Interactions of plasmalogens and their diacyl analogs with singlet oxygen in selected model systems

Abstract

Plasmalogens (Plg) are phospholipids containing vinyl ether linkage at the sn-1 position of the glycerophospholipid backbone. In spite of being quite abundant in humans, the biological role of plasmalogens remains speculative. It has been postulated that plasmalogens are physiological antioxidants with the vinyl ether functionality serving as sacrificial trap for free radicals and singlet oxygen. However, no quantitative data on the efficiency of plasmalogens to scavenge these reactive species are available. In this study, rate constants of quenching of singlet oxygen, generated by photosensitized energy transfer, by several plasmalogens and, for comparison, by their diacyl analogs, were determined by time-resolved detection of phosphorescence at 1270 nm. Relative rates of the interaction of singlet oxygen, with plasmalogens and other lipids in solution and liposomal membranes were measured by electron paramagnetic resonance oximetry and product analysis, employing HPLC-EC detection of cholesterol hydroperoxides and iodometric assay of lipid hydroperoxides. Results show that singlet oxygen interacts with plasmalogens significantly faster than with the other lipids, with he corresponding rate constants being by one-two orders of magnitude greater. The quenching of singlet oxygen by plasmalogens is mostly reactive in nature and results from its preferential interaction with the vinyl ether bond. The data suggest that plasmalogens could protect unsaturated membrane lipids against oxidation induced by singlet oxygen, providing that the oxidation products are not excessively cytotoxic.

Significant abnormalities of the HDL phosphosphingolipidome in type 1 diabetes despite normal HDL cholesterol concentration

“…Due to the presence of a vinyl ether bond, plasmalogens are preferentially oxidized over diacylglycerophospholipids and the oxidative products of plasmalogens are unable to further propagate lipid peroxidation [41]. The small decrease in plasmalogens we observed in type 1 diabetic patients compared to controls did not reach statistical significance and our study suggests that plasmalogens are not responsible for the impaired anti-oxidative activity of HDL observed in type 1 diabetic patients [7].…”

Plasmalogens the neglected regulatory and scavenging lipid species

“…In a further study, oxidation of the plasmalogen vinyl-ether bond markedly prevented the oxidation of PUFAs (Engelmann, 2004). Broniec et al (2011) evaluated the efficiency of this process and showed that plasmalogens were able to protect unsaturated membrane lipids against oxidation by singlet oxygen without producing excessively toxic oxidation products. These data challenge a previous report on harmful effects of degradation products in inflammatory processes (Mankidy et al, 2010).…”

Identification of Biomarkers of Necrosis in Xenografts Using Imaging Mass Spectrometry

“…Therefore, ether GP may be seen as reservoirs for these biologically active lipid mediators, released upon PLA 2 hydrolysis. However, the most frequent role associated to ether GP is as an antioxidant, as it is generally accepted that the hydrogen atoms adjacent to the vinyl ether bond are preferentially oxidized over diacyl GP when exposed to various free radicals and singlet oxygen [10].…”