title: Involvement of hydrogen peroxide in mistletoe lectin-II-induced apoptosis of myeloleukemic U937 cells.
abstract: Mistletoe lectin-II, a major component of Korean mistletoe (Viscum album var. coloratum) induces apoptotic death in cancer cells. In this study, we demonstrated that lectin-II induced the generation of pro-oxidants and thus resulted in the apoptotic death of human myeloleukemic U937 cells. We observed that lectin-II-induced apoptotic death was inhibited by antioxidants including reduced glutathione (GSH), N-acetylcysteine (NAC), ebselen, mnTBP, catalase and pyrrolidine dithiocarbamate (PDTC). GSH and NAC also abolished the apoptotic DNA ladder pattern fragmentation of U937 cells after lectin-II stimulation. Obviously, lectin-II treatment of cells resulted in a remarkable generation of intracellular hydrogen peroxide (H2O2) as an early event, which was monitored fluorimetrically using scopoletin-horse radish peroxidase (HRP) assay and peroxide-sensitive fluorescent probe, DCF-DA. In addition, antioxidants inhibited the activation of c-Jun N-terminal kinase (JNK)/stress-activated protein kinase (SAPK) as well as cytosolic release of cytochrome c by mistletoe lectin-II. Moreover, lectin-II-induced activation of caspase-9 and 3-like protease and cleavage of poly(ADP-ribose) polymerase (PARP) were inhibited by pretreatment of cells with thiol antioxidants, GSH and NAC. Taken together, these results suggest that Korean mistletoe lectin-II is a strong inducer of pro-oxidant generation such as H2O2, which mediates the JNK/SAPK activation, cytochrome c release, activation of caspase-9 and caspase 3-like protease, and PARP cleavage in human myeloleukemic U937 cells.
authors.affiliation: Institute of Medical Science, School of Medicine, Korea.
authors.forename: Myung-Sunny
authors.initials: MS
authors.lastname: Kim
authors.forename: Jienny
authors.initials: J
authors.lastname: Lee
authors.forename: Kang-Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Sei-Hoon
authors.initials: SH
authors.lastname: Yang
authors.forename: Sujinna
authors.initials: S
authors.lastname: Choi
authors.forename: Sang-Young
authors.initials: SY
authors.lastname: Chung
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Kim
authors.forename: Won-Hun
authors.initials: WH
authors.lastname: Jeong
authors.forename: Raekil
authors.initials: R
authors.lastname: Park
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004336:Drug Antagonism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D014784:Mistletoe / Q000737:chemistry*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D037121:Plant Lectins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D028321:Plant Preparations / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010940:Plant Proteins; D010946:Plants, Medicinal; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological / Q000494:pharmacology*; D020298:U937 Cells
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D037121:Plant Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C009674:ribosome inactivating protein, Viscum; D006861:Hydrogen Peroxide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases