Extracellular Signal-regulated Kinase Plays an Essential Role in Hypertrophic Agonists, Endothelin-1 and Phenylephrine-induced Cardiomyocyte Hypertrophy

doi:10.1074/jbc.M007037200

Extracellular Signal-regulated Kinase Plays an Essential Role in Hypertrophic Agonists, Endothelin-1 and Phenylephrine-induced Cardiomyocyte Hypertrophy*

From the Departments of Cardiovascular Pharmacology,^§Neuroscience, ^¶Bone and Cartilage Biology, and ^‖Safety Assessment, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, the ^‡Department of Physiology, University of Maryland, Baltimore, Maryland 21201, and the ^**Department of Clinical Pharmacology and Toxicology, Freie Universitaet Berlin, 12200 Berlin, Germany

Abstract

The extracellular signal-regulated kinase (ERK) pathway is activated by hypertrophic stimuli in cardiomyocytes. However, whether ERK plays an essential role or is implicated in all major components of cardiac hypertrophy remains controversial. Using a selective MEK inhibitor, U0126, and a selective Raf inhibitor, SB-386023, to block the ERK signaling pathway at two different levels and adenovirus-mediated transfection of dominant-negative Raf, we studied the role of ERK signaling in response of cultured rat cardiomyocytes to hypertrophic agonists, endothelin-1 (ET-1), and phenylephrine (PE). U0126 and SB-386023 blocked ET-1 and PE-induced ERK but not p38 and JNK activation in cardiomyocytes. Both compounds inhibited ET-1 and PE-induced protein synthesis and increased cell size, sarcomeric reorganization, and expression of β-myosin heavy chain in myocytes with IC₅₀ values of 1–2 μm. Furthermore, both inhibitors significantly reduced ET-1- and PE-induced expression of atrial natriuretic factor. In cardiomyocytes transfected with a dominant-negative Raf, ET-1- and PE-induced increase in cell size, sarcomeric reorganization, and atrial natriuretic factor production were remarkably attenuated compared with the cells infected with an adenovirus-expressing green fluorescence protein. Taken together, our data strongly support the notion that the ERK signal pathway plays an essential role in ET-1- and PE-induced cardiomyocyte hypertrophy.

Footnotes

↵* 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.
↵‡ To whom correspondence should be addressed: Dept. of Cardiovascular Pharmacology, SmithKline Beecham Pharmaceuticals, 709 Swedeland Rd., P. O. Box 1539, UW2510, King of Prussia, PA 19406. Tel.: 610-270-5313; Fax: 610-270-5080; E-mail: tian-li_yue@sbphrd. com.
Published, JBC Papers in Press, September 12, 2000, DOI 10.1074/jbc.M007037200
Abbreviations:

β-MHC

β-myosin heavy chain

AdRaf−

adenovirus-expressing dominant-negative Raf

AdGFP

adenovirus-expressing green fluorescence protein

ANF

atrial natriuretic factor

ELISA

enzyme-linked immunosorbent assay

ERK

extracellular signal-regulated kinase

ET-1

endothelin-1

GPCR

G-protein-coupled receptor

JNK

c-jun N-terminal kinase

MAPK

mitogen-activated protein kinase

MEK

MAPK/ERK kinase

PE

phenylephrine

PI3K

phosphatidylinositol 3-kinase

PBS

phosphate-buffered saline

GFP

green fluorescent protein
- Received August 3, 2000.
- Revision received September 8, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.