Involvement of Rho-Kinase–Mediated Phosphorylation of Myosin Light Chain in Enhancement of Cerebral Vasospasm

• Published in: Circulation research Vol. 87; no. 3; pp. 195 - 200
• Main Authors: Sato, Motohiko, Tani, Eiichi, Fujikawa, Hirokazu, Kaibuchi, Kozo
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 04-08-2000; Lippincott; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Amides - administration & dosage; Amides - pharmacology; Animals; Basilar Artery - enzymology; Basilar Artery - pathology; Biological and medical sciences; Calcium - physiology; Calmodulin - physiology; Dogs; Dose-Response Relationship, Drug; Enzyme Inhibitors - administration & dosage; Enzyme Inhibitors - pharmacology; Intracellular Signaling Peptides and Proteins; Medical sciences; Myosin Light Chains - metabolism; Myosin-Light-Chain Phosphatase; Neurology; Phosphoprotein Phosphatases - metabolism; Phosphorylation - drug effects; Potassium Chloride - administration & dosage; Potassium Chloride - pharmacology; Protein Processing, Post-Translational - drug effects; Protein Processing, Post-Translational - physiology; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - physiology; Pyridines - administration & dosage; Pyridines - pharmacology; rho GTP-Binding Proteins - physiology; rho-Associated Kinases; Serotonin - administration & dosage; Serotonin - pharmacology; Subarachnoid Hemorrhage - complications; Vascular diseases and vascular malformations of the nervous system; Vasoconstrictor Agents - administration & dosage; Vasoconstrictor Agents - pharmacology; Vasodilator Agents - administration & dosage; Vasodilator Agents - pharmacology; Vasospasm, Intracranial - enzymology; Vasospasm, Intracranial - etiology; Vasospasm, Intracranial - pathology; Phosphorylation; Pathogenesis; Cardiovascular disease; Light peptide chain; Hemorrhage; Vascular disease; Vasomotricity; Calcium ion; Myosin; Vasospasm; Dog; Cerebrovascular disease; Fissipedia; Intracranial; Carnivora; Nervous system diseases; Enzyme; Transferases; Vasoconstriction; Basilar artery; Vertebrata; Experimental disease; Mammalia; Protein kinase; Animal; Circulatory system; Intracellular
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.res.87.3.195

Subarachnoid hemorrhage (SAH) often induces a long-term narrowing of the cerebral artery called cerebral vasospasm. Myosin light chain (MLC) in the spastic basilar artery was reported previously to be phosphorylated by Ca/calmodulin-dependent MLC kinase. Because Rho-kinase, which is activated by the small GTPase Rho, phosphorylates not only MLC but also myosin phosphatase at its myosin-binding subunit (MBS), thus inactivating myosin phosphatase, we examined whether Rho-kinase is involved in the development of vasospasm. Cerebral vasospasm was produced in the canine basilar artery by a 2-hemorrhage method, and vasocontractions were induced by topical application of 80 mmol/L KCl or 0.5 μmol/L serotonin to the canine basilar artery exposed transclivally. The phosphorylation of MLC in the basilar artery was increased concurrently with an enhancement in the intensity of vasospasm with the passage of time after SAH. In addition, Rho-kinase in the basilar artery was activated concurrently with an increase in the phosphorylation of MBS at Ser854 in vasospasm. The Rho-kinase activation levels in vasospasm on days 0 and 2 were comparable to those in KCl- and serotonin-induced sustained vasocontraction, respectively, and those in vasospasm on day 7 were markedly high. The topical application of Y-27632, a specific inhibitor of Rho-kinase, to the exposed spastic basilar artery on day 7 induced a dose-dependent dilation, and the intensities of vasospasm and the phosphorylation of MBS and MLC were simultaneously decreased by 10 μmol/L Y-27632, although the decrease in MBS phosphorylation was more marked than the decrease in MLC phosphorylation. These results indicate that the activation of Rho-kinase and the phosphorylation of MLC and MBS occur concomitantly during vasospasm induced by SAH and suggest that Rho-kinase is involved in the enhancement of cerebral vasospasm in addition to Ca/calmodulin-dependent MLC kinase by increasing the phosphorylation of MLC directly or indirectly as a result of the inhibition of myosin phosphatase by its phosphorylation.