Endothelin is a dose-dependent trophic factor and a mitogen in small arteries in vivo.
OBJECTIVE
Endothelin (ET) modulates cellular processes relevant to vascular remodeling, but there is still some debate as to the potential of ET to be a trophic factor or a mitogen. Moreover, the signaling of ET in vivo to produce these effects is largely unknown.


METHODS
3H-leucine and 3H-thymidine incorporation in rat small mesenteric arteries was studied with several doses of ET-1 (0.1-10 pmol/kg/min) administered for 26 h in vivo.


RESULTS
The EC50 for protein synthesis was four times lower than that of DNA synthesis, with maximal effects around 1 and 3 pmol/kg/min, respectively. At 5 pmol/kg/min, ET enhanced CDK2 activity by reducing the binding of its inhibitor p27(Kip1). In contrast, the binding was enhanced at 0.5 pmol/kg/min. The reduced binding observed at 5 pmol/kg/min could not be explained by changes of p27(Kip1) or CDK2 content. Phosphorylation of p27(Kip1) on serine 10 was significantly reduced at 5 pmol/kg/min ET. Although the phosphoinositide 3-kinase pathway was activated, it did not contribute to the protein or DNA synthesis responses. Administration of 1 or 5 pmol/kg/min ET-1 for 28 days increased the thickness and cross-sectional area of the small mesenteric artery due to hypertrophy and hyperplasia, respectively, thus confirming the results obtained in acute conditions.


CONCLUSIONS
ET modulates p27(Kip1) binding to CDK2, producing hypertrophy at low and hyperplasia at higher concentrations. Taken together, these results suggest that ET can act both as a trophic factor and as a mitogen in an in vivo environment, depending on its local concentration.
Dao
Huy Hao
HH
Faculty of Pharmacy, Université de Montréal, 2900 Edouard-Montpetit, Pavillon Jean-Coutu, room 3197, P.O. Box 6128, Station Centre-Ville Montréal, Québec, Canada H3C 3J7.
Bouvet
Céline
C
Moreau
Simon
S
Beaucage
Pierre
P
Larivière
Richard
R
Servant
Marc J
MJ
de Champlain
Jacques
J
Moreau
Pierre
P
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D019332:Endothelin-1 / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007553:Isotope Labeling; D007930:Leucine / Q000378:metabolism; D008638:Mesenteric Arteries; D008934:Mitogens / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D017539:Tunica Intima / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA; D004343:Drug Implants; D019332:Endothelin-1; D007930:Leucine; D008934:Mitogens; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013936:Thymidine; C493958:Cdkn1a protein, rat; C495894:CDK2 protein, human