EAhy926 Cells Research Articles

EFFECT OF SINI DECOCTION ON THE EXPRESSION OF CAVEOLIN-1 AND ENOS IN EAHY926 CELL INJURED BY HOMOCYSTEINE

ObjectivesTo detect the effect of Sini Decoction on the expression of Caveolin-1 and eNOS in EAhy926 cell injured by homocysteine.MethodsModel of EAhy926 cell injured by homocysteine was made, the protection...

S-Nitrosation of β-Catenin and p120 Catenin

Rationale: Endothelial adherens junction proteins constitute an important element in the control of microvascular permeability. Platelet-activating factor (PAF) increases permeability to macromolecules via translocation of endothelial nitric oxide synthase (eNOS) to cytosol and stimulation of eNOS-derived nitric oxide signaling cascade. The mechanisms by which nitric oxide signaling regulates permeability at adherens junctions are still incompletely understood. Objective: We explored the hypothesis that PAF stimulates hyperpermeability via S-nitrosation (SNO) of adherens junction proteins. Methods and Results: We measured PAF-stimulated SNO of β-catenin and p120-catenin (p120) in 3 cell lines: ECV-eNOSGFP, EAhy926 (derived from human umbilical vein), and postcapillary venular endothelial cells (derived from bovine heart endothelium) and in the mouse cremaster muscle in vivo. SNO correlated with diminished abundance of β-catenin and p120 at the adherens junction and with hyperpermeability. Tumor necrosis factor-α increased nitric oxide production and caused similar increase in SNO as PAF. To ascertain the importance of eNOS subcellular location in this process, we used ECV-304 cells transfected with cytosolic eNOS (GFPeNOSG2A) and plasma membrane eNOS (GFPeNOSCAAX). PAF induced SNO of β-catenin and p120 and significantly diminished association between these proteins in cells with cytosolic eNOS but not in cells wherein eNOS is anchored to the cell membrane. Inhibitors of nitric oxide production and of SNO blocked PAF-induced SNO and hyperpermeability, whereas inhibition of the cGMP pathway had no effect. Mass spectrometry analysis of purified p120 identified cysteine 579 as the main S-nitrosated residue in the region that putatively interacts with vascular endothelial-cadherin. Conclusions: Our results demonstrate that agonist-induced SNO contributes to junctional membrane protein changes that enhance endothelial permeability.

Antioxidative/oxidative effects of strontium-doped bioactive glass as bone graft. In vivo assays in ovariectomised rats

Recently, oxidative stress has been identified as a pivotal pathological factor inducing bone osteoporosis. This phenomenon is responsible for low bone density. It alters bone quality and generates bone fractures. Strontium is found to induce osteoblast activity by stimulating bone formation and reducing bone resorption by restraining osteoclasts. Bioglass (BG) has been used to repair bone defects, and, in combination with strontium (BG-Sr), offers an opportunity to treat this disease. This study investigated the potential role of BG-Sr in improving antioxidant activity and regenerative bone capacity, The effects of both BG-Sr and BG were tested on osteoblast SaOS2 and endothelial EAhy926 cell proliferation in vitro. In vivo, BG-Sr and BG were implanted in the femoral condyles of Wistar rats and compared to that of control groups. Cell proliferation increased significantly by 120% at SaOS2 and 127% at EAhy926. Superoxide Dismutase (SOD), Catalase (CAT) and Glutathione Peroxidase (GPx) were significantly enhanced in BG-Sr treated rats compared to other groups. Moreover, a significant decrease of thiobarbituric acid-reactive substances (TBARs) was observed. The Ca/P ratio increase improved progressive bone mineralization. According to these results, BG-Sr ameliorated cell proliferation and developed an antioxidative defense against ROS. The histological findings highlight the BG-Sr implications in the osteoporosis treatment confirmed by bone construction. The development of BG-Sr as a therapeutic biomaterial protecting against oxidative stress might make an effective choice for application in tissue engineering.

Abstract 5289: In human endothelial cell line Wnt-beta-catenin pathway controls transcription of lymphoid enhancer-binding factor 1, a representative of vertebrate-specific Lef1/Tcf1 sub-family enhancing matrix metalloproteinase-2 transcription and endothelial cell invasion

Abstract Background: Wnt signaling is activated in many types of cancer and normal physiological processes. Various Wnt-related secreted factors may influence angiogenesis both in the tumor microenvironment and in normal tissues by direct action on endothelial cells. The mechanism of this Wnt action in angiogenesis is not well defined. Gradl D, König A, and Wedlich D (2002) show that members of Tcf1/Lef1 sub-family generate stronger Wnt throughput and Xenopus’ secondary axis induction per protein unit than members of Tcf3/Tcf4 sub-family. This stronger activity might require different, may be, stronger chemotherapy tools for angiogenesis control than the tools necessary to prevent colon cancer where Tcf4 signaling is prominent. We hypothesize that endothelial cells are responsive to Wnt signals and that Lef1, a member of the vertebrate-specific Wnt/beta-catenin throughput-inducing transcription factors’ sub-family Lef1/Tcf1, mediates this responsiveness and promotes endothelial cell invasion. Methods: A human endothelial cell line, EAhy926 was exposed to Wnt3a or directly transfected with Lef1. Readouts included assessment of nuclear β-catenin, Wnt throughput with a SuperTOPflash reporter assay, induction of Lef1 transcription, induction of matrix metalloproteinase (MMP)-2 transcription, cell proliferation and cell invasion through a matrix in vitro. The effects on MMP2 were also evaluated in the presence of Lef1 silencing siRNA. Results: Wnt3a increased nuclear β-catenin staining identified by DNA staining of nucleus with DAPI and up-regulated Wnt/β-catenin throughput without changing the activity of negative control reporter with mutated Lef/Tcf binding sites (FOP). Wnt3a increased Lef1 transcription and activity of the Lef1 promoter. Both Wnt3a treatment and Lef1 overexpression induced MMP2 transcription but this effect was completely abrogated in the presence of Lef1 siRNA. Inhibition of Lef1 also reduced basal MMP2 levels suggesting that Lef1 regulates MMP2 expression even in the absence of exogenous Wnt pathway activation. Lef1 slightly enhanced proliferation of EAhy926 cells after prolonged periods (96 and 120 hours post-transfection) and increased invasion by more than two-fold. Conclusions: EAhy926 cell line activates canonical Wnt signaling in response to Wnt3a ligand. A representative of vertebrate-specific Lef1/Tcf1 sub-family Lef1 specifically regulates MMP2 transcription in these cells and promotes endothelial cell invasion. This cell line provides a convenient alternative to primary human umbilical vein endothelial cells (HUVEC) in the study of angiogenesis and the role of Wnt signaling on endothelial cell function. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5289. doi:1538-7445.AM2012-5289

An in vitro model of warm hypoxia–reoxygenation injury in human liver endothelial cells

BackgroundIschemia–reperfusion or hypoxia–reoxygenation (H-R) injury adversely affects hepatic function following transplantation and major resection; the death of human sinusoidal endothelial cells (SECs) by apoptosis may play a central role in this process. Caspase-3 is an important intracellular protease in the intrinsic and extrinsic pathways of apoptosis. Materials and methodsSECs and EAhy926 cells were exposed to warm hypoxia at 37°C, followed by reoxygenation at 37°C. Activity of caspase-3 was quantified using Western blotting and colorimetric kinase assays. ResultsH-R caused a significant increase in caspase-3 activity compared with controls in both cell types. ConclusionsWarm H-R injury causes apoptotic cell death of SECs and immortalized cells, but with differing patterns of caspase activity.

Antiangiogenic activity of indole-3-carbinol in endothelial cells stimulated with activated macrophages

The effect of indole-3-carbinol (I3C), a major indolic metabolite in cruciferous vegetables, on lipopolysaccharide (LPS)-activated macrophage-induced tube formation and its associated factors in endothelial EA hy926 cells was investigated. LPS significantly enhanced the capillary-like structure of endothelial cells (ECs) co-cultured with macrophages, but no such effect was observed in single-cultured ECs. I3C, on the other hand, suppressed such enhancement in concert with decreased secretions of vascular endothelial growth factor (VEGF), nitric oxide (NO), interleukin-6 (IL-6), and matrix metalloproteinases (MMPs). The results obtained from cultivating ECs with conditioned medium (CM) collected from macrophages suggested that both ECs and macrophages were inactivated by I3C. These results indicate that I3C from cruciferous vegetables may possess potential roles in preventing inflammation-associated angiogenic diseases.

Effects of polyphenol extract from olive pomace on anoxia-induced endothelial dysfunction

Anoxia modulates the expression of molecules associated with endothelial dysfunction and vascular diseases. Polyphenols have potent antioxidant properties due to their ability to modulate genes involved in oxidative tissue damage. In this study, we investigated the effect of polyphenol extract from olive pomace (PEOP) and its main constituents, Tyrosol and Oleuropein, on endothelial cells subjected to anoxia by evaluating the expression of molecules critical for endothelial function, proliferation and migration, and the signaling pathway involved.EAhy926 human endothelial cells were exposed to anoxic stress in the presence or absence of PEOP. Anoxia increased the nitric oxide (NO) level and the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNFα). These effects were prevented by PEOP treatment in a dose-dependent manner. Moreover, PEOP prevented the proliferation and migration associated with anoxia in EAhy926 cells, down-regulated the levels of matrix metalloproteinase (MMP)-2, MMP-9 and membrane type-1 MMP (MT1-MMP) and increased tissue MMP inhibitor-1 (TIMP-1) expression. Purified Oleuropein or Tyrosol restored to a basal level the anoxia-induced expression of MMP-9 and partially of MMP-2. The expression of TNFα was reduced by both polyphenols in a dose-dependent manner, but more efficiently by Tyrosol. Conversely, Oleuropein and Tyrosol had no significant effects on iNOS, COX-2 and TIMP-1 expression when used at the concentration found in PEOP. PEOP induced a time-dependent phosphorylation of p38 MAPK and ERK1/2 and inhibited anoxia-induced NF-κB activation.PEOP treatment restores the endothelial functions that are impaired by anoxia by regulating the expression of genes involved in proteolysis, angiogenesis and inflammation more efficiently than the single purified components. Therefore, the combined use of polyphenols, as in PEOP, could represent a powerful tool for the treatment and chemoprevention of endothelial dysfunction-associated vascular diseases.

Thin-layer chromatography immunostaining in detecting anti-phospholipid antibodies in seronegative anti-phospholipid syndrome

In clinical practice it is possible to find patients with clinical signs suggestive of anti-phospholipid syndrome (APS) who are persistently negative for the routinely used anti-phospholipid antibodies (aPL). Therefore, the term proposed for these cases was seronegative APS (SN-APS). We investigated the clinical usefulness of thin-layer chromatography (TLC) immunostaining in detecting serum aPL in patients presenting clinical features of SN-APS. Sera from 36 patients with SN-APS, 19 patients with APS, 18 patients with systemic lupus erythematosus (SLE), 20 anti-hepatitis C virus (HCV)-positive subjects and 32 healthy controls were examined for aPL using TLC immunostaining. Anti-β(2) -glycoprotein-I, anti-annexin II, anti-annexin V and anti-prothrombin antibodies were tested by enzyme-linked immunosorbent assays (ELISA). Eahy926, a human-derived endothelial cell line, was incubated with immunoglobulin (Ig)G fraction from SN-APS patients and analysis of phospho-interleukin (IL)-1 receptor-associated kinase (IRAK) and phospho-nuclear factor (NF)-κB was performed by Western blot, vascular cell adhesion molecule 1 (VCAM-1) expression by cytofluorimetric analysis and supernatants tissue factor (TF) levels by ELISA. TLC immunostaining showed aPL in 58·3% of SN-APS patients: anti-cardiolipin in 47·2%, anti-lyso(bis)phosphatidic acid in 41·7% and anti-phosphatidylethanolamine in 30·5%. Six of 36 patients showed anti-annexin II. Incubation of Eahy926 cells with IgG from SN-APS induced IRAK phosphorylation, NF-κB activation, VCAM-1 surface expression and TF cell release. TLC immunostaining could identify the presence of aPL in patients with SN-APS. Moreover, the results suggest the proinflammatory and procoagulant effects in vitro of these antibodies.

Investigating Metalloproteinases MMP-2 and MMP-9 Mechanosensitivity to Feedback Loops Involved in the Regulation of In Vitro Angiogenesis by Endogenous Mechanical Stresses

Angiogenesis is a complex morphogenetic process regulated by growth factors, but also by the force balance between endothelial cells (EC) traction stresses and extracellular matrix (ECM) viscoelastic resistance. Studies conducted with in vitro angiogenesis assays demonstrated that decreasing ECM stiffness triggers an angiogenic switch that promotes organization of EC into tubular cords or pseudo-capillaries. Thus, mechano-sensitivity of EC with regard to proteases secretion, and notably matrix metalloproteinases (MMPs), should likely play a pivotal role in this switching mechanism. While most studies analysing strain regulation of MMPs used cell cultured on stretched membranes, this work focuses on MMP expression during self-assembly of EC into capillary-like structures within fibrin gels, i.e. on conditions that mimics more closely the in vivo cellular mechanical microenvironment. The activity of MMP-2 and MMP-9, two MMPs that have a pivotal role in capillaries formation, has been monitored in pace with the progressive elongation of EAhy926 cells that takes place during the emergence of cellular cords. We found an increase of the zymogen proMMP-2 that correlates with the initial stages of EC cords formation. However, MMP-2 was not detected. ProMMP-9 secretion decreased, with levels of MMP-9 kept at a rather low value. In order to analyse more precisely the observed differences of EAhy926 response on fibrin and plastic substrates, we proposed a theoretical model of the mechano-regulation of proMMP-2 activation in the presence of type 2 tissue inhibitor of MMPs (TIMP-2). Using association/dissociation rates experimentally reported for this enzymatic network, the model adequately describes the synergism of proMMP-2 and TIMP-2 strain activation during pseudo-capillary morphogenesis. All together, these results provide a first step toward a systems biology approach of angiogenesis mechano-regulation by cell-generated extracellular stresses and strains.

Effect of mild hypothermia on breast cancer cells adhesion and migration

To explore the effect of mild hypothermia (35ºC) on breast cancer cells adhesion to vascular endothelial cells, a parallel plant flow chamber was used to observe the adhesion of human breast cancer cells MDA-MB-231 to endothelial cells Eahy926 under physiological flow at 35ºC and 37ºC, as well as the role of intercellular adhesion molecule 1 (ICAM-1) in this process. Further, the effect of mild hypothermia (35ºC) on migration of MDA-MB-231 was also studied. Our results show that mild hypothermia can inhibit the adhesion of tumor cells to endothelial cells and ICAM-1 plays an important role in this process. However, mild hypothermia inhibits breast cancer cell adhesion in a way independent on the change of ICAM-1 expression under our experimental conditions. Mild hypothermia can weaken the chemotaxis of breast cancer cells while it has no obvious effect on unidirectonal migration capacity. These results suggest that mild hypothermia could be used as a potentially adjunct treatment combined with surgery to decrease tumor cell adhesion and migration.

Endothelin-1 Stimulates Connective Tissue Growth Factor Expression by Endothelial Cells,

Abstract 3265An important role for Endothelin-1 (ET-1) has been proposed in patients with sickle cell disease (SCD). We, and others, have reported that endothelin-1 (ET-1) receptor antagonists in vivo ameliorate numerous complications observed in sickle transgenic mice through mechanisms that remain unclear. ET-1 is a vasoconstrictor and important regulator of endothelial cells migration that promotes structural changes in blood vessels in response to increases in vasoactive hormones, growth factors, hypoxia, shear stress and free radicals; events commonly observed in patients with SCD. Endothelial cell activation is characterized in part by increases of cytokines and growth factors that are important in vascular maintenance and fibrogenesis such as connective tissue growth factor (CTGF). CTGF plays a role in blood vessel remodeling and fibrogenesis. Indeed, there is in vitro evidence that ET-1 stimulates the production of CTGF in smooth muscle cells. We hypothesized that increasing ET-1 would stimulate CTGF production and lead to endothelial cell activation. We studied the effects of ET-1 on the human endothelial cell line, EA.hy926 (EA), as well as in primary cultures of mouse aortic endothelial cells (MAEC). We analyzed the effects ET-1 on cytosolic Ca2+ levels by spectrofluorimetry of FURA-2AM loaded EA cells and noted that, as observed in fibroblasts, incubation with 10−8 M ET-1 led to increases in cytosolic Ca2+ levels that were blocked by pre-incubation with the ET-1 receptor B antagonist, BQ-788. We performed CTGF gene expression time course experiments (0, 2, 4, 8, 16, 24 Hr) on EA cells following incubation with 100 nM ET-1 using quantitative RT-PCR with TaqMan detection probes and GAPDH and beta-actin as endogenous controls. We observed increases of CTGF and VEGF expression between 4 and 8 hr for CTGF (1.74 fold increase vs time 0, n=6, P<0.03) and 4 hr for VEGF (2.14 fold increase vs time 0, n=3, P<0.04). Additional experiments on EA cells showed that incubation with 100 nM ET-1 for 4 hr in the presence of BQ123 and BQ788, two inhibitors of ET-1 type A and B receptors, respectively, blocked the ET-1 stimulated rises in CTGF and VEGF mRNA expression. We then performed western blot analyses and showed increases in cell-associated CTGF protein levels following incubation of EA cells with 10 nM ET-1 for 24 hr that were blocked by both BQ123 and BQ788. We then studied the effect of ET-1 on CTGF production in cell supernatants at various dose and time points by sandwich ELISA immunoassay. We observed increased levels of CTGF in cellular supernatants after 48 h of exposure that peaked at 10 nM ET-1 as compared to 24 h, 12 h and vehicle treated cells (P<0.001). To study whether the effects of ET-1 were unique to EA cells, we also analyzed the effects of ET-1 on early cultures of MAEC. Consistent with our observations in human EA cells, incubation of MAEC with 100 nM ET-1 for 4 hr was associated with increases of CTGF (1.86 fold vs vehicle, n=3, P<0.03) and was blocked by pre-incubation with BQ123 and BQ788. As CTGF has been shown to be chemotactic as well, we studied the effect of supernatants isolated from EA cells following stimulation with 10 nM ET-1 for 48 hrs on ex vivo human mononuclear cells (MNC) isolated from otherwise healthy subjects. We determined MNC transmigration by Cyquant fluorescence and observed enhanced migration of cells exposed to supernatants from ET-1-stimulated cells when compared to vehicle treatment that was significantly blunted by BQ123 and BQ788 pre-incubation. Further western blot analyses of the MNC that migrated following incubation with ET-1-stimulated supernatants showed the presence of CTGF in the MNC that otherwise do not express CTGF. Thus, we conclude that ET-1 leads to activation of endothelial cells and increases in CTGF from endothelial cells and suggest that therapies designed to block ET-1 receptors will also reduce endothelial cell activation in part by reducing CTGF production leading to alterations in cellular and tissue architecture. Disclosures:No relevant conflicts of interest to declare.

Regulation of Endothelin-1 Stimulated-Ca2+-Activated K+ Channel Activity by Protein Disulfide Isomerase Gene Knockdown in Endothelial Cells

Abstract 1080Endothelial cell activation is as an important contributor to vaso-occlusion in the pathophysiology of Sickle Cell Disease. We have reported a role for dual endothelin-1 (ET-1) receptor antagonists in improving sickle cell pathophysiology in vivo via modulation of the Ca2+-activated K+ channel, KCNN4 (Rivera A., 2008, Amer J Physiol). Protein disulfide isomerase (PDI) catalyzes disulfide interchange reactions in the plasma membrane, mediates redox modifications and is up-regulated under hypoxic conditions. Thus KCNN4 maybe regulated by PDI in endothelial cells. We now report on the detection of KCNN4, PDI and ET-1 receptor B by western blot analyses in membranes from the human endothelial cell line, EA.hy926 (EA). We studied the effects ET-1 on cytosolic Ca2+ levels by spectrofluorimetry of FURA-2AM loaded endothelial cells and observed that 10−9−10−7 M ET-1 led to dose-dependent increases in cytosolic Ca2+ levels that were blocked by pre-incubation with the ET-1 receptor B antagonist, BQ-788. We then studied the effects of 100 nM ET-1 on Ca2+-activated K+ channels and observed increased activity (153.7 vs. 187.0 mmol/L × h × mg protein) that was sensitive to clotrimazole (95.8 mmol/L × h × mg protein), a well-known inhibitor of KCNN4. We then studied the effects of two well-described PDI inhibitors, monoclonal antibodies to PDI and bacitracin, on channel activity and showed that these inhibitors significantly decreased channel activity in EA cells. Consistent with these observations, we show that siRNA against PDI likewise led to a reduction in channel activity (153.7 vs 29.5 mmol/L × h × mg protein, P<0.01, n=6) that was associated with significantly reduced PDI mRNA levels but not with scrambled siRNA as determined by quantitative RT-PCR with TaqMan detection probes and GAPDH and beta-2 microglobulin as endogenous controls. We then studied the effects of ET-1 on EA cells as well as in early cultures of mouse aortic endothelial cells (MAEC) using quantitative RT-PCR with TaqMan probes and GAPDH and beta-actin as endogenous controls and observed that stimulation of EA cells with 100 nM ET-1 for 4 hr was associated with increased mRNA expression of PDI levels that was 1.89 fold greater than vehicle treated cells (n=6, P<0.04). Similar results were observed on PDI mRNA expression in MAEC incubated with 100 nM ET-1 for 4 hr. Furthermore, incubation of EA cells for 12 hr with 10 nM ET-1 led to increases in cell-associated PDI levels by western blot analyses. We then tested the in vivo effects of ET receptor antagonist in sickle transgenic BERK mice and observed a reduction of plasma PDI activity when compared to vehicle treatment (67.7±3 to 34.3±6, Relative Fluorescence Units, P<0.03, n=3). In these mice, we also observed a positive correlation in erythrocyte Gardos channel activity and PDI activity. Thus, our results implicate PDI as a novel regulator of KCNN4. We posit that regulation of PDI activity represents a novel target aimed at ameliorating complications associated with the pathophysiology of Sickle Cell Disease. Supported by NIH R01HL090632 to AR. Disclosures:No relevant conflicts of interest to declare.

Effect of flow on endothelial endocytosis of nanocarriers targeted to ICAM-1

Delivery of drugs into the endothelium by nanocarriers targeted to endothelial determinants may improve treatment of vascular maladies. This is the case for intercellular adhesion molecule 1 (ICAM-1), a glycoprotein overexpressed on endothelial cells (ECs) in many pathologies. ICAM-1-targeted nanocarriers bind to and are internalized by ECs via a non-classical pathway, CAM-mediated endocytosis. In this work we studied the effects of endothelial adaptation to physiological flow on the endocytosis of model polymer nanocarriers targeted to ICAM-1 (anti-ICAM/NCs, ~180nm diameter). Culturing established endothelial-like cells (EAhy926 cells) and primary human umbilical vein ECs (HUVECs) under 4dyn/cm2 laminar shear stress for 24h resulted in flow adaptation: cell elongation and formation of actin stress fibers aligned to the flow direction. Fluorescence microscopy showed that flow-adapted cells internalized anti-ICAM/NCs under flow, although at slower rate versus non flow-adapted cells under static incubation (~35% reduction). Uptake was inhibited by amiloride, whereas marginally affected by filipin and cadaverine, implicating that CAM-endocytosis accounts for anti-ICAM/NC uptake under flow. Internalization under flow was more modestly affected by inhibiting protein kinase C, which regulates actin remodeling during CAM-endocytosis. Actin recruitment to stress fibers that maintain the cell shape under flow may delay uptake of anti-ICAM/NCs under this condition by interfering with actin reorganization needed for CAM-endocytosis. Electron microscopy revealed somewhat slow, yet effective endocytosis of anti-ICAM/NCs by pulmonary endothelium after i.v. injection in mice, similar to that of flow-adapted cell cultures: ~40% (30min) and 80% (3h) internalization. Similar to cell culture data, uptake was slightly faster in capillaries with lower shear stress. Further, LPS treatment accelerated internalization of anti-ICAM/NCs in mice. Therefore, regulation of endocytosis of ICAM-1-targeted nanocarriers by flow and endothelial status may modulate drug delivery into ECs exposed to different physiological (capillaries vs. arterioles/venules) or pathological (ischemia, inflammation) levels and patterns of blood flow.

Protective effect of hydroxysafflor yellow A on endothelial cell injury induced by lipopolysaccharide

To observe the protective effect of hydroxyl safflor yellow A (HSYA) on endothelial cell (EC). It has been observed by RT-PCR that HSYA can inhibit the elevation of TNF-alpha, IL-6, ICAM-1 and VCAM-1 mRNA level induced by LPS. The result of immunofluorescence test suggested that HSYA can alleviate p65 subgroup of NF-kappaB nuclear translocation. The experiment on EA-HY926 cell line proved that HSYA can protect EC against inflammation injury.

Angiotensin II-induced process of angiogenesis is mediated by spleen tyrosine kinase via VEGF receptor-1 phosphorylation

Spleen tyrosine kinase (Syk), expressed in endothelial cells, has been implicated in migration and proliferation and in vasculogenesis. This study was conducted to determine the contribution of Syk and the underlying mechanism to the angiogenic effect of ANG II and VEGF. Angiogenesis was determined by tube formation from the endothelial cell line EA.hy926 (EA) and human umbilical vein endothelial cells (HUVECs) and microvessel sprouting in rat aortic rings. ANG II (10 nM), EGF (30 ng/ml), and VEGF (50 ng/ml) stimulated EA cells and HUVECs to form tubular networks and increased aortic sprouting; these effects were blocked by VEGF receptor-1 and Flt-1 antibody (Flt-1/Fc) but not by the VEGF receptor-2 (Flk-1) antagonist SU-1498. ANG II increased the phosphorylation of Flt-1 but not Flk-1, whereas VEGF increased the phosphorylation of both receptors in EA cells and HUVECs. VEGF expression elicited by ANG II was not altered by Flt-1/Fc or SU-1498. EGF stimulated tube formation from EA cells and HUVECs and Flt-1 phosphorylation and aortic sprouting, which were blocked by the EGF receptor antagonist AG-1478 and Flt-1/Fc but not by SU-1498. ANG II-, EGF-, and VEGF-induced tube formation and aortic sprouting were attenuated by the Syk inhibitor piceatannol and by Syk short hairpin interfering (sh)RNA and small interfering RNA, respectively. ANG II, EGF, and VEGF increased Syk phosphorylation, which was inhibited by piceatannol and Syk shRNA in EA cells and HUVECs. Neither piceatannol nor Syk shRNA altered ANG II-, EGF-, or VEGF-induced phosphorylation of Flt-1. These data suggest that ANG II stimulates angiogenesis via transactivation of the EGF receptor, which promotes the phosphorylation of Flt-1 and activation of Syk independent of VEGF expression.

Beclin1/PI3K-Mediated Autophagy Prevents Hypoxia-Induced Apoptosis in EAhy926 Cell Line

Although hypoxia can induce cell death, the cancer cells and endothelial cells within a solid tumor that remain active in the hypoxia microenvironment often possess an enhanced survival potential. Developing approaches aimed at increasing the sensitivity of endothelial cells to hypoxia-induced cell death represents a potentially important avenue for antiangiogenesis treatment. This study investigated approaches to increase the sensitivity of endothelial cells to hypoxia-induced apoptosis. Autophagy and apoptosis of endothelial cells induced by hypoxia were investigated by transmission electron microscopy, confocallaser microscopy, and western blotting. Moreover, cell invasion was observed by a transwell assay and F-actin quantitative analysis. In this study, it was found that hypoxia could induce both autophagy and apoptosis in hypoxia-inducible factor-1- and Beclin1-dependent endothelial cells. Hypoxia-induced autophagy was prohibited by phosphatidylinositol 3-kinase/Akt inhibitor but not mitogen-activated protein kinase inhibitor. Inhibition of autophagy promoted the rate of apoptosis. Further, the reversal of hypoxia-induced autophagy increased cell migration compared with the normoxia condition. This study concludes that hypoxia triggers a feedback mechanism that delays apoptosis of endothelial cells and that is driven by hypoxia-induced autophagy. Thus, approaches aimed at the disruption of this mechanism can be expected to enhance the susceptibility of endothelial cells to hypoxia-induced apoptosis.

Lymphoid enhancer-binding factor 1, a representative of vertebrate-specific Lef1/Tcf1 sub-family, is a Wnt-beta-catenin pathway target gene in human endothelial cells which regulates matrix metalloproteinase-2 expression and promotes endothelial cell invasion

BackgroundWnt signaling is activated in many types of cancer and normal physiological processes. Various Wnt-related secreted factors may influence angiogenesis both in the tumor microenvironment and in normal tissues by direct action on endothelial cells. The mechanism of this Wnt action in angiogenesis is not well defined. We hypothesize that endothelial cells are responsive to Wnt signals and that Lef1, a member of the vertebrate-specific Wnt/beta-catenin throughput-inducing transcription factors' sub-family Lef1/Tcf1, mediates this responsiveness and promotes endothelial cell invasion.MethodsA human endothelial cell line, EAhy926 was exposed to Wnt3a or directly transfected with Lef1. Readouts included assessment of nuclear beta-catenin, Wnt throughput with a SuperTOPflash reporter assay, induction of Lef1 transcription, induction of matrix metalloproteinase (MMP)-2 transcription, cell proliferation and cell invasion through a matrix in vitro. The effects on MMP2 were also evaluated in the presence of Lef1 silencing siRNA.ResultsWnt3a increased nuclear beta-catenin and up-regulated Wnt/beta-catenin throughput. Wnt3a increased Lef1 transcription and activity of the Lef1 promoter. Both Wnt3a treatment and Lef1 overexpression induced MMP2 transcription but this effect was completely abrogated in the presence of Lef1 siRNA. Inhibition of Lef1 also reduced basal MMP2 levels suggesting that Lef1 regulates MMP2 expression even in the absence of exogenous Wnt pathway activation. Lef1 slightly increased proliferation of EAhy926 cells and increased invasion by more than two-fold.ConclusionsEAhy926 cells activate canonical Wnt signaling in response to Wnt3a ligand. The Wnt target Lef1 specifically regulates MMP2 expression in these cells and promotes endothelial cell invasion. The EAhy926 cell line provides a convenient alternative to primary human umbilical vein endothelial cells (HUVEC) in the study of angiogenesis and the role of Wnt signaling on endothelial cell function.

Effect of phlorotannins isolated from Ecklonia cava on angiotensin I-converting enzyme (ACE) inhibitory activity.

Inhibition of angiotensin I-converting enzyme (ACE) activity is the most common mechanism underlying the lowering of blood pressure. In the present study, five organic extracts of a marine brown seaweed Ecklonia cava were prepared by using ethanol, ethyl acetate, chloroform, hexane, and diethyl ether as solvents, which were then tested for their potential ACE inhibitory activities. Ethanol extract showed the strongest ACE inhibitory activity with an IC50 value of 0.96 mg/ml. Five kinds of phlorotannins, phloroglucinol, triphlorethol-A, eckol, dieckol, and eckstolonol, were isolated from ethanol extract of E. cava, which exhibited potential ACE inhibition. Dieckol was the most potent ACE inhibitor and was found to be a non-competitive inhibitor against ACE according to Lineweaver-Burk plots. Dieckol had an inducible effect on the production of NO in EAhy926 cells without having cytotoxic effect. The results of this study indicate that E. cava could be a potential source of phlorotannins with ACE inhibitory activity for utilization in production of functional foods.

Role of Connective Tissue Growth Factor In Endothelin-Mediated Endothelial Cell Activation

AbstractAbstract 2107Endothelial cell activation and elevated levels of circulating Endothelin-1 (ET-1) have been reported in patients with atherosclerosis and sickle cell disease (SCD). ET-1 is a well-described vasoconstrictor, mitogen and regulator of endothelial cells migration that has been shown to promote structural changes in blood vessels. ET-1 is produced in response to increases in vasoactive hormones, growth factors, hypoxia, shear stress and free radicals, events that are commonly observed in patients with SCD. Endothelial cell activation is in part characterized by increases of cytokines such as monocyte chemotactic protein-1 (MCP-1) and growth factors that are important in vascular maintenance and fibrogenesis such as connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF). CTGF and VEGF are important for blood vessel remodeling, fibrogenesis and angiogenesis. Indeed there is evidence that incubation of smooth muscle cells with ET-1 leads to increases in CTGF and VEGF levels. However, the relationship between ET-1 and CTGF in endothelial cell activation is unclear. We hypothesize that increasing ET-1 would stimulate CTGF production and endothelial cell activation. We studied the effects of ET-1 on the human endothelial cell line, EA.hy926 (EA), as well as in primary cultures of mouse aortic endothelial cells (MAEC). We performed gene expression time course experiments (0, 2, 4, 8, 16, 24 Hr) on EA cells following incubation with 100nM ET-1 using quantitative RT-PCR with Taqman chemistries and GAPDH and beta-actin as endogenous controls. We observed increases of CTGF and VEGF expression between 4 and 8 hr for CTGF (1.74 fold increase vs time 0, n=6, P<0.03) and 4 hr for VEGF (2.14 fold increase vs time 0, n=3, P<0.04). Additional experiments on EA cells showed that incubation with 100nM ET-1 for 4 hr in the presence of BQ123 and BQ788, two inhibitors of ET-1 type A and B receptors, respectively, blocked the ET-1 stimulated rises in CTGF and VEGF as well as MCP-1 expression. We then performed western blot analyses (Abcam-CTGF antibody ab6992; Abcam VEGF antibody ab1316) and showed increases in cell associated CTGF protein levels following incubation of EA cells with 100nM ET-1 for 24 hr. The ET-1 stimulated rise in CTGF levels were significantly blunted by pre-incubation of EA cells with both BQ788 and BQ123. To study whether the effects of ET-1 were unique to EA cells, we also analyzed the effects of ET-1 on early cultures of MAEC isolated from C57BLJ mice. Consistent with our observations in human endothelial cells, incubation of MAEC with 100nM ET-1 for 4 hr were associated with increases of CTGF and VEGF expression (1.86 fold vs vehicle, n=3, P<0.03; 1.73 fold vs vehicle, n=3 P<0.04 respectively). Furthermore, ET-1 stimulated rises in CTGF and VEGF expressions were likewise blocked by pre-incubation with BQ123 andBQ788. We conclude that addition of ET-1 leads to activation of endothelial cells and increases in CTGF and VEGF from human and mouse endothelial cells. Thus we suggest that therapies designed to block ET-1 receptors will reduce endothelial cell activation in part by reducing CTGF production leading to alterations in cellular and tissue architecture. This work was supported by NIH R01HL090632 to AR and R01HL096518 to JRR. Disclosures:No relevant conflicts of interest to declare.

Endothelin-1 Receptor Antagonists Regulate Cell Surface-Associated Protein Disulfide Isomerase In Sickle Cell Disease

AbstractAbstract 265Erythrocyte hydration status and endothelial cell activation have been proposed as important contributors to vaso-occlusion and impaired blood flow in the pathophysiology of sickle cell disease (SCD). However, the physiological mechanism(s) that mediate the interplay between erythrocytes hydration status and the endothelium in SCD are unclear. We have recently reported a role for dual endothelin-1 receptor antagonists in improving sickle erythrocyte hydration status and K+ transport in vivo via modulation of Gardos channel activity (Rivera A., 2008, Amer J Physiol). The Gardos channel is an important contributor to sickle erythrocyte dehydration that maybe modulated by protein disulfide isomerase (PDI). PDI in leukocytes has been reported to catalyze disulfide interchange reactions, mediate redox modifications and has been observed to be up-regulated under hypoxic conditions. We report the detection of PDI by western blot analyses in membranes from both human and mouse sickle erythrocytes. We observed greater levels of cell surface associated PDI in sickle vs Hb A-containing erythrocytes. We also quantified PDI activity and observed a significant correlation between Gardos channel activity and cell surface associated PDI activity in human sickle erythrocytes and Hb A-containing cells (n=40, r2=0.3046, p=0.0002). In fact, closer examination revealed that sickle erythrocyte membranes had higher PDI activity than Hb A-containing erythrocyte membranes (5.07±0.4 vs 1.30±0.1%, n=22 and 18, respectively p<0.0001). Similar results were observed in membrane preparations of erythrocytes isolated from the BERK sickle transgenic mouse model when compared with wild-type controls. Consistent with a functional role for PDI in Gardos channel activation, we also observed that sickle erythrocytes incubated in cycles of oxygenation/de-oxygenation for 3 hr in the presence of PDI antibodies were associated with reduced sickle dense cell formation. Similar results were observed with bacitracin, another PDI inhibitor. We then treated BERK mice with dual ET-1 receptor antagonists (BQ123/BQ788) for 14 days and measured erythrocyte surface associated PDI activity. We observed that as with Gardos channel activity, cell surface associated PDI activity was significantly reduced following treatment with BQ123/BQ788 (8.80±0.5 to 6.4±0.6%, n=3 P<0.02). These changes were associated with an increase in erythrocyte MCV (31.3±1.63 to 40.4±0.35 fL, n=3, p<0.002) and a decrease in MCHC (40.4±0.8 to 27.4±3 g/dL, n=3, p<0.003). We then studied the direct effects of ET-1 on the human endothelial cell line, EA.hy926 (EA), as well as in primary cultures of BERK mouse aortic endothelial cells (BMAEC). Using quantitative RT-PCR with Taqman chemistries and GAPDH and beta-actin as endogenous controls, we observed that stimulation of EA cells with 100nM ET-1 for 4 hr was associated with increased mRNA expression of PDI levels that was 1.89 fold greater than vehicle treated cells (n=6, P<0.04). Similar results were observed on PDI mRNA expression in BMAEC isolated and cultured for 10 days then incubated with 100 nM ET-1 for 4 hr. Thus, our results strongly implicate cell surface associated PDI in cellular hydration status and its regulation by ET-1. We posit that aberrant regulation of PDI activity and/or its expression and secretion from either erythrocytes or endothelial cells represent a novel target aimed at ameliorating the complications associated with the pathophysiology of Sickle Cell Disease. Supported by NIH R01HL090632 to AR. Disclosures:No relevant conflicts of interest to declare.