Epigenetic regulation of macrophage polarization and function.
TL;DR: Emerging evidence suggests an important role for epigenetic mechanisms in modulating and transmitting signals during macrophage polarization and reprogramming and will enable development of gene-specific therapeutic approaches to enhance host defense while preserving tissue integrity and preventing chronic inflammatory diseases.
About: This article is published in Trends in Immunology.The article was published on 2013-05-01 and is currently open access. It has received 299 citations till now. The article focuses on the topics: Macrophage polarization & Tissue homeostasis.
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St. Jude Children's Research Hospital1, University of Edinburgh2, Singapore Immunology Network3, New York University4, University College London5, Heidelberg University6, University of Oxford7, Royal Melbourne Hospital8, Hospital for Special Surgery9, University of Milan10, Aix-Marseille University11, University of Maryland, College Park12, European Institute of Oncology13, Massachusetts Institute of Technology14, University of Bonn15, University of Maryland, Baltimore16, University of Eastern Piedmont17, University of Louisville18, Vrije Universiteit Brussel19, National Institutes of Health20
TL;DR: A set of standards encompassing three principles-the source of macrophages, definition of the activators, and a consensus collection of markers to describe macrophage activation are described with the goal of unifying experimental standards for diverse experimental scenarios.
4,287 citations
Cites background from "Epigenetic regulation of macrophage..."
...For example, deletion of transcription factor IRF4 or KLF6 fails to makeM(IL-4) macrophages, whereas PPARg and PPARv are required for the amplitude of the M(IL-4) state (Chawla, 2010; Date et al., 2014; Ivashkiv, 2013)....
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...…(1) removal of the stimulus, (2) enforcement of feedback and feed-forward signaling loops, including autocrine production of cytokines, and (3) epigenetic and/or developmental effects built into the life history of a macrophage (Ivashkiv, 2013; Lawrence and Natoli, 2011; Porta et al., 2009)....
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TL;DR: How cytokines and pathogen signals influence macrophages' functional phenotypes and the evidence for M1 and M2 functions is assessed and a paradigm initially based on the role of a restricted set of selected ligands in the immune response is revisited.
Abstract: Macrophages are endowed with a variety of receptors for lineage-determining growth factors, T helper (Th) cell cytokines, and B cell, host, and microbial products. In tissues, macrophages mature and are activated in a dynamic response to combinations of these stimuli to acquire specialized functional phenotypes. As for the lymphocyte system, a dichotomy has been proposed for macrophage activation: classic vs. alternative, also M1 and M2, respectively. In view of recent research about macrophage functions and the increasing number of immune-relevant ligands, a revision of the model is needed. Here, we assess how cytokines and pathogen signals influence their functional phenotypes and the evidence for M1 and M2 functions and revisit a paradigm initially based on the role of a restricted set of selected ligands in the immune response.
3,674 citations
Cites background from "Epigenetic regulation of macrophage..."
...Other mechanisms, such as microRNAs (miRNAs) [65-69], enhancer RNAs [70-72], and epigenetic enzymes, control the activation landscape [73-78]....
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TL;DR: The protective and pathogenic role of the macrophage subsets in normal and pathological pregnancy, anti‐microbial defense, anti-tumor immunity, metabolic disease and obesity, asthma and allergy, atherosclerosis, fibrosis, wound healing, and autoimmunity are discussed.
Abstract: Macrophages are heterogeneous and their phenotype and functions are regulated by the surrounding micro-environment. Macrophages commonly exist in two distinct subsets: 1) Classically activated or M1 macrophages, which are pro-inflammatory and polarized by lipopolysaccharide (LPS) either alone or in association with Th1 cytokines such as IFN-γ, GM-CSF, and produce pro-inflammatory cytokines such as interleukin-1β (IL-1β), IL-6, IL-12, IL-23, and TNF-α; and 2) Alternatively activated or M2 macrophages, which are anti-inflammatory and immunoregulatory and polarized by Th2 cytokines such as IL-4 and IL-13 and produce anti-inflammatory cytokines such as IL-10 and TGF-β. M1 and M2 macrophages have different functions and transcriptional profiles. They have unique abilities by destroying pathogens or repair the inflammation-associated injury. It is known that M1/M2 macrophage balance polarization governs the fate of an organ in inflammation or injury. When the infection or inflammation is severe enough to affect an organ, macrophages first exhibit the M1 phenotype to release TNF-α, IL-1β, IL-12, and IL-23 against the stimulus. But, if M1 phase continues, it can cause tissue damage. Therefore, M2 macrophages secrete high amounts of IL-10 and TGF-β to suppress the inflammation, contribute to tissue repair, remodeling, vasculogenesis, and retain homeostasis. In this review, we first discuss the basic biology of macrophages including origin, differentiation and activation, tissue distribution, plasticity and polarization, migration, antigen presentation capacity, cytokine and chemokine production, metabolism, and involvement of microRNAs in macrophage polarization and function. Secondly, we discuss the protective and pathogenic role of the macrophage subsets in normal and pathological pregnancy, anti-microbial defense, anti-tumor immunity, metabolic disease and obesity, asthma and allergy, atherosclerosis, fibrosis, wound healing, and autoimmunity.
2,176 citations
Cites background from "Epigenetic regulation of macrophage..."
...Interestingly, miR-155 has both pro- and antiapoptotic roles, whereas miR-21 and let-7e negatively regulate macrophage apoptosis (Ivashkiv, 2013; Porta et al., 2015; Takeuch & Akira, 2011; Van den Bossche, Neele, Hoeksema, & de Winther, 2014; Wei & Schober, 2016)....
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TL;DR: Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.
Abstract: Macrophages are a diverse set of cells present in all body compartments. This diversity is imprinted by their ontogenetic origin (embryonal versus adult bone marrow-derived cells); the organ context; by their activation or deactivation by various signals in the contexts of microbial invasion, tissue damage, and metabolic derangement; and by polarization of adaptive T cell responses. Classic adaptive responses of macrophages include tolerance, priming, and a wide spectrum of activation states, including M1, M2, or M2-like. Moreover, macrophages can retain long-term imprinting of microbial encounters (trained innate immunity). Single-cell analysis of mononuclear phagocytes in health and disease has added a new dimension to our understanding of the diversity of macrophage differentiation and activation. Epigenetic landscapes, transcription factors, and microRNA networks underlie the adaptability of macrophages to different environmental cues. Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.
681 citations
TL;DR: The mechanism of macrophage polarization from the tumor microenvironment, nanocarriers, nuclear receptor PPARγ, phagocytosis, NF-κB signaling pathways, and other pathways is analyzed.
607 citations
References
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TL;DR: The Encyclopedia of DNA Elements project provides new insights into the organization and regulation of the authors' genes and genome, and is an expansive resource of functional annotations for biomedical research.
Abstract: The human genome encodes the blueprint of life, but the function of the vast majority of its nearly three billion bases is unknown. The Encyclopedia of DNA Elements (ENCODE) project has systematically mapped regions of transcription, transcription factor association, chromatin structure and histone modification. These data enabled us to assign biochemical functions for 80% of the genome, in particular outside of the well-studied protein-coding regions. Many discovered candidate regulatory elements are physically associated with one another and with expressed genes, providing new insights into the mechanisms of gene regulation. The newly identified elements also show a statistical correspondence to sequence variants linked to human disease, and can thereby guide interpretation of this variation. Overall, the project provides new insights into the organization and regulation of our genes and genome, and is an expansive resource of functional annotations for biomedical research.
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TL;DR: It is demonstrated in macrophages and B cells that collaborative interactions of the common factor PU.1 with small sets of macrophage- or B cell lineage-determining transcription factors establish cell-specific binding sites that are associated with the majority of promoter-distal H3K4me1-marked genomic regions.
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TL;DR: This Review suggests a new grouping of macrophages based on three different homeostatic activities — host defence, wound healing and immune regulation, and proposes that similarly to primary colours, these three basic macrophage populations can blend into various other 'shades' of activation.
Abstract: Macrophages display remarkable plasticity and can change their physiology in response to environmental cues. These changes can give rise to different populations of cells with distinct functions. In this Review we suggest a new grouping of macrophage populations based on three different homeostatic activities - host defence, wound healing and immune regulation. We propose that similarly to primary colours, these three basic macrophage populations can blend into various other 'shades' of activation. We characterize each population and provide examples of macrophages from specific disease states that have the characteristics of one or more of these populations.
7,384 citations
TL;DR: The identification of mechanisms and molecules associated with macrophage plasticity and polarized activation provides a basis for Macrophage-centered diagnostic and therapeutic strategies.
Abstract: Diversity and plasticity are hallmarks of cells of the monocyte-macrophage lineage. In response to IFNs, Toll-like receptor engagement, or IL-4/IL-13 signaling, macrophages undergo M1 (classical) or M2 (alternative) activation, which represent extremes of a continuum in a universe of activation states. Progress has now been made in defining the signaling pathways, transcriptional networks, and epigenetic mechanisms underlying M1-M2 or M2-like polarized activation. Functional skewing of mononuclear phagocytes occurs in vivo under physiological conditions (e.g., ontogenesis and pregnancy) and in pathology (allergic and chronic inflammation, tissue repair, infection, and cancer). However, in selected preclinical and clinical conditions, coexistence of cells in different activation states and unique or mixed phenotypes have been observed, a reflection of dynamic changes and complex tissue-derived signals. The identification of mechanisms and molecules associated with macrophage plasticity and polarized activation provides a basis for macrophage-centered diagnostic and therapeutic strategies.
4,721 citations
TL;DR: The four stages of orderly inflammation mediated by macrophages are discussed: recruitment to tissues; differentiation and activation in situ; conversion to suppressive cells; and restoration of tissue homeostasis.
Abstract: Macrophages are strategically located throughout the body tissues, where they ingest and process foreign materials, dead cells and debris and recruit additional macrophages in response to inflammatory signals They are highly heterogeneous cells that can rapidly change their function in response to local microenvironmental signals In this Review, we discuss the four stages of orderly inflammation mediated by macrophages: recruitment to tissues; differentiation and activation in situ; conversion to suppressive cells; and restoration of tissue homeostasis We also discuss the protective and pathogenic functions of the various macrophage subsets in antimicrobial defence, antitumour immune responses, metabolism and obesity, allergy and asthma, tumorigenesis, autoimmunity, atherosclerosis, fibrosis and wound healing Finally, we briefly discuss the characterization of macrophage heterogeneity in humans
4,182 citations