Biomedical subjects

Napoleone Ferrara

Publications and source records attributed to Napoleone Ferrara.

At least 55 records · Page 3Linked to original sources

PubMed2004

Vascular endothelial growth factor as a target for anticancer therapy.

The development of a vascular supply is a critical factor in the growth and metastatic spread of malignant tumors. Of the multitude of growth factors that regulate physiological and pathological angiogenesis, vascular endothelial growth factor (VEGF) is believed to be the most important. There is evidence that overexpression of VEGF is correlated with an adverse prognosis, at least in some tumors. Tumor-expressed VEGF is particularly attractive as a target for anticancer therapy because its angiogenesis-promoting activity is at the level of the endothelial cell and, compared with agents that directly target tumor cells, tumor penetration is less critical for VEGF inhibitors. Moreover, recent work has shown that inhibiting tumor angiogenesis increases the effectiveness of coadministered chemotherapy and radiotherapy. This suggests that drugs that target VEGF or its receptors can be combined with traditional treatment modalities to ensure maximum effectiveness. A variety of agents aimed at blocking VEGF or its receptor-signaling system are currently being developed for the treatment of cancer. Of these, bevacizumab, a humanized monoclonal antibody directed at VEGF, is the most advanced in clinical development and has shown promising results in clinical trials.

Angiogenesis Inhibitors↗

PubMed2003

Cortical and retinal defects caused by dosage-dependent reductions in VEGF-A paracrine signaling.

To determine the function of VEGF-A in nervous system development, we have utilized the Nestin promoter-driven Cre recombinase transgene, in conjunction with a conditional and hypomorphic VEGF-A allele, to lower VEGF-A activity in neural progenitor cells. Mice with intermediate levels of VEGF-A activity showed decreased blood vessel branching and density in the cortex and retina, resulting in a thinner retina and aberrant structural organization of the cortex. Severe reductions in VEGF-A led to decreases in vascularity and subsequent hypoxia, resulting in the specific degeneration of the cerebral cortex and neonatal lethality. Decreased neuronal proliferation and hypoxia was evident at E11.5, leading to increased neuronal apoptosis in the cortex by E15.5. In order to address whether the observed changes in the structural organization of the nervous system were due to a direct and autocrine role of VEGF-A on the neural population, we conditionally inactivated the main VEGF-A receptor, Flk1, specifically in neuronal lineages, by using the Nestin Cre transgene. The normality of these mice ruled out the possibility that VEGF-A/Flk1 signaling has a significant autocrine role in CNS development. VEGF-A dosage is therefore a critical parameter regulating the density of the vascular plexus in the developing CNS that is in turn a key determinant in the development and architectural organization of the nervous system.

Animals↗

PubMed2003

Role of VEGF-A in vascularization of pancreatic islets.

Blood vessel endothelium has been recently shown to induce endocrine pancreatic development. Because pancreatic endocrine cells or islets express high levels of vascular endothelial growth factors, VEGFs, we investigated the role of a particular VEGF, VEGF-A, on islet vascularization and islet function. By deleting VEGF-A in the mouse pancreas, we show that endocrine cells signal back to the adjacent endothelial cells to induce the formation of a dense network of fenestrated capillaries in islets. Interestingly, VEGF-A is not required for the development of all islet capillaries. However, the few remaining capillaries found in the VEGF-A-deficient islets are not fenestrated and contain an unusual number of caveolae. In addition, glucose tolerance tests reveal that the VEGF-A-induced capillary network is not strictly required for blood glucose control but is essential for fine-tuning blood glucose regulation. In conclusion, we speculate that islet formation takes place in two sequential steps: in the first step, signals from blood vessel endothelium induce islet formation next to the vessels, and in the second step, the islets signal to the endothelium. The second step involves paracrine VEGF-A signaling to elaborate the interaction of islets with the circulatory system.

Animals↗

PubMed2003

Vascular endothelial growth factor (VEGF) receptor-2 signaling mediates VEGF-C(deltaNdeltaC)- and VEGF-A-induced angiogenesis in vitro.

Angiogenesis and lymphangiogenesis are regulated by members of the vascular endothelial growth factor (VEGF) family of cytokines, which mediate their effects via tyrosine kinase VEGF receptors -1, -2, and -3. We have used wild-type and mutant forms of VEGFs -A, -B, and -C, a pan-VEGFR tyrosine kinase inhibitor (SU5416) as well as neutralizing anti-VEGFR-2 antibodies, to determine which VEGF receptor(s) are required for bovine endothelial cell invasion and tube formation in vitro. This was compared to the ability of these cytokines to induce expression of members of the plasminogen activator (PA)-plasmin system. We found that cytokines which bind VEGFR-2 (human VEGF-A, human VFM23A, human VEGF-C(deltaNdeltaC), and rat VEGF-C(152)) induced invasion, tube formation, urokinase-type-PA, tissue-type-PA, and PA inhibitor-1, invasion and tube formation as well as signaling via the MAP kinase pathway were efficiently blocked by SU5416 and anti-VEGFR-2 antibodies. In contrast, cytokines and mutants which exclusively bind VEGFR-1 (human VFM17 and human VEGF-B) had no effect on invasion and tube formation or on the regulation of gene expression. We were unable to identify cytokines which selectively stimulate bovine VEGFR-3 in our system. Taken together, these findings point to the central role of VEGFR-2 in the angiogenic signaling pathways induced by VEGF-C(deltaNdeltaC) and VEGF-A.

Animals↗

PubMed2003

HIF-1alpha is essential for myeloid cell-mediated inflammation.

Granulocytes and monocytes/macrophages of the myeloid lineage are the chief cellular agents of innate immunity. Here, we have examined the inflammatory response in mice with conditional knockouts of the hypoxia responsive transcription factor HIF-1alpha, its negative regulator VHL, and a known downstream target, VEGF. We find that activation of HIF-1alpha is essential for myeloid cell infiltration and activation in vivo through a mechanism independent of VEGF. Loss of VHL leads to a large increase in acute inflammatory responses. Our results show that HIF-1alpha is essential for the regulation of glycolytic capacity in myeloid cells: when HIF-1alpha is absent, the cellular ATP pool is drastically reduced. The metabolic defect results in profound impairment of myeloid cell aggregation, motility, invasiveness, and bacterial killing. This role for HIF-1alpha demonstrates its direct regulation of survival and function in the inflammatory microenvironment.

Adenosine Triphosphate↗

PubMed2003

The endocrine-gland-derived VEGF homologue Bv8 promotes angiogenesis in the testis: Localization of Bv8 receptors to endothelial cells.

We recently identified an angiogenic mitogen, endocrine-gland-derived vascular endothelial growth factor (EG-VEGF), with selective activity for endothelial cells of endocrine tissues. Here we describe the characterization of a highly related molecule, Bv8, also known as prokineticin-2. Human Bv8 shares 60% identity and 75% similarity with EG-VEGF. The human and mouse Bv8 genes share a common structure. Like EG-VEGF, Bv8 is able to induce proliferation, survival and migration of adrenal cortical capillary endothelial cells. Bv8 gene expression is induced by hypoxic stress. Bv8 expression occurs predominantly in the testis and is largely restricted to primary spermatocytes. Adenoviral delivery of Bv8 or EG-VEGF to the mouse testis resulted in a potent angiogenic response. We have localized the expression of the Bv8EG-VEGF receptors within the testis to vascular endothelial cells. The testis exhibits relatively high turnover of endothelial cells. Therefore, Bv8 and EG-VEGF, along with other factors such as VEGF-A, may maintain the integrity and also regulate proliferation of the blood vessels in the testis.

Adenoviridae↗

PubMed2003

Angiogenesis-independent endothelial protection of liver: role of VEGFR-1.

The vascular endothelium was once thought to function primarily in nutrient and oxygen delivery, but recent evidence suggests that it may play a broader role in tissue homeostasis. To explore the role of sinusoidal endothelial cells (LSECs) in the adult liver, we studied the effects of vascular endothelial growth factor (VEGF) receptor activation on mouse hepatocyte growth. Delivery of VEGF-A increased liver mass in mice but did not stimulate growth of hepatocytes in vitro, unless LSECs were also present in the culture. Hepatocyte growth factor (HGF) was identified as one of the LSEC-derived paracrine mediators promoting hepatocyte growth. Selective activation of VEGF receptor-1 (VEGFR-1) stimulated hepatocyte but not endothelial proliferation in vivo and reduced liver damage in mice exposed to a hepatotoxin. Thus, VEGFR-1 agonists may have therapeutic potential for preservation of organ function in certain liver disorders.

Animals↗

PubMed2003

Differential expression of the angiogenic factor genes vascular endothelial growth factor (VEGF) and endocrine gland-derived VEGF in normal and polycystic human ovaries.

Angiogenesis is a key aspect of the dynamic changes occurring during the normal ovarian cycle. Hyperplasia and hypervascularity of the ovarian theca interna and stroma are also prominent features of the polycystic ovary syndrome (PCOS), a leading cause of infertility. Compelling evidence indicated that vascular endothelial growth factor (VEGF) is a key mediator of the cyclical corpus luteum angiogenesis. However, the nature of the factor(s) that mediate angiogenesis in PCOS is less clearly understood. Endocrine gland-derived (EG)-VEGF has been recently identified as an endothelial cell mitogen with selectivity for the endothelium of steroidogenic glands and is expressed in normal human ovaries. In the present study, we compared the expression of EG-VEGF and VEGF mRNA in a series of 13 human PCOS and 13 normal ovary specimens by in situ hybridization. EG-VEGF expression in normal ovaries is dynamic and generally complementary to VEGF expression in both follicles and corpora lutea. A particularly high expression of EG-VEGF was detected in the Leydig-like hilus cells found in the highly vascularized ovarian hilus. In PCOS ovaries, we found strong expression of EG-VEGF mRNA in theca interna and stroma in most of the specimens examined, thus spatially related to the new blood vessels. In contrast, VEGF mRNA expression was most consistently associated with the granulosa cell layer and sometimes the theca, but rarely with the stroma. These findings indicate that both EG-VEGF and VEGF are expressed in PCOS ovaries, but in different cell types at different stages of differentiation, thus suggesting complementary functions for the two factors in angiogenesis and possibly cyst formation.

Adult↗

PubMed2003

EG-VEGF and Bv8. a novel family of tissue-selective mediators of angiogenesis, endothelial phenotype, and function.

Angiogenic molecules are the focus of therapeutic efforts to promote new vessel development in ischemic or damaged tissue and, conversely, to inhibit endothelial cell growth and survival in proliferative disease. Two novel angiogenic mitogens have been characterized recently. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and the mammalian homologue of Bombina variegata peptide 8 (Bv8) are endothelial cell mitogens and chemotactic factors with restricted expression profiles and selective endothelial cell activity. These highly related peptides share two cognate G-protein-coupled receptors that are homologous to the neuropeptide Y receptor. The identification of tissue-selective angiogenic factors raises the possibility that other secreted molecules in this class exist. The potential advantage of tissue-specific angiogenic therapeutics may be the reduction of systemic side effects. Additionally, these peptides or their receptors may be attractive targets for inhibition in several disorders.

Amphibian Proteins↗

PubMed2003

The hypoxic response of tumors is dependent on their microenvironment.

To reveal the functional significance of hypoxia and angiogenesis in astrocytoma progression, we created genetically engineered transformed astrocytes from murine primary astrocytes and deleted the hypoxia-responsive transcription factor HIF-1alpha or its target gene, the angiogenic factor VEGF. Growth of HIF-1alpha- and VEGF-deficient transformed astrocytes in the vessel-poor subcutaneous environment results in severe necrosis, reduced growth, and vessel density, whereas when the same cells are placed in the vascular-rich brain parenchyma, the growth of HIF-1alpha knockout, but not VEGF knockout tumors, is reversed: tumors deficient in HIF-1alpha grow faster, and penetrate the brain more rapidly and extensively. These results demonstrate that HIF-1alpha has differential roles in tumor progression, which are greatly dependent on the extant microenvironment of the tumor.

Animals↗

PubMed2003

The biology of VEGF and its receptors.

Vascular endothelial growth factor (VEGF) is a key regulator of physiological angiogenesis during embryogenesis, skeletal growth and reproductive functions. VEGF has also been implicated in pathological angiogenesis associated with tumors, intraocular neovascular disorders and other conditions. The biological effects of VEGF are mediated by two receptor tyrosine kinases (RTKs), VEGFR-1 and VEGFR-2, which differ considerably in signaling properties. Non-signaling co-receptors also modulate VEGF RTK signaling. Currently, several VEGF inhibitors are undergoing clinical testing in several malignancies. VEGF inhibition is also being tested as a strategy for the prevention of angiogenesis, vascular leakage and visual loss in age-related macular degeneration.

Animals↗

PubMed2003

Glomerular-specific alterations of VEGF-A expression lead to distinct congenital and acquired renal diseases.

Kidney disease affects over 20 million people in the United States alone. Although the causes of renal failure are diverse, the glomerular filtration barrier is often the target of injury. Dysregulation of VEGF expression within the glomerulus has been demonstrated in a wide range of primary and acquired renal diseases, although the significance of these changes is unknown. In the glomerulus, VEGF-A is highly expressed in podocytes that make up a major portion of the barrier between the blood and urinary spaces. In this paper, we show that glomerular-selective deletion or overexpression of VEGF-A leads to glomerular disease in mice. Podocyte-specific heterozygosity for VEGF-A resulted in renal disease by 2.5 weeks of age, characterized by proteinuria and endotheliosis, the renal lesion seen in preeclampsia. Homozygous deletion of VEGF-A in glomeruli resulted in perinatal lethality. Mutant kidneys failed to develop a filtration barrier due to defects in endothelial cell migration, differentiation, and survival. In contrast, podocyte-specific overexpression of the VEGF-164 isoform led to a striking collapsing glomerulopathy, the lesion seen in HIV-associated nephropathy. Our data demonstrate that tight regulation of VEGF-A signaling is critical for establishment and maintenance of the glomerular filtration barrier and strongly supports a pivotal role for VEGF-A in renal disease.

Angiogenesis Inducing Agents↗

PubMed2003

Mouse endocrine gland-derived vascular endothelial growth factor: a distinct expression pattern from its human ortholog suggests different roles as a regulator of organ-specific angiogenesis.

We recently described human endocrine gland-derived vascular endothelial growth factor (EG-VEGF) as an endothelial cell mitogen with a novel selective activity and an expression pattern essentially limited to steroidogenic glands. Herein we present the identification and characterization of the mouse ortholog. The mouse cDNA and predicted amino acid sequences are, respectively, 86% and 88% identical with the human. Surprisingly, the mouse EG-VEGF transcript is predominantly expressed in liver and kidney. A comparison of human and mouse EG-VEGF promoter sequences revealed a potential binding site for NR5A1, which is known to be a pivotal element for steroidogenic-specific transcription, in the human but not mouse promoter. In situ hybridization studies localized expression of mouse EG-VEGF mRNA to hepatocytes and renal tubule cells. Interestingly, capillary endothelial cells in these sites share several common structural features with those found in steroidogenic glands. Within liver and kidney, EG-VEGF receptor expression was largely restricted to endothelial cells. Mouse EG-VEGF promoted proliferation and survival of endothelial cells. We propose that mouse EG-VEGF, like human EG-VEGF, plays a role in regulating the phenotype and growth properties of endothelial cells within distinct capillary beds.

Angiogenesis Inducing Agents↗

PubMed2002

The role of VEGF in normal and neoplastic hematopoiesis.

VEGF is a secreted growth factor that mediates its biological effects by binding to two transmembrane tyrosine kinase receptors, VEGFR-1 and VEGFR-2. The VEGF/receptor signaling system is involved in the regulation of two fundamental processes in vertebrates: the formation of blood vessels (angiogenesis) and of blood cells (hematopoiesis). Hematopoietic stem cells, capable of giving rise to all blood cell lineages, are often found in clusters with endothelial cells, the key cell type involved in the formation of blood vessels. Despite such proximity of VEGF-responsive cells, hematopoiesis occurs independently of neoangiogenesis in the adult bone marrow, suggesting that VEGF regulates the two processes by different mechanisms. In support of this hypothesis, the recently identified autocrine loop by which VEGF may control hematopoietic stem cell survival and repopulation, is fundamentally different from its paracrine effects regulating angiogenesis. Furthermore, coexpression of VEGF and its receptors, the prerequisite for autocrine loops, is frequently found in lymphomas and myelomas, suggesting that autocrine loops also play a role in hematological malignancies. Several therapeutic strategies blocking VEGF or VEGF-induced signaling are currently being investigated for the treatment of neoplastic diseases. They differ in their potential to interfere with the autocrine or paracrine effector functions of VEGF during angiogenesis, hematopoiesis, and tumor cell proliferation, properties which may ultimately determine their therapeutic potential.

Animals↗

PubMed2002

Vascular endothelial growth factor stimulates bone repair by promoting angiogenesis and bone turnover.

Several growth factors are expressed in distinct temporal and spatial patterns during fracture repair. Of these, vascular endothelial growth factor, VEGF, is of particular interest because of its ability to induce neovascularization (angiogenesis). To determine whether VEGF is required for bone repair, we inhibited VEGF activity during secondary bone healing via a cartilage intermediate (endochondral ossification) and during direct bone repair (intramembranous ossification) in a novel mouse model. Treatment of mice with a soluble, neutralizing VEGF receptor decreased angiogenesis, bone formation, and callus mineralization in femoral fractures. Inhibition of VEGF also dramatically inhibited healing of a tibial cortical bone defect, consistent with our discovery of a direct autocrine role for VEGF in osteoblast differentiation. In separate experiments, exogenous VEGF enhanced blood vessel formation, ossification, and new bone (callus) maturation in mouse femur fractures, and promoted bony bridging of a rabbit radius segmental gap defect. Our results at specific time points during the course of healing underscore the role of VEGF in endochondral vs. intramembranous ossification, as well as skeletal development vs. bone repair. The responses to exogenous VEGF observed in two distinct model systems and species indicate that a slow-release formulation of VEGF, applied locally at the site of bone damage, may prove to be an effective therapy to promote human bone repair.

Animals↗

PubMed2002

VEGF regulates haematopoietic stem cell survival by an internal autocrine loop mechanism.

Vascular endothelial growth factor (VEGF) is a principal regulator of blood vessel formation and haematopoiesis, but the mechanisms by which VEGF differentially regulates these processes have been elusive. Here we describe a regulatory loop by which VEGF controls survival of haematopoietic stem cells (HSCs). We observed a reduction in survival, colony formation and in vivo repopulation rates of HSCs after ablation of the VEGF gene in mice. Intracellularly acting small-molecule inhibitors of VEGF receptor (VEGFR) tyrosine kinase dramatically reduced colony formation of HSCs, thus mimicking deletion of the VEGF gene. However, blocking VEGF by administering a soluble VEGFR-1, which acts extracellularly, induced only minor effects. These findings support the involvement in HSC survival of a VEGF-dependent internal autocrine loop mechanism (that is, the mechanism is resistant to inhibitors that fail to penetrate the intracellular compartment). Not only ligands selective for VEGF and VEGFR-2 but also VEGFR-1 agonists rescued survival and repopulation of VEGF-deficient HSCs, revealing a function for VEGFR-1 signalling during haematopoiesis.

Animals↗

PubMed2002

ANGPTL3 stimulates endothelial cell adhesion and migration via integrin alpha vbeta 3 and induces blood vessel formation in vivo.

The angiopoietin family of secreted factors is functionally defined by the C-terminal fibrinogen (FBN)-like domain, which mediates binding to the Tie2 receptor and thereby facilitates a cascade of events ultimately regulating blood vessel formation. By screening expressed sequence tag data bases for homologies to a consensus FBN-like motive, we have identified ANGPTL3, a liver-specific, secreted factor consisting of an N-terminal coiled-coil domain and the C-terminal FBN-like domain. Co-immunoprecipitation experiments, however, failed to detect binding of ANGPTL3 to the Tie2 receptor. A molecular model of the FBN-like domain of ANGPTL3 was generated and predicted potential binding to integrins. This hypothesis was experimentally confirmed by the finding that recombinant ANGPTL3 bound to alpha(v)beta(3) and induced integrin alpha(v)beta(3)-dependent haptotactic endothelial cell adhesion and migration and stimulated signal transduction pathways characteristic for integrin activation, including phosphorylation of Akt, mitogen-activated protein kinase, and focal adhesion kinase. When tested in the rat corneal assay, ANGPTL3 strongly induced angiogenesis with comparable magnitude as observed for vascular endothelial growth factor-A. Moreover, the C-terminal FBN-like domain alone was sufficient to induce endothelial cell adhesion and in vivo angiogenesis. Taken together, our data demonstrate that ANGPTL3 is the first member of the angiopoietin-like family of secreted factors binding to integrin alpha(v)beta(3) and suggest a possible role in the regulation of angiogenesis.

Amino Acid Sequence↗

PubMed2002

EG-VEGF and the concept of tissue-specific angiogenic growth factors.

The endothelium of the vascular beds is extremely diverse and exquisitely distinct with respect to the specific tissue compartment served by the vessels. The molecular identity and function of the instructive signals that tailor the tissue-specific endothelial phenotype have been largely undefined. Presumably, a complex, integrated network of signals derived from the tissue parenchyma and/or stromal compartments is responsible. Recently, we identified a novel angiogenic mitogen, endocrine-gland-derived vascular endothelial growth factor, EG-VEGF, with a selective activity and very distinct expression pattern. Human EG-VEGF is expressed by steroid producing cells in the adrenal gland, placenta, testis and ovary, and is a mitogen for endothelial cells derived from these microvascular beds. EG-VEGF may represent the first of a novel class of tissue-specific angiogenic factors that function to regulate and fine-tune endothelial cell growth, structural and functional properties. The identification of other selective angiogenic molecules will allow insight into exciting, basic developmental issues and increase our armamentarium of factors for therapeutic angiogenic and anti-angiogenic strategies.

Angiogenesis Inducing Agents↗