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F.Q. Schafer, H.P. Wang, E.E. Kelley, K.L. Cueno, S.M. Martin and G.R. Buettner
Comparing ?-Carotene, Vitamin E and Nitric Oxide as Membrane Antioxidants
Singlet oxygen initiates lipid peroxidation via a nonfree radical mechanism by reacting directly with unsaturated lipids to form lipid hydroperoxides (LOOHs). These LOOHs can initiate free radical chain reactions leading to membrane leakage and cell death. Here we compare the ability and mechanism by which three smallmolecule membrane antioxidants (?carotene, ?tocopherol and nitric oxide) inhibit lipid peroxidation in membranes. We demonstrate that ?carotene provides protection against singlet oxygenmediated lipid peroxidation, but does not slow free radicalmediated lipid peroxidation. ? Tocopherol does not protect cells from singlet oxygen, but does inhibit free radical formation in cell membranes. Nitric oxide provides no direct protection against singlet oxygen exposure, but is an exceptional chainbreaking antioxidant as evident from its ability to blunt oxygen consumption during free radical mediated lipid peroxidation. These three smallmolecule antioxidants appear to have complementary mechanisms for the protection of cell membranes from detrimental oxidations.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 383, 04/2002
Pages: 671 - 681