Radioprotective effect of hypothermia on cells – a multiparametric approach to delineate the mechanisms

Abstract

We suggest that low temperature during irradiation can induce a temporary cell cycle shift, which could lead to a reduced micronucleus frequency. Future experiments focused on cell cycle progression are needed to confirm this hypothesis.

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

“…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.…”

“…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.…”

“…Cytochalasin B (Sigma Aldrich) was added at a fi nal concentration of 5.6 μ g/ml. Cells were cultured for 27 h at 37.0 ° C, 5% CO 2 and harvested as described previously (Dang et al 2012). Briefl y, cells were centrifuged and resuspended in 0.14 M KCl (Sigma Aldrich).…”

“…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.…”

“…In a recent study (Dang et al 2012) we investigated the mechanisms of hypothermia in human lymphoblastoid TK6 cells. We analyzed DNA damage signaling by inhibiting the ataxia telangiectasia mutated (ATM) kinase with the inhibitor KU55933, the role of chromatin conformation by inhibiting histone deacetylation using trichostatin A, the frequency of MN in sequentially harvested cells, the kinetics of DNA repair by the gamma-H2AX (activated histone 2AX) assay as well as clonogenic cell survival.…”