Different Effects of Antioxidants Against Ionizing Radiation: An Experimental Model of Micronuclei

There is an urgent need to find and develop radiation countermeasures for both planned and unplanned exposures. However, in recent years, radioprotective substances, such as rosmarinic acid (RA), have been described, presenting contradictory and even paradoxical results. In this paper, we evaluated the genoprotective capacity of 29 substances against chromosomal damage induced by gamma radiation in a comparative study using the same technique, i.e., cytokinesis-block micronucleus (CBMN) assay to evaluate their genoprotective capacities, at the same concentrations and administered before and after exposure to 2 Gy of gamma radiation. We then related the observed effects with their chemical characteristics to appreciate the different mechanisms of action that could explain some apparent contradictions that may emerge. In our study, before exposure to ionizing radiation, RA produced the greatest reduction in the frequency of radiation-induced micronuclei (p < 0.001), presenting the highest magnitude of protection (58%) and a dose reduction factor of 7.1 (p < 0.001); however, it loses this genoprotective capacity when administered after exposure to radiation. These results could be attributed to the different radical-scavenging and antilipoperoxidative activities of each substance tested. Antilipoperoxidant activity was found to be the most important factor in the reduction in radiation-induced chromosomal damage; thus, lipo-antioxidant substances emerged as the most effective in protecting genetic material against oxidative damage.