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Diaz, Cecilia; Lee, Anh Tuyet; McConkey, David J; Schroit, Alan J
doi: 10.1038/sj.cdd.4400484pmid: 10200572
K562 erythroleukemia cells undergo apoptosis when induced to differentiate along the erythroid lineage with hemin. This event, characterized by DNA fragmentation, correlated with downregulation of the survival protein, BCL-xL, and decrease in mitochondrial transmembrane potential (ΔΨm) that ultimately resulted in cell death. Reorientation of phosphatidylserine (PS) from the cells inner-to-outer plasma membrane leaflet and inhibition of the aminophospholipid translocase was observed upon hemin-treatment. Constitutive expression of BCL-2 did not inhibit hemin-induced alterations in lipid asymmetry or decrease in ΔΨm, and only moderately prevented DNA fragmentation. BCL-2, on the other hand, effectively inhibited actinomycin D-induced DNA fragmentation, the appearance of PS at the cells outer leaflet and the decrease in ΔΨm. The caspase inhibitor, z.VAD.fmk, blocked DNA fragmentation by both hemin and actinomycin D, but inhibited PS externalization only in the actinomycin D-treated cells. These results suggest that, unlike pharmacologically-induced apoptosis, PS externalization triggered by differentiation-induced apoptosis occurs by a mechanism that is associated with a decrease in ΔΨm, but independent of BCL-2 and caspases.
Mehlen, Patrick; Coronas, Valérie; Ljubic-Thibal, Vesna; Ducasse, Cécile; Granger, Laure; Jourdan, Francois; Arrigo, André-Patrick
doi: 10.1038/sj.cdd.4400483pmid: 10200573
The small stress protein Hsp27 is expressed during mammalian neural development. We have analyzed the role of this protein in immortalized rat olfactory neuroblasts. In the presence of dopamine a fraction of these cells differentiate into neurons while the remaining cells undergo apoptosis. We report here that the dopamine induced differentiation and apoptosis are associated with a transient and specific accumulation of Hsp27. Moreover, transfection experiments have shown that Hsp27 overexpression drastically decreases the fraction of cells undergoing apoptosis. In contrast, reduction of the endogenous level of Hsp27 led to abortion of differentiation and, therefore, drastically increased the number of apoptotic cells. Furthermore, in the normal cell population we show that Hsp27 accumulation takes place only in differentiating cells that were not undergoing apoptosis. We therefore conclude that Hsp27 may represent a key protein that controls the decision of olfactory precursor cells to undergo either differentiation or cell death.
Torriglia, Alicia; Negri, Claudia; Chaudun, Elisabeth; Prosperi, Ennio; Courtois, Yves; Counis, Marie France; Scovassi, A Ivana
doi: 10.1038/sj.cdd.4400486pmid: 10200574
We have applied to human HeLa cells two different stimuli of apoptosis: the antitumoral drug etoposide, and a more ‘physiological’ death condition, obtained by growing cells in the same medium for long time periods, for up to 10 days. Analysis of different parameters demonstrated that in both experimental systems the same apoptotic features are visible. However, the DNA degradation pattern appeared to be different, suggesting the involvement of different DNases. In this view, we have analyzed the activity and expression of Ca2+-Mg2+-dependent and acid DNases. We have observed that DNase I is not modulated during apoptosis. In contrast, the acid L-DNase II (derived from Leukocyte Elastase Inhibitor by post-translational modification), recently identified in our laboratory, is mainly active in the apoptotic pathway induced by long term-culture. Furthermore, we have provided evidence that while caspase 3 is activated by both inducers, caspase 1 is essential only for the etoposide-induced apoptosis.
Liao, Hai-Sun; Matsumoto, Akiyo; Itakura, Hiroshige; Pittman, Tamara; Kodama, Tatsushiko; Geng, Yong-Jian
doi: 10.1038/sj.cdd.4400485pmid: 10200575
The class-A macrophage scavenger receptor (MSR) is a trimeric multifunctional protein expressed selectively in differentiated monomyeloid phagocytes which mediates uptake of chemically modified lipoproteins and bacterial products. This study investigated whether MSR plays a role in the regulation of apoptosis, a model of genetically programmed cell death. De novo expression of MSR occurred in human THP-1 monocytic cells differentiated with phorbol esters, which activated a nuclear transcription factor binding to the Ap1/ets-like domain of the MSR promoter. The phorbol ester-stimulated THP-1 cells also expressed increased levels of the pro-apoptotic gene products, caspase-3 and Fas ligand, but the cells exhibited no change in apoptosis. Global activation of GTP-binding proteins with fluoride anions triggered apoptosis of THP-1 cells in a time- and concentration-dependent manner, demonstrated by nuclear shrinkage and fragmentation and internucleosomal DNA fragmentation. However, the MSR-expressing THP-1 macrophage-like cells showed a significant reduction in apoptosis compared to undifferentiated control THP-1 cells, which produce MSR at undetectable levels. Fluoride stimulation also triggered apoptosis of human Jurkat T cells. Stimulation with phorbol ester made no difference in apoptosis between treated and untreated Jurkat cells. Finally, Chinese hamster ovary (CHO) cells overexpressing the class-A MSR type I by cDNA transfection showed markedly increased resistance to G-protein-coupled apoptosis. Thus, de novo expression of MSR associated with monocyte maturation into macrophages appears to confer the resistance of macrophages to apoptotic stimulation by G-protein activation.
Burgess, David H; Svensson, Michael; Dandrea, Tiziana; Grönlund, Karina; Hammarquist, Folke; Orrenius, Sten; Cotgreave, Ian A
doi: 10.1038/sj.cdd.4400489pmid: 10200576
Apoptotic regulatory mechanisms in skeletal muscle have not been revealed. This is despite indications that remnant apoptotic events are detected following exercise, muscle injury and the progression of dystrophinopathies. The recent elicitation of a cytochrome c-mediated induction of caspases has led to speculation regarding a cytochrome c mechanism in muscle. We demonstrate that cytosols from skeletal muscle biopsies from healthy human volunteers lack the ability to activate type-II caspases by a cytochrome c-mediated pathway despite the confirmed presence of both procaspase-3 and -9. This was not due to the presence of an endogenous inhibitor, as the muscle cytosols enhanced caspase activity when added to a control cytosol, subsequently activated by cytochrome c and dATP. In addition, we demonstrate that muscle cytosols lack the apoptosis protease activator protein-1 (APAF-1), both at the protein and mRNA levels. These data indicate that human skeletal muscle cells will be refractory to mitochondrial-mediated events leading to apoptosis and thus can escape a major pro-apoptotic regulatory mechanism. This may reflect an evolutionary adaptation of cell survival in the presence of the profusion of mitochondria required for energy generation in motility.
Verhoven, Bret; Krahling, Stephen; Schlegel, Robert A; Williamson, Patrick
doi: 10.1038/sj.cdd.4400491pmid: 10200577
In lymphocytes, an asymmetric distribution of phospholipids across the plasma membrane is maintained by an ATP-dependent translocase which specifically transports aminophospholipids from the outer to the inner leaflet of the bilayer. During apoptosis, this enzyme is down-regulated and a lipid flipsite, termed the scramblase, is activated. Together, these events lead to the appearance of phosphatidylserine (PS) on the cell surface. In DO11.10 T lymphocyte hybridoma cells undergoing apoptosis, the kinetics of PS externalization are paralleled by the development of PS-sensitive phagocytosis by macrophages. This parallel is also observed when PS externalization is effected directly by application of a Ca2+ ionophore, suggesting that PS externalization is not only necessary, but sufficient, to generate a recognition signal. The broad spectrum aspartate-directed cysteine protease (caspase) inhibitor zVAD-fmk blocks externalization of PS and terminal cell lysis after induction of apoptosis by anti-CD3 antibody, but is ineffective when apoptosis is induced in the same cells by treatment with glucocorticoid. These results suggest that apoptosis induced by glucocorticoid does not require the same zVAD-sensitive caspase steps which are required for Fas/FasL-dependent death induced by anti-CD3 antibody, and that the action of these proteases is also not required for PS externalization. Extracellular Ca2+ is required to complete the later stages of apoptosis in DO11.10 cells, and its removal restores normal transport of PS, suggesting that down-regulation of the aminophospholipid translocase and up-regulation of the scramblase are not effected by irreversible protease cleavage.
Ruiz-Ruiz, María del Carmen; López-Rivas, Abelardo
doi: 10.1038/sj.cdd.4400490pmid: 10200578
Induction of CD95 (Fas/APO-1) and CD95 ligand during chemotherapeutic treatment may contribute to the death by apoptosis of some tumor cells. In this study, we have analyzed the role of the CD95 system in genotoxic drug-induced death of human breast tumor cells. Incubation of the breast tumor cell lines MCF-7 and EVSA-T with doxorubicin or methotrexate caused apoptosis after 48 h of treatment. These drugs induced a marked increase in the level of CD95 mRNA and protein in wild-type p53-expressing MCF-7 cells. On the contrary, the breast cancer cell line EVSA-T that expresses high levels of an inactive form of p53, did not up-regulate CD95 upon drug treatment. Elevation of CD95 expression by DNA-damaging drugs was notably blocked in MCF-7 cells expressing the human papillomavirus type 16 E6 protein (E6 cells) which prevented p53 accumulation upon DNA damage. However, E6 cells were still killed by the drugs. Furthermore, the genotoxic drugs did not induce the expression of CD95 ligand in MCF-7 cells at doses that caused apoptosis in these breast tumor cells. Moreover, drug-induced apoptosis of breast tumor cells was not prevented in the presence of either a CD95 antagonistic antibody or a CD95 ligand blocking antibody. We also observed a strong synergism between lower doses of DNA-damaging drugs and CD95 agonistic antibody in the induction of apoptosis in MCF-7 cells. In summary, our data indicate that drug-induced apoptosis of breast tumor cells occurs by a CD95/CD95L-independent mechanism although by elevating the tumor suppressor proteins p53 and CD95, genotoxic drugs may sensitize breast tumor cells to CD95-mediated apoptosis.
Famulski, Konrad S; Macdonald, Dawn; Paterson, Malcolm C; Sikora, Ewa
doi: 10.1038/sj.cdd.4400495pmid: 10200579
Intracellular acidification caused by agents such as UV(C), etoposide or ceramide accompanies the progression of apoptosis. It is suggested that cellular acidosis may set favorable conditions for a dormant, low pH-dependent (acidic) nuclease, which could be involved in intranucleosomal genome degradation, a hallmark of programmed cell death. Here we show that exposure of HL-60 cells to acidotic/apoptotic agents results in the several-fold activation of a novel low pH-dependent (acidic) nuclease activity, as revealed by zymography. Its activity, which resides in nuclei, is associated with four polypeptides with apparent Mr of 56, 48, 45 and 40 kDa. Treatment of HeLa cells with UV(C) or ceramide causes also the up-regulation of an acidic nuclease activity which is represented by 70 and 62 kDa polypeptides. These observations suggest that acidic nuclease activation can be induced by the same apoptotic agents in different cell types. In HL-60 cells, acidic nuclease up-regulation triggered by acidotic agents follows the induction of AP-1 transcription factor active complexes and accompanies the progression of apoptosis. Inhibition of AP-1 factor activity caused by either anti-caspase/anti-acidotic agent Zn2+ or curcumin, an inhibitor of AP-1 binding to DNA and c-jun synthesis, protects cells from genome destruction. Acidic nuclease activation, however, is only partially inhibited by these factors. We propose that (i) the up-regulation of an acidic nuclease activity is governed by a regulatory pathway different from that responsible for AP-1 factor induction, caspases activation and intracellular acidification, and (ii) activation of an acidic nuclease does not cause any deleterious effects when AP-1 transcription factor induction, caspases activation and intracellular acidification are down-regulated. Thus, the acidic nuclease up-regulation alone is not a sufficient prerequisite for apoptosis.
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