(Circulation. 2000;101:2317.)
© 2000 American Heart Association, Inc.
Basic Science Reports |
Angiopoietin-1 Inhibits Irradiation- and Mannitol-Induced Apoptosis in Endothelial Cells
From the National Creative Research Initiatives Center for Cardiac Regeneration and Institute of Cardiovascular Research, Departments of Obstetrics and Gynecology and Neurosurgery, Chonbuk National University, Chonju (H.J.K., Y.H.L., C.H.R, K.N.K., H.Y.C., G.Y.K), and the Department of Radiology, Sohae College, Kunsan (S.J.L.), Korea.
Correspondence to Gou Young Koh, MD, PhD, National Creative Research Initiatives Center for Cardiac Regeneration, Chonbuk National University School of Medicine, San 2-20, Keum-Am-Dong, Chonju, 560-180, Republic of Korea. E-mail gykoh{at}moak.chonbuk.ac.kr
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Abstract |
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Background and Purpose—Angiopoietin-1 (Ang1) is a vasculogenic factor that signals through the endothelial cell–specific Tie2 receptor tyrosine kinase. We recently reported that Ang1 prevented apoptosis induced by serum deprivation in endothelial cells. In this study, we examined whether Ang1 prevents apoptosis in endothelial cells treated with irradiation or clinical concentrations of mannitol.
Methods and Results—Ang1 prevented irradiation- and mannitol-induced apoptosis in human umbilical vein endothelial cells in a dose-dependent manner. Pretreatment with soluble Tie2 receptor, but not Tie1 receptor, blocked the antiapoptotic effect of Ang1. Two phosphatidylinositol 3'-kinase (PI3-kinase)–specific inhibitors, wortmannin and LY294002, blocked the Ang1-induced antiapoptotic effect. The antiapoptotic potency of Ang1 was similar to or greater than that of vascular endothelial growth factor, basic fibroblast growth factor, and endothelin-1. Ang1 also prevented apoptosis in cultured endothelial cells from porcine pulmonary and coronary arteries and in endothelial cells of explanted rat aorta.
Conclusions—Ang1 promotes the survival of endothelial cells in irradiation- and mannitol-induced apoptosis through Tie2 receptor binding and PI3-kinase activation. Pretreatment with Ang1 could be beneficial in maintaining normal endothelial cell integrity during intracoronary irradiation or systemic mannitol therapy.
Key Words: angiopoietin • endothelium • cells • apoptosis • radiation • mannitol
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Introduction |
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Vascular endothelium, a monolayer of cells lining the intima of the blood vessels, is involved in a variety of functions, including coagulation, vascular permeability, vascular tonus, and remodeling.1 Endothelial cells are in direct contact with the plasma and the cellular components of the blood and under certain pathological conditions are the targets of various noxious stimuli, such as toxins, drugs, and physical agents.2
Damage to the endothelium is a side effect of some types of therapy. Restenosis after coronary angioplasty is a major limitation in the treatment of atherosclerotic coronary artery disease.3 Intracoronary irradiation is a new and promising technique to prevent restenosis after angioplasty.4 However, irradiation induces apoptosis in endothelial cells,5 thereby inducing vasomotor dysfunction6 or reducing reendothelialization.7 Hyperosmotic mannitol therapy is widely used for reducing brain edema.8 9 However, clinical concentrations of mannitol induce apoptosis in endothelial cells, thereby damaging the vascular endothelium.10 Apoptosis induced by serum deprivation or irradiation in vascular endothelial cells can be prevented by several growth factors and cytokines, such as basic fibroblast growth factor (bFGF),5 vascular endothelial growth factor (VEGF),11 and endothelin-1 (ET-1).12 These molecules not only stimulate cell proliferation but also suppress apoptosis, thereby maintaining cell number.
Angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) have recently been identified as ligands of the endothelial cell–specific Tie2 receptor.13 14 In vivo analysis by targeted gene inactivation reveals that Ang1 recruits and sustains periendothelial support cells.15 Ang2 disrupts blood vessel formation in the developing embryo by antagonizing the effects of Ang1 on Tie2.14 Interestingly, transgenic overexpression16 or gene transfer17 of Ang1 increases vascularization in vivo. In vitro experiments have shown that Ang1 has specific effects on endothelial cells: it has little effect on proliferation, but it potently induces sprouting,18 chemotactic response,19 and network formation.20 Also, Ang1 is a strong apoptosis survival factor in endothelial cells under serum deprivation.20 21 22 Because Ang1 does not cause proliferation in endothelial cells,13 18 it could be a clinically useful endothelial protective factor.
In this study, we found that Ang1 prevents irradiation- and mannitol-induced apoptosis in endothelial cells through Tie2 receptor binding and phosphatidylinositol 3'-kinase (PI3-kinase) activation. These data suggest that pretreatment with Ang1 may help maintain normal endothelial cell integrity during intracoronary irradiation and systemic mannitol therapy.
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Methods |
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Materials
We obtained Ang1*, soluble Tie1 receptor-Fc (rTie1-Fc), and Tie2 receptor-Fc (rTie2-Fc) fusion proteins from Regeneron Pharmaceuticals, Inc. Ang1* is a recombinant version of Ang1 with modified NH2-terminus and mutated Cys245.13 Ang1* is easier than Ang1 to produce and purify. Mutation of the Cys245 in Ang1, which is not shared between Ang1 and Ang2, does not alter its agonistic properties. The biological activities of recombinant Ang1 and Ang1* are similar, as confirmed by their high-affinity binding to and stimulation of the Tie2 receptor in vitro.13 14 The Ang1* recombinant protein was produced from Chinese hamster ovary (CHO) cells and affinity-purified with rTie2-Fc–conjugated Sepharose according to the method described by Maisonpierre et al.14 The purity of the protein was >95%, as judged by reducing and nonreducing silver-stained SDS-PAGE. rTie1-Fc and rTie2-Fc fusion proteins were constructed, produced, and purified according to the method described by Davis et al.13 Recombinant human VEGF165 and bFGF were purchased from R&D systems. Media and serum were obtained from Life Technology, Inc. Most other biochemical reagents, including mannitol, angiotensin II, ET-1, gelatin, antibiotics, antimycotics, and trypsin-EDTA and antibodies were purchased from Sigma, unless otherwise specified.
Cell Culture
Human umbilical vein endothelial cells (HUVECs)
and porcine pulmonary arterial
endothelial cells (PPAECs) were prepared from human
umbilical cords and porcine pulmonary arteries by
collagenase digestion as previously
described.21 To obtain porcine coronary
arterial endothelial cells (PCAECs), pig
hearts were delivered within 1 hour of slaughter under sterile
conditions. A 5- to 7-cm section of coronary artery, from the
initiation area of the left coronary artery to the midportion
of the anterior interventricular artery, was carefully
isolated. Isolated arteries were washed 3 times with PBS containing
streptomycin, penicillin, and antimycotics and incubated with PBS
containing 0.2% collagenase (type II; Worthington) for 15
minutes at room temperature. The arteries were transferred onto a
sterile matrix, dissected sagittally, and fixed along the edges with
small pins. The luminal areas were rubbed gently with surgical spears
(No. 400101, Merocel Corp). The spears were dipped into PBS and swirled
5 to 6 times to detach the endothelial cells. The
detached cells were collected and seeded onto a 3.5-cm gelatin-coated
dish. When the cells reached confluence, they were replated onto
gelatin-coated dishes at split ratios of 1:2 or 1:3. Porcine
coronary artery smooth muscle cells (PCASMCs) were prepared
from a medial portion of porcine coronary artery by digestion
with collagenase and elastase (Worthington) in the
presence of soybean trypsin inhibitor. The
endothelial or muscle origin of the cultures was
confirmed by immunofluorescent detection of von
Willebrand factor or smooth muscle actin, respectively;
acceptable cultures had >95% cells positive to the corresponding
antibody. These endothelial cells were
maintained in M199 medium supplemented with 20% (vol/vol)
heat-inactivated FBS, and PCASMCs were maintained in DMEM
with 10% (vol/vol) FBS at 37°C in 5% CO2. The
primary cultured cells used in this study were between passages 2 and
4.
Induction of Apoptosis in Endothelial Cells
Endothelial cells were plated onto
gelatinized 24-well plates (5x104 cells per
well) in medium containing 5% serum and were incubated for 24 hours.
To produce irradiation-induced apoptosis, the cells were
irradiated with a linear accelerator (Siemens, 6-MV x-ray, 2
Gy/min). To produce mannitol-induced apoptosis, the cells were
grown to confluence in medium containing 20% serum, then switched to
medium with 2% serum for 24 hours before the addition of various
concentrations of mannitol.10 The final osmolarities in
the medium were confirmed with an osmometer (Advanced Instruments).
Quantitative Determination of Apoptosis
Quantitative determination of apoptosis in
cultured endothelial cells was performed as described
previously.21 Floating apoptotic cells were
collected with 2 PBS washes; adherent cells were collected by
trypsinization. The numbers and size distributions of the floating and
adherent cells were determined with a Coulter model Z1 Dual Counter
System. To quantify the apoptotic cells among the
adherent cells, the cells in a parallel well were washed with 0.9%
sodium chloride, fixed for 15 minutes with 0.5%
glutaraldehyde, and stained with Sytox green (Molecular
Probes, Inc). Two independent, blinded investigators counted the
apoptotic adherent cells identified by nuclear staining with a
fluorescence microscope (Zeiss). Approximately 250 cells were
counted in each of 4 different random locations. Interinvestigator
variation was <5%. The mean number from the 2 investigators was used
to estimate the percentage of apoptotic adherent cells. In some
cases, we confirmed our data on the number of apoptotic cells
among the adherent cells using the CytoDeath kit according to the
manufacturer’s protocol (Boehringer Mannheim). The nuclear
staining and the CytoDeath kit gave similar results. More than 97% of
floating cells were apoptotic, as confirmed by both Sytox green
staining and terminal deoxynucleotidyl
transferase–mediated dUTP nick end-labeling (TUNEL) assay (Oncor).
Therefore, the percentage of apoptotic cells is based on the
sum of the floating cells plus the apoptotic adherent cells in
a given cell population.
Application of Ang1*, Soluble Tie Receptors, and PI3-Kinase
Inhibitors to Endothelial Cells
Growth factor or cytokine was added to the cell medium
30 minutes before irradiation or mannitol treatment. Immediately after
irradiation, cells were washed, then given fresh medium with fresh
growth factor or cytokine. For mannitol treatment, the cells
were washed, then given fresh medium containing the mannitol and fresh
growth factor or cytokine. An 
5-fold molar excess of
rTie2-Fc completely inhibits Ang1*-induced Tie2
phosphorylation in an in vitro assay (data not shown).
Therefore, a 5-fold molar excess of rTie1-Fc or rTie2-Fc (2 µg/mL)
was added 30 minutes before treatment with Ang1* (200 ng/mL). In the
assay of PI3-kinase inhibitors, wortmannin (30 nmol/L; RBI,
Inc) or LY294002 (100 nmol/L; RBI, Inc) was added 1 hour before
treatment with Ang1* (200 ng/mL). The same amount of rTie1-Fc,
rTie2-Fc, wortmannin, or LY294002 was freshly added to the medium after
a wash, at the same time as the addition of Ang1. Control cultures
received the same amount of the appropriate buffer or DMSO.
Explant Culture and Detection of Apoptotic Cells in the
Endothelium of Rat Aorta
Explant culture of rat aorta was performed according to the
method described by Merrick et al.23 Abdominal aortas were
excised from male Sprague-Dawley rats. The aortas were cut into 5-mm
ring segments and washed in PBS. The rings were cultured in M199
containing 2% FBS and treated with mannitol (300 mOsm) in the absence
and presence of growth factor or cytokine as described above
for 6 hours at 37°C, 5% CO2. The rings were
washed in PBS, fixed in 10% neutral formalin, and embedded in
paraffin. Tissue blocks were sectioned at 8 µm. An anti-CD31
monoclonal antibody (clone JC70A, DAKO) was used for
endothelial staining, and the TUNEL method was used for
detection of apoptotic cells. The endothelial
cells and apoptotic cells in the endothelium of
the aortic rings were viewed, counted, and photographed with a
microscope (Axioskop, Zeiss) equipped with color CCD camera and
monitor. Five to 6 aortic rings from different animals were used for
each group. Approximately 100 to 120 endothelial cells
were counted from 1 section of each ring. Thus, 500 to 600
endothelial cells were counted per group.
Statistics
Data are expressed as mean±SD. Statistical significance between
2 groups was tested with the unpaired Student’s t test.
Statistical significance between >2 groups was tested by 1-way ANOVA
followed by the Student-Newman-Keuls test. Statistical significance was
set at P<0.05.
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Results |
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Ang1* Prevents Irradiation- and Mannitol-Induced Apoptosis in HUVECs Through the Tie2 Receptor and PI3-Kinase
Both irradiation and mannitol treatment caused apoptosis in HUVECs, as evidenced by floating cells seen with phase-contrast microscopy (Figure 1A
) and yellow nuclei in cells stained
with Sytox green (Figure 1B). In all experiments using
irradiation, the proportion of floating apoptotic cells to
total apoptotic cells was 37% to 42%; in mannitol
experiments, the proportion was 48% to 54% (data not shown). Ang1*
reduced the appearance of apoptotic cells after either
irradiation or mannitol treatment (Figure 1). Irradiation
induced apoptosis in a dose-dependent manner, from 5.6% under
control conditions to 30% after 10 Gy of irradiation (Figure 2A). Mannitol increased the percentage of
apoptotic cells in a dose-dependent manner, from 4.5% under
control conditions to 40% in cells treated with the maximum
clinical concentration of mannitol (300 mOsm; Figure 3A). Pretreatment with Ang1* (50 to 400
ng/mL) inhibited apoptosis induced by either treatment in a
dose-dependent manner (Figures 2B and 3B). Ang1* at 200
ng/mL inhibited 40% of the apoptotic events in either 10
Gy–irradiated cells (Figure 2B) or cells treated with 300 mOsm
mannitol (Figure 3B).
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A 5-fold molar excess of rTie2-Fc, but not rTie1-Fc, almost completely
blocked the antiapoptotic effects of Ang1* (Figures 2C
and 3C). Two specific inhibitors of PI3-kinase,
wortmannin and LY294002, also almost completely blocked the
antiapoptotic effect of Ang1* (Figures 2D and 3D). These results indicate that Ang1 exerts its
apoptotic effect in endothelial cells through
Tie2 receptor binding and PI3-kinase activation but not through the
Tie1 receptor.
Comparison of the Antiapoptotic Potency of Ang1 With Other
Growth Factors and Cytokines
We compared the antiapoptotic effect of Ang1 with that of
other growth factors and cytokines in HUVECs. Preliminary
experiments revealed that a maximal dose of Ang1 (400 ng/mL) produced a
further but slight increase in antiapoptotic effect, whereas a
maximal dose of VEGF (40 ng/mL), bFGF (10 ng/mL), ET-1
(5x10-7 mol/L), or angiotensin II
(5x10-7 mol/L) had no further
antiapoptotic effect beyond that of a submaximal dose.
Therefore, for comparison, a submaximal dose of each growth factor or
cytokine was applied. In irradiation-induced apoptosis,
the antiapoptotic potency of Ang1 (200 ng/mL) was similar to
that of VEGF (20 ng/mL) and bFGF (5 ng/mL) but was greater than that of
ET-1 (10-7 mol/L), although this difference was
not statistically significant (Figure 4A). In mannitol-induced
apoptosis, the antiapoptotic potency of Ang1 was
significantly greater than that of VEGF, bFGF, and ET-1 (Figure 4B). Angiotensin II (10-7
mol/L) did not produce a significant effect in either experiment
(Figure 4). Similar results were obtained in PPAECs (data not
shown). These data indicate that Ang1 is at least as effective as or
more effective than other endothelial survival
factors.
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P<0.05 vs
ET-1.
Antiapoptotic Effect of Ang1 Is Observed in PPAECs and
PCAECs but Not in PCASMCs
Endothelial cells from different locations have
different responses to growth factors and
cytokines.24 Therefore, we examined the
antiapoptotic effect of Ang1* in PPAECs and PCAECs. The
microscopic appearance of PCAECs was similar to but distinct from that
of HUVECs and PPAECs. The cultured PCAECs are rounder and smaller than
HUVECs and PPAECs but show a typical cobblestone appearance. The
mitotic response to VEGF in PCAECs was less than the response in HUVECs
and PPAECs, whereas the sprouting response to Ang1* is very active in
PPAECs, moderate in PCAECs, and very low in HUVECs (data not shown).
Although the percentages of control apoptotic cells in PPAECs
and HUVECs were similar, the percentage of apoptotic cells in
PPAECs was 10% to 15% less than in HUVECs at 24 hours after 10-Gy
irradiation (Figure 5A). However, Ang1*
inhibited 30% to 35% of the irradiation-induced apoptosis
in PPAECs (Figure 5A). The apoptotic and
antiapoptotic responses to mannitol and Ang1* in PPAECs were
similar to those in HUVECs (Figure 5B). Interestingly, PCAECs
had little apoptosis 24 hours after irradiation or 6 hours
after mannitol. However, the percentage of apoptotic cells in
PCAECs 48 hours after irradiation or 12 hours after mannitol closely
resembled those of PPAECs at shorter time points (Figure 5). In
all cases, Ang1* inhibited 30% to 35% of the irradiation- or
mannitol-induced apoptotic rate in PCAECs. In contrast, Ang1*
did not produce a significant antiapoptotic response in
PCASMCs, which lack the Tie2 receptor (Figure 5).
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Ang1 Prevents Apoptosis in the Endothelial
Cells of Explanted Rat Aorta
Aortic organ culture was used to study endothelial
cell viability in a system with intact morphology and minimal cell
division.23 Rings prepared from rat aorta were incubated
with mannitol (300 mOsm) in the absence or presence of agent for 6
hours, and apoptosis was assessed by color detection with TUNEL
labeling (Figure 6A). Incubation with
buffer alone resulted in few TUNEL-positive endothelial
cells (2.2±0.6%), whereas mannitol caused an 8.7-fold increase in
TUNEL-positive endothelial cells (Figure 6).
Pretreatment with Ang1* decreased the TUNEL-positive
endothelial cells by 40% (Figure 6). This
was significantly greater than the antiapoptotic potency of
VEGF (22%), bFGF (13%), and ET-1 (5%) (Figure 6).
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Discussion |
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Restenosis after coronary angioplasty is a major limitation in the treatment of atherosclerotic coronary artery disease.3 Intracoronary irradiation is a new and simple technique developed to prevent restenosis after angioplasty.4 In fact, a 2-year follow-up study of catheter-based radiotherapy for preventing coronary restenosis showed potentially significant clinical benefit.25 Nevertheless, intracoronary irradiation inevitably causes some injury to coronary endothelial cells.4 5 6 7 The integrity of endothelial cells and reendothelialization around areas injured by angioplasty or irradiation are essential for preventing restenosis.26 Our study indicates that Ang1 inhibits irradiation-induced apoptosis in coronary artery endothelial cells. These data suggest that pretreatment with Ang1 could prevent apoptosis in coronary artery endothelial cells during intracoronary irradiation, potentially reducing the restenosis rate.
Mannitol is a cell-impermeant, nonmetabolizable sugar administered intravenously as a hypertonic solution for treating brain edema.8 9 Mannitol is customarily administered every 3 to 4 hours in bolus doses of up to 1.5 g/kg body wt, resulting in a final serum osmolarity of 320 mOsm.27 The beneficial clinical effects of mannitol have been attributed to the consequent increase in intravascular volume and coincident decrease in extracellular fluid volume.8 9 However, mannitol may activate inflammatory mediators and adversely affect certain cell types.28 Clinical concentrations of mannitol activate tyrosine and stress kinases and induce apoptosis in bovine aortic endothelial cells.10 Thus, the clinical use of mannitol may exert direct deleterious effects on vascular endothelium. In this study, a clinical concentration of mannitol increased apoptosis in 3 different endothelial cell cultures and in the endothelial cells of explanted rat aorta. Thus, we conclude that Ang1 inhibits mannitol-induced apoptosis in the endothelial cells. This finding suggests that pretreatment with Ang1 could prevent apoptosis in endothelial cells during mannitol therapy, thereby reducing the deleterious effect on endothelial cells.
Our results indicate that the antiapoptotic effect of Ang1 in endothelial cells is mediated through binding to the Tie2 receptor in both irradiation- and mannitol-induced apoptosis. Other reports noted that soluble Tie2 receptor, but not Tie1 receptor, could block Ang1-induced sprouting,18 chemotactic effects,19 and network formation20 in endothelial cells. The intracellular second messenger signal transduction cascades initiated by Ang1-Tie2 binding are not well characterized. A recent report indicated that Tie2 activates PI3-kinase and Akt.29 The PI3-kinase and Akt pathways are common features in the transduction of the antiapoptotic effects of growth factors.30 Therefore, we examined whether the PI3-kinase pathway was involved in the antiapoptotic effect of Ang1 in endothelial cells. Wortmannin or LY294002, 2 potent inhibitors of PI3-kinase, completely reversed the antiapoptotic effect of Ang1 on both irradiation- and mannitol-induced apoptosis. Therefore, PI3-kinase activation could be an essential step in the antiapoptotic effect of Ang1.
The present results show that the antiapoptotic potency of
Ang1 in endothelial cells is higher than that of VEGF,
bFGF, or ET-1 in mannitol-induced apoptosis. As we
demonstrated, Ang1 prevents endothelial
apoptosis through the Tie2 receptor. VEGF is known to prevent
endothelial apoptosis through the Flk1
receptor.31 Tie2 and Flk1 receptors are selectively
localized in endothelial cells. Thus, Ang1 and VEGF are
therapeutic candidates for preventing endothelial cell
apoptosis under certain pathological conditions. However, VEGF
exerts multiple effects, including proliferation and vascular
permeability,32 whereas Ang1 exerts few cellular effects
in the endothelial cells. Preliminary results of
differential-display polymerase chain reaction revealed that VEGF
increases 0.25% of mRNA transcripts, whereas Ang1 increases
0.04% of mRNA transcripts among the 25 000 mRNA transcripts of
HUVECs (unpublished observations). Therefore, Ang1 could be better than
VEGF in terms of clinical safety.
In conclusion, the present data suggest that pretreatment with Ang1 may provide a beneficial effect in maintaining normal endothelial cell integrity during intracoronary irradiation and mannitol therapy through the antiapoptotic effect of Ang1 in endothelial cells. However, further in vivo studies will need to be done before clinical application.
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Acknowledgments |
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This work was supported by the Creative Research Initiatives of the Korean Ministry of Science and Technology. We thank Peter C. Maisonpierre and George D. Yancopoulos for providing critical angiopoietin- and Tie-related reagents. We thank Jennifer Macke for help in preparing the manuscript.
Received August 23, 1999; revision received December 13, 1999; accepted December 22, 1999.
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References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Warren JB. The Endothelium: An Introduction to Current Research. New York, NY: Wiley-Liss, Inc; 1990.
2.
Pober JS, Cotran RS. Cytokines and
endothelial cell biology. Physiol Rev. 1990;70:427–451.
3.
Leimgruber PP, Roubin GS, Hollman J, et al.
Restenosis after successful coronary angioplasty in
patients with single-vessel disease. Circulation. 1986;73:710–717.
4. Weinberger J, Simon AD. Intracoronary irradiation for prevention of restenosis. Curr Opin Cardiol. 1997;12:468–474.[Medline] [Order article via Infotrieve]
5.
Fuks Z, Persaud RS, Alfieri A, et al. Basic fibroblast
growth factor protects endothelial cells against
radiation-induced programmed cell death in vitro and in vivo.
Cancer Res. 1994;54:2582–2590.
6.
Wiedermann JG, Leavy JA, Amols H, et al. Effects of
high-dose intracoronary irradiation on vasomotor function and
smooth muscle histopathology. Am J Physiol. 1994;267:H125–H132.
7. Brenner DJ, Miller RC, Hall EJ. The radiobiology of intravascular irradiation. Int J Radiat Oncol Biol Phys. 1996;36:805–810.[Medline] [Order article via Infotrieve]
8. Bullock R, Chestnut RM, Clifton G, et al. Guidelines for the management of severe head injury. Brain Trauma. 1996;13:639–734.
9. Better OS, Rubinstein I, Winaver JM, et al. Mannitol therapy revisited 1940–1997. Kidney Int. 1997;52:886–894.[Medline] [Order article via Infotrieve]
10.
Malek AM, Goss GG, Jiang L, et al. Mannitol at clinical
concentrations activates multiple signaling pathways and
induces apoptosis in endothelial cells.
Stroke. 1998;29:2631–2640.
11.
Gerber H, Dixit V, Ferrara N. Vascular
endothelial growth factor induces expression of the
antiapoptotic proteins bcl-2 and A1 in vascular
endothelial cells. J Biol Chem. 1998;273:13313–13316.
12.
Shichiri M, Kato H, Marumo F, et al. Endothelin-1 as an
autocrine/paracrine apoptosis survival factor for
endothelial cells. Hypertension. 1997;30:1198–1203.
13. Davis S, Aldrich TH, Jones PF, et al. Isolation of angiopoietin-1, a ligand for the TIE2 receptor by secretion-trap expression cloning. Cell. 1996;87:1161–1169.[Medline] [Order article via Infotrieve]
14.
Maisonpierre PC, Suri C, Jones PF, et al.
Angiopoietin-2, a natural antagonist for Tie2 that disrupts
in vivo angiogenesis. Science. 1997;277:55–60.
15. Suri C, Jones PF, Patan S, et al. Requisite role of angiopoietin-1, a ligand for the TIE2 receptor, during embryonic angiogenesis. Cell. 1996;87:1171–1180.[Medline] [Order article via Infotrieve]
16.
Suri C, McClain J, Thursyon G, et al. Increased
vascularization in mice overexpressing angiopoietin-1.
Science. 1998;282:468–471.
17.
Shyu KG, Manor O, Magner M, et al. Direct intramuscular
injection of plasmid DNA encoding angiopoietin-1 but not angiopoietin-2
augments revascularization in the rabbit
ischemic hindlimb. Circulation. 1998;98:2081–2087.
18. Koblizek TI, Weiss C, Yancopoulos GD, et al. Angiopoietin-1 induces sprouting angiogenesis in vitro. Curr Biol. 1998;8:529–532.[Medline] [Order article via Infotrieve]
19. Witzenbichler B, Maisonpierre PC, Jones P, et al. Chemotactic properties of angiopoietin-1 and -2, ligands for the endothelial-specific receptor tyrosine kinase Tie2. J Biol Chem. 1998;29:18514–18521.
20. Papapetropoulos A, Garcia-Cardena G, Dengler TJ, et al. Direct actions of angiopoietin-1 on human endothelium: evidence for network stabilization, cell survival, and interaction with other angiogenic growth factors. Lab Invest. 1999;79:213–223.[Medline] [Order article via Infotrieve]
21. Kwak HJ, So J-N, Lee SJ, et al. Angiopoietin-1 is an apoptosis survival factor for endothelial cells. FEBS Lett. 1999;448:249–253.[Medline] [Order article via Infotrieve]
22.
Holash J, Maisonpierre PC, Compton D, et al. Vascular
cooption, regression and growth by tumors involving angiopoietins and
VEGF. Science. 1999;284:1994–1998.
23. Merrick AF, Shewring LD, Cunningham SA, et al. Organ culture of arteries for experimental studies of vascular endothelium in situ. Transplant Immunol. 1997;5:3–9.[Medline] [Order article via Infotrieve]
24. Risau W. Differentiation of endothelium. FASEB J. 1995;9:926–933.[Abstract]
25.
Teirstein PS, Massullo V, Jani S, et al. Two-year
follow-up after catheter-based radiotherapy to inhibit coronary
stenosis. Circulation. 1999;99:243–247.
26.
Asahara T, Bauters C, Pastore BS, et al. Local delivery
of vascular endothelial growth factor accelerates
reendothelialization and attenuates intimal hyperplasia
in balloon-injured rat carotid artery. Circulation. 1995;91:2793–2801.
27.
Paczynski RP, HE YY, Diringer MN, et al. Multiple-dose
mannitol reduces brain water content in a rat model of cortical
infarction. Stroke. 1997;28:1437–1444.
28. Shapiro L, Dinarello CA. Hyperosmotic stress as a stimulant for proinflammatory cytokine production. Exp Cell Res. 1997;231:354–362.[Medline] [Order article via Infotrieve]
29.
Kondos CD, Stauffer TP, Yang WP, et al. Tyrosine 1101
of Tie2 is the major site of association of p85 and is required for
activation of phosphatidylinositol 3-kinase and Akt. Mol Cell
Biol. 1998;18:4131–4140.
30.
Haunstetter A, Izumo S. Apoptosis: basic
mechanisms and implications for cardiovascular disease.
Circ Res. 1998;82:1111–1129.
31.
Gerber HP, McMurtrey A, Kowalski J, et al. Vascular
endothelial growth factor regulates
endothelial cell survival through the
phosphatidylinositol 3'-kinase/Akt signal transduction pathway.
J Biol Chem. 1988;273:30336–30343.
32.
Ferrara N, Davis-Smyth T. The biology of vascular
endothelial growth factor. Endocr Rev. 1997;18:4–25.
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 J.-X. Chen, H. Zeng, M. L Lawrence, T. S. Blackwell, and B. Meyrick Angiopoietin-1-induced angiogenesis is modulated by endothelial NADPH oxidase Am J Physiol Heart Circ Physiol, October 1, 2006; 291(4): H1563 - H1572. [Abstract] [Full Text] [PDF]
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 W. Kim, S.-O. Moon, S. Y. Lee, K. Y. Jang, C.-H. Cho, G. Y. Koh, K.-S. Choi, K.-H. Yoon, M. J. Sung, D. H. Kim, et al. COMP-Angiopoietin-1 Ameliorates Renal Fibrosis in a Unilateral Ureteral Obstruction Model J. Am. Soc. Nephrol., September 1, 2006; 17(9): 2474 - 2483. [Abstract] [Full Text] [PDF]
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 N. P.J. Brindle, P. Saharinen, and K. Alitalo Signaling and Functions of Angiopoietin-1 in Vascular Protection Circ. Res., April 28, 2006; 98(8): 1014 - 1023. [Abstract] [Full Text] [PDF]
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 T. Murakami, H. Takagi, K. Suzuma, I. Suzuma, H. Ohashi, D. Watanabe, T. Ojima, E. Suganami, M. Kurimoto, H. Kaneto, et al. Angiopoietin-1 Attenuates H2O2-induced SEK1/JNK Phosphorylation through the Phosphatidylinositol 3-Kinase/Akt Pathway in Vascular Endothelial Cells J. Biol. Chem., September 9, 2005; 280(36): 31841 - 31849. [Abstract] [Full Text] [PDF]
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K.-T. Kim, H.-H. Choi, M. O. Steinmetz, B. Maco, R. A. Kammerer, S. Y. Ahn, H.-Z. Kim, G. M. Lee, and G. Y. Koh Oligomerization and Multimerization Are Critical for Angiopoietin-1 to Bind and Phosphorylate Tie2 J. Biol. Chem., May 20, 2005; 280(20): 20126 - 20131. [Abstract] [Full Text] [PDF]
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S. M. Dallabrida, N. Ismail, J. R. Oberle, B. E. Himes, and M. A. Rupnick Angiopoietin-1 Promotes Cardiac and Skeletal Myocyte Survival Through Integrins Circ. Res., March 4, 2005; 96(4): e8 - e24. [Abstract] [Full Text] [PDF]
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 H. J. LEE, C.-H. CHO, S.-J. HWANG, H.-H. CHOI, K.-T. KIM, S. Y. AHN, J.-H. KIM, J.-L. OH, G. M. LEE, and G. Y. KOH Biological characterization of angiopoietin-3 and angiopoietin-4 FASEB J, August 1, 2004; 18(11): 1200 - 1208. [Abstract] [Full Text] [PDF]
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 C.-H. Cho, R. A. Kammerer, H. J. Lee, M. O. Steinmetz, Y. S. Ryu, S. H. Lee, K. Yasunaga, K.-T. Kim, I. Kim, H.-H. Choi, et al. COMP-Ang1: A designed angiopoietin-1 variant with nonleaky angiogenic activity PNAS, April 13, 2004; 101(15): 5547 - 5552. [Abstract] [Full Text] [PDF]
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C.-H. Cho, R. A. Kammerer, H. J. Lee, K. Yasunaga, K.-T. Kim, H.-H. Choi, W. Kim, S. H. Kim, S. K. Park, G. M. Lee, et al. Designed angiopoietin-1 variant, COMP-Ang1, protects against radiation-induced endothelial cell apoptosis PNAS, April 13, 2004; 101(15): 5553 - 5558. [Abstract] [Full Text] [PDF]
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E. Audero, I. Cascone, F. Maniero, L. Napione, M. Arese, L. Lanfrancone, and F. Bussolino Adaptor ShcA Protein Binds Tyrosine Kinase Tie2 Receptor and Regulates Migration and Sprouting but Not Survival of Endothelial Cells J. Biol. Chem., March 26, 2004; 279(13): 13224 - 13233. [Abstract] [Full Text] [PDF]
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 J.-x. Chen, M. L. Lawrence, G. Cunningham, B. W. Christman, and B. Meyrick HSP90 and Akt modulate Ang-1-induced angiogenesis via NO in coronary artery endothelium J Appl Physiol, February 1, 2004; 96(2): 612 - 620. [Abstract] [Full Text] [PDF]
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 A. Tadros, D. P. Hughes, B. J. Dunmore, and N. P. J. Brindle ABIN-2 protects endothelial cells from death and has a role in the antiapoptotic effect of angiopoietin-1 Blood, December 15, 2003; 102(13): 4407 - 4409. [Abstract] [Full Text] [PDF]
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B. H. Jeon, F. Khanday, S. Deshpande, A. Haile, M. Ozaki, and K. Irani Tie-ing the Antiinflammatory Effect of Angiopoietin-1 to Inhibition of NF-{kappa}B Circ. Res., April 4, 2003; 92(6): 586 - 588. [Full Text] [PDF]
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D. P. Hughes, M. B. Marron, and N. P.J. Brindle The Antiinflammatory Endothelial Tyrosine Kinase Tie2 Interacts With a Novel Nuclear Factor-{kappa}B Inhibitor ABIN-2 Circ. Res., April 4, 2003; 92(6): 630 - 636. [Abstract] [Full Text] [PDF]
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 S.M. DALLABRIDA and M.A. RUPNICK Vascular Endothelium in Tissue Remodeling: Implications for Heart Failure Cold Spring Harb Symp Quant Biol, January 1, 2002; 67(0): 417 - 428. [Abstract] [PDF]
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 I. Kim, S.-O. Moon, C.-Y. Han, Y. K. Pak, S. K. Moon, J. J. Kim, and G. Y. Koh The angiopoietin-tie2 system in coronary artery endothelium prevents oxidized low-density lipoprotein-induced apoptosis Cardiovasc Res, March 1, 2001; 49(4): 872 - 881. [Abstract] [Full Text] [PDF]
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 J. K. Chae, I. Kim, S. T. Lim, M. J. Chung, W. H. Kim, H. G. Kim, J. K. Ko, and G. Y. Koh Coadministration of Angiopoietin-1 and Vascular Endothelial Growth Factor Enhances Collateral Vascularization Arterioscler Thromb Vasc Biol, December 1, 2000; 20(12): 2573 - 2578. [Abstract] [Full Text] [PDF]
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Y. Xu and Q. Yu Angiopoietin-1, Unlike Angiopoietin-2, Is Incorporated into the Extracellular Matrix via Its Linker Peptide Region J. Biol. Chem., September 7, 2001; 276(37): 34990 - 34998. [Abstract] [Full Text] [PDF]
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