The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory for Oral Biomedicine Ministry of Education, Wuhan University, Wuhan, China.
PLoS One. 2013 Sep 9;8(9):e74464. doi: 10.1371/journal.pone.0074464. eCollection 2013.
Hypoxia, ephrin-A1 and endothelial nitric oxide synthase (eNOS) have been proved to play critical roles in tumor angiogenesis. However, how ephrin-A1 is regulated by hypoxia and whether ephrin-A1 cooperates with eNOS in modulation of angiogenesis remain to be addressed in details. Here we demonstrated that both ephrin-A1 in squamous cell carcinoma cells (SCC-9) and especially soluble ephrin-A1 in the supernatants were up-regulated under hypoxic condition. An increased nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs) was observed in ephrin-A1-induced angiogenesis which was reversed after co-culture with eNOS specific inhibitor, N-nitro-L-arginine methyl ester hydrochloride (L-NAME). Western blot analysis confirmed that both phosphorylation of Akt(Ser473) and eNOS(Ser1177) were up-regulated in ephrin-A1-stimulated HUVECs, with the total eNOS expression unchanged. The specific inhibitor of phosphatidylinositol 3-kinase (PI3K), LY294002, significantly down-regulated ephrin-A1-induced expression of phosphorylated Akt(Ser473) as well as phosphorylation of eNOS(Ser1177). These results revealed a possible novel mechanism whereby ephrin-A1 is regulated in tumor microenvironment and promotes angiogenesis through a coordinated cross-talk with PI3K/Akt-dependent eNOS activation which may relate to normal vascular development and tumor neovascularization.
缺氧、ephrin-A1 和内皮型一氧化氮合酶（eNOS）已被证明在肿瘤血管生成中发挥关键作用。然而，ephrin-A1 如何受缺氧调节，以及 ephrin-A1 是否与 eNOS 合作调节血管生成，仍需要详细研究。在这里，我们证明了缺氧条件下鳞状细胞癌细胞（SCC-9）中的 ephrin-A1 及其上清液中的可溶性 ephrin-A1 均上调。在 ephrin-A1 诱导的血管生成中观察到人脐静脉内皮细胞（HUVEC）中一氧化氮（NO）产生增加，在用 eNOS 特异性抑制剂 N-硝基-L-精氨酸甲酯盐酸盐（L-NAME）共培养后，这种增加被逆转。Western blot 分析证实，ephrin-A1 刺激的 HUVECs 中 Akt（Ser473）和 eNOS（Ser1177）的磷酸化均上调，而总 eNOS 表达不变。磷脂酰肌醇 3-激酶（PI3K）的特异性抑制剂 LY294002 显著下调了 ephrin-A1 诱导的磷酸化 Akt（Ser473）和磷酸化 eNOS（Ser1177）的表达。这些结果揭示了一种可能的新机制，即 ephrin-A1 在肿瘤微环境中受到调节，并通过与 PI3K/Akt 依赖性 eNOS 激活的协调交叉对话促进血管生成，这可能与正常血管发育和肿瘤新生血管形成有关。
