BACKGROUND/AIMS: Multidrug resistance-associated protein 4 (Mrp4, ABCC4) transports cyclic nucleotides, anti-retroviral compounds, and sulfated bile acids. Mrp4 expression is increased in farnesyl/bile acid receptor knockout mice. Our aim was to investigate Mrp4 expression and function in rat liver and kidney in obstructive cholestasis. METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL) or sham-surgery. Animals were sacrificed after 3, 7, and 14 days and tissues were harvested for Western blot analysis, real-time reverse transcriptase-mediated polymerase chain reaction (RT-PCR), and immunohistochemistry. RESULTS: Western blot analysis revealed a progressive, more than seven-fold increase (P < 0.05) of Mrp4 expression in cholestatic livers, 14 days after BDL. In contrast, Mrp4 in 14-day BDL kidneys decreased to 26+/-4% of controls (P < 0.005). Immunohistochemistry localized Mrp4 to the basolateral hepatocyte membrane and corroborated its hepatic up-regulation after BDL. Real-time RT-PCR demonstrated no major changes of Mrp4 mRNA levels in liver and kidney after BDL. Cyclic adenosine monophosphate, an MRP4 substrate, was increased in plasma and urine, consistent with these findings. CONCLUSIONS: Obstructive cholestasis in rats results in progressive up-regulation of Mrp4 protein in liver but down-regulation in kidney. The absence of corresponding changes in Mrp4 mRNA suggests posttranscriptional mechanisms as predominant regulators of Mrp4 expression in BDL rats.
BACKGROUND/AIMS: Multidrug resistance-associated protein 4 (Mrp4, ABCC4) transports cyclic nucleotides, anti-retroviral compounds, and sulfated bile acids. Mrp4 expression is increased in farnesyl/bile acid receptor knockout mice. Our aim was to investigate Mrp4 expression and function in rat liver and kidney in obstructive cholestasis. METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL) or sham-surgery. Animals were sacrificed after 3, 7, and 14 days and tissues were harvested for Western blot analysis, real-time reverse transcriptase-mediated polymerase chain reaction (RT-PCR), and immunohistochemistry. RESULTS: Western blot analysis revealed a progressive, more than seven-fold increase (P < 0.05) of Mrp4 expression in cholestatic livers, 14 days after BDL. In contrast, Mrp4 in 14-day BDL kidneys decreased to 26+/-4% of controls (P < 0.005). Immunohistochemistry localized Mrp4 to the basolateral hepatocyte membrane and corroborated its hepatic up-regulation after BDL. Real-time RT-PCR demonstrated no major changes of Mrp4 mRNA levels in liver and kidney after BDL. Cyclic adenosine monophosphate, an MRP4 substrate, was increased in plasma and urine, consistent with these findings. CONCLUSIONS:Obstructive cholestasis in rats results in progressive up-regulation of Mrp4 protein in liver but down-regulation in kidney. The absence of corresponding changes in Mrp4 mRNA suggests posttranscriptional mechanisms as predominant regulators of Mrp4 expression in BDL rats.
Authors: François R Jornayvaz; Hui-Young Lee; Michael J Jurczak; Tiago C Alves; Fitsum Guebre-Egziabher; Blas A Guigni; Dongyan Zhang; Varman T Samuel; J Enrique Silva; Gerald I Shulman Journal: Endocrinology Date: 2011-12-06 Impact factor: 4.736
Authors: Laura G Di Pasqua; Clarissa Berardo; Vittoria Rizzo; Plinio Richelmi; Anna Cleta Croce; Mariapia Vairetti; Andrea Ferrigno Journal: Mol Cell Biochem Date: 2016-06-29 Impact factor: 3.396
Authors: Katharina Brandl; Phillipp Hartmann; Lily J Jih; Donald P Pizzo; Josepmaria Argemi; Meritxell Ventura-Cots; Sally Coulter; Christopher Liddle; Lei Ling; Stephen J Rossi; Alex M DePaoli; Rohit Loomba; Wajahat Z Mehal; Derrick E Fouts; Michael R Lucey; Francisco Bosques-Padilla; Philippe Mathurin; Alexander Louvet; Guadalupe Garcia-Tsao; Elizabeth C Verna; Juan G Abraldes; Robert S Brown; Victor Vargas; Jose Altamirano; Juan Caballería; Debbie Shawcross; Peter Stärkel; Samuel B Ho; Ramon Bataller; Bernd Schnabl Journal: J Hepatol Date: 2018-04-12 Impact factor: 25.083