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Yeudall S, Upchurch CM, Leitinger N. The clinical relevance of heme detoxification by the macrophage heme oxygenase system. Front Immunol 2024; 15:1379967. [PMID: 38585264 PMCID: PMC10995405 DOI: 10.3389/fimmu.2024.1379967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 03/11/2024] [Indexed: 04/09/2024] Open
Abstract
Heme degradation by the heme oxygenase (HMOX) family of enzymes is critical for maintaining homeostasis and limiting heme-induced tissue damage. Macrophages express HMOX1 and 2 and are critical sites of heme degradation in healthy and diseased states. Here we review the functions of the macrophage heme oxygenase system and its clinical relevance in discrete groups of pathologies where heme has been demonstrated to play a driving role. HMOX1 function in macrophages is essential for limiting oxidative tissue damage in both acute and chronic hemolytic disorders. By degrading pro-inflammatory heme and releasing anti-inflammatory molecules such as carbon monoxide, HMOX1 fine-tunes the acute inflammatory response with consequences for disorders of hyperinflammation such as sepsis. We then discuss divergent beneficial and pathological roles for HMOX1 in disorders such as atherosclerosis and metabolic syndrome, where activation of the HMOX system sits at the crossroads of chronic low-grade inflammation and oxidative stress. Finally, we highlight the emerging role for HMOX1 in regulating macrophage cell death via the iron- and oxidation-dependent form of cell death, ferroptosis. In summary, the importance of heme clearance by macrophages is an active area of investigation with relevance for therapeutic intervention in a diverse array of human diseases.
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Affiliation(s)
- Scott Yeudall
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, United States
- Medical Scientist Training Program, University of Virginia School of Medicine, Charlottesville, VA, United States
| | - Clint M. Upchurch
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), University of Virginia School of Medicine, Charlottesville, VA, United States
| | - Norbert Leitinger
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, United States
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, United States
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2
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Nakayama Y, Masuda Y, Mukae T, Mikami T, Shimizu R, Kondo N, Kitagawa H, Itoh N, Konishi M. A secretory protein neudesin regulates splenic red pulp macrophages in erythrophagocytosis and iron recycling. Commun Biol 2024; 7:129. [PMID: 38272969 PMCID: PMC10811329 DOI: 10.1038/s42003-024-05802-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 01/10/2024] [Indexed: 01/27/2024] Open
Abstract
Neudesin, originally identified as a neurotrophic factor, has primarily been studied for its neural functions despite its widespread expression. Using 8-week-old neudesin knockout mice, we elucidated the role of neudesin in the spleen. The absence of neudesin caused mild splenomegaly, shortened lifespan of circulating erythrocytes, and abnormal recovery from phenylhydrazine-induced acute anemia. Blood cross-transfusion and splenectomy experiments revealed that the shortened lifespan of erythrocytes was attributable to splenic impairment. Further analysis revealed increased erythrophagocytosis and decreased iron stores in the splenic red pulp, which was linked to the upregulation of Fcγ receptors and iron-recycling genes in neudesin-deficient macrophages. In vitro analysis confirmed that neudesin suppressed erythrophagocytosis and expression of Fcγ receptors through ERK1/2 activation in heme-stimulated macrophages. Finally, we observed that 24-week-old neudesin knockout mice exhibited severe symptoms of anemia. Collectively, our results suggest that neudesin regulates the function of red pulp macrophages and contributes to erythrocyte and iron homeostasis.
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Affiliation(s)
- Yoshiaki Nakayama
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Yuki Masuda
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Takehiro Mukae
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Tadahisa Mikami
- Laboratory of Biochemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Ryohei Shimizu
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Naoto Kondo
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Hiroshi Kitagawa
- Laboratory of Biochemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Nobuyuki Itoh
- Kyoto University Graduate School of Pharmaceutical Science, Kyoto, Japan
| | - Morichika Konishi
- Laboratory of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan.
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3
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Schaer DJ, Schulthess-Lutz N, Baselgia L, Hansen K, Buzzi RM, Humar R, Dürst E, Vallelian F. Hemorrhage-activated NRF2 in tumor-associated macrophages drives cancer growth, invasion, and immunotherapy resistance. J Clin Invest 2023; 134:e174528. [PMID: 38060331 PMCID: PMC10849758 DOI: 10.1172/jci174528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 11/28/2023] [Indexed: 02/02/2024] Open
Abstract
Microscopic hemorrhage is a common aspect of cancers, yet its potential role as an independent factor influencing both cancer progression and therapeutic response is largely ignored. Recognizing the essential function of macrophages in red blood cell disposal, we explored a pathway that connects intratumoral hemorrhage with the formation of cancer-promoting tumor-associated macrophages (TAMs). Using spatial transcriptomics, we found that NRF2-activated myeloid cells possessing characteristics of procancerous TAMs tend to cluster in perinecrotic hemorrhagic tumor regions. These cells resembled antiinflammatory erythrophagocytic macrophages. We identified heme, a red blood cell metabolite, as a pivotal microenvironmental factor steering macrophages toward protumorigenic activities. Single-cell RNA-Seq and functional assays of TAMs in 3D cell culture spheroids revealed how elevated intracellular heme signals via the transcription factor NRF2 to induce cancer-promoting TAMs. These TAMs stabilized epithelial-mesenchymal transition, enhancing cancer invasiveness and metastatic potential. Additionally, NRF2-activated macrophages exhibited resistance to reprogramming by IFN-γ and anti-CD40 antibodies, reducing their tumoricidal capacity. Furthermore, MC38 colon adenocarcinoma-bearing mice with NRF2 constitutively activated in leukocytes were resistant to anti-CD40 immunotherapy. Overall, our findings emphasize hemorrhage-activated NRF2 in TAMs as a driver of cancer progression, suggesting that targeting this pathway could offer new strategies to enhance cancer immunity and overcome therapy resistance.
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4
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Hou P, Fang J, Liu Z, Shi Y, Agostini M, Bernassola F, Bove P, Candi E, Rovella V, Sica G, Sun Q, Wang Y, Scimeca M, Federici M, Mauriello A, Melino G. Macrophage polarization and metabolism in atherosclerosis. Cell Death Dis 2023; 14:691. [PMID: 37863894 PMCID: PMC10589261 DOI: 10.1038/s41419-023-06206-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 09/27/2023] [Accepted: 09/29/2023] [Indexed: 10/22/2023]
Abstract
Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of fatty deposits in the inner walls of vessels. These plaques restrict blood flow and lead to complications such as heart attack or stroke. The development of atherosclerosis is influenced by a variety of factors, including age, genetics, lifestyle, and underlying health conditions such as high blood pressure or diabetes. Atherosclerotic plaques in stable form are characterized by slow growth, which leads to luminal stenosis, with low embolic potential or in unstable form, which contributes to high risk for thrombotic and embolic complications with rapid clinical onset. In this complex scenario of atherosclerosis, macrophages participate in the whole process, including the initiation, growth and eventually rupture and wound healing stages of artery plaque formation. Macrophages in plaques exhibit high heterogeneity and plasticity, which affect the evolving plaque microenvironment, e.g., leading to excessive lipid accumulation, cytokine hyperactivation, hypoxia, apoptosis and necroptosis. The metabolic and functional transitions of plaque macrophages in response to plaque microenvironmental factors not only influence ongoing and imminent inflammatory responses within the lesions but also directly dictate atherosclerotic progression or regression. In this review, we discuss the origin of macrophages within plaques, their phenotypic diversity, metabolic shifts, and fate and the roles they play in the dynamic progression of atherosclerosis. It also describes how macrophages interact with other plaque cells, particularly T cells. Ultimately, targeting pathways involved in macrophage polarization may lead to innovative and promising approaches for precision medicine. Further insights into the landscape and biological features of macrophages within atherosclerotic plaques may offer valuable information for optimizing future clinical treatment for atherosclerosis by targeting macrophages.
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Affiliation(s)
- Pengbo Hou
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Jiankai Fang
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Zhanhong Liu
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Yufang Shi
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Massimiliano Agostini
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Francesca Bernassola
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Pierluigi Bove
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Eleonora Candi
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Valentina Rovella
- Department of System Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Giuseppe Sica
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Qiang Sun
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Ying Wang
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
- The First Affiliated Hospital of Soochow University, Institutes for Translational Medicine, State Key Laboratory of Radiation Medicine and Protection, Suzhou Medical College of Soochow University, Suzhou, China
| | - Manuel Scimeca
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy
| | - Massimo Federici
- Department of System Medicine, University of Rome Tor Vergata, Rome, Italy.
| | - Alessandro Mauriello
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy.
| | - Gerry Melino
- Department of Experimental Medicine, TOR, University of Rome Tor Vergata, Rome, Italy.
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Liu Y, Su S, Shayo S, Bao W, Pal M, Dou K, Shi PA, Aygun B, Campbell-Lee S, Lobo CA, Mendelson A, An X, Manwani D, Zhong H, Yazdanbakhsh K. Hemolysis dictates monocyte differentiation via two distinct pathways in sickle cell disease vaso-occlusion. J Clin Invest 2023; 133:e172087. [PMID: 37490346 PMCID: PMC10503794 DOI: 10.1172/jci172087] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 07/19/2023] [Indexed: 07/27/2023] Open
Abstract
Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by painful vaso-occlusive crises (VOC) and chronic hemolysis. The mononuclear phagocyte system is pivotal to SCD pathophysiology, but the mechanisms governing monocyte/macrophage differentiation remain unknown. This study examined the influence of hemolysis on circulating monocyte trajectories in SCD. We discovered that hemolysis stimulated CSF-1 production, partly by endothelial cells via Nrf2, promoting classical monocyte (CMo) differentiation into blood patrolling monocytes (PMo) in SCD mice. However, hemolysis also upregulated CCL-2 through IFN-I, inducing CMo transmigration and differentiation into tissue monocyte-derived macrophages. Blocking CMo transmigration by anti-P selectin antibody in SCD mice increased circulating PMo, corroborating that CMo-to-tissue macrophage differentiation occurs at the expense of CMo-to-blood PMo differentiation. We observed a positive correlation between plasma CSF-1/CCL-2 ratios and blood PMo levels in patients with SCD, underscoring the clinical significance of these two opposing factors in monocyte differentiation. Combined treatment with CSF-1 and anti-P selectin antibody more effectively increased PMo numbers and reduced stasis compared with single-agent therapies in SCD mice. Altogether, these data indicate that monocyte fates are regulated by the balance between two heme pathways, Nrf2/CSF-1 and IFN-I/CCL-2, and suggest that the CSF-1/CCL-2 ratio may present a diagnostic and therapeutic target in SCD.
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Affiliation(s)
| | - Shan Su
- Laboratory of Complement Biology
| | | | | | | | - Kai Dou
- Laboratory of Immune Regulation, and
| | - Patricia A. Shi
- Clinical Research in Sickle Cell Disease, New York Blood Center, New York, New York, USA
| | - Banu Aygun
- Cohen Children’s Medical Center, New Hyde Park, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA
| | - Sally Campbell-Lee
- Department of Pathology, University of Illinois at Chicago, Chicago, Illinois, USA
| | | | | | - Xiuli An
- Laboratory of Membrane Biology, New York Blood Center, New York, New York, USA
| | - Deepa Manwani
- Department of Pediatrics, Montefiore Medical Center, Albert Einstein College of Medicine, Children’s Hospital at Montefiore, New York, New York, USA
| | - Hui Zhong
- Laboratory of Immune Regulation, and
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6
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Sesti-Costa R, Costa FF, Conran N. Role of Macrophages in Sickle Cell Disease Erythrophagocytosis and Erythropoiesis. Int J Mol Sci 2023; 24:ijms24076333. [PMID: 37047304 PMCID: PMC10094208 DOI: 10.3390/ijms24076333] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/20/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023] Open
Abstract
Sickle cell disease (SCD) is an inherited blood disorder caused by a β-globin gene point mutation that results in the production of sickle hemoglobin that polymerizes upon deoxygenation, causing the sickling of red blood cells (RBCs). RBC deformation initiates a sequence of events leading to multiple complications, such as hemolytic anemia, vaso-occlusion, chronic inflammation, and tissue damage. Macrophages participate in extravascular hemolysis by removing damaged RBCs, hence preventing the release of free hemoglobin and heme, and triggering inflammation. Upon erythrophagocytosis, macrophages metabolize RBC-derived hemoglobin, activating mechanisms responsible for recycling iron, which is then used for the generation of new RBCs to try to compensate for anemia. In the bone marrow, macrophages can create specialized niches, known as erythroblastic islands (EBIs), which regulate erythropoiesis. Anemia and inflammation present in SCD may trigger mechanisms of stress erythropoiesis, intensifying RBC generation by expanding the number of EBIs in the bone marrow and creating new ones in extramedullary sites. In the current review, we discuss the distinct mechanisms that could induce stress erythropoiesis in SCD, potentially shifting the macrophage phenotype to an inflammatory profile, and changing their supporting role necessary for the proliferation and differentiation of erythroid cells in the disease. The knowledge of the soluble factors, cell surface and intracellular molecules expressed by EBI macrophages that contribute to begin and end the RBC’s lifespan, as well as the understanding of their signaling pathways in SCD, may reveal potential targets to control the pathophysiology of the disease.
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7
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Abuga KM, Nairz M, MacLennan CA, Atkinson SH. Severe anaemia, iron deficiency, and susceptibility to invasive bacterial infections. Wellcome Open Res 2023; 8:48. [PMID: 37600584 PMCID: PMC10439361 DOI: 10.12688/wellcomeopenres.18829.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2023] [Indexed: 08/22/2023] Open
Abstract
Severe anaemia and invasive bacterial infections remain important causes of hospitalization and death among young African children. The emergence and spread of antimicrobial resistance demand better understanding of bacteraemia risk factors to inform prevention strategies. Epidemiological studies have reported an association between severe anaemia and bacteraemia. In this review, we explore evidence that severe anaemia is associated with increased risk of invasive bacterial infections in young children. We describe mechanisms of iron dysregulation in severe anaemia that might contribute to increased risk and pathogenesis of invasive bacteria, recent advances in knowledge of how iron deficiency and severe anaemia impair immune responses to bacterial infections and vaccines, and the gaps in our understanding of mechanisms underlying severe anaemia, iron deficiency, and the risk of invasive bacterial infections.
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Affiliation(s)
- Kelvin M. Abuga
- Kenya Medical Research Institute (KEMRI) Centre for Geographical Medicine Research-Coast, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
- Open University, KEMRI-Wellcome Trust Research Programme – Accredited Research Centre, Kilifi, 80108, Kenya
| | - Manfred Nairz
- Department of Internal Medicine II, Medical University of Innsbruck, Innsbruck, 6020, Austria
| | - Calman A. MacLennan
- Jenner Institute, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Sarah H. Atkinson
- Kenya Medical Research Institute (KEMRI) Centre for Geographical Medicine Research-Coast, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7LG, UK
- Department of Paediatrics, University of Oxford, Oxford, OX3 9DU, UK
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8
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Pfefferlé M, Dubach IL, Buzzi RM, Dürst E, Schulthess-Lutz N, Baselgia L, Hansen K, Imhof L, Koernig S, Le Roy D, Roger T, Humar R, Schaer DJ, Vallelian F. Antibody-induced erythrophagocyte reprogramming of Kupffer cells prevents anti-CD40 cancer immunotherapy-associated liver toxicity. J Immunother Cancer 2023; 11:jitc-2022-005718. [PMID: 36593065 PMCID: PMC9809320 DOI: 10.1136/jitc-2022-005718] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2022] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Agonistic anti-CD40 monoclonal antibodies (mAbs) have emerged as promising immunotherapeutic compounds with impressive antitumor effects in mouse models. However, preclinical and clinical studies faced dose-limiting toxicities mediated by necroinflammatory liver disease. An effective prophylactic treatment for liver immune-related adverse events that does not suppress specific antitumor immunity remains to be found. METHODS We used different mouse models and time-resolved single-cell RNA-sequencing to characterize the pathogenesis of anti-CD40 mAb induced liver toxicity. Subsequently, we developed an antibody-based treatment protocol to selectively target red blood cells (RBCs) for erythrophagocytosis in the liver, inducing an anti-inflammatory liver macrophage reprogramming. RESULTS We discovered that CD40 signaling in Clec4f+ Kupffer cells is the non-redundant trigger of anti-CD40 mAb-induced liver toxicity. Taking advantage of the highly specific functionality of liver macrophages to clear antibody-tagged RBCs from the blood, we hypothesized that controlled erythrophagocytosis and the linked anti-inflammatory signaling by the endogenous metabolite heme could be exploited to reprogram liver macrophages selectively. Repeated low-dose administration of a recombinant murine Ter119 antibody directed RBCs for selective phagocytosis in the liver and skewed the phenotype of liver macrophages into a Hmoxhigh/Marcohigh/MHCIIlow anti-inflammatory phenotype. This unique mode of action prevented necroinflammatory liver disease following high-dose administration of anti-CD40 mAbs. In contrast, extrahepatic inflammation, antigen-specific immunity, and antitumor activity remained unaffected in Ter119 treated animals. CONCLUSIONS Our study offers a targeted approach to uncouple CD40-augmented antitumor immunity in peripheral tissues from harmful inflammatoxicity in the liver.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Sandra Koernig
- CSL Ltd., Research, Bio21 Institute, Parkville, Victoria, Australia
| | | | | | - Rok Humar
- University of Zurich, Zurich, Switzerland
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9
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Glaser KM, Tarrant TK, Lämmermann T. Combinatorial depletions of G-protein coupled receptor kinases in immune cells identify pleiotropic and cell type-specific functions. Front Immunol 2022; 13:1039803. [DOI: 10.3389/fimmu.2022.1039803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 11/01/2022] [Indexed: 11/16/2022] Open
Abstract
G-protein coupled receptor kinases (GRKs) participate in the regulation of chemokine receptors by mediating receptor desensitization. They can be recruited to agonist-activated G-protein coupled receptors (GPCRs) and phosphorylate their intracellular parts, which eventually blocks signal propagation and often induces receptor internalization. However, there is growing evidence that GRKs can also control cellular functions beyond GPCR regulation. Immune cells commonly express two to four members of the GRK family (GRK2, GRK3, GRK5, GRK6) simultaneously, but we have very limited knowledge about their interplay in primary immune cells. In particular, we are missing comprehensive studies comparing the role of this GRK interplay for (a) multiple GPCRs within one leukocyte type, and (b) one specific GPCR between several immune cell subsets. To address this issue, we generated mouse models of single, combinatorial and complete GRK knockouts in four primary immune cell types (neutrophils, T cells, B cells and dendritic cells) and systematically addressed the functional consequences on GPCR-controlled cell migration and tissue localization. Our study shows that combinatorial depletions of GRKs have pleiotropic and cell-type specific effects in leukocytes, many of which could not be predicted. Neutrophils lacking all four GRK family members show increased chemotactic migration responses to a wide range of GPCR ligands, whereas combinatorial GRK depletions in other immune cell types lead to pro- and anti-migratory responses. Combined depletion of GRK2 and GRK6 in T cells and B cells shows distinct functional outcomes for (a) one GPCR type in different cell types, and (b) different GPCRs in one cell type. These GPCR-type and cell-type specific effects reflect in altered lymphocyte chemotaxis in vitro and localization in vivo. Lastly, we provide evidence that complete GRK deficiency impairs dendritic cell homeostasis, which unexpectedly results from defective dendritic cell differentiation and maturation in vitro and in vivo. Together, our findings demonstrate the complexity of GRK functions in immune cells, which go beyond GPCR desensitization in specific leukocyte types. Furthermore, they highlight the need for studying GRK functions in primary immune cells to address their specific roles in each leukocyte subset.
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10
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Humar R, Schaer DJ, Vallelian F. Erythrophagocytes in hemolytic anemia, wound healing, and cancer. Trends Mol Med 2022; 28:906-915. [PMID: 36096988 DOI: 10.1016/j.molmed.2022.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 08/11/2022] [Accepted: 08/11/2022] [Indexed: 11/18/2022]
Abstract
Hemolysis is a ubiquitous pathology defined as premature red blood cell destruction within the circulation or local tissues. One of the most archetypal functions of macrophages is phagocytosis of damaged or extravasated red blood cells, preventing the extracellular release of toxic hemoglobin and heme. Upon erythrophagocytosis, spiking intracellular heme concentrations drive macrophage transformation into erythrophagocytes, leveraging antioxidative and iron recycling capacities to defend against hemolytic stress. This unique phenotype transformation is coordinated by a regulatory network comprising the transcription factors BACH1, SPI-C, NRF2, and ATF1. Erythrophagocytes negatively regulate inflammation and immunity and may modulate disease-specific outcomes in hemolytic anemia, wound healing, atherosclerosis, and cancer. In this opinion article, we outline the known and presumed functions of erythrophagocytes and their implications for therapeutic innovation and research.
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Affiliation(s)
- Rok Humar
- Department of Internal Medicine, University Hospital and University of Zurich, Zurich, Switzerland
| | - Dominik J Schaer
- Department of Internal Medicine, University Hospital and University of Zurich, Zurich, Switzerland
| | - Florence Vallelian
- Department of Internal Medicine, University Hospital and University of Zurich, Zurich, Switzerland.
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