ToxSci Advance Access originally published online on July 24, 2008
Toxicological Sciences 2008 106(1):263-283; doi:10.1093/toxsci/kfn144
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Coordinated Changes in Xenobiotic Metabolizing Enzyme Gene Expression in Aging Male Rats
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* NHEERL/ORD, US EPA, Research Triangle Park, North Carolina 27711
North Carolina Central University, Durham, North Carolina 27707
NHEERL Toxicogenomics Core, US EPA, Research Triangle Park, North Carolina 27711
1 To whom correspondence should be addressed at Chris Corton, Environmental Carcinogenesis Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, 109 T.W. Alexander Dr., MD-B143-06, Research Triangle Park, NC 27711. Fax: (919) 541-0694. E-mail: corton.chris{at}epa.gov.
Received April 25, 2008; accepted July 11, 2008
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Abstract |
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In order to gain insight into the effects of aging on susceptibility to environmental toxins, we characterized the expression of xenobiotic metabolizing enzymes (XMEs) from the livers of male F344 and Brown Norway (BN) rats across the adult lifespan. Using full-genome Affymetrix arrays, principal component analysis showed a clear age-dependent separation between young and old animals in both rat strains. Out of 1135 or 1435 genes altered between the old and young groups in the F344 or BN rats, 7 or 3% were XMEs and included members of the phase I, II, and III classes of genes. There was a 20 or 32% overlap in the gene expression profile between the two strains for F344 or BN, respectively. Lipid, ergosterol, alcohol, and fatty acid metabolism genes were also altered with age in both strains. Some of the genes altered by age exhibited a gender-dependent expression pattern in young adult rats, suggesting an increasingly feminized pattern of gene expression with age in male rats. To examine transcriptional responses across lifespan after challenge with a xenobiotic compound, BN rats were exposed to toluene by oral gavage. Toluene exposure decreased the expression of glutathione synthetase, and dramatically increased the number of phase III genes being downregulated. The expression of CYP2B2 and glutathione-S-transferase decreased with age but increased in all age groups after toluene exposure. Decreased ability to detoxify and transport chemicals out of the body with age could result in increased susceptibility to some classes of chemicals in the aging population.
Key Words: xenobiotic metabolism; aging; liver; gene expression; susceptibility; microarrays.
Disclaimer: It has been subjected to review by the National Health and Environmental Effects Research Laboratory and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.