Formyl peptide receptor (FPR) biased agonists as novel cardioprotection from myocardial ischaemia-reperfusion (I-R) injury.

Introduction: Biased G-protein-coupled receptors (GPCR) signalling has revolutionised drug discovery field, especially its capacity to limit receptor-mediated adverse effects. FPRs are integral to inflammation regulation, thus are attractive therapeutic targets for myocardial I-R injury. Methods & Results: We tested the hypothesis that biased FPR agonists provide superior cardioprotection in vivo. Using a preclinical mouse model of myocardial I-R injury (LAD ligation), the novel FPR agonist Cmpd17b (50 mg/kg/day, i.p.) elicited significant cardioprotection when administered prior to reperfusion. Cmpd17b reduced infarct size from 44+/-4% to 29+/-5% (24 h), cardiac neutrophil from 3.5+/-0.4 to 1.9+/-0.2AU (48 h), and cardiac apoptosis from 1.5+/-0.1 to 1.1+/-0.1AU (apoptotic/non-apoptotic cells, 7 days), when compare to vehicle-treated I-R mice (n=6-10; p<0.05 vs vehicle-treated I-R mice, One way ANOVA with Tukey's post-hoc test). In contrast, another FPR agonist Amgen compound43 (Cmpd43, 50 mg/kg/day, i.p.) was devoid of cardioprotection on all endpoints. Signalling fingerprints of both agonists across pERK, pAktT308, pAktS473, Ca2+-mobilisation at FPR1 and FPR2 were systemically assessed in CHO cells stablyexpressing human FPR1 or FPR2. This revealed for the first time that relative to Cmpd43, Cmpd17b signalling at both hFPRs was significantly biased away, (by 30-fold) from intracellular Ca2+-mobilisation (which can trigger inflammation and cardiomyocyte death). Stimulation of ERK1/2-Akt cell survival kinases however remained intact (n=5-6, p<0.05 vs Cmpd43). Conclusion(s): These findings demonstrate ligand-selective cardioprotection with dual FPR1/FPR2-agonist Cmpd17b. This breakthrough observation is the first to demonstrate GPCR-agonist bias in the context of cardioprotection in vivo, suggesting a new approach for development of smallmolecule FPR-pharmacotherapies for treating myocardial I-R injury.