LPS regulates a set of genes in primary murine macrophages by antagonising CSF-1 action.
We previously reported that bacterial products such as LPS and CpG DNA down-modulated cell surface levels of the Colony Stimulating Factor (CSF)-1 receptor (CSF-1R) on primary murine macrophages in an all-or-nothing manner. Here we show that the ability of bacterial products to down-modulate the CSF-1R rendered bone marrow-derived macrophages (BMM) unresponsive to CSF-1 as assessed by Akt and ERK1/2 phosphorylation. Using toll-like receptor (tlr)9 as a model CSF-1-repressed gene, we show that LPS induced tlr9 expression in BMM only when CSF-1 was present, suggesting that LPS relieves CSF-1-mediated inhibition to induce gene expression. Using cDNA microarrays, we identified a cluster of similarly CSF-1 repressed genes in BMM. By real time PCR we confirmed that the expression of a selection of these genes, including integral membrane protein 2B (itm2b), receptor activity-modifying protein 2 (ramp2) and macrophage-specific gene 1 (mpg-1), were repressed by CSF-1 and were induced by LPS only in the presence of CSF-1. This pattern of gene regulation was also apparent in thioglycollate-elicited peritoneal macrophages (TEPM). LPS also counteracted CSF-1 action to induce mRNA expression of a number of transcription factors including interferon consensus sequence binding protein 1 (Icsbp1), suggesting that this mechanism leads to transcriptional reprogramming in macrophages. Since the majority of in vitro studies on macrophage biology do not include CSF-1, these genes represent a set of previously uncharacterised LPS-inducible genes. This study identifies a new mechanism of macrophage activation, in which LPS (and other toll-like receptor agonists) regulate gene expression by switching off the CSF-1R signal. This finding also provides a biological relevance to the well-documented ability of macrophage activators to down-modulate surface expression of the CSF-1R.
Sester
David P
DP
Cooperative Research Centre for Chronic Inflammatory Diseases, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia.
Trieu
Angela
A
Brion
Kristian
K
Schroder
Kate
K
Ravasi
Timothy
T
Robinson
Jodie A
JA
McDonald
Rebecca C
RC
Ripoll
Vera
V
Wells
Christine A
CA
Suzuki
Harukazu
H
Hayashizaki
Yoshihide
Y
Stacey
Katryn J
KJ
Hume
David A
DA
Sweet
Matthew J
MJ
D000818:Animals; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects* / Q000276:immunology; D016173:Macrophage Colony-Stimulating Factor / Q000037:antagonists & inhibitors* / Q000276:immunology; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051217:Toll-Like Receptor 9
D004268:DNA-Binding Proteins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor