高密度脂蛋白氧化修饰与动脉硬化

大量流行病学研究证实 ,血清高密度脂蛋白(highdensitylipoprotein ,HDL)水平与动脉粥样硬化(atherosclerosis ,AS)性心脑血管疾病的发病率呈负相关 ,HDL水平降低是不亚于低密度脂蛋白 (lowdensitylipoprotein ,LDL) ,甚至比LDL更显著的AS血管疾病的危险因素[1] 。动脉壁处LDL氧化是AS始动及发展的关键这一观点已得到充分肯定。近年来发现 ,在某些外在或内在的诱因下 ,作为AS保护因子的HDL也发生与LDL相似的氧化修饰 ,HDL氧化后 ,不仅理化性质发生明显变化 ,生物学功能也发生显著改变。本文就HDL氧化易感性、体内可能的氧化部…     

内源性高甘油三酯血症患者血浆VLDL、LDL及HDL对血凝的影响

目的：研究内源性高甘油三酯血症(HTG)患血浆极低密度脂蛋白(VLDL)、低密度脂蛋白(LDL)及高密度脂蛋白(HDL)是否发生了氧化修饰及其对血凝的影响。方法：对2l例内源性高甘油三酯血症患与2l例年龄性别相近的正常人的血脂、脂质过氧化物进行了分析。用一次性密度梯度超速离心法分离血浆VLDL、LDL及HDL，测定这三种脂蛋白的234nm光吸收、相对电泳迁移率(REM)和硫代巴比妥酸反应物质(TBARS)，分别将这三种脂蛋白加入由正常人新鲜混合血浆构成的反应系统中，按试剂盒分别测定凝血酶原时间(PT)及活化部分凝血酶原时间(APIT)。结果：内源性HTG患血浆TG含量平均升高2．73倍，HDLC下降l.7l倍，同时LPO升高1．22倍;HTG组VLDL、LDL及HDL的REM、234nm光吸收值、TBARS含量均较对照组显增加(P＜0．01)，表明内源性HTG患血浆VLDL、LDL及LDL均发生了氧化修饰生成Ox—VLDL、Ox-LDL.PT及APTT在分别加入HTG组的VLDL、LDL及HDL后均比加入相应正常组脂蛋白明显缩短(P均＜0．05)。相关分析表明，HTG组血浆VLDL及HDL相对电泳迁移率(REM)与PT呈负相关(P＜0．01)。结论：HTG患血浆VLDL、LDL及HDL发生了氧化修饰，并使PT及APTT明显缩短。     

Modified low-density lipoproteins and high-density lipoproteins. From investigation tools to real in vivo players

It has long been known that the oxidative state of the various plasma lipoproteins modulates platelet aggregability, thereby contributing to atherogenesis. Low-density lipoprotein (LDL), occurring in vivo both in the native and oxidised forms, interacts directly with platelets, by binding to specific receptors. While the identity of the receptors for native LDL and some subfractions of high-density lipoproteins (HDL) remains disputed, apoE-containing HDL(2) binds to LRP8. The nature of these interactions as well as the distinction between candidate receptor proteins was elucidated using covalently modified apolipoproteins, which pointed to the participation of apolipoproteins in high affinity binding. However, the platelet effects initiated by binding of native lipoproteins remain controversial. Some of this ambiguity can be traced to the fact that native LDL inevitably undergoes substantial oxidisation upon modification, including by radiolabelling. The platelet-activating effects provoked by oxidised LDL are irrefutable, but many details remain unknown. The role of CD36 in platelet binding by oxidised LDL is well established, although additional receptors may exist. Much less is known about the interaction of oxidised HDL with platelets, since platelet activation was observed in some, but not all studies. Various frequently applied in vitro oxidation methods produce modified lipoprotein species that may not be relevant in vivo. Based on the reported modifications obtained by in vitro oxidation of LDL, early investigations focused mainly on the formation and the eventual effects of oxidised lipids. More recently, alterations to lipoproteins performed using hypochloric acid and myeloperoxidase redirected the attention to the role of modified apoproteins in triggering platelet responses.     

Lipoprotein-associated proteins involved in platelet signaling

Platelets and lipoproteins are both key elements in the development of atherosclerosis and thrombosis. Based on their density, five classes of lipoproteins have been identified which all influence platelets via distinct mechanisms. The activation of platelets starts with binding of apolipoproteins to different platelet receptors and is followed by the activation of signaling pathways resulting in activation or inhibition of platelet functions like aggregation or secretion. In addition to apolipoproteins, lipoproteins are also associated to a large amount of proteins, enzymes and lipids that also can induce platelet activation or inhibition. This review provides a summary of the activation of signaling pathways after platelet-lipoprotein interactions initiated by lipoprotein-associated proteins and lipids.     

Platelet interaction with bioactive lipids formed by mild oxidation of low-density lipoprotein

Oxidation of low-density lipoprotein (LDL) generates pro-inflammatory and pro-thrombotic mediators that play a crucial role in cardiovascular and inflammatory diseases. Mildly oxidized LDL (mox-LDL) and minimally modified LDL (mm-LDL) which escape the uptake of macrophage scavenger receptors accumulate in the atherosclerotic intima. Oxidatively modified LDL is also present within the electronegative LDL fraction in blood, which is elevated in patients at high risk for cardiovascular diseases. Mox-LDL and mm-LDL, but not native LDL are able to induce platelet shape change and aggregation. LDL oxidation generates lipids with platelet stimulatory properties such as lysophosphatidylcholine, certain oxidized phosphatidylcholine molecules, F(2)-isoprostanes and lysophosphatidic acid (LPA). Mox-LDL and mm-LDL are like a Trojan horse carrying these biologically active lipids and attacking cells through activation of physiological receptors and signaling mechanisms. LPA has been identified as the lipid responsible for platelet stimulation by mox-LDL, mm-LDL and also mox-HDL. These lipoproteins activate platelets by stimulating G-protein coupled LPA receptors and a Rho/Rho kinase signaling pathway leading to platelet shape change and subsequent aggregation. LPA-mediated platelet activation might contribute to arterial thrombus formation after rupture of atherosclerotic plaques and to the increased blood thrombogenicity of patients with cardiovascular diseases.     

Reduced plasma concentrations of total, low density lipoprotein and high density lipoprotein cholesterol in patients with Gaucher type I disease

Plasma lipid and serum apoprotein concentrations were determined in twenty-nine individuals with Gaucher type I disease. Plasma total cholesterol, low density lipoprotein (LDL) cholesterol and high density lipoprotein (HDL) cholesterol were all significantly reduced in the patients with Gaucher disease compared to a group of matched control subjects. Total, LDL and HDL cholesterol were lower in males than in females with Gaucher disease. These sex differences appeared to be inversely correlated with the severity of disease manifestations which were greater in the males. Serum levels of apoprotein-B and apoprotein-AI, the major structural apoproteins of LDL and HDL, respectively, were decreased in the subjects with Gaucher disease. Thus, the reductions in LDL and HDL cholesterol were associated with reduced numbers of lipoprotein particles in plasma. In contrast, apoprotein-E, a protein which is secreted by several tissues, including activated macrophages and which may mediate hepatic catabolism of lipoproteins, was elevated in the patients. Since macrophages may also catabolize lipoproteins, Gaucher disease may serve as a model for the effect of activated macrophages upon human lipoprotein metabolism.
This work was supported by the following grants: USPHS HL 23077, HD 07105, HL 25752, CA 31656 and RR-71 from the National Institutes of Health; 1–273 and 1–578 from the March of Dimes Birth Defects Foundation; grant from the New York Heart Assocation. Dr. Ginsberg is a recipient of a Research Career Development Award HL 00949 and is an Irma T. Hirschl Career Scientist. Dr. Grabowski is a recipient of a Clinical Investigator Award HD 00386.     

Salutary effects of hemodialysis on low-density lipoprotein proinflammatory and high-density lipoprotein anti-inflammatory properties in patient with end-stage renal disease

End-stage renal disease (ESRD) causes oxidative stress, inflammation, low-density lipoprotein (LDL) oxidation, high-density lipoprotein (HDL) deficiency and accelerated atherosclerosis. Uptake of oxidized LDL by macrophages results in foam cell and plaque formation. HDL mitigates atherosclerosis via reverse cholesterol transport and inhibition of LDL oxidation. ESRD heightens LDL inflammatory activity and suppresses HDL anti-inflammatory activity. The effect of hemodialysis on the LDL and HDL inflammatory properties is unknown. By removing the potential pro-oxidant/proinflammatory uremic toxins, dialysis may attenuate LDL inflammatory and HDL anti-inflammatory properties. Conversely, exposure to dialyzer membrane and tubing and influx of impurities from dialysate can intensify LDL and HDL inflammatory activities. This study examined the effect of hemodialysis on LDL and HDL inflammatory activities. Plasma samples were obtained from 12 normal control and 26 ESRD patients before and after hemodialysis with (16 patients) or without (10 patients) heparinization. HDL and LDL were isolated and tested for monocyte chemotactic activity in cultured endothelial cells. ESRD patients had increased LDL chemotactic activity, reduced HDL anti-inflammatory activity, paraoxonase and glutathione peroxidase levels, and elevated plasma IL-6 before dialysis. Hemodialysis partially improved LDL inflammatory and HDL anti-inflammatory activities and enhanced patients' HDL ability to suppress their LDL inflammatory activity. The salutary effect on LDL inflammatory activity was significantly greater in patients dialyzed with than those without heparin. ESRD heightens LDL inflammatory and impairs HDL anti-inflammatory activities. Hemodialysis partially improves LDL and HDL inflammatory activities. The salutary effects of hemodialysis are in part mediated by heparin, which is known to possess lipolytic and antioxidant properties.     

Associations of genotypes at the apolipoprotein AI-CIII-AIV, apolipoprotein B and lipoprotein lipase gene loci with coronary atherosclerosis and high density lipoprotein subclasses

Association studies were carried out in a sample of 86 patients from Sweden who had survived a myocardial infarction (MI) at a young age and 93 age-matched healthy individuals, to compare the impact of polymorphisms at the apolipoprotein (apo) AI-CIII-AIV gene cluster on among-individual differences in plasma lipid and lipoprotein traits, the five high density lipoprotein (HDL) subclasses (2b to 3c), lipoprotein lipase (LPL) activity and presence and progression of atherosclerosis. Individuals were genotyped for four polymorphisms; 5'apoAI (G/A_{_75}), 3'apoAI (PstI: P ±), apoCIII (C/T₁₁₀₀) and apoCIII (PvuII; V ±), using PCR-based techniques. Allele frequencies were similar in healthy individuals and patients (frequencies of alleles in combined population: 5'apoAI-A_-75=0.14, 3'apoAI-P-=0.05, apoCIII-T₁₁₀₀=0.27 and apoCIII-V-=0.18). In the healthy individuals, levels of low density lipoprotein (LDL) triglycerides were significantly associated with genotypes of the apoCIII-PvuII polymorphism (p=0.02), but no other associations were found between lipids or HDL subclasses and single polymorphisms in the apoAI-CIII-AIV gene cluster. Levels of triglycerides and very low density lipoprotein (VLDL) triglycerides were significantly higher in the presence of the haplotype defined by the presence of apoCIII-T₁₁₀₀ and common alleles of the other three polymorphisms, explaining 5.8% and 7.8% (p=0.03 and 0.01), respectively, of sample variance. In the patients, no associations were found between lipids or HDL subclasses and variation at the apoAI-CIII-AIV gene cluster. Associations were also examined between levels of HDL subclasses and variation at the apoE (common isoforms), apoB (signal peptide and XbaI polymorphisms) and lipoprotein lipase (PvuII, HindIII and Serine₄₄₇/Stop polymorphisms) gene loci. In the patient group only, levels of protein in HDL2b, HDL2a and HDL3b subclasses were significantly associated with genotypes of the LPL-HindIII polymorphism (22.1, 19.3 and 11.4%, respectively, of sample variance; p < 0.05). Finally, associations were examined between genotypes at the apoAI-CIII-AIV gene cluster and the extent of coronary atherosclerosis. Global severity of atherosclerosis at the first angiography was weakly associated with genotypes of the apoCIII-C/T₁₁₀₀ polymorphism, presence of the T₁₁₀₀ allele being associated with 53% lower median score (1.6 vs 0.75; p = 0.09). In this group of patients, two genotypes, one each at the LPL and apoB gene loci, had been previously found to be associated with high atherosclerosis score and, when considered together, individuals with all three of these genotypes had the highest median score (2.4) and those with none of these genotypes had the lowest (0.4) (chi-squared overall = 15.7; p = 0.001); no lipid traits measured showed a similar association with these genotypes. Thus, in this sample of young male post-infarction patients, genetic variation at these three loci is having an additive effect on the development of atherosclerosis, that cannot be explained by their observed effect on fasting lipid and lipoprotein traits.     

HB-H-8树脂吸附低密度脂蛋白的体外实验研究

目的 目前,用于降低血液中低密度脂蛋白(LDL)的吸附分离材料尚存在需要改进的地方.HB-H-8树脂在吸附LDL方面尚无应用,本研究对HB-H-8树脂的吸附性能进行了初步评价.方法 首先实验室制备HB-H-8树脂,经过处理后用其对LDL高于正常范围的患者血清标本进行体外动态和静态吸附实验.结果 体外动态吸附结果表明,HB-H-8树脂对LDL的吸附饱和时间为2h,最适吸附温度为恒温37℃,体外静态吸附结果显示HB-H-8树脂对LDL平均吸附率为63.2％,而对高密度脂蛋白(HDL)的平均吸附率为1.9％.结论 HB-H-8树脂对LDL具有良好的特异性吸附性能,有望开发为一种低密度脂蛋白的血液净化医用吸附材料.     

HDL signaling and protection against coronary artery atherosclerosis in mice

Atherosclerosis is a leading underlying factor in cardiovascular disease and stroke, important causes of morbidity and mortality across the globe. Abundant epidemiological studies demonstrate that high levels of high density lipoprotein (HDL) are associated with reduced risk of atherosclerosis and preclinical, animal model studies demonstrate that this association is causative. Understanding the molecular mechanisms underlying the protective effects of HDL will allow more strategic approaches to development of HDL based therapeutics. Recent evidence suggests that an important aspect of the ability of HDL to protect against atherosclerosis is its ability to trigger signaling responses in a variety of target cells including endothelial cells and macrophages in the vessel wall. These signaling responses require the HDL receptor, scavenger receptor class B type 1 (SR-B1), an adaptor protein (PDZK1) that binds to the cytosolic C terminus of SR-B1, Akt1 activation and (at least in endothelial cells) activation of endothelial NO synthase (eNOS). Mouse models of atherosclerosis, exemplified by apolipoprotein E or low density lipoprotein receptor gene inactivated mice (apoE or LDLR KO) develop atherosclerosis in their aortas but appear generally resistant to coronary artery atherosclerosis. On the other hand, inactivation of each of the components of HDL signaling (above) in either apoE or LDLR KO mice renders them susceptible to extensive coronary artery atherosclerosis suggesting that HDL signaling may play an important role in protection against coronary artery disease.     

The protective effect of apolipoprotein C1 on endothelial cells injured by low density lipoprotein in vitro]

High serum low density lipoprotein (LDL) level is known injurious to endothelial cell (EC) and that high density lipoprotein (HDL) protects EC from such injury. The protective effect of HDL and apolipoprotein C1 (apo C1) on the endothelial cells (EC) isolated originally from human umbilical vein and injured by LDL was studied morphologically with phase-contrast and transmission electron microscope. Additionally, their functional changes were detected by measuring the amount of lactate dehydrogenase (LDH) and 6-keto-prostaglandin F1 alpha (PGF1 alpha) released. The EC were divided into four groups: control, HDL+LDL, apo C1 + IDL and LDL group. EC after being injured by LDL showed cell contraction, increased release of LDH and decreased secretion of PGF1. Anyhow, they would be left normal on morphology, LDH release and PGF1 alpha synthesis if HDL or apo C1 had been added to the culture media before LDL injury. The results indicated that both HDL and apo C1 can resist the injurious effect of LDL on the cultured EC.     

Autoantibody against, malondialdehyde-modified low density lipoprotein in patients with non-diabetic unstable angina: a potential role in immunologic reaction of plaque instability

The role of autoantibody against oxidized low-density lipoprotein (LDL) in the pathogenesis of atherosclerosis is still unknown. The purpose of this study was to determine whether autoantibodies against malondialdehyde (MDA)-modified LDL are associated with coronary artery disease (CAD) and clinical presentations of CAD in non-diabetic patients without acute myocardial infarction (AMI). We determined the serum levels of autoantibody against MDA-modified LDL by ELISA in 71 patients with angiographically significant CAD (> or = 50% diameter stenosis in at least 1 vessel) and 80 controls without angiographically significant CAD. Among the total 151 subjects, 30 subjects did not have any clinical ischemic event, 90 subjects had stable angina symptoms, and 31 subjects had unstable angina symptoms. The autoantibody titer, expressed mean optical density units, was significantly higher in patients with CAD than in controls (0.177 +/- 0.014 versus 0.127 +/- 0.011, respectively; p=0.006) and higher in unstable angina group than in stable angina group (0.240 +/- 0.025 versus 0.145 +/- 0.007, respectively; p < 0.001). By logistic regression analysis, the high autoantibody titer was associated significantly with CAD (P=0.008), independent of age, gender, body mass index, triglyceride concentration, and the ratio of total cholesterol-high density lipoprotein (HDL) cholesterol. In multiple regression analysis, presence of CAD, smoking history and low HDL-cholesterol level were independent factors associated with a increased anti-oxLDL Ab titer. The autoantibody titer was significantly lower in nonsmoker than smoker (p=0.019) and higher in low HDL- cholesterol (< or = 35 mg/dl) group than in high HDL-cholesterol group (p=0.012). Elevated autoantibody titer was associated with CAD and the unstable clinical presentation of CAD. Our results suggest that immune response to oxidized LDL may play a role in the pathogenesis of atherosclerosis and plaque instability.     

Metabolic fate of low density lipoprotein and high density lipoprotein labeled with an ether analogue of cholesteryl ester

Summary Low density lipoprotein (LDL) metabolism by human skin fibroblasts was studied using LDL labeled with a nonhydrolyzable cholesteryl ether analogue,³H-cholesteryl linoleyl ether (CLE). The³H-CLE-LDL was taken up by the apo-B, E receptor mediated endocytosis similar to¹²⁵I-labeled LDL. This was shown by saturation kinetics of uptake with respect to³H-CLE-LDL concentration and very low uptake of³H-CLE-LDL by receptor negative cell strains. When injected into rats,³H-CLE-LDL and¹⁴C- cholesteryl ester (CE)-LDL were cleared at equal rates and about 30% of the injected LDL was recovered in the liver. Treatment with ethinyl estradiol resulted in a three-fold increase in³H-CLE-LDL uptake by the liver. The liver is also the major site of uptake of³H-CLE-high density lipoprotein (HDL) (40%–45% of the injected dose) but its uptake by the liver increased only by 20% with estradiol treatment. As³H-CLE-HDL was cleared from the circulation at a somewhat faster rate than¹²⁵I-HDL it appeared that some dissociation in the tissue uptake of the protein and CE moieties occurs.Abbreviations LDL low density lipoprotein - HDL high density lipoprotein - CLE cholesteryl linoleyl ether - CE cholesteryl ester Presented at the 42nd European Atherosclerosis Group Meeting, Munich, 5–6 March, 1984     

High‐density lipoprotein reduces inflammation from cholesterol crystals by inhibiting inflammasome activation

Interleukin‐1β (IL‐1β), a potent pro‐inflammatory cytokine, has been implicated in many diseases, including atherosclerosis. Activation of IL‐1β is controlled by a multi‐protein complex, the inflammasome. The exact initiating event in atherosclerosis is unknown, but recent work has demonstrated that cholesterol crystals (CC) may promote atherosclerosis development by activation of the inflammasome. High‐density lipoprotein (HDL) has consistently been shown to be anti‐atherogenic and to have anti‐inflammatory effects, but its mechanism of action is unclear. We demonstrate here that HDL is able to suppress IL‐1β secretion in response to cholesterol crystals in THP‐1 cells and in human‐monocyte‐derived macrophages. HDL is able to blunt inflammatory monocyte cell recruitment in vivo following intraperitoneal CC injection in mice. HDL appears to modulate inflammasome activation in several ways. It reduces the loss of lysosomal membrane integrity following the phagocytosis of CC, but the major mechanism for the suppression of inflammasome activation by HDL is decreased expression of pro‐IL‐1β and NLRP3, and reducing caspase‐1 activation. In summary, we have described a novel anti‐inflammatory effect of HDL, namely its ability to suppress inflammasome activation by CC by modulating the expression of several key components of the inflammasome.     

Alpha-lecithin:cholesterol acyltransferase deficiency. Lack of both phospholipase A2 and acyltransferase activities characteristic of high density lipoprotein lecithin:cholesterol acyltransferase in fish eye disease

The phospholipase A2 and acyltransferase activities characteristic of human plasma lecithin: cholesterol acyltransferase have been evaluated in incubation mixtures of lipoprotein depleted plasma of fish eye disease patients and autologous HDL or homologous normal HDL3. Both enzyme activities were strongly reduced as compared to those of normal controls. These findings further support the claim that fish eye disease plasma has a specific lack of high density lipoprotein lecithin:cholesterol acyltransferase (alpha-LCAT deficiency), although the cholesterol esterification of combined VLDL and LDL in such plasma proceeds at a normal rate.     

Evidence for deficiency of high density lipoprotein lecithin: cholesterol acyltransferase activity (alpha-LCAT) in fish eye disease

In a rare familial condition, fish eye disease, there is a low relative content of cholesteryl esters in the plasma high density lipoproteins (HDL) but a normal content of these lipids in the very low (VLDL) and low (LDL) density lipoproteins. Lecithin: cholesterol acyltransferase (LCAT) is the enzyme which mediates the esterification of free cholesterol in the plasma lipoproteins. In the present investigation, isolated HDL from our two fish eye disease patients were found to be excellent substrates during in vitro incubations with normal LCAT as present in lipoprotein depleted plasma from control subjects. Almost all free cholesterol of these HDL fractions became esterified and concomitantly the abnormally small fish eye disease HDL particles increased to a size in the range of that of normal HDL particles. Lipoprotein depleted plasma from fish eye disease, however, lacked the property of normal plasma to esterify the free cholesterol of HDL isolated from plasma of fish eye disease patients or control subjects. These results have led to the formulation of a new concept implying that two different LCAT activities exist in normal plasma. One of these activities, denoted alpha-LCAT, is specific for HDL (alpha-lipoproteins) and the other, beta-LCAT, is specific for VLDL-LDL (pre beta- and beta-lipoproteins). Fish eye disease according to this notion is classified as an alpha-LCAT deficiency in contrast to the classical LCAT deficiency which probably lacks both alpha- and beta-LCAT activities.     

Oxidized low-density lipoprotein: a double-edged sword on atherosclerosis

It is well known that atherosclerosis is closely related to lipoprotein metabolism, particularly to the low density lipoprotein (LDL). LDL becomes atherogenic after undergoing oxidation by vascular cells, that transform them into highly bioreactive oxidized LDL (oxLDL). oxLDL is generally though to be involved in foam cell formation, and trigger an array of proatherogenic events. However, there are accumulating evidences that low levels of oxLDL can be atheroprotective through its cytoprotection, modulation of immunity and activation of reverse cholesterol transport. Thus, oxLDL may exert biphasic effects on atherosclerosis, just like a doubled-edged sword.     

Low-density lipoprotein-lowering medication and platelet function

Elevated low-density lipoprotein (LDL) cholesterol (LDL-C) levels represent one of the most important risk factors for atherosclerosis and therefore cardiovascular morbidity and mortality. LDL-C operates at different levels and through various classic and non-classic mechanisms. In particular, increased or modified LDL enhances platelet function and increases sensitivity of platelets to several naturally occurring agonists. Agents that lower LDL-C in hypercholesterolemic patients have been shown to interfere with platelet function. Several studies, in fact, suggested that statins exert anti-thrombotic effects largely as a result of an anti-platelet activity. Among the other LDL-C-lowering agents those acting by interfering with cholesterol reabsorption from the gut (cholestyramine, colestipol) do not appear to interfere with platelet function, whereas peroxisome proliferator-activated receptor agonists (such as fibrates) can inhibit platelet function. The full potential of these drugs in vascular protection is only just being realized. Further studies are still needed to elucidate the full therapeutic benefits of these agents in plaque stabilization and thrombosis.