BACKGROUND: The mechanism by which vascular regeneration declines with aging is not fully understood. An interaction between integrin and vascular endothelial growth factor receptor-2 (VEGFR-2) plays a substantial role in angiogenesis. Here, we investigated whether aging impairs this interaction in endothelial progenitor cells (EPCs) under hypoxia. METHODS AND RESULTS: Aging reduced the blood flow and vessel density in ischemic muscles in mice. Levels of phosphorylated Src (p-Src), p-β3, and p-VEGFR-2 in acute ischemia were reduced in the muscles of aged mice compared to young mice. The hypoxia-inducible factor (HIF)-1α stabilizer deferoxamine improved the age-related impairment of angiogenesis, but this effect was diminished by LY290004, an inhibitor of phosphatidylinositol 3-kinase. Deferoxamine improved the reduction in chronic ischemia-induced β3-integrin and VEGFR-2 phosphorylation in the muscles of aged mice; this effect was also diminished by LY290004. In EPCs, we identified the molecular requirements for VEGF-mediated β3-integrin and VEGFR-2 cross-activation in vitronectin-induced cell adhesion under acute hypoxia. We demonstrated that c-Src controlled the adhesion- and VEGF-induced β3 tyrosine phosphorylation in hypoxia. Aging enhanced the hypoxia-induced EPC apoptosis and impaired several c-Src-related VEGF-induced receptor events, including β3 tyrosine activation, ligand binding, cell adhesion, and tubulogenesis in cultured EPCs of animals and those of humans. CONCLUSIONS: These data suggest that the aging-related decline in angiogenic action in response to ischemia is mediated by the impairment of cross-activation between β3 and VEGFR-2 in EPCs, which is partially associated with decreased HIF-1α stability.
BACKGROUND: The mechanism by which vascular regeneration declines with aging is not fully understood. An interaction between integrin and vascular endothelial growth factor receptor-2 (VEGFR-2) plays a substantial role in angiogenesis. Here, we investigated whether aging impairs this interaction in endothelial progenitor cells (EPCs) under hypoxia. METHODS AND RESULTS: Aging reduced the blood flow and vessel density in ischemic muscles in mice. Levels of phosphorylated Src (p-Src), p-β3, and p-VEGFR-2 in acute ischemia were reduced in the muscles of aged mice compared to young mice. The hypoxia-inducible factor (HIF)-1α stabilizer deferoxamine improved the age-related impairment of angiogenesis, but this effect was diminished by LY290004, an inhibitor of phosphatidylinositol 3-kinase. Deferoxamine improved the reduction in chronic ischemia-induced β3-integrin and VEGFR-2 phosphorylation in the muscles of aged mice; this effect was also diminished by LY290004. In EPCs, we identified the molecular requirements for VEGF-mediated β3-integrin and VEGFR-2 cross-activation in vitronectin-induced cell adhesion under acute hypoxia. We demonstrated that c-Src controlled the adhesion- and VEGF-induced β3 tyrosine phosphorylation in hypoxia. Aging enhanced the hypoxia-induced EPC apoptosis and impaired several c-Src-related VEGF-induced receptor events, including β3 tyrosine activation, ligand binding, cell adhesion, and tubulogenesis in cultured EPCs of animals and those of humans. CONCLUSIONS: These data suggest that the aging-related decline in angiogenic action in response to ischemia is mediated by the impairment of cross-activation between β3 and VEGFR-2 in EPCs, which is partially associated with decreased HIF-1α stability.
Authors: M El Assar; J M Sánchez-Puelles; I Royo; E López-Hernández; A Sánchez-Ferrer; J L Aceña; L Rodríguez-Mañas; J Angulo Journal: Br J Pharmacol Date: 2015-01-12 Impact factor: 8.739