氧化磷脂与动脉粥样硬化

磷脂是构成生物膜和脂蛋白的重要成分,容易在自由基或非自由基以及酶促条件下发生氧化修饰,形成氧化磷脂(oxidizedphospholipids,OxPLs),并进一步产生具有不同生物活性的氧化产物。临床证据表明,OxPLs在动脉粥样硬化(atherosclerosis,AS)发展过程中不断生成和转化,并在病变处积累。OxPLs是一种高度异质性混合物,可通过多种相关受体或信号通路影响AS病变进程。本文综述了磷脂氧化过程、相关产物,以及OxPLs通过与内皮细胞、单核/巨噬细胞、平滑肌细胞、血小板和脂蛋白相互作用参与AS病变过程,并对近年来将OxPLs作为抑制AS靶点的研究进展进行了总结。     

氧化低密度脂蛋白通过Wnt5a/PKCδ信号通路诱导大鼠肝星状细胞自噬

该文旨在研究氧化低密度脂蛋白(ox-LDL)对大鼠肝星状细胞(HSC-T6)自噬的影响及机制,探讨非酒精性脂肪肝炎的发病机理。体外培养的HSC-T6细胞以不同质量浓度(0、10、20、40、60μg/mL)的ox-LDL分别处理不同时间(0、3、6、12、24 h)后,用Western blot检测LC3 II、Beclin1、p62的含量。不同质量浓度(0、10、20、40、60μg/mL)的ox-LDL处理HSC-T6细胞12 h后,Western blot检测Wnt5a、p-PKCδ、p-STAT3的含量。将HSC-T6细胞分为对照组(Control)、ox-LDL组、ox-LDL+si-NC组和ox-LDL+si-Wnt5a组,经相应处理后用Western blot、qRT-PCR分别检测LC3 II、Beclin1、p62、p-PKCδ、p-STAT3的蛋白和mRNA含量变化;免疫荧光检测LC3 II的变化;油红O染色观察HSC-T6脂滴含量变化;比色法检测各组细胞培养上清中羟脯氨酸(Hyp)含量;ELISA检测细胞培养上清中透明质酸(HA)和层黏连蛋白(LN)含量。PKCδ抑制剂Rottlerin预处理细胞:将HSC-T6细胞分为对照组(Control)、ox-LDL组、ox-LDL+DMSO组和ox-LDL+Rottlerin组,检测方法与敲低Wnt5a一致。经ox-LDL处理后,HSC-T6细胞中LC3 II、Beclin1含量增加(P<0.05),p62含量减少(P<0.01),且在ox-LDL质量浓度为20μg/mL、作用12 h时达到峰值。ox-LDL质量浓度为20μg/mL、作用12 h时,HSC-T6细胞中Wnt5a、p-PKCδ、p-STAT3蛋白表达显著升高(P<0.01)。敲低Wnt5a后,HSC-T6细胞中Wnt5a、LC3 II、Beclin1 mRNA和蛋白表达水平显著降低(P<0.001),p62蛋白表达增多(P<0.01),p-PKCδ、p-STAT3蛋白表达减少(P<0.05),细胞内LC3 II点状聚集减少,脂滴含量减少,细胞培养上清中Hyp、HA、LN含量也减少(P<0.05)。抑制PKCδ后,结果与敲低Wnt5a一致。ox-LDL可通过增强Wnt5a/PKCδ通路诱导HSC-T6细胞自噬。     

Coassemble dopamine and GHK tripeptide into fluorescent nanoparticles for pH sensing

Fluorescent nanostructures have been widely applied to biomedical researches and clinical diagnosis such as biolabeling/imaging/sensing and have even acted as therapy reagents. Peptide‐based fluorescent nanostructures attract recent interest from biomedical researchers. Inspired by the natural existence of GHK‐Cu complex with a growth factor‐like effect in human blood, here we have developed a novel approach for designing nanosensors through the co‐assembling of two kinds of biomolecules. By making best use of both π‐π stacking between carbon rings and the easy‐oxidation property of an important transmitter molecule, dopamine (DA), we successfully built up a supersensitive and robust fluorescent pH nanosensor by co‐assembling oxidized DA (DA_ox) with a tripeptide GHK. The GHK‐DA_ox nanostructures have a quantum yield of 20.82%, which might be the brightest one among all the current co‐assembling structures merely through unmodified biomolecules. We envision this approach could open a new avenue for not only hybrid nanostructure construction, but also may inspire the bioengineering of in vivo luminescent probes.     

NOS1-mediated macrophage and endothelial cell interaction in the progression of atherosclerosis

Atherosclerosis is a chronic inflammatory disease arising due to an imbalance in lipid metabolism and maladaptive immune response driven by the accumulation of cholesterol-laden macrophages in the artery wall. Interactions between monocytes/macrophages and endothelial cells play an essential role in the pathogenesis of atherosclerosis. In our current study, nitric oxide synthase 1 (NOS1)-derived nitric oxide (NO) has been identified as a regulator of macrophage and endothelial cell interaction. Oxidized LDL (OxLDL) activates NOS1, which results in the expression of CD40 ligand in macrophages. OxLDL-stimulated macrophages produce some soluble factors which increase the CD40 receptor expression in endothelial cells. This increases the interaction between the macrophages and endothelial cells, which leads to an increase in the inflammatory response. Inhibition of NOS1-derived NO might serve as an effective strategy to reduce foam cell formation and limit the extent of atherosclerotic plaque expansion.     

Forthcoming Meetings 1993

The purpose of this review is to bring together the different approaches for studying the oxidation of low density lipoproteins and try to identify some critical factors which will permit greater comparability between laboratories. These issues are discussed both in terms of the variety of exogenous mediators of oxidation applied (transition metal ions, haem proteins, azo initiators, peroxynitrite, cells etc.) and their raisons d'etre, as well as the methodologies (formation of conjugated dienes, hydroperoxides, decomposition products of lipid peroxidation, altered surface charge, macrophage uptake) applicable to the different stages of the oxidation and the factors underlying their accurate execution and interpretation.     

Effect of consumption of phenols from olives and extra virgin olive oil on LDL oxidizability in healthy humans

A high intake of olive oil has been proposed as an explanation for the low incidence of coronary heart disease in Mediterranean countries, but it is unclear whether olive oil offers specific benefits beyond a low content of saturated fat. Some types of extra virgin olive oil are rich in non-polar phenols, which might be taken up by plasma LDL particles and protect these from becoming atherogenic by oxidative modification. In a pilot study we found that consumption of 47 g fortified olive oil containing 31 mg phenols significantly increased the lag time of LDL oxidation from 112 ± 5 min before to 130 ± 7 min 2h after the meal. However, this study was not controlled, and in the current study we therefore investigated whether olive oil phenols increase the lag time of LDL oxidation in postprandial samples when compared with a control group.

Twelve healthy men and women consumed four different olive oil supplements with a meal on four separate occasions: one similar to the supplement in the pilot study (positive control); one containing mainly non-polar olive oil phenols; one containing mainly polar olive oil phenols; and one without phenols (placebo). Lag time significantly increased 2 h after the meals with the positive control (8 ± 2 min), the polar phenols (8 ± 2 min), and the placebo (8 ± 2 min), but not after the non-polar phenols (-0.4 ± 3 min). Increases were not statistically different between supplements.

These results indicate that the lag time of LDL-oxidation is increased after consumption of a meal. This increase is probably due to non-specific meal or time effects and not to phenols from olives or olive oil. Furthermore, these findings stress the need for adequate controlled studies to avoid misinterpretations of the data.     

Investigation of Lipid Peroxidation in Human Low Density Lipoprotein

Human plasma low density lipoprotein (LDL) exposed to oxygen saturated buffer becomes depleted of alpha-tocopherol within 3 to 6 hours. Thereafter, lipid peroxidation commences as evidenced by the loss of 18:2 (67nmol/mg LDL) and 20:4 (12nmol/mg LDL) and the concomitant formation of 4-hydroxy-nonenal (0.28 nmol/mg LDL) and fluorescent compounds. The major fluorophor in apo B of oxidized LDL has an excitation maximum at 355 nm and an emission maximum at 430 nm. A fluorophor with the same spectral properties is produced in apo B, if LDL is incubated with 4-hydroxynonenal, whereas malonal-dehyde gives a fluorophor with excitation and emission maxima at 400/470nm. Three-dimensional fluorescence spcetroscopy proved to be an useful tool in analysing the complex fluorescence of apo B.     

Calcium Antagonists Prevent Monocyte and Endothelial Cell-Induced Modification of Low Density Lipoproteins

Low density lipoprotein (LDL) incubated in the presence of the calcium antagonists verapamil, nifedipine and flunarizine were more resistant than control LDL to human monocyte- or endothelial cell-induced modification, as assessed by electrophoretic mobility in agarose gel, thiobarbituric acid reactive substance content, and degradation by J774 macrophages. The efficiency of the drugs was: flunarizine > nifedipine > veraparml. Moreover, a 24 h preculture with calcium antagonists significantly impaired the ability of cells to modify LDL in the absence of the drugs. All the studied drugs also inhibited copper-induced autooxidation of LDL. None of the studied calcium antagonists, at concentrations up to 10^-4 M, significantly reacted with free radicals as assessed by the l,1-diphenyl-2-picrylhydrazyl test. It is suggested that such a protective effect of calcium antagonists against LDL peroxidation could play a role in the previously reported antiatherogenic effect of these drugs.     

Sphingosine-1-phosphate: A Janus-faced mediator of fibrotic diseases

Sphingosine-1-phosphate (S1P) is a pleiotropic lipid mediator that acts either on G protein-coupled S1P receptors on the cell surface or via intracellular target sites. In addition to the well established effects of S1P in angiogenesis, carcinogenesis and immunity, evidence is now continuously accumulating which demonstrates that S1P is an important regulator of fibrosis. The contribution of S1P to fibrosis is of a Janus-faced nature as S1P exhibits both pro- and anti-fibrotic effects depending on its site of action. Extracellular S1P promotes fibrotic processes in a S1P receptor-dependent manner, whereas intracellular S1P has an opposite effect and dampens a fibrotic reaction by yet unidentified mechanisms. Fibrosis is a result of chronic irritation by various factors and is defined by an excess production of extracellular matrix leading to tissue scarring and organ dysfunction. In this review, we highlight the general effects of extracellular and intracellular S1P on the multistep cascade of pathological fibrogenesis including tissue injury, inflammation and the action of pro-fibrotic cytokines that stimulate ECM production and deposition. In a second part we summarize the current knowledge about the involvement of S1P signaling in the development of organ fibrosis of the lung, kidney, liver, heart and skin. Altogether, it is becoming clear that targeting the sphingosine kinase-1/S1P signaling pathway offers therapeutic potential in the treatment of various fibrotic processes. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.