scholarly journals Secondary radicals derived from chloramines of apolipoprotein B-100 contribute to HOCl-induced lipid peroxidation of low-density lipoproteins

1999 ◽  
Vol 339 (3) ◽  
pp. 489-495 ◽  
Author(s):  
Linda J. HAZELL ◽  
Michael J. DAVIES ◽  
Roland STOCKER
Keyword(s):  
Lipid Peroxidation ◽  
Protein Oxidation ◽  
Apolipoprotein B ◽  
Oxidized Ldl ◽  
Radical Reaction ◽  
Low Density Lipoproteins ◽  
Initial Reaction ◽  
Low Density ◽  
Dependent Manner ◽  
Antioxidative Therapy

Oxidation of low-density lipoproteins (LDL) is thought to contribute to atherogenesis. Although there is increasing evidence for a role of myeloperoxidase-derived oxidants such as hypochlorite (HOCl), the mechanism by which HOCl modifies LDL remains controversial. Some studies report the protein component to be the major site of attack, whereas others describe extensive lipid peroxidation. The present study addresses this controversy. The results obtained are consistent with the hypothesis that radical-induced oxidation of LDL's lipids by HOCl is a secondary reaction, with most HOCl consumed via rapid, non-radical reaction with apolipoprotein B-100. Subsequent incubation of HOCl-treated LDL gives rise to lipid peroxidation and antioxidant consumption in a time-dependent manner. Similarly, with myeloperoxidase/H2O2/Cl- (the source of HOCl in vivo), protein oxidation is rapid and followed by an extended period of lipid peroxidation during which further protein oxidation does not occur. The secondary lipid peroxidation process involves EPR-detectable radicals, is attenuated by a radical trap or treatment of HOCl-oxidized LDL with methionine, and occurs less rapidly when the lipoprotein was depleted of α-tocopherol. The initial reaction of low concentrations of HOCl (400-fold or 800-fold molar excess) with LDL therefore seems to occur primarily by two-electron reactions with side-chain sites on apolipoprotein B-100. Some of the initial reaction products, identified as lysine-residue-derived chloramines, subsequently undergo homolytic (one-electron) reactions to give radicals that initiate antioxidant consumption and lipid oxidation via tocopherol-mediated peroxidation. The identification of these chloramines, and the radicals derived from them, as initiating agents in LDL lipid peroxidation offers potential new targets for antioxidative therapy in atherogenesis.

Antrodia Camphorata in Submerged Culture Protects Low Density Lipoproteins Against Oxidative Modification

2006 ◽  
Vol 34 (02) ◽  
pp. 217-231 ◽  
Author(s):  
Hsin-Ling Yang ◽  
You-Cheng Hseu ◽  
Jing-Yi Chen ◽  
Yi-Jen Yech ◽  
Fung-Jou Lu ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Oxidant Stress ◽  
Antioxidant Properties ◽  
Low Density Lipoproteins ◽  
Oxidative Modification ◽  
Low Density ◽  
Dependent Manner ◽  
Antrodia Camphorata ◽  
Concentration Dependent Manner ◽  
Apo B

Antrodia camphorata is well known in Taiwan as a traditional Chinese medicine. In this study, we have investigated the antioxidant properties of a fermented culture broth of Antrodia camphorata (FCBA) and the aqueous extracts of mycelia from Antrodia camphorata (AEMA) on the oxidative modification of human low-density lipoproteins (LDL), as induced by either copper sulfate ( CuSO 4) or 2,2′-azo-bis(2-amidinopropane) hydrochloride (AAPH). Under such oxidant stress, FCBA and AEMA appear to possess antioxidant properties with respect to oxidation of LDL in a time-and concentration-dependent manner, as assessed by inhibition of thiobarbituric acid-reactive substances (TBARS) formation, conjugated diene production, and cholesterol degradation of oxidized LDL. In addition, both FCBA and AEMA exhibited a remarkable ability to rescue the relative electrophoretic mobility and fragmentation of the Apo B moiety of the oxidized LDL. Furthermore, FCBA and AEMA effectively protected the endothelial cells from the damaging effects of the CuSO 4-oxidized LDL. Our findings suggest that the antioxidant properties of Antrodia camphorata may also provide effective protection from atherosclerosis.

Identification of 4-hydroxy-2-nonenal–histidine adducts that serve as ligands for human lectin-like oxidized LDL receptor-1

2012 ◽  
Vol 442 (1) ◽  
pp. 171-180 ◽  
Author(s):  
Miyuki Kumano-Kuramochi ◽  
Yuuki Shimozu ◽  
Chika Wakita ◽  
Mayumi Ohnishi-Kameyama ◽  
Takahiro Shibata ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Chinese Hamster Ovary Cells ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Chinese Hamster ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Low Density ◽  
Dependent Manner ◽  
Oxidized Low Density Lipoprotein

LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) is an endothelial scavenger receptor that is important for the uptake of OxLDL (oxidized low-density lipoprotein) and contributes to the pathogenesis of atherosclerosis. However, the precise structural motifs of OxLDL that are recognized by LOX-1 are unknown. In the present study, we have identified products of lipid peroxidation of OxLDL that serve as ligands for LOX-1. We used CHO (Chinese-hamster ovary) cells that stably express LOX-1 to evaluate the ability of BSA modified by lipid peroxidation to compete with AcLDL (acetylated low-density lipoprotein). We found that HNE (4-hydroxy-2-nonenal)-modified proteins most potently inhibited the uptake of AcLDL. On the basis of the findings that HNE-modified BSA and oxidation of LDL resulted in the formation of HNE–histidine Michael adducts, we examined whether the HNE–histidine adducts could serve as ligands for LOX-1. The authentic HNE–histidine adduct inhibited the uptake of AcLDL in a dose-dependent manner. Furthermore, we found the interaction of LOX-1 with the HNE–histidine adduct to have a dissociation constant of 1.22×10−8 M using a surface plasmon resonance assay. Finally, we showed that the HNE–histidine adduct stimulated the formation of reactive oxygen species and activated extracellular-signal-regulated kinase 1/2 and NF-κB (nuclear factor κB) in HAECs (human aortic endothelial cells); these signals initiate endothelial dysfunction and lead to atherosclerosis. The present study provides intriguing insights into the molecular details of LOX-1 recognition of OxLDL.

Sign in / Sign up

Export Citation Format

Share Document