• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2002.05a
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• pp.36-42
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• 2002

Diesel exhaust (DE) has been recognized as a noxious mutagen and/or carcinogen, because its components can form DNA adducts. Mechanisms governing the susceptibility to DE and the efficiency of such DNA adduct formation require clarification. The transcription factor Nrf2 is essential for inducible and/or constitutive expression of a group of detoxification and antioxidant enzymes, and we hypothesized that the nrf2 gene knockout mouse might serve as an excellent model system for analyzing DE toxicity. To address this hypothesis, lungs from nrf2(-/-) and nrf2(+/-) mice were examined for the production of xenobiotic-DNA adducts after exposure to DE (3 $mg/m^{3}$ suspended particulate matter) for 4 weeks. Whereas the relative adduct levels (RAL) were significantly increased in the lungs of both nrf2(+/-) and nrf2(-/-) mice upon exposure to DE, the increase of RAL in the lungs from nrf2(-/-) mice exposed to DE were approximately 2.3-fold higher than that of nrf2(+/-) mite exposed to DE. In contrail, cytochrome P4501Al mRNA levels in the nrf2(-/-)mouse lungs were similar to those in the nrf2(+/-) mouse lungs even after exposure to DE, suggesting that suppressed activity of phase II drug-metabolizing enzymes is important in giving ise to the increased level of DNA adducts in the Nrf2-null mutant mouse subjected to DE. Importantly, severe hyperplasia and accumulation of the oxidative DNA adduct 8-hydroxydeoxyguanosine were observed in the bronchial epidermis of nrf(-/-) mite following DE exposure. These results demonstrate the increased susceptibility of the nrf2 germ line mutant mouse to DE exposure and indicate the nrf2 gene knockout mouse nay represent a valuable model for the assessment of respiratory DE toxicity.

• Toxicological Research
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• v.23 no.3
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• pp.207-214
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• 2007

Chronic oxidative stress produced by exposure to environmental chemicals or pathophysiological states can lead animals to aging, carcinogenesis and degenerative diseases. Indirect antioxidative mechanisms, in which natural or synthetic agents are used to coordinately induce the expression of cellular antioxidant capacity, have been shown to protect cells and organisms from oxidative damages. Electrophile and free radical detoxifying enzymes, which were originally identified as the products of genes induced by cancer chemopreventive agents, are members of this protective system. The NFE2 family transcription factor Nrf2 was found to govern expression of these detoxifying enzymes, and screening for Nrf2-regulated genes has identified many gene categories involved in maintaining cellular redox potential and protection from oxidative damage as Nrf2 downstream genes. Further, studies using Nrf2-deficient mice revealed that these mutant mice showed more susceptible phenotypes towards exposure to environmental chemicals/carcinogens and in oxidative stress related disease models. With the finding that cancer chemopreventive efficacy of indirect antioxidants (enzyme inducers) is lost in the absence of Nrf2, a central role of Nrf2 in the antioxidative protective system has been firmly established. Promising results from cancer prevention clinical trials using enzyme inducers propose that pharmacological interventions that modulate Nrf2 can be an effective strategy to protect tissues from oxidative damage.

• The Journal of Korean Medicine
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• v.41 no.4
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• pp.64-71
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• 2020

Objectives: This study was done to look into whether Nrf2 take some role in the anti-lipogenic effect of kaurenoic acid in a nonalcoholic fatty liver disease (NAFLD) cellular model. Materials and Methods: We measured the effect of kaurenoic acid on intracellular steatosis and Nrf2 activation. Next, the effect of kaurenoic acid on SREBP-1c and some lipogenic genes in palmitate treated HepG2 cells with or without Nrf2 silencing. Results: The increased SREBP-1c expression was significantly decreased by concomitant kaurenoic acid treatment in non-targeting negative control siRNA transfected HepG2 cells. However, kaurenoic acid did not significantly inhibited increased SREBP-1c level in Nrf2 specific siRNA transfected HepG2 cells Conclusions: Kaurenoic acid has a potential to activate Nrf2, which may suppress SREBP-1c mediated intracellular steatosis in HepG2 cells.

• 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.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2002.05a
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• pp.25-35
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• 2002

Transcription factor Nrf2 is essential for the antioxidant responsive element (ARE)-mediated induction of phase II detoxifying and oxidative stress enzyme genes. Detailed analysis of differential Nrf2 activity displayed in transfected cell lines ultimately led to the identification of a new protein, which we named Keap1, that suppresses Nrf2 transcriptional activity by specific binding to its evolutionarily conserved amino-terminal regulatory domain. The closest homolog of Keap1 is a Drosophila actin-binding protein called Kelch, implying that Keap1 might be a Nrf2 cytoplasmic effector. We then showed that electrophilic agents antagonize Keap1 inhibition of Nrf2 activity in vivo, allowing Nrf2 to traverse from the cytoplasm to the nucleus and potentiate the ARE response. We postulate that Keap1 and Nrf2 constitute a crucial cellular sensor for oxidative stress, and together mediate a key step in the signaling pathway that leads to transcriptional activation by this novel Nrf2 nuclear shuttling mechanism. The activation of Nrf2 leads in turn to the induction of phase II enzyme and antioxidative stress genes in response to electrophiles and reactive oxygen species.

• BMB Reports
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• v.54 no.8
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• pp.419-424
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• 2021

Cold-induced norepinephrine activates β3-adrenergic receptors (β3-AR) to stimulate the kinase cascade and cAMP-response element-binding protein, leading to the induction of thermogenic gene expression including uncoupling protein 1 (Ucp1). Here, we showed that stimulation of the β3-AR by its agonists isoproterenol and CL316,243 in adipocytes increased the expression of Ucp1 and Heme Oxygenase 1 (Hmox1), the principal Nrf2 target gene, suggesting the functional interaction of Nrf2 with β3-AR signaling. The activation of Nrf2 by tert-butylhydroquinone and reactive oxygen species (ROS) production by glucose oxidase induced both Ucp1 and Hmox1 expression. The increased expression of Ucp1 and Hmox1 was significantly reduced in the presence of a Nrf2 chemical inhibitor or in Nrf2-deleted (knockout) adipocytes. Furthermore, Nrf2 directly activated the Ucp1 promoter, and this required DNA regions located at -3.7 and -2.0 kb of the transcription start site. The CL316,243-induced Ucp1 expression in adipocytes and oxygen consumption in obese mice were partly compromised in the absence of Nrf2 expression. These data provide additional insight into the role of Nrf2 in β3-AR-mediated Ucp1 expression and energy expenditure, further highlighting the utility of Nrf2-mediated thermogenic stimulation as a therapeutic approach to diet-induced obesity.

• BMB Reports
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• v.48 no.8
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• pp.467-472
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• 2015

Heat shock increases skin temperature during sun exposure and some evidence indicates that it may be involved in skin aging. The antioxidant response mediated by the transcription factor NF-E2-related factor 2 (Nrf2) is a critically important cellular defense mechanism that serves to limit skin aging. We investigated the effects of heat shock on collagenase expression when the antioxidant defense system was downregulated by knockdown of Nrf2. GSH and collagenases were analyzed, and the expression of inducible Nrf2, HO-1, and NQO1 was measured. HS68 cells were transfected with small interfering RNA against Nrf2. Heat shock induced the downregulation of Nrf2 in both the cytosol and nucleus and reduced the expression of HO-1, GSH, and NQO1. In addition, heat-exposed Nrf2-knockdown cells showed significantly increased levels of collagenase protein and decreased levels of procollagen. Our data suggest that Nrf2 plays an important role in protection against heat shock-induced collagen breakdown in skin. [BMB Reports 2015; 48(8): 467-472]

• Toxicological Research
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• v.17
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• pp.299-304
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• 2001

Xenobiotics and their reactive intermediates bind to cellular macromolecules and/or generate oxidative stress. which provoke deleterious effects on the cell function. Induction of xenobiotic-biotrans-forming enzymes and antioxidant molecules is an important defense mechanism against such insults. A group of genes involved in the defense mechanism. e.g. genes encoding glutathione S-transferases. NAD(P)H: quinone oxidoreductase, UDP-glucuronosyltransferase (UDP-GT) and ${\gamma}$-glutamylcysteine synthetase (GGCS). have a common regulatory sequence, Antioxidant or Electrophile Responsive Element (ARE/EpRE). Recently. Nrf2. discovered as a homologue of erythroid transcription factor p45 NF-E2, was shown to bind ARE/EpRE and induce the expression of these defense genes. Mice that lack Nrf2 show low basal levels of expression and/or impaired induction of these genes. which makes the animals highly sensitive to xenobiotic toxicity. Indeed. we show here that nrf2-deficient mice had a higher mortality than did the wild-type mice when exposed to acetaminophen (APAP). Detailed analyses of APAP hepatotoxicity in the nrf2 knockout mice indicate that a large amount of reactive APAP metabolites was generated in the livers due to the impaired basal expression of two detoxifying enzyme genes, UDP-GT (Ugt1a6) and GGCS. while the cytochrome P450 content was unchanged. Thus. the studies using the nrf2 knockout mice clearly demonstrate significance of the expression of Nrf2-regulated enzymes in protection against xenobiotic toxicity.

• Journal of Society of Preventive Korean Medicine
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• v.17 no.2
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• pp.169-178
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• 2013

Objectives : Many cancers acquired resistance to chemotherapy, thus limiting its anticancer efficacy. It is known that Glutathione (GSH) is related to the development of drug resistance. The expression of GSH synthesizing glutamylcysteine ligase (GCL) was controlled by nuclear factor-E2-related factor(Nrf2). Previous studies showed that pharmacological depletion of GSH results in ROS increase, apoptotic response, and sensitization to oxidizing stimuli. In the current study, we examined Saussurea Lappa (SL) have the inhibitory effect on Nrf2 activity using human lung cancer A549 cells overexpressing Nrf2. Methods : Cell viability of A549 cells on SL treatment was determined by MTT assay. To detect the apeptosis in SL-treated A549 cells, sub-G1 population was measured by flow cytometry analysis (FACS). The level ROS was determined by FACS and fluorescence microscopy. To investigate whether SL have effect the suppression on Nrf2, we performed western blotting analysis. The GSH content was measured since GSH plays an important role in response to oxidative stress and was regulated by Nrf2. Results : A549 cells treated with an SL extract showed a substantial decrease in cell viability, along with a concomitant increase in apoptosis compared to untreated cells. Treatment of the SL extract led to increased Reactive oxygen species (ROS) production and a suppression of Nrf2. In addition, the antioxidant NAC attenuated SL-induced ROS generation, Nrf2 inhibition, and apoptosis. Taken together, these data show that the SL extract induced the production of ROS, and the inhibition of Nrf2, consequently resulting in A549 cell death. Conclusions : These results suggest that SL might be an effective agent to enhance anticancer drug sensitivity via Nrf2 inhibition.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.4
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• pp.375-379
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• 2018

In the present study, we have investigated whether methylated marliolide could induce NRF2 thereby exerting anti-oxidant effects. MTT assay showed that methylated marliolide did not exhibit cytotoxicity on HaCaT cells. Methylated marliolide induced a higher ARE-dependent luciferase activation in HaCaT ARE-GFP-luciferase cells, compared with resveratrol. In addition, exposure of methylated marliolide to HaCaT cells significantly induced NRF2 and transcriptionally activated HO-1 and NQO1, both of which are target genes of NRF2. Finally, methylated marliolide protected HaCaT cells against TPA-induced oxidative damages on nucleotides and lipids. Together, results shows that methylated marliolide could suppress oxidative damages through induction of NRF2 which implies that methylated marliolide might serve as a good candidate for novel cosmetic ingredient with anti-oxidant effects.