3D molecular modeling, free radical modulating and immune cells signaling activities of the novel peptidomimetic L-glutamyl-histamine: possible immunostimulating role

An original representative of the patented by author family of histamine-containing peptidomimetics L-glutamyl-histamine (L-Glu-Hist) was synthesized and characterized as a biologically active compound with a role of cytokine mimic leading to cellular responses of improved specificity. The study assesses the ability of L-Glu-Hist to affect molecular modeling, modulate free radical activity and influence immune cell signaling. The energy-minimized 3D conformations of L-Glu-Hist derived from its chemical structure resulted in stabilization for Fe2+ chelating complexes. L-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulfate solution in a concentration-dependent mode and showed the ferroxidase-like activity at concentrations less than 3 mM in the phenanthroline assay, whereas in the concentration range 3-20 mM L-Glu-Hist restricted the availability of Fe2+ to phenanthroline due to binding of ferrous ions in chelating complexes. L-Glu-Hist showed stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalyzed by the superoxide anion radical (O-2(center dot-))-generating system (Fe2++ ascorbate) at low (less or about 1 MM) L-Glu-Hist concentrations and both revealed the inhibitory effect on LPO in this system of high (similar to 10 mM) L-Glu-Hist concentration. The stimulation of LPO by L-Glu-Hist was related to the ability of peptidomimetic in small (similar to 0.05 mM) concentrations to release O-2(center dot-) free radicals as determined by the superoxide dismutase-inhibitable cytochrome c reduction assay. O-2(center dot-) release by L-Glu-Hist might result from its ferroxidase-like activity, while inhibition of LPO by L-Glu-Hist was caused by its chelating activity to Fe2+ ions, prevention of free radical generation and lipid hydroperoxide-degrading ability of 5-20 MM L-Glu-Hist. L-Glu-Hist released O-2(center dot-) in concentrations which stimulated [H-3]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. L-Glu-Hist modulates the ability of oxygen free radicals to act as signaling agents at low concentrations, influencing gene expression. The structural peptide-like analogues of L-Glu-Hist such as L-Glu-Trp, carcinine (beta-alanylhistamine), but not L-Pro-Glu-Trp were active in stimulating thymidine incorporation and in inducing proliferation of mononuclear cells as compared to mitogen concanavalin A at doses 2.5-25.0 mu g/ml. Our data provide evidence that L-Glu-Hist may act as a very fast, specific and sensitive trigger for lymphocyte proliferation and immunoregulation. The cited abilities and further obtained in vivo results make Immudilin (R) ((INCI: glutamylamidoethyl imidazole, aqueous solution), L-Glu-Hist) a useful immunoregulatory agent. (c) 2004 Elsevier Inc. All rights reserved.