Computerized video time-lapse microscopy studies of ionizing radiation-induced rapid-interphase and mitosis-related apoptosis in lymphoid cells

Computerized video time-lapse (CVTL) microscopy of X-irradiated cultures of cells of the murine lymphoma cell lines ST4 and L5178Y-S and the human lym phoid cell line MOLT-4 demonstrated that these cells exhibit a wide dispari ty in the timing of induction and execution of radiation-induced cell death that included rapid-interphase apoptosis, delayed apoptosis, and postmitot ic apoptosis. ST4 cells that received 2.5 or 4 Gy of X radiation underwent rapid-interphase apoptosis within 2 h, Apoptosis commenced with a 10-20-min burst of membrane blebbing followed by swelling for 2-4 h and cell collaps e. No apoptotic bodies were formed. After a dose of 1 Gy, approximately 90% of ST4 cells died by rapid-interphase apoptosis, while the remainder compl eted several rounds of cell division prior to cell death. Postmitotic death of ST4 cells occurred with the same morphological sequence of events as du ring rapid-interphase apoptosis induced by doses of 1-4 Gy, In contrast, L5 178Y-S and MOLT-4 cells that received 4 Gy underwent apoptosis more slowly, with a complex series of events occurring over 30-60 h. Only 3% of L5178Y- S cells and 24% of MOLT-4 cells underwent apoptosis without attempting cell division. The cells became abnormally large during a long G(2)-phase delay , and then most of the cells (76-97%) attempted to divide for the first or second time at similar to 18-30 h postirradiation, However, either mitosis failed or division was aberrant; i.e., the large cells divided into three o r four fragments which eventually fused together. This process was followed by several rounds of complex and unpredictable membrane blebbing, gross di stortions of shape, fragmentation-refusion events, and formation of apoptot ic bodies, after which the cells collapsed at 36-60 h postirradiation. (C) 2000 by Radiation Research Society.