Lysophosphatidylcholine Potentiates the Mitogenic Activity of Modified LDL for Human Monocyte–Derived Macrophages

Abstract The growth of murine peritoneal macrophages is induced by oxidized LDL (Ox-LDL), and lysophosphatidylcholine (lysoPC) plays an important role in its mitogenic activity. In the present study, Ox-LDL–induced macrophage growth was examined with human monocyte–derived macrophages. The cell growth of human macrophages was significantly induced by Ox-LDL but not by acetylated LDL (acetyl-LDL). The treatment of acetyl-LDL with phospholipase A2, however, led to a marked increase in its mitogenic activity, with a concomitant conversion of 75% of its phospholipids to lysoPC. The growth-stimulating activity became positive only when both acetyl-LDL and lysoPC were coincubated, although neither of them exhibited cell growth–promoting activity. These results suggest that Ox-LDL could stimulate the growth of human monocyte–derived macrophages, and lysoPC may play an essential role in the mitogenic activity of Ox-LDL.