Brain derived neurotrophic factor induces endothelial cells angiogenesis through AKT and ERK1/2 signal pathway

Our previous studies have demonstrated the effects of brain derived neurotrophic factor (BDNF) on promoting proliferation of multiple myeloma (MM) cells and inducing angiogenesis in MM in vitro. To further investigate whether the PI3K/Akt and MEK1/ERK pathway play a role in the BDNF-induced angiogenesis in vitro and to explore the further molecular mechanisms, two ways to establish human myeloma xenograft animal model were developed, their advantages and disadvantages were elucidated. The phosphorylation of AKT and ERK1/2 were detected in human umbilical vein endothelial cells (HUVECs) by Western blot. The angiogenic activity in vitro was evaluated by transwell migration assay and tubule formation assay. Cell proliferation was determined by crystal violet staining. Cell apoptosis was detected by FITC-Annexin-V/PI double staining and flow cytometry. The results showed that the BDNF activated the PI3K/Akt and MEK1/ERK pathway in the time-dependent manner. Ly294002 and PD98059 blocked the activation of Akt and ERK1/2 respond to BDNF. 100 ng/ml BDNF significantly increased HUVEC tube formation, migration and proliferation in vitro at a similar degree of 25 ng/ml VEGF. Furthermore, tube formation of HUVECs toward BDNF was significantly inhibited by 57% and 40% with 20 micromol/L Ly294002 and 20 micromol/L PD98059 treatment, respectively. At the same time, Ly294002 and PD98059 reduced the BDNF-induced migration of HUVECs by 74% and 36%, respectively. While BDNF-induced survival was only blocked by Ly294002 and BDNF-induced proliferation was only inhibited by PD98059. It is concluded that BDNF promotes angiogenesis of HUVECs in vitro. ERK and Akt are two crucial events in BDNF-mediated signal transduction leading to HUVECs angiogenesis by different mechanisms. Moreover, the latter is more important.