Role of Rho kinases in PKG-mediated relaxation of pulmonary arteries of fetal lambs exposed to chronic high altitude hypoxia.

Abstract

An increase in Rho kinase (ROCK) activity is implicated in chronic hypoxia-induced pulmonary hypertension. In the present study, we determined the role of ROCKs in cGMP-dependent protein kinase (PKG)-mediated pulmonary vasodilation of fetal lambs exposed to chronic hypoxia. Fourth generation pulmonary arteries were isolated from near-term fetuses ( approximately 140 days of gestation) delivered from ewes exposed to chronic high altitude hypoxia for approximately 110 days and from control ewes. In vessels constricted to endothelin-1, 8-bromoguanosine-cGMP (8-Br-cGMP) caused a smaller relaxation in chronically hypoxic (CH) vessels compared with controls. Rp-8-Br-PET-cGMPS, a PKG inhibitor, attenuated relaxation to 8-Br-cGMP in control vessels to a greater extent than in CH vessels. Y-27632, a ROCK inhibitor, significantly potentiated 8-Br-cGMP-induced relaxation of CH vessels and had only a minor effect in control vessels. The expression of PKG was increased but was not accompanied with an increase in the activity of the enzyme in CH vessels. The expression of type II ROCK and activity of ROCKs were increased in CH vessels. The phosphorylation of threonine (Thr)696 and Thr850 of the regulatory subunit MYPT1 of myosin light chain phosphatase was inhibited by 8-Br-cGMP to a lesser extent in CH vessels than in controls. The difference was eliminated by Y-27632. These results suggest that chronic hypoxia in utero attenuates PKG-mediated relaxation in pulmonary arteries, partly due to inhibition of PKG activity and partly due to enhanced ROCK activity. Increased ROCK activity may inhibit PKG action through increased phosphorylation of MYPT1 at Thr696 and Thr850.

• Authors: Yuansheng Gao, Ada D Portugal, Sewite Negash, Weilin Zhou, Lawrence D Longo, J Usha Raj
• Journal: American journal of physiology. Lung cellular and molecular physiology (Am J Physiol Lung Cell Mol Physiol) Vol. 292 Issue 3 Pg. L678-84 (Mar 2007) ISSN: 1040-0605 [Print] United States
• PMID: 17085525 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Amides
• Enzyme Inhibitors
• Intracellular Signaling Peptides and Proteins
• Pyridines
• RNA, Messenger
• Y 27632
• 8-bromocyclic GMP
• Protein Serine-Threonine Kinases
• rho-Associated Kinases
• Cyclic GMP-Dependent Protein Kinases
• Myosin-Light-Chain Phosphatase
• Cyclic GMP
• Oxygen

Topics

• Amides (pharmacology)
• Animals
• Cyclic GMP (analogs & derivatives, pharmacology)
• Cyclic GMP-Dependent Protein Kinases (antagonists & inhibitors, metabolism)
• Enzyme Inhibitors (pharmacology)
• Female
• Fetus (metabolism)
• Gene Expression Regulation, Developmental
• Gene Expression Regulation, Enzymologic
• Hypoxia (metabolism)
• Intracellular Signaling Peptides and Proteins (antagonists & inhibitors, metabolism, physiology)
• Male
• Muscle, Smooth, Vascular (metabolism)
• Myosin-Light-Chain Phosphatase (metabolism)
• Oxygen (pharmacology)
• Pregnancy
• Protein Serine-Threonine Kinases (antagonists & inhibitors, metabolism, physiology)
• Pulmonary Artery (embryology, physiology)
• Pulmonary Circulation (drug effects, physiology)
• Pyridines (pharmacology)
• RNA, Messenger (analysis)
• Sheep
• Vasodilation (drug effects, physiology)
• rho-Associated Kinases