K+‐channel inhibition reduces portal perfusion pressure in fibrotic rats and fibrosis associated characteristics of hepatic stellate cells. (22nd September 2014)

• Record Type: Journal Article
• Authors: Freise, Christian; Heldwein, Silke; Erben, Ulrike; Hoyer, Joachim; Köhler, Ralf; Jöhrens, Korinna; Patsenker, Eleonora; Ruehl, Martin; Seehofer, Daniel; Stickel, Felix; Somasundaram, Rajan
• Is Part Of: Liver international. Volume 35:Number 4(2015:Apr.)
• Page Start: 1244
• Page End: 1252
• Publication Date: 2014-09-22
• Subjects: Liver -- Periodicals; Liver -- Diseases -- Periodicals; 616.362
• DOI: 10.1111/liv.12681
• Languages: English
• ISSNs: 1478-3223

Abstract

<abstract abstract-type="main" id="liv12681-abs-0001"> <title>Abstract</title> <sec id="liv12681-sec-0001" sec-type="section"> <title>Background & Aims</title> <p>In liver fibrosis, activated hepatic stellate cells (HSC) secrete excess extracellular matrix, thus, represent key targets for antifibrotic treatment strategies. Intermediate‐conductance Ca<sup>2</sup> <sup>+</sup> ‐activated K<sup>+</sup>‐channels (KCa3.1) are expressed in non‐excitable tissues affecting proliferation, migration and vascular resistance rendering KCa3.1 potential targets in liver fibrosis. So far, no information about KCa3.1 expression and their role in HSC exists. Aim was to quantify the KCa3.1 expression in HSC depending on HSC activation and investigation of antifibrotic properties of the specific KCa3.1 inhibitor TRAM‐34 <italic>in vitro</italic> and <italic>in vivo</italic>.</p> </sec> <sec id="liv12681-sec-0002" sec-type="section"> <title>Methods</title> <p>KCa3.1 expression and functionality were studied in TGF‐β1–activated HSC by quantitative real time PCR, western‐blot and patch‐clamp analysis respectively. Effects of TRAM‐34 on HSC proliferation, cell cycle and fibrosis‐related gene expression were assessed by [<sup>3</sup>H]‐thymidine incorporation, FACS‐analysis and RT‐PCR respectively. <italic>In vivo</italic>, vascular resistance and KCa3.1 gene and protein expression were determined in bile duct ligated rats by <italic>in situ</italic> liver perfusion, Taqman PCR and immunohistochemistry respectively.</p> </sec> <sec id="liv12681-sec-0003" sec-type="section"> <title>Results</title> <p>Fibrotic tissues and TGF‐β1‐activated HSC exhibited higher KCa3.1‐expressions than normal tissue and untreated cells. KCa3.1 inhibition with TRAM‐34 reduced HSC proliferation by induction of cell cycle arrest and reduced TGF‐β1‐induced gene expression of collagen I, alpha‐smooth muscle actin and TGF‐β1 itself. Furthermore, TRAM‐34 blocked TGF‐β1‐induced activation of TGF‐β signalling in HSC. <italic>In vivo</italic>, TRAM‐34 reduced the thromboxane agonist‐induced portal perfusion pressure.</p> </sec> <sec id="liv12681-sec-0004" sec-type="section"> <title>Conclusion</title> <p>Inhibition of KCa3.1 with TRAM‐34 downregulates fibrosis‐associated gene expression <italic>in vitro, </italic> and reduces portal perfusion pressure <italic>in vivo</italic>. Thus, KCa3.1 may represent novel targets for the treatment of liver fibrosis.</p> </sec> </abstract>