RESUMEN
Hypoxia stimulates angiogenesis through the binding of hypoxia-inducible factors to the hypoxia-response element in the vascular endothelial growth factor (Vegf) promotor. Here, we report that deletion of the hypoxia-response element in the Vegf promotor reduced hypoxic Vegf expression in the spinal cord and caused adult-onset progressive motor neuron degeneration, reminiscent of amyotrophic lateral sclerosis. The neurodegeneration seemed to be due to reduced neural vascular perfusion. In addition, Vegf165 promoted survival of motor neurons during hypoxia through binding to Vegf receptor 2 and neuropilin 1. Acute ischemia is known to cause nonselective neuronal death. Our results indicate that chronic vascular insufficiency and, possibly, insufficient Vegf-dependent neuroprotection lead to the select degeneration of motor neurons.
Asunto(s)
Hipoxia de la Célula/genética , Factores de Crecimiento Endotelial/genética , Linfocinas/genética , Neuronas Motoras/patología , Degeneración Nerviosa/genética , Elementos de Respuesta/genética , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Animales , Axones/fisiología , Sitios de Unión , Electrofisiología , Factores de Crecimiento Endotelial/metabolismo , Humanos , Linfocinas/metabolismo , Ratones , Ratones Noqueados , Neuronas Motoras/fisiología , Contracción Muscular , Fibras Musculares Esqueléticas/patología , Atrofia Muscular/genética , Atrofia Muscular/patología , Degeneración Nerviosa/patología , Degeneración Nerviosa/fisiopatología , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neuropilina-1 , Nervios Periféricos/patología , Regiones Promotoras Genéticas , Proteínas Tirosina Quinasas Receptoras/genética , Proteínas Tirosina Quinasas Receptoras/metabolismo , Receptores de Factores de Crecimiento/genética , Receptores de Factores de Crecimiento/metabolismo , Receptores de Factores de Crecimiento Endotelial Vascular , Eliminación de Secuencia , Médula Espinal/fisiología , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
Although tumors can activate vascular endothelial growth factor (VEGF) promoter in host stromal cells, the relative contribution to VEGF production of host versus tumor cells and the resulting vascular response have not been quantitated to date. To this end, we implanted VEGF-/- and wild-type (WT) embryonic stem (ES) cells in transparent dorsal skin windows in severe combined immunodeficient mice. VEGF-/- ES cell-derived tumors produced approximately 50% of VEGF compared with the WT tumors, suggesting significant contribution of host stromal cells. To discern the hypoxia-induced hypoxia inducible factor (HIF)-1alpha --> hypoxia response element (HRE) --> VEGF signaling cascade, we also examined tumors derived from HIF-1alpha-/- and HRE-/- ES cells. As expected, the VEGF protein level in HIF-1alpha-/- ES tumors was intermediate between VEGF-/- and WT ES cell tumors. Surprisingly, HRE-/- ES tumors produced the same level of VEGF as the VEGF-/- ES tumors, suggesting a critical role of HRE in tumor cell VEGF production. Angiogenesis in these tumors was proportional to their VEGF levels (VEGF-/- approximate to HRE-/- < HIF-1alpha-/- < WT). In contrast, vascular permeability, leukocyte-endothelial adhesion, and tumor growth were reduced in VEGF-/- and HRE-/- tumors but were comparable in HIF-1a-/- and WT tumors. This discrepancy suggests that different intracellular signaling pathways may be involved in each of these functions of VEGF. More importantly, these data suggest that host cells are active players in tumor angiogenesis and growth and need to be taken into account in the design of any therapeutic strategy.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Factores de Crecimiento Endotelial/fisiología , Linfocinas/fisiología , Neoplasias Experimentales/irrigación sanguínea , Neovascularización Patológica/metabolismo , Proteínas Nucleares/fisiología , Elementos de Respuesta/fisiología , Transducción de Señal/fisiología , Factores de Transcripción , Animales , Permeabilidad Capilar/fisiología , Comunicación Celular/fisiología , División Celular/fisiología , Proteínas de Unión al ADN/genética , Modelos Animales de Enfermedad , Factores de Crecimiento Endotelial/biosíntesis , Factores de Crecimiento Endotelial/genética , Endotelio Vascular/patología , Genes Letales/fisiología , Factor 1 Inducible por Hipoxia , Subunidad alfa del Factor 1 Inducible por Hipoxia , Leucocitos/patología , Linfocinas/biosíntesis , Linfocinas/genética , Ratones , Ratones Noqueados , Ratones SCID , Neoplasias Experimentales/metabolismo , Neoplasias Experimentales/patología , Neovascularización Patológica/patología , Proteínas Nucleares/genética , Trasplante de Células Madre , Células Madre/metabolismo , Células Madre/patología , Células del Estroma/metabolismo , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
Vascular endothelial cadherin, VE-cadherin, mediates adhesion between endothelial cells and may affect vascular morphogenesis via intracellular signaling, but the nature of these signals remains unknown. Here, targeted inactivation (VEC-/-) or truncation of the beta-catenin-binding cytosolic domain (VECdeltaC/deltaC) of the VE-cadherin gene was found not to affect assembly of endothelial cells in vascular plexi, but to impair their subsequent remodeling and maturation, causing lethality at 9.5 days of gestation. Deficiency or truncation of VE-cadherin induced endothelial apoptosis and abolished transmission of the endothelial survival signal by VEGF-A to Akt kinase and Bcl2 via reduced complex formation with VEGF receptor-2, beta-catenin, and phosphoinositide 3 (PI3)-kinase. Thus, VE-cadherin/ beta-catenin signaling controls endothelial survival.