• Molecules and Cells
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• 제28권1호
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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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• 제3권3호
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• pp.293-303
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• 1999

The influences of specific protein phosphatase and protein kinase inhibitors on the ATP-sensitive $K^+\;(K_{ATP})$ channel-opening effect of pinacidil were investigated in single rat ventricular myocytes using patch clamp technique. In cell-attached patches, pinacidil $(100\;{\mu}M)$ induced the opening of the $K_{ATP}$ channel, which was blocked by the pretreatment with H-7 $(100\;{\mu}M)$ whereas enhanced by the pretreatment with genistein $(30\;{\mu}M)$ or tyrphostin A23 $(10\;{\mu}M)$. In inside-out patches, pinacidil $(10\;{\mu}M)$ activated the $K_{ATP}$ channels in the presence of ATP (0.3 mM) or AMP-PNP (0.3 mM) and in a partial rundown state. The effect of pinacidil $(10\;{\mu}M)$ was not affected by the pretreatment with protein tyrosine phosphatase 1B $(PTP1B,\;10\;{\mu}g\;ml^{-1}),$ but blocked by the pretreatment of protein phosphatase 2A $(PP2A,\;1\;U\;ml^{-1})$. In addition, pinacidil $(10\;{\mu}M)$ could not induce the opening of the reactivated $K_{ATP}$ channels in the presence of H-7 $(100\;{\mu}M)$ but enhanced it in the presence of ATP (1 mM) and genistein $(30\;{\mu}M).$ These results indicate that the $K_{ATP}$ channel-opening effect of pinacidil is not mediated via phosphorylation of $K_{ATP}$ channel protein or associated protein, although it still requires the phosphorylation of serine/threonine residues as a prerequisite condition.

• The Korean Journal of Physiology and Pharmacology
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• 제11권3호
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• pp.107-112
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• 2007

Gap junction protein, connexin, is expressed in endothelial cells of vessels, glomerulus, and renin secreting cells of the kidney. The purpose of this study was to investigate the role of gap junction in renin secretion and its underlying mechanisms using As 4.1 cell line, a renin-expressing clonal cell line. Renin release was increased proportionately to incubation time. The specific gap junction inhibitor, 18-beta glycyrrhetinic acid (GA) increased renin release in dose-dependent and time-dependent manners. Heptanol and octanol, gap junction blockers, also increased renin release, which were less potent than GA. GA-stimulated renin release was attenuated by pretreatment of the cells with amiloride, nifedipine, ryanodine, and thapsigargin. GA dose-dependently increased intracellular $Ca^{2+}$ concentration, which was attenuated by nifedipine, nimodipine, ryanodine, and thapsigargin. However, RP-cAMP, chelerythrine, tyrphostin A23, or phenylarsine oxide did not induced any significant change in GA-stimulated increase of intracellular $Ca^{2+}$ concentration. These results suggest that gap junction plays an important role on the regulation of renin release and intracellular $Ca^{2+}$ concentration in As 4.1 cells.

• The Korean Journal of Physiology and Pharmacology
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• 제13권2호
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• pp.131-138
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• 2009

The binding of interleukin-6 (IL-6) cytokine family ligands to the gp130 receptor complex activates the Janus kinase (JAK)/ signal transducer and activator of transcription 3 (STAT3) signal transduction pathway, where STA T3 plays an important role in cell survival and tumorigenesis. Constitutive activation of STAT3 has been frequently observed in many cancer tissues, and thus, blocking of the gp130 signaling pathway, at the JAK level, might be a useful therapeutic approach for the suppression of STAT3 activity, as anticancer therapy. AG490 is a tyrphostin tyrosine kinase inhibitor that has been extensively used for inhibiting JAK2 in vitro and in vivo. In this study, we demonstrate a novel mechanism associated with AG490 that inhibits the JAK/STAT3 pathway. AG490 induced downregulation of gp130, a common receptor for the IL-6 cytokine family compounds, but not JAK2 or STAT3, within three hours of exposure. The downregulation of gp130 was not caused by enhanced degradation of gp130 or by inhibition of mRNA transcription. It most likely occurred by translation inhibition of gp130 in association with phosphorylation of the eukaryotic initiation factor-2 a. The inhibition of protein synthesis of gp130 by AG490 led to immediate loss of mature gp130 in cell membranes, due to its short half-life, thereby resulting in reduction in the STAT3 response to IL-6. Taken together, these results suggest that AG490 blocks the STAT3 activation pathway via a novel pathway.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2002년도 국제심포지엄
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• pp.113-113
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• 2002

The stimulatory effect of EGF and FSH on oocyte maturation have been reported in various mammalian species. And some reports presented FSH enhanced the effect of EGF on oocyte maturation. But, the interaction between EGF and FSH on nuclear maturation of mammalian oocytes is not fully understood. We observed the effect of EGF and FSH on nuclear maturation during in vitro maturation of mouse oocytes. Also, we examined the interaction between EGF and FSH on nuclear maturation of mouse oocytes using the EGFR inhibitor or FSH inhibitor. Germinal vesicle (GV) stage oocytes were obtained from 3-4weeks PMSG primed BCFI hybrid mice and cultured in TCM-199 medium with 0.4%PVP supplemented with/without EGF (1ng/ml), FSH (1ug/ml), EGFR specific tyrosine kinase inhibitors: Tyrphostin AG 1478 (500nM), MAP kinase kinase inhibitor : U0126 (20uM) or PD 98059 (100uM) for 14-l5hr. Rapid staining method were used for the assessment of nuclear maturation. Nuclear maturation rates of EGF indjor FSH-treated group were significantly higher than those of control group. Treatment of EGFR inhibitor significantly block the nuclear maturation of GV oocyte in EGF-treated group, but it did not block those of GV oocyte in FSH-treated or FSH and EGF-treated group. Treatment of FSH inhibitor(U0126, PD98059) significantly block the nuclear maturation of EGF-treated group, FSH-treated and FSH and EGF-treated group. These results show that EGF has a stimulatory effect as well as different action pathway with FSH on in-vitro maturation of mouse oocyte in vitro. Therefore, further studies will be needed to find the signaling pathway of EGF associated with nuclear maturation.

• Tuberculosis and Respiratory Diseases
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• 제63권1호
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• pp.42-51
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• 2007

배 경: 폐암의 새로운 치료제로 각광을 받고 있는 TRAIL은 암에 선택적으로 apoptosis를 일으킨다고 알려진 cytokine으로 알려져 있다. 또한 gefitinib (Iressa)는 폐암의 적용된 최초의표적치료제로 각광을 받고 있다. 그러나 일부의 암세포에서는 이에 대한 저항성을 보이고 있다. 본 연구에서는 암세포에서 외부의 apoptotic 자극에 저항성을 보이는 IGF-1R를 억제함으로 TRAIL 및 gefitinib의 항암작용을 증가시키고자 실험을 시행하였다. 방 법: 암세포주는 TRAIL 및 gefitinib에 민감한 NCI H460와 두 약제에 중등도의 저항성을 보이는 A549의 폐암세포주로 시행하였으며 IGF-1R의 억제는 본 연구자가 개발하였던 IGF-1 pathway를 dominant negative inhibition을 할 수 있는 adenovirus- IGF1R(482 ST, 950ST) 및 IGF-1R tyrosine kinase inhibitor인 Tyrphostin AG1024를 사용하였고 gefitinib에 대한 실험에서는 RNA interference를 이용하여 IGF-1R의 발현을 억제하는 adenovirus- shIGF-1R을 이용하였다. 결 과: TRAIL에 저항성을 보이는 폐암세포주(A549)에서 adenovirus-IGF1R(482ST, 950ST) 및 AG1024로 IGF-1R를 억제한 후 TRAIL을 투여한 경우 항암효과가 증대되었다. A549에 adenovirus- shIGF-1R을 감염시켜 IGF-1R의 발현을 억제한 결과 gefitinib에 대한 감수성이 증가되었다.