Host: The Japan Radiation Research Society, Chairman of the 52nd Annual Meeting, Toshiteru Okubo (Radiation Effects Research Foundation)
We examined relationship between delayed production of ROS and delayed mitochondrial dysfunction in normal human cells exposed to γ-rays. Mitochondria are fused their membrane together and configurated tubular morphology in inter-phase cells. But they become fragmented at mitotic-phase or in pro-apoptotic cells. Particularly, in the latter case, mitochondrial fragmentation accelerates mitochondrial membrane permeablization, indicating that mitochondrial morphology directly correlated with its function. Therefore, we investigated here the mitochondrial morphological change after γ-irradiation.
Immortalized normal human diploid cells (BJ-hTERT) were used in this study. The amount of reactive oxygen species (ROS) was determined using aminophenyl fluorescein (APF) reagent. Levels of superoxide localized within mitochondria were measured by MitoSox Red reagent. Mitochondria were visualized by staining with MitoTracher reagent, and structural change was examined under fluorescence microscope.
While most of the unirradiated cells showed tubular mitochondria, mitochondrial fragmentation was observed in about 50 % cells 3 days after 6 Gy of γ-rays. We also observed increase in intracellular ROS level 2 to 3 days after irradiation, which was accompanied by the increased level of mitochondrial superoxide.
These results indicate that mitochondrial dysfunction caused by mitochondrial fragmentation induces delayed oxidative stress after γ-irradiation.
