Deciphering Ultra-High Dose Rate Irradiation with Drosophila melanogaster

FLASH RT, which employs ultra-high dose rates (UHDR), has shown potential in reducing irradiation-induced damage to normal tissue while maintaining effective tumor targeting. For successful clinical translation, mechanistic explanation behind the so-called FLASH effect has yet to be deciphered and new in vivo model systems for mechanistic studies are therefore of high demand. We investigated the differential effects of UHDR (3000-7000 Gy/s) and conventional (CONV) (0.5 Gy/s) irradiation in D. melanogaster by irradiating adult female flies with 16 MeV and 9 MeV electron beams using an adapted clinical linear accelerator. Substantial lifespan prolongations were observed in single high-dose UHDR-irradiated groups compared to CONV irradiation groups with increasing doses (1000-1500 Gy). Split-dose UHDR irradiation further increased the lifespan compared to single high-dose UHDR irradiation. In addition, climbing deficits were induced by 300 Gy of CONV irradiation, but not by single high-dose UHDR irradiation. Additionally, we identified increased levels of lipid peroxidation in D. melanogaster brains indicating ferroptosis following CONV irradiation, which was not observed after single high-dose UHDR irradiation. Using relevant biological endpoints, we here demonstrate D. melanogaster with its advantageous characteristics to be a highly practical preclinical model organism to mechanistically investigate differential responses to UHDR and CONV irradiation.