Opposing Regulation of TNF Responses and IL-1b+ Macrophages by PGE2-cAMP Signaling and IFN-g [RNA-seq]
IL-1b-expressing macrophages elicited by cooperation between PGE2 and TNF signaling have been identified and proposed to be pathogenic in rheumatoid arthritis (RA) and pancreatic cancer, but mechanisms that induce these cells and the extent to which they contribute to arthritic phenotypes are not known. In this study we used an integrated transcriptomic and epigenomic analysis in primary human monocytes to study PGE2-TNF crosstalk, and how it is regulated by IFN-g, as occurs in RA synovial macrophages. We identified a (TNF + PGE2)-induced gene expression signature that is enriched in RA and post-immune checkpoint blockade arthritis macrophage subsets and includes genes in pathogenic IL-1, Notch and neutrophil chemokine pathways. This gene expression signature, which is distinct from canonical inflammatory NF-kB target genes such as TNF, IL6 and IL12B, was driven by cooperation of PGE2-induced AP-1, CEBP and NR4A family transcription factors with TNF-induced NF-kB activity. Unexpectedly, IFN-g suppressed induction AP-1, CEBP and NR4A activity to ablate induction of IL-1, Notch and neutrophil chemokine genes, while promoting expression of distinct inflammatory genes such as TNF and T cell chemokines like CXCL10. These results reveal the basis for synergistic induction of inflammatory genes by PGE2 and TNF, and a novel regulatory axis whereby IFN-g and PGE2 oppose each other to determine the balance between two distinct TNF-induced inflammatory gene expression programs. Overall design: We wished to understand the full spectrum of pathogenic inflammatory genes induced by cooperation between PGE2 and TNF signaling, to gain insight into mechanisms underlying signaling crosstalk, and address the important question of how PGE2-TNF crosstalk is modulated by IFN-g, as occurs in RA synovial macrophages. We performed an integrated transcriptomic and epigenomic analysis of gene expression and chromatin accessibility using primary human monocytes, which correspond directly to cells that migrate into inflamed synovium and provide an opportunity to model in vivo activation.