Modification in the expression of Mre11/Rad50/Nbs1 complex in low dose irradiated human lymphocytes

Despite the fact that high doses of radiation are detrimental, low dose radiation (LDR) often protects the organism against a subsequent exposure of lethal doses of radiation. Present study was undertaken to understand the role of Mre11, Rad50 and Nbs1 genes in the low dose radio-adapted human peripheral blood mononuclear cells (PBMCs). Optimum time interval between low dose (0.07 Gy) and high dose (5.0 Gy) of (60)Co-gamma-radiation was observed to be 5.0 hours, at which PBMCs showed maximum LDR induced resistance (RIR). At cytogenetic level, micronuclei frequency was found to be reduced in LDR pre-irradiated PBMCs subsequently exposed to high dose radiation (HDR) as compared to controls. At transcriptional level, with reference to sham-irradiated cells significantly (p< or =0.05) altered expression of Mre11, Rad50 and Nbs1 genes was observed in low dose irradiated cells. At protein level, Mre11, Rad50 and Nbs1 were enhanced significantly (p< or =0.05) in low dose pre-irradiated cells subsequently exposed to high dose of radiation as compared to only high dose irradiated cells. Transcriptional as well as translational modulation in the expression of MRN complex components upon low dose irradiation may confer its participation in repair pathways, resulting in induced resistance.