title: Increased platelet sensitivity to ADP in mice lacking platelet-type 12-lipoxygenase.
abstract: Arachidonic acid metabolism is one of several mechanisms culminating in the production of an agonist for platelet activation and recruitment. Although the proaggregatory role of thromboxane A2, a product of the aspirin-inhibitable cyclooxygenase, is well established, relatively little is known regarding the biological importance of arachidonic acid metabolism via the 12-lipoxygenase (P-12LO) pathway to 12-hydro(pero)xyeicosatetraenoic acid. We observed that platelets obtained from mice in which the P-12LO gene has been disrupted by gene targeting (P-12LO-/-) exhibit a selective hypersensitivity to ADP, manifested as a marked increase in slope and percent aggregation in ex vivo assays and increased mortality in an ADP-induced mouse model of thromboembolism. The hyperresponsiveness to ADP is independent of dense granule release, cyclooxygenase-derived eicosanoid synthesis, and protein kinase C activity. The addition of 12-hydroxyeicosatetraenoic acid to P-12LO-/- platelet-rich plasma rescues the hyperresponsive phenotype resulting in a diminished ADP-induced aggregation profile. The enhanced ADP sensitivity of P-12LO-/- mice appears to reveal a mechanism by which a product of the P-12LO pathway suppresses platelet activation by ADP.
authors.affiliation: Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: E N
authors.initials: EN
authors.lastname: Johnson
authors.forename: L F
authors.initials: LF
authors.lastname: Brass
authors.forename: C D
authors.initials: CD
authors.lastname: Funk
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / Q000096:biosynthesis; D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000172:deficiency*; D016718:Arachidonic Acid / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D018390:Gene Targeting; D051379:Mice; D008817:Mice, Mutant Strains; D010974:Platelet Aggregation / Q000235:genetics*; D015290:Second Messenger Systems; D013923:Thromboembolism / Q000209:etiology* / Q000401:mortality
chemical_list: D016718:Arachidonic Acid; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000244:Adenosine Diphosphate; D001092:Arachidonate 12-Lipoxygenase