Role for hydrogen peroxide in flow-induced dilation of human coronary arterioles

Flow-induced dilation (FID) is dependent largely on hyperpolarization of vascular smooth muscle cells (VSMCs) in human coronary arterioles (HCA) from patients with coronary disease. Animal studies show that shear stress induces endothelial generation of hydrogen peroxide (H2O2), which is proposed as an endothelium-derived hyperpolarizing factor (EDHF). We tested the hypothesis that H2O2 contributes to FID in HCA. Arterioles (135+/-7 micro m, n=71) were dissected from human right atrial appendages at the time of cardiac surgery and cannulated with glass micropipettes. Changes in internal diameter and membrane potential of VSMCs to shear stress, H2O2, or to papaverine were recorded with videomicroscopy. In some vessels, endothelial H2O2 generation to shear stress was monitored directly using confocal microscopy with 2',7'-dichlorofluorescin diacetate (DCFH) or using electron microscopy with cerium chloride. Catalase inhibited FID (%max dilation; 66+/-8 versus 25+/-7%; P<0.05, n=6), whereas dilation to papaverine was unchanged. Shear stress immediately increased DCFH fluorescence in the endothelial cell layer, whereas treatment with catalase abolished the increase in fluorescence. Electron microscopy with cerium chloride revealed shear stress-induced increase in cerium deposition in intimal area surrounding endothelial cells. Exogenous H2O2 dilated (%max dilation; 97+/-1%, ED50; 3.0+/-0.7x10(-5) mol/L) and hyperpolarized HCA. Dilation to H2O2 was reduced by catalase, 40 mmol/L KCl, or charybdotoxin plus apamin, whereas endothelial denudation, deferoxamine, 1H-(1,2,4)-oxadiazole-[4,3-a]quinoxalin-1-one, or glibenclamide had no effect. These data provide evidence that shear stress induces endothelial release of H2O2 and are consistent with the idea that H2O2 is an EDHF that contributes to FID in HCA from patients with heart disease. The full text of this article is available at http://www.circresaha.org.     

雌激素受体α在睾酮影响人脐静脉内皮细胞衰老中的重要作用

目的观察睾酮对过氧化氢(H2O2)诱导衰老的人脐静脉内皮细胞(HUVECs)的影响,并初步探讨其作用机制。方法将内皮细胞分为正常对照组、H2O2对照组、不同浓度睾酮组(3×10-9～3×10-6mol/L)、ICI182,780组和氟他胺组。用SA-β-半乳糖苷酶细胞化学检测法观察各组细胞衰老情况,Western blot法检测细胞中雌激素受体α(ERα)水平。结果与正常对照组比较,H2O2对照组可以引起HUVECs衰老细胞明显增加。3×10-9mol/L、3×10-8mol/L、3×10-7mol/L睾酮组均具有延缓H2O2诱导HUVECs衰老的趋势,3×10-6mol/L睾酮组却具有相反的作用。3×10-9～3×10-6mol/L睾酮组ERα各条带吸光度值分别为113.54±8.09、165.69±7.09、143.63±6.84、80.81±5.29。结论睾酮对H2O2诱导HUVECs衰老的影响与其剂量有关,而且睾酮还呈剂量相关性调节H2O2诱导HUVECs的ERα表达。     

三氧化二砷对人脐静脉内皮细胞作用的研究

目的 通过观察不同浓度三氧化二砷(As2O3)对内皮细胞形态及增殖活力的影响，从内皮细胞角度评价As2O3防治经皮冠状动脉成形术(PTCA)后再狭窄的作用。方法 以不同浓度As2O3（0.01 μmol/L、0.1 μmol/L、1 μmol/L和10 μmol/L）作用于传代培养的人静脉内皮细胞株（EVC-304），分别培养24 h、48 h和72 h观察细胞形态、绘制细胞生长曲线，并行MTT比色法观察As2O3对内皮细胞增殖活力〔吸光度(A)值〕的影响。结果 10 μmol/L的As2O3使细胞皱缩变圆，甚至浮起、碎裂。≤1 μmol/L的As2O3作用于内皮细胞后，细胞形态无明显变化。细胞计数显示，As2O3浓度高于1 μmol/L时，内皮细胞数明显降低。MTT比色法显示:As2O3浓度低于1 μmol/L，A值与对照组比较无差异，在1~10 μmol/L浓度范围内，A值明显降低（P<0.05），提示细胞增殖活力受到抑制。结论 高浓度As2O3对内皮细胞形态有破坏作用，并显著抑制内皮细胞增殖，且抑制作用具有时间及剂量依赖性。低浓度的As2O3则对内皮细胞形态及增殖活力无影响。     

过氧化氢上调白细胞介素1β诱导人肺上皮细胞表达环氧合酶2

目的探讨过氧化氢(H2O2)对白细胞介素1β(IL-1β)诱导人肺上皮细胞(HPEC)环氧合酶2(COX-2)表达的影响.方法应用逆转录-聚合酶链反应(RT-PCR)半定量法和酶联免疫吸附试验 (ELISA)测定IL-1β、H2O2或二者联合干预后HPEC COX-2 mRNA表达量及前列腺素E2(PGE2)释放量的变化, 以不加任何试剂的细胞为对照组.结果 (1)COX-2 mRNA表达量1、5、10 mg/L 的IL-1β处理组COX-2 mRNA表达量分别为(143.1±7.2)%、(179.9±9.0)%、(190.0±9.5)%,对照组为(32.9±1.7)%,1、5、10 mg/L 的IL-1β处理组与对照组比较差异有显著性(P均<0.05); (2)培养基上清液PGE2浓度5、10 mg/L 的IL-1β处理组培养基上清液PGE2浓度分别为 (20.86±5.23)×10-6 g/L、(31.16±2.64)×10-6 g/L,对照组为(10.49±0.36)×10-6 g/L, 5、10 mg/L 的IL-1β处理组与对照组比较差异有显著性(P<0.05);(3) COX-2 mRNA表达量 0.10、0.25、0.50 mmol/L 的H2O2和IL-1β共处理组COX-2 mRNA表达量分别为 (149.2±7.5)%、(189.6±9.5)%、(239.1±12.0)%, IL-1β单独处理组为(66.1±3.7)%, 对照组为(41.6±2.1)%, 0.10、0.25、0.50 mmol/L 的H2O2和IL-1β共处理组与IL-1β单独处理组比较,差异有显著性 (P<0.05); (4)培养基上清液PGE2浓度0.10、0.25、0.50 mmol/L的H2O2和IL-1β共处理组,培养基上清液PGE2浓度分别为 (27.01±5.16)×10-6 g/L、(32.79±3.01)×10-6 g/L、(41.13±3.41)×10-6 g/L,对照组为(10.49±0.36)×10-6 g/L,0.10、0.25、0.50 mmol/L的H2O2和IL-1β共处理组与对照组比较差异有显著性(P<0.05).0.25、0.50 mmol/L的 H2O2和IL-1β共处理组PGE2浓度均与IL-1β单独处理组[(20.86±5.23)×10-6 g/L]比较差异有显著性 (P<0.05). 结论过氧化氢上调IL-1β对HPEC COX-2的诱导表达,其调节机制可能发生在转录水平.     

Vascular endothelial growth factor protects hepatoma cells against oxidative stress-induced cell death

BACKGROUND: The aim of the present study was to examine coordination of the vascular endothelial growth factor (VEGF) and VEGF receptor (Flk-1) system and to study control of VEGF expression by oxidative stress, which is considered a model for chronic liver disease. METHODS: Cell viability was determined by test method with 3-[4, 5-dimethylthiazol-2-yl]-2, 5-dephenyl tetrazolium bromide (MTT). Expressions of cellular proteins were evaluated by western blot analysis. RESULTS: The c-Met tyrosine phosphorylation in PLC/PRF/5 hepatoma cells was increased by treatment with 20 ng/mL hepatocyte growth factor (HGF), and extracellular signal-regulated kinase (ERK) was also activated. Although Flk-1 was phosphorylated in response to VEGF (>50 ng/mL), phosphorylated ERK was not detected at these concentrations. A total of 5.0 and 10 micromol/L hydrogen peroxide (H(2)O(2)) caused cell death in a dose-dependent manner after 24 h. On western blot analysis at 1 h with H(2)O(2), rapid phosphorylation of both ERK1/2 and c-Jun NH(2)-terminal kinase (JNK) was observed. In the first 6 h, H(2)O(2) induced cell death for 58.4 +/- 6.8%, whereas the presence of 100 ng/mL VEGF improved the survival rate to 77.2 +/- 4.2%. The VEGF significantly decreased H(2)O(2)-induced cell death after 12 h, whereas HGF (20 ng/mL) did not have a similar effect. When cells were incubated with 5 micromol/L H(2)O(2), expression of VEGF protein was detected. Furthermore, H(2)O(2)-induced phosphorylation of ERK and JNK was also reduced by VEGF (100 ng/mL). In contrast, HGF did not induce phosphorylation of ERK and JNK. CONCLUSION: Hepatoma cells might be able to survive under continuous oxidative stress through expression of VEGF.     

Polaprezinc protects human colon cells from oxidative injury induced by hydrogen peroxide: relevant to cytoprotective heat shock proteins

INTRODUCTION Polaprezinc [N-(3-aminopropionyl)-L-histidinato zinc], an antiulcer drug, is a chelate compound consisting of zinc ion, L-carnosine, dipeptide of β-alanine, and L-histidine and has an antioxidant effect and anti-H pylori activity[1-4]. It ha…     

Hydrogen peroxide induced apoptosis of endothelial cells concomitantly with cycloheximide

We examined whether or not hydrogen peroxide induced apoptosis of vascular endothelial cells. Cultured vascular endothelial cells from bovine carotid arteries were used. Apoptosis was determined by a propidium iodide assay. Under serum free conditions, treatment of the endothelial cells with hydrogen peroxide (H2O2) for 6 hours induced cytotoxicity (51Cr release) in a dose-dependent manner (10 micromol/l-1 mmol/l). Under the condition containing 10% serum, H2O2 did not induce cytotoxicity even at the highest concentration (1 mmol/l). However, concomitant treatment of endothelial cells with cycloheximide at a dose of 10 microg/ml elicited endothelial cell apoptosis of by 15.6+/-1.7% at 6 hours after administration, even under the 10% serum condition. In addition, endothelial cell apoptosis due to H2O2 and cycloheximide was completely inhibited by zD-dcb (50 micromol/l), an inhibitor of caspase. 1 mmol/l of 4, 4-diisothiocyanatostilbene-2, 2-disulfonic acid (DIDS), which is a chloride bicarbonate exchanger blocker, partially inhibited the H2O2 and cycloheximide-induced endothelial cell apoptosis. On the other hand, cytotoxicity of endothelial cells due to H2O2 under serum free conditions was not inhibited by DIDS. These data suggested that hydrogen peroxide could induce endothelial cell apoptosis or cell membrane injury (51Cr release) in the presence or absence of an inhibitor of protein synthesis.     

Protective effects of trimetazidine against vascular endothelial cell injury induced by oxidation

Objective To explore the protective effects of trimetazidine on vascular endothelial cells injury induced by hydrogen peroxide (H2O2) and its pharmacological mechanisms of anti-oxidation. Methods Human umbilical vein endothelial cells (HUVECs) were injured by H2O2. Next, the cells were treated with three different concentrations of trimetazidine (1μmol/L,10μmol/L,100μmol/L, respectively). The viability of cells was detected by methyl thiazoeyl tetrazolium (MTT) assay. In addition, malondialdehyde (MDA) contents, superoxide dismutase (SOD) and secretion of NO were measured. Results Trimetazidine could enhance the viability of the injured HUVECs induced by oxidation, decrease the level of MDA, enhance the SOD activity, and increase the secretion of nitrogen monoxide. These effects were in a certain dose-dependent manner and the difference was significant among the three concentrations (P<0.05). Conclusions Our results suggest that trimetazidine may protect lipid peroxidation and prevent oxidation-induced cellular dysfunction of HUVECs.     

Indomethacin suppresses growth of colon cancer via inhibition of angiogenesis in vivo

AIM: It has been reported that regular consumption of nonsteroidal anti-inflammatory drugs like indomethacin decreases the incidence and mortality rate of a number of gastrointestinal cancers. We aimed to explore the efficacy and possible mechanisms of indomethacin on tumor growth and tumor angiogenesis of human colon cancer xenografts in nude mice. METHODS: MTT (thiazolyl blue) assay was used to assess the effect of indomethacin on cultured human colorectal cancer cell line HCT116. HCT116 cells were inoculated subcutaneously into BALB/c-nu/nu mice. After oral administration of indomethacin, 3 mg/kg·d for 4 wk, animals were sacrificed by cervical dislocation. Immunohistochemical staining was employed to determine the microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression in tumor tissues. RESULTS: Indomethacin, a non-selective COX inhibitor, significantly decreased the viability of HCT116 cells in a dose-dependent manner (P<0.05) with 50% inhibition at approximately 318.2±12.7 μmol/L Growth of HCT116 cell tumor was significantly suppressed by indomethacin. The tumor volume was significantly decreased in the treated group (458.89±32.07 mm3) compared to the control group (828.21±31.59 mm3) (P<0.05). The MVD of the treated group (19.50±5.32) was markedly decreased compared to the control group (37.40±4.93) (P<0.001). The VEGF expression of the treated group (1.19±0.17) was obviously reduced as compared to the control group (1.90±0.48) (P<0.01). The decrease in MVD was positively correlated with the decrease of VEGF expression (rs = 0.714, P<0.05). We did not see gastrointestinal complications in the treated group and no differences were noted in the body weight of the mice between the two groups throughout the study CONCLUSION: Indomethacin can significantly decrease the viability of cultured HCT116 cells and retard human colorectal HCT116 cell tumor growth via inhibiting tumor angiogenesis, which might be through reduction of VEGF expression.     

Vascular endothelial growth factor antisense oligodeoxynucleotides with lipiodol in arterial embolization of liver cancer in rats

AIM:Transcatheter arterial embolization (TAE) of the hepatic artery has been accepted as an effective treatment for unresectable hepatocellular carcinoma (HCC). However,embolized vessel recanalization and collateral circulation formation are the main factors of HCC growth and recurrence and metastasis alter TAE. Vascular endothelial growth factor (VEGF) plays an important role in tumor angiogenesis.This study was to explore the inhibitory effect of VEGF antisense oligodeoxynucleotides (ODNs) on VEGF expression in cultured Walker-256 cells and to observe the anti-tumor effect of intra-arterial infusion of antisense ODNs mixed with lipiodol on rat liver cancer.METHODS: VEGF antisense ODNs and sense ODNs were added to the media of non-serum cultured Walker-256 cells.Forty-eight hours later, VEGF concentrations of supernatants were detected by EUSA. Endothelial cell line ECV-304 cells were cultured in the supernatants. Seventy-two hours later,growth of ECV-304 cells was analyzed by NTT method. Thirty Walker-256 cell implanted rat liver tumor models were divided into 3 groups.0.2 mL lipiodol (LP group, n=10), 3OD antisense ODNs mixed with 0.2 mL lipiodol (LP+ODNs group, n=10) and 0.2 mL normal saline (control group, n=10) were infused into the hepatic artery. Volumes of tumors were measured by MRI before and 7 d alter the treatment.VEGF mRNA in cancerous and peri-cancerous tissues was detected by RT-PCR. Microvessel density (MVD) and VEGF expression were observed by immunohistochemistry.RESULTS: Antisense ODNs inhibited Walker-256 cells‘ VEGF expression, The tumor growth rate was significantly lower in LP+ODNs group than that in LP and control groups (140.1&#177;33.8%, 177.9&#177;64.9% and 403.9&#177;69.4% respectively, F=60.019,P&lt;0.01).VEGF mRNAs in cancerous and peri-cancerous tissues were expressed highest in LP group and lowest in LP+ODNs group. The VEGF positive rates showed no significant difference among LP, control and LP+ODNs groups (90%,70% and 50%, H=3.731, P&gt;0.05).The MVD in LP+ODNs group (53.1&#177;18.4) was significantly less than that in control group (73.2&#177;20.4) and LP group(80.3&#177;18.5) (F=5.44, P&lt;0.05).CONCLUSION: VEGF antisense ODNs can inhibit VEGF expression of Walker-256 cells.It may be an antiangiogenesis therapy agent for malignant tumors. VEGF antisense ODNs mixed with lipiodol embolizing liver cancer is better in inhibiting liver cancer growth, VEGF expression and microvessel density than lipiodol alone.     

原花青素对血管内皮细胞过氧化氢损伤的保护作用

目的 观察原花青素对血管内皮细胞过氧化氢损伤的保护作用及可能机制.方法 用体外培养的人脐静脉内皮细胞传代后进行实验,实验分为3组:对照组常规培养;过氧化氢损伤组;药物干预组加入原花青素低、中、高浓度组(25 mg/L、50 mg/L和100 mg/L预处理).用MTT法观察原花青素对过氧化氢损伤的内皮细胞活性的影响,各组均测定细胞中超氧化物歧化酶、丙二醛和乳酸脱氢酶的活性,用Hoechst 33258荧光染色法观察过氧化氢损伤对血管内皮细胞的凋亡情况,蛋白免疫印迹法分析各组凋亡基因bcl-2蛋白的表达.结果 (1)原花青素使过氧化氢损伤的内皮细胞的脂质过氧化物丙二醛生成减少,乳酸脱氢酶漏出液减少,超氧化物歧化酶活力增加;(2)过氧化氢损伤可以诱导内皮细胞凋亡,原花青素可显著减少过氧化氢诱导的内皮细胞的凋亡,且上调抗凋亡基因bcl-2的蛋白表达.结论 原花青素处理对过氧化氢所致的内皮细胞的损伤有保护作用,机制可能通过抗脂质过氧化,对氧自由基的清除,以及抗细胞凋亡有关.     

Protective effects of calcium channel blockers on hydrogen peroxide induced increases in endothelial permeability

STUDY OBJECTIVE--The aim was to examine the effects of calcium channel blockers on the permeability of endothelial cells and to determine whether these agents could protect against increases in endothelial permeability induced by hydrogen peroxide (H2O2). DESIGN--Endothelial cells were cultured on collagen coated micropore filters. When they were confluent on the filter, albumin transfer and electrical resistance across the endothelial monolayers were measured. EXPERIMENTAL MATERIAL--Endothelial cells were obtained from human umbilical veins. The cells at the 2nd to 4th passage were used for the experiments. MEASUREMENTS AND MAIN RESULTS--Nilvadipine (10(-8) M) suppressed endothelial albumin transfer by 37.2% (p less than 0.01) and enhanced electrical resistance by 25.8% (p less than 0.01), whereas nicardipine (10(-7) M), diltiazem (10(-7) M), and verapamil (10(-7) M) had no significant effect on either variable without the addition of H2O2. H2O2(0.2 mM) increased albumin transfer by 164% (p less than 0.01) and reduced electrical resistance by 67% (p less than 0.01) across endothelial monolayers without endothelial cell lysis. Nilvadipine (10(-8) M) and nicardipine (10(-7) M) inhibited the (0.2 mM) H2O2 induced increases in endothelial albumin transfer and decreases in electrical resistance more strongly than diltiazem and verapamil, although all of these agents significantly reduced such injury. CONCLUSIONS--Nilvadipine is a potent inhibitor of endothelial permeability and of hydrogen peroxide induced increases in permeability.     

Fluid shear stress attenuates hydrogen peroxide-induced c-Jun NH2-terminal kinase activation via a glutathione reductase-mediated mechanism

c-Jun NH2-terminal kinase (JNK) is activated by a number of cellular stimuli including reactive oxygen species (ROS). Previous studies have demonstrated that fluid shear stress (flow) inhibits cytokine-induced JNK activation in endothelial cells (ECs). In the present study, we show JNK activation by ROS in ECs and hypothesized that flow inhibits ROS-induced JNK activation in ECs via modulation of cellular protection systems against ROS. JNK was activated by 300 micro mol/L hydrogen peroxide (H2O2) in bovine lung microvascular ECs (BLMVECs) with a peak at 60 minutes after stimulation (6.3+/-1.2-fold increase). Preexposure of BLMVECs to physiological steady laminar flow (shear stress=12 dyne/cm2) for 10 minutes significantly decreased H2O2-induced JNK activation. Thioredoxin and glutathione are cellular antioxidants that protect cells against ROS. Flow induced a significant increase in the ratio of reduced glutathione to oxidized glutathione consistent with a 1.6-fold increase in glutathione reductase (GR) activity. Preincubation of BLMVECs with the GR inhibitor, 1,3 bis-(2 chloroethyl)-1-nitrosourea, abolished the inhibitory effect of flow. In contrast, preincubation of BLMVECs with azelaic acid, a specific inhibitor for thioredoxin reductase, did not alter the effect of flow on H2O2-induced JNK activation. Overexpression of GR mimicked the effect of flow to inhibit JNK activation. These results suggest that flow activates GR, an important regulator of the intracellular redox state of glutathione, and exerts a protective mechanism against oxidative stress in endothelial cells.     

Decreasing cellular hydrogen peroxide with catalase mimics the effects of hypoxia on the sensitivity of the L-type Ca2+ channel to beta-adrenergic receptor stimulation in cardiac myocytes

In cardiac myocytes, hypoxia inhibits the basal L-type Ca2+ current (I(Ca-L)) and increases the sensitivity of I(Ca-L) to beta-adrenergic receptor stimulation. We investigated whether hydrogen peroxide (H2O2) is involved in the hypoxic response. Guinea pig ventricular myocytes were dialyzed with catalase, which specifically catalyzes the conversion of H2O2 to H2O and oxygen, and then I(Ca-L) was recorded during exposure to isoproterenol (Iso). Catalase decreased the K(0.5) for activation of I(Ca-L) by Iso from 2.7+/-0.3 nmol/L (in cells dialyzed with heat-inactivated catalase) to 0.4+/-0.1 nmol/L. The increase in sensitivity to Iso by catalase may be attenuated when cells are preexposed to H2O2. A significant increase in sensitivity of I(Ca-L) to Iso was recorded when mitochondrial function was inhibited with myxothiazol or FCCP, suggesting that the source of H2O2 was from the mitochondria. Prior exposure of cells to H2O2 attenuated the inhibition of basal I(Ca-L) during hypoxia and the increase in sensitivity of I(Ca-L) to Iso during hypoxia. Additionally, extracellularly applied catalase mimicked the effect of hypoxia on basal I(Ca-L). Measurement of the rate of production of hydrogen peroxide using 5- (and 6-)chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate acetyl ester indicated that hypoxia was associated with a significant decrease in the production of hydrogen peroxide in the cells. These data suggest that hypoxia mediates changes in channel activity through a lowering in H2O2 levels and that H2O2 is a key intermediate in modifying basal channel activity and the beta-adrenergic responsiveness of the channel during hypoxia.     

胡椒碱减轻兔原代左心房肌细胞氧化应激损伤的作用

目的:利用低浓度过氧化氢（H2O2）建立兔原代左心房肌细胞氧化损伤模型,探讨胡椒碱减轻氧化应激损伤的保护作用。方法: 将18只新西兰白兔随机分为3组,每组6只:即正常对照(NC)组、H2O2组和胡椒碱组,均分别进行左心房肌细胞的原代培养。NC组对培养的心房细胞直接进行检测,H2O2组直接在培养的原代心房肌细胞中加入终浓度为100 μmol/L的H2O2培养2 h,胡椒碱组以7×10-6 mol/L浓度的胡椒碱处理细胞1 h之后,加入终浓度为100 μmol/L的H2O2共同培养2 h。检测氧化和抗氧化指标的变化。MTT法检测三组原代细胞活力,黄嘌呤氧化酶法检测超氧化物歧化酶（SOD）活力、比色法检测丙二醛（MDA）含量及还原型谷胱甘肽（GSH）含量,Fura-2 AM检测细胞内钙离子浓度,RT-PCR对线粒体mRNA进行定量分析。结果: 与NC组相比较,H2O2组细胞的活力、SOD的活力及GSH的含量明显下降（P<0.05）; MDA的含量、钙离子浓度和线粒体mRNA的表达均明显增加（P<0.05）。胡椒碱组和H2O2组比较,上述指标均有显著改善（P<0.05）。结论: 胡椒碱能够在氧自由基的产生清除等环节,减轻兔原代左心房肌细胞的氧化应激损伤。     

High glucose augments stress-induced apoptosis in endothelial cells

Hyperglycemia has been identified as one of the important factors involved in the microvascular complications of diabetes, and has been related to increased cardiovascular mortality. Endothelial damage and dysfunction result from diabetes; therefore, the aim of this study was to determine the response of endothelial cells to stressful stimuli, modelled in normal and high glucose concentrations in vitro. EAhy 926 endothelial ceils were cultured in 5 mmol/L or 30 mmol/L glucose conditions for a 24 hour period and oxidative stress was induced by exposure to hydrogen peroxide （HzO2） or tumour necrosis factor- α （TNF- α ）, following which the protective effect of the glucocorticoid dexamethasone was assessed. Apoptosis, necrosis and cell viability were determined using an ELISA for DNA fragmentation, an enzymatic lactate dehydrogenase assay and an MTT assay, respectively. High glucose significantly increased the susceptibility of EAhy 926 cells to apoptosis in the presence of 500 gmol/L H2O2 , above that induced in normal glucose （P〈0.02）. A reduction of H2O2- and TNF- a -induced apoptosis occurred in both high and low glucose after treatment with dexamethasone （P〈0.05）. Conclusion high glucose is effective in significantly augmenting stress caused by H2O2, but not in causing stress alone. These findings suggest a mechanism by which short term hyperglycemia may facilitate and augment endothelial damage.     

Effects of the reactive oxygen species hydrogen peroxide and hypochlorite on endothelial nitric oxide production

Reactive oxygen species (ROS) hydrogen peroxide (H(2)O(2)) and hypochlorite (HOCl) participate in the pathogenesis of ischemia/reperfusion injury, inflammation, and atherosclerosis. Both NO and ROS are important modulators of vascular tone and architecture and of adhesive interactions between leukocytes, platelets, and vascular endothelium. We studied the effect of H(2)O(2) and HOCl on receptor-dependent (bradykinin [10(-6) mol/L] and ADP [10(-4) mol/L]) and receptor-independent mechanisms (calcium ionophore A23187 [10(-6) mol/L]) of NO production by porcine aortic endothelial cells (ECs). Changes in the level of EC cGMP (the second messenger of NO) were used as a surrogate of NO production. EC cGMP increased 300% in response to bradykinin and A23187 and 200% in response to ADP. Exposure of ECs to H(2)O(2) (50 micromol/L) for 30 minutes significantly impaired cGMP levels in response to ADP, bradykinin, and the receptor-independent NO agonist A23187. In contrast, preincubation with HOCl (50 micromol/L) impaired cGMP production only in response to ADP and bradykinin but not A23187. These concentrations of H(2)O(2) and HOCl did not result in increased EC lethality as assessed by lactate dehydrogenase release. Neither H(2)O(2) nor HOCl affected EC cGMP production in response to NO donor sodium nitroprusside, which suggests that guanylate cyclase is resistant to these oxidants. We also demonstrated that neither H(2)O(2) nor HOCl affects endothelial NO synthase (eNOS) catalytic activity as measured by conversion of L-arginine to L-citrulline in EC homogenates supplemented with eNOS cofactors. The present studies show that H(2)O(2) impairs NO production in response to both receptor-dependent and receptor-independent agonists and that these effects are due, at least in part, to inactivation of eNOS cofactors, whereas HOCl inhibits NO production by interfering with receptor-operated mechanisms at the level of the cell membrane. Concentrations of H(2)O(2) and HOCl used in the present studies have been shown to be generated in vivo during inflammation and ischemia/reperfusion. Therefore, we infer that these effects of H(2)O(2) and HOCl on EC NO production may contribute to disregulated vascular tone and altered leukocyte-EC interactions that occur in vascular injury as a result of those causes in which ROS generation is involved.     

胡椒碱对H2O2致兔心房肌细胞动作电位时程及L型钙电流异常的保护作用

目的:研究胡椒碱(PIP)对H2O2引起的单个兔心房肌细胞动作电位时程（APD）及L型钙电流(ICa,L)异常的保护作用。方法:采用全细胞膜片钳技术,观察10和50 μmol/L的H2O2引起单个兔心房肌细胞APD及ICa,L的改变,以及预先应用7 μmol/L的PIP对其的作用。结果:7 μmol/L的PIP对正常兔心房肌细胞APD、ICa,L及L型钙通道动力学无明显影响。在10和50 μmol/L的H2O2作用下,兔心房肌细胞APD50和APD90明显缩短(P<0.05),静息膜电位（RMP）绝对值显著下降(P<0.05),ICa,L峰值由(39.3±5.4) pA/pF降低至(32.8±2.0) pA/pF(P<0.05),电流-电压曲线上移,通道稳态激活曲线右移,通道稳态失活曲线左移,但恢复时间不变。预先给予7 μmol/L的PIP可明显减轻H2O2对APD、ICa,L的抑制作用(P<0.01),对L型钙通道动力学的异常影响。结论:PIP可减轻氧化应激对心房肌细胞APD、ICa,L的影响。     

TLR9 agonist acts by different mechanisms synergizing with bevacizumab in sensitive and cetuximab-resistant colon cancer xenografts

Synthetic agonists of Toll-like receptor 9 (TLR9), a class of agents that induce specific immune response, exhibit antitumor activity and are currently being investigated in cancer patients. Intriguingly, their mechanisms of action on tumor growth and angiogenesis are still incompletely understood. We recently discovered that a synthetic agonist of TLR9, immune modulatory oligonucleotide (IMO), acts by impairing epidermal growth factor receptor (EGFR) signaling and potently synergizes with anti-EGFR antibody cetuximab in GEO human colon cancer xenografts, whereas it is ineffective in VEGF-overexpressing cetuximab-resistant GEO cetuximab-resistant (GEO-CR) tumors. VEGF is activated by EGFR, and its overexpression causes resistance to EGFR inhibitors. Therefore, we used IMO and the anti-VEGF antibody bevacizumab as tools to study IMO's role on EGFR and angiogenesis and to explore its therapeutic potential in GEO, LS174T, and GEO-CR cancer xenografts. We found that IMO enhances the antibody-dependent cell-mediated cytotoxicity (ADCC) activity of cetuximab, that bevacizumab has no ADCC, and IMO is unable to enhance it. Nevertheless, the IMO-plus-bevacizumab combination synergistically inhibits the growth of GEO and LS174T as well as of GEO-CR tumors, preceded by inhibition of signaling protein expression, microvessel formation, and human, but not murine, VEGF secretion. Moreover, IMO inhibited the growth, adhesion, migration, and capillary formation of VEGF-stimulated endothelial cells. The antitumor activity was irrespective of the TLR9 expression on tumor cells. These studies demonstrate that synthetic agonists of TLR9 interfere with growth and angiogenesis also by EGFR- and ADCC-independent mechanisms affecting endothelial cell functions and provide a strong rationale to combine IMO with bevacizumab and EGFR inhibitory drugs in colon cancer patients.     

Differentiation and expansion of endothelial cells from human bone marrow CD133+ cells

We report a method of purifying, characterizing and expanding endothelial cells (ECs) derived from CD133(+) bone marrow cells, a subset of CD34(+) haematopoietic progenitors. Isolated using immunomagnetic sorting (mean purity 90 +/- 5%), the CD133(+) bone marrow cells were grown on fibronectin-coated flasks in M199 medium supplemented with fetal bovine serum (FBS), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and insulin growth factor (IGF-1). The CD133(+) fraction contained 95 +/- 4% CD34(+) cells, 3 +/- 2% cells expressing VEGF receptor (VEGFR-2/KDR), but did not express von Willebrand factor (VWF), VE-cadherin, P1H12 or TE-7. After 3 weeks of culture, the cells formed a monolayer with a typical EC morphology and expanded 11 +/- 5 times. The cells were further purified using Ulex europaeus agglutinin-1 (UEA-1)-fluorescein isothiocyanate (FITC) and anti-FITC microbeads, and expanded with VEGF for a further 3 weeks. All of the cells were CD45(-) and CD14(-), and expressed several endothelial markers (UEA-1, VWF, P1H12, CD105, E-selectin, VCAM-1 and VE-cadherin) and typical Weibel-Palade bodies. They had a high proliferative potential (up to a 2400-fold increase in cell number after 3 weeks of culture) and the capacity to modulate cell surface antigens upon stimulation with inflammatory cytokines. Purified ECs were also co-cultivated with CD34(+) cells, in parallel with a purified fibroblastic cell monolayer. CD34(+) cells (10 x 10(5)) gave rise to 17,951 +/- 2422 CFU-GM colonies when grown on endothelial cells, and to 12,928 +/- 4415 CFU-GM colonies on fibroblast monolayers. The ECs also supported erythroid blast-forming unit (BFU-E) colonies better. These results suggest that bone marrow CD133(+) progenitor cells can give rise to highly purified ECs, which have a high proliferative capacity, can be activated by inflammatory cytokines and are superior to fibroblasts in supporting haematopoiesis. Our data support the hypothesis that endothelial cell progenitors are present in adult bone marrow and may contribute to neo-angiogenesis.