Protective effect of glutathione on the cytotoxicity caused by a combination of aluminum and iron in suspension-cultured tobacco cells

The role of endogenous glutathione (GSH) in the protection of suspension-cultured tobacco cells from aluminum (Al) toxicity was examined. Cells at the logarithmic phase of growth were treated with or without A1 in nutrient medium prepared without P(i) and EDTA. In the absence of A1, total GSH content (including oxidized glutathione [GSSG]) increased gradually. In the presence of Al, the increase of GSH was repressed. This effect was observed before the loss of plasma membrane integrity and the loss of cell viability. In contrast, GSSG content in cells increased in the presence of A1. GSH-deprived cells were prepared by culturing cells with buthionine sulfoximine (an inhibitor of γ-glutamylcysteine synthetase) for 24 h. Total GSH content in GSH-deprived cells was 6% of that in normal cells. The GSH-deprived cells exhibited a higher degree of lipid peroxidation, increased accumulation of A1, and greater loss of viability than normal cells. These results suggest that GSH protects cells from the oxidative membrane damage caused by a combination of A1 and Fe(II) possibly by both direct consumption of GSH and oxidation of GSH.