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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.

SUBMITTER: Pfefferle M

PROVIDER: S-EPMC7524492 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes.

Pfefferlé Marc M Ingoglia Giada G Schaer Christian A CA Yalamanoglu Ayla A Buzzi Raphael R Dubach Irina L IL Tan Ge G López-Cano Emilio Y EY Schulthess Nadja N Hansen Kerstin K Humar Rok R Schaer Dominik J DJ Vallelian Florence F

The Journal of clinical investigation 20201001 10

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 trans ...[more]

PMID: 32663195

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Project description:Apolipoprotein E (apoE) exerts potent antiinflammatory effects. Here, we investigated the effect of apoE on the functional phenotype of macrophages.Human apoE receptors very-low-density lipoprotein receptor (VLDL-R) and apoE receptor-2 (apoER2) were stably expressed in RAW264.7 mouse macrophages. In these cells, apoE downregulated markers of the proinflammatory M1 phenotype (inducible nitric oxide synthase, interleukin [IL]-12, macrophage inflammatory protein-1?) but upregulated markers of the antiinflammatory M2 phenotype (arginase I, SOCS3, IL-1 receptor antagonist [IL-1RA]). In addition, M1 macrophage responses (migration, generation of reactive oxygen species, antibody-dependent cell cytotoxicity, phagocytosis), as well as poly(I:C)- or interferon-?-induced production of proinflammatory cytokines; cyclooxygenase-2 expression; and activation of nuclear factor-?B, I?B, and STAT1, were suppressed in VLDL-R- or apoER2-expressing cells. Conversely, the suppression of the M2 phenotype and the enhanced response to poly(I:C) were observed in apoE-producing bone marrow macrophages derived from VLDL-R-deficient mice but not wild-type or low-density lipoprotein receptor-deficient mice. The modulatory effects of apoE on macrophage polarization were inhibited in apoE receptor-expressing RAW264.7 cells exposed to SB220025, a p38 mitogen-activated protein kinase inhibitor, and PP1, a tyrosine kinase inhibitor. Accordingly, apoE induced tyrosine kinase-dependent activation of p38 mitogen-activated protein kinase in VLDL-R- or apoER2-expressing macrophages. Under in vivo conditions, apoE-/- mice transplanted with apoE-producing wild-type bone marrow showed increased plasma IL-1RA levels, and peritoneal macrophages of transplanted animals were shifted to the M2 phenotype (increased IL-1RA production and CD206 expression).ApoE signaling via VLDL-R or apoER2 promotes macrophage conversion from the proinflammatory M1 to the antiinflammatory M2 phenotype. This effect may represent a novel antiinflammatory activity of apoE.

Project description:Activated macrophages acquire a proinflammatory (classic) or antiinflammatory (alternative) phenotype that influences atherosclerosis. The present study investigated whether sphingosine-1-phosphate (S1P), with its known antiinflammatory effects, could regulate the inflammatory phenotype of lipopolysaccharide (LPS)-stimulated mouse macrophages. Activation of macrophages by LPS significantly increases proinflammatory cytokine secretion. Pretreatment of macrophages with 500 nmol/L S1P markedly reduced LPS-mediated secretion of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and interleukin-12. Such antiinflammatory actions were also evident in LPS-stimulated macrophages treated with the S1P1 receptor-specific agonist SEW2871. Pharmacological antagonism of the S1P1 receptor on macrophages using the S1P1-specific antagonist VPC44116 also blocked proinflammatory cytokine secretion in response to LPS. Studies using bone marrow-derived macrophages from S1P2-deficient mice revealed that the S1P2 receptor did not play a pivotal role in this process. Thus, activation of the S1P1 receptor in mouse macrophages limits the expression of proinflammatory cytokines. Furthermore, we demonstrated that S1P increased arginase I activity and inhibited LPS-induced inducible NO synthase activity in LPS-treated macrophages, again through S1P1 receptor activation on macrophages. Analysis of a 1.7-kb region of the murine inducible NO synthase promoter revealed the presence of putative nuclear factor kappaB, activator protein-1, and STAT-1 response elements. Using inducible NO synthase promoter-reporter constructs, we found that S1P significantly reduced the nuclear factor kappaB-mediated induction of inducible NO synthase. These findings demonstrate an important role for S1P in the regulation of macrophage phenotypic switching. Therefore, we conclude that S1P promotes the production of an alternative antiinflammatory macrophage phenotype through activation of the macrophage S1P1 receptor.

Project description:BackgroundPre-eclampsia is a relatively common complication of pregnancy. HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome is a severe manifestation of pre-eclampsia with significant morbidity and mortality for pregnant women and their children. Corticosteroids are commonly used in the treatment of HELLP syndrome in the belief that they improve outcomes.ObjectivesTo determine the effects of corticosteroids on women with HELLP syndrome and their children.Search strategyWe searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2010).Selection criteriaRandomized controlled trials comparing any corticosteroid with placebo, no treatment, or other drug; or comparing one corticosteroid with another corticosteroid or dosage in women with HELLP syndrome.Data collection and analysisTwo review authors assessed trial quality and extracted data independently.Main resultsEleven trials (550 women) compared corticosteroids with placebo or no treatment. There was no difference in the risk of maternal death (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.28 to 3.21), maternal death or severe maternal morbidity (RR 0.27, 95% CI 0.03 to 2.12), or perinatal/infant death (RR 0.64, 95% CI 0.21 to 1.97). The only clear effect of treatment on individual outcomes was improved platelet count (standardized mean difference (SMD) 0.67, 95% CI 0.24 to 1.10). The effect on platelet count was strongest for women who commenced treatment antenatally (SMD 0.80, 95% CI 0.25 to 1.35).Two trials (76 women) compared dexamethasone with betamethasone. There was no clear evidence of a difference between groups in respect to perinatal/infant death (RR 0.95, 95% CI 0.15 to 6.17) or severe perinatal/infant morbidity or death (RR 0.64, 95% CI 0.27 to 1.48). Maternal death and severe maternal morbidity were not reported. In respect to platelet count, dexamethasone was superior to betamethasone (MD 6.02, 95% CI 1.71 to 10.33), both when treatment was commenced antenatally (MD 8.10, 95% CI 6.23 to 9.97) and postnatally (MD 3.70, 95% CI 0.96 to 6.44).Authors' conclusionsThere was no clear evidence of any effect of corticosteroids on substantive clinical outcomes. Those receiving steroids showed significantly greater improvement in platelet counts which was greater for those receiving dexamethasone than those receiving betamethasone. There is to date insufficient evidence of benefits in terms of substantive clinical outcomes to support the routine use of steroids for the management of HELLP. The use of corticosteroids may be justified in clinical situations in which increased rate of recovery in platelet count is considered clinically worthwhile.

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Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes.

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Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes.

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