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The Journal of Pharmacology and... Apr 2010The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) induces a battery of cytoprotective genes after oxidative stress. Nrf2 aids in liver...
The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) induces a battery of cytoprotective genes after oxidative stress. Nrf2 aids in liver regeneration by altering insulin signaling; however, whether Nrf2 participates in hepatic glucose homeostasis is unknown. Compared with wild-type mice, mice lacking Nrf2 (Nrf2-null) have lower basal serum insulin and prolonged hyperglycemia in response to an intraperitoneal glucose challenge. In the present study, blood glucose, serum insulin, urine flow rate, and hepatic expression of glucose-related genes were quantified in male diabetic wild-type and Nrf2-null mice. Type 1 diabetes was induced with a single intraperitoneal dose (200 mg/kg) of streptozotocin (STZ). Histopathology and serum insulin levels confirmed depleted pancreatic beta-cells in STZ-treated mice of both genotypes. Five days after STZ, Nrf2-null mice had higher blood glucose levels than wild-type mice. Nine days after STZ, polyuria occurred in both genotypes with more urine output from Nrf2-null mice (11-fold) than wild-type mice (7-fold). Moreover, STZ-treated Nrf2-null mice had higher levels of serum beta-hydroxybutyrate, triglycerides, and fatty acids 10 days after STZ compared with wild-type mice. STZ reduced hepatic glycogen in both genotypes, with less observed in Nrf2-null mice. Increased urine output and blood glucose in STZ-treated Nrf2-null mice corresponded with enhanced gluconeogenesis (glucose-6-phosphatase and phosphoenolpyruvate carboxykinase)- and reduced glycolysis (pyruvate kinase)-related mRNA expression in their livers. Furthermore, the Nrf2 activator oltipraz lowered blood glucose in wild-type but not Nrf2-null mice administered STZ. Collectively, these data indicate that the absence of Nrf2 worsens hyperglycemia in type I diabetic mice and Nrf2 may represent a therapeutic target for reducing circulating glucose levels.
Topics: Animals; Blood Glucose; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Glucose Intolerance; Glucose-6-Phosphatase; Hyperglycemia; Insulin; Liver; Liver Glycogen; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NAD(P)H Dehydrogenase (Quinone); NF-E2-Related Factor 2; Pancreas; Phosphoenolpyruvate Carboxykinase (GTP); Pyrazines; Pyruvate Kinase; RNA, Messenger; Thiones; Thiophenes; Urodynamics
PubMed: 20086057
DOI: 10.1124/jpet.109.162271 -
Chemical Research in Toxicology Aug 2009The ability of three dithiolethione cancer chemopreventives, oltipraz 1, anetholedithione (ADT) 2, 1,2-dithiole-3-thione (D3T) 3, and the major metabolite, 4, of 1, to...
The ability of three dithiolethione cancer chemopreventives, oltipraz 1, anetholedithione (ADT) 2, 1,2-dithiole-3-thione (D3T) 3, and the major metabolite, 4, of 1, to induce the cytoprotective enzyme NQO1 in Hepa 1c1c7 cells and the inhibition of this induction by catalase are demonstrated. The ability of 1, 3, and 4 to form O(2)(*) has been reported, and it is here demonstrated that 2 decomposes in the presence of GSH to form, upon addition of the nitrone spin trap DMPO, the DMPO-OH adduct that is detectable by EPR. Decomposition of 2 in the presence of GSH elicits, upon the addition of hydroethidine and excitation at 510 nm, fluorescence at 580 nm that is diminished by the addition of superoxide dismutase. The compound 4, is a product of the reduction of 1, and it is demonstrated that 2 and 3 decompose in the presence of reductants such as thiolates and NaBH(4), followed by addition of CH(3)I, to form the dimethylated products of reductive cleavage of the S(1)-S(2) bond. The same products are isolated subsequent to lysis in buffer containing CH(3)I of Hepa 1c1c7 cells treated with 2 or 3. Reductive cleavage of 2 and 3 in aqueous ethanol by NaBH(4) in an argon atmosphere, followed by acidic destruction of remaining borohydride and neutralization and introduction of O(2) results in the reformation of 2 and 3 to the extent of 80 and 33%, respectively. The data in toto are consistent with a model in which dithiolethiones, generally, undergo reductive cleavage in Hepa 1c1c7 cells, thereby resulting in the generation of O(2)(*) that dismutates to H(2)O(2), that subsequently, by direct or indirect means, effects the nuclear translocation of transcription factor Nrf2, that upregulates phase 2 enzyme expression.
Topics: Animals; Antineoplastic Agents; Antioxidants; Cyclic N-Oxides; Diglycerides; Enzyme Induction; Hepatocytes; Humans; Hydrogen Peroxide; NAD(P)H Dehydrogenase (Quinone); Neoplasms; Pyrazines; Second Messenger Systems; Thiones; Thiophenes
PubMed: 19785463
DOI: 10.1021/tx900110n -
Chemical Research in Toxicology Nov 2006Aflatoxin B1 (AFB1) is a potent carcinogen, which can significantly increase the risk of hepatocellular carcinoma development through food contamination. In past...
Aflatoxin B1 (AFB1) is a potent carcinogen, which can significantly increase the risk of hepatocellular carcinoma development through food contamination. In past decades, chemopreventive agents, such as oltipraz and chlorophyllins, have demonstrated that chemo-intervention is an effective approach to reduce hepatotoxicity by AFB1. However, because of the potential adverse effects of these agents, alternative novel mechanism-based chemopreventive agents are needed. We report here that novel cis-terpenones 1-3, which were synthesized as the precursors of natural product analogues in our laboratory, showed promising protective effects against AFB1-induced cytotoxicity in HepG2 cells. Chemo-protection was observed with increasing concentrations of cis-terpenones in the co-treatment of AFB1, and no cytotoxicity was observed with cis-terpenones alone. In addition, cis-terpenones 1-3 at 10 and microM effectively inhibited induced cytochrome P450 1A/1B activity by 50% in HepG2 cells, as indicated by an EROD assay. P450 1A/B is involved in the activation of many pre-carcinogens and is highly inducible in liver cells. These results suggested that novel terpenones 1-3 are candidates for the development of novel mechanism-based chemopreventive agents against AFB1 and other carcinogenic stimuli.
Topics: Aflatoxin B1; Carcinogens; Cell Line, Tumor; Cell Survival; Chemoprevention; Cytochrome P-450 CYP1A1; Dose-Response Relationship, Drug; Humans; Molecular Structure; Polychlorinated Dibenzodioxins; Terpenes
PubMed: 17112227
DOI: 10.1021/tx0601307 -
Molecules (Basel, Switzerland) Mar 2012Polypharmacy increasingly has become a topic of public health concern, particularly as the U.S. population ages. Drug labels often contain insufficient information to...
Modeling chemical interaction profiles: II. Molecular docking, spectral data-activity relationship, and structure-activity relationship models for potent and weak inhibitors of cytochrome P450 CYP3A4 isozyme.
Polypharmacy increasingly has become a topic of public health concern, particularly as the U.S. population ages. Drug labels often contain insufficient information to enable the clinician to safely use multiple drugs. Because many of the drugs are bio-transformed by cytochrome P450 (CYP) enzymes, inhibition of CYP activity has long been associated with potentially adverse health effects. In an attempt to reduce the uncertainty pertaining to CYP-mediated drug-drug/chemical interactions, an interagency collaborative group developed a consensus approach to prioritizing information concerning CYP inhibition. The consensus involved computational molecular docking, spectral data-activity relationship (SDAR), and structure-activity relationship (SAR) models that addressed the clinical potency of CYP inhibition. The models were built upon chemicals that were categorized as either potent or weak inhibitors of the CYP3A4 isozyme. The categorization was carried out using information from clinical trials because currently available in vitro high-throughput screening data were not fully representative of the in vivo potency of inhibition. During categorization it was found that compounds, which break the Lipinski rule of five by molecular weight, were about twice more likely to be inhibitors of CYP3A4 compared to those, which obey the rule. Similarly, among inhibitors that break the rule, potent inhibitors were 2-3 times more frequent. The molecular docking classification relied on logistic regression, by which the docking scores from different docking algorithms, CYP3A4 three-dimensional structures, and binding sites on them were combined in a unified probabilistic model. The SDAR models employed a multiple linear regression approach applied to binned 1D ¹³C-NMR and 1D ¹⁵N-NMR spectral descriptors. Structure-based and physical-chemical descriptors were used as the basis for developing SAR models by the decision forest method. Thirty-three potent inhibitors and 88 weak inhibitors of CYP3A4 were used to train the models. Using these models, a synthetic majority rules consensus classifier was implemented, while the confidence of estimation was assigned following the percent agreement strategy. The classifier was applied to a testing set of 120 inhibitors not included in the development of the models. Five compounds of the test set, including known strong inhibitors dalfopristin and tioconazole, were classified as probable potent inhibitors of CYP3A4. Other known strong inhibitors, such as lopinavir, oltipraz, quercetin, raloxifene, and troglitazone, were among 18 compounds classified as plausible potent inhibitors of CYP3A4. The consensus estimation of inhibition potency is expected to aid in the nomination of pharmaceuticals, dietary supplements, environmental pollutants, and occupational and other chemicals for in-depth evaluation of the CYP3A4 inhibitory activity. It may serve also as an estimate of chemical interactions via CYP3A4 metabolic pharmacokinetic pathways occurring through polypharmacy and nutritional and environmental exposures to chemical mixtures.
Topics: Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Environmental Pollutants; Enzyme Inhibitors; Humans; Isoenzymes; Structure-Activity Relationship
PubMed: 22421793
DOI: 10.3390/molecules17033407 -
Environmental Health Perspectives Oct 1999Corn and other crops contaminated with the fungus Aspergillus flavus give off a carcinogenic by-product called aflatoxin, which is blamed for high rates of liver cancer...
Corn and other crops contaminated with the fungus Aspergillus flavus give off a carcinogenic by-product called aflatoxin, which is blamed for high rates of liver cancer in Asia and Africa, where rice and corn are food staples. In the United States, aflatoxin's major threat is to farm animals, which can get sick or even die from consuming too much of the toxin. Scientists are working on ways to keep the deadly toxin out of the food supply. Two techniques under development identify aflatoxin-tainted corn by using infrared light to elicit telltale sounds and light from contaminated kernels. Other scientists hope to protect corn from A. flavus in the first place by designing genetically engineered aflatoxin-resistant grain species and by working with drugs such as oltipraz that reportedly detoxify aflatoxin already in the body.
Topics: Aspergillus flavus; Zea mays
PubMed: 10504167
DOI: 10.1289/ehp.99107a515 -
The Journal of Biological Chemistry Jun 1997The influence of various cytokines on the expression of glutathione S-transferases (GSTs) was investigated in rat hepatocytes in primary culture. Only treatment of...
The influence of various cytokines on the expression of glutathione S-transferases (GSTs) was investigated in rat hepatocytes in primary culture. Only treatment of hepatocytes with interleukin-1beta (IL-1) was effective, resulting in a marked decrease in GSTs. Steady-state mRNA levels of rGSTA2 and M1 were strongly down-regulated by IL-1 in a dose-dependent manner after a 24-h exposure while rGSTP1 mRNA level was increased by a 48-h treatment. Similar effects of IL-1 were observed at the protein level. The response to IL-1 appeared to be specific for each subunit within GST gene families. In addition, IL-1 strongly suppressed the induction of rGSTA2 by 3-methylcholanthrene, oltipraz (a synthetic derivative of 1, 2-dithiole-3-thione), and phenobarbital and that of rGSTM1 by oltipraz and phenobarbital, whereas it was ineffective on rGSTP1 induction by these compounds. Using in vitro nuclear run-on transcription assay and Northern blot analysis of alpha-amanitin-treated cells, IL-1-mediated rGSTM1 mRNA decrease was found to result from mRNA destabilization. These results provide the first demonstration that IL-1 regulates some major GST subunits in hepatocytes by a post-transcriptional mechanism.
Topics: Animals; Cells, Cultured; Dose-Response Relationship, Drug; Glutathione Transferase; Humans; Interleukin-1; Liver; Male; Pyrazines; RNA, Messenger; Rats; Rats, Sprague-Dawley; Thiones; Thiophenes; Transforming Growth Factor beta
PubMed: 9195908
DOI: 10.1074/jbc.272.26.16125 -
Cancer Control : Journal of the Moffitt... Mar 1997BACKGROUND: The incidence of bladder and prostate cancer continues to rise, with little accompanying improvement in management strategies. Opportunities exist for...
BACKGROUND: The incidence of bladder and prostate cancer continues to rise, with little accompanying improvement in management strategies. Opportunities exist for testing various types of chemopreventive interventions. METHODS: The authors review the biology of progression to invasive disease for cancers of the bladder and the prostate and identify intermediate disease and surrogate endpoint markers. Candidate interventions and initial clinical trial results are described. RESULTS: Markers of cellular proliferation and differentiation, as well as antigens such as Le(x), M344, DD23, and bladder tumor antigen, are promising for bladder cancer. Testing with prostate-specific antigen and prostate-specific membrane antigen is promising for prostate cancer. Several prevention intervention trials are in progress for both cancers. CONCLUSIONS: Vitamins, polyamine synthesis inhibitors, and oltipraz are undergoing clinical tests for chemopreventive effects in bladder cancer, and a large trial of finasteride to prevent prostate cancer is completing accrual. Results from these studies will direct future research.
PubMed: 10763011
DOI: 10.1177/107327489700400204 -
Free Radical Biology & Medicine Oct 2007The major metabolite of the cancer chemopreventive agent oltipraz, a pyrrolopyrazine thione (PPD), has been shown to be a phase 2 enzyme inducer, an activity thought to...
The major metabolite of the cancer chemopreventive agent oltipraz, a pyrrolopyrazine thione (PPD), has been shown to be a phase 2 enzyme inducer, an activity thought to be key to the cancer chemopreventive action of the parent compound. In cells, mitochondria are the major source of reactive oxygen species (ROS) and cytochrome c (cyt c) is known to participate in mitochondrial electron transport and confer antioxidant and peroxidase activities. To understand possible mechanisms by which PPD acts as a phase 2 enzyme inducer, a study of its interaction with cyt c was undertaken. UV-visible spectroscopic results demonstrate that PPD is capable of reducing oxidized cyt c. The reduced cyt c is stable for a long period of time in the absence of an oxidizing agent. In the presence of ferricyanide, the reduced cyt c is rapidly oxidized back to its oxidized form. Further, UV-visible spectroscopic studies show that during the reduction process the coordination environment and redox state of iron in cyt c are changed. Low-temperature EPR studies show that during the reduction process, the heme iron changes from a low-spin state of s = 1/2 to a low-spin state of s = 0. Room-temperature EPR studies demonstrate that PPD inhibits the peroxidase activity of cyt c. EPR spin trapping experiments using DMPO show that PPD inhibits the superoxide radical scavenging activity of oxidized cyt c. From these results, we propose that PPD interacts with cyt c, binding to and then reducing the heme, and this may enhance ROS levels in mitochondria. This in turn could contribute to the mechanism by which the parent compound, oltipraz, might trigger the cancer chemopreventive increase in transcription of phase 2 enzymes. The modifications of cyt c function by the oltipraz metabolite may have implications for the regulation of apoptotic cell death.
Topics: Animals; Anticarcinogenic Agents; Antioxidants; Chemoprevention; Cytochromes c; Electron Spin Resonance Spectroscopy; Electron Transport; Heart; Horses; Mass Spectrometry; Mitochondria; Neoplasms; Oxidation-Reduction; Peroxidase; Pyrazines; Reactive Oxygen Species; Spectrophotometry, Ultraviolet; Thiones; Thiophenes
PubMed: 17761303
DOI: 10.1016/j.freeradbiomed.2007.06.022 -
The Journal of Biological Chemistry Aug 1994Fetal rat liver possesses substantial levels of glutathione S-transferase (GST) activity toward aflatoxin B1-8,9-epoxide. The enzyme responsible for this activity is an...
Cloning of cDNAs from fetal rat liver encoding glutathione S-transferase Yc polypeptides. The Yc2 subunit is expressed in adult rat liver resistant to the hepatocarcinogen aflatoxin B1.
Fetal rat liver possesses substantial levels of glutathione S-transferase (GST) activity toward aflatoxin B1-8,9-epoxide. The enzyme responsible for this activity is an Alpha-class GST heterodimer comprising Yc1 and Yc2 subunits. The cDNAs encoding these polypeptides have been cloned and shown to share approximately 91% identity over 920 base pairs, extending from nucleotide -23 to the AATAAA polyadenylation signal. GST Yc2Yc2 expressed in Escherichia coli was found to exhibit 150-fold greater activity toward aflatoxin B1-8,9-epoxide than GST Yc1Yc1. Comparison between the structures of Alpha-class GST suggests that tyrosine at residue 108 and/or aspartate at residue 208 is responsible for the high aflatoxin B1 detoxication capacity of Yc2. Immunoblotting and enzyme assays have shown that liver from adult female rats contains about 10-fold greater levels of Yc2 than is found in liver from adult male rats. This sex-specific expression of Yc2 in adult rat liver may contribute to the relative insensitivity of female rats to aflatoxin B1. Dietary administration of oltipraz, a synthetic antioxidant which protects against aflatoxin-hepatocarcinogenesis, serves as an inducer of GST Yc2.
Topics: Aflatoxin B1; Amino Acid Sequence; Animals; Base Sequence; Carcinogens; Cloning, Molecular; DNA, Complementary; Drug Resistance; Enzyme Induction; Escherichia coli; Female; Glutathione Transferase; Humans; Inactivation, Metabolic; Liver; Male; Molecular Sequence Data; Peptide Fragments; Rats; Rats, Inbred F344; Sequence Homology, Amino Acid
PubMed: 8051171
DOI: No ID Found -
World Journal of Gastroenterology Oct 2000
PubMed: 11819668
DOI: 10.3748/wjg.v6.i5.647