Lysophosphatidylcholine: essential role in the inhibition of endothelium-dependent vasorelaxation by oxidized low density lipoprotein.

Endothelial cells are known to play an important role in the regulation of vascular tone. Here we demonstrate that modified low density lipoprotein (LDL) with copper oxidation or phospholipase A2 treatment elicits a potent inhibitory action on endothelium-dependent relaxations evoked by acetylcholine, although native LDL does not affect endothelium-dependent relaxations. Phosphatidylcholine of native LDL is converted to lysophosphatidylcholine during these modifications. Furthermore, lysophosphatidylcholine fraction separated from oxidized LDL (0.5mg.protein/ml) by thin layer chromatography abolished endothelium-dependent relaxations, although the remaining lipid fraction had little effects on endothelium-dependent relaxations. These results indicate that lysophosphatidylcholine is the principal substance for the impairment of endothelium-dependent relaxations by oxidized LDL and phospholipase A2 treated LDL.