Localization of oxidized HDL in atheromatous plaques and oxidized HDL binding sites on human aortic endothelial cells

Area of Science:

• Cardiovascular Biology
• Atherosclerosis Research
• Cell Biology

Background:

• Atherosclerosis is a complex disease involving lipid accumulation and inflammation in arterial walls.
• The role of oxidized high-density lipoprotein (HDL) in atherogenesis is not fully understood.
• Endothelial cells play a critical role in the initiation and progression of atherosclerosis.

Purpose of the Study:

• To investigate the presence and localization of oxidized HDL within human atheromatous plaques.
• To identify and characterize binding sites for oxidized HDL on human aortic endothelial cells (HAEC).

Main Methods:

• Histochemical analysis using a specific antibody (9F5-3a) to detect oxidized HDL in human aortic plaque intima.
• Radioligand binding assays using iodinated oxidized HDL (125I-oxidized HDL) to study binding kinetics on cultured HAEC.
• Competitive binding studies to assess the specificity of oxidized HDL binding to HAEC.
• Western blotting with oxidized HDL as a ligand to identify potential binding proteins on HAEC.

Main Results:

• Oxidized HDL was detected in the intima of human abdominal atheromatous plaques.
• HAEC exhibited saturable binding of oxidized HDL with a dissociation constant (Kd) of 1.43 micromol/L.
• Binding was most strongly competed by oxidized HDL, moderately by native HDL, and weakly by acetylated or oxidized LDL.
• A prominent 130-kDa protein band was identified in HAEC that bound oxidized HDL.

Conclusions:

• Oxidized HDL is present in atheromatous plaques.
• Endothelial cells possess specific binding sites for oxidized HDL, likely mediated by a 130-kDa protein.
• These findings suggest a potential mechanism for oxidized HDL involvement in the pathogenesis of atherosclerosis.