Peroxidation of Lipoprotein and of Certain Liposomal Lipids Depend Similarly on the Physico-Chemical Properties of the Aggregated Lipids

Abstract

In view of the complexity of biological membranes, the dependence of peroxidation on the physicochemical properties of membranes and on different antioxidants have been studied in liposomes made of different compositions, under different conditions. low molecular weight antioxidants and the dependence of these effects on various factors have also been studied. In 007, we reviewed the literature regarding these issues. Recent information clarifies several aspects of the peroxidation in these model membranes, including the promotion of copper-induced peroxidation by inclusion of negatively charged phospholipids (PA and PS), inhibition of the peroxidation of PS-containing liposomes by nano-molar concentrations of Tocopherol and other 12 (out of 37 tested) phenols of possible semi-quinone structures and promotion of copper induced peroxidation by soluble “antioxidants. Several new studies support our previous interpretation that the dependence of peroxidation on the packing of the PUFA in the bilayer (and the microviscosity of the liposomal membranes) is due to the consequent change of the rate of lateral diffusion of the PUFA-bearing phospholipids. Recent study ruled out this interpretation on the basis of the similar effects of “fluidizing” and “rigidifying” non-oxidizable phospholipids. Nonetheless, the data is insufficient to rule out the previous interpretation because both the propagation and termination of the free radical chain reaction depend similarly on the micro-viscosity (and the rate of lateral diffusion), while the results of a change in the rate of these two reactions are opposite. New data also show how peroxidation affect continuous peroxidation and demonstrate that liposomes are affected by antioxidants similar to LDL only when they contain PS.