• Mycobiology
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• v.47 no.3
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• pp.346-349
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• 2019

AMP-activated protein kinase sucrose non-fermenting 1 (Snf1) is a representative regulator of energy status that maintains cellular energy homeostasis. In addition, Snf1 is involved in the mediation of environmental stress such as salt stress. Snf1 regulates metabolic enzymes such as acetyl-CoA carboxylase, indicating a possible role for Snf1 in metabolic regulation. In this article, we performed nuclear magnetic resonance (NMR) spectroscopy to profile the metabolic changes induced by Snf1 under environmental stress. According to our NMR data, we suggest that Snf1 plays a role in regulating cellular concentrations of a variety of metabolites during environmental stress responses.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.3
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• pp.203-210
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• 2015

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism. Previous studies have shown that activation of AMPK results in suppression of cardiac myocyte hypertrophy via inhibition of the p70S6 kinase (p70S6K) and eukaryotic elongation factor-2 (eEF2) signaling pathways. Epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea, possesses multiple protective effects on the cardiovascular system including cardiac hypertrophy. However, the molecular mechanisms has not been well investigated. In this study, we found that EGCG could significantly reduce natriuretic peptides type A (Nppa), brain natriuretic polypeptide (BNP) mRNA expression and decrease cell surface area in H9C2 cardiomyocytes stimulated with phenylephrine (PE). Moreover, we showed that AMPK is activated in H9C2 cardiomyocytes by EGCG, and AMPK-dependent pathway participates in the inhibitory effects of EGCG on cardiac hypertrophy. Taken together, our findings provide the first evidence that the effect of EGCG against cardiac hypertrophy may be attributed to its activation on AMPK-dependent signaling pathway, suggesting the therapeutic potential of EGCG on the prevention of cardiac remodeling in patients with pressure overload hypertrophy.

• Journal of Life Science
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• v.13 no.6
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• pp.903-910
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• 2003

Phospholipase D (PLD) plays an important role as a signaling molecule in the activation of neutrophils. In this study, effect of nitric oxide (NO) and cGMP on the activation of PLD in human neutrophils was investigated. Sodium nitroprusside (SNP), an agent to produce NO spontaneously in cells, alone increased PLD activity and the maximal activation was obtained with 0.5 mM SNP. Dibutyryl-cAMP, an agent to increase an intracellular cAMP concentration inhibited formyl-Met-Leu-Phe (fMLP)-stimulated PLD activity but 8-bromo-cGMP (300 $\mu$M), an agent to increase an intracellular cGMP concentration did not affect basal and fMLP-stimulated PLD activity. NO-induced activation of PLD was not blocked by KT 5823, an inhibitor of cGMP-dependent protein kinase (PKG), suggesting that NO-induced PLD activation is not mediated by cGMP. NO also stimulated p38 mitogen activated protein kinase (MAPK) in human neutrophils, indicated by increased phosphorylation of p38 MAPK in Western blotting. NO-induced phosphorylation of p38 MAPK was not inhibited by KT 5823 or n-butanol. RhoA, an regulatory factor of PLD activation was trans-located from cytosolic fraction to plasma membranes by fMLP or phorbol ester, and fMLP-stimulated but not phorbol ester-stimulated translocation of RhoA was inhibited by cGMP. These results suggest that NO stimulates PLD activity through other unidentified facto.(s) than cGMP even though cGMP inhibits the artivation of RhoA.

• Journal of Oriental Physiology
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• v.14 no.2 s.20
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• pp.67-82
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• 1999

The effects of Bogi, Boyang and Onri herbs on glutamte receptor, and the regulatory mechanism of cAMP-protein kinase on the ion currents activated by Bogi, Boyang and Onri herbs using nystatin-perforated patch clamp were investigated and the following results were obtained. Ginseng radix and Astragali radix, Cervi cornu and Boshniakiae herba, and Aconiti tuber and Zingiberis rhizoma were chosen as Bogi, Boyang and Onri herbs respectively. 1. The ion currents activated by $10^{-5}M$ of glycine were used as controls. The magnitudes of the ion currents by the above named herbs were as follows; Cervi cornu>Astragali radix>Aconiti tuber>Zingiberis rhizoma>Ginseng radix>Boshniakiae herba. 2. The magnitudes of the ion currents by $10^{-5}M$ of glutamate pre-treated with 0.01 mg/ml of Bogi, Boyang and Onri herbs were sharply decreased. 3. The activity of ion channels activated by Bogi herbs pre-treated with $10^{-7}M$ of staurosporin, an inhibitor of protein kinase, for thirty seconds was observed as the experiment proceeded. Staurosporin brought about dephosphorylation of ion channels. Hence, while the activity of ion channels activated by Ginseng radix was decreased, the activity of ion channels activated by Astragali radix was increased, as time went by. 4. The activity of ion channels activated by Boyang herbs pre-treated with $10^{-7}M$ of staurosporin, an inhibitor of protein kinase and an dephosphorylating agent of ion channels, for thirty seconds was investigated. While the activity of ion channels activated by Cervi cornu was increased, the activity of ion channels activated by Boshniakiae herba was initially increased then sharply decreased. 5, The activity of ion channels activated by Onri herbs pre-treated with $10^{-7}M$ of staurosporin, an inhibitor of protein kinase and an dephosphorylating agent of ion channels, for thirty seconds was investigated. While the activity of ion channels activated by Aconiti tuber was increased, that of ion channels activated by Zingiberis rhizomal sharply declined.

• YAKHAK HOEJI
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• v.44 no.2
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• pp.162-168
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• 2000

To investigate the effects of protein kinases on endothelin-1-induced phospholipase C activation and $Ca^{2+}$ mobilization in Rat-2 fibroblast, we measured the formation of inositol phosphates and intracellular $Ca^{2+}$ concentration with [$^3$H]inositol and Fura-2/AM, respectively. Endothelin-1 dose-dependently activated phospholipase C and increased intracellular $Ca^{2+}$ concentration. Protein kinase C activator PMA, significantly inhibited both phospholipase C activity and $Ca^{2+}$ mobilization induced by endothelin-1. Tyrosine kinase inhibitor, genistein, inhibited both. On the other hand, cyclic nucleotide (cAMP and cGMP) did not have any influence on the signaling pathway of phospholipase C-Ca$^{2+}$ mobilization induced by endothelin-1. These results suggest that protein kinase C and tyrosine kinase counteract on the signaling pathway of phospholipase C-Ca$^{2+}$ mobilization induced by endothelin-1 in Rat-2 fibroblast. fibroblast.

• Journal of Ginseng Research
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• v.41 no.3
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• pp.392-402
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• 2017

Background: Previously, we reported that Korean Red Ginseng inhibited liver fibrosis in mice and reduced the expressions of fibrogenic genes in hepatic stellate cells (HSCs). The present study was undertaken to identify the major ginsenoside responsible for reducing the numbers of HSCs and the underlying mechanism involved. Methods: Using LX-2 cells (a human immortalized HSC line) and primary activated HSCs, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assays were conducted to examine the cytotoxic effects of ginsenosides. $H_2O_2$ productions, glutathione contents, lactate dehydrogenase activities, mitochondrial membrane permeabilities, apoptotic cell subpopulations, caspase-3/-7 activities, transferase dUTP nick end labeling (TUNEL) staining, and immunoblot analysis were performed to elucidate the molecular mechanism responsible for ginsenoside-mediated cytotoxicity. Involvement of the AMP-activated protein kinase (AMPK)-related signaling pathway was examined using a chemical inhibitor and small interfering RNA (siRNA) transfection. Results and conclusion: Of the 11 ginsenosides tested, 20S-protopanaxadiol (PPD) showed the most potent cytotoxic activity in both LX-2 cells and primary activated HSCs. Oxidative stress-mediated apoptosis induced by 20S-PPD was blocked by N-acetyl-$\text\tiny L$-cysteine pretreatment. In addition, 20S-PPD concentration-dependently increased the phosphorylation of AMPK, and compound C prevented 20S-PPD-induced cytotoxicity and mitochondrial dysfunction. Moreover, 20S-PPD increased the phosphorylation of liver kinase B1 (LKB1), an upstream kinase of AMPK. Likewise, transfection of LX-2 cells with LKB1 siRNA reduced the cytotoxic effect of 20S-PPD. Thus, 20S-PPD appears to induce HSC apoptosis by activating LKB1-AMPK and to be a therapeutic candidate for the prevention or treatment of liver fibrosis.

• Molecular & Cellular Toxicology
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• v.4 no.3
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• pp.224-229
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• 2008

Eucommia ulmoides (Duchung) is commonly used for treatment of diabetes in Korean traditional medicine. However, the exact mechanism of its anti-diabetic effect has not yet been fully elucidated. In this study, the effect of E. ulmoides extract on glucose uptake was investigated in L6 rat skeletal muscle cells. E. ulmoides extract stimulated the activity of phosphatidylinositol (PI) 3-kinase that is a major regulatory molecule in glucose uptake pathway. Protein kinase B (PKB) and protein kinase C-${\xi}$ (PKC-${\xi}$), downstream mediators of PI 3-kinase, were also activated by E. ulmoides extract. We assessed the activity of AMP-activated protein kinase (AMPK), another regulatory molecule in glucose uptake pathway. Phosphorylation level of AMPK did not change with treatment of E. ulmoides extract. Phosphorylations of p38 mitogen activated protein kinase (p38 MAPK) and acetyl-CoA carboxylase (ACC), downstream mediators of AMPK, were not significantly different. Taken together, our results suggest that E. ulmoides may stimulate glucose uptake through PI 3-kinase but not AMPK in L6 skeletal muscle cells.

• Journal of Life Science
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• v.32 no.7
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• pp.542-549
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• 2022

Polymethoxyflavones (PMFs) are flavonoids mainly found in citrus fruits and have been reported to exhibit a wide range of bioactivities, including anti-obesity, anti-cancer, and anti-inflammatory actions. To utilize PMFs as functional materials, it is necessary to develop a simple method of obtaining PMFs from citrus tissues containing a large amount of PMFs. It has been reported that Jinkyool (C. sunki Hort ex. Tanaka) peel contained a large amount of PMFs, but there are no studies on PMFs isolated from its leaves. In this study, we established a simple procedure for obtaining the PMF-rich fraction (PRF) from the leaves of Jinkyool and investigated the effects of PRF on lipid metabolism in 3T3-L1 cells. PRF inhibited lipogenesis during the differentiation of 3T3-L1 preadipocytes. It decreased the expression of peroxisome proliferator-activated receptor gamma (PPAR𝛾) and CCAAT/enhancer binding protein alpha (CEBP𝛼), FAS, and adipocyte fatty-acid-binding protein 2 (aP2). In mature 3T3-L1 adipocytes, PRF increases the phosphorylation of protein kinase A (PKA)/hormone-sensitive lipase (HSL), which are key factors involved in lipolysis. Moreover, it increases the phosphorylation of the AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) involved in fatty acid oxidation. These results suggest that PRF from Jinkyool leaves can be used as an anti-obesity agent with the action of inhibiting lipogenesis and promoting lipolysis and fatty acid oxidation in 3T3-L1 adipocytes.

• KSBB Journal
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• v.25 no.6
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• pp.507-512
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• 2010

In this study, we investigated the ability of luteolin, a plant derived flavonoid on hepatocarcinoma cell growth using HepG2 cell culture system. We found that luteolin increased the Smac/DIABLO releases, a mitochondrial protein that potentiates apoptosis. Luteolin also induced either transcriptional activity or expression of PPAR-gamma, a target of cancer growth that PPAR-gamma agonist sensitizes to apoptosis in certain cancer types. To find the possible upstream target molecules of PPAR-gamma activated by luteolin treatment, we used compound C, a specific inhibitor of AMP-activated protein kinase. Pre-treatment of Compound C significantly restored the activation or expression of PPAR-gamma stimulated by luteolin. This result indicated that AMPK signaling might be involved in the activation or expression of PPAR-gamma signaling pathway stimulated by luteolin. Moreover, we also found that luteolin inhibited the insulin-stimulated Akt phosphorylation as well as AICAR, a specific AMPK activator. These results propose that luteolin significantly induces cancer cell death through modulating survival signal pathways such as PPAR-gamma and Akt. AMPK signaling pathway may be an upstream regulator for survival signal pathways such as PPAR-gamma and Akt stimulated by luteolin.

• Nutrition Research and Practice
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• v.14 no.5
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• pp.478-489
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• 2020

BACKGROUND/OBJECTIVES: Morusin, a marker component of Morus alba L., possesses anti-cancer activity. The objective of this study was to determine autophagy-inducing effect of morusin in non-small cell lung cancer (NSCLC) cells and investigate the underlying mechanism. SUBJECTS/METHODS: Autophagy induction and the expression of autophagy-related proteins were analyzed by LC3 immunofluorescence and western blot, respectively. The role of autophagy and AMP-activated protein kinase (AMPK) was determined by treating NSCLC cells with bafilomycin A1, an autophagy inhibitor, and compound C, an AMPK inhibitor. Cytotoxicity and apoptosis induction were determined by MTT assay, trypan blue exclusion assay, annexin V-propidium iodide (PI) double staining assay, and cell cycle analysis. RESULTS: Morusin increased the formation of LC3 puncta in the cytoplasm and upregulated the expression of autophagy-related 5 (Atg5), Atg12, beclin-1, and LC3II in NSCLC cells, demonstrating that morusin could induce autophagy. Treatment with bafilomycin A1 markedly reduced cell viability but increased proportions of sub-G1 phase cells and annexin V-positive cells in H460 cells. These results indicate that morusin can trigger autophagy in NSCLC cells as a defense mechanism against morusin-induced apoptosis. Furthermore, we found that AMPK and its downstream acetyl-CoA carboxylase (ACC) were phosphorylated, while mammalian target of rapamycin (mTOR) and its downstream p70S6 kinase (p70S6K) were dephosphorylated by morusin. Morusin-induced apoptosis was significantly increased by treatment with compound C in H460 cells. These results suggest that morusin-induced AMPK activation could protect NSCLC cells from apoptosis probably by inducing autophagy. CONCLUSIONS: Our findings suggest that combination treatment with morusin and autophagy inhibitor or AMPK inhibitor might enhance the clinical efficacy of morusin for NSCLC.