Alzheimer's disease and low-dose radiation therapy: A new hope.

The concept of low-dose radiation (LDR)-induced hormetic responses was initially observed approximately 70 years ago and systematically reviewed along with the discovery of LDR-induced adaptive responses in a cytogenetic study in 1980s. By the end of the 1990s, discussions regarding the potential applications of LDR-induced hormesis and adaptive responses for preventing or treating chronic diseases, such as Alzheimer's disease (AD) had taken place. Until 2016, reports on radiotherapy for the subjects with AD and for genetic AD model mice were published. Subsequently, several preclinical studies with animal models of AD and clinical studies in AD subjects were conducted. A significant milestone was achieved with the online availability of a new Systematic Review based on qualified publications from these preclinical and clinical studies. This mini-review provides a concise historical introduction to LDR-induced hormesis and adaptive responses with discussion of AD radiotherapy with either LDR or relatively high dose radiation. Highlights of this Systematic Review cover promising outcomes, challenges, and new questions, followed by discussion of potential mechanisms.