title: Protein kinase C regulation of 12-lipoxygenase-mediated human platelet activation.
abstract: 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.
authors.affiliation: Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Yeung
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Apopa
authors.forename: Joanne
authors.initials: J
authors.lastname: Vesci
authors.forename: Victor
authors.initials: V
authors.lastname: Kenyon
authors.forename: Ganesha
authors.initials: G
authors.lastname: Rai
authors.forename: Ajit
authors.initials: A
authors.lastname: Jadhav
authors.forename: Anton
authors.initials: A
authors.lastname: Simeonov
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Holman
authors.forename: David J
authors.initials: DJ
authors.lastname: Maloney
authors.forename: Olivier
authors.initials: O
authors.lastname: Boutaud
authors.forename: Michael
authors.initials: M
authors.lastname: Holinstat
mesh_terms: D001092:Arachidonate 12-Lipoxygenase / Q000187:drug effects / Q000378:metabolism*; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D005434:Flow Cytometry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology
chemical_list: D016859:Lipoxygenase Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D047428:Protein Kinase Inhibitors; D001092:Arachidonate 12-Lipoxygenase; D011493:Protein Kinase C; D002118:Calcium