Irisin Induces Angiogenesis in Human Umbilical Vein Endothelial Cells In Vitro and in Zebrafish Embryos In Vivo via Activation of the ERK Signaling Pathway

As a link between exercise and metabolism, irisin is assumed to be involved in increased total body energy expenditure, reduced body weight, and increased insulin sensitivity. Although our recent evidence supported the contribution of irisin to vascular endothelial cell (ECs) proliferation and apoptosis, further research of irisin involvement in the angiogenesis of ECs was not conclusive. In the current study, it was found that irisin promoted Human Umbilical Vein Endothelial Cell (HUVEC) angiogenesis via increasing migration and tube formation, and attenuated chemically-induced intersegmental vessel (ISV) angiogenic impairment in transgenic TG (fli1: GFP) zebrafish. It was further demonstrated that expression of matrix metalloproteinase (MMP) 2 and 9 were also up-regulated in endothelial cells. We also found that irisin activated extracellular signal–related kinase (ERK) signaling pathways. Inhibition of ERK signaling by using U0126 decreased the pro-migration and pro-angiogenic effect of irisin on HUVEC. Also, U0126 inhibited the elevated expression of MMP-2 and MMP-9 when they were treated with irisin. In summary, these findings provided direct evidence that irisin may play a pivotal role in maintaining endothelium homeostasis by promoting endothelial cell angiogenesis via the ERK signaling pathway.     

A novel non-containing-nitrogen bisphosphonate inhibits both in vitro and in vivo angiogenesis

Bisphosphonates (BP) are powerful inhibitors of bone resorption and are widely used in the treatment of patients with metastasis-induced osteolysis. In the present study, we show that a novel non-nitrogen-containing BP (BP7033) that exhibits antitumor activity is a potent inhibitor of both in vivo and in vitro angiogenesis. When administered to mice, BP7033 inhibited tumoral angiogenesis (65% at 0.06mg/injection) as well as tumor growth (65% at 0.006mg/injection) in a tumor model of A431 cells xenografted in nude mice, with no sign of toxicity. Additionally, in vivo angiogenesis induced by vascular endothelial growth factor-containing Matrigel implants was reduced by 90% in the presence of BP7033 (0.6mg/plug). In vitro, BP7033 inhibited proliferation of human umbilical vein endothelial cells (HUVEC) (IC(50) value 3x10(-4) M) and completely prevented the formation of capillary-like tubules by HUVEC in Matrigel. Moreover, treatment of A431 cells by BP7033 induced an inhibition of Ras processing and a decrease in the secretion of both vascular endothelial growth factor and matrix metalloproteinase-2, two well-known stimulators of the proliferation and migration of endothelial cells. These findings indicate that this new BP compound has marked antiangiogenic properties and thus represents a promising candidate for treatment of malignant diseases with an angiogenic component.     

Stretch induces upregulation of key tyrosine kinase receptors in microvascular endothelial cells

We previously demonstrated that cyclic stretch of cardiac myocytes activates paracrine signaling via vascular endothelial growth factor (VEGF) leading to angiogenesis. The present study tested the hypothesis that cyclic stretch upregulates tyrosine kinase receptors in rat coronary microvascular endothelial cells (RCMEC) and human umbilical vein endothelial cells (HUVEC). VEGF receptor-2 (Flk-1) protein levels increased in HUVEC and RCMEC in a time-dependent manner, but the increase occurred much earlier in RCMEC than in HUVEC. The enhancement of Flk-1 protein level was not inhibited by addition of VEGF neutralizing antibodies, indicating that VEGF is not involved in stretch-induced Flk-1 expression. VEGF receptor-1 (Flt-1) protein and mRNA were not changed by stretch. However, Tie-2 and Tie-1 protein levels increased in RCMEC. Angiopoietin-1 and -2, the ligands for Tie-2, increased in cardiac myocytes subjected to cyclic stretch but were not affected by stretch in endothelial cells (EC). Stretch or incubation of RCMEC with VEGF increased cell proliferation moderately, whereas stretch + VEGF had an additive effect on proliferation. Mechanical stretch induces upregulation of the key tyrosine kinase receptors Flk-1, Tie-2, and Tie-1 in vascular EC, which underlies the increase in sensitivity of EC to growth factors and, therefore, facilitates angiogenesis. These in vitro findings support the concept that stretch of cardiac myocytes and EC plays a key role in coronary angiogenesis.     

Overexpression of HTRA1 Leads to Down-Regulation of Fibronectin and Functional Changes in RF/6A Cells and HUVECs

Multiple genetic studies have suggested that high-temperature requirement serine protease (HTRA1) is associated with polypoidal choroidal vasculopathy (PCV). To date, no functional studies have investigated the biological effect of HTRA1 on vascular endothelial cells, essential vascular components involved in polypoidal vascular abnormalities and arteriosclerosis-like changes. In vitro studies were performed to investigate the effect of HTRA1 on the regulation of fibronectin, laminin, vascular endothelial growth factor (VEGF), platelet derived growth factor receptor (PDGFR) and matrix metalloparoteinases 2 (MMP-2) and the role of HTRA1 in choroid-retina endothelial (RF/6A) and human umbilical vein endothelial (HUVEC) cells. Lentivirus-mediated overexpression of HTRA1 was used to explore effects of the protease on RF/6A and HUVEC cells in vitro. HTRA1 overexpression inhibited the proliferation, cell cycle, migration and tube formation of RF/6A and HUVEC cells, effects that might contribute to the early stage of PCV pathological lesions. Fibronectin mRNA and protein levels were significantly down-regulated following the upregulation of HTRA1, whereas the expressions of laminin, VEGF and MMP-2 were unaffected by alterations in HTRA1 expression. The decreased biological function of vascular endothelial cells and the degradation of extracellular matrix proteins, such as fibronectin, may be involved in a contributory role for HTRA1 in PCV pathogenesis.     

Zinc-chelation contributes to the anti-angiogenic effect of ellagic acid on inhibiting MMP-2 activity, cell migration and tube formation

Background

Ellagic acid (EA), a dietary polyphenolic compound, has been demonstrated to exert anti-angiogenic effect but the detailed mechanism is not yet fully understood. The aim of this study was to investigate whether the zinc chelating activity of EA contributed to its anti-angiogenic effect.

Methods and Principal Findings

The matrix metalloproteinases-2 (MMP-2) activity, a zinc-required reaction, was directly inhibited by EA as examined by gelatin zymography, which was reversed dose-dependently by adding zinc chloride. In addition, EA was demonstrated to inhibit the secretion of MMP-2 from human umbilical vein endothelial cells (HUVECs) as analyzed by Western blot method, which was also reversed by the addition of zinc chloride. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), known to down-regulate the MMP-2 activity, was induced by EA at both the mRNA and protein levels which was correlated well with the inhibition of MMP-2 activity. Interestingly, zinc chloride could also abolish the increase of EA-induced RECK expression. The anti-angiogenic effect of EA was further confirmed to inhibit matrix-induced tube formation of endothelial cells. The migration of endothelial cells as analyzed by transwell filter assay was suppressed markedly by EA dose-dependently as well. Zinc chloride could reverse these two effects of EA also in a dose-dependent manner. Since magnesium chloride or calcium chloride could not reverse the inhibitory effect of EA, zinc was found to be involved in tube formation and migration of vascular endothelial cells.

Conclusions/Significance

Together these results demonstrated that the zinc chelation of EA is involved in its anti-angiogenic effects by inhibiting MMP-2 activity, tube formation and cell migration of vascular endothelial cells. The role of zinc was confirmed to be important in the process of angiogenesis.     

Ganglioside GD1a enhances VEGF-induced endothelial cell proliferation and migration

Tumor progression requires normally quiescent endothelial cells to form new vascular networks. This angiogenesis is dependent upon several soluble factors, prominent among which is vascular endothelial growth factor (VEGF). Other tumor-associated molecules, such as gangliosides, sialic acid-containing glycosphingolipids expressed by tumor cells and shed into the tumor microenvironment, may also modulate tumor angiogenesis. Here we assessed the influence of a highly purified ganglioside, G(D1a), on responses of normal human umbilical vein endothelial cells (HUVEC) to VEGF. Preincubation of HUVEC with G(D1a) enhanced VEGF-induced cell proliferation; 10 microM G(D1a) caused a twofold increase in DNA synthesis. The migration of HUVEC across a VEGF gradient was also enhanced by 50%, even with only a brief (1 h) preexposure of the cells to the same concentration of G(D1a). These findings suggest that gangliosides shed by tumor cells can promote tumor angiogenesis by enhancing the VEGF response of endothelial cells in the tumor microenvironment.     

The Annexin a2 Promotes Development in Arthritis through Neovascularization by Amplification Hedgehog Pathway

The neovascularization network of pannus formation plays a crucial role in the development of rheumatoid arthritis (RA). Annexin a2 (Axna2) is an important mediating agent that induces angiogenesis in vascular diseases. The correlation between Axna2 and pannus formation has not been studied. Here, we provided evidence that compared to osteoarthritis (OA) patients and healthy people, the expression of Axna2 and Axna2 receptor (Axna2R) were up-regulated in patients with RA. Joint swelling, inflammation and neovascularization were increased significantly in mice with collagen-induced arthritis (CIA) that were exogenously added Axna2. Cell experiments showed that Axna2 promoted HUVEC proliferation by binding Axna2R, and could activate Hedgehog (HH) signaling and up-regulate the expression of Ihh and Gli. Besides, expression of Ihh, Patched (Ptc), Smoothened (Smo) and Gli and matrix metalloproteinase-2 (MMP-2), vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2), angiogenic growth factor of HH signaling downstream, were down-regulated after inhibition of expression Axna2R on HUVEC. Together, our research definitely observed that over-expression of Axna2 could promote the development of CIA, especially during the process of pannus formation for the first time. Meanwhile, Axna2 depended on combining Axna2R to activate and enlarge HH signaling and the expression of its downstream VEGF, Ang-2 and MMP-2 to promote HUVEC proliferation, and eventually caused to angiogenesis. Therefore, the role of Axna2 is instructive for understanding the development of RA, suppress the effect of Axna2 might provide a new potential measure for treatment of RA.     

Involvement of metalloprotease-2 in the development of human brain microvessels

The involvement of the metalloprotease-2 (MMP-2) in vessel development was investigated in the human telencephalon by double immunoreactions with antibodies to the enzyme, latent (proMMP-2) and active (aMMP-2) forms, and an antibody against collagen type IV, a constitutive component of the extracellular matrix (ECM) of the vessel basal lamina. MMP-2 is expressed in both 12- and 18-week telencephalic vessels, the proenzyme being mainly localised in endothelial cells and the active form prevailing in -actin-reactive periendothelial cells identified as pericytes. Endothelial cells intensely positive for aMMP-2 were revealed in some microvessels and appeared locally associated with discontinuities of the collagen basal lamina. No detectable expression of MMP-2 was observed in perivascular glial processes revealed by vimentin/glial fibrillary acidic protein immunostainings. Double immunoreactions performed to further investigate telencephalon angiogenesis have demonstrated that both the endothelial cells and pericytes strongly express vascular endothelial growth factor (VEGF). Taken together, the results indicate that MMP-2 is largely involved in human brain angiogenesis and suggest that endothelial cells and pericytes tightly interplay in both angiogenesis mechanisms, by ECM proteolysis, and angiogenesis regulation, by local (autocrine/juxtacrine) VEGF action.Francesco Girolamo and Daniela Virgintino contributed equally to this work     

IL-8 directly enhanced endothelial cell survival,proliferation, and matrix metalloproteinases production and regulated angiogenesis

IL-8, a member of the chemokine family, has been shown to play an important role in tumor growth, angiogenesis, and metastasis. The objective of this study was to determine the mechanism of IL-8-mediated angiogenesis. We examined the direct role of IL-8 in angiogenesis by examining IL-8 receptor expression on endothelial cells and their proliferation, survival, and matrix metalloproteinases (MMPs) production. We demonstrate that HUVEC and human dermal microvascular endothelial cells constitutively express CXCR1 and CXCR2 mRNA and protein. Recombinant human IL-8 induced endothelial cell proliferation and capillary tube organization while neutralization of IL-8 by anti-IL-8 Ab blocks IL-8-mediated capillary tube organization. Incubation of endothelial cells with IL-8 inhibited endothelial cell apoptosis and enhanced antiapoptotic gene expression. Endothelial cells incubated with IL-8 had higher levels of Bcl-x(L):Bcl-x(S) and Bcl-2:Bax ratios. Furthermore, incubation of endothelial cells with IL-8 up-regulated MMP-2 and MMP-9 production and mRNA expression. Our data suggest that IL-8 directly enhanced endothelial cell proliferation, survival, and MMP expression in CXCR1- and CXCR2-expressing endothelial cells and regulated angiogenesis.     

Long non‐coding RNA GAPLINC promotes angiogenesis by regulating miR‐211 under hypoxia in human umbilical vein endothelial cells

In this study, we investigated the role of a long non‐coding RNA GAPLINC in angiogenesis using human umbilical vein endothelial cells (HUVEC). We found that hypoxia and hypoxia‐inducible factor 1α (HIF‐1α) increased the expression of GAPLINC in HUVEC cells. Moreover, GAPLINC overexpression down‐regulated miR‐211 and up‐regulated Bcl2 protein expression. Further rescue experiments confirmed that hypoxia directly increased GAPLINC expression. GAPLINC overexpression also increased cell migration and vessel formation which promoted angiogenesis, and these changes were attributed to the increased expression of vascular endothelial growth factor receptors (VEGFR) and delta‐like canonical notch ligand 4 (DLL4) receptors. Finally, we demonstrated that GAPLINC promotes vessel formation and migration by regulating MAPK and NF‐kB signalling pathways. Taken together, these findings comprehensively demonstrate that overexpression of GAPLINC increases HUVEC cells angiogenesis under hypoxia condition suggesting that GAPLINC can be a potential target for critical limb ischaemia (CLI) treatment.     

Doxazosin inhibits human vascular endothelial cell adhesion, migration, and invasion

The quinazoline-derived alpha1-adrenoceptor antagonists, doxazosin and terazosin have been recently shown to induce an anoikis effect in human prostate cancer cells and to suppress prostate tumor vascularity in clinical specimens [Keledjian and Kyprianou, 2003]. This study sought to examine the ability of doxazosin to affect the growth of human vascular endothelial cells and to modulate vascular endothelial growth factor (VEGF)-mediated angiogenesis. Human umbilical vein endothelial cells (HUVECs) were used as an in vitro model to determine the effect of doxazosin on cell growth, apoptosis, adhesion, migration, and angiogenic response of endothelial cells. The effect of doxazosin on cell viability and apoptosis induction of human endothelial cells, was evaluated on the basis of trypan blue and Hoechst 33342 staining, respectively. Doxazosin antagonized the VEGF-mediated angiogenic response of HUVEC cells, by abrogating cell adhesion to fibronectin and collagen-coated surfaces and inhibiting cell migration, via a potential downregulation of VEGF expression. Furthermore there was a significant suppression of in vitro angiogenesis by doxazosin on the basis of VEGF-mediated endothelial tube formation (P < 0.01). Fibroblast growth factor-2 (FGF-2) significantly enhanced HUVEC cell tube formation (P < 0.01) and this effect was suppressed by doxazosin. These findings provide new insight into the ability of doxazosin to suppress the growth and angiogenic response of human endothelial cells by interfering with VEGF and FGF-2 action. This evidence may have potential therapeutic significance in using this quinazoline-based compound as an antiangiogenic agent for the treatment of advanced prostate cancer.     

新型埃博霉素衍生物对血管新生抑制作用的研究

研究新合成的新型埃博霉素单甲基衍生物对血管新生的影响,以期阐明埃博霉素在肿瘤细胞和血管新生中的效应及其所作用的重要途径,为药物新靶点的开发提供理论依据.首先,以人脐静脉内皮细胞为研究对象,利用MTT法检测细胞增殖,Transwell法检测细胞迁移和侵润,明胶酶谱分析金属基质蛋白酶MMP2的活性,RT PCR检测MMP2 RNA表达水平|然后以鸡胚绒毛尿囊膜为模型,研究该衍生物对血管新生的影响.结果表明:1）新型埃博霉素单甲基衍生物可以显著抑制人脐静脉内皮细胞HUVEC的增殖、迁移和侵润以及Ⅳ型胶原酶分泌; 2）新型埃博霉素单甲基衍生物可以使鸡胚尿囊膜产生明显的无血管区,对血管新生产生明显的抑制作用. 结果说明,新型埃博霉素单甲基衍生物可以通过抑制血管内皮细胞的增殖、迁移、侵润以及Ⅳ型胶原酶分泌等显著抑制诱导血管新生过程的步骤,最终抑制血管新生.     

Involvement of NO/cGMP signaling in the apoptotic and anti-angiogenic effects of beta-lapachone on endothelial cells in vitro

Neovascularization is an essential process in tumor development, it is conceivable that anti-angiogenic treatment may block tumor growth. In angiogenesis, nitric oxide (NO) is an important factor which mediates vascular endothelial cell growth and migration. beta-Lapachone (3,4-dihydro-2,2-dimethyl-2H-naphtho-[1,2-b]pyran-5,6-dione), a natural product extracted from the lapacho tree (Tabebuia avellanedae), has been demonstrated to possess anti-cancer and anti-viral effects. Whether beta-lapachone can induce endothelial cell death or has an anti-angiogenic effect is still an enigma. We investigated the in vitro effect of beta-lapachone on endothelial cells, including human vascular endothelial cell line, EAhy926, and human umbilical vascular endothelial cells (HUVEC). Our results revealed that (1) the intracellular cGMP levels and the mitochondria membrane potential (MMP) decreased, and calpain and caspases were activated, during beta-lapachone-induced endothelial cell death; (2) co-treatment with calpain inhibitors (ALLM or ALLN) or the intracellular calcium chelator, BAPTA, but not the general caspase inhibitor, zVAD-fmk, provided significant protection against apoptosis by preventing the beta-lapachone-induced MMP decrease and cytoplasmic calcium increase; (3) addition of NO downregulated the beta-lapachone-induced cGMP depletion and protected the cells from apoptosis by blocking the MMP decrease and the calcium increase; and (4) exogenous NO protects endothelial cells against the cell death induced by beta-lapachone, but not the anti-angiogenic effect. From all the data above, we demonstrated that NO can attenuate the apoptotic effect of beta-lapachone on human endothelial cells and suggest that beta-lapachone may have potential as an anti-angiogenic drug.     

Kaposi's sarcoma-associated herpesvirus infection promotes invasion of primary human umbilical vein endothelial cells by inducing matrix metalloproteinases

Matrix metalloproteinases (MMPs) play important roles in cancer invasion, angiogenesis, and inflammatory infiltration. Kaposi's sarcoma is a highly disseminated angiogenic tumor of proliferative endothelial cells linked to infection by Kaposi's sarcoma-associated herpesvirus (KSHV). In this study, we showed that KSHV infection increased the invasiveness of primary human umbilical vein endothelial cells (HUVEC) in a Matrigel-based cell invasion assay. KSHV-induced cell invasion was abolished by an inhibitor of MMPs, BB-94, and occurred in both autocrine- and paracrine-dependent fashions. Analysis by zymography and Western blotting showed that KSHV-infected HUVEC cultures had increased secretion of MMP-1, -2, and -9. KSHV increased the secretion of MMP-2 within 1 h following infection without upregulating its mRNA expression level. In contrast, the secretion of MMP-1 and -9 was not increased until 6 h after KSHV infection and was correlated with the upregulation of their mRNA expression levels. Promoter analysis by reporter assays and electrophoretic mobility shift assays identified an AP-1 cis-element as the dominant KSHV-responsive site in the MMP-1 promoter. Together, these results suggest that KSHV infection modulates the production of multiple MMPs to increase cell invasiveness and thus contributes to the pathogenesis of KSHV-induced malignancies.     

Annexin A2 Is a Molecular Target for TM601, a Peptide with Tumor-targeting and Anti-angiogenic Effects

TM601 is a synthetic form of chlorotoxin, a 36-amino acid peptide derived from the venom of the Israeli scorpion, Leirius quinquestriatus, initially found to specifically bind and inhibit the migration of glioma cells in culture. Subsequent studies demonstrated specific in vitro binding to additional tumor cell lines. Recently, we demonstrated that proliferating human vascular endothelial cells are the only normal cell line tested that exhibits specific binding to TM601. Here, we identify annexin A2 as a novel binding partner for TM601 in multiple human tumor cell lines and human umbilical vein endothelial cell (HUVEC). We demonstrate that the surface binding of TM601 to the pancreatic tumor cell line Panc-1 is dependent on the expression of annexin A2. Identification of annexin A2 as a binding partner for TM601 is also consistent with the anti-angiogenic effects of TM601. Annexin A2 functions in angiogenesis by binding to tissue plasminogen activator and regulating plasminogen activation on vascular endothelial cells. We demonstrate that in HUVECs, TM601 inhibits both vascular endothelial growth factor- and basic fibroblast growth factor-induced tissue plasminogen activator activation, which is required for activation of plasminogen to plasmin. Consistent with inhibition of cell surface protease activity, TM601 also inhibits platelet-derived growth factor-C induced trans-well migration of both HUVEC and U373-MG glioma cells.     

蝎毒多肽提取物的抗血管生成作用

用不同浓度的东亚钳蝎素的多肽提取物PESV(4～20μg／ml)作用于人脐静脉内皮细胞(HUVEC),观察HUVEC增殖活性和凋亡变化,增殖活性检测采用BrdU掺入的ELISA法,凋亡水平和凋亡相关基因Bcl-2和Bax表达的检测采用流式细胞术检测;用鸡胚尿囊膜(CAM)显示PESV对血管生成的抑制作用。结果显示,PESV抑制HUVEC的增殖,而对乳腺癌细胞MDA-MB-231的增殖无明显影响;PESV作用72h后,HUVEC凋亡相关基因Bcl-2表达降低,Bax表达增加,凋亡细胞比例增至10．5％,明显高于对照组;0．5mgPESV能明显抑制CAM新生血管的形成。因此,PESV具有良好的体外抗肿瘤血管生成活性,PESV作为一种肿瘤血管抑制剂的天然药物来源,其有效成分和药理作用有待进一步研究。