Mildly Oxidized Low Density Lipoprotein Induces Contraction of Human Endothelial Cells through Activation of Rho/Rho Kinase and Inhibition of Myosin Light Chain Phosphatase

doi:10.1074/jbc.274.43.30361

Mildly Oxidized Low Density Lipoprotein Induces Contraction of Human Endothelial Cells through Activation of Rho/Rho Kinase and Inhibition of Myosin Light Chain Phosphatase*

From the ^‡Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Universität München, Pettenkoferstrasse 9, 80336 München, Germany, the ^**Max-von-Pettenkofer-Institut für Medizinische Mikrobiologie, Pettenkoferstrasse 9a, 80336 München, Germany, and the ^‖Department of Biochemistry, Cardiovascular Research Institute, University of Maastricht, P. O. Box 616, 6200 MD Maastricht, The Netherlands

Abstract

Mildly oxidized low density lipoprotein (mox-LDL) is critically involved in the early atherogenic responses of the endothelium and increases endothelial permeability through an unknown signal pathway. Here we show that (i) exposure of confluent human endothelial cells (HUVEC) to mox-LDL but not to native LDL induces the formation of actin stress fibers and intercellular gaps within minutes, leading to an increase in endothelial permeability; (ii) mox-LDL induces a transient decrease in myosin light chain (MLC) phosphatase that is paralleled by an increase in MLC phosphorylation; (iii) phosphorylated MLC stimulated by mox-LDL is incorporated into stress fibers; (iv) cytoskeletal rearrangements and MLC phosphorylation are inhibited by C3 transferase from Clostridium botulinum, a specific Rho inhibitor, and Y-27632, an inhibitor of Rho kinase; and (v) mox-LDL does not increase intracellular Ca²⁺concentration. Our data indicate that mox-LDL induces endothelial cell contraction through activation of Rho and its effector Rho kinase which inhibits MLC phosphatase and phosphorylates MLC. We suggest that inhibition of this novel cell signaling pathway of mox-LDL could be relevant for the prevention of atherosclerosis.

Footnotes

↵* This study was supported by Ernst und Berta Grimmke-Stiftung, Deutsche Forschungsgemeinschaft (GRK 438), August Lenz-Stiftung, Wilhelm Sander-Stiftung and NWO grant 90268241.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ These authors contributed equally to this work.
↵¶ To whom correspondence should be addressed. Tel.: +49/89/ 5160-4376; Fax: +49/89/5160-4382; E-mail: messler@klp.med.uni- muenchen.de.
Abbreviations:

mox-LDL

mildly oxidized low density lipoprotein

HRP

horseradish peroxidase

HUVEC

human umbilical vein endothelial cell

LPA

lysophosphatidic acid

MLC

myosin light chain

MLCK

myosin light chain kinase

PBS

phosphate-buffered saline
- Received May 13, 1999.
- Revision received August 4, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.