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Papers of the Week

Papers: 7 May 2022 - 13 May 2022

Pharmacology/Drug Development


Front Pharmacol


Pharmacology of Kappa Opioid Receptors: Novel Assays and Ligands.


Sturaro C, Malfacini D, Argentieri M, Djeujo FM, Marzola E, Albanese V, Ruzza C, Guerrini R, Calo' G, Molinari P
Front Pharmacol. 2022; 13:873082.
PMID: 35529436.


The present study investigated the pharmacology of the human kappa opioid receptor using multiple assays, including calcium mobilization in cells expressing chimeric G proteins, the dynamic mass redistribution (DMR) label-free assay, and a bioluminescence resonance energy transfer (BRET) assay that allows measurement of receptor interaction with G protein and β-arrestin 2. In all assays, dynorphin A, U-69,593, and [D-Pro]dyn(1-11)-NH behaved as full agonists with the following rank order of potency [D-Pro]dyn(1-11)-NH > dynorphin A ≥ U-69,593. [Dmt,Tic]dyn(1-11)-NH behaved as a moderate potency pure antagonist in the kappa-β-arrestin 2 interaction assay and as low efficacy partial agonist in the other assays. Norbinaltorphimine acted as a highly potent and pure antagonist in all assays except kappa-G protein interaction, where it displayed efficacy as an inverse agonist. The pharmacological actions of novel kappa ligands, namely the dynorphin A tetrameric derivative PWT2-Dyn A and the palmitoylated derivative Dyn A-palmitic, were also investigated. PWT2-Dyn A and Dyn A-palmitic mimicked dynorphin A effects in all assays showing similar maximal effects but 3-10 fold lower potency. In conclusion, in the present study, multiple assays for the kappa receptor have been set up and pharmacologically validated. In addition, PWT2-Dyn A and Dyn A-palmitic were characterized as potent full agonists; these compounds are worthy of further investigation for those conditions in which the activation of the kappa opioid receptor elicits beneficial effects e.g. pain and pruritus.