Altered hepatic gene expression in liver-Cpr-null and Cpr-low mice

NADPH-cytochrome P450 reductase (CPR) is important for the functions of many enzymes, such as microsomal cytochrome P450 (P450) monooxygenases and heme oxygenases. Two mouse models with deficient CPR expression in adults were recently generated in this laboratory: liver-Cpr-null (with liver-specific Cpr deletion) (Gu et al., J. Biol. Chem., 278, 25895–25901, 2003) and Cpr-low (with reduced CPR expression in all organs examined) (Wu et al. J. Pharmacol. Expt. Ther. 312, 35-43, 2005). The phenotypes included a reduced serum cholesterol level and an induction of hepatic P450 in both models, and hepatomegaly and fatty liver in the liver-Cpr-null mouse alone. Our aim was to identify hepatic gene-expression changes related to these phenotypes. Cpr-lox mice, which have normal CPR expression (Wu et al., Genesis, 36, 177-181, 2003.), were used as the control in microarray analysis. A detailed analysis of the gene-expression changes in lipid metabolism and transport pathways revealed potential mechanisms, such as an increased activation of constitutive androstane receptor (CAR) and a decreased activation of peroxisomal proliferators activated receptor alpha (PPAR-gamma) by precursors of cholesterol biosynthesis, that underlie common changes (e.g., induction of multiple P450s and inhibition of genes for fatty acids metabolism) in response to CPR-loss in the two mouse models. Moreover, we also uncovered model-specific gene-expression changes, such as the induction of a lipid translocase (CD36 antigen) and the suppression of carnitine O-palmitoyltransferase 1 (CPT1a) and acyl-CoA synthetase long-chain family member 1 (Acsl1), that are potentially responsible for the severe hepatic lipidosis observed in liver-Cpr-null, but not Cpr-low mice. Keywords = Cytochrome P450 Keywords = NADPH-cytochrome P450 reductase Keywords = transgenic mice Keywords = liver Keywords = nuclear receptor Keywords: other