Rho-kinase activation is involved in hypoxia-induced pulmonary vasoconstriction.
Rho-associated serine/threonine kinase (Rho-kinase) is a downstream effector of small GTPase RhoA that has recently been shown to play an important role in regulating smooth muscle contraction. The present study investigated the role of Rho/ Rho-kinase in hypoxia-induced pulmonary vasoconstriction (HPV). Small pulmonary resistance vessels and cultured pulmonary arterial smooth muscle cells (PASMCs) from the rat were used. PASMCs exposed to hypoxia (PO(2) = 26 +/- 2 mm Hg) showed a significant increase in Rho-kinase activity. Exposure to hypoxia for 20, 40, 60, 90, and 120 min also resulted in a significant increase in myosin light chain (MLC) phosphorylation at all time points in PASMCs. Hypoxia-induced MLC phosphorylation was inhibited by Y-27632 (a Rho-kinase inhibitor), exoenzyme C3 (a specific Rho inhibitor), or toxin B (an inhibitor for Rho proteins). In addition, hypoxia-induced Rho-kinase activation was blocked by C3 and toxin B. Small rat intrapulmonary arterial rings, which were made hypoxic (PO(2) = 30 +/- 3 mm Hg), showed a slow sustained contraction, and Y-27632 caused a significant relaxation during the sustained phase of HPV in a concentration-dependent manner. In summary, the data show that Rho-kinase is activated by hypoxia in PASMCs, and Rho/Rho-kinase is functionally linked to hypoxia-induced MLC phosphorylation and plays a role in the sustained phase of HPV.
Wang
Z
Z
Department of Cellular/Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Jin
N
N
Ganguli
S
S
Swartz
D R
DR
Li
L
L
Rhoades
R A
RA
D000818:Animals; D002478:Cells, Cultured; D000860:Hypoxia / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011651:Pulmonary Artery / Q000166:cytology / Q000201:enzymology; D011652:Pulmonary Circulation / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000502:physiology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D047908:Intracellular Signaling Peptides and Proteins; D018994:Myosin Light Chains; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein