Concentration- and time-dependent genomic changes in the mouse urinary bladder following exposure to arsenate in drinking water for up to twelve weeks.
Concentration- and time-dependent genomic changes in the mouse urinary bladder following exposure to arsenate in drinking water for up to 12 weeks.
Sex, Age, Specimen part, Subject
View SamplesEight week old female C57BL/6 mice were exposed to arsenate in drinking water (50 ppm) for a period of twelve weeks (n = 5). Control animals received distilled deionized water (n = 5). Lung tissue was dissected and used for RNA isolation and gene expression microarray analysis.
Genome-wide analysis of DNA methylation and gene expression changes in the mouse lung following subchronic arsenate exposure.
Sex, Specimen part, Disease, Disease stage, Subject
View Samples-chloroprene (2-chloro-1,3-butadiene), a monomer used in the production of neoprene elastomers, is of regulatory interest due to the production of multi-organ tumors in mouse and rat cancer bioassays. A significant increase in female mouse lung tumors was observed at the lowest exposure concentration of 12.8 ppm while a small, but not statistically significant, increase was observed in female rats only at the highest exposure concentration of 80 ppm. The metabolism of chloroprene results in the generation of reactive epoxides and the rate of overall chloroprene metabolism is highly species dependent. To identify potential key events in the mode-of-action of chloroprene lung tumorigenesis, dose response and time course gene expression microarray measurements were made in the lungs of female mice and female rats. The gene expression changes were analyzed using both a traditional analysis of variance approach followed by pathway enrichment analysis and a pathway-based benchmark dose (BMD) analysis approach. Pathways related to glutathione biosynthesis and metabolism were the primary pathways consistent with cross-species differences in tumor incidence and transcriptional BMD values for the pathway were more similar to differences in tumor response than were estimated target tissue dose surrogates based on the total amount of chloroprene metabolized per unit mass of lung tissue per day. The closer correspondence of the transcriptional changes with the tumor response are likely due to their reflection of the overall balance between metabolic activation and detoxication reactions whereas the current tissue dose surrogate reflects only oxidative metabolism.
Cross-species transcriptomic analysis of mouse and rat lung exposed to chloroprene.
Sex, Age, Specimen part, Subject
View SamplesFormaldehyde, an important industrial chemical, is used for multiple commercial purposes throughout the industrialized world. This simple, one carbon aldehyde is a natural metabolite formed in cells throughput the body. However, it is also a rodent nasal carcinogen, when inhaled by rats every day for two-years at irritant concentrations. High tumor incidences occur at concentration of 10 ppm and above; no tumors are observed at concentrations below 6.0 ppm. The US Environmental Protection Agency (US EPA) is now (2007) conducting a risk assessment to try to evaluate possible cancer risks for much lower levels of human exposure. Sensitive methods are needed to evaluate tissue responses below those concentrations that are clearly irritant or carcinogenic. This microarray study was undertaken to evaluate the mode of action for nasal responses to inhaled formaldehyde in Fisher 344 rats over a range of exposure concentrations. The range of concentrations used spanned those at which virtually no tissue responses were observed (0.7 ppm) to those that represent the highest concentration in the cancer studies (15 ppm) that produced nasal tumors in half the exposed group of rats. The study identified doses at which there were no statistically significant changes in gene expression; intermediate doses with changes in a small number of genes not easily grouped by function; and then concentrations where changes were consistent with irritation and cell stress responses.
A method to integrate benchmark dose estimates with genomic data to assess the functional effects of chemical exposure.
Sex, Subject
View SamplesFormaldehyde (FA), an endogenous cellular aldehyde, is a rat nasal carcinogen. In this study, concentration- and exposure-duration transitions in FA mode of action (MOA) were examined with pharmacokinetic (PK) modeling for tissue formaldehyde acetal (FAcetal) and glutathione (GSH) and with histopathology and gene expression studies for tissue responses in nasal epithelium from rats exposed to 0, 0.7, 2, 6, 10 or 15 ppm FA 6 hr/day for 1, 4 or 13 weeks. The study had two goals. The first goal was to develop a basic PK model to estimate various forms of tissue formaldehyde and tissue glutathione (GSH). The second goal was to compare histopathology and gene expression changes in nasal tissues caused by inhalation of FA with changes in tissue FAcetal and free GSH calculated from the PK model. Patterns of gene expression varied with concentration and with duration. At 0.7 and 2 ppm, sensitive response genes (SRGs) - associated with cellular stress, thiol transport/reduction, inflammation, and cell proliferation - were similarly upregulated at all exposure durations. At 6 ppm and greater, gene expression changes showed enrichment of pathways involved in cell cycle, DNA repair, and apoptosis processes. ERBB, EGFR, WNT, TGF-, Hedgehog, and Notch signaling were also enriched in differentially expressed genes. Benchmark doses (BMDs) for genes in significantly enriched pathways were lower at 13 weeks than at 1 or 4-week. The transcriptional and histological changes corresponded to PK model-predicted changes in free GSH at 0.7 and 2 ppm and in FAcetal at 6 ppm. DNA-replication stress, enhanced proliferation, metaplasia, and stem cell-niche activation appear to be associated with FA carcinogenesis at 6 ppm and above. Dose dependencies in MOA, the presence of high physiological FAcetal, and non-linear FAcetal/GSH tissue kinetics indicate that FA concentrations below 150 ppb (and probably any concentrations below irritant levels, i.e., ~ 1 ppm) would not increase cancer risks of inhaled FA in the nose or any other tissue. Closer examination of dose response relationships for endogenous compound toxicity could help guide biologically relevant approaches for chemical risk assessment.
Formaldehyde: integrating dosimetry, cytotoxicity, and genomics to understand dose-dependent transitions for an endogenous compound.
Sex, Age, Specimen part, Subject, Time
View SamplesA673 cells were exposed in triplicate to three agrichemicals for 24hrs at 8 concentrations and a DMSO vehicle control (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, and 10 M plus DMSO vehicle controls). While a common set of DMSO controls was used, these CEL files were RMA normalized independently with each of the chemical treated groups. Gene expression was measured on an Affymetrix GeneTitan system. The compounds used were fenbuconazole (a.k.a FENB, CAS # 114369-43-6) a triazole fungicide, imazalil (a.k.a. IMAZ, CAS # 35554-44-0), an azole pesticide, and 2,4-dichlorophenoxyacetic acid (a.k.a. 2,4-D or 2-4-D in file names, CAS # 94-75-7), a chlorophenoxy herbicide.
A Qualitative Modeling Approach for Whole Genome Prediction Using High-Throughput Toxicogenomics Data and Pathway-Based Validation.
Specimen part, Cell line
View SamplesMCF7 cells were exposed in triplicate to three agrichemicals for 24hrs at 8 concentrations and a DMSO vehicle control (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, and 10 M plus DMSO vehicle controls). While a common set of DMSO controls was used, these CEL files were RMA normalized independently with each of the chemical treated groups. Gene expression was measured on an Affymetrix GeneTitan system. The compounds used were fenbuconazole (a.k.a FENB, CAS # 114369-43-6) a triazole fungicide, imazalil (a.k.a. IMAZ, CAS # 35554-44-0), an azole pesticide, and 2,4-dichlorophenoxyacetic acid (a.k.a. 2,4-D or 2-4-D in file names, CAS # 94-75-7), a chlorophenoxy herbicide.
A Qualitative Modeling Approach for Whole Genome Prediction Using High-Throughput Toxicogenomics Data and Pathway-Based Validation.
Specimen part, Cell line
View SamplesHepaRG cells were exposed in triplicate to three agrichemicals for 24hrs at 8 concentrations and a DMSO vehicle control (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, and 10 M plus DMSO vehicle controls). While a common set of DMSO controls was used, these CEL files were RMA normalized independently with each of the chemical treated groups. Gene expression was measured on an Affymetrix GeneTitan system. The compounds used were fenbuconazole (a.k.a FENB, CAS # 114369-43-6) a triazole fungicide, imazalil (a.k.a. IMAZ, CAS # 35554-44-0), an azole pesticide, and 2,4-dichlorophenoxyacetic acid (a.k.a. 2,4-D or 2-4-D in file names, CAS # 94-75-7), a chlorophenoxy herbicide.
A Qualitative Modeling Approach for Whole Genome Prediction Using High-Throughput Toxicogenomics Data and Pathway-Based Validation.
Specimen part, Cell line
View SamplesHpeG2 cells were exposed in triplicate to three agrichemicals for 24hrs at 8 concentrations and a DMSO vehicle control (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, and 10 M plus DMSO vehicle controls). While a common set of DMSO controls was used, these CEL files were RMA normalized independently with each of the chemical treated groups. Gene expression was measured on an Affymetrix GeneTitan system. The compounds used were fenbuconazole (a.k.a FENB, CAS # 114369-43-6) a triazole fungicide, imazalil (a.k.a. IMAZ, CAS # 35554-44-0), an azole pesticide, and 2,4-dichlorophenoxyacetic acid (a.k.a. 2,4-D or 2-4-D in file names, CAS # 94-75-7), a chlorophenoxy herbicide.
A Qualitative Modeling Approach for Whole Genome Prediction Using High-Throughput Toxicogenomics Data and Pathway-Based Validation.
Specimen part, Cell line
View SamplesTwo-year rodent bioassays play a central role in evaluating both the carcinogenic potential of a chemical and generating quantitative information on the dose-response behavior for chemical risk assessments. The bioassays involved are expensive and time-consuming, requiring nearly lifetime exposures (two years) in mice and rats and costing $2 to $4 million per chemical. Since there are approximately 80,000 chemicals registered for commercial use in the United States and 2,000 more are added each year, applying animal bioassays to all chemicals of concern is clearly impossible. To efficiently and economically identify carcinogens prior to widespread use and human exposure, alternatives to the two-year rodent bioassay must be developed. In this study, animals were exposed for 13 weeks to 10 chemicals that were positive for liver tumors in the two-year rodent bioassay, 14 chemicals that were negative for liver tumors, and two chemicals that produced an equivocal response. Matched vehicle control groups were run concurrently with each chemical treatment. Gene expression analysis was performed on the livers of the animals to assess the potential for identifying gene expression biomarkers and signaling pathways that can predict tumor formation in a two-year bioassay following a 13 week exposure.
Application of transcriptional benchmark dose values in quantitative cancer and noncancer risk assessment.
Sex, Age, Subject
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