Thymosin β4 Induces Endothelial Progenitor Cell Migration via PI3K/Akt/eNOS Signal Transduction Pathway

Thymosin beta 4, a G-actin-sequestering peptide, has been shown to play an important role in cell migration. However, little is known about the effect of thymosin beta 4 on circulating endothelial progenitor cell (EPC) directional migration, which is essential for EPC-mediated reendothelialization and neovascularization. In our study, using a transwell migration assay, we showed that thymosin beta 4 induced EPC migration in a concentration-dependent manner. Western blot analysis revealed that treatment of EPCs with thymosin beta 4 resulted in a time and concentration-dependent phosphorylation of Akt, endothelial nitric oxide synthase (eNOS), and extracellular signal-regulated kinase (ERK)1/2. Functional analysis showed that thymosin beta 4-induced EPC migration was blocked by phosphatidylinositol 3-kinase inhibitors (LY294002 or wortmannin) or eNOS inhibitor (N omega-nitro-L-arginine methyl ester) but was not significantly attenuated by mitogen-activated protein kinase (MAPK)/ERK inhibitor (PD98059). These findings suggest that thymosin beta 4 stimulates EPC directional migration via phosphatidylinositol 3-kinase/Akt/eNOS. rather than via MAPK/ERK signal transduction pathway.