Oxidative damage to membranes by a combination of aluminum and iron in suspension-cultured tobacco cells

Aluminum (Al) and ferrous iron [Fe(II)] are separately non-toxic to cultured tobacco cells in nutrient solution. However, Al and Fe(II) together cause the peroxidation of membrane lipids, the accumulation of Al and Fe, and the loss of viability [Ono et al. (1995) Plant Cell Physiol. 36: 115]. We investigated the cause-and-effect relationships of these various responses. In cells exposed to Fe(II) or Fe(III)-EDTA, both the peroxidation of lipids and the loss of viability were similarly enhanced by AlCl₃ in a dose-dependent manner. During exposure to AlCl₃, the accumulation of Al and the loss of viability became apparent rapidly and simultaneously at 8 h, whereas both the peroxidation of lipids and the accumulation of Fe occurred at later times. However, lipophilic antioxidants protected cells efficiently not only from the peroxidation of lipids but also from the loss of viability and the accumulation of Al and Fe. These results suggest that the peroxidation of lipids in the plasma membrane that is caused by both Al and Fe leads to the accumulation of Al and Fe and the loss of viability.