Novel Mixed NOP/Opioid Receptor Peptide Agonists.

Salvatore Pacifico,Claudio Trapella,Martina Marangoni,Alessandro Arcovito,Romina Nassini,Erika Marzola,Valentina Albanese,Federica Ferrari,Remo Guerrini,Davide Malfacini,Delia Preti,Davide Fattori,Chiara Sturaro,Davide Illuminati,Chiara Ruzza,Victor A.D Holanda,Ettore Lo Cascio,Girolamo Calò ,Massimo Fabbri ,S Della Longa

doi:10.1021/acs.jmedchem.0c02062

Abstract

The nociceptin/orphanin FQ (N/OFQ)/N/OFQ receptor (NOP) system controls different biological functions including pain and cough reflex. Mixed NOP/opioid receptor agonists elicit similar effects to strong opioids but with reduced side effects. In this work, 31 peptides with the general sequence [Tyr/Dmt1,Xaa5]N/OFQ(1-13)-NH2 were synthesized and pharmacologically characterized for their action at human recombinant NOP/opioid receptors. The best results in terms of NOP versus mu opioid receptor potency were obtained by substituting both Tyr1 and Thr5 at the N-terminal portion of N/OFQ(1-13)-NH2 with the noncanonical amino acid Dmt. [Dmt1,5]N/OFQ(1-13)-NH2 has been identified as the most potent dual NOP/mu receptor peptide agonist so far described. Experimental data have been complemented by in silico studies to shed light on the molecular mechanisms by which the peptide binds the active form of the mu receptor. Finally, the compound exerted antitussive effects in an in vivo model of cough.

Highlights

Nociceptin/orphanin FQ (N/OFQ; FGGFTGARKSARKLANQ) is the endogenous ligand of the N/OFQ peptide (NOP) receptor.[1,2] N/OFQ and the NOP receptor display high structural homology with peptides and receptors of the opioid family but distinct pharmacology.[3]
We further investigate the possibility of generating a mixed NOP/opioid agonist based on the following evidence: (i) mixed NOP/kappa ligands can be obtained combining the C-terminal sequence of N/OFQ with the N-terminal of dynorphin A, where amino acids in positions 5 and 6 were important for receptor selectivity;[24] (ii)
Available protected amino acids were employed as synthetic precursors of the target peptides except for Fmoc2′,6′-dimethyl-tyrosine (Fmoc-Dmt-OH) that was instead synthesized in analogy to an approach previously published by Wang et al.[39] (Scheme S1 of the Supporting Information)

Summary

Introduction

Nociceptin/orphanin FQ (N/OFQ; FGGFTGARKSARKLANQ) is the endogenous ligand of the N/OFQ peptide (NOP) receptor.[1,2] N/OFQ and the NOP receptor display high structural homology with peptides and receptors of the opioid family but distinct pharmacology.[3]. The effects of N/OFQ and selective NOP agonists in analgesiometric assays are complex depending on the dose, administration route, type of pain, and animal species.[5,6] On the contrary, strong and consistent experimental evidence suggests that the simultaneous activation of NOP and opioid receptors elicits synergistic analgesic effects.[6,7] On these bases, mixed NOP/opioid receptor agonists (cebranopadol,[8,9] AT-121,10 BU10038,11 and BPR1M9712) have been developed and investigated for their antinociceptive properties. It was consistently demonstrated that these drugs elicit similar analgesic effects to strong opioids but with substantially reduced side effects including respiratory depression, tolerance, and abuse liability (see the recent review by Kiguchi et al.[13])

Results

Discussion

Conclusion