Inherited Human gp91 Deficiency Is Associated With Impaired Isoprostane Formation and Platelet Dysfunction

Object—Platelet isoprostane 8-iso-PGF2 , a proaggregating molecule, is believed to derive from nonenzymatic oxidation of arachidonic acid. We hypothesized that NADPH is implicated in isoprostane formation and platelet activation. Methods and Results—We studied 8-iso-PGF2 in platelets from 8 male patients with hereditary deficiency of gp91, the catalytic subunit of NADPH oxidase, and 8 male controls. On stimulation, platelets from controls produced 8-iso-PGF2 , which was inhibited 8% by aspirin and 58% by a specific inhibitor of gp91. Platelets from patients with gp91 hereditary deficiency had normal thromboxane A2 formation but marked 8-iso-PGF2 reduction compared with controls. In normal platelets incubated with a gp91 inhibitor or with SQ29548, a thromboxane A2/isoprostane receptor inhibitor, platelet recruitment, an in vitro model of thrombus growth, was reduced by 44% and 64%, respectively; a lower effect ( 17%) was seen with aspirin. Moreover, thrombus formation under shear stress (blood perfusion at the wall shear rate of 1500 s ) was reduced in samples in which isoprostane formation was inhibited by NADPH oxidase inhibitors. In gp91-deficient patients, agonist-induced platelet aggregation was within the normal range, whereas platelet recruitment was reduced compared with controls. Incubation of platelets from gp91-deficient patients with 8-iso-PGF2 dose-dependently (1 to 100 pmol/L) increased platelet recruitment by mobilizing platelet Ca and activating gpIIb/IIIa; a further increase in platelet recruitment was detected by platelet coincubation with L-NAME, an inhibitor of NO synthase. Conclusion—This study provides the first evidence that platelet 8-iso-PGF2 maximally derives from gp91 activation and contributes to platelet recruitment via activation of gpIIb/IIIa. (Arterioscler Thromb Vasc Biol. 2011;31:00-00.)