Radioadaptive Responses Induced by Chronic Low Dose Ionizing Radiation in Human Lymphocytes

Objectives Despite well-established understanding of the effects of high dose radiation exposure, the effects at low doses remain unclear. Radioadaptive responses have been observed in multiple cell lines but not well-documented in human lymphocytes. This study examined whether prolonged low-dose radiation exposure can induce radioadaptive responses in human lymphocytes from a local population. Methods Peripheral blood mononuclear cells (PBMCs) and lymphoblastoid cell lines (LCLs) were primed by prolonged exposure to radioactive Caesium-137, followed by a 6-hour recovery period, before 4 Gy X-ray challenge dose. Control cells received only the challenge dose. Cell apoptosis, γH2AX levels and the expression levels of some key DNA repair genes were examined. Results Primed cells exhibited reduced γH2AX levels and apoptosis as compared to controls. The involvement of DNA repair pathway was further shown through gene expression analysis and the use of ATM inhibitor. Conclusion Low-dose radiation priming induced radioadaptive responses in human lymphocytes that reduce DNA damage and cell death following high-dose radiation. This paper is one of the few studies to demonstrate the existence of radioadaptive responses arising from chronic low dose radiation exposure in human lymphocytes and has important implications for radiation risk assessment and protection frameworks.