Effect of double bond geometry in sphingosine base on the antioxidant function of sphingomyelin |
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| Authors: | Subbaiah Papasani V Sircar Debajit Lankalapalli Ravi S Bittman Robert |
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| Institution: | a Department of Medicine, Section of Endocrinology and Metabolism, University of Illinois at Chicago, 1819 West Polk Street, Chicago, IL 60612, USA
b Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY 11367, USA |
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| Abstract: | We previously showed that sphingomyelin (SM) inhibits peroxidation of phosphatidylcholine (PC) and cholesterol. Since SM uniquely has a trans unsaturation in its sphingosine base, we investigated whether this feature is important for its antioxidant function. Substitution of the natural trans Δ4-double bond with a cis double bond (cis-SM), however, increased SM’s ability to inhibit Cu2+-mediated 16:0-18:2 PC oxidation by up to eightfold. Dihydro-SM, which lacks the double bond, was equally effective as trans-SM. In contrast to its effect in the sphingosine base, the presence of a cis double bond in the N-acyl group of trans-SM was not protective. cis-SM also inhibited the oxidation of cholesterol by FeSO4/ascorbate more efficiently than the trans isomer. The enhanced protective effect of cis-SM is selective for metal ion-promoted oxidation, and appears to arise from a decrease in the effective concentration of metal ions. These studies show that the trans double bond of SM is not essential for its antioxidant effects. |
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| Keywords: | Double bond geometry Sphingomyelin Antioxidant Cholesterol oxidation Phosphatidylcholine oxidation Liposomes |
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