Erythropoietin Increases Endothelial Biosynthesis of Tetrahydrobiopterin by Activation of Protein Kinase Bα/Akt1
Erythropoietin Increases Endothelial Biosynthesis of Tetrahydrobiopterin by Activation of Protein Kinase Bα/Akt1
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DOI：
10.1161/hypertensionaha.108.114041
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发表时间：
2008-07-01
期刊：
影响因子：
8.3
通讯作者：
Katusic, Zvonimir S.
中科院分区：
文献类型：
--
作者：
d'Uscio, Livius V.;Katusic, Zvonimir S.
四氢生物蝶呤（BH 4）是内皮细胞NO合酶活性所必需的辅因子。近年来研究表明，促红细胞生成素（EPO）的血管保护作用依赖于内皮NO合酶的激活。因此，我们的目的是表征EPO对血管壁中BH 4生物合成的影响。用重组人EPO（1 - 50 U/mL）孵育分离的C57 BL/6 J小鼠睾丸18小时，引起细胞内BH 4水平和GTP-环化水解酶I活性的浓度依赖性增加。在5 U/mL的治疗浓度下检测到BH 4的最大生物合成。内皮细胞的去除废除EPO诱导的BH 4的生物合成，表明血管内皮细胞是BH 4的主要来源。选择性磷脂酰肌醇3-激酶抑制剂渥曼青霉素治疗显着减少促红细胞生成素刺激的BH 4生物合成。EPO对血管GTP-环化水解酶I活性、BH 4产生和内皮NO合酶磷酸化的刺激作用也在用重组人EPO治疗的小鼠体内检测到。EPO的这些作用在蛋白激酶B α/Akt 1缺陷小鼠中被消除。此外，EPO显著增加了Akt 1缺陷小鼠的收缩压和循环血小板数量。我们的研究结果表明，促红细胞生成素刺激血管内皮细胞中BH 4的生物合成，并且BH 4水平的增加是由BH 4通过磷脂酰肌醇3-激酶/Akt 1途径的从头生物合成引起的。这种效应很可能是为了提供EPO诱导的内皮NO合酶活性升高所必需的辅因子的最佳细胞内浓度。（高血压。2008;52：93-99.）
Tetrahydrobiopterin (BH4) is an essential cofactor required for enzymatic activity of endothelial NO synthase. Recently, it has been shown that vascular protective effects of erythropoietin (EPO) are dependent on activation of endothelial NO synthase. Therefore, our objective was to characterize the effect of EPO on the biosynthesis of BH4 in the vascular wall. Incubation of isolated C57BL/6J mouse aortas for 18 hours with recombinant human EPO (1 to 50 U/mL) caused a concentration-dependent increase in intracellular BH4 levels and activity of GTP-cyclohydrolase I. Maximal biosynthesis of BH4 was detected at therapeutic concentrations of 5 U/mL. Removal of the endothelium abolished EPO-induced biosynthesis of BH4 demonstrating that the vascular endothelium is a major source of BH4. Treatment with a selective phosphatidylinositol 3-kinase inhibitor wortmannin significantly reduced BH4 biosynthesis stimulated by EPO. The stimulatory effect of EPO on vascular GTP-cyclohydrolase I activity, BH4 production, and phosphorylation of endothelial NO synthase was also detected in vivo in mice treated with recombinant human EPO. These effects of EPO were abolished in protein kinase B alpha/Akt1-deficient mice. In addition, EPO significantly increased systolic blood pressure and the number of circulating platelets in Akt1-deficient mice. Our results demonstrate that EPO stimulates biosynthesis of BH4 in vascular endothelium and that the increase in BH4 levels is caused by de novo biosynthesis of BH4 via the phosphatidylinositol 3-kinase/Akt1 pathway. This effect is most likely designed to provide optimal intracellular concentration of the cofactor necessary for EPO-induced elevation of endothelial NO synthase activity. (Hypertension. 2008;52:93-99.)