• IMMUNE NETWORK
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• v.20 no.5
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• pp.36.1-36.13
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• 2020

Hippo signaling pathways are evolutionarily conserved signal transduction mechanisms mainly involved in organ size control, tissue regeneration, and tumor suppression. However, in mammals, the primary role of Hippo signaling seems to be regulation of immunity. As such, humans with null mutations in STK4 (mammalian homologue of Drosophila Hippo; also known as MST1) suffer from recurrent infections and autoimmune symptoms. Although dysregulated T cell homeostasis and functions have been identified in MST1-deficient human patients and mouse models, detailed cellular and molecular bases of the immune dysfunction remain to be elucidated. Although the canonical Hippo signaling pathway involves transcriptional co-activator Yes-associated protein (YAP) or transcriptional coactivator with PDZ motif (TAZ), the major Hippo downstream signaling pathways in T cells are YAP/TAZ-independent and they widely differ between T cell subsets. Here we will review Hippo signaling mechanisms in T cell immunity and describe their implications for immune defects found in MST1-deficient patients and animals. Further, we propose that mutual inhibition of Mst and Akt kinases and their opposing roles on the stability and function of forkhead box O and β-catenin may explain various immune defects discovered in mutant mice lacking Hippo signaling components. Understanding these diverse Hippo signaling pathways and their interplay with other evolutionarily-conserved signaling components in T cells may uncover molecular targets relevant to vaccination, autoimmune diseases, and cancer immunotherapies.

• Journal of Life Science
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• v.33 no.6
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• pp.463-470
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• 2023

Desmarestia tabacoides Okamura is a brown macroalgae that is found worldwide. Although several genera of Desmarestia have been reported as having anti-tumorigenic, anti-melanogenic, and photoprotective properties, the anti-inflammatory activity of D. tabacoides Okamura has not yet been evaluated. In this study, we analyzed the anti-inflammatory mechanisms of D. tabacoides Okamura ethanol extract (DTEE) via the inhibition of nitric oxide (NO) and prostaglandin (PG) E₂ production and the expression of their corresponding enzymes, inducible NO synthase (iNOS), and cyclooxygenase (COX)-2. In addition, their upstream signaling molecules were evaluated by Western blot analysis, such as nuclear factor (NF)-κB, mitogen-activated protein kinase (MAPK), and phosphoinositide-3-kinase (PI3K)/Akt, in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The DTEE treatment significantly inhibited LPS-induced NO and PGE₂ production as well as the expression of their corresponding enzymes, iNOS, and COX-2 without cytotoxicity. The stimulated transcription factor NF-κB and upstream signaling molecules extracellular signal-regulated kinase (ERK), c-Jun NH₂-terminal kinase (JNK), and p38 were attenuated by the DTEE treatment, which was statistically significant, while Akt did not provide any inhibitory effect. Moreover, the DTEE treatment significantly mitigated the LPS-activated adaptor molecules, toll-like receptor 4 (TLR4), and myeloid differentiation primary response 88 (MyD88) in the RAW 264.7 cells. These results suggest that DTEE attenuates TLR4-mediated inflammatory responses by inhibiting NF-κB activation and suppressing MAPK phosphorylation in LPS-stimulated RAW 264.7 cells.

• Journal of Life Science
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• v.33 no.11
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• pp.859-867
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• 2023

Lupeol is a type of pentacyclic triterpene that has been reported to have therapeutic effects for treating many diseases; however, its effect on insulin resistance is unclear clear. This study examined the inhibitory effect of lupeol on the serine phosphorylation of insulin receptor substrate-1 in insulin resistance-induced 3T3-L1 adipocytes. 3T3-L1 cells were cultured and treated with tumor necrosis factor-α (TNF-α) for 24 hours to induce insulin resistance. Cells treated with different concentrations of lupeol (15 μM or 30 μM) or 100 nM of rosiglitazone were incubated. Then, lysed cells underwent western blotting. Lupeol exhibited a positive effect on the negative regulator of insulin signaling and inflammation-activated protein kinase caused by TNF-α in adipocytes. Lupeol inhibited the activation of protein tyrosine phosphatase-1B (PTP-1B)-a negative regulator of insulin signaling-and c-Jun N-terminal kinase (JNK); it was also an inhibitor of nuclear factor kappa-B kinase (IKK) and inflammation-activated protein kinases. In addition, Lupeol downregulated serine phosphorylation and upregulated tyrosine phosphorylation in insulin receptor substrate-1. Then, the downregulated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway was activated, the translocation of glucose transporter type 4 was stimulated to the cell membrane, and intracellular glucose uptake increased in the insulin resistance-induced 3T3-L1 adipocytes. Lupeol may improve TNF-α-induced insulin resistance by downregulating the serine phosphorylation of insulin receptor substrate 1 by inhibiting negative regulators of insulin signaling and inflammation-activated protein kinases in 3T3-L1 adipocytes.

• Journal of Life Science
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• v.22 no.12
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• pp.1621-1627
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• 2012

Cell motility plays an essential role in many physiological responses, such as development, immune reaction, and angiogenesis. In the present study, we showed that lysophosphatidic acid (LPA) modulates cancer cell migration by regulation of generation of reactive oxygen species (ROS). Stimulation of SKOV-3 ovarian cancer cells with LPA strongly promoted migration. but this migration was completely blocked by pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Inhibition of the ERK pathway had no effect on migration. Stimulation of SKOV-3 ovarian cancer cells with LPA significantly induced the generation of ROS in a time-dependent manner. LPA-induced generation of ROS was significantly blocked by pharmacological inhibition of PI3K or Akt, but inhibition of the ERK signaling pathway had little effect. LPA-induced generation of ROS was blocked by pretreatment of SKOV-3 ovarian cancer cells with an NADPH oxidase inhibitor, whereas inhibition of xanthine oxidase, cyclooxygenase, or mitochondrial respiratory chain complex I had no effect. Scavenging of ROS by N-acetylcysteine completely blocked LPA-induced migration of SKOV-3 ovarian cancer cells. Inhibition of NADPH oxidase blocked LPA-induced migration whereas inhibition of xanthine oxidase, cyclooxygenase, or mitochondrial respiratory chain complex I did not affect LPA-induced migration of SKOV-3 ovarian cancer cells. Given these results, we suggest that LPA induces ROS generation through the PI3K/Akt/NADPH oxidase signaling axis, thereby regulating cancer cell migration.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.8
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• pp.1197-1203
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• 2013

This study investigated the effects of endurance exercise and ginsenoside $Rb_1$ on AMP-activated protein kinase (AMPK), phosphatidylinositol 3-kinase (PI3K) protein expression and glucose uptake in the skeletal muscle of rats. A total of 32 rats were randomly divided into four groups: CON (Control group, n=8), Ex (Exercise group; 25 m/min for 1 h, 6 days/week, 2 weeks, n=8), $Rb_1$ (Ginsenoside $Rb_1$ group; n=8), and $Rb_1/Ex$ ($Rb_1$+Exercise group, n=8). The $Rb_1$ and $Rb_1/Ex$ groups were incubated in ginsenoside $Rb_1$ (KRBP buffer, $100{\mu}g/mL$) for 60 min after a 2-week experimental treatment. After 2 weeks, the expression of phosphorylated $AMPK{\alpha}$ $Thr^{172}$, total $AMPK{\alpha}$, the p85 subunit of PI3K, pIRS-1 $Tyr^{612}$, and pAkt $Ser^{473}$ were determined in the soleus muscle. Muscle glucose uptake was measured using 2-deoxy-D-[$^3H$] glucose in epitroclearis muscle. Muscle glucose uptake was significantly higher in the three experimental groups (Ex, $Rb_1$, $Rb_1/Ex$) compared to the CON group (P<0.05). The expression of $tAMPK{\alpha}$ and $pAMPK{\alpha}$ $Thr^{172}$ was significantly higher in the Ex, $Rb_1$, and $Rb_1/Ex$ groups compared to the CON group (P<0.05). The expression of pAkt $Ser^{473}$ was significantly higher in the $Rb_1$ group compared to the CON and EX groups. However, the expression of pIRS-1 $Tyr^{612}$ and the p85 subunit of PI3K were not significantly different between the four groups. Overall, these results suggest that ginsenoside $Rb_1$ significantly stimulates glucose uptake in the skeletal muscle of rats through increasing phosphorylation in the AMPK pathway, similar to the effects of exercise.

• Biomolecules & Therapeutics
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• v.25 no.2
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• pp.213-221
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• 2017

Baicalein, a natural flavonoid obtained from the rhizome of Scutellaria baicalensis Georgi, has been reported to have anticancer activities in several human cancer cell lines. However, its antimetastatic effects and associated mechanisms in melanoma cells have not been extensively studied. The current study examined the effects of baicalein on cell motility and anti-invasive activity using mouse melanoma B16F10 cells. Within the noncytotoxic concentration range, baicalein significantly inhibited the cell motility and invasiveness of B16F10 cells in a concentration-dependent manner. Baicalein also reduced the activity and expression of matrix metalloproteinase (MMP)-2 and -9; however, the levels of tissue inhibitor of metalloproteinase-1 and -2 were concomitantly increased. The inhibitory effects of baicalein on cell motility and invasiveness were found to be associated with its tightening of tight junction (TJ), which was demonstrated by an increase in transepithelial electrical resistance and downregulation of the claudin family of proteins. Additionally, treatment with baicalein markedly reduced the expression levels of lipopolysaccharide-induced phosphorylated Akt and the invasive activity in B16F10 cells. Taken together, these results suggest that baicalein inhibits B16F10 melanoma cell migration and invasion by reducing the expression of MMPs and tightening TJ through the suppression of claudin expression, possibly in association with a suppression of the phosphoinositide 3-kinase/Akt signaling pathway.

• Biomolecules & Therapeutics
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• v.28 no.5
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• pp.443-455
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• 2020

The thioredoxin (Trx) system plays critical roles in regulating intracellular redox levels and defending organisms against oxidative stress. Recent studies indicated that Trx reductase (TrxR) was overexpressed in various types of human cancer cells indicating that the Trx-TrxR system may be a potential target for anti-cancer drug development. This study investigated the synergistic effect of auranofin, a TrxR-specific inhibitor, on sulforaphane-mediated apoptotic cell death using Hep3B cells. The results showed that sulforaphane significantly enhanced auranofin-induced apoptosis by inhibiting TrxR activity and cell proliferation compared to either single treatment. The synergistic effect of sulforaphane and auranofin on apoptosis was evidenced by an increased annexin-V-positive cells and Sub-G1 cells. The induction of apoptosis by the combined treatment caused the loss of mitochondrial membrane potential (ΔΨm) and upregulation of Bax. In addition, the proteolytic activities of caspases (-3, -8, and -9) and the degradation of poly (ADP-ribose) polymerase, a substrate protein of activated caspase-3, were also higher in the combined treatment. Moreover, combined treatment induced excessive generation of reactive oxygen species (ROS). However, treatment with N-acetyl-L-cysteine, a ROS scavenger, reduced combined treatment-induced ROS production and apoptosis. Thereby, these results deduce that ROS played a pivotal role in apoptosis induced by auranofin and sulforaphane. Furthermore, apoptosis induced by auranofin and sulforaphane was significantly increased through inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway. Taken together, the present study demonstrated that down-regulation of TrxR activity contributed to the synergistic effect of auranofin and sulforaphane on apoptosis through ROS production and inhibition of PI3K/Akt signaling pathway.

• Journal of Life Science
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• v.29 no.11
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• pp.1251-1257
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• 2019

Peptidoglycan (PG) is found in atheromatous lesions of arteries, where monocytes/macrophages express inflammatory cytokines, including tumor necrosis factor-alpha ($TNF-{\alpha}$). This study investigated the effects of PG on $TNF-{\alpha}$ expression and examined possible cellular factors involved in $TNF-{\alpha}$ upregulation. The overall aim was to identify the molecular mechanisms underlying inflammatory responses to bacterial pathogen-associated molecular patterns in the artery. Exposure of human THP-1 monocytic cells to PG enhanced the secretion of $TNF-{\alpha}$ and induced its gene transcription. Inhibition of TLR-2/4 with OxPAPC significantly inhibited $TNF-{\alpha}$ gene expression, whereas inhibition of LPS by polymyxin B did not. The PG-induced expression of $TNF-{\alpha}$ was also significantly suppressed by pharmacological inhibitors that modulate activities of cellular signaling molecules; for example, U0126 (an ERK inhibitor), SB202190 (a p38 MAPK inhibitor), and SP6001250 (a JNK inhibitor) significantly attenuated PG-induced transcription of $TNF-{\alpha}$ and secretion of its gene product. $TNF-{\alpha}$ expression was also inhibited by rapamycin (an mTOR inhibitor), LY294002 (a PI3K inhibitor), and Akt inhibitor IV (an Akt inhibitor). ROS-regulating compounds, like NAC and DPI, also significantly attenuated $TNF{\alpha}$ expression induced by PG. These results suggest that PG induces $TNF-{\alpha}$ expression in monocytes/macrophages by multiple molecules, including TLR-2, PI3K, Akt, mTOR, MAPKs, and ROS.

• Journal of Life Science
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• v.33 no.11
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• pp.851-858
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• 2023

Unique cartilage matrix-associated protein (UCMA) is an extrahepatic vitamin K-dependent protein rich in γ-carboxylated (Gla) residues. UCMA has been recognized for its ability to promote osteoblast differentiation and enhance bone formation; however, its impact on osteoblasts under hyperglycemic stress remains unknown. In this paper, we investigated the effect of UCMA on MC3T3-E1 osteoblastic cells under hyperglycemic conditions. After exposure to high glucose, the MC3T3-E1 cells were treated with recombinant UCMA proteins. CellROX and MitoSOX staining showed that the production of reactive oxygen species (ROS), which initially increased under high-glucose conditions in MC3T3-E1 cells, decreased after UCMA treatment. Additionally, quantitative polymerase chain reaction revealed increased expression of antioxidant genes, nuclear factor erythroid 2-related factor 2 and superoxide dismutase 1, in the MC3T3-E1 cells exposed to both high glucose and UCMA. UCMA treatment downregulated the expression of heme oxygenase-1, which reduced its translocation from the cytosol to the nucleus. Moreover, the expression of dynamin-related protein 1, a mitochondrial fission marker, was upregulated, and AKT signaling was inhibited after UCMA treatment. Overall, UCMA appears to mitigate ROS production, increase antioxidant gene expression, impact mitochondrial dynamics, and modulate AKT signaling in osteoblasts exposed to high-glucose conditions. This study advances our understanding of the cellular mechanism of UCMA and suggests its potential use as a novel therapeutic agent for bone complications related to metabolic disorders.

• Journal of Microbiology and Biotechnology
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• v.33 no.12
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• pp.1635-1647
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• 2023

Muscle atrophy, which is defined as a decrease in muscle mass and strength, is caused by an imbalance between the anabolism and catabolism of muscle proteins. Thus, modulating the homeostasis between muscle protein synthesis and degradation represents an efficient treatment approach for this condition. In the present study, the protective effects against muscle atrophy of ethanol extracts of Morus alba L. (MA) and Angelica keiskei Koidz. (AK) leaves and their mixtures (MIX) were evaluated in vitro and in vivo. Our results showed that MIX increased 5-aminoimidazole-4-carboxamide ribonucleotide-induced C2C12 myotube thinning, and enhanced soleus and gastrocnemius muscle thickness compared to each extract alone in dexamethasone-induced muscle atrophy Sprague Dawley rats. In addition, although MA and AK substantially improved grip strength and histological changes for dexamethasone-induced muscle atrophy in vivo, the efficacy was superior in the MIX-treated group. Moreover, MIX further increased the expression levels of myogenic factors (MyoD and myogenin) and decreased the expression levels of E3 ubiquitin ligases (atrogin-1 and muscle-specific RING finger protein-1) in vitro and in vivo compared to the MA- and AK-alone treatment groups. Furthermore, MIX increased the levels of phosphorylated phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR) that were reduced by dexamethasone, and downregulated the expression of forkhead box O3 (FoxO3a) induced by dexamethasone. These results suggest that MIX has a protective effect against muscle atrophy by enhancing muscle protein anabolism through the activation of the PI3K/Akt/mTOR signaling pathway and attenuating catabolism through the inhibition of FoxO3a.