Microbeam irradiation reveals cytoplasmic damage contributes to micronuclei induction

Microbeam technology offers a valuable tool for investigating inter- and intracellular responses to radiation-induced damage. This study investigated the contribution of cytoplasmic irradiation to micronuclei (MN) induction using proton microbeams. Three irradiation conditions were employed: (N) nucleus-only, (C) cytoplasm-only, and (N + C) irradiating both. In N + C, 1000 protons were delivered to the cytoplasm. For both N and N + C, MN induction increased proportionally with nuclear proton dose (Np) within the 0 ≤ Np ≤ 100 range. However, the N + C slope was 2/3 of the N slope. N cells exhibited peak MN induction at 150 protons, while N + C peaked at 300 protons. Cytoplasmic irradiation alone also induced MNs, but with a lower slope and reaching a plateau after Np = 300. These results demonstrate that cytoplasmic damage not only contributes to MN induction but also appears to promote protective cellular responses. This highlights the complex interplay between cellular organelles during radiation exposure and emphasizes the importance of considering cytoplasmic contributions to cellular radioresistance.