Cellular Thiol Production and Oxidation of Low-Density Lipoprotein

Compelling evidence suggests that low-density lipoprotein (LDL) is oxidized by cells within the arterial intima and that, once oxidized, it is profoundly atherogenic. The precise mechanism(s) by which cells promote the oxidation of LDL in vivo are not known; in vitro, however, oxidation of LDL can be enhanced by a number of differing mechanisms, including reaction with free and protein-bound metal ions, thiols, reactive oxygen species, lipoxygenase, myeloperoxidase and peroxynitrite. This review is concerned with the mechanisms by which cells enhance the oxidation of LDL in the presence of transition metals; in particular, the regulation, pro- and anti-oxidant consequences, and mechanism of action of cellular thiol production are examined, and contrasted with thiol-independent oxidation of LDL in the presence of transition metals.     

基于高密度脂蛋白代谢与重塑的抗动脉粥样硬化研究及相关药物

动脉粥样硬化（atherosclerosis,AS）是一种主要因血脂代谢紊乱引发的慢性炎症性血管疾病,以血管内膜下巨噬细胞和血管平滑肌细胞过度蓄脂泡沫化为主要病理特征。高密度脂蛋白（high-density lipoprotein,HDL）通过胆固醇逆向转运（reverse cholesterol transport,RCT）将外周细胞中的胆固醇运输到肝脏然后经胆汁排出体外,从而改善血脂水平和细胞的过度蓄脂,被认为是HDL抗AS的基础。然而,大量流行病学证据表明,虽然血浆高密度脂蛋白胆固醇（high-density lipoprotein cholesterol,HDL-C）水平与心血管风险呈负相关,但仅仅提高HDL-C水平的治疗策略不一定能增加临床效益。因此,学术界认识到HDL水平不足以反映其RCT能力,而更多取决于HDL功能。本文综述了参与调节HDL功能的各种分子对HDL代谢与重塑过程的影响,以及针对上述过程的相关药物研究进展,为更全面评价HDL的抗AS作用提供理论参考。     

In vitro interactions of phenformin with serum lipoproteins and consequences thereof.

Turbidity developed when phenformin was added to human serum; this turbidity increased in a sigmoidal fashion with rising concentrations of phenformin (5–50 nmole/1). Centrifugation produced clearing of the solution, with collection of particulate matter on the surface of the sera.Extraction of control, and phenformin-treated sera with petroleum ether for 15 min. revealed that cholesterol and triglyceride were responsible for the turbidity. Different sera produced different turbidities with a given concentration of phenformin. No significant simple correlation existed between turbidity and serum cholesterol and/or triglyceride levels. The turbidities, produced by the addition of a constant concentration of phenformin to a series of diluted serum samples, were linearly related to the amount of serum present.The turbidities acquired by purified very-low density (VLDL), low-density (LDL), and high-density lipoprotein (HDL) fractions with phenformin were additive, and the turbidity of phenformin-treated serum was accounted for by these lipoprotein fractions. Serum free of lipoproteins did not become turbid when exposed to phenformin. Phenformin added to serum which had previously been delipidated, failed to produce turbidity. The turbidity produced by phenformin was reversible, because it could easily be cleared by dialysis.No significant differences in quantitative immunochemical reactivities were observed when control serum was compared with the subnatant of phenformin-treated serum, as determined by single radial immunodiffusion with LDL antibodies.These in vitro observations may be related to the in vivo hypolipidemic action of phenformin on hyperlipidemic subjects.     

apoA-Ⅰ的α螺旋在胆固醇流出中的作用

血浆载脂蛋白A-Ⅰ(apoA-Ⅰ)的水平与动脉粥样硬化(atherosclerosis,AS)性心血管疾病的风险呈负相关.ApoA-Ⅰ经载脂形成高密度脂蛋白(HDL),HDL通过促进胆固醇逆向转运(RCT),使细胞内的多余胆固醇流出.α螺旋是apoA-Ⅰ载脂的主要结构,在apoA-Ⅰ参与的胆固醇流出中具有重要作用.模拟α螺旋建立的apoA-Ⅰ模拟肽能通过不同方式发挥抗AS的作用.本文就α螺旋在胆固醇流出中的作用作一综述,以便进一步探索apoA-Ⅰ的结构对胆固醇流出的影响,为以apoA-Ⅰ为靶点防治AS提供理论基础.     

体育运动和脂质代谢

一般健康人总胆固醇(T-Ch)、甘油三酯(TG)、高密度和低密度脂蛋白胆固醇(HDL-ch,LDL-cH)的含量随年令而增加。中年组(45-59)HDL-Ch平均值较低,男比女低,这与中国人男性45岁以后患冠心病(CHD)多于女性相吻合。冠心病及脑中风患者的HDL-ch含量比健康人低(P<0.05)。运动员的HDL-Ch含量明显高于一般健康人(P<0.01),其均值且高于不易患动脉粥样硬化(AS)的八种哺乳动物的均值(60.40mg/d1)。运动员的T-ch、TG和HDL-Ch含量低于健康人。     

Oxidized low density lipoprotein inhibits the hemolytic activity of Asp-hemolysin from Aspergillus fumigatus

We have examined the effect of chemically modified human low density lipoproteins (LDLs) , acetylated LDL and oxidized LDL, on the hemolytic activity of Asp-hemolysin. Oxidized LDL, but not acetylated LDL, inhibited the hemolytic activity of this toxin. The inhibitory effects of oxidized LDL increased with the time of Cu²⁺-induced LDL oxidation. Similar inhibition was observed in the filtrate which was separated from the incubation mixture of Asp-hemolysin with oxidized LDL (for 2 h of oxidation) following ultrafiltration through a membrane with a molecular mass cutoff of 100 000. However, at longer LDL oxidation times, the inhibition by the filtrates was less than the control mixture without ultrafiltration. We suggest that the inhibition by oxidized LDL was due to the binding of oxidized LDL to Asp-hemolysin at shorter LDL oxidation times .     

氧化低密度脂蛋白对THP-1巨噬细胞吞噬和分泌功能的影响

目的:探讨氧化低密度脂蛋白(oxidized low density lipoprotein,ox-LDL)对巨噬细胞源性泡沫细胞吞噬功能和炎症相关因子分泌功能的影响。方法:利用佛波酯(phorbol ester,PMA)诱导THP-1细胞分化形成巨噬细胞,之后采用ox-LDL处理48小时后,诱导其形成泡沫细胞。利用中性红吞噬实验,分析泡沫细胞形成前后吞噬功能的变化;通过ELISA法,检测细胞培养上清中肿瘤坏死因子α(tumor necrosis factorα,TNF-α)含量,观察ox-LDL对THP-1巨噬细胞功能的影响。结果:细胞形态学结果表明,我们成功利用ox-LDL诱导THP-1巨噬细胞形成泡沫细胞;进一步发现ox-LDL诱导THP-1巨噬细胞表面的清道夫受体CD36表达升高,并促进细胞吞噬功能增加,进一步促进细胞内胆固醇含量显著升高(P0.05);同时,ox-LDL能够刺激巨噬细胞大量分泌TNF-α(P0.05)。结论:ox-LDL通过增强清道夫受体CD36表达,提高巨噬细胞的吞噬功能,引起大量胆固醇聚集,产生细胞毒性损伤,并促进TNF-α炎性因子的大量分泌。     

LOX-1 pathway affects the extent of myocardial ischemia-reperfusion injury

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was originally identified as a receptor for oxidized low-density lipoprotein predominantly expressed in endothelial cells. LOX-1 expression can be induced in cardiomyocytes and that activation of LOX-1 is involved in apoptosis. To investigate possible roles of LOX-1 in myocardial ischemia-reperfusion injury, rats were subjected to coronary artery ligation for 1h followed by reperfusion for 2h. Immunohistochemistry revealed that expression of LOX-1 in cardiac myocytes was induced following ischemia-reperfusion but not ischemia alone. Administration of anti-LOX-1 monoclonal antibody resulted in a nearly 50% reduction in myocardial infarction size compared with that of normal IgG or saline (P<0.05). These findings suggest that activation of the LOX-1 pathway is involved in determining the extent of myocardial ischemia-reperfusion injury and that inhibition of the LOX-1 pathway may provide a novel strategy for treatment of acute myocardial infarction in humans.     

On the Properties of the Starch Granules from Unicellular Green Algae

Starch granules from Chlorella, Chlamydomonas and Scenedesmus, grown heterotro-phically in a medium containing organic carbon sources, were isolated by means of the toluol treatment of the sonicate of alga. The toluol treatment separated the starch granules in the water layer from the cells and cell debris coagulated in the upper toluol layer.

The starch granules of Chlorella vulgaris and Chlamydomonas sp. were composed of amylose (12 to 3%) and amylopectin. The amylose content of the starch granules of Scenedesmus basilensis was 22 %. All the X-ray diffraction patterns of algal starch obtained in this investigation were of the A-type, identical to that of corn starch.     

Enzymatic Synthesis of 5-Methyluridine from Adenosine and Thymine with High Efficiency

5-Methyluridine (5MU) was synthesized efficiently from adenosine, thymine, and phosphate by a combination of adenosine deaminase (ADA), purine nucleoside phosphorylase (PUNP), pyrimidine nucleoside phosphorylase (PYNP), and xanthine oxidase (XOD). Adenosine was converted into inosine first by ADA. 5MU and hypoxanthine were synthesized from inosine and thymine by PUNP and PYNP. The hypoxanthine formed was converted into urate via xanthine by XOD. After inosine was completely consumed, an equilibrium state, in which 5MU, thymine, ribose-1-phosphate, and phosphate were involved, was achieved. At the equilibrium state, the maximum yield of 5MU was obtained. The yield of 5MU was 74%, when the initial concentrations of adenosine, thymine, and phosphate were 5 mM each. On the other hand, in the absence of ADA or XOD the yield of 5MU was 1.8%. Several kinds of nucleosides were also synthesized with high yield by the same method.     

急性期应答与胆固醇逆向转运

胆固醇逆向转运(reverse cholesterol transport,RCT)是促进外周胆固醇从细胞内流出,然后转运到肝脏进行代谢的过程,是机体抗动脉粥样硬化相关疾病的重要机制。研究表明,感染、炎症及创伤等诱导的急性期应答(acute phase response,APR)影响高密度脂蛋白的结构和功能,抑制细胞内胆固醇流出、血浆胆固醇转运及肝脏胆固醇代谢和排泌等环节,因此抑制体内RCT。APR短期抑制RCT有利于机体抗感染和组织损伤,然而,APR对RCT的进一步抑制将促进外周组织胆固醇蓄积及代谢紊乱,可能是多种感染免疫性疾病、代谢性疾病与动脉粥样硬化呈正相关的关键因素。本文就APR调节机体RCT的最新研究进展作一综述。     

Oxidized LDL autoantibodies are related to apolipoprotein E phenotype,independently of postprandial change in plasma triglycerides and LDL size,among patients with angiographically verified coronary artery disease and healthy controls

OBJECTIVE: Oxidized low-density lipoprotein (LDL) autoantibodies (oxLDLab), apolipoprotein E (apoE) phenotype, postprandial triglyceride changes and LDL size are suggested to be risk factors for coronary artery disease (CAD). Our aim was to study the interaction between these new risk factors among patients with CAD and healthy controls. METHODS: oxLDLab from 31 men with angiographically verified CAD and 31 healthy men were analyzed by enzyme-linked immunosorbent assay. Isoelectric focusing and immunoblotting were used for apoE phenotyping. Triglyceride level was measured after 12 h of fasting and 3, 5 and 7 h after a high-fat meal. Nondenaturing gradient gel electrophoresis was used to separate LDL particles according to size. RESULTS: oxLD- Lab levels increased according to apoE phenotype in the following order: E2 < E3 < E4 (p = 0.004, ANOVA). The postprandial response of triglycerides, the size of LDL particles and the concentration of LDL and high-density lipoprotein (HDL) cholesterol did not differ between apoE phenotypes, and the use of these variables as covariates did not change the statistically significant difference in oxLDLab levels between apoE phenotypes (p = 0.01, ANCOVA). oxLDLab levels did not differ between the patient and control groups. CONCLUSION: We found an association between apoE allele epsilon2 and decreased levels of oxLDLab, which was independent of the postprandial response of triglycerides, the size of LDL particles and plasma LDL and HDL cholesterol levels. The mechanism by which apoE affects oxidation of LDL remains unknown.     

Genetic analysis of murine strains C57BL/6J and C3H/HeJ to confirm the map position ofAth-1, a gene determining atherosclerosis susceptibility

Previous results suggested that strains C57BL/6J and C3H/HeJ differed in a single gene for atherosclerosis susceptibility, calledAth-1. Based on data from recombinant inbred strainsAth-1 was tentatively assigned to chromosome 1 linked toAlp-2. In this report, a cross between C57BL/6 and C3H/HeJ was carried out in order to test whether the tentative map position was correct. Parental strains and F₁ and F₂ progeny were examined. Susceptible alleles ofAth-1, found in C57BL/6, are associated with relatively low levels of high-density lipoprotein (HDL)-cholesterol in animals fed an atherogenic diet; resistant alleles ofAth-1 are associated with relatively high levels of HDL-cholesterol. F₁ progeny have HDL levels that are intermediate between these of the two parental strains. Among the F₂ progeny,Alp-2 andAth-1 cosegregated, providing confirmatory evidence thatAth-1 is linked toAlp-2 on chromosome 1. Three mice recombinant forAlp-2 andAth-1 were found among the 60 chromosomes tested, giving an estimated map distance between these two genes of 5.0±2.8 (SE) cM. The phenotypic characteristics ofAth-1 resemble a genetic trait in humans, hyperalphalipoproteinemia, which is characterized by elevated levels of HDL-cholesterol, reduced risk of heart disease, and increased longevity.This work was supported by Grant HL-32087 from the Heart, Lung, and Blood Institute, National Institutes of Health, Grant 1858 from the Council for Tobacco Research, Grant 86-1387 from the American Heart Association with funds contributed in part by the Alameda, Orange, and Santa Barbara County Chapters, and Grants 85-N132A and 85-N136A from the California Affiliate of the American Heart Association.     

Biochemical Changes in Secondary Metabolites in Wounded and Deteriorated Cassava Roots

Bluish fluorescent and phenolic components were produced in cassava roots in response to cut- injury, and in relation to physiological deterioration and microbial deterioration. The former roved to consist of five coumarin components, the main three of which were scopoletin, scopolin and esculin, and the other two were scopoletin- and esculetin-containing conjugates. A main component of the latter was (+)-catechin. Some enzymes pertaining to the production of the secondary metabolites such as acid invertase, phenylalanine ammonia lyase and peroxidase were formed in cut-injured tissue and in non-infected tissue adjacent to the soft-rotten part.