Prevention of experimental septic shock by pretreatment of mice with muramyl peptides

Muramyl peptides, immunostimulators with macrophage as a main target cell, are used for protecting mice from LPS-lethality (the experimental model of septic shock). Different protocols of pretreatment mice by muramyl peptides lead to opposite results. LPS and glycopeptides act synergistically in the induction of lethal shock, when mice receive peptides 1 day prior to lethal dose of LPS. However, extension of the period between the peptide and LPS injections to 6 days cancels the effect of synergism. Moreover, a 14-day interval between the same injections leads to protection of 70-90% animals from the toxic effect of LPS. Lipophilic analogs require 10-100 lower concentrations to protect the animals than the parent highly hydrophilic glycopeptides. Production of TNF, IL-1 and phagocytosis by macrophages was studied within the periods corresponding to "synergism" and LPS-resistance. High level of macrophage activity was observed during the "synergism" period. Low TNF production and reduced macrophage phagocyte activity corresponded to LPS-resistant state. These results partly explain the LPS-unresponsiveness in mice after their pretreatment by muramyl peptides.

Synthesis and immunological evaluation of the conjugates composed from a muramyl peptide GMDP and tuftsin

The conjugates of a muramyl dipeptide analog GMDP (N-acetylglucosaminyl beta 1-->4 N-acetylmuramyl-L-alanyl-D-isoglutamine) and tuftsin (Thr-Lys-Pro-Arg) were synthesized from unprotected GMDP by mixed anhydride procedure. The identity of the conjugates was confirmed by high resolution NMR and their immunomodulating properties were determined in various tests. It was found that the conjugate in which the GMDP carboxyl group forms an amide bond with the epsilon-amino group of tuftsin lysyl residue exceeds GMDP in all the activities determined. Synergism of GMDP and tuftsin was found in phagocytosis stimulation assay.

Dituftsin and polytuftsin induce an anti-peptide IgG response to non-immunogenic peptides in mice

The effect of covalently attaching multiple forms of the immunomodulating tetrapeptide tuftsin to normally non-immunogenic peptides was studied in BALB/c and C57Bl/6 mice. The peptides: (NANP)3 from the Plasmodium falciparum circumsporozoite protein and peptides 136-152 and 205-213 derived from the capsid protein of foot-and-mouth disease virus were coupled to polytuftsin or dituftsin. Anti-peptide IgG titers were determined after two immunizations. All of these three non-immunogenic peptides coupled to polytuftsin or dituftsin induced anti-peptide antibody production in mice while peptides alone did not elicit IgG. In addition, a conjugate of (NANP)3 and polytuftsin with built-in glycopeptide adjuvant elicited an anti-peptide response comparable in magnitude with that of a peptide-KLH conjugate. The data suggest that when non-immunogenic peptides are synthesized in tandem with dituftsin or conjugated to polytuftsin a significant immune response to the peptides may be elicited. This approach may be employed in synthetic vaccine design.

Oxidative Ring-Opening Transformation of 5-Acyl-4-pyrones as an Approach for the Tunable Synthesis of Hydroxylated Pyrones and Furans

A selective and tunable approach for oxidation of 4-pyrones has been developed via ring-opening transformations leading to various hydroxylated oxaheterocycles. The first step of the strategy includes the base-catalyzed epoxidation of 5-acyl-4-pyrones in the presence of hydrogen peroxide for the effective synthesis of pyrone epoxides in high yields. The epoxides bearing the CO2Et group are reactive molecules that can undergo both pyrone and oxirane ring-opening via deformylation to produce hydroxylated 2-pyrones or 4-pyrones. The acid-promoted transformation led to 3-hydroxy-4-pyrones (24-76% yields), whereas the K2CO3-catalyzed ring-opening process of 2-carbethoxy-4-pyrone epoxides proceeded as an attack of alcohol at the C-3 position bearing the CO2Et group to give functionalized 6-acyl-5-hydroxy-2-pyrones (27-87% yields). The base-catalyzed reaction of 2-aryl-4-pyrone epoxides was followed by ring contraction and the dearoylation process to produce 3-hydroxyfuran-2-carbaldehydes in 42-80% yields. The transformation of 3-aroylchromone epoxides led to flavonols and 3-hydroxybenzofuran-2-carbaldehyde in the acidic and basic conditions, respectively. The prepared hydroxylated heterocycles demonstrated high reactivity for further transformations and low cytotoxicity and are promising fluorophores or UV filters.