Effects of menadione and hydrogen peroxide on glutathione status in growing Escherichia coli

Menadione (MD) and H2O2 caused distinct effects on glutathione status in growing Escherichia coli. Treatment of E. coli AB1157 with 1-25 mM H2O2 did not result in an appreciable decrease in intracellular total glutathione (reduced glutathione GSH] + oxidized glutathione GSSG]). Only when cells were treated with 25 mM H2O2 an increase in GSSG and a decrease in the GSH:GSSG ratio were observed. In cells deficient in catalase HPI, such effect was observed even at 10 mM H2O2. The exposure of E. coli AB1157 to MD caused a dose-dependent decrease in intracellular total glutathione, an increase in GSSG, and a decrease in the ratio of GSH:GSSG. In E. coli deficient in cytosolic superoxide dismutase activity, a decrease in total glutathione after incubation with 0.2 mM MD was not accompanied by an increase in GSSGin, and the ratio of GSHin:GSSGin was three times higher than in the wild-type cells. The changes in the redox status of extracellular glutathione under the action of both oxidants were similar. Although the catalase activity increased several times after exposure to both oxidants, there were little or no changes in the activity of enzymes related to glutathione metabolism. A possible role of changes in redox status of glutathione under oxidative stress is discussed.