Assessment of Radiosensitivity and Monitoring of Radiation-Induced Cellular Damage

In contrast to individuals on Earth, astronauts receive much higher doses of ionizing radiation during spaceflight. Besides this, the type of radiation in space is quite different from terrestrial radiation, and consists mainly of high-energy protons and highly charged and energetic particles. It is well known that all types of ionizing radiation induce a large spectrum of DNA lesions and the global response of a cell to DNA damage triggers multiple pathways involved in sensing DNA damage, activating cell cycle checkpoints and inducing DNA repair. However, when damage is severe, apoptosis, also known as “programmed cell death”, can be induced. Ionizing radiation exposure induces biological effects, depending on the type of radiation, dose, and exposure time. In this context, radiation dosimetry on board spacecraft can be useful to estimate the cumulative equivalent doses to which astronauts are exposed. So far, the precise impact of radiation on the deterioration of the immune system in astronauts is still under investigation. Several ground-based experiments on various radiation facilities have been performed and have contributed to our general knowledge of radiation-induced immune changes. Crucially, radiation interacts with other spaceflight stressors, such as microgravity, thereby resulting in a joint effect on the immune system.