Modulation of Nrf2-mediated antioxidant and detoxifying enzyme induction by the green tea polyphenol EGCG

A nutrient-dense, high-fiber, fruit-based supplement bar increases HDL cholesterol, particularly large HDL, lowers homocysteine, and raises glutathione in a 2-wk trial

Dietary intake modulates disease risk, but little is known how components within food mixtures affect pathophysiology. A low-calorie, high-fiber, fruit-based nutrient-dense bar of defined composition (e.g., vitamins and minerals, fruit polyphenolics, β-glucan, docosahexaenoic acid) appropriate for deconstruction and mechanistic studies is described and evaluated in a pilot trial. The bar was developed in collaboration with the U.S. Department of Agriculture. Changes in cardiovascular disease and diabetes risk biomarkers were measured after 2 wk twice-daily consumption of the bar, and compared against baseline controls in 25 healthy adults. Plasma HDL-cholesterol (HDL-c) increased 6.2% (P=0.001), due primarily to a 28% increase in large HDL (HDL-L; P<0.0001). Total plasma homocysteine (Hcy) decreased 19% (P=0.017), and glutathione (GSH) increased 20% (P=0.011). The changes in HDL and Hcy are in the direction associated with decreased risk of cardiovascular disease and cognitive decline; increased GSH reflects improved antioxidant defense. Changes in biomarkers linked to insulin resistance and inflammation were not observed. A defined food-based supplement can, within 2 wk, positively impact metabolic biomarkers linked to disease risk. These results lay the groundwork for mechanistic/deconstruction experiments to identify critical bar components and putative synergistic combinations responsible for observed effects.

Naturopathic physicians: holistic primary care and integrative medicine specialists

The use of Complimentary and Alternative Medicine (CAM) is increasing in the United States; there is a need for physician level practitioners who possess extensive training in both CAM and conventional medicine. Naturopathic physicians possess training that allows integration of modern scientific knowledge and the age-old wisdom of natural healing techniques. Naturopathic philosophy provides a framework to implement CAM in concert with conventional therapies. The naturopathic physician's expertise in both conventional medicine and CAM allows a practice style that provides excellent care through employing conventional and CAM modalities while utilizing modern research and evidence-based medicine.

Anticancer activity of green tea polyphenols in prostate gland

Numerous evidences from prevention studies in humans, support the existence of an association between green tea polyphenols consumption and a reduced cancer risk. Prostate cancer is one of the most frequently diagnosed male neoplasia in the Western countries, which is in agreement with this gland being particularly vulnerable to oxidative stress processes, often associated with tumorigenesis. Tea polyphenols have been extensively studied in cell culture and animal models where they inhibited tumor onset and progression. Prostate cancer appears a suitable target for primary prevention care, since it grows slowly, before symptoms arise, thus offering a relatively long time period for therapeutic interventions. It is, in fact, usually diagnosed in men 50-year-old or older, when even a modest delay in progression of the disease could significantly improve the patients quality of life. Although epidemiological studies have not yet yielded conclusive results on the chemopreventive and anticancer effect of tea polyphenols, there is an increasing trend to employ these substances as conservative management for patients diagnosed with less advanced prostate cancer. Here, we intend to review the most recent observations relating tea polyphenols to human prostate cancer risk, in an attempt to outline better their potential employment for preventing prostate cancer.

Effects of anthocyanin-rich tea "Sunrouge" on dextran sodium sulfate-induced colitis in mice

Sunrouge, an anthocyanin-rich tea, has similar levels of catechins as "Yabukita," the most popular green tea cultivar consumed in Japan. Green tea polyphenols (GTPs) have attracted interest due to their potent antioxidative activities combined with a lack of side effects in humans at normal consumption levels. However, we previously reported that high doses (0.5 and 1%) of dietary GTPs can result in deterioration of colitis and failed to prevent colon carcinogenesis in inflamed colons. In the present study, we determined the inhibitory effects of Sunrouge on colitis in dextran sodium sulfate (DSS)-treated and untreated control mice. Five-week-old female ICR mice were administered a single dose of Yabukita or Sunrouge (extracts in 1 mL distilled water) via a stomach tube for 3 weeks. After 1 week of treatment, the mice were divided into four groups (two Yabukita and two Sunrouge groups) and given drinking water with or without 3% DSS for 2 weeks, then they were euthanized. Those treated with DSS developed watery diarrhea and bloody stools, and showed body weight loss, spleen hypertrophy, and shortening of the colon, as well as deteriorations in survival rate, liver function, colon mucosal interleukin-1β level and expression of phase II detoxification enzyme mRNA. Sunrouge improved these DSS-induced symptoms, at least in part, whereas Yabukita showed either no effect or adverse effects in regard to some those parameters. It is suggested that the differences between Yabukita and Sunrouge on DSS-induced colitis might be due to the high levels of anthocyanins found in Sunrouge tea.

Mitochondria: redox metabolism and dysfunction

Mitochondria are the main intracellular location for fuel generation; however, they are not just power plants but involved in a range of other intracellular functions including regulation of redox homeostasis and cell fate. Dysfunction of mitochondria will result in oxidative stress which is one of the underlying causal factors for a variety of diseases including neurodegenerative diseases, diabetes, cardiovascular diseases, and cancer. In this paper, generation of reactive oxygen/nitrogen species (ROS/RNS) in the mitochondria, redox regulatory roles of certain mitochondrial proteins, and the impact on cell fate will be discussed. The current state of our understanding in mitochondrial dysfunction in pathological states and how we could target them for therapeutic purpose will also be briefly reviewed.

The CDK4/6 inhibitor PD0332991 reverses epithelial dysplasia associated with abnormal activation of the cyclin-CDK-Rb pathway

Loss of normal growth control is a hallmark of cancer progression. Therefore, understanding the early mechanisms of normal growth regulation and the changes that occur during preneoplasia may provide insights of both diagnostic and therapeutic importance. Models of dysplasia that help elucidate the mechanisms responsible for disease progression are useful in highlighting potential targets for prevention. An important strategy in cancer prevention treatment programs is to reduce hyperplasia and dysplasia. This study identified abnormal upregulation of cell cycle-related proteins cyclin D1, cyclin-dependent kinase (CDK)4, CDK6, and phosphorylated retinoblastoma protein (pRb) as mechanisms responsible for maintenance of hyperplasia and dysplasia following downregulation of the initiating viral oncoprotein Simian virus 40 (SV40) T antigen. Significantly, p53 was not required for successful reversal of hyperplasia and dysplasia. Ligand-induced activation of retinoid X receptor and PPARγ agonists attenuated cyclin D1 and CDK6 but not CDK4 or phosphorylated pRb upregulation with limited reversal of hyperplasia and dysplasia. PD0332991, an orally available CDK4/6 inhibitor, was able to prevent upregulation of cyclin D1 and CDK6 as well as CDK4 and phosphorylated pRb and this correlated with a more profound reversal of hyperplasia and dysplasia. In summary, the study distinguished CDK4 and phosphorylated pRb as targets for chemoprevention regimens targeting reversal of hyperplasia and dysplasia.

Exposure to ozone modulates human airway protease/antiprotease balance contributing to increased influenza A infection

Exposure to oxidant air pollution is associated with increased respiratory morbidities and susceptibility to infections. Ozone is a commonly encountered oxidant air pollutant, yet its effects on influenza infections in humans are not known. The greater Mexico City area was the primary site for the spring 2009 influenza A H1N1 pandemic, which also coincided with high levels of environmental ozone. Proteolytic cleavage of the viral membrane protein hemagglutinin (HA) is essential for influenza virus infectivity. Recent studies suggest that HA cleavage might be cell-associated and facilitated by the type II transmembrane serine proteases (TTSPs) human airway trypsin-like protease (HAT) and transmembrane protease, serine 2 (TMPRSS2), whose activities are regulated by antiproteases, such as secretory leukocyte protease inhibitor (SLPI). Based on these observations, we sought to determine how acute exposure to ozone may modulate cellular protease/antiprotease expression and function, and to define their roles in a viral infection. We utilized our in vitro model of differentiated human nasal epithelial cells (NECs) to determine the effects of ozone on influenza cleavage, entry, and replication. We show that ozone exposure disrupts the protease/antiprotease balance within the airway liquid. We also determined that functional forms of HAT, TMPRSS2, and SLPI are secreted from human airway epithelium, and acute exposure to ozone inversely alters their expression levels. We also show that addition of antioxidants significantly reduces virus replication through the induction of SLPI. In addition, we determined that ozone-induced cleavage of the viral HA protein is not cell-associated and that secreted endogenous proteases are sufficient to activate HA leading to a significant increase in viral replication. Our data indicate that pre-exposure to ozone disrupts the protease/antiprotease balance found in the human airway, leading to increased influenza susceptibility.

Peracetylated (-)-epigallocatechin-3-gallate (AcEGCG) potently suppresses dextran sulfate sodium-induced colitis and colon tumorigenesis in mice

Previous studies reported that peracetylated (-)-epigallocatechin-3-gallate (AcEGCG) has antiproliferative and anti-inflammatory activities. Here, we evaluated the chemopreventive effects and underlying molecular mechanisms of dietary administration of AcEGCG and EGCG in dextran sulfate sodium (DSS)-induced colitis in mice. The mice were fed a diet supplemented with either AcEGCG or EGCG prior to DSS induction. Our results indicated that AcEGCG administration was more effective than EGCG in preventing the shortening of colon length and the formation of aberrant crypt foci (ACF) and lymphoid nodules (LN) in mouse colon stimulated by DSS. Our study observes that AcEGCG treatment inhibited histone 3 lysine 9 (H3K9) acetylation but did not affect histone acetyltransferase (HAT) activity and acetyl- CREB-binding protein (CBP)/p300 levels. In addition, pretreatment with AcEGCG decreased the proinflammatory mediator levels by down-regulating of PI3K/Akt/NFκB phosphorylation and p65 acetylation. We also found that treatment with AcEGCG increased heme oxygenase-1(HO-1) expression via activation of extracellular signal-regulated protein kinase (ERK)1/2 signaling and acetylation of NF-E2-related factor 2 (Nrf2), thereby abating DSS-induced colitis. Moreover, dietary feeding with AcEGCG markedly reduced colitis-driven colon cancer in mice. Taken together, these results demonstrated for the first time the in vivo chemopreventive efficacy and molecular mechanisms of dietary AcEGCG against inflammatory bowel disease (IBD) and potentially colon cancer associated with colitis. These findings provide insight into the biological actions of AcEGCG and might establish a molecular basis for the development of new cancer chemopreventive agents.

Encapsulated nanoepigallocatechin-3-gallate and elemental selenium nanoparticles as paradigms for nanochemoprevention

Chemoprevention that impedes one or more steps in carcinogenesis, via long-term administration of naturally occurring or synthetic compounds, is widely considered to be a crucial strategy for cancer control. Selenium (Se) has chemopreventive effects, but its application is limited due to a low therapeutic index as shown in numerous animal experiments. In contrast to Se, which was known for its toxicity prior to the discovery of its beneficial effects, the natural compound epigallocatechin-3-gallate (EGCG) was originally considered to be nontoxic. Due to its preventive effects on many types of cancer in various animal models, EGCG has been regarded as a prime example of a promising chemopreventive agent without major toxicity concerns. However, very recently, evidence has accumulated showing that efficacious doses of EGCG used in health promotion may not be far from its toxic dose level. Therefore, both Se and EGCG need to be modified by novel pharmaceutical technologies to attain enhanced efficacy and/or reduced toxicity. Nanotechnology may be one of these technologies. In support of this hypothesis, the characteristics of polylactic acid and polyethylene glycol-encapsulated nano-EGCG and elemental Se nanoparticles dispersed by bovine serum albumin are reviewed in this article. Encapsulation of EGCG to form nano-EGCG leads to its enhanced stability in plasma and remarkably superior chemopreventive effects, with more than tenfold dose advantages in inducing apoptosis and inhibition of both angiogenesis and tumor growth. Se at nanoparticle size (“Nano-Se”), compared with Se compounds commonly used in dietary supplements, has significantly lower toxicity, without compromising its ability to upregulate selenoenzymes at nutritional levels and induce phase II enzymes at supranutritional levels.

EGCG inhibits Tat-induced LTR transactivation: role of Nrf2, AKT, AMPK signaling pathway

AIMS

Transcription is a crucial step for human immunodeficiency virus 1 (HIV-1) gene expression in infected host cells. The HIV-1 Tat activates the nuclear factor-kappa B (NF-κB) signaling transduction pathway, which is necessary for viral replication. Epigallocatechin-3-gallate (EGCG) has antioxidant, anti-inflammatory, and anti-viral properties. In this study, we investigated the effects of EGCG on Tat-induced HIV-1 transactivation and potential mechanisms by which EGCG inhibited activation of NF-κB pathway.

MAIN METHODS

HeLa-CD4-long terminal repeat (LTR)-β-gal (MAGI) cells were transfected with Tat plasmid. Tat-induced HIV-1 LTR transactivation was determined by MAGI cell assay. The reactive oxygen species (ROS) levels and glutathione (GSH) levels were measured. In addition, the protein expressions were assayed by western blotting.

KEY FINDINGS

Tat caused a significant decrease in the intracellular glutathione (GSH) levels, a mild increase in the expression of nuclear levels of NF-E2-related factor-2 (Nrf2), a significant increase in the levels of NF-κB (phosphorylation of p65 and IKK) and a significant increase in ROS production. EGCG supplementation significantly improved the changes associated with Tat-induced oxidative stress by increasing nuclear levels of Nrf2, decreasing levels of NF-κB and ROS production. EGCG reversed Tat-mediated AKT activation and AMPK inhibition in MAGI cells. EGCG inhibited Tat-induced LTR transactivation in a dose-dependent manner.

SIGNIFICANCE

The results suggest that Nrf2 signaling pathway may be the primary target for prevention of Tat-induced HIV-1 transactivation by EGCG, and EGCG also reduce NF-κB activation by inhibiting AKT signaling pathway and activating AMPK signaling pathway.

Effect of tea catechins on regulation of cell proliferation and antioxidant enzyme expression in H2 O2 -induced primary hepatocytes of goat in vitro

Tea catechins (TC) are polyphenols that have potent antioxidant activity. The objectives of this study were to determine the effects of TC on antioxidant status of hepatocytes challenged with H2 O2 . Primary hepatocytes of goat were exposed to 1 mm H2 O2 without or with 5, 50 and 500 μg/ml TC. The cells were harvested at 48 h post-treatment to determine effects of TC on proliferation, apoptotic features and membrane integrity of cells, and expression of genes and activities of antioxidant enzymes. H2 O2 exposure caused damage to cells (p < 0.001). A lower concentration of TC (5 μg/ml) displayed a protective effect by inhibiting exorbitant cell proliferation and DNA degradation. Both H2 O2 exposure and TC pre-incubation affected expression of antioxidant enzymes at mRNA and protein levels (p < 0.001). The activities of catalase (CAT) (p = 0.027), CuZn-superoxide dismutase (CuZn-SOD) (p < 0.001) and glutathione peroxidase (GPx) (p < 0.001) increased with TC pre-incubation followed by H2 O2 challenge. Changes of CuZn-SOD activity induced by H2 O2 and TC basically paralleled the changes in the corresponding mRNA and protein levels, but the correlation in CAT and GPx expression displayed slightly different patterns at different concentrations of TC. These findings infer that oxidative stress can induce deleterious cellular responses and this unfavourable condition may be alleviated by treatment with TC.

Ellagic acid protects human keratinocyte (HaCaT) cells against UVA-induced oxidative stress and apoptosis through the upregulation of the HO-1 and Nrf-2 antioxidant genes

UV radiation from the sun is a potent environmental risk factor in the pathogenesis of skin damage. Much of the skin damage caused by ultraviolet A (UVA) irradiation from the sun is associated with oxidative stress. The aim of this study was to investigate the protective role of ellagic acid (25-75 μM), a natural antioxidant, against UVA (5-20 J/cm(2))-induced oxidative stress and apoptosis in human keratinocyte (HaCaT) cells and to reveal the possible mechanisms underlying this protective efficacy. Ellagic acid pre-treatment markedly increased HaCaT cell viability and suppressed UVA-induced ROS generation and MDA formation. Moreover, ellagic acid pre-treatment prevented UVA-induced DNA damage as evaluated by the comet assay. Ellagic acid treatment also significantly inhibited the UVA-induced apoptosis of HaCaT cells, as measured by a reduction of DNA fragmentation, mitochondria dysfunction, ER stress, caspase-3 activation, and Bcl-2/Bax deregulation. Notably, the antioxidant potential of ellagic acid was directly correlated with the increased expression of HO-1 and SOD, which was followed by the downregulation of Keap1 and the augmented nuclear translocation and transcriptional activation of Nrf2 with or without UVA irradiation. Nrf2 knockdown diminished the protective effects of ellagic acid. Therefore, ellagic acid may be useful for the treatment of UVA-induced skin damage.

Sanguisorba minor extract suppresses plasmin-mediated mechanisms of cancer cell migration

BACKGROUND

Sanguisorba minor, as well as several other edible herbs and vegetables, has been used extensively in traditional medicine. The observed beneficial effects can be attributed at least in part to the direct modulation of several enzymatic activities by its polyphenolic constituents.

METHODS

The ethanol extract of Sanguisorba minor was characterized by reversed-phase liquid chromatography, and most relevant analytes were identified by multiple stage mass spectrometry. The whole extract and the most relevant isolated constituents were tested for their ability to modulate the activity of human plasmin both toward a synthetic substrate and in human breast cancer cell culture models. Kinetic and equilibrium parameters were obtained by a concerted spectrophotometric and biosensor-based approach.

RESULTS

Quercetin-3-glucuronide was recognized as the compound mainly responsible for the in vitro plasmin inhibition by S. minor extract, with an inhibition constant in the high nanomolar range; in detail, our approach based on bioinformatic, enzymatic and binding analyses classified the inhibition as competitive. Most interestingly, cell-based assays showed that this flavonoid was effective in suppressing plasmin-induced loss of cancer cell adhesion.

GENERAL SIGNIFICANCE

Our results show that the extract from Sanguisorba minor limits plasmin-mediated tumor cell motility in vitro, mostly due to quercetin-3-glucuronide. This glucuronated flavonoid is a promising template for rational designing of anticancer drugs to be used in the treatment of pathological states involving the unregulated activity of plasmin.

Therapeutic potential of green tea in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a constellation of progressive liver disorders that are closely related to obesity, diabetes, and insulin resistance and may afflict over 70 million Americans. NAFLD may occur as relatively benign, nonprogressive liver steatosis, but in many individuals it may progress in severity to nonalcoholic steatohepatitis, fibrosis, cirrhosis, and liver failure or hepatocellular carcinoma. No validated treatments currently exist for NAFLD except for weight loss, which has a poor long-term success rate. Thus, dietary strategies that prevent the development of liver steatosis or its progression to nonalcoholic steatohepatitis are critically needed. Green tea is rich in polyphenolic catechins that have hypolipidemic, thermogenic, antioxidant, and anti-inflammatory activities that may mitigate the occurrence and progression of NAFLD. This review presents the experimental evidence demonstrating the hepatoprotective properties of green tea and its catechins and the proposed mechanisms by which these targeted dietary agents protect against NAFLD.

Green tea extract suppresses NFκB activation and inflammatory responses in diet-induced obese rats with nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is characterized by oxidative stress and inflammatory responses that exacerbate liver injury. The objective of this study was to determine whether the antioxidant and antiinflammatory activities of green tea extract (GTE) would protect against NASH in a model of diet-induced obesity. Adult Wistar rats were fed a low-fat (LF) diet or high-fat (HF) diet containing no GTE or GTE at 1% or 2% (HF+2GTE) for 8 wk. The HF group had greater (P ≤ 0.05) serum alanine (ALT) and aspartate aminotransferases and hepatic lipids than the LF group. Both GTE groups had lower ALT and hepatic lipid than the HF group. In liver and epididymal adipose, the HF group had lower glutathione as well as greater mRNA and protein expression of TNFα and monocyte chemoattractant protein-1 (MCP-1) and NFκB binding activity than the LF group. Compared to the HF group, the HF+2GTE group had greater glutathione and lower protein and mRNA levels of inflammatory cytokines in both tissues. NFκB binding activities at liver and adipose were also lower, likely by inhibiting the phosphorylation of inhibitor of NFκB. NFκB binding activities in liver and adipose (P ≤ 0.05; r = 0.62 and 0.46, respectively) were correlated with ALT, and hepatic NFκB binding activity was inversely related to liver glutathione (r = -0.35). These results suggest that GTE-mediated improvements in glutathione status are associated with the inhibition of hepatic and adipose inflammatory responses mediated by NFκB, thereby protecting against NASH.

Epigallocatechin gallate induces expression of heme oxygenase-1 in endothelial cells via p38 MAPK and Nrf-2 that suppresses proinflammatory actions of TNF-α

Epigallocatechin gallate (EGCG), the major polyphenol in green tea, acutely stimulates production of nitric oxide (NO) from vascular endothelium to reduce hypertension and improve endothelial dysfunction in spontaneously hypertensive rats. Herein, we explored additional mechanisms whereby EGCG may mediate beneficial cardiovascular actions. When compared with vehicle-treated controls, EGCG treatment (2.5 μM, 8 h) of human aortic endothelial cells (HAEC) caused a ~three-fold increase in heme oxygenase-1 (HO-1) mRNA and protein with comparable increases in HO-1 activity. This was unaffected by pretreatment of cells with wortmannin, LY294002, PD98059 or L-NAME (PI 3-kinase, MEK and NO synthase inhibitors, respectively). Pretreatment of HAEC with SB203580 (p38 MAPK inhibitor) or siRNA knockdown of p38 MAPK completely blocked EGCG-stimulated induction of HO-1. EGCG treatment also inhibited tumor-necrosis-factor-α-stimulated expression of vascular cell adhesion molecule (VCAM)-1 and decreased adhesion of monocytes to HAEC. siRNA knockdown of HO-1, p38 MAPK or Nrf-2 blocked these inhibitory actions of EGCG. In HAEC transiently transfected with a human HO-1 promoter luciferase reporter (or an isolated Nrf-2 responsive region), luciferase activity increased in response to EGCG. This was inhibitable by SB203580 pretreatment. EGCG-stimulated expression of HO-1 and Nrf-2 was blocked by siRNA knockdown of Nrf-2 or p38 MAPK. Finally, liver from mice chronically treated with EGCG had increased HO-1 and decreased VCAM-1 expression. Thus, in vascular endothelium, EGCG requires p38 MAPK to increase expression of Nrf-2 that drives expression of HO-1, resulting in increased HO-1 activity. Increased HO-1 expression may underlie anti-inflammatory actions of EGCG in vascular endothelium that may help mediate beneficial cardiovascular actions of green tea.

Antioxidant properties of natural polyphenols and their therapeutic potentials for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and most common cause of dementia. However, there is no known way to halt or cure the neurodegenerative disease. Oxidative stress is a cardinal hallmark of the disease and has been considered as therapeutic target for AD treatment. Several factors may contribute to oxidative stress in AD brains. First, mitochondrion is a key player that produces reactive oxygen species (ROS). Mitochondrial dysfunction found in AD patients may exaggerate generation of ROS and oxidative stress. Second, amyloid-beta peptide generates ROS in the presence of metal ions such as Fe(2+) and Cu(2+). Third, activated glial cells in AD brains may produce excessive amount of superoxide and nitric oxide through NADPH oxidase and inducible nitric oxide synthase, respectively. Increased ROS can cause damage to protein, lipid and nucleic acids. Numerous studies demonstrated that natural polyphenolic compounds protect against various neurotoxic insults in vitro and in vivo AD models. In these studies, dietary polyphenolic compounds exhibit neuroprotective effects through scavenging free radicals and increasing antioxidant capacity. Furthermore, they could facilitate the endogenous antioxidant system by stimulating transcription. Some epidemiological and clinical studies highlighted their therapeutic potential for AD treatment. In this review, we will briefly discuss causes of oxidative stress in AD brains, and describe antioxidant neuroprotective effects and therapeutic potential for AD of selected natural polyphenolic compounds.

The role of Nrf2 in migration and invasion of human glioma cell U251

OBJECTIVE

NF-E2-related factor 2 (Nrf2) is a transcription factor that is related to tumor cell multidrug resistance and proliferation. Here we studied the involvement of Nrf2 in the migration and invasion of human U251 glioma cells.

METHODS

Two kinds of plasmid, that is, pEGFP-Nrf2 and Si-Nrf2, were constructed and transfected to upregulate or downregulate the expression of Nrf2 in U251 glioma cell line. Blank vectors or random siRNA plasmid were used as negative control. Cells treated with lipofectamine only were set up as blank control. Protein and mRNA level of Nrf2 and matrix metalloproteinase 9 (MMP9) were investigated by reverse transcriptase-polymerase chain reaction and western blot after transfection. Wound healing assay and transwell assay were used to study migration and invasion of U251 after transfection. Gelatin zymography was performed to reveal the change of MMP9 activity after transfection.

RESULTS

The mRNA and protein level of Nrf2 was upregulated in U251-pEGFP-Nrf2 while downregulated in U251-Si-Nrf2 48 hours after transfection. In the wound healing assay, there were more cells in group pEGFP-Nrf2 crossing the scratch line than in group Si-Nrf2. Furthermore, in transwell migration and invasion assay, there were more cells in group pEGFP-Nrf2 penetrating the membranes than in group Si-Nrf2. Then we investigated the change of MMP9 activity, mRNA, and protein levels after transfection. The results suggested that upregulation of Nrf2 led to an increase in MMP9 expression and activity whereas downregulation of Nrf2 led to a decrease in MMP9 expression and activity.

CONCLUSION

Nrf2 is involved in migration and invasion of U251 cells, which may be related to MMP9.

Effect of fermented Panax ginseng extract (GINST) on oxidative stress and antioxidant activities in major organs of aged rats

The intracellular levels of oxidant and antioxidant balances are gradually distorted during the aging process. An age associated elevation of oxidative stress occurring throughout the lifetime is hypothesized to be the major cause of aging. The present study was undertaken to evaluate the putative antioxidant activity of the fermented Panax ginseng extract (GINST) on lipid peroxidation and antioxidant status of major organs of aged rats compared to young rats. Increased levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea and creatinine were observed in the serum of aged rats. Increased levels of malondialdehyde (MDA) and significantly lowered activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) were observed in the liver, kidneys, heart and lungs of aged rats, when compared with those in young rats. Quantitative analysis of the non-enzymatic antioxidants such as reduced glutathione (GSH), ascorbic acid and α-tocopherol levels showed significantly lower values in the liver, kidneys, heart and lungs of aged rats. On the other hand, administration of the fermented Panax ginseng extract (GINST) to aged rats resulted in increased activities of SOD, CAT, GPx, GR and GST as well as elevation in GSH, ascorbic acid and α-tocopherol levels. Besides, the level of MDA, AST, ALT, urea and creatinine were reduced on administration of GINST to aged rats. These results suggested that treatment of GINST can improve the antioxidant status during aging, thereby minimizing the oxidative stress and occurrence of age-related disorders associated with free radicals.

Effect of tea catechins on regulation of antioxidant enzyme expression in H2O2-induced skeletal muscle cells of goat in vitro

Skeletal muscle cells (SMCs) of goats were stress induced with 1 mM H(2)O(2) in the absence or presence of 0.5, 5, and 50 μg/mL tea catechins (TCs) incubation. Cells were harvested at 48 h postincubation with TCs to investigate the effects of TCs on cell proliferation, cell membrane integrity, antioxidant enzyme activities, and antioxidant enzyme genes and protein expression levels. Results showed that H(2)O(2) induction inhibited cell proliferation with or without TC incubation; moreover, the inhibition effect was enhanced in the presence of TCs (P < 0.001). H(2)O(2)-induced stress increased the lactate dehydrogenase (LDH) activity in the absence or presence of TC incubation, but concentrations of TCs, less than 5 μg/mL, showed protective functions against LDH leakage than in other H(2)O(2)-induced treatments. The catalase (CAT) activity increased when SMCs were stress induced with H(2)O(2) in the absence or presence of TC incubation (P < 0.001). H(2)O(2)-induced stress decreased CuZn superoxide dismutase (CuZn-SOD) and glutathione peroxidase (GPx) activities, whereas this effect was prevented by incubation with TCs in a concentration-dependent manner. H(2)O(2)-induced stress with or without TC incubation had significant effects on mRNA and protein expression levels of CAT, CuZn-SOD, and GPx (P < 0.001). CAT and CuZn-SOD mRNA expression levels were increased by different concentrations of TC incubation, and this tendency was basically consistent with corresponding protein expression levels. The GPx mRNA expression level increased with a low concentration of TCs but decreased with concentrations greater than 5 μg/mL of TCs, whereas GPx protein expression in all TC-incubated groups was lower than in the control treatment. The current findings imply that TCs had an inhibitory effect on cell proliferation and enhanced damage to the cell membrane integrity, but TCs affected antioxidant status in SMCs by modulating antioxidant enzyme activities at mRNA and protein expression levels.

Molecular pathways for cancer chemoprevention by dietary phytochemicals

Interest in dietary phytochemicals for potential cancer chemoprevention has increased substantially. Screening dietary compounds for chemopreventive activity however, requires a systematic and wide-ranging approach to encompass the complexity of carcinogenesis. We present some of the molecular pathways that underpin the broad biological processes involved in carcinogenesis. Oxidative stress, inflammation, and the evasion of apoptosis are important biological mechanisms by which carcinogenesis occurs. Subsequently, antioxidant, anti-inflammatory, and pro-apoptotic activity represent important activities for preventing, suppressing, or reversing the development of carcinogenesis. Ultimately, these mechanisms of action may provide a useful basis for screening novel phytochemicals for chemopreventive activity. In this review, we identify the important molecular processes that may be targeted in routine screenings of dietary phytochemicals to ultimately select the most effective potential candidates for cancer chemoprevention.

Potential antioxidant, antiinflammatory, and proapoptotic anticancer activities of Kakadu plum and Illawarra plum polyphenolic fractions

Kakadu plum (Terminalia ferdinandiana Exell, Combretaceae) and Illawarra plum (Podocarpus elatus Endl., Podocarpaceae) extracts were fractionated, using a bioassay-guided approach and screened for antioxidant activity [oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) assays] and antiinflammatory activity (nitrite concentration and prostaglandin E(2) release in lipopolysaccharide (LPS)-activated murine macrophages). Among 8 fractions obtained from KP and 5 fractions obtained from IP, fraction KPF5 from KP exhibited superior activity in all assays, with an ORAC value of 3,776 ± 603 μmol Trolox/g DW and a CAA value of 52.2 ± 8.6 μmol quercetin equivalents/g DW. In addition, KPF5 further demonstrated an upregulation of the Nrf2/Keap1 ratio in Hep G2 cells. KPF5 also inhibited the expression of COX-2 and iNOS in LPS-activated murine macrophages, potentially through the NF-κB, p44/42 mitogen activated protein kinase and Akt pathways. KPF5 also induced apoptosis and DNA damage in HT-29 cells, as determined by the cytokinesis block micronucleus cytome assay.

Dietary flavonoids: Role of (-)-epicatechin and related procyanidins in cell signaling

Plant polyphenols are among the most abundant phytochemicals present in human diets. Increasing evidence supports the health-promoting effects of certain polyphenols, including flavonoids. This review discusses current knowledge of the capacity of monomeric flavanols, i.e., (-)-epicatechin and (+)-catechin, and their derived procyanidins to modulate cell signaling and the associations of these actions with better health. Flavanols and procyanidins can regulate cell signaling through different mechanisms of action. Monomers and dimeric procyanidins can be transported inside cells and directly interact and modulate the activity of signaling proteins and/or prevent oxidation. Larger and nonabsorbable procyanidins can regulate cell signaling by interacting with cell membrane proteins and lipids, inducing changes in membrane biophysics, and by modulating oxidant production. All these actions would be limited by the bioavailability of flavanols at the target tissue. The protection from cardiac and vascular disease and from cancer that is associated with a high consumption of fruit and vegetables could be in part explained by the capacity of flavanols and related procyanidins to modulate proinflammatory and oncogenic signals.

Hormetics: dietary triggers of an adaptive stress response

A series of dietary ingredients and metabolites are able to induce an adaptive stress response either by generation of reactive oxygen species (ROS) and/or via activation of the Nrf2/Keap1 stress response network. Most of the molecules belong to activated Michael acceptors, electrophiles capable to S-alkylate redox sensitive cysteine thiols. This review summarizes recent advances in the (re)search of these compounds and classifies them into distinct groups. More than 60 molecules are described that induce the Nrf2 network, most of them found in our daily diet. Although known as typical antioxidants, a closer look reveals that these molecules induce an initial mitochondrial or cytosolic ROS formation and thereby trigger an adaptive stress response and hormesis, respectively. This, however, leads to higher levels of intracellular glutathione and increased expression levels of antioxidant enzymes such as glutathione peroxidase, thioredoxin reductase, and superoxide dismutase. According to this principle, the author suggests the term hormetics to describe these indirect antioxidants.

Epigallocatechin-3-gallate prevents lupus nephritis development in mice via enhancing the Nrf2 antioxidant pathway and inhibiting NLRP3 inflammasome activation

Patients with lupus nephritis show an impaired oxidative status and increased levels of interleukin (IL)-1β and IL-18, which are closely linked to inflammation and correlated with disease activity. Although epigallocatechin-3-gallate (EGCG), the major bioactive polyphenol present in green tea with antioxidant and free radical scavenging activities, has been reported to have anti-inflammatory effects by inhibiting nuclear factor-kappa B (NF-κB)-mediated inflammatory responses in vivo, its effectiveness for the treatment of lupus nephritis is still unknown. In the present study, 12-week-old New Zealand black/white (NZB/W) F1 lupus-prone mice were treated daily with EGCG by gavage until sacrificed at 34 weeks old for clinical, pathological, and mechanistic evaluation. We found that the administration (1) prevented proteinuria, renal function impairment, and severe renal lesions; (2) increased renal nuclear factor E2-related factor 2 (Nrf2) and glutathione peroxidase activity; (3) reduced renal oxidative stress, NF-κB activation, and NLRP3 mRNA/protein expression and protein levels of mature caspase-1, IL-1β, and IL-18; and (4) enhanced splenic regulatory T (Treg) cell activity. Our data clearly demonstrate that EGCG has prophylactic effects on lupus nephritis in these mice that are highly associated with its effects of enhancing the Nrf2 antioxidant signaling pathway, decreasing renal NLRP3 inflammasome activation, and increasing systemic Treg cell activity.

Dietary isothiocyanate-induced apoptosis via thiol modification of DNA topoisomerase IIα

Studies in animal models have indicated that dietary isothiocyanates (ITCs) exhibit cancer preventive activities through carcinogen detoxification-dependent and -independent mechanisms. The carcinogen detoxification-independent mechanism of cancer prevention by ITCs has been attributed at least in part to their ability to induce apoptosis of transformed (initiated) cells (e.g. through suppression of IκB kinase and nuclear factor κB as well as other proposed mechanisms). In the current studies we show that ITC-induced apoptosis of oncogene-transformed cells involves thiol modification of DNA topoisomerase II (Top2) based on the following observations. 1) siRNA-mediated knockdown of Top2α in both SV40-transformed MEFs and Ras-transformed human mammary epithelial MCF-10A cells resulted in reduced ITC sensitivity. 2) ITCs, like some anticancer drugs and cancer-preventive dietary components, were shown to induce reversible Top2α cleavage complexes in vitro. 3) ITC-induced Top2α cleavage complexes were abolished by co-incubation with excess glutathione. In addition, proteomic analysis revealed that several cysteine residues on human Top2α were covalently modified by benzyl-ITC, suggesting that ITC-induced Top2α cleavage complexes may involve cysteine modification. Interestingly, consistent with the thiol modification mechanism for Top2α cleavage complex induction, the thiol-reactive selenocysteine, but not the non-thiol-reactive selenomethionine, was shown to induce Top2α cleavage complexes. In the aggregate, our results suggest that thiol modification of Top2α may contribute to apoptosis induction in transformed cells by ITCs.

Involvement of catalase in the apoptotic mechanism induced by apigenin in HepG2 human hepatoma cells

Apigenin has been reported to inhibit proliferation of cancer cells; however, the mechanism underlying its action is not completely understood. Here, we evaluated the effects of apigenin on the levels of expression and activity of antioxidant enzymes, and the involvement of ROS in the mechanism of cell death induced by apigenin in HepG2 human hepatoma cells. Upon treatment with apigenin, HepG2 cells displayed a reduction in cell viability in a dose- and time-dependent manner, and some morphological changes. In addition, apigenin treatment induced ROS generation and significantly decreased the mRNA levels and activity of catalase and levels of intracellular GSH. On the other hand, apigenin treatment did not alter the expression or activity levels of other antioxidant enzymes. Addition of exogenous catalase significantly reduced the effects of apigenin on HepG2 cell death. We also demonstrated that HepG2 cells are more sensitive to apigenin-mediated cell death than are primary cultures of mouse hepatocytes, suggesting a differential toxic effect of this agent in tumor cells. Our results suggest that apigenin-induced apoptosis in HepG2 cells may be mediated by a H(2)O(2)-dependent pathway via reduction of the antioxidant defenses.

Mechanistic issues concerning cancer prevention by tea catechins

The cancer preventive activities of tea (Camellia sinensis, Theaceae) have been demonstrated in animal models for cancers at different organ sites and suggested by some epidemiological studies. Many mechanisms for cancer prevention have been proposed based on studies in cell lines, which demonstrated the modulation of signal transduction and metabolic pathways by (-)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. These molecular events may result in cellular changes, such as enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis. Nevertheless, it is not known whether these are the molecular mechanisms of inhibition of carcinogenesis in animals and humans. This article discusses the key issues involved in extrapolating results from cell line studies to mechanistic information in vivo and in translating animal studies to human cancer prevention.

Induction of human fetal hemoglobin via the NRF2 antioxidant response signaling pathway

Although hematopoietic stem cell transplantation and gene therapy have the potential to cure β-thalassemia and sickle cell disease, they are not currently available to most people with these diseases. In the near term, pharmacologic induction of fetal hemoglobin (HbF) may offer the best possibility for safe, effective, and widely available therapy. In an effort to define new pathways for targeted drug development for HbF induction, we evaluated the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant response element signaling pathway. We found that 3 well-known activators of this pathway increased γ-globin mRNA at nontoxic doses in K562 cells. Tert-butylhydroquinone (tBHQ), the most active of these compounds, increased cellular levels and nuclear translocation of NRF2 and binding of NRF2 to the γ-globin promoter. siRNA knockdown of NRF2 inhibited γ-globin induction by tBHQ. When tested in human primary erythroid cells, tBHQ induced NRF2 binding to the γ-globin promoter, increased γ-globin mRNA and HbF, and suppressed β-globin mRNA and HbA, resulting in a > 3-fold increase in the percentage of HbF. These results suggest that drugs that activate the NRF2/antioxidant response element signaling pathway have the potential to induce therapeutic levels of HbF in people with β-hemoglobinopathies.

Cancer prevention by tea: Evidence from laboratory studies

The cancer preventive activities of tea (Camellia sinensis Theaceae) have been studied extensively. Inhibition of tumorigenesis by green tea extracts and tea polyphenols has been demonstrated in different animal models, including those for cancers of the skin, lung, oral cavity, esophagus, stomach, small intestine, colon, bladder, liver, pancreas, prostate, and mammary glands. Many studies in cell lines have demonstrated the modulation of signal transduction and metabolic pathways by (-)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. These molecular events can result in cellular changes, such as enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis. Nevertheless, the molecular mechanisms of inhibition of carcinogenesis in animals and humans remain to be further investigated. Future research directions in this area are discussed.

The Nrf2/ARE Pathway: A Promising Target to Counteract Mitochondrial Dysfunction in Parkinson's Disease

Mitochondrial dysfunction is a prominent feature of various neurodegenerative diseases as strict regulation of integrated mitochondrial functions is essential for neuronal signaling, plasticity, and transmitter release. Many lines of evidence suggest that mitochondrial dysfunction plays a central role in the pathogenesis of Parkinson's disease (PD). Several PD-associated genes interface with mitochondrial dynamics regulating the structure and function of the mitochondrial network. Mitochondrial dysfunction can induce neuron death through a plethora of mechanisms. Both mitochondrial dysfunction and neuroinflammation, a common denominator of PD, lead to an increased production of reactive oxygen species, which are detrimental to neurons. The transcription factor nuclear factor E2-related factor 2 (Nrf2, NFE2L2) is an emerging target to counteract mitochondrial dysfunction and its consequences in PD. Nrf2 activates the antioxidant response element (ARE) pathway, including a battery of cytoprotective genes such as antioxidants and anti-inflammatory genes and several transcription factors involved in mitochondrial biogenesis. Here, the current knowledge about the role of mitochondrial dysfunction in PD, Nrf2/ARE stress-response mechanisms, and the evidence for specific links between this pathway and PD are summarized. The neuroprotection of nigral dopaminergic neurons by the activation of Nrf2 through several inducers in PD is also emphasized as a promising therapeutic approach.

Green tea and cancer prevention

Extracts of green tea and green tea polyphenols have exhibited inhibitory effects against the formation and development of tumors at different organ sites in animals. These include animal models for skin, lung, oral cavity, esophagus, stomach, intestine, colon, liver, pancreas, bladder, mammary gland, and prostate cancers. In addition to suppressing cell proliferation, promoting apoptosis, and modulating signaling transduction, green tea polyphenols, especially (-)-epigallocatechin-3-gallate, also inhibit cell invasion, angiogenesis, and metastasis. This article reviews data on the cancer preventive activities of green tea polyphenols, possible mechanisms involved, and the relationship between green tea consumption and human cancer risk.

Resveratrol protects quail hepatocytes against heat stress: modulation of the Nrf2 transcription factor and heat shock proteins

In the present study, the effects of dietary resveratrol on the induction of heat shock proteins, transcription factors and antioxidative enzyme system in liver of quails under heat stress were investigated. A total of 180 (55-day-old) female Japanese quails (Coturnix coturnix japonica) were reared either at 22 °C for 24 h/day (thermoneutral, TN) or 34 °C for 8 h/day (heat stress, HS; 09:00-17:00 hours) for 12 weeks. Birds in both environments were randomly fed one of three diets: basal diet and basal diet added with either 200 or 400 mg of resveratrol per kg of diet. The results showed that exposure to high ambient temperature induced decreases in feed intake, egg production, and hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities but increases in hepatic malondialdehyde (MDA) concentrations (p < 0.001). Liver Hsp70, Hsp90 and NF-κB expression was greater while Nrf2 expression was lower for quails reared under the heat stress than for those reared under the TN environment (p < 0.0001). There were linear increases in feed intake, egg production, hepatic SOD, CAT, and GSH-Px activities as well as Nrf2 expression, but linear decreases in hepatic MDA concentrations and Hsp70, Hsp90, and NF-κB expressions with increasing supplemental resveratrol level (p < 0.0001). Two-way treatment interactions revealed that the degree of restorations in all response variables was more notable under the high ambient temperature than that of the TN environment as dietary resveratrol concentration was increased. The results of the present study suggest that supplemental resveratrol reduces oxidative stress in heat-stressed quails through modulating the hepatic heat shock proteins and nuclear transcription factors.

Multistage carcinogenesis process as molecular targets in cancer chemoprevention by epicatechin-3-gallate

The consumption of green tea has long been associated with a reduced risk of cancer development. (-)-Epicatechin-3-gallate (ECG) or (-)-epigallocatechin-3-gallate (EGCG) are the major antioxidative polyphenolic compounds of green tea. They have been shown to exert growth-inhibitory potential of various cancer cells in culture and antitumor activity in vivo models. ECG or EGCG could interact with various molecules like proteins, transcription factors, and enzymes, which block multiple stages of carcinogenesis via regulating intracellular signaling transduction pathways. Moreover, ECG and EGCG possess pharmacological and physiological properties including induction of phase II enzymes, mediation of anti-inflammation response, regulation of cell proliferation and apoptosis effects and prevention of tumor angiogenesis, invasion and metastasis. Numerous review articles have been focused on EGCG, however none have been focused on ECG despite many studies supporting the cancer preventive potential of ECG. To develop ECG as an anticarcinogenic agent, more clear understanding of the cell signaling pathways and the molecular targets responsible for chemopreventive and chemotherapeutic effects are needed. This review summarizes recent research on the ECG-induced cellular signal transduction events which implicate in cancer management.

A novel dietary supplement containing multiple phytochemicals and vitamins elevates hepatorenal and cardiac antioxidant enzymes in the absence of significant serum chemistry and genomic changes

A novel dietary supplement composed of three well-known phytochemicals, namely, Salvia officinalis (sage) extract, Camellia sinensis (oolong tea) extract, and Paullinia cupana (guarana) extract, and two prominent vitamins (thiamine and niacin) was designed to provide nutritional support by enhancing metabolism and maintaining healthy weight and energy. The present study evaluated the safety of this dietary supplement (STG; S=sage; T=tea; G=guarana) and assessed changes in target organ antioxidant enzymes (liver, kidneys and heart), serum chemistry profiles and organ histopathology in Fisher 344 rats. Adult male and female Fisher 344 rats were fed control (no STG) or STG containing (1X and 7X, 1X=daily human dose) diets and sacrificed after 2 and 4 months. Serum chemistry analysis and histopathological examination of three vital target organs disclosed no adverse influence on protein, lipid and carbohydrate profiles, genomic integrity of the liver and/or the tissue architecture. However, analysis of the most important antioxidant components in the liver, kidney and heart homogenates revealed a dramatic increase in total glutathione concentrations, glutathione peroxidase and superoxide dismutase enzyme activities. Concomitantly, oxidative stress levels (malondialdehyde accumulation) in these three organs were less than control. Organ specific serum markers (ALT/AST for the liver; CPK/AST for the heart; BUN/creatinine for kidneys) and the genomic integrity disclosed no STG-induced alteration. Some of the serum components (lipid and protein) showed insignificant changes. Overall, STG-exposed rats were more active, and the results suggest that STG exposure produces normal serum chemistry coupled with elevated antioxidant capacity in rats fed up to seven times the normal human dose and does not adversely influence any of the vital target organs. Additionally, this study reiterates the potential benefits of exposure to a pharmacologically relevant combination of phytochemicals compared to a single phytochemical entity.

Redox control of protein-DNA interactions: from molecular mechanisms to significance in signal transduction, gene expression, and DNA replication

Protein-DNA interactions play a key role in the regulation of major cellular metabolic pathways, including gene expression, genome replication, and genomic stability. They are mediated through the interactions of regulatory proteins with their specific DNA-binding sites at promoters, enhancers, and replication origins in the genome. Redox signaling regulates these protein-DNA interactions using reactive oxygen species and reactive nitrogen species that interact with cysteine residues at target proteins and their regulators. This review describes the redox-mediated regulation of several master regulators of gene expression that control the induction and suppression of hundreds of genes in the genome, regulating multiple metabolic pathways, which are involved in cell growth, development, differentiation, and survival, as well as in the function of the immune system and cellular response to intracellular and extracellular stimuli. It also discusses the role of redox signaling in protein-DNA interactions that regulate DNA replication. Specificity of redox regulation is discussed, as well as the mechanisms providing several levels of redox-mediated regulation, from direct control of DNA-binding domains through the indirect control, mediated by release of negative regulators, regulation of redox-sensitive protein kinases, intracellular trafficking, and chromatin remodeling.

Melatonin prevents the decreased activity of antioxidant enzymes and activates nuclear erythroid 2-related factor 2 signaling in an animal model of fulminant hepatic failure of viral origin

This work was undertaken to investigate whether treatment with melatonin prevents oxidative stress and changes in the expression and activity of factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant enzymes in an animal model of fulminant hepatic failure of viral origin. Rabbits were experimentally infected with 2 x 10(4) hemagglutination units of a rabbit hemorrhagic disease virus (RHDV) isolate and received melatonin at two concentrations of 10 mg/kg and 20 mg/kg at 0, 12 and 24 hr postinfection. Blood transaminases, blood lactate dehydrogenase, liver concentration of thiobarbituric reactive acid substances and the liver oxidized to reduced glutathione ratio significantly increased at 36 hr postinfection in infected animals. Significant decreases were found in the mRNA levels and in the liver activities of Mn-superoxide dismutase, glutathione peroxidase and glutathione-S-transferase in infected rabbits. These effects were prevented by melatonin administration in a concentration-dependent manner. Melatonin treatment was not accompanied by changes in protein levels of Kelch-like ECH-associating protein 1 (Keap1) but resulted in an increased protein expression of Nrf2 in the cytoplasm and the nucleus, which was confirmed by the results of Nrf2 immunostaining. Nuclear extracts from livers of melatonin-treated rats displayed an enhanced antioxidant responsive element (ARE)-binding activity of Nrf2. Our results suggest a potential hepatoprotective role of melatonin in fulminant hepatic failure, partially mediated through the abrogation of oxidative stress and the prevention of the decreased activity of antioxidant enzymes via the Nrf2 pathways.