There is increasing evidence that endogenously generated aldehydes formed as a result of lipid peroxidation are involved in the pathophysiological effects associated with oxidative stress in cells and tissues. Malondialdehyde (MDA), a major product of lipid peroxidation, can modify amines present on the cell surface and thereby introduce negative charges that can affect the interfacial ionic layer. We show that lipid peroxidation of RBC generates MDA adducts that, similar to phosphatidylserine (PS), bind annexin V in a Ca2+-dependent manner. Like PS, these adducts also promote the "PS-dependent" prothrombinase assays, albeit to lower levels. These results indicate that annexin V binding cannot be used as an exclusive indicator of cell surface PS and raise the possibility that some phenomenon attributed to PS may, in fact, also involve aldehyde-lipid adducts.
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