Influence of Individual Radiosensitivity on the Hormesis Phenomenon: Toward a Mechanistic Explanation Based on the Nucleoshuttling of ATM Protein

Abstract

Hormesis is a low-dose phenomenon that has been reported to occur, to different extents, in animals, plants, and microorganisms. However, a review of the literature shows that only a few reports describe it in humans. Also, the diversity of experimental protocols and cellular models used makes deciphering the mechanisms of hormesis difficult. In humans, hormesis mostly appears in the 20 to 75 mGy dose range and in nontransformed, radioresistant cells. In a previous paper by Devic et al, a biological interpretation of the adaptive response (AR) phenomenon was proposed using our model that is based on the radiation-induced nucleoshuttling of the ATM protein (the RIANS model). Here, we showed that the 20 to 75 mGy dose range corresponds to a maximum amount of ATM monomers diffusing into the nucleus, while no DNA double-strand breaks is produced by radiation. These ATM monomers are suggested to help in recognizing and repairing spontaneous DNA breaks accumulated in cells and contribute to reductions in genomic instability and aging. The RIANS model also permitted the biological interpretation of hypersensitivity to low doses (HRS)—another low-dose phenomenon. Hence, for the first time to our knowledge, hormesis, AR, and HRS can be explained using the same unified molecular model.