Mukai Yasushi, Rikitake Yoshiyuki, Shiojima Ichiro, Wolfrum Sebastian, Satoh Minoru, Takeshita Kyosuke, Hiroi Yukio, Salomone Salvatore, Kim Hyung-Hwan, Benjamin Laura E, Walsh Kenneth, Liao James K
Vascular Medicine Research Unit, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
J Clin Invest. 2006 Feb;116(2):334-43. doi: 10.1172/JCI26223.
To determine whether endothelial Akt could affect vascular lesion formation, mutant mice with a constitutively active Akt transgene, which could be inducibly targeted to the vascular endothelium using the tet-off system (EC-Akt Tg mice), were generated. After withdrawal of doxycycline, EC-Akt Tg mice demonstrated increased endothelial-specific Akt activity and NO production. After blood flow cessation caused by carotid artery ligation, neointimal formation was attenuated in induced EC-Akt Tg mice compared with noninduced EC-Akt Tg mice and control littermates. To determine the role of eNOS in mediating these effects, mice were treated with N-nitro-L-arginine methyl ester (L-NAME). Neointimal formation was attenuated to a lesser extent in induced EC-Akt Tg mice treated with L-NAME, suggesting that some of the vascular protective effects were NO independent. Indeed, endothelial activation of Akt resulted in less EC apoptosis in ligated arteries. Immunostaining demonstrated decreased inflammatory and proliferative changes in induced EC-Akt Tg mice after vascular injury. These findings indicate that endothelial activation of Akt suppresses lesion formation via increased NO production, preservation of functional endothelial layer, and suppression of inflammatory and proliferative changes in the vascular wall. These results suggest that enhancing endothelial Akt activity alone could have therapeutic benefits after vascular injury.
为了确定内皮细胞中的Akt是否会影响血管病变的形成，研究人员构建了一种具有组成型活性Akt转基因的突变小鼠，该转基因可以使用四环素调控系统（tet-off系统）被诱导靶向血管内皮细胞（EC-Akt转基因小鼠）。停用强力霉素后，EC-Akt转基因小鼠的内皮特异性Akt活性和一氧化氮（NO）生成增加。在颈动脉结扎导致血流停止后，与未诱导的EC-Akt转基因小鼠和对照同窝小鼠相比，诱导型EC-Akt转基因小鼠的新生内膜形成减弱。为了确定内皮型一氧化氮合酶（eNOS）在介导这些效应中的作用，研究人员用N-硝基-L-精氨酸甲酯（L-NAME）处理小鼠。在用L-NAME处理的诱导型EC-Akt转基因小鼠中，新生内膜形成的减弱程度较小，这表明一些血管保护作用不依赖于NO。实际上，Akt的内皮细胞激活导致结扎动脉中内皮细胞凋亡减少。免疫染色显示，血管损伤后诱导型EC-Akt转基因小鼠的炎症和增殖变化减少。这些发现表明，Akt的内皮细胞激活通过增加NO生成、保留功能性内皮细胞层以及抑制血管壁的炎症和增殖变化来抑制病变形成。这些结果表明，仅增强内皮细胞Akt活性在血管损伤后可能具有治疗益处。
