Cellular Signalling and Free-Radical Modulating Activities of the Novel Peptidomimetic L-Glutamyl-Histamine

M. A. Babizhayev^1*, Yu. A. Semiletov², Yu. A. Lul^***'kin¹, N. L. Sakina³, E. L. Savel'yeva¹, A. I. Deyev¹, L. I. Alimbarova², I. F. Barinskii², J.-F. Nicolay⁴, Ch. Paillet⁴, G. Langrand⁴, and F. Seguin⁴

¹Moscow Helmholtz Research Institute of Eye Diseases, ul. Sadovaya-Chernogryazskaya 14/19, Moscow, 103064 Russia; fax: (095) 977-2387

²Ivanovskii Institute of Virology, ul. Gamalei 16, Moscow, 123098 Russia

³Emanuel Institute of Biochemical Physics, ul. Kosygina 4, Moscow, 117977 Russia

⁴Exsymol S.A.M., Monaco, Principaute de Monaco

^* To whom correspondence should be addressed.

Received October 27, 1998; Revision received February 16, 1999

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A novel histamine-containing peptidomimetic, L-glutamyl-histamine (L-Glu-Hist), has been synthesized and characterized as a possible cytokine mimic which might lead to cellular responses of improved specificity. The energy-minimized 3-D conformations of L-Glu-Hist derived from its chemical structure stabilize Fe²⁺-chelating complexes. L-Glu-Hist concentration-dependently accelerates a decrease in ferrous iron in ferrous sulfate solution and shows ferroxidase-like activity at concentrations less than 3 mM in the phenanthroline assay, whereas in the concentration range 3-20 mM it restricts the availability of Fe²⁺ to phenanthroline by chelation of iron ions. At low concentrations (less than or about 1 mM), L-Glu-Hist stimulates peroxidation of phosphatidylcholine in liposomes catalyzed by a superoxide anion radical (O₂)-generating system (Fe²⁺ + ascorbate) and, at high concentrations (*10 mM), it suppresses lipid peroxidation (LPO) in liposomes. The stimulation of LPO by L-Glu-Hist is related to its ability at low concentrations (*0.05 mM) to release O₂ free radicals as determined by the superoxide dismutase-inhibitable reduction of cytochrome c. The release of O₂ by L-Glu-Hist might result from its ferroxidase-like activity, while its inhibition of LPO is due to chelation of Fe²⁺, prevention of the formation of free radicals, and degradation of lipid hydroperoxides at 5-20 mM L-Glu-Hist concentrations. L-Glu-Hist releases O₂ at concentrations which stimulate [³H]thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and also of mononuclear cells from human blood. The induction of lymphocyte proliferation by L-Glu-Hist is dose-dependent in the 0.01-0.05 mM concentration range, although the maximal stimulation of LPO in the O₂-dependent system is observed at higher L-Glu-Hist concentrations (*1 mM). Thus, low concentrations of oxygen free radicals released by L-Glu-Hist may provide a very fast, specific, and sensitive trigger for lymphocyte proliferation and immunoregulation.

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KEY WORDS: L-glutamyl-histamine, peptidomimetic, lipid peroxidation, superoxide radical, spleen lymphocytes, blood mononuclear cells, cellular signalling, lymphocyte proliferation, antioxidant, reactive oxygen species, iron-chelating and ferroxidase-like activities

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