脂蛋白的氧化修饰对血凝及纤溶活性的影响

目的:研究脂蛋白的氧化修饰对凝血及纤溶活性的影响。方法:用Cu²⁺法及次氯酸法氧化修饰超速离心分离的正常人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)。分别将天然及氧化修饰脂蛋白N-VLDL、Ox-VLDL;N-LDL、Ox-LDL、N-HDL及Ox-HDL加入由正常人新鲜混合血浆构成的反应系统中,以相应天然脂蛋白为对照,测定凝血酶原时间(PT)、活化部分凝血酶原时间(APTT)、组织型纤溶酶原激活物(t-PA)活性、纤溶酶原激活物抑制剂1(PAI-1)活性及血小板最大聚集率。结果:VLDL、LDL及HDL经Cu²⁺法及次氯酸法氧化修饰后其REM、234nm吸光度值、TBARS含量均显著大于对照组(P<0.01)。Ox-VLDL、Ox-LDL及Ox-HDL使PT及APTT明显短于对照组(P<0.05或P<0.01),血小板聚集率明显高于对照组(P<0.01)。Ox-VLDL及Ox-LDL使t-PA活性高于对照组,PAI-1活性低于对照组(P<0.05及P<0.01),而Ox-HDL对t-PA活性及PAI-1活性的影响与对照组无明显差别。结论:N-VLDL、N-LDL及N-HDL对凝血及纤溶活性无影响。Ox-VLDL、Ox-LDL及Ox-HDL促进血凝及血栓形成;Ox-VLDL及Ox-LDL使纤溶活性增加,而Ox-HDL对纤溶活性无明显影响。     

负荷内源性高甘油三酯血症患者血清VLDL和LDL对HepG2细胞apoCIII受体功能的影响

目的和方法 :apoCIII在富含TG脂蛋白 (triglyceride-richlipoprotein ,TRL)的代谢中起重要作用 ,其过量表达往往导致血浆VLDL和TG浓度升高 ,并可能是引起内源性高甘油三酯血症 (hyperglyceridemia ,HTG)的重要原因。为了解apoCIII受体在HTG发病中的作用 ,本研究以 [12 5I]标记的apoCIII为配体 ,采用放射性配体饱和分析法 ,分别测定负荷HTG患者血清VLDL和LDL后HepG2细胞apoCIII受体的Kd 值及Bmax值 ,以探讨HTG患者血清VLDL和LDL对HepG2细胞apoCIII受体功能的影响。结果 :(1)与负荷血脂正常者血清VLDL组相比 ,负…     

血浆脂蛋白研究的某些进展

1929年,Macheboeuf首先从马血清中分离出一种含有脂类和蛋白质的物质,命名为“酸沉淀性Coenapse。其后,这种物质被称为脂蛋白。但直到1948年,脂蛋白的分类未超出α与β两类。进入50年代后,将超速离心法和电泳法用于脂蛋白的分离获得成功,脂蛋白被分为CM(原点)、VLDL(前β脂蛋白)、LDL(β脂蛋白)及HDL(α脂蛋白)等四类。尤其在发现冠心病(CHD)人血浆LDL升高、HDL降低后,血浆脂蛋白的研究引起人们极大的关注和兴趣。开始,人们的注意力集中在LDL与CHD的关系,对     

抗人载脂蛋白CⅡ单克隆抗体研制及其特性分析

载脂蛋白CⅡ(apo CⅡ)是乳糜微粒(cm)极低密度脂蛋白(VLDL)和高密度脂蛋白(HDL)的组成蛋白,分子量为8500,它是脂蛋白脂肪酶的激活剂,在富含甘油三酯脂蛋白的分解代谢中起关键作用。apo CⅡ缺乏将引起严重的高甘油三酯血症(HTG),故研究apo CⅡ结构,功能及含量的变化对探讨HTG及动脉粥样硬化的发病机理有着重要意义。     

脂蛋白的免疫遗传学与动脉粥样硬化

脂蛋白长期以来就被认为同人的动脉粥样硬化发病有关。脂蛋白分子的大小、构造、合水密度和免疫特性都是多相性的。用超速离心法和纸上电泳法从血浆样品制备出三类脂蛋白:(a)极低密度脂蛋白(VLDL),d<1.006克/毫升,或称前β—脂蛋白;(b)低密度脂蛋白(LDL),d 1.006～1.063克/毫升,或称β—脂蛋白和(c)高密度脂蛋白(HDL),d 1.063～1.21克/毫升,即α—脂蛋白。人类血浆脂蛋白的此种     

血浆脂蛋白对血小板功能的影响

脂蛋白和血小板同时与许多疾病的病理过程密切相关,包括动脉粥样硬化(冠心病)、血栓形成等。一般认为,高水的低密度脂蛋白(LDL)和低水平的高密度脂蛋白(HDL)以及血小板的高反应性是这些疾病发生发展的共同危险因素。对于以高水平LDL为特征的家族性Ⅱa型高脂血症患者的研究,更加明显地提示脂蛋白与血小板之间存在直接关系的可能性。来源于Ⅱa型高脂血症患者的血小板对许多生理刺激剂(包括肾上腺素、ADP、凝血酶、胶原等)诱导的聚集、释放以及花生四烯酸代谢的反应性均增高。能够降低血浆脂蛋白(LDL或极低密度脂蛋白VLDL)水平的烟酸和安妥明,同时也能降低Ⅱa型高脂蛋白血症患者的血小板高反应性。这些线索引起了人们对于LDL、HDL与血小板之间的直接关系进行深入探讨的兴趣。     

Lp(a)与LDL氧化修饰的比较

脂蛋白（a）［Lp（a）］是一种特殊的血浆脂蛋白,其结构、理化性质和脂质组成与低密度脂蛋白（LDL）极为相似。氧化低密度脂蛋白（Ox－LDL）在动脉粥样硬化（AS）的发生、发展中起重要作用,Lp（a）的氧化亦发生于体内动脉壁。在体外,Lp（a）能经铜离子（Cu2＋）介导发生氧化修饰,但与LDL相比,Lp（a）氧化的延迟时间是LDL的1．62倍,氧化速率和氧化程度均只有LDL的63％,故Lp（a）对氧化的敏感性和氧化程度均较LDL为低,其高度致AS作用,难以完全用较高的氧化敏感性来加以解释。     

中国人内源性高甘油三酯血症与脂蛋白脂酶基因PvuⅡ多态性关联的研究

目的：探讨中国人内源性高甘油三酯血症（hypertriglyceridemics,HTG)与脂蛋白脂酶基因PvuⅡ多态性是否关联。方法：采用聚合酶链反应和限制性片段长度多态性方法,对成都地区135例内源性高甘油三酯血症患者和193名血脂正常者脂蛋白脂酶基因内含子6PvuⅡ多态性及其对血脂及载脂蛋白（apo)水平的影响进行了研究。结果：HTG患者和正常人均以P＋等位基因为主,HTG组以P＋P＋基因型为主,而正常对照组P＋P－基因型为主。HTG组的P＋P＋基因型分布频率及P＋等位基因分布频率则显著高于正常对照组（0.460vs0.337,P＜0.05;0.689vs0.565,P＜0.01)。P＋P＋基因型者的血清甘油三酯（TG）、apoCⅡ、apoCⅢ、apoE水平及TG／HDL－C比值较P－P－基因型者显著增高（P＜0．05）。结论：脂蛋白酯酶基因P＋P＋基因型与中国人内源性高甘油三酯血症的遗传易感性有一定关联。     

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…     

用双单克隆抗体ELISA定量测定人血清载脂蛋白B100

Kane等发现,载脂蛋白B100由肝脏合成,是血浆低密度脂蛋白(LDL)及极低密度脂蛋白(VLDL)的主要组成成份,占LDL蛋白质98％以上,在转运脂质及识别脂蛋白受体上具有重要作用。大量资料证明,血浆LDL与动脉粥样硬化的发生关系密切。目前国内已报道用火箭电泳法及单向免疫扩散法检测血清apo B100。我们建立的人血清apoB100酶联免疫测定法灵敏可靠,简便易行。     

Tetrahydrobiopterin inhibits copper-induced oxidation of low density lipoprotein

The effect of tetrahydrobiopterin (BPH4) on Cu2+-induced oxidation of low density lipoprotein (LDL) prepared from rabbit plasma was examined. BPH4 (0.5-10 microM) inhibited the formation of thiobarbituric acid-reactive substances (TBARS) in LDL induced by 5 microM Cu2+ in a dose-dependent manner. BPH4 also suppressed the increase in relative electrophoretic mobility (REM) of LDL in the presence of 5 microM Cu2+. The potency of inhibitions of BPH4 on TBARS formation and REM was the same as or stronger than that of ascorbic acid and alpha-tocopherol, which are known as endogenous inhibitors of LDL oxidation. These results suggest that BPH4 could act as an efficacious endogenous inhibitor of atherogenic LDL modification.     

Lp(a) lipoprotein enters cultured fibroblasts independently of the plasma membrane low density lipoprotein receptor

Lp(a) lipoprotein shares the apoB antigen with low density lipoprotein (LDL). The Lp(a) antigen is unique for Lp(a) lipoprotein. Fibroblast association (i.e. plasma membrane binding plus intracellular accumulation), plasma membrane binding, intracellular accumulation and degradation of 125I-Lp(a) lipoprotein were studied in strains from subjects with or without autosomal dominant hypercholesterolemia (HC). Subjects without HC (non-HCs) have cell surface receptors for low density lipoprotein (LDL receptors). On the average, HC heterozygotes have half-normal LDL receptor activity and "receptor-negative" HC homozygous cell strains lack functional receptors. Fibroblast processing of 125I-Lp(a) lipoprotein was compared to fibroblast processing of 125I-LDL. LDL receptor-dependent processing of 125I-LDL was saturated at about 50 microgram apo 125I-LDL.ml-1 in non-HC fibroblasts. 125I-Lp(a) lipoprotein was, however, largely processed independently of receptor mechanisms by non-HC cells (highest concentration examined 150 microgram apo 125I-Lp(a) lipoprotein . ml-1). Lp(a) lipoprotein did not interfere with 125I-LDL for fibroblast association, but inhibited 125I-LDL degradation. The interference with 125I-LDL degradation was time dependent. Only slightly higher 125I-Lp(a) lipoprotein processing values were found in non-HC and HC heterozygous strains than in "receptor-negative" HC homozygous strains. However, non-HC cells had more than tenfold higher 125I-LDL processing values than "receptor-negative" HC homozygous cells.     

Lipoproteins in human atherosclerotic vessels. I. Biochemical properties of arterial low density lipoproteins, very low density lipoproteins, and high density lipoproteins.

Lipoproteins extracted from the human aortic intima into 1.65 M NaCl were quantitated and characterized biochemically and by electron microscopy following separation in the preparative ultracentrifuge. The arterial lipoproteins, although separated and designated according to the density classes used for the serum lipoproteins, were distinctly different from their serum counterparts. The amount of lipoproteins in the low density range of d 1.063 to 1.006 (arterial LDL) and in the very low density range of d < 1.006 (arterial VLDL) extracted from arterial intima increased with increasing intimal lipid content. In contrast, the concentration of lipoproteins in the high density range of d 1.210 to 1.063 (arterial HDL) was small and did not change with the severity of atherosclerosis.Arterial VLDL, LDL and its subfractions, LDL₁ (d 1.006 to 1.019) and LDL₂ (d 1.019 to 1.063), were markedly heterogenous and contained unusually large particles, which were isolated by Bio-Gel A-150. These particles showed a pitted and cratered appearance by scanning electron microscopy and were immunochemically unreactive and had no electrophoretic mobility. The lipid and amino acid composition of the arterial VLDL and LDL fractions as well as their electrophoretic, chromatographic and analytical flotation behavior was distinctly different from that of their serum lipoprotein counterparts. Arterial VLDL, in sharp contrast to serum VLDL, was rich in cholesteryl ester and poor in triglycerides. Arterial VLDL also showed no electrophoretic mobility and only half of the preparations reacted to LDL antisera. Acid mucopolysaccharides were detected in the arterial VLDL and LDL fractions in association with the large size particles which lacked electrophoretic mobility and immunochemical reactivity and showed only a “saw tooth” pattern in the analytical ultracentrifuge. Arterial LDL and LDL₂ contained a smaller sized population of particles as separated by Bio-Gel A-150. These particles exhibited a reaction of complete identity with serum LDL when reacted against LDL antiserum. However these particles had a greater electrophoretic mobility and different amino acid composition than did serum LDL and LDL₂. An asymmetrical peak with a mean SF of 7.3 was demonstrated by these particles in the analytical ultracentrifuge.The over-all studies suggest that lipid deposition in atherosclerotic plaques is associated with the accumulation of lipoproteins with biochemical and ultrastructural properties unlike those of serum lipoproteins. The presence of these lipoproteins in the arteries may be a result of the interaction of serum and arterial lipoproteins with acid mucopolysaccharides and of lipoprotein synthesis and degradation in the arteries.     

Very low density lipoprotein apolipoprotein B metabolism in humans

Summary The human plasma lipoproteins encompass a broad spectrum of particles of widely varying physical and chemical properties whose metabolism is directed by their protein components. Apolipoprotein B₁₀₀ (apo B₁₀₀) is the major structural protein resident in particles within the Svedberg flotation range 0–400. The largest of these, the very low density lipoprotein (VLDL), rich in triglyceride, are metabolised by sequential delipidation through a transient intermediate density lipoprotein (IDL) to cholesterol-rich low density lipoproteins (LDL). Several components contribute to the regulation of this process, including (a) the lipolytic enzymes lipoprotein lipase and hepatic lipase (b), apolipoproteins B, CII, CIII and E, and (c) the apolipoprotein B/E or LDL receptor. Lipoprotein lipase acts primarily on large VLDL of Sf 60–400. Hepatic lipase on the other hand seems to be critical for the conversion of smaller particles (Sf 12–60) to LDL (Sf 0–12). Although most apo B₁₀₀ flux is directed to the production of the delipidation end product LDL, along the length of the cascade there is potential for direct removal of particles from the system, probably via the actions of cell membrane receptors. This alternative pathway is particularly evident in hypertriglyceridaemic subjects, in whom the delipidation process is retarded.VLDL metabolism shows inter subject variability even in normal individuals. In this regard, apolipoprotein E plays an important role. Normolipidaemic individuals homozygous for the apo E₂ variant exhibit gross disturbances in the transit of B protein through the VLDL-IDL-LDL chain.Abbreviations apo B, C, E Apolipoprotein B, C, E - CETP Cholesteryl ester transfer protein - FCH Familial combined hyperlipidaemia - FH Familial hypercholesterolaemia - FHTG Familial hypertriglyceridaemia - HDL High density lipoprotein - HL Hepatic lipase - IDL Intermediate density lipoprotein - LDL Low density lipoprotein - LpL Lipoprotein lipase - RFLP Restriction fragment length polymorphism - Sf Svedberg flotation coefficient - VLDL Very low density lipoprotein - WHHL Watanabe heritable hyperlipidemic     

Elevated lipoprotein(a) levels in patients with acute myeloblastic leukaemia decrease after successful chemotherapeutic treatment

Summary Twenty-two patients with acute myeloblastic leukaemia (AML) were studied to investigate disease-associated changes in lipid metabolism. Lipoprotein (a) [Lp(a)] levels were found to be elevated at the time of diagnosis (median 23 mg/dl; 41% of patient group had levels greater than 25 mg/dl) and diminished after successful chemotherapeutic treatment in 9 of 10 cases, with a maximum decrease from 56 to 10 mg/dl. In contrast, reduced levels of total cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) (medians 137, 87 and 20 mg/dl, respectively) were observed at the time of diagnosis. Cholesterol and HDL levels increased in all 10 and LDL in 9 cases in which complete remission was achieved. These data suggest that the catabolism of LDL-cholesterol might be even more enhanced than assumed to date. Furthermore, it indicates that the Lp(a) level in acute myeloblastic leukaemia is influenced either directly or indirectly by the leukaemic blasts.Abbreviations AML acute myeloblastic leukaemia - Lp(a) lipoprotein (a) - LDL low density lipoprotein - HDL high density lipoprotein - FAB French-American-British - CALGB cancer and leukaemia group B - CR complete remission - TG triglycerides - VLDL very low density lipoprotein - RIA radioimmunoassay - apo(a) apoprotein (a) - HMG-CoA reductase 3-hydroxy-3-methylglutaryl coenzyme A reductase Supported by the Volkswagen Stiftung with a grant to A.N.     

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.     

Genetics of the low density lipoprotein receptor:

Fibroblast low density lipoprotein (LDL) plasma membrane receptor activity, measured as 125I-LDL association (plasma membrane binding plus intracellular accumulation) and degradation was determined in cell strains from 14 monozygotic (MZ) and 21 like-sexed dizygotic (DZ) normolipidemic twin pairs. The twins were between 57 and 62 years old and had liver apart for an average of 38 years (range 0-60). The intrapair differences were significantly smaller in MZ than in DZ twin pairs in fibroblast 125I-LDL association as well as degradation assays (P less than 0.05). These findings suggest a genetic influence on normal variation in LDL receptor activity in vitro. In two MZ pairs discordant for psoriasis, the psoriatic twin had markedly lower LDL receptor activity than the cotwin.     

Deficiency of hepatic lipase activity in post-heparin plasma in familial hyper-alpha-triglyceridemia

Hyper-alpha-triglyceridemia is a rare dyslipoproteinemia characterized by a pronounced increase in the concentration of triglycerides in the plasma high density lipoprotein (HDL) fraction. One case with this condition, an apparently healthy 61-year-old man, has been studied. Additional lipoprotein abnormalities were present, such as abnormally cholesterol-rich very low density lipoproteins (VLDL) with retarded electrophoretic mobility (beta-VLDL) and triglyceride enrichment of low density lipoproteins (LDL). The patient's plasma concentration of apolipoproteins A-I, A-II and B were normal and those of C-I, C-II, C-III and E were elevated. No abnormal forms of the soluble apolipoproteins of VLDL and high density lipoproteins (HDL) were found after analysis by isoelectric focusing. Lecithin:cholesterol acyltransferase activities, plasma cholesterol esterification rates and lipid transfer protein activities were normal. Post-heparin plasma activity of hepatic lipase was virtually absent and that of lipoprotein lipase was reduced by 50%. In plasma of this patient, HDL was almost exclusively present as large triglyceride-rich particles corresponding in size to particles of the HDL2 density fraction. The only brother of the patient also had hyper-alpha-triglyceridemia together with the other lipoprotein abnormalities described for the index case and deficiency of postheparin plasma activity of hepatic lipase. The findings presented below support the hypothesis that one primary function of hepatic lipase is associated with degradation of plasma HDL2. Deficiency of this enzyme activity thus causes accumulation of HDL2 in plasma leading to hyper-alpha-triglyceridemia. The results further suggest that the abnormal chemical and electrophoretic properties of VLDL and LDL in plasma from the patient, reminiscent of type III hyperlipoproteinemia, are secondary to the lack of the action of hepatic lipase on the HDL particles.     

Platelet activation by low density lipoprotein and high density lipoprotein

Cardiovascular disease is the main cause of death and disability in the Western society. Lipoproteins are important in the development of cardiovascular disease since they change the properties of different cells involved in atherosclerosis and thrombosis. The interaction of platelets with lipoproteins has been under intense investigation. Particularly the initiation of platelet signaling pathways by low density lipoprotein (LDL) has been studied thoroughly, since platelets of hypercholesterolemic patients, whose plasma contains elevated LDL levels due to absent or defective LDL receptors, show hyperaggregability in vitro and enhanced activity in vivo. These observations suggest that LDL enhances platelet responsiveness. Several signaling pathways induced by LDL have been revealed in vitro, such as signaling via p38 mitogen-activated protein kinase and p125 focal adhesion kinase. High density lipoprotein (HDL) consists of two subtypes, HDL(2) and HDL(3), which have opposing effects on platelet activation. This review provides a summary of the activation of signaling pathways after platelet-LDL and platelet-HDL interaction, with special emphasis on their role in the development of thrombosis and atherosclerosis.