Endogenous fragment of hemoglobin, neokyotorphin, as cell growth factor

It is shown that neokyotorphin (the alpha-globin fragment 137-141) stimulates proliferation of normal cells (murine embryonic fibroblasts, red bone marrow and spleen cells) and tumor cells (murine melanoma and transformed fibroblasts L929) in the absence or in the presence of fetal bovine serum. In contrast to serum deprivation conditions, the ability to potentiate L929 cell growth in the presence of fetal serum is strongly cell density dependent. The peptide also enhances the viability of L929 cells, murine embryonic fibroblasts and of the primary cultures of murine red bone marrow cells and splenocytes under serum-deprivation conditions for at least 72 h. The results of flow cytometry analysis suggest that the effect of neokyotorphin on survival of L929 cells in serum-free culture medium is due to maintenance of cell proliferation in the absence of growth factors. Along with cell cycle progression the peptide induces reversible reduction of L929 cell size.

Peptides comprising the bulk of rat brain extracts: isolation, amino acid sequences and biological activity

Chromatographic separation of rat brain extracts followed by automatic Edman sequencing of the major individual components resulted in identification of 61 endogenous peptides derived from known functional proteins (hemoglobin, myelin basic protein, cytochrome-c oxidase, etc.) or unknown precursors. The results are compared with the data obtained earlier for bovine brain. Although the sequences of bovine and rat hemoglobin contain about 20% of amino acid substitutions, the families of structurally related peptides are very similar in both extracts. Several other proteins also give rise to identical or closely related peptide fragments in the two mammalian species. The outlined similarity extends almost exclusively to the most abundant peptides present in the extracts. The minor components show less overlap. Four hemoglobin-derived peptides isolated from rat brain were shown to be biologically active in tumor cells. Eleven are identical to bioactive peptides from other species. Ten structurally overlap with bioactive peptides from other sources. The data obtained show similar biosynthetic pathways of pool components in different species, the resultant peptides being aimed at fulfilling related functions.

Neokyotorphin and neokyotorphin (1-4): secretion by erythrocytes and regulation of tumor cell growth

Human erythrocytes release neokyotorphin, the 137-141 fragment of hemoglobin alpha-chain into the supernatant of red blood cells primary culture. However, the neokyotorphin fragment 1-4 that is formed together with neokyotorphin inside the red blood cells and in various tissues is not found in the supernatant. Both neokyotorphin and its 1-4 fragment were shown to stimulate proliferation of L929 tumor cells.

Cytotoxic activity of acetylcholine receptor ligands

Acetylcholine receptor ligands were studied for cytotoxicity in K562 human erythroid leukemia tumor cells. Cytotoxicity of carbachol, an agonist of acetylcholine receptors, atropine, an antagonist of muscarinic acetylcholine receptor, neurotoxin 11 (NT II) from Naja naja oxiana cobra venom and tubocurarine, antagonists of acetylcholine receptor of nicotinic type was exhibited in the 10-7-10-5 M concentration range. Several cytolytic processes, two for carbachol and three for other ligands, corresponding to different concentrations of each ligand were detected. All acetylcholine receptor ligands induced internucleosomal DNA fragmentation.

Met-enkephalin induces cytolytic processes of apoptotic type in K562 human erythroid leukemia cells

Cytolytic activity of Met-enkephalin, an endogenous opioid peptide, was studied within the 10(-7)-10(-17) M concentration range in K562 human erythroid leukemia cells. Cytolytic activity was determined by the trypan blue inclusion method after 13, 15 and 18 h of Met-enkephalin co-incubation with target cells. Discrete maxima of cytolytic activity were detected at concentrations of 10(-9)-10(-10), 10(-13) and 10(-15) M. Cytolysis was accompanied by internucleosomal DNA fragmentation which is indicative of the mechanism of cell death being apoptosis.