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.

Nitric Oxide Is Involved in Heavy Ion-Induced Non-Targeted Effects in Human Fibroblasts

“…When nitric oxide scavenger, cPTIO, was added to the transfer medium, chromosome aberration was not increased, suggesting that nitric oxide in irradiated medium was involved in inducing chromosome aberrations in non-irradiated cells. Maeda et al reported that irradiated medium can increase sister chromatid exchange in Chinese hamster ovary cells [17]. In our experiment, medium irradiated with 0.2 Gy Fe-ions without cells did not induce chromosome aberrations in non-irradiated cells.…”

The Effect of Green and Black Tea Polyphenols on BRCA2 Deficient Chinese Hamster Cells by Synthetic Lethality through PARP Inhibition

“…Sister chromatid exchange was used for replicative stress analysis induced by PARP inhibitory effects by polyphenols (Figure 6). However, any genotoxic effects that directly or indirectly cause stress to cells can increase sister chromatid exchanges [21,22]. Therefore, observed elevation of sister chromatid exchange rate by tea polyphenols may not be solely from PARP inhibition.…”

Use of E18 Cell Model to Quantify DNA Strand Break Associated Bystander Effect (DSB-ABE)

“…Using precision micro beams, low-dose internal radiation β-particles and hadron radiations, various investigators were able to find out several end-points and effects of bystander signaling in naïve mammalian cells. These include but are not limited to genetic and epigenetic transformations that according to some estimates were previously underestimated [9], genomic instability [10] which can cause lethal mutations and altered gene expression [11], activation of several signal transduction pathways in a dose dependent manner [6,12,13], γ-H 2 AX foci formation [14], delayed apoptosis [1,[15][16][17], sister chromatid exchanges (SCE) [6,18], micronucleation [17,19] and neoplastic transformations [11].…”