LK 409

Some synthetic analogues of the immuno-modulatory agent muramyl dipeptide (MDP), i.e. phthalimido- (LK-511, LK-413, LK-512, LK-423, LK-508), adamantyl- (LK-415, LK-517), 7-oxoaIkyl-(LK-409) desmuramylpeptides were assessed for the tumour necrosis factor (TNF) inducing activity and the ability to modulate TNF production in in vitro phorbol 12-myristate 13-acetate (PMA) & ionomycin stimulated cultures of human peripheral blood mononuclear cells. A kinetic study over a 40-hour period indicated that desmuramyldipeptides were weak TNF inducers compared to romurtide, PMA & ionomycin or lipopolysaccharide. By contrast, they showed the potential to up- or down-regulate the production of TNF evoked by PMA & ionomycin, which was strongly dependent on the time of the stimulation. After 4h of stimulation, the TNF secretion was augmented by LK-508, LK-409 and LK-511, after 18 h by LK-409 and LK-423, and after 40 h by LK-423, LK-511, LK-415 and LK-512. However, LK-517 and LK-512 inhibited the secretion of TNF after the 18-h period.

N-(7-Oxoacyl)-L-alanyl-D-isoglutamines are substances with similar effects on immune system as N-acetylmuramyldipeptide (MDP). They were synthesized to eliminate some side effects of MDP: pyrogenicity, leucopenia, hypertension and fast elimination from the body. The aim of our work was to determine some physicochemical properties of a series of N-(7-oxoacyl)-L-alanyl-D-isoglutamines, that have zero to six methylene groups between terminal methyl and 7-oxo group. The following properties were examined: water solubility, lipophilicity, thermal behaviour and true density. The results were compared and it was established that the lipophilic parameter determined by high-performance liquid chromatography is increasing by the increase of alkyl chain while the water solubility is decreasing at the same time. In both cases the substance with the longest chain (N-(7-tetrakanoyl)-L-alanyl-D-isoglutamine) is an exception. The lipophilic parameter of this substance is lower and water solubility higher than with the substances with three, four and five methylene groups between terminal methyl and 7-oxo group. These results can be explained by the twisted conformation of N-(7-tetrakanoyl)-L-alanyl-D-isoglutamine molecule in water solution. By means of thermal analysis it was discovered that the melting point is decreasing with the increase of alkyl chain. From the true density and melting enthalpy measurements it is evident that with the increase of alkyl chain the arrangement of molecules in solid state is increasing up to the molecule with four methylene groups between terminal methyl and 7-oxo group. Substances with longer chains have lower true density and melting enthalpy because of the different arrangements of the molecules.