Palmitic acid but not stearic acid inhibits NO-production in endothelial cells

 

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Summary

Several studies showed a diminished production of the endothelium-derived relaxing factor nitric oxide (NO) in the early stage of atherosclerosis. The inhibition of NO-production seems to be mediated by lipoproteins, especially oxidized low-density lipoproteins (ox-LDL). There is some evidence, that the interactions of lipoproteins and NO are associated with the phospholipid fraction of lipoproteins. Since fatty acids have different atherogenic properties – depending on chain length, degree of saturation and steric configuration –, we investigated the effect of fatty acids on endothelial NO-production.

Human umbilical vein endothelial cells were incubated with palmitic acid and stearic acid in different concentrations in culture medium enriched with serum albumin for five hours. After that, NO-production was stimulated by calcium-ionophore A23187. NO-production was determined by a bioassay method using RFL-6 cells followed by radioimmunological determination of cGMP.

NO-production stimulated by calcium-ionophore A23187( 100%) was decreased by palmitic acid (10, 50, 100 µM) to 79±12%; 63±10% and 53±14%.

In contrast, incubation with stearic acid (10, 50 and 100 µM) had no effect on A23187-stimulated NO-production (94±11%; 93±11%; 104±15%).

Thus, palmitic acid but not stearic acid dose-dependently inhibited NO-release by endothelial cells. These different actions parallel the differing atherogenic potential of the two fatty acids.