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Publications (7)36.02 Total impact

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    ABSTRACT: The hereditary von Hippel-Lindau (VHL) syndrome predisposes sufferers to highly vascularized tumors such as renal clear cell carcinoma (RCC) and central nervous system hemangioblastoma. In RCC4 and RCC786-0 VHL- cells with VHL mutations, the protein of hypoxia-inducible factor-1alpha (HIF-1alpha) is constitutively stabilized and the mRNA levels of HIF target genes, including vascular endothelial growth factor (VEGF), are elevated. However, the expression of angiopoietins in these cells and their involvement in angiogenesis are not well known. In this study, we compared the mRNA levels of angiopoietins in human kidney proximal tubule epithelial (RPTE) and RCC4 and RCC786-0 VHL- cells. In RPTE cells, angiopoietin-4 (Ang-4) expression was selectively induced by hypoxia or by expression of a hybrid form of HIF-1alpha. Under normoxic conditions, the mRNA levels of Ang-4 were higher in RCC4 and RCC786-0 VHL- than RPTE cells. Angiopoietin-1 expression was detectable in RCC4 and RCC786-0 VHL- cells but not RPTE cells. In RCC786-0 VHL+ cells, which were stably transfected with a wild-type copy of VHL, the mRNA levels of VEGF and Ang-4 were suppressed and the hypoxic response was restored. We also demonstrated that stimulation of endothelial tube formation by conditioned medium harvested from RCC4 cells was inhibited by a soluble Tie-2 receptor. These results suggest that the angiopoietin/Tie-2 system may participate in the angiogenic response to hypoxia in renal tissues and in tumor angiogenesis in renal carcinoma.
    American journal of physiology. Renal physiology 11/2004; 287(4):F649-57. · 3.61 Impact Factor
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    ABSTRACT: Previous studies have shown that incubation of balloon-injured rat carotid arteries with adenoviral vectors encoding the carboxyl terminus of the beta-adrenergic receptor kinase (Ad2/betaARKct) for 30 min reduces neointima formation. However, it is unclear whether this beneficial effect of betaARKct could be achieved using a catheter-based vector delivery system and whether the observed inhibition of neointima formation translated into a reduction of vessel stenosis. In this study, Ad2/betaARKct was infused into the balloon-injured site of rabbit iliac arteries using a porous infusion catheter over 2 min. Twenty-eight days after gene transfer, angiographic and histological assessments were performed. Angiographic and histological assessments indicate significant (p < 0.05) inhibition of iliac artery neointima formation and lumen stenosis by Ad2/betaARKct. Our studies demonstrate that an inhibitory effect of Ad2/betaARKct on neointima formation is achievable using a catheter-based vector delivery system and that the inhibition of neointima formation translates into a gain in the vessel minimal luminal diameter. The extent of inhibition (35%) was comparable to that observed with adenoviral-mediated expression of thymidine kinase plus ganciclovir treatment, a cytotoxic gene therapy approach for restenosis. These results suggest that adenoviral-mediated gene transfer of betaARKct is a clinically viable cytostatic gene therapy strategy for the treatment of restenosis.
    The Journal of Gene Medicine 01/2004; 6(10):1061-1068. · 2.16 Impact Factor
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    ABSTRACT: Hypoxia-inducible factor-1 (HIF-1) mediates transcriptional activation of vascular endothelial growth factor (VEGF) and other hypoxia-responsive genes. Transgenic expression of a constitutively stable HIF-1alpha mutant increases the number of vascular vessels without vascular leakage, tissue edema, or inflammation. This study aimed to investigate the molecular basis by which HIF-1 mediates the angiogenic response to hypoxia. In primary human endothelial cells, hypoxia, desferrioxamine, or infection with Ad2/HIF-1alpha/VP16, an adenoviral vector encoding a constitutively stable hybrid form of HIF-1alpha, increased the mRNA and protein levels of VEGF, angiopoietin-2 (Ang-2), and angiopoietin-4 (Ang-4). Infection with Ad2/CMVEV (a control vector expressing no transgene) had no effect. Angiopoietin-1 (Ang-1) expression was not detected in human endothelial cells. Ang-4 was also induced by hypoxia or Ad2/HIF-1alpha/VP16 in human cardiac cells, whereas Ang-1 expression remained unchanged. Recombinant Ang-4 protein protected endothelial cells against serum starvation-induced apoptosis and increased cultured endothelial cell migration and tube formation. Ad2/HIF-1alpha/VP16 stimulated endothelial cell proliferation and tube formation. Hypoxia- or Ad2/HIF-1alpha/VP16-induced tube formation was significantly reduced by a Tie-2 inhibitor. These results suggest that HIF-1 mediates the angiogenic response to hypoxia by upregulating the expression of multiple angiogenic factors. Ang-4 can function similarly as Ang-1 and substitute for Ang-1 to participate in hypoxia-induced angiogenesis. Activation of the angiopoietin/Tie-2 system may play a role in the ability of HIF-1 to induce hypervascularity without excessive permeability.
    Circulation Research 11/2003; 93(7):664-73. · 11.86 Impact Factor
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    ABSTRACT: This study aimed to examine the effects of adenovirus-mediated expression of p35, a baculovirus gene, on apoptosis induced by hypoxia/reoxygenation (H/R) in cardiomyocytes. Neonatal rat cardiomyocytes were infected with recombinant adenoviral vectors expressing p35 (Ad2/CMVp35) or no transgene (Ad2/CMVEV) and were then subjected to H/R. Separate groups of non-infected cardiomyocytes were treated with pharmacological caspase inhibitors or antioxidants. Cell viability, apoptosis, caspase activity, and cellular reactive oxygen species (ROS) were measured using various assays. H/R decreased cell viability and increased cellular ROS levels, caspase activity, and cell apoptosis. Infection with Ad2/CMVp35 effectively inhibited the increase in cellular ROS levels, the activities of caspases 3 and 8, apoptosis, and cell death following H/R, whereas Ad2/CMVEV had no effect. Despite its ability to abolish the increase in caspase activity and partially inhibit apoptosis, the pan-caspase inhibitor ZVAD-fmk (100 microM) failed to significantly reduce cell death induced by H/R. N-acetyl-L-cysteine, an antioxidant, completely inhibited H/R-induced increase in cellular ROS levels, but reduced apoptosis and cell death by 30% only. Adenovirus-mediated expression of p35 effectively inhibits H/R-induced cardiomyocyte apoptosis by reducing cellular ROS levels and inhibiting caspase activity.
    Cardiovascular Research 09/2002; 55(2):309-19. · 5.81 Impact Factor
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    ABSTRACT: Peroxisome proliferator-activated receptors (PPAR), especially the PPARalpha and PPARgamma, are associated with an extraordinary diverse spectrum of cardiovascular diseases including hypertension, angiogenesis, cardiac hypertrophy, and atherosclerosis. PGAR (for PPAR gamma angiopoietin-related gene) is a recently identified PPAR target gene which is associated with adipose differentiation, systemic lipid metabolism, energy homeostasis, and possibly angiogenesis. We report here that WY-14643, a selective PPARalpha ligand up-regulated PGAR expression in neonatal rat cardiomyocytes. In parallel to activating the expression of vascular endothelial growth factor and glucose transporter-4, hypoxia increased PGAR mRNA levels. PGAR expression was also increased by desferrioxamine and CoCl(2), but not by sodium cyanide, results consistent with the pharmacological features of hypoxia-responsive genes. These studies are the first to demonstrate that hypoxia increases the mRNA levels of a PPAR target gene in cardiomyocytes. Furthermore, infection with adenoviral vectors encoding the wild-type or a hybrid form of HIF-1alpha highly increased PGAR mRNA levels. In contrast, neither hypoxia nor overexpression of HIF-1alpha affected the mRNA levels of PPARalpha, PPAR gamma, and muscle carnitine palmitoyltransferase, a known PPARalpha target gene. These results suggest that hypoxic activation of PGAR expression is likely mediated by HIF-1 but not the PPARalpha/RXR pathway.
    Journal of Molecular and Cellular Cardiology 08/2002; 34(7):765-74. · 5.15 Impact Factor
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    ABSTRACT: A. J. Belanger, H. Lu, T. Date, L. X. Liu, K. A. Vincent, G. Y. Akita, S. H. Cheng, R. J. Gregory and C. Jiang. Hypoxia Up-regulates Expression of Peroxisome Proliferator-activated Receptor γ Angiopoietin-related Gene (PGAR) in Cardiomyocytes: Role of Hypoxia Inducible Factor 1α. Journal of Molecular and Cellular Cardiology (2002)34 , 765–774. Peroxisome proliferator-activated receptors (PPAR), especially the PPARα and PPARγ, are associated with an extraordinary diverse spectrum of cardiovascular diseases including hypertension, angiogenesis, cardiac hypertrophy, and atherosclerosis. PGAR (for PPARγ angiopoietin-related gene) is a recently identified PPAR target gene which is associated with adipose differentiation, systemic lipid metabolism, energy homeostasis, and possibly angiogenesis. We report here that WY-14643, a selective PPARα ligand up-regulated PGAR expression in neonatal rat cardiomyocytes. In parallel to activating the expression of vascular endothelial growth factor and glucose transporter-4, hypoxia increased PGAR mRNA levels. PGAR expression was also increased by desferrioxamine and CoCl2, but not by sodium cyanide, results consistent with the pharmacological features of hypoxia-responsive genes. These studies are the first to demonstrate that hypoxia increases the mRNA levels of a PPAR target gene in cardiomyocytes. Furthermore, infection with adenoviral vectors encoding the wild-type or a hybrid form of HIF-1α highly increased PGAR mRNA levels. In contrast, neither hypoxia nor overexpression of HIF-1α affected the mRNA levels of PPARα, PPARγ, and muscle carnitine palmitoyltransferase, a known PPARα target gene. These results suggest that hypoxic activation of PGAR expression is likely mediated by HIF-1 but not the PPARα/RXR pathway.
    Journal of Molecular and Cellular Cardiology 07/2002; 34(7):765-774. · 5.15 Impact Factor
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    ABSTRACT: Hypoxia regulates expression of vascular endothelial growth factor (VEGF) by increasing its transcription and by stabilizing its mRNA. Despite the pivotal role of hypoxia-inducible factor 1 (HIF-1) in transcriptional activation of hypoxia-responsive genes, it is not known whether HIF-1 mediates hypoxia-induced stabilization of VEGF mRNA. We constructed adenoviral vectors expressing either the wild-type HIF-1 alpha (Ad2/HIF-1 alpha/FL), a constitutively stable hybrid form of HIF-1 alpha (Ad2/HIF-1 alpha/VP16), or no transgene (Ad2/CMVEV). In rat glioma (C6) cells and human cardiac, vascular smooth muscle, and endothelial cells, infection with Ad2/HIF-1 alpha/VP16 or Ad2/HIF-1 alpha/FL increased VEGF expression at both the mRNA and protein levels. Under normoxic conditions, the half-life of VEGF mRNA was 42 min in C6 cells. Hypoxia and Ad2/HIF-1 alpha/VP16 increased the half-life of VEGF mRNA to 3.3 and 2.7 h, respectively, while Ad2/CMVEV had no effect. These studies are the first to demonstrate that overexpression of HIF-1 alpha increases VEGF mRNA stability. Our results also suggest that stabilization of VEGF mRNA by hypoxia is mediated, at least in part, by HIF-1.
    Biochemical and Biophysical Research Communications 04/2002; 291(4):908-14. · 2.28 Impact Factor