• Biomolecules & Therapeutics
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• 제19권3호
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• pp.348-356
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• 2011

Liriope platyphylla is a medical herb that has long been used in Korea and China to treat cough, sputum, neurodigenerative disorders, obesity and diabetes. The aims of this study were to study the antidiabetic effects of the aqueous extract of L. platyphylla (AEtLP) through pancreatic and extrapancreatic actions. AEtLP were orally administrated to ICR mice once a day for 7 days. Of three different concentrations of AEtLP, only 10% AEtLP were low toxic to liver, based on body weight and serum biochemical analyses. However, 10% AEtLP-treated mice displayed signifi cant reduction of the glucose concentration and increased insulin concentration; no changes were noted using 5% and 15% AEtLP. Also, the increase of glucose transporter (Glut)-1 expression in liver was dependent on the concentration of AEtLP, and was regulated by the phosphorylation of Akt. The lowest expression of Glut-3 was observed in 15% AEtLP treated mice, followed by 10% AEtLP- and 5% AEtLP-treated mice. This pattern of Glut-3 expression was roughly in accord with the phosphorylation of c-Jun N-teminal kinase (JNK) in the mitogen-activated protein kinase (MAPK) pathway. Furthermore, a signifi cant rise of the superoxide dismutase activity (SOD) was detected in AEtLP-treated mice. The fi ndings suggest that AEtLP should be considered as a diabetes therapeutic candidate to induce insulin secretion from pancreatic ${\beta}$-cells and glucose uptake in liver cells.

• Biomolecules & Therapeutics
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• 제20권1호
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• pp.43-49
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• 2012

Stimulation of mast cells through the high affinity IgE receptor (Fc${\varepsilon}$RI) induces degranulation, lipid mediator release, and cytokine secretion leading to allergic reactions. Although various signaling pathways have been characterized to be involved in the Fc${\varepsilon}$RI-mediated responses, little is known about the precious mechanism for the expression of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) in mast cells. Here, we report that rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), reduces the expression of TNF-${\alpha}$ in rat basophilic leukemia (RBL-2H3) cells. IgE or specific antigen stimulation of RBL-2H3 cells increases the expression of TNF-${\alpha}$ and activates various signaling molecules including S6K1, Akt and p38 MAPK. Rapamycin specifically inhibits antigeninduced TNF-${\alpha}$ mRNA level, while other kinase inhibitors have no effect on TNF-${\alpha}$ mRNA level. These data indicate that mTOR signaling pathway is the main regulation mechanism for antigen-induced TNF-${\alpha}$ expression. TNF-${\alpha}$ mRNA stability analysis using reporter construct containing TNF-${\alpha}$ adenylate/uridylate-rich elements (AREs) shows that rapamycin destabilizes TNF-${\alpha}$ mRNA via regulating the AU-rich element of TNF-${\alpha}$ mRNA. The antigen-induced activation of S6K1 is inhibited by specific kinase inhibitors including mTOR, PI3K, PKC and $Ca^{2+}$chelator inhibitor, while TNF-${\alpha}$ mRNA level is reduced only by rapamycin treatment. These data suggest that the effects of rapamycin on the expression of TNF-${\alpha}$ mRNA are not mediated by S6K1 but regulated by mTOR. Taken together, our results reveal that mTOR signaling pathway is a novel regulation mechanism for antigen-induced TNF-${\alpha}$ expression in RBL-2H3 cells.

• Biomolecules & Therapeutics
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• 제29권3호
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• pp.321-330
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• 2021

Oxidative stress plays a crucial role in the development of neuronal disorders including brain ischemic injury. Thioredoxin 1 (Trx1), a 12 kDa oxidoreductase, has anti-oxidant and anti-apoptotic functions in various cells. It has been highly implicated in brain ischemic injury. However, the protective mechanism of Trx1 against hippocampal neuronal cell death is not identified yet. Using a cell permeable Tat-Trx1 protein, protective mechanism of Trx1 against hydrogen peroxide-induced cell death was examined using HT-22 cells and an ischemic animal model. Transduced Tat-Trx1 markedly inhibited intracellular ROS levels, DNA fragmentation, and cell death in H2O2-treatment HT-22 cells. Tat-Trx1 also significantly inhibited phosphorylation of ASK1 and MAPKs in signaling pathways of HT-22 cells. In addition, Tat-Trx1 regulated expression levels of Akt, NF-κB, and apoptosis related proteins. In an ischemia animal model, Tat-Trx1 markedly protected hippocampal neuronal cell death and reduced astrocytes and microglia activation. These findings indicate that transduced Tat-Trx1 might be a potential therapeutic agent for treating ischemic injury.