Mechanism of in vitro heme-induced LDL oxidation: effects of antioxidants

• Published in: European journal of clinical investigation Vol. 34; no. 9; pp. 619 - 625
• Main Authors: Klouche, K., Morena, M., Canaud, B., Descomps, B., Beraud, J. J., Cristol, J. P.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.09.2004; Blackwell; Blackwell Publishing Ltd
• Subjects: Antioxidant; Antioxidants - pharmacology; atherosclerosis; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Deferoxamine - pharmacology; Dose-Response Relationship, Drug; General aspects; heme; Heme - metabolism; Heme - pharmacology; Humans; Hydrogen Peroxide - metabolism; Iron Chelating Agents - pharmacology; LDL oxidation; Lipid Peroxidation - drug effects; Lipoproteins, LDL - drug effects; Medical sciences; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Oxidation-Reduction - drug effects; Protoporphyrins - metabolism; Renal failure; rhabdomyolysis-induced acute renal failure; Vitamins - pharmacology; Kidney disease; Urinary system disease; LDL oxidation; Cardiovascular disease; rhabdomyolysis-induced acute renal failure; Rhabdomyolysis; Antioxidant; In vitro; Mechanism; Vascular disease; Lipoprotein LDL; Medicine; Striated muscle disease; Atherosclerosis; Heme; Renal failure; Oxidation
• ISSN: 0014-2972; 1365-2362
• DOI: 10.1111/j.1365-2362.2004.01395.x

Background  Heme protein toxicity, owing to generation of reactive oxygen species most likely by direct interaction between heme iron and hydrogen peroxide (H2O2), may be involved in various pathologies, including atherogenesis and pigmentary acute renal failure. The aim of this study was to investigate the mechanism of heme cytotoxicity and the effects of antioxidant therapies in an in vitro model of heme‐induced low‐density lipoprotein (LDL) oxidation. Materials and methods  Human LDLs were exposed to heme, iron (Fe), protoporphyrin (PPIX) and PPIX‐Zinc (Zn) with or without H2O2. Lipid peroxidation was monitored by measurement of conjugated diene formation (at the 234‐nm absorbance). The effect of various antioxidants, such as vitamin E and vitamin C, reduced glutathione (GSH), and oxidized glutathione (GSSG), mannitol and desferoxamine (DFO) was further investigated in the established in vitro model of LDL oxidation. Results  Incubation of LDLs in the presence of heme/H2O2 induced lipid peroxidation with the optimal oxidation rate being at 5 µm heme/100 µm H2O2 doses. By contrast, incubation of LDL with H2O2, Fe, Fe/H2O2, PPIX, PPIX/H2O2, heme or PPIX‐Zn did not initiate any LDL oxidation. In vitro, the vitamin E load protected native LDLs against heme/H2O2 oxidative modifications. Incubation of LDLs with increasing doses of vitamin C, GSH and DFO conferred a dose‐dependent protection, while mannitol and GSSG had no effect. Conclusions  Initiation and propagation of heme‐induced lipid peroxidation is not mediated by a Fenton reaction but depends on specific interactions between heme and H2O2. It may result from the generation of ferryl and perferryl radicals derived from hemic Fe and H2O2 interactions. A protective effect of vitamins E, C, GSH and DFO was demonstrated in this model.