scholarly journals Caspase Activity Is Required for Engulfment of Apoptotic Cells

2013 ◽  
Vol 33 (16) ◽  
pp. 3191-3201 ◽  
Author(s):  
Boris Shklyar ◽  
Flonia Levy-Adam ◽  
Ketty Mishnaevski ◽  
Estee Kurant
Keyword(s):  
Central Nervous System ◽  
Normal Development ◽  
Function Analysis ◽  
Living Cells ◽  
Apoptotic Cells ◽  
Caspase Activity ◽  
Internal Inhibition ◽  
Content Type ◽  
Multicellular Organisms ◽  
Dying Cells

Clearance of apoptotic cells by phagocytic neighbors is crucial for normal development of multicellular organisms. However, how phagocytes discriminate between healthy and dying cells remains poorly understood. We focus on glial phagocytosis of apoptotic neurons during development of theDrosophilacentral nervous system. We identified phosphatidylserine (PS) as a ligand on apoptotic cells for the phagocytic receptor Six Microns Under (SIMU) and report that PS alone is not sufficient for engulfment. Our data reveal that, additionally to PS exposure, caspase activity is required for clearance of apoptotic cells by phagocytes. Here we demonstrate that SIMU recognizes and binds PS on apoptotic cells through its N-terminal EMILIN (EMI), Nimrod 1 (NIM1), and NIM2 repeats, whereas the C-terminal NIM3 and NIM4 repeats control SIMU affinity to PS. Based on the structure-function analysis of SIMU, we discovered a novel mechanism of internal inhibition responsible for differential affinities of SIMU to its ligand which might prevent elimination of living cells exposing PS on their surfaces.

Autofluorescence and Apoptosis in Flow Cytometry: Correlative Methods for Fluorescence and Confocal Microscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 618-619
Author(s):  
R. W. Smith
Keyword(s):  
Flow Cytometry ◽  
Confocal Microscopy ◽  
Fluorescent Protein ◽  
Statistical Evaluation ◽  
Fluorescent Proteins ◽  
Living Cells ◽  
Apoptotic Cells ◽  
Chemical Probes ◽  
Clear Separation ◽  
Dying Cells

Flow cytometry offers several advantages in evaluating cellular fluorescence and separating values from chemical probes or transfected fluorescent proteins from autofluorescence. Autofluorescence can introduce artificial values that cannot be separated by examination of the fluorescence histogram. Often a comparison of fluorescence in two detectors can separate autofluorescence from positive fluorescence. A region can be defined around the cells of interest for further statistical evaluation or for subsequent sorting.Autofluorescence is also correlated with apoptosis in that apoptotic cells often increase autofluorescence values. A clear separation of living cells from dying cells can be achieved by the introduction of a DNA stain, such as 7AAD, which will penetrate cells with disrupted or damaged cellular membranes. Intact living cells will not show the 7AAD fluorescence.This separation is important in transfected fluorescent protein studies, as the transfection process is often toxic to cells.

The final step in programmed cell death: phagocytes carry apoptotic cells to the grave

2003 ◽  
Vol 39 ◽  
pp. 105-117 ◽  
Author(s):  
Aimee M deCathelineau ◽  
Peter M Henson
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
The Body ◽  
Apoptotic Cells ◽  
Cytokines And Chemokines ◽  
Cell Clearance ◽  
And Function ◽  
Multicellular Organisms ◽  
Dying Cells ◽  
High Degree

As cells undergo apoptosis, they are recognized and removed from the body by phagocytes. This oft-overlooked yet critical final step in the cell-death programme protects tissues from exposure to the toxic contents of dying cells and also serves to prevent further tissue damage by stimulating production of anti-inflammatory cytokines and chemokines. The clearance of apoptotic-cell corpses occurs throughout the lifespan of multicellular organisms and is important for normal development during embryogenesis, the maintenance of normal tissue integrity and function, and the resolution of inflammation. Many of the signal-transduction molecules implicated in the phagocytosis of apoptotic cells appear to have a high degree of evolutionary conservation, and therefore the engulfment of apoptotic cells is likely to represent one of the most primitive forms of phagocytosis. With the realization that the signals that govern apoptotic-cell removal also serve to attenuate inflammation and the immune response, as well as initiate signals for tissue repair and remodelling in response to cell death, the study of apoptotic cell clearance is a field experiencing a dynamic increase in interest and momentum.

scholarly journals Current Understanding of the Mechanisms for Clearance of Apoptotic Cells—A Fine Balance

2013 ◽  
Vol 6 ◽  
pp. JCD.S11037 ◽  
Author(s):  
Lois A. Hawkins ◽  
Andrew Devitt
Keyword(s):  
Cell Death ◽  
Innate Immune System ◽  
Inflammatory Process ◽  
Molecular Mechanisms ◽  
Innate Immune ◽  
Apoptotic Cells ◽  
Viable Cells ◽  
Effective Removal ◽  
Multicellular Organisms ◽  
Dying Cells

Apoptosis is an important cell death mechanism by which multicellular organisms remove unwanted cells. It culminates in a rapid, controlled removal of cell corpses by neighboring or recruited viable cells. Whilst many of the molecular mechanisms that mediate corpse clearance are components of the innate immune system, clearance of apoptotic cells is an anti-inflammatory process. Control of cell death is dependent on competing pro-apoptotic and anti-apoptotic signals. Evidence now suggests a similar balance of competing signals is central to the effective removal of cells, through so called ‘eat me’ and ‘don't eat me’ signals. Competing signals are also important for the controlled recruitment of phagocytes to sites of cell death. Consequently recruitment of phagocytes to and from sites of cell death can underlie the resolution or inappropriate propagation of cell death and inflammation. This article highlights our understanding of mechanisms mediating clearance of dying cells and discusses those mechanisms controlling phagocyte migration and how inappropriate control may promote important pathologies.

scholarly journals Simu-dependent clearance of dying cells regulates macrophage function and inflammation resolution

2018 ◽  
Author(s):  
Hannah Grace Roddie ◽  
Emma Louise Armitage ◽  
Simon Andrew Johnston ◽  
Iwan Robert Evans
Keyword(s):  
Normal Development ◽  
Inflammatory Responses ◽  
Apoptotic Cell ◽  
Apoptotic Cells ◽  
Apoptotic Cell Clearance ◽  
Cell Clearance ◽  
Clearance Receptor ◽  
Inflammation Resolution ◽  
Dying Cells ◽  
Inflammatory Action

AbstractMacrophages encounter and clear apoptotic cells during normal development and homeostasis, including at numerous sites of pathology. Clearance of apoptotic cells has been intensively studied, but the effects of macrophage-apoptotic cell interactions on macrophage behaviour are poorly understood. Using Drosophila embryos, we have exploited the ease of manipulating cell death and apoptotic cell clearance in this model to identify that the loss of the apoptotic cell clearance receptor Simu leads to perturbation of macrophage migration and inflammatory responses via pathological levels of apoptotic cells. Removal of apoptosis ameliorates these phenotypes, while acute induction of apoptosis phenocopies these defects and reveals that phagocytosis of apoptotic cells is not necessary for their anti-inflammatory action. Furthermore, Simu is necessary for clearance of necrotic debris and rentention of macrophages at wounds. Thus, Simu is a general detector of damaged self and represents a novel molecular player in controlling resolution of inflammation.

scholarly journals Apoptotic Cells, Including Macrophages, Are Prominent in Theiler's Virus-Induced Inflammatory, Demyelinating Lesions

2003 ◽  
Vol 77 (7) ◽  
pp. 4383-4388 ◽  
Author(s):  
Brian P. Schlitt ◽  
Matthew Felrice ◽  
Mary Lou Jelachich ◽  
Howard L. Lipton
Keyword(s):  
Central Nervous System ◽  
T Cells ◽  
Nervous System ◽  
In Situ Hybridization ◽  
Apoptotic Cells ◽  
Theiler's Virus ◽  
Demyelinating Lesions ◽  
Encephalomyelitis Virus ◽  
Mouse Central Nervous System

ABSTRACT Theiler's murine encephalomyelitis virus (TMEV) persists in the mouse central nervous system principally in macrophages, and infected macrophages in culture undergo apoptosis. We have detected abundant apoptotic cells in perivascular cuffs and inflammatory, demyelinating lesions of SJL mice chronically infected with TMEV. T cells comprised 74% of apoptotic cells, while 8% were macrophages, 0.6% were astrocytes, and ∼17% remained unidentified. In situ hybridization revealed viral RNA in ∼1% of apoptotic cells.

scholarly journals A Developmentally Regulated Gene, ASI2, Is Required for Endocycling in the Macronuclear Anlagen of Tetrahymena

2010 ◽  
Vol 9 (9) ◽  
pp. 1343-1353 ◽  
Author(s):  
Lihui Yin ◽  
Susan T. Gater ◽  
Kathleen M. Karrer
Keyword(s):  
Signal Transduction ◽  
Mitotic Cycle ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Ciliated Protozoa ◽  
Dna Rearrangement ◽  
Developmentally Regulated ◽  
Content Type ◽  
Molecular Events ◽  
Multicellular Organisms

ABSTRACT Ciliated protozoa contain two types of nuclei, germ line micronuclei (Mic) and transcriptionally active macronuclei (Mac). During sexual reproduction, the parental Mac degenerates and a new Mac develops from a mitotic product of the zygotic Mic. Macronuclear development involves extensive endoreplication of the genome. The present study shows that endoreplication of macronuclear DNA in Tetrahymena is an example of endocyling, a variant of the mitotic cycle with alternating S and G phases in the absence of cell division. Thus, endocycling is conserved from ciliates to multicellular organisms. The gene ASI2 in Tetrahymena thermophila encodes a putative signal transduction receptor. ASI2 is nonessential for vegetative growth, but it is upregulated during development of the new Mac. Cells that lack ASI2 in the developing Mac anlagen are arrested in endoreplication of the DNA and die. This study shows that ASI2 is also transcribed in the parental Mac early in conjugation and that transcription of ASI2 in the parental Mac supports endoreplication of the DNA during early stages of development of the Mac anlagen. Other molecular events in Mac anlage development, including developmentally regulated DNA rearrangement, occur normally in matings between ASI2 knockouts, suggesting that ASI2 specifically regulates endocycling in Tetrahymena.

scholarly journals Interplay between Antibiotic Efficacy and Drug-Induced Lysis Underlies Enhanced Biofilm Formation at Subinhibitory Drug Concentrations

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Wen Yu ◽  
Kelsey M. Hallinen ◽  
Kevin B. Wood
Keyword(s):  
Cell Wall ◽  
Biofilm Formation ◽  
Cell Lysis ◽  
Living Cells ◽  
Cell Wall Synthesis ◽  
Drug Induced ◽  
Trade Off ◽  
Content Type ◽  
Subinhibitory Concentrations ◽  
Antibiotic Efficacy

ABSTRACTSubinhibitory concentrations of antibiotics have been shown to enhance biofilm formation in multiple bacterial species. While antibiotic exposure has been associated with modulated expression of many biofilm-related genes, the mechanisms of drug-induced biofilm formation remain a focus of ongoing research efforts and may vary significantly across species. In this work, we investigate antibiotic-induced biofilm formation inEnterococcus faecalis, a leading cause of nosocomial infections. We show that biofilm formation is enhanced by subinhibitory concentrations of cell wall synthesis inhibitors but not by inhibitors of protein, DNA, folic acid, or RNA synthesis. Furthermore, enhanced biofilm is associated with increased cell lysis, increases in extracellular DNA (eDNA) levels, and increases in the density of living cells in the biofilm. In addition, we observe similar enhancement of biofilm formation when cells are treated with nonantibiotic surfactants that induce cell lysis. These findings suggest that antibiotic-induced biofilm formation is governed by a trade-off between drug toxicity and the beneficial effects of cell lysis. To understand this trade-off, we developed a simple mathematical model that predicts changes in antibiotic-induced biofilm formation due to external perturbations, and we verified these predictions experimentally. Specifically, we demonstrate that perturbations that reduce eDNA (DNase treatment) or decrease the number of living cells in the planktonic phase (a second antibiotic) decrease biofilm induction, while chemical inhibitors of cell lysis increase relative biofilm induction and shift the peak to higher antibiotic concentrations. Overall, our results offer experimental evidence linking cell wall synthesis inhibitors, cell lysis, increased eDNA levels, and biofilm formation inE. faecaliswhile also providing a predictive quantitative model that sheds light on the interplay between cell lysis and antibiotic efficacy in developing biofilms.

scholarly journals Neurons Are Host Cells for Mycobacterium tuberculosis

2014 ◽  
Vol 82 (5) ◽  
pp. 1880-1890 ◽  
Author(s):  
Philippa J. Randall ◽  
Nai-Jen Hsu ◽  
Dirk Lang ◽  
Susan Cooper ◽  
Boipelo Sebesho ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Mycobacterium Tuberculosis ◽  
Host Cells ◽  
Productive Infection ◽  
Target Cells ◽  
Dependent Manner ◽  
Content Type ◽  
The Central Nervous System

ABSTRACTMycobacterium tuberculosisinfection of the central nervous system is thought to be initiated once the bacilli have breached the blood brain barrier and are phagocytosed, primarily by microglial cells. In this study, the interactions ofM. tuberculosiswith neuronsin vitroandin vivowere investigated. The data obtained demonstrate that neurons can act as host cells forM. tuberculosis.M. tuberculosisbacilli were internalized by murine neuronal cultured cells in a time-dependent manner after exposure, with superior uptake by HT22 cells compared to Neuro-2a cells (17.7% versus 9.8%). Internalization ofM. tuberculosisbacilli by human SK-N-SH cultured neurons suggested the clinical relevance of the findings. Moreover, primary murine hippocampus-derived neuronal cultures could similarly internalizeM. tuberculosis. InternalizedM. tuberculosisbacilli represented a productive infection with retention of bacterial viability and replicative potential, increasing 2- to 4-fold within 48 h.M. tuberculosisbacillus infection of neurons was confirmedin vivoin the brains of C57BL/6 mice after intracerebral challenge. This study, therefore, demonstrates neurons as potential new target cells forM. tuberculosiswithin the central nervous system.

Teratomas of the central nervous system: treatment considerations based on 34 cases

1998 ◽  
Vol 89 (5) ◽  
pp. 728-737 ◽  
Author(s):  
Yutaka Sawamura ◽  
Tsutomu Kato ◽  
Jun Ikeda ◽  
Jun-ichi Murata ◽  
Mitsuhiro Tada ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Radiation Therapy ◽  
Adjuvant Therapy ◽  
Karnofsky Performance Scale ◽  
Content Type ◽  
Treatment Considerations ◽  
Low Incidence ◽  
A Prospective Study ◽  
Fine Print

Object. The optimum clinical management of central nervous system (CNS) teratomas, particularly postsurgical adjuvant therapy, is still unclear, partly as a result of the tumors' low incidence. In this study the authors analyze 34 cases of CNS teratomas so that they may adequately indicate management of these lesions. Methods. The median age of the 34 patients was 13 years. Twenty-seven patients treated between 1970 and 1991 were retrospectively reviewed. Four of these 27 patients died as a result of radical surgery; each of them had a teratoma involving the hypothalamus. After initial treatment, which included radiation therapy, 20 patients (48%) had died. In all seven cases of mature teratomas there was no recurrence. In two cases of immature teratomas in which there was complete surgical resection there was recurrence; however, salvage therapies were effective. Seven of eight patients with highly malignant teratomas died; for these patients salvage therapies, including repeated radiation and chemotherapy, failed. Seven patients who presented with CNS teratomas between 1992 and 1996 received adjuvant chemotherapy and radiation therapy according to a prospective study protocol. All seven patients were free from recurrence with a 70 to 100% Karnofsky Performance Scale score at a median follow-up period of 41 months. Patients with CNS teratomas rarely responded completely to chemotherapy or radiation therapy; an effective adjuvant therapy produced a partial response at best. Conclusions. Because teratomas show various responses to adjuvant therapy, a misdiagnosis of their histological subtype will lead to inadequate therapy. A diverse therapeutic protocol based on histological diagnosis is necessary to plan appropriate management. Treatment recommendations are discussed in detail in the article.

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