title: Involvement of hydrogen peroxide in safingol-induced endonuclease G-mediated apoptosis of squamous cell carcinoma cells.
abstract: Safingol, a L-threo-dihydrosphingosine, induced the nuclear translocation of a mitochondrial apoptogenic mediator--endonuclease G (endo G)--and apoptosis of human oral squamous cell carcinoma (SCC) cells. Upstream mediators remain largely unknown. The levels of hydrogen peroxide (H2O2) in cultured oral SCC cells were measured. Treatment with safingol increased intracellular H2O2 levels but not extracellular H2O2 levels, indicating the production of H2O2. The cell killing effect of safingol and H2O2 was diminished in the presence of reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC). Dual staining of cells with annexin V and propidium iodide (PI) revealed that apoptotic cell death occurred by treatment with H2O2 and safingol. The number of apoptotic cells was reduced in the presence of NAC. In untreated cells, endo G distributed in the cytoplasm and an association of endo G with mitochondria was observed. After treatment with H2O2 and safingol, endo G was distributed to the nucleus and cytoplasm, indicating the nuclear translocation of the mitochondrial factor. NAC prevented the increase of apoptotic cells and the translocation of endo G. Knock down of endo G diminished the cell killing effect of H2O2 and safingol. These results suggest that H2O2 is involved in the endo G-mediated apoptosis of oral SCC cells by safingol.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. hmdmskz@dent.osaka-u.ac.jp.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hamada
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. dental_ken@yahoo.co.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Wakabayashi
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. a-masui@dent.osaka-u.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Masui
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. s-iwai@dent.osaka-u.ac.jp.
authors.forename: Soichi
authors.initials: S
authors.lastname: Iwai
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. hsc12@hotmail.com.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Imai
authors.affiliation: Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. yura@dent.osaka-u.ac.jp.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yura
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004706:Endodeoxyribonucleases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D009062:Mouth Neoplasms / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D034741:RNA, Small Interfering; D006861:Hydrogen Peroxide; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D013110:Sphingosine; C005682:safingol; D000111:Acetylcysteine