Role of Nrf2 signaling in regulation of antioxidants and phase 2 enzymes in cardiac fibroblasts: protection against reactive oxygen and nitrogen species-induced cell injury

Piper betle induces phase I & II genes through Nrf2/ARE signaling pathway in mouse embryonic fibroblasts derived from wild type and Nrf2 knockout cells

Background

Nuclear factor-erythroid 2 p45 related factor 2 (Nrf2) is a primary transcription factor, protecting cells from oxidative stress by regulating a number of antioxidants and phase II detoxifying enzymes. Dietary components such as sulforaphane in broccoli and quercetin in onions have been shown to be inducers of Nrf2. Piper betle (PB) grows well in tropical climate and the leaves are used in a number of traditional remedies for the treatment of stomach ailments and infections among Asians. The aim of this study was to elucidate the effect of Piper betle (PB) leaves extract in Nrf2 signaling pathway by using 2 types of cells; mouse embryonic fibroblasts (MEFs) derived from wild-type (WT) and Nrf2 knockout (N0) mice.

Methods

WT and N0 cells were treated with 5 and 10 μg/ml of PB for 10 and 12-h for the determination of nuclear translocation of Nrf2 protein. Luciferase reporter gene activity was performed to evaluate the antioxidant response element (ARE)-induction by PB. Real-time PCR and Western blot were conducted on both WT and N0 cells after PB treatment for the determination of antioxidant enzymes [superoxide dismutase (SOD1) and heme-oxygenase (HO-1)], phase I oxidoreductase enzymes [NAD(P)H: quinone oxidoreductase (NQO1)] and phase II detoxifying enzyme [glutathione S-transferase (GST)].

Results

Nuclear translocation of Nrf2 by PB in WT cells was better after 10 h incubation compared to 12 h. Real time PCR and Western blot analysis showed increased expressions of Nrf2, NQO1 and GSTA1 genes with corresponding increases in glutathione, NQO1 and HO-1 proteins in WT cells. Reporter gene ARE was stimulated by PB as shown by ARE/luciferase assay. Interestingly, PB induced SOD1 gene and protein expressions in N0 cells but not in WT cells.

Conclusion

The results of this study confirmed that PB activated Nrf2-ARE signaling pathway which subsequently induced some phase I oxidoreductase, phase II detoxifying and antioxidant genes expression via ARE reporter gene involved in the Nrf2 pathway with the exception of SOD1 which may not be dependent on this pathway.

Sex differences in the acute nasal antioxidant/antielectrophilic response of the rat to inhaled naphthalene

Naphthalene is a nasal carcinogen, inducing respiratory adenomas in male and olfactory neuroblastomas in female rats, respectively. The reasons for the site and sex-specific tumorigenic response are unknown. Naphthalene is bioactivated to electrophilic metabolites; cytotoxicity followed by regenerative cell proliferation is likely involved in the tumorigenic response. To examine sex differences in the acute nasal response to naphthalene, male and female F344 rats were nose-only exposed to 0, 1, 3, 10, or 30 ppm naphthalene vapor for 4 or 6 h. Following exposure, respiratory/transitional mucosa (RTM) and olfactory mucosa (OM) were isolated and analyzed for markers of oxidant/electrophilic stress and/or toxicity, including reduced/oxidized glutathione levels (GSH/GSSG), mRNA levels of electrophile-responsive genes, and epithelial cytoxicity (as measured by membrane permeability to ethidium homodimer-1). Naphthalene caused significant depletion of GSH in RTM and OM with no increase in GSSG. Cytotoxicity was apparent at concentrations of 15 and 30 ppm. No consistent sex differences were observed in these responses. Sex differences were observed in the induction of antielectrophilic genes in OM: glutamyl cysteine ligase (catalytic subunit) (Gclc), NADPH quinone oxidase 1 (Nqo1), and heme oxygenase 1 (Hmox1) were all induced to a greater extent in the male OM compared with the female. No consistent sex differences were observed in the RTM. Although the mechanism of the sex difference in the RTM adenoma response remains enigmatic, sex differences in the induction of antioxidant/electrophile-responsive genes may contribute to the heightened sensitivity of the female OM to the carcinogenic effects of naphthalene.

Respiratory Viral Infections and Subversion of Cellular Antioxidant Defenses

Reactive oxygen species (ROS) formation is part of normal cellular aerobic metabolism, due to respiration and oxidation of nutrients in order to generate energy. Low levels of ROS are involved in cellular signaling and are well controlled by the cellular antioxidant defense system. Elevated levels of ROS generation due to pollutants, toxins and radiation exposure, as well as infections, are associated with oxidative stress causing cellular damage. Several respiratory viruses, including respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and influenza, induce increased ROS formation, both intracellularly and as a result of increased inflammatory cell recruitment at the site of infection. They also reduce antioxidant enzyme (AOE) levels and/or activity, leading to unbalanced oxidative-antioxidant status and subsequent oxidative cell damage. Expression of several AOE is controlled by the activation of the nuclear transcription factor NF-E2-related factor 2 (Nrf2), through binding to the antioxidant responsive element (ARE) present in the AOE gene promoters. While exposure to several pro-oxidant stimuli usually leads to Nrf2 activation and upregulation of AOE expression, respiratory viral infections are associated with inhibition of AOE expression/activity, which in the case of RSV and hMPV is associated with reduced Nrf2 nuclear localization, decreased cellular levels and reduced ARE-dependent gene transcription. Therefore, administration of antioxidant mimetics or Nrf2 inducers represents potential viable therapeutic approaches to viral-induced diseases, such as respiratory infections and other infections associated with decreased cellular antioxidant capacity.

Modulation of mitochondrial functions by the indirect antioxidant sulforaphane: a seemingly contradictory dual role and an integrative hypothesis

The chemotherapeutic isothiocyanate sulforaphane (SFN) was early linked to anticarcinogenic and antiproliferative activities. Soon after, this compound, derived from cruciferous vegetables, became an excellent and useful trial for anti-cancer research in experimental models including growth tumor, metastasis, and angiogenesis. Many subsequent reports showed modifications in mitochondrial signaling, functionality, and integrity induced by SFN. When cytoprotective effects were found in toxic and ischemic insult models, seemingly contradictory behaviors of SFN were discovered: SFN was inducing deleterious changes in cancer cell mitochondria that eventually would carry the cell to death via apoptosis and also was protecting noncancer cell mitochondria against oxidative challenge, which prevented cell death. In both cases, SFN exhibited effects on mitochondrial redox balance and phase II enzyme expression, mitochondrial membrane potential, expression of the family of B cell lymphoma 2 homologs, regulation of proapoptotic proteins released from mitochondria, activation/inactivation of caspases, mitochondrial respiratory complex activities, oxygen consumption and bioenergetics, mitochondrial permeability transition pore opening, and modulation of some kinase pathways. With the ultimate findings related to the induction of mitochondrial biogenesis by SFN, it could be considered that SFN has effects on mitochondrial dynamics that explain some divergent points. In this review, we list the reports involving effects on mitochondrial modulation by SFN in anti-cancer models as well as in cytoprotective models against oxidative damage. We also attempt to integrate the data into a mechanism explaining the various effects of SFN on mitochondrial function in only one concept, taking into account mitochondrial biogenesis and dynamics and making a comparison with the theory of reactive oxygen species threshold of cell death. Our interest is to achieve a complete view of cancer and protective therapies based on SFN that can be extended to other chemotherapeutic compounds with similar characteristics. The work needed to test this hypothesis is quite extensive.

Sequestosome1/p62: a regulator of redox-sensitive voltage-activated potassium channels, arterial remodeling, inflammation, and neurite outgrowth

Sequestosome1/p62 (SQSTM1) is an oxidative stress-inducible protein regulated by the redox-sensitive transcription factor Nrf2. It is not an antioxidant but known as a multifunctional regulator of cell signaling with an ability to modulate targeted or selective degradation of proteins through autophagy. SQSTM1 implements these functions through physical interactions with different types of proteins including atypical PKCs, nonreceptor-type tyrosine kinase p56(Lck) (Lck), polyubiquitin, and autophagosomal factor LC3. One of the notable physiological functions of SQSTM1 is the regulation of redox-sensitive voltage-gated potassium (Kv) channels which are composed of α and β subunits: (Kvα)4 (Kvβ)4. Previous studies have established that SQSTM1 scaffolds PKCζ, enhancing phosphorylation of Kvβ which induces inhibition of pulmonary arterial Kv1.5 channels under acute hypoxia. Recent studies reveal that Lck indirectly interacts with Kv1.3 α subunits and plays a key role in acute hypoxia-induced Kv1.3 channel inhibition in T lymphocytes. Kv1.3 channels provide a signaling platform to modulate the migration and proliferation of arterial smooth muscle cells and activation of T lymphocytes, and hence have been recognized as a therapeutic target for treatment of restenosis and autoimmune diseases. In this review, we focus on the functional interactions of SQSTM1 with Kv channels through two key partners aPKCs and Lck. Furthermore, we provide molecular insights into the functions of SQSTM1 in suppression of proliferation of arterial smooth muscle cells and neointimal hyperplasia following carotid artery ligation, in T lymphocyte differentiation and activation, and in NGF-induced neurite outgrowth in PC12 cells.

Oxidative stress and Nrf2 signaling in McArdle disease

McArdle disease (MD) is a metabolic myopathy due to myophosphorylase deficiency, which leads to a severe limitation in the rate of adenosine triphosphate (ATP) resynthesis. Compensatory flux through the myoadenylate deaminase > > xanthine oxidase pathway should result in higher oxidative stress in skeletal muscle; however, oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2) mediated antioxidant response cascade in MD patients have not yet been examined. We show that MD patients have elevated muscle protein carbonyls and 4-hydroxynonenal (4-HNE) in comparison with healthy, age and activity matched controls (P < 0.05). Nuclear abundance of Nrf2 and Nrf2-antioxidant response element (ARE) binding was also higher in MD patients compared with controls (P < 0.05). The expressions of Nrf2 target genes were also higher in MD patients vs. controls. These observations suggest that MD patients experience elevated levels of oxidative stress, and that the Nrf2-mediated antioxidant response cascade is up-regulated in skeletal muscle to compensate.

Early life permethrin treatment leads to long-term cardiotoxicity

Environmental, nutritional or hormonal influences in early life may have long-term effects changing homeostatic processes and physiological parameters in adulthood. NF-kB and Nrf2, two of the main transcription factors regulating genes involved in pro-inflammatory and antioxidant responses respectively, can be modified by various stimuli. NF-kB controls immediate early genes and is required for cardiomyocyte hypertrophic growth, while Nrf2 protects the heart from oxidative stress-induced cardiovascular complications. The aim of this study was to investigate the impact of early life permethrin treatment (1/50 of LD50, from 6th to 21st day of life) on the development of cardiotoxicity in 500-day-old rats. Nrf2 and NF-kB gene expression, calcium level and heart surface area were chosen as biomarkers of toxicity. Six candidate reference genes were first examined and GAPDH resulted the most stable one for RT-qPCR. The comparative expression analysis of the target genes showed 1.62-fold increase in Nrf2 mRNA level, while the NF-kB mRNA in treated rats was not significantly changed compared to control ones. A significant decrease in heart surface area was observed in treated rats (296.59 ± 8.09, mm(2)) with respect to the control group (320.86 ± 4.93, mm(2)). Finally, the intracellular calcium influx in heart of early life treated rats increased 4.33-fold compared to the control one. In conclusion, early life pesticide exposure to low doses of permethrin insecticide, has long-term consequences leading to cardiac hypotrophy, increased calcium and Nrf2 gene expression levels in old age.

Modulation of stress related protein genes in the bass (Epinephelus guaza) caught from the Gulf of Suez, the Red Sea, Egypt

Impact of chemical pollution on expression of stress protein genes in the bass Epinephelus guaga collected from several locations including Suez Oil Production Port (Floating port), Atakah Fishing Port, Adabiya Port and Tawfik Port in Suez Governorate, Egypt, was investigated. In the current study, levels of polycyclic aromatic hydrocarbons (PAHs) in water and fish samples collected from Suez Gulf were assessed. In addition, gills and liver tissues of caught bass fish were used to address the interaction between pollution status and the expression of stress-related genes (Hsp70a, Hsp70b, Hsp47, MT and CYP1A). Our analysis demonstrated that levels of PAHs in Floating and Tawfik ports were higher than those found in the Atakah Fishing Port and the Adabiya Port. In addition, MDA and PC contents were significantly higher in gills and liver tissues collected from Floating and Tawfik ports than those collected from Adabiya and Atakah ports. In correlation to the above results, all fish collected from the Floating and Tawfik ports presented a significant increase in Hsp-, MT- and CYP1A-mRNAs. On the other hand, fish samples collected from the Atakah Fishing and Adabiya ports showed no induction of the stress-related genes transcription in such tissues. In conclusion, the current research demonstrates that remarkable increase in PAH contaminants levels in Floating and Tawfik ports are correlated with the levels stress protein-related genes transcription in E. guaga gills and liver tissues.

α-Linolenic acid attenuates doxorubicin-induced cardiotoxicity in rats through suppression of oxidative stress and apoptosis

Doxorubicin (DOX), a widely used anti-tumor drug, can give rise to severe cardiotoxicity by oxidative stress and cell apoptosis, which restricts its clinical application. α-Linolenic acid (ALA) has been shown to serve as a potent cardioprotective agent. The aim of this study was to explore the protective effects of ALA on DOX-induced cardiotoxicity and the underlying molecular mechanisms for this cardioprotection in rats. Rats were randomly divided into four groups and administrated with normal saline, ALA (500 µg/kg), DOX (2.5 mg/kg), or ALA (500 µg/kg) plus DOX (2.5 mg/kg) for 17 days. The results showed that DOX treatment significantly increased the heart weight/body weight, liver wet weight (WW)/dry weight (DW), lung WW/DW, serum levels of brain natriuretic peptide, creatine kinase-MB, lactate dehydrogenase, and cardiac troponin I, myocardial necrosis and myocardial malondialdehyde content, and induced the mRNA expression of Nrf2 in the nucleus, cleaved caspase-3, Bax, and superoxide dismutase (SOD). In addition, DOX led to a significant decrease in left ventricular end-diastolic volume, stroke volume, ejection fraction, SOD, glutathione-peroxidase, catalase, as well as the expression of Kelch-like ECH-associated protein 1 (Keap1) in the cytoplasm, phospho-AKT, phospho-ERK, and Bcl-2. Co-treatment with ALA significantly eliminated these changes induced by DOX except further reduction of Keap1 and elevation of Nrf2 and SOD mRNA. These results showed the cardioprotective effects of ALA on DOX-induced cardiotoxicity in rats. The mechanisms might be associated with the enhancement of antioxidant defense system through activating Keap1/Nrf2 pathway and anti-apoptosis through activating protein kinase B/extracellular signal regulated kinase pathway. Our results suggested a promising future of ALA-based preventions and therapies for myocardial damage after administration of DOX.

Mechanisms of Nrf2 protection in astrocytes as identified by quantitative proteomics and siRNA screening

The Nrf2 (NF-E2 related factor 2)-ARE (antioxidant response element) pathway controls a powerful array of endogenous cellular antioxidant systems and is an important pathway in the detoxification of reactive oxygen species (ROS) in the brain. Using a combination of quantitative proteomics and siRNA screening, we have identified novel protective mechanisms of the Nrf2-ARE pathway against oxidative stress in astrocytes. Studies from our lab and others have shown Nrf2 overexpression protects astrocytes from oxidative stress. However, the exact mechanisms by which Nrf2 elicits these effects are unknown. In this study, we show that induction of Nrf2 reduces levels of reactive oxygen species (ROS) produced by various oxidative stressors and results in robust cytoprotection. To identify the enzymes responsible for these effects, we used stable isotope labeling by amino acids in cell culture (SILAC) and quantitative shotgun proteomics to identify 72 Nrf2-regulated proteins in astrocytes. We hypothesized a subset of these proteins might play a critical role in Nrf2 protection. In order to identify these critical proteins, we used bioinformatics to narrow our target list of proteins and then systematically screened each candidate with siRNA to assess the role of each in Nrf2 protection. We screened each target against H2O2, tert-butyl hydroperoxide, and 4-hydroxynonenal and subsequently identified three enzymes-catalase, prostaglandin reductase-1, and peroxiredoxin-6-that are critical for Nrf2-mediated protection in astrocytes.

Oxidative stress induced by HIV-1 reverse transcriptase modulates the enzyme's performance in gene immunization

HIV-1 infection induces chronic oxidative stress. The resultant neurotoxicity has been associated with Tat protein. Here, we for the first time describe the induction of oxidative stress by another HIV-1 protein, reverse transcriptase (RT). Expression of HIV-1 RT in human embryonic kidney cells generated potent production of the reactive oxygen species (ROS), detected by the fluorescence-based probes. Quantitative RT-PCR demonstrated that expression of RT in HEK293 cells induced a 10- to 15-fold increased transcription of the phase II detoxifying enzymes human

NAD(P)H

quinone oxidoreductase (Nqo1) and heme oxygenase 1 (HO-1), indicating the induction of oxidative stress response. The capacity to induce oxidative stress and stress response appeared to be an intrinsic property of a vast variety of RTs: enzymatically active and inactivated, bearing mutations of drug resistance, following different routes of processing and presentation, expressed from viral or synthetic expression-optimized genes. The total ROS production induced by RT genes of the viral origin was found to be lower than that induced by the synthetic/expression-optimized or chimeric RT genes. However, the viral RT genes induced higher levels of ROS production and higher levels of HO-1 mRNA than the synthetic genes per unit of protein in the expressing cell. The capacity of RT genes to induce the oxidative stress and stress response was then correlated with their immunogenic performance. For this, RT genes were administered into BALB/c mice by intradermal injections followed by electroporation. Splenocytes of immunized mice were stimulated with the RT-derived and control antigens and antigen-specific proliferation was assessed by IFN-γ/IL-2 Fluorospot. RT variants generating high total ROS levels induced significantly stronger IFN-γ responses than the variants inducing lower total ROS, while high levels of ROS normalized per unit of protein in expressing cell were associated with a weak IFN-γ response. Poor gene immunogenicity was also associated with a high (per unit of protein) transcription of antioxidant response element (ARE) dependent phase II detoxifying enzyme genes, specifically HO-1. Thus, we have revealed a direct link between the propensity of the microbial proteins to induce oxidative stress and their immunogenicity.

Coenzyme Q10 depletion in medical and neuropsychiatric disorders: potential repercussions and therapeutic implications

Coenzyme Q10 (CoQ10) is an antioxidant, a membrane stabilizer, and a vital cofactor in the mitochondrial electron transport chain, enabling the generation of adenosine triphosphate. It additionally regulates gene expression and apoptosis; is an essential cofactor of uncoupling proteins; and has anti-inflammatory, redox modulatory, and neuroprotective effects. This paper reviews the known physiological role of CoQ10 in cellular metabolism, cell death, differentiation and gene regulation, and examines the potential repercussions of CoQ10 depletion including its role in illnesses such as Parkinson's disease, depression, myalgic encephalomyelitis/chronic fatigue syndrome, and fibromyalgia. CoQ10 depletion may play a role in the pathophysiology of these disorders by modulating cellular processes including hydrogen peroxide formation, gene regulation, cytoprotection, bioenegetic performance, and regulation of cellular metabolism. CoQ10 treatment improves quality of life in patients with Parkinson's disease and may play a role in delaying the progression of that disorder. Administration of CoQ10 has antidepressive effects. CoQ10 treatment significantly reduces fatigue and improves ergonomic performance during exercise and thus may have potential in alleviating the exercise intolerance and exhaustion displayed by people with myalgic encepholamyletis/chronic fatigue syndrome. Administration of CoQ10 improves hyperalgesia and quality of life in patients with fibromyalgia. The evidence base for the effectiveness of treatment with CoQ10 may be explained via its ability to ameliorate oxidative stress and protect mitochondria.

Central role of liver in anticancer and radioprotective activities of Toll-like receptor 5 agonist

Vertebrate Toll-like receptor 5 (TLR5) recognizes bacterial flagellin proteins and activates innate immune responses to motile bacteria. In addition, activation of TLR5 signaling can inhibit growth of TLR5-expressing tumors and protect normal tissues from radiation and ischemia-reperfusion injuries. To understand the mechanisms behind these phenomena at the organismal level, we assessed nuclear factor kappa B (NF-κB) activation (indicative of TLR5 signaling) in tissues and cells of mice treated with CBLB502, a pharmacologically optimized flagellin derivative. This identified the liver and gastrointestinal tract as primary CBLB502 target organs. In particular, liver hepatocytes were the main cell type directly and specifically responding to systemic administration of CBLB502 but not to that of the TLR4 agonist LPS. To assess CBLB502 impact on other pathways, we created multireporter mice with hepatocytes transduced in vivo with reporters for 46 inducible transcription factor families and found that along with NF-κB, CBLB502 strongly activated STAT3-, phenobarbital-responsive enhancer module (PREM), and activator protein 1 (AP-1-) -driven pathways. Livers of CBLB502-treated mice displayed induction of numerous immunomodulatory factors and massive recruitment of various types of immune cells. This led to inhibition of growth of liver metastases of multiple tumors regardless of their TLR5 status. The changed liver microenvironment was not, however, hepatotoxic, because CBLB502 induced resistance to Fas-mediated apoptosis in normal liver cells. Temporary occlusion of liver blood circulation prevented CBLB502 from protecting hematopoietic progenitors in lethally irradiated mice, indicating involvement of a factor secreted by responding liver cells. These results define the liver as the key mediator of TLR5-dependent effects in vivo and suggest clinical applications for TLR5 agonists as hepatoprotective and antimetastatic agents.

Cell-cycle changes and oxidative stress response to magnetite in A549 human lung cells

In a recent study, magnetite was investigated for its potential to induce toxic effects and influence signaling pathways. It was clearly demonstrated that ROS formation leads to mitochondrial damage and genotoxic effects in A549 cells. On the basis of these findings, we wanted to elucidate the origin of magnetite-mediated ROS formation and its influence on the cell cycle of A549 and H1299 human lung epithelial cells. Concentration- and size-dependent superoxide formation, measured by electron paramagnetic resonance (EPR), was observed. Furthermore, we could show that the GSH level decreased significantly after exposure to magnetite particles, while catalase (CAT) activity was increased. These effects were also dependent on particle size, albeit less pronounced than those observed with EPR. We were able to show that incubation of A549 cells prior to particle treatment with diphenyleneiodonium (DPI), a NADPH-oxidase (NOX) inhibitor, leads to decreased ROS formation, but this effect was not observed for the NOX inhibitor apocynin. Soluble iron does not contribute considerably to ROS production. Analysis of cell-cycle distribution revealed a pronounced sub-G1 peak, which cannot be linked to increased cell death. Western blot analysis did not show activation of p53 but upregulation of p21 in A549. Here, we were unexpectedly able to demonstrate that exposure to magnetite leads to p21-mediated G1-like arrest. This has been reported previously only for low concentrations of microtubule stabilization drugs. Importantly, the arrested sub-G1 cells were viable and showed no caspase 3/7 activation.

Black soybean seed coat polyphenols prevent B(a)P-induced DNA damage through modulating drug-metabolizing enzymes in HepG2 cells and ICR mice

Black soybean seed coat is a rich source of polyphenols that have been reported to have various physiological functions. The present study investigated the potential protective effects of polyphenolic extracts from black soybean seed coat on DNA damage in human hepatoma HepG2 cells and ICR mice. The results from micronucleus (MN) assay revealed that black soybean seed coat extract (BE) at concentrations up to 25μg/mL was non-genotoxic. It is noteworthy that BE (at 4.85μg/mL) and its main components, procyanidins (PCs) and cyanidin 3-glucoside (C3G), at 10μM significantly reduced the genotoxic effect induced by benzo[a]pyrene [B(a)P]. To obtain insights into the underlying mechanism, we investigated BE and its main components on drug-metabolizing enzyme expression. The results of this study demonstrate that BE and its main components, PCs and C3G, down-regulated B(a)P-induced cytochrome P4501A1 (CYP1A1) expression by inhibiting the transformation of aryl hydrocarbon receptor. Moreover, they increased expression of detoxifying defense enzymes, glutathione S-transferases (GSTs) via increasing the binding of nuclear factor-erythroid-2-related factor 2 to antioxidant response elements. Collectively, we found that PCs and C3G, which are the main active compounds of BE, down-regulated CYP1A1 and up-regulated GST expression to protect B(a)P-induced DNA damage in HepG2 cells and ICR mice effectively.

Mammary gene expression and activity of antioxidant enzymes and oxidative indicators in the blood, milk, mammary tissue and ruminal fluid of dairy cows fed flax meal

The effects of flax meal (FM) on the activity of antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)) in the blood, mammary tissue and ruminal fluid, and oxidative stress indicators (thiobarbituric acid-reactive substances(TBARS) and 1,1-diphenyl-2-picrylhydrazyl-scavenging activity) in the milk, plasma and ruminal fluid of dairy cows were determined.The mRNA abundance of the antioxidant enzymes and oxidative stress-related genes was assessed in mammary tissue. A total of eight Holstein cows were used in a double 4 x 4 Latin square design. There were four treatments in the diet: control with no FM(CON) or 5% FM (5FM), 10% FM (10FM) and 15% FM (15FM). There was an interaction between treatment and time for plasma GPx and CAT activities. Cows supplemented with FM had a linear reduction in TBARS at 2 h after feeding, and there was no treatment effect at 0, 4 and 6 h after feeding. TBARS production decreased in the milk of cows fed the 5FM and 10FM diets. There was a linear increase in nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) mRNA abundance in mammary tissue with FM supplementation.A linear trend for increased mRNA abundance of the CAT gene was observed with higher concentrations of FM. The mRNA abundance of CAT, GPx1, GPx3, SOD1, SOD2, SOD3 and nuclear factor of k light polypeptide gene enhancer in B-cells (NFKB) genes was not affected by the treatment. These findings suggest that FM supplementation can improve the oxidative status of Holstein cows as suggested by decreased TBARS production in ruminal fluid 2 h post-feeding and increased NFE2L2/nuclear factor-E2-related factor 2 (Nrf2) mRNA abundance in mammary tissue.

Hydrogen sulfide preconditions the db/db diabetic mouse heart against ischemia-reperfusion injury by activating Nrf2 signaling in an Erk-dependent manner

Hydrogen sulfide (H2S) therapy protects nondiabetic animals in various models of myocardial injury, including acute myocardial infarction and heart failure. Here, we sought to examine whether H2S therapy provides cardioprotection in the setting of type 2 diabetes. H2S therapy in the form of sodium sulfide (Na2S) beginning 24 h or 7 days before myocardial ischemia significantly decreased myocardial injury in db/db diabetic mice (12 wk of age). In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, we focused on the role of nuclear factor E2-related factor (Nrf2) signaling. Our results indicate that diabetes does not alter the ability of H2S to increase the nuclear localization of Nrf2, but does impair aspects of Nrf2 signaling. Specifically, the expression of NADPH quinine oxidoreductase 1 was increased after the acute treatment, whereas the expression of heme-oxygenase-1 (HO-1) was only increased after 7 days of treatment. This discrepancy was found to be the result of an increased nuclear expression of Bach1, a known repressor of HO-1 transcription, which blocked the binding of Nrf2 to the HO-1 promoter. Further analysis revealed that 7 days of Na2S treatment overcame this impairment by removing Bach1 from the nucleus in an Erk1/2-dependent manner. Our findings demonstrate for the first time that exogenous administration of Na2S attenuates myocardial ischemia-reperfusion injury in db/db mice, suggesting the potential therapeutic effects of H2S in treating a heart attack in the setting of type 2 diabetes.

Potential therapeutic effects of natural heme oxygenase-1 inducers in cardiovascular diseases

SIGNIFICANCE

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of α-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenols may increase the capacity of endogenous antioxidant defenses and modulate the cellular redox state. Such effects may have wide-ranging consequences for cellular growth and differentiation.

CRITICAL ISSUES

The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. One possible protective molecular mechanism of polyphenols is nuclear factor erythroid 2-related factor (Nrf2) activation, which in turn regulates a number of detoxification enzymes.

RECENT ADVANCES

Among the latter, the heme oxygenase-1 (HO-1) pathway is likely to contribute to the established and powerful antioxidant/anti-inflammatory properties of polyphenols. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to prevention of cardiovascular diseases in various experimental models.

FUTURE DIRECTIONS

The focus of this review is on the role of natural HO-1 inducers as a potential therapeutic strategy to protect the cardiovascular system against various stressors in several pathological conditions.

Diallyl trisulfide and diallyl disulfide ameliorate cardiac dysfunction by suppressing apoptotic and enhancing survival pathways in experimental diabetic rats

Cardiovascular disease is one of the major causes of mortality in diabetic patients. Mounting studies have shown that garlic exhibits, possibly through its antioxidant potential, diverse biological activities. In this study, we investigated the alleviating effects of garlic oil (GO) and its two major components, diallyl disulfide (DADS) and diallyl trisulfide (DATS), on diabetic cardiomyopathy in rats. Physiological cardiac parameters were obtained using echocardiography. Apoptotic cells were evaluated using TUNEL and DAPI staining. Protein expression levels were determined using Western blotting analysis. Our findings indicated that in diabetic rat hearts significantly decreased fractional shortening percentage, increased levels of nitrotyrosine, an elevated number of TUNEL-positive cells, enhanced levels of caspase 3 expression, and decreased PI3K-Akt signaling pathway activities were observed. Furthermore, all of these alterations were reversed following both GO and DATS (or DADS) administrations through increasing PI3K-Akt signaling pathway activities and inhibiting both the death receptor-dependent and the mitochondria-dependent apoptotic pathways. In conclusion, this study shows that DATS and DADS, with the efficacy order DATS > DADS, have the therapeutic potential for ameliorating diabetic cardiomyopathy. Furthermore, the therapeutic effects of GO on diabetic cardiomyopathy should be mainly from DATS and DADS.

Human neuronal coenzyme Q10 deficiency results in global loss of mitochondrial respiratory chain activity, increased mitochondrial oxidative stress and reversal of ATP synthase activity: implications for pathogenesis and treatment

Disorders of coenzyme Q(10) (CoQ(10)) biosynthesis represent the most treatable subgroup of mitochondrial diseases. Neurological involvement is frequently observed in CoQ(10) deficiency, typically presenting as cerebellar ataxia and/or seizures. The aetiology of the neurological presentation of CoQ(10) deficiency has yet to be fully elucidated and therefore in order to investigate these phenomena we have established a neuronal cell model of CoQ(10) deficiency by treatment of neuronal SH-SY5Y cell line with para-aminobenzoic acid (PABA). PABA is a competitive inhibitor of the CoQ(10) biosynthetic pathway enzyme, COQ2. PABA treatment (1 mM) resulted in a 54 % decrease (46 % residual CoQ(10)) decrease in neuronal CoQ(10) status (p < 0.01). Reduction of neuronal CoQ(10) status was accompanied by a progressive decrease in mitochondrial respiratory chain enzyme activities, with a 67.5 % decrease in cellular ATP production at 46 % residual CoQ(10). Mitochondrial oxidative stress increased four-fold at 77 % and 46 % residual CoQ(10). A 40 % increase in mitochondrial membrane potential was detected at 46 % residual CoQ(10) with depolarisation following oligomycin treatment suggesting a reversal of complex V activity. This neuronal cell model provides insights into the effects of CoQ(10) deficiency on neuronal mitochondrial function and oxidative stress, and will be an important tool to evaluate candidate therapies for neurological conditions associated with CoQ(10) deficiency.

Cardioprotective effect of paeonol and danshensu combination on isoproterenol-induced myocardial injury in rats

Background

Traditional Chinese medicinal herbs Cortex Moutan and Radix Salviae Milthiorrhizaeare are prescribed together for their putative cardioprotective effects in clinical practice. However, the rationale of the combined use remains unclear. The present study was designed to investigate the cardioprotective effects of paeonol and danshensu (representative active ingredient of Cortex Moutan and Radix Salviae Milthiorrhizae, respectively) on isoproterenol-induced myocardial infarction in rats and its underlying mechanisms.

Methodology

Paeonol (80 mg kg⁻¹) and danshensu (160 mg kg⁻¹) were administered orally to Sprague Dawley rats in individual or in combination for 21 days. At the end of this period, rats were administered isoproterenol (85 mg kg⁻¹) subcutaneously to induce myocardial injury. After induction, rats were anaesthetized with pentobarbital sodium (35 mg kg⁻¹) to record electrocardiogram, then sacrificed and biochemical assays of the heart tissues were performed.

Principal Findings

Induction of rats with isoproterenol resulted in a marked (P<0.001) elevation in ST-segment, infarct size, level of serum marker enzymes (CK-MB, LDH, AST and ALT), cTnI, TBARS, protein expression of Bax and Caspase-3 and a significant decrease in the activities of endogenous antioxidants (SOD, CAT, GPx, GR, and GST) and protein expression of Bcl-2. Pretreatment with paeonol and danshensu combination showed a significant (P<0.001) decrease in ST-segment elevation, infarct size, cTnI, TBARS, protein expression of Bax and Caspase-3 and a significant increase in the activities of endogenous antioxidants and protein expression of Bcl-2 and Nrf2 when compared with individual treated groups.

Conclusions/Significance

This study demonstrates the cardioprotective effect of paeonol and danshensu combination on isoproterenol-induced myocardial infarction in rats. The mechanism might be associated with the enhancement of antioxidant defense system through activating of Nrf2 signaling and anti-apoptosis through regulating Bax, Bcl-2 and Caspase-3. It could provide experimental evidence to support the rationality of combinatorial use of traditional Chinese medicine in clinical practice.

Proteome alterations induced in human white blood cells by consumption of Brussels sprouts: Results of a pilot intervention study

Epidemiological studies indicate a correlation of cruciferous vegetables consumption with reduced incidence of cancer. This study was designed to investigate molecular mechanisms, which may help to understand the beneficial effects of Brussels sprout consumption. In order to avoid the limitations of in vitro model systems, we performed a dietary intervention study with five participants. We investigated, whether sprout consumption affects the proteome profile of primary white blood cells. In order to achieve maximal sensitivity in detecting specific adaptive proteome alterations, we metabolically labelled freshly isolated cells in the presence of (35) S-methionine/cysteine and performed autoradiographic quantification of protein synthesis. Proteins were separated by 2-DE and spots of interest were cut out, digested and identified by MS. After the intervention, we found a significant up-regulation of the synthesis of manganese superoxide dismutase (1.56-fold) and significant down-regulation of the synthesis of heat shock 70 kDa protein (hsp70; 2.27-fold). Both proteins play a role in malignant transformation of cells. Hsp-70 is involved in the regulation of apoptosis, which leads to elimination of cancer cells, while SOD plays a key role in protection against reactive oxygen species mediated effects. Our findings indicate that the alteration of the synthesis of these proteins may be involved in the anticarcinogenic effects of cruciferous vegetables, which was observed in earlier laboratory studies with animals.

Impaired transcriptional activity of Nrf2 in age-related myocardial oxidative stress is reversible by moderate exercise training

Aging promotes accumulation of reactive oxygen/nitrogen species (ROS/RNS) in cardiomyocytes, which leads to contractile dysfunction and cardiac abnormalities. These changes may contribute to increased cardiovascular disease in the elderly. Inducible antioxidant pathways are regulated by nuclear erythroid 2 p45-related factor 2 (Nrf2) through antioxidant response cis-elements (AREs) and are impaired in the aging heart. Whereas acute exercise stress (AES) activates Nrf2 signaling and promotes myocardial antioxidant function in young mice (∼2 months), aging mouse (>23 months) hearts exhibit significant oxidative stress as compared to those of the young. The purpose of this study was to investigate age-dependent regulation of Nrf2-antioxidant mechanisms and redox homeostasis in mouse hearts and the impact of exercise. Old mice were highly susceptible to oxidative stress following high endurance exercise stress (EES), but demonstrated increased adaptive redox homeostasis after moderate exercise training (MET; 10m/min, for 45 min/day) for ∼6 weeks. Following EES, transcription and protein levels for most of the ARE-antioxidants were increased in young mice but their induction was blunted in aging mice. In contrast, 6-weeks of chronic MET promoted nuclear levels of Nrf2 along with its target antioxidants in the aging heart to near normal levels as seen in young mice. These observations suggest that enhancing Nrf2 function and endogenous cytoprotective mechanisms by MET, may combat age-induced ROS/RNS and protect the myocardium from oxidative stress diseases.

Hydrogen sulfide in the pathogenesis of atherosclerosis and its therapeutic potential

Hydrogen sulfide (H(2)S) was the third gaseous transmitter to be discovered, along with nitric oxide and carbon monoxide, and has been proposed to be involved in numerous physiological processes and pathology of various diseases. Hyperhomocysteinemia is an independent risk factor for cardiovascular disease, including atherosclerosis. Atherosclerosis is characterized by multiple key events including endothelial dysfunction, monocyte infiltration and their differentiation into macrophages, conversion of lesion-resident macrophages into foam cells, and smooth muscle cell proliferation. Increasing evidence has indicated that H(2)S plays a potentially significant role in all of these biological processes and that malfunction of H(2)S homeostasis may contribute to the pathogenesis of atherosclerosis. Experiments have demonstrated that H(2)S supplementation ameliorated many of these atherogenic processes and hence, such supplementation potentially may prove to be of therapeutic benefit in the prevention or treatment of atherosclerosis. H(2)S levels may be induced by the administration of H(2)S or H(2)S donors, or alternatively be reduced by the administration of specific cystathionine β-synthase or cystathionine γ-lyase inhibitors. However, issues remain with the potential use of currently available H(2)S-modulating agents in a clinical setting. This review will provide a description of the current literature on the involvement of H(2)S in these key aspects of vascular biology that contribute to the development of atherosclerosis, as well as the therapeutic potential of currently available H(2)S-modulating agents.

Isolation, identification, and biological evaluation of Nrf2-ARE activator from the leaves of green perilla (Perilla frutescens var. crispa f. viridis)

The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is a cellular defense system against oxidative stress. Activation of this pathway increases expression of antioxidant enzymes. Epidemiological studies have demonstrated that the consumption of fruits and vegetables is associated with reduced risk of contracting a variety of human diseases. The aim of this study is to find Nrf2-ARE activators in dietary fruits and vegetables. We first attempted to compare the potency of ARE activation in six fruit and six vegetables extracts. Green perilla (Perilla frutescens var. crispa f. viridis) extract exhibited high ARE activity. We isolated the active fraction from green perilla extract through bioactivity-guided fractionation. Based on nuclear magnetic resonance and mass spectrometric analysis, the active ingredient responsible for the ARE activity was identified as 2',3'-dihydroxy-4',6'-dimethoxychalcone (DDC). DDC induced the expression of antioxidant enzymes, such as γ-glutamylcysteine synthetase (γ-GCS), NAD(P)H: quinone oxidoreductase-1 (NQO1), and heme oxygenase-1. DDC inhibited the formation of intracellular reactive oxygen species and the cytotoxicity induced by 6-hydroxydopamine. Inhibition of the p38 mitogen-activated protein kinase pathway abolished ARE activation, the induction of γ-GCS and NQO1, and the cytoprotective effect brought about by DDC. Thus, this study demonstrated that DDC contained in green perilla enhanced cellular resistance to oxidative damage through activation of the Nrf2-ARE pathway.

Melatonin inhibits type 1 interferon signaling of toll-like receptor 4 via heme oxygenase-1 induction in hepatic ischemia/reperfusion

The cytoprotective mechanisms of melatonin in hepatic ischemia/reperfusion (I/R) injury associated with heme oxygenase-1 (HO-1) induction and type 1 interferon (IFN) signaling pathway downstream of toll-like receptor 4 (TLR4) were investigated. Rats were subjected to 60min of ischemia followed by 5-hr reperfusion. Melatonin (10mg/kg) or vehicle (5% ethanol in saline) was administered intraperitoneally 15min prior to ischemia and immediately before reperfusion. Rats were pretreated with zinc protoporphyrin (ZnPP, 10mg/kg, i.p.), a HO-1 inhibitor, at 16 and 3hr prior to ischemia. Melatonin attenuated the I/R-induced increase in serum alanine aminotransferase activity, and ZnPP reversed this attenuation. Melatonin augmented the levels of HO activity and HO-1 protein and mRNA expression, and this enhancement was reversed by ZnPP. Melatonin enhanced the level of NF-E2-related factor-2 (Nrf2) nuclear translocation, and ZnPP reversed this increase. Overexpression of TLR4 and its adaptor proteins, toll-receptor-associated activator of interferon (TRIF), and myeloid differentiation factor 88 (MyD88), induced by I/R, was attenuated by melatonin; ZnPP reversed the effect of melatonin on TLR4 and TRIF expression. Melatonin suppressed the increased interaction between TLR4/TRIF and TLR4/MyD88, which was reversed by ZnPP. Melatonin attenuated the increased levels of JAK2 and STAT1 activation as well as IFN-β, and ZnPP reversed these inhibitory effects of melatonin. Melatonin inhibited the level of chemokine (C-X-C motif) ligand 10 (CXCL-10), and ZnPP reversed this inhibition. Our findings suggest that melatonin protects the liver against I/R injury by HO-1 overexpression, which suppresses the type 1 IFN signaling pathway downstream of TLR4.

NRF2 and the Phase II Response in Acute Stress Resistance Induced by Dietary Restriction

Dietary restriction (DR) as a means to increase longevity is well-established in a number of model organisms from yeast to primates. DR also improves metabolic fitness and increases resistance to acute oxidative, carcinogenic and toxicological stressors - benefits with more immediate potential for clinical translation than increased lifespan. While the detailed mechanism of DR action remains unclear, a conceptual framework involving an adaptive, or hormetic response to the stress of nutrient/energy deprivation has been proposed. A key prediction of the hormesis hypothesis of DR is that beneficial adaptations occur in response to an increase in reactive oxygen/nitrogen species (ROS). These ROS may be derived either from increased mitochondrial respiration or increased xenobiotic metabolism in the case of some DR mimetics. This review will focus on the potential role of the redox-sensing transcription factor NF-E2-related factor 2 (NRF2) and its control of the evolutionarily conserved antioxidant/redox cycling and detoxification systems, collectively known as the Phase II response, in the adaptive response to DR.

Oxidative Stress and Mitochondrial Dysfunction in Down's Syndrome: Relevance to Aging and Dementia

Genome-wide gene deregulation and oxidative stress appear to be critical factors determining the high variability of phenotypes in Down's syndrome (DS). Even though individuals with trisomy 21 exhibit a higher survival rate compared to other aneuploidies, most of them die in utero or early during postnatal life. While the survivors are currently predicted to live past 60 years, they suffer higher incidence of age-related conditions including Alzheimer's disease (AD). This paper is centered on the mechanisms by which mitochondrial factors and oxidative stress may orchestrate an adaptive response directed to maintain basic cellular functions and survival in DS. In this context, the timing of therapeutic interventions should be carefully considered for the successful treatment of chronic disorders in the DS population.

Protective effect of melatonin on acute pancreatitis

Melatonin, a product of the pineal gland, is released from the gut mucosa in response to food ingestion. Specific receptors for melatonin have been detected in many gastrointestinal tissues including the pancreas. Melatonin as well as its precursor, L-tryptophan, attenuates the severity of acute pancreatitis and protects the pancreatic tissue from the damage caused by acute inflammation. The beneficial effect of melatonin on acute pancreatitis, which has been reported in many experimental studies and supported by clinical observations, is related to: (1) enhancement of antioxidant defense of the pancreatic tissue, through direct scavenging of toxic radical oxygen (ROS) and nitrogen (RNS) species, (2) preservation of the activity of antioxidant enzymes; such as superoxide dismutase (SOD), catalase (CAT), or glutathione peroxidase (GPx), (3) the decline of pro-inflammatory cytokine tumor necrosis α (TNFα) production, accompanied by stimulation of an anti-inflammatory IL-10, (4) improvement of pancreatic blood flow and decrease of neutrophil infiltration, (5) reduction of apoptosis and necrosis in the inflamed pancreatic tissue, (6) increased production of chaperon protein (HSP60), and (7) promotion of regenerative process in the pancreas. Conclusion. Endogenous melatonin produced from L-tryptophan could be one of the native mechanisms protecting the pancreas from acute damage and accelerating regeneration of this gland. The beneficial effects of melatonin shown in experimental studies suggest that melatonin ought to be employed in the clinical trials as a supportive therapy in acute pancreatitis and could be used in people at high risk for acute pancreatitis to prevent the development of pancreatic inflammation.

Starvation, detoxification, and multidrug resistance in cancer therapy

The selection of chemotherapy drugs is based on the cytotoxicity to specific tumor cell types and the relatively low toxicity to normal cells and tissues. However, the toxicity to normal cells poses a major clinical challenge, particularly when malignant cells have acquired resistance to chemotherapy. This drug resistance of cancer cells results from multiple factors including individual variation, genetic heterogeneity within a tumor, and cellular evolution. Much progress in the understanding of tumor cell resistance has been made in the past 35 years, owing to milestone discoveries such as the identification and characterization of ABC transporters. Nonetheless, the complexity of the genetic and epigenetic rewiring of cancer cells makes drug resistance an equally complex phenomenon that is difficult to overcome. In this review, we discuss how the remarkable changes in the levels of glucose, IGF-I, IGFBP-1 and in other proteins caused by fasting have the potential to improve the efficacy of chemotherapy against tumors by protecting normal cells and tissues and possibly by diminishing multidrug resistance in malignant cells.

Redox-regulating role of insulin: the essence of insulin effect

It is well-known that insulin acts as an important hormone, controlling energy metabolism, cellular proliferation and biosynthesis of functional molecules to maintain a biological homeostasis. Over the past few years, intensive insulin therapy has been believed to be benefit for the outcome of diabetic patients, in which the suppression of oxidative stress plays a role. Moreover, insulin is accepted as a key component of glucose-insulin-potassium, a treatment which has been believed to exert significant cardiovascular protective effect via the reduction of oxidative stress. Furthermore, accumulating evidence has suggested that insulin exerts important redox-regulating actions in various insulin-sensitive target organs, implying the systematic antioxidative role of insulin as a hormone. It is time for us to revisit insulin effects, through summarizing and evaluating the novel functions of insulin and their mechanisms. This review focuses on the antioxidative effect of insulin and highlights insulin-induced regulation of various antioxidant enzymes via insulin signaling pathways and the cross talk between key transcription factors, including nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor κB (NF-κB) which are responsible for the transcription of antioxidant enzymes, leading to reduced generation of reactive oxygen species (ROS) and the enhancement of the elimination of ROS.

Exogenous melatonin modulates apoptosis in the mouse brain induced by high-LET carbon ion irradiation

The aim of this study was to investigate whether melatonin, a free radical scavenger and a general antioxidant, regulates the brain cell apoptosis caused by carbon ions in mice at the level of signal transduction pathway. Young Kun-Ming mice were divided into five groups: control group, irradiation group and three melatonin (1, 5, and 10 mg/kg daily for 5 days i.p.) plus irradiation-treated groups. An acute study was carried out to determine oxidative status, apoptotic cells, and mitochondrial membrane potential (ΔΨm) as well as pro- and anti-apoptotic protein levels in a mouse brain 12 hr after irradiation with a single dose of 4 Gy. In irradiated mice, a significant rise in oxidative stress and apoptosis (TUNEL positive) was accompanied by activated expression of Bax, cytochrome c, caspase-3, and decreased ΔΨm level. Melatonin supplementation was better able to reduce irradiation-induced oxidative damage marked by carbonyl or malondialdehyde content, and stimulate the antioxidant enzyme activities (superoxide dismutase and catalase) together with total antioxidant capacity. Moreover, administration with melatonin pronouncedly elevated the expression of Nrf2 which regulates redox balance and stress. Furthermore, melatonin treatment mitigated apoptotic rate, maintained ΔΨm, diminished cytochrome c release from mitochondria, down-regulated Bax/Bcl-2 ratio and caspase-3 levels, and consequently inhibited the important steps of irradiation-induced activation of mitochondrial pathway of apoptosis. Thus, we propose that the anti-apoptotic action with the alterations in apoptosis regulator provided by melatonin may be responsible at least in part for its antioxidant effect by the abolishing of carbon ion-induced oxidative stress along with increasing Nrf2 expression and antioxidant enzyme activity.

Transforming growth factor-β and nuclear factor E2–related factor 2 regulate antioxidant responses in airway smooth muscle cells: role in asthma

RATIONALE

Aberrant airway smooth muscle cell (ASMC) function and overexpression of transforming growth factor (TGF)-β, which modulates ASMC proliferative and inflammatory function and induces oxidant release, are features of asthma. Nuclear factor E2-related factor 2 (Nrf2) activates antioxidant genes conferring protection against oxidative stress.

OBJECTIVES

To determine the role of Nrf2 in ASMCs and its modulation by TGF-β, and compare Nrf2 activity in ASMCs from subjects with severe and nonsevere asthma and healthy subjects.

METHODS

ASMCs were cultured from airways of subjects without asthma, and from airway biopsies from patients with severe and nonsevere asthma. We studied Nrf2 activation on antioxidant gene expression and proliferation, the effect of TGF-β on Nrf2 transcriptional activity, and the impact of Nrf2 activation on TGF-β–mediated proliferation and IL-6 release. Nrf2–antioxidant response elements binding and Nrf2-dependent antioxidant gene expression was determined in asthmatic ASMCs.

MEASUREMENTS AND MAIN RESULTS

Activation of Nrf2 led to up-regulation of the antioxidant genes heme oxygenase (HO)-1, NAD(P)H:quinone oxidoreductase, and manganese superoxide dismutase, and a reduction in proliferation. TGF-β reduced Nrf2-mediated antioxidant gene transcription through induction of activating transcription factor-3 expression. Nrf2 activation attenuated TGF-β–mediated reduction in HO-1,ASMC proliferation, and IL-6 release. Nrf2–antioxidant response elements binding was reduced in ASMCs from patients with severe asthma compared with ASMCs from patients with nonsevere asthma and normal subjects. HO-1 expression was reduced in ASMCs from patients with both nonsevere and severe asthma compared with healthy subjects.

CONCLUSIONS

Nrf2 regulates antioxidant responses and proliferation in ASMCs and is inactivated by TGF-β. Nrf2 reduction may underlie compromised antioxidant protection and aberrant ASM function in asthma.

Pro- and anti-oxidant effects of polyunsaturated fatty acid supplementation in HepG2 cells

PUFA are bioactive nutrients thought to be effective in the prevention of many chronic diseases. PUFA susceptibility to free radical oxidation represents the other side of the coin, and the role of PUFA as pro- or anti-oxidants is still an unanswered question. In this study we supplemented HepG2 cells with different PUFA, and observed different effects on cytotoxicity, oxidation and modulation of antioxidant defenses. These were not simply related to the length of carbon chain, or to the number and position of double bonds. ARA supply evidenced the induction of oxidative damage, while DHA supplemented cells appeared richer in antioxidant defenses. To our knowledge, our study is the first evidencing the different pro- or anti-oxidant effect of different fatty acids when supplemented to cells. Overall, this points out the importance of not generalizing dietary recommendations considering PUFA as one category, but to extend them to the individual fatty acids.

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.

AHR2 knockdown prevents PAH-mediated cardiac toxicity and XRE- and ARE-associated gene induction in zebrafish (Danio rerio)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants often present in aquatic systems as complex mixtures. Embryonic fish are sensitive to the developmental toxicity of some PAHs, but the exact mechanisms involved in this toxicity are still unknown. This study explored the role of the aryl hydrocarbon receptor (AHR) in the oxidative stress response of zebrafish to the embryotoxicity of select PAHs. Embryos were exposed to two PAHs, benzo[k]fluoranthene (BkF; a strong AHR agonist) and fluoranthene (FL; a cytochrome P4501A (CYP1A) inhibitor), alone and in combination. CYP1A, CYP1B1, CYP1C1, and redox-responsive genes glutathione s-transferase pi 2 (GSTp2), glutathione peroxidase 1 (GPx1), the glutamate-cysteine ligase catalytic subunit (GCLc), MnSOD and CuZnSOD mRNA expression was examined. CYP1 activity was measured via an in vivo ethoxyresorufin-O-deethlyase (EROD) activity assay, and the area of the pericardium was measured as an index of cardiotoxicity. BkF or FL alone caused no deformities whereas BkF+FL resulted in extreme pericardial effusion. BkF induced CYP activity above controls and co-exposure with FL inhibited this activity. BkF induced expression of all three CYPs, GSTp2, and GCLc. BkF+FL caused greater than additive induction of the three CYPs, GSTp2, GPx1, and GCLc but had no effect on MnSOD or CuZnSOD. AHR2 knockdown protected against the cardiac deformities caused by BkF+FL and significantly inhibited the induction of the CYPs, GSTp2, GPx1, and GCLc after BkF+FL compared to non-injected controls. These results further show the protective role of AHR2 knockdown against cardiotoxic PAHs and the role of AHR2 as a mediator of redox-responsive gene induction.

Angiotensin II downregulates catalase expression and activity in vascular adventitial fibroblasts through an AT1R/ERK1/2-dependent pathway

Angiotensin II (Ang II) plays a profound regulatory effect on NADPH oxidase and the functional features of vascular adventitial fibroblasts, but its role in antioxidant enzyme defense remains unclear. This study investigated the effect of Ang II on expressions and activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in adventitial fibroblasts and the possible mechanism involved. Ang II decreased the expression and activity of CAT in a dose- and time-dependent manner, but not that of SOD and GPx. The effects were abolished by the angiotensin II type 1 receptor (AT1R) blocker losartan and AT1R small-interfering RNA (siRNA). Incubation with polyethylene glycol-CAT prevented the Ang II-induced effects on reactive oxygen species (ROS) generation and myofibroblast differentiation. Moreover, Ang II rapidly induced phosphorylation of ERK1/2, which was reversed by losartan and AT1R siRNA. Pharmacological blockade of ERK1/2 improved Ang II-induced decrease in CAT protein expression. These in vitro results indicate that Ang II induces ERK1/2 activation, contributing to the downregulation of CAT as well as promoting oxidative stress and adventitial fibroblast phenotypic differentiation in an AT1R-mediated manner.

Antroquinonol reduces oxidative stress by enhancing the Nrf2 signaling pathway and inhibits inflammation and sclerosis in focal segmental glomerulosclerosis mice

Oxidative stress, inflammation, and fibrosis are involved in the development and progression of focal segmental glomerulosclerosis (FSGS), a common form of idiopathic nephrotic syndrome that represents a therapeutic challenge because it has a poor response to steroids. Antroquinonol (Antroq), a purified compound, is a major active component of a mushroom, namely Antrodia camphorata, that grows in the camphor tree in Taiwan, and it has inhibitory effects on nitric oxide production and inflammatory reactions. We hypothesized that Antroq might ameliorate FSGS renal lesions by modulating the pathogenic pathways of oxidative stress, inflammation, and glomerular sclerosis in the kidney. We demonstrate that Antroq significantly (1) attenuates proteinuria, renal dysfunction, and glomerulopathy, including epithelial hyperplasia lesions and podocyte injury; (2) reduces oxidative stress, leukocyte infiltration, and expression of fibrosis-related proteins in the kidney; (3) increases renal nuclear factor E2-related factor 2 (Nrf2) and glutathione peroxidase activity; and (4) inhibits renal nuclear factor-κB (NF-κB) activation and decreases levels of transforming growth factor (TGF)-β1 in serum and kidney tissue in a mouse FSGS model. Our data suggest that Antroq might be a potential therapeutic agent for FSGS, acting by boosting Nrf2 activation and suppressing NF-κB-dependent inflammatory and TGF-β1-mediated fibrosis pathways in the kidney.

Oltipraz upregulates the nuclear factor (erythroid-derived 2)-like 2 [corrected](NRF2) antioxidant system and prevents insulin resistance and obesity induced by a high-fat diet in C57BL/6J mice

AIMS/HYPOTHESIS

We investigated whether oltipraz, a nuclear respiratory factor 2 alpha subunit (NRF2) activator, improves insulin sensitivity and prevents the development of obesity in mice.

METHODS

C57BL/6J mice were fed with a low-fat diet (10% of energy as fat), a high-fat diet (HFD) (45% of energy as fat) or a HFD with oltipraz for 28 weeks. The effects of oltipraz on body weight, fat content, glucose disposal, insulin signalling, metabolic profiles and endogenous NRF2 functional status in the three groups of mice were investigated.

RESULTS

Oltipraz prevented or significantly attenuated the effect of HFD on glucose disposal, body weight and fat gain. Impairment of protein kinase B/Akt phosphorylation in this HFD-fed mouse model in response to intraperitoneal insulin injection was observed in adipose tissue, but not in the muscles, accompanied by inhibition of AMP-activated protein kinase signalling and activation of p70S6 kinase, as well as reduced GLUT4 content. These defects were attenuated by oltipraz administration. Nuclear content of NRF2 in adipose tissue was reduced by HFD feeding, associated with increased Keap1 mRNA expression and reduced production of haem oxygenase-1 and superoxide dismutase, increased protein oxidation, decreased plasma reduced:oxidised glutathione ratio and the appearance of macrophage marker F4/80. These defects were also restored by oltipraz. Finally, oltipraz attenuated HFD-induced inducible nitric oxide synthase overproduction.

CONCLUSIONS/INTERPRETATION

Impairment of the endogenous redox system is important in the development of obesity and insulin resistance in chronic HFD feeding. NRF2 activation represents a potential novel approach in the treatment and prevention of obesity and diabetes.

Identification of a host cell target for the thiazolide class of broad-spectrum anti-parasitic drugs

The thiazolide nitazoxanide (NTZ) and some derivatives exhibit considerable in vitro activities against a broad range of parasites, including the apicomplexans Neospora caninum and Toxoplasma gondii tachyzoites. In order to identify potential molecular targets for this compound in both parasites, RM4847 was coupled to epoxy-agarose and affinity chromatography was performed. A protein of approximately 35 kDa was eluted upon RM4847-affinity-chromatography from extracts of N. caninum-infected human foreskin fibroblasts (HFF) and non-infected HFF, but no protein was eluted when affinity chromatography was performed with T. gondii or N. caninum tachyzoite extracts. Mass spectrometry analysis identified the 35 kDa protein as human quinone reductase NQO1 (P15559; QR). Within 8h after infection of HFF with N. caninum tachyzoites, QR transcript expression levels were notably increased, but no such increase was observed upon infection with T. gondii tachyzoites. Treatment of non-infected HFF with RM4847 did also lead to an increase of QR transcript levels. The enzymatic activity of 6-histidine-tagged recombinant QR (recQR) was assayed using menadione as a substrate. The thiazolides NTZ, tizoxanide and RM4847 inhibited recQR activity on menadione in a concentration-dependent manner. Moreover, a small residual reducing activity was observed when these thiazolides were offered as substrates.

Impaired redox signaling and antioxidant gene expression in endothelial cells in diabetes: a role for mitochondria and the nuclear factor-E2-related factor 2-Kelch-like ECH-associated protein 1 defense pathway

Type 2 diabetes is an age-related disease associated with vascular pathologies, including severe blindness, renal failure, atherosclerosis, and stroke. Reactive oxygen species (ROS), especially mitochondrial ROS, play a key role in regulating the cellular redox status, and an overproduction of ROS may in part underlie the pathogenesis of diabetes and other age-related diseases. Cells have evolved endogenous defense mechanisms against sustained oxidative stress such as the redox-sensitive transcription factor nuclear factor E2-related factor 2 (Nrf2), which regulates antioxidant response element (ARE/electrophile response element)-mediated expression of detoxifying and antioxidant enzymes and the cystine/glutamate transporter involved in glutathione biosynthesis. We hypothesize that diminished Nrf2/ARE activity contributes to increased oxidative stress and mitochondrial dysfunction in the vasculature leading to endothelial dysfunction, insulin resistance, and abnormal angiogenesis observed in diabetes. Sustained hyperglycemia further exacerbates redox dysregulation, thereby providing a positive feedback loop for severe diabetic complications. This review focuses on the role that Nrf2/ARE-linked gene expression plays in regulating endothelial redox homeostasis in health and type 2 diabetes, highlighting recent evidence that Nrf2 may provide a therapeutic target for countering oxidative stress associated with vascular disease and aging.

Schisandrin B-induced glutathione antioxidant response and cardioprotection are mediated by reactive oxidant species production in rat hearts

To investigate the involvement of reactive oxidant species (ROS), presumably arising from cytochrome P-450 (CYP)-catalyzed metabolism of schisandrin B (Sch B), in triggering glutathione antioxidant response, Sch B induced reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent and CYP-catalyzed reaction and associated ROS production were examined in rat heart microsomes. Sch B analogs were also studied for comparison. Using rat heart microsomes as a source of CYP, Sch B and schisandrin C (Sch C), but not schisandrin A and dimethyl diphenyl bicarboxylate (an intermediate compound derived from the synthesis of Sch C), were found to serve as co-substrate for the CYP-catalyzed NADPH oxidation reaction, with concomitant production of ROS. The stimulation of CYP-catalyzed NADPH oxidation reaction and/or ROS production by Sch B or Sch C correlated with the increase in mitochondrial reduced glutathione level and protection against ischemia/reperfusion (I/R) injury in rat hearts. The involvement of ROS in Sch B-induced cardioprotection was further confirmed by the suppressive effect produced by N-acetylcysteine or alpha-tocopherol pretreatment. Taken together, these results suggest that Sch B-induced glutathione antioxidant response and cardioprotection may be mediated by ROS arising from CYP-catalyzed reaction.