Background & objective: How pro-caspase-3 activation lead to serial morphology changes during progress of cell apoptosis is unclear. This study was to investigate the variations and intra-localization of active Caspase-3, determine cell morphology changes in apoptotic MOLT-4 cells induced by X-ray, and evaluate their relationship.
Methods: MOLT-4 cells were irradiated by 10 Gy X-ray. Sub G(1)peak method, and DNA fragmentation assay were used to detect variations of DNA in apoptotic cells. Annexin V/PI method was used to determine the cell membrane reversion, and fluorescence labeled inhibitor of Caspases (FLICA) was used to detect the active Caspase-3 in apoptotic cells. Cell morphology and Caspase-3 intra-localization were determined by confocal microscopy.
Results: MOLT-4 cells irradiated by 10 Gy X-ray presented classical apoptotic morphology changes such as membrane reversion, and apoptotic body. Caspase-3 was activated after irradiation, and increased remarkably after irradiated for 4 hours. Activated Caspase-3 moved from sub-membrane toward cytoplasm and nucleus. Caspase-3 activity was detected 2 hours earlier than membrane reversion.
Conclusions: Caspase-3 was activated in MOLT-4 cells induced by X-ray, and its intra-localization correlated with the apoptotic morphology changes. The spatial shift of active Caspase-3 in MOLT-4 cells induced by X-ray is one of the mechanisms of apoptosis.