Angiotensin II and serotonin potentiate endothelin-1-induced vascular smooth muscle cell proliferation.
BACKGROUND
Vascular smooth muscle cell (VSMC) proliferation induced by various growth factors has been implicated in a wide variety of pathological processes, including hypertension, atherosclerosis and restenosis after angioplasty.


OBJECTIVE
To investigate the interactions among well-known potent vasoconstrictor substances, endothelin-1 (ET-1), angiotensin II (Ang II), and serotonin (5-HT), on VSMC proliferation.


METHODS
Growth-arrested rabbit VSMCs were incubated with different concentrations of ET-1 in the absence or presence of Ang II, 5-HT, or both. VSMC proliferation was examined by increases in incorporation of [3H]thymidine into DNA and in cell number.


RESULTS
ET-1, Ang II and 5-HT stimulated DNA synthesis in a dose-dependent manner. ET-1 had a maximal effect at a concentration of 0.5 micromol/l (259% of control), Ang II at 1 micromol/l (173%), and 5-HT at 50 micromol/l (205%). When added together, ET-1 (0.1 micromol/l) and Ang II (1 micromol/l) synergistically induced DNA synthesis (341%). When the vasoconstrictors were tested in combination, even non-mitogenic concentrations of ET-1 (0.01 nmol/l) potentiated 5-HT (5 micromol/l)-induced DNA synthesis (404%). Co-incubation of ET-1 (0.01 micromol/l) with Ang II (1 micromol/l) and 5-HT (5 micromol/l) synergistically induced DNA synthesis (566%). These effects on DNA synthesis were paralleled by an increase in cell number. The ETA/B non-selective receptor antagonist, TAK044 (1 micromol/l) and the ETA receptor antagonist, BQ123 (1 micromol/l), but not the ETB receptor antagonist, BQ788 (1 micromol/l), inhibited the mitogenic effect of ET-1 and its interaction with Ang II or 5-HT. In addition, TAK044 (1 micromol/l) or BQ123 (1 micromol/l) along with the angiotensin II type 1 (AT1) receptor antagonist, candesartan (1 micromol/l), the 5-HT2A receptor antagonist, sarpogrelate (10 micromol/l), or both, inhibited the interactions of ET-1 with Ang II or 5-HT.


CONCLUSIONS
Our results suggest that Ang II and 5-HT could potentiate ET-1-induced VSMC proliferation. Inhibition of ETA, AT1, and 5-HT2A may be effective in the treatment of VSMC proliferative disorders associated with hypertension, atherosclerosis and restenosis after angioplasty.
Watanabe
T
T
Department of Internal Medicine, University of Texas-Houston Health Science Center, 77030, USA.
Pakala
R
R
Katagiri
T
T
Benedict
C R
CR
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D004357:Drug Synergism; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology*
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; C034883:guanosine 5'-O-(2-thiotriphosphate); D000804:Angiotensin II; D012701:Serotonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004247:DNA