Comparative Genotoxicity of TEMPO and 3 of Its Derivatives in Mouse Lymphoma Cells.

TEMPO (2, 2, 6, 6-tetramethylphiperidine-1-oxyl) and its derivatives are stable free radical nitroxides widely used in the field of chemistry, biology, and pharmacology. TEMPO was previously found to be mutagenic and to induce micronuclei in mammalian cells. In this study, we investigated and quantified the genotoxicity of 4 structurally similar nitroxides, TEMPO and 3 of its derivatives (4-hydroxy-TEMPO, 4-oxo-TEMPO, and 4-methoxy-TEMPO), using the mouse lymphoma assay (MLA) and Comet assay in L5178Y Tk+/- cells.

Quantitative differentiation of whole smoke solution-induced mutagenicity in the mouse lymphoma assay.

In vitro genotoxicity dose-response data have been investigated for their utility in modeling and assessing potential differences in mutagenic responses between machine-generated whole smoke solutions (WSSs) from combusted cigarette tobacco products. Our previous study observed that potency ranking by benchmark dose (BMD) analysis was a useful modeling approach for quantitative assessment of differences between the mutagenicity of several structurally diverse chemical constituents of cigarette smoke. To follow-up on these observations, we used the mouse lymphoma assay (MLA) to evaluate the mutagenicity of WSSs prepared from two commercial cigarettes smoked under two different smoking machine regimens.

Quantitative analysis of the relative mutagenicity of five chemical constituents of tobacco smoke in the mouse lymphoma assay.

Quantifying health-related biological effects, like genotoxicity, could provide a way of distinguishing between tobacco products. In order to develop tools for using genotoxicty data to quantitatively evaluate the risk of tobacco products, we tested five carcinogens found in cigarette smoke, 4-aminobiphenyl (4-ABP), benzo[a]pyrene (BaP), cadmium (in the form of CdCl2), 2-amino-3,4-dimethyl-3H-imidazo[4,5-f]quinoline (MeIQ) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in the mouse lymphoma assay (MLA). The resulting mutagenicity dose responses were analyzed by various quantitative approaches and their strengths and weaknesses for distinguishing responses in the MLA were evaluated.

Reactive oxygen species and c-Jun N-terminal kinases contribute to TEMPO-induced apoptosis in L5178Y cells.

The biological consequences of exposure to piperidine nitroxides is a concern, given their widespread use in manufacturing processes and their potential use in clinical applications. Our previous study reported that TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), a low molecular weight free radical, possesses pro-oxidative activity in L5178Y cells. In this study, we investigated and characterized the role of reactive oxygen species (ROS) in TEMPO-induced toxicity in L5178Y cells.

investigation of the mutagenic potential of extracts.

A 2-year cancer bioassay in rodents with a preparation of whole leaf extract administered in drinking water showed clear evidence of carcinogenic activity. To provide insight into the identity and mechanisms associated with mutagenic components of the extracts, we used the mouse lymphoma assay to evaluate the mutagenicity of the whole leaf extract (WLE) and decolorized whole leaf extract (WLD). The WLD extract was obtained by subjecting WLE to activated carbon-adsorption.

Human sex hormone-binding globulin binding affinities of 125 structurally diverse chemicals and comparison with their binding to androgen receptor, estrogen receptor, and α-fetoprotein.

One endocrine disruption mechanism is through binding to nuclear receptors such as the androgen receptor (AR) and estrogen receptor (ER) in target cells. The concentration of a chemical in serum is important for its entry into the target cells to bind the receptors, which is regulated by the serum proteins. Human sex hormone-binding globulin (SHBG) is the major transport protein in serum that can bind androgens and estrogens and thus change a chemical's availability to enter the target cells.

Mechanistic evaluation of Ginkgo biloba leaf extract-induced genotoxicity in L5178Y cells.

Ginkgo biloba has been used for many thousand years as a traditional herbal remedy and its extract has been consumed for many decades as a dietary supplement. Ginkgo biloba leaf extract is a complex mixture with many constituents, including flavonol glycosides and terpene lactones. The National Toxicology Program 2-year cancer bioassay found that G.

Rat α-Fetoprotein binding affinities of a large set of structurally diverse chemicals elucidated the relationships between structures and binding affinities.

Endocrine disrupting chemicals interfere with the endocrine system in animals, including humans, to exert adverse effects. One of the mechanisms of endocrine disruption is through the binding of receptors such as the estrogen receptor (ER) in target cells. The concentration of any chemical in serum is important for its entry into the target cells to bind the receptors.

Similarities and differences in the expression of drug-metabolizing enzymes between human hepatic cell lines and primary human hepatocytes.

In addition to primary human hepatocytes, hepatoma cell lines, and transfected nonhepatoma, hepatic cell lines have been used for pharmacological and toxicological studies. However, a systematic evaluation and a general report of the gene expression spectra of drug-metabolizing enzymes and transporters (DMETs) in these in vitro systems are not currently available. To fill this information gap and to provide references for future studies, we systematically characterized the basal gene expression profiles of 251 drug-metabolizing enzymes in untreated primary human hepatocytes from six donors, four commonly used hepatoma cell lines (HepG2, Huh7, SK-Hep-1, and Hep3B), and one transfected human liver epithelial cell line.

Genomic analysis of microRNA time-course expression in liver of mice treated with genotoxic carcinogen N-ethyl-N-nitrosourea.

Background: Dysregulated expression of microRNAs (miRNAs) has been previously observed in human cancer tissues and shown promise in defining tumor status. However, there is little information as to if or when expression changes of miRNAs occur in normal tissues after carcinogen exposure.

Results: To explore the possible time-course changes of miRNA expression induced by a carcinogen, we treated mice with one dose of 120 mg/kg N-ethyl-N-nitrosourea (ENU), a model genotoxic carcinogen, and vehicle control.

Gene expression profiling in male B6C3F1 mouse livers exposed to kava identifies--changes in drug metabolizing genes and potential mechanisms linked to kava toxicity.

The association of kava products with liver-related health risks has prompted regulatory action in many countries. We used a genome-wide gene expression approach to generate global gene expression profiles from the livers of male B6C3F1 mice administered kava extract by gavage for 14 weeks, and identified the differentially expressed drug metabolizing genes in response to kava treatments. Analyses of gene functions and pathways reveal that the levels of significant numbers of genes involving drug metabolism were changed and that the pathways involving xenobiotics metabolism, Nrf2-mediated oxidative stress response, mitochondrial functions and others, were altered.

Analysis of gene expression changes of drug metabolizing enzymes in the livers of F344 rats following oral treatment with kava extract.

The association of kava product use with liver-related risks has prompted regulatory action in many countries. We studied the changes in gene expression of drug metabolizing enzymes in the livers of Fischer 344 male rats administered kava extract by gavage for 14 weeks. Analysis of 22,226 genes revealed that there were 14, 41, 110, 386, and 916 genes significantly changed in the 0.

Gene expression changes associated with xenobiotic metabolism pathways in mice exposed to acrylamide.

The discovery of acrylamide (AA) in a variety of fried foods has raised public health concerns. In this study, groups of male mice were administered 500 mg/L AA in drinking water for 3 weeks, and gene expression changes were evaluated in the livers of AA-treated mice within 24 hr of the last treatment. When a two-fold cutoff value and a P-value less than 0.

Cross-platform comparison of SYBR Green real-time PCR with TaqMan PCR, microarrays and other gene expression measurement technologies evaluated in the MicroArray Quality Control (MAQC) study.

Background: The MicroArray Quality Control (MAQC) project evaluated the inter- and intra-platform reproducibility of seven microarray platforms and three quantitative gene expression assays in profiling the expression of two commercially available Reference RNA samples (Nat Biotechnol 24:1115-22, 2006). The tested microarrays were the platforms from Affymetrix, Agilent Technologies, Applied Biosystems, GE Healthcare, Illumina, Eppendorf and the National Cancer Institute, and quantitative gene expression assays included TaqMan Gene Expression PCR Assay, Standardized (Sta) RT-PCRtrade mark and QuantiGene. The data showed great consistency in gene expression measurements across different microarray platforms, different technologies and test sites.

Systematic and simultaneous gene profiling of 84 drug-metabolizing genes in primary human hepatocytes.

Drug-metabolizing enzymes are an important battery of proteins that are involved in drug metabolism, xenobiotic detoxification, and drug-induced toxicity. Systematic, efficient, and simultaneous evaluation of drug-metabolizing gene expression in response to chemicals has a wide variety of implications in drug development, disease prevention, and personalized medicine and nutrition. In the current study, the authors have systematically and simultaneously evaluated the hepatic expression profile of drug-metabolizing enzymes in cultured human hepatocytes exposed to the xenobiotics rifampicin, omeprazole, and 3-methylcholanthrene (3-MC) using the Drug Metabolism RT(2)Profiler PCR Arrays.

Comparison of gene expression profiles altered by comfrey and riddelliine in rat liver.

Background: Comfrey (Symphytum officinale) is a perennial plant and has been consumed by humans as a vegetable, a tea and an herbal medicine for more than 2000 years. It, however, is hepatotoxic and carcinogenic in experimental animals and hepatotoxic in humans. Pyrrolizidine alkaloids (PAs) exist in many plants and many of them cause liver toxicity and/or cancer in humans and experimental animals.

Differential gene expression in mouse primary hepatocytes exposed to the peroxisome proliferator-activated receptor alpha agonists.

Background: Fibrates are a unique hypolipidemic drugs that lower plasma triglyceride and cholesterol levels through their action as peroxisome proliferator-activated receptor alpha (PPARalpha) agonists. The activation of PPARalpha leads to a cascade of events that result in the pharmacological (hypolipidemic) and adverse (carcinogenic) effects in rodent liver.

Results: To understand the molecular mechanisms responsible for the pleiotropic effects of PPARalpha agonists, we treated mouse primary hepatocytes with three PPARalpha agonists (bezafibrate, fenofibrate, and WY-14,643) at multiple concentrations (0, 10, 30, and 100 microM) for 24 hours.

Analysis of gene expression changes in relation to toxicity and tumorigenesis in the livers of Big Blue transgenic rats fed comfrey (Symphytum officinale).

Background: Comfrey is consumed by humans as a vegetable and a tea, and has been used as an herbal medicine for more than 2000 years. Comfrey, however, is hepatotoxic in livestock and humans and carcinogenic in experimental animals. Our previous study suggested that comfrey induces liver tumors by a genotoxic mechanism and that the pyrrolizidine alkaloids in the plant are responsible for mutation induction and tumor initiation in rat liver.

Differences in hepatotoxicity and gene expression profiles by anti-diabetic PPAR gamma agonists on rat primary hepatocytes and human HepG2 cells.

Agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) are a new class of oral drugs designed to treat insulin-resistant diabetes (i.e., type 2 diabetes).

Genome-wide estimation of gender differences in the gene expression of human livers: statistical design and analysis.

Background: Gender differences in gene expression were estimated in liver samples from 9 males and 9 females. The study tested 31,110 genes for a gender difference using a design that adjusted for sources of variation associated with cDNA arrays, normalization, hybridizations and processing conditions.

Results: The genes were split into 2,800 that were clearly expressed (expressed genes) and 28,310 that had expression levels in the background range (not expressed genes).

Comparison of basal gene expression profiles and effects of hepatocarcinogens on gene expression in cultured primary human hepatocytes and HepG2 cells.

Toxicogenomics is a relatively new discipline of toxicology. Microarrays and bioinformatics tools are being used successfully to understand the effects of toxicants on in vivo and in vitro model systems, and to gain a better understanding of the relevance of in vitro models commonly used in toxicological studies. In this study, cDNA filter arrays were used to determine the basal expression patterns of human cultured primary hepatocytes from different male donors; compare the gene expression profile of HepG2 to that of primary hepatocytes; and analyze the effects of three genotoxic hepatocarcinogens; aflatoxin B(1) (AFB(1)), 2-acetylaminofluorene (2AAF), and dimethylnitrosamine (DMN), as well as one non-gentoxic hepatotoxin, acetaminophen (APAP) on gene expression in both in vitro systems.

Phytoestrogens and mycoestrogens bind to the rat uterine estrogen receptor.

Consumption of phytoestrogens and mycoestrogens in food products or as dietary supplements is of interest because of both the potential beneficial and adverse effects of these compounds in estrogen-responsive target tissues. Although the hazards of exposure to potent estrogens such as diethylstilbestrol in developing male and female reproductive tracts are well characterized, less is known about the effects of weaker estrogens including phytoestrogens. With some exceptions, ligand binding to the estrogen receptor (ER) predicts uterotrophic activity.