title: Xanthine oxidase interaction with vascular endothelial growth factor in human endothelial cell angiogenesis.
abstract: OBJECTIVE
  Reduced capillary density occurs early in cardiovascular diseases. Oxidant stress is implicated in endothelial apoptosis. We investigated the effects of xanthine oxidase (XO) on endothelial survival signaling: protein kinase B/Akt, its cross-talk with p38 MAPK and apoptosis pathways, and its effect on vascular tube formation in vascular endothelial growth factor (VEGF)-simulated human umbilical vein cells.
  
  
  METHODS
  We studied primary cultured human endothelial cells from the umbilical cord. Reactive oxygen species (ROS) production was detected by dihydroethidium staining, cell-signaling pathways by western blots, cell survival by western blots, and nuclear chromatin and angiogenesis response by MTT proliferation assay and three-dimensional Matrigel cultures.
  
  
  RESULTS
  Exogenous XO increased cellular ROS production and caused superoxide-dependent inhibition of Akt phosphorylation and enhancement of p38 MAPK phosphorylation in a time-and dose-dependent manner. In contrast, application of the XO inhibitor oxypurinol or allopurinol inhibited VEGF-stimulated Akt phosphorylation, indicating that endogenous XO promotes VEGF-induced endothelial cell (EC) survival signaling. Exogenous XO induced activation of caspase-3 and reduced expression of the anti-apoptosis protein Bcl-2. Exogenous XO also reduced EC viability, proliferation, and vascular tube formation by p38 MAPK-dependent, phosphoinositide 3-kinase (PI3-K) reversible mechanisms; whereas VEGF promoted EC survival by PI3-K-dependent, p38 MAPK-independent effects.
  
  
  CONCLUSIONS
  Exogenous XO activity is an important contributor to endothelial mechanisms for microvascular rarefaction, by modulation of cell survival signaling pathways; however, endogenous XO is necessary for maintaining EC survival.
authors.affiliation: Department of Clinical Pharmacology & Therapeutics, Clinical Science Research Institute, Warwick Medical School, University of Warwick, UK. koubaijun@yahoo.com
authors.forename: Baijun
authors.initials: B
authors.lastname: Kou
authors.forename: Jinsong
authors.initials: J
authors.lastname: Ni
authors.forename: Manu
authors.initials: M
authors.lastname: Vatish
authors.forename: Donald R J
authors.initials: DR
authors.lastname: Singer
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology* / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008833:Microcirculation / Q000502:physiology; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010117:Oxypurinol / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism* / Q000494:pharmacology; D019820:Xanthine / Q000378:metabolism / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D019820:Xanthine; D014969:Xanthine Oxidase; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D010117:Oxypurinol