No description available.

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen involved in angiogenesis, the formation of new blood vessels. sFlt-1, a secreted form of the signal-transducing VEGF receptor Flt-1, can inhibit cellular responses to VEGF both in vitro and in vivo. sFlt-1 is generated by alternative pre-mRNA processing; removal of Flt-1 intron 13 by splicing produces the mRNA for transmembrane Flt-1, whereas cleavage/polyadenylation within this intron, preserving the exon 13/intron 13 junction, yields sFlt-1 mRNA. Despite the likely importance of sFlt-1 in VEGF signaling, little is known about the regulation of its expression. Previous studies using an Flt-1 minigene (pFIN13) revealed that intronic cleavage/polyadenylation signals can affect Flt-1 expression, and, conversely, that 3' intronic splice signals can affect sFlt-1 expression. The goal of present work was to test the hypothesis that splicing and cleavage/polyadenylation factors compete functionally on Flt-1 transcripts, by 1) assessing the influence of exon 13/14 splicing determinants on expression of Flt-1 RNA processing variants in a transfected cell model system; 2) determining the effects of altering the relative abundance of proteins principally involved in splicing or cleavage/polyadenylation; and 3) characterizing a previously-unknown splice variant, predicted to encode a novel sFlt-1 protein isoform, in cells overexpressing the spliceosomal RNA binding protein U2AF65. When the upstream exon in pFIN13 was decreased from 2135 to 309 bp, the sFlt-1:Flt-1 mRNA ratio decreased 8.9-fold and an aberrant 5'UTR/exon 14 splice decreased 60-fold, indicating that "exon definition" is a key parameter of successful Flt-1 RNA processing. Mutation of 5' or 3' intronic splice signals had little effect on Long sFlt-1:Total sFlt-1 mRNA ratio, suggesting that splicing and cleavage/polyadenylation factors may not compete physically for Flt-1 transcripts. Although co-transfection with RNA processing factor cDNAs did not generally produce the predicted pattern of effects on sFlt-1:Flt-1 mRNA ratio, a cryptic exon within intron 13 was revealed in cells overexpressing U2AF65. sFlt-1 protein apparently can be encoded by mRNAs either cleaved/polyadenylated within intron 13 or, surprisingly, by splicing of the cryptic exon "13b." Thus, the cellular decision to produce sFlt-1 or Flt-1 from a nascent RNA can no longer be viewed as a simple choice between cleavage/polyadenylation and splicing. / Ph. D.

Endometrial adenocarcinoma, originating from the glandular epithelial cells of the uterine endometrial lining, is one of the most prevalent cancers amongst women in the Western world. The prostaglandin F2α (PGF2α) receptor (FP) is upregulated in endometrial adenocarcinoma. A previous microarray analysis of endometrial adenocarcinoma cells (Ishikawa) identified numerous targets of PGF2α-FP signalling including angiogenic factors, VEGF-A, FGF-2, CXCL1 and CXCL8 and antiangiogenic factors ADAMTS1. The regulation of VEGF-A, FGF-2, CXCL1 and CXCL8 was confirmed by previous studies using an in vitro model system, of Ishikawa cells stably expressing the FP receptor to levels observed in cancer (FPS cells). In this thesis, ADAMTS1 expression was found to be upregulated in endometrial adenocarcinoma samples compared to normal endometrium. Using FPS cells, ADAMTS1 expression was regulated in an extracellular signal regulated kinase 1/2 (ERK1/2) independent manner involving activation of nuclear factor of activated T cells (NFAT). Angiogenic and antiangiogenic proteins secreted by epithelial cells, in response to PGF2α-FP receptor signalling, could therefore regulate vascular function in a paracrine manner. Hence this thesis examines the role of angiogenic factors FGF2, CXCL1 and CXCL8, secreted into PGF2α-treated FPS cell conditioned medium (P CM), in the regulation of endothelial cell function in vitro. Firstly, using an in vitro model system, treatment of human umbilical vein endothelial cells (HUVECs) with P CM increased endothelial network formation and proliferation, compared to control CM. Immunoneutralisation of FGF2, CXCL1 and CXCL8 from the P CM reduced endothelial cell network formation and proliferation (P<0.05). In addition, inhibition of their receptors (FGFR1 and CXCR2) with chemical antagonists decreased endothelial cell network formation and proliferation (P<0.05) in response to treatment with P CM. This indicates that FGF2, CXCL1 and CXCL8 are paracrine effectors of FP-mediated endothelial cell network formation and proliferation. Next, the mechanisms by which FGF2 regulates P CM-induced endothelial cell network formation and proliferation were investigated. Using specific inhibitors of cell signalling, FGF2-FGFR1 was found to regulate endothelial cell proliferation via the mTOR pathway. In contrast, FGF2-FGFR1 signalling mediated endothelial cell network formation via the regulation of COX-2 expression and PGF2α synthesis in endothelial cells. Endometrial adenocarcinoma, originating from the glandular epithelial cells of the uterine endometrial lining, is one of the most prevalent cancers amongst women in the Western world. The prostaglandin F2α (PGF2α) receptor (FP) is upregulated in endometrial adenocarcinoma. A previous microarray analysis of endometrial adenocarcinoma cells (Ishikawa) identified numerous targets of PGF2α-FP signalling including angiogenic factors, VEGF-A, FGF-2, CXCL1 and CXCL8 and antiangiogenic factors ADAMTS1. The regulation of VEGF-A, FGF-2, CXCL1 and CXCL8 was confirmed by previous studies using an in vitro model system, of Ishikawa cells stably expressing the FP receptor to levels observed in cancer (FPS cells). In this thesis, ADAMTS1 expression was found to be upregulated in endometrial adenocarcinoma samples compared to normal endometrium. Using FPS cells, ADAMTS1 expression was regulated in an extracellular signal regulated kinase 1/2 (ERK1/2) independent manner involving activation of nuclear factor of activated T cells (NFAT). Angiogenic and antiangiogenic proteins secreted by epithelial cells, in response to PGF2α-FP receptor signalling, could therefore regulate vascular function in a paracrine manner. Hence this thesis examines the role of angiogenic factors FGF2, CXCL1 and CXCL8, secreted into PGF2α-treated FPS cell conditioned medium (P CM), in the regulation of endothelial cell function in vitro. Firstly, using an in vitro model system, treatment of human umbilical vein endothelial cells (HUVECs) with P CM increased endothelial network formation and proliferation, compared to control CM. Immunoneutralisation of FGF2, CXCL1 and CXCL8 from the P CM reduced endothelial cell network formation and proliferation (P<0.05). In addition, inhibition of their receptors (FGFR1 and CXCR2) with chemical antagonists decreased endothelial cell network formation and proliferation (P<0.05) in response to treatment with P CM. This indicates that FGF2, CXCL1 and CXCL8 are paracrine effectors of FP-mediated endothelial cell network formation and proliferation. Next, the mechanisms by which FGF2 regulates P CM-induced endothelial cell network formation and proliferation were investigated. Using specific inhibitors of cell signalling, FGF2-FGFR1 was found to regulate endothelial cell proliferation via the mTOR pathway. In contrast, FGF2-FGFR1 signalling mediated endothelial cell network formation via the regulation of COX-2 expression and PGF2α synthesis in endothelial cells. Angiogenesis is maintained by a balance of pro-and antiangiogenic factors. Hence, concomitantly with the upregulation of proangiogenic factors, antiangiogenic proteins ADAMTS1 and regulator of calcineurin 1 (RCAN1) were upregulated by P CM treatment of HUVECs. They were subsequently shown to limit endothelial cell network formation and proliferation in response to P CM. Finally, the role of PGF2α in angiogenesis was investigated using two in vivo models. PGF2α treatment did not increase angiogenesis in a sponge matrigel mouse model. In a xenograft mouse model, PGF2α-FP signalling increased expression of angiogenic factors in human epithelial cells and mouse stroma but this did not enhance microvessel density. Taken together, this thesis had highlighted that PGF2α-FP receptor signalling stimulates expression of pro-and antiangiogenic factors that in turn regulate endothelial cell function. However, in vivo studies demonstrate that PGF2α-FP receptor interaction does not impact on the level of angiogenesis but may control other aspects of vascular function.

No description available.

Angiogenesis, the formation of new blood vessels from a pre-existing vasculature, is crucial during development and for many diseases including cancer. Despite tremendous progress in the understanding of the angiogenic process, many aspects are still not fully elucidated. Several attempts have been made to identify novel genes involved in endothelial cell biology and angiogenesis. Here we focused on Pald1, a recently identified, vascular-enriched gene encoding paladin. Our in vitro studies indicate that paladin is a lipid phosphatase catalyzing dephosphorylation of phosphatidylinositol phosphates, a process essential for endocytosis and intracellular vesicle trafficking. We confirmed paladin’s vascular expression pattern and revealed a shift from a broad endothelial cell expression during development to an arterial mural cell-restricted expression in several vascular beds in adult mice. Paladin expression in the lung, however, was not restricted to the vasculature, but was also observed in pneumocytes and myofibroblasts. Lungs of female, but not male, Pald1 null mice displayed an obstructive lung phenotype with increased alveolar air sacs that were already apparent early in the alveolarization process. Only endothelial cells, but not other main lung cell types, were affected by loss of paladin. Endothelial cell number was reduced in 4-week old mice, possibly due to increased endothelial turnover in Pald1 deficient lungs. Vascular defects were also found in the retina. Loss of paladin led to reduced retinal vascular outgrowth accompanied by a hyperdense and hypersprouting vascular front. Downstream signaling of the major angiogenic driver, vascular endothelial growth factor receptor 2 (VEGFR2) was sustained in Pald1 null mice, and VEGFR2 degradation was impaired. Furthermore, paladin inhibited endothelial cell junction stability and loss of paladin led to reduced vascular permeability. Whether the differences in VEGFR2 signaling and adherens junction stability are connected remains to be fully explored. The newly identified lipid phosphatase activity of paladin and its specific effects on VEGFR2 signaling and adherens junction stability indicate that paladin may be controlling the endocytic pathway.

Endometrial cancer is one of the most significant gynaecological malignancies that affect women from New Zealand and the rest of the world. One of the critical stages in the development of a tumour is the onset of hypoxia. The malignancy responds by having raised levels of Hypoxia Inducible Factor (HIF) that in turn induces increased production of Vascular Endothelial Growth Factor (VEGF). VEGF is a potent angiogenic factor that will mediate vascular supply of nutrients and oxygen to the developing tumour. The aim of this study was to investigate whether two compounds found in extracts of plant materials, Resveratrol (Resveratrol) and Epigallocatechin gallate (EGCG), altered the levels of VEGF in the supernatant of cultured endometrial cancer cells. Resveratrol is a phytoalexin that is found in many foods, such as grapes, nuts and berries, as well as in high concentrations in some red wines. 100 µM of resveratrol was added to cell cultures for 24 hours. VEGF levels in the supernatant were then analysed using ELISA. Resveratrol was found to have significant inhibitory effects in both primary endometrial cancer cell cultures and immortalised endometrial cancer cell cultures. Resveratrol was also shown to reverse the increase in VEGF caused by the hypoxia mimic cobalt chloride (CoCl₂). Epigallocatechin gallate (EGCG) is an antioxidant catechin extracted from green tea. The effect of EGCG was analysed using the same method as for resveratrol. 100 µM of EGCG was also shown to have a significant inhibitory effect on the level of VEGF in the supernatant of cultured endometrial cancer cells, as well as reducing the effect of CoCl₂. These results suggest that selected food compounds, resveratrol and EGCG, can reduce VEGF levels by inhibiting HIF. Further investigation This may have anti-tumour effects in women with endometrial cancer.

Epidemiological evidence indicates that selenium supplementation may increase risk for ocular hypertension and glaucoma. The purpose of this project was to determine the effects of selenium on the conventional "trabecular" aqueous outflow pathway, a likely site of pathology for glaucoma. Human trabecular meshwork (HTM) cells and human umbilical vein endothelial cells (HUVECs) were treated with selenium (MSeA) at or near physiologically relevant concentrations. Selenium uptake by cells was monitored using mass spectrometry. While detectible changes in intracellular selenium were observed after exposure to 1-10 uM MSeA for 24 hours, the majority remained in the conditioned medium. The high concentrations of extracellular selenium we observed raised the possibility that selenium has an extracellular target.To investigate the role of selenium in extracellular matrix turnover, I examined alterations in protein secretion and intracellular signaling. MSeA treatment (5-10 uM) led to a significant decrease in the secretion of matrix metalloproteinase -2 and its inhibitor after 6-24 hours and to a dose-dependent decrease in kinase signaling. Later, I investigated the possibility that integrins are an extracellular target of selenium by monitoring morphological changes in HTM cells and by treating them with divalent cations. MSeA stimulated morphological changes consistent with a decrease in integrin function. These occurred before (less than 3 hours) alterations in protein secretion and intracellular signaling (3-6 hours). Zinc treatment prevented MSeA-mediated alterations in protein secretion and changes in cell-matrix adhesion.Finally markers of HTM cell homeostasis were examined. MSeA treatment (5 uM) led to a 60% decrease in protein synthesis after 3 hours and a 60% reduction in protein secretion, without causing significant alterations in cell viability and total ATP. To assess the physiological relevance of my results, anterior segments were perfused with MSeA to determine its effects on aqueous outflow facility. Preliminary results suggest that MSeA leads to a decrease in outflow facility.The combination of MSeA-induced decreases in several indicators of HTM cell homeostasis (without adversely effects on cell viability at physiologically relevant doses) and decreases in outflow facility provide a possible mechanism for selenium-associated ocular hypertension.

No description available.

Endometriosis is a gynecological disease defined as the growth of endometrium outside of the uterus. Although linked to 50% of female infertility cases, current medical treatments fail to maintain fecundity. Since the survival of endometriotic lesions is dependent on their early neovascularization, antiangiogenic therapies specifically targeting blood vessel growth could be a promising therapeutic option for the treatment of endometriosis. Angiogenesis, the branching of new blood vessels from existing vasculature, promotes robust vascularization of lesions. ABT-898 (Abbott Laboratories), a thrombospondin-1 analog, induces endothelial cell apoptosis while sequestering pro-angiogenic growth factors. We postulated that ABT-898 would reduce endometriotic lesion vascularization while physiological angiogenesis and pregnancy remained unaffected in a murine model of endometriosis. The antiangiogenic effect of ABT-898 was tested in a human umbilical vein endothelial cell line revealing disruption of endothelial tube branching. Two in vivo experiments were conducted in which endometriosis was induced in female alymphoid BALB/c-Rag2-/-Il2rg-/- mice by adhering sections of human endometrium to the abdominal wall. Lesions from ABT-898 treated mice contained a reduced number of CD31+ endothelial cells and a decrease in blood flow supplying the lesion compared to 5% dextrose controls. Reproductive status was evaluated through maintenance of pregnancies up to gestation day 12 revealing unaffected implantation site structure and physiological angiogenesis. In a trans-generational study, pregnant F0 generation mice received ABT-898 or 5% dextrose injections on gestation days 7, 9, 11, 13, 15, 17, and 19. F1 generation mice were raised to reproductive age and bred resulting in litters (F2 generation) comparable in size to the F0 generation litters. Chronic exposure to ABT-898 did not affect angiogenic plasma cytokine levels in F0 generation mice. In addition, physiological angiogenesis was unaffected within the uteri of ABT-898 treated mice. Histological examination of the kidney, liver, ovary, and uterus revealed no structural abnormalities in F0 and F1 generations exposed to ABT-898. These results suggest that ABT-898 inhibits pathological angiogenesis within endometriotic lesions without affecting physiological angiogenesis involved in pregnancy and organ function across three generations of mice. Further research will establish the effects of ABT-898 on embryonic development, organ toxicity, and physiological angiogenesis in all organs. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2013-05-07 15:19:10.967

Angiogenesis and vascular permeability occur in physiological and pathological conditions. Angiogenesis denotes the process of blood vessel formation from preexisting quiescent vessels. Angiogenesis is initiated by proangiogenic factors, inducing endothelial cell sprouting, migration and anastomosis, followed by regression of the new vessels or maturation into a quiescent status. Vascular permeability is the process where blood vessels exchange nutrients, solutes and inflammatory cells with the surrounding tissue. Small molecules freely cross the endothelial wall, however macromolecules and cells leak out from the vasculature only after stimulation by certain factors, including VEGF. Angiogenesis and vascular permeability are tightly regulated physiological processes, but uncontrolled angiogenesis and excessive leakage lead to pathological conditions and the progression of several diseases. VEGF and its receptor VEGFR2 are critical players in angiogenesis and in vascular permeability. The binding of the ligand to the receptor is not the only event involved in the activation and regulation of the signaling cascade. Coreceptors, kinases, phosphatases, and other proteins involved in the trafficking of the complex modulate the signal amplitude and duration. VEGF/VEGFR2 complex combined with the coreceptor NRP1 has a strong pro-angiogenic action and a critical role in angiogenesis. Both VEGFR2 and NRP1 bind VEGF and can present VEGF in cis, when both VEGFR2 and NRP1 are expressed on the same endothelial cell or in trans, when NRP1 is expressed on an adjacent endothelial cell or another type of cell. Y949 and Y1212 are two of the main phosphorylation sites of VEGFR2 induced by VEGFA. The binding of phosphorylated Y949 to the SH2 domain of TSAd regulates vascular permeability leading to Src activation and adherens junction opening in vitro. Phospho-Y1212 is implicated in actin stress fiber remodeling via the adapter Nck, affecting the actin cytoskeleton and endothelial cell migration in vitro. Paladin is a vascular-enriched phosphatase-domain containing protein without reported phosphatase activity and is a negative regulator of insulin receptor and Toll-like receptor 9 signaling. In this thesis work, I have investigated the spatial dynamics of NRP1/VEGFR2 complex formation (in cis and in trans) for coordinating VEGF-mediated angiogenesis in physiological and in pathological conditions (Paper I). I have studied, in vivo, the role of VEGFR2 Y949 in vascular permeability and metastatic spread (Paper II) and the role of VEGFR2 Y1212 in angiogenic remodeling and vessel stability (Paper III). Furthermore, I have examined paladin’s role in regulating VEGF/VEGFR2 signaling and VE-cadherin junction stability, in angiogenic sprouting and vascular permeability (Paper IV). In conclusion, VEGF/VEGFR2 signaling is regulated by a multifactor system and each individual regulatory mechanism leads to a specific outcome in angiogenesis, vascular permeability and vessel stability.