In Vitro effects of exposure to radiofrequency on DNA damage induced by high-LET ionising radiation

Very little is known on the cooperative effects on biological systems of multiple sources of exposure, particularly of different physical characteristics such as ionising and non-ionising radiations. The majority of in vitro experimental data seem to exclude a direct DNA-damaging action by radiofrequency (RF) fields. However, it is possible that exposure to such signals may alter the repair of damage induced by ionising radiation (IR). Previously, we examined the effects of an in vitro 24-h exposure to a 1.95 GHz UMTS signal on the yield of chromosome aberrations (CAs) induced by 4Gy of x-rays in human lymphocytes [Manti et al., Radiat. Res., 2008]. We found an influence of SAR on the exchange frequency that was statistically significant after correction for donor variability although exposure to RF did not increase the fraction of x ray-induced aberrant cells. The growing use of wireless technology and the ubiquitous presence of cyto- and genotoxic agents such IR of varying quality pose concerns for the possible health hazards elicited by such combined exposure scenarios. Maintenance of genomic stability is a crucial barrier to both transformation and non-cancer late effects of IR. Here we report the results of the combined exposure of non-tumorigenic immortalised human epithelial bronchial cells (kindly donated by Dr. J. Shay, UT-Southwest Medical Centre, US) to RF signal and 5 MeV alpha-particles. Alpha-particle irradiation was carried out using the 3MV Van der Graaf Tandem accelerator at our Department. Low doses (0-0.5 Gy) of low-fluence alpha particles were delivered. Under such high-LET irradiation regime, which mimics that incurred in vivo by cells of the respiratory tract because of indoor radon inhalation, only a fraction of the irradiated cells are likely to experience a particle hit. This is known to be sufficient for genomic instability induction in several cell types. However, its modulation by concomitant exposure to RF is unknown. Cells were irradiated in purposely built wells while growing on 2.5 thick mylar as to minimize energy loss through the growth substratum. Wells are transferred to an incubator-hosted waveguide connected to a RF generator. After 24-h exposure to various SAR levels, cells are serially cultured and assayed for acute cytogenetic damage and for the onset of genome instability among the descendants of the exposed population. The latter is studied by assessing karyotype stability using m-FISH-derived karyograms and by measuring known markers of loss of genome integrity such as micronuclei and delayed reproductive death