Up-regulation of Bcl-2 expression in cultured human lymphocytes after exposure to low doses of gamma radiation

Abstract

Lymphocytes have demonstrated complex molecular responses to induced stress by ionizing radiation. Many of these reactions are mediated through modifications in gene expressions, including the genes involved in apoptosis. The primary aim of this study was to assess the effects of low doses of ionizing radiation on the apoptotic genes, expression levels. The secondary goal was to estimate the time-effect on the modified gene expression caused by low doses of ionizing radiation. Mononuclear cells in culture were exposed to various dose values ranged from 20 to 100 mGy by gamma rays from a Cobalt-60 source. Samples were taken for gene expression analysis at hours 4, 24, 48, 72, and 168 following to exposure. Expression level of two apoptotic genes; BAX (pro-apoptotic) and Bcl-2 (anti-apoptotic) were examined by relative quantitative real-time polymerase chain reaction (PCR), at different time intervals. Radio-sensitivity of peripheral blood mononucleated cells (PBMCs) was measured by the Bcl-2/BAX ratio (as a predictive marker for radio-sensitivity). The non-parametric two independent samples Mann–Whitney U-test were performed to compare means of gene expression. The results of this study revealed that low doses of gamma radiation can induce early down-regulation of the BAX gene of freshly isolated human PBMCs; however, these changes were restored to near normal levels after 168 hours. In most cases, expression of the Bcl-2 anti-apoptotic gene was up-regulated. Four hours following to exposure to low doses of gamma radiation, apoptotic gene expression is modified, this is manifested as adaptive response. Modification of these gene expressions seems to be a principle pathway in the early radioresistance response. In our study, we found that these changes were temporary and faded completely within a week.

Adaptive responses to low doses of radiation or chemicals: their cellular and molecular mechanisms

“…Microarray analysis of these cells has identified low-dose inducible genes with known roles in apoptosis regulation and cell cycle regulation. Thus low-dose γ-radiation modifies apoptotic-related gene expression in freshly isolated blood lymphocytes, inducing upregulation of Bcl -2, an anti-apoptotic molecule and down-regulation of Bax, a proapoptotic gene [103].…”

Global Gene Expression Alterations as a Crucial Constituent of Human Cell Response to Low Doses of Ionizing Radiation Exposure

“…Human PBMCs transcriptional response to LDIR as related to apoptosis was elucidated in detail [ 15 ]. The cells were exposed to various LDIR doses ranging from 2 to 10 cGy.…”

“…Samples for gene expression analysis were taken at 4, 24, 48, 72 h, and up to a week post-LDIR. LDIR was found to induce early repression of the BAX gene in human PBMCs but these changes were restored to near control levels after 168 h [ 15 ]. Generally, the expression of the BCL2 anti-apoptotic gene was elevated, and LDIR-induced changes were transient and disappeared within a week.…”

Selective ATP hydrolysis inhibition in F1Fo ATP synthase enhances radiosensitivity in non-small-cell lung cancer cells (A549)

“…Since BTB pretreatment had a marked response on X-ray irradiation-induced apoptosis, the possible molecular mechanisms were further explored. X-ray-radiation-induced apoptosis involves the Bcl-2 family and is mediated by extrinsic and intrinsic pathways [ 26 ]. Bax is a pro-apoptotic member in the Bcl-2-family with the ability of mitochondrial outer membrane permeabilization and consequently promoting the release of cytochrome c, whereas anti-apoptotic members such as Bcl-2 work as protectors of the outer membrane and preserve its integrity by opposing Bax function [ 27 ].…”