Low Doses of the Carcinogen Furan Alter Cell Cycle and Apoptosis Gene Expression in Rat Liver Independent of DNA Methylation

Abstract

BackgroundEvidence of potent rodent carcinogenicity via an unclear mechanism suggests that furan in various foods [leading to an intake of up to 3.5 μg/kg body weight (bw)/day] may present a potential risk to human health.ObjectivesWe tested the hypothesis that altered expression of genes related to cell cycle control, apoptosis, and DNA damage may contribute to the carcinogenicity of furan in rodents. In addition, we investigated the reversibility of such changes and the potential role of epigenetic mechanisms in response to furan doses that approach the maximum estimated dietary intake in humans.MethodsThe mRNA expression profiles of genes related to cell cycle, apoptosis, and DNA damage in rat liver treated with furan concentrations of 0.1 and 2 mg/kg bw were measured by quantitative polymerase chain reaction (PCR) arrays. We assessed epigenetic changes by analysis of global and gene-specific DNA methylation [methylation-specific PCR, combined bisulfite restriction analysis (COBRA), and methylated DNA immunoprecipitation chip] and microRNA (miRNA) analyses.ResultsThe expression profiles of apoptosis-related and cell-cycle–related genes were unchanged after 5 days of treatment, although we observed a statistically significant change in the expression of genes related to cell cycle control and apoptosis, but not DNA damage, after 4 weeks of treatment. These changes were reversed after an off-dose period of 2 weeks. None of the gene expression changes was associated with a change in DNA methylation, although we detected minor changes in the miRNA expression profile (5 miRNA alterations out of 349 measured) that may have contributed to modification of gene expression in some cases.ConclusionNongenotoxic changes in gene expression may contribute to the carcinogenicity of furan in rodents. These findings highlight the need for a more comprehensive risk assessment of furan exposure in humans.

Assessment of global and gene-specific DNA methylation in rat liver and kidney in response to non-genotoxic carcinogen exposure

“…LINE-1 showed little enrichment in control and OTA treated kidney samples (Fig. 5a) which is consistent with the previous reports that LINE-1 was hypomethylated in rat liver (Asada et al, 2006;Chen et al, 2010).…”

“…Gene ID determines the distribution of DNA-methylation within promoters or in the entire genome, to identify genes modulated by treatment with nongenotoxic carcinogens (Chen et al, 2010(Chen et al, , 2012. We found methylation changes using the method of MeDIP and microarray assay for MPY, TCDD and OTA while HCB, DCB, d-limonene and chloroform did not produce significant methylation changes.…”

“…4), whereas the 5′-upstream region of the H19 gene has been found to be highly methylated in the adult rat by bisulfite sequencing (Manoharan et al, 2004). Thus, c-myc and H19 could be employed as negative and positive controls, respectively (Chen et al, 2010). Repetitive sequences such as long/short interspersed nucleotide elements (LINE and SINE) in retrotransposons are methylated at different levels.…”

Downregulation of miR-151-5p Contributes to Increased Susceptibility to Arrhythmogenesis during Myocardial Infarction with Estrogen Deprivation

“…Fig. 3B shown that miR-151-5p could bind to FXYD1 gene 3′-UTR based on computational prediction using the miRNA Microcosm Targets hosted by European Bioinformatics Institute [23], [24]. Watson-Crick complementarity is shown in bold and connected by “I”, however, the matched base “G” and “U” connected by “:”.…”

Low dose assessment of the carcinogenicity of furan in male F344/N Nctr rats in a 2-year gavage study

“…This interpretation is supported by the observation that the depletion of ATP could be prevented by prior treatment with the cytochrome P450 inhibitor 1-phenylimidazole. Other low-dose effects that have been observed upon administration of furan to F344/N rats include an increase in cell proliferation, as indicated by an increase in bromodeoxyuridine incorporation in the subcapsular area of the caudate liver lobe (Mally et al ., 2010), and an increased expression of hepatic genes associated with cell cycle and apoptosis (Chen et al , 2010). …”