hide
Free keywords:
Animals
Cell Nucleus/genetics/metabolism/radiation effects
DNA Breaks, Double-Stranded/radiation effects
*DNA Damage
DNA Repair Enzymes/metabolism
DNA-Binding Proteins/metabolism
Dose-Response Relationship, Radiation
Female
Histones/*metabolism
Immunohistochemistry
Intracellular Signaling Peptides and Proteins/metabolism
Lymphocytes/metabolism/radiation effects
Microscopy, Fluorescence
Phosphorylation/radiation effects
*Radiation, Ionizing
Radiometry/methods
Reproducibility of Results
Swine
Swine, Miniature
Abstract:
Radiation accidents frequently involve acute high dose partial body irradiation leading to victims with radiation sickness and cutaneous radiation syndrome that implements radiation-induced cell death. Cells that are not lethally hit seek to repair ionizing radiation (IR) induced damage, albeit at the expense of an increased risk of mutation and tumor formation due to misrepair of IR-induced DNA double strand breaks (DSBs). The response to DNA damage includes phosphorylation of histone H2AX in the vicinity of DSBs, creating foci in the nucleus whose enumeration can serve as a radiation biodosimeter. Here, we investigated gammaH2AX and DNA repair foci in peripheral blood lymphocytes of Gottingen minipigs that experienced acute partial body irradiation (PBI) with 49 Gy (+/- 6%) Co-60 gamma-rays of the upper lumbar region. Blood samples taken 4, 24 and 168 hours post PBI were subjected to gamma-H2AX, 53BP1 and MRE11 focus enumeration. Peripheral blood lymphocytes (PBL) of 49 Gy partial body irradiated minipigs were found to display 1-8 DNA damage foci/cell. These PBL values significantly deceed the high foci numbers observed in keratinocyte nuclei of the directly gamma-irradiated minipig skin regions, indicating a limited resident time of PBL in the exposed tissue volume. Nonetheless, PBL samples obtained 4 h post IR in average contained 2.2% of cells displaying a pan-gammaH2AX signal, suggesting that these received a higher IR dose. Moreover, dispersion analysis indicated partial body irradiation for all 13 minipigs at 4 h post IR. While dose reconstruction using gammaH2AX DNA repair foci in lymphocytes after in vivo PBI represents a challenge, the DNA damage focus assay may serve as a rapid, first line indicator of radiation exposure. The occurrence of PBLs with pan-gammaH2AX staining and of cells with relatively high foci numbers that skew a Poisson distribution may be taken as indicator of acute high dose partial body irradiation, particularly when samples are available early after IR exposure.
