Stressed erythrophagocytosis weakens host immunity through heme-mediated STAT1 dysregulation
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE144902 | GEO | 2021/01/06
REPOSITORIES: GEO
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Project description:Macrophages are main effectors of heme metabolism, increasing transiently in the liver during heightened disposal of damaged or senescent RBCs (sRBCs). Macrophages are also essential in defense against microbial threats, but pathological states of heme excess may be immunosuppressive. Herein, we uncovered a mechanism whereby an acute rise in sRBC disposal by macrophages led to an immunosuppressive phenotype after intrapulmonary Klebsiella pneumoniae infection characterized by increased extrapulmonary bacterial proliferation and reduced survival from sepsis in mice. The impaired immunity to K. pneumoniae during heightened sRBC disposal was independent of iron acquisition by bacterial siderophores, in that K. pneumoniae mutants lacking siderophore function recapitulated the findings observed with the WT strain. Rather, sRBC disposal induced a liver transcriptomic profile notable for suppression of Stat1 and IFN-related responses during K. pneumoniae sepsis. Excess heme handling by macrophages recapitulated STAT1 suppression during infection that required synergistic NRF1 and NRF2 activation but was independent of heme oxygenase-1 induction. Whereas iron was dispensable, the porphyrin moiety of heme was sufficient to mediate suppression of STAT1-dependent responses in human and mouse macrophages and promoted liver dissemination of K. pneumoniae in vivo. Thus, cellular heme metabolism dysfunction negatively regulated the STAT1 pathway, with implications in severe infection.
| S-EPMC7773401 | biostudies-literature
Project description:Stressed erythrophagocytosis weakens host immunity through heme-mediated STAT1 dysregulation
| PRJNA605249 | ENA
Project description:Reticuloendothelial macrophages engulf ~0.2 trillion senescent erythrocytes daily in a process called erythrophagocytosis (EP). This critical mechanism preserves systemic heme-iron homeostasis by regulating red blood cell (RBC) catabolism and iron recycling. Although extensive work has demonstrated the various effects on macrophage metabolic reprogramming by stimulation with proinflammatory cytokines, little is known about the impact of EP on the macrophage metabolome and proteome. Thus, we performed mass spectrometry-based metabolomics and proteomics analyses of bone marrow-derived macrophages (BMDMs) before and after EP of IgG-coated RBCs. Further, metabolomics was performed on BMDMs incubated with free IgG to ensure that changes to macrophage metabolism were due to opsonized RBCs and not to free IgG binding. Uniformly labeled tracing experiments were conducted on BMDMs in the presence and absence of IgG-coated RBCs to assess the flux of glucose through the pentose phosphate pathway (PPP). In this study, we demonstrate that EP significantly alters amino acid and fatty acid metabolism, the Krebs cycle, OXPHOS, and arachidonate-linoleate metabolism. Increases in levels of amino acids, lipids and oxylipins, heme products, and RBC-derived proteins are noted in BMDMs following EP. Tracing experiments with U-13C6 glucose indicated a slower flux through glycolysis and enhanced PPP activation. Notably, we show that it is fueled by glucose derived from the macrophages themselves or from the extracellular media prior to EP, but not from opsonized RBCs. The PPP-derived NADPH can then fuel the oxidative burst, leading to the generation of reactive oxygen species necessary to promote digestion of phagocytosed RBC proteins via radical attack. Results were confirmed by redox proteomics experiments, demonstrating the oxidation of Cys152 and Cys94 of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and hemoglobin-β, respectively. Significant increases in early Krebs cycle and C5-branched dibasic acid metabolites (α-ketoglutarate and 2-hydroxyglutarate, respectively) indicate that EP promotes the dysregulation of mitochondrial metabolism. Lastly, EP stimulated aminolevulinic acid (ALA) synthase and arginase activity as indicated by significant accumulations of ALA and ornithine after IgG-mediated RBC ingestion. Importantly, EP-mediated metabolic reprogramming of BMDMs does not occur following exposure to IgG alone. In conclusion, we show that EP reprograms macrophage metabolism and modifies macrophage polarization.
2020-05-27 | PXD017788 | Pride
Project description:Klebsiella pneumoniae (KP) are extracellular Gram-negative bacteria that cause infections in lower respiratory and urinary tract, and bloodstream. STAT1 is a master transcription factor that acts to maintain T-cell quiescence under homeostatic conditions. Although STAT1 helps defend against systemic spread of acute KP intrapulmonary infection, whether STAT1 regulation of T-cell homeostasis impacts pulmonary host defense during acute bacterial infection and injury is less clear. Using a clinical KP respiratory isolate and a pneumonia mouse model, we found STAT1-deficiency led to an early neutrophil-dominant transcriptional profile and neutrophil-recruitment in the lung preceding widespread bacterial dissemination and lung injury development. Yet, myeloid cell STAT1 was dispensable for control of KP proliferation and dissemination, as myeloid cell-specific STAT1-deficient (LysMCre/WT;Stat1fl/fl) mice showed similar bacterial burden in lung, liver, and kidney as WT littermates. Surprisingly, IL-17 producing CD4+ T-cells infiltrated Stat1-/- mice lungs early during KP infection. Increase in Th17-cells in the lung was not due to preexisting immunity against KP and were consistent with circulating rather than tissue-resident CD4+ T-cells. However, blocking global IL17 signaling with anti-IL17-RC administration led to increased proliferation and dissemination of KP, suggesting IL17 provided by other innate immune cells is essential in defense against KP. Contrastingly, depletion of CD4+ T-cells reduced Stat1-/- mice lung bacterial burden indicating early CD4+ T-cell activation in the setting of global STAT1-deficiency is pathogenic. Altogether, our findings suggest STAT1 employs myeloid cell-extrinsic mechanisms to regulate neutrophil responses and provide protection against invasive KP by restricting non-specific CD4+ T-cell activation and immunopathology in the lung.
2024-01-10 | GSE251767 | GEO
Project description:Under conditions of erythrolytic stress, which accompanies many disease states, macrophages play key roles in phagocytosing damaged RBCs and preventing the toxic effects of cell-free hemoglobin and heme to maintain homeostasis. Using a genetic mouse model of spherocytosis and single-cell RNA sequencing, we show that erythrolytic stress promotes expansion of a specific macrophage population in the liver (which we named “erythrophagocytes”) expressing high levels of Marco and Hmox1 and low levels of MHC class II related genes with an anti-inflammatory gene expression signature. We confirmed the strong anti-inflammatory function of erythrophagocytes in two models of sterile inflammatory liver disease: anti-CD40 antibody-induced systemic inflammation syndrome with necrotizing hepatitis and diet-induced nonalcoholic fatty liver disease (NAFLD). The unique anti-inflammatory phenotype and function of erythrophagocytes was reproduced in vitro by heme-exposure of mouse macrophages, yielding a transcriptional profile that segregated heme-polarized from classical M1- and M2-polarized cells. Mapping transposase-accessible chromatin in single cells using sequencing (scATAC-seq) suggested NFE2L2/NRF2 as a critical driver of anti-inflammatory erythrophagocytes in the livers of hemolytic mice and heme-suppression of the inflammatory response was abolished in macrophages from Nfe2l2/Nrf2-deficient animals. Our findings point to a novel pathway that regulates macrophage functions to link RBC homeostasis and heme metabolism with innate immunity.
2020-08-13 | GSE151408 | GEO
Project description:Adult humans have about 25 trillion red blood cells (RBCs), and each second we recycle about 5 million RBCs by erythrophagocytosis (EP) in macrophages of the reticuloendothelial system. Despite the central role for EP in mammalian iron metabolism, the molecules and pathways responsible for heme trafficking during EP remain unknown. Here, we show that the mammalian homolog of HRG1, a transmembrane heme permease in C. elegans, is essential for macrophage iron homeostasis and transports heme from the phagolysosome to the cytoplasm during EP. HRG1 is strongly expressed in macrophages of the reticuloendothelial system and specifically localizes to the phagolysosomal membranes during EP. Depletion of Hrg1 in mouse macrophages causes attenuation of heme transport from the phagolysosomal compartment. Importantly, missense polymorphisms in human HRG1 are defective in heme transport. Our results reveal HRG1 as the long-sought heme transporter for heme-iron recycling in macrophages and suggest that genetic variations in HRG1 could be modifiers of human iron metabolism.
| S-EPMC3582031 | biostudies-literature
Project description:RNA-seq datasets on adult zebrafish kidneys and spleens, non-PHZ (phenylhydrazine) and PHZ treated, to compare the gene expression on Tü wild type and hrg1 knockout zebrafish.
2018-09-03 | GSE109978 | GEO
Project description:BackgroundSenescent red blood cells (RBC) are recognized, phagocytosed and cleared by tissue macrophages. During this erythrophagocytosis (EP), RBC are engulfed and processed in special compartments called erythrophagosomes. We previously described that following EP, heme is rapidly degraded through the catabolic activity of heme oxygenase (HO). Extracted heme iron is then either exported or stored by macrophages. However, the cellular localization of the early steps of heme processing and iron extraction during EP remains to be clearly defined.Methodology/principal findingsWe took advantage of our previously described cellular model of EP, using bone marrow-derived macrophages (BMDM). The subcellular localization of both inducible and constitutive isoforms of HO (HO-1 and HO-2), of the divalent metal transporters (Nramp1, Nramp2/DMT1, Fpn), and of the recently identified heme transporter HRG-1, was followed by fluorescence and electron microscopy during the earliest steps of EP. We also looked at some ER [calnexin, glucose-6-phosphatase (G6Pase) activity] and lysosomes (Lamp1) markers during EP. In both quiescent and LPS-activated BMDM, Nramp1 and Lamp1 were shown to be strong markers of the erythrophagolysosomal membrane. HRG-1 was also recruited to the erythrophagosome. Furthermore, we observed calnexin labeling and G6Pase activity at the erythrophagosomal membrane, indicating the contribution of ER in this phagocytosis model. In contrast, Nramp2/DMT1, Fpn, HO-1 and HO-2 were not detected at the membrane of erythrophagosomes.Conclusions/significanceOur study highlights the subcellular localization of various heme- and iron-related proteins during early steps of EP, thereby suggesting a model for heme catabolism occurring outside the phagosome, with heme likely being transported into the cytosol through HRG1. The precise function of Nramp1 at the phagosomal membrane in this model remains to be determined.
| S-EPMC3408460 | biostudies-literature
Project description:Klebsiella pneumoniae is an arising threat to human health. However, host immune responses in response to this bacterium remain to be elucidated. The goal of this study was to identify the dominant host immune responses associated with Klebsiella pneumoniae pulmonary infection. Pulmonary mRNA profiles of 6-8-weeks-old BALB/c mice infected with/without Klebsiella pneumoniae were generated by deep sequencing using Illumina Novaseq 6000. qRT–PCR validation was performed using SYBR Green assays. Using KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis, we identified several immune associated pathways, including complement and coagulation cascades, Toll-like receptor signaling pathway, Rap1 signaling pathway, chemokine signaling pathway, TNF signaling pathway, phagosome and NOD-like receptor signaling pathway, were involved in Klebsiella pneumoniae pulmonary infection. Using ICEPOP (Immune CEll POPulation) analysis, we found that several cell types were involved in the host immune response to Klebsiella pneumoniae pulmonary infection, including dendritic cells, macrophages, monocytes, NK (natural killer) cells, stromal cells. Further, IL-17 chemokines were significantly increased during Klebsiella pneumoniae infection. This study provided evidence for further studying the pathogenic mechanism of Klebsiella pneumoniae pneumonia infection.
2021-03-30 | GSE171048 | GEO
Project description:Under conditions of erythrolytic stress, which accompanies many disease states, macrophages play key roles in phagocytosing damaged RBCs and preventing the toxic effects of cell-free hemoglobin and heme to maintain homeostasis. Using a genetic mouse model of spherocytosis and single-cell RNA sequencing, we show that erythrolytic stress promotes expansion of a specific macrophage population in the liver (which we named “erythrophagocytes”) expressing high levels of Marco and Hmox1 and low levels of MHC class II related genes with an anti-inflammatory gene expression signature. We confirmed the strong anti-inflammatory function of erythrophagocytes in two models of sterile inflammatory liver disease: anti-CD40 antibody-induced systemic inflammation syndrome with necrotizing hepatitis and diet-induced nonalcoholic fatty liver disease (NAFLD). The unique anti-inflammatory phenotype and function of erythrophagocytes was reproduced in vitro by heme-exposure of mouse macrophages, yielding a transcriptional profile that segregated heme-polarized from classical M1- and M2-polarized cells. The phenotype of anti-inflammatory erythrophagocytes coincided with NFE2L2/NRF2 driven gene expression and was abolished in Nfe2l2/Nrf2-deficient macrophages. Our findings point to a novel pathway that regulates macrophage functions to link RBC homeostasis and heme metabolism with innate immunity.
2020-08-13 | GSE146152 | GEO