title: Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges.
abstract: When energetic particles irradiate matter, it becomes activated by nuclear reactions. Radioactivation induced cellular effects are not clearly understood, but it could be a part of bystander effects. This investigation is aimed at understanding the biological effects from radioactivation in solution induced by hadron radiation. Water or phosphate buffered saline was activated by being exposed to hadron radiation including protons, carbon- and iron-ions. 1 mL of radioactivated solution was transferred to flasks with Chinese hamster ovary (CHO) cells cultured in 5 mL of complete media. The induction of sister chromatid exchanges (SCE) was used to observe any increase in DNA damage responses. The energy spectrum and the half-lives of the radioactivation were analyzed by NaI scintillation detector in order to identify generated radionuclides. In the radioactivated solution, 511 keV gamma-rays were observed, and their half-lives were approximately 2 min, 10 min, and 20 min. They respectively correspond to the beta+ decay of 15O, 13N, and 11C. The SCE frequencies in CHO cells increased depending on the amount of radioactivation in the solution. These were suppressed with a 2-hour delayed solution transfer or pretreatment with dimethyl sulfoxide (DMSO). Our results suggest that the SCE induction by radioactivated solution was mediated by free radicals produced by the annihilated gamma-rays. Since the SCE induction and DMSO modulation are also reported in radiation-induced bystander effects, our results imply that radioactivation of the solution may have some contribution to the bystander effects from hadron radiation. Further investigations are required to assess if radioactivation effects would attribute an additional level of cancer risk of the hadron radiation therapy itself.
authors.affiliation: Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Junko
authors.initials: J
authors.lastname: Maeda
authors.affiliation: Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Yurkon
authors.affiliation: Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Inashiki, Ibaraki, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Graduate School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujisawa
authors.affiliation: Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kato
authors.affiliation: Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Colleen A
authors.initials: CA
authors.lastname: Brents
authors.affiliation: Graduate School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Uesaka
authors.affiliation: Research Center for Charged Particle Therapy, International Open Laboratory, National Institute of Radiological Sciences, Chiba, Chiba, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Fujimori
authors.affiliation: Research Development and Support Center, National Institute of Radiological Sciences, Chiba, Chiba, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kitamura
authors.affiliation: Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Takamitsu A
authors.initials: TA
authors.lastname: Kato
mesh_terms: D000818:Animals; D024201:Bystander Effect / Q000528:radiation effects; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D012854:Sister Chromatid Exchange / Q000528:radiation effects*