title: Production of superoxide and dissipation of mitochondrial transmembrane potential by vitamin K2 trigger apoptosis in human ovarian cancer TYK-nu cells.
abstract: We reported previously that vitamin K(2) selectively induces apoptosis in human ovary cancer cells (TYK-nu cells) and pancreatic cancer cells (MIA PaCa-2 cells) through a mitochondrion-dependent pathway. In the present study, we examined the details of the mechanism of vitamin K(2)-induced apoptosis in TYK-nu cells. We found that superoxide (O(2)(*-)) was produced by TYK-nu cells between 2 and 3 days after the start of treatment with vitamin K(2), whereas it was produced within 30 min after the start of treatment with geranylgeraniol. The vitamin K(2)-induced apoptosis was inhibited by anti-oxidants, such as alpha-tocopherol, Tiron and N-acetyl-L-cysteine (NAC). Furthermore, both the production of superoxide and the induction of apoptosis by vitamin K(2) were inhibited almost completely by cycloheximide, an inhibitor of protein synthesis, suggesting that the synthesis of enzymes for the production of superoxide might be required for these processes. In parallel with the production of superoxide, the mitochondrial transmembrane potential, as measured by staining with Mitotracker Red CMXRos, dissipated during treatment of TYK-nu cells with vitamin K(2) for 3 days. The vitamin K(2)-induced depolarization of mitochondrial membranes was completely inhibited by alpha-tocopherol and, to a lesser extent, by Tiron and NAC. Since alpha-tocopherol reacts with oxygen radicals, such as superoxide, within the hydrophobic environment of the mitochondrial membrane, we postulate that vitamin K(2)-induced oxidative stress in mitochondria might damage mitochondrial membranes, with subsequent release of cytochrome c, the activation of procaspase 3 and, eventually, apoptosis.
authors.affiliation: Laboratory of Biological Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Tokyo, 142-8555, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Shibayama-Imazu
authors.forename: Ikuko
authors.initials: I
authors.lastname: Sonoda
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sakairi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aiuchi
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Ann
authors.forename: Shigeo
authors.initials: S
authors.lastname: Nakajo
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Itabe
authors.forename: Kazuyasu
authors.initials: K
authors.lastname: Nakaya
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D003513:Cycloheximide / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology; D005260:Female; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D024482:Vitamin K 2 / Q000494:pharmacology* / Q000627:therapeutic use; D024502:alpha-Tocopherol / Q000494:pharmacology
chemical_list: D004224:Diterpenes; D017382:Reactive Oxygen Species; D024482:Vitamin K 2; D013481:Superoxides; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D003513:Cycloheximide; C017338:geranylgeraniol; D024502:alpha-Tocopherol; D000111:Acetylcysteine