The Effects of the Structure and Composition of the Hydrophobic Parts of Phosphatidylcholine-Containing Systems on Phosphatidylcholine Oxidation by Ozone

Abstract

The degree of lipid unsaturation is a parameter used to describe membrane susceptibility to oxidation. This paper highlights the importance of double bond distribution in the hydrophobic parts of lipid layers. The problem was studied by determining the effects induced by ozone dissolved in an aqueous phase acting on layers of unsaturated cholines of various molecular structures, including bi-unsaturated (DOPC), mono-unsaturated (POPC) and natural origin (soy PC). The destructive effects of ozone were quantified as the ratio of areas per molecule, which corresponded to a 1 mN/m rise in the layer surface pressure for oxidized to non-oxidized lipids (A lift/A lift0). The experimental results showed different behaviours among the studied lipids. Layers of DOPC with both unsaturated fatty acyl chains exhibited the greatest disruption compared with that of PC extracted from soy, which maintained stability despite high degree of unsaturation. Mono-unsaturated ozonized layers of POPC did not exhibit any disruption, but their modified properties indicated structural changes caused by the appearance of oxidation products. The stability of mixed layers (of the same unsaturation degree as the soy PC) composed of DOPC and fully saturated lipid increased, however, not reaching the soy PC level. Comparisons of the behaviour of tested systems indicated that the fraction of lipids containing one saturated acyl chain is the parameter most important for stability of the oxidized layer. The stabilizing effects of the cholesterol admixture were also quantified. Results obtained for lipid layers were supported by measurements of liposome size, zeta potential and surface tension of liposome suspension.

Impact of polyphenol-rich green tea extracts on the protection of DOPC monolayer against damage caused by ozone induced lipid oxidation

“…2a. As wehave shown previously (Rudolphi-Skórska et al, 2014;Rudolphi-Skórska et al, 2016;Rudolphi-Skórska et al, 2017), the dependence of the ratio of the lift-off area values on the ozone concentration has a characteristic S-shape. The range of ozone concentrations corresponding to an abrupt decrease in this value can be identified as threshold oxidant concentration above which significant destruction of lipid layer occurs.…”

“…The lipid layers are a sensitive detector of the amount of ozone in the aqueous subphase (Rudolphi-Skórska et al, 2014;Rudolphi-Skórska et al, 2016;Rudolphi-Skórska et al, 2017). The obtained results (Fig.…”

“…Being the strongest oxidant (standard redox potential 2.07 V), it is able to oxidize many substances including unsaturated lipids forming cell membranes. However, there are relatively few papers focused on the oxidation of lipid monolayers by O 3 dissolved in an aqueous medium (Brown et al, 2011;Qiao et al, 2013;Rudolphi-Skórska et al, 2014;Rudolphi-Skórska et al, 2016;Rudolphi-Skórska et al, 2017).…”

“…The aim of this study, which is one in a series on the various physico-chemical aspects of lipid oxidation with ozone (Rudolphi-Skórska et al, 2014;Rudolphi-Skórska et al, 2016;Rudolphi-Skórska et al, 2017), was to quantify the protective effect of green tea (GT) extract and two antioxidants present in it, namely epigallo catechin gallate (EGCG) and gallic acid (GA), against ozone-induced oxidation of the DOPC monolayer. The DOPC chosen for experiments represent the cholines which are present in large quantity in both animal and plant cell membranes (Yeagle, 2016).…”

“…The DOPC chosen for experiments represent the cholines which are present in large quantity in both animal and plant cell membranes (Yeagle, 2016). Because oxidation of unsaturated lipids leads to the creation of water-soluble products, reduction in the amount of material capable of forming a layer was adopted as a measure of the lipid oxidation (Rudolphi-Skórska et al, 2014;Rudolphi-Skórska et al, 2016;Rudolphi-Skórska et al, 2017). A decrease in the ozone concentration in the subphase after polyphenol addition was also measured.…”