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Jeon YJ, Youk ES, Lee SH, Suh J, Na YJ, Kim HM. Polychlorinated biphenyl-induced apoptosis of murine spleen cells is aryl hydrocarbon receptor independent but caspases dependent. Toxicol Appl Pharmacol 2002; 181:69-78. [PMID: 12051990 DOI: 10.1006/taap.2002.9389] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants and many of their toxic effects, including their immunotoxicities, are mediated by the activation of aryl hydrocarbon receptor (AhR). We previously reported that Aroclor 1254, one of the most widely used PCB mixtures, increased DNA fragmentation in mouse spleen cells, suggesting that apoptosis was correlated with the immunotoxicity of PCB (Yoo et al., Toxicol. Lett. 91, 83-89, 1997). In the present study we investigated the mechanism by which PCB induces apoptosis and the involvement of AhR in the PCB-mediated apoptosis of mouse spleen cells. Aroclor 1254 induced DNA fragmentation without AhR activation, and the apoptosis was unaffected by alpha-naphtoflavone, a well-known antagonist of AhR. Moreover, the PCB congeners (PCB 47, 52, 128, and 153), which have little affinity for AhR, induced DNA fragmentation, whereas congeners (PCB 77, 126, and 169) that have high affinity for AhR did not induce fragmentation. The di-ortho form of PCB (PCB 153) and Aroclor 1254 induced DNA fragmentation in the spleen cells of both AhR knockout mice and Ah low-response mice, whereas the non-ortho form of PCB (PCB 126) did not induce DNA fragmentation. In the light of these findings, it is evident that AhR is not involved in PCB-mediated apoptosis. PCB 153 significantly increased caspase-3 activity in both spleen cells and human leukemia cells, and z-VAD-fmk, a general inhibitor of caspases, prevented PCB-induced DNA fragmentation. Based on our findings, the most likely mechanism that can account for this biological effect involves the induction of caspase-dependent apoptotic cell death.
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Affiliation(s)
- Young Jin Jeon
- Department of Pharmacology, Chosun University School of Medicine, 375 Susukdong, Kwangju, Korea
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2
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Abstract
The biochemical pathways to cell death in chronic and acute forms of neurodegeneration are poorly understood, limiting the ability to develop effective therapeutic approaches. As details of the apoptotic and necrotic pathways have been revealed, an appreciation for the decisive role that mitochondria play in life-death decisions for the cell has grown. As a result, the need has arisen to reevaluate the significance to cell viability of mitochondrial Ca2+ sequestration, reactive oxygen species generation, and the membrane permeability transition. This review provides basic information on these mitochondrial functions as they relate to control over cell death.
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Affiliation(s)
- A N Murphy
- MitoKor, San Diego, California 92121, USA
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3
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Abstract
Although assessments of metabolic activation are central to studies of beta-cell function, available techniques are tedious, insensitive, and/or require cell disruption. We have investigated the use of a new water-soluble tetrazolium salt, MTS (3-[4,5,dimethylthiazol-2-yl]-5-[3-carboxymethoxy-phenyl]-2-[4- sulfophenyl]-2H-tetrazolium, inner salt), in the presence of phenazine methosulfate (PMS), an intermediate electron acceptor that amplifies its signal (fluorescence at 490 nm). During static incubations of glucose-responsive (HIT-T15 or INS-1) dispersed beta cells with increasing glucose concentrations, there was a progressive increase in MTS reduction, with a maximum signal-to-noise (S/N) ratio of 24 with HIT-T15 cells and 10 with INS-1 cells. This was associated with, but not attributable to, parallel increases in insulin secretion. Pure mitochondrial fuels (alpha-ketoisocaproate [KIC], methyl pyruvate [MP], or L-glutamine [GLN] + L-leucine [LEU]) also increased the reduction of MTS in INS-1 cells (6.5-, 4.8-, and 14.4-fold, respectively), but generally less than glucose, suggesting a major role of glycolysis in the signal induced by glucose. Inhibitors of glucose metabolism (mannoheptulose [MH], lodoacetate [IA], or 2-deoxyglucose [2-DG]) markedly reduced the glucose-stimulated MTS signal. In comparison to another tetrazolium compound, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), MTS assay provided a better S/N ratio with glucose or other nutrient secretagogues. Extant theory holds that activation of mitochondrial dehydrogenases by increments in Ca2+ influx couples glycolysis to mitochondrial oxidation of glucose-derived fuels. However, reduction of fuel-induced calcium influx (by Ca2+-free medium or diazoxide [DZX]) or direct stimulation of calcium influx (by 40 mmol/L K+) failed to significantly modulate the signal, arguing against this theory. We conclude that the MTS assay is a facile test that reflects the global metabolic function of insulin-secreting beta cells. Furthermore, since this assay does not require disruption of cells to solubilize the formazan product, and therefore also allows concomitant measurement of insulin secretion, it offers considerable advantages over earlier methods.
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Affiliation(s)
- V B Segu
- Section of Endocrinology and the Medical Service, William S. Middleton Memorial Veterans Administration Hospital, Madison, WI, USA
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4
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Petit PX, Susin SA, Zamzami N, Mignotte B, Kroemer G. Mitochondria and programmed cell death: back to the future. FEBS Lett 1996; 396:7-13. [PMID: 8906857 DOI: 10.1016/0014-5793(96)00988-x] [Citation(s) in RCA: 401] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Programmed cell death, or apoptosis, has in the past few years undoubtedly become one of the most intensively investigated biological processes. However, fundamental questions concerning the molecular and biochemical mechanisms remain to be elucidated. The central question concerns the biochemical steps shared by the numerous death induction pathways elicited by different stimuli. Heterogeneous death signals precede a common effector phase during which cells pass a threshold of 'no return' and are engaged in a degradation phase where they acquire the typical onset of late apoptosis. Alterations in mitochondrial permeability transition linked to membrane potential disruption precede nuclear and plasma membrane changes. In vitro induction of permeability transition in isolated mitochondria provokes the release of a protein factor capable of inducing nuclear chromatin condensation and fragmentation. This permeability transition is regulated by multiple endogenous effectors, including members of the bcl-2 gene family. Inhibition of these effects prevents apoptosis.
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Affiliation(s)
- P X Petit
- Centre de Génétique Moléculaire, CNRS UPR 2420, Gif-sur-Yvette, France.
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5
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Murphy AN, Bredesen DE, Cortopassi G, Wang E, Fiskum G. Bcl-2 potentiates the maximal calcium uptake capacity of neural cell mitochondria. Proc Natl Acad Sci U S A 1996; 93:9893-8. [PMID: 8790427 PMCID: PMC38525 DOI: 10.1073/pnas.93.18.9893] [Citation(s) in RCA: 327] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Expression of the human protooncogene bcl-2 protects neural cells from death induced by many forms of stress, including conditions that greatly elevate intracellular Ca2+. Considering that Bcl-2 is partially localized to mitochondrial membranes and that excessive mitochondrial Ca2+ uptake can impair electron transport and oxidative phosphorylation, the present study tested the hypothesis that mitochondria from Bcl-2-expressing cells have a higher capacity for energy-dependent Ca2+ uptake and a greater resistance to Ca(2+)-induced respiratory injury than mitochondria from cells that do not express this protein. The overexpression of bcl-2 enhanced the mitochondrial Ca2+ uptake capacity using either digitonin-permeabilized GT1-7 neural cells or isolated GT1-7 mitochondria by 1.7 and 3.9 fold, respectively, when glutamate and malate were used as respiratory substrates. This difference was less apparent when respiration was driven by the oxidation of succinate in the presence of the respiratory complex I inhibitor rotenone. Mitochondria from Bcl-2 expressors were also much more resistant to inhibition of NADH-dependent respiration caused by sequestration of large Ca2+ loads. The enhanced ability of mitochondria within Bcl-2-expressing cells to sequester large quantities of Ca2+ without undergoing profound respiratory impairment provides a plausible mechanism by which Bcl-2 inhibits certain forms of delayed cell death, including neuronal death associated with ischemia and excitotoxicity.
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Affiliation(s)
- A N Murphy
- Department of Biochemistry and Molecular Biology, George Washington University Medical Center, Washington, DC 20037, USA.
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6
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Smets LA, van den Berg JD. Bcl-2 expression and glucocorticoid-induced apoptosis of leukemic and lymphoma cells. Leuk Lymphoma 1996; 20:199-205. [PMID: 8624457 DOI: 10.3109/10428199609051608] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The lytic response of lymphoid cells to glucocorticoid hormones (GC) is prototypical of the induction of apoptosis: a special form of cellular demise for the removal of unwanted or redundant cells. Initiation and execution of a death programme are therefore major checkpoints in GC-sensitivity. Although Bcl-2 protein can prevent or delay apoptosis of lymphoma and leukemia cells, exposed to multiple cytotoxic agents, its antagonism of GC-induced apoptosis appears most critical in conferring resistance to corticosteroids. Moreover, Bcl-2 may modulate GC-signalling to apoptosis through its association with fundamental cellular processes such as energy state, Ca2+ homeostasis and transmembrane transport. However, this signalling pathway can also be interrupted by Bcl-2- independent mechanisms. This review discusses the various cellular and oncogenetic factors that control GC sensitivity of leukemia/lymphoma cells and proposes a hypothesis of how GC may induce a death programme, sensitive to blockade by Bcl-2.
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Affiliation(s)
- L A Smets
- Division of Experimental Therapy, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Huis, Amsterdam, The Netherlands
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7
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Wang JF, Jerrells TR, Spitzer JJ. Decreased production of reactive oxygen intermediates is an early event during in vitro apoptosis of rat thymocytes. Free Radic Biol Med 1996; 20:533-42. [PMID: 8904294 DOI: 10.1016/0891-5849(95)02085-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Thymocyte apoptosis is one of the best characterized experimental models of apoptosis that can be induced by a variety of stimuli such as glucocorticoids, ionizing radiation, antibodies, and toxins. Recently, it has been suggested that oxidative stress is a common mediator of apoptosis. However, little is known about the production and possible function of reactive oxygen intermediates (ROI) in thymocytes. We used a highly sensitive flow cytometric assay with the hydrogen peroxide-sensitive dye, 2',7'-dichlorofluorescin diacetate (DCFH-DA), to measure intracellular ROI production in rat thymocytes, to study its primary sources, and to compare ROI levels in normal and apoptotic thymocytes. Apoptosis was induced by incubating the cells in the presence or absence of dexamethasone (Dex) at 37 degrees C in vitro. Normal thymocytes spontaneously produced significant amounts of ROI. Catalase or superoxide dismutase did not affect this intracellular fluorescence, presumably due to their failure to penetrate into the cells. However, N-acetyl-L-cysteine significantly attenuated the fluorescence in a dose-dependent manner. Significant inhibition of the intracellular fluorescence was also observed by addition of N-nitro-L-arginine methyl ester (L-NAME), that could not be reversed by L-arginine. The addition of N-nitro-D-arginine methyl ester (D-NAME) also caused considerable inhibition. This indicates that the inhibition by L-NAME or D-NAME is due to a direct scavenging effect, and nitric oxide production is not likely to be involved. In contrast to neutrophils and macrophages whose superoxide anions are released from membrane-bound NADPH oxidase, the production of ROI in thymocytes is likely to originate mainly from mitochondria, as indicated by the inhibitory effect of the addition of rotenone or antimycin A. The addition of lymphocyte simulators phytohemagglutinin (PHA), concanavalin A (Con A), or phorbol 12-myristate 13-acetate (PMA) enhanced intracellular fluorescence of thymocytes. This increase was abrogated by addition of rotenone or antimycin A. The ROI production was decreased with time after incubation of the thymocytes for 1, 3, and 6 h in vitro. The appearance of apoptosis of thymocytes in vitro, as indicated by DNA content of cells by flow cytometry and DNA ladder formation in agarose gel electrophoresis, was delayed, as compared to the time course of the decreased ROI production. The addition of Dex to the culture medium accelerated both of these processes. The results suggest that a decreased spontaneous production of ROI in thymocytes precedes the spontaneous in vitro apoptosis and Dex exaggerates these changes.
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Affiliation(s)
- J F Wang
- Department of Physiology, Louisiana State University Medical Center, New Orleans 70112-1393, USA
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8
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Minegishi M, Minegishi N, Yanagisawa T, Tsuchiya S, Tezuka H, Kaji M, Nakamura M, Hayashi Y, Konno T. A human CD4- CD8- T-cell receptor alpha beta + T leukemic cell line undergoing phytohemagglutinin-induced apoptosis. Leuk Res 1995; 19:433-42. [PMID: 7543637 DOI: 10.1016/0145-2126(95)00016-h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A human CD4- CD8- alpha beta T-cell receptor (TCR alpha beta)+ T leukemic cell line, L-KAW, was established from the peripheral blood of a 6-year-old male patient with T-cell acute lymphoblastic leukemia. Its phenotype was found to be CD7+CD2+CD3+CD4-CD8- TCR alpha beta +. The cell line proved susceptible to killing by exposure to a mitogenic concentration of phytohemagglutinin (PHA) within several hours, with biochemical analyses demonstrating extensive degradation of DNA to oligonucleosomal bands characteristic of apoptosis. Chromatin condensation and cell shrinkage features of apoptotic cells could also be clearly identified under the electron microscope. The apoptosis-related Fas antigen was expressed on L-KAW cells and DNA fragmentation was induced by incubation with anti-Fas monoclonal antibody. The c-myc mRNA levels declined within 15 min to 3 h after the addition of PHA. These results suggest that L-KAW cells are specifically sensitive to induction of apoptosis in response to PHA without preactivation. They may, therefore, be considered an analog of activated T-cells and prove useful as a model system for characterizing biochemical and molecular mechanisms underlying the process of this type of cell death.
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MESH Headings
- Antibodies/immunology
- Antigens, CD/immunology
- Antigens, Surface/immunology
- Apoptosis/drug effects
- Apoptosis/immunology
- Child
- DNA, Neoplasm/metabolism
- Gene Rearrangement, delta-Chain T-Cell Antigen Receptor
- Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor
- Humans
- Immunophenotyping
- Leukemia-Lymphoma, Adult T-Cell/immunology
- Leukemia-Lymphoma, Adult T-Cell/metabolism
- Male
- Phytohemagglutinins/pharmacology
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins c-bcl-2
- Proto-Oncogene Proteins c-myc/genetics
- RNA, Messenger/genetics
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Tumor Cells, Cultured
- fas Receptor
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Affiliation(s)
- M Minegishi
- Department of Pediatric Oncology, Tohoku University, Sendai, Japan
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9
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Petit PX, Lecoeur H, Zorn E, Dauguet C, Mignotte B, Gougeon ML. Alterations in mitochondrial structure and function are early events of dexamethasone-induced thymocyte apoptosis. J Cell Biol 1995; 130:157-67. [PMID: 7790370 PMCID: PMC2120516 DOI: 10.1083/jcb.130.1.157] [Citation(s) in RCA: 465] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In this paper we used a multiparametric approach to analyze extensively the events occurring during apoptotic cell death of thymocytes, and furthermore, we asked whether alterations in mitochondrial structure and function are occurring in early stages of apoptosis. A multiparametric quantitative analysis was performed on normal or apoptotic thymocytes emerging from a few-hour culture performed in culture medium or in the presence of dexamethasone. Simultaneous detection of light scattering properties, integrity of plasma membrane (trypan blue exclusion), chromatin condensation (AO/EB staining of entire cells or PI staining of nuclei), and DNA fragmentation (in situ nick-translation in apoptotic cells) allowed a precise analysis of the preapoptotic and apoptotic stages. Moreover a thorough study of mitochondrial transmembrane potential (delta psi m) assessed following in a time course study the uptake by apoptotic cells of the cationic lipophilic dye DiOC6(3) or the J-aggregate-forming cation JC-1, indicates that a drop in delta psi m occurs very early in thymocyte apoptosis, before DNA fragmentation. This is associated with alteration in mitochondrial structure assessed by cytofluorimetric study of NAO uptake in apoptotic cells. Finally these dramatic alterations in mitochondrial structure and function occurring in early stages of apoptosis were confirmed by confocal and electron microscopy analysis.
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Affiliation(s)
- P X Petit
- Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France
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10
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Zamzami N, Marchetti P, Castedo M, Zanin C, Vayssière JL, Petit PX, Kroemer G. Reduction in mitochondrial potential constitutes an early irreversible step of programmed lymphocyte death in vivo. J Exp Med 1995; 181:1661-72. [PMID: 7722446 PMCID: PMC2192017 DOI: 10.1084/jem.181.5.1661] [Citation(s) in RCA: 909] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In a number of experimental systems in which lymphocyte depletion was induced by apoptosis-inducing manipulations, no apoptotic morphology and ladder-type DNA fragmentation were detected among freshly isolated peripheral lymphocytes ex vivo. Here we report that one alteration that can be detected among splenocytes stimulated with lymphocyte-depleting doses of dexamethasone (DEX) in vivo is a reduced uptake of 3,3'dihexyloxacarbocyanine iodide (DiOC6[3]), a fluorochrome which incorporates into cells dependent upon their mitochondrial transmembrane potential (delta psi m). In contrast, ex vivo isolated splenocytes still lacked established signs of programmed cell death (PCD):DNA degradation into high or low molecular weight fragments, ultrastructural changes of chromatin arrangement and endoplasmatic reticulum, loss in viability, or accumulation of intracellular peroxides. Moreover, no changes in cell membrane potential could be detected. A reduced delta psi m has been observed in response to different agents inducing lymphoid cell depletion in vivo (superantigen and glucocorticoids [GC]), in mature T and B lymphocytes, as well as their precursors. DEX treatment in vivo, followed by cytofluorometric purification of viable delta psi mlow splenic T cells ex vivo, revealed that this fraction of cells is irreversibly committed to undergoing DNA fragmentation. Immediately after purification neither delta psi mlow, nor delta psi mhigh cells, exhibit detectable DNA fragmentation. However, after short-term culture (37 degrees C, 1 h) delta psi mlow cells show endonucleolysis, followed by cytolysis several hours later. Incubation of delta psi mlow cells in the presence of excess amount of the GC receptor antagonist RU38486 (which displaces DEX from the GC receptor), cytokines that inhibit DEX-induced cell death, or cycloheximide fails to prevent cytolysis. The antioxidant, N-acetylcysteine, as well as linomide, an agent that effectively inhibits DEX or superantigen-induced lymphocyte depletion in vivo, also stabilize the DiOC6(3) uptake. In contrast, the endonuclease inhibitor, aurintricarboxylic acid acts at later stages of apoptosis and only retards the transition from the viable delta psi mlow to the nonviable fraction. Altogether, these data suggest a sequence of PCD-associated events in which a reduction in delta psi m constitutes an obligate irreversible step of ongoing lymphocyte death, preceding other alterations of cellular physiology, and thus allowing for the ex vivo assessment of PCD.
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Affiliation(s)
- N Zamzami
- Centre National de la Recherche Scientifique-UPR 420, Villejuif, France
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11
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12
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Vayssiere JL, Petit PX, Risler Y, Mignotte B. Commitment to apoptosis is associated with changes in mitochondrial biogenesis and activity in cell lines conditionally immortalized with simian virus 40. Proc Natl Acad Sci U S A 1994; 91:11752-6. [PMID: 7972136 PMCID: PMC45310 DOI: 10.1073/pnas.91.24.11752] [Citation(s) in RCA: 239] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Rodent embryo cells immortalized with temperature-sensitive mutants of simian virus 40 large tumor (T) antigen have a proliferative potential that depends on temperature. At the restrictive temperature, heat-inactivation of large T antigen causes p53 release, growth arrest, and cell death. Morphological and molecular analysis indicate that the induced cell death corresponds to apoptosis. Flow cytometric analysis using a combination of forward light scatter and side scatter allows a discrimination of cells committed to apoptosis within the whole population. These cells display a reduction in cell size and a higher cellular density, confirming the apoptotic nature of the cell death. When cells exhibiting the morphological features of apoptosis were stained with a fluorescent probe of the mitochondrial membrane potential, a decreased accumulation of the dye was recorded. Measures of cellular respiration, performed with whole-cell populations, showed that the lower mitochondrial membrane potential (delta psi m) correlates, as expected, with an uncoupling of electron transport from ATP production and is linked to the induction of apoptosis. We also show that this decrease in delta psi m is associated with a decrease in the rate of mitochondrial translation. These events are detected at early stages of the apoptotic process, when most of the cells are not irreversibly committed to death, suggesting that mitochondria could be a primary target during apoptosis.
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Affiliation(s)
- J L Vayssiere
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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13
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Kroemer G, Martínez C. Pharmacological inhibition of programmed lymphocyte death. IMMUNOLOGY TODAY 1994; 15:235-42. [PMID: 8024684 DOI: 10.1016/0167-5699(94)90249-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Programmed cell death (PCD) is a necessary process that helps to regulate the lifespan of lymphocytes and maintain the compartmental balance of lymphoid organs. In addition, PCD is required for the generation and maintenance of self-tolerance. Strategies that inhibit PCD cause profound alterations in the (patho)physiology of the immune system. Here, Guido Kroemer and Carlos Martínez-A. discuss the multiplicity of PCD-inducing pathways, which have been revealed through the use of PCD-inhibitory agents, and analyse the levels at which these agents act.
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14
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Parry SL, Holman MJ, Hasbold J, Klaus GG. Plastic-immobilized anti-mu or anti-delta antibodies induce apoptosis in mature murine B lymphocytes. Eur J Immunol 1994; 24:974-9. [PMID: 7512037 DOI: 10.1002/eji.1830240429] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
It is widely accepted that extensive cross-linking of surface immunoglobulin (sIg) receptors on mature B cells promotes their activation and progression through the cell cycle. A commonly employed method to maximize receptor cross-linking via anti-receptor antibodies is to immobilize them on tissue culture plastic. We show here that immobilizing monoclonal anti-mu or anti-delta antibodies, which are mitogenic in solution, on plastic abrogates their capacity to induce DNA synthesis in mature murine B cells, even in the presence of interleukin-4 (IL-4). The cells do become abortively activated, as evidenced by up-regulation of major histocompatibility complex class II antigen levels, but subsequently virtually all of them die, manifesting DNA fragmentation characteristic of apoptosis. The induction of apoptosis is abrogated by the inclusion of either IL-4 or anti-CD40 antibodies in the cultures, with the two stimuli acting in concert. We believe that the system represents a polyclonal model of clonal deletion tolerance in mature B cells, such as may be induced under physiological conditions by antigens with repeating epitopes.
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Affiliation(s)
- S L Parry
- National Institute for Medical Research, London
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15
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Wahl C, Miethke T, Heeg K, Wagner H. Clonal deletion as direct consequence of an in vivo T cell response to bacterial superantigen. Eur J Immunol 1993; 23:1197-200. [PMID: 8477814 DOI: 10.1002/eji.1830230536] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To date clonal deletion of peripheral mature T cells is restricted to in vivo model systems characterized by prolonged exposure of mice to antigens and clonal T cell expansion preceding clonal deletion. Here we describe that upon challenge of mice with the superantigen staphylococcal enterotoxin B two immediate events become imposed on ligand-reactive V beta 8+ T cells in lymph node cells draining the local site of injection. First, and within hours V beta selective clonal deletion is initiated via an apoptotic process. Second, the remaining V beta 8+ T cells first develop a profound state of ligand-specific unresponsiveness and subsequently initiate clonal in vivo growth. It is suggested that the dichotomy of events observed reflects a direct consequence of T cell receptor occupancy in the context of inappropriate signalling.
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Affiliation(s)
- C Wahl
- Institute of Medical Microbiology and Hygiene, Technical University of Munich, FRG
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16
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Evidence that glucocorticoid- and cyclic AMP-induced apoptotic pathways in lymphocytes share distal events. Mol Cell Biol 1992. [PMID: 1378529 DOI: 10.1128/mcb.12.8.3600] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
WEHI7.2 murine lymphocytes undergo apoptotic death when exposed to glucocorticoids or elevated levels of intracellular cyclic AMP (cAMP), and these pathways are initiated by the glucocorticoid receptor (GR) and protein kinase A, respectively. We report the isolation and characterization of a novel WEHI7.2 variant cell line, WR256, which was selected in a single step for growth in the presence of dexamethasone and arose at a frequency of approximately 10(-10). The defect was not GR-related, as WR256 expressed functional GR and underwent GR-dependent events associated with apoptosis, such as hormone-dependent gene transcription and inhibition of cell proliferation. Moreover, the glucocorticoid-resistant phenotype was stable in culture and did not revert after treatment with 5-azacytidine or upon stable expression of GR cDNA. In addition, WR256 did not exhibit the diminished mitochondrial activity commonly associated with apoptosis. Interestingly, WR256 was also found to be resistant to 8-bromo-cAMP and forskolin despite having normal levels of protein kinase A activity and the ability to induce cAMP-dependent transcription. We examined the steady-state transcript levels of bcl-2, a gene whose protein product acts dominantly to inhibit thymocyte apoptosis, to determine whether elevated bcl-2 expression could account for the resistant phenotype. Our data showed that bcl-2 RNA levels were similar in the two cell lines and not altered by either dexamethasone or 8-bromo-cAMP treatment. These results suggest that WR256 exhibits a "deathless" phenotype and has a unique defect in a step of the apoptotic cascade that may be common to the glucocorticoid- and cAMP-mediated cell death pathways.
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17
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Dowd DR, Miesfeld RL. Evidence that glucocorticoid- and cyclic AMP-induced apoptotic pathways in lymphocytes share distal events. Mol Cell Biol 1992; 12:3600-8. [PMID: 1378529 PMCID: PMC364626 DOI: 10.1128/mcb.12.8.3600-3608.1992] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
WEHI7.2 murine lymphocytes undergo apoptotic death when exposed to glucocorticoids or elevated levels of intracellular cyclic AMP (cAMP), and these pathways are initiated by the glucocorticoid receptor (GR) and protein kinase A, respectively. We report the isolation and characterization of a novel WEHI7.2 variant cell line, WR256, which was selected in a single step for growth in the presence of dexamethasone and arose at a frequency of approximately 10(-10). The defect was not GR-related, as WR256 expressed functional GR and underwent GR-dependent events associated with apoptosis, such as hormone-dependent gene transcription and inhibition of cell proliferation. Moreover, the glucocorticoid-resistant phenotype was stable in culture and did not revert after treatment with 5-azacytidine or upon stable expression of GR cDNA. In addition, WR256 did not exhibit the diminished mitochondrial activity commonly associated with apoptosis. Interestingly, WR256 was also found to be resistant to 8-bromo-cAMP and forskolin despite having normal levels of protein kinase A activity and the ability to induce cAMP-dependent transcription. We examined the steady-state transcript levels of bcl-2, a gene whose protein product acts dominantly to inhibit thymocyte apoptosis, to determine whether elevated bcl-2 expression could account for the resistant phenotype. Our data showed that bcl-2 RNA levels were similar in the two cell lines and not altered by either dexamethasone or 8-bromo-cAMP treatment. These results suggest that WR256 exhibits a "deathless" phenotype and has a unique defect in a step of the apoptotic cascade that may be common to the glucocorticoid- and cAMP-mediated cell death pathways.
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Affiliation(s)
- D R Dowd
- Department of Biochemistry, University of Arizona, Tucson 85724
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