Abstract 40: Protein Kinase C Regulation of 12-Lipoxygenase-Mediated Human Platelet Activation
Introduction: Platelet activation is important in the regulation of hemostasis and thrombosis. Uncontrolled activation of platelets may lead to arterial thrombosis which is a major cause of myocardial infarction and stroke. Following activation, metabolism of arachidonic acid (AA) by 12-lipoxygenase (12-LOX) may play a significant role in regulating the degree and stability of platelet activation as inhibition of 12-LOX significantly attenuates platelet aggregation in response to various agonists. Protein kinase C (PKC) activation is also known to be an important regulator of platelet activity.
Objectives: Using a newly developed selective inhibitor for 12-LOX and a pan-PKC inhibitor, we investigated the role of PKC in 12-LOX-mediated regulation of agonist signaling in the platelet.
Methods: To determine the role of PKC within the 12-LOX pathway, a number of biochemical endpoints were measured in human platelets including platelet aggregation, calcium mobilization, integrin activation, and phosphorylation of PKC substrates.
Results: Inhibition of 12-LOX or PKC resulted in inhibition of dense granule secretion and attenuation of both aggregation and αIIbβ3 activation. However, activation of PKC downstream of 12-LOX inhibition rescued agonist-induced aggregation and integrin activation. Additionally, direct PKC activation rescued deficits in phosphorylation of pleckstrin and other PKC substrates mediated by inhibition of 12-LOX. Finally, inhibition of 12-LOX had no effect on PKC-mediated aggregation indicating that 12-LOX is upstream of PKC.
Conclusions: These studies support an essential role for PKC downstream of 12-LOX activation in human platelets and suggest 12-LOX as a possible target for anti-platelet therapy.
- © 2012 by American Heart Association, Inc.