Novel peptide motifs from lysozyme suppress pro-inflammatory cytokines in macrophages by antagonizing toll-like receptor and LPS-scavenging action

Publication date: 30 September 2017
Source:European Journal of Pharmaceutical Sciences, Volume 107
Author(s): Hisham R. Ibrahim, Kosuke Hamasaki, Takeshi Miyata
Lysozyme is commonly found in spots where bacterial infections are most likely to enter the body. Earlier we found that lysozyme possesses five antimicrobial peptide motifs in its N-terminal region which can be generated by newborn pepsin. In this study, we explore the role of these peptides in the anti-inflammatory activity of lysozyme. The five peptides, helix1 (H1), helix2 (H2), H1 and H2 connected with a loop (HLH), H2 extended with either 2 β-strands (H2–S12) or 3 β-strands (H2–S13), were synthesized and examined for anti-inflammatory action. The five peptides dose-dependently decreased, to different degrees, expression of pro-inflammatory cytokines, TNF-α, IL-6 and IL-1β, in lipopolysaccharide (LPS)- or interferon-gamma (INF-γ)-stimulated mouse macrophage cells (RAW264.7). The HLH peptide and its individual helices (H1 and H2) were markedly the most potent anti-inflammatory. When macrophage cells were stimulated with live bacteria (E. coli), H1 peptide was the most powerful suppressor of TNF-α and IL-6 expression, providing evidence that the peptide is able to antagonize the pathogen-induced inflammatory response. Receptor binding assay and docking simulation provided evidence that H1 peptide bind specifically to the pocket for endotoxin binding of the toll-like receptor 4 (TLR-4) of macrophage. The results demonstrate, for the first time, the molecular basis of anti-inflammatory action of lysozyme that N-terminal helical peptides are the main contributors. This exciting finding offers new classes of therapeutic peptides with potential in the treatment of infection-induced inflammatory diseases.

Graphical abstract

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