• Journal of Applied Biological Chemistry
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• v.64 no.3
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• pp.317-322
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• 2021

Among the different cardiovascular disorders (CVDs), the activation of platelets is a necessary step. Based on this knowledge, therapeutic treatments for CVDs that target the disruption of platelet activation are proving to be worthwhile. One such substance, a bioactive 6,7-dihydroxy derived from coumarin, is 6,7-Dihydroxy-2H-1-benzopyran-2-one (esculetin). This compound has demonstrated several pharmacological effects on CVDS as well as various other disorders including diabetes, obesity, and renal failure. In various reports, esculetin and its effect has been explored in experimental mouse models, human platelet activation, esculetin-inhibited collagen, and washed human platelets exhibiting aggregation via arachidonic acid. Yet, esculetin affected aggregation with agonists like U46619 or thrombin in no way. This study investigated esculetin and how it affected human platelet aggregation activated through U46619. Ultimately, we confirmed that esculetin had an effect on the aggregation of human platelets when induced from U46619 and clarified the mechanism. Esculetin interacts with the downregulation of both phosphoinositide 3-kinase/Akt and mitogen-activated protein kinases, important phosphoproteins that are involved in activating platelets and their signaling process. The effects of esculetin reduced TXA₂ production, phospholipase A₂ activation, and platelet secretion of intracellular granules (ATP/serotonin), ultimately causing inhibition of overall platelet aggregation. These results clearly define the effect of esculetin in inhibiting platelet activity and thrombus formation in humans.

• Molecules and Cells
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• v.26 no.2
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• pp.200-205
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• 2008

The mitogen-activated protein kinase (MAPK) signaling pathway is activated in response to extracellular stimuli and regulates various activities in eukaryotic cells. Following exposure to stimuli, MAPK is known to be activated via dual phosphorylation at a conserved TxY motif in the activation loop; both threonine and tyrosine residues are phosphorylated by an upstream kinase. However, the mechanism underlying dual phosphorylation is not clearly understood. In the budding yeast Saccharomyces cerevisiae, the Hog1 MAPK mediates the high-osmolarity glycerol (HOG) signaling pathway. Tandem mass spectrometry and phosphospecific immunoblotting were performed to quantitatively monitor the dynamic changes occurring in the phosphorylation status of the TxY motif of Hog1 on exposure to osmotic stress. The results of our study suggest that the tyrosine residue is preferentially and dynamically phosphorylated following stimulation, and this in turn leads to the dual phosphorylation. The tyrosine residue was hyperphosphorylated in the absence of a threonine residue; this result suggests that the threonine residue is critical for the control of signaling noise and adaptation to osmotic stress.

• BMB Reports
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• v.51 no.4
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• pp.194-199
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• 2018

Mesenchymal stem cells (MSCs) have shown great potential in treating bone deficiency. Human adipose-derived stem cells (HASCs) are multipotent progenitor cells with multi-lineage differentiation potential. Human amnion-derived mesenchymal stem cells (HAMSCs) are capable of promoting osteogenic differentiation of MSCs. In this study, we investigated the effect of HAMSCs on HASCs by a transwell co-culture system. HAMSCs promoted proliferation, osteogenic differentiation, angiogenic potential and adiponectin (APN) secretion of HASCs. Moreover, the positive effect of HAMSCs was significantly inhibited by U0126, a highly selective inhibitor of extracellular signaling-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signaling pathway. These observations suggested that HAMSCs induced bone regeneration in HASCs via ERK1/2 MAPK signaling pathway.

• Archives of Pharmacal Research
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• v.26 no.9
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• pp.739-746
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• 2003

Ultraviolet B (UVB) is known to induce apoptosis in human melanocytes. Here we show the cytoprotective effect of sphingosine-1-phosphate (S1P) against UVB-induced apoptosis. We also show that UVB-induced apoptosis of melanocytes is mediated by caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage, and that S1P prevents apoptosis by inhibiting this apoptotic pathway. We further investigated three major mitogen-activated protein (MAP) kinases after UVB irradiation. UVB gradually activated c-Jun N-terminal kinase (JNK) and p38 MAP kinase, while extracellular signal-regulated protein kinase (ERK) was inactivated transiently. Blocking of the p38 MAP kinase pathway using SB203580 promoted cell survival and inhibited the activation of caspase-3 and PARP cleavage. These results suggest that p38 MAP kinase activation may play an important role in the UVB-induced apoptosis of human melanocytes. To explain this cytoprotective effect, we next examined whether S1P could inhibit UVB-induced JNK and p38 MAP kinase activation. However, S1P was not found to have any influence on UVB-induced JNK or p38 MAP kinase activation. In contrast, S1P clearly stimulated the phosphorylation of ERK, and the specific inhibition of the ERK pathway using PD98059 abolished the cytoprotective effect of S1P. Based on these results, we conclude that the activation of p38 MAP kinase plays an important role in UVB-induced apoptosis, and that S1P may show its cytoprotective effect through ERK activation in human melanocytes.

• Journal of Microbiology and Biotechnology
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• v.28 no.10
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• pp.1635-1644
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• 2018

Asterias amurensis (starfish) is a marine organism that is harmful to the fishing industry, but is also a potential source of functional materials. The present study was conducted to analyze the profiles of fatty acids extracted from A. amurensis tissues and their anti-inflammatory effects on RAW264.7 macrophage cells. In different tissues, the component ratios of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids differed; particularly, polyunsaturated fatty acids such as dihomo-gamma-linolenic acid (20:3n-6) and eicosapentaenoic acid (20:5n-3) were considerably different. In lipopolysaccharide-stimulated RAW264.7 cells, fatty acids from A. amurensis skin, gonads, and digestive glands exhibited anti-inflammatory activities by reducing nitric oxide production and inducing nitric oxide synthase gene expression. Asterias amurensis fatty acids effectively suppressed the expression of inflammatory cytokines such as tumor necrosis $factor-{\alpha}$, interleukin-$1{\beta}$, and interleukin-6 in lipopolysaccharide-stimulated cells. Cyclooxygenase-2 and prostaglandin $E_2$, which are critical inflammation biomarkers, were also significantly suppressed. Furthermore, A. amurensis fatty acids reduced the phosphorylation of nuclear $factor-{\kappa}B$ p-65, p38, extracellular signal-related kinase 1/2, and c-Jun N-terminal kinase, indicating that these fatty acids ameliorated inflammation through the nuclear $factor-{\kappa}B$ and mitogen-activated protein kinase pathways. These results provide insight into the anti-inflammatory mechanism of A. amurensis fatty acids on immune cells and suggest that the species is a potential source of anti-inflammatory molecules.

• 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.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1155-1163
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• 2004

Extracellular signal-regulated kinase (ERK) signaling pathway is one of the mitogen-activated protein kinase (MAPK) signal transduction pathways. This pathway is known as pivotal in many signaling networks that govern proliferation, differentiation and cell survival. The ERK signaling pathway comprises positive and negative feedback loops, depending on whether the terminal kinase stimulates or inhibits the activation of the initial level. In this paper, we attempt to model the ERK pathway by considering both of the positive and negative feedback mechanisms based on Michaelis-Menten kinetics. In addition, we propose a fraction ratio model based on the mass action law. We first develop a mathematical model of the ERK pathway with fraction ratios. Secondly, we analyze the dynamical properties of the fraction ratio model based on simulation studies. Furthermore, we propose a concept of an inhibitor, catalyst, and substrate (ICS) controller which regulates the inhibitor, catalyst, and substrate concentrations of the ERK signal transduction pathway. The ICS controller can be designed through dynamical analysis of the ERK signaling transduction pathway within limited concentration ranges.

• Journal of Ginseng Research
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• v.42 no.2
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• pp.233-237
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• 2018

• Molecules and Cells
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• v.25 no.3
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• pp.397-406
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• 2008

Computational modeling of signal transduction is currently attracting much attention as it can promote the understanding of complex signal transduction mechanisms. Although several mathematical models have been used to examine signaling pathways, little attention has been given to crosstalk mechanisms. In this study, an attempt was made to develop a computational model for the pathways involving growth-factor-mediated mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3'-kinase/protein kinase B (PI3K/Akt). In addition, the dynamics of the protein activities were analyzed based on a set of kinetic data. The simulation approach integrates the information on several levels and predicts systems behavior. The in-silico analysis conducted revealed that the Raf and Akt pathways act independently.

• Journal of Life Science
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• v.33 no.10
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• pp.776-782
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• 2023

Silymarin, which is derived from dried Silybum marianum (milk thistle) seeds and fruits, possesses various beneficial properties, such as hepatoprotective, antioxidative, anti-inflammatory, and anticancer activity. This research aimed to explore the antioxidative activity of silymarin against oxidative stress and understand its molecular mechanism in RAW 264.7 cells. The study employed cell viability and reactive oxygen species (ROS) formation assays and western blot analysis. The results demonstrated that silymarin effectively reduced intracellular ROS levels induced by lipopolysaccharide (LPS) in a dose-dependent manner without causing any cytotoxic effects. Moreover, silymarin treatment significantly upregulated the expression of heme oxygenase (HO)-1, a phase II enzyme known for its potent antioxidative activity. Additionally, silymarin treatment significantly induced the expression of nuclear factor-erythroid 2 p45-related factor (Nrf) 2, a transcription factor responsible for regulating antioxidative enzymes, which was consistent with the upregulated HO-1 expression. To investigate the involvement of key signaling pathways in maintaining cellular redox homeostasis against oxidative stress, the phosphorylation status of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) was estimated by western blot analysis. The results showed that silymarin potently induced HO-1 expression, which was mediated by the phosphorylation of p38 MAPK. To further validate the antioxidative potential of silymarin-induced HO-1 expression, tert-butyl hydroperoxide (t-BHP)-induced oxidative damage was employed and attenuated by silymarin treatment, as identified by a selective inhibitor for each signaling molecule. In conclusion, silymarin robustly enhanced antioxidative activity by inducing HO-1 via the Nrf2/p38 MAPK signaling pathway in RAW 264.7 cells.