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IFN-γ selectively suppresses a subset of TLR4-activated genes and enhancers to potentiate M1-like macrophage polarization [ChIP-seq II]

ABSTRACT: Complete activation of macrophage proinflammatory and antimicrobial phenotype is promoted by combined action of IFN-g and LPS. Synergistic activation of canonical inflammatory NF-kB target genes by IFN-g and LPS is well appreciated, but less is known about whether IFN-g negatively regulates components of the LPS response, and how this affects polarization. A combined transcriptomic and epigenomic approach revealed that IFN-g 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-g-mediated repression targeted enhancers with STAT sequences that bound STAT3. TLR4-activated IFN-g-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-g. These findings reveal that IFN-g suppresses feedback inhibitory and metabolic components of the TLR response to achieve full macrophage activation and provide insights into mechanisms by which IFN-g selectively inhibits TLR4-induced transcription.

ORGANISM(S): Homo sapiens

PROVIDER: GSE131294 | GEO | 2019/06/12

REPOSITORIES: GEO

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Project description:Interferon (IFN)γ and interleukin (IL)-4 are central regulators of T helper 1 (Th1) and T helper 2 (Th2) immune responses, respectively. Both cytokines have a major impact on macrophage phenotypes: IFNγ–priming and subsequent TLR4 activation induces so called classically activated macrophages that are characterized by pronounced pro-inflammatory responses, whereas IL-4–treated macrophages, commonly called alternatively activated, are known to develop enhanced capacity for endocytosis, antigen presentation, and tissue repair and are generally considered anti-inflammatory. Considering IL-4 as priming rather than activating stimulus, we now compared the TLR4–dependent global gene activation program in IFNγ– versus IL-4–pretreated mouse macrophages, which has rarely been studied so far. Although both cytokines frequently induced opposing effects on gene transcription, the subsequent activation of bone marrow-derived macrophages by lipopolysaccharide (LPS) produced a strong, priming dependent pro-inflammatory response in both macrophage types. For example, the production of key pro-inflammatory cytokines IL-6 and IL-12 was significantly higher in IL-4– versus IFNγ–primed macrophages and several cytokine genes, including Il19, Ccl17, Ccl22, Ccl24 and Cxcl5, were preferentially induced in alternatively primed and LPS activated mouse macrophages. In a subset of genes, including IL12a, IFNγ priming was actually found to suppress LPS–induced gene expression in a Stat1–dependent manner. Our data suggest that IL-4–priming is not per se anti-inflammatory but generates a macrophage that is “tissue protective” but still capable of mounting a strong inflammatory response after TLR4–dependent activation. Keywords: Gene expression profiling Gene expression was investigated in mouse bone marrow-derived macrophages (BMM). On day 7, BMM were stimulated with either IL-4 or IFNγ overnight (18h in total). LPS treatment was performed in primed and unprimed macrophages 4 h prior to harvesting. At least three independent experiments were performed for each condition.

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IFN-γ selectively suppresses a subset of TLR4-activated genes and enhancers to potentiate M1-like macrophage polarization [ChIP-seq II]

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