Plasma membrane of animal cells contains an electron transport chain driving electrons from NADH to the ascorbate free radical (AFR) that is reduced to ascorbate. This enzyme has been purified and characterized as a cytochrome b5 reductase, displaying a phospholipid-dependent NADH-CoQ reductase activity. This electron transport system maintains the antioxidant properties of both CoQ and ascorbate, and also α-tocopherol, to prevent lipid peroxidations induced by different oxidative stress mechanisms. Lipid peroxidation has been observed to induce programmed cell death. Oxidative-induced apoptosis are partially avoided when plasma membrane peroxidations are prevented by antioxidants as CoQ or ascorbate. This phenomena was observed in cells lacking Bcl-2 protein, an intracellular protein which function is to prevent apoptosis. Our results supports the idea that plasma membrane acting antioxidants protect cells to undergo apoptosis by a Bcl-2-independent pathway.
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