Modelling Of Molecular Mechanisms Of Membrane Domain Formation During The Oxidative Stress: Effect Of Palmitoyl-Oxovaleroyl-Phosphatidylcholine

The study is focused on the effect of the oxidized lipid 1-palmitoyl-2(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC) on the physicochemical properties of model membranes using two biophysical experimental methods: fluorescence video-microscopy and fluorescence spectroscopy. Two types of ternary mixtures made of sphingomyelin (SM), cholesterol (Chol) and respectively, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PDPC) were used as a model system mimicking the lipid composition of specialized cellular membrane domains, called rafts. The monounsaturated POPC and polyunsaturated (PDPC) permit revealing the effects of the degree of unsaturation at sn-2 position in the phosphatidylcholine (PC) species. Fluorescence microscopy showed a difference in the effect of POVPC on raft-like domain formation in POPC/SM/Chol and PDPC/SM/Chol mixtures. In the PDPC mixtures, the oxidized lipid increased the temperature of micron-scale L-o (liquid-ordered)/L-d (liquid-disordered) phase separation whereas in the POPC-containing ones, POVPC abolishes the phase separation. The results from fluorescence spectroscopy, giving information about the nano-scale L-o/L-d phase separation, demonstrate that POVPC promotes the raft-like domain formation in a stronger dose-dependent way in monounsaturated lipid matrix compared to the polyunsaturated one. Fluctuation spectroscopy revealed the strong softening of POPC bilayers upon addition of only 5 mol% of POVPC. We ascertained the fact that the oxidized lipid, POVPC, induced larger structural changes in the membrane organization of monounsaturated lipid matrix. Thus, the results describe a structurally protective role of docosahexaenoic acid against the presence of the oxidized lipid.