Role of myosin light chain kinase in cardiotrophin-1-induced cardiac myofibroblast cell migration

摘要

Chemotactic movement of myofibroblasts is recognized as a common means for their sequestration to the site of tissue injury. Following myocardial infarction (MI), recruitment of cardiac myofibroblasts to the infarct scar is a critical step in wound healing. Contractile myofibroblasts express embryonic smooth muscle myosin, α-smooth muscle actin, as well as collagens I and in. We examined the effects of cardiotrophin-1 (CT-1) in the induction of primary rat ventricular myofibroblast motility. Changes in membrane potential (E_m) and Ca~(2+) entry were studied to reveal the mechanisms for induction of myofibroblast migration. CT-1-induced cardiac myofibroblast cell migration, which was attenuated through the inhibition of JAK2 (25 μM AG490), and myosin light chain kinase (20μM ML-7). Inhibition of K+ channels (1 mM tetraethylammonium or 100 μM 4-aminopyr-idine) and nonselective cation channels by 10 μM gadolinium (Gd~(3+)) significantly reduced migration in the presence of CT-1. CT-1 treatment caused a significant increase in myosin light chain phosphory-lation, which could be inhibited by incubation in Ca~(2+)-free conditions or by application of AG490, ML-7, and W7 (100 μM; calmodulin inhibitor). Monitoring myofibroblast membrane potential with poten-tiometric fluorescent DiBAC4(3) dye revealed a biphasic response to CT-1 consisting of an initial depolarization followed by hyperpolar-ization. Increased intracellular Ca~(2+), as assessed by fluo 3, occurred immediately after membrane depolarization and attenuated at the time of maximal hyperpolarization. CT-1 exerts chemotactic effects via multiple parallel signaling modalities in ventricular myofibroblasts, including changes in membrane potential, alterations in intracellular calcium, and activation of a number of intracellular signaling pathways. Further study is warranted to determine the precise role of K+ currents in this process.