Uptake Of Apoptotic Bodies Research Articles

Cytofluorometric assessment of dendritic cell-mediated uptake of cancer cell apoptotic bodies.

Dendritic cells (DCs) are specialized antigen presenting cells (APCs) able to intake and crosspresent antigens (Ags) on major histocompatibility complex (MHC) class I and II molecules to T cells thus initiating primary and memory immune responses. DC-mediated Ag uptake and crosspresentation represent crucial steps toward cancer recognition and eventually elimination. Cytofluorometry is a standardized procedure to study phagocytosis. By fast and reproducible single cell measurements, flow cytometry allows for simultaneous biochemical and functional analyses of Ag intake. In this chapter, we discuss a two-color flow cytometric analysis of DC-mediated uptake of apoptotic bodies. We also show data on the adjuvanticity of Type-I-interferons (Type-I-IFNs) during Ag retention as we offer a guideline and a range of advice on sample preparation and acquisition.

Implication of Apoptosis for the Pathogenesis of Trypanosoma cruzi Infection.

Apoptosis is induced during the course of immune response to different infectious agents, and the ultimate fate is the recognition and uptake of apoptotic bodies by neighboring cells or by professional phagocytes. Apoptotic cells expose specific ligands to a set of conserved receptors expressed on macrophage cellular surface, which are the main cells involved in the clearance of the dying cells. These scavenger receptors, besides triggering the production of anti-inflammatory factors, also block the production of inflammatory mediators by phagocytes. Experimental infection of mice with the parasite Trypanosoma cruzi shows many pathological changes that parallels the evolution of human infection. Leukocytes undergoing intense apoptotic death are observed during the immune response to T. cruzi in the mouse model of the disease. T. cruzi replicate intensely and secrete molecules with immunomodulatory activities that interfere with T cell-mediated immune responses and secretion of pro-inflammatory cytokine secretion. This mechanism of immune evasion allows the infection to be established in the vertebrate host. Under inflammatory conditions, efferocytosis of apoptotic bodies generates an immune-regulatory phenotype in phagocytes, which is conducive to intracellular pathogen replication. However, the relevance of cellular apoptosis in the pathology of Chagas’ disease requires further studies. Here, we review the evidence of leukocyte apoptosis in T. cruzi infection and its immunomodulatory mechanism for disease progression.

Anti-inflammatory response following uptake of apoptotic bodies by meningothelial cells

BackgroundMeningothelial cells (MECs) are the cellular components of the meninges. As such, they provide important barrier function for the central nervous system (CNS) building the interface between neuronal tissue and the cerebrospinal fluid (CSF), and are also part of the immune response of the CNS.MethodsHuman, immortalized MECs were analyzed by flow cytometry and confocal microscopy to study the uptake of apoptotic cells. Furthermore, cytokine and chemokine production by MECs was analyzed by cytokine array and ELISA.ResultsWe found that MECs are highly active phagocytes able of ingesting and digesting large amounts of apoptotic cells. Furthermore, the uptake of apoptotic cells by MECs was immune suppressive via inhibiting the secretion of pro-inflammatory and chemoattractant cytokines and chemokines IL-6, IL-8, IL-16, MIF, and CXCL1, while increasing the secretion of anti-inflammatory IL-1 receptor antagonist by MECs.ConclusionMECs respond with the secretion of anti-inflammatory cytokines and chemokines following the uptake of apoptotic cells potentially connecting these cells to processes important for the shut-down of immune responses in the brain.

The Death Pathways in the Neonatal Gut

Dynamic equilibrium between apoptosis and mitosis facilitates growth and development of the intestinal mucosa in mammalian neonates. Groups of enterocytes observed dying together on the villi in the gut of the neonates suggest involvement of the paracrine factors in the propagation of the death signalling. The most potent death-inducing, paracrine factor for the enterocytes is the TGF-β. It is secreted from the macrophages and epithelial cells upon uptake of apoptotic bodies. Through its receptor complex (TGF-R I and II) and SMAD cascade it regulates the intracellular balance of the pro- and antiapoptotic proteins from the Bcl-2 family, sensitising enterocytes for other death signals (i. e. TNFα) and directing them towards apoptosis. Just before and after birth mitosis-to-apoptosis ratio shifts towards proliferation. First ingestion of colostrum, initiates the major remodelling of the gut mucosa. Apoptosis is enhanced, facilitating the removal of foetal-type enterocytes and closing of the gut barrier. Second major remodelling stage occurs after weaning, when the adaptation to the ingestion of solid foods takes place. Proliferation and cell death in the intestinal mucosa are under the direct control of a variety of growth factors (EGF, IGFs, TGF-βs) and tissue hormones (leptin, ghrelin, GLP, CCK, etc.) provided either by mothers colostrum and milk or produced in the neonate organism. Finally, uncontrolled apoptosis may lead to the weakening of the gut barrier, which results in the increased susceptibility to the intestinal disorders, pathogen infiltration and may lead to the development of the necrotising enterocolitis in the infants.

Horizontal gene transfer: You are what you eat

Horizontal or lateral gene transfer is an effective mechanism for the exchange of genetic information in bacteria allowing bacterial diversification and facilitating adaptation to new environments. Recent data demonstrate that DNA may also be transferred between somatic cells via the uptake of apoptotic bodies. This process allows transfer of viral genes that have been incorporated into the genome in a receptor-independent fashion. Transferred DNA is replicated and propagated in daughter cells in cell that have an inactivated DNA response which may impact tumor progression.

Purinergic receptor agonists modulate phagocytosis and clearance of apoptotic cells in macrophages

Phagocytosis plays an important role in controlling inflammation and antigen cross-presentation through the uptake of apoptotic bodies from dying cells. As dying cells are known to release nucleotides and other “danger signals”, we investigated whether extracellular nucleotides may affect phagocytosis through binding to P2 purinergic receptors on phagocytic cells. We here show that the purinergic receptor agonists, ATP, ADP, α,β-methylene ATP (α,β-meATP), 3′-O-(4-benzoyl)benzoyl ATP, UTP and UDP, increased phagocytosis of latex beads, and some of them increased endocytosis and/or macropinocytosis of dextran by macrophages. The enhanced phagocytosis could be inhibited by pre-treatment with the P2X and P2Y antagonists, pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid and suramin, and the P2Y 1-selective antagonist, MRS2179. The nucleotides induced upregulation in macrophages of the β2 integrin CD11b/CD18 (Mac-1) and the vitronectin receptor (α vβ3, CD51/CD61), both of which are involved in recognition and internalization of apoptotic cells. In addition, ATP and α,β-meATP increased adhesion of apoptotic cells to macrophages, both in vitro and in vivo, and α,β-meATP had a small effect on adhesion of necrotic cells. The nucleotides had no effect on adhesion of viable cells. We propose that engagement of the P2 receptors (P2X 1, or P2X 3) by extracellular nucleotides released from dying cells increases the ability of macrophages to bind apoptotic bodies, thus enhancing their ability to internalize and present antigens from the dying cells.

P19-05. Use of autologous apoptotic pseudovirus infected cells for vaccination against HIV, evaluation in macaques

Background Antigen-presenting dendritic cells (DC) present viral antigens to T-cells after uptake of apoptotic bodies derived from virus-infected cells. Besides, processing and presentation of ingested antigen, DC were recently shown to be able to incorporate part of the DNA from the apoptotic cells into their own chromosomes and express the encoded antigens. This mechanism could lead to a more efficient presentation of foreign antigens and activation of antigen specific naive T-cells. It was recently exploited for induction of HIV specific immune responses in a HIV-1/ MuLV mouse infection model.

Impaired receptor‐mediated endocytosis: Its role in alcohol‐induced apoptosis

Hepatocyte apoptosis, inflammation, and fibrosis are prominent features of liver disease in general and of alcoholic liver injury in particular. Although the link between these processes remains unclear, one universal characteristic of liver injury is the induction of hepatocellular damage, which results in the generation of apoptotic bodies. Work from our laboratory over the last several years has studied the effect of ethanol administration on the process of apoptosis and a role for altered endocytosis in alcoholic apoptosis. We initially focused our research on the hepatocyte by examining endocytosis using the asialoglycoprotein receptor (ASGP-R) pathway as a model and we identified multiple ethanol-induced impairments in receptor function. We also showed that uptake of apoptotic bodies is impaired in hepatocytes isolated from ethanol-fed animals compared to controls, and that this impairment is linked to altered ASGP-R function. Recent work from our laboratory is examining a link between ethanol-impaired ASGP-R function, apoptotic body accumulation, and inflammation in the liver. We are particularly interested in data showing that factors produced by Kupffer cells incubated with apoptotic bodies can lead to production of tumor necrosis factor-alpha and interleukin-6, and that this effect is exacerbated in the setting of alcohol administration. In addition, we have preliminary data showing that media from Kupffer cell cultures incubated with apoptotic bodies can induce hepatocyte killing. The goal of our future work is to show that inadequate removal of apoptotic cells, in part via altered receptor-mediated endocytosis, plays a role in the course of pathogenesis of alcoholic liver injury.

Regulation of mammalian horizontal gene transfer by apoptotic DNA fragmentation

Previously it was shown that horizontal DNA transfer between mammalian cells can occur through the uptake of apoptotic bodies, where genes from the apoptotic cells were transferred to neighbouring cells phagocytosing the apoptotic bodies. The regulation of this process is poorly understood. It was shown that the ability of cells as recipient of horizontally transferred DNA was enhanced by deficiency of p53 or p21. However, little is known with regard to the regulation of DNA from donor apoptotic cells. Here we report that the DNA fragmentation factor/caspase-activated DNase (DFF/CAD), which is the endonuclease responsible for DNA fragmentation during apoptosis, plays a significant role in regulation of horizontal DNA transfer. Cells with inhibited DFF/CAD function are poor donors for horizontal gene transfer (HGT) while their ability of being recipients of HGT is not affected.

Circulating Nucleic Acids in Plasma/Serum and Tumor Progression

The "genometastasis hypothesis" proposes that cell-free tumor nucleic acids might be able to transform host stem cells, and that this might be a pathway for the development of metastases. This theory is supported by previous experimental findings and is consistent with observations of other authors. It has been suggested that tumor DNA might be horizontally transferred by the uptake of apoptotic bodies and initiate the genetic changes that are necessary for tumor formation. In addition, apoptotic bodies have been proposed as possible vehicles that protect the nucleic acids circulating in the plasma from enzymatic degradation. In the present study, we analyzed the presence of apoptotic bodies in serum and its relationship with tumor progression in a heterotopic model of colon cancer in the rat. We injected DHD/K12-PROb cancer cells subcutaneously into BD-IX rats and divided the animals into three groups according to the time between the injection of tumor cells and euthanasia. A control group of healthy animals was included (n = 6). After euthanasia, macroscopic metastases were assessed and samples of blood were collected. To detect apoptotic bodies in the sera, each sample was mixed with FITC-conjugated annexin V antibody in combination with propidium iodide and then analyzed by flow cytometry. Detection of apoptotic bodies was only significantly increased in the sera of a few tumor-bearing animals in late stages of tumor development. Thus, such particles appear not to be the vehicle of the cell-free tumor nucleic acids that are detected at early stages of cancer.

DNase II and the Chk2 DNA Damage Pathway Form a Genetic Barrier Blocking Replication of Horizontally Transferred DNA

We have previously shown that DNA from dying tumor cells may be transferred to living cells via the uptake of apoptotic bodies and may contribute to tumor progression. DNA encoding H-ras(V12) and c-myc oncogenes may be transferred to the nucleus of the phagocyte but will only integrate and propagate in p53- and p21-deficient mouse embryonic fibroblasts, whereas normal cells are resistant to transformation. Here, we show that this protective mechanism (activation of p53 and p21 after uptake of apoptotic bodies) is dependent on DNA fragmentation, where inhibition of the caspase-activated DNase in the apoptotic cells, in conjunction with genetic ablation of lysosomal DNase II in the phagocytes, completely blocks p53 activation and consequently allows DNA replication of transferred DNA. We, therefore, suggest that there is a causal relationship between DNA degradation during apoptosis and p53 activation. In addition, we could further show that Chk2-/- cells were capable of replicating the hyg(R) gene taken up from engulfed apoptotic cells, suggesting involvement of the DNA damage response. These data show that the phagocytosing cell is sensing the degraded DNA within the apoptotic cell, hence preventing these genes from being replicated, probably through activation of the DNA damage response. We, therefore, hypothesize that DNase II together with the Chk2, p53, and p21 pathway form a genetic barrier blocking the replication of potentially harmful DNA introduced via apoptotic bodies, thereby preventing transformation and malignant development.

Partial construction of apoptotic pathway in PBMC obtained from active SLE patients and the significance of plasma TNF-α on this pathway

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder that affects various organs and systems. Increased apoptosis, together with defects in the uptake of apoptotic bodies, are thought to have a pathogenic role in SLE. By detection of chromatin condensation, 30% of apoptosis was detected in peripheral blood mononuclear cells (PBMC) from Thai patients with active SLE. Therefore, understanding of the molecular processes in PBMC apoptosis may allow us to gain insight into pathophysiology of SLE. Thus, genes involved in the apoptosis of PBMC from these patients were investigated ex vivo by cDNA array analysis. Seventeen apoptosis-related genes were stimulated in active SLE, more than twofold higher than in inactive SLE. These genes are classified into six groups, namely death receptors, death ligands, caspases, bcl-family, and neutral proteases and genes involved in endoplasmic reticulum stress-mediated apoptosis, such as caspase-4 and GADD153. Among those stimulated genes, tumor necrosis factor (TNF) and the TNF-receptor family were drastically up-regulated 60- and 19-fold higher than in healthy controls, respectively. Moreover, the degree of apoptosis correlated with the level of TNF-alpha in plasma, suggesting that the TNF family plays a role in the induction of apoptosis in SLE. To verify this hypothesis, PBMC from healthy individuals were treated with plasma from active SLE patients in the presence or absence of etanercept, a TNF inhibitor. In the presence of etanercept, active SLE plasma reduced the level of apoptosis to 26.43%. In conclusion, massive apoptotic death of PBMC occurred during the active stage of SLE. The molecular pathway of SLE-PBMC apoptosis was mediated at least via TNF/TNFR signaling pathway, which was confirmed by functional test of TNF-alpha in SLE patients' plasma.

Horizontal transfer of DNA by the uptake of apoptotic bodies.

Horizontal transfer of DNA by the uptake of apoptotic bodies.

Horizontal transfer of oncogenes by uptake of apoptotic bodies

Tumor formation involves the accumulation of a series of genetic alterations that are required for malignant growth. In most malignancies, genetic changes can be observed at the chromosomal level as losses or gains of whole or large portions of chromosomes. Here we provide evidence that tumor DNA may be horizontally transferred by the uptake of apoptotic bodies. Phagocytosis of apoptotic bodies derived from H-ras(V12)- and human c-myc-transfected rat fibroblasts resulted in loss of contact inhibition in vitro and a tumorigenic phenotype in vivo. Fluorescence in situ hybridization analysis revealed the presence of rat chromosomes or of rat and mouse fusion chromosomes in the nuclei of the recipient murine cells. The transferred DNA was propagated, provided that the transferred DNA conferred a selective advantage to the cell and that the phagocytotic host cell was p53-negative. These results suggest that lateral transfer of DNA between eukaryotic cells may result in aneuploidy and the accumulation of genetic changes that are necessary for tumor formation.

Functional Gene Transfer of HIV DNA by an HIV Receptor-Independent Mechanism

HIV-1 enters target cells mainly via binding to CD4 and its coreceptors. The presence of HIV-1 in CD4- cells suggests, however, that there exist other mechanisms for viral entry. Here it is reported that HIV-1 DNA may be transferred from one cell to another by uptake of apoptotic bodies in a CD4-independent way. This was investigated by coculturing CD4-, chemokine receptor CCR5- and CXCR4- human fetal fibroblasts with apoptotic HIV-1-infected HuT78 cells or apoptotic PBMC isolated from HIV-1-infected patients. After 2 wk of coculture, fibroblasts contained HIV-1 DNA and expressed HIV-1 proteins p24 and gp120. Transfer of HIV-1 DNA was verified by coculturing fibroblasts with apoptotic bodies derived from cells infected with a defective HIV-1 virus. These cells contain one integrated copy of a reverse transcriptase (RT)-negative HIV-1 strain (8E5/LAV RT- cells) and consequently cannot produce free virus. Intracellular HIV-1 gag DNA was detected in both fibroblasts and dendritic cells after coculture with apoptotic 8E5/LAV RT- cells. Transfer of viral DNA after uptake of apoptotic bodies may explain HIV-1 infection of CD4- cells in vivo and furthermore may be relevant for Ag presentation.

Dendritic cells infiltrating tumors cotransduced with granulocyte/macrophage colony-stimulating factor (GM-CSF) and CD40 ligand genes take up and present endogenous tumor-associated antigens, and prime naive mice for a cytotoxic T lymphocyte response.

We transduced BALB/c-derived C-26 colon carcinoma cells with granulocyte/macrophage colony-stimulating factor (GM-CSF) and CD40 ligand (CD40L) genes to favor interaction of these cells with host dendritic cells (DCs) and, therefore, cross-priming. Cotransduced cells showed reduced tumorigenicity, and tumor take was followed by regression in some mice. In vivo tumors were heavily infiltrated with DCs that were isolated, phenotyped, and tested in vitro for stimulation of tumor-specific cytotoxic T lymphocytes (CTLs). BALB/c C-26 carcinoma cells express the endogenous murine leukemia virus (MuLV) env gene as a tumor-associated antigen. This antigen is shared among solid tumors of BALB/c and C57BL/6 mice and contains two epitopes, AH-1 and KSP, recognized in the context of major histocompatibility complex class I molecules H-2Ld and H-2K(b), respectively. DCs isolated from C-26/GM/CD40L tumors grown in (BALB/c x C57BL/6)F1 mice (H-2d x b) stimulated interferon gamma production by both anti-AH-1 and KSP CTLs, whereas tumor-infiltrating DCs (TIDCs) of BALB/c mice stimulated only anti-AH-1 CTLs. Furthermore, TIDCs primed naive mice for CTL activity as early as 2 d after injection into the footpad, whereas double-transduced tumor cells required at least 5 d for priming; this difference may reflect direct DC priming versus indirect tumor cell priming. Immunohistochemical staining indicated colocalization of DCs and apoptotic bodies in the tumors. These data indicate that DCs infiltrating tumors that produce GM-CSF and CD40L can capture cellular antigens, likely through uptake of apoptotic bodies, and mature in situ to a stage suitable for antigen presentation. Thus, tumor cell-based vaccines engineered to favor the interaction with host DCs can be considered.

Horizontal Transfer of DNA by the Uptake of Apoptotic Bodies

AbstractIn this study we have raised the question of whether DNA can be transferred from one cell to another by phagocytosis of apoptotic bodies. We have used integrated copies of the Epstein-Barr virus (EBV) as a marker to follow the fate and expression pattern of apoptotic DNA in the phagocytotic host. Apoptosis was induced in EBV-carrying cell lines by irradiation before cultivation with either human fibroblasts, macrophages, or bovine aortic endothelial cells. Analysis of the expression pattern of EBV-encoded genes was performed by immunofluorescent staining as well as in situ hybridization. Cocultivation of apoptotic bodies from lymphoid cell lines containing integrated but not episomal copies of EBV resulted in expression of the EBV-encoded genes EBER and EBNA1 in the recipient cells at a high frequency. Fluorescence in situ hybridization analysis showed uptake of human chromatin as well as integrated EBV-DNA into the nuclei of bovine aortic endothelial cells. These data show that DNA may be rescued and reused from apoptotic bodies by somatic cells. In addition, our findings suggest that apoptotic bodies derived from EBV-carrying B lymphocytes may serve as the source of viral transfer to cells that lack receptors for the EBV virus in vivo.

Horizontal Transfer of DNA by the Uptake of Apoptotic Bodies

In this study we have raised the question of whether DNA can be transferred from one cell to another by phagocytosis of apoptotic bodies. We have used integrated copies of the Epstein-Barr virus (EBV) as a marker to follow the fate and expression pattern of apoptotic DNA in the phagocytotic host. Apoptosis was induced in EBV-carrying cell lines by irradiation before cultivation with either human fibroblasts, macrophages, or bovine aortic endothelial cells. Analysis of the expression pattern of EBV-encoded genes was performed by immunofluorescent staining as well as in situ hybridization. Cocultivation of apoptotic bodies from lymphoid cell lines containing integrated but not episomal copies of EBV resulted in expression of the EBV-encoded genes EBER and EBNA1 in the recipient cells at a high frequency. Fluorescence in situ hybridization analysis showed uptake of human chromatin as well as integrated EBV-DNA into the nuclei of bovine aortic endothelial cells. These data show that DNA may be rescued and reused from apoptotic bodies by somatic cells. In addition, our findings suggest that apoptotic bodies derived from EBV-carrying B lymphocytes may serve as the source of viral transfer to cells that lack receptors for the EBV virus in vivo.