| Identification of Genes Implicated in Methapyrilene-Induced Hepatotoxicity by Comparing Differential Gene Expression in Target and Nontarget Tissue J. Todd Auman,1 Jeff Chou,1 Kevin Gerrish,1 Qihong Huang,2 Supriya Jayadev,2 Kerry Blanchard,2 and Richard S. Paules1 1National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA; 2Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut, USA Abstract
Background: Toxicogenomics experiments often reveal thousands of transcript alterations that are related to multiple processes, making it difficult to identify key gene changes that are related to the toxicity of interest. Objectives: The objective of this study was to compare gene expression changes in a nontarget tissue to the target tissue for toxicity to help identify toxicity-related genes. Methods: Male rats were given the hepatotoxicant methapyrilene at two dose levels, with livers and kidneys removed 24 hr after one, three, and seven doses for gene expression analysis. To identify gene changes likely to be related to toxicity, we analyzed genes on the basis of their temporal pattern of change using a program developed at the National Institute of Environmental Health Sciences, termed "EPIG" (extracting gene expression patterns and identifying co-expressed genes) . Results: High-dose methapyrilene elicited hepatic damage that increased in severity with the number of doses, whereas no treatment-related lesions were observed in the kidney. High-dose methapyrilene elicited thousands of gene changes in the liver at each time point, whereas many fewer gene changes were observed in the kidney. EPIG analysis identified patterns of gene expression correlated to the observed toxicity, including genes associated with endoplasmic reticulum stress and the unfolded protein response. Conclusions: By factoring in dose level, number of doses, and tissue into the analysis of gene expression elicited by methapyrilene, we were able to identify genes likely to not be implicated in toxicity, thereby allowing us to focus on a subset of genes to identify toxicity-related processes. Key words: DNA microarray, gene expression, hepatotoxicity, liver, methapyrilene, toxicogenomics. Environ Health Perspect 115:572–578 (2007) . doi:10.1289/ehp.9396 available via http://dx.doi.org/ [Online 17 January 2007]
Address correspondence to R.S. Paules, NIEHS, 111 T.W. Alexander Dr., P.O. Box 12233, Mail Drop D2-03, Research Triangle Park, NC 27709 USA. Telephone: (919) 541-3710. Fax: (919) 316-4771. E-mail: paules@niehs.nih.gov Supplemental material is available online (http://www.ehponline.org/docs/2007/9396/suppl.pdf) . We thank B. Knight (Boehringer-Ingelheim) for histopathologic analysis. We also acknowledge D. Malarkey and A. Merrick for critical review of this manuscript. This research was supported in part by ES-CRADA-03-028 and the intramural research programs of the NIH and NIEHS. The authors declare they have no competing financial interests. Received 2 June 2006 ; accepted 17 January 2007.
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