Chronic hypoxia augments protein kinase G-mediated Ca2+ desensitization in pulmonary vascular smooth muscle through inhibition of RhoA/Rho kinase signaling.
Pulmonary vascular smooth muscle (VSM) sensitivity to nitric oxide (NO) is enhanced in pulmonary arteries from rats exposed to chronic hypoxia (CH) compared with controls. Furthermore, in contrast to control arteries, relaxation to NO following CH is not reliant on a decrease in VSM intracellular free calcium ([Ca(2+)](i)). We hypothesized that enhanced NO-dependent pulmonary vasodilation following CH is a function of VSM myofilament Ca(2+) desensitization via inhibition of the RhoA/Rho kinase (ROK) pathway. To test this hypothesis, we compared the ability of the NO donor, spermine NONOate, to reverse VSM tone generated by UTP, the ROK agonist sphingosylphosphorylcholine, or the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate in Ca(2+)-permeabilized, endothelium-denuded pulmonary arteries (150- to 300-microm inner diameter) from control and CH (4 wk at 0.5 atm) rats. Arteries were loaded with fura-2 AM to continuously monitor VSM [Ca(2+)](i). We further examined effects of NO on levels of GTP-bound RhoA and ROK membrane translocation as indexes of enzyme activity in arteries from each group. We found that spermine NONOate reversed Y-27632-sensitive Ca(2+) sensitization and inhibited both RhoA and ROK activity in vessels from CH rats but not control animals. In contrast, spermine NONOate was without effect on PKC-mediated vasoconstriction in either group. We conclude that CH mediates a shift in NO signaling to promote pulmonary VSM Ca(2+) desensitization through inhibition of RhoA/ROK.
Vascular Physiology Group, Department of Cell Biology MSC 08-4750, 1 Univ. of New Mexico, Albuquerque, NM 87131-0001, USA.
Nikki L
NL
Jernigan
Benjimen R
BR
Walker
Thomas C
TC
Resta
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013096:Spermine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000502:physiology
D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; C091861:spermine nitric oxide complex; D013096:Spermine; D009569:Nitric Oxide; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D020742:rhoA GTP-Binding Protein; D002118:Calcium