title: Radiation-induced reactive oxygen species formation prior to oxidative DNA damage in human peripheral T cells.
abstract: Previously, we demonstrated that human peripheral T lymphocytes revealed early apoptotic changes (annexin V-positive) and late apoptotic changes (propidium iodide-positive), at 13 and 24 h, respectively, after irradiation of 5 Gy. Changes in mitochondrial membrane potential were observed at 10 h after irradiation of 5 Gy. Subsequently, mitochondrial cytochrome c-release was confirmed. In order to elucidate the mechanism which acts prior to the mitochondrial membrane potential changes, we examined in the previous study the radiation dose and the timing of oxidative DNA damage induced in human peripheral T lymphocytes following 10 MV X-ray irradiation. As a result, the production of 8-oxoguanine, i.e., the product of oxidative DNA damage, was clearly identified starting at 10, 6, and 3 h, after 2, 5, and 20 Gy of irradiation, respectively. Therefore, we examined in the present study reactive oxygen species (ROS) formation in T lymphocytes following 5 Gy of irradiation. Using a CCD camera system, we monitored fluorescence in T lymphocytes loaded with the succinimidyl ester of dichlorodihydrofluorescein diacetate (H2DCFDA), which is non-fluorescent until oxidized by ROS. We found that ROS formation occurred immediately after irradiation, continued for several hours, and resulted in oxidative DNA damage. Therefore, the origin of hyper-radiosensitivity of T lymphocytes seemed to be the high production of ROS in the mitochondrial DNA following irradiation.
authors.affiliation: Department of Radiology, Kochi Medical School, Oko-cho, Nankoku-shi, Kochi-Prefecture 783-8505, Japan. ogaway@kochi-ms.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Akihito
authors.initials: A
authors.lastname: Nishioka
authors.forename: Shinji
authors.initials: S
authors.lastname: Kariya
authors.forename: Shinji
authors.initials: S
authors.lastname: Hamasato
authors.forename: Harumichi
authors.initials: H
authors.lastname: Seguchi
authors.forename: Shoji
authors.initials: S
authors.lastname: Yoshida
mesh_terms: D004249:DNA Damage / Q000502:physiology / Q000528:radiation effects*; D004272:DNA, Mitochondrial; D006801:Humans; D008856:Microscopy, Fluorescence; D018384:Oxidative Stress / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000528:radiation effects*; D013601:T-Lymphocytes / Q000378:metabolism* / Q000528:radiation effects; D014965:X-Rays
chemical_list: D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species