Radiation hormesis: Stimulatory effects of low doses ionizing radiation

Low to small doses of ionizing radiation conditionally show stimulatory effects in various cells and organisms, contrasting with detrimental effects induced at high doses. Radiation hormesis is defined as biopositive health effects, such as augmentation of growth and survival, enhancement of immune response, suppression of mutagenesis, and increase in resistance to damages induced by subsequent high dose exposure. Accumulating data on molecular, cellular, and organism levels demonstrate a variety of hormetic phenomena produced by low dose radiation. Living organisms have been exposed to low doses radiation since the early period of evolution, therefore, radiation hormesis may be established at least in part as a defense mechanism, and thus has important implications for health and diseases. In this review, data of radiation hormesis were presented with special emphasis on the responses of organisms. Recent studies also show potential application of low dose radiation for intervention of diseases. Research on radiation hormesis will indisputably contribute to elucidate aging processes.