title: Identification of stabilized dynorphin derivatives for suppressing tolerance in morphine-dependent rats.
abstract: OBJECTIVE
  Modulatory actions on morphine-induced effects, such as tolerance and withdrawal, have been noted for dynorphin A(1-13) [Dyn A(1-13)] and similar peptides. These are currently of limited therapeutic potential due to extensive metabolism by human metabolic enzymes resulting in a half-life of less than 1 min in human plasma. The purpose of this study was to identify stabilized dynorphin A (Dyn A) derivatives, to determine their metabolic routes in human plasma, and to assess whether the pharmacodynamic activity is retained.
  
  
  METHODS
  The stability of peptides in human plasma was tested using in vitro metabolism studies with and without enzyme inhibitors. Identification of the generated metabolites was performed by mass spectrometry after high performance liquid chromatography (HPLC) separation. The in vivo activity of a stabilized dynorphin was tested by tail-flick assay in morphine-tolerant rats.
  
  
  RESULTS
  Though amidation of the Dyn A(1-13) was able to stop the majority of C-terminal degradation, metabolism of Dyn A(1-10) amide continued by captopril sensitive enzymes, suggesting that Dyn A(1-13) amide is a better candidate for additional stabilization. Two Dyn A(1-13) amide derivatives further stabilized at the N-terminal end, [D-Tyr1]-Dyn A(1-13) amide and [N-Met-Tyr1]-Dyn A(1-13) amide, showed half-lives in plasma of 70 and 130 min, respectively. The most stable derivative [N-Met-Tyr1]-Dyn A(1-13) amide was tested successfully for retention of the pharmacological activity in modulating antinociceptive activity.
  
  
  CONCLUSIONS
  [N-Met-Tyr1]-Dyn A(1-13) amide showed significant stability and antinociceptive activity in the tail-flick test, thus pointing to the clinical potential of this derivative in the management of pain as well as its potential activity in suppressing opiate tolerance and withdrawal.
authors.affiliation: Department of Pharmaceutics, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Suliman I
authors.initials: SI
authors.lastname: Al-Fayoumi
authors.forename: Boglarka
authors.initials: B
authors.lastname: Brugos
authors.forename: Vikram
authors.initials: V
authors.lastname: Arya
authors.forename: Esther
authors.initials: E
authors.lastname: Mulder
authors.forename: Barbel
authors.initials: B
authors.lastname: Eppler
authors.forename: Andre P
authors.initials: AP
authors.lastname: Mauderli
authors.forename: Günther
authors.initials: G
authors.lastname: Hochhaus
mesh_terms: D000626:Aminopeptidases / Q000037:antagonists & inhibitors; D000700:Analgesics / Q000627:therapeutic use*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors; D004355:Drug Stability; D004361:Drug Tolerance; D004399:Dynorphins / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006207:Half-Life; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009021:Morphine Dependence / Q000188:drug therapy*; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013386:Succinates / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology
chemical_list: D000700:Analgesics; D000806:Angiotensin-Converting Enzyme Inhibitors; D004791:Enzyme Inhibitors; D013386:Succinates; D013438:Sulfhydryl Compounds; C468280:leucinethiol; D004399:Dynorphins; C022014:guanidinoethylmercaptosuccinic acid; D002216:Captopril; D002268:Carboxypeptidases; D000626:Aminopeptidases; D007930:Leucine