SRA

Complete polarization of macrophages towards an M1-like proinflammatory and antimicrobial state requires combined action of IFN-? and LPS. Synergistic activation of canonical inflammatory NF-?B target genes by IFN-? and LPS is well appreciated, but less is known about whether IFN-? negatively regulates components of the LPS response, and how this affects polarization. A combined transcriptomic and epigenomic approach revealed that IFN-? selectively abrogates LPS-induced feedback and select metabolic pathways by suppressing TLR4-mediated activation of gene enhancers. In contrast to superinduction of inflammatory genes via enhancers that harbor IRF sequences and bind STAT1, IFN-?-mediated repression targeted enhancers with STAT sequences that bound STAT3. TLR4-activated IFN-?-suppressed enhancers comprised two subsets distinguished by differential regulation of histone acetylation and recruitment of STAT3, CDK8 and cohesin, and were functionally inactivated by IFN-?. These findings reveal that IFN-? suppresses feedback inhibitory and metabolic components of the TLR response to achieve full M1 polarization, and provide insights into mechanisms by which IFN-? selectively inhibits TLR4-induced transcription. Overall design: RNA-seq analysis of transcriptional changes in human macrophages (M-CSF/GM-CSF) that were cultured with or without IFN-? and then stimulated with LPS or vice versa