Expression of angiopoietin-2 and vascular endothelial growth factor in mice cerebral cortex after permanent focal cerebral ischemia.
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AIM: To study the expressions of vascular endothelial growth factor (VEG F), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), Tie-1, and Tie-2 in C57BL/6 mouse brain after permanent focal cerebral ischemia. METHODS: The mRNA levels of VEGF, Ang-1, Ang-2, Tie-1, and Tie-2 were measured by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). The protein express ions of VEGF and Ang-2 were determined by immunohistochemistry. RESULTS: Low mRNA levels of VEGF, Ang-1, Ang-2, Tie-1, and Tie-2 were constitutively expressed in the normal cortex of mouse. After middle cerebral artery occlusion (MCAO), the expressions of VEGF, Ang-2, and Tie-2 mRNA were dramatically increased in the infarcted cortex and the elevation was remained through 7 d of ischemia. However, the levels of Ang-1 and Tie-1 mRNA were unchanged in the infarcted cortex. Immunoreactivities of Ang-2 or VEGF were hardly observed in the normal cortex. Ang-2 protein was evidently detected in the infarct core 8 h after MCAO and in t he perifocal area 1 d after MCAO. Expression of VEGF protein was elevated in the infarct core 2 h after MCAO and in the perifocal area 1 d after MCAO. Immunoreaction was restricted to endothelial cells and glial-like cells within the infarct core and perifocal area. CONCLUSION: The expressions of An g-2 and VEGF are induced after focal cerebral ischemia, which may contribute to the angiogenic response in the cortex of ischemic brain. (+info)
Neuropilin-1 binds vascular endothelial growth factor 165, placenta growth factor-2, and heparin via its b1b2 domain.
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Neuroplin-1 (NRP1), a receptor for vascular endothelial growth factor (VEGF) family members, has three distinct extracellular domains, a1a2, b1b2, and c. To determine the VEGF(165) and placenta growth factor 2 (PlGF-2)-binding sites of NRP1, recombinant NRP1 domains were expressed in mammalian cells as Myc-tagged, soluble proteins, and used in co-precipitation experiments with 125I-VEGF165 and 125I-PlGF-2. Anti-Myc antibodies immunoprecipitated 125I-VEGF165 and 125I-PlGF-2 in the presence of the b1b2 but not of the a1a2 and c domains. Neither b1 nor b2 alone was capable of binding 125I-VEGF165. In competition experiments, VEGF165 competed PlGF-2 binding to the NRP1 b1b2 domain, suggesting that the binding sites of VEGF165 and PlGF-2 overlap. The presence of the a1a2 domain greatly enhanced VEGF165, but not PlGF-2 binding to b1b2. Heparin enhanced the binding of both 125I-VEGF165 and 125I-PlGF-2 to the b1b2 domain by 20- and 4-fold, respectively. A heparin chain of at least 20-24 monosaccharides was necessary for binding. In addition, the b1b2 domain of NRP1 could bind heparin directly, requiring heparin oligomers of at least 8 monosaccharide units. It was concluded that an intact b1b2 domain serves as the VEGF165-, PlGF-2-, and heparin-binding sites in NRP1, and that heparin is a critical component for regulating VEGF165 and PlGF-2 interactions with NRP1 by physically interacting with both receptor and ligands. (+info)
Biomedical significance of endothelial cell specific growth factor, angiopoietin.
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Until recently, vascular endothelial growth factor (VEGF) was the only growth factor proven to be specific and critical for blood vessel formation. Other long-known factors, such as the fibroblast growth factors (FGFs), platelet-derived growth factor, or transforming growth factor-beta, had profound effects in endothelial cells. But such factors were nonspecific, in that they could act on many other cells, and it seemed unlikely that these growth factors would be effective targets for treatment of endothelial cell diseases. A recently discovered endothelial cell specific growth factor, angiopoietin, has greatly contributed to our understanding of the development, physiology, and pathology of endothelial cells (Davis et al., 1996; Yancopoulos et al., 2000). The recent studies that identified and characterized the physiological and pathological roles of angiopoietin have allowed us to widen and deepen our knowledge about blood vessel formation and vascular endothelial function. Therefore, in this review, we describe the biomedical significance of these endothelial cell growth factors, the angiopoietins, in the vascular system under normal and pathological states. (+info)
Effect of sulfated beta-cyclodextrin, a water soluble cycloamylose, on the promotion and/or inhibition of angiogenesis.
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Previous studies have reported that sulfated b b-cyclodextrin, a naturally occurring cycloamylose built up from six to eight glucopyranose units, when administered alone promotes angiogenesis, but administered with an angiostatic steroid inhibits angiogenesis in the cick embryo bioassay. In our experiments sulfated b b-cyclodextrin has been shown to possess many properties unrelated to its classical functions in the promotion and inhibition of angiogenesis that were not previously described. We studied the angiogenic and angiostatic properties of b b-cyclodextrin in a subcutaneous plastic sponge model in mice. We realized two set of experiments. In each set mice were randomized into five groups (n= 5 mice). The first group was treated with sulfated b b-cyclodextrin (200 ng), the second group was treated with sulfated b b-cyclodextrin (2000 ng), the third group received unsubstituted b b-cyclodextrin (2000 ng), the fourth group was treated with sulfated b b-cyclodextrin (20000 ng) and the last group was used as a control group. In all groups compounds were administered intraperitoneally 4 days after subcutaneous implantation of a sterile polyvinyl sponge on day 0, controls were not treated. Cyclodextrin administered alone at low drug concentration (200 ng) promoted angiogenesis and increased the development of venules in the sponge matrix. However, cyclodextrin administered at high drug concentration (2000 and 20 000 ng) reduced the vessel index in the sponge and areas of microhemorrhages were observed. From our results we propose that b b-cyclodextrin contains both a promoter and an inhibitor of angiogenesis and that the activation of both is drug concentration dependent. (+info)
Pamidronate induces modifications of circulating angiogenetic factors in cancer patients.
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PURPOSE: Recently, new experimental data suggested that, besides inhibiting osteoclasts, bisphosphonate may also have an antitumor effect. Antiangionetetic activity is one of the possible mechanisms of anticancer activity attributed to bisphosphonates. The purpose of this study was to evaluate the modifications in angiogenic cytokines levels after pamidronate infusion. EXPERIMENTAL DESIGN: Twenty-five consecutive cancer patients with bone metastases treated monthly with disodium pamidronate infusion were evaluated prospectively for circulating levels of vascular endothelial growth factor (VEGF), gamma-IFN, interleukin (IL)-6, and IL-8 at different time points: just before and after 1, 2, and 7 days after pamidronate infusion. RESULTS: Basal VEGF levels decreased significantly 1, 2, and 7 days after pamidronate infusion. gamma-IFN and IL-6 levels increased 1 day after the infusion but rapidly decreased after 2 days. Moreover, our data showed a statistically significant negative correlation between VEGF and gamma-IFN levels (P < 0.0001) and a positive correlation between VEGF and IL-8 (P = 0.04). CONCLUSIONS: This study confirms that pamidronate could have antiangiogenic properties through a significant and lasting decrease of VEGF serum levels. (+info)
Angiogenic gene therapy for experimental critical limb ischemia: acceleration of limb loss by overexpression of vascular endothelial growth factor 165 but not of fibroblast growth factor-2.
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Recent studies suggest the possible therapeutic effect of intramuscular vascular endothelial growth factor (VEGF) gene transfer in individuals with critical limb ischemia. Little information, however, is available regarding (1) the required expression level of VEGF for therapeutic effect, (2) the related expression of endogenous angiogenic factors, including fibroblast growth factor-2 (FGF-2), and (3) the related adverse effects due to overexpression of VEGF. To address these issues, we tested effects of overexpression of VEGF165 using recombinant Sendai virus (SeV), as directly compared with FGF-2 gene transfer. Intramuscular injection of SeV strongly boosted FGF-2, resulting in significant therapeutic effects for limb salvage with increased blood perfusion associated with enhanced endogenous VEGF expression in murine models of critical limb ischemia. In contrast, VEGF165 overexpression, 5-times higher than that of baseline on day 1, also strongly evoked endogenous VEGF in muscles, resulting in an accelerated limb amputation without recovery of blood perfusion. Interestingly, viable skeletal muscles of either VEGF165- or FGF-2-treated ischemic limbs showed similar platelet-endothelial cell adhesion molecule-1-positive vessel densities. Maturation of newly formed vessels suggested by smooth muscle cell actin-positive cell lining, however, was significantly disturbed in muscles with VEGF. Further, therapeutic effects of FGF-2 were completely diminished by anti-VEGF neutralizing antibody in vivo, thus indicating that endogenous VEGF does contribute to the effect of FGF-2. These results suggest that VEGF is necessary, but should be delicately regulated to lower expression to treat ischemic limb. The therapeutic effect of FGF-2, associated with the harmonized angiogenic effects seen with endogenous VEGF, provides important insights into therapeutic angiogenesis. (+info)
Bcr-abl-positive cells secrete angiogenic factors including matrix metalloproteinases and stimulate angiogenesis in vivo in Matrigel implants.
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To further elucidate the role of angiogenesis in the pathogenesis of chronic myelogenous leukemia (CML) we evaluated the effects of the bcr-abl translocation on the secretion of the angiogenic factors VEGF, FGF-2, HGF, IL-8 and matrix metalloproteinases (MMPs) as well as on the angiogenic potential in vivo of bcr-abl+ cells. First, we examined murine FL5.12 cells transfected with the bcr-abl constructs p185, p210 and p230 and found that the transfected cells secreted as much as four-fold more VEGF (p185 > p210 >p230) than wild-type (wt) cells, as well as MMP-9 and MMP-2. When Matrigel fragments containing these bcr-abl+ cells were implanted subcutaneously in SCID or Balb-C mice they became significantly more vascularized and hemoglobinized than implants containing normal or wt cells (p185 > p210 > p230). Similarly, we found that myeloblasts expanded from bone marrow (BM) CD34+ cells derived from Philadelphia-positive CML patients secreted up to 10 times more VEGF, FGF-2, HGF and IL-8 compared to myeloblasts derived from normal donors' BM CD34+ cells and that BM mononuclear cells (MNC) isolated from CML patients induced vascularization of Matrigel implants in mice. Moreover, we found that peripheral blood MNC expressed MMP-2 and membrane-type (MT)1-MMP in about 50% of CML patients studied, and MMP-9 in all of them. Furthermore, VEGF stimulated the secretion of MMP-9 in these primary CML cells. We conclude that stimulation of angiogenesis by angiogenic factors, including MMPs, could play an important role in the pathogenesis of CML, suggesting that therapies targeting the newly formed endothelium could be developed for CML. (+info)
The CXC chemokine cCAF stimulates precocious deposition of ECM molecules by wound fibroblasts, accelerating development of granulation tissue.
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BACKGROUND: During wound repair, fibroblasts orchestrate replacement of the provisional matrix formed during clotting with tenascin, cellular fibronectin and collagen III. These, in turn, are critical for migration of endothelial cells, keratinocytes and additional fibroblasts into the wound site. Fibroblasts are also important in the deposition of collagen I during scar formation. The CXC chemokine chicken Chemotactic and Angiogenic Factor (cCAF), is highly expressed by fibroblasts after wounding and during development of the granulation tissue, especially in areas where extracellular matrix (ECM) is abundant. We hypothesized that cCAF stimulates fibroblasts to produce these matrix molecules. RESULTS: Here we show that this chemokine can stimulate precocious deposition of tenascin, fibronectin and collagen I, but not collagen III. Studies in culture and in vivo show that tenascin stimulation can also be achieved by the N-terminal 15 aas of the protein and occurs at the level of gene expression. In contrast, stimulation of fibronectin and collagen I both require the entire molecule and do not involve changes in gene expression. Fibronectin accumulation appears to be linked to tenascin production, and collagen I to decreased MMP-1 levels. In addition, cCAF is chemotactic for fibroblasts and accelerates their migration. CONCLUSIONS: These previously unknown functions for chemokines suggest that cCAF, the chicken orthologue of human IL-8, enhances healing by rapidly chemoattracting fibroblasts into the wound site and stimulating them to produce ECM molecules, leading to precocious development of granulation tissue. This acceleration of the repair process may have important application to healing of impaired wounds. (+info)