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.

Cyclic stretch upregulates SDF-1alpha/CXCR4 axis in human saphenous vein smooth muscle cells.

Cyclic stretch (CS) mediates different cellular functions in vascular smooth muscle cells and involves in neointimal hyperplasia and subsequent atherosclerosis of vein grafts. Here, we investigated whether CS can modulate stromal cell-derived factor-1alpha (SDF-1alpha)/CXCR4 axis in human saphenous vein smooth muscle cells. We found CS induced the upregulation of SDF-1alpha and CXCR4 in human saphenous vein smooth muscle cells in vitro, which was dependent on PI3K/Akt/mTOR pathway. Furthermore, CS augmented human saphenous vein smooth muscle migration and focal adhesion kinase (FAK) activation by PI3K/Akt/mTOR pathway. Interestingly, the upregulation of SDF-1alpha/CXCR4 axis was instrumental in CS-induced saphenous vein smooth muscle cell migration and FAK activation, as showed by AMD3100, an inhibitor of SDF-1alpha/CXCR4 axis, partially but significantly blocked the CS-induced cellular effects. Thus, those data suggested SDF-1alpha/CXCR4 axis involves in CS-mediated cellular functions in human saphenous vein smooth muscle cells.

Nitric oxide induces heat shock protein 72 production and delayed protection against myocardial ischemia in rabbits via activating protein kinase C.

BACKGROUND: Nitric oxide (NO) is a biologically active molecule which has been reported to protect the heart against ischemia and reperfusion injury in different species. This study aimed to test the hypothesis that nitric oxide may induce the expression of heat shock protein 72 (HSP72) which may protect the heart against ischemia. METHODS: Rabbits were given intravenous saline or S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide donor, or Zaprinast, an inhibitor of cyclic guanosine monophosphate (GMP)-phosphodiesterase, which may increase myocardial cyclic GMP content. Twenty-four hours later, the rabbits were either sampled to measure HSP72, or induced with a 30-minute coronary occlusion followed by a 120-minute reperfusion, and then the infarct size was measured. Meanwhile, chelerythrine (CHE, an inhibitor of protein kinase C) was given intravenously 5 minutes before SNAP injection and the effect on HSP72 expression and infarct size was determined. RESULTS: Twenty-four hours after pretreatment, immunoblotting showed HSP72 expression increased in the SNAP group compared with control groups, and this was blocked by CHE. Myocardial infarct size in the SNAP group was smaller than that of the control group ((32.4 +/- 5.8)% vs (51.1 +/- 4.7)%, P < 0.05). Pretreated with CHE abolished the infarct size-limiting effect of SNAP ((46.0 +/- 5.1)%). Pretreatment with Zaprinast neither induced HSP72 expression nor reduced infarct size ((55.4 +/- 5.4)%). CONCLUSION: NO induced HSP72 expression and a delayed protection to the heart via the activities of protein kinase C by a cyclic GMP-independent pathway.