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Lysophosphatidylcholine potentiates the mitogenic activity of modified LDL for human monocyte-derived macrophages
M Sakai1, A Miyazaki, H Hakamata
1Department of Biochemistry, Kumamoto University School of Medicine, Kumamoto, Japan.
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.
Insights
Oxidized LDL (Ox-LDL) stimulates human macrophage growth. Lysophosphatidylcholine (lysoPC), a breakdown product of Ox-LDL, is crucial for this mitogenic activity, suggesting its key role in Ox-LDL-induced cell proliferation.
Area of Science:
- Cardiovascular Biology
- Cellular Biology
- Lipid Metabolism
Background:
- Oxidized low-density lipoprotein (Ox-LDL) is implicated in macrophage activation and proliferation.
- Lysophosphatidylcholine (lysoPC) is a key component derived from Ox-LDL, but its specific role in macrophage mitogenesis requires further elucidation.
Purpose of the Study:
- To investigate the role of Ox-LDL and its derivative, lysoPC, in stimulating the growth of human monocyte-derived macrophages.
- To determine if lysoPC is essential for the mitogenic activity of Ox-LDL on human macrophages.
Main Methods:
- Human monocyte-derived macrophages were treated with Ox-LDL, acetylated LDL (acetyl-LDL), and combinations of acetyl-LDL with lysoPC.
- Phospholipase A2 treatment was used to convert acetyl-LDL phospholipids to lysoPC.
- Macrophage cell growth was quantified to assess mitogenic activity.
Main Results:
- Ox-LDL significantly induced human macrophage cell growth, while acetyl-LDL alone did not.
- Treatment of acetyl-LDL with phospholipase A2 generated lysoPC and markedly increased its mitogenic activity.
- Coincubation of acetyl-LDL with lysoPC was required for significant cell growth stimulation, as neither substance alone was effective.
Conclusions:
- Ox-LDL stimulates the proliferation of human monocyte-derived macrophages.
- Lysophosphatidylcholine (lysoPC) plays an essential role in mediating the mitogenic effects of Ox-LDL on human macrophages.