共查询到20条相似文献,搜索用时 31 毫秒
1.
根据低密度脂蛋白(low density lipoprotein,LDL)颗粒的不均一性,可以利用密度梯度超速离心法和梯度凝胶电泳法将其分成若干亚组分。近年来,对于LDL亚组分分离方法的研究取得了显著进展。除对上述两种基本实验方法进行改进外,有实验室采用Western印迹法对LDL颗粒进行分离。LDL亚组分分离方法的进步,使对LDL亚组分的认识更加深入:LDL亚组分的高度不均一性、氧化易感性及电负性等不同特性与动脉粥样硬化(atherosclerosis,AS)关系密切。LDL亚组分的研究为认识动脉粥样硬化及其相关疾病提供了重要的理论依据。 相似文献
2.
动脉粥样硬化是导致心血管疾病发生的最重要因素。血液中低密度脂蛋白(LDL)浓度过高是引起动脉粥样硬化的主要原因。体外去除法是目前降低LDL浓度最有效的方法之一,吸附材料是影响LDL体外去除法降低LDL浓度效果的关键。阴离子型吸附材料是一种常用的吸附材料,因选材广泛、吸附效果佳备受关注,由发挥吸附功能的阴离子化合物配基和承载配基的载体基材组成,通过阴离子所带的负电荷与带正电的LDL产生特异性吸附。根据配基分子大小,阴离子型吸附材料主要分为大分子阴离子型和小分子阴离子型吸附材料,本文总结了国内外的阴离子型吸附材料主要研究现状及发展趋势。 相似文献
3.
LDL的氧化修饰和氧化修饰LDL的组成和结构变化 总被引:8,自引:1,他引:7
与低密度脂蛋白(LDL)相比,氧化修饰LDL(O-LDL)的组成、结构和生物学特性发生了深刻的变化,而组成和结构的改变是生物学特性改变的基础.本文根据最近文献资料.结合我们实验室的工作.对LDL的氧化修饰、O-LDL的组成、结构改变,以及它们的机理作一简要综述. 相似文献
4.
Why is glycated LDL more sensitive to oxidation than native LDL? A comparative study 总被引:5,自引:0,他引:5
Sobal G Menzel J Sinzinger H 《Prostaglandins, leukotrienes, and essential fatty acids》2000,63(4):177-186
It is well established that oxidative modification of low-density lipoprotein (LDL) plays a causal role in human atherogenesis and the risk of atherosclerosis is increased in patients with diabetes mellitus. To examine the influence of different agents which may influence LDL-glycation and oxidation, experiments including glycation with glucose, glucose 6-phosphate, metal chelators (EDTA) and antioxidants (BHT) were performed. The influence of time dependence on the glycation process and the alteration of the electrophoretic mobility of LDL under diverse glycation and/or oxidation conditions was also investigated. The formation of conjugated dienes and levels of lipid peroxides in these different LDL-modifications were estimated. The copper-induced oxidation of LDL in vitro was determined by measurement of thiobarbituric acid reactive substances (TBARS) and expressed as nmol MDA/mg of LDL protein. We found that glycated LDL is more prone to oxidation than native LDL. Using native LDL, the maximal oxidation effect was found to reach a value of 49.72 nmol MDA/mg protein after 8 h. The maximum oxidation of the 31 days, glycated LDL with glucose was 71.76 nmol MDA/mg protein amounting to 144.33% of the value found for native LDL. In the case of glucose 6-phosphate glycation, the maximum oxidation under the same conditions amounted to 173.77% of the value found for native LDL. To measure the extent of glycation, fluorescence of advanced glycation end products (AGEs) was determined (370 nm excitation and 440 nm emission). The most potent glycation agent was glucose 6-phosphate leading to the formation of very high amounts of AGEs. This process was promoted in the absence of EDTA, which prevents the oxidative cleavage of modified Amadori products (ketoamines) to AGEs. We therefore conclude that both processes, glycation and oxidation, result in the modification of LDL. The lower the glycation-rate (+/- EDTA) as measured by relative fluorescence units RFU (generation of AGEs), the lower the additional oxidation rate after glycation as measured by TBARS (generation of MDA equivalents). Glycation and/or oxidation change the electrophoretic mobility of LDL. 相似文献
5.
Bénédicte Dehouck Laurence Fenart Marie-Pierre Dehouck Annick Pierce Gérard Torpier Roméo Cecchelli 《The Journal of cell biology》1997,138(4):877-889
Lipoprotein transport across the blood–brain barrier (BBB) is of critical importance for the delivery of essential lipids to the brain cells. The occurrence of a low density lipoprotein (LDL) receptor on the BBB has recently been demonstrated. To examine further the function of this receptor, we have shown using an in vitro model of the BBB, that in contrast to acetylated LDL, which does not cross the BBB, LDL is specifically transcytosed across the monolayer. The C7 monoclonal antibody, known to interact with the LDL receptor-binding domain, totally blocked the transcytosis of LDL, suggesting that the transcytosis is mediated by the receptor. Furthermore, we have shown that cholesterol-depleted astrocytes upregulate the expression of the LDL receptor at the BBB. Under these conditions, we observed that the LDL transcytosis parallels the increase in the LDL receptor, indicating once more that the LDL is transcytosed by a receptor-mediated mechanism. The nondegradation of the LDL during the transcytosis indicates that the transcytotic pathway in brain capillary endothelial cells is different from the LDL receptor classical pathway. The switch between a recycling receptor to a transcytotic receptor cannot be explained by a modification of the internalization signals of the cytoplasmic domain of the receptor, since we have shown that LDL receptor messengers in growing brain capillary ECs (recycling LDL receptor) or differentiated cells (transcytotic receptor) are 100% identical, but we cannot exclude posttranslational modifications of the cytoplasmic domain, as demonstrated for the polymeric immunoglobulin receptor. Preliminary studies suggest that caveolae are likely to be involved in the potential transport of LDL from the blood to the brain.The maintenance of the homeostasis of brain interstitial fluid, which constitutes the special microenvironment for neurons, is established by the presence of the blood–brain barrier (BBB)1 at the transition area from endothelial cells (ECs) to brain tissue. Of primary importance in the formation of a permeability barrier by these cells is the presence of continuous tight junctions that seal together the margins of the ECs and restrict the passage of substances from the blood to the brain. Furthermore, in contrast to ECs in many other organs, the brain capillary ECs contain no direct transendothelial passageways such as fenestrations or channels. But obviously, the BBB cannot be absolute. The brain is dependent upon the blood to deliver metabolic substrates and remove metabolic waste, and the BBB therefore facilitates the exchange of selected solutes. Carrier-mediated transport systems that facilitate the uptake of hexoses, amino acids, purine compounds, and mono-carboxylic acids have been revealed in the cerebral endothelium (Betz and Goldstein, 1978), but until now little information has come to light regarding the cerebral uptake of lipids.There is growing evidence that the brain is equipped with a relatively self-sufficient transport system for maintaining cholesterol and lipid homeostasis. The presence of a low density lipoprotein (LDL) receptor has been demonstrated by immunocytochemistry in rat and monkey brains; and apolipoprotein (apo) E and apo AI-containing particles have been detected in human cerebrospinal fluid (Pitas et al., 1987). Furthermore, enzymes involved in lipid metabolism have been located within the brain: LCAT mRNA has been shown to be expressed in rat brains and cholesteryl ester transfer protein, which plays a key role in cholesterol homeostasis, has been detected in human cerebrospinal fluid and seems to be synthesized in the brain (Albers et al., 1992). The distribution of the LDL receptor-related protein, a multifunctional receptor that binds apoE, is highly restricted and limited to the gray matter, primarily associated with neuronal cell population (Wolf et al., 1992). The difference in cellular expression of ligand (apoE) and receptor (LDL receptor-related protein) may provide a pathway for intracellular transport of apoE-containing lipoproteins in the central nervous system. All these data leave little doubt that the brain is equipped with a relatively self-sufficient transport system for cholesterol.Cholesterol could be derived from de novo synthesis within the brain and from plasma via the BBB. Malavolti et al. (1991) indicate the presence of unexpectedly close communications between extracerebral and brain cholesterol. Changes in the extracerebral cholesterol levels are readily sensed by the LDL receptor in the brain and promptly provoke appropriate modifications in its activity. Méresse et al. (1989a) provided direct evidence for the occurrence in vivo of an LDL receptor on the endothelium of brain capillaries. Furthermore, the fact that enzymes involved in the lipoprotein metabolism are present in the brain microvasculature (Brecher and Kuan, 1979) and that the entire fraction of the drug bound to lipoproteins is available for entry into the brain strongly suggest that this cerebral endothelial receptor plays a role in the interaction of plasma lipoproteins with brain capillaries. These results pinpoint the critical importance of the interactions between brain capillary ECs and lipoproteins. Owing to the fact that the neurological abnormalities that result from the inadequate absorption of dietary vitamin E can be improved by the oral administration of pharmacological doses of vitamin E, Traber and Kayden (1984) have suggested that LDL functions as a transport system for tocopherol to the brain. Furthermore, the trace amounts of apolipoprotein B that were detected by Salem et al. (1987) in cerebrospinal fluid from healthy patients using a very sensitive immunoblot technique confirm that, at most, small amounts of apolipoprotein B normally pass through the BBB. However, whether LDL is involved in the exchange is not known.Using an in vitro model of the BBB that imitates an in vivo situation by culturing capillary ECs and astrocytes on opposite sides of a filter (Dehouck et al., 1990a
, 1992), we have demonstrated that in culture, like in vivo, in contrast to peripheral endothelium and in spite of the tight apposition of ECs and their contact with physiological concentrations of lipoproteins, brain capillary ECs express an LDL receptor (Méresse et al., 1991; Dehouck et al., 1994). The capacity of ECs to bind LDLs is greater when cocultured with astrocytes than in their absence. Futhermore, we have shown that the lipid requirement of astrocytes increases the expression of the LDL receptor on brain capillary ECs. Taken together, the presence of LDL receptors on brain capillary ECs and the modulation of the expression of these receptors by the lipid composition of astrocytes suggest that cholesterol used by cells in the central nervous system may be derived, at least in part, from the periphery via transport across the BBB.In the present study, we provide direct evidence that after binding to brain capillary ECs, there is a specific mechanism for the transport of LDL across the endothelial monolayer from the apical to the abluminal surface. This mechanism might be best explained by a process of receptor-mediated transcytosis. Preliminary results pinpoint the role of caveolae in the transcellular transport of LDL across the brain endothelium. 相似文献
6.
Joelle E. Romanchik Earl H. Harrison Diane W. Morel 《The Journal of nutritional biochemistry》1997,8(12):681-688
Carotenoids are dietary antioxidants transported with plasma lipoproteins, primarily low-density lipoprotein (LDL). In this study in vitro methods were used to increase the amounts of specific, individual carotenoids in LDL. By addition of carotenoid to isolated LDL or to serum, followed by (re)isolation of the lipoproteins, samples of LDL were enriched 4- to 150-fold with lutein, 2- to 15-fold with lycopene, or 3- to 25-fold with β-carotene. Enrichment with specific carotenoids was achieved without affecting the electrophoretic mobility of the lipoprotein, its cholesterol to protein ratio, or the levels of other cartenoids or -tocopherol. The distributions among lipoproteins of carotenoid added to serum were similar, but not identical, to the distributions of the endogenous carotenoids. In particular, for added lutein, a greater proportion was found in HDL, and for added β-carotene, more was found in very low-density lipoprotein (VLDL). We then studied the effect of enriching LDL with specific carotenoids on its susceptibility to oxidation by copper ions. Lutein, β-cryptoxanthin, lycopene, and β-carotene, the four major plasma carotenoids, and -tocopherol were destroyed before the formation of lipid peroxidation products. The rates of destruction of the individual carotenoids differed; lycopene was destroyed most rapidly and lutein most slowly. Upon oxidation of β-carotene-enriched LDL, the rates of destruction of β-carotene, lycopene, and lutein were slowed and the lag times before the initiation of lipid peroxidation increased from 19 to 65 min. Neither effect was observed in LDL enriched with lutein or lycopene. Thus, β-carotene was unique among the carotenoids studied in having a small, but significant effect on LDL oxidation in vitro. 相似文献
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应用人血清清蛋白代替LDS,建立了肝素释放细胞表面与受体结合的LDL的方法,并比较了人及家兔LDL结合家兔细胞表面受体的能力。在37℃不同保温时间(从0—180分钟),肝素释放的细胞表面受体~(125)I-LDL量增加缓慢而通过受体进入细胞的LDL量增加迅速。在37℃以不同剂量的LDL(13—78μg/ml)与细胞保温2小时,肝素释放的细胞表面受体LDL量也增加缓慢,而进入细胞的量增加更为迅速。结果显示LDL在细胞表面受体部位不断进入细胞内并迅速被新的LDL分子所取代,但当LDL增至78μg/ml时逐渐变慢,与Goldstein观察相似。肝素释放的~(125)LDL量在加入量约50 μg/ml时呈现平坦,与Goldstein观察相似。这说明用人血清清蛋白代替LDS同样可以观察到LDL受体的饱和特性。在同一实验条件下。肝素释放家兔的~(125)I-LDL比人高l倍,家兔通过受体进入细胞的~(125)I-LDL比人高1.7倍。二者差别非常显著(P<0.001)。显示兔血清LDL的结构可能在某些方面不同于人。 相似文献
9.
LDL受体对清道夫受体活性的影响 总被引:1,自引:0,他引:1
应用经PMA诱导衍生的THP-1巨噬细胞为模型,以单克隆抗体C7B封闭oxLDL上的LDL受体结合位点,结果发现,正常细胞在摄取oxLDL时LDL受体与清道夫受体起协同作用;但C7B作用于蓄积了脂质的THP-1巨噬细胞时,对细胞脂质蓄积程度无明显影响,清道夫受体活性不但不降低反而有所升高,说明由于脂质蓄积LDL受体的作用减弱。 相似文献
10.
应用经PMA诱导衍生的THP-1巨噬细胞为模型,以单克隆抗体C7B封闭oxLDL上的LDL受体结合位点,结果发现,正常细胞在摄取oxLDL时LDL受体与清道夫受体起协同作用;但C7B作用于蓄积了脂质的THP-1巨噬细胞时,对细胞脂质蓄积程度无明显影响,清道夫受体活性不但不降低反而有所升高,说明由于脂质蓄积LDL受体的作用减弱. 相似文献
11.
胆固醇是动物细胞细胞膜的重要组成成分,其做为细胞和环境之间的屏障调节细胞膜的流动性。胆固醇是体内所有的类固醇激素和胆酸合成的前体物质,参与体内代谢。同时胆固醇在神经系统的发育中也起着重要的作用。在血浆中胆固醇以低密度脂蛋白和高密度脂蛋白这两种胆固醇运载血脂蛋白的形式运输。动物细胞通过细胞表面的低密度脂蛋白受体(LDL receptor,LDLR)介导的内吞可以从血液中摄取富含胆固醇的低密度脂蛋白,当细胞表面的LDLR的功能缺陷时,可以导致高胆固醇血症,继而引起动脉粥样硬化、冠心病和中风等严重疾病。本文综述了LDL受体的概述及其通过内吞调节血液中低密度脂蛋白胆固醇水平的作用,并对LDL受体的调节进行了阐述。 相似文献
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牛肾上腺皮质LDL受体经Triton X-100增溶,DEAE32离子交换柱和LpB Sepharose亲和柱层析,在SDS-PAGE中有三条区带,分别在原点;Mr 160kD;Mr125kD处。进一步用8%SDS-PAGE纯化三个区带的蛋白质分别免疫新西兰大白兔所得的抗体,应用免疫印迹和ECL非同位素标记法可对牛肾上腺皮质和人皮肤纤维细胞膜上的LDL受体进行测定。 相似文献
14.
结合应用激光扫描共聚焦显微镜系统(LSCM)和DiI-AcLDL及BODIPY FL-LDL两种荧光配基选择性标记技术,可在单细胞水平上同时测定LDL受体和清道夫受体活性.C57BL/6J小鼠巨噬细胞用终浓度为5mg/L的 DiI-AcLDL及BODIPY FL-LDL,在37℃负载5 h左右的条件下可获得良好的标记效果.两种荧光配基选择性标记具有高度特异性,在激光共聚焦显微镜下可清晰、定量地观察细胞对LDL和AcLDL摄入,是一种灵敏度高且可定量研究LDL受体和清道夫受体功能的非同位素方法. 相似文献
15.
牛肾上腺皮质LDL受体经Triton X-100增溶,DEAE_(32)离子交换柱和LpB Sepharose亲和柱层析,在SDS-PAGE中有三条区带,分别在原点;Mr 160kD;Mr125kD处。进一步用8%SDS-PAGE纯化三个区带的蛋白质分别免疫新西兰大白兔所得的抗体,应用免疫印迹和ECL非同位素标记法可对牛肾上腺皮质和人皮肤纤维细胞膜上的LDL受体进行测定。 相似文献
16.
Anne Nègre-Salvayre Laurence Mabile Jean Delchambre Robert Salvayre 《Biological trace element research》1995,47(1-3):81-91
Low-density lipoproteins (LDL) mildly oxidized by copper ions or UV radiations exhibit a cytotoxic effect to cultured endothelial
cells. Rutin, a polyphenolic flavonoid, ascorbic acid, and α-tocopherol were able to inhibit the peroxidation of LDL and their
subsequent cytotoxicity. The mixture of the three compounds (rutin/ascorbic acid/α-tocopherol, 4/4/1) exhibited a supra-additive
antioxidant effect. The inhibition of the cytotoxic effect was well correlated with that of TBARS formation. Another important
conclusion is that these antioxidants were able to prevent directly at the cellular level the cytotoxic effect of oxidized
LDL, since cells preincubated with them were protected against the cytotoxic effect of previously oxidized LDL. The protective
effect of antioxidants was limited because of their own toxicity. The antioxidant mixture permitted a maximal cytoprotective
effect with relatively lower concentrations to be obtained and the cytotoxicity of high concentrations to be avoided. In conclusion,
rutin, ascorbic acid, and α-tocopherol constitute two lines of defense in protecting cells against injury owing to oxidation
of LDL (1) at the LDL level, by inhibiting the LDL oxidation and the subsequent cytotoxicity, and (2) at the cellular level,
by protecting the cells directly, i.e., by increasing their resistance against the cytotoxic effect of oxidized LDL. 相似文献
17.
This article puts forward the hypothesis that the Low Density Lipid Receptor (LDLR) is one of the molecules that is involved in the clearance of amyloid proteins in the brain and that it may play a role in Alzheimer’s Disease (AD) via its up-regulation by statins. The hypothesis is built on the following observations: a-statins (which have been shown to increase LDLR in astrocytes, see below) have a beneficial role in AD, b-defects in the LDL receptor gene are found in AD, c-molecules with similar structure to the LDLR have been shown to clear amyloid protein from the brain. 相似文献
18.
氧化修饰LDL诱导U937细胞凋亡及其机制探讨 总被引:6,自引:0,他引:6
用氧化修饰低密度脂蛋白(ox-LDL)诱导人髓系白血病细胞株U937细胞凋亡,并研究其作用机制.用脱氧核苷酸转移酶介导的dUTP切口末端标记技术(TUNEL法)、流式细胞仪和DNA断裂分析检测细胞凋亡;用免疫组化检测c-fos、c-jun和c-myc蛋白表达,RT-PCR显示c-fos、c-jun和c-myc mRNA表达水平.结果表明ox-LDL可致U937细胞凋亡,其作用具有浓度效应;ox-LDL可以上调c-fos、c-jun和c-myc基因表达,使c-fos、c-jun和c-myc蛋白合成增多,最终诱导U937细胞凋亡. 相似文献
19.
Prasad K McNair ED Qureshi AM Casper-Bell G 《Molecular and cellular biochemistry》2012,361(1-2):181-187
Lycopene is a lipophilic antioxidant that is largely transported in human blood by Low Density Lipoproteins (LDL). One of the early events in the aetiology of atherosclerosis is thought to be the oxidation of LDL. Myeloperoxidase an enzyme secreted by neutrophils and macrophages is thought to oxidise human LDL particles. In this study, isolated human LDL was challenged with myeloperoxidase or copper, and the LDL was screened for lipoperoxidation and oxidation of apolipoprotein B100, depletion of lycopene and oxidation of cholesterol. Myeloperoxidase induced oxidation of LDL through direct interaction with apolipoprotein B100. No lipoperoxidation was observed following myeloperoxidase treatment; however, 7-ketocholesterol was detected indicating the products of myeloperoxidase interact with the surface of the LDL particles. Lycopene does react with the products of myeloperoxidase in solvent, but played no role in protecting against enzyme derived oxidation of human LDL. 相似文献
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