Hypoxia induces angiogenic factors in brain microvascular endothelial cells

Hypoxia is increasingly recognized as an important contributing factor to the development of brain diseases such as Alzheimer's disease (AD). In the periphery, hypoxia is a powerful regulator of angiogenesis. However, vascular endothelial cells are remarkably heterogeneous and little is known about how brain endothelial cells respond to hypoxic challenge. The objective of this study is to characterize the effect of hypoxic challenge on the angiogenic response of cultured brain-derived microvascular endothelial cells. Brain endothelial cell cultures were initiated from isolated rat brain microvessels and subjected to hypoxia (1% O(2)) for various time periods. The results showed that hypoxia induced rapid (≤ 0.5h) expression of hypoxia-inducible factor 1α (HIF-1α) and that cell viability, assessed by MTT assay, was unaffected within the first 8h. Examination of brain endothelial cell cultures for pro- and anti-angiogenic proteins by western blot, RT-PCR and ELISA revealed that within 0.5 to 2h of hypoxia levels of vascular endothelial growth factor and endothelin-1 mRNA and protein were elevated. The expression of heme oxygenase-1 also increased but only after 8h of hypoxia. In contrast, similar hypoxia exposure evoked a decrease in endothelial nitric oxide synthase and thrombospondin-2 levels. Exposure of brain endothelial cell cultures to hypoxia resulted in a significant (p<0.001) decrease (94%) in tube length, an in vitro index of angiogenesis, compared to control cultures. The data indicate that, despite a shift toward a pro-angiogenic phenotype, hypoxia inhibited vessel formation in brain endothelial cells. These results suggest that in brain endothelial cells expression of angiogenic factors is not sufficient for the development of new vessels. Further work is needed to determine what factors/conditions prevent hypoxia-induced angiogenic changes from culminating in the formation of new brain blood vessels and what role this may play in the pathologic changes observed in AD and other diseases characterized by cerebral hypoxia.     

不同诱导因子下内皮祖细胞具有双向分化的潜能

目的探讨内皮祖细胞(EPCs)在不同诱导因子作用下的体外分化潜能。方法人脐血单个核细胞分别予50ng/ml血管内皮生长因子(VEGF组)或50ng/ml血小板源生长因子(PDGF组)诱导分化。光镜形态观察,免疫荧光鉴定。流式细胞分析CD133+EPCs分化特征。结果新鲜脐血分离单个核细胞培养1周后贴壁细胞的EPCs特异的DiI标记乙酰化低密度脂蛋白鉴定为80%阳性。在VEGF或PDGF诱导下1周,单个核细胞大量贴壁生长多呈圆形,少量梭形生长。2周时,被诱导细胞有近50%贴壁呈梭形生长,VEGF组和PDGF组无明显差异。至4周时两组出现明显的分化差异,其中VEGF组呈"铺路石"样细胞融合,血管性假血友病因子免疫荧光呈阳性;而PDGF组呈梭形或长多角形融合,予α-平滑肌肌动蛋白标记部分呈阳性。单个核细胞磁珠分选后得到CD133+较CD133-更多分化为内皮样细胞(P<0.05);而在PDGF的诱导下CD133-较CD133+更多分化为平滑肌样细胞(P<0.05)。结论单个核细胞在体外不同的诱导因子诱导下可以双向分化,CD133+EPCs具有更强的内皮细胞分化潜能。     

Endometrial endothelial cells express estrogen and progesterone receptors and exhibit a tissue specific response to angiogenic growth factors.

OBJECTIVE: To develop a reliable method for the isolation and longterm culture of microvessel endothelial cells from human endometrium and to evaluate their response to angiogenic growth factors and steroid hormones in comparison to endothelial cells derived from other organs. METHODS: Endometrial tissue from hysterectomy specimens were digested sequentially with collagenase and trypsin, cultured for 24 h, then selected by adhesion to anti-CD-34 coated magnetic beads. Alternatively, anti-CD-34-coated beads could also be substituted by Ulex europaeus agglutinin-1, anti-PECAM, or anti-E-selectin-coated beads. Characterization of the isolated cultures included expression of endothelial cell markers, regulation of E-selectin in response to TNF-alpha, proliferative response to angiogenic growth factors, and expression of progesterone and estrogen receptors. We also analyzed the relative binding affinity of VEGF on endometrial endothelial cells in comparison to other endothelial cell types. RESULTS: Selection on anti-CD-34-coated beads eliminated contaminating cells and resulted in a homogeneous population of human endometrial endothelial cells (HEEC), as assessed by expression of PECAM, von Willebrand's factor, and uptake of acetylated-LDL. HEEC also upregulated E-selectin in response to TNF-alpha in a manner similar to that seen for other endothelial cell types. Expression of progesterone and estrogen receptor was revealed by immunocytochemistry and RT-PCR consistently until passage 5. Endometrial endothelial cells were more responsive to growth stimulation by VEGF than were dermal endothelial cells isolated under similar conditions. Further characterization indicated that VEGF bound more avidly to HEEC than to other endothelial cell types. CONCLUSIONS: Human endometrial endothelial cells were isolated to homogeneity by a two-part protocol and successfully passaged under culture conditions similar to those used for other endothelial cell types. The HEEC were very responsive to VEGF growth-stimulation likely due to elevated affinity, or increased levels of, KDR and FLT-1 on the cell surface. These results indicate that HEEC are capable of maintaining a mature phenotype in culture and might provide a model for understanding the response of these cells to the recurrent cycles of proliferation imposed on the endometrium during menstruation.     

Irradiation of mechanically-injured human arterial endothelial cells leads to increased gene expression and secretion of inflammatory and growth promoting cytokines

Radiation therapy is applied to inhibit neointima formation after percutaneous transluminal coronary angioplasty (PTCA). In this study, we evaluated the effect of irradiation on re-endothelialisation of circular denuded tracks made in post-confluent cultures of arterial endothelial cells (ECs) and on cellular factors involved in this process. Image analysis and time-lapse microcinematography revealed cell migration into denuded areas starting 4h after injury. Fifty percent coverage was achieved at 14.8 +/- 2.0 h. Using competitive PCR and flow cytometry techniques, no significant changes in mRNA expression of interleukin-1beta (IL-1beta), interleukin-8 (IL-8), basic fibroblast growth factor (bFGF or FGF-2), transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor A (PDGF-A), platelet-derived growth factor B (PDGF-B) and tissue factor (TF), and surface molecule expression of anti-intercellular adhesion molecule-1 (ICAM-1), anti-vascular cell adhesion molecule-1 (VCAM-1), anti-platelet/endothelial cell adhesion molecule-1 (PECAM-1), MHC-1, TF and Fas were observed. However, injury did significantly (P < 0.05) elevate the release of IL-8 and FGF-2 protein in the cell culture supernatant, as assessed by ELISA. Radiation (15Gy) given immediately after injury did not affect the kinetics of re-endothelialisation up to 48 h, in spite of the fact that no cell divisions were observed. Thereafter cell density decreased and cultures deteriorated. Compared to cultures exposed to injury alone, radiation induced significant (P < 0.05) increases in mRNA levels of IL-8 (1.35 +/- 0.10-fold increase at 4h), FGF-2 (1.62 +/- 0.10-fold at 4h; 1.76 +/- 0.33-fold at 24h) and IL-1beta (2.76 +/- 0.40-fold at 24h), whereas mRNA levels of TGF-beta1, PDGF-A and PDGF-B increased about 1.2-fold. IL-8 and FGF-2 protein concentrations in the media were higher than those observed in non-irradiated injured cell cultures; however, this difference was not significant. Radiation induced a 2.3 +/- 0.3-fold increase (P < 0.05) in Fas surface expression only. In conclusion, irradiation of mechanically-injured human EC leads to increased gene expression and protein secretion of inflammatory and growth promoting cytokines.     

Procoagulant soluble tissue factor is released from endothelial cells in response to inflammatory cytokines

Inflammatory cytokines alter the hemostatic balance of endothelial cells (ECs). Alternatively spliced human tissue factor (asHTF), a soluble isoform of tissue factor (TF), has recently been detected in ECs, possibly contributing to procoagulability. Agonists regulating asHTF expression and release are yet unknown. This study examines the effect of TNF-alpha and IL-6 on the endothelial expression of both TF variants and delineates the impact of asHTF on the procoagulability of extracellular fluids. asHTF and TF mRNA were assessed by real-time PCR, and asHTF, TF, and tissue factor pathway inhibitor (TFPI) proteins by Western blot and fluorescence microscopy before and after stimulation with TNF-alpha (10 ng/mL) or IL-6 (10 ng/L). The procoagulability of cell supernatant was analyzed by a chromogenic assay with or without phospholipid vesicles. We found asHTF mRNA to be maximally increased 10 minutes after TNF-alpha and 40 minutes after IL-6 treatment (asHTF/GAPDH ratio 0.0223+/-0.0069 versus 0.0012+/-0.0006 for control, P<0.001 and 0.0022+/-0.0004 versus 0.0012+/-0.0007, P<0.05, respectively). Not only was asHTF increased, but also TFPI decreased after cytokine treatment. asHTF was found in the supernatant as early as 5 hours after TNF-alpha stimulation, supporting factor Xa generation after relipidation (6.55+/-1.13 U versus 2.99+/-0.59 U in control supernatant, P<0.00001). Removal of asHTF from supernatants by immunoprecipitation diminished its procoagulability to baseline. The soluble TF isoform expressed and released from ECs in response to inflammatory cytokines becomes procoagulant in the presence of phospholipids. Thus, asHTF released from ECs is a marker for and a contributor to imbalanced hemostasis.     

Expression of chemokine by human coronary-artery and umbilical-vein endothelial cells and its regulation by inflammatory cytokines

BACKGROUND: Activation of the endothelium is a critical event in the process of inflammation and is associated with the production of chemokines. OBJECTIVE: To evaluate the proinflammatory cytokine-induced chemokine repertoire of human coronary-artery endothelial cells (HCAEC) both at the messenger RNA (mRNA) level and at protein level in direct comparison with that of human umbilical-vein endothelial cells (HUVEC). METHODS: Human coronary-artery and human umbilical-vein endothelial cells were obtained commercially and experimental data were derived from cell cultures between passage levels 3 through 6. Supernatant fluids from cytokine [tumor necrosis factor-alpha (TNF-alpha), interleukin-1-alpha, and anti-TNF R55] stimulated endothelial cell cultures were used to study chemokine release. Sandwiched ELISA assays, obtained commercially, were used to estimate cell culture supernatant fluid levels of the selected chemokines: monocytic chemotactic protein-1, regulated upon activated normal T cells expressed and secreted, interleukin-8, transforming growth factor-beta-2 (TGF-beta2), and gamma interferon protein-10. Expression of messenger RNA was determined using selected labeled riboprobes (32P UTP) in a ribonuclease protection assay using total cellular mRNA. RESULTS: Upon in-vitro stimulation with TNF-alpha and interleukin-1-alpha, production of regulated-upon-activated-normal-T-cells expressed and secreted (RANTES) protein by HCAEC was significantly increased relative to that by HUVEC, the greatest effect being found with interleukin-1-alpha. The opposite effect, however, was noted for levels of monocytic-chemotactic-protein-1 protein, which were detected in HUVEC at significantly higher levels than they were in HCAEC challenged by those cytokines. Production of gamma interferon-inducible protein-10 (gammaIP-10) by HUVEC was induced by TNF-alpha and interleukin-1-alpha, whereas only a modest induction by interleukin-1-alpha was seen in HCAEC. TGF-beta-2 protein was constitutively expressed in HCAEC but not in HUVEC. Expression of mRNA was analyzed by the ribonuclease-protectionassay. RANTES mRNA was expressed in HCAEC from 3 h through 48 h after treatment with TNF-alpha, whereas only a modest induction of RANTES was expressed in HUVEC 24 h and 48 h after treatment with TNF-alpha. Monocytic-chemotactic-protein-1 mRNA was constitutively expressed by both types of cell, but the basal levels in HCAEC was significantly higher than in HUVEC. HCAEC constitutively expressed both TGF-beta-1 and TGF-beta-2 mRNA, whereas HUVEC constitutively expressed TGF-beta-1 only. CONCLUSION: Our data indicate that HCAEC and HUVEC express chemokines differently, which could contribute to or influence site-specific recruitment of subsets of leukocytes.     

流式微球阵列法检测烟雾病患者血清血管生成因子和炎性细胞因子水平

目的：检测烟雾病患者血清血管生成因子和炎性细胞因子水平,探讨其在烟雾病发病中的作用。方法利用流式细胞术微球阵列法检测56例烟雾病和26名健康对照者血清血管内皮生长因子（vascular endothelial grow th factor, VEGF ）、血管生成素－1（angiopoietin－1, Ang－1）、白细胞介素－8（interleukin－8, IL－8）、粒细胞集落刺激因子（granulocyte colony stimulating factor, G －CSF）、粒细胞－巨噬细胞集落刺激因子（granulocyte－macrophage colony stimulating factor, GM －CSF）和单核细胞趋化蛋白－1（ monocyte chemotactic protein 1, MCP－1）水平。结果烟雾病组血清 VEGF [（2.81±1.77）pg/ml 对（1.98±0.66）pg/ml; t =3.081, P =0.003]和 IL－8[（0.89±0.69）pg/ml 对（0.63±0.45）pg/ml;t'=2.0371,P <0.05]水平显著高于健康对照,而 Ang－1水平显著低于健康对照组[（830.01±289.29）pg/ml 对（961.65±232.87）pg/ml;t =－2.032,P =0.045]。结论烟雾病患者血清 VEGF、Ang－1和 IL－8水平与健康对照者存在显著差异,提示血管生成因子和炎性细胞因子可能在烟雾病发病中起着一定的作用。     

Proangiogenic role of neutrophil-like inflammatory heterophils during neovascularization induced by growth factors and human tumor cells

A quantitative in vivo angiogenesis model employing collagen onplants placed on the chick embryo chorioallantoic membrane (CAM) has been used in this study to assess the spatial and temporal associations between neutrophil-like inflammatory cells, namely chicken heterophils, and the development of new blood vessels. Previously we have demonstrated that monocytes/macrophages infiltrating the onplants were associated with extracellular matrix remodeling and angiogenesis, in particular by delivering MMP-13 collagenase. By introducing chicken gelatinase B (chMMP-9) as a specific marker for heterophils, we now show that the onset and extent of angiogenesis induced by purified growth factors or by human HT-1080 fibrosarcoma cells correlated with the initial influx of chMMP-9–positive heterophils. This early heterophil arrival was followed by the infiltration of monocytes/macrophages and appeared to sustain further blood vessel formation. The disruption of inflammatory cell influx by 2 mechanistically distinct anti-inflammatory drugs, cortisone and ibuprofen, significantly inhibited angiogenesis, indicating a functional involvement of these inflammatory cells in new blood vessel development. A direct addition of isolated heterophils or purified chMMP-9 into the HT-1080 onplants engrafted into cortisone- or ibuprofen-treated embryos reversed the antiangiogenic effects of the drugs. The exogenously added heterophils induced in vivo a further infiltration of endogenous heterophils and monocytes and dramatically rescued the impaired angiogenesis, highlighting the importance of early inflammatory leukocytes in tumor-induced angiogenesis. Moreover, purified heterophils incorporated into onplants lacking growth factors or tumor cells induced angiogenesis in nontreated embryos, further indicating a direct proangiogenic role for neutrophil-like leukocytes.     

Expression of adhesion molecules by cultured human glomerular endothelial cells in response to cytokines: comparison to human umbilical vein and dermal microvascular endothelial cells.

We investigated the expression of cell adhesion molecules on the surface of glomerular endothelial cells (GEC), dermal microvascular endothelial cells (MvE), and umbilical vein endothelial cells (HUVEC) that had or had not been stimulated by cytokines. PECAM-1 was constitutively expressed at a high level on HUVEC but its expression level decreased following stimulation by tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma). PECAM-1 was also constitutively expressed on microvascular endothelial cells MvE and GEC, but at lower levels than on HUVEC, and expression by these cells also decreased in response to TNF-alpha and IFN-gamma. There was no dose-dependent effect on MvE but there was a dose-dependent effect on the level of expression of cell adhesion molecules on GEC. TNF-alpha induced the expression of VCAM-1 on HUVEC and GEC, but not MvE, while IFN-gamma induced VCAM-1 expression only on HUVEC. TNF-alpha induced the expression of E-selectin on all three kinds of endothelial cells, but IFN-gamma had no effect on E-selectin expression. GEC therefore showed expression patterns of PECAM-1, VCAM-1, and E-selectin different from those seen in HUVEC and MvE upon treatment with TNF-alpha or IFN-gamma. The use of cultured human GEC allows us to study not only the inflammatory processes, but also the pathophysiological role of GEC in hemodynamic disturbances and their interaction with intrinsic mesangial cells at the molecular and subcellular levels.     

冠心病患者循环内皮细胞与炎性相关因子的研究

目的应用免疫磁珠分离急性心肌梗死（AMI）及不稳定性心绞痛（UA）患者外周血中循环内皮细胞（CECs）,探讨与炎性相关因子C反应蛋白质（CRP）、白细胞介素-6（IL-6）及肿瘤坏死因子α（TNFα）的相关性。方法AMI及UA患者入院时取静脉血,用携带抗CD146抗体的免疫磁珠分离外周血CECs;遗传性血友病因子（vWF）、CD31免疫组化及透射电镜对分选细胞进行鉴定;应用Annexin V-FITC／PI检测其凋亡状态;酶联免疫法检测各种炎性相关因子。结果AMI组（n = 37）及UA组（n = 12）的CECs数量[中位数（四分位数间距）分别为52（28 ～ 81．5）个／ml,29（18 ～ 61）个／ml]和血清CRP水平显著高于正常对照组（n = 42,P 〈 0．001）。AMI加UA组剔除合并糖尿病的患者后（n = 26）,CECs数量与CRP水平仍显著高于对照组（P 〈 0．001）;AMI及UA组CECs的坏死率显著高于对照组（P 〈 0．01）;分选出的细胞vWF因子、CD31表达阳性;以研究对象作为整体分析时,CECs数量与CRP及IL-6水平呈显著相关（r = 0．677,0．316,P = 0．000,0．002）,多元线性回归分析显示CRP水平及糖尿病对CECs数量有显著影响（OR = 0．620,0．164,95％ CI：3．985～6．751,0．301～21．877,P = 0．000,0．044）。结论AMI及UA患者CECs数量增加与炎症引起的血管内皮损伤有关。     

Effect of inflammatory cytokines on the metabolism of low-density lipoproteins by human vascular endothelial cells

Cytokines have been shown to activate multiple, varied metabolic pathways in endothelial cells. Little information is available concerning the effects of inflammatory cytokines on lipoprotein metabolism by vascular endothelial cells. Human umbilical vein endothelial cells (HuECs) and bovine aortic endothelial cells (BAECs) were incubated with the inflammatory cytokines recombinant human interleukin-1beta (IL-1), tumor necrosis factor alpha (TNF), interferon gamma (gamma-IF), and interferon beta (beta-IF) at increasing concentrations (0.1 to 1,000 U/mL), for increasing periods (6 to 72 hours). After the incubation period, the media were removed and replaced with serum-free media containing radiolabeled native or acetylated low-density lipoprotein (Ac-LDL) and the rates of degradation and accumulation of radiolabeled LDL were determined. The degradation and accumulation of 125I-LDL were significantly increased (P < .02) in HuECs preincubated with IL-1 (100 U/mL) compared with control incubations without the cytokine or incubations containing gamma-IF, beta-IF, or TNF. This resulted from a 38% increase in LDL receptor protein in cells incubated with IL-1. The increased rate of LDL catabolism by HuECs incubated with IL-1 was accompanied by a significant increase (P < .05) in the rate of cholesteryl ester synthesis in the cells. Cholesteryl ester synthesis rates in HuECs preincubated with gamma-IF, beta-IF, or TNF did not differ significantly from the rates in control incubations. The effect of preincubation with cytokine on the activity of the scavenger receptor was also determined. There were no significant differences in the rate of degradation or accumulation of radiolabeled Ac-LDL in control incubations compared with cultures preincubated with IL-1, gamma-IF, beta-IF, or TNF. There also were no significant differences in the rate of catabolism of native LDL or Ac-LDL in BAECs preincubated with cytokines. Although cytokines have been shown previously to alter the binding of monocytes to endothelial cells, there was no significant increase in the binding of monocytes to cultures incubated with IL-1 plus LDL compared with IL-1 alone. In summary, we now demonstrate that cytokines, specifically IL-1, may alter LDL metabolism by human vascular endothelial cells and alter endothelial cell cholesterol metabolism. These changes in endothelial cell metabolism provide additional evidence supporting the critical role of cytokines in atherogenesis.     

姜黄素对内毒素脂多糖诱导的库普弗细胞分泌炎症细胞因子的抑制作用

[目的]观察姜黄素对内毒素脂多糖（LPS）诱导的库普弗细胞（KC）分泌炎症细胞因子的影响。[方法]分离并培养KC48h后，分设不同浓度姜黄素组，作用于KC3h，确立无毒性的剂量范围；分正常组、LPS组、LPS加姜黄素组（分3种浓度），在添加姜黄素1h后，加LPS（0．1μg／ml培养液）刺激2h。取上清用ELISA法测定肿瘤坏死因子α（TNF-α）、放免法测白细胞介素1β（IL-1β）和IL-6水平；并以细胞免疫荧光化学法观察细胞TNF-α蛋白的表达和分布。[结果]不同浓度组姜黄素均能显著降低TNF-α、IL-1β和IL-6的水平以及细胞TNF-α蛋白的表达，量效关系显著。[结论]姜黄素对LPS诱导的KC炎症细胞因子分泌有显著的抑制作用。