The Impact of P2Y-Mediated Activation on Release of Angiogenic Proteins by Platelets from Healthy Individuals.

The storage and release by platelets of the pro-angiogenic protein, vascular endothelial growth factor (VEGF) and the anti-angiogenic protein, endostatin may influence not only wound healing but also tumor angiogenesis and metastasis. The intra-platelet mechanisms and platelet activators that control angiogenic protein release are incompletely elucidated. Previous work demonstrated that the proteinase-activated receptors (PARs), PAR-1 and PAR-4 differentially impact platelet release of these angiogenic proteins (Ma et al., PNAS 102:216). We determined the influence of the adenosine diphosphate (ADP) receptors, P2Y1 and P2Y12 on platelet release of VEGF and endostatin. Minimally altered whole blood from healthy volunteers was incubated with ADP alone [12.5 μM] or in combination with a reversible P2Y1 antagonist [MRS2179 (1.25 mM)] or a reversible P2Y12 antagonist [cangrelor (1mM)]. VEGF and endostatin release was measured with the use of an ELISA assay. ADP-induced activation of platelets increased the concentration of VEGF released by an average of 19.7 +/− 14 ng/mL (p= 0.019) but did not change the concentration of endostatin. Inhibition of the P2Y12 receptor prevented the ADP mediated release of VEGF and decreased VEGF release by 27.9 +/− 14 ng/ml (p=0.005) whereas inhibition of the P2Y1 receptor did not significantly reduce the release of VEGF (p=0.3, mean decrease 14.3 +/− 30 ng/ml) relative to ADP stimulated control. In summary, ADP-induced activation of platelets leads to the release of VEGF but not endostatin. Release of VEGF is attenuated by a P2Y12 but not a P2Y1 receptor antagonist. Accordingly, activation of platelets by ADP appears to be pro-angiogenic and inhibition by a P2Y12 antagonist should attenuate this effect.