Magic Peptide: Unique Properties of the LRR11 Peptide in the Activation of Leukotriene Synthesis in Human Neutrophils

Galina M Viryasova,Nina G Dolinnaya,Tatjana V Gaponova,Nataliya V Soshnikova,Yulia M Romanova,Tibor Hianik,Galina F Sud’Ina,Ekaterina A Golenkina

doi:10.3390/ijms22052671

Abstract

Neutrophil-mediated innate host defense mechanisms include pathogen elimination through bacterial phagocytosis, which activates the 5-lipoxygenase (5-LOX) product synthesis. Here, we studied the effect of synthetic oligodeoxyribonucleotides (ODNs), which mimic the receptor-recognized sites of bacterial (CpG-ODNs) and genomic (G-rich ODNs) DNAs released from the inflammatory area, on the neutrophil functions after cell stimulation with Salmonella typhimurium. A possible mechanism for ODN recognition by Toll-like receptor 9 (TLR9) and RAGE receptor has been proposed. We found for the first time that the combination of the magic peptide LRR11 from the leucine-rich repeat (LRR) of TLR9 with the CpG-ODNs modulates the uptake and signaling from ODNs, in particular, dramatically stimulates 5-LOX pathway. Using thickness shear mode acoustic method, we confirmed the specific binding of CpG-ODNs, but not G-rich ODN, to LRR11. The RAGE receptor has been shown to play an important role in promoting ODN uptake. Thus, FPS-ZM1, a high-affinity RAGE inhibitor, suppresses the synthesis of 5-LOX products and reduces the uptake of ODNs by neutrophils; the inhibitor effect being abolished by the addition of LRR11. The results obtained revealed that the studied peptide-ODN complexes possess high biological activity and can be promising for the development of effective vaccine adjuvants and antimicrobial therapeutics.

Highlights

Human neutrophils play an essential role in the initiation and resolution of the inflammatory response to bacterial and viral infections.They eliminate pathogens through phagocytosis, which activates the 5-lipoxygenase (5LOX)-mediated pathway leading to the synthesis of leukotrienes
Using synthetic oligonucleotides that mimic these DNA fragments, it was shown that G-rich ODNs capable of folding into non-B form G-quadruplex structures activated bacterial phagocytosis and the leukotriene synthesis in human neutrophils, both the secondary structure of ODNs and their ability to penetrate into cells being important for the induction of immune responses [2]
Our results suggest that the LRR11 peptide reduces the interaction of the ODN with the Toll-like receptor 9 (TLR9) receptor, “turns off” RAGE inhibition, and stimulates 5-LOX

Summary

Introduction

Human neutrophils (or polymorphonuclear leukocytes, PMNLs) play an essential role in the initiation and resolution of the inflammatory response to bacterial and viral infections. They eliminate pathogens through phagocytosis, which activates the 5-lipoxygenase (5LOX)-mediated pathway leading to the synthesis of leukotrienes. Using synthetic oligonucleotides that mimic these DNA fragments, it was shown that G-rich ODNs capable of folding into non-B form G-quadruplex structures activated bacterial phagocytosis and the leukotriene synthesis in human neutrophils, both the secondary structure of ODNs and their ability to penetrate into cells being important for the induction of immune responses [2]. It was experimentally shown that the LRR11 peptide derived from the TLR9 sequence can bind to the CpG-ODNs [8], which leads to an attenuating of TLR9 signaling and a decrease in the oligonucleotide internalization by a mouse-derived monocyte/macrophage cell line RAW 264.7 [9]

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