• BMB Reports
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• v.28 no.4
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• pp.316-322
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• 1995

The GTPase activating protein (GAP) can function both as a negative regulator and an effector of $p21^{ras}$. Overexpression of GAP in NIH-3T3 cells has been shown to inhibit transformation by ms or src. To investigate the function of GAP in a differentiative system, we overexpressed this protein in the nerve growth factor (NGF)-responsive PC12 cell line. Two-fold overexpression of GAP caused a delay of several days in the onset of NGF- but not FGF-induced neuronal differentiation of PC12 cells. However, the NGF-induced activation or tyrosine phosphorylation of upstream (Trk, PLC-${\gamma}1$, SHC) and downstream (B-Raf and $p44^{mapk/erk1}$) components of $p21^{ras}$, signalling cascade was not altered by GAP overexpression. Therefore, the change of phenotype induced by GAP was probably not due to GAP functioning as a negative regulator of $p21^{ras}$. Rather, we found that NGF-induced tyrosine phosphorylation of SNT, a specific target of neurotrophin-induced tyrosine kinase activity, was inhibited by GAP overexpression. SNT is thought to function upstream or independent of $p21^{ras}$. Thus in PC12 cells, overexpressed GAP may control the rate of neuronal differentiation through a pathway involving SNT rather than the $p21^{ras}$ signalling pathway.

• Korean Journal of Pharmacognosy
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• v.29 no.4
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• pp.265-270
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• 1998

The effects of MeOH extracts of ninety kinds of medicinal herbs on dopamine content in PC12 cells were investigated. Among them, the MeOH extracts at a concentration of $40\;{\mu}g/ml$ of Symplocarpus renifolius, Adenocaulon himalaicum and Mosla punctulata decreased $38.5{\sim}60.0%$ of dopamine content. Tyrosine hydroxylase, the rate-limiting enzyme of the catecholamine biosynthesis, was inhibited by the treatment of the MeOH extracts of Symplocarpus renifolius, Adenocaulon himalaicum and Mosla punctulata ($19.9{\sim}31.3%$ inhibition at $40\;{\mu}g/ml$). These results suggested that these bioactive herbal medicines exhibited partially an inhibitory effect on dopamine biosynthesis by the reduction of tyrosine hydroxylase activity in PC12 cells.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.231-236
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• 2016

Inhibition of Rho-associated coiled coil-containing kinase (ROCK) has been reported to promote differentiation of neuronal cells. Here, we examined the effect of Y-27632, a ROCK inhibitor, on the outgrowth of neurites in PC12 cells. Y-27632 caused a rapid induction of neurite outgrowth in PC12 cells in a time-dependent manner. The neurite outgrowth, triggered by Y-27632, was accompanied by Rac1 activation, and was attenuated by Rac1 inhibitor NSC23766, in a concentration-dependent manner. Y-27632 also induced an increase in the production of reactive oxygen species (ROS). Pretreatment with N-acetylcysteine, an ROS scavenger, inhibited the ROS generation and neurite outgrowth in response to Y-27632. These results indicate that the activation of Rac1 and the generation of ROS contribute to the neurite outgrowth triggered by Y-27632 in PC12 cells.

• Molecules and Cells
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• v.20 no.2
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• pp.280-287
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• 2005

The insulin-mediated Ras/mitogen-activated protein (MAP) kinase cascade was examined in SK-N-BE(2) and PC12 cells, which can and cannot produce reactive oxygen species (ROS), respectively. Tyrosine phosphorylation of the insulin receptor and insulin receptor substrate 1 (IRS-1) was much lower in SK-N-BE(2) cells than in PC12 cells when the cells were treated with insulin. The insulin-mediated interaction of IRS-1 with Grb2 was observed in PC12 but not in SK-N-BE(2) cells. Moreover, the activity of extracellular-signal-related kinase (ERK) was much lower in SK-N-BE(2) than in PC12 cells when the cells were treated with insulin. Application of exogenous $H_2O_2$ caused increased tyrosine phosphorylation and Grb2 binding to IRS-1 in SK-N-BE(2) cells, while exposure to an $H_2O_2$ scavenger (N-acetylcysteine) or to a phophatidylinositol-3 kinase inhibitor (wortmannin), and expression of a dominant negative Rac1, decreased the activation of ERK in insulin-stimulated PC12 cells. These results indicate that the transient increase of ROS is needed to activate ERK in insulin-mediated signaling and that an inability to generate ROS is the reason for the insulin insensitivity of SK-N-BE(2) cells.

• The Journal of Korean Medicine
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• v.23 no.1
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• pp.50-60
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• 2002

Objectives: Sunghyangjunggisan (SHJS) is a commonly prescribed drug with a wide neuropharmacological spectrum. The water extracts of SHJS were found to be protective against neurotoxicity elicited by deprivation of serum and glucose. Methods: The morphological examination and Hoechst staining of nucleus also clearly showed that the extracts attenuated the cell shrinkage, membrane blebbing, representing typical neuronal apoptotic phenomena and nucleosome-sized fragmentation under the microscope in PC 12 rat pheochromocytoma cells. Results: Activation of protein kinase A (PKA) with dibutyl-cAMP and forskolin also protected during glucose deprivation, although it was not additive with the effect provided by phorbol ester. Interestingly, treatment with the protein kinase A inhibitor, KT5720, was not neuroprotective in the presence of SHJS. Electrophoretic mobility shift assays were used to characterize the neuroprotective binding of nuclear proteins to consensus sequences for AP-l, nuclear factor kappa B ($NF-{\kappa}B$) after glucose deprivation. When PC 12 cells are induced to undergo apoptosis by serum deprivation, AP-l and $NF-{\kappa}B$ DNA binding activity transiently increases to a slight degree. This stimulation is blocked by the water extracts of SHJS. The site of action of the drugs appeared to involve specific inhibition of AP-1 and nuclear factor kB binding activity. Conclusions: Taken together, these results suggested the possibility that the extracts of SHJS might provide a neurotrophic-like activity in PC 12 cells.

• Molecules and Cells
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• v.22 no.3
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• pp.291-299
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• 2006

Vitexin, a natural flavonoid compound identified as apigenin-8-C-${\beta}$-D-glucopyranoside, has been reported to exhibit antioxidative and anti-inflammatory properties. In this study, we investigated its effect on hypoxiainducible factor-$1{\alpha}$ (HIF-$1{\alpha}$) in rat pheochromacytoma (PC12), human osteosarcoma (HOS) and human hepatoma (HepG2) cells. Vitexin inhibited HIF-$1{\alpha}$ in PC12 cells, but not in HOS or HepG2 cells. In addition, it diminished the mRNA levels of hypoxia-inducible genes such as vascular endothelial growth factor (VEGF), smad3, aldolase A, enolase 1, and collagen type III in the PC12 cells. We found that vitexin inhibited the migration of PC12 cells as well as their invasion rates, and it also inhibited tube formation by human umbilical vein endothelium cells (HUVECs). Interestingly, vitexin inhibited the hypoxia-induced activation of c-jun N-terminal kinase (JNK), but not of extracellular-signal regulated protein kinase (ERK), implying that it acts in part via the JNK pathway. Overall, these results suggest the potential use of vitexin as a treatment for diseases such as cancer.

• Korean Journal of Pharmacognosy
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• v.41 no.3
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• pp.221-226
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• 2010

The effects of sesamin on dopamine biosynthesis in PC12 cells were investigated. Sesamin at concentration ranges of 20-75 ${\mu}M$ significantly increased intracellular dopamine levels and tyrosine hydroxylase (TH) activities at 24 h: 50 ${\mu}M$ sesamin increased dopamine levels to 132% and TH activities to 128% of control levels. Sesamin (50 ${\mu}M$) induced the phosphorylation of TH, cyclic AMP-dependent protein kinase (PKA) and cyclic AMP-response element binding protein (CREB) for 0.5-24 h. Sesamin (50 ${\mu}M$) also increased the mRNA levels of TH and CREB for 3-24 h. In addition, sesamin (50 ${\mu}M$) associated with L-DOPA (50 and 100 ${\mu}M$) further increased the intracellular levels of dopamine for 24 h compared to L-DOPA alone. These results suggest that sesamin enhances dopamine biosynthesis and L-DOPA-induced increase in dopamine levels by inducing TH activity and TH gene expression, which is mediated by PKA-CREB systems in PC12 cells. Therefore, sesamin could serve as an adjuvant phytonutrient for neurodegenerative diseases.

• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.32-32
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• 1998

The effect of neurotensin (NT) was investigated in rat pheochromocytoma (PC12) cells. When PC12 cells were treated with micromolar concentrations of NT, [$^3$H]norepinephrine ([$^3$H]NE) secretion and elevation of cytosolic Ca$\^$2＋/ concentration ([Ca$\^$2＋/]i) were evoked in a concentration-dependent manner with an EC$\sub$50/ of 50 ${\mu}$M.(omitted)

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.601-615
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• 1993

A series of polycarbonate(PC)/polyamide 6(PA6) blends were prepared by three different blending methods to investigate their compatibility. From the DSC results, all of these blends have two Tg's in their own Tg regions, and there was no significant depression of the melting point and the crystallization temperature of PA6. With respect to the microstructure of the blends by SEM, the phase separation occurred at very low blend compositions, PC/PA6=95/5 and 5/95, already. In addition, a method is proposed to determine the Flory-Huggins polymer-polymer interaction parameter(${\chi}_{12}$) in polymer blend systems by using the experimentally determined Tg's. The values of ${\chi}_{12}$ obtained were 0.0381, 0.0411, 0.0418, for solution casting, solution precipitation, and extrusion blending methods, respectively. These values were higher than the critical value of ${\chi}_{12}$,($({\chi}_{12})_c$, 0.0271). Therefore it was concluded that the PC/PA6 blend system have little compatibility.

• The Korea Journal of Herbology
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• v.22 no.2
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• pp.17-24
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• 2007

Objectives : Licorice has been commonly used as a detoxification agent. We previously reported that licorice and its component, liquiritigenin, exhibits cytoprotective activity against Pb-induced toxicity. The present study was conducted to evaluate the effect of liquiritigenin on the lead-induced cytotoxicity in PC-12 cells. Methods : PC-12 cells were pre-treated with liquiritigenin, and further incubated with lead 100 ${\mu}M$ for $12^{\sim}48$ hours. The viability of PC-12 cells was measured by MTT assay, and the levels of proteins were analysed by western blot. Results : Severe cytotoxicity was induced and nitric oxide (NO) production was augmented by the exposure of lead. Liquiritigenin protected cells from lead-induced cytoxicity and reduced NO production in a dose-dependent manner. The inhibition of NO production was due to the suppression of iNOS protein via the inhibition of $NF-{\kappa}B$ nuclear translocation, determined by western blot analysis. Conclusions : These results suggest that liquiritigenin may exert cytoprotective effect against lead toxicity by inhibiting NO production.