Human Neutrophils Oxidize Low-Density Lipoprotein by a Hypochlorous Acid- Dependent Mechanism: The Role of Vitamin C

2002 ◽  
Vol 383 (3-4) ◽  
Author(s):  
A.C. Carr ◽  
B. Frei
Keyword(s):  
Vitamin C ◽  
Hypochlorous Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Human Neutrophils ◽  
Low Density ◽  
Dependent Mechanism

scholarly journals Vitamin C protects against and reverses specific hypochlorous acid- and chloramine-dependent modifications of low-density lipoprotein

2000 ◽  
Vol 346 (2) ◽  
pp. 491-499 ◽  
Author(s):  
Anitra C. CARR ◽  
Terry TIJERINA ◽  
Balz FREI
Keyword(s):  
Vitamin C ◽  
Electrophoretic Mobility ◽  
Apolipoprotein B ◽  
Hypochlorous Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cysteine Residues ◽  
Low Density ◽  
Relative Electrophoretic Mobility ◽  
Lysine Residues

Activated phagocytes produce the highly reactive oxidant hypochlorous acid (HOCl) via the myeloperoxidase-catalysed reaction of hydrogen peroxide with chloride ions. HOCl reacts readily with a number of susceptible targets on apolipoprotein B-100 of low-density lipoprotein (LDL), resulting in uncontrolled uptake of HOCl-modified LDL by macrophages. We have investigated the efects of vitamin C (ascorbate), an effective water-soluble antioxidant, on the HOCl- and chloramine-dependent modification of LDL. Co-incubation of vitamin C (25-200 μM) with LDL resulted in concentration-dependent protection against HOCl (25-200 μM)-mediated oxidation of tryptophan and lysine residues, formation of chloramines and increases in the relative electrophoretic mobility of LDL. Vitamin C also partially protected against oxidation of cysteine residues by HOCl, and fully protected against oxidation of these residues by the low-molecular-mass chloramines, Nα-acetyl-lysine chloramine and taurine chloramine, and to a lesser extent monochloramine (each at 25-200 μM). Further, we found that HOCl (25-200 μM)-dependent formation of chloramines on apolipoprotein B-100 was fully reversed by 200 μM vitamin C; however, the loss of lysine residues and increase in relative electrophoretic mobility of LDL were only partially reversed, and the loss of tryptophan and cysteine residues was not reversed. Time-course experiments showed that the reversal by vitamin C of HOCl-dependent modifications became less efficient as the LDL was incubated for up to 4 h at 37 °C. These data show that vitamin C not only protects against, but also reverses, specific HOCl- and chloramine-dependent modifications of LDL. As HOCl-mediated LDL modifications have been strongly implicated in the pathogenesis of atherosclerosis, our data indicate that vitamin C could contribute to the anti-atherogenic defence against HOCl.

Sign in / Sign up

Export Citation Format

Share Document