Impaired adenylate cyclase signaling in acute myocardial ischemia: Impact on effectiveness of P2Y12 receptor antagonists

Abstract

IntroductionP2Y12 receptor antagonists reduce risk of thrombotic complications after stent implantation but increase bleeding risk. Activation of P2Y12 receptors by ADP causes Gi-protein-mediated inhibition of adenylate cyclase (AC), thus limiting platelet response to anti-aggregatory effect of prostacyclin (PGI2). However, P2Y12 blockade reverses this ADP-induced suppression of the platelet PGI2/AC signaling pathway. We previously demonstrated that impairment of this pathway predicts poor response to clopidogrel. ObjectivesTo identify clinical correlates of variability in PGI2/AC signaling, and to assess the impact of such variability on individual responses to the direct P2Y12 receptor antagonists ticagrelor (in vivo) and 2-methyl-thioadenosine-monophosphate (2MeSAMP) (in vitro). Patients/MethodsWe compared the inhibitory effects of prostaglandin E1 (PGE1) and the PGI2 analog Iloprost (Ilt) on platelet aggregation in whole blood samples from healthy control subjects (n = 17), and patients with stable angina pectoris (SAP; n = 35) or acute coronary syndromes (ACS; n = 23), with or without associated diabetes/hyperglycemia. ResultsCompared to control subjects, patients with ACS and – to a lesser extent – those with SAP, exhibited impaired responses to PGE1, accentuated in the presence of hyperglycemia. Efficacy of ticagrelor treatment, measured as change in platelet reactivity index, was directly related to pre-treatment PGE1 response, both at univariate and multivariate analysis. There was a strong correlation between extent of inhibition of platelet aggregation, whether by PGE1 or Ilt, and the anti-aggregatory effect of 2MeSAMP in vitro. ConclusionsThe integrity of PGI2/AC signaling, which is impaired in the presence of ACS and hyperglycemia, predetermines the anti-aggregatory efficiency of P2Y12 receptor antagonists.