Distinct HDL subclasses present similar intrinsic susceptibility to oxidation by HOCl

Area of Science:

• Biochemistry
• Cardiovascular Research
• Oxidative Stress

Background:

• Myeloperoxidase (MPO) is a heme protein that catalyzes lipoprotein oxidation.
• Activated phagocytes generate hypochlorous acid (HOCl) via the MPO-H(2)O(2)-chloride system.
• HOCl is a potent oxidant that modifies antiatherogenic high-density lipoprotein (HDL).

Purpose of the Study:

• To investigate the structural heterogeneity and oxidative susceptibility of HDL particle subfractions when modified by HOCl.
• To determine if intrinsic differences between HDL subclasses affect their susceptibility to HOCl-induced oxidative damage.

Main Methods:

• Exposure of five distinct HDL subfractions to HOCl.
• Analysis of HOCl-induced modifications including tryptophan consumption, amino group changes, apolipoprotein AI cross-linking, epitope formation, electrophoretic mobility shifts, and alterations in unsaturated fatty acid content.

Main Results:

• All five HDL subfractions were modified by HOCl, exhibiting changes in protein structure and lipid composition.
• HDL3 (small, dense) showed less susceptibility than HDL2 (large, light) on a mass basis but not on a particle number basis at tested ratios.
• HOCl-modified epitopes were detected across all examined HDL subclasses.

Conclusions:

• Structural and physicochemical differences among HDL subclasses do not inherently alter their susceptibility to oxidative attack by HOCl.
• HDL particle heterogeneity does not confer differential protection against HOCl-mediated oxidation.