• Korean Journal of Head & Neck Oncology
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• v.18 no.2
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• pp.142-149
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• 2002

Objectve : Okadaic acid is a specific inhibitor of serine/threonine protein phosphatase 1 and 2A. In order to know the mechanism of apoptosis induced by okadaic acid, we treated FRTL-5 thyroid cells with okadaic acid and measured the changes of important proteins that are involved in apoptosis. Materials and Methods: We measured caspase 3 activity, $PLC-{\gamma}1$ degradation, the expression of XIAP, cIAP1, cIAP2, and cytochrome c release in okadaic acid-treated FRTL-5 thyroid cells. Results: Okadaic acid-induced caspase 3 activation and $PLC-{\gamma}1$ degradation and apoptosis were dose-dependent with a maximal effect at a concentration of 80 nmol and time-dependent with a maximal effect at 24 hours after treatment. The elevated caspase 3 activity in okadaic acid treated FRTL-5 thyroid cells are correlated with down-regulation of XIAP and cIAP1, but not cIAP2. General and potent inhibitor of caspases, z-VAD-fmk. abolished okadaic acid-induced caspase 3 activity and $PLC-{\gamma}1$ degradation. The release of cytochrome c in okadaic acid-induced FRTL-5 thyroid cells was dose-dependent with a maximal effect at a concentration of 80 nmol. Conclusions: These findings suggest that mechanism of okadaic acid-induced apoptosis is associated with cytochrome c release and increase of caspase 3 activation in FRTL-5 thyroid cells.

• Journal of Life Science
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• v.13 no.1
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• pp.118-127
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• 2003

$\rho$-Fluorophenylalanine (FPA), a phenylalanine analog, is able to induce apoptotic cell death of human acute leukemia Jurkat T cells. To better understand the mechanism by which FPA induces apoptotic cell death, the effect of ectopic expression of antiapoptotic proteins, Bcl-2 and Bcl-xL, on FPA-induced apoptosis was investigated by employing lurkat T cells transfected with Bcl-2 gene (JT/Bcl-2) or Bcl-xL gene (1/Bcl-xL) and Jurkat T cells transfected with vector (JT/Neo or J/Neo). When Jurkat T cells, JT/Neo or J/Neo, were exposed to FPA at concentrations ranging from 0.63 to 5.0 mM, the cell viability determined by MTT assay declined in a dose-dependent manner. In addition, apoptotic DNA fragmentation along with several apoptotic events such as caspase-8 activation, Bid cleavage, mitochondrial cytochrome c release, caspase-9 activation, caspase-3 activation, and degradation of PARP was induced. However, the FPA-induced cytotoxic effect, activation of caspase-8, and cleavage of Bid were significantly abrogated by ectopic expression of Bcl-2 or Bcl-xL. At the same time, there was marked reduction in the level of cytochrome c release from mitorhondria, caspase-9 activation, caspase-3 activation, and degradation of PARP. These results indicate that caspase-8 activation, Bid cleavage, and mitochondrial cytochrome c release with subsequent activation of the caspase cascade are negatively regulated by Bcl-2 or Bcl-xL, and are thus required for FPA-induced apoptosis in Jurkat T cells

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.950-956
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• 2002

The antitumor activity of the insect pathogenic fungus Paecilomyces japonica has been attributed to apoptotic cell death. However, the mechanism underlying the induced apoptosis has not yet been elucidated. In this study, we for the first time show that mitochondria-dependent caspase-3 activation were associated with the apoptotic activity of P. japonica in human acute leukemia Jurkat T cells. When Jurkat T cells were treated with the ethyl acetate extract of P japonica at concentrations ranging from $2-6{\mu}g/ml$, apoptotic cell death. accompanied by several biochemical events such as caspase-9 activation, caspase-3 activation, degradation of poly (ADP-ribose) polymerase (PARP), and apoptotic DNA fragmentation, was induced in a dose-dependent manner. In addition, the release of cytochrome c from mitochondria was detected. Under these conditions, the expression of Fas and Fas-ligand (FasL) remained unchanged. Ethyl acetate extract-induced mitochondrial cytochrome c release, caspase-3 activation, PARP cleavage, and apoptotic DNA fragmentation were suppressed by the ectopic expression of Bcl-2, which is known to block mitochondrial cytochrorme c release. Accordingly, these results demonstrate that P. japonica-induced apoptotic cell death is mediated by a cytochrome c-dependent caspase-3 activation pathway that can be interrupted by Bcl-2.

• IMMUNE NETWORK
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• v.13 no.5
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• pp.213-217
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• 2013

Enterotoxigenic Bacteroides fragilis (ETBF) is a human gut commensal bacteria that causes inflammatory diarrhea and colitis. ETBF also promotes colorectal tumorigenesis in the Min mouse model. The key virulence factor is a secreted metalloprotease called B. fragilis toxin (BFT). BFT induces E-cadherin cleavage, cell rounding, activation of the ${\beta}$-catenin pathway and secretion of IL-8 in colonic epithelial cells. However, the precise mechanism by which these processes occur and how these processes are interrelated is still unclear. E-cadherin form homophilic interactions which tethers adjacent cells. Loss of E-cadherin results in detachment of adjacent cells. Prior studies have suggested that BFT induces IL-8 expression by inducing E-cadherin cleavage; cells that do not express E-cadherin do not secrete IL-8 in response to BFT. In the current study, we found that HT29/C1cells treated with dilute trypsin solution induced E-cadherin degradation and IL-8 secretion, consistent with the hypothesis that E-cadherin cleavage causes IL-8 secretion. However, physical damage to the cell monolayer did not induce IL-8 secretion. We also show that EDTA-mediated disruption of E-cadherin interactions without E-cadherin degradation was sufficient to induce IL-8 secretion. Finally, we determined that HT29/C1 cells treated with LiCl (${\beta}$-catenin activator) induced IL-8 secretion in a dose-dependent and time-dependent manner. Taken together, our results suggest that BFT induced IL-8 secretion may occur by the following process: E-cadherin cleavage, disruption of cellular interactions, activation of the ${\beta}$-catenin pathway and IL-8 expression. However, we further propose that E-cadherin cleavage per se may not be required for BFT induced IL-8 secretion.

• Fisheries and Aquatic Sciences
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• v.19 no.9
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• pp.35.1-35.6
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• 2016

Gliotoxin has been recognized as an immunosuppressive agent for a long time. Recently, it was reported to have antitumor properties. However, the mechanisms by which it inhibits tumors remain unclear. Here, we showed that gliotoxin isolated from the marine fungus Aspergillus fumigatus inhibited proliferation and induced apoptosis in HT1080 human fibrosarcoma cells. Gliotoxin repressed phosphorylation-dependent degradation of $I{\kappa}B-{\alpha}$, an antagonist of nuclear factor kappa B ($NF-{\kappa}B$), which is a known tumor-promoting factor. This coincided with a decrease in nuclear import of $NF-{\kappa}B$, suggesting its signaling activity was impaired. Moreover, gliotoxin increased intracellular reactive oxygen species (ROS). Since ROS have been known to inhibit $NF-{\kappa}B$, this may also contribute to gliotoxin's antitumorigenic effects. These results suggest that gliotoxin suppressed the activation of $NF-{\kappa}B$ by inhibiting phosphorylation and degradation of $I{\kappa}B-{\alpha}$ and by increasing ROS, which resulted in apoptosis of HT1080 cells. Cumulatively, gliotoxin is a promising candidate antagonist of $NF-{\kappa}B$, and it should be investigated for its possible use as a selective inhibitor of human fibrosarcoma cells.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.6
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• pp.25-30
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• 2013

In nanoscale MOSFET technology, aging effects such as Negative Bias Temperature Instability(NBTI), Hot carrier Injection(HCI), Time Dependent Dielectric Breakdown (TDDB) and so on which affect circuit reliability can lead to severe degradation of digital circuit performance. Therefore, this paper has proposed the adaptive compensation circuit to overcome the aging effects of digital circuits. The proposed circuit deploys a power gating structure with variable power switch width and variable forward body-biasing voltage in order to adaptively compensate for aging induced performance degradation, and has been designed in 45nm technology.

• Earthquakes and Structures
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• v.3 no.5
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• pp.649-673
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• 2012

Recent studies have highlighted the importance of accounting for aging and deterioration of bridges when estimating their seismic vulnerability. Effects of structural degradation of multiple bridge components, variations in bridge geometry, and comparison of different environmental exposure conditions have traditionally been ignored in the development of seismic fragility curves for aging concrete highway bridges. This study focuses on the degradation of multiple bridge components of a geometrically varying bridge class, as opposed to a single bridge sample, to arrive at time-dependent seismic bridge fragility curves. The effects of different exposure conditions are also explored to assess the impact of severity of the environment on bridge seismic vulnerability. The proposed methodology is demonstrated on a representative class of aging multi-span reinforced concrete girder bridges typical of the Central and Southeastern United States. The results reveal the importance of considering multiple deterioration mechanisms, including the significance of degrading elastomeric bearings along with the corroding reinforced concrete columns, in fragility modeling of aging bridge classes. Additionally, assessment of the relative severity of exposure to marine atmospheric, marine sea-splash and deicing salts, and shows 5%, 9% and 44% reduction, respectively, in the median value bridge fragility for the complete damage state relative to the as-built pristine structure.

• KSBB Journal
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• v.8 no.5
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• pp.424-430
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• 1993

The anti-stress effect by the treatment of vitamin C was investigated in this study. The treatment of ascorbic acid in the presence of $Cu^{2+}$ion induced strong time- and dose-dependent degradation of hitamine, and also the addition of histamine accelerated time-dependent decomposition of ascorbic acid in vitro. The treatment of ascorbic acid in $ODS^{od}/_{od}$rats, which cannot synthesize ascorbic acid, significantly decreased the urinary histamine. The protreatment of ascorbic acid, dexamethasone and promethazine inhibited the lethal effect induced by immobilization stress, but that of dimethylsulfoxide did not. The addition of ascorbic and to a culture of spleen cells of $ODS^{od}/_{od}$rats significantly increased the Con A-dependent T lymphocyte proliferation.

• The Korean Journal of Zoology
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• v.36 no.3
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• pp.342-346
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• 1993

The protein level of cytoskeletons in cultured myoblasts was found to gradually decrease during the course of myogenesis. This decrease, however, could be prevented by treatiag the ceils with calpeptin (benzyloxycarbonyl-Leu-nLeu-H), a cell penetrating inhibitor of calpain. In contrast, E-64, which also is a potent inhibitor of calpain but can not be transported into the cells, showed little or no effect. In addition, the treatment of calpeptin was found to stabilize a number of specific cytoskeletal proteins from degradation but without any effect on the pattern of total cells proteins. Furthermore, calpeptin, but not E-64, blocked myoblast fusion in a dose-dependent manner. These results suggest that calpain is responsible for the myogenic time-dependent loss of cytoskeletal proteins and that the degradative process is associated with myoblast fusion. These results also suggest that the differential effects of the calpain inhibitors depend on the permeabIlity of the drugs across the cell membrane.

• Development and Reproduction
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• v.18 no.4
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• pp.225-231
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• 2014

Autophagy is a homeostatic degradation process that is involved in tumor development and normal development. Autophagy is induced in cancer cells in response to chemotherapeutic agents, and inhibition of autophagy results in enhanced cancer cell death or survival. Chloroquine (CQ), an anti-malarial drug, is a lysosomotropic agent and is currently used as a potential anticancer agent as well as an autophagy inhibitor. Here, we evaluate the characteristics of these dual activities of CQ using human colorectal cancer cell line HCT15. The results show that CQ inhibited cell viability in dose- and time-dependent manner in the range between 20 to 80 uM, while CQ did not show any antiproliferative activity at 5 and 10 uM. Cotreatment of CQ with antitumor agent NVP-BEZ235, a dual inhibitor of PI3K/mTOR, rescued the cell viability at low concentrations meaning that CQ acted as an autophagy inhibitor, but CQ induced the lethal effect at high concentrations. Acridine orange staining revealed that CQ at high doses induced lysosomal membrane permeabilization (LMP). High doses of CQ produced cellular reactive oxygen species (ROS) and cotreatment of antioxidants, such as NAC and trolox, with high doses of CQ rescued the cell viability. These results suggest that CQ may exert its dual activities, as autophagy inhibitor or LMP inducer, in concentration-dependent manner.