Oxytocin and lysophosphatidic acid induce stress fiber formation in human myometrial cells via a pathway involving Rho-kinase.
The actin cytoskeleton is important for stress fiber formation and contributes to the initiation and maintenance of smooth muscle contraction. To determine if oxytocin and lysophosphatidic acid (LPA) induce stress fiber formation, cultured human myometrial cells were exposed to oxytocin (10(-5) M) or LPA (10(-6) M), and filamentous (F) and globular (G) actin pools were stained with fluorescein isothiocyanate-phalloidin and Texas red DNase I, respectively. The F- to G-actin fluorescent-staining ratio was measured by fluorescence microscopy. Oxytocin and LPA increased stress fiber formation, as indicated by an increase in the F- to G-actin fluorescent-staining ratio. The Rho-kinase inhibitor Y-27632 markedly attenuated this increase. Oxytocin-induced stress fiber formation was completely inhibited in the presence of the oxytocin antagonist compound VI. Tyrosine kinase inhibition with tyrphostin A23 partially blocked the increase induced by oxytocin but had no effect on LPA-induced stress fiber formation. Stress fiber formation was not blocked by pertussis toxin, mitogen-activated protein kinase, or protein kinase C inhibitors. Our results show that human myometrial cells respond to oxytocin and LPA with the formation of stress fibers that may be involved in the maintenance of uterine contractions. Rho-kinase appears to be a key signaling factor in this pathway.
Gogarten
W
W
Department of Anesthesiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA.
Emala
C W
CW
Lindeman
K S
KS
Hirshman
C A
CA
D000199:Actins / Q000032:analysis; D000577:Amides / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D009215:Myometrium / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D010121:Oxytocin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D037342:Pertussis Toxin; D010590:Phalloidine; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D014590:Uterine Contraction; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D054460:rho-Associated Kinases
D000199:Actins; D000577:Amides; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; D011725:Pyridines; D010566:Virulence Factors, Bordetella; C108830:Y 27632; D010590:Phalloidine; D010121:Oxytocin; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D016650:Fluorescein-5-isothiocyanate