Enhanced Myosin Light Chain Phosphorylations as a Central Mechanism for Coronary Artery Spasm in a Swine Model With Interleukin-1β

Background Although coronary artery spasm plays an important role in a wide variety of ischemic heart diseases, the intracellular mechanism for the spasm remains to be clarified. We examined the role of myosin light chain (MLC) phosphorylations, a key mechanism for contraction of vascular smooth muscle, in our swine model with interleukin-1β (IL-1β). Methods and Results IL-1β was applied chronically to the porcine coronary arteries from the adventitia to induce an inflammatory/proliferative lesion. Two weeks after the operation, intracoronary serotonin repeatedly induced coronary hyperconstrictions at the IL-1β-treated site both in vivo and in vitro, which were markedly inhibited by fasudil, an inhibitor of protein kinases, including protein kinase C and MLC kinase. Western blot analysis showed that during serotonin-induced contractions, MLC monophosphorylation was significantly increased and sustained in the spastic segment compared with the control segment, whereas MLC diphosphorylation was noted only i...