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Bifunctional μ/δ Opioid Peptides: Variation of the Type and Length of the Linker Connecting the Two Components
Author(s) -
Ding Jinguo,
Lemieux Carole,
Chung Nga N.,
Schiller Peter W.
Publication year - 2012
Publication title -
chemical biology and drug design
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.59
H-Index - 77
eISSN - 1747-0285
pISSN - 1747-0277
DOI - 10.1111/j.1747-0285.2011.01268.x
Subject(s) - agonist , bifunctional , chemistry , linker , stereochemistry , partial agonist , antagonist , μ opioid receptor , endogenous agonist , receptor , biochemistry , computer science , dopamine receptor d1 , operating system , catalysis
On the basis of evidence that opioid compounds with a mixed μ agonist/δ antagonist profile may produce an antinociceptive effect with low propensity to induce side effects, bifunctional opioid peptides containing the μ agonist H‐Dmt‐ d ‐Arg‐Phe‐Lys‐NH 2 ([Dmt 1 ]DALDA; Dmt = 2′,6′‐dimethyltyrosine) connected tail‐to‐tail via various α,ω‐diaminoalkyl‐ or diaminocyclohexane linkers to the δ antagonists H‐Tyr‐TicΨ[CH 2 ‐NH]Cha‐Phe‐OH (TICP[Ψ]; Cha = cyclohexylalanine, Tic = 1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid), H‐Dmt‐Tic‐OH or H‐Bcp‐Tic‐OH (Bcp = 4′‐[ N ‐((4′‐phenyl)phenethyl)carboxamido]phenylalanine) were synthesized and pharmacologically characterized in vitro . Bifunctional [Dmt 1 ]DALDA→NH‐(CH 2 ) n ‐NH←TICP[Ψ] compounds ( n = 0–12) showed decreasing μ and δ receptor binding affinities with increasing linker length. As expected, several of the bifunctional peptides were μ agonist/δ antagonists with low nanomolar μ and δ receptor binding affinities. However, compounds with unexpected opioid activity profiles, including a μ partial agonist/δ partial agonist, μ antagonist/δ antagonists and μ agonist/δ agonists, were also identified. These results indicate that the binding affinities and intrinsic efficacies of these bifunctional compounds at both receptors depend on the length and type of the linker connecting the μ and δ components. An important recommendation emerging from this study is that the in vitro activity profiles of bifunctional compounds containing an agonist and an antagonist component connected via a linker need to be determined prior to their pharmacological evaluation in vivo .