Low-dose irradiation alters the radio-sensitivity of human peripheral blood lymphocytes

Abstract

DNA is the most critical target of ionizing radiation when interact with cells. Several molecular studies have demonstrated modifications in expression levels of genes involved in the processes of signal transduction, cell cycle control, DNA repair and apoptosis following to exposure to ionizing radiation. The apoptosis intrinsic pathway is the main pathway that leads to apoptosis in response to DNA damage. The latter is responsible to regulate the release of mitochondrial proteins, including cytochrome-c (cytc). The aim of this study was to evaluate role of low-doses of gamma radiation on the apoptotic genes expression in human peripheral blood lymphocytes. Mononuclear cells were isolated from whole blood samples. They were exposed in culture to different doses from 2 to 10 cGy by gamma rays from a cobalt-60 source. Two apoptotic genes; BAX (pro-apoptotic) and Bcl-2 (antiapoptotic) were examined by relative quantitative Real-Time PCR for expression level, 4 and 24 hours following to irradiation. The study revealed, low doses of gamma radiation induced down-regulation for BAX gene and up-regulation for Bcl-2 gene. The result of present study has showed that low doses of gamma radiation could increase Bcl-2/BAX ratio and radio-resistance. These findings suggest that the genotoxic effects of low doses of gamma radiation may be due to adaptive response and a reduction of apoptosis.