@article{oai:repo.qst.go.jp:00056007,
 author = {鈴木, 雅雄 and 舟山, 知夫 and 横田, 裕一郎 and 鈴木, 芳代 and 坂下, 哲哉 and 小林, 泰彦 and 鈴木 雅雄 and 舟山 知夫 and 横田 裕一郎 and 鈴木 芳代 and 坂下 哲哉 and 小林 泰彦},
 journal = {QST Takasaki Annual Report 2015},
 month = {Mar},
 note = {The last year we reported that bystander lethal effects were induced by the different mechanisms between C- and Ar-ion-irradiated cells. The bystander effect induced in C-ion-irradiated cells was dominant via the gap-junction mediated cell-cell communication and the Ar-ion induced bystander effect was dominant via secrete factor(s) to culture medium from the irradiated cells1). This year we tried to identify secreate factor(s) caused of bystander lethal effect induced in normal human fibroblasts using radical scavengers. 
  Early passaged cell cultures of normal human skin fibroblasts (Cell name : NB1RGB, Cell No. RCB0222) were obtained from Riken Bio Resource in Japan. Approximately 6 x 105 exponentially growing cells were inoculated into microbeam dishes, which were made of acrylic resin ring with 36 mm diameter and attached 7.5 µm-thick polyimide film on the bottom of the ring, 2 days before microbeam irradiation. Half of the sample dishes were treated with an inhibitor of gap-junction mediated cell-cell communication (40 µM ofγ-isomer of hexachloro-cyclohexane) from 3 h before irradiation to the end of 24 h of post-irradiation incubation. Irradiations were carried out using the 256 (16 x 16)-cross-stripe method described previous report2) using C ions (12C5+, 220 MeV), Ne ions (20Ne7+, 260 MeV) and Ar ions (40Ar13+, 460 MeV) at the HZ1 port in TIARA. The beam size of each ion microbeam was 20 µm in diameter and the irradiations in each point were performed to deliver 8 ions for carbon, 2 ions for neon and single ion for argon, respectively. The values of linear energy transfer (LET) at the sample position were estimated to be 103 keV/µm for C ions, 380 keV/µm for Ne ions and 1260 keV/µm for Ar ions. After irradiations, cells were incubated for 24 h in a CO2 incubator at 37oC, and then assayed using the colony-forming method with/without radical scavengers. We used either dimethyl sulfoxide (DMSO:0.7M) as a scavenger of reactive oxygen species or ascorbic acid (AsA:5mM) as a specific scavenger of long-lived radicals and treated them during the 24 h of post-irradiation incubation.
  Figure 1 showed the results for lethal effects at 24 h after irradiation treated with/without the scavengers in microbeam-irradiated cells (IR) and microbeam-irradiated cells with the gap-junction inhibitor (L+IR). The surviving fractions in the cells treated with DMSO were around 0.9 and no change was observed between the cells treated and non-treated with DMSO. Furthermore the data were similar with the cells between absence and presence of the gap-junction inhibitor. The surviving fraction 0.9 was significantly low beyond our expectation, indicating the bystander lethal effect, because we could estimate that the percent of Ar-ion direct hit cells was around 0.04% order of all cells in the dish by the 256 (16 x 16)-cross-stripe method. On the other hand, the surviving fraction in the cells treated with AsA were around 1.0, indicating the suppression of bystander lethal effect observed in the microbeam-irradiated cells. And also no effect was observed in the cells with/without the gap-junction inhibitor. There is clear evidence that the secret factor(s) scavenged by AsA can induce bystander lethal effect in the cells irradiated with Ar-ion microbeams.
\nReferences
1)M.Suzuki et al., JAEA Talasaki Ann. Rep. 2014 JAEA-Review 2015-022 (2016) 70.
2)M.Suzuki et al., JAEA Talasaki Ann. Rep. 2006 JAEA-Review 2007-060 (2008) 107.},
 pages = {118--118},
 title = {What Kinds of Secrete Factor(s) Can Induce Bystander Lethal Effect in Normal Human Fibroblasts Irradiated with Ar0Ion Microbeams?},
 year = {2017}
}