Kanda Shigeru, Miyata Yasuyoshi, Mochizuki Yasushi, Matsuyama Toshifumi, Kanetake Hiroshi
Division of Endothelial Cell Biology and Cytokine Signaling, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Science, Nagasaki, Japan.
Cancer Res. 2005 Aug 1;65(15):6820-7. doi: 10.1158/0008-5472.CAN-05-0522.
The angiopoietin (Ang)/Tie2 system is implicated in blood vessel formation and maturation. However, the mitogenic effects of angiopoietins remain to be elucidated. Here, we show that Ang1 is mitogenic for cultured endothelial cells. Ang1 dose-dependently induced the proliferation and increased the labeling index of a murine brain capillary endothelial cell line, IBE cells. Ang1 also increased the labeling index of human umbilical vein endothelial cells (HUVEC). Ang1 up-regulated the expression of cyclin D1 in both of these cells. Ang1 activated mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) in IBE cells and HUVECs. Activated PI3K was associated with c-Fes protein tyrosine kinase in these cells, but not with Tie2. p70 S6 kinase (p70 S6K) was activated by Ang1-treatment, although this activation was blocked by a PI3K inhibitor, LY294002. Simultaneous treatment of cells with PD98059 (MAPK/extracellular regulated kinase kinase inhibitor) and rapamycin (mTOR inhibitor) completely blocked Ang1-induced mitogenic activity for IBE cells and HUVECs. Although Ang2 at high concentration weakly activated Tie2 and p70 S6K, it failed to activate Ras and MAPK, or to induce cell proliferation. Taken together, these findings indicate that Ang1 exerts mitogenic activity on endothelial cells, which requires activation of both MAPK and p70 S6K.
血管生成素（Ang）/Tie2系统与血管形成和成熟有关。然而，血管生成素的促有丝分裂作用仍有待阐明。在此，我们表明Ang1对培养的内皮细胞具有促有丝分裂作用。Ang1以剂量依赖的方式诱导小鼠脑毛细血管内皮细胞系IBE细胞增殖并增加其标记指数。Ang1还增加了人脐静脉内皮细胞（HUVEC）的标记指数。Ang1上调了这两种细胞中细胞周期蛋白D1的表达。Ang1在IBE细胞和HUVEC中激活了丝裂原活化蛋白激酶（MAPK）和磷脂酰肌醇3激酶（PI3K）。在这些细胞中，活化的PI3K与c-Fes蛋白酪氨酸激酶相关，但与Tie2无关。p70 S6激酶（p70 S6K）通过Ang1处理被激活，尽管这种激活被PI3K抑制剂LY294002阻断。用PD98059（MAPK/细胞外调节激酶激酶抑制剂）和雷帕霉素（mTOR抑制剂）同时处理细胞完全阻断了Ang1对IBE细胞和HUVEC的促有丝分裂活性。尽管高浓度的Ang2弱激活了Tie2和p70 S6K，但它未能激活Ras和MAPK，也未能诱导细胞增殖。综上所述，这些发现表明Ang1对内皮细胞发挥促有丝分裂活性，这需要MAPK和p70 S6K的激活。
