Atherogenic levels of low-density lipoprotein increase endocytotic activity in cultured human endothelial cells.

Cultured human umbilical vein endothelial cells (EC) exposed to atherogenic low-density lipoprotein (LDL) levels for protracted periods demonstrated heightened endocytosis. Confluent EC were incubated with LDL 90 to 240 mg/dl cholesterol for 1 to 4 days and endocytosis was measured by 14C-sucrose uptake. Control EC and cells incubated with 90 mg/dl LDL cholesterol showed similar uptakes of 14C-sucrose during all measured time periods. In contrast, EC exposed to 240 mg/dl LDL cholesterol showed an increase in endocytosis beginning at 2 days, whereas 160 mg/dl LDL cholesterol promoted increased uptake by 4 days. The endocytotic activity of LDL-perturbed EC is reduced to levels seen in control cells by cytochalasin B, an actin polymerization inhibitor. This finding suggests a modulatory role for the cytoskeleton in endocytosis changes. Examination of LDL-perturbed EC cytoskeleton reveals structural remodeling resulting in a marked increase in stress fibers. Cytochalasin B exposure causes a loss of stress fibers with the formation of globular filamental aggregates. Such LDL-induced cellular functional changes may contribute mechanistically to endothelial dysfunction, which is widely held to be a major contributing factor in the pathogenesis of atherosclerosis.     

Minimally oxidized low-density lipoprotein induces tissue factor expression in cultured human endothelial cells.

Oxidatively modified low-density lipoprotein is present in atherosclerotic lesions and has been proposed to play an important role in atherogenesis through its biologic effects on vascular cells. This study examined the effects of minimally oxidized preparations of LDL (MM-LDL) on tissue factor (TF) expression by cultured human endothelial cells. Low-density lipoprotein purified from normal donors was modified by exposure to iron or by prolonged storage, resulting in levels of thiobarbituric acid-reacting substances of approximately 2.5 to 4 nmoles/mg cholesterol. Preparations had less than 2.5 pg of endotoxin per microgram LDL and had no intrinsic procoagulant activity. This form of modified but not native LDL induced TF expression in endothelial cells in a time- and dose-dependent manner. Peak TF coagulant activity in cells exposed to 40 micrograms/ml MM-LDL were observed at 4 to 6 hours, and ranged from 50 to 500 pg/10(5) cells, compared with less than 10 pg/10(5) cells exposed to native LDL. Northern blot analysis showed TF mRNA levels to increase approximately 30-fold with exposure to MM-LDL for 2 hours. Induction of TF activity was dependent on the concentration of MM-LDL from 1 microgram/ml to 80 micrograms/ml, a range in which cell viability and morphology were unaffected. The findings suggest that minimally oxidized LDL may be a local mediator promoting thrombosis in atherosclerotic lesions.     

Characteristics of high-density lipoprotein binding sites in cultured parenchymal,endothelial, and Kupffer's cells from rat liver

Liver endothelial cells posses surface high-affinity binding sites for HDL₃, whose affinity is 4 times higher than that of the sites on hepatocytes and Kupffer's cells. The maximal number of high-affinity binding sites on endothelial cells is 437 ng/mg protein, which surpasses this parameter on the hepatocyte surface several times. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 3, pp. 268–270, March, 1994     

Adherence of eosinophils from allergic and normal ponies to cultured equine endothelial cells

OBJECTIVES: To compare adherence of stimulated and unstimulated eosinophils from allergic and normal ponies to cultured equine vascular endothelial cells (equine digital vein endothelial cells; EDVEC) and examine the effect of eosinophil-derived factor(s) on cell adherence. METHODS: Eosinophil adherence to unstimulated EDVEC or EDVEC pretreated with IL-1beta or supernatants from stimulated eosinophils was measured. Supernatants were also assayed for TNFalpha and IL-1beta-like bioactivity. RESULTS: Adherence of unstimulated and rhIL-5 (10 ng/ml)-stimulated eosinophils from allergic ponies to rhIL-1beta-treated EDVEC was significantly greater than that of cells from normal ponies. Pretreatment of EDVEC with supernatants from stimulated eosinophils from both groups of ponies significantly increased adherence of autologous cells and IL-1beta- and TNFalpha-like bioactivities were detected in the supernatants. CONCLUSIONS: Mediator-induced activation of equine eosinophils may lead to further eosinophil recruitment by releasing cytokines that up-regulate endothelial cell adhesion molecule expression. Increased adherence of blood eosinophils from allergic ponies to stimulated endothelium could be explained by in vivo priming.     

HLA antigen expression on cultured human arterial endothelial cells

Flow cytometric analysis and cellular assays were used to determine constitutive and induced expression of class I HLA antigens and class II antigens encoded by the HLA-DR, -DQ and -DP subregions on cultured human arterial endothelial cells (HAEC) derived from transplant donors. Class I but no or minimal quantities of class II HLA antigens were found on HAEC. Prior incubation of HAEC with gamma-IFN increased class I HLA antigen expression and induced class II HLA antigen expression on HAEC. The induced expression of HLA-DQ was lower than that of HLA-DR, but both were significantly reduced in comparison to the frequency of these antigens on EBV transformed lymphoblastoid cell lines derived from the same donor. In addition, supernatants from class I and class II alloreactive clones were shown to induce class II antigen expression on HAEC. By PLT analysis, it was shown that these antigens are functionally capable of generating a lymphocyte response. In this regard, HAEC have proved to be a helpful tool in designing in vitro lymphocyte-endothelial cell studies.     

Synthesis and release of acetylcholine by cultured bovine arterial endothelial cells

Using cultured endothelial cells prepared from bovine carotid artery, and a specific radioimmunoassay for acetylcholine (ACh), the synthesis and release of ACh by vascular endothelial cells were investigated directly. ACh content in the culture medium after 24 h of incubation in the presence of isoflurophate, a nonspecific cholinesterase inhibitor, was about 16 times higher than that in endothelial cells, indicating that ACh synthesized inside the cells was released rapidly. The presence of ACh in the culture medium was further confirmed qualitatively using high-performance liquid chromatography with an electrocapture detection. These results represent the first direct evidence that endothelial cells can synthesize and release ACh, suggesting the possibility that ACh acts not only as a neurotransmitter but also as an autacoid under certain conditions.     

Proliferation characteristics of cultured human aortic endothelial cells and expression of adhesion molecules

Basal expression of the adhesion molecules P-selectin and ICAM-1, which mediate adhesion and transendothelial migration of leukocytes, by endothelial cells of human aorta and umbilical vein and its relationship with the proliferative behavior of these cells are studied in primary prolonged cultures. Inverse proportionality between the percentage of resting endothelial cells and those expressing the adhesion molecules in preconfluent and confluent monolayers, on the one hand, and the percentage of cells in the active cycle which do not express the adhesion molecules, on the other, is demonstrated. This relationship is one of the major causes of thein vitro functional heterogeneity of the endotheliocyte population in the expression of adhesion molecules and its adhesiveness for leukocytes. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 8, pp. 214–217, August, 1996     

Effects of low-density lipoprotein from normal rabbits on hypercholesterolemia and the development of atherosclerosis

To clarify whether or not normal LDL separated from normal rabbits is atherogenic, 0.75 mg of normal LDL-cholesterol in 6 ml of 0.85% saline and 6 ml of saline alone were injected every day for 5 weeks into the auricular vein of two groups of rabbits, respectively. The inoculated rabbits were fed a standard diet containing 0.5 and 1% cholesterol. Blood was drawn before injection and at 1, 2, 3 and 5 week intervals thereafter. After 5 weeks, all rabbits were sacrificed. Following exsanguination, the aorta was stained by Sudan III. The Sudan III staining was more extensive in rabbits injected with saline than in those that received LDL. In addition, plasma cholesterol, plasma phospholipid, VLDL-cholesterol and LDL-cholesterol levels were lower in LDL-injected rabbits than in those injected with saline. But HDL-cholesterol levels were not significantly different between LDL-cholesterol and saline-injected rabbits. Although the exact cause of antiatherogenic effect of normal LDL is not clear, it seems reasonable to suggest that at least some normal LDL acts as a 'good' lipoprotein, namely antiatherogenic lipoprotein, in our experimental protocol.     

内皮细胞信息反馈下丘脑-垂体条件培养液对内皮细胞丙二醛代谢和一氧化氮合酶表达的影响

目的：观察内皮细胞信息反馈下丘脑-垂体条件培养液对内皮细胞丙二醛(MDA)代谢和一氧化氮合酶(NOS)表达的影响,探讨下丘脑-垂体轴对动脉粥样硬化形成的调控方式。方法：将有、无联胺刺激的内皮细胞信息反馈下丘脑-垂体后的条件培养液作用于正常和受损内皮细胞,硫代巴比妥酸法检测其MDA含量,免疫细胞化学法观察NOS的表达。结果：下丘脑-垂体条件培养液(HP、HP-、HP )对正常内皮细胞MDA代谢、NOS表达的影响无明显变化;而作用受损内皮细胞后,HP 能使其MDA含量下降,NOS表达显著增强。结论：下丘脑一垂体轴对内皮细胞MDA代谢、NOS的表达有反馈调控作用。     

氧化低密度脂蛋白对人血管内皮细胞ECV-304促增殖及诱导凋亡的作用

目的:探讨氧化低密度脂蛋白(ox-LDL)对血管内皮细胞损伤作用的多样性。方法: 通过细胞形态学、台盼蓝活细胞计数、细胞毒四唑盐(MTT)比色试验、乳酸脱氢酶(LDH)、流式细胞凋亡和细胞凋亡小分子量DNA片段凝胶电泳测定法, 观察(0.1、1、10、100、150和200)mg/L的ox-LDL的条件培养液对人血管脐静脉内皮细胞ECV-304的影响。结果:(0.1-10)mg/L的ox-LDL对ECV-304细胞具有促增殖作用, 而增加浓度达100mg/L及以上时, 其表现则主要是对ECV-304的细胞毒性;而且, 这种细胞毒性以当ox-LDL的浓度达到150和200mg/L时, 在12h开始诱导ECV-304细胞出现凋亡, 分别达15.86%和21.89%。而当ox-LDL作用ECV-304细胞18h后, 则出现伴随凋亡的细胞坏死。结论:ox-LDL具有很强的细胞毒性, 其对内皮细胞的细胞毒性经历了促细胞增殖、凋亡前期、细胞凋亡和凋亡后的坏死等过程。     

Serum from diabetic patients enhances synthesis of arterial basement membrane-like material in cultured smooth muscle cells

The effect of serum from both type I and type II diabetic subjects on the metabolism of arterial basement membrane (BM)-like material was studied in cultures of rabbit aortic smooth muscle cells. The basement membrane-like material was isolated from the cell-layer by a combined sonication and centrifugation technique. Serum from type I diabetic persons added to the incubation medium increased statistically significantly the incorporation of L-[4,5]-3H-leucine into the basement membrane-like material as compared to serum from non-diabetic subjects (2P less than 0.05). The same effect was seen with serum from type II diabetic patients as compared to serum from nondiabetic subjects (2P less than 0.05). No effect of serum from type I diabetic persons was seen in degradation experiments. Incubation medium supplemented with normal serum and extra glucose neither changed the production of basement membrane-like material nor the disappearance rate of radioactive leucine from the basement membrane-like material in degradation experiments. The present study indicates that serum from diabetic subjects enhances the production of arterial basement membrane-like material from arterial smooth muscle cells in culture. The obtained data may be relevant for the understanding of the development of macroangiopathy among diabetic patients.     

Low-density lipoprotein endocytosis. II. Influence of the multivalent ligand cationized ferritin on acetylated low-density lipoprotein endocytosis in cultured cells

Interactions of the basic multivalent ligand cationized ferritin (CF) with cultured cells markedly alter their endocytic function. In this study, the influence of CF treatment on the binding, internalization, and degradation of chemically modified (acetylated) low-density lipoproteins (Ac-LDL) was examined in aortic smooth muscle cells (SMC); and in normal and FH mutant LDL receptor-negative human skin fibroblasts, which lack the Ac-LDL (scavenger) receptor; and in vascular endothelial cells, which normally express the receptor. Although CF treatment of all three cell types at 37 degrees C resulted in the induction of Pronasesensitive, high-capacity, high-affinity binding (Kd = 12.0 +/- 2.0 nM at 4 degrees C) of labeled Ac-LDL, which at 37 degrees C was accompanied by significant internalization and degradation, these processes were not receptor-mediated. CF-induced high-affinity binding was inhibited by unlabeled Ac-LDL, fucoidan, carrageenan, and dextran sulfate but was unaffected by native LDL and albumin and only partially inhibited by acetylated albumin. However, analysis of membrane preparations of the cells for "scavenger" receptor protein by solid-phase filtration assay and Western blotting identified the receptor in endothelial cells and in granuloma (positive control) macrophages, but not in either CF-treated or untreated SMC. In addition, studies with both glutaraldehyde-fixed cells and CF bound to culture dishes indicated that Ac-LDL avidly binds to CF. Further, ultrastructural studies using colloidal gold-conjugated Ac-LDL showed Ac-LDL preferentially binding to CF aggregates on the cell surface. Thus, these studies indicate that treatment of cells with CF induces an endocytic process which, although remarkably similar to the scavenger pathway, is mediated by Ac-LDL binding to membrane-associated CF. These observations have implications in terms of mechanisms that might regulate the endocytosis of modified low-density lipoproteins.     

低密度脂蛋白,高脂血清对内皮细胞膜脂流动性的影响

实验用DPH荧光偏振技术测定经人低密度脂蛋白(LDL)及兔高脂血清(HRS)孵育的牛主动脉内皮细胞(EC)的膜脂微粘度。结果表明LDL孵育EC12小时导致细胞膜脂流动性下降,过氧化脂质(Lpo)含量增高;EC经HRS作用36小时后也发生相似的变化。形态观察证明EC胞浆中有大量脂滴样结构。结果提示高胆固醇含量的LDL和HRS可能通过增加膜的胆固醇含量而降低膜的流动性,高浓度Lpo可能也起重要作用。     

Perturbation of cultured human endothelial cells by atherogenic levels of low density lipoprotein.

Cultured human umbilical vein endothelial cells (EC) exposed to atherogenic levels of low density lipoprotein (LDL) for protracted periods demonstrated no measurable evidence of overt cytotoxicity, but were perturbed as indicated by an increase in prostacyclin (PGI2) production. Confluent EC were incubated with high LDL concentrations (240 or 330 mg/dl cholesterol) for 1 to 12 days. LDL was added to culture media containing 25% human lipoprotein-deficient serum to determine the effects of LDL independent of other lipoproteins. LDL did not injure EC as assessed by cell count, vital dye exclusion, 51chromium release, and lactate dehydrogenase release. Although high concentrations of LDL did not cause EC cytotoxicity, such LDL concentrations did results in increased PGI2 generation. PGI2 accumulation in postincubation media was increased two-to-fivefold in otherwise unstimulated cells as measured by radioimmunoassay of the stable PGI2 breakdown product, 6-keto-PGF1-alpha. This elevation persisted for the entire 12-day exposure to high LDL concentrations. These results indicate that prolonged exposure to atherogenic concentrations of LDL does not effect EC viability, but does cause an endothelial perturbation as demonstrated by an increased PGI2 production.     

Non-adherent, low-density cells from human peripheral blood contain dendritic cells and monocytes, both with veiled morphology.

Dendritic cells (DC) from human peripheral blood, known to adhere transiently and to become non-adherent by 16 hr, can be separated in the low-density interface on hypertonic Metrizamide gradients. Many more low-density cells (5.8% of the mononuclear cells separated on Ficoll) were obtained from the population that was non-adherent after only 90 min. Over 95% of these low-density cells had veiled morphology. A proportion were monocytes by phenotypic and phagocytic properties. One-third of the cells (on average) were DC on the basis of lack of monocyte phenotype and of potency as stimulators in the mixed lymphocyte reaction. Including both the 16 hr and 90 min non-adherent cells, over 2% of the mononuclear cells isolated from human peripheral blood may be DC.     

衰老和低氧对体外培养大鼠肺动脉平滑肌细胞形态的影响

目的： 探讨衰老及低氧对体外培养的PASMCs形态的影响。方法： 将细胞分为年轻常氧组、老年常氧组、年轻低氧组、老年低氧组，应用光镜观察、免疫组化及免疫荧光的方法检查细胞的形态变化。结果： 低氧状态与常氧条件下培养的PASMCs形态上有明显差别，且胞浆内F-actin分布及排列均有明显差别；老年组PASMCs的 SM-α-actin 含量减少比年轻组明显；低氧组PASMCs的SM-α-actin含量比常氧组减少明显。结论： 衰老及低氧使PASMCs形态发生变化，均能直接刺激PASMCs的转化;衰老的平滑肌细胞受低氧刺激,SM-α-actin变化最为明显。     

Proliferation, morphology, and protein expression by osteoblasts cultured on poly(anhydride-co-imides).

In vitro cell biocompatibility models are crucial in the study of any newly synthesized material. Our focus has been on the development of a new class of biocompatible, degradable, high-strength polymeric materials, the poly(anhydride-co-imides), for use in bone regeneration. This study examined osteoblast cell adherence, proliferation, viability, and phenotypic preservation on the surface of the poly(anhydride-co-imide) poly[pyromellitylimidoalanine (PMA-ala):1,6-bis(carboxyphenoxy) hexane (CPH)] over a period of time. Cell proliferation on PMA-ala:CPH degradable matrices over 21 days was examined. Throughout the 21-day period of study, osteoblast proliferation was similar on PMA-ala:CPH and on tissue culture polystyrene controls. Osteoblasts maintained their characteristic morphology as demonstrated by both scanning electron microscopy and immunofluorescence studies. Alkaline phosphatase activity for cells grown on PMA-ala:CPH was confirmed. Retention of the osteoblastic phenotype was demonstrated using immunofluorescence techniques and staining with antibodies against osteocalcin (an extracellular matrix protein of bone) and osteopontin (a marker of cell adhesion). Radioimmunoassay results provided evidence that levels of osteocalcin production by osteoblasts were similar when cells were cultured on PMA-ala:CPH and on tissue culture polystyrene controls. The present study provided evidence of normal osteoblast function on PMA-ala:CPH surfaces. PMA-ala:CPH may therefore be useful as a synthetic material for orthopedic applications.     

血管紧张素II对巨噬细胞(THP-1细胞)凝集素样氧化低密度脂蛋白受体表达的影响

目的:研究AngII对人单核/巨噬细胞(THP-1细胞)凝集素样氧化低密度脂蛋白受体(LOX-1)蛋白表达和基因转录的影响,从细胞蛋白、分子水平探讨AngII和巨噬细胞LOX-1相互之间的关系,以进一步了解两者在动脉粥样硬化中的地位。方法:将不同浓度AngII(1×10^-9-1×10^-5mol/L)与经0.1μmol/L佛波酯(PMA)诱导分化后的THP-1细胞共孵育24h,以及将1×10^-6mol/L浓度的AngII与诱导分化后的THP-1细胞作用不同时间0、3、6、12、24、48h后,用细胞酶联免疫法和半定量RT-PCR分别检测LOX-1蛋白和mRNA表达的情况。结果:未经诱导的THP-1细胞不表达LOX-1mRNA;而经PMA诱导后,THP-1细胞停止增殖,由单核细胞分化成为巨噬细胞,并表达LOX-1mRNA。不同浓度的AngII作用诱导分化后的THP-1细胞24h,细胞LOX-1蛋白和mRNA的表达呈浓度依赖性显著增加。同一浓度的AngII作用THP-1细胞,可呈时间依赖性诱导LOX-1蛋白和mRNA表达,其趋势是3h左右开始增加,24h左右至最高峰,之后逐渐减低。结论:经PMA诱导分化后的THP-1细胞表达LOX-1;AngII能明显增强分化后的THP-1细胞表达LOX-1蛋白和mRNA,并呈浓度和时间依赖性。AngII这种作用可能是促进动脉粥样硬化发生、发展的机制之一。