ABSTRACT
Non-alcoholic fatty liver disease can result in changes to drug metabolism and disposition potentiating adverse drug reactions. Furthermore, arsenite exposure during development compounds the severity of diet-induced fatty liver disease. This study examines the effects of arsenite potentiated diet-induced fatty liver disease on hepatic transport in male mice. Changes were detected for Mrp2/3/4 hepatic transporter gene expression as well as for Oatp1a4/2b1/1b2. Plasma concentrations of Mrp and Oatp substrates were increased in arsenic exposure groups compared with diet-only controls. In addition, murine embryonic hepatocytes and adult primary hepatocytes show significantly altered transporter expression after exposure to arsenite alone: a previously unreported phenomenon. These data indicate that developmental exposure to arsenite leads to changes in hepatic transport which could increase the risk for ADRs during fatty liver disease.
Subject(s)
Arsenites/toxicity , Diet, High-Fat/adverse effects , Gene Expression Regulation/drug effects , Hepatocytes/drug effects , Liver/drug effects , Non-alcoholic Fatty Liver Disease/metabolism , Angiogenic Proteins/genetics , Angiogenic Proteins/metabolism , Animals , Biological Transport/drug effects , Embryo, Mammalian , Female , Fetus , Hepatocytes/metabolism , Hepatocytes/pathology , Liver/metabolism , Liver/pathology , Liver-Specific Organic Anion Transporter 1 , Male , Mice , Multidrug Resistance-Associated Proteins/genetics , Multidrug Resistance-Associated Proteins/metabolism , Non-alcoholic Fatty Liver Disease/etiology , Non-alcoholic Fatty Liver Disease/genetics , Non-alcoholic Fatty Liver Disease/pathology , Organic Anion Transporters, Sodium-Independent/genetics , Organic Anion Transporters, Sodium-Independent/metabolism , Organic Cation Transport Proteins/genetics , Organic Cation Transport Proteins/metabolism , Pregnancy , Primary Cell Culture , Signal TransductionABSTRACT
TGFß2 (transforming growth factor-ß2) is a key growth factor regulating epithelial to mesenchymal transition (EMT). TGFß2 triggers cardiac progenitor cells to differentiate into mesenchymal cells and give rise to the cellular components of coronary vessels as well as cells of aortic and pulmonary valves. TGFß signaling is dependent on a dynamic on and off switch in Smad activity. Arsenite exposure of 1.34 µM for 24-48 h has been reported to disrupt Smad phosphorylation leading to deficits in TGFß2-mediated cardiac precursor differentiation and transformation. In this study, the molecular mechanism of acute arsenite toxicity on TGFß2-induced Smad2/3 nuclear shuttling and TGFß2-mediated cardiac EMT was investigated. A 4-h exposure to 5 µM arsenite blocks nuclear accumulation of Smad2/3 in response to TGFß2 without disrupting Smad phosphorylation or nuclear importation. The depletion of nuclear Smad is restored by knocking-down Smad-specific exportins, suggesting that arsenite augments Smad2/3 nuclear exportation. The blockage in TGFß2-Smad signaling is likely due to the loss of Zn(2+) cofactor in Smad proteins, as Zn(2+) supplementation reverses the disruption in Smad2/3 nuclear translocation and transcriptional activity by arsenite. This coincides with Zn(2+) supplementation rescuing arsenite-mediated deficits in cardiac EMT. Thus, zinc partially protects cardiac EMT from developmental toxicity by arsenite.
