Sickle Cell Anemia as a Possible State of Enhanced Anti-Apoptotic Tone: Survival Effect of Vascular Endothelial Growth Factor on Circulating and Unanchored Endothelial Cells

The biologic processes of apoptosis and angiogenesis are linked in endothelial biology because some endothelial cell growth factors also exert anti-apoptotic effects. We studied whether apoptosis is occurring in circulating endothelial cells (CEC) that have lost the survival signals derived from anchorage to extracellular matrix. Consistent with this expectation, 64% ± 16% of CEC from normal donors showed evidence of apoptosis (by morphology and TdT-mediated dUTP nick end labeling [TUNEL] assay). However, only 30% ± 15% (P < .001 v normal) of CEC from donors with sickle cell anemia were apoptotic. Vascular endothelial growth factor (VEGF) levels were significantly (P = .001) higher in plasma of sickle donors (120.1 ± 81.4 pg/mL) than that of normal donors (37.6 ± 34.6 pg/mL), and there was an inverse correlation between VEGF and CEC apoptosis (r = .612,P = .001). Consistent with stimulation by VEGF, CEC from sickle donors exhibited increased expression of vβ3. In vitro experiments showed that VEGF inhibits apoptosis for cultured endothelial cells that are kept unanchored and not allowed to re-establish attachment to extracellular matrix, thus demonstrating that VEGF provides survival signals independent of its ability to promote matrix reattachment. These data suggest the hypothesis that sickle cell anemia is a state of enhanced anti-apoptotic tone for endothelial cells. If true, this has implications for disease pathobiology, particularly the development of neovascularizing retinopathy.

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Sickle Cell Anemia as a Possible State of Enhanced Anti-Apoptotic Tone: Survival Effect of Vascular Endothelial Growth Factor on Circulating and Unanchored Endothelial Cells

Blood ◽

10.1182/blood.v93.11.3824 ◽

1999 ◽

Vol 93 (11) ◽

pp. 3824-3830 ◽

Cited By ~ 68

Author(s):

Anna Solovey ◽

Lizhen Gui ◽

Sundaram Ramakrishnan ◽

Martin H. Steinberg ◽

Robert P. Hebbel

Keyword(s):

Extracellular Matrix ◽

Vascular Endothelial Growth Factor ◽

Endothelial Cells ◽

Growth Factor ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Circulating Endothelial Cells ◽

Vascular Endothelial ◽

Endothelial Growth Factor ◽

Survival Signals

Abstract The biologic processes of apoptosis and angiogenesis are linked in endothelial biology because some endothelial cell growth factors also exert anti-apoptotic effects. We studied whether apoptosis is occurring in circulating endothelial cells (CEC) that have lost the survival signals derived from anchorage to extracellular matrix. Consistent with this expectation, 64% ± 16% of CEC from normal donors showed evidence of apoptosis (by morphology and TdT-mediated dUTP nick end labeling [TUNEL] assay). However, only 30% ± 15% (P < .001 v normal) of CEC from donors with sickle cell anemia were apoptotic. Vascular endothelial growth factor (VEGF) levels were significantly (P = .001) higher in plasma of sickle donors (120.1 ± 81.4 pg/mL) than that of normal donors (37.6 ± 34.6 pg/mL), and there was an inverse correlation between VEGF and CEC apoptosis (r = .612,P = .001). Consistent with stimulation by VEGF, CEC from sickle donors exhibited increased expression of vβ3. In vitro experiments showed that VEGF inhibits apoptosis for cultured endothelial cells that are kept unanchored and not allowed to re-establish attachment to extracellular matrix, thus demonstrating that VEGF provides survival signals independent of its ability to promote matrix reattachment. These data suggest the hypothesis that sickle cell anemia is a state of enhanced anti-apoptotic tone for endothelial cells. If true, this has implications for disease pathobiology, particularly the development of neovascularizing retinopathy.

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The angiogenic function of nucleolin is mediated by vascular endothelial growth factor and nonmuscle myosin

Blood ◽

10.1182/blood-2005-07-2961 ◽

2006 ◽

Vol 107 (9) ◽

pp. 3564-3571 ◽

Cited By ~ 118

Author(s):

Yujie Huang ◽

Hubing Shi ◽

Hao Zhou ◽

Xiaomin Song ◽

Shaopeng Yuan ◽

...

Keyword(s):

Extracellular Matrix ◽

Vascular Endothelial Growth Factor ◽

Endothelial Cells ◽

Growth Factor ◽

Cell Surface ◽

Vascular Endothelial ◽

Nonmuscle Myosin ◽

Surface Nucleolin ◽

Cell Surface Nucleolin ◽

Endothelial Growth Factor

Nucleolin, originally described as a nuclear protein, was recently found to be expressed on the surface of endothelial cells during angiogenic. However, the functions of cell-surface nucleolin in angiogenic remain mysterious. Here we report that upon endothelial cells adhering to extracellular matrix components, vascular endothelial growth factor (VEGF) mobilizes nucleolin from nucleus to cell surface. Functional blockage or down-regulation of the expression of cell-surface nucleolin in endothelial cells significantly inhibits the migration of endothelial cells and prevents capillary-tubule formation. Moreover, nonmuscle myosin heavy chain 9 (MyH9), an actin-based motor protein, is identified as a nucleolin-binding protein. Subsequent studies reveal that MyH9 serves as a physical linker between nucleolin and cytoskeleton, thus modulating the translocation of nucleolin. Knocking down endogenous MyH9, specifically inhibiting myosin activity, or overexpressing functional deficient MyH9 disrupts the organization of cell-surface nucleolin and inhibits its angiogenic function. These studies indicate that VEGF, extracellular matrix, and intracellular motor protein MyH9 are all essential for the novel function of nucleolin in angiogenic.

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Vascular Endothelial Growth Factor Induces Endothelial Fenestrations In Vitro

The Journal of Cell Biology ◽

10.1083/jcb.140.4.947 ◽

1998 ◽

Vol 140 (4) ◽

pp. 947-959 ◽

Cited By ~ 414

Author(s):

Sybille Esser ◽

Karen Wolburg ◽

Hartwig Wolburg ◽

Georg Breier ◽

Teymuras Kurzchalia ◽

...

Keyword(s):

Extracellular Matrix ◽

Vascular Endothelial Growth Factor ◽

Endothelial Cells ◽

Growth Factor ◽

Epithelial Cells ◽

Choroid Plexus ◽

Vascular Endothelial ◽

Caveolin 1 ◽

Endothelial Growth Factor

Abstract. Vascular endothelial growth factor (VEGF) is an important regulator of vasculogenesis, angiogenesis, and vascular permeability. In contrast to its transient expression during the formation of new blood vessels, VEGF and its receptors are continuously and highly expressed in some adult tissues, such as the kidney glomerulus and choroid plexus. This suggests that VEGF produced by the epithelial cells of these tissues might be involved in the induction or maintenance of fenestrations in adjacent endothelial cells expressing the VEGF receptors. Here we describe a defined in vitro culture system where fenestrae formation was induced in adrenal cortex capillary endothelial cells by VEGF, but not by fibroblast growth factor. A strong induction of endothelial fenestrations was observed in cocultures of endothelial cells with choroid plexus epithelial cells, or mammary epithelial cells stably transfected with cDNAs for VEGF 120 or 164, but not with untransfected cells. These results demonstrate that, in these cocultures, VEGF is sufficient to induce fenestrations in vitro. Identical results were achieved when the epithelial cells were replaced by an epithelial-derived basal lamina-type extracellular matrix, but not with collagen alone. In this defined system, VEGF-mediated induction of fenestrae was always accompanied by an increase in the number of fused diaphragmed caveolae-like vesicles. Caveolae, but not fenestrae, were labeled with a caveolin-1–specific antibody both in vivo and in vitro. VEGF stimulation led to VEGF receptor tyrosine phosphorylation, but no change in the distribution, phosphorylation, or protein level of caveolin-1 was observed. We conclude that VEGF in the presence of a basal lamina-type extracellular matrix specifically induces fenestrations in endothelial cells. This defined in vitro system will allow further study of the signaling mechanisms involved in fenestrae formation, modification of caveolae, and vascular permeability.

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