No Evidence for DNA and Early Cytogenetic Damage in Bystander Cells after Heavy-Ion Microirradiation at Two Facilities

Abstract

The occurrence of bystander effects has challenged the evaluation of risk for heavy ions, mainly in the context of space exploration and the increasing application of carbon ions in radiotherapy. In the present study, we addressed whether heavy-ion-induced DNA and cytogenetic damage is detectable in bystander cells. The formation of gamma-H2AX foci, sister chromatid exchanges and micronuclei were used as markers of damage to DNA. Normal human fibroblasts were exposed to low fluences of carbon and uranium ions, and alternatively single cells were targeted with heavy ions using the GSI microbeam. We did not observe a significant increase in the bystander formation of gamma-H2AX foci, sister chromatid exchanges or micronuclei. In addition, we performed for the first time parallel experiments at two microbeam facilities (GSI, JAEA) using the same cell line, culture conditions and irradiation protocols. No significant enhancement of the micronucleus frequencies in bystander cells was detected after targeted carbon-ion irradiation, confirming the results. Details regarding the history, culture conditions or support of the cells might be affecting the detection of bystander effects. On the other hand, the potential X-ray- and heavy-ion-induced bystander effects investigated herein clearly do not exceed the experimental error and thus are either lacking or are less pronounced than the effects reported in the literature for similar end points after alpha-particle and X-ray exposure.

Nitric oxide-mediated bystander signal transduction induced by heavy-ion microbeam irradiation

“…Our results are consistent with previous studies, which showed that foci formation by γ -H2AX or 53BP1 in bystander cells was induced in normal human fibroblast AG01522 cells irradiated with 1 GeV/n iron (Fe) ions with 151 keV/μm (Yang et al, 2007(Yang et al, , 2011. By contrast, foci formation by γ -H2AX in bystander AG01522 cells did not increase significantly after high-LET carbon-or nickel-ion microbeam irradiation (Fournier et al, 2009). The process of DNA damage induction mediated by NO is complex and it occurs via multiple pathways (reviewed in Tomita and Maeda, 2015).…”

“…An additional excellent feature of the TIARA facility is that the same particles with similar energy in the broadbeams and microbeams can be used to expose biological materials, thereby contributing significantly to the understanding of heavy-ion-induced bystander responses (Shao et al, 2003;Funayama et al, 2005;Kanasugi et al, 2007;Hamada et al, 2008;Iwakawa et al, 2008;Harada et al, 2009;Fournier et al, 2009;Hino et al, 2010;Mutou-Yoshihara et al, 2012;Autsavapromporn et al, 2013 and so on). The significant role of NO in the bystander response was determined in studies using heavy-ion microbeams (Kanasugi et al, 2007;Mutou-Yoshihara et al, 2012).…”

Radiation induced bystander effect and DNA damage

“…It has been argued [54] that bystander induced cells generally show an up-regulation of p-53 and p-21 but a down-regulation of CDC2, cyclin B1 and Rad 51. A team recently reported [83] to have found no evidence of bystander induction in human fibroblasts by using carbon and uranium heavy ions to target single cells. They used γ-H 2 AX foci, SCEs and micronucleation as end-points.…”

Health Risks of Space Exploration: Targeted and Nontargeted Oxidative Injury by High-Charge and High-Energy Particles

“…The lack of clear knowledge about nontargeted responses (94,127,299) has been singled out by the U.S. National Academies (1) as one of the important factors limiting the prediction of radiation health risks associated with space exploration. This is because during deep space travel, only a small fraction of cells in the human body experiences extremely dense ionizations created along the tracks of the traversing particles in a given day (62).…”