首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
《Free radical research》2013,47(5-6):307-313
Oxidation-induced increase of the net negative charge on low-density lipoprotein was studied by electro-phoretic mobility and by electron paramagnetic resonance. The negative-charge increase is associated not only with neutralization of the lysine residues of apoprotein B, but also with the exposition of the excessive negatively charged residues on the lipoprotein surface. The accumulation of the negatively charged residues is believed to be brought about by the conformational change of apoprotein B, triggered by neutralization of lysines and cleavage of peptide bonds. Alternatively, reactive oxygen species could also convert histidine to aspartic acid and proline to glutamic acid.  相似文献   

2.
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.  相似文献   

3.
A stereo controlled synthesis of the biologically active neolignan, (+)-dehydrodiconiferyl alcohol (1) was achieved. This synthetic method was also efficient for preparing its enantiomer and other derivatives with biological activity.  相似文献   

4.
Neopterin and its reduced form, 7,8 dihydroneopterin afe pteridines released from macrophages and monocytes when stimulated with interferon gamma in vivo. The function of this response is unknown though there is an enormous amount of information available on the use of these compounds as clinical markers of monocyte/macrophage activation. We have found that in vitro 7,8-dihydroneopterin dramatically increases, in a dose dependent manner, the lag time of low density lipoprotein oxidation mediated by Cu++ ions or the peroxyl radical generator 2,2'-azobis (2-amidino propane) dihydrochloride (AAPH). 7,8-Dihydroneopterin also inhibits AAPH mediated oxidation of linoleate. The kinetic of the inhibition suggests that 7,8-dihydroneopterin is a potent chain breaking antioxidant which functions by scavenging lipid peroxyl radicals. No anti-oxidant activity was observed in any of the oxidation systems studied with the related compounds neopterin and pterin.  相似文献   

5.
The extent to which cells can oxidize LDL may be underestimated because of the use of standard and arbitrary 24 hour in vitro incubations of cells with LDL. Such incubations have resulted in inconsistent results regarding the ability of cell-mediated LDL oxidation to generate relatively advanced oxidation products such as 7-ketocholesterol (7-KC). We studied prolonged oxidation of low density lipoprotein (LDL) by mouse peritoneal macrophages using HPLC measurement of cholesterol, cholesteryl esters and their oxidation products 7-KC and cholesteryl linoleate hydroperoxide (CL-OOH). Cell-mediated oxidation in Ham's F10 consistently followed the successive stages previously described during 24 hour-10 μM copper-mediated LDL oxidation, always generating 7-KC if allowed to proceed for sufficient time. The degree of inhibition of LDL oxidation achieved by metal chelators EDTA and DTPA at more advanced stages of cell-mediated LDL oxidation was not predictable from the published effects of such chelators upon early stages of metal-mediated and cell-mediated LDL oxidation. EDTA and DTPA only incompletely prevented the consumption of cholesteryl esters and the loss of preformed CL-OOH when added after cell-mediated LDL oxidation was established, while effectively concurrently inhibiting the generation of 7-KC. These data indicate that progressive cell-mediated peroxidation of LDL cholesteryl esters and decomposition of CL-OOH may be less dependent upon a continuing supply of redox active metals than is the generation of 7-KC. In addition, they confirm the plausibility of prolonged cell-mediated oxidation of LDL as a source of oxysterols found in human atherosclerotic plaque, and imply that active redox cycling of metals is particularly important for their generation in vivo.  相似文献   

6.
Apolipoprotein C-II (apoC-II) is the co-factor for lipoprotein lipase (LPL) at the surface of triacylglycerol-rich lipoproteins. LPL hydrolyzes triacylglycerol, which increases local surface pressure as surface area decreases and amphipathic products transiently accumulate at the lipoprotein surface. To understand how apoC-II adapts to these pressure changes, we characterized the behavior of apoC-II at multiple lipid/water interfaces. ApoC-II adsorption to a triacylglycerol/water interface resulted in large increases in surface pressure. ApoC-II was exchangeable at this interface and desorbed on interfacial compressions. These compressions increase surface pressure and mimic the action of LPL. Analysis of gradual compressions showed that apoC-II undergoes a two-step desorption, which indicates that lipid-bound apoC-II can exhibit at least two conformations. We characterized apoC-II at phospholipid/triacylglycerol/water interfaces, which more closely mimic lipoprotein surfaces. ApoC-II had a large exclusion pressure, similar to that of apoC-I and apoC-III. However, apoC-II desorbed at retention pressures higher than those seen with the other apoCs. This suggests that it is unlikely that apoC-I and apoC-III inhibit LPL via displacement of apoC-II from the lipoprotein surface. Upon rapid compressions and re-expansions, re-adsorption of apoC-II increased pressure by lower amounts than its initial adsorption. This indicates that apoC-II removed phospholipid from the interface upon desorption. These results suggest that apoC-II regulates the activity of LPL in a pressure-dependent manner. ApoC-II is provided as a component of triacylglycerol-rich lipoproteins and is the co-factor for LPL as pressure increases. Above its retention pressure, apoC-II desorbs and removes phospholipid. This triggers release of LPL from lipoproteins.  相似文献   

7.
Purpose The low-density lipoprotein receptor (LDLr) mediates the uptake of LDL particles enriched with cholesterol, into several tissues. In contrast to other tissues, the brain is thought to obtain cholesterol solely by de novo synthesis, yet certain brain regions such as the brainstem are highly enriched with the LDLr. The goal of the present study was to assess the role of the LDLr in maintaining cholesterol concentrations in the brainstem of wildtype and LDLr knockout (LDLr−/−) mice. Cholesterol concentrations were also measured in the cortex, which served as a reference point, due to the lower expression of the LDLr, as compared to the brainstem. Methods LDLr−/− and wildtype mice consumed an AIN-93G diet ad libitum until 7 weeks of age. After microwaving, the cortex and anterior brain stem were isolated for cholesterol analysis. Cholesterol was extracted into chloroform/methanol, derivatized in trimethylsilyl chloride and measured by gas chromatography/mass spectrometry. Results Concentrations of cholesterol in the brainstem did not differ statistically between LDLr−/− (18.8 ± 1.6 mg/g wet weight brain) and wildtype (19.1 ± 2.0). Cortical cholesterol concentrations also did not differ statistically between LDLr−/− (11.0 ± 0.4 mg/g wet weight brain) and wildtype (11.1 ± 0.2) mice. Conclusion The LDLr is not necessary for maintaining cholesterol concentrations in the cortex or brainstem, suggesting that other mechanisms are sufficient to maintain brain cholesterol concentrations.  相似文献   

8.
The human hepatoblastoma cell line HepG2 is a liver model commonly used for lipid metabolism studies. Numerous cell types have been found to oxidize low-density lipoprotein (LDL) but, to our knowledge, the effects of HepG2 cells on LDL have not been investigated. We found that LDL is modified by HepG2 cells through a peroxidative mechanism, as judged by an increase in TBARS content (which was prevented in the presence of the antioxidants vitamin E, 2, 6-di-tert-butyl-cresol and probucol), increased degradation by J774 macrophages, decreased internalization by MRC5 fibroblasts, and aggregation of apo B. Aspirin and allopurinol, which inhibit cyclooxygenase and xanthine-oxidase activities, respectively, had no effect on HepG2-induced LDL modification, and neither did catalase, which dismutates hydrogen peroxide; or mannitol, which scavenges hydroxyl radicals. In contrast, superoxide dismutase, a superoxide anion scavenger, and glutamate and threonine, which alter cellular cystine uptake, prevented LDL modifications, as did the removal of cysteine/cystine from the culture medium. Oxidation of LDL by HepG2 cells might thus involve superoxide anion production and/or thiol metabolism.  相似文献   

9.
Novel missense mutation G571E (c.1775 G > A), novel silent mutation H229H (c.750 C > T), and nonsense mutation C74X (c.285 C > A), earlier described in Japan but unknown in Russia, were identified in the low-density lipoprotein (LDL) receptor gene in St. Petersburg familial hypercholesterolemia patients. The analyzed group of patients was shown to be polymorphic in many positions of the LDL receptor gene, namely, c.1171 G/A, c.1773 T/C, c.2177 C/T, and c.2231 G/A.  相似文献   

10.
Oxidation of low-density lipoprotein (LDL) by reactive oxygen species (ROS) and reactive nitrogen species (RNS) has been suggested to be involved in the onset of atherosclerosis. Oolong tea contains unique polyphenols including oolonghomobisflavan A (OFA). In this study, the effects of OFA on LDL oxidation by ROS and RNS were investigated in vitro. OFA suppressed formation of cholesterol ester hydroperoxides in LDL oxidized by peroxyl radical and peroxynitrite, and formation of thiobarbituric acid reactive substances in LDL oxidized by Cu2+. In addition, OFA inhibited fragmentation, carbonylation, and nitration of apolipoprotein B-100 (apo B-100) in the oxidized LDL, in which heparin-binding activity of apo B-100 was protected by OFA. Our results suggest that OFA exhibits antioxidant activity against both lipid peroxidation and oxidative modification of apo B-100 in LDL oxidized by ROS and RNS. Polyphenols in oolong tea may prevent atherosclerosis by reducing oxidative stress.  相似文献   

11.
An animal study was carried out to examine the beneficial influence of the known hypocholesterolemic spice principle-capsaicin on the susceptibility of low-density lipoprotein to oxidation in normal and hypercholesterolemic condition. In rats rendered hypercholeterolemic by maintaining them on a cholesterol-enriched diet for eight weeks, inclusion of capsaicin (0.015%) in the diet, produced significant hypocholesterolemic effect. Oxidation of low-density lipoprotein was induced either by copper ion in vitro after its isolation, or by ferrous ion in vivo in experimental rats under either normal or hypercholesterolemic situation and the beneficial effect of dietary capsaicin on the same was evaluated. LDL oxidation was measured by the thiobarbituric acid reactive substances (TBARS) formed and relative electrophoretic mobility of oxidized LDL. Dietary capsaicin was found to be protective to the LDL oxidation in vitro in the case of normal rats as indicated by reduction in TBARS by more than 40%. In the case of LDL isolated from hypercholesterolemic rats the extent of copper induced LDL oxidation was significantly lower than that of LDL isolated from normal rats. Dietary capsaicin did not make any difference in the extent of LDL oxidation in vitro in hypercholesterolemic rats. Ferrous ion induced in vivo oxidation of LDL was 71% lower in capsaicin fed normal rats. In high cholesterol feeding, Fe-induced in vivo oxidation of LDL was 73% lower, while the same was still marginally lower in capsaicin fed hypercholesterolemic rats. Hepatic lipid peroxidation was significantly decreased by dietary capsaicin in normal rats. While a significantly decreased level of lipid peroxidation was observed in hypercholesterolemic rats compared to normal rats, the same was not significantly altered by dietary capsaicin. Results suggest that dietary spice principle capsaicin is protective to LDL oxidation both in vivo and in vitro under normal situation, while in hypercholesterolemic situation where the extent of LDL oxidation is already lowered, capsaicin does not offer any further reduction.  相似文献   

12.
GPIHBP1 is an endothelial membrane protein that transports lipoprotein lipase (LPL) from the subendothelial space to the luminal side of the capillary endothelium. Here, we provide evidence that two regions of GPIHBP1, the acidic N-terminal domain and the central Ly6 domain, interact with LPL as two distinct binding sites. This conclusion is based on comparative binding studies performed with a peptide corresponding to the N-terminal domain of GPIHBP1, the Ly6 domain of GPIHBP1, wild type GPIHBP1, and the Ly6 domain mutant GPIHBP1 Q114P. Although LPL and the N-terminal domain formed a tight but short lived complex, characterized by fast on- and off-rates, the complex between LPL and the Ly6 domain formed more slowly and persisted for a longer time. Unlike the interaction of LPL with the Ly6 domain, the interaction of LPL with the N-terminal domain was significantly weakened by salt. The Q114P mutant bound LPL similarly to the N-terminal domain of GPIHBP1. Heparin dissociated LPL from the N-terminal domain, and partially from wild type GPIHBP1, but was unable to elute the enzyme from the Ly6 domain. When LPL was in complex with the acidic peptide corresponding to the N-terminal domain of GPIHBP1, the enzyme retained its affinity for the Ly6 domain. Furthermore, LPL that was bound to the N-terminal domain interacted with lipoproteins, whereas LPL bound to the Ly6 domain did not. In summary, our data suggest that the two domains of GPIHBP1 interact independently with LPL and that the functionality of LPL depends on its localization on GPIHBP1.  相似文献   

13.
Abstract: A primary histopathological feature of Alzheimer's disease is the accumulation of β-amyloid (Aβ) in the brain of afflicted individuals. However, Aβ is produced continuously as a soluble protein in healthy individuals where it is detected in serum and CSF, suggesting the existence of cellular clearance mechanisms that normally prevent its accumulation and aggregation. Here, we demonstrate that Aβ forms stable complexes with activated α2-macroglobulin (α2M), a physiological ligand for the low-density lipoprotein receptor-related protein (LRP) that is abundantly expressed in the CNS. These α2M/125I-Aβ complexes are immunoreactive with both anti-Aβ and anti-α2M IgG and are stable under various pH conditions, sodium dodecyl sulfate, reducing agents, and boiling. We demonstrate that α2M/125I-Aβ complexes can be degraded by glioblastoma cells and fibroblasts via LRP, because degradation is partially inhibited by receptor-associated protein (RAP), an antagonist of ligand interactions with LRP. In contrast, the degradation of free 125I-Aβ is not inhibited by RAP and thus must be mediated via an LRP-independent pathway. These results suggest that LRP can function as a clearance receptor for Aβ via a physiological ligand.  相似文献   

14.
Hemopexin, a heme-binding serum glycoprotein, is thought to play an important role in the prevention of oxidative damage that may be catalysed by free heme. Through the use of EPR techniques, the generation of free radicals from organic hydroperoxides by heme and heme-hemopexin complexes, and the concomitant formation of high oxidation-state iron species has been studied; these species are implicated as causative agents in processes such as cardiovascular disease and carcinogenesis. From the rates of production of these species from both n-alkyl and branched hydroperoxides, it has been inferred that the dramatic reduction in the yield of oxidising species generated by heme upon its complexation with hemopexin arises from steric hindrance of the access of hydroperoxide to the bound heme.  相似文献   

15.
16.
Particulate matter2.5 (PM2.5) is notorious for its strong toxic effects on the cardiovascular, skin, nervous, and reproduction systems. However, the molecular mechanism by which PM2.5 aggravates disease progression is poorly understood, especially in a water-soluble state. In the current study, we investigated the putative physiological effects of aqueous PM2.5 solution on lipoprotein metabolism. Collected PM2.5 from Seoul, Korea was dissolved in water, and the water extract (final 3 and 30 ppm) was treated to human serum lipoproteins, macrophages, and dermal cells. PM2.5 extract resulted in degradation and aggregation of high-density lipoprotein (HDL) as well as low-density lipoprotein (LDL); apoA-I in HDL aggregated and apo-B in LDL disappeared. PM2.5 treatment (final 30 ppm) also induced cellular uptake of oxidized LDL (oxLDL) into macrophages, especially in the presence of fructose (final 50 mM). Uptake of oxLDL along with production of reactive oxygen species was accelerated by PM2.5 solution in a dose-dependent manner. Further, PM2.5 solution caused cellular senescence in human dermal fibroblast cells. Microinjection of PM2.5 solution into zebrafish embryos induced severe mortality accompanied by impairment of skeletal development. In conclusion, water extract of PM2.5 induced oxidative stress as a precursor to cardiovascular toxicity, skin cell senescence, and embryonic toxicity via aggregation and proteolytic degradation of serum lipoproteins.  相似文献   

17.
Boundary element methods are used to model the free solution electrophoretic mobility of short DNA fragments. The Stern surfaces of the DNA fragments are modeled as plated cylinders that reproduce translational and rotational diffusion constants. The solvent-accessible and ion-accessible surfaces are taken to be coincident with the Stern surface. The mobilities are computed by solving simultaneously the coupled Navier–Stokes, Poisson, and ion-transport equations. The equilibrium electrostatics are treated at the level of the full Poisson–Boltzmann equation and ion relaxation is included. For polyions as highly charged as short DNA fragments, ion relaxation is substantial. At .11 M KCl, the simulated mobilities of a 20 base pair DNA fragment are in excellent agreement with experiment. At .04 M Tris acetate, pH = 8.0, the simulated mobilities are about 10–15% higher than experimental values and this discrepancy is attributed to the relatively large size of the Tris counterion. The length dependence of the mobility at .11 M KCl is also investigated. Earlier mobility studies on lysozyme are reexamined in view of the present findings. In addition to electrophoretic mobilities, the effective polyion charge measured in steady state electrophoresis and its relationship to the preferential interaction parameter γgG is briefly considered. © 1998 John Wiley & Sons, Inc. Biopoly 46: 359–373, 1998  相似文献   

18.
Abstract: Both apolipoprotein E (apoE) and the low-density lipoprotein (LDL) receptor are present in brain; however, little is known regarding the function of these proteins in brain, in particular with respect to brain cholesterol. The role of apoE and the LDL receptor in modulating the transbilayer or asymmetric distribution of cholesterol in the exofacial and cytofacial leaflets of synaptic plasma membranes (SPMs) was examined in mutant mice deficient in apoE, the LDL receptor, or both proteins by using the fluorescent sterol dehydroergosterol and fluorescent quenching procedures. Fluidity of the exofacial and cytofacial leaflets was also measured. Cholesterol asymmetry of SPMs was altered in the mutant mice, with the largest effect observed in the LDL receptor-deficient mice. There was an approximately twofold increase in the percent distribution of cholesterol in the exofacial leaflet of the LDL receptor-deficient mice (32%) compared with C57BL/6J mice (15%). Mice deficient in apoE or both proteins also showed a significantly higher percent distribution of cholesterol (23 and 26%, respectively) in the exofacial leaflet compared with the C57BL/6J mice. Although the percent distribution of cholesterol was highest in the exofacial leaflet of the LDL receptor-deficient mice, fluidity of the exofacial leaflet of that group was significantly lower. However, the cholesterol-to-phospholipid ratio of SPMs of the LDL receptor-deficient mice was significantly lower, and this difference was largely the result of a significant increase in the total amount of SPM phospholipid. This study demonstrates for the first time that SPM lipid structure is altered in mice deficient in apoE or the LDL receptor. Although the mechanism that maintains the asymmetric distribution of cholesterol in plasma membranes is not well understood, data of the present experiments indicate that both apoE and the LDL receptor are involved in maintaining the transbilayer distribution of cholesterol.  相似文献   

19.
人血浆低密度脂蛋白亚组分氧化反应敏感性的比较   总被引:6,自引:0,他引:6  
本文对3种LDL亚组分在体外对Cu^2+催化氧化反应敏感性进行了比较。结果表明,随氧化时间延长,各LDL亚组分的电泳迁移率均增加。测定脂质过氧化物的含量以及用结合二烯法测定氧化反应的潜伏期,发现较高密度的LDL亚组分更易氧化。荧光免疫测定结果显示,较高密度LDL中载脂蛋白B上新生的4-羟壬烯醛抗原决定簇的表达高于较低密度的LDL,从而证明较高密度的LDL亚组分对氧化反应的敏感性高于较低密度的亚组分  相似文献   

20.
Ansamitocins in combination with amphotericin B produced synergistic inhibition on the growth of several yeasts in liquid cultures, Ansamitocin P–3 at 5 µg/ml completely suppressed the growth of Saccharomyces cerevisiae whereas ansamitocin P–3 alone at 50 µg/ml hardly affected growth. Ansamitocin P–4 and maytansine also showed synergistic activity with amphotericin B against S. cerevisiae. The synergism also occurred in cultures of Candida albicans and Hansenula anomala. Combinations of ansamitocin P–3 with various agents revealed that the synergism depended on the specific property of amphotericin B. Ansamitocins showed no interfering activity against regeneration of protoplasts of S. cerevisiae. These results suggest that the limited activity of ansamitocins against these yeasts is due to the membrane permeability barrier of these cells.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号