scholarly journals The role of high-density lipoprotein and lipid-soluble antioxidant vitamins in inhibiting low-density lipoprotein oxidation

1993 ◽  
Vol 294 (3) ◽  
pp. 829-834 ◽  
Author(s):  
M I Mackness ◽  
C Abbott ◽  
S Arrol ◽  
P N Durrington
Keyword(s):  
High Density Lipoprotein ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipid Peroxide ◽  
Lipid Peroxides ◽  
Antioxidant Vitamins ◽  
Ldl Oxidation ◽  
Low Density ◽  
Conjugated Diene ◽  
Peroxide Formation

1. The oxidation of low-density lipoprotein (LDL) is believed to play a central role in atherogenesis. We have compared the effect of antioxidant vitamins and high-density lipoprotein (HDL) on the Cu(2+)-catalysed oxidation of LDL. 2. Antioxidant vitamin supplementation significantly reduced conjugated diene formation but did not affect the formation of lipid peroxides. 3. Conversely, HDL did not affect conjugated diene formation but inhibited the formation of lipid peroxides by up to 90%. 4. The inhibition by HDL of lipid peroxide formation in oxidized LDL was dependent on the concentration of HDL and was not due to HDL chelating Cu2+. 5. Large interindividual variations in the inhibition of lipid peroxide formation by autologous HDL were evident, which were related to the rate of lipid peroxide generation in the LDL. 6. We conclude that HDL is a powerful antioxidant or more probably inhibitor of LDL oxidation in vitro and may play an important role in vivo in preventing atherosclerosis by inhibiting LDL oxidation in the artery wall.

Increased levels of high-density lipoprotein cholesterol are ineffective in inhibiting the development of immune responses to oxidized low-density lipoprotein and atherosclerosis in transgenic rabbits expressing human apolipoprotein (apo) A-I with severe hypercholesterolaemia

2001 ◽  
Vol 100 (3) ◽  
pp. 343-355 ◽  
Author(s):  
Agnès BOULLIER ◽  
Nathalie HENNUYER ◽  
Anne TAILLEUX ◽  
Christophe FURMAN ◽  
Nicolas DUVERGER ◽  
...  
Keyword(s):  
High Density Lipoprotein ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Ldl Oxidation ◽  
Low Density ◽  
Human Apolipoprotein ◽  
Cholesterol Levels ◽  
Immunological Markers ◽  
Transgenic Rabbits

High levels of high-density lipoprotein (HDL) cholesterol have been reported to protect against the development of atherosclerosis in humans by increasing reverse cholesterol transport and inhibiting the oxidation of low-density lipoprotein (LDL) due to the paraoxonase content of HDL. The purpose of the present study was to assess if there are any relationships between in vivo increases in serum levels of immunological LDL oxidation markers [autoantibodies against oxidized LDL, autoantibodies against malondialdehyde-modified LDL, LDL immune complexes and anti-cardiolipin autoantibodies], paraoxonase activity and the development of atherosclerosis in control rabbits and in transgenic rabbits expressing human apolipoprotein (apo) A-I. A total of 13 apo A-I transgenic rabbits and 18 non-transgenic littermates were fed on a cholesterol-rich diet (0.4%, w/w) for 14 weeks, and were monitored at weeks 0, 2, 6, 10 and 14. Aortic atherosclerotic lesions were measured at the end of this period. Human apo A-I transgenic rabbits with high HDL cholesterol levels were not protected against the development of atherosclerosis when they were fed on a cholesterol-rich diet which induced dramatic hypercholesterolaemia. Immunological markers of LDL oxidation increased and serum paraoxonase activity decreased similarly in control and transgenic rabbits. In conclusion, the present study demonstrates that high HDL cholesterol levels are ineffective in inhibiting increases in immunological markers of LDL oxidation and the development of atherosclerosis in a mammal with severe hypercholesterolaemia.

scholarly journals The effects of ascorbate and dehydroascorbate on the oxidation of low-density lipoprotein

1996 ◽  
Vol 320 (2) ◽  
pp. 373-381 ◽  
Author(s):  
Suzanne E. STAIT ◽  
David S. LEAKE
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Conjugated Dienes ◽  
Ldl Oxidation ◽  
Lag Phase ◽  
Prolonged Storage ◽  
Low Density ◽  
Dependent Manner ◽  
Conjugated Diene

Ascorbate at concentrations of 60–100 µM inhibits the modification of freshly prepared low-density lipoprotein (LDL) by macrophages. With ‘moderately oxidized’ LDL (produced by prolonged storage in a refrigerator), however, ascorbate does not inhibit LDL modification by macrophages and actually modifies the LDL itself in the absence of macrophages [Stait and Leake (1994) FEBS Lett. 341, 263–267]. We have now shown that dehydroascorbate can modify both ‘fresh’ LDL and moderately oxidized LDL in a dose-dependent manner to increase its uptake by macrophages. The modification of moderately oxidized LDL by ascorbate and dehydroascorbate or of ‘fresh’ LDL by dehydroascorbate is dependent on the presence of iron or copper. In ‘fresh’ LDL, ascorbate inhibited conjugated-diene formation by copper. In moderately oxidized LDL, the number of conjugated dienes present was decreased rapidly in the presence of copper and ascorbate. Dehydroascorbate decreased the lag phase and increased the rate of copper-induced conjugated-diene formation in ‘fresh’ LDL (although in some experiments it inhibited the formation of conjugated dienes). The ascorbate-modified moderately oxidized LDL was taken up by macrophages by their scavenger receptors, as the uptake was inhibited by polyinosinic acid or fucoidan. Ascorbate and dehydroascorbate therefore have the potential to increase LDL oxidation under certain conditions, but whether or not they do so in vivo is unknown.

Heme and lipid peroxides in hemoglobin-modified low-density lipoprotein mediate cell survival and adaptation to oxidative stress

Blood ◽  
2003 ◽  
Vol 102 (5) ◽  
pp. 1732-1739 ◽  
Author(s):  
Liana Asatryan ◽  
Ouliana Ziouzenkova ◽  
Roger Duncan ◽  
Alex Sevanian
Keyword(s):  
Oxidative Stress ◽  
Cell Survival ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipid Peroxides ◽  
Ldl Oxidation ◽  
Lipid Hydroperoxides ◽  
Low Density ◽  
Atherosclerotic Lesions ◽  
Ldl Particles

AbstractLow-density lipoprotein (LDL) oxidation mediated by a variety of catalysts in atherosclerotic lesions plays a crucial role in the genesis and evolution of atherosclerotic plaques. In this study we focused on oxidative properties of hemoglobin (Hb)–modified LDL because Hb is present in atherosclerotic lesions. Under low oxygen tensions Hb was previously found to modify apolipoprotein B100 with covalent binding of Hb fragments and formation of electronegative LDL particles (LDL–). Here we show that HbLDL is highly susceptible to oxidation, but is not cytotoxic to vascular cells, as was found for LDL– isolated from human plasma. HbLDL and LDL– have similar levels of oxidized lipid products and low uptake rates; however, the virtual absence of HbLDL-induced toxicity depends on a marked adaptive oxidative stress response. This was evidenced by a time- and dose-dependent induction of heme oxygenase (HO-1). Cell survival was significantly decreased in the presence of HO-1 inhibitor, tin protoporphyrin (SnPPIX). HO-1 induction by HbLDL increased resistance of cells to toxic doses of hemin or t-BuOOH. The high sensitivity to oxidation and HO-1 induction was largely dependent on lipid hydroperoxides and heme associated with HbLDL. Reduction of pre-existing lipid peroxides using ebselen delayed HbLDL kinetics and inhibited HO-1 induction. Moreover, heme inactivation or its degradation inhibited HO-1 induction and provided an additive inhibitory effect to ebselen. We conclude that Hb-catalyzed reactions may modulate vascular cell survival and oxidative stress adaptation due to the presence of peroxides and heme, thus providing a possible mechanism for the evolution of atherosclerotic and hemorrhagic lesions.

scholarly journals When and why a water-soluble antioxidant becomes pro-oxidant during copper-induced low-density lipoprotein oxidation: a study using uric acid

1999 ◽  
Vol 340 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Marco BAGNATI ◽  
Cristina PERUGINI ◽  
Cristiana CAU ◽  
Roberta BORDONE ◽  
Emanuele ALBANO ◽  
...  
Keyword(s):  
Uric Acid ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipid Peroxides ◽  
Water Soluble ◽  
Ldl Oxidation ◽  
Lag Phase ◽  
Lipid Hydroperoxides ◽  
Low Density ◽  
Oxidant Effect

The inclusion of uric acid in the incubation medium during copper-induced low-density lipoprotein (LDL) oxidation exerted either an antioxidant or pro-oxidant effect. The pro-oxidant effect, as mirrored by an enhanced formation of conjugated dienes, lipid peroxides, thiobarbituric acid-reactive substances and increase in negative charge, occurred when uric acid was added late during the inhibitory or lag phase and during the subsequent extensive propagation phase of copper-stimulated LDL oxidation. The pro-oxidant effect of uric acid was specific for copper-induced LDL oxidation and required the presence of copper as either Cu(I) or Cu(II). In addition, it became much more evident when the copper to LDL molar ratio was below a threshold value of approx. 50. In native LDL, the shift between the antioxidant and the pro-oxidant activities was related to the availability of lipid hydroperoxides formed during the early phases of copper-promoted LDL oxidation. The artificial enrichment of isolated LDL with α-tocopherol delayed the onset of the pro-oxidant activity of uric acid and also decreased the rate of stimulated lipid peroxidation. However, previous depletion of α-tocopherol was not a prerequisite for unmasking the pro-oxidant activity of uric acid, since this became apparent even when α-tocopherol was still present in significant amounts (more than 50% of the original values) in LDL. These results suggest, irrespective of the levels of endogenous α-tocopherol, that uric acid may enhance LDL oxidation by reducing Cu(II) to Cu(I), thus making more Cu(I) available for subsequent radical decomposition of lipid peroxides and propagation reactions.

Studies on the Thromboplastic Effect of Human Plasma Lipoproteins

1976 ◽  
Vol 35 (01) ◽  
pp. 178-185 ◽  
Author(s):  
Helena Sandberg ◽  
Lars-Olov Andersson
Keyword(s):  
High Density Lipoprotein ◽  
Human Plasma ◽  
Platelet Rich Plasma ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Plasma Lipoproteins ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Free Plasma ◽  
Good Agreement

SummaryHuman plasma lipoprotein fractions were prepared by flotation in the ultracentrifuge. Addition of these fractions to platelet-rich, platelet-poor and platelet-free plasma affected the partial thromboplastin and Stypven clotting times to various degrees. Addition of high density lipoprotein (HDL) to platelet-poor and platelet-free plasma shortened both the partial thromboplastin and the Stypven time, whereas addition of low density lipoprotein and very low density lipoprotein (LDL + VLDL) fractions only shortened the Stypven time. The additions had little or no effect in platelet-rich plasma.Experiments involving the addition of anti-HDL antibodies to plasmas with different platelet contents and measuring of clotting times produced results that were in good agreement with those noted when lipoprotein was added. The relation between structure and the clot-promoting activity of various phospholipid components is discussed.

Sign in / Sign up

Export Citation Format

Share Document