• Biomolecules & Therapeutics
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• v.21 no.1
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• pp.49-53
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• 2013

A number of naturally-occurring or synthetic chemicals have been reported to exhibit prostate chemopreventive effects. Synthetic $5{\alpha}$-reductase (5-AR) inhibitors, e.g. finasteride and durasteride, gained special interests as possible prostate chemopreventive agents. Indeed, two large-scale epidemiological studies have demonstrated that finasteride or durasteride significantly reduced the incidence of prostate cancer formation in men. However, these studies have raised an unexpected concern; finasteride and durasteride increased the occurrence of aggressive prostate tumor formation. In the present study, we have observed that treatment of finasteride did not affect the growth of androgen-refractory PC-3 prostate cancer cells. Finasteride also failed to induce apoptosis or affect the expression of proto-oncogenes in PC-3 cells. Interestingly, we found that treatment of finasteride induced the expression of Nrf2 and HO-1 proteins in PC-3 cells. In particular, basal level of Nrf2 protein was higher in androgen-refractory prostate cancer cells, e.g. DU-145 and PC-3 cells, compared with androgen-responsive prostate cancer cells, e.g. LNCaP cells. Also, treatment of finasteride resulted in a selective induction of Nrf2 protein in DU-145 and PC-3 cells, but not in LNCaP cells. In view of the fact that upregulation of Nrf2-mediated phase II cytoprotective enzymes contribute to attenuating tumor promotion in normal cells, but, on the other hand, confers a selective advantage for cancer cells to proliferate and survive against chemical carcinogenesis and other forms of toxicity, we propose that finasteride-mediated induction of Nrf2 protein might be responsible, at least in part, for an increased risk of high-grade prostate tumor formation in men.

• Natural Product Sciences
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• v.24 no.1
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• pp.28-35
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• 2018

Pulegone is a naturally occurring organic compound obtained from essential oils from a variety of plants. The aim of this study was to investigate the anti-inflammatory effects through the inhibitory mechanism of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), nuclear factor kappa B ($NF-{\kappa}B$), mitogen-activated protein kinases (MAPK) pathways and the activation of nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase (HO)-1 pathways in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Results revealed that pulegone significantly inhibited NO production as well as iNOS and COX-2 expressions. Meanwhile, western blot analysis showed that pulegone down-regulated LPS-induced $NF-{\kappa}B$ and MAPKs activation in RAW 264.7 cells. Furthermore, the selected compound suppressed LPS-induced intracellular ROS production in RAW 264.7 cells, while the expression of stress response gene, HO-1, and its transcriptional activator, Nrf-2 was upregulated upon pulegone treatment. Taking together, these findings provided that pulegone inhibited the LPS-induced expression of inflammatory mediators via the down-regulation iNOS, COX-2, $NF-{\kappa}B$, and MAPKs signaling pathways as well as up-regulation of Nrf-2/HO-1 indicating that pulegone has a potential therapeutic and preventive application in various inflammatory diseases.

• Natural Product Sciences
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• v.24 no.1
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• pp.13-20
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• 2018

Estragole is a naturally occurring phenylpropanoid obtained from essential oils found in a broad diversity of plants. Although the phenylpropanoids show many biological activities, clear regulation of the inflammatory signaling pathways has not yet been determined. Here, we scrutinized the anti-inflammatory effect of estragole. The anti-inflammatory effect of estragole was determined through the inhibitory mechanisms of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), nuclear factor kappa B ($NF-{\kappa}B$), and mitogen-activated protein kinases (MAPK) pathways and the activation of nuclear factor erythroid 2-related factor 2 (Nrf-2)/heme oxygenase (HO)-1 pathways in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Estragole significantly inhibited NO production, iNOS and COX-2 expression as well as LPS-induced $NF-{\kappa}B$ and MAPK activation. Furthermore, estragole suppressed LPS-induced intracellular ROS production but up-regulated the stress response gene HO-1 via the activation of transcription factor Nrf-2. These findings demonstrate that estragole inhibits the LPS-induced expression of inflammatory mediators via the down-regulation of iNOS, COX-2, $NF-{\kappa}B$, and MAPK pathways, as well as the up-regulation of the Nrf-2/HO-1 pathway, indicating that this phenylpropanoid has potential therapeutic and preventive applications in various inflammatory diseases.

• BMB Reports
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• v.50 no.2
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• pp.91-96
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• 2017

Nuclear factor erythroid 2-related factor 2 (Nrf2) provides a cellular defense against oxidative stress by inducing the expression of antioxidant and detoxification enzymes. The calcium antagonist, verapamil, is an FDA-approved drug prescribed for the treatment of hypertension. Here, we show that verapamil acts as a potent Nrf2 activator without causing cytotoxicity, through degradation of Kelch-like ECH-associated protein 1 (Keap1), a Nrf2 repressor. Furthermore, verapamil-induced Keap1 degradation is prominently mediated by a p62-dependent autophagic pathway. Correspondingly, verapamil protects cells from acetaminophen-induced oxidative damage through Nrf2 activation. These results demonstrated the underlying mechanisms for the protective role of verapamil against acetaminophen-induced cytotoxicity.

• Korean Journal of Pharmacognosy
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• v.47 no.1
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• pp.55-61
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• 2016

Antioxidant effects and nuclear factor E2-related factor-2 (Nrf-2) signal pathway of methanol extract and 4 fractions [n-hexane, methylene chloride, ethyl acetate (EtOAc), and n-butanol fractions] from Petasites japonicus were investigated. The EtOAc fraction showed highest polyphenol and flavonoid contents among other fractions. In addition, EtOAc fraction showed stronger scavenging activity against superoxide anion radical than other fractions. Furthermore, we investigated antioxidants effects of the EtOAc fraction under cellular system using $LLC-PK_1$ cells. The EtOAc fraction dose-dependently increased the antioxidant protein expressions of heme oxygenase 1 (HO-1) and thioredoxin reductase 1 (TrxR1) known to be involved in oxidative stress, through activation of Nrf-2. The treatment of EtOAc fraction ($100{\mu}g/mL$) led to the elevation of the high expression of Nrf-2-dependent factor such as HO-1 and TrxR1. These results indicated that the EtOAc fraction of P. japonicus showed high antioxidant activity by regulation of Nrf-2 signaling pathway.

• Herbal Formula Science
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• v.25 no.1
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• pp.1-10
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• 2017

Objectives : The fruit of Prunus mume Siebold & Zucc. has been used as an alternative medicine and functional food in Korea and Japan for preventive and therapeutic purposes. However, its molecular actions and mechanism on anti-inflammatory activity have not been clearly investigated. The aim of this study was to clarify the anti-inflammatory activity of the ethanol extract of P. mume fruit (EEPM) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, and sought to understand the associated molecular mechanisms. Methods : Cytotoxicity was assessed by an MTT assay. The amount of nitric oxide (NO) production was determined by nitrite assay. The mRNA expression of inducible nitric oxide synthase (iNOS) was analyzed by RT-PCR. In addition, expression levels of iNOS, nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) protein were detected by Western blotting. Results : Our data indicated that EEPM inhibited NO production in LPS-stimulated RAW264.7 cells in a concentration-dependent manner. At the mRNA and protein levels, EEPM suppressed LPS-induced iNOS expression. On the other hand, EEPM markedly enhanced HO-1 expression, which was associated with an induction and nuclear translocation of Nrf2. Moreover, the inhibitory effect of EEPM against LPS‑induced NO production was significantly enhanced by hemin, a HO-1 inducer; however, EEPM's effect on the production of NO was abolished by zinc protoporphyrin IX, a HO-1 inhibitor. Conclusion : The results suggest that EEPM can act as a suppressor agent on NO production through an activation of Nrf2/HO-1 signaling pathway, and may be a promising candidate for the treatment of inflammatory diseases.

• Journal of Life Science
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• v.27 no.3
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• pp.310-317
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• 2017

Mammalian cells control cellular homeostasis using a variety of defensive enzymes in order to combat against environmental oxidants and electrophiles. NF-E2-related factor-2 (NRF2) is a transcription factor that, in response to an exposure to oxidative stress, translocates into the nucleus and modulates the inducible expression of various phase II cytoprotective enzymes by binding to the antioxidant response element (ARE). In the present study, we have acquired 400 ethanol extracts of traditional medicinal plants and attempted to find out possible extract(s) that can increase the NRF2/ARE-dependent gene expression in human keratinocytes. As a result, we have identified that ethanol extracts of Rheum undulatum and Inula japonica strongly activated the ARE-dependent luciferase activity in HaCaT- ARE-luciferase cells. Exposure of ethanol extracts of Rheum undulatum and Inula japonica increased the viability and activated transcription and translation of NRF2-dependent phase II cytoprotective enzymes in HaCaT cells, such as heme oxygenase-1 (HO-1) and NAD[P]H:quinone oxidorecutase-1 (NQO1). In addition, ethanol extracts of Rheum undulatum and Inula japonica suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced generation of intracellular reactive oxygen species (ROS), thereby inhibiting the formation of 8-hydroxyguanosine (8-OHG) and 4-hydroxynonenal (4-HNE) in HaCaT cells. Together, our results demonstrate that ethanol extracts of Rheum undulatum and Inula japonica exert anti-oxidant effects via the induction of NRF2/ARE-dependent gene expression in human keratinocytes.

• Molecules and Cells
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• v.38 no.5
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• pp.396-401
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• 2015

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important redox-sensitive transcription factor that regulates the expression of several cytoprotective genes. More recently, genetic analyses of human tumors have indicated that Nrf2 may cause resistance to chemotherapy. In this study, we found that the expression levels of Nrf2 and its target genes GCLC, HO-1, NQO1 were significantly higher in cisplatin-resistant A549 (A549/CDDP) cells than those in A549 cells, and this resistance was partially reversed by Nrf2 siRNA. 3,4,5,5,7-Pentamethoxyflavone (PMF), a natural flavon extracted from Rutaceae plants, sensitized A549/CDDP to CDDP and substantially induced apoptosis compared with that of CDDP alone treated group, and this reversal effect decreased when Nrf2 was downregulated by siRNA. Mechanistically, PMF reduced Nrf2 expression leading to a reduction of Nrf2 downstream genes, and in contrast, this effect was decreased by blocking Nrf2 with siRNA. Taken together, these results demonstrated that PMF could be used as an effective adjuvant sensitizer to increase the efficacy of chemotherapeutic drugs by downregulating Nrf2 signaling pathway.

• Journal of Life Science
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• v.28 no.1
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• pp.43-49
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• 2018

Chrysoeriol is a widespread flavone, and it is usually found in alfalfa, which has been used as a traditional medicine to treat dyspepsia, asthma, and urinary system disorders. Recently, analysis has been conducted on the anti-inflammatory activity of chrysoeriol, but information on its antioxidative capacity is limited. In this study, the antioxidative potential of chrysoeriol against oxidative damage and its molecular mechanisms were evaluated by analysis of the cell viability, reactive oxygen species (ROS) formation, and Western blots in the RAW 264.7 cell line. Chrysoeriol significantly scavenged lipopolysaccharide (LPS)-induced intracellular ROS formation in a dose-dependent manner, without any cytotoxicity. Heme oxygenase-1 (HO-1), a phase II enzyme that exerts antioxidative activity, was also potently induced by chrysoeriol treatment, which corresponded to the translocation of nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) into the nucleus. Moreover, mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) were analyzed due to their important role in maintaining cellular redox homeostasis against oxidative stress. As a result, chrysoeriol-induced HO-1 upregulation was mediated by extracellular signal - regulated kinase (ERK), c-Jun $NH_2$-terminal kinase (JNK), and p38 phosphorylation. To identify the antioxidative potential exerted by HO-1, tert-butyl hydroperoxide (t-BHP)-induced oxidative damage was applied and mitigated by chrysoeriol treatment, which was confirmed by the HO-1 selective inhibitor and inducer, respectively. Consequently, chrysoeriol strongly strengthened the HO-1-mediated antioxidative potential through the regulation of the Nrf2/MAPK signaling pathways.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.6
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• pp.2911-2916
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• 2014

Oxaliplatin is a first-line therapy for colorectal cancer, but cancer cell resistance to the drug compromises its efficacy. To explore mechanisms of drug resistance, we treated colorectal cancer cells (HCT116 and SW620) long-term with oxaliplatin and established stable oxaliplatin-resistant lines (HCT116-OX and SW620-OX). Compared with parental cell lines, $IC_{50}$s for various chemotherapeutic agents (oxaliplatin, cisplatin and doxorubicin) were increased in oxaliplatin-resistant cell lines and this was accompanied by activation of nuclear factor erythroid-2 p45-related factor 2 (Nrf2) and NADPH quinone oxidoreductase 1 (NQO1). Furthermore, luteolin inhibited the Nrf2 pathway in oxaliplatin-resistant cell lines in a dose-dependent manner. Luteolin also inhibited Nrf2 target gene [NQO1, heme oxygenase-1 (HO-1) and $GST{\alpha}1/2$] expression and decreased reduced glutathione in wild type mouse small intestinal cells. There was no apparent effect in Nrf2-/- mice. Luteolin combined with other chemotherapeutics had greater anti-cancer activity in resistant cell lines (combined index values below 1), indicating a synergistic effect. Therefore, adaptive activation of Nrf2 may contribute to the development of acquired drug-resistance and luteolin could restore sensitivity of oxaliplatin-resistant cell lines to chemotherapeutic drugs. Inhibition of the Nrf2 pathway may be the mechanism for this restored therapeutic response.