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Effect of furan on transcriptomic and gene-specific DNA methylation changes in the livers of Fischer 344 rats in a two-year carcinogenicity study

ABSTRACT: The carcinogenic effect of furan, a potent hepatotoxicant and rodent liver carcinogen, has been attributed to genotoxic and non-genotoxic, including epigenetic, changes in the liver; however, the mechanisms of the furan liver tumorigenicity are still unclear. The goal of the present study was to investigate the role of transcriptomic and epigenetic events in the development of hepatic lesions in Fischer (F344) rats induced by furan treatment in a classic two-year rodent tumorigenicity bioassay. Male F344 rats were distributed randomly into control and experimental groups. Rats from the experimental groups were treated by gavage 5 days/week with either 0.92 or 2.0 mg furan/kg body weight (bw) in corn oil for 104 weeks. Rats from control group received corn oil only. High-throughput whole genome microarray analyses demonstrated distinctive dose-dependent alterations in gene expression in the furan-induced liver lesions. A total of 2073 and 2422 genes was found to be differentially expressed in the furan-induced liver lesions in rats treated with 0.92 and 2.0 mg furan/kg bw, respectively, as compared to normal liver tissue. Approximately 60% (1340) of the differentially expressed genes were common to both treatment groups. In silico analysis of the common differentially expressed genes revealed the presence of CpG island in 51% (679) of the genes, suggesting that they may be epigenetically regulated. Promoter methylation analysis of individual differentially expressed CpG island-containing genes demonstrated dose-dependent gene-specific methylation changes that were highly correlated with gene expression. Our findings illustrate that gene-specific DNA methylation changes have functional consequences and may contribute to the development of furan-induced pathologic liver lesions.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE71055 | GEO | 2015/07/18

SECONDARY ACCESSION(S): PRJNA290196

REPOSITORIES: GEO

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Project description:Furan is a widely used industrial chemical and a common contaminant in heated foods. Chronic furan exposure has been shown to cause cholangiocarcinoma and hepatocellular tumors at doses of 2 mg/kg bw/day with gender differences in frequency and severity. The hepatic transcriptional alterations induced by low doses of furan (doses below those inducing liver tumors) and the potential mechanisms underlying gender differences are largely unexplored. We used DNA microarrays to examine the global hepatic mRNA and microRNA transcriptional profiles of male and female rats exposed to 0, 0.03, 0.12, 0.5 or 2 mg/kg bw/day furan over 90 days. Marked gender differences in gene expression responses to furan were observed, with many more altered genes in exposed males than females, confirming the increased sensitivity of males even at the low doses. Pathway analysis supported that key events in furan-induced hepatotoxicity in males included gene expression changes related to oxidative stress, apoptosis and inflammatory response, while pathway changes in females were consistent with primarily adaptive responses (regeneration). Pathway benchmark doses (BMDs) were estimated and compared to relevant apical endpoints. Transcriptional BMDs could be examined in males, they ranged from 0.08 – 1.43 mg/kg bw/day and approximated those derived from traditional histopathology. MiR-34a (a target of P53 signalling) was the only microRNA significantly increased at the 2 mg/kg bw/day, providing evidence in support of the importance of apoptosis and cell proliferation in furan hepatotoxicity. Overall, this study demonstrates the use of transcriptional profiling to discern mode of action and mechanisms involved in gender differences. Total RNAs from 16 liver samples (4 males and 4 females from control and 2 mg/kg bw/day dose groups) were processed using the miRNA Complete Labelling and Hybridization kit (Agilent Technologies Inc.). Labelled RNA was hybridized on 8 X 15K Agilent rat miRNA microarray slides. Arrays were scanned using an Agilent G2505B scanner (5 ?M resolution). Feature extraction (version 10.7.3.1, Agilent Tech. Inc.) was used to acquire the fluorescence intensity of each probe.

Project description:Furan is a widely used industrial chemical and a common contaminant in heated foods. Chronic furan exposure has been shown to cause cholangiocarcinoma and hepatocellular tumors at doses of 2 mg/kg bw/day with gender differences in frequency and severity. The hepatic transcriptional alterations induced by low doses of furan (doses below those inducing liver tumors) and the potential mechanisms underlying gender differences are largely unexplored. We used DNA microarrays to examine the global hepatic mRNA and microRNA transcriptional profiles of male and female rats exposed to 0, 0.03, 0.12, 0.5 or 2 mg/kg bw/day furan over 90 days. Marked gender differences in gene expression responses to furan were observed, with many more altered genes in exposed males than females, confirming the increased sensitivity of males even at the low doses. Pathway analysis supported that key events in furan-induced hepatotoxicity in males included gene expression changes related to oxidative stress, apoptosis and inflammatory response, while pathway changes in females were consistent with primarily adaptive responses (regeneration). Pathway benchmark doses (BMDs) were estimated and compared to relevant apical endpoints. Transcriptional BMDs could be examined in males, they ranged from 0.08 M-bM-^@M-^S 1.43 mg/kg bw/day and approximated those derived from traditional histopathology. MiR-34a (a target of P53 signalling) was the only microRNA significantly increased at the 2 mg/kg bw/day, providing evidence in support of the importance of apoptosis and cell proliferation in furan hepatotoxicity. Overall, this study demonstrates the use of transcriptional profiling to discern mode of action and mechanisms involved in gender differences. A total of 50 RNA samples (5 female and 5 male rats per dose group, 5 dose groups total) were labelled with Cyanine 5-CTP using Low Input Quick Amp Labelling kits (Agilent Technologies Inc.) following the manufacturerM-bM-^@M-^Ys instruction. Universal rat reference total RNA (Agilent Technologies Inc.) was labelled with Cyanine 3-CTP. Cy5-sample cRNA and Cy3-reference cRNA were hybridized to Agilent G4853A SurePrint G3 Rat GE 8 X 60K microarrays (Agilent Technologies Inc.). One microarray from the male group did not pass the quality control and was eliminated from further analyses

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Effect of furan on transcriptomic and gene-specific DNA methylation changes in the livers of Fischer 344 rats in a two-year carcinogenicity study

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