Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pretreating mice with schisandrin B (Sch B), a dibenzocyclooctadiene derivative isolated from the fruit of Schisandra chinensis, at a daily dose of 1 mmol/kg for 3 days protected against menadione-induced hepatic oxidative damage in mice, as evidenced by decreases in plasma alanine aminotransferase activity (78%) and hepatic malondialdehyde level (70%), when compared with the menadione intoxicated control. In order to define the biochemical mechanism involved in the hepatoprotection afforded by Sch B pretreatment, we examined the activity of DT-diaphorase (DTD) in hepatocytes isolated from Sch B pretreated rats. Hepatocytes isolated from Sch B pretreated (a daily dose of 1 mmol/kg for 3 days) rats showed a significant increase (25%) in DTD activity. The increase in DTD activity was associated with the enhanced rate of menadione elimination in the hepatocyte culture. The ensemble of results suggests that the ability of Sch B pretreatment to enhance hepatocellular DTD activity may at least in part be attributed to the protection against menadione hepatotoxicity.
Mol Cell Biochem 2000 May
PMID:Schisandrin B protects against menadione-induced hepatotoxicity by enhancing DT-diaphorase activity. 1093 39

Ras-induced cell transformation is mediated through distinct downstream signaling pathways, including Raf, Ral-GEFs-, and phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathways. In some cell types, strong activation of the Ras-Raf-MEK-extracellular signal-regulated kinase (ERK) cascade leads to cell cycle arrest rather than cell division. We previously reported that constitutive activation of this pathway induces sustained proliferation of primary cultures of postmitotic chicken neuroretina (NR) cells. We used this model system to investigate the respective contributions of Ras downstream signaling pathways in Ras-induced cell proliferation. Three RasV12 mutants (S35, G37, and C40) which differ by their ability to bind to Ras effectors (Raf, Ral-GEFs, and the p110 subunit of PI 3-kinase, respectively) were able to induce sustained NR cell proliferation, although none of these mutants was reported to transform NIH 3T3 cells. Furthermore, they all repressed the promoter of QR1, a neuroretina growth arrest-specific gene. Overexpression of B-Raf or activated versions of Ras effectors Rlf-CAAX and p110-CAAX also induced NR cell division. The mitogenic effect of the RasC40-PI 3-kinase pathway appears to involve Rac and RhoA GTPases but not the antiapoptotic Akt (protein kinase B) signaling. Division induced by RasG37-Rlf appears to be independent of Ral GTPase activation and presumably requires an unidentified mechanism. Activation of either Ras downstream pathway resulted in ERK activation, and coexpression of a dominant negative MEK mutant or mKsr-1 kinase domain strongly inhibited proliferation induced by the three Ras mutants or by their effectors. Similar effects were observed with dominant negative mutants of Rac and Rho. Thus, both the Raf-MEK-ERK and Rac-Rho pathways are absolutely required for Ras-induced NR cell division. Activation of these two pathways by the three distinct Ras downstream effectors possibly relies on an autocrine or paracrine loop, implicating endogenous Ras, since the mitogenic effect of each Ras effector mutant was inhibited by RasN17.
Mol Cell Biol 2000 Oct
PMID:Induction of postmitotic neuroretina cell proliferation by distinct Ras downstream signaling pathways. 1098 23

Many tumors overexpress the NQO1 gene, which encodes DT-diaphorase (NADPH:quinone oxidoreductase; EC 1.6.99.2). This obligate two-electron reductase deactivates toxins and activates bioreductive anticancer drugs. We describe the establishment of an isogenic human tumor cell model for DT-diaphorase expression. An expression vector was used in which the human elongation factor 1alpha promoter produces a bicistronic message containing the genes for human NQO1 and puromycin resistance. This was transfected into the human colon BE tumor line, which has a disabling point mutation in NQO1. Two clones, BE2 and BE5, were selected that were shown by immunoblotting and enzyme activity to stably express high levels of DT-diaphorase. Drug response was determined using 96-h exposures compared with the BE vector control. Functional validation of the isogenic model was provided by the much greater sensitivity of the NQO1-transfected cells to the known DT-diaphorase substrates and bioreductive agents streptonigrin (113- to 132-fold) and indoloquinone EO9 (17- to 25-fold) and the inhibition of this potentiation by the DT-diaphorase inhibitor dicoumarol. A lower degree of potentiation was seen with the clinically used agent mitomycin C (6- to 7-fold) and the EO9 analogs, EO7 and EO2, that are poorer substrates for DT-diaphorase (5- to 8-fold and 2- to 3-fold potentiation, respectively), and there was no potentiation or protection with menadione and tirapazamine. Exposure time-dependent potentiation was seen with the diaziquone analogs methyl-diaziquone and RH1 [2, 5-diaziridinyl-3-(hydroxymethyl)-6-methyl-1,4-benzoquinone], the latter being an agent in preclinical development. In contrast to the in vitro potentiation, there was no difference in the response to mitomycin C when BE2 and BE vector control were treated as tumor xenografts in vivo. This isogenic model should be valuable for mechanistic studies and bioreductive drug development.
Mol Pharmacol 2000 Nov
PMID:Establishment of an isogenic human colon tumor model for NQO1 gene expression: application to investigate the role of DT-diaphorase in bioreductive drug activation in vitro and in vivo. 1104 64

The effect of two different doses (50 and 100 mg/kg body wt/day for 14 days) of 80% ethanolic extract of the leaves of Adhatoda vesica were examined on drug metabolizing phase I and phase II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase and lipid peroxidation in the liver of 8 weeks old Swiss albino mice. The modulatory effect of the extract was also examined on extra-hepatic organs viz. lung, kidney and forestomach for the activities of glutathione S-transferase, DT-diaphorase, superoxide dismutase and catalase. Significant increase in the activities of acid soluble sulfhydryl (-SH) content, cytochrome P450, NADPH-cytochrome P450 reductase, cytochrome b5, NADH-cytochrome b5 reductase, glutathione S-transferase (GST), DT-diaphorase (DTD), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were observed in the liver at both dose levels of treatments. Adhatoda vesica acted as bifunctional inducer since it induced both phase I and phase II enzyme systems. Both the treated groups showed significant decrease in malondialdehyde (MDA) formation in liver, suggesting its role in protection against prooxidant induced membrane damage. The cytosolic protein was significantly inhibited at both the dose levels of treatment indicating the possibility of its involvement in the inhibition of protein synthesis. BHA has significantly induced the activities of GR and GSH in the present study. The extract was effective in inducing GST and DTD in lung and forestomach, and SOD and CAT in kidney. Thus, besides liver, other organs viz., lung, kidney and forestomach were also stimulated by Adhatoda, to increase the potential of the machinery associated with the detoxification of xenobiotic compounds. But, liver and lung showed a more consistent induction. Since the study of induction of the phase I and phase II enzymes is considered to be a reliable marker for evaluating the chemopreventive efficacy of a particular compound, these findings are suggestive of the possible chemopreventive role played by Adhatoda leaf extract.
Mol Cell Biochem 2000 Oct
PMID:Modulatory influence of Adhatoda vesica (Justicia adhatoda) leaf extract on the enzymes of xenobiotic metabolism, antioxidant status and lipid peroxidation in mice. 1112 64

The NAD(P)H:quinone oxidoreductase 1 (NQO1)*2 polymorphism is characterized by a single proline-to-serine amino acid substitution. Cell lines and tissues from organisms genotyped as homozygous for the NQO1*2 polymorphism are deficient in NQO1 activity. In studies with cells homozygous for the wild-type allele and cells homozygous for the mutant NQO1*2 allele, no difference in the half-life of NQO1 mRNA transcripts was observed. Similarly, in vitro transcription/translation studies showed that both wild-type and mutant NQO1 coding regions were transcribed and translated into full-length protein with equal efficiency. Protein turnover studies in NQO1 wild-type and mutant cell lines demonstrated that the half-life of wild-type NQO1 was greater than 18 h, whereas the half-life of mutant NQO1 was 1.2 h. Incubation of NQO1 mutant cell lines with proteasome inhibitors increased the amount of immunoreactive NQO1 protein, suggesting that mutant protein may be degraded via the proteasome pathway. Additional studies were performed using purified recombinant NQO1 wild-type and mutant proteins incubated in a rabbit reticulocyte lysate system. In these studies, no degradation of wild-type NQO1 protein was observed; however, mutant NQO1 protein was completely degraded in 2 h. Degradation of mutant NQO1 was inhibited by proteasome inhibitors and was ATP-dependent. Mutant NQO1 incubated in rabbit reticulocyte lysate with MG132 resulted in the accumulation of proteins with increased molecular masses that were immunoreactive for both NQO1 and ubiquitin. These data suggest that wild-type NQO1 persists in cells whereas mutant NQO1 is rapidly degraded via ubiquitination and proteasome degradation.
Mol Pharmacol 2001 Feb
PMID:Rapid polyubiquitination and proteasomal degradation of a mutant form of NAD(P)H:quinone oxidoreductase 1. 1116 Aug 62

Estrogens exert profound effects on the physiology of diverse target cells and these effects appear to be mediated by two estrogen receptor (ER) subtypes, ERalpha and ERbeta. We have investigated how ER ligands, ranging from pure agonists to antagonists, interact with ERalpha and ERbeta, and regulate their transcriptional activity on different genes. Mutational mapping-structure activity studies indicate that different residues of the ER ligand binding domain are involved in the recognition of structurally distinct estrogens and antiestrogens. We have identified from ligands of diverse structure, several particularly interesting ones that are high potency selective agonists via ERalpha and others that are full agonists through ERalpha while being full antagonists through ERbeta. Antiestrogens such as hydroxytamoxifen, which are mixed agonist/antagonists through ERalpha, are pure antagonists through ERbeta at estrogen response element-containing gene sites. Studies with ERalpha/beta chimeric proteins reveal that tamoxifen agonism requires the activation function 1 region of ERalpha. Through two-hybrid assays, we have isolated an ER-specific coregulator that potentiates antiestrogen antagonist effectiveness and represses ER transcriptional activity. We have also focused on understanding the distinct pharmacologies of antiestrogen- and estrogen-regulated genes. Although antiestrogens are thought to largely act by antagonizing the actions of estrogens, we have found among several new ER-regulated genes, quinone reductase (QR), a detoxifying phase II antioxidant enzyme, that has its activity up-regulated by antiestrogens in an ER-dependent manner in breast cancer cells. This response is antagonized by estrogens, thus showing 'reversed pharmacology'. Increased QR activity by antiestrogens requires a functional ER (ERalpha or ERbeta) and is, interestingly, mediated via the electrophile response element in the QR gene 5' regulatory region. The up-regulation of QR may contribute to the beneficial effects of tamoxifen, raloxifene, and other antiestrogens in breast cancer prevention and treatment. Estrogens rapidly up-regulate expression of several genes associated with cell cytoarchitectural changes including NHE-RF, the sodium hydrogen exchanger regulatory factor, also known as EBP50. NHE-RF/EBP50 is enriched in microvilli, and may serve as a scaffold adaptor protein in regulating early changes in cell architecture and signal transduction events induced by estrogen. Analyses of the regulatory regions of these primary response genes, and the antioxidant and other signaling pathways involved, are providing considerable insight into the mechanisms by which ligands, that function as selective estrogen receptor modulators or SERMs, exert their marked effects on the activities and properties of target cells. The intriguing biology of estrogens in its diverse target cells is thus determined by the structure of the ligand, the ER subtype involved, the nature of the hormone-responsive gene promoter, and the character and balance of coactivators and corepressors that modulate the cellular response to the ER-ligand complex. The continuing development of ligands that function as selective estrogens or antiestrogens for ERalpha or ERbeta should allow optimized tissue selectivity of these agents for menopausal hormone replacement therapy and the treatment and prevention of breast cancer.
J Steroid Biochem Mol Biol 2000 Nov 30
PMID:Molecular mechanisms of estrogen action: selective ligands and receptor pharmacology. 1116 36

We previously described the identification of quail MafA, a novel transcription factor of the Maf bZIP (basic region leucine zipper) family, expressed in the differentiating neuroretina (NR). In the present study, we provide the first evidence that MafA is phosphorylated and that its biological properties strongly rely upon phosphorylation of serines 14 and 65, two residues located in the transcriptional activating domain within a consensus for phosphorylation by mitogen-activated protein kinases and which are conserved among Maf proteins. These residues are phosphorylated by ERK2 but not by p38, JNK, and ERK5 in vitro. However, the contribution of the MEK/ERK pathway to MafA phosphorylation in vivo appears to be moderate, implicating another kinase. The integrity of serine 14 and serine 65 residues is required for transcriptional activity, since their mutation into alanine severely impairs MafA capacity to activate transcription. Furthermore, we show that the MafA S14A/S65A mutant displays reduced capacity to induce expression of QR1, an NR-specific target of Maf proteins. Likewise, the integrity of serines 14 and 65 is essential for the MafA ability to stimulate expression of crystallin genes in NR cells and to induce NR-to-lens transdifferentiation. Thus, the MafA capacity to induce differentiation programs is dependent on its phosphorylation.
Mol Cell Biol 2001 Jul
PMID:Phosphorylation of MafA is essential for its transcriptional and biological properties. 1141 24

Although molecular dating of cladogenetic events is possible, no molecular method has been described to date the acquisition of various tissues. Taking into account the specificity of the major protein in enamel in formation (amelogenin), we were able to develop such a method for enamel. Indeed, because the amelogenin protein is exclusively involved in enamel formation and mineralization and because it lacks pleiotropic effects, this protein is a good candidate to estimate the date of acquisition of this highly mineralized tissue. We searched DNA banks for similarities between the amelogenin sequence and other sequences. Similarities were found only to exon 2 of SPARC (osteonectin) in two protostomians and in eight deuterostomians, and to exon 2 of three SPARC-related deuterostomian genes (SC1, hevin, and QR1). The other amelogenin exons did not reveal significant similarities to other sequences. In these proteins, exon 2 mainly encodes the peptide signal that plays the essential role in enabling the protein to be ultimately localized in the extracellular matrix. We tested the significance of the exon 2 similarities. The observed values were always significantly higher than the expected randomly generated similarities. This demonstrates a common evolutionary origin of this exon. The phylogenetic analyses of exon 2 sequences indicated that exon 2 was duplicated to amelogenin from an ancestral SPARC sequence in the deuterostomian lineage before the duplication of deuterostomian SPARC and SC1/hevin/QR1. We were able to date the origin of the latter duplication at approximately 630 MYA. Therefore, amelogenin exon 2 was acquired before this date, in the Proterozoic, long before the so-called "Cambrian explosion," the sudden appearance of several bilateralian phyla in the fossil record at the Proterozoic-Phanerozoic transition. This sudden appearance has been often suggested to reflect intensive cladogenesis during this period. However, molecular dating of protostomian-deuterostomian divergence and of the cladogenesis among several major clades of Bilateralia lead to a different conclusion: many bilateralian clades were already present during the late Proterozoic. It has previously been proposed that these bilateralians were not mineralized and that they had low fossilization potential. Our results strongly suggest that late Proterozoic fossils possessing a mineralized tissue homologous to enamel might be found in the future.
Mol Biol Evol 2001 Dec
PMID:Molecular evidence for precambrian origin of amelogenin, the major protein of vertebrate enamel. 1171 63

Numerous reports have revealed an inverse association between consumption of some selective natural products and risk of developing cancer. In the present study the effect of 250 and 500 mg/kg body wt. of Spirulina was examined on drug metabolising phase I and phase II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase and lipid peroxidation in the liver of 7-week-old Swiss albino mice. The implications of these biochemical alterations have been further evaluated adopting the protocol of benzo(a)pyrene induced forestomach and 7,12 dimethylbenz(a)anthracene (DMBA) initiated and croton oil promoted skin papillomagenesis. Our primary findings reveal the 'Monofunctional' nature of Spirulina as deduced from its potential to induce only the phase II enzyme activities associated mainly with carcinogen detoxification. The glutathione S-transferase and DT-diaphorase specific activities were induced in hepatic and all the extrahepatic organs examined (lung, kidney and forestomach) by Spirulina pretreatment (significance level being from p < 0.05 to p < 0.005) except for the low dose treatment in forestomach. With reference to antioxidant enzymes viz., superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and reduced glutathione were increased significantly by both the chosen doses of Spirulina from p < 0.01 to p < 0.005. Chemopreventive response was quantitated by the average number of papillomas per effective mouse (tumor burden) as well as percentage of tumor bearing animals. There was a significant inhibition of tumor burden as well as tumor incidence in both the tumor model systems studied. In the skin tumor studies tumor burden was reduced from 4.86 to 1.20 and 1.15 by the low and high dose treatment respectively. In stomach tumor studies tumor burden was 2.05 and 1.73 by the low and high doses of Spirulina treatment against 3.73 that of control.
Mol Cell Biochem 2001 Oct
PMID:Chemomodulation of carcinogen metabolising enzymes, antioxidant profiles and skin and forestomach papillomagenesis by Spirulina platensis. 1176 36

NRF2 is a transcription factor important in the protection against carcinogenesis and oxidative stress through antioxidant response element (ARE)-mediated transcriptional activation of several phase 2 detoxifying and antioxidant enzymes. This study was designed to determine the role of NRF2 in the pathogenesis of hyperoxic lung injury by comparing pulmonary responses to 95-98% oxygen between mice with site-directed mutation of the gene for NRF2 (Nrf2-/-) and wild-type mice (Nrf2+/+). Pulmonary hyperpermeability, macrophage inflammation, and epithelial injury in Nrf2-/- mice were 7.6-fold, 47%, and 43% greater, respectively, compared with Nrf2+/+ mice after 72 h hyperoxia exposure. Hyperoxia markedly elevated the expression of NRF2 mRNA and DNA-binding activity of NRF2 in the lungs of Nrf2+/+ mice. mRNA expression for ARE- responsive lung antioxidant and phase 2 enzymes was evaluated in both genotypes of mice to identify potential downstream molecular mechanisms of NRF2 in hyperoxic lung responses. Hyperoxia-induced mRNA levels of NAD(P)H:quinone oxidoreductase 1 (NQO1), glutathione-S-transferase (GST)-Ya and -Yc subunits, UDP glycosyl transferase (UGT), glutathione peroxidase-2 (GPx2), and heme oxygenase-1 (HO-1) were significantly lower in Nrf2-/- mice compared with Nrf2+/+ mice. Consistent with differential mRNA expression, NQO1 and total GST activities were significantly lower in Nrf2-/- mice compared with Nrf2+/+ mice after hyperoxia. Results demonstrated that NRF2 has a significant protective role against pulmonary hyperoxic injury in mice, possibly through transcriptional activation of lung antioxidant defense enzymes.
Am J Respir Cell Mol Biol 2002 Feb
PMID:Role of NRF2 in protection against hyperoxic lung injury in mice. 1180 63


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