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Native low density lipoprotein (LDL) does not affect monocyte/macrophage motility. On the other hand, oxidatively modified LDL inhibits the motility of resident peritoneal macrophages yet acts as a chemotactic factor for circulating human monocytes. We now show that lysophosphatidylcholine (lyso-PtdCho), which is generated by a phospholipase A2 activity during LDL oxidation, is a potent chemotactic factor for monocytes. It is not chemotactic for neutrophils or for resident macrophages. Platelet-activating factor, after treatment with phospholipase A2, becomes chemotactic for monocytes, whereas the intact factor is not. Synthetic 1-palmitoyl-lyso-PtdCho showed chemotactic activity comparable to that of the lyso-PtdCho fraction derived from oxidized LDL. The results suggest that lyso-PtdCho in oxidized LDL may favor recruitment of monocytes into the arterial wall during the early stages of atherogenesis. Generation of lyso-PtdCho, either from LDL itself or from membrane phospholipids of damaged cells, could play a more general role in inflammatory processes throughout the body.
Quinn et al. (Fri,) studied this question.