title: Radiation-induced bystander effects induce radioadaptive response by low-dose radiation.
abstract: When normal human fibroblast cells (MRC-5) received a priming irradiation of 3-20 mGy 4 h prior to irradiation with 1000 mGy, the number of DNA double-stranded breaks (DSBs) decreased significantly to 18.2-18.7 per cell compared with 21 per cell when there was no priming irradiation. This result indicates that a priming irradiation of 3-20 mGy induces a radioadaptive response in MRC-5. The authors' previous study had indicated that DSBs induced by ≤ 20 mGy are due to a radiation-induced bystander effect. These findings suggest that radiation-induced bystander effects might contribute to induction of the radioadaptive response. To test this hypothesis, MRC-5 were suspended in lindane, an inhibitor of radiation-induced bystander effects, which was added to the medium for the priming irradiation of 3-20 mGy. Lindane inhibited the protective effect of priming irradiation on DSBs caused by subsequent irradiation with 1000 mGy. Thus, radiation-induced bystander effects may play a role in radioadaptive responses.
authors.affiliation: Department of Environmental Health Science, Oita University of Nursing and Health Sciences, 2944-9 Megusuno, Oita 840-1201, Japan. ojima@oita-nhs.ac.jp
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Ojima
authors.forename: Hirohumi
authors.initials: H
authors.lastname: Eto
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Ban
authors.forename: Michiaki
authors.initials: M
authors.lastname: Kai
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects / Q000528:radiation effects*; D024201:Bystander Effect / Q000187:drug effects / Q000528:radiation effects*; D002478:Cells, Cultured; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects*; D005455:Fluorescent Antibody Technique; D001556:Hexachlorocyclohexane / Q000494:pharmacology*; D006801:Humans; D007306:Insecticides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011836:Radiation Tolerance / Q000502:physiology*; D014965:X-Rays
chemical_list: D007306:Insecticides; D001556:Hexachlorocyclohexane