Hyperfast, early cell response to ionizing radiation

• Published in: International journal of radiation biology 2000, Vol.76 (9), p.1233-1243
• Main Author: Ponette, C. Le Péchoux, E. Deniaud-Alexandre, M. Fernet, N. Giocanti, H. Tourbez, V. Favaudon, V.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - radiation effects; Biological and medical sciences; Biological effects of radiation; Cell Line; Cell Separation; Cricetinae; DNA - radiation effects; DNA Damage - radiation effects; DNA Fragmentation - radiation effects; Dose-Response Relationship, Radiation; Fibroblasts - radiation effects; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Gamma Rays; Humans; In Situ Nick-End Labeling; Ionizing radiations; Lipid Metabolism; Mitosis - radiation effects; Oxidative Stress - radiation effects; Signal Transduction - radiation effects; Time Factors; Tissues, organs and organisms biophysics; Tumor Cells, Cultured
• ISSN: 0955-3002; 1362-3095
• DOI: 10.1080/09553000050134465

Purpose : To determine whether the oscillatory changes of radiosensitivity which occur within fractions of a second to a few minutes following flash irradiation correlate with an altered incidence of apoptosis, DNA strand breaks or lipid-coupled signalling. Materials and methods : Human tumor cells (SQ-20B, LoVo) or Chinese hamster V79 fibroblasts were exposed to split-dose, pulse irradiation with 3.5 MeV electrons at high dose-rate (12 or 120Gys -1) and the effects assessed by clonogenic assays, analysis of DNA cleavage and microscopic observation. Results : The processes underlying oscillatory radiation response were saturable, but did not correlate with an increased incidence of DNA single- or double-strand breaks or apoptosis. N -acetylcysteine and inhibitors of lipid-derived signalling also failed to alter oscillatory response. However, this response did correlate with phenotypic alterations evoking mitotic or delayed cell death. Furthermore, high dose-rate irradiation provided a lower level of instability than protracted γ-ray irradiation. Conclusions : It is proposed that the early steps of DNA damage recognition and repair following priming radiation exposure bring about rapid, synchronous remodeling of chromatin, evoking enhanced chromosome damage upon re-irradiation.