Inhibition of myosin light chain kinase provides prolonged attenuation of radial artery vasospasm.
OBJECTIVE
Current treatments for conduit vessel vasospasm are short-acting and do not inhibit all vasospastic stimuli. This study tests the hypothesis that irreversible inactivation of myosin light chain kinase provides sustained inhibition of arterial vasoconstriction stimulated by a spectrum of vasopressors.


METHODS
Canine radial artery segments were soaked for 60 min in control buffer or buffer with wortmannin, an irreversible inhibitor of myosin light chain kinase. The vessels were then thoroughly washed and contractile responses were quantified in response to a spectrum of vasopressors at 2 and 48 h after treatment. After 48 h, selected vessels were examined for morphologic changes and development of apoptosis.


RESULTS
Two hours after treatment, wortmannin-soaked vessels contracted significantly less than controls in response to norepinephrine (0.19+/-0.07 g vs. 7.22+/-0.37 g, P<0.001), serotonin (0.92+/-0.35 g vs. 9.64+/-0.67 g, P<0.001), thromboxane-mimetic U46619 (1.25+/-0.17 g vs. 10.99+/-0.50 g, P<0.001), and KCl (1.98+/-0.27 g vs.15.00+/-0.48 g, P<0.001). At 48 h, vasoconstriction remained significantly inhibited in wortmannin-treated vessels compared to control vessels in response to norepinephrine (2.36+/-0.17 vs. 6.95+/-0.47 g, P<0.001), serotonin (4.67+/-0.39 vs. 12.42+/-0.70 g, P<0.001), U46619 (5.42+/-0.34 vs. 9.29+/-0.74 g, P=0.008), and KCl (7.49+/-0.48 vs. 13.32+/-0.60 g, P<0.001). Histology of wortmannin-treated vessels revealed no overt smooth muscle or endothelial cell damage. TUNEL staining revealed a significantly greater proportion of apoptotic smooth muscle and endothelial cells in wortmannin-treated vessels as compared to controls.


CONCLUSIONS
Disengaging the smooth muscle contractile apparatus by irreversibly binding myosin light chain kinase with wortmannin significantly attenuates radial artery vasoconstriction up to 48 h after brief treatment. This novel strategy may prevent vasospasm of arterial grafts from all causes for several postoperative days.
Kerendi
Faraz
F
Cardiothoracic Research Lab, Division of Cardiothoracic Surgery, Emory University School of Medicine, 550 Peachtree Street, NE, Atlanta, GA 30308-2225, USA.
Halkos
Michael E
ME
Corvera
Joel S
JS
Kin
Hajime
H
Zhao
Zhi-Qing
ZQ
Mosunjac
Mario
M
Guyton
Robert A
RA
Vinten-Johansen
Jakob
J
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D004285:Dogs; D042783:Endothelial Cells / Q000502:physiology; D016166:Free Radical Scavengers / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017534:Radial Artery / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D013931:Thromboxanes; D014652:Vascular Diseases / Q000503:physiopathology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D016166:Free Radical Scavengers; D047428:Protein Kinase Inhibitors; D013931:Thromboxanes; D014662:Vasoconstrictor Agents; D012701:Serotonin; D011189:Potassium Chloride; D009219:Myosin-Light-Chain Kinase; D009638:Norepinephrine; D000077191:Wortmannin