title: Development and characterisation of novel fentanyl-delta opioid receptor antagonist based bivalent ligands.
abstract: BACKGROUND
  Opioid tolerance is a limiting factor in chronic pain. Delta opioid peptide (DOP)(δ) receptor antagonism has been shown to reduce tolerance. Here, the common clinical mu opioid peptide (MOP)(µ) receptor agonist fentanyl has been linked to the DOP antagonist Dmt-Tic (2',6'-dimethyl-L-tyrosyl-1,2,3,4-tetrahydrisoquinoline-3-carboxylic acid) to create new bivalent compounds.
  
  
  METHODS
  Binding affinities of bivalents(#9, #10, #11, #12 and #13) were measured in Chinese hamster ovary (CHO) cells expressing recombinant human MOP, DOP, Kappa opioid peptide (KOP)(κ) and nociceptin/orphanin FQ opioid peptide (NOP) receptors. Functional studies, measuring GTPγ[(35)S] or β-arrestin recruitment, were performed in membranes or whole cells respectively expressing MOP and DOP.
  
  
  RESULTS
  The new bivalents bound to MOP (pKi : #9:7.31; #10:7.58; #11:7.91; #12:7.94; #13:8.03) and DOP (#9:8.03; #10:8.16; #11:8.17; #12:9.67; #13:9.71). In GTPγ[(35)S] functional assays, compounds #9(pEC50:6.74; intrinsic activity:0.05) #10(7.13;0.34) and #11(7.52;0.27) showed weak partial agonist activity at MOP. Compounds #12 and #13, with longer linkers, showed no functional activity at MOP. In antagonist assays at MOP, compounds #9 (pKb:6.87), #10(7.55) #11(7.81) #12(6.91) and #13(7.05) all reversed the effects of fentanyl. At DOP, all compounds showed antagonist affinity (#9:6.85; #10:8.06; #11:8.11; #12:9.42; #13:9.00), reversing the effects of DPDPE ([D-Pen(2,5)]enkephalin). In β-arrestin assays, compared with fentanyl (with response at maximum concentration (RMC):13.62), all compounds showed reduced ability to activate β-arrestin (#9 RMC:1.58; #10:2.72; #11:2.40; #12:1.29; #13:1.58). Compared with fentanyl, the intrinsic activity was: #9:0.12; #10:0.20; #11:0.18; #12:0.09 and #13:0.12.
  
  
  CONCLUSIONS
  The addition of a linker between fentanyl and Dmt-Tic did not alter the ability to bind to MOP and DOP, however a substantial loss in MOP functional activity was apparent. This highlights the difficulty in multifunctional opioid development.
authors: Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
authors: M F
authors: MF
authors: Bird
authors: Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA.
authors: R S
authors: RS
authors: Vardanyan
authors: Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA.
authors: V J
authors: VJ
authors: Hruby
authors: Department of Medical Sciences, Section of Pharmacology, University of Ferrara and Italian Institute of Neuroscience, Ferrara, Italy.
authors: G
authors: G
authors: Calò
authors: Department of Chemical and Pharmaceutical Sciences and LTTA (Laboratorio per le Tecnologie delle Terapie Avanzate), University of Ferrara, Ferrara, Italy.
authors: R
authors: R
authors: Guerrini
authors: Department of Chemical and Pharmaceutical Sciences and LTTA (Laboratorio per le Tecnologie delle Terapie Avanzate), University of Ferrara, Ferrara, Italy.
authors: S
authors: S
authors: Salvadori
authors: Department of Chemical and Pharmaceutical Sciences and LTTA (Laboratorio per le Tecnologie delle Terapie Avanzate), University of Ferrara, Ferrara, Italy.
authors: C
authors: C
authors: Trapella
authors: Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
authors: J
authors: J
authors: McDonald
authors: Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK.
authors: D J
authors: DJ
authors: Rowbotham
authors: Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester LE2 7LX, UK dgl3@le.ac.uk.
authors: D G
authors: DG
authors: Lambert
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004151:Dipeptides / Q000494:pharmacology*; D055808:Drug Discovery; D005283:Fentanyl / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D008024:Ligands; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors* / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000502:physiology; D044005:Tetrahydroisoquinolines / Q000494:pharmacology*; D000071557:beta-Arrestins
chemical_list: C446951:2',6'-dimethyltyrosyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid; D019390:Arrestins; D004151:Dipeptides; D008024:Ligands; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D044005:Tetrahydroisoquinolines; D000071557:beta-Arrestins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D005283:Fentanyl
keywords: delta receptors; fentanyl; mu receptors; opioid; pharmacology - analgesics opioid