title: LL-37 directs macrophage differentiation toward macrophages with a proinflammatory signature.
abstract: The human cathelicidin LL-37 has broad-spectrum antimicrobial activity. It also participates at the interface of innate and adaptive immunity by chemoattracting immune effector cells, modulating the production of a variety of inflammatory mediators by different cell types, and regulating the differentiation of monocytes into dendritic cells. In this study, we investigated the effects of LL-37 on the differentiation of human monocytes into anti-inflammatory macrophages (MPhi-2; driven by M-CSF) versus proinflammatory macrophages (MPhi-1; driven by GM-CSF) as well as on fully differentiated MPhi-1 and MPhi-2. Results revealed that monocytes cultured with M-CSF in the presence of LL-37 resulted in macrophages displaying a proinflammatory signature, namely, low expression of CD163 and little IL-10 and profound IL-12p40 production on LPS stimulation. The effects of LL-37 on M-CSF-driven macrophage differentiation were dose- and time-dependent with maximal effects observed at 10 microg/ml when the peptide was present from the start of the cultures. The peptide enhanced the GM-CSF-driven macrophage differentiation. Exposure of fully differentiated MPhi-2 to LL-37 for 6 d resulted in macrophages that produced less IL-10 and more IL-12p40 on LPS stimulation than control MPhi-2. In contrast, LL-37 had no effect on fully differentiated MPhi-1. Peptide mapping using a set of 16 overlapping 22-mer peptides covering the complete LL-37 sequence revealed that the C-terminal portion of LL-37 is responsible for directing macrophage differentiation. Our results furthermore indicate that the effects of LL-37 on macrophage differentiation required internalization of the peptide. Together, we conclude that LL-37 directs macrophage differentiation toward macrophages with a proinflammatory signature.
authors.affiliation: Department of Infectious Diseases, Center for Infectious Diseases, Leiden University Medical Center, C5-P, Albinusdreef 2, 2333 ZA Leiden, The Netherlands.
authors.forename: Anne M
authors.initials: AM
authors.lastname: van der Does
authors.forename: Henry
authors.initials: H
authors.lastname: Beekhuizen
authors.forename: Bep
authors.initials: B
authors.lastname: Ravensbergen
authors.forename: Tim
authors.initials: T
authors.lastname: Vos
authors.forename: Tom H M
authors.initials: TH
authors.lastname: Ottenhoff
authors.forename: Jaap T
authors.initials: JT
authors.lastname: van Dissel
authors.forename: Jan W
authors.initials: JW
authors.lastname: Drijfhout
authors.forename: Pieter S
authors.initials: PS
authors.lastname: Hiemstra
authors.forename: Peter H
authors.initials: PH
authors.lastname: Nibbering
mesh_terms: D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000502:physiology*; D001424:Bacterial Infections / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D002454:Cell Differentiation / Q000276:immunology*; D002478:Cells, Cultured; D006706:Homeostasis / Q000276:immunology; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control; D018836:Inflammation Mediators / Q000502:physiology*; D016753:Interleukin-10 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology; D008264:Macrophages / Q000145:classification / Q000276:immunology* / Q000473:pathology*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000166:cytology / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000276:immunology; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D018836:Inflammation Mediators; D016753:Interleukin-10; D016173:Macrophage Colony-Stimulating Factor; D054804:Cathelicidins