Endothelium-derived prostacyclin and nitric oxide elevate platelet cyclic nucleotide levels and maintain quiescence. We previously demonstrated a synergistic relationship exists between cyclic nucleotides and P2Y receptor inhibition. A number of clinically approved drug classes can modulate cyclic nucleotide tone in platelets including activators of NO-sensitive guanylyl cyclase (GC) and phosphodiesterase (PDE) inhibitors. However, the doses required to inhibit platelets produce numerous side effects including headache.
We investigated using GC-activators in combination with P2Y receptor antagonists as a way to selectively amplify the anti-thrombotic effect of both drugs.
In vitro light transmission aggregation and platelet adhesion under flow were performed on washed platelets and platelet rich plasma. Aggregation in whole blood and a ferric chloride-induced arterial thrombosis model were also performed.
The GC-activator BAY-70 potentiated the action of the P2Y receptor inhibitor prasugrel active metabolite in aggregation and adhesion studies and was associated with raised intra-platelet cyclic nucleotide levels. Furthermore, mice administered sub-maximal doses of the GC activator cinaciguat together with the PDE inhibitor dipyridamole and prasugrel, showed significant inhibition of ex vivo platelet aggregation and significantly reduced in vivo arterial thrombosis in response to injury without alteration in basal carotid artery blood flow.
Using in vitro, ex vivo and in vivo functional studies, we show that low dose GC activators synergise with P2Y inhibition to produce powerful anti-platelet effects without altering blood flow. Therefore modulation of intra-platelet cyclic nucleotide levels alongside P2Y inhibition can provide a strong, focused anti-thrombotic regimen whilst minimising vasodilator side effects.

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