• YAKHAK HOEJI
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• v.52 no.1
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• pp.67-72
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• 2008

The use of doxorubicin, which is one of the most effective anticancer agents, is often limited by occurrence of acquired resistance in tumor cells. GSH has been shown to be involved in the development of this drug resistance. Transcription factor Nrf2 governs the expression of GSH synthesizing glutamylcysteine ligase (GCL), as well as multiple phase 2 detoxifying enzymes. Here we show that Nrf2 is one of factors determining doxorubicin sensitivity. Nrf2-deficient fibroblasts (murine embryonic fibroblasts, MEF) were more susceptible to doxorubicin mediated cell death than wild-type cells. Doxorubicin treatment elevated levels of Nrf2-regulated genes including NAD(P)H: quinone oxidoreductase (Nqo1) and GCL in wild-type fibroblasts, while no induction was observed in Nrf2-deficient cells. Doxorubicin resistance in human ovarian SK-OV cells was reversed by treatment with L-buthionine-sulfoxamine (BSO), which is depleting intracellular GSH. Finally, transfection of SK-OV cells with Nrf2 siRNA resulted in exacerbated cytotoxicity following doxorubicin treatment compared to scrambled RNA control. These results indicate that the Nrf2 pathway, which plays a protective role in normal cells, can be a potential target to control cancer cell resistance to anticancer agents.

• 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]

• Biomolecules & Therapeutics
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• v.30 no.4
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• pp.368-379
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• 2022

Hyaluronic acid (HA), a ligand of CD44, accumulates in some types of tumors and is responsible for tumor progression. The nuclear factor erythroid 2-like 2 (NRF2) regulates cytoprotective genes and drug transporters, which promotes therapy resistance in tumors. Previously, we showed that high levels of CD44 are associated with NRF2 activation in cancer stem like-cells. Herein, we demonstrate that HA production was increased in doxorubicin-resistant breast cancer MCF7 cells (MCF7-DR) via the upregulation of HA synthase-2 (HAS2). HA incubation increased NRF2, aldo-keto reductase 1C1 (AKR1C1), and multidrug resistance gene 1 (MDR1) levels. Silencing of HAS2 or CD44 suppressed NRF2 signaling in MCF7-DR, which was accompanied by increased doxorubicin sensitivity. The treatment with a HAS2 inhibitor, 4-methylumbelliferone (4-MU), decreased NRF2, AKR1C1, and MDR1 levels in MCF7-DR. Subsequently, 4-MU treatment inhibited sphere formation and doxorubicin resistance in MCF7-DR. The Cancer Genome Atlas (TCGA) data analysis across 32 types of tumors indicates the amplification of HAS2 gene is a common genetic alteration and is negatively correlated with the overall survival rate. In addition, high HAS2 mRNA levels are associated with increased NRF2 signaling and poor clinical outcome in breast cancer patients. Collectively, these indicate that HAS2 elevation contributes to chemoresistance and sphere formation capacity of drug-resistant MCF7 cells by activating CD44/NRF2 signaling, suggesting a potential benefit of HAS2 inhibition.

• Journal of Cancer Prevention
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• v.21 no.3
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• pp.135-143
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• 2016

Background: Fraxetin (7,8-dihydroxy-6-methoxy coumarin), a coumarin derivative, has been reported to possess antioxidative, anti-inflammatory and neuroprotective effects. A number of recent observations suggest that the induction of heme oxygenase-1 (HO-1) inhibits inflammation and tumorigenesis. In the present study, we determined the effect of fraxetin on HO-1 expression in HaCaT human keratinocytes and investigated its underlying molecular mechanisms. Methods: Reverse transcriptase-PCR and Western blot analysis were performed to detect HO-1 mRNA and protein expression, respectively. Cell viability was measured by the MTS test. The induction of intracellular reactive oxygen species (ROS) by fraxetin was evaluated by 2′,7′-dichlorofluorescin diacetate staining. Results: Fraxetin upregulated mRNA and protein expression of HO-1. Incubation with fraxetin induced the localization of nuclear factor-erythroid-2-related factor-2 (Nrf2) in the nucleus and increased the antioxidant response element-reporter gene activity. Fraxetin also induced the phosphorylation of Akt and AMP-activated protein kinase $(AMPK){\alpha}$ and diminished the expression of phosphatase and tensin homolog, a negative regulator of Akt. Pharmacological inhibition of Akt and $AMPK{\alpha}$ abrogated fraxetin-induced expression of HO-1 and nuclear localization of Nrf2. Furthermore, fraxetin generated ROS in a concentration-dependent manner. Conclusions: Fraxetin induces HO-1 expression through activation of Akt/Nrf2 or $AMPK{\alpha}/Nrf2$ pathway in HaCaT cells.

• Biomolecules & Therapeutics
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• v.20 no.2
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• pp.144-151
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• 2012

The molecular mechanisms by which a variety of naturally-occurring dietary compounds exert chemopreventive effects have been a subject of intense scientific investigations. Induction of phase II detoxification and anti-oxidant enzymes through activation of Nrf2/ARE-dependent gene is recognized as one of the major cellular defense mechanisms against oxidative or xenobiotic stresses and currently represents a critical chemopreventive mechanism of action. In the present review, the functional significance of Keap1/Nrf2 protein module in regulating ARE-dependent phase II detoxification and anti-oxidant gene expression is discussed. The biochemical mechanisms underlying the phosphorylation and expression of Keap1/Nrf2 proteins that are controlled by the intracellular signaling kinases and ubiquitin-mediated E3 ligase system as well as control of nucleocytoplasmic translocation of Nrf2 by its innate nuclear export signal (NES) are described.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1306-1313
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• 2020

The aims of this study were to determine the effects of Sapindus mukorossi fruit extracts (SME) on the anti-oxidant activity in LPS-stimulated RAW264.7 macrophages. The results showed that SME significantly reduced the production of ROS in LPS-stimulated RAW264.7 cells. The expression of pro-inflammatory proteins including COX-2 and iNOS were also obviously inhibited by SME in LPS-stimulated RAW264.7 cells. Further studies revealed that SME up-regulated HO-1 and Nrf2 expression. Additionally, SME increased phosphorylation of Akt and GSK-3β. These results suggest that SME could attenuate oxidative stress by activating the Nrf2/HO-1 signaling pathway.

• Toxicological Research
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• v.25 no.4
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• pp.159-173
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• 2009

Nuclear factor erythroid derived 2-related factor-2 (Nrf2) is a master transcription regulator of antioxidant and cytoprotective proteins that mediate cellular defense against oxidative and inflammatory stresses. Disruption of cellular stress response by Nrf2 deficiency causes enhanced susceptibility to infection and related inflammatory diseases as a consequence of exacerbated immune-mediated hypersensitivity and autoimmunity. The cellular defense capacity potentiated by Nrf2 activation appears to balance the population of $CD4^+$ and $CD8^+$ of lymph node cells for proper innate immune responses. Nrf2 can negatively regulate the activation of pro-inflammatory signaling molecules such as p38 MAPK, NF-${\kappa}B$, and AP-1. Nrf2 subsequently functions to inhibit the production of pro-inflammatory mediators including cytokines, chemokines, cell adhesion molecules, matrix metalloproteinases, COX-2 and iNOS. Although not clearly elucidated, the antioxidative function of genes targeted by Nrf2 may cooperatively regulate the innate immune response and also repress the expression of pro-inflammatory mediators.

• Molecules and Cells
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• v.46 no.3
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• pp.176-186
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• 2023

The oxidative balance of a cell is maintained by the Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway. This cytoprotective pathway detoxifies reactive oxygen species and xenobiotics. The role of the KEAP1/NRF2 pathway as pro-tumorigenic or anti-tumorigenic throughout stages of carcinogenesis (including initiation, promotion, progression, and metastasis) is complex. This mini review focuses on key studies describing how the KEAP1/NRF2 pathway affects cancer at different phases. The data compiled suggest that the roles of KEAP1/NRF2 in cancer are highly dependent on context; specifically, the model used (carcinogen-induced vs genetic), the tumor type, and the stage of cancer. Moreover, emerging data suggests that KEAP1/NRF2 is also important for regulating the tumor microenvironment and how its effects are amplified either by epigenetics or in response to co-occurring mutations. Further elucidation of the complexity of this pathway is needed in order to develop novel pharmacological tools and drugs to improve patient outcomes.

• 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.

• BMB Reports
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• v.37 no.2
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• pp.139-143
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• 2004

The antioxidant responsive element (ARE) is a cis-acting regulatory element of genes encoding phase II detoxification enzymes and antioxidant proteins, such as NAD(P)H: quinone oxidoreductase 1, glutathione S-transferases, and glutamate-cysteine ligase. Interestingly, it has been reported that Nrf2 (NF-E2-related factor 2) regulates a wide array of ARE-driven genes in various cell types. Nrf2 is a basic leucine zipper transcription factor, which was originally identified as a binding protein of locus control region of ss-globin gene. The DNA binding sequence of Nrf2 and ARE sequence are very similar, and many studies demonstrated that Nrf2 binds to the ARE sites leading to up-regulation of downstream genes. The function of Nrf2 and its downstream target genes suggests that the Nrf2-ARE pathway is important in the cellular antioxidant defense system. In support of this, many studies showed a critical role of Nrf2 in cellular protection and anti-carcinogenicity, implying that the Nrf2-ARE pathway may serve as a therapeutic target for neurodegenerative diseases and cancers, in which oxidative stress is closely implicated.