Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We and others have recently shown that loss of the mitochondrial membrane potential (Deltapsi) precedes apoptosis and chemical-hypoxia-induced necrosis and is prevented by Bcl-2. In this report, we examine the biochemical mechanism used by Bcl-2 to prevent Deltapsi loss, as determined with mitochondria isolated from a cell line overexpressing human Bcl-2 or from livers of Bcl-2 transgenic mice. Although Bcl-2 had no effect on the respiration rate of isolated mitochondria, it prevented both Deltapsi loss and the permeability transition (PT) induced by various reagents, including Ca2+, H2O2, and tert-butyl hydroperoxide. Even under conditions that did not allow PT, Bcl-2 maintained Deltapsi, suggesting that the functional target of Bcl-2 is regulation of Deltapsi but not PT. Bcl-2 also maintained Deltapsi in the presence of the protonophore SF6847, which induces proton influx, suggesting that Bcl-2 regulates ion transport to maintain Deltapsi. Although treatment with SF6847 in the absence of Ca2+ caused massive H+ influx in control mitochondria, the presence of Bcl-2 induced H+ efflux after transient H+ influx. In this case, Bcl-2 did not enhance K+ efflux. Furthermore, Bcl-2 enhanced H+ efflux but not K+ flux after treatment of mitochondria with Ca2+ or tert-butyl hydroperoxide. These results suggest that Bcl-2 maintains Deltapsi by enhancing H+ efflux in the presence of Deltapsi-loss-inducing stimuli.
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PMID:Bcl-2 prevents apoptotic mitochondrial dysfunction by regulating proton flux. 946 36

It was recently reported that the mitochondrial protein cytochrome c is required for the induction of apoptosis, and that the overexpression of Bcl-2 caused increased retention of this apoptogenic factor by mitochondria. Several cellular toxins, including H2O2, tBOOH and Ca++, induce the Mitochondrial Permeability Transition (MPT); we tested the possibility that MPT is an intracellular sensor of toxicity that results in the release of cytochrome c. We observe that the release of cytochrome c from purified mitochondria is stimulated by the classical inducers of MPT, and is inhibited by the classical inhibitor of MPT, cyclosporin A (CsA). After induction of MPT, mitochondrial supernatants gained the activity to induce cleavage of caspase 3 (CPP32) in cytosolic extracts, and this gain of activity was inhibited by CsA pretreatment of mitochondria, and was cancelled by immunodepletion of cytochrome c from the supernatants. After induction of MPT, mitochondrial supernatants mixed with or without cytosolic extract gained the activity to ladder nuclei, and this gain of activity was inhibited by CsA pretreatment of mitochondria, and cancelled by immunodepletion of cytochrome c from the supernatants. These results demonstrate that the induction of MPT causes release of cytochrome c from mitochondria, which is required for the hallmarks of cytosolic and nuclear apoptosis, caspase 3 activation and nuclear laddering, and identify the MPT as a potential intracellular sensor of oxidants and other toxins, and as a target for the pharmacological inhibition of apoptosis.
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PMID:Induction of the mitochondrial permeability transition causes release of the apoptogenic factor cytochrome c. 955 74

Beta-Lapachone a novel topoisomerase inhibitor, has been found to induce apoptosis in various human cancer cells. In this study we report that a dramatic elevation of hydrogen peroxide (H2O2) in human leukemia HL-60 cells following 1 microM beta-lapachone treatment and that this increase was effectively inhibited by treatment with antioxidant N-acetyl-L-cysteine (NAC), ascorbic acid, alpha-tocopherol. NAC strongly prevented beta-lapachone-induced apoptotic characteristics such as DNA fragmentation and apoptotic morphology. However, treatment of HL-60 cells with another topoisomerase inhibitor camptothecin (CPT) did not induce H2O2 production as compared to untreated cells. NAC also failed to block CPT-induced apoptosis. Correlated with these findings, we found that cancer cell lines K562, MCF-7, and SW620, contained high level of intracellular glutathione (GSH), were not elevated in H2O2 and were resistant to apoptosis after treatment with beta-lapachone. In contrast, cancer cell lines such as, HL-60, U937, and Molt-4 which have lower level of GSH, were readily increased of H2O2 and were sensitive to this drug. Furthermore, ectopic overexpression of Bcl-2 in HL-60 cells also attenuated beta-lapachone-induced H2O2 and conferred resistance to beta-lapachone-induced cell death. Beta-Lapachone at the concentration as low as 0.25 microM effectively induced HL-60 cells to undergo monocytic differentiation, as evidenced by CD14 antigenicity and alpha-naphthyl acetate esterase activity. Again, the beta-lapachone-induced monocytic differentiation was suppressed by NAC. These results suggest that intracellular H2O2 generation plays a crucial role in beta-lapachone-induced cell death and differentiation.
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PMID:Involvement of hydrogen peroxide in topoisomerase inhibitor beta-lapachone-induced apoptosis and differentiation in human leukemia cells. 955 79

Treatment of human premonocytic U937 cells with 500 microM H2O2 for 1h followed by 4h incubation in fresh medium to allow the cells to execute apoptotic processes caused DNA fragmentation. However, in the presence of 1mM ZnSO4 throughout the incubation, DNA ladder formation was markedly inhibited. Hydrogen peroxide treatment for 1h with or without zinc increased both Bcl-2 and Bax proteins. However, only Bax protein decreased to basal levels in the presence of zinc during the following 4h incubation, resulting in an increase of the Bcl-2/Bax ratio and prevention of apoptosis. Treatment of U937 cells with 1mM ZnSO4 alone also decreased the levels of Bax protein. Furthermore, we observed that zinc completely inhibited the activation of CPP32 by H2O2, while no significant changes of ICE activities occurred with either H2O2 and/or zinc. These results indicate that the suppression of H2O2-induced apoptosis by zinc is mediated through an increase of the Bcl-2/Bax ratio, which occurs upstream from the activation of CPP32.
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PMID:Zinc suppresses apoptosis of U937 cells induced by hydrogen peroxide through an increase of the Bcl-2/Bax ratio. 961 Mar 64

The mammalian response to stress is complex, often involving multiple signalling pathways that act in concert to influence cell fate. To examine potential interactions between the signalling cascades, we have focused on the effects of a model oxidant stress in a single cell type through an examination of the relative influences of mitogen-activated protein kinases (MAPKs) as well as two proposed apoptosis regulators, nuclear factor kappaB (NF-kappaB) and Bcl-2, in determining cell survival. Treatment of HeLa cells with H2O2 resulted in a time- and dose-dependent induction of apoptosis accompanied by sustained activation of all three MAPK subfamilies: extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38. This H2O2-induced apoptosis was markedly enhanced when ERK2 activation was selectively inhibited by PD098059. Apoptosis decreased when JNK/SAPK activation was inhibited by expression of a dominant negative mutant form of SAPK/ERK kinase 1. Inhibition of the p38 kinase activity with p38-specific inhibitors SB202190 and SB203580 had no effect on cell survival. Because NF-kappaB activation by H2O2 is potentially related to both the ERK and JNK/SAPK signalling pathways, we examined the effects of inhibiting the activation of NF-kappaB; this interference had no effect on the cellular response to H2O2. Overexpression of the anti-apoptotic protein Bcl-2 significantly decreased the apoptosis seen after treatment with H2O2 without altering ERK or JNK/SAPK activities. Our results suggest that ERK and JNK/SAPK act in opposition to influence cell survival in response to oxidative stress, whereas neither p38 nor NF-kappaB affects the outcome. Bcl-2 acts independently and downstream of ERK and JNK/SAPK to enhance the survival of H2O2-treated cells.
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PMID:The cellular response to oxidative stress: influences of mitogen-activated protein kinase signalling pathways on cell survival. 965 68

A failure of normal apoptosis, often due to mutant p53, may contribute to the formation of a cancer and to its resistance to therapy. Mesothelioma, an asbestos-induced tumor, is highly resistant to therapy but generally expresses wild-type p53. We asked whether mesothelioma was resistant to apoptosis and whether resistance was associated with altered expression of the antiapoptotic protein Bcl-2 or proapoptotic protein Bax. We found that three mesothelioma cell lines (1 with wild-type p53) were highly resistant to apoptosis induced by oxidant stimuli (asbestos, H2O2) or nonoxidant stimuli (calcium ionophore) compared with primary cultured mesothelial cells. By immunostaining, one of these three lines expressed Bcl-2 but only during mitosis. By immunoblotting, 3 of 14 additional mesothelioma lines (9 of 14 with wild type p53) expressed Bcl-2 but all 14 of 14 expressed the proapoptotic Bax, giving a low ratio of Bcl-2 to Bax. We conclude that mesothelioma cell lines are resistant to apoptosis and that the failure in apoptosis is not explained by Bcl-2 but by other mechanisms that counteract the proapoptotic effect of Bax.
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PMID:Resistance of pleural mesothelioma cell lines to apoptosis: relation to expression of Bcl-2 and Bax. 968 48

Polymorphonuclear leukocytes (PMN) isolated from the oral cavity of healthy human volunteers, spontaneously generated superoxide, nitric oxide (NO) and other reactive oxygen species (ROS) which exhibited strong luminol chemiluminescence (LCL). To understand the physiological roles of oral PMN (OPMN), biochemical properties of the cells were analyzed. Biochemical analysis revealed that OPMN were already primed under physiological conditions. Western blot analysis revealed that they strongly expressed the inducible type of NO synthase (NOS II) and exhibited the activity to catalyze tyrosine phosphorylation of various proteins including a 115 kDa protein (cbl product). OPMN also generated H2O2 and .OH by some superoxide dismutase (SOD)-sensitive mechanism and released myeloperoxidase (MPO). Kinetic analysis using specific inhibitors revealed that OCl- generated by OPMN was predominantly responsible for the enhanced LCL. During the incubation under standard culture conditions, OPMN underwent apoptosis which proceeded more rapidly than that of the circulating PMN (CPMN). Immunochemical analysis revealed that expression of apoptosis-related gene products, such as Bcl-2, Bcl-xL and Bax, was below detectable levels with both cell types. However, caspase-3 but not caspase-1 was markedly activated in OPMN. These results indicate that the primed OPMN spontaneously generate ROS and play an important role in the defense mechanism in the oral cavity and that the generated ROS activate caspase-3 thereby inducing apoptosis of the cells.
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PMID:Biochemical properties of human oral polymorphonuclear leukocytes. 970 29

Neuroprotective effects of estrogen have been demonstrated against a variety of cytotoxic insults. We present data here addressing a possible mechanism of estrogen neuroprotection in the human teratocarcinoma cell line NT2 terminally differentiated to a neuronal phenotype. Cell death induced by H2O2 or glutamate results in a dose-dependent cell death of NT2 neurons, while 24 h of estrogen pretreatment significantly enhances neuronal viability. Bcl-2 expression has been shown to reduce oxidative stress and prevent cell death. In NT2 neurons, Bcl-2 levels are dramatically elevated upon differentiation and are further enhanced with estrogen treatment. These results suggest that neuroprotective effects of estrogen may be related to increases in Bcl-2 expression.
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PMID:Modulation of Bcl-2 expression: a potential component of estrogen protection in NT2 neurons. 972 33

The mechanism by which Bcl-2 inhibits cell death is unknown. It has been suggested that Bcl-2 functions as an antioxidant. Because Bcl-2 is localized mainly to the membranes of the endoplasmic reticulum (ER) and the mitochondria, which represent the main intracellular storage sites for Ca2+, we hypothesized that Bcl-2 might protect cells against oxidant injury by altering intracellular Ca2+ homeostasis. To test this hypothesis, we examined the effect of oxidant treatment on viability in normal rat kidney (NRK) cells and in NRK cells stably transfected with Bcl-2 in the presence or absence of intracellular Ca2+, and we compared the effect of Bcl-2 expression on oxidant-induced intracellular Ca2+ mobilization and on ER and mitochondrial Ca2+ pools. NRK cells transfected with Bcl-2 (NRK-Bcl-2) were significantly more resistant to H2O2-induced cytotoxicity than control cells. EGTA-AM, an intracellular Ca2+ chelator, as well as the absence of Ca2+ in the medium, reduced H2O2-induced cytotoxicity in both cell lines. Compared with controls, cells overexpressing Bcl-2 showed a delayed rise in intracellular Ca2+ concentration ([Ca2+]i) after H2O2 treatment. After treatment with the Ca2+ ionophore ionomycin, Bcl-2-transfected cells showed a much quicker decrease after the maximal rise than control cells, suggesting stronger intracellular Ca2+ buffering, whereas treatment with thapsigargin, an inhibitor of the ER Ca2+-ATPases, transiently increased [Ca2+]i in control and in Bcl-2-transfected cells. Estimates of mitochondrial Ca2+ stores using an uncoupler of oxidative phosphorylation show that NRK-Bcl-2 cells have a higher capacity for mitochondrial Ca2+ storage than control cells. In conclusion, Bcl-2 may prevent oxidant-induced cell death, in part, by increasing the capacity of mitochondria to store Ca2+.
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PMID:Effect of Bcl-2 on oxidant-induced cell death and intracellular Ca2+ mobilization. 973 Sep 68

It is now generally accepted that massive neuronal death due to oxidative stress is a regular feature of brains in neurodegenerative diseases. However, much less attention has been given to the death of glial cells. In this study, we examined p53-sensitive apoptosis of cells by using human glioblastoma A172 cells and p53-deficient mouse astrocytes. In human A172 cells, hydrogen peroxide (H2O2) caused cell death in a time- and concentration-dependent manner, accompanied by nucleosomal DNA fragmentation and chromatin condensation. After treatment with H2O2, p53 protein was highly expressed and protein levels of Bak, p21WAF1/CIP1 and GADD45 were also enhanced. However, the protein levels of Bcl-2 and Bax did not change. On the other hand, primary cultured astrocytes from p53-deficient mouse brain grew faster than wild-type and heterozygous astrocytes. In addition, p53-deficient astrocytes were more resistant to H2O2-induced apoptosis than wild-type and heterozygous astrocytes. These results suggest that glial proliferation and the repair of damaged DNA may be regulated by p53-induced p21WAF1/CIP1 and GADD45, and that glial apoptosis caused by oxidative stress may be mediated by p53-induced Bak.
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PMID:Hydrogen peroxide-induced apoptosis mediated by p53 protein in glial cells. 989 Jun 30


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