• The Korean Journal of Physiology and Pharmacology
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• v.25 no.4
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• pp.307-319
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• 2021

Dysregulation of the Wnt pathway causes various diseases including cancer, Parkinson's disease, Alzheimer's disease, schizophrenia, osteoporosis, obesity and chronic kidney diseases. The modulation of dysregulated Wnt pathway is absolutely necessary. In the present study, we evaluated the anti-inflammatory effect and the mechanism of action of Wnt-C59, a Wnt signaling inhibitor, in lipopolysaccharide (LPS)-stimulated epithelial cells and macrophage cells. Wnt-C59 showed a dose-dependent anti-inflammatory effect by suppressing the expression of proinflammatory cytokines including IL6, CCL2, IL1A, IL1B, and TNF in LPS-stimulated cells. The dysregulation of the Wnt/β-catenin pathway in LPS stimulated cells was suppressed by WntC59 treatment. The level of β-catenin, the executor protein of Wnt/β-catenin pathway, was elevated by LPS and suppressed by Wnt-C59. Overexpression of β-catenin rescued the suppressive effect of Wnt-C59 on proinflammatory cytokine expression and nuclear factor-kappa B (NF-κB) activity. We found that the interaction between β-catenin and NF-κB, measured by co-immunoprecipitation assay, was elevated by LPS and suppressed by Wnt-C59 treatment. Both NF-κB activity for its target DNA binding and the reporter activity of NF-κB-responsive promoter showed identical patterns with the interaction between β-catenin and NF-κB. Altogether, our findings suggest that the anti-inflammatory effect of Wnt-C59 is mediated by the reduction of the cellular level of β-catenin and the interaction between β-catenin and NF-κB, which results in the suppressions of the NF-κB activity and proinflammatory cytokine expression.

• Nutrition Research and Practice
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• v.7 no.6
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• pp.423-429
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• 2013

Luteolin is a flavonoid found in abundance in celery, green pepper, and dandelions. Previous studies have shown that luteolin is an anti-inflammatory and anti-oxidative agent. In this study, the anti-inflammatory capacity of luteolin and one of its glycosidic forms, luteolin-7-O-glucoside, were compared and their molecular mechanisms of action were analyzed. In lipopolysaccharide (LPS)-activated RAW 264.7 cells, luteolin more potently inhibited the production of nitric oxide (NO) and prostaglandin E2 as well as the expression of their corresponding enzymes (inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) than luteolin-7-O-glucoside. The molecular mechanisms underlying these effects were investigated to determine whether the inflammatory response was related to the transcription factors, nuclear factor (NF)-${\kappa}B$ and activator protein (AP)-1, or their upstream signaling molecules, mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase (PI3K). Luteolin attenuated the activation of both transcription factors, NF-${\kappa}B$ and AP-1, while luteolin-7-O-glucoside only impeded NF-${\kappa}B$ activation. However, both flavonoids inhibited Akt phosphorylation in a dose-dependent manner. Consequently, luteolin more potently ameliorated LPS-induced inflammation than luteolin-7-O-glucoside, which might be attributed to the differentially activated NF-${\kappa}B$/AP-1/PI3K-Akt pathway in RAW 264.7 cells.

• Food Science and Biotechnology
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• v.15 no.2
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• pp.303-307
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• 2006

Effect of Oenanthe javanica ethanol extract (OJE) on nuclear factor-${\kappa}B$ (NF-${\kappa}B$)-mediated inflammatory reaction in RAW 264.7 macrophage cells was investigated. The OJE dose-dependently inhibited secretions of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and prostaglandins $E_2\;(PGE_2)$ from lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and blocked LPS-induced expression of cyclooxygenase-2. To clarify mechanistic basis for its inhibitions of NF-${\kappa}B$ and activator protein-1 (AP-1) activations, effects of OJE on activations of NF-${\kappa}B$ and AP-1 genes by luciferase reporter activity were examined. The LPS-stimulated activations of NF-${\kappa}B$ and AP-1 were significantly blocked by 400 and $600\;{\mu$}g/mL of OJE, implicating that OJE might regulate gene expression through more than one signaling pathway. Cytosolic degradation of I-${\kappa}B{\alpha}$ was inhibited by OJE dose-dependently, indicating that the nuclear translocation of p65 was inhibited by OJE. These findings suggest that the inhibition of LPS-stimulated COX-2 expression by OJE is due to its inhibition of NF-${\kappa}B$ activation by blocking I-${\kappa}B{\alpha}$ degradation, which may be mechanistic basis of anti-inflammatory effects of OJE.

• The Korean Journal of Food And Nutrition
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• v.30 no.2
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• pp.312-318
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• 2017

Aloe-emodin (AE) is the major bioactive component in aloe and known to exhibit anti-inflammatory activities. However, it has not been elucidated whether its anti-inflammatory potency can contribute to the elimination of obesity. The aim of the current study is to investigate the effect of AE on toll-like receptor 4 (TLR4) pathways in the presence of lipopolysaccharide (LPS) in 3T3-L1 adipocytes. 3T3-L1 adipocytes were treated with AE ($0-20{\mu}M$) for one hour, followed by LPS treatment for 30 min and then, adipokine mRNA expression levels were measured. Next, TLR4-related molecules were measured in LPS-stimulated 3T3-L1 adipocytes. AE significantly decreased the mRNA expression of the tumor necrosis $factor-{\alpha}$ ($TNF-{\alpha}$), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) in a dose-dependent manner. Moreover, AE suppressed TLR4 mRNA expression. Further study showed that AE could suppress the nuclear $factor-{\kappa}B$ ($NF-{\kappa}B$) and phosphorylation of extracellular receptor-activated kinase (pERK). The results of this study suggest that AE directly inhibits $TLR4/NF-{\kappa}B/ERK$ signaling pathways and decreases the inflammatory response in adipocytes.

• Biomolecules & Therapeutics
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• v.23 no.2
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• pp.110-118
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• 2015

According to the expansion of lifespan, neuronal disorder based on inflammation has been social problem. Therefore, we isolated shikonin from Lithospermum erythrorhizon and evaluated anti-inflammatory effects of shikonin in lipopolysaccharide (LSP)-stimulated BV2 microglial cells. Shikonin dose-dependently inhibits the expression of the proinflammatory mediators, nitric oxide (NO), prostaglandin $E_2$ ($PGE_2$), and tumor necrosis factor-${\kappa}B$ (TNF-${\alpha}$) as well as their main regulatory genes and products such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-${\alpha}$ in LPS-stimulated BV2 microglial cells. Additionally, shikonin suppressed the LPS-induced DNA-binding activity of nuclear factor-${\kappa}B$ (NF-${\kappa}B$) to regulate the key regulatory genes of the proinflammatory mediators, such as iNOS, COX-2, and TNF-${\alpha}$, accompanied with downregulation of reactive oxygen species (ROS) generation. The results indicate that shikonin may downregulate the expression of proinflammatory genes involved in the synthesis of NO, $PGE_2$, and TNF-${\alpha}$ in LPS-treated BV2 microglial cells by suppressing ROS and NF-${\kappa}B$. Taken together, our results revealed that shikonin exerts downregulation of proinflammatory mediators by interference the ROS and NF-${\kappa}B$ signaling pathway.

• Nutrition Research and Practice
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• v.14 no.6
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• pp.593-605
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• 2020

BACKGROUND/OBJECTIVES: Alzheimer's disease is common age-related neurodegenerative condition characterized by amyloid beta (Aβ) accumulation that leads cognitive impairment. In the present study, we investigated the protective effect of paeoniflorin (PF) against Aβ-induced neuroinflammation and the underlying mechanism in C6 glial cells. MATERIALS/METHODS: C6 glial cells were treated with PF and Aβ_25-35, and cell viability, nitric oxide (NO) production, and pro-inflammatory cytokine release were measured. Furthermore, the mechanism underlying the effect of PF on inflammatory responses and Aβ degradation was determined by Western blot. RESULTS: Aβ_25-35 significantly reduced cell viability, but this reduction was prevented by the pretreatment with PF. In addition, PF significantly inhibited Aβ_25-35-induced NO production in C6 glial cells. The secretion of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha was also significantly reduced by PF. Further mechanistic studies indicated that PF suppressed the production of these pro-inflammatory cytokines by regulating the nuclear factor-kappa B (NF-κB) pathway. The protein levels of inducible NO synthase and cyclooxygenase-2 were downregulated and phosphorylation of NF-κB was blocked by PF. However, PF elevated the protein expression of inhibitor kappa B-alpha and those of Aβ degrading enzymes, insulin degrading enzyme and neprilysin. CONCLUSIONS: These findings indicate that PF exerts protective effects against Aβ-mediated neuroinflammation by inhibiting NF-κB signaling, and these effects were associated with the enhanced activity of Aβ degradation enzymes.

• Molecules and Cells
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• v.38 no.1
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• pp.26-32
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• 2015

Toll-like receptors (TLR) 7 and 9 transduce a cellular signal through the MyD88-dependent pathway and induce the production of inflammatory mediators against microbial nucleotide components. The repeated stimulation of TLR4 leads to endotoxin tolerance, but the molecular mechanisms of tolerance induced through the costimulation of individual TLR has not yet been established, although endosomal TLRs share signaling pathways with TLR4. In the present study, mouse macrophages were simultaneously stimulated with the TLR7 agonist, gardiquimod (GDQ), and the TLR9 agonist, CpG ODN 1826, to examine the mechanism and effector functions of macrophage tolerance. Compared with individual stimulation, the costimulation of both TLRs reduced the secretion of TNF-${\alpha}$ and IL-6 through the delayed activation of the NF-${\kappa}B$ pathway; notably, IL-10 remained unchanged in costimulated macrophages. This tolerance reflected the early induction of suppressor of cytokine signaling-1 (SOCS-1), according to the detection of elevated TNF-${\alpha}$ secretion and restored NF-${\kappa}B$ signaling in response to the siRNA-mediated abrogation of SOCS-1 signaling. In addition, the restimulation of each TLRs using the same ligand significantly reduced the expression of both TLRs in endosomes. These findings revealed that the costimulation of TLR7 and TLR9 induced macrophage tolerance via SOCS-1, and the restimulation of each receptor or both TLR7 and TLR9 downregulated TLR expression through a negative feedback mechanisms that protects the host from excessive inflammatory responses. Moreover, the insufficient and impaired immune response in chronic viral infection might also reflect the repeated and simultaneous stimulation of those endosomal TLRs.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.41-51
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• 2016

Adult hippocampal dentate granule neurons are generated from neural stem cells (NSCs) in the mammalian brain, and the fate specification of adult NSCs is precisely controlled by the local niches and environment, such as the subventricular zone (SVZ), dentate gyrus (DG), and Toll-like receptors (TLRs). Epigallocatechin-3-gallate (EGCG) is the main polyphenolic flavonoid in green tea that has neuroprotective activities, but there is no clear understanding of the role of EGCG in adult neurogenesis in the DG after neuroinflammation. Here, we investigate the effect and the mechanism of EGCG on adult neurogenesis impaired by lipopolysaccharides (LPS). LPS-induced neuroinflammation inhibited adult neurogenesis by suppressing the proliferation and differentiation of neural stem cells in the DG, which was indicated by the decreased number of Bromodeoxyuridine (BrdU)-, Doublecortin (DCX)- and Neuronal Nuclei (NeuN)-positive cells. In addition, microglia were recruited with activating TLR4-NF-${\kappa}B$ signaling in the adult hippocampus by LPS injection. Treating LPS-injured mice with EGCG restored the proliferation and differentiation of NSCs in the DG, which were decreased by LPS, and EGCG treatment also ameliorated the apoptosis of NSCs. Moreover, pro-inflammatory cytokine production induced by LPS was attenuated by EGCG treatment through modulating the TLR4-NF-${\kappa}B$ pathway. These results illustrate that EGCG has a beneficial effect on impaired adult neurogenesis caused by LPS-induced neuroinflammation, and it may be applicable as a therapeutic agent against neurodegenerative disorders caused by inflammation.

• Biomolecules & Therapeutics
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• v.20 no.6
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• pp.532-537
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• 2012

Avicularin, quercetin-3-${\alpha}$-L-arabinofuranoside, has been reported to possess diverse pharmacological properties such as anti-inflammatory and anti-infectious effects. However, the underlying mechanism by which avicularin exerts its anti-inflammatory activity has not been clearly demonstrated. This study aimed to elucidate the anti-inflammatory mechanism of avicularin in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Avicularin significantly inhibited LPS-induced excessive production of pro-inflammatory mediators such as nitric oxide (NO) and $PGE_2$ and the protein levels of iNOS and COX-2, which are responsible for the production of NO and $PGE_2$, respectively. Avicularin also suppressed LPS-induced overproduction of pro-inflammatory cytokine IL-$1{\beta}$. Furthermore, avicularin significantly suppressed LPS-induced degradation of $I{\kappa}B$, which retains NF-${\kappa}B$ in the cytoplasm, consequently inhibiting the transcription of pro-inflammatory genes by NF-${\kappa}B$ in the nucleus. To understand the underlying signaling mechanism of anti-inflammatory activity of avicularin, involvement of multiple kinases was examined. Avicularin significantly attenuated LPS-induced activation of ERK signaling pathway in a concentration-dependent manner. Taken together, the present study clearly demonstrates that avicularin exhibits anti-inflammatory activity through the suppression of ERK signaling pathway in LPS-stimulated RAW 264.7 macrophage cells.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.2
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• pp.267-272
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• 2017

Piceatannol (PIC) is a natural hydroxylated analog of resveratrol (RSV), which is a polyphenol known to extend lifespan by stimulating sirtuins. The aim of this study was to investigate the effects of PIC and RSV on the toll-like receptor 4 (TLR4)-nuclear factor kappa B ($NF-{\kappa}B$) pathway in mouse hepatocytes and an obese/diabetic KK/HlJ mouse model. AML12 mouse hepatocytes in the absence or presence of palmitic acids (PA) were treated with PIC ($50{\mu}M$) or RSV ($50{\mu}M$). Male KK/HlJ mice at 20 weeks of age were divided into three subgroups as follows: 1) obese and diabetic control (KK), 2) KK_PIC, and 3) KK_RSV. PIC and RSV were administered orally at a dose of 10 mg/kg/d for 4 weeks. Four weeks of PIC and RSV treatment did not affect body weight or food intake in KK mice. Serum fasting blood glucose was significantly reduced in KK_PIC, and 2 h oral glucose tolerance test area under the curve was significantly reduced by PIC and RSV treatment in KK mice. PIC tended to improve homeostasis model assessment of the insulin resistance index (HOMA-IR) and HOMA beta-cells in diabetic KK mice. TLR4 and $NF-{\kappa}B$ were down-regulated by PIC and RSV treatments in hepatocytes in the absence or presence of PA. Insulin receptor, AMP-activated protein kinase, peroxisome proliferator-activated receptor gamma, nucleotide oligomerization domain-like receptor family pyrin domain-containing 3, interleukin-1, and $NF-{\kappa}B$ were altered in PIC-treated livers. Collectively, PIC and RSV inhibited the $TLR4-NF-{\kappa}B$ pathway, and PIC seems to be more effective than RSV in the regulation of analyzed targets, which are involved in insulin signaling and inflammation in vivo.