Establishment of a Hydrogen Peroxide Resistant Variant of Renal Tubular Epithelial Cells: Role of Calcium-Independent Phospholipase A2 in Cell Damage

Renal epithelial cells resistant to oxidant stress mediated by hydrogen peroxide have been isolated and characterized. African green monkey kidney epithelial cell line, BSC-1 cells, chronically exposed to 50 μM hydrogen peroxide for 15 passages exhibited increased catalase (1.5-fold) and glutathione peroxidase (2.4-fold) activity, as well as increased total cellular glutathione (1.6-fold). This was associated with the acquisition of resistance to hydrogen peroxide cytotoxicity, as judged by nuclear staining with ethidium homodimer and clonogenic survival assay. H2O2-adapted and wild-type BSC1 cells were used to examine the role of elevated cytosolic calcium concentration and the activation of phospholipase A2 in the development of lethal cell injury. Despite dramatic differences in resistance to oxidative stress, both cell types showed similar kinetics of cytosolic calcium increase in response to challenge with hydrogen peroxide. In contrast to this, oxidant-induced release of arachidonic acid correlated with the resistance of both types of BSC- 1 cells to oxidative stress. A mechanism-based inhibitor of calcium-independent phospholipase A2 (Hazen et al., J. Biol. Chem. 266, 7227, 1991) reduced oxidant-induced lethal cell injury, suggesting that this class of phospholipases contributes to damage of BSC-1 cells exposed to hydrogen peroxide. H2O2-adapted BSC1 cells may represent a valuable tool to study adaptation to oxidative stress and various mechanisms of cell injury.