Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes
Marc Pfefferlé, … , Dominik J. Schaer, Florence Vallelian
Marc Pfefferlé, … , Dominik J. Schaer, Florence Vallelian
Published July 14, 2020
Citation Information: J Clin Invest. 2020;130(10):5576-5590. https://doi.org/10.1172/JCI137282.
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Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes

Abstract

During hemolysis, macrophages in the liver phagocytose damaged erythrocytes to prevent the toxic effects of cell-free hemoglobin and heme. It remains unclear how this homeostatic process modulates phagocyte functions in inflammatory diseases. Using a genetic mouse model of spherocytosis and single-cell RNA sequencing, we found that erythrophagocytosis skewed liver macrophages into an antiinflammatory phenotype that we defined as MarcohiHmoxhiMHC class IIlo erythrophagocytes. This phenotype transformation profoundly mitigated disease expression in a model of an anti-CD40–induced hyperinflammatory syndrome with necrotic hepatitis and in a nonalcoholic steatohepatitis model, representing 2 macrophage-driven sterile inflammatory diseases. We reproduced the antiinflammatory erythrophagocyte transformation in vitro by heme exposure of mouse and human macrophages, yielding a distinctive transcriptional signature that segregated heme-polarized from M1- and M2-polarized cells. Mapping transposase-accessible chromatin in single cells by sequencing defined the transcription factor NFE2L2/NRF2 as a critical driver of erythrophagocytes, and Nfe2l2/Nrf2 deficiency restored heme-suppressed inflammation. Our findings point to a pathway that regulates macrophage functions to link erythrocyte homeostasis with innate immunity.

Authors

Marc Pfefferlé, Giada Ingoglia, Christian A. Schaer, Ayla Yalamanoglu, Raphael Buzzi, Irina L. Dubach, Ge Tan, Emilio Y. López-Cano, Nadja Schulthess, Kerstin Hansen, Rok Humar, Dominik J. Schaer, Florence Vallelian

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Figure 2

Antioxidant and antiinflammatory transcriptional phenotype of erythrophagocytes.

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Antioxidant and antiinflammatory transcriptional phenotype of erythropha...
(A) Volcano plot demonstrating differential gene expression of KCs in Sptasph/sph versus Sptawt/wt mice [–log10(P value) versus log2(fold change)]. Among the positive differentially expressed genes (DEGs), marker genes of the erythrophagocytic process are highlighted in red, genes associated with heme exposure and oxidative stress are highlighted in blue, and macrophage receptors are highlighted in green. The downregulated MHC class II–associated genes are highlighted in purple. (B) DEGs were computed by gene set enrichment analysis (GSEA). Enrichment plots of the top 3 positively (magenta) and negatively (blue) enriched hallmark gene sets are shown. Plots display running enrichment score and position of gene set members on the rank-ordered list. (C) t-SNE plot showing all cells colored by cell origin. The expression of Hmox1, Marco, Vcam1, Cd74, H2-Aa, and H2-Ab1 is presented in global t-SNE plots. Legend for relative log2 expression of each gene from lowest expression (blue dots) to the highest expression (red dots) is displayed on the top right. (D) Contour plot showing the correlation of Hmox1, Marco, or H2-Aa and Hba-a1 count data from every cell in the Sptasph/sph (red) and Sptawt/wt (blue) mouse data sets. (E) Contour plot showing the correlation of Hmox1 or H2-Aa and Marco count data from every cell in the Sptasph/sph (red) and Sptawt/wt (blue) mouse data sets. (F) t-SNE plots with color-coded expression of Marco and Marco/Hba-a1 in Sptasph/sph (left) and Sptawt/wt (right) mice. The magenta dashed line highlights the Marco/Hba-a1 double-positive erythrophagocytes.