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Regulation of tissue iron homeostasis: the macrophage "ferrostat".
Winn NC, Volk KM, Hasty AH
(2020) JCI Insight 5:
MeSH Terms: Adipose Tissue, Animals, Bone Marrow, Bone and Bones, Central Nervous System, Disease, Erythropoiesis, Health, Homeostasis, Humans, Iron, Liver, Macrophages, Muscle, Skeletal, Myocardium, Pancreas, Skin, Spleen, Wound Healing
Show Abstract · Added March 3, 2020
Iron is an essential element for multiple fundamental biological processes required for life; yet iron overload can be cytotoxic. Consequently, iron concentrations at the cellular and tissue level must be exquisitely governed by mechanisms that complement and fine-tune systemic control. It is well appreciated that macrophages are vital for systemic iron homeostasis, supplying or sequestering iron as needed for erythropoiesis or bacteriostasis, respectively. Indeed, recycling of iron through erythrophagocytosis by splenic macrophages is a major contributor to systemic iron homeostasis. However, accumulating evidence suggests that tissue-resident macrophages regulate local iron availability and modulate the tissue microenvironment, contributing to cellular and tissue function. Here, we summarize the significance of tissue-specific regulation of iron availability and highlight how resident macrophages are critical for this process. This tissue-dependent regulation has broad implications for understanding both resident macrophage function and tissue iron homeostasis in health and disease.
0 Communities
1 Members
0 Resources
19 MeSH Terms
Mass cytometry defines distinct immune profile in germinal center B-cell lymphomas.
Roussel M, Lhomme F, Roe CE, Bartkowiak T, Gravelle P, Laurent C, Fest T, Irish JM
(2020) Cancer Immunol Immunother 69: 407-420
MeSH Terms: Adult, Aged, Female, Flow Cytometry, Germinal Center, Humans, Lymphoma, Large B-Cell, Diffuse, Macrophages, Male, Middle Aged, Young Adult
Show Abstract · Added January 14, 2020
Tumor-associated macrophage and T-cell subsets are implicated in the pathogenesis of diffuse large B-cell lymphoma, follicular lymphoma, and classical Hodgkin lymphoma. Macrophages provide essential mechanisms of tumor immune evasion through checkpoint ligand expression and secretion of suppressive cytokines. However, normal and tumor-associated macrophage phenotypes are less well characterized than those of tumor-infiltrating T-cell subsets, and it would be especially valuable to know whether the polarization state of macrophages differs across lymphoma tumor microenvironments. Here, an established mass cytometry panel designed to characterize myeloid-derived suppressor cells and known macrophage maturation and polarization states was applied to characterize B-lymphoma tumors and non-malignant human tissue. High-dimensional single-cell analyses were performed using dimensionality reduction and clustering tools. Phenotypically distinct intra-tumor macrophage subsets were identified based on abnormal marker expression profiles that were associated with lymphoma tumor types. While it had been proposed that measurement of CD163 and CD68 might be sufficient to reveal macrophage subsets in tumors, results here indicated that S100A9, CCR2, CD36, Slan, and CD32 should also be measured to effectively characterize lymphoma-specific tumor macrophages. Additionally, the presence of phenotypically distinct, abnormal macrophage populations was closely linked to the phenotype of intra-tumor T-cell populations, including PD-1 expressing T cells. These results further support the close links between macrophage polarization and T-cell functional state, as well as the rationale for targeting tumor-associated macrophages in cancer immunotherapies.
3 Communities
1 Members
0 Resources
11 MeSH Terms
β1 Integrin regulates adult lung alveolar epithelial cell inflammation.
Plosa EJ, Benjamin JT, Sucre JM, Gulleman PM, Gleaves LA, Han W, Kook S, Polosukhin VV, Haake SM, Guttentag SH, Young LR, Pozzi A, Blackwell TS, Zent R
(2020) JCI Insight 5:
MeSH Terms: Aging, Alveolar Epithelial Cells, Animals, Cell Adhesion, Chemokine CCL2, Chemokines, Disease Models, Animal, Epithelium, Integrin beta1, Lung, Macrophages, Mice, Mice, Inbred C57BL, Mice, Knockout, Pneumonia, Pulmonary Disease, Chronic Obstructive, Receptors, CCR2
Show Abstract · Added March 3, 2020
Integrins, the extracellular matrix receptors that facilitate cell adhesion and migration, are necessary for organ morphogenesis; however, their role in maintaining adult tissue homeostasis is poorly understood. To define the functional importance of β1 integrin in adult mouse lung, we deleted it after completion of development in type 2 alveolar epithelial cells (AECs). Aged β1 integrin-deficient mice exhibited chronic obstructive pulmonary disease-like (COPD-like) pathology characterized by emphysema, lymphoid aggregates, and increased macrophage infiltration. These histopathological abnormalities were preceded by β1 integrin-deficient AEC dysfunction such as excessive ROS production and upregulation of NF-κB-dependent chemokines, including CCL2. Genetic deletion of the CCL2 receptor, Ccr2, in mice with β1 integrin-deficient type 2 AECs impaired recruitment of monocyte-derived macrophages and resulted in accelerated inflammation and severe premature emphysematous destruction. The lungs exhibited reduced AEC efferocytosis and excessive numbers of inflamed type 2 AECs, demonstrating the requirement for recruited monocytes/macrophages in limiting lung injury and remodeling in the setting of a chronically inflamed epithelium. These studies support a critical role for β1 integrin in alveolar homeostasis in the adult lung.
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3 Members
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17 MeSH Terms
Bacterial Pathogens Hijack the Innate Immune Response by Activation of the Reverse Transsulfuration Pathway.
Gobert AP, Latour YL, Asim M, Finley JL, Verriere TG, Barry DP, Milne GL, Luis PB, Schneider C, Rivera ES, Lindsey-Rose K, Schey KL, Delgado AG, Sierra JC, Piazuelo MB, Wilson KT
(2019) mBio 10:
MeSH Terms: Animals, Bacteria, Gene Silencing, Helicobacter pylori, Histones, Humans, Immune Evasion, Immunity, Innate, Immunoglobulins, Macrophages, Male, Metabolic Networks and Pathways, Mice, Mice, Inbred C57BL, Nitric Oxide Synthase Type II, Phosphatidylinositol 3-Kinases, Polyamines, RAW 264.7 Cells, Spermidine, Spermine, Sulfur, Transcription Factors
Show Abstract · Added November 1, 2019
The reverse transsulfuration pathway is the major route for the metabolism of sulfur-containing amino acids. The role of this metabolic pathway in macrophage response and function is unknown. We show that the enzyme cystathionine γ-lyase (CTH) is induced in macrophages infected with pathogenic bacteria through signaling involving phosphatidylinositol 3-kinase (PI3K)/MTOR and the transcription factor SP1. This results in the synthesis of cystathionine, which facilitates the survival of pathogens within myeloid cells. Our data demonstrate that the expression of CTH leads to defective macrophage activation by (i) dysregulation of polyamine metabolism by depletion of -adenosylmethionine, resulting in immunosuppressive putrescine accumulation and inhibition of spermidine and spermine synthesis, and (ii) increased histone H3K9, H3K27, and H3K36 di/trimethylation, which is associated with gene expression silencing. Thus, CTH is a pivotal enzyme of the innate immune response that disrupts host defense. The induction of the reverse transsulfuration pathway by bacterial pathogens can be considered an unrecognized mechanism for immune escape. Macrophages are professional immune cells that ingest and kill microbes. In this study, we show that different pathogenic bacteria induce the expression of cystathionine γ-lyase (CTH) in macrophages. This enzyme is involved in a metabolic pathway called the reverse transsulfuration pathway, which leads to the production of numerous metabolites, including cystathionine. Phagocytized bacteria use cystathionine to better survive in macrophages. In addition, the induction of CTH results in dysregulation of the metabolism of polyamines, which in turn dampens the proinflammatory response of macrophages. In conclusion, pathogenic bacteria can evade the host immune response by inducing CTH in macrophages.
0 Communities
2 Members
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22 MeSH Terms
Inactivation of mTORC2 in macrophages is a signature of colorectal cancer that promotes tumorigenesis.
Katholnig K, Schütz B, Fritsch SD, Schörghofer D, Linke M, Sukhbaatar N, Matschinger JM, Unterleuthner D, Hirtl M, Lang M, Herac M, Spittler A, Bergthaler A, Schabbauer G, Bergmann M, Dolznig H, Hengstschläger M, Magnuson MA, Mikula M, Weichhart T
(2019) JCI Insight 4:
MeSH Terms: Animals, Carcinogenesis, Cell Line, Tumor, Cell Proliferation, Cells, Cultured, Colitis, Ulcerative, Colon, Colorectal Neoplasms, Dextran Sulfate, Disease Models, Animal, Female, Humans, Intestinal Mucosa, Kaplan-Meier Estimate, Macrophages, Male, Mechanistic Target of Rapamycin Complex 2, Mice, Mice, Transgenic, Morpholines, Osteopontin, Primary Cell Culture, Prognosis, Survival Rate
Show Abstract · Added November 6, 2019
The mechanistic target of rapamycin complex 2 (mTORC2) is a potentially novel and promising anticancer target due to its critical roles in proliferation, apoptosis, and metabolic reprogramming of cancer cells. However, the activity and function of mTORC2 in distinct cells within malignant tissue in vivo is insufficiently explored. Surprisingly, in primary human and mouse colorectal cancer (CRC) samples, mTORC2 signaling could not be detected in tumor cells. In contrast, only macrophages in tumor-adjacent areas showed mTORC2 activity, which was downregulated in stromal macrophages residing within human and mouse tumor tissues. Functionally, inhibition of mTORC2 by specific deletion of Rictor in macrophages stimulated tumorigenesis in a colitis-associated CRC mouse model. This phenotype was driven by a proinflammatory reprogramming of mTORC2-deficient macrophages that promoted colitis via the cytokine SPP1/osteopontin to stimulate tumor growth. In human CRC patients, high SPP1 levels and low mTORC2 activity in tumor-associated macrophages correlated with a worsened clinical prognosis. Treatment of mice with a second-generation mTOR inhibitor that inhibits mTORC2 and mTORC1 exacerbated experimental colorectal tumorigenesis in vivo. In conclusion, mTORC2 activity is confined to macrophages in CRC and limits tumorigenesis. These results suggest activation but not inhibition of mTORC2 as a therapeutic strategy for colitis-associated CRC.
1 Communities
1 Members
0 Resources
24 MeSH Terms
Staphylococcus aureus Infects Osteoclasts and Replicates Intracellularly.
Krauss JL, Roper PM, Ballard A, Shih CC, Fitzpatrick JAJ, Cassat JE, Ng PY, Pavlos NJ, Veis DJ
(2019) mBio 10:
MeSH Terms: Animals, Bacterial Proteins, Cell Differentiation, Cells, Cultured, Female, Macrophages, Male, Mice, Osteoblasts, Osteoclasts, Osteomyelitis, Phagosomes, RANK Ligand, Staphylococcus aureus
Show Abstract · Added March 25, 2020
Osteomyelitis (OM), or inflammation of bone tissue, occurs most frequently as a result of bacterial infection and severely perturbs bone structure. OM is predominantly caused by , and even with proper treatment, OM has a high rate of recurrence and chronicity. While has been shown to infect osteoblasts, it remains unclear whether osteoclasts (OCs) are also a target of intracellular infection. Here, we demonstrate the ability of to intracellularly infect and divide within OCs. OCs were differentiated from bone marrow macrophages (BMMs) by exposure to receptor activator of nuclear factor kappa-B ligand (RANKL). By utilizing an intracellular survival assay and flow cytometry, we found that at 18 h postinfection the intracellular burden of increased dramatically in cells with at least 2 days of RANKL exposure, while the bacterial burden decreased in BMMs. To further explore the signals downstream of RANKL, we manipulated factors controlling OC differentiation, NFATc1 and alternative NF-κB, and found that intracellular bacterial growth correlates with NFATc1 levels in RANKL-treated cells. Confocal and time-lapse microscopy in mature OCs showed a range of intracellular infection that correlated inversely with -phagolysosome colocalization. The propensity of OCs to become infected, paired with their diminished bactericidal capacity compared to BMMs, could promote OM progression by allowing to evade initial immune regulation and proliferate at the periphery of lesions where OCs are most abundant. The inflammation of bone tissue is called osteomyelitis, and most cases are caused by an infection with the bacterium To date, the bone-building cells, osteoblasts, have been implicated in the progression of these infections, but not much is known about how the bone-resorbing cells, osteoclasts, participate. In this study, we show that can infect osteoclasts and proliferate inside these cells, whereas bone-residing macrophages, immune cells related to osteoclasts, destroy the bacteria. These findings elucidate a unique role for osteoclasts to harbor bacteria during infection, providing a possible mechanism by which bacteria could evade destruction by the immune system.
Copyright © 2019 Krauss et al.
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1 Members
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14 MeSH Terms
Fluctuations of Spleen Cytokine and Blood Lactate, Importance of Cellular Immunity in Host Defense Against Blood Stage Malaria .
Imai T, Suzue K, Ngo-Thanh H, Ono S, Orita W, Suzuki H, Shimokawa C, Olia A, Obi S, Taniguchi T, Ishida H, Van Kaer L, Murata S, Tanaka K, Hisaeda H
(2019) Front Immunol 10: 2207
MeSH Terms: Animals, CD4-Positive T-Lymphocytes, CD8-Positive T-Lymphocytes, Cytokines, Erythrocytes, Female, Immunity, Cellular, Lactates, Macrophages, Malaria, Male, Mice, Inbred C57BL, Mice, Knockout, Parasitemia, Plasmodium yoelii, Spleen
Show Abstract · Added March 3, 2020
Our previous studies of protective immunity and pathology against blood stage malaria parasites have shown that not only CD4 T cells, but also CD8 T cells and macrophages, are important for host defense against blood stage malaria infection. Furthermore, we found that 17XNL (PyNL) parasitizes erythroblasts, the red blood cell (RBC) precursor cells, which then express MHC class I molecules. In the present study, we analyzed spleen cytokine production. In CD8 T cell-depleted mice, IL-10 production in early stage infection was increased over two-fold relative to infected control animals and IL-10 CD3 cells were increased, whereas IFN-γ production in the late stage of infection was decreased. At day 16 after PyNL infection, CD8 T cells produced more IFN-γ than CD4 T cells. We evaluated the involvement of the immunoproteasome in induction of immune CD8 T cells, and the role of Fas in protection against PyNL both of which are downstream of IFN-γ. In cell transfer experiments, at least the single molecules LMP7, LMP2, and PA28 are not essential for CD8 T cell induction. The Fas mutant LPR mouse was weaker in resistance to PyNL infection than WT mice, and 20% of the animals died. LPR-derived parasitized erythroid cells exhibited less externalization of phosphatidylserine (PS), and phagocytosis by macrophages was impaired. Furthermore, we tried to identify the cause of death in malaria infection. Blood lactate concentration was increased in the CD8 T cell-depleted PyNL-infected group at day 19 (around peak parasitemia) to similar levels as day 7 after infection with a lethal strain of Py. When we injected mice with lactate at day 4 and 6 of PyNL infection, all mice died at day 8 despite demonstrating low parasitemia, suggesting that hyperlactatemia is one of the causes of death in CD8 T cell-depleted PyNL-infected mice. We conclude that CD8 T cells might control cytokine production to some extent and regulate hyperparasitemia and hyperlactatemia in protection against blood stage malaria parasites.
Copyright © 2019 Imai, Suzue, Ngo-Thanh, Ono, Orita, Suzuki, Shimokawa, Olia, Obi, Taniguchi, Ishida, Van Kaer, Murata, Tanaka and Hisaeda.
0 Communities
1 Members
0 Resources
16 MeSH Terms
Akt Signaling in Macrophage Polarization, Survival, and Atherosclerosis.
Linton MF, Moslehi JJ, Babaev VR
(2019) Int J Mol Sci 20:
MeSH Terms: Animals, Apoptosis, Atherosclerosis, Blood Cells, Cell Survival, Humans, Macrophage Activation, Macrophages, Phosphatidylinositol 3-Kinases, Protein Isoforms, Proto-Oncogene Proteins c-akt, Signal Transduction
Show Abstract · Added November 12, 2019
The PI3K/Akt pathway plays a crucial role in the survival, proliferation, and migration of macrophages, which may impact the development of atherosclerosis. Changes in Akt isoforms or modulation of the Akt activity levels in macrophages significantly affect their polarization phenotype and consequently atherosclerosis in mice. Moreover, the activity levels of Akt signaling determine the viability of monocytes/macrophages and their resistance to pro-apoptotic stimuli in atherosclerotic lesions. Therefore, elimination of pro-apoptotic factors as well as factors that antagonize or suppress Akt signaling in macrophages increases cell viability, protecting them from apoptosis, and this markedly accelerates atherosclerosis in mice. In contrast, inhibition of Akt signaling by the ablation of Rictor in myeloid cells, which disrupts mTORC2 assembly, significantly decreases the viability and proliferation of blood monocytes and macrophages with the suppression of atherosclerosis. In addition, monocytes and macrophages exhibit a threshold effect for Akt protein levels in their ability to survive. Ablation of two Akt isoforms, preserving only a single Akt isoform in myeloid cells, markedly compromises monocyte and macrophage viability, inducing monocytopenia and diminishing early atherosclerosis. These recent advances in our understanding of Akt signaling in macrophages in atherosclerosis may have significant relevance in the burgeoning field of cardio-oncology, where PI3K/Akt inhibitors being tested in cancer patients can have significant cardiovascular and metabolic ramifications.
0 Communities
1 Members
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12 MeSH Terms
Control of antiviral innate immune response by protein geranylgeranylation.
Yang S, Harding AT, Sweeney C, Miao D, Swan G, Zhou C, Jiang Z, Fitzgerald KA, Hammer G, Bergo MO, Kroh HK, Lacy DB, Sun C, Glogauer M, Que LG, Heaton NS, Wang D
(2019) Sci Adv 5: eaav7999
MeSH Terms: Adaptor Proteins, Signal Transducing, Alkyl and Aryl Transferases, Animals, Endoplasmic Reticulum, Female, Humans, Immunity, Innate, Macrophages, Alveolar, Male, Mice, Knockout, Neuropeptides, Orthomyxoviridae Infections, Protein Prenylation, Receptor-Interacting Protein Serine-Threonine Kinases, Tripartite Motif Proteins, Ubiquitin-Protein Ligases, rac GTP-Binding Proteins, rac1 GTP-Binding Protein
Show Abstract · Added March 24, 2020
The mitochondrial antiviral signaling protein (MAVS) orchestrates host antiviral innate immune response to RNA virus infection. However, how MAVS signaling is controlled to eradicate virus while preventing self-destructive inflammation remains obscure. Here, we show that protein geranylgeranylation, a posttranslational lipid modification of proteins, limits MAVS-mediated immune signaling by targeting Rho family small guanosine triphosphatase Rac1 into the mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) at the mitochondria-ER junction. Protein geranylgeranylation and subsequent palmitoylation promote Rac1 translocation into MAMs upon viral infection. MAM-localized Rac1 limits MAVS' interaction with E3 ligase Trim31 and hence inhibits MAVS ubiquitination, aggregation, and activation. Rac1 also facilitates the recruitment of caspase-8 and cFLIP to the MAVS signalosome and the subsequent cleavage of Ripk1 that terminates MAVS signaling. Consistently, mice with myeloid deficiency of protein geranylgeranylation showed improved survival upon influenza A virus infection. Our work revealed a critical role of protein geranylgeranylation in regulating antiviral innate immune response.
0 Communities
1 Members
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18 MeSH Terms
Regulation of Diabetogenic Immunity by IL-15-Activated Regulatory CD8 T Cells in Type 1 Diabetes.
Stocks BT, Wilson CS, Marshall AF, Hoopes EM, Moore DJ
(2019) J Immunol 203: 158-166
MeSH Terms: Adoptive Transfer, Animals, B-Lymphocytes, CD8 Antigens, Cells, Cultured, Diabetes Mellitus, Type 1, Disease Models, Animal, Humans, Immunotherapy, Adoptive, Interleukin-15, Macrophages, Mice, Mice, Inbred NOD, NK Cell Lectin-Like Receptor Subfamily A, T-Lymphocytes, Regulatory
Show Abstract · Added May 28, 2019
Unchecked collaboration between islet-reactive T and B lymphocytes drives type 1 diabetes (T1D). In the healthy setting, CD8 T regulatory cells (Tregs) terminate ongoing T-B interactions. We determined that specific CD8 Tregs from NOD mice lack suppressive function, representing a previously unreported regulatory cell deficit in this T1D-prone strain. NOD mice possess 11-fold fewer Ly-49 CD8 Tregs than nonautoimmune mice, a deficiency that worsens as NOD mice age toward diabetes and leaves them unable to regulate CD4 T follicular helper cells. As IL-15 is required for Ly-49 CD8 Treg development, we determined that NOD macrophages inadequately -present IL-15. Despite reduced IL-15 -presentation, NOD Ly-49 CD8 Tregs can effectively transduce IL-15-mediated survival signals when they are provided. Following stimulation with an IL-15/IL-15Ra superagonist complex, Ly-49 CD8 Tregs expanded robustly and became activated to suppress the Ag-specific Ab response. IL-15/IL-15Ra superagonist complex-activated CD8CD122 T cells also delayed diabetes transfer, indicating the presence of an underactivated CD8 T cell subset with regulatory capacity against late stage T1D. We identify a new cellular contribution to anti-islet autoimmunity and demonstrate the correction of this regulatory cell deficit. Infusion of IL-15-activated CD8 Tregs may serve as an innovative cellular therapy for the treatment of T1D.
Copyright © 2019 by The American Association of Immunologists, Inc.
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15 MeSH Terms