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)

Deletion of activated peripheral T cell clones by apoptosis requires the regulated expression of Fas ligand (FasL) and sensitization of these cells to CD95-mediated signaling. To investigate the signaling pathways responsible for FasL expression in T cells, we tested-besides subfamily-selective protein kinase C (PKC) inhibitors - the effect of constitutively active mutants of representatives of all PKC subfamilies, i.e. PKCalpha,epsilon,theta,iota, on FasL luciferase promoter reporter constructs. In synergy with a constitutively active form of protein phosphatase 2B calcineurin (CaN), only PKCtheta, but not PKCalpha,epsilon,iota, preferentially induced FasL promoter reporter activity and, consequently, FasL protein expression in Jurkat T cells. Activation of an inducible PKCtheta AE-estrogen receptor fusion mutant led to a CaN-dependent and rapid FasL reporter activity detected as early as 4 h after addition of 4-hydroxytamoxifen, incidating a direct effect of PKCtheta action on FasL expression. Consistently, in Jurkat T cells, expression of PKCtheta AE / CaN significantly enhanced FasL protein expression and apoptosis in a CD95-dependent manner since cell death was not observed in T cells co-expressing the caspase-8 inhibitor crmA. Taken together, our results support the notion that PKCtheta and CaN are sufficient to regulate apoptosis through FasL expression.
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PMID:Synergistic action of protein kinase C theta and calcineurin is sufficient for Fas ligand expression and induction of a crmA-sensitive apoptosis pathway in Jurkat T cells. 1055 9

We have shown previously that caspase-6 activity is lethal to human neurons (LeBlanc et al., 1999; Zhang et al., 2000). Here we find that 17-beta-estradiol but not 17-alpha-estradiol prevents caspase-6-mediated neuronal cell death. 17-beta-estradiol-treated neuronal extracts directly inhibit recombinant active caspase-6, caspase-3, caspase-7, and caspase-8 in vitro. We conclude that 17-beta-estradiol induces a caspase inhibitory factor (CIF) that is preventing neuronal apoptosis. The induction of CIF occurs within 10 min of 17-beta-estradiol exposure to neurons, does not require de novo protein synthesis, and involves mitogen-activated protein kinase activation. The effect is antagonized by the estrogen receptor antagonist tamoxifen. In contrast, 17-beta-estradiol does not induce CIF or prevent caspase-mediated cell death in cultured astrocytes. CIF does not act through oxidation of the caspase active site. CIF activity copurifies with proteins of between 12 and 14 kDa in size. Our results indicate that 17-beta-estradiol induces an inhibitor of active caspases through a receptor-mediated nongenomic pathway and provide an additional mechanism for the neuroprotective action of 17-beta-estradiol that is likely highly relevant to the understanding of the role of estrogen against Alzheimer's disease.
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PMID:17-beta-estradiol induces an inhibitor of active caspases. 1158 6

We studied the effects of ICI 182780 and bis(ethyl)norspermine (BE-3-3-3) on cell growth and apoptosis of estrogen receptor-positive MCF-7 breast cancer cells. Combination treatment with 100 nM ICI 182780 and 5 microM BE-3-3-3 for 6 days inhibited cell growth by 74.3+/-8.4% in MCF-7 cells, compared to that of 25.4+/-5.8 and 45.8+/-12.2%, respectively, when ICI 182780 and BE-3-3-3 were used as single agents. Treatment with 100 nM ICI 182780 and 5 microM BE-3-3-3 as single agents resulted in 9.1+/-1.0% and 35.1+/-4.5% apoptosis, respectively, as measured by APO-BRDU assay. When ICI 182780 and BE-3-3-3 were used in combination, the percentage of apoptosis was 60.6+/-3.8%. Improved efficacy of ICI 182780 and BE-3-3-3 combination on growth inhibition was observed for T-47D cells also. Western blot analysis showed that combinations of ICI 182780 and BE-3-3-3 caused down-regulation of the anti-apoptotic Bcl-2 and Bcl-XL proteins and increased the level of the pro-apoptotic Bax protein. Combination treatment also increased caspase-8 activation. Analysis of polyamine levels 48 h after combination treatment showed that spermidine and spermine levels were down regulated significantly. These studies indicate a potentially effective combination strategy for breast cancer treatment. Our results also link the down-regulation of polyamine pathway to apoptotic cell death and regulation of mediators of cell death.
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PMID:Bis(ethyl)norspermine potentiates the apoptotic activity of the pure antiestrogen ICI 182780 in breast cancer cells. 1558 9

The molecular mechanisms involved in adrenocortical tumorigenesis are still not completely understood. In this study, using the H295R cell line as a model system, we investigated the role of estrogens and estrogen receptor (ER) alpha and ER beta in the growth regulation of adrenocortical tumors. We demonstrated that H295R cells are able to convert androgens to estrogens by a constitutive expression of active cytochrome P450 aromatase protein and express ER beta to a greater extent than ER alpha. Moreover, physiological concentrations of 17beta-estradiol (E2) determined an increase of thymidine incorporation, suggesting the presence of an autocrine mechanism in maintaining H295R cell proliferation. Evaluating the response to ER antagonists like 4-hydroxytamoxifen (OHT) and ICI 182 780 (ICI), we observed an up-regulation of ER beta and a dose-dependent inhibition of H295R cell proliferation. Whereas ICI determined the growth arrest of H295R cells, OHT induced morphological changes that were characteristic of apoptosis. According to the above-mentioned observations, OHT but not ICI clearly induced a marked expression of FasL and the cleavage of both caspase-8 and caspase-3. Interestingly, the apoptotic effects of OHT in H295R cells may be consequent to the enhanced levels of ER beta which stimulate the expression of FasL interacting with activating protein (AP)-1 sites located within its promoter sequence. In conclusion, we have demonstrated that H295R cells are able to transform androgens to estrogens that activate an autocrine mechanism, mediated by their own receptors, and contribute to regulate the proliferation of these cells. Moreover, this study points towards a role for ER beta as an important mediator of the repressive effects exerted by antiestrogens on H295R cells; however, further studies are needed to clarify its role in the control of adrenocortical cell proliferation and on the potential benefits of antiestrogens for treatment of adrenocortical cancer.
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PMID:Antiestrogens upregulate estrogen receptor beta expression and inhibit adrenocortical H295R cell proliferation. 1621 6

Hepatocellular carcinoma (HCC), the major manifestation of primary liver cancer, is one of the most frequent and malignant cancers worldwide, especially in Taiwan. Estrogen receptors (ERs) have been reported to play either a proliferation- or apoptosis-enhancing role in the differentiation of cancers, including HCC. In a previous experiment, we showed that transient overexpressed estrogen receptor-alpha induced early stage HCC cell line Hep 3B cell apoptosis by increasing the hTNF-alpha gene expression in a ligand-independent manner. To further clarify if the apoptotic effect occurs in poorly differentiated HCC cell line, HA22T, and elucidate the roles of ERs and TNF-alpha, DNA fragmentation and caspase activity were measured in late stage HCC cell line, HA22T, by measuring the expression of hER-alpha and hER-beta using a Tetracycline-inducible system (Tet-on). Increased DNA fragmentation and caspase-3 activity were found in hERbeta-overexpressed HA22T cells treated with estrogen (10(-8) M) but not in hERalpha-overexpressed HA22T cells. Using RT-PCR/PCR and western blotting in HA22T cells, overexpressed hER-beta was also found to increase the expression of hTNF-alpha mRNA and induce hTNF-alpha-dependent luciferase activity in a ligand-dependent manner. Additionally, LPS treatment and hER-beta overexpression both enhance caspase-8 activities, whereas neither hER-beta nor E2 treatment affected caspase-9 activities. In addition, the overexpressed hER-beta plus E2 enhanced DNA fragmentation and caspase-8 activities were only partially reduced by anti-hTNF-alpha (0.1 ng/ml), which was possibly due to the involvement of P53 and TGF-beta. Taken together, our data indicates that overexpressed hER-beta but not hER-alpha may induce caspase-8-mediated apoptosis by increasing the hTNF-alpha gene expression in a ligand-dependent manner in poorly differentiated HA22T cells.
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PMID:Opposing action of estrogen receptors alpha and beta on tumor necrosis factor-alpha gene expression and caspase-8-mediated apoptotic effects in HA22T cells. 1663 37

Estrogen affects skeletal growth and promotes growth plate fusion in humans. High doses of estrogen have been used to limit growth in girls with predicted extreme tall stature; a treatment which has been associated with severe side effects. Selective estrogen receptor modulators (SERMs) could potentially be used as an alternative treatment. We chose to study the effects of Tamoxifen (Tam), a first generation SERM that has been used in the treatment of pubertal gynecomastia or McCune-Albright syndrome. Cultured fetal rat metatarsal bones were used to study the effects of Tam on longitudinal bone growth. In sectioned bones, chondrocyte apoptosis and proliferation were analyzed by TUNEL assay and BrdU incorporation, respectively. We also used a human chondrocytic cell line, HSC-2/8, to study the effects of Tam on apoptosis (FACS analysis and Cell Death detection ELISA) and caspase activation (caspase substrate cleavage and Western immunoblotting). Tam caused a dose-dependent growth retardation of cultured metatarsal bones. No catch-up growth was observed after Tam was removed from the culture medium. Detailed analysis of sectioned growth plate cartilage revealed increased apoptosis of chondrocytes within the resting and hypertrophic zones. HCS-2/8 cells also underwent apoptosis upon Tam treatment. Tam-induced apoptosis was caspase-dependent and completely abrogated by either caspase-8 or -9 inhibitors. A substrate assay revealed that caspase-8 is first activated followed by caspase-9 and -3. Finally, FasL secretion was stimulated by Tam and blocking of either FasL or Fas decreased Tam-induced apoptosis in chondrocytes. We here describe a novel mechanism of tamoxifen-induced apoptosis in chondrocytes, involving the activation of caspases and the FasL/Fas pathway, which diminishes the potential for bone growth.
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PMID:Tamoxifen induces permanent growth arrest through selective induction of apoptosis in growth plate chondrocytes in cultured rat metatarsal bones. 1729 77

Sulforaphane, an isothiocyanate found in cruciferous vegetables, has been shown to induce phase 2 detoxication enzymes and inhibit the growth of chemically induced mammary tumors in rats, although the exact mechanisms of action of sulforaphane are not understood. In this study, we evaluated the effects of sulforaphane on cell growth and death in several human breast cancer cell lines and examined the hypothesis that sulforaphane acts as a histone deacetylase (HDAC) inhibitor in these cell lines. Sulforaphane treatment inhibited cell growth, induced a G(2)-M cell cycle block, increased expression of cyclin B1, and induced oligonucleosomal DNA fragmentation in the four human breast cancer cell lines examined, MDA-MB-231, MDA-MB-468, MCF-7, and T47D cells. Activation of apoptosis by sulforaphane in MDA-MB-231 cells seemed to be initiated through induction of Fas ligand, which resulted in activation of caspase-8, caspase-3, and poly(ADP-ribose) polymerase, whereas apoptosis in the other breast cancer cell lines was initiated by decreased Bcl-2 expression, release of cytochrome c into the cytosol, activation of caspase-9 and caspase-3, but not caspase-8, and poly(ADP-ribose) polymerase cleavage. Sulforaphane inhibited HDAC activity and decreased the expression of estrogen receptor-alpha, epidermal growth factor receptor, and human epidermal growth factor receptor-2 in each cell line, although no change in the acetylation of H3 or H4 was seen. These data suggest that sulforaphane inhibits cell growth, activates apoptosis, inhibits HDAC activity, and decreases the expression of key proteins involved in breast cancer proliferation in human breast cancer cells. These results support testing sulforaphane in vivo and warrant future studies examining the clinical potential of sulforaphane in human breast cancer.
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PMID:Sulforaphane induces cell type-specific apoptosis in human breast cancer cell lines. 1733 67

The Myc oncoprotein serves a dual function by stimulating cells both towards growth and apoptosis. The latter functions are often abrogated during tumor development. The Hsp70 stress protein is a potent anti-apoptotic molecule, but its potential role in protecting cells from Myc-mediated apoptosis has not been investigated. Our results show that activated Myc potentiated apoptosis induced by the cancer drugs etoposide (ETO) and camptothecin (CAMP) in v-Myc-expressing human U-937 monoblastic cells and in Rat1 cells containing a conditionally active Myc/estrogen receptor (MycER) fusion protein. However, both heat shock and ectopic Hsp70 expression protected the cells from Myc-mediated apoptosis after drug treatment in both systems. The increased susceptibility to the anti-tumor drugs by activated Myc was enhanced by siRNA-mediated knockdown of Hsp70 expression in U-937 cells. Addressing the mechanisms by which Myc and Hsp70 promotes and inhibits drug-induced apoptosis, respectively, we found that v-Myc stimulated cytochrome c release and activation of effector caspase-9, -3 and -7, but not of initiator caspase-8. Inhibition of caspase-9 specifically reduced v-Myc-stimulated apoptosis, whereas inhibition of caspase-8 and -3/7 reduced apoptosis both in v-myc-expressing and parental ETO-treated U-937 cells. Interestingly, Myc-stimulated activation of effector caspases was inhibited, but cytochrome c release was not affected by Hsp70 expression, suggesting that Hsp70 interferes with the proapoptotic function of Myc downstream of mitochondria, at the level of caspase-9 and downstream caspases. In conclusion, Hsp70 seems to have key function in inhibition of apoptosis mediated by Myc and may therefore play an important role in Myc-driven oncogenesis.
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PMID:Drug-induced Myc-mediated apoptosis of cancer cells is inhibited by stress protein Hsp70. 1769 14

Resveratrol (trans-3,5,4'-trihydroxystilbene), a polyphenolic compound found in plant products, including red grapes, exhibits anticancer, antioxidant, and anti-inflammatory properties. Using an animal model of multiple sclerosis (MS), we investigated the use of resveratrol for the treatment of autoimmune diseases. We observed that resveratrol treatment decreased the clinical symptoms and inflammatory responses in experimental allergic encephalomyelitis (EAE)-induced mice. Furthermore, we observed significant apoptosis in inflammatory cells in spinal cord of EAE-induced mice treated with resveratrol compared with the control mice. Resveratrol administration also led to significant down-regulation of certain cytokines and chemokines in EAE-induced mice including tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-2, IL-9, IL-12, IL-17, macrophage inflammatory protein-1alpha (MIP-1alpha), monocyte chemoattractant protein-1 (MCP-1), regulated on activation normal T-cell expressed and secreted (RANTES), and Eotaxin. In vitro studies on the mechanism of action revealed that resveratrol triggered high levels of apoptosis in activated T cells and to a lesser extent in unactivated T cells. Moreover, resveratrol-induced apoptosis was mediated through activation of aryl hydrocarbon receptor (AhR) and estrogen receptor (ER) and correlated with up-regulation of AhR, Fas, and FasL expression. In addition, resveratrol-induced apoptosis in primary T cells correlated with cleavage of caspase-8, caspase-9, caspase-3, poly(ADP-ribose) polymerase, and release of cytochrome c. Data from the present study demonstrate, for the first time, the ability of resveratrol to trigger apoptosis in activated T cells and its potential use in the treatment of inflammatory and autoimmune diseases including, MS.
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PMID:Resveratrol (trans-3,5,4'-trihydroxystilbene) ameliorates experimental allergic encephalomyelitis, primarily via induction of apoptosis in T cells involving activation of aryl hydrocarbon receptor and estrogen receptor. 1787 69

A pharmacological dose (2.5-10 microM) of 17alpha-estradiol (17alpha-E(2)) exerted a cytotoxic effect on human leukemias Jurkat T and U937 cells, which was not suppressed by the estrogen receptor (ER) antagonist ICI 182,780. Along with cytotoxicity in Jurkat T cells, several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9, -3, and -8, PARP degradation, and DNA fragmentation were induced. The cytotoxicity of 17alpha-E(2) was not blocked by the anti-Fas neutralizing antibody ZB-4. While undergoing apoptosis, there was a remarkable accumulation of G(2)/M cells with the upregulatoin of cdc2 kinase activity, which was reflected in the Thr56 phosphorylation of Bcl-2. Dephosphorylation at Tyr15 and phosphorylation at Thr161 of cdc2, and significant increase in the cyclin B1 level were underlying factors for the cdc2 kinase activation. Whereas the 17alpha-E(2)-induced apoptosis was completely abrogated by overexpression of Bcl-2 or by pretreatment with the pan-caspase inhibitor z-VAD-fmk, the accumulation of G(2)/M cells significantly increased. The caspase-8 inhibitor z-IETD-fmk failed to influence 17alpha-E(2)-mediated caspase-9 activation, but it markedly reduced caspase-3 activation and PARP degradation with the suppression of apoptosis, indicating the contribution of caspase-8; not as an upstream event of the mitochondrial cytochrome c release, but to caspase-3 activation. In the presence of hydroxyurea, which blocked the cell cycle progression at the G(1)/S boundary, 17alpha-E(2) failed to induce the G(2)/M arrest as well as apoptosis. These results demonstrate that the cytotoxicity of 17alpha-E(2) toward Jurkat T cells is attributable to apoptosis mainly induced in G(2)/M-arrested cells, in an ER-independent manner, via a mitochondria-dependent caspase pathway regulated by Bcl-2.
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PMID:17Alpha-estradiol arrests cell cycle progression at G2/M and induces apoptotic cell death in human acute leukemia Jurkat T cells. 1860 76


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