ABSTRACT
Microarray technology was evaluated for usefulness in assessing relationships between serum corticosterone and hepatic gene expression. Nine pairs of female Swiss mice were chosen to provide a wide range of serum corticosterone ratios; cDNA microarray analysis (approximately 8000 genes) was performed on their livers. A statistical method based on calculation of 99% confidence intervals discovered 32 genes which varied significantly among the livers. Five of these ratios correlated significantly with serum corticosterone ratio, including tyrosine aminotransferase, stress-induced protein, pleiotropic regulator 1 and insulin-like growth factor-binding protein-1; the latter has a potential role in cancer development. Secondly, linear regression of gene expression vs corticosterone ratios was screened for those with r> or =0.8 (P<0.01), yielding 141 genes, including some known to be corticosterone regulated and others of interest as possible glucocorticoid targets. Half of these significant correlations involved data sets where no microarray ratio exceeded +/- 1.5. These results showed that microarray may be used to survey tissues for changes in gene expression related to serum hormones, and that even small changes in expression can be of statistical significance in a study with adequate numbers of replicate samples.
Subject(s)
Corticosterone/blood , Gene Expression Regulation, Neoplastic/genetics , Insulin-Like Growth Factor Binding Protein 1/metabolism , Liver/metabolism , Animals , Apoptosis Regulatory Proteins , Carrier Proteins/genetics , Carrier Proteins/metabolism , Female , Gene Expression Profiling/methods , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Insulin-Like Growth Factor Binding Protein 1/genetics , Mice , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Oligonucleotide Array Sequence Analysis/methods , Tyrosine Transaminase/genetics , Tyrosine Transaminase/metabolismABSTRACT
The peroxisome proliferator-activated receptor alpha (PPAR alpha) is the mediator of the biological effects of peroxisome proliferators through control of gene transcription. To determine if the toxic effects of di(2-ethylhexyl)phthalate (DEHP) are mediated by PPAR alpha, we examined its effect in PPAR alpha-null mice. Male Sv/129 mice, PPAR alpha-null (-/-) or wild-type (+/+) were fed ad libitum either a control diet or one containing 12,000 ppm DEHP for up to 24 wk. Significant body weight loss and high mortality was observed in (+/+) mice fed DEHP. By 16 wk, all DEHP-fed (+/+) mice had died of cystic renal tubular disease. In contrast, the (-/-) mice fed DEHP had no changes in body weight until later in the study nor increased mortality. Histologically, (+/+) mice fed DEHP had typical toxic lesions in liver, kidney, and testis while (-/-) mice fed DEHP had no toxic liver lesions but did show evidence of toxicity in kidney and testis after 4-8 wk of feeding, which progressed into moderate lesions by 24 wk. Analysis of hepatic and renal mRNAs showed a typical pleiotropic response in gene expression in the DEHP-fed (+/+) mice that was absent in the DEHP-fed (-/-) mice. These results provide evidence that PPAR alpha mediates the subacute-chronic toxicity of DEHP in liver, kidney, and testis. However, because (-/-) mice did develop toxic lesions in kidney and testis, DEHP can also act through PPAR alpha-independent pathways in mediating renal and testicular toxicity.
