Ursodeoxycholic acid stimulates Nrf2-mediated hepatocellular transport, detoxification, and antioxidative stress systems in mice

Abstract

The protective action of ursodeoxycholic acid (UDCA) in cholestatic liver diseases may be mediated by choleresis, detoxification, and cytoprotection against oxidative stress. Nrf2, one transcription factor, serves as a cellular stress sensor and is a key regulator for hepatic induction of detoxifying enzymes, antioxidative stress genes, and numerous Mrp family members. We aimed to investigate whether UDCA induces hepatic Mrp expression along with that of detoxifying enzymes and antioxidative stress genes via the Nrf2 transcriptional pathway. The protein level, subcellular localization, and mRNA level of Mrp family members were assessed in livers of Keap1 gene-knockdown (Keap1-kd) mice and those of UDCA-fed wild-type (WT) and Nrf2 gene-null (Nrf2-null) mice. Nuclear levels of Nrf2 in livers of Keap1-kd mice markedly increased, resulting in constitutive activation of Nrf2. Keap1-kd mice have high-level expression of hepatic Mrp2, Mrp3, and Mrp4 relative to WT mice. UDCA potently increased nuclear Nrf2 expression level in livers of WT mice, and the treatment showed maximal hepatic induction of Mrp2, Mrp3, and Mrp4 in association with enhanced membranous localizations in an Nrf2-dependent manner. UDCA similarly increased nuclear Nrf2 expression level in rat hepatocytes. Chromatin immunoprecipitation assays using mouse hepatocytes revealed the binding of Nrf2 to antioxidant response elements in the promoter regions of Mrp2, Mrp3, and Mrp4. These findings demonstrate an important role of Nrf2 in the induction of Mrp family members in livers and suggest that a therapeutic mechanism of UDCA action is, via Nrf2 activation, a stimulation of detoxification and antioxidative stress systems, along with Mrp-mediated efflux transport.

Farnesoid X Receptor Activation by Chenodeoxycholic Acid Induces Detoxifying Enzymes through AMP-Activated Protein Kinase and Extracellular Signal-Regulated Kinase 1/2-Mediated Phosphorylation of CCAAT/Enhancer Binding Protein β

“…Our data are in agreement with the observation that CDCA treatment activated Nrf2 and induced its target genes in the liver and intestinal cells (Tan et al, 2007). Ursodeoxycholic acid, another bile acid, has been used in clinical studies to treat liver diseases including primary biliary cirrhosis, and a large part of its beneficial aspect may be attributable to its property of Nrf2 activation (Okada et al, 2008;Kawata et al, 2010). Hence, it is presumed that an enhanceosome complex containing C/EBP␤ and Nrf2 may work together in inducing target genes by CDCA.…”

Highly Potent Activation of Nrf2 by Topical Tricyclic Bis(Cyano Enone): Implications for Protection against UV Radiation during Thiopurine Therapy

“…Of note, in our previous experience (unpublished), such systemic effects on any of these systems were not observed when sulforaphane, another potent Nrf2 activator, was topically administered under similar experimental conditions. MRP4 participates in the export of nucleoside monophosphate analogs (41)(42)(43), and its inducible gene expression is known to be regulated by Nrf2 (40,44,45). Furthermore, silencing of mrp4 increases the 6-TG incorporation in DNA of Hepa1c1c7 cells treated with this thiopurine (36).…”

“…The primers and probe used to measure mRNA for MRP4 (40) were synthesized by MWG-Biotech UK Ltd. Total RNA from mouse liver and skin was extracted using RNeasy and RNeasy Fibrous Tissue Kit (Qiagen Ltd.), respectively. Total RNA (500 ng) was reverse transcribed into cDNA with Omniscript Reverse Transcription Kit (Qiagen Ltd.).…”

The Role of Canalicular ABC Transporters in Cholestasis

“…Bile duct ligation or lipopolysaccharide (LPS) treatment resulted in an IL-1b-mediated RARa/RXRa downregulation, which in turn decreased ABCC2 transcription in rats (Denson et al, 2002). Oxidative stress (e.g., via toxic bile acids) can increase ABCC2 transcription via nuclear factor erythroid 2-related factor 2 in rodents (Maher et al, 2007;Okada et al, 2008). Posttranscriptional mechanisms fine tune the canalicular ABCC2 expression.…”