Endothelin-1 as a putative modulator of gene expression and cellular physiology in cultured human corporal smooth muscle cells.
OBJECTIVE
Increases in cytosolic calcium levels trigger smooth muscle contraction while nuclear calcium increases are thought to regulate gene expression. Endothelin-1 (ET-1) affects both. The goal of these studies was to further investigate the importance of ET-1 to corporal physiology by examining its actions on proliferation and immediate early gene (IEG) expression in cultured human corporal smooth muscle cells.


METHODS
Early passage (1-3) smooth muscle cells were grown in culture and exposed to either phenylephrine (PE) or ET-1 in the absence and presence of serum, the ET(A) or ET(B) selective antagonist BQ123 or IRL1038, or the L-type Ca2+ channel blocker, verapamil. Cell proliferation was assessed with a hemocytometer. The effects of ET-1 on c-myc and c-fos were evaluated using Northern blot analysis. Parametric or nonparametric statistics were used as appropriate.


RESULTS
Addition of ET-1 (100 nM) to serum-starved cultured corporal smooth muscle cells was associated with a nearly 2-fold increase in cell number, as well as 2 to 6-fold increases in c-myc and c-fos levels. Cellular proliferation was inhibited by ET(A)- or ET(B)-receptor subtype blockade with BQ123 (1 microM) or IRL1038 (1 microM), respectively, or blockade of Ca2+ channels with verapamil (10 microM). PE (3 microM) had no detectable effect on smooth muscle proliferation.


CONCLUSIONS
Cell proliferation was mediated by activation of the ET(A) and ET(B) receptor subtypes, dependent on transmembrane Ca2+ flux, and correlated with significant increases in c-myc and c-fos mRNA levels. These studies extend previous observations to indicate the potential pleotropic actions of this peptide in the regulation of human corporal smooth muscle physiology in vivo.
Giraldi
A
A
Department of Urology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Serels
S
S
Autieri
M
M
Melman
A
A
Christ
G J
GJ
D000328:Adult; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D017781:Genes, Immediate-Early / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000166:cytology*; D010413:Penis / Q000166:cytology*; D010656:Phenylephrine / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis
D003470:Culture Media; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D012333:RNA, Messenger; D010656:Phenylephrine