P2Y₁₂and EP3 antagonists promote the inhibitory effects of natural modulators of platelet aggregation that act via cAMP

Abstract

Several antiplatelet drugs that are used or in development as antithrombotic agents, such as antagonists of P2Y₁₂ and EP3 receptors, act as antagonists at G(i)-coupled receptors, thus preventing a reduction in intracellular cyclic adenosine monophosphate (cAMP) in platelets. Other antiplatelet agents, including vascular prostaglandins, inhibit platelet function by raising intracellular cAMP. Agents that act as antagonists at G(i)-coupled receptors might be expected to promote the inhibitory effects of agents that raise cAMP. Here, we investigate the ability of the P2Y₁₂ antagonists cangrelor, ticagrelor and prasugrel active metabolite (PAM), and the EP3 antagonist DG-041 to promote the inhibitory effects of modulators of platelet aggregation that act via cAMP. Platelet aggregation was measured by platelet counting in whole blood in response to the TXA₂ mimetic U46619, thrombin receptor activating peptide and the combination of these. Vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) was measured using a cytometric bead assay. Cangrelor always increased the potency of inhibitory agents that act by raising cAMP (PGI₂, iloprost, PGD₂, adenosine and forskolin). Ticagrelor and PAM acted similarly to cangrelor. DG-041 increased the potency of PGE₁ and PGE₂ as inhibitors of aggregation, and cangrelor and DG-041 together had more effect than either agent alone. Cangrelor and DG-041 were able to increase the ability of agents to raise cAMP in platelets as measured by increases in VASP-P. Thus, P2Y₁₂ antagonists and the EP3 antagonist DG-041 are able to promote inhibition of platelet aggregation brought about by natural and other agents that raise intracellular cAMP. This action is likely to contribute to the overall clinical effects of such antagonists after administration to man.

Blockade of the purinergic P2Y 12 receptor greatly increases the platelet inhibitory actions of nitric oxide

“…For example, it has been demonstrated that activation of platelet P2Y 12 receptors by ADP causes inhibition of platelet adenylyl cyclase, which reduces the ability of PGI 2 acting through prostaglandin IP receptors to elevate cAMP, and thus reduces platelet aggregation. Hence, blockade of platelet P2Y 12 receptors increases the sensitivity of platelets to the antiaggregatory and antisecretory effects of PGI 2 (8,9). This interaction is readily understandable, as both P2Y 12 receptors and PGI 2 have actions on a common signaling pathway, cAMP.…”

Post receptor determinants of acute platelet response to clopidogrel in patients with symptomatic myocardial ischemia

“…First, Fox et al [27] demonstrated that PGE 1 potentiated the anti-platelet effects of both cangrelor and clopidogrel. In a subsequent study from the same laboratory [29], it was also shown that the anti-aggregatory effects of the P2Y 12 inhibitors cangrelor, ticagrelor and the active metabolite of prasugrel were likely to be mediated, at least in part, by a potentiation of physiological activators of adenylate cyclase (such as PGI 2 /PGE 1 ). Furthermore, Cattaneo and Lecchi [28] had demonstrated that a substantial component of the effect of cangrelor in inhibiting platelet aggregation was engendered by reversing ADP-induced inhibition of adenylate cyclase signaling.…”

“…Indeed, a number of investigators have previously provided evidence that prostacyclin (PGI 2 ) and prostaglandin E 1 (PGE 1 ), powerful activators of platelet adenylate cyclase, potentiate clopidogrel effect [27][28][29].…”

Understanding the role of prostaglandin E2 in regulating human platelet activity in health and disease

“…Additionally, PGE 2 -mediated stimulation of EP3 decreased cAMP, consistent with its primary signaling in platelets being coupled to G i [73]. The selective EP3 antagonist DG-041 abolishes the pro-aggregatory effects of both sulprostone [58] and low concentrations of PGE 2 [56, 63, 74]. …”