Biomedical Engineering Reference
In-Depth Information
Fig. 1
Structure of low-density lipoprotein. Low-density lipoprotein is described as a spherical
particle containing a hydrophobic core of cholesteryl esters and triglycerides, surrounded by
an amphipathic monolayer of phospholipid and free cholesterol in which a single molecule of
apolipoprotein B-100 is located.
THE MECHANISMS OF ENDOTHELIAL ADHESION
MOLECULE EXPRESSION INDUCED BY Ox-LDL
LDL Oxidation
Circulating LDL transverses the subendothelial space of large arteries or
extravasates into the dermis of the skin. It is theorized that the subendothelial space
or dermis might be the primary site of LDL oxidation because some antioxidants
provide potent protection against LDL oxidation in plasma. h e existence of
Ox-LDL in the circulation remains a controversial subject. Indeed, only a minor
fraction of circulating LDL exhibits a high content of oxidized lipids, and human
plasma demonstrates immunoreactivity of monoclonal antibodies against epitopes
of Ox-LDL. In contrast to plasma, atherosclerotic lesions and xanthoma lesions
contain substantial amounts of oxidized lipids. Despite this evidence, homogenates
of the atherosclerotic lesions also contain ascorbate, uric acid, and α-tocopherol in
quantities sui cient to ef ectively block LDL oxidation
in vitro
.
An important aspect of LDL oxidation is a lipid peroxidation chain reaction
initiated and driven by free radicals that are generated by the endothelial cells,
smooth muscle tissue, and migratory lymphocytes. In this process, the lipid
peroxidation products fragment into reactive aldehydes such as malondialdehyde
