• Biomolecules & Therapeutics
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• v.32 no.5
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• pp.611-626
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• 2024

Leptin, an adipose tissue-derived hormone, has exhibited the potent hepatotoxic effects. However, the underlying molecular mechanisms are not fully understood. In this study, we have elucidated the mechanisms by which leptin exerts cytotoxic effects in hepatocytes, particularly focusing on the role of interleukin-1β (IL-1β) signaling. Leptin significantly induced maturation and secretion of IL-1β in cultured rat hepatocytes. Interestingly, inhibition of IL-1β signaling by pretreatment with an IL-1 receptor antagonist (IL-1Ra) or gene silencing of type I IL-1 receptor (IL-1R1) markedly abrogated leptin-induced cell cycle arrest. The critical role of IL-1β signaling in leptin-induced cell cycle arrest is mediated via upregulation of p16, which acts as an inhibitor of cyclin-dependent kinase. In addition, leptin-induced apoptotic cell death was relieved by inhibition of IL-1β signaling, as determined by annexin V/7-AAD binding assay. Mechanistically, IL-1β signaling contributes to apoptotic cell death and cell cycle arrest by suppressing AKT and activation of p38 mitogen-activated protein kinase (p38MAPK) signaling pathways. Involvement of IL-1β signaling in cytotoxic effect of leptin was further confirmed in vivo using hepatocyte specific IL-1R1 knock out (IL-1R1 KO) mice. Essentially similar results were obtained in vivo, where leptin administration caused the upregulation of apoptotic markers, dephosphorylation of AKT, and p38MAPK activation were observed in wild type mice liver without significant effects in the livers of IL-1R1 KO mice. Taken together, these results demonstrate that IL-1β signaling critically contributes to leptin-induced cell cycle arrest and apoptosis, at least in part, by modulating p38MAPK and AKT signaling pathways.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.82-83
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• 2003

Plants have evolved differently from animals having mobile activities. Thus, plants should have developed unique defense mechanisms against biotic/abiotic stresses to which plants are differently exposed, according to seasons. Most organisms have an conserved signaling network using mitogen-activated protein kinase (MAPK) cascade(s). The phenomenon implied that they are functionally very important in all organisms. In fact, they constitute one of the major components of signaling pathways involved in regulating a wide range of cellular activities from growth and development to cell death. Recently, complete MAPK cascade was first characterized in Arabidopsis from the receptor kinase (FLS2) through fellowing MEKKI -MKK4/MKK5-MPK3/MPK6-WRKY22/MRKY29 pathway. Whereas, MAPK cascade signaling pathway in monocot plant including rice (0ryza sativa L.), the most important of all food crops and an established monocot plant research model, MAPKinase kinase kinases (MAPKKK) of rice are the first upstream component of the MAPK cascade, but MAPKKK has been first identified and characterized in our lab and designated as, OsEDRl based on its homology with the Arabidopsis EDRI. The Arabidopsis EDRl was regarded as a negative regulator of defense response and the role of rice OsEDRl was analyzed. Transcriptional regulation of OsEDRl was detected under various stresses and immunoblotting analysis is going on to detect the level of OsEDRl protein in the mutants showing unique phenotype. We also introduced the constitutively active and the dominant negative forms of the OsEDRl for characterizing biological function.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.4
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• pp.357-364
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• 2023

Sjögren syndrome (SS) is a systemic inflammatory autoimmune disease that involves exocrine glands. Shikonin is extracted from comfrey, which is conventionally used as an anti-tumor, antibacterial, and antiviral drug in China. However, the application of Shikonin in SS remains unreported. This study aimed to verify the potential functions of Shikonin in SS progression. Firstly, non-obese diabetic mice were used as the SS mouse model, with C57BL/6 mice serving as the healthy control. It was demonstrated that the salivary gland damage and inflammation were aggravated in the SS mouse model. Shikonin improved salivary gland function decline and injury in the SS mouse model. Moreover, Shikonin reduced inflammatory cytokines and immune infiltration in the SS mouse model. Further experiments discovered that Shikonin attenuated the MAPK signaling pathway in the SS mouse model. Lastly, inhibition of the MAPK signaling pathway combined with Shikonin treatment further alleviated the symptoms of SS. In conclusion, Shikonin ameliorated salivary gland damage and inflammation in a mouse model of SS by modulating the MAPK signaling pathway. Our findings indicate that Shikonin may be a useful drug for SS treatment.

• Journal of Marine Bioscience and Biotechnology
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• v.15 no.2
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• pp.49-58
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• 2023

Early-stage lung cancer is the deadliest form of the disease. In this study, we investigated the anticancer activity of 5-bromoprotocatechualdehyde (BPCA) extracted from the seaweed Polysiphonia morrowii Harvey (P. morrowii) in lung cancer H460 cells. We extracted P. morrowii powder thrice with 80% aqueous methanol and separated the extract using high-performance liquid chromatography. We then tested BPCA's effects on cell viability, apoptosis, reactive oxygen species (ROS) generation, and protein expression Our results showed that BPCA inhibited tumor cell growth and ROS production and induced apoptosis through mitogen-activated protein kinase (MAPK) and AKT signaling pathways in lung cancer cells. When BPCA was combined with hydrogen peroxide, ROS production and apoptosis increased even further due to the regulation of AKT signaling and JNK-MAPKs pathways. These findings suggest that BPCA induces lung-cancer-cell death through ROS-mediated phosphorylation in AKT/MAPK signaling. This could lead to the development of new and effective treatments for early-stage lung cancer.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.5
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• pp.1299-1303
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• 2008

Since exercise training induces mechanical stress to the heart, we examined the activation pattern of mitogen-activated protein kinase(MAPK)s signaling pathway by immunohistochemistry. The immunoreactions of MAPKs signaling with c-fos and Schiff's reaction were increased in the cardiac muscle of exercised rat compared to normal one except immunoreaction for MEK1/2 and ERK1/2 and p38. However, the immunoreaction of phospho-JNK and phospho-p38 with early gene c-fos were arrested markedly in water extract of Alliium sativum (WEAS) treated rat compared to exercised one. Since MAPKs signaling does play a protective role in response to pathological stimulus in the heart, results in the present study suggest that WEAS may act as a alleviating agent for exercise-induced stress to. heart through regulating MAPKs signaling activation.

• Molecules and Cells
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• v.26 no.1
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• pp.41-47
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• 2008

Mitogen-activated protein kinase (MAPK) signaling is a crucial component of eukaryotic cells; it plays an important role in responses to extracelluar stimuli and in the regulation of various cellular activities. The signaling cascade is evolutionarily conserved in the eukaryotic kingdom from yeast to human. In response to a variety of extracellular signals, MAPK activity is known to be regulated via phosphorylation of a conserved $T{\times}Y$ motif at the activation loop in which both threonine and tyrosine residues are phosphorylated by the upstream kinase. However, the mechanism by which both residues are phosphorylated continues to remain elusive. In the budding yeast, Saccharomyces cerevisiae, Fus3 MAPK is involved in the mating signaling pathway. In order to elucidate the functional mechanism of MAPK activation, we quantitatively profiled phosphorylation of the $T{\times}Y$ motif in Fus3 using mass spectrometry (MS). We used synthetic heavy stable isotope-labeled phosphopeptides and nonphosphopeptides corresponding to the proteolytic $T{\times}Y$ motif of Fus3 and accompanying data-dependent tandem MS to quantitatively monitor dynamic changes in the phosphorylation events of MAPK. Phosphospecific immunoblotting and the MS data suggested that the tyrosine residue is dynamically phosphorylated upon stimulation and that this leads to dual phosphorylation. In contrast, the magnitude of threonine phosphorylation did not change significantly. However, the absence of a threonine residue leads to hyperphosphorylation of the tyrosine residue in the unstimulated condition, suggesting that the threonine residue contributes to the control of signaling noise.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.5
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• pp.486-493
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• 2014

Adipocytes are endocrine cells that release bioactive mediators called adipokines. In condition of obesity characterized by low-grade chronic inflammation, adipocytes release inflammatory adipokines, which is related to insulin resistance. Bojungchiseub-tang (BJCST) has been used in symptoms and signs of edema, dampness-phlegm, kidney failure, and so on in Korean medicine. BJCST is also expected to have anti-obesity activities. In the present study, we examined whether BJCST modulate the production of inflammatory adipokines and the activations of the mitogen-activated protein kinases (MAPK) signaling pathway related to induce adipocyte inflammation to elucidate the effects and its mechanism of BJCST on lowering the content of inflammatory adipokines in 3T3-L1 adipocytes. As a result, BJCST suppressed the production of proinflammatory cytokines, tumor necrosis factor (TNF) $-{\alpha}$, interleukin (IL) $-1{\beta}$, IL-6, interferon (IFN) -${\gamma}$, granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), and the production of other inflammatory mediators, prostaglandin $E_2(PGE_2)$ and nitric oxide(NO)viadownregulationofcyclooxygenase-2(COX-2)andinducible NO synthase (iNOS) gene expressions. In addition, BJCST decreased the phosphorylation of MAPK that promotes the production of inflammatory adipokines in 3T3-L1 mature adipocytes. In conclusion, BJCST could regulate the production of inflammatory adipokines and MAPK signaling pathway related to induction of adipose inflammation.

• Clinical and Experimental Reproductive Medicine
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• v.30 no.1
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• pp.5-14
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• 2003

Objective: Present study was aimed to verify the effect of granulocyte macrophage-colony stimulating factor (GM-CSF) in the preimplantation development of mouse embryos and the involvement of the mitogen activated protein kiase (MAPK) in the GM-CSF signaling. Methods: Two-cell embryos were cultured for 96 h in the presence or absence of GM-CSF (0, 0.4, 2, 10 ng/ml) and PD98059, a MEK inhibitor (10 ${\mu}M$). Morphological development, cell number per blastocyst, and apoptotic nuclei, were eamined. MAPK activity of embryonic immunoprecipitate by MAPK (ERK1/2) antibody was measured by in vitro phosphorylation of myelin basic protein. Results: At post hCG 122 h the embryonic development among the experimental groups was significantly different (p=0.018). The rate of blastocyst development and cell number per embryo were the highest in 2 ng/ml GM-CSF treatment group. The percent of apoptotic cells of the GM-CSF-treated embryos was the lowest among the group. In blastocysts, GM-CSF treatment transiently increased MAPK activity. PD098059 attenuated the effect of GM-CSF on the morphological development, increase in cell number per blastocyst, down regulation of apoptosis, and upregulation of MAPK activity, suggesting that activation of MAPK cascade possibly mediated the embryotropic effect of GM-CSF. Conclusion: This result suggested that GM-CSF potentiated the development of preimplantation mouse embryos by activation of MAPK.

• BMB Reports
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• v.40 no.1
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• pp.1-6
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• 2007

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogenactivated protein kinase (MAPK) kinase kinase that activates JNK and p38 kinases. ASK1 is activated by various stresses, such as reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, lipopolysaccharide (LPS) and calcium influx which are thought to be responsible for the pathogenesis or exacerbations of various human diseases. Recent studies revealed the involvement of ASK1 in ROS- or ER stressrelated diseases, suggesting that ASK1 may be a potential therapeutic target of various human diseases. In this review, we focus on the current findings for the relationship between pathogenesis and ASK1-MAPK pathways.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.3
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• pp.139-144
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• 2010

In this study, we evaluated the role of apurinic/apyrimidinic endonuclease1/redox factor-1 (Ref-1) on the tumor necrosis factor-$\alpha$ (TNF-$\alpha$) induced cyclooxygenase-2 (COX-2) expression using A549 lung adenocarcinoma cells. TNF-$\alpha$ induced the expression of COX-2 in A549 cells, but did not induce BEAS-2B expression. The expression of COX-2 in A549 cells was TNF-$\alpha$ dose-dependent (5~100 ng/ml). TNF-$\alpha$-stimulated A549 cells evidenced increased Ref-1 expression in a dose-dependent manner. The adenoviral transfection of cells with AdRef-1 inhibited TNF-$\alpha$-induced COX-2 expression relative to that seen in the control cells ($Ad{\beta}gal$). Pretreatment with $10\;{\mu}M$ of SB203580 suppressed TNF-$\alpha$-induced COX-2 expression, thereby suggesting that p38 MAPK might be involved in COX-2 expression in A549 cells. The phosphorylation of p38 MAPK was increased significantly after 5 minutes of treatment with TNF-$\alpha$, reaching a maximum level at 10 min which persisted for up to 60 min. However, p38MAPK phosphorylation was markedly suppressed in the Ref-1-overexpressed A549 cells. Taken together, our results appear to indicate that Ref-1 negatively regulates COX-2 expression in response to cytokine stimulation via the inhibition of p38 MAPK phosphorylation. In the lung cancer cell lines, Ref-1 may be involved as an important negative regulator of inflammatory gene expression.