Bimodal concentration-dependent effect of thrombin on endothelial cell proliferation and growth factor release in culture.
BACKGROUND
The role of thrombin in the stimulation of endothelial cell (EC) proliferation is controversial. The aim of this study was to investigate if thrombin regulates cell proliferation and production of platelet-derived growth factor (PDGF), bovine fibroblast growth factor (bFGF), and transforming growth factor beta(1) (TGF-beta(1)) by bovine aortic ECs.


METHODS
ECs, obtained from thoracic aortas of calves, were stimulated with thrombin at various concentrations (from 0.05 to 1.0 IU/ml) in serum free culture. Mitogenic activity of thrombin on ECs was determined by tritiated thymidine uptake. The release of PDGF, bFGF, and TGF-beta(1) was assessed by ELISA. PDGF release was confirmed by Western blot and bFGF and TGF-beta(1) mRNA expression was determined by polymerase chain reaction (PCR).


RESULTS
Thrombin at high concentrations did not cause any increase in EC proliferation after 72 h of culture and induced inhibition of EC proliferation after 96 h and 8 days of culture. It induced a decrease in PDGF release and an increase in TGF-beta(1) release. Thrombin at low concentrations induced a significant increase in EC proliferation at 72 h, 96 h, and 8 days of culture. It induced an increase in PDGF release and a decrease in TGF-beta(1) release. bFGF release was higher than control at all thrombin concentrations. These data were confirmed by Western blot and PCR studies.


CONCLUSIONS
Thrombin regulates EC growth through the inhibition of EC proliferation at high concentrations and through the stimulation of EC proliferation at low physiological concentrations. EC proliferation is partially mediated by autocrine production of PDGF, bFGF, and TGF-beta(1).
Borrelli
V
V
Department of Surgery Pietro Valdoni, Department of Medical Histology and Embryology, University of Rome La Sapienza, Via Scarpa, 14, 00161 Rome, Italy.
Sterpetti
A V
AV
Coluccia
P
P
Randone
B
B
Cavallaro
A
A
Santoro D'Angelo
L
L
Cucina
A
A
D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D015153:Blotting, Western; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000235:genetics; D015870:Gene Expression / Q000502:physiology; D006133:Growth Substances / Q000378:metabolism*; D006490:Hemostatics / Q000494:pharmacology*; D008934:Mitogens / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000032:analysis / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D013917:Thrombin / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1
D017077:Culture Media, Conditioned; D006133:Growth Substances; D006490:Hemostatics; D008934:Mitogens; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016222:Fibroblast Growth Factor 2; D013917:Thrombin