Background: Tyr-Tic (1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acid) and Tyr-Tic-Ala were the first peptides with 6 opioid antagonist activity lacking Phe, considered essential for opioid activity based on the N-terminal tripeptide sequence (Tyr-D-Xaa-Phe) of amphibian skin opioids. Analogs were then designed to restrain the rotational flexibility of Tyr by the substitution of 2,6-dimethyl- L-tyrosine (Dmt). Materials and Methods: Tyr and Dmt peptides were synthesized by solid phase and solution methods using Fmoc technology or condensing Boc-Dmt-OH or Boc- Tyr(But)-OH with H-L-Tic-OBut or H-D-Tic-OBut, respectively. Peptides were purified (>99%) by HPLC and characteristics determined by 'H-NMR, FAB-MS, melting point, TLC, and amino acid analyses. Results: H-Dmt-Tic-OH had high affinity (Ki, = 0.022 nM) and extraordinary selectivity (K/II(/i-K = 150,000); H-Dmt-Tic-Ala-OH had a Ki-= 0.29 nM and 6 selectivity = 20,000. Affinity and selectivity increased 8700- and 1000-fold relative to H-Tyr-Tic-OH, respectively. H-Dmt- Tic-OH and H-Dmt-Tic-NH2 fitted one-site receptor binding models (,q = 0.939-0.987), while H-Dmt-Tic-ol, H-Dmt-Tic-Ala-OH and H-Dint-Tic-Ala-NH2 best fitted two-site models (71 = 0.708-0.801, F 18.9-26.0, p < 0.0001). Amidation increased ,u affinity by 10- to 100- fold and acted synergistically with D-Tic2 to reverse selectivity (6 -,A). Dmt-Tic di- and tripeptides exhibited 6 antagonist bioactivity (Ke = 4-66 nM) with mouse vas deferens and lacked agonist ,u activity (> 10 ,uM) in guinea-pig ileum preparations. Dmt-Tic analogs weakly interacted with K receptors in the 1 to >20 p.M range. Conclusions: Dmt-Tic opioidmimetic peptides represent a highly potent class of opioid peptide antagonists with greater potency than the nonopioid 8 antagonist naltrindole and have potential application as clinical and therapeutic compounds.
Delta opioidmimetic antagonists: prototypes for designing a new generation of ultraselective opioid peptides.
SALVADORI, Severo;GUERRINI R;
1995
Abstract
Background: Tyr-Tic (1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acid) and Tyr-Tic-Ala were the first peptides with 6 opioid antagonist activity lacking Phe, considered essential for opioid activity based on the N-terminal tripeptide sequence (Tyr-D-Xaa-Phe) of amphibian skin opioids. Analogs were then designed to restrain the rotational flexibility of Tyr by the substitution of 2,6-dimethyl- L-tyrosine (Dmt). Materials and Methods: Tyr and Dmt peptides were synthesized by solid phase and solution methods using Fmoc technology or condensing Boc-Dmt-OH or Boc- Tyr(But)-OH with H-L-Tic-OBut or H-D-Tic-OBut, respectively. Peptides were purified (>99%) by HPLC and characteristics determined by 'H-NMR, FAB-MS, melting point, TLC, and amino acid analyses. Results: H-Dmt-Tic-OH had high affinity (Ki, = 0.022 nM) and extraordinary selectivity (K/II(/i-K = 150,000); H-Dmt-Tic-Ala-OH had a Ki-= 0.29 nM and 6 selectivity = 20,000. Affinity and selectivity increased 8700- and 1000-fold relative to H-Tyr-Tic-OH, respectively. H-Dmt- Tic-OH and H-Dmt-Tic-NH2 fitted one-site receptor binding models (,q = 0.939-0.987), while H-Dmt-Tic-ol, H-Dmt-Tic-Ala-OH and H-Dint-Tic-Ala-NH2 best fitted two-site models (71 = 0.708-0.801, F 18.9-26.0, p < 0.0001). Amidation increased ,u affinity by 10- to 100- fold and acted synergistically with D-Tic2 to reverse selectivity (6 -,A). Dmt-Tic di- and tripeptides exhibited 6 antagonist bioactivity (Ke = 4-66 nM) with mouse vas deferens and lacked agonist ,u activity (> 10 ,uM) in guinea-pig ileum preparations. Dmt-Tic analogs weakly interacted with K receptors in the 1 to >20 p.M range. Conclusions: Dmt-Tic opioidmimetic peptides represent a highly potent class of opioid peptide antagonists with greater potency than the nonopioid 8 antagonist naltrindole and have potential application as clinical and therapeutic compounds.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
