Su Kuo-Hui, Tsai Jin-Yi, Kou Yu Ru, Chiang An-Na, Hsiao Sheng-Huang, Wu Yuh-Lin, Hou Hsin-Han, Pan Ching-Chian, Shyue Song-Kun, Lee Tzong-Shyuan
Department of Physiology, National Yang-Ming University, Taipei, Taiwan, ROC.
Cardiovasc Res. 2009 Jun 1;82(3):468-75. doi: 10.1093/cvr/cvp091. Epub 2009 Mar 23.
Valsartan, a selective angiotensin II type 1 receptor (AT1R) blocker, has beneficial effects in the cardiovascular system in part by its increase of nitric oxide (NO) bioavailability, yet the mechanisms are unclear. We investigated the molecular mechanisms underlying this effect in endothelial cells (ECs).
NO production was examined by Griess reagent assay, DAF-2 DA fluorescence staining and cGMP ELISA kits. Protein interaction was determined by western blotting and immunoprecipitation. Treating bovine or human aortic ECs with valsartan increased NO production, as evidenced by elevated level of stable NO metabolites and intracellular cGMP. Valsartan increased the phosphorylation but not the protein level of endothelial NO synthase (eNOS). Inhibition of phosphoinositide-3 kinase (PI3K)/Akt and Src pathways by specific inhibitors suppressed valsartan-induced NO release. In addition, valsartan increased the tyrosine residue phosphorylation of AT1R, which was attenuated by inhibition of Src but not PI3K activities. Valsartan also suppressed the interaction of eNOS and AT1R, which was blocked by Src or PI3K inhibition.
Valsartan-induced NO production in ECs is mediated through Src/PI3K/Akt-dependent phosphorylation of eNOS. Valsartan-induced AT1R phosphorylation depends on Src but not PI3K, whereas valsartan-induced suppression of AT1R-eNOS interaction depends on Src/PI3K/Akt signalling. These results indicate a novel vasoprotective mechanism of valsartan in upregulating NO production in ECs.
缬沙坦是一种选择性血管紧张素II 1型受体（AT1R）阻滞剂，其在心血管系统中具有有益作用，部分原因是它能提高一氧化氮（NO）的生物利用度，但其机制尚不清楚。我们研究了内皮细胞（ECs）中这种作用的分子机制。
通过格里斯试剂法、DAF-2 DA荧光染色和cGMP ELISA试剂盒检测NO生成。通过蛋白质印迹法和免疫沉淀法测定蛋白质相互作用。用缬沙坦处理牛或人主动脉内皮细胞可增加NO生成，稳定的NO代谢产物水平和细胞内cGMP升高证明了这一点。缬沙坦增加了内皮型一氧化氮合酶（eNOS）的磷酸化水平，但不增加其蛋白水平。用特异性抑制剂抑制磷酸肌醇-3激酶（PI3K）/Akt和Src途径可抑制缬沙坦诱导的NO释放。此外，缬沙坦增加了AT1R的酪氨酸残基磷酸化，抑制Src活性可减弱这种磷酸化，但抑制PI3K活性则无此作用。缬沙坦还抑制了eNOS与AT1R的相互作用，Src或PI3K抑制可阻断这种相互作用。
缬沙坦诱导内皮细胞产生NO是通过Src/PI3K/Akt依赖的eNOS磷酸化介导的。缬沙坦诱导的AT1R磷酸化依赖于Src而非PI3K，而缬沙坦诱导的AT1R-eNOS相互作用的抑制依赖于Src/PI3K/Akt信号通路。这些结果表明缬沙坦在上调内皮细胞NO生成方面具有一种新的血管保护机制。
