Sphingosine induces the aggregation of imine-containing peroxidized vesicles.

Lipid peroxidation plays a central role in the pathogenesis of many diseases like atherosclerosis and multiple sclerosis. We have analyzed the interaction of sphingosine with peroxidized bilayers in model membranes. Cu(2+) induced peroxidation was checked following UV absorbance at 245nm, and also using the novel Avanti snoopers®. Mass spectrometry confirms the oxidation of phospholipid unsaturated chains. Our results show that sphingosine causes aggregation of Cu(2+)-peroxidized vesicles. We observed that aggregation is facilitated by the presence of negatively-charged phospholipids in the membrane, and inhibited by anti-oxidants e.g. BHT. Interestingly, long-chain alkylamines (C18, C16) but not their short-chain analogues (C10, C6, C1) can substitute sphingosine as promoters of vesicle aggregation. Furthermore, sphinganine but not sphingosine-1-phosphate can mimic this effect. Formation of imines in the membrane upon peroxidation was detected by (1)H-NMR and it appeared to be necessary for the aggregation effect. (31)P-NMR spectroscopy reveals that sphingosine facilitates formation of non-lamellar phase in parallel with vesicle aggregation. The data might suggest a role for sphingosine in the pathogenesis of atherosclerosis.

Dietary flavonoid quercetin stimulates vasorelaxation in aortic vessels.

Considerable epidemiological evidence indicates that dietary consumption of moderate levels of polyphenols decreases both the incidence of cardiovascular disease and the mortality associated with myocardial infarction. Molecular mechanisms of this cardiovascular protection remain uncertain but can involve changes in rates of nitric oxide (NO) generation by endothelial nitric oxide synthase (eNOS). We examined the vascular responses to quercetin using a combination of biochemical and vessel function criteria. Quercetin treatment for 30min enhanced relaxation of rat aortic ring segments. Moreover, the addition of L-NAME (100muM) or charybdotoxin (ChTx) blocked quercetin-mediated vasorelaxation thus demonstrating the effect was partially dependent on NOS and endothelium-derived hyperpolarizing factor (EDHF). Additionally, bovine aortic endothelial cells (BAEC) treated with quercetin showed a rapid increase of intracellular Ca(2+) concentrations as well as a dose- and time-dependent stimulation of eNOS phosphorylation with a concomitant increase in NO production. These results demonstrate that quercetin-mediated stimulation of eNOS phosphorylation increases NO bioavailability in endothelial cells and can thus play a role in the vascular protective effects associated with improved endothelial cell function.