Transcription profile of DNA damage response genes at G0 lymphocytes exposed to gamma radiation

Abstract

Ionizing radiation induces a plethora of DNA damages in human cells which may alter the level of mRNA expression. We have analyzed mRNA expression profile of DNA damage response genes involved in G(0)/G(1) check point pathway in whole blood to assess their radio-adaptive response, if any, to gamma radiation. Blood samples were collected from twenty-five random, normal, and healthy male donors with written informed consent and irradiated at doses between 0.1 and 2.0 Gy (0.7 Gy/min). DNA strand breaks were studied using comet assay, whereas DNA double-strand breaks were visualized using γH2AX as a biomarker. Dose response if any, at transcriptional level was studied for all these dose groups at 1 and 5-h post-irradiation. Adaptive response at transcriptional level was studied at three different priming doses (0.1, 0.3, and 0.6 Gy) separately followed by a challenging dose of 2.0 Gy after 4 h. For both the experiments, total RNA was isolated from PBMCs obtained from irradiated whole blood and reverse transcribed to cDNA. The level of mRNA expression of ATM, ATR, GADD45A, CDKN1A, P53, CDK2, MDM2, and Cyclin E was studied using real-time quantitative PCR. A significant dose-dependant increase in the percentage of DNA damage in tail was observed using comet assay. Similarly, increased number of foci was observed at γH2AX with increasing dose. At transcriptional level, a significant dose-dependent up-regulation at GADD45A, CDKN1A, and P53 genes up to 1.0 Gy was observed at 5-h post-irradiation (P ≤ 0.05). Radio-adaptive response at mRNA expression level was observed at CDK2, Cyclin E, and P53, whereas ATM, ATR, GADD45A, MDM2, ATM, and ATR have not shown any radio-adaptive changes in the expression profile. DNA damage response genes involved in G(0)/G(1) checkpoint pathway has important implications in terms of radiosensitivity in vivo and changes in the transcriptional profile might throw some new insights to understand the mechanism of adaptive response.

Acute exposure to high dose γ-radiation results in transient activation of bone lining cells

“…The mechanism for the protective effect of prior exposure to the lower dose radiation is incompletely understood. However, more rapid recovery of hematopoietic cells, depressed tumor suppressor gene expression, and induction of antioxidative and repair enzymes appear to contribute to the protective effects [43-46]. Whatever the precise mechanisms for improved survival, a standard radioconditioning priming dose of 0.5 mGy was ineffective in moderating the acute skeletal effects of irradiation (6 Gy) on bone.…”

Assessment of Individual Radiosensitivity in Inhabitants of Takandeang Village － A High Background Radiation Area in Indonesia

“…Here in this study, we evaluated the association between TP53 Arg72Pro polymorphism and radiosensitivity assessed using G 2 MN assay. The wild-type TP53 gene normally responds to radiation with a high level of expression and subsequently mediates cell cycle arrest and DNA repair activation [33]. Therefore, TP53 is important for monitoring radiosensitivity to both high and low doses of radiation, alone or in combination with other stressors [18].…”

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

“…Gene expression profiles of DDR genes in PBMCs were recently examined to assess their RAR [ 60 ]. Blood samples were collected from 25 healthy male donors and exposed to both LDIR and HDIR at doses between 0.1 and 2 Gy [ 60 ]. Gene expression changes were studied at 1 and 5 h post-IR.…”

“…The data showed a significant dose-dependent induction of CDKN1A and GADD45A genes up to 1 Gy at 5 h post-IR. RAR was observed only with TP53 , CDK2 , and CCNE [ 60 ].…”