Immunostimulating activities of the novel peptidomimetic L-glutamyl-histamine.

An original representative of histamine-containing peptidomimetics L-glutamyl-histamine (L-Glu-Hist) was synthesized and characterized as a cytokine mimic leading to cellular responses of improved specificity. The energy-minimized 3-D conformations of L-Glu-Hist derived from its chemical structure resulted in stabilization for Fe(2+) chelating complexes. L-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulphate 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 Fe(2+) to phenanthroline due to binding of ferrous ions in chelating complexes. L-Glu-Hist showed a stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalysed by the superoxide anion radical (O(2) (*))-generating system (Fe(2+)+ 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 ( approximately 10 mm) L-Glu-Hist concentration. L-Glu-Hist released O(2) (*) in concentrations which stimulated [(3)H]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. 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 compared to mitogen concanavalin A at doses 2.5-25.0 microg/ml. Our data provide evidence that L-Glu-Hist may act as a very fast and sensitive trigger for lymphocyte proliferation and immunoregulation.