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Inflammation. 2011 Oct;34(5):412-25. doi: 10.1007/s10753-010-9248-6.

Cathelicidin peptide LL-37 modulates TREM-1 expression and inflammatory responses to microbial compounds.

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Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, 2259 Lower Mall Research Station, Vancouver, V6T 1Z4, Canada.


Inflammatory diseases remain an important cause of morbidity and mortality. Cathelicidins are immunomodulatory and antimicrobial peptides with potent anti-endotoxic properties. Although the effects of the human cathelicidin LL-37 on cellular responses to Toll-like receptor (TLR) ligands have been investigated, its effects on responses to other pro-inflammatory stimuli have not been well studied. Triggering receptor expressed on myeloid cells (TREM-1) acts to amplify inflammatory responses and plays important roles in the pathogenesis of endotoxemia. In this work, the effects of LL-37 on responses to TREM-1 stimulation, alone and in the presence of a range of microbial compounds, were analyzed. It was shown that in peripheral blood mononuclear cells LL-37 strongly suppressed synergistic responses to TREM-1 and TLR4 stimulation, partly through the inhibition of TREM-1 expression on monocytes; similar effects were observed using the TLR2 ligand lipoteichoic acid. In contrast, LL-37 stimulated TREM-1 upregulation by peptidoglycan (PGN, TLR2 ligand that is also recognized via nucleotide-binding oligomerization domain containing 2 after fragmentation and intracellular uptake), as well as the responses to combined TREM-1 and PGN stimulation, possibly via the p38 mitogen-activated protein kinase pathway. LL-37 did not affect TREM-1-induced neutrophil degranulation or the production of reactive oxygen species and interleukin-8 by neutrophils. These findings provide further insight into the roles of LL-37 during inflammation and may have implications for its in vivo immunomodulatory properties and for the design of synthetic cathelicidin derivatives as anti-inflammatory and anti-endotoxic molecules.

[Indexed for MEDLINE]

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