Elucidation of Molecular Mechanism of the Nonopioid Β-Endorphin Action Using Synthetic Peptide TPLVTLFK

The review presents data on nonopioid action of β-endorphin and its synthetic fragment 12-19 (TPLVTLFK, octarphin), a selective agonist of a nonopioid β-endorphin receptor. Using tritium labeled octarphin, the receptor distribution in the body has been studied. It was discovered on immune cells (peritoneal macrophages, T and B-lymphocytes), endocrine (adrenal cortex, hypothalamus), cardiovascular (cardio myocytes) systems. Characteristics of the binding specificity showed that only unlabeled β-endorphin can displace the labeled octarphin from the complex with the receptor, the α-endorphin, γ-endorphin and enkephalins tested in parallel were inactive. The peptide was found to increase the activity of inducible NO-synthase (iNOS), soluble guanylate cyclase (sGC) and the content of cGMP in target cells. The results obtained suggest that the activating effect of octarphin and β-endorphin mediated through the nonopioid receptor is realized in the following way: increasing iNOS expression → increasing NO production → increasing sGC activity → increasing intracellular level of cGMP