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CNS Neuroscience & Therapeutics Sep 2022Phagocytosis is the cellular digestion of extracellular particles, such as pathogens and dying cells, and is a key element in the evolution of central nervous system... (Review)
Review
AIMS
Phagocytosis is the cellular digestion of extracellular particles, such as pathogens and dying cells, and is a key element in the evolution of central nervous system (CNS) disorders. Microglia and macrophages are the professional phagocytes of the CNS. By clearing toxic cellular debris and reshaping the extracellular matrix, microglia/macrophages help pilot the brain repair and functional recovery process. However, CNS resident and invading immune cells can also magnify tissue damage by igniting runaway inflammation and phagocytosing stressed-but viable-neurons.
DISCUSSION
Microglia/macrophages help mediate intercellular communication and react quickly to the "find-me" signals expressed by dead/dying neurons. The activated microglia/macrophages then migrate to the injury site to initiate the phagocytic process upon encountering "eat-me" signals on the surfaces of endangered cells. Thus, healthy cells attempt to avoid inappropriate engulfment by expressing "do not-eat-me" signals. Microglia/macrophages also have the capacity to phagocytose immune cells that invade the injured brain (e.g., neutrophils) and to regulate their pro-inflammatory properties. During brain recovery, microglia/macrophages engulf myelin debris, initiate synaptogenesis and neurogenesis, and sculpt a favorable extracellular matrix to support network rewiring, among other favorable roles. Here, we review the multilayered nature of phagocytotic microglia/macrophages, including the molecular and cellular mechanisms that govern microglia/macrophage-induced phagocytosis in acute brain injury, and discuss strategies that tap into the therapeutic potential of this engulfment process.
CONCLUSION
Identification of biological targets that can temper neuroinflammation after brain injury without hindering the essential phagocytic functions of microglia/macrophages will expedite better medical management of the stroke recovery stage.
Topics: Brain; Brain Injuries; Central Nervous System Diseases; Humans; Macrophages; Microglia; Phagocytes; Phagocytosis
PubMed: 35751629
DOI: 10.1111/cns.13899 -
Immunological Reviews Oct 2023Phagocytosis is a fundamental immunobiological process responsible for the removal of harmful particulates. While the number of phagocytic events achieved by a single... (Review)
Review
Phagocytosis is a fundamental immunobiological process responsible for the removal of harmful particulates. While the number of phagocytic events achieved by a single phagocyte can be remarkable, exceeding hundreds per day, the same phagocytic cells are relatively long-lived. It should therefore be obvious that phagocytic meals must be resolved in order to maintain the responsiveness of the phagocyte and to avoid storage defects. In this article, we discuss the mechanisms involved in the resolution process, including solute transport pathways and membrane traffic. We describe how products liberated in phagolysosomes support phagocyte metabolism and the immune response. We also speculate on mechanisms involved in the redistribution of phagosomal metabolites back to circulation. Finally, we highlight the pathologies owed to impaired phagosome resolution, which range from storage disorders to neurodegenerative diseases.
Topics: Humans; Phagosomes; Phagocytosis; Phagocytes
PubMed: 37551912
DOI: 10.1111/imr.13260 -
Nature Communications Nov 2022Perivascular macrophages (pvMs) are associated with cerebral vasculature and mediate brain drainage and immune regulation. Here, using reporter mouse models, whole brain...
Perivascular macrophages (pvMs) are associated with cerebral vasculature and mediate brain drainage and immune regulation. Here, using reporter mouse models, whole brain and section immunofluorescence, flow cytometry, and single cell RNA sequencing, besides the Lyve1F4/80CD206CX3CR1 pvMs, we identify a CX3CR1 pvM population that shares phagocytic functions and location. Furthermore, the brain parenchyma vasculature mostly hosts Lyve1MHCII pvMs with low to intermediate CD45 expression. Using the double Cx3cr1 x Cx3cr1-Cre;Rosa reporter mice for finer mapping of the lineages, we establish that CD45CX3CR1 pvMs are derived from CX3CR1 precursors and require PU.1 during their ontogeny. In parallel, results from the Cxcr4-CreErt2;Rosa26 lineage tracing model support a bone marrow-independent replenishment of all Lyve1 pvMs in the adult mouse brain. Lastly, flow cytometry and 3D immunofluorescence analysis uncover increased percentage of pvMs following photothrombotic induced stroke. Our results thus show that the parenchymal pvM population is more heterogenous than previously described, and includes a CD45 and CX3CR1 pvM population.
Topics: Animals; Mice; Macrophages; Leukocyte Count; Phagocytes; Flow Cytometry; Brain
PubMed: 36450771
DOI: 10.1038/s41467-022-35166-9 -
Annual Review of Immunology Apr 2023Myeloid cells are a significant proportion of leukocytes within tissues, comprising granulocytes, monocytes, dendritic cells, and macrophages. With the identification of... (Review)
Review
Myeloid cells are a significant proportion of leukocytes within tissues, comprising granulocytes, monocytes, dendritic cells, and macrophages. With the identification of various myeloid cells that perform separate but complementary functions during homeostasis and disease, our understanding of tissue myeloid cells has evolved significantly. Exciting findings from transcriptomics profiling and fate-mapping mouse models have facilitated the identification of their developmental origins, maturation, and tissue-specific specializations. This review highlights the current understanding of tissue myeloid cells and the contributing factors of functional heterogeneity to better comprehend the complex and dynamic immune interactions within the healthy or inflamed tissue. Specifically, we discuss the new understanding of the contributions of granulocyte-monocyte progenitor-derived phagocytes to tissue myeloid cell heterogeneity as well as the impact of niche-specific factors on monocyte and neutrophil phenotype and function. Lastly, we explore the developing paradigm of myeloid cell heterogeneity during inflammation and disease.
Topics: Mice; Humans; Animals; Monocytes; Neutrophils; Macrophages; Myeloid Cells; Inflammation; Cell Differentiation
PubMed: 37126421
DOI: 10.1146/annurev-immunol-081022-113627 -
ELife Oct 2022Tissue-resident macrophages represent a group of highly responsive innate immune cells that acquire diverse functions by polarizing toward distinct subpopulations. The...
Tissue-resident macrophages represent a group of highly responsive innate immune cells that acquire diverse functions by polarizing toward distinct subpopulations. The subpopulations of macrophages that reside in skeletal muscle (SKM) and their changes during aging are poorly characterized. By single-cell transcriptomic analysis with unsupervised clustering, we found 11 distinct macrophage clusters in male mouse SKM with enriched gene expression programs linked to reparative, proinflammatory, phagocytic, proliferative, and senescence-associated functions. Using a complementary classification, membrane markers LYVE1 and MHCII identified four macrophage subgroups: LYVE1-/MHCII (M1-like, classically activated), LYVE1+/MHCII (M2-like, alternatively activated), and two new subgroups, LYVE1+/MHCII and LYVE1-/MHCII. Notably, one new subgroup, LYVE1+/MHCII, had traits of both M2 and M1 macrophages, while the other new subgroup, LYVE1-/MHCII, displayed strong phagocytic capacity. Flow cytometric analysis validated the presence of the four macrophage subgroups in SKM and found that LYVE1- macrophages were more abundant than LYVE1+ macrophages in old SKM. A striking increase in proinflammatory markers ( and mRNAs) and senescence-related markers ( and mRNAs) was evident in macrophage clusters from older mice. In sum, we have identified dynamically polarized SKM macrophages and propose that specific macrophage subpopulations contribute to the proinflammatory and senescent traits of old SKM.
Topics: Mice; Male; Animals; Single-Cell Analysis; Macrophages; Phagocytes; Transcriptome; Biomarkers; Muscle, Skeletal
PubMed: 36259488
DOI: 10.7554/eLife.77974 -
Nature Immunology Feb 2022During inflammation, Ly6C monocytes are rapidly mobilized from the bone marrow (BM) and are recruited into inflamed tissues, where they undergo monocyte-to-phagocyte...
During inflammation, Ly6C monocytes are rapidly mobilized from the bone marrow (BM) and are recruited into inflamed tissues, where they undergo monocyte-to-phagocyte transition (MTPT). The in vivo developmental trajectories of the MTPT and the contribution of individual cytokines to this process remain unclear. Here, we used a murine model of neuroinflammation to investigate how granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-γ (IFNγ), two type 1 cytokines, controlled MTPT. Using genetic fate mapping, gene targeting and high-dimensional single-cell multiomics analyses, we found that IFNγ was essential for the gradual acquisition of a mature inflammatory phagocyte phenotype in Ly6C monocytes, while GM-CSF was required to license interleukin-1β (IL-1β) production, phagocytosis and oxidative burst. These results suggest that the proinflammatory cytokine environment guided MTPT trajectories in the inflamed central nervous system (CNS) and indicated that GM-CSF was the most prominent target for the disarming of monocyte progenies during neuroinflammation.
Topics: Animals; Cell Differentiation; Cytokines; Female; Granulocyte-Macrophage Colony-Stimulating Factor; Interferon-gamma; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Monocytes; Neuroinflammatory Diseases; Phagocytes
PubMed: 35102344
DOI: 10.1038/s41590-021-01117-7 -
Nature Protocols Jul 2020Macrophage phagocytosis can be triggered by diverse receptor-ligand interactions to clear pathogens and dead cells from a host. Many ways of assaying phagocytosis exist...
Macrophage phagocytosis can be triggered by diverse receptor-ligand interactions to clear pathogens and dead cells from a host. Many ways of assaying phagocytosis exist that utilize a variety of phagocytic targets with different combinations of receptor-ligand interactions, making comparisons difficult. To study how phagocytosis is affected by specific changes to the target surface, we developed an in vitro assay based on reconstituted membrane-coated target particles to which known molecules can be added. The targets are made by coating glass beads with supported lipid bilayers followed by coupling proteins and other ligands of interest. Composition of the lipid bilayer can be varied to bind and orient specific proteins, incorporate signaling and reporter lipids, and control bilayer fluidity. To quantify phagocytosis, the reconstituted target particles are incubated with macrophages in vitro for a defined period of time, imaged with fluorescence microscopy and analyzed with software that measures the amount of target particle fluorescence within each macrophage. A multi-well plate format can be used for multi-parameter studies (e.g., to investigate how phagocytosis is affected by specific receptor-ligand interactions, ligand density, lipid charge, membrane fluidity and other molecular details). As an example, we demonstrate that antibody-dependent phagocytosis is more efficient for targets with fluid membranes than non-fluid membranes. The assay protocol takes approximately 6 h and requires basic molecular biology, mammalian cell culture and fluorescence microscopy skills. This assay can also be used with other phagocytic and non-phagocytic cells to study the individual or collective roles of receptors and ligands in immune effector function.
Topics: Animals; Cytological Techniques; Macrophages; Mice; Phagocytosis; RAW 264.7 Cells
PubMed: 32561889
DOI: 10.1038/s41596-020-0330-8 -
The Journal of Experimental Medicine May 2020Failure of remyelination underlies the progressive nature of demyelinating diseases such as multiple sclerosis. Macrophages and microglia are crucially involved in the...
Failure of remyelination underlies the progressive nature of demyelinating diseases such as multiple sclerosis. Macrophages and microglia are crucially involved in the formation and repair of demyelinated lesions. Here we show that myelin uptake temporarily skewed these phagocytes toward a disease-resolving phenotype, while sustained intracellular accumulation of myelin induced a lesion-promoting phenotype. This phenotypic shift was controlled by stearoyl-CoA desaturase-1 (SCD1), an enzyme responsible for the desaturation of saturated fatty acids. Monounsaturated fatty acids generated by SCD1 reduced the surface abundance of the cholesterol efflux transporter ABCA1, which in turn promoted lipid accumulation and induced an inflammatory phagocyte phenotype. Pharmacological inhibition or phagocyte-specific deficiency of Scd1 accelerated remyelination ex vivo and in vivo. These findings identify SCD1 as a novel therapeutic target to promote remyelination.
Topics: ATP Binding Cassette Transporter 1; Animals; Brain; Cell Line; Cholesterol; Endocytosis; Fatty Acids; Foam Cells; Humans; Inflammation; Macrophages; Mice; Microglia; Myelin Sheath; Phagocytes; Phenotype; Protein Kinase C-delta; Stearoyl-CoA Desaturase
PubMed: 32097464
DOI: 10.1084/jem.20191660 -
Methods in Molecular Biology (Clifton,... 2024One hundred years have passed since the death of Élie Metchnikoff (1845-1916). He was the first to observe the uptake of particles by cells and realized the importance... (Review)
Review
One hundred years have passed since the death of Élie Metchnikoff (1845-1916). He was the first to observe the uptake of particles by cells and realized the importance of this process, named phagocytosis, for the host response to injury and infection. He also was a strong advocate of the role of phagocytosis in cellular immunity, and with this, he gave us the basis for our modern understanding of inflammation and the innate immune response. Phagocytosis is an elegant but complex process for the ingestion and elimination of pathogens, but it is also important for the elimination of apoptotic cells and hence fundamental for tissue homeostasis. Phagocytosis can be divided into four main steps: (i) recognition of the target particle, (ii) signaling to activate the internalization machinery, (iii) phagosome formation, and (iv) phagolysosome maturation. In this chapter, we present a general view of our current knowledge on phagocytosis performed mainly by professional phagocytes through antibody and complement receptors and discuss aspects that remain incompletely understood.
Topics: Phagocytosis; Humans; Animals; Phagosomes; Phagocytes; Signal Transduction; Immunity, Innate
PubMed: 38888769
DOI: 10.1007/978-1-0716-3890-3_3 -
Nature Communications Jun 2020Synthetic biology is a powerful tool to create therapeutics which can be rationally designed to enable unique and combinatorial functionalities. Here we utilize...
Synthetic biology is a powerful tool to create therapeutics which can be rationally designed to enable unique and combinatorial functionalities. Here we utilize non-pathogenic E coli Nissle as a versatile platform for the development of a living biotherapeutic for the treatment of cancer. The engineered bacterial strain, referred to as SYNB1891, targets STING-activation to phagocytic antigen-presenting cells (APCs) in the tumor and activates complementary innate immune pathways. SYNB1891 treatment results in efficacious antitumor immunity with the formation of immunological memory in murine tumor models and robust activation of human APCs. SYNB1891 is designed to meet manufacturability and regulatory requirements with built in biocontainment features which do not compromise its efficacy. This work provides a roadmap for the development of future therapeutics and demonstrates the transformative potential of synthetic biology for the treatment of human disease when drug development criteria are incorporated into the design process for a living medicine.
Topics: Animals; Antigen-Presenting Cells; Cell Line, Tumor; Escherichia coli; Genetic Engineering; Humans; Immunotherapy; Interferon Type I; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Neoplasms; Phagocytes; Signal Transduction; Synthetic Biology
PubMed: 32483165
DOI: 10.1038/s41467-020-16602-0