Genetics of a low-density lipoprotein allotype in a cattle.

The paper describes a cattle serum antigen (LdlA1) located on a low-density lipoprotein and detected by single radial diffusion. The specificity is inherited in a simple Mendelian manner and the gene controlling its synthesis is inherited independently from the one controlling the synthesis of the alpha 2 macroglobulin McA1 antigen.     

Effects of oolonghomobisflavan A on oxidation of low-density lipoprotein

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.     

Immunogenetic study on the polymorphism of serum α2-lipoprotein in mink. III. Ld1 allotype of low-density lipoprotein

Mink Ld1 antigen of serum low-density lipoprotein was demonstrated by alloantibodies. No genetic relation was found between Ld1 and the Lpm system of very-high-density lipoprotein. The existence of an autosomal dominant gene, coding for the new alloantigenic marker, is postulated on the basis of mink breeding data.     

Characterization of experimental cattle populations from Argentina with a low-density SNP genotyping panel

The objectives of the present experiment were to evaluate a low-density SNP array designed for the molecular characterisation of gene banks and to assess the genetic diversity and population structure of beef cattle herds from an Argentinean research station. Forty-nine animals from three breeds (Angus, Hereford, and Argentinean Creole) were genotyped using the multi-species IMAGE001 60-K SNP array (10 K for cattle). Genotypes of other 19 cattle populations from Argentina, other American countries, and Europe were included in the study. Of special interest was the characterization of the Argentinean Creole, the only autochthonous cattle breed in the country. Due to the merging of different datasets, approximately 5 K SNPs were effectively used. Genetic differentiation (F_ST), principal component analysis, neighbour-joining tree of Reynolds distances and ancestry analysis showed that autochthonous American breeds are clearly differentiated, but all have genetic influences of Iberian cattle. The analysed herds of Argentinean Creole showed no evidence of recent admixture and represent a unique genetic pool within local American breeds. An experimental herd and the local commercial Hereford population have also diverged, probably due to the influence of current selection objectives in the breed. Our results illustrate the utility of using low-cost, low density SNP arrays in the evaluation of animal genetic resources. This type of panels could become a very useful resource in developing countries, where most endangered cattle breeds are located. The results also reinforce the importance of experimental herds as reservoir of genetic diversity, particularly in the case of local breeds under-represented in traditional production systems.     

Protective effect of dietary capsaicin on induced oxidation of low-density lipoprotein in rats

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.     

Crystallization and preliminary X-ray diffraction data of two different human low-density lipoprotein (LDL) subfractions

Human LDL subfractions LDL-2 (d = 1.031–1.034 g/ml) and LDL-5 (d = 1.040–1.044 g/ml) were crystallized in two different crystal forms by using polyethylene glycol as a precipitant. Both fractions were from one donor. Crystals of LDL-5 were yellow, hexagonal, and showed no dichroism. Crystals of LDL-2 were of the same color, had a rodlike shape with notches at both ends, and were highly dichroitic. LDL-2 crystals diffracted to a resolution of 29 Å by using synchrotron radiation. Indexing in P1 resulted in preliminary parameters for the reduced cell of a = 171 Å, b = 438 Å, c = 519 Å, α = 102°, β = 99°, γ = 91. These dimensions are consistent with the size of LDL particles. Using Fourier transform infrared spectroscopy (FTIR) and agarose gel electrophoresis, we could further confirm that the crystals consist of LDL. The FTIR spectrum showed bands characteristic for lipids and protein. Dissolved crystals exhibited a mobility similar to native LDL in agarose gels and could be stained with anti-human apolipoprotein B (apoB). Proteins 28:293–297, 1997. © 1997 Wiley-Liss Inc.     

M41型A群链球菌的Ⅰ型胶原样蛋白与人低密度脂蛋白的相互作用

【目的】检测M41型A群链球菌(GAS)ATCC12373中Ⅰ型胶原样蛋白(Scl1)与人低密度脂蛋白(LDL)的相互作用。【方法】克隆了M41型GAS ATCC12373的Ⅰ型胶原样蛋白(Scl1)及其V区(Scl1-V)基因,并表达、纯化重组蛋白rScl1(C176)和rScl1-V(C176V)。通过重组蛋白与人血浆的亲和色谱层析、Western blot及酶联免疫吸附试验(ELISA)检测C176、C176V与LDL的相互作用;通过GAS与LDL的ELISA试验和人血浆与GAS的共孵育试验,检测GAS与LDL的相互作用。【结果】结果证明C176和C176V可以与LDL特异性结合;表达Scl1的M41型GAS可以与LDL相结合。【结论】M41型GAS的Scl1可以与LDL特异性结合。     

Dissociation of apoptosis induction and CD36 upregulation by enzymatically modified low-density lipoprotein in monocytic cells.

Modified low-density lipoprotein (LDL) has been implicated as an initiating or amplifying factor in atherogenesis. Some of its biological activities, such as apoptosis induction and upregulation of the scavenger receptor CD36, appear to share common signaling pathways in cells of the cardiovascular system. Exposure of low-differentiated monocytic cells to LDL modified with 15-lipoxygenase and secretory phospholipase A(2) induced apoptosis and upregulated CD36. Cell treatment with constituents of modified LDL, such as 13-hydroxyoctadecadienoic acid (13-HODE), 25-hydroxycholesterol, and lysophosphatidyl choline, and with an unrelated apoptogen (TNF-related apoptosis-inducing ligand) induced apoptosis. In contrast, only 13-HODE caused upregulation of CD36 expression. Cotreatment with the pan-caspase inhibitor z.VAD-fmk resulted in suppression of apoptosis, but was without any effect on CD36 expression. These data indicate that in monocytic cells enzymatically modified LDL is capable of inducing both apoptosis and upregulation of CD36 expression. However, in our cellular model, the two induction processes appear to be causally unrelated.     

Inhibition of lymphocyte mitogenesis by autoxidized low-density lipoprotein.

Mitogenic stimulation of lymphocytes is significantly inhibited by addition of human serum low-density lipoprotein that has undergone autoxidation, while no significant effect is seen with non-oxidized lipoprotein. The inhibition is effective for cells stimulated either by the plant lectin phytohemagglutinin or enzymatically by neuraminidase-galactose oxidase treatment. However, it is markedly attenuated when oxidized LDL is added to cells which have been triggered 24 hours earlier. Lipid extracts from oxidized LDL are similarly inhibitory, indicating that the effect is mediated by an oxidized lipid fraction.     

Involvement of the low-density lipoprotein receptor-related protein in the transcytosis of the brain delivery vector angiopep-2

The blood–brain barrier (BBB) restricts the entry of proteins as well as potential drugs to cerebral tissues. We previously reported that a family of Kunitz domain-derived peptides called Angiopeps can be used as a drug delivery system for the brain. Here, we further characterize the transcytosis ability of these peptides using an in vitro model of the BBB and in situ brain perfusion. These peptides, and in particular Angiopep-2, exhibited higher transcytosis capacity and parenchymal accumulation than do transferrin, lactoferrin, and avidin. Angiopep-2 transport and accumulation in brain endothelial cells were unaffected by the P-glycoprotein inhibitor, cyclosporin A, indicating that this peptide is not a substrate for the efflux pump P-glycoprotein. However, competition studies show that activated α₂-macroglobulin, a specific ligand for the low-density lipoprotein receptor-related protein-1 (LRP1) and Angiopep-2 can share the same receptor. In addition, LRP1 was detected in glioblastomas and brain metastases from lung and skin cancers. Fluorescent microscopy also revealed that Alexa488-Angiopep-2 co-localized with LRP1 in brain endothelial cell monolayers. Overall, these results suggest that Angiopep-2 transport across the BBB is, in part, mediated by LRP1.     

A polymorphic antigen displaying different molecular weights in sheep and cattle sera

The polymorphic antigen Bl is present, exhibiting different molecular weights, in both sheep and cattle sera. The molecular weight of the antigen, purified from both sera by a specific immunoabsorbent, was analysed by SDS polyacrylamide gel electrophoresis and calibrated gel filtration. Results indicate that only one subunit, 35 000 MW, forms cattle Bl while a further subunit, 60 000 MW, is present in sheep Bl. The antigen activity is localized on the 35 000 MW subunit, which appears to be the same in both species.     

Phenolic antioxidants attenuate neuronal cell death following uptake of oxidized low-density lipoprotein

Oxidative stress is implicated in neuronal loss associated with neurodegeneration such as in Parkinson’s disease, Alzheimer’s disease and age-related cognitive decline. Recent reports indicate that the consumption of flavonoid-rich fruits partly reverses the age-related neuronal and cognitive decline. In this study, cultured striatal neurons were exposed to oxidized lipids in the form of low-density lipoprotein (oxLDL) as a model for the induction of oxidative injury, and the abilities of phenolic antioxidants, flavonoids and hydroxycinnamic acid derivatives, to attenuate this neuronal damage were examined. OxLDL was demonstrated to enter neuronal cells and to be capable of eliciting neurotoxicity in a dose- and time-dependent manner, inducing DNA fragmentation and cell lysis. Flavonoids exert protective effects, which appear to be related to specific structural characteristics, particularly relevant being those defining their reduction potentials and partition coefficients. In summary, these data suggest a possible role for flavonoids in reducing neurodegeneration associated with chronic disorders in which oxidative stress is implicated.     

NOS1-derived nitric oxide facilitates macrophage uptake of low-density lipoprotein

Foam cell formation is a hallmark event during atherosclerosis. The current paradigm is that lipid uptake by a scavenger receptor in macrophages initiates necrosis core formation that characterizes atherosclerosis. We report that NOS1-derived nitric oxide (NO) facilitates low-density lipoprotein (LDL) uptake by macrophages independent of the inflammatory response. LDL uptake could be dramatically suppressed by NOS1 specific inhibitor 1-(2-trifluoromethylphenyl) imidazole (TRIM). Importantly, the notion that NOS1 can mediate uptake of lipoproteins suggests that the foam cell formation is regulated by NOS1-derived NO-mediated mechanism. This is a novel study involving NOS1 as a critical player of foam cell formation and reveals much about the key molecular proteins involved in atherosclerosis. Targeting NOS1 would be a useful strategy in reducing LDL uptake by macrophages and hence dampening the atherosclerosis progression.     

Oxidized lipoprotein lipids and atherosclerosis

Plasma lipoproteins contain variable amounts of lipid oxidation products (LOP), which are known to impair normal physiological functions and stimulate atherosclerotic processes. Recent evidence indicates that plasma lipoproteins are active carriers of LOP, low-density lipoprotein (LDL) directing transport toward peripheral tissues, and high-density lipoprotein (HDL) being active in the reverse transport. It has been proposed that the lipoprotein-specific transport of LOP could play a role in atherosclerosis-related effects of LDL and HDL. This article gives an overview of the present knowledge of lipoprotein LOP transport and its association with the risk of atherosclerosis and cardiovascular diseases (CVD). Evidence of the significance of lipoprotein LOP transport comes mainly from studies of physiological oxidative stress and is supported by studies of the functionality apolipoprotein A-1 mimetic peptides. A large body of data has accumulated indicating that lipoprotein LOP transport is connected to the risk of atherosclerosis. While high levels of LOP carried by LDL are indicative of elevated risk, high LOP level in HDL appears to associate with protection. If confirmed, the proposed lipoprotein LOP transport function would affect conception of the etiology of atherosclerosis, but would not conflict current views of the pathophysiological mechanisms. It could open new perspectives, such as the dietary origin of LOP, and the protective function of HDL in clearance of LOP. Focusing on LOP could give additional tools especially for prevention and diagnosis, but would not radically change the management of atherosclerosis and CVD.     

C-reactive protein inhibits in vitro oxidation of low-density lipoprotein

C-reactive protein (CRP) is elevated in cardiovascular disease and binds to oxidized phosphatidylcholine (oxPtC) in the low-density lipoprotein (LDL) surface. In the present study, we tested if CRP influences the susceptibility of LDL to oxidation. At physiological concentrations of 1-7mug/ml, CRP strongly inhibited copper-mediated oxidation of LDL and phospholipid liposomes in a concentration-dependent manner. Similar concentrations of different monoclonal antibodies or albumin did not influence LDL oxidation. Antioxidant activity of CRP was inhibited by phosphocholine (PC), indicating that the observed activity involves binding of CRP to oxPtC. These results suggest that CRP may limit atherogenic oxidation of LDL in vivo.