Unknown,Transcriptomics,Genomics,Proteomics

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Lack of hepatic response of microRNA in mice following chronic benzo(a)pyrene exposure (gene expression)

ABSTRACT: Benzo[a]pyrene (BaP) is a very extensively studied prototypical polycyclic aromatic hydrocarbons (PAHs). Previous work in our laboratory showed no changes of microRNA (miRNA) expression in liver following a 3 days exposure to BaP, suggesting a lack of miRNA transcriptional responses to aryl hydrocarbon receptor agonists and/or DNA damage. Here, we studied 25-week old male MutaTM Mouse exposed to 25, 50, and 75 mg/kg/day BaP by oral gavage for 28 consecutive days. MAANOVA identified 110 differentially expressed genes (adjusted p < 0.05) with fold change greater than 1.5. The genes most affected included those involved in xenobiotic metabolism, phase II metabolizing enzymes, as well as the downstream targets of p53. Pathway specific RT-PCR was used to confirm the p53 response. A single significant increase in miRNA expression was identified (mir-34a and validated using the Qiagen miScript PCR system). This miRNA is known to be transcriptionally activated by p53. Ingestion of BaP leads to widespread changes in gene expression in mouse liver, with enrichment of genes involved in cell cycle arrest, DNA damage response, and apoptosis via the p53 pathway. In contrast, miRNA expression was relatively unaffected. Only miR-34a was significantly up-regulated, and may therefore play a critical role in the post-transcriptional regulation of p53 and/or its downstream targets. Keywords: Agilent mouse 4 x 44 oligonucleotide microarrays were used to assess global gene expression in response to 25, 50, and 75 mg/kg BaP treatment Individual total RNA (200 ng) from 5 mice per treatment group (control, 24mg/kg, 50mg/kg, and 75mg/kg) and universal reference total RNA (Stratagene, Mississauga, ON, Canada) was used to synthesize double stranded cDNA.

ORGANISM(S): Mus musculus

SUBMITTER: Andrew Williams

PROVIDER: E-GEOD-24907 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Polycyclic aromatic hydrocarbons (PAHs) are widely distributed, carcinogenic environmental contaminants produced as a consequence of the incomplete combustion of fossil fuels. Benzo[a]pyrene (BaP) is a very extensively studied prototypical PAH. We recently reported a complete lack of change in microRNA (miRNA) expression in adult mouse liver following oral gavage with BaP despite a robust transcriptome response. We hypothesized that hepatic miRNAs may not be highly responsive to the treatment. Here, we analyse the pulmonary mRNA and miRNA response to BaP in the same mice. Adult male B6C3F1 mice were exposed to 5, 50, 150 and 300 mg/kg BaP by oral gavage for three consecutive days and sacrificed 4 or 24 hours after the last exposure. Serum clinical chemistry and DNA adduct levels in whole lung and liver tissues were analysed at both the time points for all the doses. Acute exposure to BaP resulted in modest decreases in serum inorganic phosphorous, calcium, glucose, alkaline phosphatase and lactate dehydrogenase in animals treated with 300 mg/kg BaP. 32P postlabeling of DNA revealed similar increases in BaP-DNA adducts in both lungs and livers of exposed mice in a dose dependent manner at the 4 hour time point. Using DNA microarrays, pulmonary mRNA and miRNA expression was analysed 4 hours after the final exposure. Over 1,000 genes were statistically differentially expressed (fold change > 1.5 and p < 0.05), encompassing numerous pathways including: oxidative stress, xenobiotic metabolism, cell proliferation, cell cycle, B and T-cell receptor signalling and primary immunodeficiency signalling pathways. Analysis of miRNA profiles revealed downregulation of miR-150, miR-142-5p, 142-3p and upregulation of miR-34c and miR-29b. These miRNAs are involved in various biological processes including immune response, cell proliferation and cell cycle, which are also the main pathways affected at the gene expression level. As BaP exposure does not result in hepatocarcinogenicity, but does cause lung cancer, these miRNAs may play an important role in the outcome of the exposure and be more predictive of carcinogenesis. Keywords: mRNA, miRNA, Pulmonary, non-target tissue, Toxicogenomics, Benzoapyrene Adult male B6C3F1 mice were exposed to 5, 50, 150 and 300 mg/kg BaP by oral gavage for three consecutive days and sacrificed 4 or 24 hours after the last exposure. Serum clinical chemistry and DNA adduct levels in whole lung and liver tissues were analysed at both the time points for all the doses. Using DNA microarrays, pulmonary mRNA and miRNA expression was analysed 4 hours after the final exposure. This submission only contains the 4hr time point, at control, 150mg/kg and 300mg/kg (except for the liver study where only the control and 300mg/kg samples were used).

Project description:In the present study we investigate the effect of maternal pulmonary exposure to titanium dioxide (UV-Titan designed for use in the paint and lacquer industry) on prenatally exposed offspring. Time-mated mice (C57BL/6BomTac) were exposed by inhalation for 1 h/day to 42 mg UV-titan/m3 aerosolized powder or filtered air during gestation days (GD) 8-18. We evaluated levels of DNA strand breaks using the comet assay in bronchioalveolar lavage (BAL) cells and liver cells of the time-mated mice, and in liver cells of the offspring. In parallel, we analyzed changes in gene expression in the liver tissue of offspring using DNA microarrays. We demonstrate that UV-Titan did not induce DNA strand breaks in the time-mated mice or their offspring. Transcriptional profiling of newborn liver tissue revealed changes in the expression of genes related to the retinoic acid (RA) signalling pathway in the females, while gene expression in male offspring was relatively unaffected by exposure. Time-mated, nulliparous mice (C57BL/6BomTac, Taconic Europe, Ejby, Denmark) were exposed to filtered clean air or approximately 42 mg/m3 UV-Titan on GD 8M-bM-^@M-^S18 for 1 hr/day by a whole-body exposure.Delivery was expected on GD 20, and designated postnatal day (PND) 0. On PND 2, one offspring (M-bM-^@M-^\newbornM-bM-^@M-^]) per litter was killed by decapitation, to yield litters with at least 5 offspring per exposure group. The newborn offspring were collected two days after birth. On PND 23-24 (M-bM-^@M-^\at weaningM-bM-^@M-^]) one male and one female per litter were killed. Organs were dissected, weighed, placed in NUNC cryotubes, snap frozen in liquid N2 and stored at -80M-BM-0C until analysis. Exposed dams were killed on PND 24-25 (26-27 days after last exposure). DNA strad break detection was carried out in bronchoalveolar lavage fluid in dams by COMET assay. Total RNA was extracted from offspring livers and gene expression profiling was carried out on whole liver tissues from offspring. 9 UV-Titan treated and 7 controls mice consisting of 8 males and 8 females mRNA, hepatic, developmental, Toxicogenomics, nano-titanium dioxide

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Lack of hepatic response of microRNA in mice following chronic benzo(a)pyrene exposure (gene expression)

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