MODULATION OF ANTIOXIDANT ENZYMES, REACTIVE OXYGEN SPECIES, AND GLUTATHIONE LEVELS IN MANGANESE SUPEROXIDE DISMUTASE-OVEREXPRESSING NIH 3T3FIBROBLASTS DURING THE CELL-CYCLE/

NIH/3T3 mouse embryo fibroblasts were transfected with the cDNA for ma nganese superoxide dismutase (MnSOD). Previous studies showed characte ristic unique AE profiles in nonsynchronous populations of parental, c ontrol plasmid-transfected, and MnSOD-overexpressing NIH/3T3 cell line s. However, the present study showed that during S and M phases of the cell cycle, antioxidant enzyme (AE) levels were altered in MnSOD-over expressing cell lines towards levels in S and M phases of parental and control plasmid-transfected cells. Because of the demonstration that MnSOD overexpression inhibits cell growth in both nonmalignant and mal ignant cells, the present study was designed to measure AEs, reactive oxygen species (ROS), and glutathione levels in various phases of the cell cycle in both parental NIH/3T3 cells and NIH/3T3 cells overexpres sing MnSOD, to try to determine whether AEs, ROS, and glutathione leve ls could have a possible regulatory role in cell cycle progression. In all cell lines studied, ROS levels were lower in M than S phase of th e cell cycle. Total glutathione and glutathione disulfide levels were greatly increased during the M phase of the cell cycle compared with q uiescence and S phase in all cell lines studied. This suggests that ox idative stress exists in M phase of the cell cycle with total glutathi one levels increased to decrease oxidative stress. Analysis of MnSOD-o verexpressing cell clones showed a correlation of decreased cell growt h with an increase in ROS in S phase of the cell cycle and a decrease in glutathione in mitosis. The data strongly suggest that specific lev els of cell redox state are necessary for cells to successfully progre ss through the various phases of the cell cycle. Cell. Physiol. 177:14 8-160, 1998. (C) 1998 Wiley-Liss, Inc.