title: Apoptosis induced by generated OH radicals inside cells after irradiation.
abstract: OH radicals play a major role in radiation-induced DNA and cell membrane damage. These types of damage can also induce death by apoptosis through activation of a pro-apoptosis pathway. We attempted to detect OH radicals inside human promyelocytic leukemia (HL60) cells and estimate the relationship between radiation-induced apoptosis and OH radicals generated inside the cells. Electron spin resonance spectroscopy showed that OH radicals were generated by X-rays within irradiated cell pellets and the relative signal intensities of OH radicals increased with the radiation dose. Agarose gel electrophoresis revealed that the death of HL60 cells by apoptosis was accompanied by internucleosomal DNA fragmentation at 2 h after irradiation with 10-30 Gy. On ultrastructure evaluation by transmission electron microscopy, certain irradiated HL60 cells demonstrated condensed chromatin forms at the nuclear membrane and nuclear fragmentation. The frequency of apoptotic cells with condensation and fragmentation of nuclear chromatin increased with radiation dose in semithin sections. The increase of quantitative DNA fragmentation and percentage of non-living cells also correlated with radiation dose. These results suggest that OH radicals are generated inside cells before apoptosis occurs. The amount of OH radicals generated correlates with apoptotic cell death.
authors.affiliation: Department of Dental Radiology, Health Sciences University of Hokkaido, School of Dentistry, Hokkaido, Japan. hosokawa@hoku-iryo-u.ac.jp
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hosokawa
authors.forename: Likinobu
authors.initials: L
authors.lastname: Tanaka
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kaneko
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Sakakura
authors.forename: Eichi
authors.initials: E
authors.lastname: Tsuruga
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Irie
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yajima
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D053938:DNA Fragmentation / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D004587:Electrophoresis, Agar Gel; D018922:HL-60 Cells; D006801:Humans; D017665:Hydroxyl Radical / Q000528:radiation effects*; D008854:Microscopy, Electron
chemical_list: D017665:Hydroxyl Radical