Stimulation of the Viability of Early Mouse Embryos Cultured in Vitro by β-Endorphin-Like Peptides

Abstract

The growth of a mammalian embryo is accompanied by complex interactions between the embryo and the mother, as well as between the embryo cells themselves. Peptide growth factors play an important role in cell division, differentiation, and morphogenesis during mammalian embryogenesis. Several families of growth factors of various origins influence preimplantation of mammalian embryos. These are insulin-like (IGF), epidermal (EGF), and platelet-derived (PDGF) growth factors, as well as transforming growth factor b (TGF-b), fibroblast growth factor (FGF), and leukemia-inhibiting factor (LIF) [1]. The growth of the blastocyst, which is the final stage of preimplantation, proved to depend on EGF and LIF [2]. These two factors promote the formation of a favorable conditions for blastocyst implantation and the subsequent growth of the embryo. β -Endorphin can be assigned to the peptide growth factors that regulate embryo growth [3]. Follicular cells around the oocyte are known to secrete β -endorphin. This seems to influence oocyte maturation and ovulation [4]; the fact that the endometrium cells secrete β -endorphin [5] suggests that this substance has an effect on the interaction between the embryo and the mother. The in vitro sensitivity of growing preimplantation mouse embryos to the agonists and antagonists of opioid receptors suggests that the latter are present on the embryos and bind β -endorphin [6]. In the 1980s, the fragment 364-377 of the heavy chain of immunoglobulin G (IgG) similar to the central part of the β -endorphin molecule has been identified in extracts of the human placenta [7]. In the Pushchino Branch of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry Institute of Biochemistry of the Russian Academy of Sciences, β -endorphin-like peptides were synthesized.These are immunorphin (SLTCLVKGFY), which is the fragment 364-373 of the heavy chain of human IgG, and its fragments: pentarphin (VKGFY), the immunorphin 6-10 fragment; cyclopentarphin, cyclo(VKGFY); and cyclodipentarphin, cyclo(VKGFYVKGFY). These substances were shown to be selective antagonists of non-opioid (naloxon-insensitive) β -endorphin receptors that were detected on cells of the rat immune system and on membranes from the rat myocardium, adrenal glands, spleen, and brain [8,9]. We have showed previously that immunorphin at a concentration of 10 -7 I stimulated early growth of mouse embryos in vitro [10]. Therefore, immunorphin may be considered a β -endorphin-like nonspecific growth factor.In this study, the effects of the β -endorphin-like peptides pentarphin ( 10 -7 I), cyclopentarphin ( 10 -7 I), and cyclodipentarphin 10 -6 I) on the growth of two-, four-, and eight-cell mouse embryos were studied in vitro. In the control group, none of the above peptides were added to the growing embryos. The specificity of the peptide effect was confirmed in experiments on the effect of a "cocktail" of amino acids constituting these peptides (Val, Lys, Gly, Phe, and Tyr; 10 -7 M) on mouse embryo preimplantation. In total, 344 and 215 ...

Investigation of beta-endorphin reception in preimplantation development of a mouse embryo in vitro

“…In other words, recep tors binding to β endorphin and immunorphine are not opioid ones. In addition, it has been shown that β endorphin like peptide immunorphine, and its 6-10 fragment pentarphine (VKGFY), stimulate the early development of mouse embryos in vitro [6,7]. Data obtained allow us to suppose the presence of hor mone nonopioid receptors at early stages of mouse embryo preimplantation development.…”

Binding of synthetic peptide TPLVTLFK to nonopioid beta‐endorphin receptor on rat brain membranes

“…We have synthesized the decapeptide SLTCLVKGFY corresponding to the amino acid sequence 364–373 of the heavy chain of human IgG of subclasses 1–4 (referred to as immunorphin)5 and found that it is a selective agonist of nonopioid (insensitive to naloxone) β‐endorphin receptor of human T‐lymphocytes6–9, mouse peritoneal macrophages10, 11, synaptic membranes of rat brain12, rat adrenal cortex membranes13, 14, and human Jurkat lymphoblastic T‐cells15. The investigations of biological activity of immunorphin showed that it increases the Con A‐induced proliferation of human T‐lymphocytes in vitro 6–9, activates mouse peritoneal macrophages in vitro and in vivo 10, 11, stimulates the growth of human lymphoblast T‐cell lines Jurkat and MT‐415, 16, inhibits the adenylate cyclase activity in rat adrenocortical membranes and the secretion of corticosterone from the adrenal glands to the bloodstream13, and stimulates cell division in early mouse blastocysts in vitro 17, 18. Study of the distribution of the nonopioid receptor of β‐endorphin in the body of the rat showed that it is present on the cells of the immune (macrophages and lymphocytes), nervous (synaptic membranes of the brain), and cardiovascular systems (myocardium membranes)19.…”