Selective potentiation of cytokine expression in human whole blood by murabutide, a muramyl dipeptide analogue.
Murabutide is a synthetic muramyl peptide which is in clinical stage of development. Its effect on cytokine production was analysed in human whole blood to reproduce the natural environment. Induced gene transcription within 2 h was associated with the release of cytokines such as tumour necrosis factor (TNF), interleukin-1 beta (IL-1 beta), IL-6, IL-8, and also the anti-inflammatory mediator IL-1ra. This synthesis was not associated with the release of IL-4, IL-12, interferon gamma (IFN-gamma), the three colony-stimulating factors (CSFs) or the soluble TNF receptors. The same series of cytokines were assayed to determine the effect of some recombinant cytokines in association with murabutide. Thus, in the presence of IL-2, IL-6, IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF), the level of cytokines induced by murabutide was enhanced with no change in the other cytokines profile. IL-3 and GM-CSF were more potent in increasing the murabutide-induced response, eliciting synergistic effects on IL-8 and IL-1Ra production, at both the mRNA accumulation and the protein release. Although neither IL-12 nor IFN-gamma were produced in cells stimulated with murabutide alone, some mRNA expression was found with combined treatments. The results indicate that association of murabutide with a cytokine could exert synergistic effects, thus reducing effective doses of the recombinant protein, increasing the release of anti-inflammatory mediators, and triggering efficient cellular immunity.