Multidrug resistance-associated proteins (Mrps) play a key role in hepatic detoxication by transporting Phase-ll conjugates and other organic compounds out of hepatocytes. Similarly, upregulation of Mrps in tumor cells confers resistance to chemotherapeutic drugs by transporting these cytotoxic compounds out of cells. The regulatory mechanisms governing Mrp expression in normal and diseased liver, and in tumor cells, are not understood. Thus, the overall goal of this application is to study the molecular mechanisms of transcriptional regulation of Mrps. Nuclear factor E2 related-factor 2 (Nrf2) is emerging as a critical transcription factor in regulation of both constitutive and inducible expression of Phase-ll enzymes. Because Mrps play a key role in the efflux of Phase-ll conjugates, we hypothesize that Mrps are coordinately regulated with Phase-ll enzymes by Nrf2. We recently examined Mrp expression in three different models: 1) mice treated with monofunctional inducers that selectively upregulate Phase-ll enzymes, 2) bile-duct ligation, a surgical model of extrahepatic cholestasis, and 3) mice with targeted disruption of glutathione synthesis. In each model, induction of Mrps and classical Nrf2 target genes was observed. Moreover, using in-silico analysis, we identified putative Nrf2-responsive sequences, known as electrophile response elements (EpREs), in the 5' flanking regions of the Mrp2, 3, and 4 genes. We hypothesize that activation and subsequent binding of Nrf2 to these EpREs results in increased expression of Mrp2, 3, and 4. Thus we propose Mrps belong to the battery of Nrf2-regulated detoxication genes. To test this hypothesis, we will determine: 1) the role of Nrf2 in Mrp induction in mice, taking advantage of Nrf2-null mice, 2) Nrf2 activation and subsequent translocation to the nucleus, 3) critical response elements by in vitro and in vivo reporter gene assay in combination with promoter deletion analysis, 4) Nrf2 binding to EpREs identified in Mrp 5' flanking regions, and 5) specificity of Nrf2 binding to Mrp promoter regions. Data from the experiments in this proposal will provide novel insight into the transcriptional regulation of Mrps. Elucidation of the role of Nrf2 in the regulation of the efflux transport process will have significant ramifications in toxicology, xenobiotics disposition, drug-drug interaction, and cancer chemoprevention. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES009716-07
Application #
7274868
Study Section
Hepatobiliary Pathophysiology Study Section (HBPP)
Program Officer
Shreffler, Carol K
Project Start
2000-08-10
Project End
2011-07-31
Budget Start
2007-08-01
Budget End
2008-07-31
Support Year
7
Fiscal Year
2007
Total Cost
$339,001
Indirect Cost
Name
University of Kansas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
016060860
City
Kansas City
State
KS
Country
United States
Zip Code
66160
Liu, Jie; Lu, Hong; Lu, Yuan-Fu et al. (2014) Potency of individual bile acids to regulate bile acid synthesis and transport genes in primary human hepatocyte cultures. Toxicol Sci 141:538-46
Zhang, Youcai; Hong, Ji-Young; Rockwell, Cheryl E et al. (2012) Effect of bile duct ligation on bile acid composition in mouse serum and liver. Liver Int 32:58-69
Wu, Kai Connie; Zhang, Youcai; Klaassen, Curtis D (2012) Nrf2 protects against diquat-induced liver and lung injury. Free Radic Res 46:1220-9
Wu, Kai Connie; Liu, Jie; Klaassen, Curtis D (2012) Role of Nrf2 in preventing ethanol-induced oxidative stress and lipid accumulation. Toxicol Appl Pharmacol 262:321-9
Martin, L A; Wilson, D T; Reuhl, K R et al. (2012) Polychlorinated biphenyl congeners that increase the glucuronidation and biliary excretion of thyroxine are distinct from the congeners that enhance the serum disappearance of thyroxine. Drug Metab Dispos 40:588-95
Cui, Julia Yue; Renaud, Helen J; Klaassen, Curtis D (2012) Ontogeny of novel cytochrome P450 gene isoforms during postnatal liver maturation in mice. Drug Metab Dispos 40:1226-37
Wu, Kai Connie; Cui, Julia Yue; Klaassen, Curtis D (2012) Effect of graded Nrf2 activation on phase-I and -II drug metabolizing enzymes and transporters in mouse liver. PLoS One 7:e39006
Zhang, Yu-Kun Jennifer; Guo, Grace L; Klaassen, Curtis D (2011) Diurnal variations of mouse plasma and hepatic bile acid concentrations as well as expression of biosynthetic enzymes and transporters. PLoS One 6:e16683
Alnouti, Yazen; Klaassen, Curtis D (2011) Mechanisms of gender-specific regulation of mouse sulfotransferases (Sults). Xenobiotica 41:187-97
Wu, Kai Connie; Cui, Julia Yue; Klaassen, Curtis D (2011) Beneficial role of Nrf2 in regulating NADPH generation and consumption. Toxicol Sci 123:590-600

Showing the most recent 10 out of 96 publications