Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that promotes the transcription of cytoprotective genes in response to oxidative and electrophilic stresses. Most functions of Nrf2 were identified by studying biological models with Nrf2 deficiency, however, little is known about the effects of graded Nrf2 activation. In the present study, genomic gene expression profiles by microarray analysis were characterized with a "gene dose-response" model in livers of Nrf2-null mice, wild-type mice, Kelch-like ECH associating protein 1 (Keap1)-knockdown (Keap1-KD) mice with enhanced Nrf2 activation, and Keap1-hepatocyte knockout (Keap1-HKO) mice with maximum hepatic Nrf2 activation. Hepatic nuclear Nrf2 protein, glutathione concentrations, and known Nrf2 target genes were increased in a dose-dependent manner. In total, 115 genes were identified to be constitutively induced and 80 genes suppressed with graded Nrf2 activation. Messenger RNA of genes encoding enzymes in the pentose phosphate pathway and enzyme were low with Nrf2 deficiency and high with Nrf2 activation, indicating that Nrf2 is important for NADPH production. NADPH is the major reducing resource to scavenge oxidative stress, including regenerating glutathione and thioredoxin and is also used for anabolic pathways including lipid synthesis. High performance liquid chromatography-ultraviolet absorbance analysis confirmed that hepatic NADPH concentration was lowest in Nrf2-null mice and highest in Keap1-HKO mice. In addition, genes involved in fatty acid synthesis and desaturation were downregulated with graded Nrf2 activation. In conclusion, the present study suggests that Nrf2 protects against environmental insults by promoting the generation of NADPH, which is preferentially consumed by aiding scavenging of oxidative stress rather than fatty acid synthesis and desaturation.

Cytochrome P450 (Cyp) enzymes from the first four families (Cyp1-4) play a major role in metabolizing xenobiotics, affecting drug pharmacokinetics and chemical-induced toxicity. Due to cloning of the mouse genome, many novel Cyp isoforms have been identified, but their tissue distribution of expression is unknown. This study compared the tissue distribution of all 78 Cyps from the Cyp1-4 families in C57BL/6 mice providing not only an indication of which tissues novel Cyps may have their greatest importance but also a cohesive comparison of the tissue distribution of all Cyp1-4 isoforms. Transcripts of the 78 Cyps were quantified by multiplex suspension arrays and quantitative real-time PCR in 14 tissues. Hierarchical clustering indicated that in male mice, 52% of the Cyp species were expressed highest in liver, 10% in kidney, 10% in duodenum/jejunum, 10% in testes, 5% in lung, and < 4% in colon, brain, heart, and stomach. Female mice had a similar pattern of Cyp messenger RNA expression; however, compared with males, females had 7% more Cyps that were liver predominant, 2% more Cyps that were stomach predominant, but 1% less Cyps that were kidney and lung predominant. Differences in gender expression were observed in 29 of the Cyps, with 24 being higher in females than males. Additionally, the data suggest a correlation between the spatial arrangement of genes within a gene cluster and their organ-predominant expression, indicating a common regulatory mechanism may be present within these clusters. In conclusion, this study provides novel data on the tissue distribution and gender-divergent expression of 78 functional mouse Cyp isoforms.

Information on the intestinal microbiota has increased exponentially this century because of technical advancements in genomics and metabolomics. Although information on the synthesis of bile acids by the liver and their transformation to secondary bile acids by the intestinal microbiota was the first example of the importance of the intestinal microbiota in biotransforming chemicals, this review will discuss numerous examples of the mechanisms by which the intestinal microbiota alters the pharmacology and toxicology of drugs and other chemicals. More specifically, the altered pharmacology and toxicology of salicylazosulfapridine, digoxin, L-dopa, acetaminophen, caffeic acid, phosphatidyl choline, carnitine, sorivudine, irinotecan, nonsteroidal anti-inflammatory drugs, heterocyclic amines, melamine, nitrazepam, and lovastatin will be reviewed. In addition, recent data that the intestinal microbiota alters drug metabolism of the host, especially Cyp3a, as well as the significance and potential mechanisms of this phenomenon are summarized. The review will conclude with an update of bile acid research, emphasizing the bile acid receptors (FXR and TGR5) that regulate not only bile acid synthesis and transport but also energy metabolism. Recent data indicate that by altering the intestinal microbiota, either by diet or drugs, one may be able to minimize the adverse effects of the Western diet by altering the composition of bile acids in the intestine that are agonists or antagonists of FXR and TGR5. Therefore, it may be possible to consider the intestinal microbiota as another drug target.

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Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that induces a battery of cytoprotective genes in response to oxidative/electrophilic stress. Kelch-like ECH associating protein 1 (Keap1) sequesters Nrf2 in the cytosol. The purpose of this study was to investigate the role of Nrf2 in regulating the mRNA of genes encoding drug metabolizing enzymes and xenobiotic transporters. Microarray analysis was performed in livers of Nrf2-null, wild-type, Keap1-knockdown mice with increased Nrf2 activation, and Keap1-hepatocyte knockout mice with maximum Nrf2 activation. In general, Nrf2 did not have a marked effect on uptake transporters, but the mRNAs of organic anion transporting polypeptide 1a1, sodium taurocholate cotransporting polypeptide, and organic anion transporter 2 were decreased with Nrf2 activation. The effect of Nrf2 on cytochrome P450 (Cyp) genes was minimal, with only Cyp2a5, Cyp2c50, Cyp2c54, and Cyp2g1 increased, and Cyp2u1 decreased with enhanced Nrf2 activation. However, Nrf2 increased mRNA of many other phase-I enzymes, such as aldo-keto reductases, carbonyl reductases, and aldehyde dehydrogenase 1. Many genes involved in phase-II drug metabolism were induced by Nrf2, including glutathione S-transferases, UDP- glucuronosyltransferases, and UDP-glucuronic acid synthesis enzymes. Efflux transporters, such as multidrug resistance-associated proteins, breast cancer resistant protein, as well as ATP-binding cassette g5 and g8 were induced by Nrf2. In conclusion, Nrf2 markedly alters hepatic mRNA of a large number of drug metabolizing enzymes and xenobiotic transporters, and thus Nrf2 plays a central role in xenobiotic metabolism and detoxification.