Nishimatsu H, Suzuki E, Nagata D, Moriyama N, Satonaka H, Walsh K, Sata M, Kangawa K, Matsuo H, Goto A, Kitamura T, Hirata Y
Department of Urology, Faculty of Medicine, University of Tokyo, Japan.
Circ Res. 2001 Jul 6;89(1):63-70. doi: 10.1161/hh1301.092498.
To study the mechanisms by which adrenomedullin (AM) induces endothelium-dependent vasorelaxation, we examined whether AM-induced endothelium-dependent vasodilation was mediated by the phosphatidylinositol 3-kinase (PI3K)/Akt-dependent pathway in rat aorta, because it was recently reported that PI3K/Akt was implicated in the activation of endothelial NO synthase. AM-induced vasorelaxation in thoracic aorta with intact endothelium was inhibited by pretreatment with PI3K inhibitors to the same level as that in endothelium-denuded aorta. AM elicited Akt phosphorylation in a time- and dose-dependent manner. AM-induced Akt phosphorylation was inhibited by pretreatment with a calmodulin-dependent protein kinase inhibitor as well as with PI3K inhibitors. When an adenovirus construct expressing a dominant-negative Akt mutant (Ad/dnAkt) was injected into abdominal aortas so that the mutant was expressed predominantly in the endothelium layer, AM-induced vasodilation was diminished to the same level as that in endothelium-denuded aortas. Finally, AM-induced cGMP production, which was used as an indicator for NO production, was suppressed by PI3K inhibition or by Ad/dnAkt infection into the endothelium. These results suggested that AM induced Akt activation in the endothelium via the Ca(2+)/calmodulin-dependent pathway and that this was implicated in the production of NO, which in turn induced endothelium-dependent vasodilation in rat aorta.
为了研究肾上腺髓质素（AM）诱导内皮依赖性血管舒张的机制，我们检测了AM诱导的内皮依赖性血管舒张是否由大鼠主动脉中的磷脂酰肌醇3激酶（PI3K）/Akt依赖性途径介导，因为最近有报道称PI3K/Akt与内皮型一氧化氮合酶的激活有关。用PI3K抑制剂预处理可抑制完整内皮的胸主动脉中AM诱导的血管舒张，使其达到与去内皮主动脉相同的水平。AM以时间和剂量依赖性方式引起Akt磷酸化。用钙调蛋白依赖性蛋白激酶抑制剂以及PI3K抑制剂预处理可抑制AM诱导的Akt磷酸化。当将表达显性负性Akt突变体（Ad/dnAkt）的腺病毒构建体注入腹主动脉，使突变体主要在内皮层表达时，AM诱导的血管舒张减弱至与去内皮主动脉相同的水平。最后，PI3K抑制或向内皮中感染Ad/dnAkt可抑制AM诱导的cGMP生成（用作NO生成的指标）。这些结果表明，AM通过Ca(2+)/钙调蛋白依赖性途径在内皮中诱导Akt激活，这与NO生成有关，进而诱导大鼠主动脉中的内皮依赖性血管舒张。
