ABSTRACT
The transcription factor Nrf2 is a key regulator for hepatic induction of detoxifying enzymes, antioxidative stress genes and Mrp efflux transporters. We aimed to investigate whether Nrf2 activation counteracts liver injury associated with cholestasis. The role of Nrf2 activation in counteracting cholestatic liver injury was studied using a bile duct-ligation (BDL) model of Keap1 gene-knockdown (Keap1-kd) mice that represent the sustained activation of Nrf2 in the liver. Upon Nrf2 activation, Keap1-kd mice showed large increases in Mrp efflux transporters, detoxifying enzymes and antioxidative stress genes in the livers. After BDL, the number of hepatic parenchymal necrosis and the reactive oxygen species content were significantly smaller in the livers of the Keap1-kd mice than in those of the WT mice. Moreover, the increase in serum bilirubin levels was attenuated in the Keap1-kd mice. In conclusion, the results suggest a hepatoprotective role of sustained Nrf2 activation against liver injury associated with cholestasis.
Subject(s)
Cholestasis/complications , Gene Expression Regulation , Jaundice, Obstructive/complications , Liver Diseases/genetics , NF-E2-Related Factor 2/metabolism , Adaptor Proteins, Signal Transducing/genetics , Animals , Cytoskeletal Proteins/genetics , Gene Knockdown Techniques , Kelch-Like ECH-Associated Protein 1 , Liver/metabolism , Liver/pathology , Liver Diseases/etiology , Liver Diseases/pathology , Mice , Mice, Inbred C57BL , Multidrug Resistance-Associated Proteins/metabolism , NF-E2-Related Factor 2/genetics , Oxidative Stress/geneticsABSTRACT
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.
Subject(s)
Antioxidants/metabolism , Liver/metabolism , Multidrug Resistance-Associated Proteins/physiology , NF-E2-Related Factor 2/physiology , Ursodeoxycholic Acid/pharmacology , ATP Binding Cassette Transporter, Subfamily B, Member 11 , ATP-Binding Cassette Transporters/metabolism , Adaptor Proteins, Signal Transducing/deficiency , Adaptor Proteins, Signal Transducing/physiology , Animals , Cytoskeletal Proteins/deficiency , Cytoskeletal Proteins/physiology , Kelch-Like ECH-Associated Protein 1 , Mice , Mice, Knockout , NF-E2-Related Factor 2/drug effects , Up-RegulationABSTRACT
PURPOSE: Rho-associated coiled-coil-forming protein kinase (ROCK) is pivotally involved in invasion by tumor cells and their evolution to metastasis. We have developed a novel inhibitor of ROCK, Wf-536 [(+)-(R)-4-(1-aminoethyl)-N-(4-pyridyl) benzamide monohydrochloride]. In the present study, we investigated its effect on in vitro invasion and in vivo pulmonary metastasis of B16 melanoma. METHODS: The following were evaluated: the anti-invasive effect of Wf-536 against the motility of mouse B16BL6 melanoma cells through a culture insert layered with reconstituted basement membrane (Matrigel); the cytotoxic effect of Wf-536 in the same cell line; the antimetastatic effect of Wf-536, administered by osmotic pump, on spontaneous pulmonary metastasis following subcutaneous injection of B16BL6 melanoma in mice; and the inhibitory effect of orally administered Wf-536, alone or in combination with the antineoplastic drug paclitaxel, on pulmonary metastasis of intravenously injected B16F10 melanoma in mice. RESULTS: Wf-536 inhibited in vitro invasion by B16BL6 cells significantly and in a concentration-dependent manner and displayed an anti-invasive effect under conditions of both chemotaxis and chemokinesis. No cytotoxic effect was observed at any of the concentrations used. In vivo, Wf-536 administration suppressed tumor colony formation on the lung surface in a dose-dependent manner (0.3-3 mg/kg per day), with a metastasis inhibition rate of 95% at 3 mg/kg per day. In experimental metastasis of B16F10 melanoma, oral administration of Wf-536 significantly decreased tumor colony formation in the lung, with an inhibition rate of 41% at 3 mg/kg per day. The inhibition rate of paclitaxel (5 mg/kg per day) was 27%. The combination of Wf-536 and paclitaxel produced a synergistic effect on B16F10 metastasis and a 68% inhibition rate. Wf-536 administration at the doses used did not alter body weight, blood pressure or the health of treated animals as compared to vehicle-treated controls. CONCLUSION: The results suggest that Wf-536 is a potentially valuable drug for preventing tumor metastasis both in monotherapy and in combination with an antineoplastic drug.
