Adaptive response of Schizosaccharomyces pombe to hydrogen peroxide and menadione

The response of Schizosaccharomyces pombe to oxidative stresses has been examined. On challenging Schiz. pombe for 60 min at early exponential phase with either 40 mM H2O2 or 6 mM menadione (MD), a superoxide-generating agent, less than 10% of the cells survived. Pretreating Schiz. pombe cells with 0.2 mM H2O2 or 0.2 mM MD for 1 h significantly increased survival of these lethal doses of each oxidant, indicating the existence of an adaptive response to oxidative stress. Furthermore, cells pretreated with a low dose of MD became resistant to a lethal dose of H2O2. However, cells pretreated with H2O2 became only partially resistant to a lethal dose of MD. Adaptation was accompanied by the induction of several oxidative defence enzymes. The presence of 0.2 mM H2O2 induced catalase by 2.8-fold and peroxidase by 2.0-fold The presence of 0.2 mM MD induced catalase by 2.0-fold, glucose-6-phosphate dehydrogenase by 1.9-fold, glutathione reductase by 2.7-fold, peroxidase by 3.0-fold, and superoxide dismutase (SOD) by 2.1-fold. The higher induction of these defence enzymes by MD may explain why MD-pretreated cells were better adapted to lethal doses of oxidants than H2O2-pretreated ones. All these enzymes except SOD and peroxidase increased more than 5.0-fold as cells proceeded into stationary phase. The GSH/GSSG ratio also increased by 60%. These changes accord with the observation that stationary phase cells survive oxidant treatment better than cells in vegetative growth.