NAD(P)H:quinone oxidoreductase1 (DT diaphorase) specifically prevents the formation of benzo[a]pyrene quinone-DNA adducts generated by cytochrome P4501A1 and P450 reductase

Modulation of adipose tissue phenotype and longevity-related gene expression by nuclear factor E2-related factor 2 knockdown in 3T3-L1 cells

PURPOSE

This study explores the role of nuclear factor E2-related factor 2 (Nrf2) in regulating adipose tissue phenotype and its potential mechanisms for promoting aging resistance in 3T3-L1 adipocytes. The study aims to evaluate the impact of Nrf2 knockdown on adipose phenotype transformation, focusing on brown adipose tissue (BAT) and white adipose tissue (WAT) marker genes, as well as longevity-related factors.

METHODS

3T3-L1 preadipocytes were differentiated into adipocytes using a standard MDI regimen. Nrf2 expression was knocked down via siRNA transfection. Gene expression was assessed using quantitative real-time PCR (qPCR), and protein levels were analyzed using Western blotting.

RESULTS

Nrf2 knockdown was confirmed by Western blot (p<0.001) and qPCR (p<0.001), showing a significant reduction in Nrf2 expression. Notably, this knockdown resulted in increased expression of BAT markers, including PGC-1α (p = 0.012), Dio2 (p = 0.020), and PRDM16 (p = 0.001), at both mRNA (PGC-1α [p = 0.012], Dio2 [p = 0.020], and PRDM16 [p = 0.001]) and protein (PGC-1α [p = 0.001]; Dio2 [p = 0.003]; PRDM16 [p = 0.007])levels. Conversely, WAT markers such as BMP4 (mRNA: p = 0.01; WB: p = 0.001), resistin (mRNA: p = 0.016; WB: p = 0.004), and Rb1 (mRNA: p = 0.03; WB: p = 0.003) were significantly downregulated. Additionally, levels of Cycs (mRNA: p = 0.024; WB: p = 0.037) and UCP1 (mRNA: p = 0.024; WB: p = 0.023) were elevated, indicating enhanced mitochondrial function and metabolic activity (P < 0.05). The knockdown also affected longevity-related proteins, Sirt1 (WB: p = 0.018) and AMPKα (WB: p = 0.021), underscoring Nrf2's role in metabolic regulation.

CONCLUSION

Nrf2 knockdown in 3T3-L1 adipocytes promotes a transition towards a brown adipose phenotype and enhances the expression of longevity-related factors, suggesting Nrf2 as a potential therapeutic target for addressing aging-related metabolic decline.

A Review of the Effects of Flavonoids on NAD(P)H Quinone Oxidoreductase 1 Expression and Activity

Cancer is a significant cause of death worldwide. It has been suggested that the consumption of flavonoids decreases the risk for cancer by increasing phase II enzymes, such as Nicotinamide Adenine Dinucleotide Phosphate Hydrogen (NAD(P)H) quinone oxidoreductase 1 (NQO1), glutathione S-transferases, and Uridine 5'-diphospho- (UDP)-glucuronosyltransferases that assist in removing carcinogens from the human body. Flavonoids are bioactive compounds found in a variety of dietary sources, including fruits, vegetables, legumes, nuts, and teas. As such, it is important to investigate which flavonoids are involved in the metabolism of carcinogens to help reduce the risk of cancer. Therefore, the objective of this narrative review was to investigate the effects of commonly consumed flavonoids on NQO1 mRNA expression, protein, and activity in human cell and murine models. PubMed was used to search for peer-reviewed journal articles, which demonstrated that selected flavonoids (e.g., quercetin, apigenin, luteolin, genistein, and daidzein) increase NQO1, and therefore, increase the excretion of carcinogens. However, more research is needed regarding the mechanisms by which flavonoids induce NQO1. Furthermore, it is suggested that future efforts focus on providing precise flavonoid recommendations to decrease the risk factors for chronic diseases.

Human NQO1 as a Selective Target for Anticancer Therapeutics and Tumor Imaging

Human NAD(P)H-quinone oxidoreductase1 (HNQO1) is a two-electron reductase antioxidant enzyme whose expression is driven by the NRF2 transcription factor highly active in the prooxidant milieu found in human malignancies. The resulting abundance of NQO1 expression (up to 200-fold) in cancers and a barely detectable expression in body tissues makes it a selective marker of neoplasms. NQO1 can catalyze the repeated futile redox cycling of certain natural and synthetic quinones to their hydroxyquinones, consuming NADPH and generating rapid bursts of cytotoxic reactive oxygen species (ROS) and H2O2. A greater level of this quinone bioactivation due to elevated NQO1 content has been recognized as a tumor-specific therapeutic strategy, which, however, has not been clinically exploited. We review here the natural and new quinones activated by NQO1, the catalytic inhibitors, and the ensuing cell death mechanisms. Further, the cancer-selective expression of NQO1 has opened excellent opportunities for distinguishing cancer cells/tissues from their normal counterparts. Given this diagnostic, prognostic, and therapeutic importance, we and others have engineered a large number of specific NQO1 turn-on small molecule probes that remain latent but release intense fluorescence groups at near-infrared and other wavelengths, following enzymatic cleavage in cancer cells and tumor masses. This sensitive visualization/quantitation and powerful imaging technology based on NQO1 expression offers promise for guided cancer surgery, and the reagents suggest a theranostic potential for NQO1-targeted chemotherapy.

Research on the effects of rs1800566 C/T polymorphism of NAD(P)H quinone oxidoreductase 1 gene on cancer risk involves analysis of 43,736 cancer cases and 56,173 controls

Objective

A two-electron reductase known as NQO1 [NAD(P)H quinone oxidoreductase 1] is regarded as an excellent anticancer target. Studies have found that rs1800566 polymorphism of NQO1 is linked to different cancers, but their associations remain controversial.

Methods

In the present work, we selected to do a comprehensive meta-analysis to analyze their correlation. We performed searches on PubMed, Embase, Google Scholar, Chinese database, and Web of Science. The results we obtained covered all publications before April 3, 2022.

Results

There were 176 case-control studies among them, with 56,173 corresponding controls and 43,736 cancer cases. We determined that the NQO1 rs1800566 polymorphism was not related to the cancer risk by calculating 95% confidence intervals and odds ratios. However, stratified genotyping showed that this polymorphism was protective against hepatocellular carcinoma, renal cell carcinoma, and gastric cancer. In addition, on dividing cancer into six systems, the association with gastrointestinal cancer decreased. In the race-based subgroup, a decreasing trend was observed in Asians, while an increasing trend was found among Caucasians, Africans, and mixed populations. The decreased correlation in the hospital-based subgroup was also detected.

Conclusion

Current study shows that rs1800566 polymorphism of NQO1 was linked to cancer susceptibility and maybe as a tumor marker in their development.

Cruciferous Vegetable Intake and Bulky DNA Damage within Non-Smokers and Former Smokers in the Gen-Air Study (EPIC Cohort)

Epidemiologic studies have indicated that cruciferous vegetables can influence the cancer risk; therefore, we examined with a cross-sectional approach the correlation between the frequent consumption of the total cruciferous vegetables and the formation of bulky DNA damage, a biomarker of carcinogen exposure and cancer risk, in the Gen-Air study within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. DNA damage measurements were performed in the peripheral blood of 696 of those apparently healthy without cancer controls, including 379 never-smokers and 317 former smokers from seven European countries by the 32P-postlabeling assay. In the Gen-Air controls, the median intake of cruciferous vegetables was 6.16 (IQR 1.16−13.66) g/day, ranging from 0.37 (IQR 0−6.00) g/day in Spain to 11.34 (IQR 6.02−16.07) g/day in the UK. Based on this information, participants were grouped into: (a) high consumers (>20 g/day), (b) medium consumers (3−20 g/day) and (c) low consumers (<3.0 g/day). Overall, low cruciferous vegetable intake was correlated with a greater frequency of bulky DNA lesions, including benzo(a)pyrene, lactone and quinone-adducts and bulky oxidative lesions, in the adjusted models. Conversely, a high versus low intake of cruciferous vegetables was associated with a reduction in DNA damage (up to a 23% change, p = 0.032); this was particularly evident in former smokers (up to a 40% change, p = 0.008). The Generalized Linear Regression models indicated an overall Mean Ratio between the high and the low consumers of 0.78 (95% confidence interval, 0.64−0.97). The current study suggests that a higher intake of cruciferous vegetables is associated with a lower level of bulky DNA adducts and supports the potential for cancer prevention strategies through dietary habit changes aimed at increasing the consumption of cruciferous vegetables.

Polymorphisms in NQO1 and MPO genes and risk for bladder cancer in Tunisian population

BACKGROUND

NAD (P) H: quinone oxidoreductase (1) (NQO1-HGNC: 2874) and myeloperoxidase (MPO-HGNC: 7218) are two enzymes involved in phase II of the xenobiotic metabolism pathway.

METHODS

In this study, a case-control analysis was conducted to investigate the relationship between genetic variations in the NQO1 (C609T, rs1800566; IVS1-27 C >G, rs689452) and MPO (G463A, rs2333227) genes and the risk for bladder cancer among Tunisian population.

RESULTS

We have found that the MPO 463GA genotype was associated with a decreased risk of developing bladder cancer (p = 0.049; OR = 0.696; 95% CI 0.484-0.999). In contrast, we have found that the NQO1 609CT genotype could increase the risk of bladder cancer patients (p = 0.0039; OR = 1.454; 95% CI = 1.017-2.078). Moreover, patients with "NQO1 609 CT/IVS1-27 CG" genotype show a 2.180-fold increasing risk for developing bladder cancer in comparison to the control group with wild genotype. This OR is estimated at 5.6-fold in smokers patients with "NQO1 609 CT/IVS1-27 CG" genotype. Lastly, study findings suggest that the NQO1 IVS-27 *CG genotype (rs689452) is associated with a risk of progression to muscle invasive bladder cancer.

CONCLUSION

Our study suggests that environmental risk factors in association to NQO1 genotypes (NQO1 609 CT/IVS1-27 CG) play an important role in the development of bladder cancer in Tunisian population.

Interactions of the antioxidant enzymes NAD(P)H: Quinone oxidoreductase 1 (NQO1) and NRH: Quinone oxidoreductase 2 (NQO2) with pharmacological agents, endogenous biochemicals and environmental contaminants

NAD(P)H

Quinone Oxidoreductase 1 (NQO1) is an antioxidant enzyme that catalyzes the two-electron reduction of several different classes of quinone-like compounds (quinones, quinone imines, nitroaromatics, and azo dyes). One-electron reduction of quinone or quinone-like metabolites is considered to generate semiquinones to initiate redox cycling that is responsible for the generation of reactive oxygen species and oxidative stress and may contribute to the initiation of adverse drug reactions and adverse health effects. On the other hand, the two-electron reduction of quinoid compounds appears important for drug activation (bioreductive activation) via chemical rearrangement or autoxidation. Two-electron reduction decreases quinone levels and opportunities for the generation of reactive species that can deplete intracellular thiol pools. Also, studies have shown that induction or depletion (knockout) of NQO1 were associated with decreased or increased susceptibilities to oxidative stress, respectively. Moreover, another member of the quinone reductase family, NRH: Quinone Oxidoreductase 2 (NQO2), has a significant functional and structural similarity with NQO1. The activity of both antioxidant enzymes, NQO1 and NQO2, becomes critically important when other detoxification pathways are exhausted. Therefore, this article summarizes the interactions of NQO1 and NQO2 with different pharmacological agents, endogenous biochemicals, and environmental contaminants that would be useful in the development of therapeutic approaches to reduce the adverse drug reactions as well as protection against quinone-induced oxidative damage. Also, future directions and areas of further study for NQO1 and NQO2 are discussed.

NADPH-quinone oxidoreductase-1 mediates Benzo-[a]-pyrene-1,6-quinone-induced cytotoxicity and reactive oxygen species production in human EA.hy926 endothelial cells

Numerous studies conducted in the past have reported deaths in the human population due to cardiovascular diseases (CVD) on exposure to air particulate matter (APM). BP-1,6-quinone (BP-1,6-Q) is one of the significant components of APM. However, the mechanism(s) by which it can exert its toxicity in endothelial cells is not yet completely understood. NAD(P)H: quinone oxidoreductase-1 (NQO1) is expressed highly in myocardium and vasculature tissues of the heart and plays a vital role in maintaining vascular homeostasis. This study, demonstrated that BP-1,6-Q diminishes NQO1 enzyme activity in a dose-dependent manner in human EA.hy926 endothelial cells. The decrease in the NQO1 enzyme causes potentiation in BP-1,6-Q-mediated toxicity in EA.hy926 endothelial cells. The enhancement of NQO1 in endothelial cells showed cytoprotection against BP-1,6-Q-induced cellular toxicity, lipid, and protein damage suggesting an essential role of NQO1 in cytoprotection against BP-1,6-Q toxicity. Using various biochemical assays and genetic approaches, results from this study further demonstrated that NQO1 also plays a crucial role in BP-1,6-Q-induced production of reactive oxygen species (ROS). These findings will contribute to elucidating BP-1,6-Q mediated toxicity and its role in the development of atherosclerosis.

Association of Genetic Variations in NRF2, NQO1, HMOX1, and MT with Severity of Coronary Artery Disease and Related Risk Factors

NRF2 is a transcription factor which, during oxidative stress, activates transcription of its target antioxidant genes. Polymorphisms in NRF2 and its target antioxidant genes: HMOX-1, NQO1, and MT, have been associated with cardiovascular diseases (CVDs) and diabetes in various ethnic groups, however, with variable results. The aim of this study was to investigate the association of NRF2, HMOX-1, NQO1, and MT gene polymorphisms with CVD risk factors in Thais. The study was conducted in two groups: group with high-risk for coronary artery disease (CAD) and health check-up group. Polymorphisms in NRF2 (rs6721961), NQO1 (rs1800566), MT1A (rs11640851), and HMOX-1 (rs2071746) were genotyped. Expressions of NRF2, HMOX-1, and NQO1 were also determined. In high-risk group, NRF2 rs6721961-TT was associated with CAD [OR (95% CI) 5.07 (1.42-18.10)] and severity of coronary atherosclerosis [Gensini score > 32, OR (95% CI) 4.31 (1.67-11.09)]; rs6721961 GT and TT revealed significant association with lower mRNA expression than GG (p = 0.021). NQO1 rs1800566 also revealed association with CAD, only in female. Combined effect of NQO1-rs1800566, HMOX1-rs2071746, and MT1A-rs11640851 was evaluated on the risks of DM and hypertension. With a combination of risk alleles as genetic risk score (GRS), the highest GRS (score 6) increased risk for hypertension, comparing with GRS 0-2 [OR (95% CI) 1.89 (1.02-3.49)]; group with score 5-6 revealed association with risk of DM [OR (95% CI) 1.481 (1.08-2.04)]. In conclusion, NRF2 rs6721961 associated with CAD and severity of coronary atherosclerosis. NQO1 rs1800566 also associated with CAD, only in female. Combined polymorphisms of three NRF2-regulated genes increased risk of DM and hypertension.

Evaluation of the risk of lung cancer associated with NAD(P)H: quinone oxidoreductase 1 (NQO1) C609T polymorphism in male current cigarette smokers from the Eastern India

NAD(P)H: quinone oxidoreductase 1 (NQO1) is an endogenous cellular defence mechanism against several carcinogenic quinones derived from cigarette smoke. NQO1 C609T polymorphism is a strong determinant of NQO1 structure and function. The people with mutant allele for this polymorphism has significantly reduced NQO1 activity. In this study, we tried to evaluate the risk of lung cancer associated with this polymorphism in male current smokers of the Eastern India. Using PCR-RFLP method, we compared the NQO1 C609T genotype distribution in male current smokers with (n=150) and without (n=200) lung cancer. We observed significant variation of genotypic distribution between these two groups. The allele frequency of the variant C609T allele were 40.3% and 32.7% in smokers with and without lung cancer, respectively. From the genotypic comparison between the two smoker groups, it was found that a higher risk (OR=1.64, 95% CI: 1.05-2.55, P<0.05) of lung cancer was associated with NQO1 C609T polymorphism.

Aryl Hydrocarbon Receptor: Its Regulation and Roles in Transformation and Tumorigenesis

AhR is an environmental response gene that mediates cellular responses to a variety of xenobiotic compounds that frequently function as AhR ligands. Many AhR ligands are classified as carcinogens or pro-carcinogens. Thus, AhR itself acts as a major mediator of the carcinogenic effect of many xenobiotics in vivo. In this concise review, mechanisms by which AhR trans-activates downstream target gene expression, modulates immune responses, and mediates malignant transformation and tumor development are discussed. Moreover, activation of AhR by post-translational modifications and crosstalk with other transcription factors or signaling pathways are also summarized.

Induction of the Antioxidant Response by the Transcription Factor NRF2 Increases Bioactivation of the Mutagenic Air Pollutant 3-Nitrobenzanthrone in Human Lung Cells

3-Nitrobenzanthrone (3-NBA) is a suspected human carcinogen present in diesel exhaust. It requires metabolic activation via nitroreduction in order to form DNA adducts and promote mutagenesis. We have determined that human aldo-keto reductases (AKR1C1-1C3) and NAD(P)H:quinone oxidoreductase 1 (NQO1) contribute equally to the nitroreduction of 3-NBA in lung epithelial cell lines and collectively represent 50% of the nitroreductase activity. The genes encoding these enzymes are induced by the transcription factor NF-E2 p45-related factor 2 (NRF2), which raises the possibility that NRF2 activation exacerbates 3-NBA toxification. Since A549 cells possess constitutively active NRF2, we examined the effect of heterozygous (NRF2-Het) and homozygous NRF2 knockout (NRF2-KO) by CRISPR-Cas9 gene editing on the activation of 3-NBA. To evaluate whether NRF2-mediated gene induction increases 3-NBA activation, we examined the effects of NRF2 activators in immortalized human bronchial epithelial cells (HBEC3-KT). Changes in AKR1C1-1C3 and NQO1 expression by NRF2 knockout or use of NRF2 activators were confirmed by qPCR, immunoblots, and enzyme activity assays. We observed decreases in 3-NBA activation in the A549 NRF2 KO cell lines (53% reduction in A549 NRF2-Het cells and 82% reduction in A549 NRF2-KO cells) and 40-60% increases in 3-NBA bioactivation due to NRF2 activators in HBEC3-KT cells. Together, our data suggest that activation of the transcription factor NRF2 exacerbates carcinogen metabolism following exposure to diesel exhaust which may lead to an increase in 3-NBA-derived DNA adducts.

NAD(P)H quinone oxidoreductase (NQO1): an enzyme which needs just enough mobility, in just the right places

NAD(P)H quinone oxidoreductase 1 (NQO1) catalyses the two electron reduction of quinones and a wide range of other organic compounds. Its physiological role is believed to be partly the reduction of free radical load in cells and the detoxification of xenobiotics. It also has non-enzymatic functions stabilising a number of cellular regulators including p53. Functionally, NQO1 is a homodimer with two active sites formed from residues from both polypeptide chains. Catalysis proceeds via a substituted enzyme mechanism involving a tightly bound FAD cofactor. Dicoumarol and some structurally related compounds act as competitive inhibitors of NQO1. There is some evidence for negative cooperativity in quinine oxidoreductases which is most likely to be mediated at least in part by alterations to the mobility of the protein. Human NQO1 is implicated in cancer. It is often over-expressed in cancer cells and as such is considered as a possible drug target. Interestingly, a common polymorphic form of human NQO1, p.P187S, is associated with an increased risk of several forms of cancer. This variant has much lower activity than the wild-type, primarily due to its substantially reduced affinity for FAD which results from lower stability. This lower stability results from inappropriate mobility of key parts of the protein. Thus, NQO1 relies on correct mobility for normal function, but inappropriate mobility results in dysfunction and may cause disease.

Nrf2 Inhibits Periodontal Ligament Stem Cell Apoptosis under Excessive Oxidative Stress

The present study aimed to analyze novel mechanisms underlying Nrf2-mediated anti-apoptosis in periodontal ligament stem cells (PDLSCs) in the periodontitis oxidative microenvironment. We created an oxidative stress model with H₂O₂-treated PDLSCs. We used real-time PCR, Western blotting, TUNEL staining, fluorogenic assay and transfer genetics to confirm the degree of oxidative stress and apoptosis as well as the function of nuclear factor-erythroid 2-related factor 2 (Nrf2). We demonstrated that with upregulated levels of reactive oxygen species (ROS) and malondialdehyde (MDA), the effect of oxidative stress was obvious under H₂O₂ treatment. Oxidative molecules were altered after the H₂O₂ exposure, whereby the signaling of Nrf2 was activated with an increase in its downstream effectors, heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1) and γ-glutamyl cysteine synthetase (γ-GCS). Additionally, the apoptosis levels gradually increased with oxidative stress by the upregulation of caspase-9, caspase-3, Bax and c-Fos levels in addition to the downregulation of Bcl-2. However, there was no alterations in levels of caspase-8. The enhanced antioxidant effect could not mitigate the occurrence of apoptosis. Furthermore, Nrf2 overexpression effectively improved the anti-oxidative levels and increased cell proliferation. At the same time, overexpression effectively restrained TUNEL staining and decreased the molecular levels of caspase-9, caspase-3, Bax and c-Fos, but not that of caspase-8. In contrast, silencing the expression of Nrf2 levels had the opposite effect. Collectively, Nrf2 alleviates PDLSCs via its effects on regulating oxidative stress and anti-intrinsic apoptosis by the activation of oxidative enzymes.

Biological interaction of cigarette smoking on the association between genetic polymorphisms involved in inflammation and the risk of lung cancer: A case-control study in Japan

Chronic inflammation serves an important role in lung carcinogenesis, thus genetic polymorphisms involved in this pathway may affect the risk of lung cancer. The present case-control study focused on the association between lung cancer risk and genetic polymorphisms involved in inflammatory pathways. The study comprised 462 lung cancer cases and 379 controls from Japan. The roles of interleukin 8 (IL8) rs4073, nuclear factor kappa B (NFκB) rs28362491, cytochrome b-245, alpha polypeptide (CYBA) rs4673, NAD(P) H dehydrogenase, quinone 1 (NQO1) rs1800566, nitric oxide synthase 2 and inducible (NOS2) rs2297518 polymorphisms in lung carcinogenesis were investigated. An unconditional logistic model was used to estimate the odds ratio (OR) and 95% confidence interval (CI) for the association between the genetic polymorphisms and lung cancer risk. The multiplicative and additive [relative excess risk due to interaction, attributable proportion due to interaction (AP) and synergy index (SI)] interactions with cigarette smoking were also determined. A significant association was revealed between the TT genotype of NQO1 rs1800566 and an increased risk of lung cancer (OR=1.78; 95% CI=1.14-2.79). The additive interaction evaluations between CYBA rs4673 (AP=0.50, 95% CI=0.15-0.85; SI=2.66, 95% CI=1.01-6.99) and smoking were also statistically significant. NQO1 rs1800566 was significantly associated with lung cancer risk and smoking may influence the association between CYBA rs4673 and the risk of lung cancer. Additional studies with larger control and case populations are warranted in order to confirm the CYBA rs4673-smoking association suggested by the present study.

Human Microdosing with Carcinogenic Polycyclic Aromatic Hydrocarbons: In Vivo Pharmacokinetics of Dibenzo[def,p]chrysene and Metabolites by UPLC Accelerator Mass Spectrometry

Metabolism is a key health risk factor following exposures to pro-carcinogenic polycyclic aromatic hydrocarbons (PAHs) such as dibenzo[def,p]chrysene (DBC), an IARC classified 2A probable human carcinogen. Human exposure to PAHs occurs primarily from the diet in nonsmokers. However, little data is available on the metabolism and pharmacokinetics in humans of high molecular weight PAHs (≥4 aromatic rings), including DBC. We previously determined the pharmacokinetics of DBC in human volunteers orally administered a microdose (29 ng; 5 nCi) of [14C]-DBC by accelerator mass spectrometry (AMS) analysis of total [14C] in plasma and urine. In the current study, we utilized a novel "moving wire" interface between ultraperformance liquid chromatography (UPLC) and AMS to detect and quantify parent DBC and its major metabolites. The major [14C] product identified in plasma was unmetabolized [14C]-DBC itself (Cmax = 18.5 ±15.9 fg/mL, Tmax= 2.1 ± 1.0 h), whereas the major metabolite was identified as [14C]-(+/-)-DBC-11,12-diol (Cmax= 2.5 ±1.3 fg/mL, Tmax= 1.8 h). Several minor species of [14C]-DBC metabolites were also detected for which no reference standards were available. Free and conjugated metabolites were detected in urine with [14C]-(+/-)-DBC-11,12,13,14-tetraol isomers identified as the major metabolites, 56.3% of which were conjugated (Cmax= 35.8 ± 23.0 pg/pool, Tmax = 6-12 h pool). [14C]-DBC-11,12-diol, of which 97.5% was conjugated, was also identified in urine (Cmax = 29.4 ± 11.6 pg/pool, Tmax = 6-12 h pool). Parent [14C]-DBC was not detected in urine. This is the first data set to assess metabolite profiles and associated pharmacokinetics of a carcinogenic PAH in human volunteers at an environmentally relevant dose, providing the data necessary for translation of high dose animal models to humans for translation of environmental health risk assessment.

Proteomic analysis of flooded soybean root exposed to aluminum oxide nanoparticles

Aluminum oxide (Al2O3) nanoparticles are used in agricultural products and cause various adverse growth effects on different plant species. To study the effects of Al2O3 nanoparticles on soybean under flooding stress, a gel-free proteomic technique was used. Morphological analysis revealed that treatment with 50 ppm Al2O3 nanoparticles under flooding stress enhanced soybean growth compared to ZnO and Ag nanoparticles. A total of 172 common proteins that significantly changed in abundance among control, flooding-stressed, and flooding-stressed soybean treated with Al2O3 nanoparticles were mainly related to energy metabolism. Under Al2O3 nanoparticles the energy metabolism was decreased compared to flooding stress. Hierarchical clustering divided identified proteins into four clusters, with proteins related to glycolysis exhibiting the greatest changes in abundance. Al2O3 nanoparticle-responsive proteins were predominantly related to protein synthesis/degradation, glycolysis, and lipid metabolism. mRNA expression analysis of Al2O3 nanoparticle-responsive proteins that displayed a 5-fold change in abundance revealed that NmrA-like negative transcriptional regulator was up-regulated, and flavodoxin-like quinone reductase was down-regulated. Moreover, cell death in root including hypocotyl was less evident in flooding-stressed with Al2O3 nanoparticles compared to flooding-treated soybean. These results suggest that Al2O3 nanoparticles might promote the growth of soybean under flooding stress by regulating energy metabolism and cell death.

Pulmonary Inflammation Impacts on CYP1A1-Mediated Respiratory Tract DNA Damage Induced by the Carcinogenic Air Pollutant Benzo[a]pyrene

Pulmonary inflammation can contribute to the development of lung cancer in humans. We investigated whether pulmonary inflammation alters the genotoxicity of polycyclic aromatic hydrocarbons (PAHs) in the lungs of mice and what mechanisms are involved. To model nonallergic acute inflammation, mice were exposed intranasally to lipopolysaccharide (LPS; 20 µg/mouse) and then instilled intratracheally with benzo[a]pyrene (BaP; 0.5 mg/mouse). BaP-DNA adduct levels, measured by (32)P-postlabeling analysis, were approximately 3-fold higher in the lungs of LPS/BaP-treated mice than in mice treated with BaP alone. Pulmonary Cyp1a1 enzyme activity was decreased in LPS/BaP-treated mice relative to BaP-treated mice suggesting that pulmonary inflammation impacted on BaP-induced Cyp1a1 activity in the lung. Our results showed that Cyp1a1 appears to be important for BaP detoxification in vivo and that the decrease of pulmonary Cyp1a1 activity in LPS/BaP-treated mice results in a decrease of pulmonary BaP detoxification, thereby enhancing BaP genotoxicity (ie, DNA adduct formation) in the lung. Because less BaP was detoxified by Cyp1a1 in the lungs of LPS/BaP-treated mice, more BaP circulated via the blood to extrapulmonary tissues relative to mice treated with BaP only. Indeed, we observed higher BaP-DNA adduct levels in livers of LPS/BaP-treated mice compared with BaP-treated mice. Our results indicate that pulmonary inflammation could be a critical determinant in the induction of genotoxicity in the lung by PAHs like BaP. Cyp1a1 appears to be involved in both BaP bioactivation and detoxification although the contribution of other enzymes to BaP-DNA adduct formation in lung and liver under inflammatory conditions remains to be explored.

NQO1-induced activation of AMPK contributes to cancer cell death by oxygen-glucose deprivation

Oxygen and glucose deprivation (OGD) due to insufficient blood circulation can decrease cancer cell survival and proliferation in solid tumors. OGD increases the intracellular [AMP]/[ATP] ratio, thereby activating the AMPK. In this study, we have investigated the involvement of NQO1 in OGD-mediated AMPK activation and cancer cell death. We found that OGD activates AMPK in an NQO1-dependent manner, suppressing the mTOR/S6K/4E-BP1 pathway, which is known to control cell survival. Thus, the depletion of NQO1 prevents AMPK-induced cancer cell death in OGD. When we blocked OGD-induced Ca²⁺/CaMKII signaling, the NQO1-induced activation of AMPK was attenuated. In addition, when we blocked the RyR signaling, the accumulation of intracellular Ca²⁺ and subsequent activation of CaMKII/AMPK signaling was decreased in NQO1-expressing cells under OGD. Finally, siRNA-mediated knockdown of CD38 abrogated the OGD-induced activation of Ca²⁺/CaMKII/AMPK signaling. Taken together, we conclude that NQO1 plays a key role in the AMPK-induced cancer cell death in OGD through the CD38/cADPR/RyR/Ca²⁺/CaMKII signaling pathway.

Pesticides, gene polymorphisms, and bladder cancer among Egyptian agricultural workers

This study examined the associations between pesticide exposure, genetic polymorphisms for

NAD(P)H

quinone oxidoreductase I (NQO1) and superoxide dismutase 2 (SOD2), and urinary bladder cancer risk among male agricultural workers in Egypt. Logistic regression was used to analyze data from a multicenter case-control study and estimate adjusted odds ratio (OR) and 95% confidence interval (CI). Exposure to pesticides was associated with increased bladder cancer risk (odds ratio (95% confidence interval): 1.68 (1.23-2.29)) in a dose-dependent manner. The association was slightly stronger for urothelial (1.79 (1.25-2.56)) than for squamous cell (1.55 (1.03-2.31)), and among participants with combined genotypes for low NQO1 and high SOD2 (2.14 (1.19-3.85)) activities as compared with those with high NQO1 and low SOD2 genotypes (1.53 (0.73-3.25)). In conclusion, among male agricultural workers in Egypt, pesticide exposure is associated with bladder cancer risk and possibly modulated by genetic polymorphism.

Idebenone and neuroprotection: antioxidant, pro-oxidant, or electron carrier?

Ubiquinone, commonly called coenzyme Q10 (CoQ), is a lipophilic electron carrier and endogenous antioxidant found in all cellular membranes. In the mitochondrial inner membrane it transfers electrons to complex III of the electron transport chain. The short chain CoQ analogue idebenone is in clinical trials for a number of diseases that exhibit a mitochondrial etiology. Nevertheless, evidence that idebenone ameliorates neurological symptoms in human disease is inconsistent. Although championed as an antioxidant, idebenone can also act as a pro-oxidant by forming an unstable semiquinone at complex I. The antioxidant function of idebenone is critically dependent on two-electron reduction to idebenol without the creation of unstable intermediates. Recently, cytoplasmic

NAD(P)H

quinone oxidoreductase 1 (NQO1) was identified as a major enzyme catalyzing idebenone reduction. While reduction allows idebenone to act as an antioxidant, evidence also suggests that NQO1 enables idebenone to shuttle reducing equivalents from cytoplasmic NAD(P)H to mitochondrial complex III, bypassing any upstream damage to the electron transport chain. In this mini-review we discuss how idebenone can influence mitochondrial function within the context of cytoprotection. Importantly, in the brain NQO1 is expressed primarily by glia rather than neurons. As NQO1 is an inducible enzyme regulated by oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway, optimizing NQO1 expression in appropriate cell types within a specific disease context may be key to delivering on idebenone's therapeutic potential.

Correlation between CYP1A1 transcript, protein level, enzyme activity and DNA adduct formation in normal human mammary epithelial cell strains exposed to benzo[a]pyrene

The polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BP) is thought to bind covalently to DNA, through metabolism by cytochrome P450 1A1 (CYP1A1) and CYP1B1, and other enzymes, to form r7, t8, t9-trihydroxy-c-10-(N(2)-deoxyguanosyl)-7,8,9,10-tetrahydro-benzo[a]-pyrene (BPdG). Evaluation of RNA expression data, to understand the contribution of different metabolic enzymes to BPdG formation, is typically presented as fold-change observed upon BP exposure, leaving the actual number of RNA transcripts unknown. Here, we have quantified RNA copies/ng cDNA (RNA cpn) for CYP1A1 and CYP1B1, as well as

NAD(P)H

quinone oxidoreductase 1 (NQO1), which may reduce formation of BPdG adducts, using primary normal human mammary epithelial cell (NHMEC) strains, and the MCF-7 breast cancer cell line. In unexposed NHMECs, basal RNA cpn values were 58-836 for CYP1A1, 336-5587 for CYP1B1 and 5943-40112 for NQO1. In cells exposed to 4.0 µM BP for 12h, RNA cpn values were 251-13234 for CYP1A1, 4133-57078 for CYP1B1 and 4456-55887 for NQO1. There were 3.5 (mean, range 0.2-15.8) BPdG adducts/10(8) nucleotides in the NHMECs (n = 16), and 790 in the MCF-7s. In the NHMECs, BP-induced CYP1A1 RNA cpn was highly associated with BPdG (P = 0.002), but CYP1B1 and NQO1 were not. Western blots of four NHMEC strains, chosen for different levels of BPdG adducts, showed a linear correlation between BPdG and CYP1A1, but not CYP1B1 or NQO1. Ethoxyresorufin-O-deethylase (EROD) activity, which measures CYP1A1 and CYP1B1 together, correlated with BPdG, but NQO1 activity did not. Despite more numerous levels of CYP1B1 and NQO1 RNA cpn in unexposed and BP-exposed NHMECs and MCF-7cells, BPdG formation was only correlated with induction of CYP1A1 RNA cpn. The higher level of BPdG in MCF-7 cells, compared to NHMECs, may have been due to a much increased induction of CYP1A1 and EROD. Overall, BPdG correlation was observed with CYP1A1 protein and CYP1A1/1B1 enzyme activity, but not with CYP1B1 or NQO1 protein, or NQO1 enzyme activity.

Electrochemical monitoring of intracellular enzyme activity of single living mammalian cells by using a double-mediator system

We evaluated the intracellular

NAD(P)H

quinone oxidoreductase (NQO) activity of single HeLa cells by using the menadione-ferrocyanide double-mediator system combined with scanning electrochemical microscopy (SECM). The double-mediator system was used to amplify the current response from the intracellular NQO activity and to reduce menadione-induced cell damage. The electron shuttle between the electrode and menadione was mediated by the ferrocyanide/ferricyanide redox couple. Generation of ferrocyanide was observed immediately after the addition of a lower concentration (10 μM) of menadione. The ferrocyanide generation rate was constant for 120 min. At a higher menadione concentration (100 μM), the ferrocyanide generation rate decreased within 30 min because of the cytotoxic effect of menadione. We also investigated the relationship between intracellular reactive oxygen species or glutathione levels and exposure to different menadione concentrations to determine the optimal condition for SECM with minimal invasiveness. The present study clearly demonstrates that SECM is useful for the analysis of intracellular enzymatic activities in single cells with a double-mediator system.

Tropomyosin-1 protects endothelial cell-cell junctions against cigarette smoke extract through F-actin stabilization in EA.hy926 cell line

The aim of the study was to estimate the effect of cigarette smoke extract (CSE) on EA.hy926 endothelial cells in culture in the context of maintenance of cell-cell junctions through the structural stabilization of the actin cytoskeleton. In the present study, F-actin was stabilized by the overexpression of tropomyosin-1, which is known to stabilize actin filaments in muscle and non-muscle cells. Our study showed that the stabilization of F-actin significantly increased the survival of cells treated with 25% CSE. In addition, after stabilization of F-actin the migratory potential of EA.hy926 cells subjected to CSE treatment was increased. Our results also showed increased fluorescence intensity of alpha- and beta-catenin after CSE treatment in cells which had stabilized F-actin. Analysis of fluorescence intensity of Zonula occludens-1 did not reveal any significant differences when EA.hy926 cells overexpressing tropomyosin-1 were compared with those lacking overexpression. It would appear that overexpression of tropomyosin-1 preserved the structure of actin filaments in the cells treated with CSE. In conclusion, the present study demonstrates that stabilization of F-actin protects EA.hy926 cells against CSE-induced loss of both adherens and tight junctions. The data presented in this study suggest that overexpression of tropomyosin-1 stabilizes the organizational structure of actin filaments and helps preserve the endothelial barrier function under conditions of strong oxidative stress.

A meta-analysis of the association between NQO1 C609T variation and acute myeloid leukemia risk

Quinone oxidoreductase (NQO1) C609T polymorphisms have been implicated in acute myeloblastic leukemia (AML) risk, but previously published studies are inconsistent and recent meta-analyses have not been adequate. To derive a more precise estimation of the relationship, a meta-analysis was performed. Medline, PubMed, Embase, and Web of Science were searched. The quality of studies was evaluated by using the Newcastle-Ottawa Scale (NOS). Crude ORs with 95% CIs were used to assess the strength of association between the NQO1 C609T polymorphisms and AML risk. A total of 14 studies including 2,245 cases and 3,310 controls were involved in this meta-analysis. Overall, significantly elevated AML risk was associated with NQO1 C609T variant genotypes when all studies were pooled into the meta-analysis (TT vs. CC: OR = 1.44, 95% CI = 1.15-1.81; dominant model: OR = 1.35, 95% CI = 1.09-1.68). In the subgroup analysis by ethnicity, significantly increased risks were found for Asians (OR = 1.47, 95% CI = 1.13-1.93, P = 0.005, I(2) = 48.4%, P = 0.071 for heterogeneity). When stratified by studies of adults or children, statistically significantly elevated risks were found among adults (OR = 1.37, 95% CI = 1.06-1.76, P = 0.017, I(2) = 42.2%, P = 0.097 for heterogeneity). The accumulated evidence indicates that NQO1 C609T seems to confer a risk factor for AML among Asians and adults. Significant between-study heterogeneity was observed, thus more studies based on larger case-control population are required to further evaluate the role of NQO1 C609T polymorphism in AML.

NQO1 rs1800566 C>T polymorphism was associated with a decreased risk of esophageal cancer in a Chinese population

BACKGROUND. Esophageal cancer was the fifth most commonly diagnosed cancer and the fourth leading cause of cancer-related death in China in 2009. Esophageal squamous cell carcinoma (ESCC) accounts for more than 90% of esophageal cancers. Genetic factors may play an important role in the carcinogenesis of ESCC. METHODS. We conducted a hospital-based case-control study to evaluate functional

NAD(P)H

quinone oxidoreductase 1 (NQO1) rs1800566 C>T and NQO2 rs2070999 G>A single-nucleotide polymorphisms on the risk of ESCC. A total of 629 patients with ESCC and 686 controls were recruited for this study. The genotypes were determined using the ligation detection reaction method. RESULTS. When the NQO1 rs1800566 CC homozygote genotype was used as the reference group, the TT genotype was associated with a significantly decreased risk of ESCC. In the recessive model, when the NQO1 rs1800566 CC/CT genotypes were used as the reference group, the TT homozygote genotype was associated with a 31% decreased risk of ESCC. A significantly decreased risk of ESCC was evident in patients with the NQO1 rs1800566 C>T polymorphism among females, those of a younger age (<63 years), those who had never smoked, those who consumed alcohol and those who did not. There was no association found between the NQO2 rs2070999 G>A polymorphism and ESCC risk. CONCLUSION. The NQO1 rs1800566 TT genotype was associated with a decreased risk of ESCC in a Chinese population. The association was evident among female patients, younger patients, patients who had never smoked, patients who consumed alcohol and those who did not. These findings need to be confirmed by repeating the study in a larger cohort of patients.

Downregulation of proteins involved in the endoplasmic reticulum stress response and Nrf2-ARE signaling in lymphoblastoid cells of spinocerebellar ataxia type 17

Spinocerebellar ataxia type 17 (SCA17) is caused by CAG repeat expansion in the TATA-box binding protein gene. Studies of several polyglutamine (polyQ) expansion diseases have suggested that the expanded polyQ proteins misfold and induce oxidative stress to contribute to cell death. Substantial deficits in peripheral tissues including lymphocytes have been shown and these peripheral abnormalities could also be found in neurons possessing polyQ disease proteins. In this study, we used a lymphoblastoid cell model to investigate the functional implication of SCA17 expanded alleles and assess the potential therapeutic strategies that may ameliorate the effects of expanded polyQ. Proteomics studies of patient/control pairs including two-dimensional (2-D) gel electrophoresis, mass spectrometry and immunoblotting were conducted. A total of 8 proteins with reduced expression changes greater than 1.3-fold were identified, including previously reported HSPA5 and HSPA8. Among 6 proteins further semi-quantified by immunoblotting and real-time PCR, the reduced expression of HYOU1, PDIA3, P4HB, NQO1 and HMOX1 was confirmed. Treatment with resveratrol and genipin up-regulated NQO1 and HMOX1 expression and reduced oxidative stress in patients' lymphoblastoid cells. The results illustrate downregulation of proteins involved in the endoplasmic reticulum stress response (HYOU1, HSPA5, PDIA3, and P4HB) and Nrf2-ARE signaling (NQO1 and HMOX1) in SCA17 lymphoblastoid cells. Compounds increasing anti-oxidative activity such as resveratrol and genipin may serve as a potential therapeutic strategy for SCA17.

Genetic polymorphisms in NQO1 and SOD2: interactions with smoking, schistosoma infection, and bladder cancer risk in Egypt

BACKGROUND

Bladder cancer is the most prevalent form of cancer in men among Egyptians, for whom tobacco smoke exposure and Schistosoma haematobium (SH) infection are the major risk factors. We hypothesized that functional polymorphisms in

NAD(P)H

quinone oxidoreductase 1 (NQO1) and superoxide dismutase 2 (SOD2), modulators of the effects of reactive oxidative species, can influence an individual's susceptibility to these carcinogenic exposures and hence the risk of bladder cancer.

METHODS

We assessed the effects of potential interactions between functional polymorphisms in the NQO1 and SOD2 genes and exposure to smoking and SH infection on bladder cancer risk among 902 cases and 804 population-based controls in Egypt. We used unconditional logistic regression to estimate the odds ratios (OR) and confidence intervals (CI) 95%.

RESULTS

Water pipe and cigarette smoking were more strongly associated with cancer risk among individuals with the TT genotype for SOD2 (OR [CI 95%] = 4.41 [1.86-10.42]) as compared with those with the CC genotype (OR [CI 95%] = 2.26 [0.97-6.74]). Conversely, the risk associated with SH infection was higher among the latter (OR [CI 95%] = 3.59 [2.21-5.84]) than among the former (OR [CI 95%] = 1.86 [1.33-2.60]). Polymorphisms in NQO1 genotype showed a similar pattern, but to a much lesser extent. The highest odds for having bladder cancer following SH infection were observed among individuals with the CC genotypes for both NQO1 and SOD2 (OR [CI 95%] = 4.41 [2.32-8.38]).

CONCLUSION

Our findings suggest that genetic polymorphisms in NQO1 and SOD2 play important roles in the etiology of bladder cancer by modulating the effects of known contributing factors such as smoking and SH infection.

Epigenetic silencing of NAD(P)H:quinone oxidoreductase 1 by hepatitis B virus X protein increases mitochondrial injury and cellular susceptibility to oxidative stress in hepatoma cells

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a phase II enzyme that participates in the detoxification of dopamine-derived quinone molecules and reactive oxygen species. Our prior work using a proteomic approach found that NQO1 protein levels were significantly decreased in stable hepatitis B virus (HBV)-producing hepatoma cells relative to the empty-vector-transfected controls. However, the mechanism and biological significance of the NQO1 suppression remain elusive. In this study we demonstrate that HBV X protein (HBx) induces epigenetic silencing of NQO1 in hepatoma cells through promoter hypermethylation via recruitment of DNA methyltransferase DNMT3A to the promoter region of the NQO1 gene. In HBV-related hepatocellular carcinoma (HCC) specimens, HBx expression was correlated negatively to NQO1 transcripts but positively to NQO1 promoter hypermethylation. Downregulation of NQO1 by HBx reduced intracellular glutathione levels, impaired mitochondrial function, and increased susceptibility of hepatoma cells to oxidative stress-induced cell injury. These results suggest a novel mechanism for HBV-mediated pathogenesis of chronic liver diseases, including HCC.

A dual role for plant quinone reductases in host-fungus interaction

Quinone reductases (QR, EC 1.5.6.2) are flavoproteins that protect organisms from oxidative stress. The function of plant QRs has not as yet been addressed in vivo despite biochemical evidence for their involvement in redox reactions. Here, using knock-out (KO) and overexpressing lines, we studied the protective role of two groups of Arabidopsis thaliana cytosolic QRs, Nqr (NAD(P)H:quinone oxidoreductase) and Fqr (flavodoxin-like quinone reductase), in response to infection by necrotrophic fungi. The KO lines nqr(-) and fqr1(-) displayed significantly slower development of lesions of Botrytis cinerea and Sclerotinia sclerotium in comparison to the wild type (WT). Consistent with this observation, the overexpressing line FQR1(+) was hypersensitive to the pathogens. Both the nqr(-) and fqr1(-) displayed increased fluorescence of 2',7'-dichlorofluorescein,‬ a reporter for reactive oxygen species in response to B. cinerea. Infection by B. cinerea was accompanied with increased Nqr and Fqr1 protein levels in the WT as revealed by western blotting. In addition, a marked stimulation of salicylic acid-sensitive transcripts and suppression of jasmonate-sensitive transcripts was observed in moderately wounded QR KO mutant leaves, a condition mimicking the early stage of infection. In contrast to the above observations, germination of conidia was accelerated on leaves of QR KO mutants in comparison with the WT and FQR1(+). The same effect was observed in water-soluble leaf surface extracts. It is proposed that the altered interaction between B. cinerea and the QR mutants is a consequence of subtly altered redox state of the host, which perturbs host gene expression in response to environmental stress such as fungal growth.‬‬‬‬‬‬

Role of NAD(P)H:quinone oxidoreductase polymorphism at codon 187 in susceptibility to lung, laryngeal and oral/pharyngeal cancers

NAD(P)H:quinone oxidoreductase (NQO1) has been proposed to play a protective role against the toxic effects of benzo[a]pyrene quinones. The C(609)T base change in the NQO1 gene, resulting in a Pro(187)Ser amino acid change in the protein, has been associated with deficient enzyme activity. We examined whether this polymorphism modified the risks of smoking-related cancers in a case-control study involving patients with lung cancer (n = 150), laryngeal cancer (n = 129), oral/pharyngeal cancer (n = 121) and control individuals (n = 172), all Caucasian smokers. No statistically significant associations were observed between the NQO1 genotypes and smoking-related cancers, although the Ser/Ser genotype was associated with a tendency towards increased risk for lung cancer (odds ratio [OR] = 2.2, 95% confidence interval [CI] 0.7-6.7) and for oral/pharyngeal cancer (OR = 2.3, 95% CI 0.6-8.2). No significant interaction between the NQO1 genotype and either smoking exposure or GSTM1 genotype was found. Our results are consistent with the hypothesis that lack of NQO1 activity may be involved in some smoking-related cancers. However, they were based on small numbers of individuals with the putative atrisk genotype, and the associations did not reach statistical significance. Moreover, these results contrast with those observed in some other ethnic populations, where a protective effect of the NQO1 Ser allele was found. Further studies are therefore clearly needed for a better understanding of the potential role of NQO1 activity in tobacco-related cancers.

Enhancement of radiation effect using beta-lapachone and underlying mechanism

Beta-lapachone (β-Lap; 3,4-dihydro-2, 2-dimethyl-2H-naphthol[1, 2-b]pyran-5,6-dione) is a novel anti-cancer drug under phase I/II clinical trials. β-Lap has been demonstrated to cause apoptotic and necrotic death in a variety of human cancer cells in vitro and in vivo. The mechanisms underlying the β-Lap toxicity against cancer cells has been controversial. The most recent view is that β-Lap, which is a quinone compound, undergoes two-electron reduction to hydroquinone form utilizing NAD(P)H or NADH as electron source. This two-electron reduction of β-Lap is mediated by NAD(P)H:quinone oxidoreductase (NQO1), which is known to mediate the reduction of many quinone compounds. The hydroquinone forms of β-Lap then spontaneously oxidizes back to the original oxidized β-Lap, creating futile cycling between the oxidized and reduced forms of β-Lap. It is proposed that the futile recycling between oxidized and reduced forms of β-Lap leads to two distinct cell death pathways. First one is that the two-electron reduced β-Lap is converted first to one-electron reduced β-Lap, i.e., semiquinone β-Lap (SQ)(·-) causing production of reactive oxygen species (ROS), which then causes apoptotic cell death. The second mechanism is that severe depletion of NAD(P)H and NADH as a result of futile cycling between the quinone and hydroquinone forms of β-Lap causes severe disturbance in cellular metabolism leading to apoptosis and necrosis. The relative importance of the aforementioned two mechanisms, i.e., generation of ROS or depletion of NAD(P)H/NADH, may vary depending on cell type and environment. Importantly, the NQO1 level in cancer cells has been found to be higher than that in normal cells indicating that β-Lap may be preferentially toxic to cancer cells relative to non-cancer cells. The cellular level of NQO1 has been found to be significantly increased by divergent physical and chemical stresses including ionizing radiation. Recent reports clearly demonstrated that β-Lap and ionizing radiation kill cancer cells in a synergistic manner. Indications are that irradiation of cancer cells causes long-lasting elevation of NQO1, thereby sensitizing the cells to β-Lap. In addition, β-Lap has been shown to inhibit the repair of sublethal radiation damage. Treating experimental tumors growing in the legs of mice with irradiation and intraperitoneal injection of β-Lap suppressed the growth of the tumors in a manner more than additive. Collectively, β-Lap is a potentially useful anti-cancer drug, particularly in combination with radiotherapy.

AMPK synergizes with the combined treatment of 1'-acetoxychavicol acetate and sodium butyrate to upregulate phase II detoxifying enzyme activities

SCOPE

Phase II enzymes play important roles in detoxifying xenobiotics. We previously reported that both 1'-acetoxychavicol acetate (ACA) and sodium butyrate individually increased phase II enzyme activities. Here, we determined the combined action of ACA and sodium butyrate on phase II enzyme activities in intestinal epithelial cells (IEC 6).

METHODS AND RESULTS

ACA and sodium butyrate synergistically increased phase II enzyme activities. Protein levels of intranuclear transcription factor NF-E2-related factor 2 (Nrf2) were increased by ACA or sodium butyrate treatment, but treatment with both did not produce a synergistic effect. Intranuclear p53 protein levels were increased by ACA but decreased by sodium butyrate alone or combined treatment with ACA and sodium butyrate. In contrast, p53 acetylation was promoted by sodium butyrate and the ACA and sodium butyrate combination. Inhibition of AMPK activity decreased phase II enzyme activities that were upregulated by treatment with ACA plus sodium butyrate or other phytochemicals, including kaempferol, quercetin, and epigallocatechin-3-gallate. Combined treatment with ACA and sodium butyrate increased phosphorylated AMPK levels.

CONCLUSION

These results suggest that ACA and sodium butyrate synergistically contribute to xenobiotics metabolism. The combined ACA and sodium butyrate treatment synergistically upregulated phase II enzyme activities through AMPK activation and p53 acetylation.

Emerging role of Nrf2 in adipocytes and adipose biology

Maintenance of a balanced redox state within the cell is of critical importance to a wide variety of biological systems. Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a critical regulator of key aspects of the antioxidant defense pathway and has long been a subject of interest regarding conditions of chronic stress such as inflammation and cancer. Recent data have emerged demonstrating that oxidative stress and Nrf2 also play critical roles in the biology of adipose tissue. This review examines data identifying the roles of Nrf2 and oxidative stress in the biological process of adipose cell differentiation as well as the implications of Nrf2 modulation on obesity. Working to understand the complex interplay among Nrf2, oxidative stress, and adipose biology could lead to a variety of possible treatments for obesity and other related disorders.

Lack of association between NADPH quinone oxidoreductase 1 (NQO1) gene C609T polymorphism and lung cancer: a case-control study and a meta-analysis

Background

The association between NAD(P)H:quinone oxidoreductase 1 (NQO1) gene C609T polymorphism (rs1800566) and lung cancer has been widely evaluated, and a definitive answer so far is lacking. We first conducted a case-control study to assess this association in northeastern Han Chinese, and then performed a meta-analysis to further address this issue.

Methodology/Principal Findings

This case-control study involved 684 patients clinically diagnosed as lung cancer and 602 age-matched cancer-free controls from Harbin city, Heilongjiang province, China. Genotyping was conducted using the PCR-LDR (ligase detection reactions) method. Meta-analysis was managed by STATA software. Data and study quality were assessed in duplicate. Our case-control association study indicated no significant difference in the genotype and allele distributions of C609T polymorphism between lung cancer patients and controls, consistent with the results of the further meta-analysis involving 7286 patients and 9167 controls under both allelic (odds ratio (OR) = 0.99; 95% confidence interval (CI): 0.92–1.06; P = 0.692) and dominant (OR = 0.98; 95% CI: 0.89–1.08; P = 0.637) models. However, there was moderate evidence of between-study heterogeneity and low probability of publication bias. Further subgroup analyses by ethnicity, source of controls and sample size detected no positive associations in this meta-analysis.

Conclusions

Our study in northeastern Han Chinese, along with the meta-analysis, failed to confirm the association of NQO1 gene C609T polymorphism with lung cancer risk, even across different ethnic populations.

The impact of Triton WR-1339 induced hyperlipidemia on the effects of benzo(a)pyrene or guaiacol on α- and γ-tocopherol pools and selected markers of pro-/antioxidative balance in rat plasma and erythrocytes

The toxicity of carcinogenic benzo(a)pyrene (BaP) can be intensified by the pro-oxidative effects of metabolic activation. The oxidatively active products can be formed during enzymatic biotransformation or in the process of co-oxygenation with lipid peroxidation. This study assesses if the acute hyperlipidemia can increase pro-oxidative effects of BaP as a factor intensifying processes of lipid peroxidation and co-oxygenation. After three days of i.p. administration of BaP or guaiacol (equimolar dose 10mg/kg b.w.) without or with the hyperlipidemia inducer-Triton WR-1339 to male Wistar rats, the levels of α- and γ-tocopherol were measured in erythrocytes and plasma together with the level of lipid peroxidation as malonyldialdehyde (MDA) concentration. Guaiacol was chosen as a reference substance due to its high ability to co-oxygenate. Additionally, the activity of superoxide dismutase (Cu,ZnSOD) in erythrocytes and plasma was monitored. In normolipaemic groups the significant decrease in erythrocyte α-tocopherol pool and the increase in lipid peroxidation level were observed after BaP or guaiacol administration. In hyperlipaemic groups, despite the increase in the level of lipid peroxidation, there were no additional effects in tocopherol pools compared to the normolipaemic groups which could be attributed to co-oxygenation. Decrease of α-tocopherol in erythrocytes was proportional to the reduction in normolipemic subjects when accounting for the migration to hyperlipemic plasma. There was no co-oxygenation effect on the activity of superoxide dismutase (Cu,ZnSOD) in blood.

Contribution of NAD(P)H quinone oxidoreductase 1 (NQO1) Pro187Ser polymorphism and risk of colorectal adenoma and colorectal cancer in Caucasians: a meta-analysis

BACKGROUND AND AIMS

The effects of polymorphism of NAD(P)H quinone oxidoreductase 1 (NQO1 Pro187Ser, rs1800566) on the risks of colorectal adenoma and cancer have been widely studied and results remain controversial. Therefore, the aim of this meta-analysis was to quantitatively assess the relationships.

METHODS

Databases of Medline, Embase and Wanfang were retrieved until May 15, 2011. Pooled odds ratio (OR) and 95% confidence interval (95% CI) as effect sizes were calculated by using fixed- or random-effect model. Cochrane Q-test was used to explore between-study heterogeneity; p <0.10 indicated statistical significance.

RESULTS

A total of 12 case-control studies with 11,700 individuals (including 5528 cases and 6172 controls) were included in this meta-analysis. Of these studies, four studies conducted in Caucasian populations were for colorectal adenoma, and eight studies were for colorectal cancer. NQO1 187Ser allele was significantly associated with increased risk of colorectal adenoma in co-dominant and dominant comparison models (OR = 1.07, 95% CI = 1.04-1.32 for ProSer vs. ProPro and OR = 1.19, 95% CI = 1.06-1.33 for Ser carries vs. ProPro), without between-study heterogeneity. Overall, NQO1 Pro187Ser was not associated with risk of colorectal cancer, without between-study heterogeneity. Subgroup analyses indicated that Ser allele was significantly associated with increased risk of colorectal cancer for Caucasians (OR = 1.14, 95% CI = 1.00-1.30 for ProSer vs. ProPro and OR = 1.16, 95% CI = 1.02-1.31 for Ser carries vs. ProPro).

CONCLUSIONS

This meta-analysis suggested that Ser allele of NQO1 Pro187Ser significantly contributed to the increased risks of colorectal adenoma and cancer in Caucasians.

System review and metaanalysis of the relationships between five metabolic gene polymorphisms and colorectal adenoma risk

The relationships between some metabolic (including EPHX1, GSTs and NQO1) gene polymorphisms and colorectal adenoma (CRA) risk have been commonly studied, and no conclusions are available up to now. Therefore, we quantitatively studied the relationships by a metaanalysis. The databases of Medline and Embase were retrieved updated to June 15th, 2011. Crude or adjusted odds ratio (crude OR or adjusted OR) and 95% confidence interval (95%CI) were calculated to present the strength of the associations. Overall, nine case-control studies for EPHX1 Tyr113His and His139Arg, five case-control studies for GSTM1, four studies for GSTP1 Ile105Val, two studies for GSTP1 Ala114Val, six studies for GSTT1 and four studies for NQO1 Pro187Ser were included in this metaanalysis. The results of combined analyses indicated that EPHX1 Tyr113His and His139Arg, GSTT1, GSTM1, GSTP1 Ile105Val and Ala114Val were not associated with CRA risk [crude OR (95%CI): 0.98 (0.90-1.07) and P ( z-test) = 0.65 for EPHX1 His carriers vs. Tyr/Tyr; 1.05 (0.97-1.15) and P ( z-test) = 0.21 for EPHX1 Arg carriers vs. His/His; 1.05 (0.92-1.20) and P ( z-test) = 0.47 for GSTT1 Null vs. Present; 1.01 (0.90-1.13) and P ( z-test) = 0.90 for GSTM1 Null vs. Present; 1.04 (0.92-1.17) and P ( z-test) = 0.56 for G carriers vs. AA for GSTP1 Ile105Val; 0.88 (0.70-1.11) and P ( z-test) = 0.28 for T carriers vs. CC for GSTP1 Ala114Val]. In contrast, Ser allele of NQO1 Ser187Pro might be a modest risk factor for CRA development [1.19 (1.06-1.33) and P ( z-test) = 0.003 for Ser carriers vs. Pro/Pro]. To get more precise evidences, adjusted ORs (95%CI) for EPHX1 Tyr113His, His139Arg, GSTP1 Ile105Val and NQO1 Ser187Pro were also calculated based on adjusted ORs (95%CIs) reported in primary studies. The results still indicated that EPHX1 Tyr113His, His139Arg and GSTP1 Ile105Val were not associated with CRA risk except for NQO1 Ser187Pro. When subgroup analyses were performed for population-based case-control studies or studies in HWE for EPHX1 Tyr113His and His139Arg, and NQO1 Ser187Pro polymorphisms, the results were persistent. Although with modest limitations and biases, this metaanalysis suggests that EPHX1 Tyr113His and His139Arg, GSTT1, GSTM1, GSTP1 Ile105Val and Ala114Val polymorphisms may be not risk factors for CRA development, while Ser allele of NQO1 Ser187 Pro may be a modest risk factor for CRA development, and may be used with other genetic markers for screening CRA in the future.

Specificity of human aldo-keto reductases, NAD(P)H:quinone oxidoreductase, and carbonyl reductases to redox-cycle polycyclic aromatic hydrocarbon diones and 4-hydroxyequilenin-o-quinone

Polycyclic aromatic hydrocarbons (PAHs) are suspect human lung carcinogens and can be metabolically activated to remote quinones, for example, benzo[a]pyrene-1,6-dione (B[a]P-1,6-dione) and B[a]P-3,6-dione by the action of either P450 monooxygenase or peroxidases, and to non-K region o-quinones, for example B[a]P-7,8-dione, by the action of aldo keto reductases (AKRs). B[a]P-7,8-dione also structurally resembles 4-hydroxyequilenin o-quinone. These three classes of quinones can redox cycle, generate reactive oxygen species (ROS), and produce the mutagenic lesion 8-oxo-dGuo and may contribute to PAH- and estrogen-induced carcinogenesis. We compared the ability of a complete panel of human recombinant AKRs to catalyze the reduction of PAH o-quinones in the phenanthrene, chrysene, pyrene, and anthracene series. The specific activities for NADPH-dependent quinone reduction were often 100-1000 times greater than the ability of the same AKR isoform to oxidize the cognate PAH-trans-dihydrodiol. However, the AKR with the highest quinone reductase activity for a particular PAH o-quinone was not always identical to the AKR isoform with the highest dihydrodiol dehydrogenase activity for the respective PAH-trans-dihydrodiol. Discrete AKRs also catalyzed the reduction of B[a]P-1,6-dione, B[a]P-3,6-dione, and 4-hydroxyequilenin o-quinone. Concurrent measurements of oxygen consumption, superoxide anion, and hydrogen peroxide formation established that ROS were produced as a result of the redox cycling. When compared with human recombinant NAD(P)H:quinone oxidoreductase (NQO1) and carbonyl reductases (CBR1 and CBR3), NQO1 was a superior catalyst of these reactions followed by AKRs and last CBR1 and CBR3. In A549 cells, two-electron reduction of PAH o-quinones causes intracellular ROS formation. ROS formation was unaffected by the addition of dicumarol, suggesting that NQO1 is not responsible for the two-electron reduction observed and does not offer protection against ROS formation from PAH o-quinones.

Nrf2-dependent induction of NQO1 in mouse aortic endothelial cells overexpressing catalase

Overexpression of catalase has been shown to accelerate benzo(a)pyrene (BaP) detoxification in mouse aortic endothelial cells (MAECs). NAD(P)H:quinone oxidoreductase-1 (NQO1) is an enzyme that catalyzes BaP-quinone detoxification. Aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor-2 (Nrf2) are transcription factors that control NQO1 expression. Here, we investigated the effects of catalase overexpression on NQO1, Nrf2, and AhR expression. The levels of NQO1 mRNA and protein were comparable in MAECs isolated from wild-type and transgenic mice that overexpress human catalase (hCatTg). BaP treatment increased NQO1 mRNA and protein levels in both groups, with a significantly greater induction in hCatTg MAECs than in wild-type cells. BaP-induced NQO1 promoter activity was dramatically higher in hCatTg MAECs than in wild-type cells. Our data also showed that the basal level of AhR and the BaP-induced level of Nrf2 were significantly higher in hCatTg MAECs than in wild-type cells. Inhibition of specificity protein-1 (Sp1) binding to the AhR promoter region by mithramycin A reversed the enhancing effect of catalase overexpression on AhR expression. Knockdown of AhR by RNA interference diminished BaP-induced expression of Nrf2 and NQO1. Knockdown of Nrf2 significantly decreased NQO1 mRNA and protein levels in cells with or without BaP treatment. NQO1 promoter activity was abrogated by mutation of the Nrf2-binding site in this promoter. In contrast, mutation of the AhR-binding site in the NQO1 promoter did not affect the promoter activity. These results suggest that catalase overexpression upregulates BaP-induced NQO1 expression by enhancing the Sp1-AhR-Nrf2 signaling cascade.

Disruption of NAD(P)H:quinone oxidoreductase 1 gene in mice leads to 20S proteasomal degradation of p63 resulting in thinning of epithelium and chemical-induced skin cancer

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme that protects cells against chemical and radiation-induced oxidative stress and skin cancer. Disruption of NQO1 gene in mice showed thinning of skin epithelium and loss of cytokeratin 14, an early marker of skin differentiation. Immunohistochemistry and western analysis demonstrated downregulation of p63 in NQO1-/- mouse skin, as compared with wild-type (WT) mouse. Further analysis including modulation of NQO1 expression revealed a direct correlation between the levels of NQO1 and p63 in skin-derived keratinocytes and dermal fibroblasts. Modulation of proteasomal activity revealed that p63 is degraded by 20S proteasome and that this degradation is significantly rescued by NQO1. Coimmunoprecipitation studies showed that NQO1 interacts directly with p63 but not 20S to protect against this degradation. In addition, benzo[a]pyrene treatment led to induction of NQO1 and stabilization of p63 in WT but not in NQO1-/- mouse skin and keratinocytes. These data suggest that NQO1 controls stabilization of p63 and progression towards keratinocyte differentiation leading to normal skin development and presumably skin carcinogenesis.

NAD(P)H:quinone oxidoreductase 1 Pro187Ser polymorphism and the risk of lung cancer: A meta-analysis

BACKGROUND

NAD(P)H:quinine oxidoreductase 1 (NQO1) is a two-electron reductase that catalyzes quinine to hydroquinone. Variant genotypes of NQO1 Pro187Ser may be related to low enzyme activity and thus are suggested as affecting the risk of lung cancer. Our purpose was to study the NQO1 Pro187Ser polymorphism and the risk of lung cancer.

METHODS

We conducted a PubMed search and a China National Knowledge Infrastructure search using "NAD(P)H quinine reductase 1" ,"lung cancer", and " polymorphism" for articles published from January 1997 to March 2010. For each study, we calculated the crude odds ratios (OR) and 95% confidence intervals (CI) for lung cancer. Summary estimates for crude as well as adjusted OR were calculated with the statistical program stata.

RESULTS

The summary OR for carrying one variant allele and the homozygous variant genotype was 1.04 (95%CI, 0.97-1.13). In the Asian population, the summary OR for carrying one variant genotype was 1.09 (95%CI, 0.95-1.25).

CONCLUSIONS

Through our meta-analysis, we found that the Pro/Ser and Ser/Ser genotypes involving NQO1 were non-significantly associated with lung cancer. In the Asian population, the combined genotype was marginally associated with increased risk of lung cancer. When stratified on gender and smoking, the meta-analysis showed that there was no statistically significant difference between men and women, smokers and non-smokers, respectively.

Colon cancer chemopreventive activities of pomegranate ellagitannins and urolithins

Pomegranate juice derived ellagitannins and their intestinal bacterial metabolites, urolithins, inhibited TCDD-induced CYP1-mediated EROD activity in vitro with IC(50) values ranging from 56.7 microM for urolithin A to 74.8 microM for urolithin C. These compounds exhibited dose- and time-dependent decreases in cell proliferation and clonogenic efficiency of HT-29 cells. Inhibition of cell proliferation was mediated through cell cycle arrest in the G(0)/G(1) and G(2)/M stages of the cell cycle followed by induction of apoptosis. These results indicate that the ellagitannins and urolithins released in the colon upon consumption of pomegranate juice in considerable amounts could potentially curtail the risk of colon cancer development, by inhibiting cell proliferation and inducing apoptosis.