ORIGINAL RESEARCH Protection from radiation-induced apoptosis by the radioprotector amifostine (WR-2721) is radiation dose dependent Rebecca J. Ormsby & Mark D. Lawrence & Benjamin J. Blyth & Katrina Bexis & Eva Bezak & Jeffrey S. Murley & David J. Grdina & Pamela J. Sykes Received: 5 September 2013 /Accepted: 9 January 2014 /Published online: 24 January 2014 # Springer Science+Business Media Dordrecht 2014 Abstract The radioprotective agent amifostine is a free radical scavenger that can protect cells from the damag- ing effects of ionising radiation when administered prior to radiation exposure. However, amifostine has also been shown to protect cells from chromosomal muta- tions when administered after radiation exposure. As apoptosis is a common mechanism by which cells with mutations are removed from the cell population, we investigated whether amifostine stimulates apoptosis when administered after radiation exposure. We chose to study a relatively low dose which is the maximum radiation dose for radiation emergency workers (0.25 Gy) and a high dose relevant to radiotherapy exposures (6 Gy). Mice were administered 400 mg/kg amifostine 30 min before, or 3 h after, whole-body irradiation with 0.25 or 6 Gy X-rays and apoptosis was analysed 3 or 7 h later in spleen and bone marrow. We observed a significant increase in radiation-induced ap- optosis in the spleen of mice when amifostine was administered before or after 0.25 Gy X-rays. In contrast, when a high dose of radiation was used (6 Gy), amifostine caused a reduction in radiation-induced apo- ptosis 3 h post-irradiation in spleen and bone marrow similar to previously published studies. This is the first study to investigate the effect of amifostine on radiation- induced apoptosis at a relatively low radiation dose and the first to demonstrate that while amifostine can reduce apoptosis from high doses of radiation, it does not mediate the same effect in response to low-dose expo- sures. These results suggest that there may be a dose threshold at which amifostine protects from radiation- induced apoptosis and highlight the importance of ex- amining a range of radiation doses and timepoints. Keywords Amifostine . Apoptosis . Free radical scavengers . Low-dose X-radiation . Radioprotectors . X-radiation Introduction The chemical radioprotector amifostine (S-2-[3- aminopropylamino]ethylphosphorothioic acid; WR- 2721; Ethyol™) is a potent free radical scavenger admin- istered prior to radiotherapy or chemotherapy treatment for certain cancers (Brizel et al. 2000; Kemp et al. 1996) to selectively reduce normal tissue damage (Grdina et al. 1999; Yuhas 1982; Yuhas and Storer 1969). While cytoprotection is only achieved when amifostine is ad- ministered prior to treatment, a number of studies have shown that amifostine can reduce the frequency of Cell Biol Toxicol (2014) 30:55–66 DOI 10.1007/s10565-014-9268-3 R. J. Ormsby : M. D. Lawrence : B. J. Blyth : K. Bexis : P. J. Sykes (*) Haematology & Genetic Pathology, Flinders Centre for Innovation in Cancer, Flinders University and Medical Centre, Flinders Drive, Bedford Park, South Australia 5042, Australia e-mail: pam.sykes@flinders.edu.au E. Bezak Department of Medical Physics, Royal Adelaide Hospital, Adelaide, South Australia 5000, Australia J. S. Murley : D. J. Grdina Department of Radiation and Cellular Oncology, The University of Chicago, Chicago, IL 60637, USA