Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.56 (caspase-3)
 35,750 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dithiocarbamates (DCs) have been reported to be potent inhibitors of apoptosis in several different model systems, which suggests a target common to the apoptotic machinery. Without further investigation, this has been assumed to reflect an antioxidant activity of the DCs. However, we have recently shown that DCs exert prooxidant effects on T cells [Nobel et al. (1995) J. Biol. Chem. 270, 26202-26208], which are dependent on their transfer of external copper into the cells and can be inhibited by the inclusion of high-affinity external copper chelators in the medium. Investigating antiapoptotic actions of DCs, we found that inclusion of a membrane-impermeable copper chelator severely compromised the inhibitory activity of reduced DCs. Since copper can promote DC oxidation to the respective DC disulfides, the inhibitory effect on lymphocyte apoptosis might be mediated by the DC disulfides. In agreement with this we observed that DC disulfides were more potent inhibitors of T cell apoptosis than their reduced counterparts. Inhibition of apoptosis by DC disulfides correlated with the inhibition of caspase-3 proenzyme processing and activation. Similar results were obtained in a cell-free model system of caspase-3 activation. Significantly, dithiothreitol reduction of the DC disulfide abolished its inhibition of in vitro proenzyme processing, thereby demonstrating thiol-disulfide exchange between the DC disulfide and a free thiol group on an activator(s) of caspase-3. Since T cell apoptosis involves the generation of mature caspase-3 and requires caspase-3-like activity, we propose that (1) DC disulfides are the active agents behind DC inhibition of apoptosis and (2) their site of action is the proteolytic activation of this enzyme. These findings also reveal the potential for other thiol-oxidizing toxicants to inhibit apoptosis by preventing the proteolytic activation of caspases.
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PMID:Mechanism of dithiocarbamate inhibition of apoptosis: thiol oxidation by dithiocarbamate disulfides directly inhibits processing of the caspase-3 proenzyme. 920 69

We investigated the relationship between manganese superoxide dismutase (Mn-SOD) activity and apoptosis induced by anticancer drugs and radiation. Although the activity of copper, zinc-SOD did not differ greatly among 9 squamous cell carcinoma (SCC) cell lines (OSC-1 to OSC-9), the Mn-SOD activity did differ among the cell lines. The Mn-SOD activity was increased by treatments with 5-fluorouracil (5-FU), peplomycin and 137Cs, reaching plateau levels at 12 h after treatment and then decreasing gradually. When OSC-1 and OSC-3, and OSC-2 and OSC-4 were examined as representative cell lines with low and high Mn-SOD activity, respectively, the decrease was more prominent in OSC-1 and OSC-3 than in OSC-2 and OSC-4. The intracellular levels of superoxide and hydrogen peroxide (H2O2) were increased after treatment with the anticancer agents, and the increases were larger in OSC-1 and OSC-3 than in OSC-2 and OSC-4. The decrease of mitochondrial membrane potential (deltapsi(m)) by the anticancer agents was marked in OSC-1 and OSC-3. Correspondingly, the release of cytochrome c, the activation of caspase-3 and the cleavage of poly(ADP-ribose)polymerase were stronger in OSC-3 than in OSC-4. In addition, apoptosis induced by the anticancer agents was prominent in OSC-3, exhibiting a close relationship with the deltapsi(m) and the H2O2 level. These results indicate that Mn-SOD in SCC cells modulates apoptosis induction and the inactivation of Mn-SOD might be a promising strategy for SCC treatment.
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PMID:Manganese superoxide dismutase negatively regulates the induction of apoptosis by 5-fluorouracil, peplomycin and gamma-rays in squamous cell carcinoma cells. 1039 Oct 96

Apoptosis may play an important role in atherogenesis. Oxidized low-density lipoprotein (oxLDL) promotes apoptosis in the arterial wall in addition to several other proatherogenic effects. Tocopherol supplements have been suggested to protect against coronary heart disease (CHD) in epidemiological studies. The effects of oxLDL and alpha- and gamma-tocopherol on apoptotic signaling pathways are poorly understood. Thus, the goal of the study was to investigate these pathways in the presence of copper-oxidized LDL and tocopherols in human coronary smooth muscle cells (SMC). We showed that oxLDL-mediated apoptosis, assessed by DNA fragmentation, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay, and caspase activation stimulated several transcription factors and proapoptotic dynamic movements of the Bcl-2 family proteins through the mitogen-activated protein kinase (MAPK) and Jun kinase pathways. alpha-Tocopherol and gamma-tocopherol significantly reduced these molecular events and cell death effectors caspase-3 and -8. Under our experimental conditions, alpha-tocopherol was significantly more effective than gamma-tocopherol, and oxLDL-mediated apoptosis increased c-Jun, cyclic AMP-responsive element-binding, Ets-like element kinase-dependent 7, and activating transcription factor-2 proteins as well as nuclear activity of the activated protein-1 complex in human coronary SMC. Moreover, our results demonstrate that tocopherols may exert their antiatherogenic effects at least in part via reduction of the MAPK and JunK cascade together with a protective profile of apoptotic genes of the Bcl-2 family. These data are consistent with the beneficial effects of tocopherols on atherogenesis seen in experimental studies and on CHD in epidemiological surveys.
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PMID:Modulation by alpha- and gamma-tocopherol and oxidized low-density lipoprotein of apoptotic signaling in human coronary smooth muscle cells. 1075 58

Metallothionein (MT) is a low-molecular-weight, sulfhydryl-rich, metal-binding protein that can protect against the toxicity of cadmium, mercury, and copper. However, the role of MT in arsenic (As)-induced toxicity is less certain. To better define the ability of MT to modify As toxicity, MT-I/II knockout (MT-null) mice and the corresponding wild-type mice (WT) were exposed to arsenite [As(III)] or arsenate [As(V)] either through the drinking water for 48 weeks, or through repeated sc injections (5 days/week) for 15 weeks. Chronic As exposure increased tissue MT concentrations (2-5-fold) in the WT but not in MT-null mice. Arsenic by both routes produced damage to the liver (fatty infiltration, inflammation, and focal necrosis) and kidney (tubular cell vacuolization, inflammatory cell infiltration, and interstitial fibrosis) in both MT-null and WT mice. However, in MT-null mice, the pathological lesions were more frequent and severe when compared to WT mice. This was confirmed biochemically, in that, at the higher oral doses of As, blood urea nitrogen (BUN) levels were increased more in MT-null mice (60%) than in WT mice (30%). Chronic As exposures produced 2-10 fold elevation of serum interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha levels, with greater increases seen by repeated injections than by oral exposure, and again, MT-null mice had higher serum cytokines than WT mice after As exposure. Repeated As injections also decreased hepatic glutathione (GSH) by 35%, but GSH-peroxidase and GSH-reductase were minimally affected. MT-null mice were more sensitive than WT mice to the effect of GSH depletion by As(V). Hepatic caspase-3 activity was increased (2-3-fold) in both WT and MT-null mice, indicative of apoptotic cell death. In summary, chronic inorganic As exposure produced injuries to multiple organs, and MT-null mice are generally more susceptible than WT mice to As-induced toxicity regardless of route of exposure, suggesting that MT could be a cellular factor in protecting against chronic As toxicity.
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PMID:Metallothionein-I/II null mice are more sensitive than wild-type mice to the hepatotoxic and nephrotoxic effects of chronic oral or injected inorganic arsenicals. 1082 79

Although zinc deficiency may contribute to age-related macular degeneration (ARMD), the pathogenic mechanism is as yet uncertain. In light of evidence that cellular zinc depletion induces apoptosis in cortical neurons and thymocytes, in the present study, we examined the possibility that the same phenomenon occurs also in retinal cells. Exposure of primary retinal cell cultures to 1-3 microM of a cell membrane-permeant zinc chelator TPEN for 24 h induced concentration-dependent death of neurons, photoreceptor cells, and astrocytes. Addition of zinc or copper reversed TPEN toxicity to all cell components, indicating the particular involvement of zinc chelation in cell death. Consistent with apoptosis, oligonucleosomal DNA fragmentation and chromatin condensation accompanied, and the protein synthesis inhibitor cycloheximide blocked the TPEN-induced retinal cell death. During TPEN-induced retinal cell apoptosis, cleavage/activation of procaspase-1, but little of procaspase-3, was observed. Consistent with this finding, a broad-spectrum caspase inhibitor (zVAD-fmk) was significantly more protective than a caspase-3-selective inhibitor (DEVD-fmk). The present study has demonstrated that depletion of intracellular zinc is sufficient to induce macromolecule synthesis- and caspase-dependent apoptosis of cultured retinal cells. In light of the possibility that zinc depletion may contribute to the pathogenesis of ARMD, the current culture model may be a useful tool for the investigation of the mechanism of zinc depletion-induced retinal cell death.
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PMID:Depletion of intracellular zinc induces macromolecule synthesis- and caspase-dependent apoptosis of cultured retinal cells. 1086 57

Antioxidant activity is believed to be an important intracellular function of metallothioneins (MT), yet the specific mechanisms of their antioxidant action are not known. Under conditions when cells are challenged with elevated concentrations of free copper as a result of metabolic disturbances or environmental and occupational exposures, MTs may be ideally suited for antioxidant function as effective copper chelators. In the study presented here, we tested this hypothesis using a recently established model of copper nitrilotriacetate-induced oxidative stress in HL-60 cells. Since copper-induced oxidative stress triggers apoptosis, we further investigated antiapoptotic function of MTs in HL-60 cells. Using a Sephadex G-75 chromatographic partial purification of MTs from cell homogenates with subsequent immuno-dot-blot assay, we showed that zinc pretreatment yielded a pronounced induction of MTs in HL-60 cells. We report that zinc-induced MTs were able to (i) completely bind intracellular copper, (ii) completely quench redox-cycling activity of copper, (iii) significantly inhibit copper-dependent oxidative stress in membrane phospholipids, and (iv) prevent copper-dependent apoptosis and its characteristic biochemical features (cytochrome c release from mitochondria into cytosol, caspase-3 activation, and externalization of phosphatidylserine in plasma membranes). In separate experiments, we used lung fibroblasts derived from MT1, MT2 knockout mice (MT(-)(/)(-)) and MT wild-type (MT(+/+)) mice. ZnCl(2) pretreatment resulted in a more than 10-fold induction of MTs in MT(+/+) cells, whereas the MT content in MT(-)(/)(-) cells remained low, at levels approximately 100-fold lower than in their MT wild-type counterparts. MT(-)(/)(-) cells were very sensitive to Cu-NTA and, most importantly, showed no response to ZnCl(2) pretreatment. In contrast, MT(+/+) cells were relatively more resistant to Cu-NTA, and this resistance was remarkably enhanced by ZnCl(2) pretreatment. Combined, our results demonstrate that metallothioneins function as effective antioxidants and an antiapoptotic mechanism in copper-challenged HL-60 cells.
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PMID:Antioxidant and antiapoptotic function of metallothioneins in HL-60 cells challenged with copper nitrilotriacetate. 1112 69

Intracellular safeguarding functions of metallothioneins (MTs) include sequestering transition and heavy metals, scavenging free radicals and protecting against electrophiles. We report that MT protection against Cu-induced cytotoxicity can be reversed and pro-oxidant and pro-apoptotic effects can be induced in HL-60 cells exposed to NO. We demonstrate that in ZnCl(2)-pretreated HL-60 cells loaded with copper nitrilotriacetate (Cu-NTA), exposure to an NO donor, S-nitroso-N-acetyl penicillamine, resulted in S-nitrosylation and oxidation of MT cysteines. This disruption of MT Cu-binding thiolate clusters caused loosening and release of redox-active Cu, enhanced redox-cycling activity of Cu and increased peroxidation of major classes of membrane phospholipids. We also found that Cu-induced oxidative stress in ZnCl(2)-pretreated/Cu-NTA-loaded HL-60 cells was accompanied by apoptosis documented by characteristic changes of nuclear morphology, internucleosomal DNA cleavage, externalization of phosphatidylserine, release of cytochrome c from mitochondria into cytosol and activation of caspase-3. We conclude that in Cu-challenged cells, NO can reverse the protective role of MTs and convert them into pro-oxidant, pro-apoptotic implements.
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PMID:Nitric oxide-dependent pro-oxidant and pro-apoptotic effect of metallothioneins in HL-60 cells challenged with cupric nitrilotriacetate. 1117 Nov 19

Disulfiram is frequently used in the treatment of alcoholism. In this study, we found that CuCl(2) (1-10 microM), but not other metal ions (Fe(2+), Zn(2+), Pb(2+)), markedly potentiated disulfiram-induced cytotoxicity by 440-fold in primary astrocytes. Thus, the molecular mechanisms of the cytotoxic effects induced by the disulfiram-Cu(2+) complex were explored. The changes in morphology (nuclear condensation and apoptotic body formation) and hypodiploidy of DNA suggested that the disulfiram-Cu(2+) complex induced an apoptotic process. Our studies of the death-signaling pathway reveal that decreased mitochondrial membrane potential, increased free radical production, and depletion of non-protein-thiols (glutathione) were involved. The disulfiram-Cu(2+) complex activated c-Jun-amino-terminal kinase (JNK) and caspase-3 followed by poly (ADP-ribose) polymerase degradation in a time-dependent manner. Moreover, the cellular Cu content was markedly increased and the copper chelator bathocuproine disulfonate abolished all of these cellular events, suggesting that Cu(2+) is essential for death signaling. The antioxidants N-acetylcysteine and vitamin C also inhibited the cytotoxic effect. Thus, we conclude that the disulfiram-Cu(2+) complex induces apoptosis and perhaps necrosis at a late stage mediated by oxidative stress followed by sequential activation of JNK, caspase-3 and poly (ADP-ribose) polymerase degradation. These findings imply that the axonal degeneration and neurotoxicity observed after the chronic administration of disulfiram are perhaps, at least in part, due to the cytotoxic effect of the disulfiram-Cu(2+) complex formed endogenously.
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PMID:Oxidative stress and c-Jun-amino-terminal kinase activation involved in apoptosis of primary astrocytes induced by disulfiram-Cu(2+) complex. 1123 17

Treatment of neuroblastoma cells with the copper chelator triethylene tetramine tetrahydrochloride induced intracellular decrease of copper content paralleled by diminished activity of the enzymes Cu, Zn superoxide dismutase, and cytochrome c oxidase. This effect appears to be specific for copper-enzymes and the treatment affects neither viability nor growth capability of cells. However, molecular markers of apoptosis Bcl-2, p53, and caspase-3 were slightly affected in these cells. When copper-deficient cells were challenged with oxidative stress generated by paraquat or puromycin, they underwent a higher degree of apoptosis with respect to copper-adequate control cells. The mechanism underlying paraquat-triggered apoptosis implies dramatic activation of caspase-3 and induction of the transcription factor p53. These results demonstrate that impairment of copper balance predisposes neuronal cells to apoptosis induced by oxidative stress. Overall findings represent a contribution to the comprehension of the link between copper-imbalance and neurodegeneration, which has recently been repeatedly suggested for the most invalidating pathologies of the central nervous system.
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PMID:Increased susceptibility of copper-deficient neuroblastoma cells to oxidative stress-mediated apoptosis. 1136 9

Hyperhomocysteinemia represents an independent risk factor for atherosclerosis, but the mechanisms leading to cellular dysfunctions remain unknown. Using ECV304 cells, we found that homocysteine (Hcy) plus copper (Cu2+) induced cytotoxic effects: loss of cell adhesion, increased permeability to PI, and the occurrence of morphologically apoptotic cells. This form of apoptosis, inhibited by Z-VAD-fmk, was associated with a loss of mitochondrial potential, a cytosolic release of cytochrome c, activation of caspase-3, degradation of poly(ADP-ribose)polymerase, and internucleosomal DNA fragmentation. However, the ability of Hcy plus Cu2+ to induce apoptosis decreased when the pretreatment culture time increased. As a positive correlation was found between the length of time of culture before treatment and the enhancement of gamma-glutamyl transpeptidase (gamma-GT) activity, we asked whether gamma-GT was involved in the control of Hcy plus Cu2+-induced apoptosis. Therefore, ECV304 cells were treated with either acivicin or dexamethasone, inhibiting and stimulating gamma-GT, respectively. In ECV304 cells and human umbilical venous endothelial cells, acivicin favored Hcy plus Cu2+-induced apoptosis whereas dexamethasone counteracted the apoptotic process. As acivicin and dexamethasone were also capable of modulating cell death in ECV304 cells treated with antitumoral drugs, our data emphasize that the involvement of gamma-GT in the control of apoptosis is not restricted to Hcy but also concerns other chemical compounds.
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PMID:Efficiency of homocysteine plus copper in inducing apoptosis is inversely proportional to gamma-glutamyl transpeptidase activity. 1153 73


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