1.Identification of endomorphin-1 and endomorphin-2 binding sites in human mu-opioid receptor by antisense oligonucleotide strategy.
Fichna J;Gach K;Perlikowska R;Poels J;Vanden Broeck J;Szemraj J;Janecka A Chem Biol Drug Des. 2008 Dec;72(6):507-12. doi: 10.1111/j.1747-0285.2008.00725.x.
The effects of phosphorothioate antisense oligodeoxynucleotides against exons-1, -2, -3 and -4 of the human mu-opioid receptor were studied in the CHO-mu-opioid receptor cells using aequorin luminescence-based calcium assay. All four antisense oligodeoxynucleotides significantly decreased the level of mu-opioid receptor mRNA in comparison with the non-treated cells, used as control. However, no statistically significant differences between antisense oligodeoxynucleotides were observed. antisense oligodeoxynucleotides against exon-2 attenuated endomorphin-1-induced intracellular calcium response in a concentration-dependent manner. antisense oligodeoxynucleotides against exons-1, -2, -3 and -4 inhibited endomorphin-2-induced intracellular calcium response in a concentration-dependent manner and the effect of antisense oligodeoxynucleotides against exons-3 and -4 was most pronounced. The mismatch oligodeoxynucleotides against respective exons failed to exert any effect. The selective actions of antisense probes directed against different exons of the human mu-opioid receptor gene, that resulted, at the protein level, in attenuation of calcium responses induced by endomorphin-1 and endomorphin-2, suggest that the binding sites for endomorphins are structurally and functionally different.
2.A Tyr-W-MIF-1 analog containing D-Pro2 acts as a selective mu2-opioid receptor antagonist in the mouse.
Watanabe H;Nakayama D;Ito K;Watanabe C;Mizoguchi H;Fujimura T;Murayama K;Kawamura S;Sato T;Sakurada C;Sakurada T;Sakurada S J Pharmacol Exp Ther. 2005 Mar;312(3):1075-81. Epub 2004 Nov 23.
The antagonistic properties of Tyr-d-Pro-Trp-Gly-NH(2) (d-Pro(2)-Tyr-W-MIF-1), a Tyr-Pro-Trp-Gly-NH(2)(Tyr-W-MIF-1) analog, on the antinociception induced by the mu-opioid receptor agonists Tyr-W-MIF-1, [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO), Tyr-Pro-Trp-Phe-NH(2) (endomorphin-1), and Tyr-Pro-Phe-Phe-NH(2) (endomorphin-2) were studied in the mouse paw-withdrawal test. d-Pro(2)-Tyr-W-MIF-1 injected intrathecally (i.t.) had no apparent effect on the thermal nociceptive threshold. d-Pro(2)-Tyr-W-MIF-1 (0.1-0.4 nmol) coadministered i.t. showed a dose-dependent attenuation of the antinociception induced by Tyr-W-MIF-1 without affecting endomorphin- or DAMGO-induced antinociception. However, higher doses of d-Pro(2)-Tyr-W-MIF-1 (0.8-1.2 nmol) significantly attenuated endomorphin-1- or DAMGO-induced antinociception, whereas the antinociception induced by endomorphin-2 was still not affected by d-Pro(2)-Tyr-W-MIF-1. Pretreatment i.t. with various doses of naloxonazine, a mu(1)-opioid receptor antagonist, attenuated the antinociception induced by Tyr-W-MIF-1, endomorphin-1, endomorphin-2, or DAMGO. Judging from the ID(50) values for naloxonazine against the antinociception induced by the mu-opioid receptor agonists, the antinociceptive effect of Tyr-W-MIF-1 is extremely less sensitive to naloxonazine than those of endomorphin-1 or DAMGO.
3.Naloxone blocks endomorphin-1 but not endomorphin-2 induced inhibition of tachykinergic contractions of guinea-pig isolated bronchus.
Fischer A;Undem BJ Br J Pharmacol. 1999 Jun;127(3):605-8.
The recently identified endogenous agonists on the mu-opioid-receptor (mu OR), endomorphin-1 (EM-1) and endomorphin-2 (EM-2), induce a concentration dependent inhibition of electrical field stimulation (EFS)-induced tachykinin-mediated contractions of the guinea-pig bronchus (ED50s < 10 nM for both compounds). Surprisingly, only endomorphin-1 effects could be blocked by naloxone (10 microM), whereas endomorphin-2 effects were not affected by specific antagonists for the mu-, kappa-, and delta-opioid-receptor.
