Effect of temperature during irradiation on the level of micronuclei in human peripheral blood lymphocytes exposed to X-rays and neutrons

Abstract

The results of experiments with DMSO indicate that the temperature effect is due to the indirect action of radiation, i.e., via reactive oxygen species. However, this is not supported by the results with neutrons and the comet assay. Possible reasons for the discrepancies are discussed.

Effect of hypothermia on radiation-induced micronuclei and delay of cell cycle progression in TK6 cells

“…Th e present results also weaken another hypothesis put forward by Brzozowska et al (2009), that the TE could be related to inhibition of the bystander effect, thus leading to a reduced level of DNA damage. Although it could be time points during which cell densities were measured varied between experiments, so fi tting allowed calculating the mean numbers of cell doublings and standard deviations.…”

“…Th e protective eff ect of hypothermia, referred to as the temperature eff ect (TE), on the level of radiation-induced chromosomal damage is a puzzling but repeatedly observed phenomenon (Bajerska and Liniecki 1969, Gumrich et al 1986, Brzozowska et al 2009, Brehwens et al 2010, Dang et al 2012, Lisowska et al 2013. Th e aim of the present study was to verify if the sequence of exposing cells to hypothermia and radiation plays a role in the TE.…”

“…Th e rational for testing if the sequence of exposing cells to hypothermia and radiation plays a role in the TE was that our earlier results (Brzozowska et al 2009) obtained after treating human peripheral blood lymphocytes with the radical scavenger dimetylsulfoxid (DMSO) indicated that TE may be related to modulation of chromatin conformation resulting in protecting the DNA from attacks by reactive oxygen species. Falk et al (2008) showed that condensation of chromatin has a radioprotective eff ect on the DNA and it could be assumed that cooling cells in ice water leads to chromatin condensation.…”

“…Prior to, or following irradiation, cells were incubated for 20 min in small water cups made of polystyrene foam at the respective irradiation temperature: 0.8 ° C (ice water) or 37.0 ° C. Th is time has previously been shown to induce the TE both in TK6 cells (Dang et al 2012) and human peripheral blood lymphocytes (Brzozowska et al 2009, Lisowska et al 2013. Irradiation was always carried out at the temperature at which cells were kept for the last 20 min.…”

“…It is assumed that all processes inhibited by hypothermia are restored at 37 ° C. However, hypothermia has been shown to act in a radioprotective manner (this is referred to as the ' temperature eff ect ' [TE]) indicating that the cooling of cells does not only lead to a transient inhibition of cellular process, but somehow infl u-ences the cellular radiosensitivity. Th e TE was detected using various endpoints such as clonogenic survival (Belli andBonte 1963, Elmroth et al 2000), survival of mice (Levan et al 1970), enzyme activity (Kempner and Haigler 1982), frequency of chromosomal aberrations (Bajerska and Liniecki 1969, Gumrich et al 1986, Lisowska et al 2013, frequency of micronuclei (MN) (Brzozowska et al 2009, Brehwens et al 2010, Dang et al 2012) and DNA supercoil unwinding (Elmroth et al 1999a(Elmroth et al , 1999b. At fi rst glance, the TE might seem trivial, but it demonstrates that variation of temperature at radiation exposure may have serious implications for the outcome of the experiment.…”