Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.61 (caspase-8)
 6,833 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human promyelocytic leukemia HL-60 cells are well known to differentiate into granulocytes or monocytes in the presence of some agents such as DMSO or PMA, respectively. Differentiated HL-60 cells become resistant to some apoptotic stimuli including anticancer drugs or irradiation though undifferentiated cells significantly respond to these stimuli. TRAIL (TNF-related apoptosis-inducing ligand) which is also known as Apo2 ligand (Apo2L), a new member of TNF family, can induce apoptosis in some tumor cells but not in many normal cells. We show here that apoptosis is well induced in HL-60 cells by TRAIL, but susceptibility to TRAIL is reduced during granulocytic differentiation by DMSO. We also suggest some possible mechanisms by which granulocytic differentiated cells become resistant to TRAIL-induced apoptosis. First, in granulocytic differentiated cells, expression of antagonistic decoy receptors for TRAIL (TRAIL-R3/TRID/DcR1/LIT and TRAIL-R4/TRUNDD/DcR2) were enhanced. In addition, expression of Toso, a cell surface apoptosis regulator, seemed to block activation of caspase-8 by TRAIL via enhanced expression of FLIPL in granulocytic differentiated cells. These findings suggest that differentiated cells are resistant using plural mechanisms against various apoptosis-inducing stimuli rather than undifferentiated cells.
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PMID:Potential mechanisms of resistance to TRAIL/Apo2L-induced apoptosis in human promyelocytic leukemia HL-60 cells during granulocytic differentiation. 1127 40

Previous studies have shown that coexposure to marginally toxic concentrations of phorbol 12-myristate 13-acetate (PMA; 10 nM) and the cyclin-dependent kinase inhibitor flavopiridol (FP; 100-200 nM) synergistically induces apoptosis in human myeloid leukemia cells U937 and HL-60 (i.e., >50% apoptotic at 24 h). Attempts have now been made to characterize the cell death pathway(s) involved in this phenomenon. In contrast to cytochrome c release and caspase-3 activation, which occur within 2.5 h of PMA/FP coexposure, caspase-8 activation and Bid cleavage appeared as later events. Such findings implicate the mitochondria-dependent pathway in the initial induction of apoptosis by PMA/FP. However, U937 cells ectopically expressing CrmA, dominant-negative caspase-8, or dominant-negative Fas-associated death domain that were highly resistant to tumor necrosis factor (TNF)/cycloheximide-induced lethality displayed significant, albeit incomplete, resistance to PMA/FP-induced apoptosis after 24 h. Furthermore, coadministration of TNF soluble receptor significantly attenuated PMA/FP-induced apoptosis in U937 (p < 0.02) and HL-60 (p < 0.03) cells at 24 h. PMA/FP coadministration also triggered substantial increases in TNFalpha mRNA and protein secretion compared with the effects of PMA administered alone. The protein kinase C (PKC) inhibitor bisindolylmaleimide (1 microM) completely blocked PMA/FP-induced TNFalpha secretion in U937 cells and attenuated apoptosis. Taken together, these results suggest that coadministration of PMA with FP in myeloid leukemia cells initially triggers mitochondrial damage, an event followed by the PKC-dependent induction and release of TNFalpha, supporting a model in which the synergistic induction of leukemic cell apoptosis by this drug combination proceeds via both mitochondrial- and TNF receptor-related apoptotic pathways.
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PMID:Synergistic induction of apoptosis in human myeloid leukemia cells by phorbol 12-myristate 13-acetate and flavopiridol proceeds via activation of both the intrinsic and tumor necrosis factor-mediated extrinsic cell death pathways. 1202 92

Glutamine is the most abundant amino acid in the body. A decrease of plasma glutamine concentrations is found in catabolic stress and is related to susceptibility to infections. Glutamine is known to modulate lymphocyte activation; however, little is known about glutamine modulation of cell death of activated human T cells. Using Jurkat T cells, we investigated glutamine modulation of T-cell apoptosis activated by PMA plus ionomycin. We found that glutamine at various concentrations significantly enhanced IL-2 production, cell proliferation, and cell viability of Jurkat T cells. Glutamine also decreased the number of apoptotic cells stimulated with PMA plus ionomycin as demonstrated by flow cytometry. Meanwhile, glutamine down-regulated CD95 and CD95L expression, but up-regulated CD45RO and Bcl-2 expression in activated T cells. Further investigation of CD95-mediated caspase activities revealed that supplementation of glutamine significantly decreased caspase-3 and caspase-8 activities in activated T cells. Since oxidative stress is closely associated with induction of lymphocyte apoptosis, we found that glutamine significantly increased glutathione (GSH), but decreased reactive oxygen species levels in activated T cells. Blockade of intracellular GSH formation enhanced, but exogenous GSH supplementation decreased, activated T-cell apoptosis. Studying normal peripheral lymphoproliferation, we also found that the presence of glutamine increased lymphoproliferation as well as Bcl-2 and CD95 expression; but decreased CD95L and activation-induced T-cell death. Taken together, glutamine appeared to augment lymphoproliferation but suppressed activation-induced T-cell death in both Jurkat T cells and human peripheral T lymphocytes.
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PMID:Glutamine protects activated human T cells from apoptosis by up-regulating glutathione and Bcl-2 levels. 1216 76

Interactions between the protein kinase inhibitor UCN-01 and the PKC activator phorbol ester (PMA) have been examined in relation to differentiation and apoptosis in human myelomonocytic leukemia cells (U937). Coadministratation of 100 nM UCN-01 with a low concentration of PMA e.g., 2 nM, inhibited rather than promoted differentiation, reflected by reduced surface expression of the monocytic maturation marker CD11b and diminished cell adherence. Instead, administration of UCN-01 with PMA led to a marked increase in mitochondrial injury (e.g, cytochrome c release), activation of caspases-3 and -8, Bid cleavage, PARP degradation, and apoptosis, accompanied by a substantial reduction in viability and clonogenic survival. These phenomena were associated with multiple perturbations in cell cycle regulatory events, including abrogation of p21(CIP1) induction, p27(KIP1) cleavage, down-regulation of cyclin D1, dephosphorylation (activation) of p34cdc2, and degradation of underphosphorylated pRb. Potentiation of PMA-mediated apoptosis was partially mimicked by caffeine suggesting the involvement of Chk1 in the potentiation of apoptosis. Induction of cell death by UCN-01 and PMA was increased in cells stably expressing a p21(CIP1) mRNA antisense construct, suggesting that p21(CIP1) expression may protect cells from the lethal effects of this drug combination. Finally, ectopic expression of a Bcl-2 but not dominant-negative caspase-8 protected cells from UCN-01/PMA-mediated apoptosis, suggesting the lethal effects of this combination primarily involves the mitochondrial rather than the TNF-related extrinsic apoptotic pathway. Taken together, these findings suggest that UCN-01 disrupts a variety of cell cycle events in leukemic cells exposed to the maturation-inducing agent PMA, causing cells to engage an apoptotic rather than a differentiation-related program.
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PMID:UCN-01 (7-hydroxystauorsporine) blocks PMA-induced maturation and reciprocally promotes apoptosis in human myelomonocytic leukemia cells (U937). 1242 43

Many apoptotic pathways culminate in the activation of caspase cascades usually triggered by the apical caspases-8 or -9. We describe a paradigm where apoptosis is initiated by the effector caspase-3. Diethylmaleate (DEM)-induced apoptotic damage in Jurkat cells was blocked by the anti-apoptotic protein Bcl-2, whereas, a peptide inhibitor of caspase-3 but not caspase-9 blocked DEM-induced mitochondrial damage. Isogenic Jurkat cell lines deficient for caspase-8 or the adaptor FADD (Fas associated death domain) were not protected from DEM-induced apoptosis. Caspase-3 activation preceded that of caspase-9 and initial processing of caspase-3 was regulated independent of caspase-9 and Bcl-2. However, inhibitors of caspase-9 or caspase-6 regulated caspase-3 later in the pathway. We explored the mechanism by which caspase-3 processing is regulated in this system. DEM triggered a loss of Erk-1/2 phosphorylation and XIAP (X-linked inhibitor of apoptosis protein) expression. The phorbol ester PMA activated a MEK-dependent pathway to block caspase-3 processing and cell death. Constitutively active MEK-1 (CA-MEK) upregulated XIAP expression and exogenous XIAP inhibited DEM-induced apoptotic damage. Thus, we describe a pathway where caspase-3 functions to initiate apoptotic damage and caspase-9 and caspase-6 amplify the apoptotic cascade. Further, we show that MEK may regulate caspase-3 activation via the regulation of XIAP expression in these cells.
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PMID:Caspase-3 activation is an early event and initiates apoptotic damage in a human leukemia cell line. 1281 79

Sesquiterpene lactones (SLs) are known to have potent anti-inflammatory and cytotoxic properties. So far, the anti-inflammatory effects have mainly been attributed to their inhibition of DNA-binding of the transcription factor NF-kappa B (p65), which is a pivotal regulator of the cellular immune response. Since NF-kappa B is involved in the transcriptional control of several pro-inflammatory and regulatory genes, we investigated the effects of one bifunctional NF-kappa B (p65) inhibiting and two monofunctional NF-kappa B (p65) inactive helenanolide-type SLs on PMA and LPS-induced mRNA expression in CD4(+) Jurkat T and human peripheral blood mononuclear cells (PBMCs) with reverse transcription real-time PCR (RT-rt-PCR). The monofunctional SLs 11 alpha,13-dihydrohelenalin acetate (DHAc) and chamissonolide significantly reduced mitogen-induced cytokine and iNOS mRNA levels in PBMCs and Jurkat T cells at low micromolar concentrations. DHAc also showed significant effects on the gene expression of the house-keeping genes GAP-DH and beta-actin, as well as on NF-ATc, p65, I-kappa B alpha, bcl-2, and cyclin D1. The bifunctional NF-kappa B inhibitor helenalin not only effectively inhibited pro-inflammatory gene expression, but also strongly down-regulated all investigated mRNA levels in a time-dependent manner. Flow cytometry and caspase-8 and -3 assays revealed that helenalin strongly and DHAc moderately induced apoptosis in Jurkat T cells, whereas chamissonolide caused cytoprotective effects. In PBMCs, DHAc and chamissonolide did not inhibit NF-kappa B (p65) DNA-binding at concentrations effective on the transcriptome. Thus, it can be concluded that the biological effects of SLs are not only due to NF-kappa B inhibition, but must be coupled to other mechanisms.
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PMID:Influence of helenanolide-type sesquiterpene lactones on gene transcription profiles in Jurkat T cells and human peripheral blood cells: anti-inflammatory and cytotoxic effects. 1460 39

Statins are lipid-lowering agents with pleiotropic effects. We investigated the apoptotic effects of fluvastatin on peripheral CD4+ T cells from healthy subjects. Fluvastatin induced apoptosis in resting CD4+ T cells but not in CD4+ T cells strongly activated with a high concentration of PMA plus ionomycin (PMA/I) analyzed with annexin V and propidium iodide staining. However, CD4+ T cells activated with a low concentration of PMA/I or with anti-CD3 antibodies were apoptotic after treatment with fluvastatin. Activities of caspases-8, -9, and -3 were increased in resting CD4+ T cells treated with fluvastatin (10 microM). In strongly activated CD4+ T cells, fluvastatin inhibited the activation of caspase-8 induced by PMA/I and increased caspase-9 activity. The caspase-3 activity did not differ between untreated and fluvastatin-treated strongly activated CD4+ T cells. Treatment with fluvastatin (10 microM) enhanced cytochrome c release and increased the Bax/Bcl-2 ratio in both resting and strongly activated CD4+ T cells. Although the in vitro concentration of fluvastatin used in this study is higher than in vivo, other factors may sensitize apoptotic cell death of CD4+ T cells in vivo. In conclusion, fluvastatin induces apoptosis in resting T cells but not in strongly activated T cells, a difference that might be due to the interaction between caspase-8 and caspase-9.
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PMID:Effect of fluvastatin on apoptosis in human CD4+ T cells. 1622 33

Protein kinase C (PKC) isozymes, a family of serine-threonine kinases, are important regulators of cell proliferation and malignant transformation. Phorbol esters, the prototype PKC activators, cause PKC translocation to the plasma membrane in prostate cancer cells, and trigger an apoptotic response. Studies in recent years have determined that each member of the PKC family exerts different effects on apoptotic or survival pathways. PKCdelta, one of the novel PKCs, is a key player of the apoptotic response via the activation of the p38 MAPK pathway. Studies using RNAi revealed that depletion of PKCdelta totally abolishes the apoptotic effect of the phorbol ester PMA. Activation of the classical PKCalpha promotes the dephosphorylation and inactivation of the survival kinase Akt. Studies have assigned a pro-survival role to PKCepsilon, but the function of this PKC isozyme remains controversial. Recently, it has been determined that the PKC apoptotic effect in androgen-dependent prostate cancer cells is mediated by the autocrine secretion of death factors. PKCdelta stimulates the release of TNFalpha from the plasma membrane, and blockade of TNFalpha secretion or TNFalpha receptors abrogates the apoptotic response of PMA. Molecular analysis indicates the requirement of the extrinsic apoptotic cascade via the activation of death receptors and caspase-8. Dissecting the pathways downstream of PKC isozymes represents a major challenge to understanding the molecular basis of phorbol ester-induced apoptosis.
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PMID:Molecular mechanisms of protein kinase C-induced apoptosis in prostate cancer cells. 1633 77

Expression of isolated beta integrin cytoplasmic domains in cultured endothelial cells was reported to induce cell detachment and death. To test whether cell death was the cause or the consequence of cell detachment, we expressed isolated integrin beta1 cytoplasmic and transmembrane domains (CH1) in cultured human umbilical vein endothelial cells (HUVEC), and monitored detachment, viability, caspase activation and signaling. CH1 expression induced dose-dependent cell detachment. At 24 h over 90% of CH1-expressing HUVEC were detached but largely viable (>85%). No evidence of pro-caspase-8,-3, and PARP cleavage or suppression of phosphorylation of ERK, PKB and Ikappa-B was observed. The caspase inhibitor z-VAD did not prevent cell detachment. At 48 h, however, CH1-expressing cells were over 50% dead. As a comparison trypsin-mediated detachment resulted in a time-dependent cell death, paralleled by caspase-3 activation and suppression of ERK, PKB and Ikappa-B phosphoyrylation at 24 h or later after detachment. HUVEC stimulation with agents that strengthen integrin-mediated adhesion (i.e. PMA, the Src inhibitor PP2 and COMP-Ang1) did not prevent CH1-induced detachment. Expression of CH1 in rat carotid artery endothelial cells in vivo caused endothelial cell detachment and increased nuclear DNA fragmentation among detached cells. A construct lacking the integrin cytoplasmic domain (CH2) had no effect on adhesion and cell viability in vitro and in vivo. These results demonstrate that isolated beta1 cytoplasmic domain expression induces caspase-independent detachment of viable endothelial cells and that death is secondary to detachment (i.e. anoikis). They also reveal an essential role for integrins in the adhesion and survival of quiescent endothelial cells in vivo.
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PMID:Expressed isolated integrin beta1 subunit cytodomain induces endothelial cell death secondary to detachment. 1636 50

The antigen binding to the B cell receptor (BCR) of pre-mature B lymphocytes induces their apoptotic cell death, although the binding to BCR of mature B lymphocytes does their activation and proliferation. The former is thought not only to function as a mechanism to exclude B cell clones possessing the ability to react with self-antigen, but also to participate as a defense mechanism from auto-immune diseases. Cross-linking of BCR of pre-mature B cell lines, including the chicken DT40 cell line, with anti-immunoglobulin antibody induces their apoptotic cell death. The PMA/ionomycin treatment, which mimics the BCR stimulation, is used to study intracellular signal transduction of B lymphocytes. Here, by analyzing the GCN5-deficient DT40 cell line, we show that GCN5 and BCR signalling are essential for apoptotic cell death. In addition, GCN5 and BCR signalling control cooperatively pre-mature B cell apoptosis via both depletions of ICAD and IAP2 (inhibitors for apoptosis) and elevations of caspase-8 and caspase-3 activities, resulting in increased activity of CAD (effector for apoptosis) followed by the DNA fragmentation. These findings should be useful in understanding the molecular mechanisms involved in negative selection of B cells as also in auto-immune diseases.
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PMID:GCN5 and BCR signalling collaborate to induce pre-mature B cell apoptosis through depletion of ICAD and IAP2 and activation of caspase activities. 1853 56


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