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Synaptic pruning through glial synapse engulfment upon motor learning. Nat Neurosci 2022; 25:1458-1469. [PMID: 36319770 DOI: 10.1038/s41593-022-01184-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 09/15/2022] [Indexed: 11/06/2022]
Abstract
Synaptic pruning is a fundamental process of neuronal circuit refinement in learning and memory. Accumulating evidence suggests that glia participates in sculpting the neuronal circuits through synapse engulfment. However, whether glial involvement in synaptic pruning has a role in memory formation remains elusive. Using newly developed phagocytosis reporter mice and three-dimensional ultrastructural characterization, we found that synaptic engulfment by cerebellar Bergmann glia (BG) frequently occurred upon cerebellum-dependent motor learning in mice. We observed increases in pre- and postsynaptic nibbling by BG along with a reduction in spine volume after learning. Pharmacological blockade of engulfment with Annexin V inhibited both the spine volume reduction and overnight improvement of motor adaptation. These results indicate that BG contribute to the refinement of the mature cerebellar cortical circuit through synaptic engulfment during motor learning.
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Rybczynska AA, Boersma HH, de Jong S, Gietema JA, Noordzij W, Dierckx RAJO, Elsinga PH, van Waarde A. Avenues to molecular imaging of dying cells: Focus on cancer. Med Res Rev 2018. [PMID: 29528513 PMCID: PMC6220832 DOI: 10.1002/med.21495] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Successful treatment of cancer patients requires balancing of the dose, timing, and type of therapeutic regimen. Detection of increased cell death may serve as a predictor of the eventual therapeutic success. Imaging of cell death may thus lead to early identification of treatment responders and nonresponders, and to “patient‐tailored therapy.” Cell death in organs and tissues of the human body can be visualized, using positron emission tomography or single‐photon emission computed tomography, although unsolved problems remain concerning target selection, tracer pharmacokinetics, target‐to‐nontarget ratio, and spatial and temporal resolution of the scans. Phosphatidylserine exposure by dying cells has been the most extensively studied imaging target. However, visualization of this process with radiolabeled Annexin A5 has not become routine in the clinical setting. Classification of death modes is no longer based only on cell morphology but also on biochemistry, and apoptosis is no longer found to be the preponderant mechanism of cell death after antitumor therapy, as was earlier believed. These conceptual changes have affected radiochemical efforts. Novel probes targeting changes in membrane permeability, cytoplasmic pH, mitochondrial membrane potential, or caspase activation have recently been explored. In this review, we discuss molecular changes in tumors which can be targeted to visualize cell death and we propose promising biomarkers for future exploration.
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Affiliation(s)
- Anna A Rybczynska
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Genetics, University of Groningen, Groningen, the Netherlands
| | - Hendrikus H Boersma
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Clinical Pharmacy & Pharmacology, University of Groningen, Groningen, the Netherlands
| | - Steven de Jong
- Department of Medical Oncology, University of Groningen, Groningen, the Netherlands
| | - Jourik A Gietema
- Department of Medical Oncology, University of Groningen, Groningen, the Netherlands
| | - Walter Noordzij
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Rudi A J O Dierckx
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.,Department of Nuclear Medicine, Ghent University, Ghent, Belgium
| | - Philip H Elsinga
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Aren van Waarde
- Molecular Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
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Spatiotemporal distribution of proliferation, proapoptotic and antiapoptotic factors in the early human limb development. Acta Histochem 2016; 118:527-36. [PMID: 27282649 DOI: 10.1016/j.acthis.2016.05.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/19/2016] [Accepted: 05/24/2016] [Indexed: 12/28/2022]
Abstract
Involvement of proliferation and apoptosis in the human limb development was analyzed electronmicroscopically and immunohistochemically in histological sections of 8 human embryos, 4(th) -10(th) week old, using apoptotic (caspase-3, AIF, BAX), anti-apoptotic (Bcl-2) and proliferation (Ki-67) markers, and TUNEL method. The data were analyzed by Mann-Whitney test, Kruskal-Wallis and Dunn's post hoc test. Initially, developing human limbs consisted of mesenchymal core and surface ectoderm with apical ectodermal ridge (AER). During progression of development, strong proliferation activity gradually decreased in the mesenchyme (from 78% to 68%) and in the epithelium (from 62% to 42%), while in the differentiating finger cartilages proliferation was constantly low (26-7%). Apoptotic caspase-3 and AIF-positive cells characterized mesenchyme and AER at earliest stages, while during digit separation they appeared in interdigital mesenchyme as well. Strong Bcl-2 expression was observed in AER, subridge mesenchyme and phalanges, while BAX expression charaterized limb areas undergoing apoptosis. Ultrastructurally, proliferating cells showed mitotic figures, while apoptotic cells were characterized by nuclear fragmentation. Macrophages were observed around the apoptotic cells. We suggest that intense proliferation enables growth and elongation of human limb primordia, and differential growth of digits. Both caspase-3 and AIF-dependant pathways of cell death control the extent of AER and numer of cells in the subridge mesenchyme at earliest developmental stages, as well as process of digit separation at later stages of limb development. Spatio-temporal co-expresson of Bcl-2 and BAX indicates their role in suppression of apoptosis and selective stimulation of growth during human limb morphogenesis.
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Nikolić M, Gardner H, Tucker K. Postnatal neuronal apoptosis in the cerebral cortex: Physiological and pathophysiological mechanisms. Neuroscience 2013; 254:369-78. [DOI: 10.1016/j.neuroscience.2013.09.035] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 09/14/2013] [Accepted: 09/17/2013] [Indexed: 12/15/2022]
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5
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Goyal G, Nam Y. Neuronal micro-culture engineering by microchannel devices of cellular scale dimensions. Biomed Eng Lett 2011. [DOI: 10.1007/s13534-011-0014-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Boersma HH, Liem IH, Kemerink GJ, Thimister PWL, Hofstra L, Stolk LML, van Heerde WL, Pakbiers MTW, Janssen D, Beysens AJ, Reutelingsperger CPM, Heidendal GAK. Comparison between human pharmacokinetics and imaging properties of two conjugation methods for 99mTc-annexin A5. Br J Radiol 2003; 76:553-60. [PMID: 12893698 DOI: 10.1259/bjr/30385847] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Annexin A5 (AnxA5) is a protein with high affinity for phosphatidyl serine, a phospholipid exposed on the cell surface during apoptosis. This phenomenon has been used for determination of cell death after myocardial infarction. To evaluate the potential of (99m)Tc-AnxA5 for in vivo scintigraphy of apoptotic cells, the pharmacokinetics and imaging properties of two radiopharmaceuticals, (99m)Tc-(n-1-imino-4-mercaptobutyl)-AnxA5 (I-AnxA5) and (99m)Tc-(4,5-bis(thioacetamido)pentanoyl)-AnxA5 (B-AnxA5), were studied. I-AnxA5 was administered intravenously to seven patients and one healthy volunteer, and B-AnxA5 was administered to 12 patients. All patients in the pharmacokinetic study had myocardial disease. Additionally, imaging was performed in a patient with acute myocardial infarction, as well as in three patients with different malignancies. The plasma concentration, excretion and biodistribution of (99m)Tc-AnxA5 were measured, as well as levels of AnxA5 antigen. The kinetic data of both radiopharmaceuticals in plasma fitted a two-compartment model. Both preparations had similar half-lives, but a different distribution over the two compartments. Plasma levels of AnxA5 antigen showed a broad variation. Both radiopharmaceuticals accumulated in the kidney, liver and gut. B-AnxA5 was excreted significantly faster than I-AnxA5. Both compounds can be used for imaging of the head/neck region, the thorax and the extremities. B-AnxA5 has a faster clearance and a lower radiation dose. Imaging of apoptosis in the abdomen will be difficult with both radiopharmaceuticals, and especially with B-AnxA5 because of its faster appearance in the gut.
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Affiliation(s)
- H H Boersma
- Department of Nuclear Medicine, University Hospital Maastricht, P.O. Box 5800, NL-6202 AZ Maastricht, The Netherlands
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Guillemain I, Fontès G, Privat A, Chaudieu I. Early programmed cell death in human NT2 cell cultures during differentiation induced by all-trans-retinoic acid. J Neurosci Res 2003; 71:38-45. [PMID: 12478612 DOI: 10.1002/jnr.10458] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Previous studies have demonstrated that programmed cell death takes place at different stages during the development of the CNS in vivo. Our purpose in this study was to detect early programmed cell death associated with the induction of differentiation by retinoic acid (RA) in the NT2 cell line. By using the annexin V labeling as a marker of apoptosis, a significant apoptotic cell death was quantified during the third and the fourth days of the RA treatment. Double-labeling studies using the staining of the genomic DNA strand breaks with the terminal deoxyribosyl-transferase-mediated dUTP nick end-labeling (TUNEL) assay and either nestin or microtubule-associated protein 2 (MAP2) showed that 1) the early apoptotic cell death affected mostly nestin-positive cells and 2) after 8 days of differentiation, although cells with neuronal phenotypes are present, no colabeled TUNEL/MAP2 cells were detected. With regard to the neuronal protein MAP2, we observed discrete immunolabeling of a few NT2 cells as early as day 3 of the differentiation and a significant emergence of MAP2-immunopositive cells at days 6-8. Thus, our results show that, when as a whole the differentiating NT2 cell population is considered, 1) the apoptotic cell death observed during the third day of differentiation occurs mostly in undifferentiated cells, 2) this process coincides with the first detection of the neuronal phenotype in NT2 cell cultures, and 3) the end of the cell death period in NT2 cell cultures is marked by both the accumulation of MAP2-positive cells and the beginning of expression of the Bcl-2 protein in the cultures.
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Lossi L, Mioletti S, Merighi A. Synapse-independent and synapse-dependent apoptosis of cerebellar granule cells in postnatal rabbits occur at two subsequent but partly overlapping developmental stages. Neuroscience 2002; 112:509-23. [PMID: 12074894 DOI: 10.1016/s0306-4522(02)00112-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
It has long been known that cells in the external granular layer die during postnatal development of the cerebellum. More recent findings indicate that at certain developmental stages, cell death occurs upon activation of an apoptotic program. We show that cerebellar granule cells in rabbits undergo programmed cell death at two different stages of maturation. At postnatal day 5 (P5), granule cell precursors and pre-migratory granule cells in the external granular layer incorporate the S-phase markers 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine with a pattern that is dependent upon the interval between the administration of the two tracers. Within 12-24 h after proliferation a significant number of labeled cells show typical ultrastructural alterations of apoptosis. DNA electrophoresis and cleavage of poly-ADP-ribose polymerase confirm the activation of the apoptotic machinery. After Southern blotting and immunodetection, incorporated 5-bromo-2'-deoxyuridine is present at the level of low size DNA oligomers as soon as 12 h after cell division. Therefore, this apoptotic phase is intrinsic to external granular layer neurons and independent of synaptic interactions with targets.Apoptotic cells, although fewer in number, are detected also in the internal granular layer and tend to increase from P5 to P10. It seems unlikely that these cells undergo DNA fragmentation in the external granular layer and subsequently migrate to their final destination, considering the data on cell cycle kinetics and the rapid tissue clearance by the glia. Parallel fiber-Purkinje spine synapses are already present in the molecular layer at P5. Therefore, the post-migratory granule cells likely undergo apoptosis as a failure to make proper synaptic contacts in the forming molecular layer. We conclude that the massive apoptosis of pre-migratory cells likely has a role in regulating the size of this rapidly expanding population of pre-mitotic neurons. The less tumultuous cell death of post-mitotic granule cells in the internal granular layer appears to be linked to the formation of the mature synaptic circuitry of the developing cerebellar cortex.
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Affiliation(s)
- L Lossi
- Department of Veterinary Morphophysiology, Via Leonardo da Vinci 44, I-10095 Grugliasco, Italy
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Krieser RJ, MacLea KS, Longnecker DS, Fields JL, Fiering S, Eastman A. Deoxyribonuclease IIalpha is required during the phagocytic phase of apoptosis and its loss causes perinatal lethality. Cell Death Differ 2002; 9:956-62. [PMID: 12181746 DOI: 10.1038/sj.cdd.4401056] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2001] [Revised: 02/12/2002] [Accepted: 03/18/2002] [Indexed: 11/10/2022] Open
Abstract
Deoxyribonuclease IIalpha (DNase IIalpha) is one of many endonucleases implicated in DNA digestion during apoptosis. We produced mice with targeted disruption of DNase IIalpha and defined its role in apoptosis. Mice deleted for DNase IIalpha die at birth with many tissues exhibiting large DNA-containing bodies that result from engulfed but undigested cell corpses. These DNA-containing bodies are pronounced in the liver where fetal definitive erythropoiesis occurs and extruded nuclei are degraded. They are found between the digits, where apoptosis occurs, and in many other regions of the embryo. Defects in the diaphragm appear to cause death of the mice due to asphyxiation. The DNA in these bodies contains 3'-hydroxyl ends and therefore stain positive in the TUNEL assay. In addition, numerous unengulfed TUNEL-positive cells are observed throughout the embryo. Apoptotic cells are normally cleared rapidly from a tissue; hence the persistence of the DNA-containing bodies and TUNEL-positive cells identifies sites where apoptosis occurs during development. These results demonstrate that DNase IIalpha is not required for the generation of the characteristic DNA fragmentation that occurs during apoptosis but is required for degrading DNA of dying cells and this function is necessary for proper fetal development.
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Affiliation(s)
- R J Krieser
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, NH 03755, USA
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11
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Chan WY, Lorke DE, Tiu SC, Yew DT. Proliferation and apoptosis in the developing human neocortex. THE ANATOMICAL RECORD 2002; 267:261-76. [PMID: 12124904 DOI: 10.1002/ar.10100] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The cell kinetics of the developing central nervous system (CNS) is determined by both proliferation and apoptosis. In the human neocortex at week 6 of gestation, proliferation is confined to the ventricular zone, where mitotic figures and nuclear immunoreactivity for proliferating cell nuclear antigen (PCNA) are detectable. Cell division is symmetric, with both daughter cells reentering mitosis. At week 7, the subventricular zone, a secondary proliferative zone, appears. It mainly gives rise to local circuit neurons and glial cells. Around week 12, the ventricular and subventricular zones are thickest, and the nuclear PCNA label is strongest, indicating that proliferation peaks at this stage. Thereafter, asymmetric division becomes the predominant mode of proliferation, with one daughter cell reentering mitosis and the other one migrating out. Towards late gestation, the ventricular and subventricular zones almost completely disappear and proliferation shifts towards the intermediate and subplate zones, where mainly glial cells are generated. A remnant of the subventricular zone with proliferative activity persists into adulthood. In general, proliferation follows a latero-medial gradient in the neocortex lasting longer in its lateral parts. Apoptotic nuclei have been detected around week 5, occurring in low numbers in the ventricular zone at this stage. Apoptotic cell death increases around midgestation and then spreads throughout all cortical layers, with most dying cells located in the ventricular and subventricular zones. This spatial distribution of apoptosis extends into late gestation. During the early postnatal period, most apoptotic cells are still located in the subcortical layers. During early embryonic development, proliferation and apoptosis are closely related, and are probably regulated by common regulators. In the late fetal and early postnatal periods, when proliferation has considerably declined in all cortical layers, apoptosis may occur in neurons whose sprouting axons do not find their targets.
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Affiliation(s)
- Wood Yee Chan
- Department of Anatomy, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China
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12
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Reutelingsperger CPM, Dumont E, Thimister PW, van Genderen H, Kenis H, van de Eijnde S, Heidendal G, Hofstra L. Visualization of cell death in vivo with the annexin A5 imaging protocol. J Immunol Methods 2002; 265:123-32. [PMID: 12072183 DOI: 10.1016/s0022-1759(02)00075-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Annexin A5 binds to phosphatidylserine (PS), which is one of the "eat me" signals at the surface of the apoptotic cell. This property has been the driving force for the research of annexin A5 as a probe to measure apoptosis in vitro and in vivo. A non-invasive imaging protocol using annexin A5 has been developed and applied successfully to measure programmed cell death programmed cell death (PCD) in patients. This review highlights the aspects of this development and discusses clinical relevance, limitations and future perspectives of this approach of visualizing cell death.
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Affiliation(s)
- Chris P M Reutelingsperger
- Department of Biochemistry of the Cardiovascular Research Institute Maastricht, University of Maastricht, P.O. Box 616, The Netherlands.
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Valavanis C, Naber S, Schwartz LM. In situ detection of dying cells in normal and pathological tissues. Methods Cell Biol 2002; 66:393-415. [PMID: 11396013 DOI: 10.1016/s0091-679x(01)66018-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Affiliation(s)
- C Valavanis
- Department of Biology, Morrill Science Center, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Williamson P, van den Eijnde S, Schlegel RA. Phosphatidylserine exposure and phagocytosis of apoptotic cells. Methods Cell Biol 2002; 66:339-64. [PMID: 11396011 DOI: 10.1016/s0091-679x(01)66016-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- P Williamson
- Department of Biology, Amherst College, Amherst, Massachusetts 01002, USA
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van den Eijnde SM, van den Hoff MJ, Reutelingsperger CP, van Heerde WL, Henfling ME, Vermeij-Keers C, Schutte B, Borgers M, Ramaekers FC. Transient expression of phosphatidylserine at cell-cell contact areas is required for myotube formation. J Cell Sci 2001; 114:3631-42. [PMID: 11707515 DOI: 10.1242/jcs.114.20.3631] [Citation(s) in RCA: 208] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cell surface exposure of phosphatidylserine (PS) is shown to be part of normal physiology of skeletal muscle development and to mediate myotube formation. A transient exposure of PS was observed on mouse embryonic myotubes at E13, at a stage of development when primary myotubes are formed. The study of this process in cell cultures of differentiating C2C12 and H9C2 myoblasts also reveals a transient expression of PS at the cell surface. This exposure of PS locates mainly at cell-cell contact areas and takes place at a stage when the structural organization of the sarcomeric protein titin is initiated, prior to actual fusion of individual myoblast into multinucleated myotubes. Myotube formation in vitro can be inhibited by the PS binding protein annexin V, in contrast to its mutant M1234, which lacks the ability to bind to PS. Although apoptotic myoblasts also expose PS, differentiating muscle cells show neither loss of mitochondrial membrane potential nor detectable levels of active caspase-3 protein. Moreover, myotube formation and exposure of PS cannot be blocked by the caspase inhibitor zVAD(OMe)-fmk. Our findings indicate that different mechanisms regulate PS exposure during apoptosis and muscle cell differentiation, and that surface exposed PS plays a crucial role in the process of myotube formation.
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Affiliation(s)
- S M van den Eijnde
- Department of Molecular Cell Biology, Cardiovascular Research Institute Maastricht, University of Maastricht, PO Box 616, 6200 MD Maastricht, The Netherlands.
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Schlegel RA, Williamson P. Phosphatidylserine, a death knell. Cell Death Differ 2001; 8:551-63. [PMID: 11536005 DOI: 10.1038/sj.cdd.4400817] [Citation(s) in RCA: 259] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2000] [Revised: 11/13/2000] [Accepted: 11/27/2000] [Indexed: 11/09/2022] Open
Abstract
Virtually every cell in the body restricts phosphatidylserine (PS) to the inner leaflet of the plasma membrane by energy-dependent transport from the outer to the inner leaflet of the bilayer. Apoptotic cells of all types rapidly randomize the asymmetric distribution, bringing PS to the surface where it serves as a signal for phagocytosis. A myriad of phagocyte receptors have been implicated in the recognition of apoptotic cells, among them a PS receptor, yet few ligands other than PS have been identified on the apoptotic cell surface. Since apoptosis and the associated exposure of PS on the cell surface is probably over 600 million years old, it is not surprising that evolution has appropriated aspects of this process for specialized purposes such as blood coagulation, membrane fusion and erythrocyte differentiation. Failure to efficiently remove apoptotic cells may contribute to inflammatory responses and autoimmune diseases resulting from chronic, inappropriate exposure of PS.
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Affiliation(s)
- R A Schlegel
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA 16802, USA
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Schlegel RA, Callahan MK, Williamson P. The central role of phosphatidylserine in the phagocytosis of apoptotic thymocytes. Ann N Y Acad Sci 2001; 926:217-25. [PMID: 11193037 DOI: 10.1111/j.1749-6632.2000.tb05614.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apoptotic thymocytes inactivate the aminophospholipid translocase, which transports phosphatidylserine (PS) to the inner leaflet of the plasma membrane, and activate the scramblase, which randomizes phospholipids across the membrane and brings PS to the cell surface. Although different macrophages use at least two different systems to recognize and engulf apoptotic thymocytes, both systems recognize PS on the apoptotic target. Thymocytes treated with Ca2+ and ionophore to inactivate the translocase and activate the scramblase immediately expose PS on their surface and are immediately recognized and phagocytosed. These targets, on which PS has been artificially exposed, are recognized by the PS exposed on their surface. However, they apparently also engage the vitronectic receptor, a lectin-like receptor and CD14. All of these receptors are implicated in the phagocytosis of apoptotic thymocytes, suggesting that loss of asymmetry and/or exposure of PS is sufficient to generate the ligands recognized by those receptors. The role of PS is not confined to the target cell surface, however. PS is constitutively exposed on the surface of macrophages and is as necessary for apoptotic cell engulfment as is recognition of PS on the target cell surface.
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Affiliation(s)
- R A Schlegel
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania 16802, USA.
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Fadok VA, Daleke DL, Henson PM, Bratton DL. Loss of phospholipid asymmetry and surface exposure of phosphatidylserine is required for phagocytosis of apoptotic cells by macrophages and fibroblasts. J Biol Chem 2001; 276:1071-7. [PMID: 10986279 DOI: 10.1074/jbc.m003649200] [Citation(s) in RCA: 468] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Removal of apoptotic cells during tissue remodeling or resolution of inflammation is critical to the restoration of normal tissue structure and function. During apoptosis, early surface changes occur, which trigger recognition and removal by macrophages and other phagocytes. Loss of phospholipid asymmetry results in exposure of phosphatidylserine (PS), one of the surface markers recognized by macrophages. However, a number of receptors have been reported to mediate macrophage recognition of apoptotic cells, not all of which bind to phosphatidylserine. We therefore examined the role of membrane phospholipid symmetrization and PS externalization in uptake of apoptotic cells by mouse macrophages and human HT-1080 fibrosarcoma cells by exposing them to cells that had undergone apoptosis without loss of phospholipid asymmetry. Neither mouse macrophages nor HT-1080 cells recognized or engulfed apoptotic targets that failed to express PS, in comparison to PS-expressing apoptotic cells. If, however, their outer leaflets were repleted with the l-, but not the d-, stereoisomer of sn-1,2-PS by liposome transfer, engulfment by both phagocytes was restored. These observations directly demonstrate that loss of phospholipid asymmetry and PS expression is required for phagocyte engulfment of apoptotic cells and imply a critical, if not obligatory, role for PS recognition in the uptake process.
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Affiliation(s)
- V A Fadok
- Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206 , USA.
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Witting A, Müller P, Herrmann A, Kettenmann H, Nolte C. Phagocytic clearance of apoptotic neurons by Microglia/Brain macrophages in vitro: involvement of lectin-, integrin-, and phosphatidylserine-mediated recognition. J Neurochem 2000; 75:1060-70. [PMID: 10936187 DOI: 10.1046/j.1471-4159.2000.0751060.x] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Microglia, the tissue macrophages of the brain, play a crucial role in recognition and phagocytic removal of apoptotic neurons. The microglial receptors for recognition of apoptotic neurons are not yet characterized. Here we established a co-culture model of primary microglia and cerebellar granule neurons to examine the receptor systems involved in recognition/uptake of apoptotic neurons. Treatment with 100 microM S-nitrosocysteine induced apoptosis of cerebellar neurons as indicated by nuclear condensation and phosphatidylserine exposure to the exoplasmic leaflet of the plasma membrane. Microglial cells were added to neurons 2 h after apoptosis induction and co-cultured for 6 h in the presence of ligands that inhibit recognition by binding to respective receptors. Binding/phagocytosis was determined after combined 4', 6-diamidino-2-phenylindole/propidium iodide (for apoptotic/necrotic neurons) and lectin staining (for microglia). Uptake of apoptotic neurons was reduced by N-acetylglucosamine or galactose, suggesting that recognition involves asialoglycoprotein-like lectins. Furthermore, the inhibition of microglial binding/uptake of apoptotic neurons by RGDS peptide suggests a role of microglial vitronectin receptor. As microglia selectively bind lipid vesicles enriched in phosphatidylserine and O-phospho-L-serine interfered with the uptake of apoptotic neurons, an involvement of phosphatidylserine receptor is rather likely. Apoptotic neurons do not release soluble signals that serve to attract or activate microglia. Collectively, these results suggest that apoptotic neurons generate a complex surface signal recognized by different receptor systems on microglia.
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Affiliation(s)
- A Witting
- Max Delbrück Center for Molecular Medicine, Cellular Neurosciences, Berlin, Germany
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Callahan MK, Williamson P, Schlegel RA. Surface expression of phosphatidylserine on macrophages is required for phagocytosis of apoptotic thymocytes. Cell Death Differ 2000; 7:645-53. [PMID: 10889509 DOI: 10.1038/sj.cdd.4400690] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cells generally maintain an asymmetric distribution of phospholipids across the plasma membrane bilayer, restricting the phospholipid, phosphatidylserine (PS), to the inner leaflet of the plasma membrane. When cells undergo apoptosis, this asymmetric transbilayer distribution is lost, bringing PS to the surface where it acts as a signal for engulfment by phagocytes. The fluorescent dye merocyanine 540 specifically stains the plasma membrane of apoptotic cells which have lost their asymmetric distribution of phospholipids. However, it also stains non-apoptotic macrophages, suggesting that phospholipid asymmetry may not be maintained in these cells, and thus that they may express PS on their surface. Here, the PS-binding protein, annexin V, was used to show that in fact normal macrophages do express PS on their surface. Furthermore, pre-treating macrophages with annexin V was found to inhibit phagocytosis of apoptotic thymocytes and thymocytes on which PS expression was artificially induced, but did not inhibit phagocytosis of latex beads or Fc receptor-mediated phagocytosis of opsonized erythrocytes. These results indicate that PS is constitutively expressed on the surface of macrophages and is functionally significant for the phagocytosis of PS-expressing target cells.
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Affiliation(s)
- M K Callahan
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, PA 16802 USA
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