Abstract 534: GPR30 Stimulates Capillary Formation by Human Endothelial Progenitor Cells
Estradiol (E2) induces vascular repair by promoting endothelial progenitor cell (EPC) growth and capillary formation. Based on our previous findings that the capillary stimulating effects of E2 are mimicked by its non-permeable analog, BSA-tagged E2, we hypothesize that the stimulatory effects are potentially mediated via the newly discovered membrane bound estrogen receptor (ER) GPR30. To investigate this, we assessed capillary formation by EPC derived endothelial cells in response to E2, and GPR30 agonists (G1) and antagonist (G15) in a matrigel based assay. Capillary formation was assessed microscopically by quantifying junction/sprout formation and capillary length. E2 (10nM) increased EPC-induced capillary formation by 126 ± 5% and these effects were mimicked by G1 (stimulated by 133 ± 8.9% and 210 ± 7.2% by 1 and 10 nM, respectively) and propyl-pyrazole-triol [PPT; stimulated by 143 ± 9%; 100 nM; ER-α agonist], but not by diarylpropionitrile (ER-β agonist). The stimulatory effects of estradiol, G1 and PPT were significantly (p<.05) abrogated by G15 (20nM), a GPR30 antagonist, suggesting a role for GPR30 in mediating the capillary stimulatory effects of E2. Interestingly, the stimulatory of estradiol, PPT and G1 were also abrogated by methyl-piperidino-pyrazole (ER-α antagonist), implying that the stimulatory effects of E2 are mediated via cross-talk between GPR30 and membrane bound ER-α. Because, receptor tyrosine kinase (RTK), hemeoxygenase (HO), and G-protein coupled mechanisms are involved in capillary formation we investigated their role in GPR30 induced capillary formation. The stimulatory effects of G1 were blocked by SU5416 (RTK inhibitor), ZnPP (HO inhibitor), pertusis toxin (G protein pathway inhibitor), and LY294002 (Akt pathway inhibitor). Moreover, treatment of EPCs with G1 induced expression of phosphorylated-Akt and HO-1, but not MAPK. We conclude that E2 via GPR30 or GPR30-coupled ER-α promotes EPC-mediated capillary formation by a mechanism that involves non-genomic activation of RTKs and HO-1 activation. E2 in particular and GPR30 agonists in general may promote healing of injured vascular beds by promoting EPC activity leading to more rapid endothelial recovery and capillary formation following injury.
- © 2012 by American Heart Association, Inc.