RESUMO
BACKGROUND: The link of aging to specific mechanisms of vascular biology is not well understood. We have previously shown that aging is associated with increased vein graft wall thickness and that this process involves the VEGF-Delta/Notch-ephrin/Eph cascade. Therefore, we examined whether Dll-4 or Notch-4 are differentially expressed, according to age, during vein graft adaptation. MATERIALS AND METHODS: Vein grafts were performed in 6-mo and 24-mo Fischer 344 rats. Gene expression was analyzed by quantitative real-time PCR, and the distribution of Dll-4 and Notch-4 was observed by immunofluorescence. RESULTS: The expression of Dll-4 and Notch-4 was reduced in vein grafts performed in aged rats compared with the expression in young adult rats. Both Dll-4 and Notch-4 were distributed in vein graft endothelium as well as the outer adventitia, with reduced amounts in the outer adventitia of aged vein grafts. Aged veins had reduced eNOS membrane targeting and colocalization with caveolin-1 as well as reduced eNOS protein expression in comparison to young adult veins. In an exchange model between young and aged animals, heterogeneous vein grafts (Yo(Ag) and Ag(Yo)) showed significantly thicker neointima compared with young (Yo(Yo)) controls, and had Notch-4-positive cells, but not Dll-4-positive cells, diminished in the adventitia. Vein grafts that were air-denuded of endothelium did not show any adaptation to the arterial environment and also lacked both Dll-4 and Notch-4 expression at 3 wk. CONCLUSIONS: During vein graft adaptation to the arterial environment, both Dll-4 and Notch-4 expression are down-regulated in an aged, but not a young, background. Loss of Notch-4 is associated with loss of attenuation of neointima. The delta-Notch signaling pathway may be active during vein graft adaptation.
Assuntos
Adaptação Fisiológica/fisiologia , Envelhecimento/fisiologia , Sobrevivência de Enxerto/fisiologia , Veias Jugulares/cirurgia , Receptores Notch/metabolismo , Enxerto Vascular/métodos , Animais , Modelos Animais de Doenças , Endotélio Vascular/fisiologia , Expressão Gênica/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Veias Jugulares/fisiologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Neointima/metabolismo , Neointima/fisiopatologia , Óxido Nítrico Sintase Tipo III/genética , Óxido Nítrico Sintase Tipo III/metabolismo , Ratos , Ratos Endogâmicos F344 , Receptor Notch4 , Receptores Notch/genética , Transdução de Sinais/fisiologiaRESUMO
Carotid angioplasty is associated with adverse events in elderly patients; it is unclear whether this is related to an altered inflammatory axis. The carotid arteries of young (6 months) or aged (22-24 months) Fischer 344 rats were balloon injured. Aged rats had reduced lumen area (0.18 ± 0.03 vs 0.24 ± 0.01 mm(2), p = .02) and increased neointimal thickening (0.15 ± 0.04 vs 0.08 ± 0.03 mm(2), p = .006). Aged rats had increased circulating monocytes (96 ± 21 vs. 54 ± 7; p = .002) as well as increased numbers of monocytes at the post-angioplasty site. Aged rats had sustained monocyte chemotactic protein-1 expression after angioplasty but young rats did not. Aged arteries also exhibited defective vasorelaxation and abnormal eNOS localization. Aged (≥80 years) human patients with high-grade carotid stenosis had increased number of monocytes (9.1% ± 0.4%) compared with younger (65-80 years) patients (8.1% ± 0.3%, p = .013). Aged rats develop neointimal hyperplasia after carotid angioplasty with increased numbers of monocytes, and elderly humans with carotid stenosis have increased numbers of circulating monocytes. These preliminary results may suggest a role for monocytes in the response to carotid angioplasty.