Department of Molecular and Medical Pharmacology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Br J Pharmacol. 2010 Feb;159(4):928-38. doi: 10.1111/j.1476-5381.2009.00594.x. Epub 2010 Jan 29.
Hyperglycaemia is known to reduce nitric oxide (NO) bioavailability by modulating endothelial NO synthase (eNOS) activity, and polyphenols are believed to have cardiovascular benefit. One possible mechanism could be through interaction with eNOS.
The effects of the oligomerized polyphenol oligonol on eNOS phosphorylation status and activity were examined in porcine aortic endothelial cells cultured in high glucose concentrations.
Exposure to high glucose concentrations strongly inhibited eNOS phosphorylation at Ser-1177 and dephosphorylation at Thr-495 in bradykinin (BK)-stimulated cells. These inhibitory effects of high glucose were significantly prevented by treatment with oligonol. Akt and p38 mitogen-activated protein kinase (MAPK) were activated in BK-stimulated cells. High glucose inhibited Akt activation but enhanced p38 MAPK activation, both of which were reversed by oligonol treatment. The phosphatidylinositol 3-kinase inhibitor wortmannin blocked the reversal by oligonol of phosphorylation at Ser-1177, but not dephosphorylation at Thr-495, in BK-stimulated cells exposed to high glucose. The effect of oligonol on BK dephosphorylation under high glucose was mimicked by protein kinase C (PKC) epsilon-neutralizing peptides. These data suggest that the effects of oligonol on high glucose-induced attenuation of eNOS Ser-1177 phosphorylation and Thr-495 dephosphorylation may be regulated by Akt activation and PKCepsilon inhibition respectively. Oligonol also prevented high glucose-induced attenuation of BK-stimulated NO production.
Oligonol prevented the impairment of eNOS activity induced by high glucose through reversing altered eNOS phosphorylation status. This mechanism may underlie the beneficial cardiovascular health effects of this oligomerized polyphenol.
高血糖可通过调节内皮型一氧化氮合酶（eNOS）活性来降低一氧化氮（NO）的生物利用度，而多酚类物质被认为对心血管有益。其可能的机制之一是通过与 eNOS 相互作用。
在高糖浓度下培养的猪主动脉内皮细胞中，检测低聚多酚 Oligonol 对 eNOS 磷酸化状态和活性的影响。
高糖浓度强烈抑制 BK 刺激细胞中 eNOS 的 Ser-1177 磷酸化和 Thr-495 去磷酸化。Oligonol 处理可显著预防高糖的这些抑制作用。Akt 和 p38 丝裂原活化蛋白激酶（MAPK）在 BK 刺激的细胞中被激活。高糖抑制 Akt 激活，但增强 p38 MAPK 激活，这两种激活均被 oligonol 处理逆转。PI3K 抑制剂wortmannin 阻断了 oligonol 对高糖暴露的 BK 刺激细胞中 Ser-1177 磷酸化的逆转，但不阻断 Thr-495 的去磷酸化。Oligonol 在高糖条件下对 BK 去磷酸化的作用可被蛋白激酶 C（PKC）ε中和肽模拟。这些数据表明，oligonol 对高糖诱导的 eNOS Ser-1177 磷酸化和 Thr-495 去磷酸化的减弱作用可能分别受到 Akt 激活和 PKCε抑制的调节。Oligonol 还可预防高糖诱导的 BK 刺激的 NO 产生减弱。
Oligonol 通过逆转 eNOS 磷酸化状态的改变来防止高糖引起的 eNOS 活性受损。这种机制可能是这种低聚多酚对心血管健康有益的基础。
