Activation of mitogen-activated protein kinases during preparation of vein grafts and modulation by a synthetic inhibitor

Objective: Long-term durability of saphenous vein grafts used for coronary artery bypass grafting is limited by neointimal formation. Arterial vascular injury is known to activate intracellular mitogen-activated protein kinases, including extracellular signal-regulated kinases and c-jun N-terminal kinases, that affect cell differentiation, proliferation, migration, and apoptosis. This study tests the hypothesis that these mitogen-activated protein kinases are activated in saphenous veins during preparation for coronary artery bypass grafting. Methods: Saphenous veins were harvested from 10 patients undergoing coronary artery bypass grafting. A specimen from each vein was placed in ice-cold lysis buffer immediately after harvesting (t = 0). The remaining tissue was incubated at room temperature in normal saline, 0.1% dimethylsulfoxide (vehicle), or 50 mmol/L PD98059 (mitogen-activated protein kinase kinase-1/2 inhibitor) until the vein was grafted (mean 50 minutes). To study kinetics of intracellular signaling pathways, canine saphenous veins were harvested, and mitogen-activated protein kinases and PI-3 kinase pathways were studied after different incubation time intervals. Extracted proteins were analyzed by Western blotting or in vitro kinase assay. Results: The human saphenous veins showed elevated levels of active extracellular signal-regulated kinase after harvesting (t = 0) and prior to implant (t = 1). Incubation with PD98059 resulted in decreased activation of extracellular signal-regulated kinase. Kinetics of canine saphenous veins showed extracellular signal-regulated kinase and c-jun N-terminal kinase activation, in a time-dependent manner, along with activation of the growth factor-regulated PI3 kinase pathway. Conclusions: This study characterizes activation of extracellular signal-regulated kinases and c-jun N-terminal kinases during vein graft preparation and demonstrates the ability to inhibit extracellular signal-regulated kinase activation by simple incubation with a specific inhibitor. Further studies are needed to evaluate the significance of these findings with respect to graft durability.