• Archives of Pharmacal Research
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• v.29 no.1
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• pp.67-72
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• 2006

The abnormal proliferation of aortic vascular smooth muscle cells (VSMCs) plays a central role in the pathogenesis of atherosclerosis and restenosis after angioplasty and possibly also in the development of hypertension. The present study was designed to examine the inhibitory effects and the mechanism of luteolin 7-glucoside (L7G) on the platelet-derived growth factor (PDGF)-BB-induced proliferation of VSMCs. L7G significantly inhibited the PDGF-BB-induced proliferation and the DNA synthesis of the VSMCs in a concentration-dependent manner. Pre-incubation of the VSMCs with L7G significantly inhibited the PDGF-BB-induced extracellular signal-regulated kinase 1/2 (ERK1/2), Akt and the phospholipase C $(PLC)-{\gamma}1$ activation. However, L7G had almost no affect on the phosphorylation of $PDGF-{\beta}$ receptor tyrosine kinase, which was induced by PDGF-BB. These results suggest that L7G inhibits the PDGF-BB-induced proliferation of VSMCs via the blocking of $(PLC)-{\gamma}1$, Akt, and ERK1/2 phosphorylation.

• Archives of Pharmacal Research
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• v.27 no.1
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• pp.94-98
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• 2004

Effects of dopaminergic drugs on the degranulation of mast cells (RBL-2H3 cells) and the nitric oxide production from macrophage cells (RAW 264.7) were studied. Among the dopaminergic agonists and antagonists tested, bromocriptine, 7-OH-DPAT, haloperidol, and clozapine showed potent inhibitions of mast cell degranualtion ($IC_{50} value, 5 \mu$ M). However, these dopaminergic agents did not affect the tyrosine phosphorylations of the signaling components of the high affinity IgE receptor ($Fc\varepsilonRI$), such as Syk, $PLC\gamma1$, and $PLC\gamma2$.; This suggested that these signaling components were not involved in the inhibition of the mast cell degranulation by these compounds. On the other hand, dopamine, bromocriptine, 7-OH-DAPT, and haloperidol markedly inhibited the nitric oxide production from RAW 264.7 cells ($IC_{50}$ values, 10-20$\mu$M). Bromocriptine, a dopamine agonist that is routinely used for the treatment of Parkinsons disease, inhibited the expression of the inducible nitric oxide synthase at an early stage of the LPS-induced protein expression in a dose-dependent manner. The results suggested that these dopaminergic agents, when used for the treatment of dopamine receptors-related diseases, such as Schizophrenia or Parkinsons disease, might have additional beneficial effects.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.592-597
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• 1997

During the screening of inhibitors against phospholipase C (PLC) and the formation of inositol phosphates (IP$_{t}$) at NIH3T3${\gamma}$1 cells from microbial secondary metabolites, we selected a fungal strain MT60109 which was capable of producing an inhibitor. By the taxonomic studies, this fungus was identified as Pseudallescheria sp. MT60109 and an inhibitor of PLC was purified by BuOH extraction and chromatographic techniques from the culture broth of Pseudallescheria sp. MT60109. The inhibitor was identified as thielavin B by the physico-chemical properties and spectroscopic analysis of UV, FAB-MS, $^{1}$H, $^{13}$C-NMR, $^{1}$H-$^{1}$H COSY and HMBC. Thielavin B showed potent inhibitory activity against PLC purified from bovine brain with an IC$_{50}$ of 20 $\mu$M. And it also inhibited the formation of inositol phosphates in platelet-derived growth factor (PDGF) -stimulated NIH3T3${\gamma}$1 cells with an IC$_{50}$ of 20 $\mu$M.

• Molecules and Cells
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• v.28 no.1
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• pp.13-17
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• 2009

Basic fibroblast growth factor (bFGF) plays an important role in angiogenesis. However, the underlying mechanisms are not clear. $Mg^{2+}$ is the most abundant intracellular divalent cation in the body and plays critical roles in many cell functions. We investigated the effect of bFGF on the intracellular $Mg^{2+}$ concentration ($[Mg^{2+}]_i$) in human umbilical vein endothelial cells (HUVECs). bFGF increased ($[Mg^{2+}]_i$) in a dose-dependent manner, independent of extracellular $Mg^{2+}$. This bFGF-induced $[Mg^{2+}]_i$ increase was blocked by tyrosine kinase inhibitors (tyrphostin A-23 and genistein), phosphatidylinositol 3-kinase (PI3K) inhibitors (wortmannin and LY294002) and a phospholipase $C{\gamma}$ ($PLC{\gamma}$) inhibitor (U73122). In contrast, mitogen-activated protein kinase inhibitors (SB202190 and PD98059) did not affect the bFGF-induced $[Mg^{2+}]_i$ increase. These results suggest that bFGF increases the $[Mg^{2+}]_i$ from the intracellular $Mg^{2+}$ stores through the tyrosine kinase/PI3K/$PLC{\gamma}$-dependent signaling pathways.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.251-260
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• 1998

Cromakalim (BRL 34915), known as an airway smooth muscle relaxant, inhibited the releases of mediators in the antigen-induced mast cell activation. It has been suggested that cromakalim, in part, inhibited mediator releases by inhibiting the initial increase of 1,2-diacylglycerol (DAG) produced by the activation of the other phospholipase system which is different from phosphatidylcholine-phospholipase D pathway. The aim of this study is to further examine the inhibitory mechanism of cromakalim on the mediator release in the mast cell activation. Guinea pig lung mast cells were purified by using enzyme digestion and percoll density gradient. In purified mast cells prelabeled with $[^3H]PIP_2$, phospholipase C (PLC) activity was assessed by the production of $[^3H]$insitol phosphates. Protein kinase C (PKC) activity was assessed by measuring the protein phosphorylated from mast cells prelabeled with $[{\gamma}-32P]ATP$, and Phospholipase $A_2\;(PLA_2)$ activity by measuring the lyso-phosphatidylcholine produced from mast cell prelabeled with 1-palmitoyl-2-arachidonyl $phosphatidyl-[^{14}C]choline$. Histamine was assayed by fluorometric analyzer, and leukotrienes by radioimmunoassay. The PLC activity was increased by activation of the passively sensitized mast cells. This increased PLC activity was decreased by cromakalim pretreatment. The PKC activity increased by the activation of the passively sensitized mast cells was decreased by calphostin C, staurosporine and cromakalim, respectively. The $PLA_2$ activity was increased in the activated mast cells. The pretreatment of cromakalim did not significantly decrease $PLA_2$ activity. These data show that cromakalim inhibits histamine release by continuously inhibiting signal transduction processes which is mediated via PLC pathway during mast cell activation, but that cromakalim does not affect $PLA_2$ activity related to leukotriene release.

• Proceedings of the PSK Conference
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• 2004.10a
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• pp.147.1-147.1
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• 2004

• The Korean Journal of Physiology and Pharmacology
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• v.15 no.3
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• pp.179-187
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• 2011

Regulation of B cell receptor (BCR)-induced $Ca^{2+}$ signaling by CD40 co-stimulation was compared in long-term BCR-stimulated immature (WEHI-231) and mature (Bal-17) B cells. In response to long-term pre-stimulation of immature WEHI-231 cells to ${\alpha}$-IgM antibody (0.5~48 hr), the initial transient decrease in BCR-induced $[Ca^{2+}]_i$ was followed by spontaneous recovery to control level within 24 hr. The recovery of $Ca^{2+}$ signaling in WEHI-231 cells was not due to restoration of internalized receptor but instead to an increase in the levels of $PLC{\gamma}2$ and $IP_3R-3$. CD40 co-stimulation of WEHI-231 cells prevented BCR-induced cell cycle arrest and apoptosis, and it strongly inhibited the recovery of BCR-induced $Ca^{2+}$ signaling. CD40 co-stimulation also enhanced BCR internalization and reduced expression of $PLC{\gamma}2$ and $IP_3R-3$. Pre-treatment of WEHI-231 cells with the antioxidant N-acetyl-L-cysteine (NAC) strongly inhibited CD40-mediated prevention of the recovery of $Ca^{2+}$ signaling. In contrast to immature WEHI-231 cells, identical long-term ${\alpha}$-IgM pre-stimulation of mature Bal-17 cells abolished the increase in BCR-induced $[Ca^{2+}]_i$, regardless of CD40 co-stimulation. These results suggest that CD40-mediated signaling prevents antigen-induced cell cycle arrest and apoptosis of immature B cells through inhibition of sustained BCR-induced $Ca^{2+}$ signaling.

• BMB Reports
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• v.33 no.6
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• pp.525-530
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• 2000

The nerve growth factor (NGF) induces neuronal differentiation and neurite outgrowth of PC12 cells, whereas epidermal growth factors (EGF) stimulate growth and proliferation of the cells. In spite of this difference, NGF-or EGF-treated PC12 cells share various properties in cellular-signaling pathways. These include the activation of the phosphoinositide (PI)-3 kinase, 70 kDa S6 kinase, and in the mitogen-activated protein (MAP) kinase pathway, following the binding of these growth factors to intrinsic receptor tyrosine kinases (RTKs). Therefore, many studies have been attempted to access the critical signaling events in determining the differentiation and proliferation of PC12 cells. In this study, we investigated the cytosolic phospholipase $A_2$ ($cPLA_2$) in neurite behavior in order to identify the differences of signaling pathways between the NGF-induced differentiation and the EGF-induced proliferation of PC12 cells. We have showed here that the $cPLA_2$ was translocated from cytosol to membrane only in NGF-treated cells. We also demonstrated that this translocation is associated with NGF-induced activation of phospholipase $C-{\gamma}(PLC-{\gamma})$, which elevates intracellular $Ca^{2+}$ concentration. These results reveal that the translocation of $cPLA_2$ may be a requisite event in the neuronal differentiation of PC12 cells. Various phospholipase inhibitors were used to confirm the importance of these enzymes in the differentiation of PC12 cells. Neomycin B, a PLC inhibitor, dramatically inhibited the neurite outgrowth, and two distinct $PLA_2$ inhibitors, 4-bromophenacyl bromide (BPB) and arachidonyltrifluoro-methyl ketone ($AACOCF_3$) also suppressed the neurite outgrowth of the cells, as well Taken together, these data indicated that $cPLA_2$ is involved in NGF-induced neuronal differentiation and neurite outgrowth of PC12 cells.

• YAKHAK HOEJI
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• v.41 no.4
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• pp.433-438
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• 1997

MT 51005 as a potent inhibitor of phospholipase C(PLC) was purified from the culture broth of a fungal strain No. 51005 isolated from soil. It was identified as a benzaldehyde d erivative, anguillosporal. by the physico-chemical properties and spectroscopic data. Anguillosporal showed the inhibitory activity against purified PLC with an $IC_{50}\;of\;13{\mu}g/ml$. And it also inhibited the formation of inositol phosphates($IP_t$) in platelet-derived growth factor(PDGF)-stimulated $NIH3T3{\gamma}1$ cells with an $IC_{50}\;of\;0.8{\mu}g/ml$.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.19-26
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• 1996

A phospholipase C (PLC) inhibitor (MT267-2B) was isolated from the culture broth of actinomycetes isolate MT2617-2 by the extraction with n-butanol and column chromatographic techniques. The molecular weight of the inhibitor was 1057, by the spectroscopic analyses of IR, $^{13}C$-and $^{1}H$-NMR and ESI-MS. The chemical structure of MT2617-2B was found to be a macrolide compound consisted of a hemiketal ring, polyhydroxyl and polymethyl groups, which had a malonate and guanidine group as its side chain. MT2617-2B produced its two isomers having the same molecular weight by standing in methanol solution at room temperature. Therefore, MT2617-2B was identified as copiamycin and niphithricin A, macrolide antibiotics. The values of $IC_{50}$ against PLC-${\gamma}$1 and PLC-${\beta}$1 were 25 and 50${\mu}$g/ml, respectively. MT2617-2B had antimicrobial activities against Staphylococcus aureus and Candida albicans, but not against Escherichia coli.