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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2007;27:e20.)
© 2007 American Heart Association, Inc.

Vascular Biology

Cholesterol Enhances Thrombin-Induced Release of Fibroblast Growth Factor-2 in Human Vascular Smooth Muscle Cells

Bernhard H. Rauch; Godehard A. Scholz; Dana Baumgärtel-Allekotte; Petra Censarek; Jens W. Fischer; Artur-Aron Weber; Karsten Schrör

From the Universitätsklinikum Düsseldorf, Institut für Pharmakologie und Klinische Pharmakologie, Düsseldorf, Germany.

Correspondence to Bernhard H. Rauch, MD, Universitätsklinikum Düsseldorf, Institut für Pharmakologie und Klinische Pharmakologie, Universiäts str. 1, 40225 Düsseldorf, Germany. E-mail rauchb{at}uni-duesseldorf.de

Objective— The mitogenic response to the G protein–coupled receptor agonist thrombin in human vascular smooth muscle cells (SMCs) depends on release of fibroblast growth factor-2 (FGF-2). Yet, intracellular mechanisms triggering FGF-2 release are unknown. The present study investigates possible effects of cholesterol enrichment and depletion, which have been shown to influence FGF-2–dependent signaling and SMC mitogenesis, on thrombin-induced FGF-2 release.

Methods and Results— Cultured human aortic and saphenous vein SMCs were enriched with cholesterol by using a cyclodextrin-cholesterol complex. Cholesterol accumulation was determined by a fluorometric assay. ELISA, Western blotting, and RT-PCR were used for quantification of FGF-2 levels. DNA synthesis was determined by [³H]-thymidine incorporation, proliferation by cell counting. Stimulation of SMCs with thrombin (30 nmol/L) resulted in release of FGF-2 into the pericellular space within 10 minutes. Preincubation with cyclodextrin-cholesterol caused accumulation of cellular cholesterol, increased thrombin-induced FGF-2 release, and stimulated FGF-2 de novo synthesis. Thrombin-induced DNA synthesis and proliferation were enhanced in cholesterol-rich SMCs. This effect was inhibited by FGF-2-neutralizing antibodies.

Conclusions— Enhanced cellular cholesterol stimulates thrombin-induced release of FGF-2 and increases the mitogenic response toward thrombin in human SMCs. This mechanism might also be relevant for thrombin-induced mitogenesis in hypercholesterolemia in vivo.

This study demonstrates that the mitogenic response toward thrombin is enhanced in cholesterol-enriched human vascular SMCs. Cholesterol-enrichment induces FGF-2 expression and its increased release by thrombin. These data suggest an important pathophysiological role of thrombin-induced mitogenesis and FGF-2 release under conditions of elevated cholesterol levels.

Key Words: thrombin • FGF-2 • cholesterol • smooth muscle cells • mitogenesis