Abstract 13471: The Angiogenic Factor Secretoneurin Activates VEGFR2 in Coronary Endothelial Cells by Operating as Endogenous Stimulator of VEGF Binding to Heparansulfate Proteoglycans
Recently it has been shown that gene therapy with the angiogenic neuropeptide Secretoneurin (SN) restores tissue integrity, function and perfusion in a mouse hind-limb ischemia model by induction of angiogenesis, arteriogenesis and vasculogenesis. Therefore we hypothesized that SN might also affect function of cardiac endothelial cells and exert beneficial effects in a rat model of myocardial infarction. In vivo, SN gene therapy was performed by intramyocardial injection of 100 µg SN-plasmid (or empty vector as control), shortly after ligation of the left anterior descending artery in Sprague-Dawley rats. SN prevented the anterior wall thinning (LVEDD 9.1 vs. 10.5 mm; p=0.04; LVESD 6.5 vs. 9.1 mm; p=0.002; n=11) and significantly improved cardiac function as revealed by histological analysis (capillaries/HPF 63.5±4 vs. 44.9±3.7; arterioles/HPF 8.5±0.5 vs. 5.8±0.6; fibrosis 21.65±1.6% vs. 35.37±2.8%; all p<0.001 and n=11); and echocardiographic measurement (ejection fraction 64.4±3.1% vs. 40.3±2.7%; p<0.001;; n=11). To investigate the effect of SN in cell culture, in vitro angiogenesis assays using human coronary artery endothelial cells (HCAEC) in the absence or presence of different concentrations of SN were performed. SN dose dependently induced angiogenesis. A specific SN- antibody and interestingly, a VEGF- antibody too, abolished the observed effect. Western blot analysis of HCAEC extracts revealed stimulation of MAPK by SN 100 ng/ml after 20 minutes and of Akt after 40 to 240 minutes, indicating involvement of the ERK1/2 and PI3-kinase/Akt signal transduction pathways. The SN induced MAPK activation could be blocked with a VEGF antibody as well as with the specific VEGFR2 inhibitor, SU1498. Receptor tyrosine kinase profiler assays and immunoprecipitation confirmed the SN mediated VEGFR2 activation. Binding studies with 125I-VEGF on HCAECs revealed an increase of mainly unspecific binding of VEGF to HCAECs in the presence of SN. The SN induced enhancement of VEGF binding to the extracellular matrix of HCAECs was annihilated by addition of heparinase. These results led to the hypothesis that SN activates VEGFR2 in coronary endothelial cells by operating as endogenous stimulator of VEGF binding to heparansulfate proteoglycans.
- © 2011 by American Heart Association, Inc.