.
Huang J.-K.
Ho C.-M.
Jan C.-R.
Abstract
Melittin, a peptide from bee venom, is thought to be a phospholipase A2 activator and Ca2+ influx inducer that can evoke cell death in different cell types. However, the effect of melittin on cytosolic free Ca2+ concentration ([Ca2+]i) and viability has not been explored in human osteoblast-like cells. This study examined whether melittin altered [Ca2+]i and killed cells in MG63 human osteosarcoma cells. [Ca2+]i changes and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Melittin at concentrations above 0.075?μM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was abolished by removing extracellular Ca2+. Melittin-induced Ca2+ entry was confirmed by Mn2+ quenching of fura-2 fluorescence at 360?nm excitation wavelength which was Ca2+-insensitive. The melittin-induced Ca2+ influx was unchanged by modulation of protein kinase-C activity with phorbol 12-myristate 13-acetate (PMA) and GF 109203X, or inhibition of phospholipase A2 with AACOCF3 and aristolochic acid; but was substantially inhibited by blocking L-type Ca2+ channels. At concentrations of 0.5?μM and 1?μM, melittin killed 33% and 45% of cells, respectively, via inducing apoptosis. Lower concentrations of melittin failed to kill cells. The cytotoxic effect of 1?μM melittin was completely reversed by pre-chelating cytosolic Ca2+ with BAPTA. Taken together, these data showed that in MG63 cells, melittin induced a [Ca2+]i increase by causing Ca2+ entry through L-type Ca2+ channels in a manner independent of protein kinase-C and phospholipase A2 activity; and this [Ca2+]i increase subsequently caused apoptosis. ? 2006.
Subjects
Apoptosis; BAPTA; Ca2+; Fura-2; Melittin; MG63 cells; Osteosarcoma cells
SDGs
Other Subjects
2 [1 (3 dimethylaminopropyl) 3 indolyl] 3 (3 indolyl)maleimide; calcium channel L type; calcium ion; ethylene glycol 1,2 bis(2 aminophenyl) ether n,n,n',n' tetraacetic acid; fluorescent dye; fura 2; manganese; melittin; phorbol 13 acetate 12 myristate; phospholipase A2; protein kinase C; wst 1; 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; bisindolylmaleimide I; calcium; calcium channel L type; drug derivative; egtazic acid; enzyme inhibitor; indole derivative; maleimide derivative; melittin; phorbol 13 acetate 12 myristate; phospholipase A; apoptosis; article; calcium signaling; calcium transport; cancer cell culture; cell killing; cell viability; chelation; concentration response; culture medium; cytosol; cytotoxicity; enzyme activity; enzyme inhibition; extracellular calcium; fluorescence; human; human cell; osteosarcoma cell; apoptosis; cell survival; drug antagonism; drug effect; metabolism; osteoblast; osteosarcoma; pathology; tumor cell line; Apoidea; Apoptosis; Calcium; Calcium Channels, L-Type; Cell Line, Tumor; Cell Survival; Egtazic Acid; Enzyme Inhibitors; Fluorescent Dyes; Fura-2; Humans; Indoles; Maleimides; Melitten; Osteoblasts; Osteosarcoma; Phospholipases A; Tetradecanoylphorbol Acetate
Type
journal article