| Abstract: | Atherosclerosis is an inflammatory disease of the vessel wall characterized by monocyte infiltration in response to pro‐atherogenic factors such as oxidized lipids. Recently, the role of specific adhesion molecules in this process has been explored. The endothelium overlying atherosclerotic lesions expresses P‐selectin and the shoulder regions express vascular cell adhesion molecule‐1 (VCAM‐1) and intercellular adhesion molecule‐1 (ICAM‐1), which is also expressed on endothelium in regions not prone to plaque development. Serum levels of soluble P‐selectin, ICAM‐1 and VCAM‐1 are elevated in patients with angina pectoris or peripheral atherosclerotic disease. Reconstituted in vitro systems using monocytes on cytokine‐activated endothelial cells under shear flow suggested the involvement of P‐selectin, L‐selectin, VCAM‐1, its ligand, VLA‐4 integrin and CD18 integrins. Studies of monocyte adhesion in isolated perfused carotid arteries harvested from atherosclerotic (apoE?/?) mice show a predominant involvement of P‐selectin and its ligand P‐selectin glycoprotein‐1 (PSGL‐1) in rolling and of VLA‐4 and VCAM‐1 in firm adhesion. Consistent with these findings, apoE?/? mice that are also deficient for P‐selectin show significantly reduced atherosclerotic lesion sizes and are almost completely protected from neointimal growth after vascular injury. Milder effects are also seen in the low‐density lipoprotein (LDL) receptor deficient (LDLR?/?) mouse. In a high cholesterol/cholate model, a role of ICAM‐1 and CD18 integrins was also shown, but this awaits confirmation in more physiologic models. Transient blockade of the VLA‐4/VCAM‐1 adhesion pathway by antibodies or peptides in apoE?/? or LDLR?/? mice reduced monocyte and lipid accumulation in lesions. These data suggest that P‐selectin, PSGL‐1, VLA‐4 and VCAM‐1 are the most important adhesion molecules involved in monocyte recruitment to atherosclerotic lesions. |
