Protein kinase C regulation of 12-lipoxygenase-mediated human platelet activation.

Methods Development
Therapeutic Approaches


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. After 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 because 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. 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. To determine the role of PKC within the 12-LOX pathway, a number of biochemical endpoints were measured, including platelet aggregation, calcium mobilization, and integrin activation. Inhibition of 12-LOX or PKC resulted in inhibition of dense granule secretion and attenuation of both aggregation and αIIbβ(3) activation. However, activation of PKC downstream of 12-LOX inhibition rescued agonist-induced aggregation and integrin activation. Furthermore, inhibition of 12-LOX had no effect on PKC-mediated aggregation, indicating that 12-LOX is upstream of PKC. 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 antiplatelet therapy.


Yeung, Jennifer; Apopa, Patrick L; Vesci, Joanne; Kenyon, Victor; Rai Bantukallu, Ganesha; Jadhav, Ajit; Simeonov, Anton; Holman, Theodore R; Maloney, David J; Boutaud, Olivier; Holinstat, Michael;


  • Arachidonate 12-Lipoxygenase/ drug effects
  • Arachidonate 12-Lipoxygenase/ metabolism
  • Blood Platelets/ drug effects
  • Blood Platelets/ enzymology
  • Blood Platelets/ metabolism
  • Blotting, Western
  • Calcium/ metabolism
  • Enzyme Activation
  • Flow Cytometry
  • Gas Chromatography-Mass Spectrometry
  • Humans
  • Lipoxygenase Inhibitors/ pharmacology
  • Platelet Activation
  • Platelet Glycoprotein GPIIb-IIIa Complex/ metabolism
  • Protein Kinase C/ antagonists & inhibitors
  • Protein Kinase C/ metabolism
  • Protein Kinase Inhibitors/ pharmacology

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