Morphogenic effects of endothelin-1 on vascular smooth muscle cells.
Endothelin-1 (ET-1), a vasoconstrictor peptide produced by endothelial and vascular smooth muscle cells (VSMC) might play a role in vascular remodelling. To investigate the proposed 'mitogenic' potential of ET-1, we examined the effects of chronic exposure of VSMC to ET-1 on cell cycle, growth/proliferation and differentiation under essentially mitogen-free culture conditions. Bulk cultures of thoracic aortic VSMC of spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats, although exhibiting genetically determined differences in growth/proliferation (due to shortened G1 and G2 phases in SHR VSMC), respond in a similar manner to ET-1 exposure: long-term exposure (12-15 days) of VSMC from both sources to ET-1 in nonmitogenic medium did not promote cycling of cells. On the contrary, ET-1 attenuated the cycling of VSMC which had already cycled beyond the S phase. For cells which had not cycled beyond the S phase, ET-1 interrupted progression through the cell cycle at the late G1/early S phase. The specific ability of SHR VSMC to grow in mitogen-free medium was abolished by ET-1, most likely via down-regulation of platelet-derived growth factor (PDGF)-alpha receptors. Subsequent to ET-1 exposure, VSMC expressed increased levels of mRNA and protein for smooth-muscle-specific alpha-actin. However, expression of smooth muscle alpha-actin did not predominate over beta-actin as observed for adult contractile VSMC in vivo. The ET-1-induced expression of smooth-muscle-specific alpha-actin mRNA was dose dependent (EC50 approx. 2 x 10(-9) M), and alpha-actin protein expressed was associated with organized actin fibers.
Hahn
A W
AW
Department of Research, University Hospital, Basel, Switzerland.
Regenass
S
S
Resink
T J
TJ
Kern
F
F
Bühler
F R
FR
D000199:Actins / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D016232:Endothelins / Q000494:pharmacology*; D007150:Immunohistochemistry; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000199:Actins; D016232:Endothelins