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  • Title: Xanthine oxidase interaction with vascular endothelial growth factor in human endothelial cell angiogenesis.
    Author: Kou B, Ni J, Vatish M, Singer DR.
    Journal: Microcirculation; 2008 Apr; 15(3):251-67. PubMed ID: 18386220.
    Abstract:
    OBJECTIVES: 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.
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