Notch signaling is activated by TLR stimulation and regulates macrophage functions.
Notch signaling is a well-conserved pathway involved in cell fate decisions, proliferation and apoptosis. We report on the involvement of Notch signaling in regulating gene expression in activated macrophages. Toll-like receptors (TLR) agonists such as bacterial lipopeptide, polyI:C, lipopolysaccharide and unmethylated CpG DNA all induced up-regulation of Notch1 in primary and macrophage-like cell lines. Notch1 up-regulation was dependent on the MyD88 pathway when stimulated through TLR2, but not TLR4. Activated Notch1 and expression of the Notch target genes, Hes1 and Deltex, were detected in activated macrophages, suggesting that Notch signaling was activated upon stimulation. Inhibiting processing of Notch receptor by gamma-secretase using a gamma-secretase inhibitor (GSI), the expression of Notch1 was down-regulated to basal levels. This treatment significantly modulated expression of TNF-alpha, IL-6, and IL-10. In addition, the amount of nitric oxide produced was significantly lower and the expression of MHC class II was up-regulated in GSI-treated cells. Treatment with GSI or silencing Notch1 resulted in decreased translocation of NF-kappaBp50 into nucleus upon stimulation. Taken together, stimulation of macrophages through the TLR signaling cascade triggered activation of Notch signaling, which in turn regulated gene expression patterns involved in pro-inflammatory responses, through activation of NF-kappaB.
Palaga
Tanapat
T
Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand. tanapat.p@chula.ac.th
Buranaruk
Chayanit
C
Rengpipat
Sirirat
S
Fauq
Abdul H
AH
Golde
Todd E
TE
Kaufmann
Stefan H E
SH
Osborne
Barbara A
BA
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis / Q000235:genetics; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015870:Gene Expression / Q000276:immunology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000276:immunology; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D051881:Receptor, Notch1 / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D051193:Toll-Like Receptors / Q000276:immunology*; D000072056:Transcription Factor HES-1; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D051881:Receptor, Notch1; D051193:Toll-Like Receptors; D000072056:Transcription Factor HES-1; D014409:Tumor Necrosis Factor-alpha; C489734:Hes1 protein, mouse; C497762:Notch1 protein, mouse