on March 21, 2002
Published online before print March 21, 2002, doi: 10.1161/01.ATV.0000015903.02749.71
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Submitted on May 10, 2001
Accepted on March 4, 2002
Lysophosphatidylcholine Activates Extracellular Signal-Regulated Kinases 1/2 Through Reactive Oxygen Species in Rat Vascular Smooth Muscle Cells
Tadashi Yamakawa *;
From the Department of Endocrinology and Diabetes (T.Y.), Yokohama City University Medical Center, Minami-ku, Yokohama, Japan; Neurobiology of Aging Laboratories (S-i.T.), Mt. Sinai School of Medicine, New York, NY; Department of Pathophysiology & Therapeutics (J.K.), Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan; Department of Anatomy and Physiology (E.D.M.), Meharry Medical College, Nashville, Tenn; and Department of Biochemistry (T.Y., Y.Y., K.N., T.I., S.E.), Vanderbilt University School of Medicine, Nashville, Tenn.
* To whom correspondence should be addressed. E-mail: yamakat{at}urahp.yokohama-cu.ac.jp.
Abstract—Lysophosphatidylcholine
(lysoPC) acts on vascular smooth muscle cells (VSMCs) to produce a
mitogenic response through the activation of extracellular
signal-regulated kinases 1/2 (ERK1/2). In the present study, we
examined the importance of reactive oxygen species (ROS) in
lysoPC-stimulated ERK1/2 activation in cultured rat VSMCs. Treatment
with lysoPC for 3 minutes caused a 2-fold increase in intracellular ROS
that was blocked by the NADH/NADPH oxidase inhibitor,
diphenylene iodonium (DPI). Antioxidants,
N-acetyl-L-cysteine,
glutathione monoester, or 
-tocopherol, inhibited ERK1/2
activation by lysoPC. Almost identical results were obtained in the
VSMC line A10. Pretreatment of VSMCs with DPI but not allopurinol or
KCN abrogated the activation of ERK1/2. The Flag-tagged p47phox
expressed in A10 cells was translocated from the cytosol to the
membrane after 2 minutes of stimulation with lysoPC. The overexpression
of dominant-negative p47phox in A10 cells suppressed lysoPC-induced ERK
activation. The ROS-dependent ERK activation by lysoPC seems to involve
protein kinase C-- and Ras-dependent raf-1 activation. Induction of
c-fos expression and enhanced
AP-1 binding activity by lysoPC were also inhibited by DPI and NAC.
Taken together, these data suggest that ROS generated by NADH/NADPH
oxidase contribute to lysoPC-induced activation of ERK1/2 and
subsequent growth promotion in
VSMCs.
Key words: vascular smooth muscle cells • lysophosphatidylcholine • extracellular signal-regulated kinases 1/2 • reactive oxygen species • signal transduction