Current therapeutic interventions for treating liver diseases are very limited;identification of a therapeutic target is a prerequisite for developing new drugs to treat liver diseases. Oxidative stress and inflammation play key roles in the pathogenesis of liver diseases. Nuclear factor 2-related factor 2 (Nrf2), a transcription factor expressed in both hepatocytes and immune cells, is a key factor in anti-oxidative and anti-inflammatory responses. In quiescent hepatocytes, Nrf2 is sequestered in cytosol by kelch-like ECH-associated protein 1 (Keap1);in Keap1-knockdown mice, nuclear translocation of Nrf2 increases, resulting in activation of Nrf2 target genes. The importance of Nrf2 in cytoprotection is recognized. Nevertheless, the role of Nrf2 in liver pathophysiology has just recently gained attention. Our long-term goal is to identify a novel drug target and develop a therapeutic/preventive strategy for liver diseases. The objective of this R01 grant proposal is to investigate in-depth the role of Nrf2 in protecting against liver pathophysiology and understand its underlying molecular mechanisms. Based upon our strong preliminary data, our central hypothesis is that Nrf2 is a master regulator of liver protection through its multifaceted roles in biotransformation/disposition, antioxidation, tissue- repair, and anti-inflammation in multiple cell types in liver.
Aim 1 will identify direct targets of Nrf2 regulation using ChIP-Sequencing and determine Nrf2-dependent mRNA induction in the Keap1-knockdown mouse.
Aim 2 will test the hypothesis that Nrf2 activation protects against chemical, dietary, and genetic models of liver disease. We will use 3 genetic models of mice with differential Nrf2 activity, namely Nrf2-null, wild-type, and Nrf2-enhanced mice, to test liver disease susceptibility in 13 different models.
Aim 3 will develop novel and specific Nrf2 activator lead candidates by high throughput screening in collaboration with the Office of Therapeutics, Discovery, and Development. Our proposed study is novel, because it utilizes 3 mouse lines with different Nrf2 activities to investigate the opposing effects of Nrf2 deficiency and Nrf2 activation on liver diseases induced via diverse mechanisms of toxicity. This proposal utilizes innovative techniques including ChIP-sequencing, multiplex mRNA analysis, and nuclear translocation high throughput screening in testing the 3 aims. Our proposed study is significant, because results from our experiments will provide solid evidence regarding the importance of Nrf2 deficiency and Nrf2 activation in liver pathophysiology and its underlying molecular mechanisms, setting the scientific foundation for developing Nrf2 activators as novel drugs to treat/prevent various liver diseases, such as chemical-induced liver injury, inflammatory liver diseases, steatohepatitis, and liver fibrosis/cirrhosis.
Liver disease is a common ailment, however in contrast to most other diseases, there are very few drugs for liver failure. We hypothesize that Nrf2, an essential transcription factor, is a drug target that can be used to prevent and treat a wide-range of liver ailments. This study will determine whether this drug target will be effective against a wide-spectrum of animal models of liver disease.
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|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|
|Lu, Yuan-Fu; Liu, Jie; Wu, Kai Connie et al. (2014) Overexpression of Nrf2 protects against microcystin-induced hepatotoxicity in mice. PLoS One 9:e93013|
|Cheng, Xingguo; Vispute, Saurabh G; Liu, Jie et al. (2014) Fibroblast growth factor (Fgf) 21 is a novel target gene of the aryl hydrocarbon receptor (AhR). Toxicol Appl Pharmacol 278:65-71|
|Cazanave, S C; Wang, X; Zhou, H et al. (2014) Degradation of Keap1 activates BH3-only proteins Bim and PUMA during hepatocyte lipoapoptosis. Cell Death Differ 21:1303-12|
|Fu, Zidong Donna; Klaassen, Curtis D (2014) Short-term calorie restriction feminizes the mRNA profiles of drug metabolizing enzymes and transporters in livers of mice. Toxicol Appl Pharmacol 274:137-46|
|Zhang, Yu-Kun Jennifer; Wu, Kai Connie; Klaassen, Curtis D (2013) Genetic activation of Nrf2 protects against fasting-induced oxidative stress in livers of mice. PLoS One 8:e59122|
|Zhang, Yu-Kun Jennifer; Lu, Hong; Klaassen, Curtis D (2013) Expression of human CAR splicing variants in BAC-transgenic mice. Toxicol Sci 132:142-50|
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|Lu, Yuan-Fu; Jin, Tao; Xu, Yasha et al. (2013) Sex differences in the circadian variation of cytochrome p450 genes and corresponding nuclear receptors in mouse liver. Chronobiol Int 30:1135-43|
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