Basic Research
Copyright ©2005 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 21, 2005; 11(47): 7418-7429
Published online Dec 21, 2005. doi: 10.3748/wjg.v11.i47.7418
Hepatocyte cytoskeleton during ischemia and reperfusion - influence of ANP-mediated p38 MAPK activation
Melanie Keller, Alexander L Gerbes, Stefanie Kulhanek-Heinze, Tobias Gerwig, Uwe Grützner, Nico van Rooijen, Angelika M Vollmar, Alexandra K Kiemer
Melanie Keller, Stefanie Kulhanek-Heinze, Tobias Gerwig, Angelika M Vollmar, Alexandra K Kiemer, Department of Pharmacy, Centre of Drug Research, University of Munich, Butenandtstr. 5-13, 81377 Munich, Germany
Alexander L Gerbes, Tobias Gerwig, Alexandra K Kiemer, Department of Medicine II, Klinikum Großhadern, University of Munich, Marchionistr. 17, 81377 Munich, Germany
Uwe Grützner, Institute for Surgical Research, Klinikum Großhadern, University of Munich, Marchionistr. 17, 81377 Munich, Germany
Nico van Rooijen, Vrije Universiteit, VUMC, Department of Molecular Cell Biology, Faculty of Medicine, 1081 BT Amsterdam, The Netherlands
Author contributions: All authors contributed equally to the work.
Supported by the Deutsche Forschungsgemeinschaft, DFG-FOR 440/1. M.K. was supported by the LMU Munich, grant GVBI.S.527
Correspondence to: Alexandra K Kiemer, PhD, Professor of Pharmaceutical Biology, Saarland University, P.O. Box 15 11 50, D-66041 Saarbrücken, Germany. pharm.bio.kiemer@mx.uni-saarland.de
Telephone: +49-681-302-57301 Fax: +49-681-302-57302
Received: January 31, 2005
Revised: April 13, 2005
Accepted: April 18, 2005
Published online: December 21, 2005
Abstract

AIM: To determine functional consequences of this activation, whereby we focused on a potential regulation of the hepatocyte cytoskeleton during ischemia and reperfusion.

METHODS: For in vivo experiments, animals received ANP (5 μg/kg) intravenously. In a different experimental setting, isolated rat livers were perfused with KH-buffer±ANP (200 nmol/L)±SB203580 (2 μmol/L). Livers were then kept under ischemic conditions for 24 h, and either transplanted or reperfused. Actin, Hsp27, and phosphorylated Hsp27 were determined by Western blotting, p38 MAPK activity by in vitro phosphorylation assay. F-actin distribution was determined by confocal microscopy.

RESULTS: We first confirmed that ANP preconditioning leads to an activation of p38 MAPK and observed alterations of the cytoskeleton in hepatocytes of ANP-preconditioned organs. ANP induced an increase of hepatic F-actin after ischemia, which could be prevented by the p38 MAPK inhibitor SB203580 but had no effect on bile flow. After ischemia untreated livers showed a translocation of Hsp27 towards the cytoskeleton and an increase in total Hsp27, whereas ANP preconditioning prohibited translocation but caused an augmentation of Hsp27 phosphorylation. This effect is also mediated via p38 MAPK, since it was abrogated by the p38 MAPK inhibitor SB203580.

CONCLUSION: This study reveals that ANP-mediated p38 MAPK activation leads to changes in hepatocyte cytoskeleton involving an elevation of phosphorylated Hsp27 and thereby for the first time shows functional consequences of ANP-induced hepatic p38 MAPK activation.

Keywords: Hormonal preconditioning; Atrial natriuretic peptide; Hsp 27; Actin; Polymerization