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Rieu Q, Bougoüin A, Zagar Y, Chatagnon J, Hamieh A, Enderlin J, Huby T, Nandrot EF. Pleiotropic Roles of Scavenger Receptors in Circadian Retinal Phagocytosis: A New Function for Lysosomal SR-B2/LIMP-2 at the RPE Cell Surface. Int J Mol Sci 2022; 23:ijms23073445. [PMID: 35408805 PMCID: PMC8998831 DOI: 10.3390/ijms23073445] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/08/2022] [Accepted: 03/17/2022] [Indexed: 11/29/2022] Open
Abstract
The retinal phagocytic machinery resembles the one used by macrophages to clear apoptotic cells. However, in the retina, the permanent contact between photoreceptor outer segments (POS) and retinal pigment epithelial (RPE) cells requires a tight control of this circadian machinery. In addition to the known receptors synchronizing POS internalization, several others are expressed by RPE cells. Notably, scavenger receptor CD36 has been shown to intervene in the internalization speed. We thus investigated members of the scavenger receptor family class A SR-AI and MARCO and class B CD36, SR-BI and SR-B2/LIMP-2 using immunoblotting, immunohisto- and immunocytochemistry, lipid raft flotation gradients, phagocytosis assays after siRNA/antibody inhibition, RT-qPCR and western blot analysis along the light:dark cycle. All receptors were expressed by RPE cell lines and tissues and colocalized with POS, except SR-BI. All receptors were associated with lipid rafts, and even more upon POS challenge. SR-B2/LIMP-2 inhibition suggested a role in the control of the internalization speed similar to CD36. In vivo, MARCO and CD36 displayed rhythmic gene and protein expression patterns concomitant with the phagocytic peak. Taken together, our results indicate that CD36 and SR-B2/LIMP-2 play a direct regulatory role in POS phagocytosis dynamics, while the others such as MARCO might participate in POS clearance by RPE cells either as co-receptors or via an indirect process.
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Affiliation(s)
- Quentin Rieu
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Antoine Bougoüin
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Yvrick Zagar
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Jonathan Chatagnon
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Abdallah Hamieh
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Julie Enderlin
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
| | - Thierry Huby
- Sorbonne Université, INSERM, UMR-S 1166, F-75013 Paris, France;
| | - Emeline F. Nandrot
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France; (Q.R.); (A.B.); (Y.Z.); (J.C.); (A.H.); (J.E.)
- Correspondence: ; Tel.: +33-1-5346-2541; Fax: +33-1-5346-2602
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Zheng C, Lu T, Fan Z. miR-200b-3p alleviates TNF-α-induced apoptosis and inflammation of intestinal epithelial cells and ulcerative colitis progression in rats via negatively regulating KHDRBS1. Cytotechnology 2021; 73:727-743. [PMID: 34629748 DOI: 10.1007/s10616-021-00490-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 08/18/2021] [Indexed: 12/20/2022] Open
Abstract
Ulcerative colitis (UC) is difficult to be treated. miRNAs are a group of gene regulators. Study demonstrated that miR-200b-3p is involved in the development of UC, but the specific molecular mechanism is still unclear. A UC model was established by injecting acetic acid into rectum of rats, which were then treated with miR-200b-3p antagonists and agonists. Weight change, fecal viscosity and fecal bleeding were measured to determine disease activity index. The ratio of colon length to weight was measured. Colon lesions were detected by H&E staining. ELISA was used to detect the expression of TGF-β in colon tissues and IL-10/CRP in serum. Intestinal epithelial cells (NCM460) were treated by TNF-α to create an inflammatory environment. MRNA and protein levels of miR-200b-3p, KHDRBS1, IL-10, IL-6, IL-1β, TGF-β, Bcl-2, Bax and C-capase-3 were detected by qRT-PCR and Western blot, respectively. TargetScan database and dual-luciferase reporter assay were conducted to predict the targeting relationship between miR-200b-3p and KHDRBS1. MTT and flow cytometry were respectively performed to detect cell proliferation and apoptosis. MiR-200b-3p expression was inhibited, leading to increased disease activity index and colonic length-weight ratio, and aggravation of lesions of the UC rat model. Up-regulation of miR-200b-3p can relieve inflammation and apoptosis of immune cells in UC rats. MiR-200b-3p targeted KHDRBS1 and inhibited its expression. Moreover, KHDRBS1 reversed the effects of miR-200b-3p on apoptosis, proliferation and inflammation of intestinal epithelial cells. MiR-200b-3p alleviates UC by negatively regulating KHDRBS1.
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Affiliation(s)
- Chunju Zheng
- Department of Anorectal, Huai'an TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Huai'an, China
| | - Ting Lu
- Department of Anorectal, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, 157 Daming Road, Qinhuai District, Nanjing, 210001 Jiangsu China
| | - Zhimin Fan
- Department of Anorectal, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, 157 Daming Road, Qinhuai District, Nanjing, 210001 Jiangsu China
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Voices from the dead: The complex vocabulary and intricate grammar of dead cells. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 116:1-90. [PMID: 31036289 DOI: 10.1016/bs.apcsb.2019.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Of the roughly one million cells per second dying throughout the body, the vast majority dies by apoptosis, the predominant form of regulated cell death in higher organisms. Long regarded as mere waste, apoptotic cells are now recognized as playing a prominent and active role in homeostatic maintenance, especially resolution of inflammation, and in the sculpting of tissues during development. The activities associated with apoptotic cells are continually expanding, with more recent studies demonstrating their ability to modulate such vital functions as proliferation, survival, differentiation, metabolism, migration, and angiogenesis. In each case, the role of apoptotic cells is active, exerting their effects via new activities acquired during the apoptotic program. Moreover, the capacity to recognize and respond to apoptotic cells is not limited to professional phagocytes. Most, if not all, cells receive and integrate an array of signals from cells dying in their vicinity. These signals comprise a form of biochemical communication. As reviewed in this chapter, this communication is remarkably sophisticated; each of its three critical steps-encoding, transmission, and decoding of the apoptotic cell's "message"-is endowed with exquisite robustness. Together, the abundance and intricacy of the variables at each step comprise the vocabulary and grammar of the language by which dead cells achieve their post-mortem voice. The combinatorial complexity of the resulting communication network permits dying cells, through the signals they emit and the responses those signals elicit, to partake of an expanded role in homeostasis, acting as both sentinels of environmental change and agents of adaptation.
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de Mello-Coelho V, Cutler RG, Bunbury A, Tammara A, Mattson MP, Taub DD. Age-associated alterations in the levels of cytotoxic lipid molecular species and oxidative stress in the murine thymus are reduced by growth hormone treatment. Mech Ageing Dev 2017; 167:46-55. [PMID: 28865931 DOI: 10.1016/j.mad.2017.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 07/24/2017] [Accepted: 08/22/2017] [Indexed: 12/13/2022]
Abstract
During age-associated thymic involution, thymocytes decrease and lipid-laden cells accumulate. However, if and how aging affects the thymic lipid profile is not well understood, nor is it known if the hormonal milieu modifies this process. Here we demonstrate a correlation between reduced thymocyte numbers and markers of inflammation and oxidative stress with age. Evaluating the lipidomics profile of the whole thymus, between the ages of 4 (young) and 18 months (old), we found increased amounts of triacylglycerides, free cholesterol, cholesterol ester and 4-hydroxynonenal (4-HNE) with age. Moreover, levels of C24:0 and C24:1 sphingomyelins and ceramide C16:0 were elevated in 12-14 month-old (middle-aged) mice while the levels of sulfatide ceramide and ganglioside GD1a increased in the old thymus. Evaluating isolated thymocytes, we found increased levels of cholesterol ester and 4-HNE adducts, as compared to young mice. Next, we treated middle-aged mice with growth hormone (GH), which has been considered a potent immunomodulator. GH reduced thymic levels of TNF-α and 4-HNE and increased the number of thymocytes as well as the thymic levels of dihydroceramide, a ceramide precursor and autophagic stimuli for cell survival. In conclusion, GH treatment attenuated inflammation and age-related increases in oxidative stress and lipotoxicity in the thymus.
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Affiliation(s)
- Valeria de Mello-Coelho
- Laboratory of Immunology, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA; Laboratory of Immunophysiology, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, 21941-902, Brazil.
| | - Roy G Cutler
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA.
| | - Allyson Bunbury
- Laboratory of Immunology, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA.
| | - Anita Tammara
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA.
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA.
| | - Dennis D Taub
- Laboratory of Immunology, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224-6825, USA; Center for Translational Studies, Medical Service, VA Medical Center-DC, Washington DC, 20422, USA.
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Nakayama Y, Masuda Y, Ohta H, Tanaka T, Washida M, Nabeshima YI, Miyake A, Itoh N, Konishi M. Fgf21 regulates T-cell development in the neonatal and juvenile thymus. Sci Rep 2017; 7:330. [PMID: 28336912 PMCID: PMC5428243 DOI: 10.1038/s41598-017-00349-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 02/22/2017] [Indexed: 11/09/2022] Open
Abstract
We have previously shown that Fibroblast growth factor 21 (Fgf21) is expressed in the thymus as well as in the liver. In line with this expression profile, Fgf21 was recently reported to protect against ageing-related thymic senescence by improving the function of thymic epithelial cells (TECs). However, the function of Fgf21 in the juvenile thymus remained to be elucidated. We investigated the physiological roles of Fgf21 in the juvenile thymus and found that young Fgf21 knockout mice, but not β-Klotho knockout mice nor adult Fgf21 knockout mice, showed a significant reduction in the percentage of single-positive CD4+ and CD8+ thymocytes without obvious alteration in TECs. Furthermore, treatment with recombinant FGF21 protein rescued the impairment in fetal thymus organ culture (FTOC) of Fgf21 knockout mice. Annexin V staining revealed FGF21 protein enhanced apoptosis of immature thymocytes undergoing selection process in FTOC, suggesting that FGF21 may facilitate the selection of developing T cells. Endocrine Fgf21 from the liver induced by metabolic stimulation did not affect juvenile thymocyte development. Our data suggest that Fgf21 acts as one of intrathymic cytokines in the neonatal and juvenile thymus, involving thymocyte development in a β-Klotho-independent manner.
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Affiliation(s)
- Yoshiaki Nakayama
- Department of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Yuki Masuda
- Department of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
| | - Hiroya Ohta
- Department of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan
- Department of Molecular Medicine and Metabolism, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan
| | - Tomohiro Tanaka
- Medical Innovation Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Laboratory of Molecular Life Science, Foundation for Biomedical Research and Innovation, Kobe, Hyogo, Japan
| | - Miwa Washida
- Laboratory of Molecular Life Science, Foundation for Biomedical Research and Innovation, Kobe, Hyogo, Japan
| | - Yo-Ichi Nabeshima
- Laboratory of Molecular Life Science, Foundation for Biomedical Research and Innovation, Kobe, Hyogo, Japan
| | - Ayumi Miyake
- Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto, Japan
| | - Nobuyuki Itoh
- Medical Innovation Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto, Japan
| | - Morichika Konishi
- Department of Microbial Chemistry, Kobe Pharmaceutical University, Kobe, Japan.
- Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto, Japan.
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McGaha TL, Karlsson MCI. Apoptotic cell responses in the splenic marginal zone: a paradigm for immunologic reactions to apoptotic antigens with implications for autoimmunity. Immunol Rev 2016; 269:26-43. [PMID: 26683143 DOI: 10.1111/imr.12382] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Apoptotic cells drive innate regulatory responses that result in tolerogenic immunity. This is a critical aspect of cell physiology as apoptotic cells expose potentially dangerous nuclear antigens on the surface in apoptotic blebs, and failure in their recognition, phagocytosis, or destruction can cause dramatic autoimmunity in experimental models and is linked to development and progression of systemic pathology in human. The marginal zone is a specialized splenic environment that serves as a transitional site from circulation to peripheral lymphoid structures. The marginal zone serves a key role in trapping of particulates and initiation of innate responses against systemic microbial pathogens. However in recent years, it has become clear the marginal zone is also important for initiation of immune tolerance to apoptotic cells, driving a coordinated response involving multiple phagocyte and lymphocyte subsets. Recent reports linking defects in splenic macrophage function to systemic lupus erythematosus in a manner analogous to marginal zone macrophages in lupus-prone mice provide an impetus to better understand the mechanistic basis of the apoptotic cell response in the marginal zone and its general applicability to apoptotic cell-driven tolerance at other tissue sites. In this review, we discuss immune responses to apoptotic cells in the spleen in general and the marginal zone in particular, the relationship of these responses to autoimmune disease, and comparisons to apoptotic cell immunity in humans.
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Affiliation(s)
- Tracy L McGaha
- Department of Immunology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Princess Margaret Cancer Center, University Health Network, Toronto, ON, Canada
| | - Mikael C I Karlsson
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden
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Scavenger receptor class-A plays diverse role in innate immunity, cell signaling and different pathologies. ASIAN PACIFIC JOURNAL OF TROPICAL DISEASE 2016. [DOI: 10.1016/s2222-1808(16)61088-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Abstract
Scavenger receptors constitute a large family of evolutionally conserved protein molecules that are structurally and functionally diverse. Although scavenger receptors were originally identified based on their capacity to scavenge modified lipoproteins, these molecules have been shown to recognize and bind to a broad spectrum of ligands, including modified and unmodified host-derived molecules or microbial components. As a major subset of innate pattern recognition receptors, scavenger receptors are mainly expressed on myeloid cells and function in a wide range of biological processes, such as endocytosis, adhesion, lipid transport, antigen presentation, and pathogen clearance. In addition to playing a crucial role in maintenance of host homeostasis, scavenger receptors have been implicated in the pathogenesis of a number of diseases, e.g., atherosclerosis, neurodegeneration, or metabolic disorders. Emerging evidence has begun to reveal these receptor molecules as important regulators of tumor behavior and host immune responses to cancer. This review summarizes our current understanding on the newly identified, distinct functions of scavenger receptors in cancer biology and immunology. The potential of scavenger receptors as diagnostic biomarkers and novel targets for therapeutic interventions to treat malignancies is also highlighted.
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Affiliation(s)
- Xiaofei Yu
- Department of Human and Molecular Genetics, Richmond, Virginia, USA; VCU Institute of Molecular Medicine, Richmond, Virginia, USA; VCU Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Chunqing Guo
- Department of Human and Molecular Genetics, Richmond, Virginia, USA; VCU Institute of Molecular Medicine, Richmond, Virginia, USA; VCU Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Paul B Fisher
- Department of Human and Molecular Genetics, Richmond, Virginia, USA; VCU Institute of Molecular Medicine, Richmond, Virginia, USA; VCU Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - John R Subjeck
- Department of Cellular Stress Biology, Roswell Park Cancer Institute, Buffalo, New York, USA.
| | - Xiang-Yang Wang
- Department of Human and Molecular Genetics, Richmond, Virginia, USA; VCU Institute of Molecular Medicine, Richmond, Virginia, USA; VCU Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA.
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9
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Cellular and molecular targeting for nanotherapeutics in transplantation tolerance. Clin Immunol 2015; 160:14-23. [PMID: 25805659 DOI: 10.1016/j.clim.2015.03.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 02/23/2015] [Accepted: 03/03/2015] [Indexed: 11/21/2022]
Abstract
The induction of donor-specific tolerance to transplanted cells and organs, while preserving immune function as a whole, remains a highly sought after and elusive strategy for overcoming transplant rejection. Tolerance necessitates modulating a diverse array of cell types that recognize and respond to alloantigens, including antigen presenting cells and T lymphocytes. Nanotherapeutic strategies that employ cellular and biomaterial engineering represent an emerging technology geared towards the goal of inducing transplant tolerance. Nanocarriers offer a platform for delivering antigens of interest to specific cell types in order to achieve tolerogenic antigen presentation. Furthermore, the technologies also provide an opportunity for local immunomodulation at the graft site. Nanocarriers delivering a combination of antigens and immunomodulating agents, such as rapamycin, provide a unique technology platform with the potential to enhance outcomes for the induction of transplant tolerance.
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Kato C, Mikami M, Saito K. The Participation of Nitric Oxide in Peritoneal Exudate Cell Cytotoxicity of Mice byFusobacterium nucleatum. Microbiol Immunol 2013; 48:607-15. [PMID: 15322341 DOI: 10.1111/j.1348-0421.2004.tb03558.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previously we reported that mice infected recurrently with live Fusobacterium nucleatum(Fn) synthesize a significant amount of NO between 12 hr and 24 hr after Fn injection. Fn is a gram-negative rod periodontal pathogen. NO could not be induced by heat-killed Fn or in untreated mice. This NO, derived from the iNOS after infection of live Fn, was not involved in the Fn reduction because Fn clearance occurs within 6 hr. We investigated in this study whether this NO was involved in cytotoxicity in peritoneal exudate cells (PEC) in vivo. The mice were divided into two groups: those treated with live Fn (immune) and those left untreated (normal). PEC number, NO production, detection of apoptosis or death cells, and lactate dehydrogenase (LDH) release activity after injection of live Fn were compared in these groups. In the immune group, the increase of the total cell numbers caused by an increase in neutrophils, a significant NO production only after injection of live Fn at 24 hr and identification of iNOS positive macrophages were confirmed. The apoptotic rate was very low and did not increase at 24 hr in vivo. Therefore, apoptosis was seldom relevant to the NO. In the immune group, LDH activity was remarkable high at 24 hr, and dead cells and macrophages phagocytizing cell fragments increased at the same time. Pretreatment of L NMMA, an inhibitor of iNOS, suppressed LDH activity and cell death. Therefore, the NO derived from the iNOS is involved in the cytotoxicity. These results suggest that NO may contribute to the inflammatory response during Fn infection in periodontitis.
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Affiliation(s)
- Chihomi Kato
- Department of Microbiology, School of Dentistry, Nippon Dental University at Niigata, 1-8 Hamuracho, Niigata 951-8580, Japan.
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Doyle HA, Yang ML, Raycroft MT, Gee RJ, Mamula MJ. Autoantigens: novel forms and presentation to the immune system. Autoimmunity 2013; 47:220-33. [PMID: 24191689 DOI: 10.3109/08916934.2013.850495] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
It is clear that lupus autoimmunity is marked by a variety of abnormalities, including those found at a macroscopic scale, cells and tissues, as well as more microenvironmental influences, originating at the individual cell surface through to the nucleus. The convergence of genetic, epigenetic, and perhaps environmental influences all lead to the overt clinical expression of disease, reflected by the presences of autoantibodies and tissue pathology. This review will address several specific areas that fall among the non-genetic factors that contribute to lupus autoimmunity and related syndromes. In particular, we will discuss the importance of understanding various protein post-translational modifications (PTMs), mechanisms that mediate the ability of "modified self" to trigger autoimmunity, and how these PTMs influence lupus diagnosis. Finally, we will discuss altered pathways of autoantigen presentation that may contribute to the perpetuation of chronic autoimmune disease.
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Affiliation(s)
- Hester A Doyle
- Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine , New Haven, CT , USA
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12
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den Haan JMM, Martinez-Pomares L. Macrophage heterogeneity in lymphoid tissues. Semin Immunopathol 2013; 35:541-52. [PMID: 23579230 DOI: 10.1007/s00281-013-0378-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 03/20/2013] [Indexed: 12/16/2022]
Abstract
Macrophages in lymphoid organs exhibit a wide variety of phenotypes and functions. These cells excel in the removal of apoptotic cells that arise during the generation of immune cells and are thereby essential for the prevention of auto-immune responses. In addition to this macrophages in the secondary lymphoid organs form an important barrier for spreading of infections by phagocytosis of pathogens and the activation of both innate and adaptive immune responses. Thus, the remarkable ability of macrophages to phagocytose and handle a wide range of self and non-self material and to produce immunomediators is effectively exploited within lymphoid organs to regulate immune activation.
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Affiliation(s)
- Joke M M den Haan
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, 1007, MB, Amsterdam, the Netherlands.
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Ravishankar B, McGaha TL. O death where is thy sting? Immunologic tolerance to apoptotic self. Cell Mol Life Sci 2013; 70:3571-89. [PMID: 23377225 DOI: 10.1007/s00018-013-1261-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/14/2012] [Accepted: 01/03/2013] [Indexed: 12/22/2022]
Abstract
In higher organisms, innate scavenging cells maintain physiologic homeostasis by removal of the billions of apoptotic cells generated on a daily basis. Apoptotic cell removal requires efficient recognition and uptake by professional and non-professional phagocytic cells, which are governed by an array of soluble and apoptotic cell-integral signals resulting in immunologically silent clearance. While apoptosis is associated with profound suppression of adaptive and innate inflammatory immunity, we have only begun to scratch the surface in understanding how immunologic tolerance to apoptotic self manifest at either the molecular or cellular level. In the last 10 years, data has emerged implicating professional phagocytes, most notably stromal macrophages and CD8α(+)CD103(+) dendritic cells, as critical in initiation of the regulatory cascade that will ultimately lead to long-term whole-animal immune tolerance. Importantly, recent work by our lab and others has shown that alterations in apoptotic cell perception by the innate immune system either by removal of critical phagocytic sentinels in secondary lymphoid organs or blockage of immunosuppressive pathways leads to pronounced inflammation with a breakdown of tolerance towards self. This challenges the paradigm that apoptotic cells are inherently immunosuppressive, suggesting that apoptotic cell tolerance is a "context-dependent" event.
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Affiliation(s)
- Buvana Ravishankar
- Cancer Immunology, Inflammation, and Tolerance Program, GRU Cancer Center, Georgia Regents University, Building CN4143, 1120 15th Street, Augusta, GA, 30904, USA
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14
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McCoy MW, Moreland SM, Detweiler CS. Hemophagocytic macrophages in murine typhoid fever have an anti-inflammatory phenotype. Infect Immun 2012; 80:3642-9. [PMID: 22868497 PMCID: PMC3457584 DOI: 10.1128/iai.00656-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 07/25/2012] [Indexed: 02/03/2023] Open
Abstract
Histiocytes are white blood cells of the monocytic lineage and include macrophages and dendritic cells. In patients with a variety of infectious and noninfectious inflammatory disorders, histiocytes can engulf nonapoptotic leukocytes and nonsenescent erythrocytes and thus become hemophagocytes. We report here the identification and characterization of splenic hemophagocytes in a natural model of murine typhoid fever. The development of a flow-cytometric method allowed us to identify hemophagocytes based on their greater than 6N (termed 6N+) DNA content. Characterization of the 6N+ population from infected mice showed that these cells consist primarily of macrophages rather than dendritic cells and contain T lymphocytes, consistent with hemophagocytosis. Most 6N+ macrophages from Salmonella enterica serovar Typhimurium-infected mice contain intact DNA, consistent with hemophagocytosis. In contrast, most 6N+ macrophages from control mice or mice infected with a different bacterial pathogen, Yersinia pseudotuberculosis, contain damaged DNA. Finally, 6N+ splenic macrophages from S. Typhimurium-infected mice express markers consistent with an anti-inflammatory M2 activation state rather than a classical M1 activation state. We conclude that macrophages are the predominant splenic hemophagocyte in this disease model but not in Y. pseudotuberculosis-infected mice. The anti-inflammatory phenotype of hemophagocytic macrophages suggests that these cells contribute to the shift from acute to chronic infection.
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Affiliation(s)
- Melissa W McCoy
- Department of Molecular Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
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Thacker RI, Janssen EM. Cross-presentation of cell-associated antigens by mouse splenic dendritic cell populations. Front Immunol 2012; 3:41. [PMID: 22566924 PMCID: PMC3342388 DOI: 10.3389/fimmu.2012.00041] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 02/19/2012] [Indexed: 11/13/2022] Open
Abstract
Cross-presentation of cell-associated antigens (Ag) plays an important role in the induction of anti-tumor responses, autoimmune diseases, and transplant rejection. While several dendritic cell (DC) populations can induce pro-inflammatory CD8(+) T cell responses to cell-associated Ag during infection, in the absence of infection, cross-priming of naïve CD8(+) T cells is highly restricted. Comparison of the main splenic DC populations in mice - including the classic, cross-presenting CD8α DC and the recently described merocytic DC (mcDC) - reveals that cross-priming DCs display a distinct phenotype in cell-associated Ag uptake, endosomal/lysosomal trafficking, lysosomal acidification, and Ag persistence compared to non-cross-priming DC populations. Although the CD8α DC and mcDC subsets utilize similar processing pathways to cross-present cell-associated Ag, cross-priming by CD8α DCs is associated with IL-12 production, while the superior priming of the mcDC is critically dependent on type I IFN production. This discussion illustrates how subtle differences in internal processing pathways and their signaling sequelae significantly affect the duration of Ag cross-presentation and cytokine production by DCs, thereby shaping the ensuing CD8(+) T cell response.
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Affiliation(s)
- Robert I Thacker
- Division of Molecular Immunology, Cincinnati Children's Hospital Research Foundation, University of Cincinnati College of Medicine Cincinnati, OH, USA
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16
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Martínez VG, Moestrup SK, Holmskov U, Mollenhauer J, Lozano F. The conserved scavenger receptor cysteine-rich superfamily in therapy and diagnosis. Pharmacol Rev 2011; 63:967-1000. [PMID: 21880988 DOI: 10.1124/pr.111.004523] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The scavenger receptor cysteine-rich (SRCR) superfamily of soluble or membrane-bound protein receptors is characterized by the presence of one or several repeats of an ancient and highly conserved protein module, the SRCR domain. This superfamily (SRCR-SF) has been in constant and progressive expansion, now up to more than 30 members. The study of these members is attracting growing interest, which parallels that in innate immunity. No unifying function has been described to date for the SRCR domains, this being the result of the limited knowledge still available on the physiology of most members of the SRCR-SF, but also of the sequence versatility of the SRCR domains. Indeed, involvement of SRCR-SF members in quite different functions, such as pathogen recognition, modulation of the immune response, epithelial homeostasis, stem cell biology, and tumor development, have all been described. This has brought to us new information, unveiling the possibility that targeting or supplementing SRCR-SF proteins could result in diagnostic and/or therapeutic benefit for a number of physiologic and pathologic states. Recent research has provided structural and functional insight into these proteins, facilitating the development of means to modulate the activity of SRCR-SF members. Indeed, some of these approaches are already in use, paving the way for a more comprehensive use of SRCR-SF members in the clinic. The present review will illustrate some available evidence on the potential of well known and new members of the SRCR-SF in this regard.
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Affiliation(s)
- Vanesa Gabriela Martínez
- Center Esther Koplowitz, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
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17
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Wu Q, Liu Y, Chen C, Ikenoue T, Qiao Y, Li CS, Li W, Guan KL, Liu Y, Zheng P. The tuberous sclerosis complex-mammalian target of rapamycin pathway maintains the quiescence and survival of naive T cells. THE JOURNAL OF IMMUNOLOGY 2011; 187:1106-12. [PMID: 21709159 DOI: 10.4049/jimmunol.1003968] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Naive T cells receive stimulation from the positive selecting ligand in the periphery for their survival. This stimulation does not normally lead to overt activation of T cells, as the T cells remain largely quiescent until they receive either antigenic or lymphopenic stimuli. The underlying mechanism responsible for survival and quiescence of the naive T cells remains largely unknown. In this study, we report that T cell-specific deletion of Tsc1, a negative regulator of mammalian target of rapamycin, resulted in both spontaneous losses of quiescence and cellularity, especially within the CD8 subset. The Tsc1-deficient T cells have increased cell proliferation and apoptosis. Tsc1 deletion affects the survival and quiescence of T cells in the absence of antigenic stimulation. Loss of quiescence but not cellularity was inhibited by rapamycin. Our data demonstrate that tuberous sclerosis complex-mammalian target of rapamycin maintains quiescence and survival of T cells.
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Affiliation(s)
- Qi Wu
- Department of Surgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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18
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Scavenger receptors as regulators of natural antibody responses and B cell activation in autoimmunity. Mol Immunol 2011; 48:1307-18. [DOI: 10.1016/j.molimm.2011.01.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Revised: 01/05/2011] [Accepted: 01/17/2011] [Indexed: 12/12/2022]
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19
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Devitt A, Marshall LJ. The innate immune system and the clearance of apoptotic cells. J Leukoc Biol 2011; 90:447-57. [DOI: 10.1189/jlb.0211095] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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20
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Marginal zone macrophages suppress innate and adaptive immunity to apoptotic cells in the spleen. Blood 2011; 117:5403-12. [PMID: 21444914 DOI: 10.1182/blood-2010-11-320028] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Marginal zone macrophages (MZMs) are a small subset of specialized splenic macrophages known to interact with apoptotic material entering the spleen from circulation. To evaluate whether MZMs regulate immunity to apoptotic material we depleted MZMs and assessed innate and adaptive immune responses to apoptotic cells administered systemically. MZM depletion altered the spatial localization of apoptotic cells, which accumulated in T-cell areas of the lymphoid follicles. MZM depletion also enhanced phagocytosis of apoptotic cells by red pulp (CD68(+)F4/80(+)) macrophages, which expressed increased CD86, MHCII, and CCR7. MZM depletion led to increased production of proinflammatory cytokines and enhanced lymphocyte responsiveness to apoptotic cell antigens. Furthermore, we found that MZM depletion accelerated autoimmune disease progression in mice genetically prone to systemic lupus erythematosus and caused significant mortality in wild-type mice repeatedly exposed to exogenous apoptotic thymocytes. These findings support the hypothesis that MZMs are central in the clearance of apoptotic cells to minimize the immunogenicity of autoantigens.
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21
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Absence of scavenger receptor A promotes dendritic cell-mediated cross-presentation of cell-associated antigen and antitumor immune response. Immunol Cell Biol 2011; 90:101-8. [PMID: 21383767 PMCID: PMC3134534 DOI: 10.1038/icb.2011.10] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Given the primary expression of scavenger receptor A (SRA) or CD204 on antigen-presenting cells, we investigate the immunoregulatory activities of SRA/CD204 in the context of cross-presentation of cell-associated antigen and the immunogenicity of dying tumor cells. Immunization with dying prostate cancer cells results in profoundly increased control of subsequently inoculated tumors in SRA/CD204 knockout mice. Using OVA-expressing RM1 prostate tumor line (RM1-OVA), we show for the first time that SRA absence greatly enhances dendritic cells (DCs)-mediated cross-presentation of OVA antigen derived from dying RM1 cells. While the phagocytic ability of DCs is not significantly impacted by the lack of SRA/CD204, DCs deficient in SRA/CD204 display increased expression of inflammatory cytokines and chemokines, as well as co-stimulatory molecules upon interaction with dying RM1 cells, implicating a suppressive regulation of the functional activation of DCs by SRA/CD204. Further, SRA/CD204-deficient DCs pulsed with dying RM1-OVA cells are more effective than wild-type counterparts in priming antigen-specific T-cell responses, resulting in improved control of RM1 tumor growth in both prophylactic and therapeutic settings. Our findings suggest that the increased immunogenicity of dying tumor cells in SRA/CD204 knockout mice is attributed to the altered functions of DCs in the absence of SRA/CD204, which underscores the important role of SRA/CD204 in host immune homeostasis. Selective downregulation or blockade of this immunoregulatory molecule may lead to enhanced potency of DC-based vaccines capable of breaking immune tolerance against cancer.
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22
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Rosenbaum S, Kreft S, Etich J, Frie C, Stermann J, Grskovic I, Frey B, Mielenz D, Pöschl E, Gaipl U, Paulsson M, Brachvogel B. Identification of novel binding partners (annexins) for the cell death signal phosphatidylserine and definition of their recognition motif. J Biol Chem 2010; 286:5708-16. [PMID: 21131363 DOI: 10.1074/jbc.m110.193086] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Identification and clearance of apoptotic cells prevents the release of harmful cell contents thereby suppressing inflammation and autoimmune reactions. Highly conserved annexins may modulate the phagocytic cell removal by acting as bridging molecules to phosphatidylserine, a characteristic phagocytosis signal of dying cells. In this study five members of the structurally and functionally related annexin family were characterized for their capacity to interact with phosphatidylserine and dying cells. The results showed that AnxA3, AnxA4, AnxA13, and the already described interaction partner AnxA5 can bind to phosphatidylserine and apoptotic cells, whereas AnxA8 lacks this ability. Sequence alignment experiments located the essential amino residues for the recognition of surface exposed phosphatidylserine within the calcium binding motifs common to all annexins. These amino acid residues were missing in the evolutionary young AnxA8 and when they were reintroduced by site directed mutagenesis AnxA8 gains the capability to interact with phosphatidylserine containing liposomes and apoptotic cells. By defining the evolutionary conserved amino acid residues mediating phosphatidylserine binding of annexins we show that the recognition of dying cells represent a common feature of most annexins. Hence, the individual annexin repertoire bound to the cell surface of dying cells may fulfil opsonin-like function in cell death recognition.
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Affiliation(s)
- Sabrina Rosenbaum
- Medical Faculty, Center for Biochemistry, University of Cologne, 50931 Cologne, Germany
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23
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Katsiari CG, Liossis SNC, Sfikakis PP. The Pathophysiologic Role of Monocytes and Macrophages in Systemic Lupus Erythematosus: A Reappraisal. Semin Arthritis Rheum 2010; 39:491-503. [DOI: 10.1016/j.semarthrit.2008.11.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Revised: 09/09/2008] [Accepted: 11/08/2008] [Indexed: 01/20/2023]
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24
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Clarke MCH, Talib S, Figg NL, Bennett MR. Vascular smooth muscle cell apoptosis induces interleukin-1-directed inflammation: effects of hyperlipidemia-mediated inhibition of phagocytosis. Circ Res 2010; 106:363-72. [PMID: 19926874 DOI: 10.1161/circresaha.109.208389] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Atherosclerosis is characterized by lipid accumulation in the vessel wall, inflammation, and both macrophage and vascular smooth muscle cell (VSMC) apoptosis. However, whereas VSMC apoptosis in mice with established atherosclerotic plaques or hyperlipidemia increases serum levels of the proatherogenic cytokines monocyte chemotactic protein (MCP)-1, tumor necrosis factor alpha, and interleukin (IL)-6, the link between hyperlipidemia, apoptosis and inflammation, and the mechanisms by which apoptotic cells promote inflammation in atherosclerosis are unknown. OBJECTIVE To determine whether hyperlipidemia affects apoptotic cell clearance, and identify the molecular pathways downstream of VSMC apoptosis that may promote inflammation. METHODS AND RESULTS We find that human VSMCs are potent and efficient phagocytes of apoptotic human VSMCs, but phagocytosis is significantly reduced by oxidized low-density lipoprotein in vitro or hyperlipidemia in vivo. Necrotic human aortic VSMCs release IL-1alpha, which induces IL-6 and MCP-1 production from viable human VSMCs in vitro. In contrast, secondary necrotic VSMCs release both IL-1alpha and caspase-activated IL-1beta, augmenting IL-6 and MCP-1 production. Conditionally inducing VSMC apoptosis in situ in hyperlipidemic SM22alpha-hDTR/ApoE(-/-) mice to levels seen in human plaques increases serum MCP-1, tumor necrosis factor alpha, and IL-6, which is prevented by blocking IL-1. CONCLUSIONS We conclude that VSMC necrosis releases IL-1alpha, whereas secondary necrosis of apoptotic VSMCs releases both IL-1alpha and beta. IL-1 from necrotic VSMCs induces the surrounding viable VSMCs to produce proinflammatory cytokines. Thus, failed clearance of apoptotic VSMCs caused by hyperlipidemia in vivo may promote the increased serum cytokines and chronic inflammation associated with atherosclerosis.
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MESH Headings
- Animals
- Apolipoproteins E/genetics
- Apolipoproteins E/metabolism
- Apoptosis/physiology
- Blotting, Western
- Cells, Cultured
- Chemokine CCL2/blood
- Chemokine CCL2/metabolism
- Heparin-binding EGF-like Growth Factor
- Humans
- Hyperlipidemias/physiopathology
- Immunohistochemistry
- Inflammation/metabolism
- Inflammation/physiopathology
- Intercellular Signaling Peptides and Proteins/genetics
- Intercellular Signaling Peptides and Proteins/metabolism
- Interleukin-1alpha/metabolism
- Interleukin-6/blood
- Interleukin-6/metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/parasitology
- Phagocytosis/physiology
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Affiliation(s)
- Murray C H Clarke
- Division of Cardiovascular Medicine, University of Cambridge, Box 110, ACCI, Addenbrooke's Hospital, Cambridge, CB2 2QQ, UK.
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25
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Komohara Y, Takemura K, Lei XF, Sakashita N, Harada M, Suzuki H, Kodama T, Takeya M. Delayed growth of EL4 lymphoma in SR-A-deficient mice is due to upregulation of nitric oxide and interferon-gamma production by tumor-associated macrophages. Cancer Sci 2009; 100:2160-6. [PMID: 19694752 PMCID: PMC11158051 DOI: 10.1111/j.1349-7006.2009.01296.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2009] [Revised: 07/15/2009] [Accepted: 07/17/2009] [Indexed: 01/20/2023] Open
Abstract
Class A scavenger receptors (SR-A, CD204) are highly expressed in tumor-associated macrophages (TAM). To investigate the function of SR-A in TAM, wild-type and SR-A-deficient (SR-A(-/-)) mice were injected with EL4 cells. Although these groups of mice did not differ in the numbers of infiltrating macrophages and lymphocytes and in neovascularization, SR-A(-/-) mice had delayed growth of EL4 tumors. Expression of inducible nitric oxide (NO) synthase and interferon (IFN)-gamma mRNA increased significantly in tumor tissues from SR-A(-/-) mice. Engulfment of necrotic EL4 cells induced upregulation of NO and IFN-gamma production by cultured macrophages, and production of NO and IFN-gamma increased in SR-A(-/-) macrophages in vitro. IFN-beta production by cultured macrophages was also elevated in SR-A(-/-) macrophages in vitro. These results suggested that the antitumor activity of macrophages increased in SR-A(-/-) mice because of upregulation of NO and IFN-gamma production. These data indicate an important role of SR-A in regulating TAM function by inhibiting toll-like receptor (TLR)4-IFN-beta signaling.
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Affiliation(s)
- Yoshihiro Komohara
- Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University, Japan
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26
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Pattern recognition scavenger receptor SRA/CD204 down-regulates Toll-like receptor 4 signaling-dependent CD8 T-cell activation. Blood 2009; 113:5819-28. [PMID: 19349620 DOI: 10.1182/blood-2008-11-190033] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Class A scavenger receptor (SRA), also known as CD204, has been shown to participate in the pathogenesis of atherosclerosis and the pattern recognition of pathogen infection. However, its role in adaptive immune responses has not been well defined. In this study, we report that the lack of SRA/CD204 promotes Toll-like receptor (TLR)4 agonist-augmented tumor-protective immunity, which is associated with enhanced activation of CD8(+) effector T cell and improved inhibition of tumor growth. Dendritic cells (DCs) deficient in SRA/CD204 display more effective immunostimulatory activities upon TLR4 engagement than those from wild-type counterparts. Silencing of SRA/CD204 by RNA interference improves the ability of DCs to prime antigen-specific CD8(+) T cells, suggesting that antigen-presenting cells, for example, DCs, play a major role in SRA/CD204-mediated immune modulation. Our findings reveal a previously unrecognized role for SRA/CD204, a non-TLR pattern recognition receptor, as a physiologic negative regulator of TLR4-mediated immune consequences, which has important clinical implications for development of TLR-targeted immunotherapeutic intervention.
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27
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Todt JC, Hu B, Curtis JL. The scavenger receptor SR-A I/II (CD204) signals via the receptor tyrosine kinase Mertk during apoptotic cell uptake by murine macrophages. J Leukoc Biol 2008; 84:510-8. [PMID: 18511575 DOI: 10.1189/jlb.0307135] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Apoptotic cells (AC) must be cleared by macrophages (Mø) to resolve inflammation effectively. Mertk and scavenger receptor A (SR-A) are two of many receptors involved in AC clearance. As SR-A lacks enzymatic activity or evident intracellular signaling motifs, yet seems to signal in some cell types, we hypothesized that SR-A signals via Mer receptor tyrosine kinase (Mertk), which contains a multisubstrate docking site. We induced apoptosis in murine thymocytes by dexamethasone and used Western blotting and immunoprecipitation to analyze the interaction of Mertk and SR-A in the J774A.1 (J774) murine Mø cell line and in peritoneal Mø of wild-type mice and SR-A-/- mice. Phagocytosis (but not adhesion) of AC by J774 was inhibited by anti-SR-A or function-blocking SR-A ligands. In resting J774, SR-A was associated minimally with unphosphorylated (monomeric) Mertk; exposure to AC induced a time-dependent increase in association of SR-A with Mertk in a direct or indirect manner. Anti-SR-A inhibited AC-induced phosphorylation of Mertk and of phospholipase Cgamma2, essential steps in AC ingestion. Relative to tissue Mø of wild-type mice, AC-induced Mertk phosphorylation was reduced and delayed in tissue Mø of SR-A-/- mice, as was in vitro AC ingestion at early time-points. Thus, during AC uptake by murine Mø, SR-A is essential for optimal phosphorylation of Mertk and subsequent signaling required for AC ingestion. These data support the Mertk/SR-A complex as a potential target to manipulate AC clearance and hence, resolution of inflammation and infections.
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Affiliation(s)
- Jill C Todt
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
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28
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Maniati E, Potter P, Rogers NJ, Morley BJ. Control of apoptosis in autoimmunity. J Pathol 2008; 214:190-8. [PMID: 18161756 DOI: 10.1002/path.2270] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Apoptosis and the subsequent removal of apoptotic cells underpin a healthy immune system. They are crucial for both the maintenance of self-tolerance and the contraction of clonally expanded lymphocytes at the conclusion of immune responses. Aberrant apoptosis and the disposal of apoptotic cells is implicated in the development of both systemic and organ-specific autoimmune disease and is a major contributing factor in disease susceptibility. Dissection of the molecular mechanisms involved in dysregulated apoptosis may reveal pathways which can be targeted for more effective therapeutic intervention. This review highlights the molecular events underlying programmed cell death and apoptotic cell uptake, and summarizes recent studies that link impaired apoptotic death to autoimmunity.
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Affiliation(s)
- E Maniati
- Molecular Genetics and Rheumatology Section, Division of Medicine, Hammersmith Campus, Imperial College London, UK
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29
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Macrophage scavenger receptors and host-derived ligands. Methods 2008; 43:207-17. [PMID: 17920517 DOI: 10.1016/j.ymeth.2007.06.004] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Accepted: 06/25/2007] [Indexed: 02/07/2023] Open
Abstract
The scavenger receptors are a large family of molecules that are structurally diverse and have been implicated in a range of functions. They are expressed by myeloid cells, selected endothelial cells and some epithelial cells and recognise many different ligands, including microbial pathogens as well as endogenous and modified host-derived molecules. This review will focus on the eight classes of scavenger receptors (class A-H) in terms of their structure, expression and recognition of host-derived ligands. Scavenger receptors have been implicated in a range of physiological and pathological processes, such as atherosclerosis and Alzheimer's disease, and function in adhesion and tissue maintenance. More recently, some of the scavenger receptors have been shown to mediate binding and endocytosis of chaperone proteins, such as the heat shock proteins, thereby playing an important role in antigen cross-presentation.
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30
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Wang XY, Facciponte J, Chen X, Subjeck JR, Repasky EA. Scavenger receptor-A negatively regulates antitumor immunity. Cancer Res 2007; 67:4996-5002. [PMID: 17510431 DOI: 10.1158/0008-5472.can-06-3138] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The scavenger receptor-A (SR-A), originally recognized by its ability to internalize modified lipoproteins, has largely been studied in relation to atherosclerosis as well as innate immunity against pathogen infection. SR-A was recently shown to be a receptor on antigen-presenting cell for heat shock protein (HSP) and was implicated in the cross-presentation of HSP-chaperoned antigens. Here, we show that SR-A is not required for antitumor immunity generated by HSP-based (e.g., grp170) vaccine approaches in vivo. The lack of SR-A significantly enhances HSP- or lipopolysaccharide-mediated vaccine activities against poorly immunogenic tumors, indicating that SR-A is able to attenuate immunostimulatory effects of adjuvants or "danger" molecules. The improved antitumor response in SR-A knockout mice is correlated with an increased antigen-specific T-cell response. Moreover, SR-A-deficient dendritic cells are more responsive to inflammatory stimuli and display a more effective antigen-presenting capability compared with wild-type cells. This is the first report illustrating that SR-A negatively regulates antigen-specific antitumor immunity, which has important clinical implications in vaccine design for cancer immunotherapy.
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Affiliation(s)
- Xiang-Yang Wang
- Department of Cellular Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
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31
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Seitz HM, Camenisch TD, Lemke G, Earp HS, Matsushima GK. Macrophages and dendritic cells use different Axl/Mertk/Tyro3 receptors in clearance of apoptotic cells. THE JOURNAL OF IMMUNOLOGY 2007; 178:5635-42. [PMID: 17442946 DOI: 10.4049/jimmunol.178.9.5635] [Citation(s) in RCA: 293] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The clearance of apoptotic cells is important for regulating tissue homeostasis, inflammation, and autoimmune responses. The absence of receptor tyrosine kinases (Axl, Mertk, and Tyro3) results in widespread accumulation of apoptotic cells and autoantibody production in mice. In this report, we examine the function of the three family members in apoptotic cell clearance by different phagocytic cell types. Mertk elimination nearly abolished macrophage apoptotic cell phagocytosis; elimination of Axl, Tyro3, or both, reduced macrophage phagocytosis by approximately half, indicating that these also play a role. In contrast, apoptotic cell clearance in splenic and bone marrow-derived dendritic cells (DCs) is prolonged compared with macrophages and relied primarily on Axl and Tyro3. The slower ingestion may be due to lower DC expression of Axl and Tyro3 or absence of GAS6 expression, a known ligand for this receptor family. In vivo, phagocytosis of apoptotic material by retinal epithelial cells required Mertk. Unlike macrophages, there did not appear to be any role for Axl or Tyro3 in retinal homeostasis. Likewise, clearance of apoptotic thymocytes in vivo was dramatically reduced in mertk(kd) mice, but was normal in axl/tyro3(-/-) mice. Thus, cell and organ type specificity is clearly delineated, with DCs relying on Axl and Tyro3, retina and thymus requiring Mertk, and macrophages exhibiting an interaction that involves all three family members. Surprisingly, in macrophages, tyrosine phosphorylation of Mertk in response to apoptotic cells is markedly diminished from axl/tyro3(-/-) mice, suggesting that the interactions of these receptors by heterodimerization may be important in some cells.
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Affiliation(s)
- Heather M Seitz
- Department of Microbiology and Immunology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
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32
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Blanco P, Pellegrin JL, Moreau JF, Viallard JF. Physiopathologie du lupus érythémateux systémique. Presse Med 2007; 36:825-34. [PMID: 17449371 DOI: 10.1016/j.lpm.2006.11.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Indexed: 01/08/2023] Open
Abstract
Innate immunity is directly implicated in the pathophysiology of lupus through the dendritic cell system and the activation by immune complexes of some toll-like receptors (TLR). Interferon-alpha plays a key role in the pathophysiology of lupus and represents a promising target for immune therapy. Dendritic cells are activated and able to capture large quantities of nuclear antigen-containing bodies to stimulate specific adaptive immune response.
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Affiliation(s)
- Patrick Blanco
- Clinique de médecine interne, Hôpital Haut-Lévêque, Pessac, France.
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33
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Lucas M, Stuart LM, Zhang A, Hodivala-Dilke K, Febbraio M, Silverstein R, Savill J, Lacy-Hulbert A. Requirements for apoptotic cell contact in regulation of macrophage responses. THE JOURNAL OF IMMUNOLOGY 2006; 177:4047-54. [PMID: 16951368 DOI: 10.4049/jimmunol.177.6.4047] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An important consequence of macrophage engulfment of apoptotic cells is suppression of inflammatory responses, which was first defined by assay of TNF-alpha release stimulated by LPS. These effects are apparently mediated in part by paracrine effects of TGF-beta released by the subset of stimulated macrophages that ingest apoptotic cells, which suppresses neighboring cells. However, the apoptotic cell-derived signal that stimulates TGF-beta release, and the nature of any additional signals required for the anti-inflammatory response remain poorly defined. In this study, we investigate the requirements for apoptotic cell engagement of macrophage surface receptors in these responses. We show that the apoptotic cell receptors CD36 and alphavbeta3 contribute to apoptotic cell phagocytosis by mouse macrophages, but are not essential for anti-inflammatory responses, suggesting that the mechanisms of response and phagocytosis are separate. In further defining requirements for response, we confirm the importance of TGF-beta in suppression by apoptotic cells, and identify an additional level of control of these effects. We show that LPS-stimulated mouse macrophage TNF-alpha release is only suppressed if macrophages have first contacted apoptotic cells, and hence, bystander macrophages are refractory to TGF-beta released by phagocytosing macrophages. We conclude that the profound suppression of LPS-driven TNF-alpha release by macrophage populations requires hitherto obscure contact-dependent licensing of macrophage responsiveness to TGF-beta by apoptotic cells.
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Affiliation(s)
- Mark Lucas
- Medical Research Council/University of Edinburgh Centre for Inflammation Research, Queen's Medical Research Institute, Edinburgh, United Kingdom
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34
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Abstract
Apoptosis is a highly regulated process of cell deletion and plays a fundamental role in the maintenance of tissue homeostasis in the adult organism. Numerous studies in recent years have revealed that apoptosis is a constitutive suicide programme expressed in most, if not all cells, and can be triggered by a variety of extrinsic and intrinsic signals. Many human diseases can be attributed directly or indirectly to a derangement of apoptosis, resulting in either cell accumulation, in which cell eradication or cell turnover is impaired, or cell loss, in which the apoptotic programme is inadvertently triggered. In addition, defective macrophage engulfment and degradation of cell corpses may also contribute to a dysregulation of tissue homeostasis. An increased understanding of the signalling pathways that govern the execution of apoptosis and the subsequent clearance of dying cells may thus yield novel targets for therapeutic intervention in a wide range of human maladies.
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Affiliation(s)
- B Fadeel
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
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35
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Yuita H, Tsuiji M, Tajika Y, Matsumoto Y, Hirano K, Suzuki N, Irimura T. Retardation of removal of radiation-induced apoptotic cells in developing neural tubes in macrophage galactose-type C-type lectin-1-deficient mouse embryos. Glycobiology 2005; 15:1368-75. [PMID: 16096344 DOI: 10.1093/glycob/cwj028] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
MGL1/CD301a is a C-type lectin that recognizes galactose and N-acetylgalactosamine as monosaccharides and is expressed on limited populations of macrophages and dendritic cells at least in adult mice. In this study, pregnant mice with Mgl1+/- genotype were mated with Mgl1+/- or Mgl1-/- genotype males, and the embryos were used to assess a hypothesis that this molecule plays an important role in the clearance of apoptotic cells. After X-ray irradiation at 1 Gy of developing embryos at 10.5 days post coitus (d.p.c.), the number of Mgl1-/- pups was significantly reduced as compared with Mgl1+/+ pups. Distributions of MGL1-positive cells, MGL2-positive cells, and apoptotic cells were histologically examined in irradiated Mgl1+/+ embryos. MGL1-positive cells were detected in the neural tube in which many cells undergo apoptosis, whereas MGL2-positive cells were not observed. Biotinylated recombinant MGL1 bound a significant portion of the apoptotic cells. When Mgl1+/+ and Mgl1-/- embryos were examined for the presence of apoptotic cells, similar numbers of apoptotic cells gave rise, but the clearance of these cells was slower in Mgl1-/- embryos than in Mgl1+/+ embryos. These results strongly suggest that MGL1/CD301a is involved in the clearance of apoptotic cells. This process should be essential in the repair and normal development of X-ray-irradiated embryos.
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Affiliation(s)
- Hiroshi Yuita
- Department of Radiation Oncology, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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36
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Palaniyar N, Clark H, Nadesalingam J, Shih MJ, Hawgood S, Reid KBM. Innate immune collectin surfactant protein D enhances the clearance of DNA by macrophages and minimizes anti-DNA antibody generation. THE JOURNAL OF IMMUNOLOGY 2005; 174:7352-8. [PMID: 15905582 DOI: 10.4049/jimmunol.174.11.7352] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dying microbes and necrotic cells release highly viscous DNA that induces inflammation and septic shock, and apoptotic cells display DNA, a potential autoantigen, on their surfaces. However, innate immune proteins that mediate the clearance of free DNA and surface DNA-containing cells are not clearly established. Pulmonary surfactant proteins (SP-) A and D are innate immune pattern recognition collectins that contain fibrillar collagen-like regions and globular carbohydrate recognition domains (CRDs). We have recently shown that collectins SP-A, SP-D, and mannose binding lectin recognize DNA and RNA via their collagen-like regions and CRDs. Here we show that SP-D enhances the uptake of Cy3-labeled fragments of DNA and DNA-coated beads by U937 human monocytic cells, in vitro. Analysis of DNA uptake by freshly isolated mouse alveolar macrophages shows that SP-D, but not SP-A, deficiency results in reduced clearance of DNA, ex vivo. Analysis of bronchoalveolar lavage fluid shows that SP-D- but not SP-A-deficient mice are defective in clearing free DNA from the lung. Additionally, both SP-A- and SP-D-deficient mice accumulate anti-DNA Abs in sera in an age-dependent manner. Thus, we conclude that collectins such as SP-A and SP-D reduce the generation of anti-DNA autoantibody, which may be explained in part by the defective clearance of DNA from the lungs in the absence of these proteins. Our findings establish two new roles for these innate immune proteins and that SP-D enhances efficient pinocytosis and phagocytosis of DNA by macrophages and minimizes anti-DNA Ab generation.
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Affiliation(s)
- Nades Palaniyar
- Medical Research Council Immunochemistry Unit, Department of Biochemistry, University of Oxford, UK.
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37
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Komohara Y, Terasaki Y, Kaikita K, Suzuki H, Kodama T, Takeya M. Clearance of apoptotic cells is not impaired in mouse embryos deficient in class A scavenger receptor types I and II (CD204). Dev Dyn 2005; 232:67-74. [PMID: 15580571 DOI: 10.1002/dvdy.20206] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Elimination of apoptotic cells is an important mechanism to maintain proper embryonal morphogenesis. The class A scavenger receptor type I, II (CD204), one of the major receptors expressed on macrophages, is a receptor actively involved in recognition and ingestion of apoptotic cells. To clarify the role of CD204 in embryonic morphogenesis, we performed immunohistochemical and immunoelectron microscopic studies using CD204-deficient mouse embryos. In control mice, almost all macrophages expressed CD204 from embryonic day 9.5 (E9.5). Phagocytes engulfing dead cells in the E13.5 interdigit region showed strong expression of CD204, indicating that CD204 was actively involved in apoptotic cell clearance. However, CD204 is not essential for the embryonic clearance of apoptotic cells, because CD204-deficient embryos developed normally without any retardation in footplate remodeling. Up-regulation of CD36 in CD204-deficient fetal macrophages suggested that CD36 substitutes for CD204 function. We also found that mesenchymal cells frequently engulfed apoptotic cells especially in early embryonal stages. These data suggest that CD204 is partially but not essentially involved in apoptotic cell clearance in embryogenesis. During early embryonal development, mesenchymal cells, rather than macrophages, play a major role in apoptotic cell clearance.
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MESH Headings
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/genetics
- Antigens, CD/physiology
- Apoptosis
- CD36 Antigens/biosynthesis
- CD36 Antigens/physiology
- Cell Differentiation
- Embryonic Development
- Immunohistochemistry
- In Situ Nick-End Labeling
- Macrophages/cytology
- Macrophages/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Inbred ICR
- Mice, Knockout
- Microscopy, Electron, Transmission
- Microscopy, Immunoelectron
- Phagocytosis
- Receptors, Immunologic/biosynthesis
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Scavenger Receptors, Class A
- Time Factors
- Up-Regulation
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Affiliation(s)
- Yoshihiro Komohara
- Department of Cell Pathology, Graduate School of Medical Science, Kumamoto University, Kumamoto, Japan
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38
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Beamer CA, Holian A. Scavenger receptor class A type I/II (CD204) null mice fail to develop fibrosis following silica exposure. Am J Physiol Lung Cell Mol Physiol 2005; 289:L186-95. [PMID: 15849212 DOI: 10.1152/ajplung.00474.2004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alveolar macrophages express the class A scavenger receptor (CD204) (Babaev VR, Gleaves LA, Carter KJ, Suzuki H, Kodama T, Fazio S, and Linton MF. Arterioscler Thromb Vasc Biol 20: 2593-2599, 2000); yet its role in vivo in lung defense against environmental particles has not been clearly defined. In the current study, CD204 null mice (129Sv background) were used to investigate the link between CD204 and downstream events of inflammation and fibrosis following silica exposure in vivo. CD204-/- macrophages were shown to recognize and uptake silica in vitro, although this response was attenuated compared with 129Sv wild-type mice. The production of tumor necrosis factor-alpha in lavage fluid was significantly enhanced in CD204 null mice compared with wild-type mice following silica exposure. Moreover, after exposure to environmental particles, CD204-/- macrophages exhibited improved cell viability in a dose-dependent manner compared with wild-type macrophages. Finally, histopathology from a murine model of chronic silicosis in 129Sv wild-type mice displayed typical focal lesions, interstitial thickening with increased connective tissue matrix, and cellular infiltrate into air space. In contrast, CD204-/- mice exhibited little to no deposition of collagen, yet they demonstrated enhanced accumulation of inflammatory cells largely composed of neutrophils. Our findings point to an important role of CD204 in mounting an efficient and appropriately regulated immune response against inhaled particles. Furthermore, these results indicate that the functions of CD204 are critical to the development of fibrosis and the resolution of inflammation.
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Affiliation(s)
- Celine A Beamer
- Univ. of Montana, Center for Environmental Health Sciences, Dept. of Biomedical and Pharmaceutical Sciences, School of Pharmacy and Allied Health Sciences, Skaggs Bldg., Rm. 155, Missoula, MT 59812-1552, USA.
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39
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Devitt A, Parker KG, Ogden CA, Oldreive C, Clay MF, Melville LA, Bellamy CO, Lacy-Hulbert A, Gangloff SC, Goyert SM, Gregory CD. Persistence of apoptotic cells without autoimmune disease or inflammation in CD14-/- mice. ACTA ACUST UNITED AC 2005; 167:1161-70. [PMID: 15611337 PMCID: PMC2172617 DOI: 10.1083/jcb.200410057] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Interaction of macrophages with apoptotic cells involves multiple steps including recognition, tethering, phagocytosis, and anti-inflammatory macrophage responses. Defective apoptotic cell clearance is associated with pathogenesis of autoimmune disease. CD14 is a surface receptor that functions in vitro in the removal of apoptotic cells by human and murine macrophages, but its mechanism of action has not been defined. Here, we demonstrate that CD14 functions as a macrophage tethering receptor for apoptotic cells. Significantly, CD14(-/-) macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process. However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14(-/-) macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells. We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.
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Affiliation(s)
- Andrew Devitt
- Medical Research Council Centre for Inflammation Research, University of Edinburgh, Edinburgh, Scotland, UK
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40
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Gregory CD, Devitt A. The macrophage and the apoptotic cell: an innate immune interaction viewed simplistically? Immunology 2004; 113:1-14. [PMID: 15312130 PMCID: PMC1782541 DOI: 10.1111/j.1365-2567.2004.01959.x] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Macrophages play important roles in the clearance of dying and dead cells. Typically, and perhaps simplistically, they are viewed as the professional phagocytes of apoptotic cells. Clearance by macrophages of cells undergoing apoptosis is a non-phlogistic phenomenon which is often associated with actively anti-inflammatory phagocyte responses. By contrast, macrophage responses to necrotic cells, including secondarily necrotic cells derived from uncleared apoptotic cells, are perceived as proinflammatory. Indeed, persistence of apoptotic cells as a result of defective apoptotic-cell clearance has been found to be associated with the pathogenesis of autoimmune disease. Here we review the mechanisms by which macrophages interact with, and respond to, apoptotic cells. We suggest that macrophages are especially important in clearing cells at sites of histologically visible, high-rate apoptosis and that, otherwise, apoptotic cells are removed largely by non-macrophage neighbours. We challenge the view that necrotic cells, including persistent apoptotic cells are, of necessity, proinflammatory and immunostimulatory and suggest that, under appropriate circumstances, persistent apoptotic cells can provide a prolonged anti-inflammatory stimulus.
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Affiliation(s)
- Christopher D Gregory
- University of Edinburgh MRC Centre for Inflammation Research, College of Medicine and Veterinary Medicine, UK.
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41
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Abstract
The immunogenic potential of nuclear antigens exposed during apoptosis, together with considerable animal data suggesting that impaired apoptotic clearance can result in systemic lupus erythematosus (SLE)-like autoimmunity, has lent support to the idea that self-immunization with apoptotic debris is a key driving mechanism in lupus. The multiple roles of complement receptors, diverse scavenger receptors, and intermediate proteins that bind to and opsonize apoptotic cells indicate a complex web of interactions leading to the clearance of apoptotic debris. Disturbances in parts of this system may lead to lupus or to lupus exacerbations. Therapy directed toward augmenting clearance and decreasing concomitant inflammation may lead to improved management of SLE.
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Affiliation(s)
- Philip L Cohen
- University of Pennsylvania School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Suite 757, Philadelphia, PA 19104, USA.
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42
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Dogusan Z, Montecino-Rodriguez E, Dorshkind K. Macrophages and stromal cells phagocytose apoptotic bone marrow-derived B lineage cells. THE JOURNAL OF IMMUNOLOGY 2004; 172:4717-23. [PMID: 15067047 DOI: 10.4049/jimmunol.172.8.4717] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It has been hypothesized that B cell precursors that undergo programmed cell death due to nonproductive Ig gene rearrangements are cleared from the bone marrow by macrophages. However, a role for macrophages in this process is supported only by micrographs showing their association with apoptotic-appearing, B lineage cells. Functional data demonstrating phagocytosis of apoptotic, bone marrow lymphocytes by macrophages have not been presented, nor have receptors potentially involved in that process been identified. The data in this report demonstrate that macrophages isolated from murine bone marrow efficiently phagocytose apoptotic murine B lineage cells using multiple receptors that include CD14, integrins, class A scavenger receptor, and CD31 (PECAM-1). In addition, the results further reveal a new role for the hemopoietic microenvironment in B cell development in view of data demonstrating that murine bone marrow stromal cells are also capable of clearing apoptotic cells via an integrin-dependent mechanism.
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Affiliation(s)
- Zeynep Dogusan
- Department of Pathology and Laboratory Medicine and the Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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43
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Hanayama R, Tanaka M, Miyasaka K, Aozasa K, Koike M, Uchiyama Y, Nagata S. Autoimmune disease and impaired uptake of apoptotic cells in MFG-E8-deficient mice. Science 2004; 304:1147-50. [PMID: 15155946 DOI: 10.1126/science.1094359] [Citation(s) in RCA: 740] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Apoptotic cells expose phosphatidylserine and are swiftly engulfed by macrophages. Milk fat globule epidermal growth factor (EGF) factor 8 (MFG-E8) is a protein that binds to apoptotic cells by recognizing phosphatidylserine and that enhances the engulfment of apoptotic cells by macrophages. We report that tingible body macrophages in the germinal centers of the spleen and lymph nodes strongly express MFG-E8. Many apoptotic lymphocytes were found on the MFG-E8-/- tingible body macrophages, but they were not efficiently engulfed. The MFG-E8-/- mice developed splenomegaly, with the formation of numerous germinal centers, and suffered from glomerulonephritis as a result of autoantibody production. These data demonstrate that MFG-E8 has a critical role in removing apoptotic B cells in the germinal centers and that its failure can lead to autoimmune diseases.
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Affiliation(s)
- Rikinari Hanayama
- Department of Genetics, Osaka University Medical School, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
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44
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Cvetanovic M, Ucker DS. Innate immune discrimination of apoptotic cells: repression of proinflammatory macrophage transcription is coupled directly to specific recognition. THE JOURNAL OF IMMUNOLOGY 2004; 172:880-9. [PMID: 14707059 DOI: 10.4049/jimmunol.172.2.880] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Physiological cell death is a process the purpose of which is the elimination of functionally inappropriate cells in a manner that does not elicit an inflammatory response. We have shown previously that the ability of apoptotic corpses to be recognized by macrophages and to modulate the proinflammatory responses of those cells represents paradoxically a gain-of-function acquired during the physiological cell death process. Cells that die pathologically (that is, necrotic vs apoptotic corpses) also are recognized by macrophages but do not down-regulate macrophage inflammatory responses; the recognition of these two classes of native dying cells occurs via distinct and noncompeting mechanisms. We have examined the apoptotic modulation of proinflammatory cytokine gene transcription in macrophages (by real-time RT-PCR analysis) and the corresponding modulation of transcriptional activators (by transcriptional reporter analyses). Our data demonstrate that apoptotic cells target the proinflammatory transcriptional machinery of macrophages with which they interact, without apparent effect on proximal steps of Toll-like receptor signaling. The modulatory activity of the corpse is manifest as an immediate-early inhibition of proinflammatory cytokine gene transcription, and is exerted directly upon binding to the macrophage, independent of subsequent engulfment and soluble factor involvement. Recognition and inflammatory modulation represent key elements of an innate immune response that discriminates live from effete cells, and without regard to self.
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Affiliation(s)
- Marija Cvetanovic
- Department of Microbiology and Immunology, University of Illinois College of Medicine, 835 South Walcott, Chicago, IL 60612, USA
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45
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Norsworthy PJ, Fossati-Jimack L, Cortes-Hernandez J, Taylor PR, Bygrave AE, Thompson RD, Nourshargh S, Walport MJ, Botto M. Murine CD93 (C1qRp) Contributes to the Removal of Apoptotic Cells In Vivo but Is Not Required for C1q-Mediated Enhancement of Phagocytosis. THE JOURNAL OF IMMUNOLOGY 2004; 172:3406-14. [PMID: 15004139 DOI: 10.4049/jimmunol.172.6.3406] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Human CD93 (known as C1qRp) has been shown to be a phagocytic receptor involved in the in vitro C1q-dependent enhancement of phagocytosis. However, binding of CD93 to C1q and its function remain controversial. In this study, we have generated CD93-deficient mice (CD93(-/-)) to investigate its biological role(s). The CD93(-/-) mice were viable and showed no gross abnormalities in their development. Thioglycolate-elicited peritoneal macrophages deficient in CD93 showed a similar enhancement in complement- and FcgammaR-dependent uptake of RBC to the wild-type macrophages when plated on C1q-coated surfaces suggesting that the lack of this receptor had no effect on these C1q-mediated events. There was no impairment in either complement- or FcgammaR-dependent phagocytic assays in vivo. By contrast, the CD93(-/-) mice had a significant phagocytic defect in the clearance of apoptotic cells in vivo (human Jurkat T cells and murine thymocytes: p=0.0006 and p=0.0079, respectively) compared with strain-matched controls. However, in vitro, the CD93(-/-) macrophages showed similar engulfment of apoptotic cells to wild-type macrophages. Furthermore, no supporting evidence for a role of CD93 as an adhesion molecule was found using intravital microscopy or analyzing peritoneal cell recruitment in response to three different inflammatory stimuli (thioglycolate, zymosan A, and IL-1beta). Thus, our findings indicate that murine CD93 is expressed on the peritoneal macrophage, especially on thioglycolate-elicited cells, but does not appear to play a key role in C1q-mediated enhancement of phagocytosis or in the intercellular adhesion events tested. However, our results suggest that it may contribute to the in vivo clearance of dying cells.
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MESH Headings
- Adjuvants, Immunologic/deficiency
- Adjuvants, Immunologic/genetics
- Adjuvants, Immunologic/physiology
- Animals
- Apoptosis/genetics
- Apoptosis/immunology
- Carrier Proteins
- Cell Movement/genetics
- Cell Movement/immunology
- Cells, Cultured
- Complement C1q/physiology
- Complement C3/metabolism
- Erythrocytes/immunology
- Erythrocytes/metabolism
- Gene Targeting
- Humans
- Hyaluronan Receptors
- Immunoglobulin G/blood
- Immunoglobulin G/metabolism
- Jurkat Cells
- Macrophage Activation/drug effects
- Macrophage Activation/genetics
- Macrophage Activation/immunology
- Macrophages, Peritoneal/drug effects
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/metabolism
- Membrane Glycoproteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mitochondrial Proteins
- Opsonin Proteins/blood
- Opsonin Proteins/metabolism
- Phagocytosis/genetics
- Phagocytosis/immunology
- Receptors, Complement/biosynthesis
- Receptors, Complement/deficiency
- Receptors, Complement/genetics
- Receptors, Complement/physiology
- Receptors, IgG/blood
- Receptors, IgG/deficiency
- Receptors, IgG/genetics
- Receptors, IgG/physiology
- Sequence Deletion/genetics
- Sequence Deletion/immunology
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- Thioglycolates/pharmacology
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Affiliation(s)
- Peter J Norsworthy
- Rheumatology Section, Division of Medicine, Faculty of Medicine, Imperial College, Hammersmith Campus, London, UK
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46
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Moreira MEC, Barcinski MA. Apoptotic cell and phagocyte interplay: recognition and consequences in different cell systems. AN ACAD BRAS CIENC 2004; 76:93-115. [PMID: 15048198 DOI: 10.1590/s0001-37652004000100009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Cell death by apoptosis is characterized by specific biochemical changes, including the exposure of multiple ligands, expected to tag the dying cell for prompt recognition by phagocytes. In non-pathological conditions, an efficient clearance is assured by the redundant interaction between apoptotic cell ligands and multiple receptor molecules present on the engulfing cell surface. This review concentrates on the molecular interactions operating in mammalian and non-mammalian systems for apoptotic cell recognition, as well as on the consequences of their signaling. Furthermore, some cellular models where the exposure of the phosphatidylserine (PS) phospholipid, a classical hallmark of the apoptotic phenotype, is not followed by cell death will be discussed.
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Affiliation(s)
- Maria Elisabete C Moreira
- Divisão de Medicina Experimental, Instituto Nacional de Câncer, Rio de Janeiro, RJ, 20231-050, Brasil.
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47
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Stolzing A, Grune T. Neuronal apoptotic bodies: phagocytosis and degradation by primary microglial cells. FASEB J 2004; 18:743-5. [PMID: 14766802 DOI: 10.1096/fj.03-0374fje] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neuronal loss via apoptosis is a key element in numerous neurodegenerative diseases. To avoid accumulation of apoptotic material, the remains of apoptotic cells should be degraded. It was suggested that microglial cells are phagocytosing and degrading apoptotic material. There is only limited information available concerning the fate of the remains of apoptotic neurons. In this study, we investigated the ability of microglial cells to take up and degrade neuronal apoptotic material. We isolated primary microglial cells and used apoptotic bodies of apoptotic neuron-like PC12 cells as a substrate. The apoptotic material was taken up and degraded within the microglial cells. The uptake is clearly activation dependent. We were able to demonstrate that the CD36 scavenger receptor is involved in the uptake of the apoptotic material via competition studies, antibody blockage, and use of a CD36 mutant rat strain. Blockage of other uptake mechanisms was also able to inhibit the uptake to some extent. Furthermore, we were able to demonstrate the role of the microglial lysosomal and proteasomal pathways in the degradation of proteins originating from apoptotic bodies.
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Affiliation(s)
- Alexandra Stolzing
- Neuroscience Research Center, Medical Faculty (Charité), Humboldt University, Berlin, Germany
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48
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Maderna P, Godson C. Phagocytosis of apoptotic cells and the resolution of inflammation. Biochim Biophys Acta Mol Basis Dis 2004; 1639:141-51. [PMID: 14636945 DOI: 10.1016/j.bbadis.2003.09.004] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Clearance of apoptotic cells by phagocytic cells plays a significant role in the resolution of inflammation, protecting tissue from harmful exposure to the inflammatory and immunogenic contents of dying cells. Apoptosis induces cell surface changes that are important for recognition and engulfment of cells by phagocytes. These changes include alterations in surface sugars, externalization of phosphatidylserine and qualitative changes in the adhesion molecule ICAM-3. Several studies have contributed to clarify the role of the receptors on the surface of phagocytes that are involved in apoptotic cell clearance. The phagocytic removal of apoptotic cells does not elicit pro-inflammatory responses; in contrast, apoptotic cell engulfment appears to activate signals that suppress release of pro-inflammatory cytokines. Therefore, clearance of apoptotic leucocytes is implicated in the resolution of inflammation and mounting evidence suggests that defective clearance of apoptotic cells contributes to inflammatory and autoimmune diseases. Defining the ligands on apoptotic cells and the corresponding receptors on phagocytes with which they engage, is likely to lead to the development of novel anti-inflammatory pro-resolution drugs. In this article, we will review the recognition and signaling mechanisms involved in the phagocytosis of apoptotic cells as well as the role of endogenous compounds that play a relevant role in the modulation of inflammation. We will also discuss what is currently known about diseases that may reflect impaired phagocytosis and the consequences on inflammation and immune responses.
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Affiliation(s)
- Paola Maderna
- Centre for Molecular Inflammation and Vascular Research, Mater Misericordiae Hospital, Dublin, Ireland
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49
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Todt JC, Hu B, Curtis JL. The receptor tyrosine kinase MerTK activates phospholipase C gamma2 during recognition of apoptotic thymocytes by murine macrophages. J Leukoc Biol 2004; 75:705-13. [PMID: 14704368 PMCID: PMC2441598 DOI: 10.1189/jlb.0903439] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Apoptotic leukocytes must be cleared efficiently by macrophages (Mø). Apoptotic cell phagocytosis by Mø requires the receptor tyrosine kinase (RTK) MerTK (also known as c-Mer and Tyro12), the phosphatidylserine receptor (PS-R), and the classical protein kinase C (PKC) isoform betaII, which translocates to Mø membrane and cytoskeletal fractions in a PS-R-dependent manner. How these molecules cooperate to induce phagocytosis is unknown. As the phosphatidylinositol-specific phospholipase (PI-PLC) gamma2 is downstream of RTKs in some cell types and can activate classical PKCs, we hypothesized that MerTK signals via PLC gamma2. To test this hypothesis, we examined the interaction of MerTK and PLC gamma2 in resident, murine peritoneal (P)Mø and in the murine Mø cell line J774A.1 (J774) following exposure to apoptotic thymocytes. We found that as with PMø, J774 phagocytosis of apoptotic thymocytes was inhibited by antibody against MerTK. Western blotting and immunoprecipitation showed that exposure to apoptotic cells produced three time-dependent changes in PMø and J774: tyrosine phosphorylation of MerTK; association of PLC gamma2 with MerTK; and tyrosine phosphorylation of PLC gamma2. Cross-linking MerTK using antibody also induced phosphorylation of PLC gamma2 and its association with MerTK. A PI-PLC appears to be required for phagocytosis of apoptotic cells, as the PI-PLC inhibitor Et-18-OCH3 and the PLC inhibitor U73122, but not the inactive control U73343, blocked phagocytosis without impairing adhesion. On apoptotic cell adhesion to Mø, MerTK signals at least in part via PLC gamma2.
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Affiliation(s)
- Jill C. Todt
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
| | - Bin Hu
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
| | - Jeffrey L. Curtis
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
- Comprehensive Cancer Center, University of Michigan Health Care System, Ann Arbor, MI, USA
- Graduate Program in Immunology, University of Michigan Health Care System, Ann Arbor, MI, USA
- Pulmonary & Critical Care Medicine Section, Medical Service, Department of Veterans Affairs Care System, Ann Arbor, MI, USA
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50
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Abstract
Maintenance of membrane lipid asymmetry is a dynamic process that influences many events over the lifespan of the cell. With few exceptions, most cells restrict the bulk of the aminophospholipids to the inner membrane leaflet by means of specific transporters. Working in concert with each other, these proteins correct for sporadic incursions of the aminophospholipids to the outer membrane leaflet as a result of bilayer imbalances created by various cellular events. A shift in the relative contribution in each of these activities can result in sustained exposure of the aminophospholipids at the cell surface, which allows capture of the cells by phagocytes before the integrity of the plasma membrane is compromised. The absence of an efficient recognition and elimination mechanism can result in uncontrolled and persistent presentation of self-antigens to the immune system, with development of autoimmune syndromes. To prevent this, phagocytes have developed a diverse array of distinct and redundant receptor systems that drive the postphagocytic events along pathways that facilitate cross-talk between the homeostatic and the immune systems. In this work, we review the basis for the proposed mechanism(s) by which apoptotic ligands appear on the target cell surface and the phagocyte receptors that recognize these moieties.
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