Antiinflammatory Actions of HDL

Atherosclerosis is an inflammatory disorder characterized by the accumulation of macrophages and T-lymphocytes in the arterial intima. The macrophages are derived from blood monocytes that adhere to, and transmigrate across, an activated or injured endothelial surface. The firm adhesion of monocytes to the endothelium requires expression of integrins such as CD11/CD18 on the monocyte surface and endothelial expression of the adhesion molecules vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin. Monocytes that are firmly tethered to the endothelium transmigrate into the subendothelial space in a process that is dependent on endothelial expression of chemokines such as monocyte chemotactic protein-1 (MCP-1).1See accompanying article on page 2071 After entering the artery wall, monocytes differentiate into macrophages in processes that are mediated by macrophage colony stimulating factor (CSF) and granulocyte-macrophage CSF.2 Macrophages express a range of scavenger receptors that bind and internalize modified LDL in an unregulated manner. This leads to a progressive accumulation of lipids in the macrophages and the formation of foam cells: the hallmark cells of atherosclerotic lesions.The results of numerous epidemiological studies have established that …