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 (Alift/Alift0). 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.
Highlights
Lipid oxidation in the presence of oxidative stress may lead to severe diseases, such as cancer, atherosclerosis and Parkinson’s disease (Roberts et al 2009; Reis and Spickett 2012)
Surface pressure isotherms obtained for various ozone contents in the subphase are presented in Fig. 1a–d for studied cholines: DPPC (a), POPC (b), soy PC (c) and DOPC (d)
The degree of ozone-induced degradation of lipid layers is largely dependent on the composition and structure of the hydrophobic parts of lipids
Summary
Lipid oxidation in the presence of oxidative stress may lead to severe diseases, such as cancer, atherosclerosis and Parkinson’s disease (Roberts et al 2009; Reis and Spickett 2012). This reaction is very important for the function of pulmonary surfactant, whose ability to decrease the surface tension within alveoli is dependent on the lipid composition. Toxic effects of ozone should be considered along with the ability of oxidized lipids, including oxidized phospholipids and cholesterol (the most abundant neutral lipid present in pulmonary surfactant), to function as signal molecules. Ozone attacks the double bonds of unsaturated fatty acids and results in the formation of ozonides, which subsequently decompose into other products, such as aldehydes and hydroxyl-hydro-peroxides.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
