Cellular adaptive response to chronic radiation exposure in interventional cardiologists

Aims Invasive cardiologists are the most exposed to ionizing radiation among health professionals and show an increased rate of somatic DNA damage. To evaluate the effects of chronic low-dose exposure to ionizing radiation on redox state and apoptotic activation. Methods and results We enrolled 10 healthy exposed professionals (all interventional cardiologists, Group II, exposed: age = 38 ± 5 years) and 10 age- and gender-matched unexposed controls (Group I, non-exposed). Exposed subjects had a median exposure of 4 mSv/year (range 1-8) by film badge dosimetry (below lead apron). We measured reduced glutathione (GSH, a marker of antioxidant response) in erythrocytes and plasma generation of hydrogen peroxide (a marker of oxyradical stress) by ferrous oxidation-xylenol orange assay in plasma. In both groups, lymphocytes were isolated and caspase-3 activity (a marker of apoptotic response) measured at baseline and following 2 Gy in vitro irradiation. Exposed subjects showed a three-fold increase in hydrogen peroxide (Group I = 2.21 ± 1.03 vs. II = 6.51 ± 1.55 μM H(2)O(2) equivalents) and a 1.7-fold increase in GSH (I = 12.37 ± 1.22 vs. II = 20.61 ± 2.16 mM). Exposed subjects also showed higher values of caspase-3 activity, both at baseline and-more strikingly-following high-dose radiation challenge. Conclusion In interventional cardiologists, chronic exposure to low-dose radiation is associated with an altered redox balance mirrored by an increase in hydrogen peroxide and with two possibly adaptive cellular responses: (i) an enhanced antioxidant defence (increase in GSH, counteracting increased oxyradical stress) and (ii) an increased susceptibility to apoptotic induction which might efficiently remove genetically damaged cells.