| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Regular Articles |
From the Department of Pathology,* University of Washington, Seattle, Washington; the Department of Pathology, Microbiology, and Immunology, Philadelphia College of Osteopathic Medicine, Philadelphia, Pennsylvania; and the Division of Pathology and Laboratory Medicine, Veterans Affairs Puget Sound Health Care System, Seattle, Washington
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
VEGF, also designated as VEGF-A, belongs to a family of growth factors with predominant endothelial target-specificity.8,9 VEGF mainly binds to and activates two different receptor tyrosine kinases, designated Flt-1 (fms-like tyrosine kinase-1, VEGF receptor-1)10 and KDR (kinase-insert domain-containing receptor, VEGF receptor-2),11 but it can activate other receptors such as neuropilin-1 and -2. VEGF promotes endothelial migration, proliferation, survival, and proteolytic activity.6
The angiopoietin family comprises at least four secreted proteins, angiopoietin (Ang)- 1, -2, -3, and -4, all of which bind to the endothelial-specific receptor tyrosine kinase Tie-2. Ang-1 and Ang-4 have the ability to phosphorylate Tie-2,12,13 whereas Ang-2 and Ang-3 are believed to act as natural antagonists.5,13 Ang-2 may also function as an agonist when used at high concentration or for prolonged incubation times in the context of a three-dimensional matrix.14,15 Ang-1 promotes endothelial migration, survival, and proteolytic activity16-18 without significantly affecting endothelial proliferation.4,19
VEGF and Ang-1 can both activate critical signaling pathways such as MAPK and Akt,20-23 but they differ significantly in their capacity to induce an angiogenic response and influence different steps of the angiogenic process.7,19 Although many studies have defined the angiogenic properties of VEGF and Ang-1, a gap remains in our understanding of how the unique biological signals elicited by these two growth factors are specifically transduced in the vessel wall during angiogenesis.
In the present study we used a modification of the rat aorta model to investigate signal transduction events occurring in the native aortic wall during angiogenesis.24 In this system, VEGF and Ang-1 generate unique temporal patterns of MAPK and AKT phosphorylation, which correlate with the presence or absence of an angiogenic response. Evaluation of these phosphorylation patterns and underlying regulatory mechanisms may provide novel insights into the early signaling events required for the initiation of the angiogenic process.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
The recombinant Ang-1 used for this study (Ang-1*) was obtained from Regeneron Pharmaceuticals, Inc. (Tarrytown, NY). Ang-1* is a genetically engineered variant of Ang-1 of which the first 77 residues are replaced with the first 73 residues of Ang-2 while a nonconserved cysteine is mutated to the corresponding serine residue of Ang-2. Endothelial basal medium (EBM) was obtained from Clonetics Corporation (San Diego, CA). The PhosphoPlus antibodies for Akt (Ser473), p44/42 MAPK (Thr202/Tyr204), and p38 MAPK (Thr180/Tyr182) were purchased from New England Biolabs Inc. (Beverly, MA). Protease inhibitors (Complete Tablet) were purchased from Boehringer Mannheim Corp. (Indianapolis, IN). The bicinchoninic acid (BCA) protein assay was from Pierce (Rockford, IL) and the enhanced chemiluminesence (ECL) system from Amersham Pharmacia Biotech (Piscataway, NJ). MAPK inhibitors U0126 (p44/42 MAPK pathway),25
SB203580 (p38 MAPK pathway),26
and the PI3 kinase inhibitor LY294002 (Akt pathway)27
were purchased from Calbiochem (La Jolla, CA). Monoclonal mouse anti-
smooth muscle actin antibody was purchased from Sigma (St. Louis, MO). Alexa Fluor 488 conjugated Griffonia isolectin B4 (I-B4), and Alexa Fluor 488-conjugated goat anti-mouse antibody or Alexa Fluor 568-conjugated goat anti-rabbit antibody were obtained from Molecular Probes (Eugene, OR).
Rat Aorta Model of Angiogenesis
Freshly cut aortic rings obtained from 5- to 10-week-old Fischer 344 male rats were embedded in collagen gels and transferred to 16-mm wells (4-well NUNC dishes) each containing 0.5 ml serum-free EBM (Clonetics Corporation), as described.24,28 The medium was changed three times a week starting from day 3. Collagen gel cultures were treated with increasing concentrations of VEGF or Ang-1. To evaluate the role of signaling pathways in this system, cultures were treated with specific p44/42 MAPK, p38 MAPK, or Akt inhibitors (see above). Inhibitors were added to the medium from the beginning of the experiment and with each feeding. Controls were treated with vehicle alone (0.2% dimethyl sulfoxide (DMSO)).
The Modified Rat Aorta Model of Angiogenesis with Quiescent Rings
Aortic rings lose their spontaneous angioformative activity after a 14-day-long pre-incubation step in repeated changes of serum-free medium before collagen embedding. This is due to the gradual decrease in the system of endogenous angiogenic factors released from the rings.24 The angiogenic activity of rings made quiescent with this treatment can be reactivated by exogenous angiogenic factors such as bFGF and VEGF. This modified rat aorta model can be used to evaluate the capacity of growth factors to induce angiogenesis. We used this approach to compare the effect on angiogenesis of VEGF and Ang-1, and to analyze the relationship between induction of angiogenesis and phosphorylation of signal transduction pathways. Collagen gel cultures of quiescent aortic rings were treated with VEGF, Ang-1, the VEGF/Ang-1 combination, or left untreated.
Measurement of Angiogenesis
The angiogenic response of aortic cultures was measured in the live cultures by counting the number of neovessels over time, according to published criteria.28 Branching morphogenesis was evaluated by counting branch points at the peak of angiogenic growth.
Signal Transduction in Quiescent Rat Aortic Rings
Quiescent aortic rings were treated with VEGF, Ang-1, or a combination of VEGF and Ang-1 for 5 minutes, 15 minutes, 1 hour, 4 hours, and 24 hours. Each group consisted of 6 to 8 rings. Rings were cultured individually in agarose-coated 16-mm wells (4-well NUNC dishes), each containing 0.5 ml serum-free medium. Mechanical disturbance of the system was minimized by carefully replacing existing medium with growth factor-supplemented fresh medium, without touching the explants. At the end of treatment, aortic rings of each group were pooled together in a 35-mm well of a 6-well plate filled with ice-cold phosphate-buffered saline (PBS). Microdissection forceps were used to move the rings from the NUNC plate to the 6-well plate. This was accomplished by gently holding each ring by its adventitial edge with the tips of the forceps during transfer. Without shaking, the rings were allowed to sink to the bottom of the well in the PBS solution. Each group of rings was then transferred to a liquid nitrogen-filled 18-mm well of a 24-well culture plate, pulverized with a pre-chilled pestle, and solubilized on ice with 100 µl ice-cold lysis buffer (50 mmol/L Tris-HCl, pH 7.5, 1% Triton X-100, 150 mmol/L NaCl, 10 mmol/L EDTA, 2 mmol/L EGTA, 0.02% sodium azide, 50 mmol/L NaF, 2 mmol/L vanadate, supplemented with protease inhibitors). The resulting slurry was then transferred to a 1.5 ml microcentrifuge tube, sonicated for 10 second on ice, and centrifuged at 1000 x g for 10 minutes at 4°C. The supernatant was used for Western blot studies. Protein concentration was measured with the BCA assay.
Western Blotting
Samples were boiled for 3 minutes in SDS-PAGE sample buffer (62.5 mmol/L Tris-HCl, pH 6.8, 10% glycerol, 2% SDS, 0.65 mmol/L dithiothreitol, 0.06% bromophenol blue, and 5% 2-mercaptoenthanol). 10-µg protein was loaded in each lane. After electrophoresis on a 4 to 20% gradient polyacrylamide gel, proteins were transferred to a nylon membrane and probed first with antibodies against the phosphorylated protein. The blots were then stripped and reprobed with an antibody against the total protein. Specific antibody binding was detected with the ECL system. The intensity of the bands was measured with a GS-710 Calibrated Imaging Densitometer (BIO-RAD, Hercules, CA). Degree of phosphorylation was obtained by calculating from the densitometric measurements the percentage of kinase phosphorylation.
Confocal Microscopy: Double Fluorescent Labeling
Double fluorescent labeling followed by confocal microscopy was used to histologically localize the phosphorylation signal in the aortic wall. Quiescent aortic rings were treated with VEGF, Ang-1, or the VEGF/Ang-1 combination to induce phosphorylation signals in the aortic explant. The rings were then embedded in OCT compound, snap-frozen in isopentane at - 100°C, cryosectioned at a thickness of 10 µm, placed on Fischer plus histology slides, and fixed in acetone at - 20°C. Frozen sections were rehydrated in PBS and double stained for 1 hour with a cocktail of cell-specific markers (1-B4 for endothelial cells or anti--SMA antibody for smooth muscle cells) and antibodies against phosphorylated signaling proteins (phospho-p44/42 MAPK, phospho-p38 MAPK, or phospho-Akt). Cell markers and phosphorylated proteins were visualized in different colors by fluorescent dyes (Alexa Fluor 488 or 568) conjugated to the appropriate secondary antibodies. For the double staining with the Griffonia isolectin B4, the lectin, which is directly conjugated with Alexa Fluor 488, was added at the same time as the Alexa Fluor 568-conjugated (Leica Microsystem, Heidelberg, Germany) secondary antibody against the signaling protein of interest. Slides were washed for 5 minutes x 3 with PBS between staining steps and mounted in Gelvatol (Monsanto, St. Louis, MO). Confocal microscopy was performed using a Leica TCS-SP Laser Scanning microscope. Images were evaluated by Z-plane analysis followed by projection and overlay using Leica software.
Statistical Analysis
Experiments included three to four observations per data point and were repeated at least two times. Results were analyzed with GraphPad Prism statistics software (GraphPad Software, Inc., San Diego, CA). Student’s t-test or one-way analysis of variance followed by Newman-Keuls multiple comparison tests were used to evaluate whether differences between groups were significant. Statistical significance was set at P < 0.05.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Aortic rings embedded in collagen gel immediately after excision from the animal produced a self-limited angiogenic response, which could be dose-dependently stimulated with VEGF, as reported.24 Angiogenesis in this system was also promoted by Ang-1, which significantly increased the number of both neovessel sprouts (162.5 ± 15.3 SEM in 0.67 µg/ml Ang-1-treated cultures versus 111.7 ± 6.8 in untreated control, n = 4, P < 0.05) and branch points (49.33 ± 6.9 SEM in 0.67 µg/ml Ang-1-treated cultures versus 17.7 ± 1.2 in untreated control, n = 4, P < 0.05).
Ang-1 Is Unable to Induce Angiogenesis but Potentiates the Effect of VEGF in Cultures of Quiescent Aortic Rings
Aortic rings pre-incubated in serum-free medium for 2 weeks under floating conditions fail to generate a significant angiogenic response when embedded in collagen gels.24,29
We used this model to determine whether Ang-1, which is capable of promoting an existing angiogenic response, is also capable of initiating neovessel sprouting from quiescent aortic explants. Unstimulated control rings exhibited only rare and short endothelial sprouts (Figure 1,A and G)
. Stimulation with VEGF greatly enhanced the angiogenic response (Figure 1, C and G)
. Conversely, Ang-1 was unable to switch on the angiogenic process (Figure 1, B and G)
. Ang-1, however, dose-dependently enhanced VEGF-induced microvessel sprouting (Figure 1, D and G)
and branching (Figure 1, E and F
; number of branch points: 49.3 ± 7.1 in VEGF/Ang-1-treated cultures versus 20.3 ± 4.5 in cultures treated with VEGF alone, n = 6, P < 0.01).
|
To elucidate the regulatory mechanisms underlying the response of the aortic wall to VEGF and Ang-1, we studied the effect of these factors on the phosphorylation of p44/42 MAPK, p38 MAPK, and Akt. Initial studies performed after a 15-minute incubation period revealed that both VEGF and Ang-1 were capable of stimulating the phosphorylation of p44/42 MAPK, p38 MAPK, and Akt. Thus, the mere phosphorylation of p44/42 MAPK, p38 MAPK, or Akt signal pathways did not appear sufficient for the induction of angiogenesis. To evaluate whether the duration of intracellular signaling might affect the angiogenic response, quiescent aortic rings were incubated with VEGF, Ang-1, or the VEGF/Ang-1 combination for different times ranging from 5 minutes to 24 hours. VEGF induced biphasic phosphorylation of p44/42 MAPK, while the effect of Ang-1 on this pathway was monophasic (Figure 2
, top panel). Phosphorylation of p44/42 MAPK in response to VEGF peaked at 15 minutes, decreased by 1 hour, increased a second time after 4 hours, and finally decreased close to baseline levels in 24 hours. Conversely, Ang-1 induced a single peak of phosphorylation at 15 minutes. When the quiescent rings were stimulated with the VEGF/Ang-1 combination, the Ang-1 pattern of p44/42 MAPK phosphorylation predominated, while the second peak of VEGF-induced phosphorylation was abrogated.
|
, middle panel). Phosphorylation of p38 MAPK increased significantly after 5 minutes, reached a peak at 15 minutes, then decreased gradually and remained around basal levels during the following 24 hours. VEGF and Ang-1 administered together had an additive effect on p38 MAPK phosphorylation at 1 hour.
VEGF induced biphasic phosphorylation of Akt kinase (Figure 2
, bottom panel), with a small peak of phosphorylation at 15 minutes, followed by a decrease at 1 hour and a second peak at 4 hours. The second wave of VEGF-induced phosphorylation of Akt remained elevated during the following 24 hours. Ang-1-induced Akt phosphorylation was monophasic and peaked at 15 minutes with a stronger signal than the one produced by VEGF during its first phase of Akt phosphorylation. Ang-1-induced Akt phosphorylation decreased gradually, reaching values close to basal level by 24 hours. In the presence of both VEGF and Ang-1, the phosphorylation pattern of Akt was characterized by a first strong peak of phosphorylation at 15 minutes, which was similar to that induced by Ang-1 and higher than the one generated by VEGF, and by a similarly robust second peak of phosphorylation at 24 hours indistinguishable from that obtained with VEGF alone. These two phases of Akt phosphorylation were separated by a slight decrease in Akt phosphorylation at 1 hour.
Localization of Phosphorylation Signals in the Aortic Wall
Confocal microscopy of VEGF-, Ang-1, or VEGF/Ang-1-stimulated aortic rings double stained at time points of maximal phosphorylation for cell markers and signal transduction proteins demonstrated phosphorylated p44/42 MAPK, p38 MAPK, and Akt predominantly in endothelial cells (Figure 3)
. This pattern was observed in rings treated with VEGF, Ang-1, or the VEGF/Ang-1 combination. Phosphorylation signals were demonstrated also in some smooth muscle cells, with p44/42 MAPK showing the strongest staining reaction. Staining for phosphorylated p44/42 MAPK, p38 MAPK, or Akt was observed in the endothelium and smooth muscle cells of unstimulated controls. Differences in intensity of staining between treated rings and untreated controls were most noticeable in cultures reacted for phospho-p38 MAPK, which on Western analysis showed the greatest increase over control values (> 5-fold).
|
To evaluate the functional role of p44/42 MAPK, p38 MAPK, and Akt signal transduction pathways in the angiogenic response of the rat aorta, collagen gel cultures of freshly cut aortic rings were treated with specific inhibitors: U0126 (p44/42 MAPK pathway), SB203580 (p38 MAPK), and LY294002 (PI 3-kinase/Akt pathway) (Figure 4)
. U0126 blocked microvessel sprouting with only minor inhibitory effects on fibroblast growth. Angiogenesis was also blocked by LY294002, which partially inhibited fibroblast outgrowth. SB203580 did not affect microvessel sprouting, but it significantly reduced the number of non-endothelial cells in the cultures. The anti-angiogenic effect of p44/42 MAPK and Akt pathway inhibitors was not due to toxicity, because aortic rings previously treated with U0126 or LY294002 produced a florid angiogenic response when re-embedded in new gels and cultured in inhibitor-free medium containing VEGF (Figure 4
, inset).
|
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
.
|
VEGF, which is able to initiate angiogenesis, elicits a biphasic and sustained phosphorylation of p44/42 MAPK and Akt kinase, whereas Ang-1 has a monophasic and transient effect on both pathways (Figure 5)
. The mechanisms and related mediators responsible for the second wave of p44/42 MAPK and Akt phosphorylation in the rat aorta model are unclear because VEGF is known to induce only transient phosphorylation of these pathways in isolated endothelial cells.20,32,33
The observation by confocal microscopy that phosphorylated p44/42 MAPK and Akt predominate in endothelial cells but can be demonstrated also in some smooth muscle cells raises the possibility that smooth muscle cells contribute to this process. More studies are, however, needed to define the significance of these observations, and to clarify the nature of the cross talk between endothelial cells and smooth muscle cells in the early stages of angiogenesis.
By comparing the biological effects of VEGF and Ang-1 and the temporal patterns of p44/42 MAPK phosphorylation by these factors, one may expect a causative link between the second peak of VEGF-mediated p44/42 MAPK phosphorylation and the induction of angiogenesis (Figure 5)
. This would also be consistent with previous reports indicating that mitogenicity correlates with growth factor ability to induce sustained phosphorylation of p44/42 MAPK.34
However, Ang-1, which potentiates the angiogenic effect of VEGF in the rat aorta model, almost completely abrogates the VEGF-induced late p44/42 MAPK phosphorylation when administered together with this factor, suggesting that the second peak of p44/42 MAPK phosphorylation is probably not required for VEGF-induced angiogenesis. The Ang-1-mediated abrogation of the second peak of p44/42 MAPK phosphorylation in cultures treated with the VEGF/Ang-1 combination may be due to the reported ability of Ang-1 to activate intracellular phosphatases.35,36
Of the signaling pathways evaluated in this study the one whose phosphorylation best correlates with induction of angiogenesis is the Akt pathway. Several points support this interpretation. First, inhibition of the Akt pathway with a specific PI-3 kinase inhibitor blocks angiogenesis. Second, induction of angiogenesis is observed only when the Akt pathway phosphorylation is sustained over a 24-hour period. Third, the potentiation of VEGF-induced angiogenesis by Ang-1 correlates with a marked enhancement of Akt phosphorylation over time. The finding of a strong link between sustained phosphorylation of the Akt pathway and induction of endothelial sprouting is consistent with previous studies indicating that genetic and pharmacological modulation of PI-3 kinase function can significantly influence angiogenesis. Akt may regulate initiation of angiogenic sprouting through its stimulatory effects on endothelial cell migration and actin reorganization, proliferation, and survival.21,22,37,38 Akt has also the capacity to mediate MMP production.39
Experiments with the p38 MAPK inhibitor SB203580 indicate that the p38 MAPK pathway, which is activated by both VEGF and Ang-1, is not required for the induction of endothelial sprouting in the rat aorta model. This interpretation is corroborated by a previous report that p38 MAPK inhibition does not block but actually enhances endothelial cell proliferation.33
Genetic ablation studies in mice, however, indicate that p38 and its upstream activator Mekk3 are required for adequate blood vessel development.40,41
A possible explanation of these results may be that the p38 MAPK pathway affects angiogenesis indirectly by influencing the behavior of nonendothelial cells critical for the successful outcome of the angiogenic process.42
In our system, we found that aortic outgrowths treated with SB203580 have a markedly reduced number of nonendothelial cells. These cells may secrete proangiogenic cytokines, whose production is regulated by the p38 MAPK pathway.43
Activation of p38 MAPK by this mechanism may regulate angiogenesis not only during development but also in reactive processes and pathological conditions.
In conclusion, this study demonstrates that VEGF and Ang-1 engage signal transduction pathways in temporally distinct manners that correlate with the biological response of the vessel wall. Our results indicate that p44/42 MAPK and Akt represent important intracellular regulators of angiogenesis, whose transient phosphorylation is, however, not sufficient for the initiation of the angiogenic process. The observation that prolonged phosphorylation of these pathways, particularly of Akt, correlates with induction of angiogenic sprouting and potentiation of the angiogenic response suggests that critical angiogenic signals are generated only under conditions of sustained phosphorylation of a selected group of signaling molecules. Identification of these mediators and their downstream targets may define key molecular checkpoints in the intracellular cascade of signaling events required for the formation of new blood vessels.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
Supported by National Institutes of Health grant HL52585 (to R.F.N.), the Medical Research Service, Department of Veterans Affairs (R.F.N.), and the National Science Foundation Engineering Research Center Program grant EEC-9529161 (to R.F.N.).
Accepted for publication May 15, 2002.
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
mitogen-activated protein kinase in placental angiogenesis. Proc Natl Acad Sci USA 2000, 97:10454-10459This article has been cited by other articles:
 |
|
 |
|
  E J Chung, S Yoo, H J Lim, S H Byeon, J H Lee, and H J Koh Inhibition of choroidal neovascularisation in mice by systemic administration of the multikinase inhibitor, sorafenib Br J Ophthalmol, July 1, 2009; 93(7): 958 - 963. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. H. Tsai and W. M.F. Lee Tie2 in Tumor Endothelial Signaling and Survival: Implications for Antiangiogenic Therapy Mol. Cancer Res., March 1, 2009; 7(3): 300 - 310. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Sarfaraz, I. A. Siddiqui, D. N. Syed, F. Afaq, and H. Mukhtar Guggulsterone modulates MAPK and NF-{kappa}B pathways and inhibits skin tumorigenesis in SENCAR mice Carcinogenesis, October 1, 2008; 29(10): 2011 - 2018. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. A. Lasater, W. K. Bessler, L. E. Mead, W. E. Horn, D. W. Clapp, S. J. Conway, D. A. Ingram, and F. Li Nf1+/- mice have increased neointima formation via hyperactivation of a Gleevec sensitive molecular pathway Hum. Mol. Genet., August 1, 2008; 17(15): 2336 - 2344. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Wasylyk, H. Zheng, C. Castell, L. Debussche, M.-C. Multon, and B. Wasylyk Inhibition of the Ras-Net (Elk-3) Pathway by a Novel Pyrazole that Affects Microtubules Cancer Res., March 1, 2008; 68(5): 1275 - 1283. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Srivastava, V. Kundumani-Sridharan, B. Zhang, A. K. Bajpai, and G. N. Rao 15(S)-Hydroxyeicosatetraenoic Acid-Induced Angiogenesis Requires STAT3-Dependent Expression of VEGF Cancer Res., May 1, 2007; 67(9): 4328 - 4336. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Cao, P. Sonveaux, S. Liu, Y. Zhao, J. Mi, B. M. Clary, C.-Y. Li, C. D. Kontos, and M. W. Dewhirst Systemic Overexpression of Angiopoietin-2 Promotes Tumor Microvessel Regression and Inhibits Angiogenesis and Tumor Growth Cancer Res., April 15, 2007; 67(8): 3835 - 3844. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Brkovic, M. Pelletier, D. Girard, and M. G. Sirois Angiopoietin chemotactic activities on neutrophils are regulated by PI-3K activation J. Leukoc. Biol., April 1, 2007; 81(4): 1093 - 1101. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. Murphy, S. Makonnen, W. Lassoued, M. D. Feldman, C. Carter, and W. M.F. Lee Inhibition of Tumor Endothelial ERK Activation, Angiogenesis, and Tumor Growth by Sorafenib (BAY43-9006) Am. J. Pathol., November 1, 2006; 169(5): 1875 - 1885. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 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]
|
|
|
|
 |
|
 H. Kobayashi, L. M. DeBusk, Y. O. Babichev, D. J. Dumont, and P. C. Lin Hepatocyte growth factor mediates angiopoietin-induced smooth muscle cell recruitment Blood, August 15, 2006; 108(4): 1260 - 1266. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. M. Kim, K. E. Kim, G. Y. Koh, Y.-S. Ho, and K.-J. Lee Hydrogen peroxide produced by angiopoietin-1 mediates angiogenesis. Cancer Res., June 15, 2006; 66(12): 6167 - 6174. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Matsuoka-Sakata, H. Tamura, H. Asada, I. Miwa, T. Taketani, Y. Yamagata, and N. Sugino Changes in vascular leakage and expression of angiopoietins in the corpus luteum during pregnancy in rats Reproduction, February 1, 2006; 131(2): 351 - 360. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Sugino, T. Suzuki, A. Sakata, I. Miwa, H. Asada, T. Taketani, Y. Yamagata, and H. Tamura Angiogenesis in the Human Corpus Luteum: Changes in Expression of Angiopoietins in the Corpus Luteum throughout the Menstrual Cycle and in Early Pregnancy J. Clin. Endocrinol. Metab., November 1, 2005; 90(11): 6141 - 6148. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Cascone, L. Napione, F. Maniero, G. Serini, and F. Bussolino Stable interaction between {alpha}5{beta}1 integrin and Tie2 tyrosine kinase receptor regulates endothelial cell response to Ang-1 J. Cell Biol., September 12, 2005; 170(6): 993 - 1004. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Kanda, Y. Miyata, Y. Mochizuki, T. Matsuyama, and H. Kanetake Angiopoietin 1 Is Mitogenic for Cultured Endothelial Cells Cancer Res., August 1, 2005; 65(15): 6820 - 6827. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. E. McMullen, P. W. Bryant, C. C. Glembotski, P. A. Vincent, and K. M. Pumiglia Activation of p38 Has Opposing Effects on the Proliferation and Migration of Endothelial Cells J. Biol. Chem., June 3, 2005; 280(22): 20995 - 21003. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. S. Moulton, B. R. Olsen, S. Sonn, N. Fukai, D. Zurakowski, and X. Zeng Loss of Collagen XVIII Enhances Neovascularization and Vascular Permeability in Atherosclerosis Circulation, September 7, 2004; 110(10): 1330 - 1336. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. L. Ward, A. L. Haninec, P. Van Slyke, J. G. Sled, C. Sturk, R. M. Henkelman, I. R. Wanless, and D. J. Dumont Angiopoietin-1 Causes Reversible Degradation of the Portal Microcirculation in Mice: Implications for Treatment of Liver Disease Am. J. Pathol., September 1, 2004; 165(3): 889 - 899. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. N. Carr, M. G. Davis, E. Eby-Wilkens, B. W. Howard, B. A. Towne, T. E. Dufresne, and K. G. Peters Tyrosine phosphatase inhibition augments collateral blood flow in a rat model of peripheral vascular disease Am J Physiol Heart Circ Physiol, July 1, 2004; 287(1): H268 - H276. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Mor, F. J. Quintana, and I. R. Cohen Angiogenesis-Inflammation Cross-Talk: Vascular Endothelial Growth Factor Is Secreted by Activated T Cells and Induces Th1 Polarization J. Immunol., April 1, 2004; 172(7): 4618 - 4623. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Jiang, A. Mezentsev, R. Kemp, K. Byun, J. R. Falck, J. M. Miano, A. Nasjletti, N. G. Abraham, and M. Laniado-Schwartzman Smooth Muscle--Specific Expression of CYP4A1 Induces Endothelial Sprouting in Renal Arterial Microvessels Circ. Res., February 6, 2004; 94(2): 167 - 174. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 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]
|
|
|
|
 |
|
 K. G. Peters, C. D. Kontos, P. C. Lin, A. L. Wong, P. Rao, L. Huang, M. W. Dewhirst, and S. Sankar Functional Significance of Tie2 Signaling in the Adult Vasculature Recent Prog. Horm. Res., January 1, 2004; 59(1): 51 - 71. [Abstract] [Full Text]
|
|
|
|
|
|
B. Ruggeri, J. Singh, D. Gingrich, T. Angeles, M. Albom, H. Chang, C. Robinson, K. Hunter, P. Dobrzanski, S. Jones-Bolin, et al. CEP-7055: A Novel, Orally Active Pan Inhibitor of Vascular Endothelial Growth Factor Receptor Tyrosine Kinases with Potent Antiangiogenic Activity and Antitumor Efficacy in Preclinical Models Cancer Res., September 15, 2003; 63(18): 5978 - 5991. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. Conway, F. Zwerts, V. Van Eygen, A. DeVriese, N. Nagai, W. Luo, and D. Collen Survivin-Dependent Angiogenesis in Ischemic Brain: Molecular Mechanisms of Hypoxia-Induced Up-Regulation Am. J. Pathol., September 1, 2003; 163(3): 935 - 946. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Babaei, K. Teichert-Kuliszewska, Q. Zhang, N. Jones, D. J. Dumont, and D. J. Stewart Angiogenic Actions of Angiopoietin-1 Require Endothelium-Derived Nitric Oxide Am. J. Pathol., June 1, 2003; 162(6): 1927 - 1936. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
