Glucagon-like peptide-1 activates endothelial nitric oxide synthase in human umbilical vein endothelial cells

Aim:

To investigate the effects of glucagon-like peptide-1 (GLP-1) on endothelial NO synthase (eNOS) in human umbilical vein endothelial cells (HUVECs), and elucidate whether GLP-1 receptor (GLP-1R) and GLP-1(9–36) are involved in these effects.

Methods:

HUVECs were used. The activity of eNOS was measured with NOS assay kit. Phosphorylated and total eNOS proteins were detected using Western blot analysis. The level of eNOS mRNA was quantified with real-time RT-PCR.

Results:

Incubation of HUVECs with GLP-1 (50–5000 pmol/L) for 30 min significantly increased the activity of eNOS. Incubation of HUVECs with GLP-1 (500–5000 pmol/L) for 5 or 10 min increased eNOS phosphorylated at ser-1177. Incubation with GLP-1 (5000 pmol/L) for 48 h elevated the level of eNOS protein, did not affect the level of eNOS mRNA. GLP-1R agonists exenatide and GLP-1(9–36) at the concentration of 5000 pmol/L increased the activity, phosphorylation and protein level of eNOS. GLP-1R antagonist exendin(9–39) or DPP-4 inhibitor sitagliptin, which abolished GLP-1(9–36) formation, at the concentration of 5000 pmol/L partially blocked the effects of GLP-1 on eNOS.

Conclusion:

GLP-1 upregulated the activity and protein expression of eNOS in HUVECs through the GLP-1R-dependent and GLP-1(9–36)-related pathways. GLP-1 may prevent or delay the formation of atherosclerosis in diabetes mellitus by improving the function of eNOS.     

人脐静脉内皮细胞Caveolin-1基因沉默模型的建立

目的:利用小干扰RNA(siRNA)技术建立人脐静脉内皮细胞(ECV304)小凹蛋白(Caveolin-1)基因沉默模型,为研究Caveolin-1基因在人脐静脉内皮细胞中的作用.方法:通过Ambion专用软件对Caveolin-1基因编码区分析,设计合成短发夹RNA(shRNA)单链.通过T4连接酶将退火反应合成的shRNA双链克隆入含RNA PollII聚合酶表达元件的pENTRTM/U6入门载体,并利用Gateway技术构建相应的慢病毒RNA干扰(RNAi)表达载体.用REAL-TIME RT-PCR、蛋白印迹法分析沉默效率.结果:测序结果显示pENTRTM/U6载体插入的Cavelin-1基因shRNA序列大小及阅读框架正确.LR重组反应后成功构建了针对Caveolin-1基因的RNAi慢病毒表达系统.转染ECV-304细胞获得对Caveolin-1的沉默效率大于85%.结论:成功地构建了针对Caveolin-1基因的RNAi慢病毒表达系统,获得了长期稳定的基因剔除效应.人脐静脉内皮细胞Caveolin-1基因沉默模型能长期保种及传代,为进一步研究Cav-eolin-1基因的功能奠定了基础.     

Genipin inhibits endothelial exocytosis via nitric oxide in cultured human umbilical vein endothelial cells

Aim： Exocytosis of endothelial Weibel-Palade bodies, which contain von Willebrand factor （VWF）, P-selectin and other modulators, plays an important role in both inflammation and thrombosis. The present study investigates whether genipin, an aglycon of geniposide, inhibits endothelial exocytosis. Methods： Human umbilical vein endothelial cells （HUVECs） were isolated from umbilical cords and cultured. The concentration of VWF in cell supernatants was measured using an ELISA Kit. P-selectin translocation on the cell surface was analyzed by cell surface ELISA. Cell viability was measured using a Cell Counting Kit-8. Mouse bleeding times were measured by amputating the tail tip. Western blot analysis was used to determine the amount of endothelial nitric oxide synthase （eNOS） and phospho-eNOS present. Nitric oxide （NO） was measured in the cell supernatants as nitrite using an NO Colorimetric Assay. Results： Genipin inhibited thrombin-induced VWF release and P-selectin translocation in HUVECs in a dose- and time- dependent manner. The drug had no cytotoxic effect on the cells at the same doses that were able to inhibit exocytosis. The functional study that demonstrated that genipin inhibited exocytosis in vivo also showed that genipin prolonged the mouse bleeding time. Furthermore, genipin activated eNOS phosphorylation, promoted enzyme activation and increased NO production. L-NAME, an inhibitor of NOS, reversed the inhibitory effects of genipin on endothelial exocytosis. Conclusion： Genipin inhibits endothelial exocytosis in HUVECs. The mechanism by which this compound inhibits exocytosis may be related to its ability to stimulate eNOS activation and NO production. Our findings suggest a novel antiinflammatory mechanism for genipin. This compound may represent a new treatment for inflammation and/or thrombosis in which excess endothelial exocytosis plays a pathophysiological role.     

Mechanisms underlying nebivolol-induced endothelial nitric oxide synthase activation in human umbilical vein endothelial cells

1. Nebivolol (NEB) has been shown to be a selective blocker of beta1-adrenoceptors with additional vasodilating properties that are mediated, at least in part, by an endothelial-dependent liberation of nitric oxide (NO). In the present study, we investigated the underlying mechanisms of NEB-induced vasodilation. 2. Immunohistochemical staining of endothelial nitric oxide synthase (eNOS) was performed in the absence and presence of NEB in human umbilical vein endothelial cells (HUVEC). In addition, we measured the release of nitric oxide (NO) using diaminofluorescein. Metoprolol (MET) was used for comparison. 3. Nebivolol, but not MET (each at 10 micromol/L), caused a time-dependent increase in NO release from HUVEC, as demonstrated by an increase in DAF fluorescence at 0 versus 10 min (+234 +/- 7 and 55 +/- 22% basal, respectively). Blockade of beta3-adrenoceptors by SR 59230A (1 micromol/L) partially reduced the NEB-induced increase in DAF fluorescence. Complete inhibition of NEB-induced NO liberation was achieved by the simultaneous blockade of beta3-adrenoceptors and oestrogen receptors (with 1 micromol/L ICI 182,780). 4. Application of NEB significantly increased eNOS translocation and serine 1177 phosphorylation of eNOS. However, NEB did not alter eNOS-phosphorylation at threonine 495 and at serine 114. 5. In conclusion, the endothelium-dependent NO liberation induced by NEB is due to stimulation of beta3-adrenoceptors and oestrogen receptors and coincides with eNOS translocation and a phosphorylation at eNOS-serine 1177. These characteristics of NEB may be beneficial not only when treating patients suffering from cardiovascular disease, but may also prevent further deterioration of endothelial dysfunction.     

Ginsenoside compound K inhibits angiogenesis via regulation of sphingosine kinase-1 in human umbilical vein endothelial cells

Ginsenoside compound K (CK) is a metabolite of the protopanaxadiol-type saponins of Panax ginseng C.A. Meyer (Araliaceae), has long been used to treat against the development of cancer, inflammation, allergies, and diabetes. This study examined the anti-angiogenic properties of CK against sphingosine 1-phosphate (S1P)-induced cell migration via regulation of sphingosine kinase 1 (SPHK1) in human umbilical vein endothelial cells (HUVEC). Studies on S1P-induced cell migration, expression of SPHK1 and MMPs and analysis of sphingolipid metabolites by LC–MS/MS were examined after the treatment of CK (2.5, 5, 10 μg/mL) in HUVEC. S1P produced by SPHK1 is also involved in cell growth, migration, and protection of apoptosis; therefore, we sought to investigate whether ginsenosides are able to regulate SPHK1. For this purpose, we developed an inhibitory assay of SPHK1 activity and an analytical method for detection of S1P and other sphingolipid metabolites in HUVEC. Ginsenoside CK inhibited 100 nM S1P-induced cell migrations in a dose-dependent manner. Among tested ginsenosides, CK exclusively inhibited S1P production, SPHK1 activity and SPHK1 expression in HUVEC, whereas expression of the pro-apoptotic sphingolipids, sphingosine and ceramide, was increased in response to CK. The major subspecies of the increased ceramide was C24:0-ceramide. CK also disrupted the sphingolipid rheostat, which ultimately influences cell fate, and dose-dependently inhibited HUVEC migration by reducing expression of metalloproteinases (MMPs). Ginsenoside CK acts as a unique HUVEC migration inhibitor by regulating MMP expression, as well as the activity of SPHK1 and its related sphingolipid metabolites.     

Effect of cicletanine on the nitric oxide pathway in human umbilical vein endothelial cells

The purpose of this study was to evaluate the effects of cicletanine, a slightly diuretic antihypertensive drug, on human vascular endothelial cells with regard to nitric oxide, intracellular calcium concentration ([Ca2+]i), cyclic nucleotide, inositol 1,4,5-trisphosphate (IP3), and prostacyclin generation. Primary cultured human umbilical vein endothelial cells were used in this study. [Ca2+]i was measured by fura-2/AM. Cyclic adenosine monophosphate (AMP), cyclic guanosine monophosphate (GMP), IP3, and prostacyclin were measured by radioimmunoassay. Nitric oxide was measured by the Griess method. Cicletanine had no effect on [Ca2+]i. Cicletanine (10(-6)-10(-4) M) increased cyclic GMP but decreased prostacyclin generation. Cicletanine had no stimulating effect on cyclic AMP or IP3 generation. IP3 increased 45Ca release from storage sites. Cicletanine decreased prostacyclin generation via increase in cyclic GMP. Cicletanine had no stimulating effect on nitrogen oxides for 2 h after incubation but increased it after 3-24 h. Pretreatment with L-N(G)-monomethyl-arginine (L-NMMA) prevented this increase. The inhibitory effect of L-NMMA was prevented by pretreatment with L-arginine. These results indicate that nitric oxide and cyclic GMP may contribute to the antihypertensive action of cicletanine.     

Polychlorinated biphenyls alter the expression of endothelial nitric oxide synthase mRNA in human umbilical vein endothelial cells

Polychlorinated biphenyls (PCBs) are a group of persistent pollutants that are detected in maternal serum and umbilical cord, suggesting that fetal exposure also needs to be considered. The effects of dioxin-like PCB congeners 3,3',4,4'-tetrachlorobiphenyl (PCB77) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) and a non-dioxin-like compound 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) on the expression of endothelial nitric oxide synthase (eNOS), known to maintain blood flow to the fetus, in human umbilical vein endothelial cells (HUVECs) were investigated. The mRNA levels of eNOS, aryl hydrocarbon receptor (AhR) and cytochrome P450 (CYP) 1A1 in cells treated with 5 microM PCBs for 24 hours were analysed by real-time RT-PCR. Cells were also treated with alpha-naphthoflavone (alpha NF), an AhR antagonist or ICI 182780, an estrogen receptor (ER) antagonist, one hour prior to PCB exposure, to observe the effects of these receptors on eNOS modulation. Each PCB increased the eNOS mRNA level by 4.5-fold that was markedly inhibited by alphaNF. ERs were also suspected of altering eNOS levels because ICI 182780 treatment resulted in a decrease in the eNOS level. These results suggest that the eNOS mRNA expression increases due to the action of PCBs related to both AhR and ERs in HUVECs, and that maternal PCB exposure could influence fetal circulation.     

Effect of nicotine on human umbilical vein endothelial cells (HUVECs) migration and angiogenesis

The effects of nicotine on vascular endothelial cells have not been completely elucidated. We performed this study to assess the changes in cellular behaviors of human umbilical vein endothelial cells (HUVECs) treated with nicotine. We examined changes in cell count and morphology and assayed cellular migration with Boyden chamber and microcapillary tube formation in a Matrigel matrix following treatment with various concentrations of nicotine. Compared to the control, nicotine stimulated cell proliferation, migration, and tube formation at concentrations similar to those found in smokers. Although there were no specific morphological changes in HUVECs treated with nicotine at the concentration similar to that in smokers, at high concentration (10(-4) M), morphological changes such as cytoplasmic vacuolization and irregular cell shape were observed, which were assumed to be the result of direct cytotoxicity of nicotine. In HUVECs, nicotine enhanced cellular proliferation, migration and angiogenesis in vitro, and thus caused a functional change, not a morphological change at a concentration similar to that in habitual smokers.     

Effects of statins on nitric oxide/cGMP signaling in human umbilical vein endothelial cells

Human umbilical vein endothelial cells (HUVECs) were established as in vitro models for the modulation of endothelial function and cell viability by statins. Emphasis was placed on the biphasic effects of the drugs on nitric oxide (NO) bioavailability and cytotoxicity, as well as drug interference with the interaction of endothelial NO synthase (eNOS) with caveolin-1 (Cav-1). Incubation of HUVECs with fluvastatin, lovastatin or cerivastatin for 24 h caused an approximately 3-fold upregulation of eNOS expression that was associated with increased eNOS activity and accumulation of cGMP. Cerivastatin exhibited the highest potency with an EC50 of 13.8 ± 2nM after 24 h, while having no effect after only 30 min. The effects of statins on eNOS expression were similar in control and Cav-1 knockdown cells, but the increase in eNOS activity was less pronounced in Cav-1-deficient cells. Statin-triggered cyto-toxicity occurred at ~10-fold higher drug concentrations (maximal toxicity at 1–10 µM), was sensitive to mevalonate, and was significantly enhanced in the presence of N^G-nitro-L-arginine. The overexpression of eNOS induced by clinically relevant concentrations of statins may contribute to the beneficial vascular effects of the drugs in patients. Stimulation of NO synthesis and cytotoxicity appear to share a common initial mechanism but involve distinct downstream signaling cascades that exhibit differential sensitivity to HMG-CoA reductase inhibition.     

Sphingosine kinase 1 is critically involved in nitric oxide-mediated human endothelial cell migration and tube formation

Background and purpose:

Sphingosine kinases (SKs) convert sphingosine to sphingosine 1-phosphate (S1P), which is a bioactive lipid that regulates a variety of cellular processes including proliferation, differentiation and migration.

Experimental approach:

We used the human endothelial cell line EA.hy926 to investigate the effect of nitric oxide (NO) donors on SK-1 expression, and on cell migration and tube formation.

Key results:

We showed that exposure of EA.hy926 cells to Deta-NO (125–1000 µM) resulted in a time- and concentration-dependent up-regulation of SK-1 mRNA and protein expression, and activity with a first significant effect at 250 µM of Deta-NO. The increased SK-1 mRNA expression resulted from an enhanced SK-1 promoter activity. A similar effect was also seen with various other NO donors. In mechanistic terms, the NO-triggered effect occurred independently of cGMP, but involved the classical mitogen-activated protein kinase cascade because the MEK inhibitor U0126 abolished the NO-induced SK-1 expression. The effect of NO was also markedly reduced by the thiol-reducing agent N-acetylcysteine, suggesting a redox-dependent mechanism. Functionally, Deta-NO triggered an increase in the migration of endothelial cells in an adapted Boyden chamber assay, and also increased endothelial tube formation in a Matrigel assay. These responses were both abolished in cells depleted of SK-1.

Conclusions and implications:

These data show that NO donors up-regulate specifically SK-1 expression and activity in human endothelial cells, and SK-1 in turn critically contributes to the migratory capability and tube formation of endothelial cells. Thus, SK-1 may be considered an attractive novel target to interfere with pathological processes involving angiogenesis.     

Testing endodontic sealers on human umbilical vein endothelial cells

The toxic potential of the endodontic sealers ingredients, especially the unreacted monomer, that can irritate the periapical tissue and interfere with the healing process, thus having a negative impact on the biocompatibility of the material. The aim of this study was to evaluate the influence of three experimental endodontic sealers on cells viability in vitro. Human umbilical vein endothelial cells (HUVEC) were used. The experiments were done with solid samples and extracts of sealers in artificial saliva and water. The experiments evaluated the cytotoxicity of the residual monomers that resulted from the tested composites. The decrease in cell viability was quantified by colorimetric measurement of formazan. The components of the sealers dissolved in artificial saliva and water were determined by high performance liquid chromatography (HPLC). The HUVEC are a novelty for testing the endodontic sealers biocompatibility, with certain advantages compared to other cell types used in the literature, e.g. HELA cells, fibroblasts. The data showed that cytotoxicity was directly linked with the unreacted monomer — 2-hydroxyethyl methacrylate (HEMA) present in these composites. Two of the three formulations had little or no cytotoxic effect, which makes them suitable for further testing in order to be used in endodontic treatment.     

P物质对血管内皮细胞一氧化氮分泌及表达的影响

目的探讨P物质（SP）对血管内皮细胞一氧化氮（NO）分泌及表达的影响.方法采用不同浓度P物质（10-9mol/L、10-8mol/L、10-7mol/L和10-6mol/L）作用于人脐静脉血管内皮细胞（HUVEC）,分别于15 min、30 min、1 h、3 h、6 h和12 h检测培养上清液中NO含量,并应用免疫组化方法检测HUVEC内诱生型一氧化氮合成酶（iNOS）和内皮型一氧化氮合成酶（eNOS）的表达.结查10-9mol/L～10-6mol/L浓度范围的SP作用15 min,均可使HUVEC内eNOS表达增强,分泌NO水平上升,并于1 h后达峰值,与对照组比较具有显著性差异（P＜0.05）,其中10-8mol/LSP浓度组作用最为明显;而不同浓度的SP对HUVEC内iNOS的表达与对照组比较无显著性差异.结论SP可通过增强HUVEC内eNOS的表达来促进NO的分泌;SP对HUVEC内iNOS的表达则无明显影响.     

Activation and up-regulation of nitric oxide synthase in human umbilical vein endothelial cells by polycyclic aromatic hydrocarbons

PAHs, including naphthalene, fluoranthene and fluorene rapidly induced extracellular Ca(2+) influx and hence elevation of intracellular Ca(2+) concentration and NO production. The effect can be inhibited by Ca(2+) channel blocker but not by P450 inhibitor. In addition to the rapid effect, we have also found that the eNOS mRNA and protein expression were augmented in HUVECs treated with PAHs at concentration as low as 0.1 microM for 24 h. These effects were abolished when the HUVECs were pretreated with the BAPTA, NiCl(2) and SKF96365, as well as SKF525A. Our results revealed that, for the first time, PAHs induce the activation of eNOS and enhance eNOS protein expression in HUVECs both in a Ca(2+)-dependent manner.     

红霉素对人脐静脉内皮细胞一氧化氮及钙离子水平的影响

目的　探讨红霉素对人脐静脉内皮细胞一氧化氮通路及钙离子的影响。方法　应用一氧化氮及一氧化氮合酶试剂盒测定内皮细胞NO的含量及NOS的活性 ,采用Fura 2负载荧光技术检测胞内游离钙水平。结果　红霉素能明显增加内皮细胞NO的产生和胞内游离钙水平 ,并能明显增强NOS的活性 ,具有浓度和时间效应。结论　红霉素对人脐静脉内皮细胞一氧化氮通路的影响可能通过胞内游离钙而起作用。     

马来酸噻吗洛尔对人脐静脉内皮细胞HUVEC的增殖、凋亡、成管的影响

目的探讨马来酸噻吗洛尔在治疗婴幼儿血管瘤的作用机制。方法培养HUVEC细胞,采用CCK-8检测细胞存活率,Annexin V-FITC/PI双染色法检测细胞凋亡,体外血管形成试验检测细胞成管情况,应用SPSS17. 0统计包进行数据分析。结果用CCK-8测定马来酸噻吗洛尔能抑制人脐静脉内皮细胞HUVEC的生长;使用Annexin V-FITC/PI双染色法结果表明马来酸噻吗洛尔对HUVEC细胞的凋亡成剂量依赖性抑制;采用体外血管形成试验,表明马来酸噻吗洛尔对HUVEC细胞的成管能力成剂量依赖性的抑制。结论马来酸噻吗洛尔可能通过对婴幼儿血管瘤肿瘤中内皮细胞增值和血管生成能力的抑制,同时诱导内皮细胞凋亡来实现治疗目的。     

Apoptosis of human umbilical vein endothelial cells induced by artesunate

Artesunate (ART), a semi-synthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, is an effective novel antimalarial drug. The present study investigated the apoptotic activity of artesunate in cultured human umbilical vein endothelial cell (HUVEC) by means of nuclear staining, DNA agarose gel electrophoresis, and flow cytometry. The observations also indicated that artesunate induced apoptosis of HUVEC in a concentration-dependent and time-dependent manner. A Western immunoblot analysis showed down-regulation of the bcl-2 protein and up-regulation of the bax protein in the artesunate-treated HUVEC. Ca2+ in cells was evaluated by fluorescent spectrophotometer using Fura 2-AM as probe. These results suggest that artesunate may be a potential apoptosis-inducing agent for endothelial cells.     

Propofol protects human umbilical vein endothelial cells from cisplatin-induced injury

The anticancer drug cisplatin can up-regulate endothelial adhesion molecule expression, and trigger vascular endothelial injury. Propofol, an intravenous anesthetic, can inhibit endothelial adhesion molecule expression in some situations. Here, we explored whether and how propofol improved cisplatin-induced up-regulation of endothelial adhesion molecules in human umbilical vein endothelial cells. Compared with control group, cisplatin reduced endothelial nitric oxide synthase dimer/monomer ratio, activated protein kinase C and enhanced endothelial nitric oxide synthase-Thr⁴⁹⁵ phosphorylation, decreased nitric oxide production, augmented intercellular adhesion molecule 1 expression and monocyte-endothelial adhesion. These cisplatin-mediated effects were attenuated by propofol treatment. Nω-Nitro-L-arginine methyl ester hydrochloride, a nitric oxide synthase inhibitor, inhibited the effect of propofol on cisplatin-induced intercellular adhesion molecule 1 expression. Propofol improved cisplatin-mediated tetrahydrobiopterin reduction and nitrotyrosine overexpression. Compared with control group, cisplatin and PMA, a protein kinase C activator, both increased endothelial nitric oxide synthase-Thr⁴⁹⁵ phosphorylation, while propofol and GFX, a protein kinase C inhibitor, both decreased cisplatin-induced endothelial nitric oxide synthase-Thr⁴⁹⁵ phosphorylation. Our data indicated that propofol, via reducing cisplatin-induced endothelial nitric oxide synthase uncoupling and endothelial nitric oxide synthase-Thr⁴⁹⁵ phosphorylation, restored nitric oxide production, intercellular adhesion molecule 1 expression and monocyte-endothelial interaction.     

Desensitization of agonist-stimulated prostacyclin release in human umbilical vein endothelial cells

Prostacyclin (PGI2) release was studied in perfused columns of human umbilical vein endothelial cells cultured on microcarrier beads. Substantial homologous desensitization of PGI2 release occurred when cells were exposed to agonist for 2 min after a previous exposure; the extent depended on the concentration and duration of the first challenge. Recovery from exposure to ATP or bradykinin was complete in less than 80 min; recovery from thrombin was incomplete after greater than 80 min, and this was apparently related to its proteolytic activity. Experiments with ibuprofen, a reversible inhibitor of cyclo-oxygenase, demonstrated that homologous desensitization did not involve inactivation of cyclo-oxygenase. ATP and bradykinin did not induce heterologous desensitization. Thrombin and trypsin induced cross-desensitization, but neither agonist significantly reduced responses to ATP or bradykinin, suggesting that a common proteolytic mechanism is responsible for their ability to induce PGI2 synthesis. We conclude that desensitization of PGI2 release in response to physiological agonists is generally agonist-specific and involves modulation of molecular events at or close to the receptors involved, rather than inactivation of prostanoid biosynthesis.