Measurement of complex DNA damage induction and repair in human cellular systems after exposure to ionizing radiations of varying linear energy transfer (LET).
Detrimental effects of ionizing radiation (IR) are correlated to the varying efficiency of IR to induce complex DNA damage. A double strand break (DSB) can be considered the simpler form of complex DNA damage. These types of damage can consist of DSBs, single strand breaks (SSBs) and/or non-DSB lesions such as base damages and apurinic/apyrimidinic (AP; abasic) sites in different combinations. Enthralling theoretical (Monte Carlo simulations) and experimental evidence suggests an increase in the complexity of DNA damage and therefore repair resistance with linear energy transfer (LET). In this study, we have measured the induction and processing of DSB and non-DSB oxidative clusters using adaptations of immunofluorescence. Specifically, we applied foci colocalization approaches as the most current methodologies for the in situ detection of clustered DNA lesions in a variety of human normal (FEP18-11-T1) and cancerous cell lines of varying repair efficiency (MCF7, HepG2, A549, MO59K/J) and radiation qualities of increasing LET, that is γ-, X-rays 0.3-1 keV/μm, α-particles 116 keV/μm and36Ar ions 270 keV/μm. Using γ-H2AX or 53BP1 foci staining as DSB probes, we calculated a DSB apparent rate of 5-16 DSBs/cell/Gy decreasing with LET. A similar trend was measured for non-DSB oxidized base lesions detected using antibodies against the human repair enzymes 8-oxoguanine-DNA glycosylase (OGG1) or AP endonuclease (APE1), that is damage foci as probes for oxidized purines or abasic sites, respectively. In addition, using colocalization parameters previously introduced by our groups, we detected an increasing clustering of damage for DSBs and non-DSBs. We also make correlations of damage complexity with the repair efficiency of each cell line and we discuss the biological importance of these new findings with regard to the severity of IR due to the complex nature of its DNA damage.
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Zacharenia
Z
Nikitaki
b Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School , Essen , Germany.
Vladimir
V
Nikolov
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Ifigeneia V
IV
Mavragani
b Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School , Essen , Germany.
Emil
E
Mladenov
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Anastasios
A
Mangelis
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Danae A
DA
Laskaratou
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Georgios I
GI
Fragkoulis
c Radiation Biology Department , German Aerospace Center (DLR), Institute of Aerospace Medicine , Linder Höhe , Köln , Germany.
Christine E
CE
Hellweg
d Research Division , Peter MacCallum Cancer Centre , Melbourne , VIC , Australia.|e Sir Peter MacCallum Department of Oncology , The University of Melbourne , Melbourne , VIC , Australia.|f Division of Radiation Oncology and Cancer Imaging , Peter MacCallum Cancer Centre , Melbourne , VIC , Australia.
Olga A
OA
Martin
g Medical Physics Laboratory , Medical School, University of Ioannina , Ioannina , Greece.
Dimitris
D
Emfietzoglou
h Laboratory of Health Physics , Radiobiology & Cytogenetics, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos" , Athens , Greece.
Vasiliki I
VI
Hatzi
h Laboratory of Health Physics , Radiobiology & Cytogenetics, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos" , Athens , Greece.
Georgia I
GI
Terzoudi
b Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School , Essen , Germany.
George
G
Iliakis
a Physics Department, School of Applied Mathematical and Physical Sciences , National Technical University of Athens (NTUA) , Zografou , Athens , Greece.
Alexandros G
AG
Georgakilas
D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D006801:Humans; D018499:Linear Energy Transfer / Q000235:genetics*; D011839:Radiation, Ionizing
Complex DNA damage; DNA repair; Monte Carlo simulation; foci colocalization; high LET ionizing radiations; non-DSB clusters