Akt-centered amplification loop plays a critical role in vascular endothelial growth factor/stromal cell-derived factor 1-α cross-talk and cardioprotection.

Background: Vascular endothelial growth factor (VEGF) is one of major mediators of angiogenesis and survival factor in some tissue, however, its direct effects on cardiomyocytes remain poorly understood.

Methods: Rat neonatal ventricular myocytes were cultured in vitro. Akt phosphorylation was measured by Western blotting; the expression of stromal cell-derived factor α (SDF-1α)/CXCR4 axis was evaluated by real-time PCR and Western blotting. LY294002 and AMD3100 were used to interfere with the signaling of VEGF and SDF-1α/CXCR4 axis. Cardiac myocytes viability and injury were evaluated by trypan blue staining and lactate dehydrogenase (LDH) release.

Results: Treatment of neonatal rat ventricular myocytes with VEGF induced phosphorylation of Akt in a dose and Flk-1 dependent manner. VEGF attenuated H2O2 induced cardiac myocyte death. The phosphoinositol-3-kinase (PI3K) inhibitor, LY294002 and Flk-1 antibody abolished the beneficial effects of VEGF on H2O2 induced cell death. In the mean time SDF-1α-CXCR4 axis was up-regulated by VEGF through PI3K-Akt signaling and contributed to the protective effects of VEGF on H2O2 induced cell death. Interestingly, SDF-1α also promoted production of VEGF in cultured cardiac myocytes and LY294002 reversed the up-regulation of VEGF induced by SDF-1α.

Conclusion: VEGF has direct protective effects on cardiomyocytes; a crosstalk between VEGF and SDF-1α through PI3K-Akt serves a survival role in cardiomyocytes in vitro.