Synergistic effect of urotensin II with serotonin on vascular smooth muscle cell proliferation.
BACKGROUND
Urotensin II (U-II), the most potent vasoconstrictor, and serotonin (5-HT) are known to play an important role in pulmonary hypertension. However, little is known about the effect of U-II and its interaction with 5-HT on vascular smooth muscle cell (VSMC) proliferation.


OBJECTIVE
We assessed the interaction between U-II and 5-HT in inducing VSMC proliferation.


METHODS
Growth-arrested rabbit VSMCs were incubated in serum-free medium with different concentrations of U-II and 5-HT. VSMC proliferation was examined by the increase in [3H]thymidine incorporation into DNA and cell number.


RESULTS
U-II or 5-HT induced [3H]thymidine incorporation in a dose-dependent manner with a maximal effect at a concentration of 50 nmol/l (161%) or 50 micromol/l (205%), respectively. When added together, low concentrations of U-II (50 nmol/l) and 5-HT (1 micromol/l) interacted synergistically in inducing [3H]thymidine incorporation (382%). These effects on [3H]thymidine incorporation were paralleled by an increase in cell number. The G-protein inactivator GDP-beta-S (100 micromol/l), protein kinase C (PKC) inhibitor Ro31-8220 (0.1 micromol/l), Src family tyrosine kinase inhibitor PP2 (1 micromol/l), and mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 (10 micromol/l) inhibited the mitogenic effects of U-II and 5-HT and also their interaction in inducing [3H]thymidine incorporation.


CONCLUSIONS
Our results suggest that U-II and 5-HT may induce the synergistic interaction in inducing VSMC proliferation via a G-protein-coupled receptor/PKC/Src tyrosine kinase/MAPK pathway, thus contributing to the relatively rapid development of atherosclerosis in hypertensive vascular disease.
Watanabe
T
T
Department of Internal Medicine, Division of Cardiology, University of Texas-Houston Health Science Center, Houston, Texas 77030, USA.
Pakala
R
R
Katagiri
T
T
Benedict
C R
CR
D000818:Animals; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008934:Mitogens / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology*; D013873:Thionucleotides / Q000494:pharmacology; D014579:Urotensins / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D005419:Flavonoids; D007211:Indoles; D008934:Mitogens; D013873:Thionucleotides; D014579:Urotensins; D006153:Guanosine Diphosphate; D012701:Serotonin; C023427:guanosine 5'-O-(2-thiodiphosphate); D004247:DNA; C029677:urotensin II; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C064758:Ro 31-8220