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Bharadwaj S, Groza Y, Mierzwicka JM, Malý P. Current understanding on TREM-2 molecular biology and physiopathological functions. Int Immunopharmacol 2024; 134:112042. [PMID: 38703564 DOI: 10.1016/j.intimp.2024.112042] [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: 02/08/2024] [Revised: 04/05/2024] [Accepted: 04/05/2024] [Indexed: 05/06/2024]
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM-2), a glycosylated receptor belonging to the immunoglobin superfamily and especially expressed in the myeloid cell lineage, is frequently explained as a reminiscent receptor for both adaptive and innate immunity regulation. TREM-2 is also acknowledged to influence NK cell differentiation via the PI3K and PLCγ signaling pathways, as well as the partial activation or direct inhibition of T cells. Additionally, TREM-2 overexpression is substantially linked to cell-specific functions, such as enhanced phagocytosis, reduced toll-like receptor (TLR)-mediated inflammatory cytokine production, increased transcription of anti-inflammatory cytokines, and reshaped T cell function. Whereas TREM-2-deficient cells exhibit diminished phagocytic function and enhanced proinflammatory cytokines production, proceeding to inflammatory injuries and an immunosuppressive environment for disease progression. Despite the growing literature supporting TREM-2+ cells in various diseases, such as neurodegenerative disorders and cancer, substantial facets of TREM-2-mediated signaling remain inadequately understood relevant to pathophysiology conditions. In this direction, herein, we have summarized the current knowledge on TREM-2 biology and cell-specific TREM-2 expression, particularly in the modulation of pivotal TREM-2-dependent functions under physiopathological conditions. Furthermore, molecular regulation and generic biological relevance of TREM-2 are also discussed, which might provide an alternative approach for preventing or reducing TREM-2-associated deformities. At last, we discussed the TREM-2 function in supporting an immunosuppressive cancer environment and as a potential drug target for cancer immunotherapy. Hence, summarized knowledge of TREM-2 might provide a window to overcome challenges in clinically effective therapies for TREM-2-induced diseases in humans.
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Affiliation(s)
- Shiv Bharadwaj
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic.
| | - Yaroslava Groza
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic
| | - Joanna M Mierzwicka
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic
| | - Petr Malý
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic.
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2
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Swain PS, Panda S, Pati S, Dehury B. Computational saturation mutagenesis to explore the effect of pathogenic mutations on extra-cellular domains of TREM2 associated with Alzheimer's and Nasu-Hakola disease. J Mol Model 2023; 29:360. [PMID: 37924367 DOI: 10.1007/s00894-023-05770-7] [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: 07/25/2023] [Accepted: 10/25/2023] [Indexed: 11/06/2023]
Abstract
CONTEXT The specialised family of triggering receptors expressed on myeloid cells (TREMs) plays a pivotal role in causing neurodegenerative disorders and activating microglial anti-inflammatory responses. Nasu-Hakola disease (NHD), a rare autosomal recessive disorder, has been associated with mutations in TREM2, which is also responsible for raising the risk of Alzheimer's disease (AD). Herein, we have made an endeavour to differentiate the confirmed pathogenic variants in TREM2 extra-cellular domain (ECD) linked with NHD and AD using mutation-induced fold stability change (∆∆G), with the computation of 12distinct structure-based methods through saturation mutagenesis. Correlation analysis between relative solvent accessibility (RSA) and ∆∆G expresses the discrete distributive behaviour of mutants associated with TREM2 in AD (R2 = 0.061) and NHD (R2 = 0.601). Our findings put an emphasis on W50 and V126 as major players in maintaining V-like domain in TREM2. Interestingly, we discern that both of them interact with a common residue Y108, which is dissolved upon mutation. This Y108 could have structural or functional role for TREM2 which can be an ideal candidate for further study. Furthermore, the residual interaction network highlights the importance of R47 and R62 in maintaining the CDR loops that are crucial for ligand binding. Future studies using biophysical characterisation of ligand interactions in TREM2-ECD would be helpful for the development of novel therapeutics for AD and NHD. METHODS ConSurf algorithm and ENDscript were used to determine the position and conservation of each residue in the wild-type ECD of TREM2. The mutation-induced fold stability change (∆∆G) of confirmed pathogenic mutants associated with NHD and AD was estimated using 12 state-of-the-art structure-based protein stability tools. Furthermore, we also computed the effect of random mutation on these sites using computational saturation mutagenesis. Linear regression analysis was performed using mutants ∆∆G and RSA through GraphPad software. In addition, a comprehensive non-bonded residual interaction network (RIN) of wild type and its mutants of TREM2-ECD was enumerated using RING3.0.
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Affiliation(s)
- Preety Sthutika Swain
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Nalco Square, Chandrasekharpur, Bhubaneswar, 751023, Odisha, India
| | - Sunita Panda
- Mycology Laboratory, ICMR-Regional Medical Research Centre, Nalco Square, Chandrasekharpur, Bhubaneswar, 751023, Odisha, India
| | - Sanghamitra Pati
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Nalco Square, Chandrasekharpur, Bhubaneswar, 751023, Odisha, India.
| | - Budheswar Dehury
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Nalco Square, Chandrasekharpur, Bhubaneswar, 751023, Odisha, India.
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McKendrick JG, Jones GR, Elder SS, Watson E, T'Jonck W, Mercer E, Magalhaes MS, Rocchi C, Hegarty LM, Johnson AL, Schneider C, Becher B, Pridans C, Mabbott N, Liu Z, Ginhoux F, Bajenoff M, Gentek R, Bain CC, Emmerson E. CSF1R-dependent macrophages in the salivary gland are essential for epithelial regeneration after radiation-induced injury. Sci Immunol 2023; 8:eadd4374. [PMID: 37922341 DOI: 10.1126/sciimmunol.add4374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 10/03/2023] [Indexed: 11/05/2023]
Abstract
The salivary glands often become damaged in individuals receiving radiotherapy for head and neck cancer, resulting in chronic dry mouth. This leads to detrimental effects on their health and quality of life, for which there is no regenerative therapy. Macrophages are the predominant immune cell in the salivary glands and are attractive therapeutic targets due to their unrivaled capacity to drive tissue repair. Yet, the nature and role of macrophages in salivary gland homeostasis and how they may contribute to tissue repair after injury are not well understood. Here, we show that at least two phenotypically and transcriptionally distinct CX3CR1+ macrophage populations are present in the adult salivary gland, which occupy anatomically distinct niches. CD11c+CD206-CD163- macrophages typically associate with gland epithelium, whereas CD11c-CD206+CD163+ macrophages associate with blood vessels and nerves. Using a suite of complementary fate mapping systems, we show that there are highly dynamic changes in the ontogeny and composition of salivary gland macrophages with age. Using an in vivo model of radiation-induced salivary gland injury combined with genetic or antibody-mediated depletion of macrophages, we demonstrate an essential role for macrophages in clearance of cells with DNA damage. Furthermore, we show that epithelial-associated macrophages are indispensable for effective tissue repair and gland function after radiation-induced injury, with their depletion resulting in reduced saliva production. Our data, therefore, provide a strong case for exploring the therapeutic potential of manipulating macrophages to promote tissue repair and thus minimize salivary gland dysfunction after radiotherapy.
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Affiliation(s)
- John G McKendrick
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Gareth-Rhys Jones
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Sonia S Elder
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Erin Watson
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Wouter T'Jonck
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Ella Mercer
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Marlene S Magalhaes
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
- Centre for Reproductive Health, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Cecilia Rocchi
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Lizi M Hegarty
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Amanda L Johnson
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | | | - Burkhard Becher
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Clare Pridans
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Neil Mabbott
- Roslin Institute & Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian EH25 9RG, UK
| | - Zhaoyuan Liu
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Florent Ginhoux
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
- Singapore Immunology Network, Agency for Science, Technology and Research, Singapore 138648, Singapore
- Translational Immunology Institute, SingHealth Duke-NUS Academic Medical Centre, Singapore, Singapore
| | - Marc Bajenoff
- Centre d'Immunologie de Marseille-Luminy, Aix Marseille Université UM2, INSERM, U1104, CNRS UMR7280, Marseille 13288, France
| | - Rebecca Gentek
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
- Centre for Reproductive Health, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Calum C Bain
- Centre for Inflammation Research, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Elaine Emmerson
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, University of Edinburgh, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
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The role of Triggering Receptor Expressed on Myeloid Cells 2 in Parkinson's disease and other neurodegenerative disorders. Behav Brain Res 2022; 433:113977. [PMID: 35752274 DOI: 10.1016/j.bbr.2022.113977] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/09/2022] [Accepted: 06/21/2022] [Indexed: 11/23/2022]
Abstract
Parkinson's disease (PD) is a progressive neurological disorder marked by cardinal clinical symptoms such as rigor, tremor, and akinesia. Albeit a loss of dopaminergic neurons from the substantia nigra pars compacta is causative for the movement impairments found in patients, molecular reasoning for this loss is still incomplete. In recent years, triggering factor expressed on myeloid cells (TREM2) gained attention in the field of neurodegeneration as it could be associated with different neurodegenerative disorders. Primarily identified as a risk factor in Alzheimer's disease, variants in TREM2 were linked to PD and multiple sclerosis, too. Expressed on phagocytic cells, such as macrophages and microglia, TREM2 puts the focus on inflammation associated conditions in PD and provides a molecular target that could at least partly explain the role of immune cells in PD. Here, we summarize expression patterns and molecular functions of TREM2, recapitulate on its role in inflammation, phagocytosis and cell survival, before turning to neurodegenerative disorders with an emphasis on PD.
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Dash R, Munni YA, Mitra S, Choi HJ, Jahan SI, Chowdhury A, Jang TJ, Moon IS. Dynamic insights into the effects of nonsynonymous polymorphisms (nsSNPs) on loss of TREM2 function. Sci Rep 2022; 12:9378. [PMID: 35672339 PMCID: PMC9174165 DOI: 10.1038/s41598-022-13120-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 05/16/2022] [Indexed: 11/09/2022] Open
Abstract
Single nucleotide variations in Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) are associated with many neurodegenerative diseases, including Nasu-Hakola disease (NHD), frontotemporal dementia (FTD), and late-onset Alzheimer's disease because they disrupt ligand binding to the extracellular domain of TREM2. However, the effects of nonsynonymous single nucleotide polymorphisms (nsSNPs) in TREM2 on disease progression remain unknown. In this study, we identified several high-risk nsSNPs in the TREM2 gene using various deleterious SNP predicting algorithms and analyzed their destabilizing effects on the ligand recognizing region of the TREM2 immunoglobulin (Ig) domain by molecular dynamics (MD) simulation. Cumulative prediction by all tools employed suggested the three most deleterious nsSNPs involved in loss of TREM2 function are rs549402254 (W50S), rs749358844 (R52C), and rs1409131974 (D104G). MD simulation showed that these three variants cause substantial structural alterations and conformational remodeling of the apical loops of the TREM2 Ig domain, which is responsible for ligand recognition. Detailed analysis revealed that these variants substantially increased distances between apical loops and induced conformation remodeling by changing inter-loop nonbonded contacts. Moreover, all nsSNPs changed the electrostatic potentials near the putative ligand-interacting region (PLIR), which suggested they might reduce specificity or loss of binding affinity for TREM2 ligands. Overall, this study identifies three potential high-risk nsSNPs in the TREM2 gene. We propose further studies on the molecular mechanisms responsible for loss of TREM2 function and the associations between TREM2 nsSNPs and neurodegenerative diseases.
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Affiliation(s)
- Raju Dash
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea
| | - Yeasmin Akter Munni
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea
| | - Sarmistha Mitra
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea
| | - Ho Jin Choi
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea
| | - Sultana Israt Jahan
- Department of Biotechnology and Genetic Engineering, Noakhali Science and Technology University, Noakhali, 3814, Bangladesh
| | - Apusi Chowdhury
- Department of Pharmaceutical Science, North-South University, Dhaka, 1229, Bangladesh
| | - Tae Jung Jang
- Department of Pathology, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea
| | - Il Soo Moon
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju, 38066, Republic of Korea.
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Ex Vivo Generation of CAR Macrophages from Hematopoietic Stem and Progenitor Cells for Use in Cancer Therapy. Cells 2022; 11:cells11060994. [PMID: 35326445 PMCID: PMC8947001 DOI: 10.3390/cells11060994] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 03/11/2022] [Indexed: 12/21/2022] Open
Abstract
Chimeric antigen receptor (CAR) T-cell therapies have shown impressive results in patients with hematological malignancies; however, little success has been achieved in the treatment of solid tumors. Recently, macrophages (MΦs) were identified as an additional candidate for the CAR approach, and initial proof of concept studies using peripheral blood-derived monocytes showed antigen-redirected activation of CAR MΦs. However, some patients may not be suitable for monocyte-apheresis, and prior cancer treatment regimens may negatively affect immune cell number and functionality. To address this problem, we here introduce primary human hematopoietic stem and progenitor cells (HSPCs) as a cell source to generate functional CAR MΦs ex vivo. Our data showed successful CAR expression in cord blood (CB)-derived HSPCs, with considerable cell expansion during differentiation to CAR MΦs. HSPC-derived MΦs showed typical MΦ morphology, phenotype, and basic anti-bacterial functionality. CAR MΦs targeting the carcinoembryonic antigen (CEA) and containing either a DAP12- or a CD3ζ-derived signaling domain showed antigen redirected activation as they secreted pro-inflammatory cytokines specifically upon contact with CEA+ target cells. In addition, CD3ζ-expressing CAR MΦs exhibited significantly enhanced phagocytosis of CEA+ HT1080 cells. Our data establish human HSPCs as a suitable cell source to generate functional CAR MΦs and further support the use of CAR MΦs in the context of solid tumor therapy.
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Qiu H, Shao Z, Wen X, Jiang J, Ma Q, Wang Y, Huang L, Ding X, Zhang L. TREM2: Keeping Pace With Immune Checkpoint Inhibitors in Cancer Immunotherapy. Front Immunol 2021; 12:716710. [PMID: 34539652 PMCID: PMC8446424 DOI: 10.3389/fimmu.2021.716710] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 08/18/2021] [Indexed: 01/21/2023] Open
Abstract
To date, immune checkpoint inhibitors have been successively approved and widely used in clinical cancer treatments, however, the overall response rates are very low and almost all cancer patients eventually progressed to drug resistance, this is mainly due to the intricate tumor microenvironment and immune escape mechanisms of cancer cells. One of the main key mechanisms leading to the evasion of immune attack is the presence of the immunosuppressive microenvironment within tumors. Recently, several studies illustrated that triggering receptor expressed on myeloid cells-2 (TREM2), a transmembrane receptor of the immunoglobulin superfamily, was a crucial pathology-induced immune signaling hub, and it played a vital negative role in antitumor immunity, such as inhibiting the proliferation of T cells. Here, we reviewed the recent advances in the study of TREM2, especially focused on its regulation of tumor-related immune signaling pathways and its role as a novel target in cancer immunotherapy.
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Affiliation(s)
- Hui Qiu
- Cancer Institute, Xuzhou Medical University, Xuzhou, China.,Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Zhiying Shao
- Cancer Institute, Xuzhou Medical University, Xuzhou, China
| | - Xin Wen
- Cancer Institute, Xuzhou Medical University, Xuzhou, China.,Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Jinghua Jiang
- Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Qinggong Ma
- Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Yan Wang
- Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Long Huang
- Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Xin Ding
- Cancer Institute, Xuzhou Medical University, Xuzhou, China.,Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Longzhen Zhang
- Cancer Institute, Xuzhou Medical University, Xuzhou, China.,Department of Radiation Oncology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
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Hall-Roberts H, Agarwal D, Obst J, Smith TB, Monzón-Sandoval J, Di Daniel E, Webber C, James WS, Mead E, Davis JB, Cowley SA. TREM2 Alzheimer's variant R47H causes similar transcriptional dysregulation to knockout, yet only subtle functional phenotypes in human iPSC-derived macrophages. Alzheimers Res Ther 2020; 12:151. [PMID: 33198789 PMCID: PMC7667762 DOI: 10.1186/s13195-020-00709-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 10/20/2020] [Indexed: 01/21/2023]
Abstract
BACKGROUND TREM2 is a microglial cell surface receptor, with risk mutations linked to Alzheimer's disease (AD), including R47H. TREM2 signalling via SYK aids phagocytosis, chemotaxis, survival, and changes to microglial activation state. In AD mouse models, knockout (KO) of TREM2 impairs microglial clustering around amyloid and prevents microglial activation. The R47H mutation is proposed to reduce TREM2 ligand binding. We investigated cell phenotypes of the R47H mutant and TREM2 KO in a model of human microglia, and compared their transcriptional signatures, to determine the mechanism by which R47H TREM2 disrupts function. METHODS We generated human microglia-like iPSC-macrophages (pMac) from isogenic induced pluripotent stem cell (iPSC) lines, with homozygous R47H mutation or TREM2 knockout (KO). We firstly validated the effect of the R47H mutant on TREM2 surface and subcellular localization in pMac. To assess microglial phenotypic function, we measured phagocytosis of dead neurons, cell morphology, directed migration, survival, and LPS-induced inflammation. We performed bulk RNA-seq, comparing significant differentially expressed genes (DEGs; p < 0.05) between the R47H and KO versus WT, and bioinformatically predicted potential upstream regulators of TREM2-mediated gene expression. RESULTS R47H modified surface expression and shedding of TREM2, but did not impair TREM2-mediated signalling, or gross phenotypes that were dysregulated in the TREM2 KO (phagocytosis, motility, survival). However, altered gene expression in the R47H TREM2 pMac overlapped by 90% with the TREM2 KO and was characterised by dysregulation of genes involved with immunity, proliferation, activation, chemotaxis, and adhesion. Downregulated mediators of ECM adhesion included the vitronectin receptor αVβ3, and consequently, R47H TREM2 pMac adhered weakly to vitronectin compared with WT pMac. To counteract these transcriptional defects, we investigated TGFβ1, as a candidate upstream regulator. TGFβ1 failed to rescue vitronectin adhesion of pMac, although it improved αVβ3 expression. CONCLUSIONS The R47H mutation is not sufficient to cause gross phenotypic defects of human pMac under standard culture conditions. However, overlapping transcriptional defects with TREM2 KO supports the hypothesised partial loss-of-function effects of the R47H mutation. Furthermore, transcriptomics can guide us to more subtle phenotypic defects in the R47H cells, such as reduced cell adhesion, and can be used to predict targets for therapeutic intervention.
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Affiliation(s)
- Hazel Hall-Roberts
- James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE UK
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Devika Agarwal
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS UK
| | - Juliane Obst
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Thomas B. Smith
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | | | - Elena Di Daniel
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Caleb Webber
- UK Dementia Research Institute, Cardiff University, Cardiff, CF24 4HQ UK
| | - William S. James
- James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE UK
| | - Emma Mead
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - John B. Davis
- Nuffield Department of Medicine Research Building, Alzheimer’s Research UK Oxford Drug Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Sally A. Cowley
- James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, OX1 3RE UK
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Gratuze M, Leyns CEG, Holtzman DM. New insights into the role of TREM2 in Alzheimer's disease. Mol Neurodegener 2018; 13:66. [PMID: 30572908 PMCID: PMC6302500 DOI: 10.1186/s13024-018-0298-9] [Citation(s) in RCA: 258] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 11/28/2018] [Indexed: 12/22/2022] Open
Abstract
Alzheimer's disease (AD) is the leading cause of dementia. The two histopathological markers of AD are amyloid plaques composed of the amyloid-β (Aβ) peptide, and neurofibrillary tangles of aggregated, abnormally hyperphosphorylated tau protein. The majority of AD cases are late-onset, after the age of 65, where a clear cause is still unknown. However, there are likely different multifactorial contributors including age, enviornment, biology and genetics which can increase risk for the disease. Genetic predisposition is considerable, with heritability estimates of 60-80%. Genetic factors such as rare variants of TREM2 (triggering receptor expressed on myeloid cells-2) strongly increase the risk of developing AD, confirming the role of microglia in AD pathogenesis. In the last 5 years, several studies have dissected the mechanisms by which TREM2, as well as its rare variants affect amyloid and tau pathologies and their consequences in both animal models and in human studies. In this review, we summarize increases in our understanding of the involvement of TREM2 and microglia in AD development that may open new therapeutic strategies targeting the immune system to influence AD pathogenesis.
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Affiliation(s)
- Maud Gratuze
- Department of Neurology, St. Louis, USA
- Hope Center for Neurological Disorders, St. Louis, USA
- Knight Alzheimer’s Disease Research Center, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Cheryl E. G. Leyns
- Department of Neurology, St. Louis, USA
- Hope Center for Neurological Disorders, St. Louis, USA
- Knight Alzheimer’s Disease Research Center, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - David M. Holtzman
- Department of Neurology, St. Louis, USA
- Hope Center for Neurological Disorders, St. Louis, USA
- Knight Alzheimer’s Disease Research Center, Washington University School of Medicine, St. Louis, MO 63110 USA
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Byers DE, Wu K, Dang-Vu G, Jin X, Agapov E, Zhang X, Battaile JT, Schechtman K, Yusen R, Pierce RA, Holtzman MJ. Triggering Receptor Expressed on Myeloid Cells-2 Expression Tracks With M2-Like Macrophage Activity and Disease Severity in COPD. Chest 2018; 153:77-86. [PMID: 29017955 PMCID: PMC5812763 DOI: 10.1016/j.chest.2017.09.044] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 07/31/2017] [Accepted: 09/20/2017] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Cell and animal models show a key role for Triggering Receptor Expressed on Myeloid Cells (TREM)-2 in chronic airway disease after viral infection, but comparable evidence in humans still needs to be established. METHODS Lung tissue samples were obtained from lung transplant recipients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage IV COPD (n = 16), nontransplantable donor lung tissues (n = 7), and resected lung tissues from patients at risk or with GOLD stage I through IV (n = 55) and were assessed for TREM-2 and TREM-1 messenger RNA (mRNA), protein expression, and other markers of a type 2 immune response. RESULTS TREM2 (but not TREM1) mRNA levels were increased in GOLD stage IV COPD lung tissues compared with non-COPD lung tissues. TREM2 mRNA was coexpressed with its signaling molecule DAP12 and the macrophage marker CD68 and M2-macrophage markers CD206 and CHIT1. TREM-2 protein was also increased in COPD lung tissues and was localized to CD14+ macrophages by flow cytometry and CD68+ and CCR2+ macrophages by tissue immunostaining. In lung samples from patients at risk and with GOLD stage I through IV COPD, TREM2 but not TREM1 mRNA levels were also increased, and the ratio of TREM2/TREM1 mRNA levels was associated with increases in CHIT1 mRNA and decreases in FEV1 and FEV1/FVC. CONCLUSIONS TREM-2 expression is increased in lung macrophages in COPD, particularly in comparison with TREM-1. Therefore, TREM-2 levels and the ratio of TREM-2/TREM-1 signifies M2 activation in COPD lung tissues and may help to guide therapeutics directed against the type 2 immune response in patients with this disease.
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Affiliation(s)
- Derek E Byers
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO.
| | - Kangyun Wu
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | | | - Xiaohua Jin
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | - Eugene Agapov
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | - Xiaofeng Zhang
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | - John T Battaile
- Department of Internal Medicine, University of Texas Southwestern, Dallas, TX
| | - Kenneth Schechtman
- Department of Medicine, Division of Biostatistics, Washington University School of Medicine, Saint Louis, MO
| | - Roger Yusen
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | - Richard A Pierce
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO
| | - Michael J Holtzman
- Department of Medicine, Drug Discovery Program in Pulmonary and Critical Care, Washington University School of Medicine, Saint Louis, MO; Department of Cell Biology, Washington University School of Medicine, Saint Louis, MO
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11
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Costa PM, Gosens I, Williams A, Farcal L, Pantano D, Brown DM, Stone V, Cassee FR, Halappanavar S, Fadeel B. Transcriptional profiling reveals gene expression changes associated with inflammation and cell proliferation following short-term inhalation exposure to copper oxide nanoparticles. J Appl Toxicol 2017; 38:385-397. [PMID: 29094763 DOI: 10.1002/jat.3548] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/20/2017] [Accepted: 09/05/2017] [Indexed: 01/09/2023]
Abstract
Our recent studies revealed a dose-dependent proinflammatory response to copper oxide nanoparticles (CuO NPs) in rats following short-term inhalation exposure for five consecutive days. Here transcriptomics approaches were applied using the same model to assess global gene expression in lung tissues obtained 1 day post-exposure and after a recovery period of 22 days from rats exposed to clean air or 6 hour equivalent doses of 3.3 mg m-3 (low dose) and 13.2 mg m-3 (high dose). Microarray analyses yielded about 1000 differentially expressed genes in the high-dose group and 200 in low-dose compared to the clean air control group, and less than 20 after the recovery period. Pathway analysis indicated cell proliferation/survival and inflammation as the main processes triggered by exposure to CuO NPs. We did not find significant perturbations of pathways related to oxidative stress. Upregulation of epithelial cell transforming protein 2 (Ect2), a known oncogene, was noted and ECT2 protein was upregulated in the lungs of exposed animals. Proliferation of alveolar epithelial cells was demonstrated based on Ki67 expression. The gene encoding monocyte chemoattractant protein 1 (or CCL2) was also upregulated and this was confirmed by immunohistochemistry. However, no aberrant DNA methylation of inflammation-associated genes was observed. In conclusion, we have found that inhalation of CuO NPs in rats causes upregulation of the oncoprotein ECT2 and the chemokine CCL2 and other proinflammatory markers as well as proliferation in bronchoalveolar epithelium after a short-term inhalation exposure. Thus, pathways known to be associated with neoplastic processes and inflammation were affected in this model.
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Affiliation(s)
- Pedro M Costa
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Ilse Gosens
- National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Canada
| | - Lucian Farcal
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Daniele Pantano
- School of Life Sciences, Heriot-Watt University, Edinburgh, UK
| | - David M Brown
- School of Life Sciences, Heriot-Watt University, Edinburgh, UK
| | - Vicki Stone
- School of Life Sciences, Heriot-Watt University, Edinburgh, UK
| | - Flemming R Cassee
- National Institute for Public Health and the Environment, Bilthoven, The Netherlands.,Institute for Risk Assessment Studies, Utrecht University, Utrecht, The Netherlands
| | - Sabina Halappanavar
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Canada
| | - Bengt Fadeel
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
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12
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Jay TR, von Saucken VE, Landreth GE. TREM2 in Neurodegenerative Diseases. Mol Neurodegener 2017; 12:56. [PMID: 28768545 PMCID: PMC5541421 DOI: 10.1186/s13024-017-0197-5] [Citation(s) in RCA: 252] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022] Open
Abstract
TREM2 variants have been identified as risk factors for Alzheimer's disease (AD) and other neurodegenerative diseases (NDDs). Because TREM2 encodes a receptor exclusively expressed on immune cells, identification of these variants conclusively demonstrates that the immune response can play an active role in the pathogenesis of NDDs. These TREM2 variants also confer the highest risk for developing Alzheimer's disease of any risk factor identified in nearly two decades, suggesting that understanding more about TREM2 function could provide key insights into NDD pathology and provide avenues for novel immune-related NDD biomarkers and therapeutics. The expression, signaling and function of TREM2 in NDDs have been extensively investigated in an effort to understand the role of immune function in disease pathogenesis and progression. We provide a comprehensive review of our current understanding of TREM2 biology, including new insights into the regulation of TREM2 expression, and TREM2 signaling and function across NDDs. While many open questions remain, the current body of literature provides clarity on several issues. While it is still often cited that TREM2 expression is decreased by pro-inflammatory stimuli, it is now clear that this is true in vitro, but inflammatory stimuli in vivo almost universally increase TREM2 expression. Likewise, while TREM2 function is classically described as promoting an anti-inflammatory phenotype, more than half of published studies demonstrate a pro-inflammatory role for TREM2, suggesting that its role in inflammation is much more complex. Finally, these components of TREM2 biology are applied to a discussion of how TREM2 impacts NDD pathologies and the latest assessment of how these findings might be applied to immune-directed clinical biomarkers and therapeutics.
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Affiliation(s)
- Taylor R. Jay
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
| | - Victoria E. von Saucken
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
| | - Gary E. Landreth
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
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Dvorkin-Gheva A, Vanderstocken G, Yildirim AÖ, Brandsma CA, Obeidat M, Bossé Y, Hassell JA, Stampfli MR. Total particulate matter concentration skews cigarette smoke's gene expression profile. ERJ Open Res 2016; 2:00029-2016. [PMID: 27995131 PMCID: PMC5165723 DOI: 10.1183/23120541.00029-2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 08/05/2016] [Indexed: 01/05/2023] Open
Abstract
Exposure of small animals to cigarette smoke is widely used as a model to study the pathogenesis of chronic obstructive pulmonary disease. However, protocols and exposure systems utilised vary substantially and it is unclear how these different systems compare. We analysed the gene expression profile of six publically available murine datasets from different cigarette smoke-exposure systems and related the gene signatures to three clinical cohorts. 234 genes significantly regulated by cigarette smoke in at least one model were used to construct a 55-gene network containing 17 clusters. Increasing numbers of differentially regulated clusters were associated with higher total particulate matter concentrations in the different datasets. Low total particulate matter-induced genes mainly related to xenobiotic/detoxification responses, while higher total particulate matter activated immune/inflammatory processes in addition to xenobiotic/detoxification responses. To translate these observations to the clinic, we analysed the regulation of the revealed network in three human cohorts. Similar to mice, we observed marked differences in the number of regulated clusters between the cohorts. These differences were not determined by pack-year. Although none of the experimental models exhibited a complete alignment with any of the human cohorts, some exposure systems showed higher resemblance. Thus, depending on the cohort, clinically observed changes in gene expression may be mirrored more closely by specific cigarette smoke exposure systems. This study emphasises the need for careful validation of animal models.
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Affiliation(s)
- Anna Dvorkin-Gheva
- Dept of Pathology and Molecular Medicine, McMaster Immunology Research Centre, Hamilton, ON, Canada
- Centre for Functional Genomics, McMaster University, Hamilton, ON, Canada
- These authors contributed equally
| | - Gilles Vanderstocken
- Dept of Pathology and Molecular Medicine, McMaster Immunology Research Centre, Hamilton, ON, Canada
- These authors contributed equally
| | - Ali Önder Yildirim
- Institute of Lung Biology and Disease (iLBD), Helmholtz Zentrum München, Neuherberg, Germany, Member of the German Center for Lung Research (DZL)
| | - Corry-Anke Brandsma
- University of Groningen, University Medical Center Groningen, GRIAC research institute, Groningen, The Netherlands
| | - Ma'en Obeidat
- The University of British Columbia Center for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Yohan Bossé
- Centre de Recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec, Quebec City, QC, Canada
- Dept of Molecular Medicine, Laval University, Quebec City, QC, Canada
| | - John A. Hassell
- Centre for Functional Genomics, McMaster University, Hamilton, ON, Canada
| | - Martin R. Stampfli
- Dept of Pathology and Molecular Medicine, McMaster Immunology Research Centre, Hamilton, ON, Canada
- Dept of Medicine, Firestone Institute of Respiratory Health at St. Joseph's Healthcare, McMaster University, Hamilton, ON, Canada
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14
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Tanaka S, Matsumoto T, Matsubara Y, Harada Y, Kyuragi R, Koga JI, Egashira K, Nakashima Y, Yonemitsu Y, Maehara Y. BubR1 Insufficiency Results in Decreased Macrophage Proliferation and Attenuated Atherogenesis in Apolipoprotein E-Deficient Mice. J Am Heart Assoc 2016; 5:JAHA.116.004081. [PMID: 27664806 PMCID: PMC5079050 DOI: 10.1161/jaha.116.004081] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Background Budding uninhibited by benzimidazole‐related 1 (BubR1), a cell cycle–related protein, is an essential component of the spindle checkpoint that regulates cell division. BubR1 insufficiency causes early aging‐associated vascular phenotypes. We generated low‐BubR1‐expressing mutant (BubR1L/L) and apolipoprotein E‐deficient (ApoE−/−) mice (BubR1L/L‐ApoE−/− mice) to investigate the effects of BubR1 on atherosclerosis. Methods and Results Eight‐week‐old male BubR1L/L‐ApoE−/− mice and age‐matched ApoE−/− mice were used in this study. Atherosclerotic lesion development after being fed a high‐cholesterol diet for 12 weeks was inhibited in BubR1L/L‐ApoE−/− mice compared with ApoE−/− mice, and was accompanied by decreased accumulation of macrophages. To address the relative contribution of BubR1 on bone marrow–derived cells compared with non‐bone marrow–derived cells, we performed bone marrow transplantation in ApoE−/− and BubR1L/L‐ApoE−/− mice. Decreased BubR1 in bone marrow cells and non‐bone marrow–derived cells decreased the atherosclerotic burden. In vitro assays indicated that decreased BubR1 expression impaired proliferation, but not migration, of bone marrow–derived macrophages. Conclusions BubR1 may represent a promising new target for regulating atherosclerosis.
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Affiliation(s)
- Shinichi Tanaka
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Takuya Matsumoto
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yutaka Matsubara
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yui Harada
- R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Ryoichi Kyuragi
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Jun-Ichiro Koga
- Department of Cardiovascular Research, Development, and Translational Medicine, Kyushu University, Fukuoka, Japan
| | - Kensuke Egashira
- Department of Cardiovascular Research, Development, and Translational Medicine, Kyushu University, Fukuoka, Japan
| | - Yutaka Nakashima
- Division of Pathology, Japanese Red Cross Fukuoka Hospital, Fukuoka, Japan
| | - Yoshikazu Yonemitsu
- R&D Laboratory for Innovative Biotherapeutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshihiko Maehara
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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15
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Yoshino Y, Kawabe K, Yamazaki K, Watanabe S, Numata S, Mori Y, Yoshida T, Iga J, Ohmori T, Ueno SI. Elevated TREM2 mRNA expression in leukocytes in schizophrenia but not major depressive disorder. J Neural Transm (Vienna) 2016; 123:637-41. [DOI: 10.1007/s00702-016-1560-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/21/2016] [Indexed: 12/18/2022]
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16
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Wortham BW, Eppert BL, Flury JL, Garcia SM, Donica WR, Osterburg A, Joyce-Shaikh B, Cua DJ, Borchers MT. Cutting Edge: CLEC5A Mediates Macrophage Function and Chronic Obstructive Pulmonary Disease Pathologies. THE JOURNAL OF IMMUNOLOGY 2016; 196:3227-31. [PMID: 26927798 DOI: 10.4049/jimmunol.1500978] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 02/12/2016] [Indexed: 12/21/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) is a devastating disease with no effective therapies. We investigated the role of the C-type lectin receptor, CLEC5A, in macrophage activation and pulmonary pathogenesis in a mouse model of COPD. We demonstrate that CLEC5A is expressed on alveolar macrophages in mice exposed long-term to cigarette smoke (CS), as well as in human smokers. We also show that CLEC5A-mediated activation of macrophages enhanced cytokine elaboration alone, as well as in combination with LPS or GM-CSF in CS-exposed mice. Furthermore, usingClec5a-deficient mice, we demonstrate that CS-induced macrophage responsiveness is mediated by CLEC5A, and CLEC5A is required for the development of inflammation, proinflammatory cytokine expression, and airspace enlargement. These findings suggest a novel mechanism that promotes airway inflammation and pathologies in response to CS exposure and identifies CLEC5A as a novel target for the therapeutic control of COPD pathogenesis.
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Affiliation(s)
- Brian W Wortham
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | - Bryan L Eppert
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | - Jennifer L Flury
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | - Sara Morgado Garcia
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | - Walter R Donica
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | - Andrew Osterburg
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
| | | | - Daniel J Cua
- Merck Research Laboratories, Palo Alto, CA 94304
| | - Michael T Borchers
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267; and
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17
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Huang WC, Shen MY, Chen HH, Lin SC, Chiang WH, Wu PH, Chang CW, Chiang CS, Chiu HC. Monocytic delivery of therapeutic oxygen bubbles for dual-modality treatment of tumor hypoxia. J Control Release 2015; 220:738-50. [DOI: 10.1016/j.jconrel.2015.09.016] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/31/2015] [Accepted: 09/09/2015] [Indexed: 01/24/2023]
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18
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Wu K, Byers DE, Jin X, Agapov E, Alexander-Brett J, Patel AC, Cella M, Gilfilan S, Colonna M, Kober DL, Brett TJ, Holtzman MJ. TREM-2 promotes macrophage survival and lung disease after respiratory viral infection. ACTA ACUST UNITED AC 2015; 212:681-97. [PMID: 25897174 PMCID: PMC4419356 DOI: 10.1084/jem.20141732] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 03/20/2015] [Indexed: 01/04/2023]
Abstract
Wu et al. use a mouse model to show that active respiratory viral infection triggers TREM-2 expression on the macrophage cell surface and thereby prevents macrophage apoptosis during the acute illness. In addition, long after viral clearance, IL-13 and DAP12 promote TREM-2 cleavage to its soluble form that unexpectedly also enhances macrophage survival and promotes chronic inflammatory disease. Viral infections and type 2 immune responses are thought to be critical for the development of chronic respiratory disease, but the link between these events needs to be better defined. Here, we study a mouse model in which infection with a mouse parainfluenza virus known as Sendai virus (SeV) leads to long-term activation of innate immune cells that drive IL-13–dependent lung disease. We find that chronic postviral disease (signified by formation of excess airway mucus and accumulation of M2-differentiating lung macrophages) requires macrophage expression of triggering receptor expressed on myeloid cells-2 (TREM-2). Analysis of mechanism shows that viral replication increases lung macrophage levels of intracellular and cell surface TREM-2, and this action prevents macrophage apoptosis that would otherwise occur during the acute illness (5–12 d after inoculation). However, the largest increases in TREM-2 levels are found as the soluble form (sTREM-2) long after clearance of infection (49 d after inoculation). At this time, IL-13 and the adapter protein DAP12 promote TREM-2 cleavage to sTREM-2 that is unexpectedly active in preventing macrophage apoptosis. The results thereby define an unprecedented mechanism for a feed-forward expansion of lung macrophages (with IL-13 production and consequent M2 differentiation) that further explains how acute infection leads to chronic inflammatory disease.
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Affiliation(s)
- Kangyun Wu
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Derek E Byers
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Xiaohua Jin
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Eugene Agapov
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Jennifer Alexander-Brett
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Anand C Patel
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110 Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Marina Cella
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Susan Gilfilan
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Marco Colonna
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Daniel L Kober
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Tom J Brett
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110 Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110 Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael J Holtzman
- Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110 Pulmonary and Critical Care Medicine, Department of Medicine, Department of Pediatrics, Department of Pathology and Immunology, Department of Biochemistry and Biophysics, and Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
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Spahn JH, Li W, Bribriesco AC, Liu J, Shen H, Ibricevic A, Pan JH, Zinselmeyer BH, Brody SL, Goldstein DR, Krupnick AS, Gelman AE, Miller MJ, Kreisel D. DAP12 expression in lung macrophages mediates ischemia/reperfusion injury by promoting neutrophil extravasation. THE JOURNAL OF IMMUNOLOGY 2015; 194:4039-48. [PMID: 25762783 DOI: 10.4049/jimmunol.1401415] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 02/04/2015] [Indexed: 12/25/2022]
Abstract
Neutrophils are critical mediators of innate immune responses and contribute to tissue injury. However, immune pathways that regulate neutrophil recruitment to injured tissues during noninfectious inflammation remain poorly understood. DAP12 is a cell membrane-associated protein that is expressed in myeloid cells and can either augment or dampen innate inflammatory responses during infections. To elucidate the role of DAP12 in pulmonary ischemia/reperfusion injury (IRI), we took advantage of a clinically relevant mouse model of transplant-mediated lung IRI. This technique allowed us to dissect the importance of DAP12 in tissue-resident cells and those that infiltrate injured tissue from the periphery during noninfectious inflammation. Macrophages in both mouse and human lungs that have been subjected to cold ischemic storage express DAP12. We found that donor, but not recipient, deficiency in DAP12 protected against pulmonary IRI. Analysis of the immune response showed that DAP12 promotes the survival of tissue-resident alveolar macrophages and contributes to local production of neutrophil chemoattractants. Intravital imaging demonstrated a transendothelial migration defect into DAP12-deficient lungs, which can be rescued by local administration of the neutrophil chemokine CXCL2. We have uncovered a previously unrecognized role for DAP12 expression in tissue-resident alveolar macrophages in mediating acute noninfectious tissue injury through regulation of neutrophil trafficking.
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Affiliation(s)
- Jessica H Spahn
- Department of Surgery, Washington University, St. Louis, MO 63110
| | - Wenjun Li
- Department of Surgery, Washington University, St. Louis, MO 63110
| | | | - Jie Liu
- Department of Surgery, Washington University, St. Louis, MO 63110
| | - Hua Shen
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06510; Department of Immunobiology, Yale School of Medicine, New Haven, CT 06510
| | - Aida Ibricevic
- Department of Medicine, Washington University, St. Louis, MO 63110; and
| | - Jie-Hong Pan
- Department of Medicine, Washington University, St. Louis, MO 63110; and
| | - Bernd H Zinselmeyer
- Department of Pathology & Immunology, Washington University, St. Louis, MO 63110
| | - Steven L Brody
- Department of Medicine, Washington University, St. Louis, MO 63110; and
| | - Daniel R Goldstein
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06510; Department of Immunobiology, Yale School of Medicine, New Haven, CT 06510
| | | | - Andrew E Gelman
- Department of Surgery, Washington University, St. Louis, MO 63110; Department of Pathology & Immunology, Washington University, St. Louis, MO 63110
| | - Mark J Miller
- Department of Medicine, Washington University, St. Louis, MO 63110; and
| | - Daniel Kreisel
- Department of Surgery, Washington University, St. Louis, MO 63110; Department of Pathology & Immunology, Washington University, St. Louis, MO 63110
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Ramsey SA, Vengrenyuk Y, Menon P, Podolsky I, Feig JE, Aderem A, Fisher EA, Gold ES. Epigenome-guided analysis of the transcriptome of plaque macrophages during atherosclerosis regression reveals activation of the Wnt signaling pathway. PLoS Genet 2014; 10:e1004828. [PMID: 25474352 PMCID: PMC4256277 DOI: 10.1371/journal.pgen.1004828] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 10/15/2014] [Indexed: 11/19/2022] Open
Abstract
We report the first systems biology investigation of regulators controlling arterial plaque macrophage transcriptional changes in response to lipid lowering in vivo in two distinct mouse models of atherosclerosis regression. Transcriptome measurements from plaque macrophages from the Reversa mouse were integrated with measurements from an aortic transplant-based mouse model of plaque regression. Functional relevance of the genes detected as differentially expressed in plaque macrophages in response to lipid lowering in vivo was assessed through analysis of gene functional annotations, overlap with in vitro foam cell studies, and overlap of associated eQTLs with human atherosclerosis/CAD risk SNPs. To identify transcription factors that control plaque macrophage responses to lipid lowering in vivo, we used an integrative strategy – leveraging macrophage epigenomic measurements – to detect enrichment of transcription factor binding sites upstream of genes that are differentially expressed in plaque macrophages during regression. The integrated analysis uncovered eight transcription factor binding site elements that were statistically overrepresented within the 5′ regulatory regions of genes that were upregulated in plaque macrophages in the Reversa model under maximal regression conditions and within the 5′ regulatory regions of genes that were upregulated in the aortic transplant model during regression. Of these, the TCF/LEF binding site was present in promoters of upregulated genes related to cell motility, suggesting that the canonical Wnt signaling pathway may be activated in plaque macrophages during regression. We validated this network-based prediction by demonstrating that β-catenin expression is higher in regressing (vs. control group) plaques in both regression models, and we further demonstrated that stimulation of canonical Wnt signaling increases macrophage migration in vitro. These results suggest involvement of canonical Wnt signaling in macrophage emigration from the plaque during lipid lowering-induced regression, and they illustrate the discovery potential of an epigenome-guided, systems approach to understanding atherosclerosis regression. Atherosclerosis, a progressive accumulation of lipid-rich plaque within arteries, is an inflammatory disease in which the response of macrophages (a key cell type of the innate immune system) to plasma lipoproteins plays a central role. In humans, the goal of significantly reducing already-established plaque through drug treatments, including statins, remains elusive. In mice, atherosclerosis can be reversed by experimental manipulations that lower circulating lipid levels. A common feature of many regression models is that macrophages transition to a less inflammatory state and emigrate from the plaque. While the molecular regulators that control these responses are largely unknown, we hypothesized that by integrating global measurements of macrophage gene expression in regressing plaques with measurements of the macrophage chromatin landscape, we could identify key molecules that control macrophage responses to the lowering of circulating lipid levels. Our systems biology analysis of plaque macrophages yielded a network in which the Wnt signaling pathway emerged as a candidate upstream regulator. Wnt signaling is known to affect both inflammation and the ability of macrophages to migrate from one location to another, and our targeted validation studies provide evidence that Wnt signaling is increased in plaque macrophages during regression. Our findings both demonstrate the power of a systems approach to uncover candidate regulators of regression and to identify a potential new therapeutic target.
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MESH Headings
- Animals
- Cells, Cultured
- Epigenesis, Genetic/drug effects
- Epigenesis, Genetic/physiology
- Female
- Gene Expression Profiling
- Genome/drug effects
- Hypolipidemic Agents/pharmacology
- Hypolipidemic Agents/therapeutic use
- Macrophages/drug effects
- Macrophages/metabolism
- Macrophages/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microarray Analysis
- Plaque, Atherosclerotic/drug therapy
- Plaque, Atherosclerotic/genetics
- Plaque, Atherosclerotic/metabolism
- Plaque, Atherosclerotic/pathology
- Receptors, LDL/genetics
- Remission Induction
- Transcriptome/drug effects
- Wnt Signaling Pathway/drug effects
- Wnt Signaling Pathway/genetics
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Affiliation(s)
- Stephen A. Ramsey
- Department of Biomedical Sciences and School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, Oregon, United States of America
| | - Yuliya Vengrenyuk
- Division of Cardiology, School of Medicine, New York University, New York, New York, United States of America
| | - Prashanthi Menon
- Division of Cardiology, School of Medicine, New York University, New York, New York, United States of America
| | - Irina Podolsky
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Jonathan E. Feig
- Division of Cardiology, School of Medicine, New York University, New York, New York, United States of America
| | - Alan Aderem
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Edward A. Fisher
- Division of Cardiology, School of Medicine, New York University, New York, New York, United States of America
- * E-mail: (EAF); (ESG)
| | - Elizabeth S. Gold
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
- * E-mail: (EAF); (ESG)
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Ulrich JD, Finn MB, Wang Y, Shen A, Mahan TE, Jiang H, Stewart FR, Piccio L, Colonna M, Holtzman DM. Altered microglial response to Aβ plaques in APPPS1-21 mice heterozygous for TREM2. Mol Neurodegener 2014; 9:20. [PMID: 24893973 PMCID: PMC4049806 DOI: 10.1186/1750-1326-9-20] [Citation(s) in RCA: 225] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Accepted: 05/20/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Recent genome-wide association studies linked variants in TREM2 to a strong increase in the odds of developing Alzheimer's disease. The mechanism by which TREM2 influences the susceptibility to Alzheimer's disease is currently unknown. TREM2 is expressed by microglia and is thought to regulate phagocytic and inflammatory microglial responses to brain pathology. Given that a single allele of variant TREM2, likely resulting in a loss of function, conferred an increased risk of developing Alzheimer's disease, we tested whether loss of one functional trem2 allele would affect Aβ plaque deposition or the microglial response to Aβ pathology in APPPS1-21 mice. RESULTS There was no significant difference in Aβ deposition in 3-month old or 7-month old APPPS1-21 mice expressing one or two copies of trem2. However, 3-month old mice with one copy of trem2 exhibited a marked decrease in the number and size of plaque-associated microglia. While there were no statistically significant differences in cytokine levels or markers of microglial activation in 3- or 7-month old animals, there were trends towards decreased expression of NOS2, C1qa, and IL1a in 3-month old TREM2+/- vs. TREM2+/+ mice. CONCLUSIONS Loss of a single copy of trem2 had no effect on Aβ pathology, but altered the morphological phenotype of plaque-associated microglia. These data suggest that TREM2 is important for the microglial response to Aβ deposition but that a 50% decrease inTREM2 expression does not affect Aβ plaque burden.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - David M Holtzman
- Department of Neurology, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
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Role of TREM1-DAP12 in renal inflammation during obstructive nephropathy. PLoS One 2013; 8:e82498. [PMID: 24358193 PMCID: PMC3864959 DOI: 10.1371/journal.pone.0082498] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/24/2013] [Indexed: 01/05/2023] Open
Abstract
Tubulo-interstitial damage is a common finding in the chronically diseased kidney and is characterized by ongoing inflammation and fibrosis leading to renal dysfunction and end-stage renal disease. Upon kidney injury, endogenous ligands can be released which are recognized by innate immune sensors to alarm innate immune system. A new family of innate sensors is the family of TREM (triggering receptor expressed on myeloid cell). TREM1 is an activating receptor and requires association with transmembrane adapter molecule DAP12 (DNAX-associated protein 12) for cell signaling. TREM1-DAP12 pathway has a cross-talk with intracellular signaling pathways of several Toll-like receptors (TLRs) and is able to amplify TLR signaling and thereby contributes to the magnitude of inflammation. So far, several studies have shown that TLRs play a role in obstructive nephropathy but the contribution of TREM1-DAP12 herein is unknown. Therefore, we studied TREM1 expression in human and murine progressive renal diseases and further investigated the role for TREM1-DAP12 by subjecting wild-type (WT), TREM1/3 double KO and DAP12 KO mice to murine unilateral ureter obstruction (UUO) model. In patients with hydronephrosis, TREM1 positive cells were observed in renal tissue. We showed that in kidneys from WT mice, DAP12 mRNA and TREM1 mRNA and protein levels were elevated upon UUO. Compared to WT mice, DAP12 KO mice displayed less renal MCP-1, KC and TGF-β1 levels and less influx of macrophages during progression of UUO, whereas TREM1/3 double KO mice displayed less renal MCP-1 level. Renal fibrosis was comparable in WT, TREM1/3 double KO and DAP12 KO mice. We conclude that DAP12, partly through TREM1/3, is involved in renal inflammation during progression of UUO.
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Thomson EM, Williams A, Yauk CL, Vincent R. Overexpression of tumor necrosis factor-α in the lungs alters immune response, matrix remodeling, and repair and maintenance pathways. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:1413-30. [PMID: 22322299 DOI: 10.1016/j.ajpath.2011.12.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 12/03/2011] [Accepted: 12/09/2011] [Indexed: 11/25/2022]
Abstract
Increased production of tumor necrosis factor (TNF)-α and matrix metalloproteinases (MMPs) is a feature of inflammatory lung diseases, including emphysema and fibrosis, but the divergent pathological characteristics that result indicate involvement of other processes in disease pathogenesis. Transgenic mice overexpressing TNF-α in type II alveolar epithelial cells under the control of the surfactant protein (SP)-C promoter develop pulmonary inflammation and emphysema but are resistant to induction of fibrosis by administration of bleomycin or transforming growth factor-β. To study the molecular mechanisms underlying the development of this phenotype, we used a microarray approach to characterize the pulmonary transcriptome of SP-C/TNF-α mice and wild-type littermates. Four-month-old SP-C/TNF-α mice displayed pronounced pulmonary inflammation, airspace enlargement, increased MMP-2 and MMP-9 levels, and altered expression of 2332 probes. The functional assessment of genes with increased expression revealed enrichment of inflammatory/immune responses and proteases, whereas genes involved in protease inhibition, angiogenesis, cross-linking of basement membrane proteins, and myofibroblast differentiation were predominantly decreased. Comparison with multiple lung disease models identified a set of genes unique to the SP-C/TNF-α model and revealed that lack of extracellular matrix production distinguished SP-C/TNF-α mice from fibrosis models. Activation of inflammatory and proteolytic pathways and disruption of maintenance and repair processes are central features of emphysema in this TNF-overexpression model. Impairment of myofibroblast differentiation and extracellular matrix production may underlie resistance to induction of fibrosis.
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Affiliation(s)
- Errol M Thomson
- Hazard Identification Division, Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
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Abstract
Asthma is characterized by airflow obstruction that is usually completely reversible either spontaneously or in response to treatment. However, a small subset of patients with asthma display FAO (fixed airflow obstruction) despite optimal treatment, a feature more commonly associated with smoking-induced COPD (chronic obstructive pulmonary disease). Why some asthma patients develop FAO is not understood, and it is not clear whether (i) they represent a subset of patients with more severe disease, (ii) they share some characteristics of patients who develop COPD, or (iii) they represent a different disease entity altogether. The present review compares the pulmonary inflammatory profile of asthma patients with FAO with those without FAO, as well as COPD sufferers. The inflammation in asthma patients with FAO can vary from neutrophilic with CD8 T-cell involvement, similar to that of COPD, to eosinophilic with CD4 Th2 cell involvement, akin to that of asthma patients without FAO. Although studies of FAO in asthma sufferers would benefit hugely from consistent inclusion criteria, further research work is also required to shed more light on the immunological processes involved.
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