Regulation of cell growth by oxidized LDL

The first reports of the influences of oxidized LDL (oxLDL) on cell function pertained to negative effects on cell growth-growth arrest, injury, and toxicity. Since these studies, it has become apparent that sublethal levels of oxLDL cause some, but not all, cells to proliferate. This review highlights the growth-promoting effects of oxLDL rather than its inhibitory or injurious effects. Smooth muscle cells (SMCs) and monocyte-macrophages proliferate after exposure to oxLDL; endothelial cells do not. Scavenger receptors are involved in the proliferative effects on monocyte-macrophages, whereas the effects of oxLDL on SMCs appear to be receptor independent. Lysophosphatidylcholine (lysoPC), and structurally related lipids are among the growth-promoting constituents of oxLDL. OxLDL exerts at least a part of its effects by inducing expression or causing the release of growth factors. OxLDL (or lysoPC) can cause the release of basic fibroblast growth factor (bFGF) from SMCs; oxLDL (or lysoPC) can induce heparin binding EGF-like growth factor (HB-EGF) synthesis and release from macrophages. An imposing array of changes in cytokine and growth factor expression and/or release can be imposed by oxLDL on a wide variety of cell types. These effects and the studies probing the cell signaling events leading to them are described.