Overexpression of the transgene for manganese superoxide dismutase (MnSOD) in 32D cl 3 cells prevents apoptosis induction by TNF-α, IL-3 withdrawal, and ionizing radiation

Objective. Stabilization of the mitochondria in IL-3-dependent hematopoietic progenitor cell line 32D cl 3 by overexpression of the transgene for manganese superoxide dismutase (MnSOD) prior to ionizing radiation prevents apoptosis. We now demonstrate that overexpression of the MnSOD transgene also protects 32D cl 3 cells from apoptosis caused by exposure to tumor necrosis factor-α (TNF-α) or withdrawal of interleukin (IL)-3. Materials and Methods. The hematopoietic progenitor cell line, 32D cl 3, and subclones overexpressing the human MnSOD transgene, 1F2 or 2C6, were radiated to 1000 cGy or were exposed to TNF-α (0 to 100 ηg/mL) or were subjected to IL-3 withdrawal. The cells were then examined at several time points for DNA strand breaks using a comet assay, depolarization of the mitochondrial membrane, activation of caspase-3, PARP cleavage, and apoptosis, and also for changes in cell cycle distribution. Results. Overexpression of the transgene for MnSOD resulted in increased survival following exposure to radiation, exposure to TNF-α, or IL-3 withdrawal. The cell lines overexpressing MnSOD (1F2 or 2C6) displayed decreased radiation-induced, TNF-α-induced, orIL-3 withdrawal–induced mitochondrial membrane permeability, caspase-3 and PARP activation, and apoptosis. Conclusions. Overexpression of the human MnSOD transgene in 32D cl 3 cells results in stabilization of the mitochondria and reduction in radiation-, TNF-α-, or IL-3 withdrawal–induced damage. Thus, MnSOD stabilization of the mitochondrial membrane is relevant to reduction of apoptosis by several classes of oxidative stress inducers.