Effect of ethanol amine plasmalogens on Fe-induced peroxidation of arachidonic acid in dipalmitoylphosphatidylcholine vesicles

We have investigated the influence of ethanolamine plasmalogens on iron-ind uced oxidation of arachidonic acid in dipalmitoylphosphatidylcholine (DPPC) vesicles. Lipoperoxidation was induced by the addition of 50 muM FeSO4 and studied above (50 degreesC) and below (15 degreesC) the gel-to liquid tran sition temperature of the vesicles, at two different pH values (7.4 or 6.4) . The extent of peroxidation was measured as thiobarbituric reactive produc t formed and the influence exerted by ethanolamine plasmalogens (PEPL) in t his process was compared to that of dipalmitoylphosphatidylethanolamine (DP PE) and diacylphosphatidylethanolamines (DAPE). The extent of peroxidation of arachidonic acid embedded in DPPC vesicles was similar at the two temper atures and greater at 50 degreesC under acidic conditions. However, the per oxidative process was significantly decreased at 50 degreesC in the presenc e of PEPL, but not of DPPE or DAPE and the inhibitory effect was enhanced a t pH 6.4. The possibility that a different phase distribution of the phosph olipids, namely a transition from a lamellar to a hexagonal phase, may play a role in the scavenger effect of ethanolamine plasmalogens is discussed.